Process for making a cross-linked polyethylene article
View Patent ↗A process for for making a cross-linked polyethylene article includes: (A) feeding a blend comprising a cross-linkable silane-group containing polyethylene copolymer and at least one additive to an extruder, (B) feeding a liquid comprising a silanol condensation catalyst to said extruder to form a mixture with said blend, (C) extruding said mixture to form an article and (D) cross-linking said article. The article may be a pipe or cable.
1. A process for making a cross-linked polyethylene article comprising:
(A) feeding a blend comprising a cross-linkable silane-group containing polyethylene copolymer and at least one additive to an extruder,
(B) feeding a liquid comprising a silanol condensation catalyst to said extruder to form a mixture with said blend,
(C) extruding said mixture to form the article and
(D) cross-linking said article.
2. The process according to claim 1 wherein the blend and the liquid are separately fed to the extruder.
3. The process according to claim 1 wherein the blend and the liquid are premixed before entering the extruder.
4. The process according to claim 1 wherein the at least one additive is an antioxidant.
5. The process according to claim 1 wherein the at least one additive is a scorch retarder.
6. The process according to claim 5 wherein the scorch retarder is a silane-containing compound.
7. The process according to claim 6 wherein the cross-linkable silane-group containing polyethylene copolymer is a copolymer of ethylene and a tri-alkoxy vinyl silane or vinyl tri-methoxy silane.
8. The process according to claim 1 wherein the cross-linkable silane-group containing polyethylene copolymer is formed in a reactor under a pressure of 500 to 4,000 kg/cm 2 .
9. The process according to claim 1 wherein the silanol condensation catalyst comprises a metal and a Lewis acid.
10. The process according to claim 1 wherein the silanol condensation catalyst is dioctyl tin laureate (DOTL) or zirconium acetylacetonate.
11. The process according to claim 1 which is peroxide free.
12. The process according to claim 1 wherein the article is a cable and the extruder is a cable extruder.
13. The process according to claim 1 wherein the blend comprises all the additives of the composition to be formed, except for the silanol condensation catalyst and optionally a drying agent.
14. The process according to claim 1 wherein the liquid consist of the silanol condensation catalyst or the silanol condensation catalyst and a drying agent.
15. The process according to claim 1 further comprising:
forming the blend prior to the feeding.
16. The process according to claim 1 , wherein the blend is in the form of pellets.
17. The process according to claim 1 , wherein the blend is in the form of a powder.
18. The process according to claim 1 , wherein the blend is in the form of a second liquid.
19. The process according to claim 1 , wherein the liquid consists of dioctyl tin laurate.
20. A process for making a cross-linked polyethylene article comprising:
(A) feeding a blend comprising a cross-linkable silane-group containing polyethylene copolymer and at least one additive to an extruder,
(B) feeding a liquid comprising a silanol condensation catalyst to said extruder to form a mixture with said blend,
(C) extruding said mixture to form the article and
(D) cross-linking said article;
wherein the blend is in the form of pellets comprising an ethylene vinyl silane copolymer and vinyl trimethoxy silane.