Copolymer rubber, rubber composition, cross-linked rubber, hose material, and sealing material

Abstract

To provide a copolymer rubber that can provide a rubber composition with excellent scorch stability and can provide crosslinked rubber with excellent compression set properties.SOLUTION: A copolymer rubber is obtained by copolymerization of a carboxyl group-containing monomer represented by general formula (1) and a radical-polymerizable monomer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copolymer rubber that can give a cross-linked rubber product that is excellent in scorch stability and compression set, and to a rubber composition, a cross-linked rubber product, a hose material, and a sealing material obtained using such a copolymer rubber. [Background technology]

[0002] Rubber products with various properties depending on the application have been developed. For example, Patent Document 1 discloses an acrylic rubber composition that is used for manufacturing sealing parts and has excellent scorch stability.

[0003] The technology described in Patent Document 1 provides an acrylic rubber composition that can be vulcanized at high speed and has excellent scorch stability. However, there is room for improvement in the compression set resistance of vulcanized molded articles obtained from the acrylic rubber composition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 117849 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a copolymer rubber that can give a cross-linked rubber product that is excellent in scorch stability and compression set. [Means for solving the problem]

[0006] As a result of intensive research conducted by the present inventors to achieve the above object, they have found that a copolymer rubber obtained by copolymerizing a specific carboxyl group-containing monomer with a radically polymerizable monomer can give a cross-linked rubber product that is excellent in scorch stability and compression set, and have thus completed the present invention.

[0007] That is, according to the present invention, there is provided a copolymer rubber obtained by copolymerizing a carboxyl group-containing monomer represented by the above general formula (1) with a radically polymerizable monomer. [ka] (In the above general formula (1), R 1 and R 2 one of which is a hydrogen atom and the other is an alkyl group, and n is an integer of 0 to 3.

[0008] In the copolymer rubber of the present invention, it is preferable that n is an integer of 0 or 1 in the general formula (1). The copolymer rubber of the present invention preferably has a glass transition temperature of 0°C or lower. In the copolymer rubber of the present invention, the content of the carboxyl group-containing monomer unit represented by the general formula (1) is preferably 0.1 to 10% by weight. In the copolymer rubber of the present invention, the radical polymerizable monomer is preferably at least one selected from the group consisting of (meth)acrylic acid esters, (meth)acrylonitrile, aromatic vinyl, conjugated dienes, (meth)acrylamide, vinyl acetate, and ethylene. In the copolymer rubber of the present invention, the radical polymerizable monomer is preferably a (meth)acrylic acid ester. The copolymer rubber of the present invention preferably has a Mooney viscosity (ML1+4, 100°C) of 10-150.

[0009] According to the present invention, there is provided a rubber composition containing the above copolymer rubber and a crosslinking agent. According to the present invention, there is provided a cross-linked rubber product obtained by cross-linking the above rubber composition. According to the present invention, there is provided a hose material or a sealing material containing the above rubber composition. [Effects of the Invention]

[0010] It is possible to provide a copolymer rubber capable of giving a cross-linked rubber product having excellent scorch stability and excellent resistance to compression set, a rubber composition obtained using such a copolymer rubber, a cross-linked rubber product, and a hose material and a sealing material obtained using the rubber composition. DETAILED DESCRIPTION OF THE INVENTION

[0011] The copolymer rubber of the present invention is a copolymer rubber obtained by copolymerizing a carboxyl group-containing monomer represented by the following general formula (1) with a radically polymerizable monomer. [ka] (In the above general formula (1), R 1 and R 2 one of which is a hydrogen atom and the other is an alkyl group, and n is an integer of 0 to 3.

[0012] <Carboxyl group-containing monomer> The carboxyl group-containing monomer used in the present invention is a compound represented by the following general formula (1). [ka] In the above general formula (1), R 1 and R 2wherein one is a hydrogen atom and the other is an alkyl group, and n is an integer of 0 to 3. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl groups, and cyclic alkyl groups such as cyclobutyl, cyclopentyl, and cyclohexyl groups. Among these, linear alkyl groups having 1 to 10 carbon atoms are preferred, linear alkyl groups having 1 to 8 carbon atoms are more preferred, and linear alkyl groups having 1 to 4 carbon atoms are even more preferred. Specific examples of linear alkyl groups having 1 to 10 carbon atoms are more preferably methyl, ethyl, butyl, and octyl groups, and even more preferably butyl groups. The alkyl group may have a substituent, and examples of the substituent include halogen atoms such as fluorine, chlorine, and bromine; alkoxy groups having 1 to 10 carbon atoms such as methoxy, ethoxy, and isopropoxy; nitro; cyano; phenyl, 4-methylphenyl, 2-chlorophenyl, 1-naphthyl, 2-naphthyl, and aryl groups having 6 to 10 carbon atoms. These substituents can be located at any position. n is preferably 0 or 1, and more preferably 1. That is, the compound represented by the above general formula (1) is preferably a compound represented by the following general formula (2). [ka] (In the above general formula (2), R 1 and R 2 is the same as in the above general formula (1).

[0013] Specific examples of the compound represented by the general formula (2) include monomethyl allylsuccinate, monoethyl allylsuccinate, monopropyl allylsuccinate, monobutyl allylsuccinate, monooctyl allylsuccinate, monocyclohexyl allylsuccinate, etc. Among these, monomethyl allylsuccinate, monoethyl allylsuccinate, monobutyl allylsuccinate, and monooctyl allylsuccinate are preferred, and monobutyl allylsuccinate is more preferred.

[0014] In addition, R in the above general formulas (1) and (2) 1 and R 2 About R 1 is a hydrogen atom, and R 2 may be an alkyl group, and conversely, R 1 is an alkyl group, and R 2 may be a hydrogen atom. In addition, the compounds represented by the above general formulas (1) and (2) may be 1 is a hydrogen atom and R 2 is an alkyl group, and R 1 is an alkyl group and R 2 In this case, in the copolymer rubber of the present invention, R 1 is a hydrogen atom and R 2 is an alkyl group, and R 1 is an alkyl group and R 2 In this case, R may contain a monomer unit in which R is a hydrogen atom. 1 is a hydrogen atom and R 2 is an alkyl group, and R 1 is an alkyl group and R 2 The ratio of the monomer units in which the aryl group is a hydrogen atom to the monomer units in which the aryl group is a hydrogen atom is arbitrary and is not particularly limited.

[0015] The units derived from the carboxyl group-containing monomer represented by the general formula (1) above act as crosslinkable monomer units in the copolymer rubber of the present invention, and since the copolymer rubber of the present invention contains units derived from the carboxyl group-containing monomer represented by the general formula (1) above, it is possible to give a crosslinked rubber product that is excellent in scorch stability and compression set.

[0016] The content of the carboxyl group-containing monomer units represented by the general formula (1) in the copolymer rubber of the present invention is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, and even more preferably 1 to 5% by weight. By having the content of the carboxyl group-containing monomer units represented by the general formula (1) within the above range, a better balance between scorch stability and the compression set of the resulting cross-linked rubber product can be achieved. In particular, by having the content of the carboxyl group-containing monomer units represented by the general formula (1) at or above the above lower limit, cross-linking can be carried out sufficiently, and the compression set of the resulting cross-linked rubber product can be reduced. On the other hand, by having the content of the carboxyl group-containing monomer units represented by the general formula (1) at or below the above upper limit, scorch of the copolymer rubber of the present invention can be suppressed (scorch stability can be improved) and the elongation of the resulting cross-linked rubber product can be increased.

[0017] When a compound represented by the general formula (2) is used as the carboxyl group-containing monomer represented by the general formula (1) used in the present invention, it can be obtained, for example, by reacting allyl succinic anhydride with an alcohol having 1 to 10 carbon atoms under heating and reflux.

[0018] The content of carboxyl groups in the copolymer rubber of the present invention, i.e., the number of moles (ephr) of carboxyl groups per 100 g of copolymer rubber, is preferably 4×10 -4 ~4×10 -1 (ephr), more preferably 1 × 10 -3 ~2×10 -1 (ephr), more preferably 5 × 10 -3 ~1×10 -1 (ephr). By making the carboxyl group content equal to or greater than the above lower limit, crosslinking can be carried out sufficiently, and the compression set of the obtained cross-linked rubber product can be reduced. On the other hand, by making the carboxyl group content equal to or less than the above upper limit, scorching of the copolymer rubber of the present invention can be suppressed and the elongation of the obtained cross-linked rubber product can be increased.

[0019] The copolymer rubber of the present invention contains units derived from the carboxyl group-containing monomer represented by the above general formula (1), but may further contain carboxyl group-containing monomer units other than the units derived from the carboxyl group-containing monomer represented by the above general formula (1) within a range that does not impair the effects of the present invention. The monomer that forms the carboxyl group-containing monomer units other than the units derived from the carboxyl group-containing monomer represented by the above general formula (1) is not particularly limited, and examples thereof include α,β-ethylenically unsaturated monocarboxylic acids, α,β-ethylenically unsaturated dicarboxylic acids, and monoesters of α,β-ethylenically unsaturated dicarboxylic acids and alkanols.

[0020] Specific examples of the α,β-ethylenically unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid. Specific examples of the α,β-ethylenically unsaturated dicarboxylic acid include butenedioic acids such as fumaric acid and maleic acid; itaconic acid; citraconic acid; chloromaleic acid; and the like. Specific examples of the monoester of an α,β-ethylenically unsaturated dicarboxylic acid and an alkanol include butenedioic acid mono-chain alkyl esters such as monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, and mono-n-butyl maleate; butenedioic acid monoesters having an alicyclic structure such as monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, and monocyclohexenyl maleate; and itaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, and monocyclohexyl itaconate. Among these, butenedioic acid mono-chain alkyl esters or butenedioic acid monoesters having an alicyclic structure are preferred, mono-n-butyl fumarate, mono-n-butyl maleate, monocyclohexyl fumarate, and monocyclohexyl maleate are more preferred, and mono-n-butyl fumarate and monocyclohexyl fumarate are even more preferred. These carboxyl group-containing monomers other than the carboxyl group-containing monomer represented by the general formula (1) above can be used alone or in combination of two or more. Note that, among the above monomers, dicarboxylic acids also include those present as anhydrides.

[0021] <Radical polymerizable monomer> The radically polymerizable monomer is not particularly limited as long as it is radically polymerizable and copolymerizable with the carboxyl group-containing monomer represented by the general formula (1) described above. Examples include (meth)acrylic acid ester monomers (meaning acrylic acid ester monomers and / or methacrylic acid ester monomers. Hereinafter, the same applies to (meth)acrylate, etc.), (meth)acrylonitrile monomers, aromatic vinyl monomers, conjugated diene monomers, (meth)acrylamide monomers, vinyl acetate monomers, and ethylene monomers. Among these, (meth)acrylic acid ester monomers are preferred, and the copolymer rubber of the present invention is particularly preferably an acrylic rubber containing (meth)acrylic acid ester monomer units as the main component in the molecule (e.g., 50% by weight or more of all monomer units in the copolymer rubber).

[0022] When the copolymer rubber of the present invention is an acrylic rubber, the (meth)acrylic acid ester monomer that forms the (meth)acrylic acid ester monomer unit as the main component of the rubber component is not particularly limited, but examples thereof include (meth)acrylic acid alkyl ester monomers and (meth)acrylic acid alkoxyalkyl ester monomers.

[0023] The (meth)acrylic acid alkyl ester monomer is not particularly limited, but is preferably an ester of an alkanol having 1 to 8 carbon atoms with (meth)acrylic acid. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, and n-butyl (meth)acrylate are preferred, with ethyl acrylate and n-butyl acrylate being particularly preferred. These can be used alone or in combination of two or more.

[0024] The (meth)acrylic acid alkoxyalkyl ester monomer is not particularly limited, but is preferably an ester of an alkoxyalkyl alcohol having 2 to 12 carbon atoms with (meth)acrylic acid, and more preferably an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms with (meth)acrylic acid. Specific examples include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 4-methoxybutyl (meth)acrylate. Among these, 2-ethoxyethyl (meth)acrylate and 2-methoxyethyl (meth)acrylate are preferred, with 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate being particularly preferred. These may be used alone or in combination of two or more.

[0025] When the copolymer rubber of the present invention is an acrylic rubber, the content of (meth)acrylic acid ester monomer units in the acrylic rubber is 50 to 100% by weight, preferably 50 to 99.9% by weight, more preferably 60 to 99.5% by weight, even more preferably 70 to 99.5% by weight, and particularly preferably 70 to 99% by weight. By setting the content of (meth)acrylic acid ester monomer units within the above range, the weather resistance, heat resistance, and oil resistance of the obtained cross-linked rubber can be improved.

[0026] In the present invention, the (meth)acrylic acid ester monomer units preferably consist of 30 to 100% by weight of (meth)acrylic acid alkyl ester monomer units and 70 to 0% by weight of (meth)acrylic acid alkoxyalkyl ester monomer units.

[0027] When the copolymer rubber of the present invention is an acrylic rubber, it may contain other crosslinkable monomer units as necessary. The crosslinkable monomers forming the other crosslinkable monomer units may be used alone or in combination of two or more. The content of the other crosslinkable monomer units in the copolymer rubber of the present invention is preferably 0 to 9.9 wt%, more preferably 0 to 6.5 wt%, even more preferably 0 to 4.5 wt%, and particularly preferably 0 to 4 wt% (however, the total amount of all crosslinkable monomer units in the copolymer rubber is preferably 0.1 to 10 wt%, more preferably 0.5 to 7 wt%, even more preferably 0.5 to 5 wt%, and particularly preferably 1 to 5 wt%). By keeping the content of these other crosslinkable monomer units below the above upper limit, it is possible to suppress scorch of the copolymer rubber of the present invention and increase the elongation of the resulting crosslinked rubber.

[0028] Furthermore, when the copolymer rubber of the present invention is an acrylic rubber, in addition to the units of the carboxyl group-containing monomer represented by the above general formula (1), the (meth)acrylic acid ester monomer units, and the crosslinkable monomer units, it may have units of other monomers copolymerizable with the (meth)acrylic acid ester monomer or other crosslinkable monomers, as necessary.

[0029] The copolymerizable other monomer is not particularly limited, but examples thereof include aromatic vinyl monomers, α,β-ethylenically unsaturated nitrile monomers, monomers having two or more acryloyloxy groups (hereinafter sometimes referred to as "polyfunctional acrylic monomers"), olefin-based monomers, conjugated diene monomers, monomers having an amide group, vinyl ester-based monomers, and vinyl ether compounds.

[0030] Specific examples of aromatic vinyl monomers include styrene, α-methylstyrene, and divinylbenzene. Specific examples of the α,β-ethylenically unsaturated nitrile monomer include acrylonitrile and methacrylonitrile. Specific examples of polyfunctional acrylic monomers include ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate. Specific examples of the olefin monomer include ethylene, propylene, 1-butene, and 1-octene. Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Monomers having an amide group include (meth)acrylamide, N-methyl(meth)acrylamide, Acrylamide and the like. Specific examples of vinyl ester monomers include vinyl acetate, vinyl propionate, and vinyl butyrate. Specific examples of the vinyl ether compound include ethyl vinyl ether and n-butyl vinyl ether.

[0031] Among these, styrene, acrylonitrile, methacrylonitrile, ethylene and vinyl acetate are preferred, and styrene, acrylonitrile and ethylene are more preferred.

[0032] The other copolymerizable monomers can be used alone or in combination of two or more. The content of units of other monomers in the copolymer rubber is preferably 0 to 50% by weight, more preferably 0 to 49.9% by weight, still more preferably 0 to 39.5% by weight, and particularly preferably 0 to 29.5% by weight.

[0033] The copolymer rubber of the present invention can be obtained by polymerizing the above-mentioned monomers. As the form of the polymerization reaction, any of emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization can be used, but emulsion polymerization is preferred from the viewpoint of ease of control of the polymerization reaction.

[0034] The emulsion polymerization may be any of a batch system, a semi-batch system, and a continuous system. The polymerization is usually carried out in the temperature range of 0 to 70°C, preferably 5 to 50°C.

[0035] The weight average molecular weight (Mw) of the copolymer rubber of the present invention is not particularly limited, but is preferably 50,000 to 5,000,000, more preferably 100,000 to 4,000,000, and even more preferably 150,000 to 3,500,000. The weight average molecular weight of the acrylic rubber can be measured, for example, by gel permeation chromatography as a polystyrene-equivalent value.

[0036] The Mooney viscosity (ML1+4, 100°C) (polymer Mooney) of the copolymer rubber of the present invention is preferably 10-150, more preferably 10-80, further preferably 20-70, and particularly preferably 25-60.

[0037] The glass transition temperature of the copolymer rubber of the present invention is preferably 0°C or lower, more preferably -70 to -5°C, and even more preferably -50 to -7°C.

[0038] The method for producing the copolymer rubber of the present invention is not particularly limited and any method may be adopted, but for example, the following method is preferred: a method for producing the copolymer rubber by emulsion polymerization of a carboxyl group-containing monomer and a radically polymerizable monomer component that form the copolymer rubber in the presence of a polymerization catalyst.

[0039] The monomer components used in the emulsion polymerization include the above-mentioned monomers, and the preferred monomers are also as described above. The amount of each monomer used may be appropriately selected so as to fall within the above-mentioned composition range.

[0040] The emulsifier is not particularly limited, and examples thereof include nonionic emulsifiers, anionic emulsifiers, and cationic emulsifiers.

[0041] The nonionic emulsifier is not particularly limited, and examples thereof include polyoxyalkylene fatty acid esters such as polyoxyethylene stearic acid ester and polyoxyethylene sorbitan alkyl ester; polyoxyalkylene alkyl ethers such as polyoxyethylene dodecyl ether; and polyoxyalkylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether. Among these, polyoxyalkylene alkyl ethers and polyoxyalkylene alkylphenyl ethers are preferred, and polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers are more preferred. The weight-average molecular weight (weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC)) of the nonionic emulsifier is not particularly limited, but is usually in the range of 300 to 50,000, preferably 500 to 30,000, and more preferably 1,000 to 15,000. These nonionic emulsifiers can be used alone or in combination of two or more.

[0042] The anionic emulsifier is not particularly limited, but examples thereof include salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; higher alcohol sulfates such as sodium lauryl sulfate; phosphates such as sodium alkylphosphates, preferably higher alcohol phosphates such as sodium phosphates of alcohols having a hydrophobic group with 6 or more carbon atoms; and alkyl sulfosuccinates. Among these anionic emulsifiers, phosphates and higher alcohol sulfates are preferred, higher alcohol phosphates and higher alcohol sulfates are more preferred, and higher alcohol phosphates are even more preferred. These anionic emulsifiers can be used alone or in combination of two or more.

[0043] Examples of cationic emulsifiers include alkyltrimethylammonium chloride, dialkylammonium chloride, and benzylammonium chloride.

[0044] These emulsifiers can be used alone or in combination of two or more. Among them, nonionic emulsifiers and anionic emulsifiers are preferred, and a combination of a nonionic emulsifier and an anionic emulsifier is more preferred. Using a combination of a nonionic emulsifier and an anionic emulsifier effectively suppresses the generation of fouling due to adhesion of polymers to the polymerization apparatus (e.g., polymerization tank) during emulsion polymerization, while reducing the amount of coagulant used in the coagulation step described below. As a result, the amount of coagulant in the final copolymer rubber can be reduced, thereby improving the water resistance of the resulting cross-linked rubber. Furthermore, using a combination of a nonionic emulsifier and an anionic emulsifier enhances the emulsifying action, thereby reducing the amount of emulsifier used. As a result, the amount of emulsifier remaining in the final copolymer rubber can be reduced, thereby further improving the water resistance of the copolymer rubber.

[0045] The amount of emulsifier used is usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 1 to 3 parts by weight, based on 100 parts by weight of the monomer components used in the polymerization. When a nonionic emulsifier and an anionic emulsifier are used in combination, the weight ratio of nonionic emulsifier / anionic emulsifier is usually 1 / 99 to 99 / 1, preferably 10 / 90 to 80 / 20, more preferably 13 / 87 to 40 / 60, and even more preferably 15 / 85 to 35 / 65.

[0046] The method for emulsifying the monomer components used in polymerization, including the carboxyl group-containing monomer and the radically polymerizable monomer, using water and an emulsifier is not particularly limited, but a method of mixing the monomer components, water, and an emulsifier is preferred, and a method of stirring the monomer components, water, and an emulsifier using a stirrer such as a homogenizer or a disk turbine is more preferred. Note that the monomer emulsion may contain polymerization secondary materials such as a particle size adjuster, a chelating agent, and an oxygen scavenger, as necessary.

[0047] The polymerization initiator is not particularly limited, and any of those commonly used in emulsion polymerization can be used without limitation. As the polymerization initiator, for example, a peroxide, an azo compound, or a redox polymerization initiator composed of a peroxide and a reducing agent is preferably used.

[0048] As the peroxide, either an inorganic peroxide or an organic peroxide may be used.

[0049] Examples of inorganic peroxides include sodium persulfate, potassium persulfate, hydrogen peroxide, ammonium persulfate, etc. Among these, potassium persulfate, hydrogen peroxide, and ammonium persulfate are preferred, with potassium persulfate being particularly preferred.

[0050] Examples of organic peroxides include 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, 1-di-(t-hexylperoxy)cyclohexane, 1,1-di-(t-butylperoxy)cyclohexane, 4,4-di-(t-butylperoxy)n-butyl valerate, 2,2-di-(t-butylperoxy)butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, benzoyl peroxide, and 1,1,3,3-tetramethylpropane. Triethylbutyl hydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, disuccinic acid peroxide, dibenzoyl peroxide, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, diisobutyryl peroxide Carbonate, di-n-propyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanate, t-hexyl peroxypivalate, t-butyl peroxyneodecanate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate, t-hexyl Examples of peroxyalkylene oxides include 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.Among these, diisopropylbenzene hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide, and benzoyl peroxide are preferred.

[0051] Examples of azo compounds include azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-(2-imidazolin-2-yl)propane, 2,2'-azobis(propane-2-carboxamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropanamide], 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}, 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane), and 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propanamide}.

[0052] These peroxides and azo compounds can be used alone or in combination of two or more. The amount of peroxide and azo compound used in the initial polymerization step is preferably 0.001 to 0.020 parts by weight, more preferably 0.002 to 0.015 parts by weight, and even more preferably 0.003 to 0.010 parts by weight, relative to 100 parts by weight of the monomer components used in the polymerization.

[0053] The reducing agent used in combination with the peroxide can be any reducing agent that can be used as a redox catalyst for emulsion polymerization without any limitations. As the reducing agent, it is preferable to use at least two kinds of reducing agents, and among them, a combination of a metal ion compound in a reduced state and another reducing agent is suitable.

[0054] The reduced metal ion compound is not particularly limited, but examples thereof include ferrous sulfate, sodium iron hexamethylenediaminetetraacetate, cuprous naphthenate, etc. Among these, ferrous sulfate is preferred.

[0055] The reduced metal ion compound can be used alone or in combination of two or more. The amount of the reduced metal ion compound used in the initial polymerization step is preferably 0.0005 to 0.0030 parts by weight, more preferably 0.0007 to 0.0025 parts by weight, and even more preferably 0.0010 to 0.0020 parts by weight, relative to 100 parts by weight of the monomer components used in the polymerization.

[0056] The reducing agent other than a metal ion compound in a reduced state is not particularly limited, but examples thereof include ascorbic acid or a salt thereof such as ascorbic acid, sodium ascorbate, or potassium ascorbate; erythorbic acid or a salt thereof such as erythorbic acid, sodium erythorbate, or potassium erythorbate; sulfinates such as sodium formaldehyde sulfoxylate; sulfites such as sodium sulfite, potassium sulfite, sodium hydrogensulfite, aldehyde sodium hydrogensulfite, and potassium hydrogensulfite; pyrosulfites such as sodium pyrosulfite, potassium pyrosulfite, sodium hydrogensulfite, and potassium pyrosulfite; thiosulfates such as sodium thiosulfate and potassium thiosulfate; phosphorous acid or a salt thereof such as phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, and potassium hydrogen phosphite; and pyrophosphorous acid or a salt thereof such as pyrophosphorous acid, sodium pyrophosphite, potassium pyrophosphite, sodium hydrogen pyrophosphite, and potassium hydrogen pyrophosphite. Among these, ascorbic acid or a salt thereof, and sodium formaldehyde sulfoxylate are preferred.

[0057] The reducing agent other than the reduced metal ion compound may be used alone or in combination of two or more. The amount of the reducing agent other than the reduced metal ion compound in the initial polymerization step is preferably 0.005 to 0.080 parts by weight, more preferably 0.010 to 0.060 parts by weight, and even more preferably 0.020 to 0.040 parts by weight, relative to 100 parts by weight of the monomer components used in the polymerization.

[0058] A preferred combination of a metal ion compound in a reduced state and a reducing agent other than a metal ion compound in a reduced state is a combination of ferrous sulfate and ascorbic acid or a salt thereof and / or sodium formaldehyde sulfoxylate, a more preferred combination is a combination of ferrous sulfate and an ascorbate salt and / or sodium formaldehyde sulfoxylate, and a particularly preferred combination is a combination of ferrous sulfate and sodium formaldehyde sulfoxylate.

[0059] The amount of water used in emulsion polymerization is preferably 5 to 500 parts by weight, more preferably 10 to 300 parts by weight, and even more preferably 20 to 200 parts by weight, per 100 parts by weight of the monomer components used in the polymerization.

[0060] In emulsion polymerization, polymerization auxiliary materials such as a molecular weight modifier, a particle size modifier, a chelating agent, and an oxygen scavenger can be used as needed.

[0061] The emulsion polymerization may be carried out by any of a batch system, a semi-batch system, and a continuous system, but a semi-batch system is preferred.

[0062] The polymerization temperature and polymerization time are not particularly limited and may be selected appropriately depending on the type of polymerization catalyst used, etc. The polymerization temperature is preferably 0 to 100°C, more preferably 5 to 80°C, and even more preferably 10 to 50°C. The polymerization time is preferably 0.5 to 100 hours, more preferably 1 to 10 hours. The polymerization conversion is not particularly limited, but is preferably 80% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more.

[0063] Furthermore, when terminating the polymerization reaction, a polymerization terminator can be used. Examples of the polymerization terminator include hydroxylamine, hydroxylamine sulfate, diethylhydroxyamine, hydroxylamine sulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, and hydroquinone. The amount of the polymerization terminator used is not particularly limited, but is preferably 0.1 to 2 parts by weight per 100 parts by weight of the monomer components used in the polymerization.

[0064] Next, the obtained emulsion polymerization liquid is brought into contact with a coagulant to coagulate it and produce water-containing crumbs.

[0065] The coagulant is not particularly limited, but examples thereof include monovalent to trivalent metal salts. Monovalent to trivalent metal salts are salts containing metals that become monovalent to trivalent metal ions when dissolved in water, and examples thereof include, but are not particularly limited to, salts of inorganic acids selected from hydrochloric acid, nitric acid, sulfuric acid, etc., or organic acids such as acetic acid, with metals selected from sodium, potassium, lithium, magnesium, calcium, zinc, titanium, manganese, iron, cobalt, nickel, aluminum, tin, etc. Hydroxides of these metals can also be used.

[0066] Specific examples of monovalent to trivalent metal salts include metal chlorides such as sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, zinc chloride, titanium chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride, aluminum chloride, and tin chloride; nitrates such as sodium nitrate, potassium nitrate, lithium nitrate, magnesium nitrate, calcium nitrate, zinc nitrate, titanium nitrate, manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, and tin nitrate; and sulfates such as sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, titanium sulfate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, aluminum sulfate, and tin sulfate. Among these, calcium chloride, sodium chloride, aluminum sulfate, magnesium chloride, magnesium sulfate, zinc chloride, zinc sulfate, and sodium sulfate are preferred. Among these, monovalent or divalent metal salts are preferred, divalent metal salts are more preferred, magnesium salts are more preferred, inorganic magnesium salts are even more preferred, and magnesium sulfate is particularly preferred. These may be used alone or in combination.

[0067] The amount of the coagulant used is preferably 0.01 to 100 parts by weight, more preferably 0.1 to 50 parts by weight, and even more preferably 1 to 30 parts by weight, relative to 100 parts by weight of the monomer components used in the polymerization. By using the coagulant in the above range, the copolymer rubber can be sufficiently coagulated, and the resulting copolymer rubber can have excellent water resistance.

[0068] The method for contacting the emulsion polymerization liquid with the coagulant is not particularly limited, but examples include a method in which the emulsion polymerization liquid is added to an aqueous solution containing the coagulant while stirring the aqueous solution containing the coagulant, or a method in which the aqueous solution containing the coagulant is added to the emulsion polymerization liquid while stirring the emulsion polymerization liquid. Alternatively, a method in which the emulsion polymerization liquid is simply added to an aqueous solution containing the coagulant without stirring, or a method in which an aqueous solution containing the coagulant is added to the emulsion polymerization liquid without stirring, may be employed. Among these, a method in which the emulsion polymerization liquid is added to an aqueous solution containing the coagulant while stirring the aqueous solution containing the coagulant is preferred. By employing such a method to perform the coagulation operation, the particle size of the hydrous crumbs produced by coagulation can be controlled within a relatively uniform range, thereby improving the efficiency of washing the produced hydrous crumbs.

[0069] The concentration of the magnesium salt in the aqueous solution containing the coagulant is not particularly limited, but from the viewpoint of more appropriately controlling the particle size of the hydrous crumbs produced by coagulation, it is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, and even more preferably 1 to 5% by weight.

[0070] The temperature of the aqueous solution containing the coagulant (i.e., the coagulation temperature) is not particularly limited, but from the viewpoint of more appropriately controlling the particle size of the water-containing crumbs produced by coagulation, it is preferably 40°C or higher, more preferably 40 to 90°C, and even more preferably 50 to 85°C.

[0071] The stirring method for stirring the aqueous solution containing the coagulant is not particularly limited, but may include a method using a stirring device that stirs with stirring blades. In this case, it is preferable to use a method in which the aqueous solution containing the coagulant is contained in a stirring tank, and the emulsion polymerization liquid is added to the stirring tank while stirring the aqueous solution containing the coagulant with stirring blades.

[0072] Furthermore, the solids concentration of the emulsion polymerization liquid used for coagulation is not particularly limited, and it may be used as obtained by emulsion polymerization. However, from the viewpoint of more appropriately controlling the particle size of the water-containing crumbs produced by coagulation, it is preferable to adjust the solids concentration to the range of 5 to 50% by weight, more preferably to the range of 10 to 45% by weight, and particularly preferably to the range of 20 to 40% by weight.

[0073] Next, the water-containing crumbs obtained by the coagulation operation are preferably washed. The washing method is not particularly limited, but examples thereof include a method in which the water-containing crumbs obtained by the coagulation operation are washed with water, and preferably a method in which the water-containing crumbs obtained by the coagulation operation are mixed with water. The temperature during water washing is not particularly limited, but is preferably 5 to 60°C, more preferably 10 to 50°C, and the mixing time is 1 to 60 minutes, more preferably 2 to 30 minutes.

[0074] Furthermore, the amount of water mixed with the hydrous crumbs during water washing is not particularly limited, but from the viewpoint of further increasing the efficiency of water washing, it is preferable to use an amount of water that is 50 parts by weight or more per 100 parts by weight of the monomer components used in the polymerization, more preferably 50 to 15,000 parts by weight, even more preferably 100 to 10,000 parts by weight, and particularly preferably 500 to 5,000 parts by weight.

[0075] The washing time is not particularly limited, but is preferably 1 to 120 minutes, more preferably 2 to 60 minutes, and even more preferably 3 to 30 minutes.

[0076] The number of water washes is not particularly limited and is preferably 1 to 10 times, more preferably 1 to 5 times, and even more preferably 1 to 3 times. In the present invention, the number of water washes refers to the number of times when one water wash is performed, which is defined as the operation of adding water to the wet crumbs, mixing for a predetermined time, and separating the wet crumbs from the water used for the water wash. That is, for example, two water washes means adding water to the wet crumbs, mixing for a predetermined time, and separating the wet crumbs from the water used for the water wash, followed by adding water to the wet crumbs, mixing for a predetermined time, and separating the wet crumbs from the water used for the water wash. When the number of water washes is two or more times, the temperature, amount of water, and time of the water washes may be the same or different.

[0077] In the present invention, after water washing, acid washing using an acid as a washing liquid may be further performed. After acid washing, water washing is preferably further performed, and the water washing conditions may be the same as those described above.

[0078] The washed hydrous crumbs may be dried. The method for drying the hydrous crumbs is not particularly limited and may be any conventional method, but examples include methods using a dryer such as a hot air dryer, a reduced pressure dryer, an expander dryer, a kneader dryer, or a screw extruder.

[0079] The drying temperature for the hydrous crumb is not particularly limited, but is preferably 80 to 250°C, more preferably 100 to 200°C, and even more preferably 110 to 180°C.

[0080] The copolymer rubber of the present invention can be produced as described above. In the present invention, the copolymer rubber may be obtained in the form of crumbs or baled rubber, i.e., rubber bales (copolymer rubber formed into chunks of a predetermined shape).

[0081] <Rubber composition> The rubber composition of the present invention contains the copolymer rubber and a crosslinking agent. The content of the copolymer rubber component of the present invention in the rubber component may be appropriately selected depending on the intended use, but is preferably 30% by weight or more, more preferably 50% by weight or more, even more preferably 70% by weight or more, and particularly preferably 100% by weight (i.e., an embodiment in which the rubber component is essentially composed of only the copolymer rubber component of the present invention).

[0082] The rubber other than the copolymer rubber of the present invention that constitutes the rubber component is not particularly limited, but examples include acrylic rubber other than the copolymer rubber of the present invention, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin-based elastomer, styrene-based elastomer, vinyl chloride-based elastomer, polyester-based elastomer, polyamide-based elastomer, polyurethane-based elastomer, polysiloxane-based elastomer, and the like.

[0083] The rubber other than the copolymer rubber of the present invention may be used alone or in combination of two or more. The shape of the copolymer rubber of the present invention and the rubber other than the copolymer rubber of the present invention is not particularly limited, and may be any shape such as a veil, a sheet, or a powder.

[0084] The crosslinking agent is not particularly limited, and examples thereof include conventionally known crosslinking agents such as polyamine compounds such as diamine compounds and their carbonates; sulfur; sulfur donors; triazine thiol compounds; polyepoxy compounds; organic carboxylic acid ammonium salts; organic peroxides; dithiocarbamic acid metal salts; polycarboxylic acids; quaternary onium salts; imidazole compounds; and isocyanuric acid compounds. These crosslinking agents can be used alone or in combination of two or more. Among these, polyamine compounds and their carbonates are preferred.

[0085] The polyamine compound and carbonate thereof are not particularly limited, but polyamine compounds having 4 to 30 carbon atoms and carbonates thereof are preferred. Examples of such polyamine compounds and carbonates thereof include aliphatic polyamine compounds and carbonates thereof, and aromatic polyamine compounds.

[0086] The aliphatic polyamine compounds and carbonates thereof are not particularly limited, but examples thereof include hexamethylenediamine, hexamethylenediamine carbamate, and N,N'-dicinnamylidene-1,6-hexanediamine, etc. Among these, hexamethylenediamine carbamate is preferred.

[0087] The aromatic polyamine compound is not particularly limited, but examples thereof include 4,4'-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(m-phenylenediisopropylidene)dianiline, 4,4'-(p-phenylenediisopropylidene)dianiline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobenzanilide, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3,5-benzenetriamine. Among these, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane is preferred.

[0088] The rubber composition of the present invention preferably further contains a crosslinking accelerator. The crosslinking accelerator is not particularly limited. However, when the copolymer rubber of the present invention has a carboxyl group as a crosslinkable group and the crosslinking agent is a polyvalent amine compound or its carbonate, guanidine compounds, diazabicycloalkene compounds, imidazole compounds, quaternary onium salts, tertiary phosphine compounds, aliphatic monovalent secondary amine compounds, and aliphatic monovalent tertiary amine compounds can be used. Among these, guanidine compounds, diazabicycloalkene compounds, and aliphatic monovalent secondary amine compounds are preferred, and guanidine compounds and diazabicycloalkene compounds are particularly preferred. These basic crosslinking accelerators can be used alone or in combination of two or more.

[0089] Specific examples of guanidine compounds include 1,3-di-o-tolylguanidine and 1,3-diphenylguanidine. Specific examples of diazabicycloalkene compounds include 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene. Specific examples of imidazole compounds include 2-methylimidazole and 2-phenylimidazole. Specific examples of quaternary onium salts include tetra-n-butylammonium bromide and octadecyltri-n-butylammonium bromide. Specific examples of tertiary phosphine compounds include triphenylphosphine and tri-p-tolylphosphine.

[0090] The aliphatic monovalent secondary amine compound is a compound in which two hydrogen atoms of ammonia are substituted with an aliphatic hydrocarbon group. The aliphatic hydrocarbon group substituting the hydrogen atom preferably has 1 to 30 carbon atoms. Specific examples of the aliphatic monovalent secondary amine compound include dimethylamine, diethylamine, dipropylamine, diallylamine, diisopropylamine, di-n-butylamine, di-t-butylamine, di-sec-butylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dicetylamine, di-2-ethylhexylamine, and dioctadecylamine.

[0091] The aliphatic monovalent tertiary amine compound is a compound in which all three hydrogen atoms of ammonia are substituted with aliphatic hydrocarbon groups. The aliphatic hydrocarbon group substituting the hydrogen atoms preferably has 1 to 30 carbon atoms. Specific examples of the aliphatic monovalent tertiary amine compound include trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, and tridodecylamine.

[0092] The content of the crosslinking accelerator in the rubber composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7.5 parts by weight, and particularly preferably 1 to 5 parts by weight, based on 100 parts by weight of the rubber component containing the copolymer rubber of the present invention. By setting the content of the crosslinking accelerator within the above range, the tensile strength and compression set resistance of the obtained crosslinked rubber product can be further improved.

[0093] The rubber composition of the present invention may further contain a filler. The filler is not particularly limited, but examples thereof include reinforcing fillers and non-reinforcing fillers, and among these, reinforcing fillers are preferred.

[0094] Examples of reinforcing fillers include carbon blacks such as furnace black, acetylene black, thermal black, channel black, and graphite; silicas such as wet silica, dry silica, and colloidal silica; and examples of non-reinforcing fillers include quartz powder, clays such as diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate, and barium sulfate.

[0095] These fillers can be used alone or in combination of two or more. The content of the filler in the rubber composition of the present invention is not particularly limited, but is preferably 1 to 200 parts by weight, more preferably 10 to 150 parts by weight, and even more preferably 20 to 100 parts by weight, per 100 parts by weight of the rubber component containing the copolymer rubber of the present invention.

[0096] The rubber composition of the present invention may also contain an antioxidant, if necessary. The antioxidant is not particularly limited, but may include the above-mentioned phenolic antioxidants; phosphite ester antioxidants such as tris(nonylphenyl)phosphite, diphenylisodecylphosphite, and tetraphenyldipropylene glycol diphosphite; sulfur ester antioxidants such as dilauryl thiodipropionate; phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonylamido)-diphenylamine, 4,4'-bis(α,α-dimethylamine), and the like. Examples of antioxidants include amine-based antioxidants such as N,N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, and butyraldehyde-aniline condensates; imidazole-based antioxidants such as 2-mercaptobenzimidazole; quinoline-based antioxidants such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; and hydroquinone-based antioxidants such as 2,5-di-(t-amyl)hydroquinone.

[0097] The antioxidant may be used alone or in combination of two or more. The content of the antioxidant in the rubber composition of the present invention is not particularly limited, but is preferably 0.01 to 15 parts by weight, more preferably 0.05 to 10 parts by weight, and even more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the rubber component containing the copolymer rubber of the present invention.

[0098] In addition to the above components, the rubber composition of the present invention may contain compounding agents commonly used in the field of rubber processing. Examples of such compounding agents include light stabilizers, scorch inhibitors, plasticizers, processing aids, adhesives, slip agents, lubricants, flame retardants, mildew inhibitors, antistatic agents, colorants, and crosslinking retarders. The amounts of these compounding agents are not particularly limited as long as they do not impair the purpose and effects of the present invention, and can be appropriately compounded in amounts depending on the purpose of the compounding.

[0099] The rubber composition of the present invention is prepared by blending a crosslinking agent and various other compounding ingredients used as needed with a rubber component containing the above-mentioned copolymer rubber of the present invention, mixing and kneading the mixture using an open roll, a Banbury mixer, various kneaders, etc., and then further kneading the mixture using a kneading roll.

[0100] The order in which the components are mixed is not particularly limited, but it is preferable to thoroughly mix the components that are resistant to reaction or decomposition by heat, and then mix the crosslinking agent and other components that are resistant to reaction or decomposition by heat for a short period of time at a temperature at which they will not react or decompose.

[0101] <Rubber cross-linked products> The cross-linked rubber product of the present invention is obtained by cross-linking the above-mentioned rubber composition of the present invention. The cross-linked rubber product of the present invention can be produced by molding the copolymer rubber composition of the present invention into a desired shape using a molding machine, such as an extruder, injection molding machine, compressor, or roll, and then heating to cause a cross-linking reaction and fix the shape as a cross-linked rubber product. In this case, cross-linking may be carried out after molding in advance or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 25 to 120°C. The cross-linking temperature is usually 130 to 220°C, preferably 150 to 190°C, and the cross-linking time is usually 2 minutes to 10 hours, preferably 3 minutes to 5 hours. The heating method may be appropriately selected from methods used for cross-linking rubber, such as press heating, steam heating, oven heating, and hot air heating.

[0102] Depending on the shape, size, etc. of the cross-linked rubber product, the cross-linked rubber product of the present invention may be further heated to carry out secondary cross-linking. The secondary cross-linking period varies depending on the heating method, cross-linking temperature, shape, etc., but is preferably carried out for 1 to 48 hours. The heating method and heating temperature may be selected appropriately.

[0103] The cross-linked rubber product of the present invention thus obtained is suitably used as sealing materials such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing sheaths, mechanical seals, wellhead seals, seals for electric and electronic equipment, and seals for air compressors; various gaskets such as a cylinder head gasket attached to the connecting portion between a cylinder block and a cylinder head, a rocker cover gasket attached to the connecting portion between a rocker cover and a cylinder head, an oil pan gasket attached to the connecting portion between an oil pan and a cylinder head or a transmission case, a fuel cell separator gasket attached between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate, and a negative electrode, and a top cover gasket for a hard disk drive; cushioning materials, vibration-proofing materials; electric wire coating materials; industrial belts; tubes and hoses; sheets; and the like.

[0104] The cross-linked rubber product of the present invention can also be suitably used as an extrusion molded product and a cross-linked product for automobile applications, for example, various hoses such as fuel oil hoses for fuel tanks, such as fuel hoses, filler neck hoses, vent hoses, vapor hoses and oil hoses, air hoses, such as turbo air hoses and mission control hoses, radiator hoses, heater hoses, brake hoses and air conditioner hoses. [Example]

[0105] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In addition, the "parts" below are based on weight unless otherwise specified. Various physical properties were measured as follows.

[0106] <Monomer composition of copolymer rubber> The monomer composition of the copolymer rubber was calculated from the amount of each monomer used in the polymerization reaction and the polymerization conversion rate. Specifically, in the emulsion polymerization reaction in each example and comparative example, no unreacted monomer was found and the polymerization conversion rate was approximately 100%, so the amount of each monomer used in the polymerization reaction was considered to be the same as the content ratio of each monomer unit constituting the copolymer rubber.

[0107] <Glass transition temperature> The copolymer rubber was measured using a differential scanning calorimetry (DSC) from -80°C to 30°C at a heating rate of 10°C / min, and the glass transition temperature was measured from the peak top of the differential curve.

[0108] <Mooney viscosity> The copolymer rubber and the rubber composition were measured for Mooney viscosity (ML1+4, 100°C) in accordance with JIS K6300-1:2013.

[0109] Scorch Stability (Moony Scorch Time t5, t35) The rubber composition was subjected to Mooney scorch measurement at 125°C in accordance with JIS K6300, and the Mooney scorch times t5 and t35 (minutes) were measured. In this measurement, the time when the Mooney viscosity increased by 5 points from the minimum Mooney viscosity value Vmin was defined as the Mooney scorch time t5, and the time when the Mooney viscosity increased by 35 points from the minimum Mooney viscosity value Vmin was defined as the Mooney scorch time t35. The longer the Mooney scorch times t5 and t35, the more excellent the scorch stability can be determined to be.

[0110] <Crosslinkability test (fluidity)> A crosslinking test was conducted on the rubber composition using a rubber vulcanization tester (product name "Moving Die Rheometer MDR", manufactured by Alpha Technologies) at 170°C for 20 minutes in accordance with JIS K6300-2. From the results of the crosslinking test, the minimum torque (ML) (unit: dN·m), the maximum torque (MH) (unit: dN·m), and the maximum torque (MH) - minimum torque (ML) were determined. For rubbers of the same composition, a higher MH-ML value generally indicates that the crosslinking reaction has progressed more efficiently, and tends to result in a better compression set.

[0111] <Normal physical properties (tensile strength, elongation at break, stress at 100% elongation, hardness)> The rubber composition was placed in a mold measuring 15 cm in length, 15 cm in width, and 0.2 cm in depth and press-molded at 170°C for 20 minutes under a pressure of 10 MPa to obtain a sheet-like cross-linked rubber product. The resulting cross-linked rubber product was then transferred to a gear oven and subjected to secondary cross-linking at 170°C for 4 hours. The resulting cross-linked rubber product was punched out with a JIS No. 3 dumbbell to prepare test specimens. The resulting test specimens were then measured for tensile strength, elongation at break, and stress at 100% elongation according to JIS K6251:2017. Furthermore, the hardness of the cross-linked rubber product was measured using a durometer hardness tester (Type A) according to JIS K6253-3.

[0112] <Compression set test> The rubber composition was molded and crosslinked by pressing at 170°C for 20 minutes to prepare cylindrical test pieces with a diameter of 29 mm and a thickness of 12.5 mm, which were then heated at 170°C for 4 hours to cause secondary crosslinking. In accordance with JIS K6262, the test pieces obtained after secondary crosslinking were left in an environment of 175°C for 72 hours while compressed by 25%, and then the compression set (%) was measured. A smaller value of the compression set (%) indicates better resistance to compression set.

[0113] <Production Example 1> (Production of monobutyl allyl succinate) Under a nitrogen atmosphere, 350 mL of dichloromethane (Fujifilm Wako Pure Chemical Industries, Ltd.) and 25.9 g (350 mmol) of n-butanol were added to a 1000 mL three-neck flask equipped with a reflux condenser. 30.7 g (420 mmol) of dimethylethylamine (Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 5 minutes. Subsequently, 49.1 g (350 mmol) of allylsuccinic anhydride (Tokyo Chemical Industry Co., Ltd.) was added, refluxed at 55 °C, stirred for 1 hour, and cooled to room temperature. The mixture was then extracted three times with 250 mL of 1.2 M dilute hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) and washed with water. The organic phase was separated, dried with anhydrous magnesium sulfate (Fujifilm Wako Pure Chemical Industries, Ltd.), and the solvent was removed under reduced pressure to yield 69 g of a yellow liquid, monobutyl allylsuccinate.

[0114] <Production Example 2> (Production of monomethyl allyl succinate) Under a nitrogen atmosphere, 436 mL of dichloromethane (Fujifilm Wako Pure Chemical Industries, Ltd.) and 13.9 g (435 mmol) of methanol were added to a 1000 mL three-neck flask equipped with a reflux condenser. 38.2 g (522 mmol) of dimethylethylamine (Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 5 minutes. Subsequently, 61.1 g (435 mmol) of allylsuccinic anhydride (Tokyo Chemical Industry Co., Ltd.) was added, refluxed at 55 °C, stirred for 1 hour, and cooled to room temperature. This was followed by extraction with 250 mL of 1.2 M dilute hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) three times and washing with water. The organic phase was separated, dried with anhydrous magnesium sulfate (Fujifilm Wako Pure Chemical Industries, Ltd.), and the solvent was removed under reduced pressure to yield 68 g of a yellow liquid, monomethyl allylsuccinate.

[0115] <Production Example 3> (Production of monooctyl allyl succinate) Under a nitrogen atmosphere, 277 mL of dichloromethane (Fujifilm Wako Pure Chemical Industries, Ltd.) and 36.1 g (277 mmol) of n-octanol were added to a 1000 mL three-neck flask equipped with a reflux condenser. 24.3 g (333 mmol) of dimethylethylamine (Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 5 minutes. Subsequently, 38.9 g (277 mmol) of allylsuccinic anhydride (Tokyo Chemical Industry Co., Ltd.) was added, refluxed at 55 °C, stirred for 1 hour, and cooled to room temperature. This was followed by extraction with 250 mL of 1.2 M dilute hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) three times and washing with water. The organic phase was separated, dried with anhydrous magnesium sulfate (Fujifilm Wako Pure Chemical Industries, Ltd.), and the solvent was removed under reduced pressure to yield 67 g of a yellow liquid, monooctyl allylsuccinate.

[0116] Example 1 (Production of copolymer rubber (A-1)) A mixing vessel equipped with a homomixer was charged with 46.294 parts of ion-exchanged water, 98.5 parts of ethyl acrylate as a monomer component, 1.5 parts of monobutyl allylsuccinate obtained in Production Example 1, and 1.8 parts of tridecyloxyhexa(oxyethylene) phosphate ester sodium salt (anionic emulsifier) ​​as an emulsifier, and the mixture was stirred to obtain a monomer emulsion.

[0117] Next, 170.853 parts of pure water and 2.962 parts of the monomer emulsion obtained above were added to a polymerization reactor equipped with a thermometer and a stirrer, and cooled to 12 ° C. under a nitrogen stream. Next, 145.132 parts of the monomer emulsion obtained above, 0.00033 parts of ferrous sulfate (reducing agent), 0.264 parts of sodium ascorbate (reducing agent), and 7.72 parts of a 2.85 wt% aqueous potassium persulfate solution (polymerization initiator) (0.22 parts as the amount of potassium persulfate) were continuously added dropwise to the polymerization reactor over a period of 3 hours while maintaining the temperature at 12 ° C. Thereafter, the reaction was continued for 1 hour while maintaining the temperature in the polymerization reactor at 23 ° C. After confirming that the polymerization conversion rate had reached approximately 100%, hydroquinone was added as a polymerization terminator to terminate the polymerization reaction, thereby obtaining an emulsion polymerization liquid.

[0118] Next, 60 parts of a 30 wt % aqueous magnesium sulfate solution adjusted to 85° C. was added to a coagulation tank equipped with a thermometer and a stirrer, and stirred with a stirring blade while heated to 85° C. Then, 100 parts of the emulsion polymerization liquid prepared above was continuously added to the aqueous magnesium sulfate solution while stirring, to coagulate the polymer, which was then filtered off to obtain hydrous crumbs.

[0119] Next, 388 parts of industrial water was added to 100 parts of the solid content of the obtained hydrous crumbs, and the mixture was stirred at room temperature for 5 minutes in a coagulation tank. After that, the water was drained from the coagulation tank, and the hydrous crumbs were washed with water. The washed hydrous crumbs were then dried in a hot air dryer at 110 ° C for 1 hour, thereby obtaining a solid copolymer rubber (A-1) with a recovery rate of 100%. The Mooney viscosity of the obtained copolymer rubber (A-1) was measured according to the method described above. The results are shown in Table 2.

[0120] (Preparation of Rubber Composition) Using a kneader, 100 parts of copolymer rubber (A-1) was mixed with 60 parts of carbon black (trade name "Seat SO" manufactured by Tokai Carbon Co., Ltd.), 2 parts of stearic acid, 1 part of an ester wax (trade name "Greg G-8205" manufactured by DIC Corporation), and 2 parts of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (trade name "Nocrac CD" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., antioxidant) at 50 ° C for 7 minutes. The resulting mixture was transferred to a roll at 50 ° C, and 0.6 parts of hexamethylenediamine carbamate (trade name "Diak No. 1" manufactured by DuPont Dow Elastomers Co., Ltd., crosslinking agent) and 2 parts of 1,3-di-o-tolylguanidine (trade name "Noccela DT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., crosslinking accelerator) were added and kneaded with the roll to obtain a rubber composition. The obtained rubber composition was used to measure the Mooney viscosity, scorch stability (Mooney scorch times t5 and t35), and fluidity, as well as the normal state physical properties (tensile strength, elongation, stress at 100% elongation, hardness) and compression set of the cross-linked rubber. The results are shown in Table 2.

[0121] <Example 2> Except for changing the amount of hexamethylenediamine carbamate used from 0.6 parts to 0.9 parts, a rubber composition was obtained in the same manner as in Example 1, and measurements and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0122] Example 3 The copolymer rubber (A-2) was produced in the same manner as the copolymer rubber (A-1), except that the amount of ethyl acrylate used was changed from 98.5 parts to 96.5 parts, and the amount of monobutyl allyl succinate used was changed from 1.5 parts to 3.5 parts. Then, except that the copolymer rubber (A-2) was used instead of the copolymer rubber (A-1), a rubber composition was obtained in the same manner as in Example 2, and measurements and evaluations were carried out. The results are shown in Table 2.

[0123] Example 4 Copolymer rubber (A-3) was produced in the same manner as copolymer rubber (A-1), except that 1.5 parts of monomethyl allylsuccinate obtained in Production Example 2 was used instead of 1.5 parts of monobutyl allylsuccinate. Then, a rubber composition was obtained in the same manner as in Example 1, and measurements and evaluations were carried out. The results are shown in Table 2.

[0124] <Example 5> Copolymer rubber (A-4) was produced in the same manner as copolymer rubber (A-1), except that 1.5 parts of monooctyl allylsuccinate obtained in Production Example 3 was used instead of 1.5 parts of monobutyl allylsuccinate. Then, a rubber composition was obtained in the same manner as in Example 1, and measurements and evaluations were carried out. The results are shown in Table 2.

[0125] <Examples 6 to 12> (Production of copolymer rubbers (A-5) to (A-11)) Copolymer rubbers (A-5) to (A-11) were produced in the same manner as copolymer rubber (A-1), except that 98.5 parts of ethyl acrylate was replaced with the monomers and their weight percentages shown in Table 1. In Example 12, polymerization was carried out under a pressure of 3 MPa.

[0126] (Preparation of Rubber Composition) Rubber compositions were obtained in the same manner as in Example 1, except that copolymer rubbers (A-5) to (A-11) shown in Table 1 were used instead of copolymer rubber (A-1), and measurements and evaluations were carried out for each. The results are shown in Table 2.

[0127] <Comparative Example 1> Copolymer rubber (A-12) was produced in the same manner as copolymer rubber (A-1), except that 1.5 parts of monobutyl fumarate was used instead of 1.5 parts of monobutyl allyl succinate. Then, a rubber composition was obtained in the same manner as in Example 1, except that copolymer rubber (A-12) was used instead of copolymer rubber (A-1), and measurements and evaluations were carried out. The results are shown in Table 2.

[0128] <Comparative Example 2> Copolymer rubber (A-13) was produced in the same manner as copolymer rubber (A-1), except that 1.5 parts of monobutyl maleate was used instead of 1.5 parts of monobutyl allyl succinate. Then, a rubber composition was obtained in the same manner as in Example 1, except that copolymer rubber (A-13) was used instead of copolymer rubber (A-1), and measurements and evaluations were carried out. The results are shown in Table 2.

[0129] <Comparative Example 3> Copolymer rubber (A-14) was produced in the same manner as copolymer rubber (A-1), except that 1.5 parts of monobutyl itaconate was used instead of 1.5 parts of monobutyl allyl succinate. Then, a rubber composition was obtained in the same manner as in Example 1, except that copolymer rubber (A-14) was used instead of copolymer rubber (A-1), and measurements and evaluations were carried out. The results are shown in Table 2.

[0130] <Comparative Example 4> Copolymer rubber (A-15) was produced in the same manner as copolymer rubber (A-1), except that 1.5 parts of monocyclohexyl fumarate was used instead of 1.5 parts of monobutyl allyl succinate. Then, a rubber composition was obtained in the same manner as in Example 1, except that copolymer rubber (A-15) was used instead of copolymer rubber (A-1), and measurements and evaluations were carried out. The results are shown in Table 2.

[0131] [Table 1]

[0132] [Table 2]

[0133] <Evaluation of Examples 1 to 12 and Comparative Examples 1 to 4> As can be seen from Table 2, the copolymer rubber obtained by copolymerizing the carboxyl group-containing monomer represented by general formula (1) with the radically polymerizable monomer had excellent scorch stability, and the obtained cross-linked rubber product had excellent compression set (Examples 1 to 12). On the other hand, in the case of copolymer rubbers obtained by copolymerizing other carboxyl group-containing monomers without using the carboxyl group-containing monomer represented by general formula (1), the resulting cross-linked rubber products had excellent compression set properties, but the scorch time of the copolymer rubbers was short, resulting in poor scorch stability (Comparative Examples 1 to 4).

Claims

1. A copolymer rubber obtained by copolymerizing a carboxyl group-containing monomer represented by the following general formula (1) with a radical polymerizable monomer: 【Chemistry 1】 (In the above general formula (1), R １ and R ２ one of which is a hydrogen atom and the other is an alkyl group, and n is an integer of 0 to 3.

2. The copolymer rubber according to claim 1, wherein n is an integer of 0 or 1 in the general formula (1).

3. 3. The copolymer rubber according to claim 1, having a glass transition temperature of 0°C or lower.

4. 4. The copolymer rubber according to claim 1, wherein the content of the carboxyl group-containing monomer unit represented by the general formula (1) is 0.1 to 10% by weight.

5. The copolymer rubber according to any one of claims 1 to 4, wherein the radical polymerizable monomer is at least one selected from the group consisting of (meth)acrylic acid esters, (meth)acrylonitrile, aromatic vinyl, conjugated dienes, (meth)acrylamide, vinyl acetate, and ethylene.

6. The copolymer rubber according to claim 5, wherein the radical polymerizable monomer is a (meth)acrylic acid ester.

7. The copolymer rubber according to any one of claims 1 to 6, having a Mooney viscosity (ML1+4, 100°C) of 10 to 150.

8. A rubber composition comprising the copolymer rubber according to any one of claims 1 to 7 and a crosslinking agent.

9. A cross-linked rubber product obtained by cross-linking the rubber composition according to claim 8.

10. A hose material or a sealing material comprising the rubber composition according to claim 8.

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