Process for copolymerizing ethylene

Claim 1

A process for copolymerizing ethylene with one or more higher α-olefin monomers employing a catalyst composition prepared by forming a precursor composition from a magnesium compound, titanium compound, and electron donor compound, and then activating the precursor composition with an organoaluminum compound to form the catalyst, characterized in that the polymerization is conducted continuously in a fluid bed reactor at a temperature of 30 to 105°C under a pressure of <69 bar (<1000 psi) in the gas phase to produce ethylene copolymer containing >90 mol percent of ethylene and <10 mol percent of one or more C 3 to C 8 a-olefins at a productivity of >50,000 kg of polymer per kg of Ti, said copolymer being produced in granular form and having a density of >0.91 to ≤0.94 g/cm 3 and a melt flow ratio of ≥22 to ≤32, by contacting the monomer charge with, in the presence of 0 to 2.0 mols of hydrogen per mol of ethylene in the gas phase reaction zone, particles of an activated precursor composition of the formula wherein R is a C, to C 14 aliphatic or aromatic hydrocarbon radical, or COR' wherein R' is a C 1 to C 14 aliphatic or aromatic hydrocarbon radical, X is selected from the group consisting of Cl, Br, I or mixtures thereof, ED is a liquid organic electron donor compound in which said precursor composition is soluble and which is selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones, m is >0.5 to <56, n is 0, 1 or 2, p is >2 to <116, and q is >2 to <85, said precursor composition being impregnated in an inert porous carrier in a weight ratio of 0.033:1 to 1:1, and being activated with an activator compound having the formula wherein X' is Cl or OR"', R" and R"' are the same or different, and are C 1 to C 14 saturated hydrocarbon radicals, d is 0 to 1.5, e is 1 or 0 and c+d+e=3, activation of said precursor composition being effected by treating the impregnated precursor composition outside the polymerization reactor in a hydrocarbon slurry with >0 to <10 mols of activator compound per mol of titanium compound in said precursor composition, drying the mixture to obtain a free-flowing solid particulate material, and feeding the impregnated precursor composition into the polymerization reactor wherein it is further activated by adding additional activator compound to the reactor in such amounts as to provide >10 to <400 total mols of said activator compound per mol of titanium compound in said precursor composition.