JP6565682B2 - Crosslinkable acrylic rubber composition and rubber cross-linked product - Google Patents

Description

  The present invention relates to a crosslinkable acrylic rubber composition, and more particularly to a crosslinkable acrylic rubber composition and a rubber crosslinkable product excellent in storage stability that give a rubber crosslinkable product excellent in heat resistance.

  Acrylic rubber is a rubber material excellent in heat resistance, oil resistance, weather resistance and the like. For this reason, it is widely used for automotive rubber parts such as gaskets, hoses, O-rings, and seals. Recently, demands for rubber materials such as heat resistance, oil resistance, and long life have increased due to higher grade and higher performance of automobiles. Cross-linking with further excellent performance such as heat resistance, oil resistance, and long life. An acrylic rubber composition has been developed.

For example, with respect to 100 parts by mass of acrylic rubber obtained by copolymerizing (a1) a crosslinkable group-containing monomer 0.1 to 10% by mass, (a2) 0.4 to 50.0 mass of liquid fluororubber A crosslinkable acrylic rubber composition containing a part has been proposed (Patent Document 1). In Patent Document 1, as a crosslinkable group-containing monomer, a crosslinkable acrylic rubber composition obtained by blending a liquid fluorine rubber with an acrylic rubber copolymerized with a monomer containing a phenolic hydroxyl group is excellent in heat resistance. Providing a rubber cross-linked product.
However, the crosslinkable acrylic rubber composition specifically disclosed in Patent Document 1 is inferior in storage stability in an uncrosslinked state. Therefore, after the preparation of the crosslinkable acrylic rubber composition, the crosslinkable acrylic rubber composition is left to stand for a predetermined time. When an attempt is made to extrude the later crosslinkable acrylic rubber composition to obtain a hose-like molded product, an extruded product with a clean molded surface (extruded product with an uneven surface and a well-shaped surface) is obtained. Not found out.

International Publication WO2013 / 153649 Pamphlet

  In view of the drawbacks of the conventional techniques as described above, an object of the present invention is to provide a crosslinkable acrylic rubber composition and a rubber cross-linked product excellent in storage stability, which give a rubber cross-linked product excellent in heat resistance.

  As a result of intensive studies by the present inventors, it has been found that when calcium silicate is used as an acid acceptor, a crosslinkable acrylic rubber composition giving a crosslinked rubber having excellent storage stability and excellent heat resistance can be obtained. It came to be completed.

（上記一般式（１）中、Ｙは−ＳＯ_２−を表す。Ｒ^ａおよびＲ^ｂはそれぞれ独立して、炭素数１〜３０の炭化水素基を表す。Ｚ^ａおよびＺ^ｂはそれぞれ独立して、化学的な単結合または−ＳＯ_２−を表す。ｎおよびｍはそれぞれ独立して、０または１であり、ｎおよびｍの少なくとも一方は１である。）
（６） さらに補強材として、シリカを含有する（１）〜（５）のいずれかに記載の架橋性アクリルゴム組成物。
（７） さらに補強材として、カーボンブラックを含有する（１）〜（５）のいずれかに記載の架橋性アクリルゴム組成物。Thus, according to the present invention, the following inventions are provided.
(1) An acrylic rubber (a) containing 0.1 to 10% by mass of a phenolic hydroxyl group-containing monomer unit, a liquid fluororubber (b), and calcium silicate (c), and the liquid fluororubber The crosslinkable acrylic rubber composition whose content of (b) is 0.4-50 mass parts with respect to 100 mass parts of said acrylic rubber (a).
(2) The crosslinkable acrylic rubber composition according to (1), wherein the acrylic rubber (a) contains a (meth) acrylic acid ester monomer unit as a main component.
(3) The crosslinkable acrylic rubber composition according to (2), wherein the content of the (meth) acrylic acid ester monomer unit is 60 to 99.9% by mass.
(4) The crosslinkable acrylic rubber composition according to (1) or (2), wherein the content of calcium silicate (c) is 0.5 to 20 parts by mass with respect to 100 parts by mass of the acrylic rubber (a). object.
(5) The crosslinkable acrylic rubber composition according to any one of (1) to (4), further comprising a compound represented by the following general formula (1) as an anti-aging agent.

(In the general formula (1), Y represents —SO ₂ —. R ^a and R ^b each independently represent a hydrocarbon group having 1 to 30 carbon atoms. Z ^a and Z ^b each independently represent And represents a chemical single bond or —SO ₂ —, wherein n and m are each independently 0 or 1, and at least one of n and m is 1.
(6) The crosslinkable acrylic rubber composition according to any one of (1) to (5), which further contains silica as a reinforcing material.
(7) The crosslinkable acrylic rubber composition according to any one of (1) to (5), which further contains carbon black as a reinforcing material.

(8) The crosslinkable acrylic rubber composition according to any one of (1) to (7), further comprising a crosslinking accelerator.
(9) A crosslinked rubber product obtained by crosslinking the crosslinkable acrylic rubber composition according to any one of (1) to (8).
(10) The rubber cross-linked product according to (9), which is a hose.

  ADVANTAGE OF THE INVENTION According to this invention, the crosslinkable acrylic rubber composition and rubber crosslinked material which are excellent in storage stability which give the rubber crosslinked material excellent in heat resistance are provided.

  The crosslinkable acrylic rubber composition of the present invention comprises an acrylic rubber (a) containing 0.1 to 10% by mass of a phenolic hydroxyl group-containing monomer unit, a liquid fluororubber (b), and calcium silicate (c). The content of the liquid fluororubber (b) is 0.4 to 50 parts by mass with respect to 100 parts by mass of the acrylic rubber (a).

(Acrylic rubber (a))
The acrylic rubber (a) used in the present invention is an acrylic rubber containing 0.1 to 10% by mass of a phenolic hydroxyl group-containing monomer unit, and contains a (meth) acrylic acid ester monomer unit as a main component. Those are preferred.
In this specification, “(meth) acrylic acid ester monomer unit” means both “methacrylic acid ester monomer unit” and “acrylic acid ester monomer unit”. It is the same.
Although it does not restrict | limit especially as a (meth) acrylic acid ester monomer which can be used, A (meth) acrylic-acid alkylester monomer and a (meth) acrylic-acid alkoxyalkylester monomer are mentioned.

From the viewpoint of improving oil resistance, the (meth) acrylic acid alkyl ester monomer is, for example, a (meth) acrylic acid alkyl ester monomer having an alkyl group having 1 to 8 carbon atoms, preferably 2 to 2 carbon atoms. (Meth) acrylic acid alkyl ester monomers having 4 alkyl groups.
Specific examples of the (meth) acrylic acid alkyl ester monomer having an alkyl group having 1 to 8 carbon atoms include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth ) Isopropyl acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and the like. These (meth) acrylic acid alkyl ester monomers may be used alone or in combination of two or more. Among these (meth) acrylic acid alkyl esters, ethyl (meth) acrylate and n-butyl (meth) acrylate are particularly preferably used because of a good balance of heat resistance, oil resistance and cold resistance.

As the (meth) acrylic acid alkoxyalkyl ester monomer, from the viewpoint of improving oil resistance, for example, a (meth) acrylic acid alkoxyalkyl having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms. An ester monomer is mentioned.
Examples of the (meth) acrylic acid alkoxyalkyl ester monomer having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms include 2-methoxyethyl (meth) acrylate and 2- (meth) acrylic acid 2- Examples include ethoxyethyl, 2-butoxyethyl (meth) acrylate, and 2-methoxypropyl (meth) acrylate. These (meth) acrylic acid alkoxyalkyl ester monomers may be used alone or in combination of two or more. Among these (meth) acrylic acid alkoxyalkyl ester monomers, 2-methoxyethyl (meth) acrylate and 2-butoxyethyl (meth) acrylate are from a good balance of heat resistance, oil resistance and cold resistance. Are particularly preferably used.

  The content of the (meth) acrylic acid ester monomer unit in all the monomer units constituting the acrylic rubber (a) is preferably 60 to 99.9% by mass, more preferably 92 to 99.7% by mass. Especially preferably, it is 95-99.5 mass%. If the content of the (meth) acrylic acid ester monomer unit is in the above range, a rubber cross-linked product having good rubber elasticity and a sufficient cross-linking density can be obtained.

  The acrylic rubber (a) used in the present invention contains 0.1 to 10% by mass of a phenolic hydroxyl group-containing monomer unit. The phenolic hydroxyl group in the acrylic rubber (a) functions as a crosslinkable group and forms a crosslinked structure together with the liquid fluororubber (b). Accordingly, the liquid fluororubber (b) has a function as a crosslinking agent in the crosslinkable acrylic rubber composition of the present invention.

  The phenolic hydroxyl group-containing monomer is not particularly limited as long as it is a monomer that contains a phenolic hydroxyl group and is copolymerizable with a (meth) acrylic acid ester monomer. Specifically, o, m, p-hydroxystyrene, α-methyl-o-hydroxystyrene, o-cabycol, p, m-hydroxybenzoic acid vinyl, 4-hydroxybenzyl (meth) acrylate, vinyl salicylate, p- Hydroxybenzoyloxy vinyl acetate, eugenol, isoeugenol, p-isopropenylphenol, o, m, p-allylphenol, 4-hydroxyphenyl (meth) acrylate, 2,2- (o, m, p-hydroxyphenyl- 4-vinylacetyl) propane and the like. These phenolic hydroxyl group-containing monomers may be used alone or in combination of two or more.

  The content of the phenolic hydroxyl group-containing monomer unit in all the monomer units constituting the acrylic rubber (a) is 0.1 to 10% by mass, preferably 0.3 to 8% by mass, more preferably 0. 0.5 to 5% by mass. If this content is low, the required rubber elasticity cannot be obtained, and conversely if it is high, appropriate rubber elasticity as a rubber cross-linked product cannot be obtained.

  The acrylic rubber (a) used in the present invention is a monomer unit other than the phenolic hydroxyl group-containing monomer unit and the (meth) acrylic acid ester monomer unit within a range that does not substantially impair the effects of the present invention. You may contain. As a monomer that forms such a monomer unit, a phenolic hydroxyl group-containing monomer and another monomer copolymerizable with a (meth) acrylic acid ester monomer can be used. Specifically, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid; complete or partial of unsaturated polycarboxylic acid such as itaconic acid, fumaric acid and maleic acid and lower alcohol Esterified products: styrene, vinyl toluene, vinyl pyridine, α-methyl styrene, chloromethyl styrene, ethylene, propylene, acrylonitrile, methacrylonitrile, acrylamide, N-methylol acrylamide, 2-chloroethyl vinyl ether, vinyl monochloroacetate, allyl chloride, Examples include vinyl acetate and vinyl chloride. These other monomers may be used alone or in combination of two or more.

  The content ratio of monomer units other than the phenolic hydroxyl group-containing monomer unit and the (meth) acrylic acid ester monomer unit is preferably 30% by mass in all monomer units constituting the acrylic rubber (a). Hereinafter, it is more preferably 7.7% by mass or less, particularly preferably 4.5% by mass or less.

  The production method of the acrylic rubber (a) used in the present invention is not particularly limited, and can be produced by a known method. For example, a monomer mixture having a desired monomer composition is polymerized by emulsion polymerization, and the resulting polymer latex is mixed with salt as a salting-out agent to coagulate the polymer component. Get a rubber crumb. Thereafter, the obtained rubber crumb can be washed with water and dried to obtain the acrylic rubber (a).

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the acrylic rubber (a) used in the present invention is usually 10 to 70, preferably 20 to 50. This Mooney viscosity can be adjusted by selecting the type and amount of a molecular weight adjusting agent or polymerization initiator used during polymerization, or by selecting the polymerization temperature.

(Liquid fluoro rubber (b))
The liquid fluororubber (b) used in the present invention is not particularly limited as long as it is a liquid fluororubber at room temperature (20 ° C.). For example, vinylidene fluoride / hexane fluoropropylene copolymer, vinylidene fluoride-hexafluoropentene-tetrafluoroethylene terpolymer, perfluoropropene oxide polymer, tetrafluoroethylene-propylene-vinylidene fluoride copolymer, etc. Is mentioned. Commercially available products such as Viton (registered trademark) LM (manufactured by DuPont), Daiel (registered trademark) G101 (manufactured by Daikin Industries, Ltd.) and Dinion FC2210 (manufactured by 3M) are used as these liquid fluororubbers (b). You can also

  The viscosity of the liquid fluororubber (b) is not particularly limited, but the viscosity at 105 ° C. is 500 to 30,000 cps from the viewpoint of good kneadability, fluidity, crosslinking reactivity, and excellent moldability. Preferably it is 550-25,000 cps.

  The amount of the liquid fluororubber (b) is 0.4 to 50 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the acrylic rubber (a). Is 1 to 10 parts by mass, particularly preferably 1 to 5 parts by mass. If the blending amount of the liquid fluororubber (b) is within this range, a more appropriate crosslinking rate can be obtained.

(Calcium silicate (c))
The crosslinkable acrylic rubber composition of the present invention contains calcium silicate (c). Calcium silicate (c) functions as an acid acceptor.
Although the compounding quantity of calcium silicate (c) is not specifically limited, Preferably it is 0.5-20 mass parts with respect to 100 mass parts of acrylic rubber (a), More preferably, it is 1-15 mass parts, More preferably, it is 2 -14 parts by mass, particularly preferably 6-12 parts by mass. If the amount is too small, a sufficient crosslinking rate cannot be obtained. Conversely, if the amount is too large, the storage stability of the crosslinkable acrylic rubber composition is not impaired, but the hardness of the rubber crosslinked product may be too high. .
In the crosslinkable acrylic rubber composition of the present invention, magnesium oxide, calcium oxide, zinc oxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide are usually blended within a range that does not substantially impair the effects of the present invention. Acid acceptors other than calcium silicate (c) such as aluminum hydroxide and hydrotalcite may be used in combination. However, since the storage stability of the crosslinkable acrylic rubber composition is likely to be impaired, it is preferable not to add an acid acceptor other than calcium silicate (c).

(Crosslinking accelerator)
The crosslinkable acrylic rubber composition of the present invention preferably contains a crosslinking accelerator so as to exhibit an appropriate crosslinking rate.
Examples of the crosslinking accelerator include quaternary ammonium salts and quaternary phosphonium salts.
Examples of the quaternary ammonium salt include tetrabutylammonium hydrogen sulfate, tetrapropylammonium hydride oxide, tetrabutylammonium hydride oxide, trimethylphenylammonium chloride, benzyltriethylammonium chloride, benzyltriethylammonium chloride, benzyltributylammonium chloride, tetramethyl Ammonium chloride, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, n-dodecyltrimethylammonium chloride, n-dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide De, cetyl dimethyl ammonium chloride, 1,6-diaza - bicyclo (5.4.0) undecene-7-cetyl pyridinium sulfate, etc. trimethylbenzylammonium benzoate.
Examples of the quaternary phosphonium salt include triphenylbenzylphosphonium chloride, triphenylbenzylphosphonium bromide, tricyclohexylbenzylphosphonium chloride, tricyclohexylbenzylphosphonium bromide and the like. These crosslinking accelerators may be used alone or in combination of two or more.
The compounding quantity of a crosslinking accelerator is 0.1-5 mass parts normally with respect to 100 mass parts of acrylic rubber (a), Preferably it is 0.2-2 mass parts. When the blending amount of the crosslinking accelerator is too small, it is difficult to obtain a sufficient crosslinking rate. Conversely, when the blending amount is too large, the scorch stability may be impaired.

(Other ingredients)
The crosslinkable acrylic rubber composition of the present invention may contain various auxiliary materials added to a normal rubber composition in addition to the above-described ones depending on the purpose. Examples of such auxiliary materials include reinforcing materials, fillers, anti-aging agents, lubricants, plasticizers, stabilizers, pigments, etc. Examples of auxiliary materials are shown below. In addition, as a subsidiary material, it is not limited to what was illustrated below.

Examples of the reinforcing material include carbon black and silica. It is preferable to add a reinforcing material for the purpose of increasing the strength of the rubber cross-linked product.
The compounding quantity of a reinforcing material is 10-100 mass parts normally with respect to 100 mass parts of acrylic rubber (a), Preferably it is 30-60 mass parts.
When silica is blended as a reinforcing material, it is preferable to blend a silane coupling agent such as 3-glycidoxypropyltrimethoxysilane in order to improve the strength of the rubber cross-linked product. The compounding quantity of a silane coupling agent is 1-10 mass parts normally with respect to 100 mass parts of silicas. Moreover, when mix | blending a silica, carbon black can be mix | blended at 5 mass parts or less with respect to 100 mass parts of acrylic rubber (a) for the objective of coloring of a crosslinkable acrylic rubber composition.

（上記一般式（１）中、Ｙは−ＳＯ_２−を表す。Ｒ^ａおよびＲ^ｂはそれぞれ独立して、炭素数１〜３０の炭化水素基を表す。Ｚ^ａおよびＺ^ｂはそれぞれ独立して、化学的な単結合または−ＳＯ_２−を表す。ｎおよびｍはそれぞれ独立して、０または１であり、ｎおよびｍの少なくとも一方は１である。）Examples of the filler include calcium carbonate, kaolin clay, talc, and diatomaceous earth.
Examples of the antiaging agent include diphenylamine derivatives and phenylenediamine derivatives. Especially, it is preferable to mix | blend the compound shown by following General formula (1) as an anti-aging agent from a viewpoint of improving the heat resistance of a rubber crosslinked material.

(In the general formula (1), Y represents —SO ₂ —. R ^a and R ^b each independently represent a hydrocarbon group having 1 to 30 carbon atoms. Z ^a and Z ^b each independently represent And represents a chemical single bond or —SO ₂ —, wherein n and m are each independently 0 or 1, and at least one of n and m is 1.

Although it does not specifically limit as a C1-C30 hydrocarbon group which comprises R ^<a> and R < ^b >, For example, a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec An alkyl group having 1 to 30 carbon atoms such as -butyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group and n-decyl group; A cycloalkyl group having 3 to 30 carbon atoms such as propyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group; phenyl group, benzyl group, α-methylbenzyl group, α, α-dimethylbenzyl group, 4- And aryl groups having 6 to 30 carbon atoms such as a methylphenyl group, a biphenyl group, a naphthyl group, and an anthranyl group.

In the present invention, R ^a and R ^b are each independently preferably a linear or branched alkyl group having 2 to 20 carbon atoms or an aryl group having 6 to 30 carbon atoms, More preferably, it is a straight or branched alkyl group having 2 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms.

Preferable specific examples of the hydrocarbon group constituting R ^a and R ^b include an α-methylbenzyl group, an α, α-dimethylbenzyl group, a t-butyl group, a phenyl group, and a 4-methylphenyl group. Among these, an α, α-dimethylbenzyl group or a 4-methylphenyl group is more preferable, and an α, α-dimethylbenzyl group is more preferable. These can be independent of each other.

Further, in the above general formula (1), and each of Z ^a and Z ^b independently, chemical single bond or -SO 2 _-, it is preferably a chemical bond.

Further, in the general formula (1), n and m are each independently 0 or 1, and at least one of n and m is 1. In addition, it is preferable that both n and m are 1.
The compound described in the general formula (1) can be synthesized by the method described in International Publication WO2011 / 093443 Pamphlet.

  Although the compounding quantity of anti-aging agent is not specifically limited, It is 0.1-10 mass parts normally with respect to 100 mass parts of acrylic rubber (a), Preferably it is 0.5-5 mass parts.

Examples of the lubricant include paraffin, hydrocarbon resin, fatty acid, fatty acid amide, fatty acid ester, fatty acid alcohol and the like.
Examples of the plasticizer include phthalic acid derivatives, adipic acid derivatives, and polyether ester derivatives.
Examples of the stabilizer include phthalic anhydride, benzoic acid, N- (cyclohexylthio) phthalimide, and sulfonamide derivatives.
Examples of the pigment include titanium oxide, carbon black, and cyanine blue.

The preparation method of the crosslinkable acrylic rubber composition of this invention is not specifically limited, A well-known preparation method can be used. For example, a crosslinkable acrylic rubber composition can be prepared by kneading each compounding component with an open roll, an internal mixer or the like usually used in the rubber industry.
Since the crosslinkable acrylic rubber composition of the present invention is excellent in storage stability, even if time elapses after preparation of the crosslinkable acrylic rubber composition, it is easy to extrude. Is excellent, and can be suitably used for extrusion molding of hoses and the like.

The rubber cross-linked product of the present invention is formed by cross-linking the cross-linkable acrylic rubber composition.
The method for preparing the rubber cross-linked product is not particularly limited, and the cross-linkable acrylic rubber composition is formed using a molding / cross-linking machine normally used in the rubber industry such as extrusion molding, hot press, injection molding machine, steam can and the like. A rubber cross-linked product can be obtained by performing molding and cross-linking operations.

  The rubber cross-linked product of the present invention makes use of its characteristics, such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, well head seals, electrical / electronic device seals, pneumatic device seals, etc. Seals: cylinder head gaskets attached to the connecting part between the cylinder block and the cylinder head, rocker cover gaskets attached to the connecting part between the rocker cover and the cylinder head, connecting parts between the oil pan and the cylinder block or the transmission case Various gas gaskets such as an oil pan gasket mounted on a fuel cell, a fuel cell separator gasket mounted between a pair of housings sandwiching a unit cell including a positive electrode, an electrolyte plate, and a negative electrode, and a hard disk drive top cover gasket Various belts; fuel hose, turbo air hose, oil hose, radiator hose, heater hose, water hose, vacuum brake hose, control hose, air conditioner hose, brake hose, power steering hose, air hose, marine hose, riser, flow line Various hoses such as CVJ boots, propeller shaft boots, constant velocity joint boots, rack and pinion boots, etc .; cushioning materials, dynamic dampers, rubber couplings, air springs, damping materials such as vibration damping materials, rubber parts, etc. In particular, it is preferably used for extrusion products such as hoses used under severe high temperatures.

 EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated concretely, these do not limit this invention at all. In the following description, “part” means part by mass and “%” means mass% unless otherwise specified.

The following were used for the Example and the comparative example.
[Acrylic rubber]
As the acrylic rubber, one obtained by the following production method was used.
In a polymerization reactor, 5 parts of dioctylsulfosuccinate sodium salt, an anionic emulsifier, dissolved in 1250 parts of deionized water, 148.2 parts of ethyl acrylate, 148.2 parts of butyl acrylate, p-hydroxybenzoic acid 3.6 parts of vinyl acid was added and emulsified by stirring. Next, after raising the temperature to 70 ° C. in a nitrogen stream, 10 parts of a 10% aqueous solution of ammonium persulfate was added to initiate polymerization. After the start of polymerization, the polymerization temperature was gradually raised to 80 ° C., and the polymerization reaction was continued in the range of 80 to 82 ° C. for 2 hours. The polymerization conversion was almost 100%. The obtained latex and salt (aqueous solution state) as a salting-out agent were mixed to obtain a crumb-like acrylic rubber. Thereafter, the crumb-like acrylic rubber was washed with water and dried to obtain acrylic rubber.
The composition of the acrylic rubber is ethyl acrylate unit: 49.4%, butyl acrylate unit: 49.4%, vinyl p-hydroxybenzoate unit: 1.2%, Mooney viscosity (ML _{1 + 4} , 100 ° C.) Was 35.

[Reinforcing material]
Silica: Nipsil ER (Tosoh Silica Corporation)
Carbon black: Seast SO (Tokai Carbon Co., Ltd.)
[Acid acceptor]
Acid acceptor 1 (calcium silicate): AD850H200M (Tonda Pharmaceutical Co., Ltd.)
Acid acceptor 2 (calcium hydroxide): Caldic 2000 (Omi Chemical Co., Ltd.)
Acid acceptor 3 (magnesium oxide): MgO # 150 (Kyowa Chemical Industry Co., Ltd.)
Acid acceptor 4 (hydrotalcite): DHT-4A-2 (Kyowa Chemical Industry Co., Ltd.)
[Liquid fluoro rubber]
Daiel G-101 (Daikin Industries, Ltd.)
(It was a viscous liquid at room temperature, and its viscosity at 105 ° C. was 2500 cps.)
[Crosslinking accelerator]
Tetrabutylammonium hydrogen sulfate: TBAHS (Guangei Chemical Industry Co., Ltd.)
[Silane coupling agent]
3-Glycidoxypropyltrimethoxysilane [Lubricant]
Organosilicone compound: Sstructol WS280 (S & S Japan Co., Ltd.)

[Anti-aging agent]
Anti-aging agent 1 (4,4′-bis (α, α-dimethylbenzyl) diphenylamine): NOCRACK CD (Ouchi Shinsei Chemical Co., Ltd.)
Anti-aging agent 2: Compound shown in (2) below

Example 1
100 parts of acrylic rubber, 40 parts of silica, 8 parts of acid acceptor 1 (calcium silicate), 1 part of silane coupling agent, 3 parts of lubricant, 1 part of anti-aging agent 2 (compound shown in (2) above), liquid fluoro rubber 1.5 parts and 0.25 parts of a crosslinking accelerator were kneaded with an open roll to prepare a crosslinkable acrylic rubber composition. The storage stability of the resulting crosslinkable acrylic rubber composition and the physical properties of the rubber cross-linked product were measured as follows. The results are shown in Table 1.
[Storage stability of crosslinkable acrylic rubber composition]
The obtained crosslinkable acrylic rubber composition was allowed to stand for 3 days in an atmosphere of 40 ° C. and a relative humidity of 90%. Then, it wound around the roll and observed the shape of the sheet | seat surface when it took out to the sheet form, and evaluated it according to the following reference | standard.
◯: The sheet surface is smooth.
X: Concavities and convexities are generated on the surface of the sheet, and a clean sheet (sheet with a well-formed surface shape) is not obtained. (Such a thing cannot be formed into a clean hose shape (a hose shape with no irregularities on the surface) when formed into a hose shape using an extruder.)
[Physical properties of crosslinked rubber]
The obtained crosslinkable acrylic rubber composition was subjected to primary crosslinking (crosslinking conditions: 180 ° C., 15 minutes) using a hot press and then secondary crosslinking (crosslinking conditions: 180 ° C., 4 hours).
The obtained rubber cross-linked product was measured for hardness, tensile properties and air heat aging. The hardness was measured according to JIS K6253 (2006 type A), and the tensile properties were measured according to JIS K6251 (2004). In addition, air heat aging is measured by measuring the tensile strength, tensile elongation at break, and hardness after heat aging in accordance with JIS K6257 (2010) at 190 ° C under test conditions of 336 hours. From the measurement results, the initial tensile strength, the rate of change with respect to the tensile elongation at break, and the amount of change with respect to the initial hardness were evaluated.

(Examples 2 to 4 and Comparative Examples 1 to 3)
A crosslinkable acrylic rubber composition was prepared in the same manner as in Example 1 except that the amount of the acid acceptor, the type of the acid acceptor, the type and amount of the antioxidant were changed as shown in Table 1. About them, the storage stability of the crosslinkable acrylic rubber composition and the physical properties of the crosslinked rubber were measured in the same manner as described above. The results are shown in Table 1.

Table 1 shows the following.
Crosslinkable acrylic rubber compositions using acid acceptors (calcium hydroxide, magnesium oxide, hydrotalcite) that have been used conventionally have poor storage stability, whereas calcium silicate is used as the acid acceptor. The crosslinkable acrylic rubber composition (Examples 1 to 4) of the present invention is excellent in storage stability and heat resistance of the rubber cross-linked product.
Moreover, about Examples 1-4, the air heat aging property was measured until after 504 hours passed at 190 degreeC. As a result, the rubber cross-linked product of the crosslinkable acrylic rubber composition (Examples 1 to 3) using the anti-aging agent 2 (compound shown in the above (2)) was used as the anti-aging agent 1 (4,4′-bis ( The heat resistance was superior to that using (α, α-dimethylbenzyl) diphenylamine) (Example 4).
Further, in Examples 1 to 4, the storage stability of the crosslinkable acrylic rubber composition was measured by extending the standing period to 5 days or 7 days. In Examples 2 to 4, it was “x” after 5 days, but in Example 1, it was “◯” even after 7 days.

(Example 5)
100 parts acrylic rubber, 50 parts carbon black, 8 parts acid acceptor 1 (calcium silicate), 3 parts lubricant, 1 part anti-aging agent 2 (compound shown in (2) above), 1.5 parts liquid fluororubber, A crosslinkable acrylic rubber composition was prepared by kneading 0.25 parts of a crosslinking accelerator with an open roll. In the same manner as in Example 1, the storage stability of the crosslinkable acrylic rubber composition and the physical properties of the crosslinked rubber were measured. The results are shown in Table 2.

(Example 6 and Comparative Example 5)
A crosslinkable acrylic rubber composition was prepared in the same manner as in Example 5 except that the amount of the acid acceptor, the type of the acid acceptor, the type and amount of the antioxidant were changed as shown in Table 2. In the same manner as in Example 1, the storage stability of the crosslinkable acrylic rubber composition and the physical properties of the rubber cross-linked product were measured. The results are shown in Table 2.

Table 2 shows the following.
Even when carbon black is used as a reinforcing material, a conventionally used crosslinkable acrylic rubber composition using an acid acceptor (calcium hydroxide) is inferior in storage stability, but receives calcium silicate. The crosslinkable acrylic rubber composition of the present invention (Examples 5 and 6) used as an acid agent is excellent in storage stability, and the heat resistance of the rubber cross-linked product is equal to or higher.
The rubber cross-linked product of the crosslinkable acrylic rubber composition (Example 5) using the anti-aging agent 2 (compound shown in the above (2)) is the anti-aging agent 1 (4,4′-bis (α, α). -Dimethylbenzyl) diphenylamine) (Example 6) is superior in heat resistance.

Claims (8)

Containing acrylic rubber (a) containing phenolic hydroxyl group-containing monomer units 0.1 to 10% by mass, liquid fluororubber (b), and calcium silicate (c),
The content of the liquid fluorine rubber (b) is, relative to the acrylic rubber (a) 100 parts by weight, Ri 0.4 to 50 parts by mass der,
The content of calcium silicate (c) are the relative acrylic rubber (a) 100 parts by weight, 0.5 to 20 parts by mass der Ru crosslinkable acrylic rubber composition. The crosslinkable acrylic rubber composition according to claim 1, wherein the content of the (meth) acrylic acid ester monomer unit in all monomer units constituting the acrylic rubber (a) is 60 to 99.9 mass%. object. Furthermore, the crosslinkable acrylic rubber composition of Claim 1 or 2 containing the compound shown by following General formula (1) as anti-aging agent.

(In the general formula (1), Y represents —SO ₂ —. R ^a and R ^b each independently represent a hydrocarbon group having 1 to 30 carbon atoms. Z ^a and Z ^b each independently represent And represents a chemical single bond or —SO ₂ —, wherein n and m are each independently 0 or 1, and at least one of n and m is 1. The crosslinkable acrylic rubber composition according to any one of claims 1 to 3 , further comprising silica as a reinforcing material. The crosslinkable acrylic rubber composition according to any one of claims 1 to 3 , further comprising carbon black as a reinforcing material. Furthermore, the crosslinkable acrylic rubber composition in any one of Claims 1-5 containing a crosslinking accelerator. Rubber cross-linked product obtained by crosslinking a crosslinkable acrylic rubber composition according to any one of claims 1-6. The rubber cross-linked product according to claim 7 which is a hose.