Investigation On The Synthesis And Application Of Waterborne Polyurethane Adhesive

The structure and properties of polyurethane was investigated in this research. According to the result of our research, an prepolymer of polyurethane (PU) with special structure was designed and synthesized. And then the synthesized PU was dispersed into water to form anionic waterborne polyurethane(WPU) succesfully.The molar ratio of HDI to IPDI(nHDI/nIPDI) on the properties of WPU dispersion has been studied when the molar ratio of–NCO to–OH(n(-NCO)/n(-OH)) kept stable in whole investigations. And results shown that viscosity of WPU dispersion increases gradually while the particle size of WPU decreases with the molar ratio of nHDI/nIPDI increasing, so the clarity of WPU emulsion turned into higher. The Tg of WPU also decreases with molar ratio of nHDI/nIPDI increasing, while the peeling strength increases first and then reduces, and it reaches maximum when the molar ratio of nHDI/nIPDI get to 1.00.The chain extender of urea and ethylenediamine(EDA) on the properties of waterborne polyurethane was compared. Results show that the viscosity of WPU emulsion increases gradually with the increasing dosage of EDA, but the urea has no significant effect to the viscosity of emulsion. With the dosage of EDA and urea increasing, the water absorption rate of WPU film decreases gradually, and it has no significant changes when urea used as chain extender.E-44, one kind of epoxy resin, was also adopted to modify WPU. In the experiments, the molar ratio of n(-NCO)/n(-OH) and the content of DMPA was set at 0.94 and 3.3wt% respectively, while the contents of E-44 was various from 3%, 4%, 5% to 6%. Results shown that viscosity of WPU emulsion was unchanged with the dosage of E-44 increasing, and there were no significant changes in law on particle diameter of E-44 modified WPU emulsion.Basing on the works of foregoing studies, adhesives of WPU for plastic soft package and for manufacture of footwear have been synthesized and their properties were also studied.The WPU, which we synthesized for soft package, has many excellent properties, such as odorless, high solids content, low viscosity, good stability, fast drying speed(50oC,16～24h) and high peeling strength. In addition, the synthetic craft of the WPU adhesive was simple, and there were no harmful emissions and byproduct. The synthetic method was green completely. Industrial production of the adhesive of WPU for plastic soft package product has been completed.Adhesion of WPU for shoes manufacture also had been researched. Initial strength reaches 147.64N/25mm (rubber/leather), and solid content of the WPU is about 45wt%.