Competitive particle growth: A tool to control the particle size distribution for the synthesis of high solids content low viscosity latexes

Abstract

The competitive particle growth of bimodal latexes during the emulsion copolymerization of methyl methacrylate/butyl acrylate/methacrylic acid (MMA/BA/MAA) was investigated. It was found that the volumetric growth ratio of the large over the small population of particles was a function of the particle size ratio and the weight fraction of each population of particles; namely, of the number of polymer particles of each population. The available models for the prediction of the competitive growth could not predict the latter dependence and therefore an empirical model was built. The model was able to reasonable fit the experimental data and the dependence over both variables. The empirical model of the competitive growth was then used to control the particle size distribution of bimodal latexes in seeded semibatch emulsion polymerization reactions. The control of the particle size distribution was the key parameter to synthesize high solids content latexes. Thus, MMA/BA/MAA copolymer latexes with solids content of 70 wt% and particle sizes smaller than 350 nm with viscosities below 1 Pa s (measured at 100 s −1) were easily produced.