The Disperse Dyes — Their Development and Application

The disperse dyes have come to be applied to a very large number and variety of fibres and have therefore achieved an importance which is probably greater than the weights used would suggest. They were the first type to be applied directly to a fibre from an insoluble suspension. Their preparation includes a process of particle size reduction and often subsequent drying, both in the presence of a dispersing agent. The mechanism of dyeing with them would seem to entail their passing from suspension through solution on to the fibre, to which they become attached by non‐polar forces. The colouring matters used in the preparation of disperse dyes belong mainly to three chemical groups. The connection between dyeing and fastness properties on the one hand and chemical constitution on the other is in general indefinite. However, the best fastnesses are obtained by moving in the direction of greater molecular complexity, but this unfortunately is accompanied by a reduction in dyeing power. The introduction in recent years of the man‐made fibres has accelerated the development of new application methods, and these are assisting the dyer to utilise these more complex dyes. This tendency emphasises that the achievement of better fastness with disperse dyes will require, as with other dyeing classes, a close understanding between, and the combined efforts of, both those working on the elaboration of new dye structures and those whose interests lie in one or other aspects of dye application.