| abstract |
Components of catalysts for the polymerization of olefins are ob tained by contacting a Ti compound of formula Ti(OR)n-yXy, where n is the valence of titanium and y is a number between 1 and n, with a pre-polymer having a porosity higher than 0.3 cc/g and containing from 0.5 to 100 g of polymer per g of solid catalyst component, the pre-polymer being obtained by (co)polymerizing an olefin or a diolefin in the presence of a catalyst comprising a Ti, V, Zr of Hf compound supported on an Mg dihalide having a mean crystallite dimension lower than 30 nm. |