Iron blue pigment, process for its pigmentation and use

US4915742A · kind A · utility

Assignee

• Degussa AG · DE

Inventors

• Everhard Gratzfeld · Wesseling, DE
• Eva Clausen · Cologne, DE
• Heinrich Winkeler · Wesseling, DE

Key dates

• Filing date: Dec 9, 1988
• Grant date: Apr 10, 1990
• Expiry date: Dec 9, 2008

Classification

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

Abstract

Iron blue characterized by an ammonium content of .+-.5.5 weight %, a potassium content of <0.1 weight %, a sodium content of <0.1 weight %, a color strength in a toluene intaglio printing ink up to 15% greater than the standard Vossen blue 705/80 (calculated in accordance with DIN 53 234) and the color spacings (determined in accordance with DIN 6174 relative to Vossen blue 705/80 as standard) of EQU .DELTA.a*:6.5.+-.0.5 EQU .DELTA.b*:1.3.+-.0.3 EQU .DELTA.c*:-1.5.+-.0.5 It is prepared by placing an aqueous solution of sodium hexacyanoferrate (II) in a reaction vessel at a pH of 7.0 and a concentration of 45.+-.5 g/l, calculated as Fe(CN).sub.6 together with ammonium sulfate having a concentration of 14.+-.1 g/l at a temperature of 22.degree.-23.degree. C., adding an aqueous iron-II sulfate solution at a pH of 2.0, a concentration of 100.+-.10 g/l, and a temperature of 22.degree.-23.degree. C., and precipitating the white dough until an excess of iron up to 1.4-1.7/1, calculated as Fe, is attained in the filtrate, then washing the white dough by decantation until the filtrate indicates a conductivity of 5000 to 5500 .mu.S and has an excess of iron of 0.1-0.2 g/l, calculated as Fe …