Patent ID: 6569960
Filing Date: 2003-05-27
Classification: C08F,Y10T

Abstract:
A process comprising polymerizing ethylene, or copolymerizing ethylene with at least one other monomer, wherein said polymerizing is conducted:in a loop reactor with isobutane as a diluent; at a temperature in a range of about 200Â° F. to about 220Â° F.; with a catalyst system comprising chromium and a support; in the presence of a trialkylboron; wherein the chromium is present in a range of about 1% by weight to about 4% by weight based on the weight of the support; wherein said support comprises silica and titania; wherein said support has a surface area of about 400 m2/gram to about 800 m2/gram and a pore volume of about 1.8 ml/gram to about 4 ml/gram; wherein the titania is present in an amount sufficient to give titanium in a range of about 0.5% by weight to about 3% by weight based on the weight of the support; wherein said catalyst system is activated at a temperature from about 1000Â° F. to about 1300Â° F.; wherein said trialkylboron is represented by the formula BR3, where R is an alkyl group of up to 12 carbon atoms; and wherein the process produces an ethylene polymer having the following properties: a high load melt index of 15 to 40 grams per ten minutes; a density of 0.952 to 0.958 grams per cubic centimeter, a shear ratio (high load melt index/melt index) of 120 to 200, a (weight average molecular weight/number average molecular weight) of 18 to 25, an Environmental Stress Crack Resistance (ASTM D1693, Condition A) of greater than 300 hours, less than 0.85% xylene solubles and less than 1.6% low molecular weight polymer.