| 摘要 |
PURPOSE:To improve the dispersibility of a magnetic material and calenderability by using a polyurethane composed of a specific polyol and org. polyisocyanate for a binder. CONSTITUTION:The polyurethane composed of the polyol (A) consisting of a high molecular polyol (A1) contg. a polyvalerolactone polyol (a) and low- molecular polyol (A2) and the org. polyisocyanate (B) is used. For example, polyvalerolactone diol or the like is preferable as the component (a) and the other high molecular polyol may be incorporated into the component A1 together with the component (a). The equiv. of the component A1 is made 200-2,000. The dispersibility of the magnetic material is low if the equiv. is out of said range. The dispersibility of the magnetic material is improved and the calenderability is improved according to the above-mentioned constitution, by which the workability is improved.
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