Claims
- 1. A multilayer crosslinked polyethylene (“PEX”) pipe comprising:
(a) an inner tubular core of high density polyethylene (“HDPE”) having a maximum wall thickness from about 28 to 100 times smaller than the nominal diameter of pipe in the range from 7 mm (0.25″) to 152 mm (6″), ratio 28 being attributable to small diameter non-SDR-9 piping, and ratio 100 being attributable to the larger diameter SDR-9 pipe, wherein the HDPE has a density in the range from 0.941 g/cc to 0.963 g/cc; and, (b) an outer tubular sheath of at least one layer of at least partially crosslinked polyethylene contiguous with the outer surface of the inner core layer.
- 2. The multilayer pipe of claim 1 wherein the HDPE has a density in the range from about 0.950 to about 0.963 g/cm3 and the PEX is crosslinked to a gel level of at least 65%.
- 3. The multilayer pipe of claim 2 wherein the inner core has a wall thickness in the range from at least 0.025 mm (1 mil) to about 1.52 mm (0.06″) thick for pipe having a nominal diameter in the range from 7 mm (0.25″) to 152 mm (6″).
- 4. The multilayer pipe of claim 3 wherein the inner core has a wall thickness in the range from about 0.05 mm (2 mil) to 0.1 mm (4 mils) for pipe having a nominal diameter in the range from 13 mm (0.5″) to 25 mm (1″) and the gel level is greater than 70%.
- 5. The multilayer pipe of claim 2 wherein the outer sheath of PEX is crosslinked by a method chosen from the addition of peroxide, electron beam irradiation, the addition of AZO compounds, and silane grafting process.
- 6. The multilayer pipe of claim 5 wherein the silane grafting process is selected from the Sioplas process or Monosil process.
- 7. The multilayer pipe of claim 3 wherein the sheath includes successive inner and outer contiguous layers of PEX melt-bonded to one and another, the outer layer being color-coded.
- 8. A three layer PEX pipe comprising:
(a) an inner tubular core layer of high density polyethylene (HDPE) having a maximum wall thickness from about 28 to 100 times smaller than the nominal diameter of pipe in the range from 7 mm (0.25″) to 152 mm (6″), ratio 28 being attributable to small diameter non-SDR-9 piping, and ratio 100 being attributable to the larger diameter SDR-9 pipe, wherein the HDPE has a density in the range from 0.941 g/cc to 0.963 g/cc; (b) an intermediate tubular layer of crosslinked polyethylene (PEX) having a gel level of at least 65% contiguously disposed radially outward from the core layer; and, (c) an outer tubular layer of PEX having a gel level of at least 65%, wherein said outer tubular layer is color-coded for installation in a chosen service.
- 9. A multilayer pipe comprising:
(a) an inner tubular core layer of high density polyethylene (HDPE) having a maximum wall thickness from about 28 to 100 times smaller than the nominal diameter of pipe in the range from 7 mm (0.25″) to 152 mm (6″), ratio 28 being attributable to small diameter non-SDR-9 piping, and ratio 100 being attributable to the larger diameter SDR-9 pipe, wherein the HDPE has a density in the range from 0.941 g/cc to 0.963 g/cc; (b) an intermediate tubular layer of crosslinked polyethylene (PEX) having a gel level of at least 65%, contiguously disposed radially outward from the core layer; (c) an oxygen barrier of material other than polyethylene disposed radially outward from said intermediate layer.
- 10. A process for producing a multilayer pipe comprising co-extruding:
(a) an inner tubular core layer of high density polyethylene (HDPE) having a maximum wall thickness from about 28 to 100 times smaller than the nominal diameter of pipe in the range from 7 mm (0.25″) to 152 mm (6″), ratio 28 being attributable to small diameter non-SDR-9 piping, and ratio 100 being attributable to the larger diameter SDR-9 pipe, wherein the HDPE has a density in the range from 0.941 g/cc to 0.963 g/cc; (b) an outer tubular core of at least one layer of crosslinkable polyethylene melt bonded to the outer surface of the inner core layer without the use of adhesive; and, (c) crosslinking at least the outer layer to have a gel content of at least 65%.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is filed pursuant to U.S. Provisional Application No. 60/397,862 filed on Jul. 23, 2002.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60397862 |
Jul 2002 |
US |