Green synthesis of reactive dye for ink-jet printing

Chloropyrimidine-based reactive dyes are reported as well suited to textile printing; however, nucleophilic aromatic substitution of chloropyrimidines with amino-containing chromophores is slow and often suffers from poor yields. In this study, a novel and simple method was developed for the synthesis of chloropyrimidine-based reactive dye under microwave irradiation. In addition, the dye was also synthesised by conventional heating for comparison, which took both the reaction time and yield into account. The progress of the synthesis reactions concerned were monitored using capillary electrophoresis and the purity of the dye obtained was assessed by thin-layer chromatography. The structure of the synthesised trichloropyrimidine dye was confirmed by Fourier Transform–infrared spectroscopy and elemental analysis. It was found that the reaction rate of the nucleophilic aromatic substitution carried out under microwave irradiation was 4-fold faster than that carried out under conventional heating, although the enhancement in product yield was modest. These results suggest that microwave irradiation is an effective technique for the synthesis of chloropyrimidine-based reactive dyes. The synthesised chloropyrimidine dye was formulated into an ink and applied onto a wool fabric by ink-jet printing. The printed fabrics were steamed at 102°C for 5-25 minutes at 5-minute intervals. Good K/S and rate of dye fixation were obtained, both of which improved with increasing steaming time. The prints obtained exhibited reasonably good light and wash fastness properties.