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Bulletin of the University of Osaka Prefecture. Ser. B, Agriculture and biology >
Vol.18 >

このアイテムの引用には次の識別子を使用してください: http://hdl.handle.net/10466/2961

タイトル: エマルジョンの分散状態に関する研究
その他のタイトル: Studies on the Dispersion State of Emulsions
著者: 松本, 幸雄
著者名の別形: MATSUMOTO, Sachio
発行日: 1966年3月31日
出版者: University of Osaka Prefecture
引用: Bulletin of the University of Osaka Prefecture. Ser. B, Agriculture and biology. 1966, 18, p.139-167
抄録: The emulsion, which is a heterogeneous system, consisting of at least one immiscible liquid intimately dispersed in another in the form of droplets, is widely used in the fields of foods, pharmaceutics, cosmetics and various chemical industries. Several studies on the emulsion state, the stability of dispersed particles, the emulsification etc. have been made by many investigators. These results, however, are difficult to apply for the emulsions used in the above industrial fields, in which many kinds of organophilic substances or emulsifiers are used, since they give only some phenomenological interpretations. The purpose of this work is to obtain practically significant informations on the dispersion state of either oil-in-water type or water-in-oil type emulsion by studying mainly the rheological properties of the systems of various combinations of emulsifiers and oil components such as ionic or nonionic emulsifiers, saturated hydrocarbons, aromatic hydrocarbons and fatty alcohols. I. Effects of emulsifiers on flow properties of oil-in-water emulsions. Viscosities of the system of anionic emulsifier does not depend on the rate of shear at dispersion concentrations below 40 vol. %. The system of nonionic emulsifier shows non-Newtonian flow over the range of dispersion concentrations at relatively low rate of shear. At higher shear rate, however, flow of the system of nonionic emulsifier tends to show Newtonian behaviour and the values of relative viscosities of the system agree with those of the system of anionic emulsifier at the same dispersion concentrations. These difference in flow behaviour of two systems may be attributed to the difference in the dispersion state, which is remarkably influenced by the nature of the surface layer on the dispersed particle. The emulsion particles in the system of anionic emulsifier, whose surfaces are negatively charged by the ionized groups of emulsifier molecules, repel each other. On the other hand, the particles in the system of nonionic emulsifier, whose surfaces are surrounded by the hydrophilic molecules, can not repel each other and will form larger aggregates without losing their identity. II. Detection of solubilizate of dispersed liquid in oil-in-water emulsions. It may be expected from the studies of Lawrence and his school for the system of soap solution with amphiphiles, that a certain amount of dispersed liquid of emulsion is solubilized by the emulsifier existing in the dispersion medium. Gas chromatographic, nephelometric and viscometric measurements were used for inspecting the existence of solubilizate of dispersed liquid in the dispersion medium. The emulsions studied were composed of n-hexane, 1-octanol or mixture of equal volume of both liquids in water, stabilized by anionic or nonionic emulsifiers, respectively. Dispersion media for measurements were separated from these emulsions by the fractionation of lower part of the emulsions after standing fifty days at 32℃. Existence of the solubilizates in the dispersion medium has been confirmed, the amount of which depends on the nature of the dispersed liquid and emulsifier, and also on the concentration of the emulsifier at constant temperature. The transparency and viscosity of the dispersion medium are influenced by the nature of the dispersed liquids and emulsifiers used for the preparation of the emulsions, as those of ordinary solubilized systems. III. Influence of polar component of dispersed liquids on dispersion state of oil-in-water emulsions. Viscosity, particle size and "creaming" volume of emulsions of n-hexane, 1-cotanol or mixture of both liquids in water, stabilized by various emulsifiers, were compared with each other. Emulsions of n-hexane in water are relatively monodisperse and their viscosities increase with increasing amount of n-hexane in a usual manner. Emulsions of the mixture of n-hexane and 1-octanol or 1-octanol alone in water have higher viscosity, smaller particle size and larger "creaming" volume than the n-hexane in water emulsions in all dispersion concentrations studied. In the latter emulsions which contained 1-octanol in the dispersed liquids, viscosity and "creaming" volume depend on the nature of the emulsifier, and are sensitive to the concentration of the emulsifier. The difference in dispersion state of emulsions stated above may be attributed to the difference in polarity between 1-octanol and n-hexane in the dispersed liquids. IV. Viscosity and particle size of oil-in-water emulsions of dispersed liquids. Viscosity and particle size have been measured for the emulsions of saturated hydrocarbons, aromatic hydrocarbons and fatty alcohols stabilized with anionic emulsifier. It has been observed that the viscosity increased and the particle size decreased with dispersed liquid in the following order; saturated hydrocarbons, aromatic hydrocarbons, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol and 1-decanol. The phenomena appear to be interpreted in terms of difference of the interaction between the emulsifiers and the dispersed substances. The various factors affecting the emulsion viscosity, such as particle size distribution, viscosity of suspending fluid or formation of aggregate between dispersed particles, are also discussed. V. The effect of suspending fluids on relative viscosity of water-in-oil emulsions. The relative viscosity of water-in-oil emulsions, stabilized by sorbitan monostearate, was found to be influenced by the species of suspending fluids. The fluids tested include n-hexane, cyclohexane, decalin, carbon tetrachloride, benzene, toluene, xylene and tetralin. The dependence of both relative viscosity and sedimentation volume of the dispersed particles upon the concentrations of emulsifier are also influenced by the suspending fluids at a constant dispersion concentration. The results can be explained in terms of the difference in aggregated states of water droplets in each suspending fluid, which is present at various concentrations of emulsifier. VI. Rheological studies of concentrated oil-in-water emulsion. The rheological behaviour of the concentrated oil-in-water emulsion in the state of so-called "cream," has been investigated by the measurements of responses in the range of low frequency, yield value under the slight deformation and the steady-flow viscosity. The concentration in weight percent of the components of system was as follows: water, 56; liquid paraffin, 35; Arlacel 169, 1; cetylalcohol, 1; Arlacel 60, 2; Tween 60, 5. The emulsion was prepared by mixing these components at 80℃, where spontaneous emulsification occurs, and its rate of cooling from the mixed temperature to 25℃ was 4, 3, 1, 0.3, 0.2 and 0.1 degrees per minute, respectively. This procedure gave six types of samples. Samples prepared at a slow rate of cooling (below 1 degrees per minutes) were already in the state of "cream" at the end of the cooling procedure, and their viscoelasticity and yield value increased with the aging time. From these results, and also from the nature of the change in the steady-flow viscosity with aging, the state of "cream" may be considered to be brought about by the formation of both thixotropic gel structure and the irreversible binding between dispersed particles. On the other hand, the samples prepared at a fast rate of cooling (above 3 degrees per minutes) showed low stiffness and no change in their rheological properties with the aging time. VII. Particle-size determination of suspensions or emulsions by viscometry. An apparatus for sedimentation analysis by the viscometric method, making possible the measurement of viscosity change with time at a fixed position in the bulk due to the sedimentation or ascension of dispersed particles, has been constructed. The new method has been examined with both a potato-starch-granule suspension and oil-in-water emulsions. It is concluded that the aggregated state of dispersed particles in the bulk of emulsions, consisting of both macroscopic droplets and solubilized micells in all the cases studied, are not only affected by the kind of emulsifiers, but also by the nature of oil phase through the interaction between the emulsifiers and the polar groups or π-electrons in the components. In view of more practical use, the emulsion in the state of so-called "cream" has been investigated by the method of mechanical responses, and it has been found that "cream" is brought about by the formation of both thixotropic gel structure and the irreversible binding between dispersed particles. A new method of particle-size determination for the dispersed systems by the viscometry has also been proposed.
URI: http://hdl.handle.net/10466/2961


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