SEMICONTINUOUS EMULSION COPOLYMERIZATION OF BUTYL ACRYLATE-STYRENE

Butylacrylate (BA)-Styrene (St) copolymers have been synthesized via a semicontinuous emulsion process in which the monomers feeding rate and weight ratios (BA/St) were varied. The feed consisted of only pure monomers which were added to an aqueous solution that contained the emulsifier and initiator. The experimental results show that monomer consumption is governed by the feeding rate as well as by the monomer's reactivity. The average molecular weight decreased as the feeding rate increased independent of the BA/St ratio. Measurement of the latex average particle size and panicle number, as a function of the reaction time. showed a complex sequence of particle formation and agglomeration. In general, the average particle diameter increased in direct proportion to the feeding rate. This fact suggests that most probably homogeneous nucleation is preferred over monomer diffusion to the previously formed particles. Additionally l the monomer reactivity ratios (r(1), r(2)) decreased as the monomer feeding rate was increased. The experimental copolymer compositions determined by gas chromatography and NMR-H+ showed that the resulting copolymers were closely homogeneous.