Study On The Synthesis And Modification Of Waterborne Alkyd Resin

As people’s awareness of environmental protection and energy saving is becomingincreasingly intensive, the application of environmentally friendly waterborne coatings hasbeen the development trend of coatings industry in recent years. The waterborne coatingshave greatly reduced the emission of VOCs compared with the traditional solvent coatings.The waterborne coatings are more safty, lower cost and more flexible construction.Waterborne alkyd resins are synthesized by using renewable vegetable oils or fatty acids asthe main raw materials which are easy to get and their price is cheap. The comprehensiveperformances of the paint film based on alkyd resins are good. However, the waterborne alkydresin also has a lot of weakness, such as the slow drying rate, low hardness, poor waterresistance and outdoor weatherability, etc. Therefore, the study on the synthesis andmodification of waterborne alkyd resin coatings has an important practical significance.The waterborne alkyd resin (WAR) was synthesized by using linseed oil (L.O.),trimethylolpropane (TMP), phthalic anhydride (PA), trimellitic anhydride (TMA) as the mainmaterials in this thesis. The results showed that when the oil length, excess alcohol, initialacid value, final acid value were45~50%,7~10%,7~10mgKOH·g-1,55mgKOH·g-1respectively, the resin possessed excellent hardness, flexibility and gloss.In order to improve the drying rate, hardness, water resistance and adhesion to PETsubstrate of WAR, the modification of WAR was further studied.(1) The study of epoxy resin modified WAR. The epoxy resin was added in thealcoholysis process, the ether glycol was generated by the reaction between epoxy groups andpolyols, and finally a clear, transparent epoxy modified WAR with excellent adhesion wassynthesized. The Fourier infrared spectrometer (FT-IR) showed that the epoxy groups werereacted. Gel permeation chromatography proved that the molecular weight of epoxy modifiedWAR increased significantly. Marvern particle size analyzer showed that the particle size anddistribution of the modified WAR had a certain increase. These mean that epoxy resin wassuccessfully introduced into the molecular chain of WAR. It was also found that when thedosage of epoxy resin E-20was6~10%, the resin had a good stability, and a enhancedadhesion on PET.(2) The study of toluene diisocyanate (TDI) modified WAR. The terminal hydroxyl alkydresin prepolymer was firstly synthesized by using L.O., TMP and PA, and then reacted withTDI as well as dimethylol propionic acid (DMPA) to produce the TDI modified WAR. Theinfluences of DMPA content, and NCO/OH mole ratio, ethylenediamine (EDA) content on the appearance, viscosity, and particle size of the dispersion, as well as the hardness,flexibility, luster properties of the film were discussed. The structure of the product wascharacterized by the FT-IR. Effects of DMPA content and NCO/OH mole ratio on the heatresistance of the film was also studied by Thermogravimetric Analysis (TG). The researchresults showed that TDI was involved in the reaction, the hydrophilic group COOH wassuccessfully introduced to the resin chain; DMPA content and NCO/OH mole ratio haveeffects on heat resistance of the film. when the DMPA content, NCO/OH mole ratio were7%,1.4respectively, the hardness, water resistance, gloss, flexibility of the resin were excellent.For the sake of preparing a kind of quick-drying waterborne alkyd resin coatings withgood solvent resistance and excellent adhesion on PET films, the epoxy resin modified WARwas mixed with amino resin, and waterborne alkyd-amino coatings with excellentperformance were obtained. The formulation and synthetic technology were optimized,CYMEL303(HMMM) was elected as amino resin. When the baking temperature was about160~180℃, WAR: HMMM=3:1(the mass ratio of solids), the mixed solvent H2O:propanediol methyl ether: ethyl acetate=2:1:2(the mass ratio), the coating was clear,transparent, good stability. The hardness and adhesion of film was3H, level1respectively.The cured and dried film with excellent water resistance can be obtained within8seconds at180℃. The performance can meet the requirements of practical application.