Study On Synthesis And Properties Of Waterborne Alkyd Resin

Waterborne alkyd resin is a polyester synthesized through ester reaction of polyols, polybasic acids and fatty acid(or fatty oils) as the main raw materials. Due to using water as solvent, the emission of volatile organic compounds(VOCs) was signicantly reduced, and it could reduce the pollution to environment and the harmness to humans’ health. However, some dawbacks of waterborne alkyd resin itself limited its development and application. Therefore, the further study on the theory and technology of waterborne alkyd resin was significantly important.In this paper, to develop a formula of waterborne alkyd resin and resolve resin performance issues, such as film drying, water-soluble, etc, relationship model between the resin properties and formulation parameters was built and waterborne alkyd resin was successfully prepared by solvent menthod and using unsaturated fatty acids, polyols and polyacids as the raw materials. The resin structure was characterized.(1) Through analysis of the synthetic material characteristics and the factors affecting the performance of waterborne alkyd resin, the results showed that using linoleic fatty acids as fatty acids, trimethylolpropane as polyols, and phthalic anhydride as polyacids was the suitable synthetic materials for waterborne alkyd resin; the oil length, hydroxyl/carboxyl molar ratio, the dosage of polyacid were several important factors that affect product performance. Besides, the additive of TDI cross-linking agent can also improve performance of waterborne alkyd resin.(2) By formulation design and calculation, the oil length(L), hydroxyl/carboxyl molar ratio(r) and alkyd resin constant(K) were choosed as the main paramrters, and a variable f, which controlled water-soluble of alkyd resin, was introduced firstly. The quantitative relationship between formulation parameters and the amount of raw materials was obtaind from the simultaneous relations of parameters.(3) In order to optimize the formulation of waterborne alkyd resin preparation, a 9-level-3-factor uniform design and regression analysis were employed to evaluate the effects of the selected variables including fatty acid content(L), hydroxyl/carboxyl molar ratio(r) and molar ratio of polyatomic acids(f) on set-to-touch time of film. A mathematical model, which was applied to predicting the film set-to-touch time of waterborne alkyd resin, was builded. The prediction model was as follows: ?Y ?189.702+738.085 L ?178.546 f.(4) According to the optimization principle of uniform design and the regression equation, the optimized formulation parameters for waterborne alkyd resin synthesis was predicated and verified as follows, i.e. L is 30%, r is 1.2, f is 2.2. The corresponding set-to-touch time was 43 min.(5) The product was characterized with FIIR and NMR, and the results indicated that the prepared waterborne alkyd resin was as expected. TGA analysis showed waterborne alkyd resin film had good heat resistance because there was no significant weight loss below 250°C. DSC analysis showed that the prepared waterborne alkyd resin had two glass transition temperature of-23.93°C and 41.34°C, the glass transition temperature of the main film-forming for waterborne alkyd resin is-23.93°C which below ambient temperature, so that the prepared resin can be cured at room temperature, but a lesser hardness. Particle size distribution analysis showed that the average particle size of the waterborne alkyd resin was 16.79 nm, indicating good water-dispersity resin was prepared.(6) Physical and chemical resistance properties of waterborne alkyd resin samples A1, A2, and A3 were measured. The results indicated that all the films had good water-solubility and dispersion stability; all the films of the resins exhibited excellent adhesion and resistance to alkaline, but poor resistance to water, acid and salt solution.