JP2000044729A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive elastomer material having a volume resistivity lowly dispersive in the medium range and a high modulus by effecting the addition reaction of a blend of an epichlorohydrin/ethylene oxide copolymer with a hydrogenated nitrile rubber with a metal unsaturated carboxylate and an organic peroxide. SOLUTION: This material can give a high-modulus rubber having a medium resistance of 108 to 1011 Ωcm when it is vulcanized with an organic peroxide. It is desirable that the copolymer is an epichlorohydrin rubber is vulcanizable with an organic peroxide, and has a volume resistivity of 107 to 109 Ωcm. The metal unsaturated carboxylate used is exemplified by zinc methacrylate. The organic peroxide is used as a crosslinking agent and is for example, 2,5- dimethyl-2,5-di(t-butylperoxy)hexane. It is desirable that 1-50 pts.wt. short microfibers composed of a polymer and a polyamide fiber having a fiber diameter of 3.0 μm or below and grafted thereonto are added to 100 pts.wt. above composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition,
More specifically, the present invention relates to a rubber composition suitable as a conductive elastomer material which has a high modulus and requires a certain resistance value.

[0002]

2. Description of the Related Art Conventionally, as a conductive rubber, rubber is mixed with conductive powder such as conductive carbon black, graphite, and metal powder, and the conductive powder is brought into contact with each other to exhibit conductivity. It is extremely difficult to uniformly disperse the conductive powder in the rubber, and the resistance value in the rubber greatly varies. Particularly, the volume resistivity is uniform in the medium resistance region (10 ⁸ to 10 ¹¹ Ωcm). No resistance value was obtained.

[0003] In order to obtain a high modulus, it is necessary to replenish the carbon black with a high filling, but there is a problem that the resistance value is reduced. On the other hand, in the case of reinforcement with silica, there was a problem in that the viscosity was increased, the workability was reduced, and the brittleness was lowered to reduce the strength.

[0004] It is also known that an antistatic function is imparted by blending a surfactant and a metal oxide filler into a rubber composition.

In recent years, ethylene-propylene rubber (EPR) and ethylene-propylene-diene rubber (E
It has been proposed to use a rubber composition in which a rubber such as PDM), natural rubber, or SBR is blended with epichlorohydrin rubber.

[0006]

However, in order to provide a sufficient antistatic function using a metal oxide, a considerable amount of the metal oxide must be added. Permanent set was sometimes impaired. When a surfactant is used, the antistatic function has no long-lasting property, and there is a problem of stickiness on the surface due to bleeding.

On the other hand, when a rubber composition in which EPR or EPDM and epichlorohydrin rubber are blended is used, such a problem is solved, but the volume resistivity of EPDM is generally 10 ¹⁵ to 10 ¹⁶ . High, 10 ⁸ -10
^In order to obtain a resistance value of ¹¹ , the blend amount of EPDM is limited to a small amount, and there is a problem that a rubber composition having a high modulus cannot be obtained.

The present invention addresses such a problem, and the volume resistivity is in the middle resistance value region (10 ⁸ to 10 ^11).
It is an object of the present invention to provide a rubber composition suitable as a conductive elastomer material that requires a small variation in Ωcm), an excellent high modulus, and a certain resistance value.

[0009]

That is, in the invention of claim 1 of the present application, a metal salt of an unsaturated carboxylic acid and an organic peroxide are added to a blend of an epichlorohydrin-ethylene oxide copolymer and a hydrogenated nitrile rubber. It is in the rubber composition added.

[0010] According to a second aspect of the present invention, there is provided a rubber composition comprising the rubber composition according to the first aspect and a micro short fiber grafted with a polymer and a polyamide fiber having a fiber diameter of 3.0 µm or less.

In the invention of claim 2 of the present application, silica is added in an amount of 1 to 100 parts by weight of a blend of an epichlorohydrin-ethylene oxide copolymer and a hydrogenated nitrile rubber.
50 parts by weight of the rubber composition.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The feature of the present invention is that a blend of an epichlorohydrin-ethylene oxide copolymer and a hydrogenated nitrile rubber mixed with a metal salt of an unsaturated carboxylic acid is added with an organic peroxide. By vulcanizing, a medium resistance value (10 ⁸ to 10 ¹¹ Ωcm) is exhibited, a variation in the resistance value is small, and a high modulus rubber is obtained.

The epichlorohydrin-ethylene oxide copolymer (CHC) referred to herein means epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer and epichlorohydrin-ethylene oxide-
It is a substance containing a propylene oxide-allyl glycidyl ether copolymer and the like, which can be vulcanized with an organic peroxide using epichlorohydrin rubber. In addition, the volume specific resistance value is 1
0 ⁷ 10 ⁹ which is in the range of Ωcm is selected.

The unsaturated carboxylic acid metal salt used for the hydrogenated nitrile rubber and the metal salt are those in which an unsaturated carboxylic acid having a carboxyl group and a metal are ion-bonded, and the unsaturated carboxylic acids include acrylic acid and methacrylic acid. Monocarboxylic acids such as, maleic acid, fumaric acid, dicarboxylic acids such as itaconic acid are preferred, as the metal beryllium,
Magnesium, calcium, strontium, barium, titanium, chromium, molybdenum, manganese, iron, cobalt, nickel, copper, silver, zinc, cadmium, aluminum, tin, lead, antimony, and the like can be used.

The amount of the metal salt of the unsaturated carboxylic acid is 5 to 2 parts by weight based on 100 parts by weight of the blend of the epichlorohydrin-ethylene oxide copolymer and the hydrogenated nitrile rubber.
00 parts by weight are blended. It is preferably 15 to 100 parts by weight. If the amount of the unsaturated carboxylic acid metal salt is less than this range, a sufficient modulus cannot be obtained, and if the amount is too large, it adheres to a rotor or a roll of a mixer and processing becomes difficult.

The organic peroxide is used as a crosslinking agent and includes di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide,
1.1-t-butylperoxy-3.3.5-trimethylcyclohexane, 2.5-di-methyl-2.5-di (t
-Butylperoxy) hexane, 2.5-di-methyl-
2.5-di (t-butylperoxy) hexane-3, bis (t-butylperoxydi-isopropyl)) benzene,
2.5-di-methyl-2.5-di (benzoylperoxy) hexane, t-butylperoxybenzoate, t-
Butylperoxy-2-ethyl-hexyl carbonate is used. Then, the blending amount is 0.2 to 10 parts by weight based on 100 parts by weight of the blend.
If the amount is less than 0.2 parts by weight, crosslinking is not sufficiently performed, and
If the amount exceeds the weight part, sufficient elasticity cannot be obtained.

Further, in the present invention, a master batch in which a metal salt of an unsaturated carboxylic acid is previously dispersed in a hydrogenated nitrile rubber is blended with the hydrogenated nitrile rubber alone, and short fibers and an organic peroxide are added and crosslinked. Can also be used.

The blend ratio of the epichlorohydrin-ethylene oxide copolymer to the hydrogenated nitrile rubber is 10/9.
0 to 90/10. If the amount of the epichlorohydrin-ethylene oxide copolymer is larger than this range, a sufficient modulus cannot be obtained, and if the amount is small, the resistance value becomes large and desired physical properties cannot be obtained.

Known co-crosslinking agents (TAIC, TAC, maleimide, quinone dioxime, trimethylolpropane trimethacrylate, sulfur, etc.) may be used in combination in order to increase the crosslinking efficiency of the organic peroxide. In addition to the organic peroxide, a vulcanizing agent for a known epichlorohydrin-ethylene oxide copolymer or epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer or epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether copolymer ( For example, lead red / ethylene thiourea, magnesium oxide / 2,4,6-trimercapto-S-triazine) may be added.

Further, a filler commonly used for rubbers such as carbon black and silica may be blended to increase the modulus. In particular, silica is effective, and the modulus is dramatically increased by blending about 20 to 50 parts by weight with respect to 100 parts by weight of the blend of the epichlorohydrin-ethylene oxide copolymer and the hydrogenated nitrile rubber.

[0021] In this blend, a polymer and a fiber diameter of 3.0 µm were added.
m or less polyamide fibers graft-bonded with fine short fibers or polymers grafted with fine particles having a particle size of 10 μm or less,
Further higher modulus can be achieved. The compounding amount is up to 30 parts by weight in terms of polyamide, and if it exceeds this, the resistance value of the blended rubber composition becomes too large and the desired physical properties cannot be obtained. The polymer to be grafted with the polyamide is at least one selected from rubber and polyolefin. If the rubber is selected to be the same as or compatible with epichlorohydrin-ethylene oxide copolymer or hydrogenated nitrile rubber, the modulus of the composition can be further increased. Hereinafter, the results of evaluating the physical properties of the vulcanized rubber obtained by crosslinking the rubber composition of the present invention will be described.

[0022]

The present invention will be described in more detail with reference to the following examples. Examples 1 to 5 and Comparative Examples 1 to 4 The components shown in Table 1 were kneaded with an open roll and vulcanized at 165 ° C for 30 minutes. The modulus of the selected vulcanized rubber at 10% elongation (low elongation stress test according to JIS K6301) and volume resistivity (high resistivity meter: Hi Lettuce UP MCP-HT450 manufactured by Mitsubishi Chemical Corporation) were measured.

[0023]

[Table 1]

As a result, in Example 1 containing 40 parts by weight of carbon black, the volume resistivity was not significantly reduced and variation was small as compared with Example 2 containing silica. You can see that it is not greatly affected by the chain of.

It can be seen that in Example 2, the modulus was much higher than that reinforced with carbon black.
Example 3 is a case where the amount of CHC is small, and is stable at a high volume resistivity. On the other hand, Example 4 is a case where the amount of CHC is large, and is stable at a low volume resistivity. Further, in the fifth embodiment, the modulus can be further increased while the volume resistivity is stable as compared with the third embodiment. On the other hand, in Comparative Example 3, CHC and HNB were used.
Since it is not a blend of R, the modulus is lower than that of the example.

[0026]

As described above, in the invention described in the claims of the present application, a metal salt of an unsaturated carboxylic acid and an organic peroxide are added to a blend of an epichlorohydrin-ethylene oxide copolymer and a hydrogenated nitrile rubber. In the rubber composition, the volume specific resistance value is in a medium resistance value region (10 ⁸ to 10 ¹¹ Ω).
cm), and shows that the rubber composition is suitable as a conductive elastomer material that requires a high resistance and a certain resistance value with a small variation.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08L 9/02 C08L 9/02 71/02 71/02

Claims (3)

[Claims] 1. A rubber composition characterized by adding a metal salt of an unsaturated carboxylic acid and an organic peroxide to a blend of an epichlorohydrin-ethylene oxide copolymer and a hydrogenated nitrile rubber. 2. The rubber composition according to claim 1, further comprising a fine short fiber graft-bonded with a polymer and a polyamide fiber having a fiber diameter of 3.0 μm or less. 3. The rubber composition according to claim 1, wherein silica is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the blend of the epichlorohydrin-ethylene oxide copolymer and the hydrogenated nitrile rubber.