Patent ID: 6096258
Filing Date: 2000-08-01
Classification: A22C

Abstract:
A process for forming a nonderivatized cellulose film suitable for direct food contact from a thermoplastic solution of cellulose, water and a tertiary amine cellulose solvent including recovering the solvent for reuse, said process comprising the steps of:a) extruding the solution comprising at least 70% solvent as a tube or film into an aqueous first bath, the first bath causing the extraction of sufficient solvent to precipitate a cellulose gel from the solution in the form of a tube or film which has a solvent content of less than 45% by weight of dry cellulose;b) maintaining the aqueous first bath at a temperature of 0 to 20.degree. C. and a solvent concentration of 5 to 30% during the course of extracting solvent from the extruded solution;c) subjecting the tube or film of cellulose gel from the aqueous first bath to a first washing for extracting solvent from the cellulose gel, the first washing being conducted by flowing demineralized water countercurrent to the passage of the cellulose gel, the temperature of the water being not more than 5 to 10.degree. C. higher than the temperature of the aqueous first bath where the cellulose gel first contacts the countercurrent flow of the first washing and between 35 and 70.degree. C. where the cellulose gel last contacts the countercurrent flow of demineralized water;d) subjecting the cellulose gel from the first washing to a second washing of hot water maintained at a temperature above the hottest temperature of the first washing and maintaining the cellulose gel in contact with the second washing for a time sufficient to further reduce the solvent content of the cellulose gel;e) drying the cellulose gel to provide a cellulose film or tube having a solvent content of not more than 40 ppm based on the weight of dry cellulose; andf) treating liquid from the aqueous first bath first and washing to recover solvent in these liquids.