Abstract: A method for the preparation of a new N-P intumescent flame retardant (NPR) was introduced,i.e.urea phosphate mother liquor and urea were droped into the reactor in the amount-of-substance ratio of 0.3~0.6,then they will react at the pressure of 0.01 MPa (ammonia atmosphere) with constant stirring speed under heating to raise temperature programmingly to 220~250 ℃ at the speed of 8 ℃/min,and after cooling,crystallization,drying,and crushing,NPR was obtained.Prepared NPR contained ammonium polyphosphate (APP) with low polymerization degree and other nitrogen and phosphorus compounds.Physical-and-chemical properties of different sizes of NPR were also studied.Finding that the NPRs with different sizes had different condensation degrees and physicochemical properties.As the particle size increased,solubility increased gradually,pH of aqueous solution and content of P₂O₅ decreased by degrees,and the content of N increased inch by inch,but all the NPR samples had the same crystal shape.

Key words: N-P intumescent flame retardant, particle size, physicochemical property