Cross-linkable polyethylene resin for pipes made by a single-site catalyst

Abstract

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.