Transparent photocatalytic composition for internal and external building construction elements

i

The present invention relates to the production of transparent photocatalytic compositions intended to serve as interior or exterior coatings for walls, ceilings, roofs, paving and paving stones, terraces, roofs as well as all exterior or interior surfaces of buildings which may receive a coating or impregnation layer.

It also relates to the methods of applying said photocatalytic compositions using the application means available to those skilled in the art.

Currently, photocatalytic coatings are known for their self-cleaning qualities, for the destruction of atmospheric pollutants such as organic solvents and nitrogen oxides, as well as for the destruction of bacteria, microorganisms, algae and various fungi, under the action ultraviolet.

Many solutions exist highlighting the qualities of coatings based on photocatalytic titanium dioxide containing an organic or inorganic binder.

The solution which the invention proposes to solve is the production of a transparent photocatalytic coating which can be used indoors as well as outdoors with excellent photocatalytic and mechanical properties in the short term as well as in the long term.

A known solution according to patent FR2776944 proposes the use of a silica sol as a binder for titanium dioxide particles. The short-term mechanical properties of a coating of this type, when the drying takes place in the air, are however insufficient to prevent the crumbling of the varnish after application. On the other hand, the use of an organic binder alone cannot be envisaged outside because the polymer would be decomposed by the photocatalysis reaction.

The object of the present invention is to remedy these drawbacks.

To this end, it provides a photocatalytic composition containing at least one photocatalytic titanium dioxide sol, a silica sol having self-bonding properties and a film-forming polymer binder in aqueous dispersion or emulsion.

It also proposes a process making it possible to obtain a photocatalytic surface, characterized in that the photocatalytic composition is applied to the surface to be treated, said photocatalytic composition forming an adherent layer to the surface of the elements to be coated.

By titanium dioxide sol is meant a colloidal dispersion of titanium dioxide, the titanium dioxide possibly being in anatase or rutile form.

According to an advantageous characteristic of the invention, the titanium dioxide is of anatase form.

According to the invention, the titanium dioxide sol is bonded with a silica sol to obtain a coating having good long-term durability.

By silica sol is meant a colloidal dispersion of silica with a particle size of between 8 and 40 nm, preferably between 15 and 30 nm.

The immediate mechanical properties, after drying of the coating, are obtained through the use of a film-forming polymer binder.

According to the invention, the film-forming polymer binder is chosen from the group formed by acrylic, styrene-acrylic or vinyl polymers or copolymers as well as polysiloxanes.

According to one characteristic of the invention, the composition comprises in proportions by weight:

- from 2% to 10%, preferably from 3% to 8% of titanium dioxide sol calculated as dry matter

- from 5% to 20%, preferably from 8% to 15% of silica sol calculated as dry matter

- from 5% to 20%, preferably from 8% to 15% of film-forming binder calculated as active material

According to another characteristic of the invention, the composition also contains mineral fillers and where mineral pigments.

The inorganic pigments are not broken down by the photocatalysis reaction and their function is to color the composition and thus make it possible to produce a colored coating making it possible to modify the aesthetics of the support.

Mineral fillers make it possible to lower the cost of the composition and to facilitate its drying.

The mineral fillers added to the composition can advantageously be chosen from transparent fillers such as feldspar, transparent glass beads, ground glass as well as mixtures thereof.

According to another characteristic of the invention, the composition thus obtained can comprise shaping additives commonly used in the paints and varnishes industry, such as antifoaming agents, dispersing agents, wetting agents, thickening agents, coalescents and agents. preservatives.

According to a particularly advantageous characteristic of the invention, the composition comprises in proportions by weight:

- from 0 to 1% wetting agent

- from 0 to 1% antifoam agent

- from 0 to 4% of coalescing agent

- from 0 to 20% mineral charges

- from 0 to 2% pigment

- from 0 to 0.5% of biocidal agent

The different raw materials are mixed together using conventional means used by those skilled in the art until a homogeneous mixture is obtained according to the usual methods of producing a paint or a varnish.

The dispersion thus obtained, according to the invention, can be kept in a closed container and stored for several months or even several years without any particular problem of sedimentation, segregation or bacterial degradation.

For the process in accordance with the invention to be entirely satisfactory, it is necessary to apply the composition to the construction elements of buildings using conventional application means used by those skilled in the art such as, for example, brush, roller, spraying using a pneumatic gun, a medium pressure gun of the Airmix® type, or even of the Airless® type.

After drying, the film obtained covers the surface of the interior or exterior elements of buildings.

By way of example, there may be mentioned, as a support, interior or exterior walls, ceilings, interior and exterior paving, paving stones, swimming pool copings, tiles and any other interior or exterior construction element.

According to the invention, between 20 ml and 100 ml, preferably from 40 ml to 80 ml of photocatalytic composition are applied per square meter of surface to be covered.

On application, this composition spreads homogeneously over the surface to be coated and, after drying, forms a film, the thickness of which is generally between 10 and 50 gm.

The film thus obtained according to the compositions and the process according to the invention then exhibits good mechanical characteristics and photocatalytic properties.

Indeed, this film when it is subjected to ultraviolet radiation of type A, under the effect of solar radiation or of artificial radiation allows the decomposition of organic materials such as organic solvents contained in the atmosphere as well as nitrogen oxides.

By way of example, mention may be made, as source of artificial radiation, of lamps of the UVA type available commercially under the name black light or black light blue or else common lighting lamps of the halogen type or fluorescent tubes.

Likewise, the photocatalytic effect prevents or delays the formation of algae, mosses and fungi on the surface of building elements, thus preventing too rapid fouling of the surfaces.

The photocatalytic effect also makes it possible to degrade under the effect of ultraviolet radiation the stains of an organic nature which could be made on the elements such as, for example, stains of mineral or vegetable oil, of wine, of wax. and other organic dyes.

In a hospital environment, the composition can be used to destroy bacteria and viruses and other microorganisms and thus facilitate cleaning and disinfection of rooms and operating theaters.

The characteristics of the process and of the transparent photocatalytic coating which form the subject of the invention will be described in more detail with reference to the examples below of compositions which can be applied by the process in accordance with the invention.

EXAMPLE 1

<td colspan="2">Composition according to the invention</td><td>Provider</td><td>Mass in g</td>

<td>Solvent Wetting agent</td><td>Water Envirogem 360</td><td>Air Products</td><td> 510,00 2,00</td>

<td>Defoamer</td><td>Clerol PLB 847</td><td>Cognis</td><td> 2,00</td>

<td>Pigment 1</td><td>Millenium S 5-300</td><td>Millennium</td><td> 200,00</td>

<td>Binder 1</td><td>Acronal S 790</td><td>BASF</td><td> 100,00</td>

<td>Binder 2</td><td>Betol KS 402</td><td>Woellner</td><td> 150,00</td>

<td>Coalescing agent</td><td>Dowanol DPNP</td><td>Dow Chemicals</td><td> 8,00</td>

<td>Thickening agent</td><td>Rheolate 678</td><td>Elementis</td><td> 25,00</td>

<td>Biocide</td><td>MBS Acticide</td><td>Thor</td><td> 3,00</td>

<td>Total</td><td></td><td></td><td> 1 000,00</td>

EXAMPLE 2

<td>Selor composition</td><td>the invention</td><td>Provider</td><td>Mass in g</td>

<td>Solvent Wetting agent</td><td>Water Envirogem 360</td><td>Air Products</td><td> 320,00 2,00</td>

<td>Defoamer</td><td>Clerol NXZ</td><td>Cognis</td><td> 2,00</td>

<td>Pigment</td><td>Millenium S 5-300</td><td>Millennium</td><td> 250,00</td>

<td>Binder 1</td><td>Acronal S 790</td><td>BASF</td><td> 100,00</td>

<td>Binder 2</td><td>Betol KS 402</td><td>Woellner</td><td> 200,00</td>

<td>Binder 3</td><td>Baysilone WA</td><td>Momentive</td><td> 100,00</td>

<td>Coalescing agent</td><td>Dowanol DPNP</td><td>Dow Chemicals</td><td> 8,00</td>

<td>Thickening agent</td><td>Rheolate 678</td><td>Elementis</td><td> 15,00</td>

<td>Biocide</td><td>MBS Acticide</td><td>Thor</td><td> 3,00</td>

<td>Total</td><td></td><td></td><td> 1 000,00</td>

EXAMPLE 3

<td colspan="2">Composition according to the invention</td><td>Provider</td><td>Mass in g</td>

<td>Solvent Wetting agent Defoamer Pigment Binder 1 Binder 2 Binder 3 Thickening agent Biocide</td><td>Water Envirogem 360 Clerol NDW Millenium S 5-300 Acronal S 559 Betol KS 402 Silres BS 45 Rheolate 678 MBS Acticide</td><td>Air Products Cognis Millenium BASF Woellner Wacker Elementis Thor</td><td> 183,00 2,00 2,00 300,00 150,00 200,00 150,00 10,00 3,00</td>

<td>Total</td><td colspan="2"></td><td> 1 000,00</td>

EXAMPLE 4

<td colspan="2">Composition according to the invention</td><td>Provider</td><td>Mass in g</td>

<td>Solvent Wetting agent</td><td>Water Envirogem 360</td><td>Air Products</td><td> 428,00 2,00</td>

<td>Defoamer</td><td>Clerol NXZ</td><td>Cognis</td><td> 2,00</td>

<td>Pigment</td><td>Millenium S 5-300</td><td>Millennium</td><td> 200,00</td>

<td>Binder 1</td><td>Vinnapas CEF 52 W</td><td>Wacker</td><td> 100,00</td>

<td>Binder 2</td><td>Betol KS 402</td><td>Woellner</td><td> 150,00</td>

<td>Binder 3</td><td>Silres BS 1306</td><td>Wacker</td><td> 100,00</td>

<td>Thickening agent</td><td>Rheolate 678</td><td>Elementis</td><td> 15,00</td>

<td>Biocide</td><td>MBS Acticide</td><td>Thor</td><td> 3,00</td>

<td>Total</td><td></td><td></td><td> 1 000,00</td>

It should be noted that the various constituents of these compositions are designated by their commercial reference.

The chemical natures of these constituents are as follows:

Envirogem 360: Wetting agent: reaction product of octanol 1 with epichlorohydrin and 2-mercaptoethanol

Acronal S790: Aqueous dispersion of acrylic styrene io Acronal S559: Aqueous dispersion of acrylic styrene

Vinnapas CEF 52W: Dispersion of vinyl acetate and vinyl chloride copolymer

Clerol NDW: mineral oil and silica type defoamer Clerol NXZ: mineral oil and silica type defoamer

Clerol NXZ: anti-foaming agent copolymer of ethylene oxide and propylene oxide

Millenium S5-300: Photocatalytic titanium dioxide sol Betol KS 402: Silica sol Silres BS 45: silicone emulsion

Silres BS 1306: silicone emulsion

Baysilone emulsion WA: silicone emulsion Rheolate 678: polyurethane thickener Acticide MBS: Microbiocide based on izotiazolone Dowanol DPNP: glycol ether

The composition in accordance with Example 1 is particularly advantageous insofar as it can be used indoors for improving air quality.

The composition in accordance with Example 2 is particularly advantageous insofar as it additionally comprises a hydrophobic character, thus limiting the fouling and the tachability.

Compositions 3 and 4 are particularly advantageous in that they do not require the use of a coalescing agent and are therefore free of organic solvent.