Processes and apparatus for liquid bath cooling of extruded foils

摘要

Process for cooling a freshly extruded, incompletely solidified foil of a thermoplastic polymer by extruding said foil into a liquid cooling bath and directing against said foil below the bath surface along a line extending the entire width of said foil at least one narrow, unbroken stream of cooling liquid. The stream(s) respectively are directed angularly against a side of said foil at right angles thereto or in a direction opposite to the direction of movement of said foil into said bath, i.e., at an angle between 0 DEG and 60 DEG relative to a plane which is normal to said foil. The apparatus embodies an extrusion nozzle for extruding the foil downwardly into a body of cooling liquid in a tank directly below said nozzle. One or more tubes are normally immersed in said body of liquid and extend longitudinally parallel to and in juxtaposition to the foil entering said body of cooling liquid and also parallel to the upper surface of the cooling liquid. The tube(s) have a longitudinal slit which faces the foil and is at least substantially coextensive with the width of nozzle and the width of the foil extruded therefrom, and a pipe within each tube to supply a cooling liquid to each tube, such pipe(s) being at least substantially coextensive with the slit and extending longitudinally inside said tube(s) in spaced relationship thereto. Such pipe(s) have a plurality of liquid discharge holes directed toward the side of the tube(s) which is directly opposite to said longitudinal slit.