| 摘要 |
PURPOSE:To produce magnetite particles excellent in oil absorption characteristic and improved in magnetic characteristic in good balance without damaging a degree of blackness by thinly applying an iron-zinc oxide on the surface of particles. CONSTITUTION:An alkali aq. soln. of more than equivalence to iron is mixed with a soln. consisting essentially of a ferrous salt to form ferrous hydroxide, and oxidizing reaction is executed at 60-100 deg.C by blowing air while maintaining free hydroxide group concn. at 1-3g/l. After oxidation, a Zn-containing ferrous salt is added to the soln. so that Zn/Fe mol. ratio in all magnetite particles becomes 0.2-1.8%, and its pH is adjusted to 6.0-9.0 and the oxidizing reaction is executed again. Then, product is washed, filtered, dried and ground to obtain the objective magnetite particles. The obtained particles have characteristics of >=79emu/g satd. magnetization, color difference meter blackness of <=19.5 and >=30ml/100g of oil absorption amount. |
