Device for continuous production of thermoplastic webs

Claim 1

Apparatus for the continuous fabrication of thermoplastic webs, particularly useful for further processing into panels or sheeets, comprising: web means for producing a continuously advancing thermoplastic melt web at a processing temperature; a double-band press arranged downstream of said web means in the advancing direction of the melt web, for receiving, calibrating and smoothing the melt web, said double-band press comprising a rigid press frame, upper and lower pairs of reversing drums rotatably supported on said rigid press frame, an upper endless press belt guided over said upper pair of reversing drums and a lower endless press belt guided over said lower pair of reversing drums, said upper and lower endless press belts having outer surfaces which face each other between said upper and lower pairs of reversing drums to define a reaction zone, said reaction zone having one end between one of said upper pair of reversing drums and an adjacent one of said lower pair of reversing drums, defining a feed zone for receiving the melt web into the reaction zone; pressure means acting on at least one of said endless press belts for exerting a pressure on the melt web in said reaction zone; and cooling means for cooling the melt web in said reaction zone; said pressure means comprising a pressure plate mounted to said press frame inside at least one of said upper and lower endless press belts, said pressure plate extending over said reaction zone and being spaced from an inside surface of said one of said upper and lower endless press belts for defining a pressure space therewith, said pressure space being provided for receiving a fluid pressure medium for applying a pressure to said one of said upper and lower press belts for exerting a pressure on said reaction zone, said pressure means including an enclosing seal extending around said pressure plate and extending between said pressure plate and the inside surface of said one of said upper and lower press belts for confining a fluid pressure medium in said pressure space; said cooling means comprising said pressure plate including a plurality of cooling fluid channels for receiving a cooling fluid to cool said pressure plate to a temperature below the processing temperature for coolin the melt web to a final temperature below the processing temperature, said cooling means including a plurality of heat conducting elements in dragging contact with the inside surface of said one of said upper and lower press belts, said heat conducting elements being connected to and in heat conducting contact with said pressure plate for conducting heat from said one of said upper and lower press belts to said pressure plate and to cooling fluid flowing in said cooling fluid channels of said pressure plate, at least some of said heat conducting elements being disposed near said cooling fluid channels and said heat conducting elements being distributed along said pressure space defined by said pressure plate so that the melt web progressively cools as it moves through said reaction zone while at the same time being smoothed and calendered in said reaction zone.