A liquid skin cleansing composition

Abstract

The present invention relates to a cleansing composition. Particularly, the present invention relates to a liquid skin cleansing composition that provides desired deposition of benefit agent hydroxystearic acid. This is ensured by including the hydroxystearic acid in a liquid skin cleansing composition with pH from 6.0 to 7.5 comprising synthetic anionic surfactant and in selective low amount of fatty acid (other than hydroxystearic acid).

Description

[0001] A LIQUID SKIN CLEANSING COMPOSITION

[0002] Field of the Invention

[0003] The present invention relates to a cleansing composition. Particularly, the present invention relates to a liquid skin cleansing composition that has a stable high viscosity when an ingredient like hydroxystearic acid is incorporated therein.

[0004] Background of the Invention

[0005] Several liquid cleansing compositions are known in the art that contain one or the other benefit agents. Such benefit agents or actives are often included in a liquid cleansing composition with an intention to deliver a benefit. For example, a moisturizing agent is included in a cleansing compositions e.g. a handwash composition and a bodywash composition, to deliver a moisturizing effect.

[0006] However, the technical effect to be achieved through including an active in a cleansing composition tends to be limited due to a variety of reasons. In general, deposition of an active on to a surface through a cleansing composition is challenging as the cleansing action generally includes a step of removing the composition (washing it off) from the surface, typically within a few seconds to a few minutes after application. Therefore, depositing an active on to a surface under such conditions is very challenging.

[0007] Therefore, need still exists to develop a liquid cleansing composition that delivers the desired functional level deposition of benefit agent.

[0008] WO 2024 / 028132A1 relates to a liquid cleansing composition that provides improved deposition of an active, an octadecanoic acid, when applied to a surface.

[0009] In the present case, the inventors were searching for a solution to the problem of enhancing deposition of benefit agent hydroxystearic acid while ensuring that the composition has a stable high viscosity.

[0010] The present inventors found that functional amount of hydroxystearic acid (HSA) could be deposited on to skin through a liquid skin cleansing composition comprising synthetic anionic surfactant and fatty acids (other than hydroxystearic acid). However, inclusion of higher amounts of HSA in such compositions caused them to thin considerably. The present inventors have solved this problem by ensuring that the fatty acid other than hydroxystearic acid is included in selective amounts to maintain the desired viscosity. The lauric acid component of the fatty acid is especially preferred to be kept in a range for ensuring this effect. It is thus an object of the present invention to deposit desired levels of hydroxy stearic acid on to skin through a liquid skin cleansing composition while ensuring that the composition has a stable high viscosity.

[0011] Summary of the Invention

[0012] The first aspect of the present invention relates to a liquid skin cleansing composition comprising

[0013] (i) 1 to 10 wt% synthetic anionic surfactant;

[0014] (ii) 0.1 to 3 wt% C10 to Cis fatty acid other than hydroxystearic acid; or salt thereof;

[0015] (iii) 0.05 to 1 wt% hydroxystearic acid, a salt or an ester thereof;

[0016] (iv) 80 to 95 wt% water; wherein the pH of the composition is in the range of 6.0 to 7.5; wherein the fatty acid other than hydroxystearic acid comprises 0.15 to 0.5% lauric acid by weight of the composition.

[0017] It is especially preferred that the fatty acid other than hydroxystearic acid is included such that it comprises 0.15 to 0.50% lauric acid or salt thereof, by weight of the composition.

[0018] Detailed Description of the Invention

[0019] Any feature of one aspect of the present invention may be utilized 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. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description 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. Unless specified otherwise, amounts as used herein are expressed in percentage by weight based on total weight of the composition and may be abbreviated as “wt%”. The use of any and all examples or exemplary language e.g. “such as” provided herein is intended merely to better illuminate the invention and does not in any way limit the scope of the invention otherwise claimed. The terms ‘Skin’ as used herein, preferably means to include skin on any part of the body e.g. face, neck, chest, back, arms, underarms, hands, legs, buttocks and scalp. By a skin cleansing composition as per this invention is meant a composition used to clean topical surfaces of the body. This is achieved by applying the composition preferably diluted with water on to the desired skin surface, and then substantially removing the composition from the surface. The composition may be removed by rinsing with copious amount of water or by wiping the surface with a desired wipe.

[0020] The present invention relates to a liquid skin cleansing composition comprising (i) 1 to 10 wt% synthetic anionic surfactant; (ii) 0.1 to 3 wt% C10 to Cis fatty acid other than hydroxystearic acid; or salt thereof; (iii) 0.05 to 1 wt% hydroxystearic acid; (iv) 80 to 95 wt% water; wherein the composition; wherein the pH of the composition is in the range of 6.0 to 7.5

[0021] One class of anionic surfactants for use in the composition of the present invention is selected from alkyl sulfates, alkyl ether sulfates (AES), alpha olefin sulfonates (AOS) and mixtures thereof. More preferably, the anionic surfactant is selected from alkyl sulfates, alkyl ether sulfates and mixtures thereof. Even more preferably, alkyl ether sulfates may be used as the anionic surfactant in the composition. Examples of alkyl sulfates that may be used as anionic surfactant in the composition include sodium lauryl sulfate (SLS), sodium myristyl sulfate; and mixtures thereof.

[0022] Examples of AES that may be used as the anionic surfactants include those of the general formula:

[0023] R1-(OR’)n-O-SO3- M+, wherein: R1 is saturated or unsaturated C8-C16, preferably C12-C14 alkyl chain; preferably, R1 is a saturated C8-C16, more preferably a saturated C12-C14 alkyl chain;

[0024] R’ is ethylene; n is from 1 to 18; preferably from 1 to 15, more preferably from 1 to 10 and even more preferably from 1 to 5,

[0025] M+ is a suitable cation which provides charge neutrality, preferably sodium, calcium, potassium, or magnesium, more preferably a sodium cation.

[0026] Examples of AES that may be used as the anionic surfactants include sodium lauryl ether sulfate (SLES), sodium myristyl ether sulfate and sodium palmityl ether sulfate and mixtures thereof. Preferred AES is SLES having 1 to 3 ethylene oxide units per molecule. SLES having 1 to 2 ethylene oxide units per molecule is more preferred.

[0027] When the above class of anionic surfactants are used, the composition comprises from 1 to 10 wt%, more preferably from 2 to 8 wt% anionic surfactant.

[0028] Alternately and more preferably, the anionic surfactant classes as described below are used.

[0029] The anionic surfactant system in this class may be selected from one or both of salts of acyl isethionate and alkyl taurate. The salts are preferably alkali metal salts.

[0030] Acyl isethionate surfactant is commonly produced by the direct esterification of a fatty acid (e.g., C10 to Ci6 fatty acid such as lauric acid) and isethionate (e.g., HOCH2CH2SO3M+’ where M+may be, for example, a sodium or potassium counterion) in a process commonly known as the “DEFI” process, where DEFI refers to directly esterified fatty acid isethionate.

[0031] Preferred isethionate sulfonates include cocoyl isethionate and lauroyl isethionate, preferably having sodium or potassium as counterions.

[0032] A suitable example of alkyl taurates is alkyl taurate amides which may be made by reaction of a taurine; methyl taurine; or a corresponding taurate salt (e.g., NH2CH2CH2SO3 M+, where M+may be sodium or potassium counterion) with the appropriate fatty acid. Preferably alkyl taurate amides include sodium methyl cocoyl taurate and sodium methyl lauroyl taurate.

[0033] An especially preferred mixture of anionic surfactant for use in the composition of the invention is a combination of alkali metal acyl isethionate and alkali metal alkyl taurate which may be included in total amount of 1 to 10%, preferably 2 to 8% by weight of the composition. When alkyl isethionate is included it is preferably present in 0.5 to 5 wt% of the composition. When alkyl taurate is included, it is preferably present in 0.5 to 5 wt% of the composition.

[0034] The composition of the invention comprises hydroxystearic acid (HSA), a salt or an ester thereof. It is also possible that the HSA is partially or fully neutralised i.e it may be present as a salt. It is preferred that the hydroxystearic acid is 10-hydroxystearic acid, 12-hydroxystearic acid or trihydoxystearic acid (e.g. 9,10,13-trihydroxystearic acid) or trihydroxy stearin or compounds that yield one or more molecules of hydroxystearic acid or hydroxystearate on their breakdown like mono, di or tri ester of glycerol with hydroxystearic acid. Of these, hydroxysteric acid is preferably selected from one or more of 12-hydroxystearic acid, 10-hydroxysteric acid, trihydroxystearin, or tri hydroxy stearic acid; preferably 12-hydroxystearic acid. 12-HSA has the structure as given below:

[0035] Hydroxystearic acid is included in 0.01 to 1 wt%, more preferably 0.02 to 0.5 wt% of the composition.

[0036] The composition of the invention includes 0.1 to 3 wt% fatty acid other than hydroxystearic acid; and salts thereof. By 0.1 to 3 wt% fatty acid other than hydroxy stearic acid and salts thereof is meant that the total amount of all fatty acids other than hydroxystearic acid is in the range of 0.1 to 3 wt% of the composition. The fatty acids so included is preferably a C8 to C18 fatty acid, preferred ones being lauric acid, myristic acid, palmitic acid, stearic acid and mixtures thereof. It is preferred that the composition includes a specific amount of lauric acid in the range of 0.15 to 0.5% lauric acid by weight of the composition in order to ensure the optimal amount of deposition of hydroxystearic acid. Most preferred amount of lauric acid is from 0.15 to 0.45% by weight of the composition. As especially preferred aspect relates an aspect wherein the fatty acid other than hydroxystearic acid is 0.15 to 0.45% lauric acid by weight of the composition. The composition may also comprise preferred amount of stearic acid in the range of 0.1 to 0.5% by weight of the composition. An especially preferred amount of C12 to Cis fatty acid (other than hyroxystearic acid) is from 0.1 to 1 .0% by weight of the composition.

[0037] The composition comprises water from 80 to 95 wt%, more preferably from 80 to 90 wt%.

[0038] The composition of the invention may additionally comprise an amphoteric surfactant. Preferably, amphoteric surfactant is selected from an amine oxide, hydroxysultaines, alkyl mono ethanol amine (e.g. coco mono ethanol amine), a betaine e.g. cocamidopropyl betaine (CAPB), sulfobetaine, cocoamphoacetate and mixtures thereof. More preferably, amophoteric surfactant is selected from a betaine, a sulfobetaine and mixtures thereof. Further more preferably, amphoteric surfactant is CAPB.

[0039] Preferably, the composition comprises from 0.1 to 20 wt%, more preferably from 1 to 10 wt%, amphoteric surfactant.

[0040] The pH of the composition is in the range from 6.0 to 7.5 preferably in the range of 6.3 to 7.0.

[0041] The pH of the composition is measured as follows: pH is measured after storing the samples at room temperature (about 25 °C) overnight. The pH of the samples was measured with Mettler Toledo pH measurement instrument, which was calibrated for 4.01 , 7 and 10.01 prior to use.

[0042] It has been found that by way of this invention, that the amount of hydroxystearic acid that can be deposited on to skin is in the range of 0.1 to 0.3 micrograms / cm2. This level of deposition delivers sufficient amount of bioactivity like skin barrier health and melanin reduction. It has also been found that the inclusion of the fatty acids along with HSA in the composition of the invention ensures excellent consumer attributes like amount of lather, lather creaminess, speed of lather and other user attributes like ‘in use slip’. The composition of the invention is also seen to be an isotropic liquid. Without wishing to be bound by theory the inventors believe that maintaining low selective amounts of fatty acid (other than hydroxystearic acid) especially by reducing the lauric acid level impacts the surfactant packing. Further, the concentration of lauric acid has an impact on the surfactant micelle and the degree to which it influences formation of worm-like structures (at the given formulation condition) which also influences the overall viscosity. With inclusion of HSA, the extent of formation of worm-like micelles are controlled to deliver the desired stable viscosity.

[0043] The composition of the invention may optionally comprise certain ingredients as given below to deliver other known desirable properties to the composition.

[0044] Preferably, the composition may comprise small amounts of viscosity modifying polymers. Preferably, the composition comprises 0.01 to 1 wt% viscosity modifying polymers. Suitable viscosity modifying polymers are selected from water soluble / or dispersible polymers including carbohydrate gums such as modified cellulose, guar gum, modified guar gum, agar, xanthan gum, carregeenan and mixtures thereof; starch and modified starch granules; emulsion polymers such as Aculyn® 28, Aculyn® 22 or Carbopol® Aqua SF1 ; cationic polymer such as modified polysaccharides including cationic guar Also suitable are high molecular weight polyethylene glycols such as Polyox® WSR-205 (PEG 14M), Polyox® WSR-N-60K (PEG 45), and Polyox® WSR-301 (PEG 90M).

[0045] Preferably, the composition further comprises preservatives to protect the composition against the growth of potentially harmful microorganisms. Particularly preferred preservatives include hydantoin derivatives, propionate salts, a variety of quaternary ammonium compounds, phenoxyethanol, imidazolidinyl urea, sodium dehydroacetate, sodium benzoate and benzyl alcohol. Preservatives are preferably used in amounts ranging from 0.01 wt% to 2 wt% and more preferably from 0.1 to 1 wt%.

[0046] The composition may further comprise emollients, such as stearyl alcohol, glyceryl monoricinoleate, mink oil, cetyl alcohol, isopropyl isostearate, isobutyl palmitate, isocetyl stearate, oleyl alcohol, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol, isocetyl alcohol, eicosanyl alcohol, behenyl alcohol, cetyl palmitate, silicone oils such as dimethylpolysiloxane, di- n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polyethylene glycol, triethylene glycol, lanolin, cocoa butter, corn oil, cotton seed oil, olive oil, palm kernel oil, rape seed oil, safflower seed oil, evening primrose oil, soybean oil, sunflower seed oil, avocado oil, sesame seed oil, coconut oil, arachis oil, castor oil, acetylated lanolin alcohols, petroleum jelly, mineral oil, butyl myristate, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate, myristyl myristate. Preferably, emollients are added in relatively low amount e.g. 0 to 3 wt% and 1 to 2 wt%.

[0047] The compositions may further comprise a wide range of other optional components e g. antioxidants, buffering agents, colorants, astringents, perfume, humectants, conditioners, pH adjusters, skin soothing agents and skin healing agents.

[0048] The invention also relates to a method of ensuring enhanced deposition of hydroxystearic acid on skin while ensuring that the composition has a high stable viscosity comprising the step of washing the skin with a composition of the invention preferably diluted with water followed by the step of rinsing the skin with water or wiping the skin with a wipe to be substantially free of the composition. The viscosity of the composition is preferably in the range of 6000 to 13000 cps. The invention will now be demonstrated with the help of the following non-limiting examples.

[0049] Examples

[0050] Effect of increasing amount of 12HSA

[0051] Various compositions as shown in Table -1 and 2 below were prepared. The viscosity of the compositions were measured using an RV viscometer using spindle #5 at 20 rpm for 30 seconds. The viscometer was zero calibrated without spindle prior to use. The measured viscosity values are summarized in Table - 2.

[0052] Table - 1

[0053] Table - 2

[0054] The data in Table - 2 (read with Table -1) above indicates that inclusion of 12-HSA in increasing quantities (Examples B and C) causes drastic reduction of viscosity. However adjusting the amount of other fatty acids e.g. lower amount of lauric acid (Examples 2 and 3) causes the viscosity to increase to the desired high range (similar to that of Example A). Various compositions as per the invention

[0055] Various compositions as shown in Table -3 and 4 below were prepared. The viscosity of the compositions were measured at a shear rate of 4 s’1, 12 hours after they were prepared and the values are summarized in Table - 2. Table - 3

[0056] Table - 4

[0057] The data in Table - 4 (read with Table -3) above indicates that in a 12-HSA containing composition inclusion of fatty acid (other than 12HSA) in the claimed range delivers viscosity in the desired range.

[0058] Deposition of 12HSA:

[0059] Various samples as per Table -3 were prepared except that lauric acid was maintained at 0.4% while 12HSA was varied at 0.2%, 0.4% and 0.6% respectively. The deposition of 12HSA was measured using an invitro method. The method used to measure deposition is given below:

[0060] A model skin substate was taken and prewetted with fixed amount of deionized water. Excess water was drained by shaking the substrate. A certain amount of the composition was applied on to the substrate and lathered for about 20 seconds with fingertip using latex gloves. Lather was retained for 30 seconds and then rinsed off with 100 ml of distilled water. The active (12HSA) deposited on to the substrate was extracted with methanol and quantitatively measured using LCMS. The deposition value is given in Table -5 below:

[0061] Table - 5

[0062] The data in the table -5 above indicates that 12HSA can be effectively deposited using compositions as per the invention.

Claims

Claims1. A liquid skin cleansing composition comprising(i) 1 to 10 wt% synthetic anionic surfactant;(ii) 0.1 to 3 wt% C10 to Cis fatty acid other than hydroxystearic acid; or salt thereof;(iii) 0.01 to 1 wt% hydroxystearic acid, a salt or an ester thereof;(iv) 80 to 95 wt% water; wherein pH of the composition is in the range of 6.0 to 7.5; wherein the fatty acid other than hydroxystearic acid comprises 0.15 to 0.5% lauric acid by weight of the composition.

2. A composition as claimed in claim 1 comprising 3 to 8 wt% anionic surfactant.

3. A composition as claimed in any one of the preceding claims wherein the anionic surfactant is alkyl isethionate, alkyl taurate or combinations thereof.

4. A composition as claimed in any one of the preceding claims wherein the synthetic anionic surfactant is a combination of alkyl isethionate and alkyl taurate.

5. A composition as claimed in any one of claims 3 or 4 comprising 0.5 to 5 wt% alkyl isethionate.

6. A composition as claimed in any one of the claims 3 to 5 comprising 0.5 to 5 wt% alkyl taurate.

7. A composition as claimed in any one of the preceding claims 3 to 6 wherein the alkyl isethionate is selected from one or more of cocoyl isethionate and lauroyl isethionate.

8. A composition as claimed in any one of the preceding claims 3 to 7 wherein the alkyl taurate is selected from one or more of methyl cocoyl taurate and methyl lauroyl taurate.

9. A composition as claimed in any one of the preceding claims wherein the hydroxystearic acid, a slat or ester thereof is selected from one or more of 12-hydroxystearic acid, 10- hydroxysteric acid, tri hydroxy stearin, or trihydroxystearic acid; preferably 12- hydroxystearic acid.

10. A composition as claimed in any one of the preceding claims additionally comprising an amphoteric surfactant.

11. A composition as claimed in claim 10 wherein the amphoteric surfactant is a betaine preferably coco amido propyl betaine.

12. A composition as claimed in claim 10 or 11 comprising 0.1 to 20 wt% amphoteric surfactant.

13. A composition as claimed in any one of the preceding claims comprising 80 to 90 wt% water.