Acrylic rubber composition and rubber crosslinked product

Abstract

Provided is an acrylic rubber composition comprising: an acrylic rubber having a glass transition temperature of -29°C or lower; and a carbon black in which "nitrogen adsorption specific surface area / iodine adsorption amount" equals 1.00×103 m2 / g or more, and the nitrogen adsorption specific surface area is 25 m2 / g or more.

Description

Acrylic rubber composition and cross-linked rubber

[0001] The present invention relates to an acrylic rubber composition that is excellent in roll processability and can give a cross-linked rubber product that is excellent in cold resistance and tensile strength, and to the cross-linked rubber product.

[0002] Rubber products with various properties depending on the application have been developed. For example, Patent Document 1 discloses an acrylic rubber composition used for heat-resistant hoses.

[0003] The technology described in Patent Document 1 discloses an acrylic rubber composition for heat-resistant hoses that contains carbon black and has high electrical resistance and high strength. However, there is room for improvement in roll processability and in the cold resistance and tensile strength of the cross-linked rubber obtained from the acrylic rubber composition.

[0004] JP 2016-150525 A

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition that is excellent in roll processability and that can give a cross-linked rubber product that is excellent in cold resistance and tensile strength, and a cross-linked rubber product obtained by cross-linking such a rubber composition.

[0006] As a result of intensive research, the inventors of the present invention have found that the nitrogen adsorption specific surface area / iodine adsorption amount is 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ The present inventors have found that the above object can be achieved by using an acrylic rubber composition containing carbon black having a viscosity of 1 / 2 g or more, and have completed the present invention.

[0007] That is, according to the first aspect of the present invention, an acrylic rubber having a glass transition temperature of −29° C. or lower and a nitrogen adsorption specific surface area / iodine adsorption amount of 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ and carbon having a molecular weight of 1 / 2 g or more.

[0008] According to the second aspect of the present invention, a rubber composition comprising an acrylic rubber and a rubber composition having a nitrogen adsorption specific surface area / iodine adsorption capacity of 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ / g or more of carbon black, and a plasticizer, wherein the content of the plasticizer is 3 parts by weight or more per 100 parts by weight of the rubber component containing the acrylic rubber.

[0009] According to a third aspect of the present invention, there is provided the acrylic rubber composition of the first aspect, further comprising a plasticizer.

[0010] According to a fourth aspect of the present invention, the carbon black has a nitrogen adsorption specific surface area of ​​25 to 60 m ２ / g, and the nitrogen adsorption specific surface area / iodine adsorption amount of the carbon black is 1.10×10 ３ ~1.50 x 10 ３ m ２ / g.

[0011] According to a fifth aspect of the present invention, the carbon black has a DBP absorption of 90 to 180 cm ３ 5. The acrylic rubber composition of any one of Aspects 1 to 4, wherein the acrylic rubber composition has a viscosity of 1000 MPa / 100 g.

[0012] A sixth aspect of the present invention provides the acrylic rubber composition of any one of the first to fifth aspects, wherein, when a nuclear magnetic resonance signal of the carbon black in a spin-spin relaxation process observed by a solid echo method is expressed as the sum of a first signal and a second signal having a larger time constant than the first signal, the amount of hydrogen expressed as a signal intensity per unit mass of the first signal at time 0 is 150 to 250 / g.

[0013] According to a seventh aspect of the present invention, the carbon black has a refractive index of 1340 to 1360 cm when the excitation wavelength is 532 nm. ―１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 260 to 290 cm －１ 7. The acrylic rubber composition according to any one of Aspects 1 to 6, wherein

[0014] According to an eighth aspect of the present invention, the carbon black has a nitrogen adsorption specific surface area of ​​25 to 60 m ２ / g, and the nitrogen adsorption specific surface area / iodine adsorption amount of the carbon black is 1.10×10 ３ ~1.50 x 10 ３ m ２ / g, and the DBP absorption of the carbon black is 90 to 180 cm ３ / 100g, and when a nuclear magnetic resonance signal of the spin-spin relaxation process observed by a solid echo method is expressed as a sum of a first signal and a second signal having a time constant larger than that of the first signal, the amount of hydrogen expressed as a signal intensity per unit mass of the first signal at time 0 is 150 to 250 / g, and when an excitation wavelength is 532 nm, the amount of hydrogen is 1340 to 1360 cm ―１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 260 to 290 cm －１ 3. The acrylic rubber composition according to claim 1, wherein

[0015] According to a ninth aspect of the present invention, there is provided a cross-linked rubber product obtained by cross-linking the acrylic rubber composition according to any one of the first to eighth aspects with an amine compound.

[0016] According to the present invention, it is possible to provide an acrylic rubber composition that is excellent in roll processability and can give a cross-linked rubber product that is excellent in cold resistance and tensile strength, as well as a cross-linked rubber product obtained by cross-linking such an acrylic rubber composition.

[0017] <<First Embodiment>> The acrylic rubber composition according to the first embodiment of the present invention comprises an acrylic rubber having a glass transition temperature of −29° C. or lower and an acrylic rubber having a nitrogen adsorption specific surface area / iodine adsorption amount of 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ / g or more of carbon black.

[0018] <Acrylic Rubber> The acrylic rubber used in the present invention is a rubbery polymer containing (meth)acrylic acid ester monomer units (meaning acrylic acid ester monomers and / or methacrylic acid ester monomers; hereinafter, the same applies to methyl (meth)acrylate, etc.) as the main component in the molecule (preferably accounting for 30% by weight or more of all monomer units constituting the acrylic rubber).

[0019] The (meth)acrylic acid ester monomer forming the (meth)acrylic acid ester monomer unit that is 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.

[0020] The (meth)acrylic acid alkyl ester monomer is not particularly limited, but is preferably an ester of an alkanol having 1 to 12 carbon atoms and (meth)acrylic acid (a (meth)acrylic acid ester having an alkyl group having 1 to 12 carbon atoms), more preferably an ester of an alkanol having 1 to 8 carbon atoms and (meth)acrylic acid (a (meth)acrylic acid ester having an alkyl group having 1 to 8 carbon atoms), and even more preferably an ester of an alkanol having 2 to 6 carbon atoms and (meth)acrylic acid (a (meth)acrylic acid ester having an alkyl group having 2 to 6 carbon atoms).

[0021] Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Among these, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred, and ethyl acrylate and n-butyl acrylate are more preferred. These can be used alone or in combination of two or more.

[0022] The (meth)acrylic acid alkoxyalkyl ester monomer is not particularly limited, but is preferably an ester of an alkoxyalkyl alcohol having 2 to 12 carbon atoms and (meth)acrylic acid (a (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 12 carbon atoms), more preferably an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms and (meth)acrylic acid (a (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 8 carbon atoms), and even more preferably an ester of an alkoxyalkyl alcohol having 2 to 6 carbon atoms and (meth)acrylic acid (a (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 6 carbon atoms).

[0023] Specific examples of the (meth)acrylic acid alkoxyalkyl ester monomer include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 4-methoxybutyl (meth)acrylate. Among these, 2-ethoxyethyl (meth)acrylate and 2-methoxyethyl (meth)acrylate are preferred, and 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate are particularly preferred. These can be used alone or in combination of two or more.

[0024] The content of (meth)acrylic acid ester monomer units in all monomer units constituting the acrylic rubber used in the present invention is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70 to 99.9% by weight, still more preferably 80 to 99.5% by weight, and particularly preferably 90 to 99% by weight. If the content of (meth)acrylic acid ester monomer units is too low, the weather resistance, heat resistance, and oil resistance of the obtained cross-linked rubber may decrease.

[0025] Furthermore, the acrylic rubber used in the present invention preferably contains at least a (meth)acrylic acid alkoxyalkyl ester monomer unit as a (meth)acrylic acid ester monomer unit. By containing the (meth)acrylic acid alkoxyalkyl ester monomer unit, the resulting cross-linked rubber can be made to have excellent cold resistance and engine oil resistance. Furthermore, by containing the (meth)acrylic acid alkoxyalkyl ester monomer unit, the effect of suppressing coloration and odor generation can be further enhanced. The content of the (meth)acrylic acid alkoxyalkyl ester monomer unit in all monomer units constituting the acrylic rubber used in the present invention is preferably 1 to 70 wt%, more preferably 1 to 60 wt%, even more preferably 5 to 60 wt%, and particularly preferably 5 to 50 wt%.

[0026] The acrylic rubber used in the present invention may contain, in addition to the (meth)acrylic acid ester monomer units, crosslinkable monomer units as necessary. The crosslinkable monomer that forms the crosslinkable monomer units is not particularly limited, but examples include monomers having a reactive polar functional group, such as an α,β-ethylenically unsaturated carboxylic acid monomer, a monomer having an epoxy group, and a monomer having a halogen atom; a diene monomer; and the like. From the viewpoint of crosslinkability, the crosslinkable monomer is preferably a monomer having a reactive polar functional group. Among the monomers having a reactive polar functional group, an α,β-ethylenically unsaturated carboxylic acid monomer, a monomer having an epoxy group, or a monomer having a halogen atom is more preferred, an α,β-ethylenically unsaturated carboxylic acid monomer or a monomer having a halogen atom is even more preferred, and an α,β-ethylenically unsaturated carboxylic acid monomer is particularly preferred.

[0027] The α,β-ethylenically unsaturated carboxylic acid monomer is not particularly limited, but examples thereof include α,β-ethylenically unsaturated monocarboxylic acids, α,β-ethylenically unsaturated dicarboxylic acids, and α,β-ethylenically unsaturated dicarboxylic acid monoesters, etc. By using an α,β-ethylenically unsaturated carboxylic acid monomer, the acrylic rubber can be made into a carboxyl group-containing acrylic rubber having carboxyl groups as crosslinking points, and this makes it possible to further improve the compression set resistance when the crosslinked rubber is made.

[0028] The α,β-ethylenically unsaturated monocarboxylic acid is not particularly limited, but is preferably an α,β-ethylenically unsaturated monocarboxylic acid having 3 to 12 carbon atoms, specific examples of which include acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid. The α,β-ethylenically unsaturated dicarboxylic acid is not particularly limited, but is preferably an α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms, specific examples of which include butenedioic acids such as fumaric acid and maleic acid, itaconic acid, citraconic acid, and chloromaleic acid. The α,β-ethylenically unsaturated dicarboxylic acid monoester is not particularly limited, but is preferably a monoester of an α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and an alkanol having 1 to 12 carbon atoms, more preferably a monoester of an α,β-ethylenically unsaturated dicarboxylic acid having 4 to 6 carbon atoms and an alkanol having 2 to 8 carbon atoms, and even more preferably a monoester of butenedioic acid having 4 carbon atoms and an alkanol having 2 to 6 carbon atoms. Specific examples of the α,β-ethylenically unsaturated dicarboxylic acid monoester 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.

[0029] Among these, α,β-ethylenically unsaturated dicarboxylic acid monoesters are preferred, butenedioic acid mono-chain alkyl esters or butenedioic acid monoesters having an alicyclic structure are more preferred, mono-n-butyl fumarate, mono-n-butyl maleate, monocyclohexyl fumarate, and monocyclohexyl maleate are even more preferred, and mono-n-butyl fumarate is particularly preferred. These α,β-ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. Note that, among the above-mentioned monomers, dicarboxylic acids also include those that exist as anhydrides.

[0030] The monomer having an epoxy group is not particularly limited, but examples thereof include epoxy group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate; epoxy group-containing ethers such as allyl glycidyl ether and vinyl glycidyl ether; and the like.

[0031] The monomer having a halogen atom is not particularly limited, and 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. Note that the monomer having a halogen atom preferably contains a chlorine atom as the halogen atom.

[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.

[0033] 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 halomethyl group-containing aromatic vinyl compounds include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, and p-chloromethyl-α-methylstyrene.

[0034] Specific examples of halogen-containing unsaturated amides include N-chloromethyl(meth)acrylamide, etc. Specific examples of haloacetyl group-containing unsaturated monomers include 3-(hydroxychloroacetoxy)propyl allyl ether and p-vinylbenzyl chloroacetic acid ester.

[0035] The diene monomer includes a conjugated diene monomer and a non-conjugated diene monomer. Specific examples of the conjugated diene monomer 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.

[0036] The content of crosslinkable monomer units in all monomer units constituting the acrylic rubber used in the present invention is preferably 0.01% by weight or more, more preferably 0.01 to 20% by weight, even more preferably 0.1 to 10% by weight, still more preferably 0.5 to 5% by weight, and particularly preferably 1 to 3% by weight. By setting the content of crosslinkable monomer units within the above range, it is possible to improve the mechanical properties and heat resistance of the obtained cross-linked rubber product, while more appropriately increasing the compression set resistance.

[0037] Furthermore, the acrylic rubber used in the present invention may contain, in addition to the (meth)acrylic acid ester monomer units and the crosslinkable monomer units used as needed, units of other monomers copolymerizable therewith. Such other copolymerizable monomers are not particularly limited, but include aromatic vinyl monomers, α,β-ethylenically unsaturated nitrile monomers, acrylamide monomers, α,β-ethylenically unsaturated dicarboxylic acid diester monomers, other olefinic monomers, etc.

[0038] Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, and divinylbenzene.

[0039] Examples of the α,β-ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, etc. Examples of the acrylamide monomer include acrylamide, methacrylamide, etc. Examples of the α,β-ethylenically unsaturated dicarboxylic acid diester monomer include dialkyl maleates such as dimethyl maleate and di-n-butyl maleate, wherein the alkyl group has 1 to 18 carbon atoms; dialkyl fumarate esters such as dimethyl fumarate and di-n-butyl fumarate, wherein the alkyl group has 1 to 18 carbon atoms; dicycloalkyl maleates such as dicyclopentyl maleate and dicyclohexyl maleate, wherein the cycloalkyl group has 4 to 16 carbon atoms; dicycloalkyl fumarate esters such as dicyclopentyl fumarate and dicyclohexyl fumarate, wherein the cycloalkyl group has 4 to 16 carbon atoms; dialkyl itaconate esters such as dimethyl itaconate and di-n-butyl itaconate, wherein the alkyl group has 1 to 18 carbon atoms; and dicycloalkyl itaconate esters such as dicyclohexyl itaconate, wherein the cycloalkyl group has 4 to 16 carbon atoms. Other olefinic monomers include ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, ethyl vinyl ether, and butyl vinyl ether.

[0040] Among these copolymerizable other monomers, styrene, acrylonitrile, methacrylonitrile, ethylene and vinyl acetate are preferred, and acrylonitrile, methacrylonitrile and ethylene are more preferred.

[0041] The other copolymerizable monomers can be used alone or in combination of two or more. The content of the units of these other copolymerizable monomers in the monomer units constituting the acrylic rubber used in the present invention is preferably 49.9% by weight or less, more preferably 29.9% by weight or less, even more preferably 15% by weight or less, still more preferably 9% by weight or less, and particularly preferably 4.5% by weight or less.

[0042] In addition, when the acrylic rubber used in the present invention contains units of other copolymerizable monomers, the content thereof may be within the above range, but in particular, when it contains ethylene units, the content of ethylene units in the monomer units constituting the acrylic rubber used in the present invention is preferably 9% by weight or less, more preferably 4.5% by weight or less. Similarly, when the acrylic rubber used in the present invention contains acrylonitrile units or methacrylonitrile units, the total content of acrylonitrile units and methacrylonitrile units is preferably 9% by weight or less, more preferably 4.5% by weight or less.

[0043] 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, it is preferable to use emulsion polymerization under normal pressure, which is a commonly used method for producing conventionally known acrylic rubber.

[0044] Emulsion polymerization may be performed batchwise, semi-batchwise, or continuous. Polymerization is typically carried out at a temperature ranging from 0 to 70°C, preferably from 5 to 50°C. The above-mentioned monomers do not necessarily need to be supplied in their entirety to the reaction site from the beginning of the reaction; they may be added continuously or intermittently throughout the reaction time, or may be introduced all at once or in portions during or after the reaction, taking into account factors such as copolymerization reactivity ratios and reaction conversion rates. The ratios of the monomers added in the polymerization reaction may be adjusted based on the reactivity of each monomer. However, because the polymerization reaction often proceeds nearly quantitatively, the ratios may be determined based on the monomer unit composition of the acrylic rubber to be produced, taking these factors into consideration. After polymerization, solidification and drying are performed to obtain a solid acrylic rubber.

[0045] The glass transition temperature (Tg) of the acrylic rubber used in the present invention is −29° C. or lower, preferably −30° C. or lower, and more preferably −32° C. or lower. There are no particular restrictions on the lower limit of the glass transition temperature of the acrylic rubber, but it is preferably −80° C. or higher, preferably −60° C. or higher, and more preferably −40° C. or higher. By setting the glass transition temperature (Tg) within the above range, the acrylic rubber can have an excellent balance between heat resistance and cold resistance.

[0046] The acrylic rubber used in the present invention may contain a phenolic antioxidant as an antioxidant. The phenolic antioxidant is not particularly limited as long as it is a compound having a phenol structure (i.e., a structure having a benzene ring and an OH group bonded to the benzene ring). Examples of the phenolic antioxidant include doubly hindered phenolic antioxidants, semi-hindered phenolic antioxidants, less hindered phenolic antioxidants, and phenolic antioxidants that do not have a hindered group.

[0047] The pH of the acrylic rubber used in the present invention is not particularly limited, but is preferably 6 or less, more preferably 2 to 6, even more preferably 2.5 to 5.5, and particularly preferably 3 to 5. By setting the pH within the above range, the storage stability of the acrylic rubber composition can be further improved.

[0048] The weight average molecular weight (Mw) of the acrylic rubber contained in the acrylic rubber composition of the present invention is not particularly limited, but from the viewpoint of improving mechanical strength and processability, it is preferably 800,000 or more, more preferably 800,000 to 2,600,000, even more preferably 900,000 to 2,300,000, and particularly preferably 1,000,000 to 2,000,000. The molecular weight distribution of the acrylic rubber is also not particularly limited, but the Mw / Mn value is preferably 1.50 to 10.0, more preferably 1.70 to 8.00, and even more preferably 2.00 to 6.00, and the Mz / Mw value is preferably 1.30 to 3.00, more preferably 1.45 to 2.70, and even more preferably 1.60 to 2.50. The weight average molecular weight and molecular weight distribution of the acrylic rubber can be determined as the absolute molecular weight and absolute molecular weight distribution by, for example, a GPC-MALS method using a GPC (Gel Permeation Chromatography) device incorporating a multi-angle laser light scattering photometer (MALS).

[0049] <Acrylic Rubber Composition> The acrylic rubber composition of the present invention comprises a rubber component containing the above-described acrylic rubber and a rubber component having a nitrogen adsorption specific surface area / iodine adsorption capacity of 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ / g or more of carbon black.

[0050] The proportion of the acrylic rubber component in the rubber component of the acrylic rubber composition may be selected appropriately depending on the intended use, but is preferably 30% by weight or more, more preferably 50% by weight or more, even more preferably 70% by weight or more, and particularly preferably 100% by weight (i.e., an embodiment in which the rubber component is composed essentially of the acrylic rubber component).

[0051] The rubber other than the acrylic rubber used in the present invention that constitutes the rubber component is not particularly limited, but examples include acrylic rubber other than the acrylic rubber used in the present invention, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin-based elastomers, styrene-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, and polysiloxane-based elastomers.

[0052] The rubber other than the acrylic rubber may be used alone or in combination of two or more. The shape of the acrylic rubber used in the present invention and the shape of the rubber other than the acrylic rubber used in the present invention are not particularly limited, but may be any of a veil shape, a sheet shape, a powder shape, etc.

[0053] The nitrogen adsorption specific surface area / iodine adsorption amount of the carbon black used in the present invention is 1.00×10 ３ m ２ / g or more, preferably 1.10 × 10 ３ m ２ / g or more, more preferably 1.20 × 10 ３ m ２ / g or more, and particularly preferably 1.30 × 10 ３ m ２ The upper limit of the nitrogen adsorption specific surface area / iodine adsorption amount of carbon black is not particularly limited, but is preferably 1.50×10 ３ m ２ / g or less, more preferably 1.40 × 10 ３ m ２ / g or less. The nitrogen adsorption specific surface area / iodine adsorption amount represents the surface activity of the carbon black. By setting the nitrogen adsorption specific surface area / iodine adsorption amount of the carbon black within the above range, the acrylic rubber composition can be made to have excellent roll processability, and the obtained cross-linked rubber product can be made to have excellent tensile strength.

[0054] The nitrogen adsorption specific surface area of ​​carbon black is 25 m ２ / g or more, preferably 35m ２ / g or more, more preferably 45m ２ The upper limit of the nitrogen adsorption specific surface area of ​​carbon black is not particularly limited, but is preferably 60 m ２ / g or less, more preferably 55m ２ The nitrogen adsorption specific surface area of ​​carbon black can be measured in accordance with JIS K6217-7:2013.

[0055] The iodine adsorption capacity of carbon black is preferably 60 mg / g or less, more preferably 50 mg / g or less. The lower limit of the iodine adsorption capacity of carbon black is not particularly limited, but is preferably 17 mg / g or more, more preferably 30 mg / g or more. The iodine adsorption capacity of carbon black can be measured in accordance with JIS K6217-1997.

[0056] The DBP absorption of carbon black is preferably 90 to 180 cm ３ / 100g, more preferably 115 to 135cm ３ / 100g. The DBP absorption represents the structure (degree of aggregation) of carbon black, and can be measured in accordance with JIS K 6217-1997. When the DBP absorption is within the above range, the acrylic rubber composition can be made to have excellent roll processability, and the obtained cross-linked rubber product can be made to have excellent tensile strength.

[0057] The carbon black preferably has a hydrogen content of 150 to 250 / g as determined by nuclear magnetic resonance (NMR) spectroscopy. When the hydrogen content of the carbon black is within the above range, the dispersibility of the carbon black is improved, and the resulting cross-linked rubber product can have excellent tensile strength.

[0058] The hydrogen content of carbon black can be determined by the following method. First, a Bruker Biospin Minispec mq20 pulsed magnetic resonance spectrometer is used. After drying carbon black at 110°C for 30 minutes, 0.2 g of the carbon black is filled into a glass sample tube. The measurement sample is measured using the spin-spin relaxation time (transverse relaxation time) T2 under the following measurement conditions to obtain a T2 relaxation curve (free induction decay curve). <Measurement conditions> Measurement nuclide: 1H, pulse mode: solid echo method (90°x-γ-90°y), 90°, pulse width: 2.7 μs, measurement time: 2 ms, waiting time: 500 ms, number of integrations: 52, measurement temperature: 40°C, Gain: 90. Note that since the mass of carbon black is constant at 0.2 g and the instrument function is also constant (Gain = 90), the signal intensity of the resulting T2 relaxation curve (free induction decay curve) increases or decreases in proportion to the 1H concentration of the object being measured.

[0059] Next, the obtained autoinduction decay curve is fitted by the linear least squares method using fitting software (TD-NMR-A for Windows 7) attached to the pulsed nuclear magnetic resonance spectrometer to obtain an approximate curve represented by the following equation f(t): f(t) = A(1) exp(-t / T2(1)) + A(2) exp(-t / T2(2)) where T2(1) is the relaxation time of the component with a short relaxation time, T2(2) is the relaxation time of the component with a long relaxation time, A(1) is the signal intensity of the component with a short relaxation time at t=0, and A(2) is the signal intensity of the component with a long relaxation time at t=0.

[0060] Finally, the amount of hydrogen in the carbon black can be obtained by dividing the signal intensity A(1) by the mass (g) of the measurement sample.

[0061] Due to the difference in the time constant, the signal intensity A(1) can be identified as hydrogen atoms on the surface of the carbon black, and the signal intensity A(2) can be identified as moisture or liquid polycyclic aromatic hydrocarbon compounds adsorbed on the surface of the carbon black. The signal intensity A(1) corresponds to the "first signal" in this invention, and the signal intensity A(2) corresponds to the "second signal" in this invention.

[0062] The carbon black used as a reference in measuring the hydrogen content is SEAT 9 (trade name) manufactured by Tokai Carbon Co., Ltd., which has a hydrogen content of 114 / g. The hydrogen content of the carbon black used in the present invention is determined by adjusting the measurement conditions that affect the signal intensity so that the hydrogen content of SEAT 9 is 114 / g.

[0063] Carbon black has a Raman spectrum of 1340 to 1360 cm when measured at an excitation wavelength of 532 nm using a laser Raman spectrometer. －１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 260 to 290 cm ―１ It is preferable that the above range is satisfied. ΔD represents the degree of disorder in the crystalline structure on the surface of the carbon black, i.e., crystallinity. When ΔD is within the above range, the carbon black has high dispersibility, the acrylic rubber composition can have excellent roll processability, and the obtained cross-linked rubber product can have excellent tensile strength.

[0064] ΔD can be measured by the following method. First, carbon black is measured by laser Raman spectroscopy at an excitation wavelength of 532 nm to obtain a Raman spectrum. In the obtained Raman spectrum, ―１ The measurement wavelength at the peak top position in the range of Dmax (cm ―１ ), and the detection position on the low wavelength side where the detection intensity is half the peak intensity at Dmax is defined as D50 (cm ―１ ) ΔD can be calculated by the following formula (1): ΔD = (Dmax - D50) x 2 (1)

[0065] The carbon black used as the standard in the Raman spectroscopy measurement is Seast G-SO (trade name) manufactured by Tokai Carbon Co., Ltd., and its ΔD value is 249 cm ―１ The ΔD of the carbon black used in the present invention is 249 cm ―１ The measurement conditions that affect ΔD are adjusted so that the value is as follows:

[0066] The content of carbon black in the acrylic rubber composition is not particularly limited, but is preferably 5 to 100 parts by weight, more preferably 10 to 70 parts by weight, and even more preferably 50 to 70 parts by weight, per 100 parts by weight of the rubber component containing the acrylic rubber.

[0067] The acrylic rubber composition of the present invention contains carbon black having the above-mentioned properties. Acrylic rubber compositions containing an acrylic rubber having a glass transition temperature of -29°C or lower and carbon black normally used in acrylic rubber tend to have poor roll processability. On the other hand, in the present invention, by using the above-mentioned carbon black, even when combined with an acrylic rubber having a glass transition temperature of -29°C or lower, the acrylic rubber composition can be made to have excellent roll processability, and the resulting cross-linked rubber can have excellent tensile strength.

[0068] The acrylic rubber composition of the present invention may contain, in addition to the carbon black, other reinforcing fillers and non-reinforcing fillers.

[0069] Examples of reinforcing fillers include carbon blacks such as furnace black, acetylene black, thermal black, channel black, and graphite; and silicas such as wet silica, dry silica, and colloidal silica. Examples of non-reinforcing fillers include quartz powder, clays such as diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate, and barium sulfate. The carbon black used as a reinforcing filler differs from the carbon black used in the present invention in that it does not satisfy the above-mentioned requirements for the nitrogen adsorption specific surface area / iodine adsorption amount, the nitrogen adsorption specific surface area, the iodine adsorption amount, the DBP absorption amount, the hydrogen amount determined by NMR, and the full width at half maximum ΔD of the Raman scattering peak.

[0070] The carbon black and other fillers may be used singly or in combination of two or more. The content of the carbon black and other fillers in the acrylic rubber composition of the present invention is not particularly limited, but is preferably 1 to 200 parts by weight, more preferably 10 to 150 parts by weight, and still more preferably 20 to 100 parts by weight, per 100 parts by weight of the rubber component of the acrylic rubber composition.

[0071] The Mooney viscosity (ML1+4, 100°C) of the acrylic rubber composition of the present invention is preferably 10 to 80, more preferably 20 to 70, and even more preferably 30 to 60. By setting the Mooney viscosity of the acrylic rubber composition within the above range, it is possible to achieve a high level of balance between the roll processability and strength properties of the acrylic rubber composition.

[0072] The acrylic rubber composition of the present invention preferably further contains a plasticizer. The plasticizer may be any plasticizer commonly used for rubber, and is not particularly limited. However, an ester compound of a dicarboxylic acid and an ether bond-containing alcohol is preferred. Examples of such plasticizers include adipic acid ether ester-based plasticizers.

[0073] The content of the plasticizer in the acrylic rubber composition is preferably 0 to 40 parts by weight, more preferably 1 to 30 parts by weight, and even more preferably 3 to 20 parts by weight, relative to 100 parts by weight of the rubber component containing the acrylic rubber. By setting the content of the plasticizer in the acrylic rubber composition within the above range, the obtained cross-linked rubber product can be made to have excellent cold resistance.

[0074] The acrylic rubber composition of the present invention preferably further contains a crosslinking agent. The crosslinking agent is not particularly limited, but may be, for example, a conventionally known crosslinking agent such as a polyamine compound such as a diamine compound and its carbonate; sulfur; a sulfur donor; a triazine thiol compound; a polyepoxy compound; an organic carboxylic acid ammonium salt; an organic peroxide; a dithiocarbamic acid metal salt; a polycarboxylic acid; a quaternary onium salt; an imidazole compound; or an isocyanuric acid compound. These crosslinking agents may be used alone or in combination of two or more. Among these, it is preferable to use a polyamine compound and its carbonate.

[0075] The content of the crosslinking agent in the acrylic rubber composition is preferably 0 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, and even more preferably 0.2 to 1 part by weight, relative to 100 parts by weight of the rubber component containing the acrylic rubber. By setting the content of the crosslinking agent within the above range, the obtained crosslinked rubber product can be made to have superior tensile strength.

[0076] The polyamine compound and carbonate thereof are not particularly limited, but polyamine compounds having 4 to 30 carbon atoms and carbonates thereof are preferred. Examples of such polyamine compounds and carbonates thereof include aliphatic polyamine compounds and carbonates thereof, and aromatic polyamine compounds.

[0077] 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.

[0078] The aromatic polyvalent amine 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. Of these, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane is preferred.

[0079] The acrylic rubber composition of the present invention preferably further contains a crosslinking accelerator. The crosslinking accelerator is not particularly limited. However, when the acrylic rubber has a carboxyl group as a crosslinkable group and the crosslinking agent is a polyvalent amine compound or its carbonate, a guanidine compound, a diazabicycloalkene compound, an imidazole compound, a quaternary onium salt, a tertiary phosphine compound, an aliphatic monovalent secondary amine compound, or an aliphatic monovalent tertiary amine compound can be used. Among these, a guanidine compound, a diazabicycloalkene compound, or an aliphatic monovalent secondary amine compound is preferred, with a guanidine compound and a diazabicycloalkene compound being particularly preferred. These basic crosslinking accelerators can be used alone or in combination of two or more.

[0080] Specific examples of guanidine compounds include 1,3-di-o-tolylguanidine and 1,3-diphenylguanidine. Specific examples of diazabicycloalkene compounds include 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene. Specific examples of imidazole compounds include 2-methylimidazole and 2-phenylimidazole. Specific examples of quaternary onium salts include tetra-n-butylammonium bromide and octadecyltri-n-butylammonium bromide. Specific examples of tertiary phosphine compounds include triphenylphosphine and tri-p-tolylphosphine.

[0081] The aliphatic monovalent secondary amine compound is a compound in which two hydrogen atoms of ammonia are substituted with an aliphatic hydrocarbon group. The aliphatic hydrocarbon group substituting the hydrogen atom preferably has 1 to 30 carbon atoms. Specific examples of the aliphatic monovalent secondary amine compound include dimethylamine, diethylamine, dipropylamine, diallylamine, diisopropylamine, di-n-butylamine, di-t-butylamine, di-sec-butylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dicetylamine, di-2-ethylhexylamine, and dioctadecylamine.

[0082] The aliphatic monovalent tertiary amine compound is a compound in which all three hydrogen atoms of ammonia have been substituted with aliphatic hydrocarbon groups. The aliphatic hydrocarbon group substituting the hydrogen atoms preferably has 1 to 30 carbon atoms. Specific examples of the aliphatic monovalent tertiary amine compound include trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, and tridodecylamine.

[0083] The content of the crosslinking accelerator in the acrylic rubber composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7.5 parts by weight, and particularly preferably 1 to 5 parts by weight, relative to 100 parts by weight of the rubber component containing the acrylic rubber. By setting the content of the crosslinking accelerator within the above range, the tensile strength and compression set resistance of the obtained crosslinked rubber product can be further improved.

[0084] The acrylic rubber composition of the present invention may contain an antioxidant as needed. The antioxidant is not particularly limited, but examples thereof include the above-mentioned phenol-based antioxidants; phosphite ester-based antioxidants such as tris(nonylphenyl)phosphite, diphenylisodecylphosphite, and tetraphenyldipropylene glycol diphosphite; sulfur ester-based antioxidants such as dilauryl thiodipropionate; phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonylamido)-diphenylamine, 4,4'-bis(α,α-dimethylamine); amine-based antioxidants such as N,N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, and butyraldehyde-aniline condensates; imidazole-based antioxidants such as 2-mercaptobenzimidazole; quinoline-based antioxidants such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; and hydroquinone-based antioxidants such as 2,5-di-(t-amyl)hydroquinone.

[0085] The antioxidant may be used alone or in combination of two or more. The content of the antioxidant in the rubber composition of the present invention is not particularly limited, but is preferably 0.01 to 15 parts by weight, more preferably 0.05 to 10 parts by weight, and even more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the rubber component containing the copolymer rubber of the present invention.

[0086] In addition to the above-mentioned components, the acrylic rubber composition of the present invention can also contain compounding agents commonly used in the field of rubber processing. Examples of such compounding agents include light stabilizers, scorch inhibitors, processing aids, adhesives, slip agents, lubricants, flame retardants, mildew inhibitors, antistatic agents, colorants, crosslinking retarders, etc. The amounts of these compounding agents to be added are not particularly limited as long as they do not impair the purpose and effects of the present invention, and can be appropriately added in amounts depending on the purpose of addition.

[0087] The acrylic rubber composition of the present invention is prepared by blending a rubber component containing an acrylic rubber with a crosslinking agent and various other compounding ingredients used as needed, mixing and kneading the mixture using an open roll, a Banbury mixer, various kneaders, or the like, and then further kneading the mixture using a kneading roll.

[0088] The order of mixing the components is not particularly limited, but it is preferable to thoroughly mix the components that are resistant to reaction or decomposition by heat, and then mix the crosslinking agent and other components that are resistant to reaction or decomposition by heat for a short period of time at a temperature at which they will not react or decompose.

[0089] <Rubber Cross-Linked Product> The rubber cross-linked product of the present invention is obtained by cross-linking the above-described acrylic rubber composition of the present invention.

[0090] The cross-linked rubber product of the present invention can be produced by using the acrylic rubber composition of the present invention and molding it into a desired shape using a molding machine, such as an extruder, injection molding machine, compressor, or roll, followed by heating to cause a cross-linking reaction and fix the shape as a cross-linked rubber product. In this case, cross-linking may be carried out after molding in advance or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 25 to 120°C. The cross-linking temperature is usually 130 to 220°C, preferably 150 to 190°C, and the cross-linking time is usually 2 minutes to 10 hours, preferably 3 minutes to 5 hours. The heating method may be appropriately selected from methods commonly used for cross-linking rubber, such as press heating, steam heating, oven heating, and hot air heating.

[0091] Depending on the shape, size, etc. of the cross-linked rubber product, the cross-linked rubber product of the present invention may be further heated to carry out secondary cross-linking. The secondary cross-linking time varies depending on the heating method, cross-linking temperature, shape, etc., but is preferably carried out for 1 to 48 hours. The heating method and heating temperature may be selected appropriately.

[0092] The cross-linked rubber product of the present invention thus obtained is suitably used as sealing materials such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing sheaths, mechanical seals, wellhead seals, seals for electric and electronic devices, and seals for air compressors; various gaskets such as a cylinder head gasket attached to the connecting portion between a cylinder block and a cylinder head, a rocker cover gasket attached to the connecting portion between a rocker cover and a cylinder head, an oil pan gasket attached to the connecting portion between an oil pan and a cylinder head or a transmission case, a fuel cell separator gasket attached between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate, and a negative electrode, and a top cover gasket for a hard disk drive; cushioning materials, vibration-proofing materials; wire coating materials; industrial belts; tubes and hoses; sheets; and the like.

[0093] The cross-linked rubber product of the present invention can also be suitably used as an extrusion molded product and a cross-linked product for automobile applications, for example, various hoses such as fuel oil hoses for fuel tanks, such as fuel hoses, filler neck hoses, vent hoses, vapor hoses and oil hoses, air hoses, such as turbo air hoses and mission control hoses, radiator hoses, heater hoses, brake hoses and air conditioner hoses.

[0094] Second Embodiment Next, an acrylic rubber composition according to a second embodiment of the present invention will be described.

[0095] The acrylic rubber composition in the second embodiment is a rubber composition comprising an acrylic rubber and an acrylic rubber having a nitrogen adsorption specific surface area / iodine adsorption amount of 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ / g or more of carbon black and a plasticizer, and the content of the plasticizer is 3 parts by weight or more per 100 parts by weight of the rubber component containing the acrylic rubber.

[0096] Examples of monomer units constituting the acrylic rubber used in the second embodiment include the same monomer units constituting the acrylic rubber in the first embodiment. The acrylic rubber used in the second embodiment can be obtained by polymerizing the monomers used in the acrylic rubber in the first embodiment by emulsion polymerization or the like.

[0097] The glass transition temperature of the acrylic rubber used in the second embodiment is not particularly limited, but is preferably −10° C. to −40° C. By setting the glass transition temperature (Tg) within the above range, the acrylic rubber can have an excellent balance of heat resistance and cold resistance.

[0098] The acrylic rubber composition in the second embodiment has a nitrogen adsorption specific surface area / iodine adsorption amount of 1.00×10 as in the first embodiment. ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ / g or more. Acrylic rubber compositions containing acrylic rubber, carbon black normally used in acrylic rubber, and 3 parts by weight or more of a plasticizer per 100 parts by weight of the rubber component tend to have poor roll processability. On the other hand, in the present invention, by using the above-mentioned carbon black, an acrylic rubber composition containing 3 parts by weight or more of a plasticizer can be made to have excellent roll processability, and the resulting cross-linked rubber product can have excellent tensile strength.

[0099] As with the carbon black used in the first embodiment, the carbon black used in the second embodiment preferably has a nitrogen adsorption specific surface area / iodine adsorption amount, a nitrogen adsorption specific surface area, an iodine adsorption amount, a DBP absorption amount, a hydrogen amount determined by NMR, and a full width at half maximum ΔD of a Raman scattering peak, each of which falls within a predetermined range.

[0100] That is, the nitrogen adsorption specific surface area / iodine adsorption amount of carbon black is 1.10×10 ３~1.50 x 10 ３ m ２ / g, and the nitrogen adsorption specific surface area is preferably 25 to 60 m ２ The iodine adsorption is preferably 17 to 60 mg / g. The DBP absorption of carbon black is preferably 90 to 180 cm ３ The hydrogen content determined by NMR is preferably 150 to 250 / g. In addition, the Raman spectrum obtained when measured using a laser Raman spectrometer at an excitation wavelength of 532 nm has a peak at 1340 to 1360 cm ―１ The full width at half maximum ΔD of the Raman scattering peak that appears in the range of 260 to 290 cm ―１ It is preferable that:

[0101] The content of carbon black in the acrylic rubber composition is preferably 5 to 100 parts by weight, more preferably 10 to 70 parts by weight, and even more preferably 50 to 70 parts by weight.

[0102] The content of the plasticizer in the acrylic rubber composition in the second embodiment is 3 parts by weight or more, preferably 5 parts by weight or more, and more preferably 7 parts by weight or more, relative to 100 parts by weight of the rubber component containing the acrylic rubber. The upper limit of the content of the plasticizer in the acrylic rubber composition is not particularly limited, but is preferably 30 parts by weight or less, and more preferably 20 parts by weight or less. By setting the content of the plasticizer in the acrylic rubber composition within the above range, the obtained cross-linked rubber product can be made to have excellent cold resistance.

[0103] The plasticizer used in the second embodiment may be the same as the plasticizer used in the first embodiment.

[0104] The acrylic rubber composition in the second embodiment may contain, in addition to the above components, the crosslinking agent, crosslinking accelerator, antioxidant, and other commonly used compounding agents described in the first embodiment. The acrylic rubber composition in the second embodiment is prepared by compounding a rubber component containing an acrylic rubber with a crosslinking agent and various other compounding agents used as needed, mixing and kneading the mixture using an open roll, a Banbury mixer, various kneaders, or the like, and then further kneading the mixture using a kneading roll.

[0105] The cross-linked rubber product in the second embodiment can be obtained by the same method as the method described in the first embodiment, using the above acrylic rubber composition.

[0106] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In addition, the "parts" below are based on weight unless otherwise specified. Various physical properties were measured as follows.

[0107] <Glass Transition Temperature> The glass transition temperature of the acrylic rubber was measured using a differential scanning calorimetry (DSC).

[0108] <Rolling processability> Using a kneader (8-inch roll), the acrylic rubber composition was wound around a roll at a temperature of 50°C, and the rolling processability was judged from the workability. ◯: Rolling work possible without problems △: Rolling work possible, although there was strong adhesion to the roll ×: There was very strong adhesion to the roll, and rolling work was difficult

[0109] <Normal state physical properties (tensile strength)> The rubber composition was placed in a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and press-molded at 170°C for 20 minutes while applying a pressure of 10 MPa to obtain a sheet-like cross-linked rubber product. The obtained cross-linked rubber product was then transferred to a gear oven and subjected to secondary cross-linking at 170°C for 4 hours, and the obtained cross-linked rubber product in sheet form was punched out with a JIS No. 3 dumbbell to prepare a test specimen. Then, using the obtained test specimen, the tensile strength of the cross-linked rubber product was measured in accordance with JIS K6251:2017.

[0110] <Cold Resistance Test> The acrylic rubber composition was placed in a mold measuring 15 cm in length, 15 cm in width, and 0.2 cm in depth, and press-molded at 170°C for 20 minutes while applying pressure to form a sheet-like cross-linked product. Secondary cross-linking was then carried out at 170°C for 4 hours to obtain a sheet-like cross-linked rubber product. Using the obtained sheet-like cross-linked product, the cold resistance of the cross-linked rubber product was measured by a TR test (low-temperature elastic recovery test) in accordance with JIS K6261-4:2017. Specifically, an elongated test specimen was frozen, and the temperature was continuously increased to measure the recovery of the elongated test specimen, and the temperature TR10 at which the length of the test specimen contracted (recovered) by 10% due to the temperature increase was measured. It can be determined that the lower the temperature TR10, the better the cold resistance.

[0111] Example 1 Preparation of Acrylic Rubber Composition Using a kneader, 100 parts of carboxylic acid-based acrylic rubber (trade name "NipolAR14", manufactured by Zeon Corporation) was mixed with 60 parts of MAF (Medium Abrasion Furnace) carbon (carbon black), 5 parts of a polyether ester-based plasticizer (trade name "Adekacizer RS-735", manufactured by ADEKA Corporation), 2 parts of stearic acid, 0.5 parts of a crosslinking agent (trade name "VC-1", manufactured by Chemours Corporation), and a crosslinking aid (trade name "RHENOGRAN"). XLA-60 (GE2014) manufactured by RheinChemie, and 2 parts of DBU 60% (including the portion that is zinc dialkyl diphosphate salt) were blended and kneaded with a roll to obtain an acrylic rubber composition. Using the obtained acrylic rubber composition, roll processability was measured, and the tensile strength and cold resistance of the cross-linked rubber were measured. The results are shown in Table 1. The carbon black used was a rubber having a nitrogen adsorption specific surface area / iodine adsorption of 1.33 x 10 ３ m ２ / g, and the nitrogen adsorption specific surface area is 53 m ２ / g, iodine adsorption capacity is 40 mg / g, DBP absorption capacity is 120 cm ３ / 100g, the amount of hydrogen measured by the above method is 150 to 250 / g, and the full width at half maximum ΔD of the Raman scattering peak measured by the above method is 260 to 290 cm ―１ The following was used.

[0112] Example 2 An acrylic rubber composition was obtained in the same manner as in Example 1, and evaluations were similarly performed, except that 100 parts of a chlorine-based acrylic rubber (trade name "NipolAR74X", manufactured by Zeon Corporation) was used instead of 100 parts of the carboxylic acid-based acrylic rubber, and 0.3 parts of sulfur, 3 parts of a crosslinking aid (trade name "NonSal SN-1", manufactured by NOF Corporation) and 0.5 parts of a crosslinking aid (trade name "NonSal SK-1", manufactured by NOF Corporation) were used instead of 0.5 parts of the crosslinking agent (VC-1) and 2 parts of the crosslinking aid (XLA-60). The results are shown in Table 1.

[0113] Example 3 An acrylic rubber composition was obtained in the same manner as in Example 1, except that 100 parts of a carboxylic acid-based acrylic rubber (trade name "NipolAR12", manufactured by Zeon Corporation) was used instead of 100 parts of the carboxylic acid-based acrylic rubber (NipolAR14), and the amount of carbon black used was 65 parts, and evaluation was performed in the same manner. The results are shown in Table 1.

[0114] Example 4 An acrylic rubber composition was obtained in the same manner as in Example 2, except that 100 parts of a chlorine-based acrylic rubber (trade name "NipolAR71", manufactured by Zeon Corporation) was used instead of 100 parts of the chlorine-based acrylic rubber (NipolAR12), and the amount of plasticizer used was 15 parts, and evaluation was performed in the same manner. The results are shown in Table 1.

[0115] Example 5 An acrylic rubber composition was obtained in the same manner as in Example 2, and evaluations were carried out in the same manner, except that 100 parts of an epoxy-based acrylic rubber (trade name "NipolAR42W", manufactured by Zeon Corporation) was used instead of 100 parts of the chlorine-based acrylic rubber, the amount of carbon black used was 65 parts, and the amount of plasticizer used was 10 parts. The results are shown in Table 1.

[0116] Example 6 Except for not using a plasticizer, an acrylic rubber composition was obtained in the same manner as in Example 1, and evaluations were carried out in the same manner. The results are shown in Table 1.

[0117] Comparative Examples 1-2 and 5 Acrylic rubber compositions were obtained in the same manner as in Example 1, except that the types and amounts of the acrylic rubber and compounding ingredients were changed as shown in Table 1, and were evaluated in the same manner.

[0118] Comparative Example 3 An acrylic rubber composition was obtained and evaluated in the same manner as in Example 1, except that 60 parts of carbon black (product name "N330", manufactured by Cabot Japan Co., Ltd.) was used instead of 60 parts of the carbon black used in Example 1. The results are shown in Table 1.

[0119] Comparative Example 4 An acrylic rubber composition was obtained and evaluated in the same manner as in Example 1, except that 60 parts of carbon black (product name "N550", manufactured by Cabot Japan Co., Ltd.) was used instead of 60 parts of the carbon black used in Example 1. The results are shown in Table 1.

[0120]

[0121] From Table 1, acrylic rubbers with glass transition temperatures of −29°C or lower and acrylic rubbers with nitrogen adsorption specific surface area / iodine adsorption of 1.00×10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ The acrylic rubber composition containing carbon black having a nitrogen adsorption specific surface area / iodine adsorption amount of 1.00×10 and 1.00×10 / g or more was excellent in roll processability and was able to give a cross-linked rubber product having excellent cold resistance and tensile strength (Examples 1-2 and 6). ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ / g or more of carbon black and 3 parts by weight or more of a plasticizer per 100 parts by weight of the rubber component were excellent in roll processability, and were able to give cross-linked rubber products excellent in cold resistance and tensile strength (Examples 3-5).

[0122] On the other hand, acrylic rubber and a nitrogen adsorption specific surface area / iodine adsorption amount of 1.00 × 10 ３ m ２ / g or more, and the nitrogen adsorption specific surface area is 25 m ２ Even in the case of an acrylic rubber composition containing carbon black having a carbon black content of 1 / g or more, when the content of the plasticizer was less than 3 parts by weight, the cold resistance of the obtained cross-linked rubber product was poor (Comparative Examples 1-2 and 5).

[0123] In addition, the nitrogen adsorption specific surface area / iodine adsorption amount was 1.00×10３ m ２ The acrylic rubber composition using carbon black with a viscosity of less than 1 / g was inferior in roll processability (Comparative Examples 3-4), and the tensile strength of the cross-linked rubber product was inferior (Comparative Example 4).

Claims

1. Acrylic rubber with a glass transition temperature of -29°C or lower, Nitrogen adsorption specific surface area / Iodine adsorption amount is 1.00 × 10 ３ I understand ２ The nitrogen adsorption specific surface area is 25 m² or more, and the nitrogen adsorption specific surface area is 25 m². ２ An acrylic rubber composition containing carbon black in a quantity of 1g or more.

2. Acrylic rubber and Nitrogen adsorption specific surface area / Iodine adsorption amount is 1.00 × 10 ３ I understand ２ The nitrogen adsorption specific surface area is 25 m² or more, and the nitrogen adsorption specific surface area is 25 m². ２ Carbon black that is 1g or more, It contains a plasticizer, An acrylic rubber composition in which the plasticizer content is 3 parts by weight or more per 100 parts by weight of the rubber component containing the acrylic rubber.

3. The acrylic rubber composition according to claim 1, further containing a plasticizer.

4. The nitrogen adsorption specific surface area of ​​the carbon black is 25 to 60 m². ２ / g, The nitrogen adsorption specific surface area / iodine adsorption amount of the carbon black is 1.10×10 ３ ~1.50×10 ３ m ２ / g, and the acrylic rubber composition according to claim 1 or 2.

5. The DBP absorption capacity of the aforementioned carbon black is 90-180 cm³. ３ The acrylic rubber composition according to claim 1 or 2, wherein the amount is / 100g.

6. The acrylic rubber composition according to claim 1 or 2, wherein, in the carbon black, when the nuclear magnetic resonance signal of the spin-spin relaxation process observed by the solid echo method is expressed as the sum of a first signal and a second signal having a larger time constant than the first signal, the amount of hydrogen expressed as the signal intensity per unit mass of the first signal at time 0 is 150 to 250 / g.

7. In the carbon black described above, when the excitation wavelength is 532 nm, the range is 1340 to 1360 cm⁻¹. ―１ The full width at half maximum (FMAX) ΔD of the Raman scattering peak appearing in this range is 260–290 cm. －１ The acrylic rubber composition according to claim 1 or 2.

8. The nitrogen adsorption specific surface area of ​​the carbon black is 25 to 60 m². ２ / g, The ratio of the nitrogen adsorption specific surface area of ​​the carbon black to the iodine adsorption amount is 1.10 × 10 ３ ~1.50 x 10 ３ I understand ２ / g, The DBP absorption capacity of the aforementioned carbon black is 90-180 cm³. ３ / 100g, In the carbon black, when the nuclear magnetic resonance signal of the spin-spin relaxation process observed by the solid echo method is expressed as the sum of a first signal and a second signal having a larger time constant than the first signal, the amount of hydrogen expressed by the signal intensity per unit mass of the first signal at time 0 is 150 to 250 / g. In the carbon black described above, when the excitation wavelength is 532 nm, the range is 1340 to 1360 cm⁻¹. ―１ The full width at half maximum (FMAX) ΔD of the Raman scattering peak appearing in this range is 260–290 cm. －１ The acrylic rubber composition according to claim 1 or 2.

9. A rubber crosslinked product obtained by crosslinking the acrylic rubber composition according to claim 1 or 2 with an amine compound.