Dyeability of Acid Dyes on Wool Fabrics Treated with Ozone and an Enzyme

Abstract

In a previous paper, the dyeability of leveling acid dyes for shrink-proofed wool fabrics treated with permonosulfate (PMS) and a keratinase was discussed on the basis of the dyeing rate and sorption isotherms. In the present study, ozone was employed instead of PMS for the pretreatment of wool fabrics to achieve a zero-AOX shrink-resist process. Three kinds of leveling acid dyes, which have one, two, or three sulfonate groups, were used. The dyeing rate and sorption isotherms were determined to elucidate the effects of the dye structure and the treatment of the wool fibers. The apparent diffusion coefficients were considerably diminished by the ozone treatment, but they were restored by the subsequent treatment with the enzyme. The sorption isotherms were analyzed using dual sorption mechanism to evaluate the three sorption parameters, which are the number of binding site, S, the intrinsic binding constant for the Langmuir type sorption, KL, and the partition coefficient, KP. The equilibrium dye uptake and the S values were almost unchanged by the ozone treatment. The KL values for the ozone-treated fibers were slightly decreased compared to those of the untreated ones. The ESCA spectra showed the presence of cystine monoxide (-SO-S-), cystine dioxide (-SO2-S-), and cysteic acid (-SO3-) after the treatment with ozone. If cysteic acid was generated on the fiber surface and also cell membrane complex (CMC) after the ozone treatment, the dyeing behavior should be influenced by the repulsion between the negatively charged cysteic acid and negatively charged acid dyes. The decreased dyeing rate and the unchanged dye uptake after the ozone treatment suggest that the action of ozone is limited onto the fiber surface and CMC, and does not affect the bulk structure of the fibers.