Patent ID: 6844026

Claim:
A process for the preparation of particles comprising at least one metal ion which comprises the following stages: a) at least one precursor comprising a metal cation is dissolved or dispersed in an aqueous medium; b) a partial hydrolysis of said precursor is optionally carried out, c) the precursor resulting from state a) or the partially hydrolyzed precursor resulting from stage b) is brought into contact with at least one water-soluble comb copolymer comprising a complexing anionic hydrophilic backbone and nonionic stabilizing hydrophilic side chains or a combination of said comb copolymer with at least one complexing anionic hydrophilic polymer; the water-soluble comb copolymer, optionally combined with the water-soluble polymer, is chosen so that the comb copolymer, optionally combined with the hydrophilic polymer, forms a transparent solution at 10% by weight in water at a temperature which is the lowest temperature to which said comb copolymer, optionally combined with the hydrophilic polymer, is subjected in said process, said backbone being obtained from monomers chosen from unsaturated monocarboxylic acids, unsaturated polycarboxylic acids or their anhydride form, or unsaturated sulfonic acids, optionally in combination with one or more water-insoluble monomers, the monomers forming the nonionic side chains are macromonomer entities selected from the group consisting of macromonomers of poly(ethylene glycol) (meth)acrylate, poly(vinyl alcohol) (meth)acrylate, poly(hydroxy(C 1 -C 4 )alkyl (meth)acrylate) (meth)acrylate, poly(N-methylolacrylamide) (meth)acrylate and poly((meth)acrylamide) (meth)acrylate); and d) a partial or complete hydrolysis of the product obtained during stage c) is carried out, then e) optionally, a stage of maturing is further carried out at a temperature of between 10° C. and a temperature of less than or equal to the boiling point of said dispersion, f) optionally, after stage d) or after stage e), a stage of concentration of the dispersion is carried out, and g) the particles having a mean size of between 2 and 500 nm are recovered.