IMPROVEMENTS IN MAGNETIC COMPOSITIONS AND IN METHODS OF MAKING THEM

摘要

1300019 Making magnetic metallic flakes INTERNATIONAL BUSINESS MACHINES CORP 22 Sept 1971 [28 Dec 1970] 44093/71 Heading B3A [Also in Division H1] A magnetic composition comprises metal flakes (0À001-1 micron thick, 0À01-5 microns diameter; coercivity more than 250 Oe) coated with a leafing lubricant. The flakes are made by milling metallic magnetic particles in presence of the lubricant and a volatile solvent. The magnetic particles, e.g. cobalt-phosphorus, iron or steel may be derived by vaporization or carbonyl techniques, electrodeposition on liquid cathodes, or chemical decomposition of plating baths. The lubricant may be a C 14-22 alkyl or alkenyl fatty acid, e.g. stearic acid; a derivative thereof, e.g. a metal soap; a petroleum or hydrogenated vegetable oil lubricant or a fluorocarbon resin. The size and thickness of the flakes is a function of the milling time and amount of metal particles present, and can range from hours to days. The flakes may also be made by other conventional procedures such as hammer or dry stamping or by attriting. In examples, chemically - produced cobalt - phosphorus particles (0À1 micron) (650 g.), stearic acid (20 g.) and mineral spirits (350 g.) are milled for 48 hours at 103 r.p.m. on a steel ball mill fitted with lifters. The wet slurry is washed with mineral spirit and filtered. Magnetic recording media are made by mixing a polymeric binder with the lubricant-coated flakes and coating the resulting paste on to a substrate (see Division H1).