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In a reactive dye, a
Reactive dyes are categorized by functional group.Stig Hjortshøj (1999), pp. 44–45.
Fundamental Chemistry of reactive dyesAdvancements in Reactive Textile Dyes
{{Dyeing Dyes
chromophore
A chromophore is the part of a molecule responsible for its color. The word is derived .
The color that is seen by our eyes is that of the light not Absorption (electromagnetic radiation), absorbed by the reflecting object within a certain wavele ...
(an atom or group whose presence is responsible for the colour of a compound) contains a substituent
In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule.
The suffix ''-yl'' is used when naming organic compounds that contain a single bond r ...
that reacts with the substrate. Reactive dyes have good fastness properties owing to the covalent bonding that occurs during dyeing. Reactive dyeing is the most important method for coloring cellulose fibers. Reactive dyes can also be applied on wool
Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...
and nylon
Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups.
Nylons are generally brownish in color and can possess a soft texture, with some varieti ...
; in the latter case they are applied under weakly acidic conditions. Reactive dyes have a low utilization degree compared to other types of dyestuff, since the functional group also bonds to water, creating hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
.Horst Tappe, Walter Helmling, Peter Mischke, Karl Rebsamen, Uwe Reiher, Werner Russ, Ludwig Schläfer and Petra Vermehren "Reactive Dyes"in Ullmann's Encyclopedia of Industrial Chemistry 2000, Wiley-VCH, Weinheim.
Usage
Reactive dyes had been tested in the late 1800s involving both adding functionalized dyes to the substrate and then activating the substrate first followed by fixation of the dye. The first commercial success was described in the early 1950s. Rattee and Stephens atImperial Chemical Industries
Imperial Chemical Industries (ICI) was a British Chemical industry, chemical company. It was, for much of its history, the largest manufacturer in Britain. Its headquarters were at Millbank in London. ICI was listed on the London Stock Exchange ...
(ICI) popularized the chlorotriazines as linkers between the substrate and the chromophore.
Trichlorotriazine remain a popular platform for reactive dyes. The chromophore, with an amine functional group
In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...
, is attached to the triazine, displacing one chloride:
: (NCCl)3 + dye-NH2 → N3C3Cl2(NHdye) + HCl
The resulting dichlorotriazine can then be affixed to the cellulose fibre by displacement of one of the two chloride groups:
: N3C3Cl2(NHdye) + HO-cellulose → N3C3Cl(NHdye)(O-cellulose) + HCl
The fixation process is conducted in a buffered alkaline
In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...
dye bath.
An alternative fixation process that is more dominant commercially is the vinylsulfonyl group. Like the chlorotriazines, this functional group adds to the hydroxyl groups of cellulose. The most popular version of this technology is Remazol. The dye is first attached to the ethylsulfonyl group.
Reactive dyes are categorized by functional group.Stig Hjortshøj (1999), pp. 44–45.
Bi- and polyfunctional reactive dyes
Dyestuffs with only one functional group sometimes have a low degree of fixation. To overcome this deficiency, dyestuffs containing two (or more) different reactive groups were developed. These dyestuffs containing two groups are also known as bifunctional dyestuffs although some still refer to the original combination. Some contain two monochlorotriazines, others have a combination of the triazines and one vinyl sulfone group). Bifunctional dyes can be more tolerant to temperature deviations (better process). Other bifunctionals have been created, some with fastness (better quality) or only fixation degree (better environment or economy) in mind.See also
* Carbene dye * Cationization of cotton for salt-free dyeing * Dyeing * Dispersing agent for dyeingFootnotes
External links
For more infFundamental Chemistry of reactive dyes
{{Dyeing Dyes