A soap bar composition for enhanced delivery of water-soluble benefit agents

Abstract

The present invention relates to a soap bar composition that provides enhanced delivery of water-soluble skin benefit agents so that the desired benefit agent activity is observed for a long time after washing. This is achieved by absorbing / coating the benefit agent onto a specific clay and then further coating with a hydrophobic material selected from wax or petrolatum.

Description

Technical Field

[0001] The present invention relates to a soap bar composition that provides enhanced delivery of water-soluble skin benefit agents. More specifically, the present invention relates to a soap bar that is used to cleanse topical surfaces of the body and is capable of delivering water-soluble actives, especially cationic actives, to the skin sufficiently so that the desired activity of the benefit agents is observed for a long time after washing. Background Art

[0002] Products for cleaning local surfaces of the human body are delivered via cleaning compositions. They can be used to clean hair, face, body or hands. Most of these compositions contain anionic surfactants made from natural sources (such as soap) or can be synthetic in origin. Such compositions are also used to provide benefits other than cleaning, such as moisturizing, skin whitening, anti-aging, anti-inflammatory, conditioning or antimicrobial benefits. Such cleaning compositions also include many antimicrobial actives, such as triclocarban, triclosan, chloroxylenol, benzalkonium chloride, etc. Actives with cationic charges are considered to be highly effective antimicrobial actives. Due to the charge neutralization of such actives in anionic surfactant systems, it has always been a challenge to include cationic actives in such products. It is also a challenge to ensure that a sufficient amount of water-soluble actives are deposited by such compositions, because they usually tend to be washed off by rinse water. Compounds with high charge density, such as polymeric cationic actives, are even more difficult to incorporate into such systems.

[0003] Soap bars that claim to deliver actives to the skin have been disclosed before. US2005003975 (P&G) discloses fragrance compositions containing defined high impact accords and personal cleansing compositions, especially soap bars, containing those fragrance compositions. In a preferred aspect, the fragrance composition is encapsulated in starch or the like so as to release the scent when exposed to water, such as in a shower.

[0004] US2005123574 (Unilever) discloses a massage bar composition containing disintegrable aggregates that provide both exfoliation and massage to the skin and hair. The aggregates are made by treating with a hydrophilic liquid, a hydrophobic liquid, or a combination thereof. This treatment makes the aggregates softer, but not so soft that they break apart during the soap bar manufacturing process.

[0005] While the above cited publications disclose aggregates which purport to deliver actives to the skin, it has been found desirable that they be capable of delivering water soluble actives, particularly cationic compounds, through the soap bar which ensure that the desired effect is exhibited long after the washing action is complete.

[0006] Therefore, there is a need in the art to provide enhanced delivery of water-soluble or cationic actives in cleaning compositions containing large amounts of anionic surfactants. The inventors of the present invention have achieved this by including the actives in porous clay particles or by coating them on porous clay particles and further providing a coating thereon with a hydrophobic component such as petrolatum or wax. The inventors of the present invention have also surprisingly found that the present invention is effective when the coated clay particles are incorporated into solid cleaning compositions such as soap bars, whereas delivery is poor when formulated in liquid compositions.

[0007] An advantage of the present invention is that such water soluble benefit agents are kept separate from other soap bar ingredients with which they may interact during manufacturing and storage, yet are available in sufficiently high amounts to ensure effective deposition thereon when the bar is used by one in the personal washing process.

[0008] It is therefore an object of the present invention to provide a composition comprising anionic surfactants for enhanced delivery of water-soluble skin benefit agents.

[0009] It is another object of the present invention to provide enhanced delivery of cationic antimicrobial actives through such rinse-off soap bar compositions. Summary of the invention

[0010] According to a first aspect of the present invention, there is provided a soap bar composition for enhanced delivery of a water-soluble benefit agent comprising

[0011] (a) 40 to 80% soap;

[0012] (b) porous clay particles having a water retention capacity ranging from 10 to 50% by weight, coated with a water-soluble benefit agent having a solubility in water of at least 0.001 wt% at 25°C, and further coated with a hydrophobic material selected from wax or petrolatum.

[0013] A second aspect of the present invention relates to a method for preparing coated clay particles for use in the soap bar composition of the first aspect, comprising the steps of:

[0014] (a) mixing porous clay particles with an aqueous solution of a water-soluble benefit agent;

[0015] (b) drying the porous particles until they are substantially free of moisture;

[0016] (c) mixing the dried porous particles in a solution mixture of an organic solvent and a hydrophobic material;

[0017] (d) separating the particulate material from the solution mixture and drying the particulate material to prepare coated particles.

[0018] A third aspect of the present invention is directed to a method of delivering a water-soluble active to the skin, the method comprising the steps of washing the skin with a solution of the soap composition of the first aspect and then rinsing the skin with water until it is substantially free of soap. DETAILED DESCRIPTION

[0019] By reading the following detailed description and the appended claims, these and other aspects, features and advantages will become apparent to those of ordinary skill in the art. For the avoidance of doubt, any feature of one aspect of the present invention may be used in any other aspect of the present invention. The word "comprising" means "including", but not necessarily "consisting of" or "composed of". In other words, the steps or options listed do not have to be exhaustive. It should be noted that the examples given in the following description are intended to illustrate the present invention, rather than to limit the present invention to these examples themselves. Similarly, unless otherwise indicated, all percentages are weight / weight percentages. Except in the operating and comparative examples, or where otherwise explicitly stated, all numbers in this specification and claims represent the amount of material or reaction conditions, the physical properties of the material and / or the use thereof should be understood to be modified by the word "about". Numerical ranges expressed in the format of "from x to y" are understood to include x and y. When multiple preferred ranges are described in the format of "from x to y" for a particular feature, it should be understood that all ranges combining different endpoints are also considered. In other words, when specifying any range of values, any particular upper value can be associated with any particular lower value.

[0020] The disclosure of the invention as found herein is deemed to cover all embodiments as found in the claims as if they were multiply dependent on each other, regardless of the fact that the claims might be found without multiple dependency or redundancy.

[0021] Where features are disclosed with respect to a particular aspect of the invention (eg, a composition of the invention), such disclosure should also be considered applicable mutatis mutandis to any other aspect of the invention (eg, a method or process related to the invention).

[0022] A soap bar composition refers to a composition in the form of a shaped solid and is used to clean a local surface of the body and mainly includes soap (salts of fatty acids). This composition is diluted with water to form a solution / dispersion and is generally applied to the desired local surface of the body for a period of time ranging from a few seconds to a maximum of several minutes. Thereafter, the composition is generally rinsed off with water so that the surface is substantially free of soap. It includes any product that is applied to the human body and is also used to improve appearance, cleaning, odor control or general aesthetics. The soap bar composition of the present invention can be used for washing hair (such as shampoo or conditioner) or can be used for washing hands, washing face or washing body. More preferably, it is used to disinfect hands or other parts of the human body or for delivering / depositing other skin benefit agents thereon.

[0023] The present invention relates to a soap bar composition formulated to ensure enhanced delivery of water-soluble skin benefit agents. The soap bar composition comprises 40 to 80% soap; and coated porous clay particles. The porous clay particles are selected to have a water retention capacity in the range of 10 to 50% by weight.

[0024] This means that for every 100 grams of clay particles, it is able to absorb or hold 10 to 50 grams of water without appearing too wet, i.e., the water is mainly absorbed into the pores of the clay. In other words, even after absorbing water, it appears to flow freely. The clay particles are coated with a water-soluble benefit agent having a solubility in water of at least 0.001 wt % at 25°C. The water-soluble benefit agent does not have to be coated only on the outer surface of the clay particles. "Coated with" means that the water-soluble benefit agent can be partially absorbed into the pores of the clay particles, while the rest is coated to at least partially form a layer on the outer surface of the clay particles. The clay particles thus coated with the water-soluble benefit agent are further coated thereon with a hydrophobic material selected from wax or petrolatum.

[0025] The soap is preferably a C8-C24 soap, more preferably a C10-C20 soap, and most preferably a C12-C18 soap. The cation of the soap may be an alkali metal, an 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, most preferably sodium.

[0026] A typical fatty acid blend consists of 5 to 30% coconut fatty acids and 70 to 95% tallow fatty acids by weight of the soap. Fatty acids derived from other suitable oils / fats (e.g., peanut, soybean, tallow, palm, palm kernel, etc.) may also be used in other desired proportions.

[0027] The soap is present in an amount of 40-80%, preferably 50-75% by weight of the soap bar composition.

[0028] Any water-soluble skin benefit agent that meets the 0.001 wt% water solubility standard at 25°C can be used, but preferably one or more of an antimicrobial cationic active; a water-soluble vitamin or derivative thereof; a water-soluble sunscreen; an alpha or beta hydroxy acid; or a water-soluble alkali metal or alkaline earth metal salt. Of the above actives, more preferred are one or more of an antimicrobial cationic active; a water-soluble vitamin or derivative thereof; or a water-soluble sunscreen. The most preferred active is an antimicrobial polymeric cationic active.

[0029] The antimicrobial polymeric cationic active material that may be preferably included in the emulsion composition is one or more of polydiallyldimethylammonium chloride (PDADMAC) or chitosan, preferably PDADMAC. PDMAMAC is a homopolymer of diallyldimethylammonium chloride (DADMAC). The preferred PDADMAC for use in the present invention has a molecular weight range of 2,00,000-20,00,000, preferably 4,00,000-6,00,000. It is a cationic polymer with a high charge density, preferably above 2 meq / gm, and a viscosity in the range of 10,000-20,000 mPas. The polymer is available from Lubrizol Inc. under the trade name Merquat-100 (INCI: Polyquaternium-6). The water-soluble vitamin or derivative thereof that may be included is selected from one or more of vitamin C, E, B3, B5 or N-methylnicotinamide, more preferably vitamin B3. The water-soluble sunscreen agent may be included and is selected from one or more of 2-phenylbenzimidazole-5-sulfonic acid (sold as Enulizole) or ethylhexyl salicylate (sold as Neoheliopan OS). The alpha-hydroxy acid may be included and is selected from one or more of lactic acid, glycolic acid or salicylic acid, preferably lactic acid. The water-soluble benefit agent is preferably included at 1 to 20% by weight of the clay particle.

[0030] The water-soluble skin benefit agent is included in and / or coated on the porous clay particles. The clay is preferably one of the montmorillonite class. The preferred clay is kaolin, bentonite or china clay.

[0031] Clays are finely ground natural rock or soil materials. Based on physical and chemical properties, these clays are further classified into many clay mineral groups. For example, the structure of kaolinite is tetrahedral silica sheets alternating with octahedral aluminum oxide sheets. The charges within the structural units are balanced. The common molecular formula for the kaolinite group is Al2Si2O5(OH)4.

[0032] Bentonite has the ability to form a thixotropic gel with water, has the ability to absorb large amounts of water, with a volume increase of up to 12-15 times its dry volume, and has a high cation exchange capacity. These cations are exchangeable due to their loose association, and together with the broken bonds (about 20% of the exchange capacity), give montmorillonite a fairly high (about 100 meq / 100 g) cation exchange capacity, which is almost unaffected by particle size.

[0033] These clays can be procured from companies like English India Clays (EICL), Clariant, Ashapura Minehem Ltd., Shree Ram Minerals etc.

[0034] The porous clay particles are included at 1-25%, preferably 2-10% by weight of the soap bar composition.

[0035] The porous clay particles incorporated / coated with the water soluble skin benefit agent are then further coated with a hydrophobic material selected from wax or petrolatum, preferably petrolatum.

[0036] Any type of wax may be used, namely microcrystalline wax, beeswax or carnauba wax. Microcrystalline wax consists of a petroleum-derived plastic material that differs from paraffin wax by having finer and less distinct crystals and a higher melting point and viscosity. The melting point range is higher than paraffin wax, with commercial grades ranging from 63° to 93°C. Chemically, microcrystalline wax consists of saturated aliphatic hydrocarbons.

[0037] Beeswax is a natural wax produced by bees of the genus Apis. Beeswax is a tough wax formed by a mixture of several compounds. The approximate chemical formula of beeswax is C 15 H 31 COOC 30 H 61 Its main components are palmitate, palmitoleate and oleate esters of long chain (30-32 carbon) aliphatic alcohols. Beeswax has a relatively low melting point range of 62 to 64°C.

[0038] Carnauba wax, also known as Brazilian wax or palm wax, is the wax of palm leaves. It is mainly composed of fatty esters, diesters of 4-hydroxycinnamic acid, ω-hydroxycarboxylic acids and fatty alcohols. These compounds are mainly derived from acids and alcohols in the C26-C30 range. Carnauba wax is unique in that it contains high levels of diesters as well as methoxycinnamic acid. The melting point is generally in the range of 82-86°C.

[0039] Petrolatum, also known as vaseline, is a purified mixture of semisolid hydrocarbons obtained from petroleum, with a carbon chain length of 25 or more. Petrolatum has excellent moisturizing properties and a melting point of about 37°C. It is colorless or pale yellow (when not highly distilled), translucent, and has no taste or odor when pure. It is insoluble / immiscible in water. Petrolatum is also commonly referred to as petrolatum. The preferred petrolatum for use in the present invention is a petrolatum having a slip melting point in the range of 45 to 75°C. The hydrophobic phase may also contain smaller amounts of other hydrophobic substances, such as fatty acids, triglycerides or polysiloxanes.

[0040] The hydrophobic material is included at 0.1 to 10% by weight of the clay particle.

[0041] The soap bar composition of the present invention may optionally include other anionic surfactants. They are preferably selected from alkyl ether sulfates, primary alkyl sulfates, secondary alkyl sulfonates, alkylbenzene sulfonates or ethoxylated alkyl sulfates. Preferred anionic surfactants other than soap in the soap bar composition of the present invention are alkyl ether sulfates, preferably those with 1-3 ethylene oxide groups, from natural or synthetic sources, and / or sulfonic acids. Particularly preferred is sodium lauryl ether sulfate. Alkyl polyglucosides may also be present in the composition, preferably those with a carbon chain length between C6 and C16. Preferred compositions may include other known ingredients such as fragrances, pigments, preservatives, emollients, sunscreens, gelling agents and thickeners. The choice of these ingredients depends largely on the form of the composition. Water is the preferred carrier. When water is present, it is preferably present in an amount of at least 1%, more preferably at least 2%, and even more preferably at least 5% by weight of the composition. When water is the carrier, the preferred cleaning composition comprises 10 to 40% by weight, more preferably 12 to 25% by weight of water.

[0042] The soap bar composition is preferably prepared using a conventional milling and plodding soap making process. In the milling and plodding route, the soap is prepared with a high water content, then spray dried to reduce the moisture content and the soap is cooled, then other ingredients are added, and then the soap is extruded through a plodder, and optionally cut and punched to prepare the final soap bar. The milled and plodded soap typically has a high TFM in the range of 60 to 80 wt%. Alternatively, the soap is prepared by a relatively dry mixing method in a ploughshare mixer. Thereafter, it can be extruded in a conventional manner. Milled and plodded soap bars are also referred to as extruded soap bars. They consist of many different types of soaps. Most soap compositions contain both water-insoluble soaps and water-soluble soaps. Their structure is typically characterized by a brick and mortar type structure. Insoluble soaps (called bricks) typically consist of higher chain C16 and C18 soaps (palmitic acid and stearic acid soaps). They are typically included in soap bars to provide a structured benefit, i.e., they provide a shape to the soap bar. Soap bars also consist of water-soluble soap (acting as the mortar), which is typically unsaturated C18: 1 and 18:2 sodium soaps (oleic soaps) combined with short chain fatty acids (typically C8 to C12 or even up to C14 soaps). Water-soluble soaps generally aid in cleaning.

[0043]

[0046] In the soap bar compositions of the present invention, the coated clay particles for inclusion in the soap bar compositions of the present invention are generally prepared by the following method.

[0044] The aqueous solution of the beneficial agent is slowly added to the dry porous clay medium and mixed for several minutes, such as from about 5 minutes to one hour. The particles coated with the beneficial agent are then dried in an oven to reduce the moisture to a low level sufficiently to make it free-flowing, such as a moisture content of about 1 to 5 wt%. There may be particle aggregation after this coating step. The aggregated particles are broken into the desired fine powder size in a particle crusher. The resulting coated powder is mixed in a solution mixture of the desired organic solvent in which the hydrophobic material is dissolved. The solvent is recovered from the powder solution by a solvent recovery extraction process, and the coated clay particles are dried to a free-flowing state.

[0045] The present invention also relates to a method for delivering skin benefit agents to the skin, comprising the step of applying the composition of the present invention to the desired skin surface. The soap is then substantially removed from the surface after a specific amount of time. Typically people spend about 10 seconds to 2 minutes washing their body parts, and it is expected that the desired active substance deposition should occur within this time frame. The washing time is preferably from 10 seconds to one minute, more preferably from 10 seconds to 30 seconds. Removal of the composition from the surface can be achieved by wiping the composition from the surface using a suitable wipe. Alternatively and more preferably, it can be achieved by rinsing the surface with water to make it substantially free of soap. The composition is typically applied to the desired skin surface after diluting the composition with water. The composition can be diluted with water to a concentration of 1-50%, preferably 2-20%, of the weight of the diluted solution.

[0046] The invention will now be illustrated with the aid of the following non-limiting examples.

[0047] Example

[0048] Soap bars were prepared as given in Table 1 below

[0049] Example A: Control

[0050] Example B: Soap Bar with Uncoated Clay

[0051] Example C: Soap Bar with Clay + PDADMAC

[0052] Example 1: Soap Bar with Petrolatum Coated PDADMAC Clay (According to the Invention) The clay was coated with PDADMAC and then petrolatum using the method given below:

[0053] An aqueous solution of polydiallyldimethylammonium chloride was added to a dry porous clay medium (Supershine Plus Kaolin, EICL, India) in a sequential manner and mixed for about 45 minutes. The particles coated with the beneficial agent were then dried in an oven to substantially reduce the moisture to a low level of about 2%. Any aggregated particles were broken into the desired fine powder size in a particle crusher. The resulting coated powder was mixed in a solution mixture of an organic solvent hexane in which petrolatum was dissolved. The solvent was separated from the coated clay particles and dried to a free-flowing state.

[0054] Table-1

[0055]

[0056] The soap bars were tested for regrowth of S. aureus on the skin in vitro 6 hours after washing.

[0057] The procedure used for the measurements was as follows:

[0058] a) 5×5cm 2 Sterile in vitro skin was placed in a petri dish and washed with 2 ml of sterile water before any treatment. After 10 minutes, the water was removed and the skin was kept in a fresh petri dish to dry.

[0059] b) Allow the skin to dry for 20 minutes. The skin is not over-dried and the wet half-cut soap bar is rubbed horizontally on the test area for 15 seconds. After 15 seconds, 1 ml of water is added to the VITRO-SKIN using a pipette and the L-shaped applicator is used to cover the test area horizontally and vertically for 45 seconds (this will cause the soap to foam).

[0060] c) After one minute (45+15 seconds), remove the in vitro-skin at a 45 degree angle with one hand, while with the other hand pour distilled water (about 20-30 ml) on the skin. No soap traces should remain on the skin. Then dry the skin for 30 minutes.

[0061] d) After drying for 30 minutes, add 100 μl of 10 6 A bacterial inoculum (Staphylococcus aureus) was added and applied using an L-shaped applicator. The bacteria were allowed to fully adsorb on the skin surface and dry.

[0062] e) The treated skin was placed on a TSA plate and the plate was incubated in a 37 degree incubator for 6 hours. After 6 hours, the treated skin was immediately added to a 9 ml BPB neutralizer tube and vigorously shaken for 3 minutes using a Griffin shaker to dislodge the bacteria on the skin. A 10-fold serial dilution was performed and then inoculated in TSA medium.

[0063] The remaining log cfu / ml are summarized in Table 2 below.

[0064] Table-2

[0065] Example Log cfu / ml A 6.1 B 6.4 C 6.3 1 5.2

[0066] The data in Table-2 above demonstrates that the soap bar according to the present invention (Example-1) is an order of magnitude more effective than the soap bars prepared using the same ingredients but without the desired coating configuration (Examples B and C).

Claims

1. A soap bar composition for enhanced delivery of a water-soluble benefit agent, comprising (a) 40 to 80% soap; (b) porous clay particles having a water-retention capacity in the range of 10 to 50% by weight, coated with a water-soluble benefit agent having a solubility in water of at least 0.001 wt% at 25°C, and further coated with a hydrophobic material selected from wax or petrolatum, wherein the water-soluble benefit agent is an antimicrobial cationic active substance, and wherein the water-retention capacity means that the porous clay particles are capable of absorbing or retaining 10 to 50 grams of water per 100 grams; wherein the porous clay particles are included at 1 to 25% by weight of the composition, wherein the benefit agent is included at 1 to 20% by weight of the porous clay particles; and The hydrophobic material is included in an amount of 0.1 to 10% by weight of the porous clay particles.

2. The composition of claim 1, wherein the antimicrobial cationic active is polydiallyldimethylammonium chloride.

3. A composition according to claim 1 or 2, wherein the hydrophobic material is petrolatum.

4. The composition of claim 1 or 2, wherein the clay is a smectite clay.

5. The composition according to claim 1 or 2, wherein the clay is kaolin, bentonite or china clay.

6. The composition according to claim 1 or 2, wherein the porous clay particles are included in an amount of 2 to 10% by weight of the composition.

7. A method for preparing coated clay particles for use in a composition according to any one of claims 1 to 6, comprising the steps of: (a) mixing the porous clay particles with an aqueous solution of the water-soluble beneficial agent; (b) drying the porous clay particles until they are free of moisture; (c) mixing the dried porous clay particles in a solution mixture of an organic solvent and the hydrophobic material; (d) separating a particulate material from the solution mixture and drying the particulate material to produce coated particles.

8. The method according to claim 7, wherein the organic solvent is selected from hexane, heptane, octane or carbon tetrachloride.

9. A method for delivering a water-soluble active substance to the skin, comprising the steps of: The skin is washed with a solution of the soap bar composition according to any one of claims 1 to 6 and then rinsed with water to be free of the soap.

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