The Effect of Solvents in Wool Dyeing

Abstract

In order to study the mechanism of solvent‐assisted wool dyeing, using benzyl alcohol as the solvent, measurements have been made of ( a ) the sorption of the solvent from aqueous solution by wool, ( b ) the solubility of the solvent, and ( c ) its effect on the surface tension of water at different temperatures. The heats and entropies of sorption, surface formation and solution are consistent with the hypothesis that the sorption of benzyl alcohol by wool most probably consists merely of physical adsorption on the intermicellar surfaces in the fibre. Increased swelling of the wool fibres in aqueous solutions of the solvent is not apparent, and the accelerated rate of dyeing is shown to depend on the affinity of the dye for the solvent, as measured by the partition ratio of dye in the solvent to dye in the water. The solvent lowers the activation heat barrier, but increases the activation entropy barrier: whether it accelerates or retards dyeing depends on which is affected to the greater extent.