BE1020337A3 - ANTI-MICROBILIC COMMUNICATION BOARD. - Google Patents

Description

Antimicrobial communication board.

The present invention relates to a visual communication board, whether or not interactively enameled, be it a board that can be written and erased with, for example, dry-wipe-out markers, or a chalkboard that can be written on with chalk or the like.

Communication boards in offices and classrooms are used daily by several people, which makes the board a potential risk of spreading microorganisms as a result of contamination by touching or coughing, for example, where the board serves as a transfer disc for microorganisms.

Users of such boards are interested in a board with antimicrobial action to limit the use of antimicrobial agents in the classroom or office.

In general, antimicrobial materials and coatings are obtained by adding specific agents with a microbicidal activity.

Inorganic antimicrobial agents, such as metals Ag, Cu, Au, Zn, etc. or metal oxides such as ZnO, CaO or MgO or salts, such as AgNCb, are preferred because they are temperature resistant as opposed to organic antimicrobial agents.

For metals, the metal ions (Ag +, Cu2 +, Zn2 +, ...) are in fact the active ingredient. This means that humidity must be present in the environment to allow the metal to form ions.

The antimicrobial activity of metal oxides such as ZnO is attributed to the formation of H2O2, 0 'and OH "that can penetrate the cell wall and kill the bacterium.

The most popular metals are Ag and Cu, which can be added in various forms: as nanoparticles, as metal oxide particles, as metal salt or even more complex forms, but also directly as ions on an ion-exchange support, such as zeolite.

Communication boards made from enamelled steel offer specific advantages, such as their dry-wipeability, their acid and color resistance and their wear-resistant · durability.

Antimicrobial enamel in which the antimicrobial agent is included in the enamel itself has already been described: US 6,303,183 (2001) describes antimicrobial porcelain enamel in which preferably metallic silver is used in a concentration of 0.1 to 3.0%, but zinc or copper is also used.

The antimicrobial effect of silvery enamel was clearly demonstrated by Voss et al. (Evaluation of bacterial growth on various materials, 20th International Enamellers Congress, 15-19 May 2005, Istanbul).

WO 2006/133075 describes a cost-effective and practically acid-resistant porcelain enamel with antimicrobial properties for steel substrates. The porcelain enamel contains an optimum amount of zinc and other components with good antimicrobial properties without having to sacrifice other important properties such as acid resistance.

More recently, a study by Luca Pignatti et al. Described adding Ag20, CuO and ZnO to various types of email compositions. Antimicrobial tests clearly demonstrate the antimicrobial effects (Definition of a new range of porcelain enamels with antibacterial characteristics and the method of antibacterial power control, 21st International enamellers Congress, 18-22 May 2008, Shanghai).

However, enamelled communication boards need an antimicrobial layer that is located on the enamel layer, where the antimicrobial action is required, but which is nevertheless durable, to maintain the antimicrobial action.

This certainly applies to enamelled communication boards of the interactive type where their position coding pattern must remain optically readable, also after prolonged use, and where the reading instrument must remain able to form a positioned electronic representation of the information written on the communication panel.

Such an interactive communication board and the accompanying reading instruments were described in detail in WO. 01/16872, the contents of which are incorporated in the current text by reference thereto.

WO 2009/000053 describes an interactive communication board of enameled steel, on which a position coding pattern is applied by applying a print in a ceramic material that is burnt onto the enamel layer at temperatures above 500 ° C.

To obtain antimicrobial surfaces on the enamel surface, a biocide in the form of a metal such as silver nanoparticles could be incorporated in layers that are cast on the surface of a substrate via sol-gel coating, such as in WO 2005/115151 described.

A disadvantage of such sol-gel layers is that they are difficult to apply in a position coding pattern for an interactive communication board.

A further disadvantage is that applying such layers via sol-gel coating is cumbersome in that it comprises several steps, such as the generation of nanoparticles of the metal separately from the coating process itself, and is therefore less suitable for a continuous industrial production process with high transfer speed and low cost.

One technique that allows the application of an antimicrobial layer of metallic nanoparticles and a metal oxide on a metal substrate at a high throughput speed is chemical vapor deposition.

Chemical vapor deposition at atmospheric pressure is particularly attractive because it is suitable for continuous or semi-continuous production processes with a high throughput speed.

This technique is used for applying a layer to metal such as anti-corrosion layers or scratch-resistant layers.

With thermal chemical vapor deposition at atmospheric pressure, temperatures above 500 ° C can be achieved in order to achieve the desired characteristics of hardness, durability and structure.

At such high temperatures, however, the oxidizing action of the vapor-deposited chemicals affects the hot metal surface and undesirable surface properties arise, making this technique less suitable for coating metal itself.

GB 2,466,805 describes a technique for allowing the coating of iron or steel materials with chemical vapor deposition under atmospheric pressure.

Flame-assisted chemical vapor deposition at atmospheric pressure is used for this purpose. The flame provides all or part of the energy required to activate the vapor deposition process.

There are two variants of this: chemical vapor deposition with combustion, where the precursor or its solvent are flammable and thus contribute to the energy of the flame, or flame assisted chemical vapor deposition with little or no energy coming from the precursor itself or its solvent.

GB 2,466,805 uses this technique to apply an antimicrobial layer to a metal substrate at a higher temperature (for example 300 ° C).

Chemical precursors and solvents with low costs and low toxicity are used for this purpose.

For example, an aqueous solution of a silver salt was atomized in a combustible carrier gas such as propane, which yields vapor-deposited silver on the metal substrate at 300 ° C and wherein the silver layer consists of islets of metallic silver a few tens of nm at a mutual distance of a few tens or hundreds. nm, whereby good transparency and durability were obtained.

A second layer consisting of silica was applied over this, about 20 nm to 1 µm thick, depending on the desired properties.

The amount of silver that diffuses into this silica layer can be controlled by the temperature.

Alternatively, the silver can also be applied in one layer with the silica in a single vapor deposition process.

The antimicrobial effect can be further enhanced by re-coating with silver in a flame-assisted chemical vapor deposition step as a final finishing step.

Because this technique is suitable for applying antimicrobial layers in a continuous process at high temperature (500 ° C), we have also tested it on a metal communication board with an enamel layer on the writing side and back.

Such communication boards are indeed manufactured by enamelling a steel support at temperatures above 500 ° C, whereafter the enamelled steel formed is provided with an antimicrobial layer immediately and continuously by means of atmospheric chemical vapor deposition.

The present invention aims at the aforementioned and. other disadvantages by offering an antimicrobial communication board which is provided with an enamel layer on both the writing side and the rear side of the communication board and on which an antimicrobial coating is applied on the writing side consisting of a composition with nanoparticles of an antimicrobial metal or of a metal oxide which are applied to the surface in one or two layers by means of a sol-gel dip coating or by chemical vapor deposition under atmospheric pressure of a sol-gel coating.

An advantage of such a communication board is that the write side has a high antimicrobial effect, without adversely affecting the properties useful for use as a communication board.

Indeed, the high scratch resistance and durability of such antimicrobial communication boards is retained, as well as good wipeability, good acid and color resistance, and this even after many cycles of use.

The antimicrobial effect is ensured from a wear-resistant layer that remains a source of antimicrobial metal ions during the lifetime of the board, because silver ions can continuously diffuse into the sol-gel layer.

The chemical vapor deposition technique offers the advantage that it can be part of a continuous production process of the communication boards, whereby production time is saved and in which material losses and in particular silver losses can be avoided.

An advantage of silver or silver oxide is that its antimicrobial action already occurs at low doses of silver ions, so that the amount of silver or silver oxide in the antimicrobial coating should not exceed 10% by weight, and from 0.1% by weight the antimicrobial action already noticeable.

With the insight to better demonstrate the features of the invention, a preferred embodiment of an enameled visual communication board according to the invention is described below as an example without any limiting character, with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically and in detail: perspective view of an antimicrobial communication board according to the invention; figure 2 represents a continuous production process of an antimicrobial communication board according to the invention in perspective; Figure 3 shows a non-continuous production process for applying an antimicrobial sol-gel layer on an enamel communication board.

The antimicrobially enameled communication board 1 as shown in Figure 1 consists essentially of a steel plate 2 of 0.35 mm thickness in this case, which is provided with a ground enamel layer 5 of 0.035 in this case on the front side 3 and also on the back side 4 mm thick, on which on one side 3 a second, mainly white, enamel layer 6 is applied. An antimicrobial sol-gel layer 7 of 10 to 200 nm thick is then applied to this.

Figure 2 shows the continuous production process according to the invention of an antimicrobial communication board 1, in which in a first step steel 2 is enamelled on both sides at a temperature of 820 ° C; in a second step, a substantially white cover enamel layer is applied to the visible side 6 and burned in at a temperature of +/- 800 ° C; in a third step is coated by means of thermal chemical vapor deposition with an antimicrobial coating 7 with an antimicrobial metal and a metal oxide in one layer 7 or in two layers 8, 9 by chemical vapor deposition at atmospheric pressure; shortening the coated communication board to the desired format or rolling it up on a roll for later processing, all in one production run.

Figure 3 shows the production process for applying an antimicrobial sol-gel layer 12 to an enameled communication board 1 in which the process is not continuous but batchwise, and in which the steel 2 is first provided with a ground enamel layer 5 on both sides at high temperature. , a cover enamel layer 6 at high temperature and then cooled and shortened. The enamelled communication boards 1 are subsequently treated in batches in a bath 13 with the desired sol-gel 12 coating, which is applied by dip coating.

Experimental part

An enameled communication board 1 was provided with a silver-containing finishing layer by, on the one hand, dip coating with a silver-containing sol-gel 12 layer or, on the other hand, by chemical vapor deposition at atmospheric pressure in subsequent experiments.

The antimicrobial action of the cast sol-gel layer 12 and of the vapor-deposited layer was each time measured by means of an antimicrobial test according to ISO 22196 (JIS Z 2801) in which a reduction factor of certain bacterial strains is measured by the action of the antimicrobial layer. The reduction factor is expressed on a logarithmic scale as the difference between the number of bacteria per cm2 without and the number per cm2 with the antimicrobial layer.

For example, if the number of bacteria has fallen from 1 million / cm 2 (Log 6) to 100 / cm 2 (Log 2), the difference is Log 4, or the logarithmic reduction factor is 4.

EXPERIMENT 1

A solution with the following composition was prepared.

1) 94% 2-propanol 2) 4% TEOS (tetraethyl orthosilicate)

3) 1% AgNO 3 solution of 1 M

4) 0.8% HNO3

To this end, 17.71 g of TEOS was added to 22.7 g of 2-propanol. This mixture was mixed with 3.41 g of AgNCb 1 M solution and acidified with 3.41 HNO 3 1M. The mixture was then mixed for 20 minutes. After mixing, an additional 360.40 g of 2-propanol was added.

The solution was applied by dip coating, whereby a layer thickness of 40 to 60 nm was obtained, followed by a thermal curing step at 400 ° C for 10 minutes.

To perform the antimicrobial test, use was made of 1) a suspension medium: nutrient broth 1/500 NB; 2) a test inoculum: a bacterial suspension in 1/500 NB was diluted to obtain a bacterial concentration between 2.5 x 105 and 10 x 105 cells / ml, with the target concentration of 6 x 105 cells / ml; 3) the following bacterial strains: - Staphylococcus aureus; - Escherichia coli.

4) an incubation: the samples inoculated with the bacterial suspension were incubated at a temperature of 35 +/- 1 ° C for 24 +/- 1 h at a relative humidity of not less than 90%.

The following antimicrobial activity was measured for the Escherichia coli bacterial strain:

Without antimicrobial layer: 13,666,667 CFU / ml or 854,167 CFU / cm2 (Log 7.13 or Log 5.88).

With antimicrobial layer: 17 CFU / ml or 1 CFU / cm2 (Log 1.23 or Log 0).

The reduction factor due to the antimicrobial layer is therefore Log 5.9 or a reduction by a factor of approximately one million.

EXPERIMENT 2

A solution with the following composition was prepared.

1) 94% 2-propanol 2) 4% TEOS (tetraethyl orthosilicate)

3) 1% AgNC> 3 solution of 1 M

4) 0.8% HNO3

To this end, 17.71 g of TEOS was added to 22.7 g of 2-propanol. This mixture was mixed with 3.41 g of AgNO 3 1 M solution and acidified with 3.41 HNO 3 1M. The mixture was then mixed for 20 minutes. After mixing, an additional 360.40 g of 2-propanol was added.

The solution was applied by chemical evaporation with combustion by spraying in propane, the energy of the flame being used for the thermal curing of the coating. Layer thicknesses of 40 to 60 nm were obtained.

Antimicrobial tests were performed as described above for Escherichia coli, with the following result.

Without antimicrobial layer: 12,100,000 CFU / ml or 756,250 CFU / cm2 (Log 7.08 or Log 5.88).

With antimicrobial layer: 99,017 CFU / ml or 6,245 CFU / cm2 (Log 5.0 or Log 3.8).

The reduction factor due to the antimicrobial layer is therefore Log 2.1 or a reduction by a factor of more. then one hundred in 24 hours.

It goes without saying that the continuous production process that uses chemical vapor deposition of antimicrobial agents is much more efficient and cost-effective than the discontinuous production process that uses liquid coating with antimicrobial sol-gel solutions.

The present invention is by no means limited to the exemplary embodiments described in the figures, but such a communication board provided with antimicrobial metals or metal oxides can be realized in other embodiments which coat antimicrobial solels or chemically vaporize antimicrobial components without outside within the scope of the invention.

Claims (7)

An antimicrobial communication board (1) provided with an enamel layer (5) burned in at temperatures above 500 ° C on both the writing side and the rear side of the communication board and on which an antimicrobial coating (7) is provided on the writing side consisting of a composition with nanoparticles of an antimicrobial metal or an antibacterial metal oxide or an antibacterial metal salt applied to the surface in one (7) or two (8, 9) layers by means of sol-gel (12) dip coating or by chemical vapor deposition under atmospheric pressure of a sol-gel coating. Antimicrobial communication board (1) according to claim 1, characterized in that the antimicrobial metal is silver or copper. Antimicrobial communication board (1) according to claim 1, characterized in that the metal oxide is a silicate. The antimicrobial communication board (1) according to claim 1, characterized in that the chemical vapor deposition is a flame assisted or a combustion chemical vapor deposition at atmospheric pressure. The antimicrobial communication board (1) according to claim 1 or 2, characterized in that the metal and the metal oxide or metal salt consist of silver, silver oxide or silver nitrate. The antimicrobial communication board (1) according to claim 1, characterized in that the action of the antimicrobial coating (6) reduces the number of E. coli bacteria per unit area by a factor of at least 100 in 24 hours. Method for manufacturing an antimicrobial communication board (1) as claimed in claim 1, characterized in that the method provides for a continuous production process in which in a first step steel (2) is enamelled on both sides at a temperature of 820 ° C; in a second step on the visible side 6 a substantially white cover enamel layer is applied and burnt in at a temperature of +/- 800 ° C; in a third step is coated by means of thermal chemical vapor deposition with an antimicrobial coating 7 with an antimicrobial metal and a metal oxide in one layer (7) or in two layers (8), (9); shortening the coated communication board to the desired format or rolling it up on a roll for later processing, all in one production run.