BATCH AND SEMICONTINUOUS EMULSION COPOLYMERIZATION OF VINYLIDENE-CHLORIDE AND BUTYL METHACRYLATE .1. KINETICS IN VDC BMA EMULSION POLYMERIZATION AND SURFACE AND COLLOIDAL PROPERTIES OF VDC BMA LATEXES

Vinylidene chloride (VDC)-butyl methacrylate (BMA) comonomer mixtures with various composition (83: 17, 60: 40, 33: 67 in mol %) were polymerized at 25-degrees-C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization. The reactivity ratios determined in VDC (M1)-BMA (M2) emulsion copolymerization system were r1 = 0.22 and r2 = 2.41. Seven 35% solids (83: 17 mol %) VDC-BMA copolymer latexes were prepared: one batch (G), one seeded batch (F), and 5 seeded semicontinuous polymerizations of 5 different monomer feed rates ranging from 0.27 (A) to 1.10 wt % / min (E). The kinetic studies of seeded semicontinuous polymerizations A-E showed that the rates of polymerizations (R(p)) were controlled by the monomer addition rates (R(a)). The conversion versus time curves for the polymerizations of 0: 100-100: 0 VDC-BMA mixtures by batch polymerization showed that the rate of polymerization (R(p)) was a function of the number of particles, and that the rate of polymerization in a latex particle (R(pp)) increased with increasing proportions of butyl methacrylate in the monomer mixture. All of the latexes had narrow particle size distributions. The greater particle number density in VDC polymerization and the greater water solubility of VDC suggest that the homogeneous nucleation mechanism is operative in VDC-BMA copolymerizations. The latex copolymers prepared by semicontinuous polymerization had lower number- and weight-average molecular weights than those of the corresponding batch copolymers, resulting from the monomer starvation occurring during the semicontinuous polymerization. The surface characterization study of the cleaned latexes showed that for the latexes by batch process, the surface charge density derived from strong-acid groups decreased with increasing proportion of VDC in the monomer mixture. On the other hand, for the latexes prepared by semicontinuous polymerization, the surface charge density derived from strong-acid groups did not depend on the monomer composition of the copolymers.