PURPOSE: To obtain a heat-insulating pipe enhanced in heat resistance, having sufficient heat-insulating effect and excellent in economical efficiency and handling properties by applying a polystyrene copolymer containing liquefied hydrocarbon gas to the outer peripheral surface of a metal pipe by extrusion coating and foaming the same to form a foamed polystyrene copolymer coating layer.
CONSTITUTION: An adhesive resin is extruded from a ring die 12 to be applied to the surface of a metal pipe 11 to form an adhesive layer 17. Thereafter, the metal pipe 11 is fed to a heating device 13 to be heated and the heated metal pipe 11 is fed to crosshead dies 14, 15. A polystyrene copolymer containing 0.5-10wt.% of liquefied hydrocarbon gas is extruded from a first extruder through the crosshead die 14 to be applied to the adhesive layer 17 formed on the surface of the metal pipe 11 to form a foamed polystyrene copolymer coating layer 18 which is, in turn, foamed by 3-20 times to form a foamed polystyrene copolymer coated pipe. By this constitution, a heat insulating pipe coated with a foamed resin can be produced by only one process.
OSUGA SHOICHI
MORIOKA YOSHIYUKI
