3-Other Dyes and Reactive Dyes

8/6/2019 3-Other Dyes and Reactive Dyes

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Dyes types and reactiveDyes types and reactive

dyesdyes

Spring 2009Spring 2009


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Direct Dyes. water-soluble anionic dyes, when dyed from aqueous solution in the presence of

electrolytes, are substantive to, i.e., have high affinityfor, cellulosic fibers.

Their principal use is the dyeing of cotton andregenerated cellulose, paper, leather, and, to a lesserextent, nylon.

Most of the dyes in this class are polyazo compounds,along with some stilbenes, phthalocyanines, andoxazines.

Aftertreatments, frequently applied to the dyedmaterial to improve wash fastness properties, includechelation with salts of metals (usually copper orchromium),

and treatment with formaldehyde or a cationic dye-complexing resin.


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Vat Dyes. water-insoluble dyes applied mainly to cellulosic fibers as

soluble leuco salts after reduction in analkaline bath, by sodium Hydrosulphite

Following exhaustion onto the fiber, theleuco forms are reoxidized to the insolubleketo forms and aftertreated, usually bysoaping, to redevelop the crystalstructure.

The principal chemical classes of vat dyesare anthraquinone and indigoid.

Sulfur Dyes. These dyes are applied to cotton from an

alkaline reducing bath with sodium sulfideas the reducing agent.

Numerically this is a relatively small groupof dyes.

The low cost and good washfastnessproperties of the dyeings make this classimportant from an economic standpoint

However, they are under pressure froman environmental viewpoint.


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Cationic (Basic) Dyes. water-soluble cationic dyes are applied to paper,polyacrylonitrile (e.g. Dralon), modified nylons,and modified polyesters.

Their original use was for silk, wool, and tannin-mordanted cotton when brightness of shade wasmore important than fastness to light andwashing.

Basic dyes are water-soluble and yield coloredcations in solution.

For this reason they are frequently referred to ascationic dyes.

The principal chemical classes arediazahemicyanine, triarylmethane, cyanine,hemicyanine, thiazine, oxazine, and acridine.

Some basic dyes show biological activity and areused in medicine as antiseptics.

Acid Dyes. These water-soluble anionic dyes are applied tonylon, wool, silk, and modified acrylics.

They are also used to some extent for paper, leather, ink-jet printing, food, and cosmetics.

Solvent Dyes. These water-insoluble but solvent-solubledyes are devoid of polar solubilizing groups such as sulfonicacid, carboxylic acid, or quaternary ammonium.

They are used for coloring plastics, gasoline, oils, andwaxes.

The dyes are predominantly azo and anthraquinone, butphthalocyanine and triarylmethane dyes are also used.


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Reactive DyesReactive Dyes

The first commercially available dyecapable of covalent reaction with a textilefibre is believed to be Supramine OrangeR (CI Acid Orange 30).

For wool 1930

It contained a chloroacetylaminosubstituent from which the labile chlorineatom can be readily displaced underconventional weakly acidic dyeingconditions at the boil to form a dyefibrebond

1952 Hoechst marketed two Remalanvinylsulphone dyes that were capable of reactingwith wool.

Near Neutral Conditions

Nucleophilic addition across the activated doublebond of the vinylsulphone group.

1950 ICI developed dichloro-s-triazine reactivesystem

Alkaline condition + salt additions salt enhances substantivity and

lowering of the pH to minimise hydrolysis of thehighly reactive dichlorotriazine system,


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DCT later developedDCT later developed less reactiveaminochloro-s-triazine derivatives,which ultimately became the mostsuccessful of all reactive dyesystems.


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Dyes of the aminochlorotriazine typewere launched simultaneously asCibacron (Ciba) and Procion H (ICI)brands shortly after thedichlorotriazine dyes had beenintroduced

More stable pad liquors could beformulated using these less reactivedyes.

Reactive SystemsReactive SystemsThe characteristic features of a typical

reactive dye molecule include:(1) the chromogen, contributing the colour

and much of the substantivity for the fibre;(2) the reactive system, enabling the dye to

form a covalent bond w ith the fibre andoften also contributing some substantivity;

(3) a bridging group that links the reactivesystem to the chromogen and often exertsimportant influences on reactivity, stabilityand substantivity;

(4) one or more solubilising groups, usuallysulphonic acid substituents on the aryl ringsof the chromogen;

(5) in some instances, as w ith the importantaminochlorotriazine system, a colourlessarylamino or other residue attached to thereactive grouping that also modifiessolubility and substantivity.


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Important reactive systems forcellulosic dyeing

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3-Other Dyes and Reactive Dyes