Aqueous polyurethane-polyurea dispersions

1. Method for producing aqueous polyurethane-polyurea dispersions, wherein in a first step (I) an isocyanate-functional prepolymer free from urea groups is produced by complete or partial reaction of compounds

A) polyisocyanates,

B) polyols having number-average molecular weights of 400 to 8000 g/mol,

C′) low-molecular-weight compounds having a molecular weight of 60 to 400, which in total have two or more hydroxyl groups,

D′) optionally compounds having one hydroxyl group,

E) isocyanate-reactive, ionically or potentially ionically hydrophilising compounds,

F) isocyanate-reactive, non-ionically hydrophilising compounds,

optionally already in at least one organic solvent, or in a second step (II), if not in step (I), this isocyanate-functional prepolymer is dissolved in at least one organic solvent in such a way that a solution of the isocyanate-functional prepolymer is produced in a concentration of 20 wt. % to 70 wt. %, relative to all components of the solution,

in a third step (III) the optional addition of

C″) low-molecular weight compounds having a molecular weight of 32 to 400, which in total have two or more amino groups and/or hydroxyl groups, or

D″) optionally compounds having one amino group

takes place and then dispersion takes place by mixing water with the polymer solution with simultaneous distillation of the organic solvent in a dispersion and distillation unit, with the proviso that the volumetric content of the dispersion and distillation unit is 50 vol. % to 95 vol. %, and then a largely solvent-free polyurethane-polyurea dispersion having a residual content of organic solvent of 0.0 wt. % to 5 wt. % and a concentration of polyurethane-polyurea polymer particles of 20 wt. % to 70 wt %, relative in each case to all components of the polyurethane-polyurea dispersion, is obtained.

2. Method according to claim 1 , characterised in that in step (I) the substance ratio of isocyanate groups to isocyanate-reactive groups is 1.0 to 3.5.

3. Method according to claim 1 , characterised in that the reaction temperature in the first step is between 20 and 130° C.

4. Method according to claim 1 , characterised in that acetone or 2-butanone is used as the organic solvent.

5. Method according to claim 1 , characterised in that the volumetric content of the dispersion and distillation unit is 50 vol. % to 80 vol. %.

6. Method according to claim 1 , characterised in that dispersion water heated to a constant temperature of 20 to 95° C. is used.

7. Method according to claim 1 , characterised in that the temperature of the reaction mixture during the chain extension in step (III) is between 30 and 70° C.