Process for the production of iron oxide red pigments

US4234348A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Horst Brunn · Meerbusch, DE
• Heribert Bade · Krefeld, DE
• Franz Hund · Krefeld, DE

Key dates

• Filing date: May 22, 1979
• Grant date: Nov 18, 1980
• Expiry date: May 22, 1999

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/60
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

In the production of an iron oxide red pigment by reducing nitrobenzene with metallic iron in the presence of an acidic iron (II) salt solution, separating off the iron oxide pigment obtained from the reaction medium by washing out, and calcining the pigment at a temperature in the range of about 600.degree. to 1100.degree. C., the improvement which comprises adding an aluminum salt solution over a period of about 5 to 360 minutes at a temperature of about 20.degree. to 100.degree. C. to the iron oxide suspension accumulating during reduction of the nitrobenzene, the suspension containing about 150 to 600 g of iron/l and a residual iron (II) chloride content of about 20 to 160 g/l expressed as iron, the initial pH-value of the iron oxide suspension of about 3 to 5 being adjusted over a period of about 5 to 180 minutes to a final pH-value of about 5.5 to 6.5.