Process for the preparation of a magnetic dispersion for magnetic recording media and magnetic recording media produced therewith

摘要

A process for the preparation of high-quality magnetic dispersions having an Hc>120 kA/m, a residual induction Mr/Mm>=0.9 and an orientation ratio of about 2.7 achieves, with a self-purging single-shaft blade-type kneading apparatus, very advantageous magnetic values of the magnetic coatings and excellent tape characteristics if at least the following features are fulfilled:a) the radial shear gradient in the gap between blade circumference and housing wall is from about 150 to about 1600, in particular from about 500 to about 1400, l/secb) the circumferential velocity of the kneading blade is from about 20 to about 80, in particular from about 35 to about 60, cm/sec.The magnetic dispersion prepared can be used in particular for data and video recording media having high recording and storage rates.