Chloroprene polymers and immersion molded products

Abstract

Provided is a chloroprene polymer which has high tensile strength at break and a low modulus at 100% elongation, and which makes it possible to obtain a dip-molded product having excellent texture. The present invention provides a chloroprene polymer, wherein the loss tangent tanδ in the 10 Hz frequency region of a film containing the chloroprene polymer, as obtained when the tensile-type dynamic viscoelasticity is measured in accordance with the non-resonant forced vibration technique at a temperature of 25°C and under a strain of 0.75%, is 0.08 to 0.14, and the film is obtained by drying chloroprene polymer latex containing the chloroprene polymer for three days at 23°C or lower.

Description

Technical Field

[0001] The present invention relates to chloroprene polymers and dip molded articles.

Background Art

[0002] Chloroprene 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 and chloroprene polymer immersion molded products for immersion molded product applications. 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 a chloroprene polymer immersion molded article that exhibits excellent flexibility even without the inclusion of a vulcanization accelerator by mixing chloroprene polymer latex and isoprene polymer latex. Patent Document 6 describes a immersion molded article that exhibits excellent mechanical properties by mixing nitrile-butadiene polymer (NBR) latex or isoprene polymer latex with a chloroprene 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 project] [Problems that the invention aims to solve]

[0006] Chloroprene polymers are used as materials for immersion-molded products such as medical surgical gloves, medical examination gloves, industrial gloves, balloons, catheters, and rubber boots. In particular, for medical rubber glove applications, there is a demand for chloroprene polymers that can produce immersion-molded products with high tensile strength at break, low modulus at 100% elongation, and excellent texture.

[0007] This invention has been made in view of these circumstances, and provides a chloroprene polymer that can produce immersion molded articles having high tensile strength at break, low modulus at 100% elongation, and excellent texture. [Means for solving the problem]

[0008] According to the present invention, a chloroprene polymer is provided, wherein the loss tangent tanδ in the 10Hz frequency region of a film containing the chloroprene polymer, obtained by tensile dynamic viscoelasticity measurement in accordance with the non-resonant forced vibration method under conditions of a temperature of 25°C and a strain of 0.75%, is 0.080 to 0.140, and the film is obtained by drying a chloroprene polymer latex containing the chloroprene polymer at 23°C for 3 days.

[0009] Through diligent research, the inventors discovered that by controlling the loss tangent tanδ in the 10Hz frequency range of a film containing a chloroprene polymer to a specific value when performing tensile dynamic viscoelasticity measurements according to the non-resonant forced vibration method under conditions of 25°C and 0.75% strain, it is possible to obtain a chloroprene polymer that has low tensile strength at break, low modulus at 100% elongation, and excellent texture, resulting in 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 chloroprene polymer is one in which, when the tetrahydrofuran-soluble portion of the chloroprene polymer is measured by gel permeation chromatography, a peak with a weight-average molecular weight of 5,000 to 80,000 is detected. Preferably, the chloroprene polymer is the chloroprene polymer described above, which contains monomer units derived from 2,3-dichloro-1,3-butadiene.

[0011] According to another aspect of the present invention, a dipping molded article comprising the chloroprene polymer described above is provided. Preferably, the immersion molded product is an industrial or general household glove, a medical glove, a balloon, a catheter, or a boot. [Effects of the Invention]

[0012] According to the chloroprene polymer of the present invention, it is possible to obtain immersion molded articles that have high tensile strength at break, low modulus at 100% elongation, and excellent texture. [Modes for carrying out the invention]

[0013] 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.

[0014] 1. Chloroprene polymer The chloroprene polymer according to the present invention is a polymer containing monomer units derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene). Furthermore, the 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, and two or more of these monomers may be used in combination. The chloroprene polymer according to one embodiment of the present invention preferably contains monomer units derived from 2,3-dichloro-1,3-butadiene. The chloroprene polymer according to one embodiment of the present invention may also be sulfur-free, and the chloroprene polymer according to one embodiment of the present invention may also be one that does not have a sulfur-derived -SS- structure in the main chain.

[0015] The chloroprene-based polymer according to one embodiment of the present invention may be obtained by mixing two or more different chloroprene-based polymers. The chloroprene-based polymer preferably contains at least one selected from the group consisting of a homopolymer of chloroprene (2-chloro-1,3-butadiene), a copolymer of chloroprene and 1-chloro-1,3-butadiene, a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene, and a copolymer of chloroprene, 1-chloro-1,3-butadiene and 2,3-dichloro-1,3-butadiene, and more preferably contains at least one of a homopolymer of chloroprene and a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene.

[0016] The chloroprene-based polymer according to one embodiment of the present invention can contain 50 to 100% by mass of monomer units derived from chloroprene when the chloroprene-based polymer contained in the chloroprene-based polymer latex composition is 100% by mass, and preferably contains 70 to 100% by mass. The content of the monomer units derived from chloroprene 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 values exemplified here.

[0017] The chloroprene-based polymer according to one embodiment of the present invention can contain 0 to 30% by mass of monomer units derived from 2,3-dichloro-1,3-butadiene when the chloroprene-based polymer contained in the chloroprene-based polymer latex composition is 100% by mass. The content of the monomer units derived from 2,3-dichloro-1,3-butadiene is, 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, 30% by mass, and may be within the range between any two of the values exemplified here.

[0018] The chloroprene-based polymer according to one embodiment of the present invention may contain monomer units derived from chloroprene and monomer units derived from 2,3-dichloro-1,3-butadiene. In this case, when the total of the monomer units derived from chloroprene and the monomer units derived from 2,3-dichloro-1,3-butadiene contained in the chloroprene-based polymer is 100% by mass, the monomer units derived from 2,3-dichloro-1,3-butadiene are preferably contained in an amount of 0 to 30% by mass, and more preferably 5 to 25% by mass.

[0019] When the chloroprene-based polymer is a mixture of two or more different chloroprene-based polymers, the content of each monomer unit means the total of each monomer unit in all the chloroprene-based polymers contained in the chloroprene-based polymer latex composition.

[0020] When the chloroprene-based polymer according to one embodiment of the present invention is 100% by mass of the chloroprene-based polymer contained in the chloroprene-based polymer latex composition, the content of the sulfur-modified chloroprene-based polymer contained in the chloroprene-based polymer latex composition is preferably 20% by mass or less. The content of the sulfur-modified chloroprene-based polymer is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20% by mass, and may be within the range between any two of the values exemplified herein. The chloroprene-based polymer according to one embodiment of the present invention may not contain a sulfur-modified chloroprene-based polymer.

[0021] The chloroprene polymer according to the present invention, when subjected to tensile dynamic viscoelasticity measurement in accordance with the non-resonant forced vibration method under conditions of a temperature of 25°C and a strain of 0.75%, has a loss tangent tanδ in the 10Hz frequency range of a film containing the chloroprene polymer that is preferably 0.080 to 0.140, more preferably 0.090 to 0.140, and more preferably 0.100 to 0.140. The loss tangent tanδ in the 10Hz frequency range is, for example, 0.080, 0.085, 0.090, 0.095, 0.100, 0.105, 0.110, 0.115, 0.120, 0.125, 0.130, 0.135, or 0.140, and may be within the range of any two of the values ​​exemplified here.

[0022] Here, the film containing the chloroprene polymer is obtained by drying chloroprene polymer latex containing the chloroprene polymer at 23°C for 3 days. As an example, a dried sheet obtained by pouring chloroprene polymer latex containing the chloroprene polymer into an iron frame to a thickness of about 1.5 mm and letting it stand at 23°C for 3 days to evaporate volatile components can be used as the film containing the chloroprene polymer. In other words, the film containing the chloroprene polymer is obtained by removing water from chloroprene polymer latex containing the chloroprene polymer at room temperature, and the film containing the chloroprene polymer can be obtained without heat treatment at temperatures that cause crosslinking or vulcanization reactions in the chloroprene polymer. The chloroprene polymer contained in the film may not have a thermal history of, for example, 100°C or higher after polymerization is complete, preferably not having a thermal history of 80°C or higher, and more preferably not having a thermal history of 60°C or higher.

[0023] Films containing chloroprene polymers may have components that chloroprene polymer latex may contain. Chloroprene polymer latex will be discussed later. A film containing a chloroprene polymer may have a chloroprene polymer as its main component, and when the film is considered as 100% by mass, it may contain 70% by mass or more of the chloroprene polymer, preferably 80% by mass or more, and more preferably 90% by mass or more. The content of the chloroprene polymer in the film when the film is considered as 100% by mass may be, for example, 70, 75, 80, 85, 90, 95, 96, 97, or 98% by mass, and may be within the range of any two of the values ​​exemplified here.

[0024] The thickness of the film containing the chloroprene polymer may be 0.5 to 1.5 mm. For example, the thickness of the film containing the chloroprene polymer may be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 mm, and may be within the range of any two of the values ​​exemplified here. The thickness of the film containing the chloroprene polymer can be adjusted by the solid content concentration of the chloroprene polymer latex.

[0025] Tensile dynamic viscoelasticity measurements according to the non-resonant forced vibration method can be performed by cutting out a film containing the above-mentioned chloroprene polymer, preparing strip-shaped test pieces (width: 4.5 mm, length: 30 mm, thickness: 0.80-0.90 mm), and using the obtained strip-shaped test pieces. The measurement conditions can be a static tension of 5 gf, a temperature of 25°C, a strain of 0.75%, and a chuck spacing of 20 mm, and can be measured specifically by the method described in the examples.

[0026] The chloroprene polymer according to the present invention is a chloroprene polymer that, by setting the loss tangent tanδ in the 10 Hz frequency range to a specific numerical range, can produce immersion molded articles with high tensile strength at break, low modulus at 100% elongation, and excellent texture. The loss tangent tanδ in the 10 Hz frequency range can be controlled by adjusting the type and amount of raw materials used, the type and amount of chemicals used, and the polymerization conditions (e.g., polymerization temperature and whether or not raw material monomers are added during the polymerization process) when polymerizing chloroprene polymers, as well as the type and amount of monomer units contained in the resulting chloroprene polymer, the weight-average molecular weight, and the mixing ratio of the chloroprene polymers.

[0027] In the chloroprene polymer according to one embodiment of the present invention, it is preferable that a peak with a weight-average molecular weight of 5,000 to 80,000 is detected in the molecular weight distribution obtained when the sol portion of the chloroprene polymer soluble in tetrahydrofuran is measured by gel permeation chromatography. The peak positions of the peaks detected in the range of 5,000 to 80,000 are, 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, These are 000, 21,000, 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. The chloroprene polymer according to one embodiment of the present invention may be a mixture of two or more different chloroprene polymers, and preferably includes a chloroprene polymer having a weight-average molecular weight of 5,000 to 80,000.

[0028] The chloroprene polymer according to one embodiment of the present invention may further include a chloroprene polymer having a weight-average molecular weight of 200,000 to 1,500,000. That is, in the molecular weight distribution obtained when the sol portion of the chloroprene polymer soluble in tetrahydrofuran is measured by gel permeation chromatography, a peak with a weight-average molecular weight of 200,000 to 1,500,000 may be detected. The peak positions for peaks detected in the weight-average molecular weight range of 200,000 to 1,500,000 are, 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, and 1,500,000, and may also be within the range of any two of the values ​​exemplified here.

[0029] The molecular weight distribution of the sol portion of chloroprene polymers soluble in tetrahydrofuran can be obtained by weight-average molecular weight measurement using gel permeation chromatography (GPC). The GPC measurement conditions can be as described in the examples. The weight-average molecular weight of chloroprene polymers can be controlled by adjusting the formulation, such as the type and amount of chain transfer agent, polymerization temperature, polymerization time, and polymerization conversion rate, during the polymerization of each chloroprene polymer. Furthermore, as described later, the loss tangent tanδ can be adjusted by adjusting the weight-average molecular weight of the chloroprene polymer or the blending ratio of chloroprene polymers having different weight-average molecular weights.

[0030] In the chloroprene polymer according to one embodiment of the present invention, it is preferable that, when the sol portion of the chloroprene polymer soluble in tetrahydrofuran is measured by gel permeation chromatography, 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. That is, it is preferable that the chloroprene polymer according to one embodiment of the present invention includes a chloroprene polymer with a weight-average molecular weight of 5,000 to 80,000 and a chloroprene polymer with a weight-average molecular weight of 200,000 to 1,500,000.

[0031] The chloroprene polymer according to one embodiment of the present invention preferably contains 10 to 40% by mass of a chloroprene polymer having a weight-average molecular weight of 5,000 to 80,000 when the chloroprene polymer is considered to be 100% by mass, and more preferably contains 15 to 30% by mass. The chloroprene polymer according to one embodiment of the present invention may contain, for example, 10, 15, 20, 25, 30, 35, or 40% by mass of a chloroprene polymer having a weight-average molecular weight of 5,000 to 80,000 when the chloroprene polymer is considered to be 100% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0032] The chloroprene polymer according to one embodiment of the present invention preferably contains 60 to 90% by mass of a chloroprene polymer having a weight-average molecular weight of 200,000 to 1,500,000, when the chloroprene polymer is considered to be 100% by mass, and more preferably contains 70 to 85% by mass. The chloroprene polymer according to one embodiment of the present invention may contain, for example, 60, 65, 70, 75, 80, 85, or 90% by mass of a chloroprene polymer having a weight-average molecular weight of 200,000 to 1,500,000, when the chloroprene polymer is considered to be 100% by mass, and may be within the range of any two of the values ​​exemplified herein.

[0033] By adjusting the content of chloroprene polymers having different weight-average molecular weights within the above numerical range, the loss tangent tanδ can be adjusted more appropriately.

[0034] The chloroprene polymer according to one embodiment of the present invention preferably has a tensile strength at break of 17.0 MPa or higher, and more preferably 20.0 MPa or higher, as measured according to JIS K6251 for immersion molded articles containing the chloroprene polymer. The tensile strength at break may be, for example, 17.0, 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 also be within the range of any two of the values ​​exemplified here.

[0035] The chloroprene polymer according to one embodiment of the present invention preferably has a modulus at 100% elongation of 0.70 MPa or less, and more preferably 0.5 MPa or less, as measured according to JIS K6251 for immersion molded products 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, 0.65, or 0.70 MPa, and may be within the range of any two of the values ​​exemplified herein.

[0036] Here, the immersion-molded article containing the chloroprene polymer can be an immersion-molded article obtained by immersion-molding a chloroprene polymer latex composition containing the chloroprene polymer by an immersion-coagulation method, and then heating and drying the immersion-molded article at 150°C for 60 minutes. The immersion-molded article can also contain the chloroprene polymer as a base polymer, and when the immersion-molded article is considered as 100% by mass, it can contain 70% by mass or more of the chloroprene polymer, preferably 80% by mass or more, and more preferably 90% by mass or more. The content of the chloroprene polymer in the immersion-molded article when the immersion-molded article is considered as 100% by mass can 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. The immersion-molded article can be specifically obtained by the method described in the examples. The methods for measuring the modulus at 100% elongation and the tensile strength at break can be as described in the examples.

[0037] The modulus at 100% elongation and tensile strength at break of a dipping molded product containing a chloroprene polymer can be controlled by adjusting the type (weight-average molecular weight, type and content of monomer units, etc.) and amount of the chloroprene polymer contained in the dipping molded product.

[0038] 2. Chloroprene-based polymer latex A chloroprene polymer latex according to one embodiment of the present invention contains the chloroprene polymer according to the present invention. The chloroprene polymer latex can be a chloroprene polymer dispersed in water, and can contain at least one selected from the group consisting of a chloroprene homopolymer, a copolymer of chloroprene and 1-chloro-1,3-butadiene, a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene, and a copolymer of chloroprene, 1-chloro-1,3-butadiene, and 2,3-dichloro-1,3-butadiene dispersed in water. It may contain a chloroprene homopolymer or a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene dispersed in water.

[0039] 3. Method for producing chloroprene polymer latex A method for producing chloroprene polymer latex according to one embodiment of the present invention may include a polymerization step of polymerizing a monomer containing chloroprene to obtain chloroprene polymer latex. Furthermore, the method for producing chloroprene polymer latex may further include a mixing step of mixing two or more chloroprene polymer latexes having different weight-average molecular weights.

[0040] In the polymerization process, the monomer may contain chloroprene and other monomers copolymerizable with chloroprene. Examples of other monomers copolymerizable with chloroprene include 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, isoprene, styrene, methacrylic acid, acrylonitrile, and sulfur. The monomer may also contain chloroprene and 2,3-dichloro-1,3-butadiene.

[0041] It is preferable to adjust the type and amount of each monomer so that the amount of each monomer in the resulting chloroprene polymer falls within the numerical range described above. For example, the copolymerization amount of 2,3-dichloro-1,3-butadiene in the chloroprene polymer contained in the chloroprene polymer latex can be in the range of 0 to 30% by mass relative to 100% by mass of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene contained in the chloroprene polymer. In this case, it is preferable to set the amount of 2,3-dichloro-1,3-butadiene added before the start of emulsion polymerization to be in the range of 0 to 30 parts by mass relative to 100 parts by mass of the total of chloroprene monomer and 2,3-dichloro-1,3-butadiene monomer. From the viewpoint of polymerization control, it is more preferable to use 5 to 25 parts by mass of 2,3-dichloro-1,3-butadiene for every 100 parts by mass of chloroprene monomer and 2,3-dichloro-1,3-butadiene monomer combined.

[0042] In the polymerization process, it is possible to load all of the raw material monomers to be used in the polymerization process into the polymerization vessel before starting the polymerization, or to load at least a portion of the raw material monomers to be used in the polymerization process into the polymerization vessel before starting the polymerization, and then add the remaining raw material monomers (for example, a portion of chloroprene) after the polymerization has started. When at least a portion of the raw material monomers is added before polymerization begins and the remaining raw material monomers are added after polymerization begins, the remaining raw material monomers, such as chloroprene, can be added in one or more installments, or continuously at a constant flow rate. For example, in a polymerization process to obtain a latex containing a chloroprene-based polymer with a weight-average molecular weight of 5,000 to 80,000, at least a portion of the raw material monomers can be added separately.

[0043] When producing chloroprene polymers, 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.

[0044] Emulsion polymerization is a type of radical polymerization in which raw material monomers are added 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., and polymerization is carried out.

[0045] The type of chain transfer agent used in emulsion polymerization is not particularly limited, and known chain transfer agents commonly used in the emulsion polymerization of chloroprene 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.

[0046] By adjusting the type and amount of chain transfer agent, the weight-average molecular weight of the resulting chloroprene polymer latex can be adjusted.

[0047] For example, to obtain a latex containing a chloroprene polymer with a weight-average molecular weight of 5,000 to 80,000, that is, to obtain a chloroprene polymer latex in which a peak indicating a weight-average molecular weight of 5,000 to 80,000 is detected in the molecular weight distribution, it is preferable to charge the chain transfer agent before the start of emulsion polymerization in an amount of 0.5 to 10.0 parts by mass per 100 parts by mass of 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.

[0048] Furthermore, as an example, in order to obtain a latex containing a chloroprene polymer with a weight-average molecular weight of 200,000 or more, preferably 200,000 to 1,500,000, that is, in order to obtain a chloroprene polymer latex in which a peak indicating a weight-average molecular weight of 200,000 or more, preferably 200,000 to 1,500,000, is detected in the molecular weight distribution, it is preferable to charge the amount of chain transfer agent before the start of emulsion polymerization to less than 0.01 to 0.10 parts by mass per 100 parts by mass of monomer (for example, 100 parts by mass of chloroprene and 2,3-dichloro-1,3-butadiene). From the viewpoint of obtaining a chloroprene polymer latex in which a peak indicating a weight-average molecular weight of 500,000 or more is detected, the amount of chain transfer agent to be charged is more preferably 0.02 to 0.05 parts by mass, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 parts by mass, or less than 0.10 parts by mass, and may be within the range of any two of the values ​​exemplified here. If the amount of chain transfer agent, particularly long-chain alkyl mercaptans, charged is 0.01 parts by mass or more, the flexibility of the immersion molded product obtained by immersion molding from the obtained chloroprene polymer latex is improved, and if the amount charged is less than 0.10 parts by mass, particularly less than 0.05 parts by mass, the tensile strength at break of the immersion molded product obtained by immersion molding from the obtained chloroprene polymer latex is further increased.

[0049] Examples of emulsifiers include anionic emulsifiers and nonionic emulsifiers. Examples of anionic emulsifiers include fatty acid salts such as potassium tallow fatty acid, partially hydrogenated potassium tallow fatty acid, potassium oleate, and sodium oleate; resin salts such as potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, and hydrogenated sodium rosinate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; and sodium salts of β-naphthalene sulfonic acid formalin condensate. Examples of nonionic emulsifiers include polyethylene glycol ester type emulsifiers and polyvinyl alcohol. Among these, anionic emulsifiers are preferred, resin salts are preferred, rosin acids including rosin acid and rosin salts are preferred, and at least one selected from the group consisting of potassium rosinate and sodium rosinate is more preferred. These emulsifiers can be used individually or in combination of two or more. The amount of emulsifier used is preferably 1.0 to 6.5 parts by mass per 100 parts by mass of monomer.

[0050] In particular, the emulsifier used in emulsion polymerization preferably contains anionic emulsifiers, and more preferably contains resin salts, especially rosin acids. Using rosin acids allows for a higher degree of prevention of rubber solid aggregation and pH fluctuations when blended with base chloroprene polymer latex. Rosin acids include disproportionate rosin acids, conjugated resin acids, alkali metal salts of disproportionate rosin acids, and alkali metal salts of conjugated resin acids. Examples of disproportionate rosin acids include sesquiterpenes, 8,5-isopimalic acid, dihydropimalic acid, secodehydroabietic acid, dehydroabietic acid, dihydroabietic acid, disopropyldehydroabietic acid, and demethyldehydroabietic acid. Examples of conjugated resin acids include abietic acid, palastic acid, neoabietic acid, and levopimaric acid. From the viewpoint of achieving higher tensile strength at break of the immersion molded product obtained by immersing the resulting chloroprene polymer latex, it is preferable to use conjugated resin acids, and it is preferable that the rosin acids include at least one selected from the group consisting of abietic acid, palastic acid, neoabietic acid, and levopimal acid.

[0051] Furthermore, in the method for producing chloroprene polymer latex according to one embodiment of the present invention, in addition to rosin acids, other commonly used emulsifiers and fatty acids can also be used in combination. Other emulsifiers preferably include, for example, an anionic emulsifier, and in addition to the above-mentioned anionic emulsifiers, metal salts of aromatic sulfinic acid formalin condensates, sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, sodium alkyldiphenyl ethersulfonate, potassium alkyldiphenyl ethersulfonate, sodium polyoxyethylene alkyl ethersulfonate, sodium polyoxypropylene alkyl ethersulfonate, potassium polyoxyethylene alkyl ethersulfonate, potassium polyoxypropylene alkyl ethersulfonate, potassium polyoxypropylene alkyl ethersulfonate, and the like.

[0052] The content of anionic emulsifiers other than rosin acids is preferably 0.2 to 1.0% by mass relative to 100% by mass of the chloroprene polymer contained in the chloroprene polymer latex. For this reason, it is preferable to set the amount of anionic emulsifiers other than rosin acids added before the start of emulsion polymerization to within the range of 0.2 to 0.9 parts by mass per 100 parts by mass of monomer (for example, the sum of chloroprene and 2,3-dichloro-1,3-butadiene).

[0053] The pH of the aqueous emulsion at the start of emulsion polymerization is preferably 10.5 to 13.5. The aqueous emulsion refers to a mixture of the chain transfer agent and monomers (chloroprene, 2,3-dichloro-1,3-butadiene, etc.) 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.

[0054] The polymerization temperature for emulsion polymerization 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 chloroprene monomer.

[0055] Potassium persulfate, benzoyl peroxide, ammonium persulfate, and hydrogen peroxide, which are commonly used in radical polymerization, can be used as polymerization initiators.

[0056] The polymerization conversion rate is preferably in the range of 50-95%. The polymerization reaction is stopped by adding a polymerization inhibitor. When the polymerization conversion rate is 50% or higher, the tensile strength at break of the resulting dipped molded film tends to be high. It is also advantageous from the standpoint of production costs. If the polymerization conversion rate is less than 95%, a decrease in polymerization reactivity due to a reduction in unreacted monomers can be avoided, thus preventing a decrease in productivity.

[0057] Examples of polymerization inhibitors include diethylhydroxylamine, thiodiphenylamine, 4-tert-butylcatechol, and 2,2'-methylenebis-4-methyl-6-tert-butylphenol. Unreacted monomers after emulsion polymerization can be removed by conventional methods such as vacuum distillation.

[0058] Furthermore, the chloroprene polymer latex 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.

[0059] A method for producing chloroprene polymer latex according to one embodiment of the present invention may further include a mixing step after the polymerization step, in which two or more chloroprene polymer latexes having different weight-average molecular weights are mixed. In the mixing step, two or more chloroprene polymer latexes can be mixed by known methods. In the mixing step, for example, chloroprene polymer latex may be obtained by stirring and mixing with a paddle blade at 30 to 300 rpm for 20 seconds to 3 minutes, or, as an example, at 100 rpm for 2 minutes.

[0060] 4. Chloroprene-based polymer latex composition A chloroprene polymer latex composition according to one embodiment of the present invention contains a chloroprene polymer latex comprising the chloroprene polymer according to the present invention. In addition to the chloroprene polymer latex, the chloroprene polymer latex composition may also contain a metal oxide, an antioxidant, and other necessary agents. The types and amounts of metal oxides, antioxidants, and other necessary agents that the chloroprene polymer latex composition may contain will be described later as components that may be included in the immersion molded product.

[0061] 5. Method for producing chloroprene polymer latex compositions A method for producing a chloroprene polymer latex composition may include a raw material mixing step in which raw materials containing chloroprene polymer latex, a metal oxide, an antioxidant, and other necessary agents are mixed. In the mixing process, an aqueous dispersion containing the metal oxide, antioxidant, and other necessary chemicals can be prepared in advance, and then the chloroprene polymer latex can be mixed with the aqueous dispersion. The mixing process can be carried out using a known mixing device such as a ball mill.

[0062] 6. Immersion molded products (Immersion molded product coatings / films) An immersion-molded article according to one embodiment of the present invention is obtained using a chloroprene polymer latex composition containing the above-mentioned chloroprene polymer latex. The immersion-molded article of this embodiment can be obtained by immersion molding after using the aforementioned chloroprene polymer latex composition alone or blended with other chloroprene polymer latex compositions. The immersion-molded article according to the present invention can be obtained by immersion molding a chloroprene polymer latex composition containing a chloroprene polymer by an immersion solidification method, and then heating and drying the immersion-molded article at 150°C for 60 minutes. The immersion-molded article according to the present invention has high tensile strength at break, low modulus at 100% elongation, and excellent texture. The immersion-molded article can be suitably used as industrial and general household gloves, medical gloves, balloons, catheters, and boots.

[0063] The immersion molded article according to the present invention may contain components included in the chloroprene polymer latex described above. Furthermore, the immersion molded article may contain a chloroprene polymer as a base polymer, and when the immersion molded article is considered as 100% by mass, it may contain 70% by mass or more of the chloroprene polymer, preferably 80% by mass or more, and more preferably 90% by mass or more. The content of the chloroprene polymer 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.

[0064] The immersion molded articles containing the chloroprene polymer according to the present invention have low tensile strength at break and modulus at 100% elongation, and possess excellent texture, regardless of whether or not vulcanizing agents and vulcanization accelerators are added. Furthermore, the chloroprene polymer latex composition 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. The components that the immersion molded articles according to the present invention may contain will be described in detail below.

[0065] 6.1 Metal Oxides The immersion molded article of the chloroprene polymer according to the present invention may contain a metal oxide. The metal oxides contained in the chloroprene polymer latex composition used to obtain the immersion molded product are not particularly limited, and examples 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. Furthermore, these metal oxides may be used individually or in mixtures of two or more types.

[0066] 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 latex contained in the chloroprene polymer latex composition used to obtain the immersion molded product. 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 product with excellent flexibility can be obtained. Furthermore, from the viewpoint of balancing the physical properties of the obtained immersion molded product, flexibility and tensile strength at break, the amount of metal oxide added is more preferably 0.5 to 5.0 parts by mass.

[0067] 6.2 Antioxidants The immersion molded article of the chloroprene polymer according to the present invention may also contain an antioxidant. There are no particular restrictions on the antioxidants used; phenolic antioxidants, amine antioxidants, heat-resistant antioxidants (aging inhibitors), ozone-resistant antioxidants, etc., can be used. When the resulting immersion molded product is used for medical gloves, phenolic antioxidants can be adopted from the viewpoint of color tone, texture, and hygiene of the immersion molded product. In particular, hindered phenolic antioxidants have a strong effect. Examples of hindered phenolic 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), butylation reaction products 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 preferred from the viewpoint of being generally dispersible in aqueous materials. Furthermore, these compounds may be used individually or as a mixture of two or more.

[0068] 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 latex contained in the chloroprene polymer latex composition used to obtain the immersion molded product. The amount of antioxidant added 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. If the amount of antioxidant added is 0.5 parts by mass or more, an effect of suppressing color change of the immersion molded product can be obtained. If the amount of antioxidant added is 10.0 parts by mass or less, the stability of the chloroprene polymer latex composition is ensured. Furthermore, from the viewpoint of balancing the physical properties of the obtained immersion molded product, flexibility and tensile strength at break, the amount of antioxidant added is more preferably 0.5 to 5.0 parts by mass.

[0069] 6.3 Vulcanizing agents and vulcanization accelerators A chloroprene polymer immersion molded article according to one embodiment of the present invention may also contain a vulcanizing agent and / or a vulcanization accelerator. Furthermore, the chloroprene polymer latex composition used to obtain the immersion molded article may not contain sulfur and the aforementioned thiram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenicate-based, thiazole-based, and other vulcanization accelerators. In other words, chloroprene polymer latex composition molded articles include those containing a vulcanizing agent but not a vulcanization accelerator, those containing a vulcanizing agent but not a vulcanizing agent, those containing both a vulcanizing agent and a vulcanization accelerator, and those not containing either a vulcanizing agent or 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.

[0070] 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 solids of the chloroprene polymer latex contained in the chloroprene polymer latex composition. The amount of vulcanizing agent added can be, for example, 0, 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.

[0071] 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.

[0072] Commonly used vulcanization accelerators for the vulcanization of chloroprene polymer latex include, but are not limited to, thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenicate-based, and thiazole-based accelerators. These are used individually or in combination of two or more types as needed.

[0073] Examples of thiram-based vulcanization accelerators include tetramethylthiram disulfide, tetraethylthiram disulfide, tetrabutylthiram disulfide, tetrakis(2-ethylhexyl)thiram disulfide, tetramethylthiram monosulfide, and dipentamethylenethiram tetrasulfide.

[0074] 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.

[0075] Examples of thiourea-based vulcanization accelerators include ethylenethiourea, N,N'-diethylthiourea, trimethylthiourea, and N,N'-diphenylthiourea.

[0076] 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.

[0077] Examples of xanthogenic acid-based vulcanization accelerators include zinc butylxanthonate and zinc isopropylxanthonate.

[0078] 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.

[0079] The amount of vulcanization accelerator added can be 0 to 5.0 parts by mass per 100 parts by mass of solids of chloroprene polymer latex contained in the chloroprene polymer latex 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.

[0080] 6.4 Other drugs (heteroaromatic ring compounds) The immersion molded product of the chloroprene polymer according to the present invention may contain heteroaromatic ring compounds in the chloroprene polymer. The heteroaromatic ring compound contained in the chloroprene polymer latex composition used to obtain the immersion molded product 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.

[0081] [ka]

[0082] 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 types.

[0083] 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.

[0084] The amount of heteroaromatic ring compound added is preferably 0.2 to 10.0 parts by mass per 100 parts by mass of solids of the chloroprene polymer latex contained in the chloroprene polymer latex 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 product obtained using this composition exhibits a very high tensile strength at break. If the amount added is 10.0 parts by mass or less, the stability of the chloroprene polymer latex composition is ensured. Furthermore, from the viewpoint of balancing the physical properties of the obtained immersion molded product, flexibility and tensile strength at break, the amount added is more preferably 0.3 to 5.0 parts by mass.

[0085] 6.5 Characteristics of immersion molded products The tensile strength at break of the immersion-molded article according to the present invention, as measured according to JIS K6251, is preferably 17.0 MPa or higher, and more preferably 20.0 MPa or higher. The tensile strength at break is, for example, 17.0, 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, and 40.0 MPa, and may be within the range of any two of the values ​​exemplified here. In particular, the ASTM standard "D3577" for surgical gloves specifies that the tensile strength at break (breaking strength) must be 17 MPa or higher, and 20 MPa indicates even more sufficient mechanical properties.

[0086] The immersion-molded product according to one embodiment of the present invention preferably has a modulus at 100% elongation of 0.70 MPa or less, and more preferably 0.5 MPa or less, as measured according to JIS K6251. The modulus at 100% elongation may be, for example, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, or 0.70 MPa, and may be within the range of any two of the values ​​exemplified herein.

[0087] 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 other chemicals. 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.

[0088] Furthermore, as described above, the tensile strength at break and modulus at 100% elongation of an immersion molded product containing a chloroprene polymer latex composition can be controlled by adjusting the type and amount of raw materials used, the type and amount of chemicals used, and the polymerization conditions when polymerizing the chloroprene polymer, and by adjusting the type and amount of monomer units contained in the resulting chloroprene polymer, as well as the weight-average molecular weight and the mixing ratio of the chloroprene polymer.

[0089] 6.5 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 polymer latex composition, the solid content concentration of the chloroprene polymer latex composition, 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 chloroprene polymer latex composition.

[0090] The immersion molded articles obtained from the chloroprene polymer latex composition may contain sulfur or a vulcanization accelerator. However, even without sulfur and a vulcanization accelerator, the immersion molded articles possess mechanical properties equivalent to or better than those of vulcanized immersion molded articles obtained from conventional chloroprene polymer latex. For this reason, the chloroprene polymer latex composition is suitably used as a raw material for the immersion molded articles (immersion molded bodies) of the chloroprene polymer in this embodiment.

[0091] 7. Method for manufacturing immersion molded products The method for producing an immersion molded product containing a chloroprene polymer according to the present invention is: A molding process to obtain an immersion molded body by molding a chloroprene polymer latex composition containing the above-mentioned chloroprene polymer using a calcium-based coagulation solution by immersion coagulation, and Drying process to obtain a dipped molded product by subjecting the obtained dipped molded body to a heat drying treatment. It can include...

[0092] The molding method for producing the immersion molded body of one embodiment of the present invention is not particularly limited and can be molded according to a conventional method. Examples of molding methods include immersion solidification, simple immersion, heat-sensitive immersion, and electrodeposition. From the viewpoint of ease of manufacture 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 coagulation solution is immersed in a chloroprene polymer latex composition to solidify the chloroprene polymer latex composition. After removing water-soluble impurities by leaching and drying, an immersion molded film (rubber coating) is formed by heating and vulcanization, and then the immersion molded film is released from the mold. This makes it possible to obtain a film-like immersion molded body.

[0093] Furthermore, a method for producing a dipping molded article according to one embodiment of the present invention may include a step of subjecting the obtained dipping molded article to a heat-drying treatment and vulcanizing the unvulcanized dipping molded article. The heat-drying temperature can be appropriately set according to the composition of the chloroprene polymer latex composition, and may be 100 to 220°C or 120 to 180°C. The vulcanization temperature can be, for example, 100, 110, 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 heat-drying time can be appropriately set according to the composition of the chloroprene polymer latex composition, the shape of the unvulcanized molded article, etc., and may be 10 to 300 minutes. The heating and drying 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 subjected to a heating and drying treatment at 150°C for 1 hour. [Examples]

[0094] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0095] (Example 1) <Preparation of chloroprene polymers> (Example 1) (Synthesis Example 1) In a 30L polymerization tank, 86 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 aqueous solution of gum rosin-based disproportionated potassium rosinate (product name "Londis K-25", 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 mass aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 50%, 5 parts by mass of chloroprene (monomer) were added. When the polymerization rate reached 83%, 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 then concentrated to obtain latex a with a solid content of 55% by mass. The weight-average molecular weight of latex a was measured using the method described later and was found to be 735,432.

[0096] (Synthesis Example 2) 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 aqueous solution of gum rosin-based disproportionated potassium rosinate (product name "Londis K-25", manufactured by Arakawa Chemical Industries, Ltd.), 3.6 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 mass aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 80%, 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 then concentrated to obtain latex b with a solid content of 55% by mass.

[0097] (Preparation of chloroprene polymer I) Next, latex a and b were mixed in a mass ratio of a / b = 80 / 20 to obtain a latex containing chloroprene polymer I. For physical property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0098] (Preparation of samples for dynamic viscoelasticity measurement) The sampled latex was poured into an iron frame (150 mm x 210 mm) to a height of approximately 1.5 mm, and left to stand at 23°C for 3 days to evaporate volatile components, thereby obtaining a dried sheet. Dynamic viscoelasticity measurements were performed using the obtained dried sheet. The results are shown in Table 1. The measurement conditions will be described later.

[0099] (Preparation of samples for measuring weight-average molecular weight and 2,3-dichloro-1,3-butadiene content in chloroprene polymers) The sampled latex was mixed with a large amount of methanol to precipitate the rubber component (polymer), which was then filtered and dried to obtain a sample of chloroprene polymer I. The weight-average molecular weight of the chloroprene copolymer was measured from the obtained sample. In addition, the 2,3-dichloro-1,3-butadiene content (mass%) in the chloroprene copolymer was determined by analysis. The analysis results are shown in Table 1. The measurement method will be described later.

[0100] (Example 2) (Synthesis Example 3) Polymerization was carried out using the same procedure as in Synthesis Example 2, 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 latex c with a solid content of 55% by mass.

[0101] (Preparation of Chloroprene Polymer II) Chloroprene-based polymer latex II was obtained by mixing latex a and latex c, obtained using the same procedure as in Synthesis Example 1, in a mass ratio of a / c = 80 / 20. For physical property measurement, 200 ml of the obtained latex was sampled, and an immersion film for evaluation was prepared using the remaining latex.

[0102] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0103] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0104] (Example 3) (Synthesis Example 4) Polymerization was carried out using the same procedure as in Synthesis Example 2, 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 latex d with a solid content of 55% by mass.

[0105] (Preparation of Chloroprene Polymer III) Chloroprene-based polymer latex III was obtained by mixing latex a and latex d, obtained using the same procedure as in Synthesis Example 1, in a mass ratio of a / d = 80 / 20. For physical property measurement, 200 ml of the obtained latex was sampled, and an immersion film for evaluation was prepared using the remaining latex.

[0106] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0107] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0108] (Example 4) (Synthesis Example 5) Polymerization was carried out using the same procedure as in Synthesis Example 2, 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 latex e with a solid content of 55% by mass.

[0109] (Preparation of chloroprene polymer IV) Chloroprene-based polymer latex IV was obtained by mixing latex a and latex e, obtained using the same procedure as in Synthesis Example 1, in a mass ratio of a / e = 80 / 20. For physical property measurement, 200 ml of the obtained latex was sampled, and an immersion film for evaluation was prepared using the remaining latex.

[0110] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0111] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0112] (Example 5) (Synthesis Example 6) Polymerization was carried out using the same procedure as in Synthesis Example 1, except that 95 parts by mass of chloroprene (monomer) and 0 parts by mass of 2,3-dichloro-1,3-butadiene were used. When the polymerization rate reached 50%, 5 parts by mass of chloroprene (monomer) were added. When the polymerization rate reached 83%, 0.1 parts by mass of diethylhydroxylamine, a polymerization inhibitor, was added to stop the polymerization and obtain the polymerization solution. The obtained polymerization solution was removed from unreacted monomers by vacuum distillation and concentrated to obtain latex f with a solid content of 55% by mass. The weight-average molecular weight of latex f was measured using the method described later and was found to be 689,512.

[0113] (Synthesis Example 7) Polymerization was carried out using the same procedure as in Synthesis Example 2, except that 100 parts by mass of chloroprene (monomer) and 0 parts by mass of 2,3-dichloro-1,3-butadiene were used. The resulting polymerization solution was removed by vacuum distillation to remove unreacted monomers, and then concentrated to obtain latex g with a solid content of 55% by mass.

[0114] (Preparation of chloroprene polymer V) Next, chloroprene polymer latex V was obtained by mixing these latexes f and g in a mass ratio of f / g = 80 / 20. For property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0115] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0116] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0117] (Example 6) Polymerization was carried out using the same procedure as in Synthesis Example 1. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex a with a solid content of 55% by mass.

[0118] Polymerization was carried out using the same procedure as in Synthesis Example 2. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex b with a solid content of 55% by mass.

[0119] (Preparation of chloroprene polymer VI) Next, chloroprene polymer latex VI was obtained by mixing latex a and b in a mass ratio of a / b = 60 / 40. For physical property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0120] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0121] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0122] (Example 7) Polymerization was carried out using the same procedure as in Synthesis Example 1. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex a with a solid content of 55% by mass.

[0123] Polymerization was carried out using the same procedure as in Synthesis Example 2. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex b with a solid content of 55% by mass.

[0124] (Preparation of Chloroprene Polymer VII) Next, chloroprene polymer latex VII was obtained by mixing latex a and b in a mass ratio of a / b = 90 / 10. For property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0125] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0126] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0127] (Example 8) (Synthesis Example 8) In a 30L polymerization tank, 86 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 90 parts by mass of pure water, 4.4 parts by mass of potassium salt of conjugated resin acid rosinic acid (product name "Hartol R-WW", manufactured by Harima Chemicals Co., 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 mass aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 50%, 5 parts by mass of chloroprene (monomer) were added. When the polymerization rate reached 83%, 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 then removed by vacuum distillation to remove unreacted monomers, and a latex h with a solid content of 55% by mass was obtained by concentration.

[0128] (Synthesis Example 9) In a 30L polymerization tank, 91 parts by mass of chloroprene (monomer), 9 parts by mass of 2,3-dichloro-1,3-butadiene, 90 parts by mass of pure water, 4.4 parts by mass of potassium salt of conjugated resin acid rosinic acid (product name "Hartol R-WW", manufactured by Harima Chemicals Co., Ltd.), 3.6 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 mass aqueous solution of potassium persulfate as a polymerization initiator. When the polymerization rate reached 80%, 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 then concentrated to obtain latex i with a solid content of 55% by mass.

[0129] (Preparation of Chloroprene Polymer VIII) Next, chloroprene polymer latex VIII was obtained by mixing these latexes h and i in a mass ratio of h / i = 80 / 20. For property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0130] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0131] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0132] (Comparative Example 1) Polymerization was carried out using the same procedure as in Synthesis Example 1. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex a with a solid content of 55% by mass.

[0133] 200 ml of latex a was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0134] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0135] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0136] (Comparative Example 2) Polymerization was carried out using the same procedure as in Synthesis Example 1. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex a with a solid content of 55% by mass.

[0137] Polymerization was carried out using the same procedure as in Synthesis Example 2. The resulting polymerization solution was then subjected to vacuum distillation to remove unreacted monomers, and a concentration operation was performed to obtain latex b with a solid content of 55% by mass.

[0138] (Preparation of chloroprene polymer IX) Next, chloroprene polymer latex IX was obtained by mixing latex a and b in a mass ratio of a / b = 50 / 50. For property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0139] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0140] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0141] (Comparative Example 3) (Synthesis Example 10) In a 30L polymerization tank, 100 parts by mass of chloroprene (monomer), 80 parts by mass of pure water, 4 parts by mass of gum rosin-based disproportionated potassium rosinate (aqueous solution) (product name "Londis K-25", manufactured by Arakawa Chemical Industries, Ltd.), 0.05 parts by mass of n-dodecyl mercaptan, 0.4 parts by mass of sodium hydroxide, and 0.7 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol N", manufactured by Kao Corporation) were added. Polymerization was carried out at a polymerization temperature of 40°C under a nitrogen atmosphere by continuously adding 0.35% by mass of potassium persulfate aqueous solution as a polymerization initiator. When the polymerization rate reached 90%, polymerization was stopped by adding 0.05% by mass of 2,6-tertiary butyl-4-methylphenol as a polymerization stopper to obtain the polymerization solution. The polymerization solution was removed by vacuum distillation, and latex j with a solid content of 55% by mass was obtained by concentration.

[0142] (Synthesis Example 11) Polymerization was carried out using the same procedure as in Synthesis Example 10, except that 0.25 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 latex k with a solid content of 55% by mass.

[0143] (Preparation of chloroprene polymer X) Next, chloroprene polymer latex X was obtained by mixing these latexes j and k in a mass ratio of j / k = 50 / 50. For property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0144] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0145] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0146] (Comparative Example 4) (Synthesis Example 12) Polymerization was carried out using the same procedure as in Synthesis Example 10, except that 90 parts by mass of chloroprene (monomer), 10 parts by mass of 2,3-dichloro-1,3-butadiene, and 0.07 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 latex l with a solid content of 55% by mass.

[0147] (Synthesis Example 13) Polymerization was carried out in the same procedure as in Synthesis Example 10, except that 90 parts by mass of chloroprene (monomer), 10 parts by mass of 2,3-dichloro-1,3-butadiene, and 0.31 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 latex m with a solid content of 55% by mass.

[0148] (Preparation of chloroprene polymer XI) Next, chloroprene polymer latex XI was obtained by mixing these latexes l and m in a mass ratio of l / m = 30 / 70. For property measurement, 200 ml of the obtained latex was sampled, and the remaining latex was used to prepare an immersion film for evaluation.

[0149] Using the sampled latex, a dried sheet was obtained using the same procedure as in Example 1, and its dynamic viscoelasticity was measured in the same manner as in Example 1. The results are shown in Table 1.

[0150] Using the sampled latex, the weight-average molecular weight of the chloroprene copolymer and the 2,3-dichloro-1,3-butadiene content (mass%) were determined by analysis using the same procedure as in Example 1. The analysis results are shown in Table 1.

[0151] The chloroprene polymers were analyzed using the following method. <Measurement of dynamic viscoelasticity of chloroprene polymers> The dried sheets of each example and comparative example were used as films containing chloroprene polymers. The films containing chloroprene polymers from each example and comparative example were cut to prepare strip-shaped test pieces (width: 4.5 mm, length: 30 mm, thickness: 0.80-0.90 mm). Using these strip-shaped test pieces, tensile dynamic viscoelasticity measurements (chuck spacing: 20 mm) were performed according to the non-resonant forced vibration method. The measurement conditions were a static tension of 5 gf, a temperature of 25°C, and a strain of 0.75%, and the loss tangent tanδ in the 10 Hz frequency range was measured. The measurement device used was the DDV-25FP manufactured by Orientec Co., Ltd. The results are shown in Table 1.

[0152] <Measurement of weight-average molecular weight of chloroprene polymers> The weight-average molecular weight was measured by gel permeation chromatography (GPC) under the measurement conditions described below, using a sample obtained by dissolving a polymer precipitated from latex containing a chloroprene 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).

[0153] <Measurement of 2,3-dichloro-1,3-butadiene content in chloroprene polymers> Polymers precipitated from latex containing chloroprene polymers were cut into 0.05 mg test pieces and measured by pyrolysis gas chromatography. The area ratio of the peak derived from chloroprene to the peak derived from 2,3-dichloro-1,3-butadiene was determined. Using a calibration curve between the area ratio of the peaks derived from chloroprene and 2,3-dichloro-1,3-butadiene and the 2,3-dichloro-1,3-butadiene content, the 2,3-dichloro-1,3-butadiene content (mass%) in the chloroprene polymer was determined.

[0154] [Gas chromatogram measurement conditions] Measurement conditions for pyrolysis gas chromatogram Device name: HP5890-II Column: DB-5 0.25mmφ×30m (film thickness 1.0μm) Column temperature: 50°C (5 min) → 10°C / min → 150°C → 25°C / min → 300°C Inlet temperature: 250℃ Detector temperature: 280℃ Detector: FID

[0155] The following method was used to evaluate immersion molded products containing chloroprene polymers. <Preparation of immersion-molded products for tensile property evaluation> A chloroprene polymer latex composition was prepared by mixing 100 parts by mass of the solid content of latex containing each chloroprene polymer with 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.), 2 parts by mass of dibutyldithiocarbamic acid (trade name "Nocrac BZ", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 1 part by mass of sulfur, 0.1 parts by mass of the sodium salt of β-naphthalene sulfonic 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 obtained chloroprene polymer latex composition contains, per 100 parts by mass of chloroprene polymer latex solids, 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.), 2 parts by mass of dibutyldithiocarbamic acid (trade name "Nocrac BZ", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 1 part by mass of sulfur, 0.1 parts by mass of the sodium salt of β-naphthalene sulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), and water.

[0156] A 7.5-size surgical glove-shaped mold made of ceramic (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 calcium 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 a chloroprene-based polymer latex composition prepared by the above procedure. Subsequently, it was washed with running water at 45°C for 1 minute and dried at 150°C for 60 minutes to produce a glove-shaped immersion molded film for texture evaluation. Similarly, an immersion molded film for tensile property evaluation was prepared using a 50 mm outer diameter cylindrical mold made of ceramic using the same procedure.

[0157] <Tensile properties> (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 used for tensile property evaluation was measured at three points in the center, and the minimum thickness was obtained as the thickness of the evaluation film. The results are shown in Table 1.

[0158] (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 Table 1.

[0159] <Evaluation of the texture of glove-shaped immersion molded products> Five subjects were asked to touch the resulting immersion-molded product (glove-like film) and evaluate its texture by touching, stretching, and bending its surface. The evaluation was conducted according to the following criteria, and the average of each subject's evaluation was rounded to the nearest whole number.

[0160] (Texture evaluation criteria) 3: It was extremely soft, pleasant to the touch, and had a superior texture. 2: It was soft, the feel was perfectly fine for practical use, and the texture was good. 1: It didn't feel very soft, it felt somewhat hard to the touch, and the texture wasn't good.

[0161] [Table 1]

Claims

1. A chloroprene polymer, Under conditions of 25°C and 0.75% strain, when a tensile-type dynamic viscoelasticity measurement was performed according to the non-resonant forced vibration method, the loss tangent tanδ of the film containing the chloroprene polymer in the 10 Hz frequency range was 0.08 to 0.

14. The aforementioned film is obtained by drying a chloroprene polymer latex containing the chloroprene polymer at 23°C for 3 days. A chloroprene polymer in which, when the tetrahydrofuran-soluble portion of the chloroprene polymer is measured by gel permeation chromatography, peaks with a weight-average molecular weight of 5,000 to 80,000 are detected.

2. The chloroprene polymer according to claim 1, wherein the chloroprene polymer contains monomer units derived from 2,3-dichloro-1,3-butadiene.

3. A dipping molded article comprising the chloroprene polymer described in claim 1 or claim 2.

4. The immersion molded product according to claim 3, which is an industrial or general household glove, a medical glove, a balloon, a catheter, or a boot.

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