Definition and History of Disperse Dye
by : Rahul Sharma
Disperse Dye:
A class of sightly water - soluble dyes originally introduced for dyeing acetate and usually applied from fine aqueous suspensions. Disperse dyes are widely used for dyeing most of the manufactured fibers.
Dyes are colored, unsaturated organic chemical comounds capable of giving colour a substrate, i.e. colouring or dyeing it.
The term "Disperse Dye" have been applied to the organic colouring substances which are free from ionizing groups, are of low water solubility and are suitable for dyeing hydrophobic fibers. The dye has derived its name for its insoluble aqueous properties and the need to apply it from an aqueous dispersion. Of all the dyes, they are of the smallest molecular size.
Disperse dyes have substantivity for one or more hydrophobic fibers e.g. cellulose acetate, nylon, polyester, acrylic and other synthetic fibers.
The negative charge on the surface of hydrophobic fibers like polyester can not be reduced by any means, so non-ionic dyes like disperse dyes are used which are not influenced by that surface charge.
History of Disperse Dye:
In 1922, Green and Saunders made one type of coloured azo compoud, in which a solubilizing group ( for example - methyl sulphate, -CH-SO3H) is attached to amino group. In dye bath, they are slowly hydrolyzed and produce azo compouned and formaldehyde bi sulphate. This free azo compound was capable of dyeing cellulose acetate fibers. This dyes was named "ionamine". But this ion amine did not give satisfactory result in dyeing.
Later in 1924, Baddiley and Ellis produced sulpho ricinoleic and (SRA) for dyeing acetate fibers. This SRA was used as dispersing agent. Later it was seen that SRA was capable of dyeing Nylon, polyester, acrylic etc. In 1953 this dye was named as "Disperse Dye"
