To obtain a composition having an excellent processability and an excellent balance of specific gravity, elastic modulus, strength and hardness by blending a specific amount of each of a thermoplastic elastomer and a short fiber with a rubber.
This rubber composition comprises 100 pts.wt. of a rubber component obtained by blending 100 pts.wt. of a rubber such as a natural rubber, a styrene-butadiene rubber or the like and 5-100 pts.wt. of a thermoplastic elastomer, 5-20 pts.wt. of a short fiber and optionally additives such as a filler like carbon black, a process oil, a wax, stearic acid, zinc oxide, sulfur, a vulcanization promoter or the like. The thermoplastic elastomer has a Mooney viscosity [ML(1+4)130°C] of 30-60 and a softening point of 80-130°C. A styrene-butadiene block copolymer and a thermoplastic polyolefin can be mentioned as the thermoplastic elastomer. The short fiber has an average diameter of 0.1-100 μm and an average fiber length of 50-5,000 μm. An aromatic polyamide such as poly-p- phenyleneterephthalamide or the like, an aliphatic polyamide such as nylon 6 or the like, a polyurea such as polyheptamethyleneurea can be mentioned as the material of the fiber.
MURAOKA KIYOSHIGE
YAGI NORIKO
