Kronos International, Inc.

Uwe Wilkenhoner

Heiko Frahm

Corinna Hommes

Jörg Friedrich

The invention relates to a method for coating the surface of inorganic solid particles in an aqueous suspension. The untreated particles, particularly TiObase material, are made into an aqueous suspension and subsequently disagglomerated. According to the invention, a disagglomerated suspension of untreated particles is fed (recirculated) from an intermediate vessel (vessel) in a cyclic process. The intermediate vessel contains a high-speed agitator preferably having a minimum peripheral speed of 15 m/s or a specific agitator capacity P/V of at least 30 W/m3. A pipeline mixer (e.g. inline disperser) based on the rotor/stator principle is furthermore installed in the circuit. The water-soluble precursor compounds of the coating substances, and equally any necessary pH-controlling substances, are metered into the pipeline mixer. This leads to surface coatings with greater smoothness (low specific surface area according to BET), improved density (low sulphuric-acid solubility), and less coating substance precipitated separately (improved gloss).

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Wuppertal, Germany

Uwe Wilkenhoner