| 摘要 |
PURPOSE:To improve recording density by using a polyurethane resin formed by bringing an org. diisocyanate, diol and org. compd. having active hydrogen into reaction to prepare a prepolymer and further bringing a polyester polyol into reaction with said compd. at a specific ratio as a binder for a magnetic layer. CONSTITUTION:The isocyanate terminal prepolymer is formed by bringing the org. diisocyanate A, the long chain diol B having 500-5,000mol.wt. and the org. compd. C having 2 active hydrogens in one molecule and having <500mol.wt. into reaction with each other. The polyurethane resin of 6,000-50,000mol.wt. obtd. by bringing the branched polyester polyol D of 500-5,000mol.wt. copolymerized with a tri- or higher functional polycarboxylic acid or polyol at 1-20mol% of the acid component or the alcohol component into reaction with such isocyanate terminal prepolymer at the reaction ratio expressed by formulas I, II is used as the binder for ferromagnetic powder to be coated on a nonmagnetic base. The wear resistance, durability, etc., of the magnetic recording medium is thereby improved, the dispersibility of the magnetic particles is improved and the high-density recording is made possible.
|
