| 摘要 |
PROBLEM TO BE SOLVED: To prepare an unmodified cellulose film to be used in contact with foods from a specific thermoplastic solution by a specific method which recovers the solvent for reuse. SOLUTION: This method is for producing unmodified cellulose films to be used in contact with foods from a thermoplastic solution composed of cellulose, water and a solvent of tertiary amine cellulose, comprising steps of (A) extruding the above solution, containing the solvent at 70 wt.% or more, into a first aqueous bath kept at 0 to 25 deg.C and containing the solvent at 5 to 30 wt.%, to form the films or the like; (B) treating the cellulose gel in the form of film or the like, prepared by the step A, by extracting with the solvent to reduce its solvent content to 45 wt.% or less, based on the dried cellulose, (C) bringing demineralized water into contact with the cellulose gel counter-currently at temperature higher than that of the first bath by 5 to 10 deg.C or less at first and at 35 to 70 deg.C finally (first washing step), (D) bringing water, kept at temperature higher than that for the first washing step, into contact with the cellulose gel for a sufficient time to further reduce solvent content (second washing step), (E) drying the cellulose gel to a solvent content of 40 ppm, based on the dried cellulose, and (F) recovering the solvent by treating the liquids from the first bath and first washing steps. |
