Basf Aktiengesellschaft

Badische Anilin- & Soda-fabrik Aktiengesellschaft

Hans-Joerg Hartmann

Herbert Motz

Rudolf Bachmann

Roland Falk

Heinrich Hartmann

August Lehner

Dieter Mayer

Karl Uhl

Guenter Vaeth

Dieter Schaefer

Helmut Kopke

Helmut Jakusch

Werner Balz

Norbert Schneider

Joachim Hack

Herbert Spoor

Reinhold Baur

Milan Velic

Werner Senkpiel

Job Werner Hartmann

Gustav Loewenberg

Ursula Klein

Peter Felleisen

Winfried Gutermann

Harald Frischmann

Peter Gawlik

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

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

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.

Manufacture of magnetic recording media

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 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

A magnetic recording medium consists of a non-magnetic base, on which the magnetic coating is a layer of a dispersion, containing a lubricant, of a magnetic pigment in a polymeric binder. The lubricant is a block copolymer which contains siloxane units and alkyleneoxy units of 2 to 4 carbon atoms, the alkyleneoxy units being bonded to the polysiloxane radical through a Si--O--C or Si--C group. The use of this lubricant gives a magnetic recording medium which has the advantages of good fluid lubrication and an excellent coefficient of friction which does not vary with time.

Magnetic recording medium containing lubricants

A magnetic recording medium in the form of a card having a non-magnetic support with a magnetic coating on one side of the support and a backcoating on the opposite side of the support, which backcoating exhibits improved scratch resistance and adherence to the support and improved frictional characteristics and consists essentially of 20 to 50% by weight of a binder mixture containing 10 to 60% by weight of an elastomeric polyurethane and, incorporated in the binder mixture, a non-magnetic pulverulent mixture of 10 to 40% by weight of conductive carbon powder and 60 to 90% by weight of platelet-shaped and spherical particles.

Growing community of inventors

Freinsheim, Germany

Hans-Joerg Hartmann