Process for producing photocatalytically active TiO2 particles and substrates with photocatalytic TiO2 layer

The invention relates to photocatalytically active TiO₂Particles, substrates having a photocatalytic, TiO₂ containing layer, processes for their preparation and their use.

The photocatalytic properties of TiO₂Particles have been described in the literature long been known and studied intensively. The photocatalytic effect is based on a semiconductor property of the TiO₂Wherein a hole-electron pair is formed by a photon, which has a relatively long recombination time. By diffusion of holes and electrons to the surface processes are set in motion that develop directly or indirectly through water with subsequent formation of hydrogen peroxide is a strong oxidizing effect. Here, the oxidation potential of about 3 eV is so high that virtually all organic substances in contact with such TiO₂Particles come, are oxidized. However, this process occurs only if an appreciable proportion of UV light contained in the irradiated light. As the proportion of the UV light to the visible light is relatively small, the photocatalytic action is limited by the incident photons. By recombination of the electrons with the holes, the efficiency is further lowered.

Further, it has been found that it is difficult on substrates or surface layers which are themselves oxidizable, such as. For example, with substrates or layers of organic polymers, oxidation by an applied thereto photocatalytic layer, and thus the damage to the substrate or the layer to prevent. Even with substrates or surface layers of glass has a direct application of the photocatalytic layer the disadvantage that in the glass sodium ions can diffuse into the photocatalytic layer, whereby the glass damaged and / or the photocatalytic process be disturbed.

The object of the present invention was to achieve an enhanced photocatalytic activity and / or to provide protection for substrates or surface layers which are sensitive to the photocatalytic layer.

According to a first embodiment of the present invention, a method for producing a substrate having a photocatalytic layer is provided, comprising the steps of:<ul><li>a) preparing a mixture comprising at least one hydrolyzable titanium compound, an organic solvent and water in a substoichiometric amount, based on the hydrolyzable groups of the titanium compound,</li><li>b) treating the resulting mixture at a temperature of at least 60 ° C to form a dispersion or a precipitate of doped TiO₂particles,</li><li>c) optionally, solvent exchange by removing the solvent to form a powder of TiO₂Particles and adding another solvent to form a dispersion of TiO₂particles,</li><li>d) applying the dispersion to the substrate and</li><li>e) heat-treating the applied dispersion to form a photocatalytic layer.</li></ul>

According to the invention therefore is a process for the production of TiO₂Particles provided, in addition to the aforementioned steps a) and b) the step c) the removal of the solvent to form a powder of TiO₂comprises particles.

In preferred embodiments, in the methods for preparing the TiO_2-Particles or for the production of the substrate having a photocatalytic layer in step a) additionally added at least a dopant and / or in step b) a hydrothermal treatment or heating is carried out under reflux.

The substrate which is to be provided with the photocatalytic layer may be suitable material from each for this purpose. Examples of suitable materials are metals or metal alloys, glass, ceramic, including oxide ceramic, glass ceramic or plastics. Of course, substrates can be used which have a surface layer of the above materials. When the surface layer may for example be a metallization, an enameling, a glass or ceramic layer or a paint.

Examples of metals or metal alloys are steel, including stainless steel, chromium, copper, titanium, tin, zinc, brass and aluminum. Examples of glass are soda glass, borosilicate glass, lead crystal and silica glass. It can for example be flat glass, hollow glass such as vessel glass, or laboratory equipment glass. The ceramic is, for example a ceramic based on the oxides SiO₂, Al₂O₃, ZrO₂ or MgO, or of the corresponding mixed oxides. Examples of the plastic, which, like the metal can be present as a film, are polyethylene, such as HDPE or LDPE, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polytetrafluoroethylene, polychlorotrifluoroethylene, polyacrylates, polymethacrylates such as polymethyl methacrylate, polyamide, polyethylene terephthalate , polycarbonate, regenerated cellulose, cellulose nitrate, cellulose acetate, cellulose triacetate (TAC), cellulose acetate butyrate or rubber hydrochloride. A painted surface may be formed from conventional base paints or varnishes.

To prepare a photocatalytic layer on the substrate according to the first embodiment of the invention according to the later-described sol-gel method, a TiO₂prepared particles containing dispersion. The TiO_2-Particles may also precipitate to form a precipitate. By removing the solvent, a powder is obtained.

According to the method of the first embodiment of the invention, a mixture is first comprising at least one hydrolyzable titanium compound, an organic solvent and water in a substoichiometric amount, based on the hydrolyzable groups of the titanium compound prepared according to step a), wherein the mixture also optionally at least one metal compound as may comprise a dopant.

The hydrolyzable titanium compound is in particular a compound of the formula TiX₄Wherein the hydrolysable groups X, which from one another or preferably identical, for example, hydrogen, halogen (F, Cl, Br or I, especially Cl and Br), alkoxy (preferably C_1-6Alkoxy, especially C_1-4Alkoxy, such as methoxy, ethoxy, n-propoxy, i-propoxy, butoxy, i-butoxy, sec-butoxy and tert-butoxy), aryloxy (preferably C_6-10Aryloxy, such as phenoxy), acyloxy (preferably C_1-6Acyloxy, such as acetoxy or propionyloxy) or alkylcarbonyl (preferably C_2-7Alkylcarbonyl, such as acetyl) are. An example of a halide is TiCl₄, Preferred hydrolyzable radicals X are alkoxy groups, especially C_1-4Alkoxy. Specific titanates used with preference are Ti (OCH₃)₄, Ti (OC₂H₅)₄ and Ti (OC n- or i-₃H₇)₄,

The mixture also contains water in a substoichiometric amount, based on the hydrolyzable groups of the titanium compound, that is, based on 1 mol of hydrolyzable groups in the titanium compound is less than one mole of water present. In other words, at a hydrolyzable titanium compound with four hydrolyzable groups, relative to 1 mole of titanium compound, less than 4 moles of water were added. are preferably not more than 0.7 mol, more preferably not more than 0.6 mol and in particular not more than 0.5 mol or 0.4 mol, and not less than 0.35 moles, preferably not less than 0.30 mole water, based on 1 mol of hydrolyzable groups in the titanium compound.

In the preferred embodiments for preparation of doped particles can be used as metal compound for doping any suitable metal compound, for example an oxide, a salt or a complex compound, for example, halides, nitrates, sulfates, carboxylates (eg acetates) or acetylacetonates. The connection should be suitably soluble in the solvents used for the mixture. Suitable metals include any metal, in particular a metal selected from the groups 5 to 14 of the Periodic Table of the Elements and the lanthanides and actinides. The groups are listed here according to new IUPAC system, as in Römpp Chemie Lexikon, 9th edition, reproduced. The metal may be present in the compound in any suitable oxidation state.

According to the new IUPAC system groups 1, 2 and 13 to 18 correspond to the eight main groups (IA to VIIIA by CAS), the groups 3 to 7 the secondary groups 3-7 (IIIB to VIIB according CAS), the groups 8 to 10 of the In addition to group 8 (VIII after CAS) and the groups 11 and 12 correspond to groups 1 and 2 (Cu and Zn group, IB and IIB according to CAS).

Examples of suitable metals for the metal compound are W, Mo, Cr, Zn, Cu, Ag, Au, Sn, In, Fe, Co, Ni, Mn, Ru, V, Nb, Ir, Rh, Os, Pd and Pt. Metal compounds of W (VI), Mo (VI), Cr (III), Zn (II), Cu (II), Au (III), Sn (IV), In (III), Fe (III), Co (II ), V (V) and Pt (IV) are preferably used. Very good results are achieved in particular with W (VI), Mo (VI), Zn (II), Cu (II), Sn (IV), In (III) and Fe (III). Specific examples of preferred metal compounds are WO₃ MoO₃, FeCl₃, Silver acetate, zinc chloride, copper (II) chloride, indium (III) oxide and tin (IV) acetate.

The quantity ratio between the metal compound and the titanium compound also depends on the metal and its oxidation state employed. In general, for example, those proportions are used such that a molar ratio of metal of the metal compound to titanium of the titanium compound (Me / Ti) of from 0.0005: 1 to 0.2: 1, preferably 0.001: 1 to 0.1: 1, and more preferably 0.005: 1 to 0.1: 1 results.

Instead of the metal doping may be carried out also with a doping semi-metal or non-metal elements, for example carbon, nitrogen, phosphorus, sulfur, boron, arsenic, antimony, selenium, tellurium, chlorine, bromine and / or iodine. For this purpose, either the elements as such, or suitable element compounds are used as a dopant.

The doped TiO₂Particles are characterized in particular by the fact that it a suitable choice of the doping element and litigation photocatalytic activity even when excited with visible light having a wavelength&gt; 380 nm ( "Visible-light or daylight photocatalysts").

an organic solvent is used as the solvent in which the hydrolyzable titanium compound is preferably soluble. The solvent is also preferably miscible with water. Examples of suitable organic solvents include alcohols, ketones, ethers, amides and mixtures thereof. Alcohols are preferably used, preferably lower aliphatic alcohols (C₁-C₆Alcohols) such as ethanol, 1-propanol, i-propanol, sec-butanol, tert-butanol, isobutyl alcohol, n-butanol and pentanol isomers, in particular 1-pentanol, wherein 1-propanol and 1-pentanol particularly are preferred.

The mixture preferably contains a catalyst for the hydrolysis and condensation under sol-gel conditions, in particular an acidic condensation catalyst, eg hydrochloric acid, phosphoric acid or formic acid.

The resulting mixture is then at a temperature of at least 60 ° C to form a dispersion or a precipitate of doped or undoped TiO₂treated particles. This heat treatment is preferably carried out hydrothermally or by heating under reflux. Advantageously, in the heat treatment a relatively high dilution is applied, in particular during heating under reflux.

The heat treatment is preferably carried out over a period of 0.5 to 30 h, preferably 4 to 24 h, during which the duration depends on the temperature and the optionally applied pressure. For example, anatase is obtained by hydrothermal treatment at 200 ° C and autogenous pressure after a reaction time of 1 h in nanoparticulate form in a yield of about 35% of theory

The heating is usually carried out under reflux over a period of at least 3 h. The solvents used are preferably alcohols having at least 4, preferably at least 5 C atoms are used, for example, n-pentanol, hexanol, heptanol or octanol. but it can also be applied to other polar solvent, for example thiols such as n-butyl, amyl, hexyl or heptyl.

A hydrothermal treatment refers generally a heat treatment of an aqueous solution or suspension under elevated pressure, for example at a temperature above the boiling point of the solvent and a pressure above 1 bar. In the present invention, a heat treatment is under excess pressure understood in a predominantly organic solvent which if any contains only a little water as a hydrothermal treatment.

In the hydrothermal treatment, the mixture is heat-treated in a closed container or in a closed autoclave. The treatment is preferably at a temperature in the range from 75 ° C to 300 ° C, preferably above 200 ° C, more preferably 225 to 275 ° C, eg about 250 ° C. Due to the heating, in particular above the boiling point of the solvent, in the closed vessel or autoclave, a pressure is built up (autogenous pressure). The pressure may be, for example, about 1 bar, in particular 50 to 500 bar or more, preferably 100 to 300 bar, for example 200 bar, respectively. In general, the hydrothermal treatment is carried out at least 0.5 h and preferably up to 7 or 8 h.

The heat treatment according to step b) is continued until the desired doped or undoped TiO₂Particles are formed. The dispersion or precipitation can be used directly or after solvent exchange for coating the substrate. to TiO₂to obtain particles in powder form, the solvent is removed.

The obtained doped or undoped TiO₂Particles of the dispersion of the precipitate or the powder are predominantly crystalline and in the anatase form. Preferably, the crystalline fraction of the resulting doped TiO makes₂Particles more than 90%, preferably from more than 95% and in particular more than 97%, that is, the amorphous fraction is in particular below 3%, for example at 2%. The average particle size (X-ray-determined volume average) is preferably not more than 20 nm, more preferably not more than 10 nm. In a particularly preferred embodiment, particles are obtained with an average particle size of about 2 to 10 nm. The TiO inventively prepared₂Particles are distinguished from known TiO₂Materials by the fact that they are dispersible agglomerate. In the doping of TiO₂a particularly homogeneous distribution of the dopant metals is obtained particles.

The dispersion obtained can be used as such for coating the substrate. Conveniently, there is a preceding solvent exchange. It is preferred that from the dispersion obtained in step b) the particles are separated from the solvent. For this purpose, all known in the art method may be used. A centrifugation is particularly suitable. The separated TiO₂are particles then dried (eg at 40 ° C and 10 mbar). In this form, the particles may also be stored well.

For application to the substrate, the TiO₂Particles dispersed again in a solvent. For this purpose, for example, the solvent or water above suitable. Preferably, a water / alcohol mixture and more preferably water alone as a solvent.

In a preferred embodiment, an inorganic or organically modified inorganic matrix-forming material is added to the dispersion obtained after step b) or c). This may in particular be inorganic sols or organically modified inorganic hybrid materials or nanocomposites. Examples are optionally organically modified oxides, hydrolysates and (poly) condensates of at least a glass or ceramic-forming element M, in particular an element M selected from Groups 3 to 5 and / or 12 to 15 of the periodic table of elements, preferably Si, Al , B, Ge, Pb, Sn, Ti, Zr, V and Zn, especially those of Si and Al, most preferably Si, or mixtures thereof. Fractions of elements of Groups 1 and 2 of the periodic table (eg, Na, K, Ca and Mg) and of the Groups 5 to 10 of the Periodic Table (for example Mn, Cr, Fe and Ni), or lanthanide in the oxide, hydrolyzate or (poly) be present condensate. A preferred organically modified inorganic hybrid material are polyorganosiloxanes. Particularly preferred for this purpose are the hydrolysates of glass- or ceramic-forming elements, in particular of silicon used.

The inorganic or organically modified inorganic matrix-forming material is preferably added in an amount such that the molar ratio of titanium of the titanium compound to glass- or ceramic-forming element M 100: 0.01 to 0.01: 100, preferably 300: 1 to 1: 300 is. Very good results are obtained with a molar ratio Ti / M of from about 10: 3 to 1:30 obtained. By this addition, an improvement in adhesion is achieved. When an organically modified inorganic matrix-forming material is used, all or only part of the glass- or ceramic-forming elements M include one or more organic groups as nonhydrolyzable groups.

The inorganic or organically modified inorganic matrix-forming materials can be produced by known methods, emulsion methods eg by flame pyrolysis, plasma processes, gas-phase condensation processes, colloid techniques, precipitation, sol-gel processes, controlled nucleation and growth processes, MOCVD processes and (micro). Unless obtained from the process solvent-free particles, these are suitably dispersed in a solvent.

Preferably, the inorganic sols, and particularly the organic-modified hybrid materials can be obtained by the sol-gel method. In the sol-gel process, which can also be used for the separate preparation of the particles, are usually hydrolysable compounds with water, optionally under acidic or basic catalysis, and optionally at least partially condensed. The hydrolysis and / or condensation reactions lead to the formation of compounds or condensates with hydroxyl, oxo groups and / or oxo bridges, which serve as precursors. It can stoichiometric amounts of water, but also smaller or larger amounts. The sol which forms can by suitable parameters, for example degree of condensation, solvent or pH can be adjusted to the desired viscosity of the coating composition. Further details of the sol-gel process are described, for example in CJ Brinker, GW Scherer: "Sol-Gel Science - The Physics and Chemistry of Sol-Gel Processing", Academic Press, Boston, San Diego, New York, Sydney (1990) described.

According to the preferred sol-gel method, the oxides, hydrolysates or (poly) condensates by hydrolysis and / or condensation of the hydrolyzable compounds of the aforementioned glass- or ceramic-forming elements are obtained, which optionally additionally nonhydrolyzable for the preparation of the organic-modified inorganic hybrid material organic substituents.

Inorganic salts are formed by the sol-gel process in particular from hydrolyzable compounds of general formula MX_n , where M is the above-defined glass- or ceramic-forming element, X as in the following formula (I) is defined, where two X groups may be replaced by an oxo group, and n is the valence of the element and usually 3 or 4. Preferably, hydrolysable silicon compounds, in particular the following formula (I).

Examples of suitable hydrolysable compounds of elements M, which are different from Si, are Al (OCH₃)₃, Al (OC₂H₅)₃, Al (OnC₃H₇)₃, Al (OiC₃H₇)₃, Al (OnC₄H₉)₃, Al (O-sec-C₄H₉)₃, AlCl₃, AlCl (OH)₂, Al (OC₂H₄OC₄H₉)₃, TiCl₄, Ti (OC₂H₅)₄, Ti (OnC₃H₇)₄, Ti (OiC₃H₇)₄, Ti (OC₄H₉)₄, Ti (2-ethylhexoxy)₄, ZrCl₄, Zr (OC₂H₅)₄, Zr (OnC₃H₇)₄, Zr (OiC₃H₇)₄, Zr (OC₄H₉)₄, ZrOCl₂, Zr (2-ethylhexoxy)₄, And Zr compounds which have complexing radicals, such as β-diketone and (meth) acrylic radicals, sodium acetate, potassium acetate, boric acid, BCl₃, B (OCH₃)₃, B (OC₂H₅)₃, SnCl₄, Sn (OCH₃)₄, Sn (OC₂H₅)₄, VOCl₃ and VO (OCH₃)₃,

The discussion below is the preferred silicon also apply mutatis mutandis to the other elements M. Particular preference is the sol or the organically modified inorganic hybrid material of one or get more hydrolyzable and condensable silanes, optionally at least one silane having a nonhydrolyzable organic radical. one or more silanes having the following general formulas (I) and / or (II) are particularly preferably used:          SiX₄     (I) wherein the radicals X are identical or different and are hydrolysable groups or hydroxyl groups,          R_aSiX_(4-a)     (II) wherein R is the same or different and represents a non-hydrolysable radical, optionally having a functional group, X has the above meaning and a has the value 1, 2 or 3, preferably 1 or 2, has.

In the above formulas, the hydrolysable groups X, for example, hydrogen or halogen (F, Cl, Br or I), alkoxy (preferably C_1-6Alkoxy, such as methoxy, ethoxy, n-propoxy, i-propoxy and butoxy), aryloxy (preferably C_6-10-Aryloxy, such as phenoxy), acyloxy (preferably C_1-6Acyloxy, such as acetoxy or propionyloxy), alkylcarbonyl (preferably C_2-7Alkylcarbonyl, such as acetyl), amino, monoalkylamino or dialkylamino having preferably 1 to 12, especially 1 to 6 carbon atoms in the alkyl group (s).

The nonhydrolyzable radical R is, for example, alkyl (preferably C_1-6Alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl and t-butyl, pentyl, hexyl or cyclohexyl), alkenyl (preferably C_2-6Alkenyl, such as vinyl, 1-propenyl, 2-propenyl and butenyl), alkynyl (preferably C_2-6Alkynyl such as acetylenyl and propargyl) and aryl (preferably C_6-10Aryl, such as phenyl and naphthyl).

The radicals R and X above may optionally one or more customary substituents, such as halogen, ether, phosphoric acid, sulfonic acid, cyano, mercapto, amide, thioether or alkoxy groups as functional groups.

The radical R may contain a functional group via which crosslinking is possible. Specific examples of the functional groups of the radical R are epoxy, hydroxyl, amino, monoalkylamino, dialkylamino, carboxyl, allyl, vinyl, acrylic, acryloxy, methacrylic, methacryloxy, cyano, aldehyde - and alkylcarbonyl. These groups are preferably linked through alkylene, alkenylene or arylene bridge groups, which may be interrupted by oxygen or sulfur atoms or -NH groups on the silicon atom. The bridging groups are derived, for example, from the alkyl, alkenyl or aryl groups mentioned above. The bridging groups of the radicals R preferably contain from 1 to 18, especially 1 to 8 carbon atoms.

Particularly preferred hydrolysable silanes of general formula (I) are tetraalkoxysilanes such as tetramethoxysilane and in particular tetraethoxysilane (TEOS). obtained by acidic catalysis inorganic sols such as TEOS hydrolysates are particularly preferred. Particularly preferred organosilanes of the general formula (II) are methyltriethoxysilane (MTEOS) and MTEOS hydrolysates, epoxysilanes such as 3-glycidyloxypropyltrimethoxysilane (GPTS), methacryloxypropyltrimethoxysilane and acryloxypropyltrimethoxysilane, wherein GPTS hydrolysates can be used with advantage.

When an organically modified inorganic hybrid material is produced exclusively silanes of formula (II) or a mixture of silanes of the formula (I) and (II) can be used. The inorganic sols silicon based solely silanes of the formula (I) may be used, where appropriate, fractions of hydrolyzable compounds of the above formula MX_n be added.

If the inorganic sol consists of particles dispersed in the solvent discrete oxide particles, they can improve the hardness of the layer. These particles are in particular nanoscale inorganic particles. The particle size (X-ray-determined volume average) is for example in the range ≤ 200 nm, especially ≤100 nm, preferably ≤ 50 nm, such as 1 nm to 20 nm.

According to the invention such as inorganic sols of SiO₂, ZrO₂, GeO₂, CeO₂, ZnO, Ta₂O₅, SnO₂ and Al₂O₃ (In all modifications, in particular as boehmite AlO (OH)), preferably sols of SiO₂, Al₂O₃, ZrO₂, GeO₂ and mixtures thereof can be used as nanoscale particles. Such sols are also commercially available in some cases, for example, silica sols, as the Levasils® Bayer AG.

The inorganic or organically modified inorganic matrix-forming material, a combination of such nanoscale particles with existing as hydrolysates or (poly) condensates inorganic sols or organically modified hybrid materials can be used, which is referred to here with nanocomposites.

Optionally, organic monomers, oligomers or polymers of all kinds may be present as organic matrix-forming materials, which serve as plasticisers, which may be conventional organic binders. These can be used for improving the coating ability. In general, they are degraded photocatalytically after completion of the layer. The oligomers and polymers may have functional groups through which crosslinking is possible. This networking option is also optionally possible with the above-described organically modified inorganic matrix-forming materials. Mixtures of inorganic, organically modified inorganic and / or organic matrix-forming materials are also possible.

Examples of usable organic matrix-forming materials are polymers and / or oligomers containing polar groups such as hydroxyl, primary, secondary or tertiary amino, carboxyl or carboxylate groups, have. Typical examples are polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyvinylpyridine, polyallylamine, polyacrylic acid, polyvinyl acetate, Polymethylmethacrylsäure, starch, gum arabic, other polymeric alcohols such as polyethylene-polyvinyl alcohol copolymers, polyethylene glycol, polypropylene glycol and poly (4-vinylphenol) or derived from monomers or oligomers. The polyvinyl alcohol can be used as the commercially available Mowiol.RTM 18-88 from Messrs. Hoechst.

The degree of dilution to be applied in step d) dispersion depends inter alia on the desired layer thickness. Generally, the dispersion has a solids content of less than 50 wt .-%, in particular less than 20 wt .-%, and preferably less than 10 wt .-%, such as 2.5 wt .-%.

the conventional methods are used for the job, for example, dipping, rolling, knife coating, flooding, drawing, spraying, spinning or spreading. The applied dispersion is dried and optionally heat-treated, for example for curing or compaction. The heat treatment used for this naturally depends on the substrate. For plastic substrates or plastic surfaces, which have usually a barrier layer (see below), not very high temperatures can be used naturally. Thus, polycarbonate (PC) substrates, for example, at about 130 ° C to be heat-treated for 1 h. In general, the heat treatment is carried out for example at a temperature of 100 to 200 ° C and, if no plastic is present, up to 500 ° C or more. The heat treatment is for example 15 minutes to 2 hours. In general, layer thicknesses of 50 nm to 30 microns can be obtained, preferably from 100 nm to 1 micron, such as 50 to 700 nm.

The inorganic sol or the organically modified inorganic hybrid material not only serve as a matrix forming material for the photocatalytic layer, but also the improved coating adhesion. TiO₂ may be present in the layer as a matrix-forming component and / or as particles.

The photocatalytic layer is optionally and preferably activated by irradiation with visible and / or UV light, for example with a high-pressure mercury lamp of 700 W for 1 to 5 minutes, or a xenon lamp of 750 W for 1 to 10 min. High-pressure mercury lamps have a relatively high proportion of UV light, the spectrum of xenon lamps corresponds approximately to sunlight. Preferably is irradiated with UV light or a high proportion of UV light. This gives exceptionally active photocatalytic layers, the efficiency compared to the prior art can be increased approximately up to 10 times.

As already mentioned above, an immediate order are in substrates that are made of a photosensitive material or a surface layer having (for example, a lacquer or a enamel) of such sensitive material, or only possible with difficulty. There may be a barrier layer between the substrate (optionally with surface coating) and the photocatalytic layer. For this purpose, an inorganic layer are used from an inorganic matrix-forming material, for which the inorganic sols described above can be used.

It was further concluded that it is possible to obtain a photocatalytic layer with "built-in" barrier layer by a concentration gradient of TiO₂ is formed in the photocatalyst layer. This barrier layer can be used not only for the inventively prepared photocatalytic layers, but also in the customary photocatalytic layers advantage.

Accordingly can be provided a substrate having a photocatalytic layer, the photocatalytically active TiO₂ and comprising a matrix material, the TiO₂ is contained in such a concentration gradient that the concentration of the TiO₂ is concentrated at the surface of the photocatalytic layer, wherein between the photocatalytically active TiO₂ and the substrate is a purely inorganic barrier layer is formed.

These photocatalytic layers having such a concentration gradient of TiO₂, That the concentration of TiO₂ is at the surface of the photocatalytic layer is greatest, can be made by a process in particular, wherein the surface-modified TiO₂Particles by themselves form a concentration gradient in a matrix-forming material.

It can doped or undoped TiO₂Particles are used. The doping can be carried out with according to the known in the prior art method, whereby the known in the art, metallic or non-metallic dopants can be used, for example, those mentioned above for the first inventive embodiment metals and nonmetals. By doping an increase in activity and also often photocatalytic activity in the visible light range ( "Visible-light photocatalysts") are surprisingly achieved.

Preference is given by the sol-gel method resulting TiO₂Particles used. The abovementioned hydrolyzable titanium compounds can be used. Are used particles produced according to the first embodiment of the invention according to steps a) and b), said doped or non-doped TiO₂Particles can be used.

Of the TiO₂a dispersion particles generally prepared in a solvent. Suitable for this purpose, for example toluene. It may also be a slurry of TiO₂Particles in a solvent or a powder of TiO₂Particles are used without solvent. For this purpose, a surface-modifying agent is added which comprises at least one hydrophobic or hydrophilic group, hydrophobic groups are preferred.

Suitable surface modifiers are suitable (preferably low molecular weight or oligomeric, but optionally also polymeric) compounds which have on the one hand via one or more groups reactive with the surface of the TiO_2-Particles existing reactive groups (such as OH groups) react or at least interact, and have the other at least one hydrophobic or hydrophilic group.

A surface modification of the TiO₂particles can as by mixing the particles with suitable compounds illustrated below, where appropriate in a solvent and in the presence of a catalyst. Frequently stirring of surface-modifying agent with the particles is sufficient at room temperature over a period of time, for example about 1 to 3 h. Advantageously, often also acts as a treatment in the ultrasonic bath from.

The surface modifier can eg both covalent (including coordinate bonds in the form of complexes) and ionic (salt-like) bonds to the surface of the TiO₂Particles forming, while the pure interactions include-dipole interactions, hydrogen bonds and van der Waals interactions are mentioned. Preference is given to the formation of covalent bonds.

According to the invention it is also preferred that the surface-modifying agent having a relatively low molecular weight. For example, the molecular weight is less than 1,500, in particular below 1000 and preferably below 700th This of course a significantly higher molecular weight of the compounds not (for example, up to 2,000 or more).

As a surface modifying agent having groups reactive with the surface groups of the TiO₂can react or interact with particles, for example, hydrolyzable silanes, carboxylic acids, carboxylic acid halides, carboxylic acid esters, carboxylic anhydrides, oximes, β-dicarbonyl compounds such as β-diketones, alcohols, polyethers and functionalized polyethers are useful (eg trioxadecanoic acid), amines, alkyl halides and derivatives thereof.

The concept of hydrophilicity / hydrophobicity is to the expert best known as the basic concept of chemistry. Hydrophobic substances or groups repel water, while hydrophilic substances or groups attract water. The hydrophilic character can be formed, for example by hydroxyl, oxy, carboxylate, sulfate, sulfonate or polyether in the substance. As hydrophobic group, for example, long-chain aliphatic hydrocarbon groups, for example having 3 to 30 or more carbon atoms, in particular alkyl groups, aromatic groups, or groups having a fluorine atom at least, which are preferably hydrocarbon groups, in particular alkyl groups having 3 to 20 or more are carbon atoms and 1 to 30 fluorine atoms is.

Suitable surface modifiers preferably hydrolyzable silanes are used having at least one non-hydrolysable hydrophobic or hydrophilic groups, those are particularly preferably with a hydrophobic group. It is particularly preferred hydrolyzable silanes which have at least one non-hydrolysable group containing at least one fluorine atom (fluorine silanes) or a long-chain aliphatic hydrocarbon group, for example having 3 to 30 carbon atoms, preferably an alkyl group, or an aromatic group.

The usable in addition to the hydrolyzable silane surface modifying agent having hydrophobic groups can for example have the formula R ° -Y, wherein Y is -COOH, -OH, -COZ, -Z (with Z = halide, such as F, Cl, Br or I), -C (O) O (O) CB (wherein B is any radical of a carboxylic acid or R ° or a functional group of the other compounds described above (optionally comprising a further group as B), and R ° is a long-chain aliphatic hydrocarbon group, preferably a is alkyl group, for example with 3 to 30 carbon atoms, or an aromatic group such as optionally substituted phenyl or naphthyl, or a hydrocarbon group, preferably an alkyl group, with at least one fluorine atom. In the case of a carboxylic acid ester may, for example the rest of the carboxylic acid and / or rest of the alcohol form the hydrophobic group.

The preferred hydrolysable silanes with long-chain aliphatic hydrocarbon group as a hydrophobic group have in particular the above-mentioned formula (II) (R_aSiX (_4-a)) To, wherein A and X are as defined above, where a is preferably 1, and R is a long chain aliphatic hydrocarbon group, for example with 3 to 30 C-atoms. In the long-chain aliphatic hydrocarbon group is preferably an alkyl group. Optionally, silanes of the formula (II) can be used, wherein R is an optionally substituted aromatic group.

According to particularly preferred hydrolyzable silane compounds may be at least one non-hydrolyzable radical used as a hydrophobic group, the general formula          Rf (R)_bSiX_(3-b)     (III) which X and R as defined in formula (I) or (II) are defined, Rf is a nonhydrolysable group which has bound 1 to 30 fluorine atoms to carbon atoms, preferably by at least two atoms, preferably an ethylene, propylene -, ethyleneoxy or propyleneoxy group, are separated from Si, and b is 0, 1 or 2, preferably 0 or 1, is. R is in particular a radical without a functional group, preferably an alkyl group, in particular C_1-4Alkyl such as methyl or ethyl. The groups Rf preferably 3 to 25 and in particular 3 to 21 fluorine atoms which are attached to aliphatic (including cycloaliphatic) carbon atoms. Rf is preferably a fluorinated alkyl group having 3 to 20 carbon atoms, which is optionally interrupted by one or more oxygen atoms.

Examples of Rf are CF₃CH₂CH₂, C₂F₅CH₂CH₂, nC₆F₁₃CH₂CH₂, iC₃F₇0CH₂CH₂CH₂, nC_8thF₁₇CH₂CH₂ and nC₁₀F₂₁-CH₂CH₂,

Fluorine atoms, which are optionally bonded to aromatic carbon atoms (for example C₆F₄), will not be considered. In the fluorine-containing group Rf may be also be a chelate ligand. It is also possible that one or more fluorine atoms are located on a carbon atom from which a double or triple bond. Examples of usable Fluorosilanes are CF₃CH₂CH₂SiCl₂(CH₃), CF₃CH₂CH₂SiCl (CH₃)₂, CF₃CH₂CH₂Themselves₃) (OCH₃)₂, C₂F₅-CH₂CH₂-SiZ₃, nC₆F_13-CH₂CH₂SiZ₃, nC_8thF₁₇-CH₂CH₂-SiZ₃, nC₁₀F₂₁-CH₂CH₂-SiZ₃ with (Z = OCH₃, OC₂H₅ or Cl); iC₃F₇O-CH₂CH₂CH₂--SiCl₂(CH₃) NC₆F₁₃-CH₂CH₂-Si (OCH₂CH₃)₂, nC₆F_13-CH₂CH₂--SiCl₂(CH₃) And nC₆F₁₃-CH₂CH₂--SiCl (CH₃)₂, Preferably 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl triethoxysilane (FTS) is used.

Examples of hydrolyzable silanes with long-chain aliphatic hydrocarbon group are hexadecyl (HDTMS) dodecyltriethoxysilane and propyltrimethoxysilane. Further examples of surface modifying agent having hydrophobic groups are heptadecafluorononanoic, stearic acid, Heptafluorbuttersäurechlorid, hexanoyl chloride, hexanoate, Perfluorheptansäuremethylester, Perfluoroctansäureanhydrid, hexanoic anhydride, 2-heptanone oxime, 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione-2- oxime, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, 1H, 1H-Pentadecafluoroctanol, octanol, hexyl chloride and Nonafluorbutylchlorid.

Suitable surface modifiers having hydrophilic groups are, in addition above mentioned classes of compounds and unsaturated carboxylic acids, β-carbonylcarboxylic acids, with polymerizable double bonds, ethylenically unsaturated alcohols and amines, amino acids, epoxides and diepoxides.

Specific examples of organic compounds for surface modification with hydrophilic groups are diepoxides such as 3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexane carboxylate, bis- (3,4-epoxycyclohexyl) adipate, Cyclohexandimethanoldiglycidether, Neopentylglycoldiglycidether, 1,6-hexanediol diglycidyl ether, Propylenglycoldiglycidether, bisphenol-A diglycidyl ether, bisphenol F diglycidyl ether, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and β-diketones such as acetylacetonate.

Further particularly preferred compounds for surface modification with hydrophilic groups are hydrolyzable silanes having at least (and preferably) one non-hydrolysable radical by a hydroxyl, carboxylate or epoxy or glycidyloxy group, wherein it is in particular silanes of the formula (II). Examples are glycidyloxyalkyltrialkoxysilanes, such as 3-glycidoxypropyltrimethoxysilane and 3-glycidyloxypropyltriethoxysilane.

Other examples of surface modifiers include diphosphates, polyphosphates, polyvinyl alcohol, polyvinyl pyrrolidone and methyl vinyl ether-maleic anhydride copolymers.

The surface modification can be for 1 g TiO₂Powder, for example, 10 ml of solvent used. The resultant dispersion with the surface-modifying agent is simply stirred, eg 2 h, so that the surface modification of the particles is achieved. The ratio of TiO₂ is added to the surface modification agent, based on moles, preferably 1: 0.005 to 1: 0.1 and especially from 1: 0.01 to 1: 0.02, and this in particular applies to the surface-modifying agent with at least one fluorine atom.

Then preferably a solvent exchange with another organic solvent such as methyl ethyl ketone, acetone, chloroform or petroleum ether.

Then an inorganic or organically modified matrix-forming material may be added. For this purpose, for example, an inorganic sol or an organically modified inorganic hybrid material are added, as explained above. It may also contain the abovementioned nanoscale particles.

The surface modifier is used to generate the concentration gradient in the matrix of the matrix-forming material. In a hydrophilic matrix surface modifiers are used with a hydrophobic group and hydrophobic matrix surface modifiers are used with hydrophilic group. Thereby, a potential difference is achieved, which leads to separation, so that the surface-modified TiO₂Particles are concentrated at the surface. As the matrix-forming materials and the solvent used, usually are hydrophilic, is preferably surface-modified with hydrophobic groups.

The order of the obtained dispersion to the substrate and the heat treatment is carried out in the usual manner, for example as described above. Due to the hydrophobic character of the hydrophobic groups on the surface of the TiO₂Particles results in a separation in the dispersion thus obtained, wherein the surface-modified TiO₂Particles are enriched, after application to the substrate at the surface of the photocatalytic layer. Thus, in the curing of the coated layer, a concentration gradient of the surface-modified TiO₂Particles formed in the other inorganic or organically modified matrix-forming material or in the matrix formed therefrom. In the bottom layer disposed predominantly the inorganic or organically modified inorganic matrix-forming material or the matrix formed therefrom.

In case of exposure, at least the hydrophobic organic groups are destroyed by the photocatalytic activity of the layer, as demonstrated by a significant reduction in contact angle after irradiation. By the concentration gradient at the interface with the substrate mainly by the matrix of the inorganic or organically modified matrix-forming materials which there is substantially no TiO₂ contains. If organically modified inorganic matrix-forming material was used, found in the area in the photocatalytic layer in which TiO_2-enriched regions and substantially TiO₂-free regions adjoin, the above in the "isolated" barrier layer explained photocatalytic oxidation of the organic components takes place, that also forms there an inorganic barrier layer. Thus, a form of "incorporated" barrier layer of inorganic material that can protect the substrate underneath.

Again, all the above-mentioned substrates may be used in principle. Particularly advantageously, the photocatalytic layer is applied with a built-barrier layer on a substrate of glass or plastic or a surface layer of the substrate made of this material.

It was further found that a specific hybrid layer of organically modified inorganic material provides an excellent barrier. This barrier layer can be used not only for the inventively prepared photocatalytic layers, but also in the customary photocatalytic layers advantage.

According to one embodiment, therefore, a substrate having a photocatalytic, TiO₂ containing layer provided, which is characterized in that between the substrate and a photocatalytic layer is provided a hybrid layer of an organically modified inorganic material. It is formed during the activation by irradiation due to the oxidation of the organic components, a gradient in carbon content at the surface of the barrier layer of. The thus obtained gradient has on the surface a photocatalytically active, TiO₂ containing inorganic layer, followed by an inorganic barrier layer which merges with increasing layer depth in the inorganic-organic hybrid material. The diffusion of the TiO₂Particles in the surface of the barrier layer at the film formation also forms a gradient in the TiO₂Concentration of.

This barrier layer has on the one hand the advantage that reliable protection is ensured of sensitive materials before the photocatalyst layer, on the other hand, the barrier layer can be applied wet-chemically in a simple manner and be applied in the desired layer thickness readily cracks. Due to the organic components a certain degree of flexibility is achieved in the coating, surprisingly, in spite of the organic components of a safe locking effect is achieved.

As the substrate, all substrates mentioned above can be used in principle. With particular advantage, the barrier layer is applied to a substrate made of glass or plastic, or a surface layer of the substrate of this material.

The barrier layer is a hybrid layer of an organically modified inorganic material, the organic components at least at the interface to the photocatalytic TiO₂Layer have been photocatalytically decomposed to form a purely inorganic protective layer.

To produce these hybrid layer, the above-described organic-modified inorganic hybrid material is used as coating composition. It all above apply for this material listed explanations, unless otherwise stated, the hybrid material but not to the TiO_2--containing dispersion is added, but is applied as such to the substrate.

It is preferably such an organically modified inorganic hybrid material is used in which not more 10 mol%, preferably not more than 5 mol% and in particular not more than 3 mol%, and preferably at least 0.1 mol%, more preferably at least 0.5 mol% and in particular at least 1 mol%, eg 0.1 to 10 mol%, preferably 1 to 3 mol%, the contained glass- or ceramic-forming elements M comprise one or more organic groups. ie, preferably not more than 10 mol% and especially not more than 3 mol%, zBzB 0.1 to 10 mol%, preferably 1 to 3 mol%, the contained glass- or ceramic-forming elements M comprise one or more organic groups on. Preferably, at least a part or all of the organic groups have a functional group via which crosslinking is possible. The hybrid material is preferably prepared by the sol-gel method. Suitable solvents are those mentioned above into consideration. Particularly preferred is a hydrolyzate or condensate of silanes of formula (I) and formula (II). Optionally, at least a portion of the silanes of formula (I) are replaced by other hydrolyzable compounds of glass- or ceramic-forming member M.

Preferably, a stoichiometric amount of water is added to the hydrolysable compounds for the production of the hybrid material. The coating composition is, for example, as 1 to 70 wt .-% sol / gel (based on the solids content) is used in an alcohol. A particularly preferably used combination of hydrolyzable compounds is TEOS or MTEOS and GPTS.

The organically modified inorganic hybrid material may preferably comprise the above-mentioned nanoscale particles to form a nanocomposite. To the organically modified inorganic hybrid material, no organic polymers are preferably added, ie, the coating composition is preferably free from organic polymers.

The order of the hybrid material is effected in customary manner, for example by the processes described above. The coated layer is optionally dried and cured, can wherein the curing by heat or irradiation occur. If necessary, can be carried out together with the photocatalytic layer the heat treatment. Regarding the temperature and the duration of the conditions mentioned above for the photocatalytic layer apply. The layer thickness is, for example, 50 nm to 1 micron, preferably 100 nm to 1 micron, such as 100 to 700 nm.

On the hybrid layer, the TiO₂applied -containing composition, the surface-modified TiO₂Particles containing. Here are surface-modified TiO₂Particles used as explained above for the second embodiment of the invention. It can surface modifiers having hydrophobic or hydrophilic groups are used.

In general, photocatalytically active TiO₂Particles dispersed in a matrix, the TiO₂ can also be part of the matrix. The layer can also only of TiO₂ consist. The matrix may be generally formed from inorganic or organic-modified inorganic matrix materials. Accordingly, the composition may also contain inorganic or organically modified inorganic matrix-forming materials, as discussed above. It may also contain the abovementioned nanoscale particles. but the composition may also only TiO₂contain particles, so that a photocatalytic layer only TiO₂ is formed.

It has been found that the layer of the hybrid material passes through photocatalytic oxidation of the organic component at least at the interface to the photocatalytic layer in a purely inorganic system. This is done by overlapping photocatalytically active layer, a photocatalytic oxidation of the organic constituents of the underlying hybrid layer. This process is often limited to a few nanometers of the top layer of this layer, since the diffusion of holes and electrons is sufficient only very briefly. The implementation of the uppermost layer of the hybrid layer to an inorganic layer of the destruction process is stopped and one obtains an effective barrier layer that prevents diffusion of sodium ions from glass substrates in the photocatalytic layer and protects sensitive plastic substrates against damage by the photocatalytic layer. In addition, the organic groups of the surface-modified TiO₂ photocatalytically decomposed.

In all the described embodiments to further increase the photo-catalytic effect can be obtained when using, under the photocatalytic layer, an electrically conductive base and / or in the photocatalytic layer is added to specific electrically conductive particles.

The doped metal oxides used as electrically conductive particles may, for example doped tin oxide such as ITO (indium tin oxide), ATO (antimony-doped tin oxide) and FTO (fluorine-doped tin oxide), and / or aluminum-doped zinc oxide act. It can also be an electrically conductive polymer, BAYTRON as are used by the Bayer AG. As semiconductors is for example, optionally doped germanium or silicon into consideration. The electrically conductive particles may be added for example as a powder or in the form of a dispersion in a solvent for dispersion of the photocatalytic layer.

Preferably highly transparent conductive particles are used. This is a high light absorption, such as caused by conductive metal particles z. B., avoided and there are still more effective photocatalytic layers.

Alternatively or simultaneously, can be provided as a layer under the photocatalytically active layer, an electrically conductive surface. When electrically leitfäh strength substrate can be a metal, a semiconductor, an electrically conductive polymer or a doped metal oxide. Examples of the doped metal oxide, the semiconductor, or the electrically conductive polymer are the same that have been mentioned above as examples of the electrically conductive particles. Examples of the metal which may also be a metal alloy, are steel, including stainless steel, chromium, copper, titanium, tin, zinc, brass and aluminum.

The support may be present as a layer on the substrate or the substrate itself. For the application of an electrically conductive layer as a pad on a substrate which the expert is familiar methods may be used, for example, wet chemical processes, deposition processes (sputtering) or a metallization. Generally, thin layers are sufficient.

In all illustrated embodiments the substrates with the photocatalytic layers can be baked to obtain purely inorganic layers. Moreover, particles with a larger diameter, for example, can be installed in the micrometer range in all layers.

The substrates of the invention with the photocatalytic layers for example can be used as self-cleaning surfaces (optionally supported by irradiation with light) are used for air cleaning or.

The substrates according to the invention having a photocatalytic layer suitable for various applications for antimicrobial purposes and / or self-cleaning, eg for machines, paints, coating materials, furniture, facades, roofs, textiles, vehicles, signaling systems, films, Protective Partitions, traffic engineering , automobiles, aircraft and railway vehicles, windows, doors, greenhouses, walls, tiles, floors, tents, tarpaulins, outdoor equipment, fences, natural stone, concrete, plaster, plaster, flooring, monuments, wood, panels, paneling, window frames, textiles, covers, concrete, plastic surfaces of all kinds, plastic glazing, helmets, visors, housing, outdoor facilities, equipment of all kinds, such as medical equipment, household appliances, traffic signs, steel structures and steel facades. The layers are also useful as anti-fogging coatings, for example on glass, mirrors, panels or screens. Further, magnetic, for example superparamagnetic particles can be coated.

A special application is the sterilization or the protection of instruments of all kinds, and especially medical, including veterinary and dental equipment and devices of the sanitary facilities, to contamination, for example by infectious substances such as prions (eg for the fight against BSE). Other important areas of application are food technology and dairy farming.

Examples

It uses the following abbreviations:<dl id="dl0001" compact="compact"><dt>TEOS:</dt><dd>tetraethoxysilane</dd><dt>FTS:</dt><dd>(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) triethoxysilane</dd><dt>GPTS:</dt><dd>(3-Glycidyloxypropyl) trimethoxysilane</dd><dt>HDTMS:</dt><dd>hexadecyl</dd></dl>

example 1

Hydrothermal Preparation of TiO

<u>2</u>

(Anatase)

9.6 g (0.034 mol) of titanium isopropoxide (Ti (OⁱPr)₄) Are added to 14.5 g of n-propanol and added to 37% HCl after 5 min at room temperature while stirring with 0.67 g (0.0068 mol). After 20 min, 0.712 g (0.063 mol) of water were added with intensive stirring.

The mixture is then diluted with 41.9 g of n-propanol, then treated at 250 ° C and 200 bar pressure for 7 hours. The resulting anatase is centrifuged and dried at 50 ° C and 10 mbar.

example 2

Hydrothermal preparation of doped TiO

<u>2</u>

(Anatase, dopant Sn (CH

<u>3</u>

CO

<u>2</u>

)

<u>4</u>

)

9.6 g (0.034 mol) of titanium isopropoxide (Ti (OⁱPr)₄) Are added to 14.5 g of n-propanol and added to 37% HCl after 5 min at room temperature while stirring with 0.67 g (0.0068 mol). After 20 min, 0.712 g (0.063 mol) of water were added with intensive stirring.

The mixture is then diluted with 41.9 g of n-propanol, then the mixture with 0.635 g (0.0018 mol) Sn (CH₃CO₂)₄ mixed and treated at 250 ° C and 200 bar pressure for 7 hours. The resulting anatase is centrifuged and dried at 50 ° C and 10 mbar.

example 3

Hydrothermal preparation of doped TiO

<u>2</u>

(Anatase, dopant WO

<u>3</u>

)

9.6 g (0.034 mol) of titanium isopropoxide (Ti (OⁱPr)₄) Are added to 14.5 g of n-propanol and added to 37% HCl after 5 min at room temperature while stirring with 0.67 g (0.0068 mol). After 20 min, 0.712 g (0.063 mol) of water were added with intensive stirring.

The mixture is then diluted with 41.9 g of n-propanol, then the mixture with 0.039 g (0.00017 mole) of WO₃ mixed and treated at 250 ° C and 200 bar pressure for 7 hours. The resulting anatase is centrifuged and dried at 50 ° C and 10 mbar.

example 4

Surface modification of TiO

<u>2</u>

(Anatase) Powder with FTS

From the TiO prepared according to Examples 1 to 3₂Powders is 1.0 g each with 8.67 g of toluene is stirred and then added with 0.077 g of FTS. After stirring for 2 hours the toluene is removed in a rotary evaporator.

<u>example 5</u>

Surface modification of TiO

<u>2</u>

(Anatase) Powder with HDTMS

From the TiO prepared according to Examples 1 to 3₂Powders are respectively 1.0 g with 8.67 g of toluene is stirred and then treated with 0.312 g HDTMS. After stirring for 2 hours the toluene is removed in a rotary evaporator.

example 6

Producing a photocatalytic layer with undoped TiO

<u>2</u>

To prepare a GPTS hydrolyzate 23.6 g (0.1 mol) GPTS with 5.4 g (0.3 mol) are added to water. The mixture is then stirred overnight at room temperature.

0.05 g of the prepared in Example 4 FTS-modified, undoped TiO_2-Powder in 1.56 g of MEK (methyl ethyl ketone) dispersed and then added with 0.44 g of formamide. The dispersion obtained is mixed under stirring with 4.14 g of GPTS produced hydrolyzate.

The resulting coating composition is applied using a spin coater (spin coater) with 1000 U / min on polycarbonate sheets (PC sheet) of 10 cm x 10 cm. Subsequently, the plates are cured at 128 ° C for 1 h. The layer thicknesses from 2 to 3 microns. The contact angle of the obtained layers to water is 101 °.

The coated plates are PC 4 min with a xenon lamp (750 W) irradiated. After irradiation, the contact angle of the PC plaques was only 10 ° against water.

To determine the photocatalytic activity of the obtained PC boards, the change in the light absorbance at 553 nm of a rhodamine B solution is determined. For this purpose, 20 ml of an aqueous Rhodamine B are brought solution (concentration 6 ppm) with the PC board into contact (750 W) is irradiated with a xenon lamp. The absorption of the Rhodamine B solution at 553 nm is measured at intervals to track the degradation of rhodamine B. After approximately one hour the entire Rhodamine B is degraded.

example 7

Producing a photocatalytic layer with Sn-doped TiO

<u>2</u>

0.05 g of the produced according to Example 5 HDTMS-modified, Sn-doped TiO₂Powder are dispersed in 1.56 g of petroleum ether and then added with 0.44 g of formamide. The dispersion obtained is mixed under stirring with 4.14 g of the as prepared in Example 6 GPTS hydrolyzate.

The resulting coating composition is applied using a spin coater (spin coater) with 1000 U / min on polycarbonate sheets (PC sheet) of 10 cm x 10 cm. Subsequently, the plates are cured at 128 ° C for 1 h. The layer thicknesses from 2 to 3 microns. The contact angle of the obtained layers to water is 92 °.

The coated plates are PC 4 min with a xenon lamp (750 W) irradiated. After irradiation, the contact angle of the PC plaques toward water was less than 10 °.

The photocatalytic activity of the obtained PC sheets is determined by the same experimental setup as in Example 6 by determining the light absorption at 553 nm of a rhodamine B solution. The entire Rhodamine B is degraded after 35 minutes.

example 8

Preparation of photocatalytic layers TEOS hydrolyzate

To prepare a TEOS hydrolyzate 12.36 g (0.0594 mol) of TEOS are added to 15.96 g of ethanol with 9.06 g of water. Then, with stirring, 0.2 g of concentrated (37%) HCl are added. After stirring for 1 h 0.28 g of GPTS were added and stirred at room temperature overnight. a TEOS hydrolyzate obtained with 2 mol% GPTS.

Of the prepared in Example 4 FTS-modified TiO₂Powders (undoped, doped with Sn and doped with W), a 2.5 weight percent solution in methyl ethyl ketone are prepared respectively and with 0.2 g of TEOS produced hydrolyzate containing 2 mol% GPTS (molar ratio Ti: Si = 10: 5), mixed.

The resulting coating composition is applied by a spin coater on polycarbonate sheet (PC sheet) of 10 cm x 10 cm. Subsequently, the plates are cured at 128 ° C for 1 h.

example 9

Determine the photocatalytic activity of layers with doped TiO

<u>2</u>

To determine the photocatalytic activity, layers with doped TiO₂ examined. For this purpose, Sn-doped TiO₂Powder (Sn (IV)), W-doped TiO_2-Powder (W (VI)), Fe-doped TiO₂Powder (Fe (III)) and In-doped TiO₂Powder (in (iii)) in different ratios of Ti used for doping metal.

The Sn and W-doped TiO₂Powder will be in accordance with Examples 2 and 3 with Sn (CH₃CO₂)₄ and where₃ prepared, the amounts used can be varied according to the desired ratio of Ti to dopant (0.5 to 10 mol% of dopants). Analogously, doped TiO₂Powder with FeCl₃ and in₂O₃ produced. For comparison, unmodified anatase is also prepared under identical conditions.

Of the produced doped TiO₂Powders are prepared respectively, a 2.5 weight percent solution in methyl ethyl ketone and 0.2 g of as prepared in Example 8 TEOS hydrolyzate containing 2 mol% GPTS mixed.

The resulting coating composition is applied (PC sheet) by means of a spin coater on polycarbonate sheets. The plaques are hardened at 128 ° C for 1 h.

The photocatalytic activity is again with a Rhodamine B solution (6 ppm in H₂O) determined. The coated panels are each contacted with 20 ml of the rhodamine B solution and then irradiated for 10 min with UV light. After the absorption of the Rhodamine B solution at 553 nm is measured. For comparison, measurements on Rhodamine B without contact with photocatalytic layers and in contact be carried out with undoped anatase also in the same manner. The results are shown in the following table. This shows that some significant faster reduction rates can be achieved by doping.<tables id="tabl0001" num="0001"><table frame="all"><title>Table: absorbance at 553 nm after 10 min UV-irradiation</title><tgroup cols="5" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="36mm" colsep="1" /><colspec colnum="2" colname="col2" colwidth="13mm" colsep="1" /><colspec colnum="3" colname="col3" colwidth="13mm" colsep="1" /><colspec colnum="4" colname="col4" colwidth="15mm" colsep="1" /><colspec colnum="5" colname="col5" colwidth="15mm" colsep="1" /><thead><row><entry namest="col1" nameend="col1" align="center" valign="top" /><entry namest="col2" nameend="col5" colsep="1" rowsep="1" align="center" valign="top">dopant</entry></row><row><entry namest="col1" nameend="col1" align="center" valign="top">Amount (mol%)</entry><entry namest="col2" nameend="col2" align="center" valign="top">Fe (III)</entry><entry namest="col3" nameend="col3" align="center" valign="top">W (VI)</entry><entry namest="col4" nameend="col4" align="center" valign="top">Sn (IV)</entry><entry namest="col5" nameend="col5" align="center" valign="top">In (III)</entry></row></thead><tbody><row><entry namest="col1" nameend="col1" align="center" valign="top">-^*</entry><entry namest="col2" nameend="col2" align="center" valign="top">1.46</entry><entry namest="col3" nameend="col3" align="center" valign="top">1.42</entry><entry namest="col4" nameend="col4" align="center" valign="top">1.08</entry><entry namest="col5" nameend="col5" align="center" valign="top">1.07</entry></row><row><entry namest="col1" nameend="col1" align="center" valign="top">0^**</entry><entry namest="col2" nameend="col2" align="center" valign="top">0.24</entry><entry namest="col3" nameend="col3" align="center" valign="top">0.31</entry><entry namest="col4" nameend="col4" align="center" valign="top">0,125</entry><entry namest="col5" nameend="col5" align="center" valign="top">0.12</entry></row><row><entry namest="col1" nameend="col1" align="center" valign="top">0.5</entry><entry namest="col2" nameend="col2" align="center" valign="top">0.31</entry><entry namest="col3" nameend="col3" align="center" valign="top">0.04</entry><entry namest="col4" nameend="col4" align="center" valign="top">0,065</entry><entry namest="col5" nameend="col5" align="center" valign="top">0,009</entry></row><row><entry namest="col1" nameend="col1" align="center" valign="top">1.0</entry><entry namest="col2" nameend="col2" align="center" valign="top">0.46</entry><entry namest="col3" nameend="col3" align="center" valign="top">0.03</entry><entry namest="col4" nameend="col4" align="center" valign="top">0.103</entry><entry namest="col5" nameend="col5" align="center" valign="top">-0.043</entry></row><row><entry namest="col1" nameend="col1" align="center" valign="top">5</entry><entry namest="col2" nameend="col2" align="center" valign="top">0.27</entry><entry namest="col3" nameend="col3" align="center" valign="top">0,284</entry><entry namest="col4" nameend="col4" align="center" valign="top">-0.06</entry><entry namest="col5" nameend="col5" align="center" valign="top">0,023</entry></row><row><entry namest="col1" nameend="col1" align="center" valign="top">10</entry><entry namest="col2" nameend="col2" align="center" valign="top">0,084</entry><entry namest="col3" nameend="col3" align="center" valign="top">0.20</entry><entry namest="col4" nameend="col4" align="center" valign="top">-0.08</entry><entry namest="col5" nameend="col5" align="center" valign="top">0,084</entry></row></tbody></tgroup><tgroup cols="5" rowsep="0"><colspec colnum="1" colname="col1" colwidth="36mm" /><colspec colnum="2" colname="col2" colwidth="13mm" /><colspec colnum="3" colname="col3" colwidth="13mm" /><colspec colnum="4" colname="col4" colwidth="15mm" /><colspec colnum="5" colname="col5" colwidth="15mm" /><tbody><row><entry namest="col1" nameend="col5" align="justify" valign="top">* Measurement without photocatalytic layer</entry></row><row><entry namest="col1" nameend="col5" align="justify" valign="top">** Undoped anatase</entry></row></tbody></tgroup></table></tables>

example 10

TiO

<u>2</u>

- (Anatase) manufacturing

reflux

To 29.02 g of 1-pentanol 19.2 g (0.068 mol) of titanium isopropoxide (Ti (OⁱPr)₄), And minutes after 5 s. Stirring added 37% HCl at room temperature with 1.33 g (0.0136 mol). After 20 min, 1.42 g (0.079 mol) of water was added rapidly with vigorous stirring and further stirred for 20 min at room temperature. The mixture is then cooked at 132 ° C for 16 h under reflux. The resulting anatase is centrifuged and dried at 50 ° C and 10 mbar.

Surface Modification of Reflux TiO

<u>2</u>

(Anatase) Powder with TODA

Of the TiO obtained above₂Powder is gerürht each 1 g with 4 g of water, and then with 0.2 g of TODA (trioxadecanic). After 10 min. Sonication obtained a transparent solution.

Dispersion of reflux-TiO

<u>2</u>

(Anatase) Powder with toluene

Of the TiO obtained above₂Powder 1 g with 1.5 g of toluene is stirred. After 1 min. Sonication is obtained a transparent solution.