| abstract |
1438043 Coated mica MERCK PATENT GmbH 12 March 1974 [17 March 1973] 10952/74 Heading C1A [Also in Divisions C4-C5 C3 and A5] An iron-containing pigment based on mica flakes or on mica flakes provided on both sides with a coating of titanium dioxide and/or zirconium dioxide or of a hydrate thereof the coating adhering to the mica flakes, wherein the ironcontaining layers, provided on both sides of the flakes, consist homogeneously of magnetite or of α-, #- or γ-ferric oxide hydroxide or of α- or γ-Fe 2 O 3 resulting therefrom after drying and/or calcining at temperatures of below 1100 C. may be prepared in a process wherein an aqueous solution of an iron salt is allowed to flow slowly, at constant temperature and pH value, into an aqueous suspension of mica flakes which are optionally coated on both sides with titanium dioxide and/or zirconium dioxide or a hydrate thereof, in the presence of an oxidation agent, whereafter the mica flakes, which are homogeneously coated on both sides with magnetite or with α-, #- or γ-ferric oxide hydroxide are separated, washed, dried and, if desired, thereafter calcined at temperatures below 1100 C. In the examples muscovite, optionally coated with titanium dioxide and/or zironium dioxide is treated in an aqueous suspension with sulphuric acid, ammonia, ferrous sulphate solution, concentrated sulphuric acid, sodium hydroxide, potassium nitrate and aluminium chloride solution. The pigments are allowed to settle, filtered off, washed, dried and calcined. |