METHOD FOR PRODUCING HIGHLY CONDENSED AMMONIUM POLYPHOSPHATE Russian patent published in 2023 - IPC C01B25/38 C01B25/40 C01B25/28 C01C1/28 C09K21/04 

FIELD: fire-retardant coatings.

SUBSTANCE: invention can be used in the manufacture of materials for fire-retardant coatings and fire-resistant structural materials. The method for producing highly condensed ammonium polyphosphate (APP) includes the interaction of a phosphorus-containing compound selected from the group: phosphoric acid or its ammonium salts, or phosphoric anhydride of the formula P₂O₅, in the presence of anhydrous oxalic acid, and carbamide at a temperature of 110°C to form a low molecular weight condensation product, heating the resulting product to 230-270°C. The method is carried out continuously in a rotating drum with grinding bodies with external heating, into which reagents are loaded. After heating to 110°C, the reaction mass is heated with exposure in the range of 110-155°C for at least 2 hours. Then at least one ammonium salt or a mixture thereof is added to the reaction mass in an amount of 2-7 wt.% of the mass of the loaded reagents. After heating to 230°C, the reaction mass is heated with exposure in the range of 230-270°C for at least 2 hours.

EFFECT: invention makes it possible to obtain APP with a high degree of polycondensation using a simplified technology while reducing the synthesis time and energy consumption.

5 cl, 7 ex