DE102008010663A1 - Alkali metal and / or alkaline earth metal doped titanium oxide nanoparticles and process for their preparation - Google Patents

Abstract

The invention relates to nanoscale titanium dioxide particles having greatly reduced or suppressed photocatalytic activity and to processes for their preparation. Furthermore, the invention relates to compositions containing these nanoscale particles and their use in optical materials.

Description

Field of the invention

The The invention relates to nanoscale titanium dioxide particles with greatly reduced or suppressed photocatalytic activity, and process for their preparation. Furthermore, the invention relates Compositions containing these nanoscale particles and their use in optical materials.

State of the art

nanoscale Particles play a role in the manufacture of optical materials major role. Thus, by using such nanoscale particles, that is, particles which have a have average particle size below 50 nm, optical materials produced with very high refractive indices become. Such materials are also referred to as composite materials. The particles used usually consist of doped or undoped Oxides such as indium tin oxide (ITO), zirconia, Barium titanate or titanium dioxide.

Especially Titanium Dioxide is due to its good availability and its especially high refractive index used very often. Of the three naturally occurring crystal modifications Brookit, Rutil and Anatas are just the last two of technical Importance. By treatment with high temperatures, Anatase is in Rutile convertible. Both are due to their electronic structure able to absorb UV light. So are coatings or Titanium dioxide particles are often used as additives in UV light-absorbing layers or compositions, for example in sunscreens. However, due to the semiconductor properties of titanium dioxide form upon absorption of UV light reactive electron / hole pairs, which have a relatively long recombination time. Therefore, you can Holes and electrons migrate to the surface and available there for chemical reactions. This property is also called photocatalytic activity or photocatalytic effect of titanium dioxide called. After a Theory is opposed to the photocatalytic effect of anatase the rutile due to its larger band gap of 3.05 eV (rutile) and 3.23 eV (anatase) are significantly more pronounced.

The The aforementioned photocatalytic activity is exemplified for the production of self-cleaning surfaces or used for cleaning wastewater.

For the use in optical materials represents the photocatalytic Activity is a big problem, as it is, for example leads to the decomposition of the matrix surrounding the particles.

In order to suppress the photocatalytic activity, there are basically two possibilities. On the one hand, it is known that special coatings, for example of Al ₂ O ₃ , SiO ₂ or ZrO ₂ , can prevent the diffusion of the electron / hole pairs to the surface. On the other hand, recombination possibilities for the electron / hole pairs can be generated by lattice doping of the titanium dioxide, so that likewise diffusion of the electron / hole pairs to the surface is prevented.

This is how the pamphlets describe WO 03/068682 , respectively. US 2005/0233146 doping with trivalent ions such as Al ^{+ 3,} Fe ^{+ 3,} or Rh ^3+. WO 99/060994 describes the doping with manganese or chromium ions.

Furthermore, it is known that sodium ions can interfere with the photocatalytic activity of titanium dioxide. This occurs, for example, if intentionally photocatalytic layers are applied to glass containing sodium ions and the sodium ions diffuse into the photocatalytic layer ( DE 102 35 803 , respectively. WO 04/005577 ).

simultaneously plays the size of the particles for optical Materials a big role. Particles of one size more than 70 nm break the light and are therefore no longer transparent. In addition, increases with the increase in specific surface area for smaller particles also their photocatalytic activity.

Lots Process for the preparation of nanoscale titanium dioxide particles are described in the literature. However, only a few describe Process the production of titanium dioxide particles which are also disperse to their primary particle size and have a size of less than 20 nm.

So describes DE 102 35 803 , respectively. WO 04/005577 the production of redispersible nanoscale titanium dioxide particles, which, however, have an increased photocatalytic activity by lattice doping.

The addition of tin, ammonium or sodium salts in the conversion of amorphous titanium dioxide particles into the rutile modification is for example WO 03/068682 , respectively. US 2005/0233146 known, but there they serve to reduce the particle size, while the particles themselves are doped with aluminum ions. A lattice doping with sodium ions to reduce the photocatalytic activity is not described.

task

task the invention is to provide nanoscale titanium dioxide particles, wherein the photocatalytic activity by the lattice doping reduced or completely suppressed. The In addition, particles should be based on primary particle size redispersible and by simple and inexpensive processes be produced.

solution

These Task is by the inventions with the characteristics of the independent Claims solved. Advantageous developments The inventions are characterized in the subclaims. The wording of all claims hereby by reference to the content of this description. The invention also includes all meaningful and especially all mentioned Combinations of independent and / or dependent Claims.

The The task is solved by nanoscale titanium dioxide particles at least one or more alkali metal ions and / or alkaline earth metal ions contain a type of alkali metal and / or alkaline earth metal ions. As a result, the electron / hole pairs caused by UV radiation are centers available for recombination.

Under Doping is inventively a share of up to 30 mol .-% of dopant in titanium dioxide based on Titanium understood.

Of the Proportion of doping is preferably between 0.01 to 30 mol .-% preferably between 1 to 15 mol%.

A average particle size of less than 20 nm, for example determined by X-ray, allows transparent UV-absorbing compositions, preferably a middle one Particle size below 10 nm, particularly preferred between 1 and 10 nm.

Furthermore are the particles of the invention on primary part size redispersible. This is as indicated above for incorporation For example, in plastics needed.

With Advantageous are the alkali metal ions and / or alkaline earth metal ions selected from the group comprising sodium, potassium, Lithium, calcium and magnesium ions, preferably sodium, potassium and lithium ions, more preferably sodium ions.

The Particles according to the invention can be used as anatase available.

The Inventive, particle-containing composite materials according to the invention or preparations can be obtained by shaping processes known to those skilled in the art, such as film casting, extrusion, electrophoresis, Further processing of injection molding and pressing. Possibly they can also be surface-modified z. B. with polymerizable or hydrophobic groups. This is off known in the art.

• (a) Herstellen einer Mischung umfassend mindestens eine hydrolysierbare Titanverbindung, ein organisches Lösungsmittel, einen sauren Kondensationskatalysator und mindestens eine Alkalimetallverbindung und/oder Erdalkalimetallverbindung;
• (b) Zugabe von Wasser in einer unterstöchiometrischen Menge, bezogen auf die hydrolysierbaren Gruppen der Titanverbindung;
• (c) Behandeln der sich ergebenden Mischung bei einer Temperatur von mindestens 60°C unter Bildung einer Dispersion oder eines Niederschlags von Titandioxid-Teilchen;
• (d) Entfernen des Lösungsmittels unter Bildung einer Paste oder eines Pulvers von Titandioxid-Teilchen.

The nanoscale particles of the invention are prepared by the following process:

• (a) preparing a mixture comprising at least one hydrolyzable titanium compound, an organic solvent, an acidic condensation catalyst and at least one alkali metal compound and / or alkaline earth metal compound;
• (b) adding water in a substoichiometric amount based on the hydrolyzable groups of the titanium compound;
• (c) treating the resulting mixture at a temperature of at least 60 ° C to form a dispersion or precipitate of titanium dioxide particles;
• (d) removing the solvent to form a paste or powder of titanium dioxide particles.

in the Below individual process steps are described in more detail. The steps do not necessarily have to be in the specified Order to be performed, and the procedure to be described may also have other, unspecified steps.

In particular, the hydrolyzable titanium compound is a compound of the formula TiX ₄ , where the hydrolyzable groups X, which are different 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, for example, methoxy, ethoxy, n-propoxy, isopropoxy, butoxy, isobutoxy, 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 for example, acetyl). An example of a halide is TiCl ₄ . Preferred hydrolyzable radicals X are alkoxy groups, in particular C _1-4 -alkoxy. Concrete 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 .

As the solvent, use is made of an organic solvent in which the hydrolyzable titanium compound is preferably soluble. The solvent is also preferably miscible with water. Examples of suitable organic solvents Means are, inter alia, alcohols, ketones, ethers, amides and mixtures thereof. Alcohols are preferably used, preferably lower aliphatic alcohols (C ₁ -C ₆ -alcohols), such as ethanol, 1-propanol, i-propanol, sec-butanol, tert-butanol, isobutyl alcohol, n-butanol and the pentanol isomers , in particular 1-pentanol, with 1-propanol and 1-pentanol being particularly preferred.

The Mixture also contains water in a substoichiometric Amount, based on the hydrolyzable groups of the titanium compound, d. H. based on 1 mole of hydrolyzable groups in the titanium compound There are less than one mole of water available. In other words are in a hydrolyzable titanium compound having 4 hydrolyzable groups, based on 1 mole of titanium compound, added less than 4 moles of water. Preferably not more than 0.7 mole, 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 0.30 mol, more preferably not less than 0.35 Mol of water based on 1 mol of hydrolyzable groups in the titanium compound.

The Mixture also contains a catalyst for the hydrolysis and condensation under sol-gel conditions, in particular a acidic condensation catalyst, e.g. Hydrochloric acid, phosphoric acid or formic acid.

When Alkali metal compound and / or alkaline earth compound can all compounds suitable for doping are used with Advantage, the compounds used are not basic. The hydrolysis The titanium compound takes place under acidic conditions. If basic compounds raise the pH of the mixture too much, There is a strong growth of the resulting titanium dioxide particles and it is no longer possible according to the invention To get particles. As basic compounds are compounds which anions of acids with a pKa of greater than 15, for example, alcoholates or hydroxyde. Will now try the pH of the mixture by the addition of acids, for example hydrochloric acid or nitric acid, may be encountered the solubility of the corresponding alkali metal and / or Alkaline salt exceeded in the solvent used and the ion intended for doping precipitates out as salt.

In an advantageous embodiment of the invention are used Alkali metal and / or alkaline earth metal compounds ionic, d. H. they are present as salts, including complex compounds therein are. Preferred cations are sodium, potassium, lithium, magnesium, and / or calcium ions, more preferably sodium ions. preferred Anions are halides, especially chloride or bromide, sulfate, Hydrogen sulfate, sulfite, hydrogen sulfite, nitrate, nitrite, sulfide, Phosphate, hydrogen phosphate, carbonate, bicarbonate, cyanide, thiocyanate, Isocyanate or anions of the oxo acids of halides, such as Perchlorate. Further preferred anions are the anions of mono- and polycarboxylic acids (carboxylates), such as formate, acetate, Oxalate, stearate, oleate or 3,6,9-trioxodecanate.

Prefers are alkali halides and alkali salts of fatty acids (including fatty acid derivatives with heteroatoms in the chain). Particular preference is given to sodium chloride, sodium acetate, sodium formate, Sodium oleate and sodium 3,6,9-trioxodecanate.

The Amount ratio between or provided for doping Alkali metal and / or alkaline earth metal compounds, is given as molar ratio (Me / Ti), between 0.0005: 1 to 0.3: 1, preferably 0.001: 1 to 0.2: 1, more preferably 0.005: 1 to 0.2: 1.

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

The Heat treatment preferably takes place via a Period of at least 1 h to 30 h, preferably at least 4 h to 24 h, with the duration of the temperature and one if necessary applied pressure depends.

The Heating under reflux is carried out appropriately over a period of at least 16 h, z. B. when 1-pentanol as solvent is used. Here comes the hydrothermal, lyothermal or the solvothermal treatment is used.

Under Lyothermal treatment is generally understood as a heat treatment a solution or suspension under pressure, z. At a temperature above the boiling point of the solvent and a pressure above 1 bar.

in the Special case of an aqueous solution or suspension the process is called a hydrothermal process. In the The present invention also provides a heat treatment in a predominantly organic solvent, the if there is little water at all, under overpressure understood as a hydrothermal treatment.

at The hydrothermal treatment is the mixture in a pressure vessel or an autoclave heat treated. The treatment is done preferably at a temperature in the range of 75 ° C to 300 ° C, preferably over 200 ° C, more preferably 225 ° C up to 275 ° C, z. B. about 250 ° C. By the warming, in particular the boiling point of the solvent, is in the closed container or autoclave Pressure built up (autogenous pressure). The resulting pressure can z. B. over 1 bar, in particular 50 to 500 bar or more, preferably 100 to 300 bar, z. B. 200 bar, amount. 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 c) is as long carried out until the desired doped titanium dioxide particles are formed.

The Dispersion or precipitate may be directly or after a solvent exchange further processed, for example for coating compositions, be used. In order to obtain the powder of titanium dioxide particles, As in the solvent exchange, the solvent away. Methods for removing the solvent are described below.

The obtained doped titanium dioxide particles of the dispersion, the precipitate or the powder are predominantly crystalline in the anatase form in front. Preferably, the crystalline portion of the resulting doped Titanium dioxide particles more than 90%, preferably more than 95% and in particular more than 97%, d. H. the amorphous portion is in particular below 3%, z. At 2%. The average particle size (X-ray determined volume average) is preferably no longer than 20 nm, more preferably not more than 10 nm. In one particular preferred embodiment, particles having a mean Particle size of about 2 to 10 nm obtained. The Titanium dioxide particles have a particularly homogeneous distribution of Doping metals on.

Around to get the particles as powders, it is necessary the particles, which are present as a dispersion, to be separated off from the solvent. For this purpose, all methods known in the art be used. Centrifugation is particularly suitable. The separated titanium dioxide particles are then dried (e.g. at 40 ° C and 10 mbar). In this form, the Particles can also be stored well.

The Dispersion obtained may also be in an advantageous embodiment further processed without removal of the solvent as such For example, to prepare a composition for Coatings Alternatively, a solvent exchange respectively. For this purpose, z. As those listed above Solvent or water. Preference is given to a water / alcohol mixture and more preferably, water is used alone as the solvent.

In this method are with alkali metal and / or alkaline earth metal ions doped titanium dioxide in just a few steps easily available. According to the application, both the degree, as well as the type the doping can be easily controlled.

So far required coatings or conversion to rutile to the to reduce photocatalytic activity are not required.

The Particles are known for all types known to those skilled in the art Further processing available. So, for example Surface modifications are introduced or Coatings are applied to the particles.

The Nanoscale particles according to the invention are preferred available according to this presented method. This Method is especially for the production of inventive Titanium dioxide particles in the anatase modification suitable.

The titanium dioxide particles according to the invention can be reacted with the aid of surface-modifying agents in order to supplement them with functional groups. By such functionalization particles can be provided with desired properties as needed. Thus, for example, they can be improved compared to other materials with which they are to be mixed, if appropriate, for improved compatibility. For example, hydrophobic or hydrophilic properties can be introduced. Preferably, one or more functional groups are introduced on the surface of the particles via the functional group. About these are then z. B. also possible reactions with other materials or between the particles. Particular preference is given to functional groups which are suitable for the crosslinking reactions. For surface modification, the particles of the invention are reacted with a surface modifier. These are known methods, as described by the applicant z. In DE 102 35 803 , respectively. WO 04/005577 described.

The invention also includes a composition containing the particles of the invention and an organic, inorganic or organically modified inorganic matrix-forming material. These may in particular be inorganic sols or organically modified inorganic hybrid materials or nanocomposites. Examples of these are optionally organically modified oxides, hydrolyzates 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, in particular those Si and Al, most preferably Si, or mixtures thereof. It is also possible proportionally to elements of groups 1 and 2 of the periodic table (for example Na, K, Ca and Mg) and groups 5 to 10 of the periodic table (for example Mn, Cr, Fe and Ni) or lanthanides in the oxide , Hydrolyzate or (poly) condensate. A preferred organically modified inorganic hybrid material is polyorganosiloxanes. For this purpose, particular preference is given to using hydrolysates of glass-forming or ceramic-forming elements, in particular of silicon.

The inorganic or organically modified inorganic matrix-forming Material is preferably added in an amount such that the molar ratio of titanium of titanium dioxide particles to glass or ceramic forming Element M is 100: 0.01 to 0.01: 100, preferably 300: 1 to 1: 300. Very good results are obtained at a Ti / M molar ratio of about 10: 3 to 1:30 received. Unless an organically modified inorganic matrix-forming material is used all or part of the contained glass or ceramic forming Elements M one or more organic groups as non-hydrolyzable Have groups.

The inorganic or organically modified inorganic matrix-forming Materials can be prepared by known methods be, for. By flame pyrolysis, plasma process, gas phase condensation process, Colloid techniques, precipitation method, sol-gel method, controlled nucleation and growth processes, MOCVD method and (micro) emulsion method. If from the process solvent-free Particles are obtained in an appropriate manner Solvent dispersed. Procedures are in the state of Technology described in detail.

Preferably, the inorganic sols and in particular the organically modified hybrid materials are obtained by the sol-gel method. In the sol-gel process, usually hydrolyzable compounds are 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. It is possible to use stoichiometric amounts of water, but also smaller or larger quantities. The forming sol may be replaced by suitable parameters, e.g. For example, degree of condensation, solvent or pH, are set to the desired viscosity for the coating composition. Further details of the sol-gel process are for. B. at 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.

To the preferred sol-gel process are the oxides, hydrolyzates or (poly) condensates by hydrolysis and / or condensation hydrolyzable compounds of the above-mentioned glass or ceramic-forming Obtained elements, where appropriate, for the preparation of the organically modified Inorganic hybrid material additionally not hydrolyzable bear organic substituents.

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

Examples of usable hydrolyzable compounds of elements M other than 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 (OnC ₄ H ₉ ) _{3 ,} Al (O-sec-C ₄ H ₉ ) _{3 ,} AlCl ₃ , AlCl (OH) ₂ , Al (OC ₂ H ₄ OC ₄ H 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 ₂ 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, the complexing radicals have, such. B. β-diketone and (meth) acrylic radicals, 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 following statements on the preferred silicon also apply mutatis mutandis to the other elements M. More preferably, the sol or the organically modified inorganic hybrid material is obtained from one or more hydrolyzable and condensable silanes, optionally wherein at least one silane has a non-hydrolyzable organic radical. One or more silanes having 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, R _a SiX _(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 abovementioned meaning and a is 1, 2 or 3, preferably 1 or 2, has.

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 having preferably 1 to 12, in particular 1 to 6 carbon atoms in the or the alkyl group (s).

The non-hydrolyzable radical R is, for example, alkyl (preferably C _1-6 -alkyl, such as, for example, 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 R and X mentioned may optionally be one or several common substituents, such as. Halogen, ether, Phosphoric acid, sulfonic acid, cyano, amide-mercapto, Thioether or alkoxy groups, as functional groups.

Of the Radical R may contain a functional group via which networking is possible. Concrete 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 via alkylene, alkenylene or arylene bridging groups represented by oxygen or sulfur atoms or -NH groups may be interrupted to the silicon atom bound. The bridging groups mentioned lead to the Example of the abovementioned alkyl, alkenyl or aryl radicals from. The bridging groups of the radicals R preferably contain 1 to 18, especially 1 to 8 carbon atoms.

Especially preferred hydrolyzable silanes of the general formula (I) are Tetraalkoxysilanes such as tetramethoxysilane and especially tetraethoxysilane (TEOS). Inorganic sols obtained by acid catalysis, e.g. B. TEOS hydrolysates are particularly preferred. Especially preferred Organosilanes of the general formula (II) are epoxysilanes such as 3-glycidyloxypropyltrimethoxysilane (GPTS), methacryloxypropyltri methoxysilane and acryloxypropyltrimethoxysilane, where GPTS hydrolysates can be used with advantage.

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 silicon-based inorganic sols, only silanes of the formula (I) are used, with proportionally hydrolyzable compounds of the above formula MX _{n being} added, if appropriate.

Provided the inorganic sol dispersed in the solvent discrete oxide particles, they can reduce the hardness improve the layer. These particles are in particular around nanoscale inorganic particles. The particle size (X-ray detected volume average) is z. B. in the range of below 200 nm, especially below 100 nm, preferably below 50 nm, z. B. 1 nm to 20 nm.

According to the invention z. As 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, especially as boehmite AlO (OH)), preferably brine of SiO ₂ , Al ₂ O ₃ , ZrO ₂ , GeO ₂ and mixtures thereof may be used as nanoscale particles. Such sols are also available in part in the trade, for. As silica sols, as the Levasil® ^® from HC Starck.

When inorganic or organically modified inorganic matrix-forming Material can also be a combination of such nanoscale particles with inorganic hydrolyzates or (poly) condensates Solen or organically modified hybrid materials are used, what is called nanocomposites here.

Possibly may also be organic monomers, oligomers or polymers of all kinds may be included as organic matrix-forming materials, the serve as flexibilizers, which are customary organic Binder can act. These can help to improve the coating ability can be used. The oligomers and polymers may have functional groups via the networking is possible. This networking opportunity is also optionally organic in the above-mentioned modified inorganic matrix-forming materials possible. Also mixtures of inorganic, organically modified inorganic and / or organic matrix-forming materials are possible.

Examples of usable organic ma Trix forming materials are polymers and / or oligomers having polar groups, such as hydroxyl, primary, secondary or tertiary amino, carboxyl or carboxylate groups. Typical examples are polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyvinylpyridine, polyallylamine, polyacrylic acid, polyvinyl acetate, polymethylmethacrylic acid, starch, gum arabic, other polymeric alcohols such. As polyethylene-polyvinyl alcohol copolymers, polyethylene glycol, polypropylene glycol and poly (4-vinylphenol) or derived therefrom monomers or oligomers.

The Composition can be, for example, a coating composition, a molding composition, a resin composition, paste, solution or Be cream.

there In the case of a coating composition, the usual Method be used, for. As diving, rolling, doctoring, flooding, Pulling, spraying, spinning or painting. The angry Dispersion is optionally dried and heat treated, for hardening or compaction. By the reduced or suppressed photocatalytic activity Titanium dioxide particles can also be sensitive substrates, such as plastics are coated directly. The one for it used heat treatment depends of course Substrate off. For plastic substrates or plastic surfaces naturally can not be very high temperatures be used. Thus, polycarbonate (PC) substrates z. B. at heat treated at about 130 ° C for 1 h. Generally the heat treatment z. B. at a temperature from 100 to 200 ° C and, if no plastic is present, up to 500 ° C or more. The heat treatment takes place z. B. 15 min to 2 h. As a rule, layer thicknesses of 50 nm obtained to 30 microns, preferably 100 nm to 1 micron, z. B. 50 to 700 nm.

A or more coating compositions of the invention Of course, they can also be combined with others Coatings are used.

The inorganic sol or the organically modified inorganic hybrid material serve not only as a matrix-forming material, but also the improved layer adhesion. Titanium dioxide can be used in the layer as matrix-forming component and / or present as particles.

Furthermore Such compositions can also be poured into molds and serve for the production of moldings.

The Nanoscale titanium dioxide particles according to the invention have high refractive index, which is slightly reduced by the doping can be reduced. Due to their good redispersibility and their reduced or suppressed photocatalytic activity They are suitable for many applications, especially when high Refractive indices are needed, for example for the production of high-index composite materials. At the same time they are through the two specified methods in a simple manner accessible.

So For example, the particles of the invention may be in refractive or diffractive optical elements, lenses, films, holographic materials, optical fibers, UV-absorbing coatings, UV-absorbing compositions, such as sunscreens, or Pigments are used.

Furthermore can the composition of the invention in optical Elements, lenses, foils, holographic materials, optical fibers, UV absorbing coatings, UV absorbing compositions, such as sunscreens, or pigments are used. The one used for this Matrix can according to the desired properties be adjusted.

Further Details and features will become apparent from the following description of preferred embodiments in connection with the dependent claims. Here, the respective features alone or in combination with each other be realized. The possibilities to solve the task are not limited to the embodiments. For example, ranges always include all - not - intermediate values and all conceivable subintervals.

embodiments

1st embodiment of a Reflux treatment with sodium methoxide

To a mixture of 107.5 g of titanium isopropylate and 162.45 g of 1-pentanol 3.4 g of sodium methylate is added to a first step and stirred vigorously until the end of the reaction. After 10 minutes to be this solution 7.5 g of 37% hydrochloric acid and after further 10 min in a third step 7.98 g of water each carefully added. The solutions are mixed intensively and under Normal pressure at max. 130 ° C cooked for around 17 h. After cooling, the mother liquor is discarded, the sediment is at max. Dried at 50 ° in vacuo.

2nd embodiment to a Lyothermal treatment with sodium acetate

To a mixture of 97.1 g of titanium isopropoxide and 105.5 g of propanol is a first step Added 0.56 g of sodium acetate and stirred until transferred to the autoclaving tank intensive. After 10 minutes, solutions of 6.69 g of 37% strength hydrochloric acid in 20 g of 1-propanol and, in a third step, 8.05 g of water in 40 g of propanol are added slowly and carefully to this solution. The 135 g of the solution is placed in a 250 ml autoclave with Teflon inliner and brought to 250 ° C within 30 min and maintained at this temperature for 2 h. After cooling, the mother liquor is discarded, the sediment is at max. Dried at 50 ° in vacuo.

3rd embodiment of a Reflux treatment with sodium 3,6,9-trioxodecanate

To 81.2 g of propanol is a first step 53.75 g of titanium isopropylate added dropwise and stirred vigorously until the end of the reaction. To 10 minutes to this solution 3.73 g of 37% hydrochloric acid and in a third step, after a further 10 minutes, a mixture of 0.378 g of sodium hydroxide and 1.7 g of 3,6,9-trioxodecanoic acid carefully and slowly added in 4 g of water. The solutions are mixed intensively and under normal pressure at max. 130 ° C cooked for around 16 h. After cooling, the Mother liquor discarded, the sediment is at max. 50 ° in the Vacuum dried.

4. Determination of the photocatalytic activity

to Determination of the photocatalytic activity of the invention Titanium dioxide nanoparticles became thin films of the particulate material produced on glass substrates and the photocatalytic activity by investigating the photocatalytic degradation of 4-chlorophenol (4-CP) determined.

For this purpose, suspensions of 1 g of TiO ₂ particles in 19 g of a mixture of ethanol / water 1: 1 with the aid of 1 g of 3,6,9-Trioxadecansäure prepared as a dispersion aid. These were coated in a dip coating process at a pull rate of 2 mm / s onto suitable glass substrates (e.g., microscope slides to give a coated area of approximately 9.25 cm ² ) and cured at 300 ° C for 1 h.

When Comparison were analogously prepared thin layers of a commercially available, active titanium dioxide (eg Degussa 225) and uncoated empty substrates (for the determination of self-photolysis the 4-CP used under UV irradiation).

To each was a coated substrate in a 50 ml aqueous Solution of 50 .mu.mol / l 4-CP contained, irradiation over a period of 60 h in a solar simulator Atlas Suntester CPS + exposed by means of a 750 W xenon arc lamp. The concentration of the 4-CP at the beginning and at the end of an experiment was by UV-vis spectroscopy (Varian Cary 5000).

at An active control sample was able to do so during the course of such an experiment a reduction of the 4-CP content by 50% can be observed. Using the particles of the invention was the reduction of the 4-CP content in the range of 14-20% depending of the sodium concentration used to prepare the particles, in the case of titanium dioxide-free blank substrates, a reduction was observed Photolysis detected by 15%.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 03/068682 [0007, 0012]
• US 2005/0233146 [0007, 0012]
• WO 99/060994 [0007]
• - DE 10235803 [0008, 0011, 0048]
• WO 04/005577 [0008, 0011, 0048]

Cited non-patent literature

• CJ Brinker, GW Scherer: "Sol-Gel Science - The Physics and Chemistry of Sol-Gel Processing", Academic Press, Boston, San Diego, New York, Sydney (1990) [0052]

Claims (21)

Nanoscale titanium oxide particles having greatly reduced or suppressed photocatalytic activity, characterized in that they contain (a) at least one or more alkali metal ions and / or alkaline earth metal ions; (b) have an average particle size of less than 20 nm; (c) are redispersible to primary particle size. Nanoscale titanium dioxide particles according to claim 1, characterized in that the alkali metal ions and / or alkaline earth metal ions are selected from the group containing sodium, potassium, Lithium, calcium and magnesium ions. Nanoscale titanium dioxide particles according to one of the claims 1 or 2, characterized in that it has an average particle size of less than 10 nm. Nanoscale titanium dioxide particles according to one of the preceding Claims, characterized in that they are in the anatase modification available. Process for producing nanoscale titanium dioxide particles with strongly reduced or suppressed photocatalytic Activity with the following steps: (a) manufacture a mixture comprising at least one hydrolyzable titanium compound, an organic solvent, an acidic condensation catalyst and at least one alkali metal compound and / or alkaline earth metal compound; (B) Adding water in a substoichiometric amount, based on the hydrolyzable groups of the titanium compound; (C) Treat the resulting mixture at a temperature of at least 60 ° C to form a dispersion or a Precipitation of titanium dioxide particles; (d) removing the solvent to form a powder of titanium dioxide particles. Method according to claim 5, characterized in that in that the at least one alkali metal compound and / or alkaline earth metal compound are not basic. Method according to one of claims 5 or 6, characterized in that the at least one alkali metal compound and / or alkaline earth metal compound is ionic. Method according to one of claims 5 to 7, characterized in that the at least one alkali metal compound and / or alkaline earth metal compound containing cations from the group containing sodium, potassium, lithium, magnesium and Calcium ions. Method according to one of claims 5 to 8, characterized in that the mixture in step c) is lyothermic, hydrothermally or by heating under reflux is treated. Method according to one of claims 5 to 9, characterized in that the mixture in step c) under autogenous pressure is treated. Method according to one of claims 5 to 10, characterized in that in step a), based on 1 mol hydrolysable Groups in the titanium compound, not more than 0.7 mol of water added become. Method according to one of claims 5 to 11, characterized in that the titanium dioxide particles with a Surface modifiers are mixed to form a Surface modification of the particles to effect. Method according to one of claims 5 to 12, characterized in that nanoscale titanium dioxide particles with a mean particle size of less than 20 nm are obtained, preferably below 10 nm. Method according to one of claims 5 to 13, characterized in that for further processing in step d) particles obtained in the preparation used or dispersed in a new solvent. Method according to one of claims 5 to 14, characterized in that the solvent is not removed is, but the dispersion of step c) processed directly becomes. Composition comprising nanoscale particles after one of claims 1 to 4 and a matrix-forming material. Composition according to Claim 16, characterized that the nanoscale particles by surface modification Compatibilized or decompatibilized to the matrix-forming material can be made Composition according to Claim 17, characterized that the nanoscale particles at least partially by surface modification have functional groups with functional groups of the Matrix-forming material can undergo crosslinking reactions. Composition according to any one of Claims 16 to 18, characterized in that the Zu Composition is a coating composition, a molding composition is a liquid, an emulsion, a resin composition, paste and / or cream. Use of nanoscale particles after one of claims 1 to 4 as part of refractive or diffractive optical elements, lenses, films, holographic Materials, optical fibers, coatings, UV-absorbing Coatings, UV-absorbing compositions or pigments. Use of the composition according to any one of the claims 16 to 20 for refractive or diffractive optical elements, Lenses, films, coatings, holographic materials, optical fibers, pastes or UV-absorbing creams.