Preparation method of phosphorus-containing flame-retardant thermoplastic polyurethane elastomer

The invention relates to a preparation method of a phosphorus-containing flame-retardant thermoplastic polyurethane elastomer. The phosphorus-containing flame-retardant thermoplastic polyurethane elastomer comprises the following raw materials in percentage by weight: 65%-80% of phosphorus-containing polyester diol, 11%-30% of TDI, 1.7%-3.7% of 1,4-butanediol, 1.0%-2.5% of glacial acetic acid and 0.2%-0.3% of dibutyltin dilaurate. The preparation method comprises the following preparation steps of by taking the phosphorus-containing polyester diol subjected to dehydration treatment and the TDI as monomers, dripping the TDI at formula ratio to a reactor added with the phosphorus-containing polyester diol, then adding dibutyltin dilaurate at the formula ratio, and carrying out heat preservation at 85 DEG C; measuring the content of NCO contained in a prepolymer every 0.5 hour by using a di-n-butylamine method, adding 1,4-butanediol and glacial acetic acid used for end capping in steps after the content of the NCO is stable and invariant within 30 minutes, reacting for 0.5 hour, then pouring into a preheated self-made mould, placing into a drying box at 110-120 DEG C, and curing for 6 hours to obtain the phosphorus-containing flame-retardant thermoplastic polyurethane elastomer.