POWDERS AND GRANULES AND METHOD OF PRODUCING SUCH POWDERS AND GRANULES Russian patent published in 2021 - IPC C11D3/33 C11D11/00 C07C227/00 C07C229/16 

FIELD: chemical or physical processes.

SUBSTANCE: present invention relates to a method of producing powder or granules. Described is a method of producing powder or granules containing: (A) at least one chelating agent selected from alkali metal salts of methylglycine diacetic acid (MGDA), where said alkali metal salts are selected from compounds according to general formula (Ia) [CH₃-CH(COO)-N(CH₂-COO)₂]M_3-xH_x (Ia), where M is selected from cations of alkali metals selected from sodium, potassium or a combination of sodium and potassium, and x ranges from zero to 1.0, wherein said method includes steps of: (a) adding an aqueous solution or aqueous suspension of the corresponding chelating agent (A) to the spray granulator and removing a large portion of said water by spray granulation, using gas with inlet temperature from 125 to 250 °C, (b) extraction of granules from spray granulator, (c) separating fine particles from said granules, said fine particles having a maximum particle diameter of 350 mcm, (d) separating lumps from said granules, where said lumps have diameter of 1,000 mcm or more, (e) milling said lumps to maximum particle diameter of 500 mcm in case of granules, (f) repeated introduction of said fine particles from step (c) and crushed lumps from step (e) into a spray granulator, where fine particles share is in range from 4 to 18 wt % of total chelating agent (A) extracted in step (b), and the fraction of milled lumps from step (e) ranges from 20 to 40 wt % of the total chelating agent (A) recovered in step (b).

EFFECT: technical result is providing chelating agents in solid form, which are less hygroscopic and do not or almost do not cause yellowing when contacting percarbonate.

8 cl, 2 tbl, 5 ex