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US 4,536,362 AGranted
Method for producing longitudinally ribbed plastic film
AssigneeMobil Oil Corporation
InventorJack J. Donaldson
Life of this patent
Estimating the term…
Abstract
A longitudinally ribbed plastic film is produced by extruding through a pair of die lips, at least one of which is provided with slots which run at an angle to the direction of resin flow across the die lips. Impurities in the resin tend to collect in the slots, and thus in the ribs of the film. This occurs because of the shear stress field created by the slots. A high melt viscosity component of a multi-layer coextrusion behaves in a fashion similar to the impurities and is substantially extruded in the ribs.
Claims8
A process for extruding a plastic film, comprising:
- transporting molten resin to an extrusion die inlet;
- flowing said resin under pressure from said inlet to a narrow outlet, comprising two spaced, substantially planar lips, said resin flowing in a given direction across said lips, one of said lips being interrupted by a plurality of substantially parallel slots, said slots running at an angle to the given direction, and being spaced so that resin flowing in said given direction across said slotted die lip passes across at least one of said slots;
- drawing said extruded film from said outlet in a direction substantially the same as said given direction to produce an extruded film having ribs formed by said slots extending in the given direction.
Dependencies are inferred from the claim text.