GB2077620A - Sulphoxide-bearing emulsifier; cosmetic emulsions - Google Patents

Abstract

A process for the preparation of a stable emulsion by using a compound having emulsifying properties and comprising a lipophilic part having a sulphoxide group. It may have formula: <IMAGE> where R<1> = hydrocarbyl, R<2> = H or hydrocarbyl, n = 1 to 20 and A is a hydrophilic group. The emulsion may be a water-in-oil emulsion such as a cosmetic cream.

Description

SPECIFICATION A process of preparation for stable water-in-oil type emulsions, by use of compounds bearing a sulfoxy group The invention relates to compounds which include a sulfoxy group in the molecule, having emulsifying properties and particularly able to give stable emulsions of the water-in-oil type.

In spite of the great number of compounds which are already known for their ability to form emulsions, there was still a need for an emulsifier which would allow there to be reliably obtained an oil-in-water type emulsion stable enough to avoid phase demixing. In certain cases it would be advantageous to store a water-in-oil type emulsion for long periods of time. For instance, in the field of cosmetology, creams exhibit improved hydrating and protective properties for the skin when they are composed of a dispersion of very small water droplets in a continuous fat phase. But, it often happens that conventional emulsifiers exhibit risks of demixing; it is always difficult to obtain new formulations comprising such emulsions and the preservation of such properties over an extended period of time is uncertain.

The products currently on the market proposed for such water in-oil type emulsions comprise a fatty aliphatic chain and a hydrophilic portion. The aliphatic part may or may not be saturated and may bear a free or ethoxylated hydrophilic group. The hydrophilic part may be a carboxylate, glycerol ester, sorbitol ester, polyoxide ethylene ester or phosphate group.

Thus, compounds derived from oleic acid, castor oil or lanoline are well-known emulsifiers widely used in cosmetological composition. Their structure allows them to dissolve in oil and to generate water-in-oil type emulsions; the essential cohesion of the film at the interface between the oily and the water phases is provided by Van Der Waals forces or by hydrogen bonds. But these cohesion forces are weak and therefore the stability of these emulsions is hard to maintain. The perfection of water-in-oil type formulations is difficult, especially when an attempt is made to lower the percentage of the oily phase.

The present invention improves the performance of emulsions, enabling the above drawbacks to be overcome. Particularly, it allows the preparation of very stable emulsions, especially of the water-in-oil type. With regard to applications in the field of cosmetology, the invention provides products which offer improved protection for the epidermis due to the greater affinity of the novel emulsifiers towards the skin.

The invention is based on the discovery of compounds comprising a lipophilic part bearing a sulfoxide group and a hydrophilic part. The applicants have found that the the introduction of the said

group into the molecule of a compound bearing a hydrophilic group (the compound itself may be a surface active compound known per se) directs the action of this compound towards the formation of water-in-oil type emulsions and stabilizes the built-up emulsions.It is possible that this influence of the sulfoxy group comes from its strong polarisation, added to the conventional intermediate bonds of the Van Der Waalstype and the dipolar bonds, the whole having a stabilizing effect on the interface of the phases of the emulsion; in any case, the advantage due to the introduction of

groups in the compounds comprising a hydrophilic part is not derived from the known art.

The novel emulsifying agents of the invention are characterized in that they are compounds comprising an hydrophilic part, the chain of this part bearing a sulfoxy group substituted on the lipophilic part of the hydrocarbon molecule.

These emulsifiers are, in fact, chemical compounds of the general formula:

in which R1 is a hydrocarbon group; R2 is a hydrogen atom, a hydrocarbon sustituent, n is an integer from 1 to 20 and A is the hydrophilic part of the molecule.

More particularly, R1 is an alkyl, alkenyl, aryl, aralkyl, or cycloalkyl group; usually, it comprises from 1 to 20 carbon atoms; R2 can be the same as or different to R2. Preferably, n is an integer from 4 to 18.

Although the structure of the hydrophilic part of the surfactants is well known, in the art, the nature of A defined herein above is furthermore specified in the more current examples given herein-below. The A group can be, particularly, a carboxylic group COOT, sulphonic group -SO,, sulfuric group -SO; or phosphoric -PO;, free or esterified with, for instance, a polyol such as the glycerol or a sorbitol, or salified with an alkali or earth-alkali metal, an amine or a quaternary amine of imidazolinium or of other nitrogenous base.The A group can also be a polyoxyalkylenyl chain, particularly poyoxyethylene (-CH2CH2O-),,,H or polyoxypropylene, m being comprised between 2 and 20; in another embodiment the A groups can be, for instance, amino acid groups such as:

In order to ensure that the emulsifiers of the invention are well adapted to the formation and stabilization of emulsions of which the dispersed phase is aqueous, the sulfoxy group needs to be far enough removed from the hydrophilic part A. The best results are obtained with compounds in which the sulfoxy group is included in a fat phase, where it can act in order to stabilize the blade of the surface active agent which ensures the interface. Thus, the vaiues of the integer n are greater than 4, and preferably, even greater than 6.

The sulfoxidized emulsifiers of the invention are used in the same way as the emulsifiers of the prior art and thus will not be further defined herein it will simply be noted, by way of example, that good results can be obtained with percentages ranging from 0.01 to 10% by weight with respect to the emulsion to be prepared and, preferably, from 1 to 3%.

To adapt the emulsification system to the nature of the material subject to emulsification, it may be necessary to use one or several emulsifiers known per se. But as the stabilizing effect is always very pronounced, it is worthwhile adding a sulfoxy compound of the invention in order to stabilize the emulsion. Thus, the emulsifying agents of the invention can be used as a mixture with one another or with emulsifying agents known per se, within the limits of compatibility rules for surface active agents or surfactants, i.e. surfactants of opposite ionic character must not be associated.

The novel surfactants of the invention are not only suitable for the preparation of emulsions, one phase of which is aqueous, but also for the case where non-miscible, non-aqueous products have to be emulsionated as, inter alia, in the case of different pesticidal or fungicidal compositions, where, for instance, halgogeno benzenes or other organic chloro compounds ("Chlordan", "DDT"... etc) must be emulsifiated with kerosene, xylene or similar substance.

The invention will be better understood in the light of the following examples given by way of illustration but without in any way limiting said invention.

Although the preparation of the corresponding sulphide and sulphoxide is, generally, well known, the following examples illustrate the preparation of products of the invention by the use of known processes.

EXAMPLE 1 Preparation of dodecysulphoxyundecanoic acid a) Preparation of the sulphide by chemical route In a heated reactor filled with a reflux cooler, 300ml of ethanol, 450ml of water containing 1 20g of NaOH, 3989 (1.5 mole) of bromoundecanoic acid and 303.69 (1.5 mole) of laurylmercaptan are successively added under stirring. During the mixing, the temperature increases to about 80"C. The reaction mixture is maintained under vigorous stirring at this temperature, in order to avoid crystallization of the product formed, on the one hand, and, on the other hand, to avoid an overflowing due to the foaming produced by the boiling.

After 6 hours on the run, the mixture is acidified according to pH 2 at a temperature of 80"C, with concentrated hydrochloric acid. Two layers appear. The lower aqueous layer is discarded and the upper layer is poured into benzene.

The product, crystalline at room temperature, is filtered washed with benzene and dried at 50"C under a pressure of 1 33 Pa. Thus, 4349 (70% yield) of a crystalline product are obtained, having a melting point of 70-72"C.

An elementary analysis of the product gives the following results: found C % 71.92 H % 12.68 calc. C % 71.50 H % 11.92 b) Preparation of the sulphide by the photochemical route A heated, 3 liter reactor fitted with a mercury vapor medium pressure lamp of 1 25 watts is used. The optical path of this reactor is 7cm. Stirring is provided by a, external circulating loop.

Into this reactor are introduced 1288g (7 moles) of undecylenic acid, 14149 (7 moles) of lauryl mercaptan, 5.4g of benzophenone and 5.49 of trimethylphosphite. The mixture is allowed to react at 80"C during 3 hours. At the end of the reaction, the reaction mixture is poured into 4.51 of petroleum ether and the product is allowed to crystallize at room temperature. After filtration and washing of the crystals with acetone, 23619 of product are obtained (yield = 87.5%).

c) Conversion to sulphoxide A solution of 965g (2.5 moles) of dodecylthioundecanoic acid in 300mi of acetone is heated to the reflux temperature of the acetone under very vigorous stirring. 270ml of H202 at 33% (2.6 moles H202) are slowly added. The reaction is completed after 3 hours. After cooling, the crystals are filtered, washed with acetone and dried at 50"C under 1 33 Pa. The melting point of the product obtained is 95-96"C; its acidity is 99.6% of the theory.

An elementary analysis of the product gives the following results: found C % 68.85 H % 11.54 S % 11.50 cal. C % 68.66 H % 11.44 S % 11.94 EXAMPLE 2 Preparation of methylthioundecanoic acid by chemical route In a heated rector filled with a reflux cooler, a solution containing 16009 (40moles) of sodium hydroxide, 960g (20 moles) of methylmercaptan and 4500ml of water is added, then, a solution comprising 53009 (20 moles) of bromoundecanoic acid in 1200ml of methanol. The mixture is then heated at the reflux temperature during 3 hours. Then, 201 of hexane are added.

The mixture is kept at 40"C during 6 hours and acidified until pH 2 with 1900ml of Hcl at 13%. The aqueous phase is decanted and discarded. The organic layer is washed with water at 40-50"C until neutrality. 1 31 of hexane are evaporated and the solution is crystallized at about 50,C. The crystals are filtered and dried. 44509 (yield = 95.5%) of a crystalline product having a melting point of 45"C and an acidity of 100% of the theory is obtained.

An elementary analysis of the product gives the following results: found C % 62.15 H % 10.70 calc. C % 62.06 H % 10.54 Preparation of methylthioundecanoic acid by the photochemical route A reactor of 3 liters, heated and fitted with a mercury vapor lamp of medium pressure of 1 25 watts is used. The optical path of this reactor is 7cm. Stirring is provided by an external recirculation loop. Into this reactor are introduced 2245g (12 moles) of undecylenic acid, 5.49 of benzophenone and 5.4g of trimethylphosphite. The atmosphere is purged with nitrogen.

When the mixture is melted, the mixture is allowed to circulate through the external loop and the temperature is adjusted at 55"C. The lamp is switched on and the methylmercaptan is introduced at the bottom of the reactor through a sintered glass plate.

After 7 hours on run, methylmercaptan excess is swept off with nitrogen and the reactor content is poured into 31 hexane. The solution is crystallized at 5"C, filtered and washed with cold hexane. After drying, 2637g (yield = 93.7%) of a crystalline product are obtained, with a melting point of 44.5"C. The acidity of the product is 99.6% of the theory.

An elementary analysis of the product gives the following results: found C % 62.04 H% 10.67 calc. C % 62.06 H % 10.34 Methylsulfoxyundecanoic acid A solution of 10009 (4.31 moles) of methylthioundecanoic acid in 2350ml of acetone is refluxed during 6 hours with 449 ml of H202 at 33% (4.3 moles H202).

After evaporation of the acetone and drying, 10709 of crystalline product melting at 85-87"C are obtained. The acidity of the product is 100% of the theory.

An elementary analysis of the product gives the following results: found C % 50.03 H % 9.35 calc C % 50.08 H % 9.68 EXAMPLE 3 Glyceryl monomethylthioundecanoate A mixture of 6969 (3 moles)of methylthioundecanoic acid and 8289 (9 moles) of glycerol are heated at 180"C under 2660 Pa in a reactor fitted with a reflux cooler. After 8 hours, the residual acidity is 0.06 moles. Upon cooling at 60"C, the reaction mixture produces two layers which are then separated.

The upper layer is dissolved in 11 of ether and washed with water. After evaporation of ether and drying, 8319 of a dough-like product are obtained (yield = 90.5%).

The under layer is re-cycled in the next batch.

Glycerol monomethylsulfoxyundecanoate A solution containing 7709 (2.5 moles) of glycerol monomethylthioundecanoate, 260ml of H202 at 33% is 1500ml of acetone are refluxed during 4 hours.

After evaporation of the acetone and drying, 8109 of crystalline product are obtained. The melting point of the product is 49-52"C and its KOH number is 1 84.

An elementary analysis of the product gives the following results: found C % 55.89 H % 9.49 calc C % 56.42 H % 9.33 EXAMPLE 4 Glycerol monododecylthioundecanoate A mixture of 9659 (2.5 moles) of dodecylthioundecanoic acid and 6969 (2.5 moles) of glycerol are heated at 195-200"C under 2660 Pa in a reactor fitted with a reflux cooler.

After 7 hours on run, there is no further acid in the medium. Upon cooling at 75"C, the mixture separates into two layers. The lower layer is re-cycled in the nextbatch. The upper layer appears as a solid mass which has a melting point of 62-71"C. Its KOH number is 1 28.

Glyceryl m onododecylsulfoxyun decanoate A solution of 8749 (2 moles) of glyceryl monododecylundecanoate and 200ml (2 moles) of H202 at 33% in 1500ml of acetone is refluxed during 6 hours.

The acetone is distilled off and the product is crystallized and dried. 9109 of product having a melting point of 95-100" is obtained.

The KOH number of the product is 1 22.

An elementary analysis of the product gives the following results: found C % 64.87 H % 16.72 calc 0% 65.54 H % 16.81 EXAMPLE 5 To 45 parts of Vaseline (Registered Trade Mark) oil at 20"C are added 2 parts of an emulsifier of which the nature will be stated herein-below. After the addition of 55 parts of distilled water, the mixture is stirred for 3 minutes with a rotative stirrer. The emulsion thus obtained is poured into a 100ml test tube kept in an oven at 40"C. The changes in the emulsion are checked every day.

The known emulsifier sold under the tradename of "NON1ONIC 218" and a corresponding sulfoxy compound were tested.

NONIONIC 218 : tert. dodecyl-polyethylene glycol thioether C12H25-S-(CH2CH2O)12H SULFOXIDE : tert. dodecyl-sulfoxy-polyethylene glycol

The emulsion obtained with NONIONIC 218 remains stable during about 17 days whereas with the sulfoxy compounds there is no visible separation after 40 days.

EXAMPLE 6 The foaming power in aqueous medium was determined by the ROSS MILES method, with 0.1 % of each of the following compounds. The results are given here-under.

Height of the foam in mm Emulsifier initial after 10 mins triethanolamine lauryl-ether sulfate 1 80 1 20 lauryl-ether lauramide (0.1%) 230 190 triethanolamine methyl-sulfoxy undecanoate 230 200 It is established that the sulfoxy compound of the invention is much better than the lauryl ether sulfate alone and that it gives a foam somewhat more stable than this ether added to laurylamide.

EXAMPLES 7 AND 8 Emulsions constituting creams for cosmetological applications, particularly night creams, were prepared with the usual ingredients and also with the addition of sulfoxy compounds of the invention. They were subjected to centrifugation test, stoving test and stocking test. The results of these tests are reported in the table herein-below, under the formulations of said creams.

The superiority of the creams IB and lIB over respectively IA and IIA is clearly due to the addition of dodecylsulfoxyundecanoic acid, one of the compounds of the invention.

EXAMPLE 7 Weight % FORMULATION IA IB Arlacel 471 (sorbitan sesquistearate) 6.80 6.80 Vaseline 1.40 1.40 Cholesterol 0.08 0.08 Marcol 82 (vaseline oil) 41 40 Bees wax 2.20 2.20 Paraffin 50/52 10.50 10.50 Stearine triple pressure 1.60 1.60 Cetylic alcohol 0.47 0.47 propyl p. hydroxybenzoate 0.15 0.15 dodecylsulfoxy undecanoic acid 1 Water 34.70 34.60 Magnesium sulfate 0.50 0.50 Triethanolamine 0.10 Preserval LL (preservative agent) 0.20 0.20 T 100 860 (Perfume) 0.40 0.40 100 100 EXAMPLE 8 Weight % FORMULATION IIA lIB Vegetal wax 8 8 Vegetal butter 5 5 Isododecane 10 10 Isopropyl myristate 5 5 Imwitor 780 K(glycerol monoisostearate) 2 2 Montane 73 (sorbitan sesquiisostearate) 1 1 Simulsol 989 (hydrogenated and ethoxylated castor oil) 0.5 0.5 Dodecylsulfoxy undecanoic acid -- Hostaphat KO 300 N (trioleylphosphate) 2 Bentone 27 (Hectorite dimethylbenzylsteary ammonium) 1.5 1.5 Bentone 38 (hectorite quaternium-18) 2 2 Preservative agent 0.2 0.2 Water 56.2 56.1 Magnesium sulfate 1 1 Magnesium hydroxide - 0.1 Glycerine 5 5 Preservative agent 0.6 0.6 100 100 RESULTS Age of the preparation TESTS FORMULA I FORMULA II A B A B 48H Centrifugation 400t/mn 200mn slight demixing stable demixing stable stoving at 40 C 48h stable stable stable stable stoving at 50 48h slight demixing stable stable stable 4 months centrifugation 4000t/mn 200mn demixing stable demixing stable stoving at 40 48h stable stable demixing stable stoving at 50 48h slight demixing stable demixing stable observation after shelving some droplets homogeneous some droplets homogeneous 1 year centrifugation 400t/mn 20mn stable observations after shelving demixing homogeneous EXAMPLE 9 AND 10 In the preceding examples describing the preparation of beauty creams the dodecylsulfoxyundecanoic acid is replaced by the methylsulfoxyundecanoic acid (Example 9) and by the glyceryl) monododecylsulfoxyundecanoate (Example 10).

Just as in Example 5, it is found that creams comprising the sulfoxy compounds have a much better stability for long periods of time than creams without these compounds.

EXAMPLE 11 Cream formulation % by weight Isododecane 12.00 Avocado oil 2.00 Corn germ oil 1.00 PPG 3 myristyl ether 2.00 Ethylhexyl acetoxystearate 1.50 Sorbitan monooleate 0.50 Polyglycerol ether dimerised soya bean oil 1.00 Soya lecithin 0.40 Dodecylsulfoxy undecanoic acid 0.90 Glyceryl monododecylsulfoxy undecanoate 1.00 Propyl parahydroxybenzoate 0.10 Sodium hyroxide 10% 1.00 Glycerine 2.50 Magnesium sulfate 0.50 Methylparahydroxybenzoate 0.20 Distilled water 73.40 This cream comprises two sulfoxy compounds of the invention and has an excellent stability during extended periods of time.

Moreover, this formulation with a continuous oily phase is particularly noteworthy since it comprises 75% water.

Such a formulation with a continuous oily phase containing 75% water was never previously obtained with conventional emulgators; it is thus particularly illustrative of the interest of the products of the instant invention.

Claims (17)

1. A process for the preparation of a stable oil-in-water type emulsion by using a compound having emulsifying properties and comprising a lipophilic part having a sulfoxide group.

2. A process according to claim 1, wherein the compound having emulsifying properties has the formular:

in which R' is a hydrocarbon group, R2 is a hydrogen atom or hydrocarbon substitutent, n is a integer from 4 to 18, and A is a hydrophilic group.

3. A process according to claim 2 wherein A is an acid which can be esterified or salified, a polyoxyalkylene chain, a tetravalent nitrogen cation or an amino-acid group.

4. A process according to claim 2 or 3, wherein R' is an alkyl, alkenyl, aryl, alkaryl, arakly or cycloaralkyl group.

5. A process according to claim 3, wherein R' has from 1 to 20 carbon atoms.

6. A process according to any of claims 2 to 5, wherein R2 is a hydrocarbon group identical to R'.

7. A process according to any one of claims 2 to 5 wherein R2 is a hydrocarbon group different to R'.

8. A process according to any of claims 2 to 5, wherein A is -COOH -SO, -SO4- or PO4, and can be in the free state, or esterified or salified.

9. A process according to claim 6, in which A is esterified with a polyol.

10. A process according to claim 9, in which the polyol is glycerol or sorbitol.

11. A process according to claim 6, in which A is salified with an alkali metal or with quaternary ammonium.

12. A process according to any of claims 2 to 5. wherein A is a nitrogenous cationic group.

1 3. A process according to claim 12, wherein said nitrogenous cationic group is quaternary ammonium or imidazolinium.

1 4. A process according to any of claims 2 to 5, wherein A is a polyoxyalkylene chain.

1 5. A process according to claim 14, wherein said polyoxyalkylene chain is a polyoxyethylene or polyoxypropylene chain.

1 6. A process according to any of claims 2 to 5, wherein A is an amino-acid group.

17. A process according to claim 16, wherein A is a amino-acid group of the

type, which can be substituted with nitrogen.

1 8. A process according to any of claims 2 to 5, wherein the emulsifying compound used is dodecylsulfoxyundecanoic acid, methylsufloxyundecanoic acid, glyceryl monododecylsulfoxyundecanoate.

1 9. A cosmetological composition comprising a stable oil-in-water emulsion, containing a compound having emulsifying properties and comprising a lipophilic part having a sulphoxide group.