JP2000080206A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject rubber composition for tire tread that is imparted the water retention properties, increase the discharge to the air via the moisture in the tread and can give a tire tread of low electric resistance. SOLUTION: (A) 100 pts.wt. of the rubber component are combined with (B) 50-150 pts.wt. of silica, (C) 4-15 pts.wt. of a silane coupling agent, for example, bis(3-triethoxysilylpropyl) tetrasulfide or the like and (D) 5-20 pts.wt. of a water-soluble, water-absorbing resin, (suitably a polyvinyl alcohol having a spherical shape with the particle size of 20-100 μm). In a preferred embodiment, (E) <=10 pts.wt. of carbon black having an iodine adsorption of >=80 mg/g is additionally formulated to the rubber composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rubber composition for a tire tread.

[0002]

2. Description of the Related Art Conventionally, in order to achieve both rolling resistance and wet grip performance of a tire, it has been practiced to compound only silica without compounding carbon black into a rubber composition for a tire tread.

However, when a rubber composition containing only silica is applied to a tire tread, there is a problem in that silica has poor conductivity, causing static electricity to accumulate in an automobile, causing radio noise and harm to an electric system. Was. Also,
Sparks occur when the charged static electricity is discharged at once,
At the time of refueling, the fuel could ignite.

[0004] In order to prevent such electrification, an antistatic agent such as polyethylene glycol ester is blended into a rubber composition for a tire tread. However, there is a problem that the effect of improvement is not sufficient even if the content is large, and that other performances such as abrasion resistance are lowered.

[0005] Incidentally, static electricity is generally strongly charged in a dry state, and is discharged through moisture in the air under high humidity conditions.

Accordingly, the present inventors have paid attention to the fact that if the rubber composition for a tire tread is imparted with water retention to enhance the discharge property of the surface of the tire tread, a tire which is hardly charged and has a small electric resistance can be provided. Thus, the present invention has been completed.

The rubber composition constituting the tire described in Japanese Patent Application Laid-Open No. 60-259503 contains a water absorbing agent in order to improve the skid effect. But,
The water-absorbing agent used here is a water-insoluble hydrophilic substance, and has a problem that it is inferior in water retention as compared with a water-soluble resin.

[0008]

That is, an object of the present invention is to provide a rubber composition having a high discharge property capable of providing a tire tread having a small electric resistance.

[0009]

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 50 to 150 parts by weight of silica, 4 to 15 parts by weight of a silane coupling agent, and 5 to 20 parts by weight of a water-soluble water-absorbent resin with respect to 0 parts by weight.

In this case, the amount of carbon black having an iodine adsorption of 80 mg / g or more is preferably 10 parts by weight or less.

It is preferable that the shape of the water-soluble water-absorbent resin is particulate, and the particle size is 20 to 100 μm.

Preferably, the water-soluble water-absorbing resin is polyvinyl alcohol.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As described at the outset, the most significant feature of the present invention is that a rubber composition for a tire tread is blended with a water-soluble water-absorbent resin to impart water retention, and the resulting tire tread has a water content. To increase the discharge to the atmosphere including
It is to provide a tire tread with low electric resistance.
In addition, by using a water-soluble water-absorbing resin, it is possible to obtain an advantage that the water-soluble resin is eluted into a water film between the tire and the road surface, and wet grip properties are improved.

The water-soluble water-absorbing resin that can be used in the present invention is preferably one that imparts water retention to the obtained rubber composition to improve dischargeability and gradually elutes into water between the road surface and the resin. Specific examples include water-soluble cellulose derivatives such as polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose and sodium carboxy cellulose. Among these, it is preferable to use polyvinyl alcohol from the viewpoint of the balance between price and effect.

The shape of the water-soluble water-absorbing resin used in the present invention may be any shape as long as it can be uniformly dispersed in the rubber composition, and examples thereof include a particle shape and a short fiber shape.

The size of the water-soluble water-absorbing resin may be within a range that does not impair the dispersibility in the obtained rubber composition.
In particular, in the case of particles, the particle diameter is preferably 20 to 100 μm. If it exceeds 100 μm, it becomes a breaking nucleus to lower the strength of the rubber composition, and if it is less than 20 μm, the dispersibility is poor. Further, from the viewpoint of the balance between the strength and the dispersibility, it is particularly preferred that the thickness is 20 to 60 μm.

The amount of the water-soluble water-absorbing resin may be 5 to 20 parts by weight based on 100 parts by weight of a rubber component described later. When the amount is less than 5 parts by weight, the amount of the water-soluble water-absorbent resin present on the tread surface is reduced, so that sufficient water retention and discharge properties cannot be obtained, and reduction in electric resistance of the obtained tire cannot be expected. The reason is that if it exceeds 20 parts by weight, the obtained tread has poor abrasion resistance. Further, the amount is preferably 5 to 10 parts by weight from the viewpoint of a balance between discharge performance and wear resistance.

The rubber component that can be used in the present invention is not particularly limited as long as it has been conventionally applied to a tire tread.
R), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), isobutylene rubber (IIR) and the like. These rubber components can be used alone or in any combination. However, it is preferable to use SBR and BR from the viewpoint of good wet grip properties. In addition, SBR
Those skilled in the art can appropriately select the ratio between the two when BR and BR are used, as long as the effects of the present invention are not impaired.

The silica used in the present invention is not particularly limited as long as it has been conventionally used in the field of tires.

The mixing amount of silica is preferably 100 parts by weight of the rubber component.
It is sufficient if it is 50 to 150 parts by weight with respect to parts by weight, but from the viewpoint of the balance between wet grip and rolling resistance,
It is preferably 50 to 100 parts by weight.

The silane coupling agent blended in the rubber composition of the present invention is not particularly limited as long as it is conventionally used in combination with silica in the field of tires. (Ethoxysilylpropyl) tetrasulfide, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like. These can be used alone or in any combination. Among them, from the viewpoint of good reactivity and effect with silica,
It is preferred to use bis (3-triethoxysilylpropyl) tetrasulfide.

The amount of the silane coupling agent is as follows:
The amount based on silica is preferably 8 to 10% by weight. The amount may be 4 to 15 parts by weight with respect to 100 parts by weight of the rubber component.
It is preferably in parts by weight.

The rubber composition for a tread of the present invention comprises:
Even if it does not contain carbon black, it has excellent discharge performance, but when added to further improve discharge performance,
Preferably, carbon black having an iodine adsorption of 80 mg / g or more is used in an amount of 10 parts by weight or less based on 100 parts by weight of the rubber component. Further, in order to bring out the properties of silica, it is particularly preferable to suppress the amount to 2 to 6 parts by weight.

The rubber composition of the present invention may further contain, in addition to the above components, a filler such as clay, a softening agent such as a paraffinic, aroma or naphthenic process oil, a coumarone indene resin, a rosin resin, Tackifiers such as cyclopentadiene-based resins, vulcanizing agents such as sulfur and peroxides, vulcanization accelerators, vulcanization aids such as stearic acid and zinc oxide, antioxidants, etc., impair the effects of the present invention. It can be appropriately compounded as needed within the range not present. In addition, fillers such as silica and carbon black other than silica and carbon black satisfying the above requirements may be blended as long as the effects of the present invention are not impaired.

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

The rubber composition of the present invention obtained as described above can be applied to a tire tread by a conventional method, and can provide a tire tread having low electric resistance since it has excellent dischargeability.

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

[0028]

EXAMPLES First, materials used in the examples are shown below.

SBR: Nipo manufactured by Zeon Corporation
19520 (35% by weight of styrene content, 37.5 parts by weight of oil) BR: BR150B manufactured by Ube Industries, Ltd. Silica: Nipsil VN manufactured by Nippon Silica Industry Co., Ltd.
3. Silane coupling agent: X-5 manufactured by Degussa Japan
0-S (100: 100 (weight ratio) mixture of bis (3-triethoxysilylpropyl) tetrasulfide and carbon black (N330, iodine adsorption amount 82 g / kg)). The carbon black contained here is referred to as carbon black B.

Carbon black A: N220 manufactured by Showa Cabot Corporation (Iodine adsorption amount 121 g / kg) Water-soluble water-absorbent resin A: Kuraron K- manufactured by Kuraray Co., Ltd.
II (polyvinyl alcohol powder) with 200 mesh (7
5 μm).

Examples 1 and 2 The above-mentioned materials were kneaded using a Banbury mixer so that the mixing ratios shown in Table 1 were obtained, thereby obtaining tire tread rubber compositions 1 and 2 of the present invention.

The obtained rubber compositions 1 and 2 are extruded in the form of tread by an ordinary method using an extruder.
6. The tires 1 and 2 of the size 6 were produced, and then the internal pressure was set to 2.
It was assembled on a 7-1 / 2JJ aluminum rim as 2 ksc. The tires 1 and 2 were evaluated by the following methods. Table 1 shows the results.

[Evaluation Method] Measurement of Tire Electrical Resistance In order to evaluate the chargeability of the tire, the electrical resistance under load was measured using the obtained tires 1 and 2. The measurement method is “wdk” published in Germany in October 1995.
The load is 450kg according to "110 Blatt 3"
f. To evaluate the effect of the tread surface on atmospheric humidity, the humidity was set to 28% and 62%,
Measurements were taken after the tires were left in these humidity environments for 24 hours. Generally, if the electric resistance value is 100 MΩ or less, it is considered that inconvenience of the tire due to electrification is small.

Measurement of Rolling Resistance The rolling resistance at a speed of 80 km was measured by a drum type rolling resistance measuring machine having a diameter of 1707.6 mm. Result is,
The case of Comparative Example 1 to be described later is indicated by an index with 100 being set.
The larger the index, the lower the rolling resistance, which is preferable.

The ABS is operated on a 3000 cc passenger car with an ABS, and the braking friction coefficient is determined from the deceleration from the initial speed of 40 km / h to 20 km / h.
As an index. The larger the index, the higher and better the braking force.

Wear resistance The obtained tire was mounted on a 3000 cc passenger car and
The amount of abrasion after running at 000 km was measured, and was indicated by an index with the value of Comparative Example 1 described later as 100. The larger the index, the better the wear resistance.

Radio noise When traveling for evaluating abrasion resistance, the occurrence of radio noise when traveling on a dry road surface was evaluated. A indicates that no radio noise was generated, B indicates a case where radio noise was slightly generated, and C indicates a case where radio noise was generated.

Comparative Examples 1 to 4 Comparative rubber compositions 1 to 4 were obtained in the same manner as in Example 1 except that the mixing ratios shown in Table 1 were changed, and the same tests as those in Examples were performed. Table 1 shows the results.

[0039]

[Table 1]

According to Table 1, the amount of the water-soluble water-absorbing resin was 5
When the amount is less than 10 parts by weight, the reduction of the electric resistance is insufficient and it is understood that noise occurs (Comparative Examples 2 and 3). It can be seen that the reduction can be achieved, but the wear resistance is poor.

Further, it can be seen from Examples 1 and 2 of the present invention that the electric resistance can be reduced without sacrificing other performances within the composition range of the present invention.

[0042]

According to the present invention, it is possible to obtain a highly dischargeable rubber composition capable of providing a tire tread having a small electric resistance.

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Claims (4)

[Claims] 1. Silica is 50 to 150 parts by weight, and a silane coupling agent is 4 to 15 parts by weight based on 100 parts by weight of a rubber component.
A rubber composition for a tire tread, comprising 5 parts by weight and 5 to 20 parts by weight of a water-soluble water-absorbent resin. 2. The compounding amount of carbon black having an iodine adsorption of 80 mg / g or more is 10 parts by weight or less.
The rubber composition for a tire tread according to the above. 3. The rubber composition for a tire tread according to claim 1, wherein the shape of the water-soluble water-absorbent resin is particulate, and the particle size is 20 to 100 μm. 4. The rubber composition for a tire tread according to claim 1, wherein the water-soluble water-absorbent resin is polyvinyl alcohol.