US Patent 7335715 Ethylene-alpha-olefin copolymer

An ethylene-α-olefin copolymer having monomer units derived from ethylene and monomer units derived from an α-olefin of 3 to 20 carbon atoms, a density of 906 to 970 kg/m3, an activation energy of flow of 50 kJ/mol or more and a heat quantity of fusion of a cold xylene soluble part of 30 J/g or more, and satisfying specific relations among a rate of the cold xylene soluble part in the copolymer, the density, a melt flow rate and a characteristic relaxation time.