CARBOXYMETHYLCELLULOSE SYNTHESIS IN ORGANIC MEDIA CONTAINING ETHANOL AND OR ACETONE/

A study of the carboxymethylation of wood pulp cellulose and cotton li nters cellulose in different organic media, namely, ethanol, acetone, and ethanol-acetone mixtures, is performed. Previously, the ethanol-ac etone 1 : 1 (w/w) mixture used as reaction medium was found to give a higher degree of substitution (DS) than the pure solvents separately. In the present work, the kinetic investigation of cellulose carboxymet hylation was carried out in ethanol-acetone 3 : 7 (w/w) mixture, as we ll as in acetone as reaction media, and the same synergistic effect of the solvents mixture was observed. The data suggested a pseudo-first- order kinetic behavior satisfactorily described by the following equat ion: In(1.11 - DS) = -kt. The two reaction steps observed are related to the transformations of less ordered regions with higher reaction ra te and more ordered regions with smaller reaction rates, respectively. A possible explanation for this behaviour is given, taking into accou nt the different structural changes of cellulose crystallinity and acc essibility produced by ethanol-acetone 3 : 7 (w/w) mixture, ethanol, a nd acetone, as revealed by X-ray diffraction and calorimetry determina tions. (C) 1998 John Wiley & Sons, Inc.