Process For Formation of Emulsion Containing Liquid Crystal Structure

Abstract

The use of specified homogenizer configuration, i.e., stator and rotor and shear energy density, to form a liquid crystal structure between the negatively charged phospholipid and/or phospholipid derivative and fatty alcohol is disclosed.

Claims

1. A process for ensuring molecular level association between (1) a negatively charged phospholipid and/or phospholipid derivative; and (2) a fatty alcohol, comprising: using a three-stage rotor and stator homogenizer configuration.

2. A process for ensuring molecular level association between (1) a negatively charged phospholipid and/or phospholipid derivative; and (2) a fatty alcohol, comprising: using high homogenizer energy.

3. The process of claim 1, further comprising: employing an energy of at least about 0.18 hp/lb/min for three stages of rotor and stator homogenization.

4. A composition prepared according to the process of claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0018] FIG. 1 shows (A) product prepared using a comparative method (white specks); and (B) product prepared in accordance with the process of the invention (no white specks).

[0019] FIGS. 2(A)-2(D) show different stages of stator and rotor.

[0020] FIGS. 3(A)-3(E) show the appearance of product upon using different homogenizers.

[0021] FIG. 4 shows a polarized light microscopy image of individual crystals within a speck aggregate.

[0022] FIG. 5 shows SEM-EDS elemental analysis of white speck in the product.

[0023] FIG. 6 shows SEM-EDS elemental analysis of Emulsiphos.

[0024] FIGS. 7(A)-7(D) shows FT-IR chromatory graph results.

[0025] FIGS. 8(A)-8(D) shows DSC results.

[0026] FIG. 9 shows the lamellar liquid crystalline structures of the stratum corneum.

[0027] FIG. 10 shows the lamellar liquid crystalline structures of Emulsiphos and cetyl alcohol.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Naturally occurring skin lipids and sterols, as well as artificial or natural oils, humectants, emollients, lubricants, etc., may be part of the composition the invention.

[0029] An emollient is an additive that has the quality of softening or soothing the skin. Emollients are generally complex mixtures of chemical compounds that hold water in the skin after application and help smooth the skin. Emollients increase the skin's hydration (water content) by reducing evaporation. Preferred emollients are cocoglycerides, which are mixtures of mono, di and triglycerides derived from coconut oil.

[0030] An emollient wax or wax is an additive that (1) has the properties of an emollient; (2) is oil-based; (3) is solid at room temperature. A preferred emollient wax is cetyl alcohol, a fatty alcohol-palmitate/ester that is also known as hexadecan-1-ol or palmityl alcohol, available as Lanette16 from BAS F Care Creations, Monheim, Germany. Lanette 16 is a cetyl alcohol that is used for viscosity regulation in cosmetic and pharmaceutical oil-in-water emulsions. It is a white to light yellowish hydrophilic wax that is supplied in pellets or flakes. This product has a hydroxyl value of 228-234, a hydrocarbon content of max. 0.5%, and a solidification point of 47-50 C. The HLB value of cetyl alcohol is about 15.5. Other examples include petrolatum and silicone-derived ingredients, such as cyclomethicone.

[0031] An emulsifier is an additive that stabilizes a mixture of two or more liquids that are normally immiscible. An example of an emulsifier is Emulsiphos, a phospholipid derivative that is a potassium salt of a complex mixture of esters of phosphoric acid available from Symrise GmbH & Co., Holzmiden, Germany.

[0032] A gelling agent is an additive that can form a polymer gelled composition by crosslinking or neutralization. Gelling agents can also stabilize emulsions, form gels, increase viscosity, etc. Examples of gelling agents include polyacrylate (such as carbomer) and polysaccharide (such as cellulose). A preferred gelling agent is carbomer, which is a polymeric chemical composed of acrylic acid monomers.

[0033] The composition according to the present invention preferably contains the following amounts of the specified ingredients: [0034] an emollient, preferably cocoglyceride, from about >0% to about 10%, preferably from about 2% to about 6%; more preferably from about 3 to about 6%; [0035] an emollient wax, preferably a cetyl alcohol, from about >0% to about 8%, preferably from about 1% to about 4%; more preferably from about 1.5% to about 3%; [0036] an emulsifier, preferably a cetyl phosphate, from about 0.2% to about 1.4%, preferably from about 0.4% to about 1.4%; more preferably from about 0.5% to about 0.6%; [0037] a gelling agent, preferably a carbomer, from about 0.4% to about 0.6%, preferably from about 0.4% to about 0.55%; and [0038] from about 60% to about 90% water.

[0039] All percentages (%) are by weight unless otherwise specified herein.

[0040] The chassis was developed to achieve similarity of the lamellar structure formed by Emulsiphos, Symrise, Inc., Branchburg, N.J. (potassium cetyl phosphate, hydrogenated palm glycerides) and cetyl alcohol to the lipid phase under the skin. See FIG. 9. The structure for this formula can be seen in FIG. 10, which shows a polar head for Emulsiphos and a polar head for cetyl alcohol. The intercalation of the cetyl alcohol (fatty alcohol) disturbs the rigidity of the structure, thus making the product more fluid-like.

[0041] From a processing standpoint, the right homogenizer configuration, i.e., stator and rotor and shear energy density, ensured proper formation, i.e., successful intercalation of the fatty alcohol to the phospholipid, which resulted in good appearance, stability profile, and skin barrier protection.

Examples

[0042] Three stages of rotor and stator have been proposed for this invention to solve the problem. As shown below, through increased residence time and more turbulent mixing, multiple stages enhance the mixing and interaction between the ingredients in the composition.

[0043] The process of the invention was used on the formula in Table 1 to obtain the desired properties.

[0044] The composition of Table 1 may be prepared following the procedures described below: [0045] In the main vessel introduce water, disodium EDTA and carbomer. [0046] Control good dispersion of carbomer and then heat to 80 C. [0047] Add glycerin and control temperature (80 C.). [0048] Add Emulsiphos, cocoglyceride and cetyl alcohol. [0049] Control that the Emulsiphos is completely melted: 15 min emulsion phase at 80 C. [0050] Neutralize with an aqueous solution of sodium hydroxide, p-anisic acid to a target pH=5.6. [0051] Start cooling down to 35 C. [0052] When temperature reaches 40 C., optionally add ethylhexylglycerin; phenoxyethanol, then corn starch. [0053] Check the good dispersion of purity and pH. Adjust pH if needed with sodium hydroxide to pH=5.6.

TABLE-US-00001 TABLE 1 US INCI Name % Function Water 85.362 Vehicle Glycerin 5 Humectant Disodium EDTA 0.2 Chelating agent Carbomer 0.4 Viscosity Increasing Agent p-Anisic Acid 0.15 Masking Agent Sodium Hydroxide 0.188 pH Adjuster Potassium Cetyl Phosphate; 0.5 Emulsifier Hydrogenated Palm Glycerides (Emulsiphos) Cetyl Alcohol 2 Emollient Cocoglycerides 4 Emollient Ethylhexylglycerin; 0.6 Preservative Phenoxyethanol Ethylhexylglycerin 0.2 Skin Conditioner Zea Mays (Corn) Starch 1 Absorbent Water; Pyrus Malus (Apple) 0.1 Skin Conditioning Fruit Extract; Agent Occlusive Citric Acid; Sodium Benzoate; Potassium Sorbate Fragrance 0.3 Fragrance

[0054] Compositions were prepared on a larger scale in accordance with the process conditions set forth in Table 2 below.

TABLE-US-00002 TABLE 2 1 2 3 Tank Size 35 gallon Batch size 275 lbs Emulsification 75-80 80-85 Temperature C. Order of Addition Add Cetyl Alcohol Add Emulsiphos of the Emulsifiers Then add Then add Cetyl Alcohol Emulsiphos Homogenizer Silverson 375 IKA DR*2000/05 Homogenizer 2 10 horse power (hp) Energy Density 0.04 0.22 (hp/lbs/min) Homogenizer #of 1 3 stator & rotor Homogenizer Round Hole Square Hole Coarse/Medium/ generator type Medium Results Fail of Fail of Pass apperance apperance

[0055] The inventors determined that an energy density at least higher than 0.18 to 0.30 (hp/lb/min) for three stages of rotor and stator homogenizers resulted in a product having the desired characteristics.

Methods and Results

Differential Scanning Calorimeter

[0056] Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and a reference is measured as a function of temperature. Both sample and reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. The reference sample should have a well-defined heat capacity over the range of temperatures to be scanned. DSC is used herein to confirm the hydration of fatty alcohol, which in this case is cetyl alcohol. DSC can reveal the hydration of emulsifiers, various intercomponent interactions, and the nature of the binding forces in the gel structure..sup.10. FIG. 8 shows that a relatively higher peak was observed during heating of cetyl alcohol as compared to Emulsiphos, which might be due to the fact of less hydration of cetyl alcohol.

FT-IR

[0057] Fourier-transform infrared spectroscopy (FT-IR) is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid or gas. An FT-IR spectrometer simultaneously collects high-spectral-resolution data over a wide spectral range. This confers a significant advantage over a dispersive spectrometer, which measures intensity over a narrow range of wavelengths at a time. FT-IR is used to characterize and confirm the components of the white specks. FIG. 7 demonstrates that the white specks are confirmed to be crystals of cetyl alcohol.

SEM-EDS

[0058] Energy Dispersive X-Ray Spectroscopy (EDS) is a chemical microanalysis technique used in conjunction with scanning electron microscopy (SEM). Energy-Dispersive X-Ray Spectroscopy (EDS) Interaction of an electron beam with a sample target produces a variety of emissions, including x-rays. EDS can be used to find the chemical composition of materials down to a spot size of a few microns, and to create element composition maps over a much broader raster area. A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface topography and composition. White specks are mainly composed of cetyl alcohol as confirmed by SEM (see FIG. 4 and FIG. 5). SEM-elemental analysis revealed that white specks were composed of carbon and oxygen, a trace of sodium and chlorine, but phosphorous was not detected, however which is clearly detected in Emulsiphos. Therefore, the white specs are confirmed to be cetyl alcohol.

Comparison of Global Homogenizers

[0059] To further understand the importance of homogenization on the formation of the liquid crystal structure, the same process as above except that different homogenizers were employed. Results are captured and summarized in Table 3. Final appearances are shown in FIGS. 3(A)-3(E). The results demonstrate that a 3-stage rotor and stator and relatively high energy density obtains product with good appearance. It is hypothesized that higher energy obtained from the homogenizer ensures better association of the Emulsiphon and the cetyl alcohol, thus ensuring successful formation of the liquid crystal structure.

TABLE-US-00003 TABLE 3 Item 1 2 3 4 5 Homogenizer QUADRO SILVERSON EL-Z48 inline QUADRO Silverson Type Z1 375 dispering Ytron Z3 L4RT Emulsifier Homogenizer 3 stage rotor 1 stage rotor 1 stage rotor 3 stage rotor 1 stage rotor configuration and stator and stator and stator and stator and stator Energy Density 0.23 0.04 0.27 0.45 N/A Ev (hp/lb/min) Results pass Fail fail pass pass

CONCLUSION

[0060] It is confirmed that the white specks came from the aggregates of crystalline cetyl alcohol. The apparent discrepancy between the above results may be because of droplet size reduction through homogenization on the molecular association of fatty alcohols with anionic surfactants.

[0061] With regard to the results for Item 5, wherein only 1 stage and rotor was employed, Silverson L4RT lab equipment employs technology that is different than that in pilot and production runs. In this equipment, the pump could be used to control the flow rate of product, which in turn, could control the energy density. The lab instrument basically uses one strong shear energy and applied it to the small scale amount of lab product.

[0062] To better ensure the molecular level association between two emulsifiers, a three-stage rotor and stator and high homogenization energy is required. To further prove the hypothesis, another batch was prepared. The appearance of this batch turned out to be acceptable. See FIG. 1(B).

[0063] It will be understood that, while various aspects of the present disclosure have been illustrated and described by way of example, the invention claimed herein is not limited thereto, but may be otherwise variously embodied according to the scope of the claims presented in this and/or any derivative patent application.

REFERENCES

[0064] 1) Ayannides, C. A. et al. (2002) J. Cosmet, Sci., 53: 165-173. [0065] 2) Schueller, R et al. (1998) Cosmet. Toiletries, 113: 39-44. [0066] 3) Gilsane G. Morais, etc. Influence of Mixing Speed in Liquid Crystal Formation and Rheology of 0/W Emulsions containing Vegetable Oils. Journal of Dispersion Science and Technology, 35:1551-1556, 2014. [0067] 4) Bruna Galdorfini Chiari et al. (Dec. 12, 2012). Cosmetics' Quality Control, Latest Research into Quality Control Isin Akyar, IntechOpen, DOI: 10.5772/51846. Available from: https://www.intechopen.com/books/latest-research-into-quality-control/cosmetics-quality-control. [0068] 5) Yihan Liu et al. Role of liquid crystal in the emulsification of a gel emulsion with high internal phase fraction. Journal of Colloid and Interface Science 340 (2009) 261-268. [0069] 6) Jochen Weiss, Emulsion ProcessingHomogenization, Food Structure and Functionality Workshop, Department of Food Science and Biotechnology, University of Honeheim, Emulsion Workshop, Nov. 13-14, 2008, Amherst, Mass. [0070] 7) J. Vilasau etc. Phase behavior of a mixed ionic/nonionic surfactant system used to prepare stable oil-in-water paraffin emulsion. Colloids and Surfaces A; Physicochem. Eng. Aspects 384 (2011) 473-481. [0071] 8) Guiillaume Toquer et al., Colloidal shape controlled by molecular adsorption at liquid crystal interface. The Journal of Physical Chemistry 2008, 112, 4157-4160. [0072] 9) J. M Ashua, Polymer dispersion: principles and applications. [0073] 10) Provost Christine. The application of DSC in the physico-chemical characterization of transparent oil-water gels. Bull. Soc. Chem. Belg. Vol. 98. No. 7 (1989):423-427.