WO2016131627A1

WO2016131627A1 - Personal cleansing composition

Info

Publication number: WO2016131627A1
Application number: PCT/EP2016/051767
Authority: WO
Inventors: Ningning LI; Joseph Muscat; Neil Scott Shaw; Sally Elizabeth WOOD
Original assignee: Unilever NV; Conopco Inc
Current assignee: Unilever NV; Conopco Inc
Priority date: 2015-02-18
Filing date: 2016-01-28
Publication date: 2016-08-25
Anticipated expiration: 2017-08-18

Abstract

The invention provides a personal cleansing composition with pH 2 to 6, comprising: (a) an aqueous continuous phase including at least one cleansing surfactant selected from alkyl ether sulfates; (b) dispersed particles of emulsified silicone, and (c) from 0.5 to 1.1% (by weight based on the total weight of the composition), of stearic acid (C18:0).

Description

PERSONAL CLEANSING COMPOSITION

Field of the Invention The present invention relates to personal cleansing compositions such as liquid soaps, body washes and shampoos.

Background and Prior Art Acyl isethionates are noted for their creamy lather, excellent skin compatibility, mildness, and beneficial emollient properties in personal cleansing formulations. However, they are prone to hydrolysis and instability in an acid medium. This represents a potential problem for the formulator. A mildly acidic pH is often desirable in shampoos for reasons such as reduced hair fibre swelling, improved hair lustre, better compatibility with acidic skin or hair care actives in the formulation and optimized efficacy of certain organic preservative systems.

The present invention addresses this problem. Compositions of the invention also provide superior conditioning benefits on wet hair.

Summary of the Invention

The present invention provides a personal cleansing composition with pH 2 to 6, comprising:

(a) an aqueous continuous phase including at least one cleansing surfactant selected from alkyl ether sulfates;

(b) dispersed particles of emulsified silicone, and

(c) from 0.5 to 1 .1 % (by weight based on the total weight of the composition),

of stearic acid (C18:0).

Detailed Description and Preferred Embodiments The composition of the invention has a pH in the range of 2 to 6, preferably from 3 to 5.5, more preferably from 3.5 to 4.5, most preferably from 3.8 to 4.2 and ideally around 4.0. The compositions may be adjusted to this pH range with an acidifying or pH control agent. Suitable agents include citric acid, boric acid, phosphoric acid, ascorbic acid and mixtures thereof. Citric acid is preferred. These materials tend to have a buffering effect within the desired pH range when used in combination with the alkyl ether sulfate cleansing surfactant. In each case the proper buffering capacity is obtained by adjusting the final pH of the composition to within the desired range, using a strong acid or a strong base (e.g. HCI or NaOH) as may be needed.

The amount of acidifying or pH control agent employed in the composition depends on the particular material chosen but is generally from about 0.3% to about 6%, preferably from about 1 % to about 5% (by weight based on the total weight of the composition). The composition of the invention comprises an aqueous continuous phase. By "aqueous continuous phase" is meant a continuous phase which has water as its basis.

Suitably, the composition of the invention will comprise from about 50 to about 90%, preferably from about 55 to about 85%, more preferably from about 60 to about 85%, most preferably from about 65 to about 83% water (by weight based on the total weight of the composition).

The at least one cleansing surfactant included in aqueous continuous phase (a) is preferably selected from alkyl ether sulfates of general formula:

R-0-(CH₂CH2-0)n-S0₃-M⁺

in which R is a straight or branched chain alkyl group having 8 to 14, preferably 10 to 12 carbon atoms, n is a number that represents the average degree of ethoxylation and ranges from 1 to 5, preferably from 2 to 3.5, and M is a alkali metal, ammonium or alkanolammonium cation, preferably sodium, potassium, monoethanolammonium or triethanolammonium, or a mixture thereof. Specific examples of such preferred cleansing surfactants include the sodium, potassium, ammonium or ethanolamine salts of Cio to C12 alkyl ether sulfates (for example sodium lauryl ether sulfate). Mixtures of any of the above described materials may also be used.

In a typical composition according to the invention the level of cleansing surfactant will generally range from 5 to 26% (by weight based on the total weight of the composition). The dispersed particles of emulsified silicone (b) in the composition of the invention are typically emulsified droplets having a mean droplet diameter (D3,2) of 4 micrometres or less. Preferably the mean droplet diameter (D3,2) is 1 micrometre or less, more preferably 0.5 micrometre or less, and most preferably 0.25 micrometre or less. A suitable method for measuring the mean droplet diameter (D3,2) is by laser light scattering using an instrument such as a Malvern Mastersizer.

Preferably the silicone is non-volatile, meaning that it has a vapour pressure of less than 1000 Pa at 25°C.

Suitable silicones for use in the invention include polydiorganosiloxanes, in particular polydimethylsiloxanes (dimethicones), polydimethyl siloxanes having hydroxyl end groups (dimethiconols), and amino-functional polydimethylsiloxanes (amodimethicones). Suitable silicones preferably have a molecular weight of greater than 100,000 and more preferably a molecular weight of greater than 250,000.

All molecular weights as used herein are weight average molecular weights, unless otherwise specified.

Suitable silicones preferably have a kinematic viscosity of greater than 50,000 cS (mm².s^" ¹) and more preferably a kinematic viscosity of greater than 500,000 cS (mm².s^"1). Silicone kinematic viscosities in the context of this invention are measured at 25°C and can be measured by means of a glass capillary viscometer as set out further in Dow Corning Corporate Test Method CTM004 July 20, 1970. Suitable silicones for use in compositions of the invention are available as pre-formed silicone emulsions from suppliers such as Dow Corning and GE Silicones. The use of such pre-formed silicone emulsions is preferred for ease of processing and control of silicone particle size. Such pre-formed silicone emulsions will typically additionally comprise a suitable emulsifier, and may be prepared by a chemical emulsification process such as emulsion polymerisation, or by mechanical emulsification using a high shear mixer. Pre-formed silicone emulsions having a mean droplet diameter (D3,2) of less than 0.15 micrometers are generally termed microemulsions.

Examples of suitable pre-formed silicone emulsions include emulsions DC2-1766, DC2- 1784, DC-1785, DC-1786, DC-1788, DC-1310, DC-7123 and microemulsions DC2-1865 and DC2-1870, all available from Dow Corning. These are all emulsions/microemulsions of dimethiconol. Also suitable are amodimethicone emulsions such as DC939 (from Dow Corning) and SME253 (from GE Silicones). Mixtures of any of the above described silicone emulsions may also be used.

The amount of silicone in compositions of the invention may suitably range from 0.05 to 10%, preferably from 0.2 to 8% (by total weight silicone based on the total weight of the composition).

Stearic acid (also termed n-octadecanoic acid, or C18:0) is usually obtained from natural animal or vegetable oils and fats such as cottonseed oil, coconut fat, cocoa butter, palm kernel oil, corn oil, castor oil, rapeseed oil, soybean oil, sunflower oil, beef tallow, lard and mixtures thereof. Commercial grades of stearic acid generally contain from about 39 to 95% by weight stearic acid, in admixture with varying relative concentrations of other fatty acids depending on the sources and processing methods used. The commercial grades of stearic acid which are most widely used in personal care are mixtures of stearic acid and palmitic acid which are obained by the saponification of tallow and separation of the solid fatty acid fraction. A "triple-pressed" material obtained in this way is typically a mixture comprising about 35 to 55% palmitic acid, 45 to 60% stearic acid and small amounts of myristic acid, pentadecanoic acid, heptadecanoic acid and oleic acid (by weight based on the total weight of the mixture).

Another commercial grade of stearic acid used in personal care is obtained by hardening, (i.e. by hydrogenation of the unsaturated fractions of tallow fatty acid). A material obtained in this way is typically a mixture comprising about 25 to 30% by weight palmitic acid, 60 to 65% by weight stearic acid and small amounts of myristic acid, pentadecanoic acid, heptadecanoic acid, oleic acid and arachic acid (by weight based on the total weight of the mixture).

A preferred source of stearic acid for use in the invention is a mixture comprising about 40 to 50% by weight palmitic acid, about 50 to 55% by weight stearic acid and about 1 to 3% by weight myristic acid (by weight based on the total weight of the mixture). A commercially available example is VSTEARIN™ SA1 1 Stearic Acid (ex Vantage

Oleochemicals). The content of stearic acid (C18:0) per se in the composition of the invention preferably ranges from 0.5 to 1 .0%, and is optimally around 0.8% (by weight based on the total weight of the composition).

A particularly preferred composition according to the invention comprises from 1.0 to 2.0% (by weight based on the total weight of the composition) of the mixture specified above which comprises about 40 to 50% by weight palmitic acid, about 50 to 55% by weight stearic acid and about 1 to 3% by weight myristic acid (by weight based on the total weight of the mixture).

The composition of the invention preferably includes one or more cationic polymers. Such polymers may enhance the delivery of conditioning agents and thereby improve the conditioning benefits obtained.

Cationic polymers typically contain cationic nitrogen-containing groups such as quaternary ammonium or protonated amino groups. The cationic protonated amines can be primary, secondary, or tertiary amines (preferably secondary or tertiary). The average molecular weight of the cationic polymer is preferably from 5,000 to 10 million. The cationic polymer preferably has a cationic charge density of from 0.2 meq/gm to 7 meq/gm. The term "cationic charge density" in the context of this invention refers to the ratio of the number of positive charges on a monomeric unit of which a polymer is comprised to the molecular weight of the monomeric unit. The charge density multiplied by the polymer molecular weight determines the number of positively charged sites on a given polymer chain.

The cationic nitrogen-containing moiety of the cationic polymer is generally present as a substituent on all, or more typically on some, of the repeat units thereof. The cationic polymer may be a homo-polymer or co-polymer of quaternary ammonium or cationic amine-substituted repeat units, optionally in combination with non-cationic repeat units. Particularly suitable cationic polymers for use in the invention include polysaccharide polymers, such as cationic cellulose derivatives, cationic starch derivatives, and cationic guar gum derivatives.

A particularly suitable type of cationic polysaccharide polymer that can be used is a cationic guar gum derivative, such as guar hydroxypropyltrimethylammonium chloride,

(commercially available from Rhodia® in their JAGUAR® trademark series). Examples of such materials are JAGUAR ® C13S, JAGUAR ® C14, JAGUAR® C15 and JAGUAR ® C17.

Mixtures of any of the above described cationic polymers may also be used.

When included, the total level of cationic polymer in the composition is preferably from 0.05% to 2% and more preferably from 0.1 to 0.5% by weight based on the total weight of the composition.

The composition of the invention preferably includes one or more amphoteric surfactants. Suitable amphoteric surfactants are betaines, such as those having the general formula R(CH3)2N⁺CH2COO^", where R is an alkyl or alkylamidoalkyl group, the alkyl group preferably having 10 to 16 carbon atoms. Particularly suitable betaines are oleyl betaine, caprylamidopropyl betaine, lauramidopropyl betaine, isostearylamidopropyl betaine, and cocoamidopropyl betaine. When included, the total level of amphoteric surfactant is generally from 0.1 % to 20%, preferably from 1 % to 10%, more preferably from 1 % to 5% by weight based on the total weight of the composition.

The composition of the invention preferably includes one or more suspending agents. Suitable suspending agents include polyacrylic acids, cross-linked polymers of acrylic acid, copolymers of acrylic acid with a hydrophobic monomer, copolymers of carboxylic acid-containing monomers and acrylic esters, cross-linked copolymers of acrylic acid and acrylate esters, heteropolysaccharide gums and crystalline long chain acyl derivatives. Mixtures of any of the above suspending agents may be used. Preferred is a mixture of cross-linked polymer of acrylic acid and crystalline long chain acyl derivative.

When included, the total level of suspending agent is generally 0.1 to 10%, preferably from 0.5 to 6%, more preferably from 0.9 to 4% by weight based on the total weight of the composition. The composition of the invention may also include one or more hydrocarbon oils to provide dry conditioning benefits to the hair. Suitable hydrocarbon oils in this context have a kinematic viscosity of 1 to 35 cS (mm2.s-1 ) at 40°C and a specific gravity of 0.76 to 0.87 at 25°C. Examples of such materials include saturated, non-polar straight or branched- chain aliphatic or alicyclic hydrocarbons having from about 10 to about 50 carbon atoms, and mixtures thereof. A preferred hydrocarbon oil in the context of the present invention is light mineral oil. Mineral oils are clear oily liquids obtained from petroleum oil, from which waxes have been removed, and the more volatile fractions removed by distillation. The fraction distilling between 250°C to 300°C is termed mineral oil, and it consists of a mixture of hydrocarbons, in which the number of carbon atoms per hydrocarbon molecule generally ranges from Cio to C₄₀.

The mineral oil may be characterised in terms of its viscosity, where light mineral oil is less viscous than heavy mineral oil. A suitable light mineral oil will generally have a kinematic viscosity of 3.9 to 5.0 cS (mm².s^"1) at 40°C and a specific gravity of 0.810 to 0.830 at 25°C. Such materials are commercially available under the brand name Lytol®.

When included, the level of hydrocarbon oil in compositions of the invention generally ranges from about 0.5 to about 1 .5%, preferably from about 0.8 to about 1.2% (by weight based on the total weight of the composition)

An inorganic electrolyte may be used in the composition of the invention to provide viscosity to the composition (which suitably ranges from 0.2 to 40 Pa.s, preferably from 2 to 20 Pa.s, when measured at 25°C and 20s^"1).

Suitable inorganic electrolytes include metal chlorides (such as sodium chloride, potassium chloride, calcium chloride, magnesium chloride, zinc chloride, ferric chloride and aluminium chloride) and metal sulfates (such as sodium sulfate and magnesium sulfate). Examples of preferred inorganic electrolytes for use in the invention include sodium chloride, potassium chloride, magnesium sulfate and mixtures thereof.

Mixtures of any of the above described materials may also be suitable.

When included, the level of inorganic electrolyte in compositions of the invention generally ranges from about 0.01 to about 5%, preferably from about 0.1 to about 2% (by total weight inorganic electrolyte based on the total weight of the composition). A composition of the invention may contain further optional ingredients to enhance performance and/or consumer acceptability. Examples of such ingredients include fragrance, dyes and pigments and preservatives or antimicrobials. Each of these ingredients will be present in an amount effective to accomplish its purpose. Generally these optional ingredients are included individually at a level of up to 5% by weight based on the total weight of the composition.

The composition of the invention is primarily intended for topical application to the body, preferably the hair and scalp. Most preferably the composition of the invention is topically applied to the hair and then massaged into the hair and scalp. The composition is then rinsed off the hair and scalp with water prior to drying the hair.

The invention will be further illustrated by the following, non-limiting Examples, in which all percentages quoted are by weight based on total weight unless otherwise stated. EXAMPLES

Hair cleansing shampoo formulations were prepared, having ingredients as shown in Table 1 below. Examples 1 and 2 represent formulations according to the invention. Examples A, B and C represent comparative examples (not according to the invention).

C⁾ VSTEARIN™ SA11 Stearic Acid (ex. Vantage Oleochemicals); a fatty acid blend with about 45% palmitic acid, 52% stearic acid and 2% myristic acid (by weight based on the total weight of the blend). The above formulations were made by preparing a premix of fatty acid in sufficient surfactant solution. The premix ingredients were heated to about 5°C above the melting point of the fatty acid and stirred. The premix was then allowed to cool down to ambient temperature (20°C) and mixed with the remaining ingredients to achieve a homogeneous product.

Evaluation

The formulations were evaluated as follows: 0.7g test formulation is applied to 7g of wet hair switches. The formulation is massaged on hair for 30 seconds followed by rinsing with warm water for 30 seconds. This treatment is repeated once.

12 panellists were recruited to evaluate the 'ease of fingersliding' and 'ease of combing' of the wet hair samples. The least performing hair is ranked with 1 point whilst the most performing hair is ranked 5 points. Each panel has to rank three times for one

formulation. The average scores of the formulations are given below

Comparison table of means

Test formulation

Attribute Example A Example B Example 1 Example 2 Example C

Finger slide 2.22 2.42 4.14 3.36 2.86

Ease of 2.69 2.42 4.1 1 3.25 2.53 comb An R-index analysis shows that Examples 1 and 2 are significantly better than Example A.

The results are shown graphically in Figure 1 . It can be seen from Figure 1 that the observed wet hair conditioning benefits tend to disappear at fatty acid levels which are either above or below 1 to 2% by weight.

Claims

A personal cleansing composition with pH 2 to 6, comprising: an aqueous continuous phase including at least one cleansing surfactant selected from alkyl ether sulfates;

dispersed particles of emulsified silicone, and

from 0.5 to 1 .1 % (by weight based on the total weight of the composition), of stearic acid (C18:0).

A composition according to claim 1 , in which the content of stearic acid (C18:0) ranges from 0.6 to 1 .0% (by weight based on the total weight of the composition).

A composition according to claim 1 or claim 2, in which the source of stearic acid is a mixture comprising about 40 to 50% by weight palmitic acid, about 50 to 55% by weight stearic acid and about 1 to 3% by weight myristic acid (by weight based on the total weight of the mixture).

A composition according to any preceding claim, having a phi in the range of from 3.8 to 4.2.

5. A composition according to any preceding claim, in which the dispersed particles of emulsified silicone (b) are emulsified droplets having a mean droplet diameter (D3,2) of 0.25 micrometre or less. A composition according to any preceding claim, which further comprises from 0.5 to 1 .5% (by weight based on the total weight of the composition) of hydrocarbon oil having a kinematic viscosity of 1 to 35 cS (mm².s^"1) at 40°C and specific gravity of 0.76 to 0.87 at 25°C.

A method of cleansing and conditioning hair, comprising the following sequential steps:

(i) topically applying a composition according to any one of claims 1 to 6 to the hair;

(ii) massaging the composition into the hair and scalp;

(iii) rinsing the composition off the hair and scalp with water, and

(iv) drying the hair.