Chloroprene polymer composition, dip-molded body, and production method of these

Abstract

To provide a production method of a chloroprene polymer composition capable of obtaining a dip-molded body having an excellent breaking strength.SOLUTION: A production method of a chloroprene polymer composition containing a chloroprene polymer includes: a polymerization process of polymerizing a monomer including chloroprene by a polymerization rate of 20% or more to obtain a polymer composition containing a chloroprene polymer; and a mixing process of mixing the polymer composition with rosin including at least one conjugated resin acid component selected from the group consisting of abietic acid, neoabietic acid, palstric acid, levopimaric acid, and salts of these, where a mixing amount of the rosin in the mixing process is more than 0 pt.mass and less than 23 pts.mass to 100 pts.mass of a solid content of the polymer composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a chloroprene polymer composition, a dip-molded article, and methods for producing the same. [Background technology]

[0002] Chloroprene polymer compositions containing chloroprene polymers are used in various fields such as dipping molded bodies (dipping products), fiber treatment agents, paper processing agents, pressure sensitive adhesives, adhesives, elastic asphalt (modified asphalt), and elastic cement. In particular, for dipping molded bodies, chloroprene polymer compositions are used as the main raw material for various gloves for household use, industrial use, surgical use, and the like. Conventionally, natural rubber has been mainly used for gloves, but the use of synthetic rubber gloves has been recommended due to the problem of allergies caused by proteins contained in natural rubber. Among them, chloroprene polymers have been considered as an alternative material to natural rubber because they have physical properties similar to those of natural rubber in terms of feel, etc. (see, for example, Patent Documents 1 and 2 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 009038 [Patent Document 2] Patent Publication No. 2019-143002 Summary of the Invention [Problem to be solved by the invention]

[0004] A dip-molded article (glove, etc.) obtained by using a chloroprene polymer composition may have a lower breaking strength than a dip-molded article using natural rubber or isoprene rubber, and therefore, it is required to improve the breaking strength of the dip-molded article of the chloroprene polymer composition.

[0005] An object of one aspect of the present invention is to provide a method for producing a chloroprene polymer composition capable of obtaining a dip-molded article having excellent breaking strength.Another object of the present invention is to provide a chloroprene polymer composition capable of obtaining a dip-molded article having excellent breaking strength.Another object of the present invention is to provide a dip-molded article having excellent breaking strength and a method for producing the same. [Means for solving the problem]

[0006] A first embodiment of one aspect of the present invention relates to a method for producing a chloroprene polymer composition containing a chloroprene polymer, the method comprising: a polymerization step of polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more to obtain a polymer composition containing a chloroprene polymer; and a mixing step of mixing the polymer composition with a rosin containing at least one conjugated resin acid component selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof, wherein the amount of the rosin mixed in the mixing step is more than 0 part by mass and not more than 23 parts by mass per 100 parts by mass of the solids content of the polymer composition.

[0007] A second embodiment of one aspect of the present invention relates to a method for producing a chloroprene polymer composition containing a chloroprene polymer, the method comprising: a first polymerization step of polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more to obtain a first polymer composition containing a polymer; a mixing step of mixing the first polymer composition with a rosin containing at least one conjugated resin acid component selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof; and a second polymerization step of polymerizing a monomer containing chloroprene in the presence of the polymer and the conjugated resin acid component to obtain a second polymer composition containing a chloroprene polymer.

[0008] Another aspect of the present invention relates to a chloroprene polymer composition containing a chloroprene polymer, in which, in gas chromatography of an extract extracted from a dip-molded body of the chloroprene polymer composition using an ethanol-toluene azeotropic mixture, the ratio of the peak area of ​​conjugated resin acid components, which are abietic acid, neoabietic acid, palustric acid, levopimaric acid and salts thereof, is more than 0% and not more than 60%, based on the total peak area given by the extract.

[0009] Another aspect of the present invention relates to a dip-molded article of the above-mentioned chloroprene polymer composition.

[0010] Another aspect of the present invention relates to a chloroprene polymer composition obtained by the above-mentioned method for producing a chloroprene polymer composition, or a method for producing a dip-molded article, which comprises dip-molding the above-mentioned chloroprene polymer composition. Effect of the Invention

[0011] According to one aspect of the present invention, there is provided a method for producing a chloroprene polymer composition capable of obtaining a dip-molded article having excellent breaking strength. According to another aspect of the present invention, there is provided a chloroprene polymer composition capable of obtaining a dip-molded article having excellent breaking strength. According to another aspect of the present invention, there are provided a dip-molded article having excellent breaking strength and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the preferred embodiments. However, the present invention is not limited to the preferred embodiments described below.

[0013] The term "A or more" in a numerical range means A and a range exceeding A. The term "A or less" in a numerical range means A and a range less than A. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range in another stage. In the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more types. The content of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved. "Room temperature" means 25°C.

[0014] <Chloroprene polymer composition and method for producing same> The method for producing a chloroprene polymer composition according to this embodiment (including the method for producing a chloroprene polymer composition according to the first embodiment and the method for producing a chloroprene polymer composition according to the second embodiment; the same applies below) is a method for producing a chloroprene polymer composition containing a chloroprene polymer.

[0015] The method for producing a chloroprene polymer composition according to the first embodiment includes a polymerization step A for obtaining a polymer composition A containing a chloroprene polymer by polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more, and a mixing step A for mixing the polymer composition A with a rosin containing at least one conjugated resin acid component C selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof, wherein the amount of rosin mixed in the mixing step A is more than 0 parts by mass and not more than 23 parts by mass per 100 parts by mass of the solid content of the polymer composition A.

[0016] The method for producing a chloroprene polymer composition according to the second embodiment includes a polymerization step B1 (first polymerization step) of obtaining a polymer composition B1 (first polymer composition) containing a polymer B by polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more, a mixing step B of mixing the polymer composition B1 with a rosin containing at least one conjugated resin acid component C selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof, and a polymerization step B2 (second polymerization step) of polymerizing a monomer containing chloroprene in the presence of the polymer B (polymer obtained in the polymerization step B1) and the conjugated resin acid component C to obtain a polymer composition B2 (second polymer composition) containing a chloroprene polymer.

[0017] The chloroprene polymer composition according to the present embodiment is a chloroprene polymer composition containing a chloroprene polymer, and can be obtained by the method for producing a chloroprene polymer composition according to the present embodiment. In the chloroprene polymer composition according to the present embodiment, in gas chromatography of an extract extracted from a dip-molded product of the chloroprene polymer composition using an ethanol-toluene azeotropic mixture, the ratio of the peak area of ​​conjugated resin acid components, which are abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof, to the total peak area given by the extract is more than 0% and not more than 60%.

[0018] The chloroprene polymer composition according to this embodiment contains a chloroprene polymer and at least one conjugated resin acid component C selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof. The chloroprene polymer composition according to this embodiment may contain at least one non-conjugated resin acid component N selected from the group consisting of dehydroabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid, and salts thereof. The chloroprene polymer composition according to this embodiment may be a chloroprene polymer latex in which a chloroprene polymer is dispersed in water.

[0019] According to the chloroprene polymer composition and the method for producing the same of this embodiment, it is possible to obtain a dip-molded article having excellent breaking strength, and for example, as shown in the examples described later, excellent breaking strength can be obtained in a dip-molded article obtained using a composition containing a chloroprene polymer, sulfur, zinc oxide, etc. According to the chloroprene polymer composition and the method for producing the same of this embodiment, a breaking strength of 20.0 MPa or more can be obtained as measured in accordance with JIS K 6251.

[0020] The conjugated resin acid component has a conjugated double bond and is contained in rosin. In addition to such a conjugated resin acid component, rosin contains a non-conjugated resin acid component that does not have a conjugated double bond, and can be used as an emulsifier for synthetic rubber polymerization. It is generally known that the conjugated double bonds in an emulsifier inhibit a polymerization reaction, and there is a tendency to use an emulsifier obtained by eliminating the conjugated double bonds in the conjugated resin acid component through a disproportionation reaction. On the other hand, in the method for producing a chloroprene polymer composition according to this embodiment, although a conjugated resin acid component having a conjugated double bond is used, various physical properties can be suitably obtained by satisfying the above-mentioned characteristics.

[0021] According to the chloroprene polymer composition and the method for producing the same of the present embodiment, excellent breaking elongation can be obtained in the dip-molded article. For example, according to the chloroprene polymer composition and the method for producing the same of the present embodiment, breaking elongation of 1000% or more can be obtained as measured in accordance with JIS K 6251.

[0022] According to the chloroprene polymer composition and the method for producing the same of the present embodiment, it is possible to obtain an excellent modulus at extension (flexibility) in a dip-molded article. For example, according to the chloroprene polymer composition and the method for producing the same of the present embodiment, it is possible to obtain a modulus at 25% extension of 1.4 MPa or less as measured in accordance with JIS K 6251, and a modulus at 300% extension of 2.5 MPa or less as measured in accordance with JIS K 6251.

[0023] According to the chloroprene polymer composition and the production method thereof of this embodiment, it is possible to obtain an excellent mechanical strength while favorably maintaining flexibility in the dip molded article, and it is possible to obtain an excellent breaking strength and breaking elongation while favorably maintaining flexibility in the dip molded article.

[0024] In the polymerization steps A, B1, and B2 (hereinafter collectively referred to simply as "polymerization steps"), a monomer containing chloroprene (2-chloro-1,3-butadiene) is polymerized to obtain a polymer composition containing a chloroprene polymer. In the polymerization steps A and B1, a monomer containing chloroprene may be polymerized in the substantial absence of a conjugated resin acid component C. In the polymerization step B2, a monomer containing chloroprene is polymerized in the presence of the polymer B and the conjugated resin acid component C to obtain a polymer composition containing a chloroprene polymer. In the polymerization step B2, a monomer such as chloroprene may be added.

[0025] The chloroprene polymer obtained in the polymerization step and the chloroprene polymer in the chloroprene polymer composition according to this embodiment (hereinafter, these are collectively referred to simply as "chloroprene polymer") have chloroprene as a monomer unit (a monomer unit of chloroprene; monomer unit = structural unit) and can have a monomer unit derived from chloroprene. Examples of the chloroprene polymer include a chloroprene homopolymer and a chloroprene copolymer (a copolymer of chloroprene and a monomer copolymerizable with chloroprene), and a mixture of these polymers may also be used. In the polymerization step, chloroprene may be polymerized alone, or chloroprene may be copolymerized with a monomer copolymerizable with chloroprene.

[0026] Examples of monomers copolymerizable with chloroprene include esters of (meth)acrylic acid (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.), hydroxyalkyl (meth)acrylates (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.), (meth)acrylic acid, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, (meth)acrylonitrile, etc. The monomers copolymerizable with chloroprene are not limited to one type, and for example, a chloroprene copolymer may be a copolymer obtained by copolymerizing three or more types of monomers including chloroprene.

[0027] The chloroprene polymer may include at least one selected from the group consisting of chloroprene homopolymers and copolymers of chloroprene and 2,3-dichloro-1,3-butadiene, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded body.

[0028] The amount of chloroprene used in the method for producing a chloroprene polymer composition according to this embodiment (the total amount of the polymerization step B1 and the polymerization step B2 in the method for producing a chloroprene polymer composition according to the second embodiment) may be within the following ranges based on the total amount of monomers used in polymerization of the chloroprene polymer, or the total amount of chloroprene and 2,3-dichloro-1,3-butadiene, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded article. The amount of chloroprene used may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 88% by mass or more, or 90% by mass or more. The amount of chloroprene used may be 100% by mass or less, less than 100% by mass, 98% by mass or less, 95% by mass or less, 93% by mass or less, 92% by mass or less, 91% by mass or less, or less than 91% by mass. From these viewpoints, the amount of chloroprene used may be 50 to 100% by mass, 70 to 98% by mass, or 80 to 95% by mass.

[0029] From the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in a dip-molded article, the content of the chloroprene monomer unit in the chloroprene polymer may be within the following ranges based on the total amount of monomer units constituting the chloroprene polymer or the total amount of the chloroprene monomer unit and the 2,3-dichloro-1,3-butadiene monomer unit. The content of the chloroprene monomer unit may be 50 mass% or more, 60 mass% or more, 70 mass% or more, 75 mass% or more, 80 mass% or more, 85 mass% or more, 88 mass% or more, or 90 mass% or more. The content of the chloroprene monomer unit may be 100 mass% or less, less than 100 mass%, 98 mass% or less, 95 mass% or less, 93 mass% or less, 92 mass% or less, 91 mass% or less, or less than 91 mass%. From these viewpoints, the content of the chloroprene monomer unit may be 50 to 100% by mass, 70 to 98% by mass, or 80 to 95% by mass.

[0030] The monomers polymerized in the polymerization step may contain chloroprene and 2,3-dichloro-1,3-butadiene, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded body. The amount of 2,3-dichloro-1,3-butadiene used in the production method for the chloroprene polymer composition according to this embodiment (the total amount of the polymerization step B1 and the polymerization step B2 in the production method for the chloroprene polymer composition according to the second embodiment) may be in the following range based on the total amount of monomers used in polymerization of the chloroprene polymer or the total amount of chloroprene and 2,3-dichloro-1,3-butadiene, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded body. The amount of 2,3-dichloro-1,3-butadiene used may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, 12% by mass or less, or 10% by mass or less. The amount of 2,3-dichloro-1,3-butadiene used may be 0% by mass or more, more than 0% by mass, 2% by mass or more, 5% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, or more than 9% by mass. From these viewpoints, the amount of 2,3-dichloro-1,3-butadiene used may be 0 to 50% by mass, 2 to 30% by mass, or 5 to 20% by mass.

[0031] The chloroprene polymer may have a monomer unit of chloroprene and a monomer unit of 2,3-dichloro-1,3-butadiene from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded product. The content of the monomer unit of 2,3-dichloro-1,3-butadiene in the chloroprene polymer (copolymerization amount of 2,3-dichloro-1,3-butadiene) may be in the following range based on the total amount of monomer units constituting the chloroprene polymer or the total amount of the monomer units of chloroprene and the monomer units of 2,3-dichloro-1,3-butadiene. The content of the monomer unit of 2,3-dichloro-1,3-butadiene may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, 12% by mass or less, or 10% by mass or less. The content of the 2,3-dichloro-1,3-butadiene monomer unit may be 0% by mass or more, more than 0% by mass, 2% by mass or more, 5% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, or more than 9% by mass. From these viewpoints, the content of the 2,3-dichloro-1,3-butadiene monomer unit may be 0 to 50% by mass, 2 to 30% by mass, or 5 to 20% by mass. The content of the 2,3-dichloro-1,3-butadiene monomer unit can be determined by pyrolysis gas chromatography of a chloroprene polymer obtained by freeze-drying the chloroprene polymer composition.

[0032] The chloroprene polymer may not have at least one (meth)acrylic acid selected from the group consisting of acrylic acid and methacrylic acid as a monomer unit. The content of the acrylic acid monomer unit or the methacrylic acid monomer unit may be less than 2.0 mass%, less than 1.0 mass%, 0.5 mass% or less, or 0.1 mass% or less, based on the total amount of the monomer units constituting the chloroprene polymer, or may be 0 mass%. In the polymerization step, the amount of acrylic acid used (the total amount of the polymerization step B1 and the polymerization step B2 in the production method of the chloroprene polymer composition according to the second embodiment; the same applies to the amount of methacrylic acid used) or the amount of methacrylic acid used may be less than 2.0 mass%, less than 1.0 mass%, 0.5 mass% or less, or 0.1 mass% or less, based on the total amount of the monomers used in the polymerization of the chloroprene polymer.

[0033] The chloroprene polymer may be a sulfur-modified chloroprene polymer, a mercaptan-modified chloroprene polymer, a xanthogen-modified chloroprene polymer, a dithiocarbonate-based chloroprene polymer, a trithiocarbonate-based chloroprene polymer, a carbamate-based chloroprene polymer, or the like.

[0034] In the polymerization step, the monomers including chloroprene can be polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, etc. Among these polymerization methods, the monomers may be polymerized by emulsion polymerization from the viewpoints of ease of control, ease of extracting the chloroprene polymer from the polymer composition after polymerization, and a relatively fast polymerization rate.

[0035] Emulsion polymerization is a type of radical polymerization, and can be carried out by charging monomers into a polymerization tank together with water, an emulsifier, an emulsification aid, a chain transfer agent, a polymerization initiator (catalyst), a reducing agent (e.g., sodium hydrogen sulfite), etc. Examples of emulsifiers include rosin acid, alkali metal salts of rosin acid, disproportionated rosin, anionic emulsifiers (e.g., sodium salts of β-naphthalenesulfonic acid-formalin condensates), nonionic emulsifiers, etc., and a combination of two or more of these may be used.

[0036] The chain transfer agent may be a chain transfer agent used in the emulsion polymerization of normal chloroprene. Examples of the chain transfer agent include long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan; dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide; and iodoform. The amount of the chain transfer agent used may be 1 part by mass or less, 0.5 parts by mass or less, 0.1 parts by mass or less, 0.08 parts by mass or less, 0.05 parts by mass or less, less than 0.05 parts by mass, or 0.04 parts by mass or less, based on 100 parts by mass of the monomer used in the polymerization of the chloroprene polymer. The amount of the chain transfer agent used may be 0.001 parts by mass or more, 0.005 parts by mass or more, or 0.01 parts by mass or more, based on 100 parts by mass of the monomer used in the polymerization of the chloroprene polymer.

[0037] Examples of the polymerization initiator include organic peroxides such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and benzoyl peroxide.

[0038] The polymerization temperature may be from 5 to 55°C or from 15 to 45°C, from the viewpoint of easily maintaining the stability of the flexibility of the chloroprene polymer composition over time.

[0039] In the polymerization steps A and B1, monomers including chloroprene are polymerized at a polymerization rate (unit: mass%) of 20% or more. By carrying out the mixing steps A and B after such a polymerization rate is obtained, a state suitable for forming a dip-molded product is easily maintained in the subsequent steps (for example, a sudden increase in viscosity of the polymer composition in the polymerization step B2 is unlikely to occur, making it easy to maintain stability during polymerization), and therefore a dip-molded product having excellent mechanical strength (breaking strength, breaking elongation, etc.) while maintaining good flexibility can be obtained.

[0040] The polymerization rate in the polymerization step A (polymerization rate when mixing the rosin in the mixing step A, unit: mass %) may be in the following range. From the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded body, the polymerization rate in the polymerization step A may be 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, or 90% or more. The polymerization rate in the polymerization step A may be less than 100%, 95% or less, or 90% or less.

[0041] The polymerization rate in the polymerization step B1 (the polymerization rate when mixing the rosin in the mixing step B) may be in the following ranges. From the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.), the polymerization rate in the polymerization step B1 may be 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 85% or more. From the viewpoint of easily maintaining flexibility, the polymerization rate in the polymerization step B1 may be less than 100%, 95% or less, 90% or less, 85% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less.

[0042] The total polymerization rate (unit: mass%) of the polymerization step B1 and the polymerization step B2 in the production method of the chloroprene polymer composition according to the second embodiment may be in the following range. From the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded article, the polymerization rate may be 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, or 90% or more. The polymerization rate may be less than 100%, 95% or less, or 90% or less.

[0043] When the polymerization rate reaches a certain value, the polymerization can be stopped by using a polymerization terminator such as thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), diethylhydroxylamine, etc.

[0044] The method for producing a chloroprene polymer composition according to the first embodiment may include a polymerization step of polymerizing a monomer containing chloroprene in the presence of the polymer (chloroprene polymer) obtained in the polymerization step A and the conjugated resin acid component C after the mixing step A, i.e., a rosin containing the conjugated resin acid component C may be mixed during the polymerization of the monomer containing chloroprene. The method for producing a chloroprene polymer composition according to the first embodiment may not include such a polymerization step after the mixing step A, i.e., a rosin containing the conjugated resin acid component C may be mixed after the entire polymerization is completed. In this case, after a specified polymerization rate is reached in the polymerization step A, the mixing step A may be performed after removing and / or concentrating the unreacted monomer.

[0045] In the mixing steps A and B (hereinafter collectively referred to as the "mixing step"), the polymer composition obtained in the polymerization step A or B1 is mixed with a rosin containing at least one conjugated resin acid component C selected from the group consisting of abietic acid, neoabietic acid, parastric acid, levopimaric acid, and salts thereof (e.g., metal salts). Examples of the salts of abietic acid, neoabietic acid, parastric acid, and levopimaric acid include alkali metal salts such as sodium salts and potassium salts.

[0046] In the mixing step, the polymer composition obtained in the polymerization step A or polymerization step B1 may be mixed with a rosin containing a conjugated resin acid component C and a non-conjugated resin acid component. The non-conjugated resin acid component may be at least one selected from the group consisting of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and salts thereof. Examples of the salts of dehydroabietic acid, pimaric acid, isopimaric acid, and dihydroabietic acid include alkali metal salts such as sodium salts and potassium salts.

[0047] Rosin is usually a solid, and tends to be used after dissolving in an aqueous alkali metal salt solution. Examples of metal salts of rosin acid in rosin include alkali metal salts such as sodium rosinate and potassium rosinate. Rosin is not a single compound, but a mixture of various isomers of resin acids. Resin acids contained in rosin include conjugated resin acids with conjugated double bonds, such as abietic acid, neoabietic acid, palustric acid, and levopimaric acid, and non-conjugated resin acids without conjugated double bonds, such as pimaric acid, isopimaric acid, and dehydroabietic acid, and the content of each resin acid varies depending on the type of rosin. Rosin is classified into tall rosin, gum rosin, wood rosin, etc. depending on the manufacturing method. Since wood rosin accounts for less than 1% of the total rosin, tall rosin, gum rosin, etc. are often used.

[0048] From the viewpoint of obtaining a dip-molded article having excellent breaking strength, the amount of rosin mixed in the mixing step A is more than 0 part by mass and not more than 23 parts by mass relative to 100 parts by mass of the solid content of the polymer composition A obtained in the polymerization step A. From the viewpoint of easily obtaining excellent breaking elongation and easily maintaining flexibility, the amount of rosin mixed may be 20 parts by mass or less, 18 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, 8.0 parts by mass or less, 6.0 parts by mass or less, 5.5 parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, or 1.0 part by mass or less. From the viewpoint of easily obtaining excellent breaking strength, the amount of rosin mixed may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, 4.5 parts by mass or more, 5.0 parts by mass or more, 8.0 parts by mass or more, 10 parts by mass or more, 12 parts by mass or more, 15 parts by mass or more, 18 parts by mass or more, or 20 parts by mass or more. From these viewpoints, the amount of rosin mixed may be 0.1 to 23 parts by mass, 1.0 to 20 parts by mass, or 5.0 to 10 parts by mass.

[0049] The amount of rosin mixed in the mixing step B may be in the following ranges relative to 100 parts by mass of monomer (monomer used in polymerization of chloroprene polymer) from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded body. The amount of rosin mixed may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, or 4.5 parts by mass or more. The amount of rosin mixed may be 10 parts by mass or less, 8.0 parts by mass or less, 6.0 parts by mass or less, 5.0 parts by mass or less, or 4.5 parts by mass or less. From these viewpoints, the amount of rosin mixed may be 0.1 to 10 parts by mass, 1.0 to 8.0 parts by mass, or 3.0 to 5.0 parts by mass.

[0050] The amount of rosin mixed in the mixing step B may be in the following range with respect to 100 parts by mass of the solid content of the polymer composition B2 obtained in the polymerization step B2, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded product. The amount of rosin mixed may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, 4.5 parts by mass or more, or 5.0 parts by mass or more. The amount of rosin mixed may be 23 parts by mass or less, 20 parts by mass or less, 18 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, 8.0 parts by mass or less, 6.0 parts by mass or less, 5.5 parts by mass or less, or 5.0 parts by mass or less. From these viewpoints, the amount of rosin mixed may be 0.1 to 23 parts by mass, 1.0 to 10 parts by mass, or 3.0 to 6.0 parts by mass. The mixing amount (relative amount) of the rosin per 100 parts by mass of the solid content of the polymer composition B2 can be adjusted by the amount of the rosin used, the polymerization rate in the polymerization step B2, and the like.

[0051] The total amount of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts (total amount of conjugated resin acid component C) in the rosin mixed with the polymer composition in the mixing step may be in the following range based on the total mass of the rosin, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded product. The total amount may be 5 mass% or more, 10 mass% or more, 15 mass% or more, 20 mass% or more, 25 mass% or more, 30 mass% or more, or 35 mass% or more. The total amount may be 60 mass% or less, 55 mass% or less, 50 mass% or less, 45 mass% or less, or 40 mass% or less. From these viewpoints, the total amount may be 5 to 60 mass%, 10 to 50 mass%, or 20 to 40 mass%.

[0052] The total amount of dehydroabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid, and salts thereof (total amount of non-conjugated resin acid component N) in the rosin mixed with the polymer composition in the mixing step may be in the following range based on the total mass of the rosin, from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded product. The total amount may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more. The total amount may be 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less. From these viewpoints, the total amount may be 10 to 70% by mass, 20 to 60% by mass, or 30 to 50% by mass.

[0053] The total amount of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts (total amount of conjugated resin acid component C) in the rosin mixed with the polymer composition in the mixing step may be in the following range per 100 parts by mass of the total amount of dehydroabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid, and their salts (total amount of non-conjugated resin acid component N), from the viewpoint of easily obtaining excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility in the dip-molded product. The total amount may be 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, or 70 parts by mass or more. The total amount may be 150 parts by mass or less, 120 parts by mass or less, 100 parts by mass or less, less than 100 parts by mass, 90 parts by mass or less, or 80 parts by mass or less. From these viewpoints, the total amount may be 20 to 150 parts by mass, 50 to 100 parts by mass, or 60 to 80 parts by mass.

[0054] In the method for producing the chloroprene polymer composition according to this embodiment, the chloroprene polymer may be mixed with a pH adjuster, a freeze stabilizer, an emulsion stabilizer, a viscosity adjuster, an antioxidant, a preservative, or the like after the polymerization step.

[0055] In the method for producing the chloroprene polymer composition according to the present embodiment, after the polymerization step, the unreacted monomers may be removed, and then the solid content concentration may be adjusted by a concentration treatment. The solid content concentration of the chloroprene polymer composition according to the present embodiment may be, for example, 45 to 65% by mass.

[0056] The content of the conjugated resin acid component C in the chloroprene polymer composition according to this embodiment (the total amount of compounds corresponding to the conjugated resin acid component C) may be in the following range based on the total mass of the solid content of the chloroprene polymer composition. From the viewpoint of easily obtaining excellent breaking strength, the content of the conjugated resin acid component C may be 0.1 mass% or more, 0.2 mass% or more, 0.4 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 1.5 mass% or more, 1.9 mass% or more, 2.0 mass% or more, 3.0 mass% or more, 4.0 mass% or more, 5.0 mass% or more, 6.0 mass% or more, 7.0 mass% or more, or 7.5 mass% or more. The content of the conjugated resin acid component C may be 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less, 9.0% by mass or less, or 8.5% by mass or less, 8.0% by mass or less, 7.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.9% by mass or less, 1.5% by mass or less, 1.0% by mass or less, 0.5% by mass or less, or 0.4% by mass or less, from the viewpoint of easily obtaining excellent elongation at break and easily maintaining flexibility. From these viewpoints, the content of the conjugated resin acid component C may be 0.1 to 20% by mass, 0.4 to 10% by mass, or 1.0 to 9.0% by mass. The content of the conjugated resin acid component C in the chloroprene polymer composition according to the present embodiment can be calculated by gas chromatography of the solid content of the chloroprene polymer composition, and can be calculated by gas chromatography described in the examples.

[0057] The content of the conjugated resin acid component C in the chloroprene polymer composition according to this embodiment (the total amount of compounds corresponding to the conjugated resin acid component C) may be in the following range based on the total mass of the chloroprene polymer. From the viewpoint of easily obtaining excellent breaking strength, the content of the conjugated resin acid component C may be 0.1% by mass or more, 0.2% by mass or more, 0.4% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 1.5% by mass or more, 2.0% by mass or more, 3.0% by mass or more, 4.0% by mass or more, 5.0% by mass or more, 6.0% by mass or more, 7.0% by mass or more, or 8.0% by mass or more. From the viewpoint of easily obtaining excellent elongation at break and easily maintaining flexibility, the content of the conjugated resin acid component C may be 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less, 9.0% by mass or less, 8.5% by mass or less, 8.0% by mass or less, 7.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, 0.5% by mass or less, or 0.4% by mass or less. From these viewpoints, the content of the conjugated resin acid component C may be 0.1 to 20% by mass, 0.4 to 10% by mass, or 1.0 to 9.0% by mass.

[0058] The average particle size of the solid content of the chloroprene polymer composition according to the present embodiment may be in the following ranges from the viewpoint of easily obtaining a dip-molded product having excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility. The average particle size may be 50 nm or more, 80 nm or more, 100 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 145 nm or more, 150 nm or more, or 160 nm or more. The average particle size may be 200 nm or less, 180 nm or less, 160 nm or less, 150 nm or less, 145 nm or less, 140 nm or less, or 130 nm or less. From these viewpoints, the average particle size may be 50 to 200 nm, 100 to 160 nm, or 120 to 150 nm.

[0059] The viscosity (25°C) of the chloroprene polymer composition according to this embodiment may be in the following range. From the viewpoint of easily obtaining a dip-molded product having excellent mechanical strength (breaking strength, breaking elongation, etc.) while favorably maintaining flexibility, the viscosity may be 1000 mPa·s or less, 800 mPa·s or less, 500 mPa·s or less, 300 mPa·s or less, 200 mPa·s or less, 150 mPa·s or less, 140 mPa·s or less, 130 mPa·s or less, 125 mPa·s or less, 120 mPa·s or less, 100 mPa·s or less, or 90 mPa·s or less. The viscosity may be 50 mPa·s or more, 80 mPa·s or more, 90 mPa·s or more, 100 mPa·s or more, 120 mPa·s or more, 125 mPa·s or more, 130 mPa·s or more, or 140 mPa·s or more. From these viewpoints, the viscosity may be 50 to 1000 mPa·s, 90 to 500 mPa·s, or 100 to 200 mPa·s. The viscosity can be measured under conditions of a temperature of 25° C. and a rotation speed of 30 rpm.

[0060] In the chloroprene polymer composition of this embodiment, from the viewpoint of obtaining excellent breaking strength in a dip-molded body, in gas chromatography of an extract extracted from a dip-molded body of the chloroprene polymer composition using an ethanol-toluene azeotropic mixture, the ratio of the peak area of ​​conjugated resin acid components, which are abietic acid, neoabietic acid, palustric acid, levopimaric acid and their salts, is more than 0% and not more than 60%, based on the total peak area given by the extract (the total peak area detected by gas chromatography).

[0061] The extract for obtaining the above-mentioned peak area ratio of the conjugated resin acid component can be extracted using an ethanol-toluene azeotropic mixture (ETA solution, volume ratio, ethanol:toluene=70:30). The immersion molded body having the above-mentioned peak area ratio of the conjugated resin acid component can be obtained by the following procedure. (1) A cylinder with an outer diameter of 50 mm is immersed for 1 second in a coagulation liquid (room temperature) obtained by mixing 61 parts by mass of water, 36 parts by mass of potassium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate, and then the cylinder is removed. (2) Dry at room temperature for 3 minutes, then dry at 70°C for 1 minute. (3) The cylinder is immersed in a chloroprene polymer latex composition (room temperature, solids concentration: 30% by mass) for 2 minutes. (4) Dry at 130°C for 3 minutes, then wash at 45°C for 1 minute. (5) Vulcanize at 130°C for 30 minutes.

[0062] From the viewpoint of easily obtaining excellent breaking strength, the proportion of the peak area of ​​the conjugated resin acid component may be 0.1% or more, 0.2% or more, 0.4% or more, 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, 4.0% or more, 4.6% or more, 4.7% or more, 4.8% or more, 5.0% or more, 8.0% or more, 10% or more, 15% or more, 17% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more. From the viewpoint of easily obtaining excellent elongation at break and easily maintaining flexibility, the peak area ratio of the conjugated resin acid component may be 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 17% or less, 15% or less, 10% or less, 8.0% or less, 5.0% or less, 4.8% or less, 4.7% or less, 4.6% or less, 4.0% or less, 3.0% or less, 2.0% or less, 1.0% or less, 0.5% or less, or 0.4% or less. From these viewpoints, the peak area ratio of the conjugated resin acid component may be 0.1 to 50%, 0.4 to 40%, or 4.0 to 20%. The peak area ratio of the conjugated resin acid component can be adjusted by the amount of the conjugated resin acid component C used when obtaining the chloroprene polymer composition.

[0063] The chloroprene polymer composition according to the present embodiment may contain additives such as a vulcanizing agent, a vulcanization accelerator, an antiaging agent (an antioxidant, for example, an ozone antiaging agent), a filler, a plasticizer, a pigment, a colorant, a wetting agent, an antifoaming agent, etc. The chloroprene polymer composition according to the present embodiment may be a mixed liquid for dip molding that contains a chloroprene polymer and these additives.

[0064] Examples of the vulcanizing agent include sulfur (molecular sulfur, for example, cyclic sulfur such as S8); metal oxides such as zinc oxide, lead oxide, and trimead tetroxide; and magnesium oxide. The content of the vulcanizing agent may be 0.5 to 10 parts by mass relative to 100 parts by mass of the solid content of the mixture obtained by excluding the above-mentioned additives from the chloroprene polymer composition, from the viewpoint of easily proceeding crosslinking and easily obtaining suitable tensile strength, modulus, and the like of the dip-molded article, and from the viewpoint of easily obtaining a suitable tactile feel of the dip-molded article.

[0065] Examples of the vulcanization accelerator include thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, and thiazole-based vulcanization accelerators.

[0066] Examples of the antiaging agent include diphenylamine-based compounds such as octylated diphenylamine, p-(p-toluene-sulfonylamido)diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N,N'-diphenyl-p-phenylenediamine (DPPD), and N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD). Examples of the anti-ozone agent include N,N'-diphenyl-p-phenylenediamine (DPPD) and N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD). Examples of the antiaging agent include bound phenol-based antioxidants when the appearance (particularly color tone) or hygiene is important, such as in medical gloves. The content of the antiaging agent may be 0.1 to 5 parts by mass with respect to 100 parts by mass of the solid content of the mixture obtained by removing the above-mentioned additives from the chloroprene polymer composition, from the viewpoint of easily obtaining a sufficient antiaging effect.

[0067] <Methods of production of vulcanized products and dip-molded products> A vulcanizate may be obtained by vulcanizing the chloroprene polymer composition according to this embodiment. The vulcanizate according to this embodiment is a vulcanizate of the chloroprene polymer composition according to this embodiment, and is obtained by vulcanizing the chloroprene polymer composition according to this embodiment. A method for producing a vulcanizate according to this embodiment includes a step of vulcanizing the chloroprene polymer composition according to this embodiment to obtain a vulcanizate. The vulcanizate according to this embodiment may be in the form of a film.

[0068] The dip-molded article according to the present embodiment is a dip-molded article of the chloroprene polymer composition according to the present embodiment. The dip-molded article according to the present embodiment is a dip-molded article using the chloroprene polymer composition according to the present embodiment, and is obtained by dip-molding the chloroprene polymer composition according to the present embodiment. The dip-molded article according to the present embodiment may be a dip-molded film formed on a substrate. The dip-molded article according to the present embodiment has excellent breaking strength and breaking elongation while favorably maintaining flexibility. The dip-molded article according to the present embodiment may be a molded article of the vulcanizate according to the present embodiment. The dip-molded article according to the present embodiment may be a glove, a balloon, a catheter, or a boot.

[0069] The thickness of the dip-molded product (for example, the minimum thickness) may be 0.01 to 0.50 mm, 0.10 to 0.50 mm, 0.10 to 0.30 mm, or 0.10 to 0.25 mm. The thickness of the dip-molded product can be adjusted by the time for which the mold is immersed in the chloroprene polymer composition, the solids concentration of the chloroprene polymer composition, and the like. To reduce the thickness of the dip-molded product, the immersion time may be shortened or the solids concentration of the chloroprene polymer composition may be reduced.

[0070] In the method for producing the dip-molded product according to the present embodiment, the chloroprene polymer composition obtained by the method for producing the chloroprene polymer composition according to the present embodiment or the chloroprene polymer composition according to the present embodiment is dip-molded. As a molding method for producing the dip-molded product according to the present embodiment, a known method can be used, and examples thereof include a simple dipping method, an adhesion dipping method, a heat-sensitive dipping method, and an electrodeposition method. From the viewpoint of ease of production and ease of obtaining a dip-molded product of a certain thickness, the adhesion dipping method can be used. Specifically, a molding die coated with a flocculant is dipped in the chloroprene polymer composition, and then the chloroprene polymer composition is solidified. Then, water-soluble impurities are removed by leaching, and the composition is dried, and further vulcanized to form a dip-molded film (rubber film), and the dip-molded film is released from the mold. This allows a film-like dip-molded product to be obtained. EXAMPLES

[0071] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[0072] <Preparation of Chloroprene Polymer Latex> (Example A1) In a polymerization vessel having an internal volume of 40 L, 90.5 parts by mass of chloroprene (monomer), 9.5 parts by mass of 2,3-dichloro-1,3-butadiene (monomer), 0.032 parts by mass of n-dodecyl mercaptan, 84.3 parts by mass of pure water, 4.8 parts by mass of disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name: LONDISU K-25), 0.75 parts by mass of potassium hydroxide, 0.40 parts by mass of sodium hydrogen sulfite, and 0.40 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N) were added. After adding 0.1 parts by mass of potassium persulfate as a polymerization initiator, polymerization was carried out under a nitrogen gas flow at a polymerization temperature of 40°C. When the polymerization rate reached 90%, 0.007 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to terminate the polymerization, thereby obtaining latex A1.

[0073] The latex A1 was distilled under reduced pressure to remove unreacted monomers, and then concentrated to obtain a latex A2 (solid content concentration: 60% by mass) containing a chloroprene polymer. The gel content (toluene insoluble content) of the solid content of the latex A2 was measured and found to be 88% by mass.

[0074] Next, rosin (Harima Chemicals, product name: Hartall R-WW) was dissolved in an aqueous potassium hydroxide solution to obtain a rosin solution (solid content concentration: 12.5% ​​by mass). This rosin solution was mixed with Latex A2 in a ratio of 1.0 part by mass of potassium salt of rosin acid (rosin containing a conjugated resin acid component) per 100 parts by mass of the solid content of Latex A2 to obtain a chloroprene polymer latex.

[0075] (Examples A2 to A4) A chloroprene polymer latex was obtained in the same manner as in Example A1, except that the amount of the rosin solution mixed with Latex A2 was changed to mix the potassium salt of rosin acid (rosin containing a conjugated resin acid component) in the amount shown in Table 1 with respect to 100 parts by mass of the solid content of Latex A2.

[0076] (Comparative Example A1) Latex A2 of Example A1 was used as the chloroprene polymer latex without mixing the rosin solution therein.

[0077] (Comparative example A2) A rosin solution (solid content concentration: 12.5% ​​by mass) was obtained by dissolving disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name: Longis K-25, conjugated resin acid 0%, non-conjugated resin acid 93.9%) in an aqueous potassium hydroxide solution. This rosin solution was mixed with Latex A2 of Example A1 to obtain a chloroprene polymer latex containing 5 parts by mass of potassium salt of disproportionated rosin per 100 parts by mass of solid content of Latex A2.

[0078] (Comparative example A3) A rosin solution (solid content concentration: 12.5% ​​by mass) was obtained by dissolving disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name: Longis K-25, conjugated resin acid 0%, non-conjugated resin acid 93.9%) in an aqueous potassium hydroxide solution. This rosin solution was mixed with Latex A2 of Example A1 to obtain a chloroprene polymer latex containing 20 parts by mass of potassium salt of disproportionated rosin per 100 parts by mass of solid content of Latex A2.

[0079] (Comparative example A4) A chloroprene polymer latex was obtained in the same manner as in Example A1, except that the amount of the rosin solution mixed with Latex A2 was changed so that 25 parts by mass of potassium salt of rosin acid (rosin containing a conjugated resin acid component) was mixed with 100 parts by mass of the solid content of Latex A2.

[0080] Example B1 Into a polymerization vessel having an internal volume of 40 L, 90.5 parts by mass of chloroprene (monomer), 9.5 parts by mass of 2,3-dichloro-1,3-butadiene (monomer), 0.032 parts by mass of n-dodecyl mercaptan, 84.3 parts by mass of pure water, 4.8 parts by mass of disproportionated rosin (manufactured by Arakawa Chemical Industries, Ltd., product name: Longis K-25), 0.75 parts by mass of potassium hydroxide, 0.40 parts by mass of sodium hydrogen sulfite, and 0.40 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N) were added. After adding 0.1 parts by mass of potassium persulfate as a polymerization initiator, polymerization was carried out under a nitrogen gas flow at a polymerization temperature of 40°C. When the polymerization rate reached 20%, 4.5 parts by mass of potassium salt of rosin acid (rosin containing conjugated resin acid component) was added using a rosin solution (solid content concentration: 12.5% ​​by mass) obtained by dissolving rosin (manufactured by Harima Chemicals Co., Ltd., product name: Hartall R-WW) in an aqueous potassium hydroxide solution. Thereafter, polymerization was continued, and when the polymerization rate reached 90%, 0.007 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to terminate the polymerization, thereby obtaining latex B. The amount of potassium salt of rosin acid (rosin containing conjugated resin acid component) added was 5.0 parts by mass relative to 100 parts by mass of solid content of latex B. This latex B was distilled under reduced pressure to remove unreacted monomers, and then concentrated to obtain a chloroprene polymer latex.

[0081] (Example B2) A chloroprene polymer latex was obtained by the same procedure as in Example B1, except that when the polymerization rate reached 85% instead of 20%, a potassium salt of rosin acid (rosin containing a conjugated resin acid component) was added using a rosin solution.

[0082] (Comparative Example B1) A chloroprene polymer latex was obtained by the same procedure as in Example B1, except that when the polymerization rate reached 15% instead of 20%, a potassium salt of rosin acid (rosin containing a conjugated resin acid component) was added from a rosin solution.

[0083] <Content of resin acid components in rosin> The contents of conjugated resin acid components and non-conjugated resin acid components in the above-mentioned rosin (manufactured by Harima Chemical Co., Ltd., product name: Hartall R-WW) were measured by the following procedure for the total amount of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts (content of conjugated resin acid component C), and the total amount of dehydroabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid, and their salts (content of non-conjugated resin acid component N).The content of conjugated resin acid component C was 38.7% by mass, and the content of non-conjugated resin acid component N was 48.4% by mass, based on the total mass of the rosin.

[0084] First, 0.30 g of rosin was dissolved in 10 mL of ETA solution (volume ratio, ethanol:toluene = 70:30) and then treated with hydrochloric acid to obtain a solution (rosin: 3 mass%). 5 mL of this solution collected with a whole pipette was placed in a 10 mL measuring flask and then diluted with ETA solution to obtain a solution (rosin: 1.5 mass%). Gas chromatography was performed using this solution under the following conditions. From the results of gas chromatography measurement, the peak areas of the abietic acid component (abietic acid and its salts. The same applies to other resin acid components), neoabietic acid component, palustric acid component, and levopimaric acid component were obtained, and the peak areas of the dehydroabietic acid component, pimaric acid component, isopimaric acid component, and dihydroabietic acid component were obtained. As the peak area of ​​the conjugated resin acid component, the sum of the peak areas of the abietic acid component, the neoabietic acid component, the parastric acid component, and the levopimaric acid component was calculated, and then the ratio of the peak area of ​​the conjugated resin acid component based on the sum of the peak areas detected by gas chromatography was calculated as the content of the conjugated resin acid component C. As the peak area of ​​the non-conjugated resin acid component, the sum of the peak areas of the neoabietic acid component, the parastric acid component, and the levopimaric acid component was calculated, and then the ratio of the peak area of ​​the non-conjugated resin acid component based on the sum of the peak areas detected by gas chromatography was calculated as the content of the non-conjugated resin acid component N.

[0085] [Gas chromatography conditions] Gas chromatograph mass spectrometer: Product name "JEOL Jms-Q1050GC", manufactured by JEOL Ltd. Column used: FFAP 0.32mmφ×25m (film thickness 0.3μm) Column temperature: 200℃→250℃ Heating rate: 10℃ / min ·Inlet temperature: 270℃ ·Injection volume: 1μL Interface temperature: 270℃ Ion source temperature: 270℃ Ionization current: 50μA Ionization voltage: 70eV Detector: FID Detector voltage: -1000V Detector voltage: EI method Detector temperature: 270℃

[0086] <Content of conjugated resin acid component in chloroprene polymer latex> The above-mentioned chloroprene polymer latex was freeze-dried and 3 g of the solid content was cut into 2 mm squares to obtain a test piece. The test piece was placed in a pear-shaped flask equipped with a condenser, extracted with an ETA solution (volume ratio, ethanol:toluene = 70:30), and then treated with hydrochloric acid to obtain an extract, which was then subjected to gas chromatography under the same conditions as those for the analysis of the content of conjugated resin acid components and non-conjugated resin acid components in the above-mentioned rosin, to calculate the content of conjugated resin acid components in the chloroprene polymer latex (the total amount of abietic acid, neoabietic acid, parastric acid, levopimaric acid, and their salts). The content of conjugated resin acid components was calculated based on the total mass of the solid content of the chloroprene polymer latex and the total mass of the chloroprene polymer. The proportion of the chloroprene polymer in the solid content of the chloroprene polymer latex can be calculated based on the amounts of monomer and disproportionated rosin used, the polymerization rate, etc., and the content of the conjugated resin acid component based on the total mass of the chloroprene polymer is 1.05 times the content of the conjugated resin acid component based on the total mass of the solid content of the chloroprene polymer latex. The results are shown in Tables 1 and 2.

[0087] <Average particle size of solids in chloroprene polymer latex> Using a light scattering diffraction particle size measuring device (manufactured by Otsuka Electronics Co., Ltd., model: ELSZ-2), the particle size distribution based on scattering intensity in the solid content of the chloroprene polymer latex was measured. The average particle size was calculated based on the measurement results of the particle size distribution based on scattering intensity. The results are shown in Tables 1 and 2.

[0088] <Viscosity of chloroprene polymer latex> The viscosity of the chloroprene polymer latex was measured using a rotational viscosity measuring device (manufactured by Toki Sangyo Co., Ltd., model: TV-25) at a temperature of 25° C. and a rotation speed of 30 rpm. The results are shown in Tables 1 and 2.

[0089] <Preparation of Chloroprene Polymer Latex Composition> Using a ceramic ball mill, 1 part by mass of sulfur, 2 parts by mass of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., product name: zinc oxide type 2), 2 parts by mass of a vulcanization accelerator (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name: Noccela BZ), 2 parts by mass of an antioxidant (manufactured by OMNOVA SOLUTIONS, product name: Wingstay-L), 0.1 parts by mass of a sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, product name: Demol N), and 10.7 parts by mass of water were mixed at 20° C. for 16 hours to prepare an aqueous dispersion. The above-mentioned chloroprene polymer latex (solid content 100 parts by mass) was mixed with this aqueous dispersion (solid content 7.1 parts by mass), and water was added to adjust the total solid content concentration to 30% by mass, thereby preparing a chloroprene polymer latex composition.

[0090] <Preparation of evaluation film> A coagulation liquid was obtained by mixing 61 parts by mass of water, 36 parts by mass of potassium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate. A ceramic cylinder (material: ceramics, manufactured by Shinko Co., Ltd.) having an outer diameter of 50 mm was immersed in this coagulation liquid (room temperature) for 1 second, and then the cylinder was taken out. After drying at room temperature for 3 minutes, it was dried at 70°C for 1 minute. Then, the cylinder was immersed in the above-mentioned chloroprene polymer latex composition (room temperature) for 2 minutes. Then, it was dried at 130°C for 3 minutes, and washed in a water tank with a capacity of 11 L at 45°C for 1 minute. Then, it was vulcanized at 130°C for 30 minutes to prepare an evaluation film (dip-molded product, vulcanized film) on the outer peripheral surface of the cylinder. The evaluation film was peeled off from the outer peripheral surface of the cylinder and the following evaluation was performed. However, in Comparative Example B1, the particle size of the solid content in the chloroprene polymer latex increased, and the viscosity increased excessively, so that the evaluation film could not be prepared.

[0091] <Thickness of the film to be evaluated> The thickness (film thickness) of the evaluation film was measured at three points in the center of the evaluation film using a test piece thickness gauge (manufactured by Kobunshi Keiki Co., Ltd., product name: ASKER SDA-12), and the minimum thickness was taken as the evaluation film thickness. The results are shown in Tables 1 and 2.

[0092] <Ratio of peak area of ​​conjugated resin acid component in evaluation film> The film for evaluation was put into an ETA solution (volume ratio, ethanol:toluene = 70:30) and refluxed at 90 ° C for 1 hour to obtain an extract. The ETA solution was evaporated to extract the rosin component, and then hydrochloric acid was added to evaporate the acidic solution obtained. Then, using the extract made up to 20 mL by adding methanol, gas chromatography was performed under the same conditions as the content of the resin acid component in the rosin described above. The peak area of ​​the conjugated resin acid component was calculated by the sum of the peak areas of the abietic acid component, neoabietic acid component, parastolic acid component, and levopimaric acid component, and then the ratio of the peak area of ​​the conjugated resin acid component based on the sum of the peak areas detected by gas chromatography was calculated. The results are shown in Tables 1 and 2.

[0093] <Physical properties of the evaluation film> The modulus at 25% elongation, modulus at 300% elongation, breaking strength and breaking elongation of the evaluation film were measured in accordance with JIS K 6251. The results are shown in Tables 1 and 2. A breaking strength of 20.0 MPa or more was judged to be good.

[0094] [Table 1]

[0095] [Table 2]

[0096] According to the present invention, the following embodiments are provided. [1] A method for producing a chloroprene polymer composition containing a chloroprene polymer, comprising: a polymerization step of polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more to obtain a polymer composition containing a chloroprene polymer; and a mixing step of mixing the polymer composition with a rosin containing at least one conjugated resin acid component selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid and salts thereof, wherein the amount of the rosin mixed in the mixing step is more than 0 part by mass and not more than 23 parts by mass per 100 parts by mass of the solid content of the polymer composition. [2] A method for producing a chloroprene polymer composition containing a chloroprene polymer, comprising: a first polymerization step of polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more to obtain a first polymer composition containing a polymer; a mixing step of mixing the first polymer composition with a rosin containing at least one conjugated resin acid component selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof; and a second polymerization step of polymerizing a monomer containing chloroprene in the presence of the polymer and the conjugated resin acid component to obtain a second polymer composition containing a chloroprene polymer. [3] The method for producing a chloroprene polymer composition according to [2], wherein the amount of the rosin mixed in the mixing step is more than 0 parts by mass and not more than 23 parts by mass per 100 parts by mass of the solid content of the second polymer composition. [4] The method for producing a chloroprene polymer composition according to any one of [1] to [3], wherein the total amount of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof in the rosin is 30 mass% or more based on the total mass of the rosin. [5] The method for producing a chloroprene polymer composition according to any one of [1] to [4], wherein the monomer further contains 2,3-dichloro-1,3-butadiene. [6] A chloroprene polymer composition containing a chloroprene polymer, wherein, in gas chromatography of an extract extracted from a dipping molded body of the chloroprene polymer composition using an ethanol-toluene azeotropic mixture, the ratio of the peak area of ​​conjugated resin acid components, which are abietic acid, neoabietic acid, palustric acid, levopimaric acid and their salts, is more than 0% and not more than 60%, based on the total peak area given by the extract. [7] The chloroprene polymer composition according to [6], wherein the content of the conjugated resin acid component is 0.4 to 10 mass % based on the total mass of the chloroprene polymer. [8] A dip-molded article of the chloroprene polymer composition according to [6] or [7]. [9] The dip-molded article according to [8], which is a glove, a balloon, a catheter or a boot.

[10] A method for producing a dip-molded product, comprising dip-molding a chloroprene polymer composition obtained by the method for producing a chloroprene polymer composition according to any one of [1] to [5], or the chloroprene polymer composition according to [6] or [7].

Claims

[Claim 1] A method for producing a chloroprene polymer composition containing a chloroprene polymer, comprising the steps of: a polymerization step of polymerizing a monomer containing chloroprene at a polymerization rate of 20% or more to obtain a polymer composition containing a chloroprene polymer; A mixing step is provided for mixing the polymer composition with a rosin containing at least one conjugated resin acid component selected from the group consisting of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and salts thereof, The method for producing a chloroprene polymer composition, wherein the amount of the rosin mixed in the mixing step is more than 0 part by mass and 23 parts by mass or less per 100 parts by mass of a solid content of the polymer composition.

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