Processing extruded thermoplastic foam - high pressures at e.g. extruder screw tip are isolated from subsequent processing tools by suitable form of back flow valve

摘要

Thermoplastic foams are produced in the form of tubes, profiled sections and sheets by means of single or multiple-screw extruders and the necessary processing equipment. This equipment is operated with the material at a pressure of 50 to 1,000 bar which is kept separated from the lower pressure material by a valve; the high pressure is not allowed to act on the extruder even though the material is fed from the extruder to the processing tool. ADVANTAGES - The system prevents the difficulties which arise when the high material pressure at the extruder screw tip is allowed to reach the processing equipment, especially if the latter is extruding thermoplastic foam.