Synthesis and Characterization of Anionic Polyurethane Dispersants for Waterborne Paints

Anionic polyurethane dispersants (APUDs) were used as dispersing agents in formulation of waterborne paints. The APUDs were synthesized by three steps. In the first step, macromonomer diisocyanate having carboxylic acid was prepared by isophorone diisocyanate (IPDI), dimethylol propionic acid (DMPA) in the presence of acetone as solvent and dibutyltin dilaurate (DBTDL) as catalyst. Then, carboxylic polyurethane was prepared by reaction macromonomer diisocyanate having carboxylic acid groups with alcohols. In this work, alcohols were 1,4-butanediol and 1,6-hexanediol as difunctional alcohols, trimethylol propane as trifunctional alcohol and pentaerythritol as tetrafunctional alcohol. The final step involved neutralization and dispersion in water, where acidic polyurethane was neutralized by the addition of triethylamine (TEA). The polymers have been characterized with 1H-NMR and FT-IR. The dispersion of APUDs depends on their molecular weights and chemical structures. Dispersion of titanium dioxide in typical waterborne acrylic resin has been investigated.