Polyvinyl acetal and intermediate film for a laminated glass containing the same

A polyvinyl acetal obtained by acetalizing a polyvinyl alcohol, the polyvinyl saponification degree of alcohol is 50 to 99.99 mol%, viscosity average degree of polymerization of 200-5000, the alkali metal content of the alkali metal salts of carboxylic acids and the in the mass conversion 0.5% by weight or less, when the polyvinyl alcohol that has been heated for 3 hours at 120 ° C. were measured by gel permeation chromatography, a peak top molecular weight measured with a differential refractive index detector (a) If, spectrophotometric detector (measuring wavelength 280 nm) peak top molecular weight measured by (B) is the following formula (1) (A-B) / A <0.75 (1) The filled, and the absorbance at the peak top molecular weight (B) is a polyvinyl acetal to be Accordingly, small amount of coarse particles produced in the process of acetalization, less coloration due to heating, it is possible to provide a polyvinyl acetal which can yet obtain foreign matter (undissolved) less film.