Ziegler natra catalyst for the polymerization of olefins

摘要

Catalyst for the polymerization of olefins CH₂═CHR, wherein R is hydrogen or a hydrocarbon radical having 1-12 carbon atoms, comprising (I) a solid catalyst component comprising Mg, Ti, Cl, and OR groups, where R is a C1-C10 alkyl group optionally containing heteroatoms, in which the Ti/Mg weight radio is from 2 to 6.5 the Cl/Ti weight ratio is from 1.5 to 3.5 to and the OR/Ti weight ratio is from 0.7 to 2.5 and at least 50% of the titanium atoms are in a valence state lower than 4 and (II) an alkyaluminum halide as cocatalyst. The said catalysts allow the preparation of ethylene copolymers with a low content of xylene soluble fractions.