JP2008019334A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for a tire tread having improved wet performance, low fuel consumption and reduction in viscosity (mixing processability) while securing abrasion resistance by mixing specific solution polymerization SBR with a fixed amount of active zinc oxide. <P>SOLUTION: The rubber composition for a tire tread is obtained by mixing 100 parts wt. of diene-based rubber comprising ≥30 parts wt. of solution polymerization SBR having an Mw of ≥800,000 and an Mw/Mn of ≥2.0 with 5-35 parts wt. of active zinc oxide having an average particle diameter of 0.05-0.20μm and a BET specific surface area of 50-150m<SP>2</SP>/g in 30-150 parts wt. of the total reinforcing filler. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread, and more specifically, while blending a specific solution-polymerized styrene-butadiene copolymer rubber (solution-polymerized SBR) and active zinc oxide, while ensuring wear resistance. The present invention relates to a rubber composition for a tire tread that achieves wet performance, low fuel consumption, and reduced viscosity (mixed processability).

  Today, in many passenger car tires, it is common to add silica to the tread portion in order to improve wet handling stability and low rolling resistance. However, there is a constant demand for improvements in performance and processing, such as further improvement of these properties and reduction of compound viscosity during processing by silica blending.

The following Patent Document 1 contains 0.1 to 20 parts by weight of zinc oxide (active zinc oxide) having a specific surface area of 10 m ² / g or more in the diene rubber composition, while maintaining grip performance. A rubber composition having both low rolling resistance and high wear resistance is proposed. Patent Document 2 discloses a rubber composition containing natural rubber and a diene rubber having a glass transition temperature of −70 ° C. or lower. In addition, by adding 1 to 30 parts by weight of high specific surface area zinc oxide (active zinc oxide) having a nitrogen adsorption specific surface area of 20 m ² / g or more by BET method, the performance on ice is improved without impairing the wear resistance. Studless tires have been proposed.

JP 2003-55505 A Japanese Patent Laid-Open No. 2002-265673

  In the present invention, wet performance, low fuel consumption, and reduced viscosity (mixed processability) are improved while ensuring wear resistance by blending a specific amount of specific solution polymerized SBR and active zinc oxide. It aims at providing the rubber composition for tire treads.

According to the present invention, the total reinforcing filler is 30 to 150 parts by weight with respect to 100 parts by weight of diene rubber containing 30 parts by weight or more of solution-polymerized SBR with Mw = 800,000 or more and Mw / Mn = 2.0 or more. Among them, there is provided a rubber composition for a tire tread comprising 5 to 35 parts by weight of active zinc oxide having an average particle size of 0.05 to 0.20 μm and a BET specific surface area of 50 to 150 m ² / g.

  In the present invention, when a predetermined amount of active zinc oxide is blended with a diene rubber containing a predetermined amount of solution-polymerized SBR having a high molecular weight and a wide molecular weight distribution, the strength of the rubber matrix is ensured, so that the wear resistance is improved. In addition, it has been found that since the dispersion of active zinc oxide is promoted, the effects of wet performance, low rolling resistance and viscosity reduction can be improved.

  As a rubber component used in the rubber composition for a tire tread of the present invention, at least 30 parts by weight of solution polymerization SBR having Mw = 800,000 or more and Mw / Mn = 2.0 or more in 100 parts by weight of a diene rubber. The diene rubber composition containing the above is used. Here, Mw represents a weight average molecular weight, and Mn represents a number average molecular weight. The molecular weight (Mw) and molecular weight distribution (Mw / Mn) were selected from the viewpoints of wear resistance and strength of the resulting rubber composition. The total amount of the diene rubber component may be the specific solution polymerization SBR. If the specific solution polymerization SBR contained in the diene rubber is 30 parts by weight or less, the desired effect cannot be obtained, which is not preferable.

  Examples of the diene rubber component excluding the specific solution-polymerized SBR in the present invention include diene rubbers generally used in such tire tread parts, such as natural rubber (NR), various butadiene rubbers (BR), and various styrene-butadiene copolymers. Polymer rubber (SBR), polyisoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene- Butadiene copolymer rubber and isoprene-butadiene copolymer rubber can be used. These diene rubbers may be used alone or as a blend rubber of two or more.

In the rubber composition for a tire tread of the present invention, the active zinc oxide used in combination with the specific solution polymerization SBR described above has an average particle diameter from the viewpoint of wear resistance and cohesiveness of the resulting rubber composition. Specific active zinc oxide having a BET specific surface area of 50 to 150 m ² / g is selected and used, and the blending amount of the active zinc oxide is 100 parts by weight of the diene rubber. It is blended and used in an amount of 5 to 35 parts by weight based on the weight. If the blending amount is less than 5 parts by weight, the desired effect cannot be obtained, and if it exceeds 35 parts by weight, the strength and wear resistance are lowered, which is not preferable.

  The rubber composition for a tire tread of the present invention further includes a reinforcing agent such as carbon black and silica, a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, a silane coupling agent, various oils, an antiaging agent, and a filler. Various compounding agents blended in tire rubber compositions such as plasticizers can be blended, and these compounding agents can be kneaded by a general method to form a rubber composition, which can be vulcanized or crosslinked. it can. 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 demonstrate this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Sample preparation In the formulation (parts by weight) shown in Tables 1 and 2, the components other than the vulcanization accelerator and sulfur were kneaded for 5 minutes using a 1.7 L closed Banbury mixer and released when the temperature reached 150 ° C. To obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this masterbatch with an open roll to obtain a rubber composition. A part of the obtained rubber composition was used for the following Mooney viscosity test. Next, the remaining rubber composition was vulcanized at 160 ° C. for 30 minutes in a predetermined mold to prepare a vulcanized rubber sheet, which was subjected to the following wet performance, rolling resistance and abrasion resistance tests.

Test Method 1) Viscosity (Mooney Viscosity): In accordance with JIS 6300, an L-shaped rotor (38.1 mm diameter, 5.5 mm thickness) was used with a Mooney viscometer, the preheating time was 1 minute, and the rotor rotation time was 4 Measured at 100 ° C. and 2 rpm. Table 1 shows an index with Comparative Example 1 as 100, and Table 2 shows an index with Comparative Example 5 as 100. The larger the value, the lower the viscosity and the better the workability.
2) Wet performance (tan δ (0 ° C.)) Using a viscoelastic spectrometer manufactured by Ueshima Seisakusho, tan δ (0 ° C.) was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz. Table 1 shows an index with Comparative Example 1 as 100, and Table 2 shows an index with Comparative Example 5 as 100. It shows that wet performance is excellent, so that a numerical value is large.
3) Rolling resistance (tan δ (60 ° C.)): Using a viscoelastic spectrometer manufactured by Ueshima Seisakusho Co., Ltd., tan δ (60 ° C.) was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz. Table 1 shows an index with Comparative Example 1 as 100, and Table 2 shows an index with Comparative Example 5 as 100. It shows that it is excellent in rolling resistance, so that a numerical value is large.
4) Abrasion resistance (Lambourne wear): A wear loss volume was measured at room temperature, a slip rate of 50%, and a load of 15 N using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264. Table 1 shows an index with Comparative Example 1 as 100, and Table 2 shows an index with Comparative Example 5 as 100. It shows that abrasion resistance is so favorable that a numerical value is large.

Examples 1-3 and Comparative Examples 1-6
The results are shown in Tables 1 and 2.

  According to Tables 1 and 2, the rubber composition of the present invention containing a specific amount of the specific solution-polymerized SBR and active zinc oxide according to the present invention has a reduced processing viscosity and improved wet performance, rolling resistance and wear resistance. You can see that

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

Claims (1)

Average particle diameter of 30 to 150 parts by weight of total reinforcing filler with respect to 100 parts by weight of diene rubber containing 30 parts by weight or more of solution-polymerized SBR with Mw = 800,000 or more and Mw / Mn = 2.0 or more A rubber composition for a tire tread formed by blending 5 to 35 parts by weight of active zinc oxide having 0.05 to 0.20 μm and a BET specific surface area of 50 to 150 m ² / g.