Process for the preparation of alkali-metal salts of carboxyalkoxy succinates

Abstract

It is disclosed that high purity alkali metal salts of carboxyalkoxy succinic acid are produced from maleic acid and a hydroxy organic acid by reaction of zinc or alkaline earth metal salts of said acids to form a zinc or alkaline earth metal carboxyalkoxy succinate, by reacting the zinc or alkaline earth metal carboxyalkoxy succinate with an alkali metal carbonate in a stoichiometric deficiency of carbonate to selectively react with the alkaline earth metal carboxyalkoxy succinate, leaving the impurities as insoluble alkaline earth metal salts, removing the zinc or alkaline earth metal as insoluble carbonate, and recovering an alkali metal carboxyalkoxy succinate solution which is then evaporated to dryness.

I claim: 
     
       1. A process for producing a high purtiy alkali metal carboxyalkoxy succinate from a zinc or alkaline earth metal carboxyalkoxy succinate contaminated with zinc or alkaline earth metal salt of at least one of maleic acid, fumaric acid and hydroxy organic acid which comprises, selectively reacting the zinc or alkaline earth metal carboxyalkoxy succinate with a stoichiometric deficiency ratio of alkali metal carbonate for complete reaction of all zinc or alkaline earth metal salt present to form a solution of alkali metal carboxyalkoxy succinate containing a carbonate of the zinc or alkaline earth metal, and   recovering the soluble alkali metal carboxyalkoxy succinate solution from the zinc or alkaline earth metal salt residue of maleic acid, fumaric acid or hydroxy organic acid remaining after the selective reaction of the carboxyalkoxy succinate.   
     
     
       2. A process as in claim 1 wherein the zinc or alkaline earth metal carboxyalkoxy succinate is produced by a reaction of zinc or alkaline earth metal salts of glycolic acid and maleic acid at a pH of at least about 8 as measured at 25° C. 
     
     
       3. A process as in claim 1 wherein the zinc or alkaline earth metal carboxyalkoxy succinate is produced by a reaction of calcium glycolate and calcium maleate at a pH of at least about 8 as measured at 25° C. to form carboxymethoxy succinic acid, calcium salt, contaminated with calcium glycolate, calcium maleate and calcium fumarate. 
     
     
       4. A process of claim 1 wherein the alkali metal carbonate is sodium carbonate and the amount used is from about 25 to about 100 percent of the stoichiometric amount required to react selectively to convert the zinc or alkaline earth metal carboxyalkoxy succinate present to alkali metal carboxyalkoxy succinate. 
     
     
       5. A process in claim 1 wherein the alkali metal carbonate is sodium carbonate and the amount is from about 50 to about 90 percent of the stoichiometric amount required to react selectively to convert the zinc or alkaline earth metal carboxyalkoxy succinate present to alkali metal carboxyalkoxy succinate. 
     
     
       6. A process in claim 1 wherein the alkali metal carbonate is sodium carbonate and the amount is from about 60 to about 80 percent of the stoichiometric amount required to react selectively to convert the zinc or alkaline earth metal carboxyalkoxy succinate present to alkali metal carboxyalkoxy succinate. 
     
     
       7. A process as in claim 1 wherein the alkali metal carbonate is sodium carbonate and it is reacted with carboxymethoxy succinic acid, calcium salt to produce carboxymethoxy succinic acid, sodium salt at a temperature of from about 70° to about 100° precipitating calcium carbonate. 
     
     
       8. A process as in claim 1 wherein the purified alkali metal carboxyalkoxy succinate solution is dried at a temperature of from about 25° to about 150° C. 
     
     
       9. A process as in claim 1 wherein the water is evaporated from the alkali metal carboxymethoxy succinate at a temperature of from about 25° to about 50° C. 
     
     
       10. A process as in claim 1 wherein the alkaline earth metal carboxyalkoxy succinate is washed with water at a temperature of from about 50° to about 100° C. prior to the selective reaction. .Iadd. 11. A process as in claim 4, wherein the zinc or alkaline earth metal carboxyalkoxy succinate is added to a water solution of sodium carbonate..Iaddend.