JPH09241430A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for pneumatic tire treads capable of remarkably improving fracture resistance and wet skid characteristics and reducing rolling resistance without deteriorating the abrasion resistance characteristics. SOLUTION: This rubber composition for tire treads is obtained by blending 100 pts.wt. rubber component comprising 20-80wt.% halogenated butyl rubber, 20-80wt.% polyisoprene rubber and/or natural rubber and <=50wt.% other diene- based rubbers with 20-60 pts.wt. carbon black and 0.5-2.0 pts.wt. alkylphenol disulfide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition for a tire tread, and in particular, it has a remarkable breaking property, steering stability on wet road surface and braking property (wet skid resistance property) without lowering wear resistance. The present invention relates to a rubber composition which is improved and has reduced rolling resistance, and which can be suitably used for a tread of a pneumatic tire.

[0002]

2. Description of the Related Art In recent years, due to social demands for resource saving and energy saving, research on reducing rolling resistance of tires has become important in order to save fuel consumption of automobiles. It is generally known that if the rolling resistance of a tire is reduced, the fuel consumption of an automobile is reduced and the tire becomes a so-called low fuel consumption tire. It is also known that in order to reduce the rolling resistance of a tire, a material having a small hysteresis loss may be generally used for the tread rubber of the tire.

On the other hand, from the requirement of running stability, a rubber material having a large frictional resistance (wet skid resistance) on a wet road surface has been strongly desired. However, the wet skid resistance and the above-mentioned low rolling resistance of the tire have a trade-off relationship, and it has been extremely difficult to satisfy both characteristics.

By the way, recently, the correspondence between the rolling resistance and wet skid resistance of a tire and the viscoelastic properties of a rubber composition has been theoretically shown. According to this, in order to reduce the hysteresis loss of the tread rubber in order to reduce the rolling resistance during tire running, viscoelasticity shows that the loss tangent (tan) at a temperature during tire running at 50 to 70 ° C.
It has been shown that lowering δ) is effective.
As a method of lowering tan δ at the temperature of 50 to 70 ° C., it is general to use a material having a low glass transition temperature such as high cis polybutadiene rubber or a material having a high impact resilience such as natural rubber.

On the other hand, the wet skid resistance is 10 to 2
It is known that it correlates well with the loss tangent near 0 ° C. under the frequency of 0 Hz, and according to this, it is necessary to increase the loss tangent near 0 ° C. to improve the grip performance of the tire. .

[0006]

However, 50-
Wet skid resistance is extremely reduced in rubber of a material having a low glass transition temperature and a material having high impact resilience, which is effective in lowering tan δ at a temperature of 70 ° C.,
Therefore, it has been theoretically proved that it is extremely difficult to achieve both running stability and low rolling resistance in the prior art.

Therefore, an object of the present invention is to overcome the problems that have been theoretically difficult in the past, to significantly improve the fracture resistance and the wet skid resistance without lowering the wear resistance, and to improve the rolling resistance. It is intended to provide a rubber composition for a pneumatic tire tread capable of reducing the above.

[0008]

The rubber composition for a tire tread of the present invention comprises a halogenated butyl rubber of 20 to 80% by weight, a polyisoprene rubber and / or a natural rubber 2
20 to 60 parts by weight of carbon black and 0.5 to 2.0 parts by weight of alkylphenol disulfide with respect to 100 parts by weight of a rubber component consisting of 0 to 80% by weight and 50% by weight or less of other diene rubber. It is characterized by being mixed.

The halogenated butyl rubber is preferably a modified copolymer obtained by halogenating a copolymer of isomonoolefin and p-alkylstyrene.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The halogenated butyl rubber used as the rubber component of the rubber composition of the present invention includes bromobutyl rubber, branched bromobutyl rubber, isomonoolefin and p-
Examples thereof include modified copolymers obtained by halogenating a copolymer composed of alkylstyrene, and preferably halogenated, particularly brominated, a copolymer composed of isomonoolefin and p-alkylstyrene as described above. Alternatively, it is a chlorinated modified copolymer. Specific examples thereof include a modified copolymer in which isomonoolefin is isobutylene, p-alkylstyrene is p-methylstyrene, and a halogen atom used for modifying the copolymer is bromine or chlorine.

Other diene rubbers used in the rubber composition of the present invention include butadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, ethylene-propylene copolymer rubber (E
Examples thereof include rubber (EPDM) which is a terpolymer obtained by adding a diene monomer to PM) and EPM.

In the present invention, the halogenated butyl rubber is required to account for 20 to 80% by weight of the rubber component. If it is less than 20% by weight, tan δ (0 ° C) is low,
Wet skid performance is inferior, while when it exceeds 80% by weight, fracture strength and wear resistance are inferior, and tan δ (5
(0 ° C.) is high and the rolling resistance is low.

The rubber composition of the present invention contains 0.5 to 100 parts by weight of the rubber component as a part of the crosslinking agent.
One of the features is that 2.0 parts by weight of alkylphenol disulfide is used. If the amount is less than 0.5 parts by weight, the effect of improving fracture characteristics and wear resistance is small, while if it exceeds 2.0 parts by weight, workability becomes poor.

Further, 20 to 60 parts by weight of carbon black is used for 100 parts by weight of the rubber component in the rubber composition of the present invention. If the blending amount is less than 20 parts by weight, the vulcanizate has insufficient abrasion resistance and fracture properties, while if it exceeds 60 parts by weight, the low hysteresis loss property is deteriorated.

The rubber composition of the present invention is used by appropriately blending an antioxidant, zinc white, stearic acid, a vulcanization accelerator, a vulcanizing agent and the like in addition to the above-mentioned alkylphenol disulfide and carbon black.

[0016]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Brominated butyl rubber (Br-IIR), which is a halogenated butyl rubber used in Examples and Comparative Examples, and a modified copolymer obtained by brominating a copolymer of isomonoolefin and p-methylstyrene (PMS) (commercial product). Name:
The PMS concentration and bromine concentration of Exxpro90-10 and Exxpro93-5) are shown in Table 1 below.

[0017]

[Table 1]

Further, the compounding amounts of the compounding agents other than the rubber component and carbon black, which are commonly used in Examples and Comparative Examples, are shown in Table 2 below with respect to 100 parts by weight of the rubber component.

[0019]

[Table 2] * 1: N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine * 2: Diphenylguanidine

Rubber compositions were prepared according to the compounding recipes shown in Table 2 above and Tables 3 and 4 below. Further, the obtained rubber composition was vulcanized under the conditions of 145 ° C. for 33 minutes, and the tan δ value, fracture characteristics and abrasion resistance of the vulcanized product were evaluated. The evaluation method is as follows.

(A) Low hysteresis loss characteristic (tan δ
(50 ° C.) Using a dynamic spectrometer manufactured by Rheometrics Co., USA, dynamic shear strain (amplitude 1.0%, frequency 15 Hz) is applied at 50 ° C. to measure the tan δ value, and the reciprocal of this value is calculated. The value in Comparative Example 8 was set as 100 and displayed as an index. Therefore, the larger the value, the smaller the hysteresis loss and the better. (B) Wet skid resistance property (tan δ (0 ° C.)) The tan δ value was measured at 0 ° C. in the same manner as above, and the value in Comparative Example 8 was set to 100 and displayed as an index. Therefore, the larger the value, the better the wet skid resistance. (C) Destruction characteristics It was measured according to JIS K-6301. (D) Abrasion resistance It was measured by the Lambourn abrasion method. 2.0k load
g, the wear amount at a slip ratio of 25% at room temperature was measured, and the reciprocal thereof was used to calculate the value in Comparative Example 8 as 1.
The index was indicated as 00. Therefore, the larger the value, the better the wear resistance. The obtained results are also shown in Tables 3 and 4 below.

[0022]

[Table 3]

[0023]

[Table 4] * S-SBR is a solution-polymerized styrene-butadiene rubber having a bound styrene content of 20% by weight and a vinyl bond content of 70% by weight (in butadiene).

In each of the examples, the fracture characteristics and the wet skid resistance characteristics were greatly improved, and the low hysteresis loss characteristics could be realized without impairing the wear characteristics.

On the other hand, when the halogenated butyl rubber is used in a larger amount than the predetermined amount as in Comparative Example 1, the breaking property is greatly deteriorated, and the wear property and the low hysteresis loss property are also deteriorated, which is not preferable.

Further, when the halogenated butyl rubber is extremely reduced as in Comparative Examples 3 to 5, the wet skid resistance is deteriorated, which is not preferable.

Further, as in Comparative Example 2, when the amount of the alkylphenol disulfide as the vulcanizing agent is less than the predetermined amount, the breaking property and the abrasion resistance are deteriorated, which is not preferable.

Furthermore, when the carbon black is extremely reduced as in Comparative Example 6, the fracture characteristics and the wear resistance are significantly reduced, which is not preferable.

Further, when carbon black is excessively increased as in Comparative Example 7, the low hysteresis loss characteristic is deteriorated, which is not preferable.

[0030]

As described above, according to the present invention,
It is possible to provide a rubber composition for a pneumatic tire tread capable of significantly improving the fracture property and the wet skid resistance property and reducing the rolling resistance without lowering the wear resistance property.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C08L 7/00 KCT C08L 7/00 KCT 23/28 LDA 23/28 LDA

Claims (2)

[Claims] 1. 20 to 80% by weight of halogenated butyl rubber, polyisoprene rubber and / or natural rubber 20
20 to 60 parts by weight of carbon black and 0.5 to 2.0 parts by weight of alkylphenol disulfide with respect to 100 parts by weight of a rubber component composed of -80% by weight and 50% by weight or less of other diene rubber. A rubber composition for a tire tread, characterized by being blended. 2. The rubber composition for a tire tread according to claim 1, wherein the halogenated butyl rubber is a modified copolymer obtained by halogenating a copolymer composed of isomonoolefin and p-alkylstyrene.