| 摘要 |
PURPOSE:To obtain acicular alpha-ferric oxide having improved acicular ratio, particle size distribution and particle independency and free from void by aging a suspension of ferric hydroxide produced by the addition of an alkaline aqueous solution to an aqueous solution of a ferric salt, adding a crystallization regulating agent to the aged solution and subjecting to hydrothermal reaction. CONSTITUTION:This acicular alpha-ferric oxide having a D104/D110 ratio of 1-2 [D104 and D110 are crystallite diameters perpendicular to (104) plane and (110) plane, respectively], an average acicular ratio of 10-15 and a specific surface area of 20-40m<2>/g is produced by adding an alkaline aqueous solution to an aqueous solution of a ferric salt having a concentration of <=1.0mol/l until the pH is raised to 7-10 while keeping the temperature of the neutralized liquid to <30 deg.C, filtering the obtained suspension of amorphous ferric hydroxide, washing the filtrate with water, suspending in water to obtain a suspension of ferric hydroxide and having a concentration of 0.1-1.0mol/l and containing <=60ppm of SiO2 and <=2,000ppm of anions originated from the ferric salt used as a raw material, adjusting the pH of the suspension to 4-8, aging at 40-100 deg.C for 2-4hrs, adding 1X10<-5> to 1X10<-1>mol of a crystallization regulating agent based on 1 mol of the ferric hydroxide and subjecting the mixture to hydrothermal reaction. |
