JP2906910B2 - Vulcanizable rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vulcanizable rubber composition comprising a partially hydrogenated unsaturated nitrile-conjugated diene copolymer, which is excellent in heat resistance, strength properties, compression set, and particularly excellent in heat generation. About.

[0002]

2. Description of the Related Art In recent years, high heat resistance has been required for rubber parts around an engine in order to prevent exhaust gas from automobiles. Under such a background, unsaturated nitrile-conjugated diene copolymers have been developed. A partially hydrogenated unsaturated nitrile-conjugated diene copolymer obtained by hydrogenating a part of the carbon-carbon double bond-containing monomer unit has been developed and used. This rubber is excellent in ozone resistance, heat resistance and the like as compared with the conventional unsaturated nitrile-conjugated diene copolymer,
Due to the small amount of residual double bonds in the rubber, when vulcanizing with a sulfur vulcanizing system, the degree of vulcanization did not increase, and the strength properties, compression set, etc. were insufficient. For this reason, various studies have been made on vulcanization accelerators used in combination with vulcanizing agents.

[0003]

SUMMARY OF THE INVENTION The inventors of the present invention have made a study on a partially hydrogenated unsaturated nitrile-conjugated diene-based copolymer having an iodine value in a specific range. And a rubber composition containing tellurium dithiocarbamate as a vulcanization accelerator has the unexpected effect of improving the strength characteristics and compression set of the vulcanized product and having low heat build-up. Thus, the present invention has been completed. An object of the present invention is to provide a sulfur vulcanizable rubber composition having improved heat resistance, strength characteristics, and compression set, and particularly excellent in heat generation.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to provide a partially hydrogenated unsaturated nitrile-conjugated diene copolymer having an iodine value of 20 or less with a sulfur vulcanizing agent and tellurium dithiocarbamate as a vulcanization accelerator. This is achieved by a rubber composition that is compounded.

The partially hydrogenated unsaturated nitrile-conjugated diene copolymer used in the present invention comprises an unsaturated nitrile-conjugated diene copolymer and a conjugated diene unit portion of an unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer copolymer. Is hydrogenated. These can be prepared by subjecting a copolymer produced by emulsion polymerization or solution polymerization to a conventional method (for example, JP-B-60-58242, JP-B-62-61).
No. 045) and the conjugated diene unit in the copolymer is hydrogenated, and its iodine value is 20 or less, preferably 10 to 20 in view of the requirement of low heat build-up.

The unsaturated nitriles constituting the partially hydrogenated unsaturated nitrile-conjugated diene copolymer of the present invention include acrylonitrile and methacrylonitrile, and the conjugated dienes include 1,3-butadiene and 2,3-butadiene. Dimethyl butadiene, isoprene, 1,3-pentadiene and the like can be mentioned. Examples of ethylenically unsaturated monomers copolymerizable with these monomers include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; methyl acrylate, butyl acrylate, dimethyl maleate, diethyl fumarate, Alkyl esters of the above carboxylic acids, such as di-n-butyl fumarate, di-n-butyl itaconate; Alkoxyalkyl esters of the unsaturated carboxylic acids, such as methoxy acrylate, ethoxyethyl acrylate, methoxyethoxy ethyl acrylate; α and β-cyanoethyl Acrylates having cyanoalkyl groups such as acrylate, α, β and γ-cyanopropyl acrylate, cyanobutyl acrylate, cyanooctyl acrylate; 2-hydroxyethyl acrylate, hydroxypropyl acrylate Acrylates having a hydroxyalkyl group such as acrylate; N-substituted (meth) acrylates such as acrylamide, methacrylamide, N-methylol (meth) acrylamide, N, N'-dimethylol (meth) acrylamide, and N-ethoxymethyl (meth) acrylamide; ) Acrylamide and the like.
In addition to these monomers, some of the unsaturated monomers may be replaced with vinyl monomers such as styrene and vinylpyridine, vinyl norbornene, dicyclopentadiene, and the like within a range that does not impair the gist of the present invention. May be substituted by a non-conjugated diene such as, 4-hexadiene.

The partially hydrogenated unsaturated nitrile-conjugated diene copolymer used in the present invention is specifically a butadiene-acrylonitrile copolymer rubber (hereinafter abbreviated as NBR), an isoprene-butadiene-acrylonitrile copolymer rubber. , Hydrogenated isoprene-acrylonitrile copolymer rubber and the like; butadiene-methyl acrylate-
Examples thereof include hydrogenated acrylonitrile copolymer rubber, butadiene-acrylic acid-acrylonitrile copolymer rubber, and butadiene-itaconate di-n-butyl-acrylonitrile copolymer rubber. The amount of the unsaturated unsaturated nitrile in the copolymer rubber is usually 5 to 60% by weight, preferably 10 to 50% by weight.

[0008] As the vulcanizing agent in the present invention, sulfur and sulfur donating compounds such as tetramethylthiuram disulfide can be used. The amount added is 0.1 to 2 parts by weight, preferably 0.5 to 1 part by weight, per 100 parts by weight of the polymer. The vulcanization accelerator used in combination therewith is a tellurium compound among metal salts of dithiocarbamic acid. Examples thereof include tellurium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, tellurium diamildithiocarbamate, and the like. The amount of these additives
The amount is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the polymer. In the present invention, other compounding agents can be used in combination as long as the effect is not impaired. As examples, various vulcanization accelerators such as guanidine, thiazole, and thiuram,
In addition to zinc white and stearic acid, reinforcing agents such as carbon black, silica, talc and calcium carbonate, fillers, plasticizers, processing oils, processing aids, antioxidants and the like are usually used. The vulcanizable rubber composition of the present invention is produced by using the above-mentioned copolymer, vulcanizing agent, vulcanization accelerator and other compounding agents with a commonly used mixer such as a roll or Banbury.

[0009]

The vulcanizate obtained by vulcanizing the rubber composition of the present invention is excellent in heat resistance, oil resistance and ozone resistance, and particularly excellent in strength characteristics, compression set and heat generation. , Can be applied to a wide range of applications. Main applications are timing belts, V-belts, V-lift belts, CVs
Various belts such as T-belt; O-ring, packing,
Rubber products for various seals such as gaskets; crankshafts, bearing seals, accelerator rotary seals,
Bearing seals such as stern tube seals; various diaphragms; hoses such as automotive fuel hoses, marine hoses, risers, and flow lines; various cushioning materials, vibration damping materials, and the like.

[0010]

EXAMPLES The composition of the present invention will be specifically described below with reference to examples. In the examples, each physical property is JISK63.
01 was measured. The exothermicity (HBU) and the dynamic compression set (PS) were measured by a flexometer manufactured by Goodrich. The measurement was performed at a measurement temperature of 100 ° C., after applying a load of 25 pounds to the sample and applying a rotation of 1800 times / minute and a vibration width of 0.175 inch for 25 minutes.

Example 1 An acrylonitrile-butadiene copolymer rubber having a bound acrylonitrile content of 36% by weight prepared by a conventional emulsion polymerization method was dissolved in methyl isobutyl ketone, and Pd / SiO
The butadiene unit in the rubber was hydrogenated using _two catalysts to obtain a partially hydrogenated acrylonitrile-butadiene copolymer rubber having an iodine value of 15 (95% hydrogenation). Using this copolymer rubber, the mixture was kneaded with a roll according to each of the compounding recipes a to f in Table 1 to prepare rubber compounds 1 to 6. This was pressurized and heated at 160 ° C. for 20 minutes to obtain a sheet-shaped vulcanized product having a thickness of 2 mm, and each physical property was measured. The results are shown in Table 2.

[0012]

[Table 1]

* 1-substituted diphenylamine type antioxidants,
Shiraishi calcium company

[0014]

[Table 2]

As can be seen from Table 2, when the tellurium dithiocarbamate of the present invention was used as a vulcanization accelerator, the strength properties (100% tensile stress) increased, the HBU value, and the compression set increased. The strain value is reduced and both are improved.

Example 2 A hydrogenation reaction was carried out using the same acrylonitrile-butadiene copolymer rubber as in Example 1, and the iodine value was 10,2.
Three types of partially hydrogenated acrylonitrile-butadiene copolymer rubbers 0 and 30 were prepared. For compound numbers 7 to 9, the compounding agent of compounding formula b was added to these three types of rubbers and kneaded with a roll. On the other hand, for compound numbers 10 to 12, the compounding agent of compounding formula d was similarly added to the three types of rubber, and kneaded with a roll in the same manner to prepare a rubber compound. 160 ° C, 2
Pressurized and heated for 0 minutes to form a 2 mm thick sheet vulcanizate,
Each physical property was measured. Table 3 shows the results.

[0017]

[Table 3]

As can be seen from Table 3, the rubber vulcanizate obtained by vulcanizing the rubber composition of the present invention is excellent in compression set and greatly improved in heat generation (HBU). FIG. 1 shows the relationship between the iodine value and the heat buildup.

[0019]

FIG.

[0020]

[Brief description of the drawings]

Figure 1 shows the iodine value of the copolymer rubber and the HBU of the vulcanizate.
6 is a graph showing a relationship with (° C.).

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C08K 5: 405: 48) (C08K 13/02 3:06 5:48) (56) References JP-A-63-254145 (JP, A) JP-A-59-210960 (JP, A) JP-A-58-40332 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08L 7/00-21/02 C08K 3 / 00-13/08

Claims (1)

(57) [Claims] 1. A partially hydrogenated unsaturated nitrile-conjugated diene copolymer having an iodine value of 20 or less is blended with a sulfur-based vulcanizing agent and a tellurium dithiocarbamate compound represented by Chemical Formula 1 as a vulcanization accelerator. A rubber composition comprising: Embedded image (Wherein R ¹ and R ² may form a lower alkyl group having 1 to 8 carbon atoms or a ring)