Facile Synthesis And Properties Of Alkali-clearable Azo Disperse Dye Containing Carboxylic Acid Ethyl Ester

Azo dye is one of the largest category of disperse dye yield. However, some dye particles may remain on the fiber surface after the dyeing is completed and cause reduced color fastness on washing and rubbing. Therefore, the commonly used method for polyester fabrics is reduction clearing, namely, the dyed fabrics were treated by a solution containing 2 g/L sodium hydrosulfite(as reductant) and 1 g/L sodium hydroxide. However, the reduction clearing process causes serious water pollution because of the addition of chemicals and increases the treatment difficulty of the effluents. Additionally, disperse dyes containing azo groups can also be cleaved to aromatic amines and some of them might be toxic and carcinogenic. Therefore, elimination of treatment of reduction clearing in the dyeing polyester process with disperse dyes can significantly reduce the costs of effluent treatments. Encouragingly, alkali-clearable disperse dyes offer a means of resolving the problem. Alkali-clearable dyes, which can be solubilized by the solo action of alkali, have been developed in recent years. These water soluble dyes generated after alkali clearing are readily washed off without generation of harmful primary aromatic amines, even if there are some azo groups in their chromophores. These alkali-clearable disperse dyes are not only easy to recycle, but also have a good application prospect and environmental benefits.Firstly, one kind of azo disperse dye containing carboxylic acid ethyl ester was synthesized by alcoholysis reaction using goods containing cyano azo disperse dyes C.I. orange 25 and C.I.red 145, the other kind of azo disperse dye containing carboxylic acid ethyl ester was synthesized by ester exchange reaction using commodity azo disperse dyes containing carboxylic acid methyl ester groups C.I. blue 148 and C.I. brown 19. Then optimize the preparation process and purification products. Finally, the molecular structure of these four disperse dyes were characterized by IR, MS,1H-NMR and1C-NMR.Secondly, having a further study of the four carboxylate dyes, their hydrolysis kinetics and application performance were studied. The hydrolysis of the carboxylate dye in buffered alkaline solution followed pseudo first-order kinetics and the reaction series is independent of the structure carboxylate group number. Besides, according to the results of hydrolysis kinetics, we obtained the optimum caustic process of dyed fabric: D1, D4, 0.04 g / L NaOH, 70℃, 20min; D2,D3, 0.004 g / L NaOH, 80℃, 20 min. Finally, The synthesised dyes were also applied to polyester(PET) and the dyeing and wash fastness properties examined. The results shows four carboxylatedyes perform excellent dyeing behavior on PET fabrics, the sorption rates are more than 85%with good K/S value. After caustic process the ratings of crocking, washing and sublimation fastness of dyed fabrics can reach more than 4, indicating that carboxylate disperse dyes alkaline cleaning process can replace the traditional reduction clearing, and obtains the same, or even better results compared with reducing cleaning.