| 摘要 |
PURPOSE:To improve electromagnetic conversion characteristics, durability and dispersibility, by permitting magnetic powder to contain as binder components a vinyl chloride-vinyl acetate copolymer containing a specific amount of vinyl alcohol unit, low-molecular-weight polyol and low-molecular weight polyisocyanate. CONSTITUTION:Mangetic powder contains as binder components at least three kind of components-a vinyl chloride-vinyl acetate copolymer, such as a ternary cpolymer consisting of vinyl chloride, vinyl acetate and vinyl alcohol as polymerizing unit components, containing a >=10wt% vinyl alcohol unit, low-molecular-weight polyol of, for example, <=10,000 molecular weight having hydroxyl group at both terminals of principal chain, and low-molecular-weight polyisocyanate. Consequently, the strength of the magnetic layer is improved and while the wear resistance, thermal resistance and solvent resistance are improved, electromagnetic conversion characteristics such as the output and SN ratio are also improved. |
