JP2011001428A - Acrylic rubber composition and crosslinked product thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic rubber composition which gives a crosslinked product excellent in heat resistance (particularly, heat resistance when exposed to high temperatures for many hours) and compression set resistance.SOLUTION: The acrylic rubber composition includes an acrylic rubber having 90-99.5 wt.% monomer unit (A) of a (meth)acrylic ester having a 1-4C alkyl group or a 3-8C alkoxyalkyl group and 0.5-10 wt.% monomer unit (B) of a butenedioic acid monoester and a phenothiazine derivative represented by formula (1) (wherein Ris hydrogen, a 4-8C alkyl group which may be branched or an aralkyl group and Ris a 4-24C alkyl group which may be branched or an aralkyl group) and the content of the phenothiazine derivative is 0.1-20 pts.wt. based on 100 pts.wt. acrylic rubber.

Description

  The present invention relates to an acrylic rubber composition and a cross-linked product thereof, and more particularly to an acrylic rubber composition and a cross-linked product thereof that give a cross-linked product excellent in heat resistance and compression set resistance.

  Rubber parts for automobiles, especially rubber parts in the engine compartment, have been used to improve the heat resistance performance of the rubber parts due to the high performance of the engine and the increased ambient temperature in the engine compartment due to recent exhaust gas regulations. It has been demanded.

  Acrylic rubber is known as a rubber having excellent heat resistance, but various studies have been made on acrylic rubber in order to further improve heat resistance. For example, Patent Document 1 discloses a cross-linked product obtained by cross-linking a cross-linkable acrylic rubber composition containing an aromatic secondary amine compound, nickel dialkyldithiocarbamate and a cross-linking agent with respect to an acrylic rubber having a carboxyl group. It is disclosed that it is excellent in heat resistance and the like. However, this crosslinked product may still have insufficient heat resistance, particularly when used at high temperatures.

  Patent Document 2 discloses that an acrylic rubber composition having excellent heat resistance can be obtained by blending a carboxyl group-containing acrylic rubber with a guanidine compound, a diamine compound, and a phenolic anti-aging agent. Has been. However, with this technique, particularly when used at high temperatures, the heat resistance may still be insufficient. Therefore, an acrylic rubber having further excellent heat resistance has been demanded.

JP 2001-207008 A JP 2004-175840 A

  An object of the present invention is to provide an acrylic rubber composition that provides a crosslinked product having excellent heat resistance (particularly, heat resistance when exposed to a high temperature for a long time) and compression set resistance. Another object of the present invention is to provide a crosslinked product obtained using such an acrylic rubber composition.

  As a result of intensive studies to achieve the above object, the present inventors have found that a specific phenothiazine derivative is added to an acrylic rubber having a predetermined (meth) acrylic acid ester monomer unit and a butenedionic acid monoester monomer unit. By adding, it discovered that the said objective could be achieved and came to complete this invention.

  That is, according to the present invention, 90 to 99.5% by weight of (meth) acrylic acid ester monomer unit (A) having an alkyl group having 1 to 4 carbon atoms or an alkoxyalkyl group having 3 to 8 carbon atoms, and Acrylic rubber having 0.5 to 10% by weight of butenedionic acid monoester monomer unit (B), and the following general formula (1):

（上記一般式（１）中、Ｒ^１が水素、又は分岐していてもよい炭素数４〜８のアルキル基若しくはアラルキル基、Ｒ^２が分岐していてもよい炭素数４〜２４のアルキル基またはアラルキル基である）
で表されるフェノチアジン誘導体とを含有し、前記アクリルゴム１００重量部に対する、前記フェノチアジン誘導体の含有割合が０．１〜２０重量部であるアクリルゴム組成物が提供される。

(In the above general formula (1), R ¹ is hydrogen, or an optionally branched alkyl group having 4 to 8 carbon atoms or an aralkyl group, and R ² may be branched alkyl group having 4 to 24 carbon atoms. Or an aralkyl group)
An acrylic rubber composition containing 0.1 to 20 parts by weight of the phenothiazine derivative with respect to 100 parts by weight of the acrylic rubber is provided.

Furthermore, among the phenothiazine derivatives represented by the above general formula (1), R ¹ and R ² may be the same or different, and include a phenothiazine derivative that is a branched alkyl group having 4 to 8 carbon atoms. An acrylic rubber composition is preferred.

Furthermore, among the phenothiazine derivatives represented by the above formula (1), more preferably, R ¹ and R ² are optionally branched alkyl groups having 4 to 8 carbon atoms, specifically 3, 7-dibutylphenothiazine, 3,7-dioctylphenothiazine, or the following general formula (2):

（上記一般式中、ｍおよびｎは、０または正の整数であり、ｍ＋ｎ＝１〜３を満たす）
で表されるスチレン化フェノチアジンを含むアクリルゴム組成物が好ましい。

(In the above general formula, m and n are 0 or a positive integer and satisfy m + n = 1 to 3)
An acrylic rubber composition containing a styrenated phenothiazine represented by

  Moreover, according to this invention, the crosslinked material formed by bridge | crosslinking the composition containing one of the said acrylic rubber compositions and a crosslinking agent is provided.

  According to the present invention, an acrylic rubber composition that gives a cross-linked product excellent in heat resistance (particularly heat resistance when exposed to a high temperature for a long time) and compression set, and obtained by cross-linking this. Thus, a crosslinked product having excellent heat resistance and compression set resistance can be provided.

(Acrylic rubber composition)
The acrylic rubber composition of the present invention is a (meth) acrylic acid ester monomer unit (A) having an alkyl group having 1 to 4 carbon atoms or an alkoxyalkyl group having 3 to 8 carbon atoms (A) 90 to 99.5% by weight, Further, 0.1 to 20 parts by weight of a specific phenothiazine derivative described later is contained with respect to 100 parts by weight of acrylic rubber having 0.5 to 10% by weight of butenedionic acid monoester monomer unit (B).

  The (meth) acrylic acid ester monomer unit (A) (hereinafter referred to as “monomer” as appropriate) having an alkyl group having 1 to 4 carbon atoms or an alkoxyalkyl group having 3 to 8 carbon atoms constituting the acrylic rubber used in the present invention. (Meth) acrylic acid ester monomer (a) having a C 1-4 alkyl group or C 3-8 alkoxyalkyl group (hereinafter referred to as “unit (A)”). Monomer (a) ") is methyl (meth) acrylate (meaning methyl acrylate and methyl methacrylate. Hereinafter," (meth) "is used in the same meaning in the present invention). C1-C4 alkyl such as ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, etc. (Meth) acrylic acid ester monomer having: (meth) acrylic acid methoxyethyl, (meth) acrylic acid ethoxymethyl, (meth) acrylic acid ethoxyethyl, (meth) acrylic acid propoxyethyl, (meth) acrylic acid butoxy And (meth) acrylic acid ester monomers having a C3-C8 alkoxyalkyl group such as ethyl, methoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, and the like. These may use multiple types together. Of these, ethyl acrylate and n-butyl acrylate are preferred.

  The content ratio of the monomer unit (A) in the acrylic rubber is 90 to 99.5% by weight, preferably 92 to 99% by weight, more preferably 95 to 99% by weight in all the monomer units. It is. When the content rate of a monomer unit (A) is too low, the intensity | strength and elongation of the crosslinked product obtained may fall. On the other hand, if the content is too high, it may not be sufficiently crosslinked.

  A butenedionic acid monoester monomer unit (B) forming the butenedionic acid monoester monomer unit (B) (hereinafter referred to as “monomer unit (B)” as appropriate) constituting the acrylic rubber used in the present invention. ) (Hereinafter referred to as “monomer (b)” as appropriate) is monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monocyclopentyl fumarate, monocyclohexyl fumarate, monocycloheptyl fumarate. Monomethyl maleate, monoethyl maleate, mono-n-butyl maleate, monocyclopentyl maleate, monocyclohexyl maleate, monocycloheptyl maleate and the like. These may use multiple types together. Among these, since the effect of the present invention becomes more remarkable, a butenedionic acid monoalkyl ester monomer is preferable, and a butenedionic acid monoalkyl ester monomer having an alkyl group having 3 to 6 carbon atoms is more preferable. Mono n-butyl maleate is particularly preferred. The monomer (b) acts as a crosslinkable monomer that reacts with a crosslinking agent or a vulcanizing agent to form a crosslinked structure after polymerization.

  The content ratio of the monomer unit (B) in the acrylic rubber is 0.5 to 10% by weight, preferably 1 to 8% by weight, more preferably 1 to 5% by weight, based on all monomer units. It is. If the content ratio of the monomer unit (B) is too low, the cross-linked density of the obtained cross-linked product may not be sufficient and good mechanical properties may not be obtained. On the other hand, if the content is too high, the elongation of the resulting crosslinked product may be reduced.

The acrylic rubber contains a carboxyl group, and the amount thereof is preferably 5 × 10 ⁻⁴ to 4 × 10 ⁻¹ ephr, more preferably 2 × 10 ⁻³ to 2 × 10 ⁻¹ ephr, and particularly preferably 4 ×. 10 ⁻³ to 1 × 10 ⁻¹ ephr. Here, “ephr” represents the molar equivalent of a carboxyl group in 100 g of rubber. If the number of carboxyl groups in the acrylic rubber is too small, the crosslinked product may not be sufficiently crosslinked, and the crosslinked product may not be maintained. On the other hand, if the amount is too large, the crosslinked product may become hard and lose rubber elasticity.

  In addition to the monomer unit (A) and monomer unit (B) described above, the acrylic rubber used in the present invention can be copolymerized with the monomer (a) and monomer (b) that form them. The monomer unit may be contained. Such copolymerizable monomers include conjugated diene monomers, non-conjugated diene monomers, aromatic vinyl monomers, α, β-ethylenically unsaturated nitrile monomers, amide group-containing ( Examples include meth) acrylic monomers, polyfunctional di (meth) acrylic monomers, and aliphatic vinyl monomers.

  Examples of the conjugated diene monomer include 1,3-butadiene, chloroprene, piperylene and the like. Examples of the non-conjugated diene monomer include 1,2-butadiene, 1,4-pentadiene, dicyclopentadiene, ethylidene norbornene, 1,4-hexadiene, norbornadiene, and the like. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, divinylbenzene, and the like. Examples of the α, β-ethylenically unsaturated nitrile monomer include acrylonitrile and methacrylonitrile. Examples of the amide group-containing (meth) acrylic monomer include acrylamide and methacrylamide. Examples of the polyfunctional di (meth) acrylic monomer include ethylene glycol diacrylate, propylene glycol diacrylate, ethylene glycol dimethacrylate, and propylene glycol dimethacrylate. Examples of the aliphatic vinyl monomer include ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, ethyl vinyl ether, and butyl vinyl ether.

  In the case where these copolymerizable monomer units are contained, the content ratio in all the monomer units is preferably 9.5% by weight or less, more preferably 5% by weight or less.

  The acrylic rubber used in the present invention is a polymerization of a monomer mixture comprising the above-mentioned monomers (a), monomers (b), and monomers copolymerizable with these as required. Can be obtained. As the 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. From the viewpoint of easy control of the polymerization reaction, etc., a conventionally known method for producing acrylic rubber It is preferable to use an emulsion polymerization method under normal pressure, which is generally used.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the acrylic rubber used in the present invention is preferably 10 to 70, more preferably 20 to 60, and particularly preferably 30 to 50. If the Mooney viscosity is too low, the moldability and the mechanical strength of the cross-linked product may be lowered. On the other hand, if the Mooney viscosity is too high, the moldability may be lowered.

  The acrylic rubber composition of the present invention has the following general formula (1):

（上記一般式（１）中、Ｒ^１が水素、又は分岐していてもよい炭素数４〜８のアルキル基若しくはアラルキル基、Ｒ^２が分岐していてもよい炭素数４〜２４のアルキル基またはアラルキル基であるフェノチアジン誘導体）
で表されるフェノチアジン誘導体を特定量含有させてなるものである。

(In the above general formula (1), R ¹ is hydrogen, or an optionally branched alkyl group having 4 to 8 carbon atoms or an aralkyl group, and R ² may be branched alkyl group having 4 to 24 carbon atoms. Or a phenothiazine derivative which is an aralkyl group)
A specific amount of a phenothiazine derivative represented by the formula:

Furthermore, among the phenothiazine derivatives represented by the general formula (1), more preferably, R ¹ and R ² are optionally branched alkyl groups having 4 to 8 carbon atoms, specifically 3, 7-dibutylphenothiazine, 3,7-dioctylphenothiazine, or the following formula (2):

（上記一般式（２）中、ｍおよびｎは、０または正の整数であり、ｍ＋ｎ＝１〜３を満たす）で表されるスチレン化フェノチアジンである。なお、ｍ又はｎが０の場合、一般式（２）のスチレン化されていない単結合は、水素原子と結合する。

(In the general formula (2), m and n are 0 or a positive integer and satisfy m + n = 1 to 3). In addition, when m or n is 0, the single bond which is not styrenated of General formula (2) couple | bonds with a hydrogen atom.

  By including such a phenothiazine derivative, the obtained crosslinked product can be excellent in heat resistance (particularly heat resistance when exposed to high temperature for a long time) and compression set resistance.

  The content ratio of the phenothiazine derivative in the acrylic rubber composition is 0.1 to 20 parts by weight, preferably 0.1 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the acrylic rubber. Part.

  The acrylic rubber composition of the present invention may contain a crosslinking agent in addition to the above-described acrylic rubber and phenothiazine derivative. By incorporating a crosslinking agent into the acrylic rubber composition of the present invention, a crosslinkable rubber composition can be obtained.

  Examples of such cross-linking agents include polyvalent amine compounds (excluding polyvalent tertiary amine compounds described later), polyvalent epoxy compounds, polyvalent isocyanate compounds, aziridine compounds, sulfur compounds, basic metal oxides, and organic compounds. A conventionally known crosslinking agent usually used for crosslinking of acrylic rubber such as metal halide can be used. Of these, polyvalent amine compounds are preferably used. Among polyvalent amine compounds, polyvalent primary amine compounds are particularly preferably used.

  Specific examples of the polyvalent primary amine compound include aliphatic divalent primary amine compounds such as hexamethylenediamine, ethylenediamine, and cyclohexanediamine; salts of aliphatic divalent primary amine compounds such as hexamethylenediamine carbamate and ethylenediamine carbamate; bis ( Hexamethylene) triamine, 3,3′-diaminodipropylamine, aliphatic trivalent primary amine compounds such as cyclohexanetriamine; 4,4′-methylenedianiline, m-phenylenediamine, 4,4′-diaminodiphenyl ether, 3 , 4'-diaminodiphenyl ether, 4,4 '-(m-phenylenediisopropylidene) dianiline, 4,4'-(p-phenylenediisopropylidene) dianiline, 2,2'-bis [4- (4-amino Phenoxy) phenyl] Aromatic divalent primary amine compounds such as lopan, 4,4′-diaminobenzanilide, 4,4′-bis (4-aminophenoxy) biphenyl; N, N ′, N ″ -triphenyl-1,3 Aromatic trivalent primary amine compounds such as 5-benzenetriamine; and the like. These may use multiple types together. Among these, an aliphatic divalent primary amine compound, an aromatic divalent primary amine compound, or a salt thereof is preferable, and hexamethylenediamine carbamate, 4,4′-diaminodiphenyl ether, 4,4 ′-(m-phenylenediisopropyl ether. Ridene) dianiline, 4,4 ′-(p-phenylenediisopropylidene) dianiline and 2,2′-bis [4- (4-aminophenoxy) phenyl] propane are more preferred, and 2,2′-bis [4- (4-Aminophenoxy) phenyl] propane is particularly preferred.

  The amount of the crosslinking agent is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 4 parts by weight, and still more preferably 0.2 to 3 parts by weight with respect to 100 parts by weight of the acrylic rubber. If the blending amount of the crosslinking agent is too small, the strength and heat resistance of the crosslinked product may be significantly reduced. On the other hand, if the amount is too large, the crosslinked product may become too hard, the elongation of the crosslinked product may decrease, or the elongation after aging may become too small.

  The acrylic rubber composition of the present invention may further contain a crosslinking accelerator in addition to the crosslinking agent. The crosslinking accelerator is not particularly limited, and examples thereof include guanidine compounds, imidazole compounds, quaternary onium salts, polyvalent tertiary amine compounds, tertiary phosphine compounds, weak acid alkali metal salts, and the like.

Examples of the guanidine compound include 1,3-diphenylguanidine, 1,3-diortolylguanidine and the like. Examples of the imidazole compound include 2-methylimidazole and 2-phenylimidazole. Examples of the quaternary onium salt include tetra n-butylammonium bromide and octadecyltri n-butylammonium bromide. Examples of the polyvalent tertiary amine compound include triethylenediamine and 1,8-diaza-bicyclo [5.4.0] undecene-7. Examples of the tertiary phosphine compound include triphenylphosphine and tri-p-tolylphosphine. Examples of the alkali metal salt of a weak acid include inorganic weak acid salts such as sodium or potassium phosphates and carbonates, and organic weak acid salts such as sodium or potassium stearates and laurates.
As the crosslinking accelerator, those having a base dissociation constant of 10 ⁻¹² to 10 ⁶ at 25 ° C. in water are preferable.

  The amount of the crosslinking accelerator is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 15 parts by weight, and particularly preferably 0.3 to 10 parts by weight with respect to 100 parts by weight of the acrylic rubber. When the blending amount of the crosslinking accelerator is too small, the tensile strength of the resulting crosslinked product may be remarkably lowered, or the elongation change or the tensile strength change after heat load may be too large. On the other hand, if the amount is too large, the crosslinking rate may become too fast during crosslinking, the crosslinking accelerator blooms on the surface of the crosslinked product, or the resulting crosslinked product may become too hard.

  The acrylic rubber composition of the present invention may further contain a monoamine compound. By blending a monoamine compound, the acrylic rubber composition can be made less susceptible to scorching, and the heat resistance, cold resistance, and deterioration oil resistance of the resulting crosslinked product can be improved. Examples of the monoamine compound include a mono primary amine compound, a mono secondary amine compound, and a mono tertiary amine compound. These may be used alone or in combination of two or more.

  Mono primary amine compounds are compounds in which one of the hydrogen atoms of ammonia is substituted with a hydrocarbon group, such as aliphatic mono primary amines, alicyclic mono primary amines, aromatic mono primary amines, amino alcohols, aminooxo compounds, and the like. Can be mentioned. Among these, an aliphatic monoprimary amine is preferable, and an aliphatic monoprimary amine having 8 to 20 carbon atoms is more preferable. Aliphatic mono primary amines include methylamine, ethylamine, propylamine, isopropylamine, n-butylamine, t-butylamine, sec-butylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine , Tridecylamine, tetradecylamine, pentadecylamine, cetylamine, 2-ethylhexylamine, octadecylamine, allylamine, cis-2-butenylamine, 10-undecenylamine, trans-2-octadecenylamine, cis-9- Octadecenylamine, nonadecylamine, etc., among them octylamine, decylamine, dodecylamine, tetradecylamine, cetylamine, octadecylamine, nona Shiruamin, cis-9-octadecenyl amine is preferred. Examples of the alicyclic mono-primary amine include cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine and the like. Aromatic mono primary amines include aniline, o-toluidine, m-toluidine, benzylamine, α-naphthylamine, β-naphthylamine and the like. Examples of amino alcohols include aminoethanol, aminopropanol, D, L-alaninol, 2-aminobutyl alcohol, 2-amino-2-methylpropanol, 2-amino-2-hydroxymethyl-1,3-propanediol, 2- Amino-2-methylpropane-1,3-diol, 2-amino-2-ethyl-1,3-propanediol, 1-chloro-3-aminopropan-2-ol, 3-amino-1,2-propane Examples thereof include amino alcohols such as diol and 2-amino-1,3-propanediol. Examples of aminooxo compounds include 3-methoxypropylamine and 3-ethoxypropylamine.

  Mono secondary amine compounds are compounds in which two hydrogen atoms of ammonia are substituted with hydrocarbon groups, and include aliphatic mono secondary amines and aromatic mono secondary amines. preferable. The aliphatic hydrocarbon group of the aliphatic mono-secondary amine that is substituted with a hydrogen atom preferably has 1 to 30 carbon atoms, and more preferably has 8 to 20 carbon atoms. Specific examples of the aliphatic mono-secondary amine 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, dioctadecylamine, di-cis-9-octa Examples are decenylamine and dinonadecylamine. Among these, dioctylamine, didecylamine, didodecylamine, ditetradecylamine, dicetylamine, dioctadecylamine, di-cis-9-octadecenylamine and dinonadecylamine are preferable, and didodecylamine is particularly preferable.

  Mono tertiary amine compounds are compounds in which all three hydrogen atoms of ammonia are substituted with hydrocarbon groups, and examples include aliphatic mono tertiary amines and aromatic mono tertiary amines. Is preferred. The aliphatic hydrocarbon group that substitutes for a hydrogen atom in the aliphatic mono-tertiary amine preferably has 1 to 30 carbon atoms, and more preferably has 1 to 22 carbon atoms. Specifically, trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexylamine, triheptylamine, trioctylamine, Trinonylamine, tridecylamine, triundecylamine, tridodecylamine, tritridecylamine, tritetradecylamine, tripentadecylamine, tricetylamine, tri-2-ethylhexylamine, trioctadecylamine, tri-cis- 9-octadecenylamine, trinonadecylamine, N, N-dimethyldecylamine, N, N-dimethyldodecylamine, N, N-dimethyltetradecylamine, N, N-dimethylcetylamine, N, N-di Tyloctadecylamine, N, N-dimethylbehenylamine, N-methyldidecylamine, N-methyldidodecylamine, N-methylditetradecylamine, N-methyldicetylamine, N-methyldioctadecylamine, N- Examples include methyl dibehenylamine. Among these, N, N-dimethyldodecylamine, N, N-dimethyltetradecylamine, N, N-dimethylcetylamine, N, N-dimethyloctadecylamine, N, N-dimethylbehenylamine and the like are preferable.

  The compounding amount of the monoamine compound is preferably 0.05 to 20 parts by weight, more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the acrylic rubber. If the amount of the monoamine compound is too small, the processability of the acrylic rubber composition tends to decrease. When the compounding amount of the monoamine compound is too large, the monoamine compound blooms when the crosslinked product is obtained, the strength of the obtained crosslinked product is remarkably reduced, or the compression set tends to increase. Moreover, the compounding quantity of a monoamine compound is the molar ratio of "monoamine compound / crosslinking agent", Preferably it is 0.01-10, More preferably, it is 0.1-9, More preferably, it is 0.2-8.

  Acrylic rubber composition of the present invention, if necessary, reinforcing material, filler, light stabilizer, plasticizer, processing aid, lubricant, adhesive, lubricant, flame retardant, antifungal agent, antistatic agent, You may contain additives, such as a coloring agent.

Moreover, the acrylic rubber composition of the present invention may further contain an elastomer, a resin, or the like other than the above-described acrylic rubber, if necessary. Specific examples include olefin elastomers, styrene elastomers, vinyl chloride elastomers, polyester elastomers, polyamide elastomers, polyurethane elastomers, polysiloxane elastomers, and the like; polyolefin resins, polystyrene resins, polyacrylic Resins such as resins, polyphenylene ether resins, polyester resins, polycarbonate resins, and the like can be blended.
The total amount of the elastomer and the resin is preferably 30 parts by weight or less, particularly preferably 10 parts by weight or less, based on 100 parts by weight of the acrylic rubber.

  In preparing the acrylic rubber composition of the present invention, conventionally known mixing methods such as roll mixing, Banbury mixing, screw mixing, and solution mixing can be employed. The order of mixing is not particularly limited, but after components that are not easily decomposed by heat are sufficiently mixed, components that are easily reacted by heat or components that are easily decomposed, for example, a crosslinking agent that is added as necessary reacts or decomposes. Mixing in a short time at a difficult temperature.

  The molding method of the acrylic rubber composition of the present invention is not particularly limited. Any method such as compression molding, injection molding, transfer molding or extrusion molding can be used. Moreover, what is necessary is just to select the crosslinking method according to the shape etc. of a crosslinked material, and any of the method of performing shaping | molding and bridge | crosslinking simultaneously and the method of crosslinking after shaping | molding may be sufficient.

(Crosslinked product)
The crosslinked product of the present invention is obtained by heating the acrylic rubber composition of the present invention containing a crosslinking agent. The heating temperature is preferably 130 to 220 ° C, more preferably 140 ° C to 200 ° C, and the crosslinking time is preferably 30 seconds to 5 hours. As a heating method, a method usually used for crosslinking of rubber such as press heating, steam heating, oven heating, hot air heating and the like may be appropriately selected. In addition, after crosslinking once, in order to ensure crosslinking to the inside of the crosslinked product, crosslinking may be performed after heating over time. Post-crosslinking is preferably performed for 1 to 48 hours, although it varies depending on the heating method, crosslinking temperature, shape, and the like. What is necessary is just to select a heating method and heating temperature suitably.

  Since the crosslinked product of the present invention thus obtained is obtained using the acrylic rubber composition of the present invention, heat resistance (particularly, heat resistance when exposed to high temperature for a long time), and Excellent compression set resistance.

  Therefore, the rubber cross-linked product of the present invention can be suitably used in a wide range as a material for rubber parts such as seals, hoses, vibration-proof materials, tubes, belts, boots and the like, taking advantage of the above characteristics.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, unless otherwise indicated, the part and% in each example are a basis of weight.

(Acrylic rubber composition)
The content ratio of each monomer unit constituting the acrylic rubber was measured by pyrolysis gas chromatography.

(Mooney viscosity)
The Mooney viscosity of the acrylic rubber was measured at 100 ° C. according to JIS K6300.

(Carboxyl group content)
To 0.2 g of 2 mm square acrylic rubber, add 20 ml of ethanol and 10 ml of water, and with stirring, use 0.02N aqueous ethanol solution of potassium hydroxide and titrate with thymolphthalein as an indicator at room temperature to give 100 g of acrylic rubber. It calculated | required as a mole number of the carboxyl group with respect to (unit is ephr).

(Normal properties: tensile strength, elongation, hardness)
The tensile strength, elongation, and hardness (durometer A hardness) of the crosslinked product were measured according to JIS K6251.

(Heat-resistant)
As an evaluation of the heat resistance of the cross-linked product, in accordance with JIS K6257, heat aging is performed in air at 175 ° C. for 1000 hours, and the tensile strength and elongation of the cross-linked product after heat aging are measured in accordance with JIS K6251. The rate of change when compared with the tensile strength and elongation before heat aging was evaluated. The smaller the change in tensile strength and elongation after heat aging, the better the heat resistance.

(Compression set)
The compression set rate of the cross-linked product was determined by using a cylindrical test piece in accordance with JIS K6262 and leaving it under compression at 25% in an environment of 175 ° C. for 70 hours, and then releasing the compression. It measured using the piece. The smaller the compression set rate, the better the compression set resistance.

(Production Example 1)
In a polymerization reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a decompressor, 200 parts of water, 3 parts of sodium lauryl sulfate, 60 parts of ethyl acrylate, 38 parts of n-butyl acrylate, and mono-n-maleate After adding 2 parts of butyl and repeating degassing by depressurization and nitrogen substitution to sufficiently remove oxygen, 0.002 part of sodium formaldehyde sulfoxylate and 0.005 part of cumene hydroperoxide were added, and at normal pressure and room temperature. The emulsion polymerization reaction was started, the reaction was continued until the polymerization conversion rate reached 95%, and a polymerization terminator was added to stop the polymerization. Next, the obtained emulsion polymerization solution was coagulated with an aqueous calcium chloride solution, washed with water and dried to obtain an acrylic rubber. The resulting acrylic rubber had an ethyl acrylate unit content of 60%, an n-butyl acrylate unit content of 38%, and a mono n-butyl maleate unit content of 2%, and a carboxyl group content of 8 × 10 ^{− 3} ephr, Mooney viscosity (ML _{1 + 4} , 100 ° C.) 40.

Example 1
100 parts of acrylic rubber obtained in Production Example 1, carbon black (trade name Seast SO, classified according to ASTM D1765; N550, manufactured by Tokai Carbon Co., Ltd.), 2 parts of stearic acid (carbon black dispersant, softener), plastic 5 parts of an agent (trade name Adeka Sizer RS735, manufactured by Adeka), 1 part of ester wax (trade name Greg G8205, processing aid, manufactured by Dainippon Ink), and 2 parts of 3,7-dibutylphenothiazine at 50 ° C Kneading in a banbury, and then adding 1 part of 2,2′-bis [4- (4-aminophenoxy) phenyl] propane (crosslinking agent) and 2 parts of didodecylamine (monoamine compound) at 40 ° C. An acrylic rubber composition was obtained by kneading with an open roll. 3,7-dibutylphenothiazine is a phenothiazine derivative (R ¹ and R ² : t-butyl group) represented by the above general formula (1).

  Next, the obtained acrylic rubber composition was molded and cross-linked by pressing at 170 ° C. for 20 minutes under the condition of 10 MPa to produce a 15 cm × 15 cm × 2 mm test piece, and for post-crosslinking, 170 ° C. For 4 hours. Then, using the obtained test piece, the tensile strength, elongation, and hardness of the cross-linked product were measured. Further, the test piece was subjected to air heat aging, and the tensile strength and elongation of the cross-linked product after heat aging were measured. Was measured. Separately, the acrylic rubber composition was molded and crosslinked by pressing at 170 ° C. for 20 minutes under the condition of 10 MPa, and further allowed to stand at 170 ° C. for 4 hours for post-crosslinking, thereby having a diameter of 29 mm and thickness. A cylindrical test piece having a thickness of 12.5 mm was produced, and the compression set was measured. The results are shown in Table 1.

(Example 2)
An acrylic rubber composition and a crosslinked product were prepared in the same manner as in Example 1 except that the amount of 3,7-dibutylphenothiazine was changed to 4 parts, and evaluation was performed in the same manner as in Example 1. . The results are shown in Table 1.

(Examples 3 and 4)
Instead of 2 parts of 3,7-dibutylphenothiazine, the same as Example 1 except that 2 parts (Example 3) and 4 parts (Example 4) of 3,7-dioctylphenothiazine were used, respectively. Then, an acrylic rubber composition and a crosslinked product were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. 3,7-dioctylphenothiazine is a phenothiazine derivative (R ¹ and R ² : t-octyl group) represented by the above general formula (1).

(Examples 5 and 6)
Acrylic rubber in the same manner as in Example 1 except that 2 parts (Example 5) and 4 parts (Example 6) of styrenated phenothiazine were used instead of 2 parts of 3,7-dibutylphenothiazine, respectively. A composition and a crosslinked product were prepared and evaluated. The results are shown in Table 1. The styrenated phenothiazine is a mixture of phenothiazine derivatives represented by the above general formula (2) (by weight ratio, 3-α-methylbenzylphenothiazine: 3,7-di-α-methylbenzylphenothiazine: 3- (α- Methylbenzyl) -7- (1-methyl-1,3-diphenylpropyl) phenothiazine = 1: 5: 4).

(Comparative Example 1)
An acrylic rubber composition and a crosslinked product were prepared in the same manner as in Example 1 except that 2 parts of p, p′-dicumyldiphenylamine was used instead of 2 parts of 3,7-dibutylphenothiazine. Evaluation was carried out in the same manner as above. The results are shown in Table 1.

(Comparative Example 2)
An acrylic rubber composition and a crosslinked product were produced in the same manner as in Example 1 except that 2 parts of 3,7-dibutylphenothiazine were not used, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

  As shown in Table 1, a crosslinked product obtained by crosslinking an acrylic rubber composition obtained by blending a predetermined amount of a predetermined phenothiazine derivative with a predetermined acrylic rubber of the present invention has normal properties (tensile strength, (Elongation and hardness) were good, and heat resistance and compression set resistance were excellent (Examples 1 to 6). On the other hand, when p, p'-dicumyldiphenylamine was used instead of the predetermined phenothiazine derivative, the resulting crosslinked product was inferior in heat resistance (Comparative Example 1). Furthermore, when an anti-aging agent was not added, the obtained vulcanizate was a product that was extremely inferior in heat resistance (Comparative Example 2).

  The acrylic rubber composition of the present invention is suitable as a material for constituting a member required for heat resistance or the like.

Claims (6)

(Meth) acrylic acid ester monomer unit (A) having 90 to 99.5% by weight of alkyl group having 1 to 4 carbon atoms or alkoxyalkyl group having 3 to 8 carbon atoms, and butenedionic acid monoester monomer unit (B) an acrylic rubber having 0.5 to 10% by weight;
The following general formula (1)

(In the above general formula (1), R ¹ is hydrogen, or an optionally branched alkyl group having 4 to 8 carbon atoms or an aralkyl group, and R ² may be branched alkyl group having 4 to 24 carbon atoms. Or an aralkyl group)
A phenothiazine derivative represented by
The acrylic rubber composition whose content rate of the said phenothiazine derivative is 0.1-20 weight part with respect to 100 weight part of said acrylic rubber. ^2. The acryl according to claim 1, wherein the phenothiazine derivative is an alkyl group having 4 to 8 carbon atoms in which R ¹ and R ² may be the same or different in the general formula (1) and may be branched. Rubber composition.   The acrylic rubber composition according to claim 1, wherein the phenothiazine derivative is 3,7-dibutylphenothiazine.   The acrylic rubber composition according to claim 1, wherein the phenothiazine derivative is 3,7-dioctylphenothiazine. The phenothiazine derivative is represented by the following general formula (2)

(In the above general formula, m and n are 0 or a positive integer and satisfy m + n = 1 to 3).
The acrylic rubber composition according to claim 1, which is a styrenated phenothiazine represented by the formula:   The crosslinked material formed by bridge | crosslinking the composition containing the acrylic rubber composition and crosslinking agent in any one of Claims 1-5.