Aqueous hair cleansing agent

An aqueous hair cleansing agent contains a sulfate-type anionic surfactant having a specific structure, an ether carboxylate-type anionic surfactant having a specific structure, and an organic carboxylic acid or salt thereof, thereby has a pH of 1 to 5 at 25° C. when diluted 20-fold with water.

TECHNICAL FIELD

The present invention relates to an aqueous hair cleansing agent.

BACKGROUND ART

A principal purpose of a hair cleansing agent resides in removing dirt on hair and scalp, preventing dandruff and itchiness of the scalp, and keeping the hair and scalp clean. In view of obtaining a hair cleansing agent having high cleansing performance, it is preferable to use, as a main cleansing component, an anionic surfactant electrically charged at the equivalent level with the hair and scalp. It is more preferable to use a strong-acid-based anionic surfactant having a sulfuric acid group or sulfonic acid group in the anionic portion thereof, in view of preventing re-adsorption of dirt. Among others, an alkyl sulfate and alkyl ether sulfate are most generally used as the main component of a hair cleansing agent, by virtue of their rich foaming property and excellent cleansing performance.

The alkyl sulfate and alkyl ether sulfate, however, still have problems in terms of mildness to the scalp. Horny layer cells which form 10 to 20 layers in the surficial portion of the skin have important roles of keeping moisture within the skin, and protection from an external stimulation. The above-described alkyl sulfate and alkyl ether sulfate, however, permeate into the horny layer, strongly swell the cells, and elutes natural moisturizing components, such as an amino acid or lipid inherent to the cells, out from the cells. Accordingly, repetitive use of such hair cleansing agent, containing these surfactants as the main component, may tend to dry the skin due to the lowered moisture content of the scalp, and tend to induce itchiness of the scalp or provide a larger amount of dandruff because the surfactant and some stimulating substance may more readily permeate into the skin.

As low-stimulus cleansing bases, Patent Document 1 proposes an amino-acid-based surfactant such as an anionic surfactant in the form of alkyloylalkyl taurine salt, and Patent Document 2 proposes a weakly-acidic anionic surfactant such as polyoxyethylene alkyl ether carboxylate. The amino-acid-based surfactant and the polyoxyethylene alkyl ether carboxylate are less likely to swell the horny layer, and are mild to the skin. They, however, still have room for improvement as for basic performance of the cleansing agent, such as foamability and cleansing performance.

Patent Document 3 describes a technique of adding conditioning performance to a hair treatment composition. The document describes that a composition excellent in the conditioning performance may be obtained, without degrading the basic performances of the hair conditioner such as foamability and viscosity, by using a specific polyxoyalkylene alkenyl ether acetate.

RELATED DOCUMENT

Patent Document

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided an aqueous hair cleansing agent which includes components (A), (B) and (C):

(A) a sulfate-type anionic surfactant represented by the following general formula (1):
R1O(CH2CH2O)nSO3M  (1)
wherein, in the general formula (1), R1represents an alkyl group or alkenyl group having 10 to 18 carbon atoms, M represents a cation derived from alkali metal, alkali earth metal, ammonium, alkanolamine or basic amino acid, and n represents a number from 0 to 5 estimated based on weight average;

(B) an ether carboxylate-type anionic surfactant represented by the following general formula (2) or (3):
R2O(CH2CH2O)mCH2COOX  (2)
R2C(═O)NH(CH2CH2O)mCH2COOX  (3)
wherein, in the general formulae (2) and (3), R2represents an alkyl group having 12 to 16 carbon atoms, X represents a cation derived from alkali metal, alkali earth metal, ammonium, alkanolamine or basic amino acid, and m represents a number of 0.5 to 10 estimated based on weight average; and

(C) an organic carboxylic acid or salt thereof.

The aqueous hair cleansing agent has a pH of 1 to 5 at 25° C. when diluted 20-fold with water.

DESCRIPTION OF THE EMBODIMENTS

The present inventor investigated a hair cleansing agent which contains a sulfate-type anionic surfactant, more specifically alkyl sulfate or alkyl ether sulfate as a main cleansing component, aiming at improving mildness to the scalp, while keeping the basic performances of a cleansing agent. It was finally found that the technique described in Patent Document 3, previously mentioned in BACKGROUND ART, still has room for improvement in terms of a good balance between suppression of stimulation or itchiness of the scalp, and foamability.

From further investigations from the viewpoint of providing a hair cleansing agent, which is capable of ensuring rich foamability and reduced stimulation and itchiness of the scalp, the present inventor found that an aqueous hair cleansing agent excellent in foamability, which is a basic performance of a cleansing agent, suppressive to swelling of the horny layer of the skin, and less stimulus to the scalp, such as being less causative of itchiness, may be obtained by using a sulfate-type anionic surfactant, together with a specific alkyl ether carboxylate, and an organic carboxylic acid or salt thereof, and by adjusting the pH at 25° C. to 1 to 5 when diluted 20-fold by weight with water.

According to the present invention, an aqueous hair cleansing agent capable of ensuring rich foam, low stimulation and less itchiness to the scalp may be provided.

The aqueous hair cleansing agent of the present invention contains the components (A), (B) and (C) described below, and occasionally contains water. Note that all numerical ranges expressed using “to” in this specification are defined to include the upper and lower limits of the ranges. The individual components will specifically be explained.

(A) Sulfate-Type Anionic Surfactant Represented by the Following General Formula (1):
R1O(CH2CH2O)nSO3M  (1)
(in the general formula (1), R1represents an alkyl group or alkenyl group having 10 to 18 carbon atoms, M represents a cation derived from alkali metal, alkali earth metal, ammonium, alkanolamine or basic amino acid, and n represents a number from 0 to 5 estimated based on weight average.)
(B) Ether Carboxylate-Type Anionic Surfactant Represented by the Following General Formula (2) or (3):
R2O(CH2CH2O)mCH2COOX  (2)
R2C(═O)NH(CH2CH2O)mCH2COOX  (3)
(in the general formulae (2) and (3), R2represents an alkyl group having 12 to 16 carbon atoms, X represents a cation derived from alkali metal, alkali earth metal, ammonium, alkanolamine or basic amino acid, and m represents a number from 0.5 to 10 estimated based on weight average.)

First, the component (A) will be explained.

In the aqueous hair cleansing agent of the present invention, the component (A) is a sulfate-type anionic surfactant, and more specifically, an alkyl sulfate or alkyl ether sulfate represented by the general formula (1) in the above.

From the viewpoint of stably obtaining rich foam, it is preferable for the general formula (1) to assume R1having 12 to 14 carbon atoms, 1 to 2 estimated based on weight average for n, and ammonium or sodium for M.

Among these, in view of ensuring quick foaming and excellent cleansing performance, polyoxyethylene alkyl ether sulfate having an alkyl group of 12 to 14 carbon atoms for R1, 1 to 2 for n estimated based on weight average, and ammonium or sodium for M in the general formula (1), is preferable.

The component (A) may be a single species, or may be a combination of two or more species. In view of further improving the foamability, the content of component (A) may be adjusted typically to 1% by weight or more of the total aqueous hair cleansing agent, preferably 5% by weight or more, and more preferably 8% by weight or more. From another viewpoint of low dermal stimulation, the content of component (A) relative to the total aqueous hair cleansing agent may be adjusted typically to 25% by weight or less, preferably 23% by weight or less, and more preferably 20% by weight or less.

From still another viewpoint of ensuring a good balance among rich foam, pH during use, and finger combability during rinsing, the content is preferably 1 to 25% by weight relative to the total aqueous hair cleansing agent of the present invention, more preferably 5 to 23% by weight, and even more preferably 8 to 20% by weight.

Next, the component (B) will be explained.

In the aqueous hair cleansing agent of the present invention, the ether carboxylate-type anionic surfactant composing the component (B) means a group of compounds each having a hydrophobic group and a carboxyl group bound via a polyoxyethylene chain placed in between, and therefore includes alkyl ether carboxylate and alkylamide ether carboxylate, which are represented by the general formulae (2) and (3) in the above, respectively.

In view of further improving a balance between foamability and suppression of swelling of the horny layer, R2in the formulae (2) and (3) is preferably an alkyl group having 12 to 16 carbon atoms, and more preferably an alkyl group having 12 carbon atoms.

In the general formulae (2) and (3), while an average molar number m of addition of ethylene oxide is 0.5 to 10, it is preferably 1 to 6 from the view point of foamability.

The counter ion X in the general formula (2) and (3) may be exemplified by alkali metal such as sodium and potassium;

alkali earth metal such as calcium and magnesium;

ammonium derived from alkanolamine such as monoethanolamine, diethanolamine, and triethanolamine; and

cation derived from basic amino acid such as arginine and lysine.

From the viewpoints of foamability and effect of suppressing swelling of the horny layer, the component represented by the general formula (2) in the above is preferable as the component (B).

The component (B) may be a single species, or may be a combination of two or more species.

From the viewpoint of suppressing swelling of the horny layer, content of the component (B) may typically be 0.5% by weight or more of the total aqueous hair cleansing agent, preferably 1% by weight or more, and more preferably 2% by weight or more. In view of further improving the foamability, the content of the component (B) relative to the total aqueous hair cleansing agent may be adjusted typically to 10% by weight or less, preferably 8% by weight or less, and more preferably 6% by weight or less.

In view of further improving a balance among suppression of swelling of the horny layer, rich foam, and finger combability during rinsing, the content of component (B) relative to the total aqueous hair cleansing agent of the present invention is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, and even more preferably 2 to 6% by weight.

From the viewpoint of excellent foamability, the components (A) and (B) preferably give the weight ratio of the component (B) relative to the total of the components (A) and (B) (i.e. (B)/((A)+(B))) of from, of 50% or less, more preferably 40% or less, and even more preferably 30% or less. From another viewpoint of mildness to the scalp, the weight ratio given by (B)/((A)+(B))×100(%) may typically be 5% or larger, and preferably 10% or larger.

While the reason why the balance between foamability during cleansing and low stimulation to the scalp is improved, as a result of inclusion of the component (A) and the component (B) as essential components, is not exactly clear, it is supposedly because the component (B) properly adsorbs onto the surface of the horny layer of the scalp to thereby form a protective film, and effectively suppresses swelling of the horny layer, while function of the component (A) is kept unchanged.

The aqueous hair cleansing agent of the present invention further contains one or more species of organic carboxylic acid or salt thereof which composes the component (C). The component (C) will be explained below.

In the aqueous hair cleansing agent of the present invention, the organic carboxylic acid composing the component (C) preferably has 2 to 6 carbon atoms, and is more preferably dicarboxylic acid (which may have hydroxy groups) or hydroxymonocarboxylic acid. More specifically, the dicarboxylic acid may be exemplified by malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, and oxalic acid. The dicarboxylic acid having hydroxy groups may be exemplified by malic acid and tartaric acid. The hydroxymonocarboxylic acid may be exemplified by glycolic acid, lactic acid, hydroxyacrylic acid, oxybutyric acid, glyceric acid, and gluconic acid. Among these organic carboxylic acids, preferable examples include glycolic acid, lactic acid, malonic acid, maleic acid, and malic acid. Salts of these organic carboxylic acids may be exemplified by those formed with alkali metal, alkali earth metal, ammonia, and organic amine compound.

The component (C) may be a single species, or may be a combination of two or more species, wherein the content of which is preferably 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, and even more preferably 0.5 to 2% by weight of the aqueous hair cleansing agent, in view of ensuring a sufficient level of scalp improvement.

Next, pH of the aqueous hair cleansing agent of the present invention will be explained.

In view of maximizing the effect of improving scalp conditions by the organic carboxylic acid composing the component (C), the aqueous hair cleansing agent of the present invention, containing such component (C), preferably has a pH value of 2 to 4.5, and more preferably 3 to 4.5, at 25° C. when diluted 20-fold by weight with water.

From another viewpoint of maximizing the effect of suppressing swelling of the horny layer by the ether carboxylate-type anionic surfactant composing the component (B), the aqueous hair cleansing agent of the present invention preferably has a pH value of 1 to 5, more preferably 2 to 4.5, and even more preferably 3 to 4.5, at 25° C. when diluted 20-fold by weight with water.

Since the ether carboxylate composing the component (B) is a weak acid, it exists in a form of acid (undissociated form) under low pH, whereas it exists in a form of anion (dissociated form) under high pH. More specifically, most of the ether carboxylate exists in a form of acid at 25° C. under pH 1 to 5 when diluted 20-fold with water, and is particularly effective for suppressing swelling of the horny layer.

In addition, the dandruff suppressive effect may more effectively be expressed under pH 1 to 5, by virtue of its anti-bacterial effect against resident bacteria. Accordingly, the aqueous hair cleansing agent of the present invention typically has excellent foamability and anti-dandruff performance, and is also capable of suppressing itchiness of the scalp as a result of suppression of swelling of the horny layer.

For the purpose of adjusting pH to 1 to 5 in the present invention, inorganic or organic acid, or alkali agent may be used while being appropriately combined and quantified.

Of these, the inorganic acid may be exemplified by hydrochloric acid, sulfuric acid, and phosphoric acid.

The organic acid may be exemplified by citric acid and glutamic acid, besides the above-described organic carboxylic acid. In the present invention, an additional effect of preventing dandruff and itchiness may be obtained, particularly by using one or more species of organic carboxylic acid or salt thereof, which composes the component (C).

An aqueous hair cleansing agent which is further well balanced among foamability, anti-dandruff performance, and low stimulation, and also excellent in stability in manufacturing, may be obtained by using the alkyl sulfate or alkyl ether sulfate represented by the general formula (1), that is the component (A), as the base, together with the alkylether carboxylate composing the component (B), and the organic acid salt composing the component (C), and by adjusting pH at 25° C. to 1 to 5 when diluted 20-fold with water.

The aqueous hair cleansing agent of the present invention may also reduce volume of water for rinsing, since the surfactant contained therein is less likely to remain on the hair or scalp.

The aqueous hair cleansing agent of the present invention may further be configured to contain at least one species of an anti-inflammatory agent.

Examples of the anti-inflammatory agent includes glycyrrhetinic acid, glycyrrhizic acid and derivatives thereof; and also include components having an anti-inflammatory function, such as E-aminocaproic acid, allantoin, sodium guaiazulene sulfonate, d-camphor, l-menthol, urea, pyridoxine dipalmitate, glycyrrhetinyl stearate, tranexamic acid, vitamin A oil, hydrocortisone, prednisolone, pyridoxine hydrochloride, Kankohso (photosensitizer) 301, zinc oxide, and hydrocortisone acetate. The derivatives of glycyrrhetinic acid or glycyrrhizic acid include salts which include alkali metal salts represented by sodium salt and potassium salt, and ammonium salt; and esters such as glycerin ester and stearyl ester. More specifically, dipotassium glycyrrhizinate, disodium glycyrrhizinate, trisodium glycyrrhizinate, monoammonium glycyrrhizinate, glycerin glycyrrhetinate, and stearyl glycyrrhetinate may be exemplified.

The anti-inflammatory agent may be a single species, or may be a combination of two or more species, wherein the content of which is preferably 0.001 to 10% by weight, more preferably 0.005 to 5% by weight, and even more preferably 0.01 to 1% by weight.

In view of further improving the cleansing performance, the aqueous hair cleansing agent of the present invention may contain a nonionic surfactant or amphoteric surfactant.

Among these, polyoxyalkylene solbitan fatty acid ester such as polyoxyethylene solbitan fatty acid ester, polyoxyalkylene fatty acid ester such as polyoxyalkylene (C8to C20) fatty acid ester, and polyoxyalkylene (hydrogenated) castor oil such as polyoxyethylene hydrogenated castor oil, and alkylglycoside are preferable.

Also fatty acid alkanolamide is a preferable nonionic surfactant, allowing either monoalkanolamide or dialkanolamide. Those having an acyl group of 8 to 18 carbon atoms, in particular 10 to 16 carbon atoms are preferable. Also those having a hydroxyalkyl group of 2 to 3 carbon atoms are preferable, which are exemplified by oleic acid diethanolamide, palm kernel oil fatty acid diethanolamide, coconut oil fatty acid diethanolamide, lauric acid diethanolamide, polyoxyethylene coconut oil fatty acid monoethanolamide, coconut oil fatty acid monoethanolamide, lauric acid isopropanolamide, and lauric acid monoethanolamide.

The amphoteric surfactant may be exemplified by betaine-based surfactants. Among these, alkyl dimethyl aminoacetic acid betaine, fatty acid amidopropyl betaine, and alkyl hydroxy sulfobetaine are more preferable, wherein fatty acid amidopropyl betaine is more preferable. The fatty acid amidopropyl betaine preferably has an acyl group of 8 to 18 carbon atoms, in particular 10 to 16 carbon atoms, wherein more preferable examples include lauric acid amidopropyl betaine, palm kernel oil fatty acid amidopropyl betaine, and coconut oil fatty acid amidopropyl betaine.

Each of these surfactants may be a single species, or may be a combination of two or more species contained in the aqueous hair cleansing agent. In view of obtaining the aqueous hair cleansing agent of the present invention in the form of a water-based liquid cleaner, it is preferable to use fatty acid amidopropyl betaine, fatty acid alkanolamide, or mono alkylglyceryl ether, together with the components (A), (B), not only because the foamability is improved, but also because the appropriate level of pH may be obtained.

The content of these surfactant is preferably 0.1 to 15% by weight in the hair cleansing agent of the present invention, in view of obtaining a good effect of enhancing the foamability. From this point of view, the content is more preferably 0.5 to 8% by weight, and even more preferably 1 to 6% by weight.

The aqueous hair cleansing agent of the present invention may further contain a cationic surfactant, cationized polymer or silicones, for the purpose of improving the finger combability during rinsing, and of improving styling of hair after being dried.

This is exemplified by those represented by the following general formula:
R4—N+(CH3)3Q−
(in the general formula, R4represents an alkyl group having 12 to 22 carbon atoms, and Q−represents a halogen (chlorine or bromine) ion.)

This is exemplified by those represented by the following general formula:
R5—O—R6—N(CH3)3Q−
(in the formula, R5represents an alkyl group having 12 to 22 carbon atoms, R6represents an ethylene group or propylene group, and Q−is same as described in the above.)

This is exemplified by those represented by the following general formula:
R72—N+(CH3)2Q−
(in the general formula, R7represents an alkyl group having 12 to 22 carbon atoms or benzyl group, and Q−is same as described in the above.)

More specifically, distearyl dimethyl ammonium chloride may be exemplified.

This is exemplified by those represented by the following general formula:
R8—N(CH3)2
(in the general formula, R8represents an alkyl group having 12 to 22 carbon atoms.)

More specifically, organic acid salts of behenyl dimethylamine and stearyl dimethylamine may be exemplified.

This is exemplified by those represented by the following general formula:
R9—O—R10—N(CH3)2
(in the general formula, R9represents an alkyl group having 12 to 22 carbon atoms, and R10represents an ethylene group or propylene group.)
(vi) Alkylamide Dimethylamine Salt

This is exemplified by those represented by the following general formula:
R11—C(═O)NH—R12—N(CH3)2
(in the general formula, R11represents an alkyl group having 11 to 21 carbon atoms, and R12represents an ethylene group or propylene group.)

Two or more species of the cationic surfactant may be combined, wherein the content of which is preferably 0.01 to 10% by weight of the aqueous hair cleansing agent of the present invention, more preferably 0.05 to 5% by weight, and even more preferably 0.1 to 2% by weight, in view of smoothness over a period from washing to rinsing.

Two or more species of these cationized polymers may be combined, wherein the content of which is preferably 0.01 to 3% by weight of the aqueous hair cleansing agent of the present invention, more preferably 0.05 to 2% by weight, and even more preferably 0.1 to 1% by weight, in view of smoothness over a period from washing to rinsing.

The silicones may be exemplified by (I) to (III) listed below.

This is exemplified by those represented by the following general formula (4):
(CH3)3Si—[(CH3)2SiO]d—Si(CH3)3(4)
(in the general formula (4), d represents a number of 3 to 20,000.)

The dimethylpolysiloxane exist as dispersed particles in the aqueous hair cleansing agent, wherein average particle size of the dispersed particles is preferably 0.1 to 100 μm, more preferably 0.1 to 50 μm, even more preferably 0.1 to 4 μm, and even more preferably 0.1 to 2 μm, in view of excellence of finishing after drying, and storage stability of the hair cleansing agent.

The average particle size of the polydimethylsiloxane emulsion herein means the median diameter measured by laser light scattering method, and may be measured using a general particle analyzer based on laser light scattering, such as LS-130 from Coulter Corporation.

This sort of dimethylpolysiloxane adoptable herein is commercially available under the name of “Silicone CF2450” from Dow Corning Toray Co., Ltd. which contains 60% by weight of dimethylpolysiloxane oil represented by the general formula (4) with d=300 to 6,500, and has an average particle size of 0.8 μm; or under the name of “Silicone CF2460” from Dow Corning Toray Co., Ltd., which contains 75% by weight of dimethylpolysiloxane oil with d=300 to 6,500, and has an average particle size of 20 μm.

The dimethylpolysiloxane is preferably contained in an amount of from 0.01 to 10% by weight of the aqueous hair cleansing agent of the present invention, preferably 0.05 to 6% by weight, more preferably 0.3 to 3% by weight, and even more preferably 0.5 to 2% by weight, in view of improving foam texture, and touch or gloss of hair after being dried.

While various amino-modified silicones may be adoptable, a product listed under the name of Amodimethicone in CTFA Dictionary (Cosmetic Ingredient Dictionary, USA), 9th Edition, 2002, Volume 1, p. 107, having an average molecular weight of approximately 3000 to 100,000, is preferable. The commercially available products may be exemplified by SM 8704C (from Dow Corning Toray Co., Ltd.), DC 929 (from Dow Corning Corporation), KT 1989 (from Momentive Performance Materials Inc.), 8500 Conditioning Agent, DOW CORNING TORAY SS-3588, and DOW CORNING TORAY SILSTYLE 104 (from Dow Corning Toray Co., Ltd.).

Two or more species of these amino-modified silicone and other silicones may be combined, wherein the content of which is preferably 0.01 to 5% by weight of the aqueous hair cleansing agent of the present invention, more preferably 0.05 to 2% by weight, and even more preferably 0.1 to 1% by weight, in view of smoothness over a period from washing to rinsing.

The aqueous hair cleansing agent of the present invention may further contain a pearlescent agent containing ethylene glycol monofatty acid ester, ethylene glycol difatty acid ester, ethylene glycol mono alkyl ether or ethylene glycol dialkyl ether.

The ethylene glycol monofatty acid ester may be exemplified by ethylene glycol monostearate and ethylene glycol monobehenate, and the ethylene glycol difatty acid ester may be exemplified by ethylene glycol distearate and ethylene glycol dibehenate. The ethylene glycol mono alkyl ether may be exemplified by ethylene glycol monostearyl ether, and the ethylene glycol dialkyl ether may be exemplified by ethylene glycol distearyl ether.

Each of them may be a combination of two or more species, wherein the content of which is preferably 0.1 to 10% by weight of the aqueous hair cleansing agent of the present invention, more preferably 0.5 to 5% by weight, and even more preferably 1 to 4% by weight, in view of improving storage stability, smoothness during foaming and rinsing, and stability of the hair cleansing agent.

The aqueous hair cleansing agent of the present invention may contain an oil component as another conditioning agent. The oil component may be exemplified by hydrocarbon oils such as squalene, squalane, liquid paraffin, liquid isoparaffin, and cycloparaffin;

other materials such as isostearyl glyceryl ether, and poly(oxypropylene)butyl ether. Among these, higher fatty acids, higher alcohol, and glyceride are preferable, and lauric acid, myristyl alcohol, cetyl alcohol, stearyl alcohol, sunflower oil, and camellia oil are more preferable. These oil components may be a single species, or may be a combination of two or more species, wherein the content of which is preferably 0.1 to 2% by weight of the aqueous hair cleansing agent of the present invention, more preferably 0.2 to 1.5% by weight, and even more preferably 0.3 to 1% by weight.

The aqueous hair cleansing agent of the present invention may contain a viscosity adjusting agent. The viscosity adjusting agent may be exemplified by hydroxyethylcellulose, methylcellulose, polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, isoprene glycol, ethanol, glycerin, benzyl alcohol, benzyloxy ethanol, phenoxy ethanol, and clay minerals, salts (sodium chloride, ammonium chloride, sodium citrate, and so forth), among which benzyl alcohol, ethanol, polypropylene glycol, sodium chloride, and sodium citrate are preferable. The viscosity adjusting agent may be a single species, or may be a combination of two or more species, wherein the content of which is preferably 0.01 to 5% by weight of the aqueous hair cleansing agent of the present invention, more preferably 0.05 to 4% by weight, and even more preferably 0.1 to 3% by weight, in view of richness and quality of foam.

Besides the above-described components, any components adopted to a general hair cleansing agent may appropriately be added to the aqueous hair cleansing agent of the present invention, depending on the need. The components may be exemplified by antiseptic agent; chelating agent; moisturizers such as sorbitol and panthenol; colorants such as dye and pigment; extracts such as polar solvent extract of eucalyptus, protein obtained from shell having a nacreous layer or from pearl, or hydrolysate thereof, honey, royal jelly, silk-derived protein or hydrolysate thereof, protein-containing extract obtained from leguminous plant seed,Panax ginsengextract, rice germ extract, bladderwrack extract, aloe extract, Alpinia leaf extract, and chlorella extract; pearl pigment such as mica-titanium; perfume; UV absorber; antioxidant; and other components listed in Encyclopedia of Shampoo Ingredients (written by Anthony L. L. Hunting, 1983, published by Micelle Press)).

While the existing form of the aqueous hair cleansing agent of the present invention may appropriately be selectable from liquid, gel and so forth, it is preferable to use water or lower alcohol, and particularly water, as a medium.

EXAMPLES

Examples 1 to 7 and Comparative Examples 1 to 8

Aqueous hair cleansing agents listed in Table 1 were prepared, and evaluated by the methods described below. Results are shown in Table 1. Note that the pH values herein were measured at 25° C. after 20-fold dilution with water.

Methods of Evaluation

(1) Quickness of Foaming

Quickness of foaming was evaluated using the method and the apparatus described in Japanese Patent Publication No. JP-A-H10-73584.

More specifically,FIG. 1illustrates an apparatus for evaluating foamability, having a container10for housing an article to be applied with the cleansing agent (hair1), projections21,22which are brought into contact with the hair1, a gauge50for measuring foam produced in the container10, a lid20which covers the container10, and guides the foam produced in the container10towards the gauge50, and a motor30for moving the container10so as to bring the hair1housed in the container10and the projections21,22into sliding contact. The hair1was wet with an equal volume of water, 1.5 mL of each sample to be evaluated and 0.3 mL of model sebum composed of lanolin were injected through an injection port25, and the amount of foam was measured. Quickness of foaming was evaluated by time required for the amount of foam to reach 250 mL.

The hair1used herein was 90 mm long, 30 g in weight in total, and attached onto a disk of approximately 160 mm in diameter. The container10was a cylinder of 160 mm in diameter and 20 mm high. The lid20had three first cylindrical projections21each having a diameter of 15 mm and a height of 12 mm, and nine second projections22each of which being 10 mm long, 2 mm wide, and 12 mm high. Number of rotations of the container10driven by the motor was set to 70 revolutions per minute.

Ten male subjects were asked to wash their hair with each cleansing agent once a day for one month, then to stop washing for two days after the last washing. Hair of each subject was then washed twice using 3 g each of the same cleansing agent, and the whole volume of washate from the washing repeated twice was collected. The whole volume of collected washate was filtered through a 50 nylon mesh so as to remove unnecessary dust and hair. The whole volume of filtrate was filtered through a 255 nylon mesh (100×100 μm) preliminarily weighed, the nylon mesh was allowed to dry for approximately 48 hours at room temperature, and the amount of increase of weight thereof was determined as the weight of dandruff. Average values of weight of dandruff from ten subjects were determined, and evaluated according to the criteria below:⊚: weight of dandruff≦30 mg;∘: 30 mg<weight of dandruff≦40 mg;Δ: 40 mg<weight of dandruff≦50 mg; andx: 50 mg<weight of dandruff.
(3) Swellability of the Horny Layer

Human heel was disinfected with ethanol, the horny layer was scratched off, and then thoroughly dried to obtain a horny layer powder. Twenty milligrams of the thus-dried horny layer powder was placed in a 5-mm-diameter tube for NMR measurement, 0.8 mL of each hair cleansing agent diluted 20-fold with deionized water was injected thereinto, and the level of height of the mixture after being allowed to stand for 2 hours was measured. Evaluation was expressed by a relative value while assuming the level of height, attained when 0.8 mL of deionized water was added to 20 mg of the horny layer powder, as 100%. Larger value herein means larger level of swelling of the horny layer. Judgment criteria are as follows:⊚: less than 110%;∘:110% or more, less than 120%;Δ: 120% or more, less than 125%; andx: 125% or more.
(4) Anti-Itching Effect

Ten male subjects were asked to use each cleansing agent and to wash their hair once a day for one month. After one month, itchiness of the scalp as washed was evaluated according to a scale of 1 to 5. The average of ten subjects of 4.0 or larger was rated “⊚”, 3.2 to 3.9 was rated “∘”, 2.5 to 3.1 was rated “Δ”, and 2.4 or smaller was rated “x”:

It was found from Table 1 that the compositions of Examples 1 to 7 were excellent in foamability and anti-dandruff performance, highly effective in suppressing swelling of the horny layer, and effective in suppressing itchiness of the scalp.

The hair cleansing agents of Examples 8 to 10 were found to be excellent in foamability and anti-dandruff performance, and to have effects of suppressing swelling of the horny layer and itchiness of the scalp.

Example 11, Comparative Examples 9 and 10

In these Examples, suppressive performance of samples containing the component (A) against swelling of the horny layer was evaluated according to the method described below. Compositions and pH of the samples are listed in Table 2.

The components below were used as the surfactant.

In Example 11, malic acid and sodium hydroxide were used to adjust the pH of the sample to 3.7. On the other hand, in Comparative Example 9 and Comparative Example 10, malic acid and sodium hydroxide were used to adjust the pH of the sample to 6.0 or 3.7.

Samples were measured according to (3) Swellability of the horny layer for Examples 1 to 7 and Comparative Examples 1 to 8, described in the above.

More specifically, the components (A) and (B) or (B′) were added to deionized water, so as to adjust the surfactant concentration, or the total concentration of the components (A) and (B) or (B′), to 30 mM, to thereby prepare surfactant samples having various concentrations as listed in Table 2. The surfactant concentration herein corresponds to a concentration of the shampoo when foamed on hair during washing.

On the other hand, 20 mg of the horny layer powder was placed into the NMR measurement tube, and 0.8 mL of each of the above-described surfactant samples was added and mixed.

Following addition of each surfactant sample, the level of height of the horny layer after being allowed to stand for two hours was measured. Results are shown inFIG. 2. InFIG. 2, “swellability of the horny layer” on the ordinate is given by relative values of the level of height of the horny layer swelled with the individual samples, while assuming the level of height, attained when 0.8 mL of deionized water, in place of the surfactant samples, was added to 20 mg of the horny layer powder and allowed to stand for two hours, as 100%. Larger value herein means larger level of swelling of the horny layer.

It was found fromFIG. 2that Example 11 was capable of further effectively suppressing swelling of the horny layer, only with a small amount of addition, by using the component (A) together with the component (B), still also with the component (C), and by lowering the pH. Also Comparative Example 9, with its pH adjusted to 6.0, was found to be more effective in suppressing swelling of the horny layer, as compared with Comparative Example 10 having no component (B) contained therein. Example 11 showed a more distinctive effect of suppressing swelling of the horny layer. Example 11 was found to be excellent, also in terms of more stably obtaining a sample well balanced between the swellability and foamability.

This application claims priority right based on Japanese Patent Application No. 2009-085836 filed on Mar. 31, 2009, the entire content of which is incorporated hereinto by reference.

The present invention also includes the embodiments described below:

[1] An aqueous hair cleansing agent which includes components (A) and (B):

(A) a sulfate-type anionic surfactant represented by the following general formula (1):
R1O(CH2CH2O)nSO3M  (1)
(in the general formula (1), R1represents an alkyl group or alkenyl group having 10 to 18 carbon atoms, M represents a cation derived from alkali metal, alkali earth metal, ammonium, alkanolamine or basic amino acid, and n represents a number from 0 to 5 estimated based on weight average); and

(B) an ether carboxylate-type anionic surfactant represented by the following general formula (2) or (3):
R2O(CH2CH2O)mCH2COOX  (2)
R2C(═O)NH(CH2CH2O)mCH2COOX  (3)
(in the general formulae (2) and (3), R2represents an alkyl group or alkenyl group having 10 to 18 carbon atoms, X represents a cation derived from alkali metal, alkali earth metal, ammonium, alkanolamine or basic amino acid, and m represents a number of 0.5 to 10 estimated based on weight average.),

and further including water,

the aqueous hair cleansing agent having a pH of 1 to 5 at 25° C. when diluted 20-fold with water;

[2] The aqueous hair cleansing agent described in [1], further containing component (C) an organic carboxylic acid or salt thereof;

[3] The aqueous hair cleansing agent described in [1] or [2], wherein ratio of the component (B), relative to the total of the components (A) and (B), is 50% or less based on the weight ratio; and

[4] The aqueous hair cleansing agent described in any one of [1] to [3], further containing at least one species of anti-inflammatory agent in an amount of from 0.001 to 10% by weight.