WO2020074049A1 - Antimicrobial composition based on polyoxometalates, method for the production thereof, and uses thereof - Google Patents

Abstract

The invention relates to a method for producing an antimicrobial composition comprising the following steps: (i) reacting a purely inorganic metal salt or a hydrate thereof in an aqueous solution with a base at a temperature in the region of 50 to 100°C, wherein the metal in the metal salt is selected from the group consisting of Al, Ga, In and Bi; (ii) optionally cooling the reaction solution from step (i) to a temperature in the region of 5 to 20°C; (iii) dissolving a water-soluble tungsten compound in an aqueous H2O2 solution; (iv) optionally heating the solution from step (iii) to a temperature in the region of 70 to 90°C and cooling to a temperature in the region of 5 to 20°C; (v) adding the solution from step (iii) or (iv) to the reaction solution from step (i) or (ii), or vice versa, and processing and drying the resulting precipitate. The invention also relates to an antimicrobial composition which can be obtained using the method according to the invention, and the uses thereof.

Description

 ANTIMICROBIAL COMPOSITION BASED ON POLYOXOMETALLATE, METHOD FOR THE PRODUCTION THEREOF AND ITS USES THEREOF

Field of the Invention

The invention relates to a method for producing an antimicrobial composition, a composition obtainable by this method and uses of the antimicrobial composition.

State of the art

Antimicrobial compositions based on polyoxometalates are known from the prior art.

For example, WO 2014/122225 A1 describes the use of compounds composed of heteropolyoxometalate anions and quaternary ammonium or phosphonium or tertiary sulfonium cations for disinfection purposes and in antimicrobial surfaces, paints or coatings.

[04] WO 2017/092920 A2 and WO 2017/093475 A1 disclose another group of compounds composed of heteropolyoxometalate anions and quaternary ammonium or phosphonium or tertiary sulfonium cations, which simultaneously impart antimicrobial properties to a surface of a substrate and reduce the growth of a biofilm on the surface of the substrate. [05] A disadvantage of the compounds known from the prior art has proven, however, that they are present as a gel and are therefore difficult to handle in certain applications. In addition, they are only thermally stable to a limited extent, ie they change color at higher temperatures, which also limits the areas of application.

The object of the present invention is therefore to provide easier-to-handle and thermally stable antimicrobial compositions with polyoxometalates as anions.

Summary of the invention

[07] According to the invention, this object is achieved by a method for producing an antimicrobial composition with the following steps:

(i) reacting a purely inorganic metal salt or a hydrate thereof in aqueous solution with a base at a temperature in the range from 50 to 100 ° C., the metal in the metal salt being selected from the group consisting of Al, Ga, In and Bi ;

(ii) optionally cooling the reaction solution from step (i) to a temperature in the range from 5 to 20 ° C .;

(iii) dissolving a water-soluble tungsten compound in an aqueous H2C> 2 solution,

(iv) optionally heating the solution from step (iii) to a temperature in the range from 70 to 90 ° C. and Cooling to a temperature in the range of 5 to 20 ° C;

(iv) adding the solution from step (iii) or (iv) to the reaction solution from step (i) or (ii) or vice versa and working up and drying the resulting precipitate.

[08] A metal halide or hydrate thereof is preferably used as the metal salt or hydrate thereof in step (i).

[09] AlCl3 6H20 is particularly preferably used as the metal halide hydrate.

[10] In one embodiment of the invention, an alkali metal hydroxide solution is used as the base in step (i).

[11] Sodium hydroxide solution is particularly preferably used as the alkali hydroxide solution.

[12] In a preferred embodiment of the invention, ammonium metatungstate (NH _{4) 6 (} H2W12O40) · cH2q is used as the water-soluble tungsten compound in step (iii).

The invention also relates to an antimicrobial composition which can be obtained by the process according to the invention.

[14] Finally, a further subject of the invention is the use of an antimicrobial composition according to the invention omposition as an admixture to the mass of a plastic _Z for the preparation of closures of food or beverage containers or inserts therein.

The method according to the invention surprisingly leads to an antimicrobial composition based on a mixture of purely inorganic salts of the metals aluminum (Al), gallium (Ga), indium (In) or bismuth (Bi) as cations and a mixture of

Isopolyoxotungstates as anions, which can be obtained in the form of white powder, is thermally stable and is therefore easy to use for a wide range of applications.

[16] In the first stage of the process, a purely inorganic metal salt, such as a metal halide, of the above-mentioned metals or a hydrate thereof is reacted in aqueous solution and with heating with a base, such as an alkali metal hydroxide solution, whereby the pH is raised to a value of preferably more than 4. This reaction is known from the prior art and leads to polynuclear complexes, for example to Al13O4 (OH) 24 (H2O) i2 ⁷⁺ in the case of Al salts (T. Tsuchida et al., "Formation of Crystalline Sulfates from

Al13 Polymer Solutions: Effect of Washing on Transformation of Type I to Type II Crystals ", J. Mater. Chem., 1995, 5 (8), 1233-1236).

[17] The second step is a water-soluble one

Tungsten compound, such as, for example, ammonium metatungstate

(NH ₄ ) ₆ (H ₂ W ₁₂ O ₄₀ ) · cH ₂ q, dissolved in aqueous H ₂ C> ₂ solution and heated if necessary. This reaction creates a mixture of Isopolyoxotungstate polyanions, the exact composition and structure of which has not yet been fully elucidated. In addition to the above-mentioned ammonium metatungstate, other metatungstates (for example with Li, Na, K as cations) and hydrates thereof, paratungstates (H ₂ W ₁₂ O ₄₂ ¹⁰ ) and hydrates thereof also come as water-soluble tungsten compounds, for example

Tungsten (WO ₄ ² ) and hydrates thereof and tungstic acid (H2WC> 4 or W0 ₃ -H ₂ 0) into consideration.

[18] When the two solutions prepared as described above are mixed, a precipitate forms spontaneously, which after preparation and drying gives a white powder. The order of mixing is basically arbitrary. In terms of handling, it is easier to add the solution with the isopoly anions based on tungsten to the solution with the inorganic cation.

The white powder obtained from the reaction according to the invention, which has antimicrobial properties, can be used in a wide variety of ways, for example for all the uses which are listed for the antimicrobial compounds in the publications mentioned above.

[20] Currently, the use of the novel antimicrobial composition as an admixture with a plastic mass is particularly preferred for the manufacture of closures for food or beverage containers or inserts therein. Because of the purely inorganic nature of the antimicrobial composition according to the invention, there are no fundamental restrictions for the plastic. For the applications mentioned, thermoplastic elastomers based on synthetic rubber are mainly used, such as, for example, Wakol 4081 from Wakol GmbH.

Amounts of 0.5-2.5% by weight, preferably 1-2% by weight, particularly preferably approximately 1% by weight, are sufficient to achieve a satisfactory to very good antimicrobial effect. It has proven to be an additional advantage that the composition according to the invention is thermally very stable, that is, when processed with plastics, it does not lead to discolouration, as occurs in the compounds known from the prior art based on heteropolyoxometalates.

[22] Further features and advantages of the invention emerge from the examples below.

Examples

Manufacturing example

[23] 300 g of aluminum chloride hexahydrate (AlCl _{3 '} 6H ₂ 0) are dissolved in 4 1 of water and then to 90 ° C in one

Water bath heated. 3 1 IM

Sodium hydroxide (NaOH) solution is added dropwise with vigorous stirring, the solution temperature being kept above 80 ° C. The solution is then cooled to approximately 10 ° C. in a cold water / ice bath (solution A). [24] 200 g ammonium metatungstate, (NH ₄ ) 6 (H2W12O40) · cH2q, are dissolved in 1 1 30% H2O2 and heated to 80 ° C for 1 h. The yellow solution is left for a few hours to cool to room temperature (solution B).

[25] Solution B is then quickly added to solution A with vigorous stirring. A light yellow precipitate forms immediately. This is decanted, filtered and washed with water and then dried in an oven at 50 ° C for 15 h, resulting in a white powder.

Application example

A corresponding amount of a plastic (Wakol 4081) is melted at approx. 180 ° C. In each case 1.0% by weight of a composition known from the above-mentioned prior art, namely tetraorgano-P-cation and PWi ₂ 0 ₄ o ³ heteropolyanion (as a gel), or that according to the invention obtained according to the preparation example above, are added to this melt The composition (as a powder or predispersed in mineral oil) was mixed in with a Cowles dissolver at approx. 1,500 rpm. A film of approx. 1 mm thickness is cast from the correspondingly additized plastic material, which after hardening is processed into disks with a diameter of approx. 26 mm.

[27] These discs are used as inserts in closures of 0.51 bottles. The bottles are filled with still water, the bottle opening is coated with a microbe mixture (see below) and the bottles are closed with the prepared closures and at approx. 23 ° C stored. Half of the bottles were opened after 4 days, the other half after 6 weeks and the inserts of the closures were examined for microbial colonization.

[28] The results are summarized in Table 1 below:

Table 1

 E = Excellent

G = Good, with slightly discernible growth R = Delayed, but with clearly discernible growth

[29] From Table 1 it can be seen that the added compound from the prior art in some

Microbe species showed only a slight antimicrobial effect and discolored the inserts unacceptably, so it is not suitable for admixing to plastic mass. In contrast, the composition according to the invention was sufficiently heat-stable and consistently showed excellent to good antimicrobial results in the uses.

[30] The features of the invention disclosed in the above description and the claims can be essential both individually and in any combination for the implementation of the invention in its various embodiments.

Claims

Claims: 1. A method for producing an antimicrobial composition comprising the following steps: (i) reacting a purely inorganic metal salt or a hydrate thereof in aqueous solution with a base at a temperature in the range from 50 to 100 ° C., the metal in the metal salt being selected from the group consisting of Al, Ga, In and Bi ; (ii) optionally cooling the reaction solution from step (i) to a temperature in the range from 5 to 20 ° C .; (iii) dissolving a water-soluble tungsten compound in an aqueous H2C> 2 solution, (iv) optionally heating the solution from step (iii) to a temperature in the range from 70 to 90 ° C and cooling to a temperature in the range from 5 to 20 ° C; (iv) adding the solution from step (iii) or (iv) to the reaction solution from step (i) or (ii) or vice versa and working up and drying the resulting precipitate. 2. The method according to claim 1, characterized in that a metal halide or hydrate thereof is used as the metal salt or hydrate thereof in step (i). 3. The method according to claim 2, characterized in that AlCl _{3 '} 6H ₂ 0 is used as the metal halide hydrate. 4. The method according to any one of claims 1 to 3, characterized in that as a base in step (i) Alkali hydroxide solution is used. 5. The method according to claim 4, characterized in that sodium hydroxide solution is used as the alkali hydroxide solution. 6. The method according to any one of claims 1 to 5, characterized in that ammonium metatungstate (NH _{4) 6 (} H2W12O40) -xtkO is used as the water-soluble tungsten compound in step (iii). 7. Antimicrobial composition, available with a Method according to one of claims 1 to 6. 8. Use of an antimicrobial composition after Claim 7 as an admixture to the mass of a _C omposition plastic for the production of Closure of food or beverage containers or inserts therein.