Study On Synthesis And Application Of Etherified Melamine-formaldehyde Resin As Cross-linker

Expoxy resin is one of the most important resin which is widely used because of its high adhesive and good chemical resistant. But epoxy resin in common use is indissolvable in water, Yang xunlan of our lab invented a new method to resolve this question, that was : epoxy resin can be modified by acrylic acid, then be neutralized to water dispersion. This kind of aqueous coating has excellent performance, but the biggest disadvantage is that the temperature of coating film is high when baking, and the brittleness of film is big. From a lot of literatures, we find that, etherified melamine-formaldehyde resin is usually used as a cross-linking agent, then the temperature of coating film will be fell down and the brittleness could be improved.This paper deals with the polymerizing conditions of which is used as a cross-linker agent, with the action of alkalescent catalyzer and acidic catalyzer, formaldehyde and methanol are added into melamine, then etherified melamine-formaldehyde resin formed can be dissolved in water and alcohols. This experiment is divided into two steps: the hydroxymethylation reaction -- melamine resin was produced through the addition reaction using melamine and the formaldehyd; the etherification reaction - etherfied melamine resin was obtained by methyl alcohol used as etherifying agent. Then through the optimization of single factor, reaction time, temperature, catalyst, the pH were respectively carried on. The resin of low viscosity, low formaldehyde and good water-soluble was got through the phenomenon judgment, the viscosity, the percentage of the formaldehyde dissociate and methylol respectively. Finally, the reaction principle of cross linker is proved by infra-red spectrum(IR). The stabilization of cross-linking agent is also proofed by testing the environment of solution and stability of dilution.The curing regularity of film coatingis investigated too. A series of coating films of different curing ratio, curing temperature and curing time were prepared. The curing regularity was determined by testing resistance to water and degree of cross linking of the coating film. The condition of curing is also defined: the ratio of melamine resin and epoxy-acrylic resin is 1:3, the temperature is 130.degree.C,the time is 25min. The performance index such as hardness, adhesive power, flexility, resistance to water and corrosion resistance are also tested. It is proved that the cross linker could fall down the curing temperature and meliorate the brittleness. The curing film has splendid performance, especially in adhesive power, flexility and corrosion resistance. So it is a suitable cross linker to aqueous coating...