PRODUCTION METHOD AND PRODUCTION DEVICE FOR POLYVINYL ALCOHOL

摘要

Provided are a method and an apparatus for producing a polyvinyl alcohol that can remove unreacted monomers from the polymerization solution efficiently and reduce the amount of methanol injected. A polymerization solution obtained by polymerization of one or more vinyl esters or copolymerization of a vinyl ester with other monomers copolymerizable therewith is adjusted to a particular concentration by addition of liquid methanol and then brought into contact with methanol vapor in counter-current flow for separation into a monomer-free polymer solution and a monomer/methanol mixture. The monomer-free polymer solution is then saponified in the presence of a catalyst to give a polyvinyl alcohol.