ABSTRACT
The emergence of magnetic tape as a format for data, video, and audio recording as well as for the distribution of precorded information of all three varieties is a remarkable recent phenomenon. Magnetic tape consists of magnetic particles dispersed in a flexible polymeric binder coated on a polymeric substrate. The classical surfactant materials (lecithin, phosphates, etc.) used in magnetic tapes are clearly major contributors to the growth of the filming agents. Two kneading methods are in use for magnetic tape mix preparation: continuous and batch high pressure systems. Several developments are under way to achieve the good dispersion properties of sand milling, especially the minimization of particle breakage, while preventing a weakness commonly called "by-pass" or "short pass." This problem allows partially aggregated material to pass through the mill unseparated, and it is very much an issue of concern for magnetic tape pigment dispersions.
