TWO-STAGE PROCESS FOR PRODUCING POLYPROPYLENE COMPOSITIONS

摘要

A process for polymerizing propylene in the presence of a polymerization catalyst by polymerizing propylene with a comonomer selected from the group of ethylene and C4-C10 alpha-olefins in two polymerization stages where the comonomer is present in at least one of the polymerization stages. The first polymerization stage is conducted in a loop reactor and the second polymerization stage in a gas phase reactor. The polymer produced in first polymerization stage has a higher melt flow rate and a lower content of comonomer units than the final polymer mixture. The process can be operated with a high throughput and catalyst productivity. The polymers are useful for making films.