Preparation method of polylactic acid and product thereof

The invention discloses a preparation method of polylactic acid and a product thereof, and the preparation method comprises the following steps: pre-dewatering lactic acid under the condition of a closed system to obtain a dewatered lactic acid raw material; the method comprises the following steps: physically blending a dehydrated lactic acid raw material and a tin catalyst at room temperature, and stirring and reacting for 2-24 hours at the temperature of 80-130 DEG C and the pressure of 0.01-0.08 MPa; the pressure is reduced to 2-300 Pa, the temperature is increased to 150-190 DEG C, stirring reaction continues to be conducted for 24-36 h, and an obtained viscous homogeneous solution is purified and dried to obtain a polylactic acid product. The invention provides the preparation method of the polylactic acid, the polylactic acid is formed by one-step direct melt polycondensation through regulation and control of the catalyst and the process, and the method for synthesizing the polylactic acid from the lac