JP2010059227A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition excellent in both wear resistance and foaming resistance. <P>SOLUTION: The rubber composition comprises 10 to 110 pts.wt. of a pitch-based carbon fiber having a random structure and having an average fiber length of 60 to 300 μm, based on 100 pts.wt. of a hydrogenated nitrile rubber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly, to a rubber composition excellent in wear resistance and foam resistance.

Sealing materials are used as sealing members for sliding parts of automobile engines, transmissions, air conditioners such as air conditioners, and refrigerators. Such a sealing material is placed in a harsh environment such as an environment with a high PV value or a gas atmosphere such as CO ₂ . Even under such a harsh environment, excellent wear resistance is required.

  For example, Patent Documents 1 and 2 disclose rubber materials that improve sliding characteristics such as wear resistance by incorporating carbon fibers into hydrogenated nitrile rubber.

  Patent Documents 3 and 4 disclose that hydrogenated nitrile rubber is highly filled with carbon fiber to improve wear resistance.

However, in the above documents, only the blending amount of the carbon fiber is defined, and the type and shape thereof are not considered at all. Further, particularly in a CO ₂ atmosphere, there was a problem that foaming due to CO ₂ gas was generated in the sealing material, resulting in poor sealing performance.
JP 2002-80639 A Japanese Patent No. 3982536 JP 2006-131700 A JP 2004-217851 A

  This invention is made | formed in view of such an actual condition, The objective is to provide the rubber composition which is excellent in both abrasion resistance and foaming resistance.

In order to achieve the above object, the rubber composition according to the present invention comprises:
Hydrogenated nitrile rubber,
Carbon fiber, and
The carbon fiber is a pitch-based carbon fiber having a random structure,
The carbon fiber has an average fiber length of 60 to 300 μm,
The carbon fiber is contained in an amount of 10 to 110 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  In the present invention, the hydrogenated nitrile rubber is excellent in wear resistance and foam resistance by containing carbon fibers having the above-mentioned specific types and shapes in a specific range. An excellent rubber composition can be obtained.

The sealing material according to the present invention uses the above rubber composition, and is particularly suitable for a CO ₂ refrigerant. Furthermore, it is also suitable as a supercritical extraction device or a seal in a high PV region.

  According to the present invention, a rubber composition excellent in wear resistance and foam resistance can be obtained only by adding a specific amount of the specific carbon fiber to the hydrogenated nitrile rubber.

The sealing material using this rubber composition is excellent in wear resistance because it wears without the carbon fiber on the sliding surface falling off. Therefore, it is suitable as a sealing material used under severe conditions such as sliding under a high PV value environment or a gas atmosphere such as CO ₂ .

  Hereinafter, each component contained in the rubber composition of the present embodiment will be described.

Hydrogenated nitrile rubber In the rubber composition of this embodiment, the hydrogenated nitrile rubber is obtained by hydrogenating double bonds of butadiene units contained in the main chain of NBR which is a copolymer rubber of acrylonitrile and butadiene. What is obtained (HNBR) is preferred. However, the hydrogenated nitrile rubber is not limited to HNBR, and may be one obtained by replacing a part or all of butadiene with isoprene (NBIR, NIR).

  The amount of bound acrylonitrile in the hydrogenated nitrile rubber is preferably 30 to 50% by weight.

The iodine value is not particularly limited, but is preferably 0 to 28 mg / 100 mg. Moreover, Mooney viscosity (ML1 _{+ 4} , 100 degreeC) is although it does not specifically limit, Preferably, it is 100 or less, More preferably, it is 50-85.

  As said hydrogenated nitrile rubber, what is necessary is just to select according to a desired characteristic. Specifically, the thing of the Nippon Zeon Co., Ltd. product Zetpol series can be used.

Carbon fiber In the rubber composition of this embodiment, the carbon fiber is a pitch-based carbon fiber. Carbon fibers mainly include pitch-based carbon fibers and PAN-based carbon fibers. Pitch-based carbon fibers are produced from petroleum coal tar and the like, and PAN-based carbon fibers are produced from polyacrylonitrile.

In the present invention, pitch-based carbon fibers are contained as carbon fibers. When PAN-based carbon fiber is contained, the foam resistance at the time of rapid decompression and rapid heating deteriorates after exposure to a gas atmosphere such as CO ₂ gas, which is not preferable.

  The carbon fiber contained in the present invention is a pitch-based carbon fiber having a random structure. Therefore, for example, pitch-based carbon fibers having a radial structure are not preferable because the carbon fibers themselves are easily worn.

  The average fiber length of the carbon fiber is 60 to 300 μm, preferably 70 to 250 μm.

  If the average fiber length of the carbon fiber is too large, the elongation of the rubber composition tends to be greatly reduced, and if the average fiber length is too small, the wear resistance tends to deteriorate. In addition, when the average fiber length of the carbon fiber is too large, in order not to reduce the elongation of the rubber composition, it is necessary to reduce the content of the carbon fiber, so that the wear resistance tends to be lacking. .

  The content of the carbon fiber is 10 to 110 parts by weight, preferably 20 to 110 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber. If the carbon fiber content is too small, the wear resistance tends to deteriorate. On the other hand, if it is too much, the elongation tends to decrease and the wear resistance tends to deteriorate.

Carbon Black The rubber composition of the present embodiment preferably further contains carbon black. By containing carbon black, the wear resistance can be further improved. The carbon black used in the present invention is not particularly limited, and SRF, GPF, FEF, HAF, IISAF, ISAF, SAF and the like can be used.

  The content of carbon black is preferably 30 to 150 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber.

Graphite The rubber composition of the present embodiment preferably further contains graphite. Graphite improves wear resistance especially when used in combination with carbon black. The graphite used in the present invention is not particularly limited, and commercially available products can be used.

  The content of graphite is preferably 10 to 60 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber.

Crosslinking agent The rubber composition of the present embodiment preferably further contains a crosslinking agent. The crosslinking agent is preferably an organic peroxide and is preferably contained in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  Specific organic peroxides include dicumyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, 1,1-di (tertiary butyl peroxy) -3,3,5-trimethylcyclohexane. 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3,1,3-di ( 3-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, n-butyl-4,4-di (Tertiary butyl peroxy) valerate and the like.

Other Additives The rubber composition of the present embodiment includes a crosslinking accelerator, a reinforcing agent, a processing aid, a light stabilizer, a plasticizer, a lubricant, an adhesive, a lubricant, a flame retardant, and an antifungal agent as necessary. Further, additives such as an antistatic agent, a colorant, and a filler may be contained.

  As a method for preparing the rubber composition, an appropriate mixing method such as kneader mixing, roll mixing, Banbury mixing, screw mixing or the like can be adopted. The order of blending is not particularly limited, but after sufficiently mixing components that are not easily reacted or decomposed by heat, components that are easily reacted by heat or components that are easily decomposed, such as crosslinking agents and crosslinking accelerators, are not reacted or decomposed. What is necessary is just to mix in a short time at the temperature which is not.

  After mixing, the molded product having a desired product shape can be obtained by heating at about 150 to 200 ° C. for about 3 to 60 minutes by a molding method such as extrusion molding, injection molding, transfer molding or compression molding.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
First, Nippon Zeon Co., Ltd. Zetpol 2000: 100 parts by weight as hydrogenated nitrile rubber, Osaka Gas Chemical pitch-based carbon fiber (average fiber length 180 μm): 50 parts by weight as carbon fiber, Nippon Steel Chemical as SRF carbon black Niteron # 75: 70 parts by weight manufactured by Chuetsu Graphite Industries Co., Ltd .: 20 parts by weight as graphite, ANTAGE 6C manufactured by Kawaguchi Chemical Industry as anti-aging agent: 3 parts by weight, and perbutyl manufactured by Nippon Oil & Fats Co., Ltd. as a crosslinking agent P: 6 parts by weight was blended. This was kneaded with a 3 L kneader and a 10 inch roll. The kneaded product was molded into a 2 mm-thick sheet rubber composition and a lip-type seal with a compression molding machine at 185 ° C. for 5 minutes.
Zetpol 2000 had an acrylonitrile amount of 36.2%, an iodine value of 7 or less, and a Mooney viscosity of 85.

  Using the obtained sheet-like rubber composition and lip-type seal, normal properties, foam resistance and wear resistance were evaluated as follows. The results are shown in Table 1.

Normal state properties Using the obtained sheet having a thickness of 2 mm, tensile strength and elongation were measured as normal state properties. Tensile strength and elongation were measured according to JIS-K-6251.

Foaming resistance First, the obtained lip seal was placed in a pressure vessel, and the inside of the pressure vessel was purged with CO ₂ gas. And it was allowed to stand for 24 hours under the conditions of temperature: normal temperature and pressure: 6 MPa. Thereafter, the lip type seal was heated to 180 ° C., and it was evaluated whether or not foaming occurred in the cross section of the seal. This was performed for 10 cross sections of the seal, and the number of cross sections where foaming occurred was calculated.

  The abrasion resistance was evaluated by the following two types of rotation tests.

Rotation test 1
For the obtained lip type seal, engine oil (turbine oil VG32) was used as a sealing fluid, peripheral speed: 5 m / sec, fluid pressure: 3 MPa, fluid temperature: 170 ° C., test time: 10 hours A rotation test was performed below. The wear depth and fluid leakage of the lip seal after the test were measured.

Rotation test 2
Using the compressor oil (PAG oil) as the sealing fluid for the obtained lip type seal, the peripheral speed: 5 m / sec, fluid temperature: 150 ° C., CO ₂ gas pressure: 5 MPa, test time: 10 hours Under the conditions, a rotation test was performed. The wear depth and fluid leakage of the lip seal after the test were measured.

Examples 2 and 3
Except for using carbon fiber pitch-based carbon fiber (average fiber length 100 μm) (Example 2) and Kureha pitch-based carbon fiber (average fiber length 300 μm) (Example 3) A rubber composition was prepared and molded in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Examples 4 and 5
A rubber composition was prepared and molded in the same manner as in Example 1 except that the carbon fiber content was 80 parts by weight (Example 4) and 20 parts by weight (Example 5). Evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Examples 1 and 2
Except for using carbon fiber pitch-based carbon fiber (average fiber length 500 μm) (Comparative Example 1) and Toray PAN-based carbon fiber (average fiber length 130 μm) (Comparative Example 2) A rubber composition was prepared and molded in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 3 and 4
A rubber composition was prepared and molded in the same manner as in Example 1 except that the carbon fiber content was 120 parts by weight (Comparative Example 3) and 5 parts by weight (Comparative Example 4). Evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Example 5
A rubber composition was prepared and molded in the same manner as in Example 1 except that pitch-based carbon fiber (average fiber length 50 μm) (Comparative Example 5) manufactured by Mitsubishi Chemical Corporation was used as the carbon fiber. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1. The pitch carbon fiber manufactured by Mitsubishi Chemical Corporation has a radial structure.

Comparative Example 6
A rubber composition was prepared and molded in the same manner as in Example 1 except that pitch-based carbon fiber (average fiber length 40 μm) manufactured by Osaka Gas Chemical was used as the carbon fiber, and evaluation was performed in the same manner as in Example 1. Went. The results are shown in Table 1.

From Evaluation Table 1, as carbon fibers, pitch-based carbon fibers having a uniform structure, and when the average fiber length and content are within the scope of the present invention (Examples 1 to 5), foaming occurs. It can be confirmed that good wear resistance is exhibited for both of the two rotation tests. Moreover, the elongation in a normal state is also good.
On the other hand, when the average fiber length of the pitch-based carbon fiber is outside the range of the present invention (Comparative Example 1), the foaming resistance and the wear resistance are good, but the normal elongation is greatly reduced. You can confirm that
Moreover, when a PAN-based carbon fiber is used as the carbon fiber (Comparative Example 2), it can be confirmed that the foam resistance is extremely deteriorated.
When the content of the pitch-based carbon fiber is larger than the range of the present invention (Comparative Example 3), it can be confirmed that the wear resistance is good, but the normal elongation is greatly reduced. Moreover, when content of pitch-type carbon fiber is less than the range of this invention (comparative example 4), it can confirm that there exists a tendency for abrasion resistance to deteriorate.
Further, even when the average fiber length and content are within the range of the present invention, when a pitch-based carbon fiber having a radial structure that is not a random structure is used (Comparative Example 5), the carbon fiber itself is worn. Since it is easy, it can be confirmed that both the foam resistance and the wear resistance are deteriorated.
In addition, when the average fiber length of the pitch-based carbon fiber is shorter than 60 μm (Comparative Example 6), it is confirmed that although the foam resistance and the normal elongation are good, the wear resistance is greatly reduced. it can.

Claims (3)

Hydrogenated nitrile rubber,
Carbon fiber, and
The carbon fiber is a pitch-based carbon fiber having a random structure,
The carbon fiber has an average fiber length of 60 to 300 μm,
A rubber composition containing 10 to 110 parts by weight of the carbon fiber with respect to 100 parts by weight of the hydrogenated nitrile rubber.   A sealing material comprising the rubber composition according to claim 1. CO ₂ refrigerant seal material obtained by using the rubber composition according to claim 1.