Single-kettle polymerization reactor

Disclosed is a single kettle polymerization reactor for terephthalic acid or dimethyl terephthalate and dihydric alcohol to carry the discontinuous esterifying, interchange esterification and fasculation; and the single kettle polymerization reactor comprises a kettle body (2), a kettle cover (3), a long shaft (4) and the like. A clamping sleeve (1) is externally arranged on the kettle body (2); the kettle cover (3) is arranged at the top part of the kettle body (2); the long shaft (4) is arranged in the central position through hole of the kettle cover (3); a stirring mill (5) is connected at the lower end of the long shaft (4); the upper end of the long shaft (4) is connected with a speed-reducing motor (7) which is externally supported on the kettle body (2) through a mechanical seal (6); the polyester slice preparation can be finished through the PTA method technology and the DMT method technology in the same reactor; at the same time, the occupied area needed by the required reactor to prepare the polyes