POLYPROPYLENE/PROPYLENE-ETHYLENE COPOLYMER COMPOSITION AND PROCESS FOR THE PREPARATION THEREOF

摘要

A polypropylene/propylene-ethylene copolymer composition which is excellent in moldability and well balanced among rigidity, toughness, impact resistance and so on; and a process for the preparation thereof. The composition is one having a melt flow rate (ASTM D-1238) of 30 to 250 g/10 min and being prepared through the first step of polymerizing propylene in the presence of a highly stereoregular polymerization catalyst and hydrogen to prepare a propylene polymer having a melt flow rate of 100 to 1000 g/10 min and a tie molecule volume fraction ( beta ) of 1.10 or above in an amount of 90 to 95 wt.% based on the final composition and the second step of adding ethylene and propylene to the product of the first step in such amounts as to give an ethylene content of 25 to 40 wt.% to prepare a propylene-ethylene copolymer in an amount of 5 to 10 wt.% based on the final composition.