Synthesis of Blocked Polyisocyanates

Blocked polyisocyanates with low release temperature(110～120 ℃) were synthesized with methyl ethyl ketoxime as blocking agent.The effects of the mole ratio,reacting temperature and time on blocking reaction for prepolymer were studied.The release reaction of blocked prepolymer are discussed and release temperature are determined.The IR spectra for prepolymer,blocked prepolymer and blocked prepolymer release by heating are compared.