Manufacture of acicular cobalt-modified magnetic iron oxide

US4188302A · kind A · utility

Assignee

• BASF SE

Inventors

• Hans-Juergen Becker · Putlitz, DE
• Christof Jaeckh · Heidelberg, DE
• Eberhard Koester · Bischofswerda, DE
• Werner Loeser · Ludwigshafen, DE
• Manfred Ohlinger · Bischofswerda, DE
• Werner Steck · Ludwigshafen, DE

Key dates

• Filing date: Jan 25, 1978
• Grant date: Feb 12, 1980
• Expiry date: Jan 25, 1998

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/42
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

A process for the manufacture of an acicular magnetic iron oxide containing from 0.5 to 10 percent by weight of cobalt and up to 24 percent by weight of divalent iron, each based on the amount of iron(III) oxide, wherein an aqueous suspension of gamma-iron(III) oxide, containing cobalt(II) and iron(II) ions, the suspension having a hydroxyl ion concentration of more than 3.6.times.10.sup.-6 moles/liter, is heated at from 50.degree. to 100.degree. C. for at least 15 minutes, and the resulting precipitate is filtered off, washed until neutral, dried at below 100.degree. C. and thereafter heated at from 100.degree. to 200.degree. C. The products thus obtained give, even when their cobalt content is low, a very high coercive force, while the effect of temperature on the coercive force and residual induction is very slight.