Primer mixture of crosslinking initiator and promoter
View Patent ↗A primer mixture intended for crosslinking polyethylene, including at least an initiator of free radicals chosen from organic peroxides, azo compounds or mixtures thereof, wherein the mixture has said free-radical initiator and at least one crosslinking promoter chosen from the cycloalkanes having 5 to 7 carbon atoms, substituted by 1 to 3 vinyl, allyl or isopropenyl groups, the aromatic compounds substituted by 1 to 3 vinyl, allyl or isopropenyl groups, the methacrylate, acrylate and maleimide monomers being multi-substituted, and in that the weight ratio of free-radical initiator to the crosslinking promoter is greater than or equal to 1, and preferably between 1.5 and 4. Also, a method and to a use related to this primer mixture.
1. A primer mixture configured for crosslinking polyethylene, comprising at least one free-radical initiator chosen from organic peroxides, azo compounds or mixtures thereof, and at least one crosslinking promoter chosen from cycloalkanes containing 5 to 7 carbon atoms, substituted with 1 to 3 vinyl or allyl groups,
wherein the weight ratio of free-radical initiator to crosslinking promoter is greater than or equal to 1, and
wherein the primer mixture is subjected to a dissolution and homogenization operation, which results in dissolution of the free-radical initiator in the crosslinking promoter.
2. The mixture of claim 1 , wherein the crosslinking promoter is trivinylcycloalkane.
3. The mixture of claim 1 , wherein the free-radical initiator is dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane or bis[(t-butylperoxy)isopropyl]benzene or a mixture of these initiators.
4. The mixture of claim 1 , wherein the primer mixture is in liquid form at room temperature.
5. A process for manufacturing crosslinked polyethylene, comprising a final step of crosslinking polyethylene, wherein:
a free-radical initiator is chosen from organic peroxides, azo compounds or mixtures thereof, wherein
at least one crosslinking promoter is chosen from cycloalkanes containing 5 to 7 carbon atoms, substituted with 1 to 3 vinyl or allyl groups, and
wherein a step of dilution of said free-radical initiator with said crosslinking promoter is initially performed, and impregnation of polyethylene with the primer mixture thus formed of claim 1 , in liquid form.
6. The process of claim 5 , wherein the crosslinking promoter is present in liquid form at room temperature and ambient pressure.
7. The process of claim 5 , wherein the step of crosslinking polyethylene is performed by extrusion or by injection-molding.
8. A method of producing cables comprising forming a cable from the primer mixture of claim 1 , wherein the cable is configured for transporting fluid or electrical current.
9. The mixture of claim 1 , wherein the weight ratio of free-radical initiator to crosslinking promoter is between 1.5 and 4.
10. The mixture of claim 1 , wherein the primer mixture is in liquid form at least for a temperature of between 10° C. and 50° C. at ambient pressure (1 bar).
11. The process of claim 5 , wherein said initiator is chosen from dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane and bis[(t-butylperoxy)isopropyl]benzene or a mixture of these initiators.
12. The process of claim 5 , wherein-the crosslinking promoter is present in liquid form at a temperature of between 10° C. and 50° C. at a pressure of 1 bar.
13. A process for manufacturing crosslinked polyethylene, comprising:
dissolution and homogenization of a free-radical initiator in at least one crosslinking promoter to form a primer mixture in liquid form, wherein said free-radical initiator is chosen from organic peroxides, azo compounds or mixtures thereof, and wherein said at least one crosslinking promoter is chosen from cycloalkanes containing 5 to 7 carbon atoms, substituted with 1 to 3 vinyl or allyl groups, aromatic compounds substituted with 1 to 3 vinyl or allyl groups, multi-substituted monomers based on methacrylate, acrylate, maleimide, and in that the weight ratio of free-radical initiator to crosslinking promoter is greater than or equal to 1;
wherein the primer mixture is impregnated into granules of polyethylene; and
crosslinking the polyethylene.
14. The process of claim 13 , wherein the crosslinking promoter is present in liquid form at room temperature and ambient pressure.
15. The process of claim 13 , wherein the crosslinking polyethylene is performed by extrusion or by injection-molding.
16. The process of claim 13 , wherein said free-radical initiator is chosen from dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane and bis[(t-butylperoxy)isopropyl]benzene or a mixture thereof, and
wherein said crosslinking promoter is chosen from trivinylcycloalkane and/or divinylbenzene.
17. The process of claim 13 , wherein-the crosslinking promoter is present in liquid form at a temperature of between 10° C. and 50° C. at a pressure of 1 bar.