Importance

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Abstract

A system and method for extruding film with a thickened profile section. In some embodiments, the film forms bags with integral zipper profiles. Plastic film is extruded to form a tube. During extrusion, cooling jets direct cooling gases toward the thickened profile section below the frost line to preferentially cool the thickened profile sections. In some embodiments, warm air is drawn out of the tube interior through hot air intakes located below the frost line. In certain embodiments, the film is extruded at a higher rate of speed than conventional processes. Likewise, the extruded film tube is expanded at a lower blow up ratio than conventional processes in certain preferred embodiments. In some embodiments, the extrusion system includes an air flow surface oriented relative to the film tube to define an air flow gap of substantially uniform thickness.

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First Claim