Abstract

This paper examines the synthesis of a novel dispersant-free azo reactive disperse dyes obtained by using para derivatives (2,4-dibromo) as the substituents in the coupling components 2-amino-4- (2,4-dibromo phenyl) thiophene-3- carbonitrile with monochlorotriazine (MCT)/sulphatoethylsulphone (SES) diazo component. The study aims at eliminating the major problem of reactive dyes which is incomplete fixation and hydrolysis. The coupling component and synthesized dyes were purified by recrystallization and the purity was tested by thin-layer chromatography using pre-coated silica gel G plates. Dyes were characterized by Proton and Carbon NMR, GC/MS and Infra-red analysis. The spectroscopic properties of the dye in various solvents were also examined and the dye showed a bathochromic shift when the solvent was changed to more polar solvents. The dye also showed positive and negative halochromism with the addition of a few drops of hydrochloric acid (HCl) at a concentration of 2 X 10^-5mol/dm³. The dyeing performance of the dye was evaluated on wool and nylon 6.6 fabrics. The introduction of two temporarily anionic sulphatoethylsulphone (SES) and monochlorotriazine (MCT) reactive groups into the reactive disperse dye molecule was found to promote the fixation and the buildup. The dyed fabrics showed good to moderate light fastness rating of 4 for wool and 5 for nylon 6.6 as well as very good to excellent wash fastness ratings of 3-4 for wool and 4-5 for nylon and perspiration rating of 4-5 for both wool and nylon 6.6 respectively. The dye bath exhaustion on wool and nylon 6.6 was found to be very good and the fixation values were 72% for wool and 61% for nylon 6. This study showed that dyes containing MCT and SES groups possess better fastness and fixation properties than convectional azo disperse or reactive dyes which can be attributed to the covalent bond formed between the dye molecules and the fibre.