Method for producing chloroprene seed polymer composition, and method for producing impregnated rubber product

Abstract

One embodiment of the present invention relates to a method for producing a chloroprene seed polymer composition, the method comprising a first polymerization step and a second polymerization step, the first polymerization step is a step for obtaining a chloroprene polymer by subjecting at least a chloroprene monomer to emulsion radical polymerization. The second polymerization step is a step in which at least a specific monomer (B-1) or (B-2) is subjected to emulsion seed polymerization with the chloroprene polymer in an amount of 3-20 parts by mass per 100 parts by mass of the total of the chloroprene polymer and the monomer (B-1) or (B-2).

Description

Technical Field

[0001] One embodiment of the present invention relates to a method for manufacturing a chloroprene seed polymer composition or a method for manufacturing a rubber-impregnated product. Background Technology

[0002] Materials made from chloroprene (2-chloro-1,3-butadiene) polymer latexes have good general rubber properties, weather resistance, heat resistance, and chemical resistance, and are therefore widely used in applications such as gloves (impregnation), adhesives and bonding agents, elastic asphalt (modified asphalt), and elastic cement in civil engineering and construction.

[0003] In the use of disposable medical gloves, especially surgical gloves, anaphylaxis caused by allergies to natural rubber poses a serious hygiene and life-threatening problem for both patients and medical professionals. To address this issue, chloroprene rubber (hereinafter referred to as "CR"), which has softness and mechanical properties close to natural rubber and is relatively inexpensive, is used as the material for surgical gloves. Specifically, chloroprene rubber has the advantages of a close fit (comfort) similar to natural rubber and excellent responsiveness (follow-me-notch) to the fine movements of the fingertips.

[0004] Methods for improving softness in surgical gloves by using chloroprene-based polymer latex have been proposed (e.g., Patent Document 1, Patent Document 2, etc.).

[0005] However, due to the insufficient polymer structure in traditional chloroprene rubber latex, the use of vulcanization accelerators was indispensable to obtain vulcanized rubber with the target strength. In recent years, gloves made of synthetic rubber have also caused contact dermatitis, a condition known as type IV allergy, caused by vulcanization accelerators used in molding chloroprene latex. Therefore, there is an increasing demand for gloves that do not contain vulcanization accelerators that are allergens associated with type IV allergies.

[0006] Due to such demand, rubber compositions containing chloroprene-based polymer latex have been proposed, which can crosslink with chloroprene rubber suitable for applications such as surgical gloves without the use of vulcanization accelerators (e.g., Patent Document 3, etc.).

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2007-106994

[0010] Patent Document 2: Japanese Patent Publication No. 2009-501833

[0011] Patent Document 3: International Publication No. 2016 / 166998 Summary of the Invention

[0012] Inventions aim to solve problems.

[0013] In the case of Patent Document 1, the use of a vulcanization accelerator is necessary, and the problem of type IV allergy remains unresolved.

[0014] In addition, in the case of Patent Document 2, there are problems with the mechanical properties of the rubber. For example, it is difficult to form a film when the concentration of solid components is low, and when the concentration of solid components is high, the storage stability of the compound deteriorates, it is easy to aggregate, and it damages the appearance of the product.

[0015] Furthermore, in the case of Patent Document 3, the mechanical properties of the rubber were improved by adjusting the amount of tetrahydrofuran-insoluble components in the chloroprene polymer latex, but the solution to improve the physical properties of chloroprene rubber without using vulcanization accelerators is limited.

[0016] The present invention was made in view of the above circumstances, and its object is to provide a method for manufacturing a chloroprene polymer composition capable of forming molded articles with excellent strength and rubber elasticity.

[0017] Problem-solving methods

[0018] In order to solve the problem, the inventors conducted in-depth research and found that the molded article obtained from a composition containing chloroprene seed polymer latex (chloroprene seed polymer composition) obtained by a specific manufacturing method can solve the above-mentioned problem.

[0019] That is, the embodiments of the present invention are shown below [1] to [7].

[0020] [1]. A method for manufacturing a chloroprene seed polymer composition, comprising a first polymerization step and a second polymerization step, characterized in that,

[0021] The first polymerization step is a step in which chloroprene monomer is subjected to emulsion free radical polymerization to obtain chloroprene polymer.

[0022] The second polymerization step is a step of emulsion seed polymerization of a monomer (B-2) having a glass transition temperature or melting point of at least 30°C or higher than that of the homopolymer with the chloroprene polymer in an amount of 3 to 20 parts by mass relative to a total of 100 parts by mass of the chloroprene polymer and the monomer (B-2).

[0023] [2]. A method for manufacturing a chloroprene seed polymer composition, comprising a first polymerization step and a second polymerization step, characterized in that,

[0024] The first polymerization step is a step in which chloroprene monomer is subjected to emulsion free radical polymerization to obtain chloroprene polymer.

[0025] The second polymerization step is a step of emulsion seed polymerization of a (meth)acrylate monomer (B-1) having an alkyl group having 1 to 4 carbon atoms and the straight chain of the alkyl group having 3 or fewer carbon atoms, with the chloroprene polymer in an amount of 3 to 20 parts by mass relative to a total of 100 parts by mass of the chloroprene polymer and the monomer (B-1).

[0026] [3]. The method for manufacturing the chloroprene seed polymer composition as described in [1], wherein the monomer (B-2) is ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate or 2,3-dichloro-1,3-butadiene.

[0027] [4]. The method for manufacturing the chloroprene seed polymer composition as described in [2], wherein the monomer (B-1) is ethyl methacrylate, methyl methacrylate, isobutyl methacrylate or tert-butyl methacrylate.

[0028] [5]. A method for manufacturing a rubber-impregnated product, wherein the rubber-impregnated product is manufactured using a chloroprene seed polymer composition obtained by any one of the manufacturing methods [1] to [4].

[0029] [6]. The method for manufacturing a rubber-impregnated product as described in [5], wherein the rubber-impregnated product is a glove.

[0030] [7]. The method for manufacturing rubber-impregnated products as described in [6], wherein the gloves are medical disposable gloves.

[0031] Invention Effects

[0032] According to one embodiment of the present invention, a chloroprene seed polymer latex with a specific structure is obtained, and the molded articles obtained from the composition containing the polymer latex have excellent strength and rubber elasticity.

[0033] Furthermore, the composition obtained by the manufacturing method according to one embodiment of the present invention can fully exert the above-mentioned effects even without the presence of vulcanization accelerators that cause type IV allergies. Therefore, it is suitable for use in molded products that require avoidance of type IV allergies, such as gloves, blood pressure cuffs, and rubber-impregnated articles. Detailed Implementation

[0034] The following is a detailed description of matters related to the implementation method. Furthermore, in this specification, the numerical range indicated by “~” means that the values ​​before and after the “~” are considered as lower and upper limits.

[0035] The following describes in detail a method for manufacturing a chloroprene seed polymer composition and a method for manufacturing a rubber-impregnated product according to one embodiment of the present invention. Furthermore, this embodiment is merely an example illustrating the present invention, and the present invention is not limited to this embodiment. Various modifications or improvements can be made to this embodiment, and such modifications or improvements are also included in the present invention.

[0036] Method for manufacturing chloroprene seed polymer compositions

[0037] A method for manufacturing a chloroprene seed polymer composition according to an embodiment of the present invention comprises a first polymerization step for obtaining a chloroprene polymer latex and a second polymerization step for obtaining a chloroprene seed polymer latex.

[0038] Generally, "latex" refers to a lipophilic substance that has been emulsified by an emulsifier and dispersed as particles in water. In this embodiment, the chloroprene polymer latex or chloroprene seed polymer latex is a substance in which chloroprene polymer or chloroprene seed polymer particles are dispersed in water.

[0039] <First Polymerization Process>

[0040] The first polymerization step is a step in which at least one chloroprene monomer (hereinafter also referred to as "monomer (A-1)") is subjected to emulsion free radical polymerization to synthesize a chloroprene polymer. This yields a chloroprene polymer latex in which the chloroprene polymer particles are dispersed in water. In the first polymerization step, monomer (A-2) may be used in conjunction with monomer (A-1).

[0041] Chloroprene polymers can be homopolymers of monomer (A-1) or copolymers of monomer (A-1) and monomer (A-2).

[0042] As a monomer (A-2), it is not particularly limited to any monomer that can copolymerize with chloroprene (2-chloro-1,3-butadiene). Examples include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, 1,3-butadiene, isoprene, styrene, methacrylic acid, acrylic acid, itaconic acid, 2-ethylhexyl methacrylate, and butyl acrylate. Preferred monomers are 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, 1,3-butadiene, methacrylic acid, and acrylic acid.

[0043] The monomer (A-2) can be used alone or in combination with two or more monomers.

[0044] When using monomer (A-2), there is no particular limitation on the ratio of monomer (A-1) to monomer (A-2). When the total amount of monomer (A-1) and monomer (A-2) used is 100% by mass, the preferred ratio of monomer (A-1) is 70 to 99.9% by mass, more preferably 90 to 99% by mass, and the preferred ratio of monomer (A-2) is 0.1 to 30% by mass, more preferably 1 to 10% by mass.

[0045] Chloroprene polymers, specifically, can be synthesized by adding an emulsifier and water to a monomer (A-1) and a monomer (A-2) to obtain an aqueous emulsion, and then adding a polymerization initiator to it to carry out a free radical polymerization reaction.

[0046] Examples of emulsifiers used in the first polymerization step include anionic emulsifiers and nonionic emulsifiers.

[0047] As anionic emulsifiers, specific examples include alkali metal salts of disproportionated rosin acid; sodium dodecylbenzene sulfonate, triethanolamine dodecylbenzene sulfonate, and other dodecylbenzene sulfonates; sodium diphenyl ether sulfonate, ammonium diphenyl ether sulfonate, and other diphenyl ether sulfonates; sodium salt of β-naphthalene sulfonic acid formaldehyde condensate and other naphthalene sulfonates; and alkali metal salts of fatty acids such as potassium laurate.

[0048] As nonionic emulsifiers, examples include some saponified polyvinyl alcohol, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene lauryl ether.

[0049] As an emulsifier in the first polymerization step, an anionic emulsifier is preferred, and more preferably an alkali metal salt (sodium or potassium salt) or naphthalene sulfonate of disproportionated rosin acid.

[0050] Emulsifiers can be used alone or in combination with two or more.

[0051] The amount of emulsifier added in the first polymerization step is preferably 1 to 10 parts by mass relative to 100 parts by mass of monomer components, and more preferably 3 to 8.5 parts by mass.

[0052] In addition, regarding "monomer components in the first polymerization process", when monomer (A-1) is used alone, it refers to monomer (A-1), and when monomer (A-2) is used together, it refers to the total of monomer (A-1) and monomer (A-2).

[0053] The polymerization temperature of the first polymerization step is preferably 10–50°C, more preferably 15–45°C. If the polymerization temperature is within this range, agglomerates are less likely to form, and the film-forming properties of the resulting chloroprene seed polymer latex and the strength of the molded product are easily maintained. Furthermore, if the polymerization temperature is within this range, polymerization proceeds rapidly, thus enabling efficient production of chloroprene polymer latex.

[0054] There are no particular restrictions on the polymerization initiator in the first polymerization step; general free radical polymerization initiators can be used.

[0055] Examples of free radical polymerization initiators include organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, ammonium persulfate, cumene hydrogen peroxide, and tert-butyl hydrogen peroxide; and azo compounds such as azobisisobutyronitrile.

[0056] Polymerization initiators can be used alone or in combination with two or more.

[0057] The amount of polymerization initiator added in the first polymerization step is preferably 0.001 to 2.0 parts by mass relative to 100 parts by mass of monomer components, more preferably 0.01 to 0.5 parts by mass.

[0058] In the first polymerization step, a co-catalyst can also be used in conjunction with the polymerization initiator. There are no particular limitations on the co-catalyst; any general co-catalyst can be used.

[0059] Examples of co-catalysts include anthraquinone sulfonates, potassium sulfite, sodium bisulfite, sodium sulfite, tetraethylenepentamine, and N,N-dimethyl-p-toluidine.

[0060] One type of catalyst can be used alone, or two or more types can be used in combination.

[0061] When a co-catalyst is used in the first polymerization step, the amount of co-catalyst added is preferably 0.0001 to 5.0 parts by mass relative to 100 parts by mass of monomer components, more preferably 0.0005 to 0.50 parts by mass.

[0062] In the first polymerization step, a molecular weight regulator may be added to obtain a chloroprene polymer with the desired molecular weight and molecular weight distribution. There are no particular limitations on the molecular weight regulator; general chain transfer agents can be used.

[0063] Examples of molecular weight regulators include diisopropyl xanthate disulfide, diethyl xanthate disulfide, dicyclohexyl xanthate disulfide, dilauryl xanthate disulfide, dibenzyl xanthate disulfide, and other disulfide xanthates; alkyl thiols such as dodecyl thiols, decyl thiols, and octyl thiols, with alkyl thiols being preferred.

[0064] As a molecular weight regulator, it can be used alone or in combination with two or more.

[0065] When a molecular weight regulator is used in the first polymerization step, the amount of the molecular weight regulator added is preferably 0.01 to 0.1 parts by mass relative to 100 parts by mass of the monomer component, more preferably 0.03 to 0.08 parts by mass.

[0066] The monomer conversion rate in the first polymerization step is preferably 60% to 100%. Furthermore, regarding the monomer conversion rate in the first polymerization step, when monomer (A-1) is used alone, it refers to the conversion rate of monomer (A-1); when monomer (A-2) is used in combination, it refers to the combined conversion rate of monomer (A-1) and monomer (A-2). If the conversion rate is within the above range, a chloroprene polymer latex with the solids concentration described later can be easily obtained, and it has the ability to suppress the tendency for unreacted monomer (A-1) or monomer (A-2) residues to generate odor, or to suppress the tendency for the film-forming properties of the obtained chloroprene seed polymer latex or the reduction in the strength of the molded product. In addition, it can suppress the reaction of unreacted monomer (A-1) and monomer (A-2) in the subsequent second polymerization step, which could cause sudden exothermic reactions. Furthermore, after the first polymerization step, it is not necessary to remove unreacted volatile components (e.g., unreacted monomer (A-1) and monomer (A-2)), or even if removal is performed, a light-load treatment is sufficient.

[0067] At the end of the polymerization reaction in the first polymerization step, in order to obtain a chloroprene polymer with the desired molecular weight and molecular weight distribution, a polymerization stop agent can be added when the specified polymerization rate is reached to stop further polymerization reactions.

[0068] There are no particular limitations on polymerization stoppers. Specific examples include phenothiazine, p-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, diethylhydroxylamine, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxo radical.

[0069] As a polymerization stopper, one type can be used alone, or two or more types can be used in combination.

[0070] When a polymerization stop agent is used in the first polymerization step, the amount of polymerization stop agent added is preferably 0.001 to 5 parts by mass relative to 100 parts by mass of monomer components, more preferably 0.01 to 3 parts by mass.

[0071] The process may include a step to remove unreacted volatile components (e.g., unreacted monomers (A-1) and (A-2)) after the first polymerization step and before the second polymerization step.

[0072] There are no particular limitations on any known method for removing unreacted volatile components, but steam stripping is preferred from the viewpoint that it is possible to easily obtain chloroprene polymer latex with the solid component concentration described later.

[0073] The solids concentration of the chloroprene polymer latex obtained from the first polymerization step is preferably 35 to 65% by mass. If the solids concentration is within the above range, it is easier to maintain the colloidal stability of the chloroprene polymer latex and to minimize the formation of agglomerates.

[0074] In addition, in this invention, the solid content concentration of chloroprene polymer latex and chloroprene seed polymer latex described later is determined by the method described in the examples described later.

[0075] Furthermore, the content of tetrahydrofuran-insoluble components (tetrahydrofuran-insoluble component rate) in the chloroprene polymer latex is not particularly limited, but from the viewpoint that the target chloroprene seed polymer latex can be easily prepared in the second polymerization process, it is preferably 10 to 99.9% by mass relative to 100% by mass of the chloroprene polymer, more preferably 20 to 99% by mass, and even more preferably 30 to 95% by mass.

[0076] Here, "tetrahydrofuran-insoluble components" refers to gel-like substances that are insoluble in tetrahydrofuran, and are hard and lack elasticity.

[0077] The content of tetrahydrofuran-insoluble components in chloroprene polymer latex can be controlled by the types of emulsifiers and polymerization initiators used in the first polymerization step, as well as the types of molecular weight regulators and polymerization stoppers used as needed, polymerization temperature, monomer conversion rate, and other polymerization conditions.

[0078] In addition, in this invention, the percentage of tetrahydrofuran-insoluble components in chloroprene polymer latex and chloroprene seed polymer latex described later is determined by the method described in the examples described later.

[0079] <Second Polymerization Process>

[0080] The second polymerization step involves emulsion seeding polymerization of a monomer containing a carbon-carbon double bond (hereinafter referred to as "monomer (B)") on the chloroprene polymer obtained in the first polymerization step to synthesize a chloroprene seed polymer, thereby obtaining a chloroprene seed polymer latex in which the particles of the chloroprene seed polymer are dispersed in water.

[0081] The chloroprene polymer obtained from the first polymerization step has carbon-carbon double bonds in its main chain, originating from monomer (A-1) or (A-2). Therefore, since monomer (B) has carbon-carbon double bonds, the carbon-carbon double bonds in the chloroprene polymer can react with the carbon-carbon double bonds in monomer (B) to carry out seed polymerization.

[0082] The polymer obtained through seed polymerization has a core particle (e.g., a chloroprene polymer) coated with a layer (shell) of polymer (e.g., a polymer obtained by polymerizing monomer (B)), becoming a particle (seed polymer) with a core / shell structure. The structure of the particle can be confirmed by, for example, scanning probe microscopy (SPM) measurements.

[0083] (First Implementation)

[0084] In a first embodiment of the present invention, the second polymerization step involves emulsion seed polymerization of a (meth)acrylate monomer (B-1) having at least 1 to 4 alkyl groups as monomer (B) and the straight chain of the alkyl group having 3 or fewer carbon atoms.

[0085] The amount of monomer (B-1) used in the second polymerization step is 3 to 20 parts by mass relative to the total of 100 parts by mass of the chloroprene polymer and monomer (B-1), preferably 4 to 15 parts by mass, and more preferably 5 to 10 parts by mass. When monomer (B-1) is used within the above range, it is easy to obtain a chloroprene seed polymer having structural units derived from monomer (B-1) within the range described later.

[0086] The conversion rate of monomer (B-1) in the second polymerization step is preferably 70-100%, and more preferably 75-100%. If the conversion rate is within the above range, a chloroprene seed polymer having structural units derived from monomer (B-1) within the range described later can be easily obtained. Furthermore, a chloroprene seed polymer latex having the solids content described later can be easily obtained. Moreover, it tends to suppress the emission of odor due to unreacted monomer (B-1) residue, and to suppress the film-forming properties of the obtained chloroprene seed polymer latex and the reduction in the strength of the molded product. Additionally, after the second polymerization step, it is not necessary to remove unreacted components (e.g., unreacted chloroprene polymer or monomer (B-1)), or even if removal is performed, a light-load treatment is sufficient.

[0087] The chloroprene seed polymer obtained in this embodiment preferably contains 3 to 20% by mass of structural units derived from monomer (B-1), more preferably 5 to 10% by mass.

[0088] It can be considered that chloroprene seed polymers containing monomer (B-1) within the above-mentioned range can fully maintain the strength and flexibility of the resulting molded articles because the properties of the chloroprene polymer in the core portion of the core / shell structure can be exerted without damage to the shell portion. Furthermore, it can be considered that because the core / shell structure allows for sufficient interparticle crosslinking, the polymer latex has excellent film-forming properties, and the resulting molded articles exhibit excellent rubber elasticity.

[0089] (Meth)acrylates are of the general formula CH2=CR 1 -CO-OR 2 The compound represented by the general formula, R 1 R represents a methyl or hydrogen atom. 2 The alkyl group refers to an alkyl group having 1 to 4 carbon atoms, and the straight chain of the alkyl group has 3 or fewer carbon atoms. Furthermore, in this specification, "(meth)acrylate" refers to methacrylates and / or acrylates, and "(meth)acrylic acid" refers to methacrylic acid and / or acrylic acid.

[0090] Examples of monomers (B-1) include, for example, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-propyl methacrylate, n-propyl acrylate, isopropyl methacrylate, isopropyl acrylate, isobutyl methacrylate, isobutyl acrylate, tert-butyl methacrylate, and tert-butyl acrylate. Methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, isobutyl methacrylate, or tert-butyl methacrylate are preferred, and ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, or tert-butyl methacrylate are more preferred.

[0091] As a monomer (B-1), it can be used alone or in combination with two or more.

[0092] In the second polymerization step, monomers other than monomer (B-1) may be copolymerized without compromising the effects of the present invention.

[0093] Other monomers besides monomer (B-1) include, for example, chloroprene, 2,3-dichloro-1,3-butadiene, vinyl chloride, styrene, acrylonitrile, acrylic acid, methacrylic acid, n-butyl methacrylate, n-butyl acrylate, and (meth)acrylates having alkyl groups having 5 to 12 carbon atoms, with chloroprene being preferred.

[0094] (Second Implementation)

[0095] In a second embodiment of the present invention, in the second polymerization step, a monomer (B-2) having a glass transition temperature (Tg) or melting point (Tm) of at least 30°C or higher is used as monomer (B) for emulsion seed polymerization.

[0096] The lower limit of Tg or Tm of the homopolymer of monomer (B-2) is preferably above 40°C, more preferably above 60°C, and even more preferably above 80°C. There is no particular limitation on the upper limit, but it is preferably below 180°C, more preferably below 150°C, and even more preferably below 135°C.

[0097] The amount of monomer (B-2) used in the second polymerization step is 3 to 20 parts by mass relative to the total of 100 parts by mass of the chloroprene polymer and monomer (B-2), preferably 4 to 15 parts by mass, and more preferably 5 to 10 parts by mass. When monomer (B-2) is used within the above range, it is easy to obtain a chloroprene seed polymer having structural units derived from monomer (B-2) within the range described later.

[0098] The conversion rate of monomer (B-2) in the second polymerization step is preferably 70-100%, and more preferably 75-100%. If the conversion rate is within the above range, a chloroprene seed polymer having structural units derived from monomer (B-2) within the range described later can be easily obtained. Furthermore, a chloroprene seed polymer latex having the solids content described later can be easily obtained. Moreover, it tends to suppress odors emitted due to unreacted monomer (B-2) residues, and to suppress the reduction in film-forming properties and strength of the obtained chloroprene seed polymer latex. Additionally, after the second polymerization step, it is not necessary to remove unreacted components (e.g., unreacted chloroprene polymer or monomer (B-2)), or even if removal is performed, a light-load treatment is sufficient.

[0099] The chloroprene seed polymer obtained in this embodiment preferably contains 3 to 20% by mass of structural units derived from monomer (B-2), more preferably 5 to 10% by mass.

[0100] It can be considered that chloroprene seed polymers containing monomer (B-2) within the above-mentioned range can fully maintain the strength and flexibility of the resulting molded articles because the properties of the chloroprene polymer in the core portion of the core / shell structure can be exerted without damage to the shell portion. Furthermore, it is believed that because the core / shell structure allows for sufficient interparticle crosslinking, the polymer latex has excellent film-forming properties, and the resulting molded articles exhibit excellent rubber elasticity.

[0101] Examples of monomers (B-2) include 2,3-dichloro-1,3-butadiene (homopolymer Tm: 130℃), vinyl chloride (homopolymer Tg: 87℃), styrene (homopolymer Tg: 100℃), acrylonitrile (homopolymer Tg: 104℃), methyl methacrylate (homopolymer Tg: 90-100℃), ethyl methacrylate (homopolymer Tg: 65℃), isobutyl methacrylate (homopolymer Tg: 50-60℃), tert-butyl methacrylate (homopolymer Tg: 107℃), acrylic acid (homopolymer Tg: 106℃), and so on. Acrylic acid (Tg: 185℃ for homopolymer), preferably 2,3-dichloro-1,3-butadiene, vinyl chloride, styrene, acrylonitrile, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate or methacrylic acid, more preferably 2,3-dichloro-1,3-butadiene, vinyl chloride, styrene, acrylonitrile, methyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate or methacrylic acid, and even more preferably 2,3-dichloro-1,3-butadiene, ethyl methacrylate, methyl methacrylate, isobutyl methacrylate or tert-butyl methacrylate.

[0102] The monomer (B-2) can be used alone or in combination with two or more monomers.

[0103] In this specification, the Tg of the homopolymer is the temperature obtained by the method described in JIS K 7121:2012.

[0104] In addition, in this specification, the Tm of the homopolymer is the temperature obtained by the method described in JIS K0064:1992.

[0105] In the second polymerization step, monomers other than monomer (B-2) may be copolymerized without impairing the effects of the present invention.

[0106] Other monomers besides monomer (B-2) include, for example, chloroprene, methyl acrylate, ethyl acrylate, n-butyl methacrylate, and 2-ethylhexyl acrylate, with chloroprene being preferred.

[0107] The second polymerization step, as described above, involves seeding monomer (B) onto a chloroprene polymer to synthesize a chloroprene seed polymer. This yields a chloroprene seed polymer latex with particles of the chloroprene seed polymer dispersed in water.

[0108] Specifically, by adding monomer (B) and polymerization initiator to the chloroprene polymer latex obtained from the first polymerization step, the chloroprene polymer and monomer (B) can undergo seed polymerization to synthesize a chloroprene seed polymer.

[0109] Emulsifiers and water may also be added to the chloroprene polymer latex obtained from the first polymerization process, as needed.

[0110] Emulsifiers used in the second polymerization step can be categorized as anionic and nonionic emulsifiers.

[0111] As anionic emulsifiers, specific examples include alkali metal salts of disproportionated rosin acid; sodium dodecylbenzene sulfonate, triethanolamine dodecylbenzene sulfonate, and other dodecylbenzene sulfonates; sodium diphenyl ether sulfonate, ammonium diphenyl ether sulfonate, and other diphenyl ether sulfonates; sodium salt of β-naphthalene sulfonic acid formaldehyde condensate and other naphthalene sulfonates; and alkali metal salts of fatty acids such as potassium laurate.

[0112] As nonionic emulsifiers, examples include some saponified polyvinyl alcohol, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene lauryl ether.

[0113] The emulsifier used in the second polymerization step is preferably an anionic emulsifier, and more preferably an alkali metal salt (sodium or potassium salt) of fatty acids.

[0114] Emulsifiers can be used alone or in combination with two or more.

[0115] When an emulsifier is used in the second polymerization step, the amount of emulsifier added is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the monomer component, more preferably 0.5 to 3.0 parts by mass.

[0116] In addition, the monomer component in the second polymerization process refers to the sum of the amount of chloroprene polymer latex multiplied by the solid component rate and the amount of monomer (B).

[0117] The polymerization temperature in the second polymerization step is preferably 10–50°C, more preferably 15–45°C. If the polymerization temperature is within this range, agglomerates are less likely to form, and the film-forming properties of the resulting chloroprene seed polymer latex and the strength of the molded product are easily maintained. Furthermore, if the polymerization temperature is within this range, polymerization proceeds rapidly, thus enabling efficient production of chloroprene seed polymer latex.

[0118] There are no particular limitations on the polymerization initiator used in the second polymerization step; general free radical polymerization initiators can be used. Examples of free radical polymerization initiators include organic or inorganic peroxides such as benzoyl peroxide, potassium persulfate, ammonium persulfate, cumene hydroperoxide, and tert-butyl hydroperoxide; and azo compounds such as azobisisobutyronitrile, with organic peroxides being preferred.

[0119] Polymerization initiators can be used alone or in combination with two or more.

[0120] The amount of polymerization initiator added in the second polymerization step is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of monomer components, more preferably 0.05 to 1 part by mass.

[0121] In the second polymerization step, a co-catalyst can also be used in conjunction with the polymerization initiator. There are no particular limitations on the co-catalyst; any general co-catalyst can be used.

[0122] Examples of co-catalysts include anthraquinone sulfonates, potassium sulfite, sodium bisulfite, sodium sulfite, tetraethylenepentamine, and N,N-dimethyl-p-toluidine.

[0123] One type of catalyst can be used alone, or two or more types can be used in combination.

[0124] When a co-catalyst is used in the second polymerization step, the amount of co-catalyst added is preferably 0.0005 to 1.0 parts by mass relative to 100 parts by mass of monomer components, more preferably 0.001 to 0.5 parts by mass.

[0125] In the second polymerization step, a molecular weight regulator can be added to obtain a chloroprene seed polymer with the desired molecular weight and molecular weight distribution. There are no particular limitations on the molecular weight regulator; general chain transfer agents can be used.

[0126] Examples of molecular weight regulators include diisopropyl xanthate disulfide, diethyl xanthate disulfide, dicyclohexyl xanthate disulfide, dilauryl xanthate disulfide, dibenzyl xanthate disulfide, and other disulfide xanthates; alkyl thiols such as dodecyl thiols, decyl thiols, and octyl thiols, with alkyl thiols being preferred.

[0127] As a molecular weight regulator, it can be used alone or in combination with two or more.

[0128] When a molecular weight regulator is used in the second polymerization step, the amount of the molecular weight regulator added is preferably 0.001 to 0.3 parts by mass relative to 100 parts by mass of the monomer component, more preferably 0.01 to 0.2 parts by mass.

[0129] In the second polymerization step, at the end of the polymerization reaction, in order to obtain chloroprene seed polymers with the desired molecular weight and molecular weight distribution, a polymerization stop agent can be added when the specified polymerization rate is reached to stop further polymerization reactions.

[0130] There are no particular limitations on polymerization stoppers. Specific examples include phenothiazine, p-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, diethylhydroxylamine, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxo radical.

[0131] Polymerization stoppers can be used alone or in combination with two or more.

[0132] When a polymerization stop agent is used in the second polymerization step, the amount of polymerization stop agent added is preferably 0.005 to 0.15 parts by mass relative to 100 parts by mass of monomer components, more preferably 0.01 to 0.1 parts by mass.

[0133] The solid content of the chloroprene seed polymer latex obtained through the second polymerization step is preferably 35-65% by mass. If the solid concentration is within the above range, it is easier to maintain the colloidal stability of the chloroprene seed polymer latex and to minimize the formation of agglomerates.

[0134] Furthermore, from the viewpoint of improving the strength of the resulting molded article, the content of tetrahydrofuran insoluble component (tetrahydrofuran insoluble component rate) in the chloroprene seed polymer latex is preferably 50 to 99.9% by mass relative to 100% by mass of the chloroprene seed polymer, more preferably 60 to 99% by mass, and even more preferably 85 to 99% by mass.

[0135] The content of tetrahydrofuran-insoluble components in chloroprene seed polymer latex can be controlled by the types of emulsifiers and polymerization initiators used in the second polymerization step, as well as the types of molecular weight regulators and polymerization stoppers used as needed, polymerization temperature, and monomer (B) conversion rate, among other polymerization conditions. Alternatively, it can be adjusted based on the content of tetrahydrofuran-insoluble components in the chloroprene polymer latex used.

[0136] <Other Processes>

[0137] In the chloroprene polymer latex obtained from the first polymerization step or the chloroprene seed polymer latex obtained from the second polymerization step, metal oxides, antioxidants, pH adjusters, surfactants, fillers, tackifiers, pigments, colorants, wetting agents, defoamers, thickeners, etc., may be appropriately added without prejudice to the purpose of this invention.

[0138] These additives can be added directly to polymer latex. For additives that are insoluble in water or destabilize the colloidal state of polymer latex, they can be added after preparing an aqueous dispersion.

[0139] (Metal oxides)

[0140] Since chloroprene and chloroprene polymers contain halogens, halogen donors are usually not required during polymerization, but it is preferable to use them in conjunction with hydrogen halide acid acceptors such as metal oxides.

[0141] Examples of metal oxides include zinc oxide, lead oxide, and lead tetroxide, with zinc oxide being preferred. A single metal oxide can be used alone, or two or more can be used in combination.

[0142] When using metal oxides, the amount of metal oxide added is preferably 1 to 10 parts by mass relative to 100 parts by mass of the solid component of the polymer latex, more preferably 2 to 8 parts by mass, and even more preferably 3 to 6 parts by mass. Adding metal oxides within the above range can sometimes result in a composition with sufficient tensile strength and flexibility.

[0143] (Antioxidants)

[0144] Chloroprene polymers, such as chloroprene polymers and chloroprene seed polymers, are generally prone to degradation due to oxygen. Therefore, sometimes by combining them with antioxidants, the degradation caused by oxygen can be inhibited.

[0145] As antioxidants, hindered phenolic antioxidants are preferred in applications such as medical gloves where appearance, especially color and hygiene, are important. Antioxidants can be used alone or in combination of two or more.

[0146] When using antioxidants, the amount of antioxidant added is preferably 0.1 to 5 parts by weight relative to 100 parts by weight of the solid component of the polymer latex. When the amount of antioxidant added is above the lower limit, the antioxidant effect is improved; when the amount of antioxidant added is below the upper limit, there is a tendency to promote crosslinking or improve the color tone.

[0147] (pH adjuster)

[0148] From the perspective of colloidal stability and film thickness adjustment, alkalis such as potassium hydroxide and ammonia, and weak acids such as amino acids (e.g., glycine), acetic acid, and citric acid are preferred as pH adjusters. It is preferable to aqueous the solution before use, diluting it to a level that will not irritate the colloid.

[0149] When using a pH adjuster, the amount of pH adjuster added relative to 100 parts by weight of the solid component of the polymer latex is preferably 0.01 to 5 parts by weight, more preferably 0.5 to 4 parts by weight, and even more preferably 1.5 to 3.5 parts by weight. When the amount of pH adjuster added is above the lower limit, it is easy to stabilize the colloid and adjust the film thickness. When the amount of pH adjuster added is below the upper limit, it tends to coagulate sufficiently or inhibit the formation of aggregates in the complex.

[0150] (surfactant)

[0151] When adding a weak acid as a pH adjuster, from the viewpoint of colloidal stability, it is preferable to add a surfactant to the polymer latex in advance.

[0152] Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, with anionic surfactants being preferred. Examples of anionic surfactants include alkyl sulfate salts such as sodium lauryl sulfate and triethanolamine lauryl sulfate.

[0153] When using a surfactant, the amount of surfactant added is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the solid component of the polymer latex, more preferably 0.05 to 3 parts by mass.

[0154] Chloroprene Seed Polymer Composition

[0155] The chloroprene seed polymer composition (hereinafter also referred to as "the composition") obtained by the manufacturing method according to one embodiment of the present invention comprises at least chloroprene seed polymer latex synthesized by a first polymerization step and a second polymerization step.

[0156] Even without the vulcanization accelerators typically used in molding, the resulting molded articles possess the basic rubber properties inherent in chloroprene polymers (e.g., tensile strength, rubber elasticity).

[0157] Examples of vulcanization accelerators commonly used in the vulcanization of chloroprene polymer latex include thiuram-based, dithiocarbamate-based, thiourea-based, and guanidine-based accelerators. Examples of thiuram-based accelerators include tetraethylthiuram disulfide and tetrabutylthiuram disulfide. Examples of dithiocarbamate-based accelerators include sodium dibutyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc diethyldithiocarbamate. Examples of thiourea-based accelerators include ethylene thiourea, diethyl thiourea, trimethyl thiourea, and N,N'-diphenyl thiourea, with N,N'-diphenyl thiourea being particularly preferred. Examples of guanidine-based accelerators include diphenylguanidine and di-o-tolylguanidine.

[0158] Vulcanization accelerators can cause type IV allergies, so from the point of view that they can be used safely as medical gloves without worrying about allergies, this composition is preferably free of vulcanization accelerators.

[0159] The molded articles obtained from this composition are suitable for use in rubber-impregnated products such as gloves, blood pressure cuffs, and threaded rubber, especially for medical disposable gloves such as surgical gloves.

[0160] Manufacturing Method of Rubber Impregnated Products

[0161] Rubber-impregnated products can be manufactured by known methods. Specifically, using this composition, after impregnation and coagulation by known methods, the processes of leaching (removal of water-soluble impurities), drying, and then cross-linking are performed sequentially to obtain a molded article (rubber-impregnated product) of the desired shape.

[0162] In the crosslinking process, to achieve the desired degree of crosslinking, the crosslinking temperature tends to be higher than that required for natural rubber. The crosslinking temperature is typically 120–140°C, and the crosslinking time is 30 minutes to 2 hours. To avoid product appearance issues such as bubbles and pinholes, it is sometimes necessary to pre-dry at a lower temperature in the range of 70–100°C before crosslinking. Crosslinking is preferably carried out sufficiently, for example, within a range where tensile strength and elongation at break do not deteriorate.

[0163] The molded article obtained from this composition preferably has a tensile strength (tensile strength at cut, hereinafter also referred to as "Tb") of 16 MPa or more, more preferably 17 MPa or more from the viewpoint of use as a medical glove, further preferably 18 MPa or more, and particularly preferably 20 MPa or more.

[0164] Furthermore, the molded article obtained from this composition preferably has a rubber elasticity (M100 retention rate) of 73% or more, more preferably 75% or more, and even more preferably 78% or more. If the M100 retention rate is within the above range, it can be said that the rubber elasticity of the molded article is sufficiently excellent.

[0165] The tensile strength (e.g., tensile strength at cut) and rubber elasticity (e.g., M100 retention rate) of the molded article can be determined using a film-shaped molded article produced by the manufacturing method of the rubber impregnated product described above, specifically by the method described in the examples below.

[0166] Example

[0167] The present invention will be specifically described below through embodiments, but the present invention is not limited to the following embodiments.

[0168] [Example 1]

[0169] (1) Preparation of chloroprene polymer latex

[0170] In a 5L reactor, add 1555g of chloroprene, 145g of 2,3-dichloro-1,3-butadiene (8.5% by mass relative to 100% of the total mass of chloroprene and 2,3-dichloro-1,3-butadiene), 1367g of pure water, 73g of disproportionated rosin, 20g of potassium hydroxide, 18g of sodium hydroxide, 1.0g of n-dodecyl mercaptan, 4.8g of potassium sulfite, and 9.0g of sodium salt of β-naphthalenesulfonic acid formalin condensate, and emulsify them.

[0171] 0.3 g of potassium persulfate was added to the obtained emulsion as a polymerization initiator, and polymerization was carried out at 40 °C in a nitrogen atmosphere. When the desired polymerization rate was reached, 18.8 g of phenothiazine emulsion (containing 0.3 g of phenothiazine) was added immediately to stop the polymerization. The solid content of the obtained product was 48% by mass, and the monomer conversion rate (total conversion rate of chloroprene and 2,3-dichloro-1,3-butadiene) was 88%. Then, unreacted chloroprene was removed by steam stripping to obtain chloroprene polymer latex [1] (solid content concentration 50% by mass, tetrahydrofuran insoluble content: 45%).

[0172] (2) Preparation of chloroprene seed polymer latex

[0173] Add 1500g of chloroprene polymer latex [1] obtained in (1), 26.5g of glycine, 84g of ethyl methacrylate (10 parts by mass relative to the total 100 parts by mass of chloroprene polymer and ethyl methacrylate), 1.85g of potassium sulfite, 126g of pure water, 5.6g of sodium lauryl sulfate and 0.126g of n-dodecyl mercaptan to a reactor with an internal volume of 3L, and emulsify it.

[0174] 10.8 g of a 70% (w / w) aqueous solution of tert-butyl hydroperoxide was added to the obtained emulsion as a polymerization initiator, and seed polymerization was carried out at 40 °C under a nitrogen atmosphere. After about 6 hours of reaction, 0.92 g of a 10% (w / w) aqueous solution of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxo radical was added to stop the polymerization, yielding chloroprene seed polymer latex (solids concentration 50.1% (w / w), tetrahydrofuran insoluble content: 90.0%). At this point, the conversion rate of ethyl methacrylate was 95.5%.

[0175] [Examples 2-11, Comparative Examples 1-3]

[0176] (1) Preparation of chloroprene polymer latex

[0177] Perform the same operation as in Example 1 (1) to obtain chloroprene polymer latex [1].

[0178] (2) Preparation of chloroprene seed polymer latex

[0179] Except for changing the type and amount of monomers used for seed polymerization on the chloroprene polymer as described in Table 1, the same operation as in Example 1 (2) was performed to obtain a chloroprene seed polymer latex. The solids content concentration of the obtained chloroprene seed polymer latex is shown in Table 1.

[0180] Additionally, in Tables 1 and 2, EMA refers to ethyl methacrylate (Tg: 65℃ for homopolymer), MMA refers to methyl methacrylate (Tg: 90-100℃ for homopolymer), i-BMA refers to isobutyl methacrylate (Tg: 50-60℃ for homopolymer), t-BMA refers to tert-butyl methacrylate (Tg: 107℃ for homopolymer), DCB refers to 2,3-dichloro-1,3-butadiene (Tm: 130℃ for homopolymer), and n-BMA refers to n-butyl methacrylate (Tg: 20℃ for homopolymer).

[0181] [Example 12]

[0182] (1) Preparation of chloroprene polymer latex

[0183] Without adding a molecular weight regulator, the same operation as in Example 1 (1) was performed to obtain chloroprene polymer latex [2] (solid content concentration: 50% by mass, monomer conversion rate: 88%, tetrahydrofuran insoluble content: 80%).

[0184] (2) Preparation of chloroprene seed polymer latex

[0185] Except for converting the chloroprene polymer into a chloroprene polymer latex [2], the same operation as in (2) of Example 6 was performed to obtain a chloroprene seed polymer latex. The solid content concentration of the obtained chloroprene seed polymer latex is shown in Table 2.

[0186] [Example 13]

[0187] (1) Preparation of chloroprene polymer latex

[0188] Perform the same operation as in Example 12 (1) to obtain chloroprene polymer latex [2].

[0189] (2) Preparation of chloroprene seed polymer latex

[0190] Except for changing the type and amount of monomers used for seed polymerization on the chloroprene polymer as described in Table 2, the same operation as in Example 12 (2) was performed to obtain a chloroprene seed polymer latex. The solids content concentration of the obtained chloroprene seed polymer latex is shown in Table 2.

[0191] [Comparative Example 4]

[0192] (1) Preparation of chloroprene polymer latex

[0193] Perform the same operation as in Example 1 (1) to obtain chloroprene polymer latex [1].

[0194] [Comparative Example 5]

[0195] (1) Preparation of chloroprene polymer latex

[0196] Perform the same operation as in Example 12 (1) to obtain chloroprene polymer latex [2].

[0197] <Evaluation of Polymer Latex>

[0198] The conversion rate and tetrahydrofuran insoluble content of the polymer latexes (chloroprene polymer latex or chloroprene seed polymer latex) obtained in the examples and comparative examples were evaluated using the following methods.

[0199] • Evaluation of conversion rate

[0200] The polymer latex after polymerization was collected, and the monomer conversion rate was calculated based on the solid composition after drying at 141°C for 30 minutes. Furthermore, the solid composition concentration and monomer conversion rate were obtained using the following formulas, and the polymer yield was calculated by subtracting the non-polymer solids from the solid composition concentration. The results are shown in Tables 1 and 2.

[0201] Solid component concentration (mass%) =

[0202] [(Weight of latex after drying at 141°C for 30 minutes) / (Weight of latex before drying)] × 100

[0203] Monomer conversion rate [%] = [(polymer generated / monomer added)] × 100

[0204] However, in the seed polymerization of chloroprene polymers, when the content of the seed polymer shell is less than 5 parts by mass relative to 100 parts by mass of the seed polymer, the change in solid composition is small, but the value deviation is large, so sometimes an accurate value cannot be calculated. Therefore, when the amount of monomer (B) used in the preparation of chloroprene seed polymer latex is less than 5 parts by mass relative to the total of 100 parts by mass of chloroprene polymer and monomer (B) (Examples 2-5), it is recorded as "N / A" and no evaluation is performed.

[0205] Evaluation of the percentage of tetrahydrofuran-insoluble components (gel weight)

[0206] Approximately 0.5 g of polymer latex was added dropwise to 100 ml of THF (tetrahydrofuran). After shaking overnight, the dissolved phase of the supernatant was separated using a centrifuge. The THF was then evaporated and dried at 100 °C for 1 hour. The amount of dissolved portion was calculated. This amount was subtracted from the amount of polymer latex used to calculate the percentage of insoluble tetrahydrofuran [mass %]. The results are shown in Tables 1 and 2.

[0207] (Tetrahydrofuran insoluble component percentage [mass%] = (mass after evaporation and drying) ÷ (mass of polymer latex) × 100)

[0208] <Evaluation of physical properties after cross-linking>

[0209] (1) Preparation of chloroprene seed polymer composition

[0210] Relative to 100 parts by weight of the solid content of the chloroprene seed polymer latex or chloroprene polymer latex obtained in the Examples and Comparative Examples, 3 parts by weight of potassium hydroxide (based on solid content) and 5 parts by weight of zinc oxide (based on solid content) were added to a mixing tank equipped with a Three-one motor and stirred for at least 5 minutes to achieve homogenization, thereby preparing the chloroprene seed polymer composition. Furthermore, potassium hydroxide was added as a 3% by weight aqueous solution, and zinc oxide was added as a 50% by weight aqueous dispersion.

[0211] (2) Preparation of test strips

[0212] A 30% by mass calcium nitrate aqueous solution was used as a coagulating solution to obtain an impregnated film from the obtained chloroprene seed polymer composition. The film was then leached in warm water at 50°C for 2 minutes to remove water-soluble components. It was then dried at 70°C for 30 minutes.

[0213] The obtained film was vulcanized in a conventional oven by heating at 130°C for 30 minutes. The vulcanized sheet was then appropriately cut according to the evaluation criteria to obtain test pieces with a thickness of 0.15–0.25 mm. Using these test pieces, tensile strength and M100 retention were evaluated using the following methods.

[0214] Evaluation of tensile strength (tensile strength at cut)

[0215] Using the test pieces described above, the tensile strength of the composition at cut was determined according to the method of JIS K6251:2017. A dumbbell-shaped No. 6 test piece was used. The tensile strength at room temperature was determined using this test. The results are shown in Tables 1 and 2.

[0216] • Evaluation of rubber elasticity (M100 retention rate)

[0217] Using the test piece described above, the modulus of the composition was determined according to the method of JIS K6251:2017. A dumbbell-shaped No. 6 test piece was used. The dumbbell was stretched at 200 mm / min, and the stretching was stopped at 100%. In this test, the modulus (M100) at 100% elongation was measured immediately at 100% elongation and again after 2 minutes. The retention rate after 2 minutes was calculated using the following formula. The results are shown in Tables 1 and 2.

[0218] M100 retention rate [%] = (M100 after 2 minutes) / (M100 immediately upon elongation) × 100

[0219]

[0220]

[0221] As shown in Tables 1 and 2, the compositions used in Examples 1-13 resulted in molded articles with high tensile strength (Tb) (above 16 MPa) and high M100 retention (above 73%). This indicates that the resulting molded articles exhibit excellent strength and rubber elasticity. In Comparative Example 1, where n-butyl methacrylate was used as the seed polymer monomer, although tensile strength increased, rubber elasticity was lost, and the M100 retention rate decreased significantly. In Comparative Example 2, where 30 parts by mass of ethyl methacrylate were introduced relative to 100 parts by mass of the seed polymer, film formation was not possible. In Comparative Example 3, where only 1 part by mass of ethyl methacrylate was polymerized relative to 100 parts by mass of the seed polymer, the strength derived from ethyl methacrylate was not observed, rubber elasticity was lost, and the M100 retention rate decreased. In Comparative Examples 4 and 5, where chloroprene polymer latex obtained through the first polymerization step was used, the tensile strength from chloroprene was sufficient, but the M100 retention rate decreased due to insufficient crosslinking.

Claims

1. A method for producing a neoprene seed polymer composition, which is a method for producing a neoprene seed polymer composition provided with a first polymerization step and a second polymerization step, characterized in that the first polymerization step is a step of obtaining a neoprene polymer by at least subjecting a neoprene monomer to emulsion radical polymerization, and the second polymerization step is a step of subjecting the neoprene polymer to emulsion seed polymerization with a monomer B-2 having a glass transition temperature or a melting point of 30°C or higher in an amount of 3 to 20 parts by mass relative to 100 parts by mass in total of the neoprene polymer and the monomer B-2.

2. A method for producing a neoprene seed polymer composition, which is a method for producing a neoprene seed polymer composition provided with a first polymerization step and a second polymerization step, characterized in that the first polymerization step is a step of obtaining a neoprene polymer by at least subjecting a neoprene monomer to emulsion radical polymerization, and the second polymerization step is a step of subjecting the neoprene polymer to emulsion seed polymerization with a (meth)acrylate monomer B-1 having an alkyl group having 1 to 4 carbon atoms and a straight chain of the alkyl group having 3 or fewer carbon atoms in an amount of 3 to 20 parts by mass relative to 100 parts by mass in total of the neoprene polymer and the monomer B-1.

3. The method for producing a neoprene seed polymer composition according to claim 1, wherein the monomer B-2 is ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, or 2,3-dichloro-1,3-butadiene.

4. The method for producing a neoprene seed polymer composition according to claim 2, wherein the monomer B-1 is ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, or t-butyl methacrylate.

5. A method for producing a rubber impregnated product, which produces a rubber impregnated product using the neoprene seed polymer composition obtained by the method for producing a neoprene seed polymer composition according to any one of claims 1 to 4.

6. The method for producing a rubber impregnated product according to claim 5, wherein the rubber impregnated product is a glove.

7. The method for producing a rubber impregnated product according to claim 6, wherein the glove is a medical disposable glove. ​ ​ ​ ​

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