AU604363B2 - Cosmetic composition of monoester of citric acid - Google Patents

Description

T

T 'i AUSTRALIAi PATENTS ACT 1 0 4 DJ Form COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: 4r4r

U

44 I 4 1 4~ TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: UNILEVER PLC UNILEVER HOUSE

BLACKFRIARS

LONDON EC4

ENGLAND

14 I 4.

4 '4 14; Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: COSMETIC COMPOSITION o- The following statement is a full description of this invention including the best method of performing it known to me:-

~PALI~

i'/e 0EW DECLARED atnd, En~nthsj day of A-c 2 g '9 x f J. 6008 COSMETIC COMPOSITION 4044 4044 *4 44 0~ I 0 4 .444 44 4 ''44

I

44. 4 o i 4 44 44 4 4 4.4 4 4 4~ FIELD OF THE INVENTION The invention relates to compositions comprising e-ffc~ctive amounts of a salt of a monoester of citric acid.

Such compositions are suitable for topical application to skin and hair and impart improved smoothness and softness 10 to skin. When used as hair treatments the compositions of the invention give rise to a product which is exceptionally mild but which retains good foaming properties. Additionally, an improved method of synthesizing monoesters of citric acid is claimed.

BACKGROUND AND PRIOR ART Compositions containing citric acid derivatives Many compositions used for treating hum~an skin impart unpleasant feel to the skin during or after use. Thus, 4A 2 J.6008 many compositions containing soap, detergent or both and intended for cleansing the skin may dry the skin and leave it leave it feeling rough, chapped and flaky. The drying effect of these compositions, which include toilet bars, liquid or powder hand washing and bubble bath o compositions, may be extremely pronounced in certain seasons, as in dry winter months. Use of such washing compositions during these seasons may dry the skin to the point of scaliness or brittleness, with resultant cracking, reddening, bleeding and soreness.

Compositions for application to the hair such as shampoos, conditions and hair setting compositions can also have adverse effects on the skin. The repeated use S w 15 of certain detergents can contribute to an abnormal water 4 loss from the skin which results in the skin becoming dry with a loss of skin flexibility, the skin becoming rough or flaky. Contact between the skin and detergents can also give rise to irritation of the skin.

Other products applied directly to the skin such as Sshaving creams, foams or oils may also have a drying effect on skin. Moreover, the skin is stretched, scraped and often cut or punctured during shaving. These operations accompanying use of these products may exacerbate skin drying and increase skin feeling of roughness, flakiness and brittleness.

Products for the treatment of skin dryness include oils, balms, creams, lotions, liniments, ointments, unguents and gels. While these products may moisten skin and reduce or reverse roughness, cracking and brittleness of dry skin, many such products leave an unpleasant residue causing the sk.n to feel sticky, stiff, inflexible and waxy or unduly oily and greasy. Other products which may leave an unpleasant residue on the skin or which could FI :i 3 J.6008 benefit by improvement in skin treatment qualities include insect repellent and bite compositions, antiseptics and skin burn compositions (for burns from heat, sun or wind).

Additionally, compositions for chapped lips such as lip balm or cream may impart an unpleasantly waxy or greasy feEling to the lips.

Citric acid and certain of its derivatives have been proposed for use in cosmetic products. For example, emulsifiers derived from citric acid, useful in the foods industry or cosmetology, are disclosed in US Patent No.

3,929,870 (David et Specific citric acid derivatives in cosmetics include certain triesters of citric acid for shampoos disclosed in US Patent No.

4,176,176 (Cella) and 1-25% of citric and or acetylcitric 4 a~ 4.

acid esterified by aliphatic alcohols having 1-6 carbon ife atoms for deodorant stic'ks and sprays disclosed in US face Patent No. 4,010,253 (Reese et European Patent 8105 (BASF) describes cosmetic preparations having 4-40% of 20 citric acid esters carrying branched-chain alcohol radicals having 8-13 carbon atoms such as Tris-isodecyl citrate. German Patent No. 2,361,716 (Henkel) describes cosmetic preparations having 0.5-15% of coesters made from a) aliphatic diols, b) citric or acetylcitric acid, and c) K 25 aliphatic monofunctional alcohols having 12-30 carbon atoms. Preparations incorporating the coester are said to be soft and to produce no unpleasant feeling of sticking to the skin.

Citric acid or its derivatives have also been incorporated in toilet bars. Romanian Patent No. 72,330 (Grigorescu) describes incorporating citric acid in a cosmetic soap. US Patent No. 4 292 192 (Hooper) states that incorporating 0.3 to 3% of citric or acetylcitric acid esterified by an alkyl group of 1 to 4 carbon atoms imparts a deodorancy property to personal washing bars.

4 J.6008 European Patent No. 199,131 (Raffineria Olii Lubrificanti), published October 29, 1986, describes surfactants derived from citric acid, namely citric acid mono-, di- and triesters with alkoxylated alcohols described therein. Mixtures of these esters are said to be very efficient surfactants with excellent detergent and biodegradability properties and with little or no toxicity or skin irritancy. Mixtures of the esters are also said to be suitable for a liquid detergent for kitchenware as well as liquid or creamy skin detergents or bath foam, as set out in the Examples.

(ii) Synthesis of citric acid esters 15 Some conventional methods of synthesizing monoesters of citric acid yield a mix of mono-, di- and triesters of citric acid. The mixed mono-, di- and triester products of these methods is impractical in many applications.

Only the monoester is soluble in alkaline aqueous systems.

Additionally, the di- and triesters severely limit foaming. Thus, it would be desirable to produce monoesters of citric acid in a pure form, or in such predominance that the problems due to di- and triesters would be insignificant.

L

g While most methods of synthesizing monoesters of citric acid produce a mixture of mono-, di- and triesters, the relative molar amounts of citric acid and alcohol affect whether the mono-, di- or triester product predominates. Thus, reacting substantially equal molar amounts of citric acid and alcohol (or a greater amount of the former) favors monoester, while diester predominates when a molar amount of alcohol double that of citric acid is used.

li L il- C-~CIC-' i i 5 J.6008 One process which exploits this effect is described in US Patent No. 2,518,678. Citric acid is dissolved in dry pylidine. Stearyl alcohol is added to the solution and heated for 20 hours. Since only a small concentration of stearyl alcohol is said to be soluble in the pyridine solution, a small concentration of the alcohol is continually reacted with a large concentration of citric acid, favoring monoester formation.

However, even this process produces a mixture of mono-, di- and triesters, requiring expensive and cumbersome steps to purify the monoester such as the techniques of factional crystallization and selective extraction with suitable solvent systems described in US Patent Nos. 2,518,678 and 2,523, 792.

A J Repta et al. "Synthesis, Isolation, and Some Chemistry of Citric Acid Anydride", Journal of SPharmaceutical Sciences 58, (September 1969), pp.

1110-1114, describes synthesis of citric acid anhydride at page 1, col. 2, lines 14-31 and page 2. Suggested uses of the anhydride are as a desiccant or an ingredient in formulations for carbonation.

|i BACKGROUND TO THE INVENTION It has now been discovered that salts of certain monoesters of citric acid impart desirable qualities to 1 30 compositions, suitable for topical application to skin and hair.

It has also been discovered that monoesters of citric acid may be produced with minimal levels of di- and triester if citric acid is first reacted to form citric acid anhydride then reacted to form the monoester.

6 J.6008 i DESCRIPTION OF THE INVENTION This invention embraces a composition and a process, The process concerns synthesis of particular compounds, monoesters of citric acid, while the composition concerns salt forms of those compounds. Thus, while synthesis of, for example, monododecyl citrate or the monoester of citric acid derived from triethoxylated dodecyl alcohol via the steps described below falls within the process of the invention, it is incorporation of a disalt such as disodium salt of the monoester into a j physiologically acceptable carrier which comes within the I composition part of the invention.

i COMPOSITIONS CONTAINING SALTS OF MONOESTERS OF CITRIC ACID SThe composition aspect concerns a composition suitable for topical application to skin or hair comprising 1-35% of a salt of a monoester of citric acid and a physiologically acceptable carrier. It has been discovered that this composition has the desirable qualities of exceptional mildness in hair treatment compositions and of imparting to skin a marked smooth and S creamy feel. It has further been discovered that toilet bars incorporating a salt of a monoester of citric acid themselves have an unusually pleasant smoothness and slip and that shampoos incorporating the salt have surprisingly good foaming properties.

i The salt of the monoester of citric acid has one of the following formulae: -7 J,6008 CH COOR CH COOM 2 1 2 HO C -COOM HO C COOR CH COOM CH -COOM 2 2

(II)

R has the structure of a moiety derived from R 1

-OH,

which alcohol is chosen from alkanols, alkenols and arylalkanols having 10 to 18 carbon atoms and alcohols of the formula: R2-A-(O-R 3 -OH (III) or

R

3

R

2

-(O-R

3 -OH (IV) 4 1 where R 2 is a hydrocarbon chain having 10 to 18 carbon atoms, A is an aryl group, R 3 is an alkyl chain having 2 to 4 carbon atoms and x is an integer from 1 to 7. Each M S 20 is a cation independently chosen from alkali metals, alkaline earth metals, ammonium and substituted ammonium, particularly including mono-, di- and trialkanol ammonium.

Compositions of this invention include a salt of an ester of citric acid. This ester of citric acid may consist essentially of the monoester of citric acid or may comprise of mixture of mono-, di- and triesters of citric acid.

it The compounds of formulae and (II) are isomeric forms of a salt of a monoester of citric acid, (II) being a symmetrical and an asymmetrical isomer.

w i, S- 8 J.6008 Compositions of the present invention may have either isomer or a mixture of both.

I In a preferred embodiment, when both isomers are present, the relative amount of (II) to may be about 3:1. Additionally, the monoester salts of citric acid need not all have identical R 1 groups. Furthermore, each molecule of the salt of a monoester of citric acid may have two of the same or different cations; if all the salt molecules have the same cations, the cations need not be the same from molecule to molecule.

R

1 may more particularly have the structure of a moiety derived from R1-OH, which alcohol is chosen from straight chain alkanols and alkenols having 10 to 18 carbon atoms; or chosen from alkanols and alkenols having 12 to 15 carbon atoms. One commercially available mixture of alkanols which is suitable for esterifying citric acid has primary alcohols with 14 to 15 carbon atoms, sold as NEODOL 45. The alcohol can also be chosen from alcohols of formula (III) or (IV) with R 2 having 12 to 15 carbon atoms. Suitable mixtures of alkoxyl groups include the (3EO) ethoxylated primary alcohols with 12 to 15 or 14 to carbon atoms, sold respectively as NEODOL 25-3 or 45-3.

The NEODOL products are available ex Shell Oil Company, One Shell Plaza, Houston, TX 770022.

1 Instead of the 1 to 35% of a salt of a monoester of citric acid the composition of the inventions may more particularly include from 5 to 30% or from 10 to 25% of the salt of a monoester of citric acid. At levels over compositions which are intended to be solid may become soft, mushy and pliable. (All component amounts expressed in percentages indicate percent weight unless otherwise stated).

1 i 9 J.6008 When the compositions of the invention are intended for direct application to the skin the compounds of formulae I and II may be incorporated in a physiologically acceptable carrier of petroleum jelly, lanolin, paraffin wax, alkanols, water and mixtures thereof as well as the carriers of the examples below. More particularly, the water may be a 1-5% solution of an appropriate buffer, such as sodium bicarbonate. The physiologically acceptable carrier may comprise soap or detergent toilet bars, or liquid or powder hand washing compositions, antiseptics, insect repellant and bite compositions, shaving creams, oils and foams, and compositions for treatment of dry, rough or chapped skin. Some formulations of the composition may be applied briefly and washed off as in washing hands with a toilet bar within the invention, while other formulations such as a cream or ointment described below, may be left on indefinitely.

44 4 4444 4 4I 44d C 6 Such compositions may take any of the following 20 forms: lotion, liniment, solution, suspensions, oil, ointment, cream, gel, balm, unguent, paste, stick or aerosol and may be applied directly to the skin.

Application may also take place in using one of the consumer products listed above, e.g. in washing hands with a toilet soap bar. Alternatively, composition of this invention may be incorporated in pads or pre-moistened towelettes for a wiping application to the skin or onto bandages, dressings or plasters for a longer application.

The bandages, dressings, pads, plasters and pre-moistened towelettes may be optionally medicated with substances in addition to the composition of the invention.

The compositions of the invention comprising 1-35% of a salt of a monoester of citric acid may also be formulated as hair treatment compositions such as shampoo, conditioner, styling lotion, styling mousse or hairspray.

il.~nraraa~- -j-i~.-il-Y1~L -L l.i:-i li__iY.ii.-^ l -11 10 J.6008 These compositions may be packaged in a bottle with a closure, a pump dispenser, aerosol or non-aerosol spray canister.

Conventional soap compositions typically are comprised of from 25 to 90% by weight of soap from 1 to water. When such compositions further incorporate salt of monoester of citric acid within one of the above-recited ranges, the compositions come within the present invention. The term "soap" is used herein to mean the alkali metal or alkanol ammonium salts of aliphatic alkane- or alkene monocarboxylic acids having about 12 to about 20 carbons atoms, and preferably about 12 to 18 carbon atoms.

2O It is preferred to use soaps having the fatty acid derived from coconut oil, tallow, or mixtures thereof, since these are among the most readily available fats.

The proportion of fatty acids having at least 12 carbon atoms in coconut oil soap is about 65%. This proportion will be greater when mixtures of fatty acids derived from fats such as tallow, palm oil, or non-tropical nut oils or fats are used, wherein the principal chain lengths are of sixteen carbon atoms or more.

Derivation of fatty acids from oils and fats for use in this invention is by known methods, e.g., saponification of said oil or fat.

Additionally, optional ingredients may be included in soap formulations within the present invention, free fatty acids, emollients, suds boosting agents, germicides, opacifiers (such as titanium dioxide) and colorants, pigments, perfumes, preservatives, electrolyte salts and mixtures thereof. A typical listing of the classes and species of optional ingredients useful in soap i

I

it 11 J.6008 compositions appears in US Patent No. 4,260,507 incorporated herein by reference. It should be understood, of course, that these lists of optional ingredients and mixtures for soap compositions are only representative of such materials and is not intended to be limiting.

Soap compositions within the present invention may be in liquid or solid form. The latter form is well known commercially as the toilet bar. Requirements for a good toilet bar are well known and enumerated in US Patent No.

2,894,912. The properties of soap toilet bars within the present invention are similar to those of conventional bars with the addition of properties herein disclosed.

Soaps and Detergents, Thomssen and McCutcheon, MacNair-Dorland Company, 1949, pp. 195-207 and Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley Sons, 1983, Vol. 4, pp. 173-177 describe techniques of toilet bar-making including milling, plodding, framing and shaping, by means of which the soap compositions of this invention may be shaped into bars. A bar of toilet soap may be formed by these techniques from the following composition: about 80% of fatty acids derived from tallow and coconut, about 10% water and about 10% of disodium salt of a monoester of citric acid esterified with C 12

-C

1 (3 EO) primary alcohols. The bar itself has a remarkable smoothness and slip; washing one's skin with the bar imparts a pleasant smoothness to the washed skin.

Non-soap skin cleansing compositions may also come within this invention. These skin-washing compositions, with detergent active compounds replacing all or part of the soap in the toilet soap bars, are comprised of from about 10% to about 70% by weight of a detergent active compound, about 2% to about 20% suds booster, about 10% to 4 -r

CH

2 COOM CH COOM 2

(XX}

/2 7 12 J.6008 about 40% by weight aliphatic fatty acid, about 2.5% to about 25% by weight water-soluble aliphatic fatty acid soap, about 1% to about 35% by weight of a salt or salts of monoester of citric acid and about 1% to about 10% by weight water. Additionally, the optional ingredients which may be included in these compositions are the same as those listed above for soaps.

Examples of detergent active compounds usable to form I 10 these compositions are found in "Surface Active Agents" by Schwartz Perry (Interscience 1949) and "Surface Active I Agents" by Schwartz, Perry Berch (Interscience 1958) and J those set forth in US Patent No. 2,894,912 and US Patent No. 3,070,547, each of which is hereby incorporated by reference. More particularly, the detergent active may be selected from the group consisting of alkali metal, i magnesium or ammonium salts of detergents selected from the group consisting of C 12

-C

16 hydroxyalkane sulfonates, C 8-C18 N-acyl taurates, C12-C18 alkyl sulfates, C 12

-C

18 alkyl ether sulfates, C 12

-C

16 alkyl phosphonates and phosphates, C 12

-C

16 mono-alkyl succinates and maleates, C6-C1 dialkylsulfosuccinates, C16-C20 alkane disulfonates, C 8

-C

18 alkene sulfonates, alkylbenzene sulfonates and mixtures thereof. Further, the detergent active may be an alkali metal, magnesium or ammonium salt I of a fatty acyl ester of isethionic acid, in particular I fatty acyl esters derived from fatty acids having from I to 18 carbon atoms; more particularly the fatty acyl groups may be derived from fatty acids derived from r 30 coconut oil.

These skin cleansing compositions may be liquid or solid. The solid compositions may be formed into toilet bars according to the steps set forth in Thomssen and McCutcheon for soap bars. The properties of the detergent toilet bars of the present invention are similar to those c 13 J.6008 of soap bars as well as to those cf conventional bars with the addition of properties herein disclosed.

Skin cleansing compositions of the present invention i 5 may incorporate soap or detergent active compounds or both. In addition to 10-35% of one of the soaps or detergent active compounds discussed above, or a mixture of both, a liquid hand cleansing composition of the present invention comprises 1 to 35% of a salt of a monoester of citric acid, 0-5% sodium chloride, and balance water. Optionally, this composition may further include 1-5% of a suds boosting agent, for example, coco Smonoethanolamide and 0.2-0.5% of a preservative, for example, EDTA.

When the composition of this invention is a toilet bar or liquid hand cleansing composition, it is desirable that little or no triester or salt of diester of citric acid be present, as these have been found to limit foaming i 20 and are insoluble in alkaline aqueous systems.

j Shaving creams within the present invention comprise 1 to 35% of a salt of a monoester of citric acid, 25-50% I stearic acid, 5-20% coconut oil, 10-25% glycerol, 1-15% mineral oil and 5-45% water.

A composition for treating dry, rough or chapped skin i such as chapped lips under the present invention may be in solid form for use as a stick-type composition. Such i 30 compositions comprise from 1 to 35% of a salt of a Smonoester of citric acid, and from 50% to 98%, preferably to 90%, of an emollient. This composition may further comprise from 1% to 20%, preferably 5% to 15%, of a suitable thickening agent, and optionally emulsifiers and water.

1 _I

I_

14 J.6008 A typical listing of suitable thickening agents, emollients and emulsifiers useful in solid compositions appears in US Patent No. 4,560,549 (Ritchey et al.) incorporated herein by reference. It should be i 5 understood, of course, that the list of optional ingredients and mixtures there described is representative only and is not intended to be limiting. Additives commonly found in topical compositions such as preservatives, e.g. methyl and ethyl paraben, dyes and i 10 perfumes are advantageously included in any of the i above-described solid compositions for treating dry, rough or chapped lips.

Compositions for treating dry, rough or chapped skin further may be in ointment form comprising 1 to 35% of a salt of a monoester or citric acid, 1 to 5% anhydrous wool fat, 5 to 20% viscous paraffin, 0 to 5% cetyl alcohol and 65-95% white petroleum jelly. More particularly, the cetyl alcohol may be present at 0.5-2.5%.

When a skin treatment composition according to the present invention is in cream form, it comprises 1 to of a salt of a monoester of citric acid, from 50 to i preferably 25 to 10% of an emollient, and the balance water. Optionally, the cream form contains a suitable i emulsifier. The emollients and emulsifiers described above for compositions of the invention in stick form are Sequally suitable here.

4 30 The compositions of this invention may also be fornmulated in solution form, comprising from 1 to 35% of a salt of a monoester of citric acid, and 65 to 99% of a suitable organic solvent. Suitable organic materials useful as the solvent or a part of a solvent system are as follows: propylene glycol, glycerine, ethanol, sorbitol esters, 1,2,6-hexanetriol, isopropanol, diethyl tartrate, i- L rl

LIO

I 15 J.6008 K butanediol, and mixtures thereof. Such solvent systems can also contain water.

The compositions of this invention may also be formulated in aerosol form by incorporating the solution formulation described above in a closed metal container fitted with an aerosol cap and pressurized using conventional methods at from 25 psi'up to 100 psi pressure with an aerosol propellant such as butane gas or CAP In gel form, the present invention comprises 1 to of a salt of a monoester of citric acid, 5 to 75% and preferably 10-50% of an organic solvent, 0.5 to preferably 1 to 10% of a thickening agent, the balance being water. Suitable thickening agents include those recited above for compositions in solid form. Suitable organic solvents include but are not limited to glycerine, sorbitol esters, 1,2,6-hexanetriol, ethanol, isopropanol, i diethyl tartrate, butanediol and mixtures thereof.

jI Without in any way limiting the scope of the present I invention to the following theoretical considerations, applicants would like to emphasize their belief that it is the salt of the monoester of citric acid (rather than any i 25 di- or triester which may be present at very low levels) which contributes to the beneficial effects of the compositions of the invention, and that maximizing the :level of the monoester salt in these compositions results in markedly improved products. Moreover, it is important that the R 1 chain of the monoester be long enough to impart adequate hydrophobicity to the composition and to produce the smoothness and slip of such compositions.

Consequently, it is monoesters having higher R 1 chain lengths which are included in the compositions of the invention. These R 1 chains are typically straight chains, unbranched and not alkyl substituted.

-i I ir 4i.jy -Cov= anL uInp-easant resiaue on tne skin or which could L I Ir. I- 16 J.6008 PROCESS FOR THE SYNTHESIS OF SALTS OF MONOESTERS OF CITRIC ACID The process aspect of this invention concerns synthesis of monoesters of citric acid. Pure or predominantly monoester is desirable for reasons stated above. It has been discovered that monoesters of citric i acid may be synthesized with minimal production of di- or triesters: about 95% of the esterified citric acid is in monoester form, the balance being an acetyl derivative of the monoester. This new synthetic process produces higher yields in less time (75% and above in less than 12 hours) of a nearly pure monoester, and avoids the expense and difficulties associated with the solvent dioxane and purification of the monoester from the di-and triesters.

The process comprises mixing citric acid with an organic anhydride of the formula 0 R C I 54 C 3

II---

where R 4 and R 5 are independently selected from the group consisting of hydrocarbon chains having from 1 to 5 carbon atoms or, with R 4 and R 5 taken together, containing 6 to 8 carbon atoms linked to form a cycloaliphatic or aromatic anhydride or substituted derivative thereof. More particularly, the anhydride may be acetic anhydride. The i amount in moles of anhydride added is substantially equal to or slightly greater than the amount in moles of citric acid.

i I I UY I~-llr ULIL 3 i 17 J.6008 In a preferred embodiment, the citric acid and anhydride reaction mixture is heated to a temperature of fomnt 60 0 C to 90°C for 15 to 45 minutes, producing citric acid anhydride, which is believed to have one of the following formulae: O O Ii CH- CH- C 2 2 HOOC -C OH O HO- C C i /I 0 CH C CH CO H 2 2 2 (VI)

(VII)

Regardless of the structure of any product or any intermediate in the reaction mixture at this stage, an alcohol of the formula R -OH may be added directly to the reaction mixture, R 1 -OH being selected from the group 20 previously defined. The amount in moles of alcohol added Sis substantially equal to or slightly less than the amount in moles of citric acid used to form the initial reaction mixture.

i 25 The citric acid anhydride and alcohol are subjected to heat and continuous distillation under reduced pressure to remove volatiles and produce predominantly the monoester of citric acid. In a preferred embodiment, the reaction mixture is heated to 60°-80°C and continuously distilled at reduced pressure for 5-10 hours.

The monoester is in solution at this point. To isolate the monoester as a dication salt, the solution is cooled, diluted and neutralised with an organic or 18 J.6008 inorganic base. For example, the solution may be cooled to room temperature (25 0 C) or below, diluted with a solvent such as ethanol or methanol, then neutralized to a pH of about 6.0 to about 8.5 with the solution at 15 0 C or below. Organic or inorganic bases such as sodium hydroxide, potassium hydroxide, ammonia solutions, ammonium or substituted ammonium (particularly monoethanolamines), or salts thereof, alkali metal carbonates or alkaline earth metal carbonates or bicarbonates, or mixtures thereof may be used to neutralize the solution. The choice of the neutralizing ruagent is governed by which salt or salts of the monoester of citric acid one wishes to form since the cation of the neutralizing reagent becomes the cation of the monoester salt. The solid precipitate which forms is Sthe salt of a monoester of citric acid of formula or (II) above.

i Alternatively, in another reaction mode, the citric acid may initially be placed in a solvent, such as acetone or an acid of the formula R 6 -COOH, where R 6 is selected from the group consisting of hydrocarbon atoms having from 1 to 5 carbon atoms, An amount in moles of organic anhydride of the above formula substantially equal to or slightly greater than the amount in moles of citric acid is added to the solution. The remainder of the steps are similar to those above.

Preferably, the citric acid used to form the monoester is anhydrous, to prevent lower yields due to hydrolysis of the anhydride reagent by water which may otherwise be present. Solvents employed for the citric acid preferably are also anhydrous.

It is an advantage of this process that predominantly monoesters are produced, about 95% of the esterified £tI~~~±b~JCfl L.L 19 J.6008 citric acid, the balance being an acetyl derivative of the monoester and minimal levels of di- and or triesters of citric acid. The synthesis of the present invention thus produces nearly pure monoester of citric acid.

Like the conventional direct esterification methods, the instant synthetic method yields a mixture of symmetrical and unsymmetrical isomers of citric acid monoester. However, the two methods yield relatively different isomeric products: the anhydride synthesis yields mainly symmetrical isomer predominating by about a factor of three over the unsymmetrical ester, while direct esterification yields mainly unsymmetrical ester precominating by roughly the same factor.

iThese isomers may be isolated from one another by known methods, among which are re-crystallization techniques. A preferred approach for isolating the I symmetrical isomer of citric acid monoester from the 1 20 unsymmetrical isomer follows: the monoester may be dissolved in a solvent system comprising 9 parts heptane I and two parts ethyl ether. Adding an additional 1.5 parts ethyl ether induces precipitation. Once precipitation is Icomplete, the solution may be filtered yielding pure symmetrical ester with melting point of 78-80.5'C.

In addition to the two isomeric forms of the monoester of citric acid, the citric acid anhydride process may form small amounts of diesters. However, the second ester linkage of this diester forms at the hydroxyl group of citric acid rather than at one of the carboxyl groups. The diesters apparently result from the reaction of the citric acid hydroxyl group with the short chain organic anhydride, the acid solvent, when used, or with the acid formed from hydrolysis of the anhydride. Thus, when acetic anhydride reactant for example is used to form IL I

A-

20 J.6008 citric acid anhydride, there may be formed some acetyl -ste3 of citric anhydride. Subsequent reaction of the* latter compound with long chain alcohols, for example, leads to formation of diesters. Such compounds usually comprise less than 10% of the citric acid monoester product and often comprise far less than

EXAMPLES

For a further understanding of this invention, rf refirncc may be made to the following examples: i EXAMPLE I ij 15 Anhydrous citric acid (0.2 moles) and acetic 2 anhydride (0.24 moles) are rapidly mixed then heated to i, for 2C-30 minutes. Dodecyl alcohol (0.18 moles) is added to thi reaction mixture, which is then subjected to continuous distillation under reduced pressure at 70-75°C for 5 hours to remove acetic acid.

The reaction mixture is cooled to 20 0 C and diluted with ethanol, then neutralized at 15 0 C to pH of Sodium carbonate (0.4 moles) is added and the disodium salt of monododecyl citrate is recovered as a precipitate which can be used in the composition of the invention as follows: A toilet soap bar having the following composition is made by mixing the first three components in a Brabender kneader for 35 minutes at 50 0 c then adding the last two components and mixing for 10 minutes more: '4

I

,u -l 21 J.6008 by weight Disodium salt of monododecylcitrate 17.6 Mixture of sodium salts of fatty acids, of which 02% are derived from tallow and 18% are derived from coconut oil 76.5 TiO 2 1 Perfume 1 Water balance EXAMPLE II Anhydrous citric acid (0.2 moles) and acetic anhydride (0.24 moles) are rapidly mixed then heated to 70 0

C

for 20-30 minutes. Triethoxylated dodecyl alcohol (0.18 rmoJes) is added to the reaction mixture, which is then subjected to continuous distillation under reduced pressure at 70-75 0 C for 5 hours to remove acetic acid.

The reaction mixture is cooled to 20 0 C and diluted with ethanol, then neutralized at 15 0 C to pH of Sodium carbonate (0.4 moles) is added and the disodium salt of the monoester of citric acid derived from triethoxylated dodecyl alcohol is recovered as a precipitate which can be used in the composition of the invention as follows: A solution formulation is prepared by mixing the following components at room temperature: 22 J.6008 by weight Glycerine Disodium salt of the monoester of citric acid derived from triethoxylated dodecyl alcohol Water balance The solution is applied to the skin to relieve a S:feeling of dryness, roughness or scaliness.

Advantageously the solution is applied every four to twelve hours while dryness persists.

EXAMPLE III 20 Anhydrous citric acid (0.2 moles) is placed in a i i i vessel and suspended in acetic acid. Acetic acid anhydride (0.24 moles) is rapidly added to the vessel and the mixture is heated to 80 0 C for 30 minutes. A mixture of saturated C14-C15 aliphatic primary alcohols is added to the vessel. The reaction mixture is continuously distilled at reduced pressure at 700C for 10 hours, then I cooled to 250C.

Ethanol (50 ml) is added to the vessel, then I 30 aqueous NaOH is added to neutralize the mixture to about pH 7. The disodium salts of monotetradecyl ester and monopentadecyl ester of citric acid are recovered as precipitate.

y usy suAon, styling mousse or hairspray.

23 The yield of the disodium acid is from 65% to J.6008 salt of monoester of citric The precipitate prepared as above can be used to prepare a gel formulation by mixing the following ingredients: by weight Disodium salt of monoester of citric acid esterified with

C

14

-C

15 primary alcohols 1,2,6-Hexanetriol Bintonite Water balance 3 33 3 3 EXAMPLE IV A toilet soap bar having the following composition is made by mixing the first three components in a Brabender kneader for 35 minutes at 50 0 C then adding the last two components and mixing for 10 minutes more: i 24 J.6008 by weight Disodium salt of the monoester of citric acid derived from dipropoxylated dodecyl- 2-ene alcohol Mixture of sodium salt of fatty acids of which 82% are derived from tallow and 18% from coconut oil TiO 2 1 SPerfum 1 Water balance Toilet soap bars made in the above manner impart a creaminess and smoothness to the skin. Additionally, the bars themselves have a markedly pleasant smooth hand feel.

j EXAMPLE V A detergent toilet bar is made having the following composition: 10% of dipotassium salt of citric acid monoester derived from tetraethoxylated primary alcohols having 14 to 15 carbon atoms, 9% water, 50% of disodium salt of lauroyl ester of isethionic acid, 10% unesterified sodium salt of isethionic acid, 10% of potassium lauryl sulfate as a suds-boosting detergent salt, and 10% of i paraffin wax as a binder-plasticizer. The toilet bar is Sformed by the conventional steps of toilet bar formation, and has the properties of the bar of Example IV.

25 J.6008 IEXAMPLE VI An ointment formulation is prepared by thorough mixing of the following ingredients.

l~j by weight Dipotassium salt of a monoester of citric acid esterified saturated primary alcohols having 12 to carbon atoms and three ethylene oxide units SAnhydrous wool fat 2 15 Viscous paraffin White petroleum jelly balance The resultant ointment is applied to the skin to xelieve a feeling of dryness, roughness or scaliness.

Advantageously, the ointment is applied every four to twelve hours while dryness persists.

EXAMPLE VII A cream is prepared by mixing the following 1ingredients together: by weight i Disodium mono-n-tetradecylcitrate Ethoxylated cholesterol Sorbitol Water balance

I

C- I- 26 J.6008 The resulting cream is applied to the skin to relieve dryness in the same manner as that described for the ointment in Example VI.

EXAMPLE VIII A solid stick according to this invention containing a salt of a monoester of citric acid is prepared by shaping and moulding the following ingredients: by weight Disodium mono-n-decylcitrate Lanolin wax Glycerol Methylcellulose Water balance The resultant solid stick of this Example is applied upon the skin to relieve a feeling of dryness, roughness or scaliness.

EXAMPLE IX A shampoo is formulation is prepared by mixing the following ingredients: i e ll*.n;rtrnrrrri iu~~ 27 Disodium monododecvl citrate Coconut diethanolamide Sodium chloride Formaldehyde (40% aqueous solution) Water pH adjusted to 7.4 with lactic acid.

J.6008 by weight 14.0 2.2 0.08 balance The resultant shampoo foams well and is mild to th- Ec lp in use.

-g ii i i i i i i, r i i r i :1 1 i EXAMPLE X A shampoo formulation is prepared by mixing the following ingredients: Disodium monododecyl citrate Monoethanolamine lauryl sulphate Lauric isopropanolamide Phosphate ester (Briphos 03D) Silicone glycol Sodium chloride pH adjustor Preservative Water by weight 10.2 0.15 0.15 balance r _i _i 28 J.6008 The resultant shampoo foams well and is mild to the scalp in use.

EXAMPLE XI A hair styling mousse is prepared by mixing the following ingredients: I Disodium salt of monododecyl citrate 15.0 Empigen OB Absolute Alcohol 0.1 Preservdtive Water balance The above composition is packed in a closed metal container, filled with an aerosol cap and pressurized with by weight CAP c B i i i

Claims (21)

1. A composition suitable for topical application to skin and hair comprising from 1% to 35% by weight of a dication salt of a monoester of citric acid having one of the following formulae: *888 '4 0 0 doe 840 so e 90 0 8098O 8808a 88 8 48 CH2 HO C CH2 COOP COON -COOM CH 2 HO C COOM COOR 1 COON 4848 ft 4 4 l 4 84ff 4 4 CH 2 (Ti) where R has the structure of a moiety derived from R 1 -OH, which alcohol is chosen from alkanols, alkenols and arylalkanols having from 10 to 18 carbon atoms; and from alcohols of the formula: 8088 .8 4 8848 8 48 48 4 or R 2 -A(O-R 3 -OH R 2 (O-R 3 -OH (III) 488 4488 4 48 8488 8 84 48 44 4 844 4 (IV) where R2 is a hydrocarbon chain having 10 to 18 carbon atoms, A is an aryl group, R 3 is an alkyl chain having 2 to 4 carbon atoms and x is an integer from 1 to 7; each M is a cation chosen from alkali metal, the alkaline earth metals, ammonium, substituted ammonium and a mixture thereof; and a cosmetically acceptable carrier for said monoester.

2. A composition according to claim 1, wherein R -OH is 30 J6008 AUS chosen from straight hydrocarbon chain alkanols and alkenols having from 10 to 18 carbon atoms.

3. A composition according to claims 1 or 2, wherein R,-OH is chosen from alkanols and alkenols having from 12 to 15 carbon atoms.

4. A composition according to claims 1, 2 or 3, wherein R 1 -OH is dodecyl alcohol. t it

5. A composition according to any preceding claim, wherein the salt of the citric acid monoester is the disodium salt of monododecyl citrate.

6. A composition according to claim 1, wherein the salt of the citric acid monoester is the disodium salt of triethoxylated monododecyl citrate.

7. A composition according to any preceding claim, wherein the monoester of citric acid is comprised of symmetrical and asymmetrical isomers in a relative ratio of about 3:1.

8. A composition according to any preceding claim, 4*t t further comprising from 25% to 90% by weight of soap.

9. A composition according to any preceding claim, further comprising 10 to 70% by weight of a detergent active compound.

A composition according to claims 8 or 9, wherein the composition is formed into a toilet bar.

11. A composition according to any of claims 1 to 9, in the form of a solid stick. COLI .u~irr~ii"*a~llL- C sIrrsr il i 31 J6008 AUS

12. A composition according to the form of a cream.

13. A composition according to the form of a lotion.

14. A composition according to the form of a shampoo.

A composition according to the form of a hair conditioner.

16. A composition according to form of a hair styling mousse.

17. A process for synthesizing comprising: any of claims 1 to 9, in any of claims 1 to 9, in any of claims 1 to 9, in any of claims 1 to 9, in any claims 1 to 9, in the a monoester of citric acid a. mixing citric acid and an organic anhydride to form a reaction mixture, the organic anhydride having the formula: R C 4 0 R -c/ 5 where R 4 and R 5 are independently chosen from hydrocarbon chains having from 1 to 5 carbon atoms or, with R 4 and R 5 taken together, having 6 to 8 carbon atoms linked to form a cycloaliphatic or aromatic anhydride or a substituted derivative thereof, and the amount in moles of anhydride being substantially equal to or slightly greater than the i _L -u A -32- J6008 AUS amount in moles of citric acid; b. heating the reaction mixtures to at least 60 0 C for up to 45 minutes; c. adding an amount in moles of fatty alcohol to the reaction mixture substantially equal to the amount in moles of the citric acid in the initial reaction mixture, the fatty alcohol having the formula: R -OH where RIOH is chosen from alkanols, alkenols and to 18 carbon atoms, or alcohols of the formula; R2-A-(O-R3)x-OH (III) or R 2 -(O-R 3 -OH (IV) where R 2 is a hydrocarbon chain having 10 to 18 carbon atoms, A is an aryl group, R 3 is an alkyl chain having 2 to 4 carbon atoms, and x is an integer from 1 to 7; and d. heating and continuously distilling the reaction mixture and fatty alcohol forming a monoester of Icitric acid.

18. A process for synthesizing a monoester of citric acid according to claim 17, further comprising: a. cooling the reaction mixture; 33 J6008 AUS b. diluting the reaction mixture; c. neutralising the reaction mixture with an organic or inorganic base; and d. collecting the disalt of the monoester of citric acid as a precipitate. o

19. A process for synthesizing a monoester of citric acid according to claims 17 or 18, wherein citric acid is o n placed in a solvent before the anhydride is added, the o o solvent being acetone or an acid of the formula: o R -COOH o 6 where R 6 is chosen from hydrocarbon chains having from 1 to 5 carbon atoms. o,

20. A process for synthesizing a monoester of citric acid 1 according to claims 17, 18 or 19, wherein the citric acid *F 0 o, used is anhydrous citric acid.

21. A process for synthesizing a monoester of citric acid according to claim; 18 further comprising: a. cooling the reaction mixture to 25 0 C or lower after distilling; b. diluting the reaction mixture with an organic solvent chosen from organic alcohols having from 1 to 4 carbon atoms; and L 1 ~1 34 c. neutralising the mixture to a pH of from 6.0 to with organic or inorganic base while maintaining the reaction mixture temperature at 15 0 C or lower. DATED THIS 5TH DAY OF SEPTEMBER 1990 UNILEVER PLC By its Patent Attorneys: GRIFFITH HACK CO i Fellows Institute of Patent Attorneys of Australia. i i