Method for producing metal particles, metal particles produced thereby, and the use thereof

1. Process for producing silver metal particle sols having a metal particle content of ≧1 g/l, comprising the steps of

a) reacting a silver metal salt solution having a silver metal salt concentration of ≧0.1 to ≦0.5 mol/l with a solution containing hydroxide ions at a concentration of ≧0.1 to ≦0.5 mol/l, thereby forming silver metal oxides or hydrates thereof, silver metal hydroxides or hydrates thereof, mixed silver metal oxide hydroxides or hydrates thereof, or any combination thereof,

b) reacting the solution obtained from step a) with a reducing agent,

wherein at least one of the solutions in step a) comprises a dispersing assistant and whereby both steps a) and b) are performed continuously in a microreactor.

2. Process according to claim 1 , wherein the dispersing assistant is selected from the group consisting of alkoxylates, alkylolamides, esters, amine oxides, alkylpolyglucosides, alkylphenols, arylalkylphenols, water-soluble homopolymers, random copolymers, block copolymers, graft polymers, polyethylene oxides, polyvinyl alcohols, copolymers of polyvinyl alcohols and polyvinyl acetates, polyvinylpyrrolidones, cellulose, starch, amino acid polymers, polylysine, polyaspartic acid, polyacrylates, polyethylenesulphonates, polystyrenesulphonates, polymethacrylates, condensation products of aromatic sulphonic acids with formaldehyde, naphthalenesulphonates, lignosulphonates, copolymers of acrylic monomers, polyethyleneimines, polyvinylamines, polyallylamines, poly(2-vinylpyridines) and polydiallyldimethylammonium chloride.

3. Process according to claim 1 , wherein the dispersing assistant is present in at least one reactant solution in a concentration of ≧0.1 g/l to ≦100 g/l.

4. Process according to claim 1 , wherein the solution comprising hydroxide ions is obtained from the reaction of bases selected from the group consisting of LiOH, NaOH, KOH, Mg(OH) 2 , Ca(OH) 2 , aliphatic amines, aromatic amines, alkali metal amides and alkoxides.

5. Process according to claim 1 , wherein the reducing agent is selected from the group consisting of polyalcohols, aminophenols, amino alcohols, aldehydes, sugars, tartaric acid, citric acid, ascorbic acid and salts thereof, triethanolamine, hydro quinone, sodium dithionite, hydroxymethanesulphinic acid, sodium disulphite, formamidinesulphinic acid, sulphurous acid, hydrazine, hydroxylamine, ethylenediamine, tetramethylethylenediamine, hydroxylamine sulphate, sodium borohydride, formaldehyde, alcohols, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, ethylene glycol, ethylene glycol diacetate, glycerol and dimethylaminoethanol.

6. Metal particles produced by the process according to claim 1 .

7. Metal particles according to claim 6 , having a particle size d 50 value of ≧0.01 μm to ≦0.5 μm.

8. A method for producing catalysts, coating materials, functional layers, transparent conductive layers, metallurgic products, electronic products, electroceramics, optical materials, biolabels, inks for inkjet printing and screen printing, conductive microstructures, materials for forgeryproof marking, polymer composites, antimicrobial materials and/or active ingredient formulations which comprises producing same from the metal particles of claim 7 .