JP2010018641A - Rubber composition for tire tread and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tire treads which has excellent on-ice performance, and to provide a pneumatic tire. <P>SOLUTION: The rubber composition for tire treads includes 1-30 pts.wt. of a diatomaceous earth and 1-30 pts.wt. of a plant granular material with an average particle size of 100-600 μm based on 100 pts.wt. of a diene-based rubber. As the diatomaceous earth, an uncalcined diatomaceous earth is preferably used. The diatomaceous earth also preferably has an average particle size of 0.5-45 μm. A pneumatic tire having a tread consisting of the rubber composition is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread that is suitably used for a tread of a winter tire (winter tire) such as a studless tire or a snow tire, and a pneumatic tire using the rubber composition.

  On snowy and snowy roads, the friction coefficient is significantly lower than that on ordinary roads, making it easier to slip. Therefore, in winter tires such as studless tires, measures are taken to make the tread rubber that contacts the road surface less slippery.

  For example, Patent Document 1 below discloses that particles having a scratching effect such as plant granules obtained by pulverizing seed shells or fruit nuclei are added to improve the frictional performance on ice by the scratching effect. ing. In particular, in this document, the plant granule is surface-treated with a rubber adhesion improver mainly composed of a mixture of resorcin / formalin resin initial condensate and latex, thereby chemically bonding to the tread rubber and scratching effect. The point which improves is proposed.

  It is also known to improve the anti-slip effect by blending diatomaceous earth with tread rubber such as studless tires. For example, in Patent Document 2 below, non-reinforcing powder particles such as diatomaceous earth are additionally added to a rubber composition that has already been kneaded with carbon to achieve both frictional force on ice and improved wear performance. Is disclosed.

  In addition, as a technique regarding anti-slip using diatomaceous earth, 100 to 1000 parts by weight of diatomaceous earth powder having an average particle diameter of 0.5 to 150 μm is blended in Patent Document 3 below with respect to 100 parts by weight of the organic polymer material. An anti-slip material is disclosed. Although this document discloses that it is effective for preventing slipping of automobile tires, specifically, a solution is formed on the tread ground surface by applying a solution of the above-described slip-preventing material, or in the form of a sheet in advance. It is intended for use by sticking the formed material to the tread ground surface, and is not related to a technique for blending diatomaceous earth with tread rubber.

  Further, Patent Document 4 below discloses that the frictional force is augmented with diatomaceous earth, but diatomaceous earth and crushed stone powder are mixed with the back of a shoe, a tire of a vehicle, an iron road, a track, or a road surface. It is a technique for coating powder by applying, spraying or spraying, and is not related to a technique for blending diatomaceous earth with tread rubber.

On the other hand, Patent Document 5 below discloses that diatomaceous earth is blended with tire tread rubber, but this document improves dispersibility of the inorganic filler and has excellent processability, wet grip properties and low properties. In order to improve rolling resistance, the point which mix | blends diatomaceous earth as an inorganic filler by previously processing with polyethyleneglycol is disclosed, and the characteristic of this invention which is excellent in on-ice performance is not suggested.
JP-A-10-007841 JP 2002-60553 A JP-A-61-106686 Japanese Patent Application Laid-Open No. 11-14426 Japanese Patent Laid-Open No. 11-343366

  In the above-described prior art, there is room for improvement in order to exhibit sufficient on-ice performance, and in particular, it is required to exhibit excellent braking performance on both the on-ice road surface and the ice / water mixed road surface.

  This invention is made | formed in view of the above point, and it aims at providing the rubber composition for tire treads which has the outstanding performance on ice, and a pneumatic tire.

  The rubber composition for a tire tread according to the present invention contains 1 to 30 parts by weight of diatomaceous earth and 1 to 30 parts by weight of plant granules having an average particle diameter of 100 to 600 μm with respect to 100 parts by weight of a diene rubber. Is. Moreover, the pneumatic tire according to the present invention includes a tread made of such a rubber composition.

  According to the present invention, due to the scratching effect by the Mohs hardness 2 to 5 of the plant granular material, the scratching effect by the Mohs hardness 5 to 7 of the diatomaceous earth, and the water absorption effect by the porous structure having hydrophilicity, Excellent braking performance can be exhibited on both water-mixed road surfaces.

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

  Examples of the diene rubber used as the rubber component in the rubber composition of the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and styrene-isoprene. Examples include various diene rubbers that are usually used in rubber compositions for tire treads such as polymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. These diene rubbers can be used alone or in a blend of two or more.

  As the rubber component, a blend of natural rubber and another diene rubber is preferably used, and a blend rubber of natural rubber (NR) and butadiene rubber (BR) is particularly preferably used. In that case, if the ratio of BR is too small, it is difficult to obtain low temperature characteristics of the rubber composition. Conversely, if the ratio is too large, the processability tends to deteriorate and the tear resistance tends to decrease, so the ratio of NR / BR is It is preferably 30/70 to 80/20, more preferably about 40/60 to 70/30.

  A vegetable granule is mix | blended with the rubber composition of this invention. Plant granules are plant-like hard granules obtained by pulverizing seed shells or fruit nuclei, and seed shells such as walnuts and strawberries, or fruit nuclei such as peaches and plums. A pulverized product obtained by pulverization by a known method can be used. Since these have a Mohs hardness of about 2 to 5 and are harder than ice with a Mohs hardness of about 1 to 2.5, they can exhibit a scratching effect on the road surface on ice.

  The plant granular material has an average particle diameter of 100 to 600 μm in order to exhibit a scratching effect and prevent dropping from the tread. Here, the average particle diameter of the vegetable granule is a value measured by a laser diffraction particle size distribution measuring apparatus.

  In addition, as a vegetable granular material, in order to improve the compatibility with rubber and prevent falling off, it may be used that which has been surface-treated with a rubber adhesion improver, or surface-treated and surface-treated. It can also be used by mixing with those not. As the rubber adhesion improver, for example, those having a mixture of resorcin / formalin resin initial condensate and latex as main components (RFL solution) can be mentioned.

  The plant granule can be blended in the range of 1 to 30 parts by weight with respect to 100 parts by weight of the diene rubber. The blending amount of the plant granules is preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight, in order to suppress a decrease in tensile strength and tear strength.

  In the rubber composition of the present invention, diatomaceous earth particles are blended together with the plant granules. Diatomaceous earth has a Mohs hardness of about 5 to 7 and is harder than ice, so it can exert a scratching effect on the road surface on ice. Moreover, since diatomaceous earth is harder than the said plant granular material and the hardness difference with ice is large, it can exhibit the more excellent scratching effect. In addition, while the asphalt has a Mohs hardness of about 8, diatomaceous earth is softer than this, and asphalt damage can be prevented. Also, by combining plant granules with Mohs hardness 2-5 and diatomaceous earth with Mohs hardness 5-7, from the area of ice (Mohs hardness 1-2.5) to the area just before asphalt (Mohs hardness 8) A scratch effect can be exerted on road surfaces having a wide range of hardness. Moreover, since diatomaceous earth is a granular material having a porous structure having a hydroxyl group on the particle surface, that is, has a hydrophilic porous structure, water on the road surface can be absorbed into the pore. Therefore, excellent braking performance can be exhibited not only on the road surface on ice but also on the road surface in which ice and water are mixed.

  Examples of diatomaceous earth include unfired diatomaceous earth (dried diatomaceous earth), fired diatomaceous earth, and flux fired diatomaceous earth. Of these, fired diatomaceous earth and flux fired diatomaceous earth are generally commercially available, and even these can exhibit sufficient effects, but unfired unfired diatomaceous earth exhibits better effects. Can be preferred. This is because when diatomaceous earth is baked, silicon dioxide as a main component changes from amorphous to crystalline, and the hydroxyl groups on the particle surface decrease. Since uncalcined diatomaceous earth has many hydroxyl groups present on the particle surface, the reinforcing effect is high, and it is considered that the hydrophilicity of the particle surface can be increased and the water absorption into the pores can be improved.

  As the diatomaceous earth, those having an average particle diameter of 45 μm or less are preferably used, and more preferably the average particle diameter is 20 μm or less. Abrasion resistance can be improved by using such a diatomaceous earth with a small particle diameter. Moreover, by using together with the vegetable granule with an average particle diameter of 100-600 micrometers, a catch generate | occur | produces with respect to the unevenness | corrugation of various magnitude | sizes which exist on the ice surface, and it can improve the scratching effect. Although the minimum of the average particle diameter of diatomaceous earth is not specifically limited, Usually, a 0.5 micrometer or more thing is used suitably. Here, the average particle diameter of diatomaceous earth is a value measured by a laser diffraction type particle size distribution measuring apparatus, as in the case of plant granules.

  Diatomaceous earth can be mix | blended within the range of 1-30 weight part with respect to 100 weight part of diene rubbers. By using a diatomaceous earth having a small particle size as described above, it can be blended in a larger amount than the plant granular material, and the scratching effect and the water absorption effect can be enhanced. The blending amount of diatomaceous earth is more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the diene rubber.

  Carbon black and / or silica can be blended in the rubber composition of the present invention. When silica is blended, it is preferable to use a silane coupling agent in combination. The compounding amount of these carbon black and silica is not particularly limited, but is preferably 10 to 100 parts by weight, more preferably 30 to 70 parts by weight in total with respect to 100 parts by weight of the diene rubber. It is.

  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, plasticizers, anti-aging agents, zinc white, stearic acid, vulcanizing agents, vulcanization accelerators and the like. Various additives used can be blended.

  The rubber composition of the present invention can be prepared by kneading using a commonly used mixer such as a Banbury mixer or a kneader. The rubber composition is suitably used as a rubber composition for a tread portion of a winter tire (winter tire) such as a studless tire or a snow tire, and the tread portion is formed by vulcanization molding according to a conventional method. can do.

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

  Using a Banbury mixer, a tread rubber composition for studless tires was prepared according to the formulation shown in Table 1 below. Each component in Table 1 is as follows.

・ Natural rubber: RSS # 3,
-Butadiene rubber: “BR150B” manufactured by Ube Industries, Ltd.

-Plant granules: walnut shell pulverized product ("Soft Grip # 46" manufactured by Walnut Japan, surface-treated with an RFL treatment solution according to the method described in JP-A-10-7841. After treatment The average particle size of the plant granular material is 300 μm (measured with a particle size distribution measuring device “SALD-2000A” manufactured by Shimadzu Corporation. The same applies hereinafter))
Diatomaceous earth A: Flux-baked diatomaceous earth, “Radiolite F” (average particle size = 7 μm) manufactured by Showa Chemical Industry Co., Ltd.
Diatomaceous earth B: calcined diatomaceous earth, “Radiolite Fine Flow A” manufactured by Showa Chemical Industry Co., Ltd. (average particle size = 12 μm),
Diatomaceous earth C: calcined diatomaceous earth, “Radiolite # 500” manufactured by Showa Chemical Industry Co., Ltd. (average particle size = 35 μm),
Diatomaceous earth D: Unbaked diatomaceous earth (dried product), “Radiolite SPF” (average particle size = 10 μm), manufactured by Showa Chemical Co., Ltd.
Diatomaceous earth E: Unbaked diatomaceous earth (dried product), a classification product of “Radiolite SPF” manufactured by Showa Chemical Industry Co., Ltd. (average particle size = 5 μm).

  In each rubber composition, carbon black (“Seast KH” manufactured by Tokai Carbon Co., Ltd.) 25 parts by weight, silica (“Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.), and 100 parts by weight of diene rubber are commonly used. 25 parts by weight, silane coupling agent (“Si69” manufactured by Degusa) 3.0 parts by weight, paraffin oil (“JOMO Process P200” manufactured by Japan Energy Co., Ltd.) 20 parts by weight, stearic acid (“Lunac S” manufactured by Kao Corporation) -25 ") 2 parts by weight, 2 parts by weight of zinc white (" Zinc Flower 1 "manufactured by Mitsui Mining & Smelting Co., Ltd.), 2 parts by weight of anti-aging agent (" Antigen 6C "manufactured by Sumitomo Chemical Co., Ltd.), wax (Nippon Seiki 2 parts by weight of “OZOACE0355” manufactured by Sakai Co., Ltd., 2.1 parts by weight of sulfur (manufactured by Tsurumi Chemical Co., Ltd.), vulcanization accelerator (“SO Shinoru CZ ") was blended 1.5 parts by weight.

  About each obtained rubber composition, hardness (-5 degreeC, 23 degreeC) was measured. Also, studless tires were prepared using each rubber composition, and the wear resistance and braking performance on the road surface on ice (on-ice braking performance) were evaluated. The tire size was 185 / 65R14, and each rubber composition was applied to the tread and vulcanized and molded according to a conventional method. Each rim used was 14 × 5.5 JJ. Each measurement / evaluation method is as follows.

・ Hardness: Samples vulcanized at 160 ° C. for 20 minutes (thickness of 12 mm or more) according to JIS K6253, using a type A durometer, the hardness at −5 ° C. and the hardness at 23 ° C. It was measured.

Abrasion resistance: The above tire is mounted on a 2000 cc FF vehicle, rotated back and forth every 2500 km, and the remaining grooves after running 10,000 km (average value of remaining grooves of four tires) were measured. It was displayed as an index with a value of 100. A larger index indicates better wear resistance.

・ Ice braking performance: The above tire is mounted on a 2000 cc FF vehicle, and the braking distance is measured by running ABS from 40 km / h on each ice board road at −2 ° C. and −10 ° C. (average value of n = 10) ) And an index with the value of Comparative Example 2 as 100. The larger the index, the shorter the braking distance and the better the braking performance. In addition, the ice board road of -10 degreeC is equivalent to an on-ice road surface, and the ice board road of -2 degreeC is equivalent to an ice and water mixed road surface.

  A result is as showing in Table 1, and the braking performance which was excellent in both an on-ice road surface and an ice / water mixed road surface is comparative examples 2 which blended only plant granular materials as it is Examples 1-11. Obtained. Moreover, as shown in Examples 1-4 and 6-11, abrasion resistance was improving by making the average particle diameter of diatomaceous earth into 20 micrometers or less. Furthermore, by using unfired diatomaceous earth as a diatomaceous earth combined with plant granules, braking performance on ice was further improved as shown in Examples 6-11.

  The rubber composition for a tire tread according to the present invention can be used for a tread of a pneumatic tire, and can be particularly suitably used for various winter tires such as a studless tire and a snow tire.

Claims (4)

  A rubber composition for a tire tread containing 1 to 30 parts by weight of diatomaceous earth and 1 to 30 parts by weight of a vegetable granule having an average particle diameter of 100 to 600 μm with respect to 100 parts by weight of a diene rubber.   The rubber composition for a tire tread according to claim 1, wherein the diatomaceous earth is unfired diatomaceous earth.   The rubber composition for a tire tread according to claim 1 or 2, wherein the diatomaceous earth has an average particle size of 0.5 to 45 µm.   The pneumatic tire provided with the tread which consists of a rubber composition of any one of Claims 1-3.