MAGNETITE PARTICLE POWDER, ITS PRODUCTION AND MAGNETIC TONER COMPRISING MAGNETITE PARTICLE POWDER

摘要

PURPOSE:To improve preventing effects on filming by adding a caustic alkali and/or an alkali carbonate to an aqueous solution of a ferrous salt, aerating an oxygen-containing gas and simultaneously adding an Mg compound until the ferrous salt attains a specific oxidation ratio. CONSTITUTION:An aqueous solution of a caustic alkali such as NaOH and/or an alkali carbonate such as Na2CO3 at 0.1-0.5mol/l concentration in >= equiv. amount is added to an aqueous solution of a ferrous salt such as FeCl2 while aerating a stirred type reactional vessel with N2 gas. The reactional vessel is then aerated with an oxygen-containing gas such as air at a prescribed reactional temperature and a prescribed flow velocity and an Mg compound such as MgSO4 is added simultaneously with the oxidation reaction during a period until the oxidation ratio of the ferrous salt attains 60%. Thereby, the objective magnetite particle powder is obtained. This magnetite particle powder has 0.1-0.3mum average particle diameter and 0.5-0.8g/cm<3> apparent density and contains an Mg oxide in an amount of 0.5-2.5wt.% expressed in terms of Mg based on the Fe. Granular protrusions are present in the particle powder and this powder has preventing effects on filming.