Bayer Aktiengesellschaft

Toda Kogyo Corporation

Karl-Heinz Van Bonn

Gunter Linde

Gerhard Franz

Bernd Krockert

Hendrik Kathrein

Cobalt coated, needle shaped berthollide iron oxide pigments are disclosed which have a core of the composition (Fe.sub.x.sup.2+, Fe.sub.2.sup.3+)O.sub.3+x wherein 0.3&lt;x&lt;0.75, optionally also including an intermediate coating of Zn-containing benhollide between the core and the cobalt coating. The pigments are prepared by first coating the core with berthollide and a soluble zinc compound, followed by coating with a cobalt compound.

Low coercive iron oxide pigments and a process for their preparation

A method for coloring building materials is disclosed, wherein a pigment suspension is added to the building materials. The pigment suspension based on pigment granules contains at least one pigment such as iron oxide, and a soluble phosphate salt. The soluble phosphate salt has a number ratio of monofunctional metal ions to phosphorus of 2:1 to 1:1, and is exemplified by sodium pyrophosphate, sodium polyphosphate, and sodium hexametaphosphate.

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Moers, Germany

Karl-Heinz Van Bonn