| 摘要 |
1265504 Magnetic coating compositions MEMOREX CORP 9 June 1969 [11 June 1968] 29161/69 Addition to 1189041 Index C3R 29 L4H C6X C8B L6G C12 C9B C25 C14A T1 L2X A coating composition comprises magnetic particles, e.g. V.Fe 2 O 3 , dispersed in a thermosetting binder comprising a high equivalent weight epoxy resin (A), a low equivalent weight epoxy resin (B), an amine-aldehyde condensation product (C), and a polyamine having at least one primary amino group per molecule. (A) has a molecular weight per epoxy group of 400-4000, and an average of 1-3 epoxy groups per molecule, and may be a condensation polymer of epichlorohydrin and bisphenol A. (B) has a molecular weight per epoxy group of 130- 200 and an average of 3-4 epoxy groups per molecule, and may be an epoxylated phenolic novolac. (C) has at least two secondary amino groups per molecule and may be an alkylated melamine formaldehyde resin. (D) may be N. aminoethylpiperazine. The ratio of the number of epoxy groups in (A) to the number in (B) is 3:1 to 1:3; the number of primary amino groups in (D) is 3-15% of the total number of epoxy groups in the polymers; and the number of epoxy groups in the polymers is 0À5-1À5 times the total number of H atoms on the primary and secondary amino groups in the polyamine (D) and the condensation product (C). The binder is dissolved in solvents and the composition coated on to a substrate, e.g. polyester tape, or a plastics or aluminium disc, and cured, e.g. at 185‹C.
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