Chloroprene polymer latex composition and impregnation molded body

Abstract

A chloroprene polymer latex composition, comprising a mixture of chloroprene polymer latex A and chloroprene polymer latex B, wherein the copolymer content of 2,3-dichloro-1,3-butadiene in the chloroprene polymer of chloroprene polymer latex B is 3% by mass or more, the toluene-insoluble component of the chloroprene polymer of chloroprene polymer latex B is 70% by mass or more, the weight average molecular weight of the toluene-soluble component in chloroprene polymer latex A is 5,000 to 250,000, and a specific mass ratio b / a is 0.10 or more.

Description

Technical Field

[0001] This invention relates to chloroprene polymer latex compositions and dip-molded articles. More specifically, this invention relates to chloroprene polymer latex compositions comprising a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene, and dip-molded articles using the chloroprene polymer latex compositions. Background Technology

[0002] Chloroprene polymers are known to be used as materials for impregnated molded products such as medical surgical gloves, medical examination gloves, industrial gloves, balloons, catheters, and rubber boots.

[0003] Various techniques related to improving the flexibility of chloroprene polymers or using chloroprene polymers for impregnated molded articles have been proposed. Patent Document 1, for applications in vibration-damping rubber, describes how mixing low molecular weight chloroprene polymers in the range of 500 to 50,000 improves damping performance. Patent Document 2, for applications in impregnated molded articles, describes a polychloroprene latex with a pH of 7 to 14, containing 100 parts by weight of modified polychloroprene obtained by copolymerizing chloroprene with methacrylic acid, 90 to 150 parts by weight of water, 1 to 5 parts by weight of emulsifier, and 0.5 to 2.5 parts by weight of potassium ions. Patent Document 3, for use in dip-molded articles, describes a thiol-modified polychloroprene latex, wherein chloroprene is copolymerized with 2,3-dichloro-1,3-butadiene, and the peak areas (A), (B), and (C) of the polychloroprene in the 13C-solid-state NMR spectrum are within the ranges shown in general formula (I). Patent Document 4, for use in dip-molded articles, describes a chloroprene polymer latex that, by comprising both high-molecular-weight and low-molecular-weight components, simultaneously achieves excellent softness and mechanical properties in vulcanized rubber produced by dip molding.

[0004] [Mathematical Expression 1]

[0005]

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 7-292165

[0009] Patent Document 2: Japanese Patent Application Publication No. 2014-114342

[0010] Patent Document 3: International Publication No. 2019 / 009038

[0011] Patent Document 4: Japanese Patent Application Publication No. 2019-143002 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] As impregnation molded products, chloroprene polymer impregnation films typically exhibit excellent mechanical strength through the addition of crosslinking agents such as sulfur and vulcanization accelerators. Chloroprene polymer latex is used as the rubber latex raw material in impregnation films for gloves, balloons, boots, and tubing. On the other hand, there is a tendency to demand impregnation films with the same high level of softness as those obtained using natural rubber or polyisoprene, especially in glove applications, where there is a desire to improve the physical properties of chloroprene polymer latex that are directly related to the softness of the material, which is crucial for wearing comfort and the feel of the film.

[0014] Furthermore, the sulfur and vulcanization accelerators that are ideal for improving mechanical strength are substances that are type IV allergens and can cause adverse effects on the human body. Additionally, there is a need to reduce costs in manufacturing impregnated films that do not contain these components. Therefore, it is desirable to provide chloroprene polymer latexes that are free of sulfur and vulcanization accelerators and possess excellent flexibility while exhibiting excellent tensile strength.

[0015] Therefore, the main objective of this invention is to provide a chloroprene polymer latex composition that can produce a chloroprene polymer impregnation molding film with high tensile strength and excellent flexibility, even without the use of sulfur and vulcanization accelerators.

[0016] Methods for solving problems

[0017] Specifically, the present invention relates to a chloroprene polymer latex composition, which is a mixture of chloroprene polymer latex A and chloroprene polymer latex B, wherein both chloroprene polymer latex A and chloroprene polymer latex B contain chloroprene polymers, and the chloroprene polymer in chloroprene polymer latex B comprises a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene, wherein the 2,3-dichloro-1,3-butadiene in the chloroprene polymer of chloroprene polymer latex B... The copolymerization amount of olefin (the content of monomer units of 2,3-dichloro-1,3-butadiene; the same below) is 3% by mass or more relative to 100% by mass of the total of chloroprene and 2,3-dichloro-1,3-butadiene; the toluene-insoluble component of the aforementioned chloroprene polymer latex B is 70% by mass or more; the weight-average molecular weight of the toluene-soluble component in the aforementioned chloroprene polymer latex A is 5,000 to 250,000; and the ethanol / toluene azeotropic mixture (JIS) is used. In the gas chromatography-mass spectrometry determination of the extract obtained from the dried matter obtained by freeze-drying the aforementioned chloroprene polymer latex composition (the ethanol / toluene azeotropic mixture specified in K 6229), the mass ratio b of the total amount of abietic acid, neoabietic acid, longleaf abietic acid, L-piperidine and their salts relative to the total amount a of dehydroabietic acid, piratic acid, isopiratic acid, dihydroabietic acid and their salts is 0.10 or more. It should be noted that in this invention, "JIS" refers to Japanese Industrial Standards.

[0018] The above-mentioned chloroprene polymer latex composition can be the following chloroprene polymer latex composition, wherein the toluene-insoluble component of the aforementioned chloroprene polymer in the aforementioned chloroprene polymer latex A is less than 5% by mass.

[0019] The above-mentioned chloroprene polymer latex composition can be the following chloroprene polymer latex composition, wherein the toluene-insoluble component of the aforementioned chloroprene polymer in the aforementioned chloroprene polymer latex B is 70-95% by mass.

[0020] The above-mentioned chloroprene polymer latex composition can be the following chloroprene polymer latex composition, wherein the proportion of the aforementioned chloroprene polymer latex A is 0.50 to 30.0 parts by mass relative to a total of 100 parts by mass of the aforementioned chloroprene polymer latex A and the aforementioned chloroprene polymer latex B, and the toluene-insoluble component of the chloroprene polymer contained in the chloroprene polymer latex composition is 50 to 85 parts by mass.

[0021] Furthermore, the present invention relates to impregnated molded articles using the aforementioned chloroprene polymer latex composition. Such impregnated molded articles may be free of sulfur and vulcanization accelerators. These impregnated molded articles can be gloves, balloons, tubing, or boots.

[0022] Invention Effects

[0023] According to the present invention, a chloroprene polymer latex composition for impregnating a chloroprene polymer film can be provided even without the use of sulfur and vulcanization accelerators, which are type IV allergens that have adverse effects on the human body. In such a chloroprene polymer latex composition, since the weight-average molecular weight of the toluene-soluble component is relatively low (i.e., 250,000 or less), the plasticity of the low molecular weight polymer can be utilized to obtain very excellent softness. According to the present invention, even without the use of sulfur and vulcanization accelerators, a chloroprene polymer impregnating film with high tensile strength and elongation at break, and excellent softness, can be obtained. Detailed Implementation

[0024] The embodiments of the present invention will now be described in detail. It should be noted that the present invention is not limited to the embodiments described below.

[0025] In this specification, "above A" in a numerical range refers to A and the range greater than A. "Below A" in a numerical range refers to A and the range less than A. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain stage's numerical range can be arbitrarily combined with the upper or lower limits of other stages' numerical ranges. In the numerical ranges described in this specification, the upper or lower limit can be replaced with the values ​​shown in the examples. "A or B" can refer to either A or B, or both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. Regarding the content of each component in the composition, in the case where multiple substances belonging to each component are present in the composition, unless otherwise specified, it refers to the total amount of the multiple substances present in the composition. "(Meth)acrylic acid" refers to at least one of acrylic acid and its corresponding methacrylic acid, and the same applies to "(meth)acrylate" and other similar expressions. In the determination of "toluene soluble components" and "toluene insoluble components", toluene at room temperature (23°C) can be used.

[0026] <Chloroprene Polymer Latex Composition>

[0027] First, the chloroprene polymer latex composition according to the first embodiment of the present invention will be described. The chloroprene polymer latex composition according to this embodiment (hereinafter referred to as "mixed chloroprene polymer latex composition") is a mixture of chloroprene polymer latex A and chloroprene polymer latex B.

[0028] The mixed chloroprene polymer latex composition according to this embodiment can be obtained, for example, by using a paddle jet to stir and mix two or more chloroprene polymer latexes, including chloroprene polymer latex A and B, at 100 rpm for 1 minute. The mixed chloroprene polymer latex composition according to this embodiment can also be obtained by mixing chloroprene polymer latexes other than chloroprene polymer latex A and B. For example, when surface hardness is required in the impregnated molded body obtained using the mixed chloroprene polymer latex composition, a chloroprene polymer latex that is not copolymerized with 2,3-dichloro-1,3-butadiene and has high crystallinity can be cited as an example.

[0029] (Chloroprene polymer)

[0030] Chloroprene polymer latex A contains a chloroprene polymer. A chloroprene polymer is a polymer having chloroprene (2-chloro-1,3-butadiene) as a monomer unit, and can be a homopolymer of chloroprene or a copolymer of chloroprene with other monomers (such as a copolymer of chloroprene with 2,3-dichloro-1,3-butadiene). Chloroprene polymer latex B contains a chloroprene polymer, which comprises a copolymer of chloroprene with 2,3-dichloro-1,3-butadiene.

[0031] The copolymer of chloroprene and 2,3-dichloro-1,3-butadiene is a polymer having chloroprene and 2,3-dichloro-1,3-butadiene as monomer units, which can be obtained by polymerizing a monomer composition containing chloroprene and 2,3-dichloro-1,3-butadiene.

[0032] Copolymers of chloroprene and 2,3-dichloro-1,3-butadiene can contain monomer units of monomers other than chloroprene and 2,3-dichloro-1,3-butadiene. Examples of such monomers include esters of (meth)acrylic acid (methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, etc.), hydroxyalkyl esters of (meth)acrylic acid (2-hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, etc.), (meth)acrylic acid, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, (meth)acrylonitrile, etc. On the other hand, the copolymer of chloroprene and 2,3-dichloro-1,3-butadiene may also not have monomer units other than chloroprene and 2,3-dichloro-1,3-butadiene, and may be substantially a copolymer formed of monomer units of chloroprene and monomer units of 2,3-dichloro-1,3-butadiene.

[0033] At least one of the groups selected from chloroprene polymer latex A and chloroprene polymer latex B may contain at least one of the groups selected from rosin acid, sodium rosinate, and potassium rosinate, and at least one of the groups selected from sodium hydroxide and potassium hydroxide. To prevent aggregation of the solid components of the rubber and pH changes during blending, it is desirable that the emulsion system of chloroprene polymer latex A and B be consistent with the base latex.

[0034] (Toluene-insoluble components)

[0035] For the toluene-insoluble component of chloroprene polymer, after dissolving the chloroprene polymer obtained by freeze-drying chloroprene polymer latex A, B, or a mixed chloroprene polymer latex composition with toluene, centrifuging is performed, and the insoluble component (gel component) is further separated using a 200-mesh metal mesh. The product is then dried, and the mass of the dried product is determined.

[0036] The toluene-insoluble component (gel component) of the chloroprene polymer in chloroprene polymer latex A is preferably 10% by mass or less relative to 100% by mass of the chloroprene polymer. If the toluene-insoluble component is 10% by mass or less, the modulus value at 100% elongation, which is an indicator of the softness of the impregnated molded film obtained using the mixed chloroprene polymer latex composition, tends to be lower, and excellent softness is easily obtained.

[0037] From the viewpoint of easily obtaining excellent softness, the toluene-insoluble content of the chloroprene polymer in chloroprene polymer latex A can be less than 8% by mass, less than 6% by mass, less than 5% by mass, less than 5% by mass, less than 4% by mass, less than 3% by mass, less than 2% by mass, or less than 1.5% by mass. The toluene-insoluble content can be more than 0% by mass, more than 0% by mass, more than 1% by mass, more than 1.5% by mass, more than 2% by mass, more than 3% by mass, more than 4% by mass, more than 5% by mass, or more than 6% by mass. From these viewpoints, the toluene-insoluble content can be greater than 0% by mass and less than 10% by mass, 1 to 10% by mass, 1.5 to 10% by mass, greater than 0% by mass and less than 6% by mass, 1 to 6% by mass, 1.5 to 6% by mass, greater than 0% by mass and less than 3% by mass, 1 to 3% by mass, or 1.5 to 3% by mass.

[0038] The toluene-insoluble component (gel component) of the chloroprene polymer in chloroprene polymer latex B is 70% by mass or more relative to 100% by mass of the chloroprene polymer. If the toluene-insoluble component is 70% by mass or more, excellent softness can be obtained in the impregnation-molded film obtained using the mixed chloroprene polymer latex composition, and a cross-linked structure is formed through the entanglement (geling) of the polymers, thereby increasing the mechanical strength of the impregnation-molded film.

[0039] From the perspective of easily obtaining excellent flexibility and easily increasing mechanical strength, the toluene-insoluble content of the chloroprene polymer in chloroprene polymer latex B can be 75% by mass or more, 80% by mass or more, 82% by mass or more, 85% by mass or more, 86% by mass or more, or 90% by mass or more. From the perspective of easily avoiding the reduction in polymerization reactivity due to the reduction of unreacted monomers, the toluene-insoluble content can be 95% by mass or less, 90% by mass or less, 86% by mass or less, 85% by mass or less, 82% by mass or less, 80% by mass or less, or 75% by mass or less. From these perspectives, the toluene-insoluble content can be 70–95% by mass, 70–90% by mass, 70–85% by mass, 75–95% by mass, 75–90% by mass, or 75–85% by mass.

[0040] The toluene-insoluble component (gel component) of the chloroprene polymer in the mixed chloroprene polymer latex composition can be within the following ranges relative to 100% by mass of the chloroprene polymer: The toluene-insoluble component can be 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, or 80% by mass or more. The toluene-insoluble component can be less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, or less than 55% by mass. From these perspectives, the toluene-insoluble component can be 50–85% by mass, 50–80% by mass, 50–75% by mass, 60–85% by mass, 60–80% by mass, or 60–75% by mass. The numerical range of the toluene-insoluble component can be adjusted by the mixing ratio of chloroprene polymer latex A to chloroprene polymer latex B.

[0041] (Weight-average molecular weight of toluene-soluble components)

[0042] The toluene-soluble component (sol component soluble in toluene) in chloroprene polymer latex A has a weight-average molecular weight of 5,000 to 250,000. If the weight-average molecular weight is below 250,000, the plasticity of the low molecular weight polymer can be utilized to obtain an impregnated film exhibiting excellent flexibility. If the weight-average molecular weight is above 5,000, an ideal impregnated film can be obtained.

[0043] From the viewpoint of easily achieving both excellent flexibility and tensile strength, the weight-average molecular weight of the toluene-soluble component can be within the following ranges: 6,000 or more, 7,000 or more, 10,000 or more, 12,000 or more, 15,000 or more, 16,000 or more, 18,000 or more, 20,000 or more, 22,000 or more, or 24,000 or more. The weight-average molecular weight can be below 240,000, below 220,000, below 200,000, below 180,000, below 100,000, below 50,000, below 25,000, below 24,000, below 22,000, below 20,000, below 18,000, below 16,000, below 15,000, below 12,000, below 10,000, or below 7,000. From these perspectives, the weight-average molecular weight can be 5,000–240,000, 5,000–180,000, 6,000–240,000, 6,000–200,000, 6,000–100,000, 6,000–50,000, 6,000–25,000, 7,000–100,000, 7,000–50,000, 7,000–25,000, 10,000–100,000, 10,000–50,000, 10,000–25,000, 20,000–100,000, 20,000–50,000, or 20,000–25,000.

[0044] The weight-average molecular weight of the toluene-soluble component can be obtained by dissolving chloroprene polymer latex A in toluene and then determining the weight-average molecular weight of the dissolved component (sol component) using gel permeation chromatography (GPC). The measured weight-average molecular weight varies depending on factors such as the amount of chain transfer agent added.

[0045] [Determination of weight-average molecular weight based on gel permeation chromatography]

[0046] GPC determination was performed under the following conditions. Molecular weight was calculated using polystyrene conversion.

[0047] • Gel permeation chromatography (GPC) apparatus: TOSOH Corporation, gel permeation chromatograph (HLC-8320)

[0048] • Chromatographic column: TOSOH Corporation, TSKgel ALPHA-M

[0049] • Eluent: Tetrahydrofuran (manufactured by Kanto Chemical Co., Ltd.)

[0050] • Elution buffer flow rate: 1.0 ml / min

[0051] Column temperature: 40℃

[0052] • Detection method: Differential refractive index (RI) meter

[0053] • Standard curve: made using standard polystyrene.

[0054] (Chloroprene copolymer content)

[0055] When the chloroprene polymer contained in chloroprene polymer latex A is a copolymer of chloroprene and other monomers, from the viewpoint of easily obtaining excellent flexibility in the impregnation molding film, the chloroprene copolymer content (the content of chloroprene monomer units; the same below) in the chloroprene polymer can be in the following range, relative to 100% by mass of the total amount of monomer units in the chloroprene polymer, or 100% by mass of the combined chloroprene copolymer content and 2,3-dichloro-1,3-butadiene copolymer content in the chloroprene polymer. The chloroprene copolymer content can be 99% by mass or less, 97% by mass or less, 95% by mass or less, 92% by mass or less, 90% by mass or less, 88% by mass or less, 85% by mass or less, 82% by mass or less, or 80% by mass or less. The copolymerization amount of chloroprene can be 50% by mass or more, greater than 50% by mass, 60% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 82% by mass or more, 85% by mass or more, 88% by mass or more, or 90% by mass or more. From these perspectives, the copolymerization amount of chloroprene can be 50–99% by mass, 70–99% by mass, 80–99% by mass, 85–90% by mass, 90–99% by mass, 50–90% by mass, 70–90% by mass, 80–90% by mass, 85–90% by mass, 50–85% by mass, 70–85% by mass, 80–85% by mass, 50–80% by mass, or 70–80% by mass.

[0056] From the viewpoint of easily obtaining excellent flexibility in impregnation molding films, the amount of chloroprene copolymer in the chloroprene polymer of chloroprene polymer latex B can be within the following ranges, relative to 100% by mass of the total amount of monomer units in the chloroprene polymer, or 100% by mass of the combined amount of chloroprene copolymer and 2,3-dichloro-1,3-butadiene copolymer in the chloroprene polymer. The amount of chloroprene copolymer can be 99% by mass or less, 97% by mass or less, 95% by mass or less, 92% by mass or less, 90% by mass or less, 88% by mass or less, 85% by mass or less, 82% by mass or less, or 80% by mass or less. The amount of chloroprene copolymer can be 70% by mass or more, 75% by mass or more, 80% by mass or more, 82% by mass or more, 85% by mass or more, 88% by mass or more, 90% by mass or more, 92% by mass or more, or 95% by mass or more. From these perspectives, the copolymerization amount of chloroprene can be 70–99% by mass, 70–97% by mass, 70–95% by mass, 70–90% by mass, 80–99% by mass, 80–97% by mass, 80–95% by mass, 80–90% by mass, 85–99% by mass, 85–97% by mass, 85–95% by mass, or 85–90% by mass.

[0057] (2,3-Dichloro-1,3-butadiene copolymer content)

[0058] When the chloroprene polymer contained in chloroprene polymer latex A is a copolymer of chloroprene and other monomers, from the viewpoint of easily obtaining excellent flexibility in impregnation molding films, the copolymer content of 2,3-dichloro-1,3-butadiene in the chloroprene polymer can be within the following range, relative to 100% by mass of the total amount of monomer units in the chloroprene polymer, or 100% by mass of the combined copolymer content of chloroprene and 2,3-dichloro-1,3-butadiene in the chloroprene polymer. The copolymer content of 2,3-dichloro-1,3-butadiene can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, 10% by mass or more, 12% by mass or more, 15% by mass or more, 18% by mass or more, or 20% by mass or more. The copolymerization amount of 2,3-dichloro-1,3-butadiene can be less than 50% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 25% by mass, less than 20% by mass, less than 18% by mass, less than 15% by mass, less than 12% by mass, or less than 10% by mass. From these perspectives, the copolymerization amount of 2,3-dichloro-1,3-butadiene can be 1–50% by mass, 1–30% by mass, 1–20% by mass, 1–15% by mass, 1–10% by mass, 10–50% by mass, 10–30% by mass, 10–20% by mass, 10–15% by mass, 15–50% by mass, 15–30% by mass, 15–20% by mass, 20–50% by mass, or 20–30% by mass.

[0059] From the viewpoint of easily obtaining excellent softness in impregnated films, the amount of 2,3-dichloro-1,3-butadiene copolymer in the chloroprene polymer of chloroprene polymer latex B is preferably 3% by mass or more, relative to 100% by mass of the total amount of monomer units in the chloroprene polymer, or 100% by mass of the combined amount of chloroprene copolymer and 2,3-dichloro-1,3-butadiene copolymer in the chloroprene polymer. If the amount of 2,3-dichloro-1,3-butadiene copolymer is 3% by mass or more, excellent softness is easily obtained in the impregnated film. From the viewpoint of easily obtaining excellent softness in the impregnated film, the amount of 2,3-dichloro-1,3-butadiene copolymer can be in the following ranges: 5% by mass or more, 8% by mass or more, 10% by mass or more, 12% by mass or more, 15% by mass or more, 18% by mass or more, or 20% by mass or more. The copolymerization amount of 2,3-dichloro-1,3-butadiene can be less than 30% by mass, less than 25% by mass, less than 20% by mass, less than 18% by mass, less than 15% by mass, less than 12% by mass, less than 10% by mass, less than 8% by mass, or less than 5% by mass. From these perspectives, the copolymerization amount of 2,3-dichloro-1,3-butadiene can be 3–30% by mass, 5–30% by mass, 10–30% by mass, 3–20% by mass, 5–20% by mass, 10–20% by mass, 3–15% by mass, 5–15% by mass, or 10–15% by mass.

[0060] The copolymerization amount of 2,3-dichloro-1,3-butadiene can be determined by measuring the pyrolysis gas chromatograph of the chloroprene polymer obtained by freeze-drying the chloroprene polymer latex.

[0061] [Determination by Pyrolysis Gas Chromatography]

[0062] Pyrolysis gas chromatography can be performed under the following determination conditions.

[0063] • Column used: DB-5 0.25mmφ×30m (film thickness 1.0μm)

[0064] • Column temperature: 50℃→10℃ / min→120℃→25℃ / min→300℃

[0065] Injection port temperature: 270℃

[0066] • Detector temperature: 280℃

[0067] • Sample size: 0.05 mg

[0068] (mass ratio b / a)

[0069] In the gas chromatography-mass spectrometry analysis of the extract obtained from the dried product (chloroprene polymer) obtained by freeze-drying the mixed chloroprene polymer latex composition involved in this embodiment using an ethanol / toluene azeotropic mixture (the ethanol / toluene azeotropic mixture specified in JIS K 6229), the mass ratio b / a (total amount b / total amount a) of the combined amount b of abietic acid, neoabietic acid, longleaf abietic acid, L-piperidine and their salts relative to the combined amount a of dehydroabietic acid, piratic acid, isopiratic acid, dihydroabietic acid and their salts is 0.10 or more. By making the mass ratio b / a 0.10 or more, excellent tensile strength can be obtained.

[0070] From the viewpoint of easily obtaining excellent fracture strength, the mass ratio b / a can be 0.20 or higher, 0.30 or higher, 0.40 or higher, 0.50 or higher, 0.60 or higher, 0.70 or higher, 0.80 or higher, 0.90 or higher, 1.00 or higher, 1.20 or higher, 1.40 or higher, or 1.60 or higher. The mass ratio b / a can be 2.00 or lower, 1.80 or lower, 1.60 or lower, 1.40 or lower, 1.20 or lower, 1.00 or lower, 0.90 or lower, 0.80 or lower, 0.70 or lower, 0.60 or lower, 0.50 or lower, 0.40 or lower, or 0.30 or lower. From these perspectives, the mass ratio b / a can be 0.10–2.00, 0.10–1.20, 0.10–1.00, 0.10–0.80, 0.10–0.70, 0.30–2.00, 0.30–1.20, 0.30–1.00, 0.30–0.80, 0.30–0.70, 0.50–2.00, 0.50–1.20, 0.50–1.00, 0.50–0.80, 0.50–0.70, 0.80–2.00, 0.80–1.20, 0.80–1.00, or 1.00–2.00.

[0071] After the dried product obtained by freeze-drying the mixed chloroprene polymer latex composition is cut, it is placed in a flask equipped with a condenser and extracted using an ethanol / toluene azeotropic mixture as specified in JIS K 6229. Following hydrochloric acid treatment, gas chromatography-mass spectrometry (GC-MS) determination is performed. The peak area values ​​of each component are considered as their content, thereby calculating the total amount 'a' and total amount 'b'. The mass ratio b / a is determined by the type of rosin acid and rosin acid metal salt added as emulsifiers.

[0072] [Gas Chromatography-Mass Spectrometry Determination Conditions]

[0073] Gas chromatography-mass spectrometry can be performed under the following determination conditions.

[0074] • Column used: FFAP 0.32mmφ×25m (film thickness 0.3μm)

[0075] Column temperature: 200℃→250℃

[0076] • Heating rate: 10℃ / min

[0077] Injection port temperature: 270℃

[0078] Injection volume: 1μL

[0079] • Interface temperature: 270℃

[0080] • Ion source temperature: 270℃

[0081] • Ionization current: 50μA

[0082] • Ionization voltage: 70 eV

[0083] • Detector voltage: -1000V

[0084] • Detector voltage: EI method

[0085] (Mixing ratio of chloroprene polymer latex)

[0086] From the viewpoint of easily achieving both tensile strength and flexibility in impregnated films obtained using mixed chloroprene polymer latex compositions, the proportion (mixing ratio) of chloroprene polymer latex A relative to a total of 100 parts by weight of chloroprene polymer latex A and chloroprene polymer latex B, based on the solid component ratio, can be within the following ranges: The proportion of chloroprene polymer latex A can be 0.5 parts by weight or more, 1 part by weight or more, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, or 30 parts by weight or more. The proportion of chloroprene polymer latex A can be 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less. From these perspectives, the proportion of chloroprene polymer latex A can be 0.5–50 parts by weight, 0.5–30 parts by weight, 0.5–25 parts by weight, 0.5–20 parts by weight, 0.5–15 parts by weight, 5–50 parts by weight, 5–30 parts by weight, 5–25 parts by weight, 5–20 parts by weight, 5–15 parts by weight, 10–50 parts by weight, 10–30 parts by weight, 10–25 parts by weight, 10–20 parts by weight, or 10–15 parts by weight.

[0087] (Effects obtained from the mixed chloroprene polymer latex composition)

[0088] According to the mixed chloroprene polymer latex composition of this embodiment, a chloroprene polymer impregnated molded film with high tensile strength and excellent flexibility can be obtained even without the use of sulfur and vulcanization accelerators. Specifically, when tested according to JIS K 6251, the impregnated molded film obtained by vulcanizing the mixed chloroprene polymer latex composition at 130°C for 4 hours without the use of sulfur and vulcanization accelerators meets the following requirements: a modulus of 0.40 to 0.75 MPa at 100% elongation and a tensile strength of 17 MPa or more. In particular, the tensile strength is specified as 17 MPa or more in ASTM standard "D3577" for surgical gloves. This impregnated molded film has excellent flexibility and sufficient mechanical strength even without sulfur and vulcanization accelerators.

[0089] For conventional chloroprene polymers, the use of sulfur or vulcanization accelerators is indispensable to obtain vulcanized rubber with the target mechanical strength. Sulfur and vulcanization accelerators are causative agents of type IV allergies, which can trigger skin diseases such as dermatitis. Therefore, reducing or eliminating the use of sulfur and vulcanization accelerators has become an important issue. Furthermore, eliminating sulfur and vulcanization accelerators not only reduces allergies but also lowers costs. Therefore, it is desirable to obtain chloroprene polymer latex compositions that produce impregnated molded articles with excellent softness and sufficient mechanical strength without the use of sulfur and vulcanization accelerators.

[0090] The impregnation-molded film obtained from the mixed chloroprene polymer latex composition according to this embodiment may also contain sulfur and / or a vulcanization accelerator. However, even without sulfur and a vulcanization accelerator, the above-mentioned impregnation-molded film possesses mechanical properties equivalent to or higher than those of vulcanized impregnation-molded films obtained from conventional chloroprene polymer latex. Therefore, the mixed chloroprene polymer latex composition according to this embodiment can be suitably used as a raw material for impregnation-molded films.

[0091] (Manufacturing methods of chloroprene polymer latex A and B)

[0092] Next, the manufacturing methods of chloroprene polymer latex A and B will be explained.

[0093] A method for manufacturing chloroprene polymer latex A includes a polymerization step of emulsion polymerization of a monomer composition comprising at least one monomer selected from the group consisting of chloroprene and 2,3-dichloro-1,3-butadiene. The polymerization step may be a step of emulsion polymerization of chloroprene, 2,3-dichloro-1,3-butadiene, and alkyl thiols to obtain the chloroprene polymer latex.

[0094] The method for manufacturing chloroprene polymer latex B includes a polymerization step of emulsion polymerization of a monomer composition comprising chloroprene and 2,3-dichloro-1,3-butadiene. The polymerization step may be a step of emulsion polymerization of chloroprene, 2,3-dichloro-1,3-butadiene, and alkyl thiols to obtain the chloroprene polymer latex.

[0095] As described above, relative to 100% by mass of the total monomer units in the chloroprene polymer, or 100% by mass of the total chloroprene and 2,3-dichloro-1,3-butadiene in the chloroprene polymer of the chloroprene polymer latex B, the copolymerization amount of 2,3-dichloro-1,3-butadiene in the chloroprene polymer can be 3% by mass or more (e.g., 3 to 30% by mass). In this case, relative to 100 parts by mass of the total monomers used to obtain the chloroprene polymer, or 100 parts by mass of the total chloroprene and 2,3-dichloro-1,3-butadiene, the amount of 2,3-dichloro-1,3-butadiene incorporated (added) in the polymerization step (before the start of emulsion polymerization) can be 3 parts by mass or more (e.g., 3 to 30 parts by mass).

[0096] There are no particular limitations on the type of chain transfer agent used in emulsion polymerization. For example, known chain transfer agents commonly used in the emulsion polymerization of chloroprene, such as long-chain alkyl thiols like n-dodecyl mercaptan (1-dodecyl mercaptan) and tert-dodecyl mercaptan, dialkyl disulfide xanthates like diisopropyl disulfide and diethyl disulfide xanthate, and iodoform, can be used.

[0097] In chloroprene polymer latex A, the weight-average molecular weight can be adjusted by the amount of chain transfer agent added (input amount) before the start of emulsion polymerization. For example, relative to 100 parts by mass of chloroprene and 2,3-dichloro-1,3-butadiene, the amount of chain transfer agent (e.g., the amount of thiol-based chain transfer agent (such as n-dodecyl mercaptan)) is preferably 0.50 to 10.0 parts by mass. This makes it easy to adjust the weight-average molecular weight of the toluene-soluble component to 5,000 to 250,000, and the flexibility of the impregnated film obtained using the mixed chloroprene polymer latex composition is easily improved.

[0098] In chloroprene polymer latex B, the amount (addition amount) of the chain transfer agent (e.g., alkyl thiol) before the start of emulsion polymerization is preferably 0.01 to 0.1 parts by mass, more preferably 0.02 to 0.05 parts by mass, relative to 100 parts by mass of chloroprene and 2,3-dichloro-1,3-butadiene. If the amount of chain transfer agent is 0.01 parts by mass or more, the storage stability of the latex is easily improved. If the amount of chain transfer agent is 0.1 parts by mass or less, the toluene-insoluble component increases, and the strength of the impregnated film obtained using the mixed chloroprene polymer latex composition is easily increased.

[0099] From the viewpoint of easily obtaining excellent tensile strength, the emulsifier used in emulsion polymerization is preferably abietic acid, more preferably abietic acid including abietic acid, neoabietic acid, longleaf abietic acid, L-piperidine and their salts. In addition, by using abietic acids, the aggregation of the solid components of the rubber and pH changes can be prevented when blended with the base latex.

[0100] Alternatively, other commonly used emulsifiers, fatty acids, etc., can also be used. Examples of other emulsifiers include metal salts of aromatic sulfonic acid formaldehyde condensates (e.g., sodium salt of β-naphthalenesulfonic acid formaldehyde condensate), sodium dodecylbenzene sulfonate, potassium dodecylbenzene sulfonate, sodium alkyl diphenyl ether sulfonate, potassium alkyl diphenyl ether sulfonate, sodium polyoxyethylene alkyl ether sulfonate, sodium polyoxypropylene alkyl ether sulfonate, potassium polyoxyethylene alkyl ether sulfonate, and potassium polyoxypropylene alkyl ether sulfonate.

[0101] The content of anionic surfactants other than rosin acid is preferably 0.2 to 1.0% by mass relative to 100% by mass of chloroprene polymer contained in the chloroprene polymer latex. Therefore, it is preferable that the amount of anionic surfactants other than rosin acid added before the start of emulsion polymerization is in the range of 0.2 to 0.9 parts by mass relative to 100 parts by mass of the total of chloroprene and 2,3-dichloro-1,3-butadiene.

[0102] The preferred pH of the aqueous emulsion at the start of emulsion polymerization is 10.5–13.5. An aqueous emulsion refers to a mixture of alkyl thiols, chloroprene, 2,3-dichloro-1,3-butadiene, etc., before the start of emulsion polymerization, but it also includes cases where the composition is altered by subsequent addition or batch addition of components. If the pH of the aqueous emulsion at the start of emulsion polymerization is above 10.5, the polymerization reaction can be controlled more stably. If the pH is below 13.5, excessive viscosity increase during polymerization is suppressed, allowing for more stable control of the polymerization reaction.

[0103] The polymerization temperature for emulsion polymerization can be in the range of 5–55°C. If the polymerization temperature is above 5°C, the emulsion is less likely to freeze. If the polymerization temperature is below 55°C, the evaporation and boiling of chloroprene monomer are easily inhibited.

[0104] As polymerization initiators, potassium persulfate, benzoyl peroxide, ammonium persulfate, hydrogen peroxide, etc., which are commonly used in free radical polymerization, can be used.

[0105] The polymerization conversion rate can range from 50% to 95%. The polymerization reaction can be stopped by adding a polymerization inhibitor. If the polymerization conversion rate is above 50%, the toluene-insoluble component increases, resulting in a stronger impregnated film and improved production costs. If the polymerization conversion rate is below 95%, the decrease in polymerization reactivity due to the reduction of unreacted monomers can be avoided, thus preventing a decrease in productivity.

[0106] Examples of polymerization inhibitors include diethylhydroxyamine, thiodiphenylamine, 4-tert-butylcatechol, and 2,2'-methylenebis-4-methyl-6-tert-butylphenol. Unreacted monomers after emulsion polymerization can be removed using conventional methods such as vacuum distillation.

[0107] In addition, freeze stabilizers, emulsion stabilizers, viscosity modifiers, antioxidants, preservatives, etc., can be added arbitrarily to chloroprene polymer latex A and B after polymerization.

[0108] <Immersion Molded Body>

[0109] Next, the dip-molded body according to the second embodiment of the present invention will be described. The dip-molded body according to this embodiment is a dip-molded body using the mixed chloroprene polymer latex composition of the first embodiment described above. For example, it is a molded body obtained by dip-molding the mixed chloroprene polymer latex composition of the first embodiment alone (a molded body obtained by dip-molding the mixed chloroprene polymer latex composition of the first embodiment without mixing with other chloroprene polymer latexes); or, a molded body obtained by dip-molding the mixed chloroprene polymer latex composition of the first embodiment mixed with other chloroprene polymer latexes. That is, the dip-molded body according to this embodiment can be a dip-molded body using the mixed chloroprene polymer latex composition of the first embodiment alone, or a dip-molded body using a mixed latex composition obtained by mixing the mixed chloroprene polymer latex composition of the first embodiment with other chloroprene polymer latexes. The dip-molded body according to this embodiment has a low modulus at 100% elongation and is soft, and has excellent mechanical properties such as strength and elongation. The impregnation molded body involved in this embodiment can be a glove, a balloon, a tube, or a boot.

[0110] As a manufacturing method (molding method) for the impregnated molded body involved in this embodiment, the coagulation liquid impregnation method can be cited as an example, but it is not limited to this, and molding can be carried out according to conventional methods.

[0111] The dip-molded body according to this embodiment may contain at least one selected from the group consisting of a vulcanizing agent and a vulcanization accelerator, or it may contain at least one selected from the group consisting of a vulcanizing agent and a vulcanization accelerator. That is, the dip-molded body according to this embodiment includes the following methods: containing a vulcanizing agent but not a vulcanization accelerator, containing a vulcanizing accelerator but not a vulcanizing agent, containing both a vulcanizing agent and a vulcanization accelerator, and not containing either a vulcanizing agent or a vulcanization accelerator. Whether to include a vulcanizing agent and a vulcanization accelerator depends on the dip-molded body being targeted.

[0112] Examples of vulcanizing agents include sulfur, zinc oxide, and magnesium oxide, but they are not limited to these.

[0113] Vulcanization accelerators are agents added during the vulcanization of raw rubber to increase the vulcanization rate, shorten vulcanization time, lower vulcanization temperature, reduce the amount of vulcanizing agent, and improve the physical properties of vulcanized rubber. Vulcanization accelerators generally refer to agents that promote the sulfur vulcanization reaction.

[0114] Commonly used vulcanizing accelerators in the vulcanization of chloroprene polymer latex include thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based accelerators, but are not limited to these. Vulcanizing accelerators can be used alone or in combination of two or more as needed, but are not limited to these.

[0115] Examples of thiuram-based accelerators include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetra(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, and bispentylthiuram tetrasulfide.

[0116] Examples of dithiocarbamate-based sulfidation accelerators include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, iron dimethyldithiocarbamate, and tellurium diethyldithiocarbamate, with zinc dibutyldithiocarbamate being particularly preferred.

[0117] Examples of thiourea-based sulfidation accelerators include ethyl thiourea, N,N'-diethyl thiourea, trimethyl thiourea, and N,N'-diphenyl thiourea.

[0118] Examples of guanidine-based sulfidation accelerators include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolyldiguanidine, and di-o-tolylguanidine salts of di-o-catechol borate.

[0119] Examples of xanthate-based sulfurization accelerators include zinc butyl xanthate and zinc isopropyl xanthate.

[0120] Examples of thiazole-based sulfidation accelerators include 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and 2-(4'-morpholinodithio)benzothiazole.

[0121] For the dip-molded articles involved in this embodiment, they exhibit excellent mechanical properties regardless of the presence or absence of sulfur and vulcanization accelerators. However, from the viewpoint of reducing allergies and lowering costs, it is preferable to avoid sulfur and vulcanization accelerators.

[0122] Example

[0123] The present invention will now be described in more detail based on embodiments, comparative examples and reference examples, but the present invention is not limited to these embodiments.

[0124] <Example 1>

[0125] (Preparation of Chloroprene Polymer Latex A)

[0126] Add 80 parts by mass of chloroprene monomer, 20 parts by mass of 2,3-dichloro-1,3-butadiene monomer, 3 parts by mass of 1-dodecyl mercaptan, 90 parts by mass of pure water, 4.5 parts by mass of rosin acid X (mass ratio b / a = 0.80), 1.50 parts by mass of potassium hydroxide, and 0.50 parts by mass of sodium salt of β-naphthalenesulfonic acid formaldehyde condensate (trade name "Demol N", manufactured by Kao Corporation) to a polymerization tank with an internal volume of 40 liters. The pH of the aqueous emulsion before polymerization is 12.9. Add 0.1 parts by mass of potassium persulfate as a polymerization initiator, and polymerize at a polymerization temperature of 20°C under a nitrogen stream. At the time point when the polymerization conversion reaches 85%, add 0.01 parts by mass of diethylhydroxylamine as a polymerization inhibitor to stop the polymerization, obtaining a latex.

[0127] The above latex was subjected to vacuum distillation to remove unreacted monomers and water, thereby obtaining chloroprene polymer latex A (thiol-modified chloroprene polymer latex) with a solid content of 55%.

[0128] (Preparation of Chloroprene Polymer Latex B)

[0129] Add 95 parts by mass of chloroprene monomer, 5 parts by mass of 2,3-dichloro-1,3-butadiene monomer, 0.04 parts by mass of 1-dodecyl mercaptan, 90 parts by mass of pure water, 4.3 parts by mass of rosin acid X (mass ratio b / a = 0.80), 1.50 parts by mass of potassium hydroxide, and 0.50 parts by mass of sodium salt of β-naphthalenesulfonic acid formaldehyde condensate (trade name "Demol N", manufactured by Kao Corporation) to a polymerization tank with an internal volume of 40 liters. The pH of the aqueous emulsion before polymerization is 13.2. Add 0.1 parts by mass of potassium persulfate as a polymerization initiator, and polymerize at a polymerization temperature of 15°C under a nitrogen stream. At the time point when the polymerization conversion reaches 70%, add 0.01 parts by mass of diethylhydroxylamine as a polymerization inhibitor to stop the polymerization and obtain a latex.

[0130] The above latex was subjected to vacuum distillation to remove unreacted monomers and water, thereby obtaining chloroprene polymer latex B (thiol-modified chloroprene polymer latex) with a solid content of 55%.

[0131] (Determination of the mass ratio b / a of rosin acid)

[0132] A 1.5% solution of the aforementioned abietic acid X was prepared by dissolving it in an ethanol / toluene azeotropic mixture (ethanol / toluene azeotropic mixture, ETA solution as specified in JIS K 6229), followed by hydrochloric acid treatment and determination using gas chromatography-mass spectrometry. The content was determined by considering the percentage of the total peak area relative to the total peak area detected by gas chromatography-mass spectrometry as the content, calculating the total amount 'a' of dehydroabietic acid, piratic acid, isopiratic acid, dihydroabietic acid and their salts, and the total amount 'b' of abietic acid, neoabietic acid, longleaf abietic acid, levopiratic acid and their salts, and calculating the mass ratio 'b / a' of the total amount 'b' relative to the total amount 'a'.

[0133] Among the conjugated resin acid components, abietic acid (abietic acid and its salts, and the same applies to other resin acid components) was detected at 31.2%, neoabietic acid at 0.8%, longleaf abietic acid at 4.0%, and L-piperidine at 2.7%, with a total area of ​​38.7%. Among the non-conjugated resin acid components, dehydroabietic acid was detected at 35.3%, piratic acid at 7.5%, isopiratic acid at 3.2%, and dihydroabietic acid at 2.4%, with a total area of ​​48.4%. Therefore, the value of "(content of conjugated resin acid component) ÷ (content of non-conjugated resin acid component)" (mass ratio b / a) for rosin acid X is "38.7 ÷ 48.4 = 0.80". The same analysis was performed on abietic acid Y (mass ratio b / a = 1.87) and abietic acid Z (mass ratio b / a = 0; abietic acid, neoabietic acid, longleaf abietic acid, L-piperidine and their salts were not detected), to obtain the mass ratio b / a.

[0134] (Determination of toluene-insoluble components in chloroprene polymer latexes A and B)

[0135] 1 g of chloroprene polymer obtained by freeze-drying the above-mentioned chloroprene polymer latexes A and B was cut into 2 mm square pieces to obtain small flakes. These flakes were then placed in a conical beaker and dissolved in toluene for 16 hours. After centrifugation, the gel component was separated using a 200-mesh metal mesh and dried. The mass of the dried product was determined, and the toluene-insoluble content was calculated. The toluene-insoluble content of chloroprene polymer latex A was 1.1% by mass, and the toluene-insoluble content of chloroprene polymer latex B was 82% by mass.

[0136] (Determination of the weight-average molecular weight of the toluene-soluble component of chloroprene polymer latex A)

[0137] The sol component (sol component) of the chloroprene polymer latex A dissolved in toluene was determined by weight-average molecular weight based on gel permeation chromatography using polystyrene conversion, and the result was 24,000.

[0138] (Determination of the copolymer content of 2,3-dichloro-1,3-butadiene)

[0139] The chloroprene polymer obtained by freeze-drying the above-mentioned chloroprene polymer latexes A and B was cut into 0.05 mg test pieces and analyzed using a pyrolysis gas chromatograph. The 2,3-dichloro-1,3-butadiene copolymer content of the chloroprene polymer latex, as determined by the pyrolysis gas chromatograph, was 21% by mass for chloroprene polymer latex A and 4.6% by mass for chloroprene polymer latex B, relative to 100% by mass of the total chloroprene and 2,3-dichloro-1,3-butadiene in the chloroprene polymer. This analytical value confirms that the 2,3-dichloro-1,3-butadiene copolymer content in the chloroprene polymer is generally correlated with the amount (input) of 2,3-dichloro-1,3-butadiene.

[0140] (Preparation of mixed latex compositions)

[0141] When the total mass of chloroprene polymer latex A and chloroprene polymer latex B is set at 100 parts by mass, the mixture is stirred and mixed at a ratio of 10 parts by mass of chloroprene polymer latex A and 90 parts by mass of chloroprene polymer latex B (solid component ratio) to obtain a mixed latex composition (mixed chloroprene polymer latex composition).

[0142] (Determination of the mass ratio b / a of rosin acid in the mixed latex composition)

[0143] 3g of the dried product (chloroprene polymer) obtained by freeze-drying the above-mentioned mixed latex composition was cut into 2mm squares to obtain small pieces. These small pieces were placed in a flask equipped with a condenser and dissolved in an ethanol / toluene azeotropic mixture (ethanol / toluene azeotropic mixture, ETA solution as specified in JIS K 6229) to prepare a 1.5% solution. The solution was then treated with hydrochloric acid and analyzed using gas chromatography-mass spectrometry (GC-MS). The content was determined by considering the percentage of the total peak area relative to the total peak area detected by GC-MS as the content, calculating the total amount 'a' of dehydroabietic acid, piratic acid, isopiratic acid, dihydroabietic acid and their salts, and the total amount 'b' of abietic acid, neoabietic acid, longleaf abietic acid, L-piperidine and their salts, and calculating the mass ratio 'b / a' of the total amount 'b' relative to the total amount 'a'. The mass ratio 'b / a' was 0.80.

[0144] (Determination of toluene-insoluble components in mixed latex compositions)

[0145] 1 g of chloroprene polymer obtained by freeze-drying the above mixed latex composition was cut into 2 mm square pieces to obtain small flakes. These flakes were then placed in a conical beaker and dissolved in toluene for 16 hours. After centrifugation, the gel component was separated using a 200-mesh metal mesh and dried. The mass of the dried product was determined, and the toluene-insoluble content was calculated. The toluene-insoluble content of the mixed latex composition was 72% by mass.

[0146] (Evaluation sample preparation)

[0147] After mixing 4.1 parts by mass of an aqueous dispersion into 100 parts by mass of the solid component of the above-mentioned mixed latex composition, water was added to adjust the overall solid component concentration of the complex to 30% by mass, thus producing a molding composition free of sulfur and vulcanization accelerator. The above-mentioned aqueous dispersion was prepared as follows: at 20°C, using a ceramic ball mill, 2 parts by mass of zinc oxide (vulcanizing agent, trade name "Zinc Oxide 2 Types", manufactured by Sakai Chemical Industry Co., Ltd.), 2 parts by mass of the butylation reaction product of p-cresol and dicyclopentadiene (trade name "NOCRAC PBK", manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), 0.1 parts by mass of the sodium salt of β-naphthalenesulfonic acid formaldehyde condensate (trade name "Demol N", manufactured by Kao Corporation), and 13 parts by mass of water were mixed for 16 hours.

[0148] A ceramic cylinder (manufactured by Shinko Ind. Ltd.) with an outer diameter of 50 mm was immersed in a coagulation solution containing 62 parts by mass of water, 35 parts by mass of potassium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate for 1 second, and then removed. After drying at room temperature (23°C) for 3 minutes, the cylinder was immersed in the molding composition for 10 seconds. Then, it was washed with running water at 45°C for 1 minute, and then vulcanized at 130°C for 4 hours to produce a vulcanized film (impregnation molding film; vulcanized film without sulfur and vulcanization accelerator) as an evaluation sample. The vulcanized film was peeled off from the outer peripheral surface of the cylinder and evaluated.

[0149] (Evaluation of the evaluation sample)

[0150] For the above-mentioned vulcanized film, the modulus at 100% elongation, the breaking strength and the elongation at break were determined in accordance with JIS K 6251.

[0151] <Examples 2-9, Comparative Examples 1-5 and Reference Examples 1-2>

[0152] The vulcanized films were prepared and evaluated in the same manner as in Example 1, according to the conditions shown in Tables 1 to 3. In Examples 6 to 9 and Comparative Examples 4 to 5, abietic acid Y (mass ratio b / a = 1.87) was used. In Examples 5 to 9 and Comparative Example 3, abietic acid Z (mass ratio b / a = 0; abietic acid, neoabietic acid, longleaf abietic acid, L-piperidine and their salts were not detected).

[0153] <Results>

[0154] The results of Examples 1-9, Comparative Examples 1-5, and Reference Examples 1-2 are shown in Tables 1-3.

[0155] [Table 1]

[0156]

[0157] [Table 2]

[0158]

[0159] [Table 3]

[0160]

[0161] As can be confirmed from Tables 1 to 3, the impregnated molded films (impregnated molded bodies) obtained using the mixed latex compositions of Examples 1 to 9 have very low modulus at 100% elongation (very excellent softness) and excellent mechanical properties (break strength and elongation at break).

[0162] In Comparative Example 1, the weight-average molecular weight of chloroprene polymer latex A is greater than 250,000, and the modulus value at 100% elongation is high, resulting in poor softness.

[0163] In Comparative Example 2, the weight-average molecular weight of chloroprene polymer latex A was less than 5,000. When attempting to make an impregnation molded film, the low molecular weight chloroprene polymer in chloroprene polymer latex A seeped out, becoming so sticky that it could not be made into an impregnation molded film.

[0164] In Comparative Example 3, rosin acid Z (mass ratio b / a = 0) was used as an emulsifier in both chloroprene polymer latex A and B. The mass ratio b / a of the mixed latex composition was 0, resulting in poor tensile strength.

[0165] In Comparative Example 4, 2,3-dichloro-1,3-butadiene was not copolymerized in the chloroprene polymer latex B. As a result, the chloroprene polymer in the impregnated film had higher crystallinity, higher modulus at 100% elongation, and poorer softness.

[0166] In Comparative Example 5, the polymerization conversion rate of chloroprene polymer latex B was low, resulting in less toluene-insoluble component (gel component) and poor tensile strength. Furthermore, the modulus at 100% elongation was higher, indicating poor flexibility.

[0167] In Reference Example 1, an impregnated coating was prepared using only chloroprene polymer latex B without mixing with chloroprene polymer latex A. As a result, although the tensile strength was excellent, the modulus at 100% elongation was high, indicating poor flexibility. This demonstrates that by mixing chloroprene polymer latex A containing a low molecular weight chloroprene polymer, the plasticity provided by the low molecular weight chloroprene polymer can be utilized, resulting in an impregnated coating with excellent flexibility.

[0168] In Reference Example 2, an impregnation molding film was made using only chloroprene polymer latex A without mixing chloroprene polymer latex B. As a result, the low molecular weight chloroprene polymer caused severe stickiness, making it impossible to make an impregnation molding film.

Claims

1. A neoprene polymer latex composition which is a mixture of a neoprene polymer latex A and a neoprene polymer latex B, the neoprene polymer latex A and the neoprene polymer latex B contain a neoprene polymer, the neoprene polymer of the neoprene polymer latex B comprises a copolymer of neoprene and 2,3-dichloro-l,3-butadiene, a copolymerization amount of 2,3-dichloro-l,3-butadiene in the neoprene polymer of the neoprene polymer latex B is 3 mass% or more relative to 100 mass% of a total of neoprene and 2,3-dichloro-l,3-butadiene, a toluene-insoluble component of the neoprene polymer of the neoprene polymer latex B is 70 mass% or more, a weight average molecular weight of a toluene-soluble component in the neoprene polymer latex A is 5,000 to 250,000, a mass ratio b / a of a total amount b of abietic acid, neoabietic acid, palustric acid, levopimaric acid and salts thereof relative to a total amount a of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid and salts thereof is 0.10 or more in a measurement result of gas chromatography mass spectrometry of an extract extracted from a dry substance obtained by freeze-drying the neoprene polymer latex composition using an ethanol / toluene azeotrope which is an ethanol / toluene azeotrope prescribed in JIS K 6229, a toluene-insoluble component of the neoprene polymer of the neoprene polymer latex A is 10 mass% or less.

2. The chlorobutadiene polymer latex composition of claim 1, wherein, a toluene-insoluble component of the neoprene polymer of the neoprene polymer latex B is 70 to 95 mass%.

3. The chlorobutadiene polymer latex composition of claim 1 or 2, wherein, a proportion of the neoprene polymer latex A is 0.5 to 30 mass parts relative to 100 mass parts of a total of the neoprene polymer latex A and the neoprene polymer latex B, a toluene-insoluble component of a neoprene polymer contained in the neoprene polymer latex composition is 50 to 85 mass%.

4. A dip-molded body which uses the neoprene polymer latex composition described in any one of claims 1 to 3.

5. The dip-molded body of claim 4, wherein, It does not contain sulfur and a vulcanization accelerator.

6. The dip-molded body described in claim 5 is a glove, a balloon, a catheter or a boot.

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