Statistical experimental strategies approach to emulsion copolymerization of styrene and n-butyl acrylate

摘要

A batch emulsion copolymerization for the preparation of styrene-n-butylacrylate (St/BA) copolymer latexes is investigated. A series of n-butylacrylate-styrene copolymer latexes were obtained by emulsion copolymerization in the presence of K2S2O8 (KPS) as initiator and with/without emulsifier (sodium lauryl sulfate). The effect of such preparation conditions as initiator concentration, the Sti BA ratio, reaction temperature, agitation rate, and emulsifier concentration on the polymerization rate, particle size of copolymer latex, and molecular weight distribution of the resulting copolymer (similar to 80% conversion), respectively, is systematically studied using fractional factorial design methodology. Fractional factorial analysis indicates that the effects of the St/BA ratio, reaction temperature, emulsifier concentration, as well as the two-factor interaction of temperature and emulsifier concentration, are the key variables influencing the polymerization rate. At similar to 80% monomer conversion, statistical analysis clearly isolates emulsifier concentration as the dominant factor affecting average particle size of copolymer latex; results also indicate that the effects of the St/BA ratio, reaction temperature, and emulsifier concentration are major effects influencing the polydispersity of polymer molecular-weight distribution. For 7.30 g KPS/100 g monomer and 500 rpm agitation rate, the conditions for minimizing molecular-weight distribution (similar to 80% conversion) occur for a reaction temperature, St/BA ratio, and surfactant concentration of 70 degrees C, similar to 3.59/1, and similar to 2.08 g/100 g monomer, respectively, generating a minimum molecular-weight polydispersity of similar to 3.0. (C) 1998 John Wiley & Sons, Inc. [References: 28]