Magnetic discs having a multi-component binder

Claim 1

A process for the manufacture of magnetic discs by applying a thin layer of a fluid dispersion of finely divided magnetic pigment in a binder, containing added volatile organic solvents and, optionally, conventional additives, to the non-magnetic base disc and drying the magnetic layer applied and subsequently grinding and polishing its surface, wherein the binder used consists essentially of a curable mixture of A. from 60 to 90 percent by weight of a solid curable polycondensate of 2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin with an epoxide equivalent weight of approximately 400 to 5,000, B. from 5 to 25 percent by weight of a curable allyloxybenzene-formaldehyde condensate of the resol type with free or alcohol-etherified methylol groups and having a molecular weight of less than 1,000 and C. from 5 to 30 percent by weight of a curable melamine-formaldehyde condensate with more than two alcohol-etherified methylol groups and a molecular weight of less than 3,000, in which from 10 to 35 percent by weight of the component A are replaced by D. a free-radical polymerization product of D 1. at least 10 percent by weight of a reaction product of (d1) a polycondensate, containing epoxy groups, of 2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin with (d2) the N-methylolamide of a copolymerizable olefinically unsaturated carboxylic acid of 3 to 5 carbon atoms; and D 2. 0 to 90 percent by weight of at least one olefinically unsaturated monomer selected from the group consisting of alkyl esters of acrylic or methacrylic acid with from 1 to 20 carbon atoms in the alkyl radical, vinylaromatic compounds, hydroxyalkyl acrylates or methacrylates, N-methylolamides of olefinically unsaturated carboxylic acids of 3 to 5 carbon atoms and the ethers of said N-methylolamides with aliphatic alcohols.