Studies on mixture dyeing. IV. Equilibrium adsorption of direct dyes

Abstract

AbstractChrysophenine G (C.I. Direct Yellow 12), Benzopurpurine 4B (Red 2), Sirius Red 4B (Red 81), Sirius Supra Blue BRR (Blue 71) and Sky Blue 6B (Blue 1) were selected as typical direct dyes, and the equilibrium adsorptions on cellulose (Cellophane) from the 1:1 and 2:1 molar mixture dye baths were investigated at 90° and 70°C. The standard affinity in mixture dyeing was obtained by the equation derived from the assumption of monodispersed and diffusive adsorption. The standard affinity in mixture dyeing was nearly equal to that in single dyeing, except for the Chrysophenine G–Sky Blue 6B system. However, judging from the fiber and solution log sum plots, there was a definite difference between mixture and single dyeing. It was explained by the change of activity of dye and sodium ions on substrate followed by the marked change of the total adsorption. The adsorption behavior of direct dyes is discussed in detail from the viewpoint of concentration dependence of the activity coefficient of dye and sodium ions on the substrate.