A PROCESS FOR PREPARING AN IN SITU POLYETHYLENE BLEND

摘要

A process comprising contacting ethylene and one or two alpha-olefin comonomers, each having 3 to 8 carbon atoms, with a transition metal catalyst system including a hydrocarbylaluminum cocatalyst in each of two fluidized bed reactors connected in series, in the gas phase, under polymerization conditions. The copolymer formed in the first reactor has a flow index in the range of about 0.1 to about 75 grams per 10 minutes and a density in the range of 0.865 to 0.930 gram per cubic centimeter and the copolymer formed in the second reactor has a melt index in the range of about 0.2 to about 100 grams per 10 minutes and a density in the range of about 0.900 to about 0.965 gram per cubic centimeter, the weight ratio of the first reactor copolymer to second reactor copolymer being in the range of about 70:30 to about 30:70, and the in situ blend has a flow index in the range of about 5 to 100 grams per 10 minutes; a melt flow ratio in the range of about 10 about 100; a density in the range of 0.880 to 0.960 gram per cubic centimeter; and an Mw/Mn ratio in the range of about 2 to about 20.