Atsuo Ishida

SECONDARY DROPLET EMULSION : MECHANISM AND EFFECTS OF LIQUID CRYSTAL FORMATION IN O/W EMULSION

Abstract The structure and formation mechanism of secondary droplets in O/W emulsions and the contribution of their formation to the properties of emulsions were investigated. It was found that the secondary droplets were the aggregates of the emulsion droplets surrounded by the liquid crystal of closed lamella type composed of surfactant, fatty alcohol, and water. In order to form the secondary droplets, the presence of an appropriate amount of fatty alcohol and the control of HLB in an appropriate range were necessary. The formation mechanism of the secondary droplets was explained by the dissolved state of fatty alcohol during emulsification. The physicochemical properties of the emulsion changed greatly due to the formation of the secondary droplets: a yield value newly appeared ; the stability and water-retaining ability of the emulsion were improved. All of these results are attributed to the fact that the liquid crystal is formed in the continuous phase of the emulsion, thus fixing the emulsion dro...

New oil‐gelling agents for cosmetics: formation mechanism of oil gels

New oil‐gelling agents have been developed composed of a long‐chain dialkyl phosphate (DP) surfactant and aluminium ion or multinuclear aluminum ion (MAI) which provide good oil‐gel systems. One such gelling agent is the aluminum salt of DP (DP‐Al) prepared as a precipitate by mixing DP with aluminum chloride in aqueous solutions. Addition of small amounts of the salt to non‐polar oils led to hardening of the oil solutions at temperature below the melting point of the alkyl chain (Tc) of DP‐Al. Results obtained by X‐ray diffraction techniques and with scanning electron microscopy (SEM) revealed that linearly‐polymerized assemblies of DP‐Al expand in oils three‐dimensionally, which suggests that the excellent stability of the gel systems arises from the highly ordered structure. The gelling agent of DP‐Al offered the ideal rheological property to waxy cosmetic products such as lipsticks. The complexes of DP with MAI particles (1 nm diameter) of aluminum chlorohydrate, Al13O4(OH)24(H2O)12CI7, provided the ideal thixotropic behaviour in non‐polar oils. The DP‐MAI particle complexes were found to interact weakly by cohesive forces which makes a highly ordered structure of the DP‐MAI particle complexes. The DP‐MAI particle complexes gave excellent stability and transparency to cosmetic products such as w/o creams.

New Oil Gelling Agents for Cosmetics: Formation Mechanism of Oil Gels

We developed new oil gelling agents composed of a long-chain dialkyl phosphate (DP) surfactant and aluminum ion or multinuclear aluminum ion (MAI) which provide the ideal oil-gel systems. One such gelling agent is the aluminum salt of DP (DP-Al) prepared as a precipitate by mixing DP with aluminum chloride in aqueous solutions. Addition of small amounts of the salt to nonpolar oils led to hardening of the oil solutions at temperature below the melting point of alkyl chain (Tc) of DP-Al. Results obtained by X-ray diffraction techniques and with scanning electron microscopy (SEM) revealed that linearly-polymerized assemblies of DP-Al expand in oils three-dimensionally, which suggests that the excellent stability of the gel systems arises from the highly ordered structure. The gelling agent of DP-Al offered the ideal rheological property of waxy cosmetic products such as lip sticks. The complexes of DP with MAI particles (1nm diameter) of aluminum chlorohydrate, Al13O4(OH)24(H2O)12Cl7, provided the ideal thixotropic behavior in non-polar oils. The DP-MAI particle complexes were found to weakly interact by cohesive forces which makes a highly ordered structure of the DP-MAI particle complexes. The DP-MAI particle complexes offered the excellent stability and transparency of cosmetic products such as W/O creams.

Effect of Occlusivity of oil Film by the States of oil Film on thc Skin Surface

The occlusivity of oils was determined in vivo by measuring the suppression of transepidermal water loss (TEWL) of the skin. Various emollients were applied to human skin in various forms including powders, solutions, and emulsions of different types having different size distributions and the residual states of the oil films on the skin surface were examined with time. In order to discuss the occlusivity in relation with the individual skin conditions, the surface temperature of the skin and the casual lipid level were also determined in each subject. The followings are the results obtained from these experiments.1. The occlusivity of the oil films varied with time, nature of the oil, amount of the oil, physical forms of the oil, type of the emulsion, and droplet diameter of the emulsion.2. The occlusion effect of the oil also depended upon the characteristics of the skin such as casual lipid level and TEWL.These results could be explained by the differences in such as uniformity, spreadability, and porosity of the oil films on the skin surface in the residual state. It is believed that the emolliency of the oil can be influenced by these differences.