| abstract |
A catalyst component comprising Ti, Mg, Al, Cl, and optionally OR 1 groups in which R 1 is a C1-C20 hydrocarbon group, optionally containing heteroatoms, up to an amount such as to give a molar OR 1 /Ti ratio lower than 0.5, characterized by the fact that substantially all the titanium atoms are in valence state of 4, that the porosity (P F ), measured by the mercury method and due to pores with radius equal to or lower than 1 μm, is at least 0.3 cm 3 /g, and by the fact that the Cl/Ti molar ratio is lower than 29. n The said catalysts are characterized by high morphological stability under the low molecular weight ethylene polymerization conditions while at the same time maintaining characteristics of high activity. |