IRON OXIDE PIGMENT

PURPOSE:To provide a magnetized flaky iron oxide pigment having metallic luster and clear color tone, by forming a coating film composed mainly of a transparent metal oxide (including hydrated oxide) to the surface of a flaky particle of ferromagnetic hexagonal ferrite. CONSTITUTION:Flaky ferrite particles having particle diameter of 1-15mum, a thickness of about 0.1-0.5mum, extremely smooth surface and uniform particle seize, and exhibiting hexagonal crystal structure is synthesized e.g. by adding an aqueous solution of an alkali to an aqueous solution containing a salt of a metal such as Ba, etc. and an iron salt, and subjecting the resultant coprecipitate to hydrothermal treatment. The surface of the above particle is coated with a coating film composed mainly of a transparent metal oxide having high refractive index, e.g. TiO2, ZrO2, etc. The coating can be carried out by immersing the above ferrite particle in an aqueous solution containing titanyl, sulfate, zirconium sulfate, etc. and acidified with sulfuric acid, heating the solution to effect the precipitation of hydrated oxide to the surface of the ferrite particle by hydrolysis, and heating the product at a high temperature in air.