Production method for modified vinyl alcohol polymer particle and particle obtained thereby

A method for producing modified vinyl alcohol-based polymer particles, the method comprising:

• mixing vinyl alcohol-based polymer particles with a mixed medium comprising an unsaturated carboxylic acid, an acid catalyst, and water, wherein by mixing the vinyl alcohol-based polymer particles with the mixed medium, the vinyl alcohol-based polymer particles are reacted with the unsaturated carboxylic acid to obtain modified vinyl alcohol-based polymer particles comprising a vinyl ester unit, having a vinyl alcohol unit content based on a total constitutional units of 60 mol % or more and less than 95 mol %, and having an average particle diameter from 50 to 2000 μm,
• wherein the unsaturated carboxylic acid is a compound of formula (1):
• wherein X denotes a carbon-carbon bond or a divalent saturated hydrocarbon group having a carbon number from 1 to 10 optionally having a branched structure, Y denotes a hydrogen atom or a saturated hydrocarbon group having a carbon number from 1 to 6 optionally having a branched structure, and Z denotes a hydrogen atom or a methyl group, and
• the vinyl ester unit is a unit of formula (2):