Patent ID: 6858677

Claim:
A polyolefin pipe having a hydrostatic design basis at 23° C. of equal or greater than 1250 psi and a ductile-brittle failure transition of at least 2000 hours when measured at 8000 under a minimum hoop stress of 900 psi prepared from a multimodal polyolefin resin comprising not less than 80 weight % of ethylene and up to 20 weight % of one or more C 3-10 alpha olefins, said composite resin having a density greater than 0.940 g/cm 3 ; a melt index determined according to ASTM D 1238 under a load of 2.16 kg and a temperature of 190° C. greater than 0.01 g/10 minutes, a polydispersity greater than 3.5; and a CDBI of greater than 50 comprising at least: a) from 5 to 50 weight % of a high molecular weight component having a density greater than 0.940 g/cm 3 ; a weight average molecular weight greater than 250,000; a polydispersity from 1.5 to 3.5: and a short chain branch content from 0.0 to 4.4 short chains per 1000 carbon atoms in the polymer backbone; and b) from 50 to 95 weight % of a lower molecular weight component having a density from 0.930 to 0.960 g/cm 3 ; a weight average molecular weight greater than 25,000; a polydispersity from 2.0 to 3.5; and a short chain branch content from 0.5 to 6.1 short chains per 1000 carbon atoms in the polymer backbone.