| 摘要 |
PURPOSE:To obtain a binder having excellent resistance to hydrolysis and an excellent electromagnetic conversion characteristic and running durability by incorporating a specific ratio of polycaprocatone polyurethane into the binder. CONSTITUTION:The binder to be used together with pulverized CrO2 powder in the medium having a nonmagnetic base and a magnetic layer contg. the pulverized CrO2 powder dispersed in the binder on said base contains 30-90wt% polycaprocatone polyurethane. The polycaprocatone polyurethane is particularly preferably used at 40-85wt% by the total weight of the binder and the other binders which can be used in combination are preferably used at 10-70wt%, more particularly preferably at 15-60wt%. The polycaprocatone polyurethane is obtd. by condensing polyol, polyisocyanate and if necessary, chain extender. The hydrolysis of the binder is thereby extremely lessened when the medium is subjected to a high temp. and high humidity for a long period of time and therefore, the deterioration of the electromagnetic conversion characteristic and running durability is extremely lessened.
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