Bactericidal ceramic enamel and application thereof

Description of the invention

The subject of the present invention is bactericidal ceramic enamel, its production method and its use. The subject of the present invention is in the technical field of ceramic enamels for wall, floor and similar coverings, such as wall tiles, floor tiles, sanitary appliances (sinks, bathtubs, all ceramic complementary bathroom components), etc.

Wafers manufactured by the Japanese company Toto, having a photocatalytic layer of titanium dioxide enamel finished with a copper-silver compound, are known. When light is absorbed by the photocatalytic layer, metal ions are activated, which kill the bacteria that come into contact with the ceramic plate.

However, it was noticed that in this solution with the passage of time, the purity of colors and the effectiveness of operation changed.

The bactericidal ceramic enamel according to the invention is characterized by the fact that it consists of SiO2 in the amount of 35-55% by weight, ALO;, in the amount of 5-15% by weight, CaO in the amount of 5-10% by weight, CeO2 in the amount of 2-10% by weight and ZnO in an amount of 5-10% by weight.

Preferably, it also consists of BaO in an amount of 0-5% by weight, B2O3 in an amount of 0-10% by weight, K2O in an amount of 0-5% by weight, Na2O in an amount of 0-5% by weight and ZrO2 in an amount of 0-5%. by weight.

The method of producing a bactericidal ceramic enamel according to the invention is characterized in that the glaze components mentioned above are mixed or melted.

The invention also relates to the use of ceramic enamel for the production of bactericidal ceramic wall and floor coverings.

The present inventors have created a new type of ceramic enamels, which so far have not been found in the ceramics department, because they combine highly desirable optical properties, such as, for example, high refractive index (glossy material) with a bactericidal effect.

Moreover, the produced material exhibits high-quality performance characteristics as it ultimately does not undergo any color purity changes or wear, as is the case with prior art products of this type.

The subject matter of the invention in an exemplary embodiment is shown in the drawing, in which Fig. 1 shows electron transfer in solids that affects optical properties, indicating the energy levels for the two atoms, Ά and B, together with several characteristics of the electronic states for solids.

The ceramic enamel according to the present invention contains rare earth oxides. Thanks to this, it is a material inside which electronic transitions are possible, caused by the interaction of light-matter. Electronic transitions may be capable of inducing redox processes on living matter (e.g. bacteria) ultimately on or in close contact with the enamel surface, thus exhibiting a bactericidal effect.

The ceramic enamel according to the invention was obtained by fusing the glaze components or by mixing. A combination of frits and / or formulations with the indicated characteristics within the above composition range (set of ingredients) was produced. Each enamel was applied to the tiles as a base enamel, serigraphically and / or dusted and then sintered in an industrial furnace.

The absorption properties of the ceramic enamel according to the invention were determined by visible and ultraviolet light spectrophotometry using wavelengths in the range between 800 and 200 nm (nanometers).

In the absorption spectrum of the ceramic enamel according to the invention, a broad band in the range from 400 to 200 nm (ultraviolet range) is observed, which is attributed to the electron charge energy transitions or the passage of electrons from one energy level to another. The electron charge transfer usually takes place between the base level and the higher level and is related to the absorption of light at wavelengths corresponding to the area of ​​the next spectrum in the ultraviolet light spectrum and the visible spectrum.

Fig. 1 is a general illustration of the path resulting from the transfer of electrons in solids. The reference numerals which appear in Fig. 1 have the following meanings: 1 - conduction band activation, 2 - band differences (GAP), 3 - excitation dd, ff, 4 - valence band activation, 5 - charge transfer.

Likewise, emission tests of the enamels according to the invention were carried out in order to characterize their specific properties. The excitation and emission spectra of the obtained bactericidal ceramic enamel were investigated. The maximum values ​​of the excitations and emission spectra were in the wavelength range between 270 and 400 nm.

The enamel coated tiles of the invention were also subjected to gloss tests using a Multi-Gross 268 gloss tester measuring photoelectrically reflected light at an angle of 20 °.

Gloss values ​​ranging from 88-99 GU (GU gloss unit, gloss unit) were obtained.

Tests on the bactericidal activity of the enamels according to the invention were carried out in specialized microbiological laboratories, obtaining very satisfactory results. At concentrations of bacteria similar to those that may be present on the walls, no bacterial growth was observed on the enamel coated tiles according to the invention.

In addition, research has been carried out on the effect that the intensity and type of lighting may have on the bactericidal effect.

Example 1

The following oxides were mixed and melted in an oven at 1500 ° C.

Oxide Percentage composition (wt%)

SiO2 50.8

AkOs 7.8

B2O3 5.8

CaO 8.3

ZnO 9.6

ZrO2 3.7

Na2O 2.4

K2O 2.9

CeO2 8.7

In order to use the above frit in a single sintering on a porous furnace support, it was necessary to prepare an aqueous slurry of the above ingredients.

The application of the obtained suspension was carried out on raw plates with dimensions of 20x30 cm with single sintering to obtain a porous sinter, which was previously covered with clay material and enameled with cloudy glass.

6 grams of the slurry was sprayed onto the above-mentioned plaques.

In the last step, after applying the bactericidal suspension, the tiles were baked in an industrial oven at 1120 ° C in circulation for 40 minutes.

Example 2

The ceramic enamel was prepared by mixing or preparing a frit from the ingredients in amounts in the above-mentioned ranges. The range of ingredients amounts was given in order to enable the adaptation of the material composition to the required sintering temperatures of the developed enamels. Thus, the enamels of the invention can be prepared in an accelerated dual sintering cycle, single sintering to porous sintering, and single sintering to stoneware.

The frit is ground and applied as a base enamel, serigraphically and / or sprinkled onto the engobe and / or onto the enamel support (enamel if not applied as a base enamel). It was sintered in an industrial furnace at a temperature and time characteristic for the type of ceramic support used, within the following ranges: 11201200 ° C and 40-80 minutes for stoneware products, 1100-1170 ° C and 30-70 minutes for porous supports and 1000- 1120 ° C and 25-60 minutes for the accelerated cycle.

Absorption spectrum

The bandwidth from 400 to 200 nm was determined with a PERKIN-ELMER spectrophotometer, model UV / VIS LAMBDA 19, using the solid-reflectance blur method.

Gloss factor

The gloss of 88-99 GU was measured with a MultiGross 268 gloss measuring device at a 20 ° measuring angle.

Microbiological tests

After baking, the plates were cut into 5 x 5 cm pieces and transferred to a microbiology laboratory where they were initially autoclaved.

Then, each of the plates was placed in a petri dish and painted with a standard solution of Staphylococcus aureus of various degrees of haze (0.001 and 0.002 MacFarlan haze). Control plates, i.e. those not covered with bactericidal enamel, were also tested.

PL 194 298 B1

In all cases, tests were performed in quadruplets, using four bacterial treated and four untreated plates.

After 12 hours of cultivation and subjected to light from 36 watt fluorescent tubes, ceramic plates were placed with an enamel surface in contact with chocolate agar in petri dishes. The plate was left under these conditions for another hour in order to allow sufficient time for any viable bacteria on the plates to be converted to agar where they continued to grow.

After this experiment, the growth of the bacteria was tested. This increase was negligible or completely absent in the enamel tiles according to the invention, whereas bacterial growth was observed on the tiles that did not contain the ceramic enamel according to the invention.