Abstract: Use of a catalyst composition treated with a surface modifier in the polymerization of olefins for lowering the gel content in the resulting polyolefin, wherein the surface modifier has a polar residue capable of interacting with the surface of the catalyst composition and a lipophilic residue and is selected from carboxylate metal salts, nitrogen containing catalyst surface modifiers, phosphorus containing catalyst surface modifiers, oxygen containing catalyst surface modifiers, sulfur containing catalyst surface modifiers, fluoro containing polymeric catalyst surface modifiers or mixtures thereof and wherein the gel content is determined by using pressed plate gel analysis method.

Abstract: A procatalyst composition which is suitable for the homo- and copolymerization of alpha olefins together with an organometallic cocatalyst compound and which is prepared by treating an inorganic carrier with a component system containing a complex of a magnesium halide and a tetraalkyl titanate, and a chlorinating compound which does not contain a transition metal compound. In order to raise the Mg:Ti ratio, the component system additionally contains an organomagnesium compound.

Abstract: The present invention relates to a procatalyst composition for the polymerization of alpha-olefines, which has been prepared in steps, in which is arranged a carrier agent based on at least one inorganic oxide, having few or no hydroxyl groups on its surface, and the carier agent is reacted with the magnesium compound and one or more transition metal compounds of the groups IVB and VB of the periodic table.

Abstract: A problem in the conventional olefin polymerization catalyst systems, the procatalysts of which are based on a solid carrier and a titanium compound and an electron donor on its surface, is that unsufficiently high activities are achieved by the morphology of the carrier. Moreover, the active age of such a catalyst in the polymerization is too short. These problems have now been solved by the olefin polymerization catalyst system according to the invention, the procatalyst of which comprises a solid carrier and a layer on its surface consisting of a titanium compound, a magnesium compound and an electron donor. The advantages of the invention become more emphasized when using monocyclopentadienyl titaniumtrichloride as the titanium compound.