Studies on bleaching of lac I. Action of sodium hypochlorite on the resin

Abstract

A study was made of physical and chemical changes that take place during bleaching of Rangeeni and Kusmi, the two main varieties of lac, by the improved hypochlorite bleaching process. The physical changes studied include life, flow and keeping quality. The chemical changes observed were oxidation, addition, substitution and partial hydrolysis. Fractionation and intrinsic viscosity, however, showed little overall molecular change.

Characterisation and discrimination of various types of lac resin using gas chromatography mass spectrometry techniques with quaternary ammonium reagents

“…AMDIS software was found to be a valuable tool for the detection of the markers at very low levels. The presence of these compounds is consistent with studies of bleached shellac that have established that a small amount of Cl is incorporated into the resin as a consequence of bleaching with hypochlorite [7,16,51]. Research at the PMA dealing with the characterisation of the chlorinated marker compounds and their use for the identification of bleached shellac has been described in detail in previous publications [21,22].…”

Halogen-free bleaching of shellac using electrochemically generated peroxodicarbonate

“…3 Industrial bleaching processes use active chlorine species such as sodium hypochlorite (NaOCl). [25][26][27] However, bleaching damages include oxidation of alcohol and aldehyde functionalities as well as double bond chlorination of the sesquiterpenes. 28 Consequently, the obtained bleached shellac contains toxic organochlorine moieties, causing rapid aging and polymerization, limiting the shelf life of the bleached shellac.…”