Hydrophobic self-cleaning coating compositions
A super hydrophobic self cleaning coating composition that can be applied by conventional methods such as by spraying the composition onto a surface creating a wet and dry dirt repellent coating on the surface. The super hydrophobic self cleaning coatings are used on exterior automotive and boat surfaces, and in many other applications, to produce a self cleaning surface, reduce adherence of dirt and contaminants to a treated surface, and reduce drag in some applications providing an energy savings. The coating utilizes a blend of organic and/or inorganic polymers with hydrophobic nanoparticles of fumed silica and/or titania in a volatile solvent which evaporates at ambient temperature. The coating solves the problem of poor resistance to UV light, opaque appearance, and/or some abrasion resistance not found in previous coatings of similar nature. A preferred coating has good resistance to UV light and some resistance to abrasion. Clear, nearly transparent and translucent coatings are produced as compared to conventional coatings of comparable hydrophobicity which are typically white or opaque. The coating can be applied by a single and easy spraying method and the super hydrophobic property can be achieved by drying the film by evaporation of the solvent at ambient temperature for 5 to 10 minutes. Embodiments of the super hydrophobic self-cleaning coating composition result in a clear coating or in some cases a translucent dirt repellant film for coating on painted material, plastic, metal, glass, ceramic, fiberglass or a polymer substrate. The coating utilizes a blend of organic and/or inorganic polymers with hydrophobic nanoparticles of fumed silica and/or titania in a volatile solvent. At least one preferred coating composition comprising an effective amount of a treated fumed silica in a solvent resulting in a coated surface providing a contact angle of at least 165 degrees as compared to water having a contact angle of from 10 to 15 degrees on a noncoated surface. The composition imparts a degree of hydrophobicity to a surface so that the surface will have a tilt angle of sliding of less than 2 degrees as compared to water on a noncoated surface having a tilt angle of sliding of 90 degrees or higher. The coating composition is removed by washing with a detergent or applying pressure to the coating wiping same from the treated surface. Exposure to water in the form of rain or snow does not remove the coating composition.
1 . A super hydrophobic self-cleaning coating composition for forming an almost clear, translucent dirt repellant film on a painted material, plastic, metal, glass, ceramic, fiberglass, wood, waxed or polymer substrate, consisting essentially of a treated fumed silica in a solvent forming a film having a contact angle of at least 165 degrees as compared to water having a contact angle of from 50 to 60 degrees on a noncoated surface, said composition imparting a degree of hydrophobicity to said surface so that said surface has a tilt angle of sliding of less than 2 degrees as compared to water on a noncoated surface having a tilt angle of sliding of 90 degrees or higher.
2 . The composition of claim 1 , wherein said effective amount of said treated fumed silica is about 0.5 wt % solid of the silica/solvent composition.
3 . The composition of claim 1 , wherein said composition is clear upon application.
4 . The composition of claim 1 , wherein said composition is translucent upon application.
5 . The composition of claim 1 , including an aerosol.
6 . The composition of claim 1 , wherein said composition is dispersed in an aerosol propellant containing a solvent selected from the group consisting of an alcohol, a hydrocarbon, a ketone, or a combination of these selected solvents.
7 . The composition of claim 1 , wherein said aerosol propellant is selected from the group consisting of a carbon dioxide, a hydrocarbon, a fluorocarbon, or compressed air.
8 . The composition of claim 7 , wherein said hydrocarbon, comprises propane/isobutane.
9 . The composition of claim 1 , including a binding agent, producing a super hydrophobic self-cleaning coating composition.
10 . The composition of claim 9 , wherein said binding agent contains up to 0.05% of zinc oxide nanoparticles together with a hydrophobic polymer selected from the group consisting of an acrylic, a hydroxy-functional silicone modified polyacrylate, polycarboxylate, polyether, polyvinylacetate, and an amino functional siloxane.
11 . The hydrophobic coating composition of claim 9 , wherein said UV stable hydrophobic polymer comprises a perfluoro alkyl substituted acrylic polymer or a trimethylsilyl end capped siloxane.
12 . The composition of claim 10 , wherein said treated binding agent comprises about 0.05% by weight of said solution.
13 . The composition of claim 1 wherein said nanoparticles of a treated fumed silica have a particle size ranging from about 7 to about 100 nanometers.
14 . A method of forming a super hydrophobic self-cleaning dirt repellant film on a the surface of a substrate without using a binder polymer comprising a painted material, plastic, metal, glass, ceramic, fiberglass, wood, waxed or polymer material consisting essentially of a treated fumed silica in a solvent forming a film having a contact angle of at least 165 degrees as compared to water having a contact angle of from 50 to 60 degrees on a noncoated surface, said composition imparting a degree of hydrophobicity to said surface so that said surface has a tilt angle of sliding of less than 2 degrees as compared to water on a noncoated surface having a tilt-angle of sliding of 90 degrees or higher.
15 . A super hydrophobic self-cleaning coating composition for forming an almost clear, translucent dirt repellant film on a painted material, plastic, metal, glass, ceramic, fiberglass, wood, waxed or polymer substrate, consisting essentially of a treated fumed silica in a solvent selected from the group consisting of an alcohol, a hydrocarbon, a ketone, or a combination thereof forming a film having a contact angle of at least 165 degrees as compared to water having a contact angle of from 50 to 60 degrees on a noncoated surface, said composition imparting a degree of hydrophobicity to said surface so that said surface has a tilt angle of sliding of less than 2 degrees as compared to water on a noncoated surface having a tilt angle of sliding of 90 degrees or higher.