| 摘要 |
PURPOSE:To improve the dispersibility of magnetic powder and to obtain a magnetic recording medium having an excellent electromagnetic conversion characteristic and soft error by using a modified urethane resin essentially consisting of a shellac resin modified material. CONSTITUTION:A mixed solvent composed of cyclohexanone/MEK (cyclohexanone/MEK=7/3) is put into a 1l flask with a stirrer and cooler and 300g refined and dewaxed shellac resin (250 hydroxyl value) is dissolved. After 1.5g dibutyl tin laurate is added as a reaction catalyst thereto, 45g octadecyl isocyanate is added thereto under stirring to partially urethanize the shellac resin, by which the shellac resin modified soln. is prepd. The resulted magnetic coating liquid is uniformly coated on both faces of a PE terephthalate film having 75mum thickness uniformly in such a manner that the coating thickness after drying attains 1.5mum. The surface of the magnetic layer is smoothed by a calender treatment after drying. |
