MULTIPLICITY OF MOLECULAR-WEIGHT DISTRIBUTION OF POLYETHENE PRODUCED WITH MODIFIED-POLYPROPENE-SUPPORTED ZIEGLER CATALYST SYSTEMS

The molecular weight and molecular weight distribution of polyethene p repared with a modified-polypropene-supported Ziegler catalyst were in vestigated in terms of the variation of the polymerization conditions, such as the kind of co-catalyst, its concentration, and polymerizatio n temperature. Ethene polymerization with the catalyst in the presence of triethylaluminium proceeded in heterogeneous system to give a poly ethene with extremely broad molecular weight distribution. The result was completely changed upon replacing the triethylaluminium by other a lkylaluminium compounds, such as diethylaluminium chloride. Polyethene s with very broad, narrow, bimodal, and multimodal molecular weight di stributions were obtained by simply varying the co-catalyst. The molec ular weight distributions of polyethenes obtained were also very sensi tive to co-catalyst concentration and polymerization temperature. From the results obtained, it is suggested that the modified-polypropene-s upported Ziegler catalyst is feasible as a novel candidate for a catal yst system giving polyethenes with controlled molecular weight distrib utions in a wide range of molecular weight.