JPWO2019003342A1 - Acrylic rubber and its rubber cross-linked product - Google Patents

Abstract

An object of the present invention is to provide an acrylic rubber which is excellent in roll processability and can give a crosslinked product having excellent heat resistance and acid resistance. Another object of the present invention is to provide a crosslinkable acrylic rubber composition obtained by adding a crosslinking agent to such acrylic rubber, and an acrylic rubber crosslinked product obtained by crosslinking the crosslinkable acrylic rubber composition. . (A) a structural unit derived from a (meth) acrylic acid ester having an alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group having 2 to 8 carbon atoms with respect to 100% by mass of all structural units, 5 to 98 The acrylic rubber which contains in the range of 9 mass%, and contains the structural unit (B) derived from ethylenically unsaturated dicarboxylic acid diester in the range of 1 to 30 mass% with respect to 100 mass% of all the structural units.

Description

  The present invention relates to an acrylic rubber, and more particularly to an acrylic rubber which is excellent in processability such as roll processability and can give a crosslinked product excellent in heat resistance and acid resistance.

  Generally, acrylic rubber is a rubber containing acrylic acid ester as a main component and is known as a material excellent in various physical properties related to durability. For example, industrial rubber such as engine gasket, oil hose, air hose, O-ring, and automobile and automobile. Widely used as a rubber.

  However, it is known that the raw material of acrylic rubber has a large adhesive force, so that it easily adheres to a roll during kneading and has poor roll processability. In addition, with the recent improvement in the performance of automobiles, excellent durability such as excellent heat resistance and acid resistance has been required.

  As a measure for increasing heat resistance and acid resistance, a crosslinking monomer having an active crosslinking point is usually copolymerized in an amount of about 1 to 5% by mass. As the crosslinkable monomer, chlorine-based monomers such as 2-chloroethyl vinyl ether and vinyl chloroacetate, and epoxy-based monomers such as allyl glycidyl ether and glycidyl methacrylate are generally used.

  Further, as the crosslinkable monomer, those other than the above have been studied, and for example, in Patent Document 1, a double bond is generated by dehydrofluorination reaction of a (meth) acrylate monomer having a difluoromethylene group to crosslink. Is proposed. Further, Patent Document 2 discloses an acrylic rubber using a butenedioic acid monoester having an alicyclic structure such as monocyclohexyl fumarate.

  However, rubber parts used in fields related to automobiles are required to have further heat resistance and acid resistance, and higher quality acrylic rubber has been desired.

JP, 10-139828, A JP-A-2004-18567

  In view of the problems of the above-mentioned conventional techniques, it is an object of the present invention to provide an acrylic rubber which is excellent in roll processability and can give a crosslinked product having excellent heat resistance and acid resistance. Further, it is an object of the present invention to provide a crosslinkable acrylic rubber composition obtained by adding an internal crosslinking agent to such an acrylic rubber, and an acrylic rubber crosslinked product obtained by crosslinking the crosslinkable acrylic rubber composition. To do.

As a result of various investigations by the present inventors,
Acrylic containing (A) a structural unit derived from a (meth) acrylic acid ester having an alkyl group or an alkoxyalkyl group, and (B) a structural unit derived from an ethylenically unsaturated dicarboxylic acid diester in a predetermined ratio The inventors have found that rubber can achieve the above object and completed the present invention.

The aspects of the present invention are as follows.
Item 1.
(A) a structural unit derived from a (meth) acrylic acid ester having an alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group having 2 to 8 carbon atoms is 5 to 98 with respect to 100% by mass of all the structural units. Included in the range of 9 mass%,
(B) An acrylic rubber containing a structural unit derived from an ethylenically unsaturated dicarboxylic acid diester in a range of 1 to 30 mass% with respect to 100 mass% of all structural units.
Item 2.
Item 2. The acrylic rubber according to Item 1, wherein the (B) ethylenically unsaturated dicarboxylic acid diester is a diester of fumaric acid or itaconic acid.
Item 3.
The acrylic rubber according to item 1 or 2, further comprising (C) a structural unit derived from an ethylenically unsaturated monomer having an active group.
Item 4.
Item 3. The acrylic rubber according to item 3, which contains the structural unit derived from the ethylenically unsaturated monomer having an active group (C) in the range of 0.1 to 20% by mass based on 100% by mass of all the structural units.
Item 5.
An acrylic rubber composition comprising the acrylic rubber according to claim 1 and a crosslinking agent.
Item 6.
An acrylic rubber crosslinked product obtained by crosslinking the acrylic rubber composition obtained in Item 5.

  According to the acrylic rubber of the present invention, it is possible to provide an acrylic rubber that is excellent in processability such as roll processability and is excellent in normal state properties and various physical properties such as heat resistance and acid resistance. Further, the acrylic rubber of the present invention can be applied to various rubber members and rubber products required to have various physical properties such as electrophotographic equipment and automobile applications.

  First, the acrylic rubber in the present invention will be described. Acrylic rubber is an elastomeric polymer containing alkyl acrylate and / or alkoxyalkyl acrylate as a main component.

  The acrylic rubber of the present invention contains (A) a structural unit derived from a (meth) acrylic acid ester having an alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group having 2 to 8 carbon atoms, and 100% by mass of all the structural units. The content of the structural unit derived from the ethylenically unsaturated dicarboxylic acid diester (B) in the range of 5 to 98.9% by mass, relative to 100% by mass of the total structural unit, 1 to 30% by mass. It is an acrylic rubber contained in the range of. The constitutional unit refers to a unit derived from a monomer used during rubber production, and when the unit is modified (for example, esterified) after polymerization, the entire constitution is based on the mass of the unit after the modification. Determine the mass of the unit. In the acrylic rubber of the present invention, roll processability, normal physical properties, heat resistance, and acid resistance can be improved by using (A) and (B) together.

(A) A structural unit derived from a (meth) acrylic acid ester having an alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group having 2 to 8 carbon atoms is a basic unit of acrylic rubber, and is a basic unit based on the structural unit. The physical properties are determined. The carbon number contained in the alkoxyalkyl group having 2 to 8 carbon atoms means the carbon number contained in the entire alkoxyalkyl group, and is the total of the carbon number of the alkoxy and the carbon number of the alkyl. The (A) is a structural unit derived from (A-1) a (meth) acrylic acid ester having an alkyl group having 1 to 3 carbon atoms or an alkoxyalkyl group having 2 to 3 carbon atoms (hereinafter, referred to as C _1-3 It may be referred to as a constitutional unit derived from a type (meth) acrylic acid ester), and (A-2) together with (A-2) an alkyl group having 4 to 8 carbon atoms or a carbon number. Containing a structural unit derived from a (meth) acrylic acid ester having 4 to 8 alkoxyalkyl groups (hereinafter may be referred to as a structural unit derived from a C _4-8 type (meth) acrylic acid ester). Is more preferable.

  (A-1) Specific examples of the (meth) acrylic acid ester having an alkyl group having 1 to 3 carbon atoms or an alkoxyalkyl group having 2 to 3 carbon atoms include methyl (meth) acrylate and ethyl (meth) acrylate. , N-propyl (meth) acrylate, isopropyl (meth) acrylate, methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate and the like. These may be used alone or in admixture of two or more. Among these, ethyl (meth) acrylate and methoxyethyl (meth) acrylate are particularly preferable.

  (A-2) Specific examples of the (meth) acrylic acid ester having a C4-8 alkyl group or a C4-8 alkoxyalkyl group include n-butyl (meth) acrylate and (meth) acrylic. Acid isobutyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid Cyclohexyl, 2-ethoxyethyl (meth) acrylate, 2-propoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxy (meth) acrylate Propyl, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, (meth) acryl Le acid 4-methoxy-butyl, and (meth) 4-ethoxy butyl acrylate. These may be used alone or in combination of two or more. Among these, n-butyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate are particularly preferable. The alkyl group preferably has 4 to 6 carbon atoms, and the alkoxyalkyl group preferably has 4 to 6 carbon atoms.

  The total content of the structural unit (A) in the acrylic rubber of the present invention is 5 to 98.9% by mass in 100% by mass of all structural units, preferably 10% by mass or more, and more preferably 20% by mass. Mass% or more, more preferably 30 mass% or more, particularly preferably 50 mass% or more, most preferably 70 mass% or more, preferably 98 mass% or less, more preferably 97.5 mass% or less, further preferably 95. It is 0 mass% or less, and particularly preferably 90.0 mass% or less. If the content ratio of the structural unit (A) is too low, the tackiness of the acrylic rubber, especially the tackiness of the crosslinkable rubber composition is increased, and the roll processability is deteriorated. On the other hand, if the content ratio of the structural unit (A) is too high, the cold resistance decreases.

The content ratio of the structural unit derived from (A-1) C _1-3 type (meth) acrylic acid ester in the acrylic rubber of the present invention is 5 to 98.9% by mass in 100% by mass of all structural units. It is more preferably 10 mass% or more, further preferably 15 mass% or more, particularly preferably 20 mass% or more, more preferably 98 mass% or less, still more preferably 97.5 mass% or less. By setting the content ratio of the structural unit (A-1) to 5% by mass or more, it is possible to more effectively prevent the tackiness of the acrylic rubber, particularly the tackiness of the crosslinked rubber composition from increasing. The roll workability is further improved. On the other hand, when the content ratio of the structural unit (A-1) is 98.9 mass% or less, cold resistance can be further improved.

The content ratio of the structural unit derived from (A-2) C _4-8 type (meth) acrylic acid ester in the acrylic rubber of the present invention is 0 to 93.9 mass% in 100 mass% of all structural units. preferable. By setting the content ratio of the structural unit (A-2) to 93.9 mass% or less, roll processability can be further improved. The content ratio of the structural unit (A-2) is more preferably 88.9% by mass or less, still more preferably 80% by mass or less, particularly preferably 70% by mass or less, and most preferably 100% by mass of all structural units. It is 60 mass% or less. Further, the content ratio of the structural unit (A-2) may be less than 49.0 mass% in 100 mass% of all the structural units, for example, 45 mass% or less. The lower limit of the content ratio of the structural unit (A-2) is not particularly limited, but is more preferably 5 mass% or more, further preferably 10 mass% or more, particularly preferably 15 mass% or more in 100 mass% of all structural units. Is.

In the acrylic rubber of the present invention, a structural unit derived from the above (A-1) C _1-3 type (meth) acrylic acid ester and a (A-2) C _4-8 type (meth) acrylic acid ester derived structural unit When both of the constituent units are included, the ratio [(A-1) / (A-2)] of the amount of (A-1) to the amount of (A-2) is 0.5 to 4. It is preferably 0. The above ratio is more preferably 0.6 or more, further preferably 0.7 or more, more preferably 3.5 or less, and further preferably 3.3 or less.

  The acid resistance of the crosslinked acrylic rubber can be improved by including (B) a constitutional unit derived from an ethylenically unsaturated dicarboxylic acid diester.

  As the ethylenically unsaturated dicarboxylic acid constituting the ethylenically unsaturated dicarboxylic acid diester, a compound having an ethylenically unsaturated group and two carboxylic acid groups can be appropriately used, and an aliphatic hydrocarbon having an ethylenic double bond A compound having a group and two carboxylic acid groups is preferable, and for example, an ethylenically unsaturated bond exists between two carboxylic acids such as fumaric acid, maleic acid, citraconic acid, mesaconic acid, and 2-pentenedioic acid. Chained dicarboxylic acid; Chained dicarboxylic acid having two carboxylic acids such as itaconic acid on one side of ethylenically unsaturated bond (such as dicarboxylic acid containing exomethylene); Cyclic dicarboxylic acid such as cyclohexenedicarboxylic acid; Acetylenedicarboxylic acid, etc. And a chain dicarboxylic acid is preferable. Is, more preferably fumaric acid, and itaconic acid. The carbon number of the ethylenically unsaturated dicarboxylic acid is, for example, about 4 to 10, preferably 4 to 6, and more preferably 4 to 5, including the carbon number of the carboxylic acid (total 2).

  Further, as the alcohol forming an ester with the ethylenically unsaturated dicarboxylic acid, an alcohol having only a saturated aliphatic hydrocarbon group such as alkanol and alkoxyalkanol and an oxygen atom is preferable. The alcohol having only a saturated aliphatic hydrocarbon group and an oxygen atom has, for example, 1 to 8 carbon atoms. Specific examples of such alcohols include alcohols having 1 to 3 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, methoxymethanol, methoxyethanol and ethoxymethanol; n-butanol, isobutanol, n-pentanol, n. -Hexanol, n-heptanol, n-octanol, 2-ethylhexan-1-ol, cyclohexanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, 2-methoxypropan-1-ol, 2-ethoxy. The number of carbon atoms of propan-1-ol, 3-methoxypropan-1-ol, 3-ethoxypropan-1-ol, 4-methoxybutan-1-ol, 4-ethoxybutan-1-ol and the like is 4 to 8, Preferably, the carbon number is 4 to 6, and more preferable. May be mentioned alcohol 4-5 carbon atoms. The two alkanols forming the diester may be the same or different, but are preferably the same.

  The constitutional unit derived from the ethylenically unsaturated dicarboxylic acid diester composed of the above ethylenically unsaturated dicarboxylic acid and the above alcohol is (B-1) diester of dicarboxylic acid and alkanol having 1 to 3 carbon atoms. Although the structural unit derived from and the structural unit derived from the diester of (B-2) dicarboxylic acid and alkanol having 4 to 8 carbon atoms may be used in combination, at least (B-2) is preferably used. . By using (B-2), the acid resistance of the crosslinked acrylic rubber can be further improved.

Specific examples of the ethylenically unsaturated dicarboxylic acid diester include:
Dimethyl fumarate, diethyl fumarate, dipropyl fumarate, di-n-butyl fumarate, diisobutyl fumarate, dicyclohexyl fumarate; dimethyl maleate, diethyl maleate, dipropyl maleate, di-n-butyl maleate; dimethyl citraconate, Diethyl citraconic acid, Dipropyl citraconic acid, Di-n-butyl citraconic acid; Dimethyl mesaconic acid, Diethyl mesaconate, Dipropyl mesaconate, Di-n-butyl mesaconic acid; Dimethyl itaconate, Diethyl itaconate, Di-n-butyl itaconate, Itaconic acid Dicyclohexyl acid; Dimethyl 2-pentenedioate, Diethyl 2-pentenedioate, Dipropyl 2-pentenedioate, Di-n-butyl 2-pentenedioate; Dimethyl acetylenedicarboxylate, Diethyl acetylenedicarboxylate, Acetile Diesters of ethylenically unsaturated dicarboxylic acids with alkanols and the like; dipropyl dicarboxylic acid, acetylene dicarboxylic di n- butyl, acetylene dicarboxylic acid dicyclohexyl;
Di (methoxymethyl) fumarate, Di (methoxyethyl) fumarate, Di (ethoxymethyl) fumarate, Di (2-ethoxyethyl) fumarate, Di (2-methoxypropyl) fumarate, Di (3-fumarate) Methoxypropyl), di (4-methoxybutyl) fumarate; di (methoxymethyl) maleate, di (methoxyethyl) maleate, di (ethoxymethyl) maleate, di (2-ethoxyethyl) maleate, maleic acid Di (2-methoxypropyl), maleic acid di (3-methoxypropyl), maleic acid di (4-methoxybutyl); citraconic acid di (methoxymethyl), citraconic acid di (methoxyethyl), citraconic acid di (ethoxymethyl) ), Citraconic acid di (2-ethoxyethyl), citraconic acid di (2-methoxypropyl), citraconic acid (3-methoxypropyl), di (4-methoxybutyl) citraconic acid; di (methoxymethyl) mesaconic acid, di (methoxyethyl) mesaconate, di (ethoxymethyl) mesaconate, di (2-ethoxyethyl) mesaconate , Di (2-methoxypropyl) mesaconate, di (3-methoxypropyl) mesaconate, di (4-methoxybutyl) mesaconate; di (methoxymethyl) itaconic acid, di (methoxyethyl) itaconic acid, di itaconic acid (Ethoxymethyl), itaconic acid di (2-ethoxyethyl), itaconic acid di (2-methoxypropyl), itaconic acid di (3-methoxypropyl), itaconic acid di (4-methoxybutyl); Examples thereof include diesters of saturated dicarboxylic acids and alkoxyalkanols. These may be used alone or in combination of two or more. Among these, diethyl fumarate, dipropyl fumarate, di-n-butyl fumarate, diisobutyl fumarate, dimethyl itaconate, and di-n-butyl itaconate are particularly preferable. In particular, heat resistance can be improved by using itaconic acid diester.

  The content ratio of the structural unit (B) in the acrylic rubber of the present invention is 1 to 30% by mass in total of 100% by mass of all structural units, preferably 1.5% by mass or more, and more preferably 2% by mass. It is above, preferably 25 mass% or less, more preferably 20 mass% or less. When the content ratio of the structural unit (B) is too low, the effect of the structural unit (B) cannot be sufficiently obtained and the acid resistance is not improved. On the other hand, if the content ratio of the structural unit (B) is too high, the oil resistance and the cold resistance decrease.

  The content ratio of the structural unit derived from the diester of (B-1) dicarboxylic acid and alkanol having 1 to 3 carbon atoms in the acrylic rubber of the present invention is 0 to 30% by mass in 100% by mass of all structural units. preferable. When the content ratio of the structural unit (B-1) is 30% by mass or less, oil resistance and cold resistance can be further improved. The content ratio of the structural unit (B-1) is more preferably 10% by mass or less, still more preferably 5% by mass or less, in 100% by mass of all structural units. Although the lower limit of the content ratio of the structural unit (B-1) is not particularly limited, it is more preferably 1% by mass or more and further preferably 2% by mass or more in 100% by mass of all the structural units.

  The content ratio of the structural unit derived from the diester of (B-2) dicarboxylic acid and alkanol having 4 to 8 carbon atoms in the acrylic rubber of the present invention is 1 to 30% by mass in 100% by mass of all structural units. preferable. By setting the content ratio of the structural unit (B-2) to 1% by mass or more, acid resistance can be further improved. The content ratio of the structural unit (B-2) is more preferably 3% by mass or more, and further preferably 5% by mass or more, in 100% by mass of all structural units. On the other hand, when the content ratio of the structural unit (B-2) is 30 mass% or less, oil resistance and cold resistance can be further improved. The content ratio of the structural unit (B-2) is more preferably 20% by mass or less, still more preferably 15% by mass or less, in 100% by mass of all structural units.

  In the acrylic rubber of the present invention, a structural unit derived from a diester of (B-1) dicarboxylic acid and an alkanol having 1 to 3 carbon atoms and a diester of (B-2) dicarboxylic acid and an alkanol having 4 to 8 carbon atoms When both of the structural units derived from are contained, the ratio [(B-1) / (B-2)] of the amount of (B-1) and the amount of (B-2) is set to 1 or less. Preferably. The above ratio is more preferably 0.8 or less, still more preferably 0.6 or less. The lower limit of the ratio is not particularly limited, but is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.3 or more.

  The total content of the structural units (A) and (B) in the acrylic rubber of the present invention is preferably 11 to 100% by mass in 100% by mass of all structural units, more preferably 80% by mass or more, and further preferably 90%. It is not less than 9% by mass, more preferably not more than 99.5% by mass, further preferably not more than 99% by mass.

  The acrylic rubber of the present invention contains, in addition to the above structural units (A) and (B), a structural unit (C) derived from an ethylenically unsaturated monomer having an active group (including a crosslinking group and a crosslinking point). It is preferable. The active group is not particularly limited, but examples thereof include a crosslinking group such as a halogen group (eg, chlorine group), a carboxylic acid group, and an epoxy group. Examples of the ethylenically unsaturated monomer having a halogen group (especially chlorine group) include 2-chloroethyl vinyl ether, 2-chloroethyl acrylate, vinylbenzyl chloride, vinyl chloroacetate, allyl chloroacetate and the like. Examples of the ethylenically unsaturated monomer having a carboxylic acid group include ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid, crotonic acid, 2-pentenoic acid and cinnamic acid; fumaric acid, maleic acid, itaconic acid, etc. And an ethylenically unsaturated dicarboxylic acid monoester thereof. Examples of the ethylenically unsaturated monomer having an epoxy group include glycidyl (meth) acrylate and (meth) allyl glycidyl ether.

  Among these compounds, ethylenically unsaturated dicarboxylic acid monoester is particularly preferable. By containing the ethylenically unsaturated dicarboxylic acid monoester, the heat resistance of the acrylic rubber is further improved. Examples of the ethylenically unsaturated dicarboxylic acid monoester include monoesters of α, β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and alkanol having 1 to 8 carbon atoms.

  Examples of the ethylenically unsaturated dicarboxylic acid constituting the ethylenically unsaturated dicarboxylic acid monoester include those similar to the ethylenically unsaturated dicarboxylic acid constituting the above-mentioned ethylenically unsaturated dicarboxylic acid diester, and preferred examples are also the same. Is. As the alcohol constituting the ethylenically unsaturated dicarboxylic acid monoester, the same alcohols as those constituting the above-mentioned ethylenically unsaturated dicarboxylic acid diester are exemplified, and the preferable examples are also the same. As the ethylenically unsaturated dicarboxylic acid monoester, fumaric acid monoalkyl ester, maleic acid monoalkyl ester, itaconic acid monoalkyl ester and the like are particularly preferable. Specific examples include monomethyl fumarate, monoethyl fumarate, mono n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-n-butyl maleate butenedioic acid mono-chain alkyl ester; monocyclopentyl fumarate, fumarate. Acid monocyclohexyl, maleic acid monocyclopentyl, maleic acid monocyclohexyl, etc. butenedionic acid monocyclic alkyl ester; itaconic acid monomethyl, itaconic acid monoethyl, itaconic acid mono-n-butyl, itaconic acid monocyclohexyl ester, etc .; Can be mentioned. Among these, monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monoethyl itaconate, monopropyl itaconate and monobutyl itaconate are preferable.

  Further, the ethylenically unsaturated monomer having an active group is not limited to the above-mentioned monomer having a cross-linking group such as a halogen group, a carboxylic acid group and an epoxy group, and a substituent and / or a cross-linking group which cross-link each other. Any ethylenically unsaturated monomer may be used as long as it has a substituent that crosslinks via the agent. The ethylenically unsaturated monomer having an active group (including a crosslinking group and a crosslinking point) can be used alone or in combination of two or more kinds.

  After polymerization of the ethylenically unsaturated dicarboxylic acid monoester, it reacts with a crosslinking agent to form a crosslinked structure.

  When the constituent unit (C) derived from an ethylenically unsaturated monomer having an active group is contained, the content ratio of the constituent unit (C) in the acrylic rubber is 0.1 to 20% by mass based on all constituent units. It is more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, more preferably 15% by mass or less, still more preferably 10% by mass or less. If the content ratio of the structural unit (C) is too low, the crosslinked density of the obtained acrylic rubber crosslinked product may be insufficient and good crosslinked physical properties may not be obtained. On the other hand, if the content ratio of the structural unit (C) is too high, the elongation of the obtained acrylic rubber crosslinked product may decrease.

  The total content of the structural units (A), (B) and (C) in the acrylic rubber of the present invention is preferably 11.1 to 100% by mass, more preferably 95% by mass, based on 100% by mass of all the structural units. As described above, more preferably 99% by mass or more.

  Further, the acrylic rubber of the present invention may contain, in addition to the above structural units (A) to (C), other monomer structural units copolymerizable with them. Other structural units include a structural unit derived from an ethylenically unsaturated carboxylic acid, a structural unit derived from an ethylenically unsaturated nitrile, a structural unit derived from a (meth) acrylamide-based monomer, and an aromatic vinyl-based monomer. , A structural unit derived from a conjugated diene monomer, a structural unit composed of non-conjugated dienes, a structural unit composed of esters, a structural unit derived from other olefinic monomers, etc. Is mentioned.

  Examples of the ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid, itaconic acid, maleic acid and citraconic acid. The carboxylic acid group may be a carboxylic acid anhydride group, or may be a structural unit derived from a carboxylic acid anhydride such as maleic anhydride or citraconic acid anhydride.

  Examples of the ethylenically unsaturated nitrile include acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, and vinylidene cyanide.

  Examples of (meth) acrylamide monomers include acrylamide, methacrylamide, diacetone acrylamide, diacetone methacrylamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide, N-butoxyethyl acrylamide, N-butoxyethyl methacrylamide, N. -Methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-propoxymethylacrylamide, N-propoxymethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N, N-dimethylacrylamide, N, N-dimethyl Methacrylamide, N, N-diethyl acrylamide, N, N-diethyl methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, Takuriruamido, crotonamide, cinnamic acid amide, maleic diamide, Itakonjiamido, methyl maleate amide, methyl itaconate amides, maleimide, itaconimide, and the like.

  Aromatic vinyl monomers include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, α-fluorostyrene, p-trifluoromethylstyrene, p-methoxy. Styrene, p-aminostyrene, p-dimethylaminostyrene, p-acetoxystyrene, styrenesulfonic acid or its salt, α-vinylnaphthalene, 1-vinylnaphthalene-4-sulfonic acid or its salt, 2-vinylfluorene, 2- Vinyl pyridine, 4-vinyl pyridine, divinyl benzene, diisopropenyl benzene, vinyl benzyl chloride etc. are mentioned.

  Examples of the conjugated diene-based monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene and 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, piperylene and the like.

  Examples of the non-conjugated dienes include 1,4-pentadiene, 1,4-hexadiene, ethylidene norbornene, norbornadiene and dicyclopentadiene.

  Examples of the esters include dicyclopentanyl acrylate, dicyclopentanyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, dicyclopentenyl oxyethyl acrylate, dicyclopentenyl oxyethyl methacrylate and the like. .

  Other olefinic monomers include 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, butyl vinyl ether and the like can be mentioned.

  When containing these other copolymerizable monomer structural units, the content ratio in all structural units is 0 to 45% by mass, preferably 1% by mass or more, more preferably 2% by mass or more, It is preferably 20% by mass or less, more preferably 10% by mass or less.

<Method for producing acrylic rubber>
The acrylic rubber used in the present invention can be obtained by polymerizing the above-mentioned various known monomers. Any of the monomers used may be a commercially available product and is not particularly limited.

  As a form of the polymerization reaction, any of an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, and a solution polymerization method can be used, but from the viewpoint of easy control of the polymerization reaction, a conventionally known acrylic rubber is used. It is preferable to use an emulsion polymerization method under normal pressure which is generally used as a method for producing

  In the case of polymerization by emulsion polymerization, a usual method may be used, and as a polymerization initiator, an emulsifier, a chain transfer agent, a polymerization terminator and the like, generally used conventionally known compounds can be used.

  The emulsifier used in the present invention is not particularly limited, and nonionic emulsifiers and anionic emulsifiers generally used in the emulsion polymerization method can be used. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester and Examples thereof include polyoxyethylene sorbitan fatty acid ester, and examples of the anionic emulsifier include alkylbenzene sulfonate, alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate ester salt, polyoxyalkylene alkyl ether phosphate ester or salt thereof, and fatty acid salt. , Sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, triethanolamine dodecyl sulfate, etc. It may be used alone or in combination.

  The amount of the emulsifier used in the present invention may be the amount generally used in the emulsion polymerization method. Specifically, it is preferably in the range of 0.01 to 10% by mass, more preferably 0.03% by mass or more, further preferably 0.05% by mass or more, and more preferably the amount of the charged monomer. It is 7 mass% or less, more preferably 5 mass% or less. When a reactive surfactant is used as the monomer component, it is not always necessary to add an emulsifier.

  The polymerization initiator used in the present invention is not particularly limited, and a polymerization initiator generally used in the emulsion polymerization method can be used. Specific examples thereof include inorganic peroxide-based polymerization initiators represented by persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, 2,2-di (4,4-di- (t-butyl). Peroxy) cyclohexyl) propane, 1-di- (t-hexylperoxy) cyclohexane, 1,1-di- (t-butylperoxy) cyclohexane, 4,4-di- (t-butylperoxy) valeric acid n-butyl, 2,2-di (t-butylperoxy) butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3 -Tetramethylbutyl hydroperoxide, t-butyl cumyl peroxide, di-t-butyl peroxide, -T-hexyl peroxide, di (2-t-butylperoxyisopropyl) benzene, dicumyl peroxide, diisobutyryl peroxide, di (3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, Disuccinic acid peroxide, dibenzoyl peroxide, di (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (4- t-butylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, cumylperoxyneodecanate, 1,1,3,3-tetramethylbutane Ruperoxy neodecanate, t-hexyl peroxy neodecanoate, t-butyl peroxy neodecaneate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 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-3,5,5-trimethylhexanate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t- Butyl peroxy 2-ethylhexyl monocarbonate, 2,5-dimethyl -2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (t-butylperoxy) (Oxy) hexane and other organic peroxide-based polymerization initiators, hydroperoxide, azobisisobutyronitrile, 4-4′-azobis (4-cyanovaleric acid), 2-2′-azobis [2- ( 2-Imidazolin-2-yl) propane, 2-2'-azobis (propane-2-carbamidine) 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-me Trimethylolpropane) and 2-2'-azobis {2-methyl-N-[1,1-bis (hydroxymethyl) -2-hydroxyethyl] propanamide} like azo-based polymerization initiators, and the like. These polymerization initiators may be used alone or in combination of two or more.

  The amount of the polymerization initiator used in the present invention may be the amount generally used in the emulsion polymerization method. Specifically, it is preferably 0.01 to 5% by mass, more preferably 0.01% by mass or more, further preferably 0.02% by mass or more, and more preferably 4% by mass or less, with respect to the amount of charged monomers. , And more preferably 3% by mass or less.

  Moreover, the organic peroxide and the inorganic peroxide as the polymerization initiator can be used as a redox polymerization initiator by combining with a reducing agent. The reducing agent used in combination is not particularly limited, but a compound containing a metal ion in a reduced state such as ferrous sulfate and cuprous naphthenate; a methane compound such as sodium methanesulfonate; an amine such as dimethylaniline Compounds; ascorbic acid and salts thereof; inorganic salts having reducing properties such as alkali metal salts of sulfite and thiosulfate, and the like. These reducing agents may be used alone or in combination of two or more. The amount of the reducing agent used is preferably 0.0003 to 10.0 parts by mass with respect to 100 parts by mass of the peroxide.

  A chain transfer agent can be used if necessary. 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, 2,4-diphenyl-4. Xanthogen compounds such as -methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene, dimethylxanthogen disulfide, diisopropylxanthogendisulfide, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide Thiuram type compounds such as sulfides, 2,6-di-t-butyl-4-methylphenol, phenol type compounds such as styrenated phenol, allyl compounds such as allyl alcohol, di- Halogenated hydrocarbon compounds such as chloromethane, dibromomethane and carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile and α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein , Thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate and the like, and one or more of these may be used. The amount of these chain transfer agents is not particularly limited, but is usually 0 to 5 parts by mass with respect to 100 parts by mass of the charged monomer.

  Examples of the polymerization terminator include hydroxylamine, hydroxyamine sulfate, diethylhydroxyamine, hydroxyaminesulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, and the like. The amount of the polymerization terminator used is not particularly limited, but is usually 0 to 2 parts by mass with respect to 100 parts by mass of the charged monomer.

  Furthermore, the pH of the polymer obtained by the above method can be adjusted by using a base as a pH adjusting agent, if necessary. Specific examples of the base include sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, inorganic ammonium compounds, organic amine compounds and the like. The pH range is preferably pH 1 to 11, more preferably pH 1.5 or higher, even more preferably pH 2 or higher, more preferably pH 10.5 or lower, and further preferably pH 10 or lower.

  In addition to these, a polymerization auxiliary material such as a particle size adjusting agent, a chelating agent and an oxygen scavenger can be used if necessary.

  The emulsion polymerization may be a batch system, a semi-batch system or a continuous system. The polymerization time and the polymerization temperature are not particularly limited. Although it can be appropriately selected depending on the type of the polymerization initiator used, the polymerization temperature is generally 20 to 100 ° C., and the polymerization time is 0.5 to 100 hours.

The thus-produced acrylic rubber used in the present invention has a molecular weight range of Mooney viscosity (ML _{1 + 4} ) at 100 ° C. in a Mooney scorch test of JIS K 6300-1, preferably 10 to 100. And more preferably 15 or more, further preferably 20 or more, more preferably 90 or less, and further preferably 80 or less.

<Crosslinkable acrylic rubber composition>
The cross-linking agent used in the cross-linkable acrylic rubber composition of the present invention includes an active group (for example, a halogen group, a carboxylic acid group, an epoxy group) contained in the structural unit (C) derived from an ethylenically unsaturated monomer having an active group. It is not limited as long as it reacts with a group) to form a crosslinked structure.

  When the active group is a halogen group, trithiocyanuric acid, triazine derivatives such as 2,4,6-trimercapto-s-triazine, organic carboxylic acid ammonium salts such as ammonium benzoate and ammonium adipate, metal soaps and sulfur are usually used. The conventionally known cross-linking agent used can be used.

  When the above-mentioned active group is a carboxylic acid group, a polyvalent amine compound, a polyvalent hydrazide compound, a polyvalent epoxy compound, a polyvalent isocyanate compound, an aziridine compound, a conventionally known cross-linking agent usually used for cross-linking a rubber, etc. Can be used. Among these, polyvalent amine compounds are preferably used.

  Examples of the polyvalent amine compound include aliphatic polyvalent amine compounds such as hexamethylenediamine, hexamethylenediaminecarbamate, and N, N′-dicinnamylidene-1,6-hexanediamine, 4,4′-methylenedianiline, and 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-benzene Aromatic polyvalent amine compounds such Riaminomechiru like.

  As the polyhydric hydrazide compound, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, hydrazide dihydrazide, sebacic acid dihydrazide, dehydrazide, dehydrazide, dehydrazide, hydrazide dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, dihydrazide dihydrazide, sebacic acid dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, sebacic acid dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, hydrazide dihydrazide, sebacic acid Acid dihydrazide, terephthalic acid dihydrazide, isophthalic acid dihydrazide, acetone dicarboxylic acid dihydrazide, fumaric acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, naphthalic acid dihydrazide 1, trimellitic acid dihydrazide 1, 5-benzenetricarboxylic acid dihydrazide, pyromellitic acid dihydrazide, aconitic acid dihydrazide and the like can be mentioned.

  Examples of the polyvalent epoxy compound include compounds having two or more epoxy groups in the molecule. Phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, cresol type epoxy compounds, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds. Examples thereof include glycidyl ether type epoxy compounds such as compounds, brominated bisphenol A type epoxy compounds, brominated bisphenol F type epoxy compounds, and hydrogenated bisphenol A type epoxy compounds.

  Examples of the polyvalent isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, Diisocyanate compounds such as m-phenylene diisocyanate and 1,5-naphthylene diisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, bicycloheptane triisocyanate And other triisocyanate compounds.

  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.

  When the active group is an epoxy group, use of a conventionally known cross-linking agent such as ammonium benzoate, dithiocarbamate, polyamine and its derivatives, imidazoles, polycarboxylic acid and quaternary ammonium salt or phosphonium salt. You can

  These cross-linking agents may be used alone or in combination of two or more. The amount of the cross-linking agent is preferably 0.05 to 20 parts by mass, more preferably 0.1 part by mass or more, and further preferably 10 parts by mass or less with respect to 100 parts by mass of the acrylic rubber.

  In addition, the crosslinkable acrylic rubber composition of the present invention contains other additives usually used in the art, such as lubricants, antioxidants, light stabilizers, fillers, reinforcing agents, plasticizers, processing aids. , Pigments, colorants, cross-linking accelerators, cross-linking aids, cross-linking retarders, antistatic agents, foaming agents, etc.

  Further, it is possible to blend with a rubber, an elastomer, a resin or the like which is usually carried out in the technical field within a range not departing from the gist of the present invention. Examples of the rubber used in the present invention include butadiene rubber, styrene-butadiene rubber, isoprene rubber, natural rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-isoprene rubber, ethylene-propylene-diene rubber, and epichlorohydrin rubber. Examples of resins include PMMA (polymethylmethacrylate) resin, PS (polystyrene) resin, PUR (polyurethane) resin, PVC (polyvinyl chloride) resin, EVA (ethylene / vinyl acetate) resin, AS (styrene / acrylonitrile). ) Resin, PE (polyethylene) resin and the like.

  The total compounding amount of the above rubber, elastomer and resin is preferably 50 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 1 part by mass or less with respect to 100 parts by mass of the acrylic rubber of the present invention.

  As a method for compounding the crosslinkable acrylic rubber composition of the present invention, any means conventionally used in the field of polymer processing, such as an open roll, a Banbury mixer, various kneaders, etc., can be used.

  As the compounding procedure, a usual procedure which is carried out in the field of polymer processing can be carried out. For example, the procedure is such that first, only the polymer is kneaded, then the A kneading compound is prepared by adding the compounding agents other than the crosslinking agent and the crosslinking accelerator, and then the B compounding is performed by adding the crosslinking agent and the crosslinking accelerator. be able to.

  The acrylic rubber composition of the present invention can be usually converted to a crosslinked product, that is, an acrylic rubber crosslinked product by heating at 100 to 250 ° C. The crosslinking time varies depending on the temperature, but it is usually 0.5 to 300 minutes. The cross-linking molding can be carried out by integrally performing cross-linking and molding, or by heating the previously molded cross-linkable acrylic rubber composition again to form a cross-linked product. Any of the cases where the product is processed for molding may be used. As a specific method of cross-linking molding, any method such as compression molding with a mold, injection molding, steam can, air bath, infrared ray, or heating with microwave can be used.

  Since the acrylic rubber cross-linked product of the present invention thus obtained is obtained by using the acrylic rubber of the present invention, it is excellent in roll processability during processing, and in the case of a cross-linked product. It has excellent normal state properties, heat resistance, and acid resistance.

  Therefore, the acrylic rubber cross-linked product of the present invention makes use of the above-mentioned characteristics, and O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, well head seals, electric / electronic device seals, pneumatic devices. Seals, cylinder head gaskets attached to the connection between the cylinder block and the cylinder head, rocker cover gaskets attached to the connection between the rocker cover and the cylinder head, and the connection between the oil pan and the cylinder block or the transmission case. Various gaskets such as an oil pan gasket to be mounted, a gasket for a fuel cell separator mounted between a pair of housings that sandwich a unit cell including a positive electrode, an electrolyte plate and a negative electrode, a gasket for a top cover of a hard disk drive, etc. It is preferably used as bets.

  Further, the crosslinked acrylic rubber in the present invention is a fuel oil system hose around a fuel tank such as a fuel hose, a filler neck hose, a vent hose, a vapor hose and an oil hose as an extrusion molded product and a mold crosslinked product used for automobiles. It can be suitably used for various hoses such as an air system hose such as a turbo air hose and an emission control hose, a radiator hose, a heater hose, a brake hose, and an air conditioner hose.

  The present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to these.

  In the present examples and comparative examples, the production of acrylic rubber and the obtained acrylic rubber were mixed with a crosslinking agent, and the physical properties of the uncrosslinked rubber composition and the rubber crosslinked product obtained were evaluated.

(Experiment 1)
[Example 1]
(Production of acrylic rubber A)
200 parts by mass of water, 3 parts by mass of sodium dodecyl sulfate, 39.7 parts by mass of ethyl acrylate, and 49.0 parts by mass of n-butyl acrylate were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a pressure reducing device. Parts, 10.0 parts by mass of di-n-butyl itaconate, and 1.3 parts by mass of monoethyl fumarate were charged, and deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, and then sodium formaldehyde sulfoxylate was added. 12 parts by mass and 0.1 part by mass of cumene hydroperoxide are added to start the emulsion polymerization reaction under normal pressure and normal temperature, the reaction is continued until the polymerization conversion rate reaches 95%, and a polymerization terminator is added. The polymerization was stopped. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber A.

[Example 2]
(Production of acrylic rubber B)
In a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a pressure reducing device, 200 parts by mass of water, 3 parts by mass of sodium dodecylbenzene sulfonate, 39.7 parts by mass of ethyl acrylate, n-butyl acrylate 49. 0 parts by mass, diisobutyl fumarate 10.0 parts by mass, and monoethyl fumarate 1.3 parts by mass were charged, and deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, and then sodium bisulfite 0.18 parts by mass. And 0.15 parts by mass of potassium persulfate were added to start the emulsion polymerization reaction under normal pressure and normal temperature, and the reaction was continued until the polymerization conversion rate reached 95%, and a polymerization terminator was added to terminate the polymerization. . The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber B.

[Example 3]
(Production of acrylic rubber C)
200 parts by mass of water, 3 parts by mass of sodium dodecylsulfate, 39.2 parts by mass of ethyl acrylate, 49.5 parts by mass of n-butyl acrylate were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a pressure reducing device. Parts, di-n-butyl fumarate 10.0 parts by mass, and monoethyl fumarate 1.3 parts by mass were charged, and after deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, sodium bisulfite 0.18 parts by mass. Parts and 0.15 parts by mass of potassium persulfate are added to start the emulsion polymerization reaction at normal pressure and room temperature, and the reaction is continued until the polymerization conversion rate reaches 95%, and a polymerization terminator is added to stop the polymerization. did. The obtained emulsion polymerization liquid was coagulated with a calcium chloride aqueous solution, washed with water and dried to obtain an acrylic rubber C.

[Example 4]
(Production of acrylic rubber D)
200 parts by mass of water, 3 parts by mass of sodium dodecylsulfate, 39.0 parts by mass of ethyl acrylate, and 50.2 parts by mass of n-butyl acrylate were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a pressure reducing device. Parts, di-n-butyl itaconate 7.0 parts by mass, diethyl fumarate 2.5 parts by mass, and monoethyl fumarate 1.3 parts by mass were charged, and deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen. After that, 0.12 parts by mass of sodium formaldehyde sulfoxylate and 0.1 parts by mass of cumene hydroperoxide are added to start the emulsion polymerization reaction under normal pressure and room temperature, and the reaction is continued until the polymerization conversion rate reaches 95%. Then, a polymerization terminator was added to terminate the polymerization. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber D.

[Example 5]
(Production of acrylic rubber E)
200 parts by mass of water, 3 parts by mass of sodium dodecyl sulfate, 40.2 parts by mass of ethyl acrylate, 49.5 parts by mass of n-butyl acrylate were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a decompression device. Parts, dimethyl itaconate 3.0 parts by mass, di-n-butyl fumarate 6.0 parts by mass, and monoethyl fumarate 1.3 parts by mass were charged, and deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen. After that, 0.12 parts by mass of sodium formaldehyde sulfoxylate and 0.1 parts by mass of cumene hydroperoxide are added to start the emulsion polymerization reaction under normal pressure and room temperature, and the reaction is continued until the polymerization conversion rate reaches 95%. Then, a polymerization terminator was added to terminate the polymerization. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber E.

[Comparative Example 1]
(Production of acrylic rubber F)
200 parts by mass of water, 3 parts by mass of sodium dodecylbenzenesulfonate, 54.0 parts by mass of ethyl acrylate, n-butyl acrylate 44. 7 parts by mass and 1.3 parts by mass of monoethyl fumarate were charged, and deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, and then 0.12 parts by mass of sodium formaldehyde sulfoxylate and cumene hydroperoxide of 0.1. 1 part by mass was added to start the emulsion polymerization reaction under normal pressure and normal temperature, the reaction was continued until the polymerization conversion rate reached 95%, and a polymerization terminator was added to terminate the polymerization. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber F.

[Comparative Example 2]
(Manufacture of acrylic rubber G)
200 parts by mass of water, 3 parts by mass of sodium dodecyl sulfate, 50.2 parts by mass of ethyl acrylate, and 48.5 parts by mass of n-butyl acrylate were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a decompression device. And 1.3 parts by mass of monoethyl fumarate were charged, deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, and then 0.18 parts by mass of sodium hydrogen sulfite and 0.15 parts by mass of potassium persulfate were added. The emulsion polymerization reaction was started at normal pressure and room temperature, and the reaction was continued until the polymerization conversion rate reached 95%, and a polymerization terminator was added to terminate the polymerization. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber G.

  Table 1 below shows values obtained by converting the charged amount of each monomer into a mass fraction when the total amount of the monomers charged in the polymerization reactor is 100% by mass.

The polymer Mooney viscosity (ML _{1 + 4} ) of the obtained acrylic rubber was measured at a measurement temperature of 100 ° C. using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. in a Mooney scorch test defined in JIS K6300-1.

  Next, in order to evaluate the rubber physical properties of the obtained acrylic rubber, an uncrosslinked sheet and a secondary crosslinked product were prepared and various physical properties were evaluated.

(Production of crosslinkable rubber composition)
100 parts by weight of the acrylic rubber obtained by the above reaction, 60 parts by weight of carbon black (classification according to ASTM D1765; N550), 2 parts by weight of stearic acid (dispersing agent of carbon black, softening agent) and 4,4'-bis 2 parts by mass of (α, α-dimethylbenzyl) diphenylamine (antiaging agent) were kneaded in a Banbury at 120 ° C., and then 0.6 parts by mass of hexamethylenediaminecarbamate (aliphatic diamine crosslinking agent), di-o-tolyl. 2 parts by mass of guanidine (crosslinking accelerator) was added and kneaded with a kneading roll at room temperature to prepare crosslinkable rubber compositions.

The roll processability when kneading with the kneading roll was evaluated according to the following criteria.
Good: The raw material of acrylic rubber does not excessively adhere to the roll, and the roll processability is good.
X: The raw material of acrylic rubber excessively adheres to the roll or does not wind around the roll, resulting in poor roll processability.

(Preparation of uncrosslinked rubber sheet)
Each rubber composition obtained above was kneaded with a kneader and an open roll to prepare an uncrosslinked rubber sheet which is an uncrosslinked rubber composition having a thickness of 2 to 2.5 mm.

(Moonies coach test)
Using the obtained uncrosslinked rubber sheet, Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. was used to perform a Mooney scorch test defined in JIS K 6300-1, and a Mooney scorch time (t5) was measured at a measurement temperature of 125 ° C.

(Preparation of secondary crosslinked product)
The uncrosslinked rubber sheet obtained above was pressed at 180 ° C. for 10 minutes to obtain a primary crosslinked product having a thickness of 2 mm. Further, this was heated in an air oven at 180 ° C. for 3 hours to obtain a secondary crosslinked product.

(Evaluation of normal physical properties)
A tensile test and a hardness test were performed using the obtained secondary crosslinked product. The tensile test was performed according to the method described in JIS K 6251, and the elongation (EB) was measured. The hardness test was performed according to the method described in JIS K6253, and the hardness (HS) was measured.

(Acid resistance test)
The secondary crosslinked product was cut into 2 cm square to prepare a sample for acid resistance test. Further, 1 ml of sulfuric acid, 1.5 ml of 60% nitric acid aqueous solution and 300 μl of acetic acid were added to 500 ml of water to prepare an acidic aqueous solution of pH 1. The above sample was put into 50 ml of the adjusted acidic aqueous solution and stored in an autoclave at 125 ° C. for 216 hours. The volume of the sample was measured before and after the test, and the volume change rate (ΔV) was calculated. After drying the sample, the hardness was measured before and after the test in the same manner as in the evaluation of the normal state physical properties, and the change in hardness (ΔHS) was calculated.

(Heat resistance aging test)
A heat aging test was conducted by heating the secondary crosslinked product under the condition of 185 ° C. for 500 hours. Before and after heat aging, a tensile test and a hardness test were performed in the same manner as in the evaluation of the normal state physical properties, and the elongation change rate (ΔEB) and the hardness change (ΔHS) were calculated.

Table 1 shows the test results of Examples and Comparative Examples obtained by each test method.

  As shown in Table 1, Examples 1 to 5 containing the structural unit (B) of the ethylenically unsaturated dicarboxylic acid diester were compared with Comparative Examples 1 and 2 in the volume change rate (ΔV) and hardness of the acid resistance test. The change (ΔHS) became smaller. Further, in Examples 1 to 5, also in the heat aging test, the elongation change rate (ΔEB) and the hardness change (ΔHS) after heat aging were small. In the heat aging test, the results were further improved especially when the itaconic acid diester was used. From these results, it is understood that the acrylic rubber of the present invention and the rubber cross-linked product thereof have improved acid resistance, and the rate of change in elongation (ΔEB) and the change in hardness (ΔHS) after heat aging.

(Experiment 2)
[Example 6]
(Production of acrylic rubber H)
200 parts by mass of water, 3 parts by mass of sodium dodecyl sulfate, 60.0 parts by mass of ethyl acrylate, 5.0 parts by mass of methoxyethyl acrylate were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introducing pipe and a pressure reducing device. , N-butyl acrylate 24.0 parts by mass, diisobutyl fumarate 10.0 parts by mass, and monoethyl fumarate 1.0 part by mass were charged, and after deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, 0.18 parts by mass of sodium bisulfite and 0.15 parts by mass of potassium persulfate are added to start an emulsion polymerization reaction under normal pressure and room temperature, and the reaction is continued until the polymerization conversion rate reaches 95%, and a polymerization terminator. Was added to stop the polymerization. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber H.

[Comparative Example 3]
(Production of acrylic rubber I)
Acrylic rubber I was obtained under the same conditions as in Example 6 except that diisobutyl fumarate was not used and the amount of ethyl acrylate charged was 70.0 parts by mass.

  When the total amount of the monomers charged in the polymerization reactor is 100% by mass, the values obtained by converting the charged amounts of the respective monomers into mass fractions are shown in Table 2 below.

The polymer Mooney viscosity (ML _{1 + 4} ) of the obtained acrylic rubber was measured under the same conditions as in Experiment 1 above.

  Next, in order to evaluate the rubber physical properties of the obtained acrylic rubber, an uncrosslinked sheet and a secondary crosslinked product were prepared, and various physical properties were evaluated under the same conditions as in Experiment 1 except for the acid resistance test and the heat aging test. went.

  The acid resistance test was performed under the same conditions as in Experiment 1 above, except that the acid resistance test was stored at 125 ° C. for 240 hours in the autoclave instead of at 125 ° C. for 216 hours.

  The heat aging test was conducted under the same conditions as in Experiment 1 except that the secondary crosslinked product was heated at 190 ° C. for 300 hours instead of being heated at 185 ° C. for 500 hours.

表２で示すように、エチレン性不飽和ジカルボン酸ジエステルの構成単位（Ｂ）を含む実施例６は、比較例３と比較して耐酸性試験の体積変化率（ΔＶ）および硬度変化（ΔＨＳ）が小さくなった。また実施例６は、耐熱老化試験においては、耐熱老化後の伸び変化率（ΔＥＢ）が小さい結果となった。これらの結果から、本発明のアクリルゴムおよびそのゴム架橋物は、耐酸性、耐熱性が向上していることがわかる。Table 2 shows the test results of Examples and Comparative Examples obtained by each test method.

As shown in Table 2, in Example 6 containing the structural unit (B) of the ethylenically unsaturated dicarboxylic acid diester, the volume change rate (ΔV) and hardness change (ΔHS) in the acid resistance test were compared with Comparative Example 3. Became smaller. Further, in Example 6, in the heat aging test, the elongation change rate (ΔEB) after heat aging was small. From these results, it can be seen that the acrylic rubber and the rubber cross-linked product thereof of the present invention have improved acid resistance and heat resistance.

(Experiment 3)
[Example 7]
(Manufacture of acrylic rubber J)
200 parts by mass of water, 3 parts by mass of sodium dodecyl sulfate, 88.0 parts by mass of ethyl acrylate, and di-n-butyl itaconate 10.0 were placed in a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a pressure reducing device. Mass parts and 2.0 parts by mass of vinyl chloroacetate were charged, and deaeration under reduced pressure and nitrogen substitution were repeated to sufficiently remove oxygen, and then 0.12 parts by mass of sodium formaldehyde sulfoxylate and 0.1 parts of cumene hydroperoxide. An emulsion polymerization reaction was started at normal pressure and normal temperature by adding parts by mass, and the reaction was continued until the polymerization conversion rate reached 95%, and a polymerization terminator was added to terminate the polymerization. The obtained emulsion polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber J.

[Comparative Example 4]
(Manufacture of acrylic rubber K)
Acrylic rubber K was obtained under the same conditions as in Example 7 above, except that di-n-butyl itaconate was not used and the amount of ethyl acrylate charged was 98.0 parts by mass.

  When the total amount of the monomers charged in the polymerization reactor is 100% by mass, the value obtained by converting the charged amount of each monomer into a mass fraction is shown in Table 3 below.

The polymer Mooney viscosity (ML _{1 + 4} ) of the obtained acrylic rubber was measured under the same conditions as in Experiment 1 above.

  Next, in order to evaluate the rubber physical properties of the obtained acrylic rubber, an uncrosslinked sheet and a secondary crosslinked product were prepared and various physical properties were evaluated.

(Production of crosslinkable rubber composition)
100 parts by weight of the acrylic rubber obtained by the above reaction, 60 parts by weight of carbon black (classification according to ASTM D1765; N550), 2 parts by weight of stearic acid (dispersing agent of carbon black, softening agent) and 4,4'-bis 2 parts by mass of (α, α-dimethylbenzyl) diphenylamine (antiaging agent) was kneaded in a Banbury at 120 ° C., and then 2.5 parts by mass of sodium stearate, 0.5 parts by mass of potassium stearate and 0.3 of sulfur. By adding parts by mass and kneading with a kneading roll at room temperature, a crosslinkable rubber composition was prepared.

  The roll processability when kneading with the kneading roll was evaluated according to the same criteria as in Experiment 1.

  Using each of the rubber compositions obtained above, an uncrosslinked rubber sheet was prepared under the same conditions as in Experiment 1, and a Mooney scorch test was performed under the same conditions as in Experiment 1 above, and the Mooney scorch time (t5) was measured.

  Using the uncrosslinked rubber sheet obtained above, a secondary crosslinked product was produced under the same conditions as in Experiment 1 above, and a tensile test and a hardness test were conducted under the same conditions as in Experiment 1 above to determine elongation (EB) and hardness. (HS) was measured.

  Using the above secondary crosslinked product, an acid resistance test was conducted under the same conditions as in Experiment 2 above, except that the secondary crosslinked product was stored in an autoclave at 125 ° C for 240 hours instead of being stored at 125 ° C for 240 hours. ) And hardness change (ΔHS) were calculated.

  The same conditions were used as in Experiment 1 above, except that the above secondary crosslinked product was used, and instead of heating at 185 ° C. for 500 hours, it was heated at 185 ° C. for 336 hours.

表３に示すように、実施例７と比較例４は、Ｃ_1-3型（メタ）アクリル酸エステルから誘導される構成単位（Ａ−１）を含有し、Ｃ_4-8型（メタ）アクリル酸エステルから誘導される構成単位（Ａ−２）を含有しない例である。比較例４は、エチレン性不飽和ジカルボン酸ジエステルの構成単位（Ｂ）を含有していない。その結果、耐酸性試験を行った結果、試験片の形状を維持できず、ヘドロ状になり、耐酸性を評価できなかった。一方、実施例７は、エチレン性不飽和ジカルボン酸ジエステルの構成単位（Ｂ）を含有している。その結果、比較例４と比べて、耐酸性を改善できた。また実施例７は、耐熱老化試験においても、耐熱老化後の伸び変化率（ΔＥＢ）および硬度変化（ΔＨＳ）が小さい結果となった。Table 3 shows the test results of Examples and Comparative Examples obtained by each test method.

As shown in Table 3, Example 7 and Comparative Example 4 contain a structural unit (A-1) derived from a C _1-3 type (meth) acrylic acid ester, and a C _4-8 type (meth). This is an example containing no structural unit (A-2) derived from an acrylate ester. Comparative Example 4 does not contain the structural unit (B) of the ethylenically unsaturated dicarboxylic acid diester. As a result, as a result of performing an acid resistance test, the shape of the test piece could not be maintained, and it became sludge-like, and the acid resistance could not be evaluated. On the other hand, Example 7 contains the structural unit (B) of an ethylenically unsaturated dicarboxylic acid diester. As a result, acid resistance could be improved as compared with Comparative Example 4. Also, in the heat aging test of Example 7, the elongation change rate (ΔEB) and hardness change (ΔHS) after heat aging were small.

INDUSTRIAL APPLICABILITY The acrylic rubber of the present invention can be widely used as a material for rubber products and resin products utilizing excellent heat resistance, acid resistance, weather resistance, ozone resistance, and abrasion resistance, or as a raw material for adhesives and coating materials. Is. In particular, the crosslinked acrylic rubber is extremely effective for automotive applications such as fuel hoses, air hoses, and tube materials.

Claims (6)

  (A) a structural unit derived from a (meth) acrylic acid ester having an alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group having 2 to 8 carbon atoms is 5 to 98 with respect to 100% by mass of all the structural units. It is contained in the range of 0.9 mass%, and contains (B) a structural unit derived from an ethylenically unsaturated dicarboxylic acid diester in a range of 1 to 30 mass% with respect to 100 mass% of all structural units. And acrylic rubber.   The acrylic rubber according to claim 1, wherein the (B) ethylenically unsaturated dicarboxylic acid diester is a diester of fumaric acid or itaconic acid.   The acrylic rubber according to claim 1 or 2, further comprising (C) a structural unit derived from an ethylenically unsaturated monomer having an active group.   The constitutional unit derived from the ethylenically unsaturated monomer having an active group (C) is contained in an amount of 0.1 to 20% by mass based on 100% by mass of all the constitutional units. Acrylic rubber according to item 3.   An acrylic rubber composition comprising the acrylic rubber according to claim 1 and a crosslinking agent.   An acrylic rubber crosslinked product obtained by crosslinking the acrylic rubber composition obtained in claim 5.