Process for the preparation of a mixture of chelating agents, mixture of chelating agents and methods of using them

A process for the preparation of a mixture of at least two chelating agents

• the process comprising a first step of reacting the hydroxyl groups of a compound having a formula (Ia)
• wherein A is H or methyl, B is a carboxylic acid group or a salt thereof, and R1 and R2 are H, with maleic acid or a salt thereof in alkaline conditions in the presence of a lanthanide catalyst to form a mixture comprising
• a. compounds having formula (Ib)
• wherein A is H or methyl, B is a carboxylic acid group or a salt thereof, and R1 and R2 are succinic acid groups or salts thereof, and
• b. compounds having formula (Ic)
• wherein A is H or methyl, B is a carboxylic acid group or a salt thereof, and one of R1 and R2 is a succinic acid group or a salt thereof, and the other is H,
• followed by a second step of adding a 2-halocarboxylic acid or a salt thereof which reacts with intermediates having formula (Ic) to form a mixture comprising
• a. compounds having formula (Id)
• wherein A is H or methyl, B is a carboxylic acid group or a salt thereof, and R1 and R2 are succinic acid groups or a salts thereof (GES5), and
• b. compounds having formula (Ie)
• wherein A is H or methyl, B is a carboxylic acid group or a salt thereof, and one of R1 and R2 is a succinic acid group or a salt thereof, and the other is a carboxymethyl or 1-carboxyethyl group or a salt thereof (GES4).