Method for producing chloroprene polymer compositions

Abstract

Provided is a method for producing a chloroprene-based polymer composition that supports a high recovery ratio from the polymerization vessel and that makes it possible to obtain dip-molded articles having a low 100% elongation modulus and an excellent tensile strength at break. The present invention provides a method for producing a chloroprene-based polymer composition, wherein the chloroprene-based polymer composition comprises a diene-based polymer A and a chloroprene-based polymer B and the diene-based polymer A and the chloroprene-based polymer B have different weight-average molecular weights. The method for producing this chloroprene-based polymer composition comprises a polymerization step for polymerizing the chloroprene-based polymer B in the presence of the diene-based polymer A.

Description

Technical Field

[0001] The present invention relates to a method for producing a chloroprene-based polymer composition.

Background Art

[0002] Chloroprene-based polymers are known as materials for dip-molded products such as medical surgical gloves, medical examination gloves, industrial gloves, balloons, catheters, and rubber boots.

[0003] Various technologies have been proposed for improving the flexibility of chloroprene polymers, including chloroprene polymer latex for immersion-molded products and chloroprene polymer immersion-molded articles. Patent Document 1 describes a polychloroprene latex with a pH of 7 to 14, containing 100 parts by mass of modified polychloroprene obtained by copolymerizing chloroprene and methacrylic acid, 90 to 150 parts by mass of water, 1 to 5 parts by mass of an emulsifier, and 0.5 to 2.5 parts by mass of potassium ions, for use in immersion-molded products. Patent Document 2 describes a mercaptan-modified polychloroprene latex for use in immersion-molded products, obtained by copolymerizing chloroprene and 2,3-dichloro-1,3-butadiene, such that the 13C-solid-state NMR spectrum of polychloroprene shows peak areas of 126.2-127.6 ppm (A), 122.0-126.2 ppm (B), and 129.9-130.3 ppm (C) within the range shown by the following general formula (I). Patent Document 3 describes a chloroprene polymer latex for use in immersion-molded products, which, by containing high and low molecular weight materials, can achieve both excellent flexibility and mechanical properties in vulcanized rubber produced by immersion molding. Patent Document 4 describes a chloroprene-based polymer latex obtained by copolymerizing chloroprene monomer and isoprene monomer, a raw material for isoprene rubber, which exhibits excellent flexibility and mechanical properties even under mild vulcanization conditions. Patent Document 5 describes an immersion molded article of an isoprene / chloroprene polymer that exhibits excellent flexibility even without containing a diphenylguanidine-based reagent, which is a vulcanization accelerator, by mixing isoprene-based polymer latex and chloroprene-based polymer latex. Patent Document 6 describes an immersion molded article that exhibits excellent mechanical properties by mixing nitrile-butadiene polymer (NBR) latex or isoprene-based polymer latex with a chloroprene-based polymer latex base.

[0004]

number

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-114342 [Patent Document 2] International Publication No. 2019 / 009038 [Patent Document 3] Japanese Patent Publication No. 2019-143002 [Patent Document 4] International Publication No. 2021-132460 [Patent Document 5] Special Publication No. 2017-508840 [Patent Document 6] Japanese Patent Publication No. 2020-189963 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Chloroprene polymer compositions, including chloroprene polymers, have been widely used in applications such as gloves, balloons, boots, and catheters. Furthermore, particularly in medical rubber glove applications, there is a growing demand for chloroprene polymer compositions that can produce immersion molded products with excellent flexibility and superior tensile strength at break, similar to those obtained using natural rubber or polyisoprene. Additionally, when adjusting the manufacturing conditions of chloroprene polymers to obtain immersion molded products with a low modulus at 100% elongation, the resulting chloroprene polymer composition can become sticky and adhere to the polymerization container, leading to reduced recovery rates.

[0007] The present invention has been made in view of these circumstances, and provides a method for producing a chloroprene polymer composition that can obtain an immersion molded product having a high recovery rate from the polymerization vessel, a low modulus at 100% elongation, and excellent tensile strength at break. [Means for solving the problem]

[0008] The present invention provides a method for producing a chloroprene polymer composition, wherein the chloroprene polymer composition comprises a diene polymer A and a chloroprene polymer B, the diene polymer A and the chloroprene polymer B having different weight-average molecular weights, and the method for producing the chloroprene polymer composition includes a polymerization step of polymerizing the chloroprene polymer B in the presence of the diene polymer A.

[0009] Through diligent research, the inventors discovered that a chloroprene polymer composition containing diene polymer A and chloroprene polymer B with different weight-average molecular weights can be produced by a manufacturing method that includes a polymerization step of polymerizing chloroprene polymer B in the presence of diene polymer A. This method yields a chloroprene polymer composition that exhibits a high recovery rate from the polymerization vessel, a low modulus at 100% elongation, and excellent tensile strength at break, resulting in a immersion molded product. This discovery led to the completion of the present invention.

[0010] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other. Preferably, the method for producing the chloroprene polymer composition described above is such that the difference between the weight-average molecular weight of the diene polymer A and the weight-average molecular weight of the chloroprene polymer B is 100,000 or more. Preferably, the weight-average molecular weight of the diene polymer A is 5,000 to 80,000, in the method for producing the chloroprene polymer composition described above. Preferably, in the polymerization step of polymerizing the chloroprene polymer B, the amount of diene polymer A charged is 5.0 to 60.0 parts by mass when the amount of chloroprene monomer or raw material monomer charged is 100 parts by mass, which is the method for producing the chloroprene polymer composition described above. Preferably, the method for producing the chloroprene polymer composition described above is that the diene polymer A is at least one selected from natural rubber, isoprene polymer, butadiene polymer, styrene-butadiene polymer, chloroprene polymer, and acrylonitrile-butadiene polymer. [Effects of the Invention]

[0011] The chloroprene polymer according to the present invention provides a chloroprene polymer composition that yields immersion molded articles with a high recovery rate from the polymerization vessel, a low modulus at 100% elongation, and excellent tensile strength at break. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below with reference to embodiments of the present invention. The present invention is not limited in any way by these descriptions. The features of the embodiments of the present invention shown below can be combined with each other. Furthermore, each feature constitutes an invention independently.

[0013] 1. Method for producing chloroprene polymer compositions The method for producing the chloroprene polymer composition according to the present invention includes a polymerization step of polymerizing chloroprene polymer B in the presence of diene polymer A. Furthermore, the chloroprene polymer composition according to the present invention comprises diene polymer A and chloroprene polymer B, and diene polymer A and chloroprene polymer B have different weight-average molecular weights. First, the diene polymer A and chloroprene polymer B according to the present invention will be described below.

[0014] 1.1 Diene Polymer A In the present invention, diene polymer A means a polymer containing diene monomer units derived from a diene monomer. Diene polymer A may also contain monomer units derived from monomers other than diene monomers, etc., to the extent that it does not impair the objective of the present invention.

[0015] When the diene polymer A according to one embodiment of the present invention is 100% by mass, it can contain 50 to 100% by mass of monomer units derived from diene monomers, and preferably contains 70 to 100% by mass. The content of monomer units derived from diene monomers is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100% by mass, and may be within the range between any two of the numerical values exemplified here.

[0016] The diene monomer can be a conjugated diene monomer having 4 to 6 carbon atoms, and specifically, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, chloroprene, 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene can be mentioned. The diene polymer A preferably contains chloroprene monomer units.

[0017] The diene polymer A according to one embodiment of the present invention preferably contains at least one selected from natural rubber, isoprene-based polymer, butadiene-based polymer, styrene-butadiene-based polymer, chloroprene-based polymer, acrylonitrile-butadiene-based polymer.

[0018] The diene polymer A according to one embodiment of the present invention preferably contains monomer units derived from chloroprene, and further preferably contains monomer units derived from 2,3-dichloro-1,3-butadiene. The diene polymer A according to one embodiment of the present invention can also be sulfur-free, and the diene polymer A according to one embodiment of the present invention can also have no -S-S- structure caused by sulfur in the main chain.

[0019] The diene polymer A according to one embodiment of the present invention may contain 50 to 100% by mass of monomer units derived from chloroprene when the diene polymer A is considered to be 100% by mass, and preferably contains 70 to 100% by mass. The content of monomer units derived from chloroprene may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0020] The diene polymer A according to one embodiment of the present invention may contain 0 to 30% by mass of monomer units derived from 2,3-dichloro-1,3-butadiene when the diene polymer A is considered as 100% by mass. The content of monomer units derived from 2,3-dichloro-1,3-butadiene may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, and may be within the range of any two of the values ​​exemplified here.

[0021] The diene polymer A according to the present invention has a different weight-average molecular weight from the chloroprene polymer B. The difference between the weight-average molecular weight of the diene polymer A according to one embodiment of the present invention and the weight-average molecular weight of the chloroprene polymer B described later is preferably 100,000 or more, and more preferably 400,000 or more. The difference between the weight-average molecular weight of the diene polymer A and the weight-average molecular weight of the chloroprene polymer B described later is, for example, 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,200,000, 1,300,000, 1,400,000, and 1,500,000, and may be within the range of any two of the values ​​exemplified here.

[0022] For example, the weight-average molecular weight of diene polymer A can be smaller than the molecular weight of chloroprene polymer B. The weight-average molecular weight of diene polymer A can be 5,000 to 80,000. The weight-average molecular weight of diene polymer A can be, for example, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, 21,000, These are 22,000, 23,000, 24,000, 25,000, 26,000, 27,000, 28,000, 29,000, 30,000, 35,000, 40,000, 50,000, 60,000, 70,000, and 80,000, and may also be within the range of any two of the numbers exemplified here.

[0023] As another example, the weight-average molecular weight of diene polymer A can be greater than the molecular weight of chloroprene polymer B. The weight-average molecular weight of diene polymer A can be between 200,000 and 1,500,000. The weight-average molecular weight of diene polymer A can be, for example, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, or 1,500,000, and may also be within the range of any two of the values ​​exemplified here.

[0024] The weight-average molecular weight of diene polymer A can be determined by analyzing a sample obtained by dissolving the polymer A in a polymerization solution containing diene polymer A (for example, latex mixed with a large amount of methanol, precipitated, filtered, and dried) in tetrahydrofuran using gel permeation chromatography (GPC). The GPC measurement conditions can be as described in the examples. The weight-average molecular weight of diene polymer A can be controlled during polymerization by adjusting the polymerization formulation, the type and amount of chain transfer agent, polymerization temperature, polymerization time, polymerization conversion rate, etc., and in particular, by adjusting the type and amount of chain transfer agent.

[0025] 1.2 Method for producing diene polymer A The method for producing the diene polymer A according to the present invention is not particularly limited. For example, the diene polymer A according to one embodiment of the present invention may include a diene polymer A polymerization step in which raw material monomers containing a diene monomer are polymerized to obtain a diene polymer.

[0026] In the polymerization process, the raw material monomers include one or more diene monomers and may also include other monomers copolymerizable with the diene monomers. Examples of diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, chloroprene, 2,3-dichloro-1,3-butadiene, and 1-chloro-1,3-butadiene. Examples of other monomers copolymerizable with diene monomers include styrene, methacrylic acid, acrylonitrile, and sulfur.

[0027] It is preferable to adjust the type and amount of each monomer to be charged so that the content of each monomer unit in the resulting diene polymer A falls within the numerical range described above. For example, if diene polymer A contains chloroprene monomer units and 2,3-dichloro-1,3-butadiene monomer units, and contains 0 to 30% by mass of 2,3-dichloro-1,3-butadiene monomer units relative to 100% by mass of the total of chloroprene monomers and 2,3-dichloro-1,3-butadiene, it is preferable to charge 2,3-dichloro-1,3-butadiene in the range of 0 to 30 parts by mass relative to 100 parts by mass of the total of chloroprene monomers and 2,3-dichloro-1,3-butadiene monomers.

[0028] When producing diene polymer A, the raw material monomers are polymerized using polymerization methods such as emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization. Among these polymerization methods, emulsion polymerization is preferred because it offers various advantages, such as ease of control, ease of extracting the polymer from the polymerization completion solution, and a relatively fast polymerization rate.

[0029] In the polymerization process of diene polymer A, the raw material monomers can be polymerized by adding them to a polymerization vessel along with a polymerization initiator, a chain transfer agent, and other necessary chemicals such as a solvent. For example, when polymerizing diene polymer A by emulsion polymerization, the raw material monomers can be polymerized by adding them to a reaction vessel along with a chain transfer agent, water, alkali (e.g., metal hydroxides such as potassium hydroxide and sodium hydroxide), emulsifier (dispersant), reducing agent (e.g., sodium bisulfite), polymerization initiator, etc.

[0030] There are no particular restrictions on the polymerization initiator; known polymerization initiators commonly used for the polymerization of diene polymers can be used. Examples of polymerization initiators include potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and organic peroxides such as t-butyl hydroperoxide.

[0031] The type of chain transfer agent used in emulsion polymerization is not particularly limited, and known chain transfer agents commonly used in the polymerization of diene polymers can be used, such as long-chain alkyl mercaptans like n-dodecyl mercaptan and tert-dodecyl mercaptan, dialkyl xanthogen disulfides like diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, and iodoform. Long-chain alkyl mercaptans are preferred as chain transfer agents, and n-dodecyl mercaptan is more preferred.

[0032] By adjusting the type and amount of chain transfer agent, the weight-average molecular weight of the resulting diene polymer A can be adjusted.

[0033] As an example, to obtain a diene polymer A with a weight-average molecular weight of 5,000 to 80,000, it is preferable to charge 0.5 to 10.0 parts by mass of the chain transfer agent before the start of emulsion polymerization, per 100 parts by mass of the monomer. In this case, the amount charged may be, for example, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0034] As an example, to obtain a diene polymer A with a weight-average molecular weight of 200,000 or more, preferably 500,000 to 1,500,000, it is preferable to use 0 to less than 0.40 parts by mass of the chain transfer agent per 100 parts by mass of the monomer. More preferably, the amount of the chain transfer agent is 0.02 to 0.05 parts by mass, for example, 0, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.20, 0.30 parts by mass, or less than 0.40 parts by mass, and may be within the range of any two of the values ​​exemplified here. In particular, when trying to obtain a diene polymer A with a weight-average molecular weight of 200,000 or more, the chain transfer agent may not be used.

[0035] In emulsion polymerization, the pH of the aqueous emulsion is preferably 10.5 to 13.5. The aqueous emulsion refers to the mixture of chain transfer agent and monomer immediately before the start of emulsion polymerization, but it also includes cases where the composition changes due to the later addition or partial addition of each component. If the pH of the aqueous emulsion at the start of emulsion polymerization is 10.5 or higher, the polymerization reaction can be controlled more stably. If the pH is 13.5 or lower, excessive viscosity increase during polymerization is suppressed, and the polymerization reaction can be controlled more stably.

[0036] In the polymerization process, the monomer may contain chloroprene and 2,3-dichloro-1,3-butadiene, and may also contain other monomers copolymerizable with chloroprene and 2,3-dichloro-1,3-butadiene. Other monomers are as described above as monomer units that the chloroprene polymer may contain. Furthermore, it is preferable to adjust the type and amount of each monomer used so that the content of each monomer unit in the resulting chloroprene polymer falls within the numerical range described above.

[0037] The emulsifier preferably contains rosin acid and / or a rosin salt. Examples of rosin salts include alkali metal salts such as sodium salts and potassium salts. The amount of rosin acid and rosin salt added can be 3.0 to 7.0 parts by mass per 100 parts by mass of the raw material monomer used. The amounts of rosin acid and rosin salt added may be, for example, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, or 7.0 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0038] The emulsifier may include emulsifiers and dispersants other than rosin acid and rosin salts, and cationic, anionic, and nonionic emulsifiers and dispersants other than rosin acid and rosin salts can be used. In one embodiment of the present invention, the emulsifier used in the emulsion polymerization step may include rosin acid and / or rosin salts and anionic emulsifiers and dispersants. As anionic emulsifiers and dispersants, it is preferable to use sulfate-based or sulfonate-based anionic emulsifiers and dispersants in combination from the viewpoint of stabilizing the chloroprene polymer latex when a pH adjuster is added. Specifically, examples include alkyl sulfonates with 8 to 20 carbon atoms, alkylaryl sulfates, condensates of sodium β-naphthalene sulfonate and formaldehyde, and sodium alkyldiphenyl ether disulfonate. The amount of anionic emulsifier or dispersant added can be 0.05 to 5 parts by mass per 100 parts by mass of the raw material monomer. The amount of anionic emulsifiers and dispersants added is, for example, 0.05, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass per 100 parts by mass of the raw material monomer, and may be within the range of any two of the values ​​exemplified here.

[0039] The polymerization temperature is preferably within the range of 5 to 55°C. A temperature above 5°C is preferable because the emulsion does not freeze, and a temperature below 55°C is preferable because there is no evaporation or boiling of the diene monomer.

[0040] The polymerization conversion rate is preferably in the range of 50 to 95%. The polymerization reaction is stopped by adding a polymerization inhibitor. The polymerization conversion rate can be adjusted by stopping the polymerization reaction by adding a polymerization inhibitor when the desired polymerization conversion rate is reached, or by stopping the addition of the polymerization initiator.

[0041] Examples of polymerization inhibitors include diethylhydroxylamine, thiodiphenylamine, 4-tert-butylcatechol, and 2,2'-methylenebis-4-methyl-6-tert-butylphenol. In the polymerization step of diene polymer A according to one embodiment of the present invention, a polymerization inhibitor may not be used. Unreacted monomers after polymerization can be removed by conventional methods such as vacuum distillation.

[0042] Furthermore, a composition (e.g., latex) containing the diene polymer A obtained by the manufacturing method of one embodiment of the present invention may optionally contain freeze stabilizers, emulsifying stabilizers, viscosity modifiers, antioxidants, preservatives, etc., after polymerization, to the extent that they do not impair the effects of the present invention.

[0043] In the polymerization process of diene polymer A, it is possible to start polymerization after loading all the raw material monomers and chemicals to be used in the polymerization process into the polymerization vessel, or to load at least a portion of the raw material monomers and / or chemicals to be used in the polymerization process into the polymerization vessel before starting polymerization, and then add the remainder after polymerization has started.

[0044] When at least a portion of the raw material monomers and chemicals are placed in the polymerization vessel before polymerization begins, and the remaining raw material monomers and / or chemicals are added after polymerization has started, the remaining raw material monomers and / or chemicals can be added in one or more installments, or continuously at a constant flow rate. In one embodiment of the present invention, at least a portion of the raw material monomers can be added in installments after polymerization has started. For example, when chloroprene and 2,3-dichloro-1,3-butadiene are used as raw material monomers, a portion of the chloroprene can be added in installments after polymerization has started.

[0045] As an example, the addition of the remaining raw material monomers and / or chemicals can be started when the polymerization rate of the raw material monomers charged before polymerization begins reaches 50-95%. The polymerization rate at which addition begins can be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95%, and may be within the range of any two of the values ​​exemplified here.

[0046] When adding at least a portion of the raw material monomers after polymerization has started, up to 50 parts by mass of the total 100 parts by mass of raw material monomers used in the polymerization process can be added after polymerization has started. In this case, the amount of raw material monomers added after polymerization has started can be, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 parts by mass, and may be within the range of any two of the values ​​exemplified here. As an example, the addition of raw material monomers, such as chloroprene, can be carried out continuously over a period of 30 to 300 minutes.

[0047] 1.3 Chloroprene-based polymer B In the present invention, a chloroprene polymer means a polymer containing monomer units derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene). Furthermore, a chloroprene polymer according to one embodiment of the present invention may be a copolymer of chloroprene and another monomer copolymerizable with chloroprene. Examples of other monomers include 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, isoprene, styrene, methacrylic acid, acrylonitrile, and sulfur. Two or more of these monomers may be used in combination. It is preferable that chloroprene polymer B according to one embodiment of the present invention contains monomer units derived from 2,3-dichloro-1,3-butadiene. Chloroprene polymer B according to one embodiment of the present invention may not contain sulfur, and chloroprene polymer B according to one embodiment of the present invention may not have a sulfur-derived -SS- structure in the main chain.

[0048] The chloroprene polymer B according to one embodiment of the present invention may contain 50 to 100% by mass of monomer units derived from chloroprene when the chloroprene polymer B is considered as 100% by mass, and preferably contains 70 to 100% by mass. The content of monomer units derived from chloroprene may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified here.

[0049] The chloroprene polymer B according to one embodiment of the present invention may contain 0 to 30% by mass of monomer units derived from 2,3-dichloro-1,3-butadiene when the chloroprene polymer B is considered as 100% by mass. The content of monomer units derived from 2,3-dichloro-1,3-butadiene may be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% by mass, and may be within the range of any two of the values ​​exemplified here.

[0050] The chloroprene polymer B according to the present invention has a different weight-average molecular weight from the diene polymer A. As described above, the difference between the weight-average molecular weight of the diene polymer A according to one embodiment of the present invention and the weight-average molecular weight of the chloroprene polymer B described later is preferably 100,000 or more, and more preferably 400,000 or more.

[0051] For example, the weight-average molecular weight of chloroprene polymer B can be greater than that of diene polymer A. The weight-average molecular weight of chloroprene polymer B can be between 200,000 and 1,500,000. The weight-average molecular weight of chloroprene polymer B can be, for example, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, or 1,500,000, and may also be within the range of any two of the values ​​exemplified here.

[0052] As another example, the weight-average molecular weight of chloroprene polymer B can be smaller than the molecular weight of chloroprene polymer B. The weight-average molecular weight of chloroprene polymer B can be 5,000 to 80,000. For example, the weight-average molecular weight of chloroprene polymer B can be 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, 21,000. These are 22,000, 23,000, 24,000, 25,000, 26,000, 27,000, 28,000, 29,000, 30,000, 35,000, 40,000, 50,000, 60,000, 70,000, and 80,000, and may be within the range of any two of the numbers exemplified here.

[0053] The weight-average molecular weight of chloroprene polymer B can be determined by analyzing a sample obtained by dissolving the chloroprene polymer B obtained from a polymerization solution containing chloroprene polymer B, for example, a chloroprene polymer composition (latex), in tetrahydrofuran, after precipitation, filtration, and drying, using gel permeation chromatography (GPC). The GPC measurement conditions can be as described in the examples. The weight-average molecular weight of chloroprene polymer B can be controlled by adjusting the polymerization formulation, the type and amount of chain transfer agent, polymerization temperature, polymerization time, polymerization conversion rate, etc., during the polymerization of chloroprene polymer B, and in particular, by adjusting the type and amount of chain transfer agent.

[0054] 1.4 Polymerization method of chloroprene polymer B The method for producing a chloroprene polymer composition according to the present invention includes a polymerization step of polymerizing a chloroprene polymer B in the presence of a diene polymer A. According to the present invention, a chloroprene polymer composition can be obtained by polymerizing a chloroprene polymer B in the presence of a diene polymer A, thereby obtaining an immersion molded product that has a high recovery rate from the polymerization vessel, a low modulus at 100% elongation, and excellent tensile strength at break.

[0055] The mechanism by which a chloroprene polymer composition can be obtained by polymerizing chloroprene polymer B in the presence of diene polymer A, resulting in a chloroprene polymer composition that exhibits a high recovery rate from the polymerization vessel, a low modulus at 100% elongation, and excellent tensile strength at break, is not entirely clear. However, it is presumed that the chloroprene polymer composition obtained by polymerizing chloroprene polymer B in the presence of diene polymer A exhibits superior physical properties to a chloroprene polymer composition obtained by polymerizing diene polymer A and chloroprene polymer B separately and then mixing them, because the diene polymer A and chloroprene polymer B in the chloroprene polymer composition are highly uniformly mixed.

[0056] The diene polymer A may be added to the polymerization solution in any form; for example, the polymerization solution obtained by polymerizing diene polymer A may be used as is. For example, if diene polymer A is polymerized by emulsion polymerization, the latex containing diene polymer A may be added to the polymerization solution of chloroprene polymer B. Alternatively, for example, diene polymer A may be precipitated from the polymerization solution obtained by polymerizing diene polymer A, and the precipitated diene polymer A may be added to the polymerization solution of chloroprene polymer B. For example, if diene polymer A is polymerized by emulsion polymerization, diene polymer A may be precipitated from the latex containing diene polymer A using methanol and added to the polymerization solution of chloroprene polymer B, or diene polymer A obtained by freeze-drying the latex containing diene polymer A may be added to the polymerization solution of chloroprene polymer B.

[0057] In the polymerization step for polymerizing chloroprene polymer B, when the amount of chloroprene monomer (or raw material monomer) charged is 100 parts by mass, the amount of diene polymer A charged can be 5.0 to 60.0 parts by mass, or 40.0 to 95.0 parts by mass. In one embodiment of the present invention, if the weight-average molecular weight of diene polymer A is smaller than that of chloroprene polymer B, for example, if the weight-average molecular weight of diene polymer A is 5,000 to 80,000, then the amount of diene polymer A charged can be 5.0 to 60.0 parts by mass for every 100 parts by mass of chloroprene monomer (or raw material monomer). If the molecular weight of diene polymer A is larger than that of chloroprene polymer B, for example, if the weight-average molecular weight of diene polymer A is 200,000 to 1,500,000, then the amount of diene polymer A charged can be 40.0 to 95.0 parts by mass for every 100 parts by mass of chloroprene monomer (or raw material monomer).

[0058] If the weight-average molecular weight of diene polymer A is smaller than the weight-average molecular weight of chloroprene polymer B, the amount of diene polymer A charged per 100 parts by mass of chloroprene monomer (or raw material monomer) is, for example, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 50.0, or 60.0 parts by mass, and may be within the range of any two of the values ​​exemplified here. If the molecular weight of diene polymer A is greater than the molecular weight of chloroprene polymer B, the amount of diene polymer A charged per 100 parts by mass of chloroprene monomer (or raw material monomer) may be, for example, 40.0, 50.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, or 95.0 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0059] In the polymerization process, the raw material monomers include chloroprene and may also include other monomers copolymerizable with chloroprene. Examples of other monomers include 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, styrene, methacrylic acid, acrylonitrile, and sulfur.

[0060] It is preferable to adjust the type and amount of each monomer used so that the content of each monomer unit in the resulting chloroprene polymer B falls within the numerical range described above.

[0061] When producing chloroprene polymer B, the raw material monomers are polymerized using polymerization methods such as emulsion polymerization, solution polymerization, suspension polymerization, and bulk polymerization. Among these polymerization methods, emulsion polymerization is preferred because it offers various advantages, such as ease of control, ease of extracting the polymer from the polymerization completion solution, and a relatively fast polymerization rate.

[0062] In the polymerization process of chloroprene polymer B, the raw material monomers can be polymerized by adding them to a polymerization vessel along with necessary chemicals such as polymerization initiators, chain transfer agents, and solvents. For example, when polymerizing chloroprene polymer B by emulsion polymerization, the raw material monomers can be polymerized by adding them to a reaction vessel along with a chain transfer agent, water, alkali (e.g., metal hydroxides such as potassium hydroxide and sodium hydroxide), emulsifier (dispersant), reducing agent (e.g., sodium bisulfite), polymerization initiator, etc.

[0063] There are no particular restrictions on the polymerization initiator; known polymerization initiators commonly used for the polymerization of chloroprene polymers can be used. Examples of polymerization initiators include potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and organic peroxides such as t-butyl hydroperoxide.

[0064] The type of chain transfer agent used in emulsion polymerization is not particularly limited, and known chain transfer agents commonly used in chloroprene polymerization can be used, such as long-chain alkyl mercaptans like n-dodecyl mercaptan and tert-dodecyl mercaptan, dialkyl xanthogen disulfides like diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, and iodoform. Long-chain alkyl mercaptans are preferred as the chain transfer agent, and n-dodecyl mercaptan is more preferred.

[0065] By adjusting the type and amount of the chain transfer agent, the weight-average molecular weight of the resulting chloroprene polymer B can be adjusted.

[0066] As an example, to obtain chloroprene polymer B having a weight-average molecular weight of 200,000 or more, preferably 500,000 to 1,500,000, it is preferable to use less than 0 to 0.40 parts by mass of chain transfer agent per 100 parts by mass of monomer. More preferably, the amount of chain transfer agent is 0 to 0.05 parts by mass, for example, 0, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.20, 0.30 parts by mass, or less than 0.40 parts by mass, and may be within the range of any two of the values ​​exemplified here. In particular, when trying to obtain chloroprene polymer B with a weight-average molecular weight of 200,000 or more, it is not necessary to use a chain transfer agent.

[0067] Furthermore, as an example, to obtain a chloroprene polymer B with a weight-average molecular weight of 5,000 to 80,000, it is preferable to charge 0.5 to 10.0 parts by mass of the chain transfer agent before the start of emulsion polymerization per 100 parts by mass of the monomer. In this case, the amount charged may be, for example, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0068] By adjusting the weight-average molecular weights of diene polymer A and chloroprene polymer B within the above numerical range, and by adjusting the amount of diene polymer A charged to 100 parts by mass of chloroprene monomer within the above numerical range, a chloroprene polymer composition is obtained that results in a dipping molded product with a low modulus at 100% elongation and excellent tensile strength at break.

[0069] In emulsion polymerization, the pH of the aqueous emulsion is preferably 10.5 to 13.5. The aqueous emulsion refers to the mixture of chain transfer agent and monomer immediately before the start of emulsion polymerization, but it also includes cases where the composition changes due to the later addition or partial addition of each component. If the pH of the aqueous emulsion at the start of emulsion polymerization is 10.5 or higher, the polymerization reaction can be controlled more stably. If the pH is 13.5 or lower, excessive viscosity increase during polymerization is suppressed, and the polymerization reaction can be controlled more stably.

[0070] In the polymerization process, the monomer may contain chloroprene and 2,3-dichloro-1,3-butadiene, and may also contain other monomers copolymerizable with chloroprene and 2,3-dichloro-1,3-butadiene. Other monomers are as described above as monomer units that the chloroprene polymer may contain. Furthermore, it is preferable to adjust the type and amount of each monomer used so that the content of each monomer unit in the resulting chloroprene polymer falls within the numerical range described above.

[0071] The emulsifier preferably contains rosin acid and / or a rosin salt. Examples of rosin salts include alkali metal salts such as sodium salts and potassium salts. The amount of rosin acid and rosin salt added can be 3.0 to 7.0 parts by mass per 100 parts by mass of the raw material monomer used. The amounts of rosin acid and rosin salt added may be, for example, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, or 7.0 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0072] The emulsifier may include emulsifiers and dispersants other than rosin acid and rosin salts, and cationic, anionic, and nonionic emulsifiers and dispersants other than rosin acid and rosin salts can be used. In one embodiment of the present invention, the emulsifier used in the emulsion polymerization step may include rosin acid and / or rosin salts and anionic emulsifiers and dispersants. As anionic emulsifiers and dispersants, it is preferable to use sulfate-based or sulfonate-based anionic emulsifiers and dispersants in combination from the viewpoint of stabilizing the chloroprene polymer latex when a pH adjuster is added. Specifically, examples include alkyl sulfonates with 8 to 20 carbon atoms, alkylaryl sulfates, condensates of sodium β-naphthalene sulfonate and formaldehyde, and sodium alkyldiphenyl ether disulfonate. The amount of anionic emulsifier or dispersant added can be 0.05 to 5 parts by mass per 100 parts by mass of the raw material monomer. The amount of anionic emulsifiers and dispersants added is, for example, 0.05, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 parts by mass per 100 parts by mass of the raw material monomer, and may be within the range of any two of the values ​​exemplified here.

[0073] The polymerization temperature is preferably within the range of 5 to 55°C. A temperature above 5°C is preferable because the emulsion does not freeze, and a temperature below 55°C is preferable because there is no evaporation or boiling of the chloroprene monomer.

[0074] The polymerization conversion rate is preferably in the range of 50-95%. The polymerization reaction is stopped by adding a polymerization inhibitor. When the desired polymerization conversion rate is reached, the polymerization can be stopped by adding a polymerization inhibitor.

[0075] Examples of polymerization inhibitors include diethylhydroxylamine, thiodiphenylamine, 4-tert-butylcatechol, and 2,2'-methylenebis-4-methyl-6-tert-butylphenol. Unreacted monomers after polymerization can be removed by conventional methods such as vacuum distillation.

[0076] Furthermore, a chloroprene polymer composition (e.g., latex) containing diene polymer A and chloroprene polymer B obtained by a manufacturing method according to one embodiment of the present invention may optionally contain freeze stabilizers, emulsifying stabilizers, viscosity modifiers, antioxidants, preservatives, etc., after polymerization, to the extent that they do not impair the effects of the present invention.

[0077] In the polymerization process of chloroprene polymer B, it is possible to start polymerization after loading all the raw material monomers and chemicals to be used in the polymerization process into the polymerization vessel, or to load at least a portion of the raw material monomers and / or chemicals to be used in the polymerization process into the polymerization vessel before starting polymerization, and then add the remainder after polymerization has started.

[0078] When at least a portion of the raw material monomers and chemicals are placed in the polymerization vessel before polymerization begins, and the remaining raw material monomers and / or chemicals are added after polymerization has started, the remaining raw material monomers and / or chemicals can be added in one or more installments, or they can be added continuously at a constant flow rate. In one embodiment of the present invention, at least a portion of the raw material monomers and / or chemicals can be added in installments after polymerization has started. For example, a portion of the polymerization initiator can be added in installments after polymerization has started.

[0079] 1.5 Chloroprene-based polymer composition A chloroprene polymer composition according to one embodiment of the present invention comprises a diene polymer A and a chloroprene polymer B, wherein the diene polymer A and the chloroprene polymer B have different weight-average molecular weights.

[0080] In the chloroprene polymer composition according to one embodiment of the present invention, when the chloroprene polymer composition is mixed with a large amount of methanol, precipitated, filtered, and dried to obtain a polymer, and the resulting polymer is dissolved in tetrahydrofuran, a sample obtained by gel permeation chromatography is preferably shown with a peak having a weight-average molecular weight of 5,000 to 80,000 and a peak having a weight-average molecular weight of 200,000 to 1,500,000 in the molecular weight distribution, more preferably with a peak having a weight-average molecular weight of 5,000 to 50,000 and a peak having a weight-average molecular weight of 300,000 to 1,500,000, and even more preferably with a peak having a weight-average molecular weight of 8,000 to 30,000 and a peak having a weight-average molecular weight of 500,000 to 1,500,000. Furthermore, the chloroprene polymer composition according to one embodiment of the present invention preferably contains a diene polymer A having a weight-average molecular weight of 5,000 to 80,000 and a chloroprene polymer B having a weight-average molecular weight of 200,000 to 1,500,000, or a chloroprene polymer B having a weight-average molecular weight of 5,000 to 80,000 and a diene polymer A having a weight-average molecular weight of 200,000 to 1,500,000, and preferably contains a diene polymer A having a weight-average molecular weight of 5,000 to 50,000 and a chloroprene polymer having a weight-average molecular weight of 300,000 to 1,500,000. It is more preferable to include polymer B, or a chloroprene polymer B having a weight-average molecular weight of 5,000 to 50,000 and a diene polymer A having a weight-average molecular weight of 300,000 to 1,500,000. It is even more preferable to include a diene polymer A having a weight-average molecular weight of 8,000 to 30,000 and a chloroprene polymer B having a weight-average molecular weight of 500,000 to 1,500,000, or a chloroprene polymer B having a weight-average molecular weight of 8,000 to 30,000 and a diene polymer A having a weight-average molecular weight of 500,000 to 1,500,000.

[0081] The chloroprene polymer composition according to one embodiment of the present invention preferably contains 5 to 40% by mass of polymers having a weight-average molecular weight of 5,000 to 80,000, when the polymer contained in the chloroprene polymer composition is considered as 100% by mass. The content of polymers having a weight-average molecular weight of 5,000 to 80,000 can be, for example, 5, 10, 15, 20, 25, 30, 35, or 40% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0082] The chloroprene polymer composition according to one embodiment of the present invention preferably contains 60 to 95% by mass of polymers having a weight-average molecular weight of 200,000 to 1,500,000, when the polymer contained in the chloroprene polymer composition is considered as 100% by mass. The content of polymers having a weight-average molecular weight of 200,000 to 1,500,000 may be, for example, 60, 65, 70, 75, 80, 85, 90, or 95% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0083] In the chloroprene polymer composition according to one embodiment of the present invention, it is preferable that the recovery rate of the chloroprene polymer composition in the polymerization step of chloroprene polymer B is 95.0% by mass or more. The recovery rate may be, for example, 95.0, 95.5, 96.0, 96.5, 97.0, 97.5, 98.0, 98.5, 99.0, 99.5, or 100.0% by mass, and may be within the range of any two of the values ​​exemplified herein. In one embodiment of the present invention, a chloroprene polymer composition is polymerized in the presence of a diene polymer A, thereby reducing adhesion of the chloroprene polymer composition to the polymerization vessel and increasing the recovery rate. The recovery rate of the chloroprene polymer composition in the polymerization step of chloroprene polymer B can be determined by the method described in the examples.

[0084] The chloroprene polymer composition according to one embodiment of the present invention preferably has a tensile strength at break of 18.0 MPa or higher, and more preferably 19.0 MPa or higher, as measured according to JIS K 6251 for immersion molded articles obtained using the chloroprene polymer composition. The tensile strength at break is, for example, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0, 30.0, 31.0, 32.0, 33.0, 34.0, 35.0, 36.0, 37.0, 38.0, 39.0, or 40.0 MPa, and may be within the range of any two of the values ​​exemplified here.

[0085] The chloroprene polymer composition according to one embodiment of the present invention preferably has a modulus at 100% elongation of 0.65 MPa or less, and more preferably 0.60 MPa or less, as measured according to JIS K 6251 for immersion molded articles obtained using the chloroprene polymer composition. The modulus at 100% elongation may be, for example, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or 0.65 MPa, and may be within the range of any two of the values ​​exemplified herein.

[0086] The immersion-molded article obtained using the chloroprene polymer composition can be obtained by an immersion molding step in which an immersion-molded article is formed by immersion molding a composition for forming an immersion-molded article containing the chloroprene polymer composition, and a drying step in which the immersion-molded article is heated and dried at 140°C for 1 hour to obtain an immersion-molded article. The composition for forming an immersion-molded article contains the chloroprene polymer composition and may also contain other necessary agents such as metal oxides and antioxidants, and can be specifically formulated as in the examples. The immersion-molded article may contain diene polymer A and chloroprene polymer B as base polymers, and when the immersion-molded article is considered as 100% by mass, it may contain 70% by mass or more of diene polymer A and chloroprene polymer B, preferably 80% by mass or more, and more preferably 90% by mass or more. The content of diene polymer A and chloroprene polymer B in the immersion molded product, when the immersion molded product is considered to be 100% by mass, may be, for example, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified here.

[0087] The tensile strength at break and modulus at 100% elongation of a dipping molded article containing a chloroprene polymer composition can be controlled by adjusting the weight-average molecular weight of diene polymer A and chloroprene polymer B contained in the dipping molded article, the types and content of monomer units included, the polymerization conditions of each polymer, and the blending ratio. The methods for measuring the tensile strength at break and modulus at 100% elongation can be as described in the examples.

[0088] 2. Method for manufacturing immersion molded products A method for manufacturing an immersion molded product according to one embodiment of the present invention is: A dipping molding process to obtain a dipping molded body by dipping a composition for forming a dipping molded body containing the chloroprene polymer composition described above, and The method may include a drying step in which the immersion-molded body is heated and dried to obtain an immersion-molded product.

[0089] 2.1 Composition for forming immersion molded bodies A composition for forming immersion molded articles according to one embodiment of the present invention includes the chloroprene polymer composition described above. In addition to the chloroprene polymer composition, a composition for forming immersion molded articles according to one embodiment of the present invention may include a metal oxide, an antioxidant, and other necessary agents. A composition for forming immersion molded articles according to one embodiment of the present invention may not contain vulcanizing agents and vulcanization accelerators, and may not contain sulfur or vulcanization accelerators such as thiram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenicate-based, or thiazole-based agents.

[0090] 2.1.1 Metal Oxides A composition for forming immersion molded articles according to one embodiment of the present invention may contain a metal oxide. The metal oxides are not particularly limited and include zinc oxide, lead oxide, trilead tetroxide, magnesium oxide, aluminum oxide, iron oxide, beryllium oxide, and titanium oxide. It is preferable that the metal oxides include zinc oxide. Zinc oxide is generally considered to function as a scavenger for dechlorinating atoms in chloroprene polymers. These metal oxides may be used individually or in mixtures of two or more.

[0091] The amount of metal oxide added is preferably 0.5 to 15.0 parts by mass per 100 parts by mass of solids of the chloroprene polymer composition contained in the immersion molded body forming composition. If the amount of metal oxide added is 0.5 parts by mass or more, an improvement in tensile strength at break can be expected due to the crosslinking effect between polymers. If the amount of metal oxide added is 15.0 parts by mass or less, an immersion molded body with excellent flexibility can be obtained. Furthermore, from the viewpoint of balancing the physical properties of the obtained immersion molded body, such as flexibility and tensile strength at break, the amount of metal oxide added is more preferably 0.5 to 5.0 parts by mass.

[0092] 2.1.2 Antioxidants The immersion molded article formation composition according to one embodiment of the present invention may also contain an antioxidant. The antioxidant is not particularly limited, and phenolic antioxidants, amine-based antioxidants, heat-resistant oxidation (aging) inhibitors, ozone-resistant antioxidants, etc., can be used. When the resulting immersion molded article is used for medical gloves, a phenolic antioxidant can be used from the viewpoint of the color tone, texture, and hygiene of the immersion molded article. In particular, hindered phenolic antioxidants have a strong effect. Examples of hindered phenol-based antioxidants include 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-butylidene(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), the butylation reaction product of p-cresol and dicyclopentadiene, 2,5'-di-t-butylhydroquinone, and 2,5'-di-t-amylhydroquinone. Among these, the butylation reaction product of p-cresol and dicyclopentadiene is generally preferred from the viewpoint of being dispersible in aqueous materials. Furthermore, these compounds may be used individually or in combination of two or more.

[0093] The amount of antioxidant added is preferably 0.5 to 10.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer composition contained in the immersion molded body forming composition. The amount of antioxidant added may be, for example, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, and may be within the range of any two of the values ​​exemplified here. If the amount of antioxidant added is 0.5 parts by mass or more, an effect of suppressing color changes in the immersion molded body can be obtained. If the amount of antioxidant added is 10.0 parts by mass or less, the stability of the immersion molded body forming composition is ensured. Furthermore, from the viewpoint of balancing the physical properties of the resulting immersion molded body, flexibility and tensile strength at break, the amount of antioxidant added is more preferably 0.5 to 5.0 parts by mass.

[0094] 2.1.3 Vulcanizing agents and vulcanization accelerators The immersion molded article formation composition according to one embodiment of the present invention may also contain a vulcanizing agent and / or a vulcanization accelerator. Furthermore, the immersion molded article formation composition according to one embodiment of the present invention may not contain sulfur and the aforementioned vulcanization accelerators such as thiram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenicate-based, and thiazole-based agents. In other words, the immersion molded article formation composition includes those containing a vulcanizing agent but not a vulcanization accelerator, those containing a vulcanizing agent but including a vulcanization accelerator, those containing a vulcanizing agent and a vulcanization accelerator, and those not containing a vulcanizing agent and a vulcanization accelerator. Whether or not to include a vulcanizing agent and a vulcanization accelerator should be determined according to the target immersion molded article.

[0095] Examples of vulcanizing agents include, but are not limited to, sulfur. The amount of vulcanizing agent added can be 0 to 10.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer composition contained in the immersion molded body forming composition. The amount of vulcanizing agent added can be, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0096] A vulcanization accelerator is a chemical added to raw rubber during the vulcanization process to increase the vulcanization rate, shorten the vulcanization time, lower the vulcanization temperature, reduce the amount of vulcanizing agent used, and improve the physical properties of the vulcanized rubber. It usually refers to a chemical that accelerates the sulfur vulcanization reaction.

[0097] Examples of vulcanization accelerators include, but are not limited to, thiram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenicate-based, and thiazole-based agents. These can be used alone or in combination of two or more as needed.

[0098] Examples of thiram-based vulcanization accelerators include tetramethylthiram disulfide, tetraethylthiram disulfide, tetrabutylthiram disulfide, tetrakis(2-ethylhexyl)thiram disulfide, tetramethylthiram monosulfide, and dipentamethylenethiram tetrasulfide.

[0099] Examples of dithiocarbamate-based vulcanization accelerators include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, and tellurium diethyldithiocarbamate, with zinc dibutyldithiocarbamate being particularly preferred.

[0100] Examples of thiourea-based vulcanization accelerators include ethylenethiourea, N,N'-diethylthiourea, trimethylthiourea, and N,N'-diphenylthiourea.

[0101] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salts of dicatecholborate.

[0102] Examples of xanthogenic acid-based vulcanization accelerators include zinc butylxanthonate and zinc isopropylxanthonate.

[0103] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, 2-mercaptobenzothiazole zinc salt, cyclohexylamine salt of 2-mercaptobenzothiazole, and 2-(4'-morpholinodithio)benzothiazole.

[0104] The amount of vulcanization accelerator added can be 0 to 5.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer composition contained in the immersion molded body forming composition. The amount of vulcanization accelerator added can be, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, and may be within the range of any two of the values ​​exemplified here.

[0105] 2.1.4 Other drugs (heteroaromatic ring compounds) The immersion molded body formation composition according to one embodiment of the present invention may contain a heteroaromatic ring compound in the chloroprene polymer. The heteroaromatic ring compound contained in the immersion molded body forming composition used to obtain the immersion molded product according to one embodiment of the present invention can be represented by chemical formula (1) and has a benzimidazole structure. Compounds having this structure are sometimes used as secondary aging inhibitors in the formulation of rubber compositions.

[0106] [ka]

[0107] In chemical formula (1), X in the mercapto group represents a hydrogen atom or a metal atom. X can be a hydrogen atom and may have a thiol group. Alternatively, X can be a metal atom, and examples of metal atoms include zinc, sodium, copper, nickel, and tellurium, with zinc being preferred. In chemical formula (1), R1 to R4 represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted ether group, a nitro group, an amino group, and a carboxyl group, respectively. R1 to R4 may be the same or different. Furthermore, the heteroaromatic ring compound may be used individually or as a mixture of two or more.

[0108] Examples of heteroaromatic ring compounds include 2-mercaptobenzimidazole, 5-methyl-2-mercaptobenzimidazole, 4-methyl-2-mercaptobenzimidazole, 5-methoxy-2-mercaptobenzimidazole, 4-methoxy-2-mercaptobenzimidazole, 5-nitro-2-mercaptobenzimidazole, 5-amino-2-mercaptobenzimidazole, 5-carboxy-2-mercaptobenzimidazole, or zinc salts of 2-mercaptobenzimidazole. Among these, zinc salts of 2-mercaptobenzimidazole, 5-methyl-2-mercaptobenzimidazole, 4-methyl-2-mercaptobenzimidazole, 5-methoxy-2-mercaptobenzimidazole, 4-methoxy-2-mercaptobenzimidazole, and 2-mercaptobenzimidazole are preferred.

[0109] The amount of heteroaromatic ring compound added is preferably 0.2 to 10.0 parts by mass per 100 parts by mass of the solid content of the chloroprene polymer composition contained in the immersion molded article formation composition. The amount of heteroaromatic ring compound added is, for example, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 parts by mass, and may be within the range of any two of the values ​​exemplified here. If the amount added is 0.2 parts by mass or more, the immersion molded article obtained using this composition exhibits very high breaking strength. If the amount added is 10.0 parts by mass or less, the stability of the immersion molded article formation composition is ensured. Furthermore, from the viewpoint of balancing the physical properties of the obtained immersion molded article, flexibility and breaking strength, the amount added is more preferably 0.3 to 5.0 parts by mass.

[0110] A method for producing a composition for forming an immersion molded body according to one embodiment of the present invention may include a raw material mixing step of mixing raw materials containing a chloroprene polymer composition, a metal oxide, an antioxidant, and other necessary agents. In the mixing process, an aqueous dispersion containing a metal oxide, an antioxidant, and other necessary chemicals can be prepared in advance, and then the chloroprene polymer composition can be mixed with the aqueous dispersion. The mixing process can be carried out using a known mixing device such as a ball mill.

[0111] 2.2 Dip molding process A method for producing an immersion-molded article according to one embodiment of the present invention may include an immersion molding step in which a composition for forming an immersion-molded article, which contains the chloroprene polymer composition obtained by the method for producing the chloroprene polymer composition described above, is immersed in the process to obtain an immersion-molded article.

[0112] Examples of immersion molding methods for one embodiment of the present invention include immersion solidification method, simple immersion method, heat-sensitive immersion method, and electrodeposition method. From the viewpoint of ease of manufacturing and ease of obtaining an immersion molded body of a certain thickness, the immersion solidification method can be used. Specifically, a ceramic mold coated with a calcium-based solidification solution is immersed in an immersion molded body forming composition, and the immersion molded body forming composition is solidified. After removing water-soluble impurities by leaching, it is dried, and then heated and vulcanized to form an immersion molded film (rubber coating), after which the immersion molded film is released from the mold. This makes it possible to obtain a film-like immersion molded body.

[0113] 2.3 Drying process A method for manufacturing a dipping molded product according to one embodiment of the present invention may include a drying step of heating and drying the dipping molded body to obtain a dipping molded product.

[0114] The heat drying temperature can be set appropriately according to the composition of the chloroprene polymer composition, and may be between 120 and 180°C. The heating temperature is preferably between 120 and 150°C. The heating temperature can be, for example, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, or 220°C, and may be within the range of any two of the values ​​exemplified here. The heating time can be set appropriately depending on the composition of the chloroprene polymer composition, the shape of the unvulcanized molded article, etc., and may be between 10 and 300 minutes. The heating time can be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300 minutes, and may be within the range of any two of the values ​​exemplified here. As an example, an immersion molded product according to one embodiment of the present invention can be obtained by heating and drying at 140°C for 1 hour.

[0115] 3. Immersion molded products (Immersion molded product coatings / films) An immersion-molded article according to one embodiment of the present invention can be obtained using the above-mentioned chloroprene polymer composition. The immersion-molded article can be obtained by immersion molding after using the aforementioned immersion-molding article formation composition alone or blended with other immersion-molding article formation compositions. The immersion-molded article according to the present invention can be obtained by immersion molding the immersion-molding article formation composition by an immersion solidification method, and then heating and drying the immersion-molded article at 140°C for 1 hour. The immersion-molded article according to the present invention has high tensile strength at break and low modulus at 100% elongation. Furthermore, the immersion-molded article can be produced efficiently because it has a high recovery rate from the polymerization container. The immersion-molded article according to one embodiment of the present invention can be suitably used as industrial and general household gloves, medical gloves, balloons, catheters, and boots.

[0116] The immersion-molded article according to the present invention may contain components included in the above-mentioned composition for forming immersion-molded articles. Furthermore, the immersion-molded article may contain diene polymer A and chloroprene polymer B as base polymers, and when the immersion-molded article is considered as 100% by mass, it may contain 70% by mass or more of diene polymer A and chloroprene polymer B, preferably 80% by mass or more, and more preferably 90% by mass or more. The content of diene polymer A and chloroprene polymer B in the immersion-molded article when the immersion-molded article is considered as 100% by mass may be, for example, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% by mass, and may be within the range of any two of the values ​​exemplified here.

[0117] The immersion molded article containing the chloroprene polymer according to the present invention exhibits high tensile strength at break and low modulus at 100% elongation, regardless of whether or not a vulcanizing agent and vulcanization accelerator are added. Furthermore, the immersion molded article according to one embodiment of the present invention may not contain a vulcanizing agent and vulcanization accelerator, and may not contain sulfur or vulcanization accelerators such as thiram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenicate-based, or thiazole-based agents.

[0118] 3.1 Characteristics of immersion molded products In the immersion molded product according to one embodiment of the present invention, when the soluble components obtained by dissolving the immersion molded product in tetrahydrofuran are measured by gel permeation chromatography, it is preferable that a peak with a weight-average molecular weight of 5,000 to 80,000 and a peak with a weight-average molecular weight of 200,000 to 1,500,000 are detected in the molecular weight distribution, more preferably a peak with a weight-average molecular weight of 5,000 to 50,000 and a peak with a weight-average molecular weight of 300,000 to 1,500,000 are detected, and even more preferably a peak with a weight-average molecular weight of 8,000 to 30,000 and a peak with a weight-average molecular weight of 500,000 to 1,500,000 are detected. The weight-average molecular weights and blending ratios of the low molecular weight components and high molecular weight components can be as described above.

[0119] The chloroprene polymer composition according to one embodiment of the present invention preferably has a tensile strength at break of 18.0 MPa or higher, and more preferably 19.0 MPa or higher, as measured according to JIS K6251 for immersion molded articles containing the chloroprene polymer composition. The tensile strength at break is, for example, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0, 30.0, 31.0, 32.0, 33.0, 34.0, 35.0, 36.0, 37.0, 38.0, 39.0, or 40.0 MPa, and may be within the range of any two of the values ​​exemplified here.

[0120] The chloroprene polymer composition according to one embodiment of the present invention preferably has a modulus at 100% elongation of 0.65 MPa or less, and more preferably 0.60 MPa or less, as measured according to JIS K6251 for immersion molded articles containing the chloroprene polymer. The modulus at 100% elongation may be, for example, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or 0.65 MPa, and may be within the range of any two of the values ​​exemplified herein.

[0121] The immersion-molded article may contain a chloroprene polymer and further contain antioxidants and metal oxides. The immersion-molded article may also contain vulcanizing agents, vulcanization accelerators, and anti-aging agents. The method for manufacturing the immersion-molded article, and the method for measuring the tensile strength at break and the modulus at 100% elongation, can be as described in the examples.

[0122] Furthermore, the tensile strength at break and the modulus at 100% elongation of the immersion-molded product can be controlled by adjusting the type and amount of raw materials used when polymerizing diene polymer A and chloroprene polymer B, the type and amount of chemicals used, and the polymerization conditions.

[0123] 3.2 Shape of immersion molded product The thickness of the immersion molded product (for example, the minimum thickness) may be 0.01 to 0.50 mm. The thickness of the immersion molded product may be, for example, 0.01, 0.05, 0.10, 0.20, 0.30, 0.40, or 0.50 mm, and may be within the range of any two of the values ​​exemplified here. The thickness of the immersion molded product can be adjusted by the time the mold is immersed in the composition for forming the immersion molded product, the solid content concentration of the composition for forming the immersion molded product, etc. If you want to make the thickness of the immersion molded product thinner, you can shorten the immersion time or lower the solid content concentration of the composition for forming the immersion molded product.

[0124] The immersion-molded article may contain sulfur or a vulcanization accelerator. However, even without sulfur and a vulcanization accelerator, the immersion-molded article possesses mechanical properties equivalent to or better than those of vulcanized immersion-molded articles obtained from conventional compositions for forming immersion-molded articles containing chloroprene polymers. For this reason, the chloroprene polymer composition according to the present invention is suitably used as a raw material for the immersion-molded article (immersion-molded article) of the chloroprene polymer in this embodiment.

[0125] Furthermore, a method for producing a dipping molded product according to one embodiment of the present invention may include a step of subjecting the obtained dipping molded product to a heat drying treatment and vulcanizing the unvulcanized dipping molded product. [Examples]

[0126] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0127] <Preparation of Chloroprene Polymer A> (Synthesis example A-1) In a 30L polymerization tank, 64 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 77 parts by mass of pure water, 17.6 parts by mass of gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 3.4 parts by mass of n-dodecyl mercaptan, 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), and 0.5 parts by mass of sodium bisulfite were added. Polymerization was carried out at a polymerization temperature of 35°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate of the added monomer reached 80%, 27 parts by mass of chloroprene (monomer) were continuously added over 100 minutes. The polymerization solution was obtained by stopping the addition of potassium persulfate aqueous solution when the polymerization rate of the initially added monomer and the continuously added monomer reached 91%. The polymerization solution was then removed by vacuum distillation to remove unreacted monomers and concentrated to obtain a latex of chloroprene polymer A-1 with a solid content of 60% by weight. The obtained latex was used in the preparation of chloroprene polymer B in Example 7. In addition, a portion of the obtained latex was precipitated as chloroprene polymer A-1 using a method described later, and used for analysis and in the preparation of chloroprene polymer B in Examples 1 to 3.

[0128] (Precipitation of chloroprene polymer A with methanol) The latex of the obtained chloroprene polymer A-1 was mixed with a large amount of methanol to precipitate the rubber component (chloroprene polymer A-1), which was then filtered and dried to obtain a sample of chloroprene polymer A-1. The weight-average molecular weight of the chloroprene polymer was measured from the obtained sample. This sample was also used to prepare chloroprene polymer B in Examples 1 to 3 described later. The analysis results are shown in Table 1. The measurement method will be described later.

[0129] (Synthesis example A-2) Polymerization was carried out using the same procedure as in Synthesis Example A-1, except that 5.3 parts by mass of n-dodecyl mercaptan were used. The resulting polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain a latex of chloroprene polymer A-2 with a solid content of 60% by weight. Chloroprene polymer A-2 was precipitated from the obtained latex using the same procedure as in Synthesis Example A-1, and this latex was used in the preparation of chloroprene polymer B. The weight-average molecular weight of chloroprene polymer A-2 was also measured, as in Synthesis Example A-1. The analytical results are shown in Table 1.

[0130] (Synthesis example A-3) Polymerization was carried out using the same procedure as in Synthesis Example A-1, except that 2.4 parts by mass of n-dodecyl mercaptan were used. The resulting polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain a latex of chloroprene polymer A-3 with a solid content of 60% by weight. Chloroprene polymer A-3 was precipitated from the obtained latex using the same procedure as in Synthesis Example A-1, and this latex was used in the preparation of chloroprene polymer B. The weight-average molecular weight of chloroprene polymer A-3 was also measured, as in Synthesis Example A-1. The analytical results are shown in Table 1.

[0131] (Synthesis example A-4) Polymerization was carried out using the same procedure as in Synthesis Example A-1, except that 1.5 parts by mass of n-dodecyl mercaptan was used. The resulting polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain a latex of chloroprene polymer A-4 with a solid content of 60% by weight. Chloroprene polymer A-4 was precipitated from the obtained latex using the same procedure as in Synthesis Example A-1, and this latex was used in the preparation of chloroprene polymer B. The weight-average molecular weight of chloroprene polymer A-4 was also measured, as in Synthesis Example A-1. The analytical results are shown in Table 1.

[0132] (Synthesis example A-5) In a polymerization tank with an internal volume of 30 L, 64 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 351 parts by mass of pure water, 92 parts by mass of gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 3.4 parts by mass of n-dodecyl mercaptan, 4 parts by mass of potassium hydroxide, 2 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), and 0.5 parts by mass of sodium bisulfite were added to bring the total volume of the charged liquid to 18 L. Polymerization was carried out at a polymerization temperature of 35°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate of the charged monomer reached 80%, 27 parts by mass of chloroprene (monomer) were continuously added over 100 minutes. The polymerization solution was obtained by stopping the addition of potassium persulfate aqueous solution when the polymerization rate of the initially added monomer and the continuously added monomer reached 91%. The latex of the obtained chloroprene polymer A-5 (solid content concentration 21.8% by mass) was used in Example 8. Chloroprene polymer A-5 was also precipitated using the same procedure as in Synthesis Example A-1, and the weight-average molecular weight of chloroprene polymer A-5 was measured. The analytical results are shown in Table 1.

[0133] (Synthesis example A-6) In a polymerization tank with an internal volume of 30 L, the following components were added to bring the total volume of the added liquid to 25 L: 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 100 parts by mass of pure water, 17.6 parts by mass of a gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.03 parts by mass of n-dodecyl mercaptan, 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium bisulfite, and 0.04 parts by mass of thiourea dioxide. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, the addition of potassium persulfate aqueous solution was stopped to halt the polymerization and obtain the polymerization solution. The latex of the obtained chloroprene polymer A-6 (solid content concentration 41.7% by mass) was used in Example 9. Chloroprene polymer A-6 was also precipitated using the same procedure as in Synthesis Example A-1, and the weight-average molecular weight of chloroprene polymer A-6 was measured. The analytical results are shown in Table 1.

[0134] [Table 1]

[0135] <Preparation of Chloroprene Polymer B> (Example 1) In a 30L polymerization tank, 21.3 parts by mass of chloroprene polymer A-1 prepared and precipitated in synthesis example A-1, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 87 parts by mass of pure water, 17.6 parts by mass of gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers and concentrated to obtain the latex of chloroprene polymer B-1 with a solid content of 60% by weight, i.e., the chloroprene polymer composition. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel and the actual weight of the chloroprene polymer composition after polymerization was measured. From the measured actual weight of the chloroprene polymer composition after polymerization, the recovery rate of the chloroprene polymer composition during the polymerization of chloroprene polymer B was calculated. The calculation results are shown in Table 2. The calculation method will be described later.

[0136] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0137] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-1. The weight-average molecular weight of chloroprene polymer B-1 was measured from the obtained sample. The analysis results are shown in Table 2. The measurement method will be described later.

[0138] (Examples 2 and 3) Polymerization was carried out using the same procedure as in Example 1, with the raw material amounts and polymerization conditions shown in Table 2. The resulting polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain a latex of chloroprene polymer B with a solid content of 60% by weight, i.e., a chloroprene polymer composition. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition during the polymerization of chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0139] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0140] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B. The weight-average molecular weight of chloroprene polymer B was measured from the obtained sample. The analytical results are shown in Table 2.

[0141] (Example 4) In a 30L polymerization tank, 21.3 parts by mass of the rubber component of chloroprene polymer A-2 prepared in synthesis example A-2, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 87 parts by mass of pure water, 17.6 parts by mass of gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers and concentrated to obtain a latex of chloroprene polymer B-4 with a solid content of 60% by weight, i.e., a chloroprene polymer composition. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition during the polymerization of chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0142] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0143] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-4. The weight-average molecular weight of chloroprene polymer B-4 was measured from the obtained sample. The analytical results are shown in Table 2.

[0144] (Example 5) In a 30L polymerization tank, 21.3 parts by mass of the rubber component of chloroprene polymer A-3 prepared in synthesis example A-3, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 87 parts by mass of pure water, 17.6 parts by mass of a gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers, and a latex of chloroprene polymer B-5 with a solid content of 60% by weight, i.e., a chloroprene polymer composition, was obtained by concentration. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition during the polymerization of chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0145] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0146] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-5. The weight-average molecular weight of chloroprene polymer B-5 was measured from the obtained sample. The analytical results are shown in Table 2.

[0147] (Example 6) In a 30L polymerization tank, 21.3 parts by mass of the rubber component of chloroprene polymer A-4 prepared in synthesis example A-4, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 87 parts by mass of pure water, 17.6 parts by mass of gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to stop the polymerization and obtain a polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers, and a latex of chloroprene polymer B-6 with a solid content of 60% by weight, i.e., a chloroprene polymer composition, was obtained by concentration. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition containing chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0148] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0149] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-6. The weight-average molecular weight of chloroprene polymer B-6 was measured from the obtained sample. The analytical results are shown in Table 2.

[0150] (Example 7) In a 30L polymerization vessel, 39 parts by mass of latex of chloroprene polymer A-1 prepared in synthesis example A-1, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 74 parts by mass of pure water, 13.6 parts by mass of gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.6 parts by mass of potassium hydroxide, 0.4 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.4 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers, and a latex of chloroprene polymer B-7 with a solid content of 60% by weight, i.e., a chloroprene polymer composition, was obtained by concentration. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition containing chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0151] After measuring the actual weight of the latex after polymerization, 50 ml of the chloroprene polymer composition was sampled, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0152] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-7. The weight-average molecular weight of chloroprene polymer B-7 was measured from the obtained sample. The analytical results are shown in Table 2.

[0153] (Example 8) In a polymerization vessel with an internal volume of 30 L, 130.8 parts by mass of the latex of chloroprene polymer A-5 prepared in synthesis example A-5, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 0.5 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35 wt% aqueous potassium persulfate solution as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization arrestor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain the latex of chloroprene polymer B-8, i.e., a chloroprene polymer composition, with a solid content of 60 wt%. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization tank, and the recovery rate of the chloroprene polymer composition during polymerization of chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0154] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0155] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-8. The weight-average molecular weight of chloroprene polymer B-8 was measured from the obtained sample. The analytical results are shown in Table 2.

[0156] (Example 9) In a 30 L polymerization vessel, 1000 parts by mass of the latex of chloroprene polymer A-6 prepared in synthesis example A-6, 74 parts by mass of chloroprene (monomer), 7 parts by mass of 2,3-dichloro-1,3-butadiene, 2.7 parts by mass of n-dodecyl mercaptan, 0.4 parts by mass of sodium bisulfite, and 0.03 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35 wt% aqueous potassium persulfate solution as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization arrestor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain the latex of chloroprene polymer B-9, i.e., a chloroprene polymer composition, with a solid content of 60 wt%. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization tank, and the recovery rate of the chloroprene polymer composition containing chloroprene polymer B was calculated using the same procedure as in Example 1. The calculation results are shown in Table 2.

[0157] After measuring the actual weight of the chloroprene polymer composition after polymerization, a 50 ml sample of the chloroprene polymer composition was taken, and the remaining chloroprene polymer composition was used to prepare immersion molded products for evaluation.

[0158] The sampled chloroprene polymer composition was mixed with a large amount of methanol to precipitate the rubber component, and then filtered and dried to obtain a sample of chloroprene polymer B-9. The weight-average molecular weight of chloroprene polymer B-9 was measured from the obtained sample. The analytical results are shown in Table 2.

[0159] (Comparative Example 1) In a 30L polymerization tank, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 77 parts by mass of pure water, 17.6 parts by mass of a gum rosin-based disproportionated rosin aqueous solution (product name "Londis K-25", solid content 25% by mass, manufactured by Arakawa Chemical Industries, Ltd.), 0.02 parts by mass of n-dodecyl mercaptan, 0.8 parts by mass of potassium hydroxide, 0.5 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation), 0.5 parts by mass of sodium bisulfite, and 0.04 parts by mass of thiourea dioxide were added. Polymerization was carried out at a polymerization temperature of 13°C under a nitrogen atmosphere by continuously adding a 0.35% by weight aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 85%, 0.1 parts by mass of diethylhydroxylamine, a polymerization arrestor, was added to stop the polymerization and obtain the polymerization solution. The polymerization solution was subjected to vacuum distillation to remove unreacted monomers, and a latex of chloroprene polymer C with a solid content of 60% by weight, i.e., a chloroprene polymer composition, was obtained by concentration. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition of chloroprene polymer C was calculated using the same procedure as in Example 1. The calculation results are shown in Table 3. Furthermore, immersion molded articles for evaluation were prepared using the obtained chloroprene polymer composition. In addition, a portion of the obtained chloroprene polymer composition was used in Comparative Example 2.

[0160] (Comparative Example 2) Polymerization was carried out using the same procedure as in Synthesis Example A-1. The resulting polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain a latex of chloroprene polymer D with a solid content of 60% by weight, i.e., a chloroprene polymer composition. The entire amount of the obtained chloroprene polymer composition was withdrawn from the polymerization vessel, and the recovery rate of the chloroprene polymer composition was calculated using the same procedure as in Example 1. The calculation results are shown in Table 3.

[0161] A chloroprene polymer composition of chloroprene polymer E was obtained by mixing the chloroprene polymer composition of chloroprene polymer C obtained in Comparative Example 1 with the chloroprene polymer composition of chloroprene polymer D in a weight ratio of C / D = 80 / 20. An immersion molded product for evaluation was prepared using the obtained chloroprene polymer composition.

[0162] Chloroprene polymers A and B were analyzed using the following method. <Measurement of weight-average molecular weight of chloroprene polymers A and B> As described above, the weight-average molecular weight was measured by gel permeation chromatography (GPC) under the measurement conditions described below, using samples obtained by methanol precipitation of the latex of chloroprene polymer A and the latex containing the chloroprene polymer, i.e., the chloroprene polymer composition, followed by filtration and drying of the polymer, and then dissolving the resulting polymer in 20 ml of tetrahydrofuran. Device name: HLC-8320 (manufactured by Tosoh Corporation) Column: Three TSKgel GMHHR-H columns in series. Temperature: 40℃ Detection: Differential refractive index Solvent: tetrahydrofuran Calibration curve: Prepared using standard polystyrene (PS).

[0163] The recovery rate of the chloroprene polymer composition was evaluated using the following method. <Recovery rate of chloroprene polymer composition> For each example and comparative example, the recovery rate of the chloroprene polymer composition was calculated based on the actual weight of the polymerized chloroprene polymer composition when it was withdrawn from the piping at the bottom of the polymerization tank, and the amount of chloroprene polymer composition charged during polymerization, using the following formula. When the chloroprene polymer composition is withdrawn from the piping at the bottom of the polymerization tank, the more viscous the chloroprene polymer composition is, the more of the chloroprene polymer composition adheres to the walls of the polymerization tank, resulting in a smaller recovery amount. The theoretical weight is the amount of chloroprene polymer composition present in the polymerization tank immediately before the recovery operation, obtained by subtracting the amount removed from the system by vacuum distillation and concentration operations for unreacted monomers from the amount of piping charged. (Recovery rate of chloroprene polymer composition) = (Actual weight of chloroprene polymer composition) / (Theoretical weight of chloroprene polymer composition) × 100

[0164] A composition for forming immersion molded articles containing the above-mentioned latex, i.e., a chloroprene-based polymer composition, was prepared using the following method. This composition was then immersed to obtain an immersion molded article, and the immersion molded article was further subjected to heat drying to produce an immersion molded product which was then evaluated.

[0165] <Preparation of immersion molded products> A composition for forming immersion molded bodies was prepared by mixing 100 parts by mass of solids of a chloroprene polymer composition containing each chloroprene polymer with 7.1 parts by mass of an aqueous dispersion, and then adding water to adjust the overall solid content concentration of the mixture to 30% by mass. The aqueous dispersion was prepared by mixing 2 parts by mass of two types of zinc oxide, 2 parts by mass of the butylation reaction product of p-cresol and dicyclopentadiene (trade name "Nocrac PBK", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.7 parts by mass of the heteroaromatic compound 2-mercaptobenzimidazole (trade name "Nocrac MB", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.1 parts by mass of the sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation) and 10.7 parts by mass of water using a ceramic ball mill at 20°C for 16 hours. The resulting immersion molded body formation composition contains, per 100 parts by mass of the solid content of the chloroprene polymer composition, 2 parts by mass of two types of zinc oxide, 2 parts by mass of the butylation reaction product of p-cresol and dicyclopentadiene (trade name "Nocrack PBK", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.7 parts by mass of the heteroaromatic compound 2-mercaptobenzimidazole (trade name "Nocrack MB", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.1 parts by mass of the sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), and 10.7 parts by mass of water.

[0166] A 50mm outer diameter cylindrical ceramic mold (manufactured by Shinko Co., Ltd.) was immersed for 1 second in a coagulation solution prepared by mixing 62 parts by mass of water, 35 parts by mass of potassium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate, and then removed. After drying for 3 minutes, it was immersed for 2 minutes in the immersion molded body forming composition prepared by the procedure described above. Subsequently, it was washed with running water at 45°C for 1 minute and dried at 140°C for 1 hour to prepare an immersion molded film for evaluation.

[0167] (Film thickness) Using a specimen thickness gauge (manufactured by Polymer Instruments Co., Ltd., product name: ASKER SDA-12), the thickness (film thickness) of the immersion molded film for tensile property evaluation was measured at three points in the center, and the minimum thickness was obtained as the thickness of the immersion molded film for evaluation. The results are shown in Tables 2 and 3.

[0168] (Measurement of tensile properties) Using immersion-molded films for tensile property evaluation, the modulus at 100% elongation and tensile strength at break were measured in accordance with JIS K 6251. The results are shown in Tables 2 and 3.

[0169] [Table 2]

[0170] [Table 3]

Claims

1. A method for producing a chloroprene polymer composition, The chloroprene polymer composition comprises diene polymer A and chloroprene polymer B. The diene polymer A and the chloroprene polymer B have different weight-average molecular weights. The aforementioned diene polymer A contains 60 to 100% by mass of monomer units derived from a diene monomer, when the diene polymer A is considered to be 100% by mass. The method for producing the chloroprene polymer composition includes a polymerization step of polymerizing a raw material monomer containing chloroprene in the presence of the diene polymer A to obtain the chloroprene polymer B. A method for producing a chloroprene polymer composition, wherein in the polymerization step, 3.0 to 7.0 parts by mass of rosinic acid and / or rosinate salt are added to 100 parts by mass of the raw material monomer.

2. A method for producing a chloroprene polymer composition, The chloroprene polymer composition comprises diene polymer A and chloroprene polymer B. The diene polymer A and the chloroprene polymer B have different weight-average molecular weights. The diene polymer A contains 50 to 100% by mass of monomer units derived from chloroprene, when the diene polymer A is considered to be 100% by mass. The method for producing the chloroprene polymer composition includes a polymerization step of polymerizing a raw material monomer containing chloroprene in the presence of the diene polymer A to obtain the chloroprene polymer B. A method for producing a chloroprene polymer composition, wherein in the polymerization step, 3.0 to 7.0 parts by mass of rosinic acid and / or rosinate salt are added to 100 parts by mass of the raw material monomer.

3. A method for producing a chloroprene polymer composition according to claim 1 or claim 2, wherein the difference between the weight-average molecular weight of the diene polymer A and the weight-average molecular weight of the chloroprene polymer B is 100,000 or more.

4. A method for producing a chloroprene polymer composition according to claim 1 or claim 2, wherein the weight-average molecular weight of the diene polymer A is 5,000 to 80,000.

5. A method for producing a chloroprene polymer composition according to claim 1 or claim 2, wherein, in a polymerization step for polymerizing the chloroprene polymer B, when the amount of chloroprene monomer or raw material monomer charged is 100 parts by mass, the amount of diene polymer A charged is 5.0 to 60.0 parts by mass.

6. A method for producing a chloroprene polymer composition according to claim 1 or claim 2, wherein the diene polymer A is at least one selected from natural rubber, isoprene polymer, butadiene polymer, styrene-butadiene polymer, chloroprene polymer, and acrylonitrile-butadiene polymer.

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