JP3840230B2 - Rubber composition - Google Patents

Description

  The present invention relates to a rubber composition used for a sealing device that seals carbon dioxide or a fluid containing carbon dioxide, and in particular, a gasket, packing, and the like that prevent leakage of a refrigerant in an air conditioning system using carbon dioxide as a refrigerant. The present invention relates to a rubber composition used for sealing devices such as O-rings and oil seals.

  Conventionally, in refrigeration air conditioners such as car air conditioners, a fluorocarbon refrigerant HFC-134a is mainly used as a refrigerant from the viewpoint of environmental problems such as ozone layer destruction. However, in recent years, HFC-134a has been pointed out as having an impact on global warming, and its use has been restricted. As an alternative, carbon dioxide refrigerant, which has a low global warming potential and is also a natural refrigerant, is an alternative candidate.

  The refrigeration and air conditioning system using a carbon dioxide refrigerant is used under a high-pressure environment condition of about 7 MPa or more as compared with a conventional chlorofluorocarbon-based refrigerant. Moreover, the influence which a carbon dioxide refrigerant has with respect to the rubber composition used for a sealing device is also different from a fluorocarbon refrigerant.

  For this reason, various rubber compositions suitable for carbon dioxide refrigerants have been studied. For example, Patent Document 1 mainly uses hydrogenated nitrile rubber crosslinked with an organic peroxide for preventing leakage of carbon dioxide refrigerant. A rubber seal is described. In this sealing material, hydrogenated nitrile rubber having a bound acrylonitrile amount of 32 to 40% by weight is used. Patent Document 2 describes a rubber seal material using hydrogenated nitrile rubber having a combined acrylonitrile amount of 45% by weight or more.

  By the way, it is generally known that, in a rubber containing an acrylonitrile group in its structure, such as a hydrogenated nitrile rubber, the properties of the rubber change depending on the amount of acrylonitrile group bonded. That is, as the amount of bound acrylonitrile increases, the gas permeability decreases, and conversely when it decreases, the gas permeability increases. On the other hand, the cold resistance of rubber deteriorates as the amount of bound acrylonitrile increases.

  Therefore, when a substance having a high permeability to the rubber composition such as carbon dioxide is to be sealed, there is a problem that the permeability of carbon dioxide is increased when the amount of bound acrylonitrile is as small as 32 to 40% by weight. . On the other hand, if the amount of bound acrylonitrile is increased to 45% by weight or more, the permeability can be kept low, but the cold resistance is deteriorated. As a means for improving cold resistance while maintaining the amount of bound acrylonitrile as high as possible, use of a plasticizer that improves cold resistance can be considered. However, in this case, it is necessary to use a large amount of a plasticizer, which causes a problem that the rubber physical properties such as compression set are greatly adversely affected and the carbon dioxide permeability is also increased.

Moreover, by using chlorinated polyethylene as the main raw material, the permeability of carbon dioxide can be reduced as compared with the case where hydrogenated nitrile rubber having a bound acrylonitrile amount of 32 to 40% by weight is used. However, even in this case, there is a phenomenon that the cold resistance is deteriorated.
JP 2002-146342 A JP 2003-246976 A

  Accordingly, an object of the present invention is to provide a rubber composition excellent in carbon dioxide permeation resistance, cold resistance, and compression set characteristics, which can be used in a sealing device that seals carbon dioxide or a fluid containing carbon dioxide. It is to be.

  In order to solve the above-mentioned problems, the present inventors have reduced the carbon dioxide permeability by adding an epoxidized vegetable oil plasticizer to a rubber composition mainly composed of hydrogenated nitrile rubber or chlorinated polyethylene. Addition of acid ester plasticizer improves cold resistance. When hydrogenated nitrile rubber is used as the main raw material, the epoxidized vegetable oil plasticizer and organic acid ester are used in the region where the amount of bound acrylonitrile is 40 to 45% by weight. The present invention has been completed by finding that a rubber composition having excellent carbon dioxide permeability and cold resistance can be obtained while blending a plasticizer with good compression set characteristics. .

That is, the present invention is as follows.
(1) A rubber composition for sealing devices to be sealed the fluid containing carbon dioxide or carbon dioxide, characterized in that it comprises a hydrogenated Nitorirugo arm, and epoxidized vegetable oil plasticizer as main components Rubber composition.
(2) A rubber composition according to bound acrylonitrile amount of water hydride nitrile rubber is 40 to 45% by weight (1).
(3) further comprises an organic acid ester plasticizer, combined with epoxidized vegetable oil plasticizer these two total content of hydrogenated Nitorirugo beam 1 00 parts by weight per plasticizer is 5 to 20 parts by weight The rubber composition according to (1) or (2).

The rubber composition for a sealing device for a fluid containing carbon dioxide or carbon dioxide according to the present invention a sealed, by blending an epoxidized vegetable oil plasticizer in the rubber composition of the hydrogenated Nitorirugo beam as a main material, Carbon dioxide permeability was suppressed and sealing performance was improved. Moreover, cold resistance improved by mix | blending an organic acid ester plasticizer.

  Further, in a rubber composition for a sealing device in which the main raw material is a hydrogenated nitrile rubber, the amount of bound acrylonitrile of the hydrogenated nitrile rubber is 40 to 45% by weight, an epoxidized vegetable oil-based plasticizer and, optionally, an organic ester plastic By blending the agent, it was possible to obtain a rubber composition excellent in carbon dioxide permeability resistance and cold resistance while maintaining good compression set characteristics.

  The sealing device made by the rubber composition of the present invention is intended to seal carbon dioxide or a fluid containing carbon dioxide, for example, a refrigeration air conditioner such as a car air conditioner using carbon dioxide as a refrigerant, a refrigerator refrigerator, etc. Examples include, but are not limited to, gaskets, packings, O-rings, oil seals, and mechanical seals.

  Since the epoxidized vegetable oil plasticizer used in the present invention is incompatible with carbon dioxide, the solubility of carbon dioxide can be reduced by blending it with the rubber composition. Therefore, the permeability of carbon dioxide can be suppressed by blending the epoxidized vegetable oil-based plasticizer with a rubber composition mainly composed of hydrogenated nitrile rubber or chlorinated polyethylene. At the same time, the cold resistance can be improved.

  As the epoxidized vegetable oil plasticizer, epoxidized soybean oil can be used, and its blending amount is 5 parts by weight or less with respect to 100 parts by weight of hydrogenated nitrile rubber or chlorinated polyethylene as the main raw material. The effect of suppressing the permeability is poor, and if it is 20 parts by weight or more, the compression set is inferior, so 5-20 parts by weight is preferable.

  Specific examples of the epoxidized vegetable oil-based plasticizer include Capox S-6 (manufactured by Kao Corporation), Paraplex G-60 (manufactured by CP Hall), Adeka Sizer O-130P (manufactured by Asahi Denka Kogyo Co., Ltd.), Adeka Sizer O-180P (manufactured by Asahi Denka Kogyo Co., Ltd.), Edenol D81 (manufactured by Cognis Japan Co., Ltd.), Edenol B316 (manufactured by Cognis Japan Co., Ltd.), SUNSOSIZER E-2000H (manufactured by Shin Nippon Rika Co., Ltd.), SUNSOSIZER E- 9000H (Shin Nippon Rika Co., Ltd.) etc. are mentioned.

  Hydrogenated nitrile rubber (hereinafter abbreviated as “HNBR”) is a polymer material obtained by hydrogenating an unsaturated site of acrylonitrile butadiene rubber (hereinafter abbreviated as “NBR”) obtained by copolymerizing acrylonitrile and butadiene. HNBR is known to be superior in heat resistance and wear resistance to NBR, and is used for oil seals, O-rings, gaskets, and the like as automotive rubber parts.

Specific examples of HNBR include Zetpol 1010 (manufactured by Nippon Zeon Co., Ltd., bonded acrylonitrile amount 44 wt%), Zetpol 1020 (manufactured by Nippon Zeon Co., Ltd., bonded acrylonitrile amount 44 wt%), Therban A4307 (manufactured by Bayer Co., Ltd., bonded acrylonitrile) 43% by weight), Therban A4309 (manufactured by Bayer, 43% by weight of bound acrylonitrile), Therban C4367 (manufactured by Bayer, 43% by weight of bound acrylonitrile), Therban C4369 (manufactured by Bayer, 43% by weight of bound acrylonitrile) Etc.

  Specific examples of chlorinated polyethylene include Daisolac MR104 (Daiso Co., Ltd., chlorine content 40 wt%), Daisolac H135 (Daiso Co., Ltd., chlorine content 35 wt%), Daisolac C130 (Daiso Co., Ltd., contained) Chlorine content 30% by weight), Eraslen 301A (Showa Denko Co., Ltd., containing chlorine content 32% by weight), Eraslen 351A (Showa Denko Co., Ltd. containing chlorine content 36% by weight), Eraslen 401A (Showa Denko Co., Ltd., The chlorine content is 40% by weight).

  In order to obtain a rubber composition excellent in both carbon dioxide permeation resistance and cold resistance while keeping the compression set small, the amount of bound acrylonitrile in the HNBR of the present invention is preferably 40 to 45% by weight.

  In addition, it is preferable to add an organic acid ester plasticizer to a rubber composition containing hydrogenated nitrile rubber or chlorinated polyethylene as a main raw material because cold resistance is improved. The reason why the cold resistance is improved is that the freezing point of the plasticizer is low and the compatibility with the rubber composition is good. This organic acid ester plasticizer is a plasticizer that contains an ester bond in its structure. Polyether ester plasticizer, phthalate ester plasticizer, adipate ester plasticizer, trimellitic acid ester A plasticizer, a sebacic acid ester plasticizer, a phosphoric acid ester plasticizer, or the like is used. As specific examples, Adeka Sizer RS-700, Adeka Sizer RS-735, Adeka Sizer C-8, Adeka Sizer C-9N (manufactured by Asahi Denka Kogyo Co., Ltd.), di- (2-ethylhexyl) sebacate, di- ( 2-ethylhexyl) adipate, tricresyl phosphate, di- (2-ethylhexyl) phthalate and the like.

  When blending both an epoxidized vegetable oil plasticizer and an organic acid ester plasticizer, carbon dioxide containing 100 parts by weight of HNBR or chlorinated polyethylene and 5 parts by weight or less of epoxidized vegetable oil plasticizer The effect of suppressing the permeability is poor, and if the total amount of both plasticizers is 20 parts by weight or more, the compression set is inferior. Therefore, the total amount is preferably 5 to 20 parts by weight.

  As a cross-linking agent for cross-linking HNBR and chlorinated polyethylene, an organic peroxide is preferably used. Specific examples include t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, dicumyl peroxide. , T-butylcumyl peroxide, 1,1-di-t-butylperoxy-cyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 1,3-bis (t -Butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate and the like.

  As a compounding quantity of an organic peroxide, it is preferable to set it as 2-20 weight part with respect to 100 weight part of HNBR or chlorinated polyethylene.

  In addition, a crosslinking aid, a filler, a metal oxide, an antiaging agent, a lubricant and the like can be appropriately blended and used as long as the object of the present invention is not impaired.

  As the crosslinking aid, an acrylic crosslinking aid, a maleimide crosslinking aid, and a methacrylate crosslinking aid are used. As specific examples, for acrylic crosslinking aids, triallyl isocyanurate, for maleimide crosslinking aids, N, N'-m-phenylene dimaleimide, for methacrylate crosslinking aids, ethylene glycol dimethacrylate, trimethylolpropane Methacrylate is mentioned.

  Carbon black is used as the reinforcing filler. As specific examples, HAF carbon black, MAF carbon black, FEF carbon black, SRF carbon black, GPF carbon black, FT carbon black, MT carbon black and the like are used alone or in combination of two or more. Further, fillers other than carbon black can be used alone or in combination depending on the application.

  As the metal oxide, zinc oxide, calcium hydroxide, magnesium oxide, or the like can be used alone or in combination of two or more.

  Antiaging agents include diphenylamines such as 4,4- (α, α-dimethylbenzyl) diphenylamine and alkylated diphenylamine, and benzimidazoles such as 2-mercaptobenzimidazole and 2-mercaptobenzimidazole zinc salt. .

  As the lubricant, paraffin and hydrocarbon resin, fatty acid, fatty acid amide, fatty acid ester, aliphatic alcohol, and the like are used.

Hereinafter, the present invention will be described using test results for Examples and Comparative Examples. However, the present invention is not limited to these examples.
In Examples and Comparative Examples, the amount of FEF carbon black added as a filler was varied because the change in the hardness of the rubber composition accompanying the difference in the amount of plasticizer was adjusted. This is to increase the validity of the comparison by setting the hardness to approximately the same.

Example 1:
Example 1 is a blending example in which an epoxidized vegetable oil-based plasticizer is used for HNBR having an amount of 44% by weight of bound acrylonitrile.
In this example, 1,3-bis (t-butylperoxyisopropyl) as a crosslinking agent with respect to 100 parts by weight of HNBR (Zetpol 1020, manufactured by Nippon Zeon Co., Ltd., amount of bound acrylonitrile 44% by weight) as a main raw material. ) 4 parts by weight of benzene, 20 parts by weight of HAF carbon black as filler, 60 parts by weight of FEF carbon black, 10 parts by weight of epoxidized vegetable oil plasticizer (Adekasizer O-130P, manufactured by Asahi Denka Kogyo Co., Ltd.) 5 parts by weight of N, N′-m-phenylene dimaleimide as a crosslinking aid, 1.5 parts by weight of alkylated diphenylamine as an anti-aging agent, 3 parts by weight of zinc oxide as a metal oxide, 1 part by weight of stearic acid as a lubricant, 0.3 parts by weight of polyethylene wax was used.

Example 2:
Example 2 is a blending example in which an epoxidized vegetable oil-based plasticizer is used for HNBR having a bound acrylonitrile amount of 41% by weight.
In this example, 65 parts by weight of HNBR (Zetpol 1020, manufactured by Nippon Zeon Co., Ltd.) having a combined acrylonitrile amount of 44% by weight and 35% by weight of HNBR (Zetpol 2020, manufactured by Nippon Zeon Co., Ltd.) having a combined acrylonitrile amount of 36% by weight are used. By blending a part, HNBR was 100 parts by weight with a bound acrylonitrile amount of 41% by weight. Other than that, it is the same composition as Example 1.

Example 3:
Example 3 is a blending example in which an epoxidized vegetable oil-based plasticizer and an organic acid ester-based plasticizer are used for HNBR with a combined acrylonitrile content of 44% by weight.
In this example, 10 parts by weight of a polyether ester plasticizer (Adeka Sizer RS700, manufactured by Asahi Denka Kogyo Co., Ltd.) is newly added as an organic acid ester plasticizer, and 70 weights of FEF carbon black as a filler is added. The same formulation as in Example 1 except for the parts.

Comparative Example 1:
Comparative Example 1 is a blending example in which HNBR with a bound acrylonitrile amount of 49% by weight is used and no epoxidized vegetable oil plasticizer or organic acid ester plasticizer is used.
In this comparative example, HNBR (Zetpol 0020, manufactured by Nippon Zeon Co., Ltd.) having a combined acrylonitrile amount of 49% by weight was used, and an epoxidized vegetable oil plasticizer was not added, and 50 parts by weight of FEF carbon black as a filler was used. Except for this, the composition is the same as in Example 1.

Comparative Example 2:
Comparative Example 2 is a blending example using HNBR with a bound acrylonitrile amount of 49% by weight and a large amount of organic acid ester plasticizer used to improve cold resistance.
In this comparative example, HNBR (Zetpol 0020, manufactured by Nippon Zeon Co., Ltd.) having a combined acrylonitrile amount of 49% by weight was used as 100 parts by weight, and a polyether ester plasticizer (Adekasizer RS700, Asahi Denka Kogyo Co., Ltd.) as the organic acid ester plasticizer. The composition is the same as that of Example 1 except that 30 parts by weight of a stock company) and 80 parts by weight of FEF carbon black as a filler are used.

Comparative Example 3:
Comparative Example 3 is a blending example using HNBR with a combined acrylonitrile amount of 36% by weight.
In this comparative example, HNBR (Zetpol 2020, manufactured by Nippon Zeon Co., Ltd.) having a bound acrylonitrile amount of 36% by weight was used, and no epoxidized vegetable oil plasticizer was added, and 50 parts by weight of FEF carbon black was used. Is the same formulation.

Reference example 4
Reference Example 4 is a blending example in which an epoxidized vegetable oil-based plasticizer is used for the main raw material chlorinated polyethylene.
In this reference example, 2,5-dimethyl-2,5-di as a crosslinking agent with respect to 100 parts by weight of chlorinated polyethylene (Daisolac MR104, manufactured by Daiso Co., Ltd., containing 40% by weight of chlorine) as the main raw material 4 parts by weight of (t-butylperoxy) hexane, 40 parts by weight of FEF carbon black as a filler, and 10 parts by weight of an epoxidized vegetable oil plasticizer (Adekasizer O-130P, manufactured by Asahi Denka Kogyo Co., Ltd.) as a plasticizer In addition, 3 parts by weight of triallyl isocyanurate was used as a crosslinking aid, and 10 parts by weight of magnesium oxide was used as a metal oxide.

Reference example 5:
Reference Example 5 is a blending example in which an epoxidized vegetable oil plasticizer and an organic acid ester plasticizer are used as the main raw material chlorinated polyethylene.
In this reference example, 10 parts by weight of an organic acid ester plasticizer (Adekasizer RS700, manufactured by Asahi Denka Kogyo Co., Ltd.) was newly added as a plasticizer, and the filler FEF carbon black was changed to 50 parts by weight. The composition is the same as in Reference Example 4.

Comparative Example 4:
Comparative Example 4 is a blending example in which chlorinated polyethylene is used and no epoxidized vegetable oil plasticizer and organic acid ester plasticizer are used.
In this comparative example, the same composition as in Example 4 was obtained except that no epoxidized vegetable oil plasticizer was added and 30 parts by weight of FEF carbon black was used.

  The vulcanized rubber sheet and the O-ring for measurement were prepared by kneading each of the above rubber compounds with an 8-inch open roll, and pressing and molding the kneaded material at 180 ° C. for 6 minutes. Further post-curing was then performed in an oven at 150 ° C. for 4 hours.

The physical tests of the vulcanized rubbers of Examples 1 to 3, Reference Examples 4 and 5 and Comparative Examples 1 to 4 were carried out by the following measuring methods.
[Normal physical properties]
Measurement of hardness of vulcanized rubber conforms to JIS K 6253 “Testing method for hardness of vulcanized rubber and thermoplastic rubber”. Measurement of tensile strength and elongation is JIS K 6251 “Tensile test method of vulcanized rubber” Measured according to
[Compression set]
The compression set by the O-ring was measured in accordance with JIS K 6262 “Testing methods for permanent set of vulcanized rubber and thermoplastic rubber”.
[CO2 permeability coefficient]
A 90 mm x 90 mm x 2 mm sample was cut from the vulcanized rubber sheet, and a gas permeation tester manufactured by Toyo Seiki Co., Ltd. was used. The measurement was performed under the conditions of a temperature of 24 ° C. and a pressure of 0.1 MPa.
[Cold resistance measurement]
A 10 mg sample was cut from the vulcanized rubber sheet, and the glass transition temperature was measured with a differential scanning calorimeter DSC8230 manufactured by Rigaku Corporation.

  Table 1 shows the results of the above measurements for Examples 1 to 3 and Comparative Examples 1 to 3 of rubber compositions in which the main raw material is HNBR.

Table 2 shows the results of the above measurements for Reference Examples 4 and 5 and Comparative Example 4 of rubber compositions in which the main raw material was chlorinated polyethylene.

From the above measurement results, the following could be confirmed.
(1) When HNBR is used as the main raw material (Table 1), as can be seen from Comparative Example 3, when HNBR with a combined acrylonitrile content of 36% by weight is used, the carbon dioxide permeability coefficient is 13.6 [× 10 ^-16 (mol · m / m ² · s · Pa)].

(2) Further, as can be seen from Comparative Example 1, when HNBR having a combined acrylonitrile amount of 49% by weight is used, the permeability coefficient of carbon dioxide is 3.5 [× 10 ⁻¹⁶ (mol · m / m ² · s · Pa)], but the glass transition temperature, which is an index of cold resistance, is inferior to −10 ° C.

(3) In order to improve the cold resistance of Comparative Example 1, as shown in Comparative Example 2, when 30 parts by weight of the organic acid ester plasticizer is used with respect to HNBR having a bound acrylonitrile amount of 49% by weight, the cold resistance is Although the glass transition temperature is improved at -22 ° C, the compression set rate is greatly inferior at 92%, and the carbon dioxide permeability coefficient is 5.1 [× 10 ^-16 (mol · m / m ² · s · Pa). It gets worse.

(4) On the other hand, as shown in Example 1, the formulation using an epoxidized vegetable oil-based plasticizer with respect to HNBR having a bound acrylonitrile amount of 44% by weight is compared with that of Comparative Example 1 having a bound acrylonitrile amount of 49% by weight. Then, the permeability coefficient of carbon dioxide is ^3.7 [× 10 ⁻¹⁶ (mol · m / m ² · s · Pa)) and 3.5 [× 10 ⁻¹⁶ (mol · m / m ² ) of Comparative Example 1. It was found that the cold resistance was excellent at a glass transition temperature of −19 ° C.

(5) Also, as shown in Example 2, with respect to HNBR in which the amount of bound acrylonitrile was 41% by weight, the formulation using an epoxidized vegetable oil plasticizer had a glass transition temperature of −22 ° C. as cold resistance. Carbon dioxide permeability coefficient 4.1 [× 10 ^-16 (× 10 ^-16 (mol · m / m ² · s · Pa)) of carbon dioxide as shown in Comparative Example 2 mol · m / m ² · s · Pa)].

(6) Furthermore, as shown in Example 3, by adding an epoxidized vegetable oil plasticizer and an organic acid ester plasticizer to HNBR with a bound acrylonitrile amount of 44% by weight, the cold resistance is made to have a glass transition temperature of -23. The carbon dioxide permeability coefficient shown in Comparative Example 2 was 5.1 [× 10 ⁻¹⁶ (mol · m / m ² · s · Pa)] as shown in Comparative Example 2 while improving to 4 ° C. 1 [× 10 ⁻¹⁶ (mol · m / m ² · s · Pa)], and the compression set was found to be as good as 69%.

(7) Similarly, in the case of using chlorinated polyethylene as a main raw material (Table 2), as shown in Reference Example 4, by adding an epoxidized vegetable oil-based plasticizer, carbon dioxide The transmission coefficient can be reduced to 2.2 [× 10 ⁻¹⁶ (mol · m / m ² · s · Pa)].

(8) Further, as can be seen from Reference Example 5, the cold resistance is improved to a glass transition temperature of −24 ° C. by blending an epoxidized vegetable oil plasticizer and an organic acid ester plasticizer with chlorinated polyethylene as a main raw material. However, it was found that the permeability coefficient of carbon dioxide was 2.6 [× 10 ⁻¹⁶ (mol · m / m ² · s · Pa)), which was lower than that of Comparative Example 4.

Thus, in a rubber composition mainly composed of hydrogenated nitrile rubber (particularly the amount of bound acrylonitrile is 40 to 45% by weight) or chlorinated polyethylene, an epoxidized vegetable oil-based plasticizer and optionally an organic acid ester-based plasticizer are added. By blending, a rubber composition excellent in carbon dioxide permeability resistance, cold resistance, and compression set characteristics could be obtained.

Claims (3)

A rubber composition for sealing devices to be sealed the fluid containing carbon dioxide or carbon dioxide, and hydrogenation Nitorirugo beam as main components, a rubber composition which comprises an epoxidized vegetable oil plasticizer . A rubber composition according to claim 1 bound acrylonitrile amount of water hydride nitrile rubber is 40 to 45 wt%. Further comprising an organic acid ester plasticizer, claim 1 total content of these two types of plasticizer combined with epoxidized vegetable oil plasticizer is hydrogenated Nitorirugo beam 1 00 parts by weight per 5 to 20 parts by weight Or the rubber composition of 2.