一步法制备脲醛树脂微胶囊过程的研究

Direct Preparation Process of Microcapsules by in situ Polymerization of Urea-Formaldehyde

通过直接原位聚合法制备了以有机溶剂为内相的脲醛树脂微胶囊。考察了系统改性剂、pH值、反应时间等条件对微胶囊化过程和微胶囊形貌的影响。结果表明,以PVA作为系统改性剂,在pH值为2.5或更低的条件下,制备的微胶囊具有光滑的囊壁,但强度较低;而以PAA作为系统改性剂,在pH值为3.5的条件下,制备的微胶囊具有良好的光滑度、透明度和强度。分析了一步法中脲醛树脂微胶囊的形成过程。分析表明,体系中的相界面特性对微胶囊化过程有重要影响,要制备具有良好形貌和强度的微胶囊,需要在适当的系统改性剂条件下,控制反应速度,使体系发生平缓和充分的液液相分离。

Microcapsules containing an organic solvent as an internal phase were prepared by the in situ polymerization of urea-formaldehyde without prepolymerization. The influences of system modifiers, pH value, and reaction time on the process of microencapsulation and the morphology of the microcapsules were investigated. When the microencapsulation is conducted in a system modified by PVA and with a pH value of 2.5 or lower, the microcapsule shells have good smoothness but less strength. When the system modifier is PAA and the pH value is 3.5, the shells of the microcapsules are of good smoothness, transparency and strength. The process of direct preparation of microcapsules by in situ polymerization of urea-formaldehyde was analyzed. It is shown that the interfacial behavior of the phases in the system plays an important role in the process of microencapsulation, and a slow and sufficient liquid/liquid phase separation effected by an appropriate system modifier under appropriate conditions is necessary for producing microcapsules of good morphology and mechanical strength.