Polyvinyl acetals with improved adhesion

摘要

Low molecular polyvinyl acetals are obtained by saponification or ester interchange of low viscosity vinyl ester resins followed by acetal formation of the low viscosity polyvinyl alcohol obtained. Low molecular polyvinyl acetals (PVA) of solution viscosity 2-12 mPas (DIN 53015, by the Hoppler method, 10% solution in ethanol), degree of polymerization Pw less than 200, are obtained by saponification of vinyl ester polymerizate and acetal formation from the low molecular polyvinyl alcohol obtained, using one or more aldehydes from 1-15C aliphatic or aromatic aldehydes. The vinyl ester polymerizate is obtained from one or more monomers from the group including vinyl esters of optionally branched alkyl 1-15C carboxylic acids, and optionally one or more monomers from a group including ethylenically unsaturated mono- and dicarboxylic acids, ethylenically unsaturated carboxylic acid amides and nitriles, fumaric and maleic acid monoesters, ethylenically unsaturated sulfonic acids and their salts, of solution viscosity 1.0 to 1.6 mPas (DIN 53015, Hoppler method, 10% solution in ethyl acetate), which are saponified (sic). The saponification results in a content of≥50 mole% vinyl alcohol units and production of a PVA of solution viscosity 1.0-2.0 mPas (DIN 53015, Hoppler method, 4% aqueous solution). An Independent claim is also included for preparation of low molecular PVA involving: (a) a vinyl ester polymerizate from one or more monomers from the group including: vinyl esters of optionally branched 1-15C alkyl carboxylic acids, and optionally one or more monomers from the group including ethylenically unsaturated monomers of dicarboxylic acids, ethylenically unsaturated carboxylic acid amides and nitriles, fumaric and maleic acid monoesters, ethylenically unsaturated sulfonic acids and their salts, of solution viscosity 1.0 to 1.6 mPas (DIN 53015, Hoppler method, 10% solution in ethyl acetate), which are saponified (sic), the saponification resulting in a content of≥50 mole% vinyl alcohol units and production of a polyvinyl acetate of solution viscosity 1.0-2.0 mPas (DIN 53015, Hoppler method, 4% aqueous solution); and (b) acetal formation from the polyvinyl alcohol obtained as in (a) with one or more aldehydes from a group including: 1-15C aliphatic and aromatic aldehydes to a degree of acetal formation of 1-80 mole%.