Surfactant composition containing N-acyl amino acid or a salt thereof and method for producing the same

Abstract

To provide a novel technology for surfactant compositions containing N-acyl amino acids or their salts that can suppress odor and further improve color stability. [Solution] A surfactant composition comprising an N-acyl amino acid represented by general formula (1) or a salt thereof, wherein the content ratio of the amino acid represented by general formula (2) and its salt thereof is 1% by weight or less. JPEG2026045795000015.jpg27170 JPEG2026045795000016.jpg27170 (In the formula, R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R2 represents a linear or branched alkyl group having 1 to 4 carbon atoms which may have a hydrogen atom or one hydroxyl group, R3 represents -COOH or -SO3H, and n represents 1, 2, or 3.)

Description

Technical Field

[0006] , , , ,

[0001] The present invention relates to a surfactant composition containing an N-acyl amino acid or a salt thereof.

Background Art

[0002] As amino acid type surfactants, N-acyl amino acids and their salts are less irritating than conventional alkyl benzene sulfonic acids and their salts, etc., so they are highly safe and have good foaming and foam touch. Therefore, N-acyl amino acids and their salts are widely used as bases for liquid detergents such as facial cleansers, body soaps, hand soaps, shampoos, etc. and cosmetics, or for the purpose of improving the usability.

[0003] As methods for producing N-acyl amino acids and their salts, the Schotten-Baumann method of reacting a fatty acid chloride with an alkaline aqueous solution of an amino acid, or the method of reacting a fatty acid chloride in an amino acid aqueous solution containing a hydrophilic solvent in the presence of an alkali, which is an improved invention exemplified in Patent Document 1 and Patent Document 2, is widely used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the objects of the present invention is to provide a novel technology for a surfactant composition containing an N-acyl amino acid or a salt thereof, which can suppress odor and further enhance hue stability.

Means for Solving the Problems

[0006] N-acyl amino acid surfactants tend to discolor over time compared to conventional surfactants and may have a distinctive odor. Therefore, it is conceivable to add preservatives such as antioxidants to prevent discoloration over time, or to add large amounts of fragrance to cosmetics to mask the distinctive odor. However, in order to design ethical cosmetics that are liquid, highly transparent, and free of preservatives, which are required for high-value-added hair and body cleansers, for which demand has been increasing in recent years, it is preferable to use surfactants that have little odor and high color stability without the addition of preservatives. The inventors of this invention conducted diligent research to solve the above problems and, to their surprise, discovered that the aforementioned odor and color stability were strongly correlated with the trace amounts of residual amino acids used as raw materials. The inventors then developed a technology to reduce the amount of residual amino acids, leading to the present invention.

[0007] The gist of this invention is as follows: (A) General formula (1) [ka] (In formula (1), R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R2 represents a linear or branched alkyl group having 1 to 4 carbon atoms which may have a hydrogen atom or one hydroxyl group, R3 represents -COOH or -SO3H, and n represents 1, 2, or 3.) It contains an N-acyl amino acid or a salt thereof, as shown by General formula (2) [ka] (In equation (2), R2, R3, and n are the same as defined above.) A surfactant composition having a content ratio of 1% by weight or less of the amino acids and their salts indicated by [the specified formula]. (B) General formula (1) [ka] (In formula (1), R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R2 represents a linear or branched alkyl group having 1 to 4 carbon atoms which may have a hydrogen atom or one hydroxyl group, R3 represents -COOH or -SO3H, and n represents 1, 2, or 3.) A method for producing a surfactant composition containing an N-acyl amino acid or a salt thereof, as shown by In the presence of an alkali, a reaction solution containing water as a solvent reacts with fatty acid chloride and general formula (2) [ka] (In equation (2), R2, R3, and n are the same as defined above.) The amino acid represented by the above general formula (1) is reacted with the above general formula (1) to produce the N-acyl amino acid, The pH of the reaction solution containing the N-acyl amino acid represented by the general formula (1) above is set to 2 or less. The reaction solution, whose pH is reduced to 2 or less, is separated at a temperature of 80°C or higher. The production method comprising washing a phase containing an N-acyl amino acid represented by the general formula (1) with water. (C) The manufacturing method according to (B), wherein the phase containing the N-acyl amino acid represented by the general formula (1) is washed with water in an amount of 1 to 30 times the amount of the phase. (D) General formula (1) [ka] (In formula (1), R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R2 represents a linear or branched alkyl group having 1 to 4 carbon atoms which may have a hydrogen atom or one hydroxyl group, R3 represents -COOH or -SO3H, and n represents 1, 2, or 3.) A method for suppressing odor and improving color stability of a surfactant composition containing an N-acyl amino acid or a salt thereof, as shown in In the presence of an alkali, a reaction solution containing water as a solvent reacts with fatty acid chloride and general formula (2) [ka] (In formula (2), R2, R3, and n are the same as the above definitions.) react with the amino acid represented by to produce the N-acyl amino acid represented by the general formula (1), adjust the pH of the reaction solution containing the N-acyl amino acid represented by the general formula (1) to 2 or less, separate the reaction solution with a pH of 2 or less at 80°C or higher, The method includes washing the phase containing the N-acyl amino acid represented by the general formula (1) or a salt thereof with water. (E) The method according to (D), wherein the phase containing the N-acyl amino acid represented by the general formula (1) is washed with water in an amount of 1 to 30 times the amount of the phase. [Advantages of the Invention]

[0008] According to the present invention, a novel technique can be provided that can suppress the odor and enhance the hue stability of a surfactant composition containing an N-acyl amino acid or a salt thereof. [Embodiments for Carrying Out the Invention]

[0009] Hereinafter, one embodiment of the present invention will be described. The present invention is not limited only to the following embodiments. This embodiment relates to a surfactant composition and contains an N-acyl amino acid represented by the general formula (1) or a salt thereof.

[0010] <0(000)109> [Chemical Formula]

[0011] In formula (1), R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R2 represents a hydrogen atom or an alkyl group which may have one hydroxyl group and is a straight-chain or branched-chain having 1 to 4 carbon atoms, R3 represents -COOH or -SO3H, and n represents 1, 2, or 3. The aliphatic acyl group R1CO, having 8 to 22 carbon atoms, may be an acyl group derived from a saturated or unsaturated fatty acid having 8 to 22 carbon atoms, or an acyl group derived from a mixed fatty acid containing two or more of these fatty acids. For example, examples of aliphatic acyl groups having 8 to 22 carbon atoms include capryloyl, caproyl, lauroyl, myristoyl, palmitoyl, stearoyl, oleyl, behenoyl, coconut oil fatty acid acyl group, and palm kernel oil fatty acid acyl group, with lauroyl, myristoyl, oleyl, coconut oil fatty acid, and palm kernel oil fatty acid being preferred.

[0012] Furthermore, the surfactant composition of this embodiment may contain an amino acid represented by general formula (2) or a salt thereof. Examples of amino acids represented by general formula (2) and salts thereof include precursors of N-acyl amino acids represented by general formula (1) and salts thereof.

[0013] [ka]

[0014] In formula (2), R2 represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, which may have one hydroxyl group; R3 represents -COOH or -SO3H; and n represents 1, 2, or 3.

[0015] Examples of linear or branched alkyl groups having 1 to 4 carbon atoms that may have one hydroxyl group include methyl, ethyl, propyl, butyl, isopropyl, isobutyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxyisopropyl, hydroxybutyl, and hydroxyisobutyl groups. Furthermore, hydrogen atoms, methyl groups, and hydroxyethyl groups are preferred as R2 because they have high foaming properties and low irritancy.

[0016] Specific examples of amino acids represented by general formula (2) include sarcosine, β-alanine, N-methyl-β-alanine, N-hydroxyethyl-β-alanine, and N-methyl-taurine. Similarly, specific examples of N-acyl amino acids represented by general formula (1) include acylsarcosine, acyl-β-alanine, acyl-N-methyl-β-alanine, acyl-N-hydroxyethyl-β-alanine, and acyl-N-methyl-taurine.

[0017] As described above, the surfactant composition of this embodiment may contain a salt of an N-acyl amino acid represented by general formula (1) and / or a salt of an amino acid represented by general formula (2). Specifically, examples include salts with alkali metals, alkaline earth metals, ammonia, or organic ammonium compounds. Examples of alkali metals include potassium and sodium. Examples of alkaline earth metals include calcium and magnesium. Examples of organic ammonium compounds include alkanolamines and alkylamines. In the case of salts with divalent alkali metals or alkaline earth metals, a 1 / 2 salt can be formed. Of these, selecting a salt with an alkali metal salt such as potassium and / or sodium, or a salt with an organic ammonium such as an alkanolamine, is preferable because it results in a composition that is highly foamy, low in irritation, and transparent.

[0018] In the surfactant composition of this embodiment, the content of amino acids represented by general formula (2) and their salts is reduced, resulting in suppressed odor and improved color stability. In the surfactant composition of this embodiment, the content ratio of the compound of general formula (2), which is an amino acid, and its salt is preferably 1% by weight or less, more preferably 0.5% by weight or less, and even more preferably 0.3% by weight or less, from the viewpoint of odor suppression and improvement of color stability. While not particularly limited, the content of the N-acyl amino acid represented by general formula (1) or its salt in the surfactant composition of this embodiment can be, for example, 15% by weight or more and 100% by weight or less, and preferably 25% by weight or more and 100% by weight or less. Furthermore, if the surfactant composition of this embodiment is an aqueous solution, the content of the N-acyl amino acid represented by general formula (1) or its salt is more preferably 25% by weight or more and 35% by weight or less. Setting the concentration of the aqueous solution to 25% or more makes it easier to improve handling in relation to the amount of water that can be used during formulation, and setting it to 35% or less can suppress gelation and solidification in low-temperature environments during winter. The surfactant composition of this embodiment can also be made into a solvent-free powder or mass using known methods such as spray drying and freeze-drying.

[0019] The surfactant composition of this embodiment may contain other components in addition to the N-acyl amino acid represented by general formula (1) or a salt thereof, and the amino acid represented by general formula (2), as long as the objectives of the present invention can be achieved. For example, the surfactant composition of this embodiment may contain free fatty acids. There are no particular restrictions on the amount of free fatty acids contained in the surfactant composition of this embodiment, but their inclusion provides a refreshing feeling during washing and contributes to improved foam density. Furthermore, it is preferable to limit the free fatty acid content to 10% by weight or less, as this can suppress odor, improve stability by suppressing gelation, and improve transparency at low temperatures when the surfactant composition is transparent.

[0020] The surfactant composition of this embodiment exhibits higher color stability over time even without the use of preservatives. On the other hand, the surfactant composition of this embodiment may contain preservatives. Examples of such preservatives include antioxidants and chelating agents, such as diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), N-(2-acetamide)iminodiacetic acid (ADA), N-(2-hydroxyethyl)iminodiacetic acid (HIDA), etidronic acid (HEDP), pyrophosphate, neridronic acid, alendronic acid, 2-pyridinol-1-oxide (HPNO), and hinokitiol.

[0021] The surfactant composition of this embodiment is, for example, In the presence of an alkali, a fatty acid chloride is reacted with an amino acid represented by general formula (2) in a reaction solution containing water as a solvent to produce an N-acyl amino acid represented by general formula (1). The pH of the reaction solution containing the N-acyl amino acid represented by general formula (1) is set to 2 or less. The reaction solution, with a pH of 2 or less, is separated at a temperature of 80°C or higher. It can be produced by a method that includes washing with water a phase containing an N-acyl amino acid represented by general formula (1).

[0022] Specifically, the surfactant composition of this embodiment can be manufactured, for example, as follows. First, an N-acylamino acid represented by general formula (1) is produced as an acylated product derived from the amino acid of general formula (2) with a fatty acid derivative. This step can be carried out by a so-called Schotten-Baumann reaction, in which the amino acid corresponding to general formula (2) and a fatty acid chloride are condensed in the presence of an alkali, and water can be used as the reaction solvent. On the other hand, if the dispersibility of the amino acid represented by general formula (2) in water is low and the reaction does not proceed, a hydrophilic organic solvent that is inert to the fatty acid chloride can be added to form a mixed solvent with water. Examples of such inert hydrophilic organic solvents include acetone, methyl ethyl ketone, and tetrahydrofuran. In order to further reduce the content of the amino acid represented by general formula (2) and its salt, the amount of hydrophilic organic solvent added is preferably 50% by weight or less, more preferably 10% by weight or less, and even more preferably 0% by weight relative to the water used as the solvent. As the fatty acid from which R1CO in general formula (1) is derived, fatty acids derived from natural plant oils are preferred because they are renewable raw materials with low environmental impact, have a low possibility of depletion, and can be used stably. In the case of mixed fatty acids, one or more fatty acids can be used in combination, and any mixing ratio of fatty acids can be used to achieve the desired feel.

[0023] The amount of fatty acid chloride relative to the amino acid corresponding to general formula (2) in the Schotten-Baumann reaction is preferably 0.9 equivalents or more but less than 1 equivalent. Using 0.9 equivalents or more maintains economic advantages, while using less than 1 equivalent suppresses the decrease in transparency due to an increase in free fatty acids when the composition is transparent. The alkali used in the reaction can be added entirely beforehand or in conjunction with the addition of the acid chloride, as long as it is between 1 and 1.2 equivalents relative to the acid chloride used. Adding 1 equivalent or more of alkali suppresses the increase in free fatty acids due to the slower reaction. Adding 1.2 equivalents or less avoids the need for a large amount of acid during the subsequent neutralization step. The alkali used is not particularly limited as long as it can neutralize the chlorine produced in the Schotten-Baumann reaction; readily available sodium hydroxide and potassium hydroxide can be used.

[0024] The reaction temperature can be arbitrarily selected within the range of 10°C to 60°C, and is preferred. Setting the temperature above 10°C can suppress the increase in free fatty acids due to the hydrolysis of fatty acid chloride, which slows down the reaction. Setting the temperature below 60°C can suppress the increase in free fatty acids due to the rapid hydrolysis of fatty acid chloride. From the viewpoint of suppressing the amount of free fatty acids produced after the acylation reaction, the reaction temperature is preferably between 20°C and 50°C, and more preferably between 30°C and 45°C. The reaction time is not particularly limited as long as exothermic control is possible, and a maturation time can be provided after the completion of the reaction as needed.

[0025] After the acylation reaction, the pH of the reaction solution is reduced to 2 or less using an acid, and the solution is separated at 80°C or higher. Subsequently, the phase containing the acyl amino acid represented by general formula (1) is washed with water. Performing these steps after the acylation reaction can reduce the content of the amino acid represented by general formula (2). The acid used for pH adjustment is preferably sulfuric acid and / or hydrochloric acid. Sulfuric acid is particularly preferred because it minimizes the amount of wastewater separated and is a divalent acid with low odor. As mentioned above, liquid-liquid separation can be carried out at a reaction solution temperature of 80°C or higher. The amount of water used for washing can be set appropriately by those skilled in the art and is not particularly limited, but from the viewpoint of reducing the content of amino acids and their salts represented by general formula (2) and increasing yield, it is preferable to use an amount of 1 to 30 times the amount of the phase containing acyl amino acids represented by general formula (1). Furthermore, the temperature during washing is not particularly limited, but for example, it can be the same temperature as in the liquid-liquid separation step.

[0026] After rinsing, the acyl amino acid represented by general formula (1) may be neutralized with an alkali metal, alkaline earth metal, or organic ammonium, depending on the purpose.

[0027] As described above, according to this embodiment, the odor of the surfactant composition containing N-acyl amino acids can be suppressed and the color stability can be improved. In the surfactant composition of this embodiment, for example, no fragrance is added for masking purposes, making it possible to contribute to the provision of ethical toiletry products such as preservative-free shampoos, body soaps, and facial cleansers that are of high interest to general consumers. [Examples]

[0028] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited in any way by these examples. Furthermore, unless otherwise specified, the raw materials used in the following examples and comparative examples were reagents manufactured by Kanto Chemical Co., Ltd. or Sigma-Aldrich Co. LLC.

[0029] Method for measuring the amino acid content represented by general formula (2) in a surfactant composition In a tightly sealed flask, 1.0 g of a surfactant composition containing N-acyl amino acids was mixed with 30 g of distilled water and 1.1 g of caustic soda (48%, 1.8 equivalents relative to benzoyl chloride) and 1.0 g of benzoyl chloride was added. The mixture was stirred for at least 1 hour in a warm bath at 30-45°C. Subsequently, the mixture was analyzed by high-performance liquid chromatography (JASCO Corporation, Inertsil ODS-2 (4.6 mmφ × 150 mm), column temperature: 40°C, 0.1 M NaH2PO4 (pH 2.1) / CH3OH = 65 / 35, flow rate: 1.0 mL / min, sample volume: 20 μL, UV wavelength: 220 nm). The amino acid represented by general formula (2) was derivatized with benzoyl chloride using the same procedure as for the N-acyl amino acids represented by general formula (1), extracted with ethyl acetate, concentrated to dryness, and purified by column chromatography with hexane / ethyl acetate (MB-4B, Fuji Silysia Chemical). The resulting sample was used as a standard and quantified by absolute calibration curve to determine the content of the amino acid represented by general formula (2) remaining in the surfactant composition according to the following calculation formula. Unless otherwise specified, the measurement methods were performed according to the provisions of 2.01 Liquid Chromatography, General Test Methods, Supplement 1, 18th Edition of the Japanese Pharmacopoeia. The content (by weight) of the amino acid represented by general formula (2) = Content of the amino acid represented by general formula (2) (g) / (Content of the amino acid represented by general formula (2) (g) + Content of the N-acyl amino acid represented by general formula (1) (g)) × 100

[0030] Evaluation of the odor of surfactant compositions The odor of the surfactant compositions was evaluated on a four-point scale, from weakest to strongest: "almost no odor," "a barely perceptible odor," "a faint odor that can be identified," and "an easily perceptible odor." Comparative Example 5, described below, was used as a control. Products that were evaluated as having a weaker odor than the control were evaluated as having suppressed odor. Furthermore, evaluations of "almost no odor" and "a barely perceptible odor" were evaluated as favorable results, as they indicated that the odor was at a level where, for example, a fragrance for masking the odor derived from the amino acids represented by general formula (2) in the formulation was not required.

[0031] Evaluation of color stability of surfactant compositions 100 g of the surfactant composition was sealed in a glass vial (S-112, manufactured by Toyo Glass Co., Ltd.) and left to stand in an 80°C constant temperature bath for 18 hours. After that, the Hazen unit color number (APHA) was measured using a Spectrometer SE7700 (Nippon Denshoku Industries Co., Ltd.). Comparative Example 5, described below, was used as a control. A lower APHA value than that of the control was considered to indicate improved hue stability.

[0032] Example 1 In a 1L four-necked flask equipped with a stirring device, 156g of a 27 wt% aqueous solution of N-methyl-β-alanine sodium, 210g of tap water, and 13g of 48 wt% sodium hydroxide were charged, and the temperature was adjusted to 30°C in a water bath. 72g of lauric acid chloride and 13g of 48 wt% sodium hydroxide were added dropwise from separate dropping funnels over 1 hour at a temperature of 30-40°C, and the mixture was aged for 0.5 hours at the same temperature range. After aging, 50g of 75 wt% sulfuric acid was added to adjust the pH to 1.5, and the mixture was heated to 80°C, then allowed to stand for 1 hour before liquid-liquid extraction. 120g of water was added to the upper layer, and the mixture was heated to 80°C, allowed to stand for 1 hour, and then liquid-liquid extraction was performed twice. Subsequently, 200g of water and 26g of 48% sodium hydroxide were added to obtain 310g of a 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium as a surfactant composition. The N-methyl-β-alanine sodium residue in the obtained 30% by weight aqueous solution was 0.02% by weight, it had almost no odor, and the APHA after the color stability test was 10.

[0033] Example 2 The reaction was carried out in the same manner as in Example 1, except that lauric acid chloride was replaced with coconut oil fatty acid chloride, and 330 g of a 25 wt% aqueous solution of N-cocoyl-N-methyl-β-alanine sodium was obtained as a surfactant composition. The residual amount of N-methyl-β-alanine sodium in the obtained 25 wt% aqueous solution of N-cocoyl-N-methyl-β-alanine sodium was 0.1 wt%, it had almost no odor, and the APHA after the color stability test was 10.

[0034] Example 3 The reaction was carried out in the same manner as in Example 1, except that the amount of sulfuric acid used during neutralization was 35 g and the pH was adjusted to 2, yielding 310 g of a 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium as the surfactant composition. The residual amount of N-methyl-β-alanine sodium in the obtained 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was 1 wt%, it had a barely perceptible odor, and the APHA after the color stability test was 20.

[0035] Example 4 The reaction was carried out in the same manner as in Example 1, except that 175 g of water was used for rinsing, to obtain 310 g of a 30% by weight aqueous solution of N-lauroyl-N-methyl-β-alanine sodium as a surfactant composition. The residual amount of N-methyl-β-alanine sodium in the obtained 30% by weight aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was 0.2% by weight, it had almost no odor, and the APHA after the color stability test was 15.

[0036] Example 5 The reaction was carried out in the same manner as in Example 2, except that the sodium N-methyl-β-alanine in Example 2 was replaced with 123 g of a 30 wt% aqueous solution of sodium β-alanine, the 48 wt% sodium hydroxide used for salt formation after washing with water was replaced with 34 g of 48 wt% potassium hydroxide, and the N-acyl amino acid concentration was changed to 25 wt%. 370 g of a 25% aqueous solution of potassium N-cocoyl-β-alanine was obtained as a surfactant composition. The residual amount of potassium β-alanine in the obtained 25% aqueous solution of potassium N-cocoyl-β-alanine was 0.1 wt%, it had almost no odor, and the APHA after the color stability test was 20.

[0037] Example 6 In Example 1, the N-methyl-β-alanine sodium was replaced with 150 g of a 30% by weight aqueous solution of N-hydroxyethyl-β-alanine sodium. 100 g of tetrahydrofuran was added as the organic solvent, and the reaction was carried out. After washing with water and desolving, neutralization was performed as in Example 1 to obtain 300 g of a 30% by weight aqueous solution of N-lauroyl-N-hydroxyethyl-β-alanine sodium as a surfactant composition. The residual amount of N-hydroxyethyl-β-alanine sodium in the obtained 30% by weight aqueous solution of N-lauroyl-N-hydroxyethyl-β-alanine sodium was 1.0% by weight. The odor was almost nonexistent, and the APHA after the color stability test was 10.

[0038] Example 7 The reaction was carried out in the same manner as in Example 1, except that N-methyl-β-alanine sodium was replaced with 90 g of a 30 wt% aqueous solution of sodium sarcosinate, and 350 g of a 30 wt% aqueous solution of N-lauroyl sarcosinate was obtained as a surfactant composition. The amount of sodium sarcosinate remaining in the obtained 30 wt% aqueous solution of N-lauroyl sarcosinate was 0.05 wt%, it had almost no odor, and the APHA after the color stability test was 10.

[0039] Comparative Example 1 Except for using 28 g of 75% sulfuric acid and adjusting the pH to 3, the procedure was carried out in the same manner as in Example 1 to obtain 220 g of a 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium as a surfactant composition. The residual amount of N-methyl-β-alanine sodium in the obtained 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was 1.5 wt%, it had a faint odor that could be identified, and the APHA after the color stability test was 15.

[0040] Comparative Example 2 Except for replacing the 75% sulfuric acid in Example 1 with glacial acetic acid, using 20 g, and adjusting the pH to 4, the procedure was carried out in the same manner as in Example 1 to obtain 250 g of a 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium as the surfactant composition. The residual amount of N-methyl-β-alanine sodium in the obtained 30 wt% aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was 5 wt%, it had a readily detectable odor, and the APHA after the color stability test was 30.

[0041] Comparative Example 3 The procedure was carried out in the same manner as in Example 1, except that the separation temperature was set to 60°C. However, a large amount of intermediate layer was formed, making separation impossible. When the mixture was cooled to room temperature, a large amount of salt precipitated, so the analysis was abandoned.

[0042] Comparative Example 4 Except for using 28 g of 75% by weight sulfuric acid and adjusting the pH to 3, the procedure was carried out in the same manner as in Example 6 to obtain 220 g of a 30% aqueous solution of N-lauroyl-N-hydroxyethyl-β-alanine sodium as a surfactant composition. The remaining amount of N-hydroxyethyl-β-alanine sodium in the obtained 30% by weight aqueous solution of N-lauroyl-N-hydroxyethyl-β-alanine sodium was 3% by weight, it had an easily detectable odor, and the APHA after the color stability test was 50.

[0043] Comparative Example 5 The same procedure as in Example 1 was followed up to the first liquid-liquid separation step, and the neutralization step was performed without a water washing step. 320 g of a 30% by weight aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was obtained as the surfactant composition. The residual amount of N-methyl-β-alanine sodium in the obtained 30% by weight aqueous solution was 1.5% by weight, it had a faint odor that could be identified, and the APHA after the color stability test was 25.

[0044] Reference example In Comparative Example 2, a 30% by weight aqueous solution of sodium N-lauroyl-N-methyl-β-alanine was prepared, and 100 ppm of etidronic acid was added to it for a color stability test. The APHA after the color stability test was 10.

[0045] From the above test results for the examples and comparative examples, it can be understood that reducing the content of the amino acid of general formula (2) in the surfactant composition suppresses odor and improves color stability. Furthermore, when the content of the amino acid of general formula (2) is 1% or less, a surfactant composition containing N-acyl amino acid or its salt with even less odor and higher color stability can be obtained.

[0046] Example of a hair cleansing composition formulation The following fragrance-free hair shampoos were prepared. All of these hair shampoo compositions had little odor and showed no change in color during stability tests.

[0047] (Prescription example 1) Surfactant composition of Example 1 6.0 Sodium cocoyl methyl taurate 4.5 Cocamidopropyl betaine 5.0 Lauroyl propyl betaine 2.0 PPG2-Cocamide 1.0 Polyquaternium-10 0.5 Adjust the pH of the citric acid to 6.0. Water remaining (adjust so that the total above equals 100)

[0048] (Prescription example 2) Surfactant composition of Example 7 7.0 Surfactant composition of Example 6 3.5 Lauroyl propyl betaine 6.5 Cocamide DEA 0.5 PPG2-Cocamide 0.7 Polyquaternium-10 0.3 Adjust the pH of the citric acid to 6.0. Water remaining (adjust so that the total above equals 100)

[0049] The following fragrance-free hair shampoos were prepared. All of these hair shampoo compositions had an odor derived from the raw amino acids, and their color changed during stability testing.

[0050] (Comparative Example of Prescription 1) Surfactant composition of Comparative Example 1 6.0 Sodium cocoyl methyl taurate 4.5 Cocamidopropyl betaine 5.0 Lauroyl propyl betaine 2.0 PPG2-Cocamide 1.0 Polyquaternium-10 0.5 Adjust the pH of the citric acid to 6.0. Water remaining (adjust so that the total above equals 100)

[0051] (Comparative Example of Prescription 2) Surfactant composition of Example 7 7.0 Surfactant composition of Comparative Example 4 3.5 Lauroyl propyl betaine 6.5 Cocamide DEA 0.5 PPG2-Cocamide 0.7 Polyquaternium-10 0.3 Adjust the pH of the citric acid to 6.0. Water remaining (adjust so that the total above equals 100)

Claims

1. General formula (1) 【Chemistry 1】 (In formula (1), R １ CO represents an aliphatic acyl group with 8 to 22 carbon atoms, R ２ R represents an alkyl group which is a linear or branched chain having 1 to 4 carbon atoms, which may have a hydrogen atom or one hydroxyl group. ３ is -COOH or -SO ３ (H represents H, and n represents 1, 2, or 3.) It contains an N-acyl amino acid or a salt thereof, as shown by General formula (2) 【Chemistry 2】 (In formula (2), R ２ , R ３ (And n are the same as defined above.) A surfactant composition having a content ratio of 1% by weight or less of the amino acids and their salts indicated by [the specified formula].

2. General formula (1) 【Transformation 3】 (In formula (1), R １ CO represents an aliphatic acyl group having 8 to 22 carbon atoms, and R ２ represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms which may have one hydroxyl group, and R ３ represents -COOH or -SO ３ H, and n represents 1, 2 or 3.) A method for producing a surfactant composition containing an N-acyl amino acid or a salt thereof, as shown by In the presence of an alkali, a reaction solution containing water as a solvent reacts with fatty acid chloride and general formula (2) 【Chemistry 4】 (In formula (2), R ２ , R ３ (and n are the same as defined above.) The amino acid represented by the above general formula (1) is reacted with the above general formula (1) to produce the N-acyl amino acid, The pH of the reaction solution containing the N-acyl amino acid represented by the general formula (1) above is set to 2 or less. The reaction solution, whose pH is reduced to 2 or less, is separated at a temperature of 80°C or higher. The production method comprising washing a phase containing an N-acyl amino acid represented by the general formula (1) with water.

3. The manufacturing method according to claim 2, wherein the phase containing the N-acyl amino acid represented by the general formula (1) is washed with water in an amount of 1 to 30 times the amount of the phase.

4. General formula (1) 【Transformation 5】 (In formula (1), R １ CO represents an aliphatic acyl group with 8 to 22 carbon atoms, R ２ R represents an alkyl group which is a linear or branched chain having 1 to 4 carbon atoms, which may have a hydrogen atom or one hydroxyl group. ３ is -COOH or -SO ３ (H represents H, and n represents 1, 2, or 3.) A method for suppressing odor and improving color stability of a surfactant composition containing an N-acyl amino acid or a salt thereof, as shown in In the presence of an alkali, a reaction solution containing water as a solvent reacts with fatty acid chloride and general formula (2) 【Transformation 6】 (In formula (2), R ２ , R ３ (and n are the same as defined above.) The amino acid represented by the above general formula (1) is reacted with the above general formula (1) to produce the N-acyl amino acid, The pH of the reaction solution containing the N-acyl amino acid represented by the general formula (1) above is set to 2 or less. The reaction solution, whose pH is reduced to 2 or less, is separated at a temperature of 80°C or higher. The method comprising washing with water a phase containing an N-acyl amino acid represented by the general formula (1) or a salt thereof.

5. The method according to claim 4, wherein the phase containing the N-acyl amino acid represented by the general formula (1) is washed with water in an amount of 1 to 30 times the amount of the phase.

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