Phosphorus-nitrogen flame retardant and preparation method thereof

The invention provides a phosphorus-nitrogen flame retardant and a preparation method thereof. The preparation method comprises the following steps of: (1) adding 2,2-dihydroxytoluene-3-nitryl-1-propyl alcohol into a reaction container filled with a solvent, adding an acid-binding agent, and dispersing uniformly with the stirring speed of 200-300rpm; (2) dropwise adding the solvent dissolved with phosphorus oxychloride into the reaction container, after dropwise adding, controlling the temperature at 0-80 degrees centigrade, and reacting at constant temperature for 5-10h, wherein the dropwise adding speed is 0.5-1ml/min, the stirring speed is 200-500rpm; and (3) distilling the reactant of the step (2), recycling the solvent, washing the residue repeatedly by de-ionnized water, filtering, drying the obtained solid for 4-6g at 30-50 degrees centigrade, so as to obtain the phosphorus-nitrogen flame retardant. The flame retardant provided by the invention excludes halogen, the flame retardant efficiency is high, the application range is wide, and the environmental requirement is met.