A METHOD OF PREPARING LOW OR MEDIUM-DENSITITY STRAIGHT-CHAIN POLYETHYLENE

摘要

Low or medium-density straight-chain ethylene polymers are prepared by copolymerising ethylene with a C4-C6 alpha-olefin at elevated temperature and pressure in a tubular reactor and in the presence of a Ziegler-type catalyst comprising a trialkyl aluminum as co-catalyst and a solid component, the solid component being obtained: - by spray-drying an ethanolic solution of magnesium chloride to obtain a solid substrate of magnesium chloride particles containing alcoholic hydroxylis, - by reacting the substrate with titanium tetrachloride to form an activated substrate, and - by reacting the activated substrate with an alkyl aluminium chloride to chlorinate the titanium and partially or completely reduce the titanium from the tetravelent to the trivalent state.