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

摘要

An object of this invention is to provide a polypropylene/propylene-ethylene copolymer composition having satisfactory moldability and an excellent balance among rigidity, toughness, impact resistance, etc. This invention provides a polypropylene/propylene-ethylene copolymer composition having a melt flow rate (ASTM D-1238) of from 30 to 250 g/10 min obtained through: a first stage (polymerization step (I)) in which propylene is polymerized in the presence of a highly stereoregular catalyst and hydrogen to produce a propylene polymer having a melt flow rate of from 100 to 1,000 g/10 min and a tie molecule volume content ( beta ) of 1.10 or higher in an amount of from 90 to 95% by weight based on the total amount of the composition to be finally obtained; and a second stage (polymerization step (II)) in which ethylene and propylene are subsequently fed to the product of the first stage in such a proportion as to result in an ethylene content of from 25 to 40% by weight to produce a propylene-ethylene copolymer in an amount of from 5 to 10% by weight based on the total amount of the composition to be finally obtained. A process for producing the composition is also provided.