Color-intensive iron oxide black pigments and process for their production

US4631089A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Jakob Rademachers · Krefeld, DE
• Rolf Naumann · Krefeld, DE
• Gunther Teichmann · Krefeld, DE

Key dates

• Filing date: Nov 7, 1984
• Grant date: Dec 23, 1986
• Expiry date: Nov 7, 2004

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/80
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

Highly pure and highly color intensive black anisometric magnetite iron oxide pigment having an FeO content of from 26 to 29% by weight and manganese content of less than 0.1% by weight, said pigment further having a specific BET surface area of from 5 to 15 square meters per gram and being needle shaped particles with an average needle diameter of 0.1 to 0.2 .mu.m and an average needle length of from 0.6 to 0.8 .mu.m are produced by producing .alpha.-FeOOH particles by alkali precipitation of an iron salt solution with a nuclear formation stage oxidation and a pigment growth stage oxidation followed by reduction and passivation.