JPH0967471A - Composition for sealing material and sealing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sealing material composition and a sealing material excellent in freeze resistance, useful for an air conditioner and a refrigerator, a sealing material composition and a sealing material applicable to an air conditioner using Fleon 134 ((R)fluorocarbon) used in a coed district. SOLUTION: The sealing material composition and the sealing material comprise 100 pts.wt. of the total of 65-85 pts.wt. of a hydrogenated acrylonitrile- butadiene rubber having 10-30 (g/100g) iodine value and 30-40% acrylonitrile content and 10-35 pts.wt. of an acrylonitrile-butadiene rubber having 10-25% acrylonitrile content 2-15 pts.wt. of an organic peroxide, 50-150 pts.wt. of a reinforcing agent and 5-20 pts.wt. of a plasticizer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sealing material useful for an air conditioner machine or a refrigerator used in a cold region, and a novel rubber composition suitable as a material for the sealing material. More specifically, the present invention relates to a sealant and a composition for the sealant applicable to a vehicle air conditioner machine using Freon 134a used as a refrigerant in cold regions.

[0002]

BACKGROUND OF THE INVENTION Some or all of the carbon-carbon double bonds in a nitrile group-containing polymer rubber such as acrylonitrile-butadiene rubber have been hydrogenated, or other ethylene-based monomer. The hydrogenated nitrile rubber replaced in body units has excellent heat resistance, ozone resistance, and oil resistance.
It is widely used in various fields as a sealant composition for rings, packings and the like.

The seal material is used, for example, in a refrigerator,
There are cooling devices for air conditioners, compressors for air conditioners, etc. In particular, air conditioners for vehicles such as automobiles and refrigerators are required to have the following characteristics. (1) The maximum temperature of the air conditioner machine is 140-15
The heat resistance of the sealing material is 15 because it reaches 0 ℃.
It is required to be 0 ° C. (2) The compression set is the most important physical property showing the sealing performance of the sealing material, and it is required that the compression set is small. (3) As one of the important physical properties of the sealing material for an air conditioner machine, it is required to have good foaming resistance to CFC, which is a refrigerant. The term "foaming resistance" means that the elastomer does not foam even after being immersed in a refrigerant and subjected to a high temperature.

By the way, conventionally, CFC 12 has been used as a refrigerant for air conditioners and refrigerators for vehicles such as automobiles. In recent years, however, destruction of the ozone layer by CFC has become an environmental problem, and CFC 12 has replaced it. Freon 134a, which does not destroy the ozone layer, has come into use. Nitrile rubber and fluororubber have been used as conventional sealing materials for Freon 12, but these materials are used as Freon 13
When applied to the sealing material of 4a, nitrile rubber has insufficient heat resistance, and fluororubber has problems such as large swelling due to Freon 134a.

Sealing materials using ethylene propylene rubber or chlorinated polyethylene are also known, but these materials have poor oil resistance to refrigerating machine oil added to a refrigerant such as mineral oil, and thus hydrogenated acrylonitrile-butadiene. The mixed seal material of rubber and chlorinated polyethylene has a problem that the oil resistance to mineral oil is poor.

[0006] In order to solve such a problem, there is a composition for a sealing material, which comprises a hydrogenated acrylonitrile-butadiene rubber, a cross-linking agent, a cross-linking aid, a metal oxide, a reinforcing agent and a plasticizer (Japanese Patent Application No. 5-108733). ). (4) However, it has been found that the above-mentioned composition for a sealing material has the following problems. That is, when the composition for a sealing material is used for a sealing material for a vehicle air conditioner such as an automobile, it may be cooled to about -40 ° C before dawn in an extremely cold region. The temperature may drop below the boiling point (about -26 ° C) of CFCs 134a used as a refrigerant for air conditioners. If this happens, CFCs 134a will liquefy, and the pressure inside the sealant will decrease, so that the atmosphere becomes a sealant. There was a risk that it would permeate and mix into the refrigerant. In order to solve this problem, the sealing material is also required to have cold resistance capable of withstanding an operating environment in an extremely cold region of about -40 ° C.

Conventionally, as a sealant having cold resistance,
There was a composition consisting of hydrogenated acrylonitrile-butadiene rubber and ethylene propylene rubber-based, isoprene rubber or butyl rubber (Japanese Patent Publication No. 6-39544). However, although the above composition has a certain degree of cold resistance, the above-mentioned other properties such as foaming resistance and heat resistance of the 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, that is,
It is intended to provide a rubber composition having heat resistance, compression set characteristics, foaming resistance, and cold resistance. Another object of the present invention is to
It is to provide a novel sealing material for a refrigerant.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor specified the amount of acrylonitrile even in the case of acrylonitrile-butadiene rubber which is said to have poor heat resistance, and When blended with a specific hydrogenated acrylonitrile-butadiene rubber and cross-linked with an organic peroxide, the acrylonitrile-butadiene rubber exerts a function as a crosslinking aid for the hydrogenated acrylonitrile-butadiene rubber and does not impair heat resistance. The present invention has been completed based on the knowledge that cold resistance can be improved. That is, the present inventor has solved the above problems by a composition for a sealing material 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, they have found that they have excellent properties as a sealing material for Freon 134a especially in cold regions, and have completed the present invention.

Therefore, the gist of the present invention is that the hydrogenated acrylonitrile-butadiene rubber 65 having an iodine value of 10 to 30 (g / 100 g) and an acrylonitrile amount of 30 to 40% is used in the present invention. 85 parts by weight and 15 to 35 parts by weight of acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25%, 100 parts by weight in total of rubber components, 2 to 15 parts by weight of 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.

Hydrogenated acrylonitrile used in the present invention
The butadiene rubber (hereinafter, also referred to as H-NBR) is obtained by hydrogenating a conjugated diene unit portion of an unsaturated nitrile-conjugated diene copolymer rubber, unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer ternary polymer. Examples thereof include, but are not limited to, a compounded rubber, a rubber obtained by hydrogenating a conjugated diene unit portion of the rubber, and an unsaturated nitrile-ethylenically unsaturated monomer copolymer rubber. Further, these H-NBR can be obtained by a usual polymerization means and hydrogenation method, but the means is not particularly limited.

Specific examples of the above H-NBR include acrylonitrile-butadiene copolymer rubber, isoprene-acrylonitrile-butadiene polymer rubber, isoprene-
Hydrogenated acrylonitrile copolymer rubber,
Hydrogenated 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-
Examples thereof include those obtained by hydrogenating an acrylonitrile polymer rubber, but the invention is 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 the acrylonitrile content is 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 / 100g), the compression set tends to increase, and if it exceeds 30 (g / 100g), the heat resistance tends to decrease. If the acrylonitrile content is less than 30% by weight, the oil resistance tends to decrease, and if it exceeds 40% by weight, the 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 thereof include, but are not limited to, unsaturated nitrile-ethylenically unsaturated monomer copolymer rubber.

Specific examples of the 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, etc. are exemplified. But,
It is not limited to these.

The NBR used in the present invention has an acrylonitrile content of 10 to 25%.
The amount of acrylonitrile is preferably 12 to 20%, more preferably 15 to 1 from the viewpoint of cold resistance and oil resistance.
8%. When the amount of acrylonitrile is less than 10%, problems in oil resistance tend to occur, and when it exceeds 25%, problems in cold resistance tend to occur.

As the rubber component of the composition of the present invention, a mixture of the above specific H-NBR and specific NBR is used.
The mixing ratio of H-NBR and NBR is H-NBR65-
It may be blended so 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. From the viewpoint of cold resistance and heat resistance, H-NB is preferable.
The total amount of the rubber components of R70 to 80 parts by weight and NBR 20 to 30 parts by weight is 100 parts by weight. If the amount of H-NBR is too large, cold resistance tends to be a problem, and NB
If the amount of R is too large, heat resistance tends to be a problem.

An organic peroxide is essential in the present invention, and examples of the organic peroxide used in the present invention include benzoyl peroxide and 1,1-bis-t-butyl-.
Peroxy-3,3,5-trimethylcyclohexane,
1,1-bis (t-butylperoxy) cyclododecane, n-butyl-4,4-bis-t-butylperoxyvalerate, 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 Examples include syn-3 and t-butylperoxycumene. In the present invention, the above organic peroxides are used alone or in combination of two or more.

The blending amount of the above organic peroxide is 65 to 85 parts by weight of hydrogenated acrylonitrile-butadiene rubber having an iodine value of 10 to 30 (g / 100 g) and an acrylonitrile amount of 30 to 40%. 2 to 15 parts by weight per 100 parts by weight of the total amount of the rubber component together with 15 to 35 parts by weight of acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25%, and preferably 2.5 to 5 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, compression set characteristics and foaming resistance will tend to be lowered, and if it exceeds 15 parts by weight, problems will occur in mechanical properties.

In the present invention, a reinforcing agent is indispensable for improving mechanical properties. Examples of the reinforcing agent used in the present invention include natural silicic acid (talc, wax, kaolin clay, calcined clay, etc.), Examples include silicates, carbonates (heavy calcium carbonate, soft calcium carbonate, magnesium carbonate, etc.), carbon black (channel black, furnace black, acetylene black, thermal black, graphite, graphite, etc.), and compression set characteristics. From the above point, carbon black, particularly thermal black is preferable. The above reinforcing agents are used alone or in combination of two or more.

The amount of the reinforcing agent blended is such that the iodine value is 10 to 10.
30 (g / 100g) and 65-85 parts by weight of hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile content of 30-40% and an acrylonitrile content of 1
0-25% acrylonitrile-butadiene rubber 1
50-150 parts by weight, preferably 50-120 parts by weight, more preferably 60 from the viewpoint of improving mechanical properties, based on 100 parts by weight of the total amount of the rubber component of 5 to 35 parts by weight.
˜110 parts by weight. If the compounding 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 characteristics tend to decrease.

The plasticizer used in the present invention is not particularly limited as long as it is one generally used for nitrile rubbers, but phthalic acid diester, adipic acid diester,
In addition to isophthalic acid diester, trimellitic acid triester and the like, low volatility plasticizers such as polyester ether, polyether and adipic acid polyester are suitable. The above plasticizers are used alone or in combination of two or more, and the blending amount of the plasticizer is such that the iodine value is 10 to 30.
(G / 100 g), and the acrylonitrile amount is 30 to 40%, and the hydrogenated acrylonitrile-butadiene rubber is 65 to 85 parts by weight and the acrylonitrile amount is 10 to
25% acrylonitrile-butadiene rubber 15-
5 to 20 parts by weight, preferably 5 to 15 parts by weight, more preferably 7 to 7 parts by weight based on 100 parts by weight of the total of 35 parts by weight of the rubber component.
It is 12 parts by weight. If the compounding 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 characteristics tend to deteriorate.

Further, the composition of the present invention may be used in combination with a crosslinking aid such as a maleimide crosslinking aid, a methacrylate crosslinking aid, an allyl crosslinking aid and the like. Examples of the maleimide-based crosslinking aid are N, Nm-phenylene dimaleimide, and examples of the allyl-based crosslinking aid are 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,
Examples include trimethylolpropene trimethacrylate. The cross-linking aids may be used alone or in combination of two or more. A sealing material made of a composition containing a large amount of a crosslinking aid has good compression set characteristics,
Since the foaming resistance tends to decrease, the blending amount of the cross-linking aid is 65 to 85 parts by weight of hydrogenated acrylonitrile-butadiene rubber having an acrylonitrile amount of 30 to 40% and acrylonitrile amount of 10 to 25%. -0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, more preferably 2 in terms of foaming resistance, based on 100 parts by weight of the total amount of the rubber component together with 15 to 35 parts by weight of butadiene rubber. It is about 4 parts by weight.

A metal oxide may be added to the composition of the present invention. The metal oxide is not particularly limited as long as it is one commonly used as an additive for rubber, for example, Z
Alkaline substances such as nO, SbO, MgO, PbO and CaO are preferably used. The above metal oxides are used alone or in combination of two or more. The amount of the metal oxide compounded is a rubber of hydrogenated acrylonitrile-butadiene rubber 65-85 parts by weight having an acrylonitrile amount of 30-40% and acrylonitrile-butadiene rubber 15-35 parts by weight having an acrylonitrile amount of 10-25%. 1 to 20 parts by weight based on 100 parts by weight of the total amount of components, preferably 2 to 15 in terms of compression set characteristics and foaming resistance.
Parts by weight, more preferably about 3 to 10 parts by weight.

In the composition of the present invention, in addition to the above-mentioned additives, if necessary, additives such as an antiaging agent, a stabilizer and a coupling agent generally used in this field are impaired for the purpose of the invention. It can be added in the range not present.

[0026]

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, a sheet, a gasket, etc. by an appropriate method such as compression molding, injection molding, extrusion molding, etc., and is crosslinked by an appropriate means such as heat, light and ultraviolet rays to produce a sealing material. can do. The obtained sealing material is used for a cooling device such as an air conditioner machine or a refrigerator.

The present invention is described in detail below with reference to examples and comparative examples, but the present invention is not limited to these.

(Examples 1 to 4, Comparative Examples 1 to 10) The specimens were prepared by compression-molding the sealant compositions having the compositions shown in Tables 1 and 2 below in a mold at 180 ° C. for 5 minutes. It was made.

The following tests were conducted to evaluate the composition for a sealing material of the present invention. (1) Heat resistance An air heating aging test was performed according to the vulcanized rubber physical test method of JIS K6301 (aging conditions: temperature 150 ° C., 7
0 hours). As the sample, a JIS No. 3 punched dumbbell piece having a thickness of 2 mm was used. The rate of change in tensile strength and elongation of the specimen after the test under the above aging conditions was obtained. When the rate of change was ± 20% or less, it was evaluated as ○, and when it exceeded ± 20%, it was evaluated as ×.

(2) Compression set characteristics It was carried out according to JIS K6301 (aging condition: temperature 1
50 ° C, 70 hours). A sample having a thickness of about 13 mm was compressed by 25% with a compression jig, and the compression set after air aging was determined. Those having a compression set of 15% or less were marked with ◯, and those with a compression set exceeding 15% were marked with x.

(3) Anti-foaming property The test sample was an O-ring of JIS B2401 P26. Immersion in Freon 134a at 25 ° C. for 70 hours was immediately followed by placing in a 150 ° C. oven, and the presence or absence of foaming was observed. By observing the appearance, those without foaming were marked with ◯, and those with foaming were marked with x.

(4) Cold resistance According to ASTM D 1329, TR50 / 10 value was measured. In addition, TR is Temperature Ret
TR50 / 10 value means that the sample is extended by 50% and frozen at -70 ° C or lower, and then 1 ° C.
It is the value of the temperature at which the temperature is raised in 1 minute and the elongation is recovered by 10%. For example, if the TR50 / 10 value is -30 ° C, it can withstand even a use environment of about -40 ° C.

The results are shown in Tables 1 and 2. The example compositions fulfilled all the criteria and proved to have suitable properties as sealing materials.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

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 made 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 very good. (3) Good resistance to foaming against the refrigerant (CFC 134a). An O-ring made of the composition of the present invention was used as Freon 134.
Foaming does not occur even if it is immersed in a at 70 ° C. for 25 hours at 25 ° C. and immediately put in an oven at 150 ° C. (4) Since the cold resistance can be improved without deteriorating the characteristics of (1) to (4) above, the atmosphere is a sealant even in a use environment of about -40 ° C in the presence of the Freon 134a. It does not permeate into and mix with the refrigerant. As described above, the composition of the present invention has excellent properties as a sealing material for Freon 134a, and is suitable as an air conditioner, particularly as an air conditioner for vehicles such as automobiles and as a refrigerant sealing material for refrigerators.

Claims (3)

[Claims] 1. An iodine value of 10 to 30 (g / 100g)
And hydrogenated acrylonitrile-butadiene rubber 65-85 having an acrylonitrile amount of 30-40%
100 parts by weight of the total amount of rubber components of 15 to 35 parts by weight of acrylonitrile-butadiene rubber having an acrylonitrile amount of 10 to 25%, 2 to 15 parts by weight of organic peroxide, 50 to 150 parts by weight of a reinforcing agent, And plasticizer 5-20
A composition for a sealing material, which comprises 1 part by weight. 2. A device for an air conditioner machine.
The composition for a sealing material as described above. 3. A sealing material comprising the composition for a sealing material according to claim 1 or 2.