Vinyl chloride seeded emulsion polymerization

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

In the seeded emulsion polymerization of some monomers —e.g., styrene—it is possible to obtain final latexes with uniform, large particles by adjusting, during polymerization, the quantity of added emulsifier the formation of new particles is prevented by the limited amount of emulsifier. For vinyl chloride, limited emulsifier is not sufficient to prevent the formation of new particles in fact, to obtain a monodispersed latex, the surface of the particles seeded in a given water volume must be controlled. It is assumed that the growth of new nuclei is related either to the rate of formation of primary useful radicals or to the rate that these are taken by the surface of sized particles. 

Few works have appeared on the seeded emulsion polymerization of vinyl chloride (VC). Giskehaug (5) recently used this technique in a kinetic study of the emulsion polymerization of VC, but he has not determined the number and distribution of particles in the final latexes. Kotlyar et al. (6) do not give sufficient experimental data for an exhaustive analysis of the results moreover, most of the growth experiments seem to have been carried out in the presence of free emulsifier. The data reported in some industrial patents (1,9) point out only the impor-... 

Patsiga et al. (I9W) and Giskehaug (I96S) carried out tbe seeded emulsion polymerizations of vinyl acetate and of vinyl chloride, respectively, and found that in both systems the rate of polymerization was proportional only to the 0.15-0.20 power of the number of polymer particles. From this finding they concluded that the main locus of the emulsion polymerization of water oluble monomers must be in the water fJiase. This conclusion seems reasonable because the solubilities of these monomers are about 100... 

This theoretical equation explains very well the rate of seeded emulsion polymerization of vinyl acetate and vinyl chloride found by Patsiga et al. 

Seeded Thermal Emulsion Polymerization of Vinyl Chloride with Gradual... 

Some prelimarily work to illustrate this last point is reported below. This work, by Lee and Poehlein (18), is based on the analysis of the data published by Berens (19) for the emulsion polymerization of vinyl chloride in a seed-fed CSTR. Berens reported both the seed and effluent PSD s for steady-state polymerization in a CSTR, These data are shown in Figure 7. Since the seed latex is not monodisperse the model presented previously was modified by subdiving the seed distribution into twelve parts which were considered to be monodisperse with the mean diameter of the part. The previous model was applied to each part and the results added to predict the effluent PSD. Since the volume of the seed particles were distributed, the mean seed particle volume, , was used in the appropriate dimensionless groups. 

Tauer and Petruschke [116] investigated the effect of PVC-seeded polymer particles on the kinetics of the emulsion polymerization of vinyl chloride. Figure 6 shows that the rate of polymerization increases with increasing concentration of seed particles. The kinetic data summarized in Tables 4-6 indicates that the polymerization is strongly influenced by the emulsifier and seed particle concentrations. From these results it follows that the rate of polymerization is a function of 1) the particle size of seeded PVC particles, 2) the emulsifier concentration, and 3) the number of particles or the product N D,. For all polymerizations, the following rate expression was derived... 

Table 4. Variation of the rate of polymerization in the emulsion polymerization of vinyl chloride with the number of seeded PVC particles [116] ...

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