关键词: 精细化学工程, 成核机理, 胶束成核, 均相成核, 粒径及其分布

Abstract: In semicontinuous emulsion polymerization with methyl methacrylate (MMA) and butyl acrylate (BA) as the monomers, the influences of the ratio of MMA to MMA and the pH buffer (NaHCO₃) on the nucleation process were investigated. The nucleation mechanism was deduced by analyzing the growth of particle size and its distribution during the polymerization process. Experiment results show that the nucleation mechanisms are determined by the molar fraction of MMA (f_MMA), when f_MMA increases the reaction time of nucleation t_1,2 decreases, but the number of emulsion particles N^max_p increases at the end of nucleation except BA homogenous polymerization; when f_MMA=0.5763, as the amount of NaHCO₃ increases the conversion rate of the monomers increases, but t_1,2 remains constant, 16 min, which indicates the coexistence of the“micellar nucleation” and “homogenous nucleation” mechanisms. The coexistence of the two nucleation mechanisms can also be verified by the analysis of the particle size and distribution of the emulsions.

Key words: fine chemistry engineering, nucleation mechanism, micellar nucleation, homogeneous nucleation, particle size and distribution