“History” Reactive dyes first appeared commercially in 1956, after their invention in 1954 by Rattee and Stephens at the Imperial Chemical Industries Dyestuffs Division site in Blackley, Manchester, United Kingdom

• Various developments – including new chemical types

• 1980’s Mixed bifunctional dyes (esp. Sumitomo – Sumifix Supra dye

“About Reactive Dye” Reactive dyes are used to dye cellulosic fibres. The dyes contain a reactive group, either a halo heterocycle or an activated double bond, that, when applied to a fibre in an alkaline dye bath, forms a chemical bond with an hydroxyl group on the cellulosic fibre. Reactive dyeing is now the most important method for the coloration of cellulosic fibres. Reactive dyes can also be applied on wool and nylon; in the latter case they are applied under weakly acidic conditions. Reactive dyes have a low utilization degree compared to other types of dyestuff.

General Features of a Reactive Dye Molecule:

W = water solubilising groupD = chromophoreB = bridging groupRG = reactive groupX = leaving group

“Types of Reactive Dyes”

1. Sulphatoethyl sulphone dyes:

Vinyl sulphone dye (Remazol Brilliant Blue R, C.I. Reactive Blue 19)

2. Monochloro- s -triazine dyes:

Monochloro-s-triazine dye (Procion Red H-3B, C.I. Reactive Red 3)

O

O

NH2

SO3Na

NH

SO2CH2CH2OSO3Na

SO3Na

NH N

NN

Cl

NH

SO3NaNaSO3

OH

NN

3. Bis (monochloro- s -triazine) dyes :

Bis(monochloro-s-triazine) dye (Procion Red HE-3B, C.I. Reactive Red 120

4. Mixed Bifunctional reactive dyes:

General structure of Sumifix Supra dyes MCT-SES or MCT-VS[Reactron Supra F dyes are similar

NaSO3SO3Na N

N

N

NH N

NN

Cl

NH

SO3NaNaSO3

OH NH NH

Cl

NaSO3 SO3Na

OHN

NN

N

N

N

N

NH

SO2CH2CH2OSO3Na

NH

Cl

Dye

“Reactions of Reactive Dyes”

Nucleophilic addition:

ß-elimination of ß-sulphatoethylsulphone to vinyl sulphone and reaction with cellulose.

DYE S

O

O

DYE S

O

O

DYE S

O

O

NaHSO4

DYE S

O

O

CH2

+Cellulose O-

CelluloseS

O

O

DYE-

Cellulose

+

C C CH

C

C C

OSO3Na

H H

H H

CHCH

H

H

O

H2O

+ OH-O

H H

HH

CH2

-

Nucleophilic substitution:

Competing nucleophilic substitution reactions of s-triazine dyes

“Application Methods”

• Continuous:– eg. Pad - Thermofix

• Semi-Continuous:– eg. Pad - Batch

• Batchwise Exhaustion: – eg. Winch, Jet, Package and Beam Dyeing

• Printing:– eg. Print - Thermofix

N

N

N

Cl

Cl

NH

Dye

N

N

N

Cl

NH

Dye

ClX

N

N

N

OH

Cl

NH

Dye

N

N

N

O

Cl

NH

Dye

Cellulose

OR+ X-

..- Cl-

Advantages:

• Full Colour Gamut• Brilliant, bright colours• Colvalent fixation à high WashFastness (WF)• Varying reactivities

– Various temperaturesincluding low energy (cold dyeing)

• Various methods of application• Inexpensive to apply (but dyes expensive)

Disadvantages:

• Incomplete fixation (problem with hydrolysis)• Need for wash-off (for high WF)• Need for high concentrations of salt

– Affect natural balance of watercourses• High pH• Some dyes are “AOX” – potentially harmful to the environment

“Hot And Cold Dyeing Brands”

Cold Dyeing Brand:

Reactive Cold Brand Dyestuffs are fibre reactive dyes which form a chemical linkage with Hydroxyl groups of Cellulose and thus give dyeing and printing good fastness to wet treatments.

Hot Dyeing Brand:

He Dyes are Reactive Dyes for Cellulosic material and designed to give high fixation by exhaust dyeing method when applied at the temperature 75ºC - 95ºC.

The other misconception that people have is that they assume the Hot dye is more colour-fast than the Cold one because you have boiled the colour in. This is not so. Cold dyes are more robust and colours will remain brighter for longer than Hot dyes. The cooler process is not only a little easier, it is also more lasting.

Cold reactive dyes are very reliable and used throughout the global clothing and textile industries to permanently colour fabrics made from plant fibres. The dyes react with the fibre on a molecular level to produce a permanent bond that withstands wash after wash. The colour becomes part of the fabric.