Patent ID: 6418732
Filing Date: 2002-07-16
Classification: B29C

Abstract:
A process for cooling extruded plastic hollow sections having inner walls, the plastic hollow sections being useful for making pipes, comprising:directing liquid or supercritical carbon dioxide through an extruder head by disbursing the liquid or supercritical carbon dioxide from several nozzles that are arranged axisymmetrically with the extruded hollow section in or with an annular nozzle that is arranged coaxially with the hollow section, while the hollow sections are extruded therefrom, and depressurizing the carbon dioxide before the carbon dioxide comes into contact with the inner wall so that carbon dioxide in gaseous and solid form is produced to cool the interior of the plastic hollow sections as the sections are extruded by the extruder head; wherein the carbon dioxide that is in gaseous form is brought into heat exchange with the inner wall of the hollow sections only to the extent that the inner wall of the hollow sections is not damaged.