Polyolefin composition for water pipes with good resistance to chlorine dioxide and low migration

A pipe comprising a polyolefin composition comprising

• a) a polyolefin base resin (A) consisting of a polyethylene homo- or copolymer,
• b) an antioxidant (B) according to formula (I):
• wherein R1, R2, R3, R4 and R5 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
• R6, R7 and R8 independently are non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals which may comprise OH-groups,
• X1, X2, and X3 independently are H or OH, with the provisio that at least one of X1, X2 and X3 is OH,
• the entire molecule does not comprise an ester group, and
• the concentration of antioxidant (C) in the polyolefin composition is at least 1200 ppm, based on the total composition.

Method for increasing the resistance of a polyolefin composition against degradation caused by contact with chlorine dioxide-containing water, using a combination of antioxidants (B) and (C) wherein said antioxidants have the following formulae:

• antioxidant (B) according to formula (I):
• wherein R1, R2, R3, R4 and R5 independently are H, or non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals which may comprise heteroatoms,
• antioxidant (C) according to formula (II):
• wherein
• R6, R7 and R8 independently are non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals which may comprise OH-groups,
• X1, X2, and X3 independently are H or OH, with the provisio that at least one of X1, X2 and X3 is OH,
• the entire molecule does not comprise an ester group, and
• the concentration of antioxidant (C) in the polyolefin composition is at least 1200 ppm, based on the total composition.