| 摘要 |
PURPOSE:To increase the dispersing property and wear resistance of magnetic powder, by using a polyurethane resin consisting of a mixture between a specified macromolecular polyol and low molecular polyol including >=3 functional groups low molecular polyol, and of an aromatic polyisocyanate as a binder. CONSTITUTION:A polyurethane resin (C) can be obtd. by reacting a mixed polyol A including a macromolecular polyol (A1) 150-2,000 equivalent having 150- 2,000 equivalent of polytetramethylene glycol (a1) or including the polyol (a1) plus >=50wt% of polycaprolactone polyol, and low molecular polyol (A2) including >=3 functional groups of low molecular polyol (a2), with an aromatic polyisocyanate (B). In the polyol (a2), 1-40 equivalent % of the a2 is included in the polyol A as methylolpropane and the A2 is included in the A in 20-29 equivalent %. The NCO/OH equivalent ratio of the B to A is taken as 0.6-1.5. This resin C is used for a binder and the magnetic recording material excellent in durability can be obtd. |
