Mitsui Chemicals, Inc.

Takasi Nakagawa

Mamoru Takahashi

Masaaki Ohgizawa

A process for preparing an ethylene/&agr;-olefin copolymer, which includes the steps of (A) copolymerizing ethylene and an &agr;-olefin of 3 to 20 carbon atoms by continuous vapor phase polymerization; (B) copolymerization is conducted in the presence of a prepolymerized catalyst obtained by prepolymerizing an olefin in the presence of (a) a transition metal compound, (b) an organoaluminum oxy-compound, (c) a fine particle carrier, and optionally (d) an organoaluminum compound; and (C) copolymerization is conducted under such condition that the partial pressure of sum total of ethylene and &agr;-olefin is 10 to 28 kg/cm . The resulting ethylene/&agr;-olefin copolymer has the following properties: (i) the density is in the range of 0.880 to 0.960 g/cm , (ii) the melt flow rate of 190&deg; C. under a load of 2.16 kg is in the range of 0.1 to 100 g/10 min, (iii) the melt tension (MT (g)) at 190&deg; C. and the melt flow rate (MFR (g/10 min)) satisfy the relation MT&lE;2.2&times;MFR .

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Wako-cho, Japan

Takasi Nakagawa