Abstract
The preparation of biodegradable polyester emulsions was investigated as the first step of the utilization studies of adhesives and criteria for the emulsifier selection was extensively investigated. Aliphatic saturated polyester solutions with organic solvents and aqueous solutions of a number of emulsifiers, consisting of surface active agents and water soluble high polymers, were used as oil phase and aqueous phase, respectively. The preparation process of the emulsion consisted of mixing and subsequent solvent evaporation.Depending on the emulsifiers employed three different kind of products were obtained; In the first oil phase was almost entirely coagulated whereas partial coagulation took place in the second. The third was stable emulsion. From the fact that a large number of tiny particles were microscopically observed in the coagula, destabilization is believed to result from the flocculation due to collisions between primary particles formed by the emulsification.Three factors, the interfacial tension, the emulsifier adsorption on the particles, and the molecular weight (MW) of the emulsifier, were examined and two major factors were identified for obtaining the stable emulsions whose particle size is ca.1μ. The interfacial tension was found to be below an upper value γ* and the Mw of the emulsifiers was found to be above a lower value, MW*. Those two factors seem to be the important criteria fo rpreparation of the stablebiodegradable polyester emulsions. When the polyester is polycaprolactone, γ* and MW* are found to be 11.0 mN/m(20℃) and 20000, respectively in the present studies.
