Glycerol-based / polyethylene glycol-based aspartic acid monoester amphoteric-nonionic surfactants and methods for their preparation

Abstract

The application discloses a glycerol / polyethylene glycol-based aspartic acid monoester amphoteric-nonionic surfactant and a preparation method thereof, and belongs to the technical field of special surfactants. The application takes maleic anhydride, a low-melting-point polyol with excellent mutual solubility and a primary aliphatic amine as raw materials, and prepares the target product through three steps of selective monoesterification, Michael addition and neutralization of acid-base equivalent, and can select a reaction atmosphere according to the material characteristics of the polyol. The application avoids the use of high-boiling-point solvents throughout the whole process, can realize directional monoester synthesis, and effectively solves the technical pain points of traditional aspartic acid ester products, such as disordered components, purification difficulty and limited industrial production. The product has the dual advantages of mild and low irritation of amphoteric surfactants and acid and alkali resistance and salt resistance of nonionic surfactants, and has the advantages of green and simple overall preparation process, adjustable performance and suitable scale industrial production, and has a wide application prospect in the fields of daily chemicals, medicines and industrial emulsification.

Description

Technical Field

[0001] This invention relates to the fields of fine chemicals and surfactant synthesis technology, specifically to a glycerol / polyethylene glycol aspartic acid monoester amphoteric-nonionic surfactant and its preparation method. Background Technology

[0002] Amphoteric-nonionic composite surfactants combine the performance advantages of both types of surfactants, exhibiting characteristics such as resistance to hard water and electrolytes, strong compatibility, and excellent wetting and emulsifying properties. They represent a mainstream research direction in the fields of green daily chemicals and industrial additives. Among these, aspartic acid surfactants, relying on the aspartic acid molecular skeleton, possess green properties such as low toxicity, low irritation, and easy biodegradability, aligning with the industry's green and sustainable development philosophy. However, traditional aspartic acid surfactants generally suffer from insufficient water solubility, limited performance characteristics, and limited applicability, making it difficult to meet the needs of large-scale industrial applications.

[0003] Current research and development of aspartic acid surfactants mainly focuses on single amphoteric structures or simple complex systems, and there is still room for optimization in structural design and process systems. Among the existing public technologies, WO1999048901A3 discloses an aspartic acid sucrose ester surfactant. This scheme utilizes the polyhydroxy structure of sucrose to improve the hydrophilicity of the product and has a certain degree of biocompatibility, providing a basic reference for the research and development of this type of surfactant. However, it still has certain limitations in terms of process adaptability and industrialization adaptability.

[0004] Specifically, this technology uses sucrose as a hydrophilic backbone. However, sucrose and its esterification intermediates have limited solubility in low-boiling-point organic solvents. The synthesis process often requires significant amounts of high-boiling-point polar organic solvents such as DMF and DMSO for dissolution, leading to complex solvent recovery processes and high environmental costs. Furthermore, the reaction system is prone to solid precipitation and viscosity increases, which can negatively impact mass and heat transfer, affecting the reaction conversion rate. In addition, sucrose molecules contain multiple active hydroxyl groups, and the esterification reaction lacks fixed reaction sites, easily generating a mixture of monoesters, diesters, and polyesters. This results in complex product composition, making separation and purification difficult, and leading to generally low product yield and product quality stability, making it challenging to adapt to continuous and stable industrial production conditions.

[0005] Based on the aforementioned limitations of existing technologies, this invention optimizes and improves the molecular structure and synthesis process. It selects glycerol / polyglycerol / polyethylene glycol, which has a low melting point and excellent melt miscibility, to replace traditional sucrose as the nonionic hydrophilic backbone. Combined with a stepwise, controllable synthesis process involving esterification followed by addition, it prepares amphoteric nonionic aspartic acid monoester surfactants with clear molecular structures, high product purity, and flexibly controllable performance. This invention effectively improves the compatibility and controllability of the reaction system, overcomes the shortcomings of traditional processes such as difficult product separation, limited yield, and limited performance, and compensates for the deficiencies in the preparation process and product performance of traditional poorly soluble polyol-based aspartic acid esters. It aligns with the trend of green chemical development and possesses good industrialization value and application prospects. Summary of the Invention

[0006] This invention aims to provide a glycerol / polyethylene glycol-based aspartic acid monoester amphoteric-nonionic surfactant and its preparation method, thereby improving upon the shortcomings of traditional aspartic acid ester surfactants in terms of raw material solubility, synthesis process, product purity, and industrial compatibility. This invention combines the mild and low-irritant properties of amphoteric surfactants with the acid, alkali, and salt resistance of nonionic surfactants. It selects a room-temperature liquid or low-melting-point polyol with excellent melt miscibility as the hydrophilic matrix to construct a well-defined and stable monoester-type composite surfactant. Simultaneously, by matching differentiated reaction protective atmospheres according to the physicochemical properties of the raw materials, the preparation process is simplified and the synthesis route optimized, achieving high-yield, high-purity, and green preparation of the product. This results in a novel, multifunctional surfactant with a simple process, adjustable performance, and suitability for large-scale production.

[0007] To achieve the above objectives, the surfactant of the present invention has the following general chemical formula: R 1 OOC-CH(NH-R 2 )-CH2-COOR 3 Among them, R 1 It is a hydrogen or water-soluble inorganic cation, the latter including any one or more of alkali metal ions, alkaline earth metal ions, and ammonium ions; R 2 It is an alkyl, alkenyl, dienyl, or trienyl group having 2 to 28 carbon atoms, or a mixture thereof, preferably having 6 to 22 carbon atoms, more preferably 12 to 18 carbon atoms; R 3 The polyglycerol group is a monosubstituted glycerol group, a polyglycerol group with a degree of polymerization m=2~40, or a polyethylene glycol group with a degree of polymerization n=2~40. The preferred degrees of polymerization for the polyglycerol group and the polyethylene glycol group are 2~10 and 2~22, respectively, thus broadening the range of raw material compatibility.

[0008] According to R 1 Depending on the type of functional group, the surfactants of this invention are classified into two configurations: when R 1 When R is a hydrogen atom, the molecule has an amino acid internal salt structure; when R... 1When it is an inorganic cation, it is a basic salt type; the critical micelle concentration of the product is 0.01~100 mmol / L, and it has excellent interfacial activity, as well as excellent emulsifying, wetting and dispersing properties.

[0009] This invention uses maleic anhydride, a polyol matrix, and aliphatic primary amines as core raw materials, and prepares the target product through a three-step controllable reaction involving selective esterification, Michael addition, and acid-base equivalent neutralization modification. The specific process steps are as follows: Maleic anhydride and the polyol matrix are added at a molar ratio of 1:1.0~1.5. The polyol is selected as a room-temperature liquid or low-melting-point solid glycerol / polyglycerol / polyethylene glycol. The reaction uses a solvent-free system or a low-boiling-point inert organic solvent system, and high-boiling-point polar solvents are not used throughout the process. The reaction atmosphere is selected according to the differences in the physicochemical properties of the polyols. Polyols that are not sensitive to oxygen and moisture can react directly in an air atmosphere. Easily oxidized polyols are isolated from air by nitrogen or argon. The choice of protective gas depends only on the type of material and is independent of the reaction temperature. The system temperature is controlled at 40~120°C. o At temperature C, the reaction proceeds for 2–10 h, resulting in the directed formation of a single-structured maleic acid monoester intermediate. The obtained intermediate then reacts with the aliphatic primary amine R… 2 A homogeneous system was constructed using NH2 mixtures and low-boiling-point solvents such as water, alcohols, esters, and ethers, within the range of 0–110 °C. o The reaction was carried out under C conditions for 2–24 h. After filtration, recrystallization, drying, and purification, a high-purity internal salt type aspartic acid surfactant was obtained. Finally, alkali metal hydroxide, alkaline earth metal hydroxide, ammonia or ammonia water were used as alkaline materials, and a neutralization reaction was carried out according to the acid-base equivalence ratio. This method is suitable for monobasic strong base, dibasic strong base, and weak base systems, avoiding stoichiometric errors of bases with different valence states, and precisely controlling the ion existence form of the product, ultimately obtaining a basic salt type aspartic acid monoester product with tunable performance.

[0010] This invention possesses numerous advantages through the aforementioned technical design: It selects low-melting-point polyol raw materials with excellent melt miscibility, effectively improving the problems of high melting point, general solubility, and limited reaction compatibility of traditional sugar hydrophilic matrices; the process is flexible and adaptable, allowing for air-exposed or inert gas-protected reactions depending on material characteristics, resulting in simple operation and good production controllability; through directional and selective monoesterification design, disordered esterification side reactions are effectively avoided, resulting in a single product component, convenient purification, and excellent product purity; the entire process uses a solvent-free or low-boiling-point recyclable solvent system, making the process green and environmentally friendly, with easy solvent recovery and low energy consumption, reducing the difficulty of industrial scale-up; simultaneously, the salt structure and surface activity of the product can be controlled by equivalent neutralization of different alkali sources, adapting to various application conditions, and the overall product performance and industrial adaptability are superior to existing technical solutions. Attached Figure Description

[0011] Figure 1 for Nγ-(logC) curve of hexadecyl aspartic monoglyceride measured by the maximum bubble method Figure 2 for N γ-(logC) curve of sodium hexadecyl aspartate monoglyceride measured by the maximum bubble method. Detailed Implementation

[0012] Example 1: N - Cetyl aspartic acid monoglyceride amphoteric nonionic surfactant: (1) Under solvent-free conditions, 9.81 g maleic anhydride (0.100 mol) and 11.97 g glycerol (0.130 mol) were mixed at 60°C. o Heat at 90°C for 2 hours. o C continued the reaction for 4 h to obtain an intermediate mixture of maleic acid monoglycerides; (2) The obtained intermediate maleic acid monoglycerides (appropriate amount of solvent ethyl acetate) were reacted with 24.15 g of cetylamine (0.100 mol, appropriate amount of solvent ethyl acetate) in a round-bottom flask and heated to 30 °C. o After the reaction at C for 4 hours, the temperature was further increased to 42°C. o C. After the overnight reaction was completed, a white solid product was obtained by filtration. The crude product was washed three times with an appropriate amount of ethyl acetate and dried to obtain a white paste-like solid product with a yield of 91.8%; (3) Two portions of 0.05 mol / L glycerol were prepared with ultrapure water. N A solution of hexadecyl aspartic acid monoester, one portion of which was neutralized with an equimolar amount of NaOH aqueous solution (1 mol / L) to obtain glycerol. N - Sodium hexadecyl aspartate monoester solution; then then using the maximum bubble method at 25 o The surface tension of two surfactants tested in the C-water system was obtained as a γ-(-logC) curve. The inflection point is their CMC value, as shown in the appendix. Figure 1 and attached Figure 2 (4) Glycerin N - Critical micelle concentration of hexadecyl aspartic acid monoester is 0.79 mmol / L, and surface tension decreases to 32.3 mN / m; glycerol N The critical micelle concentration of sodium hexadecyl aspartate monoester was 0.16 mmol / L, and the surface tension decreased to 26.8 mN / m.

[0013] Example 2: PEG-400 base N -Dodecyl aspartic acid monoester amphoteric nonionic surfactant: (1) Under solvent-free conditions, 4.90 g maleic anhydride (0.050 mol) and 26 g PEG-400 (0.065 mol) were used in an argon atmosphere at 60 °C. o Heat at 90°C for 2 hours.o C continued the reaction for 4 h to obtain the intermediate PEG-400-based maleic acid monoester mixture; (2) the obtained intermediate PEG-400-based maleic acid monoester (appropriate amount of solvent ethyl acetate) and 9.27 g of dodecyl primary amine (0.050 mol, appropriate amount of solvent ethyl acetate) were heated to 30 °C under argon protection. o After the reaction at C for 4 hours, the temperature was further increased to 50°C. o C. After the overnight reaction was completed, a white solid product was obtained by filtration. The crude product was washed three times with an appropriate amount of ethyl acetate and dried to obtain a pale yellow paste-like solid product with a yield of 89.6%; (3) 0.01 mol of PEG-400-based soluble ethanol was dissolved in 10 ml of ethanol. N- Dodecyl aspartic acid monoester, neutralized with 0.005 mol potassium carbonate, 30 o Stirring at C for 1 h, followed by vacuum distillation, yielded a pale yellow solid PEG-400. N- Potassium salt of dodecyl aspartic acid monoester.

[0014] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, simple improvements, etc., made within the spirit and principles of the present invention and based on ordinary technical knowledge and common methods in the art should be included within the scope of protection of the present invention. Processes, proportions, and equipment parameters not described in detail in the present invention are all conventional technical means in the art and do not constitute a limitation on the inventiveness of the present invention.

Claims

1. A glycerol / polyethylene glycol-based aspartic acid monoester amphoteric nonionic surfactant, characterized in that, It has the following general chemical structural formula (I): R 1 OOC-CH(NH-R 2 )-CH2-COOR 3 (I) Where: R 1 It is a hydrogen or water-soluble inorganic cation; R 2 It is a straight-chain or branched aliphatic hydrocarbon group; R 3 It is a monosubstituted, easily soluble, low-melting-point polyol group, wherein the polyol group is glycerol group, polyglycerol group or polyethylene glycol group.

2. The surfactant according to claim 1, characterized in that: The R 1 It can be any one or more of alkali metal ions, alkaline earth metal ions, and ammonium ions.

3. The surfactant according to claim 2, characterized in that: The R 1 It can be any one or more of sodium ions, potassium ions, and ammonium ions.

4. The surfactant according to claim 1, characterized in that: The R 2 It is an alkyl, alkenyl, dienyl or trienyl group having 2 to 28 carbon atoms, or a mixture thereof.

5. The surfactant according to claim 4, characterized in that: The R 2 It is an alkyl, alkenyl, dienyl or trienyl group having 6 to 22 carbon atoms, or a mixture thereof.

6. The surfactant according to claim 1, characterized in that: R 3 When it is polyglycerol-based, the degree of polymerization m = 2~14; when it is polyethylene glycol-based, the degree of polymerization n = 2~40.

7. The surfactant according to claim 6, characterized in that: R 3 When it is polyglycerol-based, the degree of polymerization m = 2~10; when it is polyethylene glycol-based, the degree of polymerization n = 2~22.

8. The surfactant according to claim 1, characterized in that: R 1 When it is hydrogen, it is an internal salt type, R 1 When it is an inorganic cation, it is a basic salt type; the critical micelle concentration of the surfactant is 0.01~100 mmol / L.

9. A method for preparing the surfactant according to any one of claims 1 to 8, characterized in that, Includes the following steps: 1) Selective esterification: Maleic anhydride and a polyol matrix are mixed at a molar ratio of 1:1.0~1.

5. The polyol is a room-temperature liquid or a low-melting-point solid, selected from glycerol, polyglycerol, and polyethylene glycol. The reaction is carried out in a solvent-free or low-boiling-point inert organic solvent system, and the atmosphere is selected according to the properties of the polyol: oxygen- and water-resistant polyols are treated with an air atmosphere, while easily oxidized polyols are treated with a protective gas. The reaction is carried out at 40~120 ℃ for 2~10 h to obtain maleic acid monoester intermediates. This reaction system has high reactivity and produces a single product component. 2) Michael addition: The above intermediate is dissolved with aliphatic primary amine in a suitable solvent and reacted at 0~110 ℃ for 2~24 h. After filtration, recrystallization and drying, an internal salt type aspartic acid surfactant is obtained. 3) The inner salt product obtained in step 2 is neutralized with a basic compound according to the acid-base equivalent ratio to adjust the ionic form of the product and prepare a basic salt-type aspartic acid monoester product.

10. The preparation method according to claim 9, characterized in that: Step 1) The protective gas is nitrogen or argon. Whether or not to ventilate depends solely on the type of polyol and is independent of the reaction conditions.

11. The preparation method according to claim 9, characterized in that: Step 2) The solvent is selected from one or more of the following: water, alcohols, esters, ethers, aliphatic hydrocarbons, aromatic hydrocarbons, and ketones.

12. The preparation method according to claim 9, characterized in that: Step 3) The alkaline compound is an alkali metal hydroxide, an alkaline earth metal hydroxide, ammonia gas, or ammonia water.

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