JP2001329115A - Rubber composition for studless tires - Google Patents

Abstract

(57) [Summary] [Problem] Even when the surface of a snow-ice road is melted and a water film is formed, the effect of increasing the adhesion friction and the effect of increasing the friction coefficient are sufficiently exhibited to prevent slip on the snow-ice road. Of studless tires with improved wear resistance and improved wear resistance. SOLUTION: The average particle diameter is 10 to 200 parts per 100 parts by weight of a rubber component composed of 40 to 80% of a diene synthetic rubber having a glass transition point of -70 ° C or less and 60 to 20% of a natural rubber.
1 to 20 parts by weight of a porous thermosetting resin particle having a thickness of μm, a nitrogen adsorption specific surface area of 60 to 135 m ² / g, and DBP
The value of oil absorption is 30 to 55 from the value of nitrogen adsorption specific surface area.
A rubber composition for a studless tire containing 20 to 90 parts by weight of a large carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition used for a tire mounted on an automobile running on a road covered with snow and ice, a tread of a so-called studless tie.

[0002]

[Prior art]

[0003] A rubber composition which is widely used for tires by blending carbon black with an essential compounding agent such as sulfur, a vulcanization accelerator, zinc white, stearic acid and the like has a low coefficient of friction against ice and a studless tie. When the tire is used for a tread, it is slippery when traveling on a snow-ice road surface, and various methods for increasing the friction coefficient have been proposed. For example, Japanese Patent Application Laid-Open No. 60-197751 discloses that a glass transition point is
By using a rubber composition having a relatively low hardness in which a large amount of a softener and an α-olefin oligomer are blended in an SBR of 70 ° C. or less, the adhesive friction is increased, and the rigidity is increased even at a temperature below the freezing point. A method for preventing the friction from lowering, Japanese Patent Laid-Open No. 2-272042 discloses a method in which a hard granular material having an average particle size of 0.01 to 5 mm, such as alumina, granite, or quartz, is blended in addition to a general compounding agent to protrude from the tread surface. A method of forming a large number of microprojections to increase the coefficient of friction by a micro-spike effect of piercing the microprojections into the ice surface. Japanese Patent Laid-Open No. 4-11743, a method of blending granules and increasing the coefficient of friction by a large number of microprojections formed by projecting the granules from the tread surface. How to increase the coefficient of friction by particle size is roughened tread surface by blending carbonaceous powder 0.5~200μm are disclosed.

[0004]

In the conventional tire of the above method, when the temperature becomes higher than -5.degree. C., or in the case of sunshine, ice melts due to frictional heat generated when the tire is running on snowy and iced roads, and the tire has a problem. A water film is constantly interposed between the ground contact surface and the ice, so that a part of the tire surface does not directly contact the road surface, and the frictional force is reduced. On the other hand, in the tire in which the tread is formed of the rubber composition containing the granular material, the granular material having high rigidity is rubbed during traveling and damages the matrix phase in which the granular material is dispersed, and the adhesion is loosened and falls off. At the same time, the effect of increasing friction is reduced, and at the same time, micro cracks are generated in the matrix phase, and the matrix phase is easily worn. If carbon black having a small particle size is used or the amount of carbon black is increased in order to increase abrasion resistance, adhesion friction is reduced. For the above reasons, it is difficult to improve the slip resistance on snow and ice roads while maintaining the wear resistance at the level of a general tire, and the slip resistance on snow and ice roads has not yet reached a sufficiently satisfactory state.

According to the present invention, even when the surface of the snow and ice road is melted and a water film is formed, the effect of increasing the adhesion friction and the effect of increasing the friction coefficient are sufficiently exhibited to improve the slip resistance on the snow and ice road. An object of the present invention is to provide a studless tire having improved abrasion resistance.

[0006]

According to the present invention, an average particle size is determined based on 100 parts by weight of a rubber component comprising 40 to 80% of a diene-based synthetic rubber having a glass transition point of -70 ° C or less and 60 to 20% of a natural rubber. 1 to 20 parts by weight of porous thermosetting resin particles having a particle diameter of 10 to 200 μm, and a nitrogen adsorption specific surface area of 60 to 1
35 m ² / g and at the same time ml / 100 g D
The value of BP oil absorption is 30 to
This is a rubber composition for a studless tire containing 55 to 90 parts by weight of carbon black.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The rubber component has a glass transition point of -70.
By using a diene-based synthetic rubber having a temperature of not more than 0 ° C., the tread can be prevented from being hardened at a low temperature and a decrease in cohesive friction does not occur, and a tear resistance of the diene-based synthetic rubber having a glass transition point of −70 ° C. or less can be obtained. However, natural rubber is used in an amount of 20 to 60% in order to improve the disadvantages. Examples of the diene-based synthetic rubber having a glass transition point of -70 ° C or lower include butadiene rubber and a solution-polymerized styrene-butadiene rubber having a styrene content of 25% by weight or less.

[0008] The porous thermosetting resin particles blended as an anti-slip material are softer and more easily elastically deformed because they are more porous than conventional particles having high hardness, such as alumina, quartz, and walnut shell. Therefore, even when used in a tire and rubbed during running, the matrix phase is less likely to be damaged than the conventional granular material. The porous thermosetting resin granules (hereinafter, the porous thermosetting resin granules are abbreviated as porous granules) blended in the composition and dispersed in the tread are exposed so as to protrude to the tread surface and tread. The surface of the tread becomes rough at the same time as a large number of minute holes having holes of the porous granular material are formed on the surface. The microholes are removed in a short time by wiping off a water film formed by melting the surface of the snow and ice road surface interposed between the tread and ice, so that the tread surface is brought into direct contact with the road surface. Even when the temperature of the snow and ice road surface becomes high due to the water film removing action of the micro holes and slippery conditions occur, the use of low glass transition point rubber increases the cohesive friction effect and the roughened tread surface increases the friction on ice The effect is exhibited. The average particle diameter of the porous granular material is preferably from 10 to 200 μm, and the compounding amount is preferably from 1 to 20 parts based on 100 parts of the rubber component. Particle size is 10μ
If the amount is less than m or the amount is less than 1 part, the effect of the granular material is not sufficient, so that the effect of removing the water film and the effect of increasing the friction on ice are small. When the particle size is larger than 200 μm or when the amount is more than 20 parts, the abrasion resistance decreases.

In general, a conventional rubber composition using carbon black tends to have a reduced friction coefficient on ice if the wear resistance increases. However, the nitrogen adsorption specific surface area is 60
DB up to 135 m ² / g expressed in ml / 100 g
Carbon black whose P oil absorption value (hereinafter, DBP oil absorption value is referred to as DBP) is 30 to 55 larger than nitrogen adsorption specific surface area value (hereinafter, nitrogen adsorption specific surface area is referred to as N2SA), The friction coefficient of the rubber composition on ice (hereinafter, the friction coefficient on ice, adhesion friction and frictional force are referred to as friction on ice) although the wear resistance is higher than that of the same particle size. Maintained equally. Therefore, even if the wear resistance is reduced by blending the porous granules, if the wear resistance is increased by using the carbon black as a reinforcing agent, the reduced wear resistance can be achieved without impairing the friction on ice. You can recover. The compounding amount is the same as when conventional carbon black is used for a rubber composition for a tread of a studless tire. That is, 100 parts by weight of the rubber component (hereinafter, referred to as
(Parts by weight are simply referred to as parts). Preferably it is 30 to 70 parts. N2SA is 13
If it is larger than 5, the effect of improving the abrasion resistance due to poor dispersion and an increase in N2SA does not appear in proportion to the increase in N2SA. Not preferred. DBP to N2S
If the value obtained by subtracting A is less than 30, the friction on ice is impaired if N2SA is increased to increase the abrasion resistance, and if the value is larger than 55, the hardness on ice is increased and the friction on ice is reduced.

The dynamic elastic modulus at a temperature of 0 ° C. of a composition obtained by removing the porous granules from the composition of the rubber composition of the present invention, that is, the matrix phase rubber composition in which the porous granules are dispersed, is 5 to 15 MPa. Preferably. When the dynamic elastic modulus is less than 5 MPa, the tread rigidity is reduced and steering stability is reduced, and when it is greater than 15 MPa, friction on ice is reduced.

The rubber composition of the present invention is generally used for rubber compositions for treads such as vulcanization accelerators, sulfur, zinc white, stearic acid, oils, antioxidants, etc., in addition to carbon black and porous granules. The compounding agent is compounded in a general amount.

[0012]

EXAMPLE 50 parts of natural rubber and 50 parts of cis-butadiene rubber
Parts of the rubber component consisting of 100 parts by weight, carbon black having the colloidal properties shown in Table 1 (hereinafter, carbon black is abbreviated as carbon), an average sold under the trade name of Airpolic EY-01 by Shiroishi Central Research Institute. Porous thermosetting resin particles having a particle size of 35 μm and other compounding agents shown in Table 2 were blended in the ratio (parts by weight) shown in Table 2 to obtain a mixed rubber. A tread was formed by forming a tread with the obtained mixed rubber. Each prototype tire was evaluated for braking on ice and abrasion resistance by the following method, and the results are shown in Table 2.

[0013]

[Table 1]

[0014]

[Table 2]

Evaluation method of braking on ice After mounting the same kind of prototype tire on a passenger car and running it 200 km, the vehicle was driven on a snow-and-ice road at a temperature of -1 to 0 ° C at a speed of 40 / h.
A sudden brake was applied during running at km, and the stopping distance from the point where the sudden brake was applied to the stop was measured. The result was shown by an index calculated by the following equation. The larger the value, the better. (Comparative Example 1 stopping distance of tire) × 100 / (stop distance of each prototype tire)

Evaluation method of wear resistance After traveling about 10,000 km with two types of tires mounted on one passenger car, the depth of the grooves is measured, and the tire wear is determined from the difference between the groove depths before and after traveling. The amount was determined, and the result was indicated by an index calculated by the following equation. The larger the value, the better. (Comparative Example 1 Wear amount of tire) × 100 / (wear amount of each prototype tire)

Comparative Example 1 is a general rubber composition usually used for a tread of a tire. In Comparative Example 2 in which the porous granular material was added thereto, the braking performance on ice was improved as compared with Comparative Example 1, but the wear resistance was reduced. Examples in which the carbon N339 used in Comparative Example 2 was replaced with Carbon A or B had better braking performance on ice than Comparative Example 1, and had the same or greater wear resistance. The examples show that carbon A or B can restore reduced abrasion resistance without impairing braking performance on ice by blending porous granular materials. In Comparative Example 3 in which the amount of the porous granular material is more than 20 parts, the braking performance on ice is greatly improved, but the abrasion resistance is poor. Comparative Example 4, in which the porous granular material of Example 1 was replaced with alumina granular material having an average particle size of 100 μm, showed a small improvement in braking performance on ice, and showed that the porous granular material had a greater anti-slip action on ice. I have. Abrasion resistance is also a little low.

[0018]

According to the present invention, a rubber component consisting of natural rubber and a diene rubber having a glass transition point of -70 ° C. or less, which has been conventionally used in rubber compositions for studless tires, has an average particle size of 10 to 200 μm. By blending 1 to 20 parts by weight of the porous granular material, the slip resistance on snow and ice roads is improved, and as a reinforcing agent, the nitrogen adsorption specific surface area is 60 to 135 m ^2.
/ G and 20 to 90 parts by weight of carbon black having a DBP oil absorption value of 30 to 55 greater than the value of the nitrogen adsorption specific surface area in ml / 100 g. This has the effect of restoring the decrease in wear resistance without impairing the slip resistance and improving the slip resistance on snow and ice roads while maintaining the wear resistance when used in a tread of a studless tire.

Claims (1)

[Claims] An average particle diameter of 10 to 200 parts by weight per 100 parts by weight of a rubber component comprising 40 to 80% of a diene synthetic rubber having a glass transition point of -70 ° C or lower and 60 to 20% of natural rubber.
The value of the DBP oil absorption expressed in ml / 100 g is the value of the nitrogen adsorption specific surface area at the same time as 1 to 20 parts by weight of the porous thermosetting resin particles of μm and the nitrogen adsorption specific surface area of 60 to 135 m ² / g. A rubber composition for a studless tire, wherein 20 to 90 parts by weight of carbon black having a size of 30 to 55 is blended.