Stabilization of polyolefins in permanent contact with chlorinated water

1. A composition comprising

a) a polyolefin which is in permanent contact with chlorinated water, and

b) as stabilizer at least a compound selected from the group consisting of

i) an epoxidized fatty acid having 3 to 22 carbon atoms or an alkyl ester thereof having 1 to 18 carbon atoms; and

iii) a compound containing at least one radical of the formula A1 or B1

wherein

R 10 , R 11 , R 12 and R 13 , independently of one another, are hydrogen, C 1 –C 10 alkyl, C 2 –C 12 alkyl which is interrupted by oxygen; hydroxyl-substituted C 1 –C 10 alkyl; C 3 –C 6 alkenyl, C 5 –C 8 cycloalkyl, phenyl or C 7 –C 9 phenylalkyl,

R 14 is hydrogen, C 1 –C 10 alkyl or phenyl, and

R 15 and R 16 , independently of one another, are hydrogen, C 1 –C 10 alkyl, phenyl or C 7 –C 9 phenylalkyl.

2. A composition according to claim 1 , wherein component (b)(i) is an ester of an epoxidized fatty acid having 16 to 22 carbon atoms or an alkyl ester thereof having 6 to 10 carbon atoms.

3. A composition according to claim 1 , wherein component (a) is polyethylene, polypropylene or polybutylene or a copolymer thereof with a monoolefin or diolefin.

4. A composition according to claim 1 , wherein component (b) is present in an amount of 0.02 to 5%, based on the weight of component (a).

5. A composition according to claim 1 , comprising in addition, besides components (a) and (b), further additives.

6. A composition according to claim 5 , comprising as further additives phenolic antioxidants, light-stabilizers and/or processing stabilizers.

7. A process for stabilizing polyolefin mouldings which are in permanent contact with chlorinated water, which comprises incorporating in or applying to said mouldings at least a component (b) according to claim 1 .

8. A process according to claim 7 , wherein the polyolefin moulding is a pipe or geomembrane.