Production of ammonium polyphosphates from melamine phosphates

摘要

Ammonium polyphosphates are prepared by a process which comprises heating melamine orthophosphate prepared from impure wet-process phosphoric acid in a stream of gaseous ammonia at a temperature between 150 DEG C and 210 DEG C to produce a mixture of melamine and relatively pure short-chain ammonium polyphosphates. The solid product is extracted with water to remove the ammonium polyphosphates and free the insoluble, crystalline melamine for recycle. Thus, the only starting materials consumed in the process are phosphoric acid and ammonia.