Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
1995-02-10
2001-01-30
Lovering, Richard D. (Department: 1712)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S070120, C424S070121, C424S070122, C424S070130, C514S938000, C514S975000, C516S076000, C516S925000, C516S928000
Reexamination Certificate
active
06180117
ABSTRACT:
FIELD OF THE INVENTION
The instant invention comprises a method for preparing microemulsions. The process of the invention comprises blending an amino silicone fluid MQ resin mixture with a surfactant having a high phase inversion temperature adding an approximately equal amount of water at a temperature approximately equal to the phase inversion temperature of the surfactant, acidifying, followed by rapidly adding water. The instant invention further comprises personal care products comprising the microemulsion prepared by the process of the invention.
BACKGROUND OF THE INVENTION
The instant invention is related to a method of making microemulsion blends having an average particle size of from about 0.001 microns to about 0.05 microns whereby the blend comprises at least one of a low amino content silicone, a resin or an MQ resin and a surfactant having a high phase inversion temperature. The instant invention is further related to personal care products comprising said microemulsions.
Microemulsions containing silicone fluids have been found to be useful in a variety of personal care products. As defined herein, the term “microemulsions” refers to transparent, mechanically and thermally stable systems comprising small droplets having a mean or average particle diameter usually not more than 0.05 microns in diameter, preferably not more than 0.040 microns in diameter and most preferably not more than 0.025 microns in diameter. The small size of the droplets imparts a high degree of transparency to the emulsion.
The use of microemulsions is known in the art, see for example U.S. Pat. Nos. 4,797,272 (Linn et al.) and 4,620,878 (Gee). U.S. Pat. No. 4,797,272 to Linn et al. discloses water-in-oil microemulsion compositions having a mean droplet size ranging from about 0.001 microns to about 0.200 microns. U.S. Pat. No. 4,620,878 to Gee discloses a polyorganosiloxane emulsion that contains a polyorganosiloxane containing at least one polar radical such as an amino or ammonium radical attached to the silicon of the siloxane by Si—C or Si—O—C bonds or at least one silanol radical and at least one surfactant that is insoluble in the polyorganosiloxane. Water is added forming a translucent oil concentrate. The translucent oil concentrate is then rapidly dispersed in water to prepare emulsions with fairly low particle sizes. A drawback of Gee's teachings is that the oil concentrate must be diluted with very large quantities of water such that the final emulsion rarely contains more than about 5 wt. % silicone solids. The emulsions prepared by Gee typically have an average particle size of less than 0.14 microns.
Microemulsions of volatile silicones are taught in the art, for example U.S. Pat. Nos. 4,782,095 and 4,801,447, however these microemulsions have required large amounts of surfactants. The high levels of surfactants required in the prior art applications are detrimental in many applications.
Chrobaczek and Tschida in U.S. Pat. No. 5,057,572 teach the preparation of an aminoalkyl substituted polysiloxane where the silicone fluid, a water-soluble emulsifier, in contrast to Gee, water and an acid are combined and heated to 50° C. The necessity for a specific sequence of process steps, such as order of addition, is not taught by Chrobaczek. While Chrobaczek teaches this procedure is applicable to silicone fluids with an amino content of 0.1 meq./gr., in practice microemulsions result only when the amino content is above a threshold of about 0.12 to 0.14 meq./gr. Below this threshold level the particle size of the emulsion is such that the emulsion is hazy, and therefore not a true microemulsion, true microemulsions possess optical transparency to a greater or lesser degree, as measured by an ASTM haze number of less than about 150.
Breneman et al. in U.S. Pat. No. 5,234,495 teach the preparation of microemulsions through a process utilizing the blending of an organo modified polysiloxane, e.g. an aminofunctional polysiloxane, an organo modified polysiloxane emulsifier, water, and an alkaline metal salt Heating such a blend above the cloud point of the mixture and simultaneously subjecting the mixture to high shear mixing produces a liquid phase that can be cooled to form a microemulsion.
Microemulsions of aminofunctional silicones, particularly high viscosity aminofunctional silicone fluids or gums, provide beneficial results when used in personal care product formulations. Further MQ resins impart desirable properties to personal care products. Similarly methods of incorporating MQ resins into personal care products and preparing microemulsions of MQ resins are desirable. It continues to be desirable to provide alternative or improved methods for preparing microemulsions of small average particle size.
SUMMARY OF THE INVENTION
In one embodiment, the instant invention comprises a transparent oil-in-water microemulsion comprising: (a) a microemulsifiable amino silicone fluid or gum, (b) an MQ (or alternatively a siloxysilicate) resin or mixture thereof, (c) a surfactant having a high phase inversion temperature, and (d) water.
In another aspect, the instant invention provides a method of preparing a transparent polyorganosiloxane microemulsion having a mean particle size of from about 0.001 to about 0.050 microns, preferably from about 0.010 to about 0.030 microns, and most preferably from about 0.010 to about 0.025 microns, comprising a microemulsifiable high viscosity amino silicone fluid or gum and at least one surfactant having a high phase inversion temperature.
Other aspects of the invention are microemulsions of polydimethylsiloxane MQ resin mixtures and personal care products comprising the microemulsions of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The instant invention is based upon the discovery that functionalized silicones such as amino functional silicone fluids or gums are capable of forming microemulsions and may be blended with surfactants having a high phase inversion temperature and the blend processed such that the mixture forms a microemulsion. It has been discovered that when blended with other resins, particularly MQ resins, that the amino functional silicone MQ resin blend may be microemulsified. Such microemulsions are generally transparent or translucent. By transparent applicants mean the absence of turbidity or haze wherein haze is defined by an ASTM test, specifically ASTM test number D871 using turbidity suspension standards and wherein said haze or turbidity is below an upper limit of about 150. At levels of the haze number above about 50 the microemulsions of the present invention begin to gradually change from transparent to translucent. The haze numbers of the microemulsions of the present invention range from 0 to about 150, more preferably from about 0 to about 80 and most preferably from 0 to about 50. The turbidity suspension standards used in the ASTM test D871 are available from Hellige Incorporated of Garden City, N.Y. Applicants note that pure distilled water is 0 on the haze scale.
Polyorganosiloxane microemulsions prepared by the method of the instant invention have a mean particle size of from about 0.005 to about 0.050 microns, preferably from about 0.010 to about 0.030 microns, and most preferably from about 0.010 to about 0.025 microns. Generally haze and average particle size correlate with one another but they are also affected by the relative amounts of the three major components of the emulsion, the silicone oil or mixtures thereof, the emulsifier and the water. Thus while at a constant oil to water ratio the haze and average particle size might correlate, haze by itself is not both a necessary and sufficient criterion to be an indicator of average particle size in a microemulsion unless other constraints are specified.
By microemulsifiable applicants define the term to mean capable of forming a microemulsion wherein the mean particle size of the emulsion ranges from 0.0001 microns to about 0.050 microns. By microemulsifiable silicone applicants define a silicone or a mixture of silicones that can form a mi
Berthiaume Marianne D.
Merrifield James H.
Riccio Donna A.
General Electric Company
Lovering Richard D.
Wheelock Kenneth S.
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