| 摘要 |
<p>The present application is concerned with a process for preparing polymers comprising vinyl acetate-, vinyl alcohol- and vinyl acetal-units by alcoholyzing and acetalyzing a polyvinyl acetate having a relatively low molecular weight in a solution in an organic solvent having a high polyvinyl acetate concentration in the presence of a strong acid catalyst at elevated temperatures, preferably 40 to 65°C, adding an alkaline agent after completion of the alcoholysis and acetalyzation to the desired degree to neutralize the acid catalyst, separating the salt formed on neutralization and recovering the produced polymer. This process is characterized by the fact that the separation of the formed salt is carried out by sedimentation. By this process it is possible to separate very easily the produced polymer from the salt nearly quantitatively.</p> |
