(114e) Starch Esterification Using Reactive Extrusion

Starch acetate esters were prepared using reactive extrusion at high temperatures in the presence of iodine, as a Lewis acid catalyst. Extrusions were done using a Brabender TSE-20 twin screw extruder. Iodine was dissolved in acetic anhydride and the solution was sprayed onto the starch. This formulation was then extruded at high temperature to produce starch acetate. To increase the residence time, an extruder die extension was used. Iodine was found to be an extremely effective catalyst which gave a high degree of substitution (DS) even with a short residence time. The effects of selected reaction conditions on the DS of starch acetate were investigated. Reactive extrusion was found to be an extremely effective method for preparing starch acetate esters. It is continuous and solvent-free and, hence, is much faster process than the conventional batch process involving base catalysts. Starch acetate may be a useful bio-sourced and biodegradable, thermoplastic polymer for packaging and insulation applications.