A contribution to the semicontinuous emulsion polymerization. III. Particle formation and particle size

Semicontinuous emulsion copolymerization of butyl methacrylate and butyl acrylate with a monomer emulsion feed has been investigated. The distribution of a constant amount of anionic emulsifier between the initial reactor charge and the emulsion of monomers was varied. The surface tension during the feeding of the monomer emulsion as well as the size distribution and average particle size in the final latices were measured. It was found, that the distribution of emulsifier affected the mechanism of the particle growth and the final particle size. At a high content of emulsifier in the initial reactor charge a large number of small particles appeared, which underwent extensive limited flocculation during the later stages of polymerization. The extent of the flocculation was controlled by the overall amount of emulsifier. In case of a very low content of emulsifier in the initial reactor charge no flocculation occured and even a nucleation of new particles took place towards the end of the monomer emulsion feeding.