| 摘要 |
1,202,115. Magnetic compositions. FUJI SHASHIN FILM K.K. 6 Sept., 1968 [8 Sept., 1967], No. 42585/68. Heading H1H. The binder for the magnetic layer of a recording medium comprises a mixture of a polyether glycol/polyisocyanate prepolymer having terminal NCO groups and a cellulose derivative having 7À5-40% free OH groups. The ratio by weight of the prepolymer to the cellulose derivative may be 1: 2 to 20:1. The polyether may be tetraethylene-, polyethylene-, or polypropylene-ether glycol, or a polyalkylene arylene ether glycol, or polyalkylene- or polyalkylene arylene-ether thioether glycol. The polyisocyanate may be 2,4-tolylene, m-phenylene, 4,4<SP>1</SP> - biphenylene, 1,4 - cyclohexylene, 1,5- tetrahydronaphthalene, 1,6 - hexamethylene, 4 - chloro - 1,3 - phenylene, or 1,5 - naphthalene diisocyanate. The cellulose derivative may be nitrocellulose, acetyl butyral cellulose, or ethyl cellulose. The magnetic powder may be γFe 2 O 3 , Fe 3 O 4 , FeCoNi alloy, CrO 2 , Ba ferrite, or Co-containing Fe 3 O 4 . The dispersion of magnetic powder in the binder and solvent, e.g. butyl acetate, may be coated on a polyethylene terephthalate base having a subcoating of polyester. |
