METHOD AND APPARATUS FOR PRODUCING HOLLOW MOLDED PRODUCT

摘要

PROBLEM TO BE SOLVED: To reduce the deformation of an end surface by heating the outer surface of a preparatory hollow molded product formed by cooling and solidifying an uncured hollow molded product of an extruded molten thermoplastic resin and reheating the part of the outer surface side while keeping the solidified state of the inner surface of the molded product and the part in the vicinity thereof to temp. relaxing the internal stress of the resin before cooling the same. SOLUTION: The uncured hollow molded object 6 extruded from an extrusion mold 5 in a molten state is introduced into a vacuum spray water tank 2 at first and cooled from the outer surface side thereof by water while shaped by a cooling shaping mold to form a preparatory hollow molded object 7. Next, the preparatory hollow molded object 7 is immediately introduced into a far infrared heater 3 to be heated from the outer surface thereof and the part of the outer surface side of the preparatory hollow molded object is reheated to the m.p. of -20-+80 deg.C of the thermoplastic resin constituting the molded object and the temp. of the inner surface held to a solidified state of the molded object and the part in the vicinity thereof is held to the m.p. of -40 deg.C or lower of the thermoplastic resin. Finally, a hollow molded object 8 remelted on the outer surface side thereof is introduced into a spray water tank 4 and cooled from the outer surface thereof by water to continuously obtain a hollow molded object 9.