Nippon Unicar Company Limited

Youichi Kawasaki

Kenji Igarashi

Seiho Taniguchi

A process for the co-extrusion of an outer layer, a middle layer, and an inner layer, each layer including a thermoplastic resin, around a conductive medium in three extruders, one extruder for each layer, connected by a triple crosshead, each of said extruders having an extrusion zone comprising a die plate and, downstream of the die plate, a die, and, downstream of the extrusion zone, a common crosslinking zone, comprising passing the thermoplastic resins through the extrusion zones, under extrusion conditions including an extrusion temperature in the range of at least 150 degrees C. to below the decomposition temperature of the organic peroxide referred to hereinafter, and passing the extrudate into the crosslinking zone, under crosslinking conditions, the improvement comprising introducing an organic peroxide having a half life of one minute at a temperature of about 150 to about 200 degrees C. into the middle layer extruder downstream of the die plate and prior to the point about directly beneath the die plate of the outer layer extruder.

Process for the production of power cable

The disclosure of this application is directed to a semi-conductive composition, based on a polyolefin, carbon black and a polyethylene glycol, which is suitable for use as a semi-conductive layer, bonded to an insulation layer of an electrical cable, serving to protect the insulation from tree-like degradation, commonly referred to as water trees.

Semi-conductive polyolefin compositions and cables covered with same

A polyolefin composition for electrical insulation which comprises polyolefin or crosslinked polyolefin and a small quantity of high-molecular weight polyethylene glycol. This composition is far less vulnerable to the deterioration that occurs as dendroid voids when employed as an electrical insulation of high-tension power cables which are operated under water. The polyethylene glycol has more than 44 carbon atoms and is used in an amount from 0.3 to 10 wt % based on polyolefin.

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Yokohama, Japan

Youichi Kawasaki