Surfactant composition containing N-acylamino acid or its salt and method for producing same

Abstract

The present invention provides a novel technology that can suppress odor and further improve color stability for a surfactant composition containing an N-acylamino acid or a salt thereof. [Solution] A surfactant composition containing an N-acylamino acid represented by general formula (1) or a salt thereof, and containing an amino acid represented by general formula (2) and a salt thereof in an amount of 1 wt % or less. JPEG0007673312000013.jpg27170 JPEG0007673312000014.jpg27170 (In the formula, 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, R 3 -COOH or -SO 3 H, and n is 1, 2 or 3.

Description

[Technical field]

[0001] The present invention relates to a surfactant composition comprising an N-acylamino acid or a salt thereof. [Background technology]

[0002] N-acylamino acids and their salts, which are amino acid-based surfactants, are less irritating and therefore more safe than conventional alkylbenzenesulfonic acids and their salts, and have good foaming properties and a good feel to the touch. For this reason, N-acylamino acids and their salts are widely used as bases for liquid cleansers and cosmetics, such as face washes, body soaps, hand soaps, and shampoos, or to improve the feel of use.

[0003] Methods widely used for producing N-acylamino acids and their salts include the Schotten-Baumann method, in which an aqueous alkaline solution of amino acids is reacted with fatty acid chloride, and an improved version of the method, as exemplified by Patent Documents 1 and 2, in which fatty acid chloride is reacted in an aqueous solution of amino acids containing a hydrophilic solvent in the presence of alkali. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 46-8685 [Patent Document 2] Special Publication No. 51-38681 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a novel technology that can suppress odor and further improve color stability for a surfactant composition containing an N-acylamino acid or a salt thereof. [Means for solving the problem]

[0006] N-acylamino acid surfactants tend to color over time compared to conventional surfactants, and may have a peculiar odor. Therefore, it is possible to add a preservative such as an antioxidant to prevent coloring over time, or to add a large amount of a fragrance to cosmetics to mask the peculiar odor. However, in order to design ethical cosmetics that are liquid, highly transparent, and do not use preservatives, which are required for high-added-value hair cleansers and body cleansers that have been in high demand in recent years, it is preferable that the surfactant has a low odor and high color stability even without the addition of preservatives. The present inventors have conducted extensive research to solve the above problems, and have surprisingly found that the odor and color stability are strongly correlated with trace amounts of residual amino acids used as raw materials. The present inventors have then developed a technique for reducing the amount of residual amino acids used as raw materials, thereby completing the present invention.

[0007] The gist of the present 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 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.) or a salt thereof, General formula (2) [ka] (In formula (2), R2, R3 and n are defined as above.) The surfactant composition according to claim 1, wherein the content of the amino acid represented by the formula (I) and its salt is 1% by weight or less. (B) General formula (1) [ka] (In formula (1), R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, 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.) A method for producing a surfactant composition containing an N-acylamino acid represented by the following formula (I) or a salt thereof, In the presence of an alkali, a fatty acid chloride and a compound represented by the general formula (2) are reacted in a reaction solution containing water as a solvent. [ka] (In formula (2), R2, R3 and n are defined as above.) to produce an N-acylamino acid represented by the general formula (1), Adjusting the pH of the reaction solution containing the N-acylamino acid represented by the general formula (1) to 2 or less; The reaction solution with a pH of 2 or less is separated at 80° C. or higher, The above production method, which comprises washing the phase containing the N-acylamino acid represented by the general formula (1) with water. (C) The method according to (B), further comprising washing the phase containing the N-acylamino acid represented by the general formula (1) with water in an amount of at least 1 and at most 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 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.) A method for improving odor control and color stability of a surfactant composition containing an N-acylamino acid represented by the formula: In the presence of an alkali, a fatty acid chloride and a compound represented by the general formula (2) are reacted in a reaction solution containing water as a solvent. [ka] (In formula (2), R2, R3 and n are defined as above.) to produce an N-acylamino acid represented by the general formula (1), Adjusting the pH of the reaction solution containing the N-acylamino acid represented by the general formula (1) to 2 or less; The reaction solution with a pH of 2 or less is separated at 80° C. or higher, The above process, which comprises washing the phase containing the N-acylamino 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-acylamino acid represented by the general formula (1) is washed with water in an amount of at least 1 time and at most 30 times the amount of the phase. Effect of the Invention

[0008] According to the present invention, it is possible to provide a novel technology that can suppress odor and further improve color stability for a surfactant composition containing an N-acylamino acid or a salt thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] [ka]

[0011] In formula (1), R1CO represents an aliphatic acyl group having 8 to 22 carbon atoms, 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. The aliphatic acyl group having 8 to 22 carbon atoms, which is R1CO, 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 the aliphatic acyl group having 8 to 22 carbon atoms include a capryloyl group, a caproyl group, a lauroyl group, a myristoyl group, a palmitoyl group, a stearoyl group, an oleyl group, a behenoyl group, a coconut oil fatty acid acyl group, and a palm kernel oil fatty acid acyl group, and the like are mentioned, with a lauroyl group, a myristoyl group, an oleyl group, a coconut oil fatty acid, and a palm kernel oil fatty acid being preferred.

[0012] The surfactant composition of the present embodiment may contain an amino acid represented by general formula (2) or a salt thereof. Examples of the amino acid represented by general formula (2) and its salt include a precursor of the N-acylamino acid represented by general formula (1) and its salt.

[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 which may have one hydroxyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, an isobutyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxyisopropyl group, a hydroxybutyl group, and a hydroxyisobutyl group. As R2, a hydrogen atom, a methyl group, or a hydroxyethyl group is preferred because of its high foaming property and low irritation.

[0016] Specific examples of the amino acid compound represented by general formula (2) include sarcosine, β-alanine, N-methyl-β-alanine, N-hydroxyethyl-β-alanine, and N-methyl-taurine. Specific examples of the N-acylamino acid compound represented by general formula (1) include acyl sarcosine, 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 the present embodiment may contain a salt of an N-acylamino acid represented by general formula (1) and / or a salt of an amino acid represented by general formula (2). Specific examples include salts with alkali metals, alkaline earth metals, ammonia, or organic ammonium. Examples of alkali metals include potassium and sodium. Examples of alkaline earth metals include calcium and magnesium. Examples of organic ammonium include alkanolamines and alkylamines. In the case of salts with divalent alkali metals or alkaline earth metals, they can be made to form 1 / 2 salts. Among these, it is preferable to select salts with potassium and / or sodium, which are alkali metal salts, or salts with alkanolamine, which is an organic ammonium salt, since this results in a transparent composition with high foaming properties and low irritation.

[0018] In the surfactant composition of the present embodiment, the content of the amino acid represented by the general formula (2) and its salt is reduced, and as a result, odor is suppressed and color stability is improved. The content of the compound of general formula (2) and its salt, which are amino acids, in the surfactant composition of the present embodiment 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 viewpoints of odor suppression and improvement of color stability. Although not particularly limited, the content of the N-acylamino acid or its salt represented by the general formula (1) 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. If the surfactant composition of this embodiment is an aqueous solution, the content of the N-acylamino acid or its salt represented by the general formula (1) is more preferably 25% by weight or more and 35% by weight or less. By making the concentration of the aqueous solution 25% or more, it is easy to improve the operability in relation to the amount of water that can be used during blending, and by making it 35% or less, it is possible to suppress gelation and solidification in low temperature environments in winter. The surfactant composition of this embodiment can also be made into a powder or a mass that does not contain a solvent using a known method such as spray drying or freeze drying.

[0019] The surfactant composition of the present embodiment may contain other components in addition to the N-acylamino acid represented by general formula (1) or a salt thereof, and the amino acid represented by general formula (2) or a salt thereof, as long as the object of the present invention can be achieved, and is not particularly limited. For example, the surfactant composition of this embodiment may contain free fatty acid. The amount of free fatty acid contained in the surfactant composition of this embodiment is not particularly limited, but the inclusion of free fatty acid provides a refreshing feeling during washing and contributes to improving foam density. In addition, by making the content ratio of free fatty acid 10% by weight or less, odor can be suppressed, stability can be improved by suppressing gelation, and transparency at low temperatures can be improved when the surfactant composition is transparent, which is preferable.

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

[0021] The surfactant composition of the present embodiment may be, 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-acylamino acid represented by general formula (1); Adjusting the pH of a reaction solution containing the N-acylamino acid represented by general formula (1) to 2 or less; The reaction solution with a pH of 2 or less is separated at 80°C or higher. The preparation can be carried out by a method including washing the phase containing the N-acylamino acid represented by the general formula (1) with water.

[0022] Specifically, the surfactant composition of the present embodiment can be produced, for example, as follows. First, an N-acylamino acid represented by general formula (1) is produced as an acylated product derived from an amino acid represented by general formula (2) by acylation with a fatty acid derivative. This step can be a so-called Schotten-Baumann reaction step in which an amino acid represented by 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, when 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 inactive to the fatty acid chloride can be added to prepare a mixed solvent with water. Examples of the inactive hydrophilic organic solvent include acetone, methyl ethyl ketone, and tetrahydrofuran. In order to reduce the content of the amino acid represented by general formula (2) and its salt, the amount of the 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, based on the amount of water used as the solvent. As the fatty acid from which R1CO in the general formula (1) is derived, fatty acids derived from natural vegetable oils and fats are preferable because they are renewable raw materials with low environmental impact, are unlikely to be depleted, and can be used stably. In the case of mixed fatty acids, one or more fatty acids can be mixed and used, and fatty acids can be used in any mixing ratio for the purpose of expressing the desired feeling of use.

[0023] The amount of fatty acid chloride for the amino acid corresponding to the general formula (2) in the Schotten-Baumann reaction is preferably 0.9 equivalents or more and less than 1 equivalent. By using 0.9 equivalents or more, economic advantages can be maintained, and by using less than 1 equivalent, the decrease in transparency due to the increase in free fatty acid when the composition is transparent can be suppressed. The amount of alkali used in the reaction can be added in advance or added together with the addition of the acid chloride, as long as it is 1 equivalent or more and 1.2 equivalents or less relative to the acid chloride used. By adding the amount of alkali at 1 equivalent or more, the increase in free fatty acid due to the slow progress of the reaction can be suppressed. In addition, by adding 1.2 equivalents or less, the need for a large amount of acid during neutralization in the next step can be avoided. The alkali used is not particularly limited as long as it can neutralize the chlorine generated in the Schotten-Baumann reaction, and sodium hydroxide and potassium hydroxide, which are easily available, can be used.

[0024] The reaction temperature can be selected from the range of 10°C to 60°C, and is preferable. By setting the temperature at 10°C or higher, the increase in free fatty acids due to the progress of hydrolysis of fatty acid chlorides, which is caused by the slow progress of the reaction, can be suppressed. In addition, by setting the temperature at 60°C or lower, the increase in free fatty acids due to the rapid progress of hydrolysis of fatty acid chlorides can be suppressed. From the viewpoint of suppressing the amount of free fatty acids produced after the acylation reaction, the reaction temperature is preferably 20°C to 50°C, and more preferably 30°C to 45°C. The reaction time is not particularly limited as long as it is within a range in which heat generation can be controlled, and a maturation time can be set as necessary after the end of the reaction.

[0025] After the acylation reaction, the pH of the reaction solution is adjusted to 2 or less using an acid, the solution is separated at 80° C. or higher, and then the phase containing the acylamino acid represented by general formula (1) is washed with water. By carrying out these steps after the acylation reaction, the content of the amino acid represented by general formula (2) can be reduced. The acid used for adjusting the pH is preferably sulfuric acid and / or hydrochloric acid, and sulfuric acid, which is a divalent acid and has little odor due to the acid, is particularly preferred because it can minimize the amount of wastewater that is separated into layers. As described above, separation can be carried out by heating the reaction solution to 80° C. or higher. The amount of water used for washing can be appropriately determined by those skilled in the art and is not particularly limited, but from the viewpoint of reducing the content of the amino acid represented by general formula (2) and its salt and increasing the yield, the amount of water used is preferably 1-fold and 30-fold the amount of the phase containing the acylamino acid represented by general formula (1). The temperature in washing is not particularly limited, but can be, for example, the same temperature as that in the liquid separation step.

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

[0027] As described above, according to this embodiment, the odor of the surfactant composition containing an N-acylamino acid can be suppressed and the color stability can be improved. In the surfactant composition of the present embodiment, for example, no fragrance is added for masking purposes, and the surfactant composition can contribute to the provision of ethical toiletry products such as preservative-free shampoos, body soaps, and facial cleansers, which are of great 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 to these examples. Furthermore, the raw materials used in the following examples and comparative examples were reagents manufactured by Kanto Chemical Co., Ltd. or Sigma-Aldrich Co. LLC, unless otherwise specified.

[0029] Method for measuring content of amino acid represented by general formula (2) in surfactant composition In a sealed flask, 1.0 g of a surfactant composition containing an N-acylamino acid was mixed with 30 g of distilled water and caustic soda (48%, 1.1 g (1.8 equivalents to benzoyl chloride)), 1.0 g of benzoyl chloride was added, and the mixture was stirred for 1 hour or more in a warm bath at 30 to 45°C. Then, 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 amount: 20 μL, UV wavelength: 220 nm). The amino acid represented by the general formula (2) was derivatized with benzoyl chloride in the same manner as the N-acyl amino acid represented by the general formula (1), extracted with ethyl acetate, concentrated to dryness, and purified by column chromatography (MB-4B, manufactured by Fuji Silysia Chemical Co., Ltd.) with hexane / ethyl acetate as a standard, and the content of the amino acid represented by the general formula (2) remaining in the surfactant composition was determined according to the following calculation formula by the absolute calibration curve method. For measurement methods not specifically described, the measurements were performed according to the provisions of the Japanese Pharmacopoeia, 18th Edition, Supplement 1, General Tests 2.01, Liquid Chromatography. Content (wt%) of amino acid represented by general formula (2)=Content (g) of amino acid represented by general formula (2) / (Content (g) of amino acid represented by general formula (2)+Content (g) of N-acyl amino acid represented by general formula (1))×100

[0030] Evaluation of the odor of surfactant compositions The odor of the surfactant composition was rated on a four-point scale, from weakest to strongest: "almost no odor," "barely detectable odor," "weak odor that is recognizable," and "easily detectable odor." Comparative Example 5 described below was used as a control. The odor was evaluated as being suppressed when the odor was weaker than that of the control. In addition, the odors evaluated as "almost no odor" and "barely detectable odor" were evaluated as favorable results, since the odor was such that no fragrance was required to mask the odor derived from the amino acid represented by the general formula (2) in the formulation.

[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 allowed to stand in a thermostatic chamber at 80° C. for 18 hours, after which the Hazen color unit number (APHA) was measured using a Spectrometer SE7700 (manufactured by Nippon Denshoku Industries Co., Ltd.). Comparative Example 5 described below was used as a control. When the APHA value was smaller than that of the control, it was evaluated that the color stability was improved.

[0032] Example 1 In a 1L four-neck flask equipped with a stirrer, 156g of 27% by weight aqueous solution of N-methyl-β-alanine sodium, 210g of city water, and 13g of 48% by weight 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% by weight sodium hydroxide were dropped from separate dropping funnels over 1 hour at a temperature range of 30 to 40°C, and aging was performed for 0.5 hours after the dropping. After the aging was completed, 50g of 75% by weight sulfuric acid was added, the pH was adjusted to 1.5, and the mixture was heated to 80°C, and then left to stand for 1 hour for liquid separation. 120g of water was added to the upper layer, and the mixture was heated to 80°C, and then left to stand for 1 hour for liquid separation. This operation was repeated twice. Then, 200g of water and 26g of 48% sodium hydroxide were added, and 310g of 30% by weight aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was obtained as a surfactant composition. The amount of N-methyl-β-alanine sodium remaining in the obtained 30% by weight aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was 0.02% by weight, there was 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 the lauric acid chloride in Example 1 was changed to 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%, there was 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 in Example 1 was 35 g and the pH was adjusted to 2, and 310 g of a 30 wt % aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was obtained 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 wt %, it had a barely detectable 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 the water used in washing in Example 1 was 175 g, and 310 g of a 30 wt % aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was obtained 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 0.2 wt %, there was 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 N-methyl-β-alanine sodium of Example 2 was replaced with 123 g of 30 wt% aqueous solution of β-alanine sodium, 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-acylamino acid concentration was changed to 25 wt%, and 370 g of 25 wt% aqueous solution of N-cocoyl-β-alanine potassium was obtained as a surfactant composition. The residual amount of β-alanine potassium in the obtained 25 wt% aqueous solution of N-cocoyl-β-alanine potassium was 0.1 wt%, there was almost no odor, and the APHA after the color stability test was 20.

[0037] Example 6 The N-methyl-β-alanine sodium of Example 1 was replaced with 150g of 30% by weight aqueous solution of N-hydroxyethyl-β-alanine sodium, 100g of tetrahydrofuran was added as an organic solvent, and the reaction was carried out. After washing with water, the mixture was desolized, and neutralized as in Example 1, to obtain 300g of 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, there was almost no odor, 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 the N-methyl-β-alanine sodium was replaced with 90 g of a 30 wt% aqueous solution of sodium sarcosine, to obtain 350 g of a 30 wt% aqueous solution of sodium N-lauroyl sarcosine as a surfactant composition. The residual amount of sodium sarcosine in the obtained 30 wt% aqueous solution of sodium N-lauroyl sarcosine was 0.05 wt%, there was almost no odor, and the APHA after the color stability test was 10.

[0039] Comparative Example 1 The same procedure as in Example 1 was carried out, except that the amount of 75% sulfuric acid used in Example 1 was changed to 28 g and the pH was adjusted to 3, 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%, and it had a weak odor that was easy to identify, and the APHA after the color stability test was 15.

[0040] Comparative Example 2 The same procedure as in Example 1 was carried out, except that the 75% sulfuric acid in Example 1 was replaced with glacial acetic acid, the amount used was 20 g, and the pH was adjusted to 4, to obtain 250 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 5 wt%, it had an easily detectable odor, and the APHA after the color stability test was 30.

[0041] Comparative Example 3 The same procedure as in Example 1 was carried out except that the separation temperature was changed to 60°C. However, a large amount of intermediate layer was produced and separation was not possible. When the mixture was cooled to room temperature, a large amount of salt was precipitated, and the analysis was abandoned.

[0042] Comparative Example 4 The same procedure as in Example 6 was carried out, except that the amount of 75% by weight sulfuric acid used in Example 6 was changed to 28 g and the pH was adjusted to 3, to obtain 220 g of 30% 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 3% by weight, the odor was easily detectable, and the APHA after the color stability test was 50.

[0043] Comparative Example 5 The same operation as in Example 1 was carried out up to the first liquid separation step, and the water washing step was not carried out, and the neutralization step was carried out. As a surfactant composition, 320g of 30% by weight aqueous solution of N-lauroyl-N-methyl-β-alanine sodium was obtained. 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 1.5% by weight, and it had a weak odor that was easy to recognize, and the APHA after the color stability test was 25.

[0044] Reference example A color stability test was carried out by adding 100 ppm of etidronic acid to the 30 wt % aqueous solution of sodium N-lauroyl-N-methyl-β-alanine produced in Comparative Example 2, and the APHA after the color stability test was 10.

[0045] From the above test results for the Examples and Comparative Examples, it can be seen that the odor is suppressed and the color stability is improved by decreasing the content of the amino acid of general formula (2) in the surfactant composition. In addition, when the content of the amino acid of general formula (2) is 1% or less, a surfactant composition containing an N-acylamino acid or its salt with less odor and higher color stability can be obtained.

[0046] Hair cleansing composition formulation example The following fragrance-free hair shampoos were prepared. All of these hair shampoo compositions had a low odor and showed no change in color in a stability test.

[0047] (Prescription Example 1) Surfactant composition of Example 1 6.0 Sodium methyl cocoyl taurate 4.5 Cocamidopropyl Betaine 5.0 Lauroyl Propyl Betaine 2.0 PPG2-Cocamido 1.0 Polyquaternium-10 0.5 Citric acid pH adjusted to 6.0 Water Remainder (adjust so that the total of the above is 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-Cocamido 0.7 Polyquaternium-10 0.3 Citric acid pH adjusted to 6.0 Water Remainder (adjust so that the total of the above is 100)

[0049] The following fragrance-free hair shampoos were prepared. All of these hair shampoo compositions had an odor derived from the amino acids used as raw materials, and changed color in a stability test.

[0050] (Comparative Formulation Example 1) Surfactant composition of Comparative Example 1 6.0 Sodium methyl cocoyl taurate 4.5 Cocamidopropyl Betaine 5.0 Lauroyl Propyl Betaine 2.0 PPG2-Cocamide 1.0 Polyquaternium-10 0.5 Citric acid pH adjusted to 6.0 Water Remainder (adjust so that the total of the above is 100)

[0051] (Comparative Formulation Example 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-Cocamido 0.7 Polyquaternium-10 0.3 Citric acid pH adjusted to 6.0 Water Remainder (adjust so that the total of the above is 100)

Claims

1. General formula (1) 【Chemistry 1】 (In formula (1), R １ CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R 3 represents --COOH, n represents 1 or 2, when n is 1, R 2 represents a methyl group, and when n is 2, R 2 represents a hydrogen atom, a methyl group, or a hydroxyethyl group. or a salt thereof, General formula (2) 【Chemistry 2】 (In formula (2), R 2 , R 3 and n are the same as defined above.) A method for producing a surfactant composition, comprising the steps of: In the presence of an alkali, a fatty acid chloride is reacted with an amino acid represented by the general formula (2) in a reaction solution containing only water as a solvent to produce an N-acylamino acid represented by the general formula (1); The pH of the reaction solution containing the N-acylamino acid represented by the general formula (1) is adjusted to 2 or less; The reaction solution having a pH of 2 or less is subjected to liquid separation at 80° C. or higher; The above production method further comprises washing the phase containing the N-acylamino acid represented by the general formula (1) with water.

2. 2. The method according to claim 1, wherein the phase containing the N-acylamino acid represented by the general formula (1) is washed with water in an amount of at least 1 time and at most 30 times the amount of the phase.

3. General formula (1) 【Chemistry 3】 (In formula (1), R １ CO represents an aliphatic acyl group having 8 to 22 carbon atoms, R 3 represents --COOH, n represents 1 or 2, when n is 1, R 2 represents a methyl group, and when n is 2, R 2 represents a hydrogen atom, a methyl group, or a hydroxyethyl group. A method for improving odor control and color stability of a surfactant composition containing an N-acylamino acid represented by the formula: In the presence of an alkali, a fatty acid chloride and a compound represented by the general formula (2) are reacted in a reaction solution containing only water as a solvent. 【Chemistry 4】 (In formula (2), R ２ , R ３ and n is as defined above. to produce an N-acylamino acid represented by the general formula (1), The pH of the reaction solution containing the N-acylamino acid represented by the general formula (1) is adjusted to 2 or less; The reaction solution having a pH of 2 or less is subjected to liquid separation at 80° C. or higher; The above process, which comprises washing the phase containing the N-acylamino acid represented by the general formula (1) or a salt thereof with water.

4. 4. The method according to claim 3, wherein the phase containing the N-acylamino acid represented by the general formula (1) is washed with water in an amount of at least 1 and at most 30 times the amount of the phase.

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