The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 27, 2002
Filed:
Apr. 10, 2001
Mats Bäckman, Göteborg, SE;
Eeva-Leena Heino, Helsinki, FI;
Solveig Johansson, Stenungsund, SE;
Jussi Laurell, Borgå, FI;
Arja Lehtinen, Helsinki, FI;
Jarmo Lindroos, Tolkkinen, FI;
Marja Ora, Vantaa, FI;
Elisabeth Ribarits, Spekeröd, SE;
Teija Sihvonen, Borgå, FI;
Jari {umlaut over (Aa)}rilä, Borgå, FI;
Borealis Technology Oy, Porvoo, FI;
Abstract
A multimodal polymer composition for pipes is disclosed as well as a pipes made thereof. The polymer is a multimodal polyethylene with a density of 0.930-0.965 g/cm , and a viscosity at a shear stress of 747 Pa of at least 650 Pa.s, said multimodal polyethylene comprising a low molecular weight (LMW) ethylene homopolymer fraction and a high molecular weight (HMW) ethylene copolymer fraction, said HMW fraction having a weight ratio of the LMW fraction to the HMW fraction of (35-55):(65-45). Preferably, the multimodal polyethylene has a viscosity at a shear stress of 2.7 kPa of 260-450 kPa.s; and a shear thinning index (SHI) defined as the ratio of the viscosities at shear stresses of 2.7 and 210 kPa, respectively, of SHI =50-150, and a storage modulus (G′) at a loss modulus (G″) of 5 kPa, of G′ ≧3000 Pa. The pipe is made of the multimodal polymer composition and withstands a stress of 8.0 MPa gauge during 50 years at 20° C. (MRS8.0). Preferably, the pipe has a rapid crack propagation (RCP) S4-value, determined according to ISO 13477:1997(E), of −5° C. or lower and a slow crack propagation resistance, determined according to ISO 13479:1997, of at least 500 hrs at 4.6 MPa/80° C. The polymer composition affords good non-sagging properties to pipe made thereof.