Rubber material, rubber composition, vulcanizate, foam and diving suit

Abstract

A rubber material which is a rubber material containing a sulfur-modified chloroprene polymer, the content X (mass%) of sulfur constituting the aforementioned sulfur-modified chloroprene polymer, and the total amount Y (mass%) of a conjugated resin acid and a salt of a conjugated resin acid satisfy the following formula (A) with respect to the total amount of the rubber material being 1.00 mass% or more.13.90X - 5.10 ≤ Y...(A)

Description

TECHNICAL FIELD

[0001] The present application relates to a rubber material, a rubber composition, a vulcanizate, a foam, a wetsuit, and the like. BACKGROUND

[0002] Chloroprene polymers are used in various fields because of their excellent properties. For example, chloroprene polymers are used as materials for general industrial belts, air springs for automobiles, anti-vibration rubbers, and the like because of their excellent dynamic properties. In addition, foams obtained by foaming a rubber composition containing a chloroprene polymer are used in various fields such as automobile parts, the construction field, leisure goods, and the like.

[0003] As such a foam, there are known a foam obtained by heat-foaming a rubber composition containing a chloroprene rubber, an organic peroxide, a blowing agent, a softener, a filler, and a reinforcing agent (for example, see Patent Literature 1 below), a foam obtained by foaming a rubber composition containing a chloroprene rubber, a butadiene rubber, a softener, and a blowing agent by pressureless open vulcanization (for example, see Patent Literature 2 below), and the like.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2012-067235

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. Hei 10-298328 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] According to the present inventors' insight, when a rubber composition containing a chloroprene polymer is foamed to obtain a foam, there are cases in which the foam shrinks over time. If the foam shrinks excessively, wrinkles and the like are generated, and thus it is required to suppress the shrinkage after foaming. In addition, for a rubber composition containing a chloroprene polymer, it is required to obtain a foam having excellent ozone resistance while suppressing such shrinkage.

[0010] An object of one aspect of the present application is to provide a rubber material that can suppress shrinkage after foaming and obtain a foam having excellent ozone resistance. An object of another aspect of the present application is to provide a rubber composition containing the aforementioned rubber material. An object of another aspect of the present application is to provide a vulcanizate of the aforementioned rubber composition. An object of another aspect of the present application is to provide a foam of the aforementioned rubber material. An object of another aspect of the present application is to provide a wetsuit provided with the aforementioned foam.

[0011] Means for solving the problem

[0012] One aspect of the present application relates to a rubber material containing a sulfur-modified chloroprene polymer, wherein the content X (mass%) of sulfur constituting the aforementioned sulfur-modified chloroprene polymer, and the total content Y (mass%) of a conjugated resin acid and a salt of a conjugated resin acid satisfy the following formula (A), and the aforementioned total content Y is 1.00 mass% or more, based on the total amount of the rubber material.

[0013] 13.90X - 5.10 ≤ Y... (A)

[0014] According to such a rubber material, shrinkage after foaming can be suppressed, and a foamed body having excellent ozone resistance can be obtained.

[0015] Another aspect of the present application relates to a first embodiment of a rubber composition containing the aforementioned rubber material, and a vulcanizing agent. Another aspect of the present application relates to a second embodiment of a rubber composition containing the aforementioned rubber material, and a foaming agent. Another aspect of the present application relates to a vulcanizate of the rubber composition of the first embodiment. Another aspect of the present application relates to a foamed body of the rubber composition of the second embodiment. Another aspect of the present application relates to a diving suit provided with the aforementioned foamed body.

[0016] Effects of the Invention

[0017] According to one aspect of the present application, it is possible to provide a rubber material capable of suppressing shrinkage after foaming, and obtaining a foamed body having excellent ozone resistance. According to another aspect of the present application, it is possible to provide a rubber composition containing the aforementioned rubber material. According to another aspect of the present application, it is possible to provide a vulcanizate of the aforementioned rubber composition. According to another aspect of the present application, it is possible to provide a foamed body of the aforementioned rubber material. According to another aspect of the present application, it is possible to provide a diving suit provided with the aforementioned foamed body. BRIEF DESCRIPTION OF DRAWINGS

[0018] [ Figure 1 ] is a graph showing the relationship between the content of bonded sulfur and the content of a conjugated resin acid component in a rubber material. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present application will be described. The embodiments described below show one example of representative embodiments of the present application, and the scope of the present application is not construed to be narrowed by this.

[0020] "A or more" of a numerical range means A and a range greater than A. "A or less" of a numerical range means A and a range less than A. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range of a certain stage can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of the other stage. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range can be replaced with the value shown in the examples. As long as A and B are included, "A or B" can also include both. Unless otherwise specified, the materials exemplified in the present specification can be used alone as one kind, or two or more kinds can be used in combination. As for the content of each component in the composition, in the case where a plurality of substances belonging to each component is present in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition. The term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the desired effect of the process can be achieved. Unless otherwise specified, "alkyl" can be any of linear, branched, or cyclic.

[0021] <Rubber material>

[0022] The rubber material according to the present embodiment contains a sulfur-modified chloroprene polymer. In the rubber material according to the present embodiment, the content X (mass%) of sulfur constituting the sulfur-modified chloroprene polymer, and the total amount Y (mass%) of the conjugated resin acid and the salt of the conjugated resin acid satisfy the following formula (A) based on the total amount of the rubber material, and the total amount Y is 1.00 mass% or more.

[0023] 13.90X - 5.10 ≤ Y... (A)

[0024] A foamed body can be obtained by foaming the rubber material according to the present embodiment. According to the rubber material according to the present embodiment, by foaming the rubber material, it is possible to suppress shrinkage after foaming, and obtain a foamed body having excellent ozone resistance. The rubber material according to the present embodiment can be used for various uses without foaming, as long as it has a state in which the above-described foamed body can be obtained when the rubber material is foamed.

[0025] As a result of intensive studies by the inventors of the present application, it was found that adjusting the content X of sulfur constituting the sulfur-modified chloroprene polymer, and the total amount Y of the conjugated resin acid and the salt of the conjugated resin acid is effective for suppressing shrinkage after foaming and improving ozone resistance, and on this basis, it was found that in the case where the total amount Y satisfies the formula (A) having a linear boundary with respect to the content X, and is 1.00 mass% or more, it is possible to suppress shrinkage after foaming, and obtain a foamed body having excellent ozone resistance.

[0026] The sulfur-modified chloroprene polymer can have chloroprene (2-chloro-1,3-butadiene) as a monomer unit (monomer unit of chloroprene. Monomer unit = structural unit), having a monomer unit from chloroprene. As the sulfur-modified chloroprene polymer, a homopolymer of chloroprene, a copolymer of chloroprene (copolymer of chloroprene, and a monomer copolymerizable with chloroprene), and the like can be given, and a mixture of these polymers can also be used. From the viewpoint of easily suppressing shrinkage after foaming, and obtaining a foamed body having excellent ozone resistance, the sulfur-modified chloroprene polymer can include a homopolymer of chloroprene. The polymer structure of the sulfur-modified chloroprene polymer is not particularly limited.

[0027] As the monomer copolymerizable with chloroprene, esters of (meth)acrylic acid (methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like), hydroxyalkyl (meth)acrylate (2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and the like), 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, acrylonitrile, and the like can be given. The monomer copolymerizable with chloroprene is not limited to one, and for example, the copolymer of chloroprene can also be a copolymer of three or more monomers including chloroprene.

[0028] The content of the monomer unit of chloroprene can be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 92% by mass or more, 95% by mass or more, 98% by mass or more, or 99% by mass or more, based on the total amount of the monomer units constituting the sulfur-modified chloroprene polymer.

[0029] The sulfur-modified chloroprene polymer has sulfur (bonded sulfur, sulfur bonded in the sulfur-modified chloroprene polymer) constituting the sulfur-modified chloroprene polymer. The sulfur constituting the sulfur-modified chloroprene polymer is chemically bonded directly or indirectly with the monomer unit of chloroprene to constitute the sulfur-modified chloroprene polymer. The sulfur-modified chloroprene polymer can have a single sulfur bond and / or a polysulfide bond (for example, S2 to S8) constituting the sulfur-modified chloroprene polymer.

[0030] The content X of sulfur (bonded sulfur) constituting the sulfur-modified chloroprene polymer can be greater than 0 mass% based on the total amount of the rubber material, and can be in the following ranges. From the viewpoint of easily suppressing shrinkage after foaming, the content X can be 0.10 mass% or greater, 0.15 mass% or greater, 0.20 mass% or greater, 0.25 mass% or greater, more than 0.25 mass%, 0.27 mass% or greater, 0.28 mass% or greater, 0.30 mass% or greater, 0.35 mass% or greater, 0.40 mass% or greater, 0.41 mass% or greater, 0.42 mass% or greater, 0.43 mass% or greater, 0.45 mass% or greater, or 0.50 mass% or greater. From the viewpoint of easily obtaining excellent ozone resistance, the content X can be 1.00 mass% or less, 0.90 mass% or less, 0.80 mass% or less, 0.70 mass% or less, 0.60 mass% or less, 0.55 mass% or less, 0.52 mass% or less, 0.50 mass% or less, 0.45 mass% or less, 0.43 mass% or less, 0.42 mass% or less, 0.41 mass% or less, 0.40 mass% or less, 0.35 mass% or less, 0.30 mass% or less, 0.28 mass% or less, or 0.27 mass% or less. From these viewpoints, the content X can be 0.10 to 1.00 mass%, 0.25 to 0.60 mass%, 0.25 to 0.55 mass%, 0.25 to 0.50 mass%, 0.25 to 0.45 mass%, 0.25 to 0.41 mass%, 0.25 to 0.30 mass%, 0.30 to 0.60 mass%, 0.40 to 0.60 mass%, 0.50 to 0.60 mass%, 0.30 to 0.50 mass%, or 0.40 to 0.50 mass%. The content X can also be 0.52 mass% or greater, 0.55 mass% or greater, or 0.60 mass% or greater. The content X can be measured using the oxygen flask combustion method prescribed in JIS K6233-1. The content X has, for example, a tendency to increase as the amount of sulfur used in the polymerization of the sulfur-modified chloroprene polymer increases.

[0031] The sulfur-modified chloroprene polymer can not have at least one of the structures represented by the following General Formula (I) and the structure represented by the following General Formula (II) at the molecular terminal. 1 represents an alkyl group having 1 to 4 carbon atoms, R 2 represents an alkyl group having 8 to 20 carbon atoms.

[0032] -S-C(=S)-OR 1 …(I)

[0033] -S-R 2 (II)

[0034] From the viewpoint of easily suppressing shrinkage after foaming and obtaining a foamed body having excellent ozone resistance, the rubber material according to the present embodiment can contain sulfur (free sulfur, sulfur not bonded to the sulfur-modified chloroprene polymer) that does not constitute the sulfur-modified chloroprene polymer. The sulfur that does not constitute the sulfur-modified chloroprene polymer is not chemically bonded directly and indirectly to the monomer unit of chloroprene, and does not constitute the sulfur-modified chloroprene polymer.

[0035] The content C1 of the sulfur (free sulfur) that does not constitute the sulfur-modified chloroprene polymer can be in the following range, based on the total amount of the rubber material. From the viewpoint of easily suppressing shrinkage after foaming, the content C1 can be 0.10% by mass or more, 0.15% 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, 0.28% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.36% by mass or more, 0.38% by mass or more, 0.40% by mass or more, or 0.43% by mass or more. From the viewpoint of easily obtaining excellent ozone resistance, the content C1 can be 1.00% by mass or less, 0.90% by mass or less, 0.80% by mass or less, 0.70% by mass or less, 0.60% by mass or less, 0.55% by mass or less, 0.52% by mass or less, 0.50% by mass or less, 0.45% by mass or less, 0.43% by mass or less, 0.40% by mass or less, 0.38% by mass or less, 0.36% by mass or less, 0.35% by mass or less, 0.30% by mass or less, 0.28% by mass or less, 0.25% by mass or less, 0.23% by mass or less, or 0.21% by mass or less. From these viewpoints, the content C1 can be 0.10 to 1.00% by mass, 0.20 to 0.60% by mass, 0.20 to 0.50% by mass, 0.20 to 0.43% by mass, 0.20 to 0.40% by mass, 0.20 to 0.30% by mass, 0.20 to 0.25% by mass, 0.25 to 0.60% by mass, 0.30 to 0.60% by mass, 0.40 to 0.60% by mass, 0.25 to 0.50% by mass, or 0.25 to 0.43% by mass. The content C1 can also be 0.45% by mass or more, 0.50% by mass or more, or 0.52% by mass or more. The content C1 can also be 0.20% by mass or less. The content C1 can be measured by liquid chromatography. The content C1 has a tendency to increase, for example, due to an increase in the amount of sulfur used when polymerizing the sulfur-modified chloroprene polymer.

[0036] The total amount C2 of sulfur (bonded sulfur) constituting the sulfur-modified chloroprene polymer and sulfur (free sulfur) not constituting the sulfur-modified chloroprene polymer can be greater than 0 mass% based on the total amount of the rubber material, and can be in the following ranges. From the viewpoint of easily inhibiting shrinkage after foaming, the total amount C2 can be 0.20 mass% or more, 0.30 mass% or more, 0.40 mass% or more, 0.45 mass% or more, 0.47 mass% or more, 0.49 mass% or more, 0.50 mass% or more, 0.55 mass% or more, 0.58 mass% or more, 0.60 mass% or more, 0.63 mass% or more, 0.65 mass% or more, 0.70 mass% or more, 0.75 mass% or more, 0.79 mass% or more, 0.80 mass% or more, 0.83 mass% or more, 0.85 mass% or more, 0.90 mass% or more, or 0.93 mass% or more. From the viewpoint of easily obtaining excellent ozone resistance, the total amount C2 can be 2.00 mass% or less, 1.50 mass% or less, 1.20 mass% or less, 1.12 mass% or less, 1.10 mass% or less, 1.00 mass% or less, 0.97 mass% or less, 0.95 mass% or less, 0.93 mass% or less, 0.90 mass% or less, 0.85 mass% or less, 0.83 mass% or less, 0.80 mass% or less, 0.79 mass% or more, 0.75 mass% or less, 0.70 mass% or less, 0.65 mass% or less, 0.63 mass% or less, 0.60 mass% or less, 0.58 mass% or less, 0.55 mass% or less, 0.50 mass% or less, or 0.49 mass% or less. From these viewpoints, the total amount C2 can be 0.20 to 2.00 mass%, 0.40 to 1.20 mass%, 0.40 to 1.00 mass%, 0.40 to 0.93 mass%, 0.40 to 0.80 mass%, 0.40 to 0.70 mass%, 0.40 to 0.60 mass%, 0.40 to 0.50 mass%, 0.50 to 1.20 mass%, 0.70 to 1.20 mass%, 0.80 to 1.20 mass%, 0.90 to 1.20 mass%, 0.50 to 1.00 mass%, 0.70 to 1.00 mass%, or 0.80 to 1.00 mass%. The total amount C2 can also be 0.95 mass% or more, 0.97 mass% or more, 1.00 mass% or more, 1.10 mass% or more, or 1.12 mass% or more. The total amount C2 can also be 0.47 mass% or less.

[0037] The rubber material according to the present embodiment contains at least one conjugated resin acid component selected from the group consisting of a conjugated resin acid and a salt of a conjugated resin acid. As the salt of a conjugated resin acid, for example, an alkali metal salt (sodium salt, potassium salt, etc.) can be given. The conjugated resin acid component is a compound that can be contained in rosin acids. The conjugated resin acid component can be a residue of an emulsifier used in a polymerization step for obtaining a sulfur-modified chloroprene polymer, or can be contained in rosin acids mixed with the sulfur-modified chloroprene polymer after the sulfur-modified chloroprene polymer is obtained.

[0038] The "rosin acids" include a conjugated resin acid, a disproportionated rosin acid, an alkali metal salt of a conjugated resin acid (for example, a potassium salt of a conjugated resin acid), an alkali metal salt of a disproportionated rosin acid (for example, a potassium salt of a disproportionated rosin acid), and the like. The conjugated resin acid contains at least one selected from the group consisting of abietic acid, palustric acid, neoabietic acid, and levopimaric acid. As the disproportionated rosin acid, a sesquiterpene, 8,5-isopimaric acid, dihydro pimaric acid, secodehydroabietic acid, dehydroabietic acid, dihydroabietic acid, desisopropyldehydroabietic acid, desmethyldehydroabietic acid, and the like can be given.

[0039] From the viewpoint of suppressing shrinkage after foaming and obtaining a foamed body having excellent ozone resistance, the total amount Y of the conjugated resin acid and the salt of a conjugated resin acid is 1.00% by mass or more based on the total amount of the rubber material. The total amount Y can be measured by gas chromatography. The total amount Y has, for example, the following tendency: the total amount Y increases as the amount of rosin acids used as an emulsifier at the time of polymerization of the sulfur-modified chloroprene polymer, the amount of rosin acids mixed with the sulfur-modified chloroprene polymer after the sulfur-modified chloroprene polymer is obtained, and the like increase. As the total amount Y, the total of the contents of abietic acid components, palustric acid components, neoabietic acid components, and levopimaric acid components can be used.

[0040] The total amount Y can be in the following ranges, based on the total amount of the rubber material. From the viewpoint of excellent balance of the shrinkage after foaming and ozone resistance, the total amount Y can be 1.10% by mass or more, 1.20% by mass or more, 1.30% by mass or more, 1.40% by mass or more, 1.45% by mass or more, 1.50% by mass or more, 1.60% by mass or more, 1.80% by mass or more, 2.00% by mass or more, 2.20% by mass or more, or 2.30% by mass or more. From the viewpoint of excellent balance of the shrinkage after foaming and ozone resistance, the total amount Y can be 10.00% by mass or less, 5.00% by mass or less, 4.50% by mass or less, 4.00% by mass or less, 3.70% by mass or less, 3.60% by mass or less, 3.50% by mass or less, 3.30% by mass or less, 3.26% by mass or less, 3.20% by mass or less, 3.00% by mass or less, 2.50% by mass or less, 2.40% by mass or less, 2.30% by mass or less, 2.20% by mass or less, 2.00% by mass or less, 1.80% by mass or less, 1.60% by mass or less, 1.50% by mass or less, or 1.45% by mass or less. From these viewpoints, the total amount Y can be 1.00 to 10.00% by mass, 1.20 to 4.00% by mass, 1.20 to 3.70% by mass, 1.20 to 3.00% by mass, 1.20 to 2.50% by mass, 1.20 to 2.30% by mass, 1.20 to 2.20% by mass, 1.40 to 3.70% by mass, 1.50 to 3.70% by mass, 2.00 to 3.70% by mass, 2.20 to 3.70% by mass, 2.30 to 3.70% by mass, 1.40 to 3.20% by mass, 1.50 to 3.20% by mass, 2.00 to 3.20% by mass, or 2.20 to 3.20% by mass. The total amount Y can also be 2.40% by mass or more, 2.50% by mass or more, 3.00% by mass or more, 3.20% by mass or more, 3.26% by mass or more, 3.30% by mass or more, 3.50% by mass or more, or 3.60% by mass or more. The total amount Y can also be 1.40% by mass or less or 1.30% by mass or less.

[0041] In the rubber material according to the present embodiment, from the viewpoint of suppressing the shrinkage after foaming and obtaining a foamed product having excellent ozone resistance, the content X (mass%) of sulfur constituting the sulfur-modified chloroprene polymer, and the total amount Y (mass%) of the conjugated resin acid and the salt of the conjugated resin acid satisfy the following formula (A), based on the total amount of the rubber material.

[0042] 13.90X - 5.10 ≤ Y... (A)

[0043] The rubber material according to the present embodiment can contain a sulfur-modified chloroprene polymer, a conjugated resin acid component, and a component other than sulfur that does not constitute the sulfur-modified chloroprene polymer (free sulfur). As such a component, there can be mentioned a residue of a component used for polymerization of the sulfur-modified chloroprene polymer, a residue of a component used for plasticization of the sulfur-modified chloroprene polymer, a component mixed after polymerization and before plasticization, and the like, and specifically, various monomers, an emulsifier (excluding the conjugated resin acid component), a plasticizer, and the like. The emulsifier can be added at the time of polymerization or after polymerization and before plasticization.

[0044] 13.90 < X - 4.00 ≤ Y... (B)

[0045] For the rubber material according to the present embodiment, from the viewpoint that the balance between the shrinkage after foaming and the ozone resistance is excellent and that particularly excellent ozone resistance is easily obtained, it can be in a manner in which the content X and the total amount Y satisfy the formula (B), the content X is 0.25 to 0.55 mass%, and the total amount Y is 1.40 mass% or more.

[0046] The rubber material according to the present embodiment can contain a sulfur-modified chloroprene polymer, a conjugated resin acid component, and a component other than sulfur that does not constitute the sulfur-modified chloroprene polymer (free sulfur). As such a component, there can be mentioned a residue of a component used for polymerization of the sulfur-modified chloroprene polymer, a residue of a component used for plasticization of the sulfur-modified chloroprene polymer, a component mixed after polymerization and before plasticization, and the like, and specifically, various monomers, an emulsifier (excluding the conjugated resin acid component), a plasticizer, and the like. The emulsifier can be added at the time of polymerization or after polymerization and before plasticization.

[0047] As the emulsifier, a known emulsifier that can be used for emulsion polymerization of chloroprene can be used. As the emulsifier, there can be mentioned rosin acids, fatty acids, metal salts of aromatic sulfonic acid formaldehyde condensates (for example, a sodium salt of β-naphthalenesulfonic acid formaldehyde condensate), sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, sodium alkyl diphenyl ether sulfonate, potassium alkyl diphenyl ether sulfonate, sodium polyoxyethylene alkyl ether sulfonate, sodium polyoxypropylene alkyl ether sulfonate, potassium polyoxyethylene alkyl ether sulfonate, potassium polyoxypropylene alkyl ether sulfonate, and the like. As the fatty acids, there can be mentioned fatty acids (for example, saturated or unsaturated fatty acids having 6 to 22 carbon atoms), metal salts of fatty acids (for example, sodium lauryl sulfate), and the like.

[0048] As the plasticizer that can be used as a constituent material of the rubber material, there can be mentioned tetraalkyl thiuram disulfides (for example, tetraethyl thiuram disulfide and the like having alkyl groups having 1 to 7 carbon atoms), dialkyl dithiocarbamic acid salts (for example, nickel dibutyl dithiocarbamate and the like having alkyl groups having 1 to 7 carbon atoms), and the like.

[0049] The content of the plasticizer in the rubber material according to the present embodiment can be less than 1 mass%, can be 0.1 mass% or less, or can be 0.01 mass% or less, based on the total amount of the rubber material.

[0050] The rubber material according to the present embodiment includes a latex obtained by plasticizing a sulfur-modified chloroprene polymer obtained by polymerizing chloroprene alone or polymerizing chloroprene with other monomers in the presence of sulfur (e.g., S8), and a rubber material obtained by drying and washing the latex.

[0051] The method for producing the rubber material according to the present embodiment includes a polymerization step of obtaining a sulfur-modified chloroprene polymer by polymerizing (e.g., emulsion polymerizing) chloroprene in the presence of sulfur (e.g., S8). In the polymerization step, chloroprene can be polymerized alone, or chloroprene can be polymerized with the above-described monomer copolymerizable with chloroprene. In the polymerization step, chloroprene can be polymerized (e.g., emulsion polymerized) in the presence of sulfur and a conjugated resin acid component, thereby obtaining a polymer. In the polymerization step, emulsion polymerization can be performed using a conjugated resin acid component as an emulsifier, or emulsion polymerization can be performed using a rosin acid containing a conjugated resin acid component as an emulsifier.

[0052] In the polymerization step, sulfur can be introduced into the chloroprene polymer (e.g., the main chain of the chloroprene polymer), for example, a single sulfur bond and / or a polysulfide bond (S2 to S8) can be introduced. The amount of sulfur (e.g., S8) used can be 0.30 to 0.85 parts by mass with respect to 100 parts by mass of the monomers (total of the monomers subjected to polymerization).

[0053] In the case where emulsion polymerization is performed in the polymerization step, the pH of the emulsion (e.g., aqueous emulsion) at the start of emulsion polymerization can be 10.5 or higher. The "emulsion" is a mixture of chloroprene and other components (monomers copolymerizable with chloroprene, emulsifiers, sulfur, and the like) immediately before the start of emulsion polymerization. The "emulsion" also includes a case where the composition is sequentially changed by subsequent addition, batch addition, or the like of these other components. By setting the pH of the emulsion to 10.5 or higher, it is possible to prevent the precipitation of the polymer during polymerization and the like, and to stably control the polymerization. This effect can be particularly desirably obtained in the case where a rosin acid is used as an emulsifier. The pH of the emulsion can be adjusted by the amount of an alkali component such as sodium hydroxide, potassium hydroxide, or the like present at the time of emulsion polymerization.

[0054] From the viewpoint of excellent polymerization controllability and productivity, the polymerization temperature of the polymerization can be 0 to 55°C or 30 to 55°C.

[0055] As the polymerization initiator, a compound generally used in radical polymerization can be used, and potassium persulfate, benzoyl peroxide, ammonium persulfate, hydrogen peroxide, or the like can be used. The polymerization rate of polymerization can be 60 to 90% or 70 to 80%. After the target polymerization rate is obtained, a polymerization termination agent (polymerization inhibitor) can be added to stop the polymerization. As the polymerization termination agent, diethylhydroxylamine, thiodianiline, 4-tert-butylcatechol, 2,2'-methylenebis-4-methyl-6-tert-butylphenol, or the like can be given.

[0056] The manufacturing method of the rubber material according to the present embodiment can include, after the polymerization step, a step of adding a rosin acid containing a conjugated resin acid component to a polymerized polymerization liquid (for example, an aqueous emulsion after emulsion polymerization) containing the sulfur-modified chloroprene polymer.

[0057] The manufacturing method of the rubber material according to the present embodiment can include, after the polymerization step, a step of removing unreacted monomers. The unreacted monomers can be removed by, for example, distillation under reduced pressure.

[0058] The manufacturing method of the rubber material according to the present embodiment can include, after the polymerization step, a step of plasticizing the sulfur-modified chloroprene polymer. In this case, the Mooney viscosity of the rubber material can be reduced. In the plasticizing step, the sulfur-modified chloroprene polymer can be mixed with a plasticizer, and thus the molecular chain of the sulfur-modified chloroprene polymer can be cut. The plasticizer can be added to a polymerized polymerization liquid (for example, an aqueous emulsion after emulsion polymerization) containing the sulfur-modified chloroprene polymer. The plasticizer can be added before or after the removal of the unreacted monomers, or can be added both before and after the removal of the unreacted monomers.

[0059] The manufacturing method of the rubber material according to the present embodiment can include, after the polymerization step and the plasticizing step, a step of separating the rubber material. In the separating step, the rubber material can be separated by, for example, a freeze-coagulation method.

[0060] The manufacturing method of the rubber material according to the present embodiment can include, after the polymerization step and the plasticizing step, and before the separating step, a step of adjusting the pH of the polymerization liquid. In the pH adjusting step, the pH can be adjusted to 5.5 to 7.5 from the viewpoint of easily separating the rubber material by suppressing the generation of coagulates. The pH can be adjusted by, for example, an acid such as acetic acid.

[0061] < Rubber composition >

[0062] The rubber composition (sulfur-modified chloroprene rubber composition) according to the present embodiment contains the rubber material according to the present embodiment, and also contains an additive different from the rubber material. The rubber composition according to the present embodiment can be obtained in the form of a compounded composition by mixing the rubber material and the additive using a roll, a Banbury mixer, an extruder, or the like.

[0063] As the additive, a known ingredient that can be mixed with the rubber material obtained by polymerization, plasticization, pH adjustment, or the like of a chloroprene polymer can be used. As the additive, a vulcanizing agent, a blowing agent, a processing aid, a stabilizer, a metal compound (excluding a compound belonging to the vulcanizing agent), a plasticizer, a filler, or the like can be cited. The rubber composition according to the present embodiment can be in a manner containing the rubber material according to the present embodiment and a vulcanizing agent. In addition, the rubber composition according to the present embodiment can be in a manner containing the rubber material according to the present embodiment and a blowing agent. The rubber composition according to the present embodiment can contain the rubber material according to the present embodiment, a vulcanizing agent, and a blowing agent.

[0064] As the vulcanizing agent, a metal oxide or the like can be cited. As the metal oxide, zinc oxide, magnesium oxide, lead oxide, leady oxide, iron trioxide, titanium dioxide, calcium oxide, hydrotalcite, or the like can be cited. The content of the vulcanizing agent can be 3 to 15 parts by mass relative to 100 parts by mass of the rubber material.

[0065] As the blowing agent, an organic blowing agent, an inorganic blowing agent (sodium bicarbonate, ammonium carbonate, or the like), or the like can be cited. From the viewpoint of easily obtaining a high foaming ratio, the blowing agent can include an organic blowing agent. As the organic blowing agent, a hydrazide blowing agent, a nitroso blowing agent, an azo blowing agent, or the like can be cited. From the viewpoint of easily obtaining a high foaming ratio, the organic blowing agent can include a hydrazide blowing agent. As the hydrazide blowing agent, p,p'-oxybisbenzenesulfonyl hydrazide, benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, biurea, or the like can be cited. As the nitroso blowing agent, N,N'-dinitrosopentamethylene tetramine or the like can be cited. As the azo blowing agent, diazoaminobenzene, azodicarbonamide, azobisisobutyronitrile, barium azodicarboxylate, or the like can be cited. The content of the blowing agent can be 1 to 20 parts by mass, 3 to 15 parts by mass, or 5 to 10 parts by mass relative to 100 parts by mass of the rubber material.

[0066] As the processing aid, a fatty acid such as stearic acid; a paraffin processing aid (paraffin wax) such as polyethylene; a fatty acid ester; a fatty acid amide; a sulfur factice, or the like can be cited. The content of the processing aid can be 0.5 to 5 parts by mass relative to 100 parts by mass of the rubber material.

[0067] A stabilizer can be used to prevent changes in the Mooney viscosity on storage. As the stabilizer, phenyl-α-naphthylamine, octylated diphenylamine, 2,6-di-t-butyl-4-phenylphenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-thiobis-(6-t-butyl-3-methylphenol), and the like can be given.

[0068] A metal compound is a compound that can be added in order to adjust the vulcanization speed of the rubber material, or in order to adsorb chlorine sources such as hydrogen chloride generated by the deacidification reaction of the rubber material, and the like, to suppress deterioration of the rubber material. As the metal compound, oxides or hydroxides of zinc, titanium, magnesium, lead, iron, beryllium, calcium, barium, germanium, zirconium, vanadium, molybdenum, tungsten, and the like can be given. The content of the metal compound is not particularly limited, and from the viewpoint of easily improving the tear strength of the foam obtained using the rubber material, it can be 3 to 15 parts by mass relative to 100 parts by mass of the rubber material.

[0069] A plasticizer can be used to reduce the hardness of the rubber material (to improve the foaming efficiency) to improve the hand feeling of the foam. As the plasticizer, dioctyl phthalate, dioctyl adipate (alias: bis(2-ethylhexyl) adipate), white oil, silicone oil, naphthenic oil (for example, naphthenic operating oil), aromatic oil (for example, aromatic operating oil), triphenyl phosphate, tricresyl phosphate, and the like can be given. The content of the plasticizer is not particularly limited, and from the viewpoint of easily maintaining the tear strength of the foam, and obtaining a foam in which the balance between the shrinkage after foaming and the ozone resistance is excellent, it can be greater than 0 parts by mass and 50 parts by mass or less relative to 100 parts by mass of the rubber material.

[0070] A filler is a component that can be added as a reinforcing material for the rubber material. As the filler material, carbon black, DIXIE CLAY, silica, clay, talc, calcium carbonate, and the like can be given. The content of the filler material is not particularly limited, and from the viewpoint of easily maintaining the moldability of the rubber material, and obtaining a foam in which the balance between the shrinkage after foaming and the ozone resistance is excellent, it can be greater than 0 parts by mass and 100 parts by mass or less relative to 100 parts by mass of the rubber material.

[0071] The content of the polyisobutylene in the rubber composition according to the present embodiment can be 3 parts by mass or less, 1 part by mass or less, 0.1 part by mass or less, or 0.01 part by mass or less, or can be 0 parts by mass, relative to 100 parts by mass of the rubber material. The content of the boric acid in the rubber composition according to the present embodiment can be less than 0.01 part by mass, can be 0.001 part by mass or less, or 0.0001 part by mass or less, or can be 0 parts by mass, relative to 100 parts by mass of the rubber material.

[0072] The content of the rubber material according to the present embodiment can be in the following range based on the total mass of the rubber composition. From the viewpoint of easily suppressing shrinkage after foaming and obtaining a foam having excellent ozone resistance, the content of the rubber material can be 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more. From the viewpoint of easily suppressing shrinkage after foaming and obtaining a foam having excellent ozone resistance, the content of the rubber material can be 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 55% by mass or less. From these viewpoints, the content of the rubber material can be 10 to 90% by mass, 30 to 80% by mass, or 40 to 60% by mass.

[0073] <foam, molded article, laminate, and diving suit>

[0074] The vulcanizate according to the present embodiment is a vulcanizate obtained using the rubber material according to the present embodiment. The vulcanizate according to the present embodiment is a vulcanizate of the rubber material according to the present embodiment, or a vulcanizate of the rubber composition according to the present embodiment, and can be obtained by vulcanizing the rubber material according to the present embodiment, or the rubber composition according to the present embodiment. For example, the vulcanizate according to the present embodiment can be obtained by vulcanizing a rubber composition containing the rubber material according to the present embodiment, and a vulcanizing agent.

[0075] The foam according to the present embodiment is a foam obtained using the rubber material according to the present embodiment. The foam according to the present embodiment is a foam of the rubber material according to the present embodiment, or a foam of the rubber composition according to the present embodiment, and can be obtained by foaming the rubber material according to the present embodiment, or the rubber composition according to the present embodiment. For example, the foam according to the present embodiment can be obtained by vulcanizing a rubber composition containing the rubber material according to the present embodiment, and a foaming agent.

[0076] The molded article according to the present embodiment is a molded article formed of the vulcanizate according to the present embodiment (a molded article using the vulcanizate), or a molded article formed of the expanded body according to the present embodiment (a molded article using the expanded body), and can be obtained by molding the vulcanizate according to the present embodiment or the expanded body according to the present embodiment. As the molded article, a power transmission belt, a conveyor belt, a vibration isolator, an air spring (for example, an air spring for a vehicle), a hose (a hose product), a sponge (a sponge product), or the like can be given. The molded article can be obtained by mixing the components of the rubber composition (a rubber material, a vulcanizing agent, a foaming agent, or the like), molding into a desired shape, and further performing a vulcanization treatment and / or a foaming treatment. Alternatively, the molded article can be obtained by mixing the components of the rubber composition, performing a vulcanization treatment and / or a foaming treatment, and further molding into a desired shape.

[0077] The first mode of the laminate according to the present embodiment includes the vulcanizate according to the present embodiment, and a fiber base material laminated to the vulcanizate. The second mode of the laminate according to the present embodiment includes the expanded body according to the present embodiment, and a fiber base material laminated to the expanded body. In a case where the vulcanizate or the expanded body has opposite faces, the fiber base material can be laminated to one face or both faces of the vulcanizate or the expanded body. As the fiber base material, a jersey cloth, a polyester fiber, a nylon fiber, or the like can be given. The second mode of the laminate according to the present embodiment can be used as a clothing material for a diving suit.

[0078] The diving suit according to the present embodiment is a diving suit including the expanded body according to the present embodiment. The diving suit according to the present embodiment includes the laminate according to the second mode described above, and includes the expanded body according to the present embodiment and a fiber base material laminated to the expanded body. The diving suit according to the present embodiment can be obtained, for example, by slicing the expanded body according to the present embodiment into a desired thickness, laminating (laminating) a fiber base material to one face or both faces of the obtained expanded base material to obtain a clothing material, and sewing the clothing material.

[0079] Example

[0080] Hereinafter, the present application will be described in more detail based on examples and comparative examples, but the present application is not limited to these examples.

[0081] <Manufacture of Rubber Material>

[0082] (Example 1)

[0083] To a polymerization tank having a content of 30 L, chlorobutadiene (monomer) 100 parts by mass, sulfur 0.40 parts by mass, pure water 120 parts by mass, a potassium salt of a conjugated resin acid type rosin acid (trade name "HARTALL R-WW", manufactured by HARIMA CHEMICALS, INC.) A 2.99 parts by mass, sodium hydroxide 0.82 parts by mass, and a sodium salt of a β-naphthalene sulfonic acid formaldehyde condensate (trade name "Demol N", manufactured by Kawaguchi Chemical Industry Co., Ltd.) 0.5 parts by mass were added. After adding potassium persulfate 0.1 parts by mass as a polymerization initiator, polymerization was performed under a nitrogen stream at a polymerization temperature of 40°C. At the time point when the polymerization rate became 70%, diethylhydroxylamine 0.1 parts by mass was added as a polymerization terminator to stop the polymerization, whereby a polymerization solution was obtained. To the polymerization solution after the polymerization was completed, a potassium salt of a conjugated resin acid type rosin acid B (same content as the potassium salt of a conjugated resin acid type rosin acid A) 0.52 parts by mass was added. Then, unreacted monomers were removed by performing reduced pressure distillation, whereby a latex before plasticization (latex after the polymerization was completed) was obtained.

[0084] Next, to the latex before plasticization, a plasticizer emulsion formed of chlorobutadiene 3.0 parts by mass, tetraethylthiuram disulfide (trade name "Nocceler TET", manufactured by ONO SANGYO CO., LTD.) 2.0 parts by mass, a sodium salt of a β-naphthalene sulfonic acid formaldehyde condensate 0.05 parts by mass, and sodium lauryl sulfate 0.05 parts by mass was added, and then, plasticization was performed by keeping the temperature at 50°C for 1 hour while stirring, whereby a latex after plasticization was obtained.

[0085] Then, the latex after plasticization was cooled, and acetic acid was added to adjust the pH to 6.0. Next, separation was performed by a freeze-coagulation method of a conventional method, whereby a rubber material containing a sulfur-modified chlorobutadiene polymer and the like was obtained.

[0086] (Example 2)

[0087] The amount of use of sulfur was changed to 0.40 parts by mass, the amount of use of the potassium salt of a conjugated resin acid type rosin acid A was changed to 3.85 parts by mass, the amount of use of the potassium salt of a conjugated resin acid type rosin acid B was changed to 1.24 parts by mass, and otherwise, the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0088] (Example 3)

[0089] The amount of use of sulfur was changed to 0.40 parts by mass, the amount of use of the potassium salt of a conjugated resin acid type rosin acid A was changed to 4.30 parts by mass, the amount of use of the potassium salt of a conjugated resin acid type rosin acid B was changed to 0.88 parts by mass, and otherwise, the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0090] (Example 4)

[0091] The amount of use of sulfur was changed to 0.49 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt A was changed to 3.01 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt B was changed to 0.46 parts by mass, and otherwise the same as in Example 1 was operated, whereby a rubber material was obtained.

[0092] (Example 5)

[0093] The amount of use of sulfur was changed to 0.50 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt A was changed to 4.22 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt B was changed to 0.98 parts by mass, and otherwise the same as in Example 1 was operated, whereby a rubber material was obtained.

[0094] (Example 6)

[0095] The amount of use of sulfur was changed to 0.60 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt A was changed to 3.71 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt B was changed to 1.41 parts by mass, and otherwise the same as in Example 1 was operated, whereby a rubber material was obtained.

[0096] (Example 7)

[0097] The amount of use of sulfur was changed to 0.58 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt A was changed to 3.03 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt B was changed to 0.45 parts by mass, and otherwise the same as in Example 1 was operated, whereby a rubber material was obtained.

[0098] (Example 8)

[0099] The amount of use of sulfur was changed to 0.60 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt A was changed to 1.87 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt B was changed to 1.12 parts by mass, and otherwise the same as in Example 1 was operated, whereby a rubber material was obtained.

[0100] (Example 9)

[0101] The amount of use of sulfur was changed to 0.66 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt A was changed to 3.31 parts by mass, the amount of use of the conjugated resin acid type rosin acid potassium salt B was changed to 1.27 parts by mass, and otherwise the same as in Example 1 was operated, whereby a rubber material was obtained.

[0102] (Example 10)

[0103] The amount of sulfur was changed to 0.66 parts by mass, the amount of the conjugated resin acid-based potassium abietate A was changed to 4.53 parts by mass, the amount of the conjugated resin acid-based potassium abietate B was changed to 3.67 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0104] (Example 11)

[0105] The amount of sulfur was changed to 0.68 parts by mass, the amount of the conjugated resin acid-based potassium abietate A was changed to 4.55 parts by mass, the amount of the conjugated resin acid-based potassium abietate B was changed to 2.72 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0106] (Example 12)

[0107] The amount of sulfur was changed to 0.77 parts by mass, the amount of the conjugated resin acid-based potassium abietate A was changed to 3.44 parts by mass, the amount of the conjugated resin acid-based potassium abietate B was changed to 3.97 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0108] (Example 13)

[0109] The amount of sulfur was changed to 0.77 parts by mass, the amount of the conjugated resin acid-based potassium abietate A was changed to 4.07 parts by mass, the amount of the conjugated resin acid-based potassium abietate B was changed to 4.12 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0110] (Comparative Example 1)

[0111] The amount of sulfur was changed to 0.34 parts by mass, a dismutation abietic acid potassium salt (trade name "BANDIS G-25K", manufactured by HARIMA CHEMICALS, INC.) was used instead of the conjugated resin acid-based potassium abietate A in an amount of 4.03 parts by mass, the amount of the conjugated resin acid-based potassium abietate B was changed to 0 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0112] (Comparative Example 2)

[0113] The amount of sulfur was changed to 0.50 parts by mass, a dismutation abietic acid potassium salt (trade name "BANDIS G-25K", manufactured by HARIMA CHEMICALS, INC.) was used instead of the conjugated resin acid-based potassium abietate A in an amount of 3.95 parts by mass, the amount of the conjugated resin acid-based potassium abietate B was changed to 0 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0114] (Comparative Example 3)

[0115] The amount of sulfur was changed to 0.50 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt A was changed to 1.83 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt B was changed to 0 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0116] (Comparative Example 4)

[0117] The amount of sulfur was changed to 0.60 parts by mass, 3.82 parts by mass of a disproportionated rosin acid potassium salt (trade name "BANDIS G-25K", manufactured by HARIMA CHEMICALS, INC.) was used instead of the conjugated resin acid type rosin acid potassium salt A, the amount of the conjugated resin acid type rosin acid potassium salt B was changed to 0 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0118] (Comparative Example 5)

[0119] The amount of sulfur was changed to 0.66 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt A was changed to 3.05 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt B was changed to 0.65 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0120] (Comparative Example 6)

[0121] The amount of sulfur was changed to 0.67 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt A was changed to 1.76 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt B was changed to 0 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0122] (Comparative Example 7)

[0123] The amount of sulfur was changed to 0.71 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt A was changed to 4.34 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt B was changed to 0.67 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0124] (Comparative Example 8)

[0125] The amount of sulfur was changed to 0.77 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt A was changed to 4.21 parts by mass, the amount of the conjugated resin acid type rosin acid potassium salt B was changed to 0.92 parts by mass, and otherwise the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0126] (Comparative Example 9)

[0127] The amount of sulfur was changed to 0.82 parts by mass, the amount of the conjugated rosin acid potassium salt A was changed to 3.81 parts by mass, the amount of the conjugated rosin acid potassium salt B was changed to 4.63 parts by mass, and otherwise, the same operation as in Example 1 was performed, whereby a rubber material was obtained.

[0128] <Measurement of the content X of the bonded sulfur in the rubber material>

[0129] The above rubber material was purified with a mixed solution of benzene:methanol = 3:5 (mass ratio), and then freeze-dried, whereby a sample was obtained. Using the sample, the content X (unit: mass%) of the bonded sulfur (sulfur constituting the sulfur-modified chloroprene polymer) in the rubber material was measured by the oxygen flask combustion method prescribed in JIS K6233-1. The measurement results of the content X are shown in Tables 1 and 2 as a value A (= 13.90X - 5.10) corresponding to the left side of the above formula (A) and a value B (= 13.90X - 4.00) corresponding to the left side of the above formula (B).

[0130] <Measurement of the content C1 of the free sulfur in the rubber material>

[0131] The above rubber material was cut, whereby a test piece was obtained. 20 mg of the test piece was dissolved in THF (tetrahydrofuran) 10 g, and a solution obtained thereby was used to perform liquid chromatography under the following conditions. The peak area of the free sulfur (sulfur not constituting the sulfur-modified chloroprene polymer) was calculated from the measurement results of the liquid chromatography.

[0132] [Conditions of the liquid chromatography]

[0133] • Column used: Shodex KF-803L

[0134] • Detector: UV (UV detection wavelength: 264 nm)

[0135] • Column temperature: 40°C

[0136] • Flow rate: 1 mL / min

[0137] The content (unit: ppm) of the free sulfur in the THF solution corresponding to the peak area obtained by the above measurement was obtained using a standard curve showing the relationship between the peak area of the free sulfur and the content. The standard curve was prepared separately using two kinds of THF solutions having sulfur contents of 1 ppm and 10 ppm. Next, the content C1 (unit: mass%) of the free sulfur in the rubber material was obtained using the content of the free sulfur in the THF solution. The measurement results of the content C1 and the total amount (total amount of sulfur) C2 of the content X and the content C1 are shown in Tables 1 and 2.

[0138] Measurement of the total amount Y of the conjugated resin acid components in the rubber material

[0139] The rubber material described above was cut to thereby obtain a test piece. The test piece 3.0 g was charged into a flask attached to a condenser, and then extraction was performed using an ethanol / toluene azeotropic mixture (ETA solution) prescribed in JIS K 6229, and the extract thus obtained was subjected to acid treatment with hydrochloric acid and diluted to 50 mL with hydrochloric acid. The diluted liquid was used to perform gas chromatography under the following conditions. The peak area of each of the conjugated resin acid components of the abietic acid component (abietic acid and salts thereof, and the same applies to other conjugated resin acids), the palustric acid component, the neoabietic acid component, and the levopimaric acid component was found from the measurement results of the gas chromatography.

[0140] [Conditions of the gas chromatography]

[0141] • Column used: FFAP 0.32 mmφ x 25 m (film thickness: 0.3 μm)

[0142] • Detector: FID

[0143] • Column temperature: 200°C→250°C

[0144] • Temperature increase rate: 10°C / min

[0145] • Injection port temperature: 270°C

[0146] • Detector temperature: 270°C

[0147] • Injection amount: 2 μL

[0148] Using a standard curve indicating the relationship between the peak area of the conjugated resin acid components and the content, the content (unit: g / ml) of the conjugated resin acid components in the ETA solution corresponding to the peak area found by the above measurement was found for each of the conjugated resin acid components of the abietic acid component, the palustric acid component, the neoabietic acid component, and the levopimaric acid component. The standard curve was made separately for each of the conjugated resin acid components of the abietic acid component, the palustric acid component, the neoabietic acid component, and the levopimaric acid component using three kinds of ETA solutions in which the content of the conjugated resin acid components was 1 g / ml, 2.5 g / ml, and 5 g / ml. Next, using the content of the conjugated resin acid components in the ETA solution, the content (unit: mass%) of each of the abietic acid component, the palustric acid component, the neoabietic acid component, and the levopimaric acid component in the rubber material was found.

[0149] The sum of the contents of abietic acid components, palustric acid components, neoabietic acid components, and levopimaric acid components in the rubber material was obtained as the total amount Y (unit: mass%) of conjugated resin acid components (conjugated resin acids and salts of conjugated resin acids). The results of measurement of the total amount Y of conjugated resin acid components, the size relationship between the total amount Y and the value A, and the size relationship between the total amount Y and the value B are shown in Table 1 and Table 2. In addition, the relationship between the content X (amount of bonded sulfur) and the total amount Y (amount of conjugated resin acid components) is shown in Table 3. Figure 1 .

[0150] <Manufacture of Foams>

[0151] According to JIS K 6299, 100 parts by mass of the above rubber material, 5 parts by mass of zinc oxide (trade name "Zinc Oxide 2 kinds", manufactured by KANTO KAGAKU KOGYO CO., LTD.), 4 parts by mass of magnesium oxide (trade name "KYOWA MAG 150", manufactured by KYOWA CHEMICAL INDUSTRIES, LTD.), 8 parts by mass of p,p'-oxobenzhydrazide (trade name "CELLMIC S", manufactured by SANKO CHEMICAL INDUSTRIES, LTD.), 1 part by mass of stearic acid, 1 part by mass of paraffin wax (trade name "Paraffin Wax-130", manufactured by NIPPON SEIRO CO., LTD.), 2 parts by mass of a fatty acid ester-based lubricant (trade name "WB-212", manufactured by S&S Japan Co., LTD.), 1 part by mass of octylated diphenylamine (trade name "NONFLEX OD-3", manufactured by SEIKA CHEMICAL CO., LTD.), 1 part by mass of nickel dibutyldithiocarbamate (trade name "NOC LAK NBC", manufactured by ONO PHARMA CO., LTD.), 15 parts by mass of a naphthene-based process oil (trade name "NP-24", manufactured by IDEN KOSAN CO., LTD.), 20 parts by mass of an aromatic-based process oil (trade name "AH-16", manufactured by IDEN KOSAN CO., LTD.), 10 parts by mass of carbon black (trade name "N990", manufactured by Cancarb), 10 parts by mass of DIXIE CLAY (trade name "DIXIE CLAY", manufactured by Vanderbilt), and 15 parts by mass of sulfur ointment (trade name "Brown #21", manufactured by Tenma Factice Manufacturing Co., Ltd.) were mixed, and then kneaded, thereby obtaining an unvulcanized rubber compound. The kneading was performed by using a kneader equipped with 8-inch rollers whose roller temperature was set to 40°C.

[0152] To the above-mentioned unvulcanized rubber compound, secondary press vulcanization was performed in accordance with JIS K 6299, whereby a foam was produced. Specifically, as primary vulcanization (first press vulcanization), 102 g of the unvulcanized rubber compound was charged into a mold having a cavity area of 100 mm in the longitudinal direction, 95 mm in the lateral direction, and 8 mm in height, and vulcanization was performed in the cavity area at a pressure of 3.5 MPa and at 150°C for 10 minutes. Then, the primary vulcanized compound was left to stand at 23°C under atmospheric pressure for 10 minutes, whereby a primary vulcanized compound was obtained. Subsequently, as secondary vulcanization (second press vulcanization), the primary vulcanized compound was charged into a mold having a cavity area of 175 mm in the longitudinal direction, 170 mm in the lateral direction, and 16 mm in height, and vulcanization was performed in the cavity area at a pressure of 3.5 MPa and at 155°C for 20 minutes.

[0153] <evaluation of the foam>

[0154] (shrinkage rate)

[0155] After the above-mentioned foam was left to stand at 23°C under atmospheric pressure for 168 hours, the surface layer of the foam was sliced in a thickness of 2 mm ± 0.20 mm, whereby a foam sheet was obtained. The dimensions of the foam sheet immediately after slicing were measured, and the length in the longitudinal direction H0 (mm) and the length in the lateral direction L0 (mm) of the foam sheet were obtained. Then, after the foam sheet was left to stand at 23°C under atmospheric pressure for 168 hours, the dimensions of the foam sheet were measured again, and the length in the longitudinal direction H1 (mm) and the length in the lateral direction L1 (mm) of the foam sheet were obtained. Using the dimensions of the foam sheet before and after standing, the shrinkage rate (%) was calculated by the following equation. The results are shown in Tables 1 and 2. A case where the shrinkage rate was 6.00% or less was determined to be good.

[0156] Shrinkage rate (%) = [(H0 x L0 - H1 x L1) / (H0 x L0)] x 100

[0157] (ozone test)

[0158] Test pieces were produced in accordance with JIS K 6250. Dynamic ozone deterioration tests were performed in accordance with JIS K 6259-1, and cracks were observed when the test pieces were continuously exposed to ozone under conditions in which the test temperature was 40°C, the ozone concentration was 50 pphm, and the elongation was 20%. The cracks were observed by visual observation, and a magnifying glass was used as necessary. Evaluation based on the number of cracks (number of cracks a) and evaluation based on the size and depth of the cracks (size of cracks b) were performed in accordance with JIS K 6259-1, and scoring was performed in accordance with the following criteria. In addition, as an evaluation index for ozone resistance, the product (a x b) of the number of cracks a and the size of cracks b was calculated. The results are shown in Table 1 and Table 2. Cases in which the product (a x b) was 9 points or less were determined to be good.

[0159] [Classification based on the number of cracks (number of cracks a)]

[0160] 1 point: small number of cracks

[0161] 3 points: large number of cracks

[0162] [Classification based on the size and depth of the cracks (size of cracks b)]

[0163] 1 point: cracks that are not visible to the naked eye but can be confirmed using a magnifying glass of 10 times

[0164] 2 points: cracks that can be confirmed with the naked eye

[0165] 3 points: deep and large cracks (less than 1 mm)

[0166] 4 points: deep and large cracks (1 mm or more and less than 3 mm)

[0167] [Table 1]

[0168]

[0169] [Table 2]

[0170]

[0171] As shown in Table 1 and Table 2, it was confirmed that by satisfying formula (A) for the content X and the total amount Y, and by making the total amount Y 1.00% by mass or more, shrinkage after foaming could be suppressed, and a foam having excellent ozone resistance could be obtained.

Claims

1. A rubber material which is a rubber material containing a sulfur-modified chloroprene polymer, a content X of sulfur constituting the sulfur-modified chloroprene polymer, and a total amount Y of a conjugated resin acid and a salt of a conjugated resin acid satisfy the following formula (A) with respect to the total amount of the rubber material, the content X is 0.25 to 0.60 mass%, the total amount Y is 1.00 to 3.70 mass%, 13.90X - 5.10 ≤ Y... (A).

2. The rubber material of claim 1, wherein, the content X and the total amount Y satisfy the following formula (B) with respect to the total amount of the rubber material: 13.90X - 4.00 ≤ Y... (B).

3. The rubber material of claim 1 or 2, wherein, the total amount Y is 1.40 mass% or more.

4. The rubber material of claim 1 or 2, wherein, a total amount of sulfur constituting the sulfur-modified chloroprene polymer and sulfur not constituting the sulfur-modified chloroprene polymer is 0.50 to 1.00 mass% with respect to the total amount of the rubber material.

5. A rubber composition containing the rubber material according to any one of claims 1 to 4, and a vulcanizing agent.

6. A rubber composition containing the rubber material according to any one of claims 1 to 4, and a foaming agent.

7. A vulcanizate of the rubber composition according to claim 5.

8. A foam of the rubber composition according to claim 6.

9. A diving suit provided with the foam according to claim 8.

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