These dyes were originally developed for the dyeing
of cellulose acetate, and are substantially water insoluble. These dyes
are finely grounded in the presence of a dispersing agents and then sold
as a paste, or spray-dried and sold as powder. These can also be used
for dyeing nylon, cellulose triacetate, polyester and acrylic fibers. In
some cases, a dyeing temperature of 130 °C is required, and a
pressurized dye bath is used for this purpose. The very fine particle
size gives a large surface area that aids dissolution to allow uptake by
the fiber. The dyeing rate can be significantly influenced by the choice
of dispersing agent used during the grinding.
Polyester generally requires the use of disperse
dyes. Other methods of dyes leave the color of polyester almost entirely
unchanged. While novices happily charge into dyeing with acid dyes (for
wool or nylon) and fiber reactive dyes (for cotton and rayon), often
with the most effective results, the immersion dyeing of polyester is a
different story.
Disperse dyes work excellent on synthetics, of course - that's what
it's for. Only wool, rayon, silk, and cotton refuse to take it. Nylon
extensively prefers disperse dye. All others fibers which are synthetic
that dyed with disperse dye, so there is some darkness behind the mostly
undyed natural fibers.