Preparation And Properties Of Air-drying And Cationnic Waterborne Coatings Of Acrylic/Alkyd Resin

Alkyd resins are polyester resins that are derived from natural materials.It has many advantages,such as low price,coating fullness,high gloss,good leveling,strong adhesion and the stable synthesis process.However,the disadvantages are that coating film drys slowly and hardness is low.Meanwhile,the water resistance and the weather resistance is poor,and the coating contains high content of organic solvent.Therefore,developing the high performance environment-friendly alkyd paint is very necessary.In this paper,acrylic/alkyd resin hybrid emulsion was prepared by solution phase-reversed emulsion polymerization to improve the alkyd resin performances in the drying speed,hardness,weatherability,water resistance and other aspects.The waterborne acrylic/alkyd resin coating was prepared by using the hybrid emulsion as the film forming material,adding white powder slurry and coating aid.By analyzing the influence of various factors on the performance of hybrid emulsion and coating,the ratio between the synthetic hybrid emulsion and the components of the coating was optimized.(1)Acrylic resin modified alkyd resin hybrid emulsion: the acrylic/alkyd resin hybrid emulsion was synthesized by using dimethylaminoethyl methacrylate(DM),methyl methacrylate(MMA),butyl acrylate(BA)and alkyd resin(BTS-SZ)as raw materials.The effects of polymerization conditions,acrylic monomer ratio and the ratio between the acrylic resin and the alkyd resin on monomer conversion,grafting rate,hybrid emulsion particle size,rheological behavior,stability,viscosity,polymer glass transition temperature,flatness of coating surface,water absorption,gloss,drying time and mechanical properties of the coating were studied.The results showed that when the monomer dropping time was 2 h,the polymerization temperature was 85 ℃,the dosage of hydrophilic monomer DM was 4.76%,the ratio of m(MMA)∶m(BA)was 18:2,the amount of BTS-SZ was 55%,the content of initiator was 1.62% and theco-solvent was propylene glycol methyl ether,the coating has good drying performance,hardness,gloss,adhesion and impact resistance,but the emulsion storage stability and water resistance are poor,so it needs further modification.(2)Octadecyl acrylate(SA)participation system modification reaction: the acrylic/alkyd resin hybrid emulsion was prepared by using DM,MMA,BA,BTS-SZ and SA as raw materials.A series of hybrid emulsions was synthesized by adjusting the amount of SA,the performance of the hybrid emulsion and its coating showed that,the introduction of could significantly improve the stability of the emulsion.Atomic force microscopy(AFM)analysis showed that the surface roughness of the coating improved.When the amount of SA was 1.54%,the coating showed good mechanical properties,and the water absorption was still high.(3)γ-methacryloxypropyltrimethoxysilane(KH-570)was involved in the modification reaction: Fourier transform infrared spectroscopy(FT-IR)tests show that KH-570 is involved in the copolymerization between the acrylate monomer and the alkyd resin.The thermal analysis curve(TGA)analysis showed that the addition of KH-570 improved the thermal stability of the coating,meanwhile improving the hardness and adhesion of the coating,and reducing the water absorption of the film.(4)When the acrylate monomer dropping time was 2 h,the reaction temperature was 85 ℃,the dosage of DM was 4.76%,m(MMA)∶m(BA)was18:2,BTS-SZ was 55%,SA was 1.54%,KH-570 was 0.62%,hybrid emulsion and coating showed better overall performance.Transmission electron microscopy(TEM)tests showed that the latex particles had a typical core-shell structure.Gel permeation chromatography(GPC)tests showed that the molecular weight and distribution of the alkyd resin were increased after the modification of acrylic resin.Analysis of emulsion rheological behavior indicated that the emulsion had good thixotropy.(5)Waterborne paint additives on the coating performance studies show that,when the dosage of dispersant was 4%,the titanium dioxide was 15%,the leveling agent was 0.2%,the film forming agent was 2%,the drier was 0.6%,the thickener was 0.2%,the coating exhibits excellent comprehensive performance,meanwhile it had good thixotropy.AFM test results showed that the coatingsurface exhibits a rugged nanostructure.Compared with the properties of modified waterborne alkyd paints and oily alkyd paints,the modified waterborne acrylic/alkyd resin coating performance significantly improved in terms of drying performance,hardness and water resistance of the coating film compared with alkyd resin,the gloss and impact resistance of the coating decreased slightly.