Chloroprene-based block copolymer, latex, latex composition, and rubber composition

Abstract

To provide a chloroprene block copolymer, a latex, a latex composition, and a rubber composition with which it is possible to obtain a molded body having excellent tensile strength at break and tensile elongation at break even with use of less or no vulcanizing agent or vulcanization accelerator. [Solution] A chloroprene block copolymer including 30-60 mass% of a polymer block (A) derived from a monomer that yields a polymer having a glass transition temperature of 80°C or more when homopolymerized and 40-70 mass% of a chloroprene polymer block (B) having a chloroprene monomer unit and a polyfunctional monomer unit.

Description

[Technical Field]

[0001] The present invention relates to a chloroprene-based block copolymer, a latex, a latex composition, and a rubber composition.

[0002] Various techniques relating to chloroprene-based block copolymers have been proposed. For example, Known copolymers include copolymers obtained by polymerizing chloroprene using polystyrene containing the above as an initiator (see, for example, Patent Document 1), copolymers obtained by polymerizing dithiocarbamated polychloroprene with an aromatic vinyl monomer (see, for example, Patent Document 2), copolymers obtained by linking a hydrophilic oligomer or hydrophilic polymer to a chloroprene polymer (see, for example, Patent Document 3), copolymers having blocks of aromatic vinyl compound polymers and blocks of chloroprene polymers, with the overall number average molecular weight and the number average molecular weight of the chloroprene polymer blocks being specified (see, for example, Patent Document 4), and copolymers having blocks of acrylic ester polymers and blocks of chloroprene polymers (see, for example, Patent Document 5).

[0003] Furthermore, the technique described in Patent Document 6 is known as a method for chemically bonding molecules without vulcanization. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-207710 [Patent Document 2] Japanese Patent Application Publication No. 3-212414 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-297502 [Patent Document 4] International Publication No. 2018 / 181801 [Patent Document 5] International Publication No. 2019 / 026914 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-221901 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, in order to obtain the desired mechanical strength of polychloroprene rubber compositions, it has been necessary to use vulcanizing agents such as sulfur, zinc oxide, and magnesium oxide, and vulcanization accelerators such as thiuram-based, dithiocarbamate-based, thiourea-based, guanidine-based, xanthogenate-based, and thiazole-based vulcanization accelerators. Because vulcanization accelerators are causative agents of type IV allergies that cause skin diseases such as dermatitis, reducing or eliminating the use of vulcanization accelerators has become an important theme. Furthermore, reducing or eliminating the use of vulcanization accelerators not only reduces allergies but also cuts costs. Therefore, there is a demand for rubber compositions that can exhibit sufficient mechanical strength even with reduced amounts of vulcanization accelerators.

[0006] Therefore, an object of the present invention is to provide a chloroprene-based block copolymer, latex, latex composition and rubber composition which can give a molded article having excellent tensile strength at break, tensile elongation at break and 25% modulus even with reduced amounts of or no vulcanizing agents or vulcanization accelerators. [Means for solving the problem]

[0007] The present invention provides a chloroprene-based block copolymer comprising 30 to 60 mass% of a polymer block (A) derived from a monomer that, upon homopolymerization, gives a polymer having a glass transition temperature of 80°C or higher, and 40 to 70 mass% of a chloroprene-based polymer block (B) having a chloroprene monomer unit and a polyfunctional monomer unit.

[0008] As a result of extensive investigations, the present inventors have found that by preparing a block copolymer containing a polymer block (A) having a structure derived from a specific type of monomer and a chloroprene-based polymer block (B) having chloroprene monomer units and polyfunctional monomer units in specific contents, it is possible to obtain a chloroprene-based block copolymer, latex, latex composition, and rubber composition from which molded articles having excellent tensile strength at break, tensile elongation at break, and 25% modulus can be obtained, even with reduced amounts of or no vulcanizing agents or vulcanization accelerators, and thus have completed the present invention.

[0009] According to another aspect of the present invention, there is provided a latex containing the above-described chloroprene-based block copolymer. According to another aspect of the present invention, there is provided a latex composition comprising 100 parts by mass of the above-described latex and 0.5 to 5.0 parts by mass of an antioxidant. According to another aspect of the present invention, there is provided a rubber composition containing the above-described chloroprene-based block copolymer. According to another aspect of the present invention, there is provided a rubber composition containing the above-described latex.

[0010] Various embodiments according to this aspect will be described below. The embodiments described below can be combined with each other. [1] A chloroprene-based block copolymer comprising 30 to 60 mass% of a polymer block (A) derived from a monomer that, upon homopolymerization, gives a polymer having a glass transition temperature of 80°C or higher, and 40 to 70 mass% of a chloroprene-based polymer block (B) having a chloroprene monomer unit and a polyfunctional monomer unit. [2] The chloroprene-based block copolymer according to [1], wherein a molded article of a latex composition containing the chloroprene-based block copolymer has a 25% modulus of 2.5 MPa or more as measured in accordance with JIS K6251 after heat-treating the molded article at 130°C for 30 minutes. [3] The chloroprene block copolymer according to [1], wherein a molded article of a latex composition containing the chloroprene block copolymer has a tensile strength at break of 20 MPa or more as measured in accordance with JIS K 6251 after heat-treating the molded article at 130°C for 30 minutes. [4] The chloroprene block copolymer according to any one of [1] to [3], wherein the polymer block (A) has a number average molecular weight of 10,000 or more. [5] The chloroprene block copolymer according to any one of [1] to [4], wherein the molecular weight distribution of the polymer block (A) is 2.0 or less. [6] The chloroprene block copolymer according to any one of [1] to [5], wherein the polymer block (A) is a polymer block composed of aromatic vinyl monomer units. [7] The chloroprene block copolymer according to any one of [1] to [6], wherein the polyfunctional monomer is a monomer represented by chemical formula (1) or an aromatic polyene monomer.

[0011] [ka] (In chemical formula (1), R1 and R2 each independently represent hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, or a substituted or unsubstituted heterocyclyl group. W1 represents a saturated or unsaturated hydrocarbon group, a saturated or unsaturated cyclic hydrocarbon group, a saturated or unsaturated hydrocarbon group containing a heteroatom, or a saturated or unsaturated cyclic hydrocarbon group containing a heteroatom. Z1 represents oxygen, sulfur, or a structure represented by -NR0-. R0 represents hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, or a substituted or unsubstituted heterocyclyl group.) [8] The chloroprene block copolymer according to any one of [1] to [7], which has a functional group having a structure represented by chemical formula (2) or chemical formula (3).

[0012] [ka] (In chemical formula (2), R3 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, and a substituted or unsubstituted heterocyclyl group.)

[0013] [ka] [9] A latex containing the chloroprene block copolymer according to any one of [1] to [8].

[10] A latex composition comprising 100 parts by mass of the latex according to [9] and 0.5 to 5.0 parts by mass of an antioxidant.

[11] A rubber composition comprising the chloroprene block copolymer according to any one of [1] to [8].

[12] A rubber composition comprising the latex according to [9]. [Effects of the Invention]

[0014] According to the present invention, there are provided a chloroprene-based block copolymer, a latex, a latex composition, and a rubber composition which can give a molded article having excellent tensile strength at break, tensile elongation at break, and 25% modulus even with reduced amounts of a vulcanizing agent or a vulcanization accelerator or without using any vulcanizing agent or vulcanization accelerator. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below by illustrating embodiments of the present invention. The present invention is not limited by these descriptions. The various features of the embodiments of the present invention shown below can be combined with each other. Furthermore, each feature can be an invention independently. In this specification and claims, the expression "A to B" means A or more and B or less.

[0016] <Chloroprene-based block copolymer> The chloroprene-based block copolymer is a block copolymer containing a polymer block (A) derived from a monomer that, upon homopolymerization, gives a polymer having a glass transition temperature of 80°C or higher, and a chloroprene-based polymer block (B) containing a chloroprene monomer and a polyfunctional monomer unit. The chloroprene-based block copolymer also includes those having a structure in which block copolymers are chemically bonded to each other via the polyfunctional monomer unit contained in the chloroprene-based polymer block (B).

[0017] [Polymer block (A)] The polymer block (A) is a polymer block derived from a monomer that, upon homopolymerization, yields a polymer having a glass transition temperature of 80°C or higher. The use of such a monomer improves the tensile strength at break of the resulting chloroprene-based block copolymer. Preferably, a monomer that yields a polymer having a glass transition temperature of 85°C or higher is used. From the viewpoint of moldability, a monomer that yields a polymer having a glass transition temperature of 150°C or lower is preferred, and a monomer that yields a polymer having a glass transition temperature of 120°C or lower is particularly preferred. The glass transition temperature may be, for example, 80, 85, 90, 95, 100, 105, 110, 120, 130, 140, or 150°C, or may be within a range between any two of the values ​​exemplified here.

[0018] In this specification, the glass transition temperature refers to the extrapolated glass transition end temperature (T eg) measured in accordance with JIS K 7121, and can be measured using a differential scanning calorimeter, for example, DSC1 (manufactured by Mettler Toledo).

[0019] When the polymer block (A) is a polymer block obtained by polymerizing a monomer (A), the monomer (A) is preferably a monomer having the above-mentioned glass transition temperature when the monomer A is homopolymerized to give a homopolymer (A) having a number average molecular weight of 10,000 to 100,000, and more preferably a monomer having the above-mentioned glass transition temperature when the homopolymer (A) has a number average molecular weight of 30,000 to 700,000.

[0020] Examples of monomer units constituting the polymer block (A) include aromatic vinyl monomer units, methyl methacrylate monomer units, and acrylonitrile monomer units. Preferably, units derived from aromatic vinyl monomers are used, with styrene units being preferred. The polymer block (A) may be a polymer block obtained by copolymerization of these monomers, or a polymer block composed of monomer units copolymerizable with these monomers, as long as the object of the present invention is not impaired.

[0021] The number-average molecular weight of the polymer block (A) is preferably 10,000 or more from the viewpoint of the tensile properties and moldability of the resulting chloroprene-based block copolymer. The number-average molecular weight of the polymer block (A) is, for example, 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, or 100,000, and may be within a range between any two of the values ​​exemplified here. Furthermore, from the viewpoint of moldability, the molecular weight distribution of the polymer block (A) is preferably 2.0 or less. The molecular weight distribution of the polymer block (A) can be, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0, and may be within a range between any two of the numerical values ​​exemplified here. In this specification, the number average molecular weight and weight average molecular weight are values ​​measured by gel permeation chromatography (GPC) in terms of polystyrene, and are values ​​measured under the measurement conditions described below. Device name: HLC-8320 (Tosoh Corporation) Column: Three TSKgel GMHHR-H columns in series Temperature: 40℃ Detection: Differential refractive index Solvent: tetrahydrofuran Calibration curve: Prepared using standard polystyrene (PS).

[0022] [Chloroprene polymer block (B)] The chloroprene polymer block (B) is a polymer block having chloroprene monomer (2-chloro-1,3-butadiene) units and polyfunctional monomer units. Note that the chloroprene polymer block (B) may be a polymer block consisting of chloroprene monomer units, polyfunctional monomer units, and monomer units copolymerizable with these monomers, as long as the object of the present invention is not impaired.

[0023] The content of each structural unit in the chloroprene polymer block (B) is not particularly limited, but is preferably 90 to 99.95 mass% for chloroprene monomer units and 0.05 to 10 mass% for polyfunctional monomer units. The content of the polyfunctional monomer units in the chloroprene polymer block (B) is, for example, 0.05, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00, 6.00, 7.00, 8.00, 9.00, or 10.00 mass%, and may be within a range between any two of the values ​​exemplified here.

[0024] [Multifunctional Monomer] The polyfunctional monomer according to the present invention is a compound having two or more radically polymerizable groups in the molecule. The polyfunctional monomer preferably has a plurality of polymerizable substituents that are independent of each other. The polyfunctional monomer preferably has at least one pair of non-conjugated polymerizable substituents. Of the plurality of polymerizable substituents, at least one pair of polymerizable substituents is preferably spaced apart by at least one atom, preferably three or more atoms, and more preferably five or more atoms. The polymerizable substituent may be a vinyl group or a carbon-carbon double bond. From the viewpoints of flexibility, tensile strength at break, and moldability of the resulting chloroprene-based block copolymer, a monomer represented by chemical formula (1) or an aromatic polyene monomer is preferably used. As the monomer represented by chemical formula (1), 1,9-nonanediol dimethacrylate, 1,9-nonanediol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, and N,N'-diacryloyl-4,7,10-trioxa-1,13-tridecanediamine are particularly preferably used. The aromatic polyene monomer is an aromatic polyene having 10 to 30 carbon atoms and having multiple double bonds (vinyl groups) and one or more aromatic groups. Examples of the aromatic polyene monomer include units derived from aromatic polyene monomers such as o-divinylbenzene, p-divinylbenzene, m-divinylbenzene, 1,4-divinylnaphthalene, 3,4-divinylnaphthalene, 2,6-divinylnaphthalene, 1,2-divinyl-3,4-dimethylbenzene, and 1,3-divinyl-4,5,8-tributylnaphthalene. Preferably, one or a mixture of two or more of ortho-divinylbenzene units, para-divinylbenzene units, and meta-divinylbenzene units is suitably used.

[0025] [ka] (In chemical formula (1), R1 and R2 each independently represent hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, or a substituted or unsubstituted heterocyclyl group. W1 represents a saturated or unsaturated hydrocarbon group, a saturated or unsaturated cyclic hydrocarbon group, a saturated or unsaturated hydrocarbon group containing a heteroatom, or a saturated or unsaturated cyclic hydrocarbon group containing a heteroatom. Z1 represents oxygen, sulfur, or a structure represented by -NR0-. R0 represents hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, or a substituted or unsubstituted heterocyclyl group.)

[0026] Examples of the monomer unit copolymerizable with the chloroprene monomer unit and the polyfunctional monomer unit include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, and butadiene. The polyfunctional monomer may also be one that does not include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, or butadiene. A chloroprene-based copolymer according to one embodiment of the present invention may have chloroprene monomer units and polyfunctional monomer units derived from a polyfunctional monomer other than 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, and butadiene. Chloroprene monomer unit Polyfunctional monomer units derived from polyfunctional monomers other than 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, and butadiene Monomer units copolymerizable with chloroprene monomer units and polyfunctional monomer units It can have the following.

[0027] The content of each structural unit of the chloroprene-based block copolymer is 30 to 60 mass% for polymer block (A) and 40 to 70 mass% for chloroprene-based polymer block (B). Preferably, the polymer block (A) is more than 30 mass% but not more than 60 mass%, and the chloroprene-based polymer block (B) is 40 mass% or more but less than 70 mass%. When the polymer block (A) is at least the lower limit, the tensile strength at break of the resulting chloroprene-based block copolymer is improved. When the polymer block (A) is at most the upper limit, the elongation at break is improved. When the chloroprene-based block copolymer is taken as 100 mass%, the content of polymer block (A) in the chloroprene-based block copolymer is, for example, 30, 31, 32, 33, 34, 35, 40, 45, 50, 55, or 60 mass%. It can be more than 30 mass%, and may be within a range between any two of the values ​​exemplified here.

[0028] A chloroprene-based block copolymer according to one embodiment of the present invention may be composed of polymer block (A) and polymer block (B), and may not contain any other polymer block. The chloroprene-based block copolymer may be a diblock copolymer of polymer block (A) and polymer block (B).

[0029] The weight average molecular weight of the chloroprene-based block copolymer is not particularly limited, but from the viewpoint of moldability, it is preferably 50,000 to 600,000, and particularly preferably 100,000 to 500,000.

[0030] The chloroprene-based block copolymer of this embodiment preferably has a tensile strength at break of 20 MPa or more when a molded article of a latex composition containing the chloroprene-based block copolymer is heat-treated at 130°C for 30 minutes and then measured in accordance with JIS K 6251. The tensile strength at break is more preferably more than 25 MPa, even more preferably 30 MPa or more, and even more preferably 32 MPa or more. There is no particular upper limit, but it is, for example, 50 MPa or less.

[0031] Furthermore, the chloroprene-based block copolymer of this embodiment preferably has an elongation at break of 450% or more, more preferably 600% or more, and even more preferably 800% or more, as measured in accordance with JIS K 6251 after a molded article of a latex composition containing the chloroprene-based block copolymer is heat-treated at 130°C for 30 minutes. The upper limit is not particularly limited, but is, for example, 1300% or less.

[0032] The chloroprene block copolymer of this embodiment preferably has a modulus at 25% elongation of 2.5 MPa or more, more preferably 3.0 MPa, and even more preferably more than 5.0 MPa, as measured in accordance with JIS K 6251 after heat-treating a molded article of a latex composition containing the chloroprene block copolymer at 130°C for 30 minutes. The upper limit is not particularly limited, but is, for example, 9.0 MPa or less.

[0033] The chloroprene-based block copolymer of this embodiment can be molded into a rubber composition and a latex composition containing a latex containing the chloroprene-based block copolymer, and the molded article can have the above-mentioned tensile strength, elongation at break, and modulus at 25% elongation after heat treatment at 130°C for 30 minutes. The molded article can be molded without using a vulcanizing agent or vulcanization accelerator. The molded article for measuring tensile strength can be obtained by the method described in the examples.

[0034] The tensile strength at break, elongation at break and modulus at 25% elongation of the molded article of the latex composition containing the chloroprene-based block copolymer can be adjusted by adjusting the content of the polyfunctional monomer unit contained in the chloroprene-based polymer block (B) or by adjusting the content of the polymer block (A) in the chloroprene-based block copolymer.

[0035] [Method for producing chloroprene-based block copolymer] The method for producing the chloroprene-based block copolymer according to the present invention will be described. The polymerization method is not particularly limited, and the copolymer can be produced by known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. However, emulsion polymerization is preferred for obtaining the desired chloroprene-based block copolymer.

[0036] The polymerization method is not particularly limited as long as the desired chloroprene-based block copolymer can be obtained, but it is preferable to produce the copolymer by a two-stage polymerization process consisting of polymerization step 1 for synthesizing polymer block (A) followed by polymerization step 2 for synthesizing chloroprene-based polymer block (B).

[0037] (Polymerization step 1) In the polymerization step 1, the monomers constituting the polymer block (A) are subjected to living radical polymerization to synthesize the polymer block (A). As described above, the polymer block (A) obtained here preferably has the glass transition temperature described above. The emulsifier used in the polymerization is not particularly limited, but anionic or nonionic emulsifiers are preferred from the viewpoint of emulsion stability. In particular, alkali metal rosinate salts are preferred because they can impart appropriate strength to the resulting chloroprene-based block copolymer and prevent excessive shrinkage and breakage. From the viewpoint of efficient polymerization reaction, the concentration of the emulsifier is preferably 5 to 50% by mass relative to 100% by mass of the monomers constituting the polymer block (A). Known radical polymerization initiators can be used, such as potassium persulfate, benzoyl peroxide, hydrogen peroxide, and azo compounds. The polymerization temperature can be determined appropriately depending on the type of monomer, but is preferably 10 to 100°C, and more preferably 20 to 80°C.

[0038] (Polymerization step 2) In the polymerization step 2, a chloroprene monomer and a polyfunctional monomer are added to the latex containing the polymer block (A) obtained in the polymerization step 1 and polymerized to obtain a latex containing the target chloroprene-based block copolymer. The chloroprene monomer and the polyfunctional monomer may be added all at once or in portions. The polymerization temperature in the polymerization step 2 is preferably 10 to 50°C from the viewpoint of ease of polymerization control. The polymerization reaction is terminated by adding a polymerization terminator. Examples of the polymerization terminator include thiodiphenylamine, 4-tert-butylcatechol, and 2,2'-methylenebis-4-methyl-6-tert-butylphenol. After the completion of the polymerization, unreacted monomers can be removed by a conventional method such as vacuum distillation.

[0039] To the latex containing the chloroprene-based block copolymer obtained in the polymerization step 2, a freezing stabilizer, an emulsion stabilizer, a viscosity modifier, an antioxidant, a preservative, etc. may be optionally added after polymerization within a range that does not impair the object of the present invention.

[0040] (Recovery process) The method for recovering the chloroprene-based block copolymer from the latex containing the chloroprene-based block copolymer is not particularly limited, and known methods can be used, such as a method of recovering the chloroprene-based block copolymer by immersing the copolymer in a coagulation liquid or a method of precipitating the copolymer using a poor solvent such as methanol.

[0041] The chloroprene-based block copolymer preferably has a functional group having a structure represented by the following chemical formula (2) or (3).

[0042] [ka] (In chemical formula (2), R3 represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, and a substituted or unsubstituted heterocyclyl group.) [ka]

[0043] The terminal structure represented by the above chemical formula (2) or chemical formula (3) is introduced into a chloroprene-based block copolymer by polymerization in the presence of a known RAFT agent. The compound that leads to the structure represented by the above chemical formula (2) is not particularly limited, and common compounds can be used, such as dithiocarbamates and dithioesters. Specific examples include benzyl 1-pyrrolecarbodithioate (common name: benzyl 1-pyrroledithiocarbamate), benzyl phenylcarbodithioate, 1-benzyl-N,N-dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethylimidazolecarbodithioate (common name: 1-phenylethylimidazoledithiocarbamate), benzyl-1-(2-pyrrolidinone)carbodithioate, and the like. oate) (trivial name: benzyl-1-(2-pyrrolidinone)dithiocarbamate), benzyl phthalimidyl carbodithioate, (trivial name: benzyl phthalimidyl dithiocarbamate), 2-cyanoprop-2-yl-1-pyrrole carbodithioate, (trivial name: 2-cyanoprop-2-yl-1-pyrrole dithiocarbamate), 2-cyanoprop-2-yl-1-pyrrole carbodithioate, (trivial name: 2-cyanoprop-2-yl- 1-Pyrrolidinedithiocarbamate), benzyl-1-imidazolecarbodithioate, (common name benzyl-1-imidazoledithiocarbamate), 2-cyanoprop-2-yl-N,N-dimethyldithiocarbamate, benzyl-N,N-diethyldithiocarbamate, cyanomethyl-1-(2-pyrrolidone)dithiocarbamate, 2-(ethoxycarbonylbenzyl)prop-2-yl-N,N-diethyldithiocarbamate, 1-phenyl Nylethyl dithiobenzoate, 2-phenylprop-2-yldithiobenzoate, 1-acetate-1-yl-ethyl dithiobenzoate, 1-(4-methoxyphenyl)ethyl dithiobenzoate, benzyl dithioacetate, ethoxycarbonylmethyl dithioacetate, 2-(ethoxycarbonyl)prop-2-yldithiobenzoate, 2-cyanoprop-2-yldithiobenzoate, tert-butyl dithiobenzoate, 2,4,4-Trimethylpent-2-yldithiobenzoate, 2-(4-chlorophenyl)-prop-2-yldithiobenzoate, 3-vinylbenzyl dithiobenzoate, 4-vinylbenzyl dithiobenzoate, benzyl diethoxyphosphinyldithioformate, tert-butyl trithioperbenzoate, 2-phenylprop-2-yl-4-chlorodithiobenzoate, naphthalene-1-carboxylic acid-1-methyl-1-phenyl-ethyl ester, 4-cyano-4-methyl-4-thiobenzylsulfanylbutyric acid, dibenzyl tetrathioterephthalate, carboxymethyl dithiobenzoate, poly(ethylene oxide) with dithiobenzoate end groups, poly(ethylene oxide) with 4-cyano-4-methyl-4-thiobenzylsulfanylbutyric acid end groups, 2-[(2-phenylethanethioyl)sulfanyl]propanoic acid, 2-[(2-phenylethanethioyl)sulfanyl]cobalamin Acid, 3,5-dimethyl-1H-pyrazole-1-carbodithioate potassium, cyanomethyl-3,5-dimethyl-1H-pyrazole-1-carbodithioate, cyanomethylmethyl-(phenyl)dithiocarbamate, benzyl-4-chlorodithiobenzoate, phenylmethyl-4-chlorodithiobenzoate, 4-nitrobenzyl-4-chlorodithiobenzoate, phenylprop-2-yl-4-chlorodithiobenzoate, 1-cyano Examples of suitable dithiobenzoates include 1-methylethyl-4-chlorodithiobenzoate, 3-chloro-2-butenyl-4-chlorodithiobenzoate, 2-chloro-2-butenyldithiobenzoate, benzyldithioacetate, 3-chloro-2-butenyl-1H-pyrrole-1-dithiocarboxylic acid, 2-cyanobutan-2-yl 4-chloro-3,5-dimethyl-1H-pyrazole-1-carbodithioate, and cyanomethylmethyl(phenyl)carbamodithioate. Of these, benzyl 1-pyrrolecarbodithioate and benzylphenylcarbodithioate are particularly preferred.

[0044] The compound leading to the structure represented by the above chemical formula (3) is not particularly limited, and a general compound can be used, for example, 2-cyano-2-propyldodecyltrithiocarbonate, dibenzyltrithiocarbonate, butylbenzyltrithiocarbonate, 2-[[(butylthio)thioxomethyl]thio]propionic acid, 2-[[(dodecylthio)thioxomethyl]thio]propionic acid, 2-[[(butylthio)thioxomethyl]thio]succinic acid, 2-[[(dodecylthio)thioxomethyl]thio]succinic acid, 2-[[(dodecylthio)thioxomethyl]thio] ]-2-methylpropionic acid, 2,2'-[carbonothioylbis(thio)]bis[2-methylpropionic acid], 2-amino-1-methyl-2-oxoethylbutyl trithiocarbonate, benzyl 2-[(2-hydroxyethyl)amino]-1-methyl-2-oxoethyltrithiocarbonate, 3-[[[(tert-butyl)thio]thioxomethyl]thio]propionic acid, cyanomethyldodecyltrithiocarbonate, diethylaminobenzyltrithiocarbonate, dibutylaminobenzyltrithiocarbonate, and other trithiocarbonates are particularly preferred.

[0045] <Latex> The latex according to the present embodiment is a latex containing the above-described chloroprene-based block copolymer. The latex can be immersed in a coagulation liquid and molded to obtain a dip-molded article. The dip-molded article can be suitably used for gloves, balloons, catheters, boots, etc.

[0046] The latex of the present embodiment can be obtained by a method in which the liquid obtained at the end of polymerization by the polymerization method described in the above-mentioned method for producing a chloroprene-based block copolymer is used as a latex as it is, or by a method in which the recovered chloroprene-based block copolymer is forcibly emulsified using an emulsifier to obtain a latex, but the method in which the liquid obtained at the end of polymerization is used as a latex as it is is preferred because a latex can be obtained easily.

[0047] <Latex composition / rubber composition> The latex composition according to this embodiment contains a chloroprene-based block copolymer. The rubber composition according to this embodiment is a rubber composition containing the above-described chloroprene-based block copolymer. Raw materials other than the chloroprene-based block copolymer are not particularly limited and can be appropriately selected depending on the purpose and application. Examples of raw materials that can be contained in the latex composition / rubber composition containing the chloroprene-based block copolymer include vulcanizing agents, vulcanization accelerators, fillers or reinforcing agents, plasticizers, processing aids, lubricants, antioxidants, and silane coupling agents. The rubber composition according to this embodiment can also be made from the above-described latex. The rubber composition according to this embodiment can also be made from a latex composition.

[0048] The latex composition or rubber composition of this embodiment may contain a vulcanizing agent or vulcanization accelerator. When the latex composition or rubber composition of this embodiment contains a vulcanizing agent and / or a vulcanization accelerator, the total content of the vulcanizing agent and vulcanization accelerator can be 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass, based on 100% by mass of the latex composition or rubber composition. However, the latex composition or rubber composition of this embodiment exhibits sufficient mechanical strength even without vulcanization. Therefore, from the perspectives of reducing allergies and reducing costs, those that do not contain a vulcanizing agent or vulcanization accelerator are preferred.

[0049] Antiaging agents are used to improve the heat resistance of rubber compositions. They include primary antioxidants, which trap radicals to prevent autoxidation, and secondary antioxidants, which neutralize hydroperoxides. These antioxidants can be added in amounts of 0.1 to 10 parts by mass, preferably 2 to 5 parts by mass, per 100 parts by mass of the latex component in the latex composition / rubber composition. These antioxidants can be used alone or in combinations of two or more. Examples of primary antioxidants include phenolic antioxidants, amine antioxidants, acrylate antioxidants, imidazole antioxidants, metal carbamates, and waxes. Examples of secondary antioxidants include phosphorus-based antioxidants, sulfur-based antioxidants, and imidazole-based antioxidants. Examples of antioxidants include, but are not limited to, N-phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamido)diphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, 1,1,3-tris-(2-methyl-4-hydroxypropyl)-p-phenylenediamine, hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis-(3-methyl-6-t-butylphenol), 2,2-thiobis(4-methyl-6-t-butylphenol), 7-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, pentaerythritol-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy)-hydrocinnamamide, 2,4-bis[(octylthio)methyl]-o-crylene azole, 3,5-di-t-butyl-4-hydroxybenzyl-phosphonate-diethyl ester, tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate ester and 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, tris(nonylphenyl)phosphite, thiazolinone, Tris(mixed mono- and di-nonylphenyl)phosphite, diphenyl mono(2-ethylhexyl)phosphite, diphenyl monotridecyl phosphite, diphenyl isodecyl phosphite, diphenyl isooctyl phosphite, diphenyl nonylphenyl phosphite, triphenyl phosphite, tris(tridecyl)phosphite, triisodecyl phosphite, tris(2-ethylhexyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, tetraphenyldipropyl Diethylene glycol diphosphite, tetraphenyltetra(tridecyl)pentaerythritol tetraphosphite, 1,1,3-tris(2-methyl-4-di-tridecylphosphite-5-t-butylphenyl)butane, 4,4'-butylidenebis-(3-methyl-6-t-butyl-di-tridecylphosphite), 2,2'-ethylidenebis(4,6-di-t-butylphenol)fluorophosphite, 4,4'-isopropylidene-diphenol alkyl (C12-C15) phosphite, cyclic neopentanetetraylbis(2,Examples include 4-di-t-butylphenyl phosphite), cyclic neopentanetetraylbis(2,6-di-t-butyl-4-phenyl phosphite), cyclic neopentanetetraylbis(nonylphenyl phosphite), bis(nonylphenyl)pentaerythritol diphosphite, dibutyl hydrogen phosphite, distearyl pentaerythritol diphosphite, hydrogenated bisphenol A pentaerythritol phosphite polymer, 2-mercaptobenzimidazole, and butylated reaction products of p-cresol and dicyclopentadiene.

[0050] The rubber composition can be produced in accordance with a conventional method using known machines and devices. [Example]

[0051] The present invention will be explained below by giving examples and comparative examples, but these are merely illustrative examples and do not limit the scope of the present invention.

[0052] Example 1 (Polymerization step 1) Synthesis of polymer block (A-1) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1119 g of styrene monomer, and 6.38 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 4.01 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2.

[0053] The sampled latex was mixed with a large amount of methanol to precipitate the resin, which was then filtered and dried to obtain a sample of polymer block (A-1). The number average molecular weight and molecular weight distribution of the polymer block (A-1) were determined from the obtained sample by analysis. The analysis results of the number average molecular weight are shown in Table 1. The molecular weight distribution was 1.43. The glass transition temperature of the polymer block (A-1) was confirmed to be 100°C. The measurement method will be described later.

[0054] (Polymerization step 2) Synthesis of chloroprene-based polymer block (B-1) After polymerization step 1, when the internal temperature had dropped to 45°C, 3198 g of chloroprene monomer and 65.3 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to carry out polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and the unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation.

[0055] The sampled latex was mixed with a large amount of methanol to precipitate the resin, which was then filtered and dried to obtain a chloroprene-based block copolymer sample. The obtained sample was analyzed to determine the contents (mass%) of the polymer block (A-1) and the chloroprene-based polymer block (B-1) of the chloroprene-based block copolymer. The analysis results are shown in Table 1. The measurement method will be described later.

[0056] Example 2 (Polymerization step 1) Synthesis of polymer block (A-2) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1733 g of styrene monomer, and 6.59 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 4.14 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-2) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0057] (Polymerization step 2) Synthesis of chloroprene-based polymer block (B-2) After polymerization step 1, when the internal temperature had dropped to 45°C, 2595 g of chloroprene monomer and 53.0 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for physical property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-2) and the chloroprene polymer block (B-2) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0058] Example 3 (Polymerization step 1) Synthesis of polymer block (A-3) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 2390 g of styrene monomer, and 6.81 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 4.29 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-3) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0059] (Polymerization step 3) Synthesis of chloroprene-based polymer block (B-3) After polymerization step 1, when the internal temperature had dropped to 45°C, 1952 g of chloroprene monomer and 39.8 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-3) and the chloroprene polymer block (B-3) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0060] Example 4 (Polymerization step 1) Synthesis of polymer block (A-4) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1119 g of styrene monomer, and 6.38 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. 4.01 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) was added as a polymerization initiator to initiate polymerization. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-4) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0061] (Polymerization step 4) Synthesis of chloroprene-based polymer block (B-4) After polymerization step 1, when the internal temperature dropped to 45°C, 3230 g of chloroprene monomer and 32.6 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for physical property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-4) and the chloroprene polymer block (B-4) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0062] Example 5 (Polymerization step 1) Synthesis of polymer block (A-5) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1113 g of styrene monomer, and 28.5 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 18.0 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-5) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0063] (Polymerization step 5) Synthesis of chloroprene-based polymer block (B-5) After polymerization step 1, when the internal temperature dropped to 45°C, 3182 g of chloroprene monomer and 64.9 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for physical property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-5) and the chloroprene polymer block (B-5) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0064] Example 6 (Polymerization step 1) Synthesis of polymer block (A-6) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1120 g of styrene monomer, and 2.87 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 1.81 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-6) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0065] (Polymerization step 6) Synthesis of chloroprene-based polymer block (B-6) After polymerization step 1, when the internal temperature had dropped to 45°C, 3200 g of chloroprene monomer and 65.31 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine (a polymerization terminator), and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-6) and the chloroprene polymer block (B-6) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0066] Example 7 (Polymerization step 1) Synthesis of polymer block (A-7) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1119 g of styrene monomer, and 6.38 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. 4.01 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) was added as a polymerization initiator to initiate polymerization. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-7) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0067] (Polymerization step 7) Synthesis of chloroprene-based polymer block (B-7) After polymerization step 1, when the internal temperature had dropped to 45°C, 3198 g of chloroprene monomer and 65.3 g of 1,9-nonanediol dimethacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-7) and the chloroprene polymer block (B-7) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0068] Example 8 (Polymerization step 1) Synthesis of polymer block (A-8) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1119 g of styrene monomer, and 6.37 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 4.01 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-8) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0069] (Polymerization step 8) Synthesis of chloroprene-based polymer block (B-8) After the polymerization step 1, when the internal temperature had dropped to 45°C, 3198 g of chloroprene monomer and 65.3 g of divinylbenzene were slowly added over 2 hours to carry out polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for physical property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-8) and the chloroprene polymer block (B-8) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0070] Example 9 (Polymerization step 1) Synthesis of polymer block (A-9) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1119 g of methyl methacrylate monomer, and 6.37 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. 4.01 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) was added as a polymerization initiator to initiate polymerization. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-9) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0071] (Polymerization step 9) Synthesis of chloroprene-based polymer block (B-9) After polymerization step 1, when the internal temperature had dropped to 45°C, 3198 g of chloroprene monomer and 65.3 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-9) and the chloroprene polymer block (B-9) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0072] Example 10 (Polymerization step 1) Synthesis of polymer block (A-10) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1112 g of styrene monomer, and 31.7 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 19.9 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-10) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0073] (Polymerization step 10) Synthesis of chloroprene-based polymer block (B-10) After polymerization step 1, when the internal temperature had dropped to 45°C, 3179 g of chloroprene monomer and 64.9 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-10) and the chloroprene polymer block (B-10) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0074] (Comparative Example 1) (Polymerization step 1) Synthesis of polymer block (A-11) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 731 g of styrene monomer, and 5.00 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 3.14 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-11) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0075] (Polymerization step 11) Synthesis of chloroprene-based polymer block (B-11) After polymerization step 1, when the internal temperature had dropped to 45°C, 3580 g of chloroprene monomer and 73.1 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-11) and the chloroprene polymer block (B-11) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0076] (Comparative Example 2) (Polymerization step 1) Synthesis of polymer block (A-12) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 2853 g of styrene monomer, and 6.97 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. Polymerization was initiated by adding 4.38 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) as a polymerization initiator. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-12) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0077] (Polymerization step 12) Synthesis of chloroprene-based polymer block (B-12) After polymerization step 1, when the internal temperature had dropped to 45°C, 1498 g of chloroprene monomer and 30.6 g of 1,9-nonanediol diacrylate were slowly added over 2 hours to conduct polymerization. When the polymerization rate of the chloroprene monomer reached 80%, the polymerization was terminated by adding a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, and unreacted chloroprene monomer was removed by vacuum distillation. A 20 ml sample of the resulting latex was taken for physical property measurement, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-12) and the chloroprene polymer block (B-12) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0078] (Comparative Example 3) (Polymerization step 1) Synthesis of polymer block (A-13) Polymerization was carried out in a 10 L autoclave equipped with a stirrer and a heating / cooling jacket. 4666 g of purified water, 224 g of disproportionated potassium rosinate (Harima Chemicals Group Co., Ltd.), 36.4 g of potassium hydroxide, 18.7 g of sodium salt of β-naphthalenesulfonic acid formalin condensate (Kao Corporation, product name: Demol N), 1119 g of styrene monomer, and 6.38 g of butylbenzyl trithiocarbonate were charged. The internal temperature was raised to 80 °C and the mixture was stirred at 200 rpm under a nitrogen stream. 4.01 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrogen chloride (Fujifilm Wako Pure Chemical Industries, Ltd., product name: VA-044) was added as a polymerization initiator to initiate polymerization. A 20 ml sample of the resulting latex was taken for property measurements, and the remaining latex was used in polymerization step 2. The number average molecular weight of the polymer block (A-13) was determined by analysis in the same manner as in Example 1. The analysis results are shown in Table 1.

[0079] (Polymerization step 13) Synthesis of chloroprene-based polymer block (B-13) After the polymerization step 1, when the internal temperature had dropped to 45°C, 3263 g of chloroprene monomer was slowly added over 2 hours to carry out polymerization. When the polymerization rate of the chloroprene monomer reached 80%, a 10 wt% aqueous solution of N,N-diethylhydroxylamine, a polymerization terminator, was added to terminate the polymerization, and unreacted chloroprene monomer was removed by vacuum distillation. For property measurement, 20 ml of the obtained latex was sampled, and the remaining latex was used to prepare a film for evaluation. The contents (mass%) of the polymer block (A-13) and the chloroprene polymer block (B-13) of the chloroprene-based block copolymer were determined by analysis in the same manner as in Example 1. The analytical results are shown in Table 1.

[0080] [analysis] (Measurement of number average molecular weight and molecular weight distribution of polymer block (A)) The number average molecular weight and molecular weight distribution are values ​​measured by gel permeation chromatography (GPC) in terms of polystyrene under the measurement conditions described below. Device name: HLC-8320 (Tosoh Corporation) Column: Three TSKgel GMHHR-H columns in series Temperature: 40℃ Detection: Differential refractive index Solvent: tetrahydrofuran Calibration curve: Prepared using standard polystyrene (PS).

[0081] (Glass transition temperature of polymer block (A)) The glass transition temperature was measured using a differential scanning calorimeter in accordance with JIS K 7121 by the following method. Device name: DSC1 (Mettler Toledo) Procedure: Under a nitrogen flow of 50 ml / min, the sample was heated to 120°C at a rate of 10°C / min, kept at 120°C for 10 minutes, then cooled to -60°C, and heated to 120°C at a rate of 10°C / min. The DSC curve obtained was used to determine the glass transition temperature, which was the temperature at the intersection of a straight line extending the base line on the high temperature side toward the low temperature side and a tangent line drawn at the point where the slope of the curve on the high temperature side of the peak is maximum.

[0082] (Measurement of the content of polymer block (A) and chloroprene-based polymer block (B) in chloroprene-based block copolymer) Measurements were carried out using pyrolysis gas chromatogram and 1H-NMR as follows. Pyrolysis Gas Chromatogram Instrument name: HP5890-II Column: DB-5 0.25 mm diameter x 30 m (film thickness 1.0 μm) Column temperature: 50°C (5 min) → 10°C / min → 150°C → 25°C / min → 300°C Inlet temperature: 250℃ Detector temperature: 280℃ Detector: FID 1H-NMR instrument name: JNM-ECX-400 (manufactured by JEOL Ltd.) Procedure: A chloroprene-based block copolymer consisting of polymer block (A) and a chloroprene-based polymer block (B) containing no polyfunctional monomer units was measured by pyrolysis gas chromatography, and a calibration curve was prepared from the area ratio of the peak derived from polymer block (A) to the peak derived from chloroprene-based polymer block (B) and the contents of polymer block (A) and chloroprene-based polymer block (B) in the chloroprene-based block copolymer obtained by 1H-NMR measurement. The sampled latex was mixed with methanol to precipitate a chloroprene-based block copolymer sample, which was then measured by pyrolysis gas chromatography. The contents of polymer block (A) and chloroprene-based polymer block (B) in the chloroprene-based block copolymer were determined from the area ratio of the peak derived from polymer block (A) to the peak derived from chloroprene-based polymer block (B) using the calibration curve prepared above.

[0083] [Preparation of samples for tensile tests] (Preparation of latex containing chloroprene-based block copolymer) To 100 parts by mass (solid content equivalent) of the chloroprene-based block copolymer in the latex obtained in polymerization step 2, 2 parts by mass of a butylated compound of ρ-cresol and dicyclopentadiene condensate (Nocrac PBK manufactured by Ouchi Shinko Chemical Co., Ltd.) as an anti-aging agent, 0.3 parts by mass of sodium lauryl sulfate (trade name "EMAL 10" manufactured by Kao Corporation), and water were added to adjust the solid content concentration of the blend to 30% by mass, and the mixture was mixed at 20°C for 16 hours using a ceramic ball mill to prepare the blend. (Film Preparation) A ceramic cylinder with an outer diameter of 50 mm was immersed for 1 second 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, and then removed. After drying for 4 minutes, it was immersed in the latex prepared above for 2 minutes. It was then washed with running water at 45°C for 1 minute and heat-treated at 130°C for 30 minutes to remove moisture, producing a film (140 x 150 mm, thickness: 0.2 mm) for tensile testing.

[0084] [Evaluation of tensile properties] The prepared film was heat-treated at 130°C for 30 minutes, and then the modulus at 25% elongation, tensile strength at break and elongation at break were measured in accordance with JIS K 6251, and each was evaluated according to the following criteria. (Tensile strength at break) ◎◎: 32 MPa or more ◎:30MPa or more ○: Over 25 MPa, under 30 MPa △:20MPa or more, 25MPa or less ×: Less than 20 MPa (elongation at break) ◎: 800% or more ○: 600% or more, less than 800% △: 450% or more, less than 600% ×: Less than 450% (Modulus at 25% elongation) ◎: Over 5.0 MPa ○: 2.5 MPa or more, 5.0 MPa or less △: 1.0 MPa or more, less than 2.5 MPa ×: Less than 1.0 MPa A modulus at 25% elongation of 2.5 MPa or more, a tensile strength at break of 20 MPa or more, and an elongation at break of 450% or more were deemed acceptable.

[0085] [Table 1]

Claims

1. A chloroprene-based block copolymer comprising 30 to 60% by mass of a polymer block (A) derived from a monomer that, upon homopolymerization, gives a polymer having a glass transition temperature of 80°C or higher, and 40 to 70% by mass of a chloroprene-based polymer block (B) having a chloroprene monomer unit and a polyfunctional monomer unit, The polyfunctional monomer has at least one set of polymerizable substituents that are non-conjugated, The chloroprene-based block copolymer, wherein the content of the polyfunctional monomer unit in the chloroprene-based polymer block (B) is 0.05 to 10.00 mass %.

2. 2. The chloroprene block copolymer according to claim 1, wherein a molded article of a latex composition containing the chloroprene block copolymer has a 25% modulus of 2.5 MPa or more as measured in accordance with JIS K 6251 after heat-treating the molded article of the latex composition at 130°C for 30 minutes.

3. 2. The chloroprene-based block copolymer according to claim 1, wherein a molded article of a latex composition containing the chloroprene-based block copolymer has a tensile strength at break of 20 MPa or more as measured in accordance with JIS K 6251 after heat-treating the molded article of the latex composition at 130°C for 30 minutes.

4. 3. The chloroprene block copolymer according to claim 1, wherein the polymer block (A) has a number average molecular weight of 10,000 or more.

5. 3. The chloroprene-based block copolymer according to claim 1, wherein the molecular weight distribution of the polymer block (A) is 2.0 or less.

6. 3. The chloroprene block copolymer according to claim 1, wherein the polymer block (A) is a polymer block comprising an aromatic vinyl monomer unit.

7. 3. The chloroprene-based block copolymer according to claim 1, wherein the polyfunctional monomer is a monomer represented by chemical formula (1) or an aromatic polyene monomer. 【Chemistry 1】 (In chemical formula (1), R １ and R ２ each independently represents hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, or a substituted or unsubstituted heterocyclyl group. １ represents a saturated or unsaturated hydrocarbon group, a saturated or unsaturated cyclic hydrocarbon group, a saturated or unsaturated hydrocarbon group containing a hetero atom, or a saturated or unsaturated cyclic hydrocarbon group containing a hetero atom. １ is oxygen, sulfur or -NR ０ represents a structure represented by R ０ represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, and a substituted or unsubstituted heterocyclyl group.

8. The chloroprene-based block copolymer according to claim 1 or 2, which has a functional group having a structure represented by chemical formula (2) or chemical formula (3). 【Chemistry 2】 (In chemical formula (2), R ３ represents any one of hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted mercapto group, and a substituted or unsubstituted heterocyclyl group. 【Transformation 3】

9. A latex comprising the chloroprene-based block copolymer according to claim 1 or 2.

10. A latex composition comprising 100 parts by mass of the latex according to claim 9 and 0.5 to 5.0 parts by mass of an antioxidant.

11. A rubber composition comprising the chloroprene-based block copolymer according to claim 1 or 2.

12. A rubber composition comprising the latex according to claim 9.

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