Production of aqueous shellac dispersions by high pressure homogenisation

The use of shellac for coating purposes in pharmacy, food and nutriceutical industry generally involves the use of organic solvents. An aqueous shellac dispersion has been developed by applying high pressure homogenisation. Shellac was dissolved in alkaline solution, precipitated by HCl addition and the obtained suspension homogenised at 1500 bar applying 20 cycles. The volume diameter 50% was 2 microm, a distinct fraction of particles was in the nanometer range. This surfactant-free shellac dispersion with 20% solid content proved to be physically stable and showed good film forming properties.