PURPOSE: To obtain the title composition excellent in heat aging resistance, weather resistance, low-temperature flexibility, etc., by adding a vulcanizer and a filler to a random copolymer rubber having a specified composition and specified properties.
CONSTITUTION: The composition is prepared by adding a vulcanizer and a filler to a copolymer rubber which is a random copolymer rubber comprising ethylene, propylene and 7-methyl-1,6-octadiene and has an ethylene/propylene molar ratio of 55/45 to 80/20, an iodine value of 7-30, an intrinsic viscosity of 2-6dl/g as measured in decalin at 135°C, a Tαβ/Tαα intensity ratio in a carbon isotope NMR spectrum of 0.5 or below, a B value of 1-1.5 wherein the B value is calculated from the NMR spectrum data according to the equation wherein PE is the molar fraction of the ethylene contained in the rubber; PO is the molar fraction of the propylene contained in the rubber; and POE is the rate of the number of the propylene/ethylene chains to the total number of the diad chains and a glass transition temperature of -53°C or below.
NAKAHAMA HIDENARI
HONMA KIYOSHI
