JP5464738B2 - Hydrogenated nitrile rubber composition for lip seals - Google Patents

Description

  The present invention relates to a hydrogenated nitrile rubber composition. More specifically, the present invention relates to a hydrogenated nitrile rubber composition that is excellent in gas shielding properties and that is suitably used as a molding material for a sealing material by suppressing the sag of a sealing portion.

  A rubber composition having hydrogenated nitrile rubber as a base polymer is excellent in gas shielding properties, mechanical properties, and heat resistance, and is particularly used as a molding material for various sealing materials. In particular, a sealing material used under severe conditions such as high temperature, high pressure, and high speed is required to have high durability in order to maintain the sealing ability of the seal portion. Further, when a gas that easily permeates a rubber material such as hydrogen, helium, oxygen, carbon dioxide, and chlorofluorocarbon is used as a sealing fluid to be sealed, it is extremely important to achieve both gas shielding and durability.

  In a rubber composition that meets such requirements, the type and ratio of various fillers constituting the rubber composition together with the type of base polymer have a very important influence on the mechanical properties and heat resistance.

  For example, Patent Documents 1 and 2 disclose conventional techniques that define the type of base polymer and the type and amount of filler in the rubber composition in order to improve the durability of the sealing material. The rubber composition according to the prior art uses, for example, hydrogenated nitrile rubber having an acrylonitrile bond amount of 30% or more as a base polymer, and carbon fiber (carbon fiber) as a filler with respect to 100 parts by weight of hydrogenated nitrile rubber. About 60 to 200 parts by weight.

  The rubber composition as described above has improved wear resistance by blending a large amount of carbon fiber. However, since a large amount of carbon fiber as described above increases the modulus value of the rubber composition, particularly in a dynamic seal portion, the force (stressing force) for pressing the sealing material against the shaft or the like becomes large, resulting in There arises a problem of increasing sliding heat generation. When the sliding heat generation is large, the deterioration of the compression set resistance property of the sealing material molded from the rubber composition becomes prominent at an early stage, causing a sag in the sealing portion and contributing to a decrease in sealing ability. Further, these rubber compositions tend to impair the inherent elastic material properties of rubber by blending a large amount of filler, and from this point, permanent distortion is likely to occur.

  Moreover, as another prior art regarding a rubber composition, there exist some which were disclosed by patent document 3 and 4, for example. Such a rubber composition according to the prior art has improved wear resistance and heat resistance by blending a predetermined amount or more of a filler such as carbon black.

However, among such rubber compositions, those using hydrogenated nitrile rubber having an acrylonitrile bond amount of 38% or less do not have sufficient gas shielding properties. Further, those using hydrogenated nitrile rubber having an acrylonitrile bond amount of 40% or more have high gas shielding properties but have problems in durability. That is, since the rubber composition according to the prior art focuses only on blending a large amount of a filler such as carbon black, the mechanical strength increases, but the modulus value also increases at the same time. Therefore, when these rubber compositions are used as a sealing material, there is a problem that the tightening force of the seal portion is large, and as a result, sliding heat generation is large. When the sliding heat generation is large, the deterioration of the compression set resistance property of the sealing material molded from the rubber composition becomes prominent at an early stage, causing a sag in the sealing portion and contributing to a decrease in sealing ability. Further, these rubber compositions tend to impair the inherent elastic material properties of rubber by blending a large amount of filler, and from this point, permanent distortion is likely to occur.
JP 2006-131700 A JP 2004-217851 A JP 2002-80639 A Republished WO 2004/022643

  Provided is a hydrogenated nitrile rubber composition that is suitably used as a molding material or the like for a sealing material by being excellent in gas shielding properties and suppressing the sag of a sealing portion.

  As a result of intensive studies to achieve the above object, the present inventor has identified hydrogen nitrile rubber, carbon black, graphite, and carbon fiber with an acrylonitrile bond amount in a specific range, and specified these. It was found that a rubber material excellent in all of compression set resistance, gas shielding properties and mechanical strength properties can be obtained by blending in a limited weight ratio range, and the present invention has been completed.

  That is, the rubber composition according to the present invention achieves unsolved problems in the prior art when a base polymer having excellent gas shielding properties is used, that is, suppression of sliding heat generation and sag. In particular, with regard to the sealing material according to the rubber composition, it is possible to achieve both gas shielding properties and compression set resistance properties at an extremely high level, and the effect thereof is that the blending amount of the filler is set to a predetermined upper limit value and lower limit value. It has been found for the first time by the present inventor that it can be obtained only when it is between.

That is, the rubber composition of the present invention is a rubber composition obtained by blending at least carbon black, graphite, and carbon fiber with a hydrogenated nitrile rubber having an acrylonitrile bond amount of 40% or more and 48% or less,
The total blending amount of the carbon black, the graphite, and the carbon fiber is 110 parts by weight or more and 135 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  Further, for example, the compounding amount of the carbon black may be 40 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  Further, for example, the blending amount of the graphite may be 20 parts by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  For example, the compounding amount of the carbon fiber may be 35 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber.

  Further, for example, in the rubber composition according to the present invention, the total amount of the carbon black, the graphite, and the carbon fiber is 115 parts by weight or more and 125 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber. There may be.

  By blending the base polymer and various fillers in the range of the weight ratio limited as described above, a rubber material excellent in all of compression set resistance, gas shielding properties and mechanical strength properties can be obtained.

For example, the hydrogenated nitrile rubber may have a Mooney viscosity ML _{1 + 4} (100 ° C.) (based on JIS K6395) of 65 or more and 85 or less (central value) and an iodine value (central value) of 26 or less.

  By using the hydrogenated nitrile rubber as described above, a rubber material excellent in gas shielding properties, compression set resistance, and the like can be obtained more reliably.

  For example, the rubber composition according to the present invention may have a 30% modulus of 7 MPa or more and 15 MPa or less.

  By setting the modulus value within the above range, it is possible to suppress pressure deformation and sliding heat generation of the seal portion when used as a seal material, and it is possible to more reliably suppress the sag of the seal portion. In addition, problems such as excessive wear of the seal portion due to the low strength of the material and cracking of the seal portion due to the small elongation of the material can be avoided.

FIG. 1 is a schematic cross-sectional view of a sealing device in which a rubber composition according to an embodiment of the present invention is applied to an end face lip seal. FIG. 2 is a schematic cross-sectional view of an end face lip seal used for evaluation of rubber compositions according to examples and comparative examples of the present invention. FIG. 3 is a cross-sectional view of the main part showing the evaluation criteria of the rotation test of the end face lip seal according to the example of the present invention and the comparative example.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings. The rubber composition according to the present invention will be described as an example of a sealing device applied to an end face lip seal, but the application of the rubber composition according to the present invention is not limited to an end face lip seal, but may be applied to other sealing devices, etc. It is also possible to do.

  FIG. 1 shows an example of a sealing device 1 to which a rubber composition according to an embodiment of the present invention is applied. An end face lip seal 4 formed by molding a rubber composition according to an embodiment of the present invention seals between the rotating shaft 2 and the stationary ring 10. The shaft 2 has a large diameter portion 2a and a small diameter portion 2c, and a step portion 2b is formed between the large diameter portion 2a and the small diameter portion 2c. The end face lip seal 4 is formed in a ring shape so that the outer periphery of the shaft 2 can be sealed in the circumferential direction on the entire circumference.

  As shown in the enlarged view of FIG. 2, the end face lip seal 4 is constituted by a lip seal main body portion 5 formed from a rubber composition and a reinforcing ring 8 formed integrally with the lip seal main body portion 5. The lip seal main body part 5 passes from the base part 5a in contact with the large diameter part 2a of the shaft 2 to the tip part 5c in contact with the small diameter part 2c of the shaft 2 through the intermediate part 5b in contact with the stepped part 2b of the shaft 2. , Extending in the axial direction along the outer periphery of the shaft 2.

  A lip portion 5d is formed at the tip in the axial direction of the tip portion 5c. The lip portion 5d extends in the axial direction from the tip portion 5c while being slightly inclined outward in the radial direction of the shaft. The lip portion 5d seals the atmosphere side and the sealing fluid side by sliding on the stationary ring 10 of the sealing device 1. The reinforcing ring 8 extends from the base 5a of the lip seal body 5 to the root of the lip 5d, and reinforces the lip seal body 5.

  The sealed fluid to which the sealing device of the present invention is applied is not particularly limited, and examples thereof include gas that easily permeates a rubber material such as hydrogen, helium, and oxygen. The other sealed fluid may be a refrigerant gas such as a chlorofluorocarbon refrigerant or a natural refrigerant, or may be a liquid such as water, oil, or a chemical solution, or a mixed fluid of gas and liquid.

  Hereinafter, each component contained in the rubber composition applied to the lip seal main body 5 will be described.

Hydrogenated nitrile rubber In the rubber composition according to the present embodiment, the hydrogenated nitrile rubber includes a double bond of a butadiene unit contained in the main chain of NBR which is a copolymer rubber of acrylonitrile and butadiene. Those obtained by hydrogenation (HNBR) are 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 hydrogenated nitrile rubber has an acrylonitrile bond amount of 40 to 48%, preferably 43 to 45%. If the amount of acrylonitrile bond is too small, the gas shielding property is deteriorated. If it is too large, the glass transition temperature of the hydrogenated nitrile rubber is increased, so that the cold resistance as a seal is deteriorated and it cannot be put into practical use.

Further, the iodine value (center value) is not particularly limited, but is preferably 26 or less. If the iodine value is too large, the heat resistance decreases, and for example, the amount of wear at high temperatures increases. Moreover, Mooney viscosity (ML1 _{+ 4} , 100 degreeC) is although it does not specifically limit, Preferably, it is 65-85. When the Mooney viscosity is out of this range, kneading with various fillers tends to be difficult, and it is difficult to obtain a desired shape and characteristics after molding.

  If the amount of acrylonitrile bond is within the above range, hydrogenated nitrile rubber can be selected according to the desired properties. Specifically, the ZEPOL series manufactured by Nippon Zeon Co., Ltd. Can be used.

Carbon black In the rubber composition according to the present embodiment, the amount of carbon black used as one of the fillers is preferably 40 to 60 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber. More preferably, it is 45-55 weight part. If the blending amount of the carbon black is larger than the above range, the modulus value increases, so that the tightening force and the heat generation amount of the seal portion increase. When the amount of heat generated at the seal portion increases, the deterioration of the compression set resistance property of the seal material becomes prominent at an early stage, sag occurs at the seal portion, and the performance of the seal deteriorates. If the carbon black content is less than the above range, the strength of the rubber composition will be insufficient. As a result, the wear resistance of the sealing material will decrease and the amount of deformation of the sealing material will be large, so the amount of sag will be large. Tend to be.

Graphite In the rubber composition according to the embodiment, the amount of graphite used as one of the fillers is preferably 20 to 40 parts by weight, more preferably 100 parts by weight of hydrogenated nitrile rubber. 25 to 35 parts by weight. If the blending amount of graphite is larger than the above range, the modulus value increases, so that the tightening force and the heat generation amount of the seal portion increase. When the amount of heat generated at the seal portion increases, the deterioration of the compression set resistance property of the seal material becomes prominent at an early stage, sag occurs at the seal portion, and the performance of the seal deteriorates. Furthermore, the elongation of the rubber composition tends to decrease. On the other hand, if the blending amount of graphite is less than the above range, the strength of the rubber composition is insufficient, resulting in a decrease in the wear resistance of the sealing material or a large amount of deformation of the sealing material. The amount tends to increase. Further, the lubricity of the sliding surface is deteriorated, and the friction and wear characteristics tend to be deteriorated.

Carbon fiber In the rubber composition according to the present embodiment, the blending amount of the carbon fiber used as one of the fillers is preferably 35 to 50 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber. More preferably, it is 40-45 weight part. If the blending amount of the carbon fiber is larger than the above range, the modulus value increases, and therefore the tightening force and the heat generation amount of the seal portion increase. When the amount of heat generated at the seal portion increases, the deterioration of the compression set resistance property of the seal material becomes prominent at an early stage, sag occurs at the seal portion, and the performance of the seal deteriorates. Moreover, if the blending amount of the carbon fiber is less than the above range, the strength of the rubber composition is insufficient, resulting in a decrease in the wear resistance of the sealing material or a large amount of deformation of the sealing material. Tend to be larger.

  In the rubber composition according to this embodiment, the total amount of carbon black, graphite, and carbon fiber is 95 parts by weight or more and 150 parts by weight or less, preferably 110 parts by weight or more with respect to 100 parts by weight of the hydrogenated nitrile rubber. 135 parts by weight or less, more preferably 115 parts by weight or more and 125 parts by weight or less. If the total blending amount is larger than the above range, the modulus value increases, so that the tightening force and the heat generation amount of the seal portion increase. When the amount of heat generated at the seal portion increases, the deterioration of the compression set resistance property of the seal material becomes prominent at an early stage, sag occurs at the seal portion, and the performance of the seal deteriorates. Further, if the total blending amount is larger than the above-mentioned range, the ratio of the base polymer in the rubber composition is reduced, so that the molded product tends to generate permanent distortion, and from this point, it tends to become a material that is easily lost. is there. Further, if the total amount of the filler is less than the above range, the rubber composition is insufficient in strength. As a result, the wear resistance of the sealing material is reduced, and the amount of deformation of the sealing material is large. The amount tends to increase.

Crosslinking agent In the rubber composition according to the present embodiment, the crosslinking agent for the hydrogenated nitrile rubber is preferably an organic peroxide, and preferably about 1 to 10 parts per 100 parts by weight of the hydrogenated nitrile rubber. Contained in parts by weight.

  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 according to the present embodiment includes an anti-aging agent, a reinforcing agent, a processing aid, a light stabilizer, a plasticizer, a lubricant, an adhesive, a lubricant, a difficult agent, as necessary. You may mix | blend additives, such as a flame retardant, an antifungal agent, an antistatic agent, a coloring agent, and a filler.

  As a method for preparing the rubber composition, an appropriate mixing method such as kneader mixing, Banbury mixing, screw mixing, or the like can be adopted. The order of blending is not particularly limited, but after 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 a crosslinking agent, are kneaded at a temperature at which reaction or decomposition does not occur. That's fine.

  After kneading, it is heated at about 160 to 220 ° C. for about 3 to 10 minutes (primary crosslinking) by a molding method such as extrusion molding, injection molding, transfer molding or compression molding, and further, if necessary, about 1 at about 150 to 200 ° C. It can be heated for ~ 30 hours (secondary crosslinking) to obtain a molded product having a desired product shape.

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

Example 1
Zeonpol 1000L manufactured by Nippon Zeon Co., Ltd. as hydrogenated nitrile rubber (acrylonitrile bond amount 44.2%, iodine value (center value) 7, Mooney viscosity ML _{1 + 4} (100 ° C.) 70): 100 parts by weight, new as carbon black Niteron # 75 manufactured by Nippon Steel Chemical Co., Ltd .: 50 parts by weight, graphite as APR manufactured by Chuetsu Graphite Industries Co., Ltd .: 30 parts by weight, carbon fiber manufactured by Mitsubishi Chemical Co., Ltd. DIALEAD M6371M: 45 parts by weight, What blended 6 parts by weight of perbutyl P manufactured by NOF Corporation as an organic peroxide and 2 parts by weight of ANTAGE 6C manufactured by Kawaguchi Chemical Industry Co., Ltd. as an anti-aging agent using a 3 L kneader and a 10 inch roll Kneaded. This kneaded product was molded and vulcanized at 170 ° C. for 8 minutes to obtain a sheet material having a thickness of about 2 mm and an end face lip seal 4 as shown in FIGS.

  The sheet material was used for evaluation of normal properties of the rubber composition. The end face lip seal 4 was formed by molding integrally with the reinforcing ring 8 and used for static test and rotation test. The inner diameter of the end face lip seal 4 used for the evaluation is φ11 mm, and the diameter of the tip of the lip portion 5 d is φ15 mm before being incorporated into the seal device 1.

  The following evaluation was performed on the sheet material and the end face lip seal 4 according to the rubber composition thus obtained. The evaluation results are shown in Table 1.

Normal properties (tensile strength, elongation, 30% modulus)
Evaluation was performed according to JIS K6251.

Static test (lip pressing force, gas leakage)
Regarding the lip pressing force, the end face lip seal 4 is attached to a dedicated jig, the lip portion 5d is compressed to the proper seal attachment position, and the repulsive force of the lip portion 5d at that time is measured by a universal load tester (Shimadzu Corporation). Shimadzu Autograph AG-50kNG, load cell capacity 200N manufactured by Seisakusho Co., Ltd. For the amount of gas leakage, the end face lip seal 4 is attached to a dedicated jig and installed in a thermostatic chamber, and the amount of CO ₂ gas permeation leakage from the end face lip seal 4 at a temperature of 130 ° C. and a CO ₂ gas pressure of 5 MPa is measured. Converted to leakage weight per year. The gas leak amount shown in the result does not include the gas leak amount from other than the seal portion by the end face lip seal 4.

Rotation test (sliding surface temperature, residual tightening allowance, wear type classification)
In the rotation test, the end face lip seal 4 is incorporated in the form of the sealing device 1 as shown in FIG. 1, PAG oil (kinematic viscosity: 48 mm ² / s (40 ° C.)) is sealed up to the shaft core, the oil temperature is 110 ° C., The test was carried out for 22 hours under conditions of a CO ₂ gas pressure of 5 MPa and a peripheral speed of 6.3 m / s. For the sliding surface temperature, a thermocouple was embedded 1 mm below the sliding surface of the stationary ring 10, and the sliding surface temperature during steady rotation was measured. As shown in FIG. 3, the remaining tightening allowance is obtained by cutting the end face lip seal 4 after the rotation test by a plane passing through the center of the rotation axis, and sliding the fixed ring at the normal seal mounting position with respect to the shape of the cut surface. The position of the surface 10a was calculated by overlapping. The residual fastening allowance is an evaluation of compression set resistance, that is, difficulty of settling.

As for the classification of the wear forms, the end face lip seal 4 after the rotation test was cut by a plane passing through the center of the rotation axis as shown in FIG. 3 and then observed by observing the shape of the lip portion 5d on the cut surface. The classification criteria are shown below.
Class 1 (FIG. 3A): Wear on the lip portion 5d is slight. The wear resistance of the end face lip seal according to the rubber composition classified in this class is good.
Type 2 (FIG. 3B): Local excessive wear occurred during the test. In the rotation test of the sealing material classified in this category, seal squealing, sliding surface temperature hunting, sealing fluid ejection leakage, etc. occurred, and the 22-hour rotation test could not be performed. Therefore, data on sliding surface temperature and residual interference allowance could not be obtained. The performance of the end face lip seal according to the rubber composition classified in this class is not satisfactory because the basic performance as a seal, that is, the friction and wear characteristics and durability are not satisfied.

  The rubber composition according to Example 1 had a 30% modulus value of 14.0 MPa, which was a preferable range. Since the 30% modulus value is appropriate, the lip pressing force is within an appropriate range (about 45 to 60 N), and a reliable seal can be realized while suppressing the sliding surface temperature. The amount of gas leakage was 9.0 g / year, which satisfied the target value (10 g / year). Therefore, it was confirmed that the gas barrier properties of the end face lip seal 4 according to Example 1 are extremely good. Further, in association with the lip pressing force being suppressed to 46.4 N, the sliding surface temperature was also suppressed to a low temperature of 177 ° C. The residual tightening margin was as large as 0.24 mm, and the wear form was also classified as the first class and was good. From the results of such residual tightening allowance and wear form, it was confirmed that the compression set and wear resistance of the end face lip seal 4 according to the rubber composition of Example 1 were extremely good. That is, it was confirmed that the rubber composition according to Example 1 can provide a sealing material excellent in all of compression set resistance properties, gas shielding properties, and wear resistance.

Example 2
A sheet material and an end face lip seal 4 were prepared in the same manner as in Example 1 except that Niteron # 10 manufactured by Nippon Steel Chemical Co., Ltd. was used as carbon black, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The rubber composition according to Example 2 had a 30% modulus value of 12.7 MPa, which was a preferable range as in Example 1. The results of the static test and the rotation test of the end face lip seal 4 according to Example 2 also satisfied the target value as in Example 1. Therefore, it was confirmed that the rubber composition according to Example 2 provides a sealing material that is excellent in all of compression set resistance, gas shielding properties, and wear resistance.

Example 3
Example 1 except that Zettopol 1020 (acrylonitrile bond amount 44.2%, iodine value (center value) 24, Mooney viscosity ML _{1 + 4} (100 ° C.) 78) manufactured by Nippon Zeon Co., Ltd. was used as the hydrogenated nitrile rubber. In the same manner as above, a sheet material and an end face lip seal 4 were prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The rubber composition according to Example 3 had a 30% modulus value of 13.9 MPa, which was a preferable range as in Example 1 or 2. The results of the static test and the rotation test of the end face lip seal 4 according to Example 3 also satisfied the target value as in Example 1. Therefore, it was confirmed that the rubber composition according to Example 3 can provide a sealing material having excellent compression set resistance, gas shielding properties, and wear resistance.

Example 4
A sheet material and an end face lip seal 4 were produced in the same manner as in Example 1 except that the blending amount of the carbon fiber was changed to 35 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The rubber composition according to Example 4 had a 30% modulus value of 9.3 MPa, which was a preferable range as in Example 1. Moreover, the results of the static test and the rotation test of the end face lip seal 4 according to Example 4 also satisfied the target value as in Examples 1-3. Therefore, it was confirmed that the rubber composition according to Example 4 provides a sealing material excellent in all of compression set resistance properties, gas shielding properties, and wear resistance.

Example 5
Zettopol 1020 manufactured by Nippon Zeon Co., Ltd. (acrylonitrile bond amount: 44.2%, iodine value (center value) 24, Mooney viscosity ML _{1 + 4} (100 ° C.) 78) is used as hydrogenated nitrile rubber, and carbon fiber is blended A sheet material and end face lip seal 4 were produced in the same manner as in Example 1 except that the amount was changed to 35 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The rubber composition according to Example 5 had a 30% modulus value of 12.4 MPa, which was a preferable range as in Example 1. Moreover, the results of the static test and the rotation test of the end face lip seal 4 according to Example 5 also satisfied the target value as in Examples 1 to 4. Therefore, it was confirmed that the rubber composition according to Example 5 provides a sealing material excellent in all of compression set resistance, gas shielding properties and wear resistance.

Comparative Example 1
Zeonpol 2000 (manufactured by Nippon Zeon Co., Ltd., 36.2% acrylonitrile bond, iodine value (center value) 7, Mooney viscosity ML _{1 + 4} (100 ° C.) 85) was used as the hydrogenated nitrile rubber, and the amount of carbon black blended The sheet material and the end face lip seal 4 were produced in the same manner as in Example 1 except that the amount was changed to 90 parts by weight and the amount of graphite was changed to 15 parts by weight. The same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  Since the end face lip seal 4 made of the rubber composition according to Comparative Example 1 had a gas leakage amount of 14.6 g / year, the target value (10 g / year) was not satisfied. Further, the residual tightening margin was extremely small as 0.04 mm, and the target value (0.2 mm or more) was not satisfied. Therefore, the sealing material according to the rubber composition of Comparative Example 1 was inferior in gas shielding properties and compression set resistance properties.

Comparative Example 2
The sheet material and the end face lip seal were the same as in Example 1 except that the amount of carbon black was changed to 90 parts by weight, the amount of graphite was changed to 15 parts by weight, and the amount of carbon fiber was changed to 65 parts by weight. 4 was produced and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The end face lip seal 4 made of the rubber composition according to Comparative Example 2 has a high target lip pressing force of 76.0 N and a sliding surface temperature of 211 ° C. The value (0.2 mm or more) is not satisfied. That is, the sealing material according to the rubber composition of Comparative Example 2 was inferior in compression set resistance.

Comparative Example 3
As a hydrogenated nitrile rubber, Zeonpol 2000L manufactured by Nippon Zeon Co., Ltd. (acrylonitrile bond amount 36.2%, iodine value (center value) 7, Mooney viscosity ML _{1 + 4} (100 ° C.) 65) is used. The sheet material and the end face lip seal 4 were prepared in the same manner as in Example 1 except that the amount of graphite was changed to 90 parts by weight, the amount of graphite was changed to 15 parts by weight, and the amount of carbon fiber was changed to 65 parts by weight. Evaluation similar to Example 1 was performed. The evaluation results are shown in Table 1.

  Since the end face lip seal 4 made of the rubber composition according to Comparative Example 3 had a gas leakage amount of 14.2 g / year, the target value (10 g / year) was not satisfied. Further, in relation to the lip pressing force being as high as 64.3 N and the sliding surface temperature being as high as 201 ° C., the residual fastening allowance does not satisfy the target value (0.2 mm or more). Therefore, the sealing material according to the rubber composition of Comparative Example 3 was inferior in gas shielding properties and compression set resistance properties.

Comparative Example 4
A sheet material and an end face lip seal 4 were produced in the same manner as in Example 1 except that the blending amount of carbon black was changed to 90 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The end face lip seal 4 made of the rubber composition according to Comparative Example 4 has a high lip pressing force of 85.2 N and a sliding surface temperature as high as 217 ° C. The value (0.2 mm or more) is not satisfied. That is, the sealing material according to the rubber composition of Comparative Example 4 was inferior in compression set resistance.

Comparative Example 5
A sheet material and an end face lip seal 4 were produced in the same manner as in Example 1 except that the amount of graphite was changed to 10 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The end face lip seal 4 made of the rubber composition according to Comparative Example 5 was inferior because the wear mode was classified into two types. In addition, it is estimated that the cause of the defect was that the strength of the sealing material was insufficient in relation to the low tensile strength. Further, it is estimated that other causes of defects were poor lubricity on the sliding surface and poor friction and wear characteristics.

Comparative Example 6
A sheet material and an end face lip seal 4 were produced in the same manner as in Example 1 except that the amount of graphite was changed to 50 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The end face lip seal 4 made of the rubber composition according to Comparative Example 6 was inferior because the wear mode was classified into two types. In addition, it is estimated that the cause of the defect was that the sliding surface temperature was high in relation to the high lip pressing force.

Comparative Example 7
A sheet material and an end face lip seal 4 were prepared in the same manner as in Example 1 except that the amount of carbon fiber was changed to 25 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The end face lip seal 4 made of the rubber composition according to Comparative Example 7 was inferior because the wear mode was classified into two types. In addition, it is estimated that the cause of the defect was that the strength of the sealing material was insufficient in relation to the low tensile strength.

Comparative Example 8
A sheet material and an end face lip seal 4 were produced in the same manner as in Example 1 except that the blending amount of carbon black was changed to 30 parts by weight, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  The end face lip seal 4 made of the rubber composition according to Comparative Example 8 was inferior because the wear mode was classified into two types. In addition, it is estimated that the cause of the defect was that the strength of the sealing material was insufficient in relation to the low tensile strength.

Comprehensive evaluation When the examples and comparative examples are combined, hydrogenated nitrile rubber having an acrylonitrile bond amount of 40% or more and 48% or less is used as a base polymer, and the total blending amount of carbon black, graphite and carbon fiber is hydrogen. Only the sealing materials according to Examples 1 to 5 with 110 parts by weight or more and 135 parts by weight or less with respect to 100 parts by weight of the nitrile rubber gave good results in all items. Therefore, it was confirmed that by setting the base polymer and the filler in the above range, a rubber composition excellent in all of compression set resistance, gas shielding properties and wear resistance can be obtained.

Claims (4)

A hydrogenated nitrile rubber composition for lip seals comprising at least carbon black, graphite and carbon fiber blended with a hydrogenated nitrile rubber having an acrylonitrile bond amount of 40% or more and 48% or less,
The total blending amount of the carbon black, the graphite and the carbon fiber is 110 parts by weight or more and 135 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber ,
The compounding amount of the carbon black is 40 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber,
The compounding amount of the graphite is 20 parts by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber,
The hydrogenated nitrile rubber composition for lip seals , wherein the compounding amount of the carbon fiber is 35 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the hydrogenated nitrile rubber. The carbon black, the total amount of the graphite and the carbon fibers, the lip according to claim 1, characterized in that with respect to the hydrogenated nitrile rubber 100 parts by weight, 125 parts by weight 115 parts by weight or more Hydrogenated nitrile rubber composition for sealing . Said hydrogenated nitrile rubber has a Mooney viscosity ML1 + 4 (100 ℃) ( JIS K6395 compliant) is 65 or more 85 or less (center value), in claim 1 or 2, characterized in that iodine value (central value) is 26 or less The hydrogenated nitrile rubber composition for lip seals as described. The hydrogenated nitrile rubber composition for lip seals according to any one of claims 1 to 3, wherein a 30% modulus is 7 MPa or more and 15 MPa or less.

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