Prepared By : Mazadul Hasan sheshirID: 201000040000813th Batch (session 2009-2013)Department : Wet Processing Technology Email: mazadulhasan@yahoo.comBlog : www. Textilelab.blogspot.com (visit)

Southeast University Department Of Textile Engineering

I/A 251,252 Tejgaon Dhaka Bangladesh

Prepared By :

Total Textile Process at a Glance

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 .

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.

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

Factors that make difference between the Dyes and Pigments

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

Synthetic Dyes Synthetic Dyes

Nitro dyesNitro dyes

Azo dyesAzo dyes

DiphenlymethaneDiphenlymethane

TriphenlymethaneTriphenlymethane

PhthaeleinsPhthaeleins

XantheneXanthene

SulfurSulfur

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……

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.

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

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

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.

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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