JP2000044732A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition excellent in friction on ice by compounding a rubber component with porous particles having a specified or smaller mean pore diameter in a specified ratio. SOLUTION: One hundred pts.wt. rubber component is compounded with 3-40 pts.wt. porous particles having a mean particle pore diameter of 20 Åor smaller. It is desirable that the porous particles are particles of crystalline zeolite and that silica and a silane coupling agent are added. The rubber component is exemplified by a natural rubber, a butadiene rubber, or a styrene/ butadiene rubber, and is desirably a combination of a natural rubber with a butadiene rubber. The silica is desirably the one having a nitrogen adsorption specific surface area of 50-300 m2/g and is used in an amount of 10-100 pts.wt. It is desirable that the silane coupling agent is bis(3-triethoxysilylpropyl) tetrasulfide and is used in an amount of 2-20 wt.% based on the amount of the silica added. The small-pore-diameter porous particles existing on the surface of a tire tread selectively adsorbs water by capillarity and exhibit a water- removing effect.

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 a tire tread having excellent frictional force even on ice and snow surfaces.

[0002]

2. Description of the Related Art Conventionally, spike tires having spike pins have been used in order to improve performance on icy and snowy road surfaces. However, there has been a problem that the dust of the tire leads to pollution and the spike pins damage the road. Thus, in recent years, studless tires without using spike pins have been developed.

For example, Japanese Patent Application Laid-Open No. 9-302153 discloses a technique in which porous particles having an average pore diameter on the surface of 40 to 1000 ° are compounded in a rubber composition for a tread. That is, the frictional property is improved by using the scratching effect of the porous particles present on the surface of the tire tread on the ice surface, and the braking performance on ice, wear resistance and crack resistance are improved.

However, since the porous particles used in the art have a relatively large pore size, they cannot express a sufficient frictional force particularly on an ice surface having a water scale. In the ice state, there is a problem that the effect of improving the braking performance is not seen.

[0005]

The present inventors have found that the above problem can be solved by using porous particles having a smaller average pore diameter.

[0006] That is, an object of the present invention is to obtain a rubber composition having excellent friction properties on ice.

[0007]

According to the present invention, there is provided a rubber component comprising:
The present invention relates to a rubber composition for a tire tread, comprising 3 to 40 parts by weight of porous particles having an average pore diameter of less than 20 ° with respect to 0 parts by weight.

[0008] In this case, the porous particles are preferably crystalline zeolites.

It is preferable that the rubber composition contains silica and a silane coupling agent.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The most important feature of the present invention is that porous particles having a smaller average pore size are present on the tire tread surface than in the prior art, and the water present on ice is selectively adsorbed by a so-called capillary phenomenon. Another object of the present invention is to provide a rubber composition capable of providing a tire tread excellent in frictional properties on ice by a mechanism having a water removing effect.

The porous particles used in the present invention include organic porous particles and inorganic porous particles. Among them, those having a particle diameter of less than 20 ° are used because they selectively adsorb low molecules. Examples of the inorganic porous particles having an average pore size of less than 20 ° include crystalline zeolites. As the organic porous particles, for example, molecular sieving carbon (average pore diameter: 5
Å) and the like. These can be used alone or in any combination. Above all,
It is preferable to use crystalline zeolite from the viewpoint that the metal cations existing in the crystal lattice more strongly adsorb water molecules as polar molecules, exhibiting a water removing effect, and improving friction on ice.

The average pore size of the porous particles may be less than 20 ° as described above, but the lower limit is usually 3 °.
In addition, from the viewpoint of more selectively adsorbing water, 3 to
It is preferably 15 °, and more preferably 3 to 12 °, because vulcanization is not slowed down.

The average particle size of the porous particles is 0.1.
The thickness may be from 1 to 500 μm, but is preferably from 0.1 to 100 μm from the viewpoint of increasing the specific surface area.

Among the "porous particles having an average pore size of less than 20 mm" which can be used in the present invention, commercially available ones include, for example, Molecular Sieve 4A (crystalline zeolite, average pore size 4 mm) manufactured by Union Showa KK. ,
Molecular sieve 3A (crystalline zeolite, average pore size 3Å, average particle size 5 μm) Molecular sieve 5A (crystalline zeolite, average pore size 5Å, average particle size 5 μm) Molecular sieve 13X (crystalline zeolite, average pore size) 10 °, average particle size of 4 μm).

The amount of the porous particles having an average pore diameter of 20 ° or less may be 3 to 40 parts by weight with respect to 100 parts by weight of a rubber component described later, from the viewpoint that the wear resistance is not reduced. The amount is preferably 5 to 30 parts by weight from the viewpoint that the effect of the on-ice braking state is high.

The rubber component used in the present invention is not particularly limited as long as it has been conventionally used in the field of tires. For example, natural rubber (NR),
Butadiene rubber (BR), styrene-butadiene rubber (SBR) and the like can be mentioned, and they can be used alone or in any combination. Among them, natural rubber and butadiene rubber are preferably used in combination because of their low glass transition point (Tg).

In addition, the rubber composition for a tire tread of the present invention preferably contains silica for reinforcement in addition to the porous particles that play a role of removing a water film on ice as described above. .

The silica preferably has a nitrogen adsorption specific surface area of 50 to 300 m ² / g. Also D
The BP adsorption amount is preferably 100 to 300 ml / 100 g. If the nitrogen adsorption specific surface area is less than 50 m ² / g, dispersibility in the rubber composition of the silica and poor reinforcing property of the rubber composition, the nitrogen adsorption specific surface area of 300 meters ²
/ G and the DBP adsorption amount is 300 ml / 1
If it exceeds 00 g, the dispersibility of silica in the rubber composition is poor.

Commercially available silicas usable in the present invention include, for example, Nipsil VN3 and Nipsil AQ manufactured by Nippon Silica Co., Ltd., and Ultrasil VN3 manufactured by Degussa.

The compounding amount of silica may be 10 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and furthermore, it is excellent in frictional force on ice and snow, from the viewpoint of obtaining a sufficient reinforcing effect of the rubber. In order to reduce the hardness of the rubber to some extent, the amount is preferably 10 to 50 parts by weight.

When silica is used, it is preferable to use a silane coupling agent in combination to enhance the dispersibility in the obtained rubber composition and to improve the strength of the vulcanizate.

The silane coupling agent that can be used in the present invention is not particularly limited as long as it is conventionally used in combination with silica.
Triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltriethoxysilane, 2-
Mercaptoethyltrimethoxysilane and the like,
Among them, the effect of improving the physical properties of vulcanized rubber is high,
It is preferred to use bis (3-triethoxysilylpropyl) tetrasulfide.

The amount of the silane coupling agent is as follows:
From the viewpoint of enhancing the dispersibility of silica and improving the physical properties of the vulcanized rubber, it is sufficient that the amount is 2 to 20% by weight of the blending amount of silica.
Preferably, it is １５15% by weight.

The rubber composition of the present invention may further comprise, in addition to the above components, a softening agent such as a paraffinic, aroma or naphthenic process oil, a coumarone indene resin, a rosin resin or a cyclopentadiene resin. Tackifiers, sulfur, vulcanizing agents such as peroxides, vulcanization accelerators, stearic acid, vulcanization aids such as zinc oxide, anti-aging agents, etc., within the scope of not impairing the effects of the present invention, are required. It can be appropriately compounded depending on the situation.

The rubber composition of the present invention can be obtained by a conventional method using a closed kneader such as a Banbury mixer or a kneader, an open roll, or the like.

The rubber composition of the present invention obtained as described above can be suitably used for a tread of a tire.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0028]

Example 1 According to the compounding ratio shown in Table 1, the rubber composition 1 of the present invention was kneaded by a conventional method using a Banbury mixer.
Was manufactured. Mitsubishi Chemical Corporation as carbon black
Diamond Black I, silica is Degussa (Deg
ussil) Ultrasil VN3, silane coupling agent used is Degussa Si69
(Bis (3-triethoxysilylpropyl) tetrasulfen) and the porous particles A are Union Showa Co., Ltd.
Ltd. molecular sieves 4A (Na ₁₂ [AlO _2)
12 (SiO ₂ ) ₁₂ ] · 27H ₂ O, average pore diameter 4 °, average particle diameter 5 μm). Further, as an anti-aging agent, Nocrack 6C (N-phenyl-
N '-(1,3-dimethylbutyl) -p-phenylenediamine) was used. The obtained rubber composition 1 was evaluated according to the following method. Table 1 shows the results.

[Evaluation method] Friction test on ice A test sample was prepared by subjecting a rubber sheet vulcanized at 170 ° C. for 15 minutes to a surface buff from the obtained rubber composition. The weight and the weight placed on the sample were extruded under the conditions of a normal force of 5 kgf / cm ² and an extrusion speed of 800 mm / min. The braking distance of the sample was measured by measuring the distance. The results of Comparative Example 1 described later were evaluated by an index with 100 being the value. The higher the index, the better the friction on ice.

Lambourn abrasion test Using a Lambourn tester, the amount of abrasion of the sample was measured under the conditions of a load of 1.5 kgf and a slip ratio of 40%. The results of Comparative Example 1 described later were evaluated by an index with 100 being the value. The larger the index, the smaller the amount of wear and the better the wear resistance.

Comparative Examples 1 to 4 Comparative rubber compositions 1 to 4 were prepared and evaluated in the same manner as in Example 1 except that the porous particles having an average pore diameter of less than 20 ° were changed to silica gel described later. Table 1 shows the results.

As silica gel A, Merck (M
erck) 9385-2M (silica gel, average pore size 60 °, average particle size 50 μm), silica gel B: Merck (Merck) 10180-2M (silica gel, average pore size 40 °, average particle size 10 μm), silica gel C 10184- manufactured by Merck
M (silica gel, average pore size 100 °, average particle size 10μ)
m) was used.

[0033]

[Table 1]

From Table 1, it can be seen that the average pore size is 40 °, 60 °, 1
When using silica gel as large as 00 大 き い (Comparative Example 2
And 3) the abrasion at -5 ° C is improved,
It can be seen that the improvement in abrasion is not sufficient.

Examples 2 to 4 Rubber compositions 2 to 4 were produced and evaluated in the same manner as in Example 1 except that the amount of the porous particles was changed. Table 2 shows the results. Table 2 also shows the results of Example 1 for comparison.

Comparative Examples 5 to 6 Comparative rubber compositions 5 to 6 were produced and evaluated in the same manner as in Example 1, except that the amount of the porous particles was changed.
Table 2 shows the results.

[0037]

[Table 2]

As shown in Table 2, when the amount of the porous particles having an average pore diameter of less than 20 ° is less than 4 parts by weight or more than 40 parts by weight, the well-balanced improvement of friction and wear resistance cannot be achieved. It turns out that.

[0039]

According to the present invention, a rubber composition having excellent frictional properties on ice can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 7/24 C08K 7/24

Claims (3)

[Claims] 1. A rubber composition for a tire tread comprising 3 to 40 parts by weight of porous particles having an average pore diameter of less than 20 ° based on 100 parts by weight of a rubber component. 2. The rubber composition according to claim 1, wherein the porous particles are crystalline zeolites. 3. The rubber composition according to claim 1, comprising silica and a silane coupling agent.