United States  Patent  [19J  Smith  [11]  Patent Number:  5,087,740  [45]  Date of Patent:  Feb. 11, 1992  US005087740A  [54]  PROCESS FOR  PURIFYING  N-PHOSPHONOMETHYLGLYCINE  [75]  Inventor:  Lowell  R.  Smith, Kirkwood,  Mo.  [73]  Assignee:  Monsanto Company,  St. Louis, Mo.  [21]  Appl. No.:  561,483  [22]  Filed:  Jul.  30, 1990  Related U.S. Application  Data  [63]  Continuation  of Ser. No. 394,998,  Aug. 17, 1989,  aban- doned.  [51]  Int.  Cl.5  ................................................  C07F  9/38  [52]  U.S. Cl  .......................................................  562/17  [58]  Field of Search  ..........................................  562/17  [56]  References  Cited  U.S. PATENT  DOCUMENTS  4,197,254  4/1980 Gaertner  ...............................  562/17  4,439,428  3/1984 Cox  .........................................  71/86  4,605,522  8/1986 Robbins  ............................  260/502.5  4,684,483  8/1987 Richard  et al.  .......................  562/17  FOREIGN PATENT  DOCUMENTS  127415 11/1978  Japan .  Primary Examiner-].  E. Evans  Attorney, Agent,  or  Firm-Frank  D. Shearin  [57]  ABSTRACT  8 Claims, No Drawings  N-Phosphonomethylglycine  can be purified  and con› centrated from  aqueous solutions  containing N-phos› phonomethylglycine  and  impurities, such  as  N-formyl› N-phosplionomethylglycine,  phosphorous  acid, and the  like, by passing  the aqueous  solution through  an ion  exchange column  containing  a weakly basic  ion ex› change resin  to remove such  impurities. 