Basic dyes are called so since they are salts of organic bases. They are also known as cationic dyes because of the presence of positive charge in the dye molecules under dyeing conditions. During dye application, the negatively charged acrylic fiber attracts the positively charged dye cations for ionic bonding. Due to high attraction between the oppositely charged fiber and dye molecules, there is risk of unlevel dyeing because of high rate of dyeing. This risk may be reduced by careful control of dyeing temperature and used of suitable retarding agents.

The basic dyestuffs are well known for their intense hues and brilliant shades, unrivalled by any other class of dyes. Basic dye has excellent light fastness because of their resistance to destructive effect of ultraviolet radiations in sunlight. Their washing fastness is also quite good, which may be attributed to hydrophobic nature of the acrylic fiber and good substantivity of the dye for the fiber. The basic dyestuff are most commonly used for dyeing polyacryonitrile or acrylic materials. Basic dye is also used for dyeing wool and silk fibers.

The general characteristic of a basic dye is the cationic group, which leads to formation of an ionic bonding to anionic groups present in the fiber polymer. Representative examples for basic dye are given in below Figure.

Basic Orange 31 Basic Orange 31 Basic Orange 31 Basic Orange 31 Basic Orange 31  Basic Orange 31 Basic Orange 31 Basic Orange 31 Basic Orange 31