Each colour of disperse dyes requires different raw materials. Because the range of colours is very large each colour has its own manufacturing process. The difference in the processes is primarily in the reaction period.

1. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
Manufacturing Process of Disperse dyes:
Each colour of disperse dyes requires different raw materials. Because the range of
colours is very large each colour has its own manufacturing process. The
difference in the processes is primarily in the reaction period.
The general steps involved in the production are:
(a) Diazotisation
(b) Coupler preparation
(c) Coupling
(d) Filteration
(e) Dispersion
(f) Drying
The detailed manufacturing process of celliton scarlet B is given below and the
economics is based on the production of the above said dye. Some of the important
disperse dyes, method of preparation are given at the end of the article. A typical
azo disperse dye, celli ton sca6rlet B is made by diazotising pnitroaniline
and coupling with 2-N-(ethyl-anilino) ethanol. Diazotization is the process of
reacting a primary aromatic amine with nitrous acid in the presence of excess
mineral acid to produce a diazo (-N=N-) compound. For the manufacture of this
dye, 152 kg of p-nitroaniline is added to a mixture of 1500 litres of water and 560
litres of hydrochloric acid (110Be). The contents are stirred and 1300 kg of ice
added. The diagotization is carried out by adding 330 litres of sodium nitrite (23%
solution). In the meantime 198 kg of 2-N-ethylanilino ethanol is added to 275 litres
of hydrochloric acid (110Be) and stirred for 90 minutes, when the dissolution is
complete. The solution is diluted with 3000 litres of water and 1000 kg of ice
added to bring down the temperature to woe.
The diazo solution is run into the above solution in 2 hours at 10150e. The contents
are stirred for 15 minutes and 2000 litres of water, 200 kg sodium bicarbonate and
200 kg ice are added in 3 hours. The stirring is continued overnight. The contents
are diluted and filtered. The actual dye is formed as relatively large particles during
the last stage of its manufacture and in this form it is unsuitable for dyeing.
Stabilisation of the
dyebath involves incorporation of large amounts of suitable dispersing agents,
followed by grinding. In one method the dye in the form of the filter cake is mixed
with a concentrated solution of the dispersing agent in water, partially dried or a
drum dryer and converted into a sticky mass. This mass is then fed to rollers

2. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
situated close to each other, but rotating at different speeds. The shearing action
exerted on the dye by the rotation of the roller reduces the particle size of the dye.
This is followed by further drying and grinding. In another method, the dye paste is
milled in the presence of a large excess of a dispersing agent and then drying in a
spray dryer, in which the paste is sprayed into a steam of hot air, when the water
present is rapidly
evaporated.
Cellulose sulphite waste liquor (lignin sulphonates), condensation products of
naphthalene-beta-sulphonate and formaldehyde, and product obtained by
condensing cresol with formaldehyde in the presence of sodium sulphite and
further condensing with beta-naphthol-6-sulphonic acid are some of the dispersing
agents
recommended. Azo and anthraquinonoid disperse dyes amount to about 85% of all
commercial disperse dyes. Azo disperse dyes are made by diazotising aromatic
amines and coupling with suitable components.
Dyes for synthetic fibres are provided in the form of dispersed powders (except the
cationic types). Dyeing is accomplished by the use of a water dispersion of the dye
together with wetting agent, at about 60-800C. The dyeing operation is generally
through the formation of solid solution involving the dye and the fiber. Except for
pure green anthraquinone dyes for synthetic fibres have quite a broad spectrum
extending from pink through orange, red, violet and blue. Some of the important
disperse dyes and their preparations are shown below:

3. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
Anthraquinone Dyes for Synthetic Fibres

4. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
Various intermediates used in the manufacture of disperse dyes are given below:
1. P-Amino acetanilide
2. 1-Amino-4-bromo-2-anthraquinone-sulphonic acid
3. P-Amino phenol
4. 4-Amino xanthopurpurin
5. Aniline
6. Anilino methane sulphonic acid
7. I-Benzamido-4-chloro-anthraquinone
8. 3-Bromo benzanthrone
9. I-Bromo-4-methyl amino anthraquinone
10. I-Chloro-2, 4-dinitrobenZene
11. 2-Chloro-4-nitroaniline
12. 4-Chloro-3-nitrobenzene sulfonyl chloride
13. 2, 2-(m-chlorophenylamino)-diethanol
14. Cresidune

5. Manufacturing of Dyes and Pigments Azmir Latif, MSc in Textile Engineering
15. o-Cresol
16. p-Cresol
17. 1,4-Diamino anthraquinone
18. 1,5-Diamino anthraquinone
19. 2, 6-Dichloro-4-nitroanioline
20. 1:5-Dihydroxy-4, 8-dinitro anthraquinone
21. N, N-Dimethyl aniline
22. 1, 5-Dinitro anthraquinone
23. 1, 8-Dinitro anthraquinone
24. Diphenylamine
25. Ethanolamine
26. 2-(N-Ethykamino) ethanol
27. I-Hydroxy anthraquinone
28. I-Hydroxy-4-nitro anthraqumone
29. Leuco-1, 4, 5, 8-tetrahydroxy anthraqumone
30. Methylamine
31. 1-Methoxy anthraquinone
32. 3-Methyl-1-phenyl-5-pyrazolone
33. 1-Naphthylamine
34. p-Nitroaniline
35. Phenol
36. p-Phenyl azoaniline
37. Quinizarin
38. p-Toluene sulfoanamide
39. 2, 2-(M-tolyamino) diethanol