Preparation And Properties Of Self-emulsifying Epoxy Resin Aqueous Dispersion

Owning to its excellent physical and mechanical properties and processing properties caused by its special molecular structure, epoxy resin was widely used in the fields of coatings, adhesives and composite materials, etc.But solvent epoxy resin system would volatilize a lot of Volatile organic compounds (VOC) which are harmful to the environment and human health. So waterborne epoxy resin system in which water is a substitute for solvents has been receiving more and more recognition and becoming hot spot in research and development in recent years.Chemical modification was adopted in this paper. The low molecular weight epoxy resin was modified by polyether through the way of introducing a fair mount of hydrophilic polyether segment into the epoxy resin molecular structure. Then the chain extension was occurred in order to form high molecular weight amphiphilic polymers. The modified epoxy resin has the function of self-emulsifying, so epoxy resin aqueous dispersion could be obtained by phase reversionThe effect of the content of prepolymer, the molecular weight of PEG, the ratio of epoxy group and phenol hydroxyl (nEP/nOH), catalyst dosage on properties of the emulsion were studied. The basic experimental formula and technological condition were determined. The emulsion structure and property were investigated by Fourier infrared spectrum (FT-IR) and Gel permeation chromatography (GPC).In the base of the basic experimental formula and technological condition, several remarkable factors were studied through orthogonal design. The optimal process were generated. First, the ring opening polymerizations of epoxide based monomers (E-51) with polyethyleneglycol (PEG-8000) were carried out to synthesize the epoxy resin oligomer with double epoxy end group. The catalyst selects to the boron trifluoride diethyl etherate (BFEE), the amount used for the reactant weight0.1%, the addition of methyl isobutyl ketone (MIBK) was18%,the reaction temperature was120℃,the reaction-time was4h; In the second step, the content of prepolymer was18%, the ratio of epoxy group and phenol hydroxyl (nEP/nOH)2.25:1, the catalyst was triphenylphosphine with the consumption of0.15%of epoxy resin, the reaction temperature was16O℃-180℃, the reaction-time was1h. To the extent, the self-emulsifying epoxy resin was synthesized, and then the epoxy resin aqueous dispersion could be obtained by phase reversion when the deionized water with the use of70%of the total mass was dropwise added into.Relative performance test to the emulsion and contrastion with the like product of Shell, the internationally known company were made. The results showed that many the properties of the self-prepared emulsion had reached or approached those of Shell’s.At last, waterborne epoxy hardener and water-based additives were choosed to compound waterborne epoxy varnish, and the film was got, the curing mechanism and film forming process were studied. The physical and chemical properties of the film were detected and found that it had excellent adhesion, good flexibility, high impact and damage tolerance, low hardness and excellent water resistance which showed very high use value and bright future.