| 摘要 |
The present invention relates to a binding agent for a magnetic recording medium which consists of a non-magnetic substrate with a magnetic layer formed thereon. The magnetic layer is composed of a finely divided ferromagnetic substance dispersed in the resinous binding agent. The binding agent consists of: a binder containing a butadiene-containing resin, having an average molecular weight of 1,000-10,000, and being selected from the group consisting of butadiene homopolymers and copolymers of butadiene with acrylonitrile and/or styrene which contains at least 60% by weight of butadiene, with the butadiene-containing resin having on the average more than 1.5 functional end groups per molecule, which are reactive with isocyanate groups; and a polyisocyanate compound having on the average not less than 2 isocyanate groups per molecule, the polyisocyanate compound being present in between 5 and 50 parts by weight, based upon 100 parts by weight of the binder. The use of this binding agent allows for greater dispersion of the ferromagnetic powder as the low molecular weight resin has a high solubility in organic solvents. Further, the butadiene-isocyanate crosslinks formed, act to improve wear resistance and make it possible to obtain a desirable elastic modulus.
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