Influence of agitation on the creation of coagulum during the emulsion polymerization of the system styrene–butylacrylate–acrylic acid

Abstract

AbstractThis paper gives the results of the estimated coagulum content in the final sample of a dispersion based on styrene–butylacrylate–acrylic acid, prepared by semicontinuous emulsion polymerization. The results were gained from experiments on 25 L and 5 m3 reactors. The dependence of the amount of coagulum on the agitation intensity was studied. It was found that it is necessary to divide the results into two regions: (a) for specific power input smaller than 80 W/m3; (b) for specific power input greater than 80 W/m3. It was found that polymerization scaling up from the point of constant coagulum content in the system studied is possible under the conditions of constant specific power input. The specific power input varied in the range from 5 to 3000 W/m2. For the first region was gained the empiric correlation Y = 2.16(ℰV)−1 and for the second region the equation Y = 3.5 × 10−5(ℰV)1.5, where Y is the amount of coagulum (wt %). For the existence of two regions we propose the following hypothesis according to which increasing mixing intensity improves the temperature and concentration nonuniformity which results in the decrease of coagulum content. From the certain value of specific power input, which is specific for each system, the amount of coagulum starts to increase due to increasing shear stress.