Hyperbranched reactive flame retardant, preparation method and rigid polyurethane foam

The invention discloses a hyperbranched reactive flame retardant, a preparation method and rigid polyurethane foam. The reactive flame retardant is prepared by the following steps: by taking 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as a raw material, firstly reacting with maleic anhydride (MA), and then reacting with diethanol amine under the condition that DMF is taken as a solvent, so as to obtain an intermediate DOPO-MAN; and finally, enabling the intermediate DOPO-MAN to react with epoxypropane to prepare the reactive flame retardant DOPO-MAH. The flame retardant and the polyester polyol are uniformly mixed, and then the catalyst, the foaming agent, the surfactant and the isocyanate are added to finally prepare the flame-retardant modified polyurethane rigid foam. The synthesized flame retardant DOPO-MAH does not contain halogen, does not release formaldehyde, and does not cause pollution to the environment. Due to the hyperbranched structure, the mechanical property of the foam is also