Novel polyvinyl chloride suspension polymerization process and product having improved plasticizer absorption

摘要

A polyvinyl chloride having high bulk density and enhanced plasticizer absorption is produced by suspension polymerization of vinyl chloride monomer and comonomers wherein the initial suspension of ingredients is generated such that the oil phase droplets formed in the suspension are compositionally equivalent with respect to initiator, and the level of suspending agent and agitation are chosen to substantially preclude agglomeration of resin particles throughout the reaction, thereby producing resin wherein the resin grain size distribution results directly from the oil phase droplet distribution created at or near the start of the reaction. The process is conducted under conditions so that the polymerization is commenced before the final distribution is established. In this manner, seed particles of resin are produced from the vinyl monomer prior to establishing the final particle distribution. The seed particles can be formed (1) by first conducting the process at low speed agitation, followed by increasing the speed of agitation so as to distribute the resin seed particles in the droplets of vinyl monomer, or (2) by preheating the aqueous medium prior to mixing with the vinyl monomer phase so as to initiate polymerization and formation of seed particles before the vinyl monomer droplets achieve their ultimate droplet size. The result of the processes of the invention is a polyvinyl chloride polymer or copolymer that has high bulk density and enhanced plasticizer absorption. A further benefit of the process is that resin deposition on the interior surfaces of the reactor is essentially eliminated.