The Toyo Rubber Industry Co., Ltd.

Toyo Tire Rubber Co., Ltd.

Masanori Kan

Tatsuo Sakashita

Takuya Okazaki

Keijiro Oda

Hideo Fujiwara

Akira Yoshida

Takyya Okazaki

The invention relates to a radial tire in which each sidewall covering and protecting the side face of the carcass is composed of a plurality of layers differing in rubber composition. In the radial tire according to the invention, the sidewall has a three-layer structure consisting of an adjesive layer adjacent to the carcass, an inner layer disposed outwardly thereon and an outer layer disposed further outwardly thereon. The rubber components in the rubber compositions respectively constituting the three layers differ in proportions of the rubber having as low degree of unsaturation and the rubber having a high degree of unsaturation and the high-unsaturation rubber content decreases in the order of adhesive layer, inner layer and out layer. While retaining the endurance characteristics and ozone resistance of the conventional tires, the radial tire according to the invention is improved in that its good appearance can be prevented from being spoiled by staining or discoloration of its side portions. In spite of the use of rubbers having a low degree of unsaturation, the invention provides a radial tire having sidewalls excellent in adhesiveness to the carcass and other portions made of a diene rubber composition.

Radial tire with a sidewall having a three-layer structure

A composition for tires containing at least 30% star shaped random styrene-butadiene copolymer obtained by solution polymerization, having a styrene content of less than 20% and more than 10% and a vinyl content of less than 50% and more than 40%, the composition value X of said copolymers being in a range of 26 to 39 obtained by using the equation; ##EQU1## wherein BR is the butadiene component, the glass transition temperature being a single one below -50.degree. C. and lower than estimated glass transition temperature following Gordon-Taylor equation by 5.degree. to 10.degree. C. and a cured composition showing loss modulus of lower than 1.times.10.sup.-7 dyn/cm.sup.2 and a ratio of rolling resistance to wet grip being smaller than 0.82.

Compositions for tires

A composition for pneumatic tires including more than 30% of star shaped styrene-butadiene copolymers by solution polymerization with or without one or more types of natural rubbers or diene series synthetic rubbers. The composition value X of the solution polymerization star shaped SBR is obtained by the following equation. ##EQU1## wherein BR is the butadiene component and the vinyl content is the content of 1, 2 bonded butadiene in butadiene component. The value X falls in the range of the lower limit of 26 to the upper limit of 39. And the coupling efficiency of the solution polymerization star shaped SBR is more than 40%.

Composition for pneumatic tires

A carcass rubber composition for tires comprising a polymer blend of diene synthetic elastomer and natural rubber. Said diene synthetic elastomer contains a solution polymerization star shaped SBR, preferably, in the ratio of 20-50 percent. 1, 2 structure in the butadiene unit is preferably less than 50 percent. The styrene content is preferably 10-20 percent.

Composition for carcass of tire

An automotive tire tread having a low rolling resistance including a cap tread rubber and a base tread rubber wherein the value of the loss tangent of the cap tread rubber is not more than 0.24 and the value of the resilience of the cap tread rubber is more than 60%. In addition, the value of the loss tangent of the base tread rubber should be less than that of the cap tread rubber.

Tire tread having low rolling resistance

A rubber composition for a side wall of tires comprising a polymer blend of 20-100 parts by weight of solution polymerization star shaped SBR and 80-0 parts by weight of natural rubber and/or diene synthetic rubber. The glass transition temperature (Tg) of said star shaped SBR is preferably less than -50.degree. C. Styrene content in said star shaped SBR is preferably less than 20% parts by weight.

Rubber composition for side wall of tire

The present invention relates to a pneumatic safety tire, which is provided with a ring-shaped projection of high rigidity along its circumferential direction, outside of at least one bead of the pneumatic tire, wherein the projection has a smaller diameter than the diameter of the rim flange to which the tire is fitted. The ring-shaped projection is designed so that it projects to the outside along the rim flange, and moreover, the tire is adhered integrally by vulcanization together with two ring-shaped elastic reinforcements and halogenated butyl rubber-containing protective layer in the inside of the tire at each position corresponding to the portion from the sidewall to the adjacent shoulder. Thus, the purpose of the invention is to provide a pneumatic safety tire, which can be driven safely without there happening such an accident as separation of the bead of the tire from the rim during running, even when the tire is run flat and moreover, has a good stability and durability in running also in such a state.

Growing community of inventors

Amagasaki, Japan

Masanori Kan