Low pressure process for the production of low density co- and terpolymers of ethylene

Claim 1

In a process for the production of low density thermoplastic ethylene copolymers by low pressure copolymerization of ethylene with 0.1 to 20 molar percent of an α-olefin comonomer selected from the group consisting of propylene, butene-1 and mixtures thereof with a particulate mixed polymerization catalyst consisting essentially of (a) titanium trichloride and (b) a trialkylaluminum or a dialkylaluminum hydride in a molar ratio Al:Ti of 0.5 - 4.0, the improvement which comprises conducting the polymerization as a liquid phase solution polymerization employing a polymerization solvent consisting essentially of C 4 or a mixture of C 3 and C 4 hydrocarbons containing 0.1-20 molar percent of said α-olefin, 1-60 molar percent of butane, propane or mixtures thereof and 20-98.0 molar percent of butene-2 to form said copolymer product substantially free of homopolymers, provided that the maximum amount of butene-1 present in the solvent mixture is not greater than 5 molar percent and the maximum amount of propylene is not greater than 3 molar percent at a polymerization temperature of 70 to 100°C.; the maximum amount of butene-1 present in the solvent mixture is not greater than 10 molar percent and the maximum amount of propylene is not greater than 5 molar percent at a polymerization temperature of 50 to 70°C.; and the maximum amount of butene-1 present in the solvent mixture is not greater than 20 molar percent and the maximum amount of propylene is not greater than 15 molar percent at a polymerization temperature of 20°to 50°C.