FINE MAGNETIC POWDER FOR MAGNETIC RECORDING AND PRODUCTION THEREOF

摘要

PURPOSE:To improve the dispersibility in a resin by forming an aluminum hydroxide film of a bayerite structure on the particle surface of the fine powder. CONSTITUTION:The aluminum hydroxide film of the bayerite structure is formed on the particle surface of the fine powder. The pH value of a suspension contg. the magnetic particles and alkali aluminate is adjusted to 11.0 to 12.5 and the aluminum hydroxide of the bayerite structure is deposited on the surface of the magnetic particles. The concn. of the alkali aluminate is preferably 0.01 to 0.2mol/l and the concn. of the aq. dispersion slurry of the magnetic powder is preferably 0.1 to 5wt.%. The crystal of the aluminum hydroxide is made into the bayerite structure if the pH of the slurry is adjusted to the alkaline side of a range from 11.0 to 12.5 and the aluminum hydroxide is deposited. The deposition of the aluminum hydroxide takes place gradually on the surface of the magnetic particles. The surface of the magnetic particles is uniformly and securely coated with the aluminum hydroxide in this way and the dispersibility in the resin is improved.