WO1996036313A1

WO1996036313A1 - Aqueous liquid cleansing composition containing fatty acid soaps

Info

Publication number: WO1996036313A1
Application number: PCT/EP1996/001883
Authority: WO
Inventors: Robert James Chatfield; Stuart Keith Pratley; Tom Matthew Forrest Salmon
Original assignee: Unilever Plc; Unilever N.V.
Priority date: 1995-05-17
Filing date: 1996-05-02
Publication date: 1996-11-21
Also published as: AU5814296A; PL323144A1; BR9608455A; KR19990014828A; GB9509939D0; CN1184418A; SK154397A3; HUP9903449A2; AR001941A1; ZA963479B; CZ356597A3

Abstract

An aqueous liquid cleansing composition comprising (a) at least one short chain C6-C10 fatty acid soap in combination with (b) at least one long chain C14-C22 fatty acid soap where the weight ration of (a) to (b) is within the range 1:20 to 5:1, and in which any C12 fatty acid soap is only present in low levels, is mild and provides good lather in use.

Description

AQUEOUS LIQUID CLEANSING COMPOSITION CONTAINING

FATTY ACID SOAPS

The present invention relates to aqueous liquid cleansing compositions containing specific fatty acid soaps. In particular, it relates to compositions suitable for cleansing human skin and hair comprising a combination of certain long and short chain fatty acid soaps. Such compositions, besides being mild, provide a good lather.

Traditionally aqueous cleansing compositions were classified according to the amount of lather they produced during use; those giving the highest lather volume considered to be the superior products. However, more recently, the need to provide products which, as well as showing good foaming/lather, are mild to hair and skin treated therewith has been identified.

A major problem associated with the provision of such products is that these two properties tend to be mutually incompatible. While high lathering surfactants are generally very harsh, mild surfactants tend to give insufficient lather.

In the past attempts have been made to overcome these problems in the area of toilet soap bars by, for example, the system described in GB 1295275, involving forming a product containing a tallow soap in combination with the salt of a C₆-C_₀ primary or secondary linear alkyl sulphate and a C₁₀-C₂₄ fatty acid soap.

It has now been found that liquid cleansing compositions which show good lather and are mild can be formed by the use of a short chain fatty acid soap in combination with a long chain fatty acid soap. It is surprising that the short chain fatty acid soap which, when used by itself, shows no effective lather can improve the lather performance of the long chain fatty acid soap.

Accordingly the invention provides an aqueous liquid cleansing composition comprising

(a) at least one short-chain fatty acid soap selected from C₆ to C₁₀ fatty acid soaps;

(b) at least one long-chain fatty acid soap selected from C₁₄ to C₂₂ fatty acid soaps; and

(c) water;

wherein the composition comprises not more than 3wt% C₁₂ fatty acid soap based on the aqueous cleansing composition, not more than 15wt% C₁₂ fatty acid soap based on the total fatty acid soap and the weight ratio of (a) to (b) is within the range 1:20 to 5:1.

Preferably the weight ratio of (a) : (b) is in the range 1:20 to 1:1.

The short chain fatty acid soap is preferably a sodium or potassium salt or a substituted ammonium ion (e.g. triethanolamine) of, for example, a fatty acid derived from animal or vegetable sources obtained by a distilled fatty acid route. Preferably the short chain fatty acid soap is a C₆-C₈ fatty acid soaps, most preferably a C₈ fatty acid soap.

The long chain fatty acid soap is preferably a sodium or potassium salt or a substituted ammonium ion (e.g. triethanolamine) of, for example, a fatty acid derived from animal or vegetable sources obtained by a distilled fatty acid route. Preferably the long chain fatty acid soap is a C₁₄ or C_18:1 (C₁₈ mono-unsaturated) fatty acid soap.

The total level of fatty acid soap present in the composition should preferably be in the range 1 to 40 wt%, preferably 5 to 30 wt%.

In the most preferred embodiment of the invention, the short fatty acid soap is a C₈ material and the long chain fatty acid soap a C₁₄ or C_18:1 material. Not only is this chain blended system milder than a composition based on a C₁₂ fatty acid soap but it also shows comparable lather performance. Low levels of C₁₂ fatty acid soap not more than 3wt%, preferably not more than 2wt%, based on the total composition, and not more than 15wt% based on the total fatty acid soap may be added to the mixed soap system. At these levels the presence of C₁₂ fatty acid soap may improve the lather performance even further without having a detrimental effect on the mildness of the composition.

Preferably the compositions according to the invention will also include a cosurfactant . The cosurfactant can be selected from any known surfactant suitable for topical application to the human body and is selected from anionic, nonionic, zwitterionic and cationic surfactants and mixtures thereof. Mild surfactants, ie. surfactants which do not damage the stratum corneum, the outer layer of skin, are particularly preferred.

Preferred anionic cosurfactants include fatty acyl isethionates, alkyl ether sulphates, alkyl glyceryl ether sulphate, sulphosuccinates, taurates, sarcosinates, sulphoacetates, alkyl phosphate, alkyl phosphate esters, acyl lactylate, alkyl glutamates and mixtures thereof. Harsh surfactants such as primary alkane sulphonate or alkyl benzene sulphonate will generally be avoided.

Suitable nonionic surface active agents include alkyl polysaccharides, lactobionamides, ethyleneglycol esters, glycerol monoethers, polyhydroxyamides (glucamide) , primary and secondary alcohol ethoxylates, especially the C_8-20 aliphatic alcohols ethoxylated with an average of from 1 to 20 moles of ethylene oxide per mole of alcohol.

Preferred zwitterionic detergents are those which have an alkyl or alkenyl group of 7 to 18 carbon atoms and comply with an overall structural formula:

O R²

II I

R¹ -[-C-NH (CH₂)_m-]_n-N⁺-X-Y

R³

where R¹ is alkyl or alkenyl of 7 to 18 carbon atoms R² and R³ are each independently alkyl, hydroxyalkyl or carboxyalkyl of 1 to 3 carbon atoms m is 2 to 4 n is 0 or 1

X is alkylene of 1 to 3 carbon atoms optionally substituted with hydroxyl, and

Zwitterionic detergents within the above general formula include simple betaines of formula:

and a ido betaines of formula:

R² R¹ - CONH ( CH₂ ) _m-N⁺-CH₂C0₂~

R³ where m is 2 or 3 .

In both formulae R¹, R² and R³ are as defined previously. R¹ may, in particular, be a mixture of C₁₂ and C₁₄ alkyl groups derived from coconut so that at least half, preferably at least three quarters of the groups R¹ have 10 to 14 carbon atoms. R² and R³ are preferably methyl.

A further possibility is a sulphobetaine of formula:

or R²

I

R¹-CONH(CH₂)_π, N⁺- (CH₂)₃S0₃ R³ where m is 2 or 3, or variants of these in which -(CH₂)₃S0₃ is replaced by

OH

I

-CH₂CHCH₂S0₃ R¹, R² and R³ in these formulae are as defined previously.

The compositions of the invention may comprise a structurant, i.e. a material added to increase the viscosity at low shear, such as less than Is^"1. Suitable materials include swelling clai :, for example laponite; fatty acids and derivatives thereof and, in particular, fatty acid monoglyceride polyglycol ethers cross-linked polyacrylates such as Carbopol (TM) (polymers available from Goodrich) ; acrylates and copolymers thereof, polyvinylpyrrolidone and copolymers thereof; polyethylene imines; salts such as sodium chloride and ammonium sulphate; sucrose esters; gellants; and mixtures thereof.

Of the clays, particularly preferred are synthetic hectorite (laponite) clay used in conjunction with an electrolyte salt capable of causing the clay to thicken. Suitable electrolytes include alkali and alkaline earth salts such as halides, ammonium salts and sulphates.

The compositions according to the invention may also comprise a thickening agent, ie a material which maintains the viscosity of the composition as the shear rate thereof is increased during use. Suitable materials include cross- linked polyacrylates such as Carbopol (TM) (polymers available from Goodrich) ; fatty acids and derivatives thereof and, in particular, fatty acid monoglyceride polyglycol ethers; natural gums including alginates, guar, xanthan and polysaccharide derivatives including hydroxy ethyl cellulose, carboxy methyl cellulose and hydroxypropyl guar; propylene glycols and propylene glycol oleates; salts such as sodium chloride and ammonium sulphate; glycerol tallowates; and mixtures thereof.

Further examples of structurants and thickeners are given in the International Cosmetic Ingredient Dictionary, Fifth Edition, 1993, published by CTFA (The Cosmetic, Toiletry & Fragrance Association) , incorporated herein by reference. Examples of other adjuncts which may be added to the compositions of the invention include opacifiers; preservatives such as para-hydroxy benzoate esters; antimicrobials such as antioxidants such as butyl hydroxy toulene; bactericides; humectants such as glycerol and sorbitol; waxes; plant extracts such as Aloe Vera, witch hazel and elderflower; colourants; and perfumes.

Compositions of the invention may be formulated for washing the skin, for example, bath or shower gels; handwashing compositions; facial washing compositions; pre- and post- shaving products; and rinse-off and wipe-off skin care products.

The compositions of the invention will generally be pourable liquids or semi-liquids, for example, pastes and will, preferably, have a viscosity n the range 100 to 100,000 mPas measured at a shear rate of 10s^"1 and 25°C in a Haake Rotoviscometer RV20.

The invention is further illustrated by the following non- limiting examples.

Examples

In the examples

1. All fatty acids were greater than 99.5% purity ex Aldrich.

2. Betaine was cocoamidopropyl betaine BDF-H 30% dispersion ex Nippon Oils and Fats. Examples 1-3

In this example the effect of chain length on lather performance was examined. The following formulations were prepared by melting the fatty acids together. Potassium hydroxide was then added slowly in an amount to fully neutralise the acids. Stirring was continued until the resultant mixture was homogeneous.

TABLE A

Example Mass/g

KOH c₈ Cn Water

1 5.61 4.81 7.61 to 500 ml at 25°C

2 5.61 7.21 11.42

3 5.61 9.61 15.23

TABLE B

Comparative Mass/g Example

KOH Fatty Acid Water

A 5.61 14.42 to 500 ml at 25°C

B 5.61 17.22 to 500 ml at 25°C

C 5.61 20.04 to 500 ml at 25°C

D 5.61 22.84 to 500 ml at 25°C The foaming properties of the various compositions were assessed by a panel of twenty persons. Each panellist wore surgical gloves which had first been washed with soap to remove any talc.

2.5 ml of test composition was dosed directly onto dry gloves, and the panellist rubbed his or her hands together to generate lather. The lather volume was measured by submersion of the panellist hands under a calibrated collecting funnel.

The results given in Table C were obtained in which comparative examples A, B, C and D were carried out with single chain length soaps.

TABLE C

Example Average Chain Length Lather Volume /cm³

1 10 45.3

2 11 46.2

3 12 47.6

A 8 0

B 10 0

C 12 39.8

D 14 30.7

The results show that the formulation comprising solely a C₁₂ soap (example C) was the highest foaming system of the comparative formulations. Example D (C₁₄ soap) foamed less well than the C₁₂ system and the C₈ and C₁₀ (examples A and B) produced no foam. The C₈/C₁₄ blends produced a lather volume which was, better than that from a pure C₁₂ system. The results demonstrate that C₈ soap boosts the lather performance of a C₁₄ soap system.

Example A

In this example tests were carried out with fully formulated products.

The following formulations were prepared by melting the fatty acids together. Potassium hydroxide was then added slowly in an amount to give 97% neutralisation of the acids. Stirring was continued until the resultant mixture was homogeneous. Thereafter, betaine was added to the soap solution with stirring. For those formulations containing sodium chloride this was added either as a 25% solution in distilled water or as crystals, both of which were stirred into the hot solution until fully dissolved and mixed. Water was then added to bring the mixture to the correct concentration.

TABLE D

Example 4 Example E Example F

Caprylic Acid 1.70 - -

Laurie Acid - - 6.80

Myristic Acid 8.50 10.20 3.40

Oleic Acid 6.80 6.80 6.80

Betaine 5.00 5.00 5.00

KOH 3.99 3.75 3.98

NaCl 1.50 - 1.00

Water — to 100% -+

E and F are comparative examples The lather performance of these formulations was determined using the same method as described in Examples 1 to 3 except 0.5g of the test product was dosed onto wet gloves.

The following results were obtained: -

TABLE E

Example Lather Volume /cm³

4 66.6

E 49.3

F 56.1

The results demonstrate the benefit, in terms of a boost in lather, of including a C₈ fatty acid soap in the formulation.

Examples 5-6

In this example two formulations according to the invention and a comparative formulation (example F above) with no C₈ component (full formulations given below) were used to wash skin. The viscosity of formulations 5 and 6 were adjusted using sodium chloride so their viscosity was similar to that of comparative example F.

TABLE F

Example 5 Example 6 Example F

Caprylic Acid 1.70 1.53 -

Laurie Acid - 1.00 6.80

Myristic Acid 8.50 7.66 3.40

Oleic Acid 6.80 6.80 6.80

Betaine 5.00 5.00 5.00

KOH 3.99 4.00 3.98

NaCl 1.70 1.70 1.00

Water - to 100% -+

The test products' skin mildness properties were evaluated using a block design in a standardised Flex Wash test. The Flex Wash test procedure consisted of three daily one minute washes of the antecubital fossa (flex area of elbow) . This method is an "exaggerated use" method designed to differentiate very mild products. Erythemal response varies only slightly with temperature and humidity fluctuations making the protocol suitable for year round testing.

Approximately 25 panellists. Panellist flex areas must be free of any skin condition (eczema, dryness, irritation, cuts or abrasions) . Anyone taking antihistamines, anti- inflammatory drugs (more than 8 per week) or topical, oral or injectable cortisone on a regular basis was excluded from the study. The 3 test products were assigned to wash sites (left or right arm) using a block design.

Following an evaluation, the panellist was instructed to moisten the left flex area and a sponge. 0.5 g of product was then dispensed onto the sponge and the "dosed" sponge was placed in the panellist's right hand. The panellist then washed the left flex area for exactly one minute. Thereupon, the flex was rinsed and patted dry. This washing procedure was repeated on the right arm with the appropriate composition. Thus, both arms are tested simultaneously. Washing by this procedure was repeated three times daily for 5 consecutive days for a total of 15 washes. Treatment times were scheduled 1.5 hours apart. Each test site was evaluated immediately prior to washing and 4 hours after the third daily wash.

One trained assessor evaluated test sites for a total of 20 evaluations. The grading scale was as follows:

0 - no erythema

0.5 - barely perceptible erythema

1 - mild spotty erythema/no edema

1.5 - mild/moderate erythema/with or without edema

2 - moderate confluent erythema/with or without edema or vesiculation.

Each test site was treated in the prescribed method until a grading of "2" or greater was attained or 15 washings had been completed. When a score of "2" or greater was attained, the treatment was discontinued on that flex. The final score was then carried through for all remaining evaluations. The remaining flex was washed until either a grading of at least "2" or 15 treatments were attained, whichever was first. In example 5 and 6 and comparative example F, the final grading, Cumulative 5 day response, is the sum total of grade scores for 20 assessments per panellist averaged over the scores from all panellists. Thus, theoretically, the average score could range from 0 to 30; the lower score indicating absolutely no skin irritation while the 30 score being the most severe. The following results were obtained: -

TABLE G

Example Cumulative 5 day response

5 8.51

6 9.04

F 15.60

The results demonstrate that compositions according to the invention are significantly milder than the comparative containing no C₈ fatty acid soap and greater than 3 wt% C₁₂ fatty acid soap. The results also show the addition of a small amount (1%) of C₁₂ fatty acid soap does not have an adverse effect on the product harshness.

Claims

1. An aqueous cleansing composition, which comprises

(c) water;

wherein the composition comprises not more than 3wt% C₁₂ fatty acid soap based on the aqueous cleansing composition, not more than 15wt% C₁₂ fatty acid soap based on the total fatty acid soap and the weight ratio of (a) : (b) is in the range 1:20 to 5:1.

2. A cleansing composition according to claim 1 further comprising a cosurfactant selected from anionic, nonionic, cationic, zwitterionic surfactants and mixtures thereof .

3. A cleansing composition according to claim 2 wherein the cosurfactant includes an zwitterionic surfactant selected from alkylbetaines, amidopropylbetaines, amidopropylsultaines and mixtures thereof.

4. A cleansing composition according to any one of claims 1 to 3, in which fatty acid soap (a) is selected from C₆ to C₈ fatty acid soaps and mixtures thereof.

5. A cleansing composition according to any one of claims 1 to 3, in which fatty acid soap (b) is selected from C₁₄ and C_18:1 fatty acid soaps and mixtures thereof.

6. A cleansing composition according to any one of claims 1 to 5 further comprising a thickener.

7. The use as a cleanser for human skin and hair of an aqueous liquid composition, which comprises

(c) water;

wherein the composition comprises not more than 3wt% C_x 2 fatty acid soap based on the aqueous cleansing composition, not more than 15wt% C₁₂ fatty acid soap based on the total fatty acid soap and the weight ratio of (a) to (b) is in the range 1:20 to 5:1.