Preparation method of melamine polyphosphate with high purity and high polymerization degree

The invention provides a preparation method of high-purity and high-polymerization-degree melamine polyphosphate, and relates to the field of melamine polyphosphate production. The preparation method of the high-purity and high-polymerization-degree melamine polyphosphate mainly comprises the following steps: mixing melamine and an anti-blocking agent, spraying, adding phosphoric acid for reaction, vacuumizing, and continuing the reaction to obtain melamine-deficient melamine polyphosphate. Finally, melamine is supplemented and added for continuous reaction, and melamine polyphosphate with high purity and high polymerization degree is obtained. According to the method, the defects in the prior art are overcome, the reaction energy consumption is effectively reduced, the yield is improved, the stability of the molar ratio of melamine to phosphoric acid is also guaranteed, meanwhile, the resistance during polymerization is reduced, the polymerization degree of the product is effectively improved, and final resi