Polymer latex composition, dip-molded body, and method for producing polymer latex composition

Abstract

Provided is a polymer latex composition from which an immersion molded body having excellent flexibility, elongation at break, and breaking strength can be obtained. This polymer latex composition comprises: a carboxy-modified acrylonitrile / butadiene copolymer (A); a carboxy-modified chloroprene copolymer (B); and a metal oxide (C), wherein the component ratio of the carboxy-modified acrylonitrile / butadiene copolymer (A) to the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is (A) / (B)=90 / 10 to 50 / 50.

Description

[Technical field]

[0001] The present invention relates to a polymer latex composition containing an acrylonitrile-butadiene copolymer and a chloroprene copolymer, a dip-molded article, and a method for producing the polymer latex composition. [Background technology]

[0002] Chloroprene latex compositions containing chloroprene polymers are used in various fields such as dipping molded products, fiber treatment agents, paper processing agents, pressure sensitive adhesives, adhesives, elastic asphalt (modified asphalt), elastic cement, etc. In particular, for dipping molded products, chloroprene latex compositions are used as the main raw material for various gloves for industrial use, examination, surgery, etc. Conventionally, natural rubber has been mainly used for gloves, but the demand for synthetic rubber gloves is increasing due to the problem of allergies caused by proteins contained in natural rubber.

[0003] Acrylonitrile-butadiene latex compositions containing acrylonitrile-butadiene copolymers are most commonly used for examination gloves, and most of the polymers are carboxy-modified acrylonitrile-butadiene copolymer latex compositions copolymerized with methacrylic acid. Dip-molded products obtained from these copolymer latex compositions have excellent breaking strength, and are difficult to tear even when they are thin gloves, but they have poor flexibility and breaking elongation, and there are issues with wearing comfort and workability.

[0004] Therefore, the addition of plasticizers is adopted to give gloves flexibility, but a large amount of plasticizer is required to achieve excellent flexibility, and there are concerns from the viewpoint of hygiene such as bleeding out. Therefore, a method of blending polymers with excellent flexibility (e.g., natural rubber, isoprene rubber, chloroprene rubber) with carboxy-modified acrylonitrile-butadiene copolymer is considered. However, adding a small amount does not provide excellent flexibility or improved elongation at break, and adding a large amount significantly reduces the breaking strength of the glove.

[0005] Blends of acrylonitrile-butadiene copolymers and chloroprene polymers have been studied (Patent Documents 1 and 2 below), and also in gloves (Patent Documents 3 and 4 below), but these did not solve the problems of improving flexibility and elongation at break. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 47-031412 [Patent Document 2] Japanese Patent Publication No. 52-060839 [Patent Document 3] International Publication No. 2015 / 074092 [Patent Document 4] Patent Publication No. 2020-189963 Summary of the Invention [Problem to be solved by the invention]

[0007] It is required to improve the flexibility and breaking elongation of dip-molded products (e.g. gloves) obtained from carboxy-modified acrylonitrile-butadiene copolymer without significantly decreasing the breaking strength.

[0008] An object of one aspect of the present invention is to provide a polymer latex composition capable of obtaining a dip-molded article having excellent flexibility, breaking elongation and breaking strength.Another object of the present invention is to provide a dip-molded article of the above-mentioned polymer latex composition.Another object of the present invention is to provide a method for producing the above-mentioned polymer latex composition. [Means for solving the problem]

[0009] As a result of intensive research by the present inventors to solve the above-mentioned problems, it has been found that the above-mentioned problems can be achieved by including a carboxy-modified acrylonitrile-butadiene copolymer, a carboxy-modified chloroprene copolymer, and a metal oxide in a polymer latex composition and specifying the mixing ratio of the carboxy-modified acrylonitrile-butadiene copolymer and the carboxy-modified chloroprene copolymer. That is, the present invention relates to a polymer latex composition containing a carboxy-modified acrylonitrile-butadiene copolymer (A), a carboxy-modified chloroprene copolymer (B), and a metal oxide (C), characterized in that the component ratio of the carboxy-modified acrylonitrile-butadiene copolymer (A) and the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is (A) / (B)=90 / 10 to 50 / 50.

[0010] According to another aspect of the present invention, there is provided a dip-molded article obtained from the polymer latex composition described above. According to another aspect of the present invention, there is provided a method for producing the polymer latex composition described above, comprising a carboxy-modified chloroprene copolymer (B) polymerization step and a mixing step, wherein in the carboxy-modified chloroprene copolymer (B) polymerization step, a raw material containing 2-chloro-1,3-butadiene monomer (B-1) and a carboxy-group-containing vinyl monomer (B-2), or a raw material containing 2-chloro-1,3-butadiene monomer (B-1), a carboxy-group-containing vinyl monomer (B-2), and a 2,3-dichloro-1,3-butadiene monomer is mixed with at least pure water, a chain transfer agent, an emulsifier, The present invention provides a method for producing a polymer latex composition, comprising: polymerizing in the presence of a pH adjuster and an initiator at a polymerization temperature of 5 to 55°C at a polymerization conversion rate of 60% to 99% to obtain a carboxy-modified chloroprene copolymer (B) latex containing a carboxy-modified chloroprene copolymer (B); and mixing the carboxy-modified acrylonitrile-butadiene copolymer (A) latex containing a carboxy-modified acrylonitrile-butadiene copolymer (A) with the carboxy-modified chloroprene copolymer (B) latex containing the carboxy-modified chloroprene copolymer (B) in the mixing step.

[0011] Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other. [1] A polymer latex composition comprising a carboxy-modified acrylonitrile-butadiene copolymer (A), a carboxy-modified chloroprene copolymer (B), and a metal oxide (C), wherein the component ratio of the carboxy-modified acrylonitrile-butadiene copolymer (A) to the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is (A) / (B)=90 / 10 to 50 / 50. [2] The polymer latex composition according to [1], characterized in that the carboxy-modified chloroprene copolymer (B) contains a monomer unit derived from a 2-chloro-1,3-butadiene monomer (B-1) and a monomer unit derived from a carboxy-group-containing vinyl monomer (B-2), and contains 0.5 to 5.0 parts by mass of the monomer unit derived from the carboxy-group-containing vinyl monomer (B-2) per 100 parts by mass of the carboxy-modified chloroprene copolymer (B). [3] The polymer latex composition according to [2], wherein the carboxyl group-containing vinyl monomer (B-2) is at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid. [4] The polymer latex composition according to any one of [1] to [3], comprising sulfur, a vulcanization accelerator, and an antioxidant. [5] The polymer latex composition according to any one of [1] to [4], wherein a dip-molded product containing the polymer latex composition is vulcanized at 120°C for 20 minutes, and the vulcanized dip-molded product has a breaking strength of 17 MPa or more and a breaking elongation of 550% or more, as measured in accordance with JIS K6251. [6] A dip-molded article obtained from the polymer latex composition according to any one of [1] to [5]. [7] The dip-molded article according to [6], which is a glove, a balloon, a catheter or a boot. [8] A method for producing a polymer latex composition according to any one of [1] to [5], comprising a carboxy-modified chloroprene copolymer (B) polymerization step and a mixing step, wherein in the carboxy-modified chloroprene copolymer (B) polymerization step, a raw material containing 2-chloro-1,3-butadiene monomer (B-1) and a carboxy-group-containing vinyl monomer (B-2), or a raw material containing 2-chloro-1,3-butadiene monomer (B-1), a carboxy-group-containing vinyl monomer (B-2), and a 2,3-dichloro-1,3-butadiene monomer is mixed with at least pure water, a chain transfer agent, A method for producing a polymer latex composition, comprising: polymerizing in the presence of an emulsifier, a pH adjuster, and an initiator at a polymerization temperature of 5 to 55°C and a polymerization conversion rate of 60% to 99% to obtain a carboxy-modified chloroprene copolymer (B) latex containing a carboxy-modified chloroprene copolymer (B); and mixing the carboxy-modified acrylonitrile-butadiene copolymer (A) latex containing a carboxy-modified acrylonitrile-butadiene copolymer (A) with the carboxy-modified chloroprene copolymer (B) latex containing the carboxy-modified chloroprene copolymer (B). Effect of the Invention

[0012] According to the polymer latex composition of the present invention, it is possible to provide a dip-molded article and a dip product thereof which are excellent in flexibility and elongation at break and exhibit high mechanical strength such as high breaking strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments. However, the present invention is not limited to the preferred embodiments described below.

[0014] 1. Polymer Latex Composition The polymer latex composition according to the present invention contains a carboxy-modified acrylonitrile-butadiene copolymer (A), a carboxy-modified chloroprene copolymer (B), and a metal oxide (C). Components that may be contained in the polymer latex composition according to the present invention will be described below.

[0015] <Carboxylic acid modified acrylonitrile-butadiene copolymer (A)> First, the carboxy-modified acrylonitrile-butadiene copolymer according to the present embodiment will be described. The carboxy-modified acrylonitrile-butadiene copolymer according to the present embodiment contains a monomer unit derived from an acrylonitrile monomer, a monomer unit derived from a butadiene monomer, and a monomer unit derived from a carboxy-containing vinyl monomer. The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may contain a monomer unit derived from a monomer other than the acrylonitrile monomer, the butadiene monomer, and the carboxy-containing vinyl monomer. The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may be composed of a ternary copolymer of a monomer unit derived from an acrylonitrile monomer, a monomer unit derived from a butadiene monomer, and a monomer unit derived from a carboxy-containing vinyl monomer.

[0016] The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may contain 25 to 40 mass% of monomer units derived from acrylonitrile monomers when the carboxy-modified acrylonitrile-butadiene copolymer is taken as 100 mass%. The content of the monomer units derived from acrylonitrile monomers in the carboxy-modified acrylonitrile-butadiene copolymer may be, for example, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0017] The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may contain 52 to 75 mass% of monomer units derived from butadiene monomer when the carboxy-modified acrylonitrile-butadiene copolymer is taken as 100 mass%. The content of the monomer units derived from butadiene monomer in the carboxy-modified acrylonitrile-butadiene copolymer may be, for example, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, or 75 mass%, or may be within a range between any two of the numerical values ​​exemplified here.

[0018] The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may contain 0.5 to 8 mass% of monomer units derived from a carboxy-containing vinyl monomer when the carboxy-modified acrylonitrile-butadiene copolymer is taken as 100 mass%. The content of the monomer units derived from a carboxy-containing vinyl monomer in the carboxy-modified acrylonitrile-butadiene copolymer may be, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, or 8 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0019] The copolymerization ratio of the carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may be 25% by mass to 40% by mass of acrylonitrile, 52% by mass to 75% by mass of butadiene, and 0.5% by mass to 8% by mass of the carboxy-containing vinyl monomer, and preferably 31% by mass to 36% by mass of acrylonitrile, 59% by mass to 69% by mass of butadiene, and 0.8% by mass to 7% by mass of the carboxy-containing vinyl monomer. The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may contain, when the carboxy-modified acrylonitrile-butadiene copolymer is taken as 100 mass%, a monomer unit derived from an acrylonitrile monomer, a monomer unit derived from a butadiene monomer, and a monomer unit derived from a carboxy group-containing vinyl monomer in a total amount of 90 mass% or more, preferably 95 mass% or more, and more preferably 98 mass% or more.

[0020] The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may have a halogen content of less than 0.2 mass%, preferably less than 0.1 mass%, when the carboxy-modified acrylonitrile-butadiene copolymer is taken as 100 mass%. The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may be free of halogen. The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may be composed of a monomer unit derived from an acrylonitrile monomer, a monomer unit derived from a butadiene monomer, and a monomer unit derived from a carboxy-containing vinyl monomer.

[0021] The carboxyl group-containing vinyl monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid, and preferably contains methacrylic acid.

[0022] The carboxy-modified acrylonitrile-butadiene copolymer according to one embodiment of the present invention may be dispersed in water, and may be a latex obtained by emulsion polymerization of a monomer in the presence of one or more emulsifiers selected from rosin acid or alkali metal salts. The latex containing the carboxy-modified acrylonitrile-butadiene copolymer contains the carboxy-modified acrylonitrile-butadiene copolymer as a main component, may contain a solvent such as water, and may contain other additives used during emulsion polymerization. The carboxy-modified acrylonitrile-butadiene copolymer latex according to one embodiment of the present invention has a solid content, which is the total of one or more emulsifiers selected from rosin acid or alkali metal salts and the carboxy-modified acrylonitrile-butadiene copolymer, of 40 to 50 mass%, more preferably 42 to 46 mass%, based on 100 mass% of the carboxy-modified acrylonitrile-butadiene copolymer latex.

[0023] <Carboxy-modified chloroprene copolymer (B)> The carboxy-modified chloroprene copolymer according to the present embodiment is a copolymer containing a monomer unit derived from a chloroprene monomer and a monomer unit derived from a carboxy-containing vinyl monomer. The carboxy-modified chloroprene copolymer according to the present embodiment is a copolymer of 2-chloro-1,3-butadiene (hereinafter also referred to as a chloroprene monomer) and a carboxy-containing vinyl monomer, or a copolymer of a chloroprene monomer, a carboxy-containing vinyl monomer, and other monomers copolymerizable therewith, and examples of the other monomers include 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, and sulfur, and two or more of these may be used in combination as the other monomers.

[0024] When the carboxy-modified chloroprene copolymer contains monomer units derived from monomers other than the chloroprene monomer and the carboxy group-containing vinyl monomer, the carboxy-modified chloroprene copolymer preferably contains 50% by mass or more of monomer units derived from the chloroprene monomer, more preferably 80% by mass or more, and even more preferably 90% by mass or more, when the entire carboxy-modified chloroprene copolymer is taken as 100% by mass.

[0025] The carboxyl group-containing vinyl monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid, and preferably includes methacrylic acid.

[0026] The copolymerization amount of the carboxy-containing vinyl monomer in the carboxy-modified chloroprene copolymer can be 0.5 to 5.0 mass% and preferably 1.0 to 4.0 mass% relative to 100 mass% of the carboxy-modified chloroprene copolymer. The content of the monomer unit derived from the carboxy-containing vinyl monomer in the carboxy-modified chloroprene copolymer is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 mass% relative to 100 mass% of the carboxy-modified chloroprene copolymer, and may be within a range between any two of the numerical values ​​exemplified here. The content of the monomer units derived from the chloroprene monomer in the carboxy-modified chloroprene copolymer can be 50 to 99.5% by mass, and particularly preferably 95.0 to 99.5% by mass, when the carboxy-modified chloroprene copolymer is taken as 100% by mass. The content of the monomer units derived from the chloroprene monomer is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99, or 99.5% by mass, and may be within a range between any two of the numerical values ​​exemplified here. The carboxy-modified chloroprene copolymer (B) according to one embodiment of the present invention may contain, when the carboxy-modified chloroprene copolymer (B) is taken as 100 mass%, 95.0 to 99.5 mass% of monomer units derived from the chloroprene monomer (B-1) and 0.5 to 5.0 mass% of monomer units derived from the carboxy group-containing vinyl monomer (B-2).

[0027] The content of monomer units other than the chloroprene monomer and the carboxy group-containing vinyl monomer in the carboxy-modified chloroprene copolymer is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 mass%, when the carboxy-modified chloroprene copolymer is taken as 100 mass%, and may be within a range between any two of the numerical values ​​exemplified here. The carboxy-modified chloroprene copolymer according to one embodiment of the present invention may contain no monomer units other than the chloroprene monomer and the carboxy-group-containing vinyl monomer.

[0028] The carboxy-modified chloroprene copolymer (B) according to one embodiment of the present invention is preferably such that the breaking strength measured according to JIS K6251 of the dip-molded product obtained by vulcanizing the carboxy-modified chloroprene copolymer (B) latex composition containing the carboxy-modified chloroprene copolymer (B) at 130° C. for 30 minutes is 8 MPa or more and the breaking elongation is 600% or more. The breaking strength is, for example, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22 MPa, and may be within a range between any two of the numerical values ​​exemplified here. The breaking elongation is, for example, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, or 1100%, and may be within a range between any two of the numerical values ​​exemplified here.

[0029] The dip-molded product made of the carboxy-modified chloroprene copolymer (B) latex composition containing the carboxy-modified chloroprene copolymer (B) may contain at least the carboxy-modified chloroprene copolymer (B) and a metal oxide (C), and may further contain a vulcanizing agent. The dip-molded product may further contain a vulcanization accelerator. The dip-molded product may further contain an antiaging agent. The dip-molded product and the dip-molded product after vulcanization may be produced according to the method of the embodiment. The thickness may be, for example, 0.10 to 0.30 mm.

[0030] The polymer latex composition according to one embodiment of the present invention may include a chloroprene-based polymer that includes a monomer unit derived from a chloroprene monomer and does not include a monomer unit derived from a carboxyl group-containing vinyl monomer. For example, the polymer latex composition according to one embodiment of the present invention may include a chloroprene polymer composed of chloroprene monomer units. The polymer latex composition according to one embodiment of the present invention preferably contains more carboxy-modified chloroprene copolymer (B) than chloroprene polymer not containing monomer units derived from carboxy-containing vinyl monomer. The content of the chloroprene polymer not containing monomer units derived from carboxy-containing vinyl monomer contained in the polymer latex composition is preferably less than 50 mass% relative to the total 100 mass% of the carboxy-modified chloroprene copolymer (B) and the chloroprene polymer not containing monomer units derived from carboxy-containing vinyl monomer contained in the polymer latex composition, and may be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 mass%, or may be within a range between any two of the numerical values ​​exemplified here.

[0031] The method for producing a carboxy-modified chloroprene copolymer (B) according to one embodiment of the present invention includes a carboxy-modified chloroprene copolymer (B) polymerization step in which a raw material containing 2-chloro-1,3-butadiene monomer (B-1) and a carboxy-containing vinyl monomer (B-2), or a raw material containing 2-chloro-1,3-butadiene monomer (B-1), a carboxy-containing vinyl monomer (B-2), and a 2,3-dichloro-1,3-butadiene monomer is polymerized in the presence of pure water, a chain transfer agent, an emulsifier, a pH adjuster, and an initiator at a polymerization temperature of 5 to 55°C and a polymerization conversion rate of 60% to 99% to obtain a carboxy-modified chloroprene copolymer (B) latex containing the carboxy-modified chloroprene copolymer (B). In the polymerization step, a dispersant and / or a reducing agent may also be added.

[0032] When producing the carboxy-modified chloroprene copolymer according to the embodiment of the present invention, the 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 the polymerization-finished liquid, and a relatively fast polymerization rate.

[0033] Emulsion polymerization is a type of radical polymerization in which raw material monomers are polymerized by being charged into a reaction vessel together with a chain transfer agent, water, a pH adjuster such as an alkali (e.g., a metal hydroxide such as potassium hydroxide or sodium hydroxide), an emulsifier, a dispersant, a reducing agent (e.g., sodium hydrogen sulfite), a polymerization initiator, etc.

[0034] The chain transfer agent may be one that is used in the emulsion polymerization of normal chloroprene. Specific examples of the chain transfer agent include long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan; and dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide. These chain transfer agents may be used alone or in combination of two or more. The amount of the chain transfer agent used is preferably 0.01 to 1 part by mass relative to 100 parts by mass of the monomer.

[0035] Examples of the emulsifier include anionic emulsifiers and nonionic emulsifiers. Examples of the anionic emulsifier include fatty acid salts such as potassium tallow fatty acid, partially hydrogenated potassium tallow fatty acid, potassium oleate, and sodium oleate; resin acid salts such as potassium rosinate, sodium rosinate, potassium hydrogenated potassium rosinate, and sodium hydrogenated rosinate; and alkylbenzene sulfonate salts such as sodium dodecylbenzene sulfonate. Examples of the nonionic emulsifier include polyethylene glycol ester emulsifiers and polyvinyl alcohol. Among these, anionic emulsifiers are preferred, and at least one selected from the group consisting of alkylbenzene sulfonate salts is more preferred. These emulsifiers can be used alone or in combination of two or more. The amount of the emulsifier used is preferably 0.5 to 6.5 parts by mass relative to 100 parts by mass of the monomer.

[0036] Examples of the dispersant include sodium salt of β-naphthalenesulfonic acid formalin condensate. The dispersant may be used alone or in combination of two or more. The amount of the dispersant used is preferably 0.1 to 3.0 parts by mass based on 100 parts by mass of the monomer. In the polymerization step, it is more preferable to use an emulsifier and a dispersant.

[0037] Examples of pH adjusters include potassium hydroxide and sodium hydroxide. The pH adjuster may be used alone or in combination of two or more kinds. Among the pH adjusters, potassium hydroxide and sodium hydroxide are preferred because they are highly effective in increasing the pH value. The amount of the pH adjuster to be added may be 0.01 to 2.0 parts by mass relative to 100 parts by mass of the monomer.

[0038] Examples of the reducing agent include potassium pyrosulfite, potassium sulfite, potassium hydrogensulfite, potassium phosphate, potassium hydrogen phosphate, sodium hydrogensulfite, etc. The amount of the reducing agent added can be 0.1 to 4.0 parts by mass with respect to 100 parts by mass of the monomer.

[0039] As the polymerization initiator, inorganic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, etc.; organic peroxides such as benzoyl peroxide, etc. can be used. These polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used is preferably 0.01 to 10 parts by mass based on 100 parts by mass of the monomer.

[0040] The amount of water used in the emulsion polymerization is preferably 50 to 300 parts by mass, more preferably 80 to 150 parts by mass, based on 100 parts by mass of the monomer.

[0041] The polymerization temperature is not particularly limited, but from the viewpoint of easily maintaining the stability of the flexibility of the carboxy-modified chloroprene copolymer over time, it is preferably in the range of 5 to 55° C., and more preferably in the range of 10 to 50° C. The polymerization temperature is, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55° C., and may be within a range between any two of the numerical values ​​exemplified here.

[0042] The polymerization rate (polymerization conversion rate) of the raw material monomer is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. The upper limit can be, for example, 99% or less. The polymerization conversion rate can be, for example, 60, 65, 70, 75, 80, 85, 90, 95, or 99%, and may be within a range between any two of the numerical values ​​exemplified here. By setting the polymerization conversion rate within this range, the solid content of the carboxy-modified chloroprene copolymer and the polymerization time during production become appropriate, resulting in excellent productivity.

[0043] As a polymerization terminator to be added when the polymerization rate of the raw material monomer reaches the target polymerization rate and the polymerization is terminated, for example, thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), diethylhydroxylamine, etc. can be used.

[0044] After the polymerization, the unreacted monomers are removed, and the solid content is adjusted to an optimum range by a concentration operation, preferably within a range of 40 to 50% by mass.

[0045] By the above-mentioned production method, a latex containing a carboxyl-modified chloroprene copolymer (B) can be obtained. The latex containing a carboxyl-modified chloroprene copolymer (B) according to one embodiment of the present invention can contain a free carboxyl-group-containing vinyl monomer that is not bonded to the carboxyl-modified chloroprene copolymer (B). The content of the free carboxyl-group-containing vinyl monomer can be 0.1 to 2.0% by mass relative to 100% by mass of the carboxyl-modified chloroprene copolymer (B). The content of the free carboxyl-group-containing vinyl monomer can be evaluated by liquid chromatography.

[0046] In the polymer latex composition according to the present embodiment, the component ratio of the carboxy-modified acrylonitrile-butadiene copolymer (A) and the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is (A) / (B)=90 / 10 to 50 / 50. When the total of the carboxy-modified acrylonitrile-butadiene copolymer (A) and the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is 100% by mass, the content of the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is 10 to 50% by mass, for example, 10, 15, 20, 25, 30, 35, 40, 45, or 50% by mass, and may be within a range between any two of the numerical values ​​exemplified here. The polymer latex composition according to the present invention contains a carboxy-modified acrylonitrile-butadiene copolymer (A), a carboxy-modified chloroprene copolymer (B), and a metal oxide (C). By controlling the component ratio (A) / (B) of the carboxy-modified acrylonitrile-butadiene copolymer (A) to the carboxy-modified chloroprene copolymer (B) in the polymer latex composition to a specific range, it becomes possible to exhibit flexibility and breaking elongation while maintaining excellent breaking strength.

[0047] <Metal oxide (C)> The polymer latex composition according to the present invention contains a metal oxide (C). As described above, both the acrylonitrile-butadiene copolymer and the chloroprene copolymer contained in the polymer latex composition according to the present invention have monomer units derived from carboxyl group-containing vinyl monomers. It is considered that the carboxyl groups contained in each copolymer are ionically crosslinked by metal ions derived from metal oxides, thereby making it possible to obtain a dip-molded product having excellent breaking strength, flexibility, and breaking elongation.

[0048] Examples of the metal oxide include zinc oxide, lead oxide, trilead tetroxide, magnesium oxide, titanium oxide, and calcium oxide. The content of the metal oxide may be 0.5 to 10 parts by mass relative to 100 parts by mass of the solid content of the polymer latex composition, from the viewpoint that crosslinking between the carboxy-modified acrylonitrile-butadiene copolymer (A) and the carboxy-modified chloroprene copolymer (B) can proceed more sufficiently and a dip-molded product excellent in flexibility, elongation at break, strength at break, modulus, etc. can be easily obtained. The solid content of the polymer latex composition means all components obtained by removing volatile matters such as water from the polymer latex composition, and includes the carboxy-modified acrylonitrile-butadiene copolymer (A) and the carboxy-modified chloroprene copolymer (B) and non-volatile matters of various additives added during emulsion polymerization. The content of the metal oxide is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here. The metal oxide may be used alone or in combination of two or more kinds.

[0049] The polymer latex composition according to one embodiment of the present invention may contain pH adjusters, freeze stabilizers, emulsifiers, viscosity adjusters, antioxidants, preservatives, and the like. As the pH adjuster, emulsifier, etc., the pH adjuster, emulsifier, etc. used in producing the latex containing the carboxy-modified chloroprene copolymer (B) can be used.

[0050] The polymer latex composition according to one embodiment of the present invention may contain additives such as vulcanizing agents, vulcanization accelerators, antiaging agents (antioxidants, e.g., antiozonants), fillers, plasticizers, pigments, colorants, wetting agents, and antifoaming agents. The polymer latex composition according to the present embodiment may be a polymer latex composition containing the carboxy-modified acrylonitrile-butadiene copolymer (A), the carboxy-modified chloroprene copolymer (B), and the metal oxide (C) and these additives, and may be a polymer latex composition for dip molding. The polymer latex composition according to one embodiment of the present invention may be an embodiment that does not contain at least one additive selected from the group consisting of vulcanizing agents, vulcanization accelerators, antiaging agents, fillers, plasticizers, pigments, colorants, wetting agents, and antifoaming agents, as an embodiment before mixing these additives.

[0051] Examples of the vulcanizing agent include sulfur (molecular sulfur, for example, cyclic sulfur such as S8). The content of the vulcanizing agent may be 0.5 to 10 parts by mass per 100 parts by mass of the solid content of the polymer latex composition, from the viewpoint of easily proceeding with crosslinking sufficiently and easily obtaining the breaking strength, modulus, etc. of the dip-molded article, and easily obtaining a suitable touch of the dip-molded article. The vulcanizing agent may be used alone or in combination of two or more kinds.

[0052] Examples of the vulcanization accelerator include thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, thiazole-based, etc. As an example, a dithiocarbamate-based vulcanization accelerator can be used, and examples of the dithiocarbamate-based vulcanization accelerator include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, tellurium diethyldithiocarbamate, etc. The amount of the vulcanization accelerator may be 0.5 to 5 parts by mass based on 100 parts by mass of the solid content of the polymer latex composition from the viewpoint of obtaining an appropriate strength. The vulcanization accelerator may be used alone or in combination of two or more kinds.

[0053] Examples of the antiaging agent include ozone antiaging agents, phenolic antiaging agents, and amine antiaging agents. Examples of the amine antiaging agents include diphenylamine compounds such as octylated diphenylamine, p-(p-toluene-sulfonylamido)diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N,N'-diphenyl-p-phenylenediamine (DPPD), and N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD). Examples of the antiaging agent include N,N'-diphenyl-p-phenylenediamine (DPPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and the like. Examples of the antiaging agent include bound phenolic antioxidants when the appearance (particularly color tone) or hygiene is important, such as in medical gloves. One example is the butylated reaction product of DCPD and p-cresol. The content of the antiaging agent may be 0.1 to 5 parts by mass per 100 parts by mass of the solid content of the polymer latex composition, from the viewpoint of easily obtaining a sufficient antiaging effect.

[0054] In the polymer latex composition according to one embodiment of the present invention, the breaking strength of a dip-molded product obtained by vulcanizing a dip-molded product containing the polymer latex composition at 120° C. for 20 minutes and then vulcanizing the dip-molded product is preferably 17 MPa or more, as measured in accordance with JIS K6251. The breaking strength is, for example, 17, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, or 40 MPa, and may be within a range between any two of the numerical values ​​exemplified here.

[0055] The polymer latex composition according to one embodiment of the present invention preferably has a breaking elongation of 550% or more, measured in accordance with JIS K6251, of a dip-molded product obtained by vulcanizing a dip-molded product containing the polymer latex composition for 20 minutes at 120° C. The breaking elongation is, for example, 550, 600, 650, 700, 750, 800, 850, 900, 950, or 1000%, and may be within a range between any two of the numerical values ​​exemplified here.

[0056] In the polymer latex composition according to one embodiment of the present invention, the modulus at 100% elongation of a vulcanized dip-molded article obtained by vulcanizing a dip-molded article containing the polymer latex composition for 20 minutes at 120° C. is preferably 2.5 MPa or less, as measured in accordance with JIS K6251. The modulus at 100% elongation is, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5 MPa, and may be within a range between any two of the numerical values ​​exemplified here.

[0057] In the polymer latex composition according to one embodiment of the present invention, the modulus at 300% elongation measured according to JIS K6251 of the vulcanized dip molded product obtained by vulcanizing a dip molded product containing the polymer latex composition at 120° C. for 20 minutes is preferably 5.0 MPa or less. The modulus at 300% elongation may be, for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0 MPa, or may be within a range between any two of the numerical values ​​exemplified here.

[0058] In the polymer latex composition according to one embodiment of the present invention, the modulus at 500% elongation of a dip-molded product obtained by vulcanizing a dip-molded product containing the polymer latex composition for 20 minutes at 120° C. and measured in accordance with JIS K6251 after vulcanization is preferably 15.0 MPa or less. The modulus at 500% elongation is, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 MPa, and may be within a range between any two of the numerical values ​​exemplified here. The above dip molding contains at least a carboxy-modified acrylonitrile-butadiene copolymer (A), a carboxy-modified chloroprene copolymer (B), and a metal oxide (C), and may further contain a vulcanizing agent. The above dip molding may further contain a vulcanization accelerator. The above dip molding may further contain an anti-aging agent. The above dip molding and the dip molding after vulcanization can be produced by the methods described in the Examples. The thickness may be, for example, 0.06 to 0.07 mm.

[0059] 2. Method for producing polymer latex composition A method for producing a polymer latex composition according to one embodiment of the present invention may include a polymerization step of the carboxy-modified chloroprene copolymer (B) and a mixing step. In the polymerization step of the carboxy-modified chloroprene copolymer (B), a raw material containing 2-chloro-1,3-butadiene monomer (B-1) and a carboxy-group-containing vinyl monomer (B-2), or a raw material containing 2-chloro-1,3-butadiene monomer (B-1), a carboxy-group-containing vinyl monomer (B-2), and a 2,3-dichloro-1,3-butadiene monomer is polymerized in the presence of at least pure water, a chain transfer agent, an emulsifier, a pH adjuster, and an initiator at a polymerization temperature of 5 to 55°C and a polymerization conversion rate of 60% to 99% to obtain a carboxy-modified chloroprene copolymer (B) latex containing the carboxy-modified chloroprene copolymer (B). In the mixing step, a carboxy-modified acrylonitrile-butadiene copolymer (A) latex containing the carboxy-modified acrylonitrile-butadiene copolymer (A) and a carboxy-modified chloroprene copolymer (B) latex containing the carboxy-modified chloroprene copolymer (B) can be mixed. The order of mixing in the mixing step is not particularly limited, but a polymer latex containing a carboxy-modified acrylonitrile-butadiene copolymer (A) and a polymer latex containing a carboxy-modified chloroprene copolymer (B) can be mixed so that the component ratio of the carboxy-modified acrylonitrile-butadiene copolymer (A) to the carboxy-modified chloroprene copolymer (B) is (A) / (B)=90 / 10 to 50 / 50, and a metal oxide (C) can be further added. In the mixing step, a mixed liquid containing the metal oxide (C) and components such as a vulcanizing agent and a vulcanization accelerator to be added as necessary can be prepared in advance, and the polymer latex containing the carboxy-modified acrylonitrile-butadiene copolymer (A) and the polymer latex containing the carboxy-modified chloroprene copolymer (B) can be added to the mixed liquid.

[0060] 3. Dip-molded body and manufacturing method thereof The dip-molded article according to one embodiment of the present invention can be a dip-molded article of the polymer latex composition according to one embodiment of the present invention. The dip-molded article according to one embodiment of the present invention is a dip-molded article using the polymer latex composition according to one embodiment of the present invention, and can be obtained by dip-molding the polymer latex composition according to one embodiment of the present invention. The dip-molded article according to one embodiment of the present invention can be obtained by immersing a substrate in a coagulation liquid containing the polymer latex composition according to one embodiment of the present invention and forming a dip-molded film on the substrate.

[0061] In the method for producing the dip-molded product according to the present embodiment, the polymer latex composition according to the present embodiment is dip-molded. As a molding method for producing the dip-molded product according to the present embodiment, a known method can be used, and examples thereof include a simple dipping method, an adhesion dipping method, a heat-sensitive dipping method, and an electrodeposition method. From the viewpoint of ease of production and ease of obtaining a dip-molded product of a certain thickness, the adhesion dipping method can be used. Specifically, a molding die coated with a coagulant is dipped into the polymer latex composition, and the polymer latex composition is coagulated. Then, after removing water-soluble impurities by leaching, the composition is dried, and further vulcanized to form a dip-molded film (rubber film), and the dip-molded film is released from the mold. This allows a film-shaped dip-molded product to be obtained.

[0062] The thickness of the immersion molded product (for example, the minimum thickness) may be 0.01 to 0.50 mm, 0.02 to 0.20 mm, or 0.04 to 0.10 mm. The thickness of the immersion molded product may be, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10 mm, and may be within a range between any two of the numerical values ​​exemplified here. The thickness of the immersion molded product can be adjusted by the time for immersing the mold in the polymer latex composition, the solid content concentration of the polymer latex composition, and the like. When it is desired to reduce the thickness of the immersion molded product, the immersion time may be shortened or the solid content concentration of the polymer latex composition may be reduced.

[0063] 4. Vulcanizates and methods for producing vulcanizates A vulcanized product (a dip-molded product after vulcanization) can be obtained by vulcanizing the polymer latex composition and the unvulcanized dip-molded product according to one embodiment of the present invention. The vulcanized product according to one embodiment of the present invention is a vulcanized product of the polymer latex composition and the unvulcanized dip-molded product according to one embodiment of the present invention, and can be obtained by vulcanizing the polymer latex composition and the unvulcanized dip-molded product according to one embodiment of the present invention. The vulcanized product according to this embodiment can be in the form of a film. The temperature at which the polymer latex composition and the unvulcanized dip-molded product are vulcanized may be appropriately set according to the composition of the polymer latex composition, and may be 100 to 220°C, or 110 to 190°C. The vulcanization time for vulcanizing the polymer latex composition and the unvulcanized dip-molded product may be appropriately set according to the composition of the rubber composition, the shape of the unvulcanized molded product, and the like, and may be 10 to 60 minutes.

[0064] The immersion molded product and vulcanizate according to one embodiment of the present invention have very high flexibility, and also have sufficient breaking strength and breaking elongation as an immersion molded product. The immersion molded product according to one embodiment of the present invention may be a molded product of the vulcanizate according to this embodiment. The immersion molded product according to one embodiment of the present invention may be a glove, a balloon, a catheter, or a boot. Examples of gloves include examination gloves, surgical gloves, and household gloves. The immersion molded product according to one embodiment of the present invention has excellent breaking strength and is not easily torn even if it is a thin glove, and also has improved flexibility and breaking elongation, so that it can be suitably used, for example, as a disposable glove or an examination glove. EXAMPLES

[0065] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[0066] Example 1 <Carboxylic acid modified acrylonitrile-butadiene copolymer (A)> The acrylonitrile-butadiene copolymer latex "LX550L" (Zeon Corporation) was used as the latex containing the carboxy-modified acrylonitrile-butadiene copolymer (A). As a result of H-NMR measurement, the composition was 33% by mass of monomer units derived from acrylonitrile monomer, 61% by mass of monomer units derived from butadiene, and 6% by mass of monomer units derived from methacrylic acid.

[0067] <Preparation of Carboxy-Modified Chloroprene Copolymer (B)> 99.0 parts by mass of 2-chloro-1,3-butadiene, 1.0 parts by mass of methacrylic acid, 0.40 parts by mass of n-dodecyl mercaptan, 90 parts by mass of pure water, 1.4 parts by mass of sodium dodecylbenzenesulfonate (manufactured by Kao Corporation, product name: G-15), 0.16 parts by mass of sodium hydroxide, 1.20 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N), and 0.41 parts by mass of sodium hydrogen sulfite were mixed. After adding 0.1 parts by mass of potassium persulfate as a polymerization initiator, polymerization was carried out at a polymerization temperature of 45°C under a nitrogen gas flow. When the polymerization rate reached 98%, a polymerization terminator was added to terminate the polymerization, unreacted monomers were removed, and 10% KOH was added to adjust the pH to 10.5. Next, a latex containing a carboxy-modified chloroprene copolymer (B) with a solid content concentration of 45% was obtained by adjusting the solid content. H-NMR measurement of the carboxy-modified chloroprene copolymer revealed that the polymer composition was 99.2% by mass of monomer units derived from chloroprene and 0.8% by mass of monomer units derived from methacrylic acid.

[0068] Next, the latex containing the carboxy-modified acrylonitrile-butadiene copolymer (A) and the latex containing the carboxy-modified chloroprene copolymer (B) were mixed in a ratio of (A) / (B) = 70 / 30 (mass ratio of solids) to obtain a polymer latex.

[0069] Example 2 A polymer latex was prepared in the same manner as in Example 1, except that the monomers used in preparing the latex containing the carboxy-modified chloroprene copolymer (B) in Example 1 were 97.5 parts by mass of 2-chloro-1,3-butadiene and 2.5 parts by mass of methacrylic acid. When H-NMR measurement was performed, the polymer composition was 98.0% by mass of monomer units derived from chloroprene and 2.0% by mass of monomer units derived from methacrylic acid.

[0070] Example 3 A polymer latex was prepared in the same manner as in Example 1, except that the monomers used in preparing a latex containing a carboxy-modified chloroprene copolymer (B) in Example 1 were 94.0 parts by mass of 2-chloro-1,3-butadiene, 6.0 parts by mass of methacrylic acid, 120 parts by mass of pure water, and 1.87 parts by mass of sodium dodecylbenzenesulfonate. When H-NMR measurement was performed, the polymer composition was 95.0% by mass of monomer units derived from chloroprene and 5.0% by mass of monomer units derived from methacrylic acid.

[0071] Example 4 A polymer latex was prepared in the same manner as in Example 1, except that the mixing ratio of the polymers was (A) / (B)=90 / 10.

[0072] Example 5 A polymer latex was prepared in the same manner as in Example 1, except that the mixing ratio of the polymers was (A) / (B)=50 / 50.

[0073] Example 6 A latex composition was prepared in the same manner as in Example 1, except that the monomers used in preparing a latex containing a carboxy-modified chloroprene copolymer (B) in Example 1 were 88.0 parts by mass of 2-chloro-1,3-butadiene, 9.5 parts by mass of 2,3-dichloro-1,3-butadiene, and 2.5 parts by mass of methacrylic acid. When H-NMR measurement was performed, the polymer composition was 98.0% by mass of monomer units derived from chloroprene and 2.0% by mass of monomer units derived from methacrylic acid.

[0074] Example 7 A latex composition was prepared in the same manner as in Example 1, except that the monomers used in preparing a latex containing a carboxy-modified chloroprene copolymer (B) in Example 1 were 97.5 parts by mass of 2-chloro-1,3-butadiene and 2.5 parts by mass of maleic acid. When H-NMR measurement was performed, the polymer composition was 98.0% by mass of monomer units derived from chloroprene and 2.0% by mass of monomer units derived from maleic acid.

[0075] Comparative Example 1 In Example 1, instead of the latex containing the carboxy-modified chloroprene copolymer (B), a chloroprene polymer produced by the following method was used. 100 parts by mass of 2-chloro-1,3-butadiene, 0.04 parts by mass of n-dodecyl mercaptan, 90 parts by mass of pure water, 1.4 parts by mass of sodium dodecylbenzenesulfonate (manufactured by Kao Corporation, product name: G-15), 0.16 parts by mass of sodium hydroxide, and 1.20 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N) were mixed. After adding 0.1 parts by mass of potassium persulfate as a polymerization initiator, polymerization was carried out under a nitrogen gas flow at a polymerization temperature of 45°C. When the polymerization rate reached 90%, a polymerization terminator was added to terminate the polymerization, and a carboxy-unmodified chloroprene polymer with a solid content concentration of 45% was obtained by removing unreacted monomers and adjusting the solid content. Thereafter, a latex composition was prepared in the same manner as in Example 1.

[0076] Comparative Example 2 A polymer latex was prepared in the same manner as in Example 1, except that the mixing ratio of the polymers was (A) / (B)=100 / 0.

[0077] Comparative Example 3 A polymer latex was prepared in the same manner as in Example 1, except that the mixing ratio of the polymers was (A) / (B)=30 / 70.

[0078] <Preparation of polymer latex composition> Using a ceramic ball mill, 1 part by mass of sulfur, 2 parts by mass of type 2 zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., product name: zinc oxide type 2), 2 parts by mass of a vulcanization accelerator (zinc dibutyldithiocarbamate, manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Noccela BZ), 2 parts by mass of an antioxidant (phenol-based antioxidant, oligomer-type hindered phenol (butylated reaction product of DCPD and p-cresol), manufactured by OMNOVA SOLUTIONS, product name: Wingstay-L), 0.1 part by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N), and 10.7 parts by mass of water were mixed at 20° C. for 16 hours to prepare an aqueous dispersion with a solids concentration of 40%. A 5% aqueous potassium hydroxide solution was added to adjust the pH to 10 in each of the polymer latexes of Examples 1 to 7 and Comparative Examples 1 to 3, and 7.1 parts by mass of the solid content of the aqueous dispersion was mixed with 100 parts by mass of the solid content of the polymer latexes. Water was then added to adjust the total solid content concentration to 13.5% by mass to prepare a polymer latex composition.

[0079] Comparative Example 4 A polymer latex was prepared in the same manner as in Example 1. Using a ceramic ball mill, 1 part by mass of sulfur, 2 parts by mass of vulcanization accelerator, 2 parts by mass of antioxidant, 0.1 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N), and 7.7 parts by mass of pure water were mixed for 16 hours at 20° C. to prepare an aqueous dispersion with a solid content of 40%. 5.1 parts by mass of the aqueous dispersion was mixed with 100 parts by mass of the solid content of a polymer latex whose pH had been adjusted to 10 by adding a 5% aqueous potassium hydroxide solution, and then water was added to adjust the total solid content to 13.5% by mass, thereby preparing a polymer latex composition.

[0080] The evaluation method is described below. <Preparation of evaluation film> A coagulation liquid was obtained by mixing 72.7 parts by mass of water, 27.3 parts by mass of potassium nitrate tetrahydrate, and 0.05 parts by mass of a surfactant (manufactured by Kao Corporation, trade name: Emulgen 109P). A ceramic cylinder (material: ceramics, manufactured by Shinko Co., Ltd.) having an outer diameter of 50 mm was immersed in this coagulation liquid for 5 seconds, and then the cylinder was taken out. After drying at room temperature for 3 minutes, it was dried at 70°C for 1 minute. Then, the cylinder was immersed in the above-mentioned latex composition for 23 seconds. Next, it was dried at 100°C for 2 minutes, and then immersed in warm water at 45°C for 1 minute and washed. Then, it was vulcanized at 120°C for 20 minutes to prepare an evaluation film (dip-molded product, vulcanized film) on the outer peripheral surface of the cylinder. The evaluation film was peeled off from the outer peripheral surface of the cylinder and evaluated.

[0081] <Evaluation method> (Amount of copolymerized monomer units derived from carboxy-group-containing vinyl monomers in carboxy-modified chloroprene copolymer) The carboxy-modified chloroprene copolymer latex was frozen at -60°C for 24 hours, and then vacuum dried for 24 hours to obtain a carboxy-modified chloroprene copolymer film. The film was cut into 2 mm squares using scissors, and immersed in an ethanol-toluene mixed solution and stirred for 1 hour. The peaks of the mass spectrum components of the carboxy group were quantitatively analyzed using a pyrolysis gas chromatograph mass spectrometer (JMS-Q1000GC, manufactured by JEOL Ltd.), and the copolymerization ratio of the carboxy-containing vinyl monomer in the carboxy-modified chloroprene copolymer was quantified.

[0082] (Thickness of the film to be evaluated) The thickness (film thickness) of the evaluation film was measured at three points in the center of the film using a test piece thickness gauge (manufactured by Kobunshi Keiki Co., Ltd., product name: ASKER SDA-12), and the minimum thickness was obtained as the evaluation film thickness.

[0083] (Physical properties of the film for evaluation) The modulus, breaking strength and breaking elongation of the evaluation film at 100%, 300% and 500% elongation were measured according to JIS K 6251. A film was judged to be good when the modulus at 300% elongation, which is an index of flexibility, was 5.0 MPa or less, the breaking elongation was 550% or more and the breaking strength was 17.0 MPa or more.

[0084] <Result> Comparison of each Example with each Comparative Example shows that, when the carboxy-modified acrylonitrile-butadiene copolymer (A) and the carboxy-modified chloroprene copolymer (B) have a component ratio (A) / (B) of 90 / 10 to 50 / 50 and contain a metal oxide, the modulus at 300% elongation is low, the flexibility is excellent, the elongation at break is large, and the breaking strength is high. Note that, for the latex containing the carboxy-modified chloroprene copolymer (B) obtained in Example 1, a polymer latex composition and a dip-molded product were prepared in the same manner as in Example 1, except that the latex containing the carboxy-modified acrylonitrile-butadiene copolymer (A) was not added, and the dip-molded product after vulcanization (thickness 0.10 to 0.30 mm) obtained by vulcanization at 130°C for 30 minutes was measured for breaking strength and breaking elongation, and it was confirmed that the breaking strength was 8 MPa or more and the breaking elongation was 600% or more.

[0085] [Table 1]

Claims

1. A polymer latex composition comprising a carboxy-modified acrylonitrile-butadiene copolymer (A), a carboxy-modified chloroprene copolymer (B), and a metal oxide (C), The polymer latex composition is characterized in that the component ratio of the carboxy-modified acrylonitrile-butadiene copolymer (A) to the carboxy-modified chloroprene copolymer (B) in the polymer latex composition is (A) / (B)=90 / 10 to 50 / 50.

2. The polymer latex composition according to claim 1, characterized in that the carboxy-modified chloroprene copolymer (B) contains a monomer unit derived from a 2-chloro-1,3-butadiene monomer (B-1) and a monomer unit derived from a carboxy group-containing vinyl monomer (B-2), and contains 0.5 to 5.0 parts by mass of the monomer unit derived from the carboxy group-containing vinyl monomer (B-2) when the carboxy-modified chloroprene copolymer (B) is taken as 100 parts by mass.

3. The polymer latex composition according to claim 2, wherein the carboxyl group-containing vinyl monomer (B-2) is at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid.

4. 3. The polymer latex composition according to claim 1, further comprising sulfur, a vulcanization accelerator, and an antioxidant.

5. 3. The polymer latex composition according to claim 1, wherein a dip-molded product containing the polymer latex composition is vulcanized at 120° C. for 20 minutes, and the vulcanized dip-molded product has a breaking strength of 17 MPa or more and a breaking elongation of 550% or more, as measured in accordance with JIS K6251.

6. A dip-molded article obtained from the polymer latex composition according to claim 1 or 2.

7. The dip-molded article according to claim 6, which is a glove, a balloon, a catheter or a boot.

8. A method for producing the polymer latex composition according to claim 1 or claim 2, comprising the steps of: The process includes a polymerization step of a carboxy-modified chloroprene copolymer (B) and a mixing step, In the carboxy-modified chloroprene copolymer (B) polymerization step, a raw material containing 2-chloro-1,3-butadiene monomer (B-1) and a carboxy-group-containing vinyl monomer (B-2), or a raw material containing 2-chloro-1,3-butadiene monomer (B-1), a carboxy-group-containing vinyl monomer (B-2), and a 2,3-dichloro-1,3-butadiene monomer is polymerized in the presence of at least pure water, a chain transfer agent, an emulsifier, a pH adjuster, and an initiator at a polymerization temperature of 5 to 55° C. and a polymerization conversion rate of 60% to 99% to obtain a carboxy-modified chloroprene copolymer (B) latex containing a carboxy-modified chloroprene copolymer (B); In the mixing step, a carboxy-modified acrylonitrile-butadiene copolymer (A) latex containing the carboxy-modified acrylonitrile-butadiene copolymer (A) and a carboxy-modified chloroprene copolymer (B) latex containing the carboxy-modified chloroprene copolymer (B) are mixed together. A method for producing a polymer latex composition.

9. The polymer latex composition according to claim 1 or claim 2, wherein the carboxy-modified acrylonitrile-butadiene copolymer (A) contains 0.5 to 8 mass% of monomer units derived from a carboxy group-containing vinyl monomer when the carboxy-modified acrylonitrile-butadiene copolymer is taken as 100 mass%.

10. The polymer latex composition according to claim 1 or claim 2, wherein a modulus at 300% elongation of a vulcanized dip-molded body obtained by vulcanizing a dip-molded body containing the polymer latex composition at 120°C for 20 minutes, as measured in accordance with JIS K6251, is 3.1 to 5.0 MPa.

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