New reactive dyes having good affinity for the fibre are obtained by introducing fluorine atoms into the vinylsulfone group of conventional reactive dyes. Researchers have found that fibre-reactive dyestuffs containing certain compounds having fluorine atoms exhibit much superior fastness properties when reactively applied to cotton. It has been found that the fastness to light, chlorine and perspiration is appreciably enhanced and additionally these dyes have very good levels of build up. Also, the dyestuffs give level shades with good contact fastness after wash off.The fluorine based reactive dyes have high Exhaustion Values, high Fixation Values, particularly on cellulosic substrates such as cotton, and hence show significant improvements in terms of reducing the spent dyestuff in effluent. The fluorine containing reactive dyes provide dyers a unique opportunity to save the overall dyeing costs because of their unique properties. Some of these are listed below :
- The fluorine based reactive dyes increase dye affinity to the substrate.
- The fluorine based reactive dyes increase the dye-substrate covalent bonding.
- The fluorine based reactive dyes increase the ability to dye substrates at room temperature.
- The fluorine based reactive dyes decrease the amount of dye that is removed during the post dyeing ‘soaping off process” and therefore simplify the post dyeing ‘soaping off process’ traditionally associated with dyeing cotton with fibre reactive dyes. This also results in reduction of staining of adjacent white fabrics.
- In addition, the fluorine based reactive dyes provide more intense dyeings and require lower levels of salt for dyeing cotton substrates.