PURPOSE: To reduce effectively the concentration of residual monomers and contents of acetaldehyde by applying selective saponification treatment at high temperature and weak alkaline pH to vinylester monomers saponifiable in alkaline conditions.
CONSTITUTION: Saponification treatment is applied to a synthetic resin aqueous dispersion obtained by polymerizing base monomers or comonomers with any one of emulsion, suspension, bulk polymerization or the like in a polymer dispersion in which polymer particles having ethylenically unsaturated monomers as their base are dispersed by polymer particles having a monomer unit of vinyl esters (preferably the polymer particles contain copolymers of vinyl acetate and a monomer unit such as vinyl ester of 3-18C carboxylic acid) at pH of 7.1 to 10 (preferably pH of 7.5 to 9) and at 20 to 100°C (preferably 40 to 80°C) preferably in the presence of chlorides of base metal compounds, with distillation treatment being applied, either after or during the said saponification treatment, under an atmospheric or reduced pressure to reduce the remaining monomers to the intended level so that the content of vinyl acetate and acetaldehyde becomes 0.01 wt.% or less.
HERUMUUTO RINNO
HANSUUURURIHI FUUTO
