Linear, substantially water-insoluble ammonium polyphosphates and process for making them

摘要

The disclosure relates to a process for making linear, substantially water-insoluble ammonium polyphosphates of the general formula (NH4PO3)10-1000 by heating and continuously mixing phosphorus pentoxide and ammonium orthophosphate in the presence of ammonia and tempering the resulting reaction product over a period of several hours at 200 DEG to 400 DEG C. in the presence of ammonia. To this end, the phosphorus pentoxide and ammonium orthophosphate are subjected at 50 DEG to 150 DEG C. to the following successive operations which provide (a) for them to be reacted with ammonia over a period of 5 to 15 minutes under an overpressure of 1-2 millibars, (b) for them to be mixed under nitrogen for 10 to 60 minutes at atmospheric pressure while arresting the supply of ammonia, (c) for them to be reacted with ammonia over a period of 1 to 3 hours under a pressure 1 to 5 millibars lower than atmospheric pressure, and the reaction product is tempered, the ammonia being used in an overall stoichiometric excess of at most 20 mol %. The disclosure is also concerned with the ammonium polyphosphates so obtainable which are characterized by the following typical data which provide: (a) for the solubility of a 10 weight % suspension in pure water at 25 DEG C. to be less than 0.8 g per 100 g suspension; (b) for the viscosity of a 10 weight % suspension in pure water at 25 DEG C. to be at most 100 mPa.s; (c) for the viscosity of a 30 weight % suspension in a polyesterpolyol at 25 DEG C. to be at most 50 Pa.s.