An announcement of great technical and commercial importance appeared in the journal of the society of dyers and colorists (1956, p55) under the column “Manufacturers Publications & Pattern cards” This concerned a circular on procion dyes (ICI) describing Procion Yellow R, Procion Brilliant Red 2B, and Procion blue 3G all belonging to a new eloss (called reactive) of dyes since the fixation to the fiber is achieved by direct chemical linkage.
Reactive dyes are water-soluble dyes containing sulphonic acid groups and reactive groups like dichloride or monochloro tniazinyl groups or sulplato ethyl sulphone groups (from which vinyl sulphone reactive groups are formed during dyeing in the presence of an alkali)
The reaction of these dyes with the functional groups of the fiber is brought about by alkali such as sodicens carbonate, hydroxide, silicate etc. Reactive dyes from covalent bond with the fiber and becomes a part of the fiber. This type of dye has some reactive group which can react with –OH group of ccllulose and –NH2 group of proteins fibers. Due to this fact, these dyes are known as reactive dyes.
Classification of reactive dye:
- A) Reactive dyes can be classified chemically into two groups:
- i) Halogenated hetero cycles Eg> Tri chloro Triazine Tetrachloropyrinmidine.
- ii) Activated vinyl compounds: Eg>D-So2-CH=CH2, vinyl sulphone is another commercially successful reactive group used in the manufacture of reactive dyes, Remeizol dyes belongs to this group.These dyes are marketed as sulphate ethyle sulphone dyes and may be represented by D-S-G-X where u is –CH2-CH2-OSO3Na G is So2, S is the solubilizing group and D is the chromogenic part.
- B) On the basis of reactivity reactive dyes can be divided into three groups:-
- i) High reactive dye: This type of reactive dyes contains two chlorine atoms and portion-M dyed of dyes fall under this group. In dyeing with this class of dyes weak alkali like NaHCO3 is used.
- ii) Moderate reactive dyes: Dyeing with this type of dye medium alkali (Na2co3) is used lavafix E falls under this class.
iii) Low reactive dye: strong alkali (NaOH) is used in this types of dyes. This type of dyes contain on chlorine atoms.
For a long time chemists have been sacking a method of joining the dye molecule to the cellulose with covalent bond. At about the end of the 1940 decade workers turned their attention to the properties of dyes containing cyanotic chloride
- i) residues or, in other words.
Triazinyl dyes is possible to make the chlorine atoms in cyanotic chloride combine with one, two or three compounds containing hydroxyl or amino groups attached to colored dye molecules.
The reaction with water, alcohols and amines are summarized be low-
NaSo3-DYE-NH- + HO cellulose
NaSo3-DYE-NH- + Hel
And this can go to a stage further, although it does not in all cases do so at 200c to link with two cellulose molecules, as in
The triazinyl dyes can, at the same time undergo hydrolysis with water to form the compound represented by
NaSo3-DYE-NH- + 2H20
NaSo3-DYE-NH- + 2Hcl
**Source: Wikipedia & Google**
Department Head (Textile & GDPM)