HUE035170T2 - Kerámia alakos test fotokatalitikusan aktív, légtisztító, átlátszó felületi bevonattal és eljárás annak gyártására - Google Patents

Description

CERAMIC MOULD WITH A PHOTO-CATALYTIC ACTIVE, AIR PURIFYING, TRANSPARENT SURFACE COATING AND METHOD OF MANUFACTURING SAME

The invention relates to a ceramic, preferably coarse ceramic, moulded body with a photo catalytic ally active, air-purifying and preferably transparent coating and a method for manufacturing the same. A ceramic moulded body, namely a roof tile, tile, brick or a façade plate, made of an oxide ceramic base material which has a self-cleaning surface is known from WO 03/101913, said moulded body having a porous oxide ceramic coating and the coating being photocatalytically active and containing T1O2 manufactured by flame hydrolysis, wherein the coating has a specific surface area in a range of about 25 m2/g to 200 m2/g. Furthermore, WO 03/101913 discloses a method for manufacturing such a coarse ceramic moulded body.

Although the method known from WO 03/101913 is well-suited for the manufacture of ceramic moulded bodies with a photocatalytically active coating, ceramic moulded bodies manufactured according to this method have only low air-purifying properties and are prone to so-called "whiteness". This whiteness is caused by light scattering on the photocatalyst particles which are generated by the so-called Tyndall effect. EP 1 659 106 A2 relates to a ceramic moulded body with a photocatalytically active coating and method for manufacture the same. JP 11061798 relates to an inorganic component coated with photocatalytically active titanium oxide. US 6,576,589 BI relates to a method for the manufacture of a T1O2 photocatalyst of the anatase type.

The object of the invention is to provide an improved ceramic moulded body and a method for manufacturing the same which, in addition to photocatalytically active self-cleaning properties, also has air-purifying properties. A further object of the invention is preferably to provide an improved ceramic moulded body which has a transparent surface coating and a method for manufacturing the ceramic moulded body. A transparent surface coating is preferably understood to mean a surface coating whose light transmission is more than 90%, preferably more than 99%. Preferably, the transparent surface coating is colourless.

Furthermore, it is preferably the object of the invention to provide an improved ceramic moulded body which has a firmly adhering surface coating and a method for manufacturing the ceramic moulded body.

The underlying object of the invention is solved according to claim 1 by means of a ceramic moulded body, namely a roof tile, tile, brick and/or a façade plate, made of an oxide ceramic base material having a capillary structure with an air-purifying surface coating which is preferably transparent.

Furthermore, the surface coating of the ceramic moulded body according to the invention may comprise peptised, non-photo catalytic ally active particles, comprise non-photocatalytically active particles, which are surrounded by a layer of peptised particles, and/or comprise non-peptised, non-photocatalytically active particles. The peptised particles can be non-photocatalytically active particles and/or photocatalytically active particles.

Peptisation or peptising of particles is understood to mean that the secondary aggregates of the particles created during the manufacture of the particles are converted to primary aggregates, which are electrostatically stabilised. This is done with the aid of a dispersant. Peptised particles are therefore preferably to be understood as particles on whose surfaces an electrostatically charged or electrostatically chargeable dispersant is deposited.

Through this deposition, which is also referred to as peptisation, the secondary aggregates created during the manufacture of the particles are converted to primary aggregates which can form stable colloidal dispersions. Preferably, these stable colloidal dispersions are storable for at least 1 year, preferably 1 year to 5 years, due to the electrostatic stabilisation. "Peptised particles" are preferably understood to mean particles to which, for example, nitric acid, citric acid and/or hydrochloric acid is/are added as dispersants, which acts against the aggregation of particles. Preferably, the peptised particles are surrounded by a monomolecular or bimolecular layer made of nitric acid molecules, citric acid molecules and/or hydrochloric acid molecules.

This prevents the peptised particles from precipitating out of the dispersions after prolonged storage. Electrostatic stabilisation is effected by the fact that preferably charged molecules are deposited on the surface of the primary aggregates. These charged molecules can also be referred to as a peptide layer. Peptised particles are understood to mean particles with a peptide layer. The peptide layer may be completely or partially closed. The peptisation or peptide layer largely prevents reaggregation of the particles and/or primary aggregates to secondary aggregates.

Preferably, the peptide layer has a thickness of 0.5 nm to 5 nm, preferably 1 nm to 2 nm, on the non-photocatalytically active peptised particles and/or on the photocatalytically active peptised particles.

The size of the secondary aggregates before peptisation is preferably 100 to 200 nm, more preferably 130 to 170 nm. The size of the primary aggregates preferably corresponds to the individual peptised particles and/or to a single spherical layer aggregate up to an aggregate size of 50 nm, preferably 25 nm, more preferably 10 nm. Spherical layered composites are preferably understood to mean individual primary agglomerates or primary aggregates consisting several less, preferably 2 to 5, peptised photocatalytically active particles or particles surrounded by peptised particles which preferably have the size specified above.

Preferably, the surface coating is hydrophilic.

In one embodiment, the surface coating is not manufactured by any sol-gel method.

In one embodiment of the ceramic moulded body according to the invention, the photocatalytically active particles have an average particle size of 2 to 20 nm, preferably 2 to 9 nm, more preferably 4 to 6 nm.

In one embodiment of the ceramic moulded body according to the invention, the photocatalytically active particles have a band gap of 3.0 to 3.5 eV.

In one embodiment of the ceramic moulded body according to the invention, the photocatalytically active particles are selected from the group consisting of TiCT in the rutile modification, TiCT in the anatase modification, ZnO, a-Fe2C>3, γ-ΛΡΟ;, SrTiO,, SnCfr, WO3, B12O3 and mixtures thereof. Preferably, T1O2 is used in the anatase modification and/or ZnO.

According to the invention, the photocatalytically active particles and/or non-photocatalytically active particles have a specific surface area determined by the BET method of 250 to 500 m2/g, most preferably of 300 to 350 m2/g.

In one embodiment of the ceramic moulded body according to the invention, the photocatalytically active particles T1O2, which in the anatase form is at least 90% by weight, more preferably at least 98% by weight, most preferably 100% by weight, based on the total weight of the TÍO2.

In one embodiment, the T1O2 is preferably manufactured by flame hydrolysis as a highly dispersed

TiO2.

Preferably, aluminium oxide is used, which is crystallographically in the δ-form. Suitable aluminium oxide is available from Evonik/Degussa as aluminium oxide C. For example, Aerosil COK 84, a mixture of 84% by weight of Aerosil and 16% by weight of aluminium oxide C, based on the total weight of Aerosil and aluminium oxide C, has proved to be very suitable. This is initially present in aggregated form but is separated by peptisation, preferably with nitric acid, into individual particles or smaller aggregates as defined above.

In one embodiment of the ceramic moulded body according to the invention, the TiCfr particles can be manufactured by a sulphate decomposition method.

In the sulphate decomposition method, metallic titanium slag is obtained, for example, from FeTiCb by reduction with coke. This titanium slag can be treated with concentrated sulphuric acid at 100 to 180°C. The decomposition cake obtained in this way can be dissolved in hot water, possibly with the addition of iron scrap. This precipitates TiCT xIFO, which can be fired at 800 to 1000°C to form TiCfr, which is preferably in the anatase form.

The titanium dioxide manufactured in the sulphate decomposition method is also preferably used in combination with aluminium oxide, which is preferably crystallographically in the δ-form.

In one embodiment of the moulded body according to the invention, the non-photo catalytic ally active particles are selected from the group consisting of a-AfrCb, S1O2 and mixtures thereof. Preferably, the non-photocatalytically active particles, measured without peptisation, have an average particle size of 5 to 25 nm, preferably 10 to 15 nm, wherein it is individual particles that are preferably not aggregated.

In one embodiment of the moulded body according to the invention, the mass ratio of the photocatalytic particles to the non-photocatalytically active particles is from 2.5:6 to 5:6, preferably from 3:6 to 4:6. Preferably titanium dioxide particles are used as photocatalytically active particles and/or S1O2 are used as non-photocatalytically active particles.

In one embodiment of the ceramic moulded body according to the invention, the surface coating comprises TiCT particles which are surrounded by a completely or partially closed layer of peptised AI2O3 particles and/or comprises peptised T1O2 particles. A metatitanic acid layer is preferably arranged between the T1O2 particles and the completely or partially closed layer of peptised AI2O3 particles and/or a metatitanic acid layer is arranged between the T1O2 particles and the peptide layer. Preferably, the metatitanic acid layer is completely closed.

The metatitanic acid layer preferably has a thickness ranging 2 to 20 nm, more preferably 2 to 5 nm.

In one embodiment of the ceramic moulded body according to the invention, the T1O2 particles, the metatitanic acid layer and the layer made of peptised AI2O3 particles form a composite having a mean particle size of 30 nm to 50 nm, preferably 35 to 45 nm.

In one embodiment of the ceramic moulded body according to the invention, the surface coating has an average pore size of 2 to 10 nm, preferably 2 to 5 nm.

In one embodiment, the surface coating has no elevations or elevations of less than 50 nm, preferably less than 30 nm. The elevation of the surface coating is preferably understood to mean the structuring of the surface coating itself. The oxide ceramic base material itself can, of course, have an additional structuring in the nano- or micrometre range. For example, the oxide ceramic base material has elevations ranging 10 to 40 pm. In a preferred embodiment, the surface coating of the ceramic moulded body according to the invention has only the distances and heights which result from the size of the photocatalytically active particles, which are arranged as the densest spherical packing.

In one embodiment of the ceramic moulded body according to the invention, the surface coating has a thickness ranging from 20 to 400 nm, 50 to 200 nm. In another embodiment, the surface coating consists only of a monomolecular layer.

In one embodiment of the ceramic moulded body according to the invention, the surface coating further comprises an organic or inorganic binder. Preferably, the inorganic binder is selected from the group consisting of water glass, silica, their derivatives, and mixtures thereof. For example, the weight ratio of binder to photocatalytically active particles is in a range from 1: 1 to 1:0.6, based on the finished surface coating.

In one embodiment of the ceramic moulded body according to the invention, an engobe or a glaze is arranged between the oxide ceramic base material having a capillary structure and the surface coating. In another embodiment of the ceramic moulded body according to the invention, an engobe or glaze is arranged between the oxide ceramic base material having a capillary structure and the surface coating.

In another embodiment, no engobe or glaze is arranged between the oxide ceramic base material having a capillary structure and the surface coating. A glaze in the context of the present invention is preferably a glassy, 0.2 to 10 mm, more preferably 1-3 mm, thin coating on a coarse ceramic moulded body. The glaze preferably has a low-melting point at a temperature of preferably below 800°C to 1300°C, more preferably at a temperature of 900°C to 1100°C, more preferably a lower melting point than the coated coarse ceramic base body. The glaze preferably evens out the roughness of the base body. In one embodiment, the glaze is impermeable to water but preferably permeable to water vapour, preferably due to microporosity such that the original properties of the ceramic moulded body, namely roof tiles, tiles, bricks and/or façade elements, are not restricted with respect to water vapour permeability. Usually, the glaze is applied for decorative purposes and can vary in colour, transparency, opacity and gloss. In one embodiment, the glaze comprises or consists of 50-80% by weight of glass frit, 10-40% by weight of clay and/or kaolin, and 0-40% by weight of colour pigments and/or opacifiers.

The glass frit is preferably a low-melting point glass powder which is obtained from a S1O2 melt with the addition of melting-point-reducing oxides, such as LÍ2O3, Na2O, K2O, B2O3, CaO, BaO, B12O3 and/or ZnO. The opacifiers used are, for example, high-melting point oxides, e.g. AI2O3, SnCfr, ZrCT, AS2O3, AS2O5, CeCfr, WO3, V2O3, and/or V2O5, which preferably do not melt and are distributed uniformly as particles in the melt. The colour pigments used are preferably coloured metal oxides, such as the CoO, CO2O3, CO3O4, NiO, N12O3, CuO, G2O3, UO2, UO3, Sb2O3, Sb2O5, MnCfr, T1O2, FeO, Fe2Cb, Fe3C>4, MgO, BeO, SrO, SeC),, E^Cb, and/or Sb2O3, or metal oxides already encapsulated in the case of toxicity, are added individually or in a mixing ratio such that the desired colour is obtained.

In contrast to the glazed roof tiles, engobe roof tiles have 60 to 100% by weight of clay and/or kaolin and/or bentonite and optionally 0 to 40% by weight of glass frit, based on the total weight of the engobe.

In one embodiment of the ceramic moulded body according to the invention, the surface coating is arranged on the entire surface of the oxide ceramic base material having a capillary structure. In another embodiment of the ceramic moulded body according to the invention, the surface coating is arranged only on the side of the ceramic moulded body which is exposed to the sunlight and/or the exhaust gases in the air.

In one embodiment, the surface coating has self-cleaning properties.

The term self-cleaning surface coating in the context of the invention is understood to mean that moulds, fungi, plant growth, for example moss and/or algae, bacterial impurities and/or impurities from industrial plants deposited on the surface coating are photo chemically decomposed and removed. The selfcleaning coating oxidises the substances or impurities mentioned, as a result of which these have a reduced adhesion properties and, when irrigated or sprinkled with water, are easily rinsed off from the surface of the moulded body according to the invention.

It is assumed that the photo catalytic ally active coating can, on the one hand, act directly on the organic impurities by oxidation. On the other hand, it is assumed that the oxidative effect of the photocatalytically active coating is indirectly performed by the generation of oxygen radicals and/or hydroxyl radicals, which subsequently oxidise and thus decompose the pollutants and/or impurities.

In one embodiment, the ceramic moulded body is suitable for decomposing both organic pollutants and inorganic pollutants, such as, for example, nitrogen oxides. An air-purifying surface coating in the sense of the invention is preferably understood to mean that harmful gases and/or pollutants present in the air, such as NOX, SOx, formaldehyde, acetaldehyde, toluene, are photocatalytically decomposed and thus clean the surrounding air.

Surprisingly, it has been found that a surface coating as defined in claim 1 also has air-purifying properties, in addition to self-cleaning.

Furthermore, it has surprisingly been found that a surface coating as defined in claim 1 has excellent adhesion to the ceramic moulded body, in particular to a glazed ceramic moulded body.

Furthermore, it was surprisingly found that the ceramic moulded body according to the invention has a transparent and/or matte surface.

In one embodiment of the moulded body according to the invention, the moulded body can be manufactured according to the method described below.

In one embodiment of the moulded body according to the invention, the peptide layer and/or the metatitanic acid layer is removed completely or partially by heating, preferably to above 100°C to 600°C, more preferably 300 to 600°C. The moulded body thus obtained has a very finely distributed surface coating. Preferably, the peptide layer is removed to at least 50% by weight, more preferably at least 90% by weight, most preferably 95% by weight, based on the total weight of the peptide layer. Preferably, the metatitanic acid layer is removed to at least 50% by weight, more preferably at least 90% by weight, most preferably 95% by weight, based on the total weight of the metatitanic acid layer.

The advantageous properties described above for the ceramic moulded body remain even after removal of the peptide layer or the peptisation since the fine distribution of the particles in the surface coating is not influenced.

The underlying object of the invention is further solved according to claim 8 by a method for the manufacture of a coarse ceramic moulded body, namely a roof tile, tile, brick and/or a façade plate, of oxide ceramic base material having a capillary structure and with an air-purifying surface coating which is preferably transparent.

In one embodiment of the method according to the invention, the layer provided in step c) is cured in a further step d) after step c) at temperatures at which the peptisation is split off.

In the method according to the invention, peptised photo catalytic ally active particles and/or photocatalytically active particles, which are surrounded by a layer of peptised particles, can be used in step a), as already defined above with respect to the moulded body according to the invention.

In the method according to the invention, peptised and/or non-peptised non-photocatalytically active particles are further added to the dispersion in step a). Preferably, the non-photocatalytically active particles are S1O2 particles. Preferably, the S1O2 particles are not peptised.

In the method according to the invention, T1O2 particles which are surrounded by a metatitanic acid layer are added to the dispersion in step a), and a completely or partially closed layer of peptised AI2O3 particles is arranged around the metatitanic acid layer in the outermost layer.

The peptised photocatalytically active particles and/or non-photocatalytically active particles can be obtained by dispersing in a dispersing agent solution. Dispersing agent solutions are preferably particle-free solutions which counteract the aggregation of the photocatalytically active particles and contain a dispersing agent. For example, dispersing agent solutions comprising citric acid, nitric acid and/or hydrochloric acid can be used as a dispersing agent. The solutions preferably contain from 1 to 20% by weight, more preferably from 5 to 10% by weight, of the dispersing agent, based on the total weight of the dispersing solution, without the particles to be peptised.

For example, the peptised photocatalytically active particles and/or non-photocatalytically active peptised particles can be manufactured analogously to the method described in EP 1175259 B1.

In one embodiment of the method according to the invention, the T1O2 particles are manufactured before step a) by a sulphate decomposition method and/or by a flame hydrolysis method.

In one embodiment of the method according to the invention, the surface coating is applied in a thickness of 20 to 400 nm, preferably 50 to 200 nm, to the oxide ceramic base material having a capillary structure in step b).

In one embodiment, an engobe or glaze is first applied to the oxide ceramic base material having a capillary structure, and the surface coating is subsequently applied. In another embodiment, the surface coating is first applied to the oxide ceramic base material having a capillary structure and then an engobe or glaze is applied. However, the surface coating can also be applied to a coarse ceramic moulded body without engobe or glaze.

In one embodiment of the method according to the invention, the dispersion prepared in step a) is adjusted to a pH value of < 3, preferably < 2, more preferably to a pH value of 1 to 2. Preferably nitric acid is used to adjust the pH value.

In one embodiment of the method according to the invention, the surface coating is dried at 10 to 90°C in step c). Preferably, steps b) and c) are carried out combined and the surface coating is applied at a surface temperature of 10 to 90°C on the oxide ceramic base material.

In one embodiment of the method according to the invention, the surface coating is cured in step d) at a temperature of from 100 to 600°C, preferably from 200°C to 450°C, more preferably from 250 to 300°C. In one embodiment of the method according to the invention, this curing process takes 2 to 20 minutes, preferably 5 to 10 minutes. The thermal after-treatment separates water from the possibly present metatitanic acid. Furthermore, the acids on the surface of the peptised particles are preferably also released. The splitting off of the metatitanic acid and/or the peptide layer may be partial or complete. A complete splitting off of the metatitanic acid and/or the peptide layer takes place at temperatures of at least 300°C.

In one embodiment of the method according to the invention, an organic or inorganic binder is additionally added to the dispersion in step a). An inorganic binder, for example water glass, silica, titanic acid, their derivatives and/or mixtures thereof, is preferably used as a binder. Preferably, in step a), the binder is admixed in an amount of from 0.01% by weight to 10% by weight, based on the total weight of the dispersion.

In one embodiment of the method according to the invention, in step a), the photocatalytically active particles without considering any potentially surrounding layers are added in an amount of 0.01% by weight to 10% by weight, preferably 1% by weight to 2.5% by weight, based on the total weight of the dispersion manufactured in step a).

In one embodiment of the method according to the invention, in step a), the non-photo catalytically active particles without considering any potentially surrounding layers are added in an amount of 0.01% by weight to 20% by weight, preferably 1% by weight to 4% by weight, based on the total weight of the dispersion manufactured in step a).

To manufacture the dispersion in step a), a polar solvent is used, for example water, short-chain mono-or polyvalent aliphatic alcohols, e.g. methanol, ethanol, and/or analogous monovalent alcohols, glycols, e.g. ethylene glycol, analogous diols and/or glycol ethers and/or other polar organic solvents such as esters, acetone, acetonitrile and/or analogous ketones and/or nitriles and/or mixtures of these solvents. Water is preferably used as a polar solvent. An alcohol-free solvent is preferably used. This simplifies the method management, since no explosion protection is necessary. In a particularly preferred embodiment, the solvent used is water together with a surfactant. In principle, all types of surfactants, for example non-ionic, ionic and/or amphoteric surfactants, are suitable. Particularly preferable for use is a non-ionic surfactant, in particular based on ethylene oxide and/or propylene oxide polymers. For example, Pluronic F-127 has proved suitable. The amount of surfactant in the dispersion is preferably from 0.1 to 0.6% by weight, more preferably from 0.2 to 0.4% by weight, based on the total weight of the dispersion.

In one embodiment, the zeta potential of the solution to be applied in step a) is -20 to -40 mV, preferably -25 to -35 mV. The zeta potential is preferably determined at room temperature (25°C). For example, the zeta potential can be determined with the Zeta Particle-Sizer DT-1200 from QuantaChrome.

The dispersion can be manufactured in step a) by stirring, ultrasound, ultrathorax or a colloid mill.

In one embodiment, the dispersion is applied in step b) to an oxide ceramic base material, preferably a roof tile, tile, brick and/or façade panel, which has a moisture content of 0.1 to 2%, based on the total weight of the coarse ceramic moulded body.

In one embodiment, the dispersion manufactured in step a) is applied by spraying, pouring, dipping or drawing in step b). The ceramic moulded body can be left to at room temperature for this and subsequently dried or preheated to a temperature range of 10° to 90°C. Preferably, in the case of subsequent drying, the temperature is 40 to 60°C or the temperature of the roof tile is 40°to 60°C during the application of the dispersion.

In one embodiment of the method according to the invention, silica particles having a particle size in a range of 3 to 7 nm, preferably 4 to 6 nm, are first dispersed in deionised water. Preferably, the silica particles are added in a final concentration of 1.0 to 4.0% by weight, based on the total weight of the dispersion.

Subsequently, peptised T1O2 particles, which are surrounded by a metatitanic acid layer and peptised with a layer of AI2O3, are dispersed. These peptised T1O2 particles, including the AI2O3 layer, have a size ranging from 30 to 50 nm, preferably from 35 to 45 nm. The T1O2 particles are preferably added in a final concentration of 1.0 to 2.5% by weight, based on the total weight of the dispersion. The weight percentage specification relates only to the weight of the T1O2 added. Subsequently, further deionised water is added and preferably a pH value of < 2, preferably a pH value of 1.5 to 2, is adjusted by means of nitric acid. The dispersion is then offset with 0 to 40% by weight of ethanol, based on the total weight of the dispersion. Alternatively, instead of the ethanol or additionally, a surfactant can also be added in a concentration of from 0.1 to 0.6% by weight, more preferably from 0.2 to 0.4% by weight, based on the total weight of the dispersion.

The concentration of the S1O2 particles is preferably 1.0 to 4.0% by weight, based on the total weight of the finished dispersion. The finished dispersion is preferably stirred further after the addition of ethanol for 10 to 15 h. Stirring at an angular speed of 600 to 800 rpm is preferable.

The ceramic moulded body can advantageously be used for purifying the air of exhaust gases and pollutants. For example, the exhaust gases or pollutants are NOX, SOX, formaldehyde, acetaldehyde and/or toluene.

Advantageously, the ceramic moulded bodies according to the invention have a matt surface, whereby the imperfections are significantly less visible.

Figures:

Figure la shows a photo catalytic ally active T1O2 particle 1 which has a peptide layer 2.

Figure lb shows a photocatalytically active T1O2 particle 1 which is spherically surrounded by non-photocatalytically active particles 3. The particles 3 each have a peptide layer 2.

Figure lc shows a photocatalytically active T1O2 particle 1 which has a metatitanic acid layer 4 and is spherically surrounded by a peptide layer 2 having non-photocatalytically active particles 3.

The examples described below are intended to illustrate in more detail, but in no way limit the present invention:

Example la

Silica particles (Levasil 200, 30%) with a mean particle size in a range of 5 nm were dispersed in deionised water at a final concentration of 20% by weight, based on the total weight of the dispersion, at a pH value less than 2. T1O2 particles were then dispersed in the anatase modification, which are surrounded by a metatitanic acid layer and peptised beforehand with a layer of AI2O3, (obtainable as Hombikat XXS100 from Sachtleben). The peptised T1O2 particles, including the AI2O3 layer, have an aggregate size ranging from 30 to 50 nm, preferably 35 to 45 nm. The T1O2 particles were added in a final concentration of 20% by weight, based on the total weight of the dispersion. The weight percentage specification relates only to the weight of the T1O2 added. The average particle size of the pure T1O2 particles without surrounding layers was 7 nm. A pH value of 2 was then adjusted by means of nitric acid. Subsequently, a concentration of 2.4% by weight of S1O2, 1.6% by weight of T1O2, 30% by weight of ethanol and 66% by weight of deionised water was adjusted by adding deionised water and ethanol in the finished dispersion. The weight percentage specification relates only to the weight of the added substances without surrounding layers. The dispersion was dispersed at an angular speed of 600 rpm for 12h. The dispersion was sprayed with a layer thickness of 187 nm onto a roof tile at a temperature of 50°C and cured at a temperature of 300°C.

Example lb

First, silica particles (Levasil 200E/20%, Evonik) with a mean particle size (primary aggregates) in a range of 35 nm in deionised water were dispersed in a final concentration of 20% by weight, based on the total weight of the dispersion, provided in a vessel and at a pH value of 3. Subsequently, peptised T1O2 particles were dispersed in the anatase modification (available as Suspension VP Disp. W740X at the company Evonik). The T1O2 particles, including the peptisation, have an aggregate size (primary aggregates) ranging from 40 to 50 nm. The T1O2 particles were added in a final concentration of 20% by weight, based on the total weight of the dispersion. The weight specification relates only to the weight of the T1O2 added.

Subsequently, a non-ionic surfactant (Pluronic F-127) was added. Subsequently, a concentration of 1.58% by weight of S1O2 and 7.4% by weight of T1O2 was adjusted by the addition of deionised water in the finished dispersion. The weight specification refers only to the weight of the added substances without surrounding layers. The dispersion was dispersed for 12 h at an angular speed of 600 rpm. The zeta potential of this dispersion was -31 mV measured with the Zeta Particle-Sizer DT-1200 from QuantaChrome at 25°C. The dispersion was sprayed with a layer thickness of approximately 200 nm onto a roof tile at a temperature of 50°C and cured at a temperature of 300°C.

Example lc

First, silica particles (Levasil 200E/20%) with a mean particle size (primary aggregates) in a range of 35 nm in deionised water were added in a final concentration of 20% by weight, based on the total weight of the dispersion in a vessel and dispersed at a pH of 3. Subsequently, peptised T1O2 particles were dispersed in the anatase modification (available as Suspension S5-300B from Millennium). The T1O2 particles, including the peptisation, have an aggregate size in a range of 20 to 30 nm (primary aggregates). The T1O2 particles were added in a final concentration of 20% by weight, based on the total weight of the dispersion. The weight specification relates only to the weight of the T1O2 added. The mean particle size of the pure T1O2 particles without peptisation was 7 nm. Subsequently, a non-ionic surfactant (Pluronic F-127) was added. Finally, a concentration of 1.58% by weight of S1O2 and 3.38% by weight of T1O2 was adjusted by the addition of deionised water in the finished dispersion. The weight specification refers only to the weight of the added substances without surrounding layers. The dispersion was dispersed for 12 h at an angular speed of 600 rpm. The zeta potential of this dispersion was -28 mV measured with the Zeta Particle-Sizer DT-1200 from QuantaChrome at 25°C. The dispersion was sprayed with a layer thickness of approximately 200 nm onto a roof tile at 50°C and cured at a temperature of 300°C.

Comparative Example 2

The dispersion was manufactured as in Example 1 with the difference that the T1O2 particles (P25 from Degussa) had a particle size of 21 nm and the S1O2 had a particle size of 5 to 15 nm. Furthermore, the T1O2 particles were not surrounded by metatitanic acid and peptised AI2O3. Furthermore, a pH value of 10 was set. The dispersion was sprayed with a layer thickness of 270 nm onto a roof tile at a temperature of 50°C and cured at a temperature of 300°C.

Example 3

The decomposition of NOx, methyl stearate and methylene blue was measured and specified as photon efficiency. The photon efficiency is the yield of the photons available at a wavelength of 350 nm with respect to the irradiated tile surface. 1. Methylene blue decomposition 1.1 Irradiation test

All tiles were pre-irradiated with 1.0 mW/cm2 UV-A light 3 days before this test.

Due to the large internal surface of the tiles, they were kept constantly moist during the adsorption test as well as during the irradiation, in order to avoid sucking up the methylene blue solutions.

For this test, a defined amount of a 0.02 mM adsorption solution (methylene blue) was first applied to the surface to be tested and stored for at least 12 h in darkness. This pre-treatment serves to saturate the highly liquid adsorbing tile with methylene blue solution, such that, in the following experiment, falsifications by methylene blue absorption of the tile due to adsorption in the tile were avoided.

Then, for the experiment, the adsorption solution was replaced by a 0.01 mM methylene blue solution and the entire system was irradiated with 1.0 mW/cm2 of UV-A black light for 3 h.

The absorbance values of this dye solution were measured before and after the irradiation at the wavelength of 663 nm in order to determine the dye concentration remaining in the solution.

Over a period of 3h, a sample was taken every 20 minutes and an absorption spectrum was measured at 663 nm. The decrease in absorption is proportional to the concentration decrease of the methylene blue, wherein the methylene blue concentration was determined by means of a known calibration curve. Thus, a decomposition rate a [nM/min] was obtained.

The whole test was repeated once more in the dark in order to determine the light-independent methylene blue loss.

The decomposition rate a measured under UV radiation was corrected by the a,i determined in the dark test: ac = a - ad = 5.65 nM/min.

It was assumed that a photon (hv) is required for decolouring a methylene blue molecule. The photon efficiency, which is an absolute measure for the photocatalytic activity, can then be determined from the decomposition rate as follows.

The Einstein relations of the frequency v and the wavelength λ to the light velocity c = v · λ and the relation of frequency to energy E = h · v, and the Avogadro number Na results in the energy of one mole (n) photons of a certain wavelength with En, λ = Na · h · c / λ.

One mole of photons of the wavelength of 350 nm thus has the energy of En, 350nm = 6.022 · 1023 mol"1 • 6.626 · IO"34 Js · 2.998 · 108 ms-7350 · IO"9 m = 3.418 · 105 J/mol.

With irradiation of a sample area A = 10.75 cm2 with UV-A light of wavelength λ = 350 nm and a radiation density of p = 1.0 mW/cm2 = 1.0 · 10"3 J/s cm2, a photon flux φ = A · p/En, 350nm = 10.75cm2 · 1.0 · 10"3 J/s cm2 · 3600s/h /3.418 · 105 J mol'1 = 1.13 · 10"4 molhv/h emerges.

The irradiated sample volume is V = 30mL = 0.03L.

The photon efficiency is then obtained from the decomposition rate and the parameters mentioned. The photon efficiency is calculated as follows ξ = 3ε·ν/φ = 5.65 nM/min · 60 min/h · 0.03 L / 1.13 · 10'4 molhv/h - = 0.009%.

The above calculation illustrates the calculation of the methylene decomposition in Example 1. The methylene decomposition in Comparative Example 2 was also calculated analogously. 2. Stearate decomposition

All tiles were pre-irradiated with 1.0 mW/cm2 UV-A light for 3 days before these tests.

Due to the large internal surface of the tiles, the tiles were constantly kept moist during 15 of these tests, in order to avoid sucking in the methyl stearate solution. A defined quantity of a 5 mM methyl stearate in n-hexane solution was applied to all test tiles and then irradiated with 1.0 mW/cm2 UV-A light for 23 hours.

After completion of the irradiation test, the methyl stearate remaining on the tiles was washed off with a likewise defined amount of n-hexane (5 mL) and quantified by means of gas chromatography (FID).

The comparison with a previously determined reference value (determined by applying the defined amount of methyl stearate and immediately washing of the methyl stearate layer with n-hexane without prior irradiation) yielded the photocatalytic activity of the tile surface.

For this series of tests, a 5 mM methyl stearate was used in n-hexane solution, resulting in a concentration of 0.5 mM relative to the washing-off quantity (5 mL n-hexane).

From the decrease of the stearate concentrations measured in the GC, the decomposition rate a [μΜ/min] was obtained. The entire test was repeated once more in the dark to determine the light-independent stearate loss.

The decomposition rate a measured under UV irradiation was corrected by the ac = a - a,i = 11.34 μΜ/h determined in the dark test aa.

It was assumed that a photon (hv) is required to destroy a methyl stearate molecule. The photon efficiency, which is an absolute measure for the photocatalytic activity, can then be determined from the decomposition rate as follows. With irradiation of a sample area A = 36 cm2 with UV-A light of wavelength λ = 350 nm and a radiation density of p = 1.0 mW/cm2 = 1.0 · 10"3 J/s cm2, a photon flux was obtained φ = A · p · / En, 350nm = 36cm2 · 1.0 · 10"3 J/s cm2 · 3600s/h · 3.418 · 105 J mol"1= 3.78 · 10"4 molhv/h.

The sample volume analysed was V = 5 mL = 0.005 L. Photon efficiency was then obtained from the decomposition rate and the parameters mentioned ς = ac · V / φ = 11.34 μΜ/hr · 0.005 L / 3.78 · 10"4 molhv/h = 0.015%.

The above calculation explains the calculation of the stearate decomposition in Example 1. The stearate decomposition was also calculated analogously in Comparative Example 2. 3. NOx decomposition

The NOx decomposition was carried out in January 2004 according to the JIS R 1701-1 standardised method in Japan. The sample body to be examined of 50 x 100 mm2 area was placed in a 50cm long UV-permeable glass tube of 50 mm diameter. The sample in the tube was irradiated with UV-A light with an intensity of 1.0 mW/cm2. Air (relative humidity 50%) was conducted through the tube with a content of 1 ppm NO and a flow rate of 3 L/min over a sample of the size 50 x 100 mm2. The analysis was carried out with a NO/NO2 analyser, which has a fluorescence detector with a detection limit of 1 ppb NO. The irradiation was carried out with UV-(A) lamps, wherein the light intensity at the sample surface was 1 mW/cm2.

An absolute measuring time is not required since it is a continuous apparatus. Thus, the NOX concentration of the air flowing through the sample at the end of the tube was measured compared to the initial concentration. From the flow rate of 3 L/min, the decomposition rates were determined as follows:

Evaluation:

The irradiation power was 1 mW/cm2, which corresponds to a total power of 50 mW for a sample size of 50 cm2. For an average irradiation wavelength of 350 nm, the following applies: 50mW = 1.47 X 10"7 molhv/s

The continuous measuring apparatus was operated at a flow rate of 3 L/min.

For an ideal gas the following applies: 24 L gas = 1 mol (at p = 1 bar and 25°) i.e., 1 mole of gas flowed over the sample in 8 minutes. Of this, 1 ppm NO, that is, 10"6 moles of NO flowed over the sample. During this time, the sample was irradiated with 1.47 X IO'7 molhv/s x 60 s/min x 8 min = 70 x 10-6 molhv.

In the case of a complete decomposition of the added NO, the photon efficiency ς was thus: ς = 10-6 mole NO / 70 x 10-6 molhv = 0.143 = 1.43%

If a decomposition of x ppm NO is measured, the photon efficiency is then calculated according to the following formula: ςχ = x (ppm) · 1.43 (% / ppm)

In Example 1, a decrease of 0.056 ppm was measured. ςχ = x (ppm) · 1.43 (% / ppm) = 0.056 ppm -1.43 (% / ppm) = 0.08%

The above calculation explains the calculation of the NOX decomposition in Example la. The NOX decomposition was analogously calculated in Examples lb and lc and Comparative Example 2.

Result of Examples la, b and c and Comparative Example 2

The roof tiles according to the invention from Examples la, b and c showed a significantly better decomposition of NOX, methyl stearate and methylene blue than the conventional roof tiles of Comparative Example 2. The roof tiles according to the invention are thus particularly suitable in congested urban areas for the decomposition of 20 pollutants from the air. Particularly for the roof tiles manufactured according to Examples lb and lc without alcohol, i.e. in aqueous dispersion, there is an enormously improved decomposition of methyl stearate and methylene blue.

Claims (11)

Kerámia alakos test fotokatalitikusan aktív, légtisztító, átlátszó felületi bevonattal és ELJÁRÁS ANNAK GYÁRTÁSÁRA Szabadalmi igénypontok

1. Kerámia alakos test, mégpedig tetőcserép, csempe, tégla és/vagy homlokzatburkoló lap, kapilláris szerkezetű oxidkerámia alapanyagból, légtisztító felületi bevonattal, ahol a felületi bevonat peptizált fotokatalitikusan aktív szemcséket és/vagy peptizált szemcsék alkotta réteggel körülvett fotokatalitikusan aktív szemcséket tartalmaz, ahol a fotokatalitikusan aktív szemcsék BET módszerrel meghatározott fajlagos felülete 250-500 m2/g, továbbá ahol a peptizált fotokatalitikusan aktív szemcsék és/vagy a fotokatalitikusan aktív szemcsék primer aggregátumként vannak kiképezve.

2. Az 1. igénypont szerinti kerámia alakos test, ahol a fotokatalitikusan aktív szemcsék peptizálás nélkül mért átlagos szemcsemérete 2-20 nm.

3. Az előző igénypontok bármelyike szerinti kerámia alakos test, ahol a fotokatalitikusan aktív szemcsék a rutil módosulatú T1O2, anatáz módosulatú T1O2, ZnO, a-Fe2C>3, y-AhCb, SrTiOß, SnCL, WO3, B12O3 és ezek keverékei alkotta csoportból vannak választva.

4. A 3. igénypont szerinti kerámia alakos test, ahol a T1O2 szemcsék szulfátos feltáró eljárással állíthatók elő.

5. Az előző igénypontok bármelyike szerinti kerámia alakos test, ahol a nem fotokatalitikusan aktív szemcsék az 01-AI2O3, S1O2 és ezek keverékei alkotta csoportból vannak választva.

6. Az előző igénypontok bármelyike szerinti kerámia alakos test, ahol a felületi bevonat peptizált AI2O3 szemcsék teljesen vagy részben zárt rétegével körülvett T1O2 szemcséket és/vagy peptizált T1O2 szemcséket tartalmaz.

7. A 6. igénypont szerinti kerámia alakos test, ahol a T1O2 szemcsék és a peptizált AI2O3 szemcsék teljesen vagy részben zárt rétege között metatitánsav réteg van elrendezve és/vagy ahol a T1O2 szemcsék és a peptidréteg között metatitánsav réteg van elrendezve.

8. Eljárás durvakerámia alakos test, mégpedig tetőcserép, csempe, tégla és/vagy homlokzatburkoló lap gyártására kapilláris szerkezetű és légtisztító felületi bevonattal rendelkező oxidkerámia alapanyagból, ahol az eljárás során a) peptizált fotokatalitikusan aktív szemcséket és/vagy peptizált szemcsék rétegével körülvett fotokatalitikusan aktív szemcséket tartalmazó diszperziót készítünk, ahol a fotokatalitikusan aktív szemcsék BET módszerrel meghatározott fajlagos felülete 250-500 m2/g, továbbá ahol a peptizált szemcséket olyan szemcsék képezik, melyekhez salétromsav-, citromsav- és/vagy sósav kapcsolódik, b) az a) lépésben előállított diszperziót a kapilláris szerkezetű oxidkerámia alapanyagra felhordjuk, és c) a b) lépésben készített réteget a felületi bevonat létrehozásához szárításnak vetjük alá.

9. A 8. igénypont szerinti eljárás, ahol az a) lépésben az 1-7. igénypontok bármelyike szerinti peptizált fotokatalitikusan aktív szemcséket és/vagy peptizált szemcsék alkotta réteggel körülvett fotokatalitikusan aktív szemcséket használunk.

10. Az 1-7. igénypontok bármelyike szerinti kerámia alakos test alkalmazása levegő füstgázoktól való megtisztítására.

11. A 10. igénypont szerinti alkalmazás, ahol a füstgázokat NOX, SOX, formaldehid, acetaldehid és/vagy toluol képezi.