Patent ID: 6162864
Filing Date: 2000-12-19
Classification: A61F,C08F,C08J

Abstract:
A polyvinyl alcohol comprising vinyl alcohol units and (i) one or more structural units represented by the following formula (I): ##STR12## wherein R.sup.1 is a hydrogen atom or a mono-valent hydrocarbon; and R.sup.2 and R.sup.3 are, independently, a mono-valent hydrocarbon group or R.sup.2 and R.sup.3 together form a ring along with the carbon atom to which R.sup.2 and R.sup.3 are bonded; or R.sup.1, R.sup.2 and R.sup.3 together form a ring along with the carbon atom to which R.sup.1, R.sup.2 and R.sup.3 are bonded,wherein the structural units of formula (I) are present at a molar fraction of 0.05 to 0.50; and(ii) at least one structural unit represented by the following formula (II): ##STR13## wherein X is a group represented by the formula --CO--Y, --Y or --COCOOH, wherein Y represents a hydrocarbon group modified with at least one polar group selected from the group consisting of carboxyl, sulfo, amino and phosphonooxy groups;or a hydrocarbon group modified with a group having at least one polar group selected from the group consisting of carboxyl, sulfo, amino and phosphonooxy groups; or X forms a phosphonooxy group together with the oxygen atom to which X is bonded,wherein the molar fraction of the structural unit represented by the formula (II) satisfies the following formula (1);{(1-C.sub.est).times.C.sub.est }.times.0.01.ltoreq.C.sub.pol <{(1-C.sub.est).times.C.sub.est }.times.2.0 (1)wherein C.sub.pol is the molar fraction of the structural unit represented by formula (II); and C.sub.est is the molar fraction of the structural unit represented by formula (I), and furtherwherein the average chain length (L.sub.est) of the structural unit represented by formula (I) is 2.0 or more, wherein the average chain length, L.sub.est, is represented by the following formula (2);L.sub.est =(C.sub.est /C.sub.met).times.2 (2)wherein L.sub.est is the average chain length of the structural unit represented by the formula (I); C.sub.est is the molar fraction of the structural unit represented by formula (I); and C.sub.met is the molar fraction of the methylene carbon interposed between a methine carbon bonded with a hydroxyl group or a group represented by the formula --OX, and a methine carbon composing the structural unit represented by formula (I), among the methylene carbons composing the main chain of the polyvinyl alcohol.