阳离子聚丙烯酰胺微球浓乳液制备及粒径演化

Preparation of cationic polyacrylamide microspheres by concentrated emulsion polymerization and its size evolution

浓乳液聚合产品稳定性好，颗粒尺寸更接近地层孔隙尺寸，在油田开发中具有较大的应用价值。基于微乳液制备了一系列甲基丙烯酰氧乙基三甲基氯化铵和丙烯酰胺的浓乳液，通过电导率测试、流变性分析、显微镜观察，研究了聚合前后浓乳液结构、粒径分布及稳定性。结果表明浓乳液的黏度及屈服应力，随着水相单体浓度（CM）增加而降低，随着油相中表面活性剂含量（mS）增加先升高后降低，乳液稳定性有相同趋势；浓乳液在CM〉40%及mS=2.5 g时的失稳，原因分别是渗滤作用和高黏度下乳化不充分；聚合前液滴粒径分布在1～30μm，聚合后微球粒径在0.4～5μm，且粒径分布由聚合前双峰变为聚合后单峰，这一现象可以由Kolmogoro-Hinze的乳化理论解释，并由微球乳液的黏度增加至原始浓乳液的10倍证实。

Concentrated emulsion polymerization has great potential use in oil production due to its product characteristics of high stability and proper particle size close to formation pore, which complements the gel particles synthesized by microemulsion polymerization and suspension polymerization. A series of concentrated emulsion were prepared based on microemulsion with acrylamide and methylacryloxylethyl trimethyl ammonium chloride as monomers. The structure, size distribution, stability of this emulsion before and after polymerization were determined by conductivity measurement, rheology analysis, and microscope observation. The results showed that both viscosity and yielding stress decreased with increasing monomer concentration （CM） in water phase and had a maximum value with increasing surfactant content （mS）. The same trend was found for emulsion stability. The emulsion destability of CM〉40% or mS=2.5 g was separately attributed to percolation effect and insufficiency emulsification in high dispersion viscosity;especially, the particle size with 1-30μm and bimodal distribution before polymerization evolved to that with 0.4-5μm and unimodal distribution after polymerization. This size evolution could be explained by Kolmogoro-Hinze emulsification theory, further testified by the phenomenon that the viscosity of microsphere emulsion was enhanced as much as ten times that of emulsion before polymerization.