| 摘要 |
<p>PURPOSE: To obtain a binder system for finely divided ferromagnetic powders corresponding to a high-density recording system by using branched polyurethane which does not contain isocyanate and soluble in tetrahydrofuran. CONSTITUTION: The polyurethane used as the binder of a magnetic layer has a sulfonate group on its branched chain, has an OH-contg. urea group at its molecule terminal, and has a mol.wt. of 4,000 to 30,000. The polyurethane is prepared from 1mol polydiol having a mol.wt. of 400 to 4,000, 0.3 to 9mol mixture, 0.01 to 1mol 3 to 25C trial or polyol, 1.25 to 13mol 6 to 30C diisocyanate and 0.05 to 4mol OH-contg. primary or secondary amine reactive with isocyanate.</p> |
