Bridgestone Corporation

Naohiro Sasaka

Kazuo Yagawa

Hiroshi Kobayashi

Kohshi Katoh

Hiroshi Mouri

Akiyoshi Shimizu

Naoto Yamagishi

Tetsunori Haraguchi

Eiji Nakamura

Yoichiro Kondo

Kazuo Hayashi

Shigeo Kimura

Masayuki Ohashi

Shizuo Iwasaki

Naofumi Ezawa

A pneumatic tire obtained by using a rubber composition containing 100 parts by mass of a rubber component comprising at least one of natural rubber and diene base synthetic rubber, 20 to 150 parts by mass of precipitated silica as a filler in which a cetyltrimethylammonium bromide-adsorbing specific surface area (CTAB) (m/g) and the mode Ain diameters (nm) of primary aggregates determined by acoustic measurement of particle size distribution satisfy equation (A) shown below and in which a difference between an ignition loss (mass reduction % when heated at 750&#xb0; C. for 3 hours) and a heating loss (mass reduction % when heated at 105&#xb0; C. for 2 hours) satisfies equation (B) shown below and 1 to 25 parts by mass of at least one specific sulfur-containing silane compound as a silane coupling agent:&#x2266;&#x2212;0.76&#xd7;(CTAB)+274&#x2003;&#x2003;(A)(ignition loss)&#x2212;(heating loss)&#x2266;3&#x2003;&#x2003;(B).

Pneumatic tire

A rubber composition and a pneumatic tire formed by using the rubber composition is provided which has excellent snow and ice control and braking performance on snowy and/or icy road surface and provides a satisfactory wet skid performance. The present invention is a rubber composition and pneumatic tire formed using the rubber composition in at least the tread portion thereof, the rubber composition comprising a 100 parts by weight of rubber component comprising (1) 5 percent by weight to 50 percent by weight of low molecular weight butadiene rubber (BR) having a cis 1,4-structure of 60 mol % to 98 mol % and a weight average molecular weight (Mw) of 5000 to 80000; and (2) 50 percent by weight to 90 percent by weight of styrene-butadiene rubber (SBR) having a bound styrene content of 15 percent by weight to 45 percent by weight and amount of a vinyl bonding in the butadiene portion of 7 mol % to 60 mol %; and 40 parts by weight to 95 parts by weight of silica.

Rubber composition and pneumatic tire formed using the rubber composition

A pneumatic radial tire comprises a tread portion having a two-layer structure of a cap rubber layer disposed outward in the radial direction and a base rubber layer disposed inward in the radial direction, in which an outer surface of said base rubber layer in the radial direction being existent in a position corresponding to not less than 20% of a depth of a main groove formed in the tread portion outward from a bottom of the main groove in the radial direction, and the base rubber layer being compounded with a recrosslinking inhibition assistant and/or an inorganic compound powder.

Pneumatic radical tire having cap base tread

The present invention provides a method for estimating a tire wear life which enables estimation of the tire wear life accurately in a short time. In this method, a rubber index Gi of a rubber test piece which is made of the same material as the material used in the tire tread portion of the tire whose tire wear life is to be estimated is measured using an abrasion tester which can be operated under a slip ratio of about 0.5 to 5% (step,). Then, friction energies of the tire in free rolling, in a state in which the tire is provided with a toe angle, in a state in which a side force is applied to the tire, in a state in which a driving force is applied to the tire and in a state in which a braking force is applied to the tire are measured (step,), respectively. An expected value of the tire wear life T1 is calculated from the rubber index Gi and the friction energies obtained above (step,). The tire wear life is estimated from the expected value of the tire wear life T1 thus obtained (step,).

Method for estimating a tire wear life

There is disclosed a rubber composition for a tire tread Which comprises 100 parts by weight of (A) a rubber component comprising a diene-based synthetic rubber or a mixture of a diene-based synthetic rubber and natural rubber and containing at least 20% by weight of a styrene-butadiene rubber; 5 to 50 parts by weight of (B) aluminum hydroxide powders; and at least 5 parts by weight of (C) silica powders, wherein the total amount of the components (B) and (C) is in the range of 40 to 80 parts by weight; and optionally chemical agents such as vulcanizing agents, vulcanization accelerators and antioxidants, and also is disclosed a pneumatic tire in which the above rubber composition is used as the tread rubber. The above rubber composition, when made into a tire tread, can maintain favorable low fuel consumption properties and low wear resistance, and besides can impart the tire with greatly improved gripping properties on wet road surfaces particularly at a low temperature. Moreover, the pneumatic tire made from the above rubber composition can exert excellent effect of maintaining a high maneuverability from the initial stage of running to and after the middle stage thereof.

Rubber composition for tire tread and pneumatic tire using same

A wear resistance index G,of a tire whose wear life is to be estimated is measured by the Lambourn abrasion tester. Then, friction energies in free rolling, when the tire is fitted with a toe angle, under application of a side force, under application of a braking force and under application of a driving force of the tire are measured. An expected value of the wear life T,is calculated using the wear resistance index G,and the friction energies thus obtained and the wear life of the tire is estimated on the basis of the expected value of the wear life T,. The wear life of a tire can be estimated accurately in a short time in accordance with the method for estimating a tire wear life of the present invention.

A pneumatic tire comprising a tread portion formed by using a rubber composition which comprises: a rubber component comprising 50 parts by weight or more of SBR in 100 parts by weight of the rubber component; optionally, 5 to 40 parts by weight of aluminum hydroxide per 100 parts of the rubber component; per 100 parts by weight of the rubber component, 20 parts by weight or more of a softener which comprises 5 to 55 parts by weight of a specific resin softener having a softening point of 35 to 150&deg; C.; and per 100 parts by weight of the rubber component, 0.2 to 10.0 parts by weight of a specific vulcanization accelerator of a dithiophosphoric acid compound or a specific vulcanization accelerator of a benzothiazole compound. The pneumatic tire exhibits excellent stability and controllability on wet roads or a combination of excellent stability and controllability on wet roads and excellent comfort of ride even when a vehicle is vibrating throughout the life of the pneumatic tire.

Pneumatic tire with tread formed with a rubber compound containing a rubber component, a softener and a benzothiazole compound type vulcanization accelerator

A pneumatic tire comprising a tread which contacts a road surface and comprises a rubber composition which contains a rubber component composed of 70% by weight or more of a copolymer of a conjugated diene and a vinyl aromatic hydrocarbon and a remaining amount of another synthetic rubber and/or natural rubber, at least one reinforcing filler selected from a group consisting of carbon black and silica, and at least one type of vulcanization accelerator, such as bis(4-methylbenzothiazolyl-2)-disulfide, bis(5-methylbenzothiazolyl-2)-dis ulfide, mercapto-4-methylbenzothiazole, and mercapto-5-methylbenzothiazole, an amount of the reinforcing filler being 45 to 120 parts by weight and an amount of the vulcanization accelerator being 0.5 to 5.0 parts by weight per 100 parts by weight of the rubber component. Decrease in chipping resistance during tire use is suppressed, and both abrasion resistance and controllability on wet roads after use of the tire are improved.

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Kodaira, Japan

Naohiro Sasaka