Patent ID: 8445718

Claim:
A method for producing phosphonic acid metal salt fine particles, comprising: a) causing a reaction of a phosphonic acid compound of Formula (I): (where R 1 and R 2 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkoxycarbonyl group having 1 to 10 carbon atoms) with a base in an aqueous medium to adjust a pH range of the reaction system to be neutral to basic; b) causing a reaction of the product obtained in a) with a metal salt to precipitate a phosphonic acid metal salt from the aqueous medium; c) removing water from the phosphonic acid metal salt precipitated in b); and d) heating and drying the phosphonic acid metal salt from which water is removed in c), wherein the phosphonic acid metal salt is at least one metal selected from the group consisting of calcium salts and zinc salts.