Preparation method of polyurethane resin

A preparation method of a polyurethane resin, comprising:

• placing a liquid polyamine compound in a continuous reaction system and circulating the liquid polyamine compound in the continuous reaction system, wherein the continuous reaction system comprises:
• a collection tank used to house the liquid polyamine compound, the solid bis(cyclic carbonate), and the solid catalyst;
• and
• a microwave reactor comprising a reaction chamber and at least one magnetron, wherein the reaction chamber has an inlet and an outlet, the inlet and the outlet are respectively coupled to the collection tank, and the heterogeneous mixture receives a microwave generated by the at least one magnetron in the reaction chamber to be heated;
• placing a solid bis(cyclic carbonate) and a solid catalyst in the continuous reactor system to mix the solid bis(cyclic carbonate), the solid catalyst, and the liquid polyamine compound to form a heterogeneous mixture;
• and
• heating the heterogeneous mixture in the continuous reaction system in a microwave manner, such that the heterogeneous mixture reacts to form a polyurethane resin.