Dew resistant coatings
The present invention relates to dew resistant coatings and articles having the dew resistant coating adhered thereto. The dew resistant coatings comprise elongate silica particles. These coatings are useful on articles or surfaces used in outdoor applications and articles and surfaces used in moist indoor environments.
1. A dew-resistant coating for a retroreflective substrate, said coating comprising:
at least about 75% by weight of elongate silica particles having an aspect ratio greater than 1;
a surfactant;
an organic binder wherein the organic binder comprises at least one hydrolysis product or at least one partial condensate of one or more silane compounds; and
spherical silica particles having an average diameter of less than 50 nanometers;
wherein the one or more silane compounds comprises cyclohexyltrimethoxysilane.
2. The dew-resistant coating of claim 1 wherein the elongate silica particles have an aspect ratio greater than 2.
3. A dew-resistant coating of claim 1 wherein the elongated silica particles have a width of about 9 to about 15 nanometers and a length of about 40 to about 300 nanometers.
4. The dew-resistant coating of claim 1 wherein the coating comprises at least about 80% by weight of elongate silica particles.
5. The dew-resistant coating of claim 1 wherein the coating is transparent.
6. The dew-resistant coating of claim 5 wherein the organic binder comprises a polymer.
7. The dew-resistant coating of claim 6 wherein the polymer is hydrophilic.
8. The dew-resistant coating of claim 1 wherein the coating includes a first layer of the fine spherical particles and a second outer layer of the elongate silica particles.
9. The dew-resistant coating of claim 1 wherein the coating has a first layer comprising the elongate silica particles and a second, outer layer of a photocatalytic layer.
10. The dew-resistant coating of claim 1 wherein the one of more silane compounds further comprises an epoxy functional silane.
11. The dew-resistant coating of claim 10 further comprising an organosilane compound not having epoxy functionality.
12. The dew-resistant coating of claim 1 wherein the one or more silane compounds further comprises at least one silane compound selected from the group consisting of glycidoxymethyltrimethoxysilane, 3-glycidoxypropyltrihydroxysilane, 3-glycidoxypropyldimethylhydroxysilane, 3-glycidoxypropyltrimeth-oxysilane, 3-glycidoxypropyltrimeth -oxysilane, 3-glycidoxypropyl-dimethoxymethylsilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyltributoxysilane, 1,3-bis(glycidoxypropyl)tetramethyldisiloxane,1,3-bis(glycidoxypropyl)tetramethoxydisiloxane, 1 ,3-bis(glycidoxypropyl)-1 ,3-dimethyl-1 ,3-dimethoxydisiloxane, 2,3 -epoxypropyl-trimethoxysilane, 3 ,4-epoxybuty Itrimethoxysilane, 6,7-epoxyheptyl-trimethoxysilane, 9, 10-epoxydecyltrimethoxysilane, 1,3-bis(2,3-epoxypropyl) tetramethoxydisiloxane, 1 ,3-bis(6, 7 -epoxyheptyl)tetramethoxydisiloxane, 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane and combinations of two or more thereof.
13. A dew-resistant coating for a retroreflective substrate comprising at least about 75% by weight of elongate silica particles having an aspect ratio greater than 1 and a surfactant wherein the coating comprises 15 to 25% by weight of an organic binder;
wherein the organic binder comprises at least one hydrolysis product or at least one partial condensate of one or more silane compounds; and
wherein the one or more silane compounds comprises cyclohexyltrimethoxysilane.
14. The dew-resistant coating of claim 1 wherein the elongate silica particles comprise chain silica.
15. The dew-resistant coating of claim 1 further comprising metal oxide nanoparticles.
16. The dew-resistant coating of claim 15 wherein the metal oxide particles comprise titanium dioxide.
17. The dew-resistant coating of claim 1 wherein the coating is a multilayer coating comprising:
a first layer comprising the elongate silica particles; and
a second layer comprising a photocatalytic composition.
18. A transparent article comprising a transparent substrate and the transparent dew resistant coating of claim 1 provided on at least a portion of a surface of the substrate.
19. The transparent article of claim 18 wherein the substrate comprises a polymeric material.
20. The transparent article of claim 18 wherein the substrate comprises glass.
21. The transparent article of claim 18 wherein the coating further comprises titanium dioxide nanoparticles.
22. The transparent article of claim 18 wherein the coating is a multilayer coating comprising a first layer comprising at least about 95% by weight of the elongate silica particles; and a second layer comprising a photocatalytic composition.
23. A method for preventing condensation or dew buildup on a substrate comprising applying to the surface the dew-resistant coating of claim 1 .
24. The method of claim 23 , wherein the substrate is plastic, wood, paper, metal, glass, ceramic, mineral based materials, leather, and textiles.
25. The method of claim 23 , wherein the substrate is a retroreflective substrate.
26. The method of claim 23 , wherein the retroreflective substrate is a sign, license plate, or a self-adhesive sticker.
27. The method of claim 23 , wherein the dew-resistant coating is applied to a portion of the surface of the retoreflective substrate.
28. The method of claim 23 , further comprising applying a protective layer over the dew-resistant coating.
29. The method of claim 28 , wherein the protective layer is removable.
30. A dew-resistant coating for a retroreflective substrate, said coating consisting of:
at least about 75% by weight of elongate silica particles having an aspect ratio greater than 1;
a surfactant; and
an organic binder wherein the organic binder comprises at least one hydrolysis product or at least one partial condensate of one or more silane compounds;
wherein the one or more silane compounds comprises cyclohexyltrimethoxysilane.