WO2018155113A1 - Method for producing synthetic polyisoprene latex - Google Patents

Abstract

A method for producing a synthetic polyisoprene latex, including a step of emulsifying a synthetic polyisoprene solution prepared by dissolving a synthetic polyisoprene in an organic solvent in water in the presence of a surfactant to produce a latex of the synthetic polyisoprene, wherein the synthetic polyisoprene has a ratio (I_B/I_A) of the intensity I_B of a peak that is the most intense in a region ranging from 1,000 to 1,200 cm^-1 to the intensity I_A of a peak that is most intense in a region ranging from 2,840 to 3,000 cm^-1 as measured by FT-IR is 0.4 or less.

Description

Method for producing synthetic polyisoprene latex

The present invention relates to a method for producing a synthetic polyisoprene latex which is excellent in stability as a latex, excellent in tensile strength and elongation, and can provide a dip-molded body having a soft texture, and such production. The present invention relates to a method for producing a latex composition using a synthetic polyisoprene latex obtained by the method, a method for producing a dip-molded product, and a method for producing an adhesive layer-forming substrate.

Conventionally, it is known that a latex composition containing latex of natural rubber is dip-molded to obtain a dip-molded body that is used in contact with a human body such as a nipple, a balloon, a glove, a balloon, and a sack. However, since natural rubber latex contains a protein that causes allergic symptoms in the human body, there are cases in which there is a problem as a dip-molded body that is in direct contact with a living mucosa or organ. Therefore, studies have been made on using synthetic rubber latex instead of natural rubber latex.

For example, Patent Document 1 discloses a technique for obtaining a latex of synthetic polyisoprene by emulsifying and concentrating a solution in which synthetic polyisoprene is dissolved in cyclohexane. However, in the technique of Patent Document 1, the resultant synthetic polyisoprene latex is made into a latex composition by adding a crosslinking agent, and when stored for a long period of time, aggregates are likely to be generated in the latex composition. In some cases, there was a problem that the tensile strength of the dip-molded product obtained using the latex composition may be insufficient.

Japanese Patent No. 5365513

The present invention has been made in view of such a situation, and is a synthesis that is excellent in stability as a latex, excellent in tensile strength and elongation, and can provide a dip-molded body having a soft texture. It aims at providing the manufacturing method of polyisoprene latex.

As a result of intensive studies to achieve the above object, the present inventors have found that the intensity ratio at two specific peaks measured by a Fourier transform infrared spectrophotometer (FT-IR) as a synthetic polyisoprene is as follows. The above-mentioned object can be achieved by obtaining a synthetic polyisoprene latex by emulsifying a synthetic polyisoprene solution obtained by dissolving the synthetic polyisoprene in an organic solvent using a composition controlled within a predetermined range. The present invention has been completed.

That is, according to the present invention, when measured by FT-IR, for the most strength is large peak intensity _{I A} in the range of 2,840 ~ 3,000 cm ^-1, of 1,000 ~ 1,200cm ^-1 the most strength is large peak intensity I _B ratio in a range (I B _{/ I a)} is a synthetic polyisoprene is 0.4 or less, the synthetic polyisoprene solution prepared by dissolving in an organic solvent, a surfactant There is provided a method for producing a synthetic polyisoprene latex comprising the step of obtaining a latex of the synthetic polyisoprene by emulsification in water in the presence.

In the present invention, the synthetic polyisoprene solution is solidified by solidifying a polymer solution obtained by solution polymerization of a monomer containing isoprene dissolved in an organic solvent. It is preferable that the product is obtained by re-dissolving the product in an organic solvent.
In this case, the synthetic polyisoprene solution is added with 0.001 to 0.3 parts by weight of an antioxidant to 100 parts by weight of the polymer component in the polymer solution. In this state, it is preferably obtained by performing the coagulation and the re-dissolution.

Alternatively, in the present invention, the synthetic polyisoprene solution is preferably obtained by solidifying a solution polymerized monomer containing isoprene dissolved in an organic solvent.
In this case, the synthetic polyisoprene solution is added with 0.001 to 0.3 parts by weight of an anti-aging agent with respect to 100 parts by weight of the synthetic polyisoprene in the synthetic polyisoprene solution. It is preferable that it is obtained by emulsifying.

In the present invention, solution polymerization is preferably performed in the presence of an organic alkali metal catalyst.

Moreover, according to this invention, the manufacturing method of a latex composition provided with the process of adding a crosslinking agent to the synthetic polyisoprene latex obtained by said manufacturing method is provided.
Furthermore, according to this invention, the manufacturing method of a dip molded object provided with the process of dip-molding the latex composition obtained by the said manufacturing method is provided.
Furthermore, according to this invention, an adhesive layer forming base material provided with the process of forming in the base material surface the adhesive bond layer formed using the synthetic polyisoprene latex obtained by said manufacturing method is provided. .

According to the present invention, a method for producing a synthetic polyisoprene latex that is excellent in stability as a latex, has excellent tensile strength and elongation, and can provide a dip-molded body having a soft texture, and such The manufacturing method of the latex composition using the synthetic polyisoprene latex obtained by the various manufacturing methods, the manufacturing method of the dip-molded product, and the manufacturing method of the adhesive layer forming substrate can be provided.

Production method of the present invention, when measured by FT-IR, for the most strength is large peak intensity _{I A} in the range of 2,840 ~ 3,000 cm ^-1, the range of 1,000 ~ 1,200cm ^-1 the most ratio of the intensity is large peak intensity _{I B (I B / I a} ) is a synthetic polyisoprene is 0.4 or less, the synthetic polyisoprene solution prepared by dissolving in an organic solvent in the presence of surfactants in Below, it is equipped with the process of obtaining the latex of synthetic polyisoprene by emulsifying in water.

Here, when the synthetic polyisoprene is measured by FT-IR, the peak with the highest intensity in the range of 2,840 to 3,000 cm ⁻¹ is the peak derived from the C—H stretching vibration in the synthetic polyisoprene. The peak having the highest intensity in the range of 1,000 to 1,200 cm ⁻¹ is estimated to be a peak derived from CO stretching vibration in the synthetic polyisoprene. Therefore, for synthetic polyisoprene, the peak intensity estimated to be derived from such CO stretching vibration (peak intensity I _B of the highest intensity in the range of 1,000 to 1,200 cm ⁻¹ ), The smaller the ratio (I _B / I _A ) to the intensity of the peak estimated to be derived from C—H stretching vibration (the intensity I _{A of the} peak having the highest intensity in the range of 2,840 to 3,000 cm ⁻¹ ), It is considered that the degree of oxidation in the synthetic polyisoprene is small (the number of C—O bonds formed by the oxidation of the synthetic polyisoprene is small).

According to the present invention, as the synthetic polyisoprene constituting the synthetic polyisoprene latex, the synthetic polyisoprene obtained by using the above-described peak intensity ratio (I _B / I _A ) controlled in the above range. With regard to latex, it is possible to suppress the generation of aggregates, and to suppress the generation of aggregates when stored for a long period of time with respect to a latex composition obtained by blending a synthetic polyisoprene latex with a crosslinking agent. While being able to improve, the tensile strength of the dip molded object manufactured using a latex composition can be improved notably.

Synthetic polyisoprene solution First, the synthetic polyisoprene solution used in the production method of the present invention will be described.
The synthetic polyisoprene contained in the synthetic polyisoprene solution used in the present invention may be a homopolymer of isoprene or a copolymer of other ethylenically unsaturated monomers copolymerizable with isoprene. It may be. The content of isoprene units in the synthetic polyisoprene is flexible, and it is easy to obtain a film molded body such as a dip molded body having excellent tensile strength. More preferred is 90% by weight or more, still more preferred is 95% by weight or more, and particularly preferred is 100% by weight (isoprene homopolymer).

Examples of other ethylenically unsaturated monomers copolymerizable with isoprene include conjugated diene monomers other than isoprene such as butadiene, chloroprene and 1,3-pentadiene; acrylonitrile, methacrylonitrile, fumaronitrile, α- Ethylenically unsaturated nitrile monomers such as chloroacrylonitrile; vinyl aromatic monomers such as styrene and alkylstyrene; methyl (meth) acrylate (meaning “methyl acrylate and / or methyl methacrylate”; The same applies to ethyl (meth) acrylate, etc.), ethylenically unsaturated carboxylic acid ester monomers such as ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate; Is mentioned. These other ethylenically unsaturated monomers copolymerizable with isoprene may be used singly or in combination.

There are four types of isoprene units in the synthetic polyisoprene, which are cis bond units, trans bond units, 1,2-vinyl bond units, and 3,4-vinyl bond units, depending on the bond state of isoprene. From the viewpoint of improving the tensile strength of a film molded product such as a dip molded product, the content ratio of cis bond units in the isoprene units contained in the synthetic polyisoprene is preferably 70% by weight or more based on the total isoprene units. More preferably, it is 90 weight% or more, More preferably, it is 95 weight% or more.

The weight average molecular weight of the synthetic polyisoprene is preferably 10,000 to 5,000,000, more preferably 500,000 to 5,000,000, and even more preferably, in terms of standard polystyrene by gel permeation chromatography analysis. Is 800,000 to 3,000,000. By setting the weight average molecular weight of the synthetic polyisoprene within the above range, the tensile strength of a film molded body such as a dip molded body is improved and the synthetic polyisoprene latex tends to be easily manufactured.

The polymer Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the synthetic polyisoprene is preferably 50 to 80, more preferably 60 to 80, and still more preferably 70 to 80.

As described above, the synthetic polyisoprene contained in the synthetic polyisoprene solution used in the present invention has a density of 2,840 to 3,000 cm ⁻¹ as measured by a Fourier transform infrared spectrophotometer (FT-IR). for the most strength is large peak intensity _{I a} in the range, the ratio of the highest intensity is large peak intensity _{I B} in the range of _{^{1,000 ~ 1,200cm -1 (I B /}} I a) is 0.4 or less Yes, preferably 0.2 or less, more preferably 0.1 or less. The lower limit of the above-described intensity ratio (I _B / I _A ) is not particularly limited, but is generally about 0.005 or more.

The method for producing the synthetic polyisoprene solution containing the synthetic polyisoprene whose strength ratio (I _B / I _A ) is controlled within the above range is not particularly limited. For example, in the presence of a polymerization catalyst, an organic solvent is used. In the polymer solution obtained by solution polymerization of isoprene and other copolymerizable ethylenically unsaturated monomers used as necessary, solidified by solidification, A method of obtaining a synthetic polyisoprene solution by re-dissolving a solid in an organic solvent can be mentioned.

In particular, as a method of controlling the above-described intensity ratio (I _B / I _A ) more appropriately within the above range, when producing a synthetic polyisoprene solution, it is used for heat history applied to the synthetic polyisoprene, or for solution polymerization. Examples thereof include a method of controlling the type and amount of the polymerization catalyst and adding an anti-aging agent to the polymer solution.

For example, by reducing the degree of thermal history during the production of a synthetic polyisoprene solution, oxidation of the resulting synthetic polyisoprene is suppressed, and as a result, the synthetic polyisoprene is derived from CO stretching vibration. Then, the peak intensity (the intensity I _{B of the} peak having the highest intensity in the range of 1,000 to 1,200 cm ⁻¹ ) is reduced, and the intensity ratio (I _B / I _A ) is effectively reduced. Will be able to. In particular, as a method of reducing the degree of heat history, when solidifying a polymer solution by solidifying the polymer solution, the drying condition is set to a lower temperature and a shorter time. Is preferred.

In addition, the above-mentioned strength ratio (depending on the type and amount of the polymerization catalyst used in solution polymerization of the monomer (isoprene and an ethylenically unsaturated monomer copolymerizable with isoprene that is used if necessary)) is also possible. I _B / I _A ) can be controlled.

The polymerization catalyst is not particularly limited, and examples thereof include a Ziegler polymerization catalyst and an organic alkali metal catalyst. However, the amount used in solution polymerization can be reduced, and as a result, the resulting synthetic polyisoprene is obtained. The amount of the polymerization catalyst remaining in the catalyst can be reduced, the oxidation of the synthetic polyisoprene due to the action of the polymerization catalyst can be suppressed, and the above intensity ratio (I _B / I _A ) can be more effectively reduced. From the viewpoint of becoming, an organic alkali metal catalyst is preferable. Alternatively, the synthetic polyisoprene obtained can have a relatively low weight average molecular weight, and when the latex composition is formed by dip molding, the synthetic polyisoprene in the latex composition It is preferable to use a Ziegler-based polymerization catalyst from the viewpoint that it can act to bond the particles of isoprene and improve the film forming property.

The organic alkali metal catalyst is not particularly limited. For example, organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, stilbenelithium; dilithiomethane, 1,4- Organic polyvalent lithium compounds such as dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-tris (lithiomethyl) benzene; organic sodium compounds such as sodium naphthalene; And organic power lithium compounds such as potassium naphthalene. Among these, it is preferable to use an organic monolithium compound, and it is more preferable to use n-butyllithium. These organic alkali metal catalysts can be used alone or in combination of two or more.

Examples of the method for adding the organic alkali metal catalyst include, for example, an organic alkali metal catalyst in a reaction vessel charged with a monomer (isoprene and an ethylenically unsaturated monomer copolymerizable with isoprene, if necessary). May be added as it is, or may be added in a state where the organic alkali metal catalyst is dissolved in an inert solvent such as hexane.

The Ziegler-based catalyst is not particularly limited, and a known catalyst can be used. For example, it is obtained by reducing titanium tetrachloride with an organoaluminum compound and further treating with various electron donors and electron acceptors. Examples include a catalyst system in which a titanium trichloride composition and an organoaluminum compound are combined, and a supported catalyst system in which titanium tetrachloride and various electron donors are brought into contact with magnesium halide. Among these, titanium tetrachloride and organic A catalyst system using an aluminum compound is preferable, and a catalyst system using titanium tetrachloride and trialkylaluminum is particularly preferable.

The amount of the polymerization catalyst used is preferably 0.0070 to 0.085 parts by weight with respect to 100 parts by weight of the monomer used for polymerization, from the viewpoint that a synthetic polyisoprene solution can be produced with high productivity. The amount is preferably 0.0076 to 0.056 parts by weight, and more preferably 0.0084 to 0.042 parts by weight.

Examples of the organic solvent used for the solution polymerization include aromatic hydrocarbon solvents such as benzene, toluene, and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane, and cyclohexene; and aliphatics such as pentane, hexane, and heptane. Hydrocarbon solvents; halogenated hydrocarbon solvents such as methylene chloride, chloroform, ethylene dichloride; and the like. Of these, alicyclic hydrocarbon solvents are preferred, with cyclohexane being particularly preferred.

The amount of the organic solvent used is preferably 2,000 parts by weight or less, more preferably 20 to 1, based on 100 parts by weight of the polymer component (synthetic polyisoprene before solidification) obtained by solution polymerization. 500 parts by weight, more preferably 500 to 1500 parts by weight.

Further, the polymerization temperature at the time of solution polymerization is preferably 40 to 80 ° C., more preferably 45 to 75 ° C. from the viewpoint that a synthetic polyisoprene solution can be produced with high productivity.

In the production method of the present invention, the polymer solution obtained by the solution polymerization described above is solidified by coagulation, and then the solid is redissolved in an organic solvent, so that a synthetic polyisoprene solution is obtained. Can be obtained. According to the production method of the present invention, impurities (for example, unreacted monomers) existing in the polymer solution can be appropriately removed by coagulating and re-dissolving the polymer solution. Thus, it is possible to more effectively suppress the occurrence of aggregates in the resulting synthetic polyisoprene latex and latex composition, and the tensile strength of the dip-molded body produced using the latex composition can be reduced. It can be improved further.

The method of coagulating the polymer solution is not particularly limited. For example, after solidifying the polymer solution in a polar solvent typified by alcohol such as methanol, the solid content obtained by coagulation is dried. By this, the method of making it a solid substance is mentioned. In this case, the degree of thermal history of the resultant synthetic polyisoprene can be made smaller, thereby suppressing the oxidation of the synthetic polyisoprene and, as a result, presumed to be derived from CO stretching vibration. The intensity of the peak (intensity I _{B of the} peak having the highest intensity in the range of 1,000 to 1,200 cm ⁻¹ ) is reduced, and the intensity ratio (I _B / I _A ) is more appropriately controlled within the above range. From the viewpoint of being able to perform the drying, it is preferable to set the drying conditions at a lower temperature and for a shorter time.

When drying the solid content of the polymer solution, the drying temperature is preferably 50 to 105 ° C, more preferably 60 to 95 ° C, and still more preferably 65 to 80 ° C. The drying time is preferably 30 seconds to 30 minutes, more preferably 1 to 20 minutes, and further preferably 1 to 15 minutes.

In addition, in the manufacturing method of this invention, it is preferable to add an anti-aging agent beforehand with respect to the polymer solution obtained by solution polymerization before performing such coagulation. Thereby, when solidifying the polymer solution, even if a thermal history is added by drying on the solid content, the oxidation of the synthetic polyisoprene can be suppressed. The intensity ratio (I _B / I _A ) can be more appropriately controlled within the above range.

The anti-aging agent is not particularly limited. For example, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t- Butyl-α-dimethylamino-p-cresol, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2,2'-methylene-bis (6-α- Methyl-benzyl-p-cresol), 4,4'-methylenebis (2,6-di-t-butylphenol), 2,2'-methylene-bis (4-methyl-6-t-butylphenol), alkylated bisphenol Phenol-based antioxidants containing no sulfur atom, such as butylated reaction product of p-cresol and dicyclopentadiene; 2,2′-thio Obis- (4-methyl-6-tert-butylphenol), 4,4′-thiobis- (6-tert-butyl-o-cresol), 2,6-di-tert-butyl-4-((4,6 -Bis (octylthio) -1,3,5-triazin-2-yl) amino) phenol and other thiobisphenol antioxidants; tris (nonylphenyl) phosphite, diphenylisodecylphosphite, tetraphenyldipropylene glycol Phosphite-based antioxidants such as diphosphite; Sulfur ester-based antioxidants such as dilauryl thiodipropionate; phenyl-α-naphthylamine, phenyl-β-naphthylamine, p- (p-toluenesulfonylamide) -diphenylamine, 4 , 4 '-(α, α-dimethylbenzyl) diphenylamine, N, N-diphenyl- Amine-based antioxidants such as -phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, butyraldehyde-aniline condensate; 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline And quinoline-based anti-aging agents such as 2,5-di- (t-amyl) hydroquinone and the like. These anti-aging agents may be used alone or in combination of two or more.

The amount of the anti-aging agent used is preferably 0.001 to 0.3 parts by weight, more preferably 0.001 parts by weight with respect to 100 parts by weight of the polymer component (synthetic polyisoprene before coagulation) in the polymer solution. 01 to 0.1 parts by weight. By making the usage-amount of an anti-aging agent within the above range, when producing a synthetic polyisoprene solution using a polymer solution, oxidation of the synthetic polyisoprene can be suppressed. The intensity ratio (I _B / I _A ) can be more appropriately controlled within the above range.

In the production method of the present invention, the method for re-dissolving the solid material obtained by coagulation is not particularly limited. For example, the solid material is used in the same organic solvent as that used for the solution polymerization described above. The method of making it melt | dissolve is mentioned.

In the production method of the present invention, as described above, a synthetic polyisoprene solution containing a synthetic polyisoprene in which the peak intensity ratio (I _B / I _A ) measured by FT-IR is controlled within the above range is prepared. Obtainable. And in the manufacturing method of this invention, synthetic polyisoprene latex is manufactured using the obtained synthetic polyisoprene solution.

In the example described above, as a method for the peak intensity ratio of _(I B _/ I _A) to produce synthetic polyisoprene solution include synthetic polyisoprene controlled in the above range, the monomer (isoprene, and optionally The polymer solution obtained by solution polymerization of the isoprene copolymerizable with the isoprene) is solidified once to obtain a solid, and then the obtained solid is recycled. Although the method of melt | dissolving was illustrated, the manufacturing method of this invention is not limited to such a method.

For example, in the production method of the present invention, a synthetic polyisoprene in which the peak intensity ratio (I _B / I _A ) is directly controlled within the above range can be obtained by solution polymerization of the monomer without solidification. An included synthetic polyisoprene solution may be obtained. As a result, since the heat history due to coagulation is not added to the synthetic polyisoprene obtained by solution polymerization, oxidation of the obtained synthetic polyisoprene can be more effectively suppressed. (I _B / I _A ) can be more appropriately controlled within the above range. When a synthetic polyisoprene solution containing a synthetic polyisoprene in which the peak intensity ratio (I _B / I _A ) is controlled within the above range is obtained by subjecting the monomer to solution polymerization without solidification. The obtained synthetic polyisoprene solution can be used as it is for the production of synthetic polyisoprene latex.

When the synthetic polyisoprene solution obtained by solution polymerization is used as it is for the production of synthetic polyisoprene latex, the polymerization catalyst used for the solution polymerization is not particularly limited. For example, a Ziegler polymerization catalyst or an organic alkali metal is used. From the viewpoint that the polymerization conversion rate can be increased and the residual amount of unreacted monomers as impurities in the synthetic polyisoprene solution can be reduced. It is preferable to use a metal catalyst.

The organic solvent used for solution polymerization can be the same as described above. The amount of the organic solvent used is preferably 2,000 parts by weight or less, more preferably 20 to 1,500 parts by weight, and still more preferably 500 to 1500 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene obtained by solution polymerization. It is.

Further, the polymerization temperature at the time of solution polymerization can be the same as described above.

When the synthetic polyisoprene solution obtained by solution polymerization is used as it is for the production of a synthetic polyisoprene latex, an anti-aging agent may be added to the synthetic polyisoprene solution before the production of the synthetic polyisoprene latex. preferable.

In this case, the anti-aging agent used may be the same as described above. The amount of the anti-aging agent used is preferably 0.001 to 0.3 parts by weight, more preferably 0.002 to 0.1 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene in the synthetic polyisoprene solution. More preferably, the amount is 0.005 to 0.05 parts by weight. By making the usage-amount of an antiaging agent into the said range, when manufacturing a synthetic polyisoprene latex using a synthetic polyisoprene solution, the oxidation of a synthetic polyisoprene can be suppressed more appropriately.

Synthetic polyisoprene latex In the production method of the present invention, a synthetic polyisoprene latex can be obtained by emulsifying the above-described synthetic polyisoprene solution in water in the presence of a surfactant.

The synthetic polyisoprene latex obtained by the production method of the present invention is a synthetic polyisoprene containing a synthetic polyisoprene in which the peak intensity ratio (I _B / I _A ) measured by FT-IR is controlled within the above range. Latex composition obtained by using this synthetic polyisoprene latex, because it is obtained using a solution, can suppress the generation of aggregates when stored for a long period of time, has excellent stability The tensile strength of the dip-molded product produced from the product can be significantly improved.

The surfactant is not particularly limited. For example, fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, sodium rosinate, potassium rosinate; sodium dodecylbenzenesulfonate Alkylbenzenesulfonates such as potassium dodecylbenzenesulfonate, sodium decylbenzenesulfonate, potassium decylbenzenesulfonate, sodium cetylbenzenesulfonate, potassium cetylbenzenesulfonate; sodium di (2-ethylhexyl) sulfosuccinate, di (2 -Ethylhexyl) alkyl sulfosuccinates such as potassium sulfosuccinate and sodium dioctyl sulfosuccinate; sodium lauryl sulfate, potassium lauryl sulfate and the like Alkyl sulfate ester salts; polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate and potassium polyoxyethylene lauryl ether sulfate; monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate; Anionic surfactants may be mentioned.

Among these anionic surfactants, fatty acid salts, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl sulfate esters and polyoxyethylene alkyl ether sulfate salts are preferred, fatty acid salts and alkylbenzene sulfonates are more preferred, Fatty acid salts are more preferable, and rosinates such as sodium rosinate and potassium rosinate are particularly preferable.

Moreover, since the polymerization catalyst (especially aluminum and titanium) derived from the synthetic polyisoprene can be removed more efficiently and the generation of aggregates during production of the latex composition is suppressed, alkylbenzene. It is preferable to use at least one selected from the group consisting of sulfonates, alkylsulfosuccinates, alkylsulfate esters and polyoxyethylene alkylether sulfates in combination with fatty acid salts, alkylbenzenesulfonates and It is particularly preferable to use a fatty acid salt in combination. Here, sodium rosinate and potassium rosinate are preferable as the fatty acid salt, and sodium dodecylbenzene sulfonate and potassium dodecylbenzene sulfonate are preferable as the alkylbenzene sulfonate. These anionic surfactants may be used alone or in combination of two or more.

As described above, the fatty acid salt is used in combination with at least one selected from the group consisting of alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt. Thus, the obtained latex contains at least one selected from alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt and a fatty acid salt. .

In addition, surfactants other than anionic surfactants may be used, and surfactants other than such anionic surfactants include α, β-unsaturated carboxylic acid sulfoesters, α, β- Examples thereof include copolymerizable surfactants such as sulfate esters of unsaturated carboxylic acids and sulfoalkylaryl ethers.

Furthermore, non-ionic such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester, etc., as long as it does not inhibit coagulation by the coagulant used for dip molding A surfactant may be used in combination.

The amount of the surfactant used is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene. In addition, when using 2 or more types of surfactant, it is preferable to make these total usage into the said range. That is, for example, when at least one selected from alkyl benzene sulfonate, alkyl sulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt and fatty acid salt are used in combination, The total amount used is preferably within the above range. If the amount of the surfactant used is too small, a large amount of aggregates may be generated during emulsification. Conversely, if the amount is too large, foaming is likely to occur, and pinholes may be generated in the resulting dip-formed product. .

Also, when an anionic surfactant is used in combination with a fatty acid salt and at least one selected from alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt The ratio of use thereof is determined by changing at least one surface activity selected from “fatty acid salts”: “alkyl benzene sulfonates, alkyl sulfosuccinates, alkyl sulfates and polyoxyethylene alkyl ether sulfates”. The weight ratio of the “total agent” is preferably in the range of 1: 1 to 10: 1, and more preferably in the range of 1: 1 to 7: 1. When the usage ratio of at least one surfactant selected from alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt is too high, when handling synthetic polyisoprene There is a possibility that foaming may become intense, and as a result, operations such as standing for a long time and addition of an antifoaming agent are required, which may lead to deterioration in workability and cost increase.

The amount of water used for emulsifying the synthetic polyisoprene solution is preferably 10 to 1,000 parts by weight, more preferably 30 to 500 parts by weight, and most preferably 50 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene solution. ~ 100 parts by weight. Examples of the water to be used include hard water, soft water, ion exchange water, distilled water, zeolite water and the like, and soft water, ion exchange water and distilled water are preferable.

An apparatus for emulsifying a solution or fine suspension of a synthetic polyisoprene dissolved or finely dispersed in an organic solvent in water in the presence of a surfactant is particularly suitable if it is generally marketed as an emulsifier or a disperser. Can be used without limitation. The method of adding the surfactant to the synthetic polyisoprene solution or fine suspension is not particularly limited, and it is previously added to either water or the synthetic polyisoprene solution or fine suspension, or both. Alternatively, during the emulsification operation, it may be added to the emulsified liquid, or may be added all at once or dividedly.

Examples of the emulsifier include batch type emulsification such as trade name “Homogenizer” (manufactured by IKA), trade name “Polytron” (manufactured by Kinematica), trade name “TK auto homomixer” (manufactured by Tokushu Kika Kogyo Co., Ltd.), etc. Machine: Trade name “TK Pipeline Homomixer” (made by Tokushu Kika Kogyo Co., Ltd.), trade name “Colloid Mill” (made by Shinko Pantech Co., Ltd.), trade name “Slasher” (made by Nippon Coke Industries, Ltd.), trade name “ "Trigonal wet milling machine" (Mitsui Miike Chemical Co., Ltd.), trade name "Cabitron" (Eurotech Co., Ltd.), trade name "Milder" (Pacific Kiko Co., Ltd.), trade name "Fine Flow Mill" (Pacific Kiko Co., Ltd.) Product name “Microfluidizer” (manufactured by Mizuho Kogyo Co., Ltd.), product name “Nanomizer” (manufactured by Nanomizer), product name “APV Gaurin” (Ga High-pressure emulsifiers such as the product name “Membrane Emulsifier” (manufactured by Chilling Industries Co., Ltd.); Ultrasonic emulsifiers such as trade name “Ultrasonic Homogenizer” (manufactured by Branson); The conditions for the emulsification operation by the emulsification apparatus are not particularly limited, and the treatment temperature, treatment time, etc. may be appropriately selected so as to obtain a desired dispersion state.

Moreover, when emulsifying by the above-described method, it is desirable to remove the organic solvent from the emulsion obtained through the emulsification operation.
As a method for removing the organic solvent from the emulsion, a method capable of setting the content of the organic solvent (preferably an alicyclic hydrocarbon solvent) in the obtained emulsion to 500 ppm by weight or less is preferable. Methods such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugation can be employed.

Further, after removing the organic solvent, if necessary, in order to increase the solid content concentration of the synthetic polyisoprene latex, a concentration operation may be performed by a method such as vacuum distillation, atmospheric distillation, centrifugation, membrane concentration, In particular, it is preferable to perform centrifugation from the viewpoint of increasing the solid content concentration of the synthetic polyisoprene latex and reducing the residual amount of the surfactant in the synthetic polyisoprene latex.

Centrifugation is performed using, for example, a continuous centrifuge, centrifugal force is preferably 100 to 10,000 G, and the solid content concentration of the synthetic polyisoprene latex before centrifugation is preferably 2 to 15% by weight. It is preferable that the flow rate to be fed into the machine is preferably 500 to 1700 Kg / hr, and the back pressure (gauge pressure) of the centrifuge is preferably 0.03 to 1.6 MPa. Synthetic polyisoprene latex can be obtained as a liquid. Thereby, the residual amount of the surfactant in the synthetic polyisoprene latex can be reduced.

The solid content concentration of the synthetic polyisoprene latex is preferably 30 to 70% by weight, more preferably 40 to 70% by weight. If the solid content concentration is too low, the solid content concentration of the latex composition described later becomes low, so that the film thickness of the dip molded product described later becomes thin and is easily broken. On the other hand, if the solid content concentration is too high, the viscosity of the synthetic polyisoprene latex becomes high, which may make it difficult to transfer it through piping or to stir in the preparation tank.

The volume average particle diameter of the synthetic polyisoprene latex is preferably 0.1 to 10 μm, more preferably 0.5 to 3 μm, and still more preferably 0.5 to 2.0 μm. By setting the volume average particle diameter in the above range, the latex viscosity becomes moderate and easy to handle, and when the synthetic polyisoprene latex is stored, the formation of a film on the latex surface can be suppressed.

Synthetic polyisoprene latex contains additives such as pH adjusters, antifoaming agents, preservatives, crosslinking agents, chelating agents, oxygen scavengers, dispersants, and anti-aging agents that are usually blended in the latex field. You may mix | blend.
Examples of the pH adjuster include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal hydrogen carbonates such as sodium bicarbonate; ammonia An organic amine compound such as trimethylamine or triethanolamine; an alkali metal hydroxide or ammonia is preferred.

Latex Composition The latex composition of the present invention is obtained by adding a crosslinking agent to the synthetic polyisoprene latex obtained by the production method of the present invention described above.

Examples of the crosslinking agent include sulfur such as powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, and the like; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, caprolactam disulfide (N, And sulfur-containing compounds such as N′-dithio-bis (hexahydro-2H-azepinone-2)), phosphorus-containing polysulfides, polymer polysulfides, and 2- (4′-morpholinodithio) benzothiazole. Among these, sulfur can be preferably used. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

The content of the crosslinking agent is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 3 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene. By making content of a crosslinking agent into the said range, the tensile strength of the dip molded object obtained can be raised more.

Moreover, it is preferable that the latex composition of this invention contains a crosslinking accelerator further.
As the crosslinking accelerator, those usually used in dip molding can be used. Acids and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthio-carbylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio) benzothiazole, 2- (4'-morpholino-dithio) benzothia And 4-morpholinyl-2-benzothiazyl disulfide, 1,3-bis (2-benzothiazyl mercaptomethyl) urea, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc 2-mercaptobenzothiazole Is preferred. A crosslinking accelerator can be used individually by 1 type or in combination of 2 or more types.

The content of the crosslinking accelerator is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene. By making content of a crosslinking accelerator into the said range, the tensile strength of the dip molding obtained can be raised more.

Moreover, it is preferable that the latex composition of this invention contains a zinc oxide further.
The content of zinc oxide is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of synthetic polyisoprene. By setting the content of zinc oxide in the above range, the tensile strength of the resulting dip-molded product can be further increased while improving the stability as a latex.

The latex composition of the present invention further comprises a compounding agent such as an anti-aging agent, a dispersant; a reinforcing agent such as carbon black, silica, or talc; a filler such as calcium carbonate or clay; an ultraviolet absorber; a plasticizer; It can mix | blend as needed.

The method for preparing the latex composition of the present invention is not particularly limited. For example, using a dispersing machine such as a ball mill, a kneader, a disper, etc., a synthetic polyisoprene latex is blended with a crosslinking agent and various blends as needed. Examples thereof include a method of mixing an agent, a method of preparing an aqueous dispersion of blending components other than the synthetic polyisoprene latex using the above-mentioned disperser, and then mixing the aqueous dispersion into the synthetic polyisoprene latex.

The latex composition of the present invention preferably has a pH of 7 or more, more preferably in the range of 7 to 13, and still more preferably in the range of 8 to 12. The solid content concentration of the latex composition is preferably in the range of 15 to 65% by weight.

The latex composition of the present invention is preferably aged (pre-crosslinked) before being subjected to dip molding from the viewpoint of further improving the mechanical properties of the resulting dip molded article. The pre-crosslinking time is not particularly limited and depends on the pre-crosslinking temperature, but is preferably 1 to 14 days, and more preferably 1 to 7 days. The pre-crosslinking temperature is preferably 20 to 40 ° C.
After pre-crosslinking, it is preferably stored at a temperature of 10 to 30 ° C. until it is used for dip molding. When stored at a high temperature, the tensile strength of the resulting dip-molded product may decrease.

Dip Molded Body The dip molded body of the present invention is obtained by dip molding the latex composition of the present invention. Dip molding is a method in which a mold is immersed in a latex composition, the composition is deposited on the surface of the mold, the mold is then lifted from the composition, and then the composition deposited on the mold surface is dried. is there. The mold before being immersed in the latex composition may be preheated. Further, a coagulant can be used as necessary before the mold is immersed in the latex composition or after the mold is pulled up from the latex composition.

Specific examples of the method of using the coagulant include a method in which the mold before dipping in the latex composition is immersed in a solution of the coagulant to attach the coagulant to the mold (anode coagulation dipping method), and the latex composition is deposited. There is a method of immersing the formed mold in a coagulant solution (Teag adhesion dipping method), etc., but the anode adhesion dipping method is preferable in that a dip-formed product with little thickness unevenness can be obtained.

Specific examples of coagulants include metal halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride, and aluminum chloride; nitrates such as barium nitrate, calcium nitrate, and zinc nitrate; acetic acid such as barium acetate, calcium acetate, and zinc acetate. Salts; water-soluble polyvalent metal salts such as calcium sulfate, magnesium sulfate, and sulfates such as aluminum sulfate; Of these, calcium salts are preferable, and calcium nitrate is more preferable. These water-soluble polyvalent metal salts can be used alone or in combination of two or more.

The coagulant is preferably used in the form of an aqueous solution. This aqueous solution may further contain a water-soluble organic solvent such as methanol or ethanol, or a nonionic surfactant. The concentration of the coagulant varies depending on the type of the water-soluble polyvalent metal salt, but is preferably 5 to 50% by weight, more preferably 10 to 30% by weight.

After lifting the mold from the latex composition, the deposit formed on the mold is usually dried by heating. What is necessary is just to select drying conditions suitably.

It is then heated to crosslink the deposit formed on the mold.
The heating conditions at the time of crosslinking are not particularly limited, but are preferably 60 to 150 ° C., more preferably 100 to 130 ° C., and preferably 10 to 120 minutes.
The heating method is not particularly limited, and there are a method of heating with warm air in an oven, a method of heating by irradiating infrared rays, and the like.

Alternatively, the mold may be washed with water or warm water to remove water-soluble impurities (for example, excess surfactant or coagulant) before or after heating the mold on which the latex composition is deposited. preferable. The hot water used is preferably 40 ° C. to 80 ° C., more preferably 50 ° C. to 70 ° C.

The dip-formed body after crosslinking is detached from the mold. Specific examples of the desorption method include a method of peeling from a mold by hand, a method of peeling by water pressure or compressed air pressure, and the like. If the dip-formed product in the middle of crosslinking has sufficient strength against desorption, it may be desorbed in the middle of crosslinking, and then the subsequent crosslinking may be continued.

The dip-molded product of the present invention is obtained by using the synthetic polyisoprene latex obtained by the production method of the present invention. Therefore, the dip molded product is excellent in tensile strength and has a soft texture, particularly as a glove. It can be used suitably. When the dip-molded body is a glove, in order to prevent the dip-molded bodies from sticking to each other at the contact surface, and to improve the slippage when attaching and detaching, the glove is made of inorganic fine particles such as talc and calcium carbonate or organic fine particles such as starch particles. It may be dispersed on the surface, an elastomer layer containing fine particles may be formed on the surface of the glove, or the surface layer of the glove may be chlorinated.

In addition to the above gloves, the dip-molded body of the present invention is a medical article such as a nipple for baby bottles, a dropper, a tube, a water pillow, a balloon sac, a catheter, and a condom; a toy such as a balloon, a doll, and a ball; It can also be used for industrial articles such as molding bags and gas storage bags;

Adhesive Layer Forming Base Material An adhesive layer forming base material of the present invention comprises a base material comprising an adhesive layer formed on the base material using the above-described synthetic polyisoprene solution of the present invention, and an adhesive layer. And composite material.

The substrate is not particularly limited, but for example, a fiber substrate can be used. The kind of fiber which comprises a fiber base material is not specifically limited, For example, polyamide fibers, such as vinylon fiber, polyester fiber, nylon, and aramid (aromatic polyamide), glass fiber, cotton, rayon etc. are mentioned. These can be appropriately selected according to the application. The shape of the fiber substrate is not particularly limited, and examples thereof include staples, filaments, cords, ropes, woven fabrics (such as canvas), and the like, and can be appropriately selected depending on the application.

Further, the adhesive layer may be formed using the above-described synthetic polyisoprene solution of the present invention, and may be used as it is without blending a compounding agent or the like in the above-described synthetic polyisoprene solution of the present invention. Or it is set as an adhesive composition by mix | blending various compounding agents, and you may form an adhesive bond layer using such an adhesive composition.

Examples of the compounding agent contained in the adhesive composition include an adhesive resin. The adhesive resin is not particularly limited, and for example, resorcin-formaldehyde resin, melamine resin, epoxy resin and isocyanate resin can be suitably used, and among these, resorcin-formaldehyde resin is preferable. As the resorcin-formaldehyde resin, known ones (for example, those disclosed in JP-A-55-142635) can be used. The reaction ratio of resorcin to formaldehyde is usually 1: 1 to 1: 5, preferably 1: 1 to 1: 3 in terms of a molar ratio of “resorcin: formaldehyde”.

In addition, the adhesive composition contains 2,6-bis (2,4-dihydroxyphenylmethyl) -4-chlorophenol or a similar compound, isocyanate, block, which has been conventionally used to further increase the adhesive strength. Isocyanate, ethylene urea, polyepoxide, modified polyvinyl chloride resin and the like can be contained.

Furthermore, the adhesive composition can contain a vulcanization aid. By including a vulcanization aid, the mechanical strength of the adhesive layer-forming substrate can be improved. Vulcanization aids include quinone dioximes such as p-quinone dioxime; methacrylic acid esters such as lauryl methacrylate and methyl methacrylate; DAF (diallyl fumarate), DAP (diallyl phthalate), TAC (triallyl cyanurate), And allyl compounds such as TAIC (triallyl isocyanurate); maleimide compounds such as bismaleimide, phenylmaleimide and N, Nm-phenylene dimaleimide; sulfur; and the like.

The content (solid content) of the synthetic rubber in the adhesive composition is preferably 5 to 60% by weight, more preferably 10 to 30% by weight.

The adhesive layer-forming substrate of the present invention can be prepared, for example, by applying the synthetic polyisoprene solution of the present invention or an adhesive composition containing the same to the surface of the substrate, or by synthesizing the substrate of the present invention. It can be obtained by forming an adhesive layer on a substrate by a method of immersing in a polyisoprene solution or an adhesive composition containing the same.

Such an adhesive layer-forming substrate of the present invention can be used as a substrate-rubber composite by adhering to rubber via an adhesive layer, for example. The base material-rubber composite is not particularly limited. For example, rubber using a base fiber-like fiber base material such as a rubber toothed belt with a core wire using a cord-like fiber base material or a canvas Examples thereof include a toothed belt.

The method for obtaining the base material-rubber composite is not particularly limited. For example, the synthetic polyisoprene solution of the present invention or the adhesive composition containing the base material is adhered to the base material by a coating method, a dipping treatment or the like. A method of obtaining an adhesive layer-forming substrate, placing the adhesive layer-forming substrate on rubber, and heating and pressurizing it is exemplified. The pressurization can be performed using a compression (press) molding machine, a metal roll, an injection molding machine or the like. The pressurizing pressure is preferably 0.5 to 20 MPa, more preferably 2 to 10 MPa. The heating temperature is preferably 130 to 300 ° C, more preferably 150 to 250 ° C. The treatment time for heating and pressing is preferably 1 to 180 minutes, more preferably 5 to 120 minutes. By the method of heating and pressurizing, rubber molding and adhesion between the adhesive layer forming substrate and the rubber can be performed simultaneously. In addition, it is preferable to form a mold for imparting a desired surface shape to the rubber of the target substrate-rubber composite on the inner surface of the compressor mold used for pressurization or the surface of the roll.

Further, as one embodiment of the base material-rubber composite, a base material-rubber-base composite can be exemplified. The base material-rubber-base material composite can be formed, for example, by combining a base material (may be a composite of two or more kinds of base materials) and a base material-rubber composite. Specifically, a core wire as a base material, rubber and a base fabric as a base material are stacked (in this case, the core wire and the base fabric are coated with the synthetic polyisoprene solution of the present invention or an adhesive composition containing the same). A base material-rubber-base material composite can be obtained by applying it while heating and applying pressure while heating.

The base material-rubber composite obtained using the adhesive layer forming base material of the present invention is excellent in mechanical strength, abrasion resistance and water resistance. Therefore, a flat belt, V belt, V ribbed belt, It can be suitably used as a belt such as a round belt, a square belt, or a toothed belt. The base material-rubber composite obtained using the base material for forming an adhesive layer of the present invention is excellent in oil resistance and can be suitably used as a belt in oil. Furthermore, the substrate-rubber composite obtained using the adhesive layer-forming substrate of the present invention can be suitably used for hoses, tubes, diaphragms and the like. Examples of the hose include a single tube rubber hose, a multilayer rubber hose, a braided reinforcement hose, and a cloth wound reinforcement hose. Examples of the diaphragm include a flat diaphragm and a rolling diaphragm.

The substrate-rubber composite obtained by using the adhesive layer-forming substrate of the present invention can be used as industrial products such as seals and rubber rolls in addition to the above uses. Examples of the seal include a moving part seal such as a rotating part, a swinging part, and a reciprocating part, and a fixed part seal. Examples of the motion part seal include an oil seal, a piston seal, a mechanical seal, a boot, a dust cover, a diaphragm, and an accumulator. Examples of the fixed part seal include an O-ring and various gaskets. As rubber rolls, rolls that are parts of OA equipment such as printing equipment and copying equipment; rolls for fiber processing such as spinning rolls for spinning and drafting rolls for spinning; rolls for iron making such as bridle rolls, snubber rolls, steering rolls, etc. Can be mentioned.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, “part” is based on weight unless otherwise specified. Tests or evaluation methods for physical properties and characteristics are as follows.

Weight average molecular weight (Mw)
The sample was diluted with tetrahydrofuran so that the solid content concentration was 0.1% by weight, and this solution was subjected to gel permeation chromatography analysis to calculate the weight average molecular weight (Mw) in terms of standard polystyrene.

Peak intensity ratio (I _B / I _A )
Using a synthetic polyisoprene solution, a synthetic polyisoprene film was produced, and the produced film was subjected to 2,840 to 3,000 cm ⁻ using FT-IR (model “IG-1000”, manufactured by Otsuka Electronics Co., Ltd.). the most intensity is large peak intensity _{I a} in ^1, and the strongest intensity is large peak _{I B} in the range of 1,000 ~ 1,200cm ^-1 measured, the intensity ratio of these peaks _{(I B} / I _A ) was calculated.

A 2 g sample was precisely weighed (weight: X2) in a solid content aluminum dish (weight: X1) and dried in a hot air drier at 105 ° C. for 2 hours. Subsequently, after cooling in a desiccator, the weight of the aluminum pan was measured (weight: X3), and the solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = (X3−X1) × 100 / X2

Aggregate content ratio The solid content concentration of the synthetic polyisoprene latex was measured, and about 100 g of the synthetic polyisoprene latex was precisely weighed and then filtered through a 200 mesh SUS wire mesh with a known weight. The synthetic polyisoprene latex was removed by washing with water. After drying this at 105 ° C. for 60 minutes, its dry weight was measured, and the aggregate content ratio (unit: wt%) was determined based on the following formula.
Aggregate content = {(α−β) / (γ × Δ)} × 10,000
Here, α represents the weight of the dried wire mesh and dried aggregate, β represents the weight of the wire mesh, γ represents the weight of the synthetic polyisoprene latex, and Δ represents the solid content concentration of the synthetic polyisoprene latex.

Stability of the latex composition The latex composition was aged at 30 ° C, and after a predetermined number of days from the start of aging, the agglomerate content of the latex composition was measured according to the above method, and the agglomerate content was The stability of the latex composition was evaluated by determining the number of days that the value of 0.2 was 0.2% by weight. In addition, the stability of a latex composition is excellent, so that the days which the aggregate content rate became 0.2 weight% are long.

Based on the tensile strength, elongation at break, and 500% tensile stress ASTM D412 of the dip-molded product, a dip-molded product having a film thickness of about 0.2 mm was obtained by dumbbell (trade name “Super Dumbbell (model: SDMK-100C). ) ", Manufactured by Dumbbell Co., Ltd.) to produce a test piece for measuring tensile strength. The test piece was pulled with a Tensilon universal tester (trade name “RTG-1210”, manufactured by Orientec Co., Ltd.) at a tensile speed of 500 mm / min, tensile strength immediately before break (unit: MPa), elongation just before break (unit:%) ) And the tensile stress (unit: MPa) when the elongation is 500%. The higher the tensile strength and the elongation at break, the better. Moreover, the smaller the tensile stress at 500%, the better the dip-formed body becomes excellent in flexibility.

Example 1
(Production of synthetic polyisoprene latex)
1150 parts of normal hexane and 100 parts of isoprene were charged into an autoclave with stirring that was dried and purged with nitrogen. Next, the temperature in the autoclave was set to 30 ° C., and while stirring, 0.03 part of titanium tetrachloride, 0.03 part of triisobutylaluminum and 0.005 part of normal butyl ether were added and reacted for 2 hours. As a result, 0.05 part of methanol was added to stop the reaction to obtain a polymer solution (A-1). The weight average molecular weight of the polymer component (synthetic polyisoprene before coagulation described later) in the polymer solution (A-1) was 1320,000. Further, in the obtained polymer solution (A-1), an anti-aging agent (2,6-di-tert-butyl-p-cresol (centralized) was added to 100 parts of the polymer component contained in the polymer solution. Product) and 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol (manufactured by Ciba Specialty Chemicals) 0.2) of a mixture of the name “IRGANOX 565”) at a weight ratio of 22: 3, and a polymer solution (B-1) to which an anti-aging agent is added by dissolving at room temperature under stirring Got.

Next, the obtained polymer solution (B-1) was coagulated with methanol and then dried at 100 ° C. for 25 minutes to obtain a solid synthetic polyisoprene (C-1). Thereafter, the synthetic polyisoprene (C-1) was redissolved in cyclohexane to obtain a synthetic polyisoprene solution (D-1) having a concentration of 8% by weight. Using a portion of the resulting synthetic polyisoprene solution (D-1), the peak intensity ratio (I _B / I _A ) was determined according to the above method. The results are shown in Table 1.

Next, 1250 parts of the synthetic polyisoprene solution (D-1) was heated to 60 ° C., and 1250 parts by weight of a sodium rosinate aqueous solution having a concentration of 1.0% by weight heated to 60 ° C. was adjusted to a weight ratio of 1: 1. The flow rate was adjusted and mixed using a line mixer, followed by emulsification using a homogenizer to obtain an emulsion (E-1).

Further, the emulsion (E-1) was heated to 80 ° C. under reduced pressure to distill off the cyclohexane to obtain an aqueous dispersion of synthetic polyisoprene. The obtained aqueous dispersion was centrifuged using a continuous centrifuge to obtain a synthetic polyisoprene latex (F-1) having a solid content concentration of 59.5% by weight as a light liquid. Using a part of the obtained synthetic polyisoprene latex (F-1), the aggregate content was measured according to the above method. The results are shown in Table 1.

(Preparation of latex composition)
While stirring the synthetic polyisoprene latex (F-1) obtained above, dodecylbenzenesulfone having a concentration of 10% by weight so as to be 1 part in terms of solid content with respect to 100 parts of synthetic polyisoprene in the latex. Acid soda was added. And while stirring the obtained mixture, 1.5 parts of zinc oxide, 1.5 parts of sulfur and an antioxidant (trade name: Wingstay L) in terms of solid content with respect to 100 parts of synthetic polyisoprene in the mixture. 3 parts, 0.3 part zinc diethyldithiocarbamate, 0.5 part zinc dibutyldithiocarbamate, and 0.7 part mercaptobenzothiazole zinc salt in the form of an aqueous dispersion, and then hydroxylated A latex composition was obtained by adjusting the pH to 10.5 by adding an aqueous potassium solution. Using a part of the obtained latex composition, the stability of the latex composition was evaluated according to the above method. On the other hand, about the latex composition which was not used for evaluation of stability of a latex composition, it age | cure | ripened for 48 hours in the constant temperature water tank adjusted to 30 degreeC.

(Manufacture of dip-molded bodies)
A commercially available ceramic hand mold (manufactured by Shinko) was washed and preheated in an oven at 70 ° C., and then 18 wt% calcium nitrate and 0.05 wt% polyoxyethylene lauryl ether (trade name “Emulgen 109P”). The product was dipped in a coagulant aqueous solution made of Kao Corporation for 5 seconds and taken out. Next, the hand mold coated with the coagulant was dried in an oven at 70 ° C. for 30 minutes or more.
Next, the hand mold coated with the coagulant was taken out of the oven and immersed in the latex composition after aging obtained above for 10 seconds. Then, after air-drying at room temperature for 10 minutes, this hand mold was immersed in 60 ° C. warm water for 5 minutes, and then the hand mold coated with the film-like synthetic polyisoprene was placed in a 130 ° C. oven. Crosslinking was performed by heating for 30 minutes. Subsequently, after cooling the hand mold | type coat | covered with the bridge | crosslinked film to room temperature, after spraying talc, it peeled from the hand mold | type, and the dip molded object (glove) was obtained. And about the obtained dip molded object (glove), according to the said method, tensile strength, elongation at break, and 500% tensile stress were measured. The results are shown in Table 1.

Example 2
The solid synthetic polyisoprene (C-2) and the synthetic polyisoprene solution (C-2) were synthesized in the same manner as in Example 1 except that the drying conditions after solidifying with methanol for the polymer solution were changed to 83 ° C. and 18 minutes. D-2), a synthetic polyisoprene latex (F-2), a latex composition, and a dip-formed product were produced and evaluated in the same manner. The results are shown in Table 1.

Example 3
The amount of the anti-aging agent added to the polymer solution was changed from 0.2 part to 0.05 part, and the drying condition after solidifying with methanol for the polymer solution was changed to 65 ° C. and 13 minutes. Except for the above, in the same manner as in Example 1, a solid synthetic polyisoprene (C-3), a synthetic polyisoprene solution (D-3), a synthetic polyisoprene latex (F-3), a latex composition and a dip-molded product were obtained. Manufactured and similarly evaluated. The results are shown in Table 1.

Example 4
In producing the polymer solution, instead of 0.03 part of titanium tetrachloride, 0.03 part of triisobutylaluminum and 0.005 part of normal butyl ether, 0.006 part of normal butyl lithium was used, and the reaction temperature was changed. A synthetic polyisoprene solution (D-4), a synthetic polyisoprene latex (F-4), a latex composition and a dip-molded body were produced in the same manner as in Example 3 except that the temperature was changed from 30 ° C to 60 ° C. Evaluation was performed in the same manner. The results are shown in Table 1.

Example 5
In place of 0.03 part of titanium tetrachloride, 0.03 part of triisobutylaluminum and 0.005 part of normal butyl ether, 0.006 part of normal butyl lithium was used, and the reaction temperature was changed from 30 ° C. to 60 ° C. In the same manner as in Example 1, a polymer solution (A-5) was obtained. As will be described later, this polymer solution (A-5) was directly used as a synthetic polyisoprene solution (D-5) for the production of synthetic polyisoprene latex (F-5). The weight average molecular weight of the polymer component (synthetic polyisoprene) in this synthetic polyisoprene solution (D-5) was 1,240,000. Further, the peak intensity ratio (I _B / I _A ) of a part of the synthetic polyisoprene solution (D-5) was determined according to the above method. The results are shown in Table 1.

Next, the synthetic polyisoprene solution (D-5) was directly emulsified to obtain an emulsified liquid (E-5). Specifically, an anti-aging agent (2,6-di-tert-butyl-p-cresol (manufactured by Chuo Kasei Co., Ltd.) and 2,6-di- hydrate with respect to 1250 parts of the synthetic polyisoprene solution (D-5) Weight ratio of tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol (trade name “IRGANOX565” manufactured by Ciba Specialty Chemicals) 22: 3 A mixture of 0.007 parts was heated to 60 ° C., and the flow rate was adjusted to 1: 1 by weight with 1250 parts of a 1.0 wt% sodium rosinate aqueous solution heated to 60 ° C. The mixture was adjusted and mixed using a line mixer, and then emulsified using a homogenizer to obtain an emulsion (E-5).

Further, the emulsion (E-5) was heated to 80 ° C. under reduced pressure to distill off normal hexane, whereby an aqueous dispersion of synthetic polyisoprene was obtained. The obtained aqueous dispersion was centrifuged using a continuous centrifuge to obtain an organic alkali metal synthetic polyisoprene latex (F-5) having a solid concentration of 62.8% by weight as a light liquid. Using a part of the obtained synthetic polyisoprene latex (F-5), the aggregate content ratio was measured according to the above method. The results are shown in Table 1.

Next, using the synthetic polyisoprene latex (F-5), a latex composition and a dip-molded product were produced in the same manner as in Example 1, and evaluated in the same manner. The results are shown in Table 1. In Example 5, the stability of the latex composition was evaluated. After 20 days, the aggregate content was less than 0.2% by weight, and thus the evaluation was stopped. Therefore, in Table 1, the evaluation result of the stability of the latex composition is described as “> 20”.

Comparative Example 1
The solid synthetic polyisoprene (C-6) and the synthetic polyisoprene solution (C-6) were prepared in the same manner as in Example 1 except that the drying conditions after the polymer solution was coagulated with methanol were changed to 120 ° C. and 45 minutes. D-6), a synthetic polyisoprene latex (F-6), a latex composition, and a dip-formed product were produced and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 2
The solid synthetic polyisoprene (C-7) and the synthetic polyisoprene solution (C-7) were prepared in the same manner as in Example 3 except that the drying conditions after solidifying with methanol for the polymer solution were changed to 110 ° C. and 35 minutes. D-7), a synthetic polyisoprene latex (F-7), a latex composition and a dip-molded product were produced and evaluated in the same manner. The results are shown in Table 1.

From Table 1, when using synthetic polyisoprene in which the peak intensity ratio (I _B / I _A ) measured by FT-IR is controlled to 0.4 or less, the obtained synthetic polyisoprene latex is agglomerated. The product content ratio is small, and when it is a latex composition, it is excellent in stability, and the dip-molded article produced using this latex composition has excellent tensile strength and elongation, and is flexible. It had a texture (Examples 1 to 5).

On the other hand, when synthetic polyisoprene having an excessively high peak intensity ratio (I _B / I _A ) measured by FT-IR is used, the resulting synthetic polyisoprene latex has a large agglomerate content ratio, and the latex composition In addition, the dip-molded product produced using this latex composition was inferior in tensile strength (Comparative Examples 1 and 2).

Claims (9)

When measured by a Fourier transform infrared spectrophotometer (FT-IR), for the most strength is large peak intensity _{I A} in the range of ^{2,840 ~ 3,000cm -1, 1,000 ~ 1,200cm} -1 the ratio of the highest intensity is large peak intensity I _B in the range of (I B _{/ I a)} is a synthetic polyisoprene is 0.4 or less, the synthetic polyisoprene solution prepared by dissolving in an organic solvent, a surfactant A method for producing a synthetic polyisoprene latex comprising the step of obtaining a latex of the synthetic polyisoprene by emulsifying in water in the presence of. The synthetic polyisoprene solution is made into a solid by solidifying a polymer solution obtained by solution polymerization of a monomer containing isoprene dissolved in an organic solvent, and then the solid is used as an organic solvent. The method for producing a synthetic polyisoprene latex according to claim 1, wherein the synthetic polyisoprene latex is obtained by re-dissolution. The synthetic polyisoprene solution is prepared by adding 0.001 to 0.3 parts by weight of an anti-aging agent to the polymer solution with respect to 100 parts by weight of the polymer component in the polymer solution. The method for producing a synthetic polyisoprene latex according to claim 2, wherein the synthetic polyisoprene latex is obtained by coagulation and re-dissolution. The method for producing a synthetic polyisoprene latex according to claim 1, wherein the synthetic polyisoprene solution is obtained by solution polymerization of a monomer containing isoprene dissolved in an organic solvent without coagulation. The synthetic polyisoprene solution is emulsified with 0.001 to 0.3 parts by weight of an anti-aging agent added to 100 parts by weight of the synthetic polyisoprene in the synthetic polyisoprene solution. The method for producing a synthetic polyisoprene latex according to claim 4, which is obtained. The method for producing a synthetic polyisoprene latex according to any one of claims 2 to 5, wherein solution polymerization is carried out in the presence of an organic alkali metal catalyst. A method for producing a latex composition comprising a step of adding a crosslinking agent to the synthetic polyisoprene latex obtained by the production method according to any one of claims 1 to 6. A method for producing a dip-molded body comprising a step of dip-molding the latex composition obtained by the production method according to claim 7. A method for producing an adhesive layer-formed base material comprising a step of forming an adhesive layer formed by using the synthetic polyisoprene latex obtained by the production method according to any one of claims 1 to 6 on the surface of the base material .