Stretching polyethylene terephthalate film in a shortened span
Abstract
Abstract A METHOD OF STRETCHING A WEB OF THERMOPLASTIC POLYMERIC FILM HAVING THICKNESS (I.E., GAUGE) VARIATIONS THEREIN. THE WEB IS HEATED TO AN ELEVATED TEMPERATURE BY INDIRECT (I.E., NON-CONTACTING) HEATING MEANS AND STRETCHED AS IT MOVES BETWEEN SLOW AND FAST STEPS OF NIP ROLLS. THE ELEVATED TEMPERATURE TO WHICH THE WEB IS HEATED IS BETWEEN A MINIMUM TEMPERATURE AND A MAXIMUM TEMPERATURE DETERMINED, IN PART, BY THE STRETCHING RATE AND SUBSTANTIALLY ALL OF THE STRETCHING TAKES PLACE IN A SHORTENED STRETCHING SPAN BETWEEN THE HEATING MEANS AND THE FAST SET OF NIP ROLLS. THE HEATING MEANS IS POSITIONED CLOSELY ADJACENT THE FAST SET OF NIP ROLLS, WHICH FAST ROLLS PREFERABLY QUENCH THE WEB BELOW ITS GLASS TRANSITION TEMPERATURE AND DEFINE, WITH THE HEATING MEANS, THE SHORTENED STRETCHING SPAN. APPARATUS IS PROVIDED FOR PERFORMING THE ABOVE-DE SCRIBED METHOD.
Inventors
- 👤 R Peet
- 👤 T Hogshead
- 👤 H Foster
- 👤 K Paulsell
Bibliographic Details
Claims Analysis
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