A METHOD FOR THE PREPARATION OF VINYL CLORIDES POLIMERS

An improved method for the polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous polymerization medium is proposed in which a water-insoluble polymerization initiator, being solid at room temperature as dispersed in the aqueous medium and having a particle size distribution of 50 mu m or finer, is added to the polymerization mixture which is maintained at a temperature where the half-life period of the initiator is 120 minutes or longer or, alternatively, over a duration equal to or shorter than one-tenth of the half-life period of the initiator at the temperature of the polymerization mixture. By this method the polymerization can be homogeneously proceeded to produce vinyl chloride polymers having a uniform particle size distribution, excellent heat stability and much less fish-eyes when fabricated into sheets.