Acrylic rubber composition and cross-linked rubber

Abstract

This acrylic rubber composition contains an acrylic rubber and a compound represented by general formula (1).　(In general formula (1), R1-R4 are each independently an optionally substituted organic group having 1-30 carbons, and R5-R10 are each independently a hydrogen atom or an optionally substituted organic group having 1-30 carbons.)

Description

[Technical field]

[0001] The present invention relates to an acrylic rubber composition, and more particularly to an acrylic rubber composition which is effectively prevented from being deteriorated by heat, and a cross-linked rubber product obtained by cross-linking such an acrylic rubber composition. [Background technology]

[0002] With the development of petrochemistry, polymers made of organic compounds have contributed to the development of mankind in various forms such as plastics, rubber, fibers, and films. Since these are used in various environments depending on the application, they have been improved so that they can be used for a long time by giving each of them durability in the expected environment. For example, products have been developed that give ultraviolet resistance to plastics used outdoors, and cold resistance to rubber that functions in extremely cold regions.

[0003] On the other hand, internal combustion engines, the use of which has increased with the development of industry, require lubricating oil and generate a great deal of heat, so the polymers used in them must be resistant to oil and high temperatures. In particular, polymers used around automobile engines must be able to maintain flexibility for long periods of time even when exposed to oil and high temperatures, and must not develop defects such as cracks. In order to meet these requirements, various oil- and heat-resistant rubbers have been developed, and among them, acrylic rubber is a polymer that has rubber elasticity and is excellent in oil resistance, heat resistance, and flexibility, and is widely used as materials for seals, gaskets, packing, hoses, and other parts around automobile engines, and its oil resistance and heat resistance are further enhanced by devising crosslinking structures, antioxidants, and compounding agents according to the required characteristics.

[0004] For example, Patent Document 1 discloses an acrylic rubber composition containing acrylic rubber, trithiocyanuric acid, a dithiocarbamic acid compound, a thiourea derivative, a white filler, and an organosilane compound having a halogen atom or a (meth)acryloxy group. According to the technology of Patent Document 1, an acrylic rubber composition having excellent storage stability can be obtained, but there is a possibility of thermal degradation due to heat in a high-temperature environment, and there has been a demand for prevention of such thermal degradation.

[0005] Patent Document 2 discloses a rubber composition containing an epoxy group-containing acrylic rubber, specific carbon black, and a vulcanizing agent. According to the technology of Patent Document 2, a rubber composition that has excellent heat resistance, small compression set under high heat conditions, and can be easily extruded into a large diameter can be obtained, but there is a need to prevent thermal degradation due to heat in a higher temperature environment (for example, an environment of 190°C or higher). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-059821 A [Patent Document 2] JP 2002-121352 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above circumstances, and has an object to provide an acrylic rubber composition in which thermal degradation due to heat is effectively prevented even in a high-temperature environment (for example, an environment of 190°C or higher). [Means for solving the problem]

[0008] As a result of intensive research into achieving the above object, the present inventors have found that the above object can be achieved by an acrylic rubber composition obtained by blending an acrylic rubber with a specific thiourea compound, and have thus completed the present invention.

[0009] That is, according to the present invention, there is provided an acrylic rubber composition containing an acrylic rubber and a compound represented by the following general formula (1). [ka] (In the above general formula (1), R 1 ~R 4 each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent; R 5 ~R 10 each independently represents a hydrogen atom or an organic group having 1 to 30 carbon atoms which may have a substituent.)

[0010] In the acrylic rubber composition of the present invention, R in the compound represented by the general formula (1) 1 ~R 4 are preferably each independently an aliphatic hydrocarbon group or aromatic heterocyclic group having 1 to 30 carbon atoms, which may have a substituent, or an aromatic hydrocarbon group having 6 to 30 carbon atoms, and more preferably each independently an optionally substituted linear, branched or cyclic alkyl group having 1 to 30 carbon atoms. In the acrylic rubber composition of the present invention, the content of the compound represented by the general formula (1) is preferably 0.1 to 50 parts by weight, and more preferably 1 to 10 parts by weight, relative to 100 parts by weight of the acrylic rubber. In the acrylic rubber composition of the present invention, the acrylic rubber is preferably a carboxyl group-containing acrylic rubber, an epoxy group-containing acrylic rubber, a halogen atom-containing acrylic rubber, or a carboxyl group- and halogen atom-containing acrylic rubber. In the acrylic rubber composition of the present invention, the acrylic rubber preferably contains 0.1 to 100% by weight of ethylene-acrylate rubber. It is preferable that the acrylic rubber composition of the present invention further contains an antioxidant other than the compound represented by the general formula (1), and the total content of the compound represented by the general formula (1) and the antioxidant is 0.1 to 50 parts by weight per 100 parts by weight of the acrylic rubber. The acrylic rubber composition of the present invention preferably further contains 0.05 to 20 parts by weight of a crosslinking agent relative to 100 parts by weight of the acrylic rubber.

[0011] According to the present invention, there is also provided a cross-linked rubber product obtained by cross-linking the above acrylic rubber composition. The cross-linked rubber product of the present invention is preferably an extrusion molded product or a sealing member. Effect of the Invention

[0012] According to the present invention, it is possible to provide an acrylic rubber composition in which thermal degradation due to heat is effectively prevented even in a high-temperature environment (for example, an environment of 190°C or higher), and a cross-linked rubber product obtained by cross-linking such an acrylic rubber composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The acrylic rubber composition of the present invention contains an acrylic rubber and a compound represented by general formula (1) described below.

[0014] <Acrylic rubber> The acrylic rubber used in the present invention is not particularly limited as long as it contains a (meth)acrylic acid ester monomer unit (meaning an acrylic acid ester monomer and / or a methacrylic acid ester monomer; hereinafter, the same applies to methyl (meth)acrylate, etc.) as a main component (in the present invention, this refers to a monomer unit that accounts for 50% by weight or more of all monomer units in the acrylic rubber) in the molecule.

[0015] The (meth)acrylic acid ester monomer forming the (meth)acrylic acid ester monomer unit as the main component of the acrylic rubber used in the present invention is not particularly limited, but examples thereof include (meth)acrylic acid alkyl ester monomers and (meth)acrylic acid alkoxyalkyl ester monomers.

[0016] 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 and (meth)acrylic acid, and specifically includes 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, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred, and ethyl acrylate is particularly preferred. These can be used alone or in combination of two or more.

[0017] The (meth)acrylic acid alkoxyalkyl ester monomer is not particularly limited, but is preferably an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms and (meth)acrylic acid, and specifically includes 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, and 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate are particularly preferred. These can be used alone or in combination of two or more.

[0018] The content of the (meth)acrylic acid ester monomer unit in the acrylic rubber used in the present invention is 50 to 100% by weight, preferably 50 to 99.9% by weight, more preferably 60 to 99.5% by weight, further preferably 70 to 99.5% by weight, and particularly preferably 70 to 99% by weight. By setting the content of the (meth)acrylic acid ester monomer unit within the above range, the weather resistance, heat resistance, and oil resistance of the obtained cross-linked rubber can be improved.

[0019] 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.

[0020] The acrylic rubber used in the present invention may contain crosslinkable monomer units in addition to the (meth)acrylic acid ester monomer units.

[0021] The crosslinkable monomer forming the crosslinkable monomer unit is not particularly limited, but examples thereof include α,β-ethylenically unsaturated carboxylic acid monomers, monomers having an epoxy group, monomers having a halogen atom, diene monomers, etc. These crosslinkable monomers can be used alone or in combination of two or more.

[0022] The α,β-ethylenically unsaturated carboxylic acid monomer is not particularly limited, but examples thereof include α,β-ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms, α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms, and monoesters of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkanols having 1 to 8 carbon atoms.

[0023] Specific examples of the α,β-ethylenically unsaturated monocarboxylic acid having 3 to 12 carbon atoms include acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid. Specific examples of the α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms include butenedioic acids such as fumaric acid and maleic acid; itaconic acid; citraconic acid; and chloromaleic acid. Specific examples of monoesters of α,β-ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms and alkanols having 1 to 8 carbon atoms 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 monocyclohexyl maleate is even more preferred. These α,β-ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. Among the above monomers, dicarboxylic acids also include those that exist as anhydrides.

[0024] In the present invention, when an α,β-ethylenically unsaturated carboxylic acid monomer is used as the crosslinkable monomer, the acrylic rubber can be a carboxyl group-containing acrylic rubber. When the acrylic rubber is a carboxyl group-containing acrylic rubber, the heat aging resistance of the obtained acrylic rubber crosslinked product can be further improved.

[0025] In the case where the acrylic rubber used in the present invention is a carboxyl group-containing acrylic rubber, the content of the α,β-ethylenically unsaturated carboxylic acid monomer unit 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 α,β-ethylenically unsaturated carboxylic acid monomer unit in the above range, the balance between the strength and elongation of the obtained cross-linked rubber product can be made more excellent. In particular, by making the content of the α,β-ethylenically unsaturated carboxylic acid monomer unit to be equal to or higher than the above lower limit, cross-linking can be sufficiently performed, and the shape of the obtained cross-linked rubber product can be easily maintained, while by making the content of the α,β-ethylenically unsaturated carboxylic acid monomer unit equal to or lower than the above upper limit, the elongation of the obtained cross-linked rubber product can be increased and the compression set rate can be reduced.

[0026] In addition, when the acrylic rubber used in the present invention is a carboxyl group-containing acrylic rubber, the content of the carboxyl groups, i.e., the number of moles (ephr) of the carboxyl groups per 100 g of the acrylic rubber, is preferably 4×10 -4 ~4×10 -1 (ephr), more preferably 1×10 -3 ~2×10 -1 (ephr), and more preferably 5 × 10 -3 ~1×10 -1 (ephr). By making the carboxyl group content equal to or higher than the above lower limit, crosslinking can be sufficiently performed, the mechanical properties of the obtained cross-linked rubber product can be improved, and the surface texture of the molded article can be made smooth. On the other hand, by making the carboxyl group content equal to or lower than the above upper limit, the elongation of the obtained cross-linked rubber product can be increased and the compression set can be reduced.

[0027] The monomer having an epoxy group is not particularly limited, but examples thereof include epoxy group-containing (meth)acrylic acid esters and epoxy group-containing ethers.

[0028] A specific example of the epoxy group-containing (meth)acrylic acid ester is glycidyl (meth)acrylate. Specific examples of epoxy group-containing ethers include allyl glycidyl ether and vinyl glycidyl ether. Among these, glycidyl methacrylate and allyl glycidyl ether are preferred. These epoxy group-containing monomers can be used alone or in combination of two or more.

[0029] In the present invention, when a monomer having an epoxy group is used as the crosslinkable monomer, the acrylic rubber can be an epoxy group-containing acrylic rubber.

[0030] When the acrylic rubber used in the present invention is an epoxy group-containing acrylic rubber, the content of the monomer unit having an epoxy group is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, and even more preferably 0.5 to 5% by weight. By having the content of the monomer unit having an epoxy group in the above range, the balance between the strength and elongation of the obtained cross-linked rubber product can be made more excellent. In particular, by making the content of the monomer unit having an epoxy group equal to or higher than the above lower limit, cross-linking can be sufficiently performed, and the shape of the obtained cross-linked rubber product can be easily maintained. On the other hand, by making the content of the monomer unit having an epoxy group equal to or lower than the above upper limit, the elongation of the obtained cross-linked rubber product can be increased and the compression set rate can be reduced.

[0031] The monomer having a halogen atom is not particularly limited, but examples thereof include unsaturated alcohol esters of halogen-containing saturated carboxylic acids, (meth)acrylic acid haloalkyl esters, (meth)acrylic acid haloacyloxyalkyl esters, (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters, halogen-containing unsaturated ethers, halogen-containing unsaturated ketones, halomethyl group-containing aromatic vinyl compounds, halogen-containing unsaturated amides, and haloacetyl group-containing unsaturated monomers.

[0032] Specific examples of unsaturated alcohol esters of halogen-containing saturated carboxylic acids include vinyl chloroacetate, vinyl 2-chloropropionate, and allyl chloroacetate. Specific examples of (meth)acrylic acid haloalkyl esters include chloromethyl (meth)acrylate, 1-chloroethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 1,2-dichloroethyl (meth)acrylate, 2-chloropropyl (meth)acrylate, 3-chloropropyl (meth)acrylate, and 2,3-dichloropropyl (meth)acrylate. Specific examples of (meth)acrylic acid haloacyloxyalkyl esters include 2-(chloroacetoxy)ethyl (meth)acrylate, 2-(chloroacetoxy)propyl (meth)acrylate, 3-(chloroacetoxy)propyl (meth)acrylate, and 3-(hydroxychloroacetoxy)propyl (meth)acrylate. Specific examples of (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters include 2-(chloroacetylcarbamoyloxy)ethyl (meth)acrylate and 3-(chloroacetylcarbamoyloxy)propyl (meth)acrylate. Specific examples of halogen-containing unsaturated ethers include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, and 3-chloropropyl allyl ether. Specific examples of halogen-containing unsaturated ketones include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, and 2-chloroethyl allyl ketone. Specific examples of the halomethyl group-containing aromatic vinyl compound include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, and p-chloromethyl-α-methylstyrene. A specific example of the halogen-containing unsaturated amide is N-chloromethyl(meth)acrylamide. Specific examples of the haloacetyl group-containing unsaturated monomer include 3-(hydroxychloroacetoxy)propyl allyl ether, p-vinylbenzyl chloroacetic acid ester, and the like.

[0033] Among these, unsaturated alcohol esters of halogen-containing saturated carboxylic acids and halogen-containing unsaturated ethers are preferred, vinyl chloroacetate and 2-chloroethyl vinyl ether are more preferred, and vinyl chloroacetate is even more preferred. These monomers having halogen atoms can be used alone or in combination of two or more.

[0034] In the present invention, when a monomer having a halogen atom is used as the crosslinkable monomer, the acrylic rubber can be a halogen atom-containing acrylic rubber.

[0035] When the acrylic rubber used in the present invention is a halogen atom-containing acrylic rubber, the content of the monomer unit having a halogen atom is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, and even more preferably 0.5 to 5% by weight. By having the content of the monomer unit having a halogen atom in the above range, the balance between the strength and elongation of the obtained cross-linked rubber product can be made more excellent. In particular, by making the content of the monomer unit having a halogen atom equal to or higher than the above lower limit, cross-linking can be sufficiently performed, and the shape of the obtained cross-linked rubber product can be easily maintained, while by making the content of the monomer unit having a halogen atom equal to or lower than the above upper limit, the elongation of the obtained cross-linked rubber product can be increased and the compression set rate can be reduced.

[0036] In the present invention, by using an α,β-ethylenically unsaturated carboxylic acid monomer and a monomer having a halogen atom as the crosslinkable monomer, the acrylic rubber can be made into an acrylic rubber containing a carboxyl group and a halogen atom.

[0037] When the acrylic rubber used in the present invention is a carboxyl group- and halogen atom-containing acrylic rubber, specific examples of the crosslinkable monomer include the same as the crosslinkable monomers in the above-mentioned carboxyl group-containing acrylic rubber and halogen atom-containing acrylic rubber, and among these, it is preferable to use methacrylic acid and p-chloromethylstyrene in combination.

[0038] In the case where the acrylic rubber used in the present invention is an acrylic rubber containing a carboxyl group and a halogen atom, the total content of the α,β-ethylenically unsaturated carboxylic acid monomer units and the monomer units having a halogen atom is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, and even more preferably 0.5 to 5% by weight. By making the total content of these α,β-ethylenically unsaturated carboxylic acid monomer units and the monomer units having a halogen atom equal to or higher than the above lower limit, crosslinking can be sufficiently performed, and the shape of the obtained cross-linked rubber can be easily maintained, while by making the total content of the α,β-ethylenically unsaturated carboxylic acid monomer units and the monomer units having a halogen atom equal to or lower than the above upper limit, the elongation of the obtained cross-linked rubber can be increased and the compression set can be reduced. The content ratio of the α,β-ethylenically unsaturated carboxylic acid monomer units to the monomer units having halogen atoms is preferably [1:1.5 to 1:10], and more preferably [1:2 to 1:8], in terms of the weight ratio of [α,β-ethylenically unsaturated carboxylic acid monomer units:monomer units having halogen atoms].

[0039] The diene monomer includes a conjugated diene monomer and a non-conjugated diene monomer. Specific examples of conjugated diene monomers include 1,3-butadiene, isoprene, and piperylene. Specific examples of the non-conjugated diene monomer include ethylidene norbornene, dicyclopentadiene, dicyclopentadienyl (meth)acrylate, and 2-dicyclopentadienylethyl (meth)acrylate.

[0040] The above-mentioned α,β-ethylenically unsaturated carboxylic acid monomer, monomer having an epoxy group, monomer having a halogen atom, and diene monomer can be used alone or in combination of two or more.

[0041] In addition, when the acrylic rubber used in the present invention is the above-mentioned carboxyl group-containing acrylic rubber, epoxy group-containing acrylic rubber, halogen atom-containing acrylic rubber, or carboxyl group and halogen atom-containing acrylic rubber, it may have other crosslinkable monomer units as necessary. The crosslinkable monomers forming the other crosslinkable monomer units can be used alone or in combination of two or more. The content of the other crosslinkable monomer units in the acrylic rubber used in the present invention is preferably 0 to 9.9% by weight, more preferably 0 to 6.5% by weight, even more preferably 0 to 4.5% by weight, and particularly preferably 0 to 4% by weight (however, the total amount of all the crosslinkable monomer units in the acrylic rubber is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, even more preferably 0.5 to 5% by weight, and particularly preferably 1 to 5% by weight). By making the content of these other crosslinkable monomer units equal to or less than the above upper limit, the elongation of the obtained rubber crosslinked product can be increased and the compression set rate can be reduced.

[0042] Furthermore, the acrylic rubber used in the present invention may, in addition to the (meth)acrylic acid ester monomer units and the crosslinkable monomer units, have units of other monomers copolymerizable with the (meth)acrylic acid ester monomer or the crosslinkable monomer, as necessary.

[0043] The other copolymerizable monomers are 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 monomers, and vinyl ether compounds.

[0044] 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 the polyfunctional acrylic monomer 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. Specific examples of the vinyl ether compound include vinyl acetate, ethyl vinyl ether, and n-butyl vinyl ether.

[0045] Among these, styrene, acrylonitrile, methacrylonitrile, ethylene and vinyl acetate are preferred, and acrylonitrile, methacrylonitrile, ethylene and vinyl acetate are more preferred.

[0046] The other copolymerizable monomers may be used alone or in combination of two or more. The content of units of other monomers in the acrylic 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.

[0047] The acrylic rubber used in 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 from the viewpoint of ease of control of the polymerization reaction, the emulsion polymerization is preferred.

[0048] 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.

[0049] The weight average molecular weight (Mw) of the acrylic rubber used in 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 further 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.

[0050] The Mooney viscosity (ML1+4, 100° C.) (polymer Mooney) of the acrylic rubber used in the present invention thus produced is preferably 10-80, more preferably 20-70, and further preferably 25-60.

[0051] In the present invention, the acrylic rubbers thus produced can be used alone or in combination of two or more.

[0052] In the present invention, the acrylic rubber thus produced may contain 0.1 to 100% by weight of ethylene-acrylate rubber.

[0053] When the acrylic rubber contains 0.1 to 100% by weight of ethylene-acrylate rubber, the ratio of the ethylene-acrylate rubber to the acrylic rubber other than the ethylene-acrylate rubber is usually "ethylene-acrylate rubber:acrylic rubber other than the ethylene-acrylate rubber" = 0.1 to 100% by weight: 99.9 to 0% by weight, preferably 10 to 100% by weight: 90 to 0% by weight, more preferably 20 to 100% by weight: 80 to 0% by weight. When the ratio of the ethylene-acrylate rubber is within the above range, the processability of the acrylic rubber, and the mechanical properties such as the strength of the obtained rubber cross-linked product, and the heat resistance can be excellent.

[0054] The ethylene-acrylate rubber is preferably a polymer containing, in the molecule, 50 to 99.9% by weight of (meth)acrylic acid ester monomer units as main components, 0.1 to 50% by weight of ethylene monomer units, and 0 to 10% by weight of crosslinkable monomer units.

[0055] As the acrylic rubber other than the ethylene-acrylate rubber, the above-mentioned polymer containing 50 to 100% by weight of the (meth)acrylic acid ester monomer unit as the main component and 0 to 10% by weight of the crosslinkable monomer unit can be used.

[0056] The (meth)acrylic acid ester monomer forming the (meth)acrylic acid ester monomer unit suitable as the main component of the ethylene-acrylate rubber is not particularly limited, but examples thereof include the above-mentioned (meth)acrylic acid alkyl ester monomer and (meth)acrylic acid alkoxyalkyl ester monomer.

[0057] The content of the (meth)acrylic acid ester monomer unit in the ethylene-acrylate rubber is preferably 50 to 99.9% by weight, more preferably 59.5 to 99% by weight, and further preferably 69 to 98% by weight. By making the content of the (meth)acrylic acid ester monomer unit equal to or higher than the above lower limit, the weather resistance, heat resistance, and oil resistance of the obtained cross-linked rubber can be improved.

[0058] In the ethylene-acrylate rubber, 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.

[0059] The ethylene-acrylate rubber used in the present invention contains ethylene monomer units as an essential component, and the content of the ethylene monomer units is preferably 0.1 to 50% by weight, more preferably 0.5 to 40% by weight, and further preferably 1 to 30% by weight. When the content of the ethylene monomer units is within the above range, the obtained cross-linked rubber is excellent in mechanical properties such as strength, weather resistance, heat resistance, and oil resistance.

[0060] The ethylene-acrylate rubber may contain a crosslinkable monomer unit in addition to the (meth)acrylic acid ester monomer unit and the ethylene monomer unit. Examples of the crosslinkable monomer unit include those mentioned above. The content of the crosslinkable monomer unit in the ethylene-acrylate rubber is preferably 0 to 10% by weight, more preferably 0.5 to 7% by weight, and further preferably 1 to 5% by weight. By making the content of the crosslinkable monomer unit equal to or less than the above upper limit, the elongation of the obtained crosslinked rubber product can be increased and the compression set can be reduced.

[0061] Among the above-mentioned crosslinkable monomers, it is preferable to use an α,β-ethylenically unsaturated carboxylic acid monomer as a crosslinkable monomer forming a part of the monomer units of the ethylene-acrylate rubber and the acrylic rubber other than the ethylene-acrylate rubber, since the ethylene-acrylate rubber used in the present invention can be made into a carboxyl group-containing ethylene-acrylate rubber having a carboxyl group as a crosslinking point, thereby improving the heat aging resistance of the acrylic rubber used in the present invention.

[0062] Furthermore, the ethylene-acrylate rubber used in the present invention may have units of other monomers copolymerizable with the (meth)acrylic acid ester monomer, ethylene, and crosslinkable monomer, if necessary, in addition to the (meth)acrylic acid ester monomer units, ethylene monomer units, and crosslinkable monomer units. Examples of the other copolymerizable monomers include those mentioned above. The content of the other monomer units in the ethylene-acrylic rubber used in the present invention is preferably 0 to 49.9% by weight, more preferably 0 to 39.5% by weight, and even more preferably 0 to 29% by weight.

[0063] The ethylene-acrylate rubber constituting the acrylic rubber used in the present invention can be obtained by polymerizing the above-mentioned monomers. As the form of the polymerization reaction, as described above, any of emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization can be used, and any polymerization method can be selected.

[0064] When the acrylic rubber used in the present invention contains an ethylene-acrylate rubber and an acrylic rubber other than the ethylene-acrylate rubber, the ethylene-acrylate rubber obtained by the above-mentioned method and the acrylic rubber other than the ethylene-acrylate rubber can be mixed by a known method to obtain the acrylic rubber used in the present invention. The mixing method is not particularly limited, but a method of isolating each acrylic rubber and then dry blending them is preferable.

[0065] <Compound represented by general formula (1)> The acrylic rubber composition of the present invention is obtained by blending the above-mentioned acrylic rubber with a compound represented by the following general formula (1). [ka] (In the above general formula (1), R 1 ~R 4 each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent; R 5 ~R 10 each independently represents a hydrogen atom or an organic group having 1 to 30 carbon atoms which may have a substituent.)

[0066] According to the present invention, by blending the compound represented by the above general formula (1) with the acrylic rubber, it is possible to prevent thermal degradation due to heat even in a high temperature environment (for example, an environment of 190° C. or higher). In particular, in a high temperature environment (for example, an environment of 190° C. or higher), the acrylic rubber gels, and such gelation can cause thermal degradation. However, according to the present invention, by blending the compound represented by the above general formula (1), it is possible to effectively suppress thermal degradation due to such gelation.

[0067] In the above general formula (1), R 1 ~R 4are each independently an organic group having 1 to 30 carbon atoms which may have a substituent, preferably an aliphatic hydrocarbon group or aromatic heterocyclic group having 1 to 30 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 30 carbon atoms which may have a substituent, and more preferably a linear, branched or cyclic alkyl group having 1 to 30 carbon atoms which may have a substituent.

[0068] R 1 ~R 4 Examples of the organic group having 1 to 30 carbon atoms which may have a substituent and which constitutes the above-mentioned formula include aliphatic hydrocarbon groups which may have a substituent, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a cyclopentyl group, an n-hexyl group, an isohexyl group, a cyclohexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, or an n-icosyl group, a phenyl group, a tolyl group, a methoxyphenyl group, a fluorophenyl group, a chlorophenyl group, a bromophenyl group, a ... Examples of the alkyl group include aromatic hydrocarbon groups which may have a substituent, such as a phenyl group, an iodophenyl group, a trifluoromethylphenyl group, a naphthyl group, or a furyl group; and aromatic heterocyclic groups which may have a substituent, such as a pyridyl group or a thienyl group. Among these, a linear, branched, or cyclic alkyl group having 1 to 30 carbon atoms which may have a substituent is preferred, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a cyclopentyl group, an n-hexyl group, an isohexyl group, a cyclohexyl group, or a phenyl group is more preferred, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, or a t-butyl group is even more preferred, and a methyl group or an isopropyl group is particularly preferred.

[0069] In the case where the organic group has a substituent, examples of the substituent include halogen atoms such as fluorine atom and chlorine atom; cyano group; N,N-dialkylamino group having 2 to 12 carbon atoms such as dimethylamino group; alkoxy group having 1 to 20 carbon atoms such as methoxy group, ethoxy group, isopropoxy group, butoxy group; alkoxy group having 1 to 12 carbon atoms substituted with alkoxy group having 1 to 12 carbon atoms such as methoxymethoxy group, methoxyethoxy group; nitro group; aromatic hydrocarbon ring group having 6 to 20 carbon atoms such as phenyl group, naphthyl group; aromatic heterocyclic group having 2 to 20 carbon atoms such as triazolyl group, pyrrolyl group, furanyl group, thienyl group, thiazolyl group, benzothiazol-2-ylthio group; cyclopropyl cycloalkyl groups having 3 to 8 carbon atoms, such as a cyclopentyl group, a cyclohexyl group, etc.; cycloalkyloxy groups having 3 to 8 carbon atoms, such as a cyclopentyloxy group, a cyclohexyloxy group, etc.; cyclic ether groups having 2 to 12 carbon atoms, such as a tetrahydrofuranyl group, a tetrahydropyranyl group, a dioxolanyl group, a dioxanyl group, etc.; aryloxy groups having 6 to 14 carbon atoms, such as a phenoxy group, a naphthoxy group, etc.; fluoroalkyl groups having 1 to 12 carbon atoms in which one or more hydrogen atoms are substituted with fluorine atoms, such as a trifluoromethyl group, a pentafluoroethyl group, -CH2CF3, etc.; a benzofuryl group; a benzopyranyl group; a benzodioxolyl group; and a benzodioxanyl group.

[0070] In addition, R 1 ~R 4 In the case where the organic group constituting R has a substituent, the number of carbon atoms of the organic group does not include the number of carbon atoms of the substituent. 1 ~R 4 The organic group constituting R may have a number of carbon atoms, excluding the carbon atoms contained in the substituent, in the range of 1 to 30. For example, R 1 ~R 4 When the organic group constituting the formula (I) is a methoxyethyl group, the number of carbon atoms in the organic group is 2. That is, in this case, since the methoxy group is a substituent, the number of carbon atoms in the organic group is the number excluding the number of carbon atoms in the methoxy group which is a substituent.

[0071] In addition, in the above general formula (1), R 5 ~R10 are each independently a hydrogen atom or an organic group having 1 to 30 carbon atoms which may have a substituent, preferably a hydrogen atom, an aliphatic hydrocarbon group or aromatic heterocyclic group having 1 to 30 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 30 carbon atoms, more preferably a hydrogen atom; R 5 ~R 10 It is particularly preferable that all of are hydrogen atoms.

[0072] R 5 ~R 10 Examples of the organic group having 1 to 30 carbon atoms, which may have a substituent, constituting the above formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a cyclopentyl group, an n-hexyl group, an isohexyl group, a cyclohexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetra ... Examples of such an alkyl group include a silyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-icosyl group, a phenyl group, a tolyl group, a methoxyphenyl group, a fluorophenyl group, a chlorophenyl group, a bromophenyl group, an iodophenyl group, a trifluoromethylphenyl group, a naphthyl group, a furyl group, a pyridyl group, and a thienyl group. Of these, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, and a phenyl group are preferred, and a methyl group is more preferred.

[0073] In addition, R 5 ~R 10 When the organic group in has a substituent, R 5 ~R 10 The substituents of the organic group in 1 ~R 4 The substituents of the organic group in the above formula can be the same as those given as examples of the substituents.

[0074] Examples of the compound represented by the above general formula (1) include N,N'-bis(2,6-dimethylphenyl)thiourea, N,N'-bis(2,4,6-trimethylphenyl)thiourea, N,N'-bis(2,6-diethylphenyl)thiourea, N,N'-bis(2,4,6-triethylphenyl)thiourea, N,N'-bis(2,6-diisopropylphenyl)thiourea, N,N'-bis(2,4,6-triisopropylphenyl)thiourea, N,N'-bis(2-ethyl-6-methylphenyl)thiourea, and N,N'-bis(2-methyl-6-isopropylphenyl)thiourea. N-(2,6-dimethylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea, N-(2,6-dimethylphenyl)-N'-(2-ethyl-6-methylphenyl)thiourea, N-(2,6-diethylphenyl)-N'-(2,6-dimethylphenyl)thiourea, N-(2,6-diethylphenyl)-N'-(2-ethyl-6-methylphenyl)thiourea, N-(2,6-dimethylphenyl)-N'-(2-methyl-6-isopropylphenyl)thiourea, thiourea, N-(2-ethyl-6-methylphenyl)-N'-(2-methyl-6-isopropylphenyl)thiourea, N-(2,6-diethylphenyl)-N'-(2-methyl-6-isopropylphenyl)thiourea, N-(2-ethyl-6-methylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea, N-(2,6-dimethylphenyl)-N'-(2,6-diisopropylphenyl)thiourea, N-(2,6-diethylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea, N-(2,6-diethylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea, N-(2,6-diethylphenyl)-N'- (2,6-diisopropylphenyl)thiourea, N-(2-methyl-6-isopropylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea, N-(2,6-diisopropylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea, N-(2,6-di-t-butylphenyl)-N'-(2,6-dimethylphenyl)thiourea, N-(2,6-di-t-butylphenyl)-N'-(2,6-diethylphenyl)thiourea, N-(2,6-di-t-butylphenyl)-N'-(2,6-diisopropylphenyl)thiourea, N-(2,6-di-t-butylphenyl)-N'-(2,4,6-trimethylphenyl)thiourea. Among these, N,N'-bis(2,6-dimethylphenyl)thiourea, N,N'-bis(2,4,6-trimethylphenyl)thiourea, N,N'-bis(2,6-diethylphenyl)thiourea, N,N'-bis(2,4,6-triethylphenyl)thiourea, N,N'-bis(2,6-diisopropylphenyl)thiourea, N,N'-bis(2,4,6-triisopropylphenyl)thiourea, N,N'-bis(2-ethyl-6-methylphenyl)thiourea, N,N'-bis(2-methyl-6-isopropylphenyl)thiourea, and N,N'-bis(2,6-di-t-butylphenyl)thiourea are preferably used. Among these, it is more preferable to use N,N'-bis(2,6-dimethylphenyl)thiourea, N,N'-bis(2,4,6-trimethylphenyl)thiourea, N,N'-bis(2,6-diisopropylphenyl)thiourea, and N,N'-bis(2-methyl-6-isopropylphenyl)thiourea, and it is particularly preferable to use N,N'-bis(2,6-dimethylphenyl)thiourea and N,N'-bis(2,6-diisopropylphenyl)thiourea.

[0075] The compound represented by the above general formula (1) can be produced by applying a known production method, for example, the reaction method described in Japanese Patent No. 5682575.

[0076] The content of the compound represented by the above general formula (1) in the acrylic rubber composition of the present invention is preferably 0.1 to 50 parts by weight, more preferably 1 to 10 parts by weight, and further preferably 2 to 5 parts by weight, based on 100 parts by weight of the acrylic rubber. When the content of the compound represented by the above general formula (1) is within the above range, the heat deterioration of the acrylic rubber composition can be more appropriately prevented when heated to a temperature of 190°C or higher.

[0077] <Other ingredients> Furthermore, the acrylic rubber composition of the present invention may further contain, in addition to the compound represented by the above general formula (1), other antioxidants other than the compound represented by the above general formula (1). Examples of other antioxidants include, but are not limited to, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-sec-butylphenol, 2-(1-methylcyclohexyl)-4,6-dimethylphenol, 2,6-di-t-butyl-α-dimethylamino-p-cresol, 2,4-bis[(octylthio)methyl]-o-cresol, and the like. Monophenol-based antioxidants such as phenol, styrenated phenol, and alkylated phenol; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-methylenebis(2,6-di-t-butylphenol), 2,2'-methylenebis(6-α-methylbenzyl-p-cresol), methylene-bridged polyhydric alkylphenols, 4,4'-butylidenebis(6-t- butyl-m-cresol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 2,2'-ethylidenebis(4,6-di-t-butylphenol), 1,1-bis-(4-hydroxyphenyl)cyclohexane, 2,2'-dihydroxy-3,3'-(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, alkylated bisphenols, butylated reaction products of p-cresol and dicyclopentadiene, 2,5-di- bis-, tris-, or polyphenol-based antioxidants such as t-butylhydroquinone and 2,5-di-t-amylhydroquinone; thiobisphenol-based antioxidants such as 4,4'-thiobis(6-t-butyl-m-cresol), 4,4'-thiobis(6-t-butyl-o-cresol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and bis(3,5-di-t-butyl-4-hydroxybenzyl) sulfide; and other phenol-based antioxidants;Phenyl-α-naphthylamine, Octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamido)diphenylamine, p-isopropoxy diphenylamine, bis(phenyl isopropylidene)-4,4-diphenylamine, N,N'-diphenyl ethylenediamine, N,N'-diphenyl propylenediamine, N,N'-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenyldiamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-furan Aromatic secondary amine compounds such as N,N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N-bis(1,4-dimethylpentyl)-p-phenylenediamine, 4-(α-phenylethyl)diphenylamine, 4,4'-bis(α-phenylethyl)diphenylamine, and 4,4'-bis(4-methylphenyl)sulfonyl)diphenylamine; nickel dialkyldithiocarbamates such as nickel dimethyldithiocarbamate, nickel diethyldithiocarbamate, and nickel dibutyldithiocarbamate; and the like can be used.

[0078] As the other antioxidant, in addition to the above-mentioned compounds, compounds represented by the following general formula (2a) or (2b) can also be used. [ka] [ka] (In the above general formula (2a), R a and R b Z each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent. a and Z bEach independently represents a chemical single bond or -SO2-. Each of n and m is independently 0 or 1, and at least one of n and m is 1. In the above general formula (2b), R c and R d Each of X independently represents an organic group having 1 to 30 carbon atoms which may have a substituent. 1 and X 2 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, a cyano group, a nitro group, -OR, -OC(=O)-R, -C(=O)-OR, -OC(=O)-OR, NRR'-, -NR-C(=O)-R', -C(=O)-NRR', or -OC(=O)-NRR', where R and R' each independently represent a hydrogen atom or an organic group having 1 to 20 carbon atoms which may have a substituent, and a plurality of X 1 and multiple X's 2 are all independently possible different substituents. n and m are each independently 0 or 1, and at least one of n and m is 1.

[0079] In the general formula (2a) above, R a and R b each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent. R a and R bThe organic group having 1 to 30 carbon atoms constituting the formula (I) is not particularly limited, and examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups; cycloalkyl groups having 3 to 30 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups; aryl groups having 6 to 30 carbon atoms, such as phenyl, biphenyl, naphthyl, and anthranyl groups; and alkoxy groups having 1 to 30 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, t-butoxy, n-pentyloxy, and n-hexyloxy groups.

[0080] In addition, the above-mentioned R a and R b The organic group constituting the formula (I) may have a substituent, and the position of the substituent may be any position. When the organic group is an alkyl group, such a substituent includes a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom; an alkoxy group having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, or an isopropoxy group; a nitro group; a cyano group; and a phenyl group which may have a substituent such as a phenyl group, a 4-methylphenyl group, or a 2-chlorophenyl group. Furthermore, when the organic group is a cycloalkyl group or an aryl group, examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, and a bromine atom; alkoxy groups having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, and an isopropoxy group; a nitro group; a cyano group; and alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, and a t-butyl group. Furthermore, when the organic group is an alkoxy group, examples of the substituent include halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; a nitro group; and a cyano group. In addition, in the above general formula (2a), R a and R bWhen the organic group constituting the formula (I) has a substituent, the number of carbon atoms of the organic group does not include the number of carbon atoms of the substituent.

[0081] R a and R b are each independently preferably an alkyl group having 2 to 20 carbon atoms which may have a substituent, or an aryl group having 6 to 30 carbon atoms which may have a substituent, more preferably a linear or branched alkyl group having 2 to 20 carbon atoms which may have a substituent, or a phenyl group which may have a substituent, or a naphthyl group which may have a substituent, further preferably a linear or branched alkyl group having 2 to 8 carbon atoms which may have a substituent, or a phenyl group which may have a substituent, and particularly preferably a linear or branched alkyl group having 2 to 8 carbon atoms which may have a substituent. Examples of these substituents include the same as those exemplified as the substituents of the alkyl group having 1 to 30 carbon atoms which may have a substituent and the aryl group having 6 to 30 carbon atoms which may have a substituent of the organic group.

[0082] Such an R a and R b Preferred specific examples of the organic group constituting the formula include an α-methylbenzyl group, an α,α-dimethylbenzyl group, a t-butyl group, a phenyl group, or a 4-methylphenyl group, and among these, an α,α-dimethylbenzyl group or a 4-methylphenyl group is more preferred, and an α,α-dimethylbenzyl group is even more preferred. These may each be independent.

[0083] In addition, in the above general formula (2a), Z a and Z b are each independently a single chemical bond or -SO2-, and are preferably a single chemical bond.

[0084] Furthermore, in the above general formula (2a), n and m are each independently 0 or 1, and at least one of n and m is 1. It is preferable that both n and m are 1.

[0085] In the present invention, the compound represented by the above general formula (2a) is preferably any of the compounds represented by the following general formulae (3) to (5). [ka] (In the above general formulas (3) to (5), R a , R b , Z a and Z b is the same as in general formula (2a) above.

[0086] Among the compounds represented by the above general formulas (3) to (5), the compounds represented by the general formulas (3) and (5) are preferred, and the compound represented by the general formula (5) is more preferred.

[0087] In addition, in the above general formulas (3) to (5), -Z a -R a , -Z b -R b are each independently preferably an α-methylbenzyl group, an α,α-dimethylbenzyl group, a t-butyl group, a phenylsulfonyl group, or a 4-methylphenylsulfonyl group, more preferably an α,α-dimethylbenzyl group or a 4-methylphenylsulfonyl group, and further preferably an α,α-dimethylbenzyl group.

[0088] That is, in the present invention, in the above general formula (2a), R a and R b each independently represents a linear or branched alkyl group having 2 to 8 carbon atoms which may have a substituent, and Z a and Z b is a single chemical bond, and it is preferred that n and m are 1.

[0089] The compound represented by the above general formula (2a) can be produced by applying a known method for producing a phenothiazine compound to obtain a precursor phenothiazine compound, and then oxidizing the obtained compound.

[0090] Specifically, the compound represented by the above general formula (2a) can be prepared by reacting a compound represented by the following general formula (6) (phenothiazine) as a starting material with a substituent (-Z a -R a , -Z b -R b ) and oxidizing the S of the phenothiazine ring to -SO2-. [ka]

[0091] In the above general formula (2b), R c and R d each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent, and is preferably an aromatic group or cyclic aliphatic group having 1 to 30 carbon atoms which may have a substituent. The aromatic group having 1 to 30 carbon atoms is not particularly limited, but examples thereof include aromatic hydrocarbon groups such as a phenyl group, a biphenyl group, a naphthyl group, a phenanthryl group, and an anthranyl group, and aromatic heterocyclic groups such as a furyl group, a pyrrolyl group, a thienyl group, a pyridyl group, and a thiazolyl group. The cyclic aliphatic group having 1 to 30 carbon atoms is not particularly limited, but examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. c and R d are each independently preferably a phenyl group or a 4-methylphenyl group. In addition, the above-mentioned R c and R dThe organic group constituting the may have a substituent, and the position of the substituent may be any position. Examples of such a substituent include halogen atoms such as fluorine atom, chlorine atom, and bromine atom, alkoxy groups having 1 to 10 carbon atoms such as methoxy group, ethoxy group, and isopropoxy group, nitro group, cyano group, and alkyl groups having 1 to 10 carbon atoms such as methyl group, ethyl group, and t-butyl group. In addition, in the above general formula (2b), R c and R d When the organic group constituting the formula (I) has a substituent, the number of carbon atoms of the organic group does not include the number of carbon atoms of the substituent.

[0092] In the above general formula (2b), X 1 and X 2 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a n-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, a n-nonyl group, or a n-decyl group, a cyano group, a nitro group, -OR, -OC(=O)-R, -C(=O)-OR, -OC(=O)-OR, NRR'-, -NR-C(=O)-R', -C(=O)-NRR', or -OC(=O)-NRR'. Here, R and R' each independently represent a hydrogen atom or an organic group having 1 to 20 carbon atoms which may have a substituent, 1 and multiple X's 2 Each X can independently be a different substituent. 1 and X 2 are preferably all hydrogen atoms. X 1 and X 2 The substituent of the alkyl group having 1 to 10 carbon atoms which may have a substituent is R a and R b Examples of the substituent of the alkyl group having 1 to 30 carbon atoms which may have a substituent include the same as those exemplified above.

[0093] In the present invention, the compound represented by the above general formula (2b) is R c and R d each independently represents an aromatic group or cyclic aliphatic group having 1 to 30 carbon atoms which may have a substituent; X 1 and X 2 It is preferable to select a compound in which n represents a hydrogen atom and n and m represent 1, and it is more preferable to select a compound represented by the following general formula (2c). [ka] (In the above general formula (2c), R c , and R d is the same as in general formula (2b) above.

[0094] The compound represented by the above general formula (2b) can be produced by applying a known production method, for example, it can be synthesized using the reaction method described in WO2011 / 058918A1.

[0095] As the other antiaging agent, in addition to the above-mentioned compounds and the compounds represented by the general formulas (2a) and (2b), a compound represented by the following general formula (7) can also be used. [ka]

[0096] In the above general formula (7), A 1 and A 2 each independently represents an arylene group having 6 to 18 carbon atoms which may have a substituent; A 3 and A 4 each independently represents an organic group having a cyclic imide structure which may have a substituent.

[0097] In the above general formula (7), A 1 and A 2are each independently an arylene group having 6 to 18 carbon atoms which may have a substituent, preferably an arylene group having 6 to 10 carbon atoms which may have a substituent, more preferably a phenylene group which may have a substituent, and further preferably a 1,4-phenylene group. In particular, A is 1 and A 2 In any case, it is particularly preferable that the substituent is a 1,4-phenylene group. Examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom, an alkoxy group having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, or an isopropoxy group, a nitro group, a cyano group, or an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, or a t-butyl group.

[0098] In addition, in the above general formula (7), A 3 and A 4 are each independently an organic group having a cyclic imide structure which may have a substituent, and are preferably an organic group represented by the following general formula (8) or (9). [ka]

[0099] In the above general formula (8), D represents a ring having 6 to 18 carbon atoms which may have a substituent, preferably a ring having 6 to 10 carbon atoms which may have a substituent, and D may be either a monocyclic or polycyclic ring. In this case, examples of the substituent include an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, -OR 11 , -OC(=O)-R 11 , -C(=O)-OR 11 , -C(=O)-NR 11 (R 12 ), -NR 11 -C(=O)-R 12 , -CN, -SR 11 , -S-(=O)-R 11 , or -S(=O)2-R 11 In addition, R 11 , R 12each independently represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, or an aromatic group having 6 to 12 carbon atoms. In addition, m represents 0 or 1, and is preferably 0.

[0100] In the above general formula (9), R 13 and R 14 are each independently a hydrogen atom, an alkyl group having 1 to 30 carbon atoms which may have a substituent, or an alkenyl group having 1 to 30 carbon atoms which may have a substituent, preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which may have a substituent, and more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent. In this case, examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom; an alkoxy group having 1 to 10 carbon atoms such as a methoxy group, an ethoxy group, or an isopropoxy group; a nitro group; a cyano group; a phenyl group, a 4-methylphenyl group, a 2-chlorophenyl group, or another phenyl group which may have a substituent; and the like. In addition, n represents 0 or 1, and is preferably 0.

[0101] A 3 and A 4 Among the organic groups represented by the above general formula (8) or (9), any of the organic groups represented by the following general formulas (10) to (15) is preferred in terms of exhibiting a more excellent anti-aging effect. [ka]

[0102] In the above general formulas (10) to (15), R 15 ~R 20 each independently represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, -OR 21 , -OC(=O)-R 21 , -C(=O)-OR 21 , -C(=O)-NR 21 (R 22 ), -NR 21 -C(=O)-R 22, -CN, -SR 21 , -S-(=O)-R 21 , or -S(=O)2-R 21 R 21 , R 22 R each independently represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, or an aromatic group having 6 to 12 carbon atoms. 15 ~R 20 are each independently preferably a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and particularly preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 15 ~R 20 When multiple are present, they may be the same or different.

[0103] Among the organic groups represented by the general formulas (10) to (15), from the viewpoint of further enhancing the anti-aging effect, the organic groups represented by the general formulas (10), (11), (13) and (14) are more preferred, the organic groups represented by the general formulas (10), (11) and (14) are even more preferred, and the organic group represented by the general formula (14) is particularly preferred.

[0104] The compound represented by the above general formula (7) is preferably any of the compounds represented by the following general formulae (16) to (19). [ka]

[0105] In the above general formulas (16) to (19), R 23 ~R 34 each independently represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, -OR 35 , -OC(=O)-R 35 , -C(=O)-OR 35 , -C(=O)-NR 35 (R 36 ), -NR 35 -C(=O)-R 36, -CN, -SR 35 , -S-(=O)-R 35 , or -S(=O)2-R 35 R 35 , R 36 R each independently represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, or an aromatic group having 6 to 12 carbon atoms. 23 ~R 34 are each independently preferably a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and particularly preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 1 and A 2 is the same as the above general formula (7).

[0106] Among the compounds represented by the above general formulas (16) to (19), the compound represented by the above general formula (17) is particularly preferred from the viewpoint of being able to further enhance the anti-aging effect.

[0107] The compound represented by the above general formula (7) can be produced by applying a known production method. For example, it can be synthesized using the reaction method described in WO2018 / 159459A1.

[0108] As the other antiaging agent, in addition to the above-mentioned compounds and the compounds represented by the general formulas (2a), (2b), and (7), a compound represented by the following general formula (20) can also be used. [ka]

[0109] In the above general formula (20), A 5 and A 6 R each independently represents an aromatic group having 1 to 30 carbon atoms which may have a substituent. 37 , R 39 , and R 40each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, a cyano group, a nitro group, -OR 1a , -OC(=O)-R 1a , -C(=O)-OR 1a , -OC(=O)-OR 1a , -NR 1b -C(=O)-R 1a , -C(=O)-NR 1a R 1c or -OC(=O)-NR 1a R 1c Represents R 1a and R 1c R each independently represents a hydrogen atom or an organic group having 1 to 30 carbon atoms which may have a substituent. 1b R each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. 1a and R 1c The organic group having 1 to 30 carbon atoms constituting the above is -O-, -S-, -OC(=O)-, -C(=O)-O-, -OC(=O)-O-, -NR 1d -C(=O)-, -C(=O)-NR 1d -, -NR 1d At least one linking group selected from the group consisting of -, -, and -C(=O)- may be present, except for the case where two or more -O- or -S- are present adjacent to each other. 1d each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0110] In the above general formula (20), R 38 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, a cyano group, a nitro group, -OC(=O)-R 1e , -C(=O)-OR 1e , -NR 1e -C(=O)-R 1f , -C(=O)-NR 1e R 1f or -OC(=O)-NR 1e R 1f Represents R 1e and R 1fR each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent. 1e and R 1f The organic groups having 1 to 30 carbon atoms are -O-, -S-, -OC(=O)-, -C(=O)-O-, -OC(=O)-O-, -NR 1d -C(=O)-, -C(=O)-NR 1d -, -NR 1d At least one linking group selected from the group consisting of -, -, and -C(=O)- may be present, except for the case where two or more -O- or -S- are present adjacent to each other. 1d each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0111] A preferred embodiment of the compound represented by the above general formula (20) is 5 is a phenylene group having 1 to 30 carbon atoms which may have a substituent, and A 6 is a phenyl group having 1 to 30 carbon atoms which may have a substituent, and R 37 , R 39 , and R 40 is a hydrogen atom, and R 38 is -OC(=O)-R 1e , -C(=O)-OR 1e , -NR 1e -C(=O)-R 1f , -C(=O)-NR 1e R 1f or -OC(=O)-NR 1e R 1f and R 1b is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 1e and R 1f can be selected from compounds which are each independently an organic group having 1 to 30 carbon atoms which may have a substituent.

[0112] Among the above-mentioned preferred embodiments of the compound represented by the general formula (20), a more preferred embodiment is a compound represented by the general formula (20) in which R 38 But -C(=O)-OR 1e and R 1ecan be selected from diarylamine compounds in which the alkyl group is a phenyl group having 1 to 18 carbon atoms which may have a substituent, or a naphthyl group having 1 to 18 carbon atoms which may have a substituent.

[0113] Among the above-mentioned more preferred embodiments of the compound represented by the above general formula (20), a further preferred embodiment is a compound represented by the above general formula (20), 38 is -C(=O)-OR 1e and R 1e is an optionally substituted alkyl group having 1 to 10 carbon atoms or an optionally substituted aromatic group having 4 to 30 carbon atoms, R 1e The substituents constituting each of the formula (I) are independently a halogen atom, an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 1 to 20 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a cyano group, a nitro group, a sulfo group, -OR e , -OC(=O)-R e , -C(=O)-OR e , -OC(=O)-OR e , -NR g -C(=O)-R e , -C(=O)-NR e R f , -OC(=O)-NR e R f , -SR e , -S(=O)-R e , or -S(=O)2-R e and R e , R f , and R g are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group; A 5 and A 6 each independently represents an aromatic group having 6 to 30 carbon atoms which may have a substituent, 5 and A 6The substituent constituting the above may be an alkyl group having 1 to 10 carbon atoms, a halogen-substituted alkyl group having 1 to 10 carbon atoms, a halogen atom, a cyano group, or a nitro group. In other words, a diarylamine compound containing a phthalimide group and having an ester group at the 4-position, represented by the following general formula (21), may be selected. [ka]

[0114] In the above general formula (21), R 41 ~R 49 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen-substituted alkyl group having 1 to 10 carbon atoms, a halogen atom, a cyano group, or a nitro group; R 1e is the same as above.

[0115] Furthermore, the diarylamine compound represented by the above general formula (20) will be specifically described.

[0116] In the above general formula (20), R 38 As an example, -C(=O)-OR 1e In view of ease of production of the compound, an ester group represented by the formula: 1e is an organic group having 1 to 30 carbon atoms which may have a substituent, R 1e As the organic group having 1 to 30 carbon atoms constituting the above, many aliphatic groups and aromatic groups such as an alkyl group, a cycloalkyl group, an aryl group, an arylalkyl group, an alkylaryl group, an arylalkylaryl group, and an alkoxy group can be selected. From the viewpoint of heat resistance, however, it is preferable to select an aromatic group, in particular, a phenyl group or a naphthyl group.

[0117] Furthermore, in the above general formula (20), R 38 But -C(=O)-OR 1e And R 1e It is particularly preferred that R is an aromatic group having 1 to 20 carbon atoms which may have a substituent, since when used as an antioxidant, the effect of improving heat resistance can be further achieved.38 But -C(=O)-OR 1e And R 1e is an ester structure in which the alkyl group is a phenyl group having 1 to 18 carbon atoms which may have a substituent or a naphthyl group having 1 to 18 carbon atoms which may have a substituent, since an even more excellent effect of improving heat resistance can be obtained, it is most preferable.

[0118] The compound represented by the above general formula (20) can be produced by applying a known production method, for example, the reaction method described in Japanese Patent No. 5732673.

[0119] When other antioxidants are used, the total content of the compound represented by the general formula (1) and the other antioxidants in the acrylic rubber composition of the present invention is preferably 0.1 to 50 parts by weight, more preferably 1 to 10 parts by weight, and further preferably 3 to 6 parts by weight, relative to 100 parts by weight of the acrylic rubber.

[0120] The content of the other antioxidants in the acrylic rubber composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, and even more preferably 0.5 to 2.5 parts by weight, based on 100 parts by weight of the acrylic rubber.

[0121] The acrylic rubber composition of the present invention may further contain a crosslinking agent. By adding a crosslinking agent to the acrylic rubber composition of the present invention, it can be made crosslinkable (crosslinkable acrylic rubber composition), and by crosslinking reaction by heating or the like, it can be made into a rubber crosslinked product.

[0122] The crosslinking agent is not particularly limited, but may be, for example, a polyamine compound such as a diamine compound and its carbonate salt, sulfur, a sulfur donor, a triazine thiol compound, an organic carboxylic acid ammonium salt, a dithiocarbamic acid metal salt, a polycarboxylic acid, a quaternary onium salt, an imidazole compound, an isocyanuric acid compound, an organic peroxide, or other conventionally known crosslinking agents, and may be appropriately selected depending on, for example, the presence or absence of a crosslinkable monomer unit in the acrylic rubber and the type of the crosslinkable monomer unit. These crosslinking agents may be used alone or in combination of two or more.

[0123] The polyamine compound and its carbonate are not particularly limited, but polyamine compounds having 4 to 30 carbon atoms and its carbonate are preferred. Examples of such polyamine compounds and their carbonates include aliphatic polyamine compounds and their carbonates, and aromatic polyamine compounds. On the other hand, those having a non-conjugated nitrogen-carbon double bond such as guanidine compounds are not included.

[0124] 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.

[0125] 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.

[0126] Examples of the sulfur donor include dipentamethylene thiuram hexasulfide and triethylthiuram disulfide. Examples of triazine thiol compounds include 1,3,5-triazine-2,4,6-trithiol, 6-anilino-1,3,5-triazine-2,4-dithiol, 6-dibutylamino-1,3,5-triazine-2,4-dithiol, 6-diallylamino-1,3,5-triazine-2,4-dithiol, and 6-octylamino-1,3,5-triazine-2,4-dithiol. Among these, 1,3,5-triazine-2,4,6-trithiol is preferred.

[0127] Examples of ammonium carboxylates include ammonium benzoate and ammonium adipate. An example of the metal dithiocarbamate is zinc dimethyldithiocarbamate. An example of the polycarboxylic acid is tetradecanedioic acid. An example of the quaternary onium salt is cetyltrimethylammonium bromide. The imidazole compound includes, for example, 2-methylimidazole. An example of the isocyanuric acid compound is ammonium isocyanurate.

[0128] In the case where a crosslinking agent is blended in the acrylic rubber composition of the present invention, the blending amount is preferably 0.05 to 20 parts by weight, more preferably 0.1 to 15 parts by weight, and further preferably 0.3 to 12 parts by weight, based on 100 parts by weight of the acrylic rubber. When the content of the crosslinking agent is within the above range, crosslinking is sufficiently performed, and when a crosslinked rubber product is produced, the obtained crosslinked rubber product can have excellent mechanical properties.

[0129] In addition to the above-mentioned components, the acrylic rubber composition of the present invention may contain compounding agents that are commonly used in the field of rubber processing. Examples of such compounding agents include reinforcing fillers such as carbon black and silica; non-reinforcing fillers such as calcium carbonate and clay; crosslinking accelerators; light stabilizers; plasticizers; processing aids; lubricants; adhesives; lubricants; flame retardants; antifungal agents; antistatic agents; colorants; silane coupling agents; crosslinking retarders; and the like. The amount of these compounding agents is not particularly limited as long as it is within a range that does not impair the purpose and effects of the present invention, and they may be appropriately compounded in an amount according to the purpose of compounding.

[0130] <Method for preparing acrylic rubber composition> The method for preparing the acrylic rubber composition of the present invention is not particularly limited, but a method in which the acrylic rubber and the compound represented by the above general formula (1) are mixed together with various compounding agents added as necessary is preferred.

[0131] The mixing method is not particularly limited, and examples thereof include a method of kneading using a kneading machine such as a roll, an intermix, a kneader, a Banbury mixer, a screw mixer, etc. Also, the mixing may be carried out in a solvent.

[0132] In addition, when a crosslinking agent is blended, each component except for the crosslinking agent and the heat-unstable crosslinking aid is kneaded in a mixer such as a Banbury mixer, a Brabender mixer, an intermixer, or a kneader, and then transferred to a roll or the like, where the crosslinking agent and the heat-unstable crosslinking aid are added, followed by secondary kneading to prepare the composition.

[0133] In this manner, the acrylic rubber composition of the present invention can be obtained. The acrylic rubber composition of the present invention contains an acrylic rubber and a compound represented by the above general formula (1). According to the acrylic rubber composition of the present invention, by blending the compound represented by the above general formula (1), heat deterioration when heated at a temperature of 190°C or higher can be effectively suppressed.

[0134] Furthermore, when a crosslinking agent is blended into the acrylic rubber composition of the present invention, a crosslinked rubber product can be obtained by crosslinking the composition. The rubber cross-linked product is produced by molding and cross-linking an acrylic rubber composition containing a cross-linking agent. The molding and cross-linking method of the acrylic rubber composition is not particularly limited, but may be, for example, a method in which a cross-linkable rubber composition is extruded using a single-screw or multi-screw extruder to form a molded body, and then heated to cross-link; a method in which the rubber composition is molded using a mold using an injection molding machine, an extrusion blow molding machine, a transfer molding machine, a press molding machine, or the like, and cross-linked by heating during molding at the same time as molding; and the like. Among these methods, the method using an extruder or an injection molding machine is preferred, and the method using an extruder is particularly preferred. There is no particular limit to whether molding and cross-linking are performed simultaneously, or whether cross-linking is performed after molding, and it may be selected according to the molding method, vulcanization method, size of the molded body, and the like.

[0135] The molding temperature when molding and crosslinking the acrylic rubber composition is preferably 15 to 220°C, more preferably 20 to 200°C. The crosslinking temperature is preferably 100°C or higher, more preferably 120°C to 250°C. The crosslinking time may be selected arbitrarily within the range of 1 minute to 5 hours. The heating method may be appropriately selected from methods normally used for crosslinking rubber, such as electric heating, steam heating, oven heating, UHF (ultra-high frequency) heating, and hot air heating.

[0136] Depending on the shape, size, etc. of the cross-linked rubber product, even if the surface is cross-linked, the inside may not be sufficiently cross-linked, so secondary cross-linking may be performed by further heating. The heating temperature during secondary cross-linking is preferably 100 to 220°C, more preferably 130 to 210°C, and the heating time is preferably 30 minutes to 10 hours, more preferably 1 to 5 hours.

[0137] The cross-linked rubber product thus obtained is obtained using the acrylic rubber composition of the present invention described above, and therefore, like the acrylic rubber composition of the present invention described above, can effectively suppress thermal degradation caused by heat when the cross-linked rubber product is heated to 190° C. or higher. Therefore, by utilizing the properties of the cross-linked rubber product thus obtained, it can be used in a wide variety of seals such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, well head seals, seals for electric and electronic equipment, and seals for pneumatic equipment; cylinder head gaskets attached to the connecting portion between a cylinder block and a cylinder head, rocker cover gaskets attached to the connecting portion between a rocker cover and a cylinder head, oil pan gaskets attached to the connecting portion between an oil pan and a cylinder block or a transmission case, fuel cell cells attached between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate, and a negative electrode, and the like. They are preferably used as: various gaskets, such as gaskets for parameters and gaskets for top covers of hard disk drives; various belts; various hoses, such as fuel hoses, turbo air hoses, oil hoses, radiator hoses, heater hoses, water hoses, vacuum brake hoses, control hoses, air conditioner hoses, brake hoses, power steering hoses, air hoses, marine hoses, risers, and flow lines; various boots, such as CVJ boots, propeller shaft boots, constant velocity joint boots, and rack and pinion boots; damping rubber parts, such as cushioning materials, dynamic dampers, rubber couplings, air springs, and vibration-proof materials; etc. EXAMPLES

[0138] 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. In addition, various physical properties were measured as follows.

[0139] [Dissolution rate and swelling degree] The film of the acrylic rubber composition was heated in air at 190° C. for 336 hours to obtain a film of the acrylic rubber composition after heating. The film of the acrylic rubber composition obtained after heating was immersed in toluene at room temperature for 24 hours to swell the film. The swollen film was separated from the toluene, and the weight of the swollen film was measured. The swollen film was then dried in a vacuum dryer at 35°C for 15 hours, and the weight of the film after vacuum drying was measured. The solubility of the acrylic rubber composition film was calculated according to the following formula. When the crosslinking reaction proceeds due to heating, it is considered that the crosslinking reaction proceeds to three-dimensionalize the film and turn it into an insoluble component, so it can be judged that the higher the solubility, the more the heat deterioration due to heat, specifically, the increase in hardness due to the crosslinking reaction proceeding due to heating, is suppressed. Dissolution rate (%) = {(weight of film after heating) - (weight of film after swelling and vacuum drying)} / (weight of film after heating) x 100 The swelling degree of the film of the acrylic rubber composition was calculated according to the following formula. When the crosslinking reaction proceeds due to heating, the crosslinking reaction increases the number of crosslinking points, and generally, the swelling degree due to the organic solvent decreases with the increase in crosslinking points. Therefore, it can be judged that the higher the swelling degree, the more the thermal deterioration due to heat, specifically, the increase in hardness due to the progress of the crosslinking reaction due to heating, is suppressed. Swelling degree (%) = (weight of swollen film) / (weight of film vacuum-dried after swelling) × 100

[0140] [Synthesis Example 1] A 300 ml four-neck flask equipped with a stirrer, a thermometer, a cooling condenser, and a hydrogen sulfide gas absorption device charged with a caustic soda solution connected to the top of the cooling condenser by a gas inlet tube was charged with 80 ml of water, 60.5 g (0.5 mol) of 2,6-dimethylaniline, and 25.3 g (0.25 mol) of triethylamine, and then 22.8 g (0.3 mol) of carbon disulfide was added dropwise over 1 hour while maintaining the internal temperature at 20-30°C. After the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the internal temperature was further raised to 80-90°C, and while maintaining this temperature, the mixture was stirred until the generation of hydrogen sulfide gas was completed, completing the reaction. Hydrogen sulfide gas generated during the reaction was collected by an absorption device outside the system. After the reaction was completed, the internal temperature was cooled to about 15° C., and the reaction product was filtered off, washed with water and a small amount of toluene, and then dried to obtain N,N'-bis(2,6-dimethylphenyl)thiourea represented by the following formula (22) (R 1 , R 2 , R 3 , R 4 = methyl group, R 5 , R 6 , R 7 , R 8 , R 9 , R 10 =H) was obtained in an amount of 62.5 g in a yield of 88.0%. [ka]

[0141] [Synthesis Example 2] N,N'-bis(2,6-diisopropylphenyl)thiourea (R 1 , R 2 , R 3 , R 4 = isopropyl group, R 5 , R 6 , R 7 , R 8 , R 9 , R 10=H) was obtained in an amount of 90.2 g in a yield of 90.0%. [ka]

[0142] [Synthesis Example 3] According to the following method, an antioxidant x represented by the following formula (24) was synthesized. [ka] That is, first, 50.0 g (250.92 mmol) of phenothiazine was added to a three-necked reactor equipped with a thermometer in a nitrogen stream and dissolved in 200 ml of toluene. Next, 59.31 g (501.83 mmol) of α-methylstyrene and 1.19 g (6.27 mmol) of p-toluenesulfonic acid monohydrate were added to this solution and reacted at 80 ° C for 1 hour. Thereafter, the reaction liquid was returned to room temperature, and 48 ml of acetic acid and 85.34 g (752.7 mmol) of 30% hydrogen peroxide solution were added, and the reaction was further carried out at 80 ° C for 2 hours. After the reaction liquid was returned to room temperature, it was poured into 630 ml of methanol. Then, the precipitated crystals were filtered and washed with 320 ml of methanol, and 85.7 g of the antioxidant represented by the above formula (24) in the form of white crystals was obtained in a yield of 73%.

[0143] [Example 1] A solution was prepared by dissolving 4 g of carboxyl group-containing acrylic rubber (product name "Hytemp AR212HR", manufactured by Zeon Corporation) in 36 g of THF, 95.6 mg of N,N'-bis(2,6-dimethylphenyl)thiourea (2.4 parts, 8.4 mmol per 100 parts of carboxyl group-containing acrylic rubber) obtained in Synthesis Example 1, and 40.0 mg of antioxidant x (above formula (24)) (1 part, 2.1 mmol per 100 parts of carboxyl group-containing acrylic rubber) obtained in Synthesis Example 3. The solution was poured into a fluororesin petri dish with a diameter of 10 cm, air-dried for 15 hours, and then vacuum-dried for 4 hours in a vacuum dryer at 30°C, to obtain a film of the acrylic rubber composition. The obtained film was cut into a size of 1.5 cm square, and the dissolution rate and swelling degree after heating at 190°C for 336 hours were calculated according to the above method. The results are shown in Table 1.

[0144] [Example 2] An acrylic rubber composition was obtained in the same manner as in Example 1, except that 132.7 mg (3.3 parts, 8.4 mmol per 100 parts of carboxyl group-containing acrylic rubber) of N,N'-bis(2,6-dimethylphenyl)thiourea obtained in Synthesis Example 2 was used instead of 95.6 mg of N,N'-bis(2,6-dimethylphenyl)thiourea, and a film of the acrylic rubber composition was obtained in the same manner as in Example 1. The obtained film of the acrylic rubber composition was then evaluated in the same manner. The results are shown in Table 1.

[0145] [Comparative Example 1] Except for not using N,N'-bis(2,6-dimethylphenyl)thiourea, an acrylic rubber composition was obtained in the same manner as in Example 1, and a film of the acrylic rubber composition was obtained in the same manner as in Example 1. The obtained film of the acrylic rubber composition was then evaluated in the same manner. The results are shown in Table 1.

[0146] [Comparative Example 2] An acrylic rubber composition was obtained in the same manner as in Example 1, except that 76.3 mg of diphenylthiourea (1.9 parts, 8.4 mmol per 100 parts of carboxyl group-containing acrylic rubber) was used instead of 95.6 mg of N,N'-bis(2,6-dimethylphenyl)thiourea, and a film of the acrylic rubber composition was obtained in the same manner as in Example 1. The obtained film of the acrylic rubber composition was then evaluated in the same manner. The results are shown in Table 1.

[0147] [Table 1]

[0148] As shown in Table 1, the acrylic rubber composition obtained by compounding an acrylic rubber with a thiourea compound having a specific structure had high solubility and swelling after heating at 190°C for 336 hours, and thermal degradation due to heat (particularly thermal degradation due to gelation) was appropriately suppressed (Examples 1 and 2). From these results, it can be said that the cross-linked rubber obtained by using the acrylic rubber composition of the present invention can also be appropriately suppressed from thermal degradation due to heat.

[0149] On the other hand, when the thiourea compound having a specific structure was not blended, the resulting acrylic rubber composition had a low solubility and swelling degree after heating at 190°C for 336 hours, and thermal degradation due to heat became significant (Comparative Example 1). In addition, when a thiourea compound other than the thiourea compound having a specific structure was blended, the resulting acrylic rubber composition had a low solubility and swelling degree after heating at 190°C for 336 hours, and thermal degradation due to heat became significant (Comparative Example 2).

Claims

1. An acrylic rubber composition comprising an acrylic rubber and a compound represented by the following general formula (1): 【Chemistry 17】 (In the above general formula (1), R １ ~R ４ each independently represents an organic group having 1 to 30 carbon atoms which may have a substituent; R ５ ~R １０ each independently represents a hydrogen atom or an organic group having 1 to 30 carbon atoms which may have a substituent.

2. R in the compound represented by the general formula (1) １ ~R ４ are each independently an aliphatic hydrocarbon group or aromatic heterocyclic group having 1 to 30 carbon atoms, which may have a substituent, or an aromatic hydrocarbon group having 6 to 30 carbon atoms, which may have a substituent.

3. R in the compound represented by the general formula (1) １ ~R ４ and each independently represent a linear, branched, or cyclic alkyl group having 1 to 30 carbon atoms which may have a substituent.

4. The acrylic rubber composition according to any one of claims 1 to 3, wherein the content of the compound represented by the general formula (1) is 0.1 to 50 parts by weight relative to 100 parts by weight of the acrylic rubber.

5. The acrylic rubber composition according to claim 4, wherein the content of the compound represented by the general formula (1) is 1 to 10 parts by weight based on 100 parts by weight of the acrylic rubber.

6. The acrylic rubber composition according to any one of claims 1 to 5, wherein the acrylic rubber is a carboxyl group-containing acrylic rubber.

7. The acrylic rubber composition according to any one of claims 1 to 5, wherein the acrylic rubber is an epoxy group-containing acrylic rubber.

8. The acrylic rubber composition according to any one of claims 1 to 5, wherein the acrylic rubber is a halogen atom-containing acrylic rubber.

9. The acrylic rubber composition according to any one of claims 1 to 5, wherein the acrylic rubber is an acrylic rubber containing a carboxyl group and a halogen atom.

10. The acrylic rubber composition according to any one of claims 1 to 9, wherein the acrylic rubber contains 0.1 to 100% by weight of an ethylene-acrylate rubber.

11. The acrylic rubber composition according to any one of claims 1 to 10, further comprising an antioxidant other than the compound represented by the general formula (1), and the total content of the compound represented by the general formula (1) and the antioxidant is 0.1 to 50 parts by weight relative to 100 parts by weight of the acrylic rubber.

12. The acrylic rubber composition according to any one of claims 1 to 11, further comprising 0.05 to 20 parts by weight of a crosslinking agent relative to 100 parts by weight of the acrylic rubber.

13. A cross-linked rubber product obtained by cross-linking the acrylic rubber composition according to claim 12.

14. The cross-linked rubber product according to claim 13, which is an extrusion molded product.

15. The cross-linked rubber product according to claim 13, which is a sealing member.

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