NEW PREPARATION PROCESSES OF PHASES II AND V AMMONIUM POLYPHOSPHATE AND THEIR USE AS FLAME RETARDANTS

Abstract

Ammonium polyphosphate with crystal phases of II and V was prepared by heating a mixture of ammonium orthophosphate and urea under atmospheric condition of wet ammonia at 280 to 305°C and 340 to 350°C, respectively. Form II APP prepared under the reaction condition had a larger average particle size than 10 μm and an average particle size of form V ammonium polyphosphate was 2 to 4 μm. Form II APP with a small average particle size of 2 to 4 μm was produced by heating phase I APP at the same reaction temperature under atmospheric condition of alternate gas flow of wet ammonia and dry air. The solubility of APP with the crystal phases of II and V was very low and the APP worked very well as flame retardants.