Synthesis And Application Of The Water-Soluble Blocked Isocyanate Monomer

The water-soluble blocked isocyanate blocking technology is of great significant to the further development and application of the single component adhesives. Due to the advantages of low unblocking temperature, low cost and almost no pollution.The blocking agent of sodium bisulfate is applied to block the-NCO groups of isophorone diisocyanate(IPDI) and hexamethylene diisocyanate (HDI). Based on the works on the IPDI/HDI with sodium bisulfate, it also well discussed the blocking technology of IPDI/HDI with sodium bisulfate and the effects of each technological parameters on the blocking reaction. After evaluated the effects of each key parameter on the blocking percentages and stabilities of each reactants, the best blocking technology for IPDI/HDI was optimized. The key parameters evaluated were charging method, combined solvent, blocking time and temperature, content of solvent, NaHSO3/NCO mole ratio, and initial NaHSO3 concentration.The thermal decomposition process and deblocking reaction of water-soluble blocked i'sophorone diisocyanate(IPDI) was studied by Thermal Gravimetric Analysis(TGA) and Differential Scanning Calorimetry (DSC) analysis. The characteristic peaks of the isocyanante groups at the different temperature were observed by Fourier transform infrared spectroscopy (FTIR). The results of the TGA and the FTIR showed that the degradation stage was the deblocking reaction of blocked adduct. The model of Friedman-Reich-Levi (FRL) and Flynn-Wall-Ozawa (FWO) were employed to investigate the apparent activation energy values respectively, and also deduced the reaction order (n) and the pre-exponential constant. Based on the double equal-double step method, it was analyzed by the apparent mechanism function that the process of deblocking accorded with the Jander equation, which indicated that reactive mechanism is three-dimensional diffusion.Based on the deblocking temperature conditions of blocking IPDI, the paper further observed the modified application in the waterborne polyurethane and acrylic emulsion adhesive. The results indicated that the single component adhesives which were modified by blocked IPDI as curing agent have good adhesive performance and long pot life.