Solid hair cleanser

Abstract

To provide a solid hair washing agent that is used by dissolving into water, which is capable of washing hair only by immersing hair into the agent, has high washability, and can suppress undissolved hair washing agent residue and re-attachment of sebum or the like onto hair.SOLUTION: A solid hair washing agent contains component (A): organic acid, component (B): carbonate, and component (C): nonionic surfactant, in which a mass ratio [{(A)+(B)} / (C)] of the total amount of component (A) and component (B) with respect to component (C) is 4.0 or more and 24.0 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a solid hair cleansing agent. [Background technology]

[0002] In recent years, changes in living environments and social conditions have led to problems in which traditional hair washing methods are no longer sufficient. For example, the declining birthrate and aging population has led to problems with labor shortages in medical and nursing care settings. As a result, patients and those receiving care cannot spend enough time washing their hair, which can lead to hair not being washed or rinsed properly. As an example of hair washing behavior for patients and care recipients, first, the hair and scalp are wetted with a small amount of water, and the excess water is absorbed by a water absorbent such as a diaper, and then a process of lathering a hair cleanser on the wet hair to wash the hair (washing process), and a process of rinsing the hair with a small amount of water, absorbing the rinse water with a water absorbent and collecting it (rinsing process), and then a process of drying the washed hair (drying process) are performed. However, the hair washing process is complicated, and washing hair with a hair cleanser in particular is a heavy burden on the work. If the hair washing process is complicated, it will lead to a decrease in the frequency of hair washing for care recipients in medical and care settings where there are few manpower.

[0003] Therefore, proposals for hair washing that can reduce the burden of hair washing in medical and nursing care settings are being considered. For example, if hair can be washed by immersing it in a hair washing solution, and the hair can be pulled out of the hair washing solution after immersion and directly subjected to a drying process, the process of lathering and rinsing the hair washing agent will be unnecessary, and there will be no risk of leaving any hair washing agent behind.

[0004] In addition, the use of false hair such as wigs and braids as a fashion item is becoming more common. In this case, it is essential to wash the hair without the false hair coming off or losing its shape, so it is basically impossible to wash the hair after putting on the false hair, which results in problems such as odor and itching. The above-mentioned hair washing behavior is expected to solve such problems.

[0005] In order to realize the above-mentioned hair washing behavior, a hair wash is required that allows washing of hair by simply immersing the hair, does not require the washing step of lathering the hair before use, and has the same level of cleaning power as hair washes that are lathered on the hair before use.

[0006] As such hair washing agents, solid hair washing agents that are dissolved in water have been proposed. For example, Patent Document 1 discloses a method of washing hair, which is characterized in that a solid bath agent containing bicarbonate, a specific organic acid, anhydrous sodium carbonate and / or anhydrous potassium carbonate has a pH of 5.5 to 9.0 immediately after dissolving the solid bath agent, and the water in which the solid bath agent is dissolved is brought into contact with hair for washing, thereby preventing bicarbonate ions in the water from being blocked by a bicarbonate ion blocking substance, and provides good hair removal when combed with hands, thickness, volume and strength of hair after drying. Patent Document 2 discloses that a soluble solid structure such as a hair shampoo, which includes fibers formed from a predetermined amount of a cleansing surfactant and a water-soluble polymer structuring agent, and preformed expandable agglomerated particles each containing a predetermined amount of a solid metal salt, a solid acid, and a binder, and in which the ratio of the fibers to the expandable agglomerated particles is about 1:0.05 to about 1:2, can be produced within desired cost and speed parameters, and further, the dissolution characteristics of the solid product can be improved, and an interesting use experience can be provided by foaming when mixed with water. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-27969 A [Patent Document 2] Special Publication No. 2020-506222 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology disclosed in Patent Document 1 has room for improvement in cleansing properties when used as a hair cleanser for soaking and cleaning hair. It is particularly important to prevent dirt such as sebum from reattaching to hair. Furthermore, there is a concern that if a solid hair cleanser remains undissolved in water, it will reattach to hair, causing a deterioration in the feel of the hair after washing. In addition, since the technology disclosed in Patent Document 2 uses a large amount of a cleansing surfactant in the soluble solid structure, it is presumed that when used as a hair cleanser, lathering and rinsing steps are required as part of the hair washing process. The present invention relates to a solid hair cleanser that is dissolved in water for use, which allows hair to be washed simply by immersing the hair in the solid hair cleanser, has high cleansing properties, and is capable of suppressing residual hair cleanser and redeposition of sebum and the like onto the hair. [Means for solving the problem]

[0009] As a result of investigations, the present inventors have found that the above-mentioned problems can be solved by a solid hair wash that contains an organic acid and a carbonate and can generate carbon dioxide gas when dissolved in water, and further contains a nonionic surfactant, in which the mass ratio of the total amount of the organic acid and the carbonate to the nonionic surfactant is within a specified range. That is, the present invention relates to the following. [1] A solid hair cleanser comprising: component (A): an organic acid; component (B): a carbonate; and component (C): a nonionic surfactant, wherein the mass ratio of the total amount of components (A) and (B) to component (C), [{(A)+(B)} / (C)], is 4.0 or more and 24.0 or less. [2] A method for washing hair, comprising the following step (I) or step (II): Step (I): adding the solid hair cleansing agent described in [1] above to water and immersing hair in the water while foaming with carbon dioxide gas. Step (II): A step of immersing hair in water and then adding the solid hair cleansing agent described in [1] above to the water. Effect of the Invention

[0010] According to the solid hair cleanser of the present invention, hair can be washed simply by immersing the hair in the solid hair cleanser, and the solid hair cleanser has high cleansing properties and can suppress the re-adhesion of the hair to the hair, as well as the residual hair cleanser and sebum, etc. When washing hair using the solid hair cleanser, the operation of lathering the cleanser on the hair to wash it and rinsing the hair after washing can be omitted, which reduces the burden of washing hair in medical and nursing care settings and also makes it possible to suppress a decrease in the frequency of washing hair. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Solid hair cleanser] The solid hair wash of the present invention contains component (A): an organic acid, component (B): a carbonate, and component (C): a nonionic surfactant, and the mass ratio of the total amount of components (A) and (B) to component (C), [{(A)+(B)} / (C)], is 4.0 or more and 24.0 or less. The solid hair cleansing agent of the present invention is a hair cleansing agent which is solid at 25° C. and is used by dissolving it in water, and its dosage form is preferably a powder or tablet, more preferably a tablet. By using the solid hair cleanser of the present invention as described above, it is possible to wash hair without foaming the cleanser on the hair and simply by immersing the hair in water containing the solid hair cleanser and foaming carbon dioxide gas, or by immersing the hair in water and then adding the solid hair cleanser to the water, thereby providing a hair cleansing agent with high cleansing properties and capable of preventing residual hair cleanser and redeposition of sebum and the like. Hereinafter, in this specification, the water used for washing hair to which the solid hair cleanser of the present invention has been added is also referred to as the "hair cleansing liquid." In addition, "residual hair cleanser and redeposition of sebum, etc." is also simply referred to as "redeposition."

[0012] The reason why the solid hair cleansing agent of the present invention exhibits the above-mentioned effects is not clear, but is thought to be as follows. The solid hair cleansing agent of the present invention contains an organic acid as component (A) and a carbonate as component (B), and generates carbon dioxide gas when dissolved in water. This provides the following effects: (1) the carbon dioxide gas bubbles are adsorbed to sebum, and the buoyancy of the bubbles rising to the gas-liquid interface physically removes dirt, and (2) the hydrophobic surface of the carbon dioxide gas bubbles adsorbs and removes dirt such as sebum. It is believed that excellent cleansing properties can be achieved simply by immersing hair in water containing the solid hair cleansing agent and foaming with carbon dioxide gas, or by immersing hair in water and then adding the solid hair cleansing agent to the water. The nonionic surfactant component (C) also has sebum cleansing properties and also has the effect of suppressing redeposition. It is believed that by setting the mass ratio [{(A)+(B)} / (C)] of the total amount of components (A) and (B) to component (C) within a specified range, a solid hair cleansing agent that is excellent in both sebum cleansing properties and redeposition suppression effects when dissolved in water can be obtained.

[0013] <Component (A): Organic acid> The solid hair cleansing agent of the present invention contains an organic acid as component (A). By containing component (A), the solid hair cleansing agent of the present invention becomes a solid hair cleansing agent that can generate carbon dioxide gas when dissolved in water by reacting with component (B) described below. This carbon dioxide foaming makes it possible to wash hair simply by immersing the hair in the agent, and also exhibits excellent cleansing properties.

[0014] Examples of component (A) include carboxylic acid compounds, organic sulfonic acid compounds, organic phosphoric acid compounds, and ascorbic acid, but from the viewpoints of carbonic foaming properties, solubility in water, and moldability, one or more selected from the group consisting of carboxylic acid compounds and ascorbic acid are preferred. The carboxylic acid compound may be a compound having at least one carboxy group, but from the viewpoint of improving carbonic foaming properties, polyvalent carboxylic acids having two or more carboxy groups are preferred. Examples of carboxylic acid compounds include aliphatic carboxylic acids and aromatic carboxylic acids, and from the viewpoints of improving cleaning properties, solubility in water, and moldability of the solid hair cleansing agent, as well as from the viewpoint of economy, aliphatic carboxylic acids are preferred. Examples of the aliphatic carboxylic acid include oxalic acid, fumaric acid, succinic acid, tartaric acid, malic acid, citric acid, maleic acid, glutaric acid, adipic acid, etc., and examples of the aromatic carboxylic acid include benzoic acid, salicylic acid, pyrrolidone carboxylic acid, etc. These organic acids can be used alone or in combination of two or more. Among the above, component (A) is preferably one or more selected from the group consisting of succinic acid, tartaric acid, malic acid, citric acid, and ascorbic acid, more preferably one or more selected from the group consisting of succinic acid, malic acid, and citric acid, and more preferably succinic acid.

[0015] <Component (B): Carbonate> The solid hair cleansing agent of the present invention contains a carbonate as component (B), which generates carbon dioxide gas by reacting with component (A) when the solid hair cleansing agent is dissolved in water, thereby enabling the solid hair cleansing agent to exhibit excellent cleansing properties.

[0016] Examples of component (B) include alkali metal carbonates such as sodium carbonate and potassium carbonate; alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate; alkali metal bicarbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate; and alkaline earth metal bicarbonates such as calcium hydrogen carbonate. One or more of these may be used. Among the above, from the viewpoint of improving cleaning properties, it is preferable that component (B) contains a bicarbonate salt, which is preferably at least one selected from the group consisting of sodium hydrogen carbonate and calcium hydrogen carbonate, more preferably contains sodium hydrogen carbonate, and even more preferably is sodium hydrogen carbonate. From the viewpoint of improving cleaning properties, the content of bicarbonate in component (B) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass.

[0017] <Component (C): Nonionic surfactant> The solid hair cleanser of the present invention contains a nonionic surfactant as component (C), which not only improves the cleansing properties but also contributes to the effect of inhibiting the re-adhesion of sebum and the like and remaining undissolved in the hair cleanser.

[0018] From the viewpoint of improving the cleaning property and the reattachment suppression effect, the HLB (hydrophilic-lipophilic balance) value of component (C) is preferably 10.0 or more, more preferably 10.5 or more, even more preferably 12.0 or more, even more preferably 14.0 or more, and preferably 20.0 or less, more preferably 18.5 or less, even more preferably 18.0 or less, even more preferably 17.0 or less, and even more preferably 16.5 or less. The HLB value of component (C) is preferably 10.0 or more and 20.0 or less, more preferably 10.5 or more and 18.5 or less, even more preferably 12.0 or more and 18.0 or less, even more preferably 14.0 or more and 17.0 or less, and even more preferably 14.0 or more and 16.5 or less. The HLB value indicates the affinity of a surfactant for water and oil, and can be calculated by the Griffin method using the following formula. HLB = 20 x [(molecular weight of hydrophilic group contained in surfactant) / (molecular weight of surfactant)] When two or more kinds of component (C) are used, it is preferable to use two or more kinds of components having HLB values ​​within the above range.

[0019] Specific examples of component (C) include one or more selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbit fatty acid esters, polyoxyethylene fatty acid esters, alkyl glucosides, alkyl alkanolamides, alkyl glyceryl ethers, higher fatty acid sucrose esters, polyglycerin fatty acid esters, polyoxyethylene hydrogenated castor oil, and alkyl saccharides. Among the nonionic surfactants exemplified above, the average number of moles of oxyethylene groups added in polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbit fatty acid esters, polyoxyethylene fatty acid esters, and polyoxyethylene hydrogenated castor oil (hereinafter referred to as "average number of moles of EO added") is preferably 2 or more, more preferably 3 or more, even more preferably 5 or more, still more preferably 6 or more, still more preferably 8 or more, and preferably 150 or less, more preferably 80 or less, still more preferably 60 or less, and still more preferably 40 or less, from the viewpoint of improving the cleaning property and the redeposition suppression effect. The average number of moles of EO added is preferably 2 or more and 150 or less, more preferably 3 or more and 80 or less, still more preferably 5 or more and 60 or less, still more preferably 6 or more and 40 or less, and still more preferably 8 or more and 40 or less. The average number of moles of EO added is a number average value.

[0020] Furthermore, among the nonionic surfactants, the alkyl group in the polyoxyethylene alkyl ether, alkyl glucoside, alkyl alkanolamide, alkyl glyceryl ether, and alkyl saccharide, the alkenyl group in the polyoxyethylene alkenyl ether, and the fatty acid in the polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyoxyethylene fatty acid ester, higher fatty acid sucrose ester, and polyglycerin fatty acid ester preferably has 8 or more and 22 or less carbon atoms, more preferably 10 or more and 22 or less carbon atoms, and even more preferably 12 or more and 20 or less carbon atoms, from the viewpoint of improving cleaning performance and suppressing redeposition.

[0021] Among the above, from the viewpoint of improving cleaning properties and redeposition inhibiting effect, component (C) is preferably one or more types selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene fatty acid esters, alkyl glyceryl ethers, and polyoxyethylene hydrogenated castor oil, each having an HLB value within the above-mentioned range, more preferably one or more types selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene sorbitan fatty acid esters, and polyoxyethylene hydrogenated castor oil, and even more preferably one or more types selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene sorbitan fatty acid esters, and polyoxyethylene hydrogenated castor oil.

[0022] Commercially available products can also be used as component (C). Specific examples include "Rheodol TW-S320V" (polyoxyethylene sorbitan tristearate (20E.O.), HLB value 10.5), "Emanon CH-25" (polyoxyethylene hydrogenated castor oil (25E.O.), HLB value 10.7), "Emulgen 108" (polyoxyethylene (6) lauryl ether, HLB value 12.1), "Emanon CH-40" (polyoxyethylene hydrogenated castor oil (40E.O.), HLB value 12.5), "Emulgen 306L" (polyoxyethylene (6) stearyl ether, HLB value 12.8), "Emulgen 420" (polyoxyethylene (13) oleyl ether, HLB value 13.6), and "Emanon Examples of such oils include "CH-60K" (polyoxyethylene hydrogenated castor oil (60E.O.), HLB value 14.0), "Emulgen 1620G" (polyoxyethylene (20) 2-hexyldecyl ether, HLB value 14.0), "Emulgen 116" (polyoxyethylene (16) lauryl ether, HLB value 14.6), "Leodol TW-S120V" (polyoxyethylene sorbitan monostearate (20E.O.), HLB value 14.9), "Emulgen 123P" (polyoxyethylene (23) lauryl ether, HLB value 16.9), "Emanon 3199VB" (PEG-150 monostearate, HLB value 18.9), and "Emanon 3299VB" (PEG-150 distearate, HLB value 19.4).

[0023] The content of each component in the solid hair wash of the present invention is preferably within the following range from the viewpoint of dissolving it in water and enabling hair washing simply by immersing the hair in the composition, and from the viewpoint of improving the cleansing properties and the effect of inhibiting redeposition.

[0024] The content of component (A) in the solid hair wash is preferably 15.0% by mass or more, more preferably 20.0% by mass or more, even more preferably 25.0% by mass or more, and even more preferably 30.0% by mass or more from the viewpoint of improving the cleansing ability, and is preferably 45.0% by mass or less, more preferably 42.0% by mass or less, and even more preferably 40.0% by mass or less from the viewpoint of solubility in water and moldability of the solid hair wash.

[0025] The content of component (B) in the solid hair cleansing agent is preferably 15.0% by mass or more, more preferably 20.0% by mass or more, even more preferably 30.0% by mass or more, and even more preferably 40.0% by mass or more from the viewpoint of improving cleansing ability, and is preferably 60.0% by mass or less, more preferably 58.0% by mass or less, and even more preferably 55.0% by mass or less from the viewpoint of solubility in water and moldability of the solid hair cleansing agent.

[0026] The content of component (C) in the solid hair wash is preferably 1.5% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and still more preferably 8.0% by mass or more, from the viewpoint of improving the cleansing ability and the redeposition inhibitory effect, and is preferably 20.0% by mass or less, more preferably 18.0% by mass or less, from the viewpoint of the redeposition inhibitory effect.

[0027] In the solid hair wash, the mass ratio of the total amount of components (A) and (B) to component (C) [{(A)+(B)} / (C)] is, from the viewpoint of improving the cleansing ability and the redeposition inhibiting effect, 4.0 or more, preferably 4.5 or more, and is 24.0 or less, preferably 20.0 or less, more preferably 15.0 or less, and even more preferably 12.0 or less.

[0028] In the solid hair cleansing agent, the mass ratio of component (A) to component (B) [(A) / (B)] is preferably 0.20 or more, more preferably 0.40 or more, and even more preferably 0.60 or more from the viewpoints of carbonation foaming property and its duration, and of improving cleansing property by setting the pH when dissolved in water in a desired range. Also, from the viewpoints of carbonation foaming property and solubility in water, it is preferably 1.50 or less, more preferably 1.20 or less, and even more preferably 1.00 or less.

[0029] The total amount of component (A) and component (B) in the solid hair wash is preferably 30.0% by mass or more, more preferably 40.0% by mass or more, even more preferably 60.0% by mass or more, and even more preferably 80.0% by mass or more, from the viewpoint of improving the cleansing ability by increasing the carbonation foaming property and its duration, and is preferably 98.5% by mass or less, more preferably 97.0% by mass or less, and even more preferably 95.0% by mass or less, from the viewpoint of improving the cleansing ability and the effect of inhibiting redeposition. Furthermore, from the viewpoint of improving the cleansing properties and the effect of inhibiting redeposition, the total amount of components (A) to (C) in the solid hair wash is preferably 40% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass.

[0030] The solid hair cleansing agent of the present invention may contain, as other components, components that are generally used in solid preparations, as appropriate. Examples of such components include synthetic water-soluble polymers such as polyethylene glycol, polyvinylpyrrolidone, sodium polyacrylate, polyethyleneimine, and polyvinyl alcohol; natural water-soluble polymers such as glue, gelatin, collagen protein, casein, sodium alginate, carrageenan, furcellaran, tamarind gum, pectin, gum arabic, guar gum, xanthan gum, tragacanth gum, locust bean gum, dextrin, dextran, agar, and starch; carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, and the like. semi-synthetic water-soluble polymers such as starch, hydroxypropyl cellulose, cellulose acetate phthalate, propylene glycol alginate, oxidized starch, esterified starch, etherified starch, cationic starch, etc.; surfactants other than component (C); inorganic salts other than component (B), such as sodium sulfate, potassium chloride, sodium chloride, potassium nitrate, sodium nitrate, sodium polyphosphate, ammonium chloride, ferrous sulfate, sodium phosphate, sodium thiosulfate, etc.; excipients such as calcium silicate and glucose; disintegration aids; medicinal ingredients such as herbal medicines; colorants; fragrances; oils; etc.

[0031] (Dosage form) The dosage form (product form) of the solid hair cleansing agent of the present invention when used is preferably a powder or tablet from the viewpoint of ease of handling when dissolved in water, and more preferably a tablet from the viewpoint of improving the sustained carbonation effervescence. Tablets include tablet-pressed and briquette-pressed agents, and tablet-pressed agents are more preferable from the viewpoint of moldability. When the solid hair cleansing agent of the present invention is in the form of a tablet or briquette, it can be produced by a conventional method such as compression molding using a press tableting machine or a briquette machine. In producing a tablet or briquette type agent, for example, all of the components constituting the solid hair cleansing agent of the present invention may be dry-blended to obtain a powder, which may then be subjected to compression molding. Alternatively, a portion of the components may be granulated or molded in advance, and then mixed with the remaining components to obtain a mixture, which may then be subjected to compression molding.

[0032] (Properties) The solid hair cleanser of the present invention is added to water and dissolved therein for use. From the viewpoint of improving cleansing properties and the effect of inhibiting redeposition, and from the viewpoint of eliminating the need for rinsing after washing hair, the pH of a 1% by mass aqueous solution of the solid hair cleanser at 25° C. is preferably 6.0 or less, more preferably 5.8 or less, even more preferably 5.5 or less, and is preferably 4.0 or more, more preferably 4.5 or more. When the pH of a 1% by mass aqueous solution of the solid hair cleanser is within the above range at 25°C, the pH of the water containing the solid hair cleanser (i.e., the hair cleansing solution) can be easily adjusted to 6.0 or less when washing hair with the solid hair cleanser, improving the cleansing properties and the effect of inhibiting redeposition, and making it possible to omit rinsing after washing hair. Specifically, the above pH can be measured by the method described in the Examples.

[0033] [How to wash hair] The present invention provides a hair washing method (hereinafter also referred to as "the method of the present invention") comprising the following step (I) or step (II): Step (I): adding the solid hair cleansing agent to water and immersing hair in the water while foaming with carbon dioxide gas. Step (II): A step of immersing hair in water and then adding the solid hair cleansing agent to the water. According to the method of the present invention, it is possible to wash hair by simply immersing the hair in the hair washing solution, without the need to foam a detergent on the hair to wash it. In addition, rinsing after washing the hair can be omitted.

[0034] In steps (I) and (II), the hair may be immersed in the hair wash solution or water while it is dry, or may be immersed after being wetted with water. In step (I), from the viewpoint of improving the cleansing ability of hair, it is preferable to immerse hair immediately after adding the solid hair cleanser to water. This is because immersing hair in the hair cleansing solution while carbon dioxide gas is being bubbled enhances the cleaning effect of hair. In step (I), after adding the solid hair cleanser to water, the hair is immersed preferably within 3 minutes, more preferably within 1 minute, and even more preferably within 0.5 minutes. From the viewpoint of enhancing the hair cleaning effect by immersing the hair in the hair wash solution during carbonation foaming, the method of the present invention may include either step (I) or step (II), and more preferably includes step (II).

[0035] In steps (I) and (II), the bath ratio between the hair and the hair wash solution or water in which the hair is immersed (hair / hair wash solution or water) is preferably 0.1 / 99.9 to 50 / 50, more preferably 0.5 / 99.5 to 30 / 70, in terms of mass ratio, from the viewpoints of improving cleansing properties and the effect of inhibiting redeposition, and from the viewpoints of eliminating the need for rinsing after hair washing. In step (I) and step (II), the bath ratio of the solid hair cleanser to the water to which the solid hair cleanser is added (solid hair cleanser / water) is, in terms of mass ratio, preferably 0.01 / 99.99 to 20 / 80, more preferably 0.1 / 99.9 to 15 / 85, and even more preferably 0.2 / 99.8 to 10 / 90, from the viewpoints of improving cleansing properties and the effect of inhibiting redeposition, and of eliminating the need for rinsing after hair washing.

[0036] In steps (I) and (II), the pH of the water after the addition of the hair cleansing agent (i.e., the hair cleansing solution) is preferably 6.0 or less, more preferably 5.8 or less, even more preferably 5.5 or less, from the viewpoint of improving cleansing properties and the effect of inhibiting redeposition, and from the viewpoint of eliminating the need for rinsing after washing the hair, and is preferably 4.0 or more, more preferably 4.5 or more. The pH can be measured by the same method as above. The temperature of the hair wash solution or water in which the hair is immersed is usually in the range of 30 to 45°C, preferably 35 to 42°C. The time for immersing the hair in the hair wash solution is not particularly limited, but from the viewpoint of improving cleansing properties and reducing the burden of washing hair, it is preferably 1 to 30 minutes, more preferably 5 to 20 minutes. In step (II), the starting point of "the time for immersing the hair in the hair wash solution" is the time when the solid hair wash agent is added to the water in which the hair is immersed.

[0037] After the step of immersing the hair in step (I) or step (II), it is preferable to remove the hair from the hair washing solution and then dry the hair. After removing the hair from the hair washing solution and before drying, a step of rinsing the hair can be performed as necessary. However, when the solid hair washing agent of the present invention is used, there is little reattachment of sebum and the like to the hair, making it unnecessary to rinse it off, so that the step of rinsing the hair can be omitted in the method of the present invention. This reduces the burden of washing the hair. The hair can be dried in a conventional manner using a towel, a water absorbent material, a dryer, or a combination of these. EXAMPLES

[0038] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of the examples.

[0039] Examples 1 to 8 and Comparative Examples 1 to 6 (Preparation and Evaluation of Solid Hair Cleansing Agents) For Examples 1 to 8, Comparative Example 2, and Comparative Examples 4 to 6, the components were blended and mixed according to the blending compositions shown in Tables 2 to 3, and the resulting powder was then compressed in a press tableting machine at a compression pressure of 5 MPa to produce tablet (compressed)-type solid hair cleansing agents with a mass of 8.00 to 12.00 g and a tablet height of 15.1 to 15.3 mm. The resulting solid hair cleansing agents were evaluated by the methods shown below. In Comparative Example 1, the evaluation was performed using deionized water. In Comparative Example 3, the evaluation was performed using an aqueous solution in which component (C) was dissolved in deionized water in the ratio shown in Table 2. The blending amount (mass %) of each component shown in the table is the amount of active ingredient.

[0040] <pH of hair washing solution> Hair washing solutions having the compositions shown in Tables 2 and 3 were prepared, and the pH of the washing solutions at 25° C. was measured using a pH meter (HM-30R, manufactured by DKK-TOA Corporation).

[0041] <Model sebum cleansing rate> 20 μL of the model sebum shown in Table 1 was dropped onto a 35 mm × 35 mm polyethylene film (mass W0 (g)), and the mass of the film was measured (W A (g)). Next, 100 mL of hair wash liquid (40°C) having the composition shown in Tables 2 to 3 was prepared, and the film was immersed for 1 minute. In detail, for Examples 1 to 8 and Comparative Examples 4 to 6, the film was immersed in 100 mL of water at 40°C, and then 1.00 g of a solid hair wash agent was added and left to stand for 1 minute. For Comparative Example 2, the film was immersed in 100 mL of water at 40°C, and then 1.00 g of a solid hair wash agent was added and left to stand for 1 minute. For Comparative Examples 1 and 3, 100 mL of hair wash liquid (40°C) having the composition shown in Table 2 was prepared, and then the film was immersed for 1 minute. After 1 minute, the film was taken out and dried overnight, and the mass of the dried film was measured (W B The cleaning rate of the model sebum was calculated using the following formula and evaluated on a four-level scale. Model sebum cleaning rate (%) = (W A -W B ) / (W A -W0) x 100 [Evaluation Criteria] A: Cleaning rate over 70% B: Cleaning rate more than 50% and less than 70% C: Cleaning rate: 30% to 50% D: Cleaning rate less than 30% [Model resin composition]

[0042] [Table 1]

[0043] <Presence or absence of precipitates after cleaning> The hair wash liquid used in the evaluation of the "cleaning rate of model sebum" was allowed to stand until the evolution of carbon dioxide gas had ceased, and then the presence or absence of precipitates was visually confirmed.

[0044] [Table 2]

[0045] [Table 3]

[0046] The components listed in the table are as follows. *1: Polyoxyethylene sorbitan monostearate (20E.O.): Polysorbate 60, Kao Corporation's "Rheodol TW-S120V", HLB value 14.9 *2: Polyoxyethylene (6) lauryl ether: Kao Corporation's "Emulgen 108", HLB value 12.1 *3: Polyoxyethylene hydrogenated castor oil (40E.O.): Kao Corporation's "Emanon CH-40", HLB value 12.5 *4: Polyoxyethylene (23) lauryl ether: Kao Corporation's "Emulgen 123P", HLB value 16.9

[0047] It can be seen from Tables 2 and 3 that the solid hair cleanser of this example has a high sebum cleansing ability. In addition, since no precipitate was found in the cleaning solution after cleaning from sebum, it is considered that there is little risk of the solid hair cleanser remaining undissolved and sebum, etc., reattaching to the hair. [Industrial Applicability]

[0048] According to the solid hair cleanser of the present invention, hair can be washed simply by immersing the hair in the solid hair cleanser, and the solid hair cleanser has high cleansing properties and can suppress the re-adhesion of the hair to the hair, as well as the residual hair cleanser and sebum, etc. When washing hair using the solid hair cleanser, the operation of lathering the cleanser on the hair to wash it and rinsing the hair after washing can be omitted, which reduces the burden of washing hair in medical and nursing care settings and also makes it possible to suppress a decrease in the frequency of washing hair.

Claims

1. Component (A): organic acid, Component (B): carbonate, and Component (C): nonionic surfactant, Contains the component (C) is one or more selected from the group consisting of polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene sorbitan fatty acid esters, and polyoxyethylene hydrogenated castor oils, A solid hair wash, in which the mass ratio of the total amount of components (A) and (B) to component (C), [{(A)+(B)} / (C)], is 4.0 or more and 24.0 or less.

2. 2. The solid hair wash according to claim 1, wherein a mass ratio of the component (A) to the component (B) [(A) / (B)] is 0.20 or more and 1.50 or less.

3. 3. The solid hair wash according to claim 1, wherein the HLB value of the component (C) is 10.0 or more and 20.0 or less.

4. The solid hair wash according to any one of claims 1 to 3, wherein the component (A) is at least one selected from the group consisting of succinic acid, tartaric acid, malic acid, citric acid, and ascorbic acid.

5. The solid hair wash according to any one of claims 1 to 4, wherein the total amount of the components (A) to (C) in the solid hair wash is 40 mass% or more.

6. The solid hair wash according to any one of claims 1 to 5, wherein a pH of a 1% by mass aqueous solution of the solid hair wash at 25°C is 6.0 or less.

7. A method for washing hair, comprising the following step (I) or step (II): Step (I): A step of adding the solid hair cleansing agent according to any one of claims 1 to 6 to water and immersing hair in the water while foaming with carbon dioxide gas. Step (II): A step of immersing hair in water and then adding the solid hair cleansing agent according to any one of claims 1 to 6 to the water.

8. The method for washing hair according to claim 7, wherein the pH of water to which the solid hair wash has been added is 6.0 or less.

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