JPH0788440B2 - Rubber composition with improved cold resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rubber composition having a nitrile group-containing copolymer rubber having a specific composition and having a small amount of unsaturated bonds, which has a low resistance to cold and has improved cold resistance. is there.

(Problems to be solved by conventional techniques and inventions) In order to prevent exhaust gas from automobiles, rubber parts around the engine are required to have high heat resistance. A nitrile group-containing highly saturated polymer rubber obtained by hydrogenating a part or all of the carbon-carbon double bond-containing monomer in a hydrocarbon rubber (eg, acrylonitrile-butadiene copolymer rubber, sometimes abbreviated as NBR hereinafter) has been developed. ,It is used.

This rubber is extremely superior in ozone resistance and heat resistance to conventional NBR, but it may be inferior in cold resistance to NBR depending on the content of the nitrile group and the degree of unsaturation.

Due to recent technological advances, the temperature of the atmosphere in which various rubber parts are used has been broadened from a lower temperature to a higher temperature, and a nitrile group-containing highly saturated polymer rubber composition having improved cold resistance has been obtained. Development is strongly demanded.

Generally, in ordinary NBR, it is possible to improve cold resistance by reducing the content of nitrile groups. For example ASTM
TR test specified in D1329 (freezing the stretched test piece and measuring the recoverability of the stretched test piece by continuously increasing the temperature. The temperature at which 10% contraction (recovery) is indicated as TR10.)
In R, TR10 is −20.5 ° C., and TR10 becomes −31 ° C. by reducing the amount of bound acrylonitrile to 28% by weight.

However, in the case of NBR containing highly saturated copolymer rubber, cold resistance is not necessarily improved even if the content of nitrile group is reduced unlike NBR. For example, in a rubber containing 5% by weight of butadiene units, 37% by weight of acrylonitrile units and the rest of hydrogenated butadiene units, TR10 is −24.5 ° C. The TR10 of this rubber does not improve the cold resistance even if the acrylonitrile content is lowered to -20 ° C.

The present inventors have conducted intensive studies to improve the cold resistance of the nitrile group-containing highly saturated polymerized rubber, and found that the cold resistance is best when the monomer composition of the rubber satisfies specific conditions. The invention was completed.

(Means for Solving Problems) Thus, according to the present invention, the content of each engaging monomer in the copolymer chain is (1) 10 to 40% by weight of the unsaturated nitrile monomer unit, (2) Unsaturated carboxylic acid ester monomer unit 1-40
%, (3) Conjugated diene-based monomer unit 20% by weight or less, (4) Hydrogenated conjugated diene-based monomer unit Remaining, and monomer unit (1) and monomer unit (2) Resistance consisting of a highly saturated nitrile group-containing copolymer rubber having a total content of 30 to 50% by weight and a total of monomer units (3) and (4) of 50 to 70% by weight and a compounding agent A rubber composition having improved properties is provided.

By using the rubber composition of the present invention, TR10 which is not obtained when the butadiene unit of NBR is highly hydrogenated
Is -26 ° C or less (SRF carbon black 40% by weight / rubber 100
It is possible to produce a vulcanized product (parts by weight and no plasticizer).

In the nitrile group-containing highly saturated copolymer rubber used in the present invention, the content of the nitrile group-containing monomer unit (1) in the rubber is preferably 10 to 40% by weight from the requirements of oil resistance and cold resistance. Ten
If it is less than 10% by weight, the oil resistance is poor, and if it exceeds 40% by weight, the effect of improving cold resistance is insufficient. The content of the ester monomer unit (2) of unsaturated carboxylic acid introduced for improving cold resistance is 1 to 40% by weight. If it is less than 1% by weight, the effect of improving the cold resistance is small, and if it exceeds 40% by weight, the cold resistance is improved but the oil resistance is lowered. Preferably 3 to 30
% By weight. From the viewpoint of heat resistance, the content of the conjugated monomer unit (3) in the rubber is 20% by weight or less, preferably 15% by weight or less. The rest of the content of each of the above monomer units is the content of the hydrogenated conjugated diene monomer unit (4).
In addition to the above requirements, in order to balance oil resistance and cold resistance, the monomer unit (1) and the monomer unit (2) in the rubber are
Must be 30 to 50% by weight, and outside this range, surprisingly, the cold resistance will not be improved. Furthermore, from the viewpoint of the balance between heat resistance and cold resistance, the monomer unit (3)
And the total amount of the monomer units (4) must be 50 to 70% by weight.

The highly saturated nitrile group-containing copolymer rubber of the present invention is a conjugated diene-based monomer in a copolymer rubber obtained by copolymerizing an unsaturated nitrile-based monomer, an unsaturated carboxylic acid monomer and a conjugated diene-based monomer. It is a rubber obtained by hydrogenating a monomer unit by a usual method.

The monomers used for producing the copolymer rubber of the present invention are exemplified below.

Examples of the unsaturated nitrile-based monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like.

As the unsaturated carboxylic acid ester-based monomer, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, 2-methyl-pentyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n
-Acrylates and methacrylates having an alkyl group of about 1 to 18 carbon atoms such as dodecyl acrylate, methyl methacrylate, ethyl methacrylate; methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate,
An acrylate having an alkoxyalkyl group having a total carbon number of about 2 to 12, such as ethoxypropyl acrylate, methoxyethoxy acrylate, and ethoxybutoxy acrylate; α and β-cyanoethyl acrylate, α, β and γ-cyanopropyl acrylate, cyanobutyl acrylate, cyano Hexyl acrylate, cyanooctyl acrylate, and other acrylates having a cyanoalkyl group having about 2 to 12 carbon atoms; 2-hydroxyethyl acrylate, hydroxypropyl acrylate, and other acrylates having hydroxyalkyl groups, monoethyl maleate, dimethyl maleate, and fumaric acid. Dimethyl, diethyl fumarate, di-n-butyl fumarate, di-2 fumarate
Ethylhexyl, dimethyl itaconate, di-itaconate
Mention may be made of mono- and dialkyl esters of unsaturated dicarboxylic acids such as n-butyl.

Examples of the conjugated diene-based monomer include 1,3-butadiene, 2,3-dimethylbutadiene, isoprene and 1,3-pentadiene. Other than these monomers, styrene, vinyl norbornene such as vinyl pyridine and vinyl norbornene, etc. within a range not impairing the gist of the present invention, a part of the total amount of monomers,
It may be replaced with a monomer copolymerizable with each of the above monomers such as non-conjugated diene-based monomers such as dicyclopentadiene and 1,4 hexadiene.

Specific examples of the nitrile group-containing highly saturated copolymer rubber used in the present invention include butadiene-butyl acrylate-acrylonitrile copolymer rubber, butadiene-isoprene-butyl acrylate-acrylonitrile copolymer rubber, and butadiene-piperylene-2-. Ethylhexyl acrylate-acrylonitrile copolymer rubber, butadiene-
Examples thereof include hydrogenated products such as methoxy acrylate-acrylonitrile copolymer rubber.

The rubber composition of the present invention is made into a compounded rubber composition by mixing a nitrile group-containing highly saturated copolymer rubber and various compounding agents that are commonly used in the rubber industry using an ordinary mixer. The type and amount of the compounding agent are determined according to the intended purpose (use) of the rubber composition and are not particularly limited in the present invention.

Compounding agents include sulfur, sulfur-donating compounds such as tetramethylthiuram disulphide, zinc white, stearic acid, various vulcanization accelerators (guanidine-based, thiazole-based, thiuram-based, dithioate-based, etc.) Sulfur vulcanization system; organic peroxide vulcanization system such as dicumyl peroxide and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; various grades such as SRF, HAF and FEA Reinforcing agents such as carbon black, silica, talc, calcium carbonate, and fillers; plasticizers, process oils, processing aids, antiaging agents and the like are usually used.

By using the rubber composition of the present invention, highly saturated TBR
TR10, which cannot be obtained with the rubber composition using -26 ° C or less (SRF carbon black 40 parts by weight / rubber 100 parts by weight,
It is possible to manufacture vulcanized rubber products (without using a plasticizer).

The rubber composition of the present invention has ozone resistance, heat resistance, and oil resistance, which are the features of nitrile group-containing highly saturated polymerized rubber, and has improved cold resistance, so it is used in contact with various oils, gases, etc. It is effective when used for manufacturing rubber products that require heat resistance and oil resistance, especially rubber products that require cold resistance.

Therefore, the rubber product of the present invention is a rubber product for various seals such as O-rings, packings and gaskets used for bearings of rotating equipment; various belts such as conveyor belts, V-belts and timing belts; valves and valve seats. Materials: backers used in oil wells, well head seals, BOP (Bllw out Preventar), bladders, etc .; various cushioning materials, anti-vibration materials, etc .; crank shaft seals,
Bearing seals, rotary seals for accelerators, bearing seals for ships or automobiles such as stern pipe seals; various via flams; automotive fuel hoses, marine hoses, risers, flow lines and other hoses; geothermal power generation and other energy applications Examples include rubber products.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples. In addition, parts and% in the examples, comparative examples and reference examples are based on weight unless otherwise specified.

Example 1 Acrylonitrile-butadiene copolymer rubber prepared by conventional emulsion polymerization and acrylonitrile-butadiene-
Each of the butyl acrylate terpolymer rubbers was dissolved in methyl isobutyl ketone, and the butadiene unit in each rubber was partially hydrogenated using a Pd / silica catalyst to obtain a highly saturated copolymer rubber. The abundance of monomer units in these rubbers is shown in Table 1.

Each of the obtained highly saturated copolymer rubbers and the compounding agent described in the compounding recipe of Table 2 were mixed on a cooling roll to obtain a rubber composition, and these were heated under pressure at 170 ° C. for 15 minutes. A vulcanizate was prepared. TR test for vulcanizates is ASTM D-13
According to 29. Other vulcanized physical properties were measured according to JIS K-6301. The results are also shown in Table 1.

As is clear from Table 1, even in the case of a copolymer rubber containing an unsaturated carboxylic acid ester unit, when the requirement of the present invention is not satisfied (Experiment No. 1), the cold resistance (TR10) includes the unit. Inferior to the highly saturated copolymer rubber (Experiment No. 4),
Not improved.

Example 2 Using a highly saturated copolymer rubber shown in Table 3 obtained in the same manner as in Example 1, a rubber composition was prepared according to the compounding recipe shown in Table 2, heated under pressure at 170 ° C. for 15 minutes and heated. A sulfide was obtained. The properties of the vulcanizates are shown in Table 3.

Example 3 A highly saturated copolymer rubber having the monomer units shown in Table 4 was prepared in the same manner as in Example 1. A vulcanized product was obtained in the same manner as in Example 1 and its properties were measured. The results are shown in Table 4.

Example 4 Butadiene-isobrene-butyl acrylate-acrylonitrile copolymer rubber (composition ratio 52
/ 10/10/28), and butadiene-isoprene-acrylonitrile copolymer rubber for the comparative example (composition ratio 62/10/28)
Was used to prepare a highly saturated copolymer rubber having the monomer units shown in Table 5.

Each of these and the compounding agents shown in Table 6 were mixed on a roll to obtain a rubber composition. A vulcanized product was prepared by heating under pressure at 160 ° C for 20 minutes, and the properties were measured. The results are also shown in Table 5.

Example 5 A rubber composition was prepared by adding and mixing the compounding agents shown in Table 6 to each of the hydrogenated polymer rubbers of Examples 1 to 4 of the present invention, and press-vulcanizing at 160 ° C. for 20 hours. TR10 of the obtained vulcanized product was measured. The result reproduced the result shown in Examples 1-4.

Claims (1)

[Claims] 1. The content of each bonding monomer unit in the copolymer chain is (1) 10 to 40% by weight of an unsaturated nitrile monomer unit, and (2) an unsaturated carboxylic acid ester monomer. Unit 1-40
%, (3) Conjugated diene-based monomer unit 20% by weight or less, (4) Hydrogenated conjugated diene-based monomer unit Remaining, and monomer unit (1) and monomer unit (2) Resistance consisting of a highly saturated nitrile group-containing copolymer rubber having a total content of 30 to 50% by weight and a total of monomer units (3) and (4) of 50 to 70% by weight and a compounding agent Rubber composition having improved