The invention relates to a method for producing large-grained
nitrofurantoin crystals, and belongs to the field of
chemical synthesis. The invention adopts a technical proposal which comprises: placing a crude product of
nitrofurantoin formed by the condensation of raw materials of 5-nitrofurfural diacetate and 1-aminohydantoin, and DMF of which the weight is two times of that of the crude product of the nitrofurantion in a
retort, heating the mixture to between 85 and 90 DEG C, stirring the mixture, maintaining the temperature for 10 minutes, stirring the mixture, opening a clamping sleeve, cooling the
retort by cooling water for 80 to 90 minutes to between 30 and 35 DEG C, stopping stirring, standing the
retort for 2.5 to 3 hours to less than 2 DEG C below zero,
casting material, and washing the material with 95 percent
ethanol to obtain odorless DMF.
Nitrofurantoin crystals prepared by the process are larger and the
granularity of 95 percent of the products is more than 80 meshes, so the process facilitates
filtration and separation and contributes to the reduction of production cost.