| abstract |
(57) [Problem] To provide a novel dihydroxyspirophosphonic acid ester which is excellent in storage stability and is useful as an additive-type flame retardant or an additive-type flame retardant. (1) A dihydroxyspirophosphonic acid ester represented by the following formula (1). Embedded image (Wherein R is a linear or branched alkyl group having 1 to 12 carbon atoms or an aryl group having 4 to 25 carbon atoms). (2) 3,9-bis (2-hydroxyethyl) -3,9-dioxa-2,4,8,10-tetraoxa-3,9 represented by the following formula 2: -Diphosphaspiro [5.5] undecane. Embedded image |