GB429739A - Improvements in the manufacture of cellulose esters - Google Patents

Abstract

Organic esters of cellulose are stabilized by treatment in an atmosphere of steam. Preferably the treatment is carried out on the cellulose ester precipitated after esterification or after ripening. The ester may be washed prior to the steam treatment or may be treated with a substance of weakly alkaline reaction to remove excess of acid present. The presence of a small amount of acid in the material, however, facilitates stabilization. The steam may have a temperature of the order of 100 to 145 DEG C., and may be employed at ordinary, reduced, or increased pressure. The steaming may be carried out in a cylinder having a perforated bottom through which the steam enters, or the cellulose ester may be carried on a conveyer through a chamber in which steam is circulated. The ester may be finally dried by steam alone, or by steam and hot air, or by hot air alone. In an example, cellulose acetate after ripening, is precipitated from solution, washed by spraying with water, and treated in an atmosphere of steam at 112 DEG C. During the last quarter of an hour of the steam treatment, hot air at 112 DEG C. may be mixed with the steam. In other examples, cellulose acetate precipitated from a ripening solution is drained of excess liquid and treated with steam at 110 DEG C. Towards the end of the treatment, hot air is mixed with the steam. The products have a high heat test and a high clarity, and are resistant to the action of hot water. They may be used in the manufacture of filaments, films, plastics, lacquers, and the like.