Aqueous polysiloxane-polyurethane dispersion, its preparation and use in coating compositions

An aqueous dispersion of polysiloxane-polyurethanes having an acid number of from about 5 to about 100 mg KOH/g polysiloxane-polyurethane solids, a hydroxyl group content of from about 0.25 to about 6.5% by weight, and a urethane group content (calculated as —NH—CO—O—) of from about 2.0 to about 25.0% by weight, based in each case on polysiloxane-polyurethane solids, wherein the polyurethanes are products, where appropriate at least partly neutralized with bases obtained by the reaction of

• a) a total of from about 3 to about 25% by weight of at least one linear polydimethylsiloxanediol of the molecular mass range about 1,500 to about 10,000,
• b) a total of from about 15 to about 90% by weight of at least one further linear polyol, selected from the group consisting of
• i) hydroxyl-containing polycarbonates of the molecular mass range about 400 to about 6,000,
• ii) hydroxyl-containing polyetherpolyols of the molecular mass range about 350 to about 3,500,
• iii) ester-functional polyesterpolyols obtained from dimer fatty acids by hydrogenating the carboxyl groups to hydroxyl groups, alkoxylating the carboxyl groups or esterifying the carboxyl groups with low molecular mass diols, and
• iv) hydroxyl-containing linear polyesterpolyols of the molecular mass range about 500 to about 4,000,
• c) a total of from about 1 to about 10% by weight of at least one acid component composed of
• i) hydroxycarboxylic acids,
• ii) aminocarboxylic acids,
• iii) aminosulfonic acids or
• iv) alkali metal salts of such acids,
• d) a total from 0 to about 20% by weight of at least one low molecular mass component comprising of at least one compound containing at least two hydroxyl and/or amino groups, of the molecular mass range about 60 to about 300,
• e) a total of from 0 to about 20% by weight of at least one hydrophylic monohydric or polyhydric alcohol containing ethylene oxide units, of the molecular mass range of about 350 to about 3,000,
• f) a total of from about 5 to about 50% by weight of at least one polyisocyanate component composed of at least one organic polyisocyanate of the molecular mass range about 168 to about 1,000, at least 50% by weight of the polyisocyanate component comprising diisocyanates of the molecular mass range about 168 to about 300,
• the stated percentages adding up to 100% by weight of the polyurethane fractions of the polysiloxane-polyurethane solids.