Abstract: A preparation process for a catalytic support, based on a special alumina modified with varying quantities of magnesium chloride is described, a higher rate of MgCl.sub.2 leading to a lesser quantity of heavy molecular chains in the final polymer. The support, prepared by milling the special alumina together with the MgCl.sub.2 previously treated with ethyl benzoate, is impregnated with TiCl.sub.4 in order to create the catalyst. The resulting catalysts show high activity, which enables the metallic residue and chloride eliminating stage to be avoided in the resin so created. Furthermore the types of molecular weight distribution and of mechanical properties are different for the polymers produced.

Abstract: A preparation process for a catalytic support, based on a special alumina modified with varying quantities of magnesium chloride is described, a higher rate of MgCl.sub.2 leading to a lesser quantity of heavy molecular chains in the final polymer. The support, prepared by milling the special alumina together with the MgCl.sub.2 previously treated with ethyl benzoate, is impregnated with TiCl.sub.4 in order to create the catalyst. The resulting catalysts show high activity, which enables the metallic residue and chloride eliminating stage to be avoided in the resin so created. Furthermore the types of molecular weight distribution and of mechanical properties are different for the polymers produced.

Abstract: Description of the preparation of a Ziegler type catalyst system through impregnation of a special alumina with 0.8-1.0% by weight of titanium derived from a dilute solution of titanium halide in n-hexane, the activator employed being triisobutylaluminum or triethylaluminum at an (Al)/(Ti) molar ratio of 2.5/1 to 80/1 in the catalyst. The catalyst system has high efficiency and yield, and leads to polyethylenes of excellent physical and mechanical properties which make it particularly suitable for use in engineering plastics.