Method for cross-linking a polymer article
View Patent ↗The present invention relates to a method for cross-linking a polymer article which comprises a cross-linkable polymer with hydrolyzable silane groups and a crystallinity level of at least 30%. The cross-linking is performed in the presence of a silanol condensation catalyst comprising a compound of formula (I): ArSO 3 H or a precursor thereof, Ar being a hydrocarbyl substituted aromatic group comprising at least 14 carbon atoms.
1. Method for cross-linking a polymer article comprising a cross-linkable polymer with an hydrolysable silane group, which has been produced by the use of a single-site catalyst and has a crystallinity level of at least 30% wherein the cross-linking is performed in the presence of a silanol condensation catalyst comprising a compound of formula (I):
ArSO 3 H (I)
or a precursor thereof, Ar being a hydrocarbyl substituted aromatic group comprising at least 14 carbon atoms.
2. Method according to claim 1 wherein the polymer article is hollow.
3. Method according to claim 1 wherein the polymer article is a pipe.
4. Method according to claim 1 wherein the cross-linking is performed at a temperature below 80° C.
5. Method according to claim 1 wherein the polymer is a polyethylene with a density of at least 923 kg/m 3 .
6. Method according to claim 1 wherein Ar is a hydrocarbyl substituted benzene or naphthalene ring, the hydrocarbyl radical or radicals containing 8 to 20 carbon atoms in the benzene case and 4 to 18 carbon atoms in the naphthalene case.
7. Method according to claim 6 , wherein the catalyst is selected from the group of dodecyl benzene sulphonic acid and tetrapropyl benzene sulfonic acid.
8. Method according to claim 1 , wherein the single-site catalyst comprises a porous particulate support material having impregnated therein a metallocene compound, the metal atom whereof is bound to an amide group which is not bound to an η-ligand of the metallocene.
9. Method according to claim 1 , wherein the polymer has been oriented in at least one direction before the cross-linking is performed.
10. Method according to claim 9 , wherein the polymer has been oriented biaxially.
11. Method according to claim 9 , wherein the polymer has been at least partially cross-linked before the orientation step.
12. Method according to claim 11 , wherein the cross-linking before the orientation step is performed to a level of at least 20%.
13. Method according to claim 2 wherein the polymer article is a pipe.
14. Method according to claim 2 wherein the cross-linking is performed at a temperature below 80° C.
15. Method according to claim 2 wherein the polymer is a polyethylene with a density of at least 923 kg/m 3 .
16. Method according to claim 4 wherein the polymer is a polyethylene with a density of at least 923 kg/m 3 .
17. Method according to claim 2 wherein Ar is a hydrocarbyl substituted benzene or naphthalene ring, the hydrocarbyl radical or radicals containing 8 to 20 carbon atoms in the benzene case and 4 to 18 carbon atoms in the naphthalene case.
18. Method according to claim 4 wherein Ar is a hydrocarbyl substituted benzene or naphthalene ring, the hydrocarbyl radical or radicals containing 8 to 20 carbon atoms in the benzene case and 4 to 18 carbon atoms in the naphthalene case.
19. Method according to claim 5 wherein Ar is a hydrocarbyl substituted benzene or naphthalene ring, the hydrocarbyl radical or radicals containing 8 to 20 carbon atoms in the benzene case and 4 to 18 carbon atoms in the naphthalene case.
20. Method according to claim 10 , wherein the polymer has been at least partially cross-linked before the orientation step.