Bayer Aktiengesellschaft

Bayer Aktiensegellschaft

Jurgen Wiese

Gunter Buxbaum

Wilfried Burow

Peter Kiemle

Friedrich Jonas

Peter Kresse

Aloys Eiling

Fritz Rodi

Rolf Schafer

Jurgen Scharschmidt

Axel Westerhaus

Peter R Schick

Isometric iron oxide pigments are prepared by an improved process by precipitation of aqueous solutions containing iron (II) salts with alkaline precipitating agents followed by oxidation of the precipitate at temperatures of from 20.degree. C. to 100.degree. C., wherein the improvement comprises adjusting the iron (III) content to 1 to 25 mol %, based on the total iron, before precipitation.

Process for the preparation of isometric magnetic iron oxide

A heat-stable iron oxide black pigment resistant to hydrothermal treatment in air at temperatures above 180.degree. C. and which has a specific BET surface of 0.5 to 5 m.sup.2 /g is useful as a coloring agent for building materials, paints, cements, bricks and so forth and is prepared by reacting an aqueous solution of FeOOH, iron (II) salts and alkalis at elevated temperature and precipitating iron oxide from the solution with Na.sub.2 CO.sub.3 at temperatures in the range from 80.degree. C. to the boiling point of the solution.

Heat-stable iron oxide black pigments, processes for their production

Acicular magnetic iron oxide pigments are disclosed which have a Co content of 1 to 5% by weight and an FeO content of 5 to 12% by weight. The pigments may optionally contain an additional dopant selected from zinc, phosphate and SiO.sub.2. The pigments are useful in magnetic recording media such as video tapes.

Co-containing magnetic pigments, processes for the production thereof

Highly-coercive isometric iron oxide useful in magnetic toners for electrostatic photo-copying processes or for magnetic printers is produced by

Highly-coercive isometric iron oxides, a process for the production and

Pigments for printing inks and magnetic toners are iron oxide pigments with a rhombic dodecahedral form and an average particle diameter of from 0.05 to 3.0 .mu.m with a standard deviation of the particle size distribution of .+-.30%.

Iron oxide pigments, a process for their preparation and their use

Improved iron oxide pigments useful in the manufacture of magnetic recording carriers or for coloring inorganic or organic materials are iron oxide pigments having an iron (II) content of at least 5% by weight calculated as FeO after-treated with a phenolic compounds of the formula ##STR1## wherein X is O or NH, and

Thermostable iron oxide pigments, processes for their preparation and

A bright, color-pure iron oxide red pigment is produced by an improved process by precipitation of iron(II) salts in aqueous solution with an alkaline precipitating agent, oxidation at temperatures of from 20.degree. C. to 100.degree. C. and annealing of the resulting precipitation products under air to form iron oxide red pigments, wherein the improvement comprises before adding the alkaline precipitating agent, the iron(III) content of the aqueous solution is adjusted to 1 to 15 mol %, based on the total iron content of the iron salt solution.

Process for the preparation of bright, color-pure iron oxide red pigments

In improved cobalt coated magnetic iron oxide having increased coercive field strength and highly efficient for use in magnetic recording devices and processes is produced by subjecting uncoated magnetic iron oxide particles to an acid treatment and then epitaxially coating the treated particles with cobalt.

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Krefeld, Germany

Jurgen Wiese