Dispersions with nanoureas
View Patent ↗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.
1. Nanourea dispersions comprising nanourea particles having a particle size of 10 to 300 nm and a zeta potential, of 0 to 40 mV and wherein the dispersions have a solids content of 40 to 65% by weight.
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 40% to 50% 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 being 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 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.
12. Process according to claim 4 , wherein the polyisocyanates are modification products of hexamethylene diisocyanate or isophorone dissocyanate containing groups selected from the group consisting of biuret, isocyanurate and uretdione groups.
13. Process according to claim 4 , wherein the nonionically hydrophilicizing compounds are monoflinctional polyalkylene oxide polyether alcohols having on average 5 to 70 ethylene oxide units per molecule.
14. Coating compositions comprising nanourea dispersions according to claim 1 .
15. Compositions comprisin g 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.
16. Nanourea dispersions according to claim 1 , wherein the nanourca particles have cationic or basic groups on the particle surface in an amount of 2 to 70 μmol per gram of solids.
17. Nanourea dispersions according to claim 1 , wherein the nanourea particles have cationic or basic groups on the particle surface in an amount of 3 to 20 μmol per gram of solids.
18. Nanourea dispersions according to claim 17 , wherein the dispersions have a solids content of 40% to 50% by weight.