JPH07119348B2 - Modified rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition which is crosslinked by heating and has excellent mechanical properties, heat aging resistance and electrical properties.

(Prior art and its problems) Ethylene / α-olefin copolymer rubber is used as a rubber having excellent chemical resistance and electrical insulation properties for automobile parts, electric parts,
It is used for general industrial parts. However, recently, there have been cases where higher strength and higher heat aging resistance are required for automobile parts and electric parts.

For this reason, for example, regarding the improvement of heat aging resistance, addition of an antiaging agent to this kind of rubber has been attempted, as seen in "Ethylene-Propylene Rubber" of Synthetic Rubber Processing Technology, but the improvement effect is not enough.

Therefore, the present invention provides a vulcanizable rubber composition that exhibits excellent chemical resistance and electrical insulation properties possessed by an ethylene / α-olefin copolymer rubber, has high strength, and is also extremely excellent in heat aging resistance. Is a technical issue.

(Means for Solving Problems) The present invention relates to a graft-modified ethylene / α-olefin copolymer rubber (A) and the following general formula (I), (R ¹ ) _a (R ² ) _b SiO ( _4-ab) ) / ₂ (I) In the formula, R ¹ is a monovalent hydrocarbon group, R ² is a vinyl group, a is a number of 1 to 2.5, and b is a number of 0.01 to 1.2. And a + b is in the range of 1.8 to 3, wherein the polyorganosiloxane (B) having an average composition represented by and the silica-based filler (C) are used in combination.

(Function) The heat-resistant rubber composition of the present invention is a graft-modified ethylene / α
-By blending the above-mentioned polyorganosiloxane (B) and silica-based filler (C) with the olefin-based copolymer rubber (A), not only excellent mechanical properties such as strength but also remarkably excellent heat resistance Shows aging.

That is, as is apparent from the examples described below, the composition of the present invention shows a surprising value of about 60% or more in the retention of 180 ° C. for 96 hours. Normal heat resistance test is 140
It can be understood that the superiority of the composition of the present invention can be understood from the fact that it can be said that it is a heat resistant formulation when it is carried out at a temperature of ° C and shows a value of 60% or more.

In the present invention, the reason why the heat aging resistance is remarkably improved is not clear yet, but the interfacial characteristics between the filler and the ethylene / α-olefin copolymer rubber are remarkably improved by the specific polyorganosiloxane. It seems to be caused by that.

(Preferred embodiment of the invention) (A) Modified ethylene / α-olefin copolymer rubber The modified ethylene / α-olefin copolymer rubber used in the present invention is selected from unsaturated carboxylic acids, their anhydrides and their esters. One or more compounds are used as a graft copolymerization monomer, and are graft-copolymerized with ethylene and an α-olefin copolymer rubber.

The ethylene / α-olefin copolymer rubber to be graft-copolymerized is composed of ethylene and an α-olefin having a C number of 3 to 10, and has an ethylene content of 50 to 95 mol%, preferably 60 to 92 mol. It is in the range of%.

The α-olefin having a C number of 3 to 10 is specifically propylene, 1-butene, 1-hexene, 4-methyl-1-
Pentene, 3-methyl-1-pentene, 1-octene,
1-decene etc. can be illustrated.

Furthermore, this ethylene / α-olefin copolymer rubber has 1
One or more polyene components may be contained.

Specifically as the polyene component, 1,4-hexadiene,
1,6-octadiene, 2-methyl-1.5-hexadiene,
Chain non-conjugated dienes such as 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-
Norbornene, 5-methylene-2-norbornene, 5-
Cyclic non-conjugated dienes such as isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5
Typical examples are trienes such as -norbornene, 2-propenyl-2,2-norbornadiene, 1.3.7-octatriene and 1,4,9-decatriene.
Suitable polyenes are cyclic non-conjugated dienes and 1,4-hexadiene, especially dicyclopentadiene or 5-ethylidene-2-norbornene. These polyene components are
The resulting copolymer is copolymerized so that the iodine value is at most 30, preferably 20 or less.

The unsaturated carboxylic acid to be graft-copolymerized with the ethylene / α-olefin-based rubber, the anhydride thereof and the ester toshite are not limited to these, but the following are used, for example.

Unsaturated carboxylic acid; acrylic acid, methacrylic acid, maleic acid, fumaric acid,
Itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid and the like.

Unsaturated carboxylic acid anhydrides; maleic anhydride, itaconic anhydride, citraconic anhydride,
Tetrahydrophthalic anhydride, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid anhydride and the like. Of these, maleic anhydride is preferred.

Unsaturated carboxylic acid ester; methyl acrylate, methyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate,
Dimethyl itaconate, diethyl citraconic acid, dimethyl tetrahydrophthalic anhydride, dimethyl bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylate and the like. Among these, methyl acrylate and ethyl acrylate are preferable.

Graft copolymerization monomers such as the unsaturated carboxylic acid,
Each of them may be used alone or in combination of two or more. In any case, the graft copolymerization is carried out in the range of 0.1 to 10 parts by weight, particularly 0.2 to 5 parts by weight, per 100 g of the ethylene / α-olefin copolymer rubber mentioned above. Is preferred.

If this graft amount is less than the above range, the desired heat aging resistance tends not to be obtained, and if it is more than the above range, the resulting rubber composition is unsatisfactory in processability and cold resistance. Tends to be

The graft copolymerization can be obtained by reacting the above-mentioned ethylene / α-olefin copolymer rubber with an unsaturated carboxylic acid or the like in the presence of a radical initiator.

The reaction may be carried out as a solution or may be carried out in a molten state. When it is carried out in the molten state, it is most efficient to carry out it continuously in the extruder.

As the radical initiator used in the graft reaction, one having a decomposition temperature in the range of 150 to 270 ° C. so that the half-life is 1 minute is preferably used.

Specifically, organic peroxides, organic peresters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (peroxybenzoate) hexyne-3, 1,4-bis (tert-butylperoxyisopropyl) benzene, lauroyl peroxide, tert-butylperacetate, 2,5-dimethyl-2,5
-Di (tert-butylperoxy) hexyne-3,2,5-
Dimethyl-2,5-di (tert-butylperoxy) hexane, tert-butylperbenzoate, tert-butylperphenylacetate, tert-butylperisobutyrate, tert-butylper-sec-octoate, tert-butylpervivarate , Cumyl pervivarate and tert
-Butyl perdiethyl acetate.

The graft-modified ethylene / α-olefin copolymer rubber described above has a Mooney viscosity [ML _{1 + 4} (100 ° C)] of 5 to 180, particularly 20 to 120 from the viewpoint of mechanical properties and processability. Are preferably used.

(B) Polyorganosiloxane The polyorganosiloxane used in the present invention has the following average composition formula: (I), (R ¹ ) _a (R ² ) _b SiO ( _4-ab ) / ₂ (I) formula Wherein R ¹ is a monovalent hydrocarbon group, R ² is a vinyl group, a is a number from 1 to 2.5, b is a number from 0.01 to 1.2, and a + b is from 1.8 to 3. Those represented by are used, and those in which the group R ¹ is a methyl group or a phenyl group are particularly preferably used.

The number average molecular weight [M _n ] of this polyorganosiloxane
Is generally in the range of 10 ^{2 to} 10 ⁶ , preferably 10 ^{3 to} 10 ⁵ , and most preferably 5 × 10 ^{3 to} 5 × 10 ⁴ .

When the degree of polymerization is higher than the above range, it is not sufficiently compatible with the graft-modified ethylene / α-olefin copolymer rubber, resulting in a decrease in strength, and when it is lower than the above range, the desired heat aging resistance is obtained. There is a tendency not to be.

(C) Silica-based filler As the silica-based filler, all known rubber compounding agents can be used. Examples thereof include dry silica, wet silica, synthetic silicate-based white carbon, talc and clay. It

Rubber composition The rubber composition in the present invention is a graft-modified ethylene /
0.5 to 30 parts by weight, preferably 1 to 25 parts by weight, and more preferably 1.5 to 2 parts by weight of the specific polyorganosiloxane (B) per 100 parts by weight of the α-olefin copolymer rubber (A).
It is mixed at a ratio of 0 part by weight.

If the polyorganosiloxane (B) is too small than the above range, the desired heat aging resistance cannot be obtained, and if it is too large, the desired strength cannot be obtained and it is extremely expensive, which is not practical.

The silica-based filler (C) is a graft-modified ethylene / α-
The olefin copolymer rubber (A) is mixed in an amount of 10 to 100 parts by weight, preferably 15 to 80 parts by weight, more preferably 20 to 60 parts by weight, with respect to 100 parts by weight.

If the silica-based filler is too small or too large, the desired strength cannot be obtained, which is not practical.

Compounding agent In the rubber composition of the present invention, a compounding agent known per se, such as a reinforcing agent for rubber, a softening agent, a vulcanizing agent, a vulcanization aid, etc., is added depending on the intended use of the vulcanized product. can do.

In this case, the total amount of the components (A) to (C) occupying in the composition is generally 60% by weight or more, and particularly preferably 80% by weight or more, though it varies depending on the application.

Examples of rubber reinforcing agents that can be used are SRF, GPF, FEF and HA.
Examples include carbon blacks such as F, ISAF, SAF, FT and MT.

These rubber reinforcing agents can be appropriately selected according to their applications and the like, but should be 50 parts by weight or less, particularly 30 parts by weight or less per 100 parts by weight of the total amount of the above-mentioned components (A) to (C). Is preferred.

As the softening agent which can be used in the present invention, a softening agent which is usually used for rubber is sufficient, but for example, a petroleum-based softening agent such as process oil, lubricating oil, synthetic lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petrolatum, coal. Coal tar-based softeners such as tar and coal tar pitch, fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil and coconut oil, tall oil; sub; waxes such as beeswax, carnauba wax and lanolin; ricinoleic acid , Fatty acids and fatty acid salts such as palmitic acid, barium stearate, calcium stearate, zinc laurate; synthetic polymer substances such as petroleum resin, atactic polypropylene, coumarone indene resin, polyester resin, or dioctyl adipate, dioctyl phthalate, etc. Ester Plasticizer Other Micro Lister phosphorus wax, and the like sub (factice).

The blending amount of these softening agents can be appropriately selected according to the application etc., but the total amount of the above-mentioned components (A) to (C) is 100
It is preferably 50 parts by weight or less, and particularly preferably 30 parts by weight or less per part by weight.

The vulcanizate from the composition of the present invention is usually prepared by once adjusting an unvulcanized compounded rubber by the method described below, and then molding the compounded rubber into an intended shape, as in the case of generally vulcanizing a rubber. It is manufactured by performing vulcanization. As a vulcanizing method, there are a method of using a vulcanizing agent for heating and a method of irradiating with an electron beam.

Organic peroxide is recommended as the vulcanizing agent used when using the vulcanizing agent. As the organic peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (tertiary butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5- Dimethyl-2,5-di (tertiary butylperoxy) hexyne-3, ditertiary butylperoxide, ditertiary butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl hydroperoxide can be exemplified, but among them, Dicumyl peroxide, ditertiary butyl peroxide, ditertiary butylperoxy-3,3,5-trimethylcyclohexane are preferably used. The organic peroxide is 3 × 10 ⁻⁴ to 5 × 10 ⁻² mol parts, preferably 1 × 10 ⁻³ to 3 × 10 ⁻² parts, per 100 parts by weight of the modified ethylene / α-olefin copolymer rubber (A). Use the molar part.

When an organic peroxide is used as a vulcanizing agent, it is preferable to use a vulcanization auxiliary together. Examples of vulcanization aids include sulfur, quinone dioximes such as p-quinone dioxime, methacrylates such as polyethylene glycol dimethacrylate, allyls such as diallyl phthalate and triallyl cyanurate, maleimides, and divinylbenzene. To be done. Such a vulcanization aid is an organic peroxide used.
It is used in an amount of 1/2 to 2 mol, preferably about equimolar to the mol.

When using an electron beam without using a vulcanizing agent as a vulcanizing method, 0.1 to 1 is added to a molded unvulcanized compounded rubber described below.
The absorption line of an electron having an energy of 0 MeV (megaelectron volt), preferably 0.3 to 2.0 MeV, is 0.5 to 35 Mrad (megarad), preferably 0.5 to 10 Mrad.
Irradiate so that The time may be used vulcanizing agent used in combination with an organic peroxide as a vulcanizing agent of the, the amount modified ethylene · alpha-olefin copolymer rubber (A) 1 × 10 to 100 parts by weight of ^{- 4} to 1 × 10 ^-1
1 part by mole, preferably 1 × 10 ⁻³ to 3 × 10 ⁻² parts by mole. Further, the composition of the present invention may contain a colorant, an antioxidant, a dispersant, and a flame retardant, if necessary.

Preparation of Rubber Composition Unvulcanized compounded rubber is prepared by the following method. That is, a modified ethylene / α-olefin copolymer rubber (A), a polyorganosiloxane (B), a silica-based filler (C) and, if necessary, a rubber reinforcing agent at 80 to 170 ° C. are mixed with a mixer such as a Banbury mixer. After kneading at the temperature for 3 to 10 minutes, rolls such as oven rolls are used to additionally mix the vulcanizing agent and, if necessary, the vulcanization accelerator or vulcanization aid, at the roll temperature of 40 to 80 ° C. After kneading for 5 to 30 minutes, dispensing is carried out to prepare a ribbon-shaped or sheet-shaped compounded rubber.

The compounded rubber thus prepared is molded into an intended shape by an extruder, calender roll, or press,
Simultaneously with molding or by introducing the molded product into a vulcanization tank and heating it at a temperature of 150 to 270 ° C. for 1 to 30 minutes, or by irradiating it with an electron beam by the method described above, a vulcanized product can be obtained. A mold may be used for this step of supplying, or it may be performed without using a mold. When a mold is not used, the molding and vulcanization steps are usually carried out continuously.

Of course, when vulcanization is performed by electron beam irradiation, compounded rubber containing no vulcanizing agent is used.

As a heating method for the vulcanized layer, a heated layer such as hot air, a glass bead fluidized bed, UHF (ultra high frequency electromagnetic wave) or steam can be used.

(Effects of the Invention) The rubber composition of the present invention thus produced is excellent in strength and heat aging resistance as shown in Examples described later, and is a wire covering, tube, belt, rubber roll, gasket, packing, rubber hose, etc. It is preferably used for.

The excellent effect of the present invention will be described in the following example.

(Example) Example 1 A modified ethylene / α-olefin copolymer rubber (A), a polyorganosiloxane (B) and a silica-based filler (C) shown below are used, and a rubber composition according to the following formulation. Was prepared.

Modified ethylene / α-olefin copolymer rubber (A) α-olefin: propylene Ethylene / propylene = 80/20 (molar ratio) Mooney viscosity ML _{1 + 4} (100 ° C): 20 Maleic anhydride content: 0.5 wt% Polyorganosiloxane (B) (CH ₂ ) _1.8 (CH ₂ = CH) _0.2 SiO M _n : 5.1 × 10 ³ · Silica-based filler (C) Dry silica: Specific surface area 200 m ² / g Kneading is carried out using an 8-inch oven roll at 60 ° C to 70 ° C for 20
I went for a minute. The mixture was then press vulcanized at 170 ° C for 10 minutes,
A vulcanized rubber sheet having a thickness of 2 mm was prepared and provided for measurement. The following items were measured according to JIS K 6301.

Normal physical properties Tensile strength (TB), elongation (EB), heat aging resistance [heat aging condition: 180 ° C-90 hours] Tensile strength retention rate AR (TB), elongation retention rate AR (EB) The results are shown in the table below. Shown in 1.

Example 2 The same procedure as in Example 1 was carried out except that the following was used as the modified ethylene / α-olefin copolymer rubber in Example 1.

α-Olefin: Propylene Ethylene / Propylene = 70/30 (molar ratio) Iodine number: 2 (vinyl norbornene) Mooney viscosity ML _{1 + 4} (100 ° C): 60 Maleic anhydride content: 0.5 wt% Example 3 In Example 1 The same procedure as in Example 1 was carried out except that the following was used as the modified ethylene / α-olefin copolymer rubber.

α-olefin: 1-butene ethylene / 1-butene = 90/10 (molar ratio) Mooney viscosity ML _{1 + 4} (100 ° C.): 15 Maleic anhydride content: 1.0 wt% Example 4 The formulation of Example 1 is as follows. Example 1 except that
And went exactly the same way.

Example 5 The average composition formula of polyorganosiloxane in Example 1 is
H ₃ ) _1.9 (CH ₂ = CH) _0.1 SiO M _n 4.5 × 10 ³ was carried out in exactly the same manner as in Example 1.

Example 6 The average composition formula of polyorganosiloxane in Example 1 is represented by (C
H ₃ ) _1.5 (CH ₂ = CH) _0.5 SiO M _n 6.1 × 10 ³ was carried out in exactly the same manner as in Example 1.

Example 7 The procedure of Example 1 was repeated except that the polyorganosiloxane had M _n of 8.0 × 10 ⁴ .

Example 8 The same procedure as in Example 1 was carried out except that the following silica fillers were used in Example 1.

Wet silica: trade name Nipsil VN ₃ (manufactured by Nihon Silica Co., Ltd.) Example 9 The same procedure as in Example 1 was carried out except that the following silica fillers were used in Example 1 and the formulation was as follows. It was

Calcined clay: Product name Satinton No1 (manufactured by Engelhard Minerals & Chem.) Comparative Example 1 The procedure of Example 1 was repeated except that the polyorganosiloxane was not used.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the following polyorganosiloxane was used in Example 1.

Polydimethylsiloxane M _n : 4.8 × 10 ³ Example 10 The same procedure as in Example 1 was carried out except that the following was used as the modified ethylene / α-olefin copolymer rubber in Example 1.

α-Olefin: 1-butene Ethylene / 1-butene = 90/10 (molar ratio) Mooney viscosity ML _{1 + 4} (100 ° C.): 30 Ethyl acrylate content: 2.0 wt% Comparative Example 3 The same procedure as in Example 9 was performed except for the following.

Combination prescription Comparative Example 4 Example 9 was repeated except that the compounding recipe in Example 9 was changed as follows.
I went the same way.

Combination prescription Trade name Lucant HC-600: manufactured by Mitsui Petrochemical Co., Ltd. Comparative Example 5 Example 3 was repeated except that the modified ethylene / α-olefin copolymer rubber was used in place of the modified ethylene / α-olefin copolymer rubber. Completely the same as in Example 9.

Claims (6)

[Claims] 1. (A) 100 parts by weight of a modified ethylene / α-olefin copolymer rubber obtained by graft copolymerizing one or more compounds selected from unsaturated carboxylic acids, their acid anhydrides and their esters. B) The following general formula (R ¹ ) _a (R ² ) _b SiO ( _4-ab ) / ₂ (I) In the formula, R ¹ is a monovalent hydrocarbon group, R ² is a vinyl group, a Is a number from 1 to 2.5, b is a number from 0.01 to 1.2, and a + b is in the range from 1.8 to 3, a polyorganosiloxane having an average composition represented by:
A modified rubber composition comprising 0.5 to 30 parts by weight and (C) 10 to 100 parts by weight of a silica-based filler as essential components. 2. The ethylene / α-olefin copolymer rubber before graft modification has an intrinsic viscosity [η] measured in decalin at 135 ° C. of 0.5 to 4.0 dl / g. The rubber composition described. 3. The ethylene / α-olefin copolymer rubber (A) before graft modification has a molar ratio of ethylene / α-olefin.
The rubber composition according to claim 1, wherein olefin is 50/50 to 95/5. 4. The rubber composition according to claim 1, wherein the graft-modified ethylene / α-olefin copolymer rubber (A) contains a maximum of 30 non-conjugated polyenes represented by iodine value. 5. The rubber composition according to claim ¹ , wherein in the general formula (I) showing the composition of the polyorganosiloxane (B), the group R ¹ is a methyl group or a phenyl group. 6. The rubber composition according to claim 1, wherein the polyorganosiloxane (B) has a number average molecular weight (M _n ) of 100 to 10 ⁶ .