JP2009029991A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire tread that reduces rolling resistance while maintaining wet performance. <P>SOLUTION: The rubber composition for a tire tread is formed by mixing a diene-based rubber containing a styrene-butadiene rubber with silica, a silane coupling agent and a peptone being a low-molecular-weight protein. Preferably the amount of the peptone mixed is 1-20 pts.wt. based on 100 pts.wt. of the diene-based rubber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition used for a tread of a pneumatic tire.

  In the recent development of pneumatic tires, silica that can improve the balance between wet performance, which is grip performance on wet roads, and low rolling resistance that contributes to low fuel consumption, is blended as a filler, that is, a filler. Often to do.

  Since such silica is generally inferior in dispersibility with respect to a diene rubber, a silane coupling agent is widely used in order to improve the affinity between the silica and the diene rubber (see Patent Document 1 below). However, the improvement is insufficient only by using silica and a silane coupling agent in combination.

On the other hand, in the rubber composition for tires, in order to improve wear resistance, it has been proposed to blend starch and cellulose with diene rubber (see Patent Document 2 below).
JP-A-11-269305 JP 2005-133025 A

  As described above, it has been proposed to improve the properties of the rubber composition for tires by compounding sugars such as starch and cellulose, but starch and cellulose are insufficient in improving the above properties in silica formulation. It is.

  In view of the above, an object of the present invention is to provide a rubber composition for a tire tread that can reduce rolling resistance while maintaining wet performance.

  The present inventor has intensively studied in view of the above problems, and has found that the characteristics of silica blending can be improved by adding peptone, which is a low molecular weight protein, and has completed the present invention.

  That is, the tire tread rubber composition according to the present invention is obtained by blending silica, a silane coupling agent, and peptone with a diene rubber containing a styrene butadiene rubber.

  Thus, in a silica compounding | blending, rolling resistance can be reduced by mix | blending peptone, maintaining wet performance.

  The peptone is preferably blended in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the diene rubber, whereby the rolling resistance can be reduced while maintaining wet performance and wear resistance.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition according to the present invention, a diene rubber containing styrene butadiene rubber (SBR) is used as the rubber component because it is for tire treads. The diene rubber may be a styrene butadiene rubber used alone or in combination with a styrene butadiene rubber and another diene rubber. When used in combination with other diene rubbers, although not particularly limited, it is preferable to use a blend rubber of 50% by weight or more of styrene butadiene rubber and 50% by weight or less of other diene rubbers.

  Other diene rubbers to be blended with styrene butadiene rubber are not particularly limited. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-isoprene copolymer rubber, butadiene-isoprene. Examples thereof include copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and nitrile rubber (NBR). These may be used alone or in combination of two or more.

Although it does not specifically limit as a silica mix | blended with the said rubber composition, It is preferable to use the wet silica which has a hydrous silicic acid as a main component. The specific surface area of the silica (BET method measured according to ISO 5794/1) is not particularly limited, but is preferably 100 to 300 m ² / g for tire treads.

  The compounding quantity of a silica should just be in the range which does not impair the effect of this invention, and is not specifically limited. Usually, it is preferable to mix | blend 20-100 weight part with respect to 100 weight part of rubber components, More preferably, it is 50-90 weight part. In addition, when there are too many compounding quantities of a silica, workability will be impaired.

  The silane coupling agent blended in the rubber composition is blended to promote the bonding between silica and diene rubber. Any silane coupling agent may be used as long as it is conventionally used in rubber compositions together with silica. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-Triethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-nitropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like.

  The amount of the silane coupling agent is not particularly limited as long as it is within the range not impairing the effects of the present invention, but it is usually preferably 5 to 15 parts by weight based on 100 parts by weight of silica, More preferably, it is 6 to 10 parts by weight.

  The peptone blended in the rubber composition is obtained by partially hydrolyzing protein with an enzyme, acid, or alkali, and has a low molecular weight. The main component is an amino acid and a low molecular weight polypeptide. It is thought that it works as a filler.

  In silica compounding, silica is hydrophilic, whereas diene rubber is hydrophobic. Therefore, a silane coupling agent is used to improve the dispersibility of silica. On the other hand, peptone is obtained by reducing the molecular weight of a protein composed of 20 kinds of amino acids. Among the 20 kinds of amino acids, there are hydrophobic structures and hydrophilic structures.

That is, a protein has a basic structure represented by the following general formula, and there are 20 types of R depending on the type of amino acid.

  Among them, for example, a hydrophobic amino acid in which R is a nonpolar group such as alanine, valine, leucine, isoleucine, phenylalanine and the like constitutes a hydrophobic site in a protein and peptone that is a degradation product thereof, for example, The hydrophilic amino acids in which R is a polar group such as serine, aspartic acid, glutamic acid, lysine and the like constitute a hydrophilic site in protein and peptone. Since this hydrophobic part has a high affinity with the diene rubber, it is highly dispersed even if it does not react with the silane coupling agent, and it seems that the effect as a filler is exhibited. And when peptone is considered as a filler, it is thought that it has moderate rigidity and a softness | flexibility, and, thereby, it is thought that improvement effects, such as reduction of rolling resistance, are show | played.

  Examples of the peptone used in the rubber composition include those used as culture medium raw materials for microbial tests or in various fermentation industrial media. Specifically, peptone obtained by degrading casein such as milk casein with an enzyme is preferably used.

  The average molecular weight of peptone is not particularly limited, but is preferably 10,000 to 100,000, and more preferably 10,000 to 50,000. The average particle size of peptone is not particularly limited, but the average particle size is preferably 0.1 to 100 μm, more preferably 0.1 to 10 μm. Here, the average particle diameter is a value measured using a laser diffraction particle size distribution measuring apparatus “SALD-2000A” manufactured by Shimadzu Corporation.

  The blending amount of peptone is preferably 1 to 20 parts by weight, more preferably 5 to 20 parts by weight, and still more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the diene rubber. If the blending amount of peptone is too small, the effect is insufficient. On the other hand, if the blending amount is too large, the wear resistance is deteriorated.

  In addition to the above components, the rubber composition according to the present invention includes other fillers such as carbon black, anti-aging agents, zinc oxide, stearic acid, softening agents, vulcanizing agents such as sulfur, and vulcanization acceleration. Various additives usually blended in the tire composition such as an agent and a vulcanization retarder can be blended.

  The rubber composition according to the present invention can be obtained, for example, by kneading using a kneader such as a Banbury mixer, a kneader, or a roller, and vulcanized and molded according to a conventional method to obtain tread rubber for various pneumatic tires. Can be configured.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, according to the formulation shown in Table 1 below, rubber compositions for tire treads of Examples and Comparative Examples were prepared. In addition, the amount of silica was appropriately reduced according to the increase of peptone, starch, or cellulose so that the reinforcing property as a whole filler would be the same. Each component in Table 1 is as follows.

E-SBR: “SBR1502” manufactured by JSR Corporation,
・ Silica: Tosoh Silica Industry Co., Ltd. “Nip seal AQ”, BET specific surface area = 215 m ² / g),
Silane coupling agent: “Si75” (bis- (3-triethoxysilylpropyl) disulfide) manufactured by Degussa.

-Peptone: “Polypeptone” manufactured by Nippon Pharmaceutical Co., Ltd. (milk casein decomposed with an animal-derived enzyme. Average molecular weight = 20,000, average particle size = 2.0 μm),
・ Starch: potato starch made by Nacalai Tesque,
Cellulose: “Cellulose” manufactured by Nacalai Tesque, Inc.

  In each rubber composition, 40 parts by weight of aroma oil ("Process X-140" manufactured by Japan Energy Co., Ltd.) and stearic acid (manufactured by Kao Corporation) are used as a common compound with respect to 100 parts by weight of E-SBR which is a diene rubber 2 parts by weight of “Lunac S-20”, 2 parts by weight of wax (“Sannok” manufactured by Ouchi Shinsei Chemical Co., Ltd.), 2 parts by weight of zinc white (“Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.), aging 2 parts by weight of inhibitor 6C (“NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.), 2 parts by weight of sulfur (“Polysulfur powder 150 mesh” manufactured by Hosoi Chemical Co., Ltd.), vulcanization accelerator CBS (Ouchi 2 parts by weight of “Noxeller CZ” manufactured by Shinsei Chemical Industry Co., Ltd. was blended.

  Each rubber composition obtained is applied to a cap tread of a tire having a tread having a cap / base structure, and a 205 / 65R15 94H pneumatic radial tire is manufactured in accordance with a conventional method, rolling resistance, wet performance and wear resistance. Sex was evaluated. Each evaluation method is as follows.

・ Rolling resistance: Rolling when running at 23km and 80km / h on a single-axis drum tester for measuring rolling resistance with a tire of 15x6.5JJ and a pneumatic pressure of 230kPa and a load of 450kgf. Resistance was measured. The results were expressed as an index with the value of Comparative Example 1 as a control taken as 100. The smaller the index, the smaller the rolling resistance and thus the better the fuel efficiency.

・ Wet performance: A 2000cc domestic FF car is equipped with four tires, runs on asphalt roads with water depth of 2-3mm, operates ABS at 90km / h, decelerates to 20km / h The braking distance was measured. The results were expressed as an index with the value of Comparative Example 1 as a control taken as 100. A larger index indicates better wet performance.

-Abrasion resistance: Four tyres were mounted on a 2000cc domestic FF vehicle, and the amount of wear was determined from the tread remaining groove depth after running 20,000 km while rotating every 5000 km on the general road surface of dry asphalt. The results were expressed as an index with the value of Comparative Example 1 as a control taken as 100. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.

  As shown in Table 1, in Examples 1 to 5 in which peptone was blended, the rolling resistance was reduced without substantially impairing the wet performance. In particular, when the blending amount of peptone was 5 parts by weight or more, an excellent effect of reducing rolling resistance was confirmed. In Example 5 where the blending amount of peptone was 30 parts by weight, although the rolling resistance reduction effect was excellent, the wear resistance was deteriorated. By setting the blending amount of peptone to 5 to 20 parts by weight, more preferably 5 to 15 parts by weight, it was possible to significantly reduce rolling resistance while ensuring wet performance and wear resistance.

  On the other hand, in the comparative example 2 which mix | blended starch instead of polypeptone, the reduction effect of rolling resistance was inadequate and the deterioration of wet performance was recognized. Moreover, in the comparative example 3 which mix | blended the cellulose, the reduction effect of rolling resistance was hardly acquired and abrasion resistance deteriorated.

  Thus, the outstanding effect which is not show | played with polysaccharides, such as starch and a cellulose, was acquired by mix | blending peptone which is a low molecular weight protein.

  According to the present invention, by adding peptone to the silica compound, it is possible to reduce rolling resistance while maintaining wet performance. Therefore, it is suitable for treads of various pneumatic tires including radial tires for passenger cars. It can be used, and the fuel efficiency of the tire can be improved.

Claims (2)

  A rubber composition for a tire tread comprising a diene rubber containing styrene butadiene rubber and silica, a silane coupling agent, and peptone.   The rubber composition for a tire tread according to claim 1, wherein 1 to 20 parts by weight of peptone is blended with 100 parts by weight of the diene rubber.