JPH1060175A - Tire tread rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an improved wet grip by mixing a rubber component containing a specified amount of a styrene/butadiene rubber with carbon black and an acylating agent. SOLUTION: 100 pts.wt. rubber component containing at least 50wt.%, desirably 75-100wt.% styrene/butadiene rubber having a styrene content of about 25wt.% is mixed with 70-110 pts.wt. carbon black having a mean particle diameter of 11-25nm, desirably 15-25nm and a CTAB specific surface area of 100-250m<2> /g, desirably 100-200m<2> /g and 0.05-8 pts.wt. silylating agent (e.g. phenyltriethoxysilane). Subsequently, the obtained mixture is mixed with additives such as an antioxidant, a softener, a vulcanizer and a vulcanization accelerator, and the resulting mixture is kneaded at about 100 deg.C to obtain a tire tread rubber composition.

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 for a high-performance tire, which has improved grip performance on wet roads (hereinafter referred to as wet grip performance).

[0002]

2. Description of the Related Art Conventionally, in order to improve wet grip performance of a tire, generally, it is necessary to increase a loss factor (tan δ) of a rubber composition. As one of means for that purpose, a method of increasing the compounding amount of carbon black in the rubber composition has been used. Natural rubber, isoprene rubber and / or butadiene rubber, and styrene-butadiene rubber are compounded as a rubber component of the tread rubber composition for tires. However, if the glass transition temperature is high, the loss coefficient increases and the wet grip performance improves. For this reason, the styrene-butadiene rubber content of the rubber component has been increased.

[0003] However, when the loss coefficient of the rubber composition is increased to improve wet grip properties, there is a problem that the rolling resistance also increases and the fuel consumption decreases accordingly (Comparative Example 2 and Comparative Example 2). 3).

[0004]

In view of the above problems,
An object of the present invention is to provide a tire tread rubber composition having improved wet grip properties while maintaining low fuel consumption.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a tire for tire comprising 100 parts by weight of a rubber component containing 60% by weight or more of styrene butadiene rubber, 70 to 110 parts by weight of carbon black, and 0.05 to 8 parts by weight of a silylating agent. The present invention relates to a tread rubber composition.

In this case, the styrene-butadiene rubber preferably contains at least 25% by weight of bound styrene.

The average particle size of carbon black is 11
２５25 nm, CTAB specific surface area 100-250 m ² /
g is preferred.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The styrene-butadiene rubber in the rubber component of the tread rubber composition of the present invention utilizes its high glass transition point to increase the loss coefficient of the obtained tread rubber composition and improve wet grip properties. It is added for the purpose of enhancing. The proportion in the rubber component may be 60% by weight or more, but preferably from 75 to 100% by weight from the viewpoint of further improving the wet gripping property, while maintaining high wet gripping property.
The amount is particularly preferably 75 to 85% by weight from the viewpoint that the increase in the rolling resistance is suppressed and the fuel efficiency is not reduced.

Further, the styrene-butadiene rubber of the present invention preferably contains 25% by weight or more of bound styrene from the viewpoint of increasing the peak temperature of tan δ and improving wet grip properties, and further improves wet grip properties. The content is preferably 30 to 60% by weight, more preferably 30 to 45% by weight, from the viewpoint that the increase in rolling resistance is suppressed and the fuel efficiency is not reduced while maintaining high wet grip properties. As commercially available products, N9520 (35% by weight of bound styrene) manufactured by Zeon Corporation can be used.

Other rubbers that may be included in the rubber component include diene-based rubbers such as natural rubber, isoprene rubber and butadiene rubber from the viewpoint of maintaining low-temperature embrittlement while suppressing a decrease in fuel efficiency due to an increase in rolling resistance. Rubber is preferably used, and these rubbers can be used alone or in any combination.

[0011] Carbon black is compounded to reinforce the obtained tread rubber composition, and its compounding ratio is 100 parts by weight of the rubber component from the viewpoint of increasing tan δ and improving wet grip properties. 70 to 110 parts by weight, preferably 85 to 110 parts by weight, more preferably 85 to 100 parts by weight from the viewpoint that the rolling resistance is not excessively increased and the fuel efficiency is not reduced while maintaining high wet grip properties. Is good.

Carbon black has an average particle size of 11 to 25 nm and a CTAB specific surface area of 100 to 250 m ² from the viewpoint of increasing tan δ and improving wet grip properties.
/ G or more in the ISAF class or higher, preferably from 15 to 15 from the viewpoint of improving dispersibility in the rubber component.
25 nm, CTAB specific surface area of 100 to 200 m ² / g, more preferably average particle size of 15 to 23 nm, CT
The specific surface area is preferably from 110 to 180 m ² / g. Commercially available products include ISA manufactured by Mitsubishi Chemical Corporation.
F (average particle diameter 20 to 25 nm, CTAB specific surface area 100
１２３123 m ² / g) and the like.

The CTAB specific surface area is a specific surface area per gram of carbon black determined from the oil absorption of trimethylammonium bromide.

As the silylating agent in the present invention, OH group, NHR group, CO
Any compound that can easily react with a functional group having an active hydrogen such as an OH group or an SH group to convert the hydrophilic compound into a hydrophobic compound may be used. Has excellent water repellency and improves wet grip properties. As the hydrophilic compound in the rubber composition of the present invention, there is mainly carbon black.

Conventional silylating agents can be used, for example, alkoxysilane compounds such as phenyltriethoxysilane and diphenyldimethoxysilane, chlorosilane compounds such as phenyltrichlorosilane and diphenyldichlorosilane, and silazane compounds such as hexamethyldisalazane. And the like, and these can be used alone or in any combination. Even when the compounding ratio of the silylating agent is 8 parts by weight or more, not all of the compounded amounts react effectively, so that 0.05 to 8 parts by weight, based on 100 parts by weight of the rubber component, It is preferably 0.1 to 8 parts by weight, and more preferably 0.1 to 5 parts by weight in terms of a reduction in abrasion resistance due to the plasticizing effect of the silylating agent.
It may be by weight.

The rubber composition for a tread of the present invention may contain a compounding agent such as an antioxidant, a softening agent, a vulcanizing agent, a vulcanization accelerator and the like, which are usually used in a tread rubber composition for a tire. Agents can be appropriately compounded as needed.

The tread rubber composition of the present invention can be prepared by a usual method using a rubber component, carbon black, a silylating agent and the above-mentioned usual compounding agents.

[0018]

EXAMPLES Next, the present invention will be described more specifically based on the following examples, but the present invention is not limited to these examples.

Example 1 A wax, an antioxidant, stearic acid, and zinc oxide were added to the composition shown in Table 1 at 150 ± 5 ° C. for 4 minutes, and the mixture was kneaded with a base. Then, 1.5 parts by weight of sulfur as a vulcanizing agent and 2.5 parts by weight of N-cyclohexyl-2-benzothiazolylsulfenamide (CZ) was added as an accelerator,
The tread rubber composition of the present invention was prepared by performing finish kneading at ± 5 ° C.

As the styrene butadiene rubber, N9520 manufactured by ZEON CORPORATION (35% by weight of bound styrene, 18% by weight of vinyl, 37.5% by weight of oil)
(SBR1), 30.0% by weight of bound styrene, 40% by weight of vinyl and 37.5% by weight of oil-extended (SB
R2) was used.

The butadiene rubber (BR) is BR1220 manufactured by Zeon Corporation and the carbon black is ISAF manufactured by Mitsubishi Chemical Corporation (average particle diameter: 20 to 25 n).
m, CTAB specific surface area 100 to 123 m ² / g).

As a silylating agent, KBE-103 (phenyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. was used. As a process oil, Diana Process AH24 manufactured by Idemitsu Kosan Co., Ltd. was used.

Comparative Examples 1 to 3 Comparative rubber compositions were prepared in the same manner as in Examples 1 to 3, except that the formulations shown in Table 1 were used. In addition, Comparative Example 1 was a composition to which the silylating agent was not added, and the effect of the silylating agent was observed in Examples 1 to 3 as a reference for evaluation described later.

Evaluation method Using the red rubber compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3, tires of 225 / 50R16 W1 were prepared, and the steering stability, rolling resistance and contact angle were measured under the following conditions. did.

[Steering stability] This is a feeling rating when the tire was mounted on a domestically produced 2600 cc FR vehicle with the internal pressure of the obtained tire being 2.0 kgf / cm ² , and was run at 150 Km / h. The measured value for the rubber composition containing no agent was set to 100, and is shown in Table 1 as a wet evaluation index. The larger the index, the better.

[Rolling Resistance] In general, the lower the rolling resistance of a tire, the better the fuel economy, and the higher the rolling resistance, the worse the fuel economy. Therefore, the internal pressure of the tire is increased to 2.0 kgf / cm
^2, and using the rim 8 J, using Kobe Machinery Co. rolling resistance tester under a load of 4.41KN, measuring the rolling resistance of tires, the measured value of Comparative Example 1 100
Table 1 shows the low fuel consumption performance index. The higher the index, the lower the rolling resistance and the better the fuel economy.

[Contact Angle] The contact angle refers to the angle of the surface contacting the boundary between the rubber surface and the water droplet in a state where the water droplet adheres to the tire surface. This indicates that the wet grip property is excellent. In the present invention, the advancing contact angle θa and the receding contact angle θr were measured by the apparatus shown in FIG. 2, and the contact angle θ was obtained by the following equation. The advancing contact angle uses the syringe of FIG.
The angle θ in FIG. 1 when the water droplet is increased, and the receding contact angle is θ in FIG. 1 when the water is absorbed and the water droplet is reduced. Table 1 shows the results. The higher the index, the higher the water repellency and the better wet grip.

[0028]

(Equation 1)

The magnitude of the water repellency can be quantitatively expressed by measuring the contact angle between water and the rubber composition. The larger the contact angle, the more water repellent. Note that the contact angle is measured by the number of samples and the number of measurements so that a difference of the unit value 1 of the average value can be detected at the 5% significance level.

[0030]

[Table 1]

From the results of the above evaluations shown in Table 1, the tread rubber composition of the present invention (Examples 1 to 3) has a wet grip property without lowering fuel economy by adding a silylating agent. The result was excellent. In Comparative Example 2, the wet evaluation index was improved by increasing the SBR content in the rubber component.
Due to the increased content, the rolling resistance is increased and the fuel economy performance is reduced. In Comparative Example 3, the wet evaluation index was improved by increasing the amount of carbon black, but the fuel economy performance was reduced due to the increase in the amount of carbon black.

[0032]

According to the tread rubber composition of the present invention,
By using the silylating agent, a tire having excellent wet grip properties can be obtained without lowering the fuel efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a contact angle between a tire surface and a water droplet.

FIG. 2 is a block diagram of a contact angle measuring device used when measuring a contact angle.

[Explanation of symbols]

 1 Tread rubber for tire 2 Water drop

Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08L 21:00)

Claims (3)

[Claims] 1. A rubber component containing 60% by weight or more of styrene butadiene rubber, 100 parts by weight of carbon black,
A tread rubber composition for a tire comprising 110 parts by weight and 0.05 to 8 parts by weight of a silylating agent. 2. The tread rubber composition according to claim 1, wherein the styrene-butadiene rubber contains at least 25% by weight of bound styrene. 3. The carbon black has an average particle size of 11 to 2.
The tread rubber composition according to claim 1, wherein the tread rubber composition has a thickness of 5 nm and a CTAB specific surface area of 100 to 250 m ² / g.