Synthesis Of Waterborne Polyester-Acrylic Resin Hybrid

With the continuous improvement of environmental protection policies in the coatings industry,the development of environmentally friendly coatings which reduce emissions of volatile organic compounds(VOCs)have become the main direction of the development of the domestic coatings industry.Waterborne coatings have the advantages of low pollution,relatively mature technology and wide application range.Waterborne polyester-acrylic resin hybrid has both excellent performance,which has the advantages of good water resistance,high hardness,high surface gloss and good weather resistance.It is one of the main research directions of waterborne automobile surface coatings.The unsaturated polyester(UPR)was synthesized by melt polycondensation using neopentyl glycol(NPG),2-butyl-2-ethyl-1,3-propanediol(BEPD),trimethylolpropane(TMP),phthalic anhydride(PA),adipic acid(AD)and Maleic anhydride(MA)as raw materials,dibutyltin oxide as catalyst and phosphorous acid as antioxidant.Under the Inducing of benzoyl peroxide(BPO),the hydroxyl terminated polyester acrylate hybrid resin was synthesized by free radical grafting polymerization of UPR and acrylic monomer such as methyl methacrylate(MMA),styrene(St),2-hydroxyethyl methacrylate(2-HEMA),butyl acrylate(BA),and acrylic acid(AA)with an unsaturated polyester,and neutralized by agent.Then,the waterborne polyester acrylic-amino baking varnish was prepared by mixing with the curing agent of hexamethoxymethyl melamine(CYMEL303).The resin aqueous dispersion and coatings was characterized by Fourier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TG),gel permeation chromatography(GPC),polarization curve and the test of film performance.In this paper,the effects of polymerization process,molecular weight of polyester,amount of acrylic acid(AA)and 2-butyl-2-ethyl-1,3-propanediol(BEPD),hybridization ratio and glass transition temperature of the acrylic resin on the properties of resin aqueous dispersion and coatings were discussed.The results show that the resin prepared by solvent-free bulk polymerization has good stability,with the molecular weight of unsaturated polyester is about 1500 and the hydroxyl value is 85,the amount of acrylic acid is 12%,the amount of 2-butyl-2-ethyl-1,3-propanediol is 12%,the glass transition temperature of the acrylic monomer is 19.8 °C,the hybridization ratio is 1:0.6 and the degree of neutralization is 105%.With hexamethoxymethyl melamine(CYMEL 303)as curing agent,the ratio of the aqueous resin and amino curing agent is 3:1,curing temperature of 150 °C and curing time of 30 min,the obtained coating has the advantages of high gloss,high hardness,good flexibility and impact resistance,and the performance degradation is not obvious after the heat storage stability test.Waterborne metal baking paint was prepared based on self-made water-based polyester-acrylic resin hybrid.The research has shown that when the pigment base ratio is 0.8:1,the amount of the aqueous dispersant TEGO 750 is 0.5%,the amount of the wetting agent TEGO Wet 270 is 0.5%,the amount of the antifoaming agent BYK-028 is 0.3%,and the dosage of BYK-333 is 0.3%,the prepared water-based metal baking paint has the best performance and will meet the application of automotive surface coating.