Coating composition with vinyl chloride polymer for magnetic recording medium

摘要

The invention provides a coating composition used for forming a magnetic layer on the surface of substrates to prepare magnetic recording media, e.g., recording tapes, of which the characteristic ingredient is a novel copolymeric resin. The copolymeric resin is a partial or complete saponification product of a copolymer obtained by the copolymerization of 4 types of comonomers in a spe-cified proportion including (1) vinyl chloride, (2) vinyl acetate, (3) a monomer having an ethylenically unsaturated polymerizable group and an epoxy group in the same molecule and (4) a monomer having an ethylenically unsaturated polymerizable group in the form of a sulfonic acid or a metal salt thereof. The vinyl acetate moiety is converted into a vinyl alcohol moiety partially or completely by the saponification. This copolymeric resin is advantageous in respect of the dispersibility of the ferromagnetic particles and the high crosslinkability which serves to improve the durability of the magnetic recording medium prepared by using the resin.