POLYURETHANE DISPERSIONS

Procedure for obtaining emulsifier-free aqueous polyurethane dispersions from: A) dihydroxy compounds with a molecular weight of 500 to 5000, B) diisocyanates C) water-soluble salts of aliphatic aminocarboxylic or aminosulfonic acids with at least one hydrogen atom bonded to the nitrogen atom and D) compounds without salt groups with two hydrogen atoms reactive against isocyanate groups and a molecular weight less than 300 as chain extender, in a molar ratio A: B (C + D) = 1: 2: 1 to 1:14:13, depending on whether components A and D are used alone or together, in the presence or absence of an inert organic solvent, which melts below 100ºC and is miscible with water with the diisocyanate (B) at a temperature of 50 to 130ºC to form a prepolymer with final isocyanate groups, characterized in that 50 to 90 mol%, relative to the total diisocyanate, of an aromatic diisocyanate is added first and then continued n 10 to 50 mol% of an aliphatic or cycloaliphatic diisocyanate, or both are added at the same time; The mass is diluted with solvents of the type mentioned at 30-50% by weight of solids content; and then it is allowed to react with a component C in aqueous solution at a temperature between 20 and 50ºC; then the desired amount of water is added and the solvent is distilled. (Machine-translation by Google Translate, not legally binding)