Production method for chloroprene seed polymer composition and production method for rubber immersion product

Abstract

One embodiment of the present invention relates to a production method for a chloroprene seed polymer composition. Said production method comprises a first polymerization step and a second polymerization step and is characterized in that: the first polymerization step is for performing emulsion radical polymerization of at least a chloroprene monomer to obtain a chloroprene polymer; and the second polymerization step is for performing emulsion seed polymerization of at least a specific monomer (B-1) or (B-2) with respect to the chloroprene polymer, in an amount of 3-20 parts by mass of with respect to 100 parts by mass of the total of the chloroprene polymer and the monomer (B-1) or (B-2).

Description

Method for producing chloroprene seed polymer composition and method for producing rubber dipped products

[0001] One embodiment of the present invention relates to a method for making a chloroprene seed polymer composition or a method for making a rubber dipped product.

[0002] BACKGROUND ART Materials using chloroprene (2-chloro-1,3-butadiene) polymer latex have been conventionally excellent in general rubber properties, weather resistance, heat resistance, chemical resistance, and the like, and have been widely used in applications such as dipping gloves, adhesives, and civil engineering and construction applications such as elastic asphalt (modified asphalt) and elastic cement.

[0003] In the use of disposable medical gloves, particularly surgical gloves, shock symptoms (anaphylaxis) caused by an allergic reaction to natural rubber pose a serious problem in terms of hygiene and lifesaving for patients and medical technicians. To solve this problem, chloroprene rubber (hereinafter also referred to as "CR"), which has flexibility and mechanical properties similar to those of natural rubber and is relatively inexpensive, is used as a surgical glove material. Specifically, chloroprene rubber is characterized by a fit (comfort) similar to that of natural rubber and excellent response (followability) to fine finger movements. Methods of improving the flexibility of surgical gloves by using chloroprene polymer latex have been proposed (e.g., Patent Documents 1 and 2).

[0004] However, conventional chloroprene rubbers require the use of a vulcanization accelerator to obtain vulcanized rubber with the desired strength because the polymer structure contained in the chloroprene polymer latex is insufficient. In recent years, contact dermatitis has been reported even with synthetic rubber gloves. This is due to the vulcanization accelerator used when molding the chloroprene polymer latex, and is known as type IV allergy. Therefore, there is a growing demand for gloves that do not contain a vulcanization accelerator, which is an allergen for type IV allergy. In response to this demand, rubber compositions containing a chloroprene polymer latex that can be crosslinked to chloroprene rubber suitable for applications such as surgical gloves without the use of a vulcanization accelerator have been proposed (e.g., Patent Document 3, etc.).

[0005] JP 2007-106994 A JP 2009-501833 A International Publication No. 2016 / 166998

[0006] In the case of Patent Document 1, the use of a vulcanization accelerator is essential, and the problem of type IV allergy is not solved. Furthermore, in the case of Patent Document 2, there are problems with the mechanical properties of the rubber, such as difficulty in film formation when the solids concentration is low, and the compound's storage stability is deteriorated and it is prone to aggregation when the solids concentration is high, impairing the appearance of the product. Furthermore, in the case of Patent Document 3, the mechanical properties of the rubber are improved by adjusting the tetrahydrofuran-insoluble content of the chloroprene polymer latex, but there are limited means for improving the physical properties of chloroprene rubber without using a vulcanization accelerator.

[0007] The present invention has been made in view of the above, and an object of the present invention is to provide a method for producing a chloroprene polymer composition which can be used to form molded articles having excellent strength and rubber elasticity.

[0008] As a result of intensive research to solve the problems, the present inventors have found that the problems can be solved by a molded article obtained from a composition containing a chloroprene seed polymer latex (chloroprene seed polymer composition) obtained by a specific production method.

[0009] That is, configuration examples of the present invention are as follows: [1] to [7] [1] A method for producing a chloroprene seed polymer composition, comprising a first polymerization step and a second polymerization step, wherein the first polymerization step is a step of emulsion radically polymerizing at least a chloroprene monomer to obtain a chloroprene polymer, and the second polymerization step is a step of emulsion seed polymerizing the chloroprene polymer with at least a monomer (B-2) having a glass transition temperature or melting point of 30°C or higher, in an amount of 3 to 20 parts by mass per 100 parts by mass of the total of the chloroprene polymer and the monomer (B-2).

[0010] [2] A method for producing a chloroprene seed polymer composition, comprising a first polymerization step and a second polymerization step, wherein the first polymerization step is a step of emulsion radically polymerizing at least a chloroprene monomer to obtain a chloroprene polymer, and the second polymerization step is a step of emulsion seed polymerizing the chloroprene polymer with 3 to 20 parts by mass of a (meth)acrylate monomer (B-1) having an alkyl group having at least 1 to 4 carbon atoms, and wherein the alkyl group has 3 or less carbon atoms in a linear chain, per 100 parts by mass of the chloroprene polymer and the monomer (B-1) in total.

[0011] [3] The method for producing a chloroprene seed polymer composition according to [1], wherein the monomer (B-2) is ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, or 2,3-dichloro-1,3-butadiene. [4] The method for producing a chloroprene seed polymer composition according to [2], wherein the monomer (B-1) is ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, or tert-butyl methacrylate. [5] A method for producing a rubber-dipped product using the chloroprene seed polymer composition obtained by the production method according to any one of [1] to [4]. [6] The method for producing a rubber-dipped product according to [5], wherein the rubber-dipped product is a glove. [7] The method for producing a rubber-dipped product according to [6], wherein the glove is a disposable medical glove.

[0012] According to one embodiment of the present invention, a chloroprene seed polymer latex having a specific structure is obtained, and a molded product obtained from a composition containing the polymer latex has excellent strength and rubber elasticity. Furthermore, the composition obtained by the production method according to one embodiment of the present invention can fully exhibit the above-mentioned effects even without containing a vulcanization accelerator that causes type IV allergies. Therefore, the composition can be suitably used for molded products that require avoidance of type IV allergies, such as dipped products such as gloves, blood pressure monitor bladders, and rubber threads.

[0013] Matters related to the embodiments will be described in detail below. In this specification, a numerical range described using "to" means that the numerical values ​​before and after "to" are included as the lower limit and upper limit.

[0014] A method for producing a chloroprene seed polymer composition and a method for producing a dipped rubber product according to one embodiment of the present invention will be described in detail below. Note that this embodiment shows only one example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0015] <<Method for Producing Chloroprene Seed Polymer Composition>> A method for producing a chloroprene seed polymer composition according to one embodiment of the present invention includes a first polymerization step for obtaining a chloroprene polymer latex, and a second polymerization step for obtaining a chloroprene seed polymer latex.

[0016] Generally, a "latex" is a substance in which a lipophilic substance is emulsified with an emulsifier and dispersed as particles in water. The chloroprene polymer latex or chloroprene seed polymer latex of this embodiment is a substance in which particles of a chloroprene polymer or a chloroprene seed polymer are dispersed in water.

[0017] <First Polymerization Step> The first polymerization step is a step of synthesizing a chloroprene polymer by emulsion radical polymerization of at least a chloroprene monomer (hereinafter also referred to as "monomer (A-1)"). This results in a chloroprene polymer latex in which particles of the chloroprene polymer are dispersed in water. In the first polymerization step, a monomer (A-2) may be used together with the monomer (A-1). The chloroprene polymer may be a homopolymer of the monomer (A-1) or a copolymer of the monomer (A-1) and the monomer (A-2).

[0018] The monomer (A-2) is not particularly limited as long as it is copolymerizable with chloroprene (2-chloro-1,3-butadiene), and examples thereof 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, with 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, 1,3-butadiene, methacrylic acid, and acrylic acid being preferred. One type of monomer (A-2) may be used alone, or two or more types may be used in combination.

[0019] When the monomer (A-2) is used, the ratio of the amounts of the monomer (A-1) and the monomer (A-2) used is not particularly limited, but when the total amount of the monomer (A-1) and the monomer (A-2) used is taken as 100 mass%, the ratio of the monomer (A-1) is preferably 70 to 99.9 mass%, more preferably 90 to 99 mass%, and the ratio of the monomer (A-2) is preferably 0.1 to 30 mass%, more preferably 1 to 10 mass%.

[0020] Specifically, the chloroprene polymer can be synthesized by adding an emulsifier and water to the monomer (A-1) and, if necessary, the monomer (A-2) to obtain an aqueous emulsion, and then adding a polymerization initiator to the aqueous emulsion to cause a radical polymerization reaction.

[0021] Examples of the emulsifier used in the first polymerization step include anionic emulsifiers and nonionic emulsifiers. Specific examples of the anionic emulsifier include alkali metal salts of disproportionated rosin acid, dodecylbenzenesulfonate salts such as sodium dodecylbenzenesulfonate and triethanolamine dodecylbenzenesulfonate, diphenylethersulfonate salts such as sodium diphenylethersulfonate and ammonium diphenylethersulfonate, naphthalenesulfonate salts such as sodium salt of β-naphthalenesulfonic acid formaldehyde condensate, and fatty acid alkali metal salts such as potassium laurate.

[0022] Specific examples of nonionic emulsifiers include partially saponified polyvinyl alcohol, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene lauryl ether.

[0023] The emulsifier used in the first polymerization step is preferably an anionic emulsifier, more preferably an alkali metal salt (sodium salt or potassium salt) of disproportionated rosin acid or a naphthalenesulfonate. One emulsifier may be used alone, or two or more emulsifiers may be used in combination.

[0024] The amount of emulsifier added in the first polymerization step is preferably 1 to 10 parts by mass, and more preferably 3 to 8.5 parts by mass, per 100 parts by mass of the monomer components. Note that the monomer components in the first polymerization step refer to the monomer (A-1) when the monomer (A-1) is used alone, and refer to the total of the monomers (A-1) and (A-2) when the monomer (A-2) is used in combination.

[0025] The polymerization temperature in the first polymerization step is preferably 10 to 50°C, more preferably 15 to 45°C. When the polymerization temperature is within this range, aggregates are less likely to occur, and the film-forming properties of the resulting chloroprene seed polymer latex and the strength of the molded product are easily maintained. Furthermore, when the polymerization temperature is within this range, the polymerization proceeds rapidly, allowing for efficient production of the chloroprene polymer latex.

[0026] The polymerization initiator in the first polymerization step is not particularly limited, and a general radical polymerization initiator can be used. Examples of the radical polymerization initiator 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. One type of polymerization initiator may be used alone, or two or more types may be used in combination.

[0027] The amount of the polymerization initiator added in the first polymerization step is preferably 0.001 to 2.0 parts by mass, more preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the monomer components.

[0028] In the first polymerization step, a co-catalyst may be used in combination with the polymerization initiator. The co-catalyst is not particularly limited, and a general co-catalyst may be used. Examples of the co-catalyst include anthraquinone sulfonate, potassium sulfite, sodium disulfite, sodium sulfite, tetraethylenepentamine, and N,N-dimethyl-p-toluidine. One type of co-catalyst may be used alone, or two or more types may be used in combination.

[0029] When a co-catalyst is used in the first polymerization step, the amount of the co-catalyst added is preferably 0.0001 to 5.0 parts by mass, more preferably 0.0005 to 0.50 parts by mass, per 100 parts by mass of the monomer components.

[0030] In the first polymerization step, a molecular weight modifier may be added for the purpose of obtaining a chloroprene polymer having the desired molecular weight and molecular weight distribution. The molecular weight modifier is not particularly limited, and a general chain transfer agent can be used. Examples of molecular weight modifiers include xanthogen disulfides such as diisopropyl xanthogen disulfide, diethyl xanthogen disulfide, dicyclohexyl xanthogen disulfide, dilauryl xanthogen disulfide, and dibenzyl xanthogen disulfide; and alkyl mercaptans such as n-dodecyl mercaptan, n-decyl mercaptan, and octyl mercaptan, with alkyl mercaptans being preferred. One type of molecular weight modifier may be used alone, or two or more types may be used in combination.

[0031] When a molecular weight modifier is used in the first polymerization step, the amount of the molecular weight modifier added is preferably 0.01 to 0.1 parts by mass, more preferably 0.03 to 0.08 parts by mass, per 100 parts by mass of the monomer components.

[0032] The monomer conversion rate in the first polymerization step is preferably 60 to 100%. The monomer conversion rate in the first polymerization step refers to the conversion rate of monomer (A-1) when monomer (A-1) is used alone, and refers to the total conversion rate of monomer (A-1) and monomer (A-2) when monomer (A-2) is used in combination. A conversion rate within the above range facilitates the production of a chloroprene polymer latex having the solids concentration described below, and tends to prevent odors due to residual unreacted monomer (A-1) or monomer (A-2), as well as deterioration in the film-forming properties of the resulting chloroprene seed polymer latex and the strength of molded articles. Furthermore, sudden heat generation due to the reaction of unreacted monomer (A-1) or monomer (A-2) in the subsequent second polymerization step can be suppressed. Furthermore, after the first polymerization step, there is no need to remove unreacted volatile components (e.g., unreacted monomer (A-1) or monomer (A-2)), or even if removal is performed, a light-load treatment is sufficient.

[0033] At the end of the polymerization reaction in the first polymerization step, a polymerization terminator may be added to terminate the further polymerization reaction when a predetermined polymerization rate is reached, in order to obtain a chloroprene polymer having the desired molecular weight and molecular weight distribution. The polymerization terminator is not particularly limited, but specific examples include phenothiazine, para-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, diethylhydroxylamine, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical. One type of polymerization terminator may be used alone, or two or more types may be used in combination.

[0034] When a polymerization terminator is used in the first polymerization step, the amount of the polymerization terminator added is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 3 parts by mass, per 100 parts by mass of the monomer components.

[0035] After the first polymerization step and before the second polymerization step, a step of removing unreacted volatile components (for example, unreacted monomer (A-1) or monomer (A-2)) may be included. The method for removing the unreacted volatile components is not particularly limited as long as it is a known method, but a steam stripping method is preferred from the viewpoint of easily obtaining a chloroprene polymer latex having a solid content concentration described below.

[0036] The solids concentration of the chloroprene polymer latex obtained in the first polymerization step is preferably 35 to 65% by mass. When the solids concentration is within this range, it is easier to maintain the colloidal stability of the chloroprene polymer latex, and the occurrence of aggregates can be minimized. In the present invention, the solids concentrations of the chloroprene polymer latex and the chloroprene seed polymer latex described below are measured by the method described in the Examples described below.

[0037] Furthermore, the content of the tetrahydrofuran-insoluble matter in the chloroprene polymer latex (tetrahydrofuran-insoluble matter rate) is not particularly limited, but from the viewpoint of facilitating the preparation of the target chloroprene seed polymer latex in the second polymerization step, it is preferably 10 to 99.9% by mass, more preferably 20 to 99% by mass, and even more preferably 30 to 95% by mass, relative to 100% by mass of the chloroprene polymer.

[0038] Here, the "tetrahydrofuran insoluble matter" refers to a gel-like substance that does not dissolve in tetrahydrofuran, and is a hard component lacking in elasticity. The content of the tetrahydrofuran insoluble matter in the chloroprene polymer latex can be controlled by the polymerization conditions, such as the types of emulsifier and polymerization initiator in the first polymerization step, and the types of molecular weight modifier and polymerization terminator used as needed, the polymerization temperature, and the monomer conversion rate. In the present invention, the tetrahydrofuran insoluble matter ratios of the chloroprene polymer latex and the chloroprene seed polymer latex described later are measured by the method described in the Examples described later.

[0039] <Second Polymerization Step> The second polymerization step is a step in which a chloroprene seed polymer obtained in the first polymerization step is subjected to emulsion seed polymerization of a monomer having a carbon-carbon double bond (hereinafter, also simply referred to as "monomer (B)") to synthesize a chloroprene seed polymer, and a chloroprene seed polymer latex in which particles of the chloroprene seed polymer are dispersed in water is obtained.

[0040] The chloroprene polymer obtained in the first polymerization step has a carbon-carbon double bond derived from the monomer (A-1) or (A-2) in the main chain. Therefore, since the monomer (B) has a carbon-carbon double bond, the carbon-carbon double bond of the chloroprene polymer reacts with the carbon-carbon double bond of the monomer (B), thereby enabling seed polymerization.

[0041] The polymer obtained by seed polymerization is a particle (seed polymer) having a core / shell structure in which a core particle (e.g., a chloroprene polymer) is coated with a layer (shell) of a polymer (e.g., a polymer obtained by polymerizing monomer (B)). The particle structure can be confirmed, for example, by scanning probe microscope (SPM) measurement.

[0042] First Embodiment In a first embodiment of the present invention, in the second polymerization step, a (meth)acrylate monomer (B-1) having an alkyl group having at least 1 to 4 carbon atoms and having a linear carbon number of 3 or less is used as the monomer (B) through emulsion seed polymerization.

[0043] The amount of monomer (B-1) used in the second polymerization step is 3 to 20 parts by mass, preferably 4 to 15 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the total of the chloroprene polymer and monomer (B-1). When monomer (B-1) is used within the above range, a chloroprene seed polymer having structural units derived from monomer (B-1) in the range described below can be easily obtained.

[0044] The conversion rate of the monomer (B-1) in the second polymerization step is preferably 70 to 100%, more preferably 75 to 100%. When the conversion rate is within the above range, a chloroprene seed polymer having structural units derived from the monomer (B-1) within the range described below can be easily obtained, and a chloroprene seed polymer latex having a solids concentration described below can be easily obtained. Furthermore, there is a tendency to suppress odors caused by remaining unreacted monomer (B-1), as well as reductions in the film-forming properties of the resulting chloroprene seed polymer latex and the strength of molded articles. Furthermore, there is no need to remove unreacted components (e.g., unreacted chloroprene polymer or monomer (B-1)) after the second polymerization step, or even if removal is performed, a light-load treatment is sufficient.

[0045] The chloroprene seed polymer obtained in this embodiment preferably contains 3 to 20 mass% of structural units derived from monomer (B-1), more preferably 5 to 10 mass%. The chloroprene seed polymer containing monomer (B-1) within this range exhibits the properties of the chloroprene polymer in the core portion of the core / shell structure without being impaired by the shell portion, and is therefore thought to adequately maintain the strength and flexibility of the resulting molded article. Furthermore, the core / shell structure provides sufficient interparticle crosslinking, and the polymer latex has sufficient film-forming properties, and the resulting molded article is thought to have excellent rubber elasticity.

[0046] (Meth)acrylates are compounds of the general formula CH ２ =CR １ -CO-OR ２ In the general formula, R １ represents a methyl group or a hydrogen atom, R ２ represents an alkyl group having 1 to 4 carbon atoms, and the number of carbon atoms in the linear chain of the alkyl group is 3 or less. In this specification, "(meth)acrylate" means methacrylate and / or acrylate, and "(meth)acrylic" means methacrylic and / or acrylic.

[0047] Examples of the monomer (B-1) include 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, with methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, isobutyl methacrylate, and tert-butyl methacrylate being preferred, and ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate being more preferred. One type of monomer (B-1) may be used alone, or two or more types may be used in combination.

[0048] In the second polymerization step, a monomer other than the monomer (B-1) may be copolymerized within a range that does not impair the effects of the present invention. Examples of the monomer other than the monomer (B-1) include 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 an alkyl group having 5 to 12 carbon atoms, with chloroprene being preferred.

[0049] Second Embodiment In a second embodiment of the present invention, in the second polymerization step, as the monomer (B), at least a monomer (B-2) having a homopolymer glass transition temperature (Tg) or melting point (Tm) of 30° C. or higher is subjected to emulsion seed polymerization. The lower limit of Tg or Tm of the homopolymer of monomer (B-2) is preferably 40° C. or higher, more preferably 60° C. or higher, and even more preferably 80° C. or higher, and the upper limit is not particularly limited, but is preferably 180° C. or lower, more preferably 150° C. or lower, and even more preferably 135° C. or lower.

[0050] The amount of monomer (B-2) used in the second polymerization step is 3 to 20 parts by mass, preferably 4 to 15 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the total of the chloroprene polymer and monomer (B-2). When monomer (B-2) is used in the above range, a chloroprene seed polymer having structural units derived from monomer (B-2) in the range described below can be easily obtained.

[0051] The conversion rate of the monomer (B-2) in the second polymerization step is preferably 70 to 100%, more preferably 75 to 100%. When the conversion rate is within the above range, a chloroprene seed polymer having structural units derived from the monomer (B-2) within the range described below can be easily obtained, and a chloroprene seed polymer latex having a solids concentration described below can be easily obtained. Furthermore, there is a tendency to suppress odors caused by remaining unreacted monomer (B-2), as well as reductions in the film-forming properties of the resulting chloroprene seed polymer latex and the strength of molded articles. Furthermore, after the second polymerization step, there is no need 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.

[0052] The chloroprene seed polymer obtained in this embodiment preferably contains 3 to 20 mass% of structural units derived from monomer (B-2), more preferably 5 to 10 mass%. The chloroprene seed polymer containing monomer (B-2) within this range exhibits the properties of the chloroprene polymer in the core portion of the core / shell structure without being impaired by the shell portion, and is therefore thought to adequately maintain the strength and flexibility of the resulting molded article. Furthermore, the core / shell structure provides sufficient interparticle crosslinking, and the polymer latex has sufficient film-forming properties, and the resulting molded article is thought to have excellent rubber elasticity.

[0053] Examples of the monomer (B-2) include 2,3-dichloro-1,3-butadiene (homopolymer Tm: 130°C), vinyl chloride (homopolymer Tg: 87°C), styrene (homopolymer Tg: 100°C), acrylonitrile (homopolymer Tg: 104°C), methyl methacrylate (homopolymer Tg: 90 to 100°C), ethyl methacrylate (homopolymer Tg: 65°C), isobutyl methacrylate (homopolymer Tg: 50 to 60°C), tert-butyl methacrylate (homopolymer Tg: 107°C), acrylic acid (homopolymer Tg: 106°C), and methacrylic acid (homopolymer Tg: 185°C). Among these, 2,3-dichloro-1,3-butadiene, vinyl chloride, styrene, acrylonitrile, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, or methacrylic acid is preferred, 2,3-dichloro-1,3-butadiene, vinyl chloride, styrene, acrylonitrile, methyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, or methacrylic acid is more preferred, and 2,3-dichloro-1,3-butadiene, ethyl methacrylate, methyl methacrylate, isobutyl methacrylate, or tert-butyl methacrylate is even more preferred. One type of monomer (B-2) may be used alone, or two or more types may be used in combination.

[0054] In this specification, the Tg of the homopolymer is a temperature obtained by the method described in JIS K 7121:2012. Also, in this specification, the Tm of the homopolymer is a temperature obtained by the method described in JIS K 0064:1992.

[0055] In the second polymerization step, a monomer other than the monomer (B-2) may be copolymerized within a range that does not impair the effects of the present invention. Examples of the monomer other than the monomer (B-2) include chloroprene, methyl acrylate, ethyl acrylate, n-butyl methacrylate, and 2-ethylhexyl acrylate, with chloroprene being preferred.

[0056] As described above, the second polymerization step is a step of synthesizing a chloroprene seed polymer by seed polymerization of a chloroprene polymer with a monomer (B). This results in a chloroprene seed polymer latex in which particles of the chloroprene seed polymer are dispersed in water. Specifically, by adding the monomer (B) and a polymerization initiator to the chloroprene polymer latex obtained in the first polymerization step, seed polymerization of the chloroprene polymer and the monomer (B) proceeds, and the chloroprene seed polymer can be synthesized. An emulsifier and water may be added to the chloroprene polymer latex obtained in the first polymerization step, as necessary.

[0057] The emulsifier used in the second polymerization step may be an anionic emulsifier or a nonionic emulsifier. Specific examples of the anionic emulsifier include alkali metal salts of disproportionated rosin acid, dodecylbenzenesulfonate salts such as sodium dodecylbenzenesulfonate and triethanolamine dodecylbenzenesulfonate, diphenylethersulfonate salts such as sodium diphenylethersulfonate and ammonium diphenylethersulfonate, naphthalenesulfonate salts such as sodium salt of β-naphthalenesulfonic acid formaldehyde condensate, and fatty acid alkali metal salts such as potassium laurate.

[0058] Specific examples of nonionic emulsifiers include partially saponified polyvinyl alcohol, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene lauryl ether.

[0059] The emulsifier in the second polymerization step is preferably an anionic emulsifier, more preferably a fatty acid alkali metal salt (sodium salt or potassium salt). One type of emulsifier may be used alone, or two or more types may be used in combination.

[0060] When an emulsifier is used in the second polymerization step, the amount of the emulsifier added is preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the monomer components. The monomer components in the second polymerization step refer to the sum of the amount of the chloroprene polymer latex multiplied by the solid content and the amount of the monomer (B).

[0061] The polymerization temperature in the second polymerization step is preferably 10 to 50°C, more preferably 15 to 45°C. When the polymerization temperature is within this range, aggregates are less likely to occur, and the film-forming properties of the resulting chloroprene seed polymer latex and the strength of the molded product are easily maintained. Furthermore, when the polymerization temperature is within this range, the polymerization proceeds rapidly, allowing the chloroprene seed polymer latex to be produced efficiently.

[0062] The polymerization initiator used in the second polymerization step is not particularly limited, and a general radical polymerization initiator can be used. Examples of the radical polymerization initiator 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. One type of polymerization initiator may be used alone, or two or more types may be used in combination.

[0063] The amount of the polymerization initiator added in the second polymerization step is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the monomer components.

[0064] In the second polymerization step, a co-catalyst may be used in combination with the polymerization initiator. The co-catalyst is not particularly limited, and a general co-catalyst may be used. Examples of the co-catalyst include anthraquinone sulfonate, potassium sulfite, sodium disulfite, sodium sulfite, tetraethylenepentamine, and N,N-dimethyl-p-toluidine. One type of co-catalyst may be used alone, or two or more types may be used in combination.

[0065] When a co-catalyst is used in the second polymerization step, the amount of the co-catalyst added is preferably 0.0005 to 1.0 part by mass, more preferably 0.001 to 0.5 part by mass, per 100 parts by mass of the monomer components.

[0066] In the second polymerization step, a molecular weight modifier may be added for the purpose of obtaining a chloroprene seed polymer having the desired molecular weight and molecular weight distribution. The molecular weight modifier is not particularly limited, and a general chain transfer agent can be used. Examples of molecular weight modifiers include xanthogen disulfides such as diisopropyl xanthogen disulfide, diethyl xanthogen disulfide, dicyclohexyl xanthogen disulfide, dilauryl xanthogen disulfide, and dibenzyl xanthogen disulfide; and alkyl mercaptans such as n-dodecyl mercaptan, n-decyl mercaptan, and octyl mercaptan, with alkyl mercaptans being preferred. One type of molecular weight modifier may be used alone, or two or more types may be used in combination.

[0067] When a molecular weight modifier is used in the second polymerization step, the amount of the molecular weight modifier added is preferably 0.001 to 0.3 parts by mass, more preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the monomer components.

[0068] At the end of the polymerization reaction in the second polymerization step, a polymerization terminator may be added to terminate the further polymerization reaction when a predetermined polymerization rate is reached, in order to obtain a chloroprene seed polymer having the desired molecular weight and molecular weight distribution. The polymerization terminator is not particularly limited, but specific examples include phenothiazine, para-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, diethylhydroxylamine, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical. One type of polymerization terminator may be used alone, or two or more types may be used in combination.

[0069] When a polymerization terminator is used in the second polymerization step, the amount of the polymerization terminator added is preferably 0.005 to 0.15 parts by mass, more preferably 0.01 to 0.1 parts by mass, per 100 parts by mass of the monomer components.

[0070] The solids concentration of the chloroprene seed polymer latex obtained in the second polymerization step is preferably 35 to 65% by mass. When the solids concentration is within this range, it is easier to maintain the colloidal stability of the chloroprene seed polymer latex, and the occurrence of aggregates can be minimized.

[0071] Furthermore, from the viewpoint of improving the strength of the obtained molded product, the content of the tetrahydrofuran-insoluble matter in the chloroprene seed polymer latex (tetrahydrofuran-insoluble matter rate) is preferably 50 to 99.9% by mass, more preferably 60 to 99% by mass, and even more preferably 85 to 99% by mass, relative to 100% by mass of the chloroprene seed polymer.

[0072] The content of the tetrahydrofuran insoluble matter in the chloroprene seed polymer latex can be controlled by the polymerization conditions such as the types of emulsifier and polymerization initiator in the second polymerization step, and the types of molecular weight modifier and polymerization terminator used as needed, the polymerization temperature, the conversion rate of monomer (B), etc. It can also be adjusted by the content of the tetrahydrofuran insoluble matter in the chloroprene polymer latex used.

[0073] <Other Steps> To the chloroprene polymer latex obtained in the first polymerization step or the chloroprene seed polymer latex obtained in the second polymerization step, metal oxides, antioxidants, pH adjusters, surfactants, fillers, tackifiers, pigments, colorants, wetting agents, antifoaming agents, thickeners, etc. can be appropriately added within a range that does not impair the object of the present invention. These additives may be added directly to the polymer latex, or those that are insoluble in water or that destabilize the colloidal state of the polymer latex may be added after preparing an aqueous dispersion in advance.

[0074] (Metal Oxide) Chloroprene and chloroprene polymers contain halogen, so they usually do not require a halogen donor during polymerization, but it is preferable to use them together with a hydrogen halide acid acceptor such as a metal oxide. Examples of metal oxides include zinc oxide, lead oxide, and trilead tetroxide, with zinc oxide being preferred. One type of metal oxide may be used alone, or two or more types may be used in combination.

[0075] When a metal oxide is used, the amount of the metal oxide added is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 6 parts by mass, relative to 100 parts by mass of the solid content of the polymer latex. When the metal oxide is added in the above range, a composition having sufficient tensile strength and flexibility may be obtained.

[0076] (Antioxidant) Chloroprene-based polymers such as chloroprene polymers and chloroprene seed polymers generally tend to be easily deteriorated by oxygen, and therefore, by incorporating an antioxidant, deterioration by oxygen can sometimes be suppressed. As the antioxidant, when appearance, particularly color tone and hygiene, are important, such as in medical gloves, hindered phenol-based antioxidants are preferred. The antioxidants may be used alone or in combination of two or more.

[0077] When an antioxidant is used, the amount of the antioxidant added is preferably 0.1 to 5 parts by mass per 100 parts by mass of the solid content of the polymer latex. When the amount of the antioxidant added is equal to or more than the lower limit, the antioxidant effect is improved, whereas when the amount is equal to or less than the upper limit, crosslinking tends to be promoted and the color tone tends to be improved.

[0078] (pH Adjusting Agent) From the viewpoint of colloid stability and film thickness adjustment, it is preferable to use, as the pH adjusting agent, alkalis such as potassium hydroxide and ammonia, and weak acids such as amino acids (e.g., glycine), acetic acid, and citric acid. It is preferable to make them into an aqueous solution before use and dilute them to an extent that does not shock the colloid.

[0079] When a pH adjuster is used, the amount of the pH adjuster added is preferably 0.01 to 5 parts by mass, more preferably 0.5 to 4 parts by mass, and even more preferably 1.5 to 3.5 parts by mass, relative to 100 parts by mass of the solid content of the polymer latex. When the amount of the pH adjuster added is equal to or greater than the lower limit, colloidal stabilization and film thickness adjustment become easy, whereas when the amount is equal to or less than the upper limit, coagulation tends to be sufficiently facilitated and the occurrence of aggregates in the blend tends to be suppressed.

[0080] (Surfactant) When a weak acid is added as a pH adjuster, it is preferable to add a surfactant to the polymer latex in advance from the viewpoint of colloidal stability, etc. Examples of the surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, with anionic surfactants being preferred. Examples of the anionic surfactant include alkyl sulfate ester salts such as sodium lauryl sulfate and triethanolamine lauryl sulfate. When a surfactant is used, the amount of the surfactant added is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, per 100 parts by mass of the solid content of the polymer latex.

[0081] <Chloroprene Seed Polymer Composition> The chloroprene seed polymer composition (hereinafter also referred to as "the composition") obtained by the production method of one embodiment of the present invention contains a chloroprene seed polymer latex synthesized through at least a first polymerization step and a second polymerization step. Even though the composition does not contain a vulcanization accelerator that is usually used when molding a molded product, the resulting molded product has the basic rubber properties (e.g., tensile strength, rubber elasticity) that a chloroprene polymer inherently has.

[0082] Examples of vulcanization accelerators include thiuram-based, dithiocarbamate-based, thiourea-based, and guanidine-based vulcanization accelerators commonly used in the vulcanization of chloroprene polymer latex. Examples of thiuram-based vulcanization accelerators include tetraethylthiuram disulfide and tetrabutylthiuram disulfide. Examples of dithiocarbamate-based vulcanization accelerators include sodium dibutylthiodicarbamate, zinc dibutylthiodicarbamate, and zinc diethylthiodicarbamate. Examples of thiourea-based vulcanization accelerators include ethylenethiourea, diethylthiourea, trimethylthiourea, and N,N'-diphenylthiourea, with N,N'-diphenylthiourea being particularly preferred. Examples of guanidine-based vulcanization accelerators include diphenylguanidine and di-orthotoluylguanidine.

[0083] Since vulcanization accelerators cause type IV allergies, it is preferable that the present composition does not contain a vulcanization accelerator from the viewpoint of safe use without worrying about allergies when used as medical gloves. Molded products obtained from the present composition are suitable for use in, for example, rubber-dipped products such as gloves, blood pressure monitor bladders, and rubber threads, particularly in disposable medical gloves such as surgical gloves.

[0084] <<Method for Producing a Dipped Rubber Product>> A dipped rubber product can be produced by a known method. Specifically, using the present composition, a molded product (dipped rubber product) having a desired shape can be obtained by a known method in which the steps of dipping and coagulation, followed by leaching (removal of water-soluble impurities), drying, and then crosslinking are carried out in this order.

[0085] In the crosslinking step, a higher crosslinking temperature tends to be required compared to natural rubber in order to obtain the desired degree of crosslinking. The crosslinking temperature is usually 120 to 140°C, and the crosslinking time is 30 minutes to 2 hours. In order to avoid problems with the product appearance, such as blisters and pinholes, rough drying at a relatively low temperature in the range of 70 to 100°C before crosslinking may be necessary. It is preferable to carry out crosslinking sufficiently within a range that does not deteriorate, for example, tensile strength or elongation at break.

[0086] The molded product obtained from the composition preferably has a tensile strength (tensile strength at break; hereinafter also referred to as "Tb") of 16 MPa or more, and from the viewpoint of use as a medical glove, more preferably 17 MPa or more, even more preferably 18 MPa or more, and particularly preferably 20 MPa or more.

[0087] Furthermore, the molded article obtained from the composition preferably has rubber elasticity (M100 retention) of 73% or more, more preferably 75% or more, and even more preferably 78% or more. When the M100 retention is within the above range, the molded article can be said to have sufficiently excellent rubber elasticity.

[0088] The tensile strength (e.g., tensile strength at break) and rubber elasticity (e.g., M100 retention rate) of the molded product can be measured using a film-like molded product produced by the above-mentioned method for manufacturing a rubber-dipped product, and specifically, the measurements were performed using the method described in the examples below.

[0089] Hereinafter, embodiments of the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

[0090] Example 1 (1) Preparation of Chloroprene Polymer Latex A 5 L reactor was charged with 1,555 g of chloroprene, 145 g of 2,3-dichloro-1,3-butadiene (8.5% by mass relative to 100% by mass of the total of chloroprene and 2,3-dichloro-1,3-butadiene), 1,367 g of pure water, 73 g of disproportionated rosin, 20 g of potassium hydroxide, 18 g of sodium hydroxide, 1.0 g of n-dodecyl mercaptan, 4.8 g of potassium sulfite, and 9.0 g of a sodium salt of a β-naphthalenesulfonic acid formalin condensate, and emulsified. To the resulting emulsion, 0.3 g of potassium persulfate was added as a polymerization initiator, and polymerization was carried out at 40°C under a nitrogen atmosphere. When the desired conversion was reached, 18.8 g of a phenothiazine emulsion (containing 0.3 g of phenothiazine) was immediately added to terminate the polymerization. The solid content of the resulting product was 48% by mass, and the monomer conversion (total conversion of chloroprene and 2,3-dichloro-1,3-butadiene) was 88%. Subsequently, unreacted chloroprene was removed by steam stripping to obtain a chloroprene polymer latex [1] (solid content: 50% by mass, tetrahydrofuran insoluble content: 45%).

[0091] (2) Preparation of chloroprene seed polymer latex: A 3 L reactor was charged with 1500 g of the chloroprene polymer latex [1] obtained in (1), 26.5 g of glycine, 84 g of ethyl methacrylate (10 parts by mass per 100 parts by mass of the chloroprene polymer and ethyl methacrylate combined), 1.85 g of potassium sulfite, 126 g of pure water, 5.6 g of sodium lauryl sulfate, and 0.126 g of n-dodecyl mercaptan, and emulsified. 10.8 g of a 70% by mass aqueous solution of t-butyl hydroperoxide was added as a polymerization initiator to the resulting emulsion, and seed polymerization was carried out at 40°C under a nitrogen gas atmosphere. After the reaction was carried out for about 6 hours, 0.92 g of a 10% by mass aqueous solution of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radical was added to terminate the polymerization, thereby obtaining a chloroprene seed polymer latex (solid concentration: 50.1% by mass, tetrahydrofuran insoluble content: 90.0%). The conversion of ethyl methacrylate at this time was 95.5%.

[0092] [Examples 2 to 11, Comparative Examples 1 to 3] (1) Preparation of chloroprene polymer latex A chloroprene polymer latex [1] was obtained by the same procedure as in (1) of Example 1. (2) Preparation of chloroprene seed polymer latex A chloroprene seed polymer latex was obtained by the same procedure as in (2) of Example 1, except that the type and amount of monomer to be seed-polymerized into the chloroprene polymer were changed as shown in Table 1. The solids concentration of the obtained chloroprene seed polymer latex is shown in Table 1.

[0093] In Tables 1 and 2, EMA refers to ethyl methacrylate (homopolymer Tg: 65°C), MMA refers to methyl methacrylate (homopolymer Tg: 90 to 100°C), i-BMA refers to isobutyl methacrylate (homopolymer Tg: 50 to 60°C), t-BMA refers to tert-butyl methacrylate (homopolymer Tg: 107°C), DCB refers to 2,3-dichloro-1,3-butadiene (homopolymer Tg: 130°C), and n-BMA refers to n-butyl methacrylate (homopolymer Tg: 20°C).

[0094] [Example 12] (1) Preparation of chloroprene polymer latex A chloroprene polymer latex [2] was obtained by the same procedure as in (1) of Example 1 without adding a molecular weight modifier (solid content concentration: 50 mass%, monomer conversion: 88%, tetrahydrofuran insoluble content: 80%). (2) Preparation of chloroprene seed polymer latex A chloroprene seed polymer latex was obtained by the same procedure as in (2) of Example 6, except that the chloroprene polymer was changed to chloroprene polymer latex [2]. The solid content concentration of the obtained chloroprene seed polymer latex is shown in Table 2.

[0095] [Example 13] (1) Preparation of chloroprene polymer latex A chloroprene polymer latex [2] was obtained by the same procedure as in (1) of Example 12. (2) Preparation of chloroprene seed polymer latex A chloroprene seed polymer latex was obtained by the same procedure as in (2) of Example 12, except that the type and amount of monomer to be seed polymerized into the chloroprene polymer were changed as shown in Table 2. The solids concentration of the obtained chloroprene seed polymer latex is shown in Table 2.

[0096] Comparative Example 4 (1) Preparation of Chloroprene Polymer Latex The same procedure as in (1) of Example 1 was carried out to obtain a chloroprene polymer latex [1].

[0097] Comparative Example 5 (1) Preparation of Chloroprene Polymer Latex The same procedure as in Example 12 (1) was carried out to obtain a chloroprene polymer latex [2].

[0098] <Evaluation of Polymer Latex> The conversion rate and the tetrahydrofuran insoluble content of the polymer latex (chloroprene polymer latex or chloroprene seed polymer latex) obtained in the examples and comparative examples were evaluated by the following methods.

[0099] Evaluation of Conversion Rate The polymer latex after polymerization was collected, and the monomer conversion rate was calculated from the solid content after drying at 141°C for 30 minutes. The solid content concentration and monomer conversion rate were calculated using the following formula, and the amount of polymer produced was calculated by subtracting the solid content other than the polymer from the solid content concentration. The results are shown in Tables 1 and 2. Solid content concentration [mass %] = [(weight of latex after drying at 141°C for 30 minutes) / (weight of latex before drying)] × 100 Monomer conversion rate [%] = [(amount of polymer produced / charged amount of monomer)] × 100 However, in the seed polymerization of chloroprene polymer, if the shell content of the seed polymer is less than 5 parts by mass per 100 parts by mass of the seed polymer, the change in solid content will be small, which will significantly affect the value and may prevent accurate calculation. Therefore, in the preparation of the chloroprene seed polymer latex, when the amount of monomer (B) used was 5 parts by mass or less relative to 100 parts by mass of the total of the chloroprene polymer and monomer (B) (Examples 2 to 5), no evaluation was performed and the result was recorded as "N / A."

[0100] Evaluation of tetrahydrofuran insoluble content (gel content) Approximately 0.5 g of polymer latex was added dropwise to 100 ml of THF (tetrahydrofuran), and the mixture was shaken overnight. The supernatant dissolved phase was then separated using a centrifuge, and the THF was evaporated to dryness at 100°C for 1 hour. The amount of dissolved content was calculated, and this was subtracted from the amount of polymer latex used to calculate the tetrahydrofuran insoluble content [mass %]. The results are shown in Tables 1 and 2. (Tetrahydrofuran insoluble content [mass %] = (mass after evaporation and drying) ÷ (mass of polymer latex) × 100

[0101] <Evaluation of physical properties after crosslinking> (1) Preparation of chloroprene seed polymer composition 3 parts by mass (as solids) of potassium hydroxide and 5 parts by mass (as solids) of zinc oxide were blended with 100 parts by mass of the solids of the chloroprene seed polymer latex or chloroprene polymer latex obtained in the Examples and Comparative Examples, and the blend was placed in a stirring tank equipped with a three-one motor and stirred for 5 minutes or more to mix and homogenize, thereby preparing a chloroprene seed polymer composition. Note that potassium hydroxide was added as a 3% by mass aqueous solution, and zinc oxide was added as a 50% by mass aqueous dispersion.

[0102] (2) Preparation of Test Pieces A dipped film was obtained from the obtained chloroprene seed polymer composition using a 30% by mass aqueous calcium nitrate solution as a coagulation liquid, and then leached (exuded) in 50°C warm water for 2 minutes to remove water-soluble components. The film was then dried at 70°C for 30 minutes. The obtained film was vulcanized by heating at 130°C for 30 minutes using a conventional oven vulcanization method. The vulcanized sheet was appropriately cut according to the evaluation items to obtain test pieces with thicknesses of 0.15 to 0.25 mm. Using these test pieces, tensile strength and M100 retention were evaluated by the following methods.

[0103] Evaluation of Tensile Strength (Tensile Strength at Break) Using the test specimens, the tensile strength at break of the compositions was measured according to JIS K 6251:2017. Regarding the dimensions of the test specimens, dumbbell-shaped No. 6 specimens were used. This test measured the tensile strength at room temperature. The results are shown in Tables 1 and 2.

[0104] Evaluation of Rubber Elasticity (M100 Retention Rate) Using the test specimen, the modulus of the composition was measured according to JIS K 6251:2017. Regarding the dimensions of the test specimen, a dumbbell No. 6 was used. The dumbbell was pulled at 200 mm / min, and the pulling was stopped when it reached 100% elongation. In this test, the modulus (M100) at 100% elongation was measured immediately after 100% elongation and after 2 minutes, and the retention rate after 2 minutes was calculated using the following formula. The results are shown in Tables 1 and 2. M100 Retention Rate [%] = (M100 after 2 minutes) / (M100 immediately after elongation) × 100

[0105]

[0106]

[0107] As shown in Tables 1 and 2, the compositions used in Examples 1 to 13 resulted in molded articles with high tensile strength (Tb) (16 MPa or higher) and high M100 retention (73% or higher). This indicates that the molded articles obtained have excellent strength and rubber elasticity. In Comparative Example 1, when n-butyl methacrylate was used as the monomer for seed polymerization, the tensile strength increased, but rubber elasticity was lost and M100 retention was significantly reduced. In Comparative Example 2, when 30 parts by mass of ethyl methacrylate was introduced per 100 parts by mass of seed polymer, film formation was not possible. In Comparative Example 3, when only 1 part by mass of ethyl methacrylate was polymerized per 100 parts by mass of seed polymer, the strength derived from ethyl methacrylate was not expressed, rubber elasticity was lost, and M100 retention was reduced. In Comparative Examples 4 and 5, when the chloroprene polymer latex obtained in the first polymerization step was used, the tensile strength derived from chloroprene was sufficient in both cases, but the M100 retention was low due to insufficient crosslinking.

Claims

1. A method for producing a chloroprene seed polymer composition comprising a first polymerization step and a second polymerization step, wherein the first polymerization step is a step of emulsion radically polymerizing at least a chloroprene monomer to obtain a chloroprene polymer, and the second polymerization step is a step of emulsion seed polymerizing the chloroprene polymer with at least a monomer (B-2) having a homopolymer glass transition temperature or melting point of 30°C or higher in an amount of 3 to 20 parts by mass per 100 parts by mass of the chloroprene polymer and the monomer (B-2).

2. A method for producing a chloroprene seed polymer composition comprising a first polymerization step and a second polymerization step, wherein the first polymerization step is a step of emulsion radically polymerizing at least a chloroprene monomer to obtain a chloroprene polymer, and the second polymerization step is a step of emulsion seed polymerizing the chloroprene polymer with 3 to 20 parts by mass of a (meth)acrylate monomer (B-1) having an alkyl group having at least 1 to 4 carbon atoms and having a linear carbon number of 3 or less in the alkyl group, per 100 parts by mass of the total of the chloroprene polymer and the monomer (B-1).

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

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

5. A method for producing a rubber dipping product, which is produced using a chloroprene seed polymer composition obtained by the method according to any one of claims 1 to 4.

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

7. The method for making a rubber dipped product according to claim 6, wherein the gloves are disposable medical gloves.

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