Patent ID: 12232495

In a first embodiment, the molybdates CaMO4, ZnMO4, BiMO4, VMO4, CuMO4and Ag2MO4with M=Mo, W are produced by intimately mixing MoO3and/or WO3with the corresponding carbonates, for example CaCO3, MgCO3, ZnCO3, BiCO3etc. in equimolar ratios and heating the mixture to temperatures of about 400° C. to 800° C. Therein, different carbonates can basically also be used to obtain corresponding mixed molybdates and mixed tungstates, respectively. The reaction can be driven towards the desired products by removing the arising CO2. As soon as carbonate is no longer detectable, the conversion has completely occurred. Alternatively, various molybdates/tungstates can be produced by dripping a metal salt solution—e.g. an AgNO3solution—to a Na2MoO4and Na2WO4solution, respectively, with subsequent separation of the formed molybdate/tungstate precipitation. The precipitation can then be washed and dried as needed. This variation of production puts itself forward in cases, in which the formed molybdate/tungstate has a lower water solubility than Na2MoO4and Na2WO4, respectively, and than the used metal salt. Besides a good antimicrobial effect, the mentioned compounds also exhibit particularly high light and UV stability. The examination of the UV resistance can be performed in accordance with DIN EN 438-2, section 27. Herein, a sample of a composite material is produced by binding one or more of the mentioned molybdates and tungstates, respectively, to a further material. Therein, the molybdates and tungstates, respectively, can be present as a layer or component of a layer and/or be present distributed in the at least one further material. The composite material is exposed to radiation for 60 minutes. The same is effected with a comparative sample (“standard product”) produced in analogous manner, but without addition of the molybdenum/tungsten compounds.

The evaluation is then effected based on a visual comparison of the antimicrobially equipped and the non-equipped sample and is for example evaluated as follows:

1: no perceptible difference to the standard product

2: hardly perceptible difference to the standard product

3: uniquely perceptible difference to the standard product

4: just acceptable difference to the standard product

5: non-acceptable difference to the standard product

Therein, values of 1 or at most 2 are always obtained for the mentioned molybdates/tungstates.

The same experiments were performed with compounds of the general formula MO3-xwith 0<x<1 and M=W, Mo. Hereto, MoO2and WO2were partially oxidized individually or in certain mixture ratios or MoO3and/or WO3were partially reduced. The resulting oxides or mixed oxides also had excellent antimicrobial characteristics if they were present as a composite material with at least one further material. Examples for this are MoO2.35to MoO2.97and WO2.35to WO2.97.

As further materials, for example plastics, paints, varnishes, silicones, gum, rubber, melamine, acrylates, methacrylates, waxes, epoxy resins, glass, metal, ceramic and further are basically possible. The material, into which the molybdenum and tungsten compound(s) is or are incorporated, respectively, for the purpose of antimicrobial equipment, can form a solid and/or liquid matrix. It can be provided that the molybdenum and tungsten compounds, respectively, are added such that they constitute between 0.1% and 10% (percent by weight or volume) of the total weight or total volume. Furthermore, it can be provided that the molybdenum and tungsten compounds, respectively, are used in particulate form with average particle sizes between 0.1 μm and 100 μm.

For example, the at least one further material can include or consist of hydrophobic polymers such as silicones, polypropylene (PP), acrylonitril-butadiene-styrene (ABS), polycarbonate (PC) or polystyrene (PS). Phenolic resins, phenol formaldehyde resins, melamine resins, melamine formaldehyde resins, urea resins, urea formaldehyde resins and polymeric diphenylmethane diisocyanate as well as any mixtures therefrom can also be provided. Furthermore, the composite material can include polyethylene (PE), polyethylene terephthalate (PET), polyvinylchloride (PVC), polystyrene (PS), polycarbonate (PC) or a poly(meth)acrylate (e.g. PAA, PAN, PMA, PBA, ANBA, ANMA, PMMA, AMMA, MABS and/or MBS) as a further material. The use of thermoplastic elastomers allows production of surfaces with rubbery-elastic characteristics, in which the at least one molybdenum/tungsten containing compound is received or retained. The thermoplastic elastomer(s) can for example belong to the classes of TPO, TPV, TPU, TPC, TPS or TPA or any mixtures hereof, wherein thermoplastic elastomers based on urethane (TPUs) have in particular proven advantageous. The use of a reactive varnish allows production of mechanically particularly resistive surfaces, wherein the reactive varnish preferably already cures at room temperature by chemical reaction. Basically, the reactive varnish can be present or used as a one- or multi-component varnish. Similarly, the composite material can basically be formed as a UV-curable varnish, acrylic varnish and/or silicone containing varnish. In case of the configuration as an UV-curable varnish, the use of light- and/or UV-stable molybdenum/tungsten containing compounds has proven advantageous to avoid discolorations. However, in reverse, light- and UV-labile molybdenum/tungsten containing compounds, respectively, can also be used and be converted at the same time with curing of the varnish. Composite material varnishes based on silicone have the advantage of a very low change of their film volume during curing due to their low portion of organic groups. Hereby, very dense layers with good film strength can be produced, in which the at least one molybdenum/tungsten containing compound is received or retained. Moreover, silicone varnishes have a high thermal resistance and are therefore suitable for coating of items, which are provided for use in the area of heat sources.

FIG.1shows a schematic sectional view of an antimicrobially effective composite material10for further illustration, which includes ZnMoO4as a molybdenum containing inorganic compound only in the area of its surface. Therein, the ZnMoO4, which is illustrated dotted, is present with a mass portion of 2% in polypropylene (PP). The ZnMoO4containing surface area preferably forms an outer side of a product produced of the composite material10.

FIG.2shows a schematic sectional view of a further antimicrobially effective composite material10, which includes WO2.97as a tungsten containing inorganic compound12. One recognizes that the tungsten oxide is present not only on the surface, but finely distributed in the entire volume of the composite material10in contrast to the preceding example, wherein a PP matrix was again used as a further material.

As further embodiments, the following composite materials were produced, which all exhibited an excellent antimicrobial efficacy:
PP+2% WO3-x(blue)+2% silica gel
PP+2% WO3(yellow)+2% silica gel
PP+2% MoO3+2% silica gel+2% Atmer
PP+2% ZnMoO4+2% silica gel+2% Atmer
PP+4% ZnMoO4
PP+4% MoO3
PP+4% WO3-x(blue)
PP+4% WO3-x(blue)+2% silica gel
PP+4% WO3(yellow)+2% silica gel
PP+4% WO3(yellow)+2% silica gel

Therein, silica gel and Atmer function as hydrophilizing and hygroscoping agents, respectively.

For production, the molybdenum and tungsten compounds, respectively, as well as optionally the hydrophilizing and hygroscoping agents, respectively, were mixed in powdered form with average particle diameters between 0.1 μm and 5 μm into the PP in a Brabender Plasticorder. It is to be emphasized that other plastics such as for example PE, TPU, PU and the like can basically also be used. Furthermore, besides die casting, injection molding materials can also be antimicrobially equipped. The same applies to composite materials, which include inorganic materials as a matrix besides molybdenum/tungsten containing compounds.

The individual samples were sprayed with water about 3 hours before the first test of the antimicrobial efficacy to ensure a sufficient residual humidity in the composite material10. The test for antimicrobial efficacy was effected after drying on dry surface. Hereto, the individual, dried composite materials were first contaminated with a germ suspension (germ number 106).Staphylococcus aureus(s.a.),Pseudomonasaeruginosa (p.a.) andEscherichia coli(E. coli) were used as germs. The respective concentration of the germ suspension was determined and adjusted via photometric measurement.

Each 10 μl of the germ suspension was applied to the composite material10with the aid of a pipette and streaked with a Drigalski spatula. After complete drying of the germ suspension (after about one hour without further contact or treatment), so-called contact tests were performed after 0, 3, 6 and 9 hours. Hereto, a Caso agar contact plate is pressed onto the contaminated surface area and thereafter incubated for 24 hours in a manner known per se. In the composite materials10, germ growth could no longer be ascertained usually after 3 hours, but at the latest after 6 hours. Corresponding results could also be achieved with the dripping method known per se.

The antimicrobial efficacy could be maintained over several weeks in very dry environments with air humidity values below 20% even in those composite materials10without hydrophilizing and hygroscoping agent, respectively. However, the use of hydrophilizing and hygroscoping agent, respectively, improves, but in particular extends the antimicrobial efficacy under very dry conditions. At very low air humidity values, the antimicrobial efficacy can be again regenerated after some days by new wetting, for example by wiping the surface with a wet cloth. At higher air humidities above about 30%, particular measures are not required to permanently maintain the antimicrobial efficacy.

The composite material10can be used for producing very different products and items. The product can for example be formed as an implant, catheter, stent, bone implant, dental implant, vascular prosthesis, endoprosthesis, exoprosthesis, cable, hose, food packaging, container, fuel tank, household product, counter, fitting, keyboard, mouse, joystick, housing, textile, item of clothing, furniture and/or interior construction part, household appliance, credit card, mobile phone case, coin, bill, door handle, refrigerator, trickling material in the cooling tower, varnish coating, tile or a part of the interior fittings of a building or public service vehicle. Furthermore, it can be provided that the product is formed as a storage and transport container or as a conduit for hydrocarbons, fuels, solvents and organic liquids. Similarly, the composite material according to the invention can be used for producing an item from the group of the housewares, medical technology, food engineering, sanitary installations, packagings, textiles, clinics, counters, seats and keyboards. Similarly, it is suitable for products being in frequent touch contact with living beings. A further advantageous use is in components for air conditioning systems. The cooling fins, which are usually composed of a Cu or Al alloy, can be advantageously coated with the composite material according to the invention or be produced from it. The ducts of air conditioning systems in buildings can also be antimicrobially configured by adding the composite material10to the duct material, coating the duct material with them or if the duct material is composed of the composite material10. Air humidifiers can also be provided with corresponding antimicrobial characteristics. In addition, the composite material can be used in cables and/or for producing cables.

In further configuration of the invention, the composite material is formed as a coating agent, in particular as a paint, varnish and/or antifouling coat. Embodiments of the composite material are understood by a paint, which have a liquid to pasty consistency and result in a physically or chemically dry coat applied to surfaces. Hereby, the advantageous characteristics of the composite material according to the invention can be particularly flexibly realized for any items and surfaces. Important configurations are for example antifouling coats, e.g. for ships, as well as antimicrobial equipment in the health system, the industry, the food sector and the private sector.

In a further embodiment, at least the surface of the composite material is hydrophilized. Here, hydrophilizing agents (e.g. Irgasurf™ HL560, TechMer PPM15560™, Bayhydur™ 304) as they are employed for PP textile fibers are particularly advantageous. Alternatively or additionally, polyethylene glycol (PEG, PEG400), the derivates thereof, hyaluronic acid, starch, oxethylated carbonic acid compounds, hydrophilic silicates, sucrose methacrylates, hydrophilized, aliphatic polyisocyanate based on hexamethylene diisocyanate (HDI) as well as diverse fibers and GMS (glycerin monostearate) as well as the derivates thereof are suitable. Further substances for providing hydrophilic characteristics are fatty alcohol phosphates as well as derivates of polyethylene oxide (PEO), in particular with hydroxyl terminal groups.

The mass content of the hydrophilizing and/or hygroscoping agent can be between 0.1% and 10%, in particular between 0.15 and 5% and preferably between 0.2% and 4% related to the mass of the composite material. For example, silica gel and Atmer (vegetable glycerol esters) with respective mass contents of about 2% can be used as hydrophilizing and/or hygroscoping agent, whereby a total mass content of 4% of hydrophilizing and hygroscoping agent, respectively, results. Alternatively, only 2% of silica gel or 2% of Atmer can for example also be used.

With the aid of the hydrophilizing and/or hygroscoping agent, the composite material can also be used in particularly dry environments with air humidity values below 20%. For activating or regenerating the antimicrobial efficacy, therein, it is sufficient to wet the surface of the composite material for example in weekly rhythm, for example to wipe it with a wet cloth.

By hygroscopic, it is to be understood that the composite material absorbs humidity at least on its surface or in the areas near the surface. For example, the composite material should absorb between 0.01 and 10 wt.-% of humidity in environments with <10% of relative air humidity. Particularly advantageous are 0.1 to 3% of equilibrium humidity, which usually appear after some minutes to hours.

The parameter values indicated in the documents for the definition of process and measurement conditions for the characterization of specific characteristics of the inventive subject matter are to be considered as encompassed by the scope of the invention also within the scope of deviations—for example due to measurement errors, system errors, weighing errors, DIN tolerances and the like.