Classification of dye ~ Textile Notes

CLASSIFICATION OF DYE

#Classification of colouring materials

colouring materials are classified in several other ways was based on
1.Source or origin
2. Chemical structure
3. Field of application
4. Ionic nature
5. solubility in water

1.source or origin is also subdivided

(i) Natural colours
(ii) Synthetic colours

(i) Natural colours:-

◆These are extracted from Natural Sources.

◆Yellow natural dyes include turmeric, kamela, tesu, marigold, larkspur, harshingar, annato, berbers and dolu.

◆Indigo (leaves of plant indigofera tinctoria) is the only natural blue vat dye, Which is synthesized too.

◆Natural dyes are two types substantive or mordant dyes which produce fast shades at boil.

◆Mordant dyes require an additional chemical to make the colour permanent.

◆Natural dyes are also extracted from unlimited sources of barks of trees and leaves of plants.

◆These are used to a limited extent owing to very high labour cost involved in the collection and preparation of dyes and difficulty in obtaining accurate Reproduction of colour and shade.

◆Natural colours are easily biodegradable and shades lack brightness and shade range is limited.

(ii) Synthetic colours:-
◆A large amount of synthetic colours are obtained through reaction of Dye intermediates e.g. anthranilic acid, beta naphthol, benzidine, napthoic acid, J-acid, metanilic acid, H-acid hydroquinone , Schaeffer's acid, G-acid R-acid etc. with other chemicals.

◆These colours are not easily biodegradable with exceptions like reactive dyes which are self hydrolysed in water.

2.Chemical structure

Colouring materials are also classified based on their chemical structure e.g. azo, nitro, nitroso, Stilbene, di and tri-phenylmethane, xanthene, acridine, quinoline, methane, thiazole, azine, oxazine, thiazine, anthraquinone, indigoid and phthalocyanine, etc.

3.Field of application

4.Ionic nature

Dyes can be classified according to electrical charge that exists in its ionized colored path before or during dying based on this
(i)Cationic (Basic dye)
(ii)Anionic(Direct, Reactive, Vat, Sulphur, Acid)
(iii) Non-ionic :-(Disperse dye)

5.Solubility in water:-

◆Water is universal Medium of dying.

◆It is cheaper, non-toxic, easily available and can be recovered and reused.

◆Direct, reactive, basic and acid dyes are water soluble dyes.

◆VAT and sulphur dyes are water insoluble but can be taken into solution by reduction and solubilisation.

#Nomenclature of colouring materials These are two ways

(i)C.I naming(Generic names)
(ii)Commercial

◆There are no symmetric nomenclature system due to which it is usual worldwide to have various names assigned to a single dye by different manufacturers called commercial names.

◆To avoid confusion on it SDC and AATCC( Society of dyers and colourists and American Association of textile chemist and colorists) have assigned CI specification to a dye, which may have different commercial names but chemical structure and properties are identical and so the international name of a dye expressed with its CI e.g.
CI VAT green 1

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Textile Notes