Personal cleansing composition comprising mild surfactant and soap

Abstract

The present invention relates to cleansing compositions that that are mild and gentle to the skin. In particular, the invention relates to liquid soaps, bodywash liquids and soap bars with pH from 6 to 8. Disclosed is a personal cleansing composition comprising 10 to 80 wt% total surfactant content comprising lauroyl isethionate and soap, where ratio of lauroyl isethionate to soap is 1:0.1 to 1:1 parts by weight, and where the soap consists of water-soluble soap and water¬ insoluble soap, wherein, ratio of water-soluble soap to the water-insoluble soap is 1:0.4 to 1:1.4 parts by weight. A balance between the total non-soap surfactant and total soap in the composition, as well as between the soluble and the insoluble soap in the total soap, makes the compositions milder (with pH 6 to 8) and with an appreciable foam, even with hard water.

Description

[0001] “PERSONAL CLEANSING COMPOSITION COMPRISING MILD SURFACTANT AND SOAP”

[0002] Field of the Invention

[0003] The present invention relates to cleansing compositions that that are mild and gentle to the skin. In particular, the invention relates to liquid soaps, bodywash liquids and soap bars with pH from 6 to 8.

[0004] Background of the invention

[0005] Fatty acyl isethionates (e.g., cocoyl isethionate and lauroyl isethionate) form a group of anionic surfactants. In general the fatty acyl isethionate surfactants are produced by esterification of isethionate which has a sulphonic acid group and a hydroxyl group, with fatty acids or fatty acid chlorides. When cocoyl fatty acids are used the corresponding cocoyl isethionate is formed which has a predominance of C12 fatty acids with other non-C12 acids depending on the fatty acid chains found in coco fatty acids or palm kernel oil.

[0006] Such isethionates are available in neat or pure form, as well as in the form of noodles which contain about 50 wt% isethionate along with free fatty acids and sodium isethionate, often along with starch contained in the noodles. The noodles are more suited for use in the commercial manufacture of soap bars and are economical alternatives to neat or concentrated isethionates.

[0007] Compositions, especially soap bars, comprising isethionate and soap are known.

[0008] US4663070 A (1987) and US5041233 A (1991), both assigned to Lever Brothers, disclose toilet bar composition having soluble sodium soap and C10 to C16 acyl isethionate salt in the ratio of about 20:1 to 1 :0.98. US5284598 A (Colgate, 1998) and US5981451 (Lever Brothers, 1999) also disclose combinations of soluble sodium soap and C10 to C16 acyl isethionate salt.

[0009] US5204014 A (P&G, 1993) discloses pH 6.5 to 8.5 mild personal cleansing bar comprising 20 to 50% isethionate and 5 to 50 wt% insoluble magnesium soap. Ratio of isethionates to soap is 10:1 to 0.4:1 parts by weight.

[0010] US5510050 A (P&G, 1996) discloses soap bars comprising 10 to 70 wt% sodium acyl (cocoyl) isethionate (SCI) and 4.5 to 50 wt% magnesium soap. Some exemplified compositions contain sodium soap however magnesium soap is always in excess. The bars are said to be mild and to lather well but the pH is from 4 to 9.

[0011] US2002039977 A1 (Unilever) discloses the addition of divalent cations to a mix of soluble soap and isethionate to react with the soluble soap dissolved in the unbound water. This addition reduces softness and stickiness during production of bars. The cations do not significantly affect the foam.

[0012] US5387362 A (P&G, 1995) discloses personal cleansing bar made with a base soap tailored with mixed counterions (Mg / K / Na) and selected saturated C14 to C18 fatty acid soaps and soap selected from lauric, oleic, and other more soluble soaps. The soap has improved mildness while maintaining acceptable lathering, rinsing and processing characteristics.

[0013] When an attempt is made to improve the foam characteristics of personal wash compositions comprising isethionate by addition of soluble soap, the pH tends to increase. An unregulated amount of soluble soap component adversely affects mildness of the composition. On the other hand, if the pH is lowered by inclusion of insoluble soap, the foam characteristics get adversely affected.

[0014] Summary of the invention

[0015] The present inventors have observed that a balance between the total non-soap surfactant and total soap in the composition, as well as between the soluble and the insoluble soap in the total soap, makes the compositions milder and yet produce an appreciable foam while in use. The non-soap surfactant needs to be lauroyl isethionate as opposed to cocoyl isethionate.

[0016] Disclosed is a personal cleansing composition comprising 10 to 80 wt% total surfactant content comprising lauroyl isethionate and soap, where ratio of lauroyl isethionate to soap is 1 :0.1 to 1 :1 parts by weight, and where the soap consists of water-soluble soap and water-insoluble soap, wherein, ratio of water-soluble soap to the water-insoluble soap is 1 :0.4 to 1 :1 .4 parts by weight. Detailed description of the invention

[0017] 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 utilized in any other aspect of the invention. The word “comprising” is intended to mean “including” but not necessarily “consisting of’ or “composed of.” It is noted that the examples given in the description below are intended to clarify the invention and not to limit the invention to those examples per se. Similarly, all percentages are weight / weight percentages unless otherwise indicated. 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. In other words, in specifying any ranges of values, any upper value can be associated with any lower value.

[0018] The cleansing composition

[0019] The personal cleansing composition of the invention comprises 10 to 80 wt% total surfactant content comprising lauroyl isethionate and soap, where the ratio of lauroyl isethionate to soap is 1 :0.1 to 1 :1 parts by weight, and where the soap consists of water-soluble soap and water-insoluble soap, wherein, ratio of water-soluble soap to the water-insoluble soap is 1 :0.4 to 1 :1 .4 parts by weight.

[0020] The personal cleansing composition of the invention comprises 10 to 80 wt% total surfactant content comprising a lauroyl isethionate and soap. More preferably the composition comprises 20 to 80 wt% surfactant comprising said lauroyl isethionate and soap. Further preferably the personal cleansing composition of the invention comprises 30 to 80 wt% total surfactant content comprising the lauroyl isethionate and soap.

[0021] The term total surfactant content means the sum of all surfactants present in the composition of the invention. Preferably the total surfactant content comprises a major proportion of lauroyl isethionate and soap, and a minor proportion of other surfactants when they are present. More preferably the total surfactant content consists of lauroyl isethionate and soap.

[0022] Lauroyl isethionate is a fatty acyl isethionate and is an anionic surfactant prepared by reacting isethionate salt such as alkali metal isethionate with an aliphatic C12 fatty acid generally having Iodine Value less than 20 g / g. Preferably the alkali metal cation is sodium. Alternatively, it is magnesium, potassium, lithium, ammonium or substituted ammonium cation or other counterion. Alternatively the composition of the invention further comprises sodium cococyl isethionate. Alternatively the composition comprises sodium lauroyl isethionate and sodium cococyl isethionate as a combination. In the combination, preferably there is major proportion of sodium lauroyl isethionate and minor proportion of sodium cococyl isethionate. By major proportion is meant at least 70 %, preferably at least 80% and more preferably at least 90% of the combination.

[0023] In one aspect of the invention the personal cleansing composition of the invention is aqueous and the total surfactant content is 10 to 25 wt%. Alternatively, the personal cleansing composition is non-aqueous and the total surfactant content is 20 to 80 wt%. In such situations the composition is in the form of a bar and preferably comprises 5 to 25 wt% free fatty acids Depending on the format of the composition the total surfactant content is variable. The bars may be of any shape such a rectangular or ovoid bar and this shape is usually achieved by the shape of the die or mould used for extrusion and stamping of the soap mass.

[0024] The lauroyl isethionate may also comprise some amount of unesterified isethionate salt for example, sodium isethionate which may eventually get incorporated into the personal wash composition.

[0025] Fatty acyl isethionates are commercially available in two forms; as flakes with an active content of about 60 to 80%, and as noodles with active content of about 40 to 50% but also containing stearic acid and CAPB. Noodles may also contain starch and glycerine. A variety of suppliers and commercial manufacturers offer a range of isethionates in the aforesaid and other forms.

[0026] Therefore, if a composition needs to be prepared comprising a certain predetermined wt% of lauroyl isethionate, then formulation scientists need to bear in mind that commercial supplies of such isethionates often contain other ingredients.

[0027] Soap

[0028] The term "soap" means alkali metal or alkaline earth metal salts of fatty acids. The ratio of lauroyl isethionate to soap is 1 :0.1 to 1 :1 parts by weight.

[0029] It is preferred that the fatty acids are derived from coconut oil, palm oil, palm kernel oil or non-tropical nut oils. Preferably the carbon chain length is C12 or higher. Preferably at least 85% fatty acids have C12 to C18 chain length. Further preferably the fatty acids comprise fatty acids derived from aforesaid oils and any other source of unsaturated fatty acids. A preferred soap feed stock is a mixture of 15 to 20% coconut fatty acids and 80 to 85% unsaturated fatty acids. The soaps may contain unsaturation in accordance with commercially acceptable standards. It is preferred that there is no excessive unsaturation in the fatty acids.

[0030] The soap consists of water-soluble soap and water-insoluble soap and ratio of water-soluble soap to the water-insoluble soap is 1 :0.4 to 1 :1 .4 parts by weight. This ratio is determined based on the total soap content of the composition. Preferably the ratio of water-soluble soap to the water-insoluble soap is 1 :0.6 to 1 :1 .4 parts by weight.

[0031] Preferably the solubility of the water-soluble soap is equal to or greater than that of 82 / 18 tallow / coconut soap, whose solubility is 1.1 g / litre at 40°C. Preferably the water-soluble soap is an alkali metal salt of C8 to C24 fatty acids. In a most preferred aspect the alkali metal is sodium. Therefore preferably the water-soluble soap is sodium soap.

[0032] Further preferably the solubility of the water-insoluble soap is less than 1.1 g / litre at 40°C. More preferably the water-soluble soap is an alkaline earth metal salt of C8 to C24 fatty acids. Preferably the alkaline earth metal salt is magnesium. Alternatively, the alkaline earth metal salt is calcium. Therefore preferably the water-insoluble soap is magnesium soap.

[0033] The present inventors have determined that a balance between the total non-soap surfactant and total soap in the composition, as well as between the soluble and the insoluble soap in the total soap, makes the compositions milder and generates appreciable foam while in use.

[0034] Whie cleansing compositions are formulated to be used with soft water, i.e. with water that has low TDS and hardness, it is observed that consumers generally have little control over the hardness of available water. In countries of the size of e.g., India and Indonesia, there is significant regional variation in hardness of waterthat is made available in the bathrooms. The water could range from very soft water (hardness less than 50 ppm) to semi-hard water (hardness around 150 ppm) to very hard water (hardness around 300 ppm). However, it is expected that the cleansing compositions are robust in their formulation so that the user or consumer is assured of certain minimum foam volume regardless of the hardness of water. In some countries, local regulations also stipulate a minimum foam volume, often about 200 ml. When the total surfactant content comprises sodium lauroyl isethionate the foam volume is high with soft water and semi-hard water and even with very hard water the foam volume can still be improved with adjustments to the ratio between the soluble soap and insoluble soap.

[0035] Filler

[0036] It is preferred that the personal cleansing composition of the invention comprises 1 to 30 wt% filler.

[0037] Preferably the composition comprises a soluble filler. Alternatively, the composition comprises an insoluble filler. Further alternatively the composition of the invention comprises at least one soluble filler and at least one insoluble filler.

[0038] It is preferred that the soluble filler is a polyol or mixture of polyols. It is preferred that the polyol is glycerol, propylene glycol, sorbitol, mannitol, sucrose, glucose, hydrolyzed starch, dextrin, maltodextrin, polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG. Preferably the personal cleansing composition of the invention comprises 1 to 5 wt%, more preferably 2 to 4 wt% soluble fillers. It is particularly preferred that the composition of the invention comprises not more than 5 wt% soluble filler, or not more than 5 wt% soluble fillers in total, when the composition comprises more than one soluble filler. Preferably the composition comprising fillers is in the form of a bar.

[0039] Alternatively the filler is an insoluble organic filler. Preferably the insoluble organic filler is natural starch or chemically modified starch. Preferably the particle size of insoluble filler is less than 300 pm. Preferably the insoluble filler is talc or calcium carbonate. Alternatively the filler is a clay (e.g., kaolin or china clay).

[0040] It is preferred that pH of the composition of the invention is 6 to 8.0, more preferably 6.5 to 7.8 and most preferably 6.5 to 7.5.

[0041] Free fatty acids

[0042] It is preferred that the composition of the invention comprises 5 to 25 wt free fatty acids (FFA), preferably 5 to 20 wt%. It is preferred that the fatty acid is stearic acid or alternatively hysteric acid. Inclusion of free fatty acids increases hardness of the soap bars. When the lauroyl isethionate is introduced in the form of noodles, some commercial supplies of noodles comprise a significant amount of stearic acid or similar fatty acid. Therefore, it is necessary to considerthe added stearic acid inherently present in the noodles of isethionate before considering the inclusion of more fatty acids in the composition.

[0043] Additional ingredients

[0044] In addition to the ingredients disclosed earlier, the composition of the invention may comprise one or more of the following ingredients. The choice of the ingredients and their wt% will largely depend on the nature of the composition, i.e. aqueous or non-aqueous as well as the format of the composition such as whether it is a soap bar.

[0045] Surfactants

[0046] The composition of the invention may comprise one or more additional non-soap surfactant other than the lauroyl isethionate.

[0047] A surfactant is necessary for basic cleansing action and the nature and type of surfactant, or surfactants, would vary largely based on the intended use of the composition. The amount of non-soap anionic surfactant could vary largely depending on the nature and purpose of the end-use composition. Preferably the non-soap anionic surfactant is alkyl sulphate, alkyl ether sulfate, alkaryl sulfonate, ester sulphonate, alkyl succinate, alkyl sulfosuccinate, alkyl ether sulfosuccinate, N-alkyl sarcosinate, alkyl phosphate, alkyl ether phosphate, and alkyl ether carboxylic acid, taurate or a glycinate. More preferably the non- soap anionic surfactant is alkyl sulphate, alkyl ether sulphate, isethionate or ester sulphonate.

[0048] Alkyl sulphates and alkyl ether sulphates

[0049] When the composition of the invention comprises an alkyl sulphate it is preferred that the composition comprises 2 to 5 wt% alkyl sulphate.

[0050] Ta urates

[0051] When the composition of the invention comprises a taurate, it is preferably comprises sodium methyl lauroyl taurate, potassium methyl lauroyl taurate, sodium methyl myristoyl taurate, potassium methyl myristoyl taurate, ammonium methyl myristoyl taurate, sodium methyl cocoyl taurate, potassium methyl cocoyl taurate, ammonium methyl cocoyl taurate, sodium methyl oleoyl taurate, potassium methyl oleoyl taurate, ammonium methyl oleoyl taurate, sodium lauroyl taurate, potassium lauroyl taurate, ammonium myristoyl taurante, sodium cocoyl taurate or potassium oleoyl taurate.

[0052] Preferably the composition comprises 1 to 10 wt% taurates.

[0053] Glycinates

[0054] When the composition of the invention comprises a glycinate, preferably the glycinate is alkyl glycinate or acyl glycinate. More preferably, the glycinate surfactant comprises C8-24 alkyl glycinate, C8-24 acyl glycinate, or a mixture thereof. It is particularly preferred that the glycinate is cocoyl glycinate and more preferably sodium cocoyl glycinate. The glycinates are generally used in the form of their salts, preferably alkali metal salt, and / or ammonium salt.

[0055] Preferably the composition comprises 1 to 10 wt% glycinates.

[0056] Alkyl succinate, alkyl sulfosuccinate, alkyl ether sulfosuccinate

[0057] When the composition of the invention comprises alkyl succinate, alkyl sulfosuccinate, alkyl ether sulfosuccinate, preferably the sulphosuccinate is cocamidomonoethanolamine sulphosuccinate, with chain length distribution of at least 90% of C8to C18fatty acid. Preferably the composition comprises 1 to 10 wt% alkyl succinate, alkyl sulfosuccinate, or alkyl ether sulfosuccinate or any combination thereof.

[0058] Sarcosinate

[0059] When the composition of the invention comprises a sarcosinate preferably the sarcosinate is one or more of Cocoyl Sarcosine, Lauroyl Sarcosine, Myristoyl Sarcosine, Oleoyl Sarcosine, Stearoyl Sarcosine, Sodium Cocoyl Sarcosinate, Sodium Lauroyl Sarcosinate, Sodium Myristoyl Sarcosinate, Ammonium Cocoyl Sarcosinate or Ammonium Lauroyl Sarcosinate. Preferably the composition comprises 1 to 10 wt% sarcosinate.

[0060] Benefit agents

[0061] The cleansing composition optionally comprises 0.5 to 10 wt% benefit agent which may be selected depending on the nature of the composition. Preferred benefit agents include moisturizers, emollients, sunscreens, and / or anti-ageing compounds, anti-oxidants, perfumes, polymers, chelating agents, colorants, deodorants, dyes, foam boosters, germicides, anti-microbials, lathering agents, pearlescers, skin conditioners, stabilizers, Sodium metabisulphite, ethylene diamine tetra acetic acid (EDTA), or ethylene hydroxy diphosphonic acid (EHDP), retinoids, resorcinol or vitamin B3.

[0062] The personal cleansing composition of the invention preferably comprises 0.01 to 5 wt% electrolytes such as sodium sulphate, sodium chloride, sodium acetate, sodium citrate, potassium chloride, potassium sulphate, sodium carbonate and other mono or di or tri salts of alkali metals, more preferred electrolytes are sodium chloride, sodium sulphate, sodium citrate, potassium chloride and an especially preferred electrolyte is sodium chloride, sodium citrate or sodium sulphate or a combination thereof. It is preferred that the electrolyte is not of alkaline earth metal because such electrolytes may affect the ratio between soluble and insoluble soap.

[0063] Conventionally, milled and plodded soap bars are made by saponification of fat and oils, forming the dried soap into noodles, mixing the various desired additives such as perfume into the soap noodles, passing the mixture formed through a mill or series of mills to form ribbons of soap, passing the milled soap mixture through a plodder to form billets of soap and cutting the billets into individual unit bars of suitable size followed by stamping the bars into the desired shape.

[0064] Shape

[0065] When the personal cleansing composition of the invention is a bar of soap, it may be in any of the regular forms in which such products are available.

[0066] Method

[0067] In accordance with a second aspect of the invention disclosed is a method of cleansing skin comprising the steps of: i) applying to a part of the body a personal cleansing composition described above; and, ii) rinsing the part of the body with water.

[0068] Preferably the method of the invention is for use on human body. The method may be practised or used to clean any relevant part of the human body. Depending on the intended use of the composition, the nature of the composition would differ. For example, if the method is to be practised on the hands, the personal cleansing composition of the invention would be a hand wash composition or a soap bar. In one aspect the invention, the method of cleansing skin comprising the steps of applying to a part of the body a personal cleansing composition of the first aspect is practiced on the body as such. Accordingly, the personal cleansing composition of the invention is preferably a hand body wash composition, a shower gel or a soap bar.

[0069] The invention will now be explained in details with the following exemplary embodiments. All chemicals are from commercial sources. To the best of the applicant’s knowledge, the invention is not based on any bioresource or biological material procured from India.

[0070] Examples

[0071] Example 1 :

[0072] A range of personal cleansing composition in the form of extruded soap bars was prepared by milling and plodding the ingredients as described in Table 1 . The bars so prepared were subjected to comparative evaluation. Further details regarding observations of these tests are also shown in Table 1 . Compositions A to C containing sodium cocoyl isethionate were outside the present invention. Compositions 1 and 2 were non-limiting embodiments of the present invention.

[0073] Table 1

[0074] The illustrated examples indicate that foam profile of the compositions 1 and 2 was significantly better than compositions A to C. The observations regarding compositions 1 and 2 indicate that a balance between the total non-soap surfactant and total soap in the composition, as well as between the soluble and the insoluble soap in the total soap makes the compositions milder (as demonstrated by pH) and with an appreciable foam, that too with hard water. The pH of all the compositions 1 and 2 was well within the range of 6 to 8, but compositions A to C had practically little foam. Foam height was measured using water with 300 ppm hardness (30 FH).

[0075] Example 2:

[0076] A range of personal cleansing composition in the form of extruded soap bars was prepared and comparatively evaluated for pH and foam volume measured using 300 ppm hard water (30 FH). This series of soap bars had the same basic chassis because all bars contained sodium lauroyl isethionate and soap (variable as in Table 2). All observations regarding foam height and pH are also included in Table 2.

[0077] Table 2

[0078] The illustrated examples indicate that it is necessary to maintain the weight ratio of sodium soap and magnesium soap in the range of 1 :04 to 1 :1 .4. If this ratio is less than 1 :0.4, then the pH of the bars could be over 8 (composition F). The pH remains within 6 to 8 even if the ratio increases to 1 :1.29 (composition 4).

[0079] Compositions 3 and 4 were inside the invention. Foam height was measured using water with 300 ppm hardness (30 FH).

[0080] The examples indicate that a balance between the total non-soap surfactant and total soap in the composition, as well as between the soluble and the insoluble soap in the total soap, makes the compositions milder (with pH 6 to 8) and with an appreciable foam, even with hard water.

Claims

WE CLAIM:1) A personal cleansing composition comprising 10 to 80 wt% total surfactant content comprising lauroyl isethionate and soap, where ratio of lauroyl isethionate to soap is 1 :0.1 to 1 :1 parts by weight, and where the soap consists of water-soluble soap and water-insoluble soap, wherein, ratio of water-soluble soap to the water-insoluble soap is 1 :0.4 to 1 :1 .4 parts by weight.2) A personal cleansing composition as claimed in claim 1 , wherein said composition comprises 20 to 80 wt% total surfactant content comprising said lauroyl isethionate and soap.3) A personal cleansing composition as claimed in claim 1 or 2, wherein said ratio of water- soluble soap to the water-insoluble soap is 1 :0.6 to 1 :1 .4 parts by weight.4) A personal cleansing composition as claimed in any of claims 1 to 3, wherein said composition comprises sodium cococyl isethionate.5) A personal cleansing composition as claimed in any of claims 1 to 4, wherein solubility of said water-soluble soap is equal to or greater than that of 82 / 18 tallow / coconut soap, whose solubility is 1 .1 g / litre at 40°C.6) A personal cleansing composition as claimed in claim 5, wherein said water-soluble soap is an alkali metal salt of C8 to C24 fatty acids.7) A personal cleansing composition as claimed in any of claims 1 to 6, wherein solubility of said water-insoluble soap is less than 1.1 g / litre at 40°C.8) A personal cleansing composition as claimed in claim 7, wherein said water-insoluble soap is an alkaline earth metal salt of C8 to C24 fatty acids.9) A personal cleansing composition as claimed in any of claims 1 to 8, wherein said composition is aqueous and the total surfactant content is 10 to 25 wt%.10) A personal cleansing composition as claimed in any of claims 1 to 8, wherein said composition is non-aqueous and the total surfactant content is 20 to 80 wt%.11) A personal cleansing composition as claimed in claim 10, wherein said composition is in the form of a bar and comprises 5 to 25 wt% free fatty acids.12) A personal cleansing composition as claimed in claim 11 , wherein said composition comprises 5 to 30 wt% filler.13) A personal cleansing composition as claimed in any of claims 1 to 12, wherein pH of said composition is 6 to 8.14) A method of cleansing skin comprising the steps of: i) applying to a part of the body a personal cleansing composition as claimed in claim 1 ; and, ii) rinsing the part of the body with water.

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