An alternative strategy for the synthesis of disazo disperse dyes and their application on polyester fabric

Abstract

Due to the limitations of dye solubility in reaction solvents, the crosslinking reaction between two monoazo disperse dyes will tend to result in low yield and multiple by-products. In this work, an alternative synthetic strategy was used to prepare three disazo disperse dyes, which involved first synthesizing crosslinked coupling components with diisocyanate compounds followed by diazotization with a double diazonium salt. The structures of these new dyes were characterized by nuclear magnetic resonance (NMR), mass spectrometry (MS), and fourier transform infrared spectroscopy (FT-IR) analysis, and the spectral characteristics of the dyes in dimethylformamide (DMF) solutions were evaluated. Three synthesized disazo dyes were applied to the polyester fabrics by high-temperature and hot-melt dyeing processes. The results showed that a higher yield was obtained for all three dyes, and each of the dyes had relatively high molar extinction coefficient and slow dyeing rate on the polyester fabric due to the existence of the double-chromophore. Therefore, a certain amount of carrier or solubilizer had to be added to the dyebath to improve the dyeing rate. At 220 °C for 2.5 min, a satisfactory dyeing effect was achieved, which demonstrated that the disazo disperse dyes exhibited excellent colorfastness properties. Compared with high-temperature dyeing, thermosol dyeing produced higher dye uptake, build-up, and fastness properties, and this process was suitable for the dyeing of polyester fabrics with the disazo disperse dyes.