Process for making ammonium glyphosate flakes

The present invention relates to preparation of a herbicidal composition useful in agriculture and in other situations where control of weeds or other vegetation is desired. In particular, it relates to preparation of a herbicidal active ingredient, namely N-phosphonomethylglycine (glyphosate) in the form of the ammonium salt thereof, as a finished product or as an intermediate useful in further processing. A process is provided for preparing ammonium glyphosate flakes, comprising (a) mixing (i) solid particulate glyphosate acid, (ii) water in an amount of about 0.5 to about 3 parts by weight per part by weight of glyphosate acid, and (iii) a base that supplies ammonium cations, in an amount of about 0.8 to about 1.25 mole equivalents of ammonia per mole of glyphosate acid, to form an aqueous reaction medium; (b) allowing the glyphosate acid to react with the base in the reaction medium to form a reaction product comprising a concentrated aqueous solution of ammonium glyphosate; (c) drying the reaction product by contact thereof with a heated surface to form, primarily by evaporation of water, a solid deposit on the heated surface; and (d) scraping the solid deposit off the heated surface to recover dry flakes of ammonium glyphosate.