Low dielectric loss power cable sheaths comprising high pressure polyolefins free of silane functionality
View Patent ↗Power cables that comprise a sheath layer, e.g., an insulation layer, are produced from a mixture of a high pressure polyolefin free of silane functionality, e.g., high pressure low density polyethylene, and a polyether polyol of which at least 50 percent of its molecules comprise no more than a single hydroxyl functionality. Preferably, the power cable is a medium or high voltage power cable, and the polyolefin is crosslinked as the sheath layer is fabricated and/or subsequent to the fabrication of the sheath layer.
1. A cable sheath comprising a crosslinked, high pressure polyolefin free of silane functionality and a hydrophobic polyether polyol of which at least 50 percent of its molecules comprise no more than a single hydroxyl functionality.
2. The cable sheath of claim 1 in which the high pressure polyolefin free of silane functionality is selected from the group consisting of: HPLDPE, ethylene vinyl acrylate, ethylene butyl acrylate, and ethylene ethyl acetate.
3. The cable sheath of claim 2 in which the polyether polyol is of the formula:
R—[O—R 1 ] n —O—R 2
in which R is hydrogen or a C 1-20 hydrocarbyl or inertly-substituted hydrocarbyl radical, R 1 is a C 2-20 hydrocarbyl or inertly-substituted hydrocarbyl radical, R 2 is an end-capping group, and n is an integer of 2-1000.
4. The cable sheath of claim 3 in which the end-capping group is an alkyl or an inertly substituted alkyl radical.
5. The cable sheath of claim 4 in which R 1 is a C 3-20 hydrocarbyl or inertly-substituted hydrocarbyl radical.
6. The cable sheath of claim 5 in which R is hydrogen.
7. The cable sheath of claim 1 in which the polyether polyol comprises less than 300 ppm of the cable sheath.
8. The cable sheath of claim 1 in the form of an insulation layer of a power cable.
9. The cable sheath of claim 1 in the form of an insulation layer of a medium or high voltage power cable.
10. The cable sheath of claim 1 comprising filler.
11. The cable sheath of claim 1 free of filler.
12. The cable sheath of claim 1 in which the weight average molecular weight of the polyether polyol is between 100 and 3,000 g/mol.