GB1189041A - A Magnetic Coating Composition, method for preparing a Magnetic Disk and the Disk thus prepared - Google Patents

Abstract

1189041 Magnetic compositions MEMOREX CORP 1 Jan 1968 [ 27 Feb 1967] 181/68 Index C3B 1 L4H C8B L6G C12 C9B C25 C14A T1A L2X D2C D2B C8R. Index C3R 29 L4H C6X C8B L6G C12 C9B C25 C14A T1 L2X A coating composition comprises magnetic particles dispersed in a binder comprising a high equivalent weight epoxy resin (A), a low equivalent weight epoxy resin (B), an aminealdehyde condensation product (C), and a primary amine (D). (A) has an average of 1-3 epoxy groups per molecule and a M. wt. of 400-1200 per epoxy group, and may be a condensation polymer of epichlorohydrin and bisphenol A of formula: - where n is 2-6. (B) has an average of 3-4 epoxy groups per molecule and a M. wt. of 130-200 per epoxy group, and may be an epoxylated phenolic novolac of formula: - where n is 1-6. (C) has at least 2 secondary amine groups per molecule and may be an alkylated melamine formaldehyde resin of monomeric formula: - where R is alkyl C 1 -C 4 , or a butylated urea formaldehyde condensation product. (D) may be N-aminoethyl piperazine, N-(trimethoxysilylpropyl) ethylene diamine, diethylenetriamine, or ethylene-diamine. The compsotiion may also contain 3, 4-epoxycyclohexyl-ethyltrimethoxy silane, glycidoxy, prooyltrimethoxy silane, silicone resin, or methylphenylpolysiloxane. The ratio of epoxy groups in (A) : (B) is 1À5 : 1 to 1 : 3. The number of primary amine groups in (D) is 3-15% of the total number of epoxy groups, which is 1-1À5 times the number of H atoms in the primary and secondary amine groups in (C) and (D). The binder is dissolved in solvents and the composition coated on to a substrate, e.g. Al, or a plastics plate or "Mylan" tape, and cured, e.g. at 185‹C. Solvents mentioned are acetone, MEK, isopropanol, xylene, "Cellosolve, " hexanol, methylcarbitol, toluene, diethyl carbitol, and nitropropane.