Preparation Of Two Kinds Of Novel Mannich Modified Waterborne Epoxy Curing Agent

Water-borne epoxy resin plays a more and more important role in the coatings asthe development of demands on the environment-protection. Epoxy curing agentwhich is an important element of epoxy resin can not satisfy with technology demandof coating, although it has been developed in the past decades. It is important toresearch water-borne epoxy coating which shows good mechanical properties andwater resistance.Two novel water-borne epoxy curing agents were synthesized in the paper. Theproperties of the cured polymers were investigated by several methods. Therelationship of these properties of the cured polymers and the structure of the epoxycuring agents were studied.Mannich-amine was synthesized by using phenol and formaldehyde to modifyDETA, and liquid epoxy resin (EP) and polyethylene glycol (PEG) as modifier. A novelepoxy curing agent was obtained by phase inversion method. The reactiontemperature and reaction time were confirmed. The influences of molecular weight ofPEG, PEG/EP ratio and polyethylene segment content on the stability and particle sizeof the dispersion were studied. The results exhibit that the prepared epoxy curingagent owns high hardness, good water resistance and long pot-life of the water-borneepoxy system.The emission of formaldehyde in the Mannich reaction is a pending problem andpresents a serious threat to public health. To obtain the Mannich structure in thecuring agent, it is benefit to use exchange reaction which is a conveniently operativeand formaldehyde-free reaction. A series of water-borne epoxy curing agents weresynthesized in this paper. The reaction temperature and reaction time of exchangereaction were discussed. The influences of different raw materials ratios andpolyethylene segment content on the properties of cured films were studied. Theobtained curing agents were cured with epoxy resin to get films at the premise ofgetting a stable waterborne epoxy curing agent. The properties of cured films weretested. The results shows the films have superior comprehensive properties.