Aqueous solutions or dispersions of polyurethanes, process for their preparation and use of them as coating agents or for the production of coating agents

Claim 2

Process for the preparation of aqueous solutions or dispersions according to Claim 1, by reaction of a) organic polyisocyanates with b) organic polyhydroxy compounds of the molecular weight range from 400 to 6000, c) compounds which contain tertiary amine nitrogen atoms and have at least one group which is reactive towards isocyanate groups, d) organic compounds of the general formula in which X   represents an organic radical which carries at least one group which is reactive towards isocyanate groups and R iv , R v and R vi represent identical or different alkyl radicals having 1 to 4 carbon atoms, if appropriate e) compounds which are mono- or difunctional in the sense of the isocyanate addition reaction and have a hydrophilic polyether chain, the chain members of which consist of ethylene oxide units to the extent of at least 40 mol % and of propylene oxide units as the remainder, and if appropriate up to 10 % by weight, based on b), f) of alcoholic, aminic and/or hydrazinic chain-lengthening agents of the molecular weight range from 32 to 399, wherein the reaction of component a) with components b) to f) takes place in the sense of a one-stage process, if appropriate with the aid of an inert water-miscible solvent, the polyurethane present in dissolved form subsequently being converted into an aqueous solution or dispersion, or wherein an NCO prepolymer is first prepared from an excess amount of component a) and components b), c), d) and if appropriate e), which are employed in any desired sequence or as a mixture, an NCO/OH equivalent ratio of 1.2:1 to 2.5:1 being maintained, and if appropriate with the aid of an inert water-miscible solvent, and the prepolymer is then converted into an aqueous solution or dispersion by mixing with water which optionally contains aminic or hydrazinic chain-lengthening agents f), chain lengthening simultaneously taking place, the equivalent ratio of isocyanate groups of the prepolymer to groups of components d), c) and f) which are reactive towards isocyanate groups being 0.8:1 to 25:1, characterised in that the incorporated tertiary nitrogen atoms are neutralised by means of an acid at the latest during the dissolving or dispersing in water, the amount of acid, which is employed in excess if appropriate, being chosen such that the resulting solution or dispersion has a pH of 3 to 6, and moreover the nature and ratios of the amounts of the starting components being chosen such that the polyurethanes present in dissolved or dispersed form correspond to features (i) to (iii) of Claim 1.

Claim 3

Process according to Claim 2, characterised in that the reaction of the starting materials is carried out at least partly in the presence of an organic water-miscible solvent, and this is removed from the aqueous solution or dispersion by distillation after preparation thereof.

Claim 4

Use of the aqueous solutions or dispersions according to Claim 1 as coating agents or for the production of coating agents for any desired substrates.