EFFECT OF PH ON NONFORMALDEHYDE DURABLE PRESS FINISHING OF COTTON FABRIC - FT-IR SPECTROSCOPY STUDY .2. FORMATION OF THE ANHYDRIDE INTERMEDIATE

Esterification of cotton cellulose by a polycarboxylic acid proceeds in two steps: the formation of a five-member cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups of the polycarboxylic acid, and the reaction between cellulose and that intermediate to form an ester. We studied the effect of finish bath pH on anhydride intermediate formation using Fourier transform infrared spectroscopy. Our previous research demonstrated that esterification of cellulose by a polycarboxylic acid was not acid-catalyzed. The infrared spectroscopy data presented here indicate that the amount of anhydride intermediate formed in a cotton fabric increases as the finish bath pH decreases from 4.5 to 1.5. Therefore, the formation of the cyclic anhydride intermediate is accelerated by an increase in proton concentration of the finish bath. Anhydride intermediate formation and cellulose esterification show different pH-dependencies.