Title: Process for purifying aminomethylenephosphonic acids
Application Number: 93108500 Application Date: 1990.07.28
Publication Number: 1091744 Publication Date: 1994.09.07
Approval Pub. Date: 1996.03.06 Granted Pub. Date: 1996.03.06
International Classifi-cation: C07F9/38;C07F9/6524
Applicant(s) Name: The Dow Chemical Company Address:
Inventor(s) Name: Joseph R. Garlich;Jaime Simon
Attorney & Agent: DONG JIAYANG
Abstract:
    High purity ethylenediaminetetra(methylenephosphonic acid) and 1,4,7,10-tetraazacyclododecane1,4,7,10-tetra(methylenephosphonic acid) are prepared by dissolving the aminomethylenephosphonic acid in an aqueous base, acidifying with a mineral acid at an elevated temperature to precipitate the crystals, maintaining the solution at an elevated temperature for a period of time sufficient to assure crystallization, cooling to a lower temperature and maintaining at that temperature for a time sufficient to precipitate the crystals and filtering the resulting crystals at that temperature, washing the crystals with water and recovering the desired high purity aminophosphonic acid. The ethylenediaminetetra(methylenephosphonic acid) is obtained in a purer state during its synthesis if the crystals are filtered hot without prior cooling.
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