Production of black iron oxide pigments

US4090888A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Jakob Rademachers · Krefeld, DE
• Franz Hund · Krefeld, DE
• Ingo Pflugmacher · Meerbusch, DE
• Gerhard Winter · Dossenheim, DE

Key dates

• Filing date: Apr 8, 1976
• Grant date: May 23, 1978
• Expiry date: Apr 8, 1996

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2002/52
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

In a two-stage process for producing black iron oxide pigments wherein an iron salt solution is alkalized in a first stage to precipitate about 55 to 70% of the iron, the solution is oxidized to convert the precipitate to goethite, the solution is further alkalized in a second stage to precipitate the balance of the iron, the precipitated iron II hydroxide is allowed to react with goethite to form magnetite, the improvement which comprises effecting the second stage in the presence of an inorganic ionic compound of at least one metal selected from the group consisting of copper, nickel, aluminum, chromium, titanium, zirconium and vanadium in about 0.05 to 5% calculated as metal based on the weight of the final pigment. The resulting pigment is of high color intensity, narrow grain distribution range and pronounced magnetite structure.