Method for preparation of additive for coatings containing metallic nanoparticles

A method of preparation of an additive to be incorporated in coatings to protect surfaces, the additive having silver nanoparticles as an active agent, said method comprises:

• (a) a first phase of pre-treatment of said active agent;
• and
• (b) a second phase of preparing of said additive;
• wherein the first phase comprises the steps of:
• i) providing an aqueous composition of silver nanoparticles, said silver nanoparticles having an average particle size between 1 nm and 100 nm;
• ii) displacing the water contained in the aqueous composition of silver nanoparticles by means of stirring said aqueous composition of silver nanoparticles and an organic solvent added thereto at least between 5 and 30 minutes, in order to substitute the contained water with the organic solvent, providing a solid phase of said silver nanoparticles, with which a change of solvent is carried out;
• iii) drying said solid phase of silver nanoparticles to a lower temperature than the boiling temperature of said organic solvent, in order to obtain dried silver nanoparticles having an average particle size of 1 nm to 100 nm, and a purity of at least 90%;
• wherein the second phase comprises the steps of:
• iv) dispersing the dried silver nanoparticles by means of a stirrer, mixing the dried silver nanoparticles with a resin, a dispersant and a solvent, wherein the stirrer operates at a peripheral velocity from 5 m/s to 30 m/s, and wherein said resin and dispersant are compatible with said coating in order that said additive is quickly and easily integrated to said coating by means of adjusting the viscosity of said additive to that of said coating;
• v) removing the finished additive from the stirrer.