| 摘要 |
PURPOSE:The title dispersion stabilizer which can give porous PVC of a sharp particle dize distribution, comprising a specified PVA. CONSTITUTION:Polyvinyl acetate obtained by polymerizing vinyl acetate and, optionally, a copolymerizable monomer (e.g., ethylene) is saponified to obtain a dispersion stabilizer for suspension polymerization of a vinyl compound, com prising a PVA having a degree of saponification of 60-95mol%, an average degree of polymerization of 50-4,000, a ratio of a weight-average degree of polymerization (Pw) to a number-average degree of polymerization (Pn), Pw/Pn, <=3.0 and having a carbonyl group and a vicinal vinyl group in the molecule, extinction coefficients at 280mmu and 320mmu as determined by UV absorption spectra of a 0.1% aqueous solution of 0.30 or above and 0.15 or above, respective ly, and a ratio of an extinction coefficient at 320mmu to that at 280mmu >=0.30.
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