AU702476B2 - Skin cleansing - UV screening composition - Google Patents

Description

1 SKIN CLEANSING UV SCREENING COMPOSITION This invention relates to skin cleansing UV screening compositions in the form of bars.

The direct exposure of the body to the sun's UV rays leads in the sort 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.

o* Various lotions, moisturisers 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 4* "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.

2 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 Sskin surface after rinsing. The disadvantage of this method is that it requires very regular application of the product to maintain the residual go 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 disadvantage 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.

'C i n i This technology relates to liquids and stable emulsions whereas the present invention is concerned with 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 4 efficient resistance to rub-off of the sunscreen agent by forming a waterresistant 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 0 0. skin cleansing bar comprising at least one UV-screening agent, at least one surfactant and from 15 to 70% by weight of the total composition of 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 the above-mentioned amount of water-insoiuble skinsubstantive 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.

S Preferably, the water insoluble, skin-substantive emollients comprise from 30 to 55% by weight of the total composition.

Suitable water-insoluble, skin-substantive emollients include materials which are selected from the following material classes:- 1) Silicone materials cyclomethicone, dimethicone, dimethicone copolyol) and their derivatives: 2) C, C3o alcohols and their derivatives (eg C,,-C 20 alcohols and their derivatives); 3) C C, 3 mono, di and triglycerides and their derivatives; 4) Emollient esters (eg. benzoate esters, straight branched chain esters, glyceryl esters) and their derivatives; Synthetic and natural oils and waxes (eg mineral oil, squalene, paraffin wax); 6 6) C 14

C

26 alkyl glucosides and polyglucosides; 7) Co C3o Fatty 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 C 4 alkyl groups.

C

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 the cleansing bar.

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 6a 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 6 o 4 WO 96/14053 PCrIGB95/02559 7 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, 4methylbenzylidene 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 waterinsoluble 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 WO 96/14053 PCT/GB95/02559 8 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 9 11 8 mole ethoxylated alcohol would be preferred to a C1214 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.

WO 96/14053 PCTIGB95/02559 EXAMPLE 1 Rinse-off skin cleansing compositions were formulated as follows:- Formulation A Component by weight APG (C12-14) 18.0 APG (C16-18) 11.0 Stearic acid Cetyl alcohol 26.0 Paraffin wax 11.0 Glycerine Octyl Methoxycinnamate (OMC) Benzophenone-3 Others (minor ingredients) qs 100 Formulation B Component Sodium cocoylisethionate (SCI) Soap base Stearic acid Paraffin wax Octyl Methoxycinnamate (OMC) Benzophenone-3 Others (minor ingredients) by weight 54.0 12.0 15.5 qs 100 Formulation A was made as follows:- The paraffin wax and stearic acid were melted at around 80 C. The APG (C1214) 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 and the APG 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 sequestrant, WO 96 14053 PCT/GB95/02559 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 1000C 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 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

by weight by weight Soap base 13.5 13.5 SCI 50.2 40.2 Steric acid 16.0 16.0 Paraffin wax 3.0 Octyle methoxycinnamate 8.0 Benzophenone-3 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).

WO 96/14053 PCT/GB95/02559 11 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 (C10/12) 9.0 0.0 Paraffin wax 5.0 0.6 Glycerine 1.0 1.8 C13/15 7EO ethoxylated alcohol 0.0 2.7 Polyethylene glycol 1000 0.0 25.0 Octyl methoxycinnamate 7.3 7.3 Butylmethoxydibenzoylmethane 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 so far untreated, is also kept free of any product.

Each of the three areas is then swabbed using cotton-wool soaked in WO 96/14053 PCT/GB95/02559 12 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 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 El X SAMPLE WT (g) From this the weight of material on the skin is determined.

WO 96/14053 PCT/GB95/02559 13 The results of the test for formulations A and B were as follows:- Compositions Ratio UV agent UV agent deposited deposited 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.

14 A further test was carried out as follows:- Adhesive Tape Strippin Test An area of the skin one forearm (area A) is marked out (20cm by A strip of SELLOTAPE (RTM) approx 5cm in length is then applied to the skin (outside area A) and placed across a holder for use in a UV S* spectrophotometer. Four more strips are then taken, each one being

S

S.applied to the same area on the forearm and then placed on top of the previous strip 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 adhesive tape 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 adhesive tape 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:- 5- .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 adhesive tape 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 The level of protection delivered from formulation F was the highest of the formulations and was achieved by the use of waterinsoluble 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.

1 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 WO 96/14053 PCT/GB95/02559 16 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 (11)

1. A rinse-off skin cleansing bar comprising at least one UV-screening agent, at least one surfactant and from 15 to 70% by weight of the total composition of at least one water-insoluble, skin-substantive emollient.

2. A rinse-off skin cleansing bar as claimed in claim 1, wherein the said surfactant comprises from 9 to 90% by weight of the total composition. oo* wherein the said surfactant comprises from 15 to 80% by weight of the total composition.

4. A rinse-off skin cleansing bar as claimed in any preceding claim, *.1 wherein the said surfactant comprises from 20 to 75% by weight of the total composition. A rinse-off skin cleansing bar as claimed in any preceding claim, wherein the said surfactant is anionic.

6. A rinse-off skin cleansing bar as claimed in any of claims 1 to 4, wherein the said surfactant is a combination of anionic surfactant with amphoteric or non-ionic surfactant.

7. A rinse-off skin cleansing bar as claimed in claim 5 or claim 6, wherein the said anionic surfactant is a salt of at least one of the following: isethionates, carboxylates, soaps, sulphates, sulphosuccinates and sulphonates.

8. A rinse-off skin cleansing bar as claimed in any preceding claim, wherein the water in-soluble skin substantive emollient comprises at least one of the following:- o a) silicone materials a b) C 4 -C 3 o alcohols c) C 6 -C 3 o mono, di and triglycerides d) emollient esters e) synthetic and natural oils and waxes C f) C 1 4 -C 26 alkyl glucosides and polyglucosides g) CIo-C 3 o fatty acids h) lanolin oils i) materials derived from glucose and sucrose.

9. A rinse-off skin cleansing bar as claimed in any preceding claim, wherein the water-insoluble skin-substantive emollients comprise from to 55% by weight of the total composition. A rinse-off skin cleansing bar as claimed in claim 8, wherein said ff 19 silicone materials comprise at least one or more of cyclomethicone, dimethicone, dimethicone copolyols and their derivatives.

11. A rinse-off skin cleansing bar as claimed in claim 8, wherein said C 4 -Cao alcohol comprises C 12 -C 20 alcohol and their derivatives.

12. A rinse-off skin cleansing bar as claimed in claim 8, wherein said emollient esters comprise at least one or more of benzoate esters, straight and branched chain esters and their derivatives. S e° •13. A rinse-off skin cleansing bar as claimed in claim 8, wherein said synthetic and natural oils and waxes comprise at least one or more of

14. A rinse-off skin cleansing bar as claimed in claim 8, wherein said glucose and sucrose derived materials comprise glucose esters and sucrose esters. A rinse-off skin cleansing bar as claimed in claim 8, wherein the said emollient further includes one or more branched alkyl groups, said groups consisting of C4-C o alkyl groups. groups consisting of C 4 -C 30 alkyl groups.

16. A rinse-off skin cleansing bar as claimed in any preceding claim, wherein the UV-screening agent comprises one or more of octyl meth oxycinnamate, 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 suiphononic acid, TEA salicylate, 4-m ethyl ben zylidene camphor, benzophenone-1, benzophenone-2, benzophenone-6, benzophenone-1 2, isopropyl di benzoylmethane, butyl methoxy dibenzoylmethane, etocrylene, PAPA, and-octyl triazone. 17 A is-f0kncensn*a scamdinaypeeigcam wheei th*Vsreigaetcmpie -0 V n susren bywih0ftettlcmoiin *ee 18 is-f kncenigbrascamdi n rc'igcam *e 17. A rinse-off skin cleansing bar ausaiedli any precing claim Sweriein t UVsreening agte coampries12%UA n V sunscerePen bytowegtoyhsoalcmoiin DAISCL0SNCV