Patent ID: 7601787
Filing Date: 2009-10-13
Classification: C08F,Y10S

Abstract:
1. A process which comprises polymerizing ethylene in the presence of a Ziegler-Natta catalyst system in a reactor consisting of two slurry reaction zones, Zone A and Zone B, connected in series, wherein from 70-95% by weight of the polyethylene is produced in Zone A and the ratio of weight average molecular weight of Zone B: Zone A polyethylene is greater than 8:1, to produce a polyethylene blend with a bimodal molecular weight distribution, a density greater than 0.935 g/cm 3 , a ratio of Z-average molecular weight to weight average molecular weight (M z /M w ) of greater than 10, and an extrudate swell (So) at a melt strength expressed as the value of complex viscosity (ETA*) in megapoise at 190° and at a complex modulus of 2×10 4 dyn/cm 2 defined by: