AB-BLOCK COPOLYMERS AS DISPERSANTS IN MAGNETIC COATING FORMULATIONS

The manufacture of wet-coated magnetic recording media requires the di spersion of the magnetic particles in a blend of resin components and solvents. For optimum quality products the magnetic particles have to be ideally dispersed, the resulting dispersion should be stable over a period of at least 24 h, and the dispersing aids should have a neutra l or positive effect on the final properties of the coating. It is now reported that AB-block copolymers are advantageous for the dispersion of magnetic pigments. Compared to conventional polymeric dispersants frequently based on vinyl chloride copolymers, a higher rate of disper sion is achieved. The influence of the structure of the dispersant on the dispersing properties is discussed.