The invention relates to fire retardants, and in particular relates to a
halogen-free
active fire retardant and a preparation method thereof. The method comprises the following steps: under the protection of
nitrogen, sequentially adding reactants, namely N-hydroxyethylaniline, 4-hydroxybenzaldehyde and a
solvent, into a container equipped with a condensate return
pipe and a
magnetic stirrer; after a heating reaction, adding DOPO to continue the reaction to obtain a light blue
solid deposit; and cooling the deposit, keeping the deposit standing, pouring out the upper-layer
solvent, washing the deposit with a
solvent, and
drying the deposit to obtain the
halogen-free
active fire retardant. Or the method comprises the following steps: under the protection of
nitrogen, sequentially adding the reactants, namely N-hydroxyethylaniline, 4-hydroxybenzaldehyde and a solvent, into a container equipped with a condensate return
pipe and a
magnetic stirrer; after a heating reaction, adding DOPO to continue the reaction to obtain a light blue solution; and concentrating the solution, and precipitating the solution with a precipitator to obtain the
halogen-free
active fire retardant. The preparation method is simple, and the halogen-free active
fire retardant contains a plurality of kinds of active groups, is well compatible with a matrix and has a good halogen-free
flame-retardant property.