| The color of exterior coatings is abundant, the veneer is flexible and diversiform, and so coating can meet deferent styles of design. Coating can be easily safeguarded and retreated, is safe and reliable, with a lightweight. Therefore it is becoming the leading factor of the exterior ornament materials. At present, the urbanization and small town development of our country is in a peak period, so high quality exterior coatings are demanded greatly and have a wide development potentialities. Using waterborne coating to replace solvent coating as exterior coating is an orientation for the development of building coating. What restricted the application and development of emulsion coating is it's insufficient of stain resistance ability. The emulsion is one of the most important determinants of emulsion coating's performance, so the stain-resistance ability of coating depends on the stain-resistance ability of emulsion to a great extent. In this article, on the basis of "the latex particle design", the emulsion whit hard-core/soft-shell structure and the emulsion with soft-core/hard-shell were prepared by multisteps polymerization, with same kind of monomers. The Tg of the core polymer and shell polymer of the latex particle that produced by core-shell emulsion polymerization are different. The soft phase provided a lower MFT to emulsion, which means the good film form ability to the exterior coating. While the hard phase contribute to a higher rigidity of exterior coating. Therefore, core-shell emulsion helps to improve the stain resistance ability of acrylic emulsion exterior coating. In this article, formula ingredients and polymerization technology were studied, the transmission electron micrograph (TEM) was adopted to test the structure of latex particle of emulsion, and the Malvern laser zatasizer nano-ZS90 was used to test the size distribution of latex particle. The influence of parameters on the comprehensive performance of core-shell emulsion and exterior coating were study systematically. The parameters include emulsifier's kind and concentration, the ratio of anionic and nonionic emulsifier, and the emulsifier dosage in two steps. The influence of shell thickness on the comprehensive performance of core-shell emulsion and latex film was studied by changing the ratio of core monomer and shell monomer. Introduce functional monomer within measure to shell polymerization to study the effect of the polarity of shell polymer on the performance of core-shell emulsion. Preparing exterior coating with these core-shell emulsions, the influence law of every factor on the stain resistance ability of them were hoped to be fined ultimately. Through the experiment the prescription design and craft were fixed, and the operation parameters were optimized. The parameters include feed method, the drop speed of monomer, the reaction temperature, mix speed, and pH value regulate etc. The test of TEM proved the latex particle is core-shell structure. And with the Malvin laser granularity distribution analyzer, it is found that most size of core-shell latex particle centralizes to 100nm. The tests showed emulsifier effect markedly on comprehensive performance of core-shell emulsion and coating film. Adopted the composite of anionic emulsifier (SDS) and non-ionic emulsifier (OP-10), the stability of the core-shell emulsion is good. With the increase of the consumption of the emulsifier, the size of particle is reduced directly, but the water absorption rate of the emulsion film rises notably. The perfect level of emulsifier is 3%~4%, the emulsifier amount ratio at core and shell stage is 2/1. Polymerized in this project, the stability of polymerization and comprehensive performance of emulsion is very well. Prepared with those emulsions, the comprehensive performance of exterior coating is good. Especially, the stain-resistance ability of the exterior coating is very well. Shell thickness is one of the key factors that influence the film form ability of core-shell emulsion and the rigidity of latex film. In the case of hard-core/soft-shell emulsion, when the ratio of hard/soft monomers is MMA /EA= 50/50 the film form ability of core-shell emulsion is better than that of normal emulsion, stain-resistance ability of the coatings prepared with core-shell emulsion is better too. In the case of soft-core/hard-shell emulsion, when the ratio of soft/hard monomers is BA /MMA= 60/40 the film form ability of core-shell emulsion and performance of latex film can get a good effect at same time. Introducing St monomer, MMA monomer etc. within measure to shell polymerization, polarity of shell polymer is affected noteblily. Finally, surface polarity and stain-resistance ability of coating film are affected. Tests proved that the core-shell emulsion has good performance in improving stain-resistance ability of exterior coating.
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