MANUFACTURE OF RESIN TUBE

PURPOSE:To manufacture a tubular body of high dimension accuracy and roundness by cooling a surface layer section of the tubular body only just after extruding crystal resin into the tubular shape, passing the same through the inside of a calibrator having its inner diameter regulating the outer diameter of the tubular body and then raising the temperature and then cooling gradually. CONSTITUTION:A tubular body 3 extruded out of an extruder 1 after passing through an extrusion mold 2 is passed through a sizing die 5, and then solidified by quenching the outer surface of the tubular body 3 down to the temperature of thermal deformation by cooling water 12 of a water cooling section A. Then the temperature control is carried out in a manner that the surface layer section of the tubular body 3 is cooled lower than the melting temperature and higher than the thermal deformation temperature a heating section B, and the tubular body 3 is heated up to the temperature lower than the melting temperature and higher than the thermal deformation temperature by passing the tubular body 3 in a calibrator 8 having the inner diameter regulating the outer diameter of the tubular body 3 and then crystallization of the tubular body 3 is in progress. When the surface layer section of the tubular body is cooled gradually to reach the temperature lower than the thermal deformation temperature, the same is quenched by cooling water 12 of a water cooling section C or cooled slowly as it is.