Patent ID: 6962955

Claim:
A polyvinyl alcohol having silyl group functionalized monomer units of formula (1): wherein R 1 represents an alkyl group having from 1 to 5 carbon atoms; R 2 represents an alkoxyl or acyloxyl group; and m is an integer of from 0 to 2, which is obtained by copolymerizing a vinyl ester monomer with a monomer having a silyl group of formula (2) to form a polyvinyl ester, and then hydrolyzing the polyvinyl ester, wherein R 1 represents an alkyl group having from 1 to 5 carbon atoms; R 2 represents an alkoxyl or acyloxyl group; m indicates in integer of from 0 to 2; and n is an integer of from 0 to 4, wherein the polyvinyl alcohol satisfies the following formulae (I) and (II): 20 <P×S <370 (I) wherein P is the viscosity-average degree of polymerization of the polyvinyl alcohol; and S is the content (mol %) of the silyl group functionalized monomer units of formula (1) in the polyvinyl alcohol, 0.1/100≦( A−B )/( B )≦50/100 (II) wherein A is the silicon atom content of the polyvinyl alcohol in ppm; B is the silicon atom content of the polyvinyl alcohol in ppm after the polyvinyl alcohol has been first washed with a sodium hydroxide-containing methanol solution and then washed by Soxhlet extraction with methanol; and A and B are measured by ICP emission spectrometry of an ashed sample of the polyvinyl alcohol, and wherein an aqueous 4% solution of the polyvinyl alcohol has a pH of from 4 to 8.