Study of particle nucleation and growth in the absence of soap micelles during the emulsion polymerization of vinyl acetate in a pilot plant reactor

A study is made of the emulsion polymerization of vinyl acetate in the absence of soap micelles in a pilot plant reactor. The effects of several variables on the particle size and the reaction rate were investigated in a series of designed experiments (factorial designs and fractional factorial designs at two levels; additional runs were included to resolve ambiguities. The variables studied were: initial initiator concentration, [I]o, monomer concentration, [M]o, presence of monomer soluble [4-tert-butyl catechol (TBC)] and water soluble impurities [oxygen, hydroquinone (HQ)] and agitation. Based on the parameters studied, it is found that the course of the reaction in the polymerizations with low soap concentrations is the same with the soap free cases; the effects of some parameters (initiator concentration, HQ) however, are more pronounced in the soap free runs. This is due to the difference in the stabilization mechanisms in the two cases. The particle stability (final particle size) in the soap free runs (where the particles are only stabilized by the initator end groups) is expected to be more sensitive to changes in the ionic strength and to the presence of small surface active chains that are created when impurities are present.