| 摘要 |
PURPOSE:To improve the dispersibility and durability of magnetic powder by adding specific polyurethane elastomer which uses TDI as an isocyanate component, and an urethane prepolymer to a binder for a magnetic layer. CONSTITUTION:A binder for a magnetic layer contains polyurethane elastomer which uses tolylenediisocyanate (TDI) as an isocyanate component and has >=10,000 mean molecular weight, and an urethane prepolymer. In this case, said polyurethane elastomer is obtained through the condensation polymerization of a polyol component and TDI as the isocyanate compnent in the usual way, and as the polyol component, a polyester polyol component of polyhydric alcohol such as 1.4 butanediol, etc., and polybasic acid such as adipic acid, various polyether polyol components, etc., are usable. Further, the urethane prepolymer uses, e.g., straight-chain and low-molecular-weight urethane resin which has free isocyanate groups at both molecular terminals and about 2,000-10,000 mean molecular weight. |
