JP4831162B2 - Hydrogenated nitrile rubber seal molding material for R152a, R134a - Google Patents

Description

  The present invention relates to a hydrogenated nitrile rubber seal molding material for R152a and R134a. More specifically, the present invention relates to a hydrogenated nitrile rubber-based seal molding material for R152a and R134a that is preferably used as a molding material for an air conditioner seal material, particularly a car air conditioner system seal material.

For R134a (CF ₃ CH ₂ F) currently used as a refrigerant for air conditioners, as described in Journal of the Japan Rubber Association Vol. 64, pages 161-167 (1991), Propylene-based copolymer rubber is most resistant, but because it is not resistant to some refrigeration oils and assembly oils, hydrogenated nitrile rubber is used as described in Japanese Patent No. 3314492. Yes.

R134a is replaced by R12 (CF ₂ Cl ₂ ) because it does not destroy ozone by so-called Freon regulation, but it is recognized that R134a is a gas that promotes global warming due to the recent global warming problem There is a need for refrigerants that do not destroy ozone and are less likely to promote global warming. From this point of view, natural refrigerants such as carbon dioxide, ammonia, and low molecular hydrocarbons such as butane are cited as refrigerant candidates, and R152a (CHF ₂ CH ₃ ) is attracting attention as one of them. is there.

  The reason is that R152a does not destroy ozone, is warming about as low as about 1/10 of R134a, and the pressure behavior with respect to temperature is close to R134a, so that the current R134a system can be used as it is. Therefore, there is a demand for a seal material that can be used not only for resistance to R152a but also for R134a.

  R152a, like R134a, is HFC (hydrofluorocarbon), and ethylene-propylene copolymer rubber resistant to R134a can be used, but ethylene-propylene copolymer that is most resistant to R134a can be used. It has been found that the polymer rubber is not sufficient for R152a because foaming occurs when it comes into contact with R152a.

  An object of the present invention is to provide a seal molding material having excellent resistance to both refrigerants R152a and R134a, and all refrigeration oils and assembly oils used in these refrigerants.

The object of the present invention is to provide 60 to 150 parts by weight of white carbon having a specific surface area (by nitrogen adsorption method) of 30 to 200 m ² / g based on 100 parts by weight of hydrogenated nitrile rubber having a bound acrylonitrile amount of 31 to 45% by weight. And a hydrogenated nitrile rubber-based seal molding material for R152a and R134a containing 0.1 to 5 parts by weight of a silane coupling agent and 0.5 to 10 parts by weight of an organic peroxide .

  In this hydrogenated nitrile rubber-based seal molding material, it can be used by substituting with nitrile rubber having a combined acrylonitrile amount of 30 to 45% by weight in a proportion of 30 parts by weight or less in 100 parts by weight of hydrogenated nitrile rubber. In the seal molding material, it is preferable to add 10 parts by weight or less of a polyfunctional unsaturated compound per 100 parts by weight of hydrogenated nitrile rubber or a blend rubber of nitrile rubber with it.

The hydrogenated nitrile rubber-based seal molding material according to the present invention is resistant to R152a with little global warming action by adding a specific white carbon to a specific hydrogenated nitrile rubber or a blend rubber of nitrile rubber with it. It is possible to provide a hydrogenated nitrile rubber-based sealing material that is not only excellent in R134a but also has R134a resistance, and this sealing material is an air conditioner that uses R152a as a refrigerant, particularly a car air conditioner system, a refrigerator, and a refrigerator. Can be suitably used as O-rings, gaskets, packings, oil seals, lip seals, etc.

  In terms of HFC resistance, R152a and R134a are expected to have a similar effect on rubber, and R134a is similar to other HFCs, such as R32 and R125, but it does not work against R134a. As shown in the results of Comparative Examples described below, which uses the most resistant EPDM, only R152a shows a different behavior from other HFCs such as R134a, and the hydrogenated nitrile rubber seal molding material according to the present invention. Was found to be resistant to such R152a.

  As the hydrogenated nitrile rubber (hydrogenated NBR), those having an amount of bound acrylonitrile (AN) of 31 to 45% by weight, preferably 35 to 40% by weight are used. Actually, commercially available products such as those of the Nippon Zeon product Zetpol series can be used as they are. When the amount of AN bond is smaller than this, the resistance to R152a is lowered, while when the amount of AN bond is larger than this, the cold resistance is lowered.

Patent Document 1 below, which is filed by the present applicant, discloses a hydrogenated nitrile rubber having an AN bond amount of 15 to 30% by weight, white carbon having a specific surface area of 200 m ² / g or less, an organic peroxide, and preferably a large amount. A hydrogenated NBR composition that contains a functional unsaturated compound and has improved its heat resistance and low-temperature properties with little loss of normal properties and oil resistance is described. However, if hydrogenated NBR in the range of 15 to 30% by weight is used, resistance to R152a cannot be ensured.
JP 2000-212333 A

Hydrogenated NBR having an AN bond amount of 31 to 45% by weight has an iodine value of 50 g / 100 g or less, preferably 2 to 30 g / 100 g, and its Mooney viscosity ML _{1 + 4} (100 ° C.) is 40 to 150, Preferably 70 to 120 are used. When the iodine value is larger than 50 g / 100 g, the heat resistance tends to deteriorate, and when the Mooney viscosity is smaller than 40, practically sufficient mechanical strength (normal physical properties) can not be maintained, whereas when it is larger than 150 The kneadability is lowered.

Hydrogenated NBR can be used as a blend rubber by replacing it with nitrile rubber (NBR) at a ratio of 30 parts by weight or less in 100 parts by weight, and if it is used at a ratio higher than this, the resistance to R152a and heat resistance will decrease. To come. NBR having an AN content of 30 to 45% by weight, preferably 35 to 40% by weight, and a Mooney viscosity ML _{1 + 4} (100 ° C.) of 20 to 120, preferably 40 to 100 is used. . Actually, commercially available products such as those of Nippon Zeon's Nipol series can be used as they are.

As the white carbon (reinforcing silica) used in a ratio of 60 to 150 parts by weight, preferably 60 to 120 parts by weight per 100 parts by weight of hydrogenated NBR or blended rubber of NBR, specific surface area (by nitrogen adsorption method) Is 30 to 200 m ² / g, preferably 50 to 150 m ² / g. These include dry decomposition methods such as thermal decomposition methods of halogenated silicic acid or organosilicon compounds and methods of heat-reducing siliceous sand and air oxidation of evaporated SiO. Wet-type white carbon produced by the above method, and commercially available products that are actually marketed for the rubber industry can be used as they are. If a material having a specific surface area smaller than this is used, a practically sufficient mechanical strength cannot be maintained, whereas if a material having a specific surface area larger than this is used, the dispersibility is lowered. Further, if it is used at an addition ratio lower than this, the resistance to R152a is lowered, while if it is used at an addition ratio higher than this, the rubber hardness becomes very high and the rubber elasticity tends to be lost.

Here, in order to improve adhesion between hydrogenated NBR and white carbon and R152a resistance, 0.1 to 5 parts by weight of silane coupling agent per 100 parts by weight of hydrogenated NBR or blended rubber of NBR and this, preferably Need to be used together at a ratio of 0.5 to 3 parts by weight. Examples of silane coupling agents include vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. It is done.

Hydrogenated NBR containing white carbon or a blend rubber of NBR with it is crosslinked by an organic peroxide. Examples of the organic peroxide include tertiary butyl peroxide, dicumyl peroxide, tertiary 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 (tert-butylperoxy) Oxyisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, n-butyl-4,4-di (tertiary 3) Butyl peroxy) valerate or the like is used in a proportion of 0.5 to 10 parts by weight, preferably 1 to 8 parts by weight, per 100 parts by weight of hydrogenated NBR or blended rubber of NBR and this.

  For organic peroxide crosslinking, polyfunctional unsaturated compound is used in combination with hydrogenated NBR or blended rubber of NBR with 10 parts by weight or less, generally 0.5 to 10 parts by weight, preferably 2 to 8 parts by weight. It is desirable to increase the crosslink density of the sealing material, thereby improving the compression set resistance and extending the life. Examples of the polyfunctional unsaturated compound include triallyl isocyanurate, triallyl cyanurate, triallyl trimellitate, N, N′-m-phenylene bismaleimide and the like. If it is used in a proportion higher than this, the rubber hardness becomes very high and the rubber elasticity tends to be lost.

In the hydrogenated NBR composition of the present invention comprising the above components, carbon black such as activated calcium carbonate , other reinforcing agents other than white carbon , fillers such as talc, clay, graphite, calcium silicate, etc. , Processing aids such as stearic acid, palmitic acid, paraffin wax, acid acceptors such as zinc oxide and magnesium oxide, anti-aging agents, plasticizers and other compounding agents commonly used in the rubber industry are required Depending on the situation, it can be added as appropriate.

  The hydrogenated NBR composition is prepared by kneading using a kneader such as intermix, kneader, banbury mixer or an open roll, and its crosslinking is performed by an injection molding machine, compression molding machine, vulcanizing press. In general, it is performed by heating at about 150 to 200 ° C. for about 3 to 60 minutes, and if necessary, secondary crosslinking is performed by heating at about 100 to 200 ° C. for about 1 to 24 hours.

  Next, the present invention will be described with reference to examples.

Example Hydrogenated NBR (Nippon Zeon product Zetpol 2020; AN binding amount
36.2%, iodine value 28g / 100g, Mooney viscosity ML _{1 + 4} (100 ° C) 78) 100 parts by weight
White carbon (specific surface area 90m ² / g) 80 〃
Vinyltrimethoxysilane 2
Zinc oxide 5 〃
Anti-aging agent (Ouchi Emerging Chemical Product Nocrack CD) 1.5 〃
Organic peroxide (dicumyl peroxide) 4 〃
The above components are kneaded with a kneader and an open roll, and the kneaded product is vulcanized by press vulcanization (primary vulcanization) at 170 ° C for 15 minutes and oven vulcanization (secondary vulcanization) at 150 ° C for 5 hours. Thus, a vulcanized sheet (150 × 150 × 2 mm) and a P-24 size O-ring were obtained.

Comparative example
In the examples, ethylene / propylene copolymer rubber (JSR product EP33) is used instead of hydrogenated NBR , carbon black is used instead of white carbon, and vinyltrimethoxysilane is not used. The amount of organic peroxide was changed to 2 parts by weight.

The following items were measured for each vulcanized sheet obtained in the above Examples and Comparative Examples.
Normal physical properties: JIS K6253, JIS K6251 compliant HFC resistance test: Test specimens of 50 × 20 × 2mm are R152a, R134a, R32 (difluoromethane), R125 (penta)
Fluoroethane), R407C (R32 / R125 / R134a = 23/25/52 wt%) or R410A (R32 /
R125 = 50/50% by weight) at 25 ° C for 70 hours, then air heated at 50 ° C for 30 minutes.
Visual observation of the appearance (whether or not foamed) when it was damaged Refrigeration oil test: Immerse in naphthenic refrigeration oil (Kignus product Sunin 4GS) at 150 ° C for 70 hours
Measure volume change rate after squeezing (JIS K6258 compliant)
For each P-24 O-ring, compression set at 150 ° C. for 70 hours was measured according to JIS K6262.

The results obtained are shown in the following table.
table
Measurement item Example Comparative example
Normal physical properties
Hardness (Durometer A) 81 80
Tensile strength (MPa) 27.7 21.6
Elongation (%) 240 190
HFC resistance test (with or without foaming)
R152a No Yes
R134a None None
R32 None None
R125a None None
R407C None None
R410A None None
Refrigeration machine oil test
Volume change rate (%) +2.1 +95.3
Compression set test
Compression set (%) 36 39

From the above results , it can be seen that the example has resistance to all HFCs, but the comparative example does not have resistance to R152a .

Claims (6)

100 parts by weight of hydrogenated nitrile rubber with a bound acrylonitrile amount of 31-45% by weight, specific surface area (by nitrogen adsorption method) of 30-200m ² Hydrogenated nitrile rubber-based seal molding material for R152a and R134a, comprising 60 to 150 parts by weight of white carbon / g, 0.1 to 5 parts by weight of a silane coupling agent, and 0.5 to 10 parts by weight of organic peroxide. 2. A hydrogenated nitrile rubber seal for R152a and R134a according to claim 1, wherein a nitrile rubber having a combined acrylonitrile content of 30 to 45% by weight is substituted in a proportion of 30 parts by weight or less in 100 parts by weight of hydrogenated nitrile rubber. Molding material. The hydrogenated nitrile rubber-based seal molding for R152a and R134a according to claim 1 or 2, further comprising 10 parts by weight or less of a polyfunctional unsaturated compound per 100 parts by weight of hydrogenated nitrile rubber or blended rubber thereof with nitrile rubber. material. A sealing material for R152a and R134a obtained by crosslinking the hydrogenated nitrile rubber-based molding material according to claim 1, 2, or 3. The sealing material for R152a and R134a according to claim 4, which is used as a sealing material for an air conditioner. The sealing material for R152a and R134a according to claim 5, which is used as a sealing material for a car air conditioner system.