Comprehensive Study on Cellulose Swelling for Completely Recyclable Nonaqueous Reactive Dyeing

Abstract

The swelling of cotton by non-nucleophilic organic solvents was investigated to achieve completely recyclable reactive dyeing. The degree of swelling was determined and correlated to the Hansen Solubility Parameter distance (<i>Ra</i>) of cellulose to the solvents and the dielectric constant of the solvents (ε). The effect of swelling temperature was also investigated. Preswelling of cotton fabrics by 150 °C <i>N</i>,<i>N</i>-dimethylacetamide (DMAc) for 1 h was found to be sufficient to accelerate dye sorption. Dyeing was carried out using C.I. Reactive Red 24 in a 40/60 mixture of DMAc and dimethylcarbonate (DMC), a cosolvent selected to facilitate dye exhaustion. The efficiency of unfixed dye removal was found to predominantly correlate to swelling (<i>R</i>² = 0.9236). Excellent colorfastness was achieved with 4 rinses by 95 °C DMAc. A 10-cycle repeated dyeing sequence was demonstrated to give 43% and 90% reduction in dye consumption and disposal. The overall reduction in material disposal was estimated to be over 99.99%. The favorable results indicated that discharge-free reactive dyeing could be made possible