Claims
- 1. A polyethylene pipe comprising a high density multimodal polyethylene having a shear ratio (SR) of 18 or more and a final high load melt index (HLMI) of 15 g/10 min or less and having a high molecular weight fraction, which high molecular weight fraction has a density (ρ) and a high load melt index (HLMI), which satisfy the following relationship:ρ×HLMI≦0.37 wherein the units of density are g/cm3 and the units of HLMI are g/10 mins, and the density is 0.930 g/cm3 or less.
- 2. A pipe according to claim 1, in which the high density multimodal polyethylene has at least 20% by weight of the high molecular weight fraction, and the high molecular weight fraction has a high load melt index (HLMI) of 0.40 g/10 mins or less.
- 3. A pipe according to claim 2, in which the high density multimodal polyethylene has a shear ratio (SR) of 18 or more and comprising at least 20% by weight of a high molecular weight fraction, which high molecular weight fraction has:(a) a density (ρ) of 0.93 g/cm3 or less; and (b) a high load melt index (HLMI) of 0.30 g/10 mins or less.
- 4. A method of pipe installation comprising forming a hole or trench for receiving a pipe and installing a polyethylene pipe formed from a high density multimodal polyethylene having a shear ratio (SR) of 18 or more and a final high load melt index (HLMI) of 15 g/10 min or less and having a high molecular weight fraction, which high molecular weight fraction has a density (ρ) and a high load melt index (HLMI), which satisfy the following relationship:ρ×HLMI≦0.37 wherein the units of density are g/cm3 aid the units of HLMI are g/10 min, and the density is 0.93 g/cm3 or less in the hole or trench.
- 5. A method according to claim 4, which method is a no-sand installation method, the pipe being installed in the hole or trench directly in contact with the earth.
- 6. A method for re-lining a pipe comprising installing a polyethylene pipe formed from a high density multimodal polyethylene having a shear ratio of 18 or more and a final high load melt index (HLMI) of 15 g/10 min or less and having a high molecular weight fraction, which high molecular weight fraction has a density (ρ) and a high load melt index (HLMI), which satisfy the following relationship:ρ×HLMI≦0.37 wherein the units of density are g/cm3 and the units of HLMI are g/10 min, and the density is 0.93 g/cm3 or less in an existing pipe.
- 7. An article having resistance to stress-cracking, the article being formed of a high density multimodal polyethylene having a shear ratio (SR) of 18 or more and a final high load melt index (HLMI) of 15 g/10 min or less and comprising a high molecular weight fraction, which high molecular weight fraction has a density (ρ) and a high load melt index (HLMI), which satisfy the following relationship:ρ×HLMI≦0.37 wherein the units of density are g/cm3 and the units of HLMI are g/10 mins, wherein the high density multimodal polyethylene comprises at least 20% by weight of the high molecular weight fraction and the density (ρ) is 0.930 g/cm3 or less and the high load melt index (HLMI) is 0.40 g/10 mins or less.
- 8. An article according to claim 7, wherein the article is a polyethylene pipe.
Priority Claims (1)
Number |
Date |
Country |
Kind |
99106461 |
Mar 1999 |
EP |
|
Parent Case Info
This application is a division of U.S. patent application Ser. No. 09/538,541, filed Mar. 30, 2000, now U.S. Pat. No. 6,433,095 B1, and entitled High Density Multimodal Polyethylene.
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EP |