加工方法对异丙甲草胺水乳剂物理稳定性的影响

通过分析Turbiscan Lab分散稳定性分析仪短期扫描图谱,以及测定所制备的水乳剂液滴平均粒径和Zeta电位,研究了不同加工方法(油水相添加顺序和乳化剂添加位置不同)对异丙甲草胺水乳剂物理稳定性的影响。结果发现:采用乳化剂添加在油相中的反相乳化法(方法 A)制备的水乳剂,短期扫描图谱中背散射光强度随时间降低的幅度很小,液滴平均粒径最小,Zeta电位绝对值最大,加速试验(54℃±2℃,14 d)后外观均一,稳定性最好;采用乳化剂添加在水相中的反相乳化法(方法 B)制备的水乳剂稳定性次之;采用乳化剂添加在水相中的直接乳化法(方法 C)和乳化剂添加在油相中的直接乳化法(方法 D)制备的水乳剂,试样短期扫描图谱中背散射光强度随时间均发生明显变化,顶部及中下部背散射光强度随时间呈更加明显的下降趋势,液滴平均粒径均较大,Zeta电位绝对值较小,加速试验后外观不均一,上层析水,下层产生少量沉淀,其中采用方法 C制备的水乳剂稳定性最差。表明采用不同加工方法制备的同一配方异丙甲草胺水乳剂的稳定性存在显著差异,以乳化剂添加在油相中的反相乳化法制备的水乳剂稳定性最好。

Influence of the processing methods on the physical stability of metolachlor emulsion in water

The influence of different processing methods, order of oil or aqueous phase and the position of emulsifiers in addition, on the physical stability of metolachlor emulsion in water (EW)was studied. Short-term scan spectrum from the Turbiscan Lab, the mean diameter of droplets and Zeta potential were evaluated. Significant stability differences were obtained for metolachlor EW with the same formulation prepared by different processing methods. In method A, emulsion was prepared by inversed phase emulsification with the emulsifier in the oil phase. The backscattered light intensity over time of the short-term scan spectrum decreased slowly, and smallest mean diameter of droplets with the largest absolute value of Zeta potential were obtained. In acceleration test (54 ℃±2 ℃, 14 d), emulsion prepared by method A showed uniform appearance and the best stability and the emulsion prepared by inversed phase emulsification with the emulsifier in the aqueous phase (method B) was the second best. For the emulsions obtained by direction emulsification with the emulsifier in the aqueous phase (method C) and direction emulsification with the emulsifier in the oil phase (method D), the short-term scan spectrum changed significantly and the backscattered light intensity in the upper and lower-middle portion decreased significantly. The mean droplets diameters were larger and the absolute value of Zeta potential was smaller. Inhomogeneous appearance was observed in acceleration test. There were aqueous layer on the top, and less precipitation at the bottom. It was demonstated that the stability of metolachlor emulsions oil in water for the same formulation prepared by different processing methods were quite different, the emulsion prepared by inversed phase emulsification with the emulsifier in the oil phase had the best stability.