Linear ethylene copolymer

Claim 1

A copolymer of ethylene with at least one C 4 -C 20 α-olefin having the following characteristics (A) to (J) (A) it has a melt flow rate, determined by ASTM D 1238E, of from 0.01 to 200 g/10 min., (B) it has a density of from 0.880 to less than 0.900 g/cm 3 (C) it has a composition distribution parameter (U), defined by the following equation (1) U-100×(Cw/Cn-1) (1) wherein Cw is the weight average degree of branching, and Cn is the number average degree of branching, of not more than 50, (D) the amount of components having a degree of branching of not more than 2/1000 carbons is not more than 10% by weight based on the ethylene copolymer, (E) the amount of components having a degree of branching of at least 30/1000 carbons is not more than 70% by weight based on the ethylene copolymer, (F) the ratio of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) it has n melting points measured by a differential scanning calorimeter (DSC) (wherein n=1 or n≦3), in which the highest melting point (T 1 ) among these DSC melting points is given by the following expression (i) (175×d-46)°C.≦T.sub.1 ≦125° C. (i) wherein d is the density (g/cm 3 ) of the copolymer, the difference between T 1 and the lowest melting point (T n ) among the DSC melting points is given by the following expression (ii) 18° C.<T.sub.1 -T.sub.1 ≦65° C. (ii), and the difference between T 1 and the second highest melting point (T 2 ) is given by the following expression (iii) 0° C.<T.sub.1 -T.sub.2 ≦20° C. (iii) provided that when the number of melting points is one (i.e., n=1), only the expression (i) is applicable and the expressions (ii) and (iii) are not applicable, (H) when n≧3 in the characteristic (G) above, the ratio of the amount of heat or crystal fusion (H 1 ) at the highest melting point T 1 to the total amount of heat of crystal fusion (H T ) is given by the following expression O<H.sub.1 /H.sub.T ≦0.40, (I) it has a crystallinity, measured by an X-ray diffraction method, of from 15 to 70%, and (J) it has a molecular weight distribution M/M wherein M is the weight average molecular weight of the copolymer and M is the number average molecular weight of the copolymer, measured by gel permeation chromatography of from 2.5 to 10.