| 摘要 |
PURPOSE:To improve the dispersibility of magnetic powder, the workability at the time of forming coated film and the durability of a medium by using polyurethane contg. a carboxylic acid (alkali metal salt) group and tertiary amine salt of sulfonic acid as a binder. CONSTITUTION:The polyurethane contg. the -COOM group (where M is H, alkali metal) and tertiary amine salt of sulfonic acid {e.g.: -SO3<->HN<+>(CH3)3} is used as the binder of a magnetic layer. Said group and salt are incorporated into the polyurethane by methods of (1) previously introducing the above- mentioned group or salt into diisocyanate or polyol which is the raw material of the polyurethane and (2) previously allowing the OH group to remain at the terminal or side chain of the polyurethane and modifying the OH group by a compd. contg. the above-mentioned group or salt or combining these methods. Other thermoplastic, thermosetting or reactive resins may be used in conjunction with the binder and further various additives may be added to the binder.
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