An N,O-difatty acylhydroxy amino acid surfactant and its preparation method

Abstract

This invention discloses an N,O-bisfatty acyl hydroxy amino acid surfactant and its preparation method, belonging to the field of fine chemical technology. Using hydroxy amino acids as raw materials, an N-acylation reaction is first carried out with fatty acyl chlorides in an alkaline solution to generate an intermediate N-fatty acyl amino acid. Then, an O-acylation reaction is carried out with fatty acyl chlorides under organic solvent / acid catalysis to generate the N,O-bisfatty acyl amino acid surfactant. The N,O-bisfatty acyl amino acid surfactant has advantages such as easy thickening, low toxicity and low irritation, strong emulsifying ability, and good compatibility. Its preparation method has advantages such as high yield, simple process, and low production cost, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to an amino acid surfactant, and more particularly to an N,O-diacylhydroxy amino acid surfactant and its preparation method, belonging to the field of chemical synthesis technology. Background Technology

[0002] Surfactants are active materials that can significantly reduce the surface tension of solutions and the interfacial tension between liquids and gases, liquids and liquids, or liquids and solids. They can perform functions such as emulsification, dispersion, solubilization, foaming, cleaning, lubrication, and softening. As an important fine chemical, they are widely used in various sectors of the national economy and are often referred to as "industrial MSG." With social development, people are paying more and more attention to environmental protection and health and safety, placing high demands on the development of surfactants for low-carbon, environmentally friendly, green, safe, and sustainable development. Therefore, using natural renewable resources to replace fossil resources to prepare green surfactants represents the development direction of the next generation of surfactants. Amino acid surfactants are a typical example of green surfactants. They not only have excellent surface activity but also have advantages such as mildness and low irritation, good skin affinity, strong antibacterial properties, high safety, easy biodegradability, and good biocompatibility. They are widely used in cosmetics, facial cleansers, shampoos, shower gels, toothpaste, and other daily necessities. Currently, the most common products are N-fatty acyl amino acid surfactants based on five amino acids: glutamic acid, glycine, sarcosine, alanine, and methyl taurine. However, N,O-difatty acyl hydroxy amino acid surfactants are rarely reported.

[0003] The industrial synthesis of N-fatty acyl amino acid surfactants typically employs the Schotten-Baumann condensation method, using fatty acyl chlorides and amino acids as raw materials, which undergo a condensation reaction in an alkaline aqueous solution or an organic solvent / alkaline solution. However, directly synthesizing N,O-diacylhydroxy amino acid surfactants from hydroxy amino acids using the Schotten-Baumann condensation method presents several problems, such as low acylation rates in the O-acylation reaction leading to low product purity; high residual fatty acid salt content in the product; and high reaction temperatures resulting in poor product color. These problems arise because the amino group on hydroxy amino acids is more reactive than the hydroxyl group, making it more prone to N-acylation. The N-acylation reaction first generates the intermediate N-acylhydroxy amino acid, which has poor solubility and is easily precipitated, making further complete O-acylation difficult. This necessitates increasing the reaction temperature and the amount of fatty acyl chloride. Even at high temperatures, the O-acylation reaction is still difficult to complete, and fatty acyl chlorides are more prone to hydrolysis, resulting in a higher residue of intermediates and fatty acid salts in the product, along with poor product color. Traditional one-step condensation methods are problematic and unsuitable for the preparation of N,O-diacylhydroxy amino acid surfactants, making the development of new synthetic methods essential. Summary of the Invention

[0004] In view of the prior art, the first objective of this invention is to provide an N,O-bisacylhydroxy amino acid surfactant that, compared with commonly used N-acylhydroxy amino acid surfactants, has stronger emulsifying ability and thickening properties.

[0005] The second objective of this invention is to provide a method for synthesizing N,O-diacylhydroxy amino acid surfactants. This method employs a stepwise synthesis strategy, in which hydroxy amino acids and long-chain fatty acyl chlorides undergo N-acylation and O-acylation reactions sequentially under different conditions. This significantly improves the acylation efficiency and has advantages such as high product yield, simple separation and purification, and high purity, thus meeting the requirements of industrial production.

[0006] To achieve the above-mentioned technical objectives, the present invention provides an N,O-difatty acylhydroxy amino acid surfactant having the following structural formula:

[0007]

[0008] in,

[0009] R 1 Hydrogen, C1 to C 12 Alkyl or C6-C 12 aryl;

[0010] R 2 and R 3 Independently selected from C7~C 17 aliphatic hydrocarbon groups;

[0011] M can be hydrogen ion, potassium ion, sodium ion, or TEA ion.

[0012] R in the N,O-difatty acyl hydroxy amino acid surfactant of the present invention 1 The group introduced into the hydroxy amino acid can be selected from hydrogen or conventional alkyl or aryl groups, and the alkyl group can be selected from C1 to C2. 12 The alkyl group can be selected from straight-chain alkyl groups. When the number of carbon atoms is greater than or equal to 3, the alkyl group can be selected from branched alkyl groups or cycloalkyl groups, such as methyl, ethyl, isopropyl, cyclohexyl, or hexyl. The aryl group can be selected from C6 to C6. 12 It is mainly composed of phenyl groups or groups derived from phenyl, such as substituted phenyl groups. Substituted phenyl groups contain conventional substituent groups such as short-chain alkyl or alkoxy groups on the benzene ring, specifically p-tolyl or p-ethylphenyl. R 2 and R 3 These are substituent groups introduced by acyl chlorides during esterification or amidation reactions, primarily C7 to C8. 17The long-chain aliphatic hydrocarbon group, specifically selected from, for example, n-heptyl, n-nonyl, n-decyl, n-undecyl, n-tridecyl, or n-pentadecanyl.

[0013] The N,O-bisfatty acylhydroxy amino acid surfactant of the present invention has a special molecular structure, with long-chain hydrophobic groups at both ends and hydrophilic groups in the middle. It can easily self-assemble into micelles in an aqueous phase. For example, in an aqueous system, the hydrophilic groups couple with water, while the hydrophobic groups associate with each other to form micelles. The terminal groups of the micelles adsorb onto different micelle particles through different hydrophobic ends and link and entangle with each other to form a thickening phenomenon, thereby exhibiting stronger emulsifying ability and thickening performance.

[0014] This invention also provides a method for preparing an N,O-difatty acylhydroxy amino acid surfactant, the method comprising the following steps:

[0015] 1) Dissolve hydroxy amino acids and organic co-solvents in an alkaline aqueous solution to form a hydroxyproline salt solution. Simultaneously add C8-C94 ... 18 The fatty acyl chloride and strong alkaline solution were subjected to N-acylation reaction. After the N-acylation reaction was completed, the reaction solution was acidified and allowed to stand for separation. The upper organic phase was poured into an acidic aqueous solution to precipitate the crude product of N-fatty acylhydroxy amino acid.

[0016] 2) Dissolve the crude N-fatty acylhydroxyamino acid product in an acidic organic solution, then add C8-C94... 18 The fatty acyl chloride undergoes an O-acylation reaction. After the O-acylation reaction is complete, the reaction solution is poured into an acidic aqueous solution to precipitate the crude product of N,O-bisfatty acyl hydroxy amino acid surfactant.

[0017] The hydroxy amino acid has the following structural formula:

[0018]

[0019] in,

[0020] R 1 Hydrogen, C1 to C 12 Alkyl or C6-C 12 Aryl groups.

[0021] As a preferred embodiment, the hydroxy amino acid is threonine, threonine salt, serine, or serine salt.

[0022] As a preferred embodiment, the organic co-solvent is at least one selected from methanol, ethanol, acetonitrile, acetone, tetrahydrofuran, and 1,4-dioxane. The preferred organic co-solvent is a hydrophilic polar organic solvent, considering that long-chain fatty acyl chlorides are insoluble in water, and the introduction of a hydrophilic organic solvent can solubilize them, thus promoting the acylation reaction between fatty acyl chlorides and hydroxy amino acids.

[0023] As a preferred embodiment, the amount of the organic co-solvent is 0.4 to 0.6 times the volume of the alkaline aqueous solution.

[0024] As a preferred embodiment, the strong alkaline solution is a sodium hydroxide and / or potassium hydroxide solution with a mass percentage concentration in the range of 5% to 50%. The alkaline aqueous solution primarily converts hydroxyl amino acids into their corresponding salts, thereby increasing their solubility in water.

[0025] As a preferred embodiment, the dropping rate of the strong alkaline solution is adjusted to control the pH of the system to 9–11 during the N-acylation reaction. The strong alkaline solution primarily neutralizes the hydrochloric acid produced during the condensation reaction, stabilizing the pH of the reaction. If the pH of the reaction is too high, it will increase the hydrolysis reaction of the fatty acyl chloride.

[0026] As a preferred embodiment, the reaction conditions for the N-acylation reaction are: a reaction temperature of 0–30°C, a reaction time of 30 min–2 h, and the hydroxyl amino acid reacting with C8–C8 amino acids. 18 The molar ratio of fatty acyl chlorides is 1:0.8 to 1.5.

[0027] As a preferred embodiment, the acidification treatment temperature is 30–60°C. The acidification treatment converts the N-fatty acyl hydroxy amino acid salt into the corresponding acid, reducing its solubility and making the solution system more prone to stratification.

[0028] As a preferred embodiment, the acidic organic solution contains at least one acid catalyst selected from phosphoric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, boron trifluoride ether, and hydrogen chloride. The acidic organic solution also contains at least one organic solvent selected from acetonitrile, trifluoroacetic acid, dichloromethane, toluene, tetrahydrofuran, and acetone. It should be noted that trifluoroacetic acid is used as both an acid catalyst and a solvent.

[0029] As a preferred embodiment, the conditions for the O-acylation reaction are: a reaction temperature of 30–80°C, a reaction time of 2–12 h, and N-fatty acylhydroxyamino acid reacting with C8–C8 fatty acids. 18 The molar ratio of fatty acyl chlorides is 1:1 to 2. An appropriate excess of fatty acyl chlorides is beneficial to improving the efficiency of the O-acylation reaction of N-fatty acyl hydroxy amino acids.

[0030] As a preferred embodiment, the crude N,O-difatty acylhydroxy amino acid product is recrystallized to obtain a high-purity product; the recrystallization uses acetone, methanol, ethanol, acetonitrile, ethanol / water, methanol / water, acetone / water or acetonitrile / water as organic solvents.

[0031] The synthesis method of the N,O-difatty acyl hydroxy amino acid surfactant of the present invention is shown in the following reaction equation:

[0032] 1) N-acylation reaction:

[0033]

[0034] Hydroxy amino acids are dissolved in an alkaline aqueous solution and an organic co-solvent is used to form a hydroxy amino acid salt solution. At a certain temperature, fatty acyl chloride and a strong alkaline solution are slowly added dropwise to the hydroxy amino acid salt solution to carry out an N-acylation reaction. After the reaction is completed, the reaction solution is acidified and allowed to stand to separate into layers. The upper organic phase is poured into an acidic aqueous solution to precipitate crude N-fatty acyl amino acid product.

[0035] 2) O-acylation reaction:

[0036]

[0037] The crude N-fatty acyl amino acid product is dissolved in an acidic organic solution, and then fatty acyl chloride is added to carry out an O-acylation reaction. After the reaction is completed, the reaction solution is poured into water to precipitate the crude N,O-bisfatty acyl hydroxy amino acid surfactant product. Finally, high-purity N,O-bisfatty acyl hydroxy amino acid is obtained by simple recrystallization; or it can be reacted with a base to obtain the corresponding N,O-bisfatty acyl hydroxy amino acid salt.

[0038] Under strong alkali conditions, using hydroxy amino acids and excess fatty acyl chlorides as raw materials, the existing one-step condensation method is insufficient for the efficient and high-quality synthesis of N,O-bisfatty acyl hydroxy amino acid surfactants. The main problems are: 1) The acylation reactivity of the amino and hydroxyl groups of hydroxy amino acids differs greatly. The N-acylation reaction first generates the intermediate N-fatty acyl hydroxy amino acid, which has poor solubility and is prone to precipitation, making further sufficient O-acylation difficult. This results in a large amount of residual N-fatty acyl hydroxy amino acid, which is difficult to separate; 2) To promote the O-acylation reaction, it is often necessary to increase the reaction temperature and the amount of fatty acyl chloride. High temperatures further promote the hydrolysis of fatty acyl chloride in alkaline solutions, leading to a large amount of residual fatty acids. In summary, the one-step condensation method for synthesizing N,O-bisfatty acyl hydroxy amino acid surfactants results in a large amount of N-fatty acyl hydroxy amino acid intermediates and fatty acids in the final product, which are difficult to purify. Furthermore, the fatty acyl groups on the N and O groups are identical. The key to this invention lies in the use of a stepwise condensation method. First, an N-acylation reaction is carried out with high selectivity under alkaline conditions in an organic solvent-water mixed solvent. This not only efficiently converts hydroxy amino acids into N-fatty acyl hydroxy amino acids but also facilitates separation. In particular, the N-fatty acyl hydroxy amino acids do not require purification and can be directly used for the subsequent O-acylation reaction. The O-acylation reaction uses an acidic organic solution, which improves the solubility of the N-fatty acyl hydroxy amino acids, thus ensuring a complete O-acylation reaction while avoiding the hydrolysis side reaction of fatty acyl chlorides in alkaline solutions. Different fatty acyl chlorides can be used for the N-acylation and O-acylation reactions, and the fatty acyl groups on the N and O groups can be arbitrarily combined.

[0039] Compared with existing technologies, the preparation method provided by this invention brings the following beneficial technical effects:

[0040] 1) The stepwise synthesis strategy significantly improves the efficiency of the acylation reaction, and the separation and purification of the product is simple and has a high yield. The product has high purity and better color.

[0041] 2) By adopting a stepwise synthesis strategy, different aliphatic acyl chlorides can be used for the N-acylation and O-acylation reactions, and the substituents on N and O can be combined arbitrarily, which greatly improves the diversity of product structure.

[0042] 3) The O-acylation reaction occurs under organic solvent / acid catalysis conditions, avoiding the large-scale hydrolysis of fatty acyl chlorides in alkaline aqueous solutions at higher temperatures.

[0043] 4) The N,O-difatty acyl hydroxy amino acid surfactant of the present invention has stronger emulsifying ability and thickening properties compared with existing amino acid surfactants. Attached Figure Description

[0044] Figure 1The image shows the 1H NMR spectrum of N,O-palmitoylserine.

[0045] Figure 2 The 1H NMR spectrum of N,O-lauroylserine is shown.

[0046] Figure 3 The 1H NMR spectrum of N-lauroyl-O-palmitoylserine.

[0047] Figure 4 The image shows the 1H NMR spectrum of N,O-palmitoylthreonine. Detailed Implementation

[0048] The following specific embodiments are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims.

[0049] Example 1

[0050] In a 500 mL four-necked round-bottom flask equipped with a stirrer, 11.04 g of L-serine, 2.80 g of sodium hydroxide, and 100 mL of water were added and stirred at room temperature to dissolve. Then, 50 mL of acetone was added, and the reaction solution was cooled to 10 °C with stirring. 27.49 g of palmitoyl chloride was slowly added dropwise, while approximately 40 g of 15% sodium hydroxide aqueous solution was added dropwise to maintain the pH at around 11. The dropwise addition process took approximately 1.5 h. After the addition was complete, the mixture was stirred at room temperature for another 1 h. 15 mL of concentrated hydrochloric acid was slowly added to acidify the solution, and the temperature was raised to approximately 40 °C to dissolve the solid. The solution was transferred to a separatory funnel, allowed to stand for separation, and the upper organic phase was separated. The organic phase was slowly poured into 300 mL of acidic water while stirring, precipitating a white solid. After filtration, washing with water, and drying, a white intermediate, crude N-palmitoylserine, was obtained. The solution was placed in a 250 mL round-bottom flask, and 50 mL of trifluoroacetic acid was added. The mixture was heated to 50 °C, stirred to dissolve, and then 32.99 g of palmitoyl chloride was slowly added dropwise over 1 hour. The reaction mixture was stirred at 50 °C for 4 hours. Most of the trifluoroacetic acid was recovered under reduced pressure. The reaction solution was slowly poured into 200 mL of water while stirring, and a white solid precipitated. After filtration, washing with water, and drying, a crude white solid was obtained. This crude solid was then subjected to simple recrystallization with ethanol / water to obtain 48.33 g of white N,O-palmitoylserine, with a yield of 83%. 1 H NMR(400MHz, DMSO-d6)δ8.00(d,J=8.1Hz,1H),6.20–6.06(m,1H),4.35(dt,J=15.0,7.8Hz, 1H), 2.12 (t, J = 7.4Hz, 3H), 1.49 (t, J = 7.2Hz, 4H), 1.23 (s, 48H), 0.84 (t, J = 6.8Hz, 6H) ppm.

[0051] Example 2

[0052] In a 500 mL four-necked round-bottom flask equipped with a stirrer, add 11.04 g L-serine, 2.80 g sodium hydroxide, and 100 mL water, and stir to dissolve at room temperature. Then add 50 mL acetone, and while stirring, cool the reaction solution to 10 °C. Slowly add 21.88 g lauroyl chloride dropwise, while simultaneously adding approximately 40 g of 15% sodium hydroxide aqueous solution to maintain the pH at around 11. The dropwise addition process takes approximately 1.5 h. After the addition is complete, stir for another 1 h at room temperature. Slowly add 15 mL concentrated hydrochloric acid to acidify, and heat the reaction solution to approximately 40 °C to dissolve completely. Transfer the solution to a separatory funnel, allow it to stand and separate into layers, and separate the upper organic phase. Slowly pour the organic phase into 300 mL of acidic water while stirring, precipitating a white solid. After filtration, washing with water, and drying, obtain the white intermediate crude N-lauroylserine. The solution was placed in a 250 mL round-bottom flask, and 50 mL of trifluoroacetic acid was added. The mixture was heated to 50 °C, stirred to dissolve, and then 26.26 g of lauroyl chloride was slowly added dropwise over 1 hour. The reaction mixture was stirred at 50 °C for 4 hours. Most of the trifluoroacetic acid was recovered under reduced pressure. The reaction solution was slowly poured into 200 mL of water while stirring, and a white solid precipitated. After filtration, washing with water, and drying, a crude white solid was obtained. This crude solid was then subjected to simple recrystallization with ethanol / water to obtain 38.64 g of white N,O-lauroylserine, with a yield of 82%. 1 H NMR (400MHz, DMSO-d6) δ8.17(d,J=8.1Hz,1H),4.55(ddd,J=8.2,6.9,4.2Hz,1H),4.30(dd,J=11.1,4.3Hz,1H),4.14(dd,J=11 .1,7.0Hz,1H),2.28–2.21(m,2H),2.11(td,J=7.3,2.3Hz,2H),1.48(q,J=7.3Hz,4H),1.23(s,33H),0.85(t,J=6.8Hz,6H)ppm.

[0053] Example 3

[0054] In a 500 mL four-necked round-bottom flask equipped with a stirrer, add 11.04 g L-serine, 2.80 g sodium hydroxide, and 100 mL water, and stir to dissolve at room temperature. Then add 50 mL acetone, and while stirring, cool the reaction solution to 10 °C. Slowly add 21.88 g lauroyl chloride dropwise, while simultaneously adding approximately 40 g of 15% sodium hydroxide aqueous solution to maintain the pH at around 11. The dropwise addition process takes approximately 1.5 h. After the addition is complete, stir for another 1 h at room temperature. Slowly add 15 mL concentrated hydrochloric acid to acidify, and heat the reaction solution to approximately 40 °C to dissolve completely. Transfer the solution to a separatory funnel, allow it to stand and separate into layers, and separate the upper organic phase. Slowly pour the organic phase into 300 mL of acidic water while stirring, precipitating a white solid. After filtration, washing with water, and drying, obtain the white intermediate crude N-lauroylserine. The mixture was placed in a 250 mL round-bottom flask, and 50 mL of trifluoroacetic acid was added. The mixture was heated to 50 °C, stirred to dissolve, and then 32.99 g of palmitoyl chloride was slowly added dropwise over 1 hour. The reaction mixture was stirred at 50 °C for 4 hours. Most of the trifluoroacetic acid was recovered under reduced pressure, and the reaction solution was slowly poured into 200 mL of water while stirring. A white solid precipitated, which was filtered, washed with water, and dried to obtain a crude white solid. This crude solid was then subjected to simple recrystallization with ethanol / water to obtain 41.68 g of white N-lauroyl-O-palmitoylserine, with a yield of 79%. 1 H NMR (400MHz, CDCl3) δ6.83–6.61(m,1H),4.77(s,1H),4.42(s,2H),2.26(dt,J =15.5,7.6Hz,4H),1.66–1.50(m,4H),1.23(s,39H),0.86(t,J=6.8Hz,6H)ppm.

[0055] Example 4

[0056] In a 500 mL four-necked round-bottom flask equipped with a stirrer, add 12.50 g L-threonine, 2.80 g sodium hydroxide, and 100 mL water, and stir to dissolve at room temperature. Then add 50 mL acetone, and while stirring, cool the reaction solution to 10 °C. Slowly add 27.49 g palmitoyl chloride dropwise, while simultaneously adding approximately 40 g of 15% sodium hydroxide aqueous solution to maintain the pH at around 11. The dropwise addition process takes approximately 1.5 h. After the addition is complete, stir for another 1 h at room temperature. Slowly add 15 mL concentrated hydrochloric acid to acidify, and heat the reaction solution to approximately 40 °C to dissolve completely. Transfer the solution to a separatory funnel, allow it to stand and separate into layers, and separate the upper organic phase. Slowly pour the organic phase into 300 mL of acidic water while stirring, precipitating a white solid. After filtration, washing with water, and drying, obtain the white intermediate crude N-palmitoylthreonine. The mixture was placed in a 250 mL round-bottom flask, and 50 mL of trifluoroacetic acid was added. The mixture was heated to 50 °C, stirred to dissolve, and then 32.99 g of palmitoyl chloride was slowly added dropwise over 1 hour. The reaction mixture was stirred at 50 °C for 4 hours. Most of the trifluoroacetic acid was recovered under reduced pressure, and the reaction solution was slowly poured into 200 mL of water while stirring. A white solid precipitated, which was filtered, washed with water, and dried to obtain a crude white solid. This crude solid was then subjected to simple recrystallization with ethanol / water to obtain 50.72 g of white N,O-palmitoylthreonine, with a yield of 85%. 1 H NMR (400MHz, DMSO-d6) δ8.97 (s, 2H), 6.48 (q, J = 7.0Hz, 2H), 2.19 (t, J = 7.4Hz, 4H), 1.63(d,J=7.1Hz,5H),1.51(t,J=7.3Hz,4H),1.24(s,48H),0.89–0.81(m,6H)ppm.

[0057] Comparative Example 1

[0058] A conventional one-step condensation method was used in comparison with Example 1.

[0059] In a 500 mL four-necked round-bottom flask equipped with a stirrer, 10.50 g of L-serine, 2.80 g of sodium hydroxide, and 100 mL of water were added and stirred until dissolved. Then, 100 mL of acetone was added and stirred until homogeneous. The reaction solution was cooled to 10 °C. Using a constant-pressure dropping funnel, 68.73 g of palmitoyl chloride (2.5 equivalents) and a 15% sodium hydroxide aqueous solution were slowly added dropwise, maintaining the pH at approximately 10. The dropwise addition process took about 1.5 h. After the addition was complete, the mixture was stirred at room temperature for another 2 h. Concentrated hydrochloric acid was slowly added for acidification, followed by dilution with water. A white solid precipitated, which was filtered, washed with water, and dried to obtain 69.22 g of white solid product. TLC and NMR analysis showed that the product consisted mostly of the intermediates N-palmitoylserine and palmitic acid, while the content of N,O-palmitoylserine was less than 10%.

[0060] Application Example 1

[0061] The N,O-lauroylserine sodium prepared in Example 2 was applied to the following shampoo formulation. The thickening performance of the product was tested according to the literature method and compared with N-lauroylserine sodium and lauroyl alanine sodium. From the viscosity test results, the thickening effect of N,O-lauroylserine sodium was much better than that of N-lauroylserine sodium and lauroyl alanine sodium products.

[0062]

[0063] Application Example 2

[0064] The prepared N-lauroyl-O-palmitoylserine sodium was applied to the following shampoo formulation, and the thickening performance of the product was tested according to the literature method. It was compared with N-lauroylserine sodium and lauroyl alanine sodium. From the viscosity test results, the thickening effect of N-lauroyl-O-palmitoylserine sodium was much better than that of N-lauroylserine sodium and lauroyl alanine sodium products.

[0065]

[0066] Application Example 3

[0067] Generally, there is a strong surface tension between the water and oil phases, and even with vigorous stirring, they cannot be truly mixed. By adding a certain amount of emulsifier, the surface tension at the interface is reduced, allowing for uniform mixing. The stability of the emulsifier is related to its bonding strength with high-quality components. An emulsion was prepared by mixing emulsifier 1 part oil, 49.5 parts water, and transferring the emulsion to a graduated centrifuge tube. After centrifugation at 4000 rpm for 15 minutes, the volume of the emulsion phase was read. The performance of the emulsifier was determined by calculating the emulsion stability % as (emulsion layer height / total liquid height) * 100. The emulsion stability of N,O-lauroylserine sodium (Example 1), N,O-palmitoylthreonine sodium (Example 4), monoglyceride, Tween 80, and lauroyl alanine sodium were compared. The results showed that Tween 80 > N,O-palmitoylthreonine sodium > N,O-lauroylserine sodium > monoglyceride > lauroyl alanine sodium.

[0068]

Claims

1. A kind N , O - A bis-fatty acyl hydroxy amino acid surfactant, characterized in that: It has the following structural formula: ； in, R 1 Hydrogen, C1~C 12 Alkyl or C6~C 12 aryl; R 2 and R 3 Independently selected from C7~C 17 aliphatic hydrocarbon groups; M is a hydrogen ion, potassium ion, sodium ion, or TEA ion; The N , O - Difatty acyl hydroxy amino acid surfactant is N , O -Lauroylserine surfactant, N -Lauroyl- O - Palmitoylserine surfactant or N , O - Palmitoylthreonine surfactant.

2. The one according to claim 1 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: Includes the following steps: 1) Dissolve the hydroxy amino acid and an organic co-solvent in an alkaline aqueous solution to form a hydroxyproline salt solution. Simultaneously add C8~C964 ... 18 Fatty acyl chloride and strong alkaline solution were subjected to N -Acylation reaction: After the N-acylation reaction is complete, the reaction solution is acidified, allowed to stand and separate into layers. The upper organic phase is poured into an acidic aqueous solution, and precipitate. N -Crude product of fatty acylhydroxyamino acid; 2) N The crude product of α-fatty acylhydroxyamino acid is dissolved in an acidic organic solution, and then C8~C2 is added. 18 fatty acyl chlorides O -Acylation reaction, to be O The acylation reaction is complete. The reaction solution is then poured into an acidic aqueous solution, and precipitate forms. N , O - Crude product of bis-fatty acyl hydroxy amino acid surfactant; The hydroxy amino acid has the following structural formula: ； in, R 1 Hydrogen, C1~C 12 Alkyl or C6~C 12 Aryl groups.

3. The one according to claim 2 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The organic co-solvent is at least one of methanol, ethanol, acetonitrile, acetone, tetrahydrofuran, and 1,4-dioxane; The amount of the organic co-solvent used is 0.4 to 0.6 times the volume of the alkaline aqueous solution.

4. The one according to claim 2 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The strong alkaline solution is a sodium hydroxide and / or potassium hydroxide solution with a mass percentage concentration in the range of 5% to 50%.

5. The one according to claim 2 or 4 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The dropping rate of the strong alkaline solution is controlled to... N The pH of the system during the acylation reaction is 9~11.

6. One according to claim 2, 3 or 4 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The reaction conditions for the N-acylation reaction are: reaction temperature of 0~30℃, reaction time of 30min~2h, and the hydroxy amino acid reacting with C8~C8... 18 The molar ratio of fatty acyl chlorides is 1:0.8~1.

5.

7. The one according to claim 2 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The acidification treatment temperature is 30~60℃.

8. The method according to claim 2 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The acidic organic solution contains at least one acid catalyst selected from phosphoric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, boron trifluoride ether, and hydrogen chloride.

9. A method according to claim 2 N , O A method for preparing a bis-fatty acyl hydroxy amino acid surfactant, characterized in that: The O The conditions for the acylation reaction are: reaction temperature of 30~80℃ and reaction time of 2~12 h. N - Fatty acylhydroxylamine and C8~C 18 The molar ratio of fatty acyl chlorides is 1:1~2.

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