Patent ID: 8063147

Claim:
A transmission belt, comprising a rubber composition comprising a Ziegler-Natta catalyst type ethylene/propylene/diene copolymer rubber, which is an ethylene/propylene/diene copolymer rubber obtained by polymerization in the presence of a Ziegler-Natta catalyst, the ethylene/propylene/diene copolymer rubber containing individual monomer components so that a weight proportion of an ethylene component is from 50 to 70% by weight, that of a propylene component is from 25 to 45% by weight, and that of a diene component is from 4 to 8% by weight, and a metallocene type ethylene/propylene/diene copolymer rubber, which is an ethylene/propylene/diene copolymer rubber obtained by polymerization in the presence of a metallocene catalyst, the ethylene/propylene/diene copolymer rubber containing individual monomer components so that a weight proportion of an ethylene component is from 50 to 70% by weight, that of a propylene component is from 25 to 45% by weight, and that of a diene component is from 4 to 8% by weight, wherein the ratio by weight of the Ziegler-Natta catalyst type ethylene/propylene/diene copolymer rubber to the metallocene type ethylene/propylene/diene copolymer rubber is from 50/50 to 90/10.