Plastics-insulated, heavy-duty, power cable - is extrusion-coated with polypropylene polyethylene compsn. applied under closely controlled processing conditions

摘要

Mfr. of a plastics-insulated, heavy-duty, power cable, comprises extrusion-coating the conductor with an insulation contg. polypropylene, and cooling. An insulating compsn. is used which has a major portion of polypropylene and a minor portion of polyethylene and/or ethylene copolymer. The compsn. is applied under conditions of supply, plasticising, compounding and discharge temp. that prevent the max. MFI of 0.65g/10 min (measured according to DIN 53735) at 190 degrees C and under 2.16kg load, from being exceeded. This processing control is achieved using an extruder screw having a suitably dimensioned zone at 250-300 degrees C and applying a temp. profile that rises in controlled manner. from the feed-in zone to beyond the plasticising zone. Subsequent cooling is effected in at least 2 different temp. stages and/or by cooling media. The insulation is thermally stable whilst still in uncrosslinked state. The resulting coated cable can be readily wound onto reels or corded together. The coating has good low-temp. resistance.