RU2850766C2 - Method for obtaining fluoropolymer, method for obtaining polytetrafluoroethylene and composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: proposed method involves the polymerisation of perfluoromonomer in an aqueous medium in the presence of polymer (1) to obtain fluoropolymer. The content of perfluoromonomer units in the fluoropolymer is 90 mol% or more relative to all fluoropolymer units, and the perfluoromonomer is a monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, simple perfluoro(alkyl vinyl ether), simple perfluoro(alkyl allyl ether). The polymer (1) contains units obtained from the monomer (1) in an amount of 50% by mass or more relative to all units in the polymer (1). The content of dimer and trimer of monomer (1) in polymer (1) is 1.0% by mass or less relative to polymer (1). The weight-average molecular weight of polymer (1) is from 1.0×10⁴ to 150.0×10⁴. The polymer (1) is obtained by polymerisation of the monomer (1), wherein the oxygen concentration in the system is maintained at a level of 0.01 m.d. to 1500 m.d. of volume throughout the polymerisation process of the monomer (1). Monomer (1) is described by the following general formula: CF₂=CF-O-Rf-SO₃M; radicals Rf and M are described in detail in paragraph 1 of the invention formula.

EFFECT: the approach allows obtaining a fluoropolymer containing a large number of sulfonic acid groups or sulfonic acid salt groups, which does not contain dimers and trimers of the monomer constituting the polymer, and contains a polymerisation unit obtained from a perfluoromonomer.

13 cl, 3 tbl, 5 ex

Description

Field of technology to which the invention relates

[0001] The present invention relates to a method for producing a fluoropolymer, a method for producing polytetrafluoroethylene and a composition.

State of the art

[0002] Patent Document 1 describes a method for producing a fluoropolymer, the method comprising emulsion polymerization of one or more fluorinated monomers in an aqueous medium, wherein the aqueous emulsion polymerization is carried out in an aqueous medium in the presence of at least one radical initiator and at least one polyfunctional dispersant [dispersant (D)], wherein

- the dispersant (D) contains a backbone containing repeating units (links) derived from one or more ethylenically unsaturated monomers,

- the dispersant (D) has such a molecular weight and distribution that it is essentially free of fractions with a molecular weight of less than 3000, and

- the dispersant (D) contains a plurality of ionizable groups selected from the group consisting of _-SO3Xa , _-PO3Xa and -COOXa ( _Xa is _H , an ammonium group or a monovalent metal) in an amount _of at least 1.75 meq _/ g relative to their mass, and the dispersant (D) is used in an amount of 0.01% by mass and 5.00% by mass relative to the total mass of the aqueous medium.

[0003] Patent Document 2 describes a method for producing a fluoropolymer, the method including a step of polymerizing a fluoromonomer in an aqueous medium in the presence of a polymer (1) containing a polymerization unit (1) obtained from a monomer represented by the general formula (1) below, thereby obtaining a fluoropolymer:

where X are the same or different and represent —H or —F; Y is —H, —F, an alkyl group or a fluoroalkyl group; Z are the same or different and represent —H, —F, an alkyl group or a fluoroalkyl group; Rf is a fluorine-containing alkylene group containing from 1 to 40 carbon atoms or a fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond; and A is —COOM, _—SO3M or _—OSO3M (M is _—H , a metal atom, ^—NR74 , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent, and ^R7 is H or an organic group), provided that at least one residue of X, Y and Z contains a fluorine atom.

[0004] Patent Document 3 describes a method for producing an aqueous dispersion of a fluoropolymer, characterized in that it includes a step A of performing ultrafiltration, microfiltration, or dialysis membrane treatment, or a combination thereof, in a pre-treatment of an aqueous dispersion containing a fluoropolymer obtained by polymerization in the presence of a polymer (I) containing a polymerization unit (I) obtained from a monomer represented by the following general formula (I) (provided that the polymer (I) is excluded):

wherein each of X ¹ and X ³ independently represents F, Cl, H, or CF ₃ ; X ² represents H, F, an alkyl group, or a fluorine-containing alkyl group; A ⁰ represents an anionic group; R represents a linking group; Z ¹ and Z ² each independently represent H, F, an alkyl group, or a fluorine-containing alkyl group; and m represents an integer equal to 1 or more.

Prior art

Patent documents

[0005] Patent Document 1: National Publication of International Patent Application No. 2020-510737.

Patent Document 2: International Publication No. WO 2019/168183.

Patent Document 3: International Publication No. WO 2020/218620.

The essence of the invention

The problem that is solved by the invention

[0006] The object of the present invention is to provide a method for producing a fluoropolymer using a polymer containing a large number of sulfonic acid groups or sulfonic acid salt groups, by which it is possible to produce a fluoropolymer that is substantially free of a dimer and trimer of a monomer constituting the polymer and contains a polymerization unit derived from a perfluoromonomer at a high content.

[0007] Another object of the present invention is to provide a method for producing polytetrafluoroethylene using a polymer containing sulfonic acid groups or sulfonic acid salt groups, by which it is possible to obtain polytetrafluoroethylene that is substantially free of the dimer and trimer of the monomer constituting the polymer and has a high molecular weight.

[0008] Another object of the present invention is to provide a composition which comprises a polymer containing a large number of sulfonic acid groups or sulfonic acid salt groups and a fluoropolymer containing a polymerization unit derived from a perfluoromonomer at a high content, and which is substantially free of a dimer and trimer of the monomer constituting the polymer.

[0009] Another object of the present invention is to provide a composition which comprises a polymer containing sulfonic acid groups or sulfonic acid salt groups and polytetrafluoroethylene having a high molecular weight, and which is substantially free of a dimer and trimer of the monomer constituting the polymer.

Solutions to the problem

[0010] The present invention provides a method for producing a fluoropolymer, the method comprising polymerizing a perfluoromonomer in an aqueous medium in the presence of a polymer (1) to obtain a fluoropolymer, wherein the content of the polymerization unit (unit) derived from the perfluoromonomer in the fluoropolymer is 90 mol% or more with respect to all the polymerization units (units) of the fluoropolymer, the polymer (1) is a polymer of the monomer (1) represented by the following general formula (1), the polymerization unit (unit) (1) derived from the monomer (1) in the polymer (1) is 50 mass% or more with respect to all the polymerization units (units) of the polymer (1), and the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0 mass% or less with respect to the polymer (1).

(In the formula, R represents a single bond or a linking group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether bond or a keto group; and M represents -H, a metal atom, ^-NR74 , _imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; ^R7 represents H or an organic group, and m is an integer of 1 or more.)

[0011] In the production method of the present invention, it is preferable that the monomer (1) is a monomer (2) represented by the following general formula (2).

(In the formula, Rf and M are as described above)

In the production method of the present invention, it is preferable that the fluoropolymer is polytetrafluoroethylene.

In the production method of the present invention, it is preferable that the fluoropolymer is a perfluoroelastomer.

[0012] The present invention also provides a method for producing polytetrafluoroethylene, the method comprising polymerizing tetrafluoroethylene in an aqueous medium in the presence of a polymer (1) to produce polytetrafluoroethylene, wherein the polytetrafluoroethylene

is high molecular weight polytetrafluoroethylene, the polymer (1) is a polymer of the monomer (1) represented by the general formula (1) below, and the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less with respect to the polymer (1).

(In the formula, R represents a single bond or a linking group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether bond or a keto group; M represents -H, a metal atom, ^-NR74 , _imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; ^R7 represents H or an organic group, and m is an integer of 1 or more.)

[0013] In the production method of the present invention, it is preferable that the monomer (1) is a monomer (2) represented by the following general formula (2).

(In the formula, Rf and M are as described above.)

[0014] The present invention also provides a composition comprising a polymer (1) and a fluoropolymer, wherein the fluoropolymer comprises a polymerization unit (unit) derived from a perfluoromonomer, and the content of the polymerization unit (unit) derived from a perfluoromonomer in the fluoropolymer is 90 mol% or more with respect to all the polymerization units (units) of the fluoropolymer, the polymer (1) is a polymer of a monomer (1) represented by the general formula (1) below, the polymerization unit (unit) (1) derived from the monomer (1) in the polymer (1) is 50 mass% or more with respect to all the polymerization units (units) of the polymer (1), and the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0 mass% or less with respect to the polymer (1).

(In the formula, R represents a single bond or a linking group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether bond or a keto group; M represents -H, a metal atom, ^-NR74 , _imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; ^R7 represents H or an organic group, and m is an integer of 1 or more.)

[0015] In the composition of the present invention, it is preferable that the monomer (1) is a monomer (2) represented by the following general formula (2).

(In the formula, Rf and M are as described above.)

In the composition of the present invention, it is preferable that the polymer (1) is a copolymer of the monomer (1) and a monomer represented by the general formula CFR ¹¹ =CR ¹¹ ₂ , where R ¹¹ is independently H, F or a perfluoroalkyl group containing from 1 to 4 carbon atoms.

In the composition of the present invention, it is preferable that the content of the polymerization unit (1) obtained from the monomer (1) is from 50 to 94% by mass relative to all the polymerization units constituting the polymer (1), and the content of the polymerization unit (M) obtained from the monomer represented by the general formula CFR ¹¹ =CR ¹¹ ₂ , where R ¹¹ independently represents H, F or a perfluoroalkyl group containing from 1 to 4 carbon atoms, is from 6 to 50% by mass relative to all the polymerization units constituting the polymer (1).

In the composition of the present invention, it is preferable that the alternation ratio of the polymerization unit (I) and the polymerization unit (M) is 40% or more.

In the composition of the present invention, it is preferred that the fluoropolymer is polytetrafluoroethylene.

In the composition of the present invention, it is preferred that the fluoropolymer is a perfluoroelastomer.

In the composition of the present invention, when the fluoropolymer is polytetrafluoroethylene or perfluoroelastomer, it is preferable that the metal content in the composition be 10 ppm by weight or less.

[0016] The present invention also provides a composition comprising a polymer (1) and polytetrafluoroethylene, wherein the polytetrafluoroethylene is high molecular weight polytetrafluoroethylene, the polymer (1) is a polymer of a monomer (1) represented by the general formula (1) below, and the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less relative to the polymer (1).

(In the formula, R represents a single bond or a linking group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether bond or a keto group; M represents -H, a metal atom, ^-NR74 , _imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; ^R7 represents H or an organic group, and m is an integer of 1 or more.)

[0017] In the composition of the present invention, it is preferable that the monomer (1) is a monomer (2) represented by the following general formula (2).

(In the formula, Rf and M are as described above.) Effects of the invention

[0018] According to the present invention, a method for producing a fluoropolymer using a polymer containing a large number of sulfonic acid groups or sulfonic acid salt groups can be provided, by which a fluoropolymer can be produced that is substantially free of a dimer and trimer of a monomer constituting the polymer and contains a polymerization unit derived from a perfluoromonomer at a high content.

[0019] According to the present invention, a method for producing polytetrafluoroethylene using a polymer containing sulfonic acid groups or sulfonic acid salt groups can also be provided, by which polytetrafluoroethylene can be produced that is substantially free of a dimer and trimer of a monomer constituting the polymer and has a high molecular weight.

[0020] According to the present invention, a composition can also be provided which comprises a polymer containing a large number of sulfonic acid groups or sulfonic acid salt groups and a fluoropolymer containing a polymerization unit derived from a perfluoromonomer at a high content and which is substantially free of a dimer and trimer of the monomer constituting the polymer.

[0021] According to the present invention, a composition can also be provided which comprises a polymer containing sulfonic acid groups or sulfonic acid salt groups and polytetrafluoroethylene having a high molecular weight and which is substantially free of a dimer and trimer of the monomer constituting the polymer.

Description of embodiments

[0022] Before describing the present invention in detail, certain terms used in the present invention will be defined or described.

[0023] In the present invention, the fluororesin is a partially crystalline fluoropolymer, which is a fluoroplastic. The fluororesin has a certain melting point and thermoplasticity, and can be either melt-processable or non-meltable.

[0024] Melt-processable in the present invention means that the polymer has the ability to be processed in a molten state using a conventional processing device such as an extruder or an injection molding machine. Thus, a melt-processable fluororesin typically has a melt flow rate of 0.01 to 500 g/10 min, as measured by a measuring method to be described later.

[0025] The fluoroelastomer of the present invention is an amorphous fluoropolymer. The term "amorphous" means that the fluoropolymer has a peak heat of fusion (ΔH) of 4.5 J/g or less, as determined by differential scanning calorimetry (DSC) (temperature increase rate: 10°C/min) or differential thermal analysis (DTA) (temperature increase rate: 10°C/min). The fluoroelastomer exhibits elastomeric properties when crosslinked. Elastomeric properties mean that the polymer has the ability to stretch and maintain its original length when the force required to stretch the polymer is no longer applied.

[0026] The partially fluorinated elastomer in the present invention means a fluoropolymer containing a fluoromonomer unit, having a perfluoromonomer unit content of less than 90% by mole relative to all polymerization units, having a glass transition temperature of 20°C or lower, and having a peak heat of melting (PHM) of 4.5 J/g or lower.

[0027] The perfluoroelastomer (perfluororubber) of the present invention means a fluoropolymer having a perfluoromonomer unit content of 90 mol% or more, preferably 91 mol% or more, with respect to all polymerization units, having a glass transition temperature of 20°C or lower, having a peak heat of melting (ΔH) of 4.5 J/g or lower, and having a fluorine atom concentration in the fluoropolymer of 71 mass% or more, preferably 71.5 mass% or more. The fluorine atom concentration in the fluoropolymer of the present invention is the concentration (mass%) of fluorine atoms contained in the fluoropolymer calculated based on the type and content of each monomer constituting the fluoropolymer.

[0028] A perfluoromonomer as used herein means a monomer that does not contain a carbon-hydrogen bond in the molecule. A perfluoromonomer may be a monomer containing carbon atoms and fluorine atoms in which some of the fluorine atoms bonded to any of the carbon atoms are replaced by chlorine atoms, and may be a monomer containing a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a boron atom, or a silicon atom in addition to carbon atoms. A perfluoromonomer is preferably a monomer in which all hydrogen atoms are replaced by fluorine atoms. A perfluoromonomer does not include a monomer that provides an active crosslinking center.

[0029] The monomer that provides the active cross-linking site is a monomer (a monomer with an active curing site) containing a cross-linkable group that provides the fluoropolymer with an active cross-linking site for cross-linking with a curing agent.

[0030] The polytetrafluoroethylene (PTFE) of the present invention is preferably a fluoropolymer having a tetrafluoroethylene unit content of 99 mol% or more relative to the total polymerization units.

[0031] The fluororesin other than polytetrafluoroethylene and the fluoroelastomer of the present invention is preferably a fluoropolymer having a tetrafluoroethylene content of less than 99% by mole relative to all polymerization units.

[0032] The content of each of the monomers constituting the fluoropolymer can be calculated in the present invention by any appropriate combination of NMR, FT-IR (Fourier transform infrared spectroscopy), elemental analysis, X-ray fluorescence analysis according to the types of monomers.

[0033] The term "unit" as used herein means "link".

The term "organic group" as used herein means a group containing one or more carbon atoms, or a group obtained by removing one hydrogen atom from an organic compound.

Examples of "organic group" include:

an alkyl group optionally containing one or more substituents,

an alkenyl group optionally containing one or more substituents,

an alkynyl group optionally containing one or more substituents,

a cycloalkyl group optionally containing one or more substituents,

a cycloalkenyl group optionally containing one or more substituents,

a cycloalkadienyl group optionally containing one or more substituents,

an aryl group optionally containing one or more substituents,

an aralkyl group optionally containing one or more substituents,

a non-aromatic heterocyclic group optionally containing one or more substituents,

a heteroaryl group optionally containing one or more substituents,

cyano group,

formyl group,

RaO-,

RaCO-,

RaSO ₂ -,

RaCOO-,

RaNRaCO-,

RaCONRa-,

RaOCO-,

RaOSO ₂ - and

RaNRbSO ₂ -,

where each R ^a independently represents

an alkyl group optionally containing one or more substituents,

an alkenyl group optionally containing one or more substituents,

an alkynyl group optionally containing one or more substituents,

a cycloalkyl group optionally containing one or more substituents,

a cycloalkenyl group optionally containing one or more substituents,

a cycloalkadienyl group optionally containing one or more substituents,

an aryl group optionally containing one or more substituents,

an aralkyl group optionally containing one or more substituents,

a non-aromatic heterocyclic group optionally containing one or more substituents, or

a heteroaryl group optionally containing one or more substituents, and

each Rb independently represents H or an alkyl group optionally containing one or more substituents.

The organic group is preferably an alkyl group optionally containing one or more substituents.

[0034] The term "substituent" as used herein means a group capable of replacing another atom or group. Examples of the "substituent" include an aliphatic group, an aromatic group, a heterocyclic group, an acyl group, an acyloxy group, an acylamino group, an aliphatic oxy group, an aromatic oxy group, a heterocyclic oxy group, an aliphatic oxycarbonyl group, an aromatic oxycarbonyl group, a heterocyclic oxycarbonyl group, a carbamoyl group, an aliphatic sulfonyl group, an aromatic sulfonyl group, a heterocyclic sulfonyl group, an aliphatic sulfonyloxy group, an aromatic sulfonyloxy group, a heterocyclic sulfonyloxy group, a sulfamoyl group, an aliphatic sulfonamide group, an aromatic sulfonamide group, a heterocyclic sulfonamide group, an amino group, an aliphatic amino group, an aromatic amino group, a heterocyclic amino group, an aliphatic oxycarbonylamino group, an aromatic oxycarbonylamino group, a heterocyclic oxycarbonylamino group, an aliphatic sulfinyl group, an aromatic sulfinyl group, an aliphatic thio group, an aromatic thio group, a hydroxy group, a cyano group, a sulfo group, a carboxy group, an aliphatic oxyamino group, an aromatic oxyamino group, a carbamoylamino group, a sulfamoyl amino group, a halogen atom, a sulfamoylcarbamoyl group, a carbamoylsulfamoyl group, a dialphatic oxyphosphinyl group, and a diaromatic oxyphosphinyl group.

[0035] The aliphatic group may be saturated or unsaturated and may include a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the aliphatic group include alkyl groups containing a total of 1 to 8, preferably 1 to 4, carbon atoms, such as a methyl group, an ethyl group, a vinyl group, a cyclohexyl group, and a carbamoylmethyl group.

[0036] The aromatic group may include, for example, a nitro group, a halogen atom, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the aromatic group include aryl groups having 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms in total, such as a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methanesulfonylphenyl group.

[0037] The heterocyclic group may contain a halogen atom, a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the heterocyclic group include 5- or 6-membered heterocyclic rings containing 2 to 12, and preferably 2 to 10, carbon atoms in total, such as a 2-tetrahydrofuryl group and a 2-pyrimidyl group.

[0038] The acyl group may contain an aliphatic carbonyl group, an arylcarbonyl group, a heterocyclic carbonyl group, a hydroxyl group, a halogen atom, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the acyl group include acyl groups containing 2 to 8, preferably 2 to 4, carbon atoms in total, such as an acetyl group, a propanoyl group, a benzoyl group, and a 3-pyridinecarbonyl group.

[0039] The acylamino group may have an aliphatic group, an aromatic group, a heterocyclic group, and the like, and may have, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, or the like. Examples of the acylamino group include acylamino groups having a total of 2 to 12, preferably 2 to 8, carbon atoms, and alkylcarbonylamino groups having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, and a propanoylamino group.

[0040] The aliphatic oxycarbonyl group may be saturated or unsaturated and may contain a hydroxy group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the aliphatic oxycarbonyl group include alkoxycarbonyl groups containing 2 to 8, preferably 2 to 4 carbon atoms in total, such as a methoxycarbonyl group, an ethoxycarbonyl group, and a (tert)-butoxycarbonyl group.

[0041] The carbamoyl group may have an aliphatic group, an aromatic group, a heterocyclic group, or the like. Examples of the carbamoyl group include an unsubstituted carbamoyl group and alkylcarbamoyl groups having a total of 2 to 9 carbon atoms, preferably an unsubstituted carbamoyl group and alkylcarbamoyl groups having a total of 2 to 5 carbon atoms, such as an N-methylcarbamoyl group, an N,N-dimethylcarbamoyl group, and an N-phenylcarbamoyl group.

[0042] The aliphatic sulfonyl group may be saturated or unsaturated and may contain a hydroxy group, an aromatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the aliphatic sulfonyl group include alkylsulfonyl groups containing from 1 to 6 carbon atoms in total, preferably from 1 to 4 carbon atoms in total, such as a methanesulfonyl group.

[0043] The aromatic sulfonyl group may contain a hydroxy group, an aliphatic group, an aliphatic oxy group, a carbamoyl group, an aliphatic oxycarbonyl group, an aliphatic thio group, an amino group, an aliphatic amino group, an acylamino group, a carbamoylamino group, or the like. Examples of the aromatic sulfonyl group include arylsulfonyl groups containing 6 to 10 carbon atoms in total, such as a benzenesulfonyl group.

[0044] The amino group may contain an aliphatic group, an aromatic group, a heterocyclic group, and the like.

[0045] The acylamino group may contain, for example, an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, a propanoylamino group, or the like. Examples of the acylamino group include acylamino groups having a total of 2 to 12 carbon atoms, preferably a total of 2 to 8 carbon atoms, and more preferably alkylcarbonylamino groups having a total of 2 to 8 carbon atoms, such as an acetylamino group, a benzoylamino group, a 2-pyridinecarbonylamino group, and a propanoylamino group.

[0046] The aliphatic sulfonamide group, the aromatic sulfonamide group and the heterocyclic sulfonamide group may be, for example, a methanesulfonamide group, a benzenesulfonamide group, a 2-pyridinesulfonamide group, respectively.

[0047] The sulfamoyl group may contain an aliphatic group, an aromatic group, a heterocyclic group, or the like. Examples of the sulfamoyl group include a sulfamoyl group, alkylsulfamoyl groups containing 1 to 9 carbon atoms in total, dialkylsulfamoyl groups containing 2 to 10 carbon atoms in total, arylsulfamoyl groups containing 7 to 13 carbon atoms in total, and heterocyclic sulfamoyl groups containing 2 to 12 carbon atoms in total, more preferably a sulfamoyl group, alkylsulfamoyl groups containing 1 to 7 carbon atoms in total, dialkylsulfamoyl groups containing 3 to 6 carbon atoms in total, arylsulfamoyl groups containing 6 to 11 carbon atoms in total, and heterocyclic sulfamoyl groups containing 2 to 10 carbon atoms in total, such as a sulfamoyl group, a methylsulfamoyl group, an N,N-dimethylsulfamoyl group, a phenylsulfamoyl group and 4-pyridinesulfamoyl group.

[0048] The aliphatic oxy group may be saturated or unsaturated and may contain a methoxy group, an ethoxy group, an isopropyloxy group, a cyclohexyloxy group, a methoxyethoxy group, or the like. Examples of the aliphatic oxy group include alkoxy groups containing a total of 1 to 8, preferably 1 to 6, carbon atoms, such as a methoxy group, an ethoxy group, an isopropyloxy group, a cyclohexyloxy group, and a methoxyethoxy group.

[0049] The aromatic amino group and the heterocyclic amino group may each contain an aliphatic group, an aliphatic oxy group, a halogen atom, a carbamoyl group, a heterocyclic group fused on a ring with an aryl group, and an aliphatic oxycarbonyl group, preferably an aliphatic group containing from 1 to 4 carbon atoms in total, an aliphatic oxy group containing from 1 to 4 carbon atoms in total, a halogen atom, a carbamoyl group containing from 1 to 4 carbon atoms in total, a nitro group, or an aliphatic oxycarbonyl group containing from 2 to 4 carbon atoms in total.

[0050] The aliphatic thio group may be saturated or unsaturated, and examples thereof include alkylthio groups having a total of 1 to 8 carbon atoms, more preferably a total of 1 to 6 carbon atoms, such as a methylthio group, an ethylthio group, a carbamoylmethylthio group, and a tert-butylthio group.

[0051] The carbamoylamino group may contain an aliphatic group, an aryl group, a heterocyclic group, or the like. Examples of the carbamoylamino group include a carbamoylamino group, alkylcarbamoylamino groups having 2 to 9 carbon atoms in total, dialkylcarbamoylamino groups having 3 to 10 carbon atoms in total, arylcarbamoylamino groups having 7 to 13 carbon atoms in total, and heterocyclic carbamoylamino groups having 3 to 12 carbon atoms in total, preferably carbamoylamino groups, alkylcarbamoylamino groups having 2 to 7 carbon atoms in total, dialkylcarbamoylamino groups having 3 to 6 carbon atoms in total, arylcarbamoylamino groups having 7 to 11 carbon atoms in total, and heterocyclic carbamoylamino groups having 3 to 10 carbon atoms in total, such as a carbamoylamino group, methylcarbamoylamino group, N,N-dimethylcarbamoylamino group, phenylcarbamoylamino group and 4-pyridinecarbamoylamino group.

[0052] The ranges expressed by endpoints in the present invention each include all numerical values in the range (e.g., the range from 1 to 10 includes 1, 4, 1, 9, 2, 33, 5.75, 9.98, and the like).

[0053] The phrase "at least one" as used herein includes all numerical values equal to or greater than 1 (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, or the like).

[0054] Next, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0055] The production method of the present invention is a method for producing a fluoropolymer, the method comprising polymerizing a perfluoromonomer in an aqueous medium in the presence of a polymer (1) to obtain a fluoropolymer (hereinafter, this may be referred to as the first production method of the present invention).

[0056] <Polymer (1)>

The polymer (1) used in the first production method of the present invention is a polymer of a monomer (1) represented by the general formula (1) given below, in which the polymerization unit (1) obtained from the monomer (1) in the polymer (1) accounts for 50% by mass or more relative to all polymerization units of the polymer (1), and the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less relative to the polymer (1).

[0057] The monomer (1) is represented by the following general formula (1).

(In the formula, R represents a single bond or a linking group; Rf represents a fluorine-containing alkylene group having 1 to 40 carbon atoms, or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether bond or a keto group; M represents H, a metal atom, NR ⁷ ₄ , imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent; R ⁷ represents H or an organic group, and m is an integer of 1 or more.)

[0058] In the production method of the present invention, one type of monomer or two or more types of monomers can be used as the monomer (1).

[0059] The polymer (1) may be a homopolymer of the monomer (1) or may be a copolymer thereof with another monomer.

[0060] R is a single bond or a linking group. The term "linking group" in the present invention refers to an (m+1)-valent linking group, and when m is 1, the linking group is divalent. It is preferable that the linking group contain at least one carbon atom, and the number of carbon atoms may be 2 or more, may be 4 or more, may be 8 or more, may be 10 or more, or may be 20 or more. Its upper limit is not limited and may be, for example, 100 or less, and may also be 50 or less.

[0061] The linking group may be linear or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and optionally contains one or more functional groups selected from the group consisting of esters, amides, sulfonamides, carbonyls, carbonates, urethanes, ureas, and carbamates. The linking group may not contain carbon atoms and may be a catenary heteroatom such as oxygen, sulfur, or nitrogen.

[0062] m is an integer equal to 1 or more, preferably 1 or 2, and more preferably 1. When m is an integer equal to 2 or more, Rf and M preferably contain.

[0063] The corresponding configuration will now be described in the case where m is equal to 1 in the general formula (1).

[0064] In the case where m is 1 in the general formula (1), it is preferable that R is a single bond.

That is, it is preferable that the monomer (1) is a monomer (2) represented by the general formula (2) shown below.

It is also preferable that the polymer (1) is a polymer (2) containing a polymerization unit (2) obtained from a monomer (2) represented by the general formula (2).

(In the formula, Rf and M are as described above.)

[0065] Rf is a fluorine-containing alkylene group containing from 1 to 40 carbon atoms, a fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond, or a fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing a keto group. A fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond is an alkylene group that does not include a structure in which an oxygen atom is terminal and contains an ether bond between carbon atoms.

[0066] The fluorine-containing alkylene group Rf preferably contains 2 or more carbon atoms. The fluorine-containing alkylene group also preferably contains 30 or less carbon atoms, more preferably 20 or less carbon atoms, even more preferably 10 or less carbon atoms, and particularly preferably 5 _or less carbon _atoms . Examples of the fluorine-containing alkylene group _{include -CF2-} , _-CH2CF2- , _CF2CF2- , _{-CF2CH2- , -CF2CF2CH2-} , -CF( _CF3 )-, _-CF ( _CF3 ) _{CF2- and} CF _{( CF3 ) CH2- , -CF2CF2CF2-} , _{and -CF2CF2CF2CF2-} . The fluorine-containing alkylene group is preferably a perfluoroalkylene group, and more preferably an unbranched linear perfluoroalkylene group.

[0067] The fluorine-containing alkylene group having an ether bond preferably contains 3 or more carbon atoms. The fluorine-containing alkylene group having an ether bond preferably contains 60 or less carbon atoms, more preferably 30 or less carbon atoms, even more preferably 12 or less carbon atoms, and particularly preferably 5 or less carbon atoms. It is also preferable that the fluorine-containing alkylene group having an ether bond be a divalent group represented by the following general formula:

where Z ¹ is F or CF ₃ ; Z ² and Z ³ are each H or F; Z ⁴ is H, F, or CF ₃ ; p1+q1+r1 is an integer from 1 to 10; s1 is 0 or 1; and t1 is an integer from 0 to 5.

[0068] Specific examples of the fluorine-containing alkylene group having an ether bond include -CF ₂ CF(CF ₃ )OCF ₂ -, CF ₂ CF(CF ₃ )OCF ₂ CF ₂ -, -CF ₂ CF(CF ₃ )OCF ₂ CF ₂ CF ₂ -, -CF(CF ₃ )CF ₂ -O-CF(CF ₃ )-, -(CF(CF ₃ )CF ₂ -O) _n -CF(CF ₃ )- (wherein n is an integer from 1 to 10), -CF(CF ₃ )CF ₂ -O-CF(CF ₃ )CH ₂ -, -(CF(CF ₃ )CF ₂ -O) _n -CF(CF ₃ )CH ₂ - (wherein n is an integer from 1 to 10), -CH ₂ CF ₂ CF ₂ O-CH ₂ CF ₂ CH ₂ -, -CF ₂ CF ₂ CF ₂ O-CF ₂ -, -CF ₂ CF ₂ CF ₂ O-CF ₂ CF ₂ -, -CF ₂ CF ₂ CF ₂ O-CF ₂ CF ₂ CF ₂ -, -CF ₂ CF ₂ CF ₂ O-CF ₂ CF ₂ CH ₂ -, -CF ₂ CF ₂ O-CF ₂ - and -CF ₂ CF ₂ O-CF ₂ CH ₂ -. The fluorine alkylene group containing an ether linkage is preferably a perfluoroalkylene group.

[0069] The fluorine-containing alkylene group containing a keto group preferably contains 3 or more carbon atoms. The fluorine-containing alkylene group containing a keto group preferably contains 60 or less carbon atoms, more preferably 30 or less carbon atoms, even more preferably 12 or less carbon atoms, and particularly preferably 5 or less carbon atoms.

[0070] Specific examples of the fluorine-containing alkylene group having a keto group include _-CF2CF ( _CF3 )CO- _CF2- , _{CF2CF (} CF3)CO _{- CF2CF2-} , -CF2CF( _{CF3 )} CO _{- CF2CF2CF2-} , and _-CF2CF ( _CF3 )CO- _{CF2CF2CF2- . The} fluorine-containing alkylene group having a keto group is preferably a _{perfluoroalkylene group} .

[0071] Water may be added to the keto group in the fluorine-containing alkylene group. Accordingly, the monomer (1) may be a hydrate. Examples of the fluorine-containing alkylene group in which water _is added to the keto group include: _{-CF2CF ( CF3} )C(OH) _{2 - CF2-} , _-CF2CF ( _CF3 )C( _OH ) _{2 -} CF2CF2-, -CF2CF( _CF3 )C(OH) ₂ - _{CF2CF2CF2- and -CF2CF} ( _CF3 ) _C (OH) _{2 - CF2CF2CF2CF2-} .

[0072] M may be the same or different in each occurrence and are H, a metal atom, NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent, and R ⁷ is H or an organic group.

[0073] R ⁷ is preferably H or a C _1-10 organic group, more preferably H or a C _1-4 organic group, and even more preferably H or a C _1-4 alkyl group.

[0074] Examples of the metal include alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K or Li are preferred.

[0075] M may be the same or different in each case and is preferably H, a metal atom or NR ⁷ ₄ , more preferably H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or NR ⁷ ₄ , even more preferably H, Na, K, Li or NH ₄ , even more preferably H, Na, K or NH ₄ , and particularly preferably H, Na or NH ₄ .

[0076] The monomer represented by the general formula (1) is preferably at least one monomer selected from the group consisting of monomers represented by the general formulas (1a), (1b), (1c), (1d) and (1e):

where n1 is an integer from 1 to 10, and M is as defined above;

where n2 is an integer from 1 to 5, and M is as defined above;

where X ¹ is F or CF ₃ , n3 is an integer from 1 to 10 and M is as defined above;

where n4 is an integer from 1 to 10, n6 is an integer from 1 to 3, and M and X ¹ M are as defined above; and

where n5 is an integer from 0 to 10, and M and X ¹ M are as defined above.

[0077] In formula (1a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. M is preferably H, Na, K, or NH ₄ .

[0078] Examples of the monomer represented by the general formula (1a) include CF ₂ =CF(OCF ₂ CF ₂ SO ₃ M), CF ₂ =CF(OCF ₂ SO ₃ M), CF ₂ =CF(OCF ₂ CF ₂ CF ₂ SO ₃ M) and CF ₂ =CFO(CF ₂ CF ₂ CF ₂ CF ₂ )SO ₃ M, where M is as defined above.

[0079] In the general formula (1b), n2 is preferably an integer of 3 or less from the viewpoint of the dispersion stability of the obtained composition. M is preferably H, Na, K, or _NH4 .

[0080] In the formula (1c), n3 is preferably an integer of 5 or less in terms of water solubility, and M is preferably H, Na, K, or NH ₄ .

[0081] In the formula (Id), X ¹ is preferably -CF ₃ from the viewpoint of the dispersion stability of the composition, n4 is preferably an integer of 5 or less from the viewpoint of water solubility, and M is preferably H, Na, K or NH ₄ .

[0082] Examples of the monomer represented by formula (Id) include CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ SO ₃ M, CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ SO ₃ M and CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CF ₂ SO ₃ M, where M is such as defined above.

[0083] In the formula (1e), n5 is preferably an integer of 5 or less from the viewpoint of water solubility, and M is preferably H, Na, K, or NH ₄ .

[0084] An example of a monomer represented by the general formula (1e) is CF ₂ =CFOCF ₂ CF ₂ CF ₂ SO ₃ M, where M is H, NH ₄ or an alkali metal.

[0085] The monomer (1) is preferably CF ₂ =CF(OCF ₂ CF ₂ SO ₃ M), where M is as defined above.

[0086] Next, the corresponding configuration will be described in the case where m is an integer of 2 or more in the general formula (1).

[0087] In the case where m is 2 in the general formula (1), it is preferable that R is a linking group containing at least one carbon atom.

It is also preferable that the monomer (1) is a monomer (3) represented by the following general formula (3).

It is also preferable that the polymer (1) is a polymer (3) containing a polymerization unit (3) obtained from a monomer (3) represented by the general formula (3).

(In the formula, Rf and M are as defined above; QF represents a single bond, a fluorine-containing alkylene group optionally containing an ether bond between carbon atoms, or a fluorine-containing oxyalkylene group,

optionally containing an ether linkage between carbon atoms)

[0088] Examples of the monomer (3) represented by the general formula (3) include:

and the like.

[008 9] The polymer (1) may be a homopolymer containing only the polymerization unit (1)/ or may be a copolymer of the polymerization unit (1) and a polymerization unit derived from another monomer copolymerizable with the monomer (1) represented by the general formula (1). From the viewpoint of solubility in an aqueous medium, a homopolymer containing only the polymerization units (1) is preferable. The polymerization units (1) may be the same or different in each case, and the polymer (1) may contain the polymerization unit (1) derived from two or more different monomers represented by the general formula (1).

[0090] Examples of another monomer copolymerized with the monomer (1) include a monomer represented by the following general formula.

General formula: CX ² = CX-O-Rf-СООМ

(In the formula, X independently represents F or CF ₃ and Rf and M are as defined in the general formula (1)).

[0091] The other monomer is preferably a monomer represented by the general formula: CFR ¹¹ =CR ¹¹ ₂ , wherein R ¹¹ is independently H, F or a perfluoroalkyl group having 1 to 4 carbon atoms. It is also preferable that the other monomer is a fluorine-containing ethylene monomer having 2 or 3 carbon atoms. Examples of the other monomer include CF ₂ =CF ₂ , CF ₂ =CFCl, CH ₂ =CF ₂ , CFH=CH ₂ , CFH=CF ₂ , CF ₂ =CFCF ₃ , CH ₂ =CFCF ₃ , CH ₂ =CHCF ₃ , CHF=CHCF ₃ (E isomer) and CHF=CHCF ₃ (Z isomer).

[0092] Of these, as the other monomer, at least one monomer selected from the group consisting of tetrafluoroethylene ( _CF2 = _CF2 ), chlorotrifluoroethylene ( _CF2 =CFCl) and vinylidene fluoride ( _CH2 = _CF2 ) is preferable from the viewpoint of achieving good copolymerizability, more preferable is at least one monomer selected from the group consisting of tetrafluoroethylene and vinylidene fluoride, and even more preferable is vinylidene fluoride. Accordingly, the polymerization unit obtained from the other monomer is preferably at least one monomer selected from the group consisting of a polymerization unit obtained from tetrafluoroethylene and a polymerization unit obtained from vinylidene fluoride, and still more preferably it is a polymerization unit obtained from vinylidene fluoride. The polymerization units derived from the other monomer may be the same or different in each case, and the fluoropolymer may contain a polymerization unit derived from two or more different other monomers.

[0093] In the case where the polymer (1) contains the polymerization unit (1) and the polymerization unit obtained from another monomer copolymerizable with the monomer (1), the content of the polymerization unit (1) obtained from the monomer (1) is preferably from 50 to 94 mass%, more preferably from 63 to 90 mass%, and even more preferably from 67 to 87 mass%, with respect to all the polymerization units constituting the polymer (1), and the content of the obtained polymerization unit obtained from another monomer is preferably from 6 to 50 mass%, more preferably from 10 to 37 mass%, and even more preferably from 13 to 33 mass%, with respect to all the polymerization units constituting the polymer (1). Such a configuration is particularly suitable in the case where the polymerization unit obtained from another monomer copolymerizable with the monomer (1) is a polymerization unit (M) obtained from a monomer represented by the general formula CFR ¹¹ = CR ¹¹ ₂ . In the case where the fluoropolymer contains the polymerization unit (1) and the polymerization unit (M), the total content of the polymerization unit (1) and the polymerization unit (M) is preferably from 80 to 100% by mass, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 99% by mass or more, with respect to all the polymerization units constituting the fluoropolymer. Furthermore, in the case where the fluoropolymer contains a polymerization unit (1) and a polymerization unit (M1) derived from a monomer represented by the formula ^CX2 =CX-O-Rf-COOM, the total content of the polymerization unit (1) and the polymerization unit (M1) is preferably 80 to 100% by mass, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 99% by mass or more, with respect to all the polymerization units constituting the fluoropolymer.

[0094] In the case where the polymer (1) comprises a polymerization unit (1) and a polymerization unit derived from another monomer copolymerizable with the monomer (1), the alternation ratio of the polymerization unit (1) and the polymerization unit derived from another monomer copolymerizable with the monomer (1) is preferably 40% or more, more preferably 50% or more, even more preferably 60% or more, even more preferably 70% or more, particularly preferably 80% or more, and most preferably 90% or more. The alternation ratio may be, for example, from 40 to 99%. Such a configuration is particularly suitable in the case where the polymerization unit derived from another monomer copolymerizable with the monomer (1) is a polymerization unit (M) derived from a monomer represented by the general formula CFR ¹¹ = CR ¹¹ ₂ .

[0095] The ratio of alternation of the polymerization unit (1) and the polymerization unit derived from another monomer copolymerized with the monomer (1) in the polymer (1) can be determined by analyzing ^{the 19} F-HMP of the fluoropolymer.

[0096] Examples of the other monomer further include a monomer represented by the following general formula (n1-2):

[0097]

[0098] where X ¹ and X ² are the same or different and each is H or F; X ³ is H, F, Cl, CH ₃ or CF ₃ ; X ⁴ and X ⁵ are the same or different and each is H or F; and a and c are the same or different and each is 0 or 1; and Rf ³ is a fluorine-containing alkyl group containing from 1 to 40 carbon atoms or a fluorine-containing alkyl group containing from 2 to 100 carbon atoms and containing an ether bond.

[0099] Specifically, preferred examples thereof include CH ₂ =CFCF ₂ -O-Rf ³ , CF ₂ =CF-O-Rf ³ , CF ₂ =CFCF ₂ -O-Rf ³ , CF ₂ =CF-Rf ³ , CH ₂ =CH-Rf ³ and CH ₂ =CH-O-Rf ³ (wherein Rf ³ is as described in the above formula (n1-2)).

[0100] Another example of another monomer is a fluorinated acrylate monomer represented by the following formula (n2-1):

[0101]

[0102] where X9 is H, F, or _CH3 ; and ^Rf4 is a fluorine-containing alkyl group containing from 1 to 40 carbon atoms, or a fluorine-containing alkyl group containing from 2 to 100 carbon atoms and containing an ether linkage. Examples of the ^Rf4 group include:

[0103]

where Z ⁸ represents H, F, or Cl; d1 represents an integer from 1 to 4; and e1 represents an integer from 1 to 10,

where e2 is an integer from 1 to 5;

[0104] where d3 is an integer from 1 to 4; and e3 is an integer from 1 to 10.

[0105] Another example of another monomer is a fluorinated vinyl ether represented by the following formula (n2-2):

CH ₂ =CHO-Rf5 (n2-2)

where Rf ⁵ is a fluorine-containing alkyl group containing from 1 to 40 carbon atoms or a fluorine-containing alkyl group containing from 2 to 100 carbon atoms and containing an ether bond.

[0106] Specific preferred examples of the monomer of general formula (n2-2) include:

[0107]

where Z ⁹ represents H or F and e4 represents an integer from 1 to 10,

where e5 is an integer from 1 to 10,

[0108] where e6 is an integer from 1 to 10.

[0109] Their more specific examples include:

[0110]

[0111] and the like.

[0112] Further examples of the other monomer include a fluorinated allyl ether represented by the following general formula (n2-3):

where Rf ⁶ is a fluorine-containing alkyl group containing 1 to 40 carbon atoms or a fluorine-containing alkyl group containing 2 to 100 carbon atoms and containing an ether bond; and a fluorine-containing vinyl monomer represented by the following general formula (n2-4):

where Rf ⁷ is a fluorine-containing alkyl group containing from 1 to 40 carbon atoms or a fluorine-containing alkyl group containing from 2 to 100 carbon atoms and containing an ether bond.

[0113] Specific examples of monomers represented by the general formulas (n2-3) and (n2-4) include monomers such as:

[0114]

[0115] and the like.

[0116] In the polymer (1), the content of the polymerization unit (1) is, in order of preference, 50% by mass or more, more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 99% by mass or more, relative to all polymerization units. It is particularly preferable that the content of the polymerization unit (1) is substantially 100% by mass, and most preferably that the polymer (1) contains only the polymerization unit (1).

[0117] In the polymer (1), the content of the polymerization unit derived from another monomer capable of copolymerizing with the monomer represented by the general formula (1) is, in the order of preference, 50% by mass or less, less than 50% by mass, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 1% by mass or less, with respect to all polymerization units. It is particularly preferable that the content of the polymerization unit derived from another monomer copolymerizable with the monomer represented by the general formula (1) is substantially 0% by mass, and it is most preferable that the polymer (1) does not contain the polymerization unit derived from another monomer.

[0118] The lower limit of the number-average molecular weight of the polymer (1) is, in order of preference, 0.3 × 10 ⁴ or more, 0.4 × ^{10 4 or} more, 0.5 × 10 ⁴ or more, 0.7 × 10 ⁴ or more, 0.8 × 10 ⁴ or more, 1.0 × 10 ⁴ or more, 1.2 × 10 ⁴ or more, 1.4 × 10 4 or more, 1.6 × 10 ⁴ or more, 1.8 × 10 ⁴ or more, 2.0 × 10 ⁴ or more, or 3.0 × 10 ⁴ or more. The upper limit of the number-average molecular weight of the polymer (1) is, in order of preference, 75.0 × 10 ⁴ or less, 50.0 × 10 ⁴ or less, 40.0 × 10 ⁴ or less, 30.0 × 10 4 or less, or 20.0 × 10 ⁴ or less.

[0119] The lower limit of the weight average molecular weight of the polymer (1) is, in order of preference, 0.4 × 10 ⁴ or more, 0.5 × ^{10 4 or} more, 0.6 × 10 ⁴ or more, 0.8 × 10 ⁴ or more, 1.0 × 10 ⁴ or more, 1.2 × 10 ⁴ or more, 1.4 × 10 ⁴ or more, 1.7 × 10 4 or more, 1.9 × 10 ⁴ or more, 2.1 × 10 ⁴ or more, 2.3 × 10 ⁴ or more, 2.7 × 10 ⁴ or more, 3.1 × 10 ⁴ or more, 3.5 × 10 ⁴ or more, 3.9 x 10 ⁴ or more, 4.3 x 10 ⁴ or more, 4.7 x 10 ⁴ or more, 5.1 x 10 ⁴ or more, 10.0 x 10 ⁴ or more, 15.0 x 10 ⁴ or more, 20.0 x 10 ⁴ or more, or 25.0 x 10 ⁴ or more. The upper limit of the weight average molecular weight of the polymer (1) is, in order of preference, 150.0 x 10 ⁴ or less, 100.0 x 10 ⁴ or less, 60.0 x 10 ⁴ or less, 50.0 x 10 ⁴ or less, or 40.0 x 10 ⁴ or less.

[0120] The molecular weight distribution (Mw/Mn) of the polymer (1) is, in order of preference, 3.0 or less, 2.7 or less, 2.4 or less, 2.2 or less, 2.0 or less, 1.9 or less, 1.7 or less, 1.5 or less, 1.4 or less, or 1.3 or less.

[0121] The number average molecular weight and the weight average molecular weight are the molecular weight values calculated by gel permeation chromatography (GPC) using monodisperse polyethylene oxide (PEO) and polyethylene glycol (PEG) as standards. Also, in the case where measurement by the GPC method is not possible, the number average molecular weight of the polymer (1) can be determined by correlation between the number average molecular weight calculated from the number of end groups obtained by NMR, FT-IR, or the like and the melt flow rate. The melt flow rate can be measured in accordance with the JIS K 7210 standard.

[0122] The polymer (1) typically contains an end group. The end group is an end group formed during polymerization, and a representative end group is independently selected from hydrogen, iodine, bromine, linear or branched alkyl groups, and linear or branched fluoroalkyl groups, and may optionally contain at least one catenary heteroatom. Preferably, the alkyl group or fluoroalkyl group has from 1 to 20 carbon atoms. These end groups are typically derived from the initiator or chain transfer agent used to form the polymer (1) or obtained during the chain transfer reaction.

[0123] It is preferred that the polymer (1) have an ion exchange ratio (IXR) of 53 or less. IXR is defined as the number of carbon atoms in the polymer backbone relative to ionic groups. Precursor groups that are ionized by hydrolysis (e.g., -SO2F) are not considered ionic groups for the purposes of determining IXR.

[0124] IXR is preferably 0.5 or more, more preferably 1 or more, even more preferably 3 or more, even more preferably 4 or more, even more preferably 5 or more, and particularly preferably 8 or more. Also, more preferably IXR is 43 or less, even more preferably 33 or less, and particularly preferably 23 or less.

[0125] The ion exchange capacity of the polymer (1) is, in order of preference, 0.80 meq/g or more, 1.50 meq/g or more, 1.75 meq/g or more, 2.00 meq/g or more, g or more, 2.20 meq/g or more, more than 2.20 meq/g, 2.50 meq/g or more, 2.60 meq/g or more, 3.00 meq/g or more, or 3.20 meq/g or more, 3.50 meq/g or more. The ion exchange capacity is the content of ionic groups (anionic groups) in the polymer and can be determined by calculation from the compositional characteristics of the polymer (1).

[0126] In the polymer (1), ionic groups (anionic groups) are generally distributed along the polymer backbone. The polymer comprises a polymer backbone together with repeating side chains linked to this backbone, and these side chains preferably contain ionic groups.

[0127] It is preferable that the polymer (1) has water solubility. The term "water solubility" refers to the property of being easily dissolved or dispersed in an aqueous medium. When the polymer has water solubility, its particle size cannot be measured, for example, by a dynamic light scattering (DLS) method, or a particle size of 10 nm or less is indicated.

[0128] It is preferable that the polymer (1) has sufficient solubility in water. In general, the higher the content of the polymer (1) in an aqueous solution, the more difficult it becomes to sufficiently dissolve or disperse the polymer (1) in an aqueous medium. Accordingly, even when the content of the polymer (1) in an aqueous solution is high, it can be said that the polymer (1), the particle size of which cannot be measured by a dynamic light scattering (DLS) method, has high water solubility. It is preferable that the particle size of the polymer (1) cannot be measured even when it is contained in an aqueous solution at a content of 1.0 mass%. It is preferable that the particle size of the polymer (1) cannot be measured even when it is contained in an aqueous solution at a content of, more preferably, 1.5 mass%, and even more preferably 2.0 mass%.

[0129] The viscosity of the aqueous solution of the polymer (1) is preferably 5.0 mPa⋅s or more, more preferably 8.0 mPa⋅s or more, even more preferably 10.0 mPa⋅s or more, particularly preferably 12.0 mPa⋅s or more, and most preferably 14.0 mPa⋅s or more, and is preferably 100.0 mPa⋅s or less, more preferably 50.0 mPa⋅s or less, even more preferably 25.0 mPa⋅s or less, and more preferably 20.0 mPa⋅s or less.

[0130] The viscosity of an aqueous solution of the polymer (1) can be determined by adjusting the content of the polymer (1) in an aqueous solution to 33% by mass with respect to the aqueous solution and measuring the viscosity of the resulting aqueous solution at 20°C using a tuning fork vibrating viscometer (model number: SV-10) manufactured by A&D Company Limited.

[0131] The critical micellar concentration (CMC) of the polymer (1) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, and preferably it is 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0132] The critical micellar concentration of the polymer (1) can be determined by measuring the surface tension. The surface tension can be measured, for example, using a surface tensiometer model CBVP-A3 manufactured by Kyowa Interface Science Co., Ltd.

[0133] The acid value of the polymer (1) is preferably 60 or more, more preferably 90 or more, still more preferably 120 or more, particularly preferably 150 or more, and most preferably 180 or more, and although its upper limit is not limited, it is preferably 300 or less.

[0134] When the polymer (1) contains -SO ₃ M other than -SO ₃ H, that is, -SO ₃ M (M is a metal atom, -NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent, or phosphonium optionally containing a substituent), the acid number of the polymer (1) can be measured by converting -SO ₃ M to -SO ₃ H and then acid-base titrating -SO ₃ H.

[0135] The polymer (1) can be obtained by a method for producing the polymer (1) by polymerizing the polymer (1).

[0136] Since the polymer (1) having an even higher molecular weight can be easily obtained, the oxygen concentration in the polymerization reaction system is preferably 1500 ppmv or less, more preferably 500 ppmv or less, still more preferably 100 ppmv or less, and particularly preferably 50 ppmv or less. The oxygen concentration in the reaction system is usually 0.01 ppmv or more. In the above-described production method, it is preferable that the oxygen concentration in the reaction system is maintained in the above-mentioned range throughout the polymerization period of the polymer (1).

[0137] The oxygen concentration in the polymerization reaction system can be controlled, for example, by circulating an inert gas such as nitrogen or argon, or, in the case of using a gaseous monomer, by circulating this gaseous monomer in the liquid phase or gas phase in the reactor. The oxygen concentration in the polymerization reaction system can be determined by measuring and analyzing the gas exiting the gas outlet line of the polymerization system using a low oxygen concentration analyzer.

[0138] Since the polymer (1) having an even higher molecular weight can be easily obtained, the polymerization temperature of the polymer (1) is preferably 70°C or lower, more preferably 65°C or lower, even more preferably 60°C or lower, even more preferably 55°C or lower, more preferably 50°C or lower, particularly preferably 45°C or lower, and most preferably 40°C or lower, and is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher.

[0139] In the above-described production method, the polymer (1) and the above-mentioned other monomer may be copolymerized.

[0140] In the above-mentioned production method, the polymerization can be carried out in the presence of a pH regulator. The pH regulator can be added before the start of the polymerization or it can be added after the start of the polymerization.

[0141] Ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium phosphate, potassium phosphate, sodium citrate, potassium citrate, ammonium citrate, sodium gluconate, potassium gluconate, ammonium gluconate, or something similar can be used as a pH adjuster. The pH can be measured using a pH meter manufactured by Orion.

[0142] The polymerization pressure is usually from atmospheric pressure to 10 MPa g. The polymerization pressure is appropriately determined according to the types of monomers used, the molecular weight of the target polymer (1), and the reaction rate.

[0143] The polymerization time is usually from 1 to 200 hours and can be from 5 to 100 hours.

[0144] In the above-described production method, the polymerization of the monomer (1) can be carried out in an aqueous medium or it can be carried out in the absence of an aqueous medium. Also, the polymerization of the monomer (1) can be carried out both in the absence of an aqueous medium and in the presence of a non-aqueous medium (for example, an organic solvent such as toluene) in an amount of less than 10% by weight relative to the amount of monomers containing the monomer (1). The polymerization of the monomer (1) can be emulsion polymerization or suspension polymerization, or it can be bulk polymerization.

[0145] The aqueous medium is the reaction medium in which the polymerization is carried out and means a liquid containing water. The aqueous medium may be any medium containing water, and it may be a medium containing water and, for example, any of the organic solvents that do not contain fluorine, such as alcohols, ethers and ketones, and/or fluorinated organic solvents having a boiling point of 40°C or lower. The aqueous medium is preferably water.

[0146] In the above-described production method, polymerization of the polymer (1) can be carried out in the presence of a polymerization initiator. The polymerization initiator can be any polymerization initiator capable of generating radicals in the polymerization temperature range, and known oil-soluble and/or water-soluble polymerization initiators can be used. The polymerization initiator can be combined with a reducing agent, for example, to form a redox agent that initiates polymerization. The concentration of the polymerization initiator is appropriately determined according to the types of monomers, the molecular weight of the target polymer (1) and the reaction rate. When the monomer (1) is polymerized in an aqueous medium, it is preferable to use a water-soluble polymerization initiator such as persulfate. When the monomer (1) is polymerized in the absence of an aqueous medium, it is preferable to use an oil-soluble polymerization initiator such as peroxide.

[0147] The polymerization initiator used may be an organic peroxide such as a persulfate (e.g., ammonium persulfate), disuccinic acid peroxide, or diglutaric acid peroxide, alone or in the form of a mixture thereof. The organic peroxide may be used together with a reducing agent such as sodium sulfite to form a redox system. In addition, a radical scavenger such as hydroquinone or catechol may be added during the polymerization, or a peroxide decomposer such as ammonium sulfite may be added to control the concentration of radicals in the system.

[0148] Among the polymerization initiators, persulfates are preferred because the polymer (1) having an even higher molecular weight can be easily obtained. Examples of persulfates include ammonium persulfate, potassium persulfate, and sodium persulfate, and ammonium persulfate is preferred.

[0149] An oil-soluble radical polymerization initiator can be used as the polymerization initiator. The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, and representative examples thereof include dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate; peroxyesters such as tert-butyl peroxyisobutyrate and tert-butyl peroxypivalate; and dialkyl peroxides such as di-tert-butyl peroxide, as well as di[perfluoro(or fluorochloro)acyl]peroxides such as di(ω-hydrododecafluorohexanoyl) peroxide, di(ω-hydrotetradecafluoroheptanoyl) peroxide, di(ω-hydrohexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chlorohexafluorobutyryl) peroxide, di(sh-chlorodecafluorohexanoyl) peroxide, di(ω-chlorotetradecafluorooctanoyl) peroxide, ω-hydrododecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl peroxide, ω-chlorohexafluorobutyryl-ωchlorodecafluorohexanoyl peroxide, ω-hydrododecafluoroheptanoylperfluorobutyryl peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide and di(undecachlorothoriumcontafluorodocosanoyl) peroxide.

[0150] The polymerization initiator can be added in any amount, and the initiator, in an amount that does not significantly reduce the polymerization rate (for example, a concentration in water of several ppm) or more, can be added immediately at the initial stage of polymerization, or it can be added sequentially or continuously. Its upper limit is in the range in which an increase in the reaction temperature is allowed, while the heat of the polymerization reaction is removed through the surfaces of the device. Its upper limit is more preferably in the range in which the heat of the polymerization reaction can be removed through the surfaces of the device.

[0151] In the above-described production method, the polymerization initiator can be added at the beginning of the polymerization, and it can also be added during the polymerization. The proportion between the amount of the polymerization initiator added at the initiation of the polymerization and the amount of the polymerization initiator added during the polymerization is preferably from 95/5 to 5/95, more preferably from 60/40 to 10/90, and even more preferably from 30/70 to 15/85. The method for adding the polymerization initiator during the polymerization is not limited, and the entire amount can be added at once, can be added in two or more portions, or can be added continuously.

[0152] In the above-mentioned production method, since the polymer (1) having an even higher molecular weight can be easily obtained, the polymerization initiator used for the polymerization is preferably added in a total amount of 0.00001 to 10 mass% with respect to the aqueous medium. The polymerization initiator used for the polymerization is preferably added in a total amount of 0.0001 mass% or more, more preferably 0.001 mass% or more, and still more preferably 0.01 mass% or more, and preferably 5 mass% or less, and more preferably 2 mass% or less.

[0153] In the above-described production method, since the polymer (1) having an even higher molecular weight can be easily obtained, the polymerization initiator used for the polymerization is preferably added in a total amount of 0.001 to 10 mol% relative to the total amount of the monomers used for the polymerization. The polymerization initiator used for the polymerization is more preferably added in a total amount of 0.005 mol% or more, even more preferably 0.01 mol% or more, even more preferably 0.1 mol% or more, and most preferably 0.5 mol% or more, and more preferably 10 mol% or less, even more preferably 5.0 mol% or less, even more preferably 2.5 mol% or less, particularly most preferably 2.2 mol% or less, and preferably 2.0 mol% or less.

[0154] In the above-mentioned production method, since the polymer (1) can be easily obtained having an even higher molecular weight, it is preferable that the amount of monomers constituting the polymer (1) present at the start of the polymerization be 20% by mass or more depending on the amount of the aqueous medium present. The amount of monomers present is more preferably 30% by mass or more, and still more preferably 40% by mass or more. The upper limit of the amount of monomers present is not limited, and from the viewpoint of smooth progress of the polymerization, it may be 200% by mass or less. The amount of monomers present at the start of the polymerization is the total amount of the polymer (1), and other monomer, if present, is present in the reactor at the start of the polymerization.

[0155] When the monomer (1) is polymerized in the absence of an aqueous medium, the total amount of the added polymerization initiator such as peroxide is preferably 0.001 to 10 mol% relative to the total amount of the monomers containing the monomer (1) (monomer mixture). The polymerization initiator used for the polymerization is added in a total amount of more preferably 0.005 mol% or more, and even more preferably 0.01 mol% or more, and more preferably 10 mol% or less, even more preferably 5.0 mol% or less, even more preferably 2.5 mol% or less, particularly most preferably 2.2 mol% or less, and preferably 2.0 mol% or less.

[0156] The polymerization of the polymer (1) can be carried out by loading the polymer (1) and an optional aqueous medium, other monomers and optional other additives into a reactor, stirring the contents of the reactor and maintaining the reactor at a predetermined polymerization temperature, and adding a predetermined amount of a polymerization initiator to thereby initiate the polymerization reaction. After the polymerization reaction has started, monomers, a polymerization initiator and other additives can be added depending on the purpose.

[0157] The polymer (1) used in the production method of the present invention is substantially free of the dimer and trimer of the monomer (1). The dimer and trimer of the monomer (1) are usually formed when the monomer (1) is polymerized to obtain the polymer (1). The content of the dimer and trimer in the polymer (1) is 1.0 mass% or less, preferably 0.1 mass% or less, more preferably 0.01 mass% or less, even more preferably 0.001 mass% or less, and particularly preferably 0.0001 mass% or less, with respect to the polymer (1).

[0158] The polymer (1) used in the production method of the present invention may be substantially free of a dimer and a trimer consisting of a polymerization unit (1) derived from the monomer (1) and a polymerization unit derived from another monomer copolymerizable with the monomer (1). The dimer and the trimer consisting of a polymerization unit (1) and a polymerization unit derived from another monomer are generally formed when the monomer (1) and another monomer copolymerizable with the monomer (1) are polymerized to obtain the polymer (1). The content of the dimer and the trimer consisting of a polymerization unit (1) and a polymerization unit derived from another monomer in the polymer (1) is 1.0% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, even more preferably 0.001% by mass or less, and particularly preferably 0.0001% by mass. or less relative to the polymer (1).

[0159] The content of dimer and trimer in polymer (1) can be determined by performing gel permeation chromatography (GPC) analysis of polymer (1) and calculating the proportion (area percentage) of the total area of dimer and trimer peaks to the total area of each peak in the chromatogram obtained by GPC analysis.

[0160] Also, when the content of the dimer and trimer in the polymer (1) is less than 0.5% by mass relative to the polymer (1), this content can be determined by measurement by liquid chromatography-mass spectrometry (LC/MS).

Specifically, aqueous solutions having five or more different levels of monomer (1) content are prepared, LC/MS analysis of aqueous solutions with the corresponding levels of content is performed, and the relationship between the content level and the area (integral value of the peak) corresponding to this content level is determined, which is plotted on a graph to construct a calibration curve of the monomer (1). Furthermore, a calibration curve of the dimer and trimer of the monomer (1) is constructed based on the calibration curve of the monomer (1).

Methanol is added to the polymer (1) to prepare a mixture, the mixture is filtered using an ultrafiltration disc (molecular weight cutoff 3000 Da) and the resulting reconstituted solution is subjected to LC/MS analysis.

The chromatogram area (integrated peak value) of the dimer and trimer monomer (I) can then be converted using calibration curves into the dimer and trimer content.

[0161] The content of the fraction having a molecular weight of 3,000 or less in the polymer (1) may be 3.7% or less, preferably 3.2% or less, even more preferably 2.7% or less, even more preferably 1.7% or less, even more preferably 1.2% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less, with respect to the polymer (1). The lower limit of the content of the fraction having a molecular weight of 3,000 or less is not limited and is, for example, 0.01%. The content of the fraction having a molecular weight of 3,000 or less can be calculated from the peak area of the GPC. The fraction having a molecular weight of 3,000 or less includes all compounds having a molecular weight of 3,000 or less.

[0162] The content of the fraction having a molecular weight of 2,000 or less in the polymer (1) may be 3.2% or less, and is preferably 2.7% or less, even more preferably 2.2% or less, even more preferably 1.7% or less, even more preferably 1.2% or less, and particularly preferably 0.6% or less, with respect to the polymer (1). The lower limit of the content of the fraction having a molecular weight of 2,000 or less is not limited and is, for example, 0.01%. The content of the fraction having a molecular weight of 2,000 or less can be calculated from the peak area of the GPC. The fraction having a molecular weight of 2,000 or less includes all compounds having a molecular weight of 2,000 or less.

[0163] The content of the fraction having a molecular weight of 1,500 or less in the polymer (1) may be 2.7% or less, preferably 2.2% or less, even more preferably 1.7% or less, even more preferably 1.2% or less, and even more preferably 0.6% or less, with respect to the polymer (1). The lower limit of the content of the fraction having a molecular weight of 1,500 or less is not limited and is, for example, 0.01%. The content of the fraction having a molecular weight of 1,500 or less can be calculated from the GPC peak area. The fraction having a molecular weight of 1,500 or less includes all compounds having a molecular weight of 1,500 or less.

[0164] The content of the fraction having a molecular weight of 1,000 or less in the polymer (1) may be 2.2% or less, preferably 1.7% or less, even more preferably 1.2% or less, and even more preferably 0.6% or less, with respect to the polymer (1). The lower limit of the content of the fraction having a molecular weight of 1,000 or less is not limited and is, for example, 0.01%. The content of the fraction having a molecular weight of 1,000 or less can be calculated from the GPC peak area. The fraction having a molecular weight of 1,000 or less includes all compounds having a molecular weight of 1,000 or less.

[0165] By using a polymer (1) substantially free of the dimer and trimer of the monomer (1) in polymerizing a perfluoromonomer in an aqueous medium, it is possible to obtain a fluoropolymer substantially free of the dimer and trimer of the monomer (1).

[0166] The polymer (1) is a polymer containing a polymerization unit (1) derived from a monomer (1). The polymer (1) used in the present invention is a polymer in which a dimer (a polymer containing two polymerization units (1)) and a trimer (a polymer containing three polymerization units (1)) are substantially removed from the polymer (1) containing two or more polymerization units (1).

[0167] By using a polymer (1) that is substantially free of a dimer and a trimer consisting of a polymerization unit (1) derived from a monomer (1) and a polymerization unit derived from another monomer copolymerizable with the monomer (1) in polymerizing a perfluoromonomer in an aqueous medium, a fluoropolymer that is substantially free of a dimer and a trimer consisting of a polymerization unit (1) and a polymerization unit derived from another monomer can be obtained even in the case of using a polymer (1) that contains a polymerization unit (1) and a polymerization unit derived from another monomer, such as the polymer (1).

[0168] The molecular weight of the monomer (1) is preferably 500 or less, and more preferably 400 or less. That is, it is preferable that the polymer (1) substantially does not contain dimers and trimers having a molecular weight of 1500 or less, and it is more preferable that the polymer (1) substantially does not contain dimers and trimers having a molecular weight of 1200 or less.

[0169] Accordingly, it is preferable that the production method of the present invention comprises polymerizing the monomer (1) represented by the general formula (1) to obtain a crude composition containing a polymer of the monomer (1), and removing the dimer and trimer of the monomer (1) contained in the crude composition from the crude composition to obtain a polymer (1) in which the content of the dimer and trimer of the monomer (1) is 1.0% by mass or less with respect to the polymer (1).

[0170] The polymerization of the monomer (1) can be carried out using the above-mentioned method. By obtaining a crude composition in this manner, it is possible to obtain a crude composition in which the polymer (1) is dispersed or dissolved in an aqueous medium.

[0171] It is preferable that the polymerization of the monomer (1) is carried out in an aqueous medium, substantially in the absence of a fluorosurfactant (except for the monomer (1) represented by the general formula (1)).

[0172] In the present specification, the expression "substantially free of a fluorosurfactant" means that the amount of the fluorosurfactant is 10 ppm by mass or less with respect to the aqueous medium. The amount of the fluorosurfactant with respect to the aqueous medium is 1 ppm by mass or less, more preferably 100 ppb by mass or less, even more preferably 10 ppb by mass or less, and even more preferably 1 ppb by mass or less.

[0173] The fluorosurfactant will be mentioned later in the description of the polymerization of the perfluoromonomer.

[0174] In the thus obtained crude composition, the dimer and trimer of the monomer (1) are usually contained in a total amount greater than 1.0% by weight relative to the weight of the polymer. For example, the content of the dimer and trimer of the monomer (1) in the polymer may be 2.0% by weight or more or 3.0% by weight or more, and may also be 30.0% by weight or less or 20.0% by weight or less relative to the polymer of the monomer (1).

[0175] Also, in the case of polymerizing the monomer (1) and another monomer copolymerizable with the monomer (1), in the resulting crude composition, the dimer and trimer consisting of the polymerization unit (1) obtained from the monomer (1) and the polymerization unit obtained from another monomer copolymerizable with the monomer (1) are usually contained in a total amount of more than 1.0% by mass relative to the mass of the polymer. For example, the content of the dimer and trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer may be 2.0% by mass or more or 3.0% by mass or more, and may be 30.0% by mass or less or 20.0% by mass or less relative to the polymer.

[0176] The dimer and trimer content of a crude composition can be determined by analyzing the crude composition using gel permeation chromatography (GPC) and calculating the proportion (area percentage) of the total area of the dimer and trimer peaks from the total area of each peak in the chromatogram obtained by the GPC method.

[0177] Then, the dimer and trimer of the monomer (1) or the dimer and trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer, contained in the crude composition obtained by polymerizing the monomer (1), are removed from the crude composition. Methods for removing the dimer and trimer are not limited, but at least one method selected from the group consisting of ultrafiltration, microfiltration, dialysis membrane treatment, liquid separation and reprecipitation is preferable, at least one method selected from the group consisting of ultrafiltration, microfiltration, liquid separation and reprecipitation are more preferable, at least one method selected from the group consisting of ultrafiltration and liquid separation is even more preferable, and ultrafiltration is particularly preferable.

[0178] Also, a fraction having a molecular weight of 3,000 or less, a fraction having a molecular weight of 2,000 or less, a fraction having a molecular weight of 1,500 or less, and a fraction having a molecular weight of 1,000 or less can be removed by appropriately selecting dimer and trimer removing means.

[0179] It is generally not known whether the polymerization of monomer (1) produces a dimer and trimer of monomer (1), with the resulting dimer and trimer of monomer (1) being incorporated into polymer (1). Although the mechanism for the formation of dimer and trimer of monomer (1) is not clearly understood, it is assumed that dimerization and trimerization of monomer (1) occurs with considerable frequency, especially as a result of the polymerization reaction in a polymerization system in which monomer (1) constitutes a large part of the monomers present in the polymerization system.

[0180] When removing the dimer and trimer, the unreacted monomer (1) is usually also removed simultaneously from the crude composition. Even when the unreacted monomer (1) is incorporated into PTFE by polymerization, this does not necessarily have an adverse effect on the function of PTFE, and therefore the unreacted monomer (1) does not necessarily need to be removed. However, by removing the unreacted monomer (1) simultaneously with the dimer and trimer, the amount of monomer undergoing polymerization can be calculated without taking into account the presence of the unreacted monomer (1), which has the advantage that a fluoropolymer having a desired monomer composition can be easily obtained. Note that even when the monomer (1) remains in the polymer (1) or when the monomer (1) is added again as a comonomer, the dimerization and trimerization of the monomer (1) hardly occur during the polymerization reaction in the polymerization system in which TFE constitutes a major part of the polymerization system among the monomers present in the polymerization system, and the dimer and trimer of the monomer (1) hardly remain in the resulting fluoropolymer.

[0181] The crude composition obtained by polymerizing the monomer (1) may be a polymerized composition obtained by polymerization, may be a composition obtained by diluting or concentrating the polymerized composition obtained by polymerization, or may be a composition immediately after polymerization, or may be a composition that has undergone a treatment to stabilize the dispersion or the like. It is also preferable to adjust the viscosity of the crude composition by such a treatment to facilitate ultrafiltration, microfiltration, or dialysis membrane treatment.

[0182] The content of the polymer of the monomer (1) in the crude composition is not limited and may be, for example, 0.1 to 20 mass%. From the viewpoint of the efficiency of removing the dimer and the trimer, the content of the polymer of the monomer (1) in the crude composition is preferably 18.0 mass% or less, more preferably 15.0 mass% or less, even more preferably 12.0 mass% or less, and particularly preferably 10.0 mass% or less, and is preferably 0.5 mass% or more, more preferably 1.0 mass% or more, even more preferably 1.2 mass% or more, particularly preferably 1.5 mass% or more, and most preferably 2.0 mass% or more. The content of the polymer of the monomer (1) in the crude composition can be adjusted, for example, by a method in which water is added to the crude composition obtained by polymerizing the monomer (1), a method in which the crude composition obtained by polymerizing the monomer (1) is concentrated, and the like.

[0183] The pH of the crude composition is preferably from -7.0 to 11.0, more preferably from -6.0 to 8.0, and even more preferably from -5.0 to 7.0. The pH of the crude composition can be adjusted by adding a pH adjuster to the crude composition obtained by polymerizing the monomer (1). The pH adjuster may be an acid or an alkali, and examples thereof include phosphates, sodium hydroxide, potassium hydroxide, and aqueous ammonia.

[0184] In the case of ultrafiltration, microfiltration, or dialysis membrane treatment, the viscosity of the crude composition is preferably 25 mPa⋅s or less, since the treatments are carried out smoothly. The viscosity of the crude composition can be adjusted, for example, by a method in which the number average molecular weight of the polymer monomer (1) is adjusted, a method in which the concentration of the polymer monomer (1) in the crude composition is adjusted, a method in which the temperature of the crude composition is adjusted, and the like.

[0185] Although ultrafiltration or microfiltration is not limited and can be either a cross-flow type or a dead-end type, the cross-flow type is preferable from the viewpoint of reducing membrane fouling.

[0186] Ultrafiltration can be carried out using an ultrafiltration membrane. Ultrafiltration can be carried out, for example, using an ultrafiltration device containing an ultrafiltration membrane, and a centrifugal ultrafiltration method, a batch ultrafiltration method, a circulation ultrafiltration method, and the like can be used.

[0187] The molecular weight cutoff of the ultrafiltration membrane is usually 0.1×10 ⁴ to 30×10 ⁴ Da. The ultrafiltration membrane preferably has a molecular weight cutoff of 0.3×10 ⁴ Da or more because it can suppress membrane fouling and effectively reduce the amount of dimers and trimers. The molecular weight cutoff is more preferably 0.5×10 ⁴ Da or more, particularly preferably 0.6×10 ⁴ Da or more, and most preferably 0.8×10 ⁴ Da or more. The molecular weight cutoff may be 1.0×10 ⁴ Da or more. Also, the molecular weight cutoff is preferably 20×10 ⁴ Da or less, and more preferably 10×10 ⁴ Da or less, from the viewpoint of the dimer and trimer removal efficiency.

[0188] The molecular weight cutoff of an ultrafiltration membrane can be determined, for example, by passing polystyrene of a known weight average molecular weight through the membrane and using the molecular weight that can be blocked by 90% as the molecular weight cutoff. Quantitative determination of polystyrene can be achieved using gel permeation chromatography.

[0189] The shape of the ultrafiltration membrane is not limited to the commonly known shapes, for example, it may be of a hollow fiber type, a flat membrane type, a spiral type, a tubular type, or the like. The hollow fiber type is preferable from the viewpoint of preventing clogging.

The internal diameter of a hollow fiber ultrafiltration membrane is not limited and can range from 0.1 to 2 mm, for example. Preferably, it ranges from 0.8 to 1.4 mm.

The length of the hollow fiber ultrafiltration membrane is not limited and can be, for example, from 0.05 to 3 m. Preferably, it is from 0.05 to 2 m.

[0190] The material of the ultrafiltration membrane is not limited, examples thereof include organic materials such as cellulose, cellulose ester, polysulfone, sulfonated polysulfone, polyethersulfone, sulfonated polyethersulfone, chlorinated polyethylene, polypropylene, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride and polytetrafluoroethylene; metals such as stainless steel; and inorganic materials such as ceramics.

The ultrafiltration membrane material is preferably an organic material, more preferably chlorinated polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polysulfone or polyethersulfone, and even more preferably polyacrylonitrile, polysulfone or polyvinylidene fluoride.

[0191] Specific examples of the ultrafiltration membrane include G-5 type, G-10 type, G-20 type, G-50 type, PW type and HWS type UF of DESAL; HFM-180, HFM-183, HFM-251, HFM-300, HFM-116, HFM-183, HFM-300, HFK-131, HFK-328, MPT-U20, MPS-U20P and MPS-U20S of KOCH; SPE1, SPE3, SPE5, SPE10, SPE30, SPV5, SPV50 and SOW30 of Synder; Microza (R) UF series of Asahi Kasei Corporation; and NTR 7410 of Nitto Diko Corporation.

[0192] Ultrafiltration is preferably performed at a pressure of 0.01 MPa or more from the viewpoint of the efficiency of removing the dimer and trimer. More preferably, it is 0.03 MPa or more, and even more preferably 0.05 MPa or more. Also, from the viewpoint of pressure resistance, the pressure is preferably 0.5 MPa or less, more preferably 0.25 MPa or less, and even more preferably 0.2 MPa or less.

[0193] Ultrafiltration is preferably performed at a flow rate of 10 ml/min or more, and more preferably at a flow rate of 50 ml/min or more, and is also preferably performed at a flow rate of 5000 ml/min or less, and more preferably at a flow rate of 1000 ml/min or less from the viewpoint of the efficiency of removing the dimer and trimer.

[0194] Microfiltration can be accomplished using a microfiltration membrane. A microfiltration membrane typically has an average pore size of 0.05 to 1.0 μm.

It is preferable for the microfiltration membrane to have an average pore size of 0.1 μm or greater, as it can effectively remove dimers and trimers. It is more preferably 0.075 μm or greater, and even more preferably 0.1 μm or greater. The average pore size is also preferably 1.00 μm or less. It is more preferably 0.50 μm or less, and even more preferably 0.25 μm or less.

The average pore size of microfiltration membrane can be measured according to ASTM F316-03 (bubble point method).

[0195] The shape of the microfiltration membrane is not limited to the commonly known shapes, for example, it can be a hollow fiber type, a flat membrane type, a spiral type, a tubular type, or the like. The hollow fiber type is preferable from the viewpoint of preventing clogging.

The internal diameter of a hollow fiber microfiltration membrane is not limited and can range from 0.1 to 2 mm, for example. Preferably, it ranges from 0.8 to 1.4 mm.

The length of the hollow fiber microfiltration membrane is not limited and can be, for example, from 0.05 to 3 m. Preferably, it is from 0.05 to 2 m.

[0196] Examples of the microfiltration membrane material include cellulosic materials, aromatic polyamide, polyvinyl alcohol, polysulfone, polyethersulfone, polyvinylidene fluoride, polyethylene, polyacrylonitrile, polypropylene, polycarbonate, polytetrafluoroethylene, ceramics, and metals. Among these, aromatic polyamide, polyvinyl alcohol, polysulfone, polyvinylidene fluoride, polyethylene, polyacrylonitrile, polypropylene, polycarbonate, or polytetrafluoroethylene are preferable, and polyacrylonitrile or polyvinylidene fluoride are particularly preferable.

[0197] Specific examples of the microfiltration membrane include Cefilt manufactured by NGK Insulators, Ltd.; Microza U series and Microza P series manufactured by Asahi Kasei Corporation; Poreflon SPMW, Poreflon OPMW, and Poreflon PM manufactured by Sumitomo Electric Industries, Ltd.; Torayfil manufactured by Toray Industries, Inc.; NADIR MP005 and NADIR MV020 manufactured by Microdyn-Nadir GmbH, and X-flow manufactured by Norit N.V.

[0198] Microfiltration is preferably performed at a pressure of 0.01 MPa or more from the viewpoint of the efficiency of removing the dimer and trimer. More preferably, it is 0.03 MPa or more, and even more preferably 0.05 MPa or more. Furthermore, from the viewpoint of pressure resistance, the pressure is preferably 0.5 MPa or less, more preferably 0.25 MPa or less, and even more preferably 0.2 MPa or less.

[0199] Microfiltration is preferably performed at a flow rate of 10 ml/min or more, and is more preferably performed at a flow rate of 50 ml/min or more, and is also preferably performed at a flow rate of 5000 ml/min or less, and is more preferably performed at a flow rate of 1000 ml/min or less from the viewpoint of the efficiency of removing the dimer and trimer.

[0200] Dialysis membrane treatment is performed using a dialysis membrane. The molecular weight cutoff of the dialysis membrane is typically between 0.05×10 ⁴ and 100×10 ⁴ Da.

The dialysis membrane preferably has a molecular weight cutoff of 0.3× ¹⁰⁴ Da or more, since this can suppress membrane clogging and effectively remove dimer and trimer. More preferably, the molecular weight cutoff is 0.5× ¹⁰⁴ Da or more, even more preferably 1.0× ¹⁰⁴ Da or more, even more preferably 1.5× ¹⁰⁴ Da or more, even more preferably 2.0× ¹⁰⁴ Da or more, particularly preferably 3.0× ¹⁰⁴ Da or more, and most preferably 5.0× ¹⁰⁴ Da or more. The molecular weight cutoff may be 8.0× ¹⁰⁴ Da or more.

In addition, the molecular weight cutoff is preferably 20×10 ⁴ Da or less, and more preferably 10×10 ⁴ Da or less, from the viewpoint of the dimer and trimer removal efficiency.

The molecular weight cutoff of a dialysis membrane can be measured, for example, in the same way as for an ultrafiltration membrane.

[0201] Although the material of the dialysis membrane is not limited, examples thereof include cellulose, polyacrylonitrile, polymethyl methacrylate, ethylene-vinyl alcohol copolymers, polysulfone, polyamide, and polyester polymer alloys.

[0202] Specific examples of dialysis membrane include Spectra/Rog (R) Float-A-Lyzer, Tube-A-Lyzer, Dialysis Tubes, 6 Dialysis Tubes, and 7 Dialysis Tubes, manufactured by Spectrum Laboratories Inc.

[0203] It is preferable that the ultrafiltration, microfiltration or dialysis membrane treatment is carried out at a temperature of 10°C or higher. More preferably, the temperature is 15°C or higher, even more preferably 20°C or higher, and particularly preferably 30°C or higher. By setting the temperature in the above range, the content of the dimer and trimer can be reduced more effectively. The temperature is preferably 90°C or lower, more preferably 80°C or lower, even more preferably 70°C or lower, and particularly preferably 60°C or lower.

[0204] Ultrafiltration, microfiltration, or dialysis membrane treatment can be performed by adding water to the crude composition or by adjusting the pH of the crude composition. Water can be added to the crude composition periodically or it can be added to the crude composition continuously.

[0205] The end point of the ultrafiltration, microfiltration, or dialysis membrane treatment can be determined accordingly and is not limited. In addition, during ultrafiltration, microfiltration, or dialysis membrane treatment, the membrane can be washed with water approximately once every 1 to 24 hours during filtration to increase the durability of the filter membrane.

[0206] Liquid separation can be accomplished, for example, by adding an organic solvent to the composition to separate it into two phases, an aqueous phase and an organic solvent phase, and collecting the aqueous phase.

[0207] Re-precipitation can be carried out, for example, by dropping the composition into a poor solvent to precipitate the polymer, collecting the precipitated polymer, dissolving the collected polymer in a good solvent, dropping the resulting solution into a poor solvent to precipitate the polymer again, and collecting the precipitated polymer.

[0208] By removing the dimer and trimer of the monomer (1) from the crude composition containing the polymer of the monomer (1), an aqueous solution containing the polymer (1) that is substantially free of the dimer and trimer is usually obtained. The polymer (1) used in the production method of the present invention may be the polymer (1) contained in the obtained aqueous solution or the polymer (1) obtained by isolating from the aqueous solution. The method for isolating the polymer (1) from the aqueous solution is not limited. For example, the polymer (1) can be separated by a method such as coagulating, washing and drying the polymer (1) in the aqueous solution.

[0209] As the polymer (1), an aqueous solution containing the polymer (1) can be used. The preferred content of the dimer and trimer of the monomer (1) or the preferred content of the dimer and trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer, as indicated above, is taken relative to the polymer (1) in the aqueous solution.

[0210] <Polymerization of perfluoromonomer>

The first method of production according to the present invention involves the polymerization of a perfluoromonomer in an aqueous medium in the presence of a polymer (1) to produce a fluoropolymer. The content of the polymerization unit derived from the perfluoromonomer in the fluoropolymer is 90% by mole or more relative to all polymerization units of the fluoropolymer.

[0211] The perfluoromonomer preferably contains at least one double bond. The perfluoromonomer is preferably at least one monomer selected from the group consisting of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether), and perfluoro(alkyl allyl ether).

[0212] The ether (perfluoroalkyl vinyl ether) is preferably, for example, at least one ether selected from the group consisting of:

fluoromonomer represented by the general formula (110): CF ₂ =CF-ORf ¹¹¹

where Rf ¹¹¹ is a perfluoroorganic group;

fluoromonomer represented by the general formula (130): CF ₂ =CFOCF ₂ ORf ¹³¹

where Rf ¹³¹ is a linear or branched perfluoroalkyl group containing from 1 to 6 carbon atoms, a cyclic perfluoroalkyl group containing from 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkyl group containing from 2 to 6 carbon atoms and containing from 1 to 3 oxygen atoms;

fluoromonomer represented by the general formula (140):

CF ₂ =CFO(CF ₂ CF(Y ¹⁴¹ )O) _m (CF ₂ ) _n F

where Y ¹⁴¹ represents a fluorine atom or a trifluoromethyl group; m represents an integer from 1 to 4; and n represents an integer from 1 to 4; and

fluoromonomer represented by the general formula (150):

CF ₂ =CF-O-(CF ₂ CFY ¹⁵¹ -O) _n -(CFY ¹⁵² ) _m -A ¹⁵¹

wherein Y ¹⁵¹ represents a fluorine atom, an -SO ₂ F group or a perfluoroalkyl group; a perfluoroalkyl group optionally containing ether oxygen and an -SO ₂ F group; n is a number from 0 to 3; n Y ¹⁵¹ are the same or different; Y ¹⁵² represents a fluorine atom or an -SO ₂ F group; m is a number from 1 to 5; m Y ¹⁵² are the same or different; A ¹⁵¹ represents -SO ₂ X ¹⁵¹ , -COZ ¹⁵¹ or -POZ ¹⁵² Z ¹⁵³ ; X ¹⁵¹ represents F, Cl, Br, I, -OR ¹⁵¹ or -NR ¹⁵² R ¹⁵³ ; Z ¹⁵¹ , Z ¹⁵² and Z ¹⁵³ are the same or different and each of them represents -NR ¹⁵⁴ R ¹⁵⁵ or -OR ¹⁵⁶ ; R ¹⁵¹ , R ¹⁵² , R ¹⁵³ , R ¹⁵⁴ , R ¹⁵⁵ and R ¹⁵⁶ are the same or different and each of them represents H, ammonium, an alkali metal or an alkyl group, an aryl group or a sulfonyl-containing group optionally containing a fluorine atom.

[0213] "Perfluoroorganic group" as used herein means an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The perfluoroorganic group optionally contains an etheric oxygen.

[0214] An example of a fluoromonomer represented by the general formula (110) is a fluoromonomer in which Rf ¹¹¹ is a perfluoroalkyl group containing 1 to 10 carbon atoms. The perfluoroalkyl group preferably contains 1 to 5 carbon atoms.

[0215] Examples of the perfluoroorganic group in the general formula (110) include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

Examples of the fluoromonomers represented by the general formula (110) also include monomers represented by the general formula (110) in which Rf ¹¹¹ is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms; those in which Rf ¹¹¹ is a group represented by the following formula:

[0216]

[0217] where m is 0 or an integer from 1 to 4; and those in which Rf is a group represented by the following formula:

[0218] CF ₃ CF ₂ CF ₂ -(O-CF(CF ₃ )-CF ₂ ) _n -

where n is an integer from 1 to 4.

[0219] Of these, the fluoromonomer represented by the general formula (110) is preferably

fluoromonomer represented by the general formula (160): CF ₂ =CF-ORf ¹⁶¹

where Rf ¹⁶¹ is a perfluoroalkyl group containing from 1 to 10 carbon atoms. Rf ¹⁶¹ is preferably a perfluoroalkyl group containing from 1 to 5 carbon atoms.

[0220] The (perfluoroalkyl vinyl ether) is preferably at least one ether selected from the group consisting of fluoromonomers represented by the general formulas (160), (130) and (140).

[0221] The fluoromonomer represented by the general formula (160) is preferably at least one monomer selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether, more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether, and even more preferably perfluoro(methyl vinyl ether).

[0222] The fluoromonomer represented by the general formula (130) is preferably at least one monomer selected from the group consisting of CF ₂ =CFOCF ₂ OCF ₃ , CF ₂ =CFOCF ₂ OCF ₂ CF ₃ and CF ₂ =CFOCF ₂ OCF ₂ CF ₂ OCF ₃ .

[0223] The fluoromonomer represented by the general formula (140) is preferably at least one monomer selected from the group consisting of CF ₂ =CFOCF ₂ CF(CF ₃ )O(CF ₂ ) ₃ F, CF ₂ =CFO(CF ₂ CF(CF ₃ )O) ₂ (CF ₂ ) ₃ F, and CF ₂ =CFO(CF ₂ CF(CF ₃ )O) ₂ (CF ₂ ) ₂ F.

[0224] The fluoromonomer represented by the general formula (150) is preferably at least one monomer selected from the group consisting of CF ₂ =CFOCF ₂ CF ₂ SO ₂ F, CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ SO ₂ F, CF ₂ =CFOCF ₂ CF(CF ₂ CF ₂ SO ₂ F) OCF ₂ CF ₂ SO ₂ F and CF ₂ =CFOCF ₂ CF(SO ₂ F) ₂ .

[0225] An example of a perfluoro(alkylallyl ether) is a fluoromonomer represented by the general formula (180):

CF ₂ =CF-CF ₂ -ORf ¹¹¹

where Rf ¹¹¹ represents a perfluoroorganic group.

[0226] Rf ¹¹¹ in the general formula (180) is the same as Rf ¹¹¹ in the general formula (110). Rf ¹¹¹ is preferably a perfluoroalkyl group containing 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group containing 1 to 10 carbon atoms. The perfluoro(alkylallyl) ether represented by the general formula (180) is preferably at least one ether selected from the group consisting of _CF2 =CF- _CF2 -O- _CF3 , _CF2 =CF-CF2-O-C2F5, _CF2 =CF _{- CF2} - _OC3F7 , _{and CF2} =CF- _{CF2 - OC4F9} , more preferably at least one ether selected from the group _consisting of _CF2 =CF- _CF2 - _OC2F5 , _CF2 =CF- _CF2 - _{OC3F7 , and CF2} =CF- _{CF2 -OC4F9 ,} and still more preferably _CF2 =CF- _CF2 -O _{- CF2CF2CF3 .}

[0227] In addition to the perfluoromonomer, a partially fluorinated monomer can also be polymerized. The partially fluorinated monomer preferably contains at least one double bond. The partially fluorinated monomer is preferably at least one monomer selected from the group consisting of chlorotrifluoroethylene (CTFE), vinyl fluoride, vinylidene fluoride (VDF), trifluoroethylene, fluoroalkyl vinyl ether, fluoroalkyl ethylene, fluoroalkyl allyl ether, trifluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, hexafluoroisobutene, a fluoromonomer represented by the general formula (100): CHX ¹⁰¹ =CX ¹⁰² Rf ¹⁰¹ (where one of X ¹⁰¹ and X ¹⁰² is H and the other is F, and Rf ¹⁰¹ is a linear or branched fluoroalkyl group containing from 1 to 12 carbon atoms), a fluorinated vinyl heterocyclic compound and a monomer that provides an active crosslinking center.

[0228] An example of a fluoroalkyl vinyl ether is a fluoromonomer represented by the general formula (120):

CF ₂ =CF-OCH ₂ -Rf ¹²¹

where Rf ¹²¹ is a perfluoroalkyl group containing from 1 to 5 carbon atoms.

[0229] The fluoromonomer represented by the general formula (100) is preferably a fluoromonomer in which Rf ¹⁰¹ is a linear fluoroalkyl group, and more preferably a fluoromonomer in which Rf ¹⁰¹ is a linear perfluoroalkyl group. Rf ¹⁰¹ preferably contains 1 to 6 carbon atoms. Examples of the fluoromonomer represented by the general formula (100) include: _CH2 = _CFCF3 , _CH2 = _{CFCF2CF3 , CH2} = _CFCF2CF2CF3 , _CH2 =CFCF2CF2CF2H _, CH2= _{CFCF2CF2CF2CF3 , CHF = CHCF3} (E isomer) and CHF= _CHCF3 (Z isomer ₎ , _of which 2,3,3,3-tetrafluoropropylene represented _by the formula _CH2 = _CFCF3 is _{preferable .}

[0230] The fluoroalkylethylene is preferably a fluoroalkylethylene represented by the general formula (170):

CH ₂ =CH-(CF ₂ ) _n -X ¹⁷¹

(where X ¹⁷¹ is H or F; and n is an integer from 3 to 10), and more preferably at least one fluoroalkylethylene selected from the group consisting of CH ₂ =CH-C ₄ F ₉ and CH ₂ =CH-C ₆ F ₁₃ .

[0231] An example of a fluorinated vinyl heterocyclic compound is a fluorinated vinyl heterocyclic compound represented by the general formula (230):

where each of X ²³¹ and X ²³² independently represents F, Cl, a methoxy group or a fluorinated methoxy group and Y ²³¹ is represented by the formula Y ²³² or the formula Y ²³³ :

[0232]

where Z ²³¹ and Z ²³² each independently represent F or a fluorinated alkyl group containing from 1 to 3 carbon atoms.

[0233] The monomer that provides the active vinyl heterocyclic crosslinking center is preferably at least one monomer selected from the group consisting of:

fluoromonomer represented by the general formula (181):

CX ¹⁸¹ ₂ =CX ¹⁸² -R _f ¹⁸¹ CHR ¹⁸¹ X ¹⁸³

wherein X ¹⁸¹ and X ¹⁸² each independently represent a hydrogen atom, a fluorine atom or CH ₃ ; Rf ¹⁸¹ represents a fluoroalkylene group, a perfluoroalkylene group, a fluoro(poly)oxyalkylene group or a perfluoro(poly)oxyalkylene group; R ¹⁸¹ represents a hydrogen atom or CH ₃ and X ¹⁸³ represents an iodine atom or a bromine atom;

fluoromonomer represented by the general formula (190):

CX ¹⁹¹ ₂ =CX ¹⁹² -R _f ¹⁹¹ X ¹⁹³

wherein X ¹⁹¹ and X ¹⁹² each independently represent a hydrogen atom, a fluorine atom or CH ₃ ; Rf ¹⁹¹ represents a fluoroalkylene group, a perfluoroalkylene group, a fluoropolyoxyalkylene group or a perfluoropolyoxyalkylene group and X ¹⁹³ represents an iodine atom or a bromine atom;

fluoromonomer represented by the general formula (200): CF ₂ =CFO(CF ₂ CF(CF ₃ )O) _m (CF ₂ ) _n -X ²⁰¹

where m is an integer from 0 to 5; n is an integer from 1 to 3 and X ²⁰¹ is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom or -CH ₂ I; and

fluoromonomer represented by the general formula (210): CH ₂ =CFCF ₂ O(CF(CF ₃ )CF ₂ O) _m (CF(CF ₃ )) _n -X ²¹¹

where m is an integer from 0 to 5; n is an integer from 1 to 3; and d X ²¹¹ is a cyano group, a carboxyl group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or -CH ₂ OH; and

monomer represented by the general formula (220):

CR ²²¹ R ²²² =CR ²²³ -Z ²²¹ -CR ²²⁴ =CR ²²⁵ R ²²⁶

wherein R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ and R ²²⁶ are the same or different and each of them represents a hydrogen atom or an alkyl group containing from 1 to 5 carbon atoms; Z ²²¹ represents a linear or branched alkylene group containing from 1 to 18 carbon atoms and optionally containing an oxygen atom, a cycloalkylene group containing from 3 to 18 carbon atoms, an at least partially fluorinated alkylene or oxyalkylene group containing from 1 to 10 carbon atoms, or a (per)fluoropolyoxyalkylene group, which is represented by the formula:

-(Q) _p -CF ₂ O-(CF ₂ CF ₂ O) _m (CF ₂ O) _n -CF ₂ -(Q) _p -

(where Q is an alkylene group or an oxyalkylene group; p is 0 or 1; and m/n is from 0.2 to 5) and has a molecular weight of from 500 to 10,000.

[0234] Each of X ¹⁸³ and X ¹⁹³ is preferably an iodine atom. Rf ¹⁸¹ and Rf ¹⁹¹ are preferably a perfluoroalkylene group containing from 1 to 5 carbon atoms. R ¹⁸¹ is preferably a hydrogen atom. X ²⁰¹ is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH ₂ I. X ²¹¹ is preferably a cyano group, an alkoxycarbonyl group, an iodine atom, a bromine atom, or —CH ₂ OH.

[0235] The monomer that provides the active cross-linking site is preferably at least one monomer selected from the group consisting of CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CN, CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ COOH, CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CH ₂ I, CF ₂ =CFOCF ₂ CF ₂ CH ₂ I, CH ₂ =CFCF ₂ OCF(CF ₃ )CF ₂ OCF(CF ₃ )CN, CH ₂ =CFCF ₂ OCF(CF ₃ )CF ₂ OCF(CF ₃ )COOH, CH ₂ =CFCF ₂ OCF(CF ₃ )CF ₂ OCF(CF ₃ )CH ₂ OH, CH ₂ =CHCF ₂ CF ₂ I, CH ₂ =CH(CF ₂ ) ₂ CH=CH ₂ , CH ₂ =CH(CF ₂ ) ₆ CH=CH ₂ and CF ₂ =CFO(CF ₂ ) ₅ CN, and more preferably is at least one monomer selected from the group consisting of CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CN and CF ₂ =CFOCF ₂ CF ₂ CH ₂ I.

[0236] In polymerization, the perfluoromonomer may be polymerized together with a non-fluorine-containing monomer. An example of a non-fluorine-containing monomer is a hydrocarbon monomer reacting with the fluoromonomer. Examples of the hydrocarbon monomer include alkenes such as ethylene, propylene, butylene, and isobutylene; alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, and cyclohexyl vinyl ether; vinyl esters such as vinyl acetate, vinyl propionate, vinyl-n-butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl versatate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl benzoate, vinyl para-tert-butyl benzoate, vinyl cyclohexane carboxylate, monochlorovinyl acetate, vinyl adipate, vinyl acrylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate, vinyl undecylenate, vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate and vinyl hydroxycyclohexane carboxylate; Alkyl allyl ethers such as ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether and cyclohexyl allyl ether; alkyl allyl esters such as ethyl allyl ester, propyl allyl ether, butyl allyl ether, isobutyl allyl ether and cyclohexyl allyl ether; and (meth)acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate and vinyl methacrylate.

[0237] The fluorine-free monomer may also be a hydrocarbon monomer containing functional groups (other than monomers that provide an active crosslinking site). Examples of the hydrocarbon monomer containing functional groups include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; fluorine-free monomers containing a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, maleic anhydride, and perfluorobutenoic acid; fluorine-free monomers containing a sulfo group such as vinyl sulfonic acid; Fluorine-free monomers containing a glycidyl group such as glycidyl vinyl ether and glycidyl allyl ether; fluorine-free monomers containing an amino group such as aminoalkyl vinyl ether and aminoalkyl allyl ether; fluorine-free monomers containing an amide group such as (meth)acrylamide and methylolacrylamide; and fluorine-free monomers containing a nitrile group such as acrylonitrile and methacrylonitrile.

[0238] In polymerization, the desired fluoropolymer particles can be obtained by polymerizing one, two or more monomers, such as perfluoromonomers.

[0239] The amount of the polymer (1) added in the polymerization is preferably more than 0.0001% by mass and 20% by mass or less with respect to the aqueous medium, more preferably 0.001% by mass or more, and more preferably 10% by mass or less, and still more preferably 5% by mass or less. When the amount of the added polymer (1) is in the above range, the polymerization of the perfluoromonomer in the aqueous medium can proceed smoothly. The amount of the added polymer (1) is the total amount of the polymer (1) added in the polymerization.

[0240] During polymerization, the polymer (1) can be added all at once or the polymer (1) can be added continuously. Adding the polymer (1) continuously means, for example, adding the polymer (1) not all at once, but adding it over time and without interruption or adding it in portions. During polymerization, an aqueous solution containing the polymer (1) and water can be prepared, and this aqueous solution can be added.

[0241] In polymerization, the presence of at least one of the polymers (1) can effectively produce a fluoropolymer. In addition, two or more compounds included in the polymer (1) can be used simultaneously, and a compound having a surfactant function other than the polymer (1) can also be used in combination, provided that the compound is volatile or it can remain in the molded mass made of the fluoropolymer or the like.

[0242] A nucleating agent may be used in the polymerization. The amount of the nucleating agent added may be appropriately selected according to the type of the nucleating agent. The amount of the nucleating agent added may be 5000 ppm by mass or less with respect to the aqueous medium, preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less, even more preferably 100 ppm by mass or less, particularly preferably 50 ppm by mass or less, and most preferably 10 ppm by mass or less.

[0243] During polymerization, it is preferable to add a nucleating agent to the aqueous medium before the polymerization begins or before the solids content of the fluoropolymer formed in the aqueous medium reaches 5.0% by weight. Adding a nucleating agent at the initial stage of polymerization makes it possible to obtain an aqueous dispersion having a small average primary particle size and excellent stability.

[0244] The amount of the nucleating agent added in the initial stage of polymerization is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more, with respect to the obtained fluoropolymer. The upper limit of the amount of the nucleating agent added in the initial stage of polymerization may be, but is not limited to, 2000% by mass.

[0245] The use of a nucleating agent makes it possible to obtain a fluoropolymer having a smaller primary particle size than in the case of polymerization in the absence of the above-mentioned nucleating agent.

[0246] Examples of the nucleating agent include dicarboxylic acids, perfluoropolyether (PFPE) acids or their salts, and hydrocarbon-containing surfactants. The nucleating agent preferably does not contain an aromatic ring and is preferably an aliphatic compound.

[0247] Although the nucleating agent is preferably added before the addition of the polymerization initiator or simultaneously with the addition of the polymerization initiator, it is also possible

control the particle size distribution by adding a nucleating agent during polymerization.

[0248] The amount of the dicarboxylic acid is preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less, and still more preferably 100 ppm by mass or less, with respect to the aqueous medium.

[024 9] Perfluoropolyether (PFPE) acids or their salts may have any chain structure in which the oxygen atoms in the main chain of the molecule are separated by saturated carbon fluoride groups containing from 1 to 3 carbon atoms. Two or more carbon fluoride groups may be present in the molecule. Representative structures contain repeating units represented by the following formulas:

[0250] These structures are described in Kasai, J. Appl. Polymer Sci., 57, 7 97 (1995). As described in this document, the PFPE acid or its salt may contain a carboxylic acid group or its salt at one end or at both ends. The PFPE acid or its salt may also contain a sulfonic acid, a phosphonic acid group or its salts at one or both ends. The PFPE acid or its salt may contain different groups at each of the end groups. Relative to monofunctional PFPE, the other end of the molecule is typically perfluorinated, but may contain a hydrogen or chlorine atom. The PFPE acid or its salt contains at least two etheric oxygen atoms, preferably at least four etheric oxygen atoms, and even more preferably at least six etheric oxygen atoms. Preferably, at least one fluorocarbon group separating the ether oxygen atoms, more preferably at least two of such fluorocarbon groups contain 2 or 3 carbon atoms. Even more preferably, at least 50% of the fluorocarbon groups separating the ether oxygen atoms contain 2 or 3 carbon atoms. It is also preferable that the PFPE acid or its salt contain at least 15 carbon atoms in total, and, for example, the preferred minimum value of n or n+m in the repeating unit structure is preferably at least 5. Two or more PFPE acids and their salts having an acid group at one end or at both ends can be used in the production method of the present invention. The PFPE acid or its salt preferably has a number average molecular weight of less than 6000 g/mol.

[0251] The hydrocarbon-containing surfactant is preferably added in an amount of 40 ppm by weight or less, more preferably 30 ppm by weight or less, and even more preferably 20 ppm by weight or less, relative to the aqueous medium. The amounts of oleophilic nucleating sites, expressed in ppm, that are present in the aqueous medium will be less than the amounts in ppm described herein when added to the aqueous medium. Thus, each amount of oleophilic nucleating sites will be less than 40 ppm by weight, 30 ppm by weight, and 20 ppm by weight, as described above. Since the oleophilic nucleating sites are considered to exist in the form of molecules, only a small amount of the hydrocarbon-containing surfactant can generate a large amount of oleophilic nucleating sites. Thus, adding as little as 1 ppm by weight of a hydrocarbon-containing surfactant to an aqueous medium can provide a beneficial effect. Its lower limit is preferably 0.01 ppm by weight.

[0252] The hydrocarbon-containing surfactant encompasses nonionic surfactants and cationic surfactants, including siloxane surfactants such as those described in U.S. Patent No. 7,897,682 (Brothers et al.) and U.S. Patent No. 7,977,438 (Brothers et al.).

[0253] The hydrocarbon-containing surfactant is preferably a non-ionic surfactant (e.g., a non-ionic hydrocarbon surfactant). In other words, the nucleating agent is preferably a non-ionic surfactant.

[0254] (Nonionic surfactant)

The nonionic surfactant used in the production method of the present invention typically lacks a charged group and contains a hydrophobic moiety, which is a long-chain hydrocarbon. The hydrophilic portion of the nonionic surfactant contains water-soluble functional groups, such as ethylene ether chains obtained by polymerization with ethylene oxide.

[0255] Examples of the nonionic surfactant include the following compounds.

Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, sorbitan alkyl ester, polyoxyethylene sorbitan alkyl ester, glycerol ester and derivatives thereof.

[0256] Specific examples of polyoxyethylene alkyl ethers: polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, and the like.

[0257] Specific examples of the polyoxyethylene alkyl phenyl ether: polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, and the like.

[0258] Specific examples of polyoxyethylene alkyl ethers include polyethylene glycol monolaurylate, polyethylene glycol monooleate, polyethylene glycol monostearate, and the like.

[0259] Specific examples of the sorbitan alkyl ester are: polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and the like.

[0260] Specific examples of the polyoxyethylene sorbitan alkyl ether are: polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, and the like.

[0261] Specific examples of glycerol ester: glycerol monomyristate, glycerol monostearate, glycerol monooleate, etc.

[0262] Specific examples of derivatives are polyoxyethylene alkylamine, polyoxyethylene alkyl phenyl formaldehyde condensate, and polyoxyethylene alkyl ether phosphate.

[0263] Ethers and esters can have an HLB value from 10 to 18.

[0264] Examples of nonionic surfactants include the Triton(R) X series (X15, X45, X100, etc.), Tergitol(R) 15-S series, Tergitol (R) TMN series (TMN-6, TMN-10, TMN-100, etc.), and Tergitol(R) L series manufactured by Dow Chemical Co., Ltd. and the Pluronic(R) R series (31R1, 17R2, 10R5, 25R4 (m ~22, n ~23), and Iconol(R) TDA series (TDA-6, TDA-9, TDA-10) manufactured by BASF.

[0265] The nonionic surfactant is preferably a fluorine-free nonionic surfactant. Examples thereof include ether-type nonionic surfactants such as polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether and polyoxyethylene alkylene alkyl ether; polyoxyethylene derivatives such as ethylene oxide and propylene oxide block copolymers; ester-type nonionic surfactants such as sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerol fatty acid esters and polyoxyethylene fatty acid esters; and amine-based nonionic surfactants such as polyoxyethylene alkylamine and alkyl alkanolamide.

[0266] The hydrophobic group of the nonionic surfactant may be any one of an alkyl phenol group, a linear alkyl group, and a branched alkyl group.

[0267] The nonionic surfactant is preferably a nonionic surfactant represented by the general formula (i):

where R ⁶ is a linear or branched primary or secondary alkyl group containing from 8 to 18 carbon atoms, and A ¹ is a polyoxyalkylene chain.

[0268] In the general formula (i), the number of carbon atoms in R ⁶ is preferably 10 to 16, and more preferably 12 to 16. When the number of carbon atoms in R ⁶ is 18 or less, it is easy to obtain excellent precipitation resistance in the composition. On the other hand, when the number of carbon atoms in R ⁶ exceeds 18, it is difficult to handle due to a high pour point. When R ⁶ contains less than 8 carbon atoms, the surface tension of the composition becomes high, so that permeability and wettability are likely to decrease.

[0269] The polyoxyalkylene chain A ¹ may be composed of oxyethylene and oxypropylene. The polyoxyalkylene chain is a polyoxyalkylene chain in which the average number of repeating oxyethylene groups is from 5 to 20, and the average number of repeating oxypropylene groups is from 0 to 2, and is a hydrophilic group. The number of oxyethylene units may have either a broad or narrow monomodal distribution, as is usually the case, or a broader or bimodal distribution, which can be obtained by mixing. When the average number of repeating oxypropylene groups exceeds 0, the oxyethylene groups and oxypropylene groups in the polyoxyalkylene chain may be arranged in blocks or randomly. From the viewpoint of viscosity and sedimentation stability of the composition, a polyoxyalkylene chain in which the average number of repeating oxyethylene groups is from 7 to 12 and the average number of repeating oxypropylene groups is from 0 to 2 is preferable. In particular, when A ¹ contains an average of 0.5 to 1.5 oxypropylene groups, good low-foaming properties are present, which is preferable.

[0270] More preferably, R ⁶ is (R')(R'')HC-, where R' and R'' are the same or different linear, branched or cyclic alkyl groups and the total number of carbon atoms is at least 5, preferably 7-17. Preferably, at least one residue of R' and R'' is a branched or cyclic hydrocarbon group.

[0271] Specific examples of polyoxyethylene alkyl ether include C ₁₃ H ₂₇ -O-(C ₂ H ₄ O) _n -H, C ₁₂ H ₂₅ -O-(C ₂ H ₄ O) _n -H, C ₁₀ H ₂₁ CH(CH ₃ )CH ₂ -O-(C ₂ H ₄ O) _n -H, C ₁₃ H ₂₇ -O-(C ₂ H ₄ O) _n -(CH(CH ₃ )CH ₂ O)-H, C ₁₆ H ₃₃ -O-(C ₂ H ₄ O) _n -H and HC(C ₅ H ₁₁ )(C ₇ H ₁₅ )-O-(C ₂ H ₄ O) _n -H (where in each formula n is an integer of 1 or more). Examples of commercially available polyoxyethylene alkyl ether products include the Genapol X series (manufactured by Clariant), of which Genapol X080 (trade name) is an example, the NOIGEN TDS series (manufactured by DKS Co., Ltd.), of which NOIGEN TDS-80 (trade name) is an example, the LEOCOL TD series (manufactured by Lion Corp.), of which LEOCOL TD-90 (trade name) is an example, the LIONOL(R) TD series (manufactured by Lion Corp.), the T-Det A series (manufactured by Harcros Chemicals Inc.), of which T-Det A 138 is an example, and the Tergitol® 15S series (manufactured by Dow Chemical Co., Ltd.).

[0272] The nonionic surfactant is preferably 2,6,8-trimethyl-4-nonanol ethoxylate containing on average from about 4 to about 18 ethylene oxide units, 2,6,8-trimethyl-4-nonanol ethoxylate containing on average from about 6 to about 12 ethylene oxide units, or mixtures thereof. This type of nonionic surfactant is also commercially available, for example, as TERGITOL TMN-6, TERGITOL TMN-10, and TERGITOL TMN-100X (all trade names, manufactured by Dow Chemical Co., Ltd.).

[0273] The hydrophobic group of the nonionic surfactant may be any one of an alkylphenol group, a linear alkyl group, and a branched alkyl group. Examples of the nonionic surfactant include a nonionic surfactant represented by the general formula (ii):

where R ⁷ is a linear or branched alkyl group containing from 4 to 12 carbon atoms, and A ² is a polyoxyalkylene chain. Specific examples of the nonionic surfactant include Triton® X-100 (trade name, manufactured by Dow Chemical Co., Ltd.).

[0274] The polyoxyalkylene chain ^A2 may be composed of oxyethylene and oxypropylene. The polyoxyalkylene chain is a polyoxyalkylene chain in which the average number of repeating oxyethylene groups is from 5 to 20, and the average number of repeating oxypropylene groups is from 0 to 2, and is a hydrophilic group. The number of ethylene oxide units may have either a broad or narrow monomodal distribution, as is usually the case, or a broader or bimodal distribution, which can be obtained by mixing. When the average number of repeating oxypropylene groups exceeds 0, the oxyethylene groups and oxypropylene groups in the polyoxyalkylene chain may be arranged in blocks or randomly. From the viewpoint of viscosity and precipitation resistance, the composition is preferably a polyoxyalkylene chain in which the average number of repeating oxyethylene groups is 7 to 12 and the average number of repeating oxypropylene groups is 0 to 2. In particular, when ^A2 contains an average of 0.5 to 1.5 oxypropylene groups, it has good low-foaming properties, which is preferable.

[0275] More preferably, R ⁷ is a primary or secondary alkyl group, and more preferably it is (R')(R'')HC-, where R' and R'' are the same or different linear, branched or cyclic alkyl groups, and the total number of carbon atoms is at least 5, preferably from 7 to 17. Preferably, at least one residue of R' and R'' is a branched or cyclic hydrocarbon group.

[0276] Examples of the nonionic surfactant also include polyol compounds. Specific examples thereof include those described in International Publication No. WO 2011/014715. Representative examples of the polyol compound include compounds containing one or more sugar units as polyol units. The sugar units can be modified to contain at least one long chain. Examples of suitable polyol compounds containing at least one long chain residue include alkyl glycosides, modified alkyl glycosides, sugar esters, and combinations thereof. Examples of sugars include, but are not limited to, monosaccharides, oligosaccharides, and sorbitans. Examples of monosaccharides include pentoses and hexoses. Representative examples of monosaccharides include ribose, glucose, galactose, mannose, fructose, arabinose, and xylose. Examples of oligosaccharides include oligomers of 2-10 identical or different monosaccharides. Examples of oligosaccharides include, but are not limited to, sucrose, maltose, lactose, raffinose, and isomaltose.

[0277] Typically, sugars suitable for use as a polyol compound include cyclic compounds containing a 5-membered ring of four carbon atoms and one heteroatom (usually oxygen or sulfur, preferably an oxygen atom), or cyclic compounds containing a 6-membered ring of five carbon atoms and one heteroatom, as described above, preferably an oxygen atom. They further contain at least two or at least three hydroxyl groups (-OH groups) bonded to the carbon atoms in the ring. Typically, the sugars are modified such that one or more hydrogen atoms of the hydroxyl group (and/or hydroxyalkyl group) bonded to the carbon ring atoms are altered by long-chain residues such that an ether or ester linkage is created between the long-chain residue and the sugar moiety. A sugar-based polyol may contain one sugar unit or multiple sugar units. A single sugar unit or multiple sugar units can be modified with long-chain residues, as described above. Specific examples of sugar-based polyol compounds include glycosides, sugar esters, sorbitan esters, and mixtures and combinations thereof.

[0278] A preferred type of polyol compound is an alkyl glucoside or modified alkyl glucoside. This type of surfactant contains at least one glucose residue. Examples of alkyl glucosides or modified alkyl glucosides include compounds represented by the formula:

where x is 0, 1, 2, 3, 4, or 5, and each of R ¹ and R ² is independently H or a long chain unit containing at least 6 carbon atoms, provided that at least one residue of R ¹ or R ² is not H. Representative examples of R ¹ and R ² include residues of aliphatic alcohols. Examples of aliphatic alcohols include hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol (lauryl alcohol), tetradecanol, hexadecanol (cetyl alcohol), heptadecanol, octadecanol (stearyl alcohol), eicosanoic acid, and combinations thereof. It is understood that the above formula represents specific examples of alkyl polyglucosides in which glucose is in the pyranose form, but other sugars or the same sugars but in different enantiomeric or diastereomeric forms may also be used.

Alkyl glucosides, produced, for example, by acid-catalyzed reactions of glucose, starch, or n-butyl glucoside with aliphatic alcohols, typically resulting in a mixture of different alkyl glucosides (Alkyl polyglycoside, Rompp, Lexikon Chemie, version 2.0, Stuttgart/New York, Georg Thieme Verlag, 1999). Examples of aliphatic alcohols include hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol (lauryl alcohol), tetradecanol, hexadecanol (cetyl alcohol), heptadecanol, octadecanol (stearyl alcohol), eicosanoic acid, and combinations thereof. Alkyl glucosides are also commercially available under the trade names GLUCOPON or DISPONIL from Cognis GmbH, Dusseldorf, Germany.

[0279] Examples of other nonionic surfactants include bifunctional block copolymers available from BASF as the Pluronic(R) R series and tridecyl alcohol alkoxylates available from BASF as the Iconol(R) TDA series.

[0280] The non-ionic surfactant is preferably at least one substance selected from the group consisting of a non-ionic surfactant represented by the general formula (i) and a non-ionic surfactant represented by the general formula (ii), and more preferably a non-ionic surfactant represented by the general formula (i).

[0281] Preferably, the nonionic surfactant does not contain an aromatic residue.

[0282] When polymerizing together with the polymer (1), a compound containing a functional group capable of interacting through radical polymerization and a hydrophilic group can be used. The compound containing the functional group capable of interacting through radical polymerization and the hydrophilic group can be the same as the modifying monomer (A), which will be described later.

[0283] In polymerization, in addition to the polymer (1) and other compounds having a surfactant function used as needed, an additive for stabilizing the compounds may also be used. Examples of the additive include a buffer, a pH adjuster, a stabilizing additive, and a dispersion stabilizer.

[0284] The stabilizing additive is preferably paraffin, a fluorinated oil, a fluorinated solvent, a silicone oil, or the like. The stabilizing additives can be used alone or in combination of two or more. The stabilizing additive is more preferably paraffin wax. The paraffin wax may be in liquid, semi-solid, or solid form at room temperature and is preferably a saturated hydrocarbon containing 12 or more carbon atoms. Paraffin wax generally preferably has a melting point of 40-65°C, and more preferably 50-65°C.

[0285] The amount of the stabilizing additive used is preferably from 0.1 to 12% by weight, and more preferably from 0.1 to 8% by weight, relative to the weight of the aqueous medium used. It is desirable that the stabilizing additive be sufficiently hydrophobic so that after polymerization, the stabilizing additive is completely separated from the aqueous dispersion and does not serve as a contaminating component.

[0286] The polymerization is carried out by loading an aqueous medium, a polymer (1), monomers and, optionally, other additives into a polymerization reactor, mixing the contents of the reactor, maintaining the reactor at a predetermined polymerization temperature and adding a predetermined amount of a polymerization initiator to thereby initiate the polymerization reaction. After initiation of the polymerization reaction, components such as monomers, a polymerization initiator, a chain transfer agent and the polymer (1) may be further added depending on the purpose. The polymer (1) may be added after the polymerization reaction has begun.

[0287] The polymerization is usually carried out at a polymerization temperature of 5 to 120°C and a polymerization pressure of 0.05 to 10 MPa g. The polymerization temperature and the polymerization pressure are appropriately determined in accordance with the types of monomers used, the target molecular weight of the fluoropolymer, and the reaction rate.

[0288] The polymerization initiator may be any polymerization initiator capable of generating radicals in the polymerization temperature range, and known oil-soluble and/or water-soluble polymerization initiators may be used. The polymerization initiator may be combined with a reducing agent, for example, to form a redox agent that initiates polymerization. The concentration of the polymerization initiator is determined appropriately depending on the types of monomers, the target molecular weight of the fluoropolymer, and the reaction rate.

[0289] The polymerization initiator used may be an oil-soluble radical polymerization initiator, a water-soluble radical polymerization initiator, or an azo compound.

[0290] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, and representative examples thereof include dialkyl peroxycarbonates such as diisopropyl peroxydicarbonate and di-sec-butyl peroxydicarbonate; peroxyesters such as tert-butyl peroxyisobutyrate and tert-butyl peroxypivalate; and dialkyl peroxides such as di-tert-butyl peroxide, as well as di[perfluoro (or fluorochloro)acyl]peroxides such as di(ω-hydrododecafluorohexanoyl) peroxide, di(ω-hydrotetradecafluoroheptanoyl) peroxide, di(ω-hydrohexadecafluorononanoyl) peroxide, di(perfluorobutyryl) peroxide, di(perfluorovaleryl) peroxide, di(perfluorohexanoyl) peroxide, di(perfluoroheptanoyl) peroxide, di(perfluorooctanoyl) peroxide, di(perfluorononanoyl) peroxide, di(ω-chlorohexafluorobutyryl) peroxide, di(ω-chlorodecafluorohexanoyl) peroxide, di(ω-chlorotetradecafluoroctanoyl) peroxide, ω-hydrododecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl peroxide, ω-chlorohexafluorobutyryl-ω-chlorohecafluorohexanoyl peroxide, ω-hydrododecafluoroheptanoylperfluorobutyryl peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide and di(undecachlorothoriumcontafluorodocosanoyl) peroxide.

[0291] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, and examples thereof include ammonium salts, potassium salts and sodium salts of persulfuric acid, perboric acid, perchloric acid, perphosphoric acid and percarbonic acid, organic peroxides such as disuccinic acid peroxide and diglutaric acid peroxide, tert-butyl permaleate and tert-butyl hydroperoxide. A reducing agent such as sulfite may also be contained, and the amount used may be from 0.1 to 20 times the amount of the peroxide.

[0292] For example, in the case where polymerization is performed at a low temperature of 30°C or lower, the polymerization initiator used is preferably a redox initiator obtained by combining an oxidizing agent and a reducing agent. Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and ceric ammonium nitrate. Examples of the reducing agent include sulfites, bisulfites, bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate, potassium persulfate, and sodium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. In order to increase the decomposition rate of the initiator, the redox initiator combination may preferably contain a copper salt or an iron salt. An example of a copper salt is copper(II) sulfate, and an example of an iron salt is iron(II) sulfate.

[0293] Examples of the redox initiator include potassium permanganate/oxalic acid, ammonium persulfate/bisulfite/ferric sulfate, manganese triacetate/oxalic acid, ammonium cerium nitrate/oxalic acid, and bromate/bisulfite, and potassium permanganate/oxalic acid is preferred. In the case of using a redox initiator, either an oxidizing agent or a reducing agent can be pre-loaded into the polymerization tank, and then the other agent can be continuously or intermittently added thereto to initiate the polymerization. For example, in the case of using potassium permanganate/oxalic acid, oxalic acid is preferably loaded into the polymerization tank and potassium permanganate is continuously added thereto.

[0294] The polymerization initiator may be added in any amount, and the initiator in an amount that does not significantly reduce the polymerization rate (for example, at a concentration of several ppm in water) or more may be added immediately at the initial stage of polymerization or may be added periodically or continuously. The upper limit of its amount is in the range in which the reaction temperature is allowed to rise while the heat of the polymerization reaction is removed through the surfaces of the device. Its upper limit is more preferably in the range in which the heat of the polymerization reaction can be removed through the surfaces of the device.

[0295] The aqueous medium is the reaction medium in which the polymerization is carried out and means a liquid containing water. The aqueous medium may be any medium containing water, and it may be a medium containing water and, for example, any of the fluorine-free organic solvents such as alcohols, ethers and ketones, and/or fluorine-containing organic solvents having a boiling point of 40°C or lower.

[0296] During polymerization, known chain transfer agents, radical scavengers, and decomposers can be added to control the polymerization rate and molecular weight depending on the purpose.

[0297] Examples of the chain transfer agent include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate and dimethyl succinate, as well as isopentane, methane, ethane, propane, methanol, isopropanol, acetone, various mercaptans, various halogenated hydrocarbons such as carbon tetrachloride and cyclohexane.

[0298] The chain transfer agent used may be a bromine compound or an iodine compound. An example of a polymerization method using a bromine compound or an iodine compound is a method of carrying out polymerization of a fluoromonomer in an aqueous medium substantially in the absence of oxygen and in the presence of a bromine compound or an iodine compound (iodine transfer polymerization). Representative examples of a bromine compound or an iodine compound to be used include compounds represented by the general formula:

R ^a I _x Br _y

where each of x and y is an integer from 0 to 2 and satisfies the condition 1≤x+y≤2; and R ^a is a saturated or unsaturated fluorocarbon or chlorofluorocarbon group containing from 1 to 16 carbon atoms, or a hydrocarbon group containing from 1 to 3 carbon atoms, each of which optionally contains an oxygen atom. When using a bromine compound or an iodine compound, iodine or bromine is introduced into the polymer and serves as a cross-linking point.

[0299] Examples of the bromine compound or the iodine compound include 1,3-diiodoperfluoropropane, 2-iodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane, diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF ₂ Br ₂ , BrCF ₂ CF ₂ Br, CF ₃ CFBrCF ₂ Br, CFClBr ₂ , BrCF ₂ CFClBr, CFBrClCFClBr, BrCF ₂ CF ₂ CF ₂ Br, BrCF ₂ CFBrOCF ₃ , 1-bromo-2-iodoperfluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, 3-bromo-4-iodoperfluorobutene-1,2-bromo-4-iodoperfluorobutene-1, the product of monoiodo- and monobromosubstitution, the product of diiodine- and monobromosubstitution, as well as the product of (2-iodoethyl)- and (2-bromoethyl)substitution of benzene. These compounds can be used individually or in any combination.

[0300] Of these, 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane and 2-iodoperfluoropropane are preferably used from the viewpoint of polymerization reactivity, cross-linkability, availability and the like.

[0301] The amount of the chain transfer agent used is usually from 1 to 50,000 ppm by weight, preferably from 1 to 20,000 ppm by weight, relative to the total amount of the fluoromonomer introduced.

[0302] The chain transfer agent may be added to the reaction vessel immediately before the start of the polymerization, may be added immediately after the start of the polymerization, may be added in several portions during the polymerization, or may be added continuously during the polymerization.

[0303] The polymerization initiator used may be an organic peroxide such as a persulfate (e.g., ammonium persulfate), disuccinic acid peroxide, or diglutaric acid peroxide, alone or as a mixture thereof. The organic peroxide may be used together with a reducing agent such as sodium sulfite to form a redox system. Additionally, a radical scavenger such as hydroquinone or catechol may be added during the polymerization, or a peroxide decomposer such as ammonium sulfite may be added to control the concentration of radicals in the system.

[0304] In the polymerization, the fluoropolymer can be obtained by polymerizing the perfluoromonomer in an aqueous medium in the presence of the polymer (1) to obtain an aqueous dispersion of fluoropolymer particles and by seed polymerization of the perfluoromonomer with the fluoropolymer particles in the aqueous dispersion of fluoropolymer particles.

[0305] The polymerization is preferably a polymerization in which the perfluoromonomer is polymerized substantially in the absence of a fluorosurfactant (except for a compound containing a functional group capable of reacting by radical polymerization and a hydrophilic group). Typically, fluorosurfactants are used to polymerize perfluoromonomers in an aqueous medium, but the production method according to the present invention makes it possible to produce a fluoropolymer even without using fluorosurfactants.

[0306] In the present invention, the expression "substantially free of a fluorosurfactant" means that the amount of the fluorosurfactant is 10 ppm by mass or less with respect to the aqueous medium. The amount of the fluorosurfactant with respect to the aqueous medium is 1 ppm by mass or less, more preferably 100 ppm by mass or less, even more preferably 10 ppm by mass or less, and still more preferably 1 ppm by mass or less.

[0307] Examples of the fluorine-containing surfactant include anionic fluorine-containing surfactants. The anionic fluorine-containing surfactant may be, for example, a surfactant containing a fluorine atom containing a total of 20 or less carbon atoms in the portion not containing an anionic group.

[0308] The fluorine-containing surfactant may also be a fluorine-containing surfactant having a molecular weight of 1000 or less, preferably 800 or less, in the anionic moiety.

"Anionic moiety" means the portion of a fluorosurfactant that does not contain a cation. For example, in the case of F( _CF2 ) _n1COOM , represented by formula (I) described below, the anionic moiety is the portion "F( _CF2 ) _n1COO ".

[0309] Examples of the fluorosurfactant also include fluorosurfactants having a Log POW of 3.5 or less. Log POW is the partition coefficient between 1-octanol and water, which is represented by Log P (where P is the ratio between the concentration of the fluorosurfactant in octanol and the concentration of the fluorosurfactant in water in a phase-separated octanol/water liquid mixture (1:1) containing the fluorosurfactant).

Log POW is determined as follows. Specifically, HPLC is carried out on standard substances (heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid), each with a known octanol/water partition coefficient, using a TOSOH ODS-120T column (ϕ4.6 mm × 250 mm, Tosoh Corp.) and an aqueous solution of acetonitrile/0.6% wt. HClO4 = ₁ /1 (% v/v) as an eluent at a flow rate of 1.0 mL/min, a sample amount of 300 μL, and a column temperature of 40°C; with a UV detection radiation of 210 nm. For each standard substance, a calibration curve is constructed taking into account the elution time and the known octanol/water partition coefficient. Based on the calibration curve, Log POW is calculated from the elution time of the liquid sample during HPLC.

[0310] Specific examples of the fluorosurfactant include those described in U.S. Patent Application Publication No. 2007/0015864, U.S. Patent Application Publication No. 2007/0015865, U.S. Patent Application Publication No. 2007/0015866, and U.S. Patent Application Publication No. 2007/027 6103, U.S. Patent Application Publication No. 2007/0117 914, U.S. Patent Application Publication No. 2007/142541, U.S. Patent Application Publication No. 2008/0015319, U.S. Patent No. 3,250,808, U.S. Patent No. 3,271,341, Japanese Patent Laid-Open No. 2003-119204, in International Publication No. WO 20 05/0425 93, International Publication No. WO 2008/060461, International Publication No. WO 2007/046377, Japanese Patent Laid-Open No. 2007-119526, International Publication No. WO 2007/046482, International Publication No. WO 2007/046345, U.S. Patent Application Publication No. 2014/0228531, International Publication No. WO 2013/189824, and International Publication No. WO 2013/18 9826.

[0311] Examples of the anionic fluorine-containing surfactant include a compound represented by the following general formula (N ⁰ ):

where Xn ⁰ is H, Cl or F; Rf ⁿ⁰ is a linear, branched or cyclic alkylene group containing from 3 to 20 carbon atoms in which all or part of the H is replaced by F; an alkylene group optionally containing one or more ether bonds in which part of the H is replaced by Cl and Y ⁰ is an anionic group.

The anionic group Y ⁰ may be -СООМ, -SO ₂ M or -SO ₃ M and may be -СООМ or -SO ₃ M.

M is H, a metal atom, NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent, where R ⁷ is H or an organic group.

Examples of metal include the alkali metals (Group 1) and alkaline earth metals (Group 2), such as Na, K, or Li.

R ⁷ may be H or a C _1-10 organic group, may be H or a C _1-4 organic group, and may be H or a C _1-4 alkyl group.

M may be H, a metal atom, or NR ⁷ ₄ , may be H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or NR ⁷ ₄ , and may be H, Na, K, Li, or NH ₄ .

Rf ⁿ⁰ may be one in which 50% or more of the H atoms are replaced by fluorine.

[0312] Examples of the compound represented by the general formula (N ⁰ ) include:

a compound represented by the following general formula (N ¹ ):

where Xn ⁰ is H, Cl or F; m1 is an integer from 3 to 15 and Y ⁰ is as defined above;

a compound represented by the following general formula (N ² ):

where Rf ⁿ¹ is a perfluoroalkyl group containing 1-5 carbon atoms; m2 is an integer from 0 to 3; X ⁿ¹ is F or CF ₃ and Y ⁰ is as defined above;

a compound represented by the following general formula (N ³ ):

where Rf ⁿ² is a partially or fully fluorinated alkyl group containing 1-13 carbon atoms and optionally containing an ether linkage; m3 is an integer from 1 to 3; Rf ⁿ³ is a linear or branched perfluoroalkylene group containing 1-3 carbon atoms; q is 0 or 1 and Y ⁰ is as defined above;

a compound represented by the following general formula (N ⁴ ):

where Rf ⁿ⁴ is a linear or branched, partially or fully fluorinated alkyl group containing from 1 to 12 carbon atoms and optionally containing an ether linkage and/or a chlorine atom and Y ⁿ¹ and Y ⁿ² are the same or different and each of them is H or F; p is 0 or 1; and

a compound represented by the general formula (N ⁵ ):

where X ⁿ² , X ⁿ³ and X ⁿ⁴ may be the same or different and each represents H, F or a linear or branched, partially or fully fluorinated alkyl group containing from 1 to 6 carbon atoms and optionally containing an ether linkage; Rf ⁿ⁵ represents a linear or branched, partially or fully fluorinated alkylene group containing from 1 to 3 carbon atoms and optionally containing an ether linkage; L represents a linking group and Y ⁰ has the meanings defined above, provided that the total number of carbon atoms in X ⁿ² , X ⁿ³ , X ⁿ⁴ and Rf ⁿ⁵ is 18 or less.

[0313] More specific examples of the compound represented by the general formula (N ⁰ ) include a perfluorocarboxylic acid (I) represented by the following general formula (I), an ω-H perfluorocarboxylic acid (II) represented by the following general formula (II), a perfluoroalkoxyfluorocarboxylic acid (III) represented by the following general formula (III), a perfluoroalkylalkylenecarboxylic acid (IV) represented by the following general formula (IV), a perfluoroalkoxyfluorocarboxylic acid (V) represented by the following general formula (V), a perfluoroalkylsulfonic acid (VI) represented by the following general formula (VI), an ω-H perfluorosulfonic acid (VII) represented by the following general formula (VII), a perfluoroalkylalkylenesulfonic acid (VIII) represented by the following general formula (VIII), an alkylalkylenecarboxylic acid (IX) represented by the following general formula (IX), a fluorocarboxylic acid (X) represented by the following general formula (X), an alkoxyfluorosulfonic acid (XI) represented by the following general formula (XI), a compound (XII) represented by the following general formula (XII), and a compound (XIII) represented by the following general formula (XIII).

[0314] Perfluorocarboxylic acid (I) is represented by the following general formula (I):

where n1 is an integer from 3 to 14 and M is H, a metal atom, NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent, where R ⁷ is H or an organic group.

[0315] ω-H perfluorocarboxylic acid (II) is represented by the following general formula (II):

where n2 is an integer from 4 to 15 and M is as defined above.

[0316] Perfluoroethercarboxylic acid (III) is represented by the following general formula (III):

where Rf ¹ is a perfluoroalkyl group containing 1-5 carbon atoms; n3 is an integer from 0 to 3 and M is as defined above.

[0317] Perfluoroalkylalkylenecarboxylic acid (IV) is represented by the following general formula (IV):

where Rf ² is a perfluoroalkyl group containing 1-5 carbon atoms; Rf ³ is a linear or branched perfluoroalkylene group containing 1-3 carbon atoms; n4 is an integer from 1 to 3 and M is as defined above.

[0318] Alkoxyfluorocarboxylic acid (V) is represented by the following general formula (V):

wherein Rf ⁴ is a linear or branched, partially or fully fluorinated alkyl group containing from 1 to 12 carbon atoms and optionally containing an ether linkage and/or a chlorine atom; Y ¹ and Y ² are the same or different and each of them is H or F and M is as defined above.

[0319] Perfluoroalkyl sulfonic acid (VI) is represented by the following general formula (VI):

where n5 is an integer from 3 to 14 and M is as defined above.

[0320] ω-H perfluorosulfonic acid (VII) is represented by the following general formula (VII):

where n6 is an integer from 4 to 14 and M is as defined above.

[0321] Perfluoroalkylalkylene sulfonic acid (VIII) is represented by the following general formula (VIII):

where Rf ⁵ is a perfluoroalkyl group containing 1-13 carbon atoms; n ⁷ is an integer from 1 to 3 and M is as defined above.

[0322] Alkyl alkylene carboxylic acid (IX) is represented by the following general formula (IX):

where Rf ⁶ is a linear or branched, partially or fully fluorinated alkyl group containing 1-13 carbon atoms and optionally containing an ether linkage; n8 is an integer from 1 to 3 and M is as defined above.

[0323] Fluorocarboxylic acid (X) is represented by the following general formula (X):

where Rf ⁷ is a linear or branched, partially or fully fluorinated alkyl group containing 1-6 carbon atoms and optionally containing an ether linkage and/or a chlorine atom; Rf ⁸ is a linear or branched, partially or fully fluorinated alkyl group containing 1-6 carbon atoms and M is as defined above.

[0324] Alkoxyfluorosulfonic acid (XI) is represented by the following general formula (XI):

wherein Rf ⁹ is a linear or branched, partially or fully fluorinated alkyl group containing 1-12 carbon atoms and optionally containing an ether linkage and optionally containing chlorine; Y ¹ and Y ² are the same or different and each represent H or F and M is as defined above.

[0325] Compound (XII) is represented by the following general formula (XII):

where X ¹ , X ² and X ³ are the same or different and represent H, F, and a linear or branched, partially or fully fluorinated alkyl group containing 1-6 carbon atoms and optionally containing an ether linkage; Rf ¹⁰ is a perfluoroalkylene group containing 1-3 carbon atoms; L is a linking group and Y ⁰ is an anionic group.

Y ⁰ may be -СООМ, -SO ₂ M, or -SO ₃ M, and may be -SO ₃ M or СООМ, where M is as defined above.

Examples of L include a single bond and a partially or fully fluorinated alkylene group containing 1 to 10 carbon atoms and optionally containing an ether linkage.

[0326] Compound (XIII) is represented by the following general formula (XIII):

where Rf ¹¹ is a fluoroalkyl group containing 1-5 carbon atoms and containing chlorine; n9 is an integer of 0-3; n10 is an integer of 0-3 and M is as defined above. An example of compound (XIII) is _CF2ClO (CF2CF( _{CF3 )} O) _n9 ( _CF2O ) _n10CF2COONH4 (a mixture having an average molecular weight of ₇₅₀ , n9 and _n10 in the formula are as described above).

[0327] As mentioned above, examples of the anionic fluorine-containing surfactant include a carboxylic acid-based surfactant and a sulfonic acid-based surfactant.

[0328] The fluorosurfactant may be a single type of fluorosurfactant or it may be a mixture containing two or more types of fluorosurfactants.

[0329] Examples of the fluorosurfactant include compounds represented by the formulas below. The fluorosurfactant may be a mixture of these compounds. In one embodiment of the polymerization, the fluoromonomer is polymerized in the substantial absence of compounds represented by the following formulas:

F(CF ₂ ) ₇ COOM,

F(CF ₂ ) ₅ COOM,

H(CF ₂ ) ₆ СООМ,

H(CF ₂ ) ₇ COOM,

CF ₃ O(CF ₂ ) ₃ OCHFCF ₂ COOM,

C ₃ F ₇ OCF(CF ₃ ) _c F ₂ OCF(CF ₃ ) COOM,

CF ₃ CF ₂ CF ₂ OCF(CF ₃ ) _with OOM,

CF ₃ CF ₂ OCF ₂ CF ₂ OCF ₂ COOM,

C ₂ F ₅ OCF(CF ₃ ) _c F ₂ OCF(CF ₃ ) _c OOM,

CF ₃ OCF(CF ₃ ) _with F ₂ OCF(CF ₃ ) _with OOM,

CF ₂ ClCF ₂ CF ₂ OCF(CF ₃ ) _c F ₂ OCF ₂ COOM,

CF ₂ ClCF ₂ CF ₂ OCF ₂ CF(CF ₃ )OCF ₂ COOM,

CF ₂ ClCF(CF ₃ )OCF(CF ₃ ) _with F ₂ OCF ₂ COOM and

CF ₂ ClCF(CF ₃ )OCF ₂ CF(CF ₃ )OCF ₂ COOM,

wherein in each formula M is H, a metal atom, NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent; and R ⁷ is H or an organic group.

[0330] An aqueous dispersion containing a fluoropolymer can be obtained by polymerization. The fluoropolymer is typically present at a concentration of 8 to 50% by weight in the aqueous dispersion obtained by polymerization. In the aqueous dispersion, the lower limit of the fluoropolymer concentration is preferably 10% by weight, more preferably 15% by weight, while the upper limit is preferably 40% by weight, and more preferably 35% by weight.

[0331] The fluoropolymer content of the aqueous dispersion is a value obtained by drying 1 g of the aqueous dispersion in an air dryer at 150°C for 60 minutes, measuring the mass of the non-volatile matter, and calculating the percentage of the mass of the non-volatile matter relative to the mass of the aqueous dispersion (1 g).

[0332] <Fluoropolymer>

According to the first method of production according to the present invention, a fluoropolymer is obtained in which the content of the polymerization unit derived from the perfluoromonomer in the fluoropolymer is 90% by mole or more relative to all polymerization units of the fluoropolymer. A fluoropolymer in which the content of the polymerization unit derived from the perfluoromonomer is 90% by mole or more does not include a partially fluorinated elastomer.

[0333] It is preferred that the fluoropolymer have an ion exchange ratio (IXR) greater than 53. A preferred fluoropolymer either contains no ionic groups at all or contains a limited number of ionic groups, resulting in an ion exchange ratio greater than about 100. The preferred ion exchange ratio of the fluoropolymer is preferably 1000 or more, more preferably 2000 or more, and even more preferably 5000 or more.

[0334] The fluorine substitution percentage in the fluoropolymer obtained by the first production method of the present invention is preferably from 90 to 100% by mass, and more preferably 95% by mass or more. The fluoropolymer may be a perfluoropolymer or a perfluoroelastomer.

[0335] The percentage of fluorine substitution can be calculated using the following equation.

Percent fluorine substitution (%) = (number of fluorine atoms bonded to the carbon atoms that make up the fluoropolymer) / ((number of hydrogen atoms bonded to the carbon atoms that make up the fluoropolymer) + (number of fluorine atoms and chlorine atoms bonded to the carbon atoms that make up the fluoropolymer)) × 100

[0336] Examples of the fluoropolymer obtained by the first production method of the present invention include polytetrafluoroethylene (PTFE); a fluororesin prepared from a melt such as a TFE/HFP copolymer (FEP), a TFE/ether (perfluoroalkyl vinyl ether) copolymer (PFA, MFA, etc.), a TFE/ether (perfluoroalkyl allyl ether) copolymer and an electrolyte precursor polymer; and a perfluoroelastomer.

[0337] Among them, the fluoropolymer is preferably at least one polymer selected from the group consisting of PTFE and a perfluoroelastomer.

[0338] The fluoropolymer may have a core-shell structure. An example of a fluoropolymer having a core-shell structure is PTFE comprising a core of high molecular weight PTFE and a shell of PTFE with a lower molecular weight or modified PTFE in a particle. An example of such PTFE is PTFE described in National Publication of International Patent Application No. 2005-527652.

[0339] The core-shell structure may have the following structures

Core: TFE homopolymer, shell: TFE homopolymer Core: modified PTFE, shell: TFE homopolymer

Core: modified PTFE, shell: modified PTFE

Core: TFE homopolymer, shell: modified PTFE

Core: low molecular weight PTFE, shell: high molecular weight PTFE

Core: high molecular weight PTFE, shell: low molecular weight PTFE

[0340] In the fluoropolymer having a core-shell structure, the lower limit of the core proportion is preferably 0.5% by mass, more preferably 1.0% by mass, even more preferably 3.0% by mass, particularly preferably 5.0% by mass, and most preferably 10.0% by mass. The upper limit of the core proportion is preferably 99.5% by mass, more preferably 99.0% by mass, even more preferably 98.0% by mass, even more preferably 97.0% by mass, particularly preferably 95.0% by mass, and most preferably 90.0% by mass.

[0341] In the fluoropolymer having a core-shell structure, the lower limit of the shell proportion is preferably 0.5 mass%, more preferably 1.0 mass%, even more preferably 3.0 mass%, particularly preferably 5.0 mass%, and most preferably 10.0 mass%. The upper limit of the shell proportion is preferably 99.5 mass%, more preferably 99.0 mass%, even more preferably 98.0 mass%, even more preferably 97.0 mass%, particularly preferably 95.0 mass%, and most preferably 90.0 mass%.

[0342] In a fluoropolymer having a core-shell structure, the core or shell may consist of two or more layers. For example, the fluoropolymer may have a three-layer structure comprising a central core portion of modified PTFE, a portion of the outer core layer of a TFE homopolymer, and a shell of modified PTFE.

[0343] Examples of a fluoropolymer having a core-shell structure also include structures in which a single fluoropolymer particle has a plurality of cores.

[0344] The above-mentioned (I) PTFE, (II) melt-processable fluororesin, and (III) perfluoroelastomer, respectively obtained by the production method of the present invention, are preferably obtained as follows.

[0345] (I) PTFE

In the first production method of the present invention, PTFE (TFE polymer) can be obtained as a fluoropolymer by polymerizing TFE as a perfluoromonomer. PTFE is preferably non-melting PTFE.

[0346] In the production method of the present invention, the polymerization of TFE is usually carried out at a polymerization temperature of 10 to 150°C and a polymerization pressure of 0.05 to 5 MPaG. For example, the polymerization temperature is more preferably 30°C or higher, and even more preferably 50°C or higher. In addition, the polymerization temperature is more preferably 120°C or lower, and even more preferably 100°C or lower. In addition, the polymerization pressure is more preferably 0.3 MPaG or higher, even more preferably 0.5 MPaG or higher, more preferably 5.0 MPaG or lower, and even more preferably 3.0 MPaG or lower. In particular, from the viewpoint of improving the yield of the fluoropolymer, the polymerization pressure is preferably 1.0 MPaG or higher, more preferably 1.2 MPaG or higher, even more preferably 1.5 MPaG or higher, and more preferably 2.0. MPa excess or higher.

[0347] In one embodiment, the polymerization reaction is initiated by loading pure water into a high-pressure reaction vessel equipped with a stirrer, a deoxidation system, loading TFE, raising the temperature to a predetermined level, and adding a polymerization initiator. As the pressure decreases as the reaction progresses, additional TFE is fed continuously or intermittently to maintain the initial pressure. When the amount of TFE fed reaches the predetermined level, the feed is stopped, and then the TFE in the reaction vessel is purged and the temperature is returned to room temperature, resulting in the completion of the reaction. Additional TFE can be added continuously or intermittently to prevent a pressure drop.

[0348] In producing a TFE (PTFE) polymer, various known modifying monomers can be used in combination. The TFE polymer of the present invention is a concept that encompasses not only a TFE homopolymer, but also a non-melting TFE copolymer and a modifying monomer (hereinafter referred to as "modified PTFE").

[0349] The modifying monomer may be any modifying monomer copolymerizable with TFE, and examples thereof include a fluoromonomer and a monomer other than a fluoromonomer. Furthermore, one or more kinds of modifying monomers may be used.

[0350] An example of a monomer other than a fluoromonomer includes, but is not limited to, a monomer represented by the general formula:

CH ₂ =CR ^Q1 -LR ^Q2

where R ^Q1 represents a hydrogen atom or an alkyl group; L represents a single bond -CO-O-*, -O-CO-*, or -O-; * represents the bond position with R ^Q2 ; and R ^Q2 represents a hydrogen atom, an alkyl group, or a nitrile group.

[0351] Examples of the monomer other than the fluoromonomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, vinyl methacrylate, vinyl acetate, acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, ethyl vinyl ether, and cyclohexyl vinyl ether. Of these, the monomer other than the fluoromonomer is preferably butyl methacrylate, vinyl acetate, or acrylic acid.

[0352] Examples of the fluoromonomer include perfluoroolefins such as hexafluoropropylene (HFP); hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF); perhaloolefins such as chlorotrifluoroethylene; perfluorovinyl ethers; (perfluoroalkyl)ethylenes; and perfluoroallyl ethers.

[0353] Examples of the perfluorovinyl ether include, but are not limited to, a perfluoro-unsaturated compound represented by the following general formula (A):

where Rf represents a perfluoroorganic group. "Perfluoroorganic group" as used herein means an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The perfluoroorganic group optionally contains an etheric oxygen.

[0354] Examples of the perfluorovinyl ether include a (perfluoroalkyl vinyl ether) (PAVE) in which Rf is a perfluoroalkyl group containing 1 to 10 carbon atoms in the general formula (A). The perfluoroalkyl group preferably contains 1 to 5 carbon atoms.

[0355] Examples of a simple perfluoroalkyl group in PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group.

[0356] Examples of the perfluorovinyl ether also include: ethers represented by the general formula (A) in which Rf is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms; ethers in which Rf is a group represented by the following formula:

[0357]

[0358] where m is 0 or an integer from 1 to 4; and those in which Rf is a group represented by the following formula:

[0359] CF ₃ CF ₂ CF ₂ -(O-CF(CF ₃ )-CF ₂ ) _n -

where n is an integer from 1 to 4.

[0360] Examples of the hydrogen-containing fluoroolefin include _CH2 = _CF2 , CFH= _CH2 , CFH= _CF2 , _CH2 = _CFCF3 , _CH2 = _CHCF3 , CHF= _CHCF3 (E isomer), and CHF= _CHCF3 (Z isomer).

[0361] Examples of (perfluoroalkyl)ethylene (PFAE) include, but are not limited to, (perfluorobutyl)ethylene (PFBE) and (perfluorohexyl)ethylene.

[0362] An example of a simple perfluoroallyl ether is a fluoromonomer represented by the general formula:

CF ₂ =CF-CF ₂ -ORf

where Rf represents the perfluoroorganic group.

[0363] Rf in the above general formula is the same as Rf in the general formula (A). Rf is preferably a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluoroalkoxyalkyl group having 1 to 10 carbon atoms. The perfluoroallyl ether is preferably at least one ether selected from the group consisting of _CF2 =CF- _CF2 - _O - _CF3 , _CF2 =CF- _CF2 - _OC2F5 , _{CF2 =} CF-CF2- _OC3F7 , and _CF2 =CF- _{CF2 - OC4F9} , more preferably at least one ether selected from the group consisting of _CF2 =CF- _CF2 - _OC2F5 , _CF2 =CF- _CF2 - _OC3F7 , and _CF2 =CF- _{CF2 - OC4F9 ,} and even more preferably _CF2 = _{CF-CF2 - O - CF2CF2CF3 .}

[0364] The modifying monomer is also preferably a modifying monomer (3) having a monomer reactivity ratio of 0.1 to 8. The presence of the modifying monomer (3) makes it possible to obtain PTFE particles having a small particle size and thereby obtain an aqueous dispersion having high dispersion stability.

[0365] Here, the ratio of monomer reactivities in copolymerization with TFE is a value obtained by dividing the rate constant in the case where the propagating radicals react with TFE by the rate constant in the case where the propagating radicals react with the modifying monomers, in the case where the propagating radicals are fewer than the repeating units derived from TFE. A lower ratio of monomer reactivities indicates a higher reactivity of the modifying monomers with TFE. The ratio of monomer reactivities can be determined by copolymerizing TFE with modifying monomers that determine the compositional features of the polymer formed immediately after initiation and calculating the ratio of monomer reactivities using the Fineman-Ross equation.

[0366] The copolymerization is carried out using 3600 g of deionized degassed water, 1000 ppm by weight of ammonium perfluorooctanoate relative to water and 100 g of paraffin wax contained in a stainless steel autoclave with an internal volume of 6.0 L at a pressure of 0.7 8 MPa g and a temperature of 70°C. The modifying monomer is added to the reactor in an amount of 0.05 g, 0.1 g, 0.2 g, 0.5 g or 1.0 g, followed by 0.072 g of ammonium persulfate (20 ppm by weight relative to water). TFE is continuously introduced into the reactor to maintain the polymerization pressure at 0.78 MPa g. When the charged amount of TFE reaches 1000 g, stirring is stopped and the pressure is released until the pressure in the reactor decreases to atmospheric pressure. After cooling, the paraffin wax is separated to yield an aqueous dispersion containing the resulting polymer. The aqueous dispersion is stirred until the resulting polymer coagulates and then dried at 150°C. The compositional properties of the resulting polymer are determined using an appropriate combination of NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis, depending on the monomer types.

[0367] The modifying monomer (3) having a monomer reactivity ratio of 0.1 to 8 is preferably at least one monomer selected from the group consisting of modifying monomers represented by formulas (3a) to (3d):

where Rf ¹ is a perfluoroalkyl group containing 1-10 carbon atoms;

where Rf ² is a perfluoroalkyl group containing 1-2 carbon atoms;

where n is 1 or 2; and

[0368]

where each of X ³ and X ⁴ is F, Cl or a methoxy group and Y is represented by the formula Y ¹ or Y ² ;

[0369]

in formula Y ^2, each of Z and Z' represents F or a fluorinated alkyl group containing from 1 to 3 carbon atoms.

[0370] The content of the modifying unit of the monomer (3) is preferably in the range of 0.00001 to 1.0 mass % with respect to all polymerization units in PTFE. The lower limit thereof is more preferably 0.0001 mass %, more preferably 0.0005 mass %, still more preferably 0.001 mass %, still more preferably 0.005 mass %. The upper limit is, in order of preference, 0.90 mass %, 0.50 mass %, 0.40 mass %, 0.30 mass %, 0.20 mass %, 0.15 mass %, 0.10 mass %, 0.08 mass %, 0.05 mass % or 0.01 mass %.

[0371] The modifying monomer is preferably at least one monomer selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, (perfluoroalkyl vinyl ethers), (perfluoroalkyl)ethylenes, ethylene and modifying monomers containing a functional group capable of reacting by radical polymerization and a hydrophilic group, in order to obtain an aqueous dispersion with a small average primary particle size, a small aspect ratio of the primary particles and excellent stability. The use of the modifying monomer makes it possible to obtain an aqueous PTFE dispersion with a smaller average primary particle size, a small aspect ratio of the primary particles and excellent dispersion stability, and it is also possible to obtain an aqueous dispersion with a small amount of uncoagulated polymer.

[0372] From the viewpoint of reactivity with respect to TFE, the modifying monomer preferably contains at least one monomer selected from the group consisting of hexafluoropropylene, (perfluoroalkyl vinyl ether) and (perfluoroalkyl)ethylene.

More preferably, the modifying monomer comprises at least one monomer selected from the group consisting of hexafluoropropylene, (perfluoromethyl vinyl ether), (perfluoropropyl vinyl ether), (perfluorobutyl)ethylene, (perfluorohexyl)ethylene and (perfluorooctyl)ethylene.

The total amount of the hexafluoropropylene unit, the (perfluoroalkyl vinyl ether) unit and the (perfluoroalkyl)ethylene unit is preferably in the range of 0.00001 to 1% by mass with respect to all polymerization units in PTFE. The lower limit of their total amount is more preferably 0.0001% by mass, more preferably 0.0005% by mass, even more preferably 0.001% by mass, and still more preferably 0.005% by mass. The upper limit is, in order of preference, 0.80% by mass, 0.70% by mass, 0.50% by mass, 0.40% by mass, 0.30% by mass, 0.20% by mass, 0.15% by mass, 0.10% by mass, 0.08% by mass, 0.05% by mass or 0.01% by mass.

[0373] The modifying monomer preferably includes a modifying monomer containing a functional group capable of reacting through radical polymerization and a hydrophilic group (hereinafter referred to as “modifying monomer (A)”).

[0374] The presence of the modifying monomer (A) makes it possible to obtain PTFE particles having a small primary particle size, and thereby to obtain an aqueous dispersion having high dispersion stability. It is also possible to reduce the amount of uncoagulated polymer. In addition, it is possible to reduce the aspect ratio of the primary particles.

[0375] The amount of the modifying monomer (A) used is preferably an amount exceeding an amount equivalent to 0.1 ppm by mass of the aqueous medium, more preferably an amount exceeding 0.5 ppm by mass, still more preferably an amount exceeding 1.0 ppm by mass, more preferably 5 ppm by mass or more, and particularly preferably 10 ppm by mass or more. When the amount of the modifying monomer (A) used is too small, the average primary particle size of the obtained PTFE may not be small enough.

The amount of modifying monomer (A) used may be within the range specified above, but, for example, the upper limit may be set at 5000 ppm by weight. In the production method, the modifying monomer (A) may also be added to the system during the reaction to improve the stability of the aqueous dispersion during or after the reaction.

[0376] Since the modifying monomer (A) has high water solubility, even if unreacted modifying monomer (A) remains in the aqueous dispersion, it can be easily removed in the concentration step or in the coagulation and washing steps.

[0377] The modifying monomer (A) is incorporated into the obtained polymer during the polymerization process, but since the concentration of the modifying monomer (A) in the polymerization system itself is low and the amount incorporated into the polymer is small, there is no problem of heat resistance of PTFE or color change after sintering.

[037 8] Examples of the hydrophilic group in the modifying monomer (A) include -NH ₂ , -PO ₃ M, -OPO ₃ M, -SO ₃ M, -OSO ₃ M and -COOM, wherein M is H, a metal atom, NR ⁷ ₄ , imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein R ^7y are H or an organic group and may be the same or different, and any two of these residues can bond to each other to form a ring. Of these, the hydrophilic group is preferably -SO ₃ M or -COOM. The organic group in R ^7y is preferably an alkyl group. R ^7y is preferably H or a C _1-10 organic group, more preferably H or a C _1-4 organic group, and even more preferably H or a C _1-4 alkyl group.

Examples of the metal atom include atoms of monovalent and divalent metals, alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K or Li are preferred.

[0379] Examples of the "functional group capable of reacting through radical polymerization" in the modifying monomer (A) include groups having an ethylenically unsaturated bond, such as a vinyl group or an allyl group. The group containing an ethylenically unsaturated bond can be represented by the following formula:

CX ^e X ^g =CX ^f R-

where X ^e , X ^{f ,} and X ^g each independently represent F, Cl, H, CF ₃ , CF ₂ H, CFH ₂ , or CH ₃ ; and R represents a linking group. Examples of the linking group R include the linking group R ^a , described below. Preferred are groups containing an unsaturated bond such as -CH=CH ₂ , -CF=CH ₂ , -CH=CF ₂ , -CF=CF ₂ , -CH ₂ -CH=CH ₂ , -CF ₂ -CF=CH ₂ , -CF ₂ -CF=CF ₂ , - (C=O)-CH=CH ₂ , -(C=O)-CF=CH ₂ , -(C=O)-CH=CF ₂ , -(C=O)-CF=CF ₂ , -(C=O)-C(CH ₃ )=CH ₂ , -(C=O)-C(CH ₃ )=CF ₂ , -(C=O)-C(CF ₃ )=CF ₂ , -(C=O)-C(CF ₃ )=CF ₂ , -O-CH ₂ -CH=CH ₂ , -O-CF ₂ -CF=CH ₂ , -O-CH ₂ -CH=CF ₂ and -O-CF ₂ -CF=CF ₂ .

[0380] Since the modifying monomer (A) contains a functional group capable of reacting via radical polymerization, it is assumed that when used during polymerization, it reacts with the fluorine-containing monomer at the initial stage of the polymerization reaction to form particles that contain a hydrophilic group derived from the modifying monomer (A) and have high stability. Thus, it is believed that polymerization in the presence of the modifying monomer (A) leads to an increase in the number of particles.

[0381] The polymerization can be carried out in the presence of one type of modifying monomer (A) or in the presence of two or more types thereof.

[0382] In polymerization, a compound containing an unsaturated bond can be used as a modifying monomer (A).

[0383] The modifying monomer (A) is preferably a compound represented by the general formula (4):

where X ⁱ , X ^j and X ^k each independently represent F, Cl, H or CF ₃ ; Y ³ represents a hydrophilic group; ^Ra represents a linking group; Z ¹ and Z ² each independently represent H, F or CF ₃ and k is 0 or 1.

Examples ^{of the hydrophilic group include -NH2, -PO3M, -OPO3M, -SO3M, -OSO3M and -COOM, wherein M is H, a metal atom, NR7y4} _{, imidazolium optionally having a substituent} , pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein ^R7y are H or an organic group and may be the same or different, and any two of these residues can bond to each other to form a ring. Of these, the hydrophilic group is preferably _-SO3M or -COOM. The organic group in ^R7y is preferably an alkyl group. ^R7y is preferably H or a _C1-10 organic group, more preferably H or a _C1-4 organic group, and even more preferably H or a _C1-4 alkyl group. Examples of the metal atom include atoms of monovalent and divalent metals, alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K or Li are preferred.

The use of a modifying monomer (A) allows for the production of an aqueous dispersion with a smaller average primary particle size and superior stability. The aspect ratio of the primary particles can also be reduced.

[0384] R ^a is a linking group. In the present invention, the term "linking group" refers to a divalent linking group. The linking group may be a single bond and preferably contains at least one carbon atom, and the number of carbon atoms may be 2 or more, 4 or more, 8 or more, 10 or more, or 20 or more. Its upper limit is not limited and may be, for example, 100 or less, and may also be 50 or less.

The linking group may be linear or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen, and nitrogen, and optionally contains one or more functional groups selected from the group consisting of esters, amides, sulfonamides, carbonyls, carbonates, urethanes, ureas, and carbamates. The linking group may not contain carbon atoms and may be a catenary heteroatom such as oxygen, sulfur, or nitrogen.

[0385] R ^a is preferably a catenary heteroatom such as oxygen, sulfur or nitrogen, or a divalent organic group.

When R ^a is a divalent organic group, the hydrogen atom bonded to the carbon atom may be replaced by a halogen other than fluorine, such as chlorine, and may or may not contain a double bond. Furthermore, R ^a may be linear or branched and may be cyclic or acyclic. R ^a may also contain a functional group (e.g., ester, ether, ketone, amine, halide, etc.).

R ^a may also be a non-fluorinated divalent organic group or a partially fluorinated or perfluorinated divalent organic group.

R ^a may be, for example, a hydrocarbon group in which a fluorine atom is not bonded to a carbon atom, a hydrocarbon group in which some hydrogen atoms bonded to a carbon atom are changed by fluorine atoms, a hydrocarbon group in which all hydrogen atoms bonded to carbon atoms are changed by fluorine atoms, -(C=O)-, -(C=O)-O-, or a hydrocarbon group containing an ether bond, and these groups optionally contain an oxygen atom, optionally contain a double bond, and optionally contain a functional group.

[0386] R ^a is preferably -(C=O)-, (C=O)-O-, or a hydrocarbon group containing from 1 to 100 carbon atoms, which optionally contains an ether linkage and optionally contains a carbonyl group, wherein some or all of the hydrogen atoms bonded to the carbon atoms in the hydrocarbon group may be replaced by fluorine.

R ^a preferably represents at least one residue selected from - (CH ₂ ) _a -, - (CF ₂ ) _a -, -O-(CF ₂ ) _a -, - (CF ₂ ) _a -O-(CF ₂ ) _b -, -O(CF ₂ ) _a -O-(CF ₂ ) _b -, - (CF ₂ ) _a -[O-(CF ₂ ) _b ] _c -, -O(CF ₂ ) _a -[O-(CF ₂ ) _b ]c-, -[(CF ₂ ) _a -O]b-[(CF ₂ ) _c -O] _d -, -O[(CF ₂ ) _a -O]b-[(CF ₂ ) _c -O] _d -, -O-[CF ₂ CF(CF ₃ )O] _a - (CF ₂ ) _b -, -(C=O)-, -(C=O)-O-, -(C=O)-(CH ₂ ) _a -, -(C=O)-(CF ₂ ) _a -, -(C=O)-O-(CH ₂ ) _a -, - (C=O)-O-(CF ₂ ) _a -, -(C=O)-[(CH ₂ ) _a -O] _b -, -(C=O)-[(CF ₂ ) _a -O] _b -, -(C=O)-O[(CH ₂ ) _a -O] _b -, -(C=O)-O[(CF ₂ ) _a -O] _b -, -(C=O)-O[(CH ₂ ) _a -O]b-(CH ₂ ) _c -, -(C=O)-O[(CF ₂ ) _a -O] _b -(CF ₂ ) _c -, -(C=O)-(CH ₂ ) _a -O-(CH ₂ ) _b -, - (C=O)-(CF ₂ ) _a -O-(CF ₂ ) _b -, -(C=O)-O-(CH ₂ ) _a -O-(CH ₂ ) _b -, -(C=O)-O-(CF ₂ ) _a -O-(CF ₂ ) _b -, -(C=O)-OC ₆ H ₄ - and their combinations.

In the formula, a, b, c, and d are independently at least 1 or more, and a, b, c, and d may independently be 2 or more, 3 or more, 4 or more, 10 or more, or 20 or more. For example, the upper limits of a, b, c, and d are 100.

[0387] Specific examples of residues useful as ^Ra include -CF ₂ -O-, -CF ₂ -O-CF ₂ -, -CF ₂ -O-CH ₂ -, -CF ₂ -O-CH ₂ CF ₂ -, -CF ₂ -O-CF ₂ CF ₂ -, -CF ₂ -O-CF ₂ CH ₂ -, -CF ₂ -O-CF ₂ CF ₂ CH ₂ -, -CF ₂ -O-CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ ) _c F ₂ -, -CF ₂ -O-CF(CF ₃ ) _c F ₂ -O-, -CF ₂ -O-CF(CF ₃ )CH ₂ -, -(C=O)-, -(C=O)-O-, -(C=O)-(CH ₂ )-, -(C=O)-(CF ₂ )-, -(C=O)-O-(CH ₂ )-, -(C=O)-O-(CF ₂ )-, -(C=O)-[(CH ₂ ) ₂ -O] _n -, -(C=O)-[(CF ₂ ) ₂ -O] _n -, -(C=O)-O[(CH ₂ ) ₂ -O] _n -, -(C=O)-O[(CF ₂ ) ₂ -O] _n -, -(C=O)-O[(CH ₂ ) ₂ -O] _n -(CH ₂ )-, -(C=O)-O[(CF ₂ ) ₂ -O] _n -(CF ₂ )-, -(C=O)-(CH ₂ ) ₂ -O-(CH ₂ )-, -(C=O)-(CF ₂ ) ₂ -O-(CF ₂ )-, -(C=O)-O-(CH ₂ ) ₂ -O-(CH ₂ )-, -(C=O)-O-(CF ₂ ) ₂ -O-(CF ₂ )- and -(C=O)-OC ₆ H ₄ -. In particular, preferred as R ^a among them are -CF ₂ -O-, -CF ₂ -O-CF ₂ -, -CF ₂ -O-CF ₂ CF ₂ -, -CF ₂ -O-CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ ) _c F ₂ -, -CF ₂ -O-CF(CF ₃ ) _c F ₂ -O-, -(C=O)-, -(C=O)-O-, -(C=O)-(CH ₂ )-, -(C=O)-O-(CH ₂ )-, -(C=O)-O[(CH ₂ ) ₂ -O] _n -, -(C=O)-O[(CH ₂ ) ₂ -O] _n -(CH ₂ )-, -(C=O)-(CH ₂ ) ₂ -O-(CH ₂ )- or - (C=O)-OC ₆ H ₄ -.

In the formula, n is an integer between 1 and 10.

[0388] -R ^a -(CZ ¹ Z ² ) _k - in the general formula (4) is preferably -CF ₂ -O-CF ₂ -, -CF ₂ -O-CF(CF ₃ )-, -CF ₂ -OC(CF ₃ ) ₂ -, -CF ₂ -O-CF ₂ -CF ₂ -, -CF ₂ -O-CF ₂ -CF(CF ₃ )-, -CF ₂ -O-CF ₂ -C(CF ₃ ) ₂ -, -CF ₂ -O-CF ₂ CF ₂ -CF ₂ -, -CF ₂ -O-CF ₂ CF ₂ -CF(CF ₃ )-, -CF ₂ -O-CF ₂ CF ₂ -C(CF ₃ ) ₂ -, -CF ₂ -O-CF(CF ₃ )-CF ₂ -, -CF ₂ -O-CF(CF ₃ )-CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ )-C(CF ₃ ) ₂ -, CF ₂ -O-CF(CF ₃ )CF ₂ -CF ₂ -, -CF ₂ -O-CF(CF ₃ )CF ₂ -CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ )CF ₂ -C(CF ₃ ) ₂ -, -CF ₂ -O-CF(CF ₃ ) CF ₂ -O-CF ₂ -, -CF ₂ -O-CF(CF ₃ )CF ₂ -O-CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ )CF ₂ -OC(CF ₃ ) ₂ -, -(C=O)-, -(C=O)-O-, (C=O)-(CH ₂ )-, -(C=O)-(CF ₂ )-, -(C=O)-O-(CH ₂ )-, -(C=O)-O-(CF ₂ )-, -(C=O)-[(CH ₂ ) ₂ -O] _n -(CH ₂ )-, -(C=O)-[(CF ₂ ) ₂ -O] _n -(CF ₂ )-, -(C=O)-[(CH ₂ ) ₂ -O] _n -(CH ₂ )-(CH ₂ )-, -(C=O)-[(CF ₂ ) ₂ -O] _n -(CF ₂ )-(CF ₂ )-, -(C=O)-O[(CH ₂ ) ₂ -O] _n -(CF ₂ )-, -(C=O)-O[(CH ₂ ) ₂ -O] _n -(CH ₂ )-(CH ₂ )-, -(C=O)-O[(CF ₂ ) ₂ -O] _n -(CF ₂ )-, -(C=O)-O[(CF ₂ ) ₂ -O] _n -(CF ₂ )-(CF ₂ )-, - (C=O)-(CH ₂ ) ₂ -O-(CH ₂ )-(CH ₂ )-, -(C=O)-(CF ₂ ) ₂ -O-(CF ₂ )-(CF ₂ )-, - (C=O)-O-(CH ₂ ) ₂ -O-(CH ₂ )-(CH ₂ )-, -(C=O)-O-(CF ₂ ) ₂ -O-(CF ₂ )-(CF ₂ )-, -(C=O)-O-(CH ₂ ) ₂ -O-(CH ₂ )-C(CF ₃ ) ₂ -, -(C=O)-O-(CF ₂ ) ₂ -O-(CF ₂ )-C(CF ₃ ) ₂ -, or -(C=O)-O-C ₆ H ₄ -C(CF ₃ ) ₂ -, and more preferably -CF ₂ -O-CF(CF ₃ )-, -CF ₂ -O-CF ₂ -CF(CF ₃ )-, -CF ₂ -O-CF ₂ CF ₂ -CF(CF ₃ )-CF ₂ -O-CF(CF ₃ )-CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ )CF ₂ -CF(CF ₃ )-, -CF ₂ -O-CF(CF ₃ )CF ₂ -O-CF(CF ₃ )-, -(C=O)-, -(C=O)-O-(CH ₂ )-, -(C=O)-O-(CH ₂ )-(CH ₂ )-, -(C=O)-O[(CH ₂ ) ₂ -O] _n -(CH ₂ )-(CH ₂ )-, -(C=O)-O-(CH ₂ ) ₂ -O-(CH ₂ )-C(CF ₃ ) ₂ - or -(C=O)-OC ₆ H ₄ -C(CF ₃ ) ₂ -.

In the formula, n is an integer between 1 and 10.

[0389] Specific examples of the compound represented by the general formula (4) include compounds represented by the following formulas:

where X ^j and Y ³ are as described above; and n is an integer from 1 to 10.

[0390] R ^a is preferably a divalent group represented by the general formula (r1):

wherein each X ⁶ is independently H, F or CF ₃ ; e is an integer from 0 to 3; f is an integer from 0 to 3; g is 0 or 1; h is 0 or 1; and i is 0 or 1, and also preferably represents a divalent group represented by the general formula (r2):

where each X ⁷ is independently H, F, or CF ₃ ; e is an integer from 0 to 3; g is 0 or 1; h is 0 or 1; and i is 0 or 1.

[0391] -R ^a -(CZ ¹ Z ² ) _k - in the general formula (4) is also preferably a divalent group represented by the following formula (t1):

wherein each X ⁶ independently represents H, F or CF ₃ ; e represents an integer from 0 to 3; f represents an integer from 0 to 3; g is 0 or 1; h is 0 or 1; i is 0 or 1; and each of Z ¹ and Z ² independently represents F or CF ₃ , and more preferably represents a group in which one of Z ¹ and Z ² represents F and the other represents CF ₃ in formula (t1).

Also, in the general formula (4), -R ^a -(CZ ¹ Z ² ) _k - is preferably a divalent group represented by the following formula (t2):

wherein each X ⁷ is independently H, F or CF ₃ ; e is an integer from 0 to 3; g is 0 or 1; h is 0 or 1; i is 0 or 1; and each Z ¹ and Z ² is independently F or CF ₃ , and more preferably is a group in which one residue of Z ¹ and Z ² is F and the other is CF ₃ in formula (t2).

[0392] The compound represented by the general formula (4) also preferably contains a CF bond and does not contain a CH bond in the portion not containing a hydrophilic group (Y ³ ). In other words, in the general formula (4), X ⁱ , X ^j , and X ^k are all F, and R ^a is preferably a perfluoroalkylene group containing 1 or more carbon atoms; the perfluoroalkylene group may be either linear or branched, may be cyclic or acyclic, and may contain at least one catenary heteroatom. The perfluoroalkylene group may contain from 2 to 20 carbon atoms or from 4 to 18 carbon atoms.

[0393] The compound represented by the general formula (4) may be partially fluorinated. In other words, the compound represented by the general formula (4) also preferably contains at least one hydrogen atom bonded to a carbon atom and at least one fluorine atom bonded to a carbon atom in the portion not containing the hydrophilic group (Y3).

[0394] The compound represented by the general formula (4) is also preferably a compound represented by the following formula (4a):

where Y ³ is a hydrophilic group; and Rf ⁰ is a perfluorinated divalent linking group, which is perfluorinated and may be linear or branched, cyclic or acyclic, saturated or unsaturated, substituted or unsubstituted, and optionally contains one or more heteroatoms selected from the group consisting of sulfur, oxygen and nitrogen.

[0395] The compound represented by the general formula (4) is also preferably a compound represented by the following formula (4b):

where Y ³ is a hydrophilic group; and Rf ⁰ is a perfluorinated divalent linking group defined in formula (4a)

[0396] In the general formula (4), Y ³ is preferably -OSO ₃ M. Examples of the compound represented by the general formula (4) when Y ³ is -OSO ₃ M include CF ₂ =CF(OCF ₂ CF ₂ CH ₂ OSO ₃ M), CH ₂ =CH((CF ₂ ) ₄ CH ₂ OSO ₃ M), CF ₂ =CF(O(CF ₂ ) ₄ CH ₂ OSO ₃ M), CF ₂ =CF(OCF ₂ CF(CF ₃ )CH ₂ OSO ₃ M), CF ₂ =CF(OCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CH ₂ OSO ₃ M), CH ₂ =CH((CF ₂ ) ₄ CH ₂ OSO ₃ M), CF ₂ =CF(OCF ₂ CF ₂ SO ₂ N(CH ₃ )CH ₂ CH ₂ OSO ₃ M), CH ₂ =CH(CF ₂ CF ₂ CH ₂ OSO ₃ M) and CF ₂ =CF(OCF ₂ CF ₂ CF ₂ CF ₂ SO ₂ N(CH ₃ )CH ₂ CH ₂ OSO ₃ M). In the formula, M is as described above.

[0397] In the general formula (4), Y ³ is preferably -SO ₃ M. Examples of the compound represented by the general formula (4) when Y ³ is -SO ₃ M include CF ₂ =CF(OCF ₂ CF ₂ SO ₃ M), CF ₂ =CF(O(CF ₂ ) ₄ SO ₃ M), CF ₂ =CF(OCF ₂ CF(CF ₃ )SO ₃ M), CF ₂ =CF(OCF ₂ CF(CF ₃ )OCF ₂ CF ₂ SO ₃ M), CH ₂ =CH(CF ₂ CF ₂ SO ₃ M), CF ₂ =CF(OCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CF ₂ CF ₂ SO ₃ M), CH ₂ =CH((CF ₂ ) ₄ SO ₃ M) and CH ₂ =CH((CF ₂ ) ₃ SO ₃ M). In the formula, M is as described above.

[0398] In the general formula (4), Y ³ is preferably -COOM. Examples of the compound represented by the general formula (4) when Y ³ is -COOM include CF ₂ =CF(OCF ₂ CF ₂ COOM), CF ₂ =CF(OCF ₂ CF ₂ CF ₂ COOM), CF ₂ =CF(O(CF ₂ ) ₅ COOM), CF ₂ =CF(OCF ₂ CF(CF ₃ )COOM), CF ₂ =CF(OCF ₂ CF(CF ₃ )O(CF ₂ ) _n COOM) (n is greater than 1), CH ₂ =CH((CF ₂ ) ₄ COOM), CH ₂ =CH(CF ₂ CF ₂ COOM), CH ₂ =CH((CF ₂ ) ₃ COOM), CF ₂ =CF(OCF ₂ CF ₂ SO ₂ NR'CH ₂ COOM), CF ₂ =CF(O(CF ₂ ) ₄ SO ₂ NR'CH ₂ COOM), CF ₂ =CF(OCF ₂ CF(CF ₃ )SO ₂ NR'CH ₂ COOM), CF ₂ =CF(OCF ₂ CF ₍ CF ₃ )OCF ₂ CF ₂ SO ₂ NR'CH ₂ COOM), CF ₂ =CF(OCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CF ₂ SO ₂ NR'CH ₂ COOM), CH ₂ =CH((CF ₂ ) ₄ SO ₂ NR'CH ₂ COOM), CH ₂ =CH(CF ₂ CF ₂ SO ₂ NR'CH ₂ COOM) and CH ₂ =CH((CF ₂ ) ₃ SO ₂ NR'CH ₂ COOM). In the formula, R' represents H or a C _1-4 alkyl group and M is as described above.

[0399] In the general formula (4), Y ³ is preferably -OPO ₃ M or -OP(O)(OM) ₂ . Examples of the compound represented by the general formula (4) when Y ³ is -OPO ₃ M or OP(O)(OM) ₂ include CF ₂ =CF(OCF ₂ CF ₂ CH ₂ OP(O)(OM) ₂ ), CF ₂ =CF(O(CF ₂ ) ₄ CH ₂ OP(O)(OM) ₂ ), CF ₂ =CF(OCF ₂ CF(CF ₃ )CH ₂ OR(O)(OM) ₂ ), CF ₂ =CF(OCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CH ₂ OP(O)(OM) ₂ ), CF ₂ =CF(OCF ₂ CF ₂ SO ₂ N(CH ₃ ) _c H ₂ CH ₂ OP(O)(OM) ₂ ), CF ₂ =CF(OCF ₂ CF ₂ CF ₂ CF ₂ SO ₂ N(CH ₃ ) _c H ₂ CH ₂ OP(O)(OM) ₂ ), CH ₂ =CH(CF ₂ CF ₂ CH ₂ OP(O)(OM) ₂ , CH ₂ =CH((CF ₂ ) ₄ CH ₂ OP(O)(OM) ₂ ) and CH ₂ =CH((CF ₂ ) ₃ CH ₂ OP(O)(OM) ₂ ). In the formula, M is as described above.

[04 00] In the general formula (4), Y ³ is preferably -PO ₃ M or -P(O)(OM) ₂ . Examples of the compound represented by the general formula (4) when ^Y3 is _-PO3M or P(O)(OM) ₂ include _CF2 =CF( _OCF2CF2P (O)(OM) ₂ ), _CF2 =CF(O( _CF2 ) _4P (O)(OM) ₂ ), _CF2 =CF( _OCF2CF ( _CF3 )P(O)(OM) ₂ ), _CF2 =CF( _OCF2CF ( _CF3 ) _OCF2CF2P (O) ₍ OM) ₂ ), _CH2 =CH( _CF2CF2P ( _O )(OM) ₂ ), _CH2 =CH(( _CF2 ) _4P (O)(OM) _{2 )} , and _CH2 =CH(( _CF2 ) _3P (O)(OM) ₂ ), where M is as described above.

[0401] The compound represented by the general formula (4) is preferably at least one compound selected from the group consisting of:

compound represented by the general formula (5):

where X are the same or different and represent -H or -F; Y is -H, -F, an alkyl group or a fluorine-containing alkyl group; Z are the same or different and represent -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf is a fluorine-containing alkylene group containing from 1 to 40 carbon atoms or a fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond and ^Y3 is as described above;

compound represented by the general formula (6):

where X are the same or different and represent -H or -F; Y represents -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf represents a fluorine-containing alkylene group containing from 1 to 40 carbon atoms or a fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond and Y3 is as described above; and

compound represented by the general formula (7):

where X are the same or different and represent -H or -F; Y represents -H, -F, an alkyl group or a fluorine-containing alkyl group; Rf represents a fluorine-containing alkylene group containing from 1 to 40 carbon atoms or a fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond and ^Y3 is as described above;

A fluorine-containing alkylene group containing from 2 to 100 carbon atoms and containing an ether bond is an alkylene group that does not include a structure in which an oxygen atom is terminal and contains an ether bond between carbon atoms.

[0402] In the general formula (5), each X is -H or -F. Both X may be -F, or at least one of them may be -H. For example, one of them may be -F and the other may be -H, or both may be -H.

[0403] In the general formula (5), Y represents -H, -F, an alkyl group or a fluorine-containing alkyl group.

An alkyl group is an alkyl group that does not contain fluorine atoms and may contain one or more carbon atoms. An alkyl group preferably contains 6 or fewer carbon atoms, more preferably 4 or fewer carbon atoms, and even more preferably 3 or fewer carbon atoms.

A fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom and may contain one or more carbon atoms. The fluorine-containing alkyl group preferably contains 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms.

Y is preferably -H, -F or _-CF3 and more preferably -F.

[0404] In the general formula (5), Z are the same or different and represent -H, -F, an alkyl group or a fluoroalkyl group.

An alkyl group is an alkyl group that does not contain fluorine atoms and may contain one or more carbon atoms. An alkyl group preferably contains 6 or fewer carbon atoms, more preferably 4 or fewer carbon atoms, and even more preferably 3 or fewer carbon atoms.

A fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom and may contain one or more carbon atoms. The fluorine-containing alkyl group preferably contains 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms.

Z is preferably -H, -F or _-CF3 and more preferably -F.

[0405] In the general formula (5), at least one of X, Y, and Z preferably contains a fluorine atom. For example, X, Y, and Z may be -H, -F, and -F, respectively.

[0406] In the general formula (5), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether bond.

The fluorine-containing alkylene group preferably contains 2 or more carbon atoms. The fluorine-containing alkylene group also preferably contains 30 or less carbon atoms, more preferably 20 or less carbon atoms, and still more preferably 10 or less carbon atoms. Examples of the fluorine-containing alkylene group include _-CF2- , _-CH2CF2- , _CF2CF2- , _-CF2CH2- , _-CF2CF2CH2- , -CF _{( CF3 )} -, -CF( _CF3 ) _CF2- and CF( _CF3 ) _CH2- . _The fluorine- _containing alkylene group is preferably _a perfluoroalkylene group.

[0407] The fluorine-containing alkylene group containing an ether bond preferably contains 3 or more carbon atoms. The fluorine-containing alkylene group containing an ether bond preferably contains 60 or less carbon atoms, more preferably 30 or less carbon atoms, and even more preferably 12 or less carbon atoms.

It is also preferable that the fluorine-containing alkylene group containing an ether bond is a divalent group represented by the following formula:

where Z ¹ is F or CF ₃ ; each of Z ² and Z ³ is H or F; Z ⁴ is H, F, or CF ₃ ; p1+q1+r1 is an integer from 1 to 10; s1 is 0 or 1; and t1 is an integer from 0 to 5.

Specific examples of the fluorine-containing alkylene group having an ether bond include -CF( _CF3 ) _CF2 -O-CF( _CF3 )-, (CF( _CF3 ) _CF2 -O) _n- CF( _CF3 )- (wherein n is an integer of 1 to 10), -CF( _CF3 ) _CF2 -O-CF( _CF3 ) _{CH2- , -} (CF( _CF3 ) _CF2 -O) _n -CF( _{CF3 ) CH2-} (wherein n is an integer _{of 1} to 10), _-CH2CF2CF2O - _CH2CF2CH2- , _{-CF2CF2CF2O - CF2CF2-} , _{-CF2CF2CF2O -CF2CF2- , -CF2CF2CF2O - CF2CF2CH2- , -CF2CF2O} - _{CF2- and} -CF ₂ CF ₂ O-CF ₂ CH ₂ -. The fluorine-containing alkylene group containing an ether bond is preferably a perfluoroalkylene group.

[0408] In the general formula (5), Y ³ is preferably -COOM, -SO ₃ M or -OSO ₃ M, wherein M is H, a metal atom, NR ^7y ₄ , imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein R ^7y is H or an organic group and may be the same or different, and any two of them may be bonded to each other to form a ring.

The organic group in R ^7y is preferably an alkyl group.

R ^7y is preferably H or a C _1-10 organic group, more preferably H or a C _1-4 organic group, and even more preferably H or a C _1-4 alkyl group.

Examples of the metal include alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K or Li are preferred.

M is preferably -H, a metal atom or -NR ⁷ ₄ , more preferably -H, an alkali metal (Group 1), an alkaline earth metal (Group 2), or -NR ⁷ ₄ , even more preferably -H, -Na, -K, -Li or -NH ₄ , more preferably -H, -Na, -K or -NH ₄ , particularly preferably -H, -Na or -NH ₄ , and most preferably -H or -NH ₄ .

Y ³ is preferably -СООМ or -SO ₃ M, and more preferably -СООМ.

[0409] The compound represented by the general formula (5) is preferably a compound (5a) represented by the general formula (5a):

where Rf and Y ³ are as described above.

[0410] Specific examples of the compound represented by the general formula (5a) include a compound represented by the following formula:

[0411]

[0412] where Z ¹ is F or CF ₃ ; each of Z ² and Z ³ is H or F; Z ⁴ is H, F or CF ₃ ; p1+q1+r1 is an integer from 0 to 10; s1 is 0 or 1; t1 is an integer from 0 to 5 and Y ³ are as described above, provided that when Z ³ and Z ⁴ are both H, p1+q1+r1+s1 is not equal to 0. More specific preferred examples include:

[0413]

[0414] Of these, the following are preferred:

[0415]

[0416].

[0417] In the compound represented by the general formula (5a), Y ³ in the formula (5a) is preferably -COOM. In particular, the compound represented by the general formula (5a) is preferably at least one compound selected from the group consisting of CH ₂ =CFCF ₂ OCF(CF ₃ )COOM and CH ₂ =CFCF ₂ OCF(CF ₃ )CF ₂ OCF(CF ₃ )COOM (wherein M is as defined above), and is more preferably CH ₂ =CFCF ₂ OCF(CF ₃ )COOM.

[0418] The compound represented by the general formula (5) is preferably a compound (5b) represented by the general formula (5b):

where any X ² are the same and each represents F or H; n5 is 0 or an integer from 1 to 10 and Y ³ is as defined above.

[0419] In the formula (5b), n5 is preferably 0 or an integer of 1 to 5, more preferably 0, 1 or 2, and even more preferably 0 or 1 from the viewpoint of the stability of the obtained aqueous dispersion. ^Y3 is preferably -COOM from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, and M is H or _NH4 from the viewpoint of reducing the possibility of retaining impurities and improving the heat resistance of the obtained molded article.

[0420] Examples of the compound represented by formula (5b) include

CH ₂ =CFCF ₂ OCF(CF ₃ )СООМ and CH ₂ =CFCF ₂ OCF(CF ₃ )CF ₂ OCF(CF ₃ )СООМ, where M is as defined above.

[0421] Examples of the compound represented by the general formula (5) further include a compound represented by the general formula (5c):

[0422]

where Rf and Y ³ are as defined above.

[0423] Their more specific examples include:

and the like.

[0424] In the general formula (6), each X is -H or -F. Both X may be -F, or at least one of them may be -H. For example, one of them may be -F and the other may be -H, or both may be -H.

[0425] In the general formula (6), Y represents -H, -F, an alkyl group or a fluorine-containing alkyl group.

An alkyl group is an alkyl group that does not contain fluorine atoms and may contain one or more carbon atoms. An alkyl group preferably contains 6 or fewer carbon atoms, more preferably 4 or fewer carbon atoms, and even more preferably 3 or fewer carbon atoms.

A fluorine-containing alkyl group is an alkyl group containing at least one fluorine atom and may contain one or more carbon atoms. The fluorine-containing alkyl group preferably contains 6 or less carbon atoms, more preferably 4 or less carbon atoms, and even more preferably 3 or less carbon atoms.

Y is preferably -H, -F or -CF ₃ , and more preferably -F.

[0426] In the general formula (6), at least one of X and Y preferably contains a fluorine atom. For example, X, Y and Z can be -H, -F and -F, respectively.

[0427] In the general formula (6), Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alkylene group having 2 to 100 carbon atoms and containing an ether moiety.

The fluorine-containing alkylene group preferably contains 2 or more carbon atoms. The fluorine-containing alkylene group also preferably contains 30 or less carbon atoms, more preferably 20 or less carbon atoms, and still more preferably 10 or less carbon atoms. Examples of the fluorine-containing alkylene group include _-CF2- , _-CH2CF2- , _CF2CF2- , _-CF2CH2- , _{-CF2CF2CH2- ,} -CF _{( CF3 )} -, -CF( _CF3 ) _{CF2- ,} and CF( _CF3 ) _CH2- . The fluorine-containing alkylene group is preferably _a perfluoroalkylene group.

[0428] In the general formula (6), Y3 is preferably -COOM, _-SO3M or _-OSO3M , wherein M is H, a metal atom, ^NR7y4 , _imidazolium optionally having a substituent, pyridinium optionally having a substituent, or phosphonium optionally having a substituent, wherein ^R7y are H or an organic group and may be the same or different, and any two of them may be bonded to each other to form a ring.

The organic group R ^7y is preferably an alkyl group. R ^7y is preferably H or a C _1-10 organic group, more preferably H or a C _1-4 organic group, and even more preferably H or a C _1-4 alkyl group.

Examples of the metal include alkali metals (Group 1) and alkaline earth metals (Group 2), and Na, K or Li are preferred.

M is preferably -H, a metal atom, or -NR ⁷ ₄ , more preferably -H, an alkali metal (Group 1), an alkaline earth metal (Group 2) or -NR ⁷ ₄ , even more preferably -H, -Na, -K, -Li or -NH ₄ , even more preferably -H, -Na, -K or -NH ₄ , particularly preferably -H, -Na or -NH ₄ , and most preferably -H or -NH ₄ .

Y ³ is preferably -СООМ or -SO ₃ M.

[0429] The compound represented by the general formula (6) is preferably at least one compound selected from the group consisting of compounds represented by the general formulas (6a), (6b), (6c), (6d) and (6e):

where n1 is an integer from 1 to 10 and Y ³ is as defined above;

where n2 is an integer from 1 to 5 and Y ³ is as defined above;

where X ¹ represents F or CF ₃ ; n3 is an integer from 1 to 10 and Y ³ is as defined above;

where n4 is an integer from 1 to 10, n6 is an integer from 1 to 3, and Y ³ and X ¹ are as defined above; and

where n5 is an integer from 0 to 10, and Y ³ and X ¹ are as defined above.

[0430] In the formula (6a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. Y ³ is preferably -COOM or -SO ₃ M from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, and M is H or NH ₄ from the viewpoint of being less likely to remain as impurities and improving the heat resistance of the resulting molded article.

[0431] Examples of the compound represented by formula (6a) include CF ₂ =CF-O-CF ₂ COOM, CF ₂ =CF(OCF ₂ CF ₂ COOM), CF ₂ =CF(OCF ₂ CF ₂ CF ₂ COOM), CF ₂ =CF-O-CF ₂ SO ₃ M, CF ₂ =CF(OCF ₂ CF ₂ SO ₃ M) and CF ₂ =CF(OCF ₂ CF ₂ CF ₂ SO ₃ M), where M is as defined above.

[0432] In the formula (6b), n2 is preferably an integer of 3 or less from the viewpoint of the stability of the obtained aqueous dispersion, ^Y3 is preferably -COOM or _-SO3M from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, and M includes H or _NH4 from the viewpoint of being less likely to remain as impurities and to improve the heat resistance of the obtained molded article.

[0433] In the formula (6c), n3 is preferably an integer of 5 or less from the viewpoint of water solubility, ^Y3 is preferably -COOM or _-SO3M from the viewpoint of obtaining appropriate water solubility and stability of an aqueous dispersion, and M is preferably H or _NH4 from the viewpoint of improving the stability of the dispersion.

[0434] In the formula (6d), X ¹ is preferably -CF ₃ from the viewpoint of the stability of the aqueous dispersion, n4 is preferably an integer of 5 or less from the viewpoint of water solubility, Y ³ is preferably -COOM or -SO ₃ M from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, and M is preferably H or NH ₄ .

[0435] Examples of the compound represented by formula (6d) include _CF2 = _CFOCF2CF ( _CF3 ) _OCF2CF2COOM , CF2=CFOCF2CF( _CF3 ) _{OCF2COOM , CF2} = _CFOCF2CF (CF3)OCF2CF2CF2COOM, _CF2 =CFOCF2CF( _{CF3 ) OCF2CF2SO3M , CF2} = _CFOCF2CF ( _{CF3 ) OCF2SO3M , and CF2} = _CFOCF2CF ( _CF3 ) _{OCF2CF2CF2SO3M , where M} is _H , _NH4 or _{an alkali metal .}

[0436] In the general formula (6e), n5 is preferably an integer of 5 or less from the viewpoint of water solubility, ^Y3 is preferably -COOM or _-SO3M from the viewpoint of obtaining appropriate water solubility and stability of an aqueous dispersion, and M is preferably H or _NH4 .

[0437] Examples of the compound represented by the general formula (6e) include CF ₂ =CFOCF ₂ CF ₂ CF ₂ COOM and CF ₂ =CFOCF ₂ CF ₂ CF ₂ SO ₃ M, wherein M is H, NH ₄ or an alkali metal.

[0438] In the general formula (7), Rf is preferably a fluorine-containing alkylene group containing 1 to 40 carbon atoms. In the general formula (7), at least one residue of X and Y preferably contains a fluorine atom.

[0439] The compound represented by the general formula (7) is preferably at least one compound selected from the group consisting of:

compound represented by the general formula (7a):

where n1 is an integer from 1 to 10 and Y ³ is as defined above; and

compound represented by the general formula (7b):

where n2 is an integer from 1 to 5 and Y ³ is as defined above.

Y ³ is preferably -SO ₃ M or -COOM and M is preferably H, a metal atom, NR ^7y ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent. R ^7y is H or an organic group.

[0440] In the formula (7a), n1 is preferably an integer of 5 or less, and more preferably an integer of 2 or less. Y ³ is preferably -COOM or -SO ₃ M from the viewpoint of obtaining appropriate water solubility and stability of the aqueous dispersion, and M is preferably H or NH ₄ from the viewpoint of being less likely to remain as impurities and for improving the heat resistance of the resulting molded article. Examples of the compound represented by the formula (7a) include CF ₂ =CFCF ₂ COOM and CF ₂ =CFCF ₂ SO ₃ M, wherein M is as defined above.

[0441] In the formula (7b), n2 is preferably an integer of 3 or less from the viewpoint of the stability of the aqueous dispersion, ^Y3 is preferably -COOM or _-SO3M from the viewpoint of obtaining adequate water solubility and stability of the aqueous dispersion, and M is preferably H or _NH4 from the viewpoint of being less likely to remain as impurities and for improving the heat resistance of the resulting molded article.

[0442] The modifying monomer preferably includes a modifying monomer (A), preferably includes at least one monomer selected from the group consisting of compounds represented by general formula (5a), general formula (5c), general formula (6a), general formula (6b), general formula (6c), and general formula (6d), and more preferably includes a compound represented by general formula (5a) or general formula (5c).

[0443] When the modifying monomer (A) is used as the modifying monomer, the unit content of the modifying monomer (A) is preferably in the range of 0.00001 to 1.0 mass % relative to all polymerization units in the TFE polymer (PTFE). The lower limit thereof is more preferably 0.0001 mass %, more preferably 0.0005 mass %, still more preferably 0.001 mass %, still more preferably 0.005 mass %. The upper limit is, in order of preference, 0.90 mass %, 0.50 mass %, 0.40 mass %, 0.30 mass %, 0.20 mass %, 0.15 mass %, 0.10 mass %, 0.08 mass %, 0.05 mass % or 0.01 mass %.

[0444] In producing the TFE polymer, the polymer (1) can be used within the scope of application described for the producing method of the present invention. The concentration of the polymer (1) is not limited as long as it is in the above-mentioned range. Too much addition of the polymer (1) causes the formation of needle-like particles with a large aspect ratio and gelation of the aqueous dispersion, deteriorating the stability. The lower limit of the amount of the polymer (1) used is preferably 0.0001% by mass, more preferably 0.001% by mass, even more preferably 0.01% by mass, and particularly preferably 0.02% by mass, with respect to the aqueous medium. The upper limit of the amount of the polymer (1) used is preferably 10% by mass, and more preferably 5% by mass, with respect to the aqueous medium.

[0445] The polymer (1) can be added to the reaction vessel immediately before the start of polymerization, can be added immediately after the start of polymerization, can be added in several portions during polymerization, or can be added continuously during polymerization.

[0446] When producing a TFE polymer, the polymerization initiator used may be an organic peroxide such as a persulfate (e.g., ammonium persulfate), disuccinic acid peroxide, or diglutaric acid peroxide, alone or in the form of a mixture thereof. The organic peroxide may be used together with a reducing agent such as sodium sulfite to form a redox system. In addition, a radical scavenger such as hydroquinone or catechol may be added during the polymerization, or a peroxide decomposer such as ammonium sulfite may be added to control the concentration of radicals in the system.

[0447] The redox polymerization initiator is preferably a redox initiator obtained by combining an oxidizing agent and a reducing agent. Examples of the oxidizing agent include persulfates, organic peroxides, potassium permanganate, manganese triacetate, and ceric ammonium nitrate. Examples of the reducing agent include sulfites, bisulfites, bromates, diimines, and oxalic acid. Examples of persulfates include ammonium persulfate and potassium persulfate. Examples of sulfites include sodium sulfite and ammonium sulfite. To increase the decomposition rate of the initiator, the redox initiator combination may preferably contain a copper salt or an iron salt. An example of a copper salt is copper(II) sulfate, and an example of an iron salt is iron(II) sulfate.

[0448] Examples of the redox initiator include potassium permanganate/oxalic acid, ammonium persulfate/bisulfite/ferric sulfate, manganese triacetate/oxalic acid, ammonium cerium nitrate/oxalic acid, and bromate/bisulfite, and potassium permanganate/oxalic acid is preferred. In the case of using a redox initiator, either an oxidizing agent or a reducing agent can be pre-loaded into the polymerization tank, and then another agent can be continuously or periodically added thereto to initiate the polymerization. For example, in the case of using potassium permanganate/oxalic acid, oxalic acid is preferably loaded into the polymerization tank and potassium permanganate is continuously added thereto.

[0449] A known chain transfer agent can be used in the production of the TFE polymer. Examples thereof include saturated hydrocarbons such as methane, ethane, propane and butane, halogenated hydrocarbons such as chloromethane, dichloromethane and difluoroethane, alcohols such as methanol, ethanol and isopropanol, and hydrogen. The chain transfer agent is preferably in a gaseous state at normal temperature and pressure.

[0450] The amount of chain transfer agent used is usually from 1 to 10,000 ppm by weight, preferably from 1 to 5,000 ppm by weight, relative to the total amount of TFE supplied.

[0451] In the production of the TFE polymer, a saturated hydrocarbon which is substantially inert to the reaction, is in a liquid state under the reaction conditions and which contains 12 or more carbon atoms for the reaction system can be used as a dispersion stabilizer in an amount of 2 to 10 parts by weight relative to 100 parts by weight of an aqueous medium. Ammonium carbonate, ammonium phosphate or the like can be added as a buffer to adjust the pH during the reaction.

[0452] Upon completion of the polymerization of TFE, a polymerization dispersion can be obtained having a solids concentration of 1.0 to 50% by weight and an average primary particle size of 50 to 500 nm.

The lower limit of solids concentration is preferably 5% by weight, and more preferably 8% by weight. Its upper limit may be, but is not limited to, 40% by weight or 35% by weight.

The lower limit of the average size of the primary particles is preferably 100 nm, and more preferably 150 nm. Its upper limit is preferably 400 nm, and more preferably 350 nm.

The average primary particle size can be measured using dynamic light scattering. The average primary particle size can be measured by preparing an aqueous dispersion with a solids concentration adjusted to 1.0% by weight and using dynamic light scattering at 25°C with 70 measurement processes in which the solvent (water) has a refractive index of 1.3328 and a viscosity of 0.8878 mPa⋅s. For dynamic light scattering, an example of an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

In addition, the average size of the primary particles can be determined by measuring the transmittance of incident light with a wavelength of 550 nm per unit length of an aqueous dispersion having a solid concentration set to 0.15% by mass, and the number average value of the length of the primary particles is determined by measuring the Feret diameter using an image obtained by a transmission electron microscope to construct a calibration curve and determine the particle size from the measured transmittance of incident light of 550 nm of each sample using the calibration curve.

[0453] A fine powder can be obtained by coagulating an aqueous dispersion of a TFE polymer. The aqueous dispersion of a TFE polymer can be converted into a fine powder by coagulation, washing and drying. The obtained fine powder can be used for various purposes. Coagulation of an aqueous dispersion of a TFE polymer is usually carried out by diluting an aqueous dispersion obtained by polymerizing a polymer latex, for example, with water to a polymer concentration of 5 to 20% by weight, optionally adjusting the pH to a neutral or alkaline value and stirring the polymer more vigorously than in a reaction in a vessel equipped with a stirrer. Coagulation can be carried out by stirring with the addition of a water-soluble organic compound such as methanol or acetone, an inorganic salt such as potassium nitrate or ammonium carbonate, or an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, as a coagulating agent. Coagulation can be carried out continuously using a device such as a flow mixer.

[0454] From the viewpoint of productivity, the concentration of the non-agglomerated TFE polymer in the waste water generated by the agglomeration is preferably low, more preferably less than 0.4% by mass, and particularly preferably less than 0.3% by mass.

[0455] A pigment-containing or filler-containing fine powder of TFE polymer in which pigments and fillers are uniformly mixed can be obtained by adding pigments for coloring and various fillers for improving mechanical properties before or during coagulation.

[0456] The wet powder obtained by coagulating the TFE polymer in an aqueous dispersion is usually dried using a vacuum, a high-frequency electromagnetic field, hot air, or the like, while maintaining the wet powder in a state in which the wet powder is less fluid, preferably in a stationary state. Friction between powder particles, especially at high temperatures, usually has an adverse effect on the TFE polymer in the form of a fine powder. This is because particles obtained from such a TFE polymer easily form fibrils even under a small shear force and lose their original, stable particle structure.

[0457] Drying is carried out at a drying temperature of 10 to 300°C, preferably 100 to 300°C.

[0458] The TFE polymer in the aqueous dispersion can be coagulated using an acid containing no elemental metals or coagulated by stirring, and the coagulated TFE polymer can be washed with a liquid medium having a reduced elemental metal content. In addition, the washed TFE polymer can be dried. By such a production method, a TFE polymer having a metal content of 10 ppm by mass or less in the TFE polymer can be obtained. The liquid medium is water, and even more preferably ultrapure water. The metal content in the liquid medium is 2 ppm by mass or less, more preferably 1 ppm by mass or less, and even more preferably 0.5 ppm by mass or less.

[0459] The resulting finely divided TFE polymer powder is preferred for molding, and its suitable applications include pipes for hydraulic systems or fuel systems of aircraft or automobiles, flexible hoses for chemicals or vapors, and sheaths of electrical wires.

[0460] An aqueous dispersion of TFE polymer is preferably mixed with a nonionic surfactant to stabilize and further concentrate the aqueous dispersion, and then further mixed, depending on its purpose, with an organic or inorganic filler to form a composition and used in various applications. When applied to a metal or ceramic substrate, the composition can provide a coating surface having non-tackiness, a low coefficient of friction and excellent gloss, smoothness, abrasion resistance, weather resistance and heat resistance, which is suitable for coating rollers and kitchen utensils and for impregnating fiberglass.

[0461] An aqueous dispersion can also be used to prepare an organosol of a TFE polymer. The organosol may contain a TFE polymer and an organic solvent, and examples of the organic solvent include ether-based solvents, ketone-based solvents, alcohol-based solvents, amide-based solvents, ester-based solvents, aliphatic hydrocarbon-based solvents, aromatic hydrocarbon-based solvents, and halogenated hydrocarbon-based solvents. N-methyl-2-pyrrolidone and dimethylacetamide are preferably used. The organosol can be prepared, for example, by the method described in International Publication No. WO 2012/002038.

[0462] An aqueous dispersion of a TFE polymer or a fine powder of a TFE polymer is also preferably used as a processing aid. When used as a processing aid, the aqueous dispersion or fine powder is mixed with a base polymer, for example, to improve the melt strength of the base polymer during melt processing, as well as to improve the mechanical strength, electrical properties, non-flammability, anti-drip properties during combustion, and slip of the resulting polymer.

[0463] The aqueous dispersion of the TFE polymer or the fine powder of the TFE polymer is also preferably used as a binder for batteries or used for dust-proof applications.

[0464] An aqueous dispersion of a TFE polymer or a fine powder of a TFE polymer is also preferably combined with a resin other than a TFE polymer to obtain a processing aid before use. The aqueous dispersion or the fine powder is suitable as a PTFE raw material described in, for example, Japanese Patent Laid-Open No. 11-49912, U.S. Patent No. 5804654, Japanese Patent Laid-Open No. 11-29679, and Japanese Patent Laid-Open No. 2003-2980. Processing aids containing the aqueous dispersion or the fine powder are not inferior to the processing aids described in the publications.

[0465] The aqueous dispersion of the TFE polymer is also preferably mixed with the aqueous dispersion of the melt-processable fluororesin so that the components coagulate to form a co-coagulated powder. The co-coagulated powder is useful as a processing aid.

[0466] Examples of melt-processable fluororesin include FEP, PFA, TFE/perfluoroallyl ether copolymers, ETFE, and ethylene/TFE/HFP copolymers (EFEP), of which PFA or FEP are preferred.

[0467] The aqueous dispersion also preferably contains a melt-processable fluororesin. Examples of the melt-processable fluororesin include FEP, PFA, TFE/perfluoroallyl ether copolymers, ETFE, and EFEP. The aqueous dispersion containing the melt-processable fluororesin can be used as a coating material. The melt-processable fluororesin ensures sufficient fusion of the TFE polymer particles, improving film formability and imparting gloss to the resulting film.

[0468] The fluorine-free resin to which the co-coagulated powder is added may be in the form of a powder, granules, or emulsion. In order to achieve sufficient mixing of the resins, the addition is preferably carried out by a known method such as extrusion kneading or roller kneading under shear.

[0469] An aqueous dispersion of a TFE polymer is also preferably used as a dust suppression treatment agent. The dust suppression treatment agent can be used in a method for suppressing dust from dust-generating substances by mixing the dust suppression treatment agent with a dust-generating substance and subjecting the mixture to compression-shear at a temperature of 20 to 200°C to fibrillate the TFE polymer, for example, as in the methods described in Japanese Patent No. 2827152 and Japanese Patent No. 2538783.

The aqueous dispersion of the TFE polymer can be suitably used for the dust suppression treatment agent composition described in International Publication No. WO 2007/004250, and can also be suitably used in the dust suppression treatment method described in International Publication No. WO 2007/000812.

[0470] The dust-control treatment agent is suitably used for dust-control treatment in the fields of building products, soil stabilizers, curing materials, fertilizers, incineration ash and hazardous substance waste heaps, and explosion-proof equipment, cosmetics, and pet excrement granules such as cat granules.

[0471] An aqueous dispersion of a TFE polymer is also preferably used as a starting material for producing TFE polymer fibers by a dispersion spinning method. The dispersion spinning method is a method in which an aqueous dispersion of a TFE polymer and an aqueous dispersion of a matrix polymer are mixed and the mixture is extruded to form an intermediate fiber structure, and then the intermediate fiber structure is calcined to decompose the matrix polymer and the TFE polymer particles are sintered, thereby obtaining TFE polymer fibers.

[0472] The high molecular weight PTFE powder obtained by polymerization has stretchability and non-melting processability, and is suitable for use as a raw material for a stretched mass (porous mass).

When the stretched mass is in the form of a film (PTFE stretched film or porous PTFE film), the stretched mass can be formed by stretching the PTFE using a known stretching method. Stretching allows for the easy formation of PTFE fibrils, resulting in a porous mass (film) of high-molecular-weight PTFE containing nodes and fibers.

Preferably, stretching the sheet or rod-shaped paste extrudate in the extrusion direction can provide a uniaxially stretched film.

Further stretching in the transverse direction using, for example, a spreading machine can produce a film stretched along two axes.

It is also preferable to carry out pre-annealing before stretching.

[0473] This expanded PTFE mass is a porous mass having high porosity, and it can be suitably used as a filter material for various microfiltration filters such as air filters and chemical filters, and as a support element for polymer electrolyte films.

PTFE expanded material is also suitable for use as a material in products used in textiles, medicine, electrochemistry, sealants, air filters, ventilation/internal pressure control systems, liquid filters and consumer goods.

Below are examples of specific applications.

[0474] masses - Field of electrochemistry

Examples of applications in this field include prepregs for dielectric materials, EMI shielding materials, and thermally conductive materials. More specifically, examples include printed circuit boards, EMI shielding materials, thermally conductive insulating materials, and insulating materials.

- Sealants area

Examples of applications in this area include gaskets, packings, pump diaphragms, pump tubes and aircraft sealants.

[0475] - Air filter area

Examples of applications in this field include ULPA filters (for semiconductor production), HEPA filters (for hospitals and semiconductor production), cylindrical cartridge filters (for industry), bag filters (for industry), high-temperature bag filters (for exhaust gas cleaning), high-temperature pleated filters (for exhaust gas cleaning), SINBRAN filters (for industry), catalytic filters (for exhaust gas cleaning), adsorbent filters (for HDD embedding), adsorbent vent filters (for HDD embedding), vent filters (e.g. for HDD embedding), purifier filters (for purifiers), general purpose multi-layer felts, GT cartridge filters (for GT replacement elements), cooling filters (for electronic device housings).

[0476] - Ventilation/Internal Pressure Adjustment Area

Examples of applications in this field include freeze-drying materials such as freeze-drying vessels, automotive ventilation materials for electronic circuits and lamps, container-related applications such as vessel lids, protective ventilation for electronic devices including small devices such as tablet I/O devices and mobile phone I/O devices, and ventilation for medical purposes.

[0477] - Liquid filter area

Examples of applications in this field include semiconductor liquid filters (for semiconductor production), hydrophilic PTFE filters (for semiconductor production), chemical filters (for chemical processing), pure water line filters (for pure water production), and backwash liquid filters (for industrial wastewater treatment).

[0478] - Consumer goods area

Examples of applications in this field include clothing, cable guides (movable wires for motorcycles), motorcycle clothing, molded liners (medical devices), filters for cleaning agents, bagpipes (musical instruments), cables (signal cables for guitars and the like), and string products (for stringed instruments).

[0479] - Textiles area

Examples of applications in this field include PTFE fibers (fibrous materials), sewing machine threads (textiles), weaving yarns (textiles), and ropes.

[0480] - Field of medical treatment

Examples of applications in this area include implants (stretchable devices), artificial blood vessels, catheters, general surgical devices (tissue reinforcement materials), head and neck devices (dural alternatives), oral health devices (tissue regenerative medicine), and orthopedics (bandages).

[0481] By the production method of the present invention, it is also possible to produce low molecular weight PTFE.

Low molecular weight PTFE can be obtained by polymerization, or it can be obtained by reducing the molecular weight of high molecular weight PTFE obtained by polymerization by a known method (e.g., thermolysis, radiolysis).

[0482] Low molecular weight PTFE having a molecular weight of 600,000 or less (also referred to as PTFE micropowder) has excellent chemical stability and very low surface energy and is less likely to form fibrils, and therefore it can be suitably used as an additive for improving lubricity and surface texture of a coating in the production of plastics, inks, cosmetics, coating materials, lubricants, office equipment parts, and toners (for example, see Japanese Patent Laid-Open No. 10-147617).

[0483] Low molecular weight PTFE can also be produced by dispersing a polymerization initiator and a polymer (1) in an aqueous medium in the presence of a chain transfer agent, and then polymerizing TFE alone or TFE and a monomer copolymerizable with TFE. In this case, the chain transfer agent is preferably at least one agent selected from the group consisting of alkanes containing 2 to 4 carbon atoms. In particular, the chain transfer agent is more preferably methane, ethane, propane, butane or isobutane, and even more preferably ethane or propane. In this case, the amount of the chain transfer agent is preferably 10 ppm by mass or more or more than 10 ppm by mass relative to the aqueous medium.

[0484] In the case of using low molecular weight PTFE obtained by polymerization in the form of powder, the powder particles can be obtained by coagulating an aqueous dispersion.

[0485] In the present invention, the high molecular weight PTFE is preferably non-meltable and fibrillable. On the other hand, the low molecular weight PTFE is preferably melt-processable and does not form fibrils.

[0486] The term "non-melting" means the property of a polymer such that its melt flow rate cannot be measured at a temperature higher than the crystalline melting point, in accordance with ASTM D 1238 and D 2116.

[0487] The presence or absence of fibrillation ability can be determined using “paste extrusion,” a typical method for molding “high molecular weight PTFE powder,” which is a TFE polymer powder. Typically,

High-molecular-weight PTFE can be extruded as a paste if it exhibits fibrillation. When the unfired molded part obtained by paste extrusion exhibits essentially no strength or elongation (e.g., when it exhibits 0% elongation and fails under tension), it can be considered non-fibrillable.

[0488] The high molecular weight PTFE preferably has a standard relative density (SSG) of 2130 to 2280. The standard relative density is determined by the water displacement method in accordance with ASTM D 792 using a specimen molded in accordance with ASTM D4895-89. As used herein, "high molecular weight" means that the standard relative density is in the range specified above.

[0489] The low molecular weight PTFE has a melt viscosity at 380°C of 1×10 ² to 7×10 ⁵ Pa⋅sec. In the present description, "low molecular weight" means that the melt viscosity is in the above-mentioned range. The melt viscosity is a value measured in accordance with ASTM D 1238 using a flow meter (manufactured by Shimadzu Corporation) and a 2ϕ-8 L die, by holding 2 g of a sample preheated to 380°C for 5 minutes at the above-mentioned temperature under a load of 0.7 MPa.

[0490] High-molecular-weight PTFE has a melt viscosity significantly higher than that of low-molecular-weight PTFE, and its melt viscosity is difficult to accurately measure. The melt viscosity of low-molecular-weight PTFE is measurable, but low-molecular-weight PTFE is difficult to produce a molded article that can be used to measure the standard relative density. Therefore, it is difficult to accurately measure its standard relative density. Accordingly, in the present description, the standard relative density is used as an indicator of the molecular weight of high-molecular-weight PTFE, while the melt viscosity is used as an indicator of the molecular weight of low-molecular-weight PTFE. It should be noted that there is no known measurement method for directly determining the molecular weight of either high-molecular-weight PTFE or low-molecular-weight PTFE.

[0491] The high molecular weight PTFE preferably has a peak temperature of 333 to 347°C, more preferably of 335 to 345°C. The low molecular weight PTFE preferably has a peak temperature of 322 to 333°C, more preferably of 324 to 332°C. The peak temperature may be indicated as the temperature corresponding to the maximum value appearing on the differential thermal curve (DTA) obtained by increasing the temperature of PTFE without heating history to a temperature of 300°C or higher at 10°C/min using a TG/DTA (synchronous thermogravimetric analyzer).

[0492] The peak temperature of PTFE can range from 322 to 347°C.

When the PTFE is high molecular weight PTFE, the upper limit of the peak temperature of the PTFE may be 347°C or lower, 346°C or lower, 345°C or lower, 344°C or lower, 343°C or lower, 342°C or lower, 341°C or lower, or 340°C or lower.

When the PTFE is high molecular weight PTFE, the lower limit of the peak temperature of the PTFE may be 333°C or higher or 335°C or higher.

When the PTFE is low molecular weight PTFE, the upper limit of the peak temperature of the PTFE may be 333°C or lower, or 332°C or lower.

When the PTFE is low molecular weight PTFE, the lower limit of the peak temperature of the PTFE may be 322°C or higher, or 324°C or higher.

[0493] The average primary particle size of the low molecular weight PTFE is preferably from 10 to 200 nm, and more preferably it is 20 nm or more, more preferably 150 nm or less, even more preferably 140 nm or less, and particularly preferably 90 nm or less. A relatively small average primary particle size can be obtained, for example, by adding a modifying monomer to the polymerization system at the initial stage of TFE polymerization.

[0494] The average primary particle size of low molecular weight PTFE can be measured by dynamic light scattering. It can be measured by first preparing an aqueous dispersion of low molecular weight PTFE with a solid polymer concentration adjusted to approximately 1.0% by mass, and then using dynamic light scattering at a measurement temperature of 25°C with 70 repetitions of measurements when the solvent (water) has a refractive index of 1.3328 and the solvent (water) has a viscosity of 0.8878 mPa⋅s. For dynamic light scattering, for example, ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0495] Preferably, the high molecular weight PTFE has at least one endothermic peak in the range of 333 to 347°C in the heat of fusion curve at a temperature increase rate of 10°C/min using a differential scanning calorimeter (DSC) for PTFE, which never heats up to 300°C or higher and has an enthalpy of fusion of 52 mJ/mg or higher at a temperature of 290 to 350°C, calculated from the heat of fusion curve. The DSC more preferably has an enthalpy of fusion of 55 mJ/mg or higher, and even more preferably 58 mJ/mg or higher.

[0496] The fine PTFE powder obtained by the above-described method can also be used to produce green tape (green tape).

[0497] (II) Melt-processable fluororesins

In the first production method of the present invention, by polymerizing a perfluoromonomer such as TFE, a melt-processable fluororesin can be produced in the form of a fluoropolymer such as a TFE/HFP (FEP) copolymer, a TFE/ether (perfluoroalkyl vinyl ether) copolymer (PFA, MFA, etc.), a TFE/ether (perfluoroalkyl allyl ether) copolymer and an electrolyte precursor polymer.

[0498] (1) In the production method of the present invention, the polymerization of FEP is preferably carried out at a polymerization temperature of 10 to 150°C and a polymerization pressure of 0.3 to 6.0 MPag.

[0499] FEP preferably has a monomer composition ratio (% by weight) of TFE:HFP=(60-95):(5-40), more preferably (85-92):(8-15).

[0500] In addition to TFE and HFP, another monomer capable of copolymerizing with these monomers can be polymerized to obtain a copolymer of TFE, HFP and another monomer as FEP. Examples of the other monomer include the above-mentioned fluorine-containing monomers (except TFE and HFP) and fluorine-free monomers. One type or several types thereof can be used as the other monomer. The other monomer is preferably a ether (perfluoroalkyl vinyl ether). The content of the other monomer unit in FEP can be from 0.1 to 2% by mass relative to all monomer units.

[0501] In the polymerization of FEP, the polymer (1) can be used within the scope of application of the production method of the present invention, and it is usually added in an amount of 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium.

[0502] In the polymerization of FEP, the chain transfer agent used is preferably cyclohexane, methanol, ethanol, propanol, ethane, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride or the like, and the pH buffer used is preferably ammonium carbonate, disodium hydrogen phosphate or the like.

[0503] In the production method of the present invention, the obtained aqueous FEP dispersion may optionally undergo subsequent processing such as concentration, and then the concentrate may be dried and converted into powder, and the powder may be extruded from the melt into granules. The aqueous medium in the aqueous FEP dispersion may optionally contain an additive such as a non-ionic surfactant, and may contain a water-soluble organic solvent such as a water-soluble alcohol, or may not contain a water-soluble organic solvent.

[0504] Melt extrusion may be carried out under any suitable extrusion conditions that typically produce pellets.

[0505] In the production method of the present invention, the obtained FEP may contain an end group such as -CF ₃ or -CF ₂ H on at least one chain of the polymer backbone and the polymer side chain, but it is preferable that the content of thermally unstable groups such as -COOH, -CH ₂ OH, -COF, -CF=CF-, -CONH ₂ or -COOCH ₃ (hereinafter referred to as "unstable end group") is low or zero.

[0506] The unstable end group is chemically unstable and thus not only reduces the heat resistance of the resin but also causes an increase in the loss of the resulting electrical wire.

[0507] The production method according to the present invention is preferably carried out in such a way as to obtain a polymer in which the total number of unstable end groups and -CF ₂ H end groups at the end of the polymerization is 50 or less per 1×10 ⁶ carbon atoms. More preferably, the number of such groups is less than 20, even more preferably 5 or less per 1×10 ⁶ carbon atoms. Also, neither unstable end groups nor -CF ₂ H end groups may be present, that is, all end groups may be only -CF ₃ end groups.

[0508] Unstable end groups and _-CF2H end groups can be fluorinated and converted into _-CF3 end groups and thereby stabilized. Examples of the fluorination method include, but are not limited to, methods of exposing the polymer to a fluorine radical source that generates fluorine radicals under fluorination conditions. Examples of the fluorine radical source include fluorine gas, _CoF3 , _AgF2 , UF6, _OF2 , _N2F2 , _{CF3OF ,} and halogen fluorides such as _IF5 and _ClF3 . Of these, a method of bringing fluorine gas and FEP obtained by the production method of the present invention into direct contact with each other is preferable. In order to control the reaction, the contact is preferably carried out using dilute fluorine gas having a fluorine gas concentration of 10 to 50% by mass. Diluted gaseous fluorine can be produced by diluting gaseous fluorine with an inert gas, such as nitrogen or argon. Fluorine gas treatment can be carried out at temperatures ranging from 100 to 250°C. The treatment temperature is not limited to this range and can be adjusted according to the situation. Fluorine gas treatment is preferably carried out by continuously or intermittently feeding diluted gaseous fluorine into the reactor. This fluorination can be carried out on dry powder after polymerization or on granules extruded from the melt.

[0509] The FEP obtained by the production method of the present invention has good moldability and is less likely to cause molding defects, and also has properties such as heat resistance, chemical resistance, solvent resistance, electrical insulation and electrical properties.

[0510] The FEP powder can be obtained by a method of drying the FEP obtained by the above-mentioned production method of the present invention to obtain the FEP powder.

[0511] The powder can be fluorinated. The fluorinated powder can be obtained by a method of supplying fluorine gas to the powder obtained by the powder production method described above to fluorinate the powder to obtain the fluorinated powder.

[0512] FEP granules can be obtained by a method of granulating FEP obtained by the above-mentioned production method of the present invention.

[0513] The granules can be fluorinated. The fluorinated granules can be produced by a method of supplying fluorine gas to the granules produced by the above-described method for producing the granules to fluorinate the granules to produce the fluorinated granules.

[0514] Thus, this FEP can be used in producing various molded articles such as coating materials for electrical wires, foamed electrical wires, cables and wires, tubes, films, sheets and threads.

[0515] (2) In the production method of the present invention, the polymerization of a TFE/(perfluoroalkyl vinyl ether) copolymer such as PFA or MFA and a TFE/(perfluoroalkyl allyl ether) copolymer is usually preferably carried out at a polymerization temperature of 10 to 100°C and a polymerization pressure of 0.3 to 6.0 MPaG.

[0516] The TFE/perfluoroalkyl vinyl ether copolymer preferably has a monomer composition ratio (mol%) of TFE:perfluoroalkyl vinyl ether = (90-99.7):(0.3-10), more preferably (97-99):(1-3). The perfluoroalkyl vinyl ether used is preferably an ether represented by the formula: CF ₂ =CFORf ⁴ , wherein Rf ⁴ is a perfluoroalkyl group containing 1-6 carbon atoms.

[0517] In addition to TFE and perfluoroalkyl vinyl ether, another monomer capable of copolymerizing with these monomers can be polymerized to obtain a copolymer of TFE, perfluoroalkyl vinyl ether, and another monomer such as a TFE/perfluoroalkyl vinyl ether copolymer. Examples of the other monomer include the above-mentioned fluorine-containing monomers (except TFE and perfluoroalkyl vinyl ether)) and monomers not containing fluorine. As the other monomer, one type or several types thereof can be used. The content of the other monomer unit in the TFE/perfluoroalkyl vinyl ether copolymer may be from 0.1 to 2 mass% based on the total monomer units.

[0518] The TFE/(perfluoroalkyl allyl ether) copolymer preferably has a monomer composition ratio (mol%) of TFE:(perfluoroalkyl allyl ether) = (90-99.7):(0.3-10), more preferably (97-99):(1-3). The (perfluoroalkyl allyl ether) used is preferably an ether represented by the formula: CF ₂ =CFCF ₂ ORf ⁴ , wherein Rf ⁴ is a perfluoroalkyl group containing 1-6 carbon atoms.

[0519] In addition to TFE and the (perfluoroalkyl allyl ether), another monomer capable of copolymerizing with these monomers can be polymerized to obtain a copolymer of TFE, the (perfluoroalkyl allyl ether), and another monomer such as a TFE/(perfluoroalkyl allyl ether) copolymer. Examples of the other monomer include the above-mentioned fluorine-containing monomers (except TFE and the (perfluoroalkyl allyl ether)) and monomers not containing fluorine. As the other monomer, one type or more types can be used. The content of the other monomer unit in the TFE/(perfluoroalkyl allyl ether) copolymer may be from 0.1 to 2 mass% based on all monomer units.

[0520] In the polymerization of the TFE/ether (perfluoroalkyl vinyl ether) copolymer and the TFE/ether (perfluoroalkyl allyl ether) copolymer, the polymer (1) can be used within the scope of application of the production method of the present invention, and is usually preferably added in an amount of 0.0001 to 10% by mass relative to 100% by mass of the aqueous medium.

[0521] In the polymerization of the TFE/(perfluoroalkyl vinyl ether) copolymer and the TFE/(perfluoroalkyl allyl ether) copolymer, the chain transfer agent used is preferably cyclohexane, methanol, ethanol, propanol, propane, butane, pentane, hexane, carbon tetrachloride, chloroform, methylene chloride, methyl chloride, methane, ethane or the like, and the pH buffer used is preferably ammonium carbonate, disodium hydrogen phosphate or the like.

[0522] An aqueous dispersion of a TFE/(perfluoroalkyl vinyl ether) copolymer, such as PFA or MFA, and a TFE/(perfluoroalkyl allyl ether) copolymer obtained by the production method of the present invention may optionally be subjected to subsequent processing such as concentration, and then the concentrate may be dried and converted into powder, and the powder may be melt-extruded into granules. The aqueous medium in the aqueous dispersion may optionally contain an additive such as a nonionic surfactant, and may contain a water-soluble organic solvent such as a water-soluble alcohol, or may not contain a water-soluble organic solvent.

[0523] Melt extrusion may be carried out under any suitable extrusion conditions that generally produce pellets.

[0524] In order to improve the heat resistance of the copolymer and enhance the chemical penetration suppression effect of the molded article, the copolymer is preferably treated with fluorine gas.

[0525] The treatment with fluorine gas is carried out by bringing fluorine gas into contact with the copolymer. However, since the reaction with fluorine is extremely exothermic, it is preferable to dilute the fluorine with an inert gas such as nitrogen. The amount of fluorine in the fluorine gas/inert gas mixture is from 1 to 100% by weight, preferably from 10 to 25% by weight. The treatment temperature is from 150 to 250°C, preferably from 200 to 250°C, and the treatment time with fluorine gas is from 3 to 16 hours, preferably from 4 to 12 hours. The treatment with fluorine gas is carried out at a gas pressure in the range of from 1 to 10 atm, preferably at atmospheric pressure. In the case of using a reactor at atmospheric pressure, the fluorine gas/inert gas mixture can be continuously passed through the reactor. This results in the conversion of the unstable end groups of the copolymer to _-CF3 end groups, thermally stabilizing the copolymer.

[0526] The copolymer and its composition may be molded by compression molding, transfer molding, extrusion molding, injection molding, blow molding, or the like, as in the case of conventional PFA.

[0527] Such a molding technology can provide a desired molded article. Examples of molded articles include sheets, films, packages, round rods, square rods, pipes, tubes, round tanks, square tanks, tanks, wafer carriers, wafer boxes, cups, filter housings, flow meters, pumps, valves, taps, connectors, nuts, electrical wires, and heat-resistant electrical wires.

[0528] Preferred among these are pipes, tubes, tanks, connectors and the like, for use in various chemical reaction apparatuses, semiconductor production apparatuses and acid or alkaline chemical feed apparatuses, each of which requires chemical impermeability.

[0529] An aqueous dispersion of a TFE/perfluoroalkyl vinyl ether copolymer, such as PFA or MFA, and a TFE/perfluoroalkyl allyl ether copolymer can also be suitably mixed with a nonionic surfactant and, optionally, with a polyethersulfone, a polyamideimide and/or a polyimide, and the metal powder is dissolved or dispersed in an organic solvent. In this way, a primer composition can be obtained. This primer composition can be used for a method of applying a fluororesin to a metal surface. The method includes applying the primer composition to a metal surface, applying a melt-processable fluororesin composition to the resulting primer layer, and baking the melt-processable fluororesin composition layer together with the primer layer.

[0530] (4) The production method of the present invention can be used to produce an electrolyte precursor polymer. In the production method of the present invention, polymerization of the electrolyte precursor polymer is preferably carried out at a polymerization temperature of 10 to 100°C and a polymerization pressure of 0.1 to 2.0 MPaG. The electrolyte precursor polymer contains a monomer containing a functional group represented by _-SO2X151 , ^{-COZ151 , or -POZ152Z153 ( X151} , ^Z151 , ^Z152 , and ^Z153 are as described below), and can be converted into an ion-exchange polymer by hydrolysis treatment.

[0531] An example of a monomer that will be used as an electrolyte precursor of the polymer is a fluorine-containing monomer represented by the general formula (150):

CF ₂ =CF-O-(CF ₂ CFY ¹⁵¹ -O) _n -(CFY ¹⁵² ) _m -A ¹⁵¹

wherein Y ¹⁵¹ represents a fluorine atom, a chlorine atom, an -SO ₂ F group or a perfluoroalkyl group; a perfluoroalkyl group optionally containing an etheric oxygen and an -SO ₂ F group; a perfluoroalkyl group optionally containing an etheric oxygen and an -SO ₂ F group; n represents an integer from 0 to 3; n Y ¹⁵¹ are the same or different; Y ¹⁵² represents a fluorine atom, a chlorine atom or a -SO ₂ F group; m represents an integer from 1 to 5; m Y ¹⁵² are the same or different; A ¹⁵¹ represents -SO ₂ X ¹⁵¹ , -COZ ¹⁵¹ or -POZ ¹⁵² Z ¹⁵³ ; X ¹⁵¹ represents F, Cl, Br, I, -OR ¹⁵¹ or -NR ¹⁵² R ¹⁵³ ; Z ¹⁵¹ , Z ¹⁵² and Z ¹⁵³ are the same or different and each is -NR ¹⁵⁴ R ¹⁵⁵ or -OR ¹⁵⁶ ; R ¹⁵¹ , R ¹⁵² , R ¹⁵³ , R ¹⁵⁴ , R ¹⁵⁵ and R ¹⁵⁶ are the same or different and each is H, ammonium, an alkali metal or an alkyl group, an aryl group or a sulfonyl-containing group optionally containing a fluorine atom. Examples of the monomer to be used as the electrolyte precursor of the polymer also include a compound containing two fluorosulfonyl groups described in International Publication No. WO 2007/013532 and a perfluoromonomer containing an -SO ₂ F group and a dioxolane ring described in International Publication No. WO 2014/175123. The electrolyte precursor of the polymer preferably has a monomer composition ratio (mol%) of TFE:vinyl ether = (50-99):(50-1), more preferably TFE:vinyl ether = (50-93):(50-7).

[0532] The electrolyte precursor of the polymer may be modified with a third monomer present in the range of 0 to 20% by weight of all monomers. Examples of the third monomer include CTFE, vinylidene fluoride, perfluoroalkyl vinyl ether, and perfluorobutenyl vinyl ether; cyclic monomers such as perfluoro-2,2-dimethyl-1,3-dioxolane and perfluoro-2-methylene-4-methyl-1,3-dioxole; multifunctional monomers such as divinylbenzene.

[0533] The electrolyte polymer precursor thus obtained can be formed into a film by subsequent hydrolysis using an alkali solution and treatment using a mineral acid, and thus used as an electrolyte polymer film for fuel cells, electrolysis devices, redox flow batteries, and the like.

The polymer electrolyte precursor can be hydrolyzed using an alkali solution while maintaining its dispersed state, thereby ensuring dispersion of the polymer electrolyte.

This dispersion can then be heated to 120°C or higher in a pressure vessel and thus dissolved, for example, in a solvent mixture of water and alcohol, i.e. converted into a solution state.

The resulting solution can be used as a binder for electrodes. Furthermore, the solution can be combined with various additives and applied to a substrate by casting to form a film, which can then be used to produce antifouling films, organic activators, or similar materials.

[0534] The melt-processed fluororesin powder is suitably used as a powder coating material. When applied to a substrate, the powder coating material obtained from the melt-processed fluororesin powder can form a film having a smooth surface. The melt-processed fluororesin powder having an average particle size of 1 μm or more and less than 100 μm is particularly suitable as a powder coating material used for electrostatic coating. The melt-processed fluororesin powder having an average particle size of 100 μm or more and 1000 μm or less is particularly suitable as a powder coating material used for rotational coating or rotational molding.

[0535] The melt-processable fluororesin powder can be obtained by a method of drying the melt-processable fluororesin obtained by the above-mentioned production method of the present invention to obtain the melt-processable fluororesin powder. The method of producing the melt-processable fluororesin powder is also one aspect of the present invention.

[0536] (III) Perfluoroelastomer

In the first production method of the present invention, by polymerizing a perfluoromonomer such as TFE, the perfluoroelastomer can be obtained as a fluoropolymer.

[0537] The perfluoromonomer used in the polymerization of the perfluoroelastomer is preferably at least one monomer selected from the group consisting of:

tetrafluoroethylene (TFE);

hexafluoropropylene (HFP);

fluoromonomer represented by the general formula: CF ₂ =CF-ORf ¹³ ,

where Rf ¹³ is a perfluoroalkyl group containing from 1 to 8 carbon atoms;

fluoromonomer represented by the general formula: CF ₂ =CFOCF ₂ ORf ¹⁴ ,

where Rf ¹⁴ is a linear or branched perfluoroalkyl group containing from 1 to 6 carbon atoms, a cyclic perfluoroalkyl group containing from 5 to 6 carbon atoms, or a linear or branched perfluorooxyalkyl group containing from 2 to 6 carbon atoms and containing from 1 to 3 oxygen atoms; and

fluoromonomer represented by the general formula: CF ₂ =CFO(CF ₂ CF(Y ¹⁵ )O)m(CF ₂ )nF,

where Y ¹⁵ represents a fluorine atom or a trifluoromethyl group, m represents a number from 1 to 4, an represents a number from 1 to 4.

[0538] Furthermore, when a perfluoromonomer is polymerized, the monomer that provides the active cross-linking center may polymerize together with the perfluoromonomer.

[0539] The polymerization of the perfluoromonomer can be carried out in the presence of a polymerization initiator. The polymerization initiator is mentioned above. The amount of the polymerization initiator added is preferably 0.0001 to 10% by mass, and more preferably 0.01 to 5% by mass, based on 100% by mass of the perfluoromonomer. When the amount of the polymerization initiator added during polymerization (the present amount) is in the above-mentioned range, the polymerization reaction of the perfluoromonomer proceeds smoothly and the perfluoroelastomer can be obtained efficiently. When the amount of the added polymerization initiator is too small, a sufficient polymerization rate cannot be obtained or a sufficient yield cannot be obtained.

[0540] The polymerization of the perfluoromonomer can be carried out in the presence of a pH regulator. By carrying out the polymerization in the presence of a pH regulator, it is possible to obtain a sufficient amount of perfluoroelastomer particles at a sufficient polymerization rate, while simultaneously suppressing the adhesion of the perfluoroelastomer to the polymerization vessel. The pH regulator can be added before the start of the polymerization or it can be added after the start of the polymerization.

[0541] Examples of the pH adjuster include an aqueous solution of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, sodium phosphate, potassium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, potassium hydrogen phosphate, potassium dihydrogen phosphate, sodium citrate, potassium citrate, ammonium citrate, sodium gluconate, potassium gluconate, and ammonium gluconate.

[0542] The perfluoroelastomer is preferably at least one elastomer selected from the group consisting of TFE-containing perfluoroelastomers, such as a copolymer containing TFE and a fluoromonomer represented by the general formula (160), (130) or (140), and a copolymer containing TFE, a fluoromonomer represented by the general formula (160), (130) or (140), and a monomer that provides an active crosslinking center.

[0543] In the case of the TFE/PMVE copolymer, its proportion in the composition is preferably 45-90/10-55 (% mol), more preferably 55-80/20-45, even more preferably 55-70/30-45, and most preferably 56-69.5/30.5-44.

[0544] In the case of a copolymer of TFE, PMVE and a monomer that provides an active cross-linking center, its proportion in the composition is preferably 45-89.9/10-54.9/0.01-4 (% mol), more preferably 55-77.9/20-49.9/0.1-3.5, even more preferably 55-69.8/30-44.8/0.2-3, and most preferably 55.3-69.5/30.3-44.5/0.2-2.8.

[0545] In the case of a copolymer of TFE and a fluoromonomer represented by the general formula (160), (130) or (140) containing 4 to 12 carbon atoms, the proportion thereof in the composition is preferably 50 to 90/10 to 50 (% mol), more preferably 60-88/12-40, even more preferably 65-85/15-35, and most preferably 66-84/16-34.

[0546] In the case of a TFE copolymer, a fluoromonomer represented by the general formula (160), (130) or (140) containing 4 to 12 carbon atoms, and a monomer that provides an active crosslinking center, the composition ratio is preferably 50-89.9/10-49.9/0.01-4 (% mol), more preferably 60-87.9/12-39.9/0.1-3.5, even more preferably 65-84.8/15-34.8/0.2-3, and most preferably 66-84.3/15.5-33.8/0.2-2.8.

[0547] When these copolymers have compositional features outside these ranges, the rubbery elastic properties are lost and the properties tend to approach those of a resin.

[0548] The perfluoroelastomer is preferably at least one elastomer selected from the group consisting of copolymers of TFE, a fluoromonomer represented by the general formula (140) and a fluoromonomer that provides an active crosslinking center, copolymers of TFE and a perfluorovinyl ether represented by the general formula (140), copolymers of TFE and a fluoromonomer represented by the general formula (160) and copolymers of TFE, a fluoromonomer represented by the general formula (160) and a monomer that provides an active crosslinking center.

[0549] Examples of the perfluoroelastomer further include perfluoroelastomers described in documents such as International Publication No. WO 97/24381, Japanese Patent Publication No. 61-57324, Japanese Patent Publication No. 04-81608, and Japanese Patent Publication No. 05-13961.

[0550] From the viewpoint of achieving excellent compression set properties at high temperature, the perfluoroelastomer preferably has a glass transition temperature of -70°C or higher, more preferably -60°C or higher, and even more preferably -50°C or higher. From the viewpoint of achieving good cold resistance, the glass transition temperature is preferably 5°C or lower, more preferably 0°C or lower, and even more preferably -3°C or lower.

[0551] The glass transition temperature can be determined as follows. Specifically, using a differential scanning calorimeter (DSC822e, manufactured by Mettler-Toledo International Inc.), 10 mg of a sample is heated at a rate of 10°C/min to obtain a DSC curve, and the position of the point at which the maximum value is reached on the differential DSC curve in the secondary transition is read as the glass transition temperature.

[0552] The perfluoroelastomer preferably has a Mooney viscosity ML (1+20) at 170°C of 30 or more, more preferably 40 or more, and even more preferably 50 or more, from the viewpoint of good heat resistance. Also, from the viewpoint of good processability, it preferably has a Mooney viscosity of 150 or less, more preferably 120 or less, and even more preferably 110 or less.

[0553] The perfluoroelastomer preferably has a Mooney viscosity ML (1+20) at 140°C of 30 or more, more preferably 40 or more, and even more preferably 50 or more, from the viewpoint of good heat resistance. Furthermore, from the viewpoint of good processability, it preferably has a Mooney viscosity of 180 or less, more preferably 150 or less, and even more preferably 110 or less.

[0554] The perfluoroelastomer preferably has a Mooney viscosity ML (1+10) at 100°C of 10 or more, more preferably 20 or more, and even more preferably 30 or more, from the viewpoint of good heat resistance. Furthermore, from the viewpoint of good processability, it preferably has a Mooney viscosity of 120 or less, more preferably 100 or less, and even more preferably 80 or less.

[0555] Mooney viscosity can be measured in accordance with JIS K6300 at 170°C, 140°C or 100°C using a Mooney viscometer model MV2000E manufactured by ALPHA TECHNOLOGIES.

[0556] According to the first production method of the present invention, an aqueous dispersion of a perfluoroelastomer can be obtained in the form of a fluoropolymer. The obtained aqueous dispersion of a perfluoroelastomer preferably has a solids concentration (perfluoroelastomer content) of 10 to 50% by mass, more preferably 15 to 40% by mass, and even more preferably 20 to 30% by mass upon completion of the polymerization.

[0557] The concentration of solids (perfluoroelastomer content) in an aqueous dispersion of the perfluoroelastomer can be determined by drying 1 g of the aqueous dispersion at 150°C for 60 minutes, measuring the mass of non-volatile matter, and calculating the ratio of the mass of non-volatile matter to the mass of the aqueous dispersion.

[0558] The aqueous dispersion of the perfluoroelastomer may be subjected to treatment such as coagulation or heating.

[0559] Coagulation can be carried out by adding a coagulating agent to the aqueous dispersion. Examples of the coagulating agent include acids such as hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, and trifluoroacetic acid, and at least one acid selected from the group consisting of nitric acid and hydrochloric acid is preferred.

[0560] The coagulated perfluoroelastomer can be washed with water to remove a small amount of impurities such as a buffer and salt present in the perfluoroelastomer, and then the washed perfluoroelastomer can be dried. The drying temperature is preferably from 40 to 200°C, more preferably from 50 to 180°C, and even more preferably from 70 to 150°C.

[0561] The form of the perfluoroelastomer obtained after coagulation is not limited, it may be a gum, crumbs, powder, granules or the like, and is preferably a gum or crumbs. The gum is small mass particles of the perfluoroelastomer. The crumbs are an amorphous mass of the perfluoroelastomer formed by fusing the particles, which cannot maintain the shape of small particles like gum at room temperature. The gum or crumbs are appropriately obtained by coagulation, drying and the like in a conventionally known manner from the aqueous dispersion obtained by the production method of the present invention.

[0562] In the production method of the present invention, a perfluoroelastomer in an aqueous dispersion can be coagulated using an acid containing no metal elements, and the coagulated perfluoroelastomer can be washed with a liquid medium having a reduced content of metal elements. In addition, in the production method of the present invention, the washed perfluoroelastomer can be dried. By such a production method, a perfluoroelastomer having a metal content of 10 ppm by mass or less in the perfluoroelastomer can be obtained. The liquid medium is water, and even more preferably ultrapure water. The metal content in the liquid medium is 2 ppm by mass or less, more preferably 1 ppm by mass or less, and even more preferably 0.5 ppm by mass or less. In addition, the production method described in International Publication No. WO 2018/225586 can be used in the production method of the present invention. According to this production method, it is possible to obtain a perfluoroelastomer with a reduced metal content, as well as a perfluoroelastomer suitable for producing components of semiconductor devices.

[0563] The polymer (1), the decomposition products and by-products of the polymer (1) generated side-by-side from the polymer (1), residual monomers and the like can be collected from the waste water generated during coagulation or washing and/or from the exhaust gas generated during drying and then purified for reuse of the polymer (1), the decomposition products and by-products of the polymer (1) generated side-by-side from the polymer (1), residual monomers and the like. The method for carrying out the collection and purification is not limited, and it can be carried out by a known method. For example, it can be carried out by the method described in the National Publication of International Patent Application No. 2011-520020.

[0564] In the production method of the present invention, when a fluoropolymer is subjected to coagulation, washing, drying or the like, waste water or exhaust gas is generated. The polymer (1), decomposition products and by-products of the polymer (1) generated side by side from the polymer (1), residual monomers and the like can be collected from the waste water generated by the coagulation or washing and/or from the exhaust gas generated by drying and then purified for reuse of the polymer (1), decomposition products and by-products of the polymer (1) generated side by side from the polymer (1), residual monomers and the like. The method for carrying out the collection and purification is not limited, and it can be carried out using a known method. For example, it can be carried out by the method described in National Publication of International Patent Application No. 2011-520020. Examples of methods further include those described in U.S. Patent Application Publication No. 2007/15937, U.S. Patent Application Publication No. 2007/25902, and U.S. Patent Application Publication No. 2007/27251. Specific examples of methods are as follows.

[0565] An example of a method for collecting a polymer (1), decomposition products and by-products of the polymer (1) generated side-by-side from the polymer (1), residual monomers and the like from waste water is a method in which the waste water is brought into contact with adsorbent particles formed from an ion-exchange resin, activated carbon, silica gel, clay, zeolite or the like so that the particles can adsorb the polymer (1) and other substances, and then the waste water and the adsorbent particles are separated. Combustion of the adsorbent particles that have adsorbed the polymer (1) and other substances can prevent the release of the polymer (1) and other substances into the environment.

[0566] Alternatively, the polymer (1) and other particles can be removed and eluted by a known method from the ion exchange resin particles adsorbed by the polymer (1) and others, and collected. For example, in the case of using anion exchange resin particles as the ion exchange resin particles, the polymer (1) and other substances can be eluted by bringing a mineral acid into contact with the anion exchange resin. When a water-soluble organic solvent is added to the resulting eluate, the mixture usually separates into two phases. Since the lower phase contains the polymer (1) and other substances, the polymer (1) and other substances can be collected by collecting and neutralizing the lower phase. Examples of the water-soluble organic solvent include polar solvents such as alcohols, ketones, and ethers.

[0567] Other methods for collecting the polymer (1) and others from the ion-exchange resin particles include a method using an ammonium salt and a water-soluble organic solvent and a method using an alcohol and, if necessary, an acid. In the latter method, ester derivatives of the polymer (1) and other substances are generated, and thus they can be easily separated from the alcohol by distillation.

[0568] When the wastewater contains fluoropolymer particles and other solids, they are preferably removed before the wastewater and adsorbent particles come into contact with each other. Examples of methods for removing fluoropolymer particles and other solids include a method of adding an aluminum salt, for example, to precipitate these components and then separating the wastewater and sediments, as well as an electrocoagulation method. The components can also be removed by a mechanical method, and examples thereof include a cross-flow filtration method, an adsorption filtration method, and a pre-layer filtration method.

From the viewpoint of performance, the waste water preferably contains the fluoropolymer in a non-agglomerated form at a low concentration, more preferably less than 0.4% by weight and particularly preferably less than 0.3% by weight.

[0569] An example of a method for collecting the polymer (1) and other polymers from the exhaust gas is a method in which a scrubber is contacted with deionized water, an aqueous alkaline solution, an organic solvent such as a glycol ether solvent, or the like to obtain a scrubbing solution containing the polymer (1) and others. When the aqueous alkaline solution used is a highly concentrated aqueous alkaline solution, the scrubbing solution can be collected in a state in which the polymer (1) and others are phase separated, and thus the polymer (1) and others can be easily collected and reused. Examples of the alkaline compound include alkali metal hydroxides and quaternary ammonium salts.

[0570] The scrubber solution containing the polymer (1) and other polymers can be concentrated, for example, using a reverse osmosis membrane. The concentrated scrubber solution typically contains fluoride ions. However, the fluoride ions can be removed by adding aluminum oxide after concentration so that the polymer (1) and other substances can be easily reused. Alternatively, the scrubber solution can be contacted with adsorbent particles so that the adsorbent particles can adsorb the polymer (1) and other substances, and thus the polymer (1) and other substances can be collected using the above method.

[0571] The polymer (1) and other polymers selected by any of the methods can be reused in the production of the fluoropolymer.

[0572] The production method of the present invention is a method for producing PTFE, wherein the method comprises polymerizing TFE in an aqueous medium to obtain PTFE, wherein PTFE is high molecular weight PTFE, the polymer (1) is a polymer of the monomer (1) represented by the general formula (1), in which the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0 mass% or less relative to the polymer (1) (hereinafter, it may be referred to as the second production method of the present invention).

[0573] Since the second production method of the present invention involves polymerizing TFE in the presence of the polymer (1), it is possible to obtain PTFE which is substantially free of the dimer and trimer of the monomer constituting the polymer (1). Also, according to the production method of the present invention, it is possible to obtain PTFE having a high molecular weight.

[0574] In the second production method of the present invention, as the polymer (1), a polymer (1) having a content of the polymerization unit (1) of 50% by mass or more may be used in the same manner as in the first production method of the present invention, or a polymer (1) having a content of the polymerization unit (1) of less than 50% by mass may be used.

[0575] In the polymer (1) used in the second production method of the present invention, the content of the polymerization unit (1) is, in the order of preference, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, with respect to all the polymerization units. It is particularly preferable that the content of the polymerization unit (1) is substantially 100% by mass, and it is most preferable that the polymer (1) contains only the polymerization units (1).

[0576] In the polymer (1) used in the second production method of the present invention, the content of the polymerization unit derived from another monomer copolymerizable with the monomer (1) is, in the order of preference, 99.0% by mass or less, 97.0% by mass or less, 95.0% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less, with respect to all the polymerization units. It is particularly preferable that the content of the polymerization unit derived from another monomer copolymerizable with the monomer (1) is substantially 0% by mass, and it is most preferable that the polymer (1) does not contain a polymerization unit derived from another monomer.

[0577] The configuration of the polymer (1) used in the second production method of the present invention is the same as the configuration of the polymer (1) used in the first production method of the present invention, except that the content of the polymerization unit (1) can be selected from a wide range.

[0578] It is preferable that the second production method according to the present invention comprises polymerizing the monomer (1) to obtain a crude composition containing a polymer of the monomer (1), and removing the dimer and trimer of the monomer (1) contained in the crude composition from the crude composition to obtain a polymer (1) in which the content of the dimer and trimer of the monomer (1) is 1.0% by mass or less with respect to the polymer (1).

[0579] In the second production method of the present invention, in the case of polymerizing the monomer (1) and another monomer copolymerizable with the monomer (1) to obtain a crude composition, the obtained crude composition usually contains a dimer and a trimer consisting of a polymerization unit (1) obtained from the monomer (1) and a polymerization unit obtained from another monomer copolymerizable with the monomer (1). By removing the dimer and the trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer contained in the crude composition from the crude composition, it is possible to obtain a polymer (1) in which the content of the dimer and the trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer is 1.0 mass% or less with respect to the polymer (1).

[0580] The polymerization of the monomer (1) can be carried out by the method described in the first production method of the present invention.

[0581] In the second production method of the present invention, it is preferable that the polymerization of the monomer (1) is carried out in an aqueous medium substantially in the absence of a fluorosurfactant (except for the monomer (1)).

[0582] The fluorosurfactant is as described above.

[0583] After polymerization of the monomer (1), the dimer and trimer of the monomer (1) contained in the crude composition obtained by polymerization of the monomer (1) are removed from the crude composition. The method for removing the dimer and trimer is indicated above.

[0584] In addition, a fraction having a molecular weight of 3,000 or less, a fraction having a molecular weight of 2,000 or less, a fraction having a molecular weight of 1,500 or less, and a fraction having a molecular weight of 1,000 or less can be removed by appropriately selecting dimer and trimer removing means.

[0585] The polymerization of TFE can be carried out using the method indicated above. In addition to TFE, the modifying monomer can also be polymerized as indicated above.

[0586] The present invention also relates to a composition comprising a polymer (1) and a fluoropolymer, wherein the fluoropolymer comprises a polymerization unit derived from a perfluoromonomer, and the content of the polymerization unit derived from the perfluoromonomer in the fluoropolymer is 90 mol% or more relative to the total polymerization units of the fluoropolymer, the polymer (1) is a polymer of the monomer (1) represented by the general formula (1), the polymerization unit (1) derived from the monomer (1) in the polymer (1) is 50 mass% or more relative to the total polymerization units of the polymer (1), and the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0 mass% or less relative to the polymer (1) (hereinafter, this may be referred to as the first composition of the present invention).

[0587] The first composition of the present invention can be obtained by the first production method of the present invention.

[0588] The form of the first composition of the present invention is not limited, but it may be in the form of, for example, an aqueous dispersion, a coagulated product, a dried product, a gum, crumbs, powder, granules, or the like. An aqueous dispersion refers to a dispersion system in which an aqueous medium is a dispersion medium and a fluoropolymer is a dispersoid. The above-mentioned aqueous medium is not limited as long as it is a liquid containing water, and it may contain, in addition to water, an organic solvent such as an alcohol, an ether, a ketone, and paraffin wax.

[0589] The first composition of the present invention may be an aqueous dispersion of a fluoropolymer in which primary particles of a fluoropolymer are dispersed in an aqueous medium. The aqueous dispersion may be any of aqueous dispersions obtained by the above-mentioned polymerization, dispersions obtained by concentrating this aqueous dispersion or subjecting the aqueous dispersion to a treatment to stabilize the dispersion, and aqueous dispersions obtained by dispersing a fluoropolymer powder in an aqueous medium in the presence of a surfactant. The composition of the present invention may also be a fluoropolymer powder. The fluoropolymer powder is obtained, for example, by coagulating a fluoropolymer in an aqueous dispersion of the fluoropolymer using a known method.

[0590] The content of the polymer (1) in the composition is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, particularly preferably 0.05% by mass or more, and most preferably 0.10% by mass or more, with respect to the fluoropolymer. Further, the content of the polymer (1) in the composition is preferably 10% by mass or less, more preferably 5.0% by mass or less, even more preferably 2.0% by mass or less, particularly preferably 1.0% by mass or less, and most preferably 0.50% by mass or less, with respect to the fluoropolymer.

[0591] The content of the polymer (1) can be determined by solid-state NMR measurement.

Also, International Publication No. WO 2014/099453, International Publication No. WO 2010/075497, International Publication No. WO 2010/075496, International Publication No. WO 2011/008381, International Publication No. WO 2009/055521, International Publication No. WO 1987/007619, Japanese Patent Laid-Open No. 61-293476, International Publication No. WO 2010/075494, International Publication No. WO 2010/075359, International Publication No. WO 2006/119224, International Publication No. WO 2013/085864, International Publication No. WO 2012/082707, International Publication No. WO 2012/082703, International Publication No. WO 2012/082454, International Publication No. WO 2012/082451, International Publication No. WO 2006/135825, International Publication No. WO 2004/067588, International Publication No. WO 2009/068528, Japanese Patent Laid-Open No. 2004-075978, Japanese Patent Laid-Open No. 2001-226436, International Publication No. WO 1992/017635, International Publication No. WO 2014/069165, Japanese Patent Laid-Open No. 11-181009, and the like, describe methods for measuring the content of the corresponding polymers described therein. The methods for measuring the corresponding polymers described therein can be used as a method for measuring polymer content (1).

[0592] In addition, when the fluoropolymer is a perfluoroelastomer, the content of the polymer (1) can be measured by the following method. It can be measured by a method in which the composition is mixed with a solvent that dissolves the perfluoroelastomer, deionized water is added to the resulting mixed solution to extract the polymer (1) from the resulting mixed solution, the upper phase (aqueous phase) containing the polymer (1) is collected, and the mass of the residue (polymer (1)) obtained by heating and drying the collected upper phase is measured to calculate the content of the polymer (1).

[0593] As a solvent that dissolves the perfluoroelastomer, a solvent containing a perhalogen in which all hydrogen atoms are changed to halogen atoms is preferable, and in particular, a perfluorinated solvent in which all hydrogen atoms are changed to fluorine atoms is preferable. Specific examples of the perfluorinated solvent include perfluoro-tertiary amines such as perfluorotri-n-butylamine and perfluorotriethylamine, perfluorinated tetrahydrofuran, perfluorobenzene, Fluorinert FC-77 (manufactured by 3M Company), Demnum solvent (manufactured by Daikin Industries, Ltd. _, main component: _C6F14 ), R-318 (manufactured by Daikin Industries, Ltd., main component: _C4F8Cl2 ) and Fluorinert FC- ₄₃ (manufactured by 3M Company, main component: ( _C4F9 ) _3N ), and among them _, perfluorotri- _n -butylamine and Fluorinert FC-77 are preferable in terms of performance properties.

[0594] Furthermore, as a solvent that dissolves the perfluoroelastomer, various fluorinated solvents other than those exemplified above are preferably used, and specific examples thereof include perfluoroalkanes, HFCs ( _{hydrofluorocarbons), HFEs (hydrofluoroethers), and HCFCs (hydrochlorofluorocarbons). Specifically, HFE-7100 (manufactured by 3M Company, main component: C4F9OCH3 )} , HFE-7200 (manufactured by _3M Company, main component: _C4F9OC2H5 ) _{, and Vertrel XF (manufactured by The Chemours Company, main component: C5H2F10 ) can be mentioned .}

[0595] In the first composition of the present invention, it is preferable that the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less, relative to the polymer (1). The content of the dimer and trimer in the first composition of the present invention is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, even more preferably 0.001% by mass or less, and particularly preferably 0.0001% by mass or less, relative to the polymer (1).

[0596] In the first composition of the present invention, it is preferable that the content of the dimer and the trimer consisting of the polymerization unit (1) obtained from the monomer (1) and the polymerization unit obtained from another monomer copolymerizable with the monomer (1) in the polymer (1) is 1.0 mass% or less, based on the polymer (1). The content of the dimer and the trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer in the first composition of the present invention is preferably 0.1 mass% or less, more preferably 0.01 mass% or less, still more preferably 0.001 mass% or less, and particularly preferably 0.0001 mass% or less, based on the polymer (1).

[0597] The content of dimer and trimer in the first composition of the present invention can be measured by a method that is the same as for the content of dimer and trimer in the polymer (1).

[0598] The polymer (1) in the first composition of the present invention may contain a fraction having a molecular weight of 3,000 or less, a fraction having a molecular weight of 2,000 or less, a fraction having a molecular weight of 1,500 or less, or a fraction having a molecular weight of 1,000 or less, in the same content as the polymer (1) used in the first production method of the present invention, or may not contain them.

[0599] The polymer (1) in the first composition of the present invention may have the same configuration as the polymer (1) used in the first production method of the present invention.

[0600] The fluoropolymer in the first composition of the present invention contains a polymerization unit derived from a perfluoromonomer, and the content of the polymerization unit derived from a perfluoromonomer in the fluoropolymer is 90 mol% or more relative to all polymerization units of the fluoropolymer. The fluoropolymer in the first composition of the present invention may have the same configuration as the configuration of the fluoropolymer obtained by the first production method of the present invention. The fluoropolymer in the first composition of the present invention may be, for example, PTFE or a perfluoroelastomer. PTFE may be a TFE homopolymer containing only a TFE unit, or a modified PTFE containing a TFE unit and a unit of a modifying monomer.

[0601] When the fluoropolymer is PTFE or a perfluoroelastomer, it is preferable that the first composition of the present invention contains little or no metal components. The metal content in the composition is preferably 10 ppm by weight or less, more preferably 7 ppm by weight or less, even more preferably 5 ppm by weight or less, and particularly preferably 1 ppm by weight or less. The composition with a reduced metal content may be a coagulated product or a dried product. The coagulated product is obtained by coagulating the fluoropolymer in an aqueous dispersion, and the dried product is obtained by drying the coagulated product.

[0602] The metal content of the composition can be determined by placing the composition in a platinum crucible, washing it with dilute nitric acid and ultrapure water, burning it to form ash using a burner and an electric furnace, heating and decomposing it with sulfuric acid and hydrofluoric acid, dissolving it in dilute nitric acid to prepare a measurement solution, measuring the content of 30 metal elements (Fe, Na, K, Li, Be, Mg, Al, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Ag, Cd, In, Sn, Cs, Ba, Pb, Bi and Th) in the resulting measurement solution using an ICP mass spectrometer (Agilent 8800, manufactured by Agilent Technologies), and summing up the corresponding measured values.

[0603] When the fluoropolymer is a perfluoroelastomer, the first composition of the present invention may further contain a curing agent (crosslinking agent), a filler, and the like. Examples of the curing agent include polyols, polyamines, organic peroxides, organic tin compounds, bis(aminophenol)tetraamine, and bis(thioaminophenol).

[0604] It is preferred that the perfluoroelastomer composition of the present invention comprises at least one material selected from the group consisting of an inorganic nitride, an organic tin compound, an ammonia-generating compound, and a crosslinking agent.

[0605] Examples of the cross-linking agent include cross-linking agents used in peroxide cross-linking, polyol cross-linking, polyamine cross-linking, triazine cross-linking, oxazole cross-linking, imidazole cross-linking, and thiazole cross-linking.

[0606] From the viewpoint of heat resistance, steam resistance, amine resistance and good cross-linking, 2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane (AFTA-Ph) is preferable as a cross-linking agent.

[0607] The content of the cross-linking agent is preferably 0.05 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the perfluoroelastomer.

[0608] Examples of the filler include organic fillers made from engineering plastics such as polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyoxybenzoate, and polytetrafluoroethylene powder; metal oxide fillers such as aluminum oxide, silicon oxide, yttrium oxide, and titanium oxide; metal carbide fillers such as silicon carbide and aluminum carbide, and metal nitride fillers such as silicon nitride and aluminum nitride; and inorganic fillers such as aluminum fluoride, fluorocarbon, barium sulfate, carbon black, silicon dioxide, clay, and talc.

[0609] The content of the filler is preferably from 0.5 to 100 parts by mass, and more preferably from 5 to 50 parts by mass, based on 100 parts by mass of the perfluoroelastomer.

[0610] In particular, in the field where high cleanliness and stain-resistant properties are not required, conventional additives are compounded with perfluoroelastomers as needed, such as processing aids, plasticizers and colorants, and one or more types of conventional cross-linking agents or cross-linking additives other than those described above may be compounded.

[0611] The present invention also relates to a composition comprising a polymer (1) and PTFE, wherein PTFE is high molecular weight PTFE, the polymer (1) is a polymer of a monomer (1) represented by the general formula (1), and the content of a dimer and a trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less relative to the polymer (1) (hereinafter, this may be referred to as the second composition of the present invention).

[0612] The second composition of the present invention can be obtained by the second production method of the present invention.

[0613] The second composition of the present invention may be an aqueous PTFE dispersion in which PTFE primary particles are dispersed in an aqueous medium. The aqueous dispersion may be any aqueous dispersion obtained by the above-mentioned polymerization, a dispersion obtained by concentrating this aqueous dispersion or treating the aqueous dispersion to stabilize the dispersion, and an aqueous dispersion obtained by dispersing PTFE powder in an aqueous medium in the presence of a surfactant. The composition of the present invention may also be a PTFE powder. The PTFE powder is obtained, for example, by coagulating PTFE in an aqueous PTFE dispersion in a known manner.

[0614] The content of the polymer (1) in the composition is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, particularly preferably 0.05% by mass or more, and most preferably 0.10% by mass or more, with respect to PTFE. Further, the content of the polymer (1) in the composition is preferably 10% by mass or less, more preferably 5.0% by mass or less, even more preferably 2.0% by mass or less, particularly preferably 1.0% by mass or less, and most preferably 0.50% by mass or less, with respect to PTFE.

[0615] The content of polymer (1) can be determined by solid-phase NMR measurement.

In addition, International Publication No. WO 2014/099453, International Publication No. WO 2010/075497, International Publication No. WO 2010/07 54 96, International Publication No. WO 2011/008381, International Publication No. WO 2009/055521, International Publication No. WO 1987/007619, Japanese Patent Laid-Open No. 61-2 9347 6, International Publication No. WO 2010/075494, International Publication No. WO 2010/075359, International Publication No. WO 2006/119224, International Publication No. WO 2013/085864, International Publication No. WO 2012/082707, International Publication No. WO 2012/082703, International Publication No. WO 2012/082454, International Publication No. WO 2012/082451, International Publication No. WO 2006/135825, International Publication No. WO 2004/067588, International Publication No. WO 2009/068528, Japanese Patent Laid-Open No. 2004-075978, Japanese Patent Laid-Open No. 2001-226436, International Publication No. WO 1992/017635, International Publication No. WO 2014/069165, Japanese Patent Laid-Open No. 11-181009 and and the like, describe methods for measuring the content of the corresponding polymers described therein. The methods for measuring the corresponding polymers described therein can be used as a method for measuring the polymer content (1).

[0616] In the second composition of the present invention, it is preferable that the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less, based on the polymer (1). The content of the dimer and trimer in the second composition of the present invention is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, even more preferably 0.001% by mass or less, and particularly preferably 0.0001% by mass or less, based on the polymer (1).

[0617] In the second composition of the present invention, it is preferable that the content of the dimer and the trimer consisting of the polymerization unit (1) obtained from the monomer (1) and the polymerization unit obtained from another monomer copolymerizable with the monomer (1) in the polymer (1) is 1.0 mass% or less, based on the polymer (1). The content of the dimer and the trimer consisting of the polymerization unit (1) and the polymerization unit obtained from another monomer in the second composition of the present invention is preferably 0.1 mass% or less, more preferably 0.01 mass% or less, even more preferably 0.001 mass% or less, and particularly preferably 0.0001 mass% or less, based on the polymer (1).

[0618] The content of dimer and trimer in the second composition of the present invention can be measured by a method that is the same as for measuring the content of dimer and trimer in the polymer (1).

[0619] The polymer (1) in the second composition of the present invention may contain a fraction having a molecular weight of 3,000 or less, a fraction having a molecular weight of 2,000 or less, a fraction having a molecular weight of 1,500 or less, or a fraction having a molecular weight of 1,000 or less, in the same content as the polymer (1) used in the second production method of the present invention.

[0620] The polymer (1) in the second composition of the present invention may have the same configuration as the polymer (1) used in the second production method of the present invention.

[0621] The PTFE in the second composition of the present invention may have the same configuration as the PTFE (high molecular weight PTFE) obtained by the second production method of the present invention. The PTFE may be a PTFE homopolymer containing only a TFE unit, or a modified PTFE containing a TFE unit and a unit of a modifying monomer.

[0622] In the first composition of the present invention and the second composition of the present invention, the modified PTFE preferably contains a polymerization unit derived from a modifying monomer (hereinafter also referred to as a "modifying monomer unit") in a range of 0.00001 to 1% by mass relative to the total polymerization units of the PTFE. The lower limit of the content of the modifying monomer unit is more preferably 0.0001% by mass, still more preferably 0.001% by mass, and still more preferably 0.005% by mass. The upper limit of the content of the modifying monomer unit is, in order of preference, 0.80% by mass, 0.70% by mass, 0.50% by mass, 0.30% by mass, 0.20% by mass, 0.15% by mass, 0.10% by mass, or 0.05% by mass. In the present invention, a unit of modifying monomer means a part of the molecular structure of PTFE as a part derived from the modifying monomer.

[0623] In the present invention, the content of each monomer unit constituting PTFE can be calculated by combining NMR, FT-IR, elemental analysis, and fluorescence X-ray analysis, depending on the type of monomer. The content of each monomer unit constituting PTFE can also be determined by calculation based on the amount of modifying monomer added for use in polymerization.

[0624] When the modifying monomer contains the modifying monomer (A), the content of the polymerization unit derived from the modifying monomer (A) is preferably in the range of 0.00001 to 1.0 mass % relative to all polymerization units in PTFE. The lower limit thereof is more preferably 0.0001 mass %, more preferably 0.0005 mass %, still more preferably 0.001 mass %, still more preferably 0.005 mass %. The upper limit is, in order of preference, 0.90 mass %, 0.50 mass %, 0.40 mass %, 0.30 mass %, 0.20 mass %, 0.15 mass %, 0.10 mass %, 0.08 mass %, 0.05 mass % or 0.01 mass %.

[0625] The average primary particle size of PTFE is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 350 nm or less. According to the production method of the present invention, primary particles having a relatively small average primary particle size can be obtained. In addition, an even smaller average primary particle size can be obtained, for example, by adding a modifying monomer to the polymerization system at the initial stage of TFE polymerization. The lower limit of the average primary particle size may be, for example, but not limited to, 50 nm or 100 nm. From the viewpoint of molecular weight, it is preferably 100 nm or more, and even more preferably 150 nm or more.

[0626] The average primary particle size of PTFE can be measured by dynamic light scattering. It can be measured by first preparing an aqueous dispersion of PTFE with a solid polymer concentration adjusted to approximately 1.0% by mass, and then using dynamic light scattering at a measurement temperature of 25°C with 70 repetitions of measurements, wherein the solvent (water) has a refractive index of 1.3328 and the solvent (water) has a viscosity of 0.8878 mPa⋅s. For dynamic light scattering, for example, ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) can be used.

[0627] It is preferable that PTFE has an aspect ratio of less than 2.00. The aspect ratio is the aspect ratio of the PTFE primary particles. The upper limit of the aspect ratio of the PTFE primary particles is, in order of preference, 1.90 or less, 1.80 or less, 1.70 or less, 1.60 or less, 1.50 or less, 1.45 or less, 1.40 or less, 1.35 or less, 1.30 or less, 1.20 or less, or 1.10 or less. According to the production method of the present invention, primary particles having a relatively small aspect ratio can be obtained. Also, an even smaller aspect ratio of the primary particles can be obtained, for example, by adding a modifying monomer to the polymerization system at the initial stage of TFE polymerization.

[0628] In the case of measuring the aspect ratio of PTFE using an aqueous PTFE dispersion, it can be determined by preparing an aqueous PTFE dispersion having a solid polymer concentration adjusted to about 1.0 mass% and observing it with a scanning electron microscopy (SEM), subjecting 400 or more randomly extracted particles to image processing and obtaining the aspect ratio from the average value of the ratios of their major axis to minor axis. In the case of measuring the aspect ratio of PTFE using a PTFE powder, it can be determined by irradiating the PTFE powder with an electron beam, then adding it to an aqueous solution of a fluorosurfactant, using ultrasonic waves to redisperse it in the aqueous solution to thereby obtain an aqueous PTFE dispersion. The aspect ratio can be obtained in the above-described manner using the aqueous dispersion thus prepared.

[0629] The standard relative density of PTFE (SSG) is preferably 2280 or less, more preferably 2200 or less, even more preferably 2190 or less, and still more preferably 2180 or less. It is also preferably 2130 or more. SSG is measured by the water displacement method in accordance with ASTM D 7 92 using a specimen molded in accordance with ASTM D 4895-89.

[0630] PTFE may have a thermal instability index (TII) of 20 or more. The thermal instability index (TII) of PTFE can be adjusted within the above-mentioned range, for example, by using the polymer (1) to produce PTFE. The TII is preferably 25 or more, more preferably 30 or more, and even more preferably 35 or more. It is particularly preferably 40 or more. The TII is measured in accordance with ASTM D 4895-89.

[0631] The weight loss temperature of 0.1% PTFE may be 400°C or lower. The weight loss temperature of 0.1% PTFE can be controlled within the above range, for example, by using the polymer (1) to produce PTFE.

[0632] The 0.1% mass loss temperature can be measured by accurately weighing approximately 10 mg of PTFE powder with no history of heating to a temperature of 300°C or higher, placing it in a special aluminum pan, and using a TG/DTA (Dynamic Thermogravimetric Analyzer). The 0.1% mass loss temperature can be defined as the temperature corresponding to the heating point of the aluminum pan in the temperature range from 25°C to 600°C at a rate of 10°C/min in an air atmosphere, when the mass decreases by 0.1% by weight.

[0633] The 1.0% weight loss temperature of PTFE may be 4 92°C or lower. The 1.0% weight loss temperature of PTFE can be controlled within the above range, for example, by using the polymer (1) to produce PTFE.

[0634] The 1.0% mass loss temperature can be measured by accurately weighing approximately 10 mg of PTFE powder with no history of heating to a temperature of 300°C or higher, placing it in a special aluminum pan, and using a TG/DTA (Dynamic Thermogravimetric Analyzer). The 1.0% mass loss temperature can be defined as the temperature corresponding to the heating point of the aluminum pan in the temperature range from 25°C to 600°C at a rate of 10°C/min in an air atmosphere, when the mass decreases by 1.0% by mass.

[0635] The peak temperature of the PTFE is preferably 347°C or lower, more preferably 346°C or lower, and even more preferably 345°C or lower. The lower limit of the peak temperature of the PTFE may be 333°C or higher or 335°C or higher.

[0636] The peak temperature of PTFE can be measured by accurately weighing approximately 10 mg of PTFE powder with no history of heating to a temperature of 300°C or higher, placing it in a special aluminum pan, and using a TG/DTA (synchronous thermogravimetric analyzer). The peak temperature can be reported as the temperature corresponding to the maximum value appearing on the differential thermal curve (DTA) obtained by increasing the temperature of PTFE with no history of heating to a temperature of 300°C or higher at 10°C/min using a TG/DTA (synchronous thermogravimetric analyzer).

[0637] In one embodiment, the first composition of the present invention and the second composition of the present invention comprise a fluorosurfactant. The composition comprising the fluorosurfactant has the advantage that it can be stably produced at high productivity using the fluorosurfactant.

[0638] In one embodiment, the first composition of the present invention and the second composition of the present invention are substantially free of fluorosurfactant. To obtain a composition substantially free of fluorosurfactant, a perfluoromonomer such as TFE must be polymerized without the use of a fluorosurfactant, but the production method of the present invention, which uses polymer (1), allows for the preparation of such a composition.

[0639] In the present description, the expression "substantially free of a fluorosurfactant" means that the content of the fluorosurfactant in the composition is 10 ppm by weight or less, and preferably it is 1 ppm by weight or less, more preferably 100 ppb by weight or less, even more preferably 10 ppb by weight or less, even more preferably 1 ppb by weight or less, and particularly preferably the fluorosurfactant is at or below the detection limit as measured by liquid chromatography-mass spectrometry (LC/MS).

[0640] The content of the fluorosurfactant can be quantified using a known method. For example, it can be quantified using LC/MS analysis.

First, methanol is added to the extraction mixture, and the resulting extracted liquid is analyzed by LC/MS. To further enhance extraction efficiency, Soxhlet extraction, ultrasonication, or similar techniques can be used.

Molecular weight information is extracted from the obtained LC/MS spectrum to confirm the structural formula match of the fluorosurfactant candidate.

Thereafter, aqueous solutions having five or more different levels of content of the confirmed fluorosurfactant are prepared and LC/MS analysis of the aqueous solutions with the corresponding content levels is performed, and the relationship between the content level and the area corresponding to that content level is displayed as a calibration curve.

Then, using the calibration curve, the LC/MS chromatogram area of the fluorosurfactant in the extracted liquid can be converted into the fluorosurfactant content.

[0641] The first composition of the present invention and the second composition of the present invention can be suitably used for the applications mentioned above.

[0642] Although embodiments have been described above, it will be understood that various changes in form and detail may be made therein without departing from the spirit and scope of the claims.

Examples

[0643] Embodiments of the present invention will now be described with reference to Examples, but the present invention is not limited solely to such Examples.

[0644] Each numerical value in the Examples is measured using the following methods.

[0645] oxygen concentration in the reactor>

The gas exiting the reactor gas pipeline in the N2 stream is measured and analyzed using a low oxygen concentration analyzer (trade name "PS-820-L" manufactured by Iijima Electronics Corporation) to thereby determine the oxygen concentration during the reaction.

[0646] <Method for measuring weight-average molecular weight (Mw), number-average molecular weight (Mn) and content of fraction having molecular weight of 3000 or less>

The Mw and Mn of a polymer (such as polymers K and L) are determined by performing gel permeation chromatography (GPC) measurements using a 1260 Infinity II manufactured by Agilent Technologies and using coupled columns manufactured by Tosoh Corporation (one TSKgel G3000PWXL and one TSGgel GMPWXL) while allowing a mixed solvent of Tris buffer and acetonitrile (Tris buffer: acetonitrile = 8:2 (volume/volume)) to flow at a flow rate of 0.5 mL/min, and the molecular weights are calculated using monodisperse polyethylene oxide (PEO) and polyethylene glycol (PEG) as standards.

[0647] (Alternation relation)

The alternation ratio is obtained by measuring ¹⁹ F-nMP on the polymer and calculating the alternation ratio from the corresponding total integral values of the two peaks (the peak appearing at -75 ppm to -80 ppm and the peak appearing at -80 ppm to -84 ppm) obtained from "OCF ₂ *" CF ₂ =CFOCF ₂ CF ₂ SO ₃ Na appearing in the NMR spectrum, according to the following formula:

Alternation ratio (%)≥(b×2)/(a+b)×100

a: The total integral value of the peak in the region from -75 ppm to -80 ppm.

b: Total integral value of the peak in the region from -80 ppm to -84 ppm.

[0648] The alternation ratio calculated above represents the proportion of the polymerization unit adjacent to the polymerization unit derived from VdF among the polymerization units derived from CF ₂ =CFOCF ₂ CF ₂ SO ₃ Na in the polymer.

The proportion of carbon atoms (C*) in the polymerization unit obtained from VdF(C*H ₂ =CF ₂ ) associated with a carbon atom (C*) in the polymerization unit obtained from CF ₂ =C*FOCF ₂ CF ₂ SO ₃ Na is obtained using the following formula:

Share (%) = (b x 2) / (a + b) x 100

The proportion of carbon atoms (carbon atom (C**) in the polymerization unit obtained from C**F ₂ =C**FOCF ₂ CF ₂ SO ₃ Na and carbon atoms (C**) in the polymerization unit obtained from VdF (CH ₂ =C**F ₂ )) other than carbon atoms (C*) in the polymerization unit obtained from VdF (C*H ₂ =CF ₂ ) bonded to carbon atoms (C*) in the polymerization unit obtained from CF ₂ =C*FOCF ₂ CF ₂ SO ₃ Na is obtained using the following formula:

Share (%) = (a-b)/(a+b)×100

[0649] (Method of measuring the content of dimer and trimer of a monomer (such as monomers K and L) in a polymer (such as polymers K and L)

(1) Extraction from aqueous solution

The solids content of the aqueous polymer solution is measured, and an amount of the aqueous solution corresponding to 0.2 g of polymer solids is weighed. Water and methanol are then added to the water in the aqueous solution to obtain a 50/50 ratio (volume %), resulting in a mixed solution containing the polymer, water, and methanol. The resulting mixed solution is then filtered using an ultrafiltration disc (molecular weight cutoff of 3000 Da), and the supernatant containing the polymer is collected as the extracted liquid.

The analysis of the extracted liquid is carried out using a liquid chromatograph-mass spectrometer (Waters, LC-MS ACQUITY UPLC/TQD) and a chromatogram of the extracted liquid is obtained.

The content of the dimer and trimer of the monomer contained in the extracted liquid is determined by converting the peak integral value obtained for the dimer and trimer of the monomer present in the chromatogram of the extracted liquid into the content of the dimer and trimer of the monomer using a calibration curve of the similar monomer.

[0650] Calibration curve for monomer

A standard monomer solution in methanol with five concentration levels of known content, ranging from 1 ng/mL to 100 ng/mL, is prepared and measured using a liquid chromatograph-mass spectrometer (Waters, LC-MS ACQUITY UPLC/TQD). The relationship between the content of each monomer and the integral value of the peak corresponding to that content is used to construct a calibration curve (first-order approximation) for each monomer. This calibration curve (first-order approximation) for each monomer is then used to create calibration curves for the dimer and trimer of each monomer.

[0651] The configuration of the LC-MS measurement equipment and conditions are as follows:

[0652] The limit of quantification in this measurement device configuration is 1 ng/mL.

[0653] <Content of unit of modifying monomer>

In order to determine the HFP unit content, a thin film disk is prepared by pressing PTFE powder, and based on its infrared absorption obtained by measuring the thin film disk with FT-IR, the value obtained by multiplying the ratio of absorption at 982 cm ^-1 / absorption at 935 cm ^-1 by 0.3 is taken as the HFP unit content.

[0654] <Concentration of polymer (such as polymers K and L)>

In a vacuum dryer, approximately 1 g of an aqueous polymer solution is dried at a temperature of 60°C for 60 minutes, the mass of the non-volatile substance is measured, and the ratio of the mass of the non-volatile substance to the mass of the aqueous polymer solution (1 g) is determined, expressed as a percentage, and taken as the polymer concentration.

[0655] <Solids concentration of aqueous dispersion containing PTFE>

1 g of aqueous dispersion is dried in an air dryer at a temperature of 150°C for 60 minutes, while the ratio of the mass of non-volatile substance to the mass of aqueous dispersion (1 g) is expressed as a percentage and taken as the concentration of solid products.

[0656] <Average Primary Particle Size>

An aqueous PTFE dispersion was prepared to bring the solids concentration to approximately 1.0% by weight. The average primary particle size was measured using 70 measurements using an ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) at 25°C. The refractive index of the solvent (water) was 1.3328, and the viscosity of the solvent (water) was 0.8878 mPa s.

[0657] <Aspect Relationship>

The aqueous dispersion is diluted to a solids concentration of approximately 1% by weight and observed using a scanning electron microscope (SEM), and 400 or more randomly extracted particles are imaged, and the aspect ratio is obtained from the average of the ratios of its major axis to its minor axis.

[0658] <Standard Relative Density (SSG)>

SSG is measured by the water displacement method in accordance with ASTM D 792 using a specimen formed in accordance with ASTM D4895-89.

[0659] <Peak Temperature>

The peak temperature is measured by accurately weighing approximately 10 mg of PTFE powder with no history of heating to a temperature of 300°C or higher, placing it in a special aluminum pan, and using TG/DTA (synchronous thermogravimetric). The aluminum pan is heated in the temperature range from 25°C to 600°C at a rate of 10°C/min in an air atmosphere to obtain a differential thermal curve (DTA), and the peak temperature is defined as the temperature corresponding to the maximum value on the obtained differential thermal (DTA) curve.

[0660] <Polymer content (polymers K, L and M) in PTFE powder>

The polymer content of PTFE powder is determined from the spectrum obtained by solid-state 19F-MAS NMR measurement.

[0661] <Extrusion Pressure>

The extrusion pressure was measured in the following manner according to the method described in Japanese Patent Laid-Open No. 2002-201217. 21.7 g of lubricant (trade name: Isopar H(R), manufactured by Exxon) was added to 100 g of PTFE powder and stirred for 3 minutes in a glass bottle at room temperature. Then, the glass bottle was left to stand at room temperature (25°C) for at least 1 hour before extrusion to obtain a lubricated resin. The lubricated resin was extruded as a paste at a contraction ratio of 100:1 at room temperature through an orifice (diameter 2.5 mm, platform length 11 mm, entry angle 30°) in the form of uniform balls (balls: extruded mass). The extrusion speed, that is, the plunger speed, was 20 inch/min (51 cm/min). The extrusion pressure is calculated by measuring the load when the extrusion load reaches equilibrium during the extrusion of the paste and dividing the measured load by the cross-sectional area of the cylinder used in the extrusion of the paste.

[0662] <Tensile Test>

The tensile test and measurement of tensile strength A are carried out by the following methods in accordance with the methods described in Japanese Patent Laid-Open No. 2002-201217.

The ball obtained by extruding the paste described above is heated at 230°C for 30 minutes to remove the lubricant from the ball. The ball (extruded mass) is then cut to the appropriate length and clamped at each end, leaving a space of 1.5 inches (38 mm) between the clamps, and heated to 300°C in an oven with air circulation. The clamps are then moved apart at the desired speed (extension rate) until the separation distance matches the desired extension (total extension) to perform the tensile test. This stretching method essentially follows the method described in U.S. Patent No. 4,576,869, except that the extrusion speed is different (51 cm/min instead of 84 cm/min). "Extension" is the increase in length due to stretching, usually expressed as a ratio to the original length. In the stretching method, the stretching rate is 1000%/sec, and the total stretch is 2400%.

[0663] <Tensile Strength A>

The stretched ball (obtained by stretching the ball) obtained in the tensile test described above is clamped by movable clamps having a design length of 5.0 cm, and a tensile test is carried out at 25°C at a speed of 300 mm/min, and the strength at the moment of failure is taken as the tensile strength A.

[0664] <Stress relaxation time>

The stress relaxation time is determined by the following methods in accordance with the methods described in Japanese Patent Laid-Open No. 2002-201217.

Both ends of the stretched ball obtained in the tensile test described above are secured in a fixture to form a highly stretched ball specimen with a total length of 8 inches (20 cm). The fixture is then inserted into the furnace through a closed slit on the side of the furnace, maintaining the furnace temperature at 390°C. The time required for the ball specimen to fracture after it is inserted into the furnace is determined as the stress relaxation time.

[0665] <Appearance of a stretched mass>

The appearance of the stretched balls (obtained by stretching the balls) obtained in the tensile test described above is observed visually and evaluated according to the following criteria.

Uniform: The appearance of the stretched balls was uniform.

Non-uniform: The appearance of the stretched beads was not uniform, such as cracks, bulges, roughness and thinning in the stretched beads.

[0666] Example of preparation 1 (preparation of polymer K)

170 g of sodium 1,1,2,2-tetrafluoro-2-((1,2,2-trifluorovinyl)oxy)ethane-1-sulfonate (monomer K), 340 g of water and ammonium persulfate (APS) in an amount corresponding to 2.0% mol with respect to the amount of monomer K are added to the reactor, and the mixture is stirred at 40°C for 72 hours under a stream of N2, thereby obtaining polymer K in an aqueous solution K-1 containing polymer K, which is a homopolymer of monomer K. The oxygen concentration in the reactor varies from 15 to 800 ppm by volume.

[0667] Water is added to the resulting aqueous solution K-1 of polymer K to bring the concentration of polymer K to 3.8% by weight, and then the solution is brought into contact with an ultrafiltration membrane (molecular weight cutoff 6000 Da, made of polysulfone) at a temperature of 25°C and a water pressure of 0.1 MPa to carry out ultrafiltration. If necessary, water is drained, ultrafiltration is continued until an aqueous filtrate 4 times greater than the volume of the aqueous solution is finally eluted, thereby obtaining an aqueous solution K-2 of polymer K. The resulting aqueous solution has a concentration of 1.6% by weight.

[0668] An aqueous solution of polymer K-2 is analyzed. The resulting polymer K has a weight-average molecular weight (Mw) of 1.0×10 ⁴ and a number-average molecular weight (Mn) of 0.8×10 ⁴ .

[0669] The content of the dimer and trimer of the monomer of the aqueous solution K-2 of polymer K is 0.1% by mass or less with respect to polymer K. The content of the fraction having a molecular weight of 3000 or less of the aqueous solution K-2 of polymer K is 0.5% or less. When this aqueous solution is subjected to DLS analysis, the particle size cannot be measured.

[0670] Example 1

In a glass reactor equipped with a stirrer with an internal capacity of 1 L, 4 96.17 g of deionized water, 30 g of paraffin wax and 34.38 g of an aqueous solution of K-2 polymer K are added, and an aqueous solution of ammonia is added to bring the pH to 10.6. Then, while the contents of the reactor are heated to 70 °C and sucked off, the reactor is purged with TFE monomer to remove oxygen in the reactor. After this, the contents are stirred. After adding 0.18 g of HFP to the reactor, TFE monomer is added until a pressure of 0.73 MPa g is reached. 2.75 mg of ammonium persulfate (APS) initiator, dissolved in 20 g of deionized water, is introduced into the reactor, and the pressure in the reactor is brought to 0.83 MPa g. After the introduction of the initiator, a drop in pressure occurs, indicating the beginning of polymerization. TFE monomer is added to the reactor to maintain pressure, and polymerization continues until approximately 60 g of TFE monomer is consumed. The reactor is then evacuated to normal pressure, the contents are removed from the reactor, and cooled. The paraffin wax supernatant is removed from the aqueous PTFE dispersion.

[0671] The solids concentration in the obtained PTFE aqueous dispersion was 9.7% by mass, and the average primary particle size was 184 nm.

[0672] The resulting aqueous PTFE dispersion is cured under high-speed stirring conditions. The cured wet powder is dried at 150°C for 18 hours. The results are shown in Table 2.

[0673] Example 2

The polymerization is carried out in the same manner as in Example 1, except that the amount of aqueous solution K-2 of polymer K is changed to 68.75 g, the amount of deionized water is changed to 462.35 g, the amount of HFP is changed to 0.54 g, and the polymerization is continued until approximately 140 g of TFE monomer is consumed in the reaction. The concentration of solids in the resulting aqueous PTFE dispersion is 20.3 wt.%, and the average primary particle size is 201 nm.

[0674] The resulting aqueous PTFE dispersion is diluted with deionized water to a solids concentration of approximately 10% by weight and cured under high-speed stirring conditions. The cured wet powder is dried at 150°C for 18 hours. The results are shown in Table 2.

[0675] Example 3

In a 6 L SUS reactor equipped with a stirrer, 3.107 g of deionized water, 104 g of paraffin wax, 448 g of an aqueous solution of K-2 polymer K, 10.74 g of an aqueous solution of isopropanol having a concentration of 0.1 wt.% and 1.25 g of an aqueous solution of Triton having a concentration of 0.1 wt.% are added. Then, an aqueous solution of ammonia is added to adjust the pH to 9.0, and while the reactor contents are heated to 70 °C and sucked off, the reactor is purged with TFE to remove oxygen in the reactor and the contents are stirred. After adding 7.68 g of HFP to the reactor, TFE is added until a pressure of 0.73 MPa g is reached. 17.9 mg of ammonium persulfate (APS) initiator dissolved in 20 g of deionized water is added to the reactor, and the reactor pressure is brought to 0.83 MPa g. After the initiator is added, the pressure drops, indicating the onset of polymerization. TFE is added to the reactor to maintain a constant pressure of 0.78 MPa g. When the TFE consumed in the reaction reaches approximately 180 g, the TFE feed and stirring are stopped.

[0676] Subsequently, the gas in the reactor is slowly released until the pressure in the reactor reaches 0.02 MPa g. After this, TFE is added until the pressure in the reactor reaches 0.78 MPa g, and stirring is started again, as a result of which the reaction continues. At the moment when the TFE consumed in the reaction reaches about 540 g, 14.3 mg of hydroquinone dissolved in 20 g of deionized water is added to the reactor, as a result of which the reaction continues. At the moment when the amount of TFE consumed in the reaction reaches about 1250 g, the supply of TFE and stirring are stopped, as a result of which the reaction is completed. Then, the reactor is evacuated to normal pressure, the contents are withdrawn from the reactor and cooled. The paraffin wax supernatant is removed from the PTFE aqueous dispersion.

[0677] The concentration of solids in the obtained PTFE aqueous dispersion is 27.5% by mass, and the average size of the primary particles is 170 nm.

[0678] The obtained PTFE aqueous dispersion was diluted with deionized water to a solids concentration of approximately 10% by weight and cured under high-speed stirring conditions, and the cured wet powder was dried at 210°C for 18 hours. Various physical properties of the obtained PTFE powder were measured. The results are shown in Table 2.

[0679] In addition, the obtained PTFE aqueous dispersion was diluted with deionized water to a solid concentration of approximately 10% by weight and cured under high-speed stirring conditions, and the cured wet powder was dried at 240°C for 18 hours. Various physical properties of the obtained PTFE powder were measured. The results are shown in Table 3.

[0680] Example of obtaining 2

300 ml of Amberlite (IR120B(H)-HG) are measured into a container, washed with water until discolored, then 500 ml of 1M-HCl are added and the mixture is stirred at room temperature for 1 hour. A column equipped with a tap is filled with Amberlite and water is passed through it until the acidity of the spent liquid becomes neutral. Polymer K in an aqueous solution K-2, obtained in Preparation Example 1, is introduced into a column equipped with a tap, and dropwise addition is started. After the dropwise addition is complete, water is allowed to flow until the dropping solution becomes neutral to obtain an aqueous solution L-1 of polymer L containing polymer L 1,1,2,2-tetrafluoro-2-((1,2,2-trifluorovinyl)oxy)ethane-1-sulfonic acid (monomer L). The resulting aqueous solution has a concentration of 1.5% by weight.

[0681] An aqueous solution L-1 of polymer L is analyzed. Polymer L has a weight average molecular weight (Mw) of 1.0×10 ⁴ and a number average molecular weight (Mn) of 0.8×10 ⁴ .

[0682] The content of the dimer and trimer of the monomer L in the aqueous solution L-1 of the polymer L is 0.1% by mass or less with respect to the polymer L. The content of the fraction having a molecular weight of 3,000 or less in the aqueous solution L-1 of the polymer L is 0.5% or less. When this aqueous solution is analyzed by DLS, the particle size cannot be measured.

[0683] Example 4

In a 6 L SUS reactor equipped with a stirrer, 3.087 g of deionized water, 104 g of paraffin wax, 477 g of an aqueous solution of L-1 polymer L, and 3.58 g of an aqueous solution of isopropanol having a concentration of 0.1 wt.% are added. Then, an aqueous ammonia solution is added to adjust the pH to 9.0, and while the reactor contents are heated to 70 °C and sucked off, the reactor is purged with TFE to remove oxygen in the reactor and the contents are stirred. After adding 5.8 g of HFP to the reactor, TFE is added until a pressure of 0.73 MPa g is reached. 17.9 mg of ammonium persulfate (APS) initiator dissolved in 20 g of deionized water are introduced into the reactor, and the pressure in the reactor is brought to 0.83 MPa g. After the introduction of the initiator, a pressure drop occurs, indicating the start of polymerization. TFE is added to the reactor to maintain a constant pressure of 0.78 MPa g. When the TFE consumed in the reaction reaches approximately 180 g, the TFE addition and stirring are stopped.

[0684] Subsequently, the gas in the reactor is slowly released until the pressure in the reactor reaches 0.02 MPa g. Then, TFE is added until the pressure in the reactor reaches 0.78 MPa g, and stirring is started again, resulting in the reaction continuing. At the point when the TFE consumed in the reaction reaches approximately 540 g, 14.3 mg of hydroquinone dissolved in 20 g of deionized water is added to the reactor, resulting in the reaction continuing. At the point when the amount of TFE consumed in the reaction reaches approximately 1250 g, the supply of TFE and stirring are stopped, resulting in the reaction being completed. Then, the reactor is evacuated to normal pressure, the contents are withdrawn from the reactor and cooled. The paraffin wax supernatant is removed from the PTFE aqueous dispersion.

[0685] The concentration of solids in the obtained PTFE aqueous dispersion is 25.5% by mass, and the average size of the primary particles is 182 nm.

[0686] The obtained PTFE aqueous dispersion was diluted with deionized water to a solids concentration of approximately 10% by weight and cured under high-speed stirring conditions, and the cured wet powder was dried at 210°C for 18 hours. Various physical properties of the obtained PTFE powder were measured. The results are shown in Table 2.

[0687] Also, the obtained PTFE aqueous dispersion was diluted with deionized water to a solids concentration of approximately 10% by weight and cured under high-speed stirring conditions, and the cured wet powder was dried at 240°C for 18 hours. Various physical properties of the obtained PTFE powder were measured. The results are shown in Table 3.

[0688] Example of obtaining 3

6.8 g of monomer K, represented by sodium 1,1,2,2-tetrafluoro-2-((1,2,2-trifluorovinyl)oxy)ethane-1-sulfonate, 34 g of water, and ammonium persulfate (APS) in an amount corresponding to 1.5% mol of the amount of monomer K are added to the reactor, and after purging with N ₂ and degassing, 3.2 g of VdF are introduced and the mixture is stirred at 60°C for 2 hours with the reactor hermetically sealed, thereby obtaining an aqueous solution of polymer M-1 containing polymer M, which is a copolymer of monomer K and VdF. The pressure inside the reactor is increased to 0.30 MPa g after heating and decreased to 0.19 MPa g as the reaction progresses.

[0689] The resulting aqueous solution M-1 of polymer M containing polymer M is contacted with a dialysis membrane (molecular weight cutoff of 3500 Da, made of cellulose) at room temperature to perform filtration, thereby obtaining an aqueous solution of the fluoropolymer. By performing dialysis membrane purification, an aqueous solution M-2 of polymer M is obtained. The resulting aqueous solution has a concentration of 2.65% by weight.

[0690] When an aqueous solution M-2 of polymer M obtained by performing dialysis is analyzed by NMR to examine the characteristics of the polymer _composition , the molar ratio of the polymerization unit obtained from the monomer K to the polymerization unit obtained from VdF contained in the polymer is 1.0/1.0. The alternation ratio of the polymerization unit obtained from _CF2 = _{CFOCF2CF2SO3Na} to the polymerization unit obtained from VdF in polymer M is 76% or _more .

[0691] The obtained polymer M has a weight average molecular weight (Mw) of 15.3×10 ⁴ and a number average molecular weight (Mn) of 7.2×10 ⁴ . The content of the dimer and trimer of the monomer K in the aqueous solution obtained by performing dialysis is 0.1% by mass or less with respect to the polymer M. Also, the content of the dimer and trimer of the polymerization unit obtained from the monomer K and the polymerization unit obtained from VdF is 0.1% by mass or less with respect to the polymer M. The content of the fraction having a molecular weight of 3,000 or less in the aqueous solution obtained by performing dialysis is 0.1% by mass or less.

[0692] Example 5

In a glass reactor equipped with a stirrer with an internal capacity of 1 L, 490 g of deionized water, 30 g of paraffin wax and 41.5 g of an aqueous solution of M-2 polymer M are added. In addition, an aqueous solution of ammonia is added to adjust the pH to 9.4. Then, while the contents of the reactor are heated to 70 °C and sucked off, the reactor is purged with TFE monomer to remove oxygen in the reactor. After this, the contents are stirred. After adding 1.26 g of TFE to the reactor, HFP monomer is added until a pressure of 0.73 MPa g is reached. 2.75 mg of ammonium persulfate (APS) initiator, dissolved in 20 g of deionized water, is introduced into the reactor, and the pressure in the reactor is brought to 0.83 MPa g. After the introduction of the initiator, a pressure drop occurs, indicating the beginning of polymerization. TFE monomer is added to the reactor to maintain a constant pressure of 0.7-8 MPa g. When the amount of TFE monomer consumed in the reaction reaches approximately 30 g, the TFE monomer feed and stirring are stopped. The gas in the reactor is then slowly released until the reactor pressure reaches 0.02 MPa g. TFE monomer is then added until the reactor pressure reaches 0.78 MPa g, and stirring is resumed, resulting in the reaction continuing. When the amount of TFE monomer consumed in the reaction reaches approximately 150 g, the TFE monomer feed and stirring are stopped, resulting in the reaction completion. The reactor is then evacuated to normal pressure, the contents are removed from the reactor and cooled. The paraffin wax supernatant is removed from the PTFE aqueous dispersion. The solids concentration in the obtained PTFE aqueous dispersion is 21.7% by mass, and the average primary particle size is 204 nm.

[0693] The resulting aqueous PTFE dispersion is diluted with deionized water to a solids concentration of approximately 10% by weight and cured under high-speed stirring conditions. The cured wet powder is dried at 210°C for 18 hours. The results are shown in Table 2.

[0694] [Table 2]

[0696] The method for producing and the composition of the perfluoroelastomer will now be described with reference to Examples.

[0697] Each numerical value in these Examples is measured using the methods described above unless otherwise noted. Values measured using methods other than those described above are measured using the following methods.

[0698] <Concentration of solids in an aqueous dispersion containing a perfluoroelastomer>

In an air dryer, 1 g of an aqueous dispersion containing a perfluoroelastomer is dried at a temperature of 150°C for 60 minutes, whereby the ratio of the mass of the non-volatile substance to the mass of the aqueous dispersion (1 g) is expressed as a percentage and taken as the concentration of solid products.

[0699] <Degree of polymer adhesion>

The ratio of the mass of the polymer adhering substance adhered to the polymerization tank after completion of polymerization to the total amount of polymer (perfluoroelastomer) after completion of polymerization (degree of adhesion to the polymerization tank) is determined by the following equation:

degree of polymer adhesion (% by weight) = mass of substance adhered to the polymer/mass of the obtained polymer (including substance adhered to the polymer) × 100

mass of the obtained polymer = mass of the aqueous dispersion × concentration of solids in the aqueous dispersion (% by mass)/100 + mass of the substance adhering to the polymer

The polymer-adhered substance includes the polymer adhering to the inner walls of the polymerization tank and to the internal parts of the polymerization tank, such as the agitator blades, after the aqueous dispersion is removed from the polymerization tank after the polymerization is completed, and the polymer that is released from the aqueous dispersion due to agglomeration and is suspended or precipitated without being dispersed in the aqueous dispersion. The mass of the polymer-adhered substance is the mass after drying and removing the moisture contained in the polymer-adhered substance at a temperature of 120°C.

[0700] <Compositional features of perfluoroelastomer>

Measurements are carried out using ¹⁹ E-NMR (solid-state NMR) and a Fourier transform infrared spectrophotometer (FT-IR).

[0701] <Glass transition temperature of perfluoroelastomer>

Regarding the glass transition temperature, a DSC curve is obtained using a differential scanning calorimeter (manufactured by Mettler-Toledo, DSC822e) and the temperature of 10 mg of the sample is increased at a rate of 10°C/min, and then the peak of the glass transition temperature is taken as the temperature of the differential curve specified in JIS K6240.

[0702] <Polymerization Rate>

The polymerization rate is calculated using the following equation:

polymerization rate = {mass of aqueous dispersion × concentration of solids/100}/{(amount of pure water used in polymerization + amount of water contained in the aqueous polymer solution (1) used in polymerization) × polymerization time}

The units for each sum in the equation are as follows.

mass of aqueous dispersion: g

solid concentration: % by mass.

amount of pure water used in polymerization: kg

the amount of water contained in the aqueous solution of the polymer (1) used in polymerization: kg

polymerization time: h polymerization rate: g/(h × kg)

[0703] <Average Particle Size>

The average particle size of the perfluoroelastomer in aqueous dispersion (cumulative average size) was calculated by the cumulant method using ELSZ-1000S (manufactured by Otsuka Electronics Co., Ltd.) and measured by the dynamic light scattering method.

[0704] <Number of perfluoroelastomer particles in aqueous dispersion>

The number of perfluoroelastomer particles in an aqueous dispersion is calculated using the following equation:

[0705]

[0706] In this equation, the average particle size is the cumulative average size calculated using the method described above, the number of polymer particles (number of perfluoroelastomer particles) is the number of particles per 1 cm ³ of water, and the density used is the measured value of the density of the perfluoroelastomer.

[0707] Example 6

Into a 0.5L stainless steel autoclave (made of SUS316, equipped with a FULLZONE type paddle stirrer and one baffle plate) without ignition source, 63.8g of deionized water and 130.0g of an L-1 polymer L aqueous solution (solid concentration: 1.5% by mass) were added, an aqueous ammonia solution was added to adjust the pH to 5.9, the system was thoroughly purged with nitrogen gas, then degassed and heated to 54°C with stirring at 1000 rpm. Then, a mixed gas of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (ratio of TFE/PMVE=24/76% by mol) was charged thereto so that the internal pressure reached 0.83 MPaG. Then, 0.259 g of _CF2 = _CFOCF2CF ( _CF3 ) _OCF2CF2CN ( _CNVE ) was added under nitrogen pressure along with 0.8 g of deionized water, and then 1.03 g of ammonium persulfate (APS) was dissolved in 2.5 g of deionized water and added under nitrogen pressure to initiate the reaction.

[0708] As the polymerization progresses, the pressure in the tank decreases, and therefore, when the pressure reaches 0.735 MPa g, 2 g of TFE and 2.2 g of PMVE are introduced into the autoclave to increase the pressure. Similarly, as the reaction progresses, TFE and PMVE are introduced under pressure at a ratio of 60/40% mol, and the pressure is periodically increased and decreased in the range from 0.735 MPa g to about 0.8 9 MPa g, so that 2 8 g of TFE and 3 0.8 g of PMVE are introduced under pressure upon completion of the polymerization. During the polymerization, _CF2 = _CFOCF2CF ( _CF3 ) _OCF2CF2CN , divided into 0.259 g portions, was injected under nitrogen pressure five times together with 0.8 g _of deionized water when the total amount of loaded TFE reached 6 g, 10 g, 14 g, 18 g, and 24 g, respectively.

[0709] The autoclave is then cooled and the unreacted monomer is recovered to yield 259 g of an aqueous dispersion with a solids concentration of 22.0 wt%.

[0710] The polymerization time was 10.1 hours. The polymer adhered inside the tank was collected, heated to remove moisture, and found to weigh 0.4 g. The adhesion rate was 0.7% by weight.

[0711] 100 g of the resulting aqueous dispersion is stirred and diluted by adding 75 g of deionized water. This stirred and diluted solution is added dropwise to 750 g of a 35% aqueous solution of hydrochloric acid. The dropwise addition is carried out while stirring the aqueous solution of hydrochloric acid.

The perfluoroelastomer is coagulated in an aqueous solution of hydrochloric acid. The coagulated perfluoroelastomer is filtered, transferred to 100 g of deionized water, and washed with stirring for 5 minutes. After 5 minutes, the perfluoroelastomer is filtered again, transferred to 100 g of deionized water, and washed with stirring for 5 minutes. The rinsing process with 100 g of deionized water is then repeated, and the perfluoroelastomer is filtered when the pH of the wash water after rinsing with water reaches 6 or more. The filtered perfluoroelastomer is dried in a vacuum at 70°C for 4-8 hours. The resulting perfluoroelastomer weighs 20.8 g.

[0712] Analysis of the obtained perfluoroelastomer shows the following results.

compositional features of perfluoroelastomer: TFE/PMVE/CNVE=54.0/45.4/0.62% mol.

glass transition temperature: -6.2°C

Metal content: 2.2 ppm

[0713] The polymerization rate is 29.4 g/(hour x kg), the cumulative average particle size of the perfluoroelastomer in the aqueous dispersion is 69.5 nm, and the number of perfluoroelastomer particles in the aqueous dispersion is 7.9×10 ¹⁴ /cm ³ .

[0714] Example 7

In a 0.5L stainless steel autoclave (made of SUS316, equipped with a FULLZONE type paddle stirrer and one baffle plate) without ignition source, 65.7g of deionized water was added, and 130.0g of an aqueous solution of L-1 polymer L (solid concentration: 1.5% by weight) and an aqueous ammonia solution were added to adjust the pH to 5.9. Then, the system was thoroughly purged with nitrogen gas, then degassed and heated to 50°C with stirring at 1000 rpm. Then, a gaseous mixture of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (TFE/PMVE ratio=25.6/74.4% mol) was charged therein so that the internal pressure reached 0.83 MPa g, and after that, 0.141 g of ammonium persulfate (APS) was dissolved in 1.5 g of deionized water and introduced under nitrogen pressure to initiate the reaction.

[0715] At the time when the pressure drops to 0.783 MPaG as the polymerization progresses, 0.416 g of the diiodine compound I( _CF2 ) _4I is pressurized as a chain transfer agent together with 1.5 g of deionized water. Then, when the pressure reaches 0.735 MPaG, 2 g of TFE and 1.8 g of PMVE are introduced into the autoclave to increase the pressure. Similarly, as the reaction progresses, TFE and PMVE are pressurized at a ratio of 64.8/35.2% mol, and the pressure is periodically increased and decreased in the range of 0.735 MPaG to about 0.89 MPaG. After the reaction starts, 0.0294 g of APS is pressurized with nitrogen together with 1.5 g of deionized water every 12 hours to continue the reaction. After completion of the pressure polymerization, 44 g TFE and 39.6 g PMVE are added.

[0716] The autoclave is then cooled and the unreacted monomer is recovered to yield 2.99 g of an aqueous dispersion with a solids concentration of 23.7% by weight.

[0717] The polymerization time is 33.0 hours. The polymer adhered inside the tank is collected, heated to remove moisture, and its mass is 0.47 g. The adhesion degree is 0.7% by mass.

[0718] 200 g of the resulting aqueous dispersion is stirred and diluted by adding 150 g of deionized water. This stirred and diluted solution is added dropwise to 1300 g of a 10% aqueous solution of hydrochloric acid. The dropwise addition is carried out while stirring the aqueous solution of hydrochloric acid.

[0719] The perfluoroelastomer is coagulated in an aqueous solution of hydrochloric acid, and the perfluoroelastomer thus coagulated is filtered, transferred into 1000 g of deionized water, and washed with stirring for 5 minutes. After 5 minutes, the perfluoroelastomer is filtered again, transferred into 100 g of deionized water, and washed with stirring for 5 minutes. After this, the operation of washing with 100 g of deionized water is repeated, and the perfluoroelastomer is filtered when the pH of the washing water after washing with water reaches 6 or more. The filtered perfluoroelastomer is dried in a vacuum at 70°C for 4-8 hours. The obtained perfluoroelastomer is 51.2 g.

[0720] Analysis of the obtained perfluoroelastomer shows the following results.

compositional features of perfluoroelastomer: TFE/PMVE=61.3/38.7% mol

iodine content: 0.18% by weight.

glass transition temperature: -6.7°C

[0721] The polymerization rate is 9.3 g/(hour x kg), the cumulative average particle size of the perfluoroelastomer in the aqueous dispersion is 129.7 nm, and the number of perfluoroelastomer particles in the aqueous dispersion is 1.3×10 ¹⁴ /cm ³ .

[0722] Example 8

In a 6-liter stainless steel autoclave (made of SUS316, equipped with a stirrer and one baffle plate) without ignition source, 831.8 g of deionized water and 1756.1 g of an aqueous solution of L-1 polymer L (solid concentration: 1.5% by weight) were added, and an aqueous ammonia solution was added to adjust the pH to 5.9. Then, the system was thoroughly purged with nitrogen gas, then degassed and heated to 50°C with stirring at 400 rpm. Then, a gaseous mixture of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (TFE/PMVE ratio=25.6/74.4% mol) was charged therein so that the internal pressure reached 0.83 MPa g, and after that, 4.257 g of ammonium persulfate (APS) was dissolved in 5.0 g of deionized water and introduced under nitrogen pressure to initiate the reaction.

[0723] At the point when the pressure reaches 0.735 MPa g as the polymerization progresses, 14 g of TFE and 12 g of PMVE are introduced into the autoclave to increase the pressure, and 5.11 g of the diiodine compound I(CF ₂ ) ₄ I are introduced under pressure as a chain transfer agent together with 5.0 g of deionized water. Similarly, as the reaction progresses, TFE and PMVE are introduced under pressure at a ratio of 65.9/34.1 mol%, and the pressure is periodically increased and decreased in the range of 0.7 35 MPa g to about 0.87 MPa g. After the reaction starts, 0.7 98 g of APS is introduced under nitrogen pressure together with 3.0 g of deionized water every 12 hours to continue the reaction. Upon completion of the polymerization, 616 g of TFE and 52.8 g of PMVE are introduced under pressure. During the polymerization, 1,1,2,2-tetrafluoro-3-iodo-1-((1,2,2-trifluorovinyl)oxy)propane, divided into 2.08 g portions, is injected under nitrogen pressure four times together with 1.5 g of deionized water when the total amount of loaded TFE reaches 308 g, 364 g, 434 g and 490 g, respectively.

[0724] The autoclave is then cooled and the unreacted monomer is recovered to yield 3776.4 g of an aqueous dispersion with a solids concentration of 29.8% by weight.

[0725] The polymerization time is 30.0 hours. The polymer adhered inside the tank is collected, heated to remove moisture, and found to weigh 0.1 g. The adhesion degree is 0.01% by weight.

[0726] 200 g of the resulting aqueous dispersion is stirred and diluted by adding 150 g of deionized water. This stirred and diluted solution is added dropwise to 1300 g of a 10% aqueous solution of hydrochloric acid. The dropwise addition is carried out while stirring the aqueous solution of hydrochloric acid.

[0727] The perfluoroelastomer is coagulated in an aqueous solution of hydrochloric acid, and the perfluoroelastomer thus coagulated is filtered, transferred into 200 g of deionized water, and washed with stirring for 5 minutes. After 5 minutes, the perfluoroelastomer is filtered again, transferred into 100 g of deionized water, and washed with stirring for 5 minutes. After this, the operation of washing with 100 g of deionized water is repeated, and the perfluoroelastomer is filtered when the pH of the washing water after washing with water reaches 6 or more. The filtered perfluoroelastomer is dried in a vacuum at 70°C for 4-8 hours. The obtained perfluoroelastomer is 56.4 g.

[0728] Analysis of the obtained perfluoroelastomer shows the following results.

compositional features of perfluoroelastomer: TFE/PMVE=64.1/35.9% mol

iodine content: 0.43% by weight.

Mooney viscosity: (ML 1+10 (100°C))=57.5

glass transition temperature: -3.1°C

[0729] The polymerization rate is 14.7 g/(hour x kg), the cumulative average particle size of the perfluoroelastomer in the aqueous dispersion is 116.2 nm, and the number of perfluoroelastomer particles in the aqueous dispersion is 2.5×10 ¹⁴ /cm ³ .

[07 30] Example 9

In a 0.5 liter internal volume stainless steel autoclave (made of SUS316, equipped with a FULLZONE type paddle stirrer and one baffle plate) without an ignition source, 118.8 g of deionized water and 78.0 g of polymer M in an M-2 aqueous solution (solid concentration: 2.65% by weight) were added, the system was thoroughly purged with nitrogen gas, then degassed and heated to 54°C with stirring at 1000 rpm. Then, a gaseous mixture of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) (ratio T FE/PMVE=2 4/7 6% mol) was charged therein so that the internal pressure reached 0.83 MPa g. Then, 0.259 g of CF ₂ =CFOCF ₂ CF(CF ₃ )OCF ₂ CF ₂ CN (CNVE) was introduced under nitrogen pressure together with 0.8 g of deionized water, and then 1.03 g of ammonium persulfate (APS) was dissolved in 2.5 g of deionized water and introduced under nitrogen pressure to initiate the reaction.

[0731] As the polymerization progresses, the pressure in the tank decreases, and therefore, when the pressure reaches 0.735 MPa g, 2 g of TFE and 2.2 g of PMVE are added to the autoclave to increase the pressure. Similarly, as the reaction progresses, TFE and PTFE are added under pressure at a ratio of 60/40% mol, and the pressure is repeatedly increased and decreased in the range from 0.735 MPa g to about 0.89 MPa g, so that 28 g of TFE and 30.8 g of PTFE are added under pressure upon completion of the polymerization. During the polymerization _{, CF2} = _CFOCF2CF ( _CF3 ) _OCF2CF2CN , divided into portions of 0.259 g, are introduced under nitrogen pressure five times together with 0.8 g of deionized water when the total amount of loaded TFE reaches 6 g, 10 g, 14 g, 18 g and 24 g, respectively.

[0732] The autoclave is then cooled and the unreacted monomer is recovered to yield 252 g of an aqueous dispersion with a solids concentration of 20.8% by weight.

[0733] The polymerization time is 5.3 hours. The polymer adhered inside the tank is collected, heated to remove moisture, and its mass is 4.0 g. The adhesion degree is 7.7% by mass.

[0734] 100 g of the resulting aqueous dispersion is stirred and diluted by adding 75 g of deionized water. This stirred and diluted solution is added dropwise to 700 g of a 10% aqueous solution of hydrochloric acid. The dropwise addition is carried out while stirring the aqueous solution of hydrochloric acid.

[0735] The perfluoroelastomer is coagulated in an aqueous solution of hydrochloric acid, and the perfluoroelastomer thus coagulated is filtered, transferred into 100 g of deionized water, and washed with stirring for 5 minutes. After 5 minutes, the perfluoroelastomer is filtered again, transferred into 100 g of deionized water, and washed with stirring for 5 minutes. After this, the operation of washing with 100 g of deionized water is repeated, and the perfluoroelastomer is filtered when the pH of the washing water after washing with water reaches 6 or more. The filtered perfluoroelastomer is dried in a vacuum at 70°C for 4-8 hours. The obtained perfluoroelastomer is 19.1 g.

[0736] Analysis of the obtained perfluoroelastomer shows the following results.

compositional features of perfluoroelastomer:

TFE/PMVE/CNVE=57.1/42.5/0.38% mol

glass transition temperature: -5.4°C

[0737] The polymerization rate was 50.3 g/(hour x kg), the cumulative average particle size of the perfluoroelastomer in the aqueous dispersion was 42.0 nm, and the number of perfluoroelastomer particles in the aqueous dispersion was 3.4×10 ¹⁴ /cm ³ .

Claims (20)

1. A method for producing a fluoropolymer comprising polymerizing a perfluoromonomer in an aqueous medium in the presence of a polymer (1) to produce a fluoropolymer, wherein the content of the polymerization unit (unit) obtained from the perfluoromonomer in the fluoropolymer is 90% mol or more relative to all the polymerization units (units) of the fluoropolymer, wherein the perfluoromonomer is at least one monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl ether) and perfluoro(alkyl allyl ether), the polymer (1) is a polymer of the monomer (1) represented by the general formula (1) given below, the polymerization unit (unit) (1) obtained from the monomer (1) in the polymer (1) accounts for 50% by mass or more with respect to all the polymerization units (units) of the polymer (1), the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less with respect to the polymer (1), the weight average molecular weight of the polymer (1) is from 1.0 × 10 ⁴ to 150.0 × 10 ⁴ , the polymer (1) is obtained by a method for producing the polymer (1) by polymerizing the monomer (1), and the oxygen concentration in the reaction system is maintained at 0.01 ppm to 1500 ppm by volume throughout the polymerization period of the monomer (1), and monomer (1) is a monomer (2) represented by the following general formula (2): CF ₂ =CF-O-Rf-SO ₃ M (2) where Rf is a fluorine-containing alkylene group containing from 1 to 5 carbon atoms, or a fluorine-containing alkylene group containing from 2 to 5 carbon atoms and containing an ether linkage, or a keto group; M is -H, a metal atom, -NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent; R ⁷ is H or an organic group. 2. The production method according to claim 1, wherein the fluoropolymer is polytetrafluoroethylene. 3. The method of production according to claim 1 or 2, wherein the fluoropolymer is a perfluoroelastomer. 4. The production method according to claim 2, wherein the polytetrafluoroethylene is high molecular weight polytetrafluoroethylene. 5. A composition used for molding, containing a polymer (1) and a fluoropolymer, wherein the fluoropolymer contains a polymerization unit (unit) obtained from a perfluoromonomer, and the content of the polymerization unit (unit) obtained from the perfluoromonomer in the fluoropolymer is 90% mol or more relative to all polymerization units (units) of the fluoropolymer, wherein the perfluoromonomer is at least one monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl ether) and perfluoro(alkyl allyl ether), the polymer (1) is a polymer of the monomer (1) represented by the general formula (1) given below, the polymerization unit (unit) (1) obtained from the monomer (1) in the polymer (1) accounts for 50% by mass or more with respect to all the polymerization units (units) of the polymer (1), the content of the dimer and trimer of the monomer (1) in the polymer (1) is 1.0% by mass or less with respect to the polymer (1), the weight average molecular weight of the polymer (1) is from 1.0 × 10 ⁴ to 150.0 × 10 ⁴ , the polymer (1) is obtained by a method for producing the polymer (1) by polymerizing the monomer (1), and the oxygen concentration in the reaction system is maintained at 0.01 ppm to 1500 ppm by volume throughout the polymerization period of the monomer (1), and monomer (1) is a monomer (2) represented by the following general formula (2): CF ₂ =CF-O-Rf-SO ₃ M (2) where Rf is a fluorine-containing alkylene group containing from 1 to 5 carbon atoms, or a fluorine-containing alkylene group containing from 2 to 5 carbon atoms and containing an ether linkage, or a keto group; M is -H, a metal atom, -NR ⁷ ₄ , imidazolium optionally containing a substituent, pyridinium optionally containing a substituent, or phosphonium optionally containing a substituent; R ⁷ is H or an organic group. 6. The composition according to claim 5, wherein the polymer (1) is a copolymer of the monomer (1) and a monomer represented by the general formula CFR ¹¹ =CR ¹¹ ₂ , where R ¹¹ independently represents H, F or a perfluoroalkyl group containing from 1 to 4 carbon atoms. 7. The composition according to claim 6, wherein the content of the polymerization unit (1) obtained from the monomer (1) is from 50 to 94% by weight in relation to all the polymerization units (units) constituting the polymer (1), and the content of the polymerization unit (M) obtained from the monomer represented by the general formula CFR ¹¹ =CR ¹¹ ₂ , where R ¹¹ independently represents H, F or a perfluoroalkyl group containing from 1 to 4 carbon atoms, is from 6 to 50% by weight in relation to all the polymerization units constituting the polymer (1). 8. The composition according to claim 7, wherein the ratio of alternation of the polymerization unit (1) and the polymerization unit (M) is 40% or more. 9. The composition according to claim 5, wherein the fluoropolymer is polytetrafluoroethylene. 10. The composition according to claim 5, wherein the fluoropolymer is a perfluoroelastomer. 11. The composition according to claim 9, wherein the metal content is 10 ppm by weight or less. 12. The composition according to claim 9, wherein the polytetrafluoroethylene is high molecular weight polytetrafluoroethylene.