JPS5974136A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. which little suffers changes in hardness with time, by blending an arom. hydrocarbon having high specific gravity and kinematic viscosity as a softening agent with a rosin acid-contg. diene rubber. CONSTITUTION:10-100pts.wt. arom. hydrocarbon softening agent having a specific gravity (15/4 deg.C) of 1.015 or above and a kinematic viscosity (98.89 deg.C) of 40cst or above (e.g. Mitsubishi -38- heavy process oil, a product of Mitsubishi Sekiyu K. K.) is blended with 100pts.wt. butadiene rubber contg. 0.1-10wt% rosin acid. Said rubber may contain not more than 45wt% styrene.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a comb composition with little change in hardness over time, and more specifically to a styrene-butadiene rubber containing 01 to 10 weight percent rosin acids and a comb composition containing 01 to 10 weight percent of rosin acid and a comb composition containing 01 to 10 weight percent of rosin acid. Specific gravity (15/4°C) 1015 or more per 100 parts by weight (sometimes) -1 kinematic viscosity (9
8,89° C.) 4 Q cst or higher, the present invention relates to a comb composition containing 10 to 100 parts by weight of an aromatic, aggressive hydrocarbon softener.

Generally, diene rubber is used for general purpose rubber such as tires, belts, etc.
It is widely used in footwear, other industrial goods, daily necessities, etc., and the required performance is wide-ranging. Among these, many primary forming agents are often added to diene rubber for the purpose of improving product processability and reducing costs. Softeners (mainly stone/III-based extender oils are classified into aromatic, naphthenic, and paraffinic types depending on their composition. However, rubber products to which large amounts of these softeners have been added have traditionally experienced hardness during use. A marked upward trend was observed.

The main cause of increase in the hardness of rubber products is usually product deterioration due to chemical and physical factors such as heat and light, but according to research by the present inventors, softening in the rubber product is also a cause other than the above. It turns out that this is because the agent is scattered due to thermal history or extracted by contact with water, etc., and decreases.

Therefore, in order to suppress the increase in hardness of the product and extend its service life, it is necessary to prevent or reduce the scattering and oil leakage of the softener in this product, and the inventors have conducted extensive research on these points. As a result, rosin acid is essential as an organic acid to be included in diene rubber, and hardness can only be improved by selecting a high viscosity and high specific gravity that is not generally used as a softening agent due to workability problems. The present invention was achieved by discovering that a rubber composition with little change over time can be obtained. That is, the present invention uses 0.1 to 10% rosin acid.
The styrene-butadiene rubber and /ox/co containing group i have a specific gravity (15 parts by weight) per 100 parts by weight of butadiene rubber.
Part 4℃) 1.015 or more, kinematic viscosity (98,89℃) 4
Q Aromatic hydrocarbon softener with cs1 or higher 10 to 10
A rubber composition containing 0 parts by weight is provided.

The diene rubber used in the present invention can be produced by emulsion polymerization or bath liquid polymerization. The styrene content of Geno rubber is preferably 0 to 45% by weight, more preferably 10 to 35% by weight. If it exceeds 45 parts by weight, it becomes resinous,
This is not desirable because the hardness increases and the elasticity is impaired.

The rosin acid content of the diene rubber is 0.1 to 10% by weight, preferably 1 to 7% by weight. If it is less than 0.1% by weight, there is no effect of reducing hardness change, and if it exceeds 10@41%, the viscosity increases and the elasticity is significantly impaired, which is not preferable.

The softening agent used in the present invention is an aromatic hydrocarbon, and it is necessary to use one with high specific gravity and kinematic viscosity in order to obtain the effects of the present invention. The effects of the present invention cannot be found with paraffinic and aromatic softeners with a specific gravity of less than 1015 and a kinematic viscosity of less than 4Q cst3.
×4°C) is 1015 or more, preferably 1017 or more. Practically speaking, it is preferable that the second limit of "Ushita" is 105 or less.

The kinematic viscosity (98.89° C.) of the softener is 4 Q cst or more, preferably 5 Q cs1 or more. The upper limit is 1
00 or less is preferred for practical use.

The amount of softener added to 100 parts by weight of diene rubber is 10
~100 parts by weight, preferably 10 to 70 parts by weight.

If it is less than 10 parts by weight, no improvement in the processability of the diene rubber will be achieved, and if it exceeds 100 parts by weight, customization will be impaired, so it is limited to the above range.

The rubber composition of the present invention can be widely used in tires, belt products, footwear, etc. by taking advantage of its characteristics, and has a long service life because its hardness does not change over time.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these.

In the examples, the rosin acid content and styrene content of the diene rubber were measured according to JI8K 6383.

The specific gravity of the softener is JTSK2249, and the kinematic viscosity is Jl8.
6A1) was determined according to 283.

The aging test of the diene rubber composition was conducted by the following method. That is, using a test tube aging tester, put activated carbon in it and measure 20 x 30 x 2 mm.
A dog vulcanized rubber test piece was immersed and kept at 100°C, and the test piece was taken out every two weeks to determine changes in the hardness, electrical resistance, and amount of acetone extracted from the comb composition. Regarding hardness, JI
S K, 6301, Jl, S for acetone extraction amount.
According to K6350, weight change was determined by the following formula.

Examples 1 to 4, Comparative Example 1 Styrene-containing i in Table 1 obtained by changing the type and amount of emulsifier,
23% styrene lysine rubber (5r31t)
Specific gravity (15 x 4℃) 1 as an aromatic hydrocarbon softener
016, kinematic viscosity (98.89°C) 57.6 cst (trade name: Mitsubishi 38 Heavy Process Oil) was used.

Kneading was carried out using a BI (type Banbury mixer) and two rolls, and 100 parts of SBR was mixed with 100 parts of IIAF black, 50 parts of softener, 5 parts of zinc white, and 1 part of stearic acid.
1.2 parts of yellow and 15 parts of N-cyclohexylbenzothiazolesulfenamide (all parts by weight) were added and kneaded. Vulcanization was performed by press vulcanization at 160° for 30 minutes.

The evaluation results are shown in Table 1. Example 5 Syntac HA-25 (Kobe Oil Chemical Single Unit)
6 AR'oMAX A5 (manufactured by Fuji Koshu) Comparative Example 2
Shout 3 (ni) I 3 :ll
:1 (〃 )-4JSRAROMA (made by Japan Synthetic Rubber) #5 Sonic process oil r (, -1000 (Kyodo Oil Base Nandene-based extender oil) ・6 Mitsubishi 10 light process oil (Mitsubishi Oil made paraffin-based extender oil) #7 From the results of Komoresox 700 (manufactured by Nippon Oil Co., Ltd.), it is clear that the rubber composition of the present invention exhibits excellent customization properties with little change in hardness over time, and is a rubber composition that has solved the problems.

Agent: Patent attorney Akira Ito

Claims (1)

[Claims] For 100 parts by weight of styrene-butadiene rubber and/or butadiene rubber having a weight coefficient of 0.1 to 10 rosin acid, specific gravity (15/4°C)], 015 or higher, kinematic viscosity (98, 89°C) 40 cst or higher) A rubber composition characterized by containing 10 to 100 critical parts of an aromatic hydrocarbon softener