PROCESS FOR THE PRODUCTION OF HIGHLY EXPANDED POLYOLEFIN INSULATED WIRES AND CABLES

摘要

The present invention relates to a method of extruding highly expanded polyolefin onto wires and cables. This insulating layer of highly expanded polyolefin foam has a foaming ratio in excess of 2.5 times (60% expansion degree), good flexibility, shows little longitudinal shrinking and tightly adheres to the inner cable. The process for producing the insulated cables comprises the steps of feeding a compound of polyolefin, nucleating agent and volatile liquid into an extruder, and heat extruding the mixture onto a conductor passing through the extruder, covering the conductor. This invention teaches over the present art in which the foaming ratio is at most about 2, the insulation adheres poorly to the conductor, and it also has poor flexibility and elasticity. For all these reasons, highly expanded polyolefin insulated wires have until now been put to very little practical use.