Plastic-insulated cable cores - by extruding filler-contg. ethylene]-vinyl]:silane copolymer on conductor, oxidising the surface and crosslinking with moisture

Prodn. of a cable core with insulation made of a moisture-crosslinked ethylene-based polymer (I), by extruding filler-contg. polymer onto an electrical conductor and subjecting the polymer layer immediately to oxidn. followed by moisture-induced crosslinking; the novelty is that (a) (I) is a -commercially-available copolymer of ethylene and vinylsilane, (b) the filler is added to the polymer during the moulding process, as a granular batch contg. above 85 wt.% filler and (c) the amt. of filler batch is such that the extruded polymer layer contains 10-20 wt.% filler. Pref., the filler batch is a conventional multi-coated and agglomerated CaCO3 (chalk). Pref. the polymer surface is oxidised, e.g. by flame treatment; a suitable filler batch is, e.g. Omyalene G 200 (RTM), and pref. polymer is a terpolymer based on ethylene-propylene, e.g. Visico (RTM); use of this filler batch enables prodn. of cable with an Al core of 150 mm2 cross-sectional area and insulation suitable for 1-kV loads, at take-off rates of 80 m/min. USE/ADVANTAGE - The process is useful esp. for the prodn. of high-voltage cables; it enables prodn. of moisture-crosslinkable polymeric insulation with improved adhesion between core and insulation (w.r.t. prior-art processes).