JPH075765B2 - Aromatic polyester film and its manufacturing method - Google Patents

Description

The present invention relates to an aromatic polyester film and a method for producing the same. More specifically, the present invention relates to a method for producing an aromatic polyester film that is free from surface defects and exhibits a uniform thickness under high productivity by closely contacting a molten film of aromatic polyester on a rotating cooling drum and cooling it, and to such an aromatic polyester film.

PRIOR ART Thermoplastic polyesters, typified by polyethylene terephthalate, have excellent physical and chemical properties and are therefore widely used in the film field for magnetic tape applications, electrical insulation applications, capacitor applications, photography applications, packaging applications, and the like.

Polyester films are usually produced by extruding a film-like molten material from an extrusion die, quenching it on the surface of a rotating cooling drum, and then biaxially stretching it in the machine and cross directions.
To eliminate surface defects and improve thickness uniformity, it is necessary to improve the adhesion between the molten film and the surface of the rotating cooling drum. One known method for improving this adhesion is to install a wire electrode between the extrusion die and the surface of the rotating cooling drum to deposit an electrostatic charge on the surface of the molten film, and then rapidly cool the molten film while it is in close contact with the surface of the cooling drum (hereinafter referred to as the electrostatic casting method) (see Japanese Patent Publication No. 6142/1962).

However, even in this electrostatic casting method, as the peripheral speed of the rotating cooling drum is increased to increase film productivity,
The adhesion of the film to the cooling drum surface decreases, causing pin-shaped defects on the film surface and resulting in a decrease in thickness uniformity.

In the production of films, particularly those stretched uniaxially or biaxially, increasing productivity and reducing production costs are important issues, along with improving film quality. The most effective way to achieve this is to increase the circumferential speed of the rotating cooling drum to increase the film production rate. Increasing the circumferential speed of the rotating cooling drum in the electrostatic casting method reduces the amount of electrostatic charge per unit area on the surface of the film-like material, thereby reducing the adhesion between the film-like material and the drum surface, resulting in pin-shaped defects on the film surface and reduced film thickness uniformity. To improve this adhesion, one method is to increase the voltage applied to the electrode to increase the amount of electrostatic charge deposited on the surface of the film-like material. However, if the applied voltage is too high, arc discharge may occur between the electrode and the surface of the rotating cooling drum, destroying the film-like material on the cooling drum surface and damaging the surface of the cooling drum. Therefore, it is practically impossible to increase the voltage applied to the electrodes above a certain level, and there is a limit to how quickly the conventional electrostatic casting method can increase the film production speed and obtain a uniform film.

In Japanese Patent Publication No. 53-40231, it is disclosed that the resistivity of the molten polymer is increased to 2×10 7 to 5×10 8 Ω by adding 0.005 to 1% by weight, preferably 0.07 to 0.3% by weight, of alkali metals, alkaline earth metals or their compounds, in order to overcome the limitations of the electrostatic casting method, improve the film-forming speed and produce a polyester film of uniform thickness ^and free of surface defects with high efficiency ^.
・cm, and as a specific example, it is proposed to improve the adhesion by adding 0.15 wt% lithium acetate.
Addition of 0.09% by weight of strontium acetate increased the resistivity to 2×10 ⁸ Ω·cm ^.
It has been shown that this can be achieved.

In addition, Japanese Patent Publication No. 56-15730 states that when alkali metal compounds or alkaline earth metal compounds are added in the direct polymerization method, the amount of diethylene glycol (DEG) produced as a by-product increases, which lowers the melting point of the polyester produced, causing problems such as the film sticking to the casting drum and the film breaking more frequently during stretching.
As a method for producing a polyester with a small amount of by-product G and improved electrostatic castability, it has been proposed to add, after the esterification reaction is substantially complete, a metal compound selected from Zn, Mg and Mn compounds and a phosphorus compound so as to satisfy the following formula: 20≦M≦1000 0.8≦M/P≦5, where M represents the total metal atomic weight (ppm) of the metal compound relative to the polyester, and M/P represents the molar ratio of the total metal compounds to phosphorus, followed by polycondensation.

Furthermore, Japanese Patent Laid-Open Publication No. 59-62627 proposes a method for overcoming the above-mentioned problems of direct polymerization, in which, when producing a polyester whose main repeating unit is ethylene terephthalate by direct polymerization, a Mg compound is added before the start of esterification so that the amount of Mg atoms is 30 to 400 ppm relative to the polyester, and between the time when the esterification rate reaches 91% or more and the end of the initial overall reaction, a P compound and alkali metal compounds of Na and K compounds are added so as to satisfy the following equations: 1.2≦Mg/P≦2.0 3.0≦M≦50, where Mg/P is the atomic ratio of Mg atoms to P atoms, and M is the amount (ppm) of the alkali metal compound added to the polyester as metal atoms.

Furthermore, it is difficult to produce high-quality films that fully satisfy market demands at high casting speeds using polyester raw materials obtained by conventional methods. In particular, when calcium compounds are used, attempts to reduce resistivity inevitably result in the precipitation of coarse particles, making it difficult to completely prevent a decrease in transparency.

In JP-A-59-62626, as a method for improving this point, when the esterification rate in the direct polymerization method reaches 91% or more, a P compound, a Ca compound, and an alkali metal compound selected from Na and K compounds are added in this order and in the following formula: 50≦Ca≦400, 1.2≦Ca/P≦3.0, 3.0≦M≦20, where Ca compound is added in terms of Ca atoms relative to the polyester (ppm), Ca/P is the atomic ratio of Ca atoms to P atoms, and M is the amount of Ca atoms added relative to the polyester.
indicates the amount (ppm) of alkali metal compound added as metal atoms to polyester, and it is proposed to add the compound so as to satisfy the following:

Furthermore, Japanese Patent Publication No. 61-40538 proposes that in order to reduce the resistivity of molten polyester, it is necessary to add a large amount of alkali metal compounds or alkaline earth metal compounds. However, in this case, particles precipitate inside the polyester, and the coarse particles can cause pinholes in the film or induce arc discharge during film formation, and the color tone of the polyester film itself can be significantly deteriorated, resulting in a polyester film with a strong yellowish tinge. Therefore, it proposes that the polyester should contain 0.01 to 2% by weight of inorganic fine powder and 0.0001 to 0.0025% by weight, calculated as the metal, of an ethylene glycol-soluble alkali metal compound.

Although the above proposals all aim to increase the amount of charge on the surface of the film by reducing the resistivity of the molten polyester, there is a limit to how much the electrostatic adhesion can be improved by reducing the resistivity.

Japanese Patent Application Laid-Open Nos. 62-187724 and 62-189133 state that the maximum casting speed increases significantly as the resistivity decreases up to approximately 0.2 x 10 ⁸ Ω·cm, but when the maximum casting speed is 50 m/min or higher, the resistivity decreases to 0.
It is explained that in the region of 2×10 ⁸ Ω·cm or less, the difference in resistivity between a maximum casting speed of 70 m/min and 80 m/min is only 0.01×10 ⁸ Ω·cm, resulting in a very poor correlation between the maximum casting speed and resistivity. JP-A-62-187724 and JP-A-62-189133 disclose the use of a polymer in which the amount of initial stored charge of molten polyester is 2.9 μc/mm ² or more, and as a means of increasing this initial stored charge, Mg compounds and P compounds are mixed so as to satisfy the following formula: 30≦Mg≦400 0.8≦Mg≦P≦3 where Mg/P is the content (ppm) of Mg compounds in the polyester as Mg atoms, and Mg/P is the atomic ratio of Mg atoms to P atoms. Furthermore, these compounds are mixed with Co, Na,
It is proposed to combine it with one or more K and Zr compounds in a specific ratio.

However, even in this case, as mentioned above, Mg and P compounds, as well as Na, K, Co, and Zr compounds, are used to increase the amount of initial stored charge, and it is difficult to avoid the increase in coarse particles and the deterioration of the polymer color tone that occurs when the amount of these compounds is increased.

On the other hand, in Japanese Patent Publication No. 47-22334, the following formula wherein A is an aliphatic group or an aromatic group, ^Y1 is a carboxylic acid ester-forming group, ^Y2 is the same group as ^Y1 , hydrogen, or a halogen atom, and ^R1 , ^R2 , ^R3 , and ^R4 are groups selected from the group consisting of hydrogen atoms, alkyl groups, aryl groups, and hydroxyalkyl groups, and l is a natural number, in an amount of 10 equivalent % or less based on the repeating units of the polyester, to produce a polyester having improved dyeability with basic dyes.

In the specification of U.S. Pat. No. 3,732,183, the following formula is described: where R is _an alkyl group such as _CH3 , _C2H5 , n _{- C3H7} ,
Disclosed is a filament-forming aromatic polyester dyeable with cationic dyes, which contains 0.5 to 5 mole % of sulfonate groups represented by the formula: n-C ₄ H ₉ , 3-sodium(sulfopropyl) group, and 4-sodium(sulfobutyl) group, based on the polyester constituent units.

In addition, Japanese Patent Publication No. 1-29500 discloses the following formula: where A is an alkyl or alkenyl group having 4 to 18 carbon atoms, a phenyl group, a phenyl group substituted with an alkyl having 1 to 18 carbon atoms, a naphthyl group, or a naphthyl group substituted with an alkyl having 1 to 18 carbon atoms, and ^R1 , ^R2 , ^R3 , and ^R4 are the same or different and are a hydrocarbon group having 1 to 18 carbon atoms or a hydrocarbon group having 1 to 18 carbon atoms and having a substituent, as an antistatic agent for polymeric materials. The publication discloses polyethylene terephthalate as the polymeric material, and recommends an addition amount of the antistatic agent of 0.1 to 10% by weight.

Furthermore, the following publications, which were published after the priority date of the present application, include the above-mentioned Japanese Patent Publication No. 47-22334, U.S. Pat.
Polyester fibers dyeable with cationic dyes using compounds similar to the phosphonium sulfonate salts disclosed in Japanese Patent Publication No. 3,732,183 and Japanese Patent Publication No. 1-29500 are disclosed.

European Patent Application Publication No. 0280026 describes the following formula: wherein A is an aromatic or aliphatic group, X ¹ is a hydrogen atom or an ester-forming group, X ² is an ester-forming group that is the same as or different from the ester-forming group of X ¹ , R ¹ ,
R ² , R ³ and R ⁴ are each independently an alkyl group or an aryl group, and n is an integer of 1 or more,
An aromatic polyester fiber containing e% is disclosed.

In Japanese Patent Laid-Open No. 1-103650, the above-mentioned European Patent Application Publication No. 02
In Japanese Patent Publication No. 80026, a method is disclosed for producing a polyester composition dyeable with cationic dyes that has excellent heat resistance during melt spinning, by blending 0.002 to 2 mol % of an alkali metal salt or alkaline earth metal salt of an organic carboxylic acid with a polyester modified with 0.05 to 20 mol % of a phosphonium sulfonate having the same general formula as described above.

In JP-A-1-103623, instead of the metal salt of organic carboxylic acid in the above-mentioned JP-A-1-103650, a compound of the following formula: HOOC-B-CCOH, where B is Also disclosed is a method for producing a polyester dyeable with a cationic dye, which similarly has excellent heat resistance during melt spinning, by blending 0.1 to 50 mol % of an aromatic dicarboxylic acid represented by the following formula:

JP-A-1-192823 discloses a composition containing 0.01 to 20 mol % of a phosphonium sulfonate having the same general formula as the above-mentioned JP-A-1-103650, 0.05 to 10 wt % of a metal sulfonate represented by the following general formula ( _RSO3 )nM, where R is an alkyl group, aryl group, or aralkyl group having 6 or more carbon atoms, M is an alkali metal or alkaline earth metal, and n is 1 or 2, and 0.
The publication discloses a polyester composition containing 0.5 to 10% by weight of the polyester. According to the publication, this polyester composition prevents static electricity generation during melt molding and provides excellent moldability.

Finally, Japanese Patent Application Laid-Open No. 1-197523 discloses the above-mentioned Japanese Patent Application Laid-Open No. 1-1036
0.005 to 0.495 mol % of a phosphonium sulfonate having the same general formula as that disclosed in Japanese Patent Application Laid-Open No. 50, and wherein _Z1 is an aromatic group or an aliphatic group, _A1 is an ester-forming functional group, _A2 is an ester-forming functional group that is the same as or different from _A1 or a hydrogen atom, M is a metal atom, and m is a positive integer,
A method for producing a modified polyester excellent in moldability and color tone has been proposed, which contains the above two types of sulfonates in a total amount of 0.01 to 0.5 mol %.

In the magnetic recording media, which are the main application of biaxially oriented polyester film, a high degree of smoothness is required for the film due to the recent dramatic increase in recording density and the trend toward higher quality video images. The presence of coarse particles, which cause dropouts, significantly reduces film quality. Furthermore, according to the inventor's research, polymers containing large amounts of alkali metal compounds or alkaline earth metal compounds tend to produce a large amount of black particles in the film, which significantly reduces the product quality.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an aromatic polyester film and a method for producing the same.

Another object of the present invention is to provide a method for producing an aromatic polyester film having no surface defects and a uniform thickness, which can be produced with high productivity by closely contacting a molten film of aromatic polyester on a rotating cooling drum and cooling it, and to provide said film.

Further objects and advantages of the present invention will become apparent from the following description.

According to the present invention, the above objects and advantages of the present invention are achieved by the first
A method for producing an aromatic polyester film by extruding a molten film of a thermoplastic aromatic polyester onto a rotating cooling drum, and then cooling the film while it is in close contact with the rotating drum, wherein the aromatic polyester contains, in its polymer chain, a sulfonic acid quaternary phosphonium salt having an ester-forming functional group in an amount of 0.1 to 45 mmol % relative to the bifunctional carboxylic acid component, and the AC volume resistivity value (F/D value) of the molten film is 6.5 x
This can be achieved by a method characterized by using an aromatic polyester having a resistivity of 10 ⁸ Ω·cm or less, and applying an electric charge to the molten surface of the film in a non-contact manner near (just before) the molten film of the aromatic polyester reaches a rotating cooling drum.

The aromatic polyester of the present invention contains, in the polymer chain, i.e., as a copolymerization component, a quaternary phosphonium sulfonate having an ester-forming functional group in an amount of 0.1 to 45 mmol % relative to the bifunctional carboxylic acid component that constitutes the polyester.

Examples of the sulfonic acid quaternary phosphonium salt having an ester-forming functional group include those represented by the following formula: wherein A is an (n+2)-valent aliphatic or aromatic group having 2 to 18 carbon atoms, X ¹ and X ² are the same or different and are hydrogen atoms or ester-forming functional groups, and n is 1.
or 2, and R ¹ , R ² , R ³ and R ⁴ are the same or different and are an alkyl group having 1 to 18 carbon atoms, a benzyl group or an aryl group having 6 to 12 carbon atoms, provided that X ₁ and X ₂ are not hydrogen at the same time.

In the above formula, A is n+2 valent, for example, trivalent (n=1
(where n=1), or tetravalent (where n=2), or an aliphatic or aromatic group having 2 to 18 carbon atoms.

The aliphatic group is preferably a linear or branched, saturated or unsaturated hydrocarbon group having, for example, 2 to 10 carbon atoms.

The aromatic group is preferably an aromatic group having 6 to 18 carbon atoms, and more preferably, for example, a trivalent or tetravalent benzene skeleton, a naphthalene skeleton, or a biphenyl skeleton. In addition to _X1 , _X2 , and a sulfonic acid quaternary phosphonium salt group, such an aromatic group can also be, for example, a group having 1 carbon atom.
It may be substituted with an alkyl group of 1 to 12.

_X1 and _X2 can be the same or different and are hydrogen or an ester-forming functional group. If both _X1 and _X2 are hydrogen, the polyester chain lacks a group to be copolymerized. _X1 and _X2 cannot both be hydrogen atoms, and at least one must be an ester-forming functional group.

Examples of the ester-forming functional group include Examples of such groups include —C—( _OCpH2p ) _qOH and —C—( _OCpH2p ) _qOH , in _which R′ is a lower alkyl group having 1 to 4 carbon atoms or a phenyl group, l is an integer of 2 _to 10, p is an integer of 2, 3, or 4, and q is an integer of 1 or more, for example, an integer of 1 to 100.

The lower alkyl group represented by R' may be either straight-chain or branched-chain, and preferred examples thereof include methyl, ethyl, n-propyl, iso-propyl, n-butyl, and sec-butyl.

n is an integer of 1 or 2.

In addition, the group constituting the sulfonate phosphonium base moiety
R ₁ , R ₂ , R ₃ and R ₄ are the same or different and each represents an alkyl group having 1 to 18 carbon atoms, a benzyl group or an aryl group having 6 to 12 carbon atoms.

The alkyl group having 1 to 18 carbon atoms may be either linear or branched, and examples thereof include methyl, ethyl, propyl, butyl, dodecyl, and stearyl.

Examples of the aryl group having 6 to 12 carbon atoms include phenyl,
Preferred examples include naphthyl, biphenyl, etc. The phenyl moiety of these aryl groups or benzyl groups may be substituted with, for example, a halogen atom, a nitro group or a lower alkyl group having 1 to 4 carbon atoms.

Specific preferred examples of the quaternary phosphonium salt of sulfonic acid include tetrabutyl phosphonium salt of 3,5-dicarboxybenzenesulfonate, ethyl tributyl phosphonium salt of 3,5-dicarboxybenzenesulfonate, benzyl tributyl phosphonium salt of 3,5-dicarboxybenzenesulfonate, phenyl tributyl phosphonium salt of 3,5-dicarboxybenzenesulfonate, tetraphenyl phosphonium salt of 3,5-dicarboxybenzenesulfonate,
-dicarboxybenzenesulfonic acid ethyltriphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid butyltriphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid benzyltriphenylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid tetrabutylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid ethyltributylphosphonium salt, 3,
5-dicarbomethoxybenzenesulfonic acid benzyltributylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid phenyltributylphosphonium salt, 3,5
- tetraphenylphosphonium salt of dicarbomethoxybenzenesulfonic acid, ethyltriphenylphosphonium salt of 3,5-dicarbomethoxybenzenesulfonic acid, butyltriphenylphosphonium salt of 3,5-dicarbomethoxybenzenesulfonic acid, benzyltriphenylphosphonium salt of 3,5-dicarbomethoxybenzenesulfonic acid, tetrabutylphosphonium salt of 3-carboxybenzenesulfonic acid,
3-carboxybenzenesulfonic acid tetraphenylphosphonium salt, 3-carbomethoxybenzenesulfonic acid tetrabutylphosphonium salt, 3-carbomethoxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-di(β-hydroxyethoxycarbonyl)benzenesulfonic acid tetrabutylphosphonium salt, 3,5-di(β-hydroxyethoxycarbonyl)benzenesulfonic acid tetraphenylphosphonium salt, 3-(β-hydroxyethoxycarbonyl)benzenesulfonic acid tetrabutylphosphonium salt, 3-(β-hydroxyethoxycarbonyl)
Benzene sulfonate tetraphenylphosphonium salt, 4
tetrabutylphosphonium 2,6-hydroxyethoxybenzenesulfonate, bisphenol A-3,3'-di(tetrabutylphosphonium sulfonate), tetrabutylphosphonium 2,6-dicarboxynaphthalene-4-sulfonate, α-tetrabutylphosphonium sulfosuccinate, etc. The above-mentioned quaternary phosphonium sulfonates may be used alone or in combination of two or more.

Such quaternary phosphonium sulfonates are generally
They can be easily produced by a known reaction between the corresponding sulfonic acid and a phosphine or a known reaction between the corresponding metal sulfonate and a quaternary phosphonium halide.

As described above, the aromatic polyester of the present invention contains the above-mentioned quaternary phosphonium sulfonate salt in a small amount of only 0.1 to 45 mmol %, preferably an even smaller amount of 0.2 to 20 mmol %, based on the bifunctional carboxylic acid component constituting the aromatic polyester.
This indicates that, unlike modified polyesters containing, for example, a quaternary phosphonium sulfonate salt in an amount sufficient to serve as dyeing sites for cationic dyes, the aromatic polyester of the present invention exhibits physical properties that are substantially comparable to those of aromatic polyesters that do not contain a quaternary phosphonium sulfonate salt, such that the deterioration in physical properties of the aromatic polyester, for example, a decrease in softening point, due to the inclusion of a quaternary phosphonium sulfonate salt is substantially negligible.

The aromatic polyesters of the present invention are those containing an aromatic dicarboxylic acid as the main dicarboxylic acid component and an alkylene glycol having 2 to 10 carbon atoms as the main diol component. For example, copolyesters containing polyethylene terephthalate, polyethylene-2,6-naphthalate, or ethylene terephthalate as the main repeating unit, and copolyesters containing ethylene-2,6-naphthalate as the main repeating unit are particularly preferred. Examples of copolymerization components of the copolyesters include aromatic dicarboxylic acids such as isophthalic acid, aliphatic dicarboxylic acids such as adipic acid, hydroxycarboxylic acids such as hydroxybenzoic acid, aliphatic dihydroxy compounds such as trimethylene glycol, tetramethylene glycol, and 1,4-cyclohexanedimethanol, and polyoxyalkylene glycols such as polyethylene glycol and polybutylene glycol. Furthermore, polycarboxylic acids such as trimellitic acid and pyromellitic acid, and polyols such as glycerin, trimethylolpropane, and pentaerythritol can be used as long as the aromatic polyester is substantially linear. The thermoplastic aromatic polyester may be blended with additives such as stabilizers and colorants, and may also be blended with or contain lubricants such as inorganic fine particles or organic fine particles to improve slip properties.

Such thermoplastic aromatic polyesters can be produced by known methods. For example, taking polyethylene terephthalate as an example for convenience, it is usually produced by a first-stage reaction in which terephthalic acid and ethylene glycol are directly esterified, or a lower alkyl ester of terephthalic acid such as dimethyl terephthalate is transesterified with ethylene glycol, or an addition reaction of terephthalic acid and ethylene oxide is carried out to produce a glycol ester of terephthalic acid and/or its oligomer, and a second-stage reaction in which the reaction product of the first stage is heated under reduced pressure to polycondense to a desired degree of polymerization. In this case, additives such as catalysts can be optionally used as needed.

In order to copolymerize the above-mentioned sulfonate quaternary phosphonium salt with such an aromatic polyester, the sulfonate quaternary phosphonium salt can be added to the reaction system at any stage before the completion of the synthesis of the aromatic polyester, for example, at any stage before the completion of the first-stage reaction. Alternatively, for example, an aromatic polyester copolymerized with a relatively large amount of sulfonate quaternary phosphonium salt is separately prepared, and an aromatic polyester copolymerized with no or a relatively small amount of sulfonate quaternary phosphonium salt is separately prepared.
The method of mixing can be exemplified by the method of using the quaternary phosphonium sulfonate salts so that the ratio of the quaternary phosphonium sulfonate salts in the resulting mixture is the predetermined ratio specified in the present invention.

As described above, the aromatic polyester to which the present invention is directed contains a sulfonic acid quaternary phosphonium salt component in an amount of 0.1 to 45 mmO.
The composition contains 1% copolymerized, and the AC volume resistivity value of the molten film (F/D value) is 6.5 x
Indicates a resistance of 10 ⁸ Ω·cm or less.

According to the inventors' research, the AC volume resistivity of the molten film is more closely related to the amount of charge that can be imparted to the surface of the molten aromatic polyester film than to the DC volume resistivity of the molten film, and it has been revealed that aromatic polyesters with an AC volume resistivity (F/D value) of 6.5 x 10 ⁸ Ω·cm or less can impart a sufficient amount of charge to adhere to the surface of a cooling drum rotating at a relatively high speed.

The aromatic polyester of the present invention preferably has an AC volume resistivity (F/D value) of 3.2 × 10
The intrinsic viscosity of the aromatic polyester of the present invention is preferably in the range of ^0.8 to 5.6×10 ⁶ Ω·cm.

In the method of the present invention, the melt of the aromatic polyester as described above is passed through a slit and poured onto a rotating cooling drum, for example, at a temperature of 10 to 1.00°C.
The film is then uniformly placed on the cooling drum and cooled on the cooling drum. The molten film extruded onto the rotating cooling drum is cooled in a non-contact manner, for example, from 300 μm away from the film surface, in the vicinity (just before) of the film reaching the drum.
The aromatic polyester of the present invention is a polyester containing a sulfonic acid quaternary phosphonium salt as described above.
The content of the charge-applying device is 0.1 to 45 mmol %, and the molten film exhibits an AC volume resistivity of 6.5 x 10 ⁸ Ω·cm or less. When the charge is applied, the film adheres uniformly to a cooling drum that rotates relatively quickly.
This is disclosed in Publication No. 2, etc.

The rotation speed of the cooling drum is, for example, at least
The rotational speed can be as high as 50 m/min. The preferred rotational speed can be in the range of 60 to 200 m/min.

The cooling surface of the cooling drum that receives the molten film of aromatic polyester can be, for example, a mirror finish or a surface having numerous channel-like microcracks, as in the cooling drum disclosed in U.S. Pat. No. 4,478,772.

When using a cooling drum with a mirror-finished cooling surface,
The peripheral rotation speed of the cooling drum is advantageously in the range of 60 to 150 m/min. When a cooling drum having a cooling surface with numerous channel-like microcracks is used, the peripheral rotation speed of the cooling drum is advantageously in the range of 80 to 200 m/min.

Furthermore, a liquid film containing water as a main component can be provided on the cooling surface of the rotating cooling drum between the cooling surface and the surface of the molten aromatic polyester film. Such a method for providing a liquid film is known per se and is disclosed, for example, in French Patent No. 2,049,046 and Japanese Patent Laid-Open Publication No. 49-99160.

As described above, the present invention can be applied to other improved methods based on the electrostatic adhesion method, thereby achieving the effect of further increasing the rotational peripheral speed of the rotating drum.

The method of the present invention provides the product obtained by separating it from the rotating cooling drum.
The cooled and solidified film is then stretched uniaxially or biaxially as it is or is taken up and then subjected to biaxial stretching according to a method known per se, and is then used in various fields.

According to the research of the present inventors, instead of the aromatic polyester, a sulfonic acid quaternary phosphonium salt having an ester-forming functional group is contained in the polymer chain in an amount of 0.1 to 45 mmol % based on the bifunctional carboxylic acid component, and further, an alkali metal or alkaline earth metal compound is contained in an amount of 0.1 to 20 mmol % based on the bifunctional carboxylic acid component, and the AC volume resistivity value (F/D value) of the molten film is 6.4 × 10 ⁸ Ω cm.
It has now been found that the objects of the present invention can be achieved in the same way using the following aromatic polyesters:

Therefore, according to the present invention, there is provided a second method for producing an aromatic polyester film by extruding a molten film of a thermoplastic aromatic polyester onto a rotary cooling drum, and then cooling the film while it is in close contact with the rotary drum, wherein the aromatic polyester contains the above-mentioned quaternary phosphonium sulfonate and an alkali metal or alkaline earth metal compound, and the molten film has an AC volume resistivity of 6.4×10 ⁸ Ω·cm or less;
and applying an electric charge to the molten surface of the film in a non-contact manner near the point where the molten film of the aromatic polyester reaches the rotating cooling drum.

The alkali metal or alkaline earth metal is:
Examples of these include lithium, sodium, potassium, magnesium, calcium, cesium, strontium, barium, rubidium, and beryllium. Compounds of these elements include oxides, chlorides, hydrides, hydroxides, sulfides, sulfates, carbonates, and the like of these elements.
Examples include phosphates and carboxylates. More specifically, for example, magnesium oxide, calcium oxide, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, calcium chloride, strontium chloride, magnesium chloride, calcium hydride, strontium hydride, magnesium hydride, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide,
Cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, barium sulfate, sodium carbonate, potassium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, sodium phosphate, potassium phosphate, magnesium phosphate, calcium phosphate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate,
Beryllium acetate, magnesium acetate, calcium acetate,
Examples include strontium acetate, barium acetate, sodium benzoate, potassium benzoate, rubidium benzoate, cesium benzoate, magnesium benzoate, calcium benzoate, strontium benzoate, barium benzoate, sodium phthalate, potassium phthalate, calcium phthalate, magnesium phthalate, barium phthalate, calcium terephthalate, barium terephthalate, etc. These may be used alone or in combination.

These compounds can be dissolved or dispersed in, for example, ethylene glycol, or can be added as they are to the reaction system for producing the aromatic polyester all at once or in several portions.

When these compounds are dispersed in glycol,
The particle size is preferably 5 μm or less, more preferably 3 μm or less. The addition time may be any stage during polyester production, as long as a good dispersion state in the aromatic polyester is obtained. These compounds may be added to an aromatic polyester copolymerized with a quaternary phosphonium sulfonate salt, or may be added to an aromatic polyester not copolymerized with a quaternary phosphonium sulfonate salt, and then mixed with an aromatic polyester copolymerized with a quaternary phosphonium sulfonate salt before film formation, so that the copolymerization ratio of the quaternary phosphonium sulfonate salt in the aromatic polyester used for film formation and the amount of the alkali metal or alkaline earth metal compound added are set to predetermined values.

The alkali metal or alkaline earth metal compound is preferably used in an amount of 0.1 to 20% by weight based on the bifunctional carboxylic acid component (excluding sulfonates) constituting the aromatic polyester.
millimol%, more preferably 0.2 to 18 millimol%
is.

The use of an alkali metal or alkaline earth metal compound and a quaternary phosphonium sulfonate salt together further improves the thermal stability of the polyester and allows for more efficient film production, although the reason is unclear. When the amount of these compounds is less than 0.1 mmol%, the benefits of adding these compounds are unclear. On the other hand, when the amount of these compounds exceeds 20 mmol%, the improvement in the thermal stability of the polyester reaches a saturation point, and it becomes difficult to achieve any further improvement than that achieved by adding 20 mmol%. There does not appear to be a specific ratio between the copolymerization ratio of the quaternary phosphonium sulfonate salt and the amount of the alkali metal or alkaline earth metal compound that produces a particularly effective effect. However, when the copolymerization ratio of the quaternary phosphonium sulfonate salt is 0.1 to 45 mmol% and the amount of the alkali metal or alkaline earth metal compound exceeds 20 mmol%, the resulting film exhibits increased surface defects and black impurities, primarily composed of antimony.

In the present invention, the aromatic polyester preferably exhibits a direct current volume resistivity value (P/D value) of the molten polymer at 285°C of 0.5 x ¹⁰⁶ to 2.0 x ¹⁰⁷ Ω·cm.

In the method of the present invention, the aromatic polyester containing an alkali metal or alkaline earth metal compound is used,
Preferably at least 60 m/min, more preferably 60 to 200 m/min
It is advantageous to rotate the cooling drum at a peripheral rotational speed of 1000 rpm.

Regarding the second method of the present invention, it should be understood that the explanations for the first method of the present invention are applicable to any explanations that are not given.

Furthermore, according to the present invention, thirdly, as an aromatic polyester, 0.1 to 45 mmol% of a difunctional carboxylic acid component is
It has been found that the object of the present invention can also be achieved by using an aromatic polyester having a quaternary phosphonium sulfonate having no ester-forming functional group dispersed in the polymer and having an AC volume resistivity (F/D value) of 6.5 x 10 ⁸ Ω·cm or less when formed into a molten film.

Examples of the quaternary phosphonium sulfonate salts having no ester-forming functional group include those represented by the following formula: In this case, A' is an aliphatic or aromatic group having 4 to 18 carbon atoms and m being a value; _R5 , _R6 , _R7 , and _R8 are each independently a monovalent hydrocarbon group having 1 to 18 carbon atoms; and m is 1 or 2.

In the above formula, A' is an m-valent aliphatic or aromatic group having 4 to 18 carbon atoms; _R5 , _R6 , _R7 and _R8 are each independently a monovalent hydrocarbon group having 1 to 18 carbon atoms; and m is 1 or 2.

Among the compounds represented by the above formula, the compound where m=1 is
This is disclosed in Japanese Patent Publication No. 1-29500. Examples of the compound represented by the above formula include the following compounds: butyl sulfonate, octyl sulfonate, lauryl sulfonate, myristyl sulfonate,
Aliphatic sulfonates such as hexadecyl sulfonate and 2-ethylhexyl sulfonate, and mixtures thereof;
Examples of the compound where m=2 include substituted phenyl sulfonates such as p-tosylate, butyl phenyl sulfonate, dodecyl phenyl sulfonate, octadecyl phenyl sulfonate, and dibutyl phenyl sulfonate, and substituted or unsubstituted naphthyl sulfonates such as naphthyl sulfonate, diisopropyl naphthyl sulfonate, and dibutyl naphthyl sulfonate.
Ethanedisulfonic acid, 1,2-ethanedisulfonic acid, phenol-2,4-disulfonic acid, phenol-2,5-disulfonic acid, 1,2-dioxybenzene-3,5-disulfonic acid,
Hydroxy-2,5-disulfonic acid, 1,4-benzenedisulfonic acid, 2,5-dimethyl-1,3-benzenedisulfonic acid,
Specific examples of the organic phosphonium cation include aliphatic phosphoniums such as 4-methyl-1,3-benzenedisulfonic acid, 5-methyl-1,3-benzenedisulfonic acid, 5-methyloxycarbonyl-1,3-benzenedisulfonic acid, 1,8-dihydroxyanthraquinone-2,7-disulfonic acid, 1,5-dihydroxyanthraquinone-2,6-disulfonic acid, 1,5-dimethoxyanthraquinone-2,6-disulfonic acid, etc. Specific examples of the organic phosphonium cation include aliphatic phosphoniums such as tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, triethylmethylphosphonium, tributylmethylphosphonium, tributylethylphosphonium, trioctylmethylphosphonium, trimethylbutylphosphonium, trimethyloctylphosphonium, trimethyllaurylphosphonium, trimethylstearylphosphonium, triethyloctylphosphonium, and tributyloctylphosphonium; triphenylmethylphosphonium;
Examples of aromatic phosphoniums include triphenylethylphosphonium, triethylbenzylphosphonium, tributylbenzylphosphonium, etc. Furthermore, phosphoniums having a substituent, such as tetramethylolphosphonium, tri(2-cyanoethyl)methylphosphonium, tri(2-cyanoethyl)ethylphosphonium, tri(2-cyanoethyl)benzylphosphonium, tri(3-hydroxypropyl)methylphosphonium, tri(3-hydroxypropyl)benzylphosphonium, trimethyl(2-hydroxyethyl)phosphonium, tributyl(2-hydroxyethyl)phosphonium, etc., can also be used.

The sulfonic acid quaternary phosphonium salt represented by the above formula is
Examples of the combination of the sulfonate and organic phosphonium cation are as follows. These sulfonate quaternary phosphonium salts are characterized in that, unlike the sulfonate quaternary phosphonium salts used in the first and second inventions, they do not have an ester-forming functional group. Therefore, the sulfonate quaternary phosphonium salts are dispersed in the aromatic polyester of the present invention without being copolymerized.

Thus, thirdly, the present invention provides a method for producing an aromatic polyester film by extruding a molten film of a thermoplastic aromatic polyester onto a rotating cooling drum, then uniformly adhering the film to the rotating drum and cooling the film, characterized in that the aromatic polyester is an aromatic polyester prepared using a sulfonic acid quaternary phosphonium salt having no ester-forming functional group as described above, and an electric charge is applied to the molten surface of the aromatic polyester in a non-contact manner near the point where the molten film reaches the rotating cooling drum.

The aromatic polyester to be treated in the third method of the present invention is prepared by mixing a sulfonic acid quaternary phosphonium salt in an amount of 0.1 with respect to the bifunctional carboxylic acid component constituting the aromatic polyester.
The aromatic polyester preferably contains 0.2 to 20 mmol % of the aromatic polyester, and has an AC volume resistivity (F/D value) of 6.5×10 ⁸ Ω·cm or less, preferably 3.2×10 ⁸ to 5.6×10 ⁶ Ω·cm.

With regard to the third method of the present invention, it should be understood that the explanations for the first method of the present invention are applicable to any explanations that are not given.

In the third method of the present invention, the sulfonate quaternary phosphonium salt can be added at any step before the aromatic polyester is melt-extruded from a die, such as during polyester polymerization, drying, or pre-extrusion treatment. However, adding the sulfonate quaternary phosphonium salt at a high concentration of more than 45 mmol% is undesirable because it increases the amount of foreign matter in the film and, particularly in the third method, tends to cause problems such as the compound adhering to the rotating cooling drum during film formation, accelerating drum fouling and reducing production efficiency due to drum cleaning.

According to the first, second and third processes of the present invention described above, a molten film of aromatic polyester can be brought into close contact with the cooling drum even when the cooling drum rotates relatively quickly, thereby enabling the production of a film of excellent quality while achieving high productivity.

Thus, according to the present invention, there are provided aromatic polyester films of excellent quality, free from surface defects and black foreign matter mainly composed of antimony, and of uniform thickness, which are produced by the first, second, and third methods.

Among these, the films that can be produced by the first and second methods have the following advantages compared to films obtained from aromatic polyesters containing a sulfonic acid sodium salt having an ester-forming functional group in the polymer chain:
It is characterized by a significant difference in electrical performance for AC.

Therefore, according to the present invention, the aromatic polyester (i) contains, in the polymer chain, a sulfonic acid quaternary phosphonium salt having an ester-forming functional group in a proportion of 0.1 to 45 mmol % relative to the bifunctional carboxylic acid component constituting the aromatic polyester, or (i)'
The film is characterized in that (ii) the aromatic polyester contains, in the polymer chain, a quaternary phosphonium sulfonate salt having an ester-forming functional group in a proportion of 0.1 to 45 mmol % relative to the bifunctional carboxylic acid component constituting the aromatic polyester, and also contains an alkali metal or alkaline earth metal compound in a proportion of 0.1 to 20 mmol % relative to the bifunctional carboxylic acid component constituting the aromatic polyester, and further, in terms of the relationship between the film AC volume resistivity and the film DC volume resistivity in the molten state, the film exhibits a smaller AC volume resistivity value at the same DC volume resistivity value than an aromatic polyester containing, in the polymer chain, a sulfonic acid sodium salt having an ester-forming functional group.

Among the above films, the aromatic polyester is mainly composed of ethylene terephthalate or ethylene-
As described above, the sulfonic acid quaternary phosphonium salt is preferably a sulfonic acid quaternary phosphonium salt represented by the following formula: wherein X ₁ , X ₂ , A, R ₁ , R ₂ , R ₃ , R ₄ and n are defined as above.

Regarding the requirement (ii) of the film of the present invention, the film of the present invention has an AC volume resistivity that is about 1/2 to 1/1 of that of a comparative film at the same DC volume resistivity.
It is advantageous to reduce it to a value of 0.

The aromatic polyester film of the present invention and the aromatic polyester film produced by the method of the present invention are useful in a wide range of applications, for example, magnetic tapes, electrical insulation, capacitors,
It is suitable for use in the film field, such as for photography and packaging.

The present invention will be further explained with reference to the following examples, in which "parts" means parts by weight, and the intrinsic viscosity and melting point of the polyester, electrostatic cast properties, volume resistivity of the polymer and film, surface defects of the film, etc. were measured and evaluated by the following methods.

1. Intrinsic viscosity Measured at 35°C using o-chlorophenol as a solvent.

2. Melting point of polymer: Measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min.

3. Electrostatic Casting: When a voltage of 7000 V was applied between the cooling drum and the polymer melt-extruded into a film by an electrode placed near the nozzle and above the extruded film, the maximum cooling drum speed at which a stable film could be produced without pinner bubbles or a decrease in thickness uniformity was determined. The maximum cooling drum speed was ranked and evaluated as follows:

Rank A: Stable film formation is possible at a casting drum speed of 70 m/min or more.

Rank B: Casting drum speed 60m/min or more and 70m/min or more
Stable film formation can be achieved in less than a minute.

Rank C: Casting drum speed 55m/min or more and 60m/min or more
Stable film formation can be achieved in less than a minute.

Rank D: Stable film formation was only possible at a casting drum speed of less than 55 m/min.

4. AC volume resistivity of polymers Using the device shown in Figure 1, a pair of electrodes (2) was inserted into the polymer (1) to be measured, and the container (3) was immersed in a heater (4). The polymer was heated to a temperature of melting point +30°C and maintained at this temperature. An AC power source (5) of 100V50 was connected externally to the electrodes (2) inserted into the polymer.
A voltage of 1000 Hz was applied. The AC volume resistivity was calculated from the readings of the ammeter (6) and voltmeter (7), the electrode area, and the distance between the electrodes.

5. Film surface defects: Evaluation of particulate foreign matter produced as a by-product during the extrusion process from the polymerization of thermoplastic polyester. The molten polymer is extruded at a temperature of the melting point + 35°C, and cooled by contacting it with a rotating cooling drum to obtain a substantially amorphous film. Then, the film is rolled in the machine direction.
The film was stretched 3.6 times in the longitudinal direction and 3.9 times in the transverse direction to produce a film having a thickness of 15 μm.

This film was observed using a phase contrast microscope, and the number of particles in the microscope image having a maximum length of 10 μm or more was counted using an image analyzer Luzex 500 (manufactured by Nippon Regulator).
A particle count of 10 particles/cm ² or less can be used in practice.

6. Thermal stability of polymer In the measurement of film surface defects in item 5, evaluation was made based on the difference between the intrinsic viscosity of the thermoplastic polyester chip and that of the film after melt extrusion and cooling.

A value of 0.052 or less was deemed to have good thermal stability and was indicated by a circle, and a value of more than 0.052 was deemed to have poor thermal stability and was indicated by an x.

7. Measurement of film volume resistivity Measurement was performed using the device shown in Figure 2. The measurement sample was a film with a thickness of approximately 150 μm. An upper electrode 13 with a diameter of 5.6 cm and a thickness of 0.2 cm was placed on the top surface of a cylindrical lower electrode 12 with a diameter of 20 cm so that a parallel gap of 150 μm could be maintained.
The measurement sample is inserted between the electrodes so that it is in close contact with the electrodes.

The lower electrode incorporates a power supply device 14 and a temperature detection tip 15, and is configured so that the variation in the surface temperature of the lower electrode on the measurement surface is within 1°C, and the temperature difference with the detection tip is within 2°C at a temperature rise rate of 8°C/min. The detected temperature is measured with a reading thermometer 7. The entire electrode is placed in an insulating box 21.

The power supply 18 applies the generated voltage between the two electrodes via a standard resistor 19, which generates a direct current of 100 V when measuring the direct current volume resistivity of the film, and a 50 Hz power supply when measuring the alternating current volume resistivity of the film. The current flowing through this circuit generates a voltage across the standard resistor 19, which is read by an electron meter 20 with an internal impedance of 100 MΩ or more.

In the present invention, the AC volume resistivity of the film during melting is measured by the above-mentioned device at a temperature rise measurement rate of the lower electrode of 8°C/
The measurement was performed at a temperature of 30°C above the melting point of the polymer measured by DSC for 1 minute, and the AC volume resistivity Z was measured at an applied voltage E, a current I, and
It can be calculated using the following formula from the electrode area S and the electrode spacing d.

Example 1 0.038 parts of manganese acetate tetrahydrate was added to a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, and the mixture was stirred for 150 minutes.
The temperature was gradually increased from 170°C to 240°C to carry out an ester exchange reaction. When the reaction temperature reached 170°C, 0.040 parts of antimony trioxide was added, and then 0.2 parts of spherical silica having an average particle size of 0.6 µm was added. Then, when the reaction temperature reached 220°C,
A mixture of 0.031 parts of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and 0.124 parts of ethylene glycol was added as a solution heated to 40° C. Subsequently, an ester exchange reaction was carried out.
Trimethyl phosphate was heated in ethylene glycol at 135°C for 5 minutes.
The solution (0.049 parts in terms of trimethyl phosphate) heated under a pressure of 1.1-1.6 kg/cm² for ¹ hour was added. The reaction product was then transferred to a polymerization reactor, heated to 290°C, and added to a 0.2 mm
The polycondensation reaction was carried out under high vacuum of less than 1000 Hg, and the intrinsic viscosity was 0.
60 polyesters were obtained.

This polyester was melt-extruded at 290°C into a film of 210µm thickness, and then solidified by electrostatic casting using a linear electrode onto the mirror-finished surface of a cooling drum. The speed of the cooling drum was gradually increased, and the maximum casting speed at which a stable cooling film could be produced without pin-shaped defects due to poor adhesion was 97m/min. The polyester film was melt-extruded at 285°C (melting point +3
The AC volume resistivity (F/D value) at 0°C is 6.3 x 10 ⁸
Ω cm, and the DC volume resistivity value (F/A value) is 4.0×10
The resistance was ⁸ Ω·cm.

Next, the cooling film (unstretched film) is stretched 3.6 mm in the longitudinal direction.
The film was sequentially biaxially stretched 3.9 times in the axial direction and 3.9 times in the transverse direction, and then heat-set at 230°C to produce a biaxially stretched film. An investigation of the film revealed that the number of particles measuring 10-20 µm was 1 particle/ ^cm² on average, with almost no particles larger than 20 µm. The results are shown in Table 1.

Examples 2 to 5 In Example 1, instead of spherical silica, silica having an average particle size of 0.6
The casting was carried out in the same manner as in Example 1, except that calcium carbonate of 100 μm in diameter was used, the amount of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt added was changed to the amount shown in Table 1, and the film thickness during casting was changed to 150 μm. The results are shown in Table 1.

Comparative Examples 1 to 4 Casting was carried out in the same manner as in Example 2, except that sodium acetate trihydrate or potassium acetate trihydrate was added in place of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate in the amounts shown in Table 1. The results are shown in Table 1.

Comparative Example 5 A biaxially stretched film having a thickness of 15 μm was produced in the same manner as in Example 1, except that the amount of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt was increased to 0.344 parts and the amount of ethylene glycol was increased to 3 parts.

As a result of evaluating the foreign matter in the film, two particles of 60 μm or more in size, five particles of 40 μm to 60 μm in size were found in an area of 100 ^cm2 .
24 black foreign objects measuring 20 μm to 40 μm were found. Analysis of the composition of these black foreign objects revealed that the main components were antimony or antimony and phosphorus.

The film was of no commercial value as a base film for optical recording materials and high-density magnetic recording materials.

Example 6: To a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol was added 0.018 part of manganese acetate tetrahydrate, and the temperature was gradually raised from 150°C to 240°C to carry out an ester exchange reaction. When the reaction temperature reached 210°C, a mixture of 0.036 parts of tetraphenylphosphonium 3,5-dicarboxybenzenesulfonate and 0.0838 parts of ethylene glycol was heated to 40°C and added. Subsequently, the ester exchange reaction was carried out, and after completion of the ester exchange reaction, 0.013 parts of trimethyl phosphate and 0.2 parts of spherical silica having an average particle size of 0.6 µm were added. Five minutes later, 0.008 parts by weight of titanium acetate was added, and the reaction product was then heated to 290°C and subjected to a polycondensation reaction under a high vacuum of 0.2 mmHg or less to produce a polyester having an intrinsic viscosity of 0.58.

A biaxially stretched film was produced in the same manner as in Example 1, except that this polyester was used and the temperature was 305° C. The results are shown in Table 1.

Example 7 To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol was added 0.038 parts of manganese acetate tetrahydrate, and the mixture was stirred for 150 minutes.
The temperature was gradually increased from 0.5°C to 240°C to carry out an ester exchange reaction.
0.2 parts of spherical silica having an average particle size of 0.6 μm was added, and after 15 minutes of reaction, 0.045 parts of antimony trioxide was added, and after another 5 minutes of reaction, 0.014 parts of tetrabutylphosphonium dodecylsulfonate was added. The mixture was then heated to 290° C. and polycondensed under a high vacuum of 0.2 mmHg or less to obtain a polyester.

This polymer was used and cast in the same manner as in Example 1, and the resulting cooled film was sequentially biaxially stretched in the same manner as in Example 1 to produce a biaxially stretched film. The results are shown in Table 1.

Example 8 In Example 1, 100 parts of dimethyl terephthalate was changed to 88 parts of dimethyl terephthalate and 12 parts of dimethyl isophthalate, and the amount of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt added was changed from 0.031 parts to 0.0
The same procedure as in Example 1 was carried out except that the amount was changed to 17 parts. The results are shown in Table 1.

Example 9 The same procedure as in Example 4 was carried out except that 0.0015 part of potassium acetate was added after the addition of antimony trioxide. The results are shown in Table 1.

Example 10: The polymer polymerized under the conditions of Example 1 was cut into a film having a thickness of 210 μm.
The film was melt-extruded and adhered by electrostatic adhesion to the surface of a cooling drum having a large number of channel cracks with a groove width of 3 μm.

Example 11 The polymer polymerized under the conditions of Example 2 was melt-extruded into a film having a thickness of 55 µm, and adhered to the surface of a cooling drum having a water-coated film having a thickness of about 2 µm by electrostatic adhesion.

Example 12 Bis-β-hydroxyethyl ester of terephthalic acid 10
0 parts and terephthalic acid 65 parts, ethylene glycol 29 parts and 3,5
The mixture was subjected to an esterification reaction at a temperature of 210-230°C. The amount of water distilled by the reaction was 13.
The reaction is considered complete when the volume of the reaction product doubles.
0.027 parts of antimony trioxide, 0.2 parts of calcium carbonate (average particle size 0.6 μm), and a solution of trimethyl phosphate (0.002 parts in terms of trimethyl phosphate) in ethylene glycol heated at 135° C. for 5 hours were added. The reaction product was then transferred to a polymerization reactor, heated to 290° C., and pressurized under 0.2 mmHg.
Polyesters were produced by polycondensation reaction under high vacuum as follows:

This polyester was used for casting in the same manner as in Example 1. The results are shown in Table 1.

Example 13: 50 parts of polyethylene terephthalate chips (lubricant content) with a particle size of 4 mm and 50 parts of polyethylene terephthalate flakes (lubricant content) with an average particle size of approximately 3 mm were mixed with 0.016 parts of a dodecylbenzenesulfonate tetrabutylphosphonium salt compound, and the mixture was melt-mixed in a twin-screw extruder while venting under vacuum. The resulting film was extruded and solidified by electrostatic adhesion onto a cooling drum. The rate of fouling of the cooling drum did not show any significant increase compared to when the phosphonium salt compound was not added. The results are shown in Table 1.

Comparative Examples 6 and 7 Casting was carried out in the same manner as in Example 2, except that 3,5-dicarboxybenzenesulfonic acid sodium salt was added in place of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt in the amounts shown in Table 1. The results are shown in Table 1.

Example 14 To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol was added 0.038 parts of manganese acetate tetrahydrate, and the mixture was stirred for 150 minutes.
The temperature was gradually raised from 100°C to 240°C to carry out an ester exchange reaction. When the reaction temperature reached 220°C, a mixture of 0.0309 parts of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and 0.124 parts of ethylene glycol was added as a solution heated to 40°C. The ester exchange reaction was then carried out. After completion of the ester exchange reaction, 0.025 parts of trimethyl phosphate was added, and the reaction was continued for 10 minutes. 0.045 parts of antimony trioxide was then added, and the reaction was continued for another 5 minutes, after which 0.00152 parts of potassium acetate was added. The reaction product was then transferred to a polymerization reactor, heated to 290°C, and subjected to a polycondensation reaction under a high vacuum of 0.2 mmHg or less to obtain a polyester (A) with an intrinsic viscosity of 0.60.

This polyester (A) was melt-extruded at 290°C,
After cooling on the surface of a cooling drum (drum surface peripheral speed: 70 m/min) using the electrostatic casting method, the film is stretched 3.6 times vertically and 3.
The film was stretched 9 times to obtain a biaxially stretched film having a thickness of 15 μm.

The results are shown in Table 2.

The reason for this is unclear for clear polymers that do not contain inorganic or organic lubricants, but they are generally more likely to develop pin-shaped defects than polymers that contain lubricants.
In the case of polymers containing 0.1 wt %, extremely small defects that would disappear in the subsequent stretching process tend to become apparent in the clear polymer, and the maximum casting speed is often 10 to 30% lower with the clear polymer.

Example 15 Bis-β-hydroxyethyl ester of terephthalic acid 10
0 parts and terephthalic acid 65 parts, ethylene glycol 29 parts and 3,5
The mixture of 0.314 parts of tetrabutylphosphonium dicarboxybenzenesulfonate was subjected to an esterification reaction at a temperature of 210-230°C. The amount of water distilled by the reaction was
The reaction was terminated when the viscosity reached 13 parts, and 0.027 parts of antimony trioxide and 0.002 parts of trimethyl phosphate were added per 100 parts of the reaction product. The reaction product was then transferred to a polymerization reactor, heated to 290°C, and subjected to a polycondensation reaction under a high vacuum of 0.2 mmHg or less to obtain polyester (B) having an intrinsic viscosity of 0.62.
obtained.

On the other hand, when producing polyester (B), 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt
0.314 parts magnesium benzoate 0.1255 without adding
Polyester (C) was obtained in the same manner as in the preparation of polyester (B), except that parts of polyester (C) were added.

Polyester (D) was obtained in the same manner as polyester (C) except that 0.1255 parts of magnesium benzoate was not added when polyester (C) was produced.

These polyesters (B), (C), and (D) were mixed, and the copolymerization amount of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and the amount of magnesium benzoate added in the polyester (F) after mixing were adjusted as shown in Table 1 below.

This polyester (F) was used to prepare a film in the same manner as in Example 14. The results are shown in Table 2.

Example 16: In Example 14, 0.0309 parts of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate was changed to 0.0035 parts, and 0.00152 parts of potassium acetate was changed to 0.00006 parts of lithium acetate.
A polyester (G) having an intrinsic viscosity of 0.60 was obtained in the same manner as in Example 14, except that the amount of the hydroxybenzoate was changed to 8 parts.

A film was produced in the same manner as in Example 14, except that this polyester was used and the drum surface speed was set to 60 m/min. The results are shown in Table 2.

Example 17 To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol was added 0.038 parts of manganese acetate tetrahydrate, and the mixture was stirred for 150 minutes.
The temperature was gradually increased from 210°C to 240°C during the ester exchange reaction.
A mixture of 0.858 parts of tetrabutylphosphonium 1-dicarboxybenzenesulfonate and 3.432 parts of ethylene glycol was added. Subsequently, an ester exchange reaction was carried out. After completion of the ester exchange reaction, 0.025 parts of trimethyl phosphate was added and the reaction was continued for 15 minutes. Then, 0.045 parts of antimony trioxide was added and the reaction was continued for another 5 minutes. The reaction product was then transferred to a polymerization reactor, heated to 290°C, and subjected to a polycondensation reaction under a high vacuum of 0.2 mmHg or less to obtain a polyester (H) having an intrinsic viscosity of 0.60.

On the other hand, polyester (I) having an intrinsic viscosity of 0.60 was obtained in exactly the same manner as polyester (H), except that the mixture of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and ethylene glycol was not added when the reaction liquid temperature reached 210°C.

Further, polyester (J) having an intrinsic viscosity of 0.60 was obtained in exactly the same manner as polyester (I), except that after completion of the ester exchange reaction, predetermined amounts of trimethyl phosphate and antimony trioxide were added, and then 10 minutes later, 0.140 parts of sodium acetate trihydrate was added.

Polyesters (H), (I), and (J) were mixed, and the amount of copolymerized tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and the amount of sodium acetate trihydrate in the polyester (K) after mixing were adjusted as shown in Table 2 below.

This polyester (K) was used to prepare a film in the same manner as in Example 16. The results are shown in Table 2.

Example 18: To a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol, 0.018g of manganese acetate tetrahydrate was added.
The transesterification reaction was carried out by gradually increasing the temperature from 150° C. to 240° C. When the temperature of the reaction mixture reached 210° C., 0.0359 parts of 3,5-dicarboxybenzenesulfonic acid tetraphenylphosphonium salt and potassium acetate were added.
40 parts of a mixture of 0.00020 parts of ethylene glycol and 0.0838 parts of ethylene glycol
The solution heated to ° C. was added. Subsequently, an ester exchange reaction was carried out. After the ester exchange reaction was completed, trimethyl phosphate was added.
After 5 minutes, 0.008 parts by weight of titanium acetate was added, and the reaction product was heated to 290°C and polycondensation reaction was carried out under high vacuum of 0.2 mmHg or less to obtain a polyester (P) with an intrinsic viscosity of 0.52.

A film was produced in the same manner as in Example 14, except that this polyester (P) was used and the temperature was 305°C.
The results are shown in Table 2.

Comparative Example 8 In Example 18, 0.0359 parts of tetraphenylphosphonium salt of 3,5-dicarboxybenzenesulfonic acid and 0.0002 parts of potassium acetate were added when the reaction temperature reached 210°C.
Polyester (Q) having an intrinsic viscosity of 0.52 was obtained in the same manner as in Example 18, except that 0.0352 parts of magnesium acetate tetrahydrate was used instead of 0.0001 parts of the hydroxybenzoate.

A film was produced in the same manner as in Example 18, except that this polyester (Q) was used and the peripheral speed of the drum surface was set to 55 m/min. The results are shown in Table 2.

Example 19 Polyester (H), polyester (I) and polyester (J) were obtained in the same manner as in Example 17.

On the other hand, 100 parts of dimethyl terephthalate and 7 parts of ethylene glycol
0.038 parts of manganese acetate tetrahydrate was added to 0 parts of the mixture.
The temperature was gradually raised from 150°C to 240°C to carry out the transesterification reaction.
parts of antimony trioxide are added and allowed to react for 15 minutes.
After adding 0.45 parts of the mixture and reacting for another 10 minutes, the average particle size of the mixture was 1.0
1.0 part of calcium carbonate of 0.2 mm was mixed with 5 parts of ethylene glycol and added.
The polycondensation reaction was carried out under high vacuum of less than 1000 Hg, and the intrinsic viscosity was 0.
60 polyesters (R) were obtained.

The polyesters (H), (I), and
(J) and (R) were mixed, and the amounts of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate and sodium acetate trihydrate in the polyester (S) after mixing were adjusted to be as shown in Table 2 below, and the content of calcium carbonate having an average particle size of 1.0 μm was adjusted to 0.10 part by weight per 100 parts by weight of the polymer.

This polyester (S) was used to prepare a film in the same manner as in Example 16. The results are shown in Table 2.

───────────────────────────────────────────────────────── Continued from the front page (51) Int.Cl. ⁶ Identification symbol Internal reference number FI Technical marking location C08L 67/02 KKB

Claims (21)

[Claims] Claim 1: A method for producing an aromatic polyester film by extruding a molten film of a thermoplastic aromatic polyester onto a rotating cooling drum, and then cooling the film while it is in close contact with the rotating drum, wherein the aromatic polyester contains, in the polymer chain, a sulfonic acid quaternary phosphonium salt having an ester-forming functional group in an amount of 0.1 to 45 mmol % relative to the bifunctional carboxylic acid component, and the molten film has an AC volume resistivity of 6.5 x 10 ⁸ Ω·cm.
A method for producing a molten film of the aromatic polyester, comprising: applying an electric charge to a molten surface of the film in a non-contact manner in the vicinity of the molten film reaching a rotating cooling drum; Claim 2: The rotational peripheral speed of the rotating cooling drum is at least 50
2. The method of claim 1, wherein the flow rate is m/min. Claim 3: The rotational peripheral speed of the rotary cooling drum is 60 to 200 mm/min
The method of claim 1, wherein 4. The method of claim 1, wherein the rotating cooling drum has a number of channel-like microcracks on its surface. Claim 5: The rotational peripheral speed of the rotary cooling drum is 80 to 200 mm/min
The method of claim 4, wherein 6. The method of claim 1, wherein the rotating cooling drum has a mirrored surface. Claim 7: The rotational peripheral speed of the rotary cooling drum is 60 to 150 mm/min
7. The method of claim 6, wherein 8. The method according to claim 1, wherein the rotating surface of the rotating cooling drum is provided with a liquid coating containing water as the main component. 9. The sulfonic acid quaternary phosphonium salt having an ester-forming functional group represented by the following formula: wherein A is an (n+2)-valent aliphatic or aromatic group having 2 to 18 carbon atoms, _X1 and _X2 are the same or different and are a hydrogen atom or an ester-forming functional group, n is 1 or 2, and _R1 , _R2 , _R3 and _R4 are the same or different and are an alkyl group having 1 to 18 carbon atoms, a benzyl group or an aryl group having 6 to 12 carbon atoms, with the proviso that _X1 and _X2 are not hydrogen at the same time. 10. A method for producing an aromatic polyester film by extruding a molten film of a thermoplastic aromatic polyester onto a rotating cooling drum, and then cooling the film while it is in close contact with the rotating drum, wherein the aromatic polyester contains, in the polymer chain, 0.1 to 45 mmol % of a quaternary phosphonium sulfonate having an ester-forming functional group relative to a bifunctional carboxylic acid component,
The bifunctional carboxylic acid component contains 0.1 to 20 mmol% of an alkali metal or alkaline earth metal compound, and the molten film has an AC volume resistivity of 6.4 x 10 ⁸ Ω·cm.
A method for producing a molten film of the aromatic polyester, comprising the steps of: applying an electric charge to a molten surface of the film in a non-contact manner immediately after the molten film of the aromatic polyester reaches a surface of a rotating cooling drum; 11. The rotating peripheral speed of the rotating cooling drum is at least
The method of claim 10, wherein the speed is 60 m/min. Claim 12: The rotational peripheral speed of the rotary cooling drum is 60 to 200 m/s
The method of claim 10, wherein the .times. ... 13. The aromatic polyester is 0.5×10 ⁶ to 2.0×1
The method of claim 10, which exhibits a value of AC volume resistivity of the molten film of 0 ⁷ Ω·cm. 14. A method for producing an aromatic polyester film by extruding a molten film of a thermoplastic aromatic polyester onto a rotating cooling drum, and then cooling the film while it is in close contact with the rotating drum, wherein the aromatic polyester contains a sulfonic acid quaternary phosphonium salt having no ester-forming functional group dispersed in the polymer in an amount of 0.1 to 45 mmol % based on the bifunctional carboxylic acid component, and the molten film has an AC volume resistivity of 6.5 x 1.
A method for producing a molten film of an aromatic polyester having a resistivity of ^0.8 Ω·cm or less, comprising contactlessly applying an electric charge to a molten surface of the film in the vicinity of where the molten film of the aromatic polyester reaches a rotating cooling drum. 15. The sulfonic acid quaternary phosphonium salt having no ester-forming functional group represented by the following formula: wherein A' is an m-valent aliphatic or aromatic group having 4 to 18 carbon atoms; _R5 , _R6 , _R7 , and _R8 are each independently a monovalent hydrocarbon group having 1 to 18 carbon atoms; and m is 1 or 2. 16. A film of a thermoplastic aromatic polyester, said aromatic polyester comprising (i) 0.
A film characterized in that (ii) the film contains, in the polymer chain, a quaternary phosphonium salt of sulfonic acid having an ester-forming functional group in a proportion of 1 to 45 mmol %, and in that, in the relationship between the AC volume resistivity and the DC volume resistivity of the film in a molten state, the film exhibits a smaller AC volume resistivity value at the same DC volume resistivity value than an aromatic polyester containing a sodium salt of sulfonic acid having an ester-forming functional group in the polymer chain. 17. The film of claim 16, wherein the aromatic polyester is composed primarily of ethylene terephthalate. 18. The film of claim 16, wherein the aromatic polyester is composed primarily of ethylene 2,6-naphthalate. 19. The sulfonic acid quaternary phosphonium salt having an ester-forming functional group represented by the following formula: wherein A is an (n+2)-valent aliphatic or aromatic group having 2 to 18 carbon atoms, _X1 and _X2 are the same or different and are a hydrogen atom or an ester-forming functional group, n is 1 or 2, and _R1 , _R2 , _R3 , and _R4 are each
are the same or different and are an alkyl group having 1 to 18 carbon atoms, a benzyl group, or an aryl group having 6 to 12 carbon atoms, provided that X ₁
and X ₂ are not hydrogen at the same time. 20. A thermoplastic aromatic polyester film, wherein the aromatic polyester comprises (i) 0.
(ii) a quaternary phosphonium sulfonate salt having an ester-forming functional group is contained in a polymer chain in a proportion of 1 to 45 mmol %, and (iii) an alkali metal or alkaline earth metal compound is contained in a proportion of 0.1 to 20 mmol % relative to a bifunctional carboxylic acid component constituting the aromatic polyester;
and (iii) a film characterized in that, in the relationship between the AC volume resistivity and the DC volume resistivity of the film in a molten state, the film exhibits a smaller AC volume resistivity value at the same DC volume resistivity value than an aromatic polyester containing a sulfonic acid sodium salt having an ester-forming functional group in the polymer chain. 21. A film produced by the method of claim 14.