To obtain a rubber compsn. which has horizontal stiffness with a low bearing pressure dependence and shear modulus not decreasing even under a high bearing pressure by specifying the ratio of modulus to static shear modu lus at a specified percentage deformation in a repeated deformation test with an autograph.
This compsn. exhibits an elasticity ratio of modulus M100 to static shear modulus Gs at the third time in a repeated 100% tensile deformation test with an autograph of 1.4 or higher and a ratio of modulus M300 at the third time in a repeated 300% tensile deformation test to M100 of 3.6 or lower. The compsn. is prepd. by compounding 100 pts.wt. rubber component comprising natural rubber alone or a mixture thereof with an isoprene rubber with up to 15 pts.wt. polymer (e.g. a chloroprene rubber) having a solubility parameter different from that of natural rubber by at least 0.3 (MPa)1/2, 1-30 pts.wt. clay mainly comprising hydrated aluminum silicate, a filler (e.g. carbon black), a vulcanizing agent (e.g. sulfur), a vulcanization aid, a vulcanization accelerator, an antioxidant, etc.
SHIMADA ATSUSHI
OISHI HIDEYUKI
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