Process for making mixtures of chelating agents

Abstract

Process for making a chelating agent according to the general formula (I), R 1 —CH(COOX 1 )—N(CH 2 COOX 1 ) 2   (I) wherein R 1 is selected from hydrogen, C 1 -C 4 -alkyl, phenyl, benzyl, CH 2 OH, and CH 2 CH 2 COOX 1 , X 1 is (M x H 1-x ), M being selected from alkali metal, x is in the range of from 0.6 to 1, said process comprising the following steps: (a) providing a solid, a slurry or a solution of a compound according to general formula (II a) R 1 —CH(COOX 2 )—N(CH 2 CN) 2   (II a) wherein X 2 is (M y H 1-y ), M being selected from alkali metal, y is in the range of from zero to 1, (b) contacting said solid or slurry or solution with an aqueous solution of alkali metal hydroxide, wherein the molar ratio of alkali metal ions to nitrile groups is in the range of from 0.6:1 to 0.95:1, (c) reacting said compound according to general formula (II a) with said alkali metal hydroxide.

1 : A process for making a chelating agent according to formula (I):
   R 1 —CH(COOX 1 )—N(CH 2 COOX 1 ) 2   (I),
   wherein:
 R 1  is selected from the group consisting of hydrogen, C 1 -C 4 -alkyl, phenyl, benzyl, CH 2 OH, and CH 2 CH 2 COOX 1 ; 
 X 1  is (M x H 1-x ), M being an alkali metal; and 
 x is in a range of from 0.6 to 1, 
   the process comprising:   (a) contacting a solid, a slurry, or a solution of a compound according to formula (II):
   R 1 —CH(COOX 2 )—N(CH 2 CN) 2   (II),
 
   wherein:
 X 2  is (M y H 1-y ), M being an alkali metal; and 
 y is in the range of from zero to 1, 
   
       with an aqueous solution of alkali metal hydroxide, wherein a molar ratio of alkali metal ions to nitrile groups is in a range of from 0.6:1 to 0.95:1; and
 (b) reacting the compound according to formula (II) with the alkali metal hydroxide. 
 
     
     
         2 : The process according to  claim 1 , wherein the reacting is performed at a temperature in a range of from 30 to 200° C. 
     
     
         3 : The process according to  claim 1 , wherein M is at least one alkali metal selected from the group consisting of sodium and potassium. 
     
     
         4 : The process according to  claim 1 , wherein, in formula (1), x is in a range of from 0.7 to 0.85. 
     
     
         5 : The process according to  claim 1 , wherein in formula (II), R 1  is methyl, and the compound of formula (II) is predominantly an L-enantiomer, wherein the ratio of L to D is in a range of from 95:1 to 100:1. 
     
     
         6 : The process according to  claim 1 , wherein the reacting comprises at least two stages (c1) and (c2), wherein stage (c2) is performed at a temperature at least 20° C. higher than stage (c1). 
     
     
         7 : The process according to  claim 1 , wherein the chelating agent according to formula (I) comprises at least one compound having a formula selected from the group consisting of formulae (III a) and (III b):
   R 1 —CH(COOX 1 )—N(CH 2 COOX 1 )(CH 2 CONH 2 )  (III a), and
     R 1 —CH(COOX 1 )—N(CH 2 CONH 2 ) 2   (III b)
   wherein the variables are defined as for formula (I).   
     
     
         8 - 16 . (canceled)