Preparation of blue iron hexacyanoferrate-III pigments, and the pigments obtained

US4451339A · kind A · utility

Assignee

• BASF SE

Inventors

• Joachim Kranz · Ludwigshafen, DE
• Wolfgang Habermann
• Harry Distler · Worms, DE
• Helmut Knittel · Ludwigsburg, DE
• Karl-Ludwig Hock · Ludwigshafen, DE
• Fritz Brunnmueller · Schifferstadt, DE
• Rolf Schneider · Burgstetten, DE

Key dates

• Filing date: Mar 24, 1982
• Grant date: May 29, 1984
• Expiry date: Mar 24, 2002

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C25B1/00
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

Blue iron hexacyanoferrate-III pigments (I) are prepared by anodic oxidation of metallic iron in hydrogen cyanide, or a reaction medium containing hydrogen cyanide, at pH<7 and at an anode potential of .ltoreq.0.76 V (measured against a standard hydrogen electrode) to complex iron-II hexacyanoferrate-II compounds (II), which are then oxidized to (I) in a conventional manner. The oxidation of (II) is advantageously carried out with air or oxygen at pH 0-4 and at from 70 to 95.degree. C., but can also be carried out at pH>8. The process gives readily dispersible pigments (I) which are of high color strength and give brilliant, glossy colorations.