CROSS-LINKABLE POLYETHYLENE RESIN FOR PIPES MADE BY A SINGLE-SITE CATALYST
An ethylene polymer with a density of less than 955 kg/m 3 obtained by polymerisation with a single-site catalyst and having a shear thinning index SHI 2.7/210 of less than 5 wherein ethylene polymer comprises two components.
1 . An ethylene polymer with a density of less than 955 kg/m 3 obtained by polymerization with a single-site catalyst and comprising a shear thinning index SHI 2.7/210 of less than 5 wherein ethylene polymer comprises two components.
2 . The ethylene polymer as claimed in claim 1 comprising an ash content of less than 250 ppm.
3 . The ethylene polymer as claimed in claim 1 comprising at least two components, a first component and a second component, wherein the first component comprises an ash content of at least 250 ppm but wherein an ash content of the ethylene polymer is less than 250 ppm.
4 . The ethylene polymer as claimed in claim 1 comprising an M w /M n of less than 3.
5 . The ethylene polymer as claimed in claim 1 comprising an SHI 2.7/210 of less than 4.
6 . The ethylene polymer as claimed in claim 1 comprising an MFR 21 of less than 5 g/10 min.
7 . The ethylene polymer as claimed in claim 1 comprising a single peak in its GPC curve.
8 . The ethylene polymer as claimed in claim 1 which is a homopolymer.
9 . The ethylene polymer as claimed in claim 1 wherein the weight ratio between the two components is 40:60 to 60:40.
10 . A cross-linked polyethylene comprising an ethylene polymer as claimed in claim 1 which has been cross-linked.
11 . The cross-linked polyethylene as claimed in claim 10 comprising a cross-linking degree of at least 70% (ASTM D2765-01, method A using Trig 145 E85).
12 . A process for the preparation of an ethylene polymer comprising:
polymerizing ethylene and optionally at least one comonomer in a first stage in the presence of a single site catalyst;
polymerizing ethylene and optionally at least one comonomer in a second stage in the presence of the same single site catalyst;
so as to form an ethylene polymer as claimed in claim 1 .
13 . A cross-linked pipe comprising an ethylene polymer as claimed in claim 10 .
14 . The cross-linked pipe as claimed in claim 13 prepared by RAM extrusion.
15 . The pipe as claimed in claim 13 wherein a cross-linking agent used is a peroxide.