The closed rubber mixer is abbreviated as the internal mixer. In order to adapt to the application of mixed waste plastics, the waste plastic internal mixer has been developed. An internal mixer is a machine that is equipped with a pair of rotors with a specific shape and relatively rotating, which can intermittently plasticize and mix polymer materials in a closed state with adjustable temperature and pressure. It is mainly composed of a mixing chamber and a rotor, rotor sealing device, feeding and pressing device, unloading device, transmission device and machine base and other parts.