JPH05339430A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber composition comprising a specific rubber and a specific thermoplastic resin in a specified ratio, excellent in resistance to group-cracking, abrasion, cut-tearing and heat generation and useful for the tires of trucks, etc. CONSTITUTION:The objective rubber composition comprises (A) 100 pts.wt. of a rubber having a cis-bond content of >=98% and containing butadiene rubber having a viscosity of >=200cps 5% in toluene solution in an amount of 10-30wt.% and (B) 0.5-5 pts.wt. of one or more kinds of thermoplastic resins selected from the group consisting of a rosin resin and a cyclopentadienic resin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition.

[0002]

2. Description of the Related Art Conventionally, in deep groove tires for trucks and buses, in order to improve resistance to groove cracks (groove bottom cracks), butadiene rubber per 100 parts by weight of rubber (hereinafter simply referred to as "parts") is used. A rubber composition containing 15 to 40 parts of is used. Here, as the butadiene rubber, what is generally called a low cis butadiene rubber (cis content: around 35%) produced by using a lithium catalyst is used. However, the use of such a low-cis butadiene rubber has the drawbacks that the wear resistance of the resulting tire is insufficient, and the groove crack resistance is not so improved and is still insufficient.

Therefore, in order to improve these performances, a butadiene rubber called a high cis butadiene rubber (cis content: 96 to 97%) produced by using a nickel catalyst or a cobalt catalyst instead of the above low cis butadiene rubber. Attempts have also been made to use. However, even with such an attempt, the groove crack resistance and wear resistance of the obtained tire are still insufficient and not satisfactory.

In deep groove tires, it is important that they have excellent groove crack resistance (flexing fatigue resistance), wear resistance, cut tear resistance and durability, and these various performances must be maintained in a well-balanced manner. Required to be present. Among the above performances, the groove crack resistance and the cut tear resistance are contradictory performances, and there is a relationship that if one performance is improved, the other performance is degraded.

[0005]

The object of the present invention is to maintain the above-mentioned various performances in a well-balanced manner, and in particular, to have excellent groove crack resistance and cut tear resistance at the same time, and it is suitable for use in deep groove tires for trucks and buses. To provide a rubber composition which can be obtained.

The present inventors have conducted extensive research to develop a rubber composition that meets the above needs. As a result, the cis content was 98% or more and the 5% toluene solution viscosity was 200 cps. The above butadiene rubber is 10 to 30
It has been found that the desired object of the present invention can be achieved by using a rubber contained in a weight percentage, and by incorporating a specific thermoplastic resin in the rubber in a specific proportion. The present invention has been completed based on such findings.

That is, according to the present invention, (1) the cis content is 98%
Above, and the viscosity of the 5% toluene solution is 200 cps.
100 parts by weight of the rubber containing the above butadiene rubber in a proportion of 10 to 30% by weight and at least one thermoplastic resin selected from the group consisting of (2) rosin resin and cyclopentadiene resin. The present invention relates to a rubber composition containing 5 to 5 parts by weight.

The butadiene rubber used in the present invention has a cis content of 98% or more and a 5% toluene solution viscosity of 200 cps. That is all. Such a butadiene rubber can be easily produced, for example, by polymerizing butadiene with a neodymium (Nd) catalyst. In the present invention, the cis content of butadiene rubber is measured by the Morello method, and is an infrared spectrophotometer [Hitachi, dispersion type 2
60-30 model]
Peaks at 10.34μ for 1,4-bonds and 10.95-10.98μ for 1,2-bonds were selected and calculated from their extinction coefficients [polymer,
Vol. 13, p. 252 (1964)]. Also, 5
% Toluene solution viscosity is 2% by dissolving butadiene rubber in toluene so that the concentration becomes 5%.
It is measured at 5 ° C. using a Canon Fenske viscous tube. When the cis content is less than 98% and the viscosity of a 5% toluene solution is 200 cps. If it is less, the groove crack resistance becomes insufficient. In the present invention, in particular, the cis content is 98% or more and the 5% toluene solution viscosity is 250 cps. It is desirable to use the above butadiene rubber.

In the present invention, a rubber containing the above-mentioned butadiene rubber in a proportion of 10 to 30% by weight is used as a rubber component. The rubber compounded with the butadiene rubber is not particularly limited, and conventionally known rubbers can be widely used. For example, natural rubber (NR) and polyisoprene rubber (I
R), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), synthetic rubbers such as butadiene rubber other than the above, and modified products thereof. These rubbers may be used alone or in combination of two or more.

If the proportion of the butadiene rubber in the rubber component is less than 10% by weight, the bending fatigue resistance tends to decrease, while if it exceeds 30% by weight, the cut tear resistance tends to decrease. In the present invention, it is preferable to use a rubber containing 15 to 20% by weight of the above-mentioned butadiene rubber as a rubber component.

In the present invention, at least one thermoplastic resin selected from the group consisting of rosin-based resins and cyclopentadiene-based resins is used for every 100 parts of the rubber component.
It is necessary to mix 5 to 5 parts. By blending such a specific thermoplastic resin in a specific amount, the intended effect of the present invention is exhibited. For example, a resin other than the above specific thermoplastic resin, specifically, an aliphatic petroleum resin [ESCOLETS 1
102, manufactured by Exxon Chemical Co., Ltd.] is added to the rubber component of the above (1) of the present invention to obtain a rubber composition which is not satisfactory in cut tear resistance, abrasion resistance and heat generation property (this leads to durability). (See Comparative Example 3 below). By incorporating the above-mentioned specific thermoplastic resin, the intended effect of the present invention, particularly the cut tear resistance, is significantly improved. The reason for this is currently under investigation, but when the thermoplastic resin penetrates between the polymer chains and undergoes elongation or strain, it improves the sliding property of the polymer, and as a result, it is resistant to cuts when subjected to external strain. It is considered that the heat resistance is improved, the hysteresis loss is increased by adding the thermoplastic resin, and the cut tear resistance is improved because the amount of the input energy from the outside is changed into heat is increased.

Specific examples of the rosin resin used in the present invention include wood rosin (manufactured by Arakawa Chemical Co., Ltd.), and specific examples of the cyclopentadiene resin include Escoletz 8
180 (manufactured by Exxon Chemical Co., Ltd.) and the like can be exemplified.

The amount of the thermoplastic resin compounded is 10 in the rubber component.
When it is less than 0.5 part per 0 part, the cut tear resistance tends to be insufficient, and when it is more than 5 parts on the contrary, not only the fatigue resistance and wear resistance are deteriorated, but also the heat resistance is deteriorated. Inferiority tends to decrease durability. In the present invention, the thermoplastic resin is used in an amount of 1 to 100 parts per 100 parts of the rubber component.
It is desirable to mix 3 parts.

In addition to the above-mentioned components, the composition of the present invention contains known vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, vulcanization retarders, organic peroxides, reinforcing agents, fillers, plasticizers. , An anti-aging agent, a tackifier, a colorant and the like can be appropriately mixed.

The rubber composition of the present invention can be easily produced by kneading the above components using a conventional processing device such as a roll, a Banbury mixer or a kneader.

[0016]

EXAMPLES The present invention will be further clarified with reference to the following examples.

Examples 1 to 4 and Comparative Examples 1 to 8 Rubber compositions were obtained with the formulations shown in Table 1 below. The groove crack resistance, cut tear resistance, abrasion resistance and heat generation temperature of the obtained rubber composition were measured by the following methods. That is, the groove crack resistance is ASTM D4
According to 482, after heat aging the sample at 70 ° C. for 5 days, a Monsanto type fatigue tester was used to measure the number of repetitions until fatigue failure under the conditions of a test temperature of 23 ° C., an elongation rate of 100% and a speed of 100 cycles / minute. The index of the rubber composition of Example 1 was shown as 100. The larger the value, the better the groove crack resistance. The cut tear resistance was expressed as an index by setting a value of 100 in the rubber composition of Example 1 by dropping a 2 kg rod on the rubber block and measuring the cut depth. The higher the number,
It shows that it has excellent cut tear resistance.
A value of 5 or more was judged to be sufficient in terms of cut tear resistance. Wear resistance is AST using a pico abrasion tester
It was tested according to MD 2228 and indexed with that of the rubber composition of Example 1 as 100. The higher the number,
It shows that the wear resistance is excellent, and a value of 90 or more was judged to be sufficient in terms of the wear resistance. The exothermic temperature was measured using a Goodrich flexometer according to ASTM D623. The smaller the value is, the more excellent the heat resistance is, and it is judged that the value of 22 ° C. or less is sufficient in terms of the heat resistance. The results are also shown in Table 1 below.

In Table 1, BR-a is BR150B.
[Ube Industries, Ltd., cis content: 98%, 5% toluene solution viscosity: 52 cps. ], BR-b is BR01 [manufactured by Nippon Synthetic Rubber Co., Ltd., cis content: 96%, 5% toluene solution viscosity: 110 cps. ], BR-c is CB22 [manufactured by Bayer, cis content: 98%, 5% toluene solution viscosity:
280 cps. ], The carbon black is ISAF carbon, the vulcanization accelerator is CBS, and the antioxidant is Santoflex 13 [manufactured by Nippon Monsanto Co.].

[0019]

[Table 1]

As is clear from Table 1, when the rubber composition of the present invention is used, groove crack resistance, abrasion resistance,
A tire having excellent cut tear resistance and heat resistance (durability) can be obtained. Comparative example 1 and comparative example 2 are 5
% Toluene solution viscosity is 52 cps. Butadiene rubber having a cis content of 96% and a 5% toluene solution viscosity of 110 cps. However, in any case, it is insufficient in terms of groove crack resistance, cut tear resistance and abrasion resistance. Comparative Example 3 is an example in which a resin other than the thermoplastic resin of the present invention is blended, but it is insufficient in terms of cut tear resistance, abrasion resistance and heat resistance. Comparative Example 4 is an example in which the compounding amount of the butadiene rubber of the present invention is too small, but it is insufficient in terms of groove crack resistance and abrasion resistance, particularly groove crack resistance. Comparative Example 5 is an example in which the compounding amount of the butadiene rubber of the present invention is too large, but it is insufficient in terms of cut tear resistance. Comparative Example 6
Is an example when the blending amount of the thermoplastic resin of the present invention is too small, but is insufficient in terms of cut tear resistance.
Comparative Example 7 is an example in which the blending amount of the butadiene rubber of the present invention is too large, but it is insufficient in terms of groove crack resistance, abrasion resistance and heat resistance, particularly heat resistance. Comparative Example 8 is an example in which the thermoplastic resin of the present invention is not blended, but is significantly inferior in cut tear resistance.

[0021]

The rubber composition of the present invention maintains various properties such as groove crack resistance, abrasion resistance, cut tear resistance and heat resistance in a well-balanced manner, and in particular, groove crack resistance and cut tear resistance. It has excellent properties and can be suitably used for deep groove tires for trucks and buses.

Claims (1)

[Claims] 1. A cis content of 98% or more and a 5% toluene solution viscosity of 200 cps. 100 parts by weight of the rubber containing the above butadiene rubber in a proportion of 10 to 30% by weight and at least one thermoplastic resin selected from the group consisting of (2) rosin resin and cyclopentadiene resin. A rubber composition comprising 5 to 5 parts by weight.