STABILITY OF CARBOXYLATED POLY(BUTYL ACRYLATE) LATICES DURING SEMIBATCH EMULSION POLYMERIZATION

The stability of latex particles in the semibatch emulsion polymerizat ion of butyl acrylate (BA) in the presence of 0-10% acrylic acid (AA) was investigated. The amount of coagulum (i.e., large flocs caused by intensive coagulation) can be greatly reduced by an increase in the co ncentration of sodium lauryl sulfate (SLS) in the monomer emulsion fee d. On the other hand, increasing the concentration of SLS in the initi al reactor charge can result in an increase in the percentage of the p article volume change (i.e., a measure of the degree of limited floccu lation) later in the process. Both the scrap and percentage of the par ticle volume change increase with an increase in the electrolyte conce ntration. Both the coagulation and secondary nucleation process can re sult in a significant deviation from the Novak model. Experimental dat a also show that latex particles comprising pure BA can lose their sta bility rapidly at higher total solids content because of the crowding effect. Incorporation of only 5% AA into the emulsion polymers greatly improves the latex stability. (C) 1996 John Wiley & Sons, Inc.