A liquid skin cleansing composition for enhanced deposition of particles

Abstract

The present invention relates to delivering instant brightening benefit to skin through a cleansing composition. The benefit is delivered through enhanced deposition of uncoated titanium dioxide through use of selected type of emollient having a low log Kow value.

Description

[0001] A LIQUID SKIN CLEANSING COMPOSITION

[0002] FOR ENHANCED DEPOSITION OF PARTICLES

[0003] Field of the Invention

[0004] The present invention relates to delivering instant brightening benefits to skin through a cleansing composition. This is ensured by enhanced deposition of uncoated titanium dioxide through use of selected type of emollient.

[0005] Background of the Invention

[0006] People’s perception of beauty varies across cultures as well as from person to person. Most people agree that a good and balanced lifestyle involving consumption of healthy food and maintaining the body through regular exercise and outdoor activities ensures an attractive and beautiful appearance of the body. For temporary enhancement of healthy appearance, many people resort to cosmetic products which are generally used on the external surfaces of the body like on hair and on skin, especially on the face. These may be of the leave-on type which are applied and left thereon on such surfaces till the next shower, bath or washing. Another type of beauty product is that of the wash-off type which are generally cleaning products like facewash or bodywash compositions and shampoos. Usually, the wash off products cleanse the skin or hair free of dirt and oil and make the skin and hair dry and clear. The consumer thereafter generally applies a leave-on composition to get the cosmetic benefits.

[0007] A bright and even skin tone on the face is much desired by consumers. This can be achieved by incorporating whitening powders like talc, titanium dioxide, mica, or zinc oxide in leave-on cosmetic products. Such brightness actives could be incorporated in to wash-off products too. However, they do not deliver the desired benefit as the primary purpose of wash-off products is to remove dirt and oils from the skin surface and together with that, the actives in the wash-off products are also highly likely to get washed away. Thus, enhanced deposition of such brightening actives through wash-off products is a difficult problem to solve.

[0008] The present applicants have used titanium dioxide in skin cleansing formulations to get instant brightening effect. One such technology is published as US7446081 where deposition aids have been used for delivery of brightening benefits. The present inventors realized that the deposition aids used therein are effective only when coated titanium dioxide is used and is not effective when uncoated titanium dioxide has to be deposited, The present inventors searched for a solution to this problem but could not find any clue in the published literature in this area. With their in depth knowledge of interfacial science and through extensive experimentation they hit upon a class of emollients having low log Kowvalue (octanol water partition coefficient) which when incorporated in wash-off compositions, was found to be effective as a deposition aid for uncoated titanium dioxide.

[0009] It is thus an object of the present invention to provide for a wash-off composition that is effective in delivering enhanced deposition of uncoated titanium dioxide, thereby ensuring that the consumer gets instant brightening benefits.

[0010] Summary of the Invention

[0011] The first aspect of the present invention provides for a liquid skin cleansing composition for enhanced deposition of uncoated titanium dioxide particles on to skin comprising

[0012] (i) 5 to 45 wt% a surfactant;

[0013] (ii) 0.1 to 5 wt% uncoated titanium dioxide having an average particle size in the range of 10 to 200 nm;

[0014] (iii) 0.5 to 10 wt% of an emollient having a log Kow value in the range of 1 .5 to 4; and

[0015] (iv) 10 to 75 wt% water.

[0016] Another aspect of the present invention relates to a method of delivering enhanced deposition of uncoated titanium dioxide on to a skin surface comprising the steps of applying the composition of the first aspect preferably diluted with water on to the desired skin surface followed by rinsing the surface with water.

[0017] Detailed Description of the Invention

[0018] These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. The word "comprising" is intended to mean "including" but not necessarily "consisting of" or "composed of." In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight / weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description and claims indicating amounts of material or conditions of reaction, physical properties of materials and / or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated.

[0019] The skin cleansing composition of the invention is meant for topical use and may also be called a personal care composition or a cosmetic composition. By a “personal care composition” as used herein, is meant to include a composition for topical application i.e external surfaces of the skin and / or hair of humans. Such a composition as per the present invention is generally of the wash off type, and includes any product applied to a human body for improving appearance, cleansing, odour control or general aesthetics. By the wash-off type is meant that the composition is generally diluted with water and applied on the topical surface e.g. the face and then rinsed off with copious amounts of water after a few minutes. Cleansing composition of the present invention is in the liquid form. It may have a viscosity in the range of 12,000 to 120,000 cps. The composition is preferably a Newtonian fluid. The viscosity of the product is measured using a Brookfield Viscometer with RV 6 spindle @ 20 rpm(60sec) at 25 °C.

[0020] "Skin" as used herein is meant to include skin on the face and parts of the body (e.g. neck, arms, hands, legs and scalp) which are the exposed parts where one generally wishes to have an instant bright benefit. Such a composition may also be used for cleansing the underarm region.

[0021] The composition of the invention relates to a liquid skin cleansing composition for enhanced deposition of uncoated titanium dioxide. Titanium dioxide may be used in cosmetic compositions for various purposes like use as a white pigment, sun-screening (UV-filtering) ability, for providing instant skin brightening properties, as a thickener etc. Titanium dioxide comes in various naturally occurring crystallographic forms like anatase, brookite and rutile, of which anatase and rutile are more common. The titanium dioxide for use in the present invention is preferably of the rutile form. Titanium dioxide is also available over a very wide particle size range all the way from 10 nm of primary particle size to micrometer size ranges. Titanium dioxide is sold in uncoated form or may be coated with very many different coating materials by the suppliers. Commonly used coating materials include inorganic materials like aluminium hydroxide and hydrated silica. Organic materials for coating include fatty acids like stearic acid and isostearic acid; silicone oils like dimethicone and hydrogen dimethicone. Certain hydrocarbons and silicone resins are also used to coat titanium dioxide particles. Combinations of the above coating materials may also be used. Depending on the coating material or combinations of coating materials used, the titanium dioxide particles deliver tailored properties. As per the present invention the titanium dioxide to be used is of the un-coated type. By uncoated is meant that at most 10%, more preferably at most 5% and most preferably no part of the surface of the titanium dioxide is coated with any other material. Uncoated titanium dioxide for use in the present invention is available from many suppliers like Tayca, Kobo, Evonik and Konark. Suitable uncoated titanium dioxide for use in the present invention are sold as MT-700B (from Tayca), *TA-100 (from KOBO), AEROXIDE® TiO2 NKT 90 (from Evonik). Uncoated titanium dioxide as per the present invention has an average particle size in the range of 10 to 200 nm preferably in the range of 30 to 150 nm, further more preferably in the range of 50 to 120 nm, preferably 60 to 110, preferably 75 to 100, preferably 80 to 95. It has been observed that the improved deposition of the particles is achieved only when uncoated titanium dioxide is used and not when the titanium dioxide is coated. The uncoated titanium dioxide is included in the composition in 0.1 to 5 wt% preferably from 0.2 to 4 wt%.

[0022] The composition of the invention comprises an emollient having a log Kowvalue in the range of 1.5 to 4. Log Kow refers to the octanol-water partition coefficient. A compound’s octanol-water partition coefficient (Kow) is a measure of its hydrophilicity / lipophilicity. Kow is defined as the equilibrium ratio of the compound’s concentrations in a two-phase system of 1- octanol and water. The Kow values of organic compounds span many orders of magnitude, and this is one reason why often log Kow, also called log P is listed rather than Kow itself. Log Kow values are typically between -3 (very hydrophilic) and +10 (extremely hydrophobic). Suitable emollients for use in the present invention which satisfy the above condition are PPG-14 butyl ether, PPG-33-Butyl Ether, and PPG-40 Butyl Ether. Preferably the emollient is PPG-14 butyl ether. This is sold under the trade name of Tegosoft PBE from Evonik. The emollient is included in 0.5 to 10%, preferably 0.5 to 8%, preferably 1 to 6%, preferably 2 to 5 %, preferably 3 to 4% by weight of the composition.

[0023] The composition of the invention comprises a surfactant which is included in 5 to 45% by weight of the composition. The surfactant may be selected from one or more of an anionic, non-ionic and amphoteric surfactant. Preferably the surfactant is selected from one or both of an anionic and an amphoteric surfactant, most preferably a combination of both.

[0024] The anionic surfactant is preferably selected from an alkyl ether sulphate, primary alkyl sulphate, secondary alkyl sulphonates, alkyl benzene sulphonates, or ethoxylated alkyl sulphates. Especially preferred are sodium lauryl ether sulphate (SLES). The SLES for use in the present invention preferably has 1 to 3 Ethoxylate (EG) groups. SLES is preferably included in 3 to 14%, preferably 6 to 12% by dry weight basis of the composition. SLES is generally available as a 70% solution in water. The other surfactant which may be included in the present invention is cocoamide monoethanol amine (CMEA). CMEA is preferably included in 1 to 3% by weight of the composition. One preferred aspect of the liquid cleansing composition of the invention relates to the surfactant which comprises a mixture of sodium lauryl ether sulphate (SLES) and coco amide monoethanol amine (CMEA). Alkyl polyglucoside may also be present in the composition, preferably those having a carbon chain length between C6and Ci6.

[0025] Another useful surfactant for inclusion in the liquid cleansing composition of the invention is an amphoteric surfactant preferably a betaine surfactant, more preferably an alkyl amidopropyl betaine surfactant for example cocam idopropyl betaine (CAPB). CAPB is especially preferred for inclusion in the composition. CAPB is generally available as a 30% solution in water. In a preferred embodiment, the composition comprises from 0.1 to 5%, preferably from 0.5 to 4%, more preferably from 1 to 3% on dry weight basis of the amphoteric surfactant.

[0026] Surfactants of the non-ionic class for inclusion in the liquid cleansing composition of the invention are preferably of the polyoxyethylene sorbitan alkyl esters class (sold as Tween surfactants)), fatty alcohol ethoxylates (sold as Brij surfactants), alkyl phenol ethoxylates (sold as Triton surfactants), fatty acid ethoxylates (sold as Myrj surfactants), and Alkyl poly glucosides (sold as Plantacare surfactants). Tween surfactant is especially preferred for inclusion in the composition of the invention. There are various Tween type surfactants available of which Tween-20 is especially preferred. When included, Tween 20 is included in 0.1 to 1.0% by weight of the composition.

[0027] One preferred aspect of the present invention relates to inclusion of synthetic surfactants as listed above to form the total amount of surfactants in the composition. In such a case, the total amount of synthetic surfactant included in the composition of the invention is preferably from 5 to 15%, more preferably 7 to 15% by weight of the composition.

[0028] It is also possible that soap which is an anionic surfactant and is generally salt of a fatty acid, may be used as a part of the surfactant. The soap is generally prepared insitu by including certain desired amount of fatty acid and including therein an alkali. The soap for preparing the cleansing composition of the invention is preferably a C8-C24 soap, more preferably C10-C20 soap and most preferably C12-C18 soap. The cation of the soap can be alkali metal, alkaline earth metal or ammonium. Preferably, the cation of the soap is selected from sodium, potassium or ammonium. More preferably the cation of the soap is sodium or potassium. Fatty acids derived from other suitable oils / fats such as groundnut, soybean, tallow, palm, palm kernel, etc. may also be used in desired proportions. Alternately, mixture of fatty acids in desired amounts may be included. Suitable fatty acids for inclusion to form the soap are one or more of stearic acid, hydroxystearic acid, palmitic acid, myristic acid, and lauric acid. An especially preferred aspect relates to inclusion of two or more or even all of the fatty acid mentioned above. The total amount of fatty acid included could range from 20 to 50 wt% preferably from 25 to 40 wt%. Most suitable alkali for inclusion is sodium hydroxide or potassium hydroxide, more preferably potassium hydroxide. The alkali is preferably included in 4 to 10%, preferably 5 to 9% by weight of the composition. When the composition comprises both, a soap and a synthetic surfactant, the system is known as a soap-syndet system. When the composition comprises a soap-syndet system the synthetic surfactant is preferably included in 1 to 5% by weight of the composition. In such a system the synthetic surfactant is preferably an alkyl glucoside.

[0029] The composition of the invention may include a humectant which is generally a polyhydric alcohol. Preferably the humectant is at least one of propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1 ,3-butylene glycol, isoprene glycol, 1 ,3 propanediol, pentylene glycol, hexylene glycol, 1 ,2,6-hexanetriol, glycerol, ethoxylated glycerol, and propoxylated glycerol. Preferred humectants are selected from one or more of glycerine, and propylene glycol, pentylene glycol, hexylene glycol, and sorbitol. Most preferred humectants are one or both of glycerol and propylene glycol. In compositions comprising predominantly synthetic surfactants, the humectant is included in lower amounts in the range of 1 to 10 wt% preferably 2 to 8 wt%. In soap-syndet systems, it is preferred that the amount of humectant is from 10 to 40 wt% more preferably from 15 to 35% by weight of the composition. Thus, in general, humectants may be included in from 1 to 40 wt% of the composition of the invention.

[0030] The composition of the invention preferably comprises a thickener which may be a crosslinked acrylate copolymer. It is liquid, acrylic rheology modifier designed to suspend, stabilize, and thicken surfactant-based personal cleansing products and soap-based cleansing systems. A particularly preferred co-polymer for use in the composition of the invention is Carbopol Aqua SF- 1 acrylic emulsion polymer from Lubrizol. It is especially useful in formulations containing high levels of surfactants. It is an alkali swellable acrylic emulsion polymer. The thickener is included in 0.1 to 10%, preferably 0.5 to 9% by weight of the composition. A thickener is generally included mostly when the composition comprises predominantly synthetic surfactants to the exclusion of soap. The composition of the invention has a pH in the range of 5.5 to 10. pH of the composition is measured using a calibrated pH meter at 25 °C. The composition comprises water in amount from 10 to 75 wt%, more preferably from 12 to 70 wt%. When the surfactant system comprises synthetic surfactant alone, it may comprise water from 55 to 75 wt%. Soap syndet system generally comprise much lesser amount of water, generally in the range of from 10 to 25 wt%.

[0031] The liquid cleansing composition of the invention may include optional ingredients such as skin care actives like vitamins, sensory actives like cooling agents, electrolytes, perfumes, pigments, preservatives, sunscreens, buffering agents or pH modifiers, and thickening agents.

[0032] The second aspect of the present invention relates to a method of delivering enhanced deposition of uncoated titanium dioxide on to a skin surface comprising the steps of applying the composition of the first aspect preferably diluted with water on to the desired skin surface followed by rinsing the surface with water. The method is preferably for cosmetic or non-therapeutic purposes.

[0033] The invention will now be illustrated with the help of the following non-limiting examples.

[0034] Examples

[0035] Compositions as shown in Table -1 below were prepared.

[0036] Table -1 The compositions A, B and 1 were tested for increase in AL using the protocol as given below: On day 1 , Episkin RHPE (skin type: VI) tissues were transferred to a fresh 24-well plate containing growth media. Nylon mesh was prepared for active application, and formulations were diluted in ultra-pure water and then applied over the mesh. Mesh with formulation was placed on top of the tissue for 30 sec. After 30seconds, the mesh was removed and tissues were washed with ultra- pure water and incubated at 37°C, 5% CO2 incubator for 48 h. The tissues were reapplied / re- dosed with formulations on day 3 and day 5. On day 7 tissues were air-dried completely and progressed for L* measurements using Minolta Spectrophotometer connected to the software. Physical measurement of reflected light, at specific wavelengths (400-700 nm) which correspond to the spectrum of visible light and colorimetric values were evaluated and expressed in terms of: L*(luminance) which gives the relative brightness on a scale from 0 (black) to 100 (white).

[0037] The AL value obtained is summarized in the table -2 below

[0038] Table - 2

[0039] The data in Table -2 above shows that the composition as per the invention (Example -1) is significantly superior in delivering instant brightness over two similar compositions out side the invention (Example -A where a coated titanium dioxide was used and Example - B where no titanium dioxide was used).

[0040] Deposition of titanium dioxide for all of the samples A-C and 1 was determined using the below procedure:

[0041] The tissues for all of the above samples were prepared for the above measurement similar to preparing for L* measurement i.e.

[0042] On day 1 , Episkin RHPE (skin type: VI) tissues were transferred to a fresh 24-well plate containing growth media. Nylon mesh was prepared for active application, and formulations were diluted in ultra-pure water and then applied over the mesh. Mesh with formulation was placed on top of the tissue for 30 sec. After 30 seconds, the mesh was removed and tissues were washed with ultra- pure water and incubated at 37°C, 5% CO2 incubator for 48 h. The tissues were reapplied / re- dosed with formulations on day 3 and day 5. On day 7 tissues were air-dried completely. The tissues were then dissolved in Solvable™ ( a tissue solubilizer from Perkin Elmer) on a dry bath at 60°C for 12-16 h with gentle shaking. The solution was filtered through 0.22 m mesh. Three repeat samples were pooled into one for titanium dioxide deposition studies using ICP MS.

[0043] The data is summarized in Table -3 below:

[0044] Table - 3

[0045] The data in the table - 3 above indicates that in Example A and B (both outside the invention) the amount of titanium dioxide deposited in less than 0.2 ppm which means that it is below the detection limit of the instrument. Further, use of uncoated titanium dioxide along with the select emollient Tegosoft PBE (Example -1) delivers vastly superior deposition as compared to a combination of coated titanium dioxide and Tegosoft PBE (Example - C).

[0046] Examples D, 2: Compositions with soap-syndet system

[0047] Compositions as shown in Table - 4 below were prepared:

[0048] Table - 4

[0049] The above compositions were tested for increase in AL using the protocol as given for table -1 :

[0050] The AL value obtained is summarized in the table -4 below:

[0051] Table - 4 The data in Table -2 above shows that the composition as per the invention (Example -2) is significantly superior in delivering instant brightness as compared to a composition outside the invention (Example -D).

Claims

Claims1. A liquid skin cleansing composition for enhanced deposition of uncoated titanium dioxide particles on to skin comprising(i) 5 to 45 wt% a surfactant;(ii) 0.1 to 5 wt% uncoated titanium dioxide having an average particle size in the range of 10 to 200 nm;(iii) 0.5 to 10 wt% of an emollient having a log Kowvalue in the range of 1.5 to 4; and(iv) 10 to 75 wt% water.

2. A composition as claimed in claim 1 wherein the emollient is selected from one or more of PPG-14 butyl ether, PPG-33-Butyl Ether, and PPG-40 Butyl Ether.

3. A composition as claimed in claim 1 or 2 wherein the surfactant is selected from one or more of an anionic, non-ionic, and amphoteric surfactant.

4. A composition as claimed in claim 3 wherein the anionic surfactant is a synthetic anionic surfactant or soap.

5. A composition as claimed in claim 4 wherein the synthetic anionic surfactant is selected from one or both of sodium lauryl ether sulphate (SLES) and cocoamide monoethanol amine (CMEA).

6. A composition as claimed in claim 5 comprising 5 to 20 wt% synthetic anionic surfactant.

7. A composition as claimed in any one of the preceding claims 4 to 6 comprising C12 to C18 fatty acid soap.

8. A composition as claimed in any one of the preceding claims 4 to 7 comprising 20 to 50 wt% soap.

9. A composition as claimed in any one of the preceding claims 3 to 8 wherein the amphoteric surfactant is alkyl amido propyl betaine.

10. A composition as claimed in claim 9 comprising 0.1 to 5 wt% alkyl amido propyl betaine.

11. A composition as claimed in any one of the preceding claims comprising a humectant preferably selected from one or both of glycerol and propylene glycol.

12. A composition as claimed in claim 11 comprising 1 to 40 wt% humectant.

13. A method of delivering enhanced deposition of uncoated titanium dioxide on to a skin surface comprising the steps of applying the composition as claimed in any one of the preceding claims preferably diluted with water on to the desired skin surface followed by rinsing the surface with water.

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