Patent ID: 8802894

Claim:
A process for preparing an aqueous solution of a methylglycine-N,N-diacetic acid trialkali metal salt by Strecker synthesis, the process comprising, in one reaction unit: reacting α-alanine with formaldehyde and hydrocyanic acid in an aqueous solution to obtain α-alanine-N,N-diacetonitrile and saponifying the α-alanine-N,N-diacetonitrile with a base to obtain a methylglycine-N,N-diacetic acid trialkali metal salt, wherein the α-alanine is partially neutralized, in the reaction the hydrocyanic acid is added to a solution of the α-alanine and formaldehyde in water and the addition of hydrocyanic acid is controlled so that the concentration of free hydrocyanic acid in the aqueous reaction mixture at any time is low and unwanted secondary reactions of formaldehyde cyanohydrin and polymerization of hydrocyanic acid are limited to take place only insofar as specification requirements for methylglycine-N,N-diacetic acid trialkali metal salt are observed.