Page 299 - Basic Principles of Textile Coloration

288 DYEING CELLULOSIC FIBRES WITH DIRECT DYES

14.2 CHEMICAL CONSTITUTIONS OF DIRECT DYES
Sulphonated azo dyes constitute the predominant group of direct dyes (1, in
Figure 14.1). These are usually bis-, tris-, or tetra-azo compounds, the latter type
often being brown and black. Direct dyes usually have long, coplanar molecular

N OH
N

O3S N OH
N

1 O3S NH2
O O
CO2H H H HO2C
HN HO OH

Cu O O Cu NH
O O

N N
N N

SO3 2 SO3

O HN SO3 N
NH N NH N

NN

HN

SO3 OH
O NH2 CO2H

3 NH SO3

Cl
SO3 N O

NH O N
Cl
4

Figure 14.1 Constitutions of typical direct dyes. 1, CI Direct Red 16 (27680); 2, CI Direct
Blue 93 (22810); 3, CI Direct Green 28 (14155); 4, CI Direct Blue 106 (51300)