Method for producing cellulose ester film

Abstract

A method for producing a film or sheet of a cellulose ester such as cellulose triacetate (TAC), cellulose diacetate, or the like, in which a film-forming solution is extruded through the slot of an extrusion die onto a support while a liquid is dropped at opposite ends of the die onto the flow of the film-forming solution emerging from the slot, thereby to prevent slugging of the solution, wherein a solvent contained in the dropping liquid contains a poor solvent for a solute in the film-forming solution in an amount in a range of from 30% to 90% by weight relative to a good solvent for the solute contained in the dropping liquid. With the invention, slugging is prevented and production efficiency improved without adversely affecting the formed film, without problems in separating the film from the support due to insufficient drying, and without requiring periodic cleaning of the support or reduction of the film production rate.

Dependencies are inferred from the claim text.