PRODUCTION OF SEAMLESS TUBE

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a large quantity of seamless tubes having a uniform electric resistance distribution in the circumferential direction at low costs. SOLUTION: In a method in which a thermoplastic resin having a prescribed conductivity is melt-extruded from a ring-shaped die 12 set in an extruder 11 in a tubular shape, cooled and solidified, and taken up continuously with its shape kept to mold a seamless tube, the volume receptivity and the surface resistivity on the circumference crossing at right angles to the take-up direction of the solidified tube T are measured. On the basis of the measured values, the temperatures of at lest two positions in the circumferential direction of the extruded tube are partially controlled by a temperature controller 15a being constituted of an electric heater, a refrigerator passage, refrigeration inlet and outlet pipes, and the like.