METAL PREPARATION AND COATINGS MADE THEREFROM

Abstract

The present invention is directed to metal preparations containing metal particles, in particular noble metal particles, to the use of such metal preparations for the production of attractive metallic decorative elements on articles having an outer silicatic surface such as of porcelain, ceramic, china, bone china, glass or enamel, to metallic coatings on such substrates and to a process for the production of coatings of this kind.

Claims

1. Metal preparation comprising A) from 5 to 60% by weight of metal particles wherein said metal particles (i) exhibit a d.sub.50 value, measured by the volume related laser diffraction method, in the range of from 30 to 300 nm, (ii) exhibit an average aspect ratio, measured by scanning electron microscopy or transmission electron spectroscopy, in the range of from 1.0 to 1.5, and (iii) are selected from Ag, Au, Ru, Ir, Pd, Pt, Cu Nb, or an alloy comprising at least one thereof, B) from 0.2 to 50% by weight of at least one organic compound of one or more elements selected from Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal or alkaline earth metal, C) from 10 to 85% by weight of a solvent, D) from 0.1 to 50% by weight of a polymeric binder, and E) from 0.01 to 30% by weight of at least one metal compound that is soluble in organic solvent, wherein the metal comprises at least one from Ag, Au, Ru, Ir, Pd, Pt, Os, and Rh, wherein the percentages are based on the total weight of the metal preparation.

2. Metal preparation as claimed in claim 1, characterized in that the metal particles are noble metal particles selected from Ag, Au, Ru, Ir, Pd, Pt, or an alloy comprising at least one thereof.

3. Metal preparation as claimed in claim 1, characterized in that the metal particles are of silver or a silver containing alloy having a silver content of at least 50% by weight, based on the weight of the alloy.

4. Metal preparation as claimed in claim 1, characterized in that organic compound B is an alcoholate, carboxylate, citrate, acetylacetonate and/or tartrate of the elements selected from Si, Ge, B, P, Nb, Sn, Zn, Zr, Ti, Sb, Al, Bi, alkali metal and alkaline earth metal.

5. Metal preparation as claimed in claim 1, characterized in that the Si containing organic compound is a silicon comprising polymer such as a polysilazane compound, a polysiloxane compound, a silicone resin, a silicone-modified alkyd resin, a silicone-polyester resin, and/or a silsesquioxane polymer.

6. Metal preparation as claimed in claim 1, characterized in that solvent C is an organic solvent or a mixture of organic solvents, having a water content in the range of from 0 to at most 10% by weight, based on the total weight of the solvent: preferably wherein the solvent is selected from at least one of the group of alcohols, aromatic solvents, ketones, esters, ethers, ether-alcohols, saturated and unsaturated aliphatic hydrocarbons, or amides.

7. (canceled)

8. Metal preparation as claimed in claim 1, wherein the polymeric binder D comprises at least one of celluloses, polyamides, polyesters, polyethers, polyvinyls, polyacetals, polyvinylacetals, polysulfone, phenolic resin, ketone resin, epoxy resin, maleic resin and rosin resin.

9. Metal preparation as claimed in claim 1, wherein metal compound E that is soluble in organic solvent at least one a resinate, a sulforesinate, a thiolate, a carboxylate or an alcoholate.

10. Metal preparation as claimed in claim 1, further comprising, as ingredient F, from 0 to 5% by weight of at least one metal salt compound, wherein the metal comprises at least one from Co, Ni, Cu, Cr, Fe, and Mn: preferably characterized in that the metal salt compound is at least one from a resinate, a sulforesinate, a thiolate, a carboxylate or an alcoholate; or further comprising, as Ingredient G, from 0 to 10% by weight of a rheology modifying additive; preferably characterized in that rheology modifying additive G comprises at least one of the additives from pine oil, castor oil, a fatty acid, a fatty acid derivative, a natural or a synthetic wax; or further comprising, as ingredient H, from 0 to 10% by weight of a dispersant; preferably wherein dispersant H comprises at least one of polyacrylic acid, polyacrylates and their copolymers, polyurethanes polyvinylpyrrolidone, non-ionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants; or further comprising, as ingredient I, at least one additive.

11-16. (canceled)

17. Process for the production of a metal preparation as claimed in claim 1, characterized in that the ingredients are intimately mixed with each other and a ready-to-use metal preparation is obtained; preferably characterized in that the mixing is carried out employing a rotor-stator-homogenizer, a triple-roll mill, or a Speedmixer.

18. (canceled)

19. Gold, platinum, or silver colored decorative elements on articles exhibiting a surface, such as porcelain, china, bone china, ceramic, glass or enamel, comprising a metal preparation as claimed in claim 1.

20. Solid coating on a substrate, comprising, based on the total weight of the solid coating, at least 60%, preferably at least 80%, by weight of metal particles of at least one metal selected from Ag, Au, Ru, Ir, Pd, Pt, Cu, No, or an alloy comprising at least one thereof, and further comprising at least 5% by weight, based on the total weight of the solid coating, of a glass matrix comprising at least one oxide of SiO.sub.2, GeO.sub.2, B.sub.2O.sub.3, P.sub.4O.sub.10, NbO.sub.2, Nb.sub.2O.sub.3, SnO, SnO.sub.2, ZnO, ZrO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, Bi.sub.2O.sub.3, Sb.sub.2O.sub.3, alkali metal oxide, and/or alkaline earth metal oxide.

21. Solid coating on a substrate as claimed in claim 20, characterized in that the metal particles are of silver or a silver comprising alloy having a silver content of at least 50% by weight, based on the total weight of the alloy.

22. Solid coating on a substrate as claimed in claim 20, characterized in that the glass matrix additionally contains one or more metals or metal oxides, the metal(s) selected from Ni, Cu, Cr, Fe, Mn, Ag, Au, Rh, Ru, Ir, Pd, Os and Pt.

23. Solid coating on a substrate as claimed in claim 20, comprising 5 to 40% by weight of the glass matrix, based on the total weight of the solid coating: preferably comprising from 10 to 30% by weight of the glass matrix, based on the total weight of the solid coating.

24. (canceled)

25. Solid coating on a substrate as claimed in claim 20, characterized in that the solid coating is composed of two layers lying on top of each other, wherein a first layer is located directly on the substrate and constitutes a densely packed metallic layer comprising aggregated metal particles, and wherein the second layer is located on top of the first layer and is a glass-like layer comprising at least one oxide of SiO.sub.2, GeO.sub.2, B.sub.2O.sub.3, P.sub.4O.sub.10, NbO.sub.2, Nb.sub.2O.sub.3, SnO, SnO.sub.2, ZnO, ZrO.sub.2, TiO.sub.2, A.sub.2O.sub.3, Bi.sub.2O.sub.3, Sb.sub.2O.sub.3, alkali metal oxide, and/or alkaline earth metal oxide.

26. Solid coating on a substrate as claimed in claim 20, characterized in that the substrate is an article exhibiting an outer surface of porcelain, china bone china, ceramic, glass or enamel.

27. Process for the production of a metal comprising coating on a substrate, characterized in that a metal preparation as claimed in claim 1 is applied onto a substrate and subsequently thermally treated at a temperature in the range of from 500 C. to 1250 C.

28. Process as claimed in claim 27, characterized in that the substrate is an article exhibiting a silicatic surface, such as porcelain, china, bone china, ceramic, glass or enamel; or characterized in that the metal preparation is directly applied onto the substrate; or characterized in that the metal preparation is applied onto the substrate by means of a transfer medium pre-coated with the said metal preparation; or characterized in that the metal preparation is applied onto the substrate or transfer medium employing a printing process; preferably characterized in that the metal preparation is applied onto the substrate or transfer medium employing thermoplastic screen printing, ink jet printing, tampon printing, or offset printing.

29-32. (canceled)

33. Process as claimed in claim 27, characterized in that the substrate coated with the metal preparation is partly or in total covered by an additional protective layer prior to thermally treating the coating.

Description

EXAMPLES

[0138] Method for the Determination of the Average Aspect Ratio of an Assemble of Metal Particles

[0139] A representative SEM or TEM image of metal particles as shown in FIG. 1 containing m=50 to m=100 countable particles is subjected to the following procedure:

[0140] Every diameter of a particle is measured at the longest position to yield a value d.sub.1. The perpendicular diameter to this position is measured as well to yield a value d.sub.2.

[0141] The aspect ratio AS is determined by the following formula considering the aspect ratio d.sub.1:d.sub.2 for every particle independent of its size:

[00001]$\mathrm{AS}=\underset{n=1}{\overset{m}{.Math.}}.Math.\left(d_1.Math.\text{:}.Math.d_2\right).Math.\text{:}.Math..Math.m$

[0142] The average aspect ratio AS is provided in the form AS=a:1, i.e. normalized to the smaller diameter as 1.

Example ASuitable Metal Particles for a Composition According to this Invention

[0143] Silver particles were prepared according to US20130270490 A1, example 1 and subsequently converted to a tripropylene glycol monomethylether-based formulation according to example 10 of the same publication (50% solids content).

[0144] The resulting silver particles were filtered off, washed with ethanol, dried and subjected to SEM analysis providing an aspect ratio of 1.15:1 at a d.sub.50 of 70 nm, d.sub.90 of 115 nm (see FIG. 1).

Comparative Example BUnsuitable Metal Particles for a Composition According to this Invention

[0145] Silver particles were prepared according to the methods described in Sabrina Daumann's doctorate dissertation titled Synthese und Charakterisierung von Nanopartikeln: Anisotrope Edelmetall-Nanopartikel und Zinkoxid-Nanopartikel, 2016, University of Duisburg-Essen, Germany. The obtained elongated silver particles were subsequently converted to tripropylene glycol monomethylether-based formulation according to example 10 in US20130270490 A1 (50% solids content).

[0146] The resulting silver particles were filtered off, washed with ethanol, dried and subjected to SEM analysis providing an average aspect ratio (AS) of 1.80:1 at a d.sub.50 of 130 nm, and d.sub.90 of 200 nm.

Example 1 (Ingredients: A, B, C, D, E)

[0147] 0.361 g of Mowital B 45 H, dissolved in dipropylene glycol monomethyl ether (DPM) (17% solids content, product of Kuraray Europe GmbH, CAS-No. 68648-78-2) are metered into a container equipped with a stirrer. 0.013 g of Durazane 1066 (product of Merck KGaA; CAS-No. 346577-55-7), 0.602 g of a paste of silver nano-sized particles (d.sub.50 of 70 nm, d.sub.90 of 115 nm, 50% solids content in tripropylene glycol monomethyl ether; cf. Example A) and 0.031 g of rhodium(III)-tris[2-ethylhexanoate] (2% in 2-ethylhexanol; product of American Elements) are subsequently added under stirring.

[0148] The resulting paste is applied onto a glass plate by means of a brush. The glass plate coated with the coating composition is then thermally treated at a temperature of 580 C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of silver colour and an upper protective glass-like layer.

[0149] The layer is composed of 92.2% by weight of silver, 0.2% by weight of Rh and 7.6% by weight of SiO.sub.2, based on the weight of the layer.

Example 2 (Ingredients A, B, C, D, E)

[0150] 41% by weight of a solution of polyvinylbutyral binder (Mowital B 45 H, product of Kuraray Europe GmbH, 10% by weight in propylene glycol monopropylether), are metered into a container equipped with a stirrer. 10% by weight of a silsesquioxane polymer preparation (MP 60LAN, product of Merck KGaA), 40% by weight of a paste of silver nanosized particles (d.sub.50 of 70 nm, 45% solids in tripropylene glycol monomethyl ether; cf. Example A), 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements), 2% by weight of bismuth(III)-tris[2-ethylhexanoate] (product of OMG Borchers GmbH) and 5% by weight of niobium(IV)-tetrakis[2-ethylhexanoate] (product of Strem Chemicals, Inc.) are subsequently added under stirring.

[0151] The resulting paste is applied onto a glass plate by means of a brush. The glass plate coated with the coating composition is then thermally treated at a temperature of 580 C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of platinum white colour and a top coat glass-like layer.

[0152] The layer is composed of 60.1% by weight of silver, 26.7% by weight of SiO.sub.2, 2.3% by weight of Bi.sub.2O.sub.3, 2.6% by weight of Nb.sub.2O.sub.5 and 8.3% by weight of Rh, based on the weight of the layer.

Example 3 (Ingredients: A, B, C, D, E)

[0153] 14% by weight of polyurethane alkyd binder (Synolac 846560, product of Arkema), dissolved in 33% by weight of propylene glycol monopropylether, are metered into a container equipped with a stirrer. 20% by weight of vinyltriethoxysilane (product of Alfa Aesar), 31% by weight of a paste of silver nanosized particles (d.sub.50 of 70 nm, 50% solids in tripropylene glycol monomethylether; cf. Example A), and 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements) are subsequently added under stirring.

[0154] The resulting paste is applied onto a glass plate by means of a brush. The glass plate coated with the coating composition is then thermally treated at a temperature of 580 C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of yellow gold colour and a top coat glass-like layer.

[0155] The layer is composed of 68.6% by weight of silver, 27.9% by weight of SiO.sub.2, and 3.5% by weight of Rh, based on the weight of the layer.

Example 4 (Ingredients: A, B, C, D, E)

[0156] 32% by weight of polyurethane alkyd binder (Synolac 846560, product of Arkema), and 5% by weight of silicone modified isophthalic acid alkyd resin based on linseed oil (Synolac 514041, product of Arkema) are metered into a container equipped with a stirrer. 10% by weight of silicon tetrakis [2-ethylhexanoate] (product of Alfa Aesar), 50% by weight of a paste of silver nanosized particles (d.sub.50 of 70 nm, 50% solids in tripropylene glycol monomethyl ether; cf. Example A), and 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements) are subsequently added under stirring.

[0157] The resulting paste is applied onto a glass plate by means of direct screen printing. The glass plate coated with the coating composition is then thermally treated at a temperature of 500-620 C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of yellow gold colour and a top coat glass-like layer.

[0158] The layer is composed of 85.4% by weight of silver, 11.2% by weight of SiO.sub.2, and 3.4% by weight of Rh, based on the weight of the layer.

Example 5 (Ingredients A, B, C, D, E)

[0159] 45% by weight of a solution of modified rosin resin (Dymerex, product of Eastman Chemical Comp., 65% by weight in dipropylene glycol monomethylether), and 10% by weight of a silsesquioxane polymer preparation (MP 60LAN, product of Merck KGaA) are metered into a container equipped with a stirrer. 50% by weight of a paste of silver nanosized particles (d.sub.50 of 70 nm, 50% solids in tripropylene glycol monomethylether; cf. Example A), 2% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements), 2% by weight of bismuth(III)-tris[2-ethylhexanoate] (product of OMG Borchers GmbH) and 1% by weight of palladium resinate (MR4601-P; product of Wako Chemicals USA, Inc.) are subsequently added under stirring.

[0160] The resulting paste is applied onto a glass plate by means of decals (transfer paper). The glass plate coated with the coating composition is then thermally treated at a temperature of 500-620 C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of platinum white colour and a top coat glass-like layer.

[0161] The layer is composed of 71.4% by weight of silver, 22.9% by weight of SiO.sub.2, 2.3% by weight of Rh, 2.0% by weight of Bi.sub.2O.sub.3, and 1.4% by weight of Pd based on the weight of the layer.

Example 6 (Ingredients A, B, C, D, E)

[0162] 45% by weight of a solution of modified rosin resin (Dymerex, product of Eastman Chemical Comp., 65% by weight in dipropylene glycol monomethylether) are metered into a container equipped with a stirrer. 45% by weight of a paste of silver nanosized particles (d.sub.50 of 70 nm, 50% solids in tripropylene glycol monomethylether; cf. Example A), 3% by weight of rhodium(III)-tris[2-ethylhexanoate] (product of American Elements), 2% by weight of bismuth(III)-tris[2-ethylhexanoate] (product of OMG Borchers GmbH) and 5% by weight of tetra-n-butyl germanium (product of Gelest, Inc.) are subsequently added under stirring.

[0163] The resulting paste is applied onto a glass plate by means of decals (transfer paper). The glass plate coated with the coating composition is then thermally treated at a temperature of 500-620 C. in air. The solvents evaporate and the organic compounds of the coating composition burn without remainings at this temperature. The resulting solid coating layer on the glass plate is composed of a glossy lower metallic layer of platinum white colour and a top coat glass-like layer.

[0164] The layer is composed of 81.6% by weight of silver, 11.6% by weight of GeO.sub.2, 2.5% by weight of Bi.sub.2O.sub.3, 4.3% by weight of Rh, based on the weight of the layer.

Comparative Example 1 (Ingredients: A, C, D, E, H)

[0165] 10 g of polyvinylpyrrolidone (PVP40; product of Sigma Aldrich) are dissolved in 80 g of ethanol. 50 g isobutanol, 5 drops of BYK 065 defoamer (product of BYK Chemie GmbH) and 50 g of Ag.sub.60Cu.sub.30Sn.sub.10 nano powder (product of American Elements) are added. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable Dispersion A.

[0166] 30 g of Dispersion A are mixed with 50 g of methylsilicone resin solution (Silres HK 46; 50% by weight methylsilicone resin in xylene/butanol 4/1; product of Wacker AG) and subjected to ultrasonic wet milling until a homogenous dispersion is obtained. The resulting paste is suitable for silkscreen printing on paper and plastic.

Comparative Example 2 (Ingredients: A, B, C, D, H)

[0167] 15 g of polyvinylpyrrolidone (PVP40; product of Sigma Aldrich) are dissolved in 80 g of ethanol. 50 g isobutanol, 10 drops of BYK 065 defoamer (product of BYK Chemie GmbH) and 50 g of Ag.sub.3.5Sn.sub.96.5 nano powder (product of American Elements) are added. The mixture is subjected to 40 min of ultrasonic wet milling to obtain a stable Dispersion A.

[0168] A mixture of equal parts by weight of a silicone modified special fatty acid isophthalic alkyd resin (Synolac 2700 WD 70; product of Arkema) and rosin resin is prepared via ultrasonic wet milling to obtain Mixture B.

[0169] Equal parts by weight of Dispersion A and Mixture B are mixed employing ultrasonic wet milling to obtain a paste for direct printing on glass.

Comparative Example 3 (Ingredients: A, B, C, D, H)

[0170] 2 parts by weight of Niobium (IV)-2-ethyl hexanoate (product of Strem Chemicals, Inc.) are mixed with 8 parts by weight of rosin resin solution (60% by weight of resin in 40% by weight of isobutanol) to obtain Mixture C.

[0171] Equal parts by weight of Dispersion A from Comparative Example 2 and Mixture C are mixed employing ultrasonic wet milling to obtain a paste for direct printing on tiles. Thermal treatment is conducted at 700 C. in air. A bright yellow and shiny metal coating is obtained.

Comparative Example 4 (Ingredients: A, B, C, H)

[0172] 50 g of Ag.sub.60Cu.sub.30Sn.sub.10 nano powder (product of American Elements), 15 g of anionic surfactant (phosphate of ethoxylated C.sub.12-C.sub.15 aliphatic alcohol, Lanphos TE 43; product of Lankem Ltd.) and 5 drops of BYK 065 defoamer (product of BYK Chemie GmbH) are mixed with 100 g of xylene. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable Dispersion A.

[0173] 30 g of Dispersion A are mixed with 50 g of methylsilicone resin solution (Silres HK 46; 50% by weight methylsilicone resin in xylene/butanol 4/1;

[0174] product of Wacker AG) and subjected to ultrasonic wet milling until a homogenous dispersion is obtained. The resulting paste is suitable for silkscreen printing on paper and plastic.

Comparative Example 5 (ingredients: A, B, C, D, H)

[0175] 50 g of Ag.sub.35Sn.sub.965 nano powder (product of American Elements), 15 g of anionic surfactant (phosphate of ethoxylated C.sub.12-C.sub.15 aliphatic alcohol, Lanphos TE 43; product of Lankem Ltd.) and 10 drops of BYK 065 defoamer (product of BYK Chemie GmbH) are mixed with 100 g of xylene. The mixture is subjected to 40 min of ultrasonic wet milling to obtain a stable Dispersion A.

[0176] A mixture of equal parts by weight of a silicone modified special fatty acid isophthalic alkyd resin (Synolac 2700 WD 70; product of Arkema) and rosin resin is prepared via ultrasonic wet milling to obtain Mixture B. Equal parts by weight of Dispersion A and Mixture B are mixed employing ultrasonic wet milling to obtain a paste for direct printing on glass.

Comparative Example 6 (Ingredients A, B, C)

[0177] 20 g of Ag nano powder of d.sub.50 of 70-150 nm (product of American Elements) and 35 g of silicone-polyester resin (Silikoftal HTL; product of Evonik Industries AG) are mixed with 55 g of dipropyleneglycol monomethyl ether. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable dispersion for direct printing on paper, plastic, metal, glass or ceramic substrate. Thermal treatment is conducted at 150 to 600 C. depending upon the employed substrate.

Comparative Example 7 (Ingredients A, B, C, D, F)

[0178] 20 g of Ag nano powder of d.sub.50 of 70-150 nm (product of American Elements), 3 g of cobalt (II) bis [2-ethylhexanoate] (product of American Elements), 5 g of tetraethoxysilane (product of Merck KGaA) and 35 g of a linoleic based nitrocellulose alkyd resin (Synolac 8026 X60; product of Arkema) are mixed with 37 g of dipropyleneglycol monomethylether. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable dispersion for direct screen printing on glass employing 120T polyester mesh fabric. Drying is conducted for 2 h at 150 C. The obtained coating is furnished with a protective coating of silicone modified isophthalic acid alkyd resin based on linseed oil (Synolac 5140 X41; product of Arkema) employing 120T polyester mesh fabric. Thermal treatment is conducted at 580 C.

Comparative Example 8 (Ingredients A, B, C, D; cf. WO 2012/059088 A2)

[0179] 22.5 g of Ag nano powder of d.sub.50 of 70-150 nm (product of American Elements), 15 g of silicon tetrakis [2-ethylhexanoate] (product of Alfa Aesar) and 30 g of a linoleic based nitrocellulose alkyd resin (Synolac 8026 X60; product of Arkema) are mixed with 32.5 g of dipropyleneglycol monomethylether. The mixture is subjected to 30 min of ultrasonic wet milling to obtain a stable dispersion for direct screen printing on glass employing 120T polyester mesh fabric. Drying is conducted for 2 h at 150 C. The obtained coating is furnished with a protective coating of silicone modified isophthalic acid alkyd resin based on linseed oil (Synolac 5140 X41; product of Arkema) employing 120T polyester mesh fabric. Thermal treatment is conducted at 550 C. to provide a yellow golden coating.

Comparative Example 9 (Ingredients: A, B, C, D, E)

[0180] The conditions and components described in Example 1 are used except for using a silver paste with particles described in Comparative Example B. The composition of the obtained layer matches the composition described in Example 1.

Example 8

[0181] Table 1 describes the performance of the various metal preparations and layers provided therefrom pursuant to the Examples and Comparative Examples.

[0182] Shelf life of metal preparations is determined by visual inspection in intervals of 1 month for a total period of 6 months. In the case of the formation of a serum or sedimentation of particles (segregation of phases) the test is stopped and shelf life is indicated as the month where no segregation is observed.

[0183] Scratch resistance is measured by scratching the layers with a water-wet Scotch-Brite flexible abrasive pad used for household cleaning. The layers are scratched without force 100 times. The result is evaluated visually on a scale of 1 to 5:

[0184] 1: strong scratching/destruction of the layer,

[0185] 5: no visual scratches.

[0186] Corrosion resistance is measured by subjecting the layers to an atmosphere of pure hydrogen sulfide in a sealed beaker for 1 day. The result is evaluated visually in comparison to a untreated layer on a scale of 1 to 5:

[0187] 1: strong black coloration

[0188] 5: no visual difference to the untreated layer.

[0189] Gloss is evaluated visually on a scale of 1 to 5:

[0190] 1: little gloss, matte appearance

[0191] 5: high gloss, silver mirror-like appearance.

TABLE-US-00001 TABLE 1 Performance of metal preparations and layers made therefrom Scratch Corrosion Aspect resistance resistance Gloss ratio Shelf life [arbitrary [arbitrary [arbitrary (AS) [months] units] units] units] Example 1 1.15:1 6 5 5 5 Example 2 1.25:1 6 4 4 5 Example 3 1.13:1 6 4 4 5 Example 4 1.13:1 6 4 5 5 Example 5 1.13:1 6 5 4 5 Example 6 1.13:1 5 5 5 5 Comp. Ex. 1 1.25:1 3 3 3 4 Comp. Ex. 2 1.19:1 4 4 2 4 Comp. Ex. 3 1.30:1 2 3 3 3 Comp. Ex. 4 1.25:1 1 4 3 5 Comp. Ex. 5 1.19:1 2 4 3 3 Comp. Ex. 6 1.30:1 4 3 2 5 Comp. Ex. 7 1.30:1 3 3 3 4 Comp. Ex. 8 1.8:1 3 5 4 3

[0192] Comparing Examples 1-6 with Comparative Examples 1-8 (where important components according to the present invention are omitted) one can clearly observe that shelf life of the Comparative formulations is significantly reduced and scratch resistance and/or corrosion resistance and/or gloss of the layers of the Comparative Examples are inferior to those of Examples 1-6.

[0193] Comparison of Example 1 with Comparative Example 8 reveals that shelf life of formulations bearing particles with an average aspect ratio of <1.5:1 and gloss of the resulting layers are higher than those of formulation bearing particles with an average aspect ratio of >1.5:1.

BRIEF DESCRIPTION OF THE FIGURES

[0194] FIG. 1:

[0195] Scanning micrographic 2-D projection of nano-sized silver particles (d.sub.50=70 nm). A representative portion of such image is employed to determine the average aspect ratio (AS) of particles.