Dispersions with nanoureas

Abstract

The invention relates to aqueous dispersions of nanoureas which have a defined charge density on the particle surface, to a process for preparing them and to their use in binder.

Description

Claims

1. Nanourea dispersions comprising nanourea particles having a particle size of 10 to 300 nm and a zeta potential (at a Ph (23° C.) of 8.0) of 0 to 40 mV.

2. Nanourea dispersions according to claim 1 wherein the nanourea particles have cationic or basic groups on the particle surface in an amount of 0 to 95 μmol per gram of solids.

3. Nanourea dispersions according to claim 1, wherein the dispersions have a solids content of 31% to 65% by weight.

4. Process for preparing the nanourea dispersions according to claim 1, comprising mixing polyisocyanates possessing non-ionic groups for hydrophilization with water and breaking the polyisocyanates down to urea groups, the ratio of hydrophilicized polyisocyanate to water being chosen so as to result in a total weight ratio of between 1:20 and 1:0.75.

5. Process according to claim 4, wherein the hydrophilized polyisocyanate is added to the water in portions, the total amount of the hydrophilicized polyisocyanate is divided into 2 to 50 equally- or differently-sized portions, and the addition of each polyisocyanate portion is followed by a pause of between 5 minutes and 12 hours before the next portion is added.

6. Process according to claim 4, wherein, subsequent to the reaction, the dispersion is evacuated, the temperatures for the evacuation being between 0° C. and 80° C. and the pressure being between 1 and 900 mbar.

7. Process according to claim 4, further comprising adding compounds containing isocyanate-reactive groups to the reaction, the ratio of the isocyanate-reactive groups to the isocyanate groups being less than 0.5.

8. Process according to claim 4, wherein the reaction takes place in a single vessel.

9. Process according to claim 4, wherein one or more catalysts are used in amounts of 0.01% to 8% by weight, based on the total solids content.

10. Process according to claim 9, wherein the catalyst is a tertiary amine.

11. Process according to claim 4, wherein the polyisocyanates are modification products of hexamethylene diisocyanate or isophorone diisocyanate containing groups selected from the group consisting of biuret, isocyanurate and uretdione groups.

12. Process according to claim 4, wherein the nonionically hydrophilicizing compounds are monofunctional polyalkylene oxide polyether alcohols having on average 5 to 70 ethylene oxide units per molecule.

13. Process according to claim 10, wherein the nonionically hydrophilicizing compounds are monofunctional mixed polyalkylene oxide polyethers which contain at least 40 mol % ethylene oxide units and not more than 60 mol % propylene oxide units.

14. Coating compositions comprising nanourea dispersions according to claim 1.

15. Compositions comprising nanourea dispersions according to claim 1, said compositions selected from the group consisting of additives, binders, auxiliaries and adjuvants for producing coating compositions, adhesives and sealants.