IRON BLUE PIGMENT, PROCEDURES TO PREPARE IT AND TO UTILISE IT

• Main Authors: CLAUSEN, EVA, REINHARDT, HELMUT, GRATZFELD, EVERHARD, SCHAEFER, HANS
• Format: Patent
• Language: English; French
• Published: 17.04.1984
• Edition: 3
• Subjects: ADHESIVES; AMMONIA; CHEMICAL PAINT OR INK REMOVERS; CHEMISTRY; COATING COMPOSITIONS, e.g. PAINTS, VARNISHES ORLACQUERS; COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSESC01D OR C01F; COMPOUNDS THEREOF; CORRECTING FLUIDS; CYANOGEN; DYES; FILLING PASTES; INKS; INORGANIC CHEMISTRY; METALLURGY; MISCELLANEOUS APPLICATIONS OF MATERIALS; MISCELLANEOUS COMPOSITIONS; NATURAL RESINS; PAINTS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; POLISHES; PREPARATION OF CARBON BLACK; TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS,TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES; USE OF MATERIALS THEREFOR; WOODSTAINS

An iron blue pigment ("DIN 55 906") is prepared by precipitating white paste and then oxidizing the white paste. Alkali metal ions such as sodium ions and potassium ions, cyanide or hexacyanoferrate(II) ions, and iron(II) ions are used as starting materials. The iron blue pigment of the present invention contains potassium in an amount of between 7.0 and 9.0% by weight, preferably between 7.6 and 9.0% by weight, sodium in an amount of between 0.5 and 2.0% by weight, preferably between 0.5 and 1.5% by weight, has a tinting strength, when tested in accordance with "DIN 53 204" and "DIN 53 234" exceeding the tinting strength of "Vosscnblau 705", the German colour standard for iron blue pigments, by between 5 and 15%, and has colour differences (determined in accordance with "DIN 53 204" and "DIN 53 239" in combination with "DIN 6174" with "Vossenblau 705" as standard) which are: .DELTA.L : - 0.7 to -1.5 .DELTA.a : - 0.5 to +0.3 .DELTA.b : - 0.6 to -2.3 .DELTA.C : + 0.5 to +2.0 To save potassium ions in the preparation of iron blue pigments of the present invention the precipitation of white paste is effected in two phases. The alkali metal ions which are used in the precipitation of white paste are potassium ions used in the first phase and sodium ions used in the second phase. The soluble byproducts of the reaction are then removed, potassium salts are added, whereupon, the white pulp is aged and oxidised, in a conventional manner, and recovered as an iron blue pigment. The iron blue pigment can be used as a pigment in the preparation of printing inks, paints, and enamels, and as a colourant in fungicides.