【作者】 吴银萍；

【导师】 沈慧芳； 夏正斌；

【作者基本信息】 华南理工大学 ， 化学工程， 2010， 硕士

【摘要】 可再分散乳胶粉是聚合物乳液经喷雾干燥或其他手段得到的粉末,它与水按一定比例混合后可再次形成性质与原乳液基本相似的聚合物乳液。因苯丙乳液具有优良的耐酸碱性和耐腐蚀性等特性,且价格低廉,可广泛应用于涂料、胶黏剂等领域。因此,制备可再分散苯丙乳胶粉在理论和应用上都具有重要意义。本研究通过核壳粒子设计理论,制备了“软核硬壳”结构的苯丙乳液;并通过喷雾干燥法制备了可再分散苯丙乳胶粉。采用半连续种子乳液聚合工艺制备了具有“软核硬壳”结构、粘度较低、性能优良的苯丙乳液。在制备过程中,考虑了乳化剂、引发剂、核壳单体质量比以及功能单体(MAA、NMA)对乳液性能的影响。结果表明:当乳化剂和引发剂用量分别为1%(占单体总量,下同)和0.5%、核壳单体质量比为2:1、功能单体MAA用量为6%、NMA单体用量为1%时,所得乳液粒径为122 nm且分布较窄,乳液粘度为91.5 mPa.s,固含量为45.2%。通过差热分析(DSC)、投射电镜(TEM)等研究发现,聚合物核壳两层分界明显,核层和壳层玻璃化温度分别为-18℃,78℃,表明本实验成功制备了核壳型苯丙乳液,适合进行喷雾干燥。采用5%NaOH(质量浓度)调节乳液pH值,并将一定量的保护胶体(聚乙烯醇溶液)加入到苯丙乳液中,采用喷雾干燥法制备出可再分散苯丙乳胶粉。研究了喷雾液pH值、保护胶体用量及进口温度等对乳胶粉性能的影响。结果表明,当喷雾液pH值调节至9左右、PVA用量为6%～8%(占乳胶粉质量)、进口温度为120℃-140℃时,乳胶粉再分散性好、易流动,含水率为2.3-2.7%,粒径为38-39μm。采用扫描电镜(SEM)分析发现,用自制苯丙乳胶粉配制的零VOC干粉涂料涂膜平整,性能较好,表明乳胶粉再分散性能好,再分散后的乳液的成膜性能优良。可再分散乳胶粉在建材领域应用广泛,但目前国内利用乳胶粉制备零VOC干粉涂料技术尚处于研发阶段。本实验制备的苯丙乳胶粉,性价比高,将之用于制备零VOC干粉涂料,具有非常重要的现实意义。更多还原

【Abstract】 Re-dispersible emulsion powder is a kind of polymer powders made from special emulsion by means of spray- drying. It can be easily re-dispersed in water and reform liquid emulsion with essentially identical properties to the original emulsion. Styrene-acrylate polymer emulsion are widely used in coatings and adhesives, because of its excellent application properties, such as acid-alkali resistance and corrosion resistance. Therefore, it’s of great significance to prepare re-dispersible styrene-acrylate emulsion powders.In this research, the core-shell structure styrene-acrylate polymer emulsion was synthesized on the basis of“the latex particle design”, and re-dispersible emulsion powders were produced by spray-drying.Seeded emulsion polymerization based on semi-continuous process was used to produce a kind of styrene-acrylate emulsion with“soft core and hard shell”structure, low viscosity and good performance. The effects of some factors, including of emulsifier, initiator, mass ratio of core to shell and functional monomer (MAA, NMA), on properties of styrene-acrylate emulsion were mainly discussed. The results showed that when the content of emulsifier, initiator was 1% (mass fraction based on the whole monomer, the same after) and 0.6% respectively, and the mass ratio of core to shell was 2/1, the stale styrene-acrylate emulsion was prepared with a narrow size distribution. The solid content was 45.2%, the viscosity was 91.5 mPa.s, the average size was 122 nm. It had been confirmed that the emulsion had an obvious core-shell structure through a series of analysis, such as Differential scanning calorimetry (DSC), Transmission election microscopy (TEM). The emulsion with good performance was suitable for spray - drying.NaOH was used to adjust the emulsion pH value, and protective colloid (PVA) was put into emulsion to improve its drying properties before spray - drying. The re-dispersible emulsion powders were obtained by spray-drying. The influence of the pH value, the content of protective colloid and the inlet temperature on re-dispersible powders properties were studied. The results showed that when the pH value was about 9, the content of PVA was between 6% and 8%( mass fraction based on re-dispersible emulsion powders, the same after), the inlet temperature was between 120℃and 140℃, the styrene-acrylate re-dispersible powders could be prepared with good redispersibility and good flowability. For the final products, the water content was 2.3-2.7%, the average size was 38-39μm. It was confirmed that the re-dispersible powders could be easily re-emulfied into liquid emulsion with good film-forming properties by scanning electron microscopy (SEM).Re-dispersible emulsion powders were widely used in powdered architecture materials, but it was seldom used to prepare zero VOC powder coatings. In this paper,zero VOC powder coatings based on the prepared re-dispersible emulsion powers were made successfully, to reduce the VOC content in common architecture coatings, which was very meaningful both in academic and in practice.更多还原