The authors designed and developed Polyoxyethylene/Polyoxypropylene Random Copolymer Dimethylether (EPDME) as an oil-soluble humectant that is freely soluble in both water and polaroils, chemically stable, does not dissolve plastics and is free of skin irritancy because it is not a surfactant. In addition, by utilizing special microemulsion formed by EPDME and nonionic surfactants for ultrafine emulsification, the manufacturing process which conventionally requires a large amount of energy and time, can now be changed to the quick and easy procedure of stirring at room temperature. According to the technique described above, it has become possible to encapsulate a polymer compound which could not be achieved conventionally in ultrafine emulsion or to solubilize a hardly soluble compound such as ultraviolet absorber in water. This technology will be outlined below.

Cationic surfactants are generally used as softening agents in textile industry, hair conditioning agents in hair conditioner, antistatic agents, and antifungal agents. In addition, it is well known that cationic surfactants are used for organically denaturing clays such as montmorillonite and enhance the cooling effect by menthol. However, they are not safe for human skin so much in general and that limits the range of application. Accordingly, we focused on distearyl dimethyl ammonium chloride (DSAC) which is one of cationic surfactants and is thought to have relatively high safety. And we expected that the practical use of them is widely extended if we can obtain fine emulsions emulsified with DSAC. As a result, we have succeeded in obtaining fine emulsions (d. ~30 nm) by using polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) as an auxiliary emulsifying agent.