Esterification of Cochineal Carmine Used for Dyeing Cationic Modified Cotton with High Color Fastness

In order to reduce the electronic cloud density for higher color fastness, ester groups were introduced into cochineal carmine matrix structure. The optimum esterification conditions were selected by varying the level of acid-binding agent, the reaction temperature, the reaction time, and the amount of acetylation reagent. The structure and properties of esterified cochineal carmine was characterized by UV-vis spectroscopy, FT-IR spectrometry and metallographic microscopy. The build-up property, dyeability, light fastness, perspiration and rubbing fastness of cochineal carmine before and after esterification on cationic modified cotton were investigated. The results show that the optimum esterification condition is treating 1.0 g cochineal carmine with 50 mL acetic anhydride and 4.0 g anhydrous sodium acetate at 80°C for 2.0 hours. The acid perspiration fastness and wet rubbing fastness of the resulting dyed samples were increased by one grade. The perspiration fastness to alkalis and the light fastness were improved by one-half grade.