Granted Patent B2

US 8,475,898 · App. 11/897,438 · Granted Jul 2, 2013

Abstract

Claims (8)

1. A blow molded pipe produced from a resin blend comprising from about 30 to about 70 wt. % of a low-molecular-weight, high-density polyethylene, and from about 30 to about 70 wt. % of a high-molecular-weight, low-density ethylene copolymer produced using a bridged indenoindolyl Group 4 metal complex having open architecture, wherein the ethylene copolymer has a weight-average molecular weight within the range of 150,000 to 500,000,

wherein the blend has a density from 0.94 to 0.96 g/cm 3 , a weight-average molecular weight (Mw) by gel permeation chromatography greater than 200,000, rheological polydispersity (E R ) of less than 1.5, and a viscosity enhancement factor (VEF), calculated from its melt viscosity (η*) at 190° C. and 0.025 radians per second, of less than 2, wherein the pipe exhibits a notched constant tensile (NCTL) value of greater than 500 hours to failure, and wherein the low molecular-weight, high-density polyethylene is produced using a polysiloxane-supplied Ziegler-Natta catalyst.

2. The pipe of claim 1 , wherein the resin blend has a high-load melt index (MI 20 ) of less than 25.

3. The pipe of claim 1 , wherein the low molecular-weight, high-density polyethylene is produced in the presence of a silane modifier.

4. The pipe of claim 3 , wherein the silane modifier is a cyclohexyl dialkoxy(alkyl)silane.

5. The pipe of claim 1 , wherein the ethylene copolymer has a density of from 0.900 to 0.925 g/cm 3 .

6. The pipe of claim 1 , wherein the ethylene copolymer has little to no long-chain branching content.

7. The pipe of claim 1 , wherein the polyethylene has a molecular weight distribution (M w /M a ) of less than 5.

Assignments (6)