PREPARATION OF LONG HEAT INSULATING PIPE

摘要

PURPOSE:To obtain a long heat insulating pipe of which the cross-sectional shape is an almost round, by providing a process for holding the cross-sectional shape of a long base pipe to an almost round prior to a process forming a heat insulating foamed layer and a skin layer to the base pipe. CONSTITUTION:A long base pipe made of a synthetic resin is corrected to an almost round in a supply process for supplying said base pipe to an extruder or in the previous process thereof and, thereafter, a heat insulating foamed layer and a skin layer are formed to the treated base pipe by the extruder. The correction process is performed by a roll molding method and the long base pipe 1 is sent out while the outer periphery thereof is pressed by four rolls 2 and the cross-sectional shape of the pipe 1 passing through the rolls 2 is corrected to an almost round and the round is prevented from collapsing by the foaming pressure of a foaming material.