Dyeing Cotton with a Reactive Dye from Polar-Nonpolar Solvent Systems

Abstract

An attempt was made to dye an aqueous alkali swollen cotton with CI Reactive Red-31 from polar/nonpolar solvent mixtures. For this purpose acetone was selected as the nonpolar solvent and the various polar solvents were water, formamide, di methylsulfoxide, dimethylformamide, and dimethylacetamide. At a suitable ratio of solvent mixture and alkali concentration used for cotton preswelling, it was possible to get 100% dye bath exhaustion and dye fixation of 79-82%, except from dimeth ylformamide-acetone and dimethylacetamide-acetone solvent mixtures. The propor tion of polar-nonpolar solvent necessary to get highest dye bath exhaustion and dye fixation was dependent on the dielectric constant of the polar solvent. Some of the polar solvents were good swelling agents for cotton as indicated by their imbibition values and high dyebath exhaustion. It was therefore possible to carry out dyeing without water preswelling; however, since the alkali used for dye fixation was insoluble in the solvents, aqueous alkali preswelling was essential. Concentration of alkali re quired during preswelling to get maximum dye exhaustion and fixation was different for different polar solvent-acetone mixtures. This was attributed to the desorption and readsorption of alkali from the solvent mixtures to different extents.