GB2442364A

GB2442364A - Microbicidal substrate

Info

Publication number: GB2442364A
Application number: GB0720323A
Authority: GB
Inventors: Catherine Jacquiod; Lethicia Gueneau; Sophie Vanpoulle; Ronan Garrec; Jean-Gerard Leconte
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2005-04-11
Filing date: 2006-04-10
Publication date: 2008-04-02
Also published as: DE212006000030U1; GB0720323D0; WO2006108985A1; KR20070122212A

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

MICROBICID SUBSTRATE

The object of the present invention is to completely or partly destroy, or at least block the development of microorganisms such as bacteria, viruses and fungi, especially in a confined space such as the inside of a building or of a transport vehicle.

The expression "blocking their development" is understood to mean that the amount of microorganisms is at the very most maintained or slightly reduced: it is then referred to, for example, as a bacteriostatic functionality, whereas a bactericidal functionality denotes a more substantial reduction in the amount of bacteria.

Thus, the invention tackles, for example, the problems: -of all nosocomial infections of which the known sources may be the air, water, the hands or clothing of the occupants, the interior surfaces of the hospital; or else -of legione1l5 that form especially in water pipes, ventilation devices/ducts, air-conditioning Systems, etc. The microorganisms targeted by the invention may or may not be pathogenic for humans. In particular, mention is made, non-lirnitingly, of: -as bacteria: Bacillus, Boxdete.Z1a Borreija Brucella, Campylobac, Chlarnydophj la, Clostrjdj, Corynebacteri urn diphterjae, Escherjchja colj, Haeinophjlus influenzae, Legionei, Listeria, Mycobacterj leprae and buberculosj5 Mycoplasma Neisseria, Pseudornonas Salmonella Staphylococcus Streptococcus Trepon6 palljd, Vibrjo cholerae, Yersinja pestis, etc. -as viruses. SARS, AIDS, flu, hepatitis herpes simplex, herpes zoster, varjcella corona virus, Ebola, etc.; and -as fungi: mycosis, Aspergjllus Candida, etc. The object of the invention, defined above, is achieved by the invention, the subject of which is a substrate comprising at least one Photocatalytic compound active under the COfldjtjo5 of illuminating an interior of a building or of a transport vehicle, intended to neutralize the microorganj8 with which it comes into Contact.

As a Photocatalytic compound, one or more of the following compounds are understood: Ti02, W03, Cd03, 1n203, Ag20, Mn02 and Cu203, Fe203, V205, Zr02, Ru02 and CR203, CoO3, Nb, Sn02, CeO2 and Nb203, KTaO3 and SrTiQ3, KNbO17, etc. Most Particularly preferred among these is Ti02, at least Partially crystallized in anatase and/or rutjle form and, to a lesser extent, SrTiO3 and K4Nb017.

The COfldjtjon5 for illuminating an interior of a building or of a transport vehicle are characterized by a spectrum composed mainly of Visible light and of a small amount of residual ultraviolet light. The photocatalytic compound according to the invention is therefore chosen so as to be active under visible light, or to have a Considerably augmented activity under ultraviolet light with respect to that of conventional Photocatalytic compounds The term "to neutralize" is understood here to mean at the very least maintaining the starting amount of microorganisms; the invention excludes an Increase of this amount. The development and proliferation of microorganisms are thus prevented and, in almost all cases, the surface area covered with microorganisms decreases, even in the case of maintaining their amount. The neutralization of the microorganj.sms may range according to the invention up to their complete destruction.

The neutralized microorganisms may be pathogenic for humans, in this case, the invention provides a benefit for human health. They may also be non-pathogenic for humans: it may then be a question of preserving the cleanliness of a transparent substrate by avoiding formation of fungi, etc. According to a first variant, said photocatalytic compound comprises T102 subjected to a heat treatment under an atmosphere of nitrogen or of nitrogen and of at least one reducing gas for a sufficient time to make it capable of absorbing photons from the visible spectrum. The heat treatment IS carried out at a temperature of at least 250 C and which may range up to 700 C, for a few fractions of seconds to a few hours.

As a reducing gas, at least one from among hydrogen and hydrocarbo5 such as methane IS used, the nitrogen/reducing gas(es) volume ratio being in particular between 100/0 and 50/50. The heat treatment is capable of corresponding to a conventional annealing treatment or to a conventional toughening treatment of a glass substrate.

According to a second variant, the substrate COnSISts of a close combination of a first photocatalytic compound and a second compound having a bandgap 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 chosen from those already mentioned and said second compound from Gap, CdS, KTa077N'b02303 CdSe, SrTjQ3, Ti02, ZnO, Fe203, wO, Nb205, V205, Eu2O in a non-limiting manner. The close combination of the two compounds may be obtained by a nonreactive process, for example, by mixing of powders and heat treatment in a binder, or by a liquid route after mixing of SOlut1o, then heat treatment and/or drying. it may also be obtained by a reactive process such as a liquid or gas pyrolysig (thermal CVD) from precursors of the two compounds, or Sputtering Using a target composed, for example, of a mixture of two metal precursors of said first and second compounds The subject of both the first and Second variant is the production of a compound that is PhOtocatalyticaiiy active under illumination of the exclusively visible spectrum, the spectrum that is present as a majority in the inside of buildings or transport vehicles.

According to a third variant, said photocatalytic compound is integrated into a mesoporous structure.

This structure based on at least one Compound -especially an 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, etc. comprises a three- dimensional network of pores having diameters between 2 and so nm that communicate with one another. One embodiment of this variant consists of a mesoporous layer based on silica integrating nanoparticles of anatase crystallized Tb2 having a size of around 50 nm. This layer may be obtained by a liquid route Using structuring agents such as bromide (CTAB) or POlYoxyethy1ene/polyox0py1 block COpolymers which are degraded by heat treatment, leaving Space for the niesopores Reference is made to Application WO 03/87002 regarding the details of this process.

This third variant makes a substrate available of which the Photocatalytic activity under ultraviolet radiation is Considerably exacerbated, which is useful, in the presence of a low illumination of residual ultraviolet light such as in the inside of a building, transport -s -vehicle, etc. According to this third variant, functional agents such as microbicides deodorants, antibacterial agents or others are advantageously contained within the pores of the structure.

According to the three variants described Previously, said photocatalytic compound advantageously comprises Tb2 doped with N and/or S and/or at least one metal ion and, in particular.

-Ti02 doped with N is obtained by a liquid route from at least one precursor Containing Ti in the presence of at least one compound having an ammonjum functional group, then heat treatment; and -Ti02 doped with v, Cr, Mn, Mo, In, Sn, Fe, Ce, Co, Cu, Nd, Zn, w, Nb, Ta, Bi, Ni, Ru at a concentration of o.s to 10 mol% is obtained by coPrecipitating a titanium compound such as an alkoxide and a metal salt, followed by a heat treatment.

Inserting at least one of these metal elements into the crystalline network of titanium oxide, the number of charge carriers was increased. This doping may thus be carried out only at the surface of the titanium oxide or where appropriate in the whole of the coating of which it is part, doping of the surface being carried out by covering at least part of the coating with a layer of metal salts or oxides.

Preferably, said photocatalytic compound, or at least part of the coating which bflcorpora5 it, are Covered by a noble metal in the form of a thin film of t, Rh, Ag or Pd type. Thus, the Photocatalytic phenomenon is amplified by increasing the yield and/or the kinetics of the photocatalytic reactions. Moreover, Ag is a microbicide Preferably, the substrate of the invention is based on glass or polymer(s), especially that are transparent, or a ceramic substrate, or glass-ceramic substrate or substrate made of architectural material of the type: façade render, concrete slabs or paving, architectonjc concrete, concrete block, brick, tile, material of cementjtjous composition terracotta, slate, Stone, metallic surface, or a fibrous substrate based on glass of the mineral insulation wool type, or glass reinforcement yarn, fabric, material for coating walls of buildings such as wallpaper, or based on wood or paint.

In particular, the substrate of the invention is made of flat, especially soda-lime, glass. The term "flat" here denotes a substrate made of a monolithic or laminated plate that is plane or that has Curved or bent sides, where appropriate assembled as multiple glazing delimiting at least one insulating gas-filled space.

In the case where the substrate is made of flat glass, said photocatalytic compound is advantageously combined with interposition of: -sublayers grown heteroepitaxially from said photocatalytjc compound; -sublayers that form a barrier to the migration of alkali metals (especially of the soda-lime glass); -sublayers having an optical functionality; -sublayers having a thermal control; and/or -sublayers that are Conductive, antistatic, etc. According to one particular advantageous embodiment, said compound is contained in a layer having a thickness between 5 nm and 1 zrn.

As regards the process for depositing said photocatalytic compound, three main variants are recommended: -by room-temperature vacuum sputtering, where appropriate magnetron and/or ion-beam sputtering, using a metallic Ti or TiOX target with x < 2 and an oxidizing atmosphere or using a Tb2 target and an inert atmosphere; -by a solid, liquid or gas pyrolysis process of the CVD type; and -by a sol-gel process.

Another subject of the invention is the use of the substrate described above: -as a surface for the inside of a public building such as a hospital or an individual house or apartment, or furniture, or of the inside of any terrestrial, water-borne or airborne transport vehicle, including clothing or any accessory worn by the Occupant; -as self-cleaning, especially antifogging, antisoiling and anticondensation glazing, especially for buildings of the multiple glazing type, double glazing, glazing for transport vehicles of the type: windshield, rear window or side window for an automobile, glazing for a train, plane or boat, utilitarian glazing such as glazing for an aquarium, shop window, greenhouse, interior furnishings -shelf or shower cubicle, for Street furniture, mirrors, screens for display systems of the computer, television or telephone type, electrically operated glazing such as electrochromjc liquid crystal or electroluminescent glazing, photovoltajc glazing or glazing for a lamp; and in the filtration of liquids or gases, aeration and/or air-conditioning devices, ventilation ducts or water pipes.

The invention is illustrated by the following example.

Example

Deposited onto the glass, still in the form of a ribbon of float glass was a sublayer based on Silicon oxycarbjd denoted for ease by SiOC (without prejudging the actual level of oxygen and of carbon in the coating) -the glass was a clear soda-1jmesiljca glass with a thickness of 4 mm, such as sold be Saint-Gobain Glass France under the name Planjl. This sublayer was deposited by CVD from Si precursors, in particular from a mixture of SIH4 and ethylene diluted in nitrogen, Using a nozzle Positioned, above and transversely to the ribbon of float glass of a flat glass production 1in, within the float chamber, when the glass was still at a temperature of about sso to 600 C. The coating obtained had a thickness of about 50 nm and a refractive index of about 1.55. Samples of 10 cm x cm in size were cut from the float glass provided with its SIOC alkali-metal barrier sublayer thus obtained; these samples were washed, rinsed, dried and subjected to a IJV/ozone treatment for 45 minutes.

A coating with a mesoporous structure was formed on the sublayer.

The liquid treatment compositj was obtained by mixing, in a first step 22.3 ml of tetraethoxysjlane 22.1 ml of absolute ethanol and 9 ml of HC1 in demineralized water (pH 1.25) until the Solution became clear, then by Placing the round-bottomed flask in a water bath at 60 C for 1 h. In a second step, added to the sol obtained above was a solutjn of a block copolymer sold by BASF under the registered trademark Pluronjc PE6800 (molar weight 8000), in proportions such that the PE68QO/S molar ratio was 0.01. This was obtained by mixing 3.78 g of PEG800, 50 ml of ethanol and 25 ml of the sol.

The Ti02 nanoparticles crystallized as anatase and approximately 50 rim in size, were added to the liquid composition thus obtained just before depositjo on the sample in an amount such that Ti/Si = 1. The deposition was carried out by spin coating, with a starting amount of 3 ml per sample. (Other equivalent deposition techniques are dip coating, spraying, laminar coating, roll coating, flow coating, etc.).

The samples were then subjected to the following annealing treatment: -30 mm 100 C, 2 h hold; -15 mm 150 C, 2 h hold; -15 mm 175 C, 2 h hold; -10 mm 200 c, no hold; -3 h 20 mm 300 C, 1 h hold; and -2 h 30 mm 450 C, 1 h hold.

The pores of the coating thus formed had a Size of 4 -5 rim.

By SIMS analysis of the coating with a mesoporous structure, it was confirmed that the Ti/Si atomic ratio was exactly identical to that of the initial liquid composition SIMS analysis was also used to Confirm that the nanoparticles were distributed uniformly in the three dimensions of the coating.

A comparative study was Carried out of the adhesion, in dynamic Conditions under ultraviolet radiation, of a bacterial culture on glass provided with the SiOC layer alone and on glass provided with the SiOC layer coated with the Ti02 layer formed as described above.

A lamp characterized by a wavelength of 312 nm and a power of 100 W/m2 was used.

The bacteria was Staphylococcus epidermis (ATCC 12228), -10 -distributed by American type culture collection. The strain kept in freeze-dried form was put back into suspension in 9 ml of TSB (tryptocase SOy broth) and incubated for 15 hours at 37 C, then the cultures were divided up into cryotubeg supplemented with glycerol (15%) and Stored at -80 C (main stock). TSB is a culture medium Composition, of which 30 g of powder were diluted in one liter of distilled water (pH = 7.3) and were distributed as follows: -bio-trypcase = 17 g -bio-soyage = 3 g -sodium chloride = 5 g -potassium biphosphate = 2.5 g -glucose = 2.5 g In order to obtain the secondary stock or working stock, recuituring was Carried out from the main stock ifl 200 ml of TSB. The broth was then incubated at 37 C.

At the end of 24 h, 15% glycerol was added to protect the bacteria The suspension obtained was then distributed into Eppendorf tubes (1 mi/tube) and kept at -20 C.

After rapid defrosting the contents of an Eppendorf tube was removed and added to 9 ml of TSB (1st reculturing or Ri). The broth was then incubated at 37 C for 24 h. The second reculturing (R2) was carried out under similar Conditions, except for the incubation time. Finally, 1 ml of R2 broth was removed and added to 200 ml of TSB (R3) Monitoring of the growth made it Possible to determine the beginning of the stationary phase achieved after incubating the R3 culture for 15 h. The study of bacterial adhesion will be Carried out on the R3 culture aged for 17 hours, which corresponds to the stationary phase of bacterial growth.

The bacterial growth was evaluated by measurements of -1]. -optical density (OD) as absorbance at the wavelength of 620 rim by using a Spectronic 40]. spectrometer (Miltron Roy). 1 ml of the R3 suspension was removed at regular time intervals and added to a cuvette which was then placed in the spectrometer in order to measure the OD.

The representation of the OD as a function of time The medium used in the various experiments was physiological saline (solution of 0.15M NaC1 or p saline) or physiological saline diluted one hundred times (solution of 0.0015M NaC1 or p2 saline). In order to have a bacterial suspension, the culture R3 was centrifuged three times for 10 minutes at 7000 rpm at a temperature of 4 C. The centrifugation pellet was resuspended either in p saline, or in çY2 saline depending on the techniques used (MATS, electrophoretic mobility, adhesion in static/dynamic conditions, etc.).

The bacterial concentration was adjusted to a value of aD (as absorption). Thus, in order to ensure that the bacterial concentration is always of the same order of magnitude for a series of experiments, the suspension was diluted so as always to have the same OD value. In order to know the bacterial concentration, the method of counting the viable cells or counting on a solid medium is used.

The tests under dynamic Conditions make it possible to monitor the kinetics of the process for bacterial adhesion on the solid surface. The support was placed in a dynamic adhesion cell. A bacterial suspension in p saline of around 3 x 10 CFU/ml was Circulated into the cell thanks to a perista].tjc pump set at a flow rate of mi/miri in order to ensure a laminar regime (Re = 10). The laminar regime, contrary to 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 surf aces themselves and on the -12 -suspending liquid.

The adhesion of the microorganisms on the glass surface was monitored using a microscope (Leica, lOx magnification). A photo was taken every 10 minutes. By computer analysis of this photo, it was possible to determine the percentage of covering of each photo and thus build a curve which represents the percentage of covering of the surface by the bacteria as a function of the contact time.

The adhesion tests under dynamic conditions were carried out with the R3 culture aged for 22 hours.

It was observed that the degree of covering achieved constant values: -of 35% in 30 hours for bare glass; -of 15% in 20 hours for the Tb2 glass.

Consequently, the bacteria adhere less well to the Ti02 glass.

Moreover, in the examples of document WO 03/087002 using the same Ti02 glass (mesoporous layer) glass, it was shown that this had a photocatalytic activity even under weak UV irradiation such as inside a building or a transport vehicle. It may be assumed that this photo-catalytic activity is not without effect on the bacteria themselves in order to explain their much lower level of covering.

Furthermore, still under the same weak 131/ irradiation, the Ti02 glass becomes more hydrophilic. A flow of water may thus detach the bacterial cells, especially dead ones, from the surface of the Ti02 glass more effectively than from the surface of the bare glass.

Thus, this example demonstrates the self-cleaning properties of the Ti02 glass with respect to the -13 -bacteria tested.

This layer is therefore recommended for applications for destroying, at least partially, or stopping the development of microorganisms especially indoors.

Claims

1. A substrate comprising at least one photocatalytic compound active under the Conditions of illuminating a building or transport vehicle interior, intended to neutralize the microorganisms with which it comes into contact.

2. The substrate as claimed in claim 1, characterized in that said photocatalytjc compound comprises Ti02 subjected to a heat treatment under an atmosphere of nitrogen or of nitrogen and of at least one reducing gas for a sufficient time to make it capable of absorbing photons from the visible spectrum.

3. The substrate as claimed in claim i or 2, characterized in that it consists of a close combination of a first photocatalytjc compound and a second compound having a bandgap between the upper level of its valence band and the lower level of its conduction band corresponding to a wavelength in the Visible range.

4. The substrate as claimed in one of the preceding claims, characterized in that said photocatalyt c compound is integrated into a mesoporous structure.

5. The substrate as claimed in claim 4, characterized in that the functional agents such as microbicjdes are contained in the pores of said structure.

6. The substrate as claimed in one of the preceding claims, characterized in that said photocatalytic compound comprises Ti02 doped with N and/or s and/or at least one metal ion.

-15 -

7. The substrate as claimed in claim 6, characterized in that TiC2 doped with N is obtained by a liquid route from at least one precursor containing Ti in the presence of at least one compound having an ammonium functional group, then heat treatment.

8. The substrate as claimed in claim 6, characterized in that TIC2 doped with V, Cr, Mn, Mo, In, Sn, Fe, Ce, Co, Cu, Nd, Zn, W, Nb, Ta, Bi, Ni, Ru at a concentration of 0.5 to 10 mol% is obtained by coPrecipitating a titanium compound such as an alkoxide and a metal salt, followed by a heat treatment.

9. The substrate as claimed in one of the preceding claims, characterized in that said photocatalytic compound, or at least part of the coating which incorporates it, are covered by a noble metal in the form of a thin film of Pt, Rh, Ag or Pd type.

10. The substrate as claimed in one of the Preceding claims, based on glass or polymer(s), especially that are transparent, or a ceramic substrate, or glass-ceramic substrate or substrate made of architectural material of the type: façade render, concrete slabs or paving, archjtectonjc concrete, concrete block, brick, tile, material of cementjtious composition, terracotta, slate, stone, metallic surface, or a fibrous substrate based on glass of the mineral insulation wool type, or glass reinforcement yarn, fabric, material for coating walls of buildings such as wallpaper, or based on wood or paint.

11. The substrate as claimed in claim 10, characterized in that it is made of flat, especially soda-lime, glass.

12. The substrate as claimed in one of the preceding -16 -claims, characterized in that said photocatalytic compound is contained in a layer having a thickness between 5 nm and 1 tm.

13. A process for preparing a substrate as claimed in one of the preceding claims, characterized in that said photocatalytic compound is deposited by room-temperature vacuum sputtering, possibly magnetron sputtering and/or ion-beam sputtering, using a metallic Ti or TIOX target with x < 2 and an oxidizing atmosphere or using a Ti02 target and an inert atmosphere.

14. The process for preparing a substrate as claimed in one of claims 1 to 12, characterized in that said photocatalytic compound is deposited by a solid, liquid or gas pyrolysis process of the CVD type.

15. The process for preparing a substrate as claimed in one of claims 1 to 12, characterized in that said photocatalytic compound is deposited by a sol-gel process.

16. The use of a substrate, as claimed in one of claims 1 to 12 as a surface for the inside of a public building such as a hospital or an individual house or apartment, or furniture, or of the inside of any terrestrial, water-borne or airborne transport vehicle, including clothing or any accessory worn by the occupant.

17. The use of a substrate, as claimed in one of claims 1 to 12 as self-cleaning, especially antifogging, antisoiling and anticondensation, glazing, especially for buildings of the multiple glazing type, double glazing, glazing for transport vehicles of the type: windshield, rear window or side window for an automobile, glazing -17 - for a train, plane or boat, utilitarian glazing such as glazing for an aquarium, shop window, greenhouse, interior furnishings -shelf or shower cubicle, for Street furniture, mirrors, screens for display systems of the computer, television or telephone type, electrically operated glazing such as electrochromic, liquid crystal or electroluminescent glazing, photovoltaic glazing or glazing for a lamp.

18. The use of a substrate as claimed in one of claims 1 to 12, in the filtration of liquids or gases, aeration and/or air-conditioning devices, ventilation ducts or water pipes.