Chloroprene polymer latex composition, dip-molded article formation composition, and dip-molded article

Abstract

Provided is a chloroprene polymer composition that makes it possible to produce a dip-molded article formation composition that has high mechanical stability and produces few aggregates when shearing force has been applied. The present invention provides a chloroprene polymer latex composition that includes a chloroprene polymer and a C7–10 aromatic compound, the total C7–10 aromatic compound content being 0.00001–0.00290 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer latex composition.

Description

Chloroprene polymer latex composition, composition for forming dip-molded body, and dip-molded body

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

[0002] Chloroprene polymer latex compositions 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 techniques have been proposed for chloroprene polymer latexes for dip-molded products and for dip-molded products of chloroprene polymers. Patent Document 1 describes a polychloroprene latex with a pH of 7 to 14 that contains 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, for use in dip-molded products.

[0004] JP 2014-114342 A

[0005] However, conventional chloroprene polymer compositions have low mechanical stability and may generate aggregates when shear force is applied. Furthermore, when a composition for forming an immersion molded body is prepared using a conventional chloroprene polymer composition to produce an immersion molded body, the composition for forming an immersion molded body has low mechanical stability and may generate aggregates when shear force is applied. The present invention has been made in view of these circumstances, and provides a chloroprene polymer composition that can provide a composition for forming an immersion molded body that has high mechanical stability and generates little aggregates when shear force is applied.

[0006] According to the present invention, there is provided a chloroprene polymer latex composition comprising a chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms, wherein the total content of the aromatic compound having 7 to 10 carbon atoms in the chloroprene polymer latex composition is 0.00001 to 0.00290 parts by mass per 100 parts by mass of solids in the chloroprene polymer latex composition.

[0007] As a result of extensive investigations, the present inventors have found that by highly precisely adjusting the amount of aromatic compounds having 7 to 10 carbon atoms in a chloroprene polymer latex composition, a chloroprene polymer composition can be obtained that can give a composition for forming a dip-molded body having excellent mechanical stability, and have thus completed the present invention.

[0008] 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 and an aromatic compound having 7 to 10 carbon atoms, wherein the total content of the aromatic compound having 7 to 10 carbon atoms is 0.00001 to 0.00290 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer latex composition. [2] The chloroprene polymer latex composition according to [1], wherein the aromatic compound having 7 to 10 carbon atoms comprises at least one selected from the group consisting of toluene, ethylbenzene, xylene, and styrene. [3] A composition for forming a dip-molded body, comprising the chloroprene polymer latex composition according to [1] or [2]. [4] A dip-molded body made from the composition for forming a dip-molded body according to [3].

[0009] The chloroprene polymer composition according to the present invention has excellent mechanical stability, generates little aggregates when shear force is applied, and exhibits excellent uniform dispersibility and storage stability of the chloroprene polymer in the chloroprene polymer composition, and is therefore suitable for use, for example, as a composition for forming an immersion molded product. Furthermore, a composition for forming an immersion molded product containing the chloroprene polymer composition according to the present invention has excellent mechanical stability, generates little aggregates when shear force is applied, and exhibits excellent uniform dispersibility and storage stability of the chloroprene polymer. Furthermore, when the chloroprene polymer composition according to the present invention is mixed with a component containing a highly lipophilic compound to prepare a composition, the composition exhibits excellent mechanical stability, uniformity, and storage stability. Therefore, the application of the chloroprene polymer composition according to the present invention is not limited to compositions for forming immersion molded products, and the composition can also be used, for example, as a paint or adhesive composition.

[0010] 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.

[0011] 1. Chloroprene Polymer Latex Composition The chloroprene polymer latex composition according to the present invention contains a chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms, and the total content of the aromatic compound having 7 to 10 carbon atoms in the chloroprene polymer latex composition is 0.00001 to 0.00290 parts by mass relative to 100 parts by mass of the solid content in the chloroprene polymer latex composition.

[0012] 1.1 Chloroprene Polymer In the present invention, chloroprene polymer latex refers to a latex containing a chloroprene polymer. Furthermore, chloroprene polymer refers to a polymer containing monomer units derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene monomer), and includes homopolymers of chloroprene monomers and copolymers containing monomer units derived from chloroprene monomers and other monomers copolymerizable with chloroprene monomers. Examples of other monomers include 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, butadiene, isoprene, styrene, acrylonitrile, acrylic acid and its esters, and methacrylic acid and its esters.

[0013] The chloroprene-based polymer according to one embodiment of the present invention may include at least one of a homopolymer of a chloroprene monomer and a chloroprene-based polymer containing a chloroprene monomer unit and a 2,3-dichloro-1,3-butadiene monomer unit.

[0014] A chloroprene-based polymer 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-based polymer. 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. A chloroprene-based polymer according to one embodiment of the present invention may be a chloroprene homopolymer. Alternatively, a chloroprene-based 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.

[0015] When the chloroprene-based polymer according to one embodiment of the present invention includes chloroprene monomer units and 2,3-dichloro-1,3-butadiene monomer units, the 2,3-dichloro-1,3-butadiene monomer units may be contained in an amount of 1 to 30% 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 units may be, for example, 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. By controlling the content of 2,3-dichloro-1,3-butadiene monomer units within the above range, the dip-molded article obtained from the chloroprene polymer latex composition will have better flexibility.

[0016] 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.

[0017] The content of 2,3-dichloro-1,3-butadiene monomer units in a chloroprene polymer can be calculated by measuring a test piece of the chloroprene polymer obtained by freeze-drying a latex containing the chloroprene polymer by pyrolysis gas chromatography, determining the area ratio of the peak derived from chloroprene to the peak derived from 2,3-dichloro-1,3-butadiene, and using a calibration curve of the 2,3-dichloro-1,3-butadiene content. The content of each monomer unit in a chloroprene polymer can be controlled by adjusting the production conditions of the chloroprene polymer, for example, the types and amounts of raw materials blended.

[0018] The toluene-insoluble content of the chloroprene polymer according to one embodiment of the present invention may be 40 to 99% by mass, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99% by mass, and may be within a range between any two of the values ​​exemplified here.

[0019] 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-based polymer obtained by freeze-drying a latex containing a chloroprene-based polymer, the resulting chloroprene-based polymer is immersed in toluene for 16 hours, and the chloroprene-based polymer after freeze-drying is taken as Ag and Bg is the gel content (insoluble content) separated from the toluene-dissolved mixture.

[0020] The toluene-insoluble content can be controlled by adjusting the production conditions of the chloroprene polymer, specifically, the polymerization recipe, the type and amount of the chain transfer agent, the polymerization temperature, the polymerization time, the polymerization conversion rate, etc. By controlling the toluene-insoluble content within the above-mentioned range, the dip-molded article obtained from the chloroprene polymer latex composition has better tensile strength at break.

[0021] 1.2 Aromatic Compound Having 7 to 10 Carbon Atoms The chloroprene polymer latex composition according to the present invention contains an aromatic compound having 7 to 10 carbon atoms. Examples of the aromatic compound having 7 to 10 carbon atoms include toluene, o-xylene, m-xylene, p-xylene, styrene, ethylbenzene, 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene, cumene, 2-propyltoluene, 3-propyltoluene, 4-propyltoluene, 1,2-diethylbenzene, 1,3-diethylbenzene, and 1,4-diethylbenzene. The aromatic compound having 7 to 10 carbon atoms may include an aromatic compound in which one or more hydrogen atoms of the above-mentioned aromatic compounds have been substituted with a hydroxyl group, an amino group, a nitro group, a carbonyl group, a carboxyl group, an isocyanate group, or the like. The aromatic compound having 7 to 10 carbon atoms may also include an aromatic compound in which one or more hydrogen atoms of the above-mentioned aromatic compounds have been substituted with a halogen (chlorine atom, bromine atom, iodine atom, or fluorine atom). The aromatic compound having 7 to 10 carbon atoms may be an aromatic compound substituted with a substituent containing a carbon atom, such as salicylic acid or acetophenone, and may also include a compound having 6 carbon atoms before the substitution. The aromatic compound having 7 to 10 carbon atoms according to the present invention may include at least one selected from the group consisting of toluene, xylene, styrene, ethylbenzene, and aromatic compounds in which one of the hydrogen atoms of these compounds has been substituted, and may include at least one selected from the group consisting of toluene, xylene, styrene, and ethylbenzene.

[0022] The aromatic compound having 7 to 10 carbon atoms according to one embodiment of the present invention may have, for example, 7, 8, 9, or 10 carbon atoms, or may be within a range between any two of the numerical values ​​exemplified herein. The aromatic compound having 7 to 10 carbon atoms according to one embodiment of the present invention may have a molecular weight of 80 to 120. The aromatic compound having 7 to 10 carbon atoms according to one embodiment of the present invention may have, for example, 80, 85, 90, 95, 100, 105, 110, 115, or 120 carbon atoms, or may be within a range between any two of the numerical values ​​exemplified herein.

[0023] In the chloroprene polymer latex composition according to the present invention, the total content of the aromatic compounds having 7 to 10 carbon atoms relative to 100 parts by mass of the solid content in the chloroprene polymer latex composition is 0.00001 to 0.00290 parts by mass, and preferably 0.00002 to 0.00250 parts by mass. The total content of the aromatic compounds having 7 to 10 carbon atoms relative to 100 parts by mass of the solid content in the chloroprene polymer latex composition is, for example, 0.00001, 0.00002, 0.00003, 0.00004, 0.00005, 0.00010, 0.00020, 0.00030, 0.00040, 0.00050, 0.00060, 0.00070, 0.00080, 0.00090, 0.00100, 0.00110, 0.00120, 0.00130, 0.00140, 0.00150, 0.00160, 0.00170, 0.00180, 0.00190, 0.00200, 0.00210, 0.00220, 0.00230, 0.00240, 0.00250, 0.00260, 0.00270, 0.00280, 0.00290, 0.00290, 0.00290, 0.00250, 0.00260, 0.00270, 0.00280, 0.0029 0.00200, 0.00210, 0.00220, 0.00230, 0.00240, 0.00250, 0.00260, 0.00270, 0.00280, 0.00290 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0024] The chloroprene polymer latex composition according to the present invention is presumably improved in dispersibility of the chloroprene polymer latex in the chloroprene polymer latex composition due to the highly adjusted total content of aromatic compounds having 7 to 10 carbon atoms per 100 parts by mass of solids in the chloroprene polymer latex composition, resulting in excellent mechanical stability. Furthermore, the composition for forming immersion molded bodies according to the present invention contains a chloroprene polymer latex composition in which the total content of aromatic compounds having 7 to 10 carbon atoms is highly adjusted, resulting in a composition in which the chloroprene polymer and various chemicals contained in the composition for forming immersion molded bodies (e.g., a chemical agent exhibiting crosslinking function, a lipophilic chemical agent, etc.) are uniformly dispersed. This is presumably improved in mechanical stability of the composition for forming immersion molded bodies and in mechanical properties such as tensile strength at break of immersion molded bodies produced from the composition for forming immersion molded bodies.

[0025] The content of aromatic compounds having 7 to 10 carbon atoms per 100 parts by mass of solids in the chloroprene polymer latex composition can be analyzed by gas chromatography, and specifically, can be calculated by the method described in the Examples. The total content of aromatic compounds having 7 to 10 carbon atoms per 100 parts by mass of solids in the chloroprene polymer latex composition can be adjusted by adding an aromatic compound having 7 to 10 carbon atoms to the chloroprene polymer latex. Furthermore, when raw materials used in the polymerization of a chloroprene polymer may contain an aromatic compound having 7 to 10 carbon atoms, or when an aromatic compound having 7 to 10 carbon atoms may be generated as a by-product during the production of a chloroprene polymer, the content of aromatic compounds having 7 to 10 carbon atoms can be controlled by adjusting the production conditions of the chloroprene polymer, including the concentration conditions and dilution conditions of the chloroprene polymer latex.

[0026] In the chloroprene polymer latex composition according to one embodiment of the present invention, the total content of 4-chlorovinylbenzene, 2-methylbenzyl chloride, and 3-methylbenzyl chloride is preferably 0.00100 parts by mass or less relative to 100 parts by mass of the solid content in the chloroprene polymer latex composition. The total content of 4-chlorovinylbenzene, 2-methylbenzyl chloride, and 3-methylbenzyl chloride relative to 100 parts by mass of the solid content in the chloroprene polymer latex composition is, for example, 0, 0.00010, 0.00020, 0.00030, 0.00040, 0.00050, 0.00060, 0.00070, 0.00080, 0.00090, or 0.00100 parts by mass, and 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 total content of compounds in which one or more hydrogen atoms bonded to an aromatic ring are substituted with a chlorine atom or a substituent containing a chlorine atom can be within the above-mentioned range, and the total content of compounds in which one or more hydrogen atoms bonded to an aromatic ring are substituted with a halogen or a substituent containing a halogen can be within the above-mentioned range, relative to 100 parts by mass of the solid content of the chloroprene polymer latex composition.

[0027] The chloroprene polymer latex composition according to one embodiment of the present invention may be free of 4-chlorovinylbenzene, 2-methylbenzyl chloride, 3-methylbenzyl chloride, and 4-methylbenzyl chloride, and may be free of a compound in which one or more hydrogen atoms bonded to an aromatic ring are substituted with a chlorine atom, or a compound substituted with a substituent containing a chlorine atom. Furthermore, the chloroprene polymer latex composition according to one embodiment of the present invention may be free of a compound in which one or more hydrogen atoms bonded to an aromatic ring are substituted with a halogen, or a compound substituted with a substituent containing a halogen. For example, the content of these compounds containing chlorine or the like can be controlled by appropriately controlling the polymerization conditions for the chloroprene polymer to suppress the production of by-products.

[0028] The chloroprene polymer latex composition according to one embodiment of the present invention preferably has a solids concentration of 60% by mass and exhibits an aggregate generation rate (mechanical stability) of 0.25% by mass or less when subjected to a shear force of 10 minutes at a load of 10 kg and a rotation speed of 1,000 rpm. The aggregate generation rate of the chloroprene polymer latex composition is, for example, 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, or 0.25% by mass, and may be within a range between any two of the values ​​exemplified here. When the aggregate generation rate of the chloroprene polymer latex composition is within the above range, the mechanical stability of a composition for forming an immersion molded body containing the chloroprene polymer latex composition is further improved, and the mechanical properties, such as the tensile strength at break, of an immersion molded body produced from the composition for forming an immersion molded body are further improved.

[0029] The aggregate formation rate can be expressed by the following formula, and specifically, can be determined by the method described in the Examples. Aggregate formation rate (mechanical stability) (mass %)=Dry mass of aggregates [g] / Solid mass of chloroprene polymer latex composition [g]×100 The aggregate formation rate of the chloroprene polymer latex composition can be controlled, for example, by adjusting the production conditions of the chloroprene polymer, including the concentration conditions and dilution conditions of the chloroprene polymer latex, or by adjusting the presence or absence of addition of an aromatic compound having 7 to 10 carbon atoms and the amount of the aromatic compound to the chloroprene polymer latex, thereby adjusting the total content of the aromatic compound having 7 to 10 carbon atoms.

[0030] In a chloroprene polymer latex composition according to one embodiment of the present invention, when a test composition for forming an immersion molded body is prepared containing 2 parts by mass of two types of zinc oxide, 1 part by mass of sulfur, 2 parts by mass of zinc di-n-butyldithiocarbamate, 2 parts by mass of a butylated reaction product of p-cresol and dicyclopentadiene, and 0.1 part by mass of a sodium salt of a β-naphthalenesulfonic acid formalin condensate relative to 100 parts by mass of the solid content of the chloroprene polymer, the test composition for forming an immersion molded body preferably has an aggregate generation rate (mechanical stability) of 0.20% by mass or less when a shear force of a load of 10 kg and a rotation speed of 1,000 rpm is applied to the test composition for forming an immersion molded body for 10 minutes. The aggregate generation rate of the test composition for forming an immersion molded body is, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or 0.20% by mass, and may be within a range between any two of the values ​​exemplified here. When the aggregate generation rate of the composition for forming an immersion molded body is within the above-mentioned range, the uniformity, dispersibility, and stability of the composition for forming an immersion molded body itself are increased, and the mechanical properties such as the tensile strength at break of an immersion molded body produced from the composition for forming an immersion molded body are improved.

[0031] The method for evaluating the aggregate formation rate is as described for the aggregate formation rate of the chloroprene polymer latex composition, and specifically, it can be determined by the method described in the Examples. The aggregate formation rate of the composition for forming a dip-molded body can be controlled, for example, by adjusting the production conditions of the chloroprene polymer, including the concentration conditions and dilution conditions of the chloroprene polymer latex, or the presence or absence and amount of an aromatic compound having 7 to 10 carbon atoms added to the chloroprene polymer latex, thereby adjusting the total content of the aromatic compounds having 7 to 10 carbon atoms, and thereby adjusting the aggregate formation rate of the chloroprene polymer latex composition.

[0032] In the chloroprene polymer latex composition according to one embodiment of the present invention, a dip-molded body obtained by dip-molding a test dip-molded body composition having the above-described formulation by a dip coagulation method and then heat-drying the body at 130°C for 50 minutes preferably has a tensile strength at break of 20.0 MPa or more, more preferably greater than 21.0 MPa. The tensile strength at break of the dip-molded body is, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 MPa, and may be within a range between any two of the values ​​exemplified here. The tensile strength at break can be measured in accordance with JIS K 6251, and specifically, can be evaluated by the method described in the examples.

[0033] 2. Method for Producing Chloroprene Polymer Latex Composition The method for producing the chloroprene polymer latex composition according to the present invention is not particularly limited. The method for producing the chloroprene polymer latex composition according to one embodiment of the present invention may include a polymerization step of polymerizing raw material monomers containing chloroprene to obtain a chloroprene polymer latex containing a chloroprene polymer.

[0034] When producing a chloroprene polymer, raw material monomers are polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, or bulk polymerization. Among these polymerization methods, emulsion polymerization is preferred because it offers various advantages, such as ease of control, ease of polymer isolation from the polymerization-terminated liquid, and a relatively fast polymerization rate. A production method according to one embodiment of the present invention may include an emulsion polymerization step in which raw material monomers including chloroprene, and optionally 2,3-dichloro-1,3-butadiene and other monomers, are polymerized in the presence of an emulsifier to obtain a chloroprene polymer latex containing a chloroprene polymer. In the emulsion polymerization step, the raw material monomers are emulsion-polymerized using an emulsifier, a dispersant, a polymerization initiator, a chain transfer agent, a reducing agent, and the like, as appropriate. When the desired polymerization rate is reached, a polymerization terminator is added to obtain a chloroprene polymer latex. Furthermore, unreacted monomers may be removed by a concentration method such as vacuum distillation. Furthermore, one or more subsequent concentration and dilution steps may be performed.

[0035] (Raw Material Monomers) In the polymerization step, the raw material monomers include chloroprene and may include 2,3-dichloro-1,3-butadiene, and may further include other monomers copolymerizable with chloroprene (and 2,3-dichloro-1,3-butadiene). The other monomers are as described above as monomers that derive the monomer units that may be contained in the chloroprene-based polymer. The type and amount of each monomer charged are preferably adjusted so that the content of each monomer unit in the resulting chloroprene-based polymer falls within the above-described numerical range.

[0036] (Emulsifier) ​​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 may be 3.0 to 10.0 parts by mass per 100 parts by mass of the raw material monomer used. The amount of rosin acid and rosin acid salt added may be, for example, 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, or 10.0 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0037] 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.

[0038] 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.

[0039] (Chain Transfer Agent) In the emulsion polymerization step, it is preferable to add a chain transfer agent to adjust the molecular weight, molecular weight distribution, and toluene insoluble content of the chloroprene polymer. The chain transfer agent may be added at the beginning of polymerization or during polymerization. Preferred chain transfer agents are long-chain alkyl mercaptans such as n-dodecyl mercaptan and t-dodecyl mercaptan, and dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide. Long-chain alkyl mercaptans are more preferred because they facilitate control of the molecular weight and toluene insoluble content. The chain transfer agent can be used alone or in combination of two or more. The total amount of chain transfer agent added during emulsion polymerization is preferably 0.005 to 0.12 parts by mass per 100 parts by mass of the raw material monomers. The total amount of chain transfer agent added is, for example, 0.005, 0.01, 0.05, 0.10, 0.11, or 0.12 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0040] (Initiator) As the polymerization initiator, a conventional radical polymerization initiator can be used. Specifically, organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, ammonium persulfate, etc., and azo compounds such as azobisisobutyronitrile, etc., can be used. Furthermore, a co-catalyst such as anthraquinone sulfonate, potassium sulfite, sodium sulfite, etc. can be used in combination as appropriate.

[0041] (Potassium hydroxide and sodium hydroxide) In the emulsion polymerization step, sodium hydroxide and / or potassium hydroxide can be used. The amount of sodium hydroxide and potassium hydroxide can be 0.01 to 2.0 parts by mass per 100 parts by mass of the raw material monomers.

[0042] (Reducing Agent) In the emulsion polymerization step, a reducing agent can be added. Examples of the reducing agent include potassium pyrosulfite, potassium sulfite, potassium hydrogen sulfite, potassium phosphate, potassium hydrogen phosphate, sodium hydrogen sulfite, sodium sulfate, and thiourea dioxide. The amount of the reducing agent added can be 0.005 to 3.0 parts by mass per 100 parts by mass of the raw material monomers used in the polymerization step.

[0043] In a polymerization process according to one embodiment of the present invention, all of the raw material monomers and chemicals to be used in the polymerization process can be charged into the polymerization vessel before the start of polymerization, and then polymerization can be initiated. Alternatively, at least a portion of the raw material monomers and / or chemicals to be used in the polymerization process can be charged into the polymerization vessel before the start of polymerization, and the remainder can be added in portions after the start of polymerization. When at least a portion of the raw material monomers and chemicals are charged into the polymerization vessel before the start of polymerization, and the remaining raw material monomers and / or chemicals are added after the start of polymerization, the remaining raw material monomers and / or chemicals can be added in portions in one or more 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 portions after the start of polymerization.

[0044] (Polymerization Conversion Rate) The polymerization conversion rate of raw material monomers during emulsion polymerization of chloroprene-based polymers and the like is preferably 50% by mass or more but less than 90% by mass. The polymerization conversion rate (mass%) is calculated by [(polymer mass / total monomer mass) × 100]. Hereinafter, the polymerization conversion rate may also be simply referred to as the polymerization rate.

[0045] (Polymerization Temperature) The chloroprene polymer can be polymerized, for example, in the range of 0 to 50° C., and is particularly preferably polymerized at 5 to 45° C. The polymerization temperature is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50° C., and may be within a range between any two of the values ​​exemplified here.

[0046] (Polymerization Terminator) Generally, in the production of chloroprene polymers, a polymerization terminator is added to terminate the reaction when a predetermined polymerization rate is reached in order to obtain a polymer with a desired molecular weight and distribution. The polymerization terminator is not particularly limited, but examples thereof include phenothiazine, p-t-butylcatechol, hydroquinone, hydroquinone monomethyl ether, and diethylhydroxylamine.

[0047] Furthermore, to the latex containing a chloroprene polymer obtained by the production method according to one embodiment of the present invention, a freezing stabilizer, an emulsion stabilizer, a viscosity modifier, an antioxidant, a preservative, etc. may be optionally added after polymerization within a range that does not impair the effects of the present invention.

[0048] The latex containing a chloroprene polymer obtained after the chloroprene polymer polymerization step can be referred to as a chloroprene polymer latex. The chloroprene polymer latex according to one embodiment of the present invention can contain a chloroprene polymer obtained in the chloroprene polymer polymerization step and water. When the polymer contained in the chloroprene polymer according to the present invention is obtained by emulsion polymerization, the chloroprene polymer latex can further contain raw materials used in the emulsion polymerization step, such as an emulsifier.

[0049] A method for producing a chloroprene polymer latex according to one embodiment of the present invention may include a concentration step such as vacuum distillation. The concentration step can remove unreacted monomers and adjust the solids concentration of the chloroprene polymer latex. The production method according to one embodiment of the present invention may include one or more concentration steps. The concentration step may be, for example, one, two, three, four, or five times, or may be within a range between any two of the values ​​exemplified herein. The production method according to one embodiment of the present invention may include a dilution step by adding water, which dilutes the concentrations of the components in the chloroprene polymer latex and adjusts the solids concentration of the chloroprene polymer latex. The production method according to one embodiment of the present invention may include one or more dilution steps. The concentration step may be, for example, one, two, three, four, or five times, or may be within a range between any two of the values ​​exemplified herein. When raw materials, reagents, and the like used in polymerization of a chloroprene polymer are likely to contain an aromatic compound having 7 to 10 carbon atoms, or when an aromatic compound having 7 to 10 carbon atoms is likely to be generated as a by-product during production of a chloroprene polymer, the content of the aromatic compound having 7 to 10 carbon atoms can be controlled by adjusting the concentration conditions and number of concentration steps, or the dilution conditions and number of dilution steps of the chloroprene polymer latex.

[0050] (Solid Content Concentration) The solid content concentration of the chloroprene polymer latex is not particularly limited, but can be adjusted to 40 to 65 mass %. The solid content concentration of the chloroprene polymer latex can be controlled by adjusting the blending ratio including a solvent such as water during emulsion polymerization of the chloroprene polymer, or by performing a concentration process and a dilution process.

[0051] A method for producing a chloroprene polymer latex composition according to one embodiment of the present invention may include an aromatic compound addition step of adding an aromatic compound having 7 to 10 carbon atoms to the chloroprene polymer latex. The types of aromatic compounds to be added are as described above. In the aromatic compound addition step, the aromatic compound having 7 to 10 carbon atoms can be added so that the total content of the aromatic compound having 7 to 10 carbon atoms per 100 parts by mass of the solid content of the chloroprene polymer latex composition obtained falls within the above-described numerical range. For example, in the aromatic compound addition step, 0.00001 to 0.00290 parts by mass of the aromatic compound having 7 to 10 carbon atoms is added per 100 parts by mass of the solid content of the chloroprene polymer latex composition. The total amount of the aromatic compounds having 7 to 10 carbon atoms added is, for example, 0.00001, 0.00002, 0.00003, 0.00004, 0.00005, 0.00010, 0.00020, 0.00030, 0.00040, 0.00050, 0.00060, 0.00070, 0.00080, 0.00090, 0.00100, 0.00110, 0.00120, 0.00 The aromatic compound content is preferably 130, 0.00140, 0.00150, 0.00160, 0.00170, 0.00180, 0.00190, 0.00200, 0.00210, 0.00220, 0.00230, 0.00240, 0.00250, 0.00260, 0.00270, 0.00280, or 0.00290 parts by mass, and may be within a range between any two of the values ​​exemplified here. The method for producing a chloroprene polymer latex composition according to one embodiment of the present invention does not need to include the aromatic compound addition step.

[0052] In one embodiment of the present invention, a composition containing a chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms, obtained after performing the concentration step, dilution step, and / or aromatic compound addition step as necessary, can be referred to as a chloroprene polymer latex composition.

[0053] 3. Composition for Forming Impregnated Molded Products A composition for forming an immersion molded product according to one embodiment of the present invention includes the chloroprene polymer latex composition described above. The composition for forming an immersion molded product according to one embodiment of the present invention includes a chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms, and it is preferable that the total content of the aromatic compound having 7 to 10 carbon atoms is 0.00001 to 0.00290 parts by mass per 100 parts by mass of the solid content of the composition for forming an immersion molded product. The composition for forming an immersion molded product according to one embodiment of the present invention may also include a metal oxide, an antioxidant, and / or other necessary chemicals.

[0054] 3.1 Metal Oxide The composition for forming an immersion molded body according to one embodiment of the present invention may contain a metal oxide. There are no particular limitations on the metal oxide, and examples include 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. These metal oxides may be used alone or in combination of two or more.

[0055] The amount of metal oxide added is preferably 0.5 to 15.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer contained in the composition for forming immersion molded bodies. When the amount of metal oxide added is 0.5 parts by mass or more, an improvement in tensile strength at break is expected due to the crosslinking effect between the polymers. When the amount of metal oxide added is 15.0 parts by mass or less, an immersion molded body with excellent flexibility can be obtained. Furthermore, from the viewpoint of the balance of physical properties between flexibility and tensile strength at break of the obtained immersion molded body, the amount of metal oxide added is more preferably 0.5 to 5.0 parts by mass.

[0056] 3.2 Antioxidant The composition for forming a dip-molded body according to one embodiment of the present invention may also contain an antioxidant. The antioxidant is not particularly limited, and phenolic antioxidants, amine-based antioxidants, heat-resistant oxidation (aging) inhibitors, ozone-resistant antioxidants, etc. can be used. When the obtained dip-molded body is used as a medical glove, a phenolic antioxidant can be used from the viewpoint of the color tone, texture, and hygiene of the dip-molded body. In particular, hindered phenolic antioxidants have a strong effect as described above. 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 desirable from the viewpoint of general dispersibility in aqueous materials. Furthermore, these compounds may be used alone or in combination of two or more.

[0057] The amount of antioxidant added is preferably 0.5 to 10.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer contained in the composition for forming an immersion molded body. The amount of antioxidant 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. When the amount of antioxidant added is 0.5 parts by mass or more, the effect of suppressing color change in the immersion molded body can be obtained. When the amount of antioxidant added is 10.0 parts by mass or less, the stability of the composition for forming an immersion molded body can be ensured. Furthermore, from the viewpoint of the balance of physical properties between the flexibility and tensile strength at break of the obtained immersion molded body, the amount of antioxidant added is more preferably 0.5 to 5.0 parts by mass.

[0058] 3.3 Vulcanizing Agent and Vulcanization Accelerator The composition for forming a dip-molded body according to one embodiment of the present invention may also contain a vulcanizing agent and / or a vulcanization accelerator.

[0059] Examples of vulcanizing agents include, but are not limited to, sulfur. The amount of vulcanizing agent added can be 0 to 10.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer contained in the composition for forming a dip-molded body. The amount of vulcanizing agent added can be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within a range between any two of the values ​​exemplified here.

[0060] A vulcanization accelerator is a chemical added during the vulcanization of raw rubber to act with the vulcanizing agent to increase the vulcanization speed, thereby shortening the vulcanization time, lowering the vulcanization temperature, reducing the amount of vulcanizing agent, and improving the physical properties of the vulcanized rubber. It usually refers to a chemical that accelerates the sulfur vulcanization reaction.

[0061] Examples of vulcanization accelerators include, but are not limited to, thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, thiazole-based, etc. These may be used alone or in combination of two or more types as required.

[0062] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, and dipentamethylenethiuram tetrasulfide.

[0063] Examples of the dithiocarbamate vulcanization accelerator include sodium di-n-butyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, and tellurium diethyldithiocarbamate, and zinc di-n-butyldithiocarbamate is particularly preferred.

[0064] Examples of the thiourea-based vulcanization accelerator include ethylene thiourea, N,N'-diethyl thiourea, trimethyl thiourea, and N,N'-diphenyl thiourea.

[0065] Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salts of dicatechol borate.

[0066] Examples of xanthogenate-based vulcanization accelerators include zinc butylxanthogenate and zinc isopropylxanthogenate.

[0067] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, 2-mercaptobenzothiazole zinc salt, 2-mercaptobenzothiazole cyclohexylamine salt, and 2-(4'-morpholinodithio)benzothiazole.

[0068] The amount of the vulcanization accelerator added may be 0 to 5.0 parts by mass relative to 100 parts by mass of the solid content of the chloroprene polymer contained in the composition for forming a dip-molded body, and may be, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, or may be within a range between any two of the values ​​exemplified here.

[0069] Furthermore, the composition for forming a dip-molded body according to one embodiment of the present invention does not need to contain sulfur or the aforementioned vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, and thiazole-based. That is, the composition for forming a dip-molded body includes those containing a vulcanizing agent but not a vulcanization accelerator, those containing no vulcanizing agent but a vulcanization accelerator, those containing a vulcanizing agent and a vulcanization accelerator, and those containing no vulcanizing agent or a vulcanization accelerator. Whether or not a vulcanizing agent and a vulcanization accelerator are blended can be determined depending on the desired dip-molded body.

[0070] The dip-molded body composition according to one embodiment of the present invention may contain an emulsifier and / or a dispersant. Examples of the emulsifier and dispersant include those listed as emulsifiers and dispersants that can be used in the polymerization step in the method for producing a chloroprene polymer latex composition.

[0071] 4. Method for Producing a Composition for Dip-Molded Body A method for producing a composition for dip-molded body according to one embodiment of the present invention may include a raw material mixing step of mixing raw materials containing a chloroprene polymer, a metal oxide, an antioxidant, a vulcanizing agent, and other required chemicals. In the mixing step, an aqueous dispersion containing the metal oxide, the antioxidant, the vulcanizing agent, and other required chemicals may be prepared in advance, and then the chloroprene polymer latex composition and the aqueous dispersion may be mixed. The mixing step may be carried out using a known mixing device such as a ball mill.

[0072] 5. Dip-molded Article The dip-molded article according to one embodiment of the present invention can be a dip-molded article made from a composition for forming a dip-molded article comprising a chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms.

[0073] A dip-molded product according to one embodiment of the present invention can be obtained by dip-molding the above-described composition for forming a dip-molded product by a dip coagulation method, and then subjecting the dip-molded product to a heat-drying treatment at 130°C for 50 minutes, for example. The dip-molded product according to the present invention has excellent mechanical properties such as tensile strength at break. The dip-molded product according to one embodiment of the present invention can be suitably used as industrial or general household gloves, medical gloves, balloons, catheters, or boots.

[0074] The immersion molded product according to the present invention may contain the components contained in the composition for forming an immersion molded product described above. The immersion molded product may contain a chloroprene polymer as a base polymer, and may contain 70% by mass or more of the chloroprene polymer, preferably 80% by mass or more, and more preferably 90% by mass or more, of the chloroprene polymer, based on 100% by mass of the immersion molded product. The chloroprene polymer content in the immersion molded product, based on 100% by mass of the immersion molded product, may be, for example, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% by mass, or may be within a range between any two of the values ​​exemplified here.

[0075] The immersion molded article according to one embodiment of the present invention preferably has a tensile strength at break of 20.0 MPa or more, and more preferably greater than 21.0 MPa, as measured in accordance with JIS K 6251. The tensile strength at break is, for example, 20.0, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0, 30.0, 31.0, 32.0, 33.0, 34.0, 35.0, 36.0, 37.0, 38.0, 39.0, or 40.0 MPa, and may be within a range between any two of the values ​​exemplified here.

[0076] The thickness of the immersion molded body (e.g., the minimum thickness) may be 0.01 to 0.50 mm. The thickness of the immersion molded body 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 immersion molded body can be adjusted by the time for immersing the mold in the composition for forming an immersion molded body, the solids concentration of the composition for forming an immersion molded body, and the like. To reduce the thickness of the immersion molded body, the immersion time may be shortened or the solids concentration of the chloroprene polymer latex composition may be reduced.

[0077] 6. 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 a composition for forming a dip-molded article, which contains the above-described chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms, by an immersion coagulation method.

[0078] Examples of dip molding methods in one embodiment of the present invention include immersion solidification, simple immersion, thermal immersion, and electrodeposition. The immersion solidification 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, and the dip-molded body composition is solidified. After leaching to remove water-soluble impurities, the composition is dried, and then heated and vulcanized to form a dip-molded film (rubber film), which is then demolded. This allows for the production of a film-like dip-molded body.

[0079] The method for producing a dip-molded body according to one embodiment of the present invention can include a heat-drying step of heating and drying the dip-molded body.

[0080] The heating and drying temperature may be set appropriately depending on the composition of the chloroprene polymer, and may be 120 to 180°C. The heating temperature is preferably 120 to 150°C. The heating and drying temperature may be, for example, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, or 220°C, or may be within a range between any two of the values ​​exemplified here. The heating time may be set appropriately depending on the composition of the chloroprene polymer, the shape of the unvulcanized molded body, and the like, and may be 10 to 300 minutes. The heat drying 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, a dip-molded body according to one embodiment of the present invention may be one that has been subjected to a heat drying treatment at 130°C for 50 minutes.

[0081] 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.

[0082] (Production of Chloroprene Polymer Latex A) A 30 L polymerization vessel was charged with 90 parts by mass of chloroprene (monomer), 10 parts by mass of 2,3-dichloro-1,3-butadiene, 90 parts by mass of pure water, 17.6 parts by mass of gum rosin-based disproportionated potassium rosinate (aqueous solution) (trade name "LONDIS K-25" manufactured by Arakawa Chemical Industries, Ltd., solids content 25% by mass), 0.02 parts by mass of n-dodecyl mercaptan, 0.8 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 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 reached 83%, 0.1 parts by mass of diethylhydroxylamine, a polymerization terminator, was added to terminate the polymerization, yielding a polymerization solution. The polymerization solution was distilled under reduced pressure to remove unreacted monomers and concentrated to a solids concentration of 63% by mass (first concentration). Water was added to the polymerization solution to a solids concentration of 55% by mass, and the mixture was again concentrated to a solids concentration of 63% by mass (second concentration). Water was further added to the polymerization solution to a solids concentration of 55% by mass, and the mixture was again concentrated to obtain a chloroprene polymer latex A having a solids concentration of 60% by mass (third concentration). The toluene-insoluble content of the chloroprene polymer contained in the chloroprene polymer latex A was 83.2%.

[0083] (Production of Chloroprene Polymer Latex B) Polymerization was carried out in the same manner as in Example 1, except that in the production of chloroprene polymer latex A, chloroprene (monomer) was used in an amount of 100 parts by mass. The obtained polymerization liquid was distilled under reduced pressure to remove unreacted monomers, and then concentrated to obtain chloroprene polymer latex B having a solids concentration of 60% by mass. The toluene-insoluble content of the chloroprene polymer contained in chloroprene polymer latex B was 82.7%.

[0084] Example 1 A chloroprene polymer latex composition according to Example 1 was obtained by adding 0.00005 parts by mass of toluene to 100 parts by mass of the solid content of the chloroprene polymer latex A.

[0085] (Examples 2 to 10, Comparative Examples 1 and 2) Chloroprene polymer latex compositions were obtained in the same manner as in Example 1, except that the type of chloroprene polymer latex and the type and amount of the aromatic compound having 7 to 10 carbon atoms to be added were as shown in Table 1.

[0086] [Evaluation of Chloroprene Polymer Latex Composition] <Concentration and Content of Aromatic Compounds Having 7 to 10 Carbon Atoms> The aromatic compounds having 7 to 10 carbon atoms in the chloroprene polymer latex composition were analyzed by gas chromatography (headspace method). 0.03 g of the chloroprene polymer latex composition was placed in a tightly sealed vial, and measurement was performed under the following measurement conditions. (Gas chromatography conditions) Apparatus: GC-1700 (Shimadzu Corporation) Column: Pora PLOT U φ0.53 mm×25 m (film thickness 20 μm) Column temperature: 130° C. → 2° C. / min → 190° C. Inlet temperature: 180° C. Detector temperature: 190° C. Detector: FID Headspace sampler: TurboMatrix HS40 The concentration [ppm] of the aromatic compound having 7 to 10 carbon atoms in the chloroprene polymer latex composition was determined using a calibration curve of the area of ​​the peak attributable to the aromatic compound having 7 to 10 carbon atoms obtained by the measurement and the content of the aromatic compound having 7 to 10 carbon atoms. The results are shown in Table 1. From the determined concentration of the aromatic compound having 7 to 10 carbon atoms in the chloroprene polymer latex composition, the amount [parts by mass] of the aromatic compound having 7 to 10 carbon atoms per 100 parts by mass of the solid content in the chloroprene polymer latex composition was calculated using the following formula. The results are shown in Table 1. Amount [parts by mass] of the aromatic compound having 7 to 10 carbon atoms per 100 parts by mass of the solid content in the chloroprene polymer latex composition = 100 × (concentration of the aromatic compound having 7 to 10 carbon atoms [ppm]) / 1,000,000 × 100 / (solid content concentration of the chloroprene polymer latex composition [% by mass])

[0087] <Mechanical Stability> Using a Marlon testing apparatus, a shear force of 10 kg load and 1,000 rpm was applied to 50 g of a chloroprene polymer latex composition having a solid content of 60% by mass for 10 minutes, and the amount of aggregates generated was evaluated. After applying the shear force under the above conditions, the aggregates adhering to the rotor of the Marlon testing apparatus were collected on a SUS80 mesh wire screen, washed with pure water, dried under reduced pressure, and then their mass was measured. The aggregate generation rate was calculated from the measured dry mass of the aggregates using the following formula to provide an index of mechanical stability. A smaller value for the aggregate generation rate indicates better stability against shear force and better mechanical stability. Aggregate generation rate (mechanical stability) (mass %) = dry mass of aggregates [g] / solid mass of chloroprene polymer latex composition [g] × 100

[0088] <Toluene-Insoluble Content of Chloroprene Polymer> The toluene-insoluble content of the chloroprene polymer contained in each chloroprene polymer latex composition was determined by the following method. First, a chloroprene polymer obtained by freeze-drying the chloroprene polymer latex was 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, a gel fraction (insoluble content) 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-insoluble content of the chloroprene polymer was determined by the following formula, where Ag is the chloroprene polymer after freeze-drying and B g is the gel fraction (insoluble content) separated from the mixture dissolved in toluene. Toluene-insoluble content (gel content) = B / A × 100 (%)

[0089] [Evaluation of Compositions for Dip-Molded Products] <Preparation of Compositions for Dip-Molded Products> 100 parts by mass of the solid content of each chloroprene polymer latex composition was mixed with an aqueous dispersion, and water was added to adjust the overall solid content of the blend to 30% by mass. The aqueous dispersion was prepared by mixing 2 parts by mass of two zinc oxides, 1 part by mass of sulfur, 2 parts by mass of zinc di-n-butyldithiocarbamate (ZnBDC), 2 parts by mass of a butylated reaction product of p-cresol and dicyclopentadiene (Nocrac PBK, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.1 parts by mass of a sodium salt of β-naphthalenesulfonic acid formalin condensate (Demol N, manufactured by Kao Corporation), and 11 parts by mass of water in a ceramic ball mill at 20°C for 16 hours. The obtained composition for forming a dip-molded body contains, relative to 100 parts by mass of the solid content of the chloroprene polymer, 2 parts by mass of two types of zinc oxide, 1 part by mass of sulfur, 2 parts by mass of zinc di-n-butyldithiocarbamate (Noccela BZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 2 parts by mass of a butylated reaction product of p-cresol and dicyclopentadiene (Nocrac PBK, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.1 parts by mass of a sodium salt of a β-naphthalenesulfonic acid formalin condensate (Demol N, manufactured by Kao Corporation), and water.

[0090] <Mechanical Stability> Using a Marlon testing apparatus, a shear force of 10 kg load and 1,000 rpm was applied to 50 g of the composition for forming a dip-molded body for 10 minutes, and the amount of aggregates generated was evaluated. After applying the shear force under the above conditions, the aggregates attached to the rotor of the Marlon testing apparatus were collected on a SUS80 mesh wire screen, washed with pure water, dried under reduced pressure, and then their mass was measured. The aggregate generation rate was calculated from the measured dry mass of the aggregates using the following formula to serve as an index of mechanical stability. A smaller value for the aggregate generation rate indicates better stability against shear force and better mechanical stability. Aggregate generation rate (mechanical stability) (mass %) = dry mass of aggregates [g] / solid mass of chloroprene polymer latex composition [g] × 100

[0091] [Evaluation of Immersion Molded Body] <Preparation of Immersion Molded Body> A ceramic cylindrical mold (manufactured by Shinko Co., Ltd.) 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 potassium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate, and then removed. After drying for 3 minutes, the molded body was immersed for 2 minutes in the composition for forming an immersion molded body prepared by the procedure described above. The molded body was then washed with running water at 45°C for 1 minute and dried at 130°C for 50 minutes to prepare an immersion molded body.

[0092] (Film Thickness) The thickness (film thickness) of the dip-molded article 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 film thickness of the dip-molded article. The results are shown in Table 1.

[0093] <Measurement of Tensile Properties> Using the dip-molded body, the tensile strength at break was measured according to JIS K 6251.

[0094]

Claims

1. A chloroprene polymer latex composition comprising a chloroprene polymer and an aromatic compound having 7 to 10 carbon atoms, wherein the total content of the aromatic compound having 7 to 10 carbon atoms is 0.00001 to 0.00290 parts by mass per 100 parts by mass of solids in the chloroprene polymer latex composition.

2. The chloroprene polymer latex composition according to claim 1, wherein the aromatic compound having 7 to 10 carbon atoms comprises at least one selected from the group consisting of toluene, ethylbenzene, xylene, and styrene.

3. A composition for forming a dip-molded product, comprising the chloroprene polymer latex composition according to claim 1 or 2.

4. A dip-molded body made from the composition for forming a dip-molded body according to claim 3.

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