Abstract
The present work investigated the effect of mixing and pH of solution on latex particle coagulation from the aspect of process intensification. Experiments were conducted in a CSTR under conditions below the critical micelle concentration of emulsifier in order to reduce emulsifier consumption. When the rotational number of a 2-bladed impeller of half-moon shape was varied as a control parameter, the reaction state depended on mixing below 200 rpm. Under these mixing conditions, the monomer conversion was low and particle coagulation was suppressed. On the other hand, at above 200 rpm the reaction state was controlled by polymerization reaction, and high monomer conversion was obtained irrespective of the rotational number of impeller. These mixing conditions enhanced particle coagulation, and larger particles were obtained. When pH of solution was varied as the other control parameter, higher pH values (pH=6 and 7) enhanced particle coagulation, the mean particle size increased up to 3 μm with time and particles of larger than 10 μm were observed in the sample obtained at the maximum mean particle size. Under these conditions, a bimodal particle size distribution was obtained in the process of particle growth to the maximum mean diameter, while a mono-dispersed distribution was obtained in the process of decreasing mean particle size from the maximum value.
