IRON OXIDE PARTICLE AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To improve various characteristics such as fluidity, dispersibility, handleability or environmental resistance in a well balanced state by preparing iron oxide particles having the surface thereof coated with a compound iron oxide layer of Al and Fe and further having a coating layer of an Si component on the compound iron oxide layer. SOLUTION: A water-soluble Al salt, a ferrous salt and an aqueous solution of an alkali are added and mixed with a slurry produced by a wet process and containing iron oxide particles and oxidation is then carried out at pH 5-12 and 60-98 deg.C to coat the iron oxide particles with a compound iron oxide layer of Al and Fe. A water-soluble Si component is subsequently added to the slurry containing the coated iron oxide particles to coat the iron oxide particles with the Si component at pH 5-9. At this time, the Al component in the compound iron oxide layer is contained in an amount of 0.05-2 wt.% based on the whole iron oxide particles and expressed in terms of Al and the amount of the Si component coated on the compound iron oxide layer is 0.05-0.5 wt.% based on the whole iron oxide particles and expressed in terms of Si. The molar ratio of the Al and Fe constituting the compound iron oxide layer is preferably about (1:100) to (100:1) of the Al:Fe.