Polyolefin pipe with improved migration behaviour
A polyolefin pipe having a polyolefin base resin (A) including a lower molecular weight fraction and a higher molecular weight fraction, stabilized with at least one stabilizer (B) having a formula: and at least one stabilizer (C) having a formula: wherein the substituents are as described in the specification. The composition demonstrates acceptable stability and low migration of additional additives from the pipe.
1. A pipe comprising a polyolefin composition comprising
a) a polyolefin base resin (A) which comprises two or more polyethylene fractions with different weight average molecular weight,
b) a stabilizer (B) according to formula (I)
or formula (II)
wherein R 1 , R 2 , R 3 , R 4 and R 5 are independently from each other non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals with not more than 50 carbon atoms each, which may comprise heteroatoms; and
c) a stabilizer (C) according to formula (III)
or formula (IV)
wherein
R 6 is hydrogen or a non-substituted or substituted aliphatic or aromatic hydrocarbyl radical, which may comprise heteroatoms,
R 7 , R 8 , R 9 and R 10 are independently from each other non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals, which may comprise heteroatoms,
R 11 and R 12 are independently from each other hydrogen or non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals, which may comprise heteroatoms, or are together a substituent ═O, and
R 13 and/or R 14 are independently from each other hydrogen or non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals, which may comprise heteroatoms.
2. The pipe according to claim 1 , wherein stabilizer (B) is according to formula (I) and stabilizer (C) is according to formula (III).
3. The pipe according to claim 1 , wherein R 1 , R 2 , R 3 and R 4 are non-substituted or substituted aliphatic or aromatic hydrocarbyl radicals, which do not comprise heteroatoms and comprise between twelve and 25 carbon atoms each.
4. The pipe according to claim 3 , wherein R 1 , R 2 , R 3 and R 4 are alkyl chains.
5. The pipe according to claim 1 , wherein R 5 is an aliphatic hydrocarbyl radical not comprising heteroatoms and comprises not more than five carbon atoms.
6. The pipe according to claim 5 , wherein R 5 is an alkyl chain.
7. The pipe according to claim 1 , wherein R 6 is a hydrogen atom or comprises an alkyl chain with 1 to 5 carbon atoms and does not comprise heteroatoms.
8. The pipe according to claim 1 , wherein R 7 , R 8 , R 9 and R 10 are alkyl chains comprising 1 to 10 carbon atoms and do not comprise any heteroatom.
9. The pipe according to claim 1 , wherein both R 11 and R 12 are hydrogen atoms.
10. The pipe according to claim 1 , wherein R 13 comprises a backbone of a polymeric structure, wherein the atom of the polymeric structure which is directly attached to the carbon atom of formula (III) or (IV) is a nitrogen atom.
11. The pipe according to claim 1 , wherein R 14 is a hydrogen atom.
12. The pipe according to claim 1 , wherein from the polyolefin composition an amount of at most 5 microgram of phenolic decomposition and/or by-products per liter of water (microg/liter) migrates into water, measured according to the migration-into-water analysis method.
13. The pipe according to claim 1 , wherein the polyolefin base resin (A) consists of two polyethylene fractions (A) and (B), wherein fraction (A) has a lower molecular weight and is an ethylene homopolymer and fraction (B) has a higher molecular weight and is an ethylene copolymer.
14. The pipe according to claim 1 , wherein the polyolefin base resin (A) has an MFR 5 (190° C., 5 kg) from 0.01 to 5.0 g/10 min.
15. The pipe according to claim 1 , wherein the polyolefin base resin (A) has a density from 930 to 960 kg/m 3 .