Magnetic recording media

Claim 1

A magnetic recording medium comprising a non-magnetic base and, applied thereto, at least one magnetizable layer, based on an anisotropic magnetic material finely dispersed in an organic binder, containing an ionomeric polyurethane elastomer, the binder used being 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, wherein a polyisocyanate is reacted with a mixture of (a) at least one acrylic or methacrylic ester diol having a molecular weight of from 146 to 3000, (b) at least one organic polyhydroxy compound which is different from (a) and has a molecular weight of from 400 to 5000, and optionally (c) at least one diol, diamine, aminoalcohol or triol which is different from (a) and has a molecular weight of from 62 to 400, or water, in an NCO/OH ratio of 0.85:1 to 15:1, the salt of a mercaptocarboxylic acid is added in such an amount to the reaction product thus obtained that the adduct contains 0.5 to 10% by weight of carboxylate groups, the solution of this adduct is then converted into an aqueous dispersion by the addition of water, and the organic solvent is removed.