Importance

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Abstract

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.

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First Claim