JP2012197945A - Rubber composition for seal member formation and seal member obtained by using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal member having excellent gas permeability resistance, blister resistance, and compression permanent strain resistance characteristics, and a rubber composition for the same.SOLUTION: The rubber composition for seal member formation includes hydrogenated nitrile rubber (I), polyvinylidine fluoride (II), and a crosslinking agent, and the content ratio of the (I) and (II) is 95/5 to 85/15 by weight ratio (I/II). The seal member is prepared by vulcanizing it.

Description

  The present invention relates to a rubber composition for forming a seal member and a seal member using the same, and more particularly, to a rubber composition for forming a seal member that is preferably used for forming a seal member of an air conditioner or a compressor of a refrigerator. The present invention relates to a seal member using the same.

It is known that a rubber composition containing nitrile rubber (NBR) and polyvinylidene fluoride can be widely used as a material for forming seal members such as hoses, gaskets, O-rings, and packings. Things are known.
For example, Patent Document 1 describes a rubber composition containing NBR and / or a hydride thereof and polyvinylidene fluoride in a weight ratio of 95/5 to 40/60, and is resistant to gasoline and gasohol. It is said to be excellent in sour gasoline resistance and compression set resistance. Patent Document 2 discloses a thermoplastic elastomer composition containing NBR 90 to 10% by weight containing 30% of a gel component insoluble in methyl ethyl ketone and 10 to 90% by weight of polyvinylidene fluoride, which does not require vulcanization during molding. It is described that it is recyclable and has excellent compression set resistance and oil resistance. Furthermore, in Patent Document 3, 5 to 50 parts by weight of polyvinyl chloride or polymethacrylic acid is used for 100 parts by weight of a composition containing 90 to 30% by weight of NBR and 10 to 70% by weight of polyvinylidene fluoride. A rubber composition containing methyl, which is a rubber composition in which polyvinylidene fluoride is cross-linked while being subjected to shear deformation during blending of NBR and polyvinylidene fluoride, and is described as gasoline permeation resistance, weather resistance, cold resistance And excellent compression set resistance and the like.

  Furthermore, Patent Document 4 discloses a composition containing 95 to 5% by weight of NBR and 5 to 95% by weight of a thermoplastic fluoropolymer, wherein the total weight ratio of acrylonitrile in NBR is 30% or more. It is described that it has chemical properties, thermomechanical properties and chemical resistance, particularly impermeability to hydrocarbons such as gasoline, and does not require a compatibilizing agent. Furthermore, Patent Document 5 includes (A) NBR having an acrylonitrile content of 20 to 29%, (B) polyvinylidene fluoride, and (C) an acrylic resin-based compatibilizer, and (A) / ( A rubber composition for a fuel hose in which B) is 95/5 to 60/40 is described, and is said to be excellent in flexibility, ozone resistance, oil resistance, fuel oil permeability and low temperature. Patent Document 6 includes (A) acrylic rubber, (B) polyvinylidene fluoride, and (C) NBR, and (A) / (B) / (C) is from 5/15/80 to A rubber composition for a fuel hose which is 55/40/5 is described, and is said to be excellent in flexibility, ozone resistance, oil resistance, fuel oil permeability, low temperature and heat resistance.

Japanese Patent Application Laid-Open No. 61-225227 Japanese Patent Laid-Open No. 01-245042 JP 07-003077 A Japanese Patent Laid-Open No. 10-204215 JP 2004-262997 A JP 2004-278777 A

  However, the rubber compositions of Patent Documents 1 to 6 have the following problems. That is, the rubber composition described in Patent Document 1 has insufficient compression set resistance characteristics, and the rubber composition described in Patent Document 2 also does not vulcanize and therefore has insufficient compression set characteristics. . In addition, the rubber composition described in Patent Document 3 solves the problem of aggregation of polyvinylidene fluoride by crosslinking polyvinylidene fluoride at the time of blending NBR and polyvinylidene fluoride. The addition of an agent inhibits the vulcanization of NBR, which may adversely affect the compression set resistance, and the addition of polyvinyl chloride and polymethyl methacrylate also adversely affects the compression set resistance. Furthermore, in the composition described in Patent Document 4, vulcanization of the crosslinked nitrile elastomer is performed by dynamic vulcanization, so that the obtained composition becomes a thermoplastic elastomer. For this reason, it is assumed that the compression set characteristics are insufficient. Furthermore, since the rubber composition described in Patent Document 5 contains an acrylic resin-based compatibilizing agent, it adversely affects the compression set resistance. In addition, since the rubber compositions described in the Examples of Patent Documents 2 to 4 or the claims of Patent Documents 5 and 6 all contain NBR that is hardly superior in heat resistance, thermal degradation occurs during high-temperature kneading. There is concern about insufficient dispersion of polyvinylidene fluoride due to the above, and the compression set resistance at high temperatures becomes insufficient.

  In air conditioners such as air conditioners and compressors of cooling devices such as refrigerators, many sealing members are used to seal refrigerant such as hydrofluorocarbon (HFC) and refrigerator oil. The seal member must have excellent heat resistance and oil resistance, small compression set, gas permeation resistance, and blister resistance (foaming) when it comes into contact with a refrigerant. Is done. The seal member used for the compressor of an air conditioner for automobiles may have a use environment temperature of 140 to 150 ° C. or higher, so that a higher level of performance, for example, a compression set resistance property under such a high temperature environment. In addition, foaming resistance (blister resistance) against HFC in such a high temperature environment is required.

  In recent years, seal members used for the shafts of air conditioners for automobiles and compressors of refrigerators have become increasingly severe in their usage environment, and in particular, demands for improving gas permeation resistance have become more severe. The rubber compositions described in Documents 1 to 6 are unlikely to be able to sufficiently cope with the above environment, and there is room for improvement because no blister resistance has been studied.

  The present invention has been made in view of such circumstances, and the problem to be solved is a sealing member having excellent gas permeation resistance, blister resistance and compression set resistance, and a rubber composition therefor Is to provide.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have found that in a rubber composition containing hydrogenated nitrile rubber (I) and polyvinylidene fluoride (II), a blend ratio of (I) and (II). However, only in a specific range, the inventors have found that the excellent HFC gas permeation suppressing effect and blister resistance improving effect are specifically expressed, and the present invention has been completed.

That is, the present invention is as follows.
(1) Hydrogenated nitrile rubber (I), polyvinylidene fluoride (II), and a crosslinking agent, wherein the content ratio of (I) and (II) is 95/5 to 5/5 by weight ratio (I / II). A rubber composition for forming a seal member, which is 85/15.
(2) The rubber composition for forming a seal member according to the above (1), which is used for forming a seal member for a compressor of an air conditioner or a refrigerator.
(3) Hydrogenated nitrile rubber (I), polyvinylidene fluoride (II) having a melting point of 120 to 200 ° C., and a crosslinking agent, and the content ratio of (I) and (II) is in a weight ratio (I / II) is a rubber composition for forming a seal member, which is 95/5 to 85/15.
(4) A seal member obtained by vulcanizing the rubber composition for forming a seal member according to any one of (1) to (3).

  According to the present invention, the addition of a compatibilizing agent or the like hardly causes aggregation of polyvinylidene fluoride and enables fine dispersion. As a result, the compression set is small even when exposed to a high temperature for a long time, blisters and cracks are hardly generated even when contacted with HFC, and the gas permeation is sufficiently suppressed. Provided are a seal member having both blister resistance and compression set resistance, and a rubber composition therefor. Therefore, the seal member of the present invention can be suitably used as a sealing body for preventing leakage of refrigerant in, for example, an air conditioner using HFC as a refrigerant or a compressor of a refrigerator.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
The rubber composition for forming a seal member of the present invention contains hydrogenated nitrile rubber (I), polyvinylidene fluoride (II), and a crosslinking agent, and the content ratio of (I) and (II) is in a weight ratio ( I / II) is 95/5 to 85/15.

  The hydrogenated nitrile rubber (hereinafter sometimes referred to as “HNBR”) is not particularly limited. For example, all or part of the conjugated diene unit of the unsaturated nitrile-conjugated diene copolymer rubber is hydrogenated. And hydrogenated all or part of conjugated diene units of α, β-unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer copolymer rubber, unsaturated nitrile-ethylenically unsaturated monomer copolymer rubber Is exemplified.

  Examples of the unsaturated nitrile and α, β-unsaturated nitrile include acrylonitrile and methacrylonitrile, and examples of the conjugated diene include 1,3-butadiene, 2,3-dimethylbutadiene, isoprene, 1, Examples include 3-pentadiene. Examples of the ethylenically unsaturated monomer include vinyl aromatic compounds such as styrene, pt-butyl styrene, and chloromethyl styrene; methyl (meth) acrylate, ethyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Unsaturated monocarboxylic acid esters such as methoxyethyl (meth) acrylate, alkoxyalkyl esters of unsaturated monocarboxylic acids such as ethoxyethyl (meth) acrylate; unsaturated compounds such as dimethyl itaconate, dimethyl maleate, and dimethyl fumarate Dialkyl esters of saturated dicarboxylic acids; unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid monoester, unsaturated dicarboxylic acids and monoesters thereof; (meth) acrylamide, N, N-dimethyl (meta )acrylic Bromide, N-N-substituted, such as methoxyethyl (meth) acrylamide (meth) acrylamide and the like. Of these, butadiene-acrylonitrile copolymer rubber is preferred. These copolymer rubbers can be used singly or in combination of two or more.

HNBR preferably has an acrylonitrile content (bound AN amount) of 45% by weight or less, more preferably 38% by weight or less from the viewpoint of cold resistance, and iodine value from the viewpoint of heat resistance. (Center value) is preferably 28 or less, more preferably 20 or less. The bound AN amount and iodine value can be measured by a known measurement method. The Mooney viscosity (ML _{1 + 4} , 100 ° C.) is preferably 50 to 150. If the Mooney viscosity is outside the above range, the processability tends to decrease. Such HNBR can be manufactured by a conventionally known method, but may be commercially obtained as, for example, Zettopol (manufactured by Nippon Zeon Co., Ltd.).

  Polyvinylidene fluoride includes a homopolymer type (hereinafter sometimes referred to as “PVDF”) and a copolymer type obtained by copolymerizing vinylidene fluoride and a small amount of other components (for example, vinylidene fluoride-hexafluoropropylene copolymer). Polymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluorovinyl ether-tetrafluoroethylene copolymer, vinylidene fluoride-propylene- Tetrafluoroethylene copolymer and the like), but the use of the copolymer type tends to lower the compression set resistance, so it is desirable to use a homopolymer type.

  The melting point of polyvinylidene fluoride is preferably 120 to 200 ° C, more preferably 160 to 180 ° C. If it is lower than 120 ° C., the compression set resistance property tends to be lowered. On the other hand, if it exceeds 200 ° C., HNBR tends to deteriorate during kneading.

  The melt mass flow rate (MFR) of polyvinylidene fluoride is preferably 0.03 to 150 g / 10 min, more preferably 0.1 to 100 g / 10 min. If it is less than 0.03 g / 10 min, the workability tends to decrease, and if it exceeds 150 g / 10 min, the compression set tends to increase. In addition, MFR means the value which applied the load 5kg to the resin heated to the temperature of 230 degreeC based on ASTMD1238, and measured the quantity of the resin which flows out from a pore for 10 minutes.

  Such polyvinylidene fluoride can be produced by a conventionally known method, and may be commercially obtained as, for example, KYNAR (manufactured by Arkema), KF polymer (manufactured by Kureha) or the like.

  The content ratio of HNBR (I) and polyvinylidene fluoride (II) is (I / II) 95/5 to 85/15 by weight ratio.

  When polyvinylidene fluoride is mixed with HNBR, the polyvinylidene fluoride is likely to aggregate. When aggregated, the effect of improving gas permeation resistance and blister resistance is considered to be small. However, according to the knowledge of the present inventors, if the content ratio (I / II) of HNBR and polyvinylidene fluoride is 95/5 to 85/15, aggregation occurs without the addition of a compatibilizer or the like. Difficult to disperse. As a result, it is possible to realize extremely excellent gas permeation suppression without deteriorating the compression set resistance property, and it is also possible to improve the blister resistance. If the content ratio of (I / II) is smaller or larger than this, the gas permeation suppressing effect is reduced, and the effect of improving the blister resistance is also reduced. Even if a resin excellent in gas permeability (for example, ethylene vinyl alcohol resin or polyacrylonitrile resin) is used in place of polyvinylidene fluoride, the compression set resistance is lowered and the gas permeability is also suppressed. The present inventors have confirmed that it becomes smaller.

  As the cross-linking agent, known ones can be used, and among them, organic peroxides are preferably used. Examples of the organic peroxide crosslinking agent include di-tertiary butyl peroxide, dicumyl peroxide, tertiary butyl cumyl peroxide, 1,1-di (tertiary butyl peroxy) -3,3,5-trimethyl. Cyclohexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 1,3- Di (tert-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, n-butyl-4 , 4-di (tert-butylperoxy) valerate and the like. These can be used individually by 1 type or in combination of 2 or more types.

  The content of the crosslinking agent is preferably 1 to 10 parts by weight, more preferably 1.5 to 5 parts by weight with respect to 100 parts by weight of the total of HNBR and polyvinylidene fluoride. If it is less than 1 part by weight, it tends to be difficult to impart compression set resistance characteristics and mechanical properties to the seal member, while if it exceeds 10 parts by weight, the rubber composition tends to be too hard.

  The rubber composition for forming a seal member of the present invention includes, for example, an anti-aging agent (for example, amine-based, phenol-based, imidazole-based), a filler (for example, carbon black, calcium carbonate, silica, talc, clay, Graphite, calcium silicate), plasticizer (for example, phthalic acid plasticizer such as dioctyl phthalate, adipic acid plasticizer such as dioctyl adipate, sebacic acid plasticizer such as dioctyl sebacate, tri- (2-ethyl to Xylyl) trimellitic acid plasticizer such as trimellitate, polymerization type plasticizer such as polyether or polyester), crosslinking aid (eg triallyl cyanurate, triallyl isocyanurate, N, N′-m-phenylenebismaleimide) , Trimethylolpropane trimethacrylate, triallyl trimellitate General in the rubber industry such as polyfunctional compounds such as 1,2-polybutadiene), metal oxides (eg zinc oxide, magnesium oxide, calcium oxide), processing aids (eg stearic acid, palmitic acid, paraffin wax) The compounding agent currently used can be suitably added as needed. In addition, the addition amount of each compounding agent can be appropriately set as necessary within a range not impairing the object of the present invention.

  The seal member of the present invention is obtained as a rubber molded product by kneading the above rubber composition for forming a seal member and then vulcanizing and molding. Specifically, the rubber composition for the seal member is kneaded using a kneader such as an open roll, an intermix, a kneader, a Banbury mixer or a twin-screw kneading extruder, and then an injection molding machine, a compression molding machine, a heating press. A sealing member can be obtained by vulcanization molding into a desired shape using a machine or the like. The rubber composition for forming a seal member is preferably kneaded with HNBR and polyvinylidene fluoride and then added with a crosslinking agent. In that case, the kneading temperature of HNBR and polyvinylidene fluoride is preferably at least the melting point of polyvinylidene fluoride (for example, about 170 ° C.), and the temperature when kneading with the addition of a crosslinking agent prevents scorching. Therefore, the temperature is preferably 100 ° C. or lower. The vulcanization molding is preferably performed at about 150 to 200 ° C. for about 3 to 60 minutes, and secondary vulcanization may be performed at 100 to 200 ° C. for 1 to 24 hours as necessary.

  The obtained seal member has a small compression set (150 ° C. × 72 hours) measured in accordance with JIS K 6262, and after being immersed in HFC134a liquid at room temperature for 1 day, even when heated to 150 ° C., rubber molding Blister (foaming) does not occur in the product, and the gas permeability of HFC134a can be sufficiently suppressed in the gas permeability test based on the ASTM D 1434 M method.

As described above, the seal member of the present invention has a small compression set even when exposed to high temperatures for a long time, is less likely to cause blisters and cracks even when in contact with HFC, and sufficiently suppresses gas permeation. , Excellent compression set properties, blister resistance and gas permeation resistance can be combined. Therefore, it can be suitably used as a sealing member for preventing leakage of refrigerant in a sealing member for sealing HFC, for example, in an air conditioner or a compressor of a refrigerator using HFC as a refrigerant. The same effect can be expected as an air conditioner using CO ₂ as a refrigerant or a compressor seal member of a refrigerator. “HFC” refers to hydrofluorocarbons such as HFC134a (hydrofluorocarbon, CH ₂ FCF ₃ ), HFC32 (CH ₂ F ₂ ), HFC125 (CHF ₂ CF ₃ ), HFC143a (C ₂ H ₃ F ₃ ), etc. Or a mixture of these (for example, R407C, R410A, R404A), CFC12 (CCl ₂ F ₂ ) and other various fluorocarbon substances.

  The shape of the seal member is not particularly limited, and is appropriately selected according to the intended use such as an O-ring, packing, gasket, lip seal (shaft seal). Further, the size of the seal member is not particularly limited, and is appropriately set according to the purpose of use.

  Examples of the present invention will be described in detail below, but the present invention is not limited to these examples. In addition, the material used in the Example etc. is as follows.

HNBR: hydrogenated acrylonitrile-butadiene copolymer rubber (bound AN amount 36% by weight) iodine value 4, Mooney viscosity (ML _{1 + 4} , 100 ° C.) 85
PVDF (A): polyvinylidene fluoride (MFR 0.6 to 0.9 g / 10 min (230 ° C., 5 kg))
PVDF (B): polyvinylidene fluoride (MFR 18-26 g / 10 min (230 ° C., 5 kg))
・ Ethylene-vinyl alcohol copolymer resin (MFR 6.4 g / 10 min (190 ° C., 2160 g), ethylene content 47 mol%)
・ Polyacrylonitrile resin (MFR 3 g / 10 min (200 ° C., 122.5 N))
Anti-aging agent: 4,4′-di (α, α-dimethylbenzyl) diphenylamine Carbon black: FEF carbon black Plasticizer: Dioctyl sebacate (DOS)
・ Crosslinking agent: 1,3-di (tert-butylperoxyisopropyl) benzene ・ Crosslinking aid: N, N′-m-phenylenebismaleimide ・ Metal oxide: Zinc oxide ・ Compatibilizer: Polymethyl methacrylate Graft ethylene -Glycidyl methacrylate copolymer

(Examples 1 to 4 and Comparative Example 2)
After kneading HNBR and PVDF in the proportions shown in Table 1 below for about 5 minutes at a roll surface temperature of about 180 ° C. with an open roll, the ingredients other than the above are sequentially added and kneaded at room temperature to 60 ° C. Prepared. Next, the rubber composition was press vulcanized at 165 ° C. for 10 minutes with a press molding apparatus, and then secondary vulcanized at 150 ° C. for 4 hours to obtain a rubber molded product. In addition, the compounding quantity of each component of Table 1 is a weight part.

(Comparative Example 1)
Rubber molding was carried out in the same manner as in Examples 1 to 4 and Comparative Example 2 except that all of the blending components shown in Table 1 below were sequentially added and kneaded with an open roll having a roll surface temperature of room temperature to 60 ° C. I got a thing.

(Comparative Example 3)
Except that the ratio of HNBR and ethylene-vinyl alcohol copolymer resin shown in Table 1 below were kneaded with an open roll at a roll surface temperature of about 170 ° C. for about 5 minutes, the same as in Examples 1 to 4 and Comparative Example 2. A rubber molding was obtained.

(Comparative Example 4)
The rubber moldings were prepared in the same manner as in Examples 1 to 4 and Comparative Example 2, except that the ratios of HNBR and polyacrylonitrile resin shown in Table 1 below were kneaded with an open roll at a roll surface temperature of about 200 ° C. for about 5 minutes. Obtained.

(Comparative Example 5)
Rubber molding in the same manner as in Examples 1 to 4 and Comparative Example 2, except that HNBR, PVDF and compatibilizers in the proportions shown in Table 1 below were kneaded with an open roll at a roll surface temperature of about 180 ° C. for about 5 minutes. I got a thing.

  The rubber moldings obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were used as samples, and the following evaluation tests (1) to (3) were performed, and comprehensive evaluation was performed based on the test results. The results are shown in Table 3.

(1) Compression set According to JIS K 6262, compression set was measured at 150 ° C. for 72 hours.

(2) Blister resistance After immersion in HFC134a solution at room temperature for 1 day, the sample was heated to 150 ° C. and visually observed for the presence or absence of blisters (foaming) in the sample, and evaluated according to the following criteria.
○: Without blister ×: With blister

(3) Gas permeability The gas permeability coefficient of HFC134a gas was measured based on ASTM D 1434 M method, and the gas permeability coefficient of Comparative Example 1 was set to 100, and each gas permeability coefficient was converted and displayed.

(4) Comprehensive evaluation It evaluated by the following reference | standard.
(I) Without Blister Based on Table 2 below, 下 記: suitable, ◯: suitable, ×: unsuitable was determined.
(Ii) When there is a blister ×: It was determined as inappropriate.

  As is clear from the results in Table 3, the rubber molded products using the rubber compositions of the examples have a low compression set at high temperatures, hardly cause blisters or cracks even when in contact with HFC, and transmit HFC. Therefore, it was confirmed that the material has excellent gas permeation resistance, blister resistance and compression set resistance.

Claims (2)

  Hydrogenated nitrile rubber (I), polyvinylidene fluoride (II) having a melting point of 120 to 200 ° C., and a crosslinking agent, and the content ratio of (I) and (II) is a weight ratio (I / II) The rubber composition for forming a seal member, which is 95/5 to 85/15.   A seal member obtained by vulcanizing the rubber composition for forming a seal member according to claim 1.