JPH0732809A - Tread rubber composition for studless tire - Google Patents

Abstract

PURPOSE:To provide tear-resistant tread rubber composition for a studless tire which shows large frictional force on the ice and excellent gripping performance. CONSTITUTION:Tread rubber composition for a studless tire is that 10-50 pts.wt. vulcanized rubber powder with a JIS A hardness of 40 or less at 20 deg.C and an average grain size of 0.2-0.8mm is compounded to 100 pts.wt. rubber component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for studless tires which can generate a large frictional force even on ice.

[0002]

2. Description of the Related Art The use of spiked tires is prohibited in order to prevent dust pollution, and the spread of studless tires is accelerating. The grip performance of studless tires has improved significantly over the past few years, and the grip performance exhibited on snow is almost the same as that of spiked tires. However, it may be inferior to the spike tire on the ice depending on the condition of the road surface, the temperature, etc. Therefore, further improvement in the grip performance of the studless tire is required.

In order to improve the grip performance, it is necessary to increase the frictional force that can be generated by the tread rubber of the tire. The following are related to the frictional force of the tread rubber.

(1) Hysteresis loss friction (2) Adhesion friction (3) Excavation (scratch) friction Among these, on a surface having a very low coefficient of friction such as on ice at -5 to 0 ° C, friction due to adhesion and excavation The influence of friction is extremely large.

In order to increase the adhesion and the friction due to excavation, it is effective to soften the rubber and increase the microscopic unevenness, and a softening agent using natural rubber or polybutadiene which hardly increases in hardness at low temperature is added. It is practiced to mix organic fibers, to use foamed rubber, and the like. However, if the rubber is made too soft, the pattern rigidity is lowered and the steering stability is impaired. There is a problem that non-uniform wear occurs, and when organic fibers are mixed or foamed rubber is used, there is a problem that the rubber content in a fixed volume decreases and the wear resistance performance deteriorates. Further, even if the friction is increased, the cut chipping performance, which is the originally required performance of the tread rubber, should not be lowered, that is, the tear resistance should not be lowered.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to generate a large frictional force even on ice so that excellent grip performance can be exerted and tear resistance. To provide an excellent tread rubber composition for studless tires.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made earnest studies on a method of increasing friction due to adhesion in order to obtain a large frictional force of tread rubber, and as a result, at least natural rubber, polyisoprene and polybutadiene which are soft even at low temperature have been obtained. By adding powder made by crushing one type of vulcanized rubber, a tread rubber that has a low friction coefficient on a road surface such as on ice, has a small deformation due to low friction and moves at a high frequency to become hard. The present inventors have found that the dynamic modulus of (1) can be lowered (softened), and as a result, the frictional force with ice can be increased by increasing the actual contact area with ice, and have completed the present invention.

That is, according to the present invention, the JI measured at 20 ° C.
10 to 50 parts (parts by weight; hereinafter the same) of vulcanized rubber powder having an SA hardness of 40 or less and an average particle size of 0.2 to 0.8 mm (100 parts by weight). The present invention relates to a tread rubber composition for studless tires.

[0009]

ACTION AND EXAMPLE As a material for the vulcanized rubber powder, J
A vulcanized rubber having a hardness measured at 20 ° C. using an IS A type hardness meter, that is, a JIS A hardness measured at 20 ° C. of 40 or less, preferably 35 or less, more preferably 30 to 35 is used. When a vulcanized rubber having a hardness of more than 40 is used, the vulcanized rubber powder tends to lose its effect of improving the adhesive friction of the tread rubber.

It is preferable that the vulcanized rubber powder consists of only a rubber component because it lowers the dynamic modulus at low temperature, but if the above hardness can be obtained, a filler such as carbon black, a general-purpose rubber additive, etc. May be added.

Preferably, the rubber component of the vulcanized rubber powder is
It contains at least one selected from the group consisting of natural rubber, polyisoprene and polybutadiene. A rubber component other than these may be contained, but at least one selected from the group consisting of natural rubber, polyisoprene and polybutadiene is at least 60% by weight based on the rubber component.
Or more, preferably 80% by weight or more, more preferably 90% by weight
It is desirable that the content is at least wt%.

The average particle size of the vulcanized rubber powder is 0.2 to 0.8.
mm, preferably 0.3 to 0.5 mm. 0.8 m
When it is larger than m, the strength of the vulcanized rubber powder itself is deteriorated, the fracture characteristics are deteriorated, and the wear resistance and cut chipping resistance of the tread rubber are deteriorated. On the other hand, when it is less than 0.2 mm, the effect of lowering the dynamic modulus on ice is extremely lowered, and the effect of increasing the frictional force on ice is hardly seen.

The vulcanized rubber powder was obtained by kneading at least one of natural rubber, polyisoprene or polybutadiene and, if necessary, other components with, for example, a Banbury mixer and vulcanizing at 150 ° C. for 30 minutes. The vulcanized rubber is obtained by freeze-grinding with liquid nitrogen at about −220 ° C. and screening with a Tyler mesh.

The rubber component of the tread rubber composition for a studless tire of the present invention is not particularly limited, but natural rubber,
Polyisoprene and polybutadiene are preferred.

In the present invention, the vulcanized rubber powder is 10 to 50 parts, preferably 15 parts to 100 parts of the rubber component.
-30 parts are blended. If it is less than 10 parts, the effect of lowering the dynamic modulus is small and no improvement in grip is observed. If it is more than 50 parts, the tear resistance tends to decrease and the cut-tapping performance tends to deteriorate.

The tread rubber composition for studless tires of the present invention contains, in addition to the rubber component and vulcanized rubber powder, a filler such as carbon black usually used for tread rubber, a vulcanization accelerator and an antioxidant. It can be obtained by an ordinary manufacturing method by mixing an agent and the like.

The present invention will be described below with reference to production examples and experimental examples, but the present invention is not limited to these.

Production Example 1 The vulcanized rubber obtained by kneading with a Banbury mixer using the formulations shown in Table 1 and vulcanizing at 150 ° C. for 30 minutes was frozen with liquid nitrogen at about −220 ° C. The vulcanized rubber powder A having an average particle size of 0.4 mm was prepared by pulverizing and selecting with a Tyler mesh. The average particle size is
It is a value calculated from the residue of the sieve in each mesh. Note that the vulcanized rubber should be stipulated in JIS at 20 ° C before freeze-grinding.
When the A hardness was measured, it was 35. That is, the vulcanized rubber powder A is a powder corresponding to the present invention.

Production Examples 2 to 5 Vulcanized rubber powders B to E having an average particle size of 0.4 mm were prepared in the same manner as in Production Example 1 using the formulations shown in Table 1. The hardness of each powder is shown in Table 1. The vulcanized rubber powders B and D have a hardness of more than 40, and are powders that do not correspond to the present invention.

[0020]

[Table 1]

Production Examples 6 and 7 Vulcanized rubber powders F and G having the same composition as in Production Example 1 and having average particle diameters of 0.9 mm and 0.1 mm were prepared.
The vulcanized rubber powders F and G have an average particle size of 0.2 to 0.8 m.
Since it is out of the range of m, the powder does not correspond to the present invention.

Example 1 Experimental Example 1 A tread rubber composition was prepared by blending the following usual components by a conventional method.

Natural rubber 50 parts Polybutadiene ¹⁾ 50 parts Carbon black ²⁾ 50 parts Stearic acid 2 parts Zinc white 4 parts Anti-aging agent ³⁾ 1 part Sulfur 1.5 parts Vulcanization accelerator ⁴⁾ 1 part In addition, 1) Polybutadiene is BR1220 manufactured by Nippon Zeon Co., Ltd. 2) Carbon black is N220 manufactured by Showa Cabot Co., Ltd. 3) Antiaging agent is 6PPD (Ozonone 6C) manufactured by Seiko Chemical Co., Ltd., vulcanization accelerator N-tert- manufactured by Ouchi Shinko Chemical Co., Ltd.
Butyl-2-benzothiazylsulfenamide was used.

Regarding this tread rubber composition, JIS
Tear resistance measured with K6301 is 45k
It was g / cm.

Further, a tire (2.745-144P) was manufactured using these tread rubber compositions, and the braking stop distance was measured. For the braking stop distance, a braking stop distance of 15 km / h → 0 km / h was measured using an 90 cc motorbike on an ice plate with an ice temperature of −1.6 ° C. and an air temperature of 2 ° C.

Experimental Examples 2 to 11 The vulcanized rubber powders A to G prepared in Production Examples 1 to 7 were added to the components used in Experimental Example 1 in the amounts shown in Table 2 to prepare a tread rubber composition by a conventional method. did. The tear resistance of each tread rubber composition was measured according to JIS K6301. The results are shown in Table 2. Further, a tire similar to Experimental Example 1 was manufactured using these tread rubber compositions, and Experimental Example 1
The braking stop distance was measured by the same method as in. The result
The distance in Experimental Example 1 is set to 100 and is indexed in Table 2. The smaller the index, the better.

[0027]

[Table 2]

The results in Table 2 show the following. That is, in Experimental Examples 2, 4, 6 and 10, 10 to 50 parts by weight of vulcanized rubber powder having a hardness of 40 or less and an average particle diameter of 0.2 to 0.8 mm was blended according to the present invention, and therefore, tearing was performed. The measurement results of the resistance and the braking stop distance are superior to the results of Production Example 1 using the normal component. On the other hand, in Experimental Example 3, the hardness of the vulcanized rubber particles B is as high as 43, so the braking stop distance is large. In Experimental Example 5, the hardness of the vulcanized rubber particles D is as high as 45, and thus the braking stop distance is large. Experimental Example 7
Has a small tear resistance because the particle size of the vulcanized rubber particles F is as large as 0.9 mm. Further, in Experimental Example 8, the particle size of the vulcanized rubber particles F is as small as 0.1 mm, so the braking stop distance is large.
Further, in Experimental Example 9, the blending amount of the vulcanized rubber particles A was as small as 5 parts, and thus the braking stop distance was large. Further, in Experimental Example 11, the compounding amount of the vulcanized rubber particles A was as large as 60 parts, and therefore the tear resistance was small.

[0029]

The tread rubber composition for a studless tire of the present invention can generate a large frictional force even on ice and can provide excellent grip performance.
High tear resistance and excellent cut chipping resistance.

Claims (3)

[Claims] 1. The JIS A hardness measured at 20 ° C. is 40.
Made of the following vulcanized rubber with an average particle size of 0.2-0.8 mm
10 to 50 parts by weight of the vulcanized rubber powder is 100 parts of the rubber component.
A tread rubber composition for a studless tire, which is compounded in parts by weight. 2. The rubber component of the vulcanized rubber powder is natural rubber,
The tread rubber composition for studless tires according to claim 1, containing at least one selected from the group consisting of polyisoprene and polybutadiene. 3. The tread rubber composition for a studless tire according to claim 1, wherein the rubber component of the tread rubber composition contains at least one selected from the group consisting of natural rubber, polyisoprene and polybutadiene.