DESC:FIELD OF THE INVENTION
The present invention relates to a microemulsion system and process for preparing the same.
BACKGROUND OF THE INVENTION
Coconut oil is the most commonly used hair oil in Asia and Middle East. It offers a high level of conditioning benefits and can be used to prevent future hair issues or to repair current problems including breakage, dry scalp, and frizz.
Unfortunately, coconut oil amongst other hair oils exhibit major disadvantages such as greasy feel, stickiness as well as requirement of large quantities of the oil for full coverage of hair.

The general alternative technique to overcome these drawbacks of using hair oils is solubilizing concentrated oils using organic solvents, dilution with light liquid paraffin or silicones, in various forms of dispersions, emulsions, suspensions etc. These formulations show drawbacks such as non-uniform distribution, being costly, can introduce fire and the toxicity hazards (in case of organic solvents), and impart malodor when organic solvents evaporate. These emulsions quickly separate into the oil and aqueous phases upon standing, often in periods measured in hours.
Moreover the oil-in-water emulsions of such hair oils directed towards various hair treatments are well known in the cosmetic and dermopharmaceutical field particularly for the preparation of cosmetic products such as hair creams and serums. However the presence of high concentration of vegetable, animal or mineral oils in some compositions makes their formulation difficult. The compositions are generally unstable during storage and the cosmetic properties are inadequate. In particular, the application of such compositions to the hair leads to a greasy feel and difficulty in rinsing. Furthermore, the dried hair lacks volume and appearance is not desirable. Such conventional emulsions are mainly targeted for superficial topical benefits and penetration action is limited.

Microemulsions have an advantage over conventional emulsions as Microemulsions are transparent, isotropic, thermodynamically stable dispersions of oil in water, solubilized by surfactant molecules as defined in Microemulsion Systems- Surfactant Science Series Volume 24. However, most of the existing microemulsions utilize lower or medium chain alcohols to develop clear microemulsion systems. The presence of alcohol may make the emulsion appear attractive by making it transparent however it is harmful to the hair shaft as it is dehydrating and toxic in nature. Further the existing microemulsions contain cationic, anionic or amphoteric surfactants which cause irritation and are toxic when used in large quantities.

US 2004/0185024 A1 relates to cosmetic compositions containing, at least one amphoteric surfactant chosen from alkylamphohydroxyalkylsulphonates and salts thereof, and at least one polyethylene glycol ester or ether containing at least one C8-C40 hydrophobic group. These compositions are used for example for washing keratin materials, such as hair or skin. With higher concentration and presence of harmful amphoteric surfactants the safety of the formulation would be affected.

EP20050291631 relates to a cosmetic hair treatment composition, of water-in-oil emulsion type, comprising at least one non-volatile, non-silicone oil, at least one cationic surfactant, at least one nonionic surfactant, the composition also uses alcohol. The presence of high levels of cationic surfactants would affect the safety of the formulation and the alcohol in the composition would amount to dehydration of the hair shafts resulting in undesirable appearance of the hair.

Therefore, there is a need for a microemulsion system, which is substantially alcohol free.
SUMMARY OF THE INVENTION
The present invention relates to a microemulsion system comprising of at least one surfactant, at least one oil component and at least one co-surfactant.

The present invention also relates to a process for preparing a microemulsion system. The process comprises of mixing at least one oil component, at least one surfactant and at least one co-surfactant to form a pre-emulsion, which is further heated to form a microemulsion.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention discloses a microemulsion system comprising of at least one surfactant, at least one oil component and at least one co-surfactant.

The surfactant is selected from the group of non-ionic, anionic surfactants or combination thereof.

The non-ionic surfactant is selected from polyoxyethylene glycol alkyl ethers, polyoxypropylene glycol alkyl ethers, polyethylene glycol -15-hydroxystearate, PEG(40) hydrogenated castor oil, POE(40) hydrogenated castor oil, mixture of PEG-150 pentaerythrityl tetrastearate, PEG-6 caprylic or capric glycerides and water, Oleth 20, ethoxylated alcohols, fatty acid esters, glucoside alkyl ethers, glycerol alkyl esters, polyoxyethylene glycol, sorbitan alkyl esters, block copolymers of polyethylene glycol and polypropylene glycol, modified polysaccharides, phospholipids or mixtures thereof.

The non-ionic surfactant with low ethoxylation having less than or equal to 40 mols ethylene oxide is preferred.

The non-ionic surfactant is preferably in the range of 1-25% of the total microemulsion system.

The anionic surfactant is selected from sulfosuccinates, phosphates, alkylbenzene sulfonates.

The co surfactant is selected from, medium and or small chain mono-diglycerides medium chain fatty acids, propylene glycol monocaprylates, sorbitan alkyl esters such as sorbitan monolaurate, glyceryl monocaprylate, PEG caprylic/capric glycerides or mixtures thereof.

The co-surfactants are preferably present in the range of 1-20% of the total microemulsion system.

The oil component is selected from vegetable oil, nut oil, animal origin oil or a mixture thereof. The oil is preferably coconut or cocos nucifera oil. The oil is preferably in the range of 1-20% of the total microemulsion system.

In an embodiment of the present invention, the microemulsion system further comprises of a co-oil component selected from extracts of carrot, methi, mustard, gunja, karanja, helianthus annuus seed oil, oryza sativa(rice) oil, hippophae rhamnoides, hippophae salicifolia, black seed, celery, caraway, cumin, citriodora, coriander, dill, basil, pumpkin, melon, jamun, pomegranate seed, cucumber, onion seed, apple seed, cherry, calophyllum inophyllum, mango kernel oil, lemon peel oil, pine nut oil or mixtures thereof.

The co-oil is preferably in the range of 1-20% of the total microemulsion system.

The oil: surfactant ratio is in the range of 1:1 – 1:2.

In one embodiment of the present invention, the microemulsion system further comprises of bioactives. The bioactives are selected from 2,4-diamino pyrimidine, saw palmetto extract, cauliflower, green peas extracts or mixtures thereof.

In one embodiment of the present invention, the microemulsion system further comprises of UV protective agents added to enhance UV protective activity of the microemulsions. The UV protective agents are selected from tocopherols, tocotrienols, tinogard, Polysilicone-15, benzophenone-4, grape seed extract, rice bran oil, raspberry seed oil, soyabean oil or mixtures thereof.
In one embodiment of the present invention, the microemulsion is a water-in-oil type clear system.

The microemulsion is preferably present in the range of 5% to 95%. In another embodiment of the present invention, the microemulsion is an oil-in water type clear system.

The microemulsions have an average globule size less than 300nm, preferably less than 200nm.

In an embodiment of the present invention, various pharmaceutically acceptable active agents and carriers having beneficiary hair attributes are added to the system.

The microemulsion system comprising of at least one surfactant, at least one oil component and at least one co-surfactant is suitable for topical transdermal application for beneficiary skin attributes.

The microemulsion system of the present invention optionally includes one or more biologically inactive components. Examples of such optional inactive components include carriers, thickening agents, gelling agents, coloring agents, perfumes, fillers, preservatives or pharmaceutically acceptable excipients.
The additional components present in the microemulsion system are cyclopentasiloxane, phenyl trimethicone, tocopheryl acetate, polyquaternium-10, bis-PEG 15-methyl ether dimethicone, propylene glycol, glycerin, disodium EDTA, panthenol, aqua and hydrolyzed vegetable protein PG-propyl silanetriol, citric acid, phenoxyethanol, methylparaben, butylparaben, ethylparaben, propylparaben and isobutylparaben, ethanol or mixtures thereof.

The microemulsion system of the present invention is substantially alcohol free thereby avoiding dehydration of the hair shaft and irritation to the scalp.

The present invention discloses a process for preparing an alcohol-free microemulsion system. The process uses a phase inversion temperature technique.
The process comprises of:
mixing at least one oil component, at least one surfactant and at least one co-surfactant to form a pre-emulsion; and
heating the pre-emulsion to form a microemulsion system.

The process includes mixing water with the mixture of surfactant, oil and co-surfactant.

The process further comprises of cooling and stirring the microemulsion system.

The temperature of the process for heating is in the range from 45-90°C. Preferably, the temperature for heating the mixture is in the range of 60-90°C.
The oil: surfactant ratio is 1:1-1:2. The oil, co-surfactant each is present in a range of 1-20% of the total microemulsion system. The surfactant is present in a range of 1-25% of the total microemulsion system.

The surfactant is selected from the group of non-ionic, anionic surfactants or combination thereof.

The non-ionic surfactant is selected from polyoxyethylene glycol alkyl ethers, polyoxypropylene glycol alkyl ethers, polyethylene glycol -15-hydroxystearate, PEG(40) hydrogenated castor oil, POE(40) hydrogenated castor oil, mixture of PEG-150 pentaerythrityl tetrastearate, PEG-6 caprylic or capric glycerides and water, Oleth 20, ethoxylated alcohols, fatty acid esters, glucoside alkyl ethers, glycerol alkyl esters, polyoxyethylene glycol, sorbitan alkyl esters, block copolymers of polyethylene glycol and polypropylene glycol, modified polysaccharides, phospholipids or mixtures thereof.

The anionic surfactant is selected from sulfosuccinates, phosphates, alkylbenzene sulfonates.

The co surfactant is selected from, medium and or small chain mono-diglycerides medium chain fatty acids, propylene glycol monocaprylates, sorbitan alkyl esters such as sorbitan monolaurate, glyceryl monocaprylate, PEG caprylic/capric glycerides or mixtures thereof.

The oil component is selected from vegetable oil, nut oil, animal origin oil or a mixture thereof. The oil is preferably coconut or cocos nucifera oil.

In an embodiment of the present invention, the microemulsion system further comprises of a co-oil component selected from extracts of carrot, methi, mustard, gunja, karanja, helianthus annuus seed oil, oryza sativa(rice) oil, hippophae rhamnoides, hippophae salicifolia, black seed, celery, caraway, cumin, citriodora, coriander, dill, basil, pumpkin, melon, jamun, pomegranate seed, cucumber, onion seed, apple seed, cherry, calophyllum inophyllum, mango kernel oil, lemon peel oil, pine nut oil or mixtures thereof.

The co-oil is preferably in the range of 1-20% of the total microemulsion system.

Additional components such bioactives, UV protective agents, pharmaceutically acceptable active agents, carriers, thickening agents, gelling agents, coloring agents, perfumes, fillers, preservatives or pharmaceutically acceptable excipients can be further added to the process and mixed with the surfactants, oil and co-surfactants.
Additional components such as cyclopentasiloxane, phenyl trimethicone, tocopheryl acetate, polyquaternium-10, bis-PEG 15-methyl ether dimethicone, propylene glycol, glycerin, disodium EDTA, panthenol, aqua and hydrolyzed vegetable protein PG-propyl silanetriol, citric acid, phenoxyethanol, methylparaben, butylparaben, ethylparaben, propylparaben and isobutylparaben, ethanol or mixtures thereof can be further added to the process and mixed with the surfactants, oil and co-surfactants.

The extracts, oils used in the present invention are not manufactured by Applicant that is no biological material was used by the Applicant. They were bought from vendors and this invention did not use any biological material for making the microemulsion system. Nonetheless, the source and geographical origin of the materials are given below:
Name Source Origin
Carrot Daucus carota Afghanistan
Methi Trigonella foenum-graecum Europe
Mustard Sinapis hirta
China
Helianthus annuus Helianthus annuus America
Rice Oryza sativa China
Hippophae Rhamnoides Hippophae rhamnoides Nepal
Hippophae salicifolia Hippophae salicifolia Europe
Celery Apium graveolens Mediterranean
Caraway Carum carvi Arabic
Cumin Cuminum cyminum Iran
Citriodora Corymbia citriodora Australia
Coriander Coriandrum sativum Europe
Dill Anethum graveolens Mediterranean
Basil Ocimum basilicum Asia
Pumpkin Cucurbita pepo America
Melon Cucurbitaceae Africa
Jamun Syzygium cumini Bangladesh
Pomegranate Punica granatum Iran
Cucumber Cucumis sativus) Asia
Onion Allium cepa Asia
Apple Malus domestica Asia
Cherry Prunus avium
Europe
Calophyllum inophyllum Calophyllum inophyllum Africa
Mango Mangifera
Asia
Lemon Citrus limon) Asia
Pine Pinus sylvestris Northern hemisphere
Coconut Cocos nucifera Asia
Saw palmetto Serenoa repens USA
Cauliflower Brassica oleracea Spain
Green peas Pisum sativum Mediterranian
Grape Vitis vinifera Georgia
Raspberry Rubus occidentalis Asia
Soyabean Glycine max China

Examples
Example 1
10g of cocos nucifera oil, 17gpolyethylene glycol-15-hydroxystearate and 8g propylene glycol monocaprylate were mixed together by an overhead stirrer in a vessel. The mixture was heated to 65°C for 5 minutes. The mixture was stirred until clear. 65g of water was added to the mixture and stirred by using an overhead stirrer at 200 rpm to obtain the microemulsion system.
Example 2
100g of cocos nucifera oil, 100g Oleth 20, 100g PEG (40) hydrogenated castor oil and 60g sorbitan monolaurate were mixed together by an overhead stirrer in a vessel. The mixture was heated to 70°C and was stirred until clear. 640g of water, was added to the mixture and stirred by using an overhead stirrer at 200 rpm to obtain the microemulsion system.
Example 3
4g of cocos nucifera oil, 1g oryza sativa (rice) bran oil, 0.75g polyethylene glycol-15-hydroxystearate, 4.5g PEG(40) hydrogenated castor oil and 9g mono glyceride diglyceride medium chain fatty acids were mixed together by an overhead stirrer in a vessel. The mixture was heated to 70 °C for 5 minutes. The mixture was stirred until clear. 80.75g water was added to the mixture and stirred by using an overhead stirrer at 200 rpm to obtain 100g of the microemulsion system.

Example 4
1.5g of helianthus annuus seed oil, 0.5g cocos nucifera oil, 1.5g oryza sativa (rice) bran oil, surfactants consisting 1g polyethylene glycol 15 hydroxystearate, 4g PEG(40) hydrogenated castor oil, and 7.5g mono glyceride diglyceride medium chain fatty acids were mixed together by an overhead stirrer in a vessel. The mixture was heated to 65°C for 5 minutes. The mixture was stirred until clear. Water q.s to 100g, , 1.5g cyclopentasiloxane, 0.25gbis-PEG 15-methyl ether dimethicone, 0.5g phenyl trimethicone, 0.05g tocopheryl acetate, 3g propylene glycol, 1g glycerin, 0.05gdisodium EDTA, 0.25g Panthenol, 0.05g citric acid, 0.75g mixture of phenoxyethanol, methylparaben, butylparaben, ethylparaben, propylparaben and isobutylparaben were added to the mixture and stirred by using an overhead stirrer at 200 rpm to obtain the microemulsion system.
Experimental data
10gms of rough damaged hair swatch was washed with 15% SLES (sodium lauryl ethyl sulphate) solution. Two sets of similar sensories were prepared using the same treatment.
1. 1gm of the microemulsion system of Example 4 was applied to the washed damped 10 gms of the hair swatch. The hair swatch was air dried.
2. 1 gm of the conventional product comprising of 15% cocos nucifera oil, 3.5% polysorbate 80, 4% sorbitan mono oleate, 2% iso propyl myristate , 0.25% ultrez 20, 0.65% tea, 1.5% cetyl alcohol, 0.75%, Glyceryl monostearate, 0.1% methyl paraben, 0.2% butylated hydroxytolene and q.s 100 water was applied to the washed damp 10 gms of the hair swatch. The hair swatch was air dried.

Various parameters such as sensory, safety and stability of the microemulsion systems were analyzed. Following were the results obtained.

Sensory: As sensorial attributes of the product are an important parameter of consumer acceptability, the microemulsion system were tested for skin and hair sensory attributes using a trained panel. The panel rated the product parity to consumer accepted marketed cream formulations in terms of softness, smoothness, shine, manageability, limpness, non-residual feel and overall likeability of hair in use and conditioned feel of hair post wash.
Both the hair swatches were analysed for softness, smoothness, shine, manageability, limpiness, non-residual feel and overall likeability. Study was conducted with panel of five consumers.
It was found that the microemulsion system of the present invention gave a much better shine and non-residual feel than the conventional product. The other parameters such as softness, smoothness, manageability, limpness and overall likeability of the microemulsion system of the present invention were found to be excellent.

Safety: Safety assessment of the prototypes was conducted using the MTT assay on fibroblast cell lines. The microemulsion system of the present invention as mentioned above fared equal to the untreated in terms of cell viability. This proved that the microemulsion system of the present invention had acceptable level of safety. These were further taken up for the 24 hr patch test on human subjects. In this test too, the microemulsion system had a score of less than 2 proving that they were safe to use.

Stability: The microemulsion system of the present invention was kept at 45° C for three months and was found to be stable even after three months. No change in transparency or particle size was observed after three months. The particle size was less than 200nm, which results in better penetration.
The system according to the present invention is a safe and stable and has a wide applicability which makes them commercially utilizable. The system has a broad-spectrum application for deep conditioning and nourishment of hair and skin. The system can be manufactured in various forms such as a liquid, semi-liquid, cream, gel or other such forms and thus can be used in a wide range of basic hair and skin products greatly enhancing their qualities.
The system according to the present invention can be prepared as a shampoo, conditioner, cream, serum, hair protection cream before styling, styling products amongst other products. The system according to the present invention has the following hair care benefits:
Hair softness, smoothness, moisturization, manageable, hair strengthening, age defying hair repair, hair repair, antiaging, split end repair, youthfulness of hair, color or heat protection, frizz control, normalizes oily or dry scalp conditions.
The microemulsion systems of the present invention are alcohol-free, easily scalable, stable, safe to use, cost effective and are aesthetically improved. These systems can be utilized as easily cleansing type of systems with less or no greasiness and is non-comodogenic in nature.
The system is unique for the following reasons:
1. The system does not include cation which is toxic when present in larger quantities.

2. The system does not include alcohol in any form as alcohol causes the hair shaft to dehydrate and also causes irritation to the scalp.

3.The system comprises of a specific range of microemulsion globules sized less than 300nm, preferably less than 200nm which are beneficial as they enable higher penetration of the system and thus enhanced conditioning and nourishment of hair and skin. The specific size of the globules has been achieved in spite of using coconut oil.

4. Safe and stable microemulsion is formed using the phase inversion temperature technique with a specific temperature range (45-90°C). This specific technique used provides the necessary energy required to ensure the molecular alignment resulting in a clear emulsion thus enables the formation of a microemulsion using coconut oil which is otherwise difficult to achieve.
,CLAIMS:We Claim:
1. A microemulsion system comprising of at least one surfactant, at least one oil component and at least one co-surfactant.

2. The microemulsion system as claimed in claim 1, wherein the surfactant is anionic, non-ionic or a mixture thereof.

3. The microemulsion system as claimed in claim 1, wherein the surfactant is a non-ionic surfactant having low ethoxylation, preferably less than or equal to 40 mols ethylene oxide and is present in the range of 1-25% of the total microemulsion system.

4. The microemulsion system as claimed in claim 1, wherein the non-ionic surfactant is selected from polyoxyethylene glycol alkyl ethers, polyoxypropylene glycol alkyl ethers, polyethylene glycol -15-hydroxystearate, PEG(40) hydrogenated castor oil, POE(40) hydrogenated castor oil, mixture of PEG-150 pentaerythrityl tetrastearate and PEG-6 caprylic or capric glycerides and water, Oleth 20, ethoxylated alcohols, fatty acid esters, glucoside alkyl ethers, glycerol alkyl esters, polyoxyethylene glycol, sorbitan alkyl esters, block copolymers of polyethylene glycol and polypropylene glycol, modified polysaccharides, phospholipids or mixtures thereof.

5. The anionic surfactant is selected from sulfosuccinates, phosphates, alkylbenzene sulfonates.

6. The microemulsion system as claimed in claim 1, wherein the oil component is selected from vegetable oil, nut oil, animal origin oil or a mixture thereof in the range of 1-20% of the total microemulsion system,

7. The microemulsion system as claimed in claim 1, wherein the oil component is coconut oil.

8.The microemulsion system as claimed in claim 1, further comprising a co-oil component selected from extracts of carrot, methi, mustard, gunja, karanja, helianthus annuus seed oil, oryza sativa(rice) oil, hippophae rhamnoides, hippophae salicifolia, black seed, celery, caraway, cumin, citriodora, coriander, dill, basil, pumpkin, melon, jamun, pomegranate seed, cucumber, onion seed, apple seed, cherry, calophyllum inophyllum, mango kernel oil, lemon peel oil, pine nut oil or mixtures thereof in the range of 1-20% of the total microemulsion system.

9. The microemulsion system as claimed in claim 1, wherein the co-surfactant is selected from medium and or small chain mono-diglycerides medium chain fatty acids, propylene glycol monocaprylates, sorbitan alkyl esters such as sorbitan monolaurate, glyceryl monocaprylate, PEG caprylic/capric glycerides or mixtures thereof in the range of 1-20% of the total microemulsion system.
10. The microemulsion system as claimed in claim 1, further comprising bioactives, UV protective agents, biologically inactive components, pharmaceutically acceptable active ingredients and carriers.

11. The microemulsion system as claimed in claim 1, wherein the microemulsion is oil-in-water or a water-in-oil type clear system.

12. The microemulsion system as claimed in claim 1, wherein the microemulsions have a globule size less than 300nm and the oil:surfactant ratio is 1:1 - 1:2.

13. A process for preparing the microemulsion system, the process comprising:

mixing at least one oil component, at least one surfactant and at least one co-surfactant to form a pre-emulsion; and
heating the pre-emulsion to form the microemulsion system.

14. The process as claimed in claim 13 comprising mixing water with the oil component, surfactant and co-surfactant.

15.The process for preparing the microemulsion system as claimed in claim 13, wherein the process is carried out at a temperature in the range of 45°-90°C, preferably 60°-90°C.

16. A topical transdermally applicable microemulsion system comprising of at least one surfactant, at least one oil component and at least one co-surfactant.

17. The microemulsion system as claimed in any of the preceding claims in the form of liquid, semi-liquid, cream, gel.

Dated this 7th day of March, 2014
FOR MARICO LIMITED
By their Agent

(GIRISH VIJAYANAND SHETH) (IN/PA 1022)
KRISHNA & SAURASTRI ASSOCIATES