CN1984724A - Multi-layer coatings with an inorganic oxide network containing layer and methods for their application - Google Patents

Abstract

A multilayer coating is disclosed, comprising (1) a first layer comprising an inorganic oxide network, and (2) a second layer applied to at least a portion of the first layer, wherein the second layer is deposited from a hydrophilic liquid composition comprising at least one substantially completely hydrolyzed organosilicon ester. A substrate coated with the multilayer coating, a method for applying the multilayer coating to the substrate, and a method for improving the antifouling, self-cleaning, easy-cleaning, and/or anti-fogging properties of articles are also disclosed.

Description

Multilayer coatings having layers comprising inorganic oxide networks and methods of applying them

Cross References to Related Applications

This application claims the benefit of US Provisional Patent Application Serial No. 60/575,438, filed May 28,2004.

field of invention

The present invention relates to a multilayer coating comprising a first layer and a second layer. These coatings are hydrophilic and durable and exhibit, for example, advantageous easy-to-clean, self-cleaning, anti-fouling, anti-fogging, antistatic and/or antibacterial properties. In certain embodiments, the coating is capable of becoming superhydrophilic upon photoexcitation of the photocatalytic material.

Background of the invention

Hydrophilic coatings are advantageous for certain coating applications, such as when a coated surface that exhibits stain repellency, ease of cleaning, self-cleaning, and/or anti-fogging properties is desired. Such coatings can be particularly useful, for example, for application to surfaces exposed to the outdoors. Building structures and other articles exposed to the outdoor environment are likely to be exposed to various pollutants such as dirt, oil, dust, clay, etc. For example, rainfall can carry such pollutants. The surface on which the hydrophilic coating is deposited can exhibit antifouling properties by preventing pollutants in rainwater from adhering to the surface when rainwater runs down the coated surface. Additionally, on sunny days, airborne pollutants may come into contact with and adhere to these surfaces. A surface coated with a hydrophilic coating may be self-cleaning and/or easy-cleaning due to the ability of the coating to wash away contaminants when the surface is exposed to water (eg, during rainfall).

Coatings having self-cleaning, easy-cleaning, and/or anti-fouling properties may also be advantageously applied to surfaces exposed to indoor pollutants, such as kitchen pollutants such as oils and/or fats. Articles deposited with a hydrophilic coating can be soaked in water, wetted with water, or rinsed with water to release contaminants from the coating and remove contaminants from the surface of the article without the use of detergents.

Coatings with anti-fogging properties are also particularly useful in many applications. For example, articles having surfaces where visibility is important, such as windshields, window panes, spectacle lenses, reflectors, and other similar articles could benefit from coatings with anti-fogging properties because they have a tendency to be condensed by steam or moisture. A surface that is fogged or obscured by water droplets adhering to its surface. It is well known that fogging of the surface of an article occurs when the surface is kept at a temperature lower than the dew point of the surrounding environment, thus causing moisture in the surrounding air to condense and form moisture condensate on the surface of the article. If the condensate particles are small enough that their diameter is about half the wavelength of visible light, the particles can cause light to scatter, whereby the surface becomes significantly opaque, causing a loss of visibility.

Surfaces deposited with hydrophilic coatings can be resistant to fogging due to the ability of such coatings to convert condensate particles into a relatively uniform film of water without the formation of discrete water droplets. Similarly, a surface deposited with a hydrophilic coating can prevent rain or splash water from forming discrete water droplets on the surface, thereby improving visibility through windows, mirrors, and/or eyeglasses.

In view of these and other advantages, various hydrophilic coating compositions have been proposed. Some of these coatings achieve their hydrophilicity through the action of photocatalytic materials dispersed in a silicon-containing matrix. For example, US Patent No. 5,755,867 ("the '867 patent") discloses a particulate photocatalyst dispersed in a coating-forming composition. The photocatalyst preferably consists of titanium dioxide particles having an average particle diameter of 0.1 micron or less, wherein titanium dioxide can be used in the form of anatase or rutile. The coating-forming ingredient is capable of forming a coating of silicone resin upon curing and consists of an organopolysiloxane formed by partial hydrolysis of a hydrolyzable silane followed by polycondensation. In the '867 patent, the polysiloxane coating-forming ingredients themselves are quite hydrophobic, but activation by the dispersed photocatalyst imparts a high affinity for water, ie, hydrophilicity, to the coating.

Japanese Patent Application JP-8-164334A discloses a coating film forming composition comprising titanium dioxide having an average particle diameter of 1 to 500 nm, a hydrolyzate of a hydrolyzable silicon compound, and a solvent. The hydrolyzable silicon compound is an alkyl silicate condensate represented by the general formula S _n O _n-1 (OR) _2n+1 (wherein n is 2-6, and R is a C1-C4 alkyl group). The hydrolyzate is obtained by hydrolysis of alkyl silicate condensates at a hydrolysis percentage of 50-1500%. However, the hydrolyzate itself is not considered to be hydrophilic.

U.S. Patent Nos. 6,013,372 and 6,090,489 disclose photocatalytic coating compositions in which particles of a photocatalyst are dispersed in a film-forming film of uncured or partially cured polysiloxane (organopolysiloxane) or its precursors. ingredients. Photocatalysts may include particles of metal oxides, such as the anatase and rutile forms of titanium dioxide. According to these patents, the coating composition is applied to the surface of the substrate and the film-forming ingredients are then cured. Then, by the photoexcitation of the photocatalyst, the organic groups bonded to the silicon atoms of the polysiloxane molecules of the film-forming component are replaced by hydroxyl groups under the photocatalytic action of the photocatalyst. The surface of the photocatalytic coating is thereby "superhydrophilized", ie the surface is rendered highly hydrophilic such that the contact angle with water becomes below about 10°. In these patents, however, the film-forming ingredients themselves are substantially hydrophobic, ie, have an initial contact angle with water greater than 50°. As a result, the coating is initially hydrophobic and is rendered hydrophilic only by excitation of the dispersed photocatalyst.

US Patent No. 6,165,256 discloses compositions capable of hydrophilizing the surface of an element to impart anti-fogging properties to the surface of the element. The composition disclosed in this patent comprises (a) photocatalytic particles of metal oxide, (b) a precursor capable of forming a silicone film or a precursor capable of forming a silica film, and (c) a solvent such as water, organic Solvents, and mixtures thereof. The solvent is added in such an amount that the total content of the photocatalytic particles and the solid matter of the precursor in the composition is 0.01-5% by weight. However, as in the previous examples, the hydrophilization of the coating formed from the composition occurs by photoexcitation of the photocatalyst, while the film-forming material itself is not hydrophilic. Therefore, the coating is not considered hydrophilic until the excitation of the photocatalyst.

However, prior art hydrophilic coatings that achieve hydrophilicity of the coating through the action of a photocatalytic material dispersed in a silicon-containing matrix have some drawbacks. A significant disadvantage is that these coatings do not exhibit hydrophilicity prior to photoexcitation of the photocatalyst. Additionally, these compositions typically require forced curing, ie, they do not cure effectively at room temperature.

US Patent No. 6,303,229 ("the '229 patent") discloses another composition that may include a photocatalytic material. The coatings disclosed in the '229 patent are formed by applying a coating composition containing a silicone resin used as a binder and obtained by hydrolysis and polycondensation of certain tetrafunctional alkoxysilanes. The coating composition may also include colloidal silica. Significantly, coating films formed from the compositions disclosed in the '229 patent may initially be hydrophilic. However, these initial hydrophilic properties are believed to be caused by the presence of colloidal silica in the composition rather than the silicone itself. It is believed that the silicone resins disclosed in the '229 patent are not inherently hydrophilic, as the desired resin pH is 3.8-6.0, suggesting that the Si-OR groups are present in amounts that prevent gelation and are hydrophilic in the resin.

It would be advantageous to provide a multilayer coating comprising a coating comprising an inorganic oxide network and a coating deposited from a liquid composition which is hydrophilic and comprises a substantially completely hydrolyzed organosilicate.

Brief description of the drawings

Figure 1 is a graph reflecting Fourier Transform Infrared Spectroscopy ("FTIR") analysis of dry films formed from base materials used in accordance with certain non-limiting embodiments of the present invention;

Figure 2 is a schematic cross-sectional view on an enlarged scale of certain non-limiting embodiments of the second layer of the multilayer coating of the present invention; and

Figure 3 is a field emission scanning electron microscope secondary electron micrograph (40,000X magnification) depicting certain non-limiting embodiments of the second layer of the multilayer coating of the present invention.

FIG. 4 is a graph illustrating the results of a durability test conducted according to the method described in Example 2. FIG.

Summary of the invention

In one aspect, the present invention is directed to a multilayer coating comprising (1) a first layer comprising an inorganic oxide network, and (2) a second layer applied over at least a portion of the first layer, wherein the second layer Deposited from at least one liquid composition that is hydrophilic and includes a substantially completely hydrolyzed organosilicate.

In another aspect, the present invention is directed to a multilayer coating comprising (1) a first layer comprising an inorganic oxide network, and (2) a second layer applied over at least a portion of the first layer, wherein the second The layer is deposited from at least one liquid composition comprising (a) a photocatalytic material, and (b) a binder which is hydrophilic and comprises a substantially completely hydrolyzed organosilicate.

In yet another aspect, the invention relates to a substrate coated with a multilayer coating of the invention.

In yet another aspect, the invention relates to a method of applying a multilayer coating to a substrate, the method comprising the steps of: (1) applying a first layer comprising an inorganic oxide network to the substrate; (2) Applying a liquid composition on at least a portion of the first layer from which a second layer is deposited, wherein the composition of the second layer is hydrophilic and includes a substantially completely hydrolyzed organosilicate; and ( 3) Curing the second layer.

The present invention also relates to a method of applying a multilayer coating to a substrate, the method comprising the steps of: (1) applying a first layer comprising an inorganic oxide network to the substrate; Applying a liquid composition on at least a portion of the first layer from which a second layer is deposited, wherein the liquid composition of the second layer includes (a) a photocatalytic material, and (b) a hydrophilic and a binder comprising a substantially completely hydrolyzed organosilicate; and (3) curing the second layer.

The present invention also relates to a method of improving the antifouling properties, self-cleaning properties, ease of cleaning and/or anti-fogging properties of an article comprising a surface deposited with a coating comprising an inorganic oxide network, the method comprising: ( 1) applying a liquid composition comprising a substantially completely hydrolyzed organosilicate on at least a portion of the surface; and (2) curing the liquid composition applied in step (1).

Detailed Description of Embodiments of the Invention

For the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences unless expressly stated to the contrary. Furthermore, except in any operative example, or when otherwise indicated, all numbers expressing amounts of ingredients such as used in the specification and claims are to be understood as modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that can vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

In this application, the use of the singular includes the plural and the plural includes the singular unless specifically stated otherwise. By way of example and without limitation, this application refers to a liquid composition comprising a "photocatalytic material". Such references to "photocatalytic material" refer to compositions comprising one photocatalytic material as well as compositions comprising more than one photocatalytic material, such as compositions comprising two different photocatalytic materials. Additionally, in this application, the use of "or" means "and/or" unless specifically stated otherwise, although "and/or" may be explicitly used in certain circumstances.

Likewise, it should be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1-10" is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, i.e., having minimum values equal to or greater than 1 and At or below the maximum value of 10.

In one aspect, the present invention is directed to a multilayer coating comprising (1) a first layer comprising an inorganic oxide network, and (2) a second layer applied over at least a portion of the first layer, wherein the second layer Deposited from at least one liquid composition that is hydrophilic and comprises a substantially completely hydrolyzed organosilicate.

The multilayer coatings of the present invention comprise a first layer comprising an inorganic oxide network. The term "network" as used herein refers to interconnected chains or groups of molecules.

In certain embodiments, the first layer of the multilayer coating of the present invention is deposited from a composition comprising a sol containing a network forming metal alkoxide such as an alkoxysilane and/or another Alkoxides of metals such as zirconium, titanium and aluminum. If used, the alkoxysilane may be an organoalkoxysilane, such as an alkylalkoxysilane or an organofunctional alkoxysilane. The alkoxylates may contain alkyl or aryl groups and may be in dimer or higher condensed form, as long as the hydrolyzable alkoxy groups remain.

In certain embodiments, the network forming metal alkoxide is an alkoxysilane of the general formula R _x Si(OR') _4-x , where R is an organic group and R' is selected from low molecular weight alkyl Such as methyl, ethyl, propyl and butyl, and x is an integer of at least 1 and less than 4. The organic group of R may be, for example, alkyl, vinyl, methoxyethyl, phenyl, γ-glycidoxypropyl, or γ-methacryloxypropyl, including their mixture. The alkoxylates are hydrolyzed according to the general reaction given below, where R, R' and x are as described above and y is less than 4.

R _x Si(OR′) _4-x +yH ₂ O→R _x Si(OR′) _4-xy (OH) _y +yR ₂ ′OH

Condensation of hydrolyzed alkoxylates proceeds according to the general reaction

or

This is followed by further hydrolysis and condensation.

In certain embodiments, the first layer of the multilayer coating of the present invention may include other components, such as ultraviolet radiation absorbers, organic film-forming polymers, and components. Non-limiting examples of compositions that can be used to form the first layer of the multilayer coatings of the present invention and their methods of production have been described in U.S. Pat. Included here for reference.

In certain embodiments, the first layer of the multilayer coating of the present invention is transparent. As used herein, the term "transparent" means that the cured coating does not substantially alter the percentage of visible light transmitted through the transparent polymeric substrate to which the coating may be applied. The tintability of a coating is a function of the amount of dye the coating acquires under certain defined conditions, expressed quantitatively as the percentage of light transmitted through the dyed coating. The colorability of a coating can be measured as described in US Patent No. 6,042,737, at column 4, line 57 to column 5, line 8, which is incorporated herein by reference.

Examples of commercially available compositions suitable for depositing the first layer of the multilayer coating of the invention are, inter alia, the Hi-Gard ^™ and SolGard(R) coating solutions commercially available from PPG Industries, Inc., commercially available from Essilor International, SA and the CrystalCoat( ^TM ) products commercially available from SDC Technologies, Inc.

The multilayer coatings of the present invention include a second layer applied over at least a portion of the first layer, wherein the second layer is deposited from at least one liquid composition comprising a substantially completely hydrolyzed organosilicate. The term "organosilicate" as used herein refers to a compound containing an organic group bonded to a silicon atom through an oxygen atom. Suitable organosilicates include, without limitation, organooxysilanes containing four organic groups bonded to silicon atoms through oxygen atoms and organooxysilanes having a siloxane backbone composed of silicon atoms ((Si-O ) _n ) organooxysiloxanes.

The organic group bonded to the silicon atom through the oxygen atom in the organosilicate is not limited and may include, for example, linear, branched or cyclic alkyl groups. Specific examples of organic groups bonded to silicon atoms through oxygen atoms in organosilicates include, without limitation, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, octyl or similar groups. Among these alkyl groups, C ₁ to C ₄ alkyl groups are often used. Examples of other suitable organic groups include aryl, xylyl, naphthyl and the like. The organosilicate may contain two or more different types of organic groups.

Specific non-limiting examples of suitable organooxysilanes are tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutyl oxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, tetraphenoxysilane, and dimethoxydiethoxysilane. These organosilicates may be used alone or in combination of any two or more of them. Among these organosilicates, tetramethoxysilane and/or its partially hydrolyzed condensate exhibit high hydrolysis reactivity and thus can easily generate silanol groups.

Specific non-limiting examples of suitable organooxysiloxanes are the condensates of the above organooxysilanes. The degree of condensation of the organooxysiloxane is not particularly limited. In certain embodiments, the degree of condensation is within the range represented by the formula:

SiO _x (OR) _y

wherein x is 0 to 1.2, and y is 1.4 to 4, with the proviso that (2x+y) is 4; and R is an organic group, such as C ₁ -C ₄ alkyl.

The coefficient or subscript x indicates the degree of condensation of the siloxane. The coefficient x refers to the average degree of condensation when the siloxane shows a molecular weight distribution. The compound represented by the above general formula in which x=0 is an organooxysilane as a monomer, and the compound represented by the above general formula in which 0<x<2 is a condensate obtained by condensation reaction of partial hydrolysis with corresponding oligomers. Meanwhile, the compound represented by the above general formula in which x=2 corresponds to SiO ₂ (silica). In certain embodiments, the degree of condensation x of the organosilicate used in the present invention is in the range of 0 to 1.2, such as 0 to 1.0. The siloxane backbone can have a linear, branched or cyclic structure or mixtures thereof. The general formula above: _SiOx (OR) _y can be determined by Si-NMR as described in US Patent No. 6,599,976, column 5, lines 10 to 41, which is incorporated herein by reference.

As previously stated, the organosilicate of the liquid composition used to deposit the second layer is substantially completely hydrolyzed. The term "substantially completely hydrolyzed organosilicate" as used herein refers to a material in which the organooxy groups of the organosilicate are substantially replaced by silanol groups such that the material becomes hydrophilic degree. The term "hydrophilic" as used herein means that the material has an affinity for water. One method of evaluating the hydrophilicity of a material is to measure the contact angle between water and a dry film formed from the material. In certain embodiments of the invention, the composition used to deposit the second layer comprises a hydrolyzed organosilicate capable of forming a dry film exhibiting a water contact angle of no more than 20°, or in other embodiments In, a water contact angle of no more than 15°, or, in yet other embodiments, a water contact angle of no more than 10°. This hydrolysis can produce network polymers, as illustrated below:

where m and n are positive numbers and m is not greater than n. In certain embodiments of the invention, substantially completely hydrolyzed organosilicates are substantially free of -OR groups as measured by FTIR or other suitable analytical techniques.

As a result, in certain embodiments of the invention, the multilayer coating exhibits an initial photocatalytic activity of no more than 20° prior to photoexcitation of any photocatalytic material that may be present in the liquid composition that may be used to deposit the second layer. The water contact angle, or in some embodiments, a water contact angle of no more than 15°, or, in yet other embodiments, a water contact angle of no more than 10°, is described below. The water contact angle reported here is a measurement value of the angle between the tangent of the drop shape at the point of contact and the surface of the substrate measured by a water drop, and was measured by using a Gaertner Scientific goniometer manufactured by Lord Manufacturing, Inc. A modified captive bubble indicator for instrument optics, determined by the sessile drop method. Place the surface to be measured in a horizontal position, facing upwards, in front of the light source. A stopped drop of water was placed on top of the surface in front of the light source so that the profile of the stopped drop could be observed and the contact angle (in degrees) measured with a goniometer optic equipped with a circular protractor scale.

Referring now to FIG. 1 , there can be seen a graph reflecting FTIR analysis of dry films formed from such hydrophilic materials. It can be clearly seen that distinct peaks are observed at the Si-OH bond wavenumber (it is 920-950) and Si-O-Si bond wavenumber (it is 1050-1100). On the other hand, it can be clearly seen that the film is substantially free of -OR groups, where R represents a C ₁ -C ₄ alkyl group, which can be detected by any significant The absence of the peaks was confirmed.

In certain embodiments, the substantially completely hydrolyzed organosilicate contained in the composition for depositing the second layer of the multilayer coating of the present invention is an organosilicate with a substantial amount of water in the presence of an acid hydrolysis catalyst. products of hydrolysis in the presence of . The hydrolysis can be performed with water present in an amount significantly greater than the stoichiometric amount capable of hydrolyzing the organooxy groups of the organosilicate. It is believed that the addition of this excess water allows the silanol groups generated by the hydrolysis of the organosilicate to exist concurrently with a large amount of water, thereby preventing the condensation reaction of the silanol groups.

Hydrolysis of organosilicates can be carried out in the presence of one or more acid hydrolysis catalysts. Specific examples of suitable catalysts include, without limitation, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, among others; organic acids, such as acetic acid, benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, ethylbenzenesulfonic acid, benzene Formic acid, phthalic acid, maleic acid, formic acid, citric acid, and oxalic acid; alkaline catalysts, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia; and organic amine compounds, other than this organosilicate Other organometallic compounds or metal alkoxides, for example, organotin compounds such as dibutyltin dilaurate, dibutyltin dioctoate and dibutyltin diacetate, organoaluminum compounds such as aluminum tris(acetylacetonate), mono Bis(ethylacetylacetonate)aluminum acetylacetonate, tris(ethylacetylacetonate)aluminum and ethylacetylacetonate aluminum diisopropionate, organic titanium compounds such as tetrakis(ethylacetylacetonate)titanium, bis( butoxy)-bis(acetylacetonate)titanium and tetra-n-butoxytitanium, and organozirconium compounds such as tetrakis(acetylacetonate)zirconium, bis(butoxy)-bis(acetylacetonate)zirconium, ( isopropoxy)-bis(acetylacetonate)zirconium and tetra-n-butoxyzirconium, and boron compounds such as tri-n-butoxyboron and boric acid; and the like.

In certain embodiments, the liquid composition used to deposit the second layer of the multilayer coating of the present invention may also include, in addition to water, organic solvents such as alcohols, glycol derivatives, hydrocarbons, esters, Ketones, ethers and more. These solvents may be used alone or in admixture of any two or more of them.

Specific examples of alcohols that may be used include, without limitation, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, acetylacetone alcohols, and the like. Specific examples of diol derivatives that can be used include, without limitation, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, etc. Specific examples of hydrocarbons that can be used include, without limitation, benzene, toluene, xylene, kerosene, n-hexane, and the like. Specific examples of esters that may be used include, without limitation, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl acetoacetate, ethyl acetoacetate, butyl acetoacetate, and the like. Specific examples of ketones that can be used include acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone and the like. Specific examples of ethers that may be used include, without limitation, diethyl ether, butyl ether, methoxyethanol, ethoxyethanol, dioxane, furan, tetrahydrofuran, and the like.

Materials suitable for use in the liquid compositions from which the second layer of the multilayer coating of the present invention is deposited, and their methods of production, are described in U.S. Patent No. 6,599,976, col. 3, lines 57 to 10 , line 58, which is included here for reference. Non-limiting examples of commercially available materials that are substantially completely hydrolyzed organosilicates and are suitable for use in the composition from which the second layer of the multilayer coating of the present invention is deposited are available from Mitsubishi Chemical Corporation, Tokyo , MSH-200, MSH-400 and MSH-500 silicates available from Japan, and Shinsui Flow MS-1200 silicate available from Dainippon Shikizai, Tokyo, Japan.

In certain embodiments, the binder is prepared in a multi-stage process, wherein in the first stage an organooxysilane (such as any of those previously mentioned) is mixed with water over an acid hydrolysis catalyst (such as any of those mentioned) in the presence of water in an amount below the stoichiometric amount of the organooxy group capable of hydrolyzing the organooxysilane. In certain embodiments, the acid hydrolysis catalyst includes an organic acid. In certain embodiments, water is present in the first stage in a stoichiometric amount capable of hydrolyzing 50% of the organooxy groups of the organooxysilane. The result of the first stage is a partially hydrolyzed polycondensation reaction product.

In certain embodiments, the first stage of the multi-stage base preparation process is carried out under conditions that limit the degree of condensation of Si-OH groups formed due to hydrolysis reactions. Such conditions can include, for example, controlling the reaction exotherm by, for example, external cooling, controlling the rate of acid catalyst addition, and/or conducting the first stage in the substantial absence (or complete absence) of any organic co-solvent hydrolysis.

In the second stage, the partially hydrolyzed polycondensation reaction product is then contacted with large quantities of water, often in the absence of an acid hydrolysis catalyst. The amount of water used in the second stage is significantly greater ("significantly greater" meaning that the resulting solution contains no more than 2% solids) than the stoichiometric amount capable of hydrolyzing the organooxy groups of the organooxysilane.

In yet other embodiments, the binder is prepared starting from tetraalkoxysilane oligomers, such as those available from Mitsubishi Chemical Corp. under the tradenames MKC Silicate MS-51, MKC Silicate MS-56 and MKC Silicate MS-60 (all trademarks; products of Mitsubishi Chemical Corp) those commercially available. Such oligomers are reacted with water in the presence of an organic acid hydrolysis catalyst (eg, acetic acid) and/or an organic solvent, wherein the water is present in an amount significantly greater than the stoichiometric amount of organooxy groups capable of hydrolyzing the tetraalkoxysilane.

In certain embodiments, the amount of organosilicate present in the liquid composition from which the second layer of the multilayer coating is deposited is 0.1-2 _wt %, calculated as SiO in the organosilicate, Such as 0.2-0.90 wt%, based on the total weight of the composition. In these embodiments, the amount of organosilicate that may be present in the liquid composition from which the second layer is deposited can be between and inclusive of any combination of the values recited above. Those skilled in the art will appreciate that the amount of organosilicate present in the liquid composition from which the second layer of the multilayer coating is deposited is determined by the properties one wishes to introduce into the composition.

In certain embodiments, the multi-layer coatings of the present invention include a second layer applied over at least a portion of the first layer, wherein the second layer is composed of (a) a photocatalytic material, and (b) a binder. At least one liquid composition is deposited. In these embodiments, the binder is hydrophilic and comprises a substantially completely hydrolyzed organosilicate, such as those discussed above. As used herein, the term "substrate" refers to a continuous material in which particles of photocatalytic material are dispersed.

In these embodiments, the second layer is deposited from a liquid composition that includes the photocatalytic material in addition to the hydrophilic base. As used herein, the term "photocatalytic material" refers to a material that can be photoexcited by exposure to radiation (eg, ultraviolet or visible radiation) and absorption of radiation. A photocatalytic material is a material that, when exposed to light of higher energy than the energy gap between the conduction and valence bands of a crystal, causes the excitation of electrons in the valence band, thereby generating conduction electrons and Holes are left in this particular valence band. In certain embodiments, the photocatalytic material includes metal oxides, such as zinc oxide, tin oxide, iron oxide, bismuth trioxide, tungsten trioxide, strontium titanate, titanium dioxide, or mixtures thereof.

In certain embodiments, at least a portion of the photocatalytic material is present in the liquid composition used to deposit the second layer in the form of particles having an average crystal diameter of 1-100 nm, such as 3-35 nm, or, in another In other embodiments, 7-20 nm. In these embodiments, the average crystal diameter of the particles can be between any combination of the recited values, inclusive of the recited values. Those skilled in the art will appreciate that the average crystal diameter of the particles can be selected based on the properties desired to be incorporated into the second layer. In some embodiments, substantially all of the photocatalytic material is present in the composition used to deposit the second layer in the form of such particles. The average crystal diameter of the photocatalytic metal oxide particles can be determined by scanning electron microscopy or transmission electron microscopy, and the crystalline phase of such particles can be determined by X-ray diffraction, as known to those skilled in the art.

As noted above, certain materials can photocatalyze upon exposure to, for example, ultraviolet ("UV") and/or visible radiation and absorption thereof. In certain embodiments, the presence of photocatalytic materials includes materials that can be photoexcited by one or more of these mechanisms. Examples of materials that can be used as part of the liquid composition from which the second layer of the multilayer coating of the present invention is deposited and that are photocatalyzed by exposure to ultraviolet radiation include, without limitation, tin oxide, zinc oxide, and titanium dioxide brookite, anatase and rutile forms. Examples of materials that can be used as part of the liquid composition from which the second layer of the multilayer coating of the invention is deposited and which are photocatalyzed by exposure to visible radiation include, without limitation, the brookite form of titanium dioxide, via Flame pyrolysis of titanium metal to chemically modified titania, nitrogen-doped titania, and plasma-treated titania.

In certain embodiments, the photocatalytic material is provided in the form of a sol (such as a titania sol) comprising particles of the photocatalytic material dispersed in water. Such sols are readily commercially available from the market. Examples of such materials suitable for use as part of the liquid composition from which the second layer of the multilayer coating of the invention is deposited include, without limitation, S5-300A and S5-33B available from Millenium Chemicals, STS-01, STS-02, and STS-21 available from Ishihara Sangyo Corporation, and NTB-1, NTB-13, and NTB-200 available from Showa Denko Corporation.

In certain embodiments, the photocatalytic material is present in the form of a sol comprising brookite titanium dioxide particles or a mixture of brookite and anatase and/or rutile titanium dioxide particles dispersed in water. Such sols can be prepared by hydrolysis of titanium tetrachloride under certain conditions, as taught by US Patent No. 6,479,031, which is incorporated herein by reference. Sols of this type suitable for use in the present invention include, without limitation, NTB-1 and NTB-13 titanium dioxide sols commercially available from Showa Denko Corporation.

In certain embodiments, the photocatalytic material includes chemically modified titanium dioxide. Examples of such materials include flame pyrolysis as described by Khan et al., Efficient Photochemical WaterSplitting by a Chemically Modified n-TiO ₂ , Science Reprint, Vol. 297, pp. 2243-2245 (2002), which is incorporated herein by reference. Reference) chemically modified titanium dioxide, nitrogen-doped titanium dioxide produced according to the method described in, for example, paragraphs [0152] to [0203] in U.S. Patent Application Publication 2002/0169076A1 (this document is hereby incorporated by reference) and/or plasma-treated titanium dioxide as described in US Patent No. 6,306,343, column 2, line 49 - column 7, line 17 (which is incorporated herein by reference).

In certain embodiments, the amount of photocatalytic material present in the liquid composition (from which the second layer of the multilayer coating is deposited) is 0.05-5 wt% solids, such as 0.1-0.75 wt% solids, wherein wt% Solids are based on the total solution weight of the composition. In these embodiments, the amount of photocatalytic material that can be present can be between any combination of the recited values, inclusive of the recited values. It will be appreciated by those skilled in the art that the amount of photocatalytic material present in the liquid composition from which the second layer of the multilayer coating is deposited is determined by the properties desired to be introduced into this layer.

In certain embodiments, the photocatalytic material and the substantially completely hydrolyzed organosilicate are present in a ratio of 0.05:0.95 to 5:0.3 (by weight), or, in other embodiments, 0.10:0.90 to 3.0:0.5 ( by weight), or in yet other embodiments, a ratio of 0.2:0.6 (by weight) is present in the liquid composition from which the second layer is deposited. In these embodiments, the ratio of photocatalytic material to organosilicate can be between any combination of the recited values, inclusive of the recited values. Those skilled in the art will understand that the ratio of photocatalytic material to organosilicate in the composition of the second layer is determined by the properties desired to be introduced into this layer, such as the refractive index the composition is desired to have (which is combined by reference to the application). It is determined by the base material of the object).

In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited includes a binder that exhibits antistatic properties, that is, the binder can form a dry film. Those skilled in the art will recognize that one way to assess the antistatic ability of the material is to measure the surface resistivity of the material. In certain embodiments, the base material of the composition of the second layer comprises a material capable of forming a dry film exhibiting 7.5×10 ⁹ to 1.5×10 ¹² ohms/cm ² , or, in other embodiments, A surface resistivity of not more than 1.0×10 ¹⁰ ohms/cm ² . The surface resistivities reported here can be obtained with an ACL Statitide Model 800 Megohmeter by using (1) a large elongated probe at several locations on the sample spaced 5 mm apart, or (2) several locations on the sample spaced at 2.75 Inches are measured by the probes on the plate of the meter. Consequently, the present invention also relates to multilayer coatings having a second layer having such antistatic properties.

In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited can further comprise inorganic particles, such as silica, alumina, including treated alumina (such as silica-treated alumina , known as α-alumina), silicon carbide, diamond powder, cubic boron nitride, and boron carbide. Such inorganic particles may, for example, be substantially colourless, such as silica, for example colloidal silicon oxide. Such materials can provide enhanced scratch and scratch resistance. Such particles can have an average particle size ranging from submicron (eg, nano-sized particles) to 10 microns, depending on the end use and desired effect of the composition.

In certain embodiments, such particles include inorganic particles having an average particle size of 1-10 microns, or 1-5 microns, prior to being introduced into the liquid composition. In other embodiments, the particles may have a diameter of from 1 nm to less than 1000 nm, such as 1 nm to 100 nm, or, in certain embodiments, 5 nm to 50 nm, before being introduced into the liquid composition. The average particle size between nanometers. In some embodiments, the inorganic particles have an average particle size of 5-50 nanometers, or 5-25 nanometers, before being introduced into the liquid composition. Granularity can be between any combination of these values, inclusive of this enumeration.

In certain embodiments, the particles may be present in the liquid composition (from which the second layer of the multilayer coating is deposited) in an amount of up to 5.0 wt%, or from 0.1-1.0 wt%; or from 0.1-0.5 wt%. ), based on the total weight of the composition. The amount of particles present in the liquid composition can be between any combination of these values, inclusive of this recitation.

In certain embodiments, the liquid composition (from which the second layer of the multilayer coating is deposited) also includes an antimicrobial enhancing material, such as a metal; such as silver, copper, gold, zinc, their compounds, or their Mixtures; quaternary ammonium compounds such as benzalkonium chloride, dialkyldimethylammonium chloride, cetyltrimethylammonium bromide, cetylpyridinium chloride, and 3-(trimethoxysilyl base)-propyldimethyl-octadecyl-ammonium chloride; phenols such as 2-benzyl-chlorophenol, o-phenylphenol, o-phenylphenate sodium, pentachlorophenol, 2(2' , 4'-dichlorophenoxy)-5-chlorophenol, and 4-chloro-3-methylphenol; halogen compounds such as trichloroisocyanurate, sodium dichloroisocyanurate, dichloroisocyanurate Potassium cyanurate, monotrichloroisocyanurate, potassium dichloroisocyanurate, 1:4 dichlorodimethylhydantoin, bromochlorodimethylhydantoin, 2,2'- Dibromo-3-nitrilopropionamide, bis(1,4-bromoacetoxy)-2-butene, 1,2-dibromo-2,4-dicyanobutane, 2-bromo-2 - nitropropane-1,3-diol, and benzyl bromoacetate; organometallic compounds such as 10,10'-oxobisphenoxy-arsine, tributyltin oxide, tributyltin fluoride, 8- Copper quinoline, copper naphthenate, chromated copper arsenate, copper ammonium arsenate, and cuprous oxide; organosulfur compounds such as methylene bisthiocyanate (MBT), vinylidene dithiocyanate esters, chloroethylene dithiocyanate, sodium dimethyldithiocarbamate, disodium ethylenebisdithiocarbamate, zinc dimethyldithiocarbamate, and bis(trichloromethyl ) sulfone; heterocyclic compounds, such as tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione (DMTT), sodium pyrithione, zinc pyrithione, 1,2-benzisothiazolin-3-one, 2-(n-octyl)-4-isothiazolin-3-one, 2-(4-thiazolyl)benzimidazole, N-(trichloromethane thiol)-4-cyclohexene-1,2-dicarboximide, N-(trichloromethylthio)-phthalimide, and 5-chloro-2-methyl- 4-isothiazolin-3-one 2-methyl-4-isothiazolin-3-one; and nitrogen compounds such as N-cocoalkyltrimethylenediamine, N-[α-(1-nitro ethyl)benzyl]-ethylenediamine, 2-(hydroxymethyl)amino-ethanol, 2-(hydroxymethyl)amino-2-methylpropanol, 2-hydroxymethyl-2-nitro- 1,3-propanediol, hexahydro-1,3,5-tris-(2-hydroxyethyl)-s-triazine, hexahydro-1,3,5-triethyl-s-triazine, 4- (2-nitrobutyl)morpholine+4,4'-(2-ethyl-2-nitro-trimethylene)-dimorpholine, glutaraldehyde, 1,3-dimethylol-5 , 5-dimethyl-hydantoin, and imidazolidinyl urea, and mixtures thereof.

In certain embodiments, the liquid composition used to deposit the second layer includes an antimicrobial agent in an amount sufficient to exhibit efficacy against microorganisms and, in particular, various fungal species. More specifically, in certain embodiments, the second layer of the multilayer coatings of the present invention may be deposited from a liquid composition containing an antimicrobial agent in an amount sufficient to inhibit the growth of microorganisms on the substrate according to MTCC (American Association of Chemists & Colorists) test method 30, Part III test. Those skilled in the art are familiar with this test method and its parameters. In certain embodiments, the amount of antimicrobial enhancing material present in the liquid composition used to deposit the second layer is 0.01-1.0 wt%, such as 0.1-1.0 wt%, based on the total weight of the composition, or at In other embodiments, 0.1-0.5 wt%. In these embodiments, the amount of antimicrobial enhancing material that can be present in the liquid composition can be between and inclusive of any combination of the values recited above.

In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited may include an optically active enhancer such as platinum, gold, palladium, iron, nickel, or soluble salts thereof . The addition of these materials to compositions including photocatalytic materials is known to enhance the redox activity of the photocatalyst, facilitating the decomposition of pollutants attached to the coating surface. In certain embodiments, the amount of optically active enhancer present in the liquid composition from which the second layer of the multilayer coating is deposited is 0.01-1.0 wt%, such as 0.1-1.0 wt%, or, at In other embodiments, 0.1-0.5 wt%, based on the total weight of the composition. In these embodiments, the amount of optically active enhancer that can be present can be between any combination of the recited values, inclusive of the recited values. In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited may include a coupling agent which, for example, improves the adhesion of the second layer to the first layer. Examples of coupling agents suitable for this purpose include, without limitation, the materials described in U.S. Patent No. 6,165,256, column 8, line 27 to column 9, line 8, which patent is incorporated herein by reference .

In certain embodiments, the amount of coupling agent present in the liquid composition (from which the second layer of the multilayer coating is deposited) is 0.01-1 wt%, such as 0.01-0.5 wt%, based on the total composition based on weight. In these embodiments, the amount of coupling agent that can be present in the liquid composition can be between any combination of the values recited above, inclusive of the recited values.

In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited may include a surfactant that, for example, assists in the application of the composition to the first layer. Improves wettability of compositions. Examples of surfactants suitable for use in the present invention include, without limitation, those described in U.S. Patent No. 6,610,777, column 37, line 22 to column 38, line 60 and U.S. Patent No. 6,657,001, column 38, Lines 46 to column 40, the material identified in line 39, are both incorporated herein by reference.

In certain embodiments, the amount of surfactant present in the liquid composition from which the second layer of the multilayer coating is deposited is 0.01-3 wt%, such as 0.01-2 wt%, or, in other embodiments Among them, 0.1-1 wt%, based on the total weight of solids in the composition. In these embodiments, the amount of surfactant that can be present in the liquid composition can be between any combination of the values recited above, inclusive of the recited values.

In certain embodiments, the liquid composition from which the second layer of the multilayer coating is deposited also includes a cleaning composition. Suitable cleaning compositions include materials including surfactants, solvent systems, water, and pH adjusting agents such as acetic acid or ammonia. Suitable cleaning compositions are disclosed in U.S. Patent No. 3,463,735, which discloses cleaning compositions comprising a solvent system comprising a low boiling point solvent, such as isopropanol, and a medium to high boiling point solvent, such as having a total of 3-8 C ₁ -C ₄ alkylene glycol alkyl ethers of carbon atoms. Suitable commercially available cleaning compositions include WINDEX(R) commercially available from SC Johnson and Son, Inc. . Consequently, certain embodiments of the present invention relate to liquid compositions that are hydrophilic and include (a) a substantially completely hydrolyzed organosilicate, and (b) a cleaning composition. Certain embodiments of such compositions also include photocatalytic materials.

In certain embodiments, the cleaning composition is present in such liquid compositions in an amount of at least 10 wt%, such as at least 20 wt%, or, in some cases, at least 25 wt%, wherein the weight percentages are based on the liquid composition gross weight.

If desired, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited can include other optional coatings known to those skilled in the art of coatings.

The liquid composition from which certain embodiments of the second layer of the multilayer coating of the present invention are deposited can be prepared by various methods. In some cases, the composition is prepared by: (i) providing a hydrophilic material comprising a substantially completely hydrolyzed organosilicate, wherein the pH of the hydrophilic material does not exceed 3.5; (ii) providing a hydrophilic material comprising A sol or slurry of a photocatalytic material dispersed in a diluent, wherein the pH of the sol does not exceed 3.5; and (iii) combining the hydrophilic material provided in (i) with the sol or slurry provided in (ii) Mixing to disperse the photocatalytic material in the hydrophilic material. Liquid compositions made by this method have been found to be stable for over 12 months with little or no agglomeration or sedimentation. The pH values reported here can be determined using an ACCUMET pH meter commercially available from Fisher Scientific.

In some cases, the liquid composition used to deposit the second layer of the multilayer coating of the present invention is produced by providing a hydrophilic material comprising a substantially completely hydrolyzed organosilicate, wherein the hydrophilic material The pH does not exceed 3.5, or in some cases, is 1.3 to 3.5, or in yet other cases, is 3.0 to 3.5. In certain embodiments, the hydrophilic material is obtained by first providing a substantially completely hydrolyzed organosilicate, wherein the pH of the hydrophilic material is greater than the desired pH, and then adding an acid to the hydrophilic material until The pH of the hydrophilic material is not more than 3.5, or in some cases from 1.3 to 3.5, or in another case from 3.0 to 3.5 is finally obtained. For example, as previously mentioned, the hydrophilic material can include MSH-200 and/or Shinsui Flow MS-1200 silicate, which are typically supplied by suppliers at a pH of 3.5 to 4.5.

In certain embodiments, the hydrophilic material may be diluted with a diluent, such as water or an organic solvent, prior to the addition of the acid, for example, to reduce the solids content of the hydrophilic material, thereby allowing thinner films to be formed.

Acids that can be added to the hydrophilic material to adjust its pH include inorganic and organic acids. Suitable inorganic acids include, without limitation, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, among others. Suitable organic acids include, inter alia, acetic acid, dichloroacetic acid, trifluoroacetic acid, benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, ethylbenzenesulfonic acid, benzoic acid, phthalic acid, maleic acid, formic acid and oxalic acid.

In some cases, the liquid composition used to deposit the second layer of the multilayer coating is produced by providing a sol or slurry comprising a photocatalytic material dispersed in a diluent, wherein the pH of the sol or slurry is not More than 3.5, or in some cases, 1.3 to 3.5, or in yet other cases, 3.0 to 3.5. In certain embodiments, the pH of the sol or slurry is substantially the same as the pH of the hydrophilic material. In certain embodiments, the sol or slurry is obtained by first providing such sol or slurry with a pH greater than the desired pH, and then adding acid to the sol or slurry until the pH of the sol or slurry does not exceed 3.5, or in some cases, 1.3 to 3.5, or in another case 3.0 to 3.5 to end up with. For example, as previously mentioned, the photocatalytic material used in certain embodiments of the liquid composition from which the second layer of the multilayer coating of the present invention is deposited may include commercially available from Showa Denko Corporation under the trade names NTB-1 and /or NTB-13 commercially available titanium dioxide sol, wherein the sol comprises brookite-type titanium dioxide particles or a mixture of brookite-type and anatase-type and/or rutile-type titanium dioxide particles dispersed in water. NTB-1 and NTB-13 are typically provided by suppliers at a pH of 2 to 4.

Acids that may be added to the sol or slurry including the photocatalytic material to adjust its pH include inorganic acids and organic acids as previously described. In certain embodiments, the acid added to the sol or slurry comprising the photocatalytic material is the same acid that is added to the hydrophilic material as previously described.

The liquid composition used for depositing the second layer of the multilayer coating of the present invention can be prepared by mixing the hydrophilic material provided by the method described above with the sol or slurry provided by the method described above to prepare the photocatalytic material Prepared by dispersing in hydrophilic material. The mixing step is not particularly limited and can be accomplished by any common mixing technique known to those skilled in the art, as long as the mixing results in a dispersion of the photocatalytic material in the hydrophilic material. As a result, certain embodiments of the present invention relate to multilayer coatings in which the second layer is deposited from a liquid composition having a pH of no more than 3.5, such as 1.3 to 3.5, or, in some cases, 3.0 to 3.5.

In other cases, the liquid composition from which the second layer of the multilayer coating of the invention is deposited is prepared by (i) providing a hydrophilic material comprising a substantially completely hydrolyzed organosilicate, wherein The pH of the hydrophilic material is 7.0-8.5; (ii) providing a sol or slurry comprising a photocatalytic material dispersed in a diluent, wherein the pH of the sol or slurry is 7.0-8.5; and (iii) will be in ( The hydrophilic material provided in i) is mixed with the sol or slurry provided in (ii) to disperse the photocatalytic material in the hydrophilic material.

In some cases, the composition from which the second layer of the multilayer coating of the present invention is deposited is produced by providing a hydrophilic material comprising a substantially completely hydrolyzed organosilicate, wherein the hydrophilic material The pH is 7.0 to 8.5, such as 7.0 to 8.0 or in some cases, 7.5 to 8.0. In certain embodiments, the hydrophilic material is obtained by first providing a substantially completely hydrolyzed organosilicate, wherein the pH of the hydrophilic material is lower than the desired pH, and then adding a base to the hydrophilic material This is ultimately achieved until the pH of the hydrophilic material is 7.0-8.5, such as 7.0-8.0, or in some cases 7.5-8.0.

In certain embodiments, the hydrophilic material may be diluted with a diluent, such as water or an organic solvent, prior to the addition of the base, eg, to reduce the solids content of the hydrophilic material, thereby allowing thinner films to be formed.

Substances that may be added to the hydrophilic material to adjust its pH include organic and inorganic bases. Specific examples of bases that can be used to raise the pH of the hydrophilic material include, without limitation, alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; ammonium hydroxide; quaternary ammonium hydroxides, such as Tetraethylammonium hydroxide and tetraethanolammonium hydroxide; ammonia; amines such as triethylamine and 3-(diethylamino)-propan-1-ol; tertiary sulfonium hydroxides such as trimethylsulfonium hydroxide and Triethylsulfonium hydroxide; quaternary phosphonium hydroxides such as tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide; organosilicon alkoxides such as γ-aminopropylsilanetriol tripotassium salt, N-(β-amino Ethyl)-γ-aminopropylsilanetriol tripotassium salt, dimethylsilanediol dipotassium salt, trimethylsilanediol potassium salt, dimethylsilanediol bis-tetramethylammonium salt, dimethylsilanediol silanediol bis-tetraethylammonium salt, and trimethylsilanol tetraethylammonium salt; sodium acetate; sodium silicate; ammonium bicarbonate; and mixtures thereof.

In some cases, the liquid composition from which the second layer of the multilayer coating of the invention is deposited is prepared by providing a sol or slurry comprising the photocatalytic material dispersed in a diluent, wherein the sol or The pH of the slurry is 7.0 to 8.5, such as 7.0 to 8.0, or in some embodiments, 7.5 to 8.0. In certain embodiments, the pH of the sol or slurry is substantially the same as the pH of the hydrophilic material. In certain embodiments, the sol or slurry is obtained by first providing such a sol or slurry with a pH lower than the desired pH, and then adding an alkaline substance to the sol or slurry until the sol or slurry A pH of 7.0 to 8.5, such as 7.0 to 8.0 or in some cases 7.5 to 8.0 is finally obtained.

Bases that can be added to the sol or slurry including the photocatalytic material to adjust its pH include inorganic bases and organic bases as previously described. In certain embodiments, the base added to the sol or slurry comprising the photocatalytic material is the same base that is added to the hydrophilic material.

The liquid composition used to deposit the second layer of the multi-layer coating of the present invention can disperse the photocatalytic material by mixing the hydrophilic material provided by the method described above with the sol or slurry provided by the method described above Made in hydrophilic material. This mixing step is not particularly limited and can be accomplished by any common mixing technique known to those skilled in the art, as long as the mixing results in a dispersion of the photocatalytic material in the hydrophilic material. As a result, certain embodiments of the present invention relate to multi-layer coatings wherein the second layer is deposited from a liquid composition having a pH of 7.0 to 8.5, such as 7.0 to 8.0, or in some cases 7.5 to 8.0.

Referring now to Figures 2 and 3, there can be found, respectively (i) schematic cross-sectional views on an enlarged scale of certain embodiments of the second layer of the multilayer coating of the present invention, and (ii) illustrating the multilayer coating of the present invention. Micrograph of an embodiment of the second layer of the coating. As can be seen from Figures 2 and 3, in certain embodiments, the second layer of the multilayer coating of the present invention is deposited from a liquid composition in which the photocatalytic material is dispersed throughout the hydrophilic matrix. In these embodiments, the second layer of the multilayer coating includes photocatalytic material in the form of nanoscale photocatalytic particles 10 (in these specific examples, the particles have an average crystal diameter of no more than 20 nanometers), which Relatively evenly dispersed throughout the hydrophilic base 20 . In particular, as shown in FIG. 3, the particles 10 are non-agglomerated, ie, all or nearly all of the particles are encapsulated and separated by the binder, rather than bonded to each other. While not being bound by any theory, it is believed that by controlling the pH of the sol or slurry of the hydrophilic material and the photocatalytic material prior to their blending, the photocatalytic particles can be sufficiently dispersed in the hydrophilic material such that coalescence This results in a low turbidity liquid composition. Thus, in certain embodiments of the invention, the second layer of the multilayer coating is deposited from a liquid composition having low haze.

One advantage of the liquid compositions from which the second layer of the multilayer coating of the present invention is deposited and/or the methods of producing them is that they can form stable one-pack liquid compositions. Thus, in certain embodiments, the second layer of the multilayer coating of the present invention is deposited from a one-package liquid composition. As used herein, the term "single-pack liquid composition" refers to a liquid composition in which the components making up the liquid composition are stored together in a single container.

One-pack liquid compositions useful for forming the second layer in the multilayer coatings of the present invention comprise at least two components, including the previously discussed photocatalytic material and the hydrophilic binder. Additionally, such single-package liquid compositions have a shelf life of at least 3 months. As used herein, the term "shelf life" refers to the time between when the components are blended in a single container and when sedimentation or aggregation occurs to the point where the cloudiness of the composition increases such that the composition is no longer capable of forming a low haze film length. In certain embodiments, the single package liquid compositions have a shelf life of at least 3 months, or in certain other embodiments, at least 6 months, or, in some cases, at least 12 months.

In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the invention is deposited has a turbidity of no more than 600 NTU after 3 months, 6 months, or in some cases 12 months degrees, or in some cases not to exceed 400 NTU (Turbidity Units). The turbidity values reported here can be determined by a Turbidity Meter Model DRT-100D manufactured by Shaban Manufacturing Inc, H.F. Instruments Division, using a 28 mm diameter x 91 mm length sample cuvette with a flat bottom. Additionally, in certain embodiments, the second layer of the multilayer coatings of the present invention has low haze. "Low haze" as used herein means that the film has a haze of not more than 0.3%. The haze values reported here can be determined with a nephelometer, such as the Hazegard(R) Model No. XL-211 commercially available from Pacific Scientific Company, Silver Spring, Md.

The present invention also relates to a method of applying a multilayer coating to a substrate, the method comprising the steps of: (1) applying a first layer comprising an inorganic oxide network to the substrate; Applying a liquid composition on at least a portion of the composition from which a second layer is deposited, wherein the composition of the second layer is hydrophilic and includes a substantially completely hydrolyzed organosilicate; and (3) curing the second layer second floor.

In these methods, the first layer comprises an inorganic oxide network and the composition used to deposit this layer can be applied by any method used in coating technology such as spraying, rolling, dipping, spin coating, flow coating, brushing and wiping. Method Apply to a substrate. After application, such compositions can cure. For example, the composition from which the first layer of a multilayer coating is deposited can be applied to a substrate as a solution of a solid in a suitable solvent such as water, an organic solvent, or mixtures thereof. The solvent can then be evaporated and the coating cured by heating to an elevated temperature, such as 80 to 130°C, for 1 to 16 hours.

In the methods of the invention, the liquid composition from which the second layer is deposited can be applied to the substrate by any method used in coating technology, such as the methods mentioned above.

In these methods of the invention, after the second layer is applied over the first layer, the second layer is cured, ie dried. While not being bound by any theory, it is believed that after curing, some of the silanol groups of the substantially fully hydrolyzed binder condense such that Si-O-Ti bonds are formed within the composition. It is believed that the presence of these groups enhances the durability of the second layer in the multilayer coatings of the present invention, as will be described in more detail below.

The liquid composition from which the second layer of the multilayer coating of the invention is deposited may be self-curing such that the composition can be cured without the aid of any curing catalyst. In addition, the liquid composition from which the second layer of the multilayer coating of the invention is deposited can be cured, for example at ambient temperature. In other words, curing of the liquid composition of the second layer can be accomplished by leaving the composition in air, ie air drying. According to some embodiments of the invention, the liquid composition is cured by exposing it to air at 25°C for 2-3 hours for superhydrophilicity and for 16 hours for long-term durability. Such liquid compositions can also be cured by drying with heat. For example, according to some embodiments of the invention, the second layer is cured by exposing it to air for 3-5 minutes and then forcing it to dry at 80°C to 100°C for at least 3 seconds.

The multilayer coatings of the present invention may be applied to polymeric, ceramic, concrete, cement, glass, wood, paper, or metal substrates, composites thereof, or other materials, including painted substrates. In certain embodiments, the multilayer coatings of the present invention can be applied to polymeric substrates. In certain embodiments, such polymeric substrates may comprise solid transparent or optically clear solid materials, as disclosed in U.S. Patent No. 6,042,737, column 6, line 66 through column 8, line 34 Those, that document is incorporated herein by reference. In certain embodiments, such polymeric substrates may include photochromic materials, such as those disclosed in U.S. Patent No. 6,042,737, column 8, line 35 through column 10, line 19, which Included here for reference.

Specific examples of articles on which the multilayer coatings of the present invention may be applied include, without limitation, windows; windshields on automobiles, aircraft, boats, etc.; indoor and outdoor reflectors; lenses, eyeglasses or other optical Instruments; protective sports goggles; masks; helmet visors; glass slides for frozen food display containers; glass enclosures; building walls; building roofs; exterior tiles on buildings; building stone; painted steel panels; Aluminum panels; window sashes; screen doors; gates; solariums; handrails; greenhouses; road signs; transparent soundproof walls; signboards; billboards; guardrails; road reflectors; decorative panels; solar cells; painted surfaces on lamps, fixtures and other articles; air conditioning systems and purifiers; kitchen and bathroom interior fittings and equipment; ceramic tiles; air filtration units; store display cases; computer monitors; air conditioning heat exchangers appliances; high-voltage cables; internal and external components of buildings; windowpanes; tableware; walls of living spaces, bathrooms, kitchens, hospital rooms, factory spaces, office spaces, etc.; sanitary appliances, such as washbasins, bathtubs, toilets, urinals, sinks, etc.; and electronic equipment, such as computer monitors.

In certain embodiments, the liquid composition from which the second layer of the multilayer coating of the present invention is deposited can have a very low solids content of about 1 wt% total solids, based on the total weight of the composition. Accordingly, such liquid compositions can be applied with extremely small film thicknesses. In particular, according to certain embodiments of the present invention, the liquid composition has a particle size of no more than 200 nanometers (0.2 microns), or in some embodiments 10 to 100 nanometers (0.01 to 0.1 microns), and in another aspect of the present invention Embodiments are applied to at least a portion of the first layer as a thin film having a dry film thickness of 20 to 60 nanometers (0.02 to 0.06 microns). The application of the second layer of the multilayer coating of the invention at this lower film thickness is particularly advantageous to provide optical films without having to match the refractive index of the composition to that of the first layer.

As previously stated, the liquid composition from which the second layer of the multilayer coating of the invention is deposited is initially hydrophilic, i.e., after application and in the composition of the second layer any Prior to the excitation of the photocatalyst, the second layer exhibits an affinity for water. The initial hydrophilicity can be expressed in terms of an initial water contact angle of no more than 20° or, in some embodiments, no more than 15°, or, in yet other embodiments, no more than 10°. The second layer of the multilayer coating of the invention can be rendered "superhydrophilic" by excitation of the photocatalytic material (if present), i.e., after excitation of the photocatalyst, the layer of the multilayer coating of the invention The second layer can exhibit a water contact angle below 5°, even as small as 0°.

The means by which the photocatalyst (if any) can be excited is present in the liquid composition used to deposit the second layer, depending on the photocatalytic material used in the composition. For example, materials that are photoexcited by exposure to visible light, such as the brookite form of titanium dioxide, and nitrogen- or carbon-doped titanium dioxide, can be exposed to any visible light source, including any radiation at a wavelength of at least 400 nanometers. On the other hand, the anatase and rutile forms of titanium dioxide, tin oxide, and zinc oxide can be photoexcited by exposure to ultraviolet radiation at wavelengths below 387 nm, 413 nm, 344 nm, and 387 nm, respectively. Suitable sources of ultraviolet radiation for photoexcitation of such photocatalysts include, without limitation, UV lamps such as those sold under the trade designation UVA-340 by the Q-Panel Company of Cleveland, Ohio, which has 28 watts on the coated surface Intensity per square meter (W/m ² ).

In certain embodiments, the multilayer coatings of the present invention exhibit a photoactivity of at least 0.5 cm ⁻¹ min ⁻¹ , eg, at least 1.0 cm ⁻¹ min ⁻¹ . Photoactivity can be evaluated as described in US Patent No. 6,027,766, column 11, line 1 to column 12, line 55, which is incorporated herein by reference.

In certain embodiments, the multilayer coatings of the present invention are rendered superhydrophilic by exposure to sunlight for 1-2 hours. Alternatively, the multilayer coatings of the present invention can be made superhydrophilic by exposure to ultraviolet radiation at an intensity of 28 W/ ^m2 for 1 hour.

As already mentioned above, the multilayer coatings of the invention can exhibit, inter alia, very advantageous hydrophilic properties, antistatic properties and/or antibacterial properties. Because they are hydrophilic, the multilayer coatings of the present invention can exhibit advantageous self-cleaning, antifouling, and/or antifogging properties. The present invention therefore also relates to a method of improving the antifouling properties, self-cleaning properties, ease of cleaning and/or anti-fogging properties of an article comprising a surface on which a coating comprising an inorganic oxide network has been deposited, the method comprising (1) applying a liquid composition comprising a substantially completely hydrolyzed organosilicate to at least a portion of a surface; and (2) curing the composition applied in step (1).

Another feature of the multilayer coatings according to the invention is that they result in a particularly durable second layer. The surprising durability of such coatings can be measured in terms of the ability of the film surface to maintain the contact angle over time under accelerated weathering conditions. The fewer contact angles that can be maintained by the sample tested over time or after several wipe cycles, the more durable the film. Simulated weathering of membranes can be obtained from a weathering chamber consisting of a Cleveland Condensing Cabinet (CCC) and a QUV Tester (product of Q-Panel Company, Cleveland, Ohio).

In certain embodiments, the photocatalytic material is sufficiently formed to maintain a contact angle of less than 10 degrees, such as less than 5 degrees, and/or maintain a photocatalyst of 3 cm ⁻¹ min ⁻¹ after exposure to a CCC cell for 4000 hours. The amount of active multilayer coating is present in the liquid composition from which the second layer of the multilayer coating of the present invention is deposited, wherein the CCC cell is operated at a vapor temperature of 140°F (60°C) in a room environment , resulting in constant water condensation on the test surface. In fact, as illustrated in the examples herein, it has been found that in certain embodiments of such compositions, compared to compositions containing a hydrophilic base of the type described herein but without photocatalytic Coatings produced with the inclusion of photocatalytic materials showed significantly improved durability. As illustrated in Figure 4, in certain embodiments, the photocatalytic material is capable of maintaining its initial water contact angle (i.e., The water contact angle is within 4 degrees of the initial water contact angle, where "initial water contact angle" refers to that observed after exposure to UV light for 2 hours as described in the Examples but before exposure to the CCC chamber water contact angle) is included in the composition (from which the second layer of the multilayer coating of the present invention is deposited), without the presence of photocatalytic material to obtain exposure at about 2000-3000 hours A coating that then fails to maintain its initial water contact angle. Indeed, this example demonstrates that the contact angle of the surface after 3500 hours of exposure in CCC in the absence of photocatalytic material increases to almost 3 times the initial contact angle. Without wishing to be bound by any theory, the inventors believe that this surprising result can be attributed to the partial crosslinking of the photocatalytic material with the organosilicate to form Si-O-Ti bonds in the coating. The inventors believe that some photocatalytic materials participate in this crosslinking, while some photocatalytic materials remain active for photocatalysis even after 4000 hours of CCC exposure.

In certain embodiments, the multilayer coatings of the present invention can be exposed for 650 hours at a black panel temperature of 65-70° C. and condensing humidity at 50° C. for 4 hours in a QUV tester equipped with fluorescent tubes (B313 nm) Then maintain a contact angle of 5-6 degrees.

The following examples illustrate the invention, however, they should not be construed as limiting the invention to their details. All parts and percentages in the following examples and throughout the specification are by weight unless otherwise indicated.

Example

Embodiment 1: Preparation of hydrolyzed organosilicate base material

The acid hydrolysis catalyst solution, referred to herein as solution "A", was prepared by adding 7,000 grams of deionized water to a neat, dry 2 gallon container. With stirring, 1.0 g of 70% nitric acid was added and allowed to stand.

15.5 grams (~0.10 moles) of 98% TMOS (tetramethoxysilane) (representing ~6 grams of _SiO2 ) was added to a neat, dry 1 liter glass beaker. 3.6 g of solution A (-0.20 molar _H2O ) was slowly added to the TMOS, controlling the exotherm by maintaining the temperature below 25°C using an ice bath. After the addition of Solution A was complete, the partially hydrolyzed silane solution was held at ~25°C for 1 hour. In a separate neat, dry beaker, 290.5 grams of ethanol and 290.5 grams of deionized water were mixed and then added to the partial hydrolyzate while stirring after a hold time of 1 hour. The pH of the dilute silane solution (pH~5) was then adjusted to pH~3.9 by adding 0.80 grams of glacial acetic acid with stirring. The resulting 1% _SiO2 matrix solution was thoroughly hydrolyzed overnight with stirring.

Coating with the above solution on test panels showed good wetting, no optical blemishes, and passed 50 rinse/dry cycles while maintaining good hydrophilicity.

Embodiment 2: Preparation of hydrolyzed organosilicate binder

15.5 grams (~0.10 moles) of 98% TMOS (representing ~6 grams of _SiO2 ) and 3.6 grams of anhydrous methanol (co-solvent) were added to a neat, dry 1 liter glass beaker. 3.6 g of solution A (~0.20 moles of _H2O ) was slowly added to the TMOS solution, the exotherm controlled by the rate of solution A addition. The peak temperature reached during the addition was 33°C. After the addition of Solution A was complete, the partially hydrolyzed silane solution was held at ~25°C for 1 hour. In a separate clean, dry beaker, 287 grams of ethanol and 290.5 grams of deionized water were mixed and then added to the partial hydrolyzate while stirring after a hold time of 1 hour. The pH of the dilute silane solution (pH~5) was then adjusted to pH~3.9 by adding 0.80 grams of glacial acetic acid with stirring. The resulting 1% _SiO2 matrix solution was thoroughly hydrolyzed overnight with stirring.

Coating on test panels with the above solution showed dewetting problems with spotting. Experimental results show that the inclusion of co-solvents ensures more efficient hydrolysis and corresponding condensation to form higher molecular weight oligomers, which accounts for the behavior observed upon coating.

Embodiment 3: Preparation of hydrolyzed organosilicate binder

15.5 grams (~0.10 moles) of 98% TMOS (tetramethoxysilane) (representing ~6 grams of _SiO2 ) was added to a neat, dry 1 liter glass beaker. 3.6 g of solution A (~0.20 moles of _H2O ) was slowly added to the TMOS with the exotherm controlled by the rate of solution A addition. The peak temperature reached during the addition was 40°C. After the addition of Solution A was complete, the partially hydrolyzed silane solution was held at ~25°C for 1 hour. In a separate neat, dry beaker, 290.5 grams of ethanol and 290.5 grams of deionized water were mixed and then added to the partial hydrolyzate while stirring after a hold time of 1 hour. The pH of the dilute silane solution (pH~5) was then adjusted to pH~3.9 by adding 0.80 grams of glacial acetic acid with stirring. Allow the 1% _SiO2 base solution to fully hydrolyze overnight with stirring.

Coating on test panels with the above solution showed dewetting problems with spotting. Experimental results show that by not controlling the exotherm and allowing the hydrolysis temperature to reach ~40°C, a much higher degree of condensation results in the formation of higher molecular weight oligomers, which illustrates the behavior observed upon coating.

Embodiment 4: Preparation of hydrolyzed organosilicate binder

Methanol and deionized water were mixed in a 1:1 (w:w) ratio with stirring. The mixture was cooled to room temperature. 10.0 g of MS-51 silicate solution (Mitsubishi Chemical Corporation, Tokyo, Japan) was added to the glass reactor, followed by 504.8 g of a premixed methanol/water solvent mixture as one portion. The solution was stirred at 20-22°C for 15 minutes. Then, 5.2 g of glacial acetic acid were added to the reactor with stirring. The solution mixture was kept stirring at ambient temperature for an additional 24 hours. The final _SiO2 content of the solution was 1% with a pH of 3.5.

Embodiment 5: Preparation of hydrolyzed organosilicate binder

1-propanol and deionized water were mixed in a 1:1 (w:w) ratio with stirring. The mixture was cooled to room temperature. In a separate container, prepare an acetic acid solution by diluting 10.0 g of glacial acetic acid with 90.0 g of 1-propanol/water solvent mixture. 5.0 g of the MS-51 silicate solution was added to the glass reactor, followed by 253.7 g of the premixed 1-propanol/water solvent mixture as one portion. The solution was stirred at 20-22°C for 15 minutes. Then, 1.4 g of the preformed acetic acid solution were added to the reactor with stirring. The solution mixture was kept stirring at ambient temperature for an additional 24 hours. The final _SiO2 content of the solution was 1%, with a pH of 4.1.

Example 6 - Preparation of Liquid Compositions

Liquid compositions A-G in Table 1 were prepared as follows. Charge I was prepared in a 1-liter glass vessel equipped with a magnetic stir bar. Charge I was prepared by adding the base material to the vessel, then adding deionized water to the vessel with agitation. The pH of the mixture was adjusted to 1.8 by adding 2N hydrochloric acid with stirring until the desired pH was reached.

Charge II was prepared in a 4 oz glass container equipped with a magnetic stir bar. Titanium dioxide sol was added to the vessel, then the pH was adjusted to 1.8 by adding 2N hydrochloric acid with stirring until the desired pH was reached. Charge II was then added to Charge I with stirring to produce hydrophilic compositions A-G.

Table 1

combination Silicate/ _TiO2 weight ratio base ¹ Deionized water Titanium dioxide sol ² Titanium dioxide sol ³ A 0.5/0.3 500g 480g 20g -- B 0.5/0.3 500g 480g 20g -- C 0.4/0.24 40g 58.4g 1.6g -- D. 0.31/0.19 31g 67.7g 1.27g -- E. 0.25/0.25 25g 73.3g 1.67g -- f 0.9/0.1 47g 2.3g 0.33g -- G 0.5/0.3 25g 24.5g -- 0.5g

¹ MSH-200 hydrolyzed organosilicate (1% solids) commercially available from Mitsubishi Chemical Corporation, Tokyo, Japan.

² NTB-1 titanium dioxide sol commercially available from Showa Denko KK, Tokyo, Japan.

³ STS-01 titanium dioxide sol commercially available from Ishihara sangyo Kaisha Ltd.

Example 7 - Float Glass Test Substrate

9" x The surface of the 12" float glass test substrate. The substrate was then rinsed with hot tap water and then with deionized water. The test substrates were sprayed with Windex(R) and wiped dry with paper towels (Kaydry(R) commercially available from Kimberly-Clark Corp.).

The liquid compositions of Example 6 were each applied to the test substrates by the wipe coating method by using a BLOODBLOC Protective Pad commercially available from Fisher Scientific. Wrap the foam applicator with the pad. Then, 1.5 grams of the hydrophilic composition was applied to the pad by using a dropper or a plastic bottle with a drip tip. The composition was then applied in straight, slightly overlapping strokes by contacting the wet pad with the glass test substrate. After coating, the substrate was allowed to dry at room temperature for at least 2 days before testing.

The results are summarized in Table 2.

Table 2

combination Ti (μg/cm ² ) ¹ PCA(cm ^-1 min ^-1 ) ² Surface resistivity (ohms/cm ² ) ³ Haze ⁴ A 1.2 3.9 3.84×10 ⁹ 0.1% B 2.3 8.1 6.25×10 ⁸ 0.2% C 0.7 2.1 -- -- D. 0.5 1.3 -- -- E. 0.7 2.6 -- -- f 0.4 0.6 -- -- G 1.9 5.5 -- --

¹ Sample analyzed using X-ray fluorescence analysis.

² Photocatalytic activity was evaluated according to the method described in US Patent No. 6,027,766, column 11, line 1 to column 12, line 55.

³ Surface resistivity was measured with an ACL Statitide Model 800 Megohmeter by using (1) a large extension probe placed 5 mm apart at several locations on the sample, or (2) at several locations on the sample 2.75 inches apart The probes on the board of the meter are evaluated.

⁴ Haze values were evaluated using a Hazegard(R) Model No. XL-211 haze meter commercially available from Pacific Scientific Company, Silver Spring, Md.

Durability Test - Test 1

The test substrates coated with liquid compositions A and B were placed in a Cleveland condensation chamber operated at 140°F (60°C). Each test substrate was removed from the chamber weekly and tested to determine water contact angle. The photoactivity of the composition was determined by measuring the difference in water contact angle before and after exposure of the substrate to UV light. Exposure intervals were 2 hours of exposure to UVA-340 lamps supplied by Q-Panel Company of Cleveland, Ohio or direct sunlight. The reported water contact angles were measured by the stopped-drop method using a modified trapping bubble indicator manufactured by Lord Manufacturing, Inc., equipped with Gartner Scientific goniometer optics. Place the surface to be measured in a horizontal position, facing upwards, in front of the light source. A stop drop of water was placed on top of the surface in front of the light source so that the profile of the stop drop could be viewed through a goniometer telescope equipped with a circular protractor scale and the contact angle (in degrees) measured. The results are summarized in Table 3.

table 3

Composition A Composition B Hours in CCC Contact angle before exposure Contact angle after exposure Contact angle before exposure Contact angle after exposure 0 20 3 12 3 498 14 3 12 3 1062 38 3 37 3 1535 32 3 27 3 2221 18 4 9 3 2573 30 3 26 3 2975 30 5 33 4 3565 -- -- 30 5 4040 -- -- 19 4

Durability Test - Test 2

The durability of test substrates coated with liquid compositions A-G was tested by measuring the water contact angle after exposure to UV light as described above, but before placing in a Cleveland condensation chamber. The same substrate was then placed in the CCC as described above for at least 4000 hours and then removed. The substrates were then exposed to UV light as described above and tested by measuring the water contact angle. The results are summarized in Table 4.

Table 4

combination Contact angle before CCC exposure Contact angle after 4000 hours CCC A 3 5 B 3 4 C 5 4 D. 5 3 E. 6 2 f 5 9 G 3 3

Durability Test - Test 3

The durability of test substrates coated with compositions of the invention was also compared to substrates coated with compositions comprising a hydrophilic organosilicate binder but no photocatalytic material. Hydrophilic compositions B and F of Example 6 and a similar composition (Composition J) having a binder to titanium dioxide ratio of 0.95/0.5 were placed in a Cleveland condensation chamber as described above, periodically as described above. removed and exposed to UV light. Comparative composition A was Shinsui Flow MS-1200 commercially available from Dainippon Shikizai, Tokyo, Japan, and comparative composition B was MSH-200 commercially available from Mitsubishi Chemical Corporation, Tokyo, Japan. The test substrates were tested for water contact angle as described above. The results are shown in FIG. 4 .

Example 8 - Preparation of Liquid Compositions

Liquid compositions H and I were prepared in the manner described in Example 6, except that WINDEX was included in the compositions in the amounts indicated in Table 5 and the base/ _TiO2 weight ratio was adjusted as indicated in Table 5. The durability of these compositions was then analyzed in the manner described in Durability Test - Test 1. The results are listed in Table 6.

table 5

combination Silicate/ _TiO2 weight ratio ^Amount of base material/ _TiO21 Amount of WINDEX h 0.35/0.25 30g 8.91g I 0.35/0.25 30g 6.26g

Table 6

Composition H Composition I Hours in CCC Contact angle before exposure Contact angle after exposure Contact angle before exposure Contact angle after exposure 0 4 4 5 4 330 27 2 twenty one 2 834 19 2 31 2 2390 26 3 twenty three 5 3374 18 3 16 3 4022 38 4 32 11

Example 9 - Turbidity of Liquid Compositions

Liquid compositions K, L, M and O were prepared in the manner described in Example 6, except that the pH was adjusted to the values listed in Table 7 and the base/ _TiO weight ratio was as shown in Table 7 adjust. Liquid compositions N, P and Q were prepared in a manner similar to Example 6, except that the pH of feed I was not adjusted, and feed II was a mixture of titania sol and deionized water, wherein the amount of deionized water was sufficient to use deionized Water dilutes the titania sol from 15% solids to 2% solids. The pH of Charge II was not adjusted, and Charge II was added to Charge I to make the liquid composition. The turbidity values of these compositions were then analyzed over time by a Nephelometer Model DRT-100D manufactured by Shaban Manufacturing Inc, HF Instruments Division, using a 28 mm diameter x 91 mm length sample cuvette with a flat bottom. The results are listed in Table 7.

Table 7

Turbidity (NTU) combination Silicate/ _TiO2 weight ratio pH initial 1 month 3 months 6 months K 0.5/0.3 1.96 490 558 569 652 L 0.5/0.3 1.57 438 552 567 653 M 0.35/0.2 1.8 321 383 393 442 N 0.35/0.2 3.25 454 412 385 425 o 0.4/0.25 1.8 415 488 511 573 P 0.5/0.1 3.1 145 143 145 153 Q 0.9/0.1 3.11 149 143 145 162

Example 10 - Anti-fogging on plastic lenses

This example is used to illustrate the anti-fogging performance of the present invention. Thermoplastic polycarbonate lenses previously coated by the supplier with an unpigmented hard coat (Gentex(R) PDQ(R), commercially available from Gentex Optics, Inc) were washed with soap and water, rinsed with deionized water and isopropanol, and Air dry for surface preparation. The lens is then plasma treated. For Example 10A, no additional coating was applied to the lens. For Example 10B, plasma surface treated lenses were coated with MSH-200 hydrolyzed organosilicate (1% solids) commercially available from Mitsubishi Chemical Corporation, Tokyo, Japan. For Example 10C, plasma surface treated lenses were coated with a composition of the type described in Example 6, Composition E, by dip coating at an extraction rate of 230 mm/min.

Fogging performance was evaluated by placing the lens on a cup filled with hot water. The lens of Example 10A was fogged over its entire area. The lens of Example 10B was fogged over 50-60% of its area. The lens of Example 10C had no fogging on its surface.

Example 11 - Stain Resistance Against Automobile Gravel Dust

This example is used to illustrate the antifouling performance of the present invention. Use masking tape to divide two aluminum alloy wheels purchased from DaimlerChrysler into five even areas. These wheels were installed on a 1996 Chrysler Cherokee Jeep with one wheel (wheel #1) mounted on the front passenger side and the other wheel (wheel #2) mounted on the front driver's side. Prior to installation, the five areas of each of Wheel #1 and Wheel #2 were processed as follows.

Wheel #1 Preparation

Prior to installation on the vehicle, the five areas of wheel #1 were processed as follows. No paint was applied to Area 1 . Area 2 was coated with Hi-Gard ^™ 1080 (an organosilane-containing coating solution commercially available from PPG Industries, Inc.) by curtain coating using a wash bottle, air dried for 5 minutes and baked at 240°F (116°C) 3 hours. Zone 3 was coated with Hi-Gard 1080 as described above for Zone #2. After baking, Zone 3 was then coated with MSH-200 hydrolyzed organosilicate (1% solids) commercially available from Mitsubishi Chemical Corporation, Tokyo, Japan by wipe coating with a soaked sponge. MSH-200 is then air dried and self-condensed. Zone 4 was coated with Hi-Gard 1080 as described above for Zone 2. After baking, area 4 was coated with a composition of the type described in Example 6, composition E and a mixture of deionized water and ethanol (50/50 by weight) by wipe application with a soaked sponge. Area 5 was coated with a composition of the type described in Example 6, Composition E.

The vehicle was driven for a week. Zones 1-5 of wheel #1 showed no significant difference in cleanliness prior to water rinsing. After rinsing with water from a garden hose, the cleanliness of areas 1-5 of wheel #1 was measured on a scale of 1-10, with higher numbers reflecting cleaner surfaces. The results are shown in Table 8.

Table 8

area Cleanliness 1 2 2 6 3 8 4 10 5 10

Wheel #2 Preparation

Prior to installation on the vehicle, the five areas of wheel #2 were processed as follows. No paint was applied to Area 1 . Area 2 was coated with SolGard(R) 330 coating (organosilane-containing coating solution commercially available from PPG Industries, Inc.) by curtain coating using a wash bottle, air dried for 5 minutes and baked at 240°F (116°C) for 3 Hour. Zone 3 was coated with Hi-Gard 1080 as described above for Zone 2. After baking, Zone 3 was then coated with MSH-200 hydrolyzed organosilicate (1% solids) commercially available from Mitsubishi Chemical Corporation, Tokyo, Japan by wipe coating with a soaked sponge. MSH-200 is then air dried and self-condensed. Zone 4 was coated with Hi-Gard 1080 as described above for Zone 2. After baking, area 4 was coated with a composition of the type described in Example 6, composition E and a mixture of deionized water and ethanol (50/50 by weight) by wipe application with a soaked sponge. Area 5 was coated with a composition of the type described in Example 6, Composition E.

The vehicle was driven for a week. Zones 1-5 of wheel #1 showed no significant difference in cleanliness prior to water rinsing. After rinsing with water from a garden hose, the cleanliness of areas 1-5 of wheel #1 was measured on a scale of 1-10, with higher numbers reflecting cleaner surfaces. The results are shown in Table 9.

Table 9

area Cleanliness 1 2 2 8 3 10 4 10 5 10

Those skilled in the art will readily recognize that modifications can be made to the invention without departing from the concepts disclosed in the foregoing specification. Such modifications are to be regarded as included in the appended claims unless the claims expressly state otherwise by their wording. Accordingly, the embodiments described in detail herein are illustrative only and do not limit the scope of the invention which is to be given the full breadth of the claims appended hereto and all equivalents thereof.

Claims (37)

1. Multi-layer coating, including: (1) comprising a first layer of an inorganic oxide network, and (2) A second layer applied over at least a portion of the first layer, wherein the second layer is deposited from at least one liquid composition that is hydrophilic and comprises a substantially completely hydrolyzed organosilicate. 2. The multilayer coating of claim 1, wherein the first layer is deposited from a composition comprising a sol containing a network-forming metal alkoxide. 3. The multilayer coating of claim 2, wherein the network-forming metal alkoxide comprises an alkoxysilane of the general formula R _x Si(OR') _4-x , wherein R is an organic group and R' is An alkyl group selected from methyl, ethyl, propyl and butyl, and x is an integer less than 4. 4. The multilayer coating of claim 1, wherein the first layer is transparent. 5. The multilayer coating of claim 1, wherein the liquid composition used to deposit the second layer further comprises a photocatalytic material. 6. The multilayer coating of claim 5, wherein the average crystal diameter is 3-35 nanometers. 7. The multilayer coating of claim 5, wherein the photocatalytic material is selected from the group consisting of brookite-type titanium dioxide, titanium dioxide chemically modified by flame pyrolysis, nitrogen-doped titanium dioxide, plasma-treated titanium dioxide, and their mixture. 8. The multilayer coating of claim 5, wherein the photocatalytic material is present in the liquid composition in an amount of 0.1 to 0.75 wt%, based on the total weight of the composition. 9. The multilayer coating of claim 1, wherein the organosilicate of the liquid composition used to deposit the second layer is selected from the group consisting of organooxysilanes, organooxysiloxanes, and mixtures thereof, wherein the organic Oxysilane is selected from tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane silane, tetra-tert-butoxysilane, tetraphenoxysilane, dimethoxydiethoxysilane, and mixtures thereof. 10. The multilayer coating of claim 1, wherein the organosilicate is present in the liquid composition used to deposit the second layer in an amount of 0.1-2 wt% calculated as _SiO2 , based on the total weight of the composition. 11. The multilayer coating of claim 1, wherein the pH of the liquid composition used to deposit the second layer does not exceed 3.5. 12. The multilayer coating of claim 1, wherein the pH of the liquid composition used to deposit the second layer is 7.0-8.5. 13. A substrate coated with the multilayer coating of claim 1. 14. The substrate of claim 13, wherein the substrate comprises a polymeric substrate. 15. The substrate of claim 14, wherein the polymeric substrate comprises a solid transparent or optically clear solid material. 16. The substrate of claim 15, wherein the polymeric substrate comprises a photochromic material. 17. The multilayer coating of claim 1, wherein the second layer is applied at a dry film thickness of 20 to 60 nanometers. 18. The multilayer coating of claim 1, wherein the base is prepared by a process selected from the group consisting of: (a) A multi-stage process comprising: a first stage in which a partially hydrolyzed polycondensation reaction product is formed by reacting an organosilicate and water in the presence of an acid hydrolysis catalyst, wherein the water is present in an amount below that capable of hydrolyzing the organosilicon a stoichiometric amount of the organooxy group of the ester, and a second stage wherein the partially hydrolyzed polycondensation reaction product is contacted with a substantial amount of water to form a substantially completely hydrolyzed organosilicate, and (b) reacting a tetraalkoxysilane oligomer with water in the presence of an organic acid hydrolysis catalyst and/or an organic solvent, wherein the water is present in an amount significantly greater than the chemical compound capable of hydrolyzing the organooxy groups of the alkoxysilane. The amount is metered to form a substantially completely hydrolyzed organosilicate. 19. The multilayer coating of claim 18, wherein the base stock is prepared by a multi-stage process. 20. The multilayer coating of claim 19, wherein water is present in the first stage in a stoichiometric amount capable of hydrolyzing 50% of the organooxy groups of the organosilicate. 21. The multilayer coating of claim 19, wherein the first stage is carried out under conditions that limit the degree of condensation of Si-OH groups formed due to hydrolysis reactions. 22. The multilayer coating of claim 21, wherein the conditions limiting the degree of condensation of the Si-OH groups formed due to the hydrolysis reaction are selected from the group consisting of controlling the reaction exotherm by external cooling, controlling the rate of addition of the acid catalyst, and/or at The first stage hydrolysis is carried out substantially in the absence of any organic co-solvent. 23. A method of improving the anti-fouling properties, self-cleaning properties, ease-of-cleaning properties, and/or anti-fogging properties of an article, wherein the article comprises a surface deposited with a coating comprising an inorganic oxide network, the method comprising the steps of: (1) applying a liquid composition comprising a substantially completely hydrolyzed organosilicate to at least a portion of a surface; and (2) Curing the composition applied in step (1). 24. The method of claim 23, wherein step (2) is accomplished by air drying. 25. The method of claim 23, wherein the coating comprising the inorganic oxide network comprises a network-forming metal alkoxide. 26. The method of claim 25, wherein the network-forming metal alkoxide comprises an alkoxysilane of the general formula R _x Si(OR') _4-x , wherein R is an organic group and R' is selected from the group consisting of radical, ethyl, propyl, and butyl, and x is an integer less than 4. 27. The method of claim 23, wherein the liquid composition applied in step (1) further comprises a photocatalytic material. 28. The method of claim 27, wherein the photocatalytic material comprises a metal oxide selected from the group consisting of zinc oxide, tin oxide, iron oxide, bismuth trioxide, tungsten trioxide, strontium titanate, titanium dioxide, and mixtures thereof. 29. The method of claim 27, wherein at least a portion of the photocatalytic material is present in the form of particles having an average crystal diameter of 3 to 35 nanometers. 30. The method of claim 27, wherein the photocatalytic material is selected from the group consisting of brookite-type titanium dioxide, titanium dioxide chemically modified by flame pyrolysis, nitrogen-doped titanium dioxide, plasma-treated titanium dioxide, and mixtures thereof. 31. The method of claim 27, wherein the photocatalytic material is present in the liquid composition applied in step (1) in an amount of 0.1-0.75 wt%, based on the total weight of the composition. 32. The method of claim 23, wherein the organosilicate of the liquid composition applied in step (1) is selected from the group consisting of organooxysilanes, organooxysiloxanes, and mixtures thereof. 33. The method of claim 23, wherein the organosilicate is present in the liquid composition applied in step (1) in an amount of 0.1 to 2 wt% as _SiO2 , based on the total weight of the composition. 34. The method of claim 23, wherein the pH of the liquid composition applied in step (1) does not exceed 3.5. 35. The method of claim 23, wherein the surface comprises a solid transparent or optically clear solid material. 36. The method of claim 23, wherein the surface includes a photochromic material. 37. The method of claim 23, wherein the liquid composition applied in step (1) is applied at a dry film thickness of 20-60 nanometers.

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