Controlling molecular distribution of ethylene (co)polymers - by controlling temp of polymerisation effected with Ziegler catalyst-hydrogen

摘要

Mol. wt. distribution of polyethylene and ethylene/alpha-olefin copolymers prepd. by gas phase (co)polymsn. in the presence of hydrogen and a Ziegler catalyst is controlled by suitably adjusting the polymsn. temp. to 85 to 115 degrees C, the temp. being increased to contract the mol. wt. distribution, and decreased to expand the mol. wt. distribution. The catalyst is prepd. by (a) combining (I) a vadadium cpd. with (II) RnAl (OR)3-n (where R is 1-12C hydrocarbyl; and n is 0.5-2.0), (b) combining the prod. with (III) a trialkylaluminium, and (c) depositing the prod. on (IV), a support. Efficient control of the mol. wt. distribution without any change in the catalyst compsn. is achieved. Polymers for a particular end use can be prepd., e.g. for injection moulding or blow moulding.