A novel approach to the fabrication of bleached shellac by a totally chlorine-free (TCF) bleaching method

Abstract

This study made use of a novel totally chlorine-free (TCF) bleaching approach to prepare bleached shellac. Some single factor experiments were employed to investigate the effects of the main factors in the H₂O₂ bleaching method. A new chlorine-free bleached shellac resin was obtained in the Box–Behnken design responsive surface optimal experimental conditions (pH, 9.0–11.0; 1.33 mL g⁻¹, concentration of 30% hydrogen peroxide; 2.0 h, dropping time of hydrogen peroxide; 7.2 h, bleaching time; 90 °C, temperature). The yield and color index of the bleached shellac obtained under the optimal experimental conditions were 80.84% and 0.5675 respectively. The result of the physicochemical property test, IR spectrum and DSC characterization indicate that the properties of H₂O₂ bleached shellac are similar to commercially refined shellac resin. Moreover, it is noteworthy that the H₂O₂ bleached shellac was remarkable in alcohol solubility and thermal lifetime tests. It had a higher acid value and a lower softening point compared with commercially refined shellac resin, which can be applied safely in many fields including food and medical industries without chlorine residues.