Abstract: Disclosed herein is a rubber composition for use in vibration insulating material, which comprises as rubber components 5-50 parts by weight of a copolymer consisting of 99.5-45% by weight of a conjugated diolefin, 0.5-30% by weight of an ethylenically unsaturated carboxylic acid and 0-40% by weight of another vinly monomer polymerizable therewith, and 50-95 parts by weight of at least one rubber selected from natural rubber and synthetic diene rubbers. This rubber composition is excellent in the breaking properties and vibration insulating properties with a small temperature dependence of hysteresis loss.

Abstract: A pneumatic radial tire comprising: (1) a cylindrical tread portion; (2) side portions located at both sides of the tread portion and extending inwardly in the radial direction; (3) bead portions located at the inner edge portions of the side portions; (4) a carcass comprising at least one ply which is reinforced with a belt arranged on the inside of the tread portion, wherein said belt and/or said carcass ply is reinforced by steel cords; and (5) a rubber composition surrounding the steel cords, wherein said rubber composition comprises: (a) 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and dienic synthetic rubber; (b) 0.1-5.0 parts by weight of alkadiene sulfone; and (c) 0.05-1.0 parts by metal weight of at least one metal salt of an organic acid selected from the group consisting of cobalt salt of an organic acid and nickel salt of an organic acid.

Abstract: A rubber composition having an improved crack growth resistance is disclosed, which contains 1-40 wt % of granular bodies having an average particle diameter of 5-500 .mu.m, which contain 2-40 wt % of micro short fibers having an average diameter of not more than 1 .mu.m, an average length of 1-30 .mu.m and an aspect ratio of not less than 8 and orientated in uniaxial or biaxial direction, and is random in the orientation axis of the micro short fiber between the granular bodies.

Abstract: Rubber compositions having improved tensile strength, elongation and modulus of unvulcanized rubbers without deteriorating physical properties of vulcanized rubbers are prepared by utilizing synergistic effect of addition of a filler having high reinforcing property and alkadiene sulfones in given amounts to natural rubber and/or dienic synthetic rubbers.