JP2008297449A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve both of wear resistance and low heat build-up property (low rolling resistance) by blending carboxylic acid-modified liquid polyisoprene rubber into a carbon black-blended cap tread compound. <P>SOLUTION: The rubber composition for a tire tread is obtained by blending 30-150 parts by weight of carbon black having a CTAB adsorption specific surface area of 80-200 m<SP>2</SP>/g and a 24M4DBP absorption amount of 80-120 mL/100g and 1-20 parts by weight of liquid isoprene having 2-10 carboxyl groups per molecule and a number average molecular weight of 10,000-60,000 into 100 parts by weight of diene-based rubber containing natural rubber and/or polyisoprene rubber in an amount of ≥50 parts by weight. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread, and more specifically, by blending a carboxylic acid-modified liquid polyisoprene rubber with a carbon black compounded cap tread compound, the opposite wear resistance and exothermicity are achieved. The present invention relates to a rubber composition for a tire tread.

  Conventionally, as a method for improving the wear resistance of a rubber composition for a tire tread, a method of using carbon black having a small particle size and a large specific surface area or increasing the amount of carbon black is known. However, these methods have a problem that the viscosity of the rubber composition is increased, the kneading workability is remarkably lowered, and the dispersion of the carbon black is further deteriorated. Conversely, in order to improve the heat build-up of the rubber composition for tire treads, there are known methods such as increasing the particle size of carbon black to be compounded or reducing the compounding amount of carbon black. However, these methods have a problem that even if the heat generation can be improved, the wear resistance is lowered. For this reason, in the rubber composition for a tire tread, the wear resistance and the heat generation are in a trade-off relationship, and it has been difficult to improve both in a balanced manner.

  Also, as a prior art, in a rubber composition for tires made of general diene rubber, the dispersibility of polar organic materials such as kneaded adhesives and phenol resins is improved, and physical properties such as adhesion durability and elastic modulus are improved. In order to improve, a technology for blending liquid polyisoprene into which maleic acid or a derivative thereof is introduced is known from Patent Document 1 below, and in the rubber composition for tire treads also comprising a diene rubber, a grip on a frozen road surface Patent Document 2 below discloses a technique for blending liquid polyisoprene having a carboxyl group in order to obtain a studless tire that is excellent in performance, acceleration performance, braking performance, and the like. However, there is still a technique for eliminating the trade-off between wear resistance and heat buildup by blending such a carboxylic acid-modified liquid polyisoprene rubber with the above-mentioned rubber composition for tire treads containing carbon black. Not proposed.

Japanese Patent Laid-Open No. 2005-226016 Japanese Unexamined Patent Publication No. 7-118445

  Therefore, in the present invention, a predetermined amount of a carboxylic acid-modified liquid polyisoprene rubber is blended with a carbon black blended cap tread compound, so that the rubber component and carbon black are maintained while maintaining wear resistance and low heat buildup at the same time. It is an object of the present invention to provide a rubber composition for a tire tread that can improve the kneadability and improve the dispersion of carbon black and can also provide high wear resistance.

According to the present invention, with respect to 100 parts by weight of diene rubber containing 50 parts by weight or more of natural rubber and / or polyisoprene rubber, CTAB adsorption specific surface area of 80 to ²⁰⁰ m ² / g, 24M4DBP absorption of 80 to 120 mL / 100 g. Tire tread rubber composition comprising 30 to 150 parts by weight of carbon black and 2 to 10 parts by weight of liquid polyisoprene having 2 to 10 carboxyl groups per molecule and a number average molecular weight of 10,000 to 60,000. Is provided.

  In the present invention, when a predetermined amount of a specific carboxylic acid-modified liquid polyisoprene is added as a processing aid to the carbon black compounded rubber composition for a tire tread, the wear resistance and low heat build-up are maintained simultaneously. It has been found that a rubber composition for a tire tread that can improve the kneadability of the rubber component and carbon black, improve the dispersion of carbon black, and can also achieve high wear resistance can be obtained. .

  The diene rubber component used in the rubber composition for a tire tread of the present invention is 50% by weight or more, preferably 60 to 50% by weight of natural rubber and / or polyisoprene rubber with respect to 100 parts by weight of the whole diene rubber. Those containing 100% by weight are used. Examples of other diene rubber components include various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber, and ethylene-propylene rubber. Examples include diene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, and the like, and these diene rubbers are included as single or two or more kinds of blend rubbers within a predetermined range. It's okay.

The rubber composition for a tire tread of the present invention has a CTAB adsorption specific surface area (measured according to JIS K6217-3) of 80 parts by weight as a reinforcing filler with respect to 100 parts by weight of the entire diene rubber component. 30 to 150 parts by weight, preferably 60 to 120 parts by weight of fine and high-structure carbon black having a weight of ˜200 m ² / g, 24M4DBP absorption (measured in accordance with JIS K6217-4) of 80 to 120 mL / 100 g Is blended in the amount of

If the CTAB adsorption specific surface area of the carbon black is less than 80 m ² / g, the wear resistance of the resulting tire tread rubber composition is deteriorated. Conversely, if it exceeds 200 m ² / g, the rolling resistance is deteriorated. Moreover, if the 24M4DBP absorption amount thereof is less than 80 mL / 100 g, the abrasion resistance of the obtained tire tread rubber composition is deteriorated, and conversely if it exceeds 120 mL / 100 g, the mixing processability is lowered, which is not preferable. Further, if the blending amount of carbon black of the reinforcing filler is less than 30 parts by weight, the desired effects of wear resistance and rolling resistance in the present invention are not exhibited. Since workability is inferior and the desired effect of the present invention is reduced, it is not preferable.

  The rubber composition for a tire tread of the present invention further has, as a processing aid, 1 to 20 parts by weight of liquid polyisoprene having 2 to 10 carboxy groups per molecule and having a number average molecular weight of 10,000 to 60,000, The amount is preferably 2 to 15 parts by weight, more preferably 2 to 10 parts by weight. If the blending amount of the processing aid is less than 1 part by weight, the desired effect cannot be exerted. Conversely, if it exceeds 20 parts by weight, the viscosity increases and the workability decreases. The liquid polyisoprene is commercially available as, for example, trade names “Claprene LIR403” and “Claprene LIR410” represented by the following general formulas (1) and (2).

  The rubber composition for a tire tread of the present invention is further compounded for general tires such as a vulcanization or cross-linking agent, a vulcanization or cross-linking accelerator, various oils, an anti-aging agent, a filler, a softener, and a plasticizer. These compounding agents can be compounded and 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 violated.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, it cannot be overemphasized that the technical scope of this invention is not limited to these Examples.

Sample preparation According to the formulation (parts by weight) shown in Table 1, each component such as rubber and carbon black excluding sulfur and vulcanization accelerator was loaded into a 1.7 L B-type Banbury mixer and mixed for 5 minutes. The master batch after releasing the rubber to the outside of the mixer and cooling to room temperature was put into the Banbury mixer again, and sulfur and a vulcanization accelerator were blended and mixed therewith to obtain a rubber composition. Next, this rubber composition was press vulcanized at 160 ° C. for 20 minutes in a predetermined mold to prepare a test sample, which was subjected to the following test.

Test Method 1) Rolling Resistance: In accordance with JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., under conditions of initial strain = 10%, amplitude = ± 2%, frequency = 20 Hz. Tan δ (60 ° C.) was measured and the rolling resistance was evaluated with this value. The results are shown as an index with Comparative Example 1 as 100. The larger the index, the better the rolling resistance.
2) Abrasion resistance: Measured under the conditions of a load of 14.7 N, a slip rate of 50%, a time of 10 minutes, and room temperature using a Lambone abrasion tester (manufactured by Iwamoto Seisakusho) according to JIS K 6264-2. The loss on wear was expressed as an index with Comparative Example 1 as 100. It shows that abrasion resistance is excellent, so that a numerical value is large.

Examples 1-3 and Comparative Examples 1-3
The results are shown in Table 1 below.

  From the results of Table 1, in the rubber compositions of Examples 1 to 3 in which a specific carboxylic acid-modified liquid polyisoprene is blended with a carbon black compounded rubber composition, both rolling resistance and wear resistance are extremely high. It turns out that it is good.

  Therefore, the rubber composition of the present invention is extremely useful when used as a rubber composition for tire treads.

Claims (1)

30 to 150 carbon black having a CTAB adsorption specific surface area of 80 to ²⁰⁰ m ² / g and a 24M4DBP absorption of 80 to 120 mL / 100 g with respect to 100 parts by weight of diene rubber containing 50 parts by weight or more of natural rubber and / or polyisoprene rubber. A rubber composition for a tire tread comprising 1 to 20 parts by weight of a liquid polyisoprene having 2 to 10 parts by weight and 2 to 10 carboxyl groups per molecule and having a number average molecular weight of 10,000 to 60,000.