JPH08311245A - Tire tread rubber composition - Google Patents

Abstract

PURPOSE: To obtain a tire tread rubber compsn. improved in digging-up friction and adhesive friction without detriment to durability. CONSTITUTION: The compsn. is prepd. by compounding 100 pt.wt. diene rubber component with 5-30 pts.wt. inorg. filler having an average particle size of 1-10μm. A pref. inorg. filler is clay baked at 600-800 deg.C. Pref. the compsn. further contains 0.1-3 pts.wt. silylating agent based on 100 pts.wt. diene rubber component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tread rubber composition suitable for a studless tire having excellent ice and snow performance.

[0002]

2. Description of the Related Art Conventionally, spike tires that grip an ice barn with spike pins have been widely used as pneumatic tires suitable for running on an ice barn. However, when running on a normal road surface with spiked tires, the pin scrapes the road surface, which causes dust pollution. In recent years, studless tires have been attracting attention as pneumatic tires that grip ice burn without using spike pins. However, compared to spike tires that grip ice burn directly with spike pins, its on-ice performance is insufficient, so various studies have been conducted to increase the friction coefficient of tread surface against ice burn in order to improve the on-ice performance of studless tires. Being tried.

However, among the friction between the tread and the road surface, there is excavation friction and adhesive friction as the main friction for securing driving force and braking force on ice and snow, and it is necessary to increase these frictions. For example, in a studless tire in which a tread is made of foamed rubber, an edge component due to a foamed hole excavates to increase friction, and an adhesive effect due to a water film removing action due to the edge is increased. However, in order to increase the digging friction and the adhesive friction, it is necessary to increase the ratio of foam holes, that is, the foaming ratio, which leads to softening of the entire tread,
As a result, it may cause deterioration of exercise performance and wear resistance in non-snowy areas.

Further, Japanese Patent Application Laid-Open No. 2-167353 discloses a pneumatic tire having a tread made of a rubber composition containing a powdered product containing a cellulose substance. Since such a cellulose powder does not form a chemical bond with the rubber component, the cellulose powder exposed on the tread surface is dropped during running, and the drop holes caused by the drop are dug up like a foamed hole, causing friction and adhesion. May contribute to increased friction. On the other hand, until the cellulose powder is exposed on the tread surface and falls off, it exists as an additive in the rubber, so it does not cause softening of the tread rubber like foamed rubber, and it is durable in non-snow areas. It does not cause deterioration of sex.

[0005]

However, the processed product of cellulose powder generally has a particle size of 100 to 150 μm.
However, since the hardness of the entire surface is reduced, a difference in hardness is generated between the vicinity of the drop hole and other portions, and the braking effect due to adhesive friction cannot be expected sufficiently. The processed cellulose powder has a large number of OH groups in its molecular structure and exhibits hydrophilicity. For this reason,
Since the hardness of the cellulose powder processed product decreases due to water absorption until it appears on the tread surface and falls off, there is a limit to increase the friction caused by excavation by the cellulose powder processed product. Therefore, in order to further enhance the digging-up friction, it is necessary to use an additive that does not reduce the hardness due to water absorption.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a rubber composition for a tread which is intended to improve the digging-up friction and the adhesive friction without lowering the durability. To provide things.

[0007]

The rubber composition for a tire tread of the present invention contains 5 to 30 parts by weight of an inorganic filler having an average particle size of 1 to 10 μm with respect to 100 parts by weight of a diene rubber component. Characterize. The rubber component of the rubber composition of the present invention is a diene rubber, and the type thereof is not particularly limited, but generally a diene rubber excellent in low temperature characteristics, for example,
Natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR)
Etc. are used.

The inorganic filler used in the present invention includes:
Inorganic substances that have no or low reactivity with rubber, and examples thereof include inorganic metal salts such as calcium carbonate and barium sulfate; natural inorganic clay minerals such as clay; synthetic inorganic substances such as zeolite; and wollastonite. None of these inorganic substances form a chemical bond with the base rubber component even when the rubber composition is vulcanized, and the inorganic filler exposed on the tread surface can be removed during running. After falling off, the falling holes can act in the same manner as the foaming holes of the foamed rubber to contribute to the increase of the digging friction and the adhesive friction. Furthermore, until it comes out and falls off on the tread surface, like the cellulose powder, it is present in the rubber as an additive, so even if a necessary and sufficient amount for grip strength is blended, the tread softens, It does not affect the durability.

Of these inorganic fillers, those having hydrophobicity are preferable in order to enhance the water removing effect. A typical example of the inorganic filler having hydrophobicity is clay, and in particular, calcined clay obtained by calcining at 600 to 800 ° C. to remove the water of crystallization is preferable because it has a large water removing effect. The size of the inorganic filler used in the present invention is 1 to 10 μm. If it exceeds 10 μm, the drop holes become too large,
There is a difference in hardness between the vicinity of the drop hole and other parts, and adhesive friction cannot be fully exerted. In addition, the dropout holes become large, which causes a decrease in wear resistance. on the other hand,
A drop hole having a diameter of 10 μm or less does not cause an extreme decrease in hardness around the drop hole, the surface hardness can be homogenized, and the adhesive friction of rubber can be exhibited. This is because if the particle diameter is less than 1 μm, there is a problem of scattering in the process, and the dropout hole diameter is insufficient, resulting in insufficient softening.

The content of the inorganic filler is diene rubber 10
5 to 30 parts by weight, preferably 10 to 20 parts by weight
Parts by weight. If it is less than 5 parts by weight, the softening of the rubber in the ground contact surface is insufficient and the compounding effect is not sufficiently exhibited, and if it exceeds 30 parts by weight, the rate of appearance on the tread surface, and by extension the drop holes, wear resistance performance deteriorates. Because it does. In the tread rubber composition of the present invention, in order to further enhance water repellency,
0.1 to 3 parts by weight of silylating agent, preferably 0.5 to 2
It is preferable to contain parts by weight. The silylating agent is a compound that replaces active hydrogen in the rubber composition with a silyl group (—SiR ₃ ), and for example, phenyltriethoxysilane is used. The silylating agent can also reduce the hydrophilic groups exposed on the tread surface and impart water repellency to the entire tread surface.

In addition to the above compounds, the tread rubber composition of the present invention may contain various additives such as sulfur, vulcanization accelerators, antioxidants and carbon black.

[0012]

EXAMPLES The present invention will be described below based on examples. Rubber composition No. 1 having the composition shown in Table 1. 1 to 6 were blended. Rubber composition No. No. 1 does not contain clay and corresponds to a comparative example. The unit of the compounding amount in Table 1 is parts by weight. The oil amount is an amount selected so that the hardness of each rubber composition is the same. The clay used had an average particle size of 5 μm, the carbon black used was N220, and the silylating agent used was phenyltriethoxysilane (KBE103) manufactured by Shin-Etsu Chemical.

Rubber composition No. A pneumatic tire having a tread composed of 1 to 6 is manufactured, and the manufactured tire (185
/ 70R14 size), the performance on ice and the abrasion resistance were evaluated based on the following evaluation methods. The results are shown in Table 1. [Evaluation Method] Performance on Ice The braking stop distance was measured when the vehicle was running on a skating rink at 15 km / h and a brake was applied. The reciprocal of the measured braking stop distance is the rubber composition No. The result was expressed as an index when the result of 1 was 100. The larger the index, the better the braking performance on ice. Abrasion resistance performance The amount of abrasion was measured using a Lambourn tester, and the rubber composition No. It is represented by an index when the wear amount of 1 is 100.
The larger the index is, the more excellent the abrasion resistance is, but 78 or more is in the allowable range. .

[0014]

[Table 1]

As can be seen from Table 1, the clay-blended rubber compositions (Nos. 2 to 6) are superior in ice performance to the rubber compositions (No. 1) containing no clay, The effect is increased in proportion to the blended amount. On the other hand, the abrasion resistance decreased with the increase of the blended amount of clay, but remained within the allowable range if the blended amount was within the range of the present invention.

Further, the rubber composition No. 4 and No. From the comparison with No. 6, it is understood that the performance on ice is increased by the addition of the silylating agent. Therefore, by using the clay and the silylating agent together, it is possible to suppress the compounding amount of the clay, in other words, to suppress the deterioration of the wear resistance and to increase the performance on ice.

[0017]

EFFECTS OF THE INVENTION The tread rubber composition of the present invention contributes to an increase in digging-up friction and adhesion friction. Therefore, by forming a tread using the tread rubber composition, a pneumatic tire capable of exhibiting excellent ice and snow performance can be obtained. Can be manufactured. Further, by using the clay and the silylating agent in combination, it is possible to obtain a tread capable of exhibiting excellent ice and snow performance while suppressing deterioration of wear resistance.

Claims (3)

[Claims] 1. To 100 parts by weight of a diene rubber component,
A rubber composition for a tire tread, comprising 5 to 30 parts by weight of an inorganic filler having an average particle diameter of 1 to 10 μm. 2. The inorganic filler is 600 to 800.
A clay which is calcined at ℃ is used.
The rubber composition for a tire tread described in. 3. Based on 100 parts by weight of the diene rubber component,
The rubber composition for a tire tread according to claim 1 or 2, further comprising 0.1 to 3 parts by weight of a silylating agent.