High solids content latexes with low viscosity

The effect of particle size distribution (PSD) on the solids content and viscosity of the multi-sized latex was investigated by blending mono-sized latexes and measuring their theological properties. The results showed that the maximum packing (highest solids content) was observed at a weight fraction 80% of large particles with respect to total solids content for both bi-modal and tri-modal latexes, and the lowest viscosity was obtained when the ratio of large to medium to small particles was approximately 80/10/10 (by weight). A two-stage technique to prepare high solids multi-sized polymer latex was developed by using a polymer latex previously made as seed and by adding small amount of additional surfactants and/or second group of polymer particles. The PSD of the latex was optimized by varying the amount of the seed, the additional surfactants, and the second group of particles. Film forming latexes with high solids (> 65%) and low viscosity were obtained.