Disazo disperse dyes crosslinked with varied characteristic groups: Their synthesis, characterization, and application on polyester fabrics

We previously synthesized a group of carbamate-linked disazo disperse dyes that showed excellent fastness properties on polyester fabric by using the thermosol dyeing process. However, the color yield of the dyed fabric was not sufficiently high to be accepted by users, especially when using a high-temperature dyeing process. To further optimize the structures of disazo disperse dyes and observe the effect of the linking groups on the dyeing properties, in this work, we used p-phenylene diisocyanate or terephthaloyl chloride as crosslinking agents and aniline derivatives containing hydroxyl or amino groups as reactants to synthesize four disazo disperse dyes containing various characteristic groups, including ester, carbamate, amide, and urea groups. The structures of these new dyes were characterized by nuclear magnetic resonance, mass spectrometry, and Fourier-transform infrared spectroscopy analyses. The spectral properties in an N,N-dimethylformamide solvent were measured, the structural parameters of the dyes were calculated using the density functional theory method, and the dyeing properties were investigated by using high-temperature and thermosol dyeing processes, and also compared with these for the commercial dye, C·I.Disperse Red 153. The results showed that there were slight differences in the molar extinction coefficients and maximum absorbance wavelengths between the new dyes, but the effects of characteristic groups on the structural features and the dyeing properties of the new dyes were significant. The ester-linked dye (D1) had the highest color depth when a high-temperature process was used in the presence of 50 mL/L of methyl salicylate because of its highest ClogP (N-octanol/water partition coefficient) value, corresponding to its more hydrophobic nature, while all the other dyes produced lower color yields. When used in the thermosol dyeing process, the carbamate-linked dye (D2) yielded the highest color depth, followed by the ester-linked dye (D1) and amide-linked dye (D3), and the urea-linked dye (D4) produced the lowest color depth due to its highest hydrophilic properties. Finally, it was demonstrated that the new dyes had excellent color fastnesses except for the urea-linked dye (D4), which exhibited a slightly lower light fastness, While the commercial dye used as the control showed a relatively poor sublimation and light fastness although its color depth and chroma value performed slightly better than the new dyes as used by the thermosol dyeing process.