Semi-batch emulsion polymerization of methyl methacrylate-butyl acrylate-methacrylic acid monomers were carried out with the addition of nano ZnO to the monomer feed, to obtain a binder for exterior architectural paints. Nano ZnO reacted spontaneously with acid groups to form zinc methacrylate or dimethacrylate which participated in crosslinking reactions. The amount of nano ZnO added was increased up to the equivalence point and in several cases exceeded for unmodified, hydrophilic or hydrophobic silane modified nano zinc oxides. The emulsions and clear polymer films obtained from them were characterized with conventional methods. FTIR and UV/Vis spectra confirmed the transformation of nano zinc oxide up to the equivalence point.