Verfahren zur Herstellung von Magnetbaendern

A magnetic layer is formed by coating a mixture of polymer solution, polymerizable monomer catalyst, and magnetic material on to a mould, polymerizing the monomer, and then stripping the coating from the mould. The constituents of the mixture may be P.V.C., 1,3-butylene dimethacrylate, t-butyl perbenzoate, and acicular g -Fe2O3 resp. with 1,1,1-trichloroethan as solvent. The mixture may include plasticizers, e.g. dioctyl phthalate, and heat stabilizers, e.g. Ba-Cd Zn, for the polymer; a wetting agent for the Fe2O3, e.g. diethylene glycol monolaurate; and a thixotropic agent to prevent settling, e.g. colloidal S1O2, or carbon black. In the example, a mixture containing the Fe2O3 was thinned with a mixture containing P.V.C., the monomer being present in both, and was sprayed on to the inner surface of a cylindrical steel mould, which may initially have been coated with a silicone, e.g. dimethylpolysiloxane. A further mixture containing P.V.C., and a non-acrylic monomer, was sprayed over the first layer (to form the base). The mould was then heated at 370 DEG F. and the layers stripped from the mould.