Acrylic copolymer composition and crosslinked product thereof

Abstract

The purpose of the present invention is to provide: an acrylic copolymer composition which has good initial vulcanization characteristics such as Mooney scorch and Vm; and an acrylic rubber crosslinked product which is obtained by crosslinking this composition and has excellent normal state physical properties, especially excellent modulus at 100% elongation. The inventors have found that the above are achieved by means of an acrylic copolymer composition which is configured to contain from 1 part by mass to 20 parts by mass of a styrene resin per 100 parts by mass of a carboxyl group-containing acrylic copolymer.

Description

[Technical Field]

[0001] The present invention relates to an acrylic copolymer composition and a crosslinked product thereof. More specifically, the acrylic copolymer composition is obtained by blending a carboxyl group-containing acrylic copolymer with a styrene resin in a certain proportion, and has good initial vulcanization properties such as Mooney scorch and Vm, while the crosslinked acrylic rubber obtained by crosslinking the composition has excellent modulus at 100% elongation in normal state properties. [Background technology]

[0002] In general, acrylic copolymers are polymers whose main raw material is acrylic ester, and are known as materials with excellent durability properties. They are widely used as industrial rubber materials such as engine gaskets, oil hoses, air hoses, and O-rings, as well as automotive rubber materials.

[0003] Highly elastic rubber is used for the hoses and packing materials used in these industrial and automotive rubber materials. In order to maintain sufficient sealing function even with continuous use, these materials must have high compression set characteristics, and good normal state physical properties such as tensile strength and modulus at 100% elongation must be ensured to ensure good compatibility with mating components.

[0004] In response to this situation, Patent Document 1 describes that the strength of the normal physical properties and the modulus at 100% elongation can be improved by using an ethylene glycol-based diacrylate compound as a co-crosslinking agent. However, the use of such a co-crosslinking agent usually has adverse effects on initial vulcanization, such as Mooney scorch and Vm.

[0005] Furthermore, Patent Document 2 describes that excellent vibration-proofing properties at high temperatures can be achieved by crosslinking an acrylic rubber composition, in which a styrene-based resin is mixed with an acrylic rubber containing a reactive halogen group or an epoxy group, using sulfur, but does not describe initial vulcanization properties such as Mooney scorch or Vm or physical properties under normal conditions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 4-214755 [Patent Document 2] Patent No. 6406433 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide an acrylic copolymer composition having good initial vulcanization properties such as Mooney scorch and Vm, and a cross-linked acrylic rubber product obtained by cross-linking the composition, which has excellent normal state physical properties, particularly excellent modulus at 100% elongation. [Means for solving the problem]

[0008] As a result of various investigations, the present inventors have found that the above-mentioned object can be achieved by an acrylic copolymer composition obtained by adding 1 to 20 parts by mass of a styrene-based resin to 100 parts by mass of a carboxyl group-containing acrylic copolymer, and have thus completed the present invention.

[0009] That is, the aspects of the present invention are as follows. Item 1. An acrylic copolymer composition comprising at least a carboxyl group-containing acrylic copolymer and a styrene-based resin, and containing 1 to 20 parts by mass of the styrene-based resin per 100 parts by mass of the carboxyl group-containing acrylic copolymer. Item 2: The carboxyl group-containing acrylic copolymer is (A) 60 to 99.9% by mass of structural units derived from an alkyl acrylate ester having an alkyl group containing 1 to 8 carbon atoms and / or structural units derived from an alkoxyalkyl (meth)acrylate ester having an alkoxyalkyl group containing 2 to 8 carbon atoms, (B) 0 to 10% by mass of structural units derived from alkyl methacrylate esters having an alkyl group having 1 to 18 carbon atoms, Item 2. The acrylic copolymer composition according to Item 1, comprising (C) 0.1 to 5% by mass of a structural unit derived from a crosslinkable monomer having a carboxyl group. Item 3. The acrylic copolymer composition according to Item 1 or 2, further comprising a crosslinking agent. Item 4. A cross-linked acrylic rubber obtained by cross-linking the acrylic copolymer composition according to item 3. [Effects of the Invention]

[0010] The acrylic copolymer composition of the present invention has good initial vulcanization properties such as Mooney scorch and Vm, and the normal state physical properties, particularly the modulus at 100% elongation, of a cross-linked acrylic rubber obtained by cross-linking the composition are excellent. Therefore, the acrylic copolymer composition of the present invention is suitable as an automotive rubber material for fuel system hoses, air system hoses, tubing materials, and sealing materials such as packings and gaskets. BEST MODE FOR CARRYING OUT THE INVENTION

[0011] The acrylic copolymer composition (acrylic rubber composition) of the present invention contains at least a carboxyl group-containing acrylic copolymer and a styrene-based resin, and contains 1 to 20 parts by mass of the styrene-based resin per 100 parts by mass of the carboxyl group-containing acrylic copolymer. This results in good initial vulcanization properties such as Mooney scorch and Vm, and the normal state physical properties, particularly the modulus at 100% elongation, of the cross-linked acrylic rubber obtained by cross-linking the composition are excellent.

[0012] <Carboxyl group-containing acrylic copolymer> Next, the carboxyl group-containing acrylic copolymer (carboxyl group-containing acrylic rubber) of the present invention will be described. The carboxyl group-containing acrylic copolymer of the present invention is not particularly limited as long as it is an acrylic copolymer (acrylic rubber) containing structural units derived from a crosslinkable monomer having a carboxyl group. However, it is preferably a carboxyl group-containing acrylic copolymer containing (A) structural units derived from an alkyl acrylate and / or structural units derived from an alkoxyalkyl (meth)acrylate, and (C) structural units derived from a crosslinkable monomer having a carboxyl group. It may also be a carboxyl group-containing acrylic copolymer containing (A) structural units derived from an alkyl acrylate and / or structural units derived from an alkoxyalkyl (meth)acrylate, (B) structural units derived from an alkyl methacrylate, and (C) structural units derived from a crosslinkable monomer having a carboxyl group. Here, the term "alkoxyalkyl (meth)acrylate" refers to either an alkoxyalkyl acrylate or an alkoxyalkyl methacrylate, and the same applies to similar expressions in the present application.

[0013] (A) The structural units derived from alkyl acrylates and / or structural units derived from alkoxyalkyl (meth)acrylates are preferably structural units derived from alkyl acrylates having an alkyl group of 1 to 8 carbon atoms and / or structural units derived from alkoxyalkyl (meth)acrylates having an alkoxyalkyl group of 2 to 8 carbon atoms, more preferably structural units derived from alkyl acrylates having an alkyl group of 2 to 6 carbon atoms and / or structural units derived from alkoxyalkyl (meth)acrylates having an alkoxyalkyl group of 2 to 6 carbon atoms, and even more preferably structural units derived from alkyl acrylates having an alkyl group of 2 to 4 carbon atoms and / or structural units derived from alkoxyalkyl (meth)acrylates having an alkoxyalkyl group of 2 to 4 carbon atoms. As the (A) structural unit derived from an alkyl acrylate and / or a structural unit derived from an alkoxyalkyl (meth)acrylate, a structural unit derived from an alkyl acrylate is preferred.

[0014] Specific examples of structural units derived from alkyl acrylate esters having an alkyl group of 1 to 8 carbon atoms include structural units derived from acrylate esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate, with structural units derived from ethyl acrylate and n-butyl acrylate being preferred. These may be derived alone or in combination of two or more types of alkyl acrylate esters.

[0015] Specific examples of structural units derived from (meth)acrylic acid alkoxyalkyl esters having an alkoxyalkyl group having 2 to 8 carbon atoms include structural units derived from (meth)acrylic acid esters such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate, and a structural unit derived from methoxyethyl (meth)acrylate is preferred. These may be derived from a single alkoxyalkyl (meth)acrylate, or two or more types of alkoxyalkyl (meth)acrylates.

[0016] In the carboxyl group-containing acrylic copolymer of the present invention, the content of (A) structural units derived from alkyl acrylate and / or structural units derived from alkoxyalkyl (meth)acrylate is, based on all structural units of the carboxyl group-containing acrylic copolymer, preferably 60% by mass or more in lower limit, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The upper limit is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less. By being in these ranges, excellent cold resistance and oil resistance are achieved. Here, the above content means the total content when multiple types (for example, a structural unit derived from an alkyl acrylate ester and a structural unit derived from an alkoxyalkyl (meth)acrylate ester, or two or more structural units derived from alkyl acrylate esters) are contained, and the same applies to other descriptions regarding the content.

[0017] In the carboxyl group-containing acrylic copolymer of the present invention, the structural unit (B) derived from an alkyl methacrylate ester is preferably a structural unit derived from an alkyl methacrylate ester having an alkyl group with 1 to 18 carbon atoms, more preferably a structural unit derived from an alkyl methacrylate ester having an alkyl group with 1 to 8 carbon atoms, and even more preferably a structural unit derived from an alkyl methacrylate ester having an alkyl group with 1 to 4 carbon atoms.

[0018] Examples of structural units derived from alkyl methacrylates having an alkyl group of 1 to 18 carbon atoms include structural units derived from alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, n-dodecyl methacrylate, n-lauryl methacrylate, and n-stearyl methacrylate. These may be structural units derived from alkyl methacrylates alone, or two or more of them may be combined.

[0019] The content of structural units derived from alkyl methacrylate esters in the carboxyl group-containing acrylic copolymer of the present invention may be, as a lower limit, 0% by mass or more, 1% by mass or more, or 1.5% by mass or more, based on all structural units of the carboxyl group-containing acrylic copolymer. The upper limit may be 10% by mass or less, 8% by mass or less, or 6% by mass or less. By having the structural units derived from alkyl methacrylate esters in the above range, the copolymer has excellent heat resistance, oil resistance, and cold resistance.

[0020] In the carboxyl group-containing acrylic copolymer of the present invention, examples of the structural unit derived from a crosslinkable monomer (C) having a carboxyl group include structural units derived from unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, 2-pentenoic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid; carboxylic anhydrides such as maleic anhydride and citraconic anhydride; butenedioic acid mono-chain alkyl esters such as monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-2-ethylhexyl maleate, and mono-n-butyl maleate; butenedioic acid monocyclic alkyl esters such as monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclopentyl maleate, and monocyclohexyl maleate; and itaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, and monocyclohexyl itaconate. Among these, preferred are structural units derived from ethylenically unsaturated dicarboxylic acid monoesters such as monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monoethyl itaconate, monopropyl itaconate, and monobutyl itaconate, more preferred are structural units derived from monoalkyl fumarate esters, and even more preferred are structural units derived from monoalkyl fumarate esters having an alkyl group with 1 to 4 carbon atoms. These may be used alone, or may be structural units derived from crosslinkable monomers having two or more types of carboxyl groups.

[0021] The content of structural units derived from crosslinkable monomers having carboxyl groups in the carboxyl group-containing acrylic copolymer of the present invention is, based on all structural units of the carboxyl group-containing acrylic copolymer, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more as a lower limit. The upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. By being within these ranges, the copolymer is excellent in physical properties such as strength and compression set, as well as processability.

[0022] The acrylic copolymer of the present invention may contain a structural unit (D) derived from a copolymerizable antioxidant, where the copolymerizable antioxidant refers to an antioxidant to which a substituent having a structure with an external double bond and / or a structure with an internal double bond is bonded. The structural unit (D) derived from the copolymerizable antioxidant may be used alone or in combination of two or more types.

[0023] Examples of structural units derived from copolymerizable antioxidants include structural units derived from copolymerizable amine-based antioxidants such as N-(4-anilinophenyl)methacrylamide, N-(4-anilinophenyl)acrylamide, N-(4-anilinophenyl)maleimide, N-(4-p-toluidinylphenyl)maleimide, N-(4-anilino-1-naphthyl)maleimide, 4-hydroxyphenylmaleimide, and 3-hydroxyphenylmaleimide; and structural units derived from copolymerizable phenol-based antioxidants such as 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, 1'-hydroxy[2,2'-ethylidenebis[4,6-bis(1,1-dimethylpropyl)benzene]]-1-yl acrylate, hydroxycinnamic acid, ferulic acid, and allyl cresol. In the present invention, the structural unit derived from a copolymerizable antioxidant is preferably a structural unit derived from a copolymerizable amine-based antioxidant or a structural unit derived from a copolymerizable phenol-based antioxidant, and more preferably a structural unit derived from a copolymerizable amine-based antioxidant.

[0024] In the carboxyl group-containing acrylic copolymer of the present invention, the content of the structural unit (D) derived from the copolymerizable antioxidant may be, as a lower limit, 0% by mass or more, 0.1% by mass or more, or 0.15% by mass or more, based on all structural units of the carboxyl group-containing acrylic copolymer. The upper limit may be 5% by mass or less, 3% by mass or less, or 2% by mass or less. These ranges are preferred in that they improve the heat resistance of the carboxyl group-containing acrylic copolymer.

[0025] In the carboxyl group-containing acrylic copolymer of the present invention, the total content of (A) constituent units derived from an alkyl acrylate and / or constituent units derived from an alkoxyalkyl (meth)acrylate, optionally present (B) constituent units derived from an alkyl methacrylate, (C) constituent units derived from a crosslinkable monomer having a carboxyl group, and optionally present (D) constituent units derived from a copolymerizable antioxidant is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may even be 100% by mass.

[0026] Furthermore, the carboxyl group-containing acrylic copolymer of the present invention may contain, in addition to the above-mentioned structural units, structural units derived from other monomers copolymerizable therewith. Examples of other structural units include structural units derived from ethylenically unsaturated nitriles, structural units derived from (meth)acrylamide monomers, structural units derived from conjugated diene monomers, structural units derived from non-conjugated dienes, and structural units derived from other olefins. These may be used alone or in combination of two or more.

[0027] Examples of constituent units derived from ethylenically unsaturated nitriles include constituent units derived from compounds such as acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, and vinylidene cyanide.

[0028] Examples of structural units derived from (meth)acrylamide monomers include structural units derived from compounds such as acrylamide, methacrylamide, diacetone acrylamide, diacetone methacrylamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide, N-butoxyethyl acrylamide, N-butoxyethyl methacrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-propioxymethyl acrylamide, N-propioxymethyl methacrylamide, N-methyl acrylamide, N-methyl methacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl acrylamide, N,N-diethyl methacrylamide, N-methylolacrylamide, N-methylol methacrylamide, ethacrylamide, crotonamide, cinnamic acid amide, maleindiamide, itacondiamide, methylmaleamide, methylitaconamide, maleimide, and itaconimide.

[0029] Examples of structural units derived from conjugated diene monomers include structural units derived from compounds such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, chloroprene, and piperylene.

[0030] Examples of structural units derived from non-conjugated dienes include structural units derived from non-conjugated diene compounds such as 1,4-pentadiene, 1,4-hexadiene, ethylidenenorbornene, norbornadiene, and dicyclopentadiene.

[0031] Examples of structural units derived from other olefin-based monomers include esters such as dicyclopentadienyl acrylate, dicyclopentadienyl methacrylate, dicyclopentadienylethyl acrylate, and dicyclopentadienylethyl methacrylate, as well as structural units derived from compounds such as ethylene, propylene, vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl acetate, vinyl fluoride, vinylidene fluoride, 1,2-difluoroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene, ethyl vinyl ether, and butyl vinyl ether.

[0032] When the carboxyl group-containing acrylic copolymer of the present invention contains structural units derived from these other copolymerizable monomers, the content of these structural units in all structural units may be 0 to 15% by mass, 0 to 10% by mass, or 0 to 5% by mass.

[0033] In the carboxyl group-containing acrylic copolymer of the present invention, the content of the structural units can be determined by nuclear magnetic resonance spectroscopy of the obtained polymer.

[0034] The molecular weight range of the carboxyl group-containing acrylic copolymer in the present invention is determined from the viewpoint of processability by determining the Mooney viscosity (ML 1+4 ) is preferably in the range of 10 to 100, more preferably in the range of 15 to 90, and even more preferably in the range of 20 to 80.

[0035] <Method of producing carboxyl group-containing acrylic copolymer> The carboxyl group-containing acrylic copolymer of the present invention can be obtained by polymerizing various monomers. The monomers used may be commercially available products and are not particularly limited.

[0036] The polymerization reaction may be carried out by any of emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization. From the viewpoint of ease of control of the polymerization reaction, however, it is preferable to carry out the polymerization by emulsion polymerization under normal pressure, which is a commonly used method for producing a conventionally known acrylic copolymer.

[0037] In the case of emulsion polymerization, a conventional method may be used, and conventionally known polymerization initiators, emulsifiers, chain transfer agents, polymerization terminators, etc. that are commonly used may be used.

[0038] The emulsifier used in the present invention is not particularly limited, and nonionic emulsifiers and anionic emulsifiers commonly used in emulsion polymerization methods can be used. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alcohol ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, polyoxyethylene fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Examples of anionic emulsifiers include alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyalkylene alkyl ether phosphates or their salts, and fatty acid salts. These may be used alone or in combination. Representative examples of anionic emulsifiers include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and triethanolamine dodecyl sulfate.

[0039] The amount of emulsifier used in the present invention may be any amount generally used in emulsion polymerization. Specifically, the lower limit of the amount of charged monomer is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and even more preferably 0.05% by mass or more. The upper limit is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. When a reactive surfactant is used as a monomer component, the addition of an emulsifier is not necessarily required.

[0040] The polymerization initiator used in the present invention is not particularly limited, and polymerization initiators generally used in emulsion polymerization methods can be used. Specific examples thereof include inorganic polymerization initiators typified by persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane, 1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 4,4-di(t-butylperoxy)n-butyl valerate, 2,2-di(t-butylperoxy)butane, t-butyl hydroperoxide, and cumene hydroperoxide. Side, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, disuccinic acid peroxide oxide, dibenzoyl peroxide, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, cumyl peroxyneodecanate, 1,1,3,3-tetramethylbutylperoxyneodecanate Canate, t-hexylperoxyneodecanate, t-butylperoxyneodecanate, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, t-butylperoxy-2-ethylhexanate, t-butylperoxylaurate, t-butylperoxy-3,5,Organic peroxide polymerization initiators such as 5-trimethylhexanate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy2-ethylhexyl monocarbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, hydroperoxides, azobisisobutyronitrile, 4-4'-azobis(4- Examples of the polymerization initiator include azo initiators such as 2-2'-azobis[2-(2-imidazolin-2-yl)propane, 2-2'-azobis(propane-2-carboxamidine), 2-2'-azobis[N-(2-carboxyethyl)-2-methylpropanamide, 2-2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}, 2-2'-azobis(1-imino-1-pyrrolidino-2-methylpropane), and 2-2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propanamide}. These polymerization initiators may be used alone or in combination.

[0041] The amount of the polymerization initiator used in the present invention may be any amount generally used in emulsion polymerization. Specifically, the lower limit of the amount of the charged monomer is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more. The upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0042] In addition, organic peroxides and inorganic peroxides used as polymerization initiators can be used as redox polymerization initiators by combining them with a reducing agent. Reducing agents that can be used in combination include, but are not limited to, compounds containing reduced metal ions such as ferrous sulfate and cuprous naphthenate, methane compounds such as sodium methanesulfonate, amine compounds such as dimethylaniline, and inorganic salts with reducing properties such as ascorbic acid and its salts, and alkali metal salts of sulfite and thiosulfate. These reducing agents can be used alone or in combination of two or more. The amount of reducing agent used is preferably 0.0003 to 10 parts by mass per 100 parts by mass of charged monomer.

[0043] A chain transfer agent can be used as needed. Specific examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan, xanthogen compounds such as 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene, dimethyl xanthogen disulfide, and diisopropyl xanthogen disulfide, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide. Examples of suitable chain transfer agents include thiuram compounds, phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane and carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile and α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, and 2-ethylhexyl thioglycolate, and these may be used alone or in combination of two or more. The amount of these chain transfer agents is not particularly limited, but is typically 0 to 5 parts by mass per 100 parts by mass of the charged monomer.

[0044] Examples of the polymerization terminator include hydroxylamine, hydroxylamine sulfate, diethylhydroxyamine, hydroxylamine sulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, and quinone compounds such as hydroquinone. The amount of the polymerization terminator used is not particularly limited, but is usually 0 to 2 parts by mass per 100 parts by mass of the charged monomer.

[0045] Furthermore, the pH of the polymer obtained by the above method can be adjusted as needed by using a base as a pH adjuster. Specific examples of bases include sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, inorganic ammonium compounds, and organic amine compounds. The lower limit of the pH range is preferably pH 1 or higher, more preferably pH 1.5 or higher, and even more preferably pH 2 or higher. The upper limit is preferably pH 11 or lower, more preferably pH 10.5 or lower, and even more preferably pH 10 or lower.

[0046] In addition, if necessary, polymerization secondary materials such as particle size adjusters, chelating agents, and oxygen scavengers can be used.

[0047] The emulsion polymerization may be carried out in a batch, semi-batch, or continuous manner. The polymerization time and temperature are not particularly limited. They can be appropriately selected depending on the type of polymerization initiator used, but generally, the polymerization temperature is 10 to 100°C, and the polymerization time is 0.5 to 100 hours.

[0048] There is no particular limitation on the method for recovering the polymer obtained by the above method, and a commonly used method can be adopted. One example of such a method is to continuously or batchwise supply the polymerization solution to an aqueous solution containing a coagulant, and this operation produces a coagulated slurry. In this case, the temperature of the aqueous solution containing the coagulant is affected by coagulation conditions such as the type and amount of monomer used, and shear force due to stirring, etc., so it cannot be uniformly specified, but it is generally 50°C or higher, preferably in the range of 60°C to 100°C.

[0049] The coagulated slurry obtained by the above method is preferably washed with water to remove the coagulant. If washing with water is not performed at all or is performed insufficiently, ion residues derived from the coagulant may be precipitated during the molding process.

[0050] The acrylic copolymer can be obtained by removing water from the coagulated slurry after washing with water and drying it. The drying method is not particularly limited, but is generally carried out using a flash dryer or a fluidized bed dryer. Furthermore, a dehydration step using a centrifuge or the like may be carried out before the drying step.

[0051] <Styrene-based resin> The styrene-based resin used in the present invention is not particularly limited as long as it is a resin having a structural unit derived from a styrene-based vinyl monomer. In addition to a homopolymer consisting of only a styrene-based vinyl monomer, a copolymer of a styrene-based vinyl monomer and another vinyl-based monomer can be used. Among these, a copolymer of a styrene-based vinyl monomer and another vinyl-based monomer is preferred. As the copolymer, a resin consisting of a conventionally known copolymer such as an alternating copolymer, a random copolymer, a block copolymer, or a graft copolymer can be used. Furthermore, the styrene-based resin (copolymer) may be a rubber (butadiene)-modified polystyrene resin modified with a rubber component such as butadiene (polybutadiene). One type of styrene-based resin may be used alone, or multiple types may be used in combination.

[0052] Examples of styrene-based vinyl monomers include styrene, α-methylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, t-butylstyrene, bromostyrene, chlorostyrene, indene, etc. These styrene-based vinyl monomers can be used alone or in combination of two or more kinds, and even copolymers using two or more kinds are treated as homopolymers of styrene-based vinyl monomers in the present invention. Among these, styrene, α-methylstyrene, ο-methylstyrene, m-methylstyrene, and p-methylstyrene are preferred, styrene and α-methylstyrene are more preferred, and styrene is more preferred.

[0053] Examples of other vinyl monomers copolymerized with the styrene-based vinyl monomer include acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylonitrile, acrylamide, methacrylonitrile, maleic anhydride, butadiene, isoprene, chloroprene, etc. These can be used alone or in combination of two or more as copolymerization components with the styrene-based vinyl monomer. Among these, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylonitrile, butadiene, and isoprene are preferred, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylonitrile, and butadiene are more preferred, and acrylic acid esters, acrylonitrile, and butadiene are even more preferred.

[0054] The content of structural units derived from styrene-based vinyl monomers in 100% by mass of the styrene-based resin is, as a lower limit, preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, particularly preferably 45% by mass or more, and most preferably 50% by mass or more, and may be, as an upper limit, 100% by mass, but is preferably 90% by mass or less, more preferably 80% by mass or less. Here, the content of the structural units in the resin can be determined by nuclear magnetic resonance spectroscopy of the resin.

[0055] The Vicat softening temperature of the styrene resin is preferably 70° C. or higher, more preferably 75° C. or higher, even more preferably 80° C. or higher, and is preferably 130° C. or lower, more preferably 120° C. or lower, even more preferably 110° C. or lower. When the Vicat softening temperature of the styrene resin is within the above range, compatibility with the carboxyl group-containing acrylic copolymer becomes better, and the effect tends to be more suitably obtained. Here, the Vicat softening temperature of the styrene-based resin is a value determined in accordance with JIS K 7206 (2016) at a temperature rise rate of 50°C / hr and a test load of 50N.

[0056] The deflection temperature under load of the styrene resin is preferably 50° C. or higher, more preferably 55° C. or higher, and even more preferably 60° C. or higher, and is preferably 110° C. or lower, more preferably 105° C. or lower, and even more preferably 100° C. or lower. When the deflection temperature under load of the styrene resin is within the above range, compatibility with the carboxyl group-containing acrylic copolymer becomes better, and the effect tends to be more suitably obtained. Here, the deflection temperature under load of the styrene resin is a value determined by Method A (load 1.80 MPa) in accordance with ISO 75-1 (2020) and ISO 75-2 (2013).

[0057] Specific examples of the styrene-based resin used in the present invention include polystyrene-based resin (PS resin), acrylonitrile-styrene-acrylate copolymer resin (ASA resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylonitrile-styrene copolymer resin (AS resin), methyl methacrylate-butadiene-styrene copolymer resin (MBS resin), acrylonitrile-ethyl acrylate-styrene copolymer resin (AES resin), and rubber (preferably butadiene)-modified polystyrene-based resin (HIPS). Among these, polystyrene-based resin (PS resin), acrylonitrile-styrene copolymer resin (AS resin), and acrylonitrile-styrene-acrylate copolymer resin are particularly preferred. Preferred are copolymer resins (ASA resins), and acrylonitrile-ethyl acrylate-styrene copolymer resins (AES resins), with polystyrene resins (PS resins), rubber-modified polystyrene resins (HIPS), acrylonitrile-styrene copolymer resins (AS resins), and acrylonitrile-styrene-acrylate copolymer resins (ASA resins) being more preferred, with rubber-modified polystyrene resins (HIPS), acrylonitrile-styrene copolymer resins (AS resins), and acrylonitrile-styrene-acrylate copolymer resins (ASA resins) being even more preferred, with acrylonitrile-styrene copolymer resins (AS resins) and acrylonitrile-styrene-acrylate copolymer resins (ASA resins) being particularly preferred.

[0058] The amount of the styrene-based resin in the present invention is, relative to 100 parts by mass of the carboxyl group-containing acrylic copolymer, preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, particularly preferably 5 parts by mass or more, and most preferably 7 parts by mass or more. The upper limit is preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and even more preferably 15 parts by mass or less. A blending amount within these ranges provides excellent properties under normal conditions and processability.

[0059] <Acrylic Copolymer Composition> The acrylic copolymer composition of the present invention preferably contains a crosslinking agent in addition to the carboxyl group-containing acrylic copolymer and styrene-based resin.

[0060] As the crosslinking agent, a conventionally known crosslinking agent that is usually used for crosslinking rubber, such as a polyamine compound, a polyepoxy compound, a polyisocyanate compound, an aziridine compound, a sulfur compound, a basic metal oxide, an organometallic halide, etc. Among these, a polyamine compound is preferably used.

[0061] Examples of the polyvalent amine compound include aliphatic polyvalent amine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, and N,N'-dicinnamylidene-1,6-hexanediamine, and aromatic polyvalent amine compounds such as 4,4'-methylenedianiline, 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, 1,3,5-benzenetriamine, 1,3,5-benzenetriaminomethyl, and isophthalic acid dihydrazide.

[0062] Examples of polyfunctional epoxy compounds include glycidyl ether epoxy compounds such as phenol novolac epoxy compounds, cresol novolac epoxy compounds, cresol epoxy compounds, bisphenol A epoxy compounds, bisphenol F epoxy compounds, brominated bisphenol A epoxy compounds, brominated bisphenol F epoxy compounds, and hydrogenated bisphenol A epoxy compounds; and other polyfunctional epoxy compounds such as alicyclic epoxy compounds, glycidyl ester epoxy compounds, glycidyl amine epoxy compounds, and isocyanurate epoxy compounds.

[0063] Examples of polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 1,5-naphthylene diisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, and bicycloheptane triisocyanate.

[0064] Examples of the aziridine compound include tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, tris[1-(2-methyl)aziridinyl]phosphinoxide, and hexa[1-(2-methyl)aziridinyl]triphosphatriazine.

[0065] Examples of sulfur compounds include sulfur, 4,4'-dithiomorpholine, tetramethylthiuram disulfide, and tetraethylthiuram disulfide.

[0066] Examples of basic metal oxides include zinc oxide, lead oxide, calcium oxide, and magnesium oxide.

[0067] The organometallic halides include dicyclopentadienyl metal dihalides, and the metals include titanium, zirconium, and the like.

[0068] These crosslinking agents may be used alone or in combination of two or more. The amount of the crosslinking agent is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the carboxyl group-containing acrylic copolymer of the present invention. The upper limit is preferably 20 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2.5 parts by mass or less.

[0069] The acrylic copolymer-containing composition of the present invention may also contain any of other additives commonly used in the art, such as lubricants, softeners, antioxidants, light stabilizers, fillers, reinforcing agents, plasticizers, processing aids, pigments, colorants, crosslinking accelerators, crosslinking aids, crosslinking retarders, antistatic agents, foaming agents, etc. These may be used alone or in combination of two or more.

[0070] The softener is not particularly limited, and examples thereof include lubricating oil, process oil, coal tar, castor oil, stearic acid, calcium stearate, etc., and the blending amount is preferably 0 to 30 parts by mass, more preferably 0 to 10 parts by mass, per 100 parts by mass of the carboxyl group-containing acrylic copolymer of the present invention.

[0071] The antioxidant is not particularly limited, and examples thereof include amines, phosphates, quinolines, cresols, phenols, and dithiocarbamate metal salts, with amines such as diphenylamine derivatives and phenylenediamine derivatives being preferred. The amount of antioxidant added is preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the carboxyl group-containing acrylic copolymer of the present invention.

[0072] The filler is not particularly limited, and may be, for example, a carbon-based material such as carbon black, graphite, etc. Among these, carbon black is preferably used, and the blending amount is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, per 100 parts by mass of the carboxyl group-containing acrylic copolymer of the present invention.

[0073] Examples of the crosslinking accelerator include guanidine compounds, amine compounds, thiourea compounds, thiazole compounds, sulfenamide compounds, thiuram compounds, and quaternary ammonium salts. Guanidine compounds and amine compounds are preferred, and guanidine compounds are more preferred.

[0074] Examples of the guanidine compound include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine.

[0075] Examples of the amine compound include secondary amine compounds such as dimethylamine, diethylamine, dipropylamine, diallylamine, diisopropylamine, di-n-butylamine, di-t-butylamine, di-sec-butylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dicetylamine, di-2-ethylhexylamine, and dioctadecylamine; and tertiary amine compounds such as trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, and tridodecylamine.

[0076] These crosslinking accelerators may be used alone or in combination of two or more. The amount of the crosslinking accelerator to be added is preferably 0.1 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the carboxyl group-containing acrylic copolymer of the present invention.

[0077] <Method of producing acrylic copolymer composition> The acrylic copolymer composition of the present invention can be produced by any means conventionally used in the field of rubber processing, such as an open roll, a Banbury mixer, or various kneaders.

[0078] The manufacturing method can be a conventional method used in the field of rubber processing. For example, it can be manufactured by going through kneading step A, in which compounding ingredients other than the crosslinking agent and crosslinking accelerator are sequentially added to prepare kneaded compound A, and kneading step B, in which the crosslinking agent and crosslinking accelerator are sequentially added to prepare kneaded compound B. The kneading conditions for each step may be those conventionally set arbitrarily in the field of rubber processing, and are set in various ways depending on the types and amounts of compounding ingredients to be kneaded. For example, the kneading temperature in kneading step A may be 100 to 200°C, and the kneading time may be 1 to 10 minutes. Furthermore, the kneading temperature in kneading step B may be 30 to 130°C, and the kneading time may be 1 to 10 minutes.

[0079] If necessary, a masterbatch in which polymer materials and / or compounding agents are pre-kneaded can be used in kneading step A. In the present invention, a masterbatch refers to a mixture of a carboxyl group-containing acrylic copolymer and a styrene-based resin and / or compounding agents (however, the blending amount of filler is preferably 5 parts by mass or less, as this affects the dispersion state of the carboxyl group-containing acrylic copolymer and the styrene-based resin). The use of a masterbatch reduces bias in the dispersion state of the polymer materials and the compounding agents, and is preferable in that it improves compatibility with the compounding agents that are sequentially blended in step A and thereafter. In the present invention, either a masterbatch in which only a carboxyl group-containing acrylic copolymer and a styrene-based resin are kneaded, or a masterbatch in which compounding agents are further kneaded, can be used.

[0080] The masterbatch can be prepared by a method typically used in the field of rubber processing, and may be prepared as a preliminary kneading step prior to kneading step A. The kneading conditions vary depending on the types and amounts of resins and compounding agents to be blended, but generally, for example, a kneading temperature of 100 to 250°C and a kneading time of 2 to 10 minutes are sufficient.

[0081] <Method of manufacturing cross-linked acrylic rubber> The acrylic copolymer composition of the present invention can be typically heated to 100 to 250°C to form a cross-linked acrylic rubber. The cross-linking time varies depending on the temperature, but is typically between 0.5 and 300 minutes. Cross-linking molding may involve integral cross-linking and molding, or a previously molded acrylic copolymer composition may be heated again to form a cross-linked product, or the cross-linked product may be heated first and then processed for molding. Specific methods for cross-linking molding include compression molding using a mold, injection molding, heating in a steam can, an air bath, infrared radiation, or microwave heating, among other methods.

[0082] The acrylic copolymer composition of the present invention thus obtained has good initial vulcanization properties such as Mooney scorch and Vm, and therefore has excellent roll processability during processing, and furthermore, the cross-linked acrylic rubber of the present invention has excellent modulus at 100% elongation in the normal state physical properties.

[0083] Therefore, taking advantage of the above-mentioned properties, the cross-linked acrylic rubber of the present invention can be suitably used as various gaskets such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electric and electronic equipment, seals for pneumatic equipment, cylinder head gaskets attached to the joint between a cylinder block and a cylinder head, rocker cover gaskets attached to the joint between a rocker cover and a cylinder head, oil pan gaskets attached to the joint between an oil pan and a cylinder block or a transmission case, fuel cell separator gaskets attached between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate, and a negative electrode, and gaskets for the top covers of hard disk drives.

[0084] The cross-linked acrylic rubber product of the present invention can be used as a rubber material, and can be suitably used as an extrusion-molded product and a mold-crosslinked product for automotive applications, such as fuel oil hoses around fuel tanks, such as fuel hoses, filler neck hoses, vent hoses, vapor hoses and oil hoses, air hoses, such as turbo air hoses and emission control hoses, radiator hoses, heater hoses, brake hoses and air conditioner hoses. [Example]

[0085] The present invention will be specifically explained by way of examples and comparative examples, but the present invention is not limited to these.

[0086] [Polymerization Example 1] A polymerization reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a pressure reducing device was charged with 200 parts by weight of water, 1.7 parts by weight of polyoxyalkylene alkyl ether phosphate ester, 49.3 parts by weight of ethyl acrylate as monomers, 49.3 parts by weight of n-butyl acrylate, and 1.4 parts by weight of monoethyl fumarate. After repeated degassing and nitrogen substitution under reduced pressure to thoroughly remove oxygen, 0.1 parts by weight of sodium ascorbate and 0.1 parts by weight of potassium persulfate were added to initiate the emulsion polymerization reaction at room temperature and atmospheric pressure. The reaction was continued until the polymerization conversion reached 95%, and then 0.0075 parts by weight of hydroquinone was added to terminate the polymerization. The resulting emulsion polymerization liquid was coagulated with aqueous sodium sulfate, washed with water, and dried to obtain carboxyl group-containing acrylic copolymer 1.

[0087] [Polymerization Example 2] Carboxylic group-containing acrylic copolymer 2 was obtained in the same manner as in Polymerization Example 1, except that the monomers used and their amounts were changed to 49.3 parts by mass of ethyl acrylate, 44.0 parts by mass of n-butyl acrylate, 4.8 parts by mass of methyl methacrylate, 0.5 parts by mass of N-(4-anilinophenyl)maleimide, and 1.4 parts by mass of monoethyl fumarate.

[0088] <Mooney viscosity (ML 1+4 , 100℃) The polymer Mooney viscosity (ML) of the carboxyl group-containing acrylic copolymers 1 and 2 was measured at a measurement temperature of 100°C using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. in accordance with the Mooney viscosity test in the physical testing method for uncrosslinked rubber in JIS K6300-1 (2013). 1+4 The results are shown in Table 1.

[0089] [Example 1] 100 parts by mass of carboxyl group-containing acrylic copolymer 1 and 5 parts by mass of rubber (butadiene) modified polystyrene resin (DIC Corporation, DIC Styrene HIPS GH-6300, containing a graft copolymer in which butadiene is graft polymerized onto polystyrene resin, Vicat softening temperature: 88°C) were pre-mixed in a pressure kneader at 200°C for 4 minutes. After cooling, 50 parts by mass of carbon black N550, which is the raw material for kneaded compound A, 2 parts by mass of stearic acid, and 2 parts by mass of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine were blended and kneaded at 100°C to produce kneaded compound A. Using an open roll, compound A was processed into a sheet, and 0.6 parts by mass of hexamethylenediamine carbamate and 2 parts by mass of di-o-tolylguanidine, which were raw materials for compound B, were added, kneaded, and formed into a sheet to obtain an uncrosslinked sheet of the acrylic copolymer composition.

[0090] (Mooney Scorch Exam (t5, Vm)) The obtained uncrosslinked sheet was subjected to the Mooney scorch test specified in JIS K 6300-1 (2013) at 125°C using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. Here, a larger t5 (min) value indicates a longer time required for vulcanization, and it can be determined that the acrylic copolymer composition has excellent scorch stability and suppresses the vulcanization acceleration effect. A t5 (min) of 5.0 or more was determined to be good. A lower Vm (M) value indicates less initial vulcanization of the acrylic copolymer composition, and it can be determined that the storage stability is excellent. A Vm (M) of 60 or less was determined to be good. The evaluation results are shown in Table 2.

[0091] (Preparation of cross-linked acrylic rubber) The uncrosslinked rubber sheet obtained above was pressed at 180°C for 10 minutes and then heated in an air oven at 180°C for 3 hours to obtain a crosslinked acrylic rubber product.

[0092] (Normal physical property test (100% modulus, strength TB, elongation EB, hardness HS)) The obtained acrylic rubber cross-linked product was subjected to tensile tests and hardness tests using an AGS-5KNY manufactured by Shimadzu Corporation. The tensile tests were performed in accordance with the methods described in JIS K 6251 (2017), and the hardness tests were performed in accordance with JIS K 6253 (2012). The evaluation results are shown in Table 2.

[0093] [Example 2] An acrylic copolymer composition was produced in the same manner as in Example 1, except that the type of styrene resin used was changed to 5 parts by mass of an acrylonitrile-styrene copolymer resin (Cevian N 020SF, manufactured by Daicel Polymers, content of structural units derived from styrene vinyl monomers: 74% by mass, Vicat softening temperature: 101°C, deflection temperature under load: 85°C). The unvulcanized sheet and cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 2.

[0094] [Example 3] An acrylic copolymer composition was produced in the same manner as in Example 1, except that the type of styrene resin added was changed to 5 parts by mass of acrylonitrile-styrene-acrylate copolymer resin (Unibright UA-1800, manufactured by Nippon A&L Co., Ltd., deflection temperature under load: 86°C). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 2.

[0095] [Example 4] An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the type of styrene resin added was changed to 3 parts by mass of acrylonitrile-styrene-acrylate copolymer resin (Unibright UA-1800, manufactured by Nippon A&L Co., Ltd.). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 2.

[0096] [Example 5] An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the type of styrene resin added was changed to 15 parts by mass of acrylonitrile-styrene-acrylate copolymer resin (Unibright UA-1800, manufactured by Nippon A&L Co., Ltd.). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 2.

[0097] [Example 6] An acrylic copolymer composition was prepared in the same manner as in Example 1, except that 100 parts by mass of carboxyl group-containing acrylic copolymer 2 was blended and the type of styrene resin was changed to 5 parts by mass of acrylonitrile-styrene-acrylate copolymer resin (Unibright UA-1800, manufactured by Nippon A&L Co., Ltd.). The obtained unvulcanized sheet and acrylic rubber cross-linked product were evaluated as described above, and the evaluation results are shown in Table 2.

[0098] [Comparative Example 1] An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the styrene resin was not blended. The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 3.

[0099] Comparative Example 2 An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the type of resin added was changed to 5 parts by mass of polypropylene resin (Novatec PP MA3N, manufactured by Japan Polypropylene Corporation). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 3.

[0100] Comparative Example 3 An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the type of resin added was changed to 5 parts by mass of polycarbonate resin (Panlite L-1225Y, manufactured by Teijin Ltd.). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 3.

[0101] Comparative Example 4 An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the amount of carboxyl group-containing acrylic copolymer 2 was 100 parts by mass and no styrene-based resin was blended. The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 3.

[0102] Comparative Example 5 An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the type of resin added was changed to 0.5 parts by mass of acrylonitrile-styrene-acrylate copolymer resin (Unibright UA-1800, manufactured by Nippon A&L Co., Ltd.). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 3.

[0103] Comparative Example 6 An acrylic copolymer composition was prepared in the same manner as in Example 1, except that the type of resin added was changed to 25 parts by mass of acrylonitrile-styrene-acrylate copolymer resin (Unibright UA-1800, manufactured by Nippon A&L Co., Ltd.). The unvulcanized sheet and the cross-linked acrylic rubber obtained were evaluated as described above, and the evaluation results are shown in Table 3.

[0104] In Tables 2 and 3, A indicates the raw material used in kneading step A, and B indicates the raw material used in kneading step B. The units for the blending are parts by mass.

[0105] [Table 1]

[0106] [Table 2]

[0107] [Table 3]

[0108] As shown in Tables 2 and 3, the acrylic copolymer composition of the present invention showed good Mooney scorch and Vm values ​​that were not significantly different from those of Comparative Examples 1 and 4, which used general rubber formulations. However, the 100% modulus (normal physical property) of the cross-linked acrylic rubber showed a higher value compared to the comparative examples. Furthermore, when polypropylene resin was used instead of the styrene-based resin in Comparative Example 2, the 100% modulus was not sufficiently improved, and the strength (TB) significantly decreased. On the other hand, when polycarbonate resin was used in Comparative Example 3, the 100% modulus significantly decreased. Furthermore, as shown by the results of Comparative Examples 5 and 6, when the styrene-based resin content was too low (0.5 parts by mass), the effect was insufficient, while when the content was too high (25 parts by mass), the Vm of the acrylic copolymer composition and the hardness of the cross-linked sheet significantly increased, making it impossible to punch out tensile test specimens under normal conditions. [Industrial Applicability]

[0109] The acrylic copolymer composition of the present invention can be widely used as a material for rubber products and resin products, taking advantage of its excellent normal physical properties. In particular, crosslinked products produced using the acrylic copolymer of the present invention are extremely useful for automotive applications such as fuel system hoses, air system hoses, and tubing materials.

Claims

1. The adhesive composition contains at least a carboxyl group-containing acrylic rubber and a styrene-based resin, The composition contains 1 to 20 parts by mass of a styrene-based resin relative to 100 parts by mass of the carboxyl group-containing acrylic rubber, The acrylic rubber composition, wherein the styrene-based resin is at least one selected from the group consisting of polystyrene-based resin (PS resin), acrylonitrile-styrene-acrylate copolymer resin (ASA resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), acrylonitrile-styrene copolymer resin (AS resin), methyl methacrylate-butadiene-styrene copolymer resin (MBS resin), acrylonitrile-ethyl acrylate-styrene copolymer resin (AES resin), and rubber-modified polystyrene-based resin (HIPS).

2. The carboxyl group-containing acrylic rubber is (A) 60 to 99.9% by mass of structural units derived from an alkyl acrylate having an alkyl group containing 1 to 8 carbon atoms and / or structural units derived from an alkoxyalkyl (meth)acrylate having an alkoxyalkyl group containing 2 to 8 carbon atoms, (B) 0 to 10% by mass of structural units derived from alkyl methacrylate esters having an alkyl group having 1 to 18 carbon atoms, The acrylic rubber composition according to claim 1, comprising 0.1 to 5% by mass of a structural unit derived from a crosslinkable monomer having a carboxyl group (C).

3. An acrylic rubber composition as described in Claim 2, wherein the (C) constituent unit derived from a crosslinkable monomer having a carboxyl group has a constituent unit derived from an ethylenically unsaturated dicarboxylic acid monoester.

4. The acrylic rubber composition according to any one of claims 1 to 3, which contains a crosslinking agent.

5. A cross-linked acrylic rubber obtained by cross-linking the acrylic rubber composition according to claim 4.

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