Ceramic molded body comprising a photocatalytic coating and method for production the same

Abstract

The invention relates to a ceramic moulded body consisting of an oxide ceramic base material and comprising a surface which self-cleans by means of water-sprinkling or percolation. Said moulded body has a porous, oxide ceramic coating which is photocatalytically active and has a specific surface of between approximately 25 m 2 /g and approximately 200 m 2 /g, preferably between approximately 40 m 2 /g and approximately 150 m 2 /g. The invention also relates to a method for producing one such ceramic moulded body.

1 . A ceramic molded body, more specifically a roof tile, tile, clinker brick or facade wall, of oxide-ceramic base material with a surface which is self-cleaning upon spraying or sprinkling with water, characterized in that the molded body has a porous oxide-ceramic coating, wherein the coating is photocatalytically active and contains TiO 2  and has a specific surface area in a range of between 25 mg 2 /g, and 200 m 2 /g, preferably between 40 m 2 /g and 150 m 2 /g, wherein the TiO 2  is produced by flame hydrolysis of TiCl 4  as highly disperse TiO 2 .  
     
     
         2 . A ceramic molded body as set forth in  claim 1  characterized in that the coating has a specific surface area in a range of between 40 m 2 /g and 100 m 2 /g.  
     
     
         3 . A ceramic molded body as set forth in  claim 1 , characterized in that the mean layer thickness of the coating is in a range of between 50 nm and about 50 μm, preferably 100 nm and 10 μm.  
     
     
         4 . A ceramic molded body as set forth in  claim 1 , characterized in that arranged between the oxide-ceramic base material and the photocatalytically active, porous, oxide-ceramic coating is at least one layer with raised portions, the oxide-ceramic base material has raised portions and/or the photocatalytically active, porous, oxide-ceramic coating is in the form of a layer with raised portions.  
     
     
         5 . A ceramic molded body as set forth in  claim 4  characterized in that the raised portions are formed by particulate material fixed to the oxide-ceramic base material.  
     
     
         6 . A ceramic molded body as set forth in  claim 5  characterized in that the particulate material is temperature-resistant ground material preferably selected from the group which consists of ground rock, fire clay, clay, minerals, ceramic powder such as SiC, glass, glass chamotte and mixtures thereof.  
     
     
         7 . A ceramic molded body as set forth in  claim 5  or  claim 6  characterized in that the size of the particles and/or the raised portions is or are in a range of up to 1500 nm, preferably of between 50 nm and 700 nm, further preferably between 50 nm and 200 nm.  
     
     
         8 . A ceramic molded body as set forth in  claim 1 , characterized in that the photocatalytically active, porous, oxide-ceramic coating includes additionally photocatalytically active, oxide-ceramic materials selected from the group which consists of Al 2 O 3 , SiO 2  and mixtures thereof.  
     
     
         9 . A ceramic molded body as set forth in  claim 1 , characterized in that the oxide-ceramic base material of the molded body includes photocatalytically active, oxide-ceramic materials selected from the group which consists of TiO 2 , Al 2 O 3 , SiO 2  and mixtures thereof.  
     
     
         10 . A ceramic molded body as set forth in  claim 1 , characterized in that the photocatalytically active, oxide-ceramic material has an average particle size in the range of between 5 nm and 100 nm, preferably between 10 nm and 50 nm.  
     
     
         11 . A ceramic molded body as set forth in  claim 1 , characterized in that the TiO 2  contained in the photocatalytically active, porous, oxide-ceramic coating and/or in the oxide-ceramic base material is present at least in part and preferably in respect of at least 40% by weight with respect to the total amount of TiO 2 , in the anatase structure.  
     
     
         12 . A ceramic molded body as set forth in  claim 1 , characterized in that the TiO 2  contained in the photocatalytically active, porous, oxide-ceramic coating and/or in the oxide-ceramic base material is present in respect of at least 70% by weight with respect to the total amount of TiO 2 , in the anatase structure.  
     
     
         13 . A ceramic molded body as set forth in  claim 1 , characterized in that the TiO 2  is present in a mixture comprising 70% by weight of anatase and 30% by weight of rutile.  
     
     
         14 . A ceramic molded body as set forth in  claim 1 , characterized in that the coating has a superhydrophobic surface, wherein the superhydrophobic surface has a contact or edge angle of at least 140° for water.  
     
     
         15 . A ceramic molded body as set forth in  claim 14  characterized in that the superhydrophobic surface of the coating is produced using Ormoceres, polysiloxane, alkylsilane and/or fluorosilane, preferably in combination with SiO 2 .  
     
     
         16 . A ceramic molded body as set forth in one of claims  14  and  15  characterized in that the superhydrophobic surface of the coating has raised portions.  
     
     
         17 . A ceramic molded body as set forth in  claim 16  characterized in that the raised portions of the superhydrophobic surface are produced using particulate material.  
     
     
         18 . A process for the production of a ceramic molded body, more specifically a roof tile, tile, clinker brick or facade wall, of oxide-ceramic base material with a surface which is self-cleaning upon spraying or sprinkling with water, wherein the molded body has a photocatalytically active, porous, oxide-ceramic TiO 2 -containing coating with a specific surface area in a range of between 25 m 2 /g and 200 m 2 /g, preferably 40 m 2 /g and 150 m 2 /g, wherein the process includes the following steps: 
 (a) mixing photocatalytically active, oxide-ceramic powder which contains TiO 2 , wherein the TiO 2  is produced by flame hydrolysis of TiCl 4  as highly disperse TiO 2 , adjusting agent and/or adhesive and a liquid phase to afford a suspension,    (b) applying the suspension produced in step (a) to the oxide-ceramic base material to produce a layer, and    (c) hardening the layer afforded in step (b) to produce a photocatalytically active, porous, oxide-ceramic coating.    
     
     
         19 . A process as set forth in  claim 18  characterized in that at least one layer with raised portions is applied to the oxide-ceramic base material in a preceding step and the suspension produced in step (a) is applied to the oxide-ceramic base material provided with a layer with raised portions and subsequently hardened in step (c).  
     
     
         20 . A process as set forth in  claim 19  characterized in that particulate material is additionally added in step (a).  
     
     
         21 . A process as set forth in  claim 18  or  claim 19  characterized in that the raised portions are formed by fixing particulate material on the oxide-ceramic base material.  
     
     
         22 . A process as set forth in  claim 20  characterized in that the particulate material is temperature-resistant ground material preferably selected from the group which consists of ground rock, fire clay, clay, minerals, ceramic powder such as SiC, glass, glass chamotte and mixtures thereof.  
     
     
         23 . A process as set forth in  claim 20 , characterized in that the mean particle size of the particulate material is in a range of up to 1500 nm, preferably between 50 nm and 700 nm, further preferably between 50 nm and 200 nm.  
     
     
         24 . A process as set forth in  claim 18 , characterized in that adjusting agent used in step (a) is an organic viscosity regulator.  
     
     
         25 . A process as set forth in  claim 24  characterized in that carboxymethylcellulose is used as the organic viscosity regulator.  
     
     
         26 . A process as set forth in  claim 18 , characterized in that adhesive used in step (a) is polysiloxane.  
     
     
         27 . A process as set forth in  claim 18 , characterized in that water is used as the liquid phase in step (a).  
     
     
         28 . A process as set forth in  claim 18 , characterized in that the adhesion between the catalytically active coating and the oxide-ceramic base material is improved by a procedure whereby the photocatalytically active, porous, oxide-ceramic coating produced in step (c) is irradiated with laser light or NIR or UV light.  
     
     
         29 . A process as set forth in  claim 18 , characterized in that the photocatalytically active, oxide-ceramic powder used in step (a) additionally includes materials selected from the group which consists of Al 2 O 3 , SiO 2  and mixtures thereof.  
     
     
         30 . A process as set forth in  claim 18 , characterized in that contained in the oxide-ceramic base material of the molded body are photocatalytically active, oxide-ceramic materials selected from the group which consists of TiO 2 , Al 2 O 3 , SiO 2  and mixtures thereof.  
     
     
         31 . A process as set forth in  claim 18 , characterized in that the photocatalytically active, oxide-ceramic powder used in step (a) includes particles in the range of between 5 nm and 100 nm, preferably between 10 nm and 50 nm.  
     
     
         32 . A process as set forth in  claim 18 , characterized in that the TiO 2  contained in the photocatalytically active, oxide-ceramic powder and/or in the oxide-ceramic base material is present at least in part and preferably in respect of at least 40% by weight with respect to the total amount of TiO 2  in the anatase structure.  
     
     
         33 . A process as set forth in  claim 18 , characterized in that the TiO 2  contained in the photocatalytically active, oxide-ceramic powder and/or in the oxide-ceramic base material is present in respect of at least 70% by weight with respect to the total amount of TiO 2  in the anatase structure.  
     
     
         34 . A process as set forth in  claim 18 , characterized in that the TiO 2  contained in the photocatalytically active, oxide-ceramic powder and/or in the oxide-ceramic base material is present in a mixture comprising 70% by weight of anatase and 30% by weight of rutile.  
     
     
         35 . A process as set forth in  claim 18 , characterized in that the layer produced in step (b) is hardened in step (c) by drying at a temperature of up to 300° C. and/or by calcining at a temperature of more than 300° C. to 1100° C.  
     
     
         36 . A process as set forth in  claim 35  characterized in that the layer produced in step (b) is at least partially pre-dried prior to the calcining operation in step (c) by evaporation of the liquid phase.  
     
     
         37 . A process as set forth in  claim 18 , characterized in that the coating hardened in step (c) is hydrophobised to provide a superhydrophobic surface, wherein the superhydrophobic surface has a contact or edge angle of at least 140° for water.  
     
     
         38 . A process as set forth in  claim 18 , characterized in that a hydrophobising agent is additionally added in step (a) and the coating produced in step (b) is hardened in step (c) by drying at a temperature of up to 300° C.  
     
     
         39 . A process as set forth in  claim 37  or  claim 38  characterized in that an inorganic-organic hybrid molecule, preferably a polysiloxane solution is used for hydrophobisation.  
     
     
         40 . A process as set forth in  claim 37  or  claim 38  characterized in that Ormoceres, alkylsilane and/or fluorosilane, preferably in a mixture with SiO 2 , is used for the hydrophobisation operation.  
     
     
         41 . A process as set forth in  claim 37  or  38 , characterized in that particulate material is added to produce a superhydrophobic surface with raised portions in the hydrophobisation operation.  
     
     
         42 . Use of highly disperse TiO 2  produced by flame hydrolysis of TiO 4  in an oxide-ceramic coating for roof tile, tile, clinker brick or a facade wall.