STUDIES ON THE DYEING OF WOOL

(PART VIII) DYEING WITH SYNTHESISED NITRSO DYE IN THE FIBRE

Abstract

Some aromatic compounds containing hydroxyl group in the ortho position to the nitroso group are isomerised to quinone oxime, which combines with metallic salt to produce coloured complex. Metal-complex possess property of very sparingly soluble in water. Showing part only of the benzene ring adjacent to a nitroso group, and its mechanism is two folds-
The typical process of its application is as follows: First, wetted loose wool are soaked at 50°C. in a bath containing 10_??_15% acetic acid and 8_??_15% naphthol sulfonic acid, the temperature of the bath is raised to boil in 30min. and kept at boiling for 1hr. Next, after the bath in drained, it is cooled slowly down to near 0°C., 3% sodium nitrite is added, cooling continued for 30_??_60min. And then after the wool is sufficiently rinsed, the colour is developed by chelation for 30min. at 100°C. in fresh bath containing 3_??_5% metallic salt and 10% acetic acid. Most compounds can produce complex by introducing nitroso group into the same bath, but in this case the necessary requirment is that it must be absorbed by the wool completly in the bath.
Amino naphthol, being cheaply available, are largely employed as intermediate of azo dyestuff for practical use, and a large range of shades are obtained from different metal, e. g. Al, Cr, Fe, ……, by taking advantage of the polygenetic character. In general, ferrous sal t gives the brightest hue and best fastness to rubbing. To dye the wool with Naphthol Green only a small quantity of nitroso dye is used, but nitrosocompounds also may be employed by making good use of its property capable of producing metal-complex.