JP2008150554A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition compounded with a large amount of silica and useful as a rubber composition for a tire tread. <P>SOLUTION: The rubber composition for a tire tread is produced by compounding 100 pts.wt. of a diene rubber with 30-100 pts.wt. of a reinforcing filler containing ≥10 pts.wt. of silica having a BET specific surface area of 100-300 m<SP>2</SP>/g, 0.1-15 wt.% silane coupling agent based on the compounded amount of the silica and 0.1-20 pts.wt. of lecithin. The invention solves the problems of retarded vulcanization, viscosity increase, etc., caused by the addition of a large amount of silica, improves various vulcanization properties and improves the productivity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for tire treads. More specifically, the present invention solves problems such as vulcanization delay and viscosity increase associated with a large amount of silica, improves various vulcanization physical properties, and at the same time increases productivity. The present invention relates to an improved silica compounded rubber composition for tire treads.

  With respect to a cap compound containing a large amount of silica, the problem is to improve the rubber physical properties of the vulcanized rubber by avoiding the high cohesiveness of the silica itself, and various processing aids have been proposed. For example, polysiloxane (patent document 1), n-alkylamine compound (patent document 2), tertiary amine compound (patent document 3), aminosilane compound (patent document 4), organosilane compound (patent document 5), etc. Techniques to do this have been proposed. However, as a solution including the problem of the vulcanization rate delay inevitably generated at the time of silica compounding, it cannot be said that it is sufficient yet, and there is room for further improvement.

JP-A-9-111044 JP 2000-17107 A Japanese Patent Laid-Open No. 10-120828 Japanese Patent Laid-Open No. 10-67884 JP 9-208749 A

  Therefore, an object of the present invention is to improve various vulcanization properties of the silica-containing rubber composition and improve productivity at the same time by adding a predetermined amount of lecithin to the silica-containing rubber compound.

According to the present invention, 30 to 100 parts by weight of a reinforcing filler containing 10 parts by weight or more of silica having a BET specific surface area of 100 to 300 m ² / g with respect to 100 parts by weight of diene rubber, and the amount of silane coupling agent added to silica A rubber composition for tire treads containing 0.1 to 20 parts by weight of lecithin in a rubber composition containing 0.1 to 15% by weight based on the weight is provided.

  In the present invention, it has been found that the above-mentioned object can be achieved by blending a predetermined amount of a predetermined lecithin into a silica-blended rubber composition, particularly a silica-blended rubber composition having a high silica content.

  Examples of the diene rubber in the present invention include natural rubber (NR), polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubbers ( Diene synthetic rubbers such as NBR) and chloroprene rubber (CR) can be used alone or in combination of two or more thereof.

In the present invention, with respect to 100 parts by weight of the diene rubber, 30 to 100 parts by weight of a reinforcing filler containing 10% by weight or more of silica having a BET specific surface area of 100 to 300 m ² / g, and a silane coupling agent is added to the silica. Further, lecithin is further blended in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, in a rubber composition blended in an amount of 0.1 to 15% by weight. If the blended amount of the lecithin is less than 0.1 parts by weight, the desired effect cannot be exhibited. Conversely, if it exceeds 20 parts by weight, bleeding occurs, which is not preferable.

  In general, lecithin is a phospholipid that is abundant in soybeans, egg yolks, and the like, and either crude or purified lecithin can be used as the lecithin used in the present invention. Crude lecithin is mainly composed of phospholipids such as phosphatidylcholine, phosphatidylserine, phosphatidylic acid, phosphatidylethanolamine, and phosphatidylinositol, and contains triglycerides, glycolipids, sterols and tocopherols, carbohydrates, and the like. Purified lecithin can be obtained by purifying components other than phospholipids contained in the crude lecithin by a purification method using the solubility of the metal salt complex of lecithin, or a column chromatography method using aluminum oxide or silicic acid. It consists of a mixture of the phospholipids removed so as to be in a small amount.

The silica of the reinforcing filler used in the rubber composition of the present invention is not particularly limited. For example, dry method white carbon, wet method white carbon, colloidal silica, and JP-A-62-62838. Examples include the disclosed precipitated silica. These silicas can be used alone or in combination of two or more. When the specific surface area of silica is, in particular, a nitrogen adsorption specific surface area (BET method) in the range of 100 to 300 m ² / g, more preferably 120 to 220 m ² / g, the reinforcing property, wear resistance, and exothermicity. It is preferable that the improvement of the above is sufficiently achieved. Here, the nitrogen adsorption specific surface area is a value measured by the BET method according to ASTM D3037-81. In the rubber composition of this invention, the said silica can be mix | blended in the range of 10-100 weight part with respect to 100 weight part of rubber components.

  In addition to the above-mentioned silica, the reinforcing filler blended in the rubber composition of the present invention further includes carbon black, clay, alumina, aluminum hydroxide, silicon carbide, calcium metasilicate, titanium dioxide, talc, calcium carbonate. Etc. may be blended in a predetermined blending amount.

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

Preparation of test sample The ingredients except the sulfur and vulcanization accelerator in the rubber compounding system shown in Table 1 below were kneaded for 3 to 5 minutes with a 1.7 L closed mixer and released when the temperature reached 165 ± 5 ° C. Sulfur and a vulcanization accelerator were added to the batch and kneaded with an 8-inch open roll to obtain a rubber composition. A part of this rubber composition was subjected to a viscosity test (Mooney viscosity). Next, the remainder of the rubber composition was press vulcanized in a 15 cm × 15 cm × 0.2 cm mold at 160 ° C. for 20 minutes to produce a test piece (rubber sheet), and the hardness, viscoelasticity test, and silica dispersion Subjected to sex test.

Test / Evaluation Method 1) Mooney Viscosity (ML _{1 + 4} ): In accordance with JIS K 6300, using Mooney viscometer with L-shaped rotor (38.1 mm diameter, 5.5 mm thickness), preheating time 1 minute The measurement was performed under the conditions of a rotor rotation time of 4 minutes, 100 ° C., and 2 rpm. The result is shown as an index with Comparative Example 1 being 100. It shows that it is so favorable that a numerical value is small.
2) Hardness: Based on JIS K 6253, the hardness at 20 ° C. was measured using a spring type A hardness tester. The result is shown as an index with Comparative Example 1 being 100. It shows that it is so favorable that a numerical value is large.
3) tan δ (0 ° C., 60 ° C.): Measured according to JISK 6394. The vulcanized rubber sheet is a 2 mm thick rubber sheet punched out into a strip with a width of 5 mm, a thickness of 2 mm and a length of 20 mm. Using a rheographic solid made by Toyo Seiki Seisakusho, initial strain = 10%, The tan δ (0 ° C.) and tan δ (60 ° C.) at 0 ° C. and 60 ° C. were measured at a mechanical strain = ± 2% and a frequency = 20 Hz. The result is shown as an index with Comparative Example 1 being 100. In tan δ (0 ° C.), the larger the value, the better. In tan δ (60 ° C.), the smaller the value, the better.
4) Silica dispersibility: Storage measured with a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. at an initial strain of 10% at room temperature and an amplitude of 0.1 to 9.5% every 0.2%. The elastic modulus E ′ and the loss elastic modulus E ″ were measured, and E ′ (0) −E ′ (∞) was calculated from the colle-core plot. The result is shown as an index with Comparative Example 1 being 100. The numerical value is large. It shows that it is so good.

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

  From the results shown in Table 1, it can be seen that when a predetermined amount of lecithin is blended in the silica-blended rubber composition, a rubber composition having excellent processability and silica dispersibility, and excellent hardness and viscoelasticity can be obtained.

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

Claims (2)

30 to 100 parts by weight of a reinforcing filler containing 10 parts by weight or more of silica having a BET specific surface area of 100 to 300 m ² / g with respect to 100 parts by weight of a diene rubber, and a silane coupling agent to 0.1 parts by weight of silica. A rubber composition for tire treads, wherein lecithin is blended in an amount of 0.1 to 20 parts by weight in a rubber composition blended in an amount of -15% by weight.   The rubber composition for a tire tread according to claim 1, wherein 0.5 to 10 parts by weight of the lecithin is blended.