A water-soluble and low stimulation sodium bisulfite blocked isophorone diisocyanate (IPDI) has been prepared. The blocking and deblocking of the blocked IPDI is observed by hot-stage Fourier transform infrared (FTIR) spectrophotometer. The experimental results reveal that IPDI is successfully blocked by sodium bisulfite and the blocked IPDI can regenerate isocyanate groups when the temperature is higher than 80 degrees C. Differential scanning calorimetry analysis indicates that blocked IPDI deblocks initially at around 85 degrees C and reaches the maximum deblocking rate at 117 degrees C. The blocked IPDI in liquid and solid states are stable after being stored for 12 months at room temperature. The blocked IPDI is used as curing agent for waterborne hydroxyl polyurethane, which has good adhesive performance and long pot life. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 597-599, 2013