Synthesis Of Waterborne Polyurethane-acrylate Modified With Epoxy Resin

With the development of environmental laws and regulations, people pay more attention to environment protection. Therefore, the use of solvent-based coatings is limited, while the exploration of waterborne counterparts becomes more and more important. Waterborne polyurethane is one kind of film formation resins with superior properties, and polyurethane emulsions could be produced through self-emulsifying in 1970s. Recent researches focus on how to modify polyurethane emulsions with superior properties. One of common ways is to add acrylic resin. Waterborne polyurethane-acrylate (PUA) produced by copolymerization takes advantages of better climate-resistance of acrylic resin and of better wear-resistance and mechanical functions of polyurethane. What’s more, it avoids their disadvantages including that acrylic resin will stick at higher temperature and become brittle at lower one, and waterborne polyurethane have the limitation of poor water-resistance and low solid content. But PUA emulsion still have deficiency in water-resistance, alcohol-resistance and hardness for high-class wood coating. That’s why epoxy resin is used to modify waterborne PUA and crosslinking is introduced in order to improve the water-resistance of waterborne PUA system as well as its resistance to solvents and rigidity.PUEA are synthesized by principal raw materials, such as toluene diisocyanate (TDI-80), polyether binary alcohol (N210), solid state epoxy resin(CYD-012), dimethylol propionic acid (DMPA) and methylmethacrylate (MMA). Polyurethane-acrylate-epoxy hybrid emulsions were prepared by mechanical mixture and copolymerization of epoxy to polyurethane-acrylate hybrid matrix respectively. The effects of the addition mode and content of epoxy on preparation process and properties of emulsion and its film have been studied. Meanwhile, some process factors, which include reaction temperature, raw material dehydration, amount of agitation, and some composition factors such as NCO/OH, DMPA content, neutralization degree , ethyl diamine have been studied. The factors influencing the preparation process of composite emulsion have been discussed including the choice of initiator and vinyl monomers MMA.Through experiments and tests it shows that the addition of epoxy was significantly aff- ected PUEA hybrid emulsion, and PUA/E hybrid emulsion by copolymerization has better performance than by the physical blend. With the increasing amount of epoxy resin, prep-aration of PUEA become more difficult, the diameter size distribution broadens, viscosity become bigger and the storage stability become poorer; the thermal stability and hardness of PUEA hybrid emulsion increases. water absorption, alkali resistance and enhance ethanol decreased. Consideration in PUEA hybrid emulsion ,epoxy is suitable for 3-4% of the mass fraction in control.The preparation of high-grade preparation PUEA composite emulsion can be used as the base material waterborne wood coatings.