Basf Aktiengesellschaft

Werner Senkpiel

Herbert Motz

Klaus Schoettle

Peter Rudolf

Werner Steck

Eberhard Koester

Helmut Jakusch

Werner Ostertag

Gerd Wunsch

Hermann Roller

Joachim Hack

Karl Uhl

Guenter Vaeth

Roland Falk

Werner Loeser

Volker Kiener

Heinrich Wittkamp

Job-Werner Hartmann

Rudolf Bachmann

Hans-Joerg Hartmann

Friedrich Fuchs

A process for stabilizing pyrophoric acicular metal particles consisting essentially of iron, by reaction with oxygen-containing gases in two stages, wherein, in the first stage, up to 1/3 of the passivating layer present in the final state is formed at from 25.degree. to 45.degree. C. and, in a subsequent second stage, the remainder of the passivating layer is formed at from 50.degree. to 70.degree. C.

Stabilization of pyrophoric ferromagnetic acicular metal particles

The invention relates to magnetic recording media comprising a non-magnetic base and, applied thereto, a firmly adhering magnetic coating based on a finely divided magnetic pigment and a special binder mixture. This binder mixture consists essentially of 20 to 90 percent by weight of an elastomeric polyurethane which is soluble in a volatile organic solvent, is practically free of isocyanate groups and has been obtained from a linear, aliphatic polyester or polyether and a diisocyanate of 6 to 24 carbon atoms, and of 10 to 80 percent by weight of a vinyl chloride copolymer which contains 50 to 90 percent by weight of vinyl chloride units and 10 to 50 percent by weight of units of one or more diesters of maleic acid with an alcohol of 1 to 3 carbon atoms, or of the reaction product of this binder mixture with a polyisocyanate of 6 to 50 carbon atoms. Magnetic coatings containing such a binder mixture are distinguished by improved surface hardness coupled with improved orientability of the magnetic particles, as a result of which such recording media are particularly suitable for modern video- and audio-recording instruments.

Magnetic recording media

The invention is directed to a tape transport mechanism for recording and playing back video signals comprising a contact winding mechanism with tape-guiding means at the capstan and a magnetic tape in which the substrate is a polyethylene terephthalate film. The coated side of the tape, during transport, is in contact with the guide surface of the guide means, and no part of the transport mechanism at which slip could occur during the tape transport is allowed to be in contact with the tape substrate. The tape is wound with its substrate on the inside and its coated side is preferably abrasive with respect to the guide surface, which latter may advantageously consist either of steel or a ceramic material. The bonding agent of the magnetic dispersion -- preferably a chromium dioxide dispersion -- may be prepared from a polyurethane/polyvinyl chloride mixture which imparts the desired hardness to the tape. The arrangement can be advantageously employed with any kind of record/playback apparatus for video signals which includes a stationary head and develops high tape advance speeds.

Tape transport mechanism for recording and playing back video signals

Magnetic recording tape especially suitable for use as video tape and computer tape, comprising a base carrying a magnetic coating which consists essentially of a dispersion of a finely divided magnetic pigment and at least one lubricant in an organic binder. The lubricant is a compound of the formula ##STR1## IN WHICH N IS AN INTEGER OF FROM 3 TO 8 AND R.sup.1 and R.sup.2 are an alkoxy or aralkoxy radical or conjointly are an alkyldioxy radical of 3 to 18 carbon atoms. A magnetic recording tape prepared with a high proportion of such a lubricant is distinguished by high abrasion resistance coupled with a minimum transfer of material to the magnetic heads even under fluctuating climatic conditions.

Magnetic recording tape

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Laudenbach, Germany

Werner Senkpiel