Basf Aktiengesellschaft

Basf Corporation

Basf Magnetics Gmbh

Basf Aktiengsellschaft

Norbert Mueller

Manfred Ohlinger

Ekkehard Schwab

Helmut Auweter

Rainer Feser

Michael W Mueller

Werner Hoffmann

Helmut Jakusch

Rudi Lehnert

Eugen Wettstein

Bernhard Boettcher

Joachim Paust

Peter Rudolf

Werner Steck

Jenoe Kovacs

Guenter Vaeth

Michael Bobrich

Karl Von Fraunberg

Ronald J Veitch

Phillip A Rossy

Harald Jachow

Werner Huebner

Hermann Dikow

Wolfgang Kochanek

Werner Hoffman

Reinhard Koerner

Gerhard Honecker

Helmut Reinicke

A magnetic recording medium comprising a nonmagnetic substrate and at least one magnetic layer applied thereon and containing an acicular chromium dioxide uniformly distributed in a polymeric binder and additives and having a coercive force of at least 60 kA/m, a mean particle length of the chromium dioxide of less than 300 nm, whose factor HD according to the formula ##EQU1## where KT is the coercive force of the magnetic layer in [kA/m], measured in an external field of 380 kA/m, L is the mean particle length and .DELTA.L is the range of the particle size distribution, determined from the numerical distribution of the particle length, both measured in [nm], is greater than 1.85, and a process for the preparation of this chromium dioxide.

Process for preparing modified chromium dioxide

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

Stabilized acicular ferromagnetic chromium dioxide is prepared by reductive treatment of the chromium dioxide with Na.sub.2 [Fe(CO).sub.4 ], and this material is present in magnetic recording media.

Preparation of stabilized chromium dioxide with sodium

An acicular, ferromagnetic material which has a high coercive force and essentially consists of iron-containing chromium dioxide is prepared by thermal decomposition of hydrated chromium(III) chromate under superatmospheric pressure.

Process for preparing acicular ferromagnetic material consisting

A process for the preparation of chromium(III) oxide by decomposing hydrated ammonium dichromate at elevated temperatures, an apparatus for carrying out this process and the use of the chromium(III) oxide thus prepared as a starting material for the synthesis of chromium dioxide.

Preparation of chromium(III) oxide

Ferromagnetic chromium dioxide is prepared by converting oxides of trivalent and hexavalent chromium under superatmospheric pressure and at elevated temperatures in the presence of water and with the addition of an antimony compound as a modifier and, if required, further additives in an amount of not more than 15% by weight, by a method in which the antimony compound is present in the form of a water-soluble salt whose anion contains one or more organic molecular moieties which are oxidized in concentrated chromic acid.

Preparation of ferromagnetic chromium dioxide

Acicular ferromagnetic chromium dioxide particles having a pH greater than 4 and a process for their preparation.

Acicular ferromagnetic chromium dioxide particles

A process for the manufacture of ferromagnetic chromium dioxide modified with foreign elements, by reacting oxides of trivalent and hexavalent chromium under superatmospheric pressure at an elevated temperature in the presence of water and of antimony(III) oxide as modifier, with or without other modifiers in an amount not exceeding 15% by weight, wherein the antimony(III) oxide employed as modifier is, to the extent of more than one-third, present as the senarmontite cubic modification, has a specific surface area, measured by the BET method, of from 1.5 to 15 m.sup.2 /g, and is added in a total amount of up to 0.5% by weight, based on the resulting chromium dioxide.

Process for the manufacture of ferromagnetic chromium dioxide

3-Halosulfonylthiophene-carboxylic acid compounds are manufactured by reacting 3-ketothiophane-carboxylic acid compounds with sulfonic acid compounds, reacting the end product from the 1st reaction stage with alkali metal polysulfides, reacting the end product from the 2nd stage with a dehydrogenating agent and finally reacting the end product from the 3rd stage with halogen and water. The products are starting compounds for the manufacture of drugs, dyes and crop protection agents and have an anti-inflammatory, analgesic and anti-rheumatic action. In particular, the end products I are starting materials for the manufacture of sweeteners which are non-toxic and free from an after-taste, flavor-improving agents, diabetic aids and feedstuffs, and provide the means of a simple and economical synthesis of thiophene-saccharins.

Manufacture of 3-halosulfonylthiophene-carboxylic acid compounds

New macrocyclic ketolactones, especially 15-methyl-15-ethyl- and 15,15-dimethyl-12-oxo-15-hydroxytetradecanecarboxylic acid lactone. The new ketolactones have an intense and delicate woody musky odor and may be employed as scents and fixatives.

Ketolactones

The nopinylamines of the general formula I ##STR1## where R.sup.1 and R.sup.2 are hydrogen or alkyl of 1 to 5 carbon atoms, and the salts of these amines with mineral acids and with alkylcarboxylic acids of 1 to 4 carbon atoms. The manufacture of I from nopinone (II) ##STR2## by aminating hydrogenation with amines (III) ##STR3## The use of I for resolving racemates of acid or acid-forming compounds, especially of DL-pantolactone.

Growing community of inventors

Friedelsheim, Germany

Norbert Mueller