Verfahren zur Herstellung von Blockmischpolymerisaten von alpha-Olefinen

摘要

A polyolefin composition is produced by the sequential polymerization of at least two different a -olefins to give a free-flowing slurry or suspension of polymer in diluent, in the presence of a catalyst comprising an organo-aluminium activator and the product obtained by reducing titanium tetrachloride in inert hydrocarbon solution by adding an aluminium dialkyl chloride gradually thereto at a temperature of between -20 and +20 DEG C. using a molar ratio of aluminium dialkyl chloride to titanium tetrachloride of from 0.55/1 to 1.5/1. Suitable organo-aluminium activators include aluminium trialkyls and triaryls, aluminium alkyl halides and aluminium alkyl hydrides. Preferably two monomers are present together in the polymerization zone so that some degree of random copolymerization may take place. In the examples propylene is first polymerized in the presence of hydrogen in a mixed aliphatic hydrocarbon diluent and then while some propylene monomer still remains ethylene is introduced. The catalyst is prepared by reducing titanium tetrachloride with aluminium diethyl chloride (using a solution of the sesquichloride) and activating the washed slurry so produced with aluminium diethyl chloride. The polymerized product is purified by treating with isopropyl alcohol, water and steam distillation.