Method for producing a surfactant-free suspension based on nanostructured, hydrophobic particles, and use of the same

1. A surfactant-free aqueous suspension, comprising water, hydrophobic nanostructured particles and an organic solvent;

wherein the surfactant-free aqueous suspension is prepared by a process comprising:

suspending the hydrophobic nanostructured particles in at least one organic solvent miscible with water and having a boiling point below 150° C. to form a concentrated organic suspension, and then

mixing the concentrated organic suspension with surfactant-free water to form the surfactant-free aqueous suspension;

wherein the surfactant-free aqueous suspension comprises at least 50.01% by weight of water;

wherein the hydrophobic nanostructured particle has an average diameter of from 30 to 100 μm and is present in an amount of from 0.01 to 1% by weight based on the total weight of the surfactant-free aqueous suspension; and

wherein the hydrophobic nanostructured particles are particles of polytetrafluoroethylene; and wherein the hydrophobic, nanostructured particles are not agglomerated.

2. The surfactant-free aqueous suspension as claimed in claim 1 , comprising from 0.1 to 49.9% by weight of at least one alcohol, wherein the alcohol is miscible with water and has a boiling point below 150° C.

3. The surfactant-free aqueous suspension as claimed in claim 1 , comprising at least 60% by weight water.

4. The surfactant-free aqueous suspension of claim 1 , wherein the organic solvent is at least one of acetone and tetrahydrofuran.

5. The surfactant-free aqueous suspension as claimed in claim 1 , wherein the organic solvent is at least one selected from the group consisting of methanol, ethanol, n-propanol and isopropanol.

6. The surfactant-free aqueous suspension as claimed in claim 1 , wherein the hydrophobic, nanostructured particles have an irregular surface nanostructured comprising a fine structure with features of from 10 to 100 nm.

7. The surfactant-free aqueous suspension as claimed in claim 1 , wherein the surfactant-free aqueous suspension consists of water, the hydrophobic nanostructured particles and the organic solvent.

8. The surfactant-free aqueous suspension as claimed in claim 1 , wherein the hydrophobic nanostructured particles are particles of a cryogenically ground polytetrafluoroethylene.

9. A process for producing a detachable, dirt- and water-repellant coating on articles, where, during a coating process, hydrophobic particles are applied to the surface of the articles and thus a surface structured with elevations is produced on the surface of the articles, and has dirt- and water-repellant properties, comprising

applying, to at least one surface, the surfactant-free aqueous suspension as claimed in claim 1 , and then

removing the water and the organic solvent.

10. The process as claimed in claim 9 , wherein the application of the surfactant-free aqueous suspension to at least one surface of an article takes place by dipping the article into the surfactant-free aqueous suspension.

11. The process as claimed in claim 9 , wherein the application of the surfactant-free aqueous suspension to at least one surface of an article takes place by spray-application of the surfactant-free aqueous suspension.

12. The process as claimed in claim 11 , wherein a spray is used to apply the surfactant-free aqueous suspension.

13. The process of claim 9 , further comprising:

after removing the water and the organic solvent, removing the coating from the article by impact with a liquid having a momentum greater than 12 mNs.

14. The method as claimed in claim 13 , wherein the liquid having a momentum of greater than 12 mNs does not contain a detergent.