Chloroprene-based polymer latex composition and immersion molded body

Abstract

Provided are a chloroprene-based polymer latex composition from which it is possible to obtain an immersion molded body that has excellent flexibility and excellent tensile strength when being cut; and an immersion molded body that is obtained from the chloroprene-based polymer latex composition and that has excellent flexibility and excellent tensile strength when being cut. The present invention provides a chloroprene-based polymer latex composition that contains a chloroprene-based polymer latex, a metal oxide, and a mercapto-based compound. The chloroprene-based polymer latex composition contains 0.3-15.0 parts by mass of the metal oxide and 0.10-10.00 parts by mass of the mercapto-based compound with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex.

Description

Chloroprene polymer latex composition and dip-molded product

[0001] The present invention relates to a chloroprene polymer latex composition and a dip-molded article.

[0002] Chloroprene-based polymers are known as materials for dip-molded products such as medical surgical gloves, medical examination gloves, industrial gloves, balloons, catheters, and rubber boots.

[0003] Various technologies have been proposed for chloroprene polymers for use in dip-molded products. Patent Document 1 describes, with respect to vibration-proof rubber applications, that mixing a low-molecular-weight chloroprene polymer with a number-average molecular weight in the range of 500 to 50,000 improves damping performance. Patent Document 2 describes, with respect to dip-molded product applications, a polychloroprene latex with a pH of 7 to 14, containing 100 parts by mass of modified polychloroprene obtained by copolymerizing chloroprene and methacrylic acid, 90 to 150 parts by mass of water, 1 to 5 parts by mass of an emulsifier, and 0.5 to 2.5 parts by mass of potassium ions. Patent Document 3, relating to applications to dip-molded products, describes a mercaptan-modified polychloroprene latex obtained by copolymerizing chloroprene and 2,3-dichloro-1,3-butadiene, in which, in the C-solid-state NMR spectrum of the polychloroprene, the peak area (A) at 126.2 to 127.6 ppm, the peak area (B) at 122.0 to 126.2 ppm, and the peak area (C) at 129.9 to 130.3 ppm are within the ranges represented by the following general formula (I): Patent Document 4, relating to applications to dip-molded products, describes a chloroprene polymer latex that contains high-molecular-weight and low-molecular-weight components, thereby enabling the vulcanized rubber produced by dip molding to have both excellent flexibility and mechanical properties.

[0004]

[0005] Japanese Patent Laid-Open No. 7-292165 Japanese Patent Laid-Open No. 2014-114342 International Publication No. 2019 / 009038 Japanese Patent Laid-Open No. 2019-143002

[0006] Dip-molded articles using chloroprene polymers tend to be required to have high flexibility, similar to dip-molded articles obtained using natural rubber or polyisoprene, and also to have high tensile strength at break. Improved flexibility is also related to improvements in wearing comfort and texture of the coating. Therefore, a chloroprene polymer latex composition capable of producing dip-molded articles having excellent flexibility and excellent tensile strength at break has been desired.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a chloroprene polymer latex composition from which a dip-molded article having excellent flexibility and tensile strength at break can be obtained, which has been difficult to obtain with conventional chloroprene polymer latex compositions, and a dip-molded article of the chloroprene polymer latex composition having excellent flexibility and tensile strength at break.

[0008] That is, the present invention provides a chloroprene polymer latex composition comprising a chloroprene polymer latex, a metal oxide, and a mercapto compound, wherein the chloroprene polymer latex composition comprises 0.3 to 15.0 parts by mass of the metal oxide and 0.10 to 10.00 parts by mass of the mercapto compound relative to 100 parts by mass of a solid content of the chloroprene polymer latex.

[0009] Various embodiments of the present invention are exemplified below. The embodiments shown below can be combined with each other. [1] A chloroprene polymer latex composition containing a chloroprene polymer latex, a metal oxide, and a mercapto compound, wherein the chloroprene polymer latex composition contains 0.3 to 15.0 parts by mass of the metal oxide and 0.10 to 10.00 parts by mass of the mercapto compound per 100 parts by mass of the solid content of the chloroprene polymer latex. [2] The chloroprene polymer latex composition according to [1], wherein the chloroprene polymer latex composition contains 0.5 to 10.0 parts by mass of an antioxidant per 100 parts by mass of the solid content of the chloroprene polymer latex. [3] The chloroprene polymer latex composition according to [1] or [2], wherein the molecular weight distribution obtained by measuring the tetrahydrofuran-soluble content in the chloroprene polymer latex by gel permeation chromatography has a peak at a weight average molecular weight of 5,000 to 80,000. [4] The chloroprene polymer latex composition according to any one of [1] to [3], wherein the chloroprene polymer latex composition has a sulfur content of 5 parts by mass or less per 100 parts by mass of the solid content of the chloroprene polymer latex. [5] A dip-molded article of the chloroprene polymer latex composition according to any one of [1] to [4]. [6] The dip-molded article according to [5], which is any one of industrial and household gloves, ordinary household gloves, medical gloves, balloons, catheters, and boots.

[0010] The chloroprene polymer latex composition according to the present invention can provide a dip-molded article having excellent flexibility and tensile strength at break. Furthermore, the obtained dip-molded article can be used as various materials requiring flexibility, tensile strength at break, etc., by taking advantage of its properties. Specifically, the dip-molded article can be used as any of industrial and household gloves, general household gloves, medical gloves, balloons, catheters, and boots.

[0011] The present invention will be described in detail below by illustrating embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. Furthermore, each feature can be an invention independently.

[0012] 1. Chloroprene Polymer Latex Composition The chloroprene polymer latex composition according to the present invention comprises a chloroprene polymer latex, a metal oxide, and a mercapto compound, and the chloroprene polymer latex composition contains 0.3 to 15.0 parts by mass of the metal oxide and 0.10 to 10.00 parts by mass of the mercapto compound per 100 parts by mass of the solids content of the chloroprene polymer latex. Components that may be contained in the chloroprene polymer latex composition according to the present invention will be described below.

[0013] 1.1 Chloroprene Polymer Latex The chloroprene polymer latex according to the present invention contains a chloroprene polymer. The chloroprene polymer according to the present invention means a polymer containing a monomer unit derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene).

[0014] The chloroprene polymer according to one embodiment of the present invention may be a copolymer of chloroprene and another monomer copolymerizable with chloroprene. The other monomer is not particularly limited as long as it is copolymerizable with the chloroprene monomer, and examples thereof include (meth)acrylic acid esters (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, unsaturated nitriles, ethylene, styrene, sulfur, etc.

[0015] A chloroprene-based polymer according to one embodiment of the present invention preferably contains chloroprene monomer units and 2,3-dichloro-1,3-butadiene monomer units. The chloroprene-based polymer according to one embodiment of the present invention preferably contains 0 to 30% by mass of 2,3-dichloro-1,3-butadiene monomer units, more preferably 8 to 20% by mass, and still more preferably 10 to 17% by mass, relative to 100% by mass of the total of the chloroprene monomer units and the 2,3-dichloro-1,3-butadiene monomer units. The content of the 2,3-dichloro-1,3-butadiene monomer unit is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0016] The chloroprene polymer latex according to one embodiment of the present invention may contain 70 to 100% by mass of chloroprene monomer units relative to 100% by mass of the chloroprene polymer contained in the chloroprene polymer latex. The content of the chloroprene monomer units may be, for example, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% by mass, or may be within a range between any two of the values ​​exemplified here.

[0017] The chloroprene polymer latex according to one embodiment of the present invention may contain 0 to 30% by mass of other monomer units other than chloroprene monomer units and 2,3-dichloro-1,3-butadiene monomer units, based on 100% by mass of the chloroprene polymer contained in the chloroprene polymer latex. The content of the other monomer units may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, or may be within a range between any two of the values ​​exemplified here. The chloroprene polymer according to one embodiment of the present invention may be composed of chloroprene monomer units and 2,3-dichloro-1,3-butadiene monomer units.

[0018] The chloroprene polymer latex composition according to one embodiment of the present invention may contain two or more different chloroprene polymers. When the chloroprene polymer latex composition according to one embodiment of the present invention contains two or more different chloroprene polymers, the content of each monomer unit in the chloroprene polymer means the total content of each monomer unit in each chloroprene polymer relative to 100% by mass of the total of all chloroprene polymers contained in the chloroprene polymer latex composition.

[0019] <Toluene-insoluble content> The chloroprene polymer latex according to the present invention preferably has a toluene-insoluble content of 50 to 95% by mass. The chloroprene polymer latex according to one embodiment of the present invention more preferably has a toluene-insoluble content of 55 to 85% by mass. The toluene-insoluble content is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95% by mass, and may be within a range between any two of the values ​​exemplified here.

[0020] The toluene-insoluble content can be calculated by the following formula, specifically by the method described in the Examples: toluene-insoluble content (gel content) = B / A × 100 (%), where Ag is the chloroprene polymer rubber obtained by freeze-drying a chloroprene polymer latex, and Bg is the gel content (insoluble content) separated from the toluene-dissolved mixture.

[0021] The toluene-insoluble content can be controlled by adjusting the production conditions of the chloroprene polymer rubber, for example, the polymerization formulation (formulation such as the type and amount of a chain transfer agent, polymerization temperature, polymerization time, polymerization conversion rate, etc.) contained in the chloroprene polymer latex, and by adjusting the type and amount of the polymer blended.

[0022] <Weight-average molecular weight> The chloroprene polymer latex according to one embodiment of the present invention can have a peak having a weight-average molecular weight of 200,000 to 1,500,000 in the molecular weight distribution obtained by measuring the tetrahydrofuran-soluble content in the chloroprene polymer latex by gel permeation chromatography. Furthermore, the chloroprene polymer latex according to one embodiment of the present invention preferably has a peak having a weight-average molecular weight of 5,000 to 80,000 in the molecular weight distribution obtained by measuring the tetrahydrofuran-soluble content in the chloroprene polymer latex by gel permeation chromatography. The chloroprene polymer latex according to one embodiment of the present invention is mixed with a large amount of methanol, precipitated, filtered, dried, and the resulting chloroprene polymer is dissolved in tetrahydrofuran to obtain a sample. In this case, the molecular weight distribution preferably has a peak having a weight-average molecular weight of 200,000 to 1,500,000 and / or a peak having a weight-average molecular weight of 5,000 to 80,000.

[0023] Furthermore, in the chloroprene polymer latex according to one embodiment of the present invention, the chloroprene polymer latex is mixed with a large amount of methanol, precipitated, filtered, and dried. The resulting chloroprene polymer is dissolved in tetrahydrofuran to obtain a sample, and the resulting sample is subjected to gel permeation chromatography. In the molecular weight distribution obtained, a peak corresponding to a weight average molecular weight of 200,000 to 1,500,000 is preferably detected, and more preferably a peak corresponding to a weight average molecular weight of 5,000 to 80,000 is preferably detected. In the molecular weight distribution, a peak corresponding to a weight average molecular weight of 300,000 to 1,500,000 is preferably detected, and more preferably a peak corresponding to a weight average molecular weight of 5,000 to 50,000 is preferably detected. In the molecular weight distribution, a peak corresponding to a weight average molecular weight of 500,000 to 1,500,000 is preferably detected, and more preferably a peak corresponding to a weight average molecular weight of 8,000 to 30,000 is preferably detected.

[0024] The chloroprene polymer latex according to one embodiment of the present invention may contain two or more polymers having different weight-average molecular weights, namely, a chloroprene polymer α and a chloroprene polymer β. The monomer units that the chloroprene polymer α and the chloroprene polymer β may contain and the amounts thereof are as described above for the monomer units that the chloroprene polymer may contain. The chloroprene polymer α according to one embodiment of the present invention may have a weight-average molecular weight different from that of the chloroprene polymer β. The difference between the weight-average molecular weight of the chloroprene polymer α according to one embodiment of the present invention and the weight-average molecular weight of the chloroprene polymer β is preferably 100,000 or more, more preferably 400,000 or more. The difference between the weight-average molecular weight of the chloroprene polymer α and the weight-average molecular weight of the chloroprene polymer β described below is, for example, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,200,000, 1,300,000, 1,400,000, or 1,500,000, and may be within a range between any two of the numerical values ​​exemplified here.

[0025] For example, the weight-average molecular weight of the chloroprene polymer α can be smaller than the molecular weight of the chloroprene polymer β. The weight-average molecular weight of the chloroprene polymer α can be 5,000 to 80,000. The weight-average molecular weight of the chloroprene polymer α can be, for example, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, or 21,000. , 22,000, 23,000, 24,000, 25,000, 26,000, 27,000, 28,000, 29,000, 30,000, 35,000, 40,000, 50,000, 60,000, 70,000, 80,000, and may be within a range between any two of the numerical values ​​exemplified here.

[0026] For example, the weight-average molecular weight of the chloroprene polymer β can be greater than the molecular weight of the chloroprene polymer α. The weight-average molecular weight of the chloroprene polymer β can be 200,000 to 1,500,000. The weight-average molecular weight of the chloroprene polymer α can be, for example, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, or 1,500,000, or can be within a range between any two of the values ​​exemplified here.

[0027] The chloroprene polymer latex according to one embodiment of the present invention preferably contains 5 to 40% by mass of the chloroprene polymer α, based on 100% by mass of the polymers contained in the chloroprene polymer latex. The content of the chloroprene polymer α may be, for example, 5, 10, 15, 20, 25, 30, 35, or 40% by mass, and may be within a range between any two of the values ​​exemplified here.

[0028] The chloroprene polymer latex according to one embodiment of the present invention preferably contains 60 to 95% by mass of the chloroprene polymer β relative to 100% by mass of the polymers contained in the chloroprene polymer latex. The content of the chloroprene polymer β is, for example, 60, 65, 70, 75, 80, 85, 90, or 95% by mass, and may be within a range between any two of the values ​​exemplified here.

[0029] The weight-average molecular weight can be determined, for example, by mixing a chloroprene polymer latex with a large amount of methanol, precipitating, filtering, and drying the resulting chloroprene polymer, dissolving the resulting chloroprene polymer in tetrahydrofuran, and analyzing the resulting sample using gel permeation chromatography (GPC). The GPC measurement conditions can be as described in the Examples. The weight-average molecular weight can be controlled by adjusting the production conditions, specifically, the polymerization formulation of the chloroprene polymer (formulation such as the type and amount of chain transfer agent, polymerization temperature, polymerization time, polymerization conversion rate, etc.).

[0030] 1.2 Method for Producing Chloroprene Polymer Latex The method for producing the chloroprene polymer latex according to the present invention is not particularly limited, and the chloroprene polymer latex can be obtained, for example, by the following method. The method for producing the chloroprene polymer latex according to the first embodiment of the present invention may include a polymerization step of polymerizing raw material monomers containing chloroprene to obtain a chloroprene polymer latex, and the obtained chloroprene polymer latex can be used as is as the chloroprene polymer latex. The method for producing the chloroprene polymer latex according to the second embodiment of the present invention may include a polymerization step of polymerizing raw material monomers containing chloroprene to obtain a chloroprene polymer latex, and a mixing step of mixing two or more types of latexes to obtain a chloroprene polymer latex. The method for producing a chloroprene polymer latex according to the third embodiment of the present invention may include: a first polymerization step of polymerizing a chloroprene polymer α by polymerizing a raw material monomer containing chloroprene, and a second polymerization step of polymerizing a chloroprene polymer β in the presence of the chloroprene polymer α; or a first polymerization step of polymerizing a chloroprene polymer β by polymerizing a raw material monomer containing chloroprene, and a second polymerization step of polymerizing the chloroprene polymer α in the presence of the chloroprene polymer β.

[0031] Hereinafter, a method for producing a chloroprene polymer latex according to a first embodiment of the present invention will be described. The method for producing a chloroprene polymer latex according to an embodiment of the present invention may include a polymerization step of polymerizing raw material monomers containing chloroprene to obtain a chloroprene polymer latex.

[0032] In the polymerization step, the raw material monomers include chloroprene and may also include other monomers copolymerizable with chloroprene. The other monomers copolymerizable with chloroprene are as described above. The type and amount of each monomer charged are preferably adjusted so that the type and content of each monomer unit in the resulting polymer fall within the above-described numerical ranges. For example, the copolymerization amount of 2,3-dichloro-1,3-butadiene in the chloroprene polymer contained in the chloroprene polymer latex may be in the range of 0 to 30% by mass relative to 100% by mass of the total of the chloroprene monomer and 2,3-dichloro-1,3-butadiene contained in the chloroprene polymer. In this case, the amount of 2,3-dichloro-1,3-butadiene charged before the start of emulsion polymerization is preferably in the range of 0 to 30 parts by mass relative to 100 parts by mass of the total of the chloroprene monomer and 2,3-dichloro-1,3-butadiene monomer. From the viewpoint of controlling the polymerization, it is more preferable to set the amount of 2,3-dichloro-1,3-butadiene charged to 5 to 25 parts by mass per 100 parts by mass of the total of the chloroprene monomer and the 2,3-dichloro-1,3-butadiene monomer.

[0033] When producing a chloroprene polymer, raw material monomers can be polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, etc. Among these polymerization methods, emulsion polymerization is preferred because it has various advantages such as ease of control, ease of extracting the polymer from a polymerization-finished liquid, and a relatively fast polymerization rate.

[0034] Emulsion polymerization is a type of radical polymerization, in which raw material monomers are charged into a reaction vessel together with a chain transfer agent, water, an alkali (e.g., a metal hydroxide such as potassium hydroxide or sodium hydroxide), an emulsifier (dispersant), a reducing agent (e.g., sodium hydrogen sulfite), a polymerization initiator, and the like, to polymerize them.

[0035] The type of chain transfer agent used in the emulsion polymerization is not particularly limited, and known chain transfer agents generally used in the emulsion polymerization of chloroprene can be used, such as long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, iodoform, etc. As the chain transfer agent, long-chain alkyl mercaptans are preferred, and n-dodecyl mercaptan is more preferred.

[0036] By adjusting the type and amount of the chain transfer agent, the weight average molecular weight of the resulting chloroprene polymer latex can be adjusted.

[0037] For example, to obtain a chloroprene polymer latex containing a chloroprene polymer β having a weight-average molecular weight of 200,000 to 1,500,000, the amount of chain transfer agent added before the start of emulsion polymerization is preferably 0.01 parts by mass or more per 100 parts by mass of raw material monomers (e.g., 100 parts by mass of chloroprene and 2,3-dichloro-1,3-butadiene in total). From the viewpoint of obtaining a chloroprene polymer latex containing a chloroprene polymer β having a weight-average molecular weight of 200,000 to 1,500,000, the amount of chain transfer agent added is more preferably 0.02 to 0.05 parts by mass, and may be, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 parts by mass, or less than 0.10 parts by mass, or may be within a range between any two of the values ​​exemplified herein. When the amount of the chain transfer agent, particularly long-chain alkyl mercaptans, added is 0.01 parts by mass or more, the storage stability of the latex is further improved. When the amount is less than 0.10 parts by mass, particularly less than 0.05 parts by mass, the toluene-insoluble matter increases, and the tensile strength at break of the obtained dip-molded product containing the chloroprene polymer latex is further increased.

[0038] As another example, to obtain a chloroprene polymer latex containing a chloroprene polymer α having a peak in the molecular weight distribution exhibiting a weight-average molecular weight of 5,000 to 80,000, the amount of the chain transfer agent added before the start of emulsion polymerization is preferably 1.0 to 10.0 parts by mass per 100 parts by mass of the monomer. In this case, the amount of the chain transfer agent added may be, for example, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, or may be within a range between any two of the values ​​exemplified here.

[0039] In the method for producing a chloroprene polymer latex according to the first embodiment of the present invention, the chloroprene polymer latex obtained in the polymerization step can be used as it is as a chloroprene polymer latex. In this case, it is preferable to obtain a chloroprene polymer latex containing a chloroprene polymer β having a weight-average molecular weight of 200,000 to 1,500,000 in the polymerization step.

[0040] The emulsifier preferably contains rosin acid and / or a rosin acid salt. Examples of rosin acid salts include alkali metal salts such as sodium salts and potassium salts. The amount of rosin acid and rosin acid salt added can be 3.0 to 7.0 parts by mass per 100 parts by mass of the raw material monomer used. The amount of rosin acid and rosin acid salt added can be, for example, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, or 7.0 parts by mass, or can be within a range between any two of the values ​​exemplified here. The use of rosin acids can prevent aggregation of rubber solids and pH fluctuations when blended with the base latex.

[0041] The rosin acid and / or rosin acid salt may contain a conjugated resin acid component and a non-conjugated resin acid component. Examples of the conjugated resin acid component include abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof. Examples of the non-conjugated resin acid component include dehydroabietic acid, pimaric acid, isopimaric acid, dihydropimaric acid, dihydroabietic acid, and salts thereof.

[0042] The rosin acid and rosin acid salts used in the emulsion polymerization step may have a ratio RB / RA of 0.10 or more and 0.70 or less, where RB is the total peak area of ​​abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts relative to RA, the total peak area of ​​dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and their salts, as determined by gas chromatography analysis of an extract extracted with an ethanol / toluene azeotrope as specified in JIS K 6229. The RB / RA of the rosin acid and rosin acid salt may be, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, or 0.70, or may be within a range between any two of the values ​​exemplified here. The RB / RA of the dip-molded product of the resulting chloroprene polymer latex composition can be adjusted by adjusting the type and amount of the rosin acid and / or rosin acid salt.

[0043] The emulsifier may also include emulsifiers and dispersants other than rosin acid and rosin acid salts. Examples of emulsifiers and dispersants other than rosin acid and rosin acid salts include cationic, anionic, and nonionic emulsifiers and dispersants. In one embodiment of the present invention, the emulsifier used in the emulsion polymerization process may include rosin acid and / or rosin acid salts, and an anionic emulsifier or dispersant. As anionic emulsifiers and dispersants, sulfate- or sulfonate-based anionic emulsifiers and dispersants are preferably used in combination to stabilize the chloroprene polymer latex when a pH adjuster is added. Specific examples include alkyl sulfonates having 8 to 20 carbon atoms, alkyl aryl sulfates, condensates of sodium β-naphthalene sulfonate and formaldehyde, and sodium alkyl diphenyl ether disulfonates. The amount of anionic emulsifier or dispersant added may be 0.05 to 5 parts by mass per 100 parts by mass of the raw material monomers. The amount of anionic emulsifier or dispersant added is, for example, 0.05, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass relative to 100 parts by mass of the raw material monomer, and may be within a range between any two of the numerical values ​​exemplified here.

[0044] The pH of the aqueous emulsion at the start of emulsion polymerization is preferably 10.5 to 13.5. The aqueous emulsion refers to a mixed solution of a chain transfer agent and a monomer (chloroprene, 2,3-dichloro-1,3-butadiene, etc.) immediately before the start of emulsion polymerization, but also includes cases where the composition changes due to the subsequent addition or divided addition of each component. When the pH of the aqueous emulsion at the start of emulsion polymerization is 10.5 or higher, the polymerization reaction can be controlled more stably. When the pH is 13.5 or lower, excessive viscosity increase during polymerization is suppressed, and the polymerization reaction can be controlled more stably.

[0045] The polymerization temperature for emulsion polymerization is preferably within the range of 5 to 55°C. If the temperature is 5°C or higher, the emulsion is less likely to freeze, and if the temperature is 55°C or lower, evaporation and boiling of the chloroprene monomer can be prevented.

[0046] As the polymerization initiator, potassium persulfate, benzoyl peroxide, ammonium persulfate, hydrogen peroxide, etc., which are used in ordinary radical polymerization, can be used.

[0047] The polymerization conversion rate is preferably in the range of 50 to 95%. The polymerization reaction is terminated by adding a polymerization terminator. If the polymerization conversion rate is 50% or higher, the toluene-insoluble content tends to increase, and the tensile strength at break of the resulting dip-molded article tends to be high. This is also advantageous from the viewpoint of production costs. If the polymerization conversion rate is less than 95%, it is possible to avoid a decrease in polymerization reactivity due to a decrease in unreacted monomer, and thus a decrease in productivity.

[0048] Examples of the polymerization terminator include diethylhydroxylamine, thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis-4-methyl-6-tert-butylphenol, etc. After the emulsion polymerization is completed, unreacted monomers can be removed by a conventional method such as vacuum distillation.

[0049] Furthermore, to the chloroprene polymer latex obtained by the production method according to one embodiment of the present invention, after polymerization, any additive such as a freeze stabilizer, an emulsion stabilizer, a viscosity modifier, an antioxidant, or a preservative may be added, as long as the effects of the present invention are not impaired.

[0050] As an example, in the polymerization step, all of the raw material monomers and chemicals to be used in the polymerization step can be charged into a polymerization vessel before the start of polymerization, and then the polymerization can be started, or at least a portion of the raw material monomers and / or chemicals to be used in the polymerization step can be charged into a polymerization vessel before the start of polymerization, and the remainder can be added in portions after the start of polymerization.

[0051] In the polymerization step, when at least a portion of the raw material monomers and chemicals are charged into a polymerization vessel before the initiation of polymerization, and the remaining raw material monomers and / or chemicals are added after the initiation of polymerization, the remaining raw material monomers and / or chemicals can be added in one or more divided portions, or can be added continuously at a constant flow rate. In one embodiment of the present invention, at least a portion of the raw material monomers can be added in divided portions after the initiation of polymerization. For example, when chloroprene and 2,3-dichloro-1,3-butadiene are used as raw material monomers, a portion of the chloroprene can be added in divided portions after the initiation of polymerization.

[0052] For example, the portionwise addition of the remaining raw material monomers and / or agents can be started when the polymerization rate of the raw material monomers charged before the start of polymerization reaches 50 to 95%. The polymerization rate at which portionwise addition starts can be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95%, and may be within a range between any two of the values ​​exemplified here.

[0053] When at least a portion of the raw material monomer is added after the initiation of polymerization, 50 parts by mass or less of 100 parts by mass of all raw material monomers used in the polymerization step can be added after the initiation of polymerization. In this case, the amount of raw material monomer added after the initiation of polymerization can be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, or may be within a range between any two of the values ​​exemplified here. As an example, the raw material monomer, for example, chloroprene, can be added portionwise continuously over a period of 30 to 300 minutes.

[0054] The method for producing a chloroprene polymer latex according to the second embodiment of the present invention will be described below. The method for producing a chloroprene polymer latex according to the second embodiment of the present invention may include a polymerization step and a mixing step.

[0055] The method for producing a chloroprene polymer latex according to the second embodiment of the present invention can include a polymerization step of polymerizing a raw material monomer containing chloroprene to obtain a chloroprene polymer latex. The polymerization step can include a polymerization step of polymerizing a raw material monomer containing chloroprene to obtain a latex containing a chloroprene polymer α, and a polymerization step of polymerizing a raw material monomer containing chloroprene to obtain a latex containing a chloroprene polymer β. In the polymerization step, it is preferable to adjust the amount of a chain transfer agent, etc., depending on the target weight-average molecular weight. The types, amounts used, polymerization conditions, etc. of each agent in the polymerization step of the second embodiment can be the same as those described for the polymerization step of the first embodiment.

[0056] The method for producing a chloroprene polymer latex according to the second embodiment of the present invention may include a mixing step of mixing two or more types of latexes to obtain a chloroprene polymer latex. In the mixing step, a latex containing a chloroprene polymer α having a weight-average molecular weight of 5,000 to 80,000 and a latex containing a chloroprene polymer β having a weight-average molecular weight of 200,000 to 1,500,000 may be mixed to obtain a chloroprene polymer latex. In the mixing step, two or more types of chloroprene polymer latexes may be mixed by a known method. In the mixing step, the chloroprene polymer latex may be obtained by stirring and mixing using a paddle blade at 30 to 300 rpm for 20 seconds to 3 minutes, e.g., at 100 rpm for 1 minute.

[0057] A method for producing a chloroprene polymer latex according to the third embodiment of the present invention will be described below. The method for producing a chloroprene polymer latex according to the third embodiment of the present invention may include: a first polymerization step of polymerizing a chloroprene polymer α by polymerizing a raw material monomer containing chloroprene, and a second polymerization step of polymerizing a chloroprene polymer β in the presence of the chloroprene polymer α, or a first polymerization step of polymerizing a chloroprene polymer β by polymerizing a raw material monomer containing chloroprene, and a second polymerization step of polymerizing the chloroprene polymer α in the presence of the chloroprene polymer β.

[0058] In the first polymerization step, it is preferable to adjust the amount of the chain transfer agent, etc., depending on the target weight-average molecular weight. In the method for producing a chloroprene polymer latex according to the third embodiment of the present invention, a polymerization terminator may not be used in the first polymerization step. Other details, such as the type, amount of each agent used, and polymerization conditions, in the first polymerization step are as described in the polymerization step of the first embodiment.

[0059] The third embodiment of the present invention may include a second polymerization step of polymerizing the chloroprene polymer β in the presence of the chloroprene polymer α, or a second polymerization step of polymerizing the chloroprene polymer α in the presence of the chloroprene polymer β.

[0060] In the second polymerization step, the chloroprene polymer α (or chloroprene polymer β) may be added to the polymerization solution in any form. For example, the polymerization solution obtained by polymerizing the chloroprene polymer α (or chloroprene polymer β) may be used as is. As an example, when the chloroprene polymer α (or chloroprene polymer β) is polymerized by emulsion polymerization, a latex containing the chloroprene polymer α (or chloroprene polymer β) may be added to the polymerization solution of the chloroprene polymer β (or chloroprene polymer α). Alternatively, for example, the chloroprene polymer α (or chloroprene polymer β) may be precipitated from a polymerization solution obtained by polymerizing the chloroprene polymer α (or chloroprene polymer β), and the precipitated chloroprene polymer α (or chloroprene polymer β) may be added to the polymerization solution of the chloroprene polymer β (or chloroprene polymer α). For example, when the chloroprene polymer α (or the chloroprene polymer β) is polymerized by emulsion polymerization, the chloroprene polymer α (or the chloroprene polymer β) may be precipitated using methanol and added to a polymerization solution of the chloroprene polymer β (or the chloroprene polymer α), or a rubber component (chloroprene polymer α (or the chloroprene polymer β) obtained by freeze-drying a latex containing the chloroprene polymer α (or the chloroprene polymer β) may be added to a polymerization solution of the chloroprene polymer β (or the chloroprene polymer α).

[0061] In the second polymerization step, when the chloroprene polymer β is polymerized, the amount of the chloroprene polymer α can be 5.0 to 60.0 parts by mass relative to 100 parts by mass of the chloroprene monomer (or raw material monomer). The amount of the chloroprene polymer α can be, for example, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 50.0, or 60.0 parts by mass, or can be within a range between any two of the values ​​exemplified here. In the second polymerization step, when the chloroprene polymer α is polymerized, the amount of the chloroprene polymer β can be 40.0 to 95.0 parts by mass relative to 100 parts by mass of the chloroprene monomer (or raw material monomer). The amount of the chloroprene polymer β charged is, for example, 40.0, 50.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, or 95.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0062] In the second polymerization step, the type and amount of each monomer are preferably adjusted so that the content of each monomer unit in the resulting chloroprene polymer latex falls within the above-mentioned range. Other details such as the type, amount used, and polymerization conditions of each agent in the second polymerization step can be as described in the above-mentioned polymerization step.

[0063] The chloroprene polymer latex according to the present invention includes the chloroprene polymer α having a weight-average molecular weight of 5,000 to 80,000 and / or the chloroprene polymer β having a weight-average molecular weight of 200,000 to 1,500,000, which is obtained by the above-described production method.

[0064] 1.3 Metal Oxide The chloroprene polymer latex composition according to the present invention contains 0.3 to 15.0 parts by mass of a metal oxide per 100 parts by mass of the solids content of the chloroprene polymer latex. The metal oxide content is, for example, 0.3, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, or 15.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. When the metal oxide content is equal to or greater than the lower limit, the tensile strength at break is improved due to the crosslinking effect between the polymers. Furthermore, when the metal oxide content is equal to or less than the upper limit, a dip-molded product with excellent flexibility can be obtained.

[0065] The type of metal oxide is not particularly limited, and can be at least one of zinc oxide, lead oxide, trilead tetroxide, magnesium oxide, aluminum oxide, iron oxide, beryllium oxide, and titanium oxide. The metal oxide preferably contains zinc oxide. Zinc oxide is generally believed to function as a scavenger for dechlorinated atoms in chloroprene-based polymers. One type of metal oxide may be used, or two or more types may be used in combination.

[0066] 1.4 Mercapto Compound The chloroprene polymer latex composition according to the present invention contains 0.10 to 10.00 parts by mass of a mercapto compound per 100 parts by mass of the solids content of the chloroprene polymer latex. The content of the mercapto compound is, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, 5.00, 6.00, 7.00, 8.00, 9.00, or 10.00 parts by mass, or may be within a range between any two of the values ​​exemplified here. By setting the content of the mercapto compound within the above range, a chloroprene polymer latex composition with excellent stability and a dip-molded article with excellent mechanical properties can be obtained.

[0067] The mercapto compound means a compound having a group represented by —S—H. When R is an organic group, the mercapto compound can be a compound represented by R—S—H.

[0068] The mercapto compound preferably contains a mercapto compound A that satisfies requirement A of being a liquid at 23°C. The content of the mercapto compound A relative to 100% by mass of the mercapto compounds contained in the chloroprene polymer latex composition is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. The mercapto compound contained in the chloroprene polymer latex composition may consist solely of the mercapto compound A. By containing the mercapto compound A that is a liquid at 23°C, the chloroprene polymer latex composition according to one embodiment of the present invention can provide a chloroprene polymer latex composition with improved stability and a dip-molded article with improved mechanical properties.

[0069] The mercapto compound preferably includes a mercapto compound B that satisfies requirement B of having a carbonyl group. Mercapto compound B more preferably has an ester bond. Mercapto compound B can be represented by the following formula (1):

[0070]

[0071] In formula (1), R １ can be an alkylene group which may have a substituent. The number of carbon atoms in the alkylene group can be 2 or more, for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10, and may be within a range between any two of the values ​​exemplified here. ２ The alkyl group may have one or more carbon atoms, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or may be within a range between any two of the values ​​exemplified here.

[0072] The mercapto compound may include a mercapto compound C that has an alkyl group and satisfies requirement C that it be represented by the following formula (2):

[0073] In formula (2), R ３ can be an alkyl group which may have a substituent. The number of carbon atoms in the alkyl group can be 5 or more, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, and may be within a range between any two of the values ​​exemplified here. By setting the number of carbon atoms in the alkyl group within the above numerical range, odor can be further suppressed. In addition, the mercapto-based compound C can also include one derived from a chain transfer agent used in chloroprene-based polymerization.

[0074] The mercapto compound may include at least one of mercapto compounds B and C. The contents of mercapto compounds B and C relative to 100% by mass of mercapto compounds contained in the chloroprene polymer latex composition are, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the numerical values ​​exemplified herein. The content of mercapto compound B relative to 100% by mass of mercapto compounds contained in the chloroprene polymer latex composition is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the numerical values ​​exemplified herein. The content of mercapto compound C relative to 100% by mass of the mercapto compounds contained in the chloroprene polymer latex composition is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. The mercapto compounds contained in the chloroprene polymer latex composition may be composed only of mercapto compounds B and / or C, may be composed only of mercapto compound B, or may be composed only of mercapto compound C. It is more preferable that mercapto compound B satisfy requirement A. That is, the mercapto compound may include a mercapto compound satisfying requirements B and A. It is more preferable that mercapto compound C satisfy requirement A. That is, the mercapto compound may include a mercapto compound satisfying requirements C and A.

[0075] When the mercapto compound D has a benzothiazole structure or a benzimidazole structure, the content of the mercapto compound D relative to 100 mass% of the mercapto compounds contained in the chloroprene polymer latex composition can be less than 50 mass%. The content of the mercapto compound D relative to 100 mass% of the mercapto compounds contained in the chloroprene polymer latex composition is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 49 mass%, or may be within a range between any two of the values ​​exemplified here. In the chloroprene polymer latex composition according to one embodiment of the present invention, the content of the mercapto compound D relative to 100 mass% of the solids content of the chloroprene polymer latex can be less than 1.0 part by mass, or less than 0.7 parts by mass. The content of the mercapto compound D relative to 100 parts by mass of the solids content of the chloroprene polymer latex is, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. The chloroprene polymer latex composition may not contain the mercapto compound D. Furthermore, the chloroprene polymer latex composition may not contain a compound containing a heteroaromatic ring.

[0076] The chloroprene polymer latex composition according to one embodiment of the present invention contains a mercapto compound, which makes it possible to obtain a chloroprene polymer latex composition having excellent stability and a dip-molded article having excellent mechanical properties, and these properties can be controlled by adjusting the type and amount of the mercapto compound as described above. The type and amount of the mercapto compound contained in the chloroprene polymer latex composition can be determined by diluting the chloroprene polymer latex composition 100 times with tetrahydrofuran and analyzing the diluted solution by gas chromatography.

[0077] 1.4 Sulfur The chloroprene polymer latex composition according to the present invention has a sulfur content of 5 parts by mass or less relative to 100 parts by mass of the solids content of the chloroprene polymer latex. The sulfur content is, for example, 0, 0.01, 0.02, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, or 5.00 parts by mass, or may be within a range between any two of the values ​​exemplified here. By setting the sulfur content of the chloroprene polymer latex composition according to the present invention to the above upper limit or less, it is possible to obtain a dip-molded article having excellent flexibility and tensile strength at break while reducing the risk of allergies and reducing costs.

[0078] 1.5 Antioxidant The chloroprene polymer latex composition according to the present invention may contain 0.5 to 10.0 parts by mass of an antioxidant per 100 parts by mass of the solid content of the chloroprene polymer latex. The type of antioxidant is not particularly limited, and phenolic antioxidants, amine-based antioxidants, heat-resistant oxidation (aging) inhibitors, ozone-resistant antioxidants, etc. may be used (however, mercapto compounds may be excluded). When the resulting dip-molded article is used as a medical glove, a phenolic antioxidant may be used from the viewpoints of the color tone, texture, and hygiene of the dip-molded article. In particular, a hindered phenolic antioxidant is preferred because of its potent effects. Examples of hindered phenol-based antioxidants include 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-butylidene(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), butylated reaction products of p-cresol and dicyclopentadiene, 2,5'-di-t-butylhydroquinone, and 2,5'-di-t-amylhydroquinone. Among these, butylated reaction products of p-cresol and dicyclopentadiene are preferred from the viewpoint of general dispersibility in aqueous materials. One type of antioxidant may be used, or two or more types may be used in combination.

[0079] The content of the antioxidant is preferably 0.5 to 10.0 parts by mass per 100 parts by mass of the solids content of the chloroprene polymer latex contained in the chloroprene polymer latex composition. The content of the antioxidant is, for example, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, and may be within a range between any two of the values ​​exemplified here. When the content of the antioxidant is equal to or greater than the lower limit, color change in the dip-molded article can be suppressed. When the amount of antioxidant added is equal to or less than the upper limit, the stability of the chloroprene polymer latex composition can be ensured. Furthermore, from the viewpoint of the balance of physical properties between the flexibility and tensile strength at break of the obtained dip-molded article, the amount of antioxidant added is more preferably 0.5 to 5.0 parts by mass. The content of the antioxidant can be calculated by analyzing the surface of the obtained dip-molded article by FT-IR.

[0080] 1.6 Vulcanization Accelerator The chloroprene polymer latex composition according to one embodiment of the present invention may contain a vulcanization accelerator. The chloroprene polymer latex composition may contain 5 parts by mass or less of the vulcanization accelerator per 100 parts by mass of the solids content of the chloroprene polymer latex. The content of the vulcanization accelerator may be, for example, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 2.00, 3.00, 4.00, or 5.00 parts by mass, or may be within a range between any two of the values ​​exemplified here. By containing the vulcanization accelerator at or below the upper limit described above, the chloroprene polymer latex composition according to the present invention can produce a dip-molded article having excellent flexibility and tensile strength at break while reducing the risk of allergies and reducing costs.

[0081] The vulcanization accelerator according to the present invention may contain at least one of thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, and xanthogenate-based vulcanization accelerators. One type of vulcanization accelerator may be used, or two or more types may be used in combination.

[0082] The thiourea-based vulcanization accelerator may be a compound having a thiourea structure, such as the compound represented by the following formula:

[0083]

[0084] In the above formula, R １１ ~R １４ can each independently represent hydrogen or an organic group, can represent hydrogen or a hydrocarbon group, and the hydrocarbon group can be an alkyl group or an aryl group. Examples of thiourea compounds include ethylene thiourea, diethyl thiourea (N,N'-diethyl thiourea), trimethyl thiourea, diphenyl thiourea (N,N'-diphenyl thiourea), 1,3-trimethylene-2-thiourea, etc.

[0085] Examples of thiuram vulcanization accelerators include compounds containing one or more structures represented by the following formula:

[0086]

[0087] In the above formula, R ２１ , R ２２ , R ２３ , R ２４ can each independently be an organic group, preferably a hydrocarbon group. The hydrocarbon group can be an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 1 to 12 carbon atoms. ２１ and R ２２ , R ２３ and R ２４ may be linked to each other to form a cyclic structure (for example, a cycloalkyl group). n can be an integer of 1 or more, and can be 1 to 4, preferably 1 or 2, and more preferably 2.

[0088] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, and dipentamethylenethiuram tetrasulfide.

[0089] Examples of dithiocarbamate vulcanization accelerators include compounds composed of ions represented by the following formula and metal ions.

[0090] In the above formula, R ３１ ~R ３２ can each independently be an organic group or a hydrocarbon group. The hydrocarbon group can be an alkyl group, an aryl group, or an aralkyl group, and R ３１ and R ３２ may be linked to form a cycloalkyl group. Examples of metal ions include zinc, sodium, copper, iron, nickel, and tellurium. Examples of dithiocarbamate vulcanization accelerators include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, and tellurium diethyldithiocarbamate.

[0091] Examples of guanidine compounds include compounds having a guanidine skeleton, such as 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salts of dicatechol borate.

[0092] Examples of xanthogenate-based vulcanization accelerators include compounds composed of ions represented by the following formula and metal ions.

[0093]

[0094] In the above formula, R ４１ can be an organic group or a hydrocarbon group. The hydrocarbon group can be an alkyl group. Examples of metal ions include zinc, sodium, copper, nickel, and tellurium. Examples of xanthogenate-based vulcanization accelerators include zinc butylxanthogenate and zinc isopropylxanthogenate.

[0095] The vulcanization accelerator may be one excluding mercapto compounds D containing a benzothiazole structure or a benzimidazole structure, and one excluding mercapto compounds containing a heteroaromatic ring. Also, the vulcanization accelerator may be one excluding mercapto compounds.

[0096] 2. Physical Properties of Chloroprene Polymer Latex Composition <Ratio RB / RA of the Total Amount RB of Peak Areas of Abietic Acid, Neoabietic Acid, Palustric Acid, Levopimaric Acid, and Their Salts to the Total Amount RA of Peak Areas of Dehydroabietic Acid, Pimaric Acid, Isopimaric Acid, Dihydroabietic Acid, and Their Salts> The chloroprene polymer latex composition according to one embodiment of the present invention is obtained by molding a chloroprene polymer latex composition by a dip coagulation method, followed by heating and drying at 150°C for 30 minutes to obtain a dip molded product, and then coagulating the product to a concentration in accordance with JIS K 1000. The ratio RB / RA, which is the ratio of the total peak area RB of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts to the total peak area RA of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and their salts, obtained by gas chromatography analysis of an extract extracted with an ethanol / toluene azeotrope as specified in JIS No. 6229, is preferably 0.10 or more, more preferably 0.10 to 0.70, and even more preferably 0.15 to 0.50. RB / RA may be, for example, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, or 0.70, or may be within a range between any two of the values ​​exemplified here. By setting RB / RA within the above range, the tensile strength at break of the dip-molded body can be further improved.

[0097] RB / RA can be determined by molding a chloroprene polymer latex composition by a dip coagulation method, heating and drying the resulting dip-molded product at 150°C for 30 minutes, placing the resulting product in a flask equipped with a condenser, extracting the product with an ethanol / toluene azeotrope as specified in JIS K 6229, treating the product with hydrochloric acid, and then analyzing the product with gas chromatography, or by calculating the ratio by the method described in the Examples. RB / RA can be controlled by adjusting the types and blending ratio of rosin acid and rosin acid salt added as emulsifiers during the production of a chloroprene polymer latex.

[0098] In the chloroprene polymer latex composition according to one embodiment of the present invention, a dip-molded product obtained by molding the chloroprene polymer latex composition by a dip coagulation method and then heating and drying the product at 150°C for 30 minutes has a modulus at 100% elongation of preferably 0.75 MPa or less, more preferably 0.70 MPa, as measured in accordance with JIS K 6251. The modulus at 100% elongation may be, for example, 0.30, 0.35, 0.4, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, or 0.75 MPa, or may be within a range between any two of the values ​​exemplified here.

[0099] In the chloroprene polymer latex composition according to one embodiment of the present invention, a dip-molded product obtained by molding the chloroprene polymer latex composition by a dip coagulation method and then heating and drying the product at 150°C for 30 minutes has a tensile strength at break of preferably 17.0 MPa or more, more preferably 19.0 MPa or more, as measured in accordance with JIS K 6251. The tensile strength at break is, for example, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, or 25.0 MPa, and may be within a range between any two of the values ​​exemplified here.

[0100] In the chloroprene polymer latex composition according to one embodiment of the present invention, the chloroprene polymer latex composition is molded by a dip coagulation method, followed by heating and drying at 150°C for 30 minutes to obtain a dip-molded product. The dip-molded product has an elongation at break, as measured in accordance with JIS K 6251, of, for example, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, or 1300%, and may be within a range between any two of the values ​​exemplified here.

[0101] The tensile strength at break, elongation at break and modulus at 100% elongation of the dip-molded product of the chloroprene polymer latex composition can be controlled by adjusting the type and amount of the chloroprene polymer latex composition, as well as the polymerization recipe and conditions, weight-average molecular weight, toluene-insoluble content and the like of the chloroprene polymer latex used.

[0102] The solid content concentration of the chloroprene polymer latex composition according to one embodiment of the present invention is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mass%, and may be within a range between any two of the values ​​exemplified here.

[0103] 3. Method for Producing Chloroprene Polymer Latex Composition A method for producing a chloroprene polymer latex composition according to one embodiment of the present invention may include a raw material mixing step of mixing raw materials containing a chloroprene polymer latex, a metal oxide, a mercapto compound, and other required chemicals. In the mixing step, an aqueous dispersion containing the metal oxide, the mercapto compound, and other required chemicals may be prepared in advance, and then the chloroprene polymer latex and the aqueous dispersion may be mixed. The mixing step may be performed using a known mixing device such as a ball mill.

[0104] 4. Dip-molded Articles (Dip-molded Coatings and Films) A dip-molded article according to one embodiment of the present invention is a dip-molded article of the chloroprene polymer latex composition described above. The dip-molded article according to one embodiment of the present invention is obtained by dip-molding the chloroprene polymer latex composition according to the present invention, either alone or in combination with another chloroprene polymer latex composition. The dip-molded article has a low modulus at 100% elongation, flexibility, and excellent mechanical properties such as strength and elongation. For example, the dip-molded article may have the above-described modulus at 100% elongation, tensile strength at break, and / or tensile strength at break. The dip-molded article can be suitably used as industrial gloves, general household gloves, medical gloves, balloons, catheters, and boots.

[0105] The thickness of the dip-molded article (e.g., the minimum thickness) may be 0.01 to 0.50 mm. The thickness of the dip-molded article may be, for example, 0.01, 0.05, 0.10, 0.20, 0.30, 0.40, or 0.50 mm, and may be within a range between any two of the values ​​exemplified here. The thickness of the dip-molded article can be adjusted by the time for which the mold is immersed in the polymer latex composition, the solids concentration of the chloroprene polymer latex composition, and the like. To reduce the thickness of the dip-molded article, the immersion time may be shortened or the solids concentration of the chloroprene polymer latex composition may be reduced.

[0106] The modulus at 100% elongation of the dip-molded article according to one embodiment of the present invention, as measured in accordance with JIS K 6251, is preferably 0.75 MPa or less, and more preferably 0.70 MPa. The modulus at 100% elongation may be, for example, 0.30, 0.35, 0.4, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, or 0.75 MPa, or may be within a range between any two of the values ​​exemplified here.

[0107] The tensile strength at break of the immersion molded article according to one embodiment of the present invention, measured in accordance with JIS K 6251, is preferably 17.0 MPa or more, and more preferably 19.0 MPa or more. The tensile strength at break may be, for example, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, or 25.0 MPa, or may be within a range between any two of the values ​​exemplified here.

[0108] The elongation at break of the dip-molded body according to one embodiment of the present invention, measured in accordance with JIS K 6251, is, for example, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, or 1300%, and may be within a range between any two of the values ​​exemplified here.

[0109] The immersion molded article according to one embodiment of the present invention preferably has no irritating odor when 30 g of the immersion molded article is placed in a 250 mL plastic bottle, the bottle is sealed with a lid, and the bottle is stored at 40°C for 24 hours. After that, the lid is opened and an olfactory panel tests the headspace gas.

[0110] 5. Method for Producing Dip-Molded Article A method for producing a dip-molded article according to one embodiment of the present invention may include a dip-molding step of dip-molding the chloroprene polymer latex composition according to the present invention to obtain a dip-molded article.

[0111] Examples of dip molding methods according to one embodiment of the present invention include the immersion coagulation method, simple immersion method, thermal immersion method, and electrodeposition method. The immersion coagulation method can be used from the viewpoints of ease of production and the ease of obtaining dip-molded bodies of a uniform thickness. Specifically, a ceramic mold coated with a calcium-based coagulation liquid is immersed in a dip-molded body composition, which is then coagulated. After leaching to remove water-soluble impurities, the composition is dried, and then heated and vulcanized to form a dip-molded coating (rubber coating), which is then demolded. This allows for the production of a film-like dip-molded body.

[0112] The method for producing a dip-molded body according to one embodiment of the present invention can include a drying step of heating and drying the dip-molded body.

[0113] The heating temperature in the heat drying step may be appropriately set depending on the composition of the chloroprene polymer latex composition, and may be 120 to 180°C. The heating temperature is preferably 120 to 150°C. The heating temperature may be, for example, 120, 130, 140, 150, 160, 170, or 180°C, or may be within a range between any two of the values ​​exemplified here. The heating time may be appropriately set depending on the composition of the chloroprene polymer latex composition, the shape of the unvulcanized molded body, and the like, and may be 10 to 300 minutes. The heating time may be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300 minutes, or may be within a range between any two of the values ​​exemplified here. As an example, the dip-molded body according to one embodiment of the present invention may be one that has been subjected to a heat drying treatment at 150°C for 30 minutes.

[0114] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited to these examples.

[0115] First, a method for producing the chloroprene polymer latex used in the examples will be described.

[0116] <Preparation of Chloroprene Polymer Latex I> (Polymerization Step of Chloroprene Polymer α-1) To a 30 L polymerization vessel were added 64 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 90 parts by mass of pure water, 4.5 parts by mass of conjugated resin acid-based rosin acid (trade name "Harthall R-WW", manufactured by Harima Chemicals Co., Ltd.), 3.4 parts by mass of n-dodecyl mercaptan, 1.6 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), and 0.5 parts by mass of sodium hydrogen sulfite. Polymerization was carried out at a polymerization temperature of 35°C under a nitrogen stream by continuously adding a 0.35% by mass aqueous potassium persulfate solution as a polymerization initiator. When the polymerization rate of the charged monomers reached 80%, 27 parts by mass of chloroprene (monomer) was continuously added over 100 minutes. When the polymerization rate of the initially charged monomers and the continuously added monomers reached 91%, the addition of the aqueous potassium persulfate solution was stopped to terminate the polymerization, thereby obtaining a polymerization liquid. The polymerization liquid was distilled under reduced pressure to remove unreacted monomers, and the resulting mixture was concentrated to obtain a latex containing a chloroprene polymer α-1 with a solids concentration of 60% by mass.

[0117] (Precipitation of chloroprene polymer with methanol) The obtained latex containing the chloroprene polymer α-1 was mixed with a large amount of methanol to precipitate the chloroprene polymer α-1, which was then filtered and dried to obtain a chloroprene polymer, which was used in the production of the chloroprene polymer β-1.

[0118] (Polymerization step of chloroprene polymer β-1) To a polymerization vessel having an internal volume of 30 L, 28.3 parts by mass of chloroprene polymer α-1, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 110 parts by mass of pure water, 5.8 parts by mass of conjugated resin acid-based rosin acid (trade name "Harthall R-WW", manufactured by Harima Chemicals Co., Ltd.), 2 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium hydrogen sulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 14°C under a nitrogen stream by continuously adding a 0.35% by mass aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine as a polymerization terminator was added to terminate the polymerization, thereby obtaining a polymerization liquid. The polymerization liquid was distilled under reduced pressure to remove unreacted monomers, and concentrated to obtain a chloroprene polymer latex I containing the chloroprene polymer β-1 and having a solids concentration of 60% by mass.

[0119] 50 ml of the chloroprene polymer latex I was sampled, and the remaining chloroprene polymer latex I was used to prepare a chloroprene polymer latex composition by the method described below, and a dip-molded article for evaluation was produced.

[0120] The sampled chloroprene polymer latex I was mixed with a large amount of methanol to precipitate a chloroprene polymer, which was then filtered and dried to obtain a chloroprene polymer sample. The weight-average molecular weight of the chloroprene polymer latex obtained was measured from the sample. Measurement of the weight-average molecular weight of the chloroprene polymer latex I confirmed a peak attributable to chloroprene polymer α-1 having a weight-average molecular weight of 5,000 to 80,000, and a peak attributable to chloroprene polymer β-1 having a weight-average molecular weight of 200,000 to 1,500,000. Furthermore, the toluene-insoluble portion of the chloroprene polymer rubber obtained by freeze-drying the chloroprene polymer latex was measured. The respective measurement methods will be described later.

[0121] <Preparation of Chloroprene Polymer Latex II> (Polymerization Step of Chloroprene Polymer β-2) A 30 L polymerization vessel was charged with 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 110 parts by mass of pure water, 4.7 parts by mass of gum rosin-based disproportionated potassium rosinate (aqueous solution) (trade name "LONDIS K-25" manufactured by Arakawa Chemical Industries, Ltd.), 0.02 parts by mass of n-dodecyl mercaptan, 1.6 parts by mass of potassium hydroxide, 0.4 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "DEMOL N" manufactured by Kao Corporation), and 0.4 parts by mass of sodium hydrogen sulfite. Polymerization was carried out at a polymerization temperature of 40°C under a nitrogen stream by continuously adding a 0.35% by mass aqueous potassium persulfate solution as a polymerization initiator. When the polymerization rate of the charged monomers reached 85%, 0.01 parts by mass of diethylhydroxylamine as a polymerization terminator was added to terminate the polymerization. The polymerization liquid was distilled under reduced pressure to remove unreacted monomers, and the mixture was concentrated to obtain a chloroprene polymer latex II containing the chloroprene polymer β-2 and having a solids concentration of 60% by mass.

[0122] <Preparation of Chloroprene Polymer Latex III> (Polymerization Step of Chloroprene Polymer β-3) A 30 L polymerization vessel was charged with 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 90 parts by mass of pure water, 4.6 parts by mass of conjugated resin acid-based rosin acid (trade name "Harthall R-WW", manufactured by Harima Chemicals Co., Ltd.), 0.03 parts by mass of n-dodecyl mercaptan, 1.6 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium hydrogensulfite, and 0.03 parts by mass of thiourea dioxide. Polymerization was carried out at a polymerization temperature of 15°C under a nitrogen stream by continuously adding a 0.35% by mass aqueous potassium persulfate solution as a polymerization initiator. When the polymerization rate reached 83%, 0.1 parts by mass of diethylhydroxylamine as a polymerization terminator was added to terminate the polymerization, yielding a polymerization liquid. The polymerization liquid was distilled under reduced pressure to remove unreacted monomers, and the resulting mixture was concentrated to yield a chloroprene polymer latex III containing the chloroprene polymer β-3 and having a solids concentration of 60% by mass.

[0123] <Method for Analyzing Chloroprene Polymer Latex> Chloroprene polymer latex was analyzed by the following method. (Measurement of Weight-Average Molecular Weight of Chloroprene Polymer Latex) As described above, the chloroprene polymer latex was precipitated with methanol, filtered, and the dried chloroprene polymer was dissolved in 20 ml of tetrahydrofuran to obtain a sample, which was then subjected to gel permeation chromatography (GPC) under the following measurement conditions. Apparatus: HLC-8320 (manufactured by Tosoh Corporation) Column: Three TSKgel GMHHR-H columns in series Temperature: 40°C Detection: Differential refractive index Solvent: Tetrahydrofuran Calibration curve: Prepared using standard polystyrene (PS).

[0124] (Toluene Insolubles) The obtained chloroprene polymer latex was freeze-dried to obtain a chloroprene polymer rubber, which was then cut into 2 mm squares to obtain a test piece. The test piece was placed in a conical beaker and dissolved in 80 g of toluene for 16 hours. Subsequently, after centrifugation, the gel fraction (insolubles) was separated using a 200-mesh wire netting. The gel fraction was then dried and the mass of the dried product was measured. The toluene insolubles in the chloroprene polymer rubber were calculated using the following formula, where Ag is the chloroprene polymer rubber after freeze-drying and B g is the gel fraction (insolubles) separated from the mixture dissolved in toluene. Toluene insolubles (gel fraction) = B / A x 100 (%)

[0125] Example 1 Preparation of Chloroprene Polymer Latex Composition Two parts by mass of two types of zinc oxide as a metal oxide, 0.75 parts by mass of a mercapto compound represented by Chemical Formula 7 as a mercapto compound, 2.0 parts by mass of Nocrac PBK as an antioxidant, and 0.1 parts by mass of a sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation) were added to water and mixed in a ceramic ball mill at 20°C for 16 hours to prepare an aqueous dispersion. The aqueous dispersion was mixed with chloroprene polymer latex I, and water was added to adjust the solids concentration to 30% by mass, to prepare a chloroprene polymer latex composition. The resulting chloroprene polymer latex composition contained each chemical in the blending amounts shown in Table 1 relative to the solids content of the chloroprene polymer latex.

[0126] <Preparation of Dip-Molded Film> A ceramic cylinder (manufactured by Shinko Corporation) with an outer diameter of 50 mm was immersed for 1 second in a coagulation liquid containing 62 parts by mass of water, 35 parts by mass of calcium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate, and then removed. After drying for 3 minutes, the cylinder was immersed for 2 minutes in the chloroprene polymer latex composition prepared by the procedure described above. The cylinder was then washed with running water at 45°C for 1 minute and dried at 150°C for 30 minutes to prepare a dip-molded film (dip-molded coating) for evaluation.

[0127] Examples 2 to 10, Comparative Examples 1 to 5 Chloroprene polymer latex compositions and dip-molded films (dip-molded coatings) for evaluation were prepared in the same manner as in Example 1, except that the types of chloroprene polymer latex used were as shown in the table and the formulation of the aqueous dispersion was adjusted so that the amounts of each agent were as shown in the table. In the chloroprene polymer latex compositions of the examples and comparative examples, the content of the mercaptan compound derived from n-dodecyl mercaptan added during the synthesis of the chloroprene polymer latex was 0.01 parts by mass or less per 100 parts by mass of the solids content of the chloroprene polymer latex.

[0128] Metal oxides Zinc oxide type 2 Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd. Zinc oxide type 2 Mercapto compounds Chemical formula 7: Mercapto compound represented by chemical formula (7), 3-mercaptopropionic acid-ethylhexyl, liquid at 23°C, molecular weight 218.4

[0129]

[0130] Chemical formula 8: A mercapto compound represented by chemical formula (8), 3-methoxybutyl mercaptoacetate, liquid at 23°C

[0131] Chemical formula 9: Mercapto compound represented by chemical formula (9), n-dodecyl mercaptan, liquid at 23°C

[0132] Antioxidant: Antioxidant: Butylated reaction product of p-cresol and dicyclopentadiene, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Nocrac PBK

[0133] <Evaluation of Dip-Molded Articles> (RB / RA) Test pieces were obtained by cutting 3 g of the above-mentioned dip-molded article film for evaluation into 2 mm squares. These test pieces were placed in a condenser-equipped eggplant-shaped flask, extracted with an ethanol / toluene azeotropic mixture (ETA solution) specified in JIS K 6229, and then treated with hydrochloric acid. Gas chromatography was performed under the following conditions using the extract. From the gas chromatography measurement results, the total amount RA of the peak areas of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and their salts was determined. In addition, the total amount RB of the peak areas of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts was determined, and the ratio RB / RA ((conjugated resin acid component b) / (non-conjugated resin acid component a)) of the total amount RB of the peak areas of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts to the total amount RA of the peak areas of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and their salts in the dip-molded film for evaluation was calculated.

[0134] [Gas chromatography measurement conditions] Column used: FFAP 0.32 mmφ×25 m (film thickness 0.3 μm) Detector: FID Column temperature: 200° C. (hold for 90 min) → 250° C. Heating rate: 10° C. / min Injection port temperature: 270° C. Detector temperature: 270° C. Injection volume: 2 μL

[0135] (Film Thickness) The thickness (film thickness) of the dip-molded film for evaluation was measured at three points in the center using a test piece thickness measuring instrument (manufactured by Kobunshi Keiki Co., Ltd., product name: ASKER SDA-12), and the smallest thickness was taken as the thickness of the dip-molded film for evaluation. The results are shown in Table 1.

[0136] (Measurement of Tensile Properties) Using the dip-molded film for evaluation, the modulus at 100% elongation, tensile strength at break, and elongation at break were measured in accordance with JIS K 6251. The results are shown in the table.

[0137] (Odor) 30 g of the above-mentioned dip-molded film for evaluation was placed in a 250 mL plastic bottle, which was then sealed with a lid and stored at 40°C for 24 hours. After that, the lid was opened and an olfactory panel measured the headspace gas and evaluated the intensity of the irritating odor according to the following criteria: ○: No irritating odor △: Slightly irritating odor ×: Strongly irritating odor

[0138]

[0139]

Claims

1. A chloroprene polymer latex composition comprising a chloroprene polymer latex, a metal oxide, and a mercapto compound, wherein the chloroprene polymer latex composition comprises 0.3 to 15.0 parts by mass of the metal oxide and 0.10 to 10.00 parts by mass of the mercapto compound per 100 parts by mass of the solid content of the chloroprene polymer latex.

2. The chloroprene polymer latex composition according to claim 1, wherein the chloroprene polymer latex composition contains 0.5 to 10.0 parts by mass of an antioxidant per 100 parts by mass of the solid content of the chloroprene polymer latex.

3. The chloroprene polymer latex composition according to claim 1 or 2, wherein a molecular weight distribution obtained by measuring a tetrahydrofuran-soluble portion in the chloroprene polymer latex by gel permeation chromatography has a peak at a weight average molecular weight of 5,000 to 80,000.

4. The chloroprene polymer latex composition according to claim 1 or 2, wherein the chloroprene polymer latex composition has a sulfur content of 5 parts by mass or less per 100 parts by mass of the solid content of the chloroprene polymer latex.

5. A dip-molded article of the chloroprene polymer latex composition according to claim 1 or 2.

6. The dip-molded article according to claim 5, which is any one of industrial and household gloves, ordinary household gloves, medical gloves, balloons, catheters, and boots.