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Abstract

The dyeing of artificial silk at one time presented many difficulties, which have, however, been overcome so far as the silk made by the Chardonnet and Viscose processes is concerned. On the other hand, the new “acetate silk” does not lend itself with equal readiness to the dyeing operation and, hitherto, some difficulty has been experienced in producing an adequate range of fast and pleasing colours. The “acetate silk” arose as an outcome of the war, when the general opinion was reached that the method of the Dreyfus Brothers for producing aeroplane dope from acetyl cellulose was the best. The large factories which were then built for the preparation of this substance had, when the war ceased, to turn their energies for the most part into other directions, and the manufacture of artificial silk was one of these. The silk is of great lustre and beauty, but as the composition of the acetyl cellulose remains unaltered even in fibre form, it does not possess any marked affinity for that large and important class of colouring matters which are substantive to cotton. This affinity can, however, be imparted to the fibre if conditions are present which cause it to undergo hydrolysis in the dyebath, and Prof. A. G. Green, working in the Research Laboratories of British Dyes Ltd., has now succeeded in isolating a new and curious series of colouring matters which are apparently particularly suited for the purpose of dyeing acetate silk. These colouring matters belong to a class of compound which is readily hydrolysed in solution, and in that form can be fixed on theacetate silk. Moreover, the “Ionamines,” as Prof. Green has named the new colours, can be made to possess a diazotisable amino group, and many beautiful shades can be obtained by diazotisation and development on the fibre. It follows also that, since the ionamines possess no affinity for the cotton fibre, it is possible to dye a fabric composed, for example, of cotton and acetate silk, two colours in one bath. Thus, in a bath containing a mixture of chlorazol green BN (a substantive cotton dye) and ionamine KA, the cotton will be dyed green and the acetate silk red. The effects, which are very striking, should go far to render the new silk popular.