Ethylene- alpha -olefin-nonconjugated polyene random copolymer

Disclosed is a process for preparing an ethylene- alpha -olefin-nonconjugated polyene random copolymer comprising random copolymerizing (a) ethylene, (b) an alpha -olefin of 3 or more carbon atoms and (c) a nonconjugated polyene in the presence of a metallocene catalyst containing a specific metallocene compound. The ethylene- alpha -olefin-nonconjugated polyene random copolymer prepared by the process has such properties that (i) the copolymer contains units derived from ethylene (a) and units derived from the alpha -olefin of 3 or more carbon atoms (b) in a molar ratio of 40/60 to 95/5 [(a)/(b)], (ii) the iodine value is 1 to 50, (iii) the intrinsic viscosity ( eta ) is more than 0.1 dl/g and less than 8.0 10 dl/g, (iv) the intensity ratio D of T alpha beta to T alpha alpha in the 13C-NMR spectrum, T alpha beta /T alpha alpha , is not more than 0.5, (v) the B value is 1.00 to 1.50, (vi) the glass transition temperature Tg is not higher than -50 DEG C., and (vii) the ratio g eta * of the intrinsic viscosity ( eta ) of this copolymer defined above to the intrinsic viscosity ( eta )blank of a straight-chain ethylene-propylene copolymer having the same weight-average molecular weight as this random copolymer and having an ethylene content of 70% by mol, ( eta )/( eta )blank, is more than 0.9. Also disclosed is a vulcanizable rubber composition containing the random copolymer. The ethylene- alpha -olefin-nonconjugated polyene random copolymer and the rubber composition are excellent in mechanical strength, weathering resistance, ozone resistance, processability, low-temperature flexibility and heat resistance.