JPH069822A - Vulcanizable rubber composition - Google Patents

Abstract

PURPOSE:To obtain a vulcanizable rubber composition having excellent heat resistance, strength characteristics, compression set, especially heat build-up by blending a partially hydrogenated unsaturated nitrile-conjugated diene-based copolymer with a sulfur-based vulcanizing agent and a specific vulcanization promoter. CONSTITUTION:(A) 100 pts.wt. a partially hydrogenated unsaturated nitrile- conjugated copolymer (e.g. isoprene-butadiene-acrylonitrile copolymer having <=20 iodine value and 5-60wt.%, preferably 10-50wt.% unsaturated nitrile amount is blended with (B) 0.1-2 pts.wt., preferably 0.5-1 pt.wt. sulfur-based vulcanizing agent (sulfur donating compound such as sulfur and tetramethylthiuram disulfide), (C) 0.1-5 pts.wt. tellurium dithiocarbamate compound of the formula (R<1> and R<2> are 1-8C lower alkyl or may form ring) and optionally another vulcanization promoter, a filler, a plasticizer, etc., to give a vulcanizable rubber composition.

Description

Detailed Description of the Invention

[0001]

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 characteristics and compression set, and is particularly excellent in heat generation. Regarding

[0002]

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

[0003]

DISCLOSURE OF THE INVENTION In these studies, the present inventors have found that a partially hydrogenated unsaturated nitrile-conjugated diene copolymer having an iodine value within a specific range is added to a sulfur-based vulcanizing agent, It has been found that a rubber composition obtained by blending tellurium dithiocarbamate as a vulcanization accelerator has an unexpected effect that the strength property and compression set of the vulcanized product are improved and the exothermic property is low. 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]

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

The partially hydrogenated unsaturated nitrile-conjugated diene-based copolymer used in the present invention is an unsaturated nitrile-conjugated diene copolymer or an unsaturated nitrile-conjugated diene-ethylenically unsaturated monomer copolymer conjugated diene unit portion. Is hydrogenated. These are obtained by subjecting a copolymer produced by emulsion polymerization or solution polymerization to a conventional method (for example, Japanese Patent Publication No. 60-58242, Japanese Patent Publication No. 62-61).
The conjugated diene unit portion in the copolymer is hydrogenated by the method described in, for example, 045), and the iodine value thereof is 20 or less, preferably 10 to 20 because of the requirement of low exothermicity.

Acrylonitrile, methacrylonitrile or the like is used as the unsaturated nitrile constituting the partially hydrogenated unsaturated nitrile-conjugated diene copolymer of the present invention, and 1,3-butadiene or 2,3-butadiene is used as the conjugated diene. Examples include dimethyl butadiene, isoprene, and 1,3-pentadiene. 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 said carboxylic acids such as di-n-butyl fumarate, di-n-butyl itaconic acid; Alkoxyalkyl esters of said unsaturated carboxylic acids such as methoxy acrylate, ethoxyethyl acrylate, methoxyethoxyethyl acrylate; α and β-cyanoethyl Acrylates, acrylates having cyanoalkyl groups such as α, β and γ-cyanopropyl acrylate, cyanobutyl acrylate, cyanooctyl acrylate; 2-hydroxyethyl acrylate, hydroxypropyl acrylate Acrylate having hydroxyalkyl group such as acrylate; N-substituted (meth) acryl amide, methacrylamide, N-methylol (meth) acrylamide, N, N'-dimethylol (meth) acrylamide, N-ethoxymethyl (meth) acrylamide ) Including acrylamide.
In addition to these monomers, a part of the unsaturated monomer may be a vinyl-based monomer such as styrene or vinylpyridine, vinyl norbornene, dicyclopentadiene, 1 or 2 within a range not impairing the gist of the present invention. It may be replaced by a non-conjugated diene such as 4,4-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), isoprene-butadiene-acrylonitrile copolymer rubber. Hydrogenated isoprene-acrylonitrile copolymer rubber; butadiene-methyl acrylate-
Examples thereof include hydrogenated acrylonitrile copolymer rubber, butadiene-acrylic acid-acrylonitrile copolymer rubber, butadiene-itaconic acid di-n-butyl-acrylonitrile copolymer rubber, and the like. The amount of bound unsaturated nitrile in the copolymer rubber is usually 5 to 60% by weight, preferably 10 to 50% by weight.

Sulfur and sulfur donating compounds such as tetramethylthiuram disulfide can be used as the vulcanizing agent in the present invention. The amount added is 0.1 to 2 parts by weight, preferably 0.5 to 1 part by weight, based on 100 parts by weight of the polymer. The vulcanization accelerator used together with these is a compound of tellurium among the metal salts of dithiocarbamic acid. Examples thereof include tellurium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, and tellurium diamyldithiocarbamate. The addition amount of these is
The amount is preferably 0.1 to 5 parts by weight with respect to 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 an example, various vulcanization accelerators such as guanidine-based, thiazole-based, thiuram-based,
In addition to zinc white and stearic acid, reinforcing agents such as carbon black, silica, talc, and calcium carbonate, fillers, plasticizers, process oils, processing aids, and antioxidants 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 ingredients in 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. It can be applied to a wide range of purposes. Timing belt, V-belt, V-ribbed belt, CV
Various belts such as T-belts; O-rings, 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 automobile fuel hoses, marine hoses, risers and flow lines; various cushioning materials, vibration damping materials, etc.

[0010]

EXAMPLES Hereinafter, the composition of the present invention will be specifically described with reference to Examples. In the examples, the physical properties are JIS K63.
It measured according to 01. Exothermicity (HBU) and dynamic compression set (PS) were measured by a Goodrich flexometer. The measurement temperature was 100 ° C., a load of 25 lbs was applied to the sample, the rotation speed was 1800 rotations / minute, and the vibration width was 0.175 inch.

Example 1 An acrylonitrile-butadiene copolymer rubber having a bound acrylonitrile amount of 36% by weight prepared by a usual emulsion polymerization method was dissolved in methyl isobutyl ketone to prepare Pd / SiO.
The butadiene unit portion in the rubber was hydrogenated using ₂ catalysts to obtain a partially hydrogenated acrylonitrile-butadiene copolymer rubber having an iodine value of 15 (hydrogenation rate 95%). Using this copolymer rubber, kneading with a roll was performed in accordance with each compounding formulation a to f in Table 1 to prepare rubber compounds 1 to 6. This was heated under pressure 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 anti-aging agent,
Shiraishi calcium company

[0014]

[Table 2]

As can be seen from Table 2, when the tellurium dithiocarbamate of the present invention is used as a vulcanization accelerator, the strength physical properties (100% tensile stress) are increased, the HBU value and the compression set are higher than those not using it. 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 or 2.
Three types of partially hydrogenated acrylonitrile-butadiene copolymer rubbers of 0 and 30 were prepared. Compound Nos. 7 to 9 were prepared by adding the compounding agent of compounding recipe b to these three kinds of rubbers and kneading with a roll. On the other hand, as for the compound numbers 10 to 12, the compounding agent of the compounding formulation d was added to the same three kinds of rubbers, and the mixture was kneaded in the same manner to prepare the rubber compounding. This is 160 ℃, 2
Pressurize and heat for 0 minutes to make a sheet-shaped vulcanizate with a thickness of 2 mm.
Each physical property was measured. The results are shown in Table 3.

[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 is greatly improved in heat buildup (HBU). This relationship between iodine value and exothermicity is shown in FIG.

[0019]

[Figure 1]

[0020]

[Brief description of drawings]

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

Claims (1)

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