PURPOSE: To obtain a PVC resin which does not undergo pale red coloration during heating, mixing, or molding, by adding a specified compound in suspension-polymerizing a vinyl chloride monomer or copolymerizing this with another vinyl monomer.
CONSTITUTION: Suspension polymerization or copolymerization of 50W100wt% vinyl chloride monomer and 50W0wt% another vinyl monomer (e.g., vinyl acetate) is started at 25W80°C in the presence of a monomer-soluble initiator (e.g., benzoyl peroxide) in an aqueous medium containing a small amount of a suspending agent (e.g., PVC), a scale-deposition preventing agent, a pH controlling agent, etc. After the conversion reaches 65wt% and before the polymerization is completed, 0.001W3wt%, based on the total monomer, compound of the formula (wherein R1 and R2 are each a 6W30 C alkyloyl, aryloyl, or alkaryloyl) is added, and then the polymerization is brought to completion.
SUEMATSU REIJI
MITSUFUJI KIYUUICHI
ISHIBASHI SEIGOU
KAMIMURA KATSUOKI
HATAUE MASAHIRO
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