Nanoemulsions comprising sulfoalkyl ester and/or amide of fatty acids in aqueous phase

Abstract

The present invention relates to novel oil-in-water pumpable 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 sulfoalkyl ester and/or amide of fatty acids as emulsifier.

Claims

1. A nanoemulsion composition comprising: a) an internal phase comprising (i) 40 to 75% by wt. of total nanoemulsion composition of 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) 0.8 to 10% by wt. nanoemulsion of a C.sub.8 to C.sub.18 fatty acid; and b) an external aqueous phase comprising 1.6 to 15% by wt. (as active) of total nanoemulsion composition of a surfactant or surfactants which are an alkali metal or ammonium salt of isethionate; alkali metal C1 to C3 alkyl, alkyl taurate; or mixture of the two, wherein the surfactant or surfactants which are an alkali metal or ammonium salt of isethionate; alkali metal C1 to C3 alkyl, alkyl taurate; or mixture of the two comprises 70% or greater of all surfactants present in said external aqueous phase of the nanoemulsion; wherein the volume average diameter of droplets of the internal phase is 100 to 400 nanometers.

2. The nanoemulsion composition according to claim 1, wherein said alkali metal or ammonium salt of isethionate is sodium acyl isethionate.

3. The nanoemulsion composition according to claim 1, wherein said alkali metal C1 to C3 alkyl and wherein said alkyl taurate is sodium methyl alkyl taurate.

4. The nanoemulsion composition according to claim 1, wherein volume average diameter is 120 to 300 nanometers.

5. The nanoemulsion composition according to claim 1 further comprising surfactant in the aqueous phase selected from the group consisting of cocobetaine, cocoamidopropyl betaine, lauroamphoacetate, hydroxysultaine and mixtures thereof.

6. The nanoemulsion composition according to claim 5, wherein said additional surfactant comprises up to 30% by wt. of aqueous phase surfactant.

7. The nanoemulsion composition according to claim 1, wherein the oil is a triglyceride oil and said 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.

8. The nanoemulsion composition according to claim 1, wherein the oil is petrolatum and the melting point of the petrolatum is 30 to 60° C.

9. The nanoemulsion composition according to claim 1, wherein the oil is an oil mixture comprising triglyceride oil and petrolatum.

10. The nanoemulsion composition according to claim 1, wherein said 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.

11. The nanoemulsion composition according to claim 10, wherein the fatty acid is present at a level of 1 to 7% by wt. of said nanoemulsion.

12. The nanoemulsion composition according to claim 1, wherein the nanoemulsion is prepared at pressure from a homogenizer or sonolator and said pressure is 5000 psi or below.

13. A process for preparing an emulsion comprising: a) an internal phase comprising (i) 40 to 75% by wt. of total nanoemulsion composition of 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) 0.8 to 10% by wt. nanoemulsion of a C.sub.8 to C.sub.18 fatty acid; and b) an external aqueous phase comprising 1.6 to 15% by wt. (as active) of total nanoemulsion composition of a surfactant or surfactants which are an alkali metal or ammonium salt of isethionate; alkali metal C1 to C3 alkyl, alkyl taurate; or mixture of the two wherein the surfactant or surfactants which are an alkali metal or ammonium salt of isethionate; alkali metal C1 to C3 alkyl, alkyl taurate sulfoalkyl ester or amide of fatty acids, or mixture of the two comprises 70% or greater of all surfactants present in the aqueous phase of the nanoemulsion; wherein the volume average diameter of the oil droplets of the internal phase is 100 to 400 nanometers wherein said process comprises: 1) heating aqueous phase to 55 to 75° C.; 2) heating oil phase to 55 to 75° C. or until molten; 3) adding oil phase to aqueous phase and mixing to form coarse emulsions using a rotor/stator high shear device at 1000 to 6000 revolutions per minute (rpm), 4) pumping the coarse emulsion once through a homogenizer at process pressure of 5000 psi or less; and 5) cooling emulsion to ambient temperature.

14. The process according to claim 13, wherein in step 3), alternatively, the coarse emulsion is formed using a homogenizer operating at pressure of 200 to 500 psi.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) 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.

(2) 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.

(3) 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.

(4) 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.

(5) The present invention provides novel nanoemulsions containing a specific selection of oils and surfactants. The nanoemulsions can be prepared using processing pressure of 5000 psi or less. The novel nanoemulsions are ideally suited for use in cleansing compositions, for example, liquid cleansing compositions or soap bars.

(6) Specifically, sulfoalkyl ester of fatty acid, such as sodium acyl isethionate, or sulfoalkyl amide of fatty acid, such as sodium methyl alkyl taurates have greater than 65%, preferably greater than 75%, preferably greater than 80% of C.sub.14 or less acyl or alkyl chain (preferably they have greater than 75% acyl or alkyl chain which are C.sub.12, C.sub.14 and mixtures thereof). The chosen emulsifiers provide multiple advantages when final nanoemulsions are mixed into fully formulated liquid personal cleansing compositions. First, the isethionate and taurate 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 personal cleansing compositions while providing minimal interference with such product structuring. Further, the selected predominantly shorter chain lengths ensure the surfactants will provide good foam.

(7) In a co-pending application, applicants claim similar nanoemulsions which comprise N-acyl derivatives of di-carboxylic amino acids and which are more expensive and can be supplied in the format of liquid solution with 20 to 35% actives. Small size oil droplets are obtained with fatty acid being used as co-emulsifier.

(8) In this application, poorly soluble anionic surfactants, e.g. sodium acyl isethionate, when used as emulsifier, tend to yield oil droplets that are larger, e.g., greater than 400 nanometer (nm) after one pass through a high pressure homogenizer at 5000 pounds per square inch (psi) pressure. Further, nanoemulsions made with sodium acyl isethionate tend to solidify at ambient temperature and are thus difficult to pump. Unexpectedly we have found that using fatty acid as co-emulsifier yields significantly smaller droplets, and these small droplet nanoemulsions are obtained more efficiently. Surprisingly, even when no solubilizer of sodium acyl isethionate is used, the subject nanoemulsion is pumpable at ambient temperature. Use of a solubilizer, however, further enhances the pumpability of nanoemulsion. Small droplet size and efficient processing is function of specific combination of specific surfactants (e.g., anionic) and specifically fatty acid. That is, a unique synergy between surfactants of the invention and fatty acid, as noted, works particularly well with oils (e.g. petroleum jelly) of the invention.

(9) In short, significantly smaller droplets are obtained (using fatty acids) when using the same materials, and these small droplet nanoemulsions are obtained more efficiently and are pumpable at ambient temperature. 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.

(10) The nanoemulsions of the invention are defined with more particularity below.

(11) Oil Phase

(12) 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.

(13) 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, shea butter, cocoa butter and fish oil. Soybean and sunflower seed oils are preferred triglycerides.

(14) 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® Petroleum Jelly from Unilever, White Petrolatum USP from Calumet Penreco, Petrolatum G2212 and White Protopet® 1S from Sonneborn.

(15) Also suitable are the vegetable oils gelled with beeswax or vegetable wax. Examples of such gelled vegetable oils include NaturalAtum from Koster Keunen, Inc. and Unpetroleum Jelly from Camden-Grey Essential Oils, Inc.

(16) The oils 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 100 to 400 nm, preferably 120 to 350 nm, more preferably 150 to 300 nm.

(17) 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.

(18) 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; antibaterial agents; mosquito repellents etc. at level of 0.01 to 5%.

(19) 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.

(20) In addition to oils, the oil phase contains C.sub.8 to C.sub.20, preferably C.sub.10 to C.sub.14 fatty acids in an amount ranging from 0.8 to 10%, preferably 1 to 7% by wt. total nanoemulsion.

(21) Examples of fatty acid which may be used include lauric acid, myristic acid, palmitic acid, stearic acid, coconut fatty acid and mixtures thereof. Preferably, lauric 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 0.9 to 8% by wt. of nanoemulsion.

(22) Aqueous Phase

(23) The aqueous phase contain poorly water soluble anionic surfactants, sodium acyl isethionate, or sodium methyl alkyl taurates or both. The solubility of these surfactants ranges from 0.01 to 1% at ambient temperature. These surfactants have greater than 65%, preferably greater than 75%, preferably greater than 80% of C.sub.14 or less acyl or alkyl chain (preferably they have greater than 75% acyl or alkyl chain which are C.sub.12, C.sub.14 and mixtures thereof). Preferred acyl isethionate is cocoyl or lauryl isethionate and preferred taurates are cocoyl or lauryl taurate. 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 cleansing compositions (e.g. liquid cleansing compositions), they help maintain or enhance foaming capacity.

(24) The acyl isethionate surfactant component is typically prepared by the reaction of an isethionates salt and an fatty acid having 8 to 20 carbon atoms and Iodine Value (measuring degree of unsaturation) of less than 20, for example:
HOR.sup.1SO.sub.3M+RCOOH.fwdarw.RCOOR.sup.1SO.sub.3M

(25) where R.sup.1 is an aliphatic hydrocarbon radical containing 2 to 4 carbons;

(26) M is alkali metal cation (e.g., sodium, potassium), ammonium or substituted ammonium cation or other counterion; and

(27) R is an aliphatic hydrocarbon radical having 7 to 21, preferably 9 to 17 carbons.

(28) Depending on the processing conditions used, the resulting fatty acyl isethionate product can be a mixture of 40 to 85% by weight of fatty acyl isethionates (which formed from the reaction) and 50 to about 12 wt. %, typically 40 to 20 wt. % of free fatty acids. In addition, product may contain isethionates salts which are present typically at levels less than 5 wt. %, and traces (less than 2 wt. %) of other impurities. The acyl chain length distribution of fatty acyl isethionate is controlled by the chain length distribution of fatty acids. Preferably, a mixture of fatty acids is used for the preparation of commercial acyl isethionates surfactants. Typically coconut fatty acid is used, which is rich in lauric acid, resulting in cocoyl isethionate. The chain length distribution can be further adjusted by blending different cuts of distilled fatty acids to enrich a certain chain length, e.g., C.sub.12, in the final reaction product. The resulting acyl isethionate surfactants (e.g., resulting from reaction of alkali metal isethionate and aliphatic fatty acid) should have more than 65 wt. %, preferably more than 75%, (on basis of acyl isethionates reaction product) of acyl group with 14 or less carbon atoms to provide both lather and mildness of the resulting acyl isethionate product. The resulting acyl isethionate surfactants and unreacted fatty acids, form poorly soluble surfactant/fatty acid crystals typically in water at ambient temperatures.

(29) Examples of commercial acyl isethionate products that are particularly useful in the subject invention are DEFI flakes, a main ingredient in Dove® bar soap produced by Unilever. DEFI (Direct Esterification of Fatty Isethionate) flakes typically contain about 68 to 85 wt. % of sodium fatty acyl isethionate and 12 to 30 wt. % free fatty acid. More than 65 wt. % and preferably more than 75% of acyl group of the resulting acyl isethionate have 14 or less carbon atoms. The acyl isethionate surfactant products are extremely mild to skin and have very good lather.

(30) Other suppliers of acyl isethionate include Huanggang Yongan (e.g. YA-SCI-65 and YA-SCI-85), Innospec (e.g. Pureact SLI), Clariant (e.g. Hostapon® SCI-85 P).

(31) Sodium methyl alkyl taurates are closely related to acyl isethionate structurally and synthetically. The precursor of sodium methyl alkyl taurates, N-methyltaurine, can be prepared from sodium isethionate economically:
H.sub.2NCH.sub.3+HOCH.sub.2CH.sub.2SO.sub.3M.fwdarw.HN(CH.sub.3)CH.sub.2CH.sub.2SO.sub.3Na+H.sub.2O
where M is alkali metal cation (e.g. sodium, potassium), ammonium or substituted ammonium or other countries.

(32) N-methyltaurine, for example, further reacts with fatty acid, resulting sodium methyl alkyl taurates:
HN(CH.sub.3)CH.sub.2CH.sub.2SO.sub.3Na+RCOOH.fwdarw.RCON(CH.sub.3)CH.sub.2CH.sub.2SO.sub.3Na

(33) R is an aliphatic hydrocarbon radical having 7 to 21, preferably 9 to 17 carbons.

(34) As with the acyl isethionate, the resulting alkyl taurate product, e.g., sodium methyl alkyl taurates, can be a mixture sodium methyl alkyl taurates, free fatty acid and other residues. The chain length distribution of fatty acids used dictates the chain length distribution of alkyl taurates. Typically coconut fatty acid is used, which is rich in lauric acid, resulting cocoyl taurates. The chain length distribution can be further adjusted by blending different cuts of distilled fatty acids to enrich a certain chain length, e.g., 12 carbons, in the final reaction product. The resulting fatty alkyl taurate surfactants should have more than 65 wt. %, preferably more than 75%, (on basis of alkyl taurate reaction product) of fatty acyl group with 14 or less carbon atoms to provide both lather and mildness of the resulting fatty alkyl taurate product. The solubility of sodium methyl cocoyl taurate in water is around 1% by weight at 25 C. It can be supplied as a paste with 20˜35% active, e.g. Pureact WS Conc., a 30% active material, from Innospec. Other suppliers include Galaxy (e.g. Galsoft SLT), Solvay Novecare (Geropon® TC-42 LQ), Croda (Adinol CT95) and Clariant (Hostapon CT Paste)

(35) When sodium cocoyl isethionate and sodium methyl cocoyl taurate are used to prepare petrolatum nanoemulsion as sole emulsifier using homogenizer at 5000 psi, both yield oil droplets well above 400 nm; moreover, the sodium cocoyl isethionate based emulsion solidifies at ambient temperature upon storage, making it unpumpable. This is due to the limited solubility of sodium acyl isethionate in water, causing it to crystalize in the aqueous phase of emulsion and making the emulsion unpumpable. The conventional way to solve the pumpability issue is to use solubilizers of sodium cocoyl isethionate in aqueous phase to help dissolve it. Such solubilizers are ionic surfactants consisting of head groups that are similar to or larger and more complicated than those of sodium acyl isethionate. Both anionic and amphoteric surfactants can serve this purpose. A major unexpected discovery of this invention is that, instead of using solubilizers, using fatty acid as co-emulsifier not only prevents the emulsion based on sodium acyl isethionate from solidifying, and thus be pumpable, but also significantly reduces the size of oil droplets to half or a third of those when no fatty acid is used. The addition of a fatty acid, especially lauric acid, as a co-emulsifier results in the formation of pumpable nanoemulsion 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 around 200 nm with only one pass through the homogenizer at 5000 psi (see Example 1).

(36) Additionally, other mild ionic cleansing surfactants, which also serves as solubilizers, can be used in the aqueous phase. Anionic surfactants which may be used include amino acid based surfactants, such as acylglutamate, acylaspartate, acylglycinate, acylalaninate and acyl sarcosinate. Amphoterics such as coco betaine, cocamidopropyl betaine, sodium lauroamphoacetate, Lauramidopropyl hydroxysultaine and Cocamidopropyl hydroxysultaine can also be used and are preferred. These co-surfactants are typically present at a level of less than 30% of total surfactants in the aqueous phase. Non-ionic surfactants should preferably be avoided in the aqueous phase as those surfactants typically yields poor lather.

(37) Overall surfactants in aqueous phase comprise 1.6 to 10% preferably 4 to 8% by wt. of total nanoemulsion. As indicated the poorly soluble sodium acyl isethionate, or sodium methyl acyl taurate or mixtures thereof are the principal surfactant of the nanoemulsion. They constitute 70% or greater, preferably 80% or greater of all surfactant in the aqueous phase. They may of course be the only surfactant present in the aqueous phase.

(38) 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.

(39) Additionally, polyols may be included in the aqueous phase. Examples of polyol are glycerol, sorbitol, hydroxypropyl sorbitol, hexyleneglycol, 1,3-butylene glycol, 1,2,6-hexanetriol, ethoxylated glycerine, propoxylated glycerine or mixtures thereof. When water soluble alkali metal (e.g. Potassium) or ammonium salt of acyl isethionate and/or alkyl taurate is used as primary anionic emulsifier, the level of polyol in the aqueous phase may be significantly high, resulting in a polyol to water weight ratio from 1:3 to 3:1. This ratio may improve the production efficiency of nanoemulsion, eliminating the need of high pressure homogenization. Minimal or no polyols (e.g. 0 to 5%, preferably 3% or less or 2% by wt or less) should be included in the aqueous phase when sodium salt of acyl isethionate and/or alkyl taurate is used as the primary anionic emulsifier due to their poor solubility in water.

(40) 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 100 nm to 350 nm, more preferably 120 to 300 nm.

(41) Nanoemulsions with droplet sizes of these ranges are obtained in the subject invention using a high pressure homogenizer or a high pressure sonolator. Pressures used are 5000 psi or less, preferably 4500 psi or less.

(42) Preparation of Nanoemulsion

(43) Nanoemulsions are typically formed in a two-stage process.

(44) The first 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.

(45) The second stage of the process is to pass the coarse emulsion through a high pressure homogenizer to form the nanoemulsion. High pressure homogenizers used in this invention 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 400 nm. The homogenizers from other suppliers can be used as long as it can be operated up to 1000-5000 psi. 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.

(46) In the examples, the following terms are defined as noted below:

(47) D[4, 3]: volume average diameter or volume mean diameter or volume average size

(48) The volume average diameters are determined by a Malvern Mastersizer.

Examples 1-4 and Comparatives A

(49) 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 phase 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 time to arrive at the desired droplet size at a process pressure of 5000 psi.

(50) TABLE-US-00001 Comp. A Example 1 Example 2 Example 3 Example 4 Ingredient Wt. % Wt % Wt % Wt % Wt % Oil Phase Petrolatum G2212 55 55 55 55 55 Lauric acid 3.5 3.5 4 4 Aqueous phase Sodium cocoyl isethionate 6.0 6.0 6.0 5 4.5 (YA-SCI-85)* Na Methyl Cocoyl 7.5 Taurate(Pureact WS-70, (1.5 active) 20%) Na Methyl Cocoyl 3.33 Taurate(Pureact WS (1 active) CONC, 30%) Na Lauroamphoacetate 6.67 (30%) (2 active) Deionized Water Q.S.** Q.S.** Q.S.** Q.S.** Q.S.** Presevative <1 <1 <1 <1 <1 D.sub.[4, 3] nm 425 215 191 231 234 pH 6.44 5.10 6.69 5.39 5.81 Pumability at ambient Solid not Cream Lotion Lotion Lotion temperature pumpable Pumpable Pumpable Pumpable pumpable *YA-SCI-85 contains 84% Sodium cocoyl isethionate, 12% fatty acid and 4% sodium isethionate **Amount needed (e.g., to obtain 100% by wt.)

(51) In Comparatives A, sodium cocoyl isethionate is the only emulsifier for preparation of nanoemulsion of petrolatum. The oil droplet size is 425 nm, above 400 nm. Most undersirably, the emulsion produced solidifies to the shape of its container when at ambient temperature upon storage due to the limited solubility of sodium cocoyl isethionate. The emulsion made in Comparison A cannot be pumped at ambient temperature due to its solid nature. In Example 1, when 3.5% fatty acid (not a solubilizer of sodium cocoyl isethionate) is used as co-emulsifier, the oil droplet size is reduced by half to 215 nm and, most unexpectedly, the nanoemulsion produced has a skin cream consistency and can be readily pumped at ambient temperature upon storage. In Examples 2˜4, both fatty acid and solubilizers of sodium cocoyl isethionate, such as Na Lauroamphoacetate and Na Methyl Cocoyl Taurate, are incorporated into the emulsion formula, resulting nanoemulsion of droplet size ranging 191˜234 nm, and the lotion like emulsions that are readily pumpable at ambient temperature upon storage.

Examples 5˜6 and Comparatives B˜C

(52) Examples 5˜6 and comparatives B˜C were prepared similarly to Examples 1-4 and Comparatives A.

(53) TABLE-US-00002 Comp. B Example 5 Comp. C Example 6 Ingredient Wt % Wt % Wt % Wt % Oil Phase Petrolatum G2212 55 55 51.56 51.56 Lauric acid 4 3.75 Aqueous Phase Na Methyl Cocoyl 30 30 28.13 28.13 Taurate(Pureact WS-70, (6 active) (6 active) (5.6 active) (5.6 active) 20% Active) Na Lauroamphoacetate 6.25 6.25 (30%) (1.88) (1.88) Deionized Water Q.S.* Q.S.* Q.S.* Q.S.* Preservatives <1 <1 <1 <1 D.sub.[4, 3] nm 606 262 469 213 pH 9.30 6.2 9.43 6.67 Pumabifity at ambient Pumpable Pumpable Pumpable Pumpable temperature *Amount needed (e.g., to obtain 100% by wt.)

(54) In comparative B, Na Methyl Cocoyl Taurate is supplied as a 20% dispersion. Due to its low solubility, the dispersion is white paste. When used as the only emulsifier, the resulting emulsion produced after being processed via homogenization at 5000 psi, yields oil droplet of 600 nm, even far greater than that in Comparative A, where sodium cocoyl isethionate is used, though the former is pumpable and latter not pumpable, possibly due to their difference in solubility in water at ambient temperature. In Example 5, with fatty acid as co-emulsifier, the oil droplet size is reduced more than half to 262 nm in the resulting nanoemulsion.

Examples 7-10

(55) 60% Petrolatum was used to form nanoemulsions, with sodium cocoyl isethionate (YA-SCI-85) as primary emulsifier in aqueous phase and lauric acid as co-emulsifier in oil phase. The coarse emulsion was prepared in a 450 lbs stirred jacketed tank, equipped with an off-center turbine, a scraper and a recirculation loop along which a pump and a Silverson in-line rotor/stator double screen mixer (Model 150/250 MS) were attached. The aqueous phase was added to the tank and heated up to 75 C, while the oil phase was heated up to 75 C in a separate tank. The oil phase was then charged into aqueous phase via the recirculation loop with the in-line rotor/stator double screen mixer running at 6000 rpm while the pump was pumping the aqueous phase through the recirculation loop. After the completion of addition of oil phase, the mixture in the stirred tank was pumped through the recirculation loop 3 theoretical passes (=volume of mixture in tank divided by the flow rate in recirculation loop) with the in-line rotor/stator double screen mixer running at 6000 rpm. The coarse emulsion was then pumped through a high pressure sonolator only once with a pressure up to 2500 psi to form nanoemulsions.

(56) TABLE-US-00003 Example Example Example Example 7 8 9 10 Ingredient Wt % Oil Phase Petrolatum G2212 60   Lauric acid 3.8 Aqueous phase Sodium cocoyl isethionate 6.0 (YA-SCI-85)* Deionized Water Q.S.** Preservative <1  Process pressure, PSI 1000 1500 2000 2500 D.sub.[4, 3] nm 368 305 245 209 pH  5.38 Pumability at ambient Pumpable temperature *YA-SCI-85 contains 84% Sodium cocoyl isethionate, 12% fatty acid and 4% sodium isethionate **Amount needed (e.g., to obtain 100% by wt.)