Process for gas-phase polymerization of olefins

Abstract

Process for the preparation of heterophasic propylene copolymer compositions (RAHECO) made from or containing a random propylene copolymer (RACO) and an elastomeric propylene copolymer (BIPO), the process being carried out in a reactor having two interconnected polymerization zones, a riser and a downcomer, wherein growing polymer particles: (a) flow through the first polymerization zone, the riser, under fast fluidization conditions in the presence of propylene and of ethylene or an alpha-olefin having from 4 to 10 carbon atoms, thereby obtaining the random propylene copolymer (RACO); (b) leave the riser and enter the second polymerization zone, the downcomer, through which the growing polymer particles flow downward in a densified form in the presence of propylene and of ethylene or an alpha-olefin having from 4 to 10 carbon atoms, wherein the concentration of ethylene or of the alpha-olefin in the downcomer is higher than in the riser, thereby obtaining the elastomeric propylene copolymer (BIPO); and (c) leave the downcomer and are reintroduced into the riser, thereby establishing a circulation of polymer between the riser and the downcomer.

Dependencies are inferred from the claim text.