Abstract: A novel supported catalyst for polymerization of ethylene or its mixtures with C.sub.3 to C.sub.8 terminal olefins composed of (a) the solid reaction product of a titanium (IV) or vanadium (V) alkoxide, a hydrated magnesium stannate and an alkylaluminum dichloride, and (b) an organo-aluminum compound promoter. The catalyst produces polyolefin in good yield without any substantial production of polymer fines and the catalyst is quite sensitive to hydrogen induced chain termination processes leading to improved molecular weight control and rheology of the polymer product.

Abstract: A process for drying polymer slurry produced in slurry or bulk phase polymerization comprising removing, in a gas stream which contains polymerizable monomer, easily vaporizable liquid components from a stirred drying zone containing a large, in comparison with the volume of slurry from said polymerization added to said zone, amount of solid polymer particulate to form substantially dry polymer particulate using in essential part polymerization heat generated in said zone by carrying out therein a fraction of the overall amount of polymerization. The resulting polymer can be finished conventionally or by transferring said particulate to a melting zone in which an easily transferable polymer melt is formed, said melting accomplished in substantial part using polymerization heat generated in said melting zone by a fraction of the overall amount of polymerization.