JP4762561B2 - Rubber composition for tire tread - Google Patents

Description

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

  Recently, with increasing interest in the environment and safety, tires have been strongly demanded to improve fuel economy and handling stability including grip performance on wet roads.

  In general, in order to reduce fuel consumption, silica is blended in the rubber composition for tire treads, and at the same time, a silane coupling agent is blended. It is difficult to achieve both low fuel consumption and handling stability with only the agent.

By the way, in the following Patent Document 1, 0.1 to 10 parts by weight of at least one saccharide selected from monosaccharides, disaccharides or more, and derivatives thereof is blended with 100 parts by weight of diene rubber. A rubber composition for a tire tread has been proposed. As the saccharides, D-glucose and D-fructose are listed as monosaccharides, maltose and lactose are listed as polysaccharides, and sugar alcohols such as inoseal and deoxy sugars are listed as derivatives thereof. And according to this rubber composition, it describes that abrasion resistance and aging resistance are improved, without impairing a fracture characteristic, wet grip property, exothermic property, and workability.
Japanese Patent Laid-Open No. 11-71481

  With the prior art of Patent Document 1, it is difficult to improve steering stability in tire performance without impairing fuel efficiency. In fact, even in the examples described in the same document, the wet grip property and the heat generation property are not improved at all by adding the saccharide, and only the performance equivalent to that in the case of no addition is obtained.

  The present invention has been made in view of the above points, and provides a rubber composition for a tire tread capable of improving grip performance and improving steering stability without impairing fuel efficiency. For the purpose.

The rubber composition for a tire tread according to the present invention that solves the above problems comprises at least one modified polysaccharide selected from the group consisting of guar gum and cellulose modified with an epoxy compound with respect to 100 parts by weight of a diene rubber. In addition to blending 0.1 to 10 parts by weight and 10 to 120 parts by weight of silica, 0.5 to 20 parts by weight of a silane coupling agent is blended with respect to 100 parts by weight of silica .

  According to the present invention, by adding such a specific modified polysaccharide, it is possible to improve steering stability without impairing fuel efficiency.

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

  In the rubber composition of the present invention, the diene rubber is not particularly limited, and various diene rubbers that are usually used in a tire tread rubber composition can be used. For example, natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated Examples thereof include butyl rubber, and these may be used alone or in combination of two or more.

  The modified polysaccharide used in the rubber composition of the present invention is a polysaccharide modified with an epoxy compound, that is, modified by substituting the hydroxyl group of the polysaccharide with an epoxy compound. Such a modified polysaccharide is conventionally used as a thickening component of a lower alcohol (see JP 2002-212298 A), and by adding this to a rubber composition for a tire tread, low fuel consumption can be achieved. An unexpected effect was found that the steering stability could be improved without loss. The reason why such an excellent effect is exhibited is not necessarily clear, but it is considered that compatibility with the diene rubber can be improved by using a modified polysaccharide modified with an epoxy compound. On the other hand, in the technique disclosed in Patent Document 1, there is a problem in the compatibility between the saccharide used and the diene rubber, and thus it is considered that the steering stability is not improved.

In the modified polysaccharide, the polysaccharide as a base, guar gum (a galactomannan), cellulose and the like, may be used and these alone or in combination.

  Although it does not specifically limit as said epoxy compound used as a modifier, It is preferable to use alkylene oxides, such as ethylene oxide, propylene oxide, butylene oxide, and these are used individually or in combination of 2 or more types, respectively. May be. As long as the modified polysaccharide is modified with an epoxy compound, the modified polysaccharide may be modified with two or more kinds of modifiers by combining an epoxy compound and another modifier.

  In the present invention, as the modified polysaccharide, a polysaccharide hydroxyalkylated with an alkylene oxide, that is, a hydroxyalkyl-modified polysaccharide is preferable. The production method of the hydroxyalkyl-modified polysaccharide is not particularly limited, but a conventionally known method of adding an alkylene oxide to a polysaccharide using an alkali such as caustic soda or caustic potassium as a catalyst can be used. Thus, alkylene oxide is added to the hydroxyl group of the polysaccharide by an ether bond, and the resulting polysaccharide has a hydroxyalkyl group.

  The modification amount of the modified polysaccharide is not particularly limited, but the degree of substitution is preferably 0.1 to 3.0, more preferably 0.4 to 1.2. Here, the degree of substitution means the number of hydroxyl groups substituted with an epoxy compound per ring structure of the saccharide. If the degree of substitution is less than 0.1, it is difficult to obtain the effect of improving the steering stability.

  The modified polysaccharide is blended in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the diene rubber. When the blending amount of the modified polysaccharide is less than 0.1 parts by weight, the above-described effects of the present invention cannot be sufficiently exerted, and when it exceeds 10 parts by weight, a lump due to poor dispersion can be formed, and the effects of the present invention can be achieved. It cannot be fully demonstrated.

  Various fillers such as carbon black, silica, titanium oxide, aluminum silicate, clay, and talc can be blended with the rubber composition of the present invention. As the filler, it is preferable to use silica alone or to use silica and carbon black in combination. In that case, the silica is preferably blended in an amount of 10 to 120 parts by weight, more preferably 30 to 100 parts by weight, based on 100 parts by weight of the diene rubber.

  It is preferable to mix | blend a silane coupling agent with the said silica in the rubber composition of this invention. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, and 3-mercaptopropyltrimethoxy. Examples thereof include silane, 3-mercaptopropyltriethoxysilane, 3-nitropropyltrimethoxysilane, and γ-aminopropyltriethoxysilane. It is preferable that the compounding quantity of a silane coupling agent is 0.5-20 weight part with respect to 100 weight part of silica, More preferably, it is 5-15 weight part.

  In addition to the components described above, the rubber composition of the present invention is generally used in rubber compositions for tire treads such as softeners, anti-aging agents, zinc white, stearic acid, vulcanizing agents, and vulcanization accelerators. Various additives can be blended.

  The rubber composition of the present invention is used as a rubber composition for a tread of a pneumatic tire, and a tread can be formed by vulcanization molding according to a conventional method.

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

(Examples 1-5 and Comparative Examples 1-3)
Using a Banbury mixer, a rubber composition was prepared according to the formulation shown in Table 1 below. The detail of each component of Table 1 is as follows.

SSBR: solution polymerization styrene-butadiene copolymer rubber “VSL5025-0HM” manufactured by LANXESS
・ BR: JSR butadiene rubber “BR01”
・ Silica: “Nippil AQ” manufactured by Tosoh Silica
Silane coupling agent: “Si69” manufactured by Degussa.

-Xanthan gum: Rhodia Nikka's unmodified xanthan gum "Lord Pole 23"
・ Guar gum: Rhodia Nikka's unmodified guar gum "Jaguar S"
-Modified guar gum 1: Hydropropylated guar gum manufactured by Rhodia Nikka (Guar gum modified with propylene oxide; the same applies hereinafter) "Jaguar HP-8" (degree of substitution = 0.4)
Modified guar gum 2: Hydropropylated guar gum “Jaguar HP-60” manufactured by Rhodia Nikka (degree of substitution = 0.6)
-Modified guar gum 3: hydroxypropylated guar gum "Jaguar HP-120" manufactured by Rhodia Nikka (degree of substitution = 1.2)
Modified cellulose: Hydroxyethylated cellulose manufactured by Akzo Nobel (cellulose modified with ethylene oxide) “Vermocol 351” (degree of substitution = 0.85).

  Each rubber composition includes 1 part by weight of a wax (“Paraffin Wax 155” manufactured by Nippon Seiki), 1 part by weight of an anti-aging agent (“NOCRACK 6C” manufactured by Ouchi Shinsei Chemical), and zinc as common additives. 2 parts by weight of Hana (Mitsui Kinzoku "Zinc Oxide 2 types"), 2 parts by weight of stearic acid (Kao "Lunac S-25"), vulcanization accelerator DPG (Ouchi Shinsei Chemical "Noxeller D") 2 Part by weight, 1.8 parts by weight of a vulcanization accelerator CZ (“Noxeller CZ” manufactured by Ouchi Shinsei Chemical) and 2 parts by weight of sulfur (“5% oil-filled fine powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.) were blended.

  Pneumatic tires were produced using the obtained rubber compositions, and low fuel consumption and steering stability were evaluated. The tire was manufactured by applying each rubber composition to a cap tread of a 205 / 65R15 94H pneumatic tire having a tread having a cap / base structure, and vulcanizing and molding the rubber composition according to a conventional method. The rim used was 15 × 6.5JJ. Each evaluation method is as follows.

-Low fuel consumption: The rolling resistance was measured with a uniaxial drum tester at a speed of 80 km / h, an air pressure of 230 kPa, and a load of 450 kg. The smaller the value, the better the fuel economy.

-Steering stability: The driver who is in charge of the actual vehicle feeling test driving a test vehicle equipped with prototype tires to judge straightness and lane changeability when driving on dry and wet roads by feeling, Comparative Example 1 ( Control tires) “+2” for better, “+1” for better, “± 0” for equivalent, “−1” for slightly inferior, “−2” for inferior evaluated.

  The results are as shown in Table 1, and in Comparative Examples 2 and 3 in which unmodified polysaccharides (xanthan gum and guar gum) were added to Comparative Example 1 (control tire), the effect of improving steering stability was obtained. In addition, the fuel economy was slightly worse. On the other hand, in Examples 1 to 4 to which hydroxypropylated guar gum was added and Example 5 to which hydroxyethylated cellulose was added, steering stability was improved without substantially impairing the fuel economy.

  Since the rubber composition according to the present invention can improve the steering stability without impairing the fuel efficiency, it can be suitably used for a tread rubber of a pneumatic tire.

Claims (3)

0.1 to 10 parts by weight of at least one modified polysaccharide selected from the group consisting of guar gum and cellulose modified with an epoxy compound and 10 to 120 parts by weight of silica are blended with 100 parts by weight of diene rubber. In addition, a rubber composition for a tire tread comprising 0.5 to 20 parts by weight of a silane coupling agent based on 100 parts by weight of the silica .   The rubber composition for a tire tread according to claim 1, wherein the modified polysaccharide is a hydroxyalkyl-modified polysaccharide modified with an alkylene oxide.   The rubber composition for a tire tread according to claim 1 or 2, wherein the degree of substitution of the modified polysaccharide is 0.1 to 3.0.