JP5150920B2 - Rubber composition and sealing material - Google Patents

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition having excellent wear resistance and a sealing material using the same.

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, in Patent Document 1, hydrogenated nitrile rubber alone or hydrogenated nitrile rubber is used as a material for a lip portion of a rotary shaft seal used in a compressor for a car air conditioner under severe conditions of high pressure, high speed, and high temperature. A material in which carbon black, a phenol resin, or the like is blended with a blending material based on the above is disclosed.

  However, since a phenol resin, which is an organic component, is used, there is a problem that the wear resistance is not sufficient, and the wear amount of the lip portion is large especially under high pressure.

  Patent Documents 2 and 3 disclose rubber materials that improve sliding characteristics such as wear resistance by incorporating carbon fibers into hydrogenated nitrile rubber. Patent Documents 4 and 5 disclose that hydrogenated nitrile rubber is highly filled with carbon fiber to improve wear resistance.

  However, in said patent documents 2-5, only the compounding quantity of carbon fiber is prescribed | regulated, The kind, shape, etc. were not considered at all. Moreover, even with such a rubber composition, the wear resistance under severe conditions was not sufficient. Further, since the elongation is small, for example, when used as a shaft seal material, there is a problem that the seal material is easily broken when inserted into the rotating shaft.

Further, in Patent Document 6, methacrylic acid is added to acrylonitrile butadiene rubber (NBR) or hydrogenated NBR (HNBR), or methacrylic acid is reacted with zinc salt or the like in NBR or HNBR. It is disclosed to produce zinc and increase the hardness of the resulting composition.
Japanese Patent Laid-Open No. 2004-19798 JP 2002-80639 A Japanese Patent No. 3982536 JP 2006-131700 A JP 2004-217851 A Japanese Patent No. 2865718

  This invention is made | formed in view of such an actual condition, The objective is to provide the rubber composition which is excellent in abrasion resistance, and has moderate elongation, and a sealing material using the same.

In order to achieve the above object, the rubber composition according to the present invention comprises:
Hydrogenated nitrile rubber, zinc methacrylate, and carbon fiber,
The zinc methacrylate is contained in an amount of 30 to 90 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber.
The carbon fiber is a pitch-based carbon fiber having a random structure,
30 to 120 parts by weight of the carbon fiber is contained with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  By adding zinc methacrylate to the hydrogenated nitrile rubber within the above range and further containing carbon fiber having a specific type and shape within a specific range, it is excellent in wear resistance and has an appropriate elongation. Can be obtained.

Preferably, a polymer alloy in which zinc methacrylate is dispersed in hydrogenated nitrile rubber,
Hydrogenated nitrile rubber containing no zinc methacrylate;
Carbon fiber, and
The content ratio of the polymer alloy and the hydrogenated nitrile rubber is in a weight ratio of polymer alloy: hydrogenated nitrile rubber = 40: 60 to 70:30,
The carbon fiber is a pitch-based carbon fiber having a random structure,
30 to 120 parts by weight of the carbon fiber is contained with respect to 100 parts by weight of the total weight of the polymer alloy and the hydrogenated nitrile rubber.

  A rubber according to the present invention can be obtained more easily while obtaining the above-mentioned effects by containing a polymer alloy in which zinc methacrylate is dispersed in a hydrogenated nitrile rubber and a hydrogenated nitrile rubber within the above weight ratio range. A composition can be obtained.

The sealing material according to the present invention uses any of the rubber compositions described above, and is suitable for applications that require wear resistance and appropriate elongation, and is particularly suitable as a CO ₂ refrigerant seal. Furthermore, it is also suitable as a supercritical extraction device or a seal in a high PV region.

The manufacturing method of the sealing material according to the present invention includes a polymer alloy in which zinc methacrylate is dispersed in hydrogenated nitrile rubber, a hydrogenated nitrile rubber not containing zinc methacrylate, and carbon fiber in the above range. A method of manufacturing a sealing material,
Preparing a polymer alloy in which zinc methacrylate is dispersed in hydrogenated nitrile rubber, and a hydrogenated nitrile rubber not containing zinc methacrylate,
Mixing the polymer alloy and the hydrogenated nitrile rubber not containing zinc methacrylate so that the content ratio of polymer alloy: hydrogenated nitrile rubber is 40:60 to 70:30 by weight ratio. Have.

  According to the present invention, the hydrogenated nitrile rubber contains zinc methacrylate in a specific ratio, and further contains a specific amount of the specific carbon fiber described above, so that the rubber has excellent wear resistance and has an appropriate elongation. A composition can be obtained.

  Furthermore, instead of simply adding zinc methacrylate to hydrogenated nitrile rubber, a polymer alloy in which zinc methacrylate is finely dispersed in hydrogenated nitrile rubber and hydrogenated nitrile rubber are mixed, and the content ratio is adjusted. By setting it as a specific range, the rubber composition according to the present invention can be obtained more easily while obtaining the above effects.

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. Moreover, since the rubber composition has an appropriate elongation, 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. .

  Such a sealing material is prepared by preparing a polymer alloy in which zinc methacrylate is finely dispersed in hydrogenated nitrile rubber, hydrogenated nitrile rubber, and carbon fiber, and finely dispersing zinc methacrylate in hydrogenated nitrile rubber. It is obtained by mixing a polymer alloy and a hydrogenated nitrile rubber containing no zinc methacrylate at a specific content ratio.

  Hereinafter, each component contained in the rubber composition of the present embodiment will be described. The rubber composition of this embodiment is a rubber composition containing a polymer alloy in which zinc methacrylate is finely dispersed in hydrogenated nitrile rubber and a hydrogenated nitrile rubber not containing zinc methacrylate in a specific ratio. is there.

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 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, It is preferable that it is 100 or less, More preferably, it is 50-85.

Polymer Alloy In the rubber composition of the present embodiment, the polymer alloy is obtained by finely dispersing zinc methacrylate in a hydrogenated nitrile rubber. The hydrogenated nitrile rubber is not particularly limited, but a hydrogenated nitrile rubber having properties such as the amount of bound acrylonitrile within the above range is preferable. Zinc methacrylate is preferably contained in an amount of 60 to 68% by weight per 100% by weight of the polymer alloy.

  In the rubber composition of the present embodiment, the polymer alloy and the hydrogenated nitrile rubber are contained in a weight ratio of 40:60 to 70:30, preferably 45:55 to 65:35. By doing in this way, the abrasion resistance of the rubber composition of this embodiment can be improved. If it is out of the above range, the wear resistance tends to deteriorate.

  In addition, when zinc methacrylate is directly contained in the hydrogenated nitrile rubber, adhesion to a kneader or a roll surface is observed during kneading, and it may be difficult to perform uniform kneading. Further, when zinc methacrylate is produced in hydrogenated nitrile rubber, a uniform rubber composition can be obtained, but physical properties such as tensile strength may vary depending on production conditions such as kneading temperature.

  Therefore, in the present embodiment, the polymer alloy in which zinc methacrylate is finely dispersed in the hydrogenated nitrile rubber and the hydrogenated nitrile rubber not containing zinc methacrylate are mixed in the above ratio, thereby achieving uniform and dispersibility. A good rubber composition is obtained. As a result, the effects of the present invention can be obtained.

Carbon fiber In the rubber composition of the present embodiment, pitch-based carbon fiber is used as the 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 wear resistance cannot be improved, 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 likely to be worn away, so that the wear resistance cannot be improved. The random structure is a structure in which the carbon network surface constituting the carbon fiber is not arranged in a specific direction, and the radial structure is a structure in which the carbon network surface constituting the carbon fiber is arranged in the radial direction. It is.

  The average fiber length of the carbon fiber is preferably 40 to 300 μm, more preferably 40 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. Further, in order not to lower the elongation, 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 30 to 120 parts by weight, preferably 30 to 110 parts by weight with respect to 100 parts by weight of the total weight of the polymer alloy and the hydrogenated nitrile rubber. If the carbon fiber content is too small, the wear resistance tends to deteriorate. On the other hand, when the amount is too large, elongation tends to decrease and 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 total weight of the polymer alloy and 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. It does not specifically limit as a graphite used by this invention, A commercially available thing can be used.

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

Crosslinking agent The rubber composition of the present embodiment preferably further contains a crosslinking agent. As a crosslinking agent, 1-10 weight part of organic peroxides are contained.

  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. By such a method, zinc methacrylate may be directly contained in the hydrogenated nitrile rubber, or zinc methacrylate may be produced in the hydrogenated nitrile rubber. However, in order to obtain a uniform rubber composition, a polymer alloy in which zinc methacrylate is finely dispersed in hydrogenated nitrile rubber and a hydrogenated nitrile rubber not containing zinc methacrylate are mixed by the above method. Is preferred. The order of blending is not particularly limited. However, 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, it can be heated 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 to obtain a molded product (sealing material) having a desired product shape. it can.

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

Example 1
First, as a polymer alloy in which zinc methacrylate is finely dispersed in hydrogenated nitrile rubber, Zeoforte ZSC2295 manufactured by Nippon Zeon Co., Ltd .: 60 parts by weight; as hydrogenated nitrile rubber not containing zinc methacrylate, Zetpol 2000 manufactured by Nippon Zeon : 40 parts by weight, pitch-based carbon fiber made by Osaka Gas Chemical as carbon fiber (average fiber length 40 μm): 100 parts by weight, Nitteron # 75 made by Nippon Steel Chemical Co., Ltd. as SRF carbon black: 20 parts by weight, as graphite Chubu graphite industry APR: 10 parts by weight, Kawaguchi Chemical Co., Ltd. Antage 6C: 3 parts by weight as an anti-aging agent, Nihon Yushi Co., Ltd. perbutyl P: 6 parts by weight as a crosslinking agent. 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.

  Zeoforte ZSC2295 contained about 64% by weight of zinc methacrylate. Therefore, 62 parts by weight of zinc methacrylate was contained with respect to 100 parts by weight of hydrogenated nitrile rubber. In addition, the amount of acrylonitrile of Zeforte ZSC2295 was 36.2%, the iodine value was 28 or less, and the Mooney viscosity was 85. Further, the amount of acrylonitrile of Zetpol 2000 was 36.2%, the iodine value was 7 or less, and the Mooney viscosity was 85.

  Using the obtained sheet-like rubber composition and the lip-type seal, normal physical properties, wear resistance, and the presence or absence of cracks during shaft insertion 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.

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

Rotation test 1
With respect to the obtained lip type seal, using engine oil (turbine oil VG32) as a sealing fluid, peripheral speed: 4 m / sec, fluid pressure: 5 MPa, fluid temperature: 150 ° C., test time: 10 hours A rotation test was performed below. After the test, the wear depth of the lip seal, the amount of fluid leakage, and the residual interference were measured.

  The residual tightening allowance is a value defined by (shaft diameter) − (inner diameter of the lip seal after the test), and becomes smaller due to wear and settling of the lip portion. Accordingly, when the residual interference is reduced, the sealing performance is deteriorated.

Rotation test 2
For the obtained lip type seal, oil for compressor (PAG oil) was used as a sealing fluid, peripheral speed: 5 m / sec, fluid temperature: 170 ° C., CO ₂ gas pressure: 5.5 MPa, test time: 18 A rotation test was performed under time conditions. After the test, the wear depth of the lip seal, the amount of fluid leakage, and the residual interference were measured.

  The following shaft insertion test was conducted as an evaluation of the ease of cracking during shaft insertion.

Shaft Insertion Test The number of cracks generated when the obtained lip seal was inserted into the shaft was evaluated under the conditions of ambient temperature: 0 ° C. and speed: 800 mm / sec. This was performed for 10 seals, and the number of seals with cracks was calculated.

Examples 2 and 3
A rubber composition was prepared and molded in the same manner as in Example 1 except that the contents of Zeoforte ZSC2295 and Zetpol 2000 were changed to the amounts shown in Table 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Examples 4 and 5
In Example 4, except for the carbon fiber content of 40 parts by weight, the same procedure as in Example 1 was carried out. In Example 5, Kureha pitch-based carbon fiber (average fiber length 150 μm) was used as the carbon fiber. A rubber composition was prepared and molded in the same manner as in Example 1 except that the content was changed to 40 parts by weight, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 6
A rubber composition was prepared and molded in the same manner as in Example 1 except that Zeoforte ZSC2095 was used as the polymer alloy and Zetpol 2030 was used as the hydrogenated nitrile rubber, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

  In addition, Zeoforte ZSC2095 contained about 64% by weight of zinc methacrylate.

Comparative Examples 1-4
A rubber composition was prepared and molded in the same manner as in Example 1 except that the content ratio (weight ratio) of the polymer alloy and the hydrogenated nitrile rubber was changed to the values shown in Table 1. Evaluation was performed. In addition, the rubber composition which concerns on the comparative example 1 is comprised only by hydrogenated nitrile rubber, and the rubber composition which concerns on the comparative example 2 is comprised only by the polymer alloy.

Comparative Examples 5 and 6
A rubber composition was prepared and molded in the same manner as in Example 1 except that the carbon fiber content was 20 parts by weight (Comparative Example 5) and 200 parts by weight (Comparative Example 6). Evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Examples 7 and 8
Except for using carbon fiber pitch-based carbon fiber (average fiber length 50 μm) (Comparative Example 7) and Toray PAN-based carbon fiber (average fiber length 130 μm) (Comparative Example 8) as carbon fibers, 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. The pitch carbon fiber manufactured by Mitsubishi Chemical Corporation has a radial structure.

From Evaluation Table 1, when the content ratio (weight ratio) of the polymer alloy and the hydrogenated nitrile rubber is within the scope of the present invention, and the content of the carbon fiber having a specific structure is within the scope of the present invention (Example 1). In ~ 6), it can be confirmed that the wear resistance in the rotation test is good. Furthermore, since it has an appropriate elongation, the occurrence of cracks in the shaft insertion test was not observed.

  On the other hand, when the weight ratio between the polymer alloy and the hydrogenated nitrile rubber is out of the range of the present invention (Comparative Examples 1 to 4), the wear resistance is deteriorated, and cracks in the shaft insertion test occur. Things were seen.

  Further, when the carbon fiber content was less than the range of the present invention (Comparative Example 5), although the elongation was large, the result was inferior in wear resistance. When the carbon fiber content is larger than the range of the present invention (Comparative Example 6), the wear resistance is good, but since the elongation is small, many cracks occurred in the shaft insertion test.

  Even when the content of the carbon fiber is within the range of the present invention, when a pitch-based carbon fiber having a radical structure that is not a random structure is used (Comparative Example 7), the carbon fiber itself is easily worn, It can be confirmed that the wearability has deteriorated.

  In addition, when PAN-based carbon fiber is used as the carbon fiber (Comparative Example 8), it can be confirmed that the wear resistance is extremely deteriorated.

Claims (5)

Hydrogenated nitrile rubber, zinc methacrylate, and carbon fiber,
The zinc methacrylate is contained in an amount of 30 to 90 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber.
The carbon fiber is a pitch-based carbon fiber having a random structure,
A rubber composition containing 30 to 120 parts by weight of the carbon fiber with respect to 100 parts by weight of the hydrogenated nitrile rubber. A polymer alloy in which zinc methacrylate is dispersed in hydrogenated nitrile rubber;
Hydrogenated nitrile rubber containing no zinc methacrylate;
Carbon fiber, and
The content ratio of the said polymer alloy and the hydrogenated nitrile rubber which does not contain the said zinc methacrylate exists in the relationship of polymer alloy: hydrogenated nitrile rubber = 40: 60-70: 30 by weight ratio. Rubber composition.   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 or 2. A method for producing the sealing material according to claim 3,
Preparing a polymer alloy in which zinc methacrylate is dispersed in hydrogenated nitrile rubber, and a hydrogenated nitrile rubber not containing zinc methacrylate,
Mixing the polymer alloy and the hydrogenated nitrile rubber not containing zinc methacrylate so that the content ratio of polymer alloy: hydrogenated nitrile rubber is 40:60 to 70:30 by weight ratio. The manufacturing method of the sealing material which has.