| abstract |
Propylene-ethylene copolymer compositions excellent in moldability and well-balanced among rigidity, tenacity, impact resistance, and so on. Specifically, a propylene-ethylene copolymer composition having a melt flow rate of 10 to 300 g/10 min, which is prepared through the polymerization step (I) of polymerizing propylene in the presence of a catalyst for highly stereoregular polymerization and hydrogen to produce 60 to 95 % by weight (based on the whole polymer) of a propylene polymer having a melt flow rate (ASTM D-1238) of 100 to 1000 g/10 min and a ratio (Cf) of the integrated amount of a propylene polymer dissolved in o-dichlorobenzene over a temperature range of lower than 112° C to that over a temperature range of 112 °C and above of 0.5 or below as determined by measuring the amounts of the propylene polymers dissolved in o-dichlorobenzene at each temperature while raising the temperature of o-dichlorobenzene continuously or stepwise, the ratio (Cf) being an indication of the intramolecular stereoregularity and molecular weight distribution of the polymer, and the polymerization step (II) of adding propylene and ethylene to the propylene polymer produced in the step (I) in such amounts that the ethylene content falls within a range of 30 to 80 % by weight and conducting polymerization to produce 5 to 40 % by weight (based on the whole polymer) of an ethylene-propylene copolymer; and another propylene-ethylene copolymer composition comprising the above composition and an α-crystal and/or β-crystal nucleating agent. |