Pipe of polyethylene having improved mechanical properties

US5908679A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Joachim Berthold · Prien am Chiemsee, DE
• Ludwig Bohm · Mainz, DE
• Werner Breuers · Eppstein, DE
• Johannes-Friedrich Enderle · Frankfurt, DE
• Manfred Fleissner · Eschborn, DE
• Rainer Lecht · Kelkheim, DE
• Hartmut Luker · Hofheim, DE
• Ulrich Schulte · Kelkheim, DE
• Heiner Bromstrup · Heidesheim, DE

Key dates

• Filing date: Oct 6, 1997
• Grant date: Jun 1, 1999
• Expiry date: Oct 6, 2017

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/1397
• WIPO field: Mechanical elements
• WIPO sector: Mechanical engineering

Abstract

The invention relates to a high strength pipe of ethylene polymer having a bimodal molecular weight distribution. Such pipe has a stress cracking resistance of .gtoreq.1400 h, a fracture toughness of .gtoreq.7 mJ/mm.sup.2 and a modulus of creep in flexure, measured according to DIN 54852-Z4, of .gtoreq.1100 N/mm.sup.2. The pipe according to the invention is produced from an ethylene polymer in which the ratio of weight of the low molecular weight fraction to the weight of the higher molecular weight fraction is in the range from 0.5 to 2.0 and which has a melt flow index MFI.sub.5/190.degree. C. of .ltoreq.0.35 g/10 min. It is particularly suitable for the transportation of gases and water.