Patent ID: 9399206
Filing Date: 2016-07-26
CPC Classification: B01J

Claim Text:
1. A process for producing encapsulated metal colloids useful as inorganic colored pigments comprising: a) reacting one or more glass-forming components according to a sol-gel process to obtain a sol; b) dispersing a metal salt in the resulting sol in the presence of a reducing agent to form metal colloids; c) converting the resulting dispersion into xerogel-encapsulated metal colloids by spray drying; and d) heating the resulting xerogel-encapsulated metal colloids to densify them, wherein the reducing agent used in step b) is at least one from the group consisting of glucose, ascorbic acid, formaldehyde, glycerol, hexamethylenetetraamine, methoxy polyethylene glycol, hydroquinone and urea, wherein the sol in step a) is obtained by hydrolysis and polycondensation of (A) at least one hydrolysable silane of the general formula (I) where the X radicals are the same or different and represent hydrolysable groups or hydroxyl groups, or an oligomer derived therefrom, and (B) at least one organosilane of the general formula (II) where R 1 is a non-hydrolysable group, R 2 is a radical bearing a functional group, X is as defined above and a and b are each 0, 1, 2 or 3 provided the sum (a+b) is 1, 2 or 3, or an oligomer derived therefrom in an amount of substance ratio for (A):(B) of 5-50:50-95, and wherein tetraalkoxysilanes are used as hydrolysable silanes (A), and wherein epoxysilanes or aminosilanes are used as organosilanes (B), and wherein the metal salts are selected from the group consisting of salts of silver, of gold, of copper, of iron, of lead, of palladium and of platinum.