The invention relates to a method for synthesizing a monomolecular
phosphorus-
nitrogen expansion
flame retardant, which is characterized by: reacting
pentaerythritol and
phosphorus oxychloride at 80-120°C for 2-12 hours, adding the first
solvent during the reaction, and the reaction ends After cooling, filtering, washing, and
vacuum drying for 12-24 hours to obtain a white
solid, the white
solid is 1-oxo-4-
hydroxymethyl-1-phospho-hetero-2,6,7-trioxabicyclo [2, 2, 2]
octane (PEPA); then add the white
solid (PEPA) into the second
solvent, stir rapidly to dissolve it, then add
isocyanate substances dropwise, and add the catalyst dropwise at the same time, stirring continuously, the reaction The time is 1 to 12 hours, the
reaction temperature is 20 to 100°C, the solution changes from clear to turbid, the product is poured into
ice water, an appropriate amount of inorganic acid is added dropwise, the pH value is adjusted to be acidic, a white solid is precipitated, and then washed with a washing
solvent for 3 The filtered product was vacuum-dried to obtain a white or light yellow solid with a yield of 90-96%. It has the advantages of no
halogen, non-
toxicity,
environmental protection, good application prospects and the like.