To provide a block copolymer that includes an aromatic vinyl compound polymer and a chloroprene polymer, has a number average molecular weight of 100,000 or more, is preferred for a rubber composition and an adhesive composition, and is suitable for industrial production. A block copolymer includes at least one aromatic vinyl compound polymer block and at least one chloroprene polymer block, has a functional group with a structure represented by Chemical Formula (1) or (2), and has a number average molecular weight of 100,000 or more. The chloroprene polymer block has a number average molecular weight of 80,000 or more in total. ##STR00001##
(In Chemical Formula (1), R.sup.1 is hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclyl group.)

A sulfur-modified chloroprene polymer latex includes an emulsifier and a sulfur-modified chloroprene polymer obtained by modifying a chloroprene polymer (A) with sulfur (B), wherein the sulfur amount Y in the sulfur-modified chloroprene polymer and the z-average particle size X of the sulfur-modified chloroprene polymer satisfy formulae (1) to (3) (formula (1): 0.10<Y<0.60; formula (2): 120<X<320; and formula (3): Y<0.0025X−0.20), the total amount of a chloroprene monomer (A-1) and a monomer (A-2) copolymerizable with the chloroprene monomer which constitute the chloroprene polymer is 100 parts by mass, the amount of sulfur (B) contained in the sulfur-modified chloroprene polymer is Y parts by mass, and the z-average particle size of the sulfur-modified chloroprene polymer is X nm. The sulfur-modified chloroprene polymer latex composition can also include a metal oxide (C), a cross-linking accelerator (D), and an antioxidant (E).

A sulfur-modified chloroprene polymer latex includes an emulsifier and a sulfur-modified chloroprene polymer obtained by modifying a chloroprene polymer (A) with sulfur (B), wherein the sulfur amount Y in the sulfur-modified chloroprene polymer and the z-average particle size X of the sulfur-modified chloroprene polymer satisfy formulae (1) to (3) (formula (1): 0.10<Y<0.60; formula (2): 120<X<320; and formula (3): Y<0.0025X−0.20), the total amount of a chloroprene monomer (A-1) and a monomer (A-2) copolymerizable with the chloroprene monomer which constitute the chloroprene polymer is 100 parts by mass, the amount of sulfur (B) contained in the sulfur-modified chloroprene polymer is Y parts by mass, and the z-average particle size of the sulfur-modified chloroprene polymer is X nm. The sulfur-modified chloroprene polymer latex composition can also include a metal oxide (C), a cross-linking accelerator (D), and an antioxidant (E).

A chloroprene-unsaturated nitrile copolymer composition containing 100 parts by mass of a chloroprene-unsaturated nitrile copolymer having 3 to 20% by mass of a structural unit derived from an unsaturated nitrile monomer, and 0.05 to 2.0 parts by mass of a xanthogen compound.

A method for producing a chloroprene-based polymer latex which can efficiently remove a residual volatile organic substance from the chloroprene-based polymer latex while suppressing the deposition of agglomerates is provided. In the method for producing a chloroprene-based polymer latex of the present invention, when the residual volatile organic substance comprised in the latex is volatilized and removed, a mixed fluid of one or more gases selected from the group consisting of inert gases and air, and water is contacted with the latex at a gas pressure higher than the saturated water vapor pressure, and a temperature of the mixed fluid is a temperature lower than a boiling point of water at the gas pressure.

A method for producing a chloroprene-based polymer latex which can efficiently remove a residual volatile organic substance from the chloroprene-based polymer latex while suppressing the deposition of agglomerates is provided. In the method for producing a chloroprene-based polymer latex of the present invention, when the residual volatile organic substance comprised in the latex is volatilized and removed, a mixed fluid of one or more gases selected from the group consisting of inert gases and air, and water is contacted with the latex at a gas pressure higher than the saturated water vapor pressure, and a temperature of the mixed fluid is a temperature lower than a boiling point of water at the gas pressure.

There is provided an adhesive agent exhibiting high adhesive strength to polyolefin. An adhesive agent contains a chloroprene copolymer latex containing a chloroprene copolymer (A) and a metal oxide (B). The chloroprene copolymer (A) is a copolymer of a monomer group containing chloroprene (A-1), α,β-unsaturated carboxylic acid (A-2), and 2,3-dichloro-1,3-butadiene (A-3). The chloroprene copolymer (A) has a tetrahydrofuran-soluble component soluble in tetrahydrofuran and the weight average molecular weight of the tetrahydrofuran-soluble component is 80000 or more and 140000 or less. When the amount of the metal oxide (B) based on 100 parts by mass of the chloroprene copolymer (A) is defined as Y part(s) by mass and the weight average molecular weight of the tetrahydrofuran-soluble component is defined as X, the content of the metal oxide (B) satisfies Formula: −1.2×X/100000+1.6<Y<−4.2×X/100000+5.7.

There is provided an adhesive agent exhibiting high adhesive strength to polyolefin. An adhesive agent contains a chloroprene copolymer latex containing a chloroprene copolymer (A) and a metal oxide (B). The chloroprene copolymer (A) is a copolymer of a monomer group containing chloroprene (A-1), α,β-unsaturated carboxylic acid (A-2), and 2,3-dichloro-1,3-butadiene (A-3). The chloroprene copolymer (A) has a tetrahydrofuran-soluble component soluble in tetrahydrofuran and the weight average molecular weight of the tetrahydrofuran-soluble component is 80000 or more and 140000 or less. When the amount of the metal oxide (B) based on 100 parts by mass of the chloroprene copolymer (A) is defined as Y part(s) by mass and the weight average molecular weight of the tetrahydrofuran-soluble component is defined as X, the content of the metal oxide (B) satisfies Formula: −1.2×X/100000+1.6<Y<−4.2×X/100000+5.7.

A rubber composition from which a vulcanized rubber simultaneously improved in three characteristics of oil resistance, cold resistance and ozone resistance can be obtained, and a molded article using the vulcanized rubber are provided. The rubber composition contains 50 to 99 parts by mass of a chloroprene rubber containing 0.01 to 20% by mass of an unsaturated nitrile monomer unit and 1 to 50 parts by mass of a non-conjugated diene rubber.

A rubber composition from which a vulcanized rubber simultaneously improved in three characteristics of oil resistance, cold resistance and ozone resistance can be obtained, and a molded article using the vulcanized rubber are provided. The rubber composition contains 50 to 99 parts by mass of a chloroprene rubber containing 0.01 to 20% by mass of an unsaturated nitrile monomer unit and 1 to 50 parts by mass of a non-conjugated diene rubber.