Reactive Dye

A dye, which is capable of reacting chemically with a substrate to form a covalent dye substrate linkage, is known as reactive dye. Here the dye contains a reactive group and this reactive group makes covalent bond with the fibre polymer and act as an integral part of fibre. This covalent bond is formed between the dye molecules and the terminal –OH (hydroxyl) group of cellulosic fibres on between the dye molecules and the terminal –NH2 (amino) group of polyamide or wool fibres.

Reactive dyes first appeared commercially in 1956, after their invention in1954 by Rattee & Stepheness at the Imperial chemical Industry (ICI). Dyestuffs Divion site in Bleckley, Manchetor. UK.

By reactive dyes the following fibres can be dyed successfully:

Cotton, rayon, flax and other cellulosic fibres.
Polyamide and wool fibres.
Silk and acetate fibres.

Properties of reactive dye:

Reactive dyes are anionic dyes, which are used for dyeing cellulose, protein and polyamide fibres.
Reactive dyes are found in power, liquid and print paste form.
During dyeing the reactive group of this dye forms covalent bond with fibre polymer and becomes an integral parts of the fibre.
Reactive dyes are soluble in water.
They have very good light fastness with rating about 6. The dyes have very stable electron arrangement and can protect the degrading effect of ultra-violet ray.
Textile materials dyed with reactive dyes have very good wash fastness with rating Reactive dye gives brighter shades and has moderate rubbing fastness.
Dyeing method of reactive dyes is easy. It requires less time and low temperature for dyeing.
Reactive dyes are comparatively cheap
Reactive dyes have good perspiration fastness with rating 4-5.
Reactive dyes have good perspiration fastness.

General structure of reactive dyes:

The general structure of reactive dye is: D-B-G-X.

Chemical structure of reactive dyes

Chemical structure of reactive dyes

Here,

D= dye part or chromogen (color producing part)
Dyes may be direct, acid, disperse, premetallised dye etc.

B = bridging part.
Bridging part may be –NH- group or –NR- group.

G = reactive group bearing part.
X= reactive group.

Classification of reactive dyes:
Reactive dyes may be classified in various ways as below:

1) On the basis of reactive group:
a) Halogen (commonly chlorine) derivatives of nitrogen containing heterocycle, like 3 types-

Triazine group
Pyridimine group
Quinoxaline dyes

Example: Triazine derivatives: procion, cibacron. Pyridimine derivatives: reactone Quinoxaline derivatives: levafix.

b) Activated vinyl compound:

Vinyl sulphone
Vinyl acrylamide
Vinyl sulphonamide.

Example:

Vinyl sulphone: remazol
Vinyl acrylamide: primazine
Vinyl sulphonamide: levafix.

2) On the basis of reactivity:
a) Lower reactive dye: Medium reactive dye: here pH is maintained 11-12 by using Na2CO3 in dye bath.
b) Higher reactive dye: here pH is maintained 10-11 by using NaHCO3 in dye bath.

3) On the basis of dyeing temperature:

a) Cold brand:
These types of dyes contain reactive group of high reactivity. So dyeing can be done in lower temperature i.e. 320-600C.

For example: PROCION M, LIVAFIX E.

b) Medium brand:
This type of dyes contains reactive groups of moderate reactivity. So dyeing is done in higher temperature than that of cold brand dyes i.e. in between 600-710C temperatures.
For example, Remazol, Livafix are medium brand dyes.

c) Hot brand:
This type of dye contains reactive groups of least reactivity. So high temperature is required for dyeing i.e. 720-930 C temperature is required for dyeing.
For example PRICION H, CIBACRON are hot brand dyes.