JPH0380611B

PURPOSE:To prevent resin in a crosslinking tube from seizing without using lubricating oil by a method wherein a lining layer made of substance, which has large releasability to resin and the coefficient of friction of which is small, is formed on the inner surface of the crosslinking tube. CONSTITUTION:Uncrosslinked resin 15 is extruded from an extrusion port 3 into a crosslinking tube 5. Pressure fluid is blasted from a feeding passage 6 to the inner surface side of a tube 5. The tube 5 lowers in the crosslinking tube 7 and is subjected to crosslinking by heating during its lowering movement. At this time, the tube 5 is brought into contact with the inner surface of the crosslinking tube 7 by pressure. However, because a lining layer 9 made of a substance which has large releasability to resin and the coefficient of friction of which is small is formed on the inner surface of the crosslinking tube 7, the tube 5 lowers with no seizure to the inner surface. The tube 5 is stretched by pressurizing force along the inner surface 10A of a divergent die 10 and diametrical expanded. at this time, also because the lining layer 9 made of substance, which has large releasability to resin and the coefficient of friction of which is small, is formed also on the inner surface of the divergent die 10, the seizure of the tube 5 is prevented from occurring. In succession, the tube 5 is cooled down near to room temperature in a cooling tubular body 11 in order to obtain a heat- shrinkable tube.