JPH06248151A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition which need not be subjected to secon dary vulcanization because it is excellent in oil resistance, low-temperature properties and mechanical properties and has a vulcanization rate and can realize sufficiently excellent properties by primary vulcanization alone. CONSTITUTION:This rubber composition comprises an ethylene/(meth)acrylate copolymer rubber (A) free from crosslinking sites other than ethylene units, an acrylic rubber (B) vulcanizable with an organic peroxide, an organic peroxide (C) and at least one crosslinking aid (D) selected from the group consisting of a sulfur-containing compound, and allyl compound, a maleimide compound and a quinone compound, wherein the (A)/(B) weight ratio is 5/95-95/5, the (C)/((A)+(B)) weight ratio is 0.1/100-10/100, and the (D)/((A)+(B)) weight ratio is 0.1/100-10/100.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition. More specifically, the present invention is excellent in oil resistance, cold resistance and mechanical properties, and does not require secondary vulcanization due to its high vulcanization speed, and rubber capable of achieving sufficiently excellent physical properties only by primary vulcanization. It relates to a composition.

[0002]

2. Description of the Related Art As a rubber composition having excellent oil resistance, cold resistance and mechanical properties, a rubber composition technology using ethylene- (meth) acrylic acid ester-third component copolymer rubber and acrylic rubber is known. Yes (for example, Japanese Patent Laid-Open No. 1-9
2251). However, this rubber composition has a problem that the vulcanization rate is slow and secondary vulcanization is required for a long time in order to obtain good physical properties, which is disadvantageous particularly from the viewpoint of industrial implementation. Was there.

[0003]

In view of the present situation, the problem to be solved by the present invention is that oil resistance, cold resistance and mechanical properties are excellent, and secondary vulcanization is not required because of high vulcanization speed. Therefore, the present invention is to provide a rubber composition that can realize sufficiently excellent physical properties only by primary vulcanization.

[0004]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the present invention is a rubber composition containing the following components (A) to (C), wherein the weight ratio of (A) / (B) is 5:
/ 95 to 95/5, (C) / ((A) + (B))
The weight ratio of 0.1 / 100 to 10/100,
The weight ratio of (D) / ((A) + (B)) is 0.1 / 100.
It is related to the rubber composition of 10/100. Component (A): Ethylene- (meth) acrylic acid ester-based copolymer rubber having no crosslinking sites other than ethylene units (B) Component: Acrylic rubber vulcanizable with organic peroxide (C) Component: Organic peroxide Oxide (D) component: at least one crosslinking aid selected from the group consisting of sulfur-containing compounds, allyl compounds, maleimide compounds and quinone compounds

The details will be described below. The component (A) of the present invention is an ethylene- (meth) acrylic acid ester-based copolymer rubber having no crosslinking sites other than ethylene units. The (meth) acrylic acid ester means an acrylic acid ester and / or a methacrylic acid ester. Acrylic acid ester or methacrylic acid ester is an ester obtained from acrylic acid or methacrylic acid and alcohol. Alcohol has 1 to 1 carbon atoms
Alcohol of 8 is preferred. Specific examples of the (meth) acrylic acid ester include methyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert.
-Butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate and the like can be mentioned. As the (meth) acrylic acid ester, one kind thereof may be used alone, or two or more kinds thereof may be used in combination.

The content ratio of ethylene and (meth) acrylic acid ester in the (A) ethylene- (meth) acrylic acid ester type copolymer rubber is 45/55 to 85 in terms of a molar ratio of ethylene / (meth) acrylic acid ester. / 15 is preferable, and more preferably 60/40 to 80/20.
If the proportion of ethylene is too high, the crystallinity of the resulting copolymer may be high, the rubber elasticity may be reduced, and the oil resistance may be poor. On the other hand, if the proportion of the (meth) acrylic acid ester is too large, the brittle point becomes high and it may be difficult to use at low temperature. The amount of (meth) acrylic acid ester when two or more (meth) acrylic acid esters are used in combination is based on the total amount of each (meth) acrylic acid ester. The (A) ethylene- (meth) acrylic acid ester-based copolymer rubber of the present invention contains, in addition to the above-mentioned ethylene and (meth) acrylic acid ester, another monomer copolymerizable therewith. May be Examples of the monomer include isobutylene, styrene and its derivatives, vinyl acetate, halogenated olefins such as tetrafluoroethylene and hexafluoropropylene, and the like.

The (A) ethylene- (meth) acrylic acid ester-based copolymer rubber of the present invention must be an ethylene- (meth) acrylic acid ester-based copolymer rubber having no crosslinking sites other than ethylene units. . When an ethylene- (meth) acrylic acid ester-based copolymer rubber having a cross-linking site other than the ethylene unit is used without the present invention, the resulting rubber composition has poor compression strain characteristics. Here, examples of the monomer that becomes a crosslinking site other than the ethylene unit include unsaturated glycidyl such as glycidyl acrylate, glycidyl methacrylate, itaconic acid diglycidyl ester, butene tricarboxylic acid triglycidyl ester, and p-styrenecarboxylic acid glycidyl ester. Epoxy group-containing monomers such as unsaturated glycidyl ethers such as esters, vinyl glycidyl ethers, allyl glycidyl ethers and methacryl glycidyl ethers; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, 2-norbornene-5-carboxylic acid Examples thereof include carboxyl group-containing monomers such as cinnamic acid, maleic anhydride, and monomethyl maleate.

The (A) ethylene- (meth) acrylic acid ester-based copolymer rubber of the present invention is JIS K67.
The melting index at 190 ° C. defined by 91 is usually 0.5 to 5
Those in the range of 00 g / 10 minutes, preferably 0.5 to 50 g / 10 minutes are used.

The (A) ethylene- (meth) acrylic acid ester-based copolymer rubber of the present invention can be produced by a conventional method such as bulk polymerization, emulsion polymerization or solution polymerization using a free radical initiator. A typical polymerization method is the method described in Japanese Examined Patent Publication No. 46-45085, in the presence of a polymerization initiator that produces free radicals, a pressure of 500 kg / cm ² or more, and a temperature of 40 to 300 ° C.
It can be manufactured under the conditions of.

The component (B) of the present invention is an acrylic rubber vulcanizable with an organic peroxide. Here, the acrylic rubber contains at least one monomer selected from acrylic acid ester, methacrylic acid ester and alkoxyalkyl acrylate as a main constituent.

Examples of acrylic acid esters are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isobutyl acrylate, n-pentyl acrylate, isoamyl acrylate, n-hexyl. Examples thereof include acrylate, 2-methylpentyl acrylate, n-decyl acrylate, n-dodecyl acrylate, n-tetradecyl acrylate, n-octadecyl acrylate, and n-eicosyl acrylate. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, n-dodecyl methacrylate, n-octadecyl methacrylate and the like. Examples of the alkoxyalkyl acrylate include alkoxyalkyl acrylates having an alkoxy group and an alkylene group such as methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, ethoxypropyl acrylate, butoxyethyl acrylate, and methoxyethoxyethyl acrylate. These monomers may be used alone or in combination of two or more.

In the present invention, from the viewpoint of balancing the mechanical strength characteristics, the low temperature characteristics and the oil resistance characteristics, an acrylate ester having an alkyl group having 1 to 8 carbon atoms or an alkyl group or an alkylene group having 1 carbon atoms. It is preferable to use acrylates of alkoxy acrylates of 4 to 4, and specific examples thereof include ethyl acrylate, propyl acrylate, butyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate and the like.

In the (B) acrylic rubber of the present invention,
In addition to the above monomers, other monomers copolymerizable with the above monomers may be used in combination. As the copolymerizable monomer,
For example, vinyl aromatic compounds such as styrene, α-methylstyrene and vinyltoluene; vinyl such as acrylonitrile and methacrylonitrile and vinylidene nitrile; vinyl monomers having a hydroxyl group such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; 2 -Cyano-substituted vinyl monomers such as cyanoethyl acrylate, 3-cyanopropyl acrylate and 4-cyanobutyl acrylate; vinyl such as acrylamide, methacrylamide, N-methylolacrylamide and vinylidene amide; vinyl acetate, vinyl propionate, vinyl butyrate, etc. Vinyl esters; conjugated dienes such as butadiene and isoprene, and the like. These monomers may be used alone or in combination of two or more. .

The acrylic rubber (B) of the present invention must be an acrylic rubber vulcanizable with an organic peroxide.
Here, in order to be vulcanizable with an organic peroxide,
It is necessary to contain a monomer having reactivity with an organic peroxide as its constitutional unit, and as a monomer having reactivity with such an organic peroxide, two or more fats can be contained in one molecule. Examples thereof include monomers having a group unsaturated group. That is, in this case, when one aliphatic unsaturated group is used for the reaction with the acrylic rubber as the component (B), the other aliphatic unsaturated group remains without being used for the reaction, and this residual The aliphatic unsaturated group participated in the crosslinking reaction by the organic peroxide,
Effective cross-linking is achieved. Examples of such a monomer having two or more aliphatic unsaturated groups in one molecule include ethylidene norbornene, methylidene norbornene, dicyclopentadiene and the like, as well as a monomer having an aliphatic unsaturated bond bonded to a silicon atom. Examples thereof include monomers, and particularly preferable are monomers having a silicon-bonded vinyl group. As the monomer having a vinyl group bonded to silicon, acrylate, methacrylate,
Examples include monomers in which vinyl silicon groups are bonded to styrene and the like. The silicon-bonded vinyl group in these monomers has poor reactivity with the acrylic acid esters used as a constituent component in the component (B), and therefore the vinyl group remains in the acrylic rubber (B). The residual vinyl group participates in the crosslinking reaction by the organic peroxide, and effective crosslinking is realized. The content of the monomer that reacts with the organic peroxide in the acrylic rubber (B) is preferably 0.1 to 10 mol%.

An acrylic rubber having an ethylene unit can also be used as the acrylic rubber vulcanizable with the (B) organic peroxide of the present invention. In this case, the amount of the ethylene unit in the acrylic rubber is 40 mol. % Or less is preferable.

The acrylic rubber (B) of the present invention can be obtained by copolymerizing each of the above-mentioned monomers by ordinary emulsion polymerization, but an acrylic rubber produced by a method other than this may be used.

The component (C) of the present invention is an organic peroxide. As the organic peroxide, those usually used for crosslinking rubber can be used, and examples thereof include di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α-bis (t-butyl). Peroxyisopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,
1,1-bis (t-butylperoxy) -3,3,5-
Trimethylcyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, 2,2-bis (t-
Butyl peroxy) octane and the like.

The component (D) of the present invention is a sulfur-containing compound,
It is at least one crosslinking aid selected from the group consisting of allyl compounds, maleimide compounds and quinone compounds. Examples of the sulfur-containing compound include sulfur, dipentamethylene thiuram and tetrasulfide, and examples of the allyl compound include divinylbenzene, diallyl phthalate and
Examples thereof include triallyl isocyanurate, triallyl trimellitate, and triallyl tricyanurate, maleimide compounds include m-phenylene bismaleimide, toluylene bismaleimide, and the like, and quinone compounds include quinone dioxime and dibenzoyl. -P
-Quinone dioxime and the like.

In the present invention, the above (A) to (D).
It is necessary to use the components in specific proportions. (A) /
The weight ratio of (B) is 5/95 to 95/5, preferably 10
/ 90 to 90/10. If the (A) component in (A) / (B) is too small, the cold resistance and mechanical properties are poor, while if the (A) component is too large, the oil resistance is poor.
The weight ratio of (C) / ((A) + (B)) is 0.1 / 10.
0 to 10/100, preferably 2/100 to 6/100
Is. When the component (C) in (C) / ((A) + (B)) is too small, the cross-linking density is insufficient and the resulting vulcanized rubber has poor mechanical strength, while the component (C) is too large. Causes problems such as foaming during vulcanization molding. (D) /
The weight ratio of ((A) + (B)) is 0.1 / 100 to 10 /.
100, preferably 1/100 to 5/100.
When the component (D) in (D) / ((A) + (B)) is too small, the crosslinking density is insufficient, and the mechanical strength and compression set of the resulting vulcanized rubber are poor, while the component (D) is used. If there is too much, the scorch will be too fast.

The method for obtaining the rubber composition of the present invention is, for example, as follows. Roll components (A) to (D) of the present invention and optionally known antioxidants, vulcanization accelerators, processing aids, zinc white, stearic acid, reinforcing agents, fillers, softeners, etc. The rubber composition of the present invention can be obtained by mixing using a conventional kneader such as a Bunbury. The rubber composition is molded into a shape suitable for the purpose, and is subjected to a vulcanization step to obtain a molded vulcanized rubber composition. Vulcanization is usually 120 ° C. or higher, preferably 150 to 2
It is carried out at a temperature of 20 ° C. for about 1 to 30 minutes.

The vulcanized rubber composition obtained by vulcanizing the rubber composition of the present invention includes various sealing materials (gasket, O, etc.).
-Rings, packing, oil seals, etc.), hoses,
It can be used for belts and rolls.

[0022]

EXAMPLES The present invention will be described with reference to Examples and Comparative Examples. Examples 1 to 7 and Comparative Examples 1 to 7 60 parts by weight of EFE black (SEATO SO manufactured by Tokai Carbon Co., Ltd.) and the composition shown in Table 1 (the parts by weight are the total amount of the components (A) and (B)). The same applies hereinafter), 1 part by weight of stearic acid, Nogard 44
2 parts by weight of 5 (amine-based anti-aging agent manufactured by Uniroyal Co., Ltd.) was kneaded using a 6-inch open roll to obtain a compound. The vulcanization rate of the compound was measured with an oscillating disc rheometer manufactured by Toyo Seiki Co., Ltd. to 170
It was measured under the condition of ° C. Also, the compound is 170 ℃
Vulcanization was performed for 20 minutes, and various physical properties of the vulcanized rubber composition obtained were measured according to JIS K6301.
The compression set was evaluated at 150 ° C. for 70 hours. The conditions and results are shown in Table 1.

The results show the following. Comparative Example 1 lacks the component (B) of the present invention and is inferior in oil resistance as compared with Examples 1 to 3. Comparative Example 2 is an ethylene- (meth) acrylic acid ester-based copolymer having a crosslinking site without using the ethylene- (meth) acrylic acid ester-based copolymer rubber having no crosslinking site, which is the component (A) of the present invention. It uses a polymer rubber and is inferior in compression set as compared with Example 2. Comparative Examples 3 to 5 use only the component (B) without using the component (A) of the present invention, and are inferior in tensile strength to Examples 2, 6 and 7. Comparative Example 6 uses a crosslinking aid other than the component (D) of the present invention and is inferior in compression set as compared with Examples 2, 4 and 5.
Comparative Example 7 is an example in which all of the components (A) to (D) are not according to the present invention, and the compression set is inferior to that of Example 2.

[0024]

[Table 1] ------------------ Example 1 2 3 4 Blend type Copolymer rubber (A) * 1 A1 A1 A1 A1 Acrylic rubber (B) * 2 B1 B1 B1 B1 Organic peroxide (C) * 3 CCCC Crosslinking aid (D) * 4 D1 D1 D1 D2 Weight ratio (A) / (B ) 70/30 50/50 30/70 50/50 (C) / ((A) + (B)) 3.5 / 100 3.5 / 100 3.5 / 100 3.5 / 100 (D) / ((A) + (B) ) 1/100 1/100 1/100 1/100 Evaluation MH kgf ・ cm * 5 26.6 23.8 21.8 25.6 ML kgf ・ cm * 6 3.8 5.1 6.5 4.6 t ^' (90 minutes) min * 7 7.5 6.6 6.0 10.5 Vulcanizate Physical properties Tensile strength Kgf / cm ² 120 104 88 106 Elongation% 240 210 180 190 Hardness JIS-A 68 66 63 66 ΔV% * 8 49 40 30 39 CS% * 9 25 28 32 31 Embrittlement temperature ℃ * 10 -33- 31 -27 -28 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0025]

[Table 2] ------------------ Example 5 6 7 Blend type Copolymer rubber (A) * 1 A1 A1 A1 Acrylic rubber (B) * 2 B1 B2 B3 Organic peroxide (C) * 3 CCC Crosslinking aid (D) * 4 D3 D1 D1 Weight ratio (A) / (B) 50/50 50/50 50/50 (C) / ((A) + (B)) 3.5 / 100 3.5 / 100 3.5 / 100 (D) / ((A) + (B)) 1/100 1/100 1/100 Rating MH kgf ・ cm * 5 24.1 25.5 28.0 ML kgf ・ cm * 6 5.0 4.5 3.2 t ^' (90 minutes) min * 7 6.5 6.0 8.0 Physical properties of vulcanizate Tensile strength Kgf / cm ² 107 101 117 Elongation% 230 170 240 Hardness JIS-A 66 65 74 ΔV% * 8 40 55 40 CS% * 9 33 32 52 Embrittlement temperature ℃ * 10 -30 -31 -25 −−−−−−−−−−−−−−−−−−−−−−−−− ---

[0026]

[Table 3] ------------------ Comparison type 1 2 3 4 Copolymer rubber (A) * 1 A1 A2--Acrylic rubber (B) * 2-B1 B1 B2 Organic peroxide (C) * 3 CCCC Crosslinking aid (D) * 4 D1 D1 D1 D1 Weight ratio (A) / (B ) 100/0 50/50 0/100 0/100 (C) / ((A) + (B)) 3.5 / 100 3.5 / 100 3.5 / 100 3.5 / 100 (D) / ((A) + (B) ) 1/100 1/100 1/100 1/100 Rating MH kgf ・ cm * 5 29.0 26.0 17.2 19.5 ML kgf ・ cm * 6 1.8 5.0 7.5 5.6 t ^' (90 minutes) min * 7 9.0 7.2 4.0 5.0 Vulcanizate Physical properties Tensile strength Kgf / cm ² 152 120 74 62 Elongation% 290 240 190 130 Hardness JIS-A 71 68 54 55 ΔV% * 8 63 39 16 43 CS% * 9 20 66 48 45 Embrittlement temperature ℃ * 10 -36- 29 -28 -41 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0027]

[Table 4] ------------------ Comparative example 567 Compounding type Copolymer rubber (A) * 1-A1 A2 Acrylic rubber (B) * 2 B3 B1 B4 Organic peroxide (C) * 3 CC * 11 Crosslinking aid (D) * 4 D1 D4 * 11 Weight ratio (A) / (B) 0/100 50/50 50/50 (C) / ((A) + (B)) 3.5 / 100 3.5 / 100 * 11 (D) / ((A) + (B)) 1/100 1/100 * 11 Rating MH kgf ・ cm * 5 18.0 19.4 20.3 ML kgf ・ cm * 6 4.1 4.4 5.9 t ^' (90 minutes) * 7 7.0 9.0 26.5 Physical properties of vulcanizate Tensile strength Kgf / cm ² 103 93 117 Elongation% 270 270 740 Hardness JIS-A 70 62 58 ΔV% * 8 19 44 37 CS% * 9 80 41 43 Embrittlement temperature ℃ * 10 -9 -31 -24 −−−−−−−−−−−−−−−−−−−−−−−− -----

* 1 Copolymer rubber (A) A1: Ethylene (67 mol%)-methyl acrylate (3
3 mol%) copolymer rubber, ethylene- (meth) acrylate copolymer rubber having no crosslinking site according to the present invention A2: ethylene (66 mol%)-methyl acrylate (3
3 mol%)-glycidyl methacrylate (1 mol%) copolymer rubber, ethylene- (meth) acrylic acid ester-based copolymer rubber having a cross-linking site not according to the present invention

* 2 Acrylic rubber (B) B1: RV-2540 manufactured by Nippon Kagaku Co., acrylic rubber vulcanizable with an organic peroxide according to the present invention B2: RV-2560 manufactured by Nihon Kagaku Co., organic peroxide according to the present invention Acrylic rubber that can be vulcanized by a material B3: ER-4200 manufactured by Denki Kagaku Co., Ltd., an acrylic rubber that can be vulcanized by the organic peroxide according to the present invention (ethylene
Vinyl acetate-acrylic acid ester copolymer rubber) B4: AR-51 manufactured by Zeon Corporation, acrylic rubber not according to the present invention

* 3 Organic peroxide (C) C: Dicumyl peroxide * 4 Cross-linking aid (D) D1: m-phenylene bismaleimide D2: triallyl isocyanurate D3: quinone dioxime D4: ethylene glycol dimethacrylate * 5 MH: Maximum torque value * 6 ML: Minimum torque value * 7 t'90: Proper vulcanization time

* 8 ΔV: JIS No. 3 oil
Volume swelling degree after treatment at 150 ° C for 70 hours * 9 CS: compression set, 150 ° C for 70 hours, J
According to IS K 6301 * 10 Brittleness temperature: According to JIS K 6301 * 11 0.8 parts by weight of isocyanuric acid, 1.5 parts by weight of octadecyltrimethylammonium bromide and 100 parts by weight of the total amount of (A) and (B). 2.3 parts by weight of diphenylurea were used

[0032]

Industrial Applicability As described above, according to the present invention, excellent oil resistance, cold resistance and mechanical properties are obtained, and since the vulcanization rate is high, secondary vulcanization is not necessary, and only primary vulcanization is sufficient. It was possible to provide a rubber composition capable of realizing excellent physical properties.

Claims (1)

[Claims] 1. A rubber composition containing the following components (A) to (C), wherein the weight ratio of (A) / (B) is 5/9.
5 to 95/5, the weight ratio of (C) / ((A) + (B)) is 0.1 / 100 to 10/100, and (D) /
The weight ratio of ((A) + (B)) is 0.1 / 100 to 10 /.
A rubber composition which is 100. Component (A): Ethylene- (meth) acrylic acid ester-based copolymer rubber having no crosslinking sites other than ethylene units (B) Component: Acrylic rubber vulcanizable with organic peroxide (C) Component: Organic peroxide Oxide (D) component: at least one crosslinking aid selected from the group consisting of sulfur-containing compounds, allyl compounds, maleimide compounds and quinone compounds