| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for producing a vinyl acetal resin that suppresses discoloration and molecular weight reduction of the obtained vinyl acetal resin, suppresses side reactions other than the acetalization reaction of aldehyde, and produces a vinyl acetal resin having a high degree of acetalization in a short time even when an amount of aldehyde used is small. <P>SOLUTION: The method for producing a vinyl acetal resin is provided, which performs an acetalization reaction of a mixed liquid containing a vinyl alcohol-based resin or a vinyl acetate-based resin and aldehyde in a high-temperature high-pressure fluid of 100-400°C and 0.2-100 MPa. The method for producing a vinyl acetal resin includes: a step 1 of carrying on the acetalization reaction until the degree of acetalization reaches 20-55 mol% while keeping the reaction temperature constant; and a step 2 of further carrying on the acetalization reaction while reducing the reaction temperature after the step 1 to the temperature lower by 10-250°C than the reaction temperature of the step 1 at the rate of 0.01-2°C/min. <P>COPYRIGHT: (C)2012,JPO&INPIT |
