Solid particles having a silicate coating
AssigneeGiesecke & Devrient GmbH
InventorsJohann Kecht, Stephan Steinlein
Life of this patent
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Abstract
A method for producing solid particles having a silica coating, by: dispersing the solid particles to be coated in an aqueous medium to produce a solid particle dispersion, adjusting the pH of the solid particle dispersion by a buffer system to produce a buffered solid particle dispersion, and adding an alkaline silicate solution to the buffered solid particle dispersion to form the silica coating on the solid particles during a coating period. The amounts of buffer system and alkaline silicate solution are selected such that the pH of the buffered solid particle dispersion before the addition of the alkaline silicate solution is at least 7.0 and after completion of the addition of the alkaline silicate solution is at most 11.0.
Claims19
1-18. (canceled)
A method for producing solid particles having a silica coating, comprising the steps:
- dispersing solid particles to be coated in an aqueous medium to produce a solid-particle dispersion, and setting the pH value of the solid-particle dispersion by a buffer system to produce a buffered solid-particle dispersion, or
- dissolving a buffer system in an aqueous medium to produce a buffer solution having a pH value, and dispersing the solid particles to be coated in the buffer solution to produce a buffered solid-particle dispersion, and
- adding a basic silicate solution to the buffered solid-particle dispersion to form the silica coating on the solid particles during a coating time,
- wherein the composition and the quantities of buffer system and of basic silicate solution are selected such that the pH value, before the addition of the basic silicate solution, is at least 7.0, and after the completion of the addition of the basic silicate solution is at most 11.0.
Dependencies are inferred from the claim text.