Basf Aktiengesellschaft

Rudolf Bachmann

Heinrich Hartmann

August Lehner

Herbert Motz

Hans-Joerg Hartmann

Werner Balz

Herbert Spoor

Guenter Vaeth

Werner Lenz

Albert Kohl

Roland Falk

Helmut Kopke

Milan Velic

Joachim Hack

Karl Uhl

Guenter Heil

Ingolf Buethe

Milena Melzer

Reinhold Baur

Werner Senkpiel

Karl Mahler

Harald Frischmann

Winfried Gutermann

Magnetic recording media comprise a non-magnetic base which is provided with a magnetic layer which consists of a dispersion of an anisotropic magnetic material in an organic binder which consists essentially of an OH-containing polyurea-urethane binder crosslinked with polyisocyanate. The OH-containing polyurea-urethane is obtained by reacting a polydiol, a diol and a primary or secondary aminoalcohol, and if appropriate a triol, with a diisocyanate.

Magnetic recording media

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.

A process for the preparation of polymerizable, primarily linear thermoplastic polyurethane elastomers with acrylate side groups comprising reacting an organic polyisocyanate with a mixture of

Process for the preparation of polymerizable polyurethane elastomers

Magnetic recording media comprising a non-magnetic base and, applied thereto, one or more magnetizable layers based on an anisotropic magnetic material finely dispersed in an organic binder containing an ionomeric polyurethane elastomer, wherein the binder used is a substantially aqueous polyurethane dispersion prepared from a polyurethane solution which has been obtained by reacting a polyisocyanate with an organic polyhydroxy compound in the presence of an organic solvent that is inert to isocyanate groups.

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 magnetic recording media, comprising a non-magnetic base and, applied thereto, one or more magnetizable layers, consisting of an anisotropic magnetic material finely dispersed in an organic binder, wherein the binder contains at least 40% of an aqueous ionomeric polyurethane dispersion which at 50.degree. C. forms films having a modulus of elasticity of from 50 to 700 N/mm.sup.2 and a DIN No. 53,157 pendulum hardness of from 20 to 110 s, the corresponding values of the modulus and hardness at room temperature being more than 3.5 times higher.

Process of making a 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.

Thermoplastic, elastic polyurethanes which are soluble in ethers and/or ketones and have a high surface hardness and high modulus of elasticity are manufactured from a polyester-ol and/or a polyether-ol, a substituted or unsubstituted diisocyanato-diphenylmethane or diisocyanato-diphenylsulfone, an aliphatic, branched-chain diol of the formula HOCH.sub.2 --CR.sup.1 R.sup.2 --CO.sub.2 OH, in which R.sup.1 is alkyl and R.sup.2 is alkyl or hydrogen, and, optionally, a triol.

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Frankenthal, Germany

Rudolf Bachmann