method for almost simultaneously by means of extrusion application of at least two layers of different thermoplastic materials to a common core.and an extrusion device for the application of this method.

摘要

1,056,133. Extruding two or more plastic materials. WESTERN ELECTRIC CO. Inc. Feb. 11, 1964 [Feb. 13, 1963], No. 5602/64. Heading B5A. Two materials having differing plasticizing temperatures are extruded through a common extrusion head after being first heated to their plasticizing temperatures, the material with the lower plasticizing temperature being fed directly to a first extrusion die mounted in the head, the other material being cooled, whilst maintained in an extrudable condition and then fed to a second die mounted in the head. In the process described a coating of polyethylene from extruder 13 and polyvinyl chloride from extruder 12 are applied to a cable 18 in extrusion head 14. The latter material passes directly from the extruder 12 to the extruder head 14, whilst the polyethylene passes first through heat exchanger 16 to cool it before it passes to the extruder head 14, to avoid charring of the polyvinyl chloride in the head 14. A heater 11 is incorporated in the heat exchanger 16 to keep the polyethylene plastic during stoppages of the process. A third material may be fed to extrusion head 14 via heat exchanger 15.