Predominantly monoaxially oriented film of thermoplastic material, as well as a method and apparatus for the production of mainly monoaxially oriented films, made of thermoplastic material

摘要

1414785 Helically oriented tubular films; laminates KONINKLIJKE EMBALLAGE INDUSTRIE VAN LEER BV 31 May 1973 [31 May 1972] 25403/72 Headings B5B B5A and B5N Tubular film is extruded from die 1, inflated, and collapsed by nip rollers 8 and oriented helically by relative rotational movement, about the axis of extrusion, between die 1 and nip rollers 8. At least one mandrel is used to maintain the required diameter; in the illustrated embodiment two mandrels 3 and 4 are used. The mandrel(s) is (are) rotatable about the extrusion axis and coolable, for instance by water supplied via pipes 6. Cooling air is supplied to the outer surface of the film, as it passes between die and mandrel, by means of air ring 10. Internal heater 7 may be used if required. If more than one mandrel is used they may be rotatable independently of each other and may even rotate in the sense opposite to that of the die or nip rollers. The process is disclosed particularly for films of polypropylene and polyethylene. The tubular film produced is helically oriented, the direction of orientation forming an angle of at least 10 degrees with the axis of the tube. In one embodiment a polyurethane adhesive is introduced via the mandrel and sprayed on to the inner surface of the film. When the film is collapsed it sticks together to form a laminate.