WO1996014053A1

WO1996014053A1 - Skin cleansing - uv screening composition

Info

Publication number: WO1996014053A1
Application number: PCT/GB1995/002559
Authority: WO
Inventors: Mark John Davey; Maxine Alethia Green
Original assignee: Cussons (International) Limited
Priority date: 1994-11-02
Filing date: 1995-10-30
Publication date: 1996-05-17
Also published as: GB9512062D0; AU702476B2; AU3751595A; PL320112A1

Abstract

A rinse-off skin cleansing composition which includes at least one UV-screening agent, at least one surfactant and at least one skin-substantive emollient. The composition is used to cleanse the skin while forming a water-resistant, protective barrier on the skin and is more resistant to rinse-off and rub-off. It is particularly suited to the delivery of UVA protection throughout the year.

Description

SKIN CLEANSING - UV SCREENING COMPOSITION

This invention relates to skin cleansing - UV screening compositions.

The direct exposure of the body to the sun's UV rays leads in the short term to sunburn and blistering of the skin. In the long term, premature ageing and cancers can develop. The skin damage varies with skin type but some protection to withstand prolonged exposure is required for all skin types if sun damage is to be avoided.

Various lotions, moistu risers and cosmetics now incorporate UV screening agents. The UV screening agent(s) is topically applied to the skin as part of the formulation. One of the main problems addressed in recent years has been the tendency of the UV screening agents to "wash-off" during perspiration, washing or bathing. Several carriers have been claimed to effect a decrease in this "wash- off" tendency. As an alternative, UV screening agents with water resistant properties have also been sought.

However, despite some success in the above mentioned fields very little progress has been made in utilising UV screening agents in skin cleansing compositions. Such compositions have an inherent difficulty. The UV screening agent has a tendency to be washed off while applying the skin cleansing composition due to the nature of the detergent/water interaction which acts to rinse oils and greases from the skin together with the UV screening agent. US 4,933, 174 and 4,701 ,321 discloses a method of applying a liquid detergent with a sunscreen agent which requires large amounts of sunscreen agent in order to leave an effective residual amount on the skin surface after rinsing. The disadvantage of this method is that it requires very regular application of the product to maintain the residual amount of UV screening agent left on the skin surface after rinsing. Such a composition results in an expensive and wasteful product due to large amounts of the screening agent being rinsed off.

EP 165329B discloses a liquid combination sunscreen detergent. The disadvantages of this technology is that it is limited to compositions based on non- ionic and amphoteric surfactants, whereas most commercially available skin cleansing products utilise anionic surfactants.

EP 0552024 discloses a rinse off cleansing composition including one or more surfactant-soluble cosmetic agents comprising a stable emulsion having a continuous and internal phase.

The disadvantage with this technology is that it is limited to liquids and stable emulsions whereas the present invention is also applicable to solid

compositions.

It is an object of the present invention to provide a skin cleansing composition which overcomes the aforementioned problems. It is an object of the present invention to provide a skin cleansing composition with UV screening agent deposition, the said deposition to be greater and more efficiently achieved than technology previously disclosed, thus requiring less regular application for the equivalent benefit. This enhanced UV screening agent deposition will in turn provide the skin with a more efficient screen against UV radiation.

A still further object of the present invention is to provide a skin cleansing composition with UV screening agent deposition which is used daily and at all times of the year. The importance of protection against UVA radiation at all times of the year has been greatly highlighted in recent years but many all-year products which claim to deliver UV protection as a secondary benefit actually give very low UVA protection. The present invention is particularly suited to the delivery of UVA protection throughout the year.

A still further object of the present invention is to yield more efficient resistance to rub-off of the sunscreen agent by forming a water-resistant, protective barrier on the skin.

It is a still further object of the present invention to provide a liquid or solid surface cleansing composition which may be utilised with nonionic, ionic or amphoteric surfactants.

According to the present invention there is provided a rinse-off skin cleansing composition comprising at least one UV-screening agent, at least one surfactant and at least one water-insoluble, skin-substantive emollient.

According to a second aspect of the present invention there is provided a method of applying a UV-screening agent using a rinse-off skin cleansing composition, the said composition comprising at least one UV-screening agent, at

least one surfactant and at least one water-insoluble, skin-substantive emollient.

Water-insoluble is defined as a material which is not readily soluble in water. Preferably, the water-insoluble material has a hydrophilic lipophilic (HLB) balance of less than 12.

The use of a water-insoluble skin-substantive emollient enables the active component of the rinse-off skin cleansing composition to remain on the skin after washing. A protective film is formed on the skin, which is primarily composed of

the skin emollient and sunscreen. The said emollient also has the requisite properties of stability and required physical properties of the composition.

Typically, the composition comprises more than one of the aforementioned

components. The surfactant may be ionic, amphoteric or non-ionic. Preferably the surfactant(s) is either anionic alone or a combination of anionic with

amphoteric or non-ionic. Examples of skin cleansing compositions include cleansing bars, shower gels, liquid soaps, facial and body washes etc. The UV

agent typically includes UVA and UVB type sunscreens. Preferably, the water-insoluble, skin-substantive emollients comprise 9-70% by weight of the total composition. More preferably they comprise 15-65% by weight of the total composition. Most preferably they comprise 30-55% in a composition of a cleansing bar product and 15-45% in a composition of a liquid product.

Suitable water-insoluble, skin-substantive emollients include materials being selected from the following material classes:-

1) Silicone materials (eg. cyclomethicone, dimethicone, dimethicone copolyol) and their derivatives;

2) C₄ - C_∞ alcohols and their derivatives (eg C₁₂-C₂₀ alcohols and their derivatives);

3) ^ce * C_∞ mono, di and triglycerides and their derivatives;

4) Emollient esters (eg. benzoate esters, straight & branched chain esters, glyceryl esters) and their derivatives;

5) Synthetic and natural oils and waxes (eg mineral oil, squalene. paraffin wax);

⁶) ^c - ^C ₂β ^alkvl glucosides and polyglucosides;

) ^Cιo - ^c∞ ^{Fattv acids}:

8) Lanolin oils and their derivatives;

9) Glucose and sucrose derived materials (eg glucose esters and sucrose esters). Any of the above mentioned materials may include branched alkyl groups, preferably C₄-C₃₀ alkyl groups.

Any of the above mentioned ingredients may also contain other functional groups.

Preferably, the surfactants comprise 9-90% by weight of the total composition. More preferably they comprise 15-80% of the total composition. Most preferably they comprise 20-75% in the composition of a cleansing bar product and 15-45% in a composition of a liquid product.

These surfactants may be selected from the following:-

Non-ionic surfactants e.g. alkylpolyglucosides, and ethoxylated alcohol compounds; anionic surfactants e.g. the salts of isethionates, carboxylates, soaps, sulphates, sulphosuccinates, sulphonates; amphoteric surfactants e.g. betaine and glycinate compounds. Any of these surfactants may also contain other functional groups such as ether or amide groups.

Preferably, the UV screening agent comprise 1-20% UVA and UVB sunscreens by weight of the total composition, most preferably, 3-15% by weight of the total composition.

The sunscreen may be selected from any available sunscreen agent and include; octyl methoxycinnamate, benzophenone-3, octyl salicylate, octyl dimethyl PABA, benzophenone-4, benzophenone-8, DEA methoxy cinnamate, Ethyl dihydroxypropyl PABA, glyceryl PABA, homosalate, menthyl anthranilate, octocrylene, PABA, phenylbenzimidazole sulphononic acid. TEA salicylate, 4- methylbenzylidene camphor, benzophenone-1 , benzophenone-2, benzophenone-6, benzophenone-12, isopropyl dibenzoyl methane, butyl methoxy dibenzoylmethane, etocrylene, PEG-25 PAPA, and octyl triazone.

The water-insoluble, skin-substantive emollients assist in increasing the deposition of UV screening agent on the skin above that which would otherwise be possible without such agents. The incorporation of UV screening agents alone into the currently available surfactant based products such as soap will result in only a very small amount of skin deposition. However, by incorporating water- insoluble skin substantive emollients in the compositions of the invention a greatly increased deposition of UV screening agent takes place. The level of deposition is then such as to become more comparable to many skin care creams and lotions which deliver UV protection as a secondary benefit. The use of such skin substantive emollients does not preclude the possibility that some of the surfactants may also deliver increased skin substantivity. In particular, some of

the surfactants used may have enhanced emollient properties as a result of long carbon chains. These longer chains make the compound more hydrophobic and thus may contribute to a small amount to skin substantivity.

The skin substantive emollients may help the formation of an emulsion during use which includes the soils previously held on the skin. The substantive

emollients are generally hydrophobic or contain a positive charge and are thus substantive to the skin. They may also act in other ways as emulsifiers, thickeners, or as improvers to bar hardness.

The hydrophobicity of the skin substantive emollient lends them a resistance to rinse off. These materials then help to form a coating which traps some of the UV screening agent on the skin.

The primary function of the surfactant system is to cleanse the skin. The ratio of surfactant to skin substantive emollient is the key to enhancing UV deposition but choice of surfactant or surfactant blend will also contribute. For instance, the use of C^ 8 mole ethoxylated alcohol would be preferred to a C₁₂.₁₄ 50 mole ethoxylated alcohol as the water solubility (hydrophilicity) is lower in the former surfactant than the latter. Nevertheless, the detergency of the former surfactant is still acceptable. The composition may also include other minor ingredients common to other rinse-off skin cleansing compositions.

The invention will now be further illustrated by way of the following examples. EXAMPLE 1

Rinse-off skin cleansing compositions were formulated as follows:-

Formulation A

Component % bv weight

APG (C12-14) 18.0

APG (C16-18) 11.0

Stearic acid 6.0

Cetyl alcohol 26.0

Paraffin wax 11.0

Glycerine 7.0

Octyl Methoxycinnamate (OMC) 7.0

Benzophenone-3 3.0

Others (minor ingredients) qs 100

Formulation B

Component % bv weight

Sodium cocoylisethionate (SCI) 54.0

Soap base 12.0

Stearic acid 15.5

Paraffin wax 3.0

Octyl Methoxycinnamate (OMC) 7.0

Benzophenone-3 3.0

Others (minor ingredients) qs 100

Formulation A was made as follows:-

The paraffin wax and stearic acid were melted at around 80° C. The APG (C₁₂.₁₄) is normally supplied as 50% active and hence this is added at this

temperature, the temperature raised to above 100°C and maintained at this such as to remove the majority of the moisture. The temperature is then lowered to

80° C and the APG (C₁₆.₁₈) added as a blend with the cetyl alcohol. Once this is melted, the heating is switched off and the glycerine, octyl methoxycinnamate, and benzophenone-3 added along with any other minor ingredients (e.g. sequestrant, salt, titanium dioxide). The molten mixture is then poured into moulds and allowed

to set. Alternatively it may be poured into trays, allowed to set, and then cut into blocks and stamped.

Formulation B was made as follows:-

To a heated mixer vessel add stearic acid and paraffin wax. These are heated to 100°C to be melted. The soap is added and mixed to ensure complete

mixing and dispersion. The sodium cocoyl isethionate is then added again with thorough mixing. Finally, the sunscreen agents and other minor ingredients are

added (with the temperature reduced to 60° C). The mix is then discharged to a mill then plodded, and finally stamped. Alternatively the mix may be poured into

moulds.

Example 2

Rinse-off cleansing compositions were formulated as follows:-

Formulation C Formulation D

% bv weiαht % bv weioht

Soap base 13.5 13.5

SCI 50.2 40.2

Steric acid 16.0 16.0

Paraffin wax 3.0 3.0

Octyle methoxycinnamate 8.0 8.0

Benzophenone-3 3.0 3.0

Others (minor ingredients) qs 100 qs 100

Cetyl alcohol 0.0 10.0

The above formulations were processed into bars using the method as that used for formulation A. (The method used for formulation B could also have been

used). Example 3

Formulations E and F were processed into bar using the same manufacturing method as used for formulation A.

Formulation (% by weight)

Component E F

Soap base 23.8 19.6

Steric acid 20.0 17.8

Cetyl alcohol 22.0 19.6

APG (C 10/12) 9.0 0.0

Paraffin wax 5.0 0.6

Glycerine 1.0 1.8

C 13/15 7EO ethoxylated alcohol 0.0 2.7

Polyethylene glycol 1000 0.0 25.0

Octyl methoxycinnamate 7.3 7.3

Buty Imeth oxydiben zoy Imetha ne 2.7 2.7

Other (minor ingredients) qs 100 qs 100

Tests were carried out in order to evaluate the amount of UV screening agent deposited onto the skin in various products. The products defined by the various formulation were compared with an ordinary soap which was mixed with the same amounts of UV agent as the compositions but without skin substantive emollients. The tests were carried out as follows:-

Forearm Wash Test

An area of the skin on one forearm (area A) marked out (20cm by 5cm) is washed with the test product for 15 seconds. The other forearm (area B) may then be washed with another product, water, or have a topical composition applied such as to give a comparison. An area of forearm skin (area C), so far untreated, is also kept free of any product.

Each of the three areas is then swabbed using cotton-wool soaked in acetone, 10 swabs are used. This will remove the top layers of the stratum corneum and any materials within or on this layer. The swabs are placed in a beaker which has been weighed. The swabs are then washed through with acetone and the solvent evaporated. The beaker is then reweighed to give the weight of material removed from the forearm.

In parallel to the above procedure the E? values of the products being tested is determined.

An absorbance spectrum is run of the skin control (area C) and this is then used as the baseline for the other materials being tested (i.e. to remove interference from skin itself). Spectra are then ran of the materials from the other two areas. Carrying out the test in this way also ensures that what is measured is the level of UV radiation absorbed over and above that absorbed by the skin itself

The percentage of active UV agent in the material removed from the skin can then be determined using the following equation :-

% ACTIVE = ABSORBANCE X DILUTION FACTOR E X SAMPLE WT (g)

From this the weight of material on the skin is determined. The results of the test for formulations A and B were as follows:-

Coiτipositions Ratio UV agent : UV agent deposited de^posited from standard

Soap & UV agents 1

Formulation A 4.7

Formulation B 2.3

The result clearly shows that UV screening agents alone added to standard, surfactant based, cleansing compositions such as soap gave only a small amount of deposition. However, by incorporating materials into the formulations which are more substantive to the skin (hydrophobic emollients such as cetyl alcohol) the level of deposition is markedly increased such as to be comparable to (albeit less than) the protection given by many skin care creams and lotions delivering protection against UV radiation as a secondary benefit. Indeed the level of UVA protection (and the level remaining on the skin over time) is greater than that from many of these products

Formulations C and D of example 2 were also tested using the forearm wash test, and the level of sunscreen material deposited on the skin was measured. The quantity of sunscreen agent on the skin was 50% more from formulation D, i.e. the incorporation of 10% cetyl alcohol (emollient) into Formulation C gives a significant increase in the level of protection given in the skin. A further test was carried out as follows:-

Sellotaoe Stripping Test

An area of the skin one forearm (area A) is marked out (20cm by 5cm). A strip of sellotape approx 5cm in length is then applied to the skin (outside area A) and placed across a holder for use in a UV spectrophotometer. Four more strips are then taken, each one being applied to the same area on the forearm and then placed on top of the previous trip on the holder. The holder is then placed in the spectrophotometer and the resulting UV spectrum used as a baseline for the tests.

The area A of forearm skin is then washed with the test product, rinsed, dried and the above sellotape stripping procedure repeated and a UV spectrum obtained. An area B of skin (20cm by 5cm) on the other forearm is then treated with the second product (rinse off product or if a typical product). The stripping procedure is then obtained to obtain the second spectrum.

The efficiency of absorption of UV radiation can then be compared either by comparison of the whole spectra or by comparing the quantity of UV radiation absorbed at specific wavelengths (290-400nm). The latter procedure is preferred. Sufficient replicates for each product are carried out to ensure consistent results are obtained. The sellotape stripping test was useful to compare the two formulations E and F. The average level of absorbance at four specific wavelengths was then measured from the spectra. The results are given below:-

WAVELENGTH (nm) ABSORBANCE

Formulation E Formulation F

290 0.62 0.89 310 0.85 1.17 340 0.59 0.83 360 0.54 0.77

Formulation E in itself had represented an improvement in the level of material deposited over formulations A-D (using the sellotape stripping test). The level of emollient in the formulation E is higher than in formulation F. However, rate of wear tests on the bars demonstrated that formulation E was actually difficult to use (wearing down a bit slower than F). The level of protection delivered from formulation F was the highest of the formulations and was achieved by the use of water- insoluble emollients at levels (and in a suitable formulation i.e. the use of PEG 1000 for easier use) such that the properties have been

optimised.

Example 4

Formulation F was compared to a commercial skin care product X which claimed delivery of UV protection as a secondary benefit to the primary moisturisation properties of the cream. The purpose of the test was to look at the UVA protection properties of the products. The method used was the sellotape stripping test. The results for absorbance at 340 and 360 mm are given below.

WAVELENGTH (nm) ABSORBANCE

Formulation F Product X

340 0.49 0.46 360 0.46 0.37

Although not measured the spectra indicated that the tail-off of absorption moving to higher wavelength (380nm) continued for product X whilst formulation F retained the same level (a factor of using butyl methoxydibenzoyl methane). Time studies showed that over time the UVA protection from product X dwindled much more rapidly than that from formulation F. These results highlighted the particular benefits of this technology for all-year round UVA protection.

The invention is not restricted to the above described embodiments and many variations and modifications can be made.

Claims

1. A rinse-off skin cleansing composition comprising at least one UV-screening agent, at least one surfactant and at least one water-insoluble, skin-substantive emollient.

2. A rinse-off skin cleansing composition according to Claim 1 , wherein the said surfactant comprises 9-90% by weight of the total composition.

3. A rinse-off skin cleansing composition according to any preceding claim, wherein the said surfactant comprises 15-80% of the total composition.

4. A rinse-off skin cleansing composition according to any preceding claim, wherein the said surfactant comprises 20-75% in the composition of a cleansing bar product.

5. A rinse-off skin cleansing composition according to any one of claims 1-13, wherein the said surfactant comprises 15-45% in the composition of a liquid product.

6. A rinse-off skin cleansing composition according to any preceding claim, wherein the said surfactant is ionic, amphoteric or non-ionic.

7. A rinse-off skin cleansing composition according to claim 6, wherein the said surfactant is anionic.

8. A rinse-off skin cleansing composition according to claim 6, wherein the said surfactant is a combination of anionic with amphoteric or non-ionic.

9. A rinse-off skin cleansing composition according to claim 6. wherein the said anionic surfactant is a salt of at least one of the following, isethionates, carboxylates, soaps, sulphates, sulphosuccinates and sulphonates.

10. A rinse-off skin cleansing composition according to claim 6, wherein the said amphoteric surfactant is at least one of betaine and glycinate compounds.

11. A rinse-off skin cleansing composition according to claim 6, wherein the said non-ionic surfactants comprise at least one of alkylpolyglucoside and ethoxylated alcohol compounds.

12. A rinse-off skin cleansing composition according to claims 9, 10 or 11 , wherein each surfactant also contains at least one of ether and amide functional groups.

13. A rinse-off skin cleansing composition according to claim 1, wherein the water soluble skin substantive emollient comprises at least one or more of the following:- a) Silicone materials b) C₄-C_∞ alcohols and derivatives c) C₆-C₃₀ mono, di and triglycerides and derivatives d) Emollient esters and their derivatives e) Synthetic and natural oils and waxes f) C 'Cze alkyl glucosides and polyglucosides 9) C₁₀-C₃o fatty acids h) Lanolin oils and derivatives i) Glucose and sucrose derived materials.

14. A rinse-off skin cleansing composition according to claim 13, wherein the water-insoluble, skin-substantive emollients comprise 9-70% by weight of the total composition.

15. A rinse-off skin cleansing composition according to claim 13, wherein the water-insoluble skin-substantive emollients comprise 15-65% by weight of the total composition.

16. A rinse-off skin cleansing composition according to claim 13, wherein the water-insoluble skin-substantive emollients comprise 15-45% in a composition of a liquid product.

17. A rinse-off skin cleansing composition according to claim 13, wherein the water-insoluble skin-substantive emollients comprise 30-55% in a composition of a cleansing bar product.

18. A rinse-off skin cleansing composition according to any one of claims 13-17, wherein said silicone materials comprise at least one or more of cyclomethicone, dimethicone, dimethicone copolyols and their derivatives.

19. A rinse-off skin cleansing composition according to any one of claims 13-18. wherein said C₄-C₃₀ alcohol comprises C₁₂-C₂₀ alcohol and their derivatives.

20. A rinse-off skin cleansing composition according to any one of claims 13-19, wherein said emollient esters comprise at least one or more of benzoate esters, straight and branched chain esters and their derivatives.

21. A rinse-off skin cleansing composition according to any one of claims 13-20, wherein said synthetic and natural oils and waxes comprise at least one or more of mineral oil, squalene and paraffin wax.

22. A rinse-off skin cleansing composition according to any one of claims 13-21. wherein said glucose and sucrose derived materials comprise glucose esters and sucrose esters.

23. A rinse-off skin cleansing composition according to any one of claims 13-22. wherein the said emollient further includes one or more branched alkyl groups, said groups consisting of C₄-C_∞ alkyl groups.

24. A rinse-off skin cleansing composition according to claim 1, wherein the UV screening agent comprises one or more of octyl methoxycinnamate, benzophenone-3, octyl salicylate, octyl dimethyl PABA, benzophenone-4, benzophenone-8, DEA methoxy cinnamate, Ethyl dihydroxypropyl PABA, glyceryl PABA, homosalate, menthyl anthranilate, octocrylene, PABA, phenylbenzimidazole sulphononic acid, TEA salicylate, 4-methylbenzylidene camphor, benzophenone-1. benzophenone-2, benzophenone-6, benzophenone-12, isopropyl dibenzoylmethane, butyl methoxy dibenzoylmethane, etocrylene, PEG-25 PAPA, and octyl triazone.

25. A rinse-off skin cleansing composition according to claim 25, wherein the UV screening agent comprises 1-20% UVA and UVB sunscreens by weight of the total composition.

26. A rinse-off skin cleansing composition according to claim 25, wherein the UV screening agent comprises 3-15% by weight of the total composition.

27. A rinse-off skin cleansing composition substantially as hereinbefore described with reference to the examples.