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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 color that is seen by our eyes is the one not absorbed by the reflecting object within a certain wavelength spectrum of visible light. The chromophore is a region in the molec ...
(an atom or group whose presence is responsible for the colour of a compound) contains a substituent
A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as '' side ...
that reacts with the substrate. Reactive dyes have good fastness properties owing to the covalent bonding
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...
that occurs during dyeing. Reactive dyeing is the most important method for coloring cellulose fiber
Cellulose fibers () are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and li ...
s. Reactive dyes can also be applied on wool
Wool is the textile fibre 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 properties similar to animal wool.
A ...
and nylon
Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic.
Nylon is a silk-like thermoplastic, generally made from petr ...
; in the latter case they are applied under weakly acidic
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
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, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolys ...
.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 company. It was, for much of its history, the largest manufacturer in Britain.
It was formed by the merger of four leading British chemical companies in 1926.
Its headquarters were at M ...
(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 a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the 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 ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic 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 s ...
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 A carbene dye is a reactive dye based on carbene chemistry.
A benzophenone is functionalised with a chromophore or group that can be easily converted to a chromophore at a later stage. The functionalised benzophenone is reacted with hydrazine hydra ...
* Cationization of cotton
Cationization of cotton is an electro kinetic phenomena ( zeta potential and electro kinetic) for surface charge of cotton. The cotton surface is charged with positive ions. Cationization alters the characterization of the surface of the cotton ...
for salt-free dyeing
* Dyeing
Dyeing is the application of dyes or pigments on textile materials such as fibers, yarns, and fabrics with the goal of achieving color with desired color fastness. Dyeing is normally done in a special solution containing dyes and particular ...
* Dispersing agent for dyeing
Footnotes
External links
For more infFundamental Chemistry of reactive dyes
{{Dyeing Dyes