| abstract |
Iron blue pigment (DIN 55 906) is produced by white paste precipitation and subsequent oxidation of the white paste. Alakli or alkali metal ions i.e. sodium and potassium ions, cyanide or complex iron cyanide ions and iron ions are used as raw materials. The iron blue pigment according to the invention is characterized by a potassium content of 0.5-4.5% by weight, preferably 0.5-2.0% by weight, a sodium content of 0.2-1.0% by weight, an ammonium content of 2.0-4.5% by weight, preferably 3.0-4.5% by weight, a coloring power in accordance with DIN 53 204 and DIN 53 234 of 5-15% above the Vossen Blue 705 Standard and the following color intervals (determined in accordance with DIN 53 204 and DIN 53 234 in conjunction with DIN 6174, in relation to Vossen Blue 705 as standard): DELTA L: -0.7 to -1.5 DELTA a: -0.5 to 1.5 DELTA b: -0.6 to -2.3 DELTA C: +0.5 to 2.0 In order to save potassium ions, the white paste precipitation of the iron blue pigment according to the invention is carried out in two phases, potassium ions being used as alkali ions in the first phase and sodium ions in the second phase. After removal of the reaction salts and addition of ammonium salts, the white paste suspension thus obtained is aged and subsequently oxidized to iron blue pigment by known methods. The iron blue pigment can be used as a pigment for the production of printing inks, colored paints, colored varnishes and as coloring agents for fungicides. |