PROCEDIMENTO PER LA POLIMERIZZAZIONE DI ETILENE

In a slurry polymerization for producing an ethylene homopolymer or ethylene- alpha -olefin copolymer in multiple stages, in which the gas phase hydrogen concentration in each stage is different, using a catalyst system comprising a transition metal compound component and an organoaluminum compound component, the improvement which comprises conducting the polymerization by the use of a solid catalyst component comprising a titanium compound and/or vanadium compound supported on a specified magnesium compound, as the transition metal compound component, in a molar ratio of gas phase hydrogen to ethylene of 0.5 to 15 in the first stage thereby obtaining 30 to 95% by weight, of the total polymer, and in the second stage in a molar ratio of gas phase hydrogen to ethylene, not exceeding 0.2. By this process, it is possible to produce polyethylene having high melt flow and good homogeneity to give molded articles having fewer fish-eyes and less unevenness.