Method for preparing flame-retardant polyethylene glycol terephthalate

The invention relates to a method for preparing flame-retardant polyethylene glycol terephthalate. The method comprises the following steps of: adding dimethyl terephthalate and ethylene glycol into untreated or uncalcined hydrotalcite for reaction according to a molar ratio of 1.0:1.5-2.2; controlling the reaction temperature to between 160 and 220 DEG C; and performing high-vacuum polycondensation at the temperature of between 260 and 290 DEG C and under the pressure to less than 150 Pa to obtain a polyethylene glycol terephthalate material with flame retardancy, wherein the amount of the hydrotalcite accounts for 0.1 to 10.0 percent of the weight of the dimethyl terephthalate; the particle size is 100nm to 50 mu m; and the calcination temperature of a hydrotalcite compound is between 250 and 700 DEG C. A polymerization result shows that a small amount of hydrotalcite makes the flame retardancy of the polyethylene glycol terephthalate excellent, and also has excellent catalytic effect, and the negative effect on the important processing properties of polyethylene synthesis such as molecular weight or the transparence of a finished product cannot change.