THERMALLY MODIFIED POLY(VINYL ALCOHOL) AS A PROTECTIVE COLLOID IN SUSPENSION POLYMERIZATION OF VINYL-CHLORIDE

Aqueous solution of poly(vinyl alcohol) or partially hydrolyzed poly(v inyl acetate) was modified either thermally or thermo-oxidatively at 1 40 to 240-degrees-C. Samples of poly(vinyl alcohol) thus obtained were tested as protective colloids in suspension polymerization of vinyl c hloride. As found, thermal modification under nitrogen was virtually i neffective; more advantageous was that in the presence of air, or even better in oxygen. The most suitable temperature at one hour expositio n was 180-200-degrees-C. Important was the formation of an unsaturated conjugated system -(C=C-)n-CO- (n = 1-3) in macromolecules of poly(vi nyl alcohol). Poly(vinyl alcohol) modified in this way, in contrast to an unmodified one or that exposed to the above-mentioned temperature in inert atmosphere, is an effective dispersant of suspension polymeri zation of vinyl chloride.