To obtain the subject compound to be compounded to an epoxy resin to give a flame-retardant cured material for the sealing material for electronic parts, a printed circuit board, etc., by carrying out addition reaction of a specific epoxy compound with a phosphonic acid ester.
The objective phosphonic acid ester expressed by the formula III and useful e.g. as a halogen-free flameretardant or nonflammable cured material usable for a precision product such as electronic part sealing material and printed circuit board is produced by the addition reaction of an epoxy compound expressed by the formula I (R14 is an organic group) with a phosphonic acid ester expressed by the formula 1II (R2 to R5 are each an organic group; (k) and (l) are each 0, 1 or 2; (m) is 0 or 1; k+l+m=2) using at least one kind of compound selected from quaternary onium salt, crown ether complex, amine compound, phosphine compound, etc., as a reaction accelerator or a catalyst.
KAMEYAMA ATSUSHI
NAKAMURA SHIGEO
