Patent ID: 8455682

Claim:
A process for preparing aminodicarboxylic acid-N,N-diacetic acids of formula (I): in which X is independently hydrogen or alkali metal, and n is 1 or 2, the process comprising: a) reacting an aminodicarboxylic acid of formula (II): with from 0.8 to 1.2 molar equivalents of formaldehyde and with from 0.8 to 1.2 molar equivalents of hydrocyanic acid, by adding formaldehyde and hydrocyanic acid, wherein the aminodicarboxylic acid is initially charged in the reaction vessel and then formaldehyde and hydrocyanic acid are added, to yield a first reaction product, wherein after completion of the addition the reaction was allowed to continue until no further evolution of heat is detectable; b) further reacting the first reaction product obtained in a) with from 0.8 to 1.2 molar equivalents of hydrocyanic acid, and with from 0.8 to 1.2 molar equivalents of formaldehyde to yield a second reaction product; c) hydrolyzing the second reaction product obtained in b).