| 摘要 |
PURPOSE:To improve the dispersibility of magnetic powder, the durability of a magnetic layer, etc., by using a thermoplastic polyurethane resin or thermoplastic polyurethane resin and polyisocyanate hardener to constitute a main binder component. CONSTITUTION:The main binder component of a magnetic recording medium consists of the OH group terminated thermoplastic polyurethane resin having the urethane bond obtd. from the reaction of the diol expressed by the formula (n=1-5, R2; CmH2m+1, m=0-6) and diisocyanate and secondary or ternary OH group and/or COOM (M is an alkali metal or hydrogen atom) group as the side chain of the molecule or the thermoplastic polyurethane resin and polyisocyanate hardener. The mol.wt. of the polyurethane resin is preferably 5,000-80,000, more preferably 10,000-60,000. The dispersibility of magnetic powder is improved and the time for preparing a magnetic coating compd. is reduced by using such binder. In addition, the durability, wear resistance, solvent resistance, adhesiveness, etc. are improved.
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