MULTISTAGE PROCESS FOR THE POLYMERIZATION OF OLEFINS

摘要

Process for preparing a polyolefin polymer from one or more olefins by gas-phase polymerization at temperatures of from 40°to 150°C and pressures of from 0.1 to 20 MPa in the presence of a polymerization catalyst in a polymerization reactor cascade comprising a fluidized-bed reactor and a multizone circulating reactor, in which multizone circulating reactor the growing polymer particles flow upward through a first polymerization zone under fast fluidization or transport conditions, leave said first polymerization zone and enter a second polymerization zone through which they flow downward under the action of gravity, leave said downcomer and are reintroduced into the riser, thus establishing a circulation of polymer, wherein the polymerization in the multizone circulating reactor is carried out in the presence of a combination of - a hydroxyester having at least one free hydroxyl group, obtained from reacting a polyalcohol with a carboxylic acid having from 4 to 22 carbon atoms and - an ethoxylated alkylamine or ethoxylated alkylamide comprising an alkyl group of from 2 to 20 carbon atoms where the total amount of hydroxyester fed to the multizone circulating reactor and to any upstream polymerization reactor is from 3 to 300 ppm with respect to the total amount of olefins fed to the multizone circulating reactor and to any upstream polymerization reactor and the amount of ethoxylated alkylamine or ethoxylated alkylamide fed to the multizone circulating reactor and to any upstream polymerization is from 5 to 1000 ppm with respect to the total amount of olefins fed to the multizone circulating reactor and to any upstream polymerization reactor.