Synthesis and properties of alkali-clearable azo disperse dyes containing a carboxylic ethyl ester group

Three alkali-clearable azo disperse dyes containing a carboxylic ethyl ester group (D1-D3) were readily synthesized using three different synthetic strategies. D1 was prepared from a carboxylic acid-containing dye by esterification with ethanol. D2 was prepared from a carboxylic ester-containing dye by transesterification with ethanol. D3 was prepared from a cyano group-containing dye by alcoholysis with ethanol and water. The molecular structures of the dyes were characterized by FTIR, mass spectrometry, ¹H NMR, ¹³C NMR, and elemental analysis. The synthesized dyes and the control dyes were used to dye poly(ethylene terephthalate) fabric, and their washing and rubbing fastness properties following different after-treatment methods (reduction clearing and alkali clearing) were examined and compared. The carboxylic ethyl ester-containing disperse dyes show good alkali clearing ability on poly(ethylene terephthalate) fabric and cause fewer environmental issues due to the absence of reductants, no production of aromatic amines with high toxicity and carcinogenicity, as well as the low toxicity of the dye hydrolysate ethanol.