JP3527331B2 - Composition for sealing material and sealing material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material useful for an air conditioner or a refrigerator used in a cold region, and a novel rubber suitable as a material for the sealing material. Composition. More specifically, the present invention relates to a sealing material applicable to a vehicle air conditioner using Freon 134a as a refrigerant and a composition for the sealing material used in cold regions. 2. Description of the Related Art Some or all of carbon-carbon double bonds in a nitrile group-containing polymer rubber such as acrylonitrile-butadiene rubber are hydrogenated or other ethylene. Since the hydrogenated nitrile rubber replaced with the system monomer unit is excellent in heat resistance, ozone resistance and oil resistance, the rubber composition containing the same is
It is widely used in various fields as a composition for sealing materials such as rings and packings. [0003] Applications of sealing materials include, for example, refrigerators,
There are cooling devices such as air conditioners, compressors for air conditioners, etc. In particular, air conditioners and refrigerators for vehicles such as automobiles are required to have the following characteristics. (1) Maximum temperature of air conditioner machine is 140 ~ 15
Since the temperature reaches 0 ° C, the heat resistance of the sealing material is 15
It is required to be 0 ° C. (2) The most important physical property representing the sealing performance of the sealing material is the compression set, which is required to have a small compression set. (3) One of the important physical properties of the sealing material for an air conditioner machine is to have good foaming resistance to Freon as a refrigerant. Here, the term "foaming resistance" means that foaming does not occur in the elastomer even if it is subjected to a high temperature after immersion in a refrigerant. Conventionally, CFCs 12 have been used as a refrigerant for air conditioners and refrigerators for vehicles such as automobiles. However, in recent years, destruction of the ozone layer by CFCs has become an environmental problem. CFCs 134a that do not destroy the ozone layer have been used. Nitrile rubber and fluorine rubber have been used as the conventional sealing material for Freon 12, but these materials are replaced by Freon 13
When applied to the sealing material of 4a, there is a problem that nitrile rubber has insufficient heat resistance, and fluororubber has a large swelling due to Freon 134a. [0005] Sealing materials using ethylene propylene rubber or chlorinated polyethylene are also known. However, these materials are inferior in oil resistance to refrigerating machine oil added to refrigerants such as mineral oil, and hydrogenated acrylonitrile-butadiene. A mixed sealing material of rubber and chlorinated polyethylene has a problem that oil resistance to mineral oil is inferior. [0006] In order to solve such a problem, there has been a sealant composition comprising a hydrogenated acrylonitrile-butadiene rubber, a crosslinking agent, a crosslinking aid, a metal oxide, a reinforcing agent, and a plasticizer (Japanese Patent Application No. 5-108733). ). (4) However, it was found that the following problems occurred in the composition for a sealing material. That is, using the composition for a sealing material, for example, when applied to a sealing material for an air conditioner machine for a vehicle such as an automobile, in an extremely cold region, it may cool down to about -40 ° C before dawn, The temperature may drop below the boiling point (about -26 ° C.) of Freon 134a used as a refrigerant for an air conditioner machine. In such a case, Freon 134a is liquefied and the pressure inside the sealing material is reduced. There was a possibility that the water would permeate and be mixed into the refrigerant. In order to solve this problem, the sealing material is required to have cold resistance that can withstand the use environment in an extremely cold region of about −40 ° C. Conventionally, as a cold-resistant sealing material,
There was a composition comprising hydrogenated acrylonitrile-butadiene rubber and ethylene propylene rubber, isoprene rubber or butyl rubber (Japanese Patent Publication No. 6-39544). However, although the above-mentioned composition has some degree of cold resistance, other properties such as the above-mentioned foaming resistance and heat resistance to Freon 134a were not sufficient. An object of the present invention is to satisfy the above-mentioned characteristics (1) to (4) required for a sealing material for a refrigerant.
An object of the present invention is to provide a rubber composition having heat resistance, compression set characteristics, foam resistance, and cold resistance. Another object of the present invention is to
An object of the present invention is to provide a novel refrigerant sealing material. Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have specified the amount of acrylonitrile even for acrylonitrile-butadiene rubber which is considered to be inferior in heat resistance. And, when blended with a specific hydrogenated acrylonitrile-butadiene rubber and crosslinked with an organic peroxide, the acrylonitrile-butadiene rubber exhibits a cross-linking auxiliary effect on the hydrogenated acrylonitrile-butadiene rubber, and exhibits heat resistance. The present inventors have obtained the finding that the cold resistance can be improved without impairment, and have completed the present invention. That is, the present inventors have solved the above-mentioned problem with a sealing material composition comprising a rubber component of a specific hydrogenated acrylonitrile-butadiene rubber and a specific acrylonitrile-butadiene rubber, an organic peroxide, a reinforcing agent, and a plasticizer. In particular, the present invention was found to have excellent properties as a sealing material for CFC 134a in a cold region, and the present invention was completed. Accordingly, the gist of the present invention is to provide a hydrogenated acrylonitrile-butadiene rubber having an iodine value of 10 to 30 (g / 100 g) and an acrylonitrile content of 30 to 40%. 85 parts by weight and 15 to 35 parts by weight of an acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25%, a total of 100 parts by weight of a rubber component, 2 to 15 parts by weight of an organic peroxide,
A sealant composition comprising 50 to 150 parts by weight of a reinforcing agent and 5 to 20 parts by weight of a plasticizer. Further, the present invention is the above-mentioned composition for a sealing material for an air conditioner machine. Further, the present invention is a sealing material comprising the above composition for a sealing material. The hydrogenated acrylonitrile used in the present invention
As butadiene rubber (hereinafter also referred to as H-NBR), hydrogenated conjugated diene units of unsaturated nitrile-conjugated diene copolymer rubber, unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer ternary polymer Examples include, but are not limited to, coalesced rubbers, hydrogenated conjugated diene units of the rubbers, and unsaturated nitrile-ethylenically unsaturated monomer copolymer rubbers. These H-NBRs can be obtained by ordinary polymerization means and hydrogenation methods, but the means is not particularly limited. Specific examples of the above-mentioned H-NBR include acrylonitrile-butadiene copolymer rubber, isoprene-acrylonitrile-butadiene polymer rubber, isoprene-
Hydrogenated acrylonitrile copolymer rubber, etc.,
Hydrogenated acrylonitrile-methyl acrylate-butadiene polymer rubber, acrylonitrile-acrylic acid-butadiene polymer rubber, etc., acrylonitrile-
Ethylene-butadiene polymer rubber, butyl acrylate-ethoxyethyl acrylate-vinyl chloroacetate-acrylonitrile polymer rubber, butyl acrylate-ethoxyethyl acrylate-vinyl norbornene-
Examples include hydrogenated acrylonitrile polymer rubbers, but are not limited thereto. The H-NBR used in the present invention has an iodine value of 10 to 30 (g / 100 g), and preferably 15 to 25 (g) in view of compression set characteristics and heat resistance.
/ 100 g) and an acrylonitrile content of 3
Those having 0 to 40% by weight and preferably 33 to 39% by weight from the viewpoint of oil resistance and cold resistance are used. If the iodine value is less than 10 (g / 100 g), the compression set tends to increase, and if it exceeds 30 (g / 100 g), the heat resistance tends to decrease. When the acrylonitrile content is less than 30% by weight, oil resistance tends to decrease, and when it exceeds 40% by weight, cold resistance tends to decrease. The acrylonitrile-butadiene rubber (hereinafter also referred to as NBR) used in the present invention includes unsaturated nitrile-conjugated diene copolymer rubber, unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer terpolymer rubber,
Examples include, but are not limited to, unsaturated nitrile-ethylenically unsaturated monomer-based copolymer rubber. Specific examples of the above NBR include acrylonitrile-butadiene copolymer rubber, isoprene-acrylonitrile-butadiene polymer rubber, isoprene-acrylonitrile copolymer rubber, acrylonitrile-methyl acrylate-butadiene polymer rubber, acrylonitrile-acrylic acid -Butadiene polymer rubber, acrylonitrile-ethylene-butadiene polymer rubber, butyl acrylate-ethoxyethyl acrylate-vinyl chloroacetate-acrylonitrile polymer rubber, butyl acrylate-ethoxyethyl acrylate-vinyl norbornene-acrylonitrile polymer rubber, and the like. But,
It is not limited to these. As the NBR used in the present invention, one having an acrylonitrile content of 10 to 25% is used.
The preferred amount of acrylonitrile is 12 to 20%, more preferably 15 to 1 in terms of cold resistance and oil resistance.
8%. If the amount of acrylonitrile is less than 10%, a problem tends to occur in terms of oil resistance, and if it exceeds 25%, a problem tends to occur in respect of cold resistance. As the rubber component of the composition of the present invention, a mixture of the above specific H-NBR and the specific NBR is used.
The mixing ratio of H-NBR and NBR is H-NBR 65 to
The blending may be performed such that the total amount of the rubber components of 85 parts by weight and 15 to 35 parts by weight of NBR becomes 100 parts by weight. H-NB is preferred from the viewpoint of cold resistance and heat resistance.
The total amount of rubber components of R 70 to 80 parts by weight and NBR 20 to 30 parts by weight is 100 parts by weight. If the compounding amount of H-NBR is too large, there is a tendency that a problem occurs in cold resistance.
If the amount of R is too large, a problem tends to occur in heat resistance. In the present invention, an organic peroxide is essential. Examples of the organic peroxide used in the present invention include benzoyl peroxide, 1,1-bis-t-butyl-
Peroxy-3,3,5-trimethylcyclohexane,
1,1-bis (t-butylperoxy) cyclododecane, n-butyl-4,4-bis-tbutylperoxyvalerate, dicumyl peroxide, t-butylperoxybenzoate, di-t-butylper oxide,
Di- (t-butylperoxy) m di-isopropylbenzene, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-t-butylperoxylhexyl Syn-3, t-butyl peroxycumene, and the like. In the present invention, the above organic peroxides are used alone or in combination of two or more. The compounding amount of the above organic peroxide is 65 to 85 parts by weight of a hydrogenated acrylonitrile-butadiene rubber having an iodine value of 10 to 30 (g / 100 g) and an acrylonitrile amount of 30 to 40%. Acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25% and a rubber component of 15 to 35 parts by weight based on 100 parts by weight of the total amount of rubber components are 2 to 15 parts by weight, preferably 2.5 to 5 parts from the viewpoint of cold resistance. Parts by weight. The amount of organic peroxide is 2
If it is less than 15 parts by weight, the compression set and foaming resistance tend to decrease, and if it exceeds 15 parts by weight, problems tend to occur in the mechanical properties. In the present invention, a reinforcing agent is indispensable for improving the mechanical properties. Examples of the reinforcing agent used in the present invention include natural silicic acid (talc, limestone, kaolin clay, calcined clay, etc.), Silicates, carbonates (heavy calcium carbonate, soft calcium carbonate, magnesium carbonate, etc.), carbon black (channel black, furnace black, acetylene black, thermal black, graphite, graphite, etc.), compression set properties In this respect, carbon black, particularly thermal black, is preferred. The above reinforcing agents are used alone or in combination of two or more. The compounding amount of the reinforcing agent is such that the iodine value is 10 to 10.
30- (g / 100 g), 65-85 parts by weight of a hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 30 to 40%, and an acrylonitrile amount of 1
Acrylonitrile-butadiene rubber 1 of 0 to 25%
50 to 150 parts by weight, preferably 50 to 120 parts by weight, more preferably 60 to 150 parts by weight, from the viewpoint of improvement of mechanical properties, based on 100 parts by weight of the total amount of the rubber component of 5 to 35 parts by weight.
To 110 parts by weight. If the amount of the reinforcing agent is less than 50 parts by weight, the foaming resistance tends to decrease, and if it exceeds 150 parts by weight, the compression set characteristic tends to decrease. The plasticizer used in the present invention is not particularly limited as long as it is generally used for nitrile rubber, but phthalic diester, adipic diester,
In addition to isophthalic acid diester and trimellitic acid triester, low volatile plasticizers such as polyester ether, polyether, and adipic acid polyester are preferable. The above-mentioned plasticizers are used alone or in combination of two or more kinds.
(G / 100 g) and 65 to 85 parts by weight of a hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 30 to 40% and an acrylonitrile amount of 10 to 10%.
25% acrylonitrile-butadiene rubber
5 to 20 parts by weight, preferably 5 to 15 parts by weight, more preferably 7 to 5 parts by weight, from the viewpoint of compression set characteristics and heat resistance, based on 35 parts by weight and the total amount of rubber components of 100 parts by weight.
It is 12 parts by weight. If the amount of the plasticizer is less than 5 parts by weight, the cold resistance tends to decrease, and if it exceeds 20 parts by weight, the compression set characteristic tends to decrease. Further, a crosslinking aid such as a maleimide-based crosslinking aid, a methacrylate-based crosslinking aid, or an allyl-based crosslinking aid may be used in combination with the composition of the present invention. Examples of the maleimide-based crosslinking aid include N, Nm-phenylenedimaleimide, and examples of the allyl-based crosslinking aid include triallyl cyanurate, diallyl fumarate, diallyl phthalate,
Tetraallyloxyethane and the like, and examples of the methacrylate-based crosslinking aid include ethylene glycol methacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,
And trimethylolpropene trimethacrylate. The crosslinking assistants are used alone or in combination of two or more. A sealing material composed of a composition containing a large amount of a crosslinking aid has good compression set characteristics,
Since the foaming resistance tends to decrease, the compounding amounts of the crosslinking aid are 65 to 85 parts by weight of a hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 30 to 40% and acrylonitrile having an acrylonitrile amount of 10 to 25%. 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, more preferably 2 to 5 parts by weight, from the viewpoint of foaming resistance, based on 100 parts by weight of the total amount of the rubber component with 15 to 35 parts by weight of butadiene rubber. About 4 parts by weight. The composition of the present invention may contain a metal oxide. The metal oxide is not particularly limited as long as it is generally used as a rubber additive.
Alkaline substances such as nO, SbO, MgO, PbO, and CaO are preferably used. The metal oxides are used alone or in combination of two or more. The compounding amount of the metal oxide is a rubber composed of 65 to 85 parts by weight of a hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 30 to 40% and 15 to 35 parts by weight of an acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25%. 1 to 20 parts by weight, preferably 2 to 15 parts by weight, from the viewpoint of compression set characteristics and foaming resistance, based on 100 parts by weight of the total amount of the components.
Parts by weight, more preferably about 3 to 10 parts by weight. In the composition of the present invention, additives such as an antioxidant, a stabilizer, a coupling agent and the like generally used in the art, if necessary, may impair the object of the invention. It can be added in a range not present. BEST MODE FOR CARRYING OUT THE INVENTION The composition for a sealing material of the present invention is prepared by mixing the above components. The composition thus obtained is molded into a ring, sheet, gasket, etc. by an appropriate method such as compression molding, injection molding, extrusion molding, etc., and subjected to cross-linking by appropriate means such as heat, light, ultraviolet rays, etc. to produce a sealing material. can do. The obtained sealing material is used for a cooling device such as an air conditioner or a refrigerator. Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Examples 1 to 4 and Comparative Examples 1 to 10) A test sample was prepared by compression-molding a sealing material composition having the composition shown in Tables 1 and 2 in a mold at 180 ° C. for 5 minutes. Produced. The following tests were conducted to evaluate the sealing material composition of the present invention. (1) Heat resistance air heating aging test was carried out according to the vulcanized rubber physical test method of JIS K6301 (aging conditions: temperature 150 ° C, 7
0 hours). The test sample used was a JIS No. 3 punched dumbbell piece having a thickness of 2 mm. The rate of change in tensile strength and elongation of the specimen after the test under the above aging conditions was determined. When the rate of change was ± 20% or less, the result was evaluated as ○, and when the rate exceeded ± 20%, the result was evaluated as ×. (2) Compression set characteristics Implemented in accordance with JIS K6301 (aging conditions: temperature 1)
50 ° C, 70 hours). A test sample having a thickness of about 13 mm was compressed by 25% using a compression jig, and the compression set after air aging was determined. A sample having a compression set of 15% or less was evaluated as ○, and a sample having a compression set exceeding 15% was evaluated as ×. (3) Foaming-resistant test pieces used were O-rings according to JIS B2401 P26. Immediately after immersion in Freon 134a at 25 ° C. for 70 hours, it was put into an oven at 150 ° C. and observed for foaming. By observing the appearance, those without foaming were evaluated as ○ and those with foaming were evaluated as ×. (4) Cold resistance According to ASTM D 1329, TR50 / 10 values were measured. Note that TR stands for Temperature Ret.
The TR50 / 10 value means that the sample was stretched by 50% and frozen at −70 ° C. or lower, and then 1 ° C.
/ 1 minute, the value at which the elongation recovered by 10%. For example, if the TR50 / 10 value is −30 ° C., it is considered that it can withstand a use environment of about −40 ° C. The results are shown in Tables 1 and 2. The example compositions meet all criteria and have been demonstrated to have suitable properties as sealing materials. [Table 1] [Table 2] The composition of the present invention has the following excellent properties as a sealing material for a refrigerant. (1) The heat-resistant temperature is 150 ° C. or higher. (2) The compression set is small. The compression set of the sealing material composed of the composition of the present invention measured by the test method of JIS K6301 is 15% or less at 150 ° C. for 70 hours, which is extremely good. (3) Good foaming resistance to the refrigerant (Freon 134a). The O-ring made of the composition of the present invention is
The foaming does not occur even if it is put in an oven at 150 ° C. immediately after immersion in a at 25 ° C. for 70 hours. (4) Since the cold resistance can be improved without impairing the characteristics of the above (1) to (4), even in the use environment of about −40 ° C. in the presence of Freon 134a, the atmosphere is sealed. And does not permeate into the refrigerant. As described above, the composition of the present invention has excellent properties as a sealing material for chlorofluorocarbon 134a, and is suitable as an air conditioner, in particular, an air conditioner for vehicles such as automobiles and a sealing material for refrigerant in refrigerators.

Claims (1)

(Claim 1) 65 to 85 parts by weight of a hydrogenated acrylonitrile-butadiene rubber having an iodine value of 10 to 30 (g / 100 g) and an acrylonitrile content of 30 to 40%. And a total amount of rubber components of 15 to 35 parts by weight of acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25%, 100 parts by weight of organic peroxide, 2 to 15 parts by weight of organic peroxide, 50 to 150 parts by weight of reinforcing agent, and plasticizer. A composition for a sealing material for an air conditioner, comprising 5 to 20 parts by weight of an agent. (Claim 2) A sealing material comprising the composition for a sealing material according to claim 1.