IRON OXIDE PARTICLES AND THEIR PRODUCTION

摘要

PROBLEM TO BE SOLVED: To obtain iron oxide particles that suppress the rise of packing density due to vibration and striking and have superior fluidity by providing iron oxide particles having a specified average particle diameter, a titanium component of a specified content inside the particles and a specified tap density. SOLUTION: The iron oxide particles have 0.1-1μm average particle diameter, contain 0.3-3.5 wt.% (expressed in terms of titanium) titanium component based on the total amount of the iron oxide particles and have <=1.2 g/cm3 tap density. When a ferrous hydroxide slurry prepared by neutralizing and mixing an aqueous ferrous salt solution and an alkali solution is oxidized to produce iron oxide particles, a water-soluble titanium salt is added before and/or during the oxidation reaction. The iron oxide particles are preferably based on magnetite and the shape of the particles are preferably spherical. The residual magnetization (σr) of the particles at 5 kOe is preferably <=8 emu/g in consideration of the effect of magnetic aggregation on fluidity and the angle of repose is preferably <=42 deg..