P-C bond-containing phosphorus flame retardant and preparation method thereof

The invention relates to a P-C bond-containing phosphorus flame retardant and a preparation method thereof. The structural form of the P-C bond-containing phosphorus flame retardant is shown in a formula I; and the preparation method comprises the following steps of: preparing N,N-dibenzylidene ethanediamine and hypophosphorous acid according to a ratio of 1.0: (2.5-3.5); with anhydrous DMF (Dimethyl Formamide) as a solvent, firstly adding N,N-dibenzylidene ethanediamine and then adding hypophosphorous acid under the condition of heating, carrying out heat reaction, cooling, carrying out suction filtration, washing by using deionized water 3-4 times, carrying out suction filtration again, and drying to obtain white solid which is the flame retardant N,N-bis(benzalphosphonic acid)ethanediamine. The flame retardant provided by the invention is free of halogens, good in flame retardant efficiency and wide in application range and reaches the environmental protection requirements; the flame retardant provided by the invention contains the P-C bond, and thus has higher heat stability and hydrolysis resistance than existing P-N bond or P-O-C bond containing flame retardants.