Abstract: The invention concerns polyethylene compositions particularly adapted for the manufacture of film and hollow bodies by blow-moulding, characterized in that they contain(a) from 50 to 98% by weight of polyethylene of high density, of at least 0.940(b) from 2 to 50% by weight of a linear, low density polyethylene, with a density below 0.930.

Abstract: The invention is addressed to solid catalysts comprising essentially compounds of magnesium and of transition metals selected from the sub-groups IVa, Va and VIa of the periodic table, applicable to the polymerization of olefins and particularly ethylene, in which the catalyst is obtained by first preparing a solid compound of magnesium, monohalogenated hydrocarbon and halogen and/or organic derivatives of the transition metal in a state of valency of at least 4 and then reacting the solid compound of magnesium and transition metal with an oxidizing compound.