Basf Aktiengesellschaft

Werner Huebner

Werner Steck

Manfred Ohlinger

Helmut Jakusch

Laszlo Marosi

Rainer Feser

Herbert Haberkorn

Ekkehard Schwab

Eberhard Koester

Dieter Mayer

Helmut Auweter

Paul Deigner

Herbert Motz

Werner Loeser

Dieter Schaefer

Michael W Mueller

Hans Henning Schneehage

Norbert Mueller

Job-Werner Hartmann

Christof Jaeckh

Peter Nagel

Friedrich Domas

Hermann Dikow

Hans Hauser

A chromium dioxide material consisting of acicular, ferromagnetic chromium dioxide particles having a nonmagnetic, hydrogen-containing protective surface layer, which material has improved stability to chemical decomposition, a process for its preparation and magnetic recording media containing this chromium dioxide and having good long-term stability of the residual magnetization under conditions of high humidity and temperature are described.

Chromium dioxide material, its preparation and magnetic recording media

Acicular ferromagnetic chromium dioxide is stabilized by treatment with an alkali metal hydroxide in an aqueous alkaline suspension at elevated temperatures.

Stabilization of acicular ferromagnetic chromium dioxide

Ferromagnetic chromium dioxide is improved by subjecting chromium dioxide materials prepared by a known method to an additional heat treatment.

Preparation of ferromagnetic chromium dioxide

A process for the manufacture of magnetic recording media by dispersing a mixture of particulate anisotropic magnetic material and additives in a solution of a polymeric binder in an organic solvent, compressing and then releasing the pressure on the dispersion, thereafter applying a layer of the dispersion to a non-magnetizable base, orienting the anisotropic magnetic material by means of a magnetic field, and drying the coating.

Manufacture of magnetic recording media

A process and apparatus for the manufacture of magnetic recording media, in which, immediately before the magnetic dispersion is applied to a base, the dispersion is subjected to shear by means of a disc rotatably mounted in a housing, by introducing it at the center of rotation of the disc and forcing it through a gap formed between the face of the disc and the wall of the housing, which gap tapers toward the rim of the disc.

Process for the manufacture of magnetic recording media

A method of preparing acicular ferromagnetic metal particles consisting essentially of iron and suitable for magnetic recording, said particles being modified at the surface with 0.02 to 0.2% by weight of carbon and with 0.5 to 1.9% by weight of phosphorus as phosphate, by reducing a finely divided acicular iron compound, wherein there are deposited on said iron compound, prior to reduction, (a) a hydrolysis-resistant substance selected from the group consisting of oxyacids of phosphorus, their esters and inorganic salts, and (b) a compound selected from the group consisting of aliphatic monobasic, dibasic and tribasic carboxylic acids of from 1 to 6 carbon atoms.

Manufacture of ferromagnetic metal particles consisting essentially of

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Frankenthal, Germany

Werner Huebner