Substrate with photocatalytic and/or hydrophilic coating

SUBSTRATE COATING PHOTOCATALYTI EU AND / OR HYDROPHILIC

The present invention relates to substrates provided with a photocatalytic coating and / or a hydrophilic coating, and their different applications.

It relates more particularly photocatalytic coatings comprising semiconductor materials based on metal oxide, in particular titanium oxide, which are capable, under the effect of a suitable wavelength of radiation, to initiate reactions radical causing the oxidation of organic products. These coatings thus possible to confer new functionalities to the materials they cover, in particular anti-fouling, fungicidal or bactericidal. They generally have jointly hydrophilic properties.

The invention also relates to purely hydrophilic coatings, which are not photocatalytic nature.

Whatever the coating, many substrates are possible. It can especially be material used in building construction, architectural material, such as facade materials, siding, roofing, decks, windows. These include, but not limited to the following materials: glass, metal, glass ceramic, ceramic, cement, brick, wood ... material reconstituted from these natural materials, material including transparent organic polymer, such as polycarbonate.

It is already known international patent applications WO97 / 10186, WO97 / 10185 and W099 / 44954 coatings containing TiO₂ granulated anatase having photocatalytic properties, coatings obtained from the thermal decomposition of suitable organometallic precursors and / or from particles of TiO₂ "Precrystallized" and embedded in an inorganic or organic binder. It is also known from the French patent application FR99 / 13937 of 5 November 1999, corresponding to PCT / Froo / 03037 of 31 October 2000, diaper hydrophilic silicon-based compound at least partially oxidized as of silicon oxide (stoichiometric or substoichiometric in oxygen), oxycarbide and / or silicon oxynitride. These layers may be deposited by sol-gel method, by vapor phase pyrolysis or by sputtering.

The invention therefore aims to improve the efficiency of these different types of coatings, in particular so that their performance (photocatalytic and / or hydrophilic) are extended in time. The invention first of all relates to a substrate provided on at least a portion of its surface with a coating having photocatalytic properties and / or hydrophilic, and which is associated with a device for distributing water on said surface coated.

The term "water" in the sense of the invention essentially any aqueous solution that may contain a number of dissolved additives, the surfactant type detergent agent.

The term "substrate" all materials mentioned above, including those of architectural type. The invention is particularly interested in transparent substrates used as glazing to equip buildings, displays, street furniture. They are generally based on rigid substrates of glass or polymeric material. They can also incorporate flexible substrates of polymeric material, which is then is assembled to rigid substrates.

Photocatalytic coatings more emphasized are those mentioned above, and comprising titanium oxide at least partially crystallized in the anatase form. The coating may further comprise another type of material generally in the form of at least one oxide, in particular an amorphous or partially crystallized. Jl may be type oxides of silicon oxide, titanium oxide, tin oxide, zirconium oxide or aluminum oxide.

The combination of a substrate and functionalized with a water dispenser is quite unexpected, but brings real improvement. Indeed, photocatalytic coatings are able to degrade dirt when they are oxidized, that is to say e n of predominantly organic nature dirt. It may be so fingerprints, gasoline residues. By cons, these coatings can not degrade the mineral soiling. These mineral soils tend to progressively cover the coating, and may after a certain_temps disable somehow. This is even more true that these coatings often have a surface roughness for increasing their active surface. But that relief is also conducive to contamination by non-degradable by oxidation stains.

The invention therefore proposes to project water at intervals up to the surface of these coatings for a double result: + one hand, water is intended to drive the mineral soiling, this drive is facilitated when the coating is hydrophilic. The glazing is also stripped of part of its soiling,

** Other hand, the water, removing the coating of these mineral soiling, makes it more effective to degrade organic stains (in the case of a photocatalytic glazing).

This dual effect helps to get a glazing which, overall, is kept clean in time a photocatalytic / hydrophilic glazing not equipped with water dispenser or a standard glazing. One can thus render cleaning "aggressive" manuals with detergents. This system can effectively compensate for insufficient rainfall or a provision of the non-exposed to rain substrate. Thus, when the glazing is set back from the facade of a building or in an unfavorable configuration, it may never be exposed to rain. The water dispenser according to the invention allows to recreate the pull of soil by rain, but much more evenly, leaving no streaks on the glass, and without randomness by geographical location or the reporting season.

The invention is thus particularly useful in three cases (can be cumulative): when the glazing is exposed to particular mineral soiling Important / abundant. This may be for example of sagging concrete or aluminum, or sodium sulfate particles that are frequently encountered in urban atmosphere and make them blurry glazing,

> When the coatings are moderately photocatalytic / hydrophilic from the start (or gradual fouling by mineral soiling in particular)

>^• when it does not rain or very little, to the windows, either because of climatic conditions or because of the glazing installation configuration (eg when the windows are mounted on a building facade so as to be flush on internal wall: it rarely rains on the glass in its upper part at least)

That mineral soils are transparent or not, they serve to reduce the photocatalytic / hydrophilic character of the coating, by a sort of passivation / "screening". The coating becomes less effective cleaning is needed again, even if they remain less frequent than for uncoated glass, which is still annoying when the windows are difficult to access (roofs including glazing).

The advantage of the invention is to allow to further reduce the frequency of cleaning "conventional" necessary to maintain clean the windows, this compared to untreated glazing or without water dispenser.

By spraying with water according to the invention, the coating restores its efficiency, capacity is improved to 'self-clean' by a simple measure, which exploits the hydrophilic nature of the coating: water according to the invention, has lead to excess mineral soiling present on the surface coatings.

It can be seen the method according to the invention two subsidiary advantages:>^• firstly, it will not need to conventional cleaning, therefore use less detergent, which is good for the environment,

> Secondly, the coatings are thus less mechanical stress (less friction with cloths, scrapers, ...) and therefore less wear.

The invention is simple in implementation. Thus, the water dispenser may include a simple water spray rail capable to be a series of discontinuous water jets, a water slide, towards the coated surface of the substrate. The dispenser may also include several spraying ramps. The simplest is to use the effect of gravity: when the coated substrate, once mounted, is inclined or vertical, but not horizontal, it is sufficient that the water ramp distributes water towards the top of the coated surface, so that the water flows on its surface by gravity until the bottom.

When the substrate is a pane mounted outdoors, equipping a building facade in particular, can be disposed ramp sprinkling water in or close to the roller shutter casing which equips this glazing.

Can also be used ramps or other spray systems disposed on or near the lateral uprights of the glazing (vertical if the glazing is in a vertical plane), the water can be sprayed for example by two ramps facing each other and projecting water to the surface of the glazing in question.

Can also be associated to the substrate coated according to the invention a device capable of collecting the water once past its surface, for example a simple gutter.

One can predict that the water distribution device, at least in its terminal part of the type ramp spray, or secured to the substrate by mechanical means, and possibly the water collection device. It is preferable that these mechanical means possible to easily replace a ramp by another in case of malfunction of the water dispenser.

The water supply can be controlled in different ways: the control can be fully manual, distributing water as soon as the window looks a little dirty. One can also opt for an automatic distribution, that fires alone at fixed time intervals. One can also provide a more sophisticated regulation, involving electronic / computing means, and taking into account for example the ambient rainfall (using a humidity sensor for example) or the degree of soiling of the coating ( optical changes).

regulation can thus be based on the blur evolution of the glazing (the diffuse transmission in the visible), choosing the threshold beyond which sprinkling is automatically triggered.

One can control the frequency of the water supply, its duration and the flow of water.

Water projected onto the substrates of the invention may be water without additive, city water, for example. so we can supply the water dispenser using an ordinary water supply, without having to store a particular liquid.

Can also be added to water one or more additives: it may be surfactants, degreasing agents, usually in small amounts. then can be subjected to the substrates in question not a spray in one step, but a cycle follow at least two spraying. It is thus possible to have a cycle of three steps: a sprinkling with water without additive, a second spraying with water provided with additives and a third with water without additive again playing the role of step rinsing. There can also be a cycle of two steps only, by deleting the first step of the cycle mentioned above. This requires having as many as spraying ramps of different liquids, or use a single spray boom where you can switch automatically feeding a fluid type to another (using tanks storage and / or water inlets).

The invention also relates to the process of implementing this combination of a functionalized substrate with a photocatalytic coating and / or hydrophilic, with a water dispenser to reactivate said coating, to reduce the frequency of cleanings or delay fouling (the water distributor being capable of supplying water without additive, or at least for part of the water with appropriate additives). The process according to the invention may thus use the water dispenser described above, it can also use other means not necessarily fixed water supply, including manually operated, such as a garden hose, a watering can or containing suitable liquid.

The invention will be described in more detail below using non-restrictive examples and Figure 1 which shows very schematically a glazing in a position where it is mounted outdoors on a facade. EXAMPLE 1 This glazing 1 consists of a glass clear silica-soda-lime of 4 mm thick, provided with a thin layer of silicon oxycarbide (SiOC) of 50 nm thick, then a photocatalytic coating comprising TiO₂ crystalline anatase according to the teaching of the patent WO99 / ​​44954 supra, specifically near its example 15. The coating deposition photocatalytic was made by sol-gel according to a technique of spray-coating from a dispersion mixing two solutions / initial dispersions 1 and 2:

+ 1 solution: the solution containing the organometallic precursor of the inorganic binder based on TiO₂ and SiO₂. This is stabilized with titanium tetrabutoxide acetylacetonate CH₃-CO-CH₂-CO-CH₃ and tetra éthylorthosilicate (TEOS) dissolved in ethanol and ethylene glycol,

+ - 2 dispersion: the liquid phase containing ethylene glycol photocatalytic crystallized particles, following characteristics: specific surface area of ​​the particles: 350 m² / G>^• particle size: 45 nm - crystallite sizes which constitute the particles: 7 nm

>^• crystalline phase: anatase greater than 80%

Adjusting the composition of the dispersion resulting from the mixture of solution 1 and dispersion 2 for the report: = rι TiO₂ (Particles) / (T1O2 binders) desired, that is to say the weight ratio of titanium oxide from the particles of the dispersion 2 of the weight of titanium oxide (1) and the silicon oxide from the solution 1. Here, the ratio X_\ is about 50/50.

There is therefore a photocatalytic coating by the presence of crystallized particles, which adhere to the substrate by the binder formed of titanium oxide and silicon oxide, amorphous rather, obtained by thermal decomposition of two precursors of titanium and silicon .

EXAMPLE 2

This example uses the same substrate as in Example 1, having a first layer of 50 nm SiOC then a layer of T1O₂ photocatalytic deposited "cell coating" from a solution containing di-isopropoxy di- titanium and titanium octylene glycolate tetra-acetylacetonate dissolved in a mixture of acetate étyle and isopropanol, in accordance with example

9 of WO97 / 10186 cited above. EXAMPLE 3

This example always uses the same substrate, having a first layer of 50 nm SiOC then a second layer of 60 nm of photocatalytic TiO2 obtained by CVD from titanium tetraisopropoxide, according to Example 7 of WO97 / 10186 cited above. The three thus functionalized glazing can be mounted in building facade. As they are then a little off, they are in fact little exposure to rain, even if any. So we add in a top water spray boom 2, also a little behind the facade so as to be almost invisible to the outside. It is connected to a source of water by a not shown appropriate duct. Automatically every week, the ramp can distribute for a few minutes the water as fillets from 3 ribbon streaming from top to bottom glazing to "regenerate" the photocatalytic coating and rid mineral dust. This dust removal is easier if the three photocatalytic coatings are highly hydrophilic.

To measure the beneficial effect of the invention on the efficiency of photocatalytic coatings was installed three windows described above, and a fourth glazing devoid of any coating for comparison, in urban areas. The glazing of dimensions 40 x 40 cm, were placed in height (50 meters) for an atmosphere of urban pollution "background" (that is to say, undisturbed by too close of gas échappemenent auto) with mineral soil mainly in the form of calcium sulphate particles. We installed a canopy of borosilicate glass (transparent to UVA) to protect the windows from the rain. It was observed that:> for the comparative glass without photocatalytic coating, its diffuse transmission from 0.2 to 5% of the total transmission in le_visible in about two months,> for the other three lenses bearing the photocatalytic coating, the diffuse transmission also increases, to a lesser extent, however, and their photocatalytic activities drop significantly after one month (about 25 to 30%).

was then installed in accordance with the present invention, under the roof, a water ramp comprises a pipe perforated with holes spaced 1 cm from each other and connected to a pump. The ramp up asparagus glazings for 1 minute once per week (flow rate: 1 liter / minute).

Under these conditions, it was observed that the diffuse transmittance of the three glazing provided with photocatalytic coatings remains less than 0.7% for at least two months. Their photocatalytic activities remained substantially the same after one month. The comparative glass without photocatalytic treatment has a diffuse transmission which reached 2% of the total transmission in the visible (T> after 2 months. This is proof that a sprinkling of water sufficient to avoid large part passivation of photocatalytic coatings and improves' antifouling efficiency.

Many configurations are possible for the spray boom: it can be mounted (removably) directly on the amount of the upper edge of the window (or on its side pillars). It can also be removable on the facade itself or in or near a roller shutter housing. It is best to choose the configuration best hiding, according to the assembly of the glazing, the building type, ....

If the glazing is not vertical, and is slightly inclined relative to the horizontal, to have a true training effect, it may be preferable that the water is circulated at high pressure. Otherwise, a simple run low flow / low pressure by gravity is more than enough: the invention is effective to enhance / extend the antifouling effect of photocatalytic coatings, and / or hydrophilic, without the need for complex equipment, and without changing structurally said coatings, which is quite advantageous. It can significantly reduce the frequency of manual cleaning, and, in parallel, the amount of detergent used during these cleanings.

The invention applies in the same way for glazings provided with hydrophilic coatings, photocatalytic without being, in particular based on SiO₂, SiON or SiOC, of ​​the type described in application FR99 / 13937 above. This is in particular oxide coatings or refractive index of silicon oxycarbide can range between 1, 45 and 1 80 (including 1, 50 to 1, 75 or 1, 55 to 1, 68) and a thickness of at least 5 nm, especially between 10 and 60 nm. Their water contact angle is generally below 35 ° C, especially less than or equal to 30 °.