Development staining
When development dyeing the synthesis is carried out of dye molecules from soluble, colorless precursors directly on the inked fibers . Water-insoluble color pigments form on the fiber. According to the reaction that triggers such a molecule formation, three types of coloration can be distinguished:
- Vat coloring
- With stain dyeing, the dyeing takes place in a water-soluble dye precursor. However, the material to be dyed must first be pretreated with a solution of metal salts, today mainly chromium salts. Only then can it be introduced into the liquor and the dye and metal ions can react with one another. Water-insoluble colored lacquers now form on the fiber . The stain dyeing supplies brilliant, washable and lightfast colors , especially on cotton , and is still used today for stage costumes. Since the process is expensive and time-consuming, it is not used on a large industrial scale, it is only still used in private dye works. Formerly important mordant dyes are z. B. the luteolin of the bowler hat and the alizarin of the madder plant .
- During the actual development coloring, two different chemical components are brought together, from which the colorant is created directly on the fiber . First of all, the material to be dyed is soaked in a soluble precursor of the later dye . Naphtol AS or its derivatives, for example, are used here, which can react with diazonium salts as coupling components . The fibers pretreated in this way are immersed in an ice-cold solution of diazonium salts. The insoluble pigment is formed from both components in a chemical reaction directly on the fiber . Adhesion to the fiber occurs through adsorption . The dyeing process is suitable for wool , cotton , silk and polyamide fibers . A high level of lightfastness can be achieved. The developing dyes include e.g. B. the variamin blue .
See also
literature
- Norbert Welsch and Claus Chr. Liebmann; Colors, nature technology, art, 2nd edition 2006, Spectrum Academic Publishing House, ISBN 3-8274-1563-2