Process for the preparation of a magnetic dispersion for magnetic recording media and magnetic recording media produced therewith
AssigneeEMTEC Magnetics GmbH
InventorsAxel Schünemann, Hans-Dieter Zettler, Peter Nagel
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Abstract
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 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, 1/sec, and b) the circumferential velocity of the kneading blade is from about 20 to about 80, in particular from about 35 to about 60, cm/sec.
Claims14
A process for the preparations of a magnetic dispersion for magnetic coating with magnetic particles having a coercive force of more than 120 kA/m, a relative residual induction of Mr/Mn of at least about 0.9 and an orientation ratio of at least 2.7 by means of a single-shaft blade-type kneading apparatus (V) having at least one kneading blade (S1-S3), the shaft (W) rotating in a housing (K) having a housing wall 5 and at the same time oscillating in the axial direction (arrow O) for kneading a mixture of magnetic particles a in a thermoplastic binder and a solvent, comprising the following features
- a) the radial shear gradient in the gap (s) between the tip of the kneading blade (S1-S3) and housing wall 5 is about 150 to 1600, 1/sec
- b) the circumferential velocity of the kneading blade (S1-S3) is from about 20 to about 80 cm/sec.
Dependencies are inferred from the claim text.