Patent ID: 8138264
Filing Date: 2012-03-20
Classification: C08F

Abstract:
1. A process for producing a bimodal high density polyethylene in two reactors in series, comprising: homopolymerizing in a first reactor from ethylene in the presence of hydrogen and a Ziegler-Natta polymerization catalyst; polymerizing in a second, serially connected, downstream reactor a second polyethylene product from ethylene and from about 0 wt % to 3 wt % of an α-olefinic comonomer comprising from 3 to 8 carbon atoms, based on the total weight of ethylene monomer, wherein the polymerization processes are carried out at a temperature of from about 38° C. to about 93° C., under an absolute pressure of from about 100 kPa to about 10,000 kPa, and the homopolymerization in the first reactor is carried out at a higher temperature than that of the second reactor; and recovering bimodal polyethylene having a density ranging from about 0.955 g/cc to about 0.959 g/cc, a high load melt index (HLMI) of from about 2 dg/min to about 30 dg/min, an environmental stress cracking resistance (ESCR) of from about 400 hours to about 2500 hours, and a 0.4% flexural modulus of from about 180,000 psi to about 260,000 psi (1,200 MPa to about 1,800 MPa).