Polyethylene pipe
AssigneeSolvay Polyolefins Europe-Belgium
InventorsAndre Scheelen, Eric Vandevijver
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Abstract
Multi-layered pipe comprising a main layer of polyethylene compound having a resistance to stress cracking NPT measured according to ISO 13479 standard of less than 8000 hours and an internal layer of polyethylene compound having a resistance to stress cracking NPT of higher than 8000 hours, the thickness of the internal layer being between 1 and 25% of the total pipe thickness but not less than 0.3 mm.
Claims10
1- Multi-layered pipe comprising a main layer of polyethylene compound having a resistance to stress cracking NPT measured according to ISO 13479 standard of less than 8000 hours and an internal layer of polyethylene compound having a resistance to stress cracking NPT of higher than 8000 hours, the thickness of the internal layer being between 1 and 25% of the total pipe thickness but not less than 0.3 mm.
2- Pipe according to claim 1, wherein the polyethylene compound of the internal layer has a resistance to stress cracking NPT of at least 10000 hours.
3- Pipe according to claim 1 or 2, wherein the polyethylene compound of the internal layer has a MRS classification according to ISOTR 9080 standard of at least 10.
4- Pipe according to any of claims 1 to 3, wherein the polyethylene compound of the internal layer comprises at least 95% by weight of a polyethylene resin comprising from 30 to 70% by weight of an ethylene polymer having a density of at least 960 kg/m3 and an melt index MI2 of at least 100 g/10 min and from 30 to 70% by weight of an ethylene-hexene copolymer comprising from 0.4 to 10 weight % of hexene, having a density between 910 and 938 kg/m3 and a melt index MI5 of between 0.01 to 2 g/10 min.
5- Pipe according to any one of claims 1 to 4, wherein the polyethylene compound of the main layer has a MRS classification according to ISO/TR 9080 standard of at least 10.
6- Pipe according to any one of claims 1 to 5, wherein the pipe comprises an external layer having an improved scratch resistance.
7- Pipe according to claim 6, wherein the external layer comprises a crosslinked silane-grafted polyethylene compound.
8- Pipe according to claim 6, wherein the external layer comprises a polyethylene compound having a resistance to stress cracking NPT measured according to ISO 13479 standard of higher than 8000 hours
9- Pipe according to claim 6 or 8, wherein the internal layer, the main layer and the external layer comprise a polyethylene compound having a MRS classification of at least 10.
10- Pipe according to any one of claims 6 to 9, wherein the thickness of the external layer is between 1 and 35% of the total pipe thickness but not less than 0.3 mm.