Polyolefin composition for water pipes with increased resistance to chlorine dioxide

Abstract

The present invention relates to a polyolefin composition with increased resistance to degradation caused by ClO 2 -containing water and to a pipe made of such a polyolefin composition. The present invention further relates to the use of the polyolefin composition for the production of a pipe and to the use of a combination of particular types of antioxidants for increasing the resistance of the polyolefin composition against degradation caused by contact with ClO 2 -containing water.

1 . A polyolefin composition comprising
 a) polyethylene homo- or copolymer base resin (A), wherein the copolymer comprises an alpha-olefin comonomer selected from the group consisting of 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene,   b) an antioxidant (B) according to formula (I):   
       
         
           
           
               
               
           
         
         wherein R 1 , R 2 , R 3 , R 4  and R 5  independently are H, or non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals which may comprise heteroatoms, 
         c) an antioxidant (C) according to formula (II): 
       
       
         
           
           
               
               
           
         
         wherein
 R 6 , R 7  and R 8  independently are non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals which may comprise OH-groups, 
 X 1 , X 2 , and X 3  independently are H or OH, with the provisio that at least one of X 1 , X 2  and X 3  is OH, 
 the entire molecule does not comprise an ester group, and 
 
         d) an antioxidant (D) according to formula (III): 
       
       
         
           
           
               
               
           
         
         wherein R and R′ is the same or different, and R and R′ independently comprise at least 6 carbon atoms and may comprise heteroatoms. 
       
     
     
         2 . The polyolefin composition according to  claim 1 , wherein the base resin (A) comprises said polyethylene copolymer. 
     
     
         3 . The polyolefin composition according to  claim 1 , wherein the sum of concentration of antioxidants (B), (C) and (D) is between 1100 and 1800 ppm. 
     
     
         4 . The polyolefin composition according to  claim 1 , wherein the base resin (A) comprises a polyethylene copolymer having from about 0.1 mol % to about 7.0 mo % of said alpha-olefin comonomer. 
     
     
         5 . The polyolefin composition according to  claim 1 , wherein the base resin (A) comprises a polyethylene copolymer having from about 0.3 mol % to about 6.0 mo % of said alpha-olefin comonomer. 
     
     
         6 . The polyolefin composition according to  claim 1 , wherein the base resin (A) comprises a polyethylene copolymer having from about 0.7 mol % to about 5.0 mo % of said alpha-olefin comonomer.