| 摘要 |
PURPOSE:To effect suspension polymerization of vinyl chloride while controlling scale deposition for a prolonged time, by polymerizing vinyl chloride in an aqueous medium in a polymerizer whose inside wall has a film formed by coating the wall with a modified PVA having a silyl group in the molecule and drying the wet film by heating. CONSTITUTION:In suspension-polymerizing vinyl chloride alone or together with a monomer copolymerizable therewith in an aqueous medium, the inside wall of a polymerizer is previously coated with a polymer scale deposition preventing agent comprising an aqueous solution of a modified polyvinyl alcohol having a silyl group in the molecule, and the wet film is dired by heating. Examples of the processes for producing the modified polyvinyl alcohols include (i) a process comprising introducing silicon into polyvinyl alcohol or a modified polyvinyl acetate containig carboxyl or hydroxyl group by post-modification with a silylating agent, and (ii) a process comprising saponifying a copolymer containing a vinyl ester and an olefinically unsaturated monomer having a silyl group in the molecule or a copolymer containing these monomers and an olefinically unsaturated monomer having an ionic hydrophilic group in the molecule.
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