NOVEL NANOEMULSIONS COMPRISING FATTY ACID AND N-ACYL DERIVATIVES OF AMINO ACID SALT

Abstract

The present invention relates to novel oil-in-water nanoemulsions. The oil phase contains oil selected from the group consisting of triglyceride oil and/or petrolatum as well as C.sub.8 to C.sub.18 fatty acid; and the aqueous phase contains specific N-acyl derivatives of amino acid salt as emulsifier.

Claims

1.-16. (canceled)

17. A process for preparing an emulsion comprising: a) an internal phase comprising (1) 40 to 75% by wt. of a total nanoemulsion composition of an oil phase containing benefit agent droplets comprising oils selected from the group consisting of triglyceride, petrolatum and mixtures thereof, wherein the melting point of the petrolatum is 30 to 60° C.; and (ii) 0.5 to 10% by wt. of the total nanoemulsion composition of a co-emulsifier comprising C.sub.8 to C.sub.18 fatty acid; and b) an external aqueous phase comprising 1.6 to 15% by wt. of the total nanoemulsion composition of a primary emulsifier comprising a surfactant or surfactants which are the salts of N-acyl derivatives of amino acid salt and wherein, said surfactant is selected from the group consisting of; i. a salt of N-acyl derivatives of di-carboxylic amino acid wherein greater than 65% of the acyl group has a chain length of C.sub.14 or less; ii. a salt of N-acyl derivatives of mono-carboxylic acid wherein greater than 65% of the acyl group has a chain length C.sub.14 or less; and iii. mixtures thereof; wherein the surfactant of (b) comprises 50% or greater of all surfactants present in the aqueous phase of the nanoemulsion; wherein a volume average diameter of the oil droplets of (a) is 20 to 400 nanometers wherein said process comprises: 1) heating the external aqueous phase to 55 to 75° C.; 2) heating the internal oil phase to 55 to 75° C. or until molten; 3) adding the internal oil phase to the external aqueous phase and mixing to form coarse emulsions in a rotor stator high shear device at 1000 to 6000 revolution per minute (rpm), or using a homogenizer at a pressure of 200 to 500 psi; 4) pumping the coarse emulsion once or multiple times through the homogenizer at process pressure of 7000 psi or less; and 5) cooling the emulsion to room temperature.

18. The process according to claim 17, wherein in step 3), the coarse emulsion is formed using a homogenizer operating at a pressure of 200 to 500 psi.

19. The process according to claim 17, wherein the salt of N-acyl derivative of dicarboxylic amino acid is a salt of acylglutamic acid, salt of acylaspartic acid, or a mixture thereof.

20. The process according to claim 17, wherein the salt of N-acyl derivative of monocarboxylic amino acid is a salt of acylgycine, salt of acylalanine, or a mixture thereof.

21. The process according to claim 17, wherein the benefit agent droplets are an oil, wherein the oil is a triglyceride oil and the triglyceride oil is selected from the group consisting of soybean oil, sunflower seed oil, coconut oil, rapeseed oil, palm oil, palm kernel oil, grape seed oil, fish oil and mixtures thereof.

22. The process according to claim 17, wherein the oil is petrolatum and the melting point of the petrolatum is 30 to 60° C.

23. The process according to claim 17, wherein the oil is an oil mixture comprising triglyceride oil and petrolatum.

24. The process according to claim 17, wherein the fatty acid having a chain length of C.sub.8-C.sub.18 is selected from the group consisting of lauric acid, myristic acid, coconut fatty acid and mixtures thereof.

25. The process according to claim 17, wherein the co-emulsifier is a fatty acid present at a level of 1 to 7% by wt.

26. The process according to claim 17, wherein the salts of N-acyl derivatives of the amino acid are mono- and/or di-sodium and/or potassium salts.

27. A nanoemulsion composition comprising: a) an internal phase comprising (1) 40 to 75% by wt. of total nanoemulsion composition of an oil phase containing benefit agent droplets comprising oils selected from the group consisting of triglyceride, petrolatum and mixtures thereof, wherein the melting point of the petrolatum is 30 to 60° C.; and (ii) 1 to 10% by wt. nanoemulsion of a co-emulsifier comprising a C.sub.8 to C.sub.18 fatty acid; and b) an external aqueous phase comprising 1.6 to 15% by wt. of total nanoemulsion composition of a primary emulsifier comprising a surfactant or surfactants which are N-acyl derivatives of amino acid salt; wherein the surfactant of (b) comprises 50% or greater of all surfactants present in said external aqueous phase of the nanoemulsion; wherein the volume average diameter of droplets of (a) is 20 to 400 nanometers, wherein the salt of N-acyl derivative of monocarboxylic amino acid is a salt of acylgycine, salt of acylalanine, or a mixture thereof.

28. The nanoemulsion composition according to claim 27, wherein the surfactant or surfactants are selected from the group consisting of (i) salt of N-acyl derivatives of dicarboxylic amino acid, wherein greater than 65% of the acyl group has chain length of C.sub.14 or less; and (ii) salt of N-acyl derivatives of monocarboxylic amino acid, wherein greater than 65% of the acyl group has chain length C.sub.14 or less; and (iii) mixtures thereof.

29. The nanoemulsion composition according to claim 27, wherein volume average diameter of the droplets is 20 to 250 nm.

30. The nanoemulsion composition according to claim 27, wherein the benefit agent droplets are an oil, wherein the oil is a triglyceride oil and the triglyceride oil is selected from the group consisting of soybean oil, sunflower seed oil, coconut oil, rapeseed oil, palm oil, palm kernel oil, grape seed oil, fish oil and mixtures thereof.

31. The nanoemulsion composition according to claim 27, wherein the oil is petrolatum and the melting point of the petrolatum is 30 to 60° C.

32. The nanoemulsion composition according to claim 27, wherein the oil is an oil mixture comprising triglyceride oil and petrolatum.

33. The nanoemulsion composition according to claim 27, wherein the fatty acid having a chain length C.sub.8-C.sub.18 is selected from the group consisting of lauric acid, myristic acid, coconut fatty acid and mixtures thereof.

34. The nanoemulsion composition according to claim 27, wherein the co-emulsifier is a fatty acid present at a level of 1 to 7% by wt.

35. The nanoemulsion composition according to claim 27, wherein the salts of N-acyl derivatives of the amino acid are mono- and/or di-sodium and/or potassium salts.

36. The nanoemulsion composition according to claim 27, wherein the surfactant of (b), prior to formation of the nanoemulsion, is a powder or liquid surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0053] Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about.” All amounts are by weight of the final composition, unless otherwise specified.

[0054] It should be noted that in specifying any range of concentration or amount, any particular upper concentration can be associated with any particular lower concentration or amount.

[0055] For the avoidance of doubt, the word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive.

[0056] The disclosure of the invention as found herein is to be considered to cover all embodiments as found in the claims as being multiply dependent upon each other irrespective of the fact that claims may be found without multiple dependency or redundancy.

[0057] The present invention provides novel nanoemulsions containing a specific selection of oils and surfactants. The nanoemulsions can be prepared using processing pressure of 7000 psi or less. The novel nanoemulsions are ideally suited for use in liquid cleansing compositions, for example, structured (e.g., micellar or lamellar structured) liquid cleansing compositions.

[0058] Specifically, the N-acyl derivatives of amino acid surfactants (e.g., acylglutamate, acylaspartate, acylglycinate, acylalanate surfactants) have greater than 65%, preferably greater than 75%, preferably greater than 80% of C.sub.14 or less acyl chain (preferably they have greater than 75% acyl chain which are C.sub.12, C.sub.14 and mixtures thereof). The chosen surfactants provide multiple advantages when final nanoemulsions are mixed into fully formulated liquid personal cleansing compositions. First, the amino acid surfactants are known to be less irritating than harsher surfactants typically used such as sodium lauryl sulphate and sodium lauryl ether sulphate (SLES). Also, as noted, the chain length is selected so the surfactants are suitable for use in structured personal cleansing liquids while providing minimal interference with such structuring. Further, the selected predominantly shorter chain lengths ensure the surfactants will provide good foam.

[0059] In a co-pending application, applicants claim similar nanoemulsions which comprise N-acyl derivatives of di-carboxylic acids and which are not specifically directed to those containing fatty acid emulsifier. Small size droplets are obtained. In this application, unexpectedly we have found that using fatty acid as co-emulsifier yields significantly smaller droplets, and these small droplet nanoemulsions are obtained more efficiently. Furthermore, using fatty acid as co-emulsifier permits use of N-acyl derivatives of amino acid surfactants which are in liquid format, containing high amount of inorganic salts and with pH as high as 10 (which were not used in co-pending cases). Surprisingly, the co-emulsifier permits production of small droplets whether the amino acid surfactants are derivatives of dicarboxylic or mono-carboxylic amino acids. Small droplet size and efficient processing is function of specific combination of specific surfactants (e.g., anionic) and specifically fatty acid. Higher amounts of fatty acid used with glutamate, for example, are more efficient (form smaller drops) than using more total surfactant, but lesser fatty acid. That is, a unique synergy between surfactants of the invention and fatty acid and, as noted, works particularly well with oils (e.g. petrolatum jelly) of the invention.

[0060] In short, significantly smaller droplets are obtained (using fatty acids) when using the same materials, and these small droplet nanoemulsions are obtained more efficiently. In general, small volume average size droplets help provide more efficient deposition. For example, cationic polymers typically used in fully formulated liquid cleanser more readily deposit the smaller droplets than larger droplets. Large oil droplets also require stabilizers to suspend the large oil droplets. The small size oil droplets from the nanoemulsion, when incorporated into a cleansing liquid, also provide greater stability. Small droplets are also viewed as more aesthetically pleasing.

[0061] The nanoemulsions of the invention are defined with more particularity below.

Oil Phase

[0062] Oils in the oil phase of the nanoemulsions may be triglyceride oil or oils (animal and/or vegetable oils); petrolatum; or mixtures of one or more triglyceride oil with petrolatum. Petrolatum is particularly preferred.

[0063] Examples of triglyceride oils which may be used include soybean oil, sunflower seed oil, coconut oil, rapeseed oil, palm oil, palm kernel oil, grape seed oil and fish oil. Soybean and sunflower seed oils are preferred triglycerides.

[0064] The oil in the oil phase may also be petrolatum. The petrolatum preferably has a melting point ranging from 30° to about 60° C. Examples of such petrolatum oils include Vaseline® Petrolatum Jelly from Unilever, White Petrolatum USP from Calumet Penreco, Petrolatum G2212 and White Protopet® 1S from Sonneborn.

[0065] The oils can range from 40% to 75% by wt., preferably 41% to 65% by wt. of the total nanoemulsion composition. The preferred volume average diameter of the triglyceride oil or petrolatum droplets is 20 to 400 nm, preferably 20 to 300 nm, more preferably 20 to 250 nm, or 20 to 200 nm. Lower level can be 20 or 30 or 40 or 50; upper level can be 300 or 250 or 200 or 175 or 150.

[0066] The choice of triglyceride oils and petrolatum helps impart emolliency and occlusivity to skin when the triglyceride oils and/or petrolatum deposit onto skin after the skin is washed with fully formulated cleansing compositions into which the nanoemulsions of this invention have been incorporated.

[0067] In addition to the triglyceride oil (or oils) and/or petrolatum, the oil phase may comprise oil soluble skin beneficial actives such as, for example, Vitamin A, Vitamin E, sun screen, fragrances, retinol palmitate, 12-hydroxy stearic acid, conjugated linoleic acid; antibacterial agents; mosquito repellents etc. at level of 0.01 to 5%.

[0068] Another ingredient which might be found in the oil phase is an oil phase stabilizer. For example, small amounts (0.01 to 2%, preferably 0.1-1% by wt. nanoemulsion) of antioxidant may be used. When the oil used is triglyceride, a preferred antioxidant which may be used is butylated hydroxytoluene (BHT). This is often used as a food grade antioxidant.

[0069] In addition to oils, the oil phase contains C.sub.8 to C.sub.18, preferably C.sub.10 to C.sub.14 fatty acids in an amount ranging from 0.5 to 10% by wt. total nanoemulsion. Examples of fatty acid which may be used include lauric acid, myristic acid, coconut fatty acid and mixtures thereof. The fatty acid is used as a co-emulsifier. For example, the oil phase may contain petrolatum ranging from 40 to 70% by wt, preferably 41 to 65% by wt. of nanoemulsion and lauric acid ranging from 0.5 to 8% by wt. of nanoemulsion.

Aqueous Phase

[0070] The aqueous phase contain salts of N-acyl derivatives of amino acids (e.g., di- or mono-carboxylic acid) as emulsifier (50% or greater, preferably 60% or greater of all surfactant present in the aqueous phase). Preferred di-carboxylic amino acid emulsifiers are acylglutamate and acylaspartate surfactants. Preferred mono-carboxylic amino acid emulsifiers are acylglycinate and acylalanate. Preferably, these are potassium and/or sodium salts of N-acyl derivatives of amino acids, wherein greater than 65% of the acyl chains has chain length C.sub.14 or less, e.g., C.sub.8 to C.sub.14 (e.g., derived from coconut fatty acid). The acyl chains preferably have greater than 75%, more preferably greater than 80% C.sub.14 or less chain length. Preferably, greater than 75%, most preferably greater than 80% of the chain length are C.sub.12, C.sub.14 or mixtures thereof. These predominantly short chain acyl groups (relative to longer chain C16 and C18, for example) ensure that, when nanoemulsions of the invention are incorporated into fully formulated liquid cleansing compositions (especially structured liquid cleansing compositions), they help maintain or enhance foaming capacity.

[0071] There are typically two formats of amino acid surfactants commercially available. One is powder or flake format, which is typically more expensive and high in purity. Examples of solid dicarboxylic amino acid surfactants include: [0072] sodium N-cocoyl-L-glutamate (e.g., Amisoft® CS-11 by Ajinomoto) [0073] sodium N-lauroyl-L-glutamate (e.g., Amisoft® LS-11 by Ajinomoto) [0074] sodium N-myristoyl-L-glutamate (Amisoft® MS-11 by Ajinomoto) [0075] potassium N-cocoyl_I-Glutamate (e.g., Amisoft® CK-11 by Ajinomoto) [0076] potassium N-myristoyl-L-glutamate (Amisoft® MK-11 by Ajinomoto) [0077] potassium N-lauroyl-L-glutamate (Amisoft® LK-11 by Ajinomoto) [0078] Sodium Lauroyl Aspartate (AminoFoamer™ FLMS-P1 by Asahi Kasei Chemical Corporation) [0079] Sodium Lauroyl Glutamate (Aminosurfact™ ALMS-P1/S1 by Asahi Kasei Chemical Corporation) [0080] Sodium Myristoyl Glutamate (Aminosurfact™ AMMS-P1/S1 by Asahi Kasei Chemical Corporation)

[0081] Examples of solid monocarboxylic amino acids surfactants include: [0082] sodium cocoyl glycinate (e.g., Amilite® GCS-11 by Ajinomoto) [0083] potassium cocoyl glycinate (e.g., Amilite® GCK-11 by Ajinomoto

[0084] One of unexpected discoveries of this invention is that, in addition to amino acids noted above (which are in powder form and are not convenient to handle in plant production), using fatty acid as co-emulsifier permits use of amino acid surfactants in liquid form, which is typically less expensive but high in pH and inorganic salt As noted in the comparative examples, in the absence of the fatty acid emulsifier, applicants could not form a coarse emulsion or droplet size was very high (much greater than 400 nm); using acylglutamate, for example, the coarse emulsion phase separated and/or, when using liquid acylglutamate with high level of citric acid to lower the pH, droplet size was about 2.5 times as large as when fatty acid is used. In the case of acylglycinate, for example, without fatty acid the droplet size was 14 times larger compared to when fatty acid was present. The addition of a fatty acid, especially lauric acid, to the industrial liquid amino acid surfactant as a co-emulsifier resulted in the formation of stable coarse emulsions and the efficient formation of smaller oil droplets to form a highly superior nanoemulsion. For example, it was possible to produce petrolatum oil droplet sizes below 200 nm with only one pass through the homogenizer at 5000 psi (see Example 6).

[0085] Liquid amino acid surfactants typically contain 20˜35% surfactant active, high in pH and inorganic salt (e.g. from 3 to 6% NaCl). Examples include: [0086] AMISOFT® ECS-22SB: Disodium Cocoyl Glutamate (30% Aqueous Solution) [0087] AMISOFT® CS-22: Disodium Cocoyl Glutamate and sodium Cocoyl Glutamate (25% Aqueous Solution) [0088] AMISOFT® CK-22: Potassium Cocoyl Glutamate (30% Aqueous Solution) [0089] AMISOFT® LT-12: TEA-Lauroyl Glutamate (30% Aqueous Solution) [0090] AMISOFT® CT-12 TEA-Cocoyl Glutamate (30% Aqueous Solution) [0091] AMILITE® ACT-12: TEA-Cocoyl Alaninate (30% Aqueous Solution) [0092] AMILITE® ACS-12: Sodium Cocoyl Alaninate (30% Aqueous Solution) [0093] AMILITE® GCK-12/GCK-12K: Potassium Cocoyl Glycinate (30% Aqueous Solution) [0094] Aminosurfact™ ACDS-L: Sodium Cocoyl Glutamate (25% Aqueous Solution) [0095] Aminosurfact™ ACDP-L: Potassium Cocoyl Glutamate (22%)+Sodium Cocoyl Glutamate (7%) [0096] Aminosurfact™ ACMT-L: TEA-Cocoyl Glutamate (30% Aqueous Solution) [0097] AminoFoamer™ FLDS-L: Sodium Lauroyl Aspartate (25% Aqueous Solution)

[0098] In addition to the Amisoft® and Amilite® series from Ajinomoto, Aminosurfact™ and AminoFoamer™ from Asahi Kasei Chemical Corporation, other suppliers of liquid amino acid surfactants include Clariant (e.g. Hostapon SG Sodium cocoyl glycinate), Solvay (e.g.Gerapon® PCG Potassium Cocoyl Glutamate aqueous solution; Gerapon® LG 3S sodium lauryl glycinate with glycerin), Galaxy (Galsoft® KCGL Potassium Cocoyl Glutamate aqueous solution; GalSoft® SCG plus sodium cocoyl glycinate, 20% active) and Sino Lion (Eversoft® USK-30K Potassium Cocoyl Glutamate aqueous solution; Eversoft® YCS-30S sodium cocoyl glycinate).

[0099] Additionally, other mild ionic cleansing surfactants can be used in the aqueous phase. Anionic surfactants which may be used include sodium cocoyl isethionate, sodium cocoyl methyl isethionate, sodium lauroyl isethionate, sodium methyl cocoyl taurate and other amino acid based surfactants, such as sodium lauroyl sarcosinate, sodium cocoyl sarcosinate. Amphoterics such as coco betaine, cocamidopropyl betaine, sodium lauroamphoacetate, Lauramidopropyl hydroxysultaine and Cocamidopropyl hydroxysultaine can also be used. These co-surfactants are typically present at a level of less than 50%, preferably less than 40%, more preferably less than 30% of total surfactants in the aqueous phase.

[0100] Overall surfactants in aqueous phase comprise 1.6 to 15% preferably 4 to 12% by wt. of total nanoemulsion. As indicated, the salts of N-acyl derivatives of amino acid, preferably acylglutamate, acylaspartate, acylglycinate, acylalaninate or mixtures thereof are the principal surfactant of the nanoemulsion. They constitute 50% or greater, preferably 60% or greater of all surfactant in the aqueous phase. Preferably they constitute greater than 70%, more preferably greater than 75%. They may of course be the only surfactant present in the aqueous phase.

[0101] Preferably, the aqueous phase may contain a preservative or preservatives. Typically, they are present at a level of 0.01 to 1.0%, preferably 0.1 to 0.5% by wt.

[0102] Nanoemulsions of the invention, have volume average diameter (also used interchangeably in and with terms “volume mean diameter” or “volume average size”) of 400 nm or less, preferably 20 nm to 300 nm, more preferably 20 to 250 nm, more preferably 20 to 200 nm.

[0103] Nanoemulsions with droplet sizes of these ranges are obtained in the subject invention using relatively low pressure applied by a high pressure homogenizer or a high pressure sonolator. Pressures used are 7000 psi or less, preferably 6000 psi or less, most preferably 5000 psi or less.

Preparation of Nanoemulsion

[0104] Nanoemulsions are typically formed in a two-stage process.

[0105] The first mixing stage is used to form a coarse emulsion. The oil phase and aqueous phase were heated up to 75° C. (55° to 75° C.) separately such that each phase was clear and uniform (oil phase heated to 55 to 75° C. or until molten); then the oil phase was mixed with the aqueous phase with intensive mixing. Intensive mixing can be accomplished via conventional means including mixing the materials in a stirred tank and passing the mixture through a rotor/stator mixer such as the Silverson® high shear in-line mixer or mixing them in the vessel with a high shear mixer such as the Scott® Turbon mixer. Alternatively, the coarse emulsion may be created by using a continuous high shear mixing device such as the standard Sonolator device produced by Sonic Corporation of Connecticut. These standard Sonolators are normally operated at pressures of 200-500 psi to form coarse emulsion.

[0106] The second stage of the process is to pass the coarse emulsion through a high pressure homogenizer to form the nano-emulsion. Suitable high pressure homogenizers are the Nano DeBee homogenizer of BEE International (Massachusetts, USA) and the High Pressure Sonolator device also produced by Sonic Corporation of Connecticut, USA. These devices can be operated up to 1000-5000 psi in order to produce nanoemulsions of less than 300 nm. For hydrophobic oils, either petrolatum or triglycerides, only one pass through the Nano DeBEE or high pressure Sonolator is required to reach the desired nano-emulsion particle size, when fatty acid is included as co-emulsifier.

[0107] In the examples, the following terms are defined as noted below: [0108] Pass #: the number of times the emulsion passes through high pressure homogenizer [0109] D[4, 3]: volume average diameter or volume mean diameter or volume average size [0110] D[3, 2]: surface area mean diameter

[0111] The average diameters are determined by a Malvern Mastersizer.

Examples 1-6 and Comparatives A-H

[0112] Coarse emulsions were prepared in a one-liter ESCO mixer equipped with a rotor/stator high shear device (ESCO-LABOR AG, Switzerland). The aqueous phase was added to the ESCO mixer and heated up to 75° C. or till clear. The oil phase was combined and heated up to 75° C. or till molten in a separate container. The oil phase was gradually added to the aqueous phase in the ESCO mixer under agitation and/or was intensively mixed by the rotor/stator device. When the addition of all oil phased was completed and the coarse emulsion was formed in the ESCO mixer, the coarse emulsion was transferred and passed through High Pressure homogenizer Nano DeBEE one or 2 times to arrive at the desired droplet size at a process pressure of 5000 psi.

Examples 1-2 and Comparatives A-C

[0113] In Examples 1-2 and Comparatives A-C, liquid potassium cocoyl glutamate (27.2% active) high in pH (about 10) and high in inorganic salt (about 3 to 6% KCl) was used as primary emulsifier. Coarse emulsions that are stable enough were passed through the Nano DeBEE once at a process pressure of 5000 psi to form nanoemulsions. The oil droplet size was measured using Malvern Mastersizer afterwards.

TABLE-US-00001 Example Example Comparative Comparative Comparative 1 2 A B C Ingredient Wt. % Wt % Wt. % Wt. % Wt. % Oil Phase White petrolatum USP .sup. 50% .sup. 50% .sup. 50% .sup. 50% .sup. 50% Lauric acid   4%   2% Aqueous Phase Potassium Cocoyl 27.4% 27.4% 27.4% 27.4% 27.4% Glutamate (Solvay, Active 27.2%) (7.5% active) (7.5% active) (7.5% active) (7.5% active) (7.5% active) Deionized Water Q.S.* Q.S.* Q.S.* Q.S.* Q.S.* Citric acid 1.28% 1.28% 1.92% DMDM Hydantoin (and) 0.40%  0.4% 0.40% 0.40%  0.4% Iodopropynyl Butylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000  5000  No coarse Coarse 5000  D.sub.[3,2] nm 127 138 emulsion emulsion 187 D.sub.[4,3] nm 186 209 formed phase 476 separated in 2 minutes pH    6.76    5.71 10.0 5.57    5.22 *Amount needed (e.g., to obtain 100% by wt.)

[0114] No coarse emulsion was formed in comparative A. When 1.28% citric acid was added to the aqueous phase as shown in Comparative B to lower the pH to the range about 5 to 6, coarse emulsion was formed with intensive mixing but phases quickly separated when the rotor/stator high shear device was stopped. When 1.92% citric acid was added to the aqueous phase as shown in Comparative C, coarse emulsion was formed and stayed uniform long enough to be passed through Nano DeBEE, yielding volume average mean droplet size of 476 nm.

[0115] When 2 to 4% Lauric acid was added to the oil phase as shown in Example 1 and 2, stable coarse emulsion formed with or without citric acid. One pass through Nano DeBEE at the same process pressure of 5000 psi, yielding volume average mean droplet size as low as 186 nm. Thus, addition of lauric acid not only diminishes amount of citric acid needed to form coarse emulsion (Example 1), but formed much smaller droplets of 209 or less in only one pass.

Example 3 and Comparative D

[0116] In Example 3 and Comparative D, liquid sodium cocoyl glycinate (20% active) high in pH (about 10) and high in inorganic salt (about 3 to 6% NaCl) was used as primary emulsifier. Coarse emulsions that are stable enough were passed via Nano DeBEE once at a process pressure of 5000 psi and the oil droplet size was measured using Malvern Mastersizer afterwards.

TABLE-US-00002 Comparative D Example 3 Ingredient Wt. % Wt % Oil Phase White petrolatum USP 50% 50% Lauric acid  0%  4% Aqueous Phase Sodium Cocoyl Glycinate 40% 40% (Galsoft, Active 20%) (8% active) (8% active) Deionized Water Q.S. Q.S. DMDM Hydantoin (and) 0.40%.sup.  0.4%  Iodopropynyl Butylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000 5000  D.sub.[3,2] nm 1900 161 D.sub.[4,3] nm 3917 266 pH    9.1    6.59

[0117] Although a coarse emulsion was formed when passing the composition through Nano DeBEE at 5000 psi once, the oil droplet size was 3917 nm; when lauric acid was added to oil phase, under the same process conditions, oil droplets of 266 nm were obtained. Particle size was thus 14 times smaller when using lauric acid than without using lauric acid.

Examples 4-5 and Comparatives E and F

[0118] The oil is soybean oil and the emulsifier is flake form of Potassium cocoyl Glutamate (AMISOFT® CK-11). With or without lauric acid added to oil phase, stable coarse emulsions were formed and passed through Nano DeBEE once either at process pressure of 5000 psi or 3000 psi. The pH of the final nanoemulsions fall between about 5.6 to 5.8. At 5000 psi, with 4% lauric acid added, the volume average droplet was reduced from 188 nm to 143 nm (see Comparative E and Example 4); at 3000 psi, with 4% lauric acid added, the volume average droplet was reduced from 268 nm to 161 nm (see Comparative F and Example 5).

TABLE-US-00003 Comparative Comparative Example Example E F 4 5 Ingredient Wt. % Wt % Wt. % Wt. % Oil Phase Soybean Oil  55%  55%  55%  55% BHT Food Grade 0.4% 0.4% 0.4% 0.4% Antioxidant Lauric acid .sup. 4% .sup. 4% Aqueous Phase Potassium cocoyl 8.8% 8.8% 8.8% 8.8% Glutamate (AMISOFT ® CK-11) Deionized Water Q.S. Q.S. Q.S. Q.S. DMDM Hydantoin (and) Iodopropynyl 0.40%  0.4% 0.40%  0.40%  Butylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000  3000  5000  3000  D.sub.[3,2] nm 127 163 113 116 D.sub.[4,3] nm 188 268 143 161 pH    5.82    5.82    5.65    5.65

Example 6 and Comparatives G and H

[0119] Stable coarse emulsion was formed using 50% White Petrolatum and Potassium cocoyl Glutamate (AMISOFT® CK-11) as primary emulsifier with or without lauric acid as co-emulsifier. Without lauric acid, the coarse emulsion passed Nano DeBEE once and two times at 5000 psi separately, yielding nanoemulsion with volume average droplet of 374 nm and 283 nm respectively. With 4% lauric acid and only one pass at 5000 psi through Nano DeBEE, the volume average droplet was reduced to 168 nm. Thus, lauric acid greatly improved the efficiency of small drop formation.

TABLE-US-00004 Compar- Compar- Example ative G ative H 6 Ingredient Wt. % Wt % Wt % Oil Phase White Petrolatum USP .sup. 50% 50% 50%  Lauric acid 4% Aqueous Phase Potasium cocoyl Glutamate   8%  8% 8% (AMISOFT ® CK-11) Deionized Water Q.S. Q.S. Q.S. DMDM Hydantoin (and) 0.40% 0.4%  0.4%.sup.  lodopropynyl Butylcarbamate(Glydant ™ Plus ™ Liquid) Process pressure, PSI 5000  5000  5000  Number of Passes  1  2  1 D.sub.[3,2] nm 188 168 120 D.sub.[4,3] nm 374 283 168 pH    5.91    5.91    5.73

[0120] Examples 7-13: 50-55% Petrolatum was used to form nanoemulsions, with potassium cocoyl glutamate (30%) or Sodium Cocoyl Glycinate (20%) in the liquid form as primary emulsifier, ranging 4 to 8.2% in active and lauric acid as co-emulsifier ranging 1 to 4%. The coarse emulsion was prepared by a low pressure sonolator at a pressure up to 450 psi, where the molten oil phase and aqueous phase at 60 to 75 C were simultaneously pumped through the orifice of a low pressure sonolator and thus formed the coarse emulsion. The coarse emulsion was further pumped through a high pressure sonolator only once with a pressure up to 2500 psi to form nanoemulsion. Examples 12 and 13 used different lower pressure in forming coarse emulsion and nanoemulsion as shown in the table.

[0121] With 4% lauric acid as co-emulsifier as shown in examples 10, 11 and 12, nanoemulsion with volume average droplet ranging from 144 to 198 nm was formed after one pass of high pressure sonolator at pressure of 2500 psi or less. With 4% lauric acid as co-emulsifier as shown in example 11 and 12, even the coarse emulsion yielded volume average droplet size below 300 nm after passing the low pressure sonolator at 450 psi or less.

[0122] Efficient production of small droplets is not believed to be just function of total surfactant amount, but rather of type and interaction of surfactants. This is seen comparing Example 7 to Example 10. Although there is less overall surfactant active in Example 10 (8% vs. 9.2% in Example 7), because of interaction of anionic glutamate and greater amounts of fatty acid, the droplet size for petrolatum of Example 10 is 158 nm versus 316 nm for Example 7.

TABLE-US-00005 Example 7 8 9 10 11 12 13 Ingredient Wt. % Wt % Wt. % Wt. % Wt. % Wt. % Wt. % Oil Phase Petrolatum G2212  .sup. 55%  .sup. 55% .sup. 55% .sup. 55% 55%  .sup. 55% White petrolatum 50% Lauric acid  .sup. 1%  .sup. 2%   2%   4%  4%  .sup. 4%  4% Aqueous Phase Potassium Cocoyl 27.3%.sup.  27.3%.sup.  13.3% 13.3% 20% 27.4%.sup.  Glutamate(Galsoft KCGL, (8.2% (8.2% (4% (4% (6% (8.2% Active 30%) active) active) active) active) active) active) Sodium Cocoyl Glycinate 40% (Galsoft SCG plus, (8% Active 20%) active) Deionized Water Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. Q.S. DMDM Hydantoin 0.158% .sup.  0.158% .sup.  0.158%  0.158%  0.158%   0.158% .sup.  0.4%  (and) Iodopropynyl Butylcarbamate(Glydant ™ Plus ™ Liquid) D.sub.[4,3], nm 855 514 560 350 279 285 334 (coarse emulsion (350 (350 formed @450 psi) psi) psi) D.sub.[4,3], nm 316 217 286 158 144 198 228 (Nanoemulsion formed (1000 2000 @2500 psi) psi) psi) pH    8.4    7.88    7.36    7.0    7.23    7.25    6.7