A benzoxazine resin-based macromolecular surfactant and a preparation method and application thereof

Abstract

The present application relates to a kind of benzoxazine resin-based macromolecular surfactant and its preparation method and application, the surfactant has the structure shown in formula (I). Unit phenol, unit amine and aldehyde are obtained by Mannich reaction to obtain benzoxazine monomer, monomer is obtained by thermal ring-opening polymerization to obtain benzoxazine resin, then under alkaline condition, benzoxazine resin is reacted with sulfonating agent to obtain the benzoxazine resin-based macromolecular surfactant of the present application. The benzoxazine resin-based macromolecular surfactant of the present application can prepare a series of oil / water emulsion, and shows high efficient emulsification.

Description

Technical Field

[0001] This invention relates to the field of macromolecular surfactants, and particularly to a benzoxazine resin-based macromolecular surfactant, its preparation method, and its application. Background Technology

[0002] Surfactants are among the most powerful and versatile materials used in the chemical industry. Based on their surface activity and self-assembly behavior, they have found applications in detergents, coatings, personal care products, emulsions, microemulsions, and solid / liquid dispersions. In most of these applications, macromolecular surfactants can be used as alternatives to traditional surfactants. Compared to traditional small-molecule surfactants, macromolecular surfactants exhibit higher surface activity in applications such as emulsion polymerization and anti-corrosion coatings, and can provide long-lasting protection to the interface. Therefore, the preparation of macromolecular surfactants has attracted considerable attention.

[0003] Benzoxazine resins are among the new resins commercialized in recent decades, characterized by their ease of incorporating functional groups and low cost. The monomers of benzoxazine resins can be easily and conveniently synthesized from phenolic derivatives, formaldehyde, and primary amine derivatives in a 1:2:1 molar ratio via the Mannich reaction. Benzoxazine monomers can undergo thermally initiated ring-opening polymerization without any catalysts or initiators. The functional groups in these polymers are highly reactive. For example, phenolic hydroxyl groups can react with acyl chloride groups and isocyanate groups; tertiary amine groups can react with dimethyl sulfate. This provides convenience for the preparation of benzoxazine resin-based macromolecular surfactants. Currently, only Syed Qutubuddin's research group has conducted studies on benzoxazine resin-based macromolecular surfactants. They synthesized carboxyl-containing benzoxazine monomers using aliphatic primary amines of different chain lengths as amine sources and p-hydroxybenzoic acid as a phenol source. Subsequently, these monomers underwent thermal ring-opening polymerization and neutralization reactions to obtain macromolecular surfactants containing sodium carboxylate groups.

[0004] Based on the above analysis, utilizing the simple and convenient polymer formation of monocyclic benzoxazine monomers and the high reactivity of phenolic hydroxyl and tertiary amine groups in the polymers, a novel class of benzoxazine resin-based macromolecular surfactants was synthesized by introducing strongly ionized sulfonic acid groups into the benzoxazine resin backbone. The aim is to achieve hydrophilicity due to the introduction of sulfonic acid groups and hydrophobicity due to the polybenzoxazine molecular backbone, while also reducing costs. Therefore, this invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a benzoxazine resin-based macromolecular surfactant, its preparation method, and its applications. Utilizing benzoxazine chemistry, by introducing hydrophilic sulfonic acid groups and leveraging the hydrophobicity of benzoxazine resin, it transforms the surfactant into a new approach and strategy for developing surfactants applicable to fields such as oil extraction and chemical engineering.

[0006] The technical solution of the present invention is as follows:

[0007] A benzoxazine resin-based macromolecular surfactant having the structure shown in formula (I):

[0008]

[0009] In formula (I):

[0010] R1 is a substituent for an amine, introduced by a monoamine compound used in the synthesis of benzoxazine monomers;

[0011] R2 is a phenolic substituent, introduced by a monophenolic compound used in the synthesis of benzoxazine monomers;

[0012] R3 is a substituent of the sulfonating agent, introduced by the sulfonating agent used during sulfonation;

[0013] Q is a positively charged group in an alkaline substance;

[0014] n = 1 to 100.

[0015] According to the present invention, preferably, the monoamine compound is selected from methylamine, ethylamine, propylamine, n-butylamine, isobutylamine, tert-butylamine, pentamine, isopentamine, neopentamine, n-hexylamine, cyclohexylamine, 4-hexylaniline, heptamine, octylamine, nonylamine, aniline, o-toluidine, p-toluidine, m-toluidine, 4-ethylaniline, 4-propylaniline, or 3-methylaniline.

[0016] According to the present invention, preferably, the monophenolic compound is selected from p-cresol, p-bromophenol, 4-fluorophenol, 4-iodophenol, 4-pentylphenol, 4-hexylphenol, 4-ethylphenol, 4-bromophenol, 4-butylphenol, 4-propylphenol, 4-heptylphenol, 4-n-octylphenol, 4-nonylphenol, 4-(methylthio)phenol or 4-methoxymethylphenol.

[0017] According to the present invention, preferably, the sulfonating agent is selected from 1,4-butanesulfonate lactone, tetrafluoroethanesulfonate lactone, 1,8-naphthalenesulfonate lactone, 1,3-propanesulfonate lactone or 1-propene-1,3-sulfonate lactone.

[0018] According to the present invention, preferably, the alkaline substance is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, trimethylethylammonium hydroxide, or tetrabutylammonium hydroxide.

[0019] According to the present invention, preferably, in formula (I):

[0020] R1 is a substituent on methylamine, ethylamine, propylamine, n-butylamine, pentamine, n-hexylamine, or p-toluidine;

[0021] R2 is a substituent on p-cresol, 4-ethylphenol, 4-methoxymethylphenol, 4-nonylphenol, or 4-heptylphenol;

[0022] R3 is 1,4-butyryl lactone, tetrafluoroethanesulfonate lactone, 1,3-propanesulfonate lactone, and 1-propene-1,3-sulfonate lactone.

[0023] Q is a positively charged group on sodium hydroxide, potassium hydroxide, lithium hydroxide, or tetrabutylammonium hydroxide;

[0024] n = 1 to 20.

[0025] According to the present invention, the preparation method of the above-mentioned benzoxazine resin-based macromolecular surfactant includes the following steps:

[0026] Benzoxazine monomers are obtained by reacting monophenols, monoamines and aldehydes with Mannich. The monomers are then subjected to thermal ring-opening polymerization to obtain benzoxazine resins. Subsequently, the benzoxazine resins are reacted with sulfonating agents under alkaline conditions to obtain the benzoxazine resin-based macromolecular surfactants.

[0027] According to the present invention, preferably, the monophenol is p-cresol, 4-ethylphenol, 4-methoxymethylphenol, 4-nonylphenol, or 4-heptylphenol.

[0028] According to the present invention, preferably, the monoamine is methylamine, ethylamine, propylamine, n-butylamine, pentamine, n-hexylamine or p-toluidine.

[0029] According to the present invention, preferably, the aldehyde is an aqueous formaldehyde solution or paraformaldehyde.

[0030] According to the present invention, preferably, the reagent that provides alkaline conditions is sodium hydroxide, potassium hydroxide, lithium hydroxide or tetrabutylammonium hydroxide.

[0031] According to the present invention, preferably, the sulfonating agent is 1,4-butanesulfonate lactone, tetrafluoroethanesulfonate lactone, 1,3-propanesulfonate lactone, or 1-propene-1,3-sulfonate lactone.

[0032] According to the present invention, the preferred mass ratio of monophenol, monoamine, aldehyde, alkali and sulfonating agent is (40-90):(30-80):(10-50):(1-30):(1-40).

[0033] According to the present invention, preferably, the Mannich reaction temperature is 40–120°C and the reaction time is 3–48 hours.

[0034] According to the present invention, preferably, the temperature for thermal ring-opening polymerization is 100-200°C, and the reaction time is 1-24 hours.

[0035] According to the present invention, preferably, the reaction temperature of benzoxazine resin with sulfonating agent is 40-120°C, and the reaction time is 1-18 hours.

[0036] According to a preferred embodiment of the method for preparing the above-mentioned benzoxazine resin-based macromolecular surfactant, the method includes the following steps:

[0037] (1) Preparation of benzoxazine monomer

[0038] 40–90 parts by weight of monophenol, 30–80 parts by weight of monoamine, 10–50 parts by weight of formaldehyde and 50–80 parts by weight of solvent were added sequentially to a reaction vessel, stirred until homogeneous, and reacted at 40–120°C for 3–48 hours. Heating was stopped, the solvent was removed, and the mixture was washed sequentially with methanol, ethanol and n-hexane. Then, it was vacuum dried at 40–80°C for 10–24 hours to obtain benzoxazine monomer.

[0039] (2) Preparation of benzoxazine resin

[0040] The benzoxazine monomer is dissolved in a solvent and polymerized at 100–200°C for 1–24 hours to obtain the benzoxazine resin.

[0041] (3) Preparation of benzoxazine resin-based macromolecular surfactants

[0042] 40–90 parts by weight of benzoxazine resin, 1–30 parts by weight of alkali and 1–40 parts by weight of sulfonating agent are added sequentially to a reaction vessel, stirred evenly, and reacted at 40–120°C for 1–18 hours. Heating is stopped, the solvent is removed, and the mixture is washed sequentially with methanol, ethanol and n-hexane. Then, it is vacuum dried at 40–80°C for 10–24 hours to obtain benzoxazine resin-based macromolecular surfactant.

[0043] According to the present invention, preferably, the solvents mentioned in steps (1), (2) and (3) are any one of toluene, water, methanol, ethanol, tetrahydrofuran, acetone, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, dioxane, chloroform, and toluene.

[0044] According to the present invention, the above-mentioned benzoxazine resin-based macromolecule, namely the compound with the structure shown in formula (I), is also provided as a surfactant;

[0045] Preferably, the above-mentioned benzoxazine resin-based macromolecules are used as surfactants in emulsion polymerization, anti-corrosion coatings, oil extraction, chemical industry, pharmaceutical industry and other fields.

[0046] According to the present invention, a surfactant emulsion is also provided, comprising the following components in parts by weight:

[0047] 0.1-10 parts of the above-mentioned benzoxazine resin-based macromolecules;

[0048] 10-80 parts of styrene;

[0049] 10-70 parts water.

[0050] The principle of this invention:

[0051] Compared to traditional small-molecule surfactants, macromolecular surfactants exhibit higher surface activity in applications such as emulsion polymerization and anti-corrosion coatings, and can provide long-lasting protection for the interface. Therefore, the preparation of macromolecular surfactants has attracted considerable attention. Based on the advantages of benzoxazine resins, such as ease of functional group introduction and low cost, this invention utilizes the simple and convenient polymer formation of monocyclic benzoxazine monomers and the high reactivity of phenolic hydroxyl and tertiary amine groups in the polymer to introduce sulfonic acid groups into the benzoxazine resin backbone, synthesizing a novel class of benzoxazine resin-based macromolecular surfactants. The desired outcome is hydrophilicity due to the introduction of sulfonic acid groups and hydrophobicity due to the polybenzoxazine molecular backbone, while maintaining low cost.

[0052] The synthetic route of the benzoxazine resin-based macromolecular surfactant of the present invention is as follows:

[0053]

[0054] The beneficial effects of this invention are:

[0055] This invention uses aldehydes such as monophenols, monoamines, and formaldehyde, along with alkalis and sulfonating reagents, as raw materials to successfully synthesize benzoxazine resin-based macromolecular surfactants via Mannich reaction, thermal stress reaction, and sulfonation reaction. These surfactants are then used as emulsifiers to prepare emulsions. This invention has the following significant advantages:

[0056] 1. A benzoxazine resin-based macromolecular surfactant containing sulfonic acid groups was synthesized for the first time.

[0057] 2. It has high surface activity and has broad application prospects in fields such as oil extraction and medicine.

[0058] 3. Studies on the gas-liquid surface tension of benzoxazine resin-based macromolecular surfactants show that its critical micelle concentration is 1.5 g / L. It can be used as a surfactant to prepare a series of oil / water emulsions. It exhibits highly efficient emulsifying properties; an addition of only 0.25 parts can stabilize a high internal phase emulsion containing 80 parts of styrene. Attached Figure Description

[0059] Figure 1 FT-IR spectrum of benzoxazine resin-based macromolecular surfactant in Example 1.

[0060] Figure 2 Surface tension curve of benzoxazine resin-based macromolecular surfactant in Experiment Example 1.

[0061] Figure 3 Photograph of the emulsion formed by the benzoxazine resin-based macromolecular surfactant in Experiment Example 2. The emulsion contained 50 parts of styrene. The amounts of the benzoxazine resin-based macromolecular surfactant added, from left to right, were 0.25 parts, 0.5 parts, 0.75 parts, and 1 part, respectively.

[0062] Figure 4 Photograph of the emulsion formed by the benzoxazine resin-based macromolecular surfactant in Experiment Example 3. The amount of benzoxazine resin-based macromolecular surfactant added was 0.25 parts. The amounts of styrene added, from left to right, were 50 parts, 60 parts, 70 parts, and 80 parts, respectively. Detailed Implementation

[0063] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0064] Example 1: Synthesis of benzoxazine resin-based macromolecular surfactant.

[0065] 0.5 g of p-cresol, 0.4 g of methylamine, and 0.2 g of formaldehyde were dissolved in 30 mL of dimethyl sulfoxide, and the mixture was heated to 90 °C and reacted for 5 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then dried under vacuum at 70 °C overnight to obtain the benzoxazine monomer, with a yield of 83%.

[0066] The benzoxazine monomer obtained in the previous step was heated at 160°C for 24 hours to obtain benzoxazine resin.

[0067] 0.5 g of benzoxazine resin, 0.1 g of sodium hydroxide, and 0.2 g of 1,3-propanesulfonate lactone were added to 20 ml of dimethyl sulfoxide, and the mixture was heated to 80 °C and reacted for 24 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then vacuum dried overnight at 70 °C to obtain a benzoxazine resin-based macromolecular surfactant with a yield of 80%.

[0068] FT-IR (KBr, cm -1 ): 3350, 1645, 1182, 1050. For example... Figure 1 As shown.

[0069] Example 2

[0070] 0.7 g of 4-nonylphenol, 0.4 g of butylamine, and 0.2 g of formaldehyde were dissolved in 30 mL of dimethyl sulfoxide, and the mixture was heated to 80 °C and reacted for 6 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The product was then dried under vacuum overnight at 70 °C to obtain the benzoxazine monomer, with a yield of 78%.

[0071] The benzoxazine monomer obtained in the previous step was heated at 180°C for 12 hours to obtain benzoxazine resin.

[0072] 0.5 g of benzoxazine resin, 0.1 g of potassium hydroxide, and 0.15 g of 1,3-propanesulfonate lactone were added to 20 ml of dimethyl sulfoxide, and the mixture was heated to 90 °C and reacted for 12 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then vacuum dried overnight at 70 °C to obtain a benzoxazine resin-based macromolecular surfactant with a yield of 83%.

[0073] Example 3

[0074] 0.5 g of 4-ethylphenol, 0.45 g of hexylamine, and 0.2 g of formaldehyde were dissolved in 30 ml of dioxane, and the mixture was heated to 100 °C and reacted for 5 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then dried under vacuum at 70 °C overnight to obtain the benzoxazine monomer, with a yield of 78%.

[0075] The benzoxazine monomer obtained in the previous step was heated at 140°C for 24 hours to obtain benzoxazine resin.

[0076] 0.5 g of benzoxazine resin, 0.1 g of tetrabutylammonium hydroxide, and 0.25 g of 1,3-propanesulfonate lactone were added to 20 ml of dioxane, and the mixture was heated to 110 °C and reacted for 12 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then vacuum dried overnight at 70 °C to obtain a benzoxazine resin-based macromolecular surfactant with a yield of 80%.

[0077] Example 4

[0078] 0.5 g of 4-butylphenol, 0.40 g of ethylamine, and 0.2 g of formaldehyde were dissolved in 20 ml of dioxane, and the mixture was heated to 100 °C and reacted for 5 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then dried under vacuum at 70 °C overnight to obtain the benzoxazine monomer, with a yield of 65%.

[0079] The benzoxazine monomer obtained in the previous step was heated at 170°C for 24 hours to obtain benzoxazine resin.

[0080] 0.5 g of benzoxazine resin, 0.2 g of sodium hydroxide, and 0.3 g of 1,3-propanesulfonate lactone were added to 20 ml of toluene, and the mixture was heated to 110 °C and reacted for 12 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then vacuum dried overnight at 70 °C to obtain a benzoxazine resin-based macromolecular surfactant with a yield of 80%.

[0081] Example 5: Preparation of Emulsion

[0082] 0.25 parts, 0.5 parts, 0.75 parts, and 1 part of the benzoxazine resin-based macromolecular surfactant prepared in Example 1 were respectively added to a container. 50 parts of water were added to dissolve the surfactant, followed by 50 parts of styrene. Finally, the mixture was stirred for 1 minute at 8000 rpm using a high-speed homogenizer to obtain an emulsion. A photograph of the resulting emulsion is shown below. Figure 3 As shown. The amounts of benzoxazine resin-based macromolecular surfactant added, from left to right, are 0.25 parts, 0.5 parts, 0.75 parts, and 1 part, respectively. (From...) Figure 3 It is known that benzoxazine resin-based macromolecular surfactants have good surface activity, and adding a small amount can stabilize styrene emulsions.

[0083] Example 6

[0084] Take 0.25 parts of the benzoxazine resin-based macromolecular surfactant prepared in Example 1, and add 20 parts, 30 parts, 40 parts, and 50 parts of water respectively to a container and dissolve completely. Then add 80 parts, 70 parts, 60 parts, and 50 parts of styrene in sequence. Finally, stir the mixture in a high-speed homogenizer at 8000 rpm for 1 minute to obtain an emulsion. A photograph of the formed emulsion is shown below. Figure 4 As shown. The amounts of styrene added, from left to right, are 50 parts, 60 parts, 70 parts, and 80 parts, respectively. (From...) Figure 4 It is known that benzoxazine resin-based macromolecular surfactants exhibit highly efficient emulsifying properties; adding a small amount can stabilize high internal phase emulsions containing 80 parts of styrene.

[0085] Comparative Example 1

[0086] 0.5 g of p-cresol, 0.4 g of methylamine, and 0.2 g of formaldehyde were dissolved in 30 mL of dimethyl sulfoxide, and the mixture was heated to 90 °C and reacted for 5 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then dried under vacuum at 70 °C overnight to obtain the benzoxazine monomer, with a yield of 83%.

[0087] The benzoxazine monomer obtained in the previous step was heated at 160°C for 24 hours to obtain benzoxazine resin.

[0088] 0.5 g of benzoxazine resin and 0.2 g of 1,3-propanesulfonate lactone were added to 20 mL of dimethyl sulfoxide, and the mixture was heated to 80 °C and reacted for 24 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane, and then dried under vacuum at 70 °C overnight. A benzoxazine resin-based macromolecular surfactant could not be obtained. This indicates that alkaline conditions are important for the synthesis of macromolecular surfactants.

[0089] Comparative Example 2

[0090] 0.5 g of p-cresol, 0.4 g of methylamine, and 0.2 g of formaldehyde were dissolved in 30 mL of dimethyl sulfoxide, and the mixture was heated to 90 °C and reacted for 5 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane. The mixture was then dried under vacuum at 70 °C overnight to obtain the benzoxazine monomer, with a yield of 83%.

[0091] The benzoxazine monomer obtained in the previous step was heated at 160°C for 24 hours to obtain benzoxazine resin.

[0092] 0.5 g of benzoxazine resin, 0.1 g of sodium hydroxide, and 0.2 g of 1,3-propanesulfonate lactone were added to 20 mL of dimethyl sulfoxide and reacted at room temperature for 24 h. Post-treatment: The solvent was removed under reduced pressure, and the mixture was washed successively with methanol, ethanol, and n-hexane, and then dried under vacuum at 70 °C overnight. A benzoxazine resin-based macromolecular surfactant could not be obtained. This indicates that the sulfonation reaction temperature is crucial for the synthesis of macromolecular surfactants.

[0093] Comparative Example 3

[0094] 1.0 g of dodecylamine, 0.7 g of p-hydroxybenzoic acid, 0.4 g of paraformaldehyde, and 20 ml of dioxane were placed in a flask and reacted at 90 °C for 24 hours with magnetic stirring. Post-treatment: The reaction mixture was poured into a large amount of water to precipitate the precipitate. The precipitate was then filtered and dried to obtain a carboxyl-containing benzoxazine monomer in 70% yield.

[0095] The benzoxazine monomer obtained in the previous step was heated at 160°C for 60 minutes to obtain a benzoxazine resin containing carboxylic acid groups. Subsequently, the carboxylic acid groups in the benzoxazine resin were neutralized with sodium hydroxide to obtain a macromolecular surfactant containing sodium carboxylic acid groups.

[0096] Experimental Example 1

[0097] The surface tension curves of the benzoxazine resin-based macromolecular surfactant prepared in Example 1 were tested, as shown below. Figure 2 As shown. By Figure 2 It can be seen that the surface tension of the aqueous solution decreases sharply with increasing surfactant concentration. At a surfactant concentration of 1.5 g / L, the surface tension is 27.8 mN / m. When the surfactant concentration exceeds 1.5 g / L, the surface tension remains essentially constant. Therefore, the critical micelle concentration of the benzoxazine resin-based macromolecular surfactant is 1.5 g / L.

[0098] Experimental Example 2

[0099] The solubility of the macromolecular surfactants obtained in Example 1 and Comparative Example 3 in aqueous solutions at different pH values ​​was tested.

[0100] The results showed that the macromolecular surfactants containing sulfonic acid groups obtained in Example 1 could all produce clear and transparent solutions after dissolving in water with pH values ​​of 1-14, indicating that their solubility was not limited by the external pH and had a wide range of applications. In contrast, the macromolecular surfactants containing carboxyl groups obtained in Comparative Example 3 could only form transparent solutions in aqueous solutions with pH values ​​greater than 7, indicating that their solubility was limited by the external environment and had a narrower range of applications.

[0101] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A benzoxazine resin-based macromolecular surfactant, characterized in that, The surfactant has the structure shown in formula (I): ； In formula (I): R1 is introduced by the monoamine used in the synthesis of benzoxazine monomers, and the monoamine is methylamine, ethylamine, propylamine, n-butylamine, pentamine, n-hexylamine or p-toluidine; R2 is introduced by a monophenol used in the synthesis of benzoxazine monomers, wherein the monophenol is p-cresol, 4-ethylphenol, 4-methoxymethylphenol, 4-nonylphenol, or 4-heptylphenol; R3 is introduced by the sulfonating agent used during sulfonation, which is 1,4-butanolactone, 1,3-propanesulfonolactone, or 1-propene-1,3-sulfonolactone. Q is a positively charged group on sodium hydroxide, potassium hydroxide, lithium hydroxide, or tetrabutylammonium hydroxide; n = 1~20。 2. The preparation method of the benzoxazine resin-based macromolecular surfactant according to claim 1, comprising the following steps: Benzoxazine monomers are obtained by reacting monophenols, monoamines and aldehydes via the Mannich reaction. The monomers are then subjected to thermal ring-opening polymerization to obtain benzoxazine resins. Subsequently, the benzoxazine resins are reacted with sulfonating agents under alkaline conditions to obtain the benzoxazine resin-based macromolecular surfactants. The monophenol is p-cresol, 4-ethylphenol, 4-methoxymethylphenol, 4-nonylphenol, or 4-heptylphenol; the monoamine is methylamine, ethylamine, propylamine, n-butylamine, pentamine, n-hexylamine, or p-toluidine; the aldehyde is formaldehyde aqueous solution or paraformaldehyde; the reagent providing alkaline conditions is sodium hydroxide, potassium hydroxide, lithium hydroxide, or tetrabutylammonium hydroxide; and the sulfonating agent is 1,4-butanolactone, 1,3-propanesulfonolactone, or 1-propene-1,3-sulfonolactone. The mass ratio of monophenols, monoamines, aldehydes, alkalis, and sulfonating reagents is (40~90):(30~80):(10~50):(1~30):(1~40); The reaction temperature for Mannich is 40~120 ℃, and the reaction time is 3~48 hours; the temperature for thermal ring-opening polymerization is 100~200 ℃, and the reaction time is 1~24 hours; the reaction temperature for benzoxazine resin and sulfonating agent is 40~120 ℃, and the reaction time is 1~18 hours.

3. The application of the benzoxazine resin-based macromolecular surfactant according to claim 1 in emulsion polymerization, anti-corrosion coatings, oil extraction, and chemical industry.

4. A surfactant emulsion comprising the benzoxazine resin-based macromolecular surfactant of claim 1, comprising the following components in parts by weight: 0.1-10 parts of benzoxazine resin-based macromolecular surfactant; 10-80 parts of styrene; 10-70 parts water.

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