Wikipedia
Disperse dye
Disperse dyes are the only water-insoluble dyes that dye polyester and acetate fibers. Disperse dye molecules are the smallest dye molecules among all dyes.
A disperse dye molecule is based on an azobenzene (as Disperse Red 1 or Disperse Orange 37) or anthraquinone molecule with nitro, amine, hydroxyl, etc. groups attached to it.