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AssigneeShin-Etsu Chemical Co., Ltd.
InventorsKenichi Itoh, Genji Noguki, Masanobu Nakahara
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The invention provides an improvement in the suspension polymerization of vinyl chloride or a monomer mixture mainly composed of vinyl chloride in an aqueous medium containing a nonionic surface active agent and in the presence of a monomer-soluble polymerization initiator, according to which the aqueous polymerization medium is admixed with a crosslinked copolymer having carboxyl group such as a copolymer of acrylic acid and diethyleneglycol bisallyl or bismethallyl ether at a moment when the percentage of the monomer conversion is in the range from 1 to 20% so that a polyvinyl chloride resin product of high quality can be obtained having an outstandingly high bulk density and plasticizer absorptivity but still containing an extremely small number of fish eyes.
In a method for the suspension polymerization of vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride in an aqueous polymerization medium containing a non-ionic surface active agent and in the presence of a monomer-soluble polymerizatin initiator, an improvement which comprises admixing the aqueous polymerization medium with a water-soluble cross-linked copolymer having carboxyl groups at a moment when the percentage of the monomer conversion is in the range from 1 to 20%, wherein the water-soluble cross-linked copolymer having carboxyl groups is a copolymer of 100 parts by weight of acrylic acid and from 0.05 to 10 parts by weight of diethyleneglycol bisallyl or bismethallyl ether.
Dependencies are inferred from the claim text.