| 摘要 |
<p>A polyvinyl acetal which has a degree of acetalization of 40 to 90 mol%, a content of a vinyl ester monomer unit of 0.1 to 20 mol%, and a viscosity-average polymerization degree of 200 to 5000, wherein when the polyvinyl acetal is heated for three hours at 230°C and subjected to gel permeation chromatography, a peak top molecular weight (A) measured by a differential refractive index detector and a peak top molecular weight (B) measured by an absorbance detector (measurement wavelength 280 nm) satisfy formula (1), (A-B)/A<0.60 (1), and absorbance at the peak top molecular weight (B) is 0.50×10-3 to 1.00×10-2. Accordingly, a polyvinyl acetal can be provided from which a film that has lower coloring due to heat and less foreign matters (undissolved fractions) can be obtained.</p> |
