JP5653605B2 - Rubber composition and seal member using the same - Google Patents

Description

  The present invention relates to a rubber composition and a seal member using the same.

  In recent years, from the viewpoint of protecting the global environment, use regulations and emission restrictions regarding chemical substances that are concerned about environmental impact have been studied and attracting attention. Refrigeration cycle refrigerants used in refrigeration systems such as car air conditioners are no exception, and alternative CFCs used as refrigerant gas considering the impact on ozone layer destruction are also concerned about the impact on global warming. In the future, regulations will be tightened.

The rubber molded product in the refrigerator seal used in such a refrigerator system is basically excellent in hardness, elongation, tensile strength, etc., has a small compression set, and is used as a refrigerator seal. It is required to have good refrigerant seal characteristics. In particular, as a countermeasure against recent environmental problems, it is required to greatly reduce the amount of refrigerant leakage from the refrigerator seal. The object to be sealed does not leak or has little leakage (low permeability), the swelling by the refrigerant that is the object to be sealed is small, and the blister (crack) due to the expansion of the refrigerant gas that has penetrated into the rubber molding It is also required not to occur (blister resistance). As the refrigerant, fluorohydrocarbon such as HFC134a (CH ₂ FCF ₃ ) having an ozone depletion coefficient of 0 is used, and the rubber composition in the seal member has resistance to the fluorohydrocarbon such as HFC134a described above. In addition, a material in which the volume change rate of the PAG (polyalkylene glycol) and POE (polyol ester) used together with the refrigerating machine oil is suppressed is required.

  Nitrile rubber and hydrogenated nitrile rubber are known as rubber compositions used for the above-described refrigerator seals, but problems still remain in terms of blister resistance and permeability. Further, ethylene propylene rubber has been studied as a rubber material having relatively good blister resistance and permeation resistance against chlorofluorocarbon gas. Ethylene propylene rubber, which is inferior in refrigeration machine oil resistance, is also a rubber composition for a seal member for a refrigerant machine. There is still a problem.

  Accordingly, hydrogenated nitrile rubber, ethylene propylene rubber, and organic peroxide vulcanized rubber compositions have been studied, and the rubber compositions described in Patent Document 1 and Patent Document 2 are made of ethylene propylene rubber having a specific Mooney viscosity. It is stated that the use improves blister resistance or Freon gas barrier properties.

Japanese Patent Laid-Open No. 9-77911 JP 2002-212362 A

The object of the present invention is that the volume change rate with respect to HFC134a refrigerant and refrigerating machine oil ( POE oil) is small, and the permeation amount of HFC134a is reduced compared with the case of using hydrogenated nitrile rubber alone. there is provided a blisters excellent sealing member.

(1) A seal member used for a refrigerant seal of a refrigerator system in which POE (polyol ester) refrigerator oil and HFC134a are used together, and the seal member has a mass of hydrogenated nitrile rubber: ethylene propylene rubber It consists of a rubber molded product obtained by molding a rubber composition containing a rubber polymer in a ratio of 40:60 to 90:10, a filler, and a crosslinking agent, and the tensile stress M at 100% elongation of the rubber molded product _A seal member using a rubber molded product having a ₁₀₀ value of 8.0 MPa or more.
(2) The filler according to (1) is carbon black, and the carbon black is formed by molding a rubber composition containing 55 to 150 parts by mass with respect to 100 parts by mass of the rubber polymer. The sealing member according to (1), which is characterized.

  The rubber polymer is a mixture of different kinds of organic polymers, and in the present invention, it is a mixture of hydrogenated nitrile rubber and ethylene propylene rubber. The rubber composition refers to one containing the rubber polymer, a filler and a crosslinking agent. The rubber molded product refers to a product obtained by molding a rubber composition.

By using a rubber molded product obtained by molding the rubber composition according to the present invention, the volume change rate (based on JIS K 6258) of both refrigerant HFC134a, PAG refrigerating machine oil, and POE refrigerating machine oil with respect to both refrigerating machine oils is + 10%. Excellent resistance at: Furthermore, the permeation amount of the refrigerant HFC134a is significantly reduced as compared with the case of using a hydrogenated nitrile rubber alone, and has excellent blister resistance against the refrigerant HFC134a. The rubber composition is capable of producing an excellent molded product as a sealing material, and facilitates quality control by measuring the tensile stress M ₁₀₀ value at 100% elongation of the chlorofluorocarbon-resistant rubber molded product. Can do. Moreover, since it has the same mechanical characteristics as the case of using a hydrogenated nitrile rubber alone, it can be expected as a material for cost reduction by suppressing the proportion of high-cost hydrogenated nitrile rubber.

  The present invention will be described in detail. The rubber composition of the present invention comprises a hydrogenated nitrile rubber, an ethylene propylene rubber, a filler, and a crosslinking agent. The mixing ratio of the hydrogenated nitrile rubber and ethylene propylene rubber of the rubber polymer is as follows: [1] From the point of volume change rate at 150 ° C. of the refrigeration machine oil (POE oil), 40 parts by mass or more is preferable. If the hydrogenated nitrile rubber is less than 40 parts by mass, the weak point of oil resistance of ethylene propylene rubber appears, and the volume change rate with respect to POE oil exceeds + 10%. [2] From the viewpoint of fluorocarbon gas permeability, ethylene propylene rubber is blended in an amount of 10 to 80 parts by mass with respect to 100 parts by mass of the rubber polymer, thereby reducing the amount of fluorocarbon gas permeated when the rubber polymer is hydrogenated nitrile rubber alone. The relative permeation ratio of 0.0 to 0.4 and the amount of fluorocarbon gas permeation can be reduced. [1] From the viewpoint of resistance to refrigerating machine oil and [2] Freon gas permeability, the content of the hydrogenated nitrile rubber in the rubber polymer is 40 parts by mass or more, preferably 40 to 90 parts by mass with respect to 100 parts by mass of the rubber polymer. Yes, more preferably 40 to 80 parts by mass.

  The hydrogenated nitrile rubber used in the present invention includes a hydrogenated part or all of the conjugated diene unit of the unsaturated nitrile-conjugated diene copolymer rubber, an unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer ternary. Examples thereof include a polymer rubber, a hydrogenated part or all of the conjugated diene unit of the rubber, and an unsaturated nitrile-ethylenically unsaturated monomer copolymer rubber. Specifically, hydrogenated butadiene-acrylonitrile copolymer rubber, isoprene-butadiene-acrylonitrile copolymer rubber, isoprene-acrylonitrile copolymer rubber, butadiene-methyl acrylate-acrylonitrile copolymer rubber, butyl acrylate-ethoxyethyl acrylate- Examples thereof include vinyl chloroacetate-acrylonitrile copolymer rubber and butyl acrylate-ethoxyethyl acrylate-vinyl norbornene-acrylonitrile copolymer rubber. The hydrogenated nitrile rubber may be used alone or in combination of two or more. These hydrogenated nitrile rubbers that are generally commercially available can be used as they are, and are not particularly limited.

  Examples of the ethylene-propylene rubber used in the present invention include ethylene-propylene copolymer rubber or ethylene-propylene-diene copolymer rubber containing a small amount of a third component diene. Yes, it is not particularly limited. Examples of the diene monomer used include ethylidene norbornene, dicyclopentadiene, 1,4-hexadiene, and the content thereof is not particularly limited.

The filler used in the present invention is carbon black, silica, talc, clay, calcium carbonate, calcium silicate, magnesium carbonate or the like, and is not particularly limited as long as it is generally used for rubber. Examples of carbon black include furnace carbon black such as HAF carbon black, MAF carbon black, FEF carbon black, SRF carbon black and GPF carbon black, and thermal carbon black such as FT carbon black and MT carbon black. Can be mentioned. The carbon black content is 55 to 150 parts by mass with respect to 100 parts by mass of the rubber polymer. Specifically, in the case of furnace carbon black, a composition containing 55 to 120 parts by mass with respect to 100 parts by mass of the rubber polymer, and thermal carbon black is preferably a composition containing 80 to 150 parts by mass with respect to 100 parts by mass of the rubber polymer. A rubber composition having more than 120 parts by mass of furnace carbon black or 150 parts by mass of thermal carbon black becomes hard and has poor mechanical properties such as reduced elongation. If the furnace carbon black is less than 55 parts by mass and the thermal carbon black is less than 80 parts by mass, the tensile stress M ₁₀₀ value at 100% elongation does not satisfy 8.0 MPa, so that blisters are generated. Compared with carbon black furnace carbon black and thermal carbon black, considering the O-ring that gives a certain amount of compression (crushing) and seals oil and refrigerant by its repulsive force, it compresses from the quality aspect of long-term sealing performance Thermal carbon black having excellent permanent strain characteristics is preferred. These carbon blacks may be used alone or in combination of two or more.

  The cross-linking agent in the present invention may be a known one and is not particularly limited. For example, o-methylbenzoyl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, lauroyl peroxide, Benzoyl peroxide, t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, dicumyl peroxide, 1,3-bis (t-butylperoxy Isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) -hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) -hexyne-3, di- An organic peroxide such as t-butyl peroxide is preferably used. You may use the said crosslinking agent individually or in combination of 2 or more types. 2-10 mass parts is preferable with respect to 100 mass parts of rubber compositions, More preferably, it is 4-8 mass parts. If it is less than 2 parts by mass, the mechanical properties and compression set properties of the molded product after crosslinking tend to be reduced. If it exceeds 10 parts by mass, the mechanical properties, particularly the elongation, are reduced, and the molded product has a problem of curing. Tend.

  The rubber composition of the present invention may contain a crosslinking aid. For example, polyfunctional compounds such as triallyl cyanurate, triallyl isocyanurate, N, N′-m-phenylenebismaleimide, trimethylolpropane trimethacrylate, triallyl trimellitate, 1,2-polybutadiene are exemplified. . The addition amount is appropriately adjusted within a range not impairing the object of the present invention.

  Further, the rubber composition of the present invention may contain a known plasticizer, anti-aging agent, lubricant, metal oxide, etc., if necessary, and the amount added does not impair the object of the present invention. Adjust as appropriate.

  Moreover, the sealing material of this invention has a rubber molding obtained by shape | molding the mix | blended rubber composition. The rubber molded product is kneaded with a rubber composition using a kneader such as a conventionally known intermix, kneader, Banbury mixer or an open roll, and then desired using an injection molding machine, a compression molding machine, an extrusion molding machine, or the like. Obtained by heating and pressure forming (primary vulcanization) at 150 to 250 ° C. for 3 to 60 minutes, and performing secondary vulcanization at 100 to 200 ° C. for 1 to 24 hours as necessary. It is done. The shape of the sealing material is not particularly limited, and is appropriately selected according to the purpose such as an O-ring, packing, a sheet, a combination of metal and other materials. Also, the size is not particularly limited and is appropriately selected according to the purpose.

  The rubber molded product thus obtained was confirmed using the following test method.

(Hardness test)
A durometer hardness (type A) test was conducted according to the measurement method defined in JIS K 6253.

(Tensile test: tensile strength, elongation at break, tensile stress at 100% elongation)
The test was conducted according to the measurement method defined in JIS K 6251.

(Compression set test)
The test was conducted according to the measurement method defined in JIS K 6262. (Heating condition: 150 ° C., 70 hours) A test piece having a thickness of 12.5 ± 0.5 mm was compressed by 25% with a compression jig, and the compression set after the heat treatment was determined.

(HFC134a immersion test)
The test was conducted according to the measurement method specified in JIS K 6258. In the HFC134a immersion test, the volume change rate was determined after immersion in HFC134a at 70 ° C. for 70 hours. If the volume change rate exceeds + 10%, the seal member may protrude from the groove and leakage may occur. Therefore, the volume change rate + 10% or less was evaluated as ◯. A value exceeding + 10% was evaluated as x.

(Refrigerator oil immersion test)
The test was conducted according to the measurement method specified in JIS K 6258. As the refrigerating machine oil, PAG oil and POE oil were used, and each was immersed for 70 hours at 150 ° C., and then the volume change rate was determined. As with the HFC134a immersion test described above, the volume change rate was + 10% or less, and the value exceeding + 10% was rated as x.

(HFC134a gas permeability test)
An O-ring-shaped specimen was prepared, mounted in a flange-type groove, a predetermined amount of HFC134a was sealed inside the flange, and was placed in a constant temperature bath at 40 ° C. The gas collected in the external collection container through the O-ring is collected, and the permeation amount of HFC134a per unit time is calculated from the result of measurement by gas chromatography. When hydrogenated nitrile rubber is used alone (Comparative Example 7) The results are shown as relative ratios when the transmission amount is 1.

(Blister resistance test (HFC134a))
The specimen was immersed in HFC134a at 25 ° C. for 24 hours, then left in a thermostatic bath at 150 ° C. for 1 hour, taken out, cooled, and then visually evaluated for blister (crack) conditions generated on the specimen surface. A sample having no cracks on the surface of the specimen was marked with ◯, and a sample with cracks was marked with ×.

Rubber molded product obtained by molding the rubber composition of the present invention, a tensile stress _{M 100} value at the time of 100% elongation can be suppressed the occurrence of HFC134a blister equal to or greater than 8.0 MPa. As for the gas permeation amount of HFC134a, the O-ring of the rubber molded product of the present invention can be reduced by 20% to 50% as compared with the O-ring in the case of using a hydrogenated nitrile rubber alone (Comparative Example 7).

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

The basic composition of the rubber composition is shown below.
・ 100 parts by mass of rubber polymer in which hydrogenated nitrile rubber and ethylene propylene rubber are mixed at a specified mixing ratio ・ Filler (thermal carbon black, furnace carbon black)
Crosslinking agent (2,5-dimethyl-2,5-di (t-butylperoxy) -hexane)
・ Cross-linking aid (triallyl isocyanurate: 4 parts by mass)
・ Metal oxide (zinc oxide: 3 parts by mass),
Anti-aging agent (4,4′-bis (α, α-dimethylbenzyl) diphenylamine: 1 part by mass)
-Plasticizer (trimellitic acid tri (2-ethylhexyl): 8 parts by mass),
Were blended in the blending amounts shown in Table 1.

  Each component was kneaded with an open roll, and the kneaded product was subjected to primary vulcanization by heating press molding machine at 175 ° C. for 10 minutes and secondary vulcanization by heating in a constant temperature bath at 150 ° C. for 4 hours, and a test sample Was made.

  In Examples 1 to 4 and Comparative Examples 1 and 2, the mixing ratios of hydrogenated nitrile rubber and ethylene propylene rubber (Mooney viscosity ML1 + 4 (100 ° C.) 90) shown in Table 1 are used. A fixed test sample was prepared and measured.

  In Examples 5 to 7 and Comparative Examples 3 and 4, as shown in Table 1, the amount of the filler thermal carbon black was changed, the amounts of the other compounding agents were fixed, and test samples were prepared and measured.

  Example 8 is a rubber composition using ethylene propylene rubber having a different Mooney viscosity ML1 + 4 (100 ° C.), and a test sample was prepared and measured using a copolymer rubber having a Mooney viscosity ML1 + 4 (100 ° C.) of 40 values.

  In Examples 9 and 10 and Comparative Example 5, as shown in Table 1, the filler was changed to furnace carbon black, the amounts of other compounding agents were fixed, and test samples were prepared and measured.

    In Comparative Example 6, as shown in Table 1, the amount of the crosslinking agent of Example 3 was reduced, and the amounts of other compounding agents were fixed, and test samples were prepared and measured.

    In Comparative Example 7, as shown in Table 1, the rubber polymer was a hydrogenated nitrile rubber alone, and the amount of the other compounding agent to be added was fixed, and a test sample was prepared and measured.

The volume change rate with respect to the POE oil can be confirmed to be + 10% or less when the hydrogenated nitrile rubber is 40 parts by mass or more with respect to 100 parts by mass of the rubber polymer. Further, from the results of the compositions in which the amount of the filler thermal carbon black was varied (Examples 3 to 5 and Comparative Examples 3 and 4), the tensile stress M ₁₀₀ value at 100% elongation was less than 8.0 MPa. It can be seen that generation of blisters of the HFC134a gas occurs. Composition by replacing the type of filler furnace carbon black (Examples 9 and 10, Comparative Example 5) also, the composition of less than 8.0MPa tensile stress _{M 100} value at the time of 100% elongation similarly blisters confirmed that has occurred, also cross-linking agent, even Comparative example 6 with a reduced amount of crosslinking aid, a tensile stress M ₁₀₀ value at the time of 100% elongation is less than 8.0 MPa, similarly blisters occurred ing. Further, from the results of Example 8 using ethylene propylene rubber having different Mooney viscosities, it is possible to suppress the occurrence of blisters when the tensile stress M ₁₀₀ value at 100% elongation is 8.0 MPa or more regardless of the Mooney viscosity value. it can.

The sealing material having a rubber molded product obtained by molding the rubber composition of the present invention has mechanical properties equivalent to those obtained when a hydrogenated nitrile rubber is used alone, and includes a fluorocarbon refrigerant (HFC134a), refrigerating machine oil (PAG oil). , POE oil), and has a smaller permeation amount of HFC134a than the case of using hydrogenated nitrile rubber alone, and can be suitably used as a sealing material that suppresses blistering to HFC134a. The quality control of the fluorocarbon rubber molding can be easily controlled by the tensile stress M ₁₀₀ value at 100% elongation.

Claims (2)

A seal member used for a refrigerant seal of a refrigerator system in which POE (polyol ester) refrigerator oil and HFC134a are mixedly used, and the seal member has a mass ratio of hydrogenated nitrile rubber: ethylene propylene rubber of 40 : A rubber molded product obtained by molding a rubber composition containing a rubber polymer of 60 to 90:10, a filler, and a crosslinking agent , and the tensile stress M ₁₀₀ value at 100% elongation of the rubber molded product is characterized Rukoto a rubber molded product comprising a higher 8.0 MPa, the sealing member. 2. The rubber composition according to claim 1, wherein the filler is carbon black, and the carbon black is formed by molding a rubber composition containing 55 to 150 parts by mass with respect to 100 parts by mass of the rubber polymer. Seal member .