| 摘要 |
PROBLEM TO BE SOLVED: To easily produce a polyvinyl acetal resin having a desired mixed acetalization degree by reacting with at least two kinds of aldehydes in high efficiency in the production of a polyvinyl acetal resin having a desired mixed acetalization degree using at least two kinds of aldehydes. SOLUTION: An aqueous solution of polyvinyl alcohol and at least two kinds of aldehydes are supplied to looped reactors 13, 15 and partially reacted with each other under circulation in the looped reactors 13, 15. The partially reacted liquid is transferred in a pot reactor 16 and the reaction is completed in the reactor 16 under stirring to obtain the objective polyvinyl acetal resin. At least two looped reactors 13,15 are connected in series and the aldehyde to be supplied to the former stage reactor 13 has a reaction rate slower than that of the aldehyde to be supplied to the latter stage reactor 15.
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