Method for imparting a self-cleaning feature to a surface, and an object provided with a surface of this type

p0001A process for producing a self-cleaning property of a surface and the object with this surface

p0002The invention relates to a method for producing a self-cleaning property of a surface and an article which has a corresponding surface.

p0003It is generally known to produce a self-cleaning property of surfaces either by providing an appropriate surface structures during the manufacture of the surface of hydrophobic polymers or by application of a powder of hydrophobic polymers or hydrophobic materials on the surface (WO 96/04123). The self-cleaning property is particularly important for those surfaces that are exposed to free the area and the weather conditions, such as roofs and building faces, materials, glazing elements, solar, tents and camping materials, housing of all types of vehicles and the like., Which mainly natural irrigation or irrigation is utilized with water to prevent the accumulation of dirt or eliminate. Therefore, efforts have recently been made, in particular ceramic surfaces, such as bricks or tiles, to be provided with surface structures of the type indicated above, one in conjunction with a hydrophobizing

p0004Self-cleaning property have (EP-A 909 747). Due to the surface structure and their hydrophobic property not wetted with irrigation or sprinkling water hitting this surface but rolls it off in drop form and takes up on the surface located with dirt. This effect has become known as the "lotus effect" (registered trademark). The invention also has for its object to produce a self-cleaning property of surfaces, but which is independent of any particular surface structure.

p0005This is the method, achieved in that a surface, in particular of a tile or tile, is coated with a titanium oxide of the anatase crystalline form; A subject of the invention thus has at least an exposed in the condition of use of the weather surface on a coating with a titanium oxide of the anatase crystal form.

p0006It has been found that the crystal form of titanium oxide anatase coated surfaces have a pronounced hydrophilic property, through which the surface wetting water can spread a fine film on the surface without forming droplets. This property is so strong that the water is especially important for ceramic surfaces due to their inherent roughness in a position under existing impurities, even greasy or oily deposits, penetrate the manner of detergents and making thereof. Upon further irrigation such contaminants are then washed away. One can therefore designate thus coated ceramic surfaces as self-cleaning; this type of treatment of ceramic surfaces thus treading a path that opposes the effort to maintain the surface for the purpose of self-cleaning as hydrophobic as possible.

p0007According to an advantageous development of the invention a surface with the titanium oxide coating having the prior art method necessary for obtaining a self-cleaning property surface structure either already or those obtained after coating with the titanium oxide, however, is not hydrophobic. Subsequently, equipped with the surface structure and coated with the titanium oxide surface is hydrophobic on one of the suitable species. A so-treated body thus has a surface which carries the coating with the titanium oxide of the layer of a hydrophobing agent. In this way, first for the self-cleaning of the hydrophobic property in connection with the exploited surface structure, which just prevents wetting of the ceramic surface and causes by rolling water droplets self-cleaning. As hydrophobizing agents can be, however, degraded or rendered ineffective by the natural UV radiation over extended periods of time, will suffer in the course of time, the self-cleaning property. This, however, provided for under the hydrophobicizing layer titanium oxide coating according to the invention freely and also effective in that it just under the UV irradiation undergoes an increase of hydrophilic property due to the titanium oxide photocatalytic own property. Therefore, the self-cleaning property so treated fields can be extended over a very long time back.

p0008For the coating of ceramic surface with titanium oxide, various methods are available. The simplest are sol-gel methods in which, for example applied the present as an organometallic compound of titanium oxide on the surface, the surface is then dried and

p0009Coating is heat treated. The heat treatment may take place in this case between 500 and 1000 ° C to remove the organic portion of the organometallic titanium oxide compound. However, it is especially for compounds in which no organic portions, even at a considerably lower temperature treatments conceivable, for example at 50 ° C. Also CVD methods are also applicable, in which the titanium oxide coating is applied by evaporation. All these application methods are known per se and need at this point no more particular explanation.

p0010Also in the described combined form, wherein the hydrophobic and the hydrophilic property of the surface are combined with each other in the form that they take effect one after the other in time sequence, the generation of the surface structure and its required for the self-cleaning property hydrophobicization can be carried out in several ways. For this, among other things, all methods available that in the part of the applicant in earlier proposals

p0011Associated with ceramic surfaces are described (EP-A 909 747, DE 199 47 524.5, DE 199 58 321.8, DE 199 58 764.7). Provided that the surface structure by the application and fixing of powder particles on produced a surface, the titanium oxide can directly form so that the powder particles and by applying the surface structure or be contained in the surveys. Deviating from the surface structure can also be produced after application of the titanium oxide layer of this out zBdurch embossing, whereby also the elevations contain the titanium oxide.

p0012According to a further embodiment of the invention hydrophobing agent can be used which are stabilized from the outset by the incorporation of titanium dioxide to UV irradiation for hydrophobization. This in turn extended by utilizing the property of titanium oxide, the durability of the water repellent layer.