Basf Aktiengesellschaft

Badische Anilin- & Soda-fabrik Aktiengesellschaft

Herbert Motz

Hans-Joerg Hartmann

Dieter Schaefer

Dieter Mayer

Roland Falk

Joachim Hack

Karl Uhl

Paul Deigner

Rudolf Bachmann

Guenter Vaeth

Heinrich Hartmann

August Lehner

Eberhard Koester

Werner Ostertag

Hermann Roller

Helmut Kopke

Job-Werner Hartmann

Peter Felleisen

Werner Senkpiel

Peter Rudolf

Manfred Ohlinger

Werner Steck

Helmut Jakusch

Norbert Schneider

Werner Balz

Gerd Wunsch

Werner Grau

Herbert Spoor

Eduard Schoenafinger

Wilhelm Sarnecki

Reinhold Baur

Volker Kiener

Horst Autzen

Werner Huebner

Milan Velic

Job Werner Hartmann

Gustav Loewenberg

Ursula Klein

Harald Frischmann

Winfried Gutermann

Peter Gawlik

Friedrich Fuchs

Ute Neumann

A process for the manufacture of acicular ferrimagnetic iron oxide by converting acicular iron(III) oxide hydroxide at from 300.degree. to 650.degree. C., by treatment with an organic compound which decomposes in this temperature range in the presence of iron oxide, the iron(III) oxide hydroxide used for the reaction being a lepidocrocite which has been heat-treated at from 300.degree. to 700.degree. C.

Manufacture of acicular ferrimagnetic iron oxide

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

A magnetic recording medium comprising a non-magnetic base and a magnetizable layer which is applied to at least one side thereof and comprises magnetic particles finely dispersed in a polymeric binder and additives, the surface of the magnetizable layer being provided with a coating of a perfluoropolyether oil mixture as a lubricant.

Rigid magnetic recording disk having perfluoropolyether lubricant

Magnetic recording media comprising a non-magnetic base and, applied thereto, a firmly adhering magnetic coating based on a finely divided magnetic pigment dispersed in a binder which contains at least 50 percent by weight of a special polyurethane elastomer, namely a thermoplastic polyurethane which is soluble in tetrahydrofuran, is free from isocyanate groups and has been manufactured from (A) 1 mole of a hydroxyl-containing polyester having a molecular weight of from 700 to 2,500, (B) from 0.3 to 3 moles of a linear aliphatic diol of 2 to 10 carbon atoms, (C) from 0.05 to 0.4 mole of a triol of 3 to 10 carbon atoms, and (D) from 1.35 to 4.7 moles of a diisocyanate of 6 to 30 carbon atoms, the amount of NCO groups being approximately equivalent to the amount of OH groups of the sum of components (A) to (C).

Magnetic recording media containing elastomeric polyurethane binders in

Chromium dioxide magnetic pigments are stabilized against loss of their magnetic properties by treating them, in aqueous and/or alcoholic suspension, with a block copolymer consisting of siloxane units and alkyleneoxy units of 2 to 4 carbon atoms, the alkyleneoxy units being bonded to the polysiloxane radical by a Si--O--C or Si--C group, in an amount of from 1 to 40% by weight based on the chromium dioxide, after which the latter is separated off and dried at from 50.degree. to 200.degree. C. The stabilized chromium dioxide magnetic pigments may be used for the manufacture of magnetic recording media exhibiting improved stability of the magnetic properties under adverse climatic conditions.

Magnetic recording medium and method of stabilization of chromium

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

The invention relates to an improved apparatus for the manufacture of magnetic discs carrying very thin magnetic layers, by applying a fluid dispersion of magnetic materials in a binder mixture to rigid base discs by the spin-coating process. Above the side of the base disc which is to be provided with the magnetic layer, there are arranged means which produce an aerodynamic boundary layer above the discs during rotation of the latter. This avoids the formation of surface irregularities and of coating streaks during production of the layer by spin-coating.

Apparatus for spin coating in the production of thin magnetic layers for

A process for the manufacture of a magnetic recording medium by producing a dispersion of a finely divided anisotropic magnetic material and conventional additives in a solution of a polymeric binder in an organic solvent, applying a layer of the dispersion to a nonmagnetizable base material, then orienting the anisotropic magnetic material by means of a magnetic field, and drying the layer, wherein a compound of the formula (I) ##STR1## where R.sup.1 is straight-chain or branched akyl of 2 to 10 carbon atoms, cycloalkyl of 6 to 10 carbon atoms or aralkyl of 7 to 14 carbon atoms and R.sup.2 is hydrogen or one of the radicals given in the definition of R.sup.1, is added to the dispersion.

This invention relates to magnetic recording media comprising a non-magnetic base and a magnetic coating firmly bonded thereto, which coating consists essentially of a dispersion of a finely divided magnetic pigment in a polyurethane-containing mixture of binders. This binder mixture contains from 30 to 90% by weight of an elastomeric polyurethane which is virtually free from isocyanate groups and is soluble in a volatile organic solvent, and from 10 to 70% by weight of a vinyl chloride copolymer containing from 5 to 50% by weight of polymerized units of a monoester obtained from an aliphatic diol of from 2 to 4 carbon atoms and acrylic or methacrylic acid. Magnetic recording media having a magnetic coating containing this binder mixture are distinguished by advantageous mechanical and electrical properties, in particular by good abrasion resistance and improved packing density combined with better orientation of the magnetic particles.

The invention relates to an improved process for the manufacture of magnetic discs carrying very thin magnetic layers, by applying a fluid dispersion of magnetic materials in a binder mixture to rigid base discs by the spin-coating process. Above the side of the base disc which is to be provided with the magnetic layer, there are arranged means which produce an aerodynamic boundary layer above the discs during rotation of the latter. This avoids the formation of surface irregularities and of coating streaks during production of the layer by spin-coating.

Manufacture of magnetic discs

Magnetic recording media comprising a base and, applied thereto, at least one firmly adhering magnetic layer based on magnetic particles dispersed in a mixture of organic binders, wherein at least the uppermost magnetic layer additionally contains non-magnetic particles of precipitated silica having a primary particle diameter of from 0.02 to 0.1.mu., a secondary particle diameter of from 2 to 4.mu. and a pH of from 5 to 8. As a result of the incorporation of such a precipitated silica into the magnetic layer, the coefficient of friction between the latter and metals remains uniformly low even after prolonged use, and no stick-slip motion occurs.

Magnetic recording media having a low coefficient of friction

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 dispersed in a binder which contains at least 50 percent by weight of a special polyurethane elastomer. This polyurethane elastomer is a thermoplastic polyurethane which is soluble in tetrahydrofuran and free from isocyanate groups, and which has been manufactured from (A) 1 mole of one or more hydroxyl-containing polyesters and/or hydroxyl-containing polyethers of molecular weight from 600 to 4,000, (B) from 3.5 to 15 moles of a branched-chain aliphatic diol of 4 to 10 carbon atoms or a mixture of aliphatic diols of 2 to 10 carbon atoms, of which at least 50 mole percent is a branched-chain aliphatic diol of 4 to 10 carbon atoms, (C) from 0 to 1 mole, but not more than 15 mole percent of the aliphatic diols according to B, of an aliphatic polyol with from 3 to 6 OH groups and 3 to 18 carbon atoms, and (D) from 4.5 to 18 moles of a diisocyanate of 6 to 30 carbon atoms, the amount of NCO groups being approximately equivalent to the amount of OH groups of the sum of the components A to C. Magnetic recording media which contain such a polyurethane in the magnetic coating are distinguished by high surface hardness coupled with a markedly improved orientation ratio, a higher packing density and more uniform dispersion of the magnetic particles in the coating.

Magnetic recording media consisting of a non-magnetic base and, applied thereto, a firmly adhering magnetic coating based on finely divided magnetic pigment dispersed in organic binders, which coating contains, according to the invention, salts of long-chain basic polyaminoamides with high molecular weight organic acid esters. Such magnetic recording media exhibit improved mechanical resistance and improved adhesion of the coating to the base, coupled with advantageous electromagnetic properties.

Magnetic recording media of improved mechanical resistance

The invention relates to a process for the manufacture of improved magnetic discs by applying a thin layer of a liquid dispersion of magnetic pigments and optionally further, non-magnetic, pigments in a binder mixture to a non-magnetic rigid base, and curing the magnetic coating which has been applied. The binder used is a mixture of polycondensates comprising 60 to 70% by weight of a solid curable polycondensate of 2,2-bis(4-hydroxyphenyl)-propane and epichlorohydrin having an epoxy equivalent weight from about 400 to 2,500 and a melting point from about 50.degree. to 150.degree. C, 10 to 30% by weight of a curable allyloxybenzene-formaldehyde condensate of the resol type with free methylol groups or with methylol groups etherified with a lower alcohol, and having a molecular weight of less than 1,000, and 10 to 30% by weight of a curable melamine-formaldehyde condensate with more than two methylol groups etherified with n-butanol or iso-butanol, and having a molecular weight of less than 2,500. A magnetic dispersion using such a binder allows the application of a firmly adhering magnetic coating, even in thicknesses of less than 4 .mu., to aluminum discs or pre-coated aluminum discs, and the magnetic coating produced has high resistance to mechanical wear.

Magnetic recording discs

Coated magnetic recording media, especially video tapes and computer tapes, comprising a non-magnetic base carrying a magnetic coating which consists of a dispersion, essentially containing a finely divided magnetic pigment in an organic binder and at least one lubricant. A compound of the formula ##STR1## in which n is an integer of from 1 to 3 and R is alkyl, alkoxyalkyl or aralkyl, each of 3 to 18 carbon atoms, is used as a lubricant. The products have high abrasion resistance coupled with only little transfer of material to the magnetic heads even under fluctuating climatic conditions.

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Beindersheim, Germany

Herbert Motz