Dyeing for Silk Fabrics by Utilising Chemical Oxidation of (+)-Catechin

摘要

The silk dyeing utilising chemical oxidation of (+)-catechin was attempted in order to establish the deep dyeing at low temperature in a short time for inventing novel human- and eco-friendly dyeing. In the study, the dyeability of the new oxidation technique was compared with the mordanting method. The compounds giving Al3+, Cu2+, Fe2+, or Fe3+ ion in aqueous solution were used as mordants for the mordanting dyeing. The oxidation by the use of O₂, H₂O₂ or NaIO₄ was tried for the oxidation dyeing. The two-step treatment was performed as the oxidation dyeing, in which the first treatment is adsorption of (+)-catechin onto the silk fabric and the second one is oxidation of the adsorbed (+)-catechin by the oxidant. The results show that O₂ and H₂O₂ are not available as oxidants for the oxidation dyeing. The silk fibre is dyed brown colours by the mordanting dyeing and deep reddish brown by the oxidation dyeing with NaIO₄ at 30 °C and pH = 7.0 for 80 min of total treatment time. The dyeability of the oxidation dyeing with NaIO₄ is much higher than that of mordanting dyeing. Colour fastness obtained by the oxidation dyeing to washing is high enough in practical use.