Chloroprene-based polymer latex composition and its dip molded article

Abstract

The present invention provides a chloroprene-based polymer latex composition by which can be obtained, through the use of a hetero-aromatic ring-based compound and the plasticizing effect of a low molecular weight polymer, a chloroprene-based polymer dip-molded article having high rupture strength while maintaining excellent flexibility even with a reduction in a vulcanization accelerator and sulfur, and having a low residue amount of mercaptans for which concerns remain regarding hygienic properties. The chloroprene-based polymer latex composition according to the present invention comprises a chloroprene-based polymer latex, a metal oxide, and a hetero-aromatic ring-based compound. The chloroprene-based polymer latex composition comprises 0.5-15.0 parts by mass of the metal oxide and 0.1-10.0 parts by mass of the hetero-aromatic ring-based compound per 100 parts by mass of solid content of the chloroprene-based polymer latex. The chloroprene-based polymer latex composition has a content of alkyl mercaptan compounds of 0.34 parts by mass or less per 100 parts by mass of solid content of the chloroprene-based polymer latex, and the hetero-aromatic ring-based compound is represented by chemical formula (1).

Description

Technical Field

[0001] The present invention relates to a chloroprene-based polymer latex composition and an immersion molded article thereof. More specifically, it relates to a chloroprene-based polymer latex composition containing chloroprene and an immersion molded article obtained using the composition.

Background Art

[0002] Chloroprene-based polymers are known as materials for immersion 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-based polymers and chloroprene-based polymers for immersion molded products have been proposed. Patent Document 1 describes that for anti-vibration rubber applications, the damping performance is improved by mixing a low molecular weight chloroprene polymer in the range of number average molecular weight of 500 to 50,000. Patent Document 2 describes a poly(chloroprene) latex having a pH of 7 to 14, containing 100 parts by mass of a modified poly(chloroprene) 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 immersion molded product applications. Patent Document 3 describes a mercaptan-modified poly(chloroprene) latex for immersion molded product applications, in which chloroprene and 2,3-dichloro-1,3-butadiene are copolymerized, and in the 13C-solid NMR spectrum of the poly(chloroprene), the peak areas (A) of 126.2 to 127.6 ppm, (B) of 122.0 to 126.2 ppm, and (C) of 129.9 to 130.3 ppm are in the range shown by the following general formula (I). Patent Document 4 describes a chloroprene polymer latex for immersion molded product applications, which contains a high molecular weight component and a low molecular weight component, and can achieve both excellent flexibility and mechanical properties in a vulcanized rubber produced by immersion molding.

[0004]

Numbers

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the case of a chloroprene-based polymer dip-formed article, there is a tendency that high flexibility is required in the same manner as in a dip-formed article obtained using natural rubber or polyisoprene, and a chloroprene-based polymer latex composition having improved physical properties related to flexibility directly related to the wearing feeling and the texture of the coating is desired. In addition, vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based, which are preferable for improving mechanical strength, fall under the category of type IV allergy-causing substances. From the viewpoint of hygiene, even if the usage amount of these compounds is reduced, and further, a chloroprene-based polymer latex composition and its dip-formed article that exhibit excellent mechanical properties without using these compounds are desired. Further, from the viewpoints of hygiene and suppressing odor, it is desirable that the residual amount of mercaptans used as a chain transfer agent for polymerization is low.

[0007] Therefore, the main object of the present invention is to provide a chloroprene-based polymer latex composition capable of obtaining a chloroprene-based polymer dip-formed article having a low residual amount of mercaptans that remains a concern for hygiene, and having very excellent flexibility and high breaking strength even when the addition amount of a vulcanization accelerator or sulfur is reduced or not used.

Means for Solving the Problems

[0008] That is, the present invention is a chloroprene-based polymer latex composition containing a chloroprene-based polymer latex, a metal oxide, and a heteroaromatic ring compound, wherein the chloroprene-based polymer latex composition contains 0.5 to 15.0 parts by mass of the metal oxide and 0.1 to 10.0 parts by mass of the heteroaromatic ring compound with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex, and the content of alkyl mercaptans compound with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex in the chloroprene-based polymer latex composition is 0.34 parts by mass or less, and the heteroaromatic ring compound is represented by Chemical Formula (1), which is a chloroprene-based polymer latex composition.

[0009]

Chemical formula

[0010] Hereinafter, various embodiments of the present invention will be exemplified. The embodiments shown below can be combined with each other. [1] A chloroprene-based polymer latex composition containing a chloroprene-based polymer latex, a metal oxide, and a heteroaromatic ring compound, wherein the chloroprene-based polymer latex composition contains 0.5 to 15.0 parts by mass of the metal oxide and 0.1 to 10.0 parts by mass of the heteroaromatic ring compound with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex, and the content of an alkyl mercaptans compound with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex in the chloroprene-based polymer latex composition is 0.34 parts by mass or less, and the heteroaromatic ring compound is represented by Chemical Formula (1), a chloroprene-based polymer latex composition.

[0011] [Chemical Formula] (In Chemical Formula (1), X represents a hydrogen atom or a metal atom. Also, R1 to R4 each represent a hydrogen atom, an alkyl group which may have a substituent, an ether group which may have a substituent, a nitro group, an amino group, or a carboxyl group. R1 to R4 may each be the same or different.) [2] The chloroprene-based polymer latex composition according to [1], which contains 0.5 to 10.0 parts by mass of an antioxidant with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex. [3] The chloroprene-based polymer latex contains at least one of a homopolymer of chloroprene and a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene, and in the molecular weight distribution obtained by gel permeation chromatography measurement of the sol fraction soluble in tetrahydrofuran in the chloroprene-based polymer latex, it has a first peak with a weight average molecular weight of 500,000 or more and a second peak with a weight average molecular weight of 7,000 to 80,000, the chloroprene-based polymer latex composition according to [1] or [2]. [4] The chloroprene-based polymer latex composition according to any one of [1] to [3], wherein the toluene-insoluble content of the chloroprene-based polymer rubber obtained by freeze-drying the chloroprene-based polymer latex is 50 to 85% by mass. [5] The chloroprene-based polymer latex is freeze-dried to obtain a chloroprene-based polymer rubber, which is cut and placed in a flask attached to a condenser, extracted with an ethanol / toluene azeotropic mixture defined in JIS K6229, and in the components measured by gas chromatography of the extract, the mass ratio b / a of the total amount b of abietic acid, neoabietic acid, parastric acid, levopimaric acid and their salts to the total amount a of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid and their salts is 0.10 or more. The chloroprene-based polymer latex composition according to any one of [1] to [4]. [6] A vulcanization accelerator of thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based, and a chloroprene-based polymer latex composition according to any one of [1] to [5] that does not contain sulfur. [7] An immersion molded article obtained by using the chloroprene-based polymer latex composition according to any one of [1] to [6]. [8] An immersion molded article according to [7], which is an industrial / general household glove, a medical glove, a balloon, a catheter or a boot. Preferably, it is an industrial / general household glove, a medical glove, a balloon, a catheter or a boot.

[0012] In the present invention, "JIS" means Japanese Industrial Standards.

Advantages of the Invention

[0013] According to the present invention, the content of alkyl mercaptan compounds in the chloroprene-based polymer latex composition is below a specific amount, and by blending a specific amount of a heteroaromatic ring compound and a metal compound into the chloroprene-based polymer latex composition, the content of alkyl mercaptan compounds, which raises concerns about hygiene, is low, and an immersion molded article of a chloroprene-based polymer having very excellent flexibility and high breaking strength can be obtained even when the addition amount of a vulcanization accelerator or sulfur is reduced or not used. A chloroprene-based polymer latex composition is provided.

Embodiments for Carrying out the Invention

[0014] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

[0015] 1. Chloroprene-based polymer latex composition First, the chloroprene-based polymer latex composition according to the first embodiment of the present invention will be described.

[0016] 1.1 Chloroprene-based polymer The chloroprene-based polymer described in this embodiment is a polymer containing monomer units derived from 2-chloro-1,3-butadiene (hereinafter also referred to as chloroprene). Further, the chloroprene-based polymer according to an embodiment of the present invention can also be a copolymer of chloroprene and other monomers copolymerizable with chloroprene. Examples of other monomers include 1-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, isoprene, styrene, methacrylic acid, acrylonitrile, sulfur, etc. As other monomers, two or more of these may be used in combination. The chloroprene-based polymer according to an embodiment of the present invention can also be free of sulfur, and the chloroprene-based polymer according to an embodiment of the present invention can also be free of an -S-S- structure caused by sulfur in the main chain.

[0017] The chloroprene-based polymer according to an 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.

[0018] The chloroprene-based polymer according to an embodiment of the present invention can contain 50 to 100% by mass of monomer units derived from chloroprene, preferably 90 to 100% by mass, 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 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 herein.

[0019] The chloroprene-based polymer according to an 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 herein.

[0020] The chloroprene-based polymer according to an embodiment of the present invention may also 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, more preferably 5 to 25% by mass.

[0021] In addition, 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.

[0022] When the chloroprene-based polymer according to an 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 also be within the range between any two of the numerical values exemplified here. The chloroprene-based polymer according to an embodiment of the present invention may also not contain a sulfur-modified chloroprene-based polymer.

[0023] 1.2 Chloroprene-based polymer latex The chloroprene-based polymer latex according to one embodiment of the present invention can be one in which a chloroprene-based polymer is dispersed in water, and at least one selected from the group consisting of a homopolymer of chloroprene, 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 is dispersed in water, and it may be one in which a homopolymer of chloroprene or a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene is dispersed in water.

[0024] 1.2.1 Alkyl mercaptan compounds contained in the chloroprene-based polymer latex composition In the chloroprene-based polymer latex composition according to the present invention, the content of the alkyl mercaptan compound is 0.34 parts by mass or less with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex. The content of the alkyl mercaptan compound is, for example, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 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 parts by mass, and it may be within the range between any two of the numerical values exemplified here.

[0025] The content of the alkyl mercaptan compound in the chloroprene-based polymer latex composition can be measured using gas chromatography. The analysis target can be the chloroprene-based polymer latex or composition. At this time, when the solid content concentration of the chloroprene-based polymer latex or composition is high and hinders component measurement, dilution with a solvent such as THF or the standard addition method may be applied. The measurement conditions of gas chromatography can be as shown in the examples.

[0026] The alkyl mercaptan compounds are not particularly limited, and examples thereof include long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan. By setting the content of the alkyl mercaptan compounds to 0.34 parts by mass or less, the odor of the obtained dip-molded article can be suppressed and the hygiene can be improved.

[0027] The alkyl mercaptan compounds are usually used as a chain transfer agent to obtain a chloroprene-based polymer contained in the chloroprene-based polymer latex composition. The content of the alkyl mercaptan compounds contained in the chloroprene-based polymer latex composition can be controlled by adjusting the charged amount as a chain transfer agent and the polymerization conversion rate in the polymerization step for obtaining the chloroprene-based polymer and the chloroprene-based polymer latex. Further, if necessary, the charged amount of the chain transfer agent and the like can also be adjusted by adding monomers typified by chloroprene monomer and 2,3-dichloro-1,3-butadiene in portions during the polymerization reaction.

[0028] 1.2.2 Weight-average molecular weight of chloroprene-based polymer latex The chloroprene-based polymer latex according to an embodiment of the present invention can have a first peak in the molecular weight distribution obtained by gel permeation chromatography measurement, in which the sol fraction soluble in tetrahydrofuran in the chloroprene-based polymer latex has a weight-average molecular weight of 400,000 or more. The first peak preferably has a weight-average molecular weight of 500,000 or more.

[0029] When the weight-average molecular weight of the first peak in the above molecular weight distribution is at least the above lower limit, the resulting dip-formed article can obtain more excellent breaking strength. From the viewpoint of easily obtaining excellent breaking strength, the weight-average molecular weight of the first peak in the above molecular weight distribution can be 500,000 or more, or can be 600,000 or more. The weight-average molecular weight of the first peak can be, for example, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,000,000, and can also be within the range between any two of the numerical values exemplified herein.

[0030] The chloroprene-based polymer latex according to one embodiment of the present invention can have a second peak in the above molecular weight distribution with a weight-average molecular weight of 7,000 to 120,000, and the second peak preferably has a weight-average molecular weight of 7,000 to 80,000.

[0031] When the weight-average molecular weight of the second peak in the above molecular weight distribution is at least the above lower limit, more excellent breaking strength can be obtained. From the viewpoint of more easily obtaining a better dip-formed article, the weight-average molecular weight of the second peak can be 10,000 or more, or can be 15,000 or more.

[0032] When the weight-average molecular weight of the second peak in the above molecular weight distribution is at most the above upper limit, more excellent flexibility can be obtained. From the viewpoint of more easily obtaining even more excellent flexibility, the weight-average molecular weight of the second peak of the chloroprene-based polymer can be 80,000 or less, 70,000 or less, 50,000 or less, or 30,000 or less.

[0033] The weight-average molecular weight of the second peak is, for example, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, 21,000, 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, 80,000, 100,000, 120,000, and may be within the range between any two of the values exemplified herein.

[0034] The chloroprene-based polymer latex according to one embodiment of the present invention preferably has a first peak and a second peak in the above molecular weight distribution.

[0035] According to the chloroprene-based polymer latex according to one embodiment of the present invention, by having the above molecular weight distribution, an immersion molded article having further excellent flexibility and breaking strength can be obtained.

[0036] The molecular weight distribution of the sol fraction soluble in tetrahydrofuran in the chloroprene-based polymer latex can be obtained by measuring the weight-average molecular weight by gel permeation chromatography. The chloroprene-based polymer latex is dissolved in tetrahydrofuran, and the eluate (sol fraction) is analyzed by gel permeation chromatography (GPC). The measurement conditions of GPC can be as described in the examples. In addition, by using the chloroprene-based polymer latex composition as the analysis target, dissolving the chloroprene-based polymer latex composition in tetrahydrofuran, and performing analysis in the same manner, the molecular weight distribution of the sol fraction soluble in tetrahydrofuran in the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition can also be determined.

[0037] By mixing two or more types of chloroprene polymer latexes with different weight average molecular weights, a chloroprene polymer latex in which a first peak and a second peak are detected in the molecular weight distribution may be obtained. When mixing two or more types of chloroprene polymer latexes, the weight average molecular weight of each chloroprene polymer latex can be controlled by adjusting the formulation such as the type and amount of the chain transfer agent, the polymerization temperature, the polymerization time, the polymerization conversion rate, etc. in the polymerization of each chloroprene polymer latex. When using two or more types of chloroprene polymer latexes, a chloroprene polymer latex may be obtained by stirring and mixing two or more types of chloroprene polymer latexes at 100 rpm for 1 minute using paddle blades.

[0038] 1.2.3 Toluene-insoluble matter of chloroprene polymer latex The toluene-insoluble matter (gel content) of the chloroprene polymer latex according to one embodiment of the present invention can be 50 to 85% by mass, more preferably 60 to 85% by mass, based on 100% by mass of the chloroprene polymer. The toluene-insoluble matter is, for example, 50, 55, 60, 65, 70, 75, 80, 85% by mass, and may be within the range between any two of the values exemplified here. By setting the toluene-insoluble matter within the above numerical range, more excellent breaking strength is exhibited. This numerical range can be adjusted by preparing two or more types of chloroprene polymer latexes with different toluene-insoluble matters and adjusting the mixing ratio thereof.

[0039] The "toluene-insoluble matter" is obtained by cutting 1 g of the chloroprene polymer rubber obtained by freeze-drying the chloroprene polymer latex into 2 mm squares, dissolving it in toluene for 16 hours, separating the insoluble matter using a 200-mesh wire mesh after centrifugation, and measuring the weight of the dried insoluble matter. The toluene-insoluble matter can be obtained from the following calculation formula. (Mass of solid obtained by separating and drying gel content) / (Mass of solid obtained by freeze-drying latex containing chloroprene polymer)×100 Incidentally, by using the chloroprene-based polymer latex composition as the analysis target and performing analysis on the dried product obtained by freezing the chloroprene-based polymer latex composition in the same manner, it is also possible to determine the toluene-insoluble content in the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition.

[0040] 1.2.4 Amount of resin acid component (mass ratio b / a) contained in chloroprene-based polymer latex The chloroprene-based polymer latex according to an embodiment of the present invention is obtained by cutting the chloroprene-based polymer rubber obtained by freeze-drying the chloroprene-based polymer latex, placing it in a flask attached to a condenser, extracting it with an ethanol / toluene azeotropic mixture defined in JIS K 6229, and measuring the extract by gas chromatography. The mass ratio b / a of the total amount b of abietic acid, neoabietic acid, palustric acid, levopimaric acid and their salts to the total amount a of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid and their salts in the measured components is preferably 0.10 or more. The above b / a is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, and may be within the range between any two of the values exemplified here. If the mass ratio b / a is 0.10 or more, a higher breaking strength is exhibited. More preferably, when the mass ratio b / a is in the range of 0.3 to 1.2, an immersion molded article having a high breaking strength and more excellent flexibility can be obtained.

[0041] In the calculation of the mass ratio b / a, after cutting the chloroprene-based polymer rubber, which is a dried product obtained by freeze-drying the chloroprene-based polymer latex, it is placed in a flask attached to a condenser, extracted with an ethanol / toluene azeotropic mixture defined in JIS K 6229, treated with hydrochloric acid, and then gas chromatograph mass spectrometry can be performed. The measurement conditions for gas chromatograph mass spectrometry can be as described in the examples. The value obtained by dividing the peak area value of the peak corresponding to each resin acid component by the total peak area value detected by gas chromatograph mass spectrometry can be regarded as the content. Also, from the peak areas of each resin acid, the total amount a, the total amount b, and the mass ratio b / a can be determined. Note that, by using the chloroprene-based polymer latex composition as the analysis target and performing analysis on the dried product obtained by freezing the chloroprene-based polymer latex composition in the same manner, the mass ratio b / a in the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition can also be determined.

[0042] The value of the mass ratio b / a can be controlled by adjusting the types of rosin acid and rosin acid salts added as emulsifiers and their blending ratios.

[0043] 1.2.5 Manufacturing method of chloroprene-based polymer latex Next, the manufacturing method of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition of the present invention will be described.

[0044] The manufacturing method of the chloroprene-based polymer latex according to an embodiment of the present invention can include a polymerization step of polymerizing a monomer containing chloroprene to obtain a chloroprene-based polymer latex. Also, the manufacturing method of the chloroprene-based polymer latex according to an embodiment of the present invention can further include a mixing step of mixing two or more types of chloroprene-based polymer latexes having different weight average molecular weights.

[0045] In the polymerization process, the monomer includes chloroprene and may also include 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, sulfur, etc. The monomer can also be one that includes chloroprene and 2,3-dichloro-1,3-butadiene.

[0046] The type and charged amount of each monomer are preferably adjusted so that each monomer in the resulting polymer falls within the above-described numerical ranges. As an example, the copolymerization amount of 2,3-dichloro-1,3-butadiene in the chloroprene-based polymer latex can also be in the range of 0 to 30% by mass based on the total 100% by mass of the chloroprene monomer and 2,3-dichloro-1,3-butadiene contained in the chloroprene-based polymer. In this case, the charged amount of 2,3-dichloro-1,3-butadiene before the start of emulsion polymerization is preferably in the range of 0 to 30 parts by mass based on the total 100 parts by mass of the chloroprene monomer and 2,3-dichloro-1,3-butadiene monomers. From the perspective of polymerization control, it is more preferable that the charged amount of 2,3-dichloro-1,3-butadiene is 5 to 25 parts by mass based on the total 100 parts by mass of the chloroprene monomer and 2,3-dichloro-1,3-butadiene monomers.

[0047] When producing a chloroprene-based polymer, the raw material monomers are polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, etc. Among these polymerization methods, emulsion polymerization, which has various advantages such as being easy to control, easy to remove the polymer from the polymerization end solution, and having a relatively high polymerization rate, is preferred.

[0048] Emulsion polymerization is a type of radical polymerization, and it is a method in which the raw material monomers are charged into a reaction vessel together with a chain transfer agent, water, an alkali (e.g., metal hydroxides such as potassium hydroxide and sodium hydroxide), an emulsifier (dispersant), a reducing agent (e.g., sodium bisulfite), a polymerization initiator, etc. and polymerized.

[0049] The type of chain transfer agent used in emulsion polymerization is not particularly limited, and for example, long-chain alkyl mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, dialkyl xanthogen disulfides such as diisopropyl xanthogen disulfide and diethyl xanthogen disulfide, and known chain transfer agents generally used in the emulsion polymerization of chloroprene such as iodoform can be used. As the chain transfer agent, long-chain alkyl mercaptans are preferred, and n-dodecyl mercaptan is more preferred.

[0050] By adjusting the type and amount of the chain transfer agent, the weight-average molecular weight of the obtained chloroprene-based polymer latex can be adjusted.

[0051] As an example, in the molecular weight distribution, in order to obtain a chloroprene-based polymer latex in which a first peak showing a weight-average molecular weight of 500,000 or more is detected, the charged amount of the chain transfer agent before the start of emulsion polymerization is preferably 0.01 part by mass or more with respect to 100 parts by mass of the monomer (for example, a total of 100 parts by mass of chloroprene and 2,3-dichloro-1,3-butadiene). From the viewpoint of obtaining a chloroprene-based polymer latex in which a first peak showing a weight-average molecular weight of 500,000 or more is detected, the charged amount of the chain transfer agent is more preferably 0.02 to 0.05 part by mass, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 part by mass, less than 0.10 part by mass, and may be within the range between any two of the numerical values exemplified here. When the charged amount of the chain transfer agent, particularly long-chain alkyl mercaptans, is 0.01 part by mass or more, the storage stability of the latex is further improved, and when the charged amount is less than 0.10 part by mass, particularly less than 0.05 part by mass, the toluene-insoluble content increases, and the breaking strength of the dip-molded article containing the obtained chloroprene-based polymer latex becomes higher.

[0052] In addition, in order to obtain a chloroprene-based polymer latex in which a second peak showing a weight average molecular weight of 7,000 to 80,000 is detected in the molecular weight distribution, it is preferable that the charged amount of the chain transfer agent before the start of emulsion polymerization be 1.0 to 10.0 parts by mass with respect to 100 parts by mass of the monomer. In this case, the charged amount is, for example, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 parts by mass, and it may also be within the range between any two of the numerical values exemplified here.

[0053] Examples of the emulsifier include anionic emulsifiers and nonionic emulsifiers. Examples of the anionic emulsifier include fatty acid salts such as potassium tallowate, partially hydrogenated potassium tallowate, potassium oleate, and sodium oleate; resin acid 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 condensates. Examples of the nonionic emulsifier include polyethylene glycol ester type emulsifiers and polyvinyl alcohol. Among these, anionic emulsifiers are preferable, resin acid salts are preferable, rosin acids which are rosin acid and rosin acid salts are preferable, and at least one selected from the group consisting of potassium rosinate and sodium rosinate is more preferable. These emulsifiers can be used alone or in combination of two or more. The amount of the emulsifier used is preferably 1.0 to 6.5 parts by mass with respect to 100 parts by mass of the monomer.

[0054] In particular, the emulsifier used in emulsion polymerization is preferably a resin acid salt, especially rosin acids. It is preferable to use rosin acids containing components having a conjugated double bond structure such as abietic acid, neoabietic acid, palustric acid, and levopimaric acid in rosin acid, as well as metal salts thereof. By using these rosin acids containing these resin acids, the breaking strength can be further improved. Also, for rosin acids, it is preferable to select the type and adjust the blending amount so that the mass ratio b / a of the total amount b of abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts to the total amount a of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and their salts contained in the chloroprene-based polymer latex is 0.10 or more. Also, by using rosin acids, aggregation of rubber solids and pH fluctuations can be prevented when blended with the base latex.

[0055] In addition, other commonly used emulsifiers and fatty acids can also be used in combination. Examples of other emulsifiers include metal salts of aromatic sulfinic acid formalin condensates, sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, 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, potassium polyoxypropylene alkyl ether ether sulfonate, and the like.

[0056] The content of the anionic surfactant excluding rosin acid is preferably 0.2 to 1.0% by mass based on 100% by mass of the chloroprene-based polymer contained in the chloroprene-based polymer latex. Therefore, it is preferable to set the charged amount of the anionic surfactant excluding rosin acid before the start of emulsion polymerization within the range of 0.2 to 0.9 parts by mass based on 100 parts by mass of the monomer (for example, the total of chloroprene and 2,3-dichloro-1,3-butadiene).

[0057] 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 mixed solution of a chain transfer agent and monomers (such as chloroprene, 2,3-dichloro-1,3-butadiene, etc.) immediately before the start of emulsion polymerization. However, cases where the composition changes due to post-addition or split addition of each component are also included. When 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. When the pH is 13.5 or lower, excessive viscosity increase during polymerization is suppressed, and the polymerization reaction can be controlled more stably.

[0058] The polymerization temperature of emulsion polymerization is preferably in the range of 5 to 55 °C. When it is 5 °C or higher, the emulsion does not freeze, and when it is 55 °C or lower, it is preferable in terms of no evaporation or boiling of the chloroprene monomer.

[0059] As the polymerization initiator, potassium persulfate, benzoyl peroxide, ammonium persulfate, hydrogen peroxide, etc., which are used in ordinary radical polymerization, can be used.

[0060] The polymerization conversion rate is preferably in the range of 50 to 95%. The polymerization reaction is stopped by adding a polymerization terminator. When the polymerization conversion rate is 50% or higher, the toluene-insoluble content tends to increase, and the strength of the resulting dip-coated film tends to be high. It is also advantageous from the perspective of production cost. If the polymerization conversion rate is less than 95%, a decrease in polymerization reactivity due to a decrease in unreacted monomers can be avoided, and a decrease in productivity can be avoided.

[0061] Examples of the polymerization terminator include diethylhydroxyamine, thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis-4-methyl-6-tert-butylphenol, etc. The unreacted monomers after the completion of emulsion polymerization can be removed by methods such as conventional vacuum distillation.

[0062] In addition, to the chloroprene-based polymer latex obtained by the production method of an embodiment of the present invention, a freezing stabilizer, an emulsion stabilizer, a viscosity modifier, an antioxidant, a preservative, etc. can be optionally added within a range that does not inhibit the effects of the present invention after polymerization.

[0063] The production method of the chloroprene-based polymer latex according to an embodiment of the present invention can further include a mixing step of mixing two or more types of chloroprene-based polymer latexes having different weight average molecular weights after the above polymerization step. In the mixing step, two or more types of chloroprene-based polymer latexes can be mixed by a known method. In the mixing step, for example, a chloroprene-based polymer latex may be obtained by stirring and mixing at 30 to 300 rpm for 20 seconds to 3 minutes, for example, at 100 rpm for 1 minute using paddle blades.

[0064] 1.3 Metal Oxides The chloroprene-based polymer latex composition according to the present invention contains a metal oxide. The metal oxide contained in the chloroprene-based polymer latex composition is not particularly limited, and examples include zinc oxide, lead oxide, red lead, magnesium oxide, aluminum oxide, iron oxide, beryllium oxide, titanium oxide, etc. The metal oxide preferably contains zinc oxide. Zinc oxide is generally considered to function as a scavenger for dechlorine atoms in chloroprene-based polymers. These metal oxides may be used alone or in combination of two or more.

[0065] The addition amount of the metal oxide is preferably 0.5 to 15.0 parts by mass with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition. When the addition amount of the metal oxide is 0.5 parts by mass or more, an improvement in breaking strength is expected due to the cross-linking effect between polymers. When the addition amount of the metal oxide is 15.0 parts by mass or less, an immersion molded article excellent in flexibility can be obtained. Further, from the viewpoint of the physical property balance between the flexibility and the breaking strength of the obtained immersion molded article, the addition amount of the metal oxide is more preferably 0.5 to 5.0 parts by mass.

[0066] 1.4 Heteroaromatic Ring Compounds The chloroprene polymer latex composition according to the present invention contains a heteroaromatic ring compound. The heteroaromatic ring compound contained in the chloroprene polymer latex composition can be represented by Chemical Formula (1) and has a benzimidazole structure. Note that a compound having this structure may mainly be employed as a secondary anti-aging agent in the formulation of a rubber composition.

[0067]

Chemical Formula

[0068] In Chemical Formula (1), X of the mercapto group represents a hydrogen atom or a metal atom. X can be a hydrogen atom to have a thiol group. Also, X can be a metal atom, and examples of the metal atom include zinc, sodium, copper, nickel, and tellurium, among which zinc is preferable. R1 to R4 in Chemical Formula (1) each represent a hydrogen atom, an alkyl group which may have a substituent, an ether group which may have a substituent, a nitro group, an amino group, or or a carboxyl group. R1 to R4 may each be the same or different. Also, the heteroaromatic ring compound may be used alone or in combination of two or more.

[0069] Examples of the 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, 2-mercaptobenzimidazole, 5-methyl-2-mercaptobenzimidazole, 4-methyl-2-mercaptobenzimidazole, 5-methoxy-2-mercaptobenzimidazole, 4-methoxy-2-mercaptobenzimidazole, and zinc salts of 2-mercaptobenzimidazole are preferred.

[0070] The addition amount of the heteroaromatic ring compound is preferably 0.2 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition. The addition amount of the heteroaromatic ring compound 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, 10.0 parts by mass, and may be within the range between any two of the values exemplified herein. When the addition amount is 0.2 parts by mass or more, the dipping molded article obtained using this composition exhibits very high breaking strength. When the addition amount is 10.0 parts by mass or less, the stability of the chloroprene-based polymer latex composition is ensured. Further, from the viewpoint of the physical property balance between the flexibility and the breaking strength of the obtained dipping molded article, the addition amount is more preferably 0.3 to 5.0 parts by mass.

[0071] 1.5 Antioxidant The chloroprene-based polymer latex composition according to the present invention may also contain an antioxidant. The antioxidant is not particularly limited, and phenolic antioxidants, amine antioxidants, heat-resistant oxidation (aging) inhibitors, ozone-resistant antioxidants, etc. can be used. When the obtained dip-molded article is used for medical gloves, a phenolic antioxidant can be employed from the viewpoints of the color tone, texture, and hygiene of the dip-molded article. In particular, hindered phenolic antioxidants have strong effects as described above. 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), the butylated reaction product of p-cresol and dicyclopentadiene, 2,5'-di-t-butylhydroquinone, and 2,5'-di-t-amylhydroquinone. Among these, from the viewpoint of being generally dispersible in aqueous materials, the butylated reaction product of p-cresol and dicyclopentadiene is desirable. Also, these compounds may be used alone or in combination of two or more.

[0072] The addition amount of the antioxidant is preferably 0.5 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition. The addition amount of the antioxidant is, for example, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 parts by mass, and may be within the range between any two of the values exemplified herein. When the addition amount of the antioxidant is 0.5 parts by mass or more, the effect of suppressing the color tone change of the dip-molded article can be obtained. When the addition amount of the antioxidant is 10.0 parts by mass or less, the stability of the chloroprene-based polymer latex composition is ensured. Also, from the viewpoint of the physical property balance with the flexibility and breaking strength of the obtained dip-molded article, the addition amount of the antioxidant is more preferably 0.5 to 5.0 parts by mass.

[0073] 1.6 Vulcanizing Agent and Vulcanization Accelerator The chloroprene-based polymer latex composition according to an embodiment of the present invention may also contain a vulcanizing agent and / or a vulcanization accelerator. Further, the chloroprene-based polymer latex composition according to an embodiment of the present invention may not contain sulfur and the above-mentioned vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, thiazole-based, etc. That is, the molded article of the chloroprene-based polymer latex composition includes those containing a vulcanizing agent and not containing a vulcanization accelerator, those not containing a vulcanizing agent and containing a vulcanization accelerator, those containing a vulcanizing agent and a vulcanization accelerator, and those not containing a vulcanizing agent and a vulcanization accelerator. Whether to blend a vulcanizing agent and a vulcanization accelerator may be determined according to the target dipped molded article.

[0074] Examples of the vulcanizing agent include, but are not limited to, sulfur, zinc oxide, magnesium oxide, etc. The addition amount of the vulcanizing agent can be 0 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition. The addition amount of the vulcanizing agent is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 parts by mass, and may be within the range between any two of the values exemplified here.

[0075] A vulcanization accelerator is a chemical added for the purpose of increasing the vulcanization rate by acting with a vulcanizing agent during the vulcanization of raw rubber, shortening the vulcanization time, lowering the vulcanization temperature, reducing the amount of the vulcanizing agent, and improving the physical properties of the vulcanized rubber, and usually refers to a chemical that promotes the sulfur vulcanization reaction.

[0076] Examples of the vulcanization accelerators generally used for the vulcanization of chloroprene-based polymer latex include, but are not limited to, thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, thiazole-based, etc. These are used alone or in combination of two or more as necessary.

[0077] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram tetrasulfide, and the like.

[0078] Examples of dithiocarbamate vulcanization accelerators include sodium dibutyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, tellurium diethyldithiocarbamate, and the like. Among them, zinc dibutyldithiocarbamate is particularly preferably used.

[0079] Examples of thiourea vulcanization accelerators include ethylene thiourea, N,N'-diethylthiourea, trimethylthiourea, N,N'-diphenylthiourea, and the like.

[0080] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, the di-o-tolylguanidine salt of dicatechol borate, and the like.

[0081] Examples of xanthate vulcanization accelerators include zinc butylxanthate, zinc isopropylxanthate, and the like.

[0082] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, zinc 2-mercaptobenzothiazole, the cyclohexylamine salt of 2-mercaptobenzothiazole, 2-(4'-morpholinodithio)benzothiazole, and the like.

[0083] The addition amount of the vulcanization accelerator can be 0 to 5.0 parts by mass with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition. The addition amount of the vulcanization accelerator is, for example, 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and may be within the range between any two of the exemplified values.

[0084] The molded article of the chloroprene-based polymer latex composition according to one embodiment of the present invention exhibits excellent mechanical properties regardless of the presence or absence of the addition of a vulcanizing agent and a vulcanization accelerator. From the viewpoints of reducing the allergy risk and cost reduction, in the chloroprene-based polymer latex composition according to one embodiment of the present invention, the content of the vulcanizing agent is 1 part by mass or less and the content of the vulcanization accelerator is 0.5 part by mass or less with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex contained in the chloroprene-based polymer latex composition. Further, the chloroprene-based polymer latex composition according to one embodiment of the present invention can also be one that does not contain a vulcanizing agent and a vulcanization accelerator, and can be one that does not contain sulfur and vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, thiazole-based ones.

[0085] 1.6 Properties of Chloroprene-Based Polymer Latex Composition The chloroprene-based polymer latex composition according to one embodiment of the present invention preferably has a breaking strength of 17 MPa or more, more preferably 20 MPa or more, as measured based on JIS K6251 of the immersed molded article after heating obtained by heating the immersed molded article containing the chloroprene-based polymer latex composition at 130 ° C for 4 hours. The breaking strength is, for example, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 MPa, and may be within the range between any two of the exemplified values.

[0086] In one embodiment of the present invention, the chloroprene-based polymer latex composition preferably has an elongation at break of 1000% or more as measured based on JIS K6251 of the immersed molded article obtained by heating the immersed molded article containing the chloroprene-based polymer latex composition at 130°C for 4 hours. The elongation at break is, for example, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400%, and may be within the range between any two of the values exemplified herein.

[0087] In one embodiment of the present invention, the chloroprene-based polymer latex composition preferably has a modulus at 100% elongation of 0.75 MPa or more, more preferably 0.70 MPa or less, as measured based on JIS K6251 of the immersed molded article obtained by heating the immersed molded article containing the chloroprene-based polymer latex composition at 130°C for 4 hours. The modulus at 100% elongation is, for example, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 MPa, and may be within the range between any two of the values exemplified herein.

[0088] The above-mentioned immersed molded article can contain a chloroprene-based polymer latex, a metal oxide, and a heteroaromatic ring compound, and can further contain an antioxidant. Also, the above-mentioned immersed molded article can be made to not contain a vulcanizing agent and a vulcanization accelerator. The manufacturing method of the immersed molded article, and the measuring methods of elongation at break, breaking strength, and 100% modulus can be as described in the examples. Also, as described above, the elongation at break, breaking strength, and modulus at 100% elongation of the immersed molded article containing the chloroprene-based polymer latex composition can be controlled by adjusting the types and amounts of the formulation of the chloroprene-based polymer latex composition, as well as the polymerization formulation and conditions, weight average molecular weight, toluene-insoluble content, etc. of the chloroprene-based polymer latex used.

[0089] The chloroprene-based polymer latex composition according to an embodiment of the present invention can achieve a modulus at 100% elongation measured based on JIS K6251 of the heat-treated dip-molded article obtained by heating the dip-molded article containing the chloroprene-based polymer latex composition at 130°C for 4 hours of 0.75 MPa or less and a breaking strength of 17 MPa or more. In particular, in the ASTM standard "D3577" for surgical glove applications, the breaking strength is specified to be 17 MPa or more, and if it is 20 MPa, it can be said that more sufficient mechanical properties are exhibited. Also, if the modulus at 100% elongation is 0.75 MPa or less, it can be said that it has sufficient flexibility, and if it is 0.70 MPa or less, it can be said that it has even more sufficient flexibility. The dip-molded article film containing the chloroprene-based polymer latex composition according to an embodiment of the present invention can be provided with flexibility and have sufficient mechanical strength without containing sulfur or vulcanization accelerators that raise concerns about hygiene.

[0090] 2. Method for producing chloroprene-based polymer latex composition The method for producing a chloroprene-based polymer latex composition according to an embodiment of the present invention can include a raw material mixing step of mixing a raw material containing a chloroprene-based polymer latex, a metal oxide, a heteroaromatic ring compound, and other required chemicals. In the mixing step, a water dispersion containing a metal oxide, a heteroaromatic ring compound, and other required chemicals can be prepared in advance and mixed with the chloroprene-based polymer latex and the water dispersion. The mixing step can be carried out using a known mixing device such as a ball mill.

[0091] 3. Dip-molded article (dip-coated film) Next, the dip-molded article according to the second embodiment of the present invention will be described. The dip-molded article according to one embodiment of the present invention is obtained using the above-described chloroprene-based polymer latex composition. The dip-molded article of the present embodiment is obtained by dip-molding the chloroprene-based polymer latex composition of the first embodiment described above alone or blended with another chloroprene-based polymer latex composition, and has a low modulus value at 100% elongation, is flexible, and is excellent in mechanical properties such as strength and elongation. The dip-molded article can be suitably used as industrial and household gloves, medical gloves, balloons, catheters, and boots.

[0092] The thickness of the dip-molded article (for example, the minimum thickness) may be 0.01 to 0.50 mm. The thickness of the dip-molded article is, for example, 0.01, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50 mm, and may be within the range between any two of the values exemplified herein. The thickness of the dip-molded article can be adjusted by the time of immersing the mold in the polymer latex composition, the solid content concentration of the chloroprene-based polymer latex composition, and the like. When it is desired to reduce the thickness of the dip-molded article, the immersion time may be shortened or the solid content concentration of the chloroprene-based polymer latex composition may be lowered.

[0093] 3.1 Manufacturing method of dip-molded article The molding method for manufacturing the dip-molded article according to one embodiment of the present invention is not particularly limited, and molding may be performed according to a conventional method. Examples of the molding method include a coagulant immersion method, a simple immersion method, a heat-sensitive immersion method, an electrodeposition method, and the like. From the viewpoint of ease of production and ease of obtaining a dip-molded article having a certain thickness, the coagulant immersion method can be used. Specifically, a mold coated with a coagulant is immersed in a chloroprene-based polymer latex composition to coagulate the chloroprene-based polymer latex composition. Then, after removing water-soluble impurities by leaching, it is dried, and further heated and vulcanized to form a dip-molded film (rubber film), and then the dip-molded film is released from the mold. Thereby, a film-like dip-molded article can be obtained. Further, the method for manufacturing the dip-molded article according to one embodiment of the present invention can include a step of heating the obtained dip-molded article and vulcanizing the polymer latex composition and the unvulcanized dip-molded article. The vulcanization temperature may be appropriately set according to the composition of the chloroprene-based polymer latex composition, and may be 100 to 220 °C, or 110 to 190 °C. The vulcanization time may be appropriately set according to the composition of the chloroprene-based polymer latex composition, the shape of the unvulcanized molded article, etc., and may be 10 to 300 minutes.

[0094] 3.2 Mechanical properties of dip-molded article (film) The dip-molded article according to one embodiment of the present invention can be a molded article having a modulus at 100% elongation of 0.75 MPa or less and a breaking strength of 17 MPa or more measured in accordance with JIS K 6251.

[0095] The dip-molded article according to one embodiment of the present invention has a breaking strength measured based on JIS K6251, for example, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 MPa, and may be within the range between any two of the values exemplified here. Further, the dip-molded article according to one embodiment of the present invention has an elongation at break measured based on JIS K6251, for example, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400%, and may be within the range between any two of the values exemplified here. The dip-molded article according to one embodiment of the present invention has a modulus at 100% elongation measured based on JIS K6251, for example, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 MPa, and may be within the range between any two of the values exemplified here. Note that the manufacturing method of the dip-molded article, as well as the measurement methods of elongation at break, breaking strength, and 100% modulus can be as described in the examples.

[0096] As described above, the dip-molded article according to one embodiment of the present invention can have flexibility and sufficient mechanical strength without containing a vulcanization accelerator that raises concerns about sulfur and hygiene. Conventional chloroprene rubber has required the use of sulfur and a vulcanization accelerator to obtain a vulcanized rubber with the desired mechanical strength. Along with this, the flexibility deteriorates, and it has been difficult to achieve both high breaking strength and excellent flexibility. In addition, the non-use of general-purpose vulcanization accelerators and sulfur for chloroprene rubber, typified by dithiocarbamic acid or thiourea systems, not only reduces the allergy risk but also leads to cost reduction. Therefore, a chloroprene-based polymer latex composition capable of obtaining a dip-molded article that exhibits sufficient mechanical strength while having excellent flexibility without using sulfur and general-purpose vulcanization accelerators is desired.

[0097] The dip-molded article obtained from the chloroprene-based polymer latex composition of the present embodiment may contain sulfur or a vulcanization accelerator. However, the above dip-molded article has mechanical properties equivalent to or better than those of a vulcanized dip-molded article obtained from a conventional chloroprene-based polymer latex even without containing sulfur and a vulcanization accelerator. For this reason, the chloroprene-based polymer latex composition of the present embodiment is suitably used as a raw material for a dip-molded article (dip-coated film).

Examples

[0098] Hereinafter, the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to these examples. In the following examples related to the synthesis of chloroprene-based polymer latex, unless otherwise specified, "parts by mass" is the amount relative to a total of 100 parts by mass of chloroprene monomer and 2,3-dichloro-1,3-butadiene monomer before the start of emulsion polymerization. Also, "mass%" is the amount relative to 100 mass% of the chloroprene-based polymer contained in the chloroprene-based polymer latex.

[0099] [Synthesis Example A1] <Production of Chloroprene-Based Polymer Latex> Into a polymerization kettle with an internal volume of 40 liters, 91 parts by mass of chloroprene monomer, 9 parts by mass of 2,3-dichloro-1,3-butadiene monomer, 0.02 parts by mass of n-dodecyl mercaptan, 90 parts by mass of pure water, 4.5 parts by mass of rosin acid X ((total amount b of each component) / (total amount a of each component)=0.80), 1.50 parts by mass of potassium hydroxide, and 0.50 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation) were added. The pH of the aqueous emulsion before the start of polymerization was 13.2. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and polymerization was carried out under a nitrogen stream at a polymerization temperature of 25°C. When the polymerization conversion rate (polymerization rate) reached 82%, 0.01 part by mass of diethylhydroxyamine, which is a polymerization terminator, was added to terminate the polymerization, and a latex was obtained.

[0100] The above latex was subjected to vacuum distillation to remove unreacted monomers and a part of the moisture, thereby obtaining a chloroprene-based polymer latex with a solid content of 60%.

[0101] [Synthesis Examples A2 to A5] Chloroprene-based polymer latex samples of Synthesis Examples A2 to A5 were prepared in the same procedure as in Synthesis Example A1, except that the charged amounts of 2,3-dichloro-1,3-butadiene and n-dodecyl mercaptan as a chain transfer agent, the type and amount of rosin acid, the polymerization temperature, and the polymerization conversion rate were as shown in Table 1 below.

[0102] [Synthesis Example B1] [Preparation of Chloroprene-based Polymer Latex] Into a polymerization tank with an internal volume of 40 liters, 60 parts by mass of 92 parts by mass of all chloroprene monomers, 8 parts by mass of 2,3-dichloro-1,3-butadiene monomer, 3.0 parts by mass of n-dodecyl mercaptan, 90 parts by mass of pure water, 4.5 parts by mass of rosin acid X ((total amount of each component b) / (total amount of each component a)=0.80), 1.50 parts by mass of potassium hydroxide, and 0.50 parts by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation) were added as the initial charge amount. The pH of the aqueous emulsion before the start of polymerization was 13.0. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and polymerization was carried out at a polymerization temperature of 40 °C under a nitrogen stream. Thereafter, 32 parts by mass of the remaining chloroprene monomer was added at the stage of a polymerization conversion rate of 65% in terms of the initial charged monomer amount. When the polymerization conversion rate reached 88%, 0.01 part by mass of diethylhydroxyamine, which is a polymerization terminator, was added to terminate the polymerization, and a latex was obtained.

[0103] The above latex was subjected to vacuum distillation to remove unreacted monomers, thereby obtaining a chloroprene-based polymer latex with a solid content of 60%.

[0104] [Synthesis Examples B2 to B5] Except that the charged amounts of 2,3-dichloro-1,3-butadiene and n-dodecyl mercaptan as a chain transfer agent, the type and amount of rosin acid, the polymerization temperature, and the polymerization conversion rate were as shown in Table 1 below, chloroprene-based polymer latex samples of Synthesis Examples B2 to B5 were prepared in the same procedure as Synthesis Example B1.

[0105] [Synthesis Example C] [Preparation of Chloroprene-Based Polymer Latex] Into a polymerization kettle with an internal volume of 40 liters, 93 parts by mass of chloroprene monomer, 7 parts by mass of 2,3-dichloro-1,3-butadiene monomer, 5.0 parts by mass of n-dodecyl mercaptan, 90 parts by mass of pure water, 4.5 parts by mass of rosin acid X ((total amount of each component b) / (total amount of each component a)=0.80), 1.50 parts by mass of potassium hydroxide, and 0.50 part by mass of sodium salt of β-naphthalene sulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation) were added. The pH of the aqueous emulsion before the start of polymerization was 13.1. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and polymerization was carried out under a nitrogen stream at a polymerization temperature of 35°C. When the polymerization conversion rate reached 85%, 0.01 part by mass of diethylhydroxyamine, which is a polymerization terminator, was added to terminate the polymerization, and a latex was obtained.

[0106] The above latex was subjected to vacuum distillation to remove unreacted monomers, thereby obtaining a chloroprene-based polymer latex with a solid content of 60%.

[0107] <Measurement of the amount of each resin acid component contained in rosin acid X and Y> The amount of each resin acid component contained in the used rosin acid X was dissolved in ethanol / toluene (ETA solution) to make a 1.5% solution, subjected to hydrochloric acid treatment, and then measured using gas chromatography-mass spectrometry.

[0108] [Measurement conditions for gas chromatography-mass spectrometry] Gas chromatography-mass spectrometry was carried out under the following measurement conditions. · Column used: FFAP 0.32 mmφ×25 m (film thickness 0.3 μm) · Column temperature: 200°C → 250°C · Heating rate: 10°C / min · Injection port temperature: 270°C · Injection volume: 1 μL · Interface temperature: 270°C · Ion source temperature: 270°C · Ionization current: 50 μA · Ionization voltage: 70 eV · Detector voltage: -1000 V · Detector voltage: EI method

[0109] The peak areas of the peaks corresponding to dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid and their salts, and the total peak area of these (total amount a), and the peak areas of the peaks corresponding to abietic acid, neoabietic acid, palustric acid, levopimaric acid and their salts, and the total peak area of these (total amount b) were determined. Also, the ratio of each of these peak area values to the total peak area value detected by gas chromatography-mass spectrometry was regarded as the content.

[0110] When rosin acid X was measured, among the conjugated resin acid components, abietic acid was detected at 31.2%, neoabietic acid at 0.8%, palustric acid at 4.0%, and levopimaric acid at 2.7%, and the total area (b) of the conjugated resin acid components was 38.7%. Among the non-conjugated resin acid components, dehydroabietic acid was detected at 35.3%, pimaric acid at 7.5%, isopimaric acid at 3.2%, and dihydroabietic acid at 2.4%, and the total area (a) of the non-conjugated resin acid components was 48.4%. Therefore, the value (b / a) of (content of conjugated resin acid components)÷(content of non-conjugated resin acid components) of rosin acid X was 38.7÷48.4 = 0.80. In the same way, rosin acid Y was analyzed. For rosin acid Y, abietic acid, neoabietic acid, palustric acid, levopimaric acid and their salts were not detected, and b / a = 0.

[0111] <Measurement of Toluene Insoluble Content of Chloroprene Polymer Latex> 1 g of chloroprene polymer rubber obtained by freeze-drying chloroprene polymer latex was cut into 2 mm squares, placed in a conical beaker and dissolved in toluene for 16 hours. Then, it was centrifuged, and the weight of the gel fraction separated using a 200-mesh wire mesh and dried was measured. The toluene insoluble content was determined from the following calculation formula. (Mass of solid obtained by separating and drying the gel fraction) / (Mass of solid obtained by freeze-drying the latex containing the chloroprene block copolymer)×100

[0112] <Measurement of Weight Average Molecular Weight of Chloroprene Polymer Latex> The obtained chloroprene-based polymer latex was dissolved in THF (tetrahydrofuran), and the weight-average molecular weight of the eluate (sol fraction) was measured by gel permeation chromatography (GPC). The first peak and the second peak can be obtained as the weight-average molecular weight in terms of polystyrene and were measured under the conditions described below.

[0113] <Measurement of weight-average molecular weight by gel permeation chromatography> GPC measurement was performed under the following conditions. The weight-average molecular weight was determined in terms of polystyrene. · Gel permeation chromatography (GPC) measuring device: Gel permeation chromatograph (HLC-8320) manufactured by Tosoh Corporation · Column: TSKgel ALPHA-M manufactured by Tosoh Corporation · Eluent: Tetrahydrofuran (manufactured by Kanto Chemical Co., Inc.) · Eluent flow rate: 1.0 ml / min · Column temperature: 40 °C · Detection method: Differential refractive index (RI) meter · Calibration curve: Prepared using standard polystyrene

[0114]

Table 1

[0115] [Example 1] When the total of the chloroprene-based polymer latex of Synthesis Example A1 and the chloroprene-based polymer latex of Synthesis Example B1 was 100 parts by mass, a mixed chloroprene-based polymer latex was obtained by stirring and mixing the Synthesis Example A1 sample at 75 parts by mass and the Synthesis Example B1 sample at 25 parts by mass.

[0116] <Measurement of the content of alkyl mercaptans compound with respect to the solid content of the chloroprene-based polymer latex> The resulting chloroprene-based polymer latex was diluted 100-fold with tetrahydrofuran (THF) and measured using gas chromatography. In this example, n-dodecyl mercaptan was used as a chain transfer agent, and the content of this compound was 0.08 parts by mass based on 100 parts by mass of the solid content of the chloroprene-based polymer latex. The measurement conditions for gas chromatography are shown below. · Column used: DB-5 0.25 mmφ×30 m (film thickness 1.0 μm) · Column temperature: 50°C → 280°C · Heating rate: 10°C / min · Injection port temperature: 280°C · Injection volume: 1 μL · Carrier gas: He 1.0 ml / min (Split 1:30)

[0117] <Measurement of weight-average molecular weight of chloroprene-based polymer latex> As a result of performing gel permeation chromatography (GPC) measurement on the THF-soluble component of the resulting chloroprene-based polymer latex, a first peak with a weight-average molecular weight (Mw) of 800,000 and a second peak with a weight-average molecular weight (Mw) of 20,200 were confirmed. The conditions for GPC measurement were the same as those for the measurement of the weight-average molecular weight in each of the above synthesis examples.

[0118] <Measurement of the amount of resin acid component contained in the chloroprene-based polymer latex> 3 g of chloroprene-based polymer rubber obtained by freeze-drying a mixed chloroprene-based polymer latex was cut into 2 mm squares, placed in an eggplant-shaped flask attached to a condenser, dissolved in ethanol / toluene (ETA solution) as described above to form a 1.5% solution, subjected to hydrochloric acid treatment, and then measured using gas chromatography-mass spectrometry. The peak areas of the peaks corresponding to dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid, and their salts, and the total peak area of these peaks (total amount a), the peak areas of the peaks corresponding to abietic acid, neoabietic acid, palustric acid, levopimaric acid, and their salts, and the total peak area of these peaks (total amount b) were determined. Also, each of these peak area values was regarded as the content relative to the total peak area value detected by gas chromatography-mass spectrometry. The value of (total amount b)÷(total amount a) was 0.80.

[0119] <Measurement of Toluene-Insoluble Content of Chloroprene-Based Polymer Latex> 1 g of chloroprene-based polymer rubber obtained by freeze-drying a mixed chloroprene-based polymer latex was cut into 2 mm squares, placed in a conical beaker, and dissolved in toluene for 16 hours. Then, it was centrifuged, and the weight of the gel fraction separated using a 200-mesh wire mesh and dried was measured. The toluene-insoluble content was determined from the following calculation formula. (Mass of solid obtained by separating and drying the gel fraction) / (Mass of solid obtained by freeze-drying the latex containing the chloroprene-based block copolymer)×100 The toluene-insoluble content of the chloroprene-based polymer latex was 67% by mass.

[0120] <Preparation of Evaluation Sample (Immersion-Molded Film)> (Preparation of Chloroprene-Based Polymer Latex Composition) To 100 parts by mass of the solid content of the chloroprene polymer latex, 5.1 parts by mass of the aqueous dispersion was mixed, water was added to adjust the total solid content concentration of the formulation to 30% by mass, and a chloroprene polymer latex composition was prepared. The above aqueous dispersion was prepared by mixing 2 parts by mass of two types of zinc oxide, 2 parts by mass of a butylated reaction product of p-cresol and dicyclopentadiene (trade name "No Crack PBK", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 2-mercaptobenzimidazole described in Chemical Formula (2) (trade name "No Crack MB", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.1 part by mass of a sodium salt of a β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), and 13 parts by mass of water at 20 °C for 16 hours using a ceramic ball mill. The obtained chloroprene polymer latex contains 2 parts by mass of two types of zinc oxide, 2 parts by mass of a butylated reaction product of p-cresol and dicyclopentadiene (trade name "No Crack PBK", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 2-mercaptobenzimidazole described in Chemical Formula (2) (trade name "No Crack MB", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 0.1 part by mass of a sodium salt of a β-naphthalenesulfonic acid formalin condensate (trade name "Demol N", manufactured by Kao Corporation), and 13 parts by mass of water with respect to 100 parts by mass of the solid content of the chloroprene polymer latex. Further, the above dipping molded article does not contain sulfur and vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based ones.

[0121]

Chem.

[0122] (Production of Dipping Molded Film) A cylinder made of ceramic with an outer diameter of 50 mm (manufactured by Shinko Co., Ltd.) was immersed in a coagulating liquid prepared by mixing 62 parts by mass of water, 35 parts by mass of potassium nitrate tetrahydrate, and 3 parts by mass of calcium carbonate for 1 second and then taken out. After drying for 3 minutes, it was immersed in a chloroprene-based polymer latex composition containing no sulfur and vulcanization accelerators prepared by the above procedure for 10 seconds. Then, it was washed with running water at 45 °C for 1 minute and dried at 130 °C for 4 hours to produce an immersion-molded body film (immersion-molded coating) for evaluation.

[0123] <Evaluation of Immersion-Molded Body> (Modulus at 100% Elongation, Tensile Strength, and Elongation at Break) For each of the immersion-molded body films containing no sulfur and vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based vulcanization accelerators, the modulus at 100% elongation, tensile strength, and elongation at break were measured in accordance with JIS K 6251. The results are shown in Table 1.

[0124] (Film Thickness) Using a test piece thickness gauge (manufactured by Kobunshi Keiki Co., Ltd., product name: ASKER SDA-12), the thicknesses (film thickness) at three locations in the central part of the evaluation film were measured, and the minimum thickness was obtained as the thickness of the evaluation film.

[0125] [Examples 2 to 15, Comparative Examples 1 to 6] An immersion molded body was produced in the same manner as in Example 1 except that the formulation of the chloroprene polymer latex was set to the conditions shown in Tables 2, 3, and 4 below. An immersion molded body film sample containing no sulfur and no vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based compounds was manufactured and evaluated. In Examples 2 to 5 and 11 and Comparative Examples 1 to 4, the addition amounts of zinc oxide as a metal oxide, 2-mercaptobenzimidazole as a heteroaromatic ring compound, and No Crack PBK as an antioxidant contained in the chloroprene polymer latex composition were changed. In Examples 6, 7, 12 to 15 and Comparative Example 5, the types and mixing ratios of the synthesized polychloroprene polymer latex were changed, and the content of alkyl mercaptans compounds and the detected value of the weight average molecular weight peak were changed. In Examples 8 to 10 and Comparative Example 6, the heteroaromatic ring compound was changed to the compounds represented by the following chemical formulas (3) to (6).

[0126] [Chemical formula]

[0127] [Chemical formula]

[0128] [Chemical formula]

[0129] [Chemical formula]

[0130] [Table 2]

[0131] [Table 3]

[0132]

Table 4

[0133] As is clear from Tables 2 and 3 above, the dip-formed articles (dip-formed coatings) obtained using the chloroprene-based polymer latex composition of the present invention from Examples 1 to 15 had high breaking strength and low modulus values at 100% elongation, that is, they had very excellent flexibility and were excellent in mechanical properties such as breaking strength and elongation at break.

[0134] In Comparative Example 1, since the complex aromatic ring compound was not contained in the chloroprene-based polymer latex composition, the breaking strength was inferior.

[0135] In Comparative Example 2, since the metal oxide (zinc oxide) in the chloroprene-based polymer latex composition was not contained, the crosslinking effect between chloroprene-based polymers did not appear, and the breaking strength was inferior.

[0136] In Comparative Example 3, since the amount of the metal oxide (zinc oxide) in the chloroprene-based polymer latex composition was large, the crosslinking effect between chloroprene-based polymers appeared too much, the modulus 100 value was high, and the flexibility decreased.

[0137] In Comparative Example 4, since the amount of the complex aromatic ring compound in the chloroprene-based polymer latex composition was large, the blending stability of the chloroprene-based polymer latex composition was very poor, and a dip-formed article could not be obtained.

[0138] In Comparative Example 5, since the content of n-dodecyl mercaptan, which is an alkyl mercaptan compound, relative to the solid content of the chloroprene-based polymer in the chloroprene-based polymer latex composition was large, the modulus 100 value was high and the flexibility decreased. In addition, there remained concerns about the hygiene regarding n-dodecyl mercaptan, and the odor derived from mercaptan became extremely bad.

[0139] In Comparative Example 6, 2-mercaptobenzothiazole (trade name "Nocceler M", manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) described in the above chemical formula (6) in which the structure of the heteroaromatic ring compound in the chloroprene polymer latex composition does not correspond to the chemical formula (1) was used, resulting in inferior breaking strength.

[0140] Also, in Example 12 using only Synthesis Example A3 and Example 15 in which the value of the weight average molecular weight of the second peak is high, the obtained dip-molded film exhibits sufficiently excellent breaking strength. Further, as in Examples 1 to 11 and 13 to 15, Synthesis Example A containing a high molecular weight chloroprene polymer and Synthesis Example B containing a low molecular weight chloroprene polymer are mixed, and in the chloroprene polymer latex, a first peak having a weight average molecular weight of 500,000 or more and a second peak having a weight average molecular weight of 7,000 to 80,000 are present. It was confirmed that a dip-molded film having a high breaking strength and further excellent flexibility can be obtained due to the plasticizing effect of the low molecular weight polymer.

Claims

1. A chloroprene-based polymer latex composition comprising a chloroprene-based polymer latex, a metal oxide, and a heteroaromatic ring compound, wherein the chloroprene-based polymer latex composition contains 0.5 to 15.0 parts by mass of the metal oxide and 0.1 to 10.0 parts by mass of the heteroaromatic ring compound with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex, the content of the alkyl mercaptans compound in the chloroprene-based polymer latex composition is 0.34 parts by mass or less with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex, and the heteroaromatic ring compound is represented by Chemical Formula (1), Chloroprene-based polymer latex composition. 【Chemical 1】 X in the chemical formula (1) represents a hydrogen atom or a metal atom. Also, R １ ~R ４ each represents a hydrogen atom, an alkyl group which may have a substituent, an ether group which may have a substituent, a nitro group, an amino group, or a carboxyl group. R １ ~R ４ may be the same or different from each other.)

2. The chloroprene-based polymer latex composition according to Claim 1, which contains 0.5 to 10.0 parts by mass of an antioxidant with respect to 100 parts by mass of the solid content of the chloroprene-based polymer latex.

3. The chloroprene-based polymer latex contains at least one of a homopolymer of chloroprene and a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene, and the chloroprene-based polymer latex composition according to Claim 1 or Claim 2 has a first peak with a weight average molecular weight of 500,000 or more and a second peak with a weight average molecular weight of 7,000 to 80,000 in the molecular weight distribution obtained by gel permeation chromatography measurement of the sol fraction soluble in tetrahydrofuran in the chloroprene-based polymer latex.

4. The chloroprene-based polymer latex composition according to Claim 1 or Claim 2, wherein the toluene-insoluble content of the chloroprene-based polymer rubber obtained by freeze-drying the chloroprene-based polymer latex is 50 to 85% by mass.

5. The chloroprene-based polymer rubber obtained by freeze-drying the chloroprene-based polymer latex was cut and placed in a flask attached to a condenser, extracted with an ethanol / toluene azeotropic mixture defined in JIS K 6229, and the mass ratio b / a of the total amount b of abietic acid, neoabietic acid, palustric acid, levopimaric acid and their salts to the total amount a of dehydroabietic acid, pimaric acid, isopimaric acid, dihydroabietic acid and their salts in the components measured by gas chromatography of the extract is 0.10 or more. The chloroprene-based polymer latex composition according to claim 1 or claim 2.

6. The chloroprene-based polymer latex composition according to claim 1 or claim 2, which contains a thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthate-based, and thiazole-based vulcanization accelerator and does not contain sulfur.

7. An immersion molded article obtained by using the chloroprene-based polymer latex composition according to claim 1 or claim 2.

8. The immersion molded article according to claim 7, which is an industrial / general household glove, a medical glove, a balloon, a catheter or a boot.

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