ROOM TEMPERATURE-INITIATED AND SELF-HEATING COPOLYMERIZATION OF ACRYLONITRILE WITH VINYL-ACETATE

A novel polymerization method [Ruckenstein and Li, Polymer Bull., 37, 43 (1996)]--room temperature-initiated, self-heating polymerization--w as applied to both bulk and concentrated emulsion copolymerization of acrylonitrile (AN) with vinyl acetate (VAc). A redox system was employ ed as an initiator, with the oxidant dissolved in the monomers and the reductants (two reductants were employed) in the aqueous phase. In th e bulk polymerization, the oxidant (cumene hydroperoxide) was dissolve d in the mixture of monomers, and the two reductants (sodium metabisul fite and ferrous sulfate) were introduced as an aqueous solution. In t he concentrated emulsion polymerization, a mixture of the monomers con taining dissolved oxidant was first used as the dispersed phase of a c oncentrated emulsion in Prater, and the aqueous solution of reductants was subsequently added to the concentrated emulsion. In both cases, t he polymerization started at room temperature, just after the reductan ts were introduced. Because the reactor was insulated, the heat genera ted by the reaction was mostly used to accelerate the polymerization, which reached a high conversion in 30 min. The effects of various para meters on the polymerization were investigated. Optimum values were fo und for the volume fraction of the dispersed phase, for the wt ratios of the two reductants and of the oxidant to reductants, and for the su rfactant and reductant concentrations. One concludes that the concentr ated emulsion polymerization method is particularly suitable for the r oom temperature-initiated, self-heating polymerization. (C) 1998 John Wiley & Sons, Inc.