Substrate with a self-cleaning coating

Translation of description of equivalent WO 03087002 A1

SUBSTRATE COATED SELF-CLEANING

p0002The invention relates to different types of material that can be found in buildings, vehicles, street furniture or in appliances, namely, in particular:

p0003- Transparent substrates of glass or polymer for use as glazing, for example display screen,

p0004- Ceramic substrates or ceramic that may be used for example in household appliances,

p0005- Architectural materials like tiles, tiles, stone, cement compositions of metal surfaces - fibrous mineral materials, such as insulation glass wool or son textile glass, which can be used as filtering material, to make false ceilings, quartz fibers, silica ...

p0006Recent studies have been done to try to improve the ease of use of these materials, in particular to facilitate maintenance. In particular it has been developed functional coating having photocatalytic properties. These include coatings comprising TiO₂ at least partially crystallized, especially in anatase form and which are described in WO 97/10185, WO 97/10186, WO 99/44954 and WO 01/66271. This type of semiconductor material based on metal oxide, optionally doped (there are also other oxides may be photocatalytic, such as ZnO ...) is capable under the effect of radiation length of adequate wave of initiating radical reactions causing the oxidation of organic compounds: this type of coating, if sufficiently exposed to the ad hoc radiation (typically ultraviolet possibly the visible range), is very effective in degrading organic dirt. In addition, it has been found that, in particular when it is based on titanium oxide coatings, they also exhibited some hydrophilicity if exposed long enough to said radiation. This coating is thus very efficient, in that it is capable of degrading organic soiling, and evacuate by its hydrophilic mineral dirt. However, its activity is linked to exposure (for sufficient time) to radiation (intense enough) ad hoc wavelength. This type of coating is thus a behavior that depends strongly on the surrounding environmental conditions in case of outdoor exposure, including sunlight conditions, rainfall. Similarly, it tends to have a nocturnal activity lower than its daytime activity, in the absence of proper lighting. The invention is therefore to further improve the functionality afforded by this type of coating "self-cleaning" or "Contamination retardants." It aims including obtaining coatings that can have increased efficiency, which can be more "versatile" for various reasons: first vis-à-vis the radiation exposure conditions, then vis-à-vis the constraints mechanical (abrasion resistance ...) finally vis-a-vis the association of other features. It relates more particularly to the production of coatings that can, even in poor sunlight conditions, even at night or indoors in particular under the action of residual ultraviolet radiation of conventional lamps or radiation ultra- purple passing through a glazing, have a certain anti-fouling activity. It also seeks the products to which a UV lamp is associated, including self-cleaning filters.

p0007The invention first of all relates to a substrate which may be substantially transparent, in particular based on glass or polymer (s), or which may be ceramic or vitro-ceramic, or which may still be in architectural material (facade coating type tile or concrete pavers, architectural concrete, tile, material cementitious composition, terracotta, slate, stone, or can even be a fibrous substrate having a glass base of mineral wool insulation type or son reinforcing glass, or a product comprising quartz or silica fiber). This substrate is characterized in that it is provided on at least a portion of its surface with a coating whose mesoporous structure exhibits photocatalytic properties and comprises titanium oxide at least partially crystallized, especially in anatase form and / or rutile. The term "mesoporous" refers to pore diameters between 2 and 50 nm. The mesoporous structure obtained in the manner to be described below, is in particular based on at least one compound of at least one of Si, W, Sb, Ti, Zr, Ta, V, B, Pb , Mg, Al, Mn, Co, Ni, Sn, Zn, in, Fe and Mo, optionally covalently bonded to elements such as O, S, N, C or the like. The titanium oxide at least partially crystallized, for example, incorporated into the mesoporous structure in the form of perfectly distinguishable particles. The entire mesoporous structure incorporating titanium oxide is substantially solid, susceptible to cohesion, mechanical strength and an excellent resistance to abrasion. The mesoporous structure is likely to be composed exclusively of titanium or a titanium compound as the oxide, especially crystallized in the anatase form, rutile ... It has been found that titanium oxide thus incorporated operates photocatalytic to an unusually high degree. Thus a residual ultraviolet radiation after passing through a single pane, double ... or residual ultraviolet radiation from an interior electrical lighting sufficient for the substrate of the invention so that it degrades a residue organic, and for the latter is then driven in a relatively uniform-liquid film formed if necessary on the rendered hydrophilic by radiation substrate. The coating of the invention combines the organic waste degradation feature -by photocatalyse- and disposal of organic waste and minerals hydrophilic -caractère / oléophile- under the influence of any liquid such as condensation. High performance procured by the invention may be attributable at least in part the pores of the interconnection network, allowing a good accessibility of pollution to the titanium oxide particles, and a good distribution in the coating photogenerated species on the surface of these particles.

p0008Moreover, abrasion resistance and durability of the photocatalytic activity to such a high degree are excellent (see examples below). The invention therefore also keeps the porosity after abrasion, so that one could rather expect that abrasion has resulted in a densification of the surface layer and thus ultimately, loss of anti-fouling properties.

p0009In addition, the mesoporous nature of the substrate makes it possible to consider after impregnation to the formation of the mesoporous structure with deodorant functional agents, antibacterial or of any other nature.

p0010Advantageously, the substrate of the invention is essentially transparent, flat or curved, glazing type because it is in this type of application that the accumulation of dirt preventing visibility is the most troublesome, and the washings are more necessary to ensure their transparency. This may be of glazing having a macroscopic relief e.g. motifs pyramids depths of the order of a few millimeters -glass printshop, or a glazing having a much smaller surface irregularities such as resulting from etching with hydrofluoric acid -glass sandblasted, matifié-.

p0011Preferably, the coating of the invention is formed with the interposition of a sublayer based on at least partially oxidized silicon derivative chosen from silicon dioxide, silicon oxides substoichiometric, oxycarbide, the oxynitride or silicon oxycarbonitride. The underlayer is useful when the underlying surface is glass, because the migration of alkali metal ions (sodium) of the glass in the coating of the invention can, under certain conditions, detrimentally affect the photocatalytic properties; Gold underlayment acts as a barrier to alkaline. The underlayer may be of the type described in WO 01/32578 cited above. It advantageously has a refractive index between 1.45 and 1.80, especially between 1.50 and 1.75, for example between 1.55 and 1.68. Such an index allows relatively low, on a transparent substrate of the glass type, to avoid a reflective effect that may be deemed unsightly. This sublayer therefore advantageously comprises Si, O, optionally carbon and nitrogen. But it can also include minority materials compared to silicon, for example metals such as Al, Zn and Zr. The sub-layer may be deposited by sol-gel or by pyrolysis, particularly by chemical vapor deposition (CVD). The latter technique allows for coatings of SiO_xC_there or SiO₂ rather easily, especially by depositing directly on the float glass ribbon in the case of glass substrates. But one can also carry the deposit by a vacuum technique, for example by sputtering using a Si target (optionally doped) or a target made of silicon suboxide (in oxidizing reactive atmosphere and / or nitriding for example).

p0012This sub-layer preferably has a thickness of at least 5 nm, in particular a thickness of between 10 and 200 nm, for example between 80 and 120 nm. According to other advantageous characteristics of the substrate of the invention:

p0013- The coating with a mesoporous structure is deposited by sol-gel;

p0014- Its thickness is between 30 and 800 nm;

p0015- Titanium oxide incorporated into the mesoporous structure is optionally doped as explained in WO 97/10185 and WO 97/10186 incorporated herein by reference, and comprises nanoparticles of diameters between 0.5 and 100 nm, especially between 1 and 80 nm, themselves consist of clusters of grains or elementary crystallites of diameters between 0.5 and 10 nm. The term "diameter" is to be taken here in the broad sense, it's more of an assessment of the size of the nanoparticle or crystallite. The shape thereof may approximate a sphere, or an elongated shaped grain of rice or a form completely random.

p0016Another object of the invention resides in a method of manufacturing a substrate as described above, comprising successively: - the preparation of a liquid composition comprising at least one precursor of the material constituting the mesoporous structure of the coating and least one organic structuring agent,

p0017- The precipitation of the precursor around the organic structuring agent and the growth of molecules derived from the precursor, - adding in the liquid composition of nanoparticles or crystallites -according explanation above definition of optionally doped titanium oxide, diameters between 0.5 and 100 nm,

p0018- The application of the composition to the surface to be coated,

p0019- The elimination of the organic structuring agent, the elementary grains or titanium oxide crystallites being incorporated into the mesoporous structure while essentially preserving their integrity, several of which may be aggregated into clusters. During such manufacture the substrate, it is not excluded that grains or crystallites of titanium oxide are aggregated with each other and / or grow, especially the small ones, according to the operating conditions (concentration, pH, temperature ...). For the manufacture of the substrate of the invention, the preparation of the liquid composition advantageously comprises:

p0020- The preparation of an oxide precursor sol (especially silica), - soil ripening, then

p0021- Mixing with the structuring agent.

p0022In fact, the ripening sol allows a preliminary condensation of the oxide precursor which promotes the structuring of fused oxide coating on the support surface in areas of large size. curing advantage include maintaining the ground at a temperature of 40 to 60 ° C for a period of 30 minutes to 24 hours, the maturing time being shorter as the temperature is high.

p0023In this case, the oxide precursor is advantageously a hydrolyzable compound, such as a halide or an alkoxide, the structuring agent is advantageously chosen from cationic surfactants, preferably of the quaternary ammonium type, such as cetyltrimethylammonium bromide, or not ion, the di-block copolymers or three-block basis_^ for example ethylene oxide or propylene oxide.

p0024The invention also provides substrates of the application object of the invention, including those which are essentially transparent, to the manufacture of glazings "self-cleaning", which can be in both antifouling, antifogging and anti -condensation. It may be glazing for the type Double glazed building, glazing for vehicle windshield type rear window, sunroof, side windows. It can also be glazing for trains, airplanes, boats. It can also act as utilitarian glazing aquarium glass, glass windows, greenhouse, or glazing used in interior furnishings, in street furniture, mirrors. It can also be used as screen glazing type display screens of TV, computer, phone. This type of coating may also be applied to electrically controllable glazing, such as heated glazings son or layer, electrochromic glazing, liquid crystal glazing film, the electroluminescent glazing, photovoltaic glazing.

p0025In the application of the substrate of the invention as glazing (based on transparent plastic or glass), one or more thin layers other than the aforementioned sub-layer based derivative at least partially oxidized silicon, may be interposed between the support surface and the coating with a mesoporous structure. These may include, antistatic layers to function, thermal (heating by providing it with current leads, low-emissive, anti-solar ...), optical (reducing the light reflection and / or making it more neutral the color in reflection of the substrate ...) of a stack of anti-reflection layers ... regarding such functional layers applied in known manner on the glass, optionally in the form of stacks, the applications WO 97 / 10186 already cited WO 02/02472 and are incorporated herein by reference.

p0026The substrate according to the invention, in addition to its application as glazing, may be used in any architectural material for making partitions, facades, roofs, floors, indoors or outdoors (metal, wood, stone, cement, concrete, terracotta , ceramic, facade coating ...) The substrate, if instead based on mineral insulation wool and textile-based reinforcing glass fibers, can be used as filter material, or serve to false ceilings, including cleaning is inconvenient.

p0027The invention also relates to the application of a woven substrate, non-woven (needled mat, felt, wool ...), knitted, woven, block sintered fiber (known as rigid silica) -based fiber diameters between 1 and 20 microns fused silica, washed glass (more than 90% silica), alumina and mullite according to claim 1, in the manufacture of anti-odor filters, decontamination of industrial effluents, anti-bacterial, interior decontamination, purification of domestic air purification interiors of transport vehicles (automobiles, rail, air, water), cigarette smoke purification purification system appliances (refrigerator ...).

p0028The invention will be described below with non-limiting examples.

EXAMPLE 1

p0030Is deposited on the glass in the form of yet a ribbon of float glass, a sublayer based on silicon oxycarbide SiOC noted by convenience (without prejudging the actual rate of oxygen and carbon in the coating) - glass is a clear soda-lime-silica 4 mm thick, as sold by Saint-Gobain Glass France under the name Planilux-. This sub-layer is deposited by CVD from Si precursors, in particular a mixture of SiH₄ and ethylene diluted in nitrogen, with a nozzle disposed above and transversely to the ribbon of float glass of a flat glass production line, in the float enclosure, when the glass is still at a temperature of about 550 to 600 ° C. The obtained coating has a thickness of about 50 nm and a refractive index of about 1, 55. Were cut samples of 10 cm x 10 cm float glass provided with its SiOC sublayer barrier to alkali metals thus obtained; these samples are washed, rinsed, dried and subjected to UV ozone treatment for 45 min.

p0031Is formed on the undercoat layer a coating with a mesoporous structure.

p0032The 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 deionized water (pH 1.25) until the solution becomes clear, then placing the ball in a water bath at 60 ° C for 1h.

p0033In a second step, is added to the sol obtained previously cetyltrimethylammonium bromide solution (CTAB) on the one hand, and a solution of a polyoxyethylene-polyoxypropylene copolymer blocks sold by BASF under the trademark Pluronic PE6800 (molar mass 8000) on the other hand, in proportions such that the molar ratios CTAB / Si = 0.1, respectively PE6800 / Si = 0.01. This is obtained by mixing: - 0.686 g CTAB, 20 ml of ethanol, and 10 ml of the sol;

p0034- 3.78 g of PE6800, 50 ml of ethanol and 25 ml of the sol.

p0035Nanoparticles of anatase crystallized T1O2 and size of about 50 nm are added in various proportions to one or other of the two liquid compositions thus obtained, just prior to deposition on sample. The deposition is done by spin coating in an amount of from 3 ml per sample. (Other equivalent deposition techniques are dip coating, spraying, laminar coating, roll coating, flow coating ...)

p0036The samples were then subjected to the following annealing treatment:

p0037- 30 min 100 ° C 2 h bearing; - 15 min 150 ° C Level 2 pm;

p0038- 15 min 175 ° C Level 2 pm;

p0039- 10 min 200 ° C not bearing;

p0040- 3 h 20 min 300 ° C Level 1 pm; - 2 h 30 min 450 ° C threshold 1h.

p0041The pores of the coating thus formed have a size of 2-3 nm when the cationic surfactant CTAB is used as a structuring agent, this size being 4-5 nm when the PE6800 copolymer is used as a structuring agent. SIMS analysis is verified by the coating with a mesoporous structure that the atomic ratio Ti / Si is exactly identical to the starting liquid composition. The SIMS analysis also ensures that the nanoparticles are distributed uniformly in the three dimensions of the coating. is set in the table below the different characteristics of the coatings to their training and after 500 cycles of the abrasion test Opel - in the latter case, indication of values ​​between parenthèses-. The Opel test (Standard Building In 1096-2 January 2001) consists in applying to a portion of the coated surface of 9.4 cm -this part length is called Track-, a felt 14 mm diameter, 10 mm thick and 0.52 g / cm² density under a load of 400 g / cm²The felt being subjected to a translation (50 roundtrip returns over the entire length of track per minute) combined with a rotation of 6 revolutions / min (1 cycle = 1 return).

p0042The thickness E of coatings in nm was measured from SIMS profiles and SEM pictures.

p0043The amount of TiO₂ in g / cm² is evaluated by X-ray fluorescence is measured photocatalytic activity as follows:

p00441- test performed on about 15 cm² coating;

p00452- weighing the sample and measuring the thickness of the substrate, the light transmission TL and the blur Td (both in%);

p00463- spray by depositing a solution of palmitic acid (8 grams of acid per 1 l of chloroform), with a glass distance / spray 20 cm, on a vertical substrate, and 3 to 4 successive passages;

p00474- sample weight after deposition of palmitic acid to evaluate the thickness of deposited palmitic acid in nanometers;

p00485- measuring the light transmission T and blur Td after filing;

p00496- measurement of the variation of the blur depending on the irradiation time under UVA intensity of approximately 50W / m² ; 7 graphics determining the time at which blurring has decreased by 50%: time called T₁ 2 (disappearance); 8- evaluation of photocatalytic activity of the coating rate of disappearance of v palmitic acid (in nm / h), which is defined as follows: v (nm / h) = (palmitic acid thickness (nm )) / (2 x T y₂ (Disappearance (h))

p0050Also shown in the table below the value of the photocatalytic activity reduced the amount of TiO₂ in the coating. Finally, it indicates the optical properties of IR light reflection and blur Td (in%). Test numbers are defined as follows: - 1 and 2: CTAB as structuring agent, Ti / Si = 0.1, respectively 0.25; - 3-7: PE6800 as structuring agent, Ti / Si = 0.1, respectively 0.25, respectively 0.5, respectively 1 and 2 respectively.

p0051<img id="imgf000011_0001" he="129" wi="153" file="imgf000011_0001.tif" img-format="tif" img-content="table" orientation="portrait" inline="no" /> The layer thicknesses range from 200 to 500 nm depending on the amount of nanoparticles of TiO₂ incorporated. Opel after 500 cycles, only the thicker coatings (450 and 500 nm) undergo a greater compaction to half their original thickness. Photoactivity of these coatings has nevertheless been tested.

p0052The coatings have photoactivités 43 nm / h for the structured coating with the cationic surfactant, and less concentrated in

p0053TiO₂ (2.2 g / cm²) At 684 nm / h for the structured coating with the copolymer and most concentrated TiO₂ (66 g / cm²). The ratio v / TiO₂ is always at least equal to 9.

p0054There is a total or partial maintenance of functionality after 500 Opel cycles, which otherwise does not affect the optical properties than for thicker layers and the more concentrated Ti0₂ (Ti / Si = 1 and 2) -in the other, the values ​​of RI and Td remain below 11.4 and 1.2% respectively- was repeated tests 3 to 7 (Tests 3 'to 7') with weak UVA irradiation of 1.5 W / m² a classical lighting lamp; the values ​​of v (nm / h) and v / TiO₂ are identified for testing N °:

p0055- 3 ': 0 and 0;

p0056- 4 ': 0 and 0; - 5 ': 13 and 0.75;

p0057- 6 ': 19 and 0.57; and

p0058- 7 ': 28 and 0.42.

p0059The inventive coated substrate is also photoactive under low UVA radiation for the degradation of palmitic acid.

EXAMPLE 2

p0061Furthermore, impregnated discs of 47 mm diameter, 8 mm thick and 1000 g / m2 surface density of needle felts of silica fibers, sold by Saint-Gobain Quartz under the name needled-punched Quartzel matt (fibers between 7 and 16 .mu.m) by immersion in the test composition No. 6 above, and then heat treatment described above. The increase in mass of the thus obtained disk is 10%. the capacity of these discs were tested to decompose a concentration of 350 ppm by volume of methanol in the nitrogen gas, for filtering a flow of 62.5 ml / mm under UV illumination (190-350 nm).

p0062At an illuminating power of 48 mW / cm2, the efficiency, that is to say the proportion of methanol decomposed, is 100%. A power of 25.6 mW / cm2, it is about 96%, and even about 58% under illumination as low as 8.22 mW / cm2.

p0063Thus the invention makes it available to a substrate capable of providing the optical quality of transparency required in glazing applications, and sustainable self-cleaning functionality in terms of erosion and weathering of the outside atmosphere. The remarkably high level of photocatalytic feature lets also consider use at night or indoors by leveraging radiation of low intensities as produced by conventional lighting or the passage of sunlight through the windows, as well as applications abatement effluent or atmospheric, filtration ...