PURPOSE: To eliminate the danger of fire caused by a coating material contg. an org. solvent as well as to solve the hygienic problems, to solve the problem of the low dispersibility of magnetic powder in an aqueous coating material, and to improve the solvent resistance, wear resistance and flexibility of a magnetic recording medium by using an emulsive four-component type copolymer contg. epoxy groups as a binder.

CONSTITUTION: When a magnetic recording medium is manufactured by forming a magnetic layer contg. magnetic powder and a binder as principal components on a support, an emulsive four-component type copolymer contg. epoxy groups is used as the binder. The copolymer has cross linkage formed by utilizing the ring opening reaction of an epoxy group in the presence of a proton donor contained in polymerizable unsatd. carboxylic acid. The copolymer is prepd. by copolymerizing 100pts.wt. acrylic or methacrylic ester with 5W100pts.wt. acrylonitrile, 0.5W50pts.wt. monomer contg. an epoxy group and 0.5W50pts.wt. polymerizable unsatd. carboxylic acid by a conventional method such as emulsion polymn.