JPS6072940A - Rubber composition - Google Patents

Abstract

PURPOSE:A composition to which excellent cut resistance is imparted without detriment to heat dissipation, processability, etc., prepared by adding a specified thermoplastic elastomer and carbon black to a diene rubber. CONSTITUTION:100pts.wt. diene rubber (e.g., polyisoprene rubber) is mixed with 1-20pts.wt. thermoplastic elastomer of a softening temperature of 70-190 deg.C (e.g., polyether/polyester copolymer), 30-80pts.wt. carbon black and, optionally, stearic acid, ZnO, wax, anti-oxidant, process oil, vulcanizing agent, cure accelerator, etc. USE:Treads or side walls of large tires for a rough road, conveyor belts, hoses, fender materials, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition, and more specifically, the present invention relates to a rubber composition, and more specifically, by using reinforcing carbon black and a thermoplastic elastomer together as fillers, cut resistance can be improved without impairing other properties. The present invention relates to improved rubber compositions, particularly for the treads and sidewalls of large tires for rough roads.

The rubber material used in tires for rough roads is less susceptible to scratches.
In other words, good cut resistance is an important issue.

General rubber compositions, such as natural rubber or blends mainly composed of natural rubber, e7++, LLI++, I-
$-PI-Mu→h-11LJ-Ki・#r4ml--,
It is known that ur44pj,l- is most effective in increasing its hardness. The easiest and most common way to do this is to increase the amount of reinforcing carbon black. However, according to this method, although the cut resistance is improved, there is a problem that not only is there a difficulty in processing, but also heat generation increases when the tire runs.

Another method to improve cut resistance is to mix styrene-butadiene copolymer rubber (SBR) in multiple amounts, but compared to rubber compositions made mainly of natural rubber, the breaking strength, especially at high temperatures, is lower. It has the disadvantage that the breaking strength of the tire decreases, and it cannot exhibit sufficient durability when used for long-distance, high-speed transportation vehicle tires.

In addition, although it has been conventionally practiced to combine thermosetting resins and the like with rubber compositions, solubility parameters (
Since they are different components with widely different SP values, molecular dispersion cannot be expected and there are problems with mixing and dispersibility, and they also have the disadvantage of acting adversely as foreign substances.

The purpose of the present invention is to provide a rubber composition that has excellent cut resistance without impairing various properties such as heat generation and processability, and is particularly applicable to the tread and sidewall parts of tires for rough roads. be done.

In accordance with the above-mentioned objective, the present inventors have made extensive research and found that a rubber composition obtained by blending carbon black and a thermoplastic elastomer as a reinforcing filler with natural rubber, diene-based synthetic rubber, or a mixture thereof in a specific range. The present invention has been achieved by discovering that the above object is satisfied.

That is, in the present invention, for 100 parts by weight of diene rubber,
A rubber composition characterized by blending 1 to 20 parts by weight of a thermoplastic elastomer with a softening point of 70 to 180°C and 30 to 80 parts by weight of carbon black.

Diene rubbers that are the raw material rubber of the present invention include natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), etc. Rubber can be used alone or in a blend.

The thermoplastic elastic body used in the present invention has a softening temperature of 1fi7
It is necessary that the temperature is in the range of 0 to 180℃, and its formulation (6
) is 1 to 20 parts by weight per 1 part of 1100ff of rubber. If the softening point is less than 70℃, the product will soften at the operating temperature, especially tires, and if the softening point exceeds 180℃,
Both are undesirable because the rubber component undergoes thermal deterioration during processing and the physical properties at break deteriorate.

The thermoplastic elastomer referred to in the present invention refers to a hard portion (hard part) with a certain length in the molecular chain, such as an ester elastomer, an ionomer elastomer, an amide elastomer, or an A-refine elastomer. segment) and a soft part with a certain length (rough 1-segment), which are two-dimensionally repeatedly connected.In other words, the molecular constraint component (hard segment) is a molecular chain formed by rocks, etc. In addition to acting as a barrier against cutting and stopping its propagation, the entropy elastic parts (ft segments) that are repeatedly connected two-dimensionally have the effect of relieving stress concentration between the matrix rubber and the matrix rubber against deformation, etc. J3, in addition to the thermoplastic elastomers exemplified above, rubber-thermoplastics made by a process of crosslinking molten plastics into rubber during mixing known as dynamic vulcanization. Blends of rubber and crystalline resins such as polypropylene and polyethylene are also included in the thermoplastic elastomer referred to in the present invention.

The carbon black used in the present invention may be ordinary reinforcing carbon black, such as SAF, 15AF1+AF
, SRF, CIPI: etc., and the blending amount thereof is 30 to 80 parts by weight, preferably 35 to 70 parts by weight, per 100 parts by weight of rubber. If the amount of carbon black is less than 30 parts, sufficient hardness cannot be obtained;
Exceeding this amount is undesirable because processability deteriorates and heat generation increases.

In the rubber composition of the present invention, in addition to the above-mentioned compounding agents, compounding agents commonly used in rubber compounding such as zinc oxide, stearic acid, wax, anti-aging agent, process oil, vulcanization accelerator, and sulfur can be appropriately used. Contains an appropriate amount.

Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples. In addition, all the formulation values shown in Table 1 J3 and Table 3 are parts by weight.

Examples 1-2L13 and Comparative Examples 1-5 Based on the formulations shown in Table 1, rubber compositions were prepared by adding raw rubber and various compounding agents. Table 2 shows the properties of the thermoplastic elastic body or elastic body used in this test.

This rubber composition was subjected to VI heating at 148° C. for 30 minutes, and the impact cut value of the resulting vulcanized rubber was measured. Shock cut value is a falling type! A conical needle weighing 2 Ky was dropped onto the sample from a height of 15 cm using an Fi impact cut tester, and the depth of the scratch caused was expressed as an index obtained by multiplying the value of Comparative Example 1 by 100. The smaller this index is, the better the cut resistance is.
゜The results are shown in Table 1.

Table 1 *2 2N-cyclohexyl-2-benzothiazolyl-sulfenamide.

In Table 1, Comparative Example 1 is a rubber composition with a basic formulation containing only carbon black as a filler. Two parts each of plastic elastic bodies A to E and elastic body F are blended.

In Examples 1 to 5, in which the thermoplastic elastomers A to E having a two-phase structure of soft segments and hard segments used in the present invention were blended, improvement in cut resistance was observed compared to Comparative Example 1. On the other hand, although the components of the thermoplastic elastic body are considered to be close to those of the thermoplastic elastic body B of Example 2, Comparative Example 2 in which elastic body F without hard segments was blended was compared to Comparative Example 1. This reduces cut resistance.

Examples 6 to 11 and Comparison 3 Rubber compositions were prepared in the same manner as in Example 1, based on the basic formulations shown in Table 3, but varying the type and amount of the thermoplastic elastomer.

This rubber composition was heated at 148°C for 30 minutes in the same manner as in Example 1.
The vulcanization properties of the vulcanized rubber obtained by vulcanization are shown in Table 4 together with the vulcanization properties of Comparative Example 1.1 The vulcanized rubber properties were tested according to the following method. In other words, the physical properties at break (tensile strength, elongation at break) are JIS No. 3 dumbbell reliquary UJI
The hardness was measured according to S K6301, the hardness was measured according to JIS A, and the tear force was measured using JISB type.

Further, the % impact cut value was measured in the same manner as in Example 1, and expressed as an index with Comparative Example 1 set as 100.

Dynamic viscoelasticity: initial strain 10%, dynamic strain ±2%, frequency 20
Measurements were performed at Hz and a temperature of 25°C. Note that E'rr represents a loss modulus, and E8 represents a complex modulus of elasticity.

As is clear from the formulations in Table 3 and the properties in Table 4, the thermoplastic elastomers A and B having soft segments and eight-domain segments were varied for Comparative Example 1. In the blended Examples 6 to 10, the addition of the thermoplastic elastomer did not significantly reduce the breaking properties, and a reliable increase in hardness and improvement in cut resistance measured by an impact cut tester were observed.

In addition, the dynamic compliance (E''/E'')', which can be called a measure of the heat generation of the tread rubber under low load conditions, is definitely reduced, and it can be seen that it is advantageous in terms of heat generation. In addition, Example 11 uses a rubber-olefin thermoplastic elastomer E made by crosslinking molten resin to rubber during mixing, and has cut resistance similar to other thermoplastic elastomers A-D. improvement was observed. On the other hand, comparative example 3
Unlike the above-mentioned example, the elastic body F which does not have a hard segment in the molecular chain is used, and it can be seen that the hardness decreases, the dynamic compliance increases, and the cut resistance decreases significantly.

12-14 and J: and 4-5 Using the rubber compositions of Example 7.9.11 and Comparative Example 1.3, the tread was divided into three parts, Comparative Example 1 - Example 7 - Example 9, Comparative Two types of 1ooo-2014PR lug type tires were made using the combinations of the respective rubber compositions of Example 1 - Comparative Example 3 and Example 11, four each, and used for evaluation of cut resistance on rough roads.

The cut resistance evaluation was as follows: The cut resistance was measured by attaching it to the rear wheel of a 10-ton dump truck and driving it once every 10,500 hours on a rough road at a crushed stone site with a pavement ratio of 0%. The cut scratches were counted, and the number of cut scratches in Comparative Example 4 was set as 100, and the index was 1j. The binding is shown in Table 5.

Table 5 [11m　- To Isshigo …7 To finger.

As shown in the results of Examples 12 to 14, a significant improvement in cut resistance was observed in tires using a thermoplastic elastomer consisting of soft segments and hard segments.On the other hand, as can be seen from Comparative Example 5, On the contrary, a decrease in cut resistance was observed in tires using an elastic body without such a two-layer structure (only soft segments).

As explained above, the rubber composition of the present invention, in which reinforcing carbon black and a thermoplastic elastomer with a softening point of 70 to 180°C are specifically blended with diene rubber, has excellent cut resistance, heat generation, Because it has various properties such as workability, it can be used for treads and sidewalls of large tires, as well as conveyor belts, hoses, fenders, rubber plates, etc. that require cut resistance. Available.

Patent applicant: Yokohama Rubber Co., Ltd. Agent: Patent Attorney Tatsuo Ito Agent: Patent Attorney Tetsuya Ito

Claims (1)

[Claims] 1. Softening point 70-1 for 100 parts by weight of diene rubber
A rubber composition comprising 1 to 201 m parts of a thermoplastic elastomer at 80°C and 30 to 80 parts by weight of carbon black.