Patent ID: 9458259
Filing Date: 2016-10-04
CPC Classification: B29B,C08F

Claim Text:
1. A process for treating polyolefin particles produced by a gas-phase polymerization of one or more olefins in the presence of a polymerization catalyst system and a C 3 -C 5 alkane as a polymerization diluent in a gas-phase polymerization reactor comprising: a) discharging the polyolefin particles continuously or discontinuously from the gas-phase polymerization reactor and transferring the particles to a first degassing vessel; b) contacting therein the polyolefin particles with a gaseous stream comprising at least 85 mol-% of C c) transferring the polyolefin particles to a second degassing vessel; d) contacting therein the polyolefin particles with a stream comprising nitrogen and steam while the polyolefin particles have an average residence time in the second degassing vessel of from 5 minutes to 2 hours, wherein the contacting is carried out using a stream comprising 2-20% by mol water vapor at conditions under which no condensation of water occurs; e) transferring the polyolefin particles to a third degassing vessel; f) contacting therein the polyolefin particles with a stream of nitrogen while the polyolefin particles have an average residence time in the third degassing vessel of from 5 minutes to 8 hours.