Patent ID: 7323084

Claim:
A method for paper sizing to confer resistance to oils, fats, and water, and anti-adhesive properties comprising surface application on a formed paper sheet of aqueous dispersions containing anionic polyurethanes from (per)fluoropolyethers consisting essentially of the following compounds: a) (per)fluoropolyether diols having a number average molecular weight from 400 to 5,000; b) diisocyanates having formula: OCN—R—NCO (VIa) wherein R has the following meanings: C 2 -C 12 aliphatic bifunctional radical; C 6 -C 18 cycloaliphatic or alkylen-cycloaliphatic, wherein optionally the cycloaliphatic ring can be substituted with one or more C 1 -C 3 alkyl groups, or R contains two cycloaliphatic rings, each having a —NCO group, linked by a C 1 -C 6 alkylene chain; and C 6 -C 18 aromatic bifunctional radical, wherein the aromatic ring can be substituted with one or more C 1 -C 3 alkyl groups, or R contains two aromatic rings, each having a —NCO group, linked by a C 1 -C 6 alkylene chain; and c) anionomeric diols, compounds containing two hydroxylic functions and one carboxylic, containing from 4 to 10 carbon atoms, the alkyl chain being optionally branched and optionally one or both the following components: d) hydrazine and/or aliphatic diamines with chain from 2 to 6 carbon atoms; e) monofunctional hydroxylic (per)fluoropolyethers having a number average molecular weight in the range 300-1,000, wherein a) is reacted with b), in a second step the compound obtained in the first step is reacted with c), in a third step optionally with d) and/or with component e), using an amount of a) such that the polyurethane is formed by a percentage from 50 to 90% by component a), the sum of the hydroxylic groups of a)+c), and optionally e) and/or the amino groups of component d), being equal to the sum of the —NCO groups of b), salification of the polyurethane with bases and subsequent dispersion in water.