DE10235803A1 - Substrate used as self-cleaning substrate for protecting objects in medicine and where hygiene is important comprises photocatalytic layer comprising photocatalytically active titanium dioxide and matrix material - Google Patents

Abstract

A substrate comprises a photocatalytic layer comprising photocatalytically active titanium dioxide and a matrix material. The titanium dioxide is contained in a concentration gradient that it is enriched on the surface of the photocatalytic layer. Independent claims are also included for the following: (1) the production of the substrate; and (2) the production of the photocatalytically active titanium dioxide.

Description

The invention relates to substrates with a photocatalytic layer containing TiO ₂ , which have improved photocatalytic activity, and to processes for their production.

The photocatalytic properties of TiO ₂ particles have long been known in the literature and have been intensively investigated. The photocatalytic effect is based on a semiconductor property of TiO ₂ , whereby a hole-electron pair is formed by a light quantum, which has a relatively long recombination time. The diffusion of holes and electrons to the surface starts processes that develop a strong oxidative effect directly or indirectly above water with subsequent hydrogen peroxide formation. The oxidation potential of over 3 eV is so high that practically all organic substances that come into contact with such TiO ₂ particles are oxidized. However, this process only takes place if a noticeable proportion of UV light is contained in the incident light. Since the proportion of UV light in visible light is relatively small, the photocatalytic effect is limited by the incident light quanta. The efficiency is further reduced by the recombination of the electrons with the holes.

It has also been shown that it is difficult on substrates or surface layers that are themselves oxidizable are, such as B. in substrates or layers of organic polymers, an oxidation by a photocatalytic applied thereon Layer and thus the damage to prevent the substrate or layer. Even with substrates or surface layers made of glass has an immediate application of photocatalytic Layer the disadvantage that sodium ions in the glass in the Diffuse photocatalytic layer, causing damage to the glass and / or the photocatalytic process can be disturbed.

The object of the present invention therefore consisted of achieving increased photocatalytic activity and / or for Layer substrates or surfaces, the opposite the photocatalytic layer are sensitive to provide protection.

• a) Herstellen einer Mischung umfassend mindestens eine hydrolysierbare Titanverbindung, ein organisches Lösungsmittel und Wasser in einer unterstöchiometrischen Menge, bezogen auf die hydrolysierbaren Gruppen der Titanverbindung,
• b) Behandeln der sich ergebenden Mischung bei einer Temperatur von mindestens 60°C unter Bildung einer Dispersion oder eines Niederschlags von dotierten TiO₂-Teilchen,
• c) gegebenenfalls Lösungsmittelaustausch durch Entfernen des Lösungsmittels unter Bildung eines Pulvers von TiO₂-Teilchen und Zugabe eines anderen Lösungsmittels unter Bildung einer Dispersion von TiO₂-Teilchen,
• d) Auftragen der Dispersion auf das Substrat und
• e) Wärmebehandlung der aufgetragenen Dispersion unter Bildung einer photokatalytischen Schicht.

According to a first embodiment of the present invention, a method for producing a substrate with a photocatalytic layer is provided, which comprises the following steps:

• 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,
• b) treating the resulting mixture at a temperature of at least 60 ° C to form a dispersion or a precipitate of doped TiO ₂ particles,
• c) optionally solvent exchange by removing the solvent to form a powder of TiO ₂ particles and adding another solvent to form a dispersion of TiO ₂ particles,
• d) applying the dispersion to the substrate and
• e) heat treatment of the applied dispersion to form a photocatalytic layer.

In preferred embodiments, in the process for producing the TiO ₂ particles or for producing the substrate with a photocatalytic layer, at least one metal compound is additionally added to the mixture as a dopant in step a) and / or treated in step b) hydrothermally or by heating under reflux , with hydrothermal treatment being preferred.

The substrate that with the photocatalytic Layer to be provided can be made of any material suitable for this purpose his. examples for suitable materials are metals or metal alloys, glass, ceramics, including Oxide ceramics, glass ceramics or plastics. Of course substrates can also be used which have a surface layer from the above have mentioned materials. The surface layer can e.g. a metallization, an enamelling, a glass or ceramic layer or trade a paint job.

Examples of metals or metal alloys are steel, including stainless steel, chrome, copper, titanium, tin, zinc, brass and aluminum. Examples of glass are soda-lime glass, borosilicate glass, lead crystal and silica glass. It can be, for example, flat glass, hollow glass such as container glass, or laboratory equipment glass. The ceramic is, for example, a ceramic based on the oxides SiO ₂ , Al ₂ O ₃ , ZrO ₂ or MgO or the corresponding mixed oxides. Examples of the plastic, which, like the metal, can be in the form of a film, are polyethylene, for example HDPE or LDPE, polypropylene, polyisobutylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polytetrafluoroethylene, polychlorotrifluoroethylene, polyacrylates, polymethacrylates such as polymethyl methacrylate, polyamide, polyethylene , Polycarbonate, regenerated cellulose, cellulose nitrate, cellulose acetate, cellulose triacetate (TAC), cellulose acetate butyrate or rubber hydrochloride. A lacquered surface can be formed from conventional primers or lacquers.

To produce a photocatalytic layer on the substrate, a dispersion containing TiO ₂ particles is prepared according to the first embodiment of the invention in accordance with the sol-gel process explained later. The TiO ₂ particles can also precipitate out with the formation of a precipitate. Removal of the solvent gives a powder.

According to the method of the first embodiment according to the invention will first according to step a) 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, prepared, the mixture optionally also at least one Can include metal compound as a dopant.

The hydrolyzable titanium compound is in particular a compound of the formula TiX ₄ , the hydrolyzable groups X, which are different from one another or preferably the same, for example hydrogen, halogen (F, Cl, Br or I, in particular Cl and Br), alkoxy (preferably C _1-6 alkoxy, in particular C _1-4 alkoxy, such as methoxy, ethoxy, n-propoxy, i-propoxy, butoxy, i-butoxy, sec-butoxy and tert-butoxy), aryloxy ( preferably C _6-10 aryloxy, such as

Phenoxy), acyloxy (preferably C _1-6 acyloxy, such as acetoxy or propionyloxy) or alkylcarbonyl (preferably C _2-7 alkylcarbonyl, such as acetyl). An example of a halide is TiCl ₄ . Preferred hydrolyzable radicals X are alkoxy groups, in particular C _1-4 alkoxy. Specific and preferably used titanates are Ti (OCH ₃ ) ₄ , Ti (OC ₂ H ₅ ) ₄ and Ti (n- or i-OC ₃ H ₇ ) ₄ .

The mixture also contains water in a substoichiometric Amount, based on the hydrolyzable groups of the titanium compound, i.e. based on 1 mole of hydrolyzable groups in the titanium compound there is less than one mole of water. In other words with a hydrolyzable titanium compound with 4 hydrolyzable Groups, based on 1 mol of titanium compound, less than 4 mol of water added. Not more than 0.7 moles are preferred, 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 mole, more preferably not less than 0.30 Moles of water, based on 1 mole of hydrolyzable groups in the titanium compound, used.

In the preferred embodiments for the production of doped particles can be used as a metal compound for Any suitable metal compound can be used, e.g. an oxide, a salt or a complex, e.g. halides, Nitrates, sulfates, carboxylates (e.g. acetates) or acetylacetonates. The connection should be in the for the mixture used solvent expediently soluble his. Any metal, in particular a metal, is suitable as the metal selected from the 5th to 14th group of the Periodic Table of the Elements and the Lanthanoids and actinides. The groups are here accordingly the new IUPAC system, as in Römpp Chemistry Lexicon, 9th edition, is reproduced. The metal can be in of the compound occur in any suitable oxidation precursor.

According to the new IUPAC system groups 1, 2 and 13 to 18 the 8 main groups (IA to VIIIA according to CAS), groups 3 to 7 subgroups 3 to 7 (IIIB to VIIB according to CAS), groups 8 to 10 of subgroup 8 (VIII according to CAS) and groups 11 and 12 subgroups 1 and 2 (Cu and Zn groups, IB and IIB according to CAS).

Examples of suitable metals for the metal compound are W, Mo, 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), 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 WO ₃ , MoO ₃ , FeCl ₃ , silver acetate, zinc chloride, copper (II) chloride, indium (III) oxide and tin (IV) acetate.

The quantitative ratio between the metal compound and the titanium compound hangs also on the metal used and its oxidation state. In general, e.g. such proportions used that a molar ratio from metal of metal compound to titanium of titanium compound (Me / Ti) from 0.0005: 1 to 0.2: 1, preferably 0.001: 1 to 0.1: 1 and more preferred 0.005: 1 to 0.1: 1 results.

An organic solvent in which the hydrolyzable titanium compound is preferably soluble is used as the solvent. 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 (C ₁ -C ₄ alcohols), such as ethanol, 1-propanol, i-propanol, sec-butanol, tert-butanol, isobutyl alcohol, n-butanol and the pentanol isomers , in particular 1-pentanol, 1-propanol and 1-pentanol being particularly preferred.

The mixture preferably contains a catalyst for the Hydrolysis and condensation under sol-gel conditions, in particular an acidic condensation catalyst, e.g. Hydrochloric acid, phosphoric acid or Formic acid.

The resulting mixture is then treated at a temperature of at least 60 ° C to form a dispersion or a precipitate of doped or undoped TiO ₂ particles. This heat treatment is preferably carried out hydrothermally or by heating under reflux. A relatively high dilution is expediently used in the heat treatment, in particular when heating under reflux.

The heat treatment is preferably carried out using a Period of at least 1 h to 30 h, preferably at least 4 h to 24 h, the duration depending on the temperature and one if necessary applied pressure depends.

Heating under reflux suitably takes place via a period of at least 16 hours, e.g. if 1-pentanol as solvent is used. Hydrothermal treatment means generally a heat treatment an aqueous solution or suspension under pressure, e.g. at a temperature above the boiling point of the solvent and a pressure over 1 bar. In the present invention, heat treatment is also performed predominantly in one organic solvents, that if anything contains little water, under pressure understood as a hydrothermal treatment.

In hydrothermal treatment the mixture is placed in a closed container or in a closed Autoclaves heat treated. The treatment is preferably carried out at a temperature in the range of 75 ° C up to 300 ° C, preferably about 200 ° C, more preferred 225 to 275 ° C, e.g. about 250 ° C. Because of the warming, especially about the boiling point of the solvent, is in the closed container or Autoclave built up a pressure (autogenous pressure). The received one Pressure can e.g. about 1 bar, especially 50 to 500 bar or more, preferably 100 to 300 bar, e.g. 200 bar. As a rule, the hydrothermal treatment takes place at least 1 h and preferably at least 6 h to 7 h.

The heat treatment according to step b) is carried out until the desired doped or undoped TiO ₂ particles are formed. The dispersion or the precipitate can be used directly or after solvent exchange for the coating of the substrate. In order to obtain the powder of TiO ₂ particles, the solvent is removed as in the solvent exchange. Solvent removal procedures are described below.

The obtained doped or undoped TiO ₂ particles of the dispersion, the precipitate or the powder are predominantly crystalline in the anatase form. The crystalline fraction of the doped TiO ₂ particles obtained preferably makes up more than 90%, preferably more than 95% and in particular more than 97%, ie the amorphous fraction is in particular below 3%, for example 2%. The average particle size (volume average determined by X-ray diffraction) is preferably not more than 20 nm, more preferably not more than 10 nm. In a particularly preferred embodiment, particles with an average particle size of about 2 to 10 nm are obtained. When doping the TiO ₂ particles, a particularly homogeneous distribution of the doping metals is obtained.

The dispersion obtained can be used as such for coating the substrate. A solvent exchange is expediently carried out beforehand. It is preferred that the particles are separated from the solvent from the dispersion obtained in step b). All methods known to the person skilled in the art can be used for this. Centrifugation is particularly suitable. The separated TiO ₂ particles are then dried (for example at 40 ° C. and 10 mbar). The particles can also be stored well in this form.

For application to the substrate, the TiO ₂ particles are dispersed again in a solvent. The solvents or water listed above are suitable for this, for example. A water / alcohol mixture and particularly preferably water alone is preferably used as the solvent.

In a preferred embodiment becomes an inorganic to the dispersion obtained after step b) or c) or organically modified inorganic matrix-forming material given. In particular, this can be inorganic brine or organically modified inorganic hybrid materials or nanocomposites act. Examples of this are optionally organically modified oxides, hydrolysates and (poly) condensates of at least one glass or ceramic-forming element M, in particular an element M from groups 3 to 5 and / or 12 to 15 of the periodic table of the elements, preferably of Si, Al, B, Ge, Pb, Sn, Ti, Zr, V and Zn, especially those of Si and Al, most preferably Si, or mixtures thereof. It can also pro rata elements of groups 1 and 2 of the periodic table (e.g. Na, K, Ca and Mg) and groups 5 to 10 of the periodic table (e.g. Mn, Cr, Fe and Ni) or lanthanoids in the oxide, hydrolyzate or (poly) condensate to be available. A preferred organically modified inorganic Hybrid materials are polyorganosiloxanes. Be particularly preferred therefor Hydrolysates of glass or ceramic-forming elements, in particular of silicon used.

The inorganic or organic modified inorganic matrix-forming material is preferred in such Amount added that the molar ratio of titanium to the titanium compound for glass or ceramic-forming element M 100: 0.01 to 0.01: 100, is preferably 300: 1 to 1: 300. Very good results will be at a molar ratio Obtain Ti / M from about 10: 3 to 1:30. By adding this one Improved liability. If an organically modified inorganic matrix-forming material is used, all or only part of the glass or ceramic-forming elements contained M one or more organic groups as non-hydrolyzable Have groups.

The inorganic or organic modified inorganic matrix-forming materials can according to known methods, e.g. by flame pyrolysis, Plasma processes, gas phase condensation processes, colloid techniques, precipitation, Sol-gel process, controlled nucleation and growth processes, MOCVD process and (micro) emulsion process. If from the procedure solventless Particles are obtained, these are suitably in one solvent dispersed.

The inorganic sols and in particular the organically modified hybrid are preferred materials obtained using the sol-gel process. In the sol-gel process, which can also be used for the separate production of the particles, hydrolyzable compounds are usually hydrolyzed with water, optionally with 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. Stoichiometric amounts of water, but also smaller or larger amounts can be used. The sol which forms can be adjusted to the viscosity desired for the coating composition by means of suitable parameters, for example degree of condensation, solvent or pH. Further details of the sol-gel process are available, for example, from 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 process the oxides, hydrolysates or (poly) condensates by hydrolysis and / or condensation from hydrolyzable compounds of the above receive the glass or ceramic-forming elements mentioned, if appropriate for the production of the organically modified inorganic hybrid material additionally wear non-hydrolyzable organic substituents.

Inorganic sols are formed by the sol-gel process, in particular from hydrolyzable compounds of the general formulas MX _n , where M is the glass or ceramic-forming element defined above, X is as defined in formula (I) below, two groups X being by an oxo group can be replaced, and n corresponds to the valence of the element and is usually 3 or 4. They are preferably hydrolyzable Si compounds, in particular of the formula (I) below.

Examples of usable hydrolyzable compounds of elements M which are different from Si are Al (OCH ₃ ) ₃ , Al (OC ₂ H ₅ ) ₃ , Al (OnC ₃ H ₇ ) ₃ , Al (OiC ₃ H ₇ ) 3, Al (On-CaH ₉ ) ₃ , Al (O-sec.-C ₄ H ₉ ) ₃ , AlCl ₃ , AlCl (OH) ₂ , Al (OC ₂ H ₄ OCaH ₉ ) ₃ , TiCl ₄ , Ti (OC ₂ H ₅ ) ₄ , Ti (OnC ₃ H ₇ ) ₄ , Ti (OiC ₃ H ₇ ) ₄ , Ti (OC ₄ H ₉ ) ₄ , Ti (2-ethylhexoxy) ₄ , ZrCl ₄ , Zr (OC _Z H ₅ ) ₄ , Zr (OnC ₃ H ₇ ) ₄ , Zr (OiC ₃ H ₇ ) ₄ , Zr (OC ₄ H ₉ ) ₄ , ZrOCl ₂ , Zr (2-ethylhexoxy) ₄ , and Zr compounds which have complexing radicals, such as, for example, β-diketone and (meth) acrylic residues, sodium methylate, potassium acetate, boric acid, BCl ₃ , B (OCH ₃ ) ₃ , B (OC ₂ H ₅ ) ₃ , SnCl ₄ , Sn (OCH ₃ ) ₄ , Sn (OC ₂ H ₅ ) ₄ , VOCl ₃ and VO (OCH ₃ ) ₃ .

The explanations given below for the preferred silicon also apply mutatis mutandis to the other elements M. The sol or the organically modified inorganic hybrid material is particularly preferably obtained from one or more hydrolyzable and condensable silanes, at least one silane optionally having a non-hydrolyzable organic radical. One or more silanes with the following general formulas (I) and / or (II) are particularly preferably used: SiX ₄ (I) in which the radicals X are identical or different and denote hydrolyzable groups or hydroxyl groups, RaSiX _{(4 – a)} (II) wherein R is the same or different and represents a non-hydrolyzable radical which optionally has a functional group, X has the above meaning and a has the value 1, 2 or 3, preferably 1 or 2.

In the above formulas, the hydrolyzable groups X are, for example, hydrogen or halogen (F, Cl, Br or I), alkoxy (preferably C _1-6 alkoxy, such as methoxy, ethoxy, n-propoxy, i-propoxy and butoxy), Aryloxy (preferably C _6-10 aryloxy such as phenoxy), acyloxy (preferably C _1-6 acyloxy such as acetoxy or propionyloxy), alkylcarbonyl (preferably C _2-7 alkylcarbonyl such as acetyl), amino, monoalkylamino or dialkylamino with preferably 1 to 12, in particular 1 to 6, carbon atoms in the alkyl group (s).

The non-hydrolyzable radical R is, for example, alkyl (preferably C _1-6 -alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl and t-butyl, pentyl, hexyl or cyclohexyl), alkenyl ( preferably C _2-6 alkenyl, such as vinyl, 1-propenyl, 2-propenyl and butenyl), alkynyl (preferably C _2-6 alkynyl, such as acetylenyl and propargyl) and aryl (preferably C _6-10 aryl, such as phenyl and naphthyl).

The radicals R and X mentioned can, if appropriate one or more common ones Substituents, e.g. Halogen, ether, phosphoric acid, sulfonic acid, cyano, Amide mercapto, Thioether or alkoxy groups, as functional groups.

The radical R can contain a functional group via which crosslinking is possible. Specific examples of the functional groups of the radical R are epoxy, hydroxy, amino, monoalkylamino, dialkylamino, carboxy, allyl, vinyl, acrylic, acryloxy, methacrylic, methacryloxy, cyano, aldehyde and alkylcarbonyl groups. These groups are preferably bonded to the silicon atom via alkylene, alkenylene or arylene bridge groups which can be interrupted by oxygen or sulfur atoms or NH groups. The bridging groups mentioned are derived, for example, from the alkyl, alkenyl or aryl radicals mentioned above. The bridging groups of the radicals R preferably contain 1 to 18, in particular 1 to 8 Koh lenstoffatome.

Particularly preferred hydrolyzable Silanes of the general formula (I) are tetraalkoxysilanes, such as tetramethoxysilane and especially tetraethoxysilane (TEOS). Obtained by acid catalysis inorganic brine, e.g. TEOS hydrolyzates are particularly preferred. Particularly preferred organosilanes of the general formula (II) are Epoxysilanes such as 3-glycidyloxypropyltrimethoxysilane (GPTS), methacryloxypropyltrimethoxysilane and acryloxypropyltrimethoxysilane, with GPTS hydrolyzates being advantageous can be used.

If an organically modified inorganic hybrid material is produced, only silanes of the formula (II) or a mixture of silanes of the formula (I) and (II) can be used. In the case of the inorganic sols based on silicon, only silanes of the formula (I) are used, where appropriate proportionally hydrolyzable compounds of the above formula MX _{n are} added.

If the inorganic sol from in solvent dispersed discrete oxide particles, they can be the hardness of the Improve layer. These particles are in particular around nanoscale inorganic particles. The particle size (x-ray determined volume average) is e.g. in the range of less than 200 nm, especially below 100 nm, preferably below 50 nm, e.g. 1 nm to 20 nm.

According to the invention, for example, inorganic sols of SiO ₂ , ZrO ₂ , GeO ₂ , CeO ₂ , ZnO, Ta ₂ O ₅ , SnO ₂ and Al ₂ O ₃ (in all modifications, in particular as boehmite AlO (OH)), preferably sols of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , GeO ₂ and mixtures thereof can be used as nanoscale particles. Some of these sols are also commercially available, for example silica sols, such as the Levasile ^® from Bayer AG.

As inorganic or organic modified inorganic matrix-forming material can also be a Combination of such nanoscale particles with as hydrolyzates or (poly) condensate inorganic sols or organically modified Hybrid materials are used, which is what with nanocomposites referred to as.

If necessary, organic monomers, Oligomers or polymers of all kinds as organic matrix-forming Materials may be included that serve as flexibilizers, where it is common can act organic binders. These can improve the coatability be used. As a rule, they will be available upon completion Layer degraded photocatalytically. The oligomers and polymers can be functional Have groups about which makes networking possible is. This networking opportunity is also optionally in the organically modified above inorganic matrix-forming materials possible. Mixtures of inorganic, organically modified inorganic and / or organic matrix-forming Materials are possible.

Examples of usable organic matrix-forming materials are polymers and / or oligomers which have polar groups, such as hydroxyl, primary, secondary or tertiary amino, carboxyl or carboxylate groups. Typical examples are polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyvinyl pyridine, polyallyl amine, polyacrylic acid, polyvinyl acetate, polymethyl methacrylic acid, starch, gum arabic, other polymeric alcohols such as, for example, polyethylene-polyvinyl alcohol copolymers, polyethylene glycol, polypropylene glycol and poly (4-vinyl phenol monomers) or poly (4-vinyl phenol monomers) thereof or oligomers. The polyvinyl alcohol can be used eg the commercially available Mowiol ^® 18-88 from Messrs. Hoechst.

The degree of dilution as per step d) the dispersion to be applied depends et al of the desired Layer thickness. Generally the dispersion has a solids content of less than 50% by weight, in particular less than 20% by weight and preferably less than 10% by weight, e.g. 2.5% by weight.

For the order will be the usual Method used, e.g. Diving, rolling, squeegees, flooding, pulling, Spray, spin or spread. The applied dispersion is optionally dried and heat treated, for hardening or Compression. The one for that heat treatment used depends of course Substrate. In the case of plastic substrates or plastic surfaces, the usually have a barrier layer (see below), naturally cannot very high temperatures can be used. So become polycarbonate (PC) substrates e.g. at about 130 ° C for 1 h heat treated. In general, the heat treatment takes place e.g. at a temperature of 100 to 200 ° C and, if no plastic is present up to 500 ° C or more. The heat treatment e.g. 15 min to 2 h. As a rule, layer thicknesses of 50 nm to 30 μm obtained, preferably 100 nm to 1 μm, e.g. 50 to 700 nm.

The inorganic sol or the organic-modified inorganic hybrid material not only serve as a matrix-forming material for the photocatalytic layer, but also for improved layer adhesion. TiO ₂ can be present in the layer as a matrix-forming component and / or as particles.

The photocatalytic layer will optionally and preferably by irradiation with visible and / or UV light activated, e.g. with a high pressure mercury lamp of 700 W for 1 to 5 min 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. Preference is given to UV light or a high proportion of UV light. It becomes exceptionally active photocatalytic Get layers, the efficiency compared to the prior art about can be increased up to 10 times.

As already mentioned above, substrates made of a sensitive material or a surface layer (for example a coating or an enamel) are made of such a sensitive material a direct order is not possible or only possible with difficulty. A barrier layer can be arranged between the substrate (optionally with a surface coating) and the photocatalytic layer. An inorganic layer made of an inorganic matrix-forming material can be used for this. The inorganic sols described above can be used for this.

Furthermore, it was found according to the invention that it is possible to obtain a photocatalytic layer with an “integrated” barrier layer by forming a concentration gradient of TiO ₂ in the photocatalytic layer. This barrier layer can be used advantageously not only for the photocatalytic layers produced according to the invention, but also for the customary photocatalytic layers.

Accordingly, according to a second embodiment of the invention, a substrate with a photocatalytic layer is provided, which comprises photocatalytically active TiO ₂ and a matrix material, the TiO _{2 being contained} in a concentration gradient such that the concentration of the TiO ₂ accumulates on the surface of the photocatalytic layer is, wherein a purely inorganic barrier layer is preferably formed between the photocatalytically active TiO ₂ and the substrate.

These photocatalytic layers with such a concentration gradient of TiO ₂ that the concentration of TiO ₂ is greatest on the surface of the photocatalytic layer can be produced in particular by a method in which surface-modified TiO ₂ particles in a matrix-forming material automatically generate a concentration gradient form.

The customary TiO ₂ particles known from the prior art can be used for surface modification, which are commercially available, for example. TiO ₂ particles are available, for example, as P25 (d ₅₀ = 30-40 nm) from Degussa.

In the second embodiment of the invention, doped or undoped TiO ₂ particles can be used. The doping can be carried out using the methods known in the prior art, it being possible to use the doping metals known in the art, for example the metals mentioned above for the first embodiment according to the invention. Surprisingly, the metal doping increases the activity.

TiO ₂ particles obtained by the sol-gel process are preferably used. The above-mentioned hydrolyzable titanium compounds can be used for this. In a preferred embodiment, particles are used which were produced in accordance with the first embodiment of the invention in accordance with steps a) and b), it being possible to produce doped or undoped TiO ₂ particles. All the details listed above also apply here. Particles produced by the hydrothermal process are preferably used. The particles are separated from the solvent as described above and dried.

A dispersion in a solvent is generally produced from the TiO ₂ particles. Toluene, for example, is suitable for this. A slurry of TiO ₂ particles in a solvent or a powder of TiO ₂ particles without a solvent can also be used. For this purpose, a surface modifier is added which has at least one hydrophobic or hydrophilic group, with hydrophobic groups being preferred.

Suitable surface modifiers are (preferably low molecular weight or oligomeric, but possibly also polymeric) compounds which, on the one hand, have one or more groups which react or at least react with reactive groups (such as OH groups) present on the surface of the TiO ₂ particles can interact, and on the other hand have at least one hydrophobic or hydrophilic group.

The surface of the TiO ₂ particles can be modified, for example, by mixing the particles with suitable compounds explained below, if appropriate in a solvent and in the presence of a catalyst. It is often sufficient to stir the surface modifier with the particles at room temperature for a certain period, for example over 1 to 3 hours.

The surface modifiers can, for example, form both covalent (including coordinative in the form of complexes) and ionic (salt-like) bonds to the surface of the TiO ₂ particles, while among the pure interactions, for example, dipole-dipole interactions, hydrogen bonds and van der Waals interactions are called. The formation of covalent bonds is preferred.

It is also preferred according to the invention that the surface modifiers have a relatively low molecular weight. For example the molecular weight may be less than 1,500, especially below 1000 and preferably less than 700. Of course, this includes much higher Molecular weight of the compounds not (e.g. up to 2,000 and more).

As Obertlächenmodifizierungsmittel having groups which react with the surface groups of the TiO ₂ particles or can echselwirken _W, for example, hydrolyzable silanes, carboxylic acids, carboxylic acid halides, Carbonsäureester, carboxylic anhydrides, oximes, β-dicarbonyl compounds such as β-diketones, alcohols, amines, alkyl halides and are their derivatives.

The concept of hydrophilicity / hydrophobicity is well known to the expert as the basic concept of chemistry. hydrophobic Collide substances or groups Water while Attract hydrophilic substances or groups of water. The hydrophilic Character can e.g. by hydroxy, oxy, carboxylate, sulfate, sulfonate functions or polyether chains are formed in the substance. As a hydrophobic Group are suitable e.g. long chain aliphatic hydrocarbon groups, e.g. with 3 to 30 or more carbon atoms, especially alkyl groups, aromatic groups, or groups containing at least one fluorine atom have, which are preferably hydrocarbon groups, especially alkyl radicals, having 3 to 20 or more carbon atoms and 1 to 30 fluorine atoms.

As a surface modifier preferably hydrolyzable silanes with at least one non-hydrolyzable hydrophobic or hydrophilic groups are used, those with a hydrophobic group are particularly preferred. It is about particularly preferred to hydrolyzable silanes, the at least one have non-hydrolyzable group having at least one fluorine atom (Fluorosilanes) or a long-chain aliphatic hydrocarbon group, e.g. with 3 to 30 carbon atoms, preferably an alkyl group, or contains an aromatic group.

The next to the hydrolyzable silanes usable surface modifiers with hydrophobic groups e.g. the formula R ° -Y where Y is -COOH, -OH, -COZ, -Z (with Z = halide as F, Cl, Br or I), -C (O) O (O) CB (where B is any residue of a carboxylic acid or R ° is or a functional group of the other compounds described above (which optionally includes a further group such as B) and R ° one long chain aliphatic hydrocarbon group, preferably one Alkyl group, e.g. with 3 to 30 C atoms, or an aromatic G group, such as optionally substituted phenyl or naphthyl, or one Hydrocarbon group, preferably an alkyl group, with at least is a fluorine atom. With a carboxylic acid ester e.g. the rest the carboxylic acid and / or the rest of the alcohol form the hydrophobic group.

The preferred hydrolyzable silanes having a long-chain aliphatic hydrocarbon group as the hydrophobic group have in particular the formula (II) (RaSiX _(4-a) ) explained above, in which 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 carbon atoms. The long-chain aliphatic hydrocarbon group is preferably an alkyl group. Optionally, silanes of the formula (II) can also be used, in which R is an optionally substituted aromatic group.

According to the invention, it is particularly preferred to use hydrolyzable silane compounds having at least one non-hydrolyzable radical as the hydrophobic group which have the general formula Rf (R) bSiX _{(3 – b)} (III) in which X and R are as defined in formula (I) or (II), Rf is a non-hydrolyzable group which has 1 to 30 fluorine atoms bonded to carbon atoms, preferably by at least two atoms, preferably one ethylene, propylene -, ethyleneoxy or propyleneoxy group, are separated from Si, and b is 0, 1 or 2, preferably 0 or 1. R is in particular a radical without a functional group, preferably an alkyl group, in particular C _1-4 alkyl such as methyl or ethyl. The groups Rf preferably contain 3 to 25 and in particular 3 to 21 fluorine atoms which are bonded to aliphatic (including cycloaliphatic) carbon atoms. Rf is preferably a fluorinated alkyl group with 3 to 20 C atoms, which is optionally interrupted by one or more oxygen atoms.

Examples of Rf are CF ₃ CH ₂ CH ₂ , C ₂ F ₅ CH ₂ CH ₂ , nC ₆ F ₁₃ CH ₂ CH ₂ , iC ₃ F ₇ OCH ₂ CH ₂ CH ₂ , nC ₈ F ₁₇ CH ₂ CH ₂ and nC ₁₀ F ₂₁ -CH ₂ CH ₂ .

Fluorine atoms that may be bound to aromatic carbon atoms (eg CsF ₄ ) are not taken into account. The fluorine-containing group Rf can also be a chelating ligand. It is also possible for one or more fluorine atoms to be located on a carbon atom from which a double or triple bond originates. Examples of fluorosilanes that can be used are CF ₃ CH ₂ CH ₂ SiCl ₂ (CH ₃ ), CF ₃ CH ₂ CH ₂ SiCl (CH ₃ ) ₂ , CF ₃ CH ₂ CH ₂ Si (CH ₃ ) (OCH ₃ ) ₂ , C ₂ F ₅ -CH ₂ CH ₂ -SiZ ₃ , nC ₆ F ₁₃ -CH ₂ CH ₂ SiZ ₃ , nC ₈ F ₁₇ -CH ₂ CH ₂ -SiZ ₃ , nC ₁₀ F ₂₁ -CH ₂ CH ₂ -SiZ ₃ with ( Z = OCH ₃ , OC ₂ H ₅ or Cl); iC ₃ F ₇ O-CH ₂ CH ₂ CH ₂ -SiCl ₂ (CH ₃ ), nC ₆ F ₁₃ -CH ₂ CH ₂ -Si (OCH ₂ CH ₃ ) ₂ , nC ₆ F ₁₃ -CH ₂ CH ₂ -SiCl ₂ (CH ₃ ) and nC ₆ F ₁₃ -CH ₂ CH ₂ -SiCl (CH ₃ ) ₂ . 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) triethoxysilane (FTS) is preferably used.

Examples of hydrolyzable silanes with long-chain aliphatic hydrocarbon group are hexadecyltrimethoxysilane (HDTMS), dodecyltriethoxysilane and propyltrimethoxysilane. Further Examples of surface modifiers with hydrophobic groups are heptadecafluoronanoic acid, stearic acid, heptafluorobutyric acid chloride, hexanoyl, hexanoate, Perfluoroheptanoic acid methyl ester, perfluorooctanoic anhydride, hexanoic, 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-pentadecafluorooctanol, octanol, hexyl chloride and nonafluorobutyl chloride.

In addition to the above-mentioned Ver, suitable surface modifiers with hydrophilic groups are suitable bond classes also unsaturated carboxylic acids, β-carbonyl carboxylic acids, with polymerizable double bonds, ethylenically unsaturated alcohols and amines, amino acids, epoxides and diepoxides.

Specific examples of organic Connections for surface modification with hydrophilic groups are diepoxides such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, Bis (3,4-epoxycyclohexyl) adipate, cyclohexanedimethanol diglycidyl ether, Neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, propylene glycol diglycidyl ether, Bisphenol A diglycidether, bisphenol F diglycidether, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and β-diketones such as acetylacetonate.

Other particularly preferred compounds for surface modification with hydrophilic groups are hydrolyzable silanes with at least (and preferably) a non-hydrolyzable residue with a hydroxy, Carboxylate or epoxy or glycidyloxy group, it being in particular are silanes of the formula (II). Examples are glycidyloxyalkyl trialkoxysilanes, such as 3-glycidyloxypropyltrimethoxysilane and 3-glycidyloxypropyltriethoxysilane.

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

For the surface modification, for example, 10 ml of solvent are used for 1 g of TiO ₂ powder. The dispersion obtained with the surface modifier is simply stirred, for example for 2 hours, as a result of which the surface modification of the particles is achieved. The ratio of TiO ₂ to added surface modifier is, based on moles, preferably 1: 0.005 to 1: 0.1 and in particular 1: 0.01 to 1: 0.02, this being particularly true for the surface modifier with at least one fluorine atom.

This is preferably followed by a Solvent exchange to another organic solvent, such as methyl ethyl ketone, acetone, chloroform or petroleum ether.

Then an inorganic or added organically modified matrix-forming material. Therefor can e.g. an inorganic sol or an organically modified one inorganic hybrid material is added as above for the first embodiment of the invention explained has been. It can too the above-mentioned nanoscale particles may be included.

The surface modifier is used to generate the concentration gradient in the matrix from the matrix-forming material. Surface modifiers with a hydrophobic group are used for a hydrophilic matrix and surface modifiers with a hydrophilic group are used for a hydrophobic matrix. This results in a potential difference that leads to segregation, so that the surface-modified TiO ₂ particles are enriched on the surface. Since the matrix-forming materials and the solvent that are used are generally hydrophilic, surface modification is preferably carried out with hydrophobic groups.

The dispersion obtained is applied to the substrate and the heat treatment is carried out in the customary manner, for example as described above. The hydrophobic character of the hydrophobic groups on the surface of the TiO ₂ particles results in segregation in the dispersion thus obtained, the surface-modified TiO ₂ particles being enriched on the surface of the photocatalytic layer after application to the substrate. During the hardening of the applied layer, a concentration gradient of the surface-modified TiO ₂ particles is thus formed in the other inorganic or organically modified matrix-forming material or in the matrix formed therefrom. In the lower area of the layer there is predominantly the inorganic or organically modified inorganic matrix-forming material or the matrix formed therefrom.

Upon exposure, the photocatalytic activity of the layer destroys at least the hydrophobic organic groups, which is evident from a considerable reduction in the contact angle after irradiation. As a result of the concentration gradient, the matrix of the inorganic or organically modified matrix-forming materials used, which essentially contains no TiO ₂ , is located at the interface with the substrate. If organically modified inorganic matrix-forming material was used, in the area in the photocatalytic layer in which areas enriched with TiO ₂ and essentially free of TiO ₂ adjoin, the photocatalytic oxidation of the organic constituents explained above for the “isolated” barrier layer takes place , so that an inorganic barrier layer is also formed there. Thus, according to the invention, a “built-in” barrier layer of inorganic material is formed, which can protect the substrate underneath.

In principle, all of the above can also be used here Substrates are used. The photocatalytic is particularly advantageous Layer with built-in barrier layer on a substrate made of glass or Plastic or a surface layer of the substrate applied from this material.

It was also found that a special hybrid layer made from an organically modified inorganic Material provides an excellent barrier layer. This barrier layer can not only for those produced according to the invention photocatalytic layers, but also in the usual photocatalytic layers can be used with advantage.

According to a third embodiment of the invention, a substrate is therefore provided with a photocatalytic layer containing TiO ₂ , which is characterized in that between the substrate and photocatalytic layer, a hybrid layer of an organically modified inorganic material is provided, the organic components of which have been photocatalytically decomposed at least at the interface with the photocatalytic TiO ₂ layer to form a purely inorganic protective layer.

This barrier layer offers on the one hand the advantage that a safe protection of sensitive materials from the photocatalytic layer is guaranteed, on the other the barrier layer can be applied wet-chemically in a simple manner and are applied without cracks in the desired layer thickness. Due to the organic components there is a certain flexibility in the Coating achieved, surprisingly despite the used organic components a secure barrier effect is achieved.

In principle, all of the above can be used as the substrate Substrates are used. The barrier layer is particularly advantageous on a substrate made of glass or plastic or a surface layer of the substrate applied from this material.

The barrier layer is a hybrid layer made of an organically modified inorganic material, the organic components of which have been photocatalytically decomposed at least at the interface with the photocatalytic TiO ₂ layer to form a purely inorganic protective layer.

To produce this hybrid layer, the above-described organic. modified inorganic hybrid material used as a coating composition. All the explanations given above for this material apply, unless stated otherwise, the hybrid material not being added to the dispersion containing TiO ₂ , but rather being applied as such to the substrate.

It will preferably be one organically modified inorganic hybrid material used, at not more than 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 mole% and especially at least 1 mole%, e.g. 0.1 to 10 mol%, preferably 1 to 3 mol%, of the glass-forming or ceramic-forming constituents contained Elements M have one or more organic groups. i.e. preferably not more than 10 mol% and in particular not more than 3 mole%, e.g. e.g. 0.1 to 10 mol%, preferably 1 to 3 mol%, of contained glass or ceramic-forming elements M have one or several organic groups. Preferably at least some have or all organic groups have a functional group via which networking possible is. The hybrid material is preferred according to the sol-gel process manufactured. As a solvent the above can be considered. Acts particularly preferred it is a hydrolyzate or condensate from silanes of the formula (I) and formula (II). If necessary, at least a part the silanes of formula (I) by other hydrolyzable compounds a glass or ceramic-forming element M to be replaced.

Is preferred for the production of Hybrid material a stoichiometric Amount of water added to the hydrolyzable compounds. The received Coating composition is e.g. as 1 to 70% by weight sol / gel (based on the solids content) used in an alcohol. A particularly preferably used combination of hydrolyzable Connections is TEOS and GPTS.

The organic-modified inorganic Hybrid material can preferably above-mentioned nanoscale particles to form a nanocomposite. To the organically modified inorganic hybrid materials are preferably not organic Polymers added, i.e. the coating composition is preferred free of organic polymers.

The hybrid material is applied on usual Manner, e.g. according to the procedure described above. The applied Layer is optionally dried and cured, the curing by Heat or Irradiation can take place. If necessary, the heat treatment done together with the photocatalytic layer. Regarding the The temperature and the duration apply to the above for the photocatalytic layer conditions mentioned. The layer thickness obtained is e.g. 50 to 1 μm, preferably 100 nm to 1 μm, e.g. 100 to 700 nm.

A TiO ₂ -containing composition which contains surface-modified TiO ₂ particles is applied to the hybrid layer. Here, surface-modified TiO ₂ particles are used, as explained above for the second embodiment of the invention. Surface modifiers with hydrophobic or hydrophilic groups can be used.

In general, photocatalytically active TiO ₂ particles are distributed in a matrix, and the TiO _{2 can} also be part of the matrix. The layer can also consist only of TiO ₂ . The matrix can generally be formed from inorganic or from organic-modified inorganic matrix materials. Accordingly, the composition can also contain inorganic or organically modified inorganic matrix-forming materials, as explained above. It can also contain the above-mentioned nanoscale particles. However, the composition can also contain only TiO ₂ particles, so that a photocatalytic layer is formed only from TiOz.

It was found that the layer made of the hybrid material changes into a purely inorganic system at least at the interface with the photocatalytic layer by means of photocatalytic oxidation of the organic portion. Here, the superimposed photocatalytically active layer causes a photocatalytic oxidation of the organic components of the hybrid layer underneath. This process is often limited to a few nanometers of the top layer of this layer because of the diffusion of holes and electrons only very short enough. By converting the top layer of the hybrid layer into an inorganic layer, the destruction process is stopped and an effective barrier layer is obtained, which prevents diffusion of sodium ions from glass substrates into the photocatalytic layer and protects sensitive plastic substrates against damage from the photocatalytic layer. In addition, the organic groups of the surface-modified TiO _{2 are} decomposed photocatalytically.

In all three embodiments described can further increase the photocatalytic effect can be achieved if one under the photocatalytic layer uses an electrically conductive base and / or the photocatalytic layer special electrically conductive particles added.

In the case of as electrically conductive particles doped metal oxides used may e.g. to endowed Tin oxide, such as ITO (indium tin oxide), ATO (antimony-doped tin oxide) and FTO (fluorine-doped tin oxide), and / or aluminum-doped Trade zinc oxide. It can also be an electrically conductive polymer, how BAYTRON are used by Bayer AG. Coming as a semiconductor for example optionally doped germanium or silicon in Consideration. The electrically conductive Particles can e.g. as a powder or in the form of a dispersion in a solvent for dispersion for be given the photocatalytic layer.

Preferably, if possible transparent conductive Particles used. This will ensure high light absorption, such as they z. B. by conductive Metal particles are avoided and still arise more effective photocatalytic layers.

Alternatively or simultaneously also an electrically conductive Underlay as a layer under the photocatalytically active layer be provided. It can be the case with the electrically conductive pad a metal, a semiconductor, an electrically conductive polymer or a doped metal oxide. Examples of the endowed Metal oxide, the semiconductor or the electrically conductive polymer are the same as the above as examples of the electrically conductive particles were called. examples for the metal, which is also a metal alloy can be steel, including Stainless steel, chrome, copper, titanium, tin, zinc, brass and aluminum.

The underlay can be applied as a layer be present in the substrate or be the substrate itself. For the application an electrically conductive Layer as a base on a substrate can be familiar to those skilled in the art Methods are used, e.g. wet chemical processes, deposition processes (Sputtering) or a metallization. Thin layers are generally sufficient out.

In all the embodiments explained, the substrates with the photocatalytic layers are fired, to get to purely inorganic layers. In addition, particles can also be found in all layers with a larger diameter, e.g. in the μm range to be built in.

The substrates according to the invention with the photocatalytic Layers can e.g. as self-cleaning surfaces (if necessary supported by irradiation with light) or be used for air purification.

The substrates produced according to the invention with photocatalytic layers are suitable for a wide variety of applications for antimicrobial Purposes and / or for self-cleaning, e.g. for machines, paints, varnishes, Furniture, Facades, roofs, Textiles, vehicles, signal systems, foils, protective and partition walls, traffic engineering, Automobiles, aircraft and rail vehicles, windows, doors, greenhouses, walls, tiles, Floors, tents, Planning, outdoor facilities, Fences, Natural stones, concrete, plasters, plasters, floor slabs, monuments, woods, slabs, Cladding, window frames, textiles, covers, concrete, plastic surfaces of all Type, plastic glazing, helmets, visors, housings, outdoor facilities, equipment of all kinds, e.g. medical equipment, Domestic appliances, Traffic signs, steel structures and steel facades. The layers are also suitable as anti-fog coatings, e.g. on glass, mirrors, Cladding or partitions. Magnetic, for example superparamagnetic, particles are coated.

A special area of application is the sterilization or protection of all kinds of instruments, and especially medical, including veterinary and dental devices and devices the sanitary area, against pollution, e.g. by infectious substances such as prions (e.g. for the Combat BSE). Important further areas of application are food technology and dairy farming.

Examples

The following abbreviations are used:
TEOS: tetraethoxysilane
FTS: (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) triethoxysilane
GPTS: (3-glycidyloxypropyl) trimethoxysilane
HDTMS: hexadecyltrimethoxysilane

example 1

Hydrothermal production of TiO ₂ (anatase)

9.6 g (0.034 mol) of titanium isopropylate (Ti (O ^I Pr) ₄ ) are added to 14.5 g of n-propanol and, after stirring for 5 minutes at room temperature, 0.67 g (0.0068 mol) of 37% HCl are added , After 20 minutes, 0.712 g (0.063 mol) of water are added with vigorous stirring.

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

Example 2

Hydrothermal production of doped TiO ₂ (anatase, dopant Sn (CH ₃ CO ₂ ) ₄ )

9.6 g (0.034 mol) of titanium isopropylate (Ti (O ^I Pr) ₄ ) are added to 14.5 g of n-propanol and, after stirring for 5 minutes at room temperature, 0.67 g (0.0068 mol) of 37% HCl are added , After 20 minutes, 0.712 g (0.063 mol) of water are added with vigorous stirring.

The mixture is then diluted with 41.9 g of n-propanol, whereupon the mixture is mixed with 0.635 g (0.0018 mol) of Sn (CH ₃ CO ₂ ) ₄ and treated at 250 ° C. and 200 bar pressure for 7 hours. The anatase formed is centrifuged off and dried at 50 ° C. and 10 mbar.

Example 3

Hydrothermal production of doped TiO ₂ (anatase, dopant WO ₃ )

9.6 g (0.034 mol) of titanium isopropylate (Ti (O ^I Pr) ₄ ) are added to 14.5 g of n-propanol and, after stirring for 5 minutes at room temperature, 0.67 g (0.0068 mol) of 37% HCl are added , After 20 minutes, 0.712 g (0.063 mol) of water are added with vigorous stirring.

The mixture is then diluted with 41.9 g of n-propanol, whereupon the mixture is mixed with 0.039 g (0.00017 mol) of WO ₃ and treated at 250 ° C. and 200 bar pressure for 7 hours. The anatase formed is centrifuged off and dried at 50 ° C. and 10 mbar.

Example 4

Surface modification of TiO ₂ (anatase) powder with FTS

In each case 1.0 g of the TiO ₂ powders prepared according to Examples 1 to 3 is mixed with 8.67 g of toluene and then mixed with 0.077 g of FTS. After stirring for 2 hours, the toluene is separated off in a rotary evaporator.

Example 5

Surface modification of TiO ₂ (anatase) powder with HDTMS

Of the TiO ₂ powders prepared according to Examples 1 to 3, 1.0 g are mixed with 8.67 g of toluene and 0.312 g of HDTMS are then added. After stirring for 2 hours, the toluene is separated off in a rotary evaporator.

Example 6 Production of a Photocatalytic Layer with Undoped TiO ₂ To produce a GPTS hydrolyzate, 5.4 g (0.3 mol) of water are added to 23.6 g (0.1 mol) of GPTS. The mixture is then stirred at room temperature overnight.

0.05 g of the FTS-modified, undoped TiO ₂ powder prepared according to Example 4 is dispersed in 1.56 g of MEK (methyl ethyl ketone) and then mixed with 0.44 g of formamide. The dispersion obtained is mixed with 4.14 g of the GPTS hydrolyzate prepared with stirring.

The coating composition obtained is applied by means of a spin coater applied at 1000 rpm on polycarbonate plates (PC plates) of 10 cm × 10 cm. Then be the plates at 128 ° C Hardened for 1 hour. The layer thicknesses are 2 to 3 μm. The contact angle of the obtained Layers against water is 101 °.

The coated PC boards are Irradiated for 4 min with a xenon lamp (750 W). After the radiation The contact angle of the PC plates against water was only 10 °.

The temporal changes are used to determine the photocatalytic activity of the PC plates obtained tion of light absorption at 553 nm determined by a rhodamine B solution. For this, 20 ml of an aqueous rhodamine B solution (concentration 6 ppm) are brought into contact with the PC plate, which is irradiated with a xenon lamp (750 W). The absorption of the rhodamine B solution at 553 nm is measured at intervals to monitor the degradation of rhodamine B. After about an hour, the entire rhodamine B is broken down.

Example 7

Production of a photocatalytic layer with Sn-doped TiO ₂

0.05 g of the HDTMS-modified, Sn-doped TiO ₂ powder prepared according to Example 5 are dispersed in 1.56 g of petroleum ether and then mixed with 0.44 g of formamide. The dispersion obtained is mixed with 4.14 g of the GPTS hydrolyzate prepared as in Example 6 with stirring.

The coating composition obtained is applied by means of a spin coater applied at 1000 rpm on polycarbonate plates (PC plates) of 10 cm × 10 cm. Then be the plates at 128 ° C Hardened for 1 hour. The layer thicknesses are 2 to 3 μm. The contact angle of the obtained Layers against water is 92 °.

The coated PC boards are Irradiated for 4 min with a xenon lamp (750 W). After the radiation the contact angle of the PC plates against water was less than 10 °.

The photocatalytic activity of the obtained PC plates are made according to the same experimental setup as in example 6 by determining the light absorption at 553 nm from a rhodamine B solution certainly. All of the rhodamine B is broken down after about 35 minutes.

Example 8

manufacturing of photocatalytic layers with TEOS hydrolyzate

For the production of a TEOS hydrolyzate 12.36 g (0.0594 mol) of TEOS in 15.96 g of ethanol with 9.06 g of water added. Then stir 0.2 g concentrated (37%) HCl added. After stirring for 1 h 0.28 g GPTS added and stirred at room temperature overnight. you receives a TEOS hydrolyzate with 2 mole% GPTS.

A 2.5% by weight solution in methyl ethyl ketone is prepared from each of the FTS-modified TiO ₂ powders (undoped, doped with Sn and doped with W) produced in Example 4 and with 0.2 g of the TEOS hydrolyzate produced, the 2nd Mol% contains GPTS (molar ratio Ti: Si = 10: 5), mixed.

The coating composition obtained is applied to polycarbonate plates by means of a spin coater (PC plates) of 10 cm × 10 cm applied. Subsequently the plates at 128 ° C Hardened for 1 hour.

Example 9

Determination of the photocatalytic activity of layers with doped TiO ₂

To determine the photocatalytic activity, layers with doped TiO _{2 are} examined. For this purpose, Sn-doped TiO ₂ powder (Sn (1V)), W-doped TiO ₂ powder (W (VI)), Fe-doped TiO ₂ powder (Fe (III)) and In-doped TiO ₂ - Powder (In (III)) used in different ratios of Ti to doping metal.

The Sn- and W-doped TiO ₂ powders are produced according to Examples 2 and 3 with Sn (CHsCO ₂ ) ₄ and WO ₃ , the amounts used corresponding to the desired ratio of Ti to dopant (0.5 to 10 mol% of dopant ) can be varied. In an analogous manner, doped TiO ₂ powders are produced with FeCl ₃ and In ₂ O ₃ . For comparison, unmodified anatase is also produced under the same conditions.

A 2.5% by weight solution in methyl ethyl ketone is prepared in each case from the doped TiO ₂ powders prepared and mixed with 0.2 g of TEOS hydrolyzate, prepared as in Example 8, which contains 2 mol% of GPTS.

The coating composition obtained is applied to polycarbonate plates by means of a spin coater (PC plates) applied. The plates are cured at 128 ° C for 1 h.

The photocatalytic activity is again determined using a rhodamine B solution (6 ppm in H ₂ O). The coated plates are each contacted with 20 ml of the Rhodamine B solution and then irradiated with UV light for 10 min. The absorption of the rhodamine B solution is then measured at 553 nm. For comparison, measurements on rhodamine B without contact with photocatalytic layers are also carried out in the same way and performed in contact with undoped anatase. The results are shown in the table below. It can be seen from this that significantly faster degradation rates can sometimes be achieved by doping. Table: Absorption at 553 nm after 10 min of UV radiation

Claims (36)

Substrate with a photocatalytic layer which comprises photocatalytically active TiO ₂ and a matrix material, the TiO _{2 being contained} in a concentration gradient such that it is enriched on the surface of the photocatalytic layer. Substrate with a photocatalytic layer according to claim 1, characterized in that a purely inorganic barrier layer is formed between the photocatalytically active TiO ₂ and the substrate. Substrate with a photocatalytic layer according to claim 1 or 2, characterized in that the photocatalytic layer comprises an inorganic or organically modified inorganic matrix material. Substrate according to one of claims 1 to 3, characterized in that the TiO _{2 is} doped. Substrate according to one of claims 1 to 4, characterized in that that there is an electrically conductive layer under the photocatalytic layer Underlay. Substrate according to one of claims 1 to 5, characterized in that that under the photocatalytic layer is a hybrid layer an organically modified inorganic material is. Substrate according to one of claims 1 to 6, characterized in that that the photocatalytic layer is microstructured. A process for producing a substrate with a photocatalytic layer, according to claim 1, comprising the steps of a) mixing TiO ₂ particles with a surface modifier to effect a surface modification of the TiO ₂ particles, b) adding an inorganic or organically modified inorganic matrix-forming material , c) applying the dispersion obtained to the substrate, d) curing the applied dispersion to form a photocatalytic layer and e) photocatalytically decomposing at least the organic groups of the surface-modified TiO ₂ particles enriched on the surface of the photocatalytic layer. A method according to claim 8, characterized in that the Surface modifiers contains at least one hydrophobic group. A method according to claim 9, characterized in that the hydrophobic group has at least one fluorine atom and / or one long chain aliphatic hydrocarbon group or an aromatic group is. Method according to one of claims 8 to 10, characterized in that that the surface modifier from hydrolyzable silane compounds, carboxylic acids, carboxylic acid halides, Carbonsäureestern, carboxylic, Oximes, β-dicarbonyl compounds, Alcohols, amines, alkyl halides and their derivatives is selected. Method according to one of claims 8 to 11, characterized in that the TiO ₂ particles have been produced by 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 , b) treating the resulting mixture at a temperature of at least 60 ° C to form a dispersion or a precipitate of TiO ₂ particles, c) optionally removing the solvent to form a powder of TiO ₂ particles and optionally replacing the solvent by adding a other solvent. Method according to one of claims 8 to 12, characterized in that that the layer obtained after step d) is activated by radiation becomes. Method according to one of claims 8 to 13, characterized in that nanoscale TiO ₂ particles are used, preferably with an average particle size below 200 nm and in particular below 50 nm. Method according to one of claims 8 to 14, characterized in that that curing through heat treatment and / or irradiation takes place, the in the case of irradiation organically modified inorganic matrix-forming material functional Has groups about which make networking possible is. Substrate with a photocatalytic layer containing TiO ₂ , characterized in that a hybrid layer made of an organically modified inorganic material is provided between the substrate and the photocatalytic layer, the organic components of which layer, at least at the interface with the photocatalytic layer containing TiO ₂ , to form a purely inorganic layer Barrier layer have been decomposed photocatalytically. A substrate according to claim 16, characterized in that the Hybrid layer at least at the interface to the substrate from one organically modified inorganic material. Substrate according to claim 16 or 17, characterized in that the TiO _{2 is} doped. Substrate according to one of claims 16 to 18, characterized in that that there is an electrically conductive layer under the photocatalytic layer Underlay. Substrate according to one of claims 16 to 19, characterized in that that the photocatalytic layer is microstructured. A method for producing a substrate according to claim 16, comprising the steps of a) applying an organically modified inorganic matrix-forming material to the substrate to form a hybrid layer, b) applying a composition containing TiO ₂ particles to the hybrid layer obtained, the TiO ₂ particles passing through Mixing of TiO ₂ particles with a surface modifier have been surface-modified to form the photocatalytic layer, c) photocatalytic decomposition of the organic groups of the surface-modified TiOz and the organic constituents of the hybrid layer, at least in the interface area with the photocatalytic, surface-modified TiO ₂ -layer, forming a pure inorganic barrier layer. A method according to claim 21, characterized in that the Surface modifiers contains at least one hydrophobic group. A method according to claim 22, characterized in that the hydrophobic group has at least one fluorine atom and / or one long chain aliphatic hydrocarbon group or an aromatic group is. Method according to one of claims 21 to 23, characterized in that that the surface modifier from hydrolyzable silane compounds, carboxylic acids, carboxylic acid halides, Carbonsäureestern, carboxylic, Oximes, β-dicarbonyl compounds, Alcohols, amines, alkyl halides and their derivatives is selected. Method according to one of claims 21 to 24, characterized in that the layer containing TiO _{2 is} activated by irradiation. Method according to one of claims 21 to 25, characterized in that that the organically modified inorganic matrix-forming material a nanocomposite with nanoscale inorganic particles, preferably below 200 nm. Method according to one of claims 21 to 26, characterized in that nanoscale TiO ₂ particles are used, preferably with an average particle size below 200 nm and in particular below 50 nm. Method according to one of claims 21 to 27, characterized in that that the organically modified inorganic matrix-forming material from an organically modified inorganic hydrolyzate and / or Polycondensate from at least one hydrolyzable compound, which does not include a non-hydrolyzable organic group, and at least a hydrolyzable compound having at least one non-hydrolyzable organic group, not more than 10 mol% of the hydrolyzable Compounds at least one non-hydrolyzable organic group contain, is formed. A method of manufacturing a substrate having a photocatalytic layer comprising the steps of 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, b) treating the resulting mixture a temperature of at least 60 ° C. to form a dispersion or a precipitate of TiO ₂ particles, c) if appropriate, solvent exchange by removing the solvent to form a powder of TiO ₂ particles and adding another solvent to form a dispersion of TiO ₂ - Particles, d) applying the dispersion to the substrate and e) heat treating the applied dispersion to form a photocatalytic layer. A method according to claim 29, characterized in that in Step a) additionally at least one metal compound added to the mixture as a dopant becomes. A method according to claim 29 or 30, characterized in that that the mixture in step b) hydrothermally or by heating under Reflux is preferably treated hydrothermally. Method according to one of claims 29 to 31, characterized in that that in step a), based on 1 mol of hydrolyzable groups in the titanium compound, no more than 0.7 mol of water are added. Method according to one of claims 29 to 32, characterized in that that the metal compound consists of a compound of W (VI), Mo (VI), Zn (II), Cu (II), Au (III), Sn (IV), In (III), Fe (III), Co (II), V (V) and Pt (IV) selected becomes. Substrate with a photocatalytic layer, available after the method of one of the claims 29 to 33. Use of a substrate with a photocatalytic layer according to one of the claims 1 to 7, 16 to 20 and 34 as a self-cleaning substrate or as substrate to be cleaned with the aid of radiation. Use according to claim 35 for the protection of medical used or hygienic area.