Study On Waterborne Acrylic Modified Alkyd Resin Composite Emulsion And Coating

Water-based alkyd-acrylate composite emulsion with water as a dispersion medium,is non-toxic and environmentally friendly,and has the advantages of two kinds of resins,making it have good application prospects in the field of coatings.However,the composite emulsion prepared by the conventional emulsion polymerization method has a low content of alkyd resin,and it is difficult to make use of the complementary advantages of the resins.Therefore,a mini-emulsion polymerization method was used to prepare a high alkyd water-based alkyd-acrylate composite emulsion to meet the application of high-grade waterborne wood paints and industrial topcoats in this study.Linseed oil,soybean oil,pentaerythritol,and phthalic anhydride were used as raw materials to prepare alkyd resins through alcoholysis and esterification reactions.The effects of different factors on the synthesis process and coating film properties of alkyd resin were investigated.The optimal synthesis process was determined as follows:the acid value was 10-15 mg·KOH·g^-1,the oil degree was 50%,the amount of Lithium hydroxide（Li OH）was 0.04%,the decomposition temperature was controlled at 240℃,the esterification temperature was controlled at 210℃,and the amount of Maleic anhydride（MA）was 8%.FT-IR and ¹HNMR confirmed the chemical structure of the synthesized alkyd resin.GPC analysis showed that the molecular weight distribution was narrow when the MA content was 8%.Based on the preparation of alkyd resin,a water-based alkyd-acrylate composite emulsion with high alkyd content was prepared by mini-emulsion polymerization.The process conditions affecting the stability of the composite emulsion were optimized to determine the optimal synthesis process:the ultrasonic power of the system was 540 W,the ultrasonic time was 15 min,the amount of Octadecyl methacrylate（SMA）was 0.6%,the amount of emulsifier of PT400S/RS-710 was 2.5%,and the compounding ratio was 2:1.The reaction temperature was determined to be 65℃,the reaction time was 6 hours,1%Potassium persulfate（KPS）/Sodium bisulfite（NaHSO₃）redox initiation system was used,the ratio of hard and soft monomers was Methyl methacrylate（MMA）:Styrene（St）:Butyl acrylate（BA）=0.9:0.6:1,the amount of functional monomer Acrylic acid（AA）was 4% and the ratio of AA/N-methylol acrylamide（N-MA）was 1/0.8.The comprehensive performance of the prepared composite emulsion was good.The organic combination of alkyd resin and acrylate resin was confirmed by FT-IR.The results of TEM and laser particle size analysis showed that the composite emulsion was regular spherical with an average particle size between 180-240 nm and a narrow particle size distribution.No cohesive agglomeration phenomenon was observed.TGA analysis showed that the thermal stability of the prepared alkyd acrylic emulsion was enhanced.Aqueous alkyd-acrylate composite emulsion prepared by mini-emulsion polymerization was used as the base resin to prepare an aqueous coating.The curing film-forming properties of the composite emulsion were studied.FT-IR results showed that both the double bond group and the reactive group in the cured resin were crosslinked.DSC and TGA curves showed that the thermal stability of the composite coating increased with increasing alkyd resin content.SEM analysis showed that the alkyd acrylate composite emulsion was successfully compounded without micro phase separation.Coating performance tests showed that as the amount of alkyd resin increased,the thermal stability,water resistance,gloss,and corrosion resistance of composite coatings increased.In addition,a phosphate ester emulsifier was used to form a passivated oxide layer with the metal substrate,which further improved the corrosion resistance of the coating.The developed water-based alkyd-acrylate composite emulsion was used to prepare a varnish.The coating flexibility was measured to be 1 mm,impact resistance was 50 Kg·cm,adhesion was level 1,gloss was 58 and water resistance was 168 hours.The coating’s salt spray resistance can reach 300 h.These results indicate that the composite emulsion has good application prospects in waterborne wood paints and industrial topcoats.