METHOD FOR COATING THE SURFACE OF INORGANIC PARTICLES, IN PARTICULAR TITANIUM DIOXIDE PIGMENT PARTICLES.

摘要

The invention relates to a method for the surface coating of particulate inorganic solids, more particularly of titanium dioxide pigment particles in an aqueous suspension. The untreated particles, especially TiO2 bodies, are made into an aqueous suspension and then deagglomerated. The deagglomerated aqueous particle suspension (2) is conveyed according to the invention from a reservoir vessel (vessel) (1) in a circulating operation (3) (pumped in circulation). Located in the reservoir vessel is a high-power agitator (4). The high-power agitator has a minimum peripheral speed of 15 m/s or a specific stirring power P/V of at least 30 W/m3. Installed in the circuit (3) also is a flow-traversed mixer (e.g. in-line disperser) (5) based on the rotor-stator principle. The water-soluble precursor compounds of the coating substances (6) and the pH control substances (7), if required, are metered into the flow-traversed mixer. Compared to its prior-art counterparts, the method of the invention, applied to titanium dioxide particles, leads to smoother surface coatings (lower BET specific surface area) with improved density (low sulphuric acid solubility). Moreover, less coating material is separately precipitated (improved gloss).