Study On Polymer Emulsion For High Performance Water-Based Coatings

With the aggravation of environmental pollution and the increasing requirement of environmental regulation,the traditional solvent-based coatings replaced by the water-based coatings have become the trend of the coating industry.The preparation of high water-based coatings must use the water-based resins which have with high performance.Therefore,it is necessary to develop the high-performance water-based resins.The epoxy-modified polyacrylate combines the advantages of epoxy resin and acrylic resin,presenting a perfect application prospects.However,the epoxy-modified polyacrylate composite emulsion can’t satisfy the request of water-based coatings on the adhesiveness,water resistance and salt spray resistance.Therefore,the study focuses on the modification of epoxy-acrylate composite emulsion to meet the requirements of high water-based coatings.Epoxy-acrylate composite emulsion was synthesized by semi-continuous seeded emulsion polymerization.The water-resistance of the coating was significantly improved by using anionic and reactive composite emulsification system instead of the conventional emulsification system.The effect of emulsifier was studied and the result showed that the best ratio of anionic emulsifier CO-458 and reactive emulsifier COPS-1 was 1:1.5 and the dosage of emulsifier was 3% to the monomers.Consequently,the water absorption of coating film reduced to 1.8%.The polymerization process was optimized and the result showed that the medium molecular epoxy resin E-51 was perfectly employed as the modified resin.When the dosage of initiator was 0.7% to the monomers and the ratio of harder monomer to softer monomer was 2.5:1,the composite emulsion coating film presented a nice performance with pencil hardness of H.For the purpose of improving the comprehensive property of coatings,vinyltriisopropoxysilane was used to modify composite emulsion.When the dosage was 0.8% to the monomers,the water resistance was up to 15 d and the hardness the coating was obviously improved.The structure of graft copolymer was characterized by FT-IR and the result showed that the copolymerization was taken place between epoxy resin,acrylic monomers and organosilicon.The morphology and particle size of composite latex particles were analyzed using TEM and laser particle size analyzer.The results showed that the latex particles had spherical structure with average particle diameter 115 nm.The coatings properties were studied with the epoxy-modified polyacrylate composite emulsion as binder to prepare the metal anti-corrosion primer.The results showed that the coatings presented perfect property when the curing temperature was120℃ and heating time was 2h.When the dosages of epoxy resin,acrylic acid,N-MA and GMA were 20%,2.0%,1.0% of the total monomer weight,respectively,the pencil hardness reached to 3H,the adhesion reached to 1 level,the impact resistance reached to50Kg·cm,the flexibility reached to 2mm.The water resistance could reach to 18 d and the acid resistance and the salt spray resistance could reach to 15 d.FT-IR result showed that the absorption peak of the epoxy group almost disappeared,which implied the reactive groups taking part in the cross-linking reaction.The DMA result showed that the peak values for tan δ could reach 1.82 and the corresponding temperature range was 22℃ to70℃,which implied that the coating material had a perfect damping property.The epoxy-acrylate composite emulsion was applied into metal anti-corrosion primer.The test results showed that the coating had excellent properties of forming membrane and constructability,such as drying time 2h,the flexibility 1mm,the adhesion 1 level,the impact resistance 50Kg·cm.In addition,the water resistance could reach to 480 h and the salt spray resistance could reach 360 h,which could meet the requirement of water metal primer.