| 摘要 |
PURPOSE:To obtain a binder for a superior magnetic recording material contg. uniformly dispersed fine magnetic iron oxide powder by adding a compound contg. active hydrogen and having a spiro ring to a specified multifunctional compound contg. active hydrogen and by reacting them with polyisocyanate. CONSTITUTION:To a multifunctional compound (A) contg. active hydrogen is added a compound (A3) having a spiro ring represented by formula I , and they are reacted with polyisocyanate (B) to obtain polyurethane resin (C). This resin is used as a binder for fine magnetic powder of gamma-Fe2O3 or the like. The compound (A) is a high molecular polyol (A1) having >=250 equiv. per OH group, or it consists of the polyol (A1) and a low mol.wt. multifunctional compound (A2) contg. active hydrogen and having 30-200 equiv. per group contg. active hyrogen. When a compound represented by formula II or III (where R is a 2-7C hydrogen group, X is a spiro ring represented by formula I , A is a polyamine residue, and m is 0 or 1) is added, the resulting polyurethane resin having 5,000- 100,000 number average mol.wt. disperses uniformly magnetic powder and gives a magnetic coating material with superior adhesive strength and superior suitability to calendering after coating. |
