JP2009203330A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire tread giving excellent driving stability and excellently maintaining steering wheel responsiveness. <P>SOLUTION: The rubber composition for a tire tread is obtained by blending 100 pts.wt. of a diene rubber containing 50 pts.wt. or more of an SBR having a glass transition temperature (Tg) of -30°C or higher and containing 30 wt.% or more of styrene, with 30-200 pts.wt. of carbon black with a CTAB adsorption specific area of 100-300 m<SP>2</SP>/g. In the rubber composition for a tire tread, 1-30 pts.wt. of a rubber gel constituting a main chain of a modified diene polymer is blended. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread, and more specifically, by maintaining a steering stability and a response to a steering wheel by blending a specific rubber gel with a specific styrene butadiene rubber (SBR) compounded rubber. The present invention relates to a rubber composition for a tire tread having excellent properties.

  Conventionally, high-performance passenger car tires have always been required to ensure a high level of motion performance, and in particular, safety by clearing requirements such as handling stability, durability and durability during extreme driving. Securing of wear and improvement of wear resistance have been issues. On the other hand, various companies have proposed adding various compounding agents, but further improvements in tire physical properties are expected in terms of recent environmental measures and ensuring safety.

  Conventionally, a rubber composition for a tire tread with improved rolling resistance and wet grip characteristics can be obtained by combining a predetermined amount of rubber gel and a specific sulfur-containing organosilicon compound with a diene rubber. Although it is disclosed in the following Patent Document 1, in this Patent Document 1, such rubber gel is compounded alone in a rubber composition for an SBR compounded tire tread, and steering stability is reduced without deteriorating extrusion processability. There has been no proposal for a rubber composition for a tire tread that is enhanced and has increased long-term durability.

JP 2001-31798 A

  In the present invention, the rubber composition for tire treads is blended by blending a specific amount of a specific rubber gel constituting a main chain with a predetermined carbon black and a modified diene polymer into a specific SBR compounding rubber compound for tire treads. An object of the present invention is to obtain a rubber composition for a tire tread having improved steering stability and less change in steering wheel response over time without deteriorating extrudability of the article.

According to the present invention, a CTAB adsorption specific surface area of 100 to 100 parts by weight of a diene rubber having a glass transition temperature (Tg) of −30 ° C. or more and containing 50 parts by weight or more of SBR having a styrene content of 30% by weight or more. In a tire tread rubber composition comprising 30 to ²⁰⁰ parts by weight of 300 m ² / g carbon black, 1 to 30 parts by weight of a rubber gel constituting a main chain of a modified diene polymer is blended. A rubber composition for a tire tread is provided.

  Moreover, according to this invention, the rubber composition for said tire tread formed by mix | blending 1-30 weight part of liquid rubbers with the said rubber component further is provided.

  In the present invention, when a predetermined amount of a specific rubber gel constituting a main chain of a predetermined carbon black and a modified diene polymer is blended with a rubber composition for a tire tread composed of the diene rubber mainly containing the specific SBR, The present inventors have found that a rubber composition for a tire tread that can achieve excellent steering stability and its steering response aging change without lowering the extrusion processability of the tire tread rubber composition is obtained.

That is, in the present invention, for tire treads, 30 to 200 parts by weight of carbon black having a CTAB adsorption specific surface area of 100 to 300 m ² / g is blended with 100 parts by weight of the diene rubber mainly containing the specific SBR. A rubber composition for a tire tread that can achieve excellent steering stability and change in steering response over time when 1 to 30 parts by weight of a specific rubber gel constituting a main chain of a modified diene polymer is blended in a rubber composition. Is obtained.

  In the present invention, the main diene rubber used in the tire tread rubber composition of the present invention is preferably 50 parts by weight or more of SBR having a glass transition temperature of −30 ° C. or more and a styrene content of 30% by weight or more. A diene rubber containing 70 parts by weight or more is used. Examples of other diene rubbers that can be used by blending with the SBR include natural rubber (NR), isoprene rubber (IR), various butadiene rubbers (BR), and acrylonitrile-butadiene copolymer rubber (NBR). It is done.

The carbon black used in the rubber composition for a tire tread of the present invention has a CTAB adsorption specific surface area (measured by JISK6217-3 test method) of 100 to 300 m ² / g, preferably 110 to 250 m ² / g, more preferably. Is a high surface area carbon black of 130-220 m ² / g. Further, the carbon black further has a 24M4DBP (measured value according to JISK6217-4 test method) of 90 to 150 ml / 100 g, more preferably 100 to 125 ml / 100 g, and a specific coloring power (according to JISK6217-5 test method). Carbon black having a measured value) of 90 to 150, more preferably 100 to 140, is preferably used. The carbon black is blended in an amount of 30 to 200 parts by weight, more preferably 50 to 160 parts by weight with respect to 100 parts by weight of the diene rubber mainly containing the SBR. If the blending amount is less than 30 parts by weight, the reinforcing effect may not be sufficient, and the wear resistance and rupture characteristics of the rubber composition may be deteriorated. This is not preferable because the composition becomes too hard and the processability deteriorates.

  As the rubber gel constituting the main chain of the modified diene polymer used in the rubber composition for tire treads of the present invention, the diene polymer constituting the main chain is an aromatic vinyl copolymer, and its terminal modification A rubber gel having an OH group, a COOH group, a primary to tertiary amine group, etc., and a glass transition temperature of −100 to 100 ° C., preferably 0 to 100 ° C., and having a particle diameter (DVN value according to DIN 53206) ) Is a rubber gel having a thickness of 5 to 1000 nm, preferably 20 to 600 nm, more preferably 30 to 100 nm. The rubber gel constituting the main chain with such a modified diene polymer is commercially available from LANXESS, for example, under the product names “Nanoprene BM 15OH” and “Nanoprene BP 40OH”, and is known before the filing of the present application.

  Moreover, as a compounding quantity of the said rubber gel used by this invention, it is used with the compounding quantity of rubber gel 1-30 weight part with respect to 100 weight part of diene rubbers, More preferably, 15-30 weight part. If the blended amount of the rubber gel is less than 1 part by weight, the desired effect of the present invention cannot be exhibited. Conversely, if it exceeds 30 parts by weight, the extrusion processability deteriorates, which is not preferable.

  When the rubber composition for tire tread according to the present invention is used in combination with the above-described rubber gel and a predetermined amount of a predetermined liquid polymer is further blended, the desired handling stability and its sustainability are further improved. As such a liquid rubber, for example, a liquid rubber having an average molecular weight of 1000 to 100,000 such as liquid IR, liquid BR, and liquid SBR is 1 to 30 parts by weight with respect to 100 parts by weight of the diene rubber mainly containing the SBR, It is preferably used in an amount of 1 to 20 parts by weight. If the blending amount of the liquid rubber is less than 1 part by weight, the desired effect cannot be obtained. Conversely, if it exceeds 30 parts by weight, the physical properties are remarkably lowered.

  The rubber composition for a tire tread according to the present invention is further blended for ordinary vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, fillers, plasticizers, and other tire rubbers. Various compounding agents can be blended, and these compounding agents can be kneaded by a general method to obtain a rubber composition, which can be vulcanized or crosslinked. The compounding amounts of these compounding agents can be set to conventional general compounding amounts as long as the object of the present invention is not adversely affected.

  Hereinafter, the present invention will be further described with reference to standard examples, comparative examples, and examples, but it goes without saying that the technical scope of the present invention is not limited to these examples.

  The rubber compositions of the standard example, comparative example 1 and examples 1 to 5 shown in Table 1 below were kneaded and prepared according to a general method, and first, extrudability based on the extrudability test of 1) below. Next, a tire for tire size 215 / 45R17 equipped with a cap tread formed using the rubber composition was manufactured, mounted on a passenger car having a displacement of 2000 cc, and a closed test course of 6 km per week. The steering stability was evaluated based on the steering stability test of 2) below, and the time course changes in the steering response of the fifth lap and the steering response of the 20th lap were Evaluation was made based on the steering response aging test of 3) below.

Each test and evaluation method 1) Extrusion processability: Using a Garvey die extruder (manufactured by Brabender), the roughness of the skin surface of a molded product obtained by extruding each rubber composition was visually evaluated, and its surface The skin condition was evaluated as acceptable or not.
2) Steering stability: Sensory evaluation by a test driver was indexed. Using the three points of the standard example as a reference, points of 1 to 5 points were assigned in increments of 0.5, and relative evaluation was performed for Comparative Example 1 and Examples 1 to 5. Moreover, when it was slightly better than these points, or when it was not slightly better, these points were marked with a plus (+) or minus (−) symbol. For example, an evaluation of “3+” is slightly better than “3” but not as good as “3.5−”. The larger the value, the better the steering stability and the better.
3) Change in steering wheel response over time: The test driver evaluated the steering wheel response at the fifth lap of lap and the handle responsiveness at the lap 20 lap, and evaluated the difference in the change over time using the above-mentioned score display. . The larger the numerical value, the smaller the change in steering wheel response over time, which is better.

Standard Example, Examples 1 to 5 and Comparative Example 1
The results are shown in Table 1 below.

  From the results shown in Table 1, in the rubber composition for tire treads of the present invention, the steering stability and the steering response lapse of time without decreasing the extrusion processability by blending a predetermined amount of the predetermined carbon black and the predetermined rubber gel. It can be seen that both improve the change.

Claims (2)

CTAB adsorption specific surface area of 100 to 300 m ² / g with respect to 100 parts by weight of diene rubber having a glass transition temperature (Tg) of −30 ° C. or more and containing 50 parts by weight or more of styrene butadiene rubber having a styrene content of 30% by weight or more. A tire tread rubber composition comprising 30 to 200 parts by weight of a carbon black of 1 to 30 parts by weight of a rubber gel constituting a main chain of a modified diene polymer. Composition.   The rubber composition for a tire tread according to claim 1, wherein the rubber component further contains 1 to 30 parts by weight of a liquid rubber.