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 Al~(3+), Cu~(2+), Fe~(2+), or Fe~(3+) ion in aqueous solution were used as mordants for the mordanting dyeing. The oxidation by the use of O_2, H_2O_2 or NaIO_4 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 O_2 and H_2O_2 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 NaIO_4 at 30 ℃ and pH = 7.0 for 80 min of total treatment time. The dyeability of the oxidation dyeing with NaIO_4 is much higher than that of mordanting dyeing. Colour fastness obtained by the oxidation dyeing to washing is high enough in practical use.