Reactive dyeing
The reactive dyeing is based on the 1954 made discovery that certain to dyes with a dichlorotriazine rest under alkaline dyeing conditions by covalent bonds bind to the fiber and thus very true-coloring can deliver.
The most important substrates for reactive dyeing are cellulose fibers, especially cotton , but wool , silk and polyamide are also suitable .
Reactive dyes
Reactive dyes consist of a coloring chromophore , one or more solubilizing groups and one or more reactive anchors, which are separated from the chromophore by bridges.
execution
The reactive dyeing on cellulose fibers takes place in the presence of a base (e.g. sodium carbonate or sodium hydroxide solution ) and an electrolyte , usually sodium sulfate or sodium chloride . The required pH and temperature conditions depend primarily on the reactive anchor system used. The optimum temperature for the so-called "cold dyes" (e.g. monofluorotriazine dyes) is 30-50 ° C, for the "hot dyes" (e.g. monochlorotriazine dyes) it is> 70 ° C.
The most important process is the exhaust process, in which all the chemicals required are added to the dye liquor at room temperature. The dye is then fixed when the dye bath is heated to the required temperature.
In the padding process, the material to be dyed is brought into contact with the dye liquor. The fixation takes place either over a period of several hours at room temperature or by treatment with hot air or steam.
An undesirable side reaction in reactive dyeing is hydrolysis of the dye. To remove the hydrolyzates, the staining material must be rinsed and washed with water after fixation.
The reactive dyeing of silk in the exhaust process takes place in a weakly basic medium. Wool is usually dyed with reactive dyes in a weakly acidic dye bath.
See also
literature
- Norbert Welsch and Claus Chr. Liebmann; Colors, nature, technology, art, 2nd edition 2006, p. 142 ff, Spektrum Akademischer Verlag, ISBN 3-82741-563-2
Web links
- The dyeing of textiles - a science in itself
- Textile dyes: a cinematic contribution to the dyeing process of textiles