Synthesis and application of urethane-containing azo disperse dyes on polyamide fabrics

A series of new azo disperse dyes containing the urethane group were synthesized through the reaction between the hydroxyl group in coupling component of disperse dyes and p-toluene isocyanate. The structures of the new dyes were fully confirmed by 1H NMR, 13C NMR, FT-IR, MS and Elemental analysis. Their characteristics for the visible-light absorption and color fastness on polyamide fibers were respectively measured and compared with those of the original dye. It was found that the new dyes exhibited hypsochromic effect, and had the nearly unchanged absorption half band and higher molar extinction coefficients, the fastness properties has been greatly improved, especially for the washing and sublimation fastness. The new dyes 2d and 2e containing double urethane groups possessed excellent fastness properties on polyamide fabrics. These two dyes for all the fastness tested, including water fastness, sublimation fastness, rubbing fastness and light fastness, had reached 4–5 and 5 rates. It was very clear that the introduction of urethane group and the increase of molecular weight can effectively improve the fastness of disperse dyes for the polyamide fibers.