WO2006108985A1 - Microbicidal substrate - Google Patents

Abstract

The invention relates to a substrate comprising at least one active photocatalytic compound for use under the conditions of illumination of an inside of a building or transport vehicle serving to neutralize the microorganisms coming in contact therewith, and to methods for preparing the microbicidal substrate as well as to uses thereof as a glazing or other substrate for disinfecting, filtering and ventilating.

Description

 MICROBICIDE SUBSTRATE

The present invention aims to destroy in whole or in part, or at least block the development of microorganisms such as bacteria, viruses, fungi including confined space such as interior building or transport vehicle.

By blocking their development, it is meant that the quantity of microorganisms is at most maintained or slightly reduced: for example, it is referred to as a bacteriostatic functionality, while bactericidal functionality refers to a more substantial decrease in the amount of microorganisms. bacteria.

Thus, the invention attacks, for example, the problems

- any nosocomial infections known sources may be air, water, hands or clothing of the occupants, the internal surfaces of the hospital, or

- legionellae forming especially in water pipes, ventilation devices / ducts, air conditioning systems ...

The microorganisms targeted by the invention are pathogenic for humans or not. In particular, and without limitation, mention is made of bacteria such as Bacillus, Bordetella, Borrelia, Brucella and Campylobacter.

Chlamydophila, Clostridium, Corynebacterium diphtheriae, Escherichia coli, Haemophilus influenzae, Legionella, Listeria, Mycobacterium leprae, Tuberculosis, Mycoplasma, Neisseria, Pseudomonas, Salmonella, Staphylococci, Streptococci, Treponema pallidum, Vibrio cholerae, Yersinia pestis ...

- as a virus: SARS, AIDS, flu, hepatitis, herpes, shingles, chickenpox, coronavirus, Ebola ...

- as fungi: mycosis, Aspergillus, Candida ...

The object of the invention, defined above, is achieved by the invention which relates to a substrate comprising at least one photocatalytic compound active under the illumination conditions of a building or transport vehicle interior intended for to neutralize the microorganisms coming into contact with it.

As photocatalytic compound is meant one or more of the compounds TiO ₂ , WO ₃ , CdO ₃ , In ₂ O ₃ , Ag ₂ O, MnO ₂ and Cu ₂ O ₃ , Fe ₂ O ₃ , V ₂ O ₅ , ZrO ₂ , RuO ₂ and Cr ₂ O ₃ , CoO ₃ , NiO, SnO ₂ , CeO ₂ and Nb ₂ O ₃ , KTaO ₃ and SrTiO ₃ , K ₄ NbO ₇ - Of these, UO 2 is particularly preferred, at least partially crystallized in anatase and / or rutile form and, to a lesser extent, SrTiO ₃ and K ₄ NbOi ₇ .

The illumination conditions of a building interior or transport vehicle are characterized by a spectrum consisting essentially of visible light and a small amount of residual ultraviolet. The photocatalytic compound according to the invention is therefore selected so as to be active under visible light, or to have a significantly increased ultraviolet activity compared to that of conventional photocatalytic compounds. By the term "neutralizing" is meant here at least the maintenance of the starting quantity of the microorganisms; the invention excludes an increase of this quantity. The development and proliferation of microorganisms are thus prevented and, in almost all cases, the recovery surface of the microorganisms decreases, even if their quantity is maintained. The neutralization of microorganisms can go according to the invention until their total destruction.

Neutralized microorganisms can be pathogenic to humans, in which case the invention provides a benefit to human health. They can also be non-pathogenic for humans: it can then be to preserve the cleanliness of a transparent substrate by avoiding the formation of fungi ...

According to a first variant, said photocatalytic compound comprises TiO 2 subjected to a heat treatment under a nitrogen or nitrogen atmosphere and at least one reducing gas for a time sufficient to render it capable of absorbing photons from the visible. The heat treatment is carried out at a temperature of at least 250 ^° C. and up to 700 ^° C., for a few fractions of seconds to a few hours. As the reducing gas, at least one of hydrogen and hydrocarbons such as methane, the nitrogen: reducing gas ratio (s) being in particular between 100: 0 and 50:50. The heat treatment is likely to correspond to a conventional annealing treatment or tempering treatment of a glass substrate.

According to a second variant, the substrate comprises, in intimate association, a first photocatalytic compound and a second compound having a jump of energy between the upper level of its valence band and the lower level of its conduction band corresponding to a wavelength in the visible range. Said first photocatalytic compound is selected from those already mentioned, and said second compound selected from GaP, CdS, KTa ₀ 7 ₇ N _{0, 23} O _3, CdSe, SrTiO _3, TiO _2, ZnO, Fe ₂ O _3, WO _3, Nb ₂ O ₅ , V ₂ O ₅ , Eu ₂ O ₃ in a non-limiting manner. The intimate association of the two compounds can be obtained by a non-reactive process, for example by mixing powders and heat treatment in a binder, or by liquid after mixing solutions, and then heat treatment and / or drying. It can also be obtained by a reactive process such as liquid or gas pyrolysis (thermal CVD) from precursors of the two compounds, or cathodic sputtering using a target consisting for example of a mixture of two metals precursors of said first and second compounds.

The first and the second variants are both intended to obtain a photocatalytically active compound under visible spectrum illumination exclusively, the spectrum predominantly present in building interior, transport vehicle.

According to a third variant, said photocatalytic compound is integrated in a mesoporous structure. This structure based on at least one compound - in particular oxide - of at least one of the elements Si, W, Sb, Ti, Zr, Ta, V, B, Pb, Mg, Al, Mn, Co, Ni, Sn, Zn, In, Fe, Mo ... comprises a three-dimensional network of pores of diameters between 2 and 50 nm communicating with each other. One embodiment of this variant consists of a mesoporous layer based on silica incorporating anatase crystallized TiO ₂ nanoparticles and approximately 50 nm in size. This layer can be obtained by liquid using structuring agents such as cetyltrimethylammonium bromide (CTAB) or polyoxyethylene-polyoxypropylene block copolymer which are degraded by heat treatment, leaving room for the mesopores. Regarding the details of this method, reference is made to WO 03/87002. This third variant provides a substrate whose photocatalytic activity under ultraviolet radiation is considerably exacerbated, which is useful in the presence of a low residual ultraviolet illumination such as inside building, transport vehicle ... According to this third variant, functional agents such as microbicides, deodorants, antibacterials or others are advantageously contained in the pores of the structure.

According to the three variants described above, said photocatalytic compound advantageously comprises TiO ₂ doped with N and / or S and / or at least one metal ion and, in particular:

- N-doped TiO ₂ is obtained by the liquid route from at least one precursor containing Ti in the presence of at least one ammonium-functional compound, and then heat treatment; TiO ₂ doped with V, Cr, Mn, Mo, In, Sn, Fe, Ce, Co, Cu, Nd, Zn, W, Nb, Ta,

Bi, Ni, Ru in a concentration of 0.5 to 10 mol% is obtained by coprecipitation of a titanium compound such as an alkoxide and a metal salt, followed by a heat treatment.

By thus inserting at least one of these metallic elements into the crystal lattice of titanium oxide, the number of charge carriers is increased. This doping can also be done only on the surface of the titanium oxide or, if appropriate, of the entire coating of which it forms part, surface doping carried out by covering at least a portion of the coating with an oxide layer or of metal salts. Preferably, said photocatalytic compound, or at least part of the coating which incorporates it, is covered with a noble metal in the form of a thin layer of the Pt, Rh, Ag, Pd type. Thus, the photocatalytic phenomenon is amplified by increasing the yield and / or the kinetics of the photocatalytic reactions. On the other hand, Ag is a microbicide. Preferably, the substrate of the invention is based on glass or polymer (s) in particular transparent or a ceramic substrate or glass-ceramic substrate or substrate of architectural material of the type coated facade, slabs or concrete pavement, architectural concrete, blockwork , brick, tile, cementitious composition material, terra-cotta, slate, stone, metal surface, or glass-based fibrous substrate of the mineral wool insulation type, or reinforcing glass wire, fabric, building wall cladding material such as wallpaper, or wood-based or paint.

In particular, the substrate of the invention is made of flat glass, in particular soda-lime glass. The term "flat" here designates a substrate in a flat plate or in faces curved or curved, monolithic or laminated, where appropriate assembled in multiple glazing delimiting at least one insulating gas strip.

In the case where the substrate is made of flat glass, said photocatalytic compound is advantageously associated with the interposition of heteroepitaxial growth sub-layers of said photocatalytic compound;

- Sub-layers that are barrier to the migration of alkali (soda-lime glass in particular);

optically functional sublayers; - thermal control underlays; and or

conductive sub-layers, antistatic ...

According to a particularly advantageous embodiment, said compound is contained in a layer with a thickness of between 5 nm and 1 μm.

With regard to the deposition process of said photocatalytic compound, three main variants are recommended:

by cathodic sputtering, at room temperature, under vacuum, where appropriate assisted by magnetic field and / or ion beam, using a Ti or TiO _x metal target with x <2 and an oxidizing atmosphere or using a TiO ₂ target and an inert atmosphere; by a solid, liquid or gaseous phase pyrolysis process of the type

CVD;

- by sol-gel process.

The invention furthermore relates to the use of the substrate described above - as an interior surface of a collective building such as a hospital or individual house or apartment, furniture, or interior of any vehicle. transportation by land, water or air, including clothing or any accessories worn by the occupant.

- as self-cleaning glazing, including anti-fog, antifouling and anti-condensation, especially for the building of the multiple glazing type, double glazing, windshield-type vehicle glazing, rear window, automotive side glazing, glazing for train, plane, boat, utility glazing such as aquarium, showcase, greenhouse, interior furnishing - tablet, shower stall -, furniture urban, mirror, computer-type display system screen, television, telephone, electrically controllable glazing such as electrochromic glazing, liquid crystal, electroluminescent, photovoltaic glazing, lamp. - in the filtration of liquid or gas, ventilation and / or air conditioning devices, ventilation ducts, water pipes.

The invention is illustrated by the following example.

Example

It is deposited on the glass still in the form of a float glass ribbon, a silicon oxycarbide based undercoating noted for convenience SiOC (without prejudging the actual rate of oxygen and carbon in the coating) - the glass is a clear glass silico-sodo-calcium 4 mm thick, as marketed by Saint-Gobain Glass France under the name Planilux-. This underlayer is deposited by CVD from precursors Si, in particular a mixture of SiH ₄ and ethylene diluted in nitrogen, using a nozzle disposed above and transversely to float glass ribbon of a flat glass production line, in the float chamber, when the glass is still at a temperature of about 550 to 600 ^° C. The coating obtained has a thickness of about 50 nm and a refractive index of about 1.55. 10 cm x 10 cm samples were cut from the float glass provided with its alkali-resistant SiOC underlayer thus obtained; these samples are washed, rinsed, dried and subjected to UV ozone treatment for 45 min.

A mesoporous structure coating is formed on the underlayer. The liquid treatment composition is obtained by mixing in a first step 22.3 ml of tetraethoxysilane, 22.1 ml of absolute ethanol, 9 ml of HCl in demineralized water (pH 1, 25) until the solution becomes clear, then placing the flask in a water bath at 60 ^° C. for 1 h.

In a second step, a solution of a polyoxyethylene-polyoxypropylene block copolymer sold by BASF under the trade name Pluronic PE6800 (molar mass 8000), in proportions such that the molar ratio PE6800 / Si = 0, is added to the soil obtained above. , 01. This is achieved by mixing 3.78 g of PE6800, 50 ml of ethanol and 25 ml of the sol.

The anatase-crystallized TiO ₂ nanoparticles of approximately 50 nm size are added to the liquid composition thus obtained just prior to the deposition on sample, in an amount such that Ti / Si = 1. The deposit is done by spin coating in a starting amount of 3 ml per sample. (Other equivalent deposition techniques are dip coating, spraying, laminar coating, roll coating, flow coating ...) The samples are then subjected to the following annealing treatment:

- 30 min 100 ⁰ C plateau 2 h; 15 min 150 ⁰ C plateau 2 h;

- 15 min 175 ⁰ C plateau 2 h;

- 10 min 200 ⁰ C no step; - 3 h 20 min 300 ⁰ C bearing 1 h;

- 2 h 30 min 450 ⁰ C bearing 1 h.

The pores of the coating thus formed have a size of 4-5 nm.

It is verified by SIMS analysis of the mesoporous structure coating that the Ti / Si atomic ratio is exactly the same as that of the starting liquid composition. The SIMS analysis also makes it possible to verify that the nanoparticles are distributed homogeneously in the three dimensions of the coating.

A comparative study is made of the adhesion under dynamic conditions under ultraviolet irradiation of a bacterial culture on glass provided with the single SiOC layer, and on glass provided with the SiOC layer coated with the TiO ₂ layer formed as described above.

A lamp characterized by the wavelength of 312 nm and a power of 100 W / m ^{2 is used} .

The bacterium is Staphylococcus epidermidis (ATCC 12228), distributed by American type culture collection. The strain kept in freeze-dried form was resuspended in 9 ml of TSB (trypto-case soy broth) and incubated for 15 hours at 37 ^° C., then the cultures were divided into cryotubes supplemented with glycerol (15%) and stored at -80 ^° C. ⁰ C (main stock). TSB is a composition of culture medium, of which 30 g of powder are diluted in one liter of distilled water (pH = 7.3) and are distributed as follows:

Bio-tripcase = 17 g

Bio-soyase = 3 g

Sodium chloride = 5 g

Potassium bisphosphate = 2.5 g Glucose = 2.5 g

To obtain the secondary stock or working stock, subculture is carried out from the main stock in 200 ml of TSB. The broth is then incubated at 37 ^° C. After 24 hours, 15% glycerol is added to protect the bacteria. The suspension obtained is then distributed in the tubes

Eppendorf (1 ml / tube) and stored at -20 ^° C.

After rapid thawing, the content of an Eppendorf tube is taken and added to 9 ml of TSB ^(1st transplanting or R1). The broth is then incubated at 37

⁰ C for 24 h. The second subculture (R2) is carried out under analogous conditions, with the exception of the incubation time. Finally, 1 ml of R2 broth was removed and added to 200 ml of TSB (R3).

Growth monitoring makes it possible to determine the beginning of the stationary phase reached after 15 hours of incubation of the R3 culture. The study of bacterial adhesion will be performed on the 17-hour old R3 culture, which corresponds to the stationary growth phase of the bacteria.

The growth of the bacteria is evaluated by optical absorbance (OD) measurements at the wavelength 620 nm using a "Spectronic 401" spectrometer (Miltron Roy). One ml of the suspension R3 is taken at regular time intervals and added to a vat which is then placed in the spectrometer to measure the OD. The representation of OD as a function of time is the growth curve.

The medium used in the various experiments is physiological water (0.15M NaCl solution or water φ) or diluted 100 times (0.0015M NaCl solution or φ-2 water). To have a bacterial suspension, the culture R3 is centrifuged 3 times 10 minutes at 7000 g at a temperature of ^{40 °} C. The pellet is resuspended either in water φ, or in water φ-2 according to the techniques used (MATS, electrophoretic mobility, adhesion under static / dynamic conditions, etc.). The bacterial concentration is adjusted to a value of OD (in absorption). Thus, to ensure that the bacterial concentration is always of the same order of magnitude for a series of manipulations, the suspension is diluted so as to always have the same value of OD. To determine the bacterial concentration, the method of counting viable cells or counting on a solid medium is used. The tests in dynamic conditions make it possible to follow the kinetics of the bacterial adhesion process on the solid surface. The support is placed in a dynamic adhesion cell. A bacterial suspension in water φ of approximately 3.10 ⁶ UFCVmI is circulated in the cell by means of a peristaltic pump set at a flow rate of 15 ml / min to ensure a laminar regime (Re = 10). The laminar regime, unlike the turbulent regime, does not favor surface-microorganism impacts. Thus, the bacterial adhesion in this case does not depend on the flow conditions, but on the properties of the surfaces themselves and the suspending liquid. The adhesion of microorganisms to the glass surface is monitored using a microscope (Leica, x10 objective). Every 10 minutes, an image is taken. By a computer analysis of it, it is possible to determine the percentage of recovery of each image and thus build a curve which represents the percentage of coverage of the surface by the bacteria as a function of the contact time.

The adhesion tests in dynamic conditions were carried out with the 22-hour old R3 culture.

It can be seen that the recovery rate reaches constant values:

- 35% in 30 hours for bare glass; - 15% in 20 hours for TiO ₂ glass.

As a result, bacteria adhere less well to TiO ₂ glass.

On the other hand, in the examples of the document WO 03/087002 implementing the same TiO ₂ glass (mesoporous layer), it is shown that it exhibits photocatalytic activity even under low UV irradiation such as inside the glass. 'a building or a transport vehicle. It can be assumed that this photocatalytic activity is not without effect on the bacteria themselves to explain their much lower recovery rate.

In addition, always under even low UV irradiation, TiO ₂ glass becomes more hydrophilic. A circulation of water can thus unhook the bacterial cells in particular dead from the surface of the TiO ₂ glass more effectively than from the surface of the bare glass.

Thus this example demonstrates the self-cleaning property of TiO ₂ glass vis-a-vis the bacteria tested. This layer is therefore indicated for applications of at least partial destruction, or stop the development of microorganisms, especially indoors.

Claims

1. Substrate comprising at least one photocatalytic compound which is active under the illumination conditions of a building interior or of a transport vehicle, intended to neutralize the microorganisms coming into contact with it. 2. Substrate according to claim 1, characterized in that said photocatalytic compound comprises TiO ₂ subjected to a heat treatment under a nitrogen or nitrogen atmosphere and at least one reducing gas for a time sufficient to make it suitable for absorb photons from the visible. 3. Substrate according to claim 1 or 2, characterized in that it comprises in intimate association a first photocatalytic compound and a second compound having a jump of energy between the upper level of its valence band and the lower level of its band. of conduction corresponding to a wavelength in the visible range. 4. Substrate according to one of the preceding claims, characterized in that said photocatalytic compound is integrated in a mesoporous structure. 5. Substrate according to claim 4, characterized in that functional agents such as microbicides are contained in the pores of said structure. 6. Substrate according to one of the preceding claims, characterized in that said photocatalytic compound comprises TiO ₂ doped with N and / or S and / or at least one metal ion. 7. Substrate according to claim 6, characterized in that N-doped TiO ₂ is obtained by a liquid route from at least one precursor containing Ti in the presence of at least one ammonium-functional compound, and then heat treatment. 8. Substrate according to claim 6, characterized in that TiO ₂ doped with V, Cr, Mn, Mo, In, Sn, Fe, Ce, Co, Cu, Nd, Zn, W, Nb, Ta, Bi, Ni, Ru, in a concentration of 0.5 to 10 mol% is obtained by coprecipitation of a titanium compound such as an alkoxide and a metal salt, followed by a heat treatment. 9. Substrate according to one of the preceding claims, characterized in that said photocatalytic compound, or at least part of the coating which incorporate it, are covered with a noble metal in the form of a thin layer of the Pt, Rh, Ag, Pd type. 10. Substrate according to one of the preceding claims, based on glass or polymer (s) in particular transparent or ceramic substrate or glass-ceramic substrate or substrate of architectural material of the type coated facade, slabs or concrete pavement, architectural concrete, breeze block , brick, tile, cementitious composition material, terra-cotta, slate, stone, metal surface, or glass-based fibrous substrate of the mineral wool insulation type, or reinforcing glass wire, fabric, building wall cladding material such as wallpaper, or wood-based or paint. 11. Substrate according to claim 10, characterized in that it is flat glass, including soda-lime. 12. Substrate according to one of the preceding claims, characterized in that said photocatalytic compound is contained in a layer of thickness between 5 nm and 1 micron. 13. Process for the preparation of a substrate according to one of the preceding claims, characterized in that the deposition of said photocatalytic compound is carried out by sputtering, at room temperature, under vacuum, where appropriate assisted by a magnetic field and / or or ion beam, using a Ti or TiO _x metal target with x <2 and an oxidizing atmosphere or using a TiO 2 target and an inert atmosphere. 14. Process for the preparation of a substrate according to one of claims 1 to 12, characterized in that the deposition of said photocatalytic compound is carried out by a method of solid phase pyrolysis, liquid or gaseous type CVD. 15. Process for preparing a substrate according to one of claims 1 to 12, characterized in that the deposition of said photocatalytic compound is carried out by a sol-gel process. 16. Use of a substrate according to one of claims 1 to 12 as an interior surface of a collective building such as hospital or individual house or apartment, furniture, or interior of any land transport vehicle, aquatic or air, including clothing or any accessories worn by the occupant. 17. Use of a substrate according to one of claims 1 to 12 as self-cleaning glazing, in particular anti-fog, antifouling and anti-condensation, especially for building type multiple glazing, double glazing, glazing for transport vehicle type windshield, rear window, automotive side glazing, glazing for train, airplane, boat, utility glazing such as aquarium, showcase, greenhouse, interior furnishing - tablet, shower cabin -, street furniture , mirror, computer-type display system screen, television, telephone, electrically controllable glazing such as electrochromic glazing, liquid crystal, electroluminescent, photovoltaic glazing, lamp. 18. Use of a substrate according to one of claims 1 to 12 in the filtration of liquid or gas, aeration devices and / or air conditioning, ventilation ducts, water pipes.