This document provides information about dyes and pigments used in textile wet processing. It defines dyes as colored, ionizing, and aromatic organic compounds that are applied in an aqueous solution and have an affinity for the substrate. Pigments are insoluble particulates dispersed in a medium. The document classifies dyes based on their chemical properties and application methods. It provides details on different dye types including reactive, vat, sulfur, and nitro dyes. A dyeing process curve is included to illustrate thermal effects. The document also lists information on a wet processing factory to show dye plant functions.

2. Prepared By : Mazadul Hasan sheshir
ID: 2010000400008
13th
Batch (session 2009-2013)
Department : Wet Processing Technology
Email: mazadulhasan@yahoo.com
Blog : www. Textilelab.blogspot.com (visit)
Southeast University
Department Of Textile Engineering
I/A 251,252 Tejgaon Dhaka Bangladesh
Prepared By :

3. Total Textile Process at a Glance

4. The dyeing of textiles is usually understood to mean giving them a color which is of
comparative permanence. This implies that it should not be possible to wash the color
out easily in laundering nor should it fade rapidly when expose to light. Dyes and
pigments are two fundamental things of Wet Processing Technology. In order to dye a
substrate a pupil should have the basics about the dyes and pigments. Such as a) what
is dye and pigment? b) Their classification c) details about individual. This paper is a
submission of those following questions. In this particular paper there are details about
Reactive dye. The groups of Reactive dyes, reactions of Reactive dyes to fibre and its
chemical approach to fibre. A process curve is also represented to explain its thermal
effect towards the dyeing. At the end, there is a Factory profile of a wet processing
plant to illustrate the function of a dyeing plant .

6. Dyes can be said to be colored, ionizing and aromatic organic compounds
which shows an affinity towards the substrate to which it is being applied.
It is generally applied in a solution that is aqueous. As for example: Four
Methyl groups are added the reddish purple dye Methyl Violet is got.

7. Pigment is a particulate solid dispersed into a medium without significant
solution or other interactions. A pigment is a material that changes the
color of reflected or transmitted lights as the result of wavelength
selective absorption. It consists of small particles that are practically
insoluble in the medium in which they are applied and have to be attached
to substrate

12. Factors that make difference between the
Dyes and Pigments

13. Dyes are classified based on their origin, application, and
chemical properties. Dye manufacturers classify dyes according
to their chemical properties, while dyers classify dyes based on
the method of application

14. Synthetic DyesSynthetic Dyes

15. Nitro dyesNitro dyes
Azo dyesAzo dyes
DiphenlymethaneDiphenlymethane
TriphenlymethaneTriphenlymethane
PhthaeleinsPhthaeleins
XantheneXanthene

16. SulfurSulfur

18. Vat dyes are insoluble in water and incapable of dyeing fibres
directly. Reduction in alkaline medium process the water
soluble alkali metal salt of the dye. In the reduced form the
dye is applied to impregnate the fibre. The dye absorbed on
the fibre is converted to its original water insoluble form by
subsequent re oxidation. As for Example Vat Blue 4
Vat Green……

22. 1. Vat dyes are water insoluble.
2. Color fastness properties is very good,
3. Vat dyes are more expensive.
4. Application process is difficult.
5. Dull shade is found.
6. All the dyes contain two or more keto (c=o) groups.
7. Light fastness of vat dye is very good with rating 7.
8. Rubbing fastness is not good.
9. Washing fastness of vat dye is very good with rating 4-5.

23. The application process of soluble vat colors consists of two
steps :
1. The exhaustion of color from alkaline , neutral or acidic
conditions.
2. The oxidation or development of exhausted leuco ester in the
presence of an acid and oxidizing agent , changing the color
into original dyestuff

24. The members of this groups are complex organic compounds
contaning sulphur. They are used to dye cheap shades of high
wet-fastness on cellolosic fibers. The colors, however, lack
brigthness. As for example Sulphur Blue 15, Sulphur Red 11

26. 1. The sulphur dyes are cheap and easy to apply.
2. The wet fastness of sulphur dye is good, and the light fastness is satisfactory.
3. It is a cheap method of dyeing cellulosic fibers.
4. Sulphur dyes all have poor fastness to chlorine.
5. It has no use for effect threads in merchandise which must be bleached with
hypo chlorite.
6. They can withstand the condition in an acids dye bath and can be
incorporated in woolen goods intended for subsequent dyeing.
7. Sulphur dyes exhaust in the presence of electrolytes and vary considerably
with regard to the temperatures at which maximum exhausion takes place.
8. Sulphur dyes are decomposed by acids,usually with the liberation of
hydrogen sulphite and the precipitation on insoluble decomposition
products.

28. Dye and pigments both have the property of imparting colour on
substrates. However, they work in different media in different
form. Their difference are also be discussed here. In this
discussion, there is given two types of classification according to
there parental structure and application. This helps to catagorise
a dye either according to their structural group or application.. Its
mechanism and process of application are also discussed.

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