Reactive dye

In a reactive dye a chromophore contains a substituent that is activated and allowed to directly react to the surface of the substrate.

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History

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.

Usage

Reactive dyes are used to dye cellulosic fibres. The dyes contain a reactive group, 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. 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.

Monofunctional

Monofunctional dyes were the first. They consist of one chromophore and one functional group that binds the dyestuff to the fibre. All other reactive dyes consist of a combination of, or multiple, functional groups.

Reactive dyes are categorized by functional group^[1].

Bifunctional

Dyestuffs with only one functional group have a low degree of fixation. To overcome this dyestuffs containing two groups (one monochlorotriazin and one vinyl sulphone) 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 proces). Other bifunctionals are created, some with fastness (better quality) or only fixation degree (better environment/economy) in mind.

Trifunctional dyestuffs also exist.

See also

• Carbene dyes

References