A process for the preparation of surface-modified nanoparticulate copper Compounds is disclosed, which comprises the steps: (a) preparation of an aqueous solution comprising copper ions (solution 1) and of an aqueous solution comprising at least one anion which forms a precipitate with copper ions and is not a hydroxide ion (solution 2), at least one of the two solutions 1 and 2 comprising at least one water-soluble polymer such as a polycarboxylate,(b) mixing of the solutions 1 and 2 prepared in step a), at a temperature in the range from 0 to 100 Deg. C, with the surface-modified nanoparticulate copper compounds forming and being precipitated from the solution with formation of an aqueous dispersion,(c) isolation of the surface-modified nanoparticulate copper compounds from the aqueous dispersion obtained in step (b), and (d) if appropriate, drying of the surface-modified nanoparticulate copper compounds obtained in step (c).
