What is the role of alkali in reactive dyeing?
A. Reactive dyes are water-soluble dyes. These water-soluble dyes get exhausted on the cellulosic fibre in the presence of Glauber’s salt at neutral pH. Under alkaline conditions fixation is carried out in which covalent bond forms between reactive sites of fibre and cellulosic material. During fixation stage alkali is necessary as it acts as a catalyst between the dyestuff and the fibre. The important point is not the type or amount of alkali, but rather the pH of the bath. In reactive dyeing for fixation purpose different alkali is used i.e. soda ash, sodium hydroxide and sodium phosphate. As these alkali puts load on effluent treatment plant, alkaline agents introduced specifically during the dyeing helps to adjust the pH of the bath and to get level dyeing. At the same time it reduces load on effluent treatment plant by reducing TDS. Aquatex UVW: 100% soda ash substitution for reactive dyeing.
