A surfactant and a method for preparing the same

Abstract

The application discloses a surfactant and a preparation method thereof, and belongs to the field of chemical engineering and fine chemicals. A novel non-ionic surfactant is prepared by condensation reaction of 2-hydroxy-3-naphthoic acid ester (2,3-acid ester) as raw material and ethylene oxide under the action of a catalyst. The hydrophobic structure of the surfactant is composed of a rigid naphthalene ring and a flexible long-chain alkyl group, and the hydrophilic segment is a polyoxyethylene ether chain. The unique double hydrophobic structure endows the surfactant with excellent emulsification and dispersion stability. Meanwhile, the naphthalene ring conjugated structure makes the surfactant have excellent salt resistance and thermal stability. The ester bond introduced in the molecule serves as a degradable site, so that the product is stable in an acidic condition, but can be quickly and completely degraded in an alkaline condition, and the environmental friendliness is outstanding. The surfactant provided by the application is a green and efficient novel non-ionic surfactant, and has important significance for promoting the sustainable development of the field of surfactants.

Description

Technical Field

[0001] This invention belongs to the field of chemical and fine chemicals, and relates to a surfactant and its preparation method. Background Technology

[0002] Surfactants are amphiphilic compounds with both hydrophilic and hydrophobic groups in their molecular structure. They can significantly reduce the surface and interfacial tension of a target system, thereby exerting multiple functions such as emulsification, solubilization, dispersion, wetting, and foaming. Their preparation methods mainly include chemical synthesis, enzymatic catalysis, and microbial fermentation, with raw materials largely relying on petrochemical products. These substances occupy an irreplaceable and important position in industrial production and daily life, and are known as "industrial MSG," having been widely used in various fields such as daily chemical detergents, cosmetics, pharmaceutical preparations, food processing, and pesticide formulations.

[0003] Surfactants can be classified into four main categories based on the charge properties of their hydrophilic groups in aqueous solutions: anionic, cationic, nonionic, and amphoteric. Anionic surfactants have hydrophilic groups that dissociate and carry a negative charge in aqueous solution. Common hydrophilic groups include carboxyl groups, sulfonate groups, and sulfate groups. Patent CN114315654A describes a method for preparing anionic surfactants. These anionic surfactants contain both carboxyl and sulfonic acid groups, exhibiting high interfacial activity, excellent wetting properties, and foaming properties. Cationic surfactants have hydrophilic groups that dissociate and carry a positive charge. Typical examples include quaternary ammonium salts and amine salts. Patent CN109678733A describes a quaternary ammonium salt rosin-based cationic surfactant, its preparation method, and its applications. The pentavalent nitrogen atoms in the molecular structure of quaternary ammonium salts give them excellent water solubility and acid-base stability. Amphoteric surfactants have hydrophilic groups that contain both dissociable positive and negative charge centers, exhibiting different charge states in aqueous solutions with different pH values. Patent CN113750906A discloses an amphoteric surfactant, its preparation method and application, which uses N-hydrogenated tallow-1,3-propanediamine as the core raw material, giving the product excellent antifoaming and emulsifying properties.

[0004] Nonionic surfactants typically exhibit superior emulsifying properties compared to ionic surfactants, while also possessing good hard water resistance, making them an indispensable core component in functional formulations such as detergents and emulsifiers. Nonionic surfactants can be classified according to the structure of their hydrophilic groups into polyoxyethylene type, polyol type, alkanolamide type, polyether type, and amine oxide type, among others. Patent CN118684873A describes a bio-based emulsifier and its preparation method, using bio-derived phloroglucinol and alcohols with different carbon numbers as raw materials to prepare a biodegradable phloroglucinol ester formaldehyde emulsifier containing ester groups, replacing the traditional alkylphenol formaldehyde emulsifier (Agricultural Emulsion 700#). Patent CN119708458A describes a bio-based dispersant and its preparation method. The method uses bio-derived phloroglucinol and alcohols with different carbon numbers as raw materials to prepare a biodegradable stilbene phloroglucinol ester dispersant containing ester groups. Its hydrophobic structure contains both soft long-chain alkyl groups and highly planar stilbene phenol, replacing the commercially available, toxic, and non-degradable tristyrene-phenol polyoxyethylene ether dispersant (also known as Agricultural Emulsion 600#). These two bio-based dispersants and emulsifiers, using bio-derived phloroglucinol as the core raw material, possess excellent basic properties due to the conjugated structure of the benzene ring and the synergistic effect of the phenolic hydroxyl and ester groups. The polyoxyethylene ether segments formed by their polymerization can regulate the hydrophilic-hydrophobic balance, allowing the dispersant and emulsifier to achieve high-dilution stability and no stratification upon standing, respectively. The segments also possess thermal stability and chemical inertness, resisting various interferences and enhancing interfacial adsorption, thus extending the shelf life of the formulation. The ether bonds and phloroglucinol ester groups form "dual degradable sites," improving biodegradability and reducing toxicity.

[0005] Naphthalene rings form a dual aromatic ring conjugated system. Compared to single benzene rings, they not only exhibit better planar and hydrophobic interactions but also provide more active sites to meet functional modification requirements. For example, the commercially available dimethyl naphthalene sulfonate (DMD) powder BX (also known as penetrant BX) has a structure of sodium dibutylnaphthalene sulfonate; emulsifier BNO-13 is a naphthol polyoxyethylene ether emulsifier, often used as an electroplating brightener. Patent CN110201600A describes a method for preparing a naphthalene sulfonate polymer anionic surfactant. The sulfonate groups in the molecular structure of naphthalene sulfonate give it excellent anionic surface activity. Patent CN115772260A describes a naphthalene-based anionic nonionic surfactant, its preparation method, and its applications. This surfactant contains a naphthalene ring, carboxylate groups, and polyoxyalkylene chains in its molecular structure, giving it high interfacial activity and good salt resistance, effectively reducing heavy oil viscosity and improving oil recovery.

[0006] 2,3-Acid (2-hydroxy-3-naphthoic acid) (as shown in the formula below) is a bio-based naphthalene-based aromatic carboxylic acid. Its core advantage lies in its conjugated structure containing a naphthalene ring and two aromatic rings: on the one hand, the naphthalene ring has excellent planarity, which significantly enhances hydrophobicity and π-π and p-π stacking interactions compared to a single benzene ring, improving the adsorption capacity and stability of the molecule at the interface; on the other hand, the naphthalene ring structure provides more active sites, offering ample space for subsequent functional modification. 2,3-Acid is often used as an essential key intermediate in the production of naphthol (AS) and its series of pigments, and is further used in the manufacture of high-grade organic pigments and ice dyes. It is also used as a pharmaceutical intermediate in the synthesis of specific drugs, serving as an important bridge connecting its unique molecular structure with a variety of high-performance downstream products. Patent CN101085875A describes a pigment dispersant and its preparation method and application. The method involves reacting a fatty alkyl primary amine with paraformaldehyde, and adding the resulting hydroxymethylene compound to a 2,3-acid to obtain the corresponding 2,3-acid amine methylated product. This pigment dispersant is used to improve the dispersibility of pigments in offset printing inks.

[0007]

[0008] 2,3-acid structural formula

[0009] This patent aims to construct a surfactant system with a 2,3-acid as its core, consisting of a carboxyl group attached to a long-chain fatty alcohol and a phenolic hydroxyl group attached to an epoxy group. Unlike other single-structure or simple composite surfactant designs, the key to this invention lies in using a 2,3-acid as the core framework. First, it introduces a hydrophobic long chain through esterification with a long-chain fatty alcohol, and then reacts with ethylene oxide to introduce a polyether hydrophilic chain. The advantages of this surfactant structure are: the hydrophobic group contains both a soft long-chain alkyl group and a highly planar naphthalene ring structure. When used as an emulsifier, it easily interacts with the dispersed substance through hydrophobic interactions and flexible entanglement, and can also exhibit in-planar stacking. The emulsifier is less likely to detach from the surface of the dispersed substance, thus preventing emulsion destabilization.

[0010] This patent invention discloses a method for constructing a surfactant with 2,3-acid as the core. The core advantages of the surfactant prepared by this patent are: (1) The hydrophobic structure of the rigid naphthalene ring and the flexible aliphatic chain can simultaneously anchor planar organic matter (such as aromatics) and linear hydrocarbons (such as alkanes) in the oil phase. The hydration layer of the amphiphilic groups can form a stable steric barrier, which significantly improves the stability of the emulsion or dispersion system; (2) The conjugated structure of the naphthalene ring and the hydrophilic groups of the polyol make it more resistant to salt and heat than traditional carboxylate surfactants under high salt concentration or high temperature conditions; (3) The ester bond and the alcohol hydroxyl group generated by the ring opening of the epoxy in the molecule are easily degraded by microorganisms. The degradation path of the naphthalene ring structure is clear and does not contain difficult-to-degrade branches or halogen groups, which can reduce environmental risks while ensuring high interfacial activity. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the present invention aims to provide a 2,3-acid derivative surfactant and its preparation method. The raw materials can be derived from biologically sourced 2,3-acids, which have the advantages of being inexpensive, readily available, having low potential toxicity, and being environmentally friendly and controllable.

[0012] This invention provides a class of surfactants containing a 2,3-acid structure and a 2,3-ester polyoxyethylene ether structure, as shown in formula (I):

[0013] (I)

[0014] Where n is a natural number from 5 to 40, and R is a straight-chain or branched alkyl group with 4 to 18 carbon atoms.

[0015] The present invention provides a method for preparing a surfactant containing a 2,3-acid structure: 2,3-acid ester and ethylene oxide are added to a reaction vessel, and a condensation reaction is carried out under certain conditions by the action of a catalyst. The mixture is then kept at a constant temperature and pressure for a period of time to obtain the surfactant.

[0016]

[0017] The R group can be any one of butyl, pentyl, hexyl, isohexyl, heptyl, octyl, isooctyl, nonyl, decyl, dodecyl, isothidecyl, tetradecyl, hexadecyl, and octadecyl.

[0018] The condensation reaction temperature is 50-120℃.

[0019] The condensation reaction is characterized in that the reaction is carried out under certain pressure conditions, namely 0.2-1 MPa.

[0020] The catalyst is boron trifluoride diethyl ether, and the molar ratio of 2,3-ester to catalyst is 100:1-10:1.

[0021] The heat preservation and pressure holding time is 1-8 hours.

[0022] The molar ratio of the 2,3-ester to ethylene oxide is 1:5 to 1:40.

[0023] Beneficial effects:

[0024] (1) This invention uses 2,3-acid as the backbone, first esterifies it with long-chain fatty alcohol to introduce hydrophobic long chains, and then reacts it with ethylene oxide to introduce polyether hydrophilic chains, thus obtaining a novel 2,3-ester polyoxyethylene ether surfactant. The raw materials are widely available and environmentally friendly.

[0025] (2) The rigid naphthalene ring in the hydrophobic group of the surfactant works synergistically with the flexible long-chain alkyl group to simultaneously anchor planar and linear organic matter in the oil phase. The emulsifier is not easy to fall off from the surface of the emulsified and dispersed substances, and the stability of the emulsion is significantly improved.

[0026] (3) The naphthalene ring conjugated structure endows the product with excellent salt resistance and thermal stability; the ester and ether bonds in the molecule have clear degradation pathways, are easy to biodegrade, and are environmentally friendly. Detailed Implementation

[0027] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0028] Example 1

[0029] 1(a) Synthesis of 2,3-oic acid n-butyl ester

[0030] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-butanol (25.94 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-butyl ester was obtained in 91% yield.

[0031] 1(b) Synthesis of surfactant 1#

[0032] At room temperature, 36.64 g of 2,3-o-butyl ester (0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (0.21 g, 0.0015 mol, 0.01 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 50 °C. Ethylene oxide (33.04 g, 0.75 mol, 5 eq) was slowly added, with the pressure not exceeding 0.2 MPa. After the ethylene oxide was added, the temperature was maintained at 70 °C for aging until the pressure remained constant for 8 hours. Finally, the reactor was cooled and discharged to obtain the finished product.

[0033] Example 2

[0034] 2(a) Synthesis of 2,3-amyl 2,3-acid pentyl ester

[0035] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-pentanol (30.85 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-pentanyl ester was obtained in 90% yield.

[0036] 2(b) Synthesis of surfactant 2#

[0037] At room temperature, 2,3-amyl 2,3-acid (38.75 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (0.42 g, 0.003 mol, 0.02 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 55 °C. Ethylene oxide (33.04 g, 0.75 mol, 5 eq) was slowly added, with the pressure not exceeding 0.2 MPa. After the ethylene oxide was added, the temperature was maintained at 75 °C for aging until the pressure remained constant for 7 hours. Finally, the reactor was cooled and discharged to obtain the finished product.

[0038] Example 3

[0039] 3(a) Synthesis of n-hexyl 2,3-acid

[0040] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-hexanol (35.76 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-hexyl ester was obtained in 89% yield.

[0041] 3(b) Synthesis of surfactant 3#

[0042] At room temperature, 40.85 g of 2,3-oxo-hexyl ester (0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (0.42 g, 0.003 mol, 0.02 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 60 °C. Ethylene oxide (33.04 g, 0.75 mol, 5 eq) was slowly added, with the pressure not exceeding 0.2 MPa. After the ethylene oxide was added, the temperature was maintained at 80 °C for aging until the pressure remained constant for 6 hours. Finally, the reactor was cooled and discharged to obtain the finished product.

[0043] Example 4

[0044] 4(a) Synthesis of 2,3-isohexyl ester

[0045] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), isohexanol (35.76 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. Isohexyl 2,3-acid was obtained in 88% yield.

[0046] 4(b) Synthesis of surfactant 4#

[0047] At room temperature, isohexyl 2,3-acid (40.85 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (0.42 g, 0.003 mol, 0.02 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 65 °C. Ethylene oxide (33.04 g, 0.75 mol, 5 eq) was slowly added, with the pressure not exceeding 0.2 MPa. After the ethylene oxide was added, the temperature was maintained at 85 °C for aging until the pressure remained constant for 5 hours. Finally, the reactor was cooled and discharged to obtain the finished product.

[0048] Example 5

[0049] 5(a) Synthesis of n-heptyl 2,3-acid

[0050] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-heptanol (40.67 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-heptyl ester was obtained in 86% yield.

[0051] 5(b) Synthesis of surfactant 5#

[0052] At room temperature, 42.95 g of 2,3-oxo-heptyl ester (0.15 mol, 30 eq) and boron trifluoride diethyl ether catalyst (0.71 g, 0.005 mol, 1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 70 °C. Ethylene oxide (66.08 g, 1.5 mol, 300 eq) was slowly added, with the pressure not exceeding 0.2 MPa. After the ethylene oxide was added, the temperature was maintained at 90 °C for aging until the pressure remained constant for 4 hours. Finally, the reactor was cooled and discharged to obtain the finished product.

[0053] Example 6

[0054] 6(a) Synthesis of octyl 2,3-acid

[0055] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-octanol (45.58 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-octyl ester was obtained in 92% yield.

[0056] 6(b) Synthesis of surfactant 6#

[0057] At room temperature, 45.06 g (0.15 mol, 30 eq) of 2,3-octyl ester and 0.71 g (0.005 mol, 1 eq) of boron trifluoride ether catalyst were added to the reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 75 °C. Ethylene oxide (66.08 g, 1.5 mol, 300 eq) was slowly added, with the pressure not exceeding 0.5 MPa. After the ethylene oxide was added, the temperature was maintained at 95 °C for aging until the pressure remained constant for 3 hours. Finally, the product was cooled and discharged to obtain the final product.

[0058] Example 7

[0059] 7(a) Synthesis of isooctyl 2,3-acid

[0060] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), isooctyl alcohol (45.58 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. Isooctyl 2,3-acid was obtained in 90% yield.

[0061] 7(b) Synthesis of surfactant 7#

[0062] At room temperature, isooctyl 2,3-acid (45.06 g, 0.15 mol, 30 eq) and boron trifluoride diethyl ether catalyst (0.71 g, 0.005 mol, 1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 80 °C. Ethylene oxide (66.08 g, 1.5 mol, 300 eq) was slowly added, with the pressure not exceeding 0.5 MPa. After the ethylene oxide was added, the temperature was maintained at 100 °C for aging until the pressure remained constant for 2 hours. Finally, the reactor was cooled and discharged to obtain the finished product.

[0063] Example 8

[0064] 8(a) Synthesis of 2,3-acid nonyl ester

[0065] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-nonyl alcohol (50.49 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-nonyl ester was obtained in 89% yield.

[0066] 8(b) Synthesis of surfactant 8#

[0067] At room temperature, nonyl 2,3-acid (47.16 g, 0.15 mol, 30 eq) and boron trifluoride diethyl ether catalyst (0.71 g, 0.005 mol, 1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 85 °C. Ethylene oxide (66.08 g, 1.5 mol, 300 eq) was slowly added, with the pressure not exceeding 0.5 MPa. After the ethylene oxide was added, the temperature was maintained at 105 °C for aging until the pressure remained constant for 1 hour. Finally, the reactor was cooled and discharged to obtain the finished product.

[0068] Example 9

[0069] 9(a) Synthesis of 2,3-octanoic acid n-decyl ester

[0070] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), n-decyl alcohol (55.40 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid n-decyl ester was obtained as a pale yellow transparent liquid, with a yield of 86%.

[0071] 9(b) Synthesis of surfactant 9#

[0072] At room temperature, 2,3-octyl 2,3-acid (49.27 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether (2.13 g, 0.015 mol, 0.1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 90 °C. Ethylene oxide (264.31 g, 6 mol, 40 eq) was slowly added, with the pressure not exceeding 0.5 MPa. After the ethylene oxide was added, the temperature was maintained at 110 °C for aging until the pressure remained constant for 1 hour. Finally, the product was cooled and discharged to obtain the final product.

[0073] Example 10

[0074] Synthesis of 10(a) 2,3-acid dodecane ester

[0075] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), dodecyl alcohol (65.22 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. Dodecyl 2,3-acid was obtained as a pale yellow transparent liquid, with a yield of 81%.

[0076] 10(b) Synthesis of surfactant 10#

[0077] At room temperature, dodecyl 2,3-acid (53.47 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (2.13 g, 0.015 mol, 0.1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 95 °C. Ethylene oxide (264.31 g, 6 mol, 40 eq) was slowly added, with the pressure not exceeding 0.5 MPa. After the ethylene oxide was added, the temperature was maintained at 115 °C for aging until the pressure remained constant for 1 hour. Finally, the product was cooled and discharged to obtain the final product.

[0078] Example 11

[0079] 11(a) Synthesis of 2,3-acid isotridecane ester

[0080] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), isotridecyl alcohol (70.13 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. 2,3-acid isotridecyl ester was obtained as a pale yellow transparent liquid, with a yield of 81%.

[0081] 11(b) Synthesis of surfactant 11#

[0082] At room temperature, 2,3-acid isotridecyl ester (55.58 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (2.13 g, 0.015 mol, 0.1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 100 °C. Ethylene oxide (264.31 g, 6 mol, 40 eq) was slowly added, with the pressure not exceeding 1 MPa. After the ethylene oxide was added, the temperature was maintained at 120 °C for aging until the pressure remained constant for 1 hour. Finally, the product was cooled and discharged to obtain the final product.

[0083] Example 12

[0084] 12(a) Synthesis of tetradecane 2,3-acid ester

[0085] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), tetradecyl alcohol (75.04 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. Tetradecyl 2,3-acid was obtained as a pale yellow transparent liquid, with a yield of 86%.

[0086] 12(b) Synthesis of surfactant 12#

[0087] At room temperature, tetradecyl 2,3-acid (57.68 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (2.13 g, 0.015 mol, 0.1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 100 °C. Ethylene oxide (264.31 g, 6 mol, 40 eq) was slowly added, with the pressure not exceeding 1 MPa. After the ethylene oxide was added, the temperature was maintained at 120 °C for aging until the pressure remained constant for 1 hour. Finally, the product was cooled and discharged to obtain the final product.

[0088] Example 13

[0089] 13(a) Synthesis of hexadecane ester of 2,3-acid

[0090] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), hexadecyl alcohol (84.85 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. Hexadecyl 2,3-acid was obtained as a pale yellow transparent liquid, with a yield of 86%.

[0091] 13(b) Synthesis of surfactant 13#

[0092] At room temperature, hexadecyl 2,3-acid (61.89 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (2.13 g, 0.015 mol, 0.1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 100 °C. Ethylene oxide (264.31 g, 6 mol, 40 eq) was slowly added, with the pressure not exceeding 1 MPa. After the ethylene oxide was added, the temperature was maintained at 120 °C for aging until the pressure remained constant for 1 hour. Finally, the product was cooled and discharged to obtain the final product.

[0093] Example 14

[0094] 14(a) Synthesis of 2,3-octadecyl ester of 2,3-acid

[0095] In a 500 mL two-necked flask, 2,3-acid (79.03 g, 0.42 mol, 1.2 eq), octadecyl alcohol (94.67 g, 0.35 mol, 1 eq), p-toluenesulfonic acid (1.20 g, 0.007 mol, 0.02 eq), and 200 mL of cyclohexane were added. A water separator was installed to collect the water generated during the reaction. The mixture was heated in an oil bath at 105 °C until cyclohexane was refluxed, and the reaction progress was monitored using thin-layer chromatography. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was washed three times with 300 mL of 7 wt% NaHCO3 aqueous solution to remove residual 2,3-acid. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. Octadecyl ester of 2,3-acid was obtained as a pale yellow transparent liquid, with a yield of 86%.

[0096] 14(b) Synthesis of surfactant 14#

[0097] At room temperature, octadecyl 2,3-acid (66.10 g, 0.15 mol, 1 eq) and boron trifluoride diethyl ether catalyst (2.13 g, 0.015 mol, 0.1 eq) were added to a reactor. The reactor was first purged with nitrogen three times, then evacuated to -0.1 MPa. The vacuum was then closed, and the temperature was raised to 100 °C. Ethylene oxide (264.31 g, 6 mol, 40 eq) was slowly added, with the pressure not exceeding 1 MPa. After the ethylene oxide was added, the temperature was maintained at 120 °C for aging until the pressure remained constant for 1 hour. Finally, the product was cooled and discharged to obtain the final product.

[0098] Performance testing

[0099] (a) Detection of surface tension properties of surfactants

[0100] There are various methods for determining the surface tension of liquids, and the ring method is characterized by high accuracy, simple operation, and direct results. The surface tension of a synthesized surfactant was determined using the ring method according to the international standard ISO 304-1985 (surfactants—determination of surface tension by the pull-up film method). The experimental results are shown in Table 1 below.

[0101] Table 1. Surface tension properties of 2,3-acid derivative surfactants (25℃)

[0102] 1# 29.3 0.13 2# 28.4 0.19 3# 27.8 0.25 4# 28.1 0.27 5# 27.5 0.51 6# 27.1 0.54 7# 27.2 0.56 8# 26.8 0.58 9# 26.5 0.69 10# 26.3 0.74 11# 26.4 0.79 12# 26.2 0.82 13# 26.3 0.86

[0103] (II) Testing of surfactant emulsion dispersion properties

[0104] Take 35g each of Pigment Red 57:1, Pigment Red 177, Pigment Red 140, Phthalocyanine Blue 15:3, Pigment Yellow 204, and Pigment Yellow 12 (all organic pigments are produced by Jiangsu Liwang Technology Co., Ltd.), 10g each of OP-10 (produced by Shanghai Yuanye Biotechnology Co., Ltd.), NP-10 (produced by Shanghai Bailingwei Chemical Technology Co., Ltd.), Lugalvan BNO 12 (produced by Guangzhou Nuohua Trading Co., Ltd.), and surfactants 5#-8# into a glass bottle. Add 100g of glass beads (particle size 2-3mm), 0.1g of defoamer BYK-024 (BYK Corporation), and 55g of deionized water. Tighten the glass bottle and place it in an SK450 vibratory mixer (Shanghai Jingxin Industrial Co., Ltd.) and vibrate for 3 hours. Remove the glass bottle and let it stand for 48 hours.

[0105] The particle size of the pigment emulsion was measured using a Mastersizer 3000 laser particle size analyzer from the pigment emulsion in the glass bottle after it had settled, and the results are shown in Table 2.

[0106] Take 2 ml of pigment emulsion from the top layer of the emulsion in a petri dish after it has settled in a glass bottle, and dry it in an oven at 100°C for 72 hours. Calculate the solid content of each sample after drying. A high solid content indicates good emulsion stability, while a lower solid content indicates more emulsion sedimentation and poor emulsion stability. The test results are shown in Table 3.

[0107] Table 2. Average particle size (D50, nm) of color in pigment paste

[0108]

[0109] Table 3. Solid content of pigment / % (after standing for 72 hours, take the upper emulsion)

[0110]

[0111] As shown in Table 2, the organic pigments prepared by surfactants 5#-8# all have particle sizes between 420nm and 460nm, with smaller particle sizes and more uniform dispersion, which are generally superior to commercially available OP-10, NP-10 and Lugalvan BNO 12.

[0112] As shown in Table 3, the solid content of the organic pigment emulsions prepared by surfactants 5#-8# is between 44.4% and 44.9% (the theoretical solid content is 45%), which is significantly higher than that of commercially available OP-10, NP-10 and Lugalvan BNO 12. The emulsions have excellent stability and the pigment particles are not easy to settle in the emulsion.

[0113] (III) Testing of the acid and alkali resistance of surfactants

[0114] (1) Alkali resistance

[0115] Accurately weigh 1.00 g of sample into a 250 mL Erlenmeyer flask, add 50 mL of deionized water and 2 mL of 10% sodium hydroxide aqueous solution, and react in a water bath at 45.0 °C for the preset time. Add 1 drop of phenolphthalein indicator, and titrate with 2% hydrochloric acid solution until the pink color disappears (endpoint). Record the volume of hydrochloric acid consumed and calculate the alkaline hydrolysis rate. The test results are shown in Table 4.

[0116] (2) Acid resistance

[0117] Accurately weigh 1.00 g of sample into a 250 mL Erlenmeyer flask, add 50 mL of deionized water and 2 mL of 5% hydrochloric acid aqueous solution, and react in a water bath at 45.0 °C for the preset time. Add 1 drop of phenolphthalein indicator and titrate with 2% sodium hydroxide solution until the solution turns pink and does not fade for 30 seconds (endpoint). Record the volume of sodium hydroxide consumed and calculate the acidolysis rate. The test results are shown in Table 5.

[0118] Table 4. Alkali resistance of surfactants

[0119]

[0120] Table 5. Acid resistance of surfactants

[0121]

[0122] As shown in Table 3, surfactants 5#-8# contain degradable ester bonds in their molecules, and can undergo controlled saponification hydrolysis under mild alkaline conditions, achieving complete degradation within 3 hours, thus exhibiting excellent alkaline degradability and environmental safety. Commercially available OP-10, NP-10, and Lugalvan BNO 12 do not contain ester bonds, are structurally stable under alkaline conditions, and do not undergo hydrolysis.

[0123] As shown in Table 4, surfactants 5#-8#, as well as commercially available OP-10, NP-10 and Lugalvan BNO 12, have stable molecular structures under acidic conditions and show no degradation, layering or turbidity within 3 hours, demonstrating excellent acid resistance.

[0124] Compared with traditional surfactants such as OP-10, NP-10, and Lugalvan BNO 12, the surfactant of this invention has the unique advantages of being both acid-stable and alkaline-degradable, making it more suitable for complex pH systems such as pesticides, pigments, and textile printing and dyeing. It has a wider range of applications and is more environmentally friendly.

[0125] (iv) Testing of the performance of imazalil water-in-oil emulsion

[0126] First, prepare a water-in-water emulsion containing the surfactant imazalil. The emulsion consists of: 45g imazalil, 20g xylene, 4g surfactant, 0.04g xanthan gum, 0.2g silicone defoamer, 8g propylene glycol, and 22.76g deionized water. After stirring and shearing, a total of 100g of water-in-water emulsion is obtained.

[0127] The appearance of the emulsifier was evaluated according to the national standard (GB / T 39671-2020). The prepared prochloraz aqueous emulsion was a milky white homogeneous liquid, without obvious caking or flocculation. The aqueous emulsions prepared with surfactants No. 5-8 had uniform appearances and could restore the homogeneous state by gently stirring; for commercially available OP-10, NP-10 and Lugalvan BNO 12, emulsion stratification and demulsification occurred.

[0128] The emulsion stability was detected according to the national standard (GB / T 1603-2001). An appropriate amount of the emulsion was diluted 200 times with standard hard water to prepare a 100 mL emulsion, which was left standing in a constant temperature water bath at 30 °C for 1 h, and the separation of the emulsion was observed. The test results are shown in Table 6.

[0129] The emulsion pourability was determined according to the national standard (GB / T 31737-2015). The residue after pouring ≤ 5.0% and the residue after washing ≤ 0.5% were considered qualified. The test results are shown in Table 6.

[0130] Table 6. Stability and pourability data of prochloraz aqueous emulsion

[0131]

[0132] As can be seen from Table 6, the stabilities of the prochloraz aqueous emulsions prepared with surfactants No. 5-8 all met the national standard, the emulsion stability was good, and they could tolerate high-fold dilution. For commercially available OP-10, NP-10 and Lugalvan BNO 12, precipitation and stratification occurred after 200-fold dilution, and they could not meet the requirements of high-fold dilution stability of the aqueous emulsion.

[0133] As can be seen from Table 6, the pourabilities of the prochloraz aqueous emulsions prepared with surfactants No. 5-8 all met the national standard, indicating that the prepared aqueous emulsion had excellent fluidity and improved the utilization rate of the aqueous emulsion. Among them, the residues after pouring of the aqueous emulsions prepared with No. 5-8 were lower than those of commercially available OP-10, NP-10 and Lugalvan BNO 12 (the lowest was 2.70%), and the residues after washing were lower (the lowest was 0.15%). The lower the residue rate, the more complete the dilution transfer and the less residue in the packaging bottle.

Claims

1. A surfactant, characterized in that... It has the structure shown in equation (I): Formula (I) Where n is a natural number from 5 to 40, and R is a straight-chain or branched alkyl group with 4 to 18 carbon atoms.

2. The surfactant as described in claim 1, characterized in that, The R group can be any one of butyl, pentyl, hexyl, isohexyl, heptyl, octyl, isooctyl, nonyl, decyl, dodecyl, isothidecyl, tetradecyl, hexadecyl, and octadecyl.

3. The surfactant as described in claim 1, characterized in that, It is prepared by the following method: reacting 2-hydroxy-3-naphthyl carboxylate (2,3-ester) with ethylene oxide in the presence of a catalyst.

4. The 2-hydroxy-3-naphthylcarbamate (2,3-ester) as described in claim 3, characterized in that... It has the structure shown in equation (II): Formula (II) Wherein, R is a straight-chain or branched alkyl group having 4 to 18 carbon atoms.

5. The method for preparing the surfactant according to claims 1 and 3, characterized in that, The molar ratio of the 2,3-ester to ethylene oxide is 1:5 to 1:

40.

6. The method for preparing the surfactant according to claims 1 and 3, characterized in that, The catalyst is boron trifluoride diethyl ether.

7. The method for preparing the surfactant according to claims 1 and 3, characterized in that, The catalyst is in a molar ratio of 1:100 to 1:10 with respect to 2,3-ester.

8. The method for preparing the surfactant according to claims 1 and 3, characterized in that, The reaction temperature is 50 to 120°C, the reaction pressure is 0.2 to 1 MPa, and the reaction time is 1 to 8 hours.

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