JPH01263133A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain the title composition capable of improving workability in use for engine mount for car and suppressing lowering of strength, by adding specific substance used as a vulcanization system to a natural rubber based material and liquid isoprene rubber having a functional group. CONSTITUTION:A natural rubber based material is blended with a functional liquid isoprene rubber having a functional group such as carboxyl group in numbers of 2-20per molecule at a weight ratio of 95:5-50:50 to afford a raw material rubber. 0.5-3.0 pts.wt. sulfur releasing type organic sulfur compound, 0.3-3.0 pts.wt. sulfur and 0.1-0.6 pts.wt. thiuram based vulcanization accelerator as a vulcanization system and aging inhibitor, etc., as others are added to 100 pts.wt. above-mentioned raw material rubber and the blend is kneaded to provide the aimed composition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a swellable rubber composition suitable for use as a vibration-proof rubber material for automobile engine mounts, body mounts, and the like.

[Conventional technology] In recent years, in the automobile industry, there has been an increasing demand for lighter vehicle bodies from the viewpoint of improving fuel efficiency and reducing costs. is being considered.

By the way, when downsizing vibration-proof rubber, it is generally necessary to increase the rubber hardness in order to maintain the spring constant of the vibration-proof rubber at the same level as before. For this reason, conventionally, a large amount of carbon black has been blended into anti-vibration rubber materials to increase the rubber hardness.

[Problems to be Solved by the Invention] However, in natural rubber materials, which are typical anti-vibration rubber materials, as hardness increases, Mooney viscosity generally increases, fluidity decreases, and processability during molding becomes difficult. descend. In order to improve this, efforts have been made to improve processability, for example, by increasing the amount of softener or adding liquid rubber, but this results in a decrease in strength and quality as a product.

The present invention was made in view of the above circumstances, and aims to obtain a rubber composition that has low viscosity when unvulcanized and high hardness and sufficient strength after vulcanization.

[Means for Solving the Problems] In order to achieve the above object, the present inventors conducted intensive studies on the type of liquid rubber to be blended with natural rubber and the vulcanization system, and arrived at the present invention.

That is, the gist of the present invention is that the natural rubber material and the liquid isoprene rubber having functional groups are mixed in a ratio of 95:5 to 50:5.
0 (parts by weight), and a sulfur-releasing organic sulfur compound, sulfur, and a thiuram-based vulcanization accelerator are added as a vulcanization system.

In the present invention, natural rubber (
NR), or butadiene rubber (BR),
Examples include blends of synthetic rubbers such as styrene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR).

In the present invention, the liquid imprene rubber blended into the natural rubber material is a functional liquid isoprene rubber having a functional group such as a carboxyl group in its structure. Imprene rubber usually has a viscosity average molecular weight Mv of 10,000 to 50,000.
It is desirable that each molecule has about 2 to 20 functional groups.

The blending ratio of the natural rubber material and the functional liquid impregnated rubber is in the range of 95:5 to 50:50 (parts by weight). If the blending ratio of liquid isoprene rubber is less than the range shown in -, no effect on viscosity reduction can be obtained. Moreover, if the amount exceeds the above range, the strength will decrease, which is not preferable.

As the sulfur-releasing type 5-organosulfur compound used as the vulcanizing agent in the present invention, a sulfur-releasing type morpholine compound is preferably used, and specifically, for example, 4,4-dithiomorpholine (represented by the following general formula) ) etc. .

The thiuram vulcanization accelerator is not particularly limited, and commonly used thiuram vulcanization accelerators,
For example, any of tetramethylthiuram disulfide, tetramethylthiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram tetrasulfide, etc. can be suitably used.

The rubber composition of the present invention is obtained by blending these sulfur-releasing organic sulfur compounds, a thiuram-based vulcanization accelerator, and sulfur into a raw rubber made of natural rubber and functionalized liquid isoprene rubber. The amount of the organic sulfur compound is usually 0.5 parts to 3.0 parts by weight, and the thiuram vulcanization accelerator is 0.1 parts to 0.6 parts by weight, per 100 parts by weight of the raw material rubber. It is preferable that the amount of sulfur is 0.3 parts by weight - 3.0 parts by weight.

At this time, other additives such as carbon black and anti-aging agents may be added. Then knead in the usual way,
The product is formed by molding and vulcanization. The vulcanization temperature is usually 150°C to 160'C1. The vulcanization time is preferably 150°C for 20 minutes and 160°C for 10 minutes.

[Function] In the present invention, since the blending ratio of natural rubber and functional liquid impregnated rubber is within an appropriate range, appropriate fluidity is imparted to the rubber composition, and processability is improved. Further, although the effect of the present invention in improving strength is not necessarily clear, it is thought that by using the vulcanization system of the present invention, co-vulcanization is improved and strength reduction is suppressed.

[Examples] Hereinafter, the present invention will be explained in detail by examples, but the present invention is not limited by these examples unless the gist thereof is exceeded.

Example 1 Using the vulcanization system of the present invention, the effect on strength was investigated when a raw rubber made of natural rubber and functionalized liquid isoprene rubber was vulcanized. 4 as a sulfur-releasing organic sulfur compound
．． 4-dithiomorpholine, tetramethylthiuram disulfide was used as a thiuram-based vulcanization accelerator.

First, 75 parts by weight of natural rubber, functional liquid isoprene rubber (Kuraprene LIR410: viscosity average molecular weight 25,000
．． Approximately 10 functional groups per molecule, manufactured by Clarei Soprene Chemical Co., Ltd. (trade name) 25 parts by weight, 1 part stearic acid, 5 parts by weight zinc white, carbon black (MA
F>50 parts by weight, 3 parts by weight of amine antioxidant, 2 parts by weight of sulfur
Parts by weight, 1 part by weight of 4,4-dithiomorpholine (Parnock R1 manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name), 0.5 part by weight of tetramethylthiuram disulfide, sulfenamide accelerator (N-cyclohexyl) After blending and kneading 0.5 parts by weight of (2-benzothiacylsulfenamide), the mixture was vulcanized at 160'C for 1 minute to prepare a test piece for testing.

Using the obtained test piece, hardness H3, tensile strength TB, elongation EB, and modulus Mi00 were measured according to JIS K6301. The results are shown in Table 1.

The Mooney viscosity (145° C.) of the unvulcanized rubber was measured and is also listed in Table 1.

Example 2 The blending ratio of natural rubber and functional liquid isoprene rubber was 50
: A test piece was prepared and tested in the same manner as in Example 1, except that the test piece was set to 50.

The results are also listed in Table 1.

Comparative Example 1.2 The blending ratio of natural rubber and functional liquid impregnated rubber was
A test piece was prepared and tested in the same manner as in Example 1, except that the proportions shown in the table were changed. The results are also listed in Table 1.

As is clear from the table, when the functionalized liquid isoprene rubber is not added, the Mooney viscosity is high and the processability is poor.

Furthermore, if the amount of functional liquid isoprene rubber blended is too large, the strength will decrease.

Comparative Example 3 A test piece was prepared and tested in the same manner as in Example 1, except that 4.4-dithiomorpholine and thiuram-based vulcanization accelerator were not used. The results are also listed in Table 1.

As is clear from the table, it can be seen that when the vulcanization system of the present invention is not used, the strength is extremely reduced.

Comparative Example 4 An example in which liquid isoprene rubber without functional groups (Kuraprene LIR50, manufactured by Clarei Soprene Chemical Co., Ltd.) was used instead of functional liquid isoprene rubber, and the blending ratio of natural rubber and liquid impregnated rubber was 75:25. A test piece was prepared and tested in the same manner as in Example 1. The results are also listed in Table 1.

As is clear from the table, if a functional liquid impregnated rubber is not used, sufficient physical properties cannot be obtained even when the vulcanization system of the present invention is used.

Comparative Example 5.6 A test piece was prepared and tested in the same manner as in Example 1, except that 4.4-dithiomorpholine or thiuram-based vulcanization accelerator was not used. The results are also listed in Table 1.

As is clear from the table, sufficient physical properties cannot be obtained without either 4,4-dithiomorpholine or thiuram-based vulcanization accelerator.

[Effects of the Invention] The rubber composition of the present invention has low viscosity and excellent processability, and products obtained by vulcanizing it exhibit high values for both hardness and strength. Therefore, it can be effectively used, for example, as a vibration-proof rubber material, and has high industrial value.

Claims (1)

[Claims] A natural rubber-based material and liquid isoprene rubber having functional groups are blended in a ratio of 95:5 to 50:50 (parts by weight), and a sulfur-releasing organic sulfur compound, sulfur, and thiuram-based vulcanization accelerator are used as the vulcanization system. A rubber composition made by adding an agent.