LAUSR

Abstract Alkali-clearable disperse dyes display high washing fastness on PET. The alkali-clearability of phthalimidyl azo disperse dyes can be explained by the hydrolysis of imido ring creating a water-soluble phthalate groups under alkaline conditions. Hydrolysis performance of six phthalimide disperse dyes were discussed and results were as follows: K/S value of dyed polyester/elastane fabrics decreased obviously as the pH value increased. In generally, the K/S values on dyed PET for all six dyes at pH = 5, 7, 9 and 11 is about equal to 78–92%, 55–67%, 25–42% and 14–29% the K/S value of pH = 3 dyed PET, respectively. Absorption spectra of phthalimide dyes dissolved in alkali solution at temperature 40 °C, 60 °C and 80 °C showed that in the case of alkali dissolving, with increasing in temperature, the absorbance at λmax tended to increase corresponding. The peak at 1770 cm−1 and 1395 cm−1 in FTIR spectra of hydrolyzed dye showed that C-O groups appeared under relatively mild alkaline conditions. Hydrolysis influence factor are electron density distribution and steric hindrance effect. Compared with DFT/B3LYP calculated electron density, steric hindrance effect is a more important influence factor than electron density in hydrolysis reaction process. High performance liquid chromatography HPLC results indicate that hydrolysis reaction of phthalimide disperse dye is nucleophilic addition-elimination reaction, which belongs to the SN2 mechanism and pseudo first-order reaction.