Originally developed for the dyeing of cellulose
acetate. They are substantially water insoluble. The dyes
are finely ground in the presence of a dispersing agent then
sold as a paste or spray dried and sold as a powder. They
can also be used to dye nylon, triacetate, polyester and acrylic
fibres. In some cases a dyeing temp. of 130 deg C is required
and a pressurised dyebath is used. The very fine particle
size gives a large surface area that aids dissolution to allow
uptake by the fibre. The dyeing rate can be significantly
