FREMGANGSMAADE TIL FREMSTILLING AF I DET VAESENTLIGE VANDUOPLOESELIGE, KAEDEFORMIGE AMMONIUMPOLYPHOSPHATER

1446260 Ammonium polyphosphates HOECHST AG 10 April 1974 [14 June 1973] 15885/74 Heading C1A Linear ammonium polyphosphates, where n=10-1000, being water-insoluble or having a controlled water-insolubility, are prepared by reacting equimolecular proportions of ammonium orthophosphate and phosphorus pentoxide with gaseous ammonia at 170-350‹ C. while continuously and simultaneously mixing, kneading and comminuting the reactants. The water-insolubility of the final product may be predetermined by the use of a certain reaction temperature, the water-insolubility increasing with increased temperature (e.g. watersolubility is 22% at 200‹ C., 13% at 210 ‹C, 9% at 230‹ C., 6% at 250‹ C. and 2-3% at 270‹ C.). The preparation may be carried out in an apparatus, Fig. 1, in which the solid reactants are delivered from reservoirs 1 and 11, via weighing means 2 and 21, through a conduit 3 to a reactor 4. The latter is a closed trough provided with a heating jacket through which a heating medium is circulated through an inlet 6 and outlet 61. Ammonia is introduced at 4 by a supply tube 7 and distributed across the surface of the reaction mass, preferably by means of a tube provided with a plurality of small perforations. Excess ammonia escapes via 9. Implements 10 (normally two double Z-shaped blades) mix, knead and comminute the reaction material. The reaction product is delivered via 14 and cooling means 11 to a sieving or screening mechanism 12. Oversize material may be returned to the reactor.