JPH08100084A - Vulcanizable acrylic rubber composition - Google Patents

Abstract

PURPOSE: To obtain a vulcanizable acrylic rubber composition which retains the satisfactory heat and oil resistances inherent in acrylic rubbers and has an excellent cold resistance by compounding an acrylic rubber with a specific highly saturated, nitrile copolymer rubber and an organic peroxide. CONSTITUTION: This rubber composition comprises 100 pts.wt. rubber blend consisting of about 20-80wt.% acrylic rubber and about 80-20wt.% highly saturated nitrile copolymer rubber obtained by hydrogenating a copolymer of an unsaturated nitrile monomer, an unsaturated carboxylic ester monomer and a conjugated diene monomer, and about 0.1-10 pts.wt. organic peroxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vulcanizable acrylic rubber composition having excellent cold resistance and mechanical strength.

[0002]

2. Description of the Related Art Acrylic rubber is a polymer containing acrylic acid ester as a main component and is generally known as a rubber having excellent heat resistance, oil resistance and ozone resistance, and is used for oil seals, O-rings and packings. It is used as a molding material. In recent years, with the increasing performance of automobiles, the required performance cannot be satisfied at the heat resistance, oil resistance, and cold resistance of conventional rubber materials, and the development of rubber with more advanced functions is required. Has been. Particularly in the use of a sealing material, it is strongly required to further improve cold resistance without impairing heat resistance, compression set, and water resistance.

By the way, it is common to use an active chlorine group-containing monomer as the crosslinkable monomer of the acrylic rubber. However, the vulcanized product has compression set resistance or metal corrosion resistance. However, various other crosslinkable monomers have also been studied. For example, conjugated diene-based monomers such as butadiene and pentadiene, and non-conjugated diene-based monomers such as dicyclopentenyl acrylate are known, and can be vulcanized using sulfur or organic peroxide. . Of these, crosslinking with an organic peroxide is effective for maintaining heat resistance, and the present inventors have developed an acrylic rubber suitable for a crosslinking reaction using an organic peroxide and have already reported ( Japanese Patent Application No. 5-86757
issue).

However, as a result of further study,
It has been found that further improvements are needed to improve mechanical strength and cold resistance. . In addition, JP-A-2-3938
Japanese Patent Laid-Open Publication No. 1994-242242 reports that blending with a saturated nitrile rubber is effective as a method for improving the mechanical strength of acrylic rubber, but improvement in cold resistance is insufficient.

[0005]

Therefore, as a result of earnest studies, the present inventors have found that by incorporating a saturated nitrile rubber in which a specific unsaturated carboxylic acid ester has been copolymerized, the original good heat resistance of acrylic rubber is obtained. It was also found that a rubber composition having excellent cold resistance can be obtained without impairing oil resistance and the like, and the present invention was completed based on this finding.

[0006]

Thus, according to the present invention, the acrylic rubber (A), the unsaturated nitrile-based monomer, the unsaturated carboxylic acid ester-based monomer, and the conjugated diene-based monomer unit are used. Provided is a vulcanizable acrylic rubber composition comprising a nitrile group-containing highly saturated copolymer rubber (B) obtained by hydrogenating a copolymer and an organic peroxide (C).

The acrylic rubber (A) used in the present invention is
(A) Acrylic ester having a C1-8 alkyl group or (b) Acrylic ester having a C1-8 alkyl group and a C1-8 alkoxy group 9
0-99.5% by weight, preferably 95-99% by weight
And (c) a crosslinkable monomer of 0.05 to 10% by weight, preferably 1 to 5% by weight, as a constituent unit, a polyacrylic acid ester system having a Mooney viscosity of 10 to 90, preferably 30 to 60. It is a copolymer.

Examples of the acrylic ester having a carbon number of 1 to 8 as the component (a) include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate and octyl acrylate. Among them, alkyl acrylate having an alkyl group having 2 to 4 carbon atoms is preferable.

Examples of the component (b) having an alkyl group and an alkoxy group having 1 to 8 carbon atoms include methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate and butoxyethyl acrylate.

These may be used alone or in combination of two or more. Especially when the component (a) and the component (b) are used in combination, an acrylic rubber having a good balance of heat resistance and weather resistance can be obtained. In that case, the ratio (% by weight) of the component (a) and the component (b) is (a) /
(B) = 90 / 10-40 / 60, preferably 8/20
~ 50/50.

The cross-linking monomer as the component (c) is an unsaturated compound known as a cross-linking component of an acrylic rubber that cross-links an organic peroxide, and is not particularly limited. Specifically, cyclic conjugated dienes such as cyclopentadiene; unsaturated norbornene compounds such as ethylidene norbornene and vinylidene norbornene; linear conjugated dienes such as isoprene and butadiene; 2-butenyl acrylate, 3-methyl-2-butenyl acrylate , Alkenyl acrylates such as 3-methyl-2-pentyl acrylate, 3-methyl-2-hexenyl acrylate and their methacrylates; tetrahydro-3-methylbenzyl acrylate, tetrahydro-3-methylbenzyl methacrylate, tetrahydrobenzyl acrylate, tetrahydrobenzyl methacrylate Alkyl-substituted tetrahydrobenzyl acrylate, etc .; and further include dicyclopentenyl acrylate, allyl acrylate, triisocyanurate, etc. Door can be. If the amount of these compounds used is too small, the acrylic rubber does not undergo a sufficient crosslinking reaction, and if it is too large, the number of crosslinking points becomes too large and the rubber elasticity decreases. Among these compounds, the use of alkyl-substituted tetrahydrobenzyl acrylate is particularly preferable because the compression strain resistance of the vulcanized rubber is dramatically improved.

Further, an ethylenically unsaturated monomer can be copolymerized within a range that does not impair the mechanical properties, oil resistance and cold resistance of the acrylic rubber. As a concrete example,
Acrylonitrile, vinyl acetate, styrene, α-methylstyrene, acrylamide, vinyl chloride, acrylic acid,
Examples thereof include monovinyl-based monomers such as acrylic acid ester and polyalkylene glycol acrylic acid ester; and monovinylidene-based monomers such as methyl methacrylate, ethyl methacrylate, methacrylonitrile, and vinylidene chloride. The amount of the monoethylenically unsaturated monomer used is 30% by weight or less based on all monomer units.

The acrylic rubber used in the present invention can be obtained by polymerizing the above-mentioned monomer mixture by a known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization and bulk polymerization using a commonly used radical initiator. Is obtained by The polymerization can be carried out by batch polymerization or by adding one or more kinds of monomer components continuously or intermittently during the polymerization. The polymerization temperature is in the range of -10 to 100 ° C, preferably 2 to 80 ° C.

The nitrile group-containing highly saturated copolymer rubber (B) used in the present invention is (a) unsaturated nitrile monomer 10
To 40% by weight and (B) unsaturated carboxylic acid ester monomer 1 to 80% by weight, preferably 15 to 60% by weight, more preferably 20 to 40% by weight and (C) conjugated diene monomer 10 A nitrile group-containing highly saturated copolymer rubber having an iodine value of 120 or less, preferably 80 or less, and a Mooney viscosity of 15 to 150 is obtained by hydrogenating a copolymer of 90 to 90% by weight.

Examples of the unsaturated nitrile monomer (a) include acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile.

(B) Examples of unsaturated carboxylic acid ester type monomers include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isononyl acrylate, n- Hexyl acrylate, 2-methyl-pentyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate, ethyl methacrylate, and other acrylates and methacrylates having an alkyl group having about 1 to 18 carbon atoms; methoxymethyl acrylate. , Methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, ethoxypropyl acrylate, methoxyethoxy acrylate Acrylate, ethoxybutoxy acrylate, and other acrylates having an alkoxyalkyl group having about 2 to 12 carbon atoms; α and β-cyanoethyl acrylate, α, β and γ-cyanopropyl acrylate, cyanobutyl acrylate, cyanohexyl acrylate, and cyanooctyl. 2 to 1 carbon atoms such as acrylate
Acrylate having about 2 cyanoalkyl groups; 2-
Acrylate having hydroxyalkyl group such as hydroxyethyl acrylate, hydroxypropyl acrylate; monoethyl maleate, dimethyl maleate, dimethyl fumarate, diethyl fumarate, di-n-fumarate.
Unsaturated dicarboxylic acid mono- and dialkyl esters such as butyl, di-2 ethylhexyl fumarate, dimethyl itaconic acid, diethyl itaconic acid, di-n-butyl itaconic acid, di-2 ethylhexyl itaconic acid; dimethylaminomethyl acrylate, diethylaminoethyl Amino group-containing unsaturated carboxylic acid ester-based monomers such as acrylate, 3- (diethylamino) -2 hydroxypropyl acrylate and 2,3-bis (difluoroamino) propyl acrylate; trifluoroethyl acrylate, tetrafluoropropyl acrylate, penta Fluoropropyl acrylate, heptafluorobutyl acrylate, octafluoropentyl acrylate, nonafluoropentyl acrylate, undecafluorohexyl acrylate, Pentadecafluorooctyl acrylate, heptadecafluorononyl acrylate, heptadecafluorodecyl acrylate, nonadecafluorodecyl acrylate, trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, octafluoropentyl methacrylate, dodecafluorohebutyl methacrylate, pentadecafluorooctyl acrylate Acrylates and methacrylates having fluoroalkyl groups such as hexadecafluorononyl methacrylate; Fluorine-substituted benzyl acrylates and methacrylates such as fluorobenzyl acrylate, difluorobenzyl acrylate, fluorobenzyl methacrylate, difluorobenzyl methacrylate; Vinyl, trifluoromethyl vinyl ether, trifluoroethyl vinyl ether, perfluoropropyl vinyl ether, fluoroalkyl vinyl ether such as perfluoro hexyl vinyl ether, o- or p- trifluoromethyl styrene, pentafluorobenzoic acid vinyl,
Examples thereof include fluorine-containing vinyl-based monomers such as difluoroethylene and tetrafluoroethylene.

(C) 1,3 as the conjugated diene monomer
-Butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene and the like.

In addition to these monomers, a part of the total amount of the monomers is a vinyl-based monomer such as styrene and vinylpyridine, vinylnorbornene, dicyclopentadiene, 1 and 1 within a range not impairing the gist of the present invention. Of the non-conjugated diene-based monomers, such as 4,4-hexadiene, they may be replaced with monomers copolymerizable with the above monomers.

The nitrile group-containing highly saturated copolymer rubber used in the present invention is a rubber obtained by copolymerizing the above-mentioned monomers by a usual polymerization method and a rubber obtained by hydrogenating a conjugated diene monomer unit of this rubber. Is. Among them, acrylonitrile-
Hydrogenated unsaturated carboxylic acid ester-butadiene copolymer rubber is preferable, and further, unsaturated unsaturated carboxylic acid ester copolymerized with unsaturated dicarboxylic acid mono- or dialkyl ester is most suitable.

The hydrogenation method is not particularly limited, and hydrogenation can be carried out according to a conventional method. As the catalyst used in the hydrogenation, for example, palladium complex, rhodium or ruthenium compound can be used (for example, JP-A-3-52405,
JP 62-125858A, JP 62-429A
37, JP-A-1-45402, JP-A-1-45402
45403, JP-A-1-45404, JP-A-1-45405, etc.).

The organic peroxide used in the present invention is not particularly limited as long as it can be used in the usual peroxide vulcanization of rubber. Examples include dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, benzoyl peroxide, 2,5-
Dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (benzoylperoxy) hexyne, α, α'-bis (t-butylperoxy-m -Isopropyl) benzene and the like. Of these, di-t-butyl peroxide is preferable. These organic peroxides are used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of rubber.

Further, examples of the cross-linking aid include unsaturated compounds used in ordinary organic peroxide vulcanization. Examples thereof include ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, polyfunctional methacrylate monomers, N, N'-m-phenylene dimaleimide, triallyl isocyanurate and the like. Of these, triallyl isocyanurate is preferable from the viewpoint of vulcanization properties. The addition amount of these is in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of rubber. The vulcanizable acrylic rubber composition of the present invention is an acrylic rubber (A) 20-8.
0% by weight, preferably 30 to 70% by weight, 80 to 20% by weight of the nitrile group-containing highly saturated copolymer rubber (B), preferably 70 to 30% by weight, based on 100 parts by weight of a rubber mixture, organic It is composed of 0.1 to 10 weight parts of peroxide.

When the blending amount of the nitrile group-containing highly saturated copolymer rubber is excessively small, the mechanical strength is lowered and the cold resistance is not improved. Further, if the compounding amount of the highly saturated copolymer rubber containing a tolyl group is excessively high, the heat resistance will be decreased, which is not preferable.

The method for preparing such a vulcanizable rubber composition is not particularly limited, and can be prepared by mixing using a kneader such as a roll or Banbury, which is usually used in the field of rubber technology.

Further, the vulcanizable acrylic rubber composition of the present invention contains a reinforcing agent such as carbon black and silica which are usually used in the rubber industry, a filler, a processing aid, a plasticizer, an antiaging agent and the like. Various compounding agents can be compounded.

The curing temperature of the vulcanizable rubber composition is about 140.
~ 220 ° C, but vulcanization temperature about 160-2
00 ° C is preferred. The vulcanization time depends on the temperature,
Generally, it is 30 seconds to 1 hour.

The vulcanized product of the acrylic rubber composition of the present invention is
It has excellent cold resistance and mechanical strength, as well as oil resistance,
Since it has an excellent balance of water resistance and compression set, it is particularly useful for applications in many fields where cold resistance is required. Examples of such applications include various rubber parts such as gaskets, hoses, conveyor belts, packings, bearing seals and oil seals.

The present invention will be specifically described with reference to the following examples. Parts and% are based on weight unless otherwise specified.

(Examples 1 to 5 and Comparative Examples 1 and 2) (Production Example of Acrylic Rubber) A thermometer, a stirrer, a nitrogen introducing tube and a decompressor were installed in a 2 liter separable flask and shown in Table 1. Polymerization formulations (I) and (II) were used to polymerize mixtures of each monomer for the two compositions listed in Table 2. As the crosslinkable monomer, tetrahydrobenzyl methacrylate and dicyclopentenyl acrylate were used. First, after charging each component of (I) into a flask, the pH of the mixture in the flask was adjusted to 7, the temperature in the system was set to 5 ° C. with stirring, and deaeration and nitrogen substitution were repeated.
Sufficiently remove oxygen in the system. Then, each component of (II) was added to initiate polymerization. The polymerization temperature is 5 ° C. and the reaction time is about 16 hours. The polymerization conversion rate was in the range of 95 to 98%. After completion of the polymerization, the polymerization product was salted out, washed thoroughly with water, and then dried in a vacuum dryer for 24 hours to obtain target acrylic rubbers A and B.

[0030]

[Table 1]

[0031]

[Table 2]

Using the above-obtained acrylic rubbers A and B, a blend with a nitrile group-containing highly saturated copolymer rubber (hereinafter referred to as HNBR) was prepared according to the blend formulation shown in Table 3. Preparation of the compound was carried out on an oven roll heated to 50 to 60 ° C. The HNB used
R is as follows.

HNBR1: Amount of bound acrylonitrile 15
%, Amount of bound carboxylic acid ester 20%, iodine value 18,
Mooney viscosity 95. HNBR2: bound acrylonitrile amount 25%, bound carboxylic acid ester amount 40%, iodine value 18, Mooney viscosity 95. HNBR3: bound acrylonitrile amount 35%, bound carboxylic acid ester amount 0%, iodine value 35, Mooney viscosity 8
5. On the other hand, the obtained compound was press-vulcanized at 170 ° C. for 20 minutes, and further heat-treated in a gear oven at 170 ° C. for 4 hours to obtain a vulcanized product. Regarding these vulcanizates, JISK-
Vulcanization characteristics were measured according to 6301, and further an air heating aging test, a compression set test, and a cold resistance measurement test were performed. Table 3 shows the obtained results.

[0034]

[Table 3]

The formulations used in Table 3 are as follows: * 1 Organic peroxide, 1,3-bis (tertiary butylperoxyisopropyl) benzene manufactured by Hercules * 2 Diphenylamine-based antioxidant manufactured by Uniroyal

From Table 3, the vulcanized product of the vulcanizable acrylic rubber composition of the present invention has further improved compressive strain resistance while maintaining the heat resistance originally possessed by conventional acrylic rubber vulcanizates. It is also found that they are excellent in cold resistance and mechanical strength.

Specific embodiments of the present invention are as follows. (Claim 1) Hydrogenated copolymer of acrylic rubber (A), unsaturated nitrile-based monomer, unsaturated carboxylic acid ester-based monomer and conjugated diene-based monomer, resulting in high saturation of nitrile group-containing A vulcanizable acrylic rubber composition obtained by blending a copolymer rubber (B) and an organic peroxide (C). (1) Nitrile obtained by hydrogenating a copolymer of acrylic rubber (A) (20 to 80 parts by weight), an unsaturated nitrile monomer, an unsaturated carboxylic acid ester monomer and a conjugated diene monomer. 80 to 20 parts by weight of the group-containing highly saturated copolymer rubber (B), and 100 parts by weight of the total amount of the acrylic rubber (A) and the nitrile group-containing highly saturated copolymer rubber (B), based on the organic peroxide. The vulcanizable acrylic rubber composition according to claim 1, which comprises 0.1 to 10 parts by weight of (C). (2) The acrylic rubber (A) comprises (a) an acrylate ester having an alkyl group having 1 to 8 carbon atoms and (b) 1 carbon atom.
2. A polyacrylic acid ester-based copolymer having an acrylic acid ester having an alkyl group of 8 to 8 and an alkoxy group of 1 to 8 carbon atoms and (c) a crosslinkable monomer as a constituent unit. Sulfurizable acrylic rubber composition. (3) The acrylic rubber (A) comprises (a) an acrylate ester having an alkyl group having 1 to 8 carbon atoms and (b) 1 carbon atom.
To 9 to 99.5% by weight of an acrylic acid ester having an alkyl group having 8 to 8 and an alkoxy group having 1 to 8 carbon atoms, and (c) an acrylate having an alkyl-substituted tetrahydrobenzyl group 0.05 to 10% by weight The vulcanizable acrylic rubber composition according to claim 1, which is a copolymer of (4) The nitrile group-containing highly saturated copolymer rubber (B) is
(A) 10 to 40% by weight of an unsaturated nitrile monomer, (b) 1 to 80% by weight of an unsaturated carboxylic acid ester monomer, and (c) 60 to 90% by weight of a conjugated diene monomer. The vulcanizable acrylic rubber composition according to claim 1, which is obtained by hydrogenating a copolymer. (5) The vulcanizable acrylic rubber composition according to claim 1, wherein the acrylic rubber (A) has a Mooney viscosity of 10 to 90, and the nitrile group-containing highly saturated copolymer rubber (B) has a Mooney viscosity of 50 to 150. (6) The vulcanizable acrylic rubber composition according to claim 1, wherein the nitrile group-containing highly saturated copolymer rubber (B) has an iodine value of 120 or less. (7) The vulcanizable acrylic rubber composition according to claim 1, wherein the nitrile group-containing highly saturated copolymer rubber (B) is obtained by hydrogenating an acrylonitrile-unsaturated dicarboxylic acid dialkyl ester-butadiene copolymer rubber. (8) The vulcanization of claim 1, wherein the nitrile group-containing highly saturated copolymer rubber (B) is obtained by hydrogenating acrylonitrile-unsaturated dicarboxylic acid dialkyl ester-butadiene copolymer rubber containing 10 to 40% by weight of bound acrylonitrile. Acrylic rubber composition. (9) The vulcanizable acrylic rubber composition according to claim 1, wherein the organic peroxide is di-t-butyl peroxide. (Claim 2) The vulcanizable acrylic rubber composition according to claim 1, which is a sealing material. Various rubber parts such as lu-seal are included.

[0038]

Thus, the vulcanizable acrylic rubber composition of the present invention has further improved cold resistance without impairing the oil resistance, water resistance, compression set and the like of conventional acrylic rubber. It is useful as a rubber material. The vulcanized product of the acrylic rubber composition of the present invention is excellent in cold resistance and mechanical strength, and is further excellent in balance of oil resistance, water resistance, compression set, and the like, so cold resistance is particularly required. It is useful for applications in many fields. Examples of such applications include various rubber parts such as gaskets, hoses, conveyor belts, packings, bearing seals and oil seals.

Claims (2)

[Claims] 1. A nitrile group-containing product obtained by hydrogenating a copolymer of acrylic rubber (A), an unsaturated nitrile monomer, an unsaturated carboxylic acid ester monomer and a conjugated diene monomer unit. A vulcanizable acrylic rubber composition comprising a highly saturated copolymer rubber (B) and an organic peroxide (C). 2. The vulcanizable acrylic rubber according to claim 1, which is a sealing material.