ISOLATION AND CHARACTERIZATION OF ACETONE-INSOLUBLE SUBSTANCES IN CELLULOSE ACETATE PREPARED BY AN ACETIC ACID ACETYLATION PROCESS

摘要

Cellulose acetate fibers are commonly made by a dry-spinning process, in which cellulose acetate is firstly dissolved in acetone and then the cellulose acetate acetone solution is extruded through spinneret orifices that have extremely small diameters. Any insoluble substances in acetone solutions could cause disruptions in fiber extrusion, and are not tolerated. In this work, acetone-insoluble substances in cellulose acetates prepared from several kinds of pulps with varying cellulose content were isolated by ultracentrifugation, and characterized by using chemical, spectroscopic and chromatographic techniques. According to the results, acetone-insoluble substances are enriched in hemicellulosc acetates, lower in the degree of substitution and higher in crystallinity in comparison with corresponding cellulose acetates. Based on analysis, a possible mechanism for the formation of insoluble substances is proposed. Hemicelluloses residues in pulps and insufficient acetylation of crystalline cellulose play important roles in forming the insoluble substances in cellulose acetate acetone solutions.