PROCESS FOR HIGH-SPEED PRODUCTION OF WEBS OF DEBOSSED AND PERFORATED THERMOPLASTIC FILM

摘要

The present invention provides a process for debossing and perforating a substantially continuous web of substantially planar thermoplastic film, using a forming structure having a patterned forming surface with holes and an opposed surface. The forming structure is open from the holes in the forming surface to the opposed surface. The forming structure moves in a direction of the length of the web of film and carries the web of film in that direction. The web of film is substantially entirely molten. A fluid differential pressure is substantially continuously applied across the thickness of the web of film from a first position along the direction of movement of the forming structure to a second position. The first and second positions are fixed relative to the moving forming structure. The fluid differential pressure is sufficiently great to cause the first surface of the web of film to be urged against the forming surface and to cause perforations to be created in the web of film. Thus a web of debossed and perforated film is formed in the image of the forming surface from the web of film. Fluid differential pressure holds the web of debossed and perforated film against the forming surface without permitting substantial spring-back of the film. Cooling fluid is applied to the second surface of the web of debossed and perforated film after the film is debossed and perforated and before the web of debossed and perforated film passes the second position. Thus the web of debossed and perforated film is cooled without permitting substantial spring-back of the film and is set by the time the web of debossed and perforated film passes the second position.