To obtain an inexpensive yellowly or greenly dyeing method that can obtain excellent clarity of hue, dyeing properties, light fastness, without having discoloration and fading of color even under alkaline conditions, without having the change of color with lime, satisfying consumers, and can obtain excellent fastness and persistance industrially advantageously, by using rutin, a water-soluble antioxidant and an alkaline substance.
Rutin is subjected to alkaline conditions to develop yellow color, and then treated with a water-soluble antioxidant to stabilize the yellow color. Rutin is contained in almost all plants, is called also vitamin P and has features such as antioxidant action, ultraviolet absorbing action, vessel strengthening effect, capillary dilation effect and antihypertensive action. It is used in the form of a fine pale yellow power chiefly obtained by extracting buds of a Japanese pagoda tree. It has very little water solubility but can develop clear yellow when alkalified. The alkalifying agent is exemplified by sodium carbonate, potassium carbonate or calcium hydroxide, and the pH is 7.5 or above. The water-soluble antioxidant is exemplified by L-ascorbic acid or sodium L-ascorbate.
IKEBE HIROYUKI
OKAZAKI SANAE
