Synthesis, Characterization And Applications Of Low-temperature Self-crosslinking Acrylate Emulsion

The water-based ink has been widely used in printing and packaging industry, since more and more people pay attention to protecting the environment and keeping healthy. Polyolefin film is a common material applying in packaging industry, which has the characteristic of low polarity, and difficult to adhered. The key point to a water-based ink for polyolefin film printing is improving the adhesion of water-based ink on polyolefin film surface. In this paper, a high-performance acrylate emulsion was synthesized as water-based ink binder to improve the performance of water-based ink.Firstly, a low-temperature self-crosslinkable acrylate emulsion was synthesized by semi-continuous emulsion polymerization technology using methyl methacrylate(MMA), butyl acrylate(BA), acrylic acid(AA) and diacetone acrylamide(DAAM) as monomers and adipic dihydrazide(ADH) as crosslinker. The influences of temperature in the process of polymerization, dosage of monomer, emulsifier and initiator on t he emulsion and film performance were discussed. As DAAM content increased, crosslinking density increased and water absorption ratio decreased, while DAAM content is more than 3%, the w(DAAM) increased, crosslinking density decreased and water absorption ratio increased,slightly.Then, transmission electron microscope(TEM) micrograph disclosed spherical emulsion particles possess core-shell structure. Fourier transform infrared(FTIR) spectrogram showed that crosslinking reaction between-CO- groups of DAAM and-NHNH2 groups of ADH can occur during coating film formation at low temperature, even at room temperature. Differential scanning calorimeter(DSC) analysis indicated that glass transition temperature(Tg) of the crosslinked film is increased by 5℃. Thermogravimetric analysis(TGA) curves demonstrated that self- crosslinking reaction improves thermal stability of film.At last, the water-based ink was prepared by the emulsion and printed on PP, PE and OPP films, the properties of ink such as adhesion, water resistence, blocking resistance and so on were measured. The influence of various factors on performances of water-based ink were discussed, such as the design of Tg, dosage of crosslinking monomer, emulsifier, initiator and crosslinking agent, and drying time research in the emulsion polymerization of emulsion particles, crosslinking monomer, emulsifier, initiator, crosslinking agent.The results indicate that as w(DAAM) and n(ADH)/w(DAAM) increased, adhesion and water resistence of water-based ink show a trend of decline after the rise at first. The adhesion of water-based ink is developed with inceasing of w(AA). DAAM distributed in shell layer complete can improve the adhesion of water-based ink greately. The structure of har scale soft design can significantly improve the water-based ink adhesion. While the w(DAAM)=3%, w(AA)=3%, dosage of emulsifier and initiator is 2.4% and 0.8%, respectively, rate of monomer of core and shell is 1:9, Tg of core and shell is 40℃ and 20℃, the water-based ink with excellent adhesion and water resistence can be obtained.