Microemulsions are clear or transparent because they contain particles smaller than the wavelength of visible light, i.e., typically 10-100 nanometer. They can contain oil droplets dispersed in water (O/W), water droplets dispersed in oil (W/O), or they may be bi-continuous in their structure. They are characterized by ultra low interfacial tension between oil and water phases.
While U.S. Pat. No. 5,705,562 (Jan. 6, 1998) teach the use of short chain or low molecular weight silicone polyethers in preparation of spontaneously formed clear silicone microemulsions, they do not teach preparing clear silicone microemulsions using long chain or high molecular weight silicone polyethers. This is not surprising as prior to this invention, there is nothing in the public domain relative to the preparation of clear silicone microemulsions using long chain or high molecular weight silicone polyethers.
The '562 patent, unlike the present invention, also fails to teach preparation of clear microemulsions from mixtures of both a volatile silicone oil and a nonvolatile silicone oil. Rather, the clear silicone microemulsions in the '562 patent are limited to oil phases containing only silicone oils which are volatile.
As a third distinction, according to the '562 patent, the composition should be free of non-essential ingredients such as cosurfactants. According to this invention, however, the composition may contain such non-essential cosurfactants, yet result in formation of clear silicone microemulsions.