METHOD OF PRODUCING HIGH-CONDENSED AMMONIUM POLYPHOSPHATE Russian patent published in 2020 - IPC C01B25/38 C01B25/28 C09K21/04 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing ammonium polyphosphate used in fire-retardant coatings and in making fire-resistant structural materials. Method of producing high-condensed ammonium polyphosphate involves, at a first step, reacting a ground phosphorus-containing compound selected from: orthophosphoric acid or its ammonium salts, or a phosphoric anhydride of formula P₂O₅ in the presence of anhydrous oxalic acid, and carbamide at temperature of 110–140 °C to form a low-molecular condensation product and at the second step heating the product obtained at the first step at 230–270 °C. At the first step, the phosphorus-containing compound and carbamide are subjected to mechanochemical activation by co-milling to particle size of less than 40 mcm.

EFFECT: technical result is obtaining ammonium polyphosphate with high degree of polycondensation, as well as high surface of reacting components, which avoids formation of lumps and sticking in the reactor at the second step of producing ammonium polyphosphate.

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