Process for the preparation of a powder comprising one or more complexing agent salts

A process for preparing a powder comprising at least one methylglycine-N,N diacetic acid complexing agent salt of formula (I):

• wherein
• R′ is
• and
• R″ is methyl;
• M is, independently, hydrogen, an alkali metal, an alkaline earth metal, ammonium or a substituted ammonium in corresponding stoichiometric amounts, provided that at least one M is not hydrogen;
• comprising:
• (a) atomizing an aqueous solution comprising a first complexing agent salt of formula (I) in the presence of a crystalline fine dust of a second complexing agent salt of formula (I), to produce a powder, and
• (b) drying the powder,
• wherein
• a concentration of the first complexing agent salt in the aqueous solution is from 10 to 80% by weight, based on a total weight of the aqueous solution;
• an upper limit for an average particle diameter of the crystalline fine dust is lower by at least a factor of 2 than a lower limit of an average particle diameter of the powder obtained by the process;
• a fraction of the crystalline fine dust is from 0.1 to 20% by weight, based on a weight of the powder obtained in the process;
• and
• the residual moisture of the powder after drying is 6.5 to 14% by weight.