| 摘要 |
<p>The invention relates to highly acetalized, coarse-grained polyvinyl acetals with a degree of acetalization of >80 mol % and an average grain size of≧100μm obtainable by acetalization of partially or fully hydrolyzed polyvinyl esters with a degree of hydrolysis of≧70 mol % with acetaldehyde, characterized by the fact that the acetalization is started at a temperature T1 of 0° C.≰T1≰+20° C. and is then continued at a temperature T2 of >+40° C., wherein the temperature T2 is held for a time period of 0.05 to 4 hours and the acetalization is performed in a closed reactor.</p> |
