Preparation of granular or powdered polypropylene@, or propylene@ mixed polymer

摘要

Preparation of granular or powdered polypropylene or propylene mixed polymers comprises: (1) polymerising the corresponding monomers using Ziegler-Natta catalysts, with alkyl alkoxysilane as stereo modifier, aluminium alkylenes and hydrogen as molecular weight regulator at 50-90 deg C; (2) evaporating excess propylene or monomer mixture, then cooling to 20-35 deg C and returning to the reactor; (3) adding fresh monomer (mixture); (4) removing the obtained polymer with the aid of unreacted monomer (mixture) by opening the discharge pipes (6) in the powder bed for a short time and degassing the monomer (mixture) dissolved in the polymer and obtaining it with the flash evaporation gas; and (5) degassing the polymer still containing monomer (mixture) over a bucket wheel sluice (10) in a degassing zone at high temperature in a nitrogen stream. The novelty is that the product is degassed at 60-70 deg C and 0.1-0.5 bar for 30-60 mins. using a 50 kg nitrogen stream.