PURPOSE: To impart good libricity to the above-mentioned medium and to great ly improve its durability by using a fatty acid having the branched chain expressed by specific formula as a lubricant.
CONSTITUTION: The branched fatty acid expressed by the formula is incorporated into the magnetic layer on a nonmagnetic base. The branched fatty acid is produced by the addition reaction of olefin and fatty acid. As the olefin, 6 to 32C, more preferably 6 to 28C α-olefins are used. As the fatty acid, 6 to 26C caproic acid, caprilic acid, lauric acid, mysistic acid, malmitic acid, stearic acid, etc., are used as the fatty acid. The charging quantity of the olefin in the above-mentioned reaction is specified to 50 to 60mol% of the fatty acid. An org. peroxide as a radical generating agent, such as dialkyl peroxide or tertiary butyl perioxide, is used at the time of the addition reaction. The branched fatty acid is used at 1 to 15 pts. wt., more preferably 3 to 10 pts.wt. in total per 100 pts.wt. magnetic powder.
TANAKA TOSHINORI
SUZUE SHIGETOSHI
