In a reactive dye a chromophore contains a substituent that is activated and allowed to directly react to the surface of the substrate. Reactive dyes have good fastness properties owing to the bonding that occurs during dyeing. Reactive dyes are most commonly used in dyeing of cellulose like cotton or flax, but also wool is dyeable with reactive dyes.
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.
The dyes contain a reactive group (often trichlorotriazine), either a haloheterocycle 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.
R = Chromophore
Cell = Cellulose
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, since the functional group also bonds to water, creating hydrolysis.
Reactive dyes are categorized by functional group.
|Functiona||Fixation||Temperature||Included in Brands|
|Monochlorotriazine||Haloheterocycle||80˚||Basilen E & P
|Monofluorochlorotriazine||Haloheterocycle||40˚||Cibacron F & C|
Drimarene K & R
|Trichloropyrimidine||Haloheterocycle||80-98˚||Drimarene X & Z
|Vinyl sulfone||activated double bond||40˚||Remazol|
|Vinyl amide||activated double bond||40˚||Remazol|
Dyestuffs with only one functional group sometimes have a low degree of fixation. To overcome this dyestuffs containing two different reactive groups (i.e. one monochlorotriazin and one vinyl sulfone) were created.
Dyestuffs containing two groups are also known as bifunctional dyestuffs, though some still refers to the original combination. Other types of bifunctional dyes has been introduced. The first bifunctional dye made where more tolerant to temperature deviations (better process). Other bifunctionals are created, some with fastness (better quality) or only fixation degree (better environment/economy) in mind.
Trifunctional dyestuffs also exist.
See also 
- Stig Hjortshøj (1999), pp. 44–45.
For more info Fundamental Chemistry of reactive dyes