Dyeing Behaviors of Acid Azo Dyes with Alkyl Groups of Different Carbon Number in Nylon

Abstract

Equilibrium sorption and diffusion rates of acid dyes in nylon dyeing were investigated. The dyes used have alkyl groups containing O-12 carbon atoms. The sorption isotherms were analysed quantitatively by a dual sorption model, consisting of partition (P) and Langumuir (L) mechanism. With increase in the number of carbon atoms, the P type contribution increases equilibrium sorption. Dyes containing alkyl groups with less than 10 of carbon atoms were sorbed stoichiometrically by the L type mechanism at the charged amino end groups of nylon. On the other hand, when the groups contained 10 and 12 of carbon atoms, the dyes were sorbed in excess of the equivalent of charged amino end groups.Diffusion profiles in the nylon substrate were determined by the cylindrical film roll method and the results were interpreted by the same dual model. The longer the alkyl group, the larger in the contribution of P type diffusion, but its contribution to total diffusion is small. The concentration dependence of the diffusion coefficient of the L type varied with the length of the alkyl chains.