抄録
Black iron oxides are used to prepare make-up products having blackish color tone.
The color of black iron oxides on the market shows yellowish and reddish black color tone. Black iron oxide is formed by the oxidation of Fe(OH)2 obtained by mixing NaOH soln. and FeSO4 soln.
The mechanistic study is investigated from Ferrous-Ferric Mixture by Prof. Machvec, Tamaura and Kiyama, et. al. In the wet method, several kinds of iron compounds are formed such as Fe(OH)2, Green Rust, Fe3O4, FeOOH, FeOOH and Polynuclear complex containing [Fe2(OH)3]3+ and Fe2(OH)2O2+. It is difficult to produce black iron oxide consisting uniform particle because the particle size and the particle shape are different by the reaction condition such as concentration of alkaline solution and iron salts solution, oxidation condition of green rust containing Fe(OH)2, kinds of iron salts and reaction temperature.
Therefore, black iron oxide having high chroma can not be produced by heterogenious precipitation method.
The chemical structure of black iron oxide is written as (FeO)x(Fe2O3)y. In black iron oxide (Fe3O4), the theoritical FeO content is 23.8%. The black iron oxide containing below 10% FeO, the color is brown. We have developed thin filler pigment coated with uniform black iron oxides in the crystal shape. The uniform black iron oxide were precipitated on the thin filler pigment by homogeneous precipitation using iron salts and urea. The particle size of black iron oxides on thin filler pigment depended on kinds of iron salts as raw materials. The pigment having 0.3um of black iron oxide in mean particle size was very stable in thermal stability and very much higher in chroma. Black iron oxide coated mica having interference color were formed from hydrolysis of Iron salts using urea.
We studied to confirm the ratio of Fe(III)/Fe(II) of the formed black iron oxide by ion chromatography in comparison with the color tone of produced pigment. And the crystal structure could be analyzed by mössbauer spectrum. The black iron oxide in interference colored pigments consisted of γ-Fe2O3 and Fe3O4.
