Bactericidal ceramic enamel and uses thereof

DESCRIPTION

Bactericidal ceramic enamel and its applications.

Technical field of the invention

The present invention falls within the technical field of ceramic glazes for wall, floor and similar coatings, such as ceramic tiles, sanitary elements (sinks, bathtubs, all ceramic accessories for a bathroom, etc.), etc.

More specifically, the present invention provides a new type of bactericidal ceramics enamels.

State of the art prior to the invention

The Japanese company Toto has developed a tile that has a photocatalytic layer of titanium dioxide enamel topped by a film of a compound of copper and silver. When this photocatalytic layer absorbs light, it activates the metalic ions, which kill the bacteria that come into contact with the ceramic tile.

However, these tiles show variations in their tonality and effectiveness over time.

Detailed description of the invention

The present invention, as indicated in its wording, refers to new bactericidal ceramic glazes.

The applicant has developed a new type of ceramic glazes, not conventional until now in the ceramic sector, which promote the development of highly desirable ooptic properties such as, for example, a high refractive onyx (shiny materials) with a bactericidal action.

In addition, the material developed is endowed with high quality features, since it does not show variation in tone or wear over time, as has happened up to now with products of this type of the previous technique.

The ceramic glaze of the present invention is characterized by the incorporation in its composition of rare earth oxides. This makes it a material susceptible to electron transfers in its interior produced by a light-matter interaction. These electron transfers may be capable of causing a redox process on living matter (for example, bacteria) eventually deposited or in close contact with the glazed surface, thereby exerting a bactericidal action.

The material of the present invention is characterized by the following composition:

<td>Oxide</td><td>Percentage (% by weight)</td>

<td>SiO2</td><td> 35-55</td>

<td>^{To the}2^OR3</td><td> 5-15</td>

<td>Beam</td><td> 0-5</td>

<td>^B2^OR3</td><td> 0-10</td>

<td>CaO</td><td> 5-10</td>

<td>CeO2</td><td> 2-10</td>

<td>ZnO</td><td> 5-10</td>

<td>K2O</td><td> 0-5</td>

<td>Na2O</td><td> 0-5</td>

<td>ZrO2</td><td> 0-5</td>

The ceramic glaze of the invention is obtained by fritting or mixing. A set of frits and / or formulations with these characteristics has been developed, within this composition range. Each of these glazes is applied to the tile in the form of a base glaze, silk-screened and / or pulverized and fired in an industrial oven.

The absorptive properties of the material of the invention have been determined by ultraviolet and visible spectrophotometry using a wavelength range between 800 and 200 nm (nanoometers).

In the absorption spectrum of the material of the invention, a broad band is observed in the range from 400 to 200 nm (ultraviolet region), which is assigned to the energetic transitions of electronic charge, or the passage of electrons from an energy level. to another. This transfer of electronic charge usually occurs between the fundamental level and a higher level and is associated with the absorption of light in the wavelengths corresponding to the zone of the near ultraviolet and the visible spectrum.

Figure 1 illustrates electron transfers in solids that affect ooptic properties, indicating the energy levels for two atoms, A and B, together with some characteristic electroonic states of solids.

Also, emission studies of the enamels of the invention have been carried out to characterize certain properties. The excitation and emission spectra of the developed bactericidal material have been studied. The maxima of the excitation and emission spectra lie between wavelengths of 270 and 400 nm.

Likewise, the tiles covered with the enamel of the invention have been subjected to gloss tests, using a Multi-Gross 268 glossmeter, which measures the photoelectrically reflected light at an angle of 20, obtaining brightness of the order of 88-99 GU (GU gross units, units of brightness).

The studies related to its bactericidal activity have been carried out in specialized microbiology laboratories, obtaining very satisfactory results since at concentrations of bacteria similar to those that may be on the walls, there has been no bacterial growth on the tiles covered with the enamels of the invention.

Studies have also been carried out on the impact that the power and type of lighting may have on the bactericidal effect.

Brief description of the figure

Figure 1 is an illustration of how electron transfers occur in solids in general. The numerical references that appear in it have the following meaning:

1. - They promoted the driving band.

2. - Differences between bands (GAP).

3. - Exciting transfers dd, ff.

Four. - Promotion to banda de valencia

5. - Cargo transfer.

Modes for carrying out the invention

A ceraomic enamel is prepared by mixing or obtaining a frit, from a composition that is within the compositional range previously exposed. The interval

ES 2 142 249 A1 composition is given to adjust the material to the firing temperature in each case, due to the fact that glazes have been developed to apply in rapid double-firing cycle, in porous monocoction and in stoneware monocoction.

Said frit is ground and applied in the form of a base glaze, screen printing and / or pulverized on an enclosed and / or glazed support (glazed, when it is not applied as a base glaze). It is fired in an industrial oven at the temperature and time characteristic of the type of ceramic support used, which usually ranges for stoneware of 1120-1200 ^ C and time of 40-80 min, for porous support of 1100-1170 ^ C and times of 30-70 min and for rapid cycle of 1000 to 112o ^ C and times of 25-60 min.

Absorbance spectrum

Wide band from 400 to 200 nm. Determined with a PERKIN-ELMER spectrophotometer, model W / VIS LAMBDA 19, applying the diffuse reflectance method for solids.

Gloss index

Gloss of 88-99 GU measured with a Multi-Gross 268 glossmeter, with a measuring angle of 20T Microbiological tests

After firing, the tiles are cut into 5 x 5 cm pieces and taken to the

Microbiology where they are first sterilized in an autoclave.

Next, each tile is placed in a Petri dish and painted with a standard solution of Staphylococcus aureus bacteria at different turbidity (0.001 and 0.002 Mac Farlan turbidity). Control tiles, ie tiles that do not have bactericidal glaze, are also tested.

The tests are carried out in quadruple in all cases, using four tiles with bactericidal treatment and another four without treatment.

After 12 hours of sowing and being exposed to the light of 36 watt fluorescent tubes, the tiles were placed with the glazed side in contact with sterile chocolate agar, in petri dishes. The tile is left to roast for an additional 1 hour, to allow time for all the live bacteria contained in the tiles to pass to the agar, where they grow.

After this experiment, bacterial growth is verified, which is very scarce and non-existent in tiles glazed with the product of the invention, while growth only occurs in tiles that did not have this material.