JP7682197B2 - Foamed rubber composition, foam and molded article - Google Patents

Description

The present invention relates to foamed rubber compositions, foams, molded articles, etc.

Taking advantage of its excellent dynamic properties, chloroprene rubber is used as a material for general industrial power transmission belts or conveyor belts, automotive air springs, anti-vibration rubber, etc. In addition, it is possible to obtain chloroprene rubber foam (chloroprene rubber sponge) by mixing chloroprene rubber with a foaming agent and heating it to foam, and chloroprene rubber foam is used in a variety of fields such as automotive parts, construction, and leisure goods.

Known examples of chloroprene rubber foams include foams obtained by blending chloroprene rubber with an organic peroxide, a foaming agent, a softener, a filler, and a reinforcing agent, and then heating and foaming the mixture (see, for example, Patent Document 1 below); and foams obtained by blending chloroprene rubber with butadiene rubber, a softener, and a foaming agent, and then vulcanizing the mixture without pressure and allowing it to foam (see, for example, Patent Document 2 below).

JP 2012-067235 A Japanese Patent Application Publication No. 10-298328

Chloroprene rubber foam is a material that has voids, and so has the problem of insufficient tear strength. For example, the techniques described in the above-mentioned Patent Documents 1 and 2 produce foams with high expansion ratios, but the tear strength of the foams is low. For this reason, there is a demand for the development of foams that can be used in applications requiring high tear strength (such as wetsuits).

In addition, because chloroprene rubber foam is a material that has voids, there is a problem that it shrinks over time. For this reason, there is a demand for the development of a foam rubber composition that uses chloroprene rubber and that gives a foam with high tear strength and low shrinkage.

One aspect of the present invention aims to provide a foamed rubber composition that can give a foam having high tear strength and small shrinkage. Another aspect of the present invention aims to provide a foam of the foamed rubber composition. Another aspect of the present invention aims to provide a molded article made of the foam.

As a result of intensive research conducted by the inventors of the present application to solve these problems, they have completed a foamed rubber composition that can produce foams with high tear strength and small shrinkage by introducing a specific structure to the molecular end of sulfur-modified chloroprene rubber and using a specific amount of a chemical foaming agent.

One aspect of the present invention provides a foamed rubber composition comprising a sulfur-modified chloroprene rubber and a chemical foaming agent, wherein the sulfur-modified chloroprene rubber has a functional group A represented by the following general formula (A) and located at a molecular end, and in the sulfur-modified chloroprene rubber, a mass ratio B/A of a content of a functional group B represented by the following general formula (B) and located at a molecular end to a content of the functional group A is 6.00 or less, a total amount of the functional groups A and B is 0.10 to 0.60 mass%, and a content of the chemical foaming agent is 3 to 16 parts by mass per 100 parts by mass of the total of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide.
(In the formula, R ^a1 and R ^a2 each independently represent a hydrogen atom, a halogen atom, a hydroxy group, an alkoxy group, a carboxy group, a carboxylate group, a cyano group, an alkyl group which may have a substituent, or an arylthio group which may have a substituent, and R ^a1 and R ^a2 may be bonded to each other to form a ring which may have a substituent.)
(In the formula, R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent.)

According to one aspect of the foamed rubber composition of the present invention, a foam having high tear strength and low shrinkage rate can be obtained.

Another aspect of the present invention provides a foam of the foamed rubber composition described above. Another aspect of the present invention provides a molded article made of the foam.

According to one aspect of the present invention, it is possible to provide a foamed rubber composition that can give a foam having high tear strength and small shrinkage. According to another aspect of the present invention, it is possible to provide a foam of the foamed rubber composition. According to another aspect of the present invention, it is possible to provide a molded article made of the foam (a molded article using the foam).

The following describes the mode for carrying out the present invention. The embodiment described below is an example of a typical embodiment of the present invention, and the scope of the present invention is not to be interpreted narrowly by this.

In this specification, the numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum and maximum values, respectively. "A or more" in the numerical range means a range exceeding A and A. "A or less" in the numerical range means a range less than A and A. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage. In the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more types. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. "Alkyl group" may be linear, branched, or cyclic, unless otherwise specified.

<Foamed Rubber Composition>
The foamed rubber composition according to the present embodiment contains a sulfur-modified chloroprene rubber and a chemical foaming agent, the sulfur-modified chloroprene rubber has a functional group A (hereinafter referred to as "terminal functional group A") which is represented by the following general formula (A) and is located at a molecular terminal, the sulfur-modified chloroprene rubber has a mass ratio B/A of a content of a functional group B (hereinafter referred to as "terminal functional group B") which is represented by the following general formula (B) and is located at a molecular terminal to a content of the terminal functional group A of 6.00 or less, the total amount of the terminal functional group A and the terminal functional group B is 0.10 to 0.60 mass%, and the content of the chemical foaming agent is 3 to 16 parts by mass per 100 parts by mass of the total of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide.

(In the formula, R ^a1 and R ^a2 each independently represent a hydrogen atom, a halogen atom, a hydroxy group, an alkoxy group, a carboxy group, a carboxylate group, a cyano group, an alkyl group which may have a substituent, or an arylthio group which may have a substituent. ^{R a1} and R ^a2 may be the same as or different from each other. R ^a1 and R ^a2 may be bonded to each other to form a ring which may have a substituent. R ^a1 and R ^a2 can be bonded to each other to form a ring which has a substituent or a ring which has no substituent.)

(In the formula, R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent.)

A foam can be obtained by foaming the foamed rubber composition (foamable rubber composition) according to this embodiment. According to the foamed rubber composition according to this embodiment, it is possible to obtain a foam having high tear strength and small shrinkage (shrinkage of the foam immediately after preparation) as a foam obtained by foaming the foamed rubber composition, and in the evaluation of the examples described later, a tear strength of 2.00 N/mm or more (preferably, 3.00 N/mm or more or 4.00 N/mm or more) and a shrinkage of less than 5.5% (preferably, 5.4% or less or 5.3% or less) can be obtained. Furthermore, according to one aspect of the foamed rubber composition according to this embodiment, in addition to having high tear strength and small shrinkage, a foam having excellent appearance can be obtained.

The sulfur-modified chloroprene rubber is a polymer having structural units derived from chloroprene (2-chloro-1,3-butadiene). The sulfur-modified chloroprene rubber contains sulfur atoms in the molecular chain and may contain sulfur atoms in the main chain. The sulfur-modified chloroprene rubber may contain polysulfide bonds (S ₂ to S ₈ ) in the molecular chain and may contain polysulfide bonds (S ₂ to S ₈ ) in the main chain.

The sulfur-modified chloroprene rubber may have structural units derived from a monomer copolymerizable with chloroprene. Examples of monomers copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid, methacrylic acid, and esters thereof. The monomers copolymerizable with chloroprene may be used alone or in combination of two or more.

Among the monomers that can be copolymerized with chloroprene, for example, the use of 2,3-dichloro-1,3-butadiene can slow the crystallization rate of the resulting sulfur-modified chloroprene rubber. Sulfur-modified chloroprene rubber with a slow crystallization rate can maintain rubber elasticity even in low-temperature environments, and can improve low-temperature compression set, for example.

When a monomer copolymerizable with chloroprene is used, the amount of the monomer copolymerizable with chloroprene (the content of the structural unit derived from the monomer copolymerizable with chloroprene) is preferably 10% by mass or less of the total monomers including chloroprene (the total amount of the structural units constituting the sulfur-modified chloroprene rubber). If the amount is 10% by mass or less, it is easy to suppress the deterioration of the processability of the obtained sulfur-modified chloroprene rubber. From the same viewpoint, the amount of chloroprene used (the content of the structural unit derived from chloroprene) is preferably 90% by mass or more, 92% by mass or more, 95% by mass or more, or 98% by mass or more of the total monomers including chloroprene (the total amount of the structural units constituting the sulfur-modified chloroprene rubber). The structural units constituting the sulfur-modified chloroprene rubber may be composed of structural units derived from chloroprene (substantially 100% by mass of the structural units constituting the sulfur-modified chloroprene rubber are structural units derived from chloroprene).

In the sulfur-modified chloroprene rubber, the terminal functional group A may be located at the end of the main chain and/or the side chain. The terminal functional group A can be obtained, for example, by using a thiazole compound in the molecular weight adjustment step described later. Examples of the substituent for the alkyl group R ^a1 or R ^a2 include a halogen atom, a hydroxy group, an alkoxy group, a carboxy group, a carboxylate group, a cyano group, a sulfo group, a sulfonate group, a nitro group, and an amino group. Examples of the substituent for the arylthio group ^{R a1} or R ^a2 include an alkyl group, a halogen atom, a hydroxy group, an alkoxy group, a carboxy group, a carboxylate group, a cyano group, a sulfo group, a sulfonate group, a nitro group, and an amino group.

In the terminal functional group A, R ^a1 and R ^a2 may be bonded to each other to form a ring which may have a substituent. Examples of the ring include an aromatic ring, an alicyclic ring, and a heterocyclic ring. Examples of the substituent for the ring include an alkyl group, a halogen atom, a hydroxy group, an alkoxy group, a carboxy group, a carboxylate group, a cyano group, a sulfo group, a sulfonate group, a nitro group, and an amino group. Examples of the alkyl group which is a substituent for the ring include an alkyl group having 1, 2, 3, or 4 carbon atoms. The terminal functional group A preferably has a benzothiazole ring formed by bonding R ^a1 and R ^a2 to each other, from the viewpoint of easily improving the tear strength, easily reducing the shrinkage rate, and easily obtaining an excellent appearance in a foam. The benzothiazole ring may not have a substituent. When the benzothiazole ring has a substituent, the substituent is preferably an alkyl group, and more preferably an alkyl group bonded to the 4th position of the benzothiazole ring, from the viewpoint of easily improving the tear strength, easily reducing the shrinkage rate, and easily obtaining an excellent appearance in a foam.

The sulfur-modified chloroprene rubber may have a terminal functional group B, or may not have a terminal functional group B. The terminal functional group B may be located at the end of the main chain and/or the side chain. The terminal functional group B can be obtained, for example, by using an alkyl xanthogen disulfide in the molecular weight adjustment step described below. Examples of the substituent for the alkyl group represented by R ^b include a halogen atom, a hydroxy group, an alkoxy group, a carboxyl group, a cyano group, a sulfo group, a sulfonate group, a nitro group, and an amino group. The alkyl group represented by R ^b may not have a substituent.

From the viewpoints of easily improving the tear strength, easily reducing the shrinkage rate, and easily obtaining an excellent appearance in a foam, R ^b is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and still more preferably an alkyl group having 2 or 3 carbon atoms.

The content of terminal functional group A is preferably in the following range based on the total amount of the sulfur-modified chloroprene rubber (i.e., the sulfur-modified chloroprene rubber preferably contains the terminal functional group A in the following numerical content (unit: parts by mass) per 100 parts by mass of the sulfur-modified chloroprene rubber): From the viewpoint of easily improving tear strength and easily obtaining an excellent appearance in the foam, the content of the terminal functional group A is preferably 0.50% by mass or less, 0.45% by mass or less, 0.42% by mass or less, 0.40% by mass or less, 0.38% by mass or less, 0.35% by mass or less, 0.30% by mass or less, 0.25% by mass or less, 0.23% by mass or less, 0.20% by mass or less, 0.18% by mass or less, 0.16% by mass or less, 0.15% by mass or less, 0.14% by mass or less, 0.13% by mass or less, 0.12% by mass or less, 0.11% by mass or less, 0.10% by mass or less, 0.09% by mass or less, 0.08% by mass or less, 0.07% by mass or less, 0.06% by mass or less, 0.05% by mass or less, or 0.04% by mass or less. From the viewpoint of easily reducing the shrinkage rate and easily obtaining an excellent appearance in the foam, the content of the terminal functional group A is preferably 0.01% by mass or more, 0.03% by mass or more, 0.04% by mass or more, 0.05% by mass or more, 0.06% by mass or more, 0.07% by mass or more, 0.08% by mass or more, 0.09% by mass or more, 0.10% by mass or more, 0.11% by mass or more, 0.12% by mass or more, 0.13% by mass or more, 0.14% by mass or more, 0.15% by mass or more, 0.16% by mass or more, 0.18% by mass or more, 0.20% by mass or more, 0.23% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.38% by mass or more, 0.40% by mass or more, or 0.42% by mass or more. From these viewpoints, the content of the terminal functional group A is preferably 0.01 to 0.50% by mass, 0.04 to 0.42% by mass, 0.04 to 0.40% by mass, 0.04 to 0.30% by mass, 0.04 to 0.20% by mass, 0.04 to 0.10% by mass, 0.05 to 0.42% by mass, 0.10 to 0.42% by mass, 0.20 to 0.42% by mass, 0.30 to 0.42% by mass, 0.05 to 0.40% by mass, or 0.08 to 0.30% by mass. The content of the terminal functional group A can be adjusted by the amount of the thiazole compound used in the molecular weight adjustment step described below, the treatment time and treatment temperature of the molecular weight adjustment step, and the like.

The content of the terminal functional group B is not particularly limited, but is preferably in the following range based on the total amount of the sulfur-modified chloroprene rubber (i.e., it is preferable that the sulfur-modified chloroprene rubber contains the terminal functional group B in the following numerical content (unit: mass parts) per 100 parts by mass of the sulfur-modified chloroprene rubber). From the viewpoint of easily improving the tear strength and easily obtaining an excellent appearance in the foam, the content of the terminal functional group B is preferably 0.50 mass% or less, 0.45 mass% or less, 0.43 mass% or less, 0.40 mass% or less, 0.35 mass% or less, 0.30 mass% or less, 0.28 mass% or less, 0.25 mass% or less, or 0.23 mass% or less. From the viewpoint of easily reducing the shrinkage rate and easily obtaining an excellent appearance in the foam, the content of the terminal functional group B is preferably 0.21% by mass or less, 0.20% by mass or less, 0.17% by mass or less, 0.16% by mass or less, 0.15% by mass or less, 0.14% by mass or less, 0.13% by mass or less, 0.12% by mass or less, 0.10% by mass or less, 0.09% by mass or less, 0.07% by mass or less, 0.06% by mass or less, 0.05% by mass or less, 0.03% by mass or less, or 0.01% by mass or less. The content of the terminal functional group B may be 0% by mass or more, and may exceed 0% by mass. The content of the terminal functional group B is preferably 0.01% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.06% by mass or more, 0.07% by mass or more, 0.09% by mass or more, 0.10% by mass or more, or 0.12% by mass or more, from the viewpoint of easily reducing the shrinkage rate and easily obtaining an excellent appearance in the foam. The content of the terminal functional group B is preferably 0.13% by mass or more, 0.14% by mass or more, 0.15% by mass or more, 0.16% by mass or more, 0.17% by mass or more, 0.20% by mass or more, 0.21% by mass or more, 0.23% by mass or more, 0.25% by mass or more, or 0.28% by mass or more, from the viewpoint of easily improving the tear strength and easily obtaining an excellent appearance in the foam. The content of the terminal functional group B may be 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, or 0.43% by mass or more. From these viewpoints, the content of the terminal functional group B is preferably 0 to 0.50% by mass, more than 0% by mass and 0.50% by mass or less, 0 to 0.43% by mass, 0 to 0.40% by mass, more than 0% by mass and 0.40% by mass or less, more than 0% by mass and 0.30% by mass or less, more than 0% by mass and 0.20% by mass or less, more than 0% by mass and 0.10% by mass or less, 0.01 to 0.40% by mass, 0.05 to 0.40% by mass, 0.10 to 0.40% by mass, 0.20 to 0.40% by mass, or 0.10 to 0.30% by mass. The content of the terminal functional group B can be adjusted by the amount of alkyl xanthogen disulfide used in the molecular weight adjustment step described below, the treatment time and treatment temperature of the molecular weight adjustment step, etc.

The mass ratio B/A of the content of terminal functional group B to the content of terminal functional group A is 6.00 or less (0 to 6.00) from the viewpoint of obtaining a small shrinkage rate in the foam.

From the viewpoint of easily obtaining a small shrinkage rate in the foam, the mass ratio B/A is preferably 5.75 or less, 5.50 or less, 5.00 or less, 4.70 or less, 4.50 or less, 4.00 or less, 3.50 or less, 3.00 or less, 2.50 or less, 2.00 or less, 1.50 or less, 1.00 or less, 0.90 or less, 0.50 or less, 0.40 or less, 0.35 or less, 0.30 or less, 0.29 or less, 0.25 or less, 0.20 or less, or 0.10 or less. The mass ratio B/A may be 0 or more, or may exceed 0. From the viewpoint of adjusting the balance between tear strength and shrinkage rate in the foam, the mass ratio B/A may be 0.10 or more, 0.20 or more, 0.25 or more, 0.29 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.50 or more, 0.90 or more, 1.00 or more, 1.50 or more, 2.00 or more, 2.50 or more, 3.00 or more, 3.50 or more, 4.00 or more, 4.50 or more, 4.70 or more, 5.00 or more, 5.50 or more, or 5.75 or more. From these viewpoints, the mass ratio B / A is more than 0 and not more than 6.00, 0.10 to 6.00, 0.20 to 6.00, 0.30 to 6.00, 0.50 to 6.00, 1.00 to 6.00, 2.00 to 6.00, 3.00 to 6.00, 4.00 to 6.00, 0.10 to 5.00, 0.10 to 4.00, 0.10 to 3.00, 0.10 to 2.00, 0.10 to 1.00, 0.10 to 0.50, 0.10 to 0.30, 0.20 to 5.00, 0.20 to 4.00, 0.20 to 2.00, or 0.20 to 1.00 is preferable.

The total amount of terminal functional group A and terminal functional group B (total content of terminal functional group A and terminal functional group B; total mass (A+B)) is 0.10 to 0.60 mass% based on the total amount of sulfur-modified chloroprene rubber. If the total mass (A+B) is less than 0.10 mass%, the foam will have an increased shrinkage rate and will not have an excellent appearance. If the total mass (A+B) exceeds 0.60 mass%, the Mooney viscosity will decrease significantly and the foam will not be practical (no foam will be obtained).

The total mass (A+B) is preferably in the following range based on the total amount of the sulfur-modified chloroprene rubber. From the viewpoint of easily reducing the shrinkage rate in the foam, the total mass (A+B) is preferably 0.15% by mass or more, 0.19% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.27% by mass or more, 0.28% by mass or more, 0.29% by mass or more, 0.30% by mass or more, 0.32% by mass or more, 0.34% by mass or more, or 0.35% by mass or more. From the viewpoint of adjusting the balance between the tear strength and the shrinkage rate in the foam, the total mass (A+B) may be 0.40% by mass or more, 0.45% by mass or more, 0.46% by mass or more, 0.47% by mass or more, 0.50% by mass or more, 0.52% by mass or more, 0.53% by mass or more, or 0.54% by mass or more. From the viewpoint of easily improving the tear strength in the foam, the total mass (A+B) is preferably 0.55 mass% or less, 0.54 mass% or less, 0.53 mass% or less, 0.52 mass% or less, 0.50 mass% or less, 0.47 mass% or less, 0.46 mass% or less, 0.45 mass% or less, 0.40 mass% or less, 0.35 mass% or less, 0.34 mass% or less, 0.32 mass% or less, 0.30 mass% or less, 0.29 mass% or less, 0.28 mass% or less, 0.27 mass% or less, 0.25 mass% or less, 0.20 mass% or less, or 0.19 mass% or less. From these viewpoints, the total mass (A+B) is preferably 0.15 to 0.55 mass%, 0.15 to 0.50 mass%, 0.15 to 0.40 mass%, 0.15 to 0.30 mass%, 0.15 to 0.25 mass%, 0.20 to 0.55 mass%, 0.25 to 0.55 mass%, 0.30 to 0.55 mass%, 0.40 to 0.55 mass%, 0.20 to 0.50 mass%, 0.30 to 0.50 mass%, or 0.30 to 0.40 mass%.

The content of terminal functional group A and terminal functional group B in sulfur-modified chloroprene rubber can be quantified using the procedure described in the examples.

The sulfur-modified chloroprene rubber may not have a functional group represented by the following general formula (C), and may not have a functional group represented by the following general formula (C) and located at a molecular terminal.
(In the formula, R ^c1 and R ^c2 each independently represent an alkyl group which may have a substituent, or an aryl group which may have a substituent.)

The method for producing sulfur-modified chloroprene rubber includes a polymerization step of emulsion-polymerizing chloroprene in the presence of sulfur (S ₈ ) to obtain a polymer, and a molecular weight adjustment step (mixing step) of mixing the polymer and a thiazole compound. One embodiment of the method for producing sulfur-modified chloroprene rubber includes a polymerization step of emulsion-polymerizing at least chloroprene and sulfur to obtain a polymerization liquid, and a molecular weight adjustment step of adding a thiazole compound to the polymerization liquid to adjust the molecular weight of the polymer in the polymerization liquid.

In the method for producing sulfur-modified chloroprene rubber, for example, it is possible to introduce sulfur into a polymer (e.g., the main chain of a polymer), and it is also possible to introduce polysulfide bonds (S ₂ to S ₈ ). The sulfur-modified chloroprene rubber includes a latex obtained by adjusting the molecular weight of a sulfur-modified chloroprene polymer, in which sulfur is introduced by emulsion polymerizing chloroprene alone or chloroprene with other monomers in the presence of sulfur, using a thiazole compound, and a sulfur-modified chloroprene rubber obtained by drying and washing this latex by a general method.

The manufacturing process of sulfur-modified chloroprene rubber is explained in detail below.

In the method for producing sulfur-modified chloroprene rubber, first, in the polymerization step, chloroprene is emulsion-polymerized in the presence of sulfur to obtain a polymer. The polymer may be a polymer in a polymerization liquid. In the polymerization step, chloroprene and the above-mentioned monomers copolymerizable with chloroprene may be emulsion-polymerized as necessary. The amount of chloroprene used or the amount of the monomers copolymerizable with chloroprene used is preferably the amount used described above.

The amount of sulfur (S ₈ ) used in emulsion polymerization is preferably within the following range per 100 parts by mass of monomer (total of monomers to be polymerized). The amount of sulfur used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, from the viewpoint of easily obtaining sufficient mechanical properties or dynamic properties of the resulting sulfur-modified chloroprene rubber. The amount of sulfur used is preferably 0.6 parts by mass or less, more preferably 0.5 parts by mass or less, from the viewpoint of easily processing the resulting sulfur-modified chloroprene rubber by preventing the adhesiveness of the resulting sulfur-modified chloroprene rubber to metal from becoming too strong. From these viewpoints, the amount of sulfur used is preferably 0.01 to 0.6 parts by mass, more preferably 0.1 to 0.5 parts by mass.

As the emulsifier used in the emulsion polymerization, one or more of known emulsifiers that can be used in the emulsion polymerization of chloroprene can be freely selected and used. Examples of the emulsifier include rosin acids, fatty acids, metal salts of aromatic sulfonic acid-formaldehyde condensates, sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, sodium alkyldiphenylethersulfonate, potassium alkyldiphenylethersulfonate, sodium polyoxyethylene alkylethersulfonate, sodium polyoxypropylene alkylethersulfonate, potassium polyoxyethylene alkylethersulfonate, and potassium polyoxypropylene alkylethersulfonate. As the emulsifier, rosin acids are preferred from the viewpoint that the tear strength of the foam is easily improved, the shrinkage rate is easily reduced, and an excellent appearance is easily obtained. "Rosin acids" means rosin acid, disproportionated rosin acid, alkali metal salts of disproportionated rosin acid (e.g., potassium disproportionated rosin acid), and the like. Constituents of disproportionated rosin acid include sesquiterpene, 8,5-isopimaric acid, dihydropimaric acid, secodehydroabietic acid, dihydroabietic acid, deisopropyldehydroabietic acid, demethyldehydroabietic acid, etc. Fatty acids include fatty acids (e.g., saturated or unsaturated fatty acids having 6 to 22 carbon atoms), metal salts of fatty acids (e.g., sodium lauryl sulfate), etc.

As the emulsifier, from the viewpoint of easily improving the tear strength, easily reducing the shrinkage rate, and easily obtaining an excellent appearance in the foam, a metal salt of an aromatic sulfonic acid formalin condensate is preferred, and a sodium salt of a β-naphthalenesulfonic acid formalin condensate is more preferred. The sodium salt of a β-naphthalenesulfonic acid formalin condensate is a commonly used emulsifier, and adding a small amount of it improves stability, allowing the latex to be stably produced without aggregation or precipitation during the production process. Other emulsifiers that are preferably used include, for example, an aqueous alkali soap solution consisting of a mixture of an alkali metal salt of a disproportionated rosin acid and a saturated or unsaturated fatty acid having 6 to 22 carbon atoms.

The pH of the emulsion (e.g., aqueous emulsion) at the start of emulsion polymerization is preferably 10.5 or more. Here, the "emulsion" refers to a mixture of chloroprene and other components (monomers copolymerizable with chloroprene, emulsifier, sulfur (S ₈ ), etc.) immediately before the start of emulsion polymerization. The "emulsion" also includes cases in which the composition is changed sequentially by subsequent addition or divided addition of these other components (monomers copolymerizable with chloroprene, sulfur (S ₈ ), etc.). By having the pH of the emulsion be 10.5 or more, polymer precipitation during polymerization can be prevented and polymerization can be stably controlled. This effect can be particularly favorably obtained when rosin acids are used as the emulsifier. The pH of the emulsion can be adjusted by the amount of an alkali component such as sodium hydroxide or potassium hydroxide present during emulsion polymerization.

The polymerization temperature for emulsion polymerization is preferably 0 to 55°C, more preferably 30 to 55°C, from the viewpoint of excellent polymerization controllability and productivity.

As a polymerization initiator, potassium persulfate, benzoyl peroxide, ammonium persulfate, hydrogen peroxide, etc., which are used in normal radical polymerization, can be used. For example, the polymerization is carried out at a polymerization rate (conversion rate) within the following range, and then a polymerization terminator (polymerization inhibitor) is added to terminate the polymerization.

From the viewpoint of excellent productivity, the polymerization rate is preferably 60% or more, and more preferably 70% or more. From the viewpoint of suppressing the development of branched structures or the formation of gels that affect the processability of the resulting sulfur-modified chloroprene rubber, the polymerization rate is preferably 95% or less, and more preferably 90% or less. From these viewpoints, the polymerization rate is preferably 60 to 95%, and more preferably 70 to 90%.

Examples of polymerization terminators include diethylhydroxylamine, thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis-4-methyl-6-tert-butylphenol, etc. One type of polymerization terminator may be used alone, or two or more types may be used in combination.

In the molecular weight adjustment step, the polymer obtained in the polymerization step and a thiazole compound are mixed. In the molecular weight adjustment step, the polymer obtained in the polymerization step and a thiazole compound are reacted to adjust the molecular weight of the polymer. For example, the molecular weight of the polymer in the polymerization solution obtained in the polymerization step can be adjusted by adding a thiazole compound to the polymerization solution. In the molecular weight adjustment step, for example, sulfur (e.g., polysulfide bonds (S ₂ to S ₈ )) present in the polymer (e.g., the main chain of the polymer) reacts with the thiazole compound to form the above-mentioned terminal functional group A derived from the thiazole compound, thereby cutting or depolymerizing the polymer. Hereinafter, the chemical used for cutting or depolymerizing the polymer is referred to as a "molecular weight regulator".

As the thiazole compound (a compound having a thiazole ring), one or more known thiazole compounds can be freely selected and used. From the viewpoint of easily improving the tear strength, easily reducing the shrinkage rate, and easily obtaining an excellent appearance in a foam, the thiazole compounds include N-cyclohexyl-2-benzothiazole sulfenamide, N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide, N-cyclohexyl-4,5-dimethyl-2-benzothiazole sulfenamide, N,N-dicyclohexyl-1,3-benzothiazole-2-sulfenamide, N-(tert-butyl)-2-benzothiazole sulfenamide, N,N-diisopropyl It is preferable that the foam rubber composition according to the present embodiment contains at least one compound selected from N-cyclohexyl-2-benzothiazole sulfenamide, 4,5-dihydrothiazole-2-sulfenamide, N-cyclohexyl-4,5-dihydrothiazole-2-sulfenamide, N-oxydiethylbenzothiazole-2-sulfenamide, 2-(4'-morpholinyldithio)benzothiazole, 2-mercaptobenzothiazole, 4,5-dihydro-2-mercaptothiazole, dibenzylthiazolyl disulfide, and 2-(morpholinodithio)benzothiazole. The thiazole compound preferably contains a benzothiazole compound (a compound having a benzothiazole ring) from the viewpoint that the tear strength is easily improved, the shrinkage rate is easily reduced, and an excellent appearance is easily obtained in the foam. The foam rubber composition according to the present embodiment may be an embodiment in which the thiazole compound does not contain N-cyclohexyl-2-benzothiazole sulfenamide and N-(tert-butyl)-2-benzothiazole sulfenamide.

The amount of the thiazole compound used (addition amount) is preferably 0.2 to 3 parts by mass per 100 parts by mass of the polymer (e.g., the polymer in the polymerization liquid). When the amount of the thiazole compound used is 0.2 parts by mass or more, the tear strength of the foam is easily improved, the shrinkage rate is easily reduced, and an excellent appearance is easily obtained. When the amount of the thiazole compound used is 3 parts by mass or less, it is easy to obtain an appropriate Mooney viscosity, and as a result, it is easy to improve the vulcanization moldability. When the amount of the thiazole compound used is 0.2 to 3 parts by mass, it is easy to adjust the content of the terminal functional group A in the sulfur-modified chloroprene rubber to 0.01 to 0.50 mass% (e.g., 0.05 to 0.40 mass%. Standard: total amount of sulfur-modified chloroprene rubber), and it is easy to adjust the content (residual amount) of the thiazole compound in the foam rubber composition to 0.0001 to 0.0200 mass parts (e.g., 0.0005 to 0.0100 mass parts. Standard: 100 parts by mass of sulfur-modified chloroprene rubber).

In the molecular weight adjustment process, a thiazole compound and an alkyl xanthogen disulfide can be used in combination as a molecular weight regulator. In the molecular weight adjustment process, the polymer obtained in the polymerization process, the thiazole compound, and the alkyl xanthogen disulfide can be mixed, and the polymer obtained in the polymerization process, the thiazole compound, and the alkyl xanthogen disulfide can be reacted. As a result, the alkyl xanthogen disulfide reacts with the thiazole compound to form a reactant that is more reactive with the sulfur in the polymer (e.g., polysulfide bonds) than when the thiazole compound alone or the alkyl xanthogen disulfide alone is used, and the Mooney viscosity can be easily adjusted. By reacting the reactant with the sulfur in the polymer (e.g., polysulfide bonds, e.g., sulfur in the main chain of the polymer), the above-mentioned terminal functional group A derived from the thiazole compound and the above-mentioned terminal functional group B derived from the alkyl xanthogen disulfide can be suitably formed.

As the alkyl xanthogen disulfide, one or more known alkyl xanthogen disulfides can be freely selected and used. The alkyl xanthogen disulfide preferably contains a dialkyl xanthogen disulfide, from the viewpoint of easily improving tear strength, easily reducing shrinkage, and easily obtaining an excellent appearance in a foam, and more preferably contains a dialkyl xanthogen disulfide in which at least one alkyl group has 1 to 6 carbon atoms, and even more preferably contains a dialkyl xanthogen disulfide in which at least one alkyl group has 2 to 4 carbon atoms. The alkyl xanthogen disulfide preferably contains at least one compound selected from dimethyl xanthogen disulfide, diethyl xanthogen disulfide, di-n-propyl xanthogen disulfide, diisopropyl xanthogen disulfide, and dibutyl xanthogen disulfide, from the viewpoint of easily improving tear strength, easily reducing shrinkage, and easily obtaining an excellent appearance in a foam.

The amount of alkyl xanthogen disulfide used (addition amount) is not particularly limited, but is preferably 0 to 6 parts by mass, more preferably more than 0 parts by mass to 6 parts by mass or less, and even more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the polymer (e.g., the polymer in the polymerization liquid). When the amount of alkyl xanthogen disulfide used is within these ranges, it becomes easier to control the Mooney viscosity, and the tear strength of the foam is easily improved and an excellent appearance is easily obtained. When the amount of alkyl xanthogen disulfide used is 0 to 6 parts by mass, it is easy to adjust the content of the terminal functional group B in the sulfur-modified chloroprene rubber to 0.50% by mass or less (e.g., 0.40% by mass or less. Standard: total amount of sulfur-modified chloroprene rubber), and it is easy to adjust the content (residual amount) of alkyl xanthogen disulfide in the foam rubber composition to 2.00 parts by mass or less (e.g., 1.50 parts by mass or less. Standard: 100 parts by mass of sulfur-modified chloroprene rubber).

The polymerization liquid that has undergone the molecular weight adjustment process may be cooled, pH adjusted, frozen, dried, etc. using conventional methods to obtain sulfur-modified chloroprene rubber.

The foamed rubber composition according to this embodiment contains a chemical foaming agent. The chemical foaming agent may include at least one selected from organic foaming agents and inorganic foaming agents. Examples of organic foaming agents include azo compounds, nitroso compounds, sulfonyl hydrazide compounds, and azide compounds.

Examples of azo compounds include azodicarbonamide, azobisformamide, azobisisobutyronitrile, 2,2'-azobisisobutyronitrile, azohexahydrobenzonitrile, and diazoaminobenzene. Examples of nitroso compounds include N,N'-dinitrosopentamethylenetetramine and N,N'-dinitroso-N,N'-dimethylphthalamide. Examples of sulfonyl hydrazide compounds include p,p'-oxybisbenzenesulfonyl hydrazide, benzenesulfonyl hydrazide, benzene-1,3-sulfonyl hydrazide, diphenylsulfone-3,3'-disulfonyl hydrazide, diphenyloxide-4,4'-disulfonyl hydrazide, and paratoluenesulfonyl hydrazide. Examples of azide compounds include terephthalazide and p-t-butylbenzazide. Examples of inorganic foaming agents include sodium hydrogen carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide, and sodium borohydride.

From the viewpoint of easily improving the tear strength, easily reducing the shrinkage rate, and easily obtaining an excellent appearance in the foam, the chemical foaming agent preferably contains an organic foaming agent, more preferably contains at least one selected from an azo compound, a nitroso compound, a sulfonyl hydrazide compound, and an azide compound, and even more preferably contains at least one selected from an azo compound and a sulfonyl hydrazide compound. The chemical foaming agent may contain at least one selected from an azo compound, a nitroso compound, a sulfonyl hydrazide compound, an azide compound, and an inorganic foaming agent.

The decomposition temperature of the chemical foaming agent is preferably 120 to 200° C., and more preferably 130 to 170° C. When the decomposition temperature of the chemical foaming agent is within this range, it is easy to control the chemical foaming and vulcanization, and the shrinkage rate of the foam is easily reduced and an excellent appearance is easily obtained.

The content of the chemical foaming agent is 3 to 16 parts by mass per 100 parts by mass of the total of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide. If the content of the chemical foaming agent is less than 3 parts by mass, the amount of foaming agent will be insufficient, and it may not be possible to obtain a sufficient amount of decomposition gas to obtain a foam. If the content of the chemical foaming agent exceeds 16 parts by mass, it will be difficult to achieve a balance between foaming and vulcanization, and the appearance or tear strength of the obtained foam may be inferior.

The content of the chemical foaming agent is preferably in the following ranges relative to 100 parts by mass of the total of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide. The content of the chemical foaming agent is preferably 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 6 parts by mass or more, 6.5 parts by mass or more, 7 parts by mass or more, or 8 parts by mass or more, from the viewpoint that the tear strength is easily improved, the shrinkage rate is easily reduced, and an excellent appearance is easily obtained in the foam. The content of the chemical foaming agent is preferably 20 parts by mass or less, 18 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, less than 10 parts by mass, 9 parts by mass or less, or 8 parts by mass or less, from the viewpoint that the tear strength is easily improved, the shrinkage rate is easily reduced, and an excellent appearance is easily obtained in the foam. The content of the chemical foaming agent may be 7 parts by mass or less, 6.5 parts by mass or less, 6 parts by mass or less, or 5 parts by mass or less. From these viewpoints, the content of the chemical foaming agent is preferably 0.1 to 20 parts by mass, 0.1 part by mass or more and less than 10 parts by mass, 1 to 15 parts by mass, 3 to 15 parts by mass, 5 to 15 parts by mass, 6 to 15 parts by mass, 7 to 15 parts by mass, 8 to 15 parts by mass, 3 to 12 parts by mass, 3 to 10 parts by mass, 3 to 8 parts by mass, 3 to 7 parts by mass, or 3 to 6 parts by mass.

The foamed rubber composition according to this embodiment may contain an unreacted molecular weight regulator (such as a thiazole compound or an alkyl xanthogen disulfide). The molecular weight regulator may be any of those described above in relation to the molecular weight adjustment process.

The content of the thiazole compound in the foamed rubber composition according to this embodiment (total amount of compounds corresponding to thiazole compounds, e.g., remaining amount) is preferably in the following range per 100 parts by mass of sulfur-modified chloroprene rubber. In addition, the content of the specific thiazole compound in the foamed rubber composition according to this embodiment (e.g., each of the thiazole compounds exemplified as described above, e.g., N-cyclohexyl-2-benzothiazole sulfenamide, N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide, etc.) is preferably in the following range per 100 parts by mass of sulfur-modified chloroprene rubber. The content of the thiazole compound (e.g., remaining amount of unreacted thiazole compound) can be adjusted by the amount of thiazole compound used in the molecular weight adjustment step, the processing time and processing temperature of the molecular weight adjustment step, etc.

From the viewpoint of easily reducing the shrinkage rate in the foam, the content of the thiazole compound is 0.0001 parts by mass or more, 0.0003 parts by mass or more, 0.0004 parts by mass or more, 0.0005 parts by mass or more, 0.0006 parts by mass or more, 0.0010 parts by mass or more, 0.0015 parts by mass or more, 0.0020 parts by mass or more, 0.0024 parts by mass or more, 0.0025 parts by mass or more, 0.0028 parts by mass or more, 0.0 It is preferable that the amount is 0.030 parts by mass or more, 0.0033 parts by mass or more, 0.0035 parts by mass or more, 0.0040 parts by mass or more, 0.0041 parts by mass or more, 0.0045 parts by mass or more, 0.0050 parts by mass or more, 0.0054 parts by mass or more, 0.0055 parts by mass or more, 0.0060 parts by mass or more, 0.0070 parts by mass or more, 0.0080 parts by mass or more, 0.0090 parts by mass or more, or 0.0100 parts by mass or more. From the viewpoint of easily improving the tear strength in the foam, the content of the thiazole compound is 0.0200 parts by mass or less, 0.0150 parts by mass or less, 0.0100 parts by mass or less, 0.0090 parts by mass or less, 0.0080 parts by mass or less, 0.0070 parts by mass or less, 0.0060 parts by mass or less, 0.0055 parts by mass or less, 0.0054 parts by mass or less, 0.0050 parts by mass or less, 0.0045 parts by mass or less, 0. 0041 parts by mass or less, 0.0040 parts by mass or less, 0.0035 parts by mass or less, 0.0033 parts by mass or less, 0.0030 parts by mass or less, 0.0028 parts by mass or less, 0.0025 parts by mass or less, 0.002 It is preferably 4 parts by mass or less, 0.0020 parts by mass or less, 0.0015 parts by mass or less, 0.0010 parts by mass or less, 0.0006 parts by mass or less, 0.0005 parts by mass or less, or 0.0004 parts by mass or less. From these viewpoints, the content of the thiazole compound is 0.0001 to 0.0200 parts by mass, 0.0003 to 0.0150 parts by mass, 0.0005 to 0.0150 parts by mass, 0.0010 to 0.0150 parts by mass, 0.0030 to 0.0150 parts by mass, 0.0050 to 0.0150 parts by mass, 0.0060 to 0.0150 parts by mass, 0.0080 to 0.0150 parts by mass, 0.009 ... Preferably, the amount is 0.0003 to 0.0100 parts by mass, 0.0003 to 0.0080 parts by mass, 0.0003 to 0.0060 parts by mass, 0.0003 to 0.0050 parts by mass, 0.0003 to 0.0030 parts by mass, 0.0003 to 0.0010 parts by mass, 0.0005 to 0.0100 parts by mass, 0.0010 to 0.0100 parts by mass, or 0.0010 to 0.0080 parts by mass.

The content of alkyl xanthogen disulfide in the foam rubber composition according to this embodiment (total amount of compounds corresponding to alkyl xanthogen disulfide, e.g., residual amount) may be in the following range per 100 parts by mass of sulfur-modified chloroprene rubber from the viewpoint of adjusting the balance between tear strength and shrinkage rate in the foam. In addition, the content of a specific alkyl xanthogen disulfide in the foam rubber composition according to this embodiment (e.g., each alkyl xanthogen disulfide exemplified as described above, diisopropyl xanthogen disulfide, diethyl xanthogen disulfide, etc.) may be in the following range per 100 parts by mass of sulfur-modified chloroprene rubber from the viewpoint of adjusting the balance between tear strength and shrinkage rate in the foam. The content of alkyl xanthogen disulfide (e.g., residual amount of unreacted alkyl xanthogen disulfide) can be adjusted by the amount of alkyl xanthogen disulfide used in the molecular weight adjustment step, the processing time and processing temperature of the molecular weight adjustment step, etc.

The content of alkyl xanthogen disulfide is 2.00 parts by mass or less, 1.80 parts by mass or less, 1.50 parts by mass or less, 1.40 parts by mass or less, 1.00 parts by mass or less, 0.90 parts by mass or less, 0.80 parts by mass or less, 0.75 parts by mass or less, 0.70 parts by mass or less, 0.60 parts by mass or less, 0.5 It may be 6 parts by mass or less, 0.55 parts by mass or less, 0.50 parts by mass or less, 0.40 parts by mass or less, 0.30 parts by mass or less, 0.25 parts by mass or less, 0.24 parts by mass or less, 0.21 parts by mass or less, 0.20 parts by mass or less, 0.10 parts by mass or less, 0.05 parts by mass or less, or 0.01 parts by mass or less. The content of the alkyl xanthogen disulfide may be 0 parts by mass or more, more than 0 parts by mass, 0.01 parts by mass or more, 0.05 parts by mass or more, 0.10 parts by mass or more, 0.20 parts by mass or more, 0.21 parts by mass or more, 0.24 parts by mass or more, 0.25 parts by mass or more, 0.30 parts by mass or more, 0.40 parts by mass or more, 0.50 parts by mass or more, 0.55 parts by mass or more, 0.56 parts by mass or more, 0.60 parts by mass or more, 0.70 parts by mass or more, 0.75 parts by mass or more, 0.80 parts by mass or more, 0.90 parts by mass or more, 1.00 parts by mass or more, 1.40 parts by mass or more, or 1.50 parts by mass or more. From these viewpoints, the content of the alkyl xanthogen disulfide may be 0 to 2.00 parts by mass, more than 0 parts by mass and not more than 2.00 parts by mass, 0 to 1.50 parts by mass, 0 to 1.00 parts by mass, more than 0 parts by mass and not more than 1.00 parts by mass, more than 0 parts by mass and not more than 0.80 parts by mass, more than 0 parts by mass and not more than 0.60 parts by mass, more than 0 parts by mass and not more than 0.50 parts by mass, more than 0 parts by mass and not more than 0.40 parts by mass, 0.20 to 1.00 parts by mass, 0.30 to 1.00 parts by mass, 0.40 to 1.00 parts by mass, 0.50 to 1.00 parts by mass, 0.60 to 1.00 parts by mass, 0.20 to 0.80 parts by mass, 0.20 to 0.60 parts by mass, or 0.30 to 0.60 parts by mass.

In the foamed rubber composition according to the present embodiment, the mass ratio D/C of the content (e.g., residual amount) D of the alkyl xanthogen disulfide to the content (e.g., residual amount) C of the thiazole compound is preferably in the following range. The mass ratio D/C is preferably 1500 or less, or 1200 or less, from the viewpoint of a better balance of the physical properties of the tear strength and shrinkage rate of the resulting foam. The mass ratio D/C may be 1000 or less, 900 or less, 800 or less, 600 or less, 500 or less, 300 or less, 200 or less, 150 or less, 120 or less, 110 or less, 100 or less, 80 or less, 75 or less, 74 or less, 50 or less, 45 or less, 40 or less, 30 or less, 10 or less, or 5 or less, from the viewpoint of adjusting the balance of the tear strength and shrinkage rate in the foam. The mass ratio D/C is 0 or more, and from the viewpoint of adjusting the balance between tear strength and shrinkage rate in the foam, may be greater than 0, and may be 5 or more, 10 or more, 30 or more, 40 or more, 45 or more, 50 or more, 74 or more, 75 or more, 80 or more, 100 or more, 110 or more, 120 or more, 150 or more, 200 or more, 300 or more, 500 or more, 600 or more, 800 or more, 900 or more, 1000 or more, or 1200 or more. From these viewpoints, the mass ratio D/C is preferably 0 to 1500, more than 0 and not more than 1500, 0 to 1200, more than 0 and not more than 1200, 0 to 1000, 0 to 900, 0 to 800, 0 to 200, 40 to 1200, 50 to 1200, 100 to 1200, 200 to 1200, 40 to 1000, 50 to 900, or 100 to 800.

The content of the thiazole compound and the content of the alkyl xanthogen disulfide can be quantified by the procedure described in the Examples. The relative amount of the thiazole compound to the sulfur-modified chloroprene rubber and the relative amount of the alkyl xanthogen disulfide to the sulfur-modified chloroprene rubber can be maintained the same before and after mixing the mixture of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide with components other than the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide.

In the foamed rubber composition according to this embodiment, the content of the sulfenamide compound may be 0.0005 parts by mass or less, less than 0.0005 parts by mass, or 0.0004 parts by mass or less, per 100 parts by mass of the sulfur-modified chloroprene rubber. In the foamed rubber composition according to this embodiment, the content of the sulfenamide compound may be 0.01 parts by mass or more, more than 0.01 parts by mass, or 0.0105 parts by mass or more, per 100 parts by mass of the sulfur-modified chloroprene rubber.

In the foamed rubber composition according to this embodiment, the content of xanthogen disulfide may be 0.1 parts by mass or less, less than 0.1 parts by mass, or 0.05 parts by mass or less per 100 parts by mass of sulfur-modified chloroprene rubber. In the foamed rubber composition according to this embodiment, the content of xanthogen disulfide may be 1.5 parts by mass or more, more than 1.5 parts by mass, or 1.6 parts by mass or more per 100 parts by mass of sulfur-modified chloroprene rubber.

In the foamed rubber composition according to this embodiment, the content of the organic peroxide may be 1 part by mass or less, less than 1 part by mass, 0.1 parts by mass or less, or 0.01 parts by mass or less, per 100 parts by mass of the sulfur-modified chloroprene rubber. The foamed rubber composition according to this embodiment may be substantially free of organic peroxide (the above-mentioned content of the organic peroxide may be substantially 0 parts by mass).

The Mooney viscosity (ML ₁₊₄ , 100° C.) of the mixture of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide is not particularly limited, but is preferably in the following range. From the viewpoint of easily maintaining processability, the Mooney viscosity is preferably 10 or more, 15 or more, or 20 or more. The Mooney viscosity may be 25 or more, or 30 or more. From the viewpoint of easily maintaining processability, the Mooney viscosity is preferably 80 or less. The Mooney viscosity may be 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, or 50 or less. From these viewpoints, the Mooney viscosity is preferably 10 to 80, or 20 to 80. The Mooney viscosity can be adjusted by the amount of molecular weight modifier added, the processing time and processing temperature of the molecular weight adjustment step, and the like. The Mooney viscosity of the mixture of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide can be measured by identifying the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide contained in the foamed rubber composition according to this embodiment.

The foamed rubber composition of this embodiment may contain additives such as vulcanizing agents, processing aids (lubricants), antioxidants, metal compounds, plasticizers, and fillers.

Examples of vulcanizing agents include metal oxides. Examples of metal oxides include zinc oxide, magnesium oxide, lead oxide, trilead tetroxide, iron trioxide, titanium dioxide, calcium oxide, hydrotalcite, etc. One type of vulcanizing agent may be used alone, or two or more types may be used in combination. The content of the vulcanizing agent is preferably in the range of 3 to 15 parts by mass per 100 parts by mass of the mixture of sulfur-modified chloroprene rubber, thiazole compound, and alkyl xanthogen disulfide.

Examples of processing aids include fatty acids such as stearic acid; paraffin-based processing aids such as polyethylene; fatty acid amides, etc. One type of processing aid may be used alone, or two or more types may be used in combination. The content of the processing aid is preferably in the range of 0.5 to 5 parts by mass per 100 parts by mass of the mixture of sulfur-modified chloroprene rubber, thiazole compound, and alkyl xanthogen disulfide.

The foamed rubber composition according to the present embodiment may contain an antioxidant (e.g., a small amount of antioxidant) to prevent changes in Mooney viscosity during storage. As the antioxidant, one or more known compounds that can be used in chloroprene rubber may be freely selected and used. Examples of the antioxidant include phenyl-α-naphthylamine, octylated diphenylamine, nickel dibutyldithiocarbamate, 2,6-di-tert-butyl-4-phenylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-thiobis-(6-tert-butyl-3-methylphenol), etc. As the antioxidant, at least one selected from octylated diphenylamine, nickel dibutyldithiocarbamate, and 4,4'-thiobis-(6-tert-butyl-3-methylphenol) is preferable.

The metal compound is a compound that can be added to adjust the vulcanization rate of the sulfur-modified chloroprene rubber, or to adsorb chlorine sources such as hydrogen chloride produced by the dehydrochlorination reaction of the sulfur-modified chloroprene rubber, thereby suppressing deterioration of the sulfur-modified chloroprene rubber. As the metal compound, oxides or hydroxides of zinc, titanium, magnesium, lead, iron, beryllium, calcium, barium, germanium, zirconium, vanadium, molybdenum, tungsten, etc., can be used. The metal compound may be used alone or in combination of two or more types.

The content of the metal compound is not particularly limited, but is preferably in the range of 3 to 15 parts by mass per 100 parts by mass of the mixture of sulfur-modified chloroprene rubber, thiazole compound, and alkyl xanthogen disulfide. By adjusting the content of the metal compound within this range, the mechanical strength of the molded product can be improved.

A plasticizer is a component that can be added to reduce the hardness of sulfur-modified chloroprene rubber and improve its low-temperature properties. It can also improve the texture of sponges produced using sulfur-modified chloroprene rubber. Examples of plasticizers include dioctyl phthalate, dioctyl adipate (also known as bis(2-ethylhexyl) adipate), white oil, silicone oil, naphthenic oil, aromatic oil, triphenyl phosphate, and tricresyl phosphate. One type of plasticizer may be used alone, or two or more types may be used in combination.

The content of the plasticizer is not particularly limited, but is preferably in the range of 50 parts by mass or less per 100 parts by mass of the mixture of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide. By adjusting the content of the plasticizer within this range, the above-mentioned effects of the plasticizer can be exhibited while maintaining the tear strength of the molded product.

Fillers are components that can be added as reinforcing materials for sulfur-modified chloroprene rubber. Examples of fillers include carbon black, silica, clay, talc, calcium carbonate, etc. Fillers may be used alone or in combination of two or more types.

<Foams and molded products>
The foam according to the present embodiment is a foam of the foamed rubber composition according to the present embodiment. The foam according to the present embodiment may be a vulcanizate or a sponge. The foam according to the present embodiment can be obtained by foaming the foamed rubber composition according to the present embodiment, and can be obtained, for example, by mixing the components of the foamed rubber composition (sulfur-modified chloroprene rubber, chemical foaming agent, metal compound, plasticizer, filler, etc.) with a roll, Banbury mixer, extruder, etc., adding a foaming agent, and vulcanizing while foaming.

The foam according to this embodiment may be sliced to a desired thickness to obtain a foam sheet, and then a fiber base material (e.g., jersey fabric of polyester fiber, nylon fiber, etc.) may be laminated on at least one surface of the foam sheet to obtain a laminated sheet. The laminated sheet according to this embodiment comprises the foam according to this embodiment and a fiber base material that supports the foam, and the foam is in a sheet form. The laminated sheet according to this embodiment can be used as a fabric for a wetsuit, and a wetsuit can be obtained by sewing the laminated sheet.

The molded product according to this embodiment is a molded product (e.g., a sponge product) made of the foam according to this embodiment, and can be obtained by molding the foam according to this embodiment. Examples of molded products include wetsuits. For the constituent materials of wetsuits, materials with excellent tear strength, shrinkage, appearance, etc. are required to improve the reliability of the product. A wetsuit, which is one aspect of the molded product according to this embodiment, has higher tear strength, smaller shrinkage, and better appearance than a wetsuit using conventional sulfur-modified chloroprene rubber.

The present invention will be described in more detail below with reference to examples. The examples described below are representative examples of the present invention, and should not be construed as narrowing the scope of the present invention.

<Preparation of evaluation samples>
Example 1
[Preparation of sulfur-modified chloroprene rubber]
Into a polymerization vessel having an internal volume of 30 L, 100 parts by mass of chloroprene, 0.55 parts by mass of sulfur, 120 parts by mass of pure water, 4.00 parts by mass of disproportionated potassium rosinate (manufactured by Harima Chemicals Co., Ltd.), 0.60 parts by mass of sodium hydroxide, and 0.6 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation, trade name "Demol N") were added. The pH of the aqueous emulsion before the start of polymerization was 12.8. After adding 0.1 parts by mass of potassium persulfate as a polymerization initiator, emulsion polymerization was carried out under a nitrogen gas flow at a polymerization temperature of 40°C. When the conversion rate reached 85%, 0.05 parts by mass of diethylhydroxylamine as a polymerization terminator was added to terminate the polymerization, thereby obtaining a polymerization liquid of chloroprene.

To the obtained polymerization liquid, 5 parts by mass of chloroprene (solvent), 1 part by mass of N-cyclohexyl-2-benzothiazole sulfenamide (molecular weight regulator, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela CZ"), 2 parts by mass of diisopropyl xanthogen disulfide (molecular weight regulator, manufactured by Sanshin Chemical Industry Co., Ltd., product name "Sanbit DIX"), 0.05 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (dispersant), and 0.05 parts by mass of sodium lauryl sulfate (emulsifier) were added to obtain a sulfur-modified chloroprene polymer latex before molecular weight adjustment.

The obtained sulfur-modified chloroprene polymer latex was distilled under reduced pressure to remove unreacted monomers, and then the mixture was stirred and held at 50°C for 1 hour to adjust the molecular weight, yielding raw rubber containing sulfur-modified chloroprene rubber (latex after molecular weight adjustment). "Raw rubber" is a mixture containing sulfur-modified chloroprene rubber and unreacted molecular weight adjuster.

{Analysis of Terminal Functional Group Content}
After cooling the raw rubber, the polymer was isolated by a conventional freeze-coagulation method to obtain a sulfur-modified chloroprene rubber. Based on the total amount of the sulfur-modified chloroprene rubber, the content of the terminal functional group (thiazole terminal species A1) derived from N-cyclohexyl-2-benzothiazole sulfenamide represented by the following formula (A1) was 0.15 mass%, and the content of the terminal functional group (xanthogen terminal species B1) derived from diisopropyl xanthogen disulfide represented by the following formula (B1) was 0.14 mass%.

The content of terminal functional groups in the sulfur-modified chloroprene rubber was quantified by the following procedure. First, the sulfur-modified chloroprene rubber was purified with benzene and methanol, and then freeze-dried again to obtain a measurement sample. Using this measurement sample, ¹ H-NMR measurement was performed according to JIS K-6239. The obtained measurement data was corrected based on the peak (7.24 ppm) of chloroform in the deuterated chloroform used as the solvent. Based on the corrected measurement data, the area of each peak having a peak top at 7.72 to 7.83 ppm, 5.60 to 5.75 ppm, and 1.30 to 1.45 ppm was calculated to quantify the content of terminal functional groups.

{Measurement of remaining amount of molecular weight regulator}
The content (residual amount) of the molecular weight modifier relative to 100 parts by mass of sulfur-modified chloroprene rubber in the raw rubber was quantified by the following procedure. First, 1.5 g of the obtained raw rubber was dissolved in 30 mL of benzene, and then 60 mL of methanol was dropped. As a result, the rubber component (polymer component) was precipitated and separated from the solvent, and a liquid phase containing non-rubber components as solvent-soluble components was collected. The precipitate was again dissolved in benzene and dropped with methanol in the same procedure to separate the rubber component, and a liquid phase containing non-rubber components as solvent-soluble components was collected. The liquid phase obtained by mixing the first and second liquid phases and then constant volumeting to 200 mL was obtained as a measurement sample. 20 μL of this measurement sample was injected into a liquid chromatograph (LC, Hitachi, Ltd., pump: L-6200, L-600, UV detector: L-4250). The mobile phase of the liquid chromatograph was used with varying ratios of acetonitrile and water, and was run at a flow rate of 1 mL/min. The column used was an Inertsil ODS-3 (φ4.6×150 mm, 5 μm, manufactured by GL Science Co., Ltd.). Peak detection times were confirmed using standard solutions of 0.05 ppm, 0.1 ppm, and 1.0 ppm of thiazole compounds (measurement wavelength: 300 nm) and standard solutions of 10 ppm, 50 ppm, and 100 ppm of alkyl xanthogen disulfide (measurement wavelength: 280 nm), and quantitative values were obtained from a calibration curve obtained from the peak areas. The quantitative values were compared with the amounts of samples used in the analysis to determine the contents of unreacted thiazole compounds and unreacted alkyl xanthogen disulfides in the raw rubber.

[Sample Preparation]
100 parts by mass of the above-mentioned raw rubber, 1 part by mass of processing aid 1 (lubricant, manufactured by New Japan Chemical Co., Ltd., product name "Stearic acid 50S"), 2 parts by mass of processing aid 2 (lubricant, manufactured by S&S Japan Co., Ltd., product name "Structol WB212"), 1 part by mass of processing aid 3 (manufactured by Nippon Seiro Co., Ltd., product name "Paraffin wax 130°F"), 1 part by mass of antioxidant 1 (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac AD-F", octylated diphenylamine), 1 part by mass of antioxidant 2 (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac NBC", nickel dibutyldithiocarbamate), 4 parts by mass of magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd., product name "Kyowamag 150"), 1 part by mass of filler 1 (manufactured by Asahi Carbon Co., Ltd. An unvulcanized compound was obtained by mixing 10 parts by mass of carbon black (manufactured by Shiraishi Calcium Co., Ltd., trade name "Asahi Thermal"), 10 parts by mass of filler 2 (manufactured by Shiraishi Calcium Co., Ltd., trade name "Dexy Clay"), 15 parts by mass of filler 3 (manufactured by Shiraishi Calcium Co., Ltd., trade name "Crown Clay"), 15 parts by mass of plasticizer 1 (manufactured by Idemitsu Kosan Co., Ltd., trade name "NP-24", naphthenic mineral oil), 20 parts by mass of plasticizer 2 (manufactured by Idemitsu Kosan Co., Ltd., trade name "AH-16", aromatic process oil), 5 parts by mass of vulcanizing agent (manufactured by Sakai Chemical Industry Co., Ltd., zinc oxide type 2), and 8 parts by mass of foaming agent 1 (manufactured by Sankyo Kasei Co., Ltd., trade name "Cellmike S", p,p'-oxybisbenzenesulfonyl hydrazide) using an 8-inch roll. Next, the unvulcanized compound was subjected to the following two press vulcanizations in accordance with JIS K 6299 to prepare an evaluation sample (sponge).

102g of unvulcanized compound (filling rate 105%) was placed in a mold with a cavity area of 100mm length, 95mm width, and 8mm height, and the cavity area was subjected to primary vulcanization (first press vulcanization) for 20 minutes under conditions of a pressure of 3.5MPa or more and 145°C. The compound was then left to stand for 10 minutes under atmospheric pressure and 23°C to obtain a primary vulcanized compound. This primary vulcanized compound was then placed in a mold with a cavity area of 175mm length, 170mm width, and 16mm height, and the cavity area was subjected to secondary vulcanization (second press vulcanization) for 20 minutes under conditions of a pressure of 3.5MPa or more and 155°C.

Example 2
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 0.5 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 4 parts by mass.

Example 3
A sample for evaluation was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 2 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 1 part by mass.

Example 4
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the molecular weight modifier, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 3 parts by mass.

Example 5
A sample for evaluation was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 0.5 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 5 parts by mass.

Example 6
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of diisopropyl xanthogen disulfide added as a molecular weight regulator was changed from 2 parts by mass to 1 part by mass.

(Example 7)
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 3 parts by mass, and diisopropyl xanthogen disulfide was not added.

(Example 8)
A sample for evaluation was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 0.3 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 4 parts by mass.

(Example 9)
A sample for evaluation was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 0.3 parts by mass, and the treatment time during molecular weight adjustment was changed from 1 hour to 3 hours.

(Example 10)
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 1.5 parts by mass, and the treatment time during molecular weight adjustment was changed from 1 hour to 15 minutes.

Example 11
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, diisopropyl xanthogen disulfide, added was changed from 2 parts by mass to 4 parts by mass, and the treatment time during molecular weight adjustment was changed from 1 hour to 15 minutes.

Example 12
An evaluation sample was obtained in the same manner as in Example 1, except that, as the molecular weight modifier, N-cyclohexyl-2-benzothiazole sulfenamide was replaced with N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide (manufactured by Chemieliva Pharma & Chem Co., LTD.) which gives a terminal functional group represented by the following formula (A2). Based on the total amount of the sulfur-modified chloroprene rubber, the content of the terminal functional group derived from N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide (thiazole terminal species A2) was 0.15 mass%, and the content of the terminal functional group derived from diisopropyl xanthogen disulfide represented by the above formula (B1) (xanthogen terminal species B1) was 0.17 mass%.

Example 13
An evaluation sample was obtained in the same manner as in Example 1, except that diisopropyl xanthogen disulfide was changed to diethyl xanthogen disulfide (manufactured by Sigma-Aldrich) which gives a terminal functional group represented by the following formula (B2) as the molecular weight regulator. Based on the total amount of the sulfur-modified chloroprene rubber, the content of the terminal functional group (thiazole terminal species A1) derived from N-cyclohexyl-2-benzothiazole sulfenamide represented by the above formula (A1) was 0.16 mass%, and the content of the terminal functional group (xanthogen terminal species B2) derived from diethyl xanthogen disulfide was 0.13 mass%.

(Example 14)
Except for changing the molecular weight regulator from N-cyclohexyl-2-benzothiazole sulfenamide to N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide which gives a terminal functional group represented by the above formula (A2), and changing diisopropyl xanthogen disulfide to diethyl xanthogen disulfide which gives a terminal functional group represented by the above formula (B2), an evaluation sample was obtained in the same manner as in Example 1. Based on the total amount of sulfur-modified chloroprene rubber, the content of the terminal functional group derived from N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide (thiazole terminal species A2) was 0.14 mass%, and the content of the terminal functional group derived from diethyl xanthogen disulfide (xanthogen terminal species B2) was 0.16 mass%.

(Example 15)
An evaluation sample was obtained in the same manner as in Example 1, except that 8 parts by mass of blowing agent 1 was changed to 5 parts by mass of blowing agent 2 (manufactured by Sankyo Kasei Co., Ltd., product name "Cellmike C", azodicarbonamide).

(Example 16)
An evaluation sample was obtained in the same manner as in Example 1, except that 8 parts by mass of blowing agent 1 was changed to 4 parts by mass of blowing agent 1 and 2.5 parts by mass of blowing agent 2 (manufactured by Sankyo Chemical Industry Co., Ltd., product name "Cellmike C", azodicarbonamide).

(Comparative Example 1)
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 3 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 6 parts by mass.

(Comparative Example 2)
A sample for evaluation was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 0.3 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 0.3 parts by mass.

(Comparative Example 3)
A sample for evaluation was obtained in the same manner as in Example 1, except that the amount of the molecular weight regulator, N-cyclohexyl-2-benzothiazole sulfenamide, added was changed from 1 part by mass to 0.5 parts by mass, and the amount of diisopropyl xanthogen disulfide added was changed from 2 parts by mass to 6 parts by mass.

(Comparative Example 4)
A sample for evaluation was obtained in the same manner as in Example 1, except that the molecular weight regulator was changed from N-cyclohexyl-2-benzothiazole sulfenamide and diisopropyl xanthogen disulfide to tetraethylthiuram disulfide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela TET") which gives a terminal functional group represented by the following formula, and the amount added was changed to 2.5 parts by mass. Based on the total amount of the sulfur-modified chloroprene rubber, the content of the terminal functional group derived from tetraethylthiuram disulfide was 0.26% by mass.

(Comparative Example 5)
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the foaming agent 1 added was changed from 8 parts by mass to 2 parts by mass.

(Comparative Example 6)
An evaluation sample was obtained in the same manner as in Example 1, except that the amount of the foaming agent 1 added was changed from 8 parts by mass to 20 parts by mass.

<Evaluation>
The above-mentioned raw rubber and evaluation samples (foams) were evaluated. The results of the examples are shown in Tables 1 and 2, and the results of the comparative examples are shown in Table 3. In Comparative Example 1, the Mooney viscosity of the raw rubber was too low, so an evaluation sample could not be prepared, and therefore no evaluations were performed. In Comparative Example 5, foaming did not occur, so an evaluation sample could not be prepared, and therefore no evaluations were performed.

(Mooney Viscosity)
The Mooney viscosity (ML ₁₊₄ ) of the above-mentioned raw rubber was measured in accordance with JIS K 6300-1, with an L-type rotor preheating time of 1 minute, a rotation time of 4 minutes, and a test temperature of 100° C. The Mooney viscosity of the raw rubber of Comparative Example 1 was too low to be measured.

(Tear strength)
According to JIS K 6400-1, a No. 4 angle-shaped test piece without a notch was prepared from the above-mentioned evaluation sample using a punching tool. Then, according to JIS K6400-5, the test piece was measured at a test speed of 500 mm/min using a constant-speed tensile tester, and the maximum tear load shown until the test piece broke was divided by the film thickness to obtain the tear strength.

(Shrinkage rate)
The above-mentioned evaluation sample (evaluation sample immediately after preparation) was left to stand for 168 hours under atmospheric pressure and 23°C conditions, and then the surface layer of the evaluation sample was sliced to a thickness of 2 mm ± 0.20 mm to prepare a sponge sheet. The length and width of the sponge sheet immediately after slicing were measured to obtain a reference value, and then the length and width of the sponge sheet after standing for 168 hours under atmospheric pressure and 23°C were measured again. The shrinkage rate was calculated from the following formula, where the length of the sponge sheet immediately after slicing is H0 (mm), the width is L0 (mm), and the length of the sponge sheet after standing for 168 hours is H1 (mm), and the width is L1 (mm).
Shrinkage rate (%) = [(H0 x L0 - H1 x L1) ÷ (H0 x L0)] x 100

(exterior)
The above-mentioned evaluation sample (evaluation sample immediately after preparation) was left to stand for 24 hours under atmospheric pressure and at 23° C., and then the surface condition of the evaluation sample was visually observed. Observation was performed for the following three items, and a sample that met the criteria of "A" in all items was evaluated as "A", and a sample that did not meet the criteria of "A" in at least one item was evaluated as "B".
[Item 1: Presence or absence of craters]
The presence or absence of crater-like irregularities caused by gas escape, etc. was confirmed. A case in which no irregularities were observed was rated as "A".
[Item 2: Presence or absence of claw marks]
The surface of the evaluation sample was lightly pressed with a fingernail and then released, and the presence or absence of a fingernail mark was observed. When no fingernail mark was left, the sample was rated as "A".
[Item 3: Observation of corners]
The corners of the evaluation samples were checked for wrinkles caused by shrinkage. Corners that remained firm were rated as "A."

As shown in Tables 1 to 3, it is confirmed that the foam obtained using the foam rubber composition of the Examples has excellent tear strength, shrinkage rate and appearance. In Comparative Example 1, the Mooney viscosity was too low and it was not possible to prepare an evaluation sample. In Comparative Example 5, no foaming occurred and it was not possible to prepare an evaluation sample.

Claims (13)

Contains sulfur-modified chloroprene rubber and chemical foaming agents.
The sulfur-modified chloroprene rubber has a functional group A represented by the following general formula (A) and located at a molecular terminal,
In the sulfur-modified chloroprene rubber, a mass ratio B/A of a content of a functional group B represented by the following general formula (B) and located at a molecular terminal to a content of the functional group A is more than 0 and is not more than 6.00,
the total amount of the functional group A and the functional group B is 0.10 to 0.60 mass %,
The foamed rubber composition has a content of the chemical foaming agent of 4 to 12 parts by mass per 100 parts by mass of the total of the sulfur-modified chloroprene rubber, the thiazole compound, and the alkyl xanthogen disulfide.

(In the formula, R ^a1 and R ^a2 each independently represent a hydrogen atom, a halogen atom, a hydroxy group, an alkoxy group, a carboxy group, a carboxylate group, a cyano group, an alkyl group which may have a substituent, or an arylthio group which may have a substituent, and R ^a1 and R ^a2 may be bonded to each other to form a ring which may have a substituent.)

(In the formula, R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent.) The foamed rubber composition according to claim 1 , wherein the functional group A has a benzothiazole ring formed by bonding R ^a1 and R ^a2 to each other. The foamed rubber composition according to claim 1 or 2 , wherein the content of the functional group A in the sulfur-modified chloroprene rubber is 0.05 to 0.40 mass %. The foamed rubber composition according to any one of claims 1 to 3 , wherein the content of the functional group B in the sulfur-modified chloroprene rubber is 0.40 mass % or less. The foamed rubber composition according to any one of claims 1 to 4 , wherein the content of the thiazole compound is 0.0005 to 0.0100 parts by mass based on 100 parts by mass of the sulfur-modified chloroprene rubber. The thiazole compound is N-cyclohexyl-2-benzothiazole sulfenamide, N-cyclohexyl-4-methyl-2-benzothiazole sulfenamide, N-cyclohexyl-4,5-dimethyl-2-benzothiazole sulfenamide, N,N-dicyclohexyl-1,3-benzothiazole-2-sulfenamide, N-(tert-butyl)-2-benzothiazole sulfenamide, N,N-diisopropyl-2-benzothiazole sulfenamide, 4, The foamed rubber composition according to any one of claims 1 to 5, comprising at least one compound selected from the group consisting of 5-dihydrothiazole-2-sulfenamide, N-cyclohexyl-4,5-dihydrothiazole-2-sulfenamide, N-oxydiethylbenzothiazole-2-sulfenamide, 2-(4'-morpholinyldithio)benzothiazole, 2-mercaptobenzothiazole, 4,5-dihydro- 2 -mercaptothiazole, dibenzylthiazolyl disulfide, and 2-(morpholinodithio)benzothiazole. The foamed rubber composition according to any one of claims 1 to 6 , wherein a content of the alkyl xanthogen disulfide is 1.50 parts by mass or less based on 100 parts by mass of the sulfur-modified chloroprene rubber. The foamed rubber composition according to any one of claims 1 to 7 , wherein the alkyl xanthogen disulfide includes at least one compound selected from the group consisting of dimethyl xanthogen disulfide, diethyl xanthogen disulfide, di-n-propyl xanthogen disulfide, diisopropyl xanthogen disulfide, and dibutyl xanthogen disulfide. The foamed rubber composition according to any one of claims 1 to 8 , wherein a mass ratio D/C of a content D of the alkyl xanthogen disulfide to a content C of the thiazole compound is 1000 or less. The foamed rubber composition according to any one of claims 1 to 9 , wherein a Mooney viscosity of the mixture of the sulfur-modified chloroprene rubber, the thiazole compound and the alkyl xanthogen disulfide is 20 to 80. The foamed rubber composition according to any one of claims 1 to 10 , wherein the chemical foaming agent comprises at least one selected from the group consisting of an azo compound, a nitroso compound, a sulfonyl hydrazide compound, an azide compound, and an inorganic foaming agent. A foamed product of the foamed rubber composition according to any one of claims 1 to 11 . A molded article comprising the foam of claim 12 .