ИСТИНА

FIELD: fire retardants. SUBSTANCE: preparation of high-condensed ammonium polyphosphate applicable as fire retardant constituent of fire-protective swelling coatings and when manufacturing fire-resistant structural materials involves heating ammonium orthophosphate/urea mixture (1:1 molar ratio) in presence of ammonium polyphosphate in ammonia gas atmosphere to form low-melting eutectic, which is then heated at rate 160-200 C/min to 230-240 C, during which period melt crystallizes, and then to 280-300 C, after which product is hold at this temperature to dehydrate at reduced pressure 0.52-1.29 kPa. Anhydrous product is cooled and crushed. Decomposition point of product is 275-285 C and its weight loss 0.22-0.05%. EFFECT: enhanced process efficiency and improved quality of product. 1 tbl