Method and apparatus for uniformly stretching thermoplastic film and products produced thereby
AssigneeClopay Plastic Products Company, Inc.
InventorsLeopoldo V. Cancio, Thomas G. Mushaben, Robert M. Mortellite, Pai-Chuan Wu
Life of this patent
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Abstract
Thermoplastic films and laminates are made by extrusion and stretching using differential speed rollers employing a short stretching gap of no more than one inch immediately after the extruded film product is formed. The method and apparatus control the thickness of the stretched film and impart desirable mechanical properties thereto such as film products with a high modulus for handling and suitable tensile for softness.
Claims51
A method of making thermoplastic film, comprising
- extruding a thermoplastic extrudate in the form of a web in its molten state,
- locating a chill roller operating at a peripheral velocity (V1) and at a temperature (T1) to receive and cool said web thereby forming a film,
- locating a second roller operating at a peripheral velocity (V2) greater than said V1 to receive said film at a temperature (T2),
- spacing said second roller from said chill roller to provide a roll gap of no more than one inch between said chill roller and said second roller for stretching said film,
- uniformly stretching said film in said roll gap at a stretch temperature between said T1 and T2 at a speed between said V1 and V2 to form stretched thermoplastic film having a substantially uniform gauge.
A method of making a breathable and liquid barrier microporous thermoplastic film comprising
- extruding a microporous formable thermoplastic molten extrudate selected from the group consisting of polypropylene, polyethylene, copolymers thereof and blends thereof, said extrudate containing a pore-forming filler,
- locating a chill roller operating at a peripheral velocity (V1) and at a temperature (T1) to cool said web thereby forming a microporous formable film,
- locating a second roller operating at a peripheral velocity (V2) greater than said V1 to receive said film at a temperature (T2),
- spacing said second roller from said chill roller to provide a roll gap of no more than one inch between said chill roller and said second roller for stretching said film,
- stretching said film in said roll gap at a stretch temperature between said T1 and T2 at a speed between said V1 and V2 to form a microporous thermoplastic film having a film thickness of about 0.25 to about 10 mils.
Dependencies are inferred from the claim text.