Modified starch dispersions as water-based binder system for paints and varnishes

Our work aimed at the optimization of the structure of starch for the preparation of concentrated water-based dispersions (> 30%) with film forming properties for the application in paints and varnishes. A degraded potato starch (Emox TSD) with a molar mass of 1.18BL105 g/mol (SEC-MALLS) was used as starting material for esterification reactions with different chain lengths (C2-C6) and varied degrees of substitution (DS)(0.05-1.1) for an increase in their hydrophobicity. The modification led to cold water dispersible products with solid contents up to 45% and viscosities in the range of 102 103 mPaBLs (100 s-1). Film casting resulted in mostly continuous films. Furthermore, the synthesized starch esters showed a significant enhancement in their adhesion properties (ISO class 0 & 1) on glass and aluminum plates compared to the non-substituted starch (class 4). In corrosion stability tests the starch butyrate with a DS of 0.6 and the starch hexanoate with a DS of 0.4 (used amount of reagent) had sound barrier properties after crosslinking them with an isocyanate (Bayhydur XP 2655).