Study Of UV-heat Dual Curing Waterborne Coatings

Water-based acrylic coating is the most widely used Species in water-based paint field. The waterborne acrylic coating has many excellent properties,such as anticorrosion,alkali-resistance,weather-resistance,good film-forming,good color retention,no pollution,safety and so on.However, the water-based acrylic paint also has some shortcomings, such as water permeability, high water absorption, thermal sticky cold crisp. UV-curing is an energy saving and effective modified method. UV-curing coatings has many excellent properties.UV-curable waterborne acrylate coatings is achieved by introducing a vinyl double bond or an acrylate double bond into waterborne acrylate resin. So it has the advantage of both UV-curing coatings and waterborne acrylate coatings. In this paper, a kind of heat-UV dual curing waterborne acrylate emulsion is prepared.Using the thermal energy of heating section, not only thermal can the crosslinking reaction be achieved, but water can be removed from coating and realize the effect of the leveling coating.On this basis, with UV-light and photoinitator, further rapid crosslinking can be achieved and excellent properties of the coating material can be obtained. Emulsion polymerization process, preparation of dual curing coatings and optimization of film-forming are the focuses of this paper.The main results are as follows:(1) Acrylic emulsion with the acetyl group had been prepared by use of methyl methacrylate, methyl acrylate, ethyl acetoacetate methyl methacrylate and acrylic acid. The influence of the polymerization temperature,the amount of initiator, the amount of emulsifier and the time of dip on emulsion polymerization were discussed. The impact of the ratio of the hard and soft monomer and glass transition temperature on the properties of latex film and the effect of the functional monomer content on the stability of emulsion were also discussed.the optimum synthesis conditions of emulsion was achieved by experiment. And the emulsion with good stability(>six months), good performance was obtained. (2) A certain amount of multi-functional monomer was added into acrylic emulsion. Then the acetoacetate group and the C=C double bonds could be reacted by Michael addition reaction at alkaline and heat conditions,and the factor of UV curing cross-linking was introduced into the structure of the polyacrylic. The heat-UV dual-curing acrylic emulsion was prepared by adding an appropriate amount of photoinitiator.(3) The influence of the heat-radiation curing process,the functional monomer content and the design of glass transition temperature of emulsion on the film properties were studied.The impact of the functional monomer content on the stability of dual curing emulsion was discussed. Meanwhile, in order to identify the equilibrium point of thermal curing and UV curing, the ratio of the polyacrylic emulsion and the multifunctional acrylate was studied. The best overall performance of waterborne dual curing coating was achieved. The results show that the cross-linking film has excellent properties:the hardness 3H, alkali-resistance 24 hours,adhesion 0 grade,ethanol-resistant wipe 158 times.