Preparation Of Hydrophobic And Oleophilic Waterborne Epoxy Emulsion And Its Application To Water/Oil Separation Filter Paper

In recent years, the rapid growth of automobile production produces a vast automotiveaftermarket repair and maintenance market for auto parts enterprises. Filter is a veryimportant way to avoid dirty and contamination of engine lubrication. Oil filter, which is inthe engine lubrication system, plays a key role in preventing harmful impurities from clean oilsupply for engine, and keep lubrication cooling effectively and cleaning, thus prolong the lifeof engine. The quality of oil will directly affect the work of engine. Therefore, it is essential touse the high-quality oil for the car. Engine oil’s temperature is generally from0to300oC.With the dramatic change in temperature, the concentration of oil will correspondingly change,which will affect the flow of oil filter. High-quality oil filter paper should separate impuritieseffectively while maintaining adequate flow property of the oil, under the condition ofdifferent temperature. It is required that the oil filter paper has special properties, such asstable ventilation rates, high stiffness and high solvent resistance, etc. The most damage to oilis water. The normal content of water in oil should be below0.03%. When the water contentis more than0.1%, the oil additives （anti-oxidants, clean dispersant） will fail to work, leadingto the deterioration of lubricating oil, viscosity decreasing, and mechanical parts rusty, evenserious mechanical accidents. Therefore, the filter paper should also have a good hydrophobicand oleophilic to prevent water resulting in damage engine.Compared to other separation methods, coalescing separation method has manyadvantages such as low cost, low energy consumption and high efficiency, which makescoalescing separation method the best method used in engines. By taking advantage of thedifferent surface tension between water and fuel oil, the filter cartridge made of porous filterpaper with excellent superhydrophobicity and superoleophilicity properties allows the fuel oilto penetrate through while water droplets are held up and therefore oil/water separation can beachieved. Filter paper made of natural fiber is the most commonly separation medium becauseof its unique advantages such as low density, low cost and small volume, but it can not satisfythe separation environment by itself. So in this paper, we aim at the preparation of one kind ofan impregnating emulsion with excellent mechanical strength and superhydrophobic /superoleophilic properties and therefore can be used as oil/water separation medium. Inorder to achieve this goal, our studies focus on the following aspects:First, the cationic waterborne novolac epoxy emulsion was synthesized for oil filterpaper. Hydrophilic groups were introduced into a multifunctional bisphenol-A novolac epoxyresin （NEP） by chemical modification. The modified NEP was neutralized to form waterborneepoxy resin and finally to realize emulsification by means of phase inversion. The structure ofthis modified NEP with different ring-opening rate was characterized by Fourier TransformInfrared Spectroscopy （FTIR）. The electrical conductivity and transmission electronmicroscope （TEM） were used to examine the stable and microscopic properties of waterbornebisphenol-A novolac epoxy resin emulsion （WNEP）. The dynamic laser scattering dataindicate that the particle size and distribution performance of WNEP emulsions （greater than15%ring-opening rate） are better than that of WNEP （10%ring-opening rate）.Polyamido-amine8536was the curing agent which was mixed with prepared WNEP to formthe impregnating agent for oil filter paper. Several samples of oil filter paper wereimpregnated by the prepared WNEP latex and other waterborne emulsions respectively, andthe mechanical properties and surface microstructure of them were determined by bendingstiffness test, bursting strength test and field emission scanning electrons microscope （SEM）.The results showed that the oil filter paper impregnated by the prepared WNEPemulsion had better bursting strength, stiffness and air permeability properties than others,including polystyrene-acrylate emulsion and bisphenol A epoxy emulsion.Secondly, the anionic waterborne epoxy resin emulsion was synthesized based onbisphenol-A novolac epoxy resin （NEP）. The modification agents were benzoic acid （BA） andmaleic anhydride （MA）. The waterborne bisphenol-A novolac epoxy （WNEP） emulsion wasprepared by phase inversion emulsification technique, and was applied to oil filter paper asimpregnating agent. The chemical structure and surface chemical composition of the WNEPwas characterized by infrared spectroscopy （FT-IR） and X-ray photoelectron spectroscopy（XPS）. The granularity measured instrument and transmission electron microscope （TEM）were used to examine the emulsion particle dispersion and microscopic properties of WNEP emulsion. The thermal degradation of WNEP with different ring-opening rate andimpregnated filter paper were studied by thermogravimetric analysis （TGA）. The contactangle between the impregnated filter paper surface and water was measured by static contactangle test. It was observed that WNEP with35%ring-opening rate showed good results, andit could significantly improve the thermal stability and water resistance of oil filter paper.A superhydrophobic and superoleophilic coating for oil filter paper was synthesizedbased on waterborne bisphenol-A novolac epoxy emulsion. The benzoic acid （BA） and maleicanhydride （MA） were modification agents in order to give the epoxy resin hydrophilic groups（carboxyl） and C=C double bonds. And the fluorinated waterborne epoxy emulsion wasprepared by free radical solution polymerization of dodecafluoroheptyl methacrylate （DFMA）monomer. The covalent bound low free energy fluorinated chains in the monomer reduce thesurface energy of solidification polymers sufficiently to give rise to superhydrophobicbehavior while conserving superoleophilic. Surfaces prepared shows a sticky property, whichexhibits a static water contact angle of152degrees for a5μl droplet that does not slid off evenwhen the sample is held upside down. Surface wettabilityis governed by both the chemicalcomposition and the geometric structure. For fabric surfaces, they have the naturalmicrometer-scale roughness coming from the fibers themselves. So we need to create micro-and nano-scale hierarchical structures on the fibers in order to reduce the contact anglehysteresis.Nano SiO₂-OH was prepared by St ber sol-gel method with TEOS as precursor, ethanolas solvent and ammonia as catalyst. After that, the MTES was used as coprecursor. Thehydrophobic SiO₂-CH₃particles were obtained via hydrolysis with hydrophobic methylcovered the SiO₂-OH. The morphologies of SiO₂-CH₃particles in the different self-assembleaging processes were observed and analyzed by TEM, SEM and AFM, and the SiO₂-CH₃filmwith5days aging time has the best micro-and nano-scale hierarchical rough structure. Themixture of fluorine waterborne epoxy resin emulsion and above prepared raspberry-like SiO₂particles were then applied to the filter paper. When the SiO₂content reaches25.0wt%, thefilter paper shows superhydrophobic properties with contact angle hysteresis lower than10°. The filter paper also has a good burst strength, stiffness, and air permeability.The oil/water separation performance of the above mentioned four kinds of impregnatedfilter paper were studied. The results showed that the oil-water separation efficiency isincreased as the increase of the water contact angle. Especially for the impregnated filterpaper with a small contact angle hysteresis by impregnation of the mixture of fluorinewaterborne epoxy resin emulsion and raspberry-like SiO₂particles, the efficiency of oil-waterseparation was improved probably due to the easy collision among emulsified water droplets.The results also show that the above emulsion demonstrated slightly low mechanicalproperties than the aqueous cationized epoxy resin emulsion, but it confers the filter papersupehydrophobic and superoleophilic characteristics, that improve the oil/water separationefficiency of the filter paper. This synthetic emulsion is simple and convenient asimpregnating agent for filter paper, which can be considered as a suitable candidate forvarious of substrates such as cotton textiles, E-glass and artificial fiber, and so on.