WO2024041888A1

WO2024041888A1 - A skin cleansing composition

Info

Publication number: WO2024041888A1
Application number: PCT/EP2023/072023
Authority: WO
Inventors: Vidula Iyer; Joseph Martin JANKOLOVITS; Rajkumar PERUMAL; Siva Rama Krishna PERALA; Maya Treesa Saji; Connor Patrick WALSH
Original assignee: Unilever Ip Holdings B.V.; Unilever Global Ip Limited; Conopco, Inc., D/B/A Unilever
Priority date: 2022-08-23
Filing date: 2023-08-09
Publication date: 2024-02-29

Abstract

The present invention relates to a skin cleansing composition, particularly a skin cleansing composition that provides improved antimicrobial benefit. The skin cleansing composition comprises a surfactant, preferably a soap and an adduct of an amine or a diamine and an acid; and pH in the range 4.0 to 10.5, wherein said acid is a mono or di carboxylic acid.

Description

A SKIN CLEANSING COMPOSITION

Field of the Invention

The present invention relates to a skin cleansing composition. Particularly, the present invention relates to a skin cleansing composition that provides improved antimicrobial benefit.

Background of the Invention

Microbes e.g. bacteria, tend to colonize on surfaces e.g. human skin. Some of these microbes may trigger harmful effects if they enter the human system e.g. through cuts in the skin and through the act of ingestion. Therefore, there is a general desire to maintain hygiene by getting rid of such harm causing microbes. For example, people tend to wash hands with a skin cleansing composition from time to time to help maintain hygiene.

Several skin cleansing compositions e.g. a handwash or a bodywash composition are known in the art that provide antimicrobial benefit. Such skin cleansing compositions are available in the form of a solid e.g. a bar such as soap bar; and in the form of a liquid e.g. a liquid handwash I bodywash composition. Generally, antimicrobial benefit delivered by such skin cleansing compositions is delivered by one or more actives that may be present in such skin cleansing compositions. For example, skin cleansing composition comprising an antibacterial active e.g. triclosan, is known in the art.

Despite the existence of antimicrobial skin cleansing compositions, people tend to look forward to newer technologies that provide improved benefits e.g. improved antimicrobial benefit like delivering the benefit in very short time frames of less than 5 minutes, preferably less than 3 minutes, more preferably less than 1 minute and ideally within 10 to 30 seconds. Another improved benefit is in killing both gram negative bacteria like E. coli and gram positive bacteria like S. aureus. Skin cleansing compositions that provide improved antimicrobial benefit is therefore still a topic of interest.

It has now been found that a skin cleansing composition comprising a surfactant, preferably a soap, and an adduct of select amines or diamines formed with an acid having pH in select range, provides improved antimicrobial benefit.

It is an object of the present invention to provide for a skin cleansing composition that delivers antimicrobial kill in very short time frames. It is yet another object of the present invention to provide for a skin cleansing composition that kills both gram negative as well as gram positive bacteria.

Summary of the Invention

In a first aspect, the present invention relates to a skin cleansing composition comprising: i. from 1 to 85 wt% surfactant; and ii. from 0.1 to 15 wt% adduct of an amine or a diamine and an acid, iii. a pH adjuster; wherein the pH of the composition is from 4.0 to 10.5; wherein said acid is a mono or di carboxylic acid.

In a second aspect, the present invention relates to a method of providing antimicrobial effect comprising the steps: a. applying to a surface the composition of the first aspect; and b. rinsing the surface within 5 minutes of carrying out step a.

In a third aspect, the present invention relates to use of an adduct of an amine or a diamine and an acid in a composition having pH from 4.0 to 10.5 comprising a surfactant, wherein said acid is a mono or di carboxylic acid, for providing an antimicrobial effect.

Detailed Description of the Invention

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. For the purpose of the present invention, the terms ‘antimicrobial benefit’ or ‘antimicrobial effect’ or ‘antimicrobial efficacy’, may be used interchangeably and they denote the same meaning. Preferably, ‘antimicrobial benefit’ or ‘antimicrobial effect’ or ‘antimicrobial efficacy’ means reduction in number of microbes e.g. bacteria, fungi and viruses. Such antimicrobial effect is obtained when the composition of the present invention is preferably applied on to a surface that may be an inanimate or animate surface; and a step of rinsing the surface is carried out within 5 minutes from the step of applying the composition. More preferably, the composition is applied to an animate substrate e.g. human skin. ‘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.

In a first aspect, the present invention relates to a skin cleansing composition according to the present invention (the composition) that comprises: i. from 1 to 85 wt% surfactant; and ii. from 0.1 to 15 wt% adduct of an amine or a diamine and an acid, and iii. a pH adjuster wherein the pH of the composition is from 4.0 to 10.5 wherein said acid is a mono or di carboxylic acid.

When used on a surface, an animate or an inanimate surface, preferably animate surface, the composition provides antimicrobial effect. Preferably, the antimicrobial effect is obtained in time frames as short as less than 5 minutes, e.g. 1 minute, 30 seconds and 15 seconds.

Adduct of an amine or a diamine and an acid

The composition comprises an adduct of an amine or a diamine and an acid, i.e. it comprises an adduct of an amine formed with an acid; or an adduct of a diamine formed with an acid. An adduct of an amine and an acid is a preferred adduct.

Preferably, the amine is selected from alkyl substituted primary or secondary or tertiary amine wherein the alkyl group is straight or branched group formed of 2 to 8 carbon atoms and contains a hydroxy (-OH) substitution. Example of alkyl substituted primary or secondary or tertiary amine wherein the alkyl group is straight or branched group formed of 2 to 8 carbon atoms and contains a hydroxy (-OH) substitution, that may be used as the amine include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), monoisopropanolamine (MIPA), diisopropanolamine (DIPA), triisopropanolamine (TIPA) and mixtures thereof. Preferably, MEA, DEA and mixtures thereof are used as the amine.

Preferably, the diamine is selected from: acyl (R-C=O) substituted diamine wherein R is an alkyl group of 1 to 8, preferably 1 to 4, linear or branched carbon atoms, an alkylene diamine wherein the alkylene group is formed of 2 to 8, preferably 2 to 4, linear or branched carbon atoms; and mixtures thereof.

Examples of the acyl substituted diamine include tetraacetyl ethylenediaimne, diacetyl ethylenediamine and mixtures thereof. Examples of alkylene diamine wherein the alkylene group is formed of 2 to 8 carbon atoms that may be used as the amine include ethylene diamine, propylene diamine, butylene diamine and mixtures thereof.

Preferably, amine or diamine so selected is a non-volatile amine.

Preferably, the acid is selected from carboxylic acids having pKa in the range from 2.5 to 5.5. The acid is preferably a mono or dicarboxylic acid. Further more preferably, the acid is selected from acetic acid (AA), glycolic acid, tartaric acid, salicylic acid, benzoic acid and mixtures thereof; and still more preferably, the acid is selected from acetic acid, glycolic acid and mixtures thereof.

An example of the adduct so formed includes an adduct formed of an amine e.g. monoethanolamine and an acid e.g. acetic acid, MEA-AA. Likewise, another examples of such adduct is diethanolamine salt of acetic acid (DEA-AA) and triethanolamine salt of acetic acid (TEA-AA). The adduct so formed is found to provide antimicrobial effect.

The composition comprises from 0.1 to 15 wt%, preferably from 0.5 to 13 wt%, more preferably from 1 to 11 wt%, even more preferably from 2 to 10 wt%, further more preferably from 3 to 7 wt% and still more preferably from 4 to 6 wt% adduct of an amine or a diamine and an acid. pH adjuster:

The composition of the invention includes a pH adjuster which is a water-soluble compound that adjusts the pH of the composition to the desired range. pH adjuster which may be used are selected from one or more of sodium bicarbonate, potassium bicarbonate, sodium bisulphate, potassium bisulphate, lactic acid, tartaric acid, citric acid, or dilute solution of mineral acids like hydrochloric acid or sulphuric acid. The pH adjuster is generally added to the composition to bring it to a pH less than 10.5 preferably less than 10.3. In the case where the composition is a soap bar, the pH adjuster is added to the soap composition prior to addition of the adduct.

Surfactant

The composition comprises surfactant. Preferably, the surfactant is selected from an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant and mixtures thereof. More preferably, the surfactant is selected from an anionic surfactant, an amphoteric surfactant and mixtures thereof.

Anionic surfactant

Preferably, an anionic surfactant is selected from a synthetic anionic surfactant, soap and mixtures thereof. More preferably, an anionic surfactant is soap.

Preferably, a synthetic anionic surfactant is selected from alkyl sulfate (AS), alkyl ether sulfate (AES), alpha olefin sulfonate (AOS) and mixtures thereof. Examples of AS that may be used as anionic surfactant in the composition include sodium lauryl sulfate (SLS), sodium myristyl sulfate, sodium palmityl sulfate and mixtures thereof. Examples of AES that may be used as an anionic surfactant include anionic surfactants of the general formula:

Ri-(OR’)_n-O-SO3' M⁺, wherein:

Ri is saturated or unsaturated Cs-Ci6, preferably C12-C14 alkyl chain; preferably, R1 is a saturated Cs-Ci6, more preferably a saturated C12-C14 alkyl chain;

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 and further more preferably from 1 to 3,

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

Examples of AES that may be used as anionic surfactant in the composition 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.

More preferably, soap is used as the anionic surfactant in the composition. Preferably, soap so used is formed of fatty acids having carbon chain length from 8 to 18, more preferably from 12 to 16. Preferably, sodium or potassium salts of fatty acids having carbon chain length from 8 to 18 e.g. lauric acid, myristic acid, palmitic acid and oleic acid, either alone or as a mixture, may be used as anionic surfactant. For example, sodium laurate, sodium myristate, sodium palmitate, sodium oleate, potassium laurate, potassium myristate, potassium palmitate, potassium oleate and mixtures thereof may be used as an anionic surfactant.

Nonionic surfactant

Preferably, nonionic surfactant may be selected from: fatty alcohol ethoxylates with saturated carbon chain and having HLB higher than 15.5 e.g. Brij® 35 (also known as Brij® L23), fatty alcohol ethoxylates with unsaturated carbon chain with HLB higher than 12, e.g. Brij® 97 and Brij® 99, alkyl phenol ethoxylates having HLB higher than 15; e.g. Triton™ X 405, polyoxyethylene sorbitan alkyl esters with saturated C12 to C16 carbon chain and having HLB higher than 12; e.g. Tween® 20, polyoxyethylene sorbitan alkyl esters with unsaturated C18 carbon chain and having HLB higher than 9; e.g. Tween® 80, Tween® 81 ; and Tween® 85; and mixtures thereof.

Amphoteric surfactant

Amphoteric surfactants provide improved foam when added in the composition. Preferably, amphoteric surfactants are selected from cocamidopropyl betaine (CAPB), cocamide monoethanolamide (CMEA), cocoamphoacetate and mixtures thereof.

Cationic surfactant

Preferably, cationic surfactants may be selected from cetyltrimethylammonium chloride, behenyltrimethylammonium chloride, cetylpyridinium chloride, tetramethylammonium chloride, tetraethylammonium chloride, octyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octyldimethylbenzylammonium chloride, decyldimethylbenzylammonium chloride, stearyldimethylbenzylammonium chloride, didodecyldimethylammonium chloride, dioctadecyldimethylammonium chloride, tallowtrimethylammonium chloride, dihydrogenated tallow dimethyl ammonium chloride (eg, Arquad 2HT/75 from Akzo Nobel), cocotrimethylammonium chloride, PEG-2-oleammonium chloride and the corresponding hydroxides thereof. Further suitable cationic surfactants include those materials having the CTFA designations Quaternium-5, Quaternium-31 and Quaternium- 18. Mixtures of any of the foregoing materials may also be suitable. A particularly useful cationic surfactant is cetyltrimethylammonium chloride, available commercially, for example as GENAMIN® CTAC. Another particularly useful cationic surfactant is behenyltrimethylammonium chloride, available commercially, for example as GENAMIN® KDMP. Yet another preferred cationic surfactant is stearamidopropyl dimethylamine.

The composition comprises from 1 to 85 wt% surfactant, preferably from 5 to 80 wt%, more preferably from 10 to 75 wt%, even more preferably from 15 to 70 wt%, yet more preferably from 25 to 66 wt%, still more preferably from 35 to 60 wt% and still further more preferably from 40 to 55 wt% surfactant.

£H

The pH of the composition is in the range from 4.0 to 10.5, preferably from 4.5 to 10.3, even more preferably from 5.0 to 10.1, further more preferably from 5.5 to 10.0, still more preferably from 6.5 to 10.0 and yet more preferably from 8.0 to 10.0. For example, pH of the composition is most preferably 7.0 or 7.5. Alternatively, the pH of the composition may be 9.5. The pH of the composition may be adjusted using suitable pH adjusting agents e.g. sodium hydroxide and sodium bicarbonate.

If the composition is in liquid form, then preferably, pH of the composition is in the range 4.0 to 10.5 when measured before dilution or preferably after diluting the composition to 50% concentration, at 25 to 35°C.

If the composition is in solid form, then preferably, pH of the composition is in the range from 4.0 to 10.5 when measured using 1 to 8% e.g. 8%, aqueous solution of the composition in demineralized water, at temperature 25 to 35°C.

Format of the composition

Preferably, the composition is in liquid form or in solid form. More preferably, the composition is in solid form e.g. a bar. Even more preferably, the composition is in the form of a soap bar.

Accordingly, the composition is preferably a liquid skin cleansing composition comprising: i. from 1 to 85 wt% surfactant; and ii. from 0.1 to 15 wt% adduct of an amine or a diamine and an acid, wherein the pH of the composition is from 4.0 to 10.5, preferably from 4.0 to 7.5; wherein said acid is a mono or di carboxylic acid

Alternatively but preferably, the composition is a solid skin cleansing composition comprising: i. from 1 to 85 wt% surfactant; and ii. from 0.1 to 15 wt% adduct of an amine or a diamine and an acid, wherein the pH of the composition is from 4.0 to 10.5, preferably from 8.0 to 10.1 ; wherein said acid is a mono or di carboxylic acid.

More preferably, the composition is a soap bar composition comprising: i. from 40 to 85 wt% soap, ii. from 0.1 to 15 wt% adduct of an amine or a diamine and an acid, wherein the pH of the composition is from 4.0 to 10.5, preferably from 8.5 to 10.1 ; wherein said acid is a mono or di carboxylic acid

Structurants

Preferably, the composition comprises a structurant. Preferably, a structurant is selected from silica, talc, calcite, pumice, tricalcium phosphate, chalk, fullers earth, kaolin, starch, gums, colloidal silica, sodium polyacrylate, tetra alkyl and/or trialkyl aryl ammonium smectites, chemically modified magnesium aluminium silicate, organically modified montmorillonite clay, hydrated aluminium silicate, fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose, ethylene glycol monostearate and mixtures thereof.

Talc is a magnesium silicate mineral material, with a sheet silicate structure and a composition of MgaSi4(OH)22 and may be available in the hydrated form. It has a plate-like morphology, and is essentially oleophilic/hydrophobic, i.e., it is wetted by oil rather than water.

Starch may be used directly or modified during the process of making the bar composition such that the starch becomes gelatinized, either partially or fully gelatinized. Another suitable starch is pre-gelatinized which is starch that has been gelatinized before it is added as an ingredient in the present bar compositions. Various forms are available that will gel at different temperatures, e.g., cold water dispersible starch. An example of pre-gelatinized starch available commercially, is FARMAL® CS 3400.

Preferably the composition comprises structurants in an amount ranging from 1 to 50 wt%, more preferably from 3 to 45 wt%, even more preferably from 10 to 30 wt and further more preferably from 15 to 25 wt%.

Preferably, the composition further comprises water soluble polymers. Preferably, such polymers are selected from polyvinyl alcohol, polyvinyl pyrrolidone, sodium carboxymethylcellulose, polyethylene glycol, methyl cellulose, hydroxypropyl methyl cellulose and mixtures thereof. Preferably, the composition comprises from 1 to 20 wt%, more preferably from 3 to 17 wt%, even more preferably from 5 to 15 wt%, further more preferably from 7 to 13 wt% and still more preferably from 9 to 12 wt% water soluble polymer.

Such polymer may be added in the composition mix or may be used to coat the composition. For example, if the composition is in the form of a bar or a tablet, such polymers may form an outer water-soluble coating on such bars or tablets.

If the composition is formulated in the form of a bar, then it preferably comprises a polyhydric alcohol (also called polyol) or mixture of polyols. Polyol is a term used herein to designate a compound having multiple hydroxyl groups (at least two, preferably at least three) which is highly water soluble, preferably freely soluble, in water. Many types of polyols are available including relatively low molecular weight short chain polyhydroxy compounds such as glycerol and propylene glycol; sugars such as sorbitol, manitol, sucrose and glucose; modified carbohydrates such as hydrolyzed starch, dextrin and maltodextrin, and polymeric synthetic polyols such as polyalkylene glycols, for example polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG). Especially preferred polyols are glycerol, sorbitol and their mixtures. Most preferred polyol is glycerol. If the composition is formulated as a bar then preferably it comprises from 0 to 8 wt%, more preferably from 1 to 7.5 wt%, even more preferably from 2 to 5 wt% polyol.

Preferably, the composition further comprises an opacifier. Examples of opacifiers include titanium dioxide, zinc oxide and the like. An alternative opacifying agent is zinc stearate.

A preferred bar may additionally include up to 30 wt% benefit agents. Preferred benefit agents include moisturizers, emollients, sunscreens and anti-ageing compounds. These agents may be added at an appropriate step during the process of making the composition.

The composition may further comprise one or more of the following ingredients:

The composition may preferably further comprise a skin-lightening agent selected from ammonium lactate, arbutin, azelaic acid, kojic acid, butyl hydroxy anisole, butyl hydroxy toluene, citrate esters, 3 diphenyl propane derivatives, ellagic acid, gluco pyranosyl-1 -ascorbate, gluconic acid, glycolic acid, hydroquinone, 4 hydroxyanisole, linoleic acid, magnesium ascorbyl phosphate, 2,4 resorcinol derivatives, 3,5 resorcinol derivatives, vitamins like vitamin B6, vitamin B12, vitamin C, vitamin A, resorcinol derivatives and mixtures thereof. If the composition is formulated in the form of solid e.g. a bar such as soap bar, then it preferably comprises water in an amount from 10 to 20 wt%, more preferably from 14 to 18 wt%. Alternatively, if the composition is formulated in the form of a liquid, then the composition preferably comprises from 40 to 90 wt% water, more preferably 60 to 85 wt% water.

The composition may preferably further comprise 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 and benzyl alcohol. Preservatives are preferably used in amounts ranging from 0.01 wt% to 2 wt%.

Diluents other than water can include liquid or solid emollients, solvents, humectants, thickeners and powders. Examples of each of these types of vehicles which can be used singly or as mixtures of one or more vehicles, are as follows:

Emollients, such as stearyl alcohol, glyceryl monoricinoleate, mink oil, cetyl alcohol, isopropyl isostearate, stearic acid, 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, isostearic acid, palmitic acid, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate, myristyl myristate.

Further, the composition preferably comprises other optional ingredients like anti-oxidants, perfumes, polymers, chelating agents, colourants, deodorants, dyes, emollients, moisturizers, enzymes, foam boosters, lathering agents, skin conditioners, pH adjusters and stabilizers may be added in suitable amounts. Preferably, these ingredients are added after the saponification step. Sodium metabisulphite, ethylene diamine tetra acetic acid (EDTA), borax or ethylene hydroxy diphosphonic acid (EHDP) are preferably added to the formulation. Such ingredients may be present in an amount from 0 to 7 wt%, more preferably from 1 to 5 wt% and even more preferably from 2 to 4 wt% in the composition. In a second aspect, the present invention relates to a method of providing antimicrobial benefit comprising the steps: a. applying to a surface the composition according to the first aspect; and b. rinsing the surface within 5 minutes of carrying out the step a.

Step a involves applying the composition of the first aspect on to a surface. The surface is preferably an inanimate or animate surface. More preferably, the surface is an animate surface e.g. human skin. ‘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. Step a is preferably carried out where a user applies the composition of the first aspect, on to a surface along with water in an amount sufficient to create lather.

The method comprises an additional step, step b, where the surface on to which the composition was applied, is rinsed with water to remove the composition from the surface. Preferably, step (b) is carried out within less than 5 minutes, more preferably within less than 3 minutes, even more preferably within less than 1 minute and furthermore preferably within less than 35 seconds e.g. 10 to 30 seconds, after step a. When the method is carried out as described in the second aspect, antimicrobial benefit is obtained, i.e. microbes e.g. bacteria, are reduced from the surface on to which the composition was so applied. Preferably, the method is non-therapeutic and/or cosmetic in nature.

In a third aspect, the present invention relates to use of an adduct of an amine or a diamine and an acid in a composition comprising a surfactant; and pH in the range from 4.0 to 10.5, for providing antimicrobial effect.

For example, in this third aspect, the present invention relates to use of MEA-AA or DEA-AA or TEA-AA in a composition comprising a surfactant and pH in the range 4.0 to 10.5 for providing antimicrobial effect. Preferably, the use is non-therapeutic and/or cosmetic in nature.

In another aspect, the present invention relates to a process of manufacturing a skin cleansing composition according to the present invention. Preferably, the composition in the form of a solid e.g. soap bar, may be prepared using the process described below:

Adduct formation:

An adduct is a product of addition reaction. The adduct in the present invention is preferably prepared by the following process. The amine is taken in a flask equipped with a magnetic bead, a reflux condenser and dropping funnel. The acid is then added drop wise to the amine solution over a period of about one hour under vigorous mixing condition. This is then continuously mixed for an additional about 8 hours to complete the reaction. Alternately, a 50% amine solution is taken in water in a flask and 50% acid solution is added in portions over about an hour which is then mixed for a further about 8 hours. The reaction mixture as such or after extraction with organic solvent is then used in making the composition as per the invention.

Soap formation:

Preferably, soap noodles are made using oils e.g. palm oil (PO) and palm kernel oil (PKO) in required ratio, e.g. 80:20 (PO:PKO), through saponification reaction with water, glycerin, electrolyte e.g. sodium chloride, sodium sulphate, sodium citrate, sodium silicate, preservative like EDTA, EHDP and/or fillers. Alternatively, soap noodles may be made using the oils in ratio such as 70:30, 85:15, 90:10 (PO:PKO). The saponification may be done either through Crutcher or continuous saponification tank or plough shear mixer route followed by cooling the end mass in temperature range 30 to 45°C and extruded into soap noodles. Preferably, soap noodles so made have PKO value e.g. 10, 20, 25, 30 and 40; with an IV (Iodine value) in the range 30 to 45. Thereafter, the soap noodles are crushed in sigma mixer for up to 5 minutes. After complete crushing of the noodles, solid ingredients such soda ash and talc are added and mixed for up to 5 minutes. A required amount of a pH adjusting agent e.g. sodium bicarbonate, is then added as necessary mixed for up to 3 minutes followed by addition of polymer and colorants, if required, and mixed for up to 3 minutes. Alternatively, colorants may be added during crushing of noodles. Preferably, the adduct of the invention, i.e. an adduct of an amine formed with an acid or an adduct of a diamine formed with an acid (as described above in the first aspect) is prepared separately. After colorants mixing, the pre-formed adduct of the present invention, e.g. MEA-AA, DEA-AA, TEA-AA, is added and mixed for up to 3 minutes. Perfume is added as the last step followed by mixing for up to 3 min. Post this mixing, the mass is processed through suitable means e.g. triple roll mill and is plodded through a plodder to get the final soap bar and stamped, as necessary. Preferably, the pH of the mass before addition of the adduct was maintained in the range 9.5 to 10.6.

The invention is now described further with reference to the following non-limiting examples: Examples:

Skin cleansing compositions in the form of soap bars (shown in table 2) were prepared as follows:

Soap noodles were made using oils e.g. palm oil (PO) and palm kernel oil (PKO) in ratio 80:20 (PO:PKO), through saponification reaction and was processed into noodles with water, glycerin, electrolyte such as sodium chloride, preservative like EDTA, EHDP and/or fillers. The saponification was done through either plough shear mixer route. The end mass was cooled to about 40°C and extruded into soap noodles. Thereafter, the soap noodles were crushed in sigma mixer for up to 5 minutes. After complete crushing of the noodles, solid ingredients such soda ash and talc were added and mixed. A required amount of a pH adjusting agent e.g. sodium bicarbonate, was added as necessary and was mixed for up to 3 minutes followed by addition of polymer and colorants, if required, and mixed for up to 3 minutes. After mixing the colorants, a pre-formed adduct of monoethanolamine and acetic acid (MEA-AA), i.e. monoethanolamine acetate, was added and further mixed for up to 3 minutes. The pH of the mass was maintained in the range 9.5 to 10.8 before addition of the pre-formed adduct. Lastly, perfume was added and mixing was carried out for up to 3 min. Post this mixing, the mass was processed through triple roll mill and was plodded through a plodder to get the final bar and stamped, as necessary.

Antimicrobial Effect:

The antimicrobial effect was assessed for compositions outlined in table 2 below using the ASTM 2783, a standard test method for assessment of antimicrobial activity for water miscible compounds using a Time -Kill procedure. Escherichia coli (ATCC 10536) and Staphylococcus aureus (ATCC 6538) were used as the test organisms.

Preparation of working culture of the test organisms: Approximately 48 hours prior to testing, a sterile tube of Tryptic Soy Broth (TSB) was inoculated from a glycerol stock containing the challenge (test) microorganism. The broth culture was incubated at 35 ± 2°C for 24 hours. Approximately 24 hours prior to testing, the broth culture was inoculated onto the surface of sterile Tryptic Soy Agar (TSA) & incubated at 35 ± 2°C for approximately 24 hours.

Bacterial Challenge Test Suspensions and Validation test Suspension (To be prepared just before use): A suspension of the challenge microorganism was prepared in sterile 0.9% saline and adjusting the optical density at 620 nm to achieve a challenge suspension concentration of approximately 7 x 10⁸ cfu/mL to 9 x 10⁸ cfu/mL. A challenge suspension was prepared for each replicate of testing. Each challenge suspension was used within 2 hours of preparation and kept at 25 ± 1°C. A neutralization challenge test suspension containing approximately 3000-10000 cfu/mL was prepared in sterile saline by diluting the challenge microorganism.

Preparation of 8% soap slurry:

Soap bar samples were finely grated and weighed 8 g into a sterile bottle. 92 mL of sterile distilled water (DW) was pre warmed at 50 ± 1°C and added 8 g of above soap sample and mixed using submersible magnetic stirrer and kept for 25 to 30 minutes to make an 8% soap slurry. After 25 to 30 minutes, 10 mL sample aliquot was transferred to a vial placed at 40 ± 1 °C and kept for 3 to 5 minutes for equilibration and mixed using submersible magnetic stirrer.

Evaluation of bacterial reduction efficacy:

10 mL of test solution was placed in a vial and kept in water bath maintained at test temperature for 3 to 5 minutes to equilibrate. A 0.1 mL aliquot of the challenge suspension was transferred to the vial containing test solution and mixed thoroughly using submersible magnetic stirrer. The challenge suspension was exposed to the test solution for required contact time e.g. less 5 minutes e.g. 30 seconds, using a calibrated minute and second timer. Upon elapse of contact time, 1 mL aliquot was transferred from the vial containing the test solution/challenge suspension to a test tube containing 9.0 mL of pre-validated neutralizer and mixed thoroughly using a vortex mixer. Additional ten-fold dilutions were prepared by transferring 1 mL aliquots into 9 mL of neutralizer (1 O’², 10’³, 10'⁴ and 10'⁵). 1.0 mL aliquots of each dilution from 10'¹ to10^-5 were plated using TSA in duplicate using pour plate technique. The plates were incubated as per given incubation conditions.

The log reduction for each challenge suspension attributable to the test solution at each timed exposure is calculated for each replicate as follows:

Log Reduction = Log average (NC) - Logwaverage (Pex), where NC = Number Control cfu/mL Population and Pex= Post exposure population cfu/mL Table 1 : Noodle Composition

Soap noodles shown in table 1 above were used to prepare final soap bars (as shown in table 2 below) using the process as described hereinabove.

Table 2: Soap bar compositions

*Polymer, colorant and fragrance

The data in Table - 2 indicates that compositions as per the invention (Examples 1 - 4) deliver better antimicrobial efficacy as compared to those outside the invention (Examples B- F).

Example A includes acetic acid and delivers good antimicrobial efficacy but is found wanting in a pleasant odour that is necessary in a consumer product like a soap bar. Acetic acid and strong inorganic acids suffer from this sensorial problem. This problem has therefore been overcome (in addition to enhanced antimicrobial efficacy) by using the adduct claimed in the present invention.

Claims

1. A skin cleansing composition comprising: i. from 1 to 85 wt% surfactant; and ii. from 0.1 to 15 wt% adduct of an amine or a diamine and an acid, and iii. a pH adjuster; wherein the pH of the composition is from 4.0 to 10.5. wherein said acid is a mono or di carboxylic acid.

2. The composition as claimed in claim 1 wherein the adduct is an adduct of an amine and an acid.

3. The composition as claimed in claims 1 or 2 wherein the amine is selected from alkyl substituted primary or secondary or tertiary amine wherein the alkyl group is straight or branched group formed of 2 to 8 carbon atoms and contains a hydroxy (-OH) substitution.

4. The composition as claimed in claim 3 wherein the amine is selected from monoethanolamie, diethanolamine, triethanolamine, monoisopropanolamine, diisopraponolamine, triisopropanolamine and mixtures thereof.

5. The composition as claimed in claim 4 wherein the amine is selected from monoethanolamine, diethanolamine and mixtures thereof.

6. The composition as claimed in claim 1 wherein the diamine is selected from: i. acyl (R-C=O) substituted diamine wherein R is an alkyl group of 1 to 8 linear or branched carbon atoms; and ii. alkylene diamine wherein the alkylene group is formed of 2 to 8 linear or branched carbon atoms; and mixtures thereof.

7. The composition as claimed in any one of claims 1 to 6 wherein the acid is selected from carboxylic acids having pKa in the range from 2.5 to 5.5.

8. The composition as claimed in claim 7 wherein the acid is selected from acetic acid, , glycolic acid, tartaric acid, salicylic acid, benzoic acid and mixtures thereof.

9. The composition as claimed in claim 8 wherein the acid is selected from acetic acid, glycolic acid and mixtures thereof. The composition as claimed in any one of the preceding claims wherein the pH adjuster is selected from sodium bicarbonate, potassium bicarbonate, lactic acid, tartaric acid, or citric acid. The composition as claimed any one of preceding claims 1 to 10 wherein the surfactant is soap formed of fatty acids having carbon chain length from 8 to 18, preferably from 12 to 16. The composition as claimed in any one of claims 1 to 11 wherein the pH of the composition is in the range from 8.0 to 10.1. The composition as claimed in any one of claims 1 to 12 wherein the composition is in solid form. A method of providing antimicrobial effect comprising the steps: i. applying to a surface the composition as claimed in any one of claims 1 to 13; and ii. rinsing the surface within 5 minutes of carrying out step a. Use of an adduct of an amine or a diamine and an acid wherein said acid is a mono or di carboxylic acid, in a skin cleansing composition having pH from 4.0 to 10.5 comprising a surfactant, for providing an antimicrobial effect.