WO2007099519A2

WO2007099519A2 - Apparatus for applying a nanostructured material onto articles, in particular tiles, glass and the like

Info

Publication number: WO2007099519A2
Application number: PCT/IB2007/051147
Authority: WO
Inventors: Andrea Capucci; Gianluca Passerini
Original assignee: Andrea Capucci; Gianluca Passerini
Priority date: 2006-03-03
Filing date: 2007-03-01
Publication date: 2007-09-07
Also published as: ITBO20060151A1; WO2007099519A3

Abstract

An apparatus for applying a nanostructured material onto articles, in particular tiles, glass and the like includes: a first station (50) for the application of a film of a liquid precursor (10) on an article (1); an operational group (67), situated downstream of the first station (50) and provoking gelation of the liquid precursor (10) and conversion of the latter into the nanostructured material.

Description

APPARATUS FOR APPLYING A NANOSTRUCTURED MZVTBRIAI. ONTO ARTICLES, IN PARTICULAR TILES, GLASS AND THE LIKE

TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus for applying a nanostructured material onto articles, in particular tiles, glass and the like.

DESCRIPTION OF THE PRIOR ART It is known that surfaces coated with materials presenting photocatalytic activity (for example titanium dioxide) are characterized by anti-bacterial and self-cleaning properties .

Normally, the titanium dioxide is obtained by spontaneous oxidation or, in order to make the thickness controllable, by anodization.

Such a compound is usually amorphous, however, operating in very particular anodization conditions, it is possible to obtain crystal oxygen, maintaining the aesthetic properties of the anodized titanium dioxide.

The crystal oxygen can assume various microstructures (for example rutile, anatase, brookite) .

Among these microstructures, the anatase presents the most relevant antibacterial and anti-polluting properties. It is also known that the titanium dioxide is a semiconductor material, stable to the light and to corrosion processes, which in the colloidal form or in . thin film reacts to the radiation of wavelength lower than 430 nm (UV spectrum) . Due to this reaction, called photocatalytic process, the organic, inorganic substances and the bacteria which deposit on the film, are decomposed and removed at room temperature as a result of irradiation of natural and/or artificial light.

Hydrogen peroxide and OH radicals, produced locally as the results of the oxidation and reduction processes, trigger oxidizing processes, which lead to the mineralization of organic pollutants, to the denaturation of the bacteria and to the neutralization of inorganic toxic compounds, such as Nox.

Therefore, the titanium dioxide, if activated by irradiation, has antibacterial and anti-polluting properties . On the basis of these facts, researches have proved the efficiency of titanium dioxide in giving different materials for civil uses the property of reducing the pollution either organic or inorganic in close and open environments.

In the production of tiles, it is currently known to use, in depressurized environments, particular products having photocatalytic properties, which are applied to the surface of the finished tiles by paint guns/atomizers.

Besides the problems deriving from the necessity to provide a depressurized environment, the above manner of product application does not assure coating of the tiles with a layer of uniform thickness, and moreover, a considerable amount of product is dispersed and consequently wasted, in the depressurized environment.

There are other known techniques for coating glass, tiles and the like with a film of a nanostructured material.

However, such techniques cause different disadvantages, such as high costs of the facilities provided for the application of the nanostructured material, reduced resistance to abrasion of the applied nanostructured material, limited capability of self-cleaning of the coated surfaces.

The Italian Patent Application No. MO2003A 000117 (Gambarelli S.r.l.) describes three types of tiles in glazed stoneware obtained substantially by mixing engobe with the titanium dioxide in the form of rutile.

SUMMARY OF THE INVENTION The object of the present invention is to propose an apparatus for applying a nanostructured material, which material presents a considerable photocatalytic activity, onto articles, in particular, tiles, glass and the like.

Another object of the present invention is to propose an apparatus, which allows to reduce, even to completely eliminate, any wastes of nanocrystal material.

A further object of the present invention is to propose an apparatus, which assures formation of a homogeneous, entirely coating and stable film on the articles surface. Still a further object of the present invention is to propose an apparatus, which allows giving antibacterial property and high hydrophily to the surface of the treated articles .

The above mentioned objects are obtained, in accordance with the contents of claims, by an apparatus for applying a nanostructured material onto articles, in particular tiles, glass and the like, coming from a production line, characterized in that it includes: a first station 50 for applying a film of a liquid precursor 10 onto an article 1; a group 67, situated downstream of said first station 50 and aimed at gelatinizing said liquid precursor 10 and at converting the precursor into said nanostructured material. BRIEF DESCRIPTION OF THE FIGURES

The characteristic features of the invention will be pointed out in the following description of a preferred, but not exclusive embodiment, with reference to the enclosed Figures, in which:

Figure 1 is a schematic, lateral view of the proposed apparatus;

Figure IA is a schematic, top view of the same apparatus.

PREFERRED EMBODIMENT OF THE INVENTION

Having regards to the Figures 1, IA, the reference numeral 100 indicates a preferred embodiment of the proposed apparatus for applying a nanostructured material onto articles, in particular tiles, glass and the like.

The apparatus 100 includes a first station 50, for application of a liquid precursor 10 e.g. to tiles 1.

For example, the liquid precursor 10 is obtained by partial or total hydrolysis of a tetravalent titanium compound under conditions in which the gelation is avoided.

An operational group 67 is placed downstream of the first station 50 and includes a second station 60 and a third station 70, described in the following.

The second station 60, situated downstream of the first station 50, provides for the gelation of the liquid precursor 10 applied previously to each tile 1.

The third station 70, situated downstream of the second station 60, provides for converting the liquid precursor 10, applied to each tile 1, into a nanostructured material, e.g. titanium dioxide in the form of nanocrystal anatase. More in detail, the first station 50 includes means for storing the liquid precursor 10, cooperating with means for transferring the latter from the storing means to the tile 1. The transferring means include a rotating roll 21, disposed with horizontal axis, covered with a first layer of elastic polyurethane, about lcm thick, and a second layer of silicone, about 2-3mm thick, and highly water-repellent.

Cavities are made in the second layer by laser technique. The cavities are preferably distributed in a uniform way and have a diameter, for example, from 0,05mm to 0,1mm, and depth from 0,1mm to 0,2mm.

The roll 21 presses elastically the tile 1.

A doctor blade 2, made of plastic material, is suitably situated in such a way, as to operate on the outer surface of the roll 21.

The storing means are preferably a container 3, aimed at releasing a selected quantity of liquid precursor 10 onto the roll 21. The second station 60 includes at least one light source, aimed at emitting an intermittent beam of light with a selected wavelength, e.g. an infrared ray lamp 4.

The third station 70 includes a furnace 6 (or a dryer), aimed at heating the compound product formed by each tile 1 and the relative precursor 10.

In particular, the furnace 6 includes: a first chamber for pre-heating the compound product formed by each tile 1 and the precursor deposited thereon; a second chamber, situated downstream of the first one, aimed at burning the product; and a third chamber, situated downstream of the second one and aimed at progressive cooling the product. The apparatus 100 is advantageously provided with a conveying belt 30, operated in step relation with the roll 21, to move the tiles 1 in a forward direction W (Figure 1) .

In particular, the peripheral speed of the roll 21 coincides with the forward movement speed W of the tiles 1.

The operation procedure of the proposed apparatus 100 will be now explained briefly, as it is easy to guess.

The precursor 10, contained in the container 3, is deposited, by gravity, on the upper portion of the roll 21 and is distributed uniformly in the cavities by the doctor blade 2.

The subsequent contact between the portion of the roll covered by the precursor 10 and the upper surface of the tiles 1 (coming, for example, from a production line) carried by the conveying belt 30, makes the precursor 10 from the cavities to the same upper surface of the tiles 1, due to capillary effect.

The film of precursor 10 applied to the surface of each tile 1, is arranged autonomously according to a plurality of micro-cones, which subsequently spread and further on tend to agglomerate forming drops, generating a colloid layer of about 400nm.

It is necessary to avoid formation of drops, in order to obtain best results. For this purpose, the precursor 10 gelation process is accelerated by conveying the tiles 1 to the second station 60.

In the above station, the tiles 1 are subjected to intermittent irradiation by the infrared lamps 4 for a selected time. Such irradiation, which occurs preferably at temperatures in a range from 80⁰C to 120⁰C, causes at least superficial heating of the film of precursor 10 applied to the tile 1, with consequent at least partial gelation of the precursor. Afterwards, the tiles 1 are conveyed to the furnace 6 and stay there preferably 10 minutes in the first chamber, 20 minutes in the second chamber with a temperature in a range from 550⁰C to about 650⁰C, and finally 10 minutes in the third chamber. During the stay in the furnace, the titanium dioxide is transformed into nanocrystal anatase.

According to an embodiment, not shown, the precursor can be applied to the tiles by the known technique,¹ the so-called double transfer. Moreover, the second station 60 can advantageously include, in a region corresponding to the infrared lamps 4, suction means 41, which remove possible gases emitted by the precursor 10 applied to the tile 1, if the precursor 10 contains solvents. Then, the gases are conveyed, by the same suction means 41, to the furnace 6, where they are burnt.

It results obvious that the treatment by the infrared lamps 4 can be substituted by the direct introduction of the tiles 1 into the pre-heating chamber of the furnace 6, which in this case, must have means for suction and elimination of the possible gases emitted by the precursor.

It is to be pointed out that the dimensions and the number of the cavities made in the outer surface of the roll 21 vary in accordance with the surface characteristics (opacity, roughness, etc.) of the tiles 1 to be treated.

When the irradiation by infrared rays occurs at temperatures higher than the ones indicated above (80⁰C ÷ 12O⁰C), the transformation process of the precursor into titanium dioxide in the form of nanocrystal anatase can begin during the same irradiation.

Such transformation process is then completed when subsequently the tiles 1 stay within the furnace 6.

Some data concerning the values of reduction of Nox on tile and glass samples treated by the system proposed by the present invention are reported later on.

Using an experimental apparatus, tests for numerous sample tiles, placed in the apparatus reactor, have been carried out, using a flow of air enriched by NO at the inlet.

The apparatus is provided with a lamp, which irradiates the sample, and with a device for measuring the reduction of Nox caused by the tiles. These experiments have been carried out at the Department of Analytic Chemistry of the University of Turin.

The experimental courses of the obtained conversion of NO/NOx are shown in the following figures .

The reactions for the conversion of NO expressed in percentage is:

conversion^ = ( C_so, miβt - C_{NOr out}i_βt) /( C_wo, _inlBt) ^• 100

for the production of NO₂ is:

convθ∑a±on_N02% = C_N02, _oαtiet / C_{mZr inlβt} ^• 200

-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Irradiation Time, minutes

Figure 2. Experimental measure of the concentrations of NO, NO₂ and NO_x for the sample tile il (white with a brown pattern) at the outlet of the reactor. . The reactor is filled with a flow of synthetic air (see up to t = -20min) , so as to have [NO] = 0 , then NO is admitted at 0, 5ppm_r time is given to balance regards the concentration as well as the temperature, and later when t = 0 the all is irradiated.

and for the conversion % of NO_x, that is the quantity of reduced NO subtracted from the quantity of product, is :

convθrslon_NOχ% convers±on_N0% - convβrs±on_N02%

The last quantity, deriving from the preceding two and reported in red in the following figures, shows how NO is degraded, not forming NO₂, that is other possible species (but not identified) , such as N₂ (gas) , ammonia (gas) or nitrates (solid on catalyst) The results reported in the following figures demonstrate that, as a whole, both the glass and the tiles are active in the reduction of NO and NO_x, although it seems that their activity decreases with time. After washing with water, the activity is resumed.

It is to be pointed out that the materials, as envisaged, become super hydrophilic.

Irradiation time, minutes

Figure 3. Percentage conversion of NO, NO₂ and NO_x of the sample #1, white tile with a brown pattern, corresponding to the data of Figure 2. During the irradiation, the tile becomes super hydrophilic.

The following diagrams report the conversions obtained on other samples .

Irradiation time, minutes Figure 4. Percentage conversion of NO, NO₂ and NO_x of the sample #2, sugar-paper-blue tile. During irradiation , the tile becomes super hydrophilic, but less than the sample #1.

20 40 60 80 100 120 140

Irradiation Time, minutes

Figure 5. Percentage conversion of NO, NO₂ and NO_x of the sample #3, glass with a thin layer (2° preparation. The glass becomes super hydrophilic.

Irradiation Time, minutes

Figure 6. Percentage conversion of N0_r NO_∑ and NO_x of the sample #4, amber glass (1° preparation. After the irradiation the glass becomes super hydrophilic.

Advantageously, the proposed apparatus allows to obtain the coating of the tiles 1 surface (or glass) with a nanocrystal film of pure anatase, stable and uniform: this confers the antibacterial and high hydrophilic properties to the surface irradiated with light having selected wavelength.

A further advantage of the present invention lies in the fact that the nanocrystal anatase film, coating the tiles 1 surface presents excellent mechanical features and high photocatalytic activity.

It can be understood from what above that the proposed apparatus, assuring the uniform coating of the entire tile 1 surface, allows to obtain a high efficiency in the reduction of polluting substances. The particular technique of transferring the precursor onto the tiles 1 allows also to avoid waste of material, which results in obvious economic advantages . Furthermore, the articles, to which the nanocrystal material is applied, are finished products and do not need to be pre- treated, as it is often required in case of the applications carried out with known techniques . It is understood that the proposed invention has been described, with reference to the enclosed figures, as a mere, not limiting example. Therefore, it is obvious that any changes or variants applied thereto remain within the protective scope defined by the following claims.

Claims

CIAIMS

1. An apparatus for applying a nanostructured material onto articles, in particular tiles, glass and the like, coming from a relative production line, characterized in that it includes: a first station (50) for the application of a film of a liquid precursor (10) on an article (1); an operational group (67), situated downstream of said first station (50) for provoking gelation of said liquid precursor (10) and conversion of the precursor into said nanostructured material.

2. An apparatus, according to claim 1, characterized in that said operational group (67) includes: a second station (60), which is situated downstream of said first station (50) and which provokes at least said gelation; a third station (70), which is situated downstream of said second station (60) and in which said conversion occurs.

3. An apparatus, according to claim 1, characterized in that said nanostructured material is titanium dioxide in the form of nanocrystal anatase.

4. An apparatus, according to claim 1, characterized in that said first station (50) includes storing means, which store said precursor (10) and cooperate with transferring means, which transfer the precursor (10) from said storing means to said article (1) .

5. An apparatus, according to claim 4, characterized in that said storing means include a container (3) , which releases a selected quantity of liquid precursor (10) onto said transferring means.

6. An apparatus, according to claim 4, characterized in that said storing means include a rotating roll (21) , having a plurality of cavities made in its surface.

7. System, according to claim 6, characterized in that said cavities are arranged in a uniform way.

8. An apparatus, according to claim 6, characterized in that said rotating roll (21) presses elastically said article (1) •

9. An apparatus, according to claim 6, characterized in that said second station (60) includes heating means, which raise temperature of at least the surface layer of the film

10. An apparatus, according to claim 9, characterized in that said heating means include at least one light source, which emits a beam of light with a selected wavelength.

11. An apparatus System, according to claim 10, characterized in that said light source includes at least one infrared lamp (4), which emits a beam of infrared rays.

12. An apparatus, according to claim 11, characterized in that said beam of infrared rays is emitted intermittently.

13. An apparatus, according to claim 2, characterized in that said third station (70) includes heating means (6).

14. An apparatus, according to claim 13, characterized in that said third station (70) operates at temperatures in a range from 550⁰C to 650⁰C.

15. An apparatus, according to claim 6, 8, characterized in that it includes a conveyor (30) , operated in step relation with said rotating roll (21), to move said articles (1) in a prefixed direction (W) .

16. An apparatus, according to claim 15, characterized in that the peripheral speed of said rotating roll (21) coincides with the speed (W) of the articles (1) forward movement .

17. An apparatus, according to claim 6, characterized in that said first station (50) includes a doctor blade (2), which acts on the outer surface of said rotating roll (21) .

18. An apparatus, according to claim 2, characterized in that said second station (60) includes suction means (41), which remove possible gasses emitted by said precursor (10) .

19. An apparatus, according to claim 2, characterized in that said third station (70) includes burning means.

20. An apparatus, according to claims 18, 19, characterized in that said suction means (41) convey said gasses toward said burning means.