EFFECT OF SOLVENT TREATMENT ON THE DYEING RATE OF WOOL FIBER

The dyeing rates of wool fibers pretreated with t-butanol-n-heptane, formic acid, chloroform/methanol and aqueous n-propanol were investigated with reference to changes in the fine structure of wool fibers. The dyeing experiments were performed using C. I. Acid Orange 7 and Acid Red 73 in an acidic dyebath. An acceleration of the rate of dyeing by the solvent treatment was observed: the apparent dyeing rate increased in the following order; uncleaned (scourd) woolheptane treated) wool<formic acid treated wool=chloroform/methanol treated wooln-propanol treated wool. From the relationship between the relative dye uptake (Ct/C∞) and the square root of the dyeing time (t1/2), it can be seen that the surface lipid-type contaminants act as a factor interfering with the dye penetration. Further, it is apparent that the solvent treatments to extract lipid and protein materials facilitate the dye penetration within the bulk phase, Since the activation energy for the dye diffusion was the same for all the pretreated wool fibers, the diffusion mechanism of dye molecule within the bulk phase for all the solvent-extracted wools assumed to be nearly the same as that for the cleaned wool.Accordingly, the increase of the apparent dyeing rate is attributable to 1) the reduction of surface barrier effect and 2) faster movement of dye molecules within the cell membrane complex (CMC) and an increase of the effective internal surface area for dye penetration caused by the modification of bulk structure in the CMC.