METHOD OF AND APPARATUS FOR STRETCHING FILM

摘要

E.I. du Pont de Nemours and Company(Levy, S.B. /A Garlington, W.D.) A method and apparatus are provided for stretching polymeric film wherein a web of film is preferentially heated and thereafter stretched, such heating being accomplished by air moving past electric heaters positioned in thermal isolation zones in a duct the bottom wall of which has an aperture located closely adjacent a surface of the film and between the inner edges of tenter frame clips carrying the film whereby, by varying the input to a selected heater, air passing through the aperture onto the web will preferentially heat it.