Лако-красочные материалы — производство

In the early days of primuline manufacture, dehydrothiotoluidine was a by-product and was remelted with sulfur to make primuline base. Today, the situation is reversed, and the previously worthless dehydro­thiotoluidine has become the main product, while primuline is the by­product. The dehydrothiotoluidine can be obtained pure by vacuum distillation.101 Unfortunately, it is not possible to conduct the fusion so that only the simple dehydrothiotoluidine is formed; statements to the contrary are incorrect.

Various types of dyes are prepared from dehydrothiotoluidine. The free base or its sulfonic acid is diazotized and coupled with various naph — tholsulfonic acids such as, for example, e acid (l-naphthol-3,8-disul — fonic acid). The resulting dye is characterized by its high purity of color and can be discharged to a pure white. Such red direct dyes are sold under various names, and are usually referred to as dyes of the erika red type. (Erika Z is the combination from dehydrothioxylidine and є acid. l-Naphthol-3,6-disulfonic acid gives a very similar dye.) In addition to the true azo dyes from dehydrothiotoluidine, two other prod­ucts are made which are important yellow dyes. One of these dyes is the naphthamine yellow NN (also called chloramine yellow) (Kalle), formed from dehydrothiotoluidinesulfonic acid by oxidation with so­dium hypochlorite. The other is thiazole yellow or Clayton yellow, which is made by combining the diazo compound of dehydrothiotolui­dinesulfonic acid with a second molecule of the same compound to form a diazoamino compound.

It should be noted in passing that alkylation of primuline produces beautiful yellow basic and acid dyes which, however, have no great importance (thioflavine T and S).