Prepolymer method is the production of CPU chain reaction (prepolymer reaction) and expanding chain crosslinking reaction in two steps, and active reaction (polyols and isocyanate polymer reaction) have enough time, reaction is thorough, the prepolymer and chain reaction, uniform elastomer structure, conducive to the hard polymer between the hydrogen bond, also conducive to hard segment and soft segment and soft segment of the strong electric negative group between hydrogen bond, make the product has good mechanical properties, repeatability, this equipment is used for the above method of prepolymer reaction kettle.