Definition and Composition of Bleached Shellac
Chemical nature: A modified natural resin composed of lactones and esters formed from fatty acids and sesquiterpene acids, appearing as light-yellow granular solid after dewaxing.
Ingredient characteristics: Contains esters of gongtong acid (9,10,16-trihydroxypalmitic acid), with a molecular formula of C30H50O11. The standard acid value is 75–92.
Solubility characteristics: Easily soluble in ethanol and alkaline solutions, insoluble in water, and slightly soluble in acetone.
Production Processes and Technical Standards
Core process:
Traditional method: Dissolve shellac → Treat with sodium carbonate solution → Bleach with sodium hypochlorite → Precipitate with sulfuric acid and dry.
Innovative Process: Totally Chlorine-Free Bleaching with Hydrogen Peroxide (TCFBS), reducing chlorine residues to ≤10 ppm and enhancing alcohol solubility.
Quality standards:
Implement the national standard GB/T 8140-2009, replacing the 1987 edition. Moisture content ≤ 2%, heavy metals ≤ 10 ppm.
Pharmaceutical grade products must meet specifications such as an acid value of 65–95 and an ash content of ≤0.5%.
Application Areas and Functional Features
Food Industry: As a moisture-proof coating agent for candies and chocolates, the maximum usage level for wafer biscuits is 0.20 g/kg; it also functions as a surfactant.
Pharmaceutical field: Enteric-coating materials for drugs, enabling pH-sensitive sustained-release effects.
Industrial applications: military coatings, electrical insulation materials, and environmentally friendly varnishes—withstanding voltages up to 30 kV/mm.