Preparation method of alpha-(unsaturated ammonium group) alkyl phosphonic acid inner salt

Abstract

The invention provides a preparation method of alpha-(unsaturated ammonium group) alkyl phosphonic acid inner salt, which is unsaturated ammonium group phosphonic acid type betaine, can be used as a functional monomer for grafting modification of free radicals on the surface of high polymer materials such as polyolefin and the like, and also can be used as a functional monomer for grafting modification of free radicals on the surface of high polymer materials such as polyolefin and the like. The amphoteric ionic polymer can be prepared by mixing or mixing acrylic ester, acrylonitrile or other olefin monomers for copolymerization, and can also be used for ring-opening grafting modification of starch, cellulose, polyurethane, polyamide and other high polymer materials containing amino groups or hydroxyl groups in the structure. Meanwhile, the obtained high polymer material is endowed with the functional effects of zwitter-ionization, hydrophilicity, antibacterial property, antifouling property and the like of the organic phosphonic acid betaine; and the chemical stability in an acid-base water environment is high.

Description

Technical Field

[0001] The present invention relates to a method for preparing a zwitterionic monomer, and particularly to a method for preparing an α-(unsaturated ammonium) alkylphosphonic acid inner salt containing a glycidyl group in its molecular structure. The α-(unsaturated ammonium) alkylphosphonic acid inner salt is an organic phosphonic acid type betaine and is mainly used for functional modification of the surface of polymer materials such as cellulose, polyurethane, polyamide, etc. containing OH or NH on the main chain or side chain, and belongs to the field of functional polymer materials. Technical Background

[0002] Aromatic polyamide composite membranes are commercially available in a variety of varieties and offer excellent performance. They are widely used in industries such as seawater desalination, brackish water desalination, industrial wastewater treatment, and purified water production. However, in desalination applications, achieving synergistic improvements in marine biofouling resistance, effectively preventing chemical damage to the aromatic polyamide active layer by trace amounts of chlorine or chlorine oxides in seawater, and maintaining a high hydrophilicity on the membrane surface have long been key research topics in the field of aromatic polyamide composite membrane technology.

[0003] Phosphorus-containing functional polymers not only chelate metal ions, enabling the enrichment, extraction, and solidification separation of low-concentration noble and heavy metal ions or rare earth elements, but also possess flame retardancy and bioactivity, making them suitable for flame-retardant polymers, antimicrobial polymers, and biopolymers. Currently, unsaturated phosphoric acid or phosphonic acid and their derivatives are primarily vinyl or allyl phosphoric acid and their derivatives, or vinyl or allyl phosphonic acid and their derivatives, as phosphine-containing functional monomers. These phosphorus-containing monomers have limited functionality and a limited variety. Phosphate esters, phosphonate esters, or quaternary phosphonium salts derived from acrylates or acrylamides as polymerizable monomers are also currently being researched. However, their relatively low chemical stability and high cost limit their practical application.

[0004] Ionic polymers made through copolymerization or graft polymerization of quaternary ammonium cationic monomers or zwitterionic monomers have been found to possess unique physical, chemical, and biological properties such as hydrophilicity, salt responsiveness, temperature responsiveness, anion exchange, antibacterial and antifouling, and biocompatibility. They have shown extremely broad application prospects in the fields of rare earth enrichment, extraction and separation, hydration and anti-pollution, ion-conducting electrolytes, biomedicine, water treatment, etc.

[0005] Based on a comprehensive analysis and evaluation of existing research and application results on antifouling, chlorine-resistant and hydrophilic modification of phosphorus-containing functional monomers, quaternary ammonium cationic monomers, and aromatic polyamide composite membranes, the present invention discloses an α-(unsaturated ammonium) hydrocarbon phosphonic acid inner salt having chelating and adsorption capabilities for heavy metal ions, high chemical stability in a weakly alkaline water environment, high biocidal and antibacterial biological activity, and high hydrophilicity. The inner salt is suitable for functional modification of polymer material surfaces, and is particularly suitable for the antibacterial, antifouling, chlorine-resistant, and hydrophilic modification needs of polymer materials containing OH or NH in the main chain or side chain. Summary of the Invention

[0006] The present invention provides a method for preparing an α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt, which is specifically achieved by the following preparation steps:

[0007] Step 1: Preparation of α-(N-alkyl-N-allylamino)alkylphosphonate

[0008] A solvent, N-alkyl-N-allylamine, aldehyde or ketone, and phosphate are weighed in sequence and added to a reactor. The mixture is stirred at room temperature for 2 hours. The temperature of the materials in the reactor is then raised to 50-110° C. and stirred for 4-40 hours to complete the Mannich reaction. The solvent and water, as well as unreacted N-alkyl-N-allylamine and phosphate, are recovered by vacuum distillation. The high-boiling-point substances remaining in the reactor are separated and purified to prepare α-(N-alkyl-N-allylamino)alkylphosphonate. Reaction Scheme 1 expresses the process of preparing α-(N-alkyl-N-allylamino)alkylphosphonate via the Mannich reaction using N-alkyl-N-allylamine, aldehyde, and phosphate as raw materials:

[0009]

[0010] Wherein R1 in reaction formula-1 is selected from C1~C 18 Hydrocarbon group, R2 is selected from C1~C3 alkoxy, or C1~C3 alkyl, R3 is selected from C1~C3 alkyl; R4, R5 are selected from H, or C1~C 12 hydrocarbon group;

[0011] The amount of the N-alkyl-N-allylamine used is 1.0 to 2.0 times the molar amount of the phosphate ester, the amount of the aldehyde / ketone used is 1.0 to 2.0 times the molar amount of the phosphate ester, and the amount of the solvent used is 0.5 to 5.0 times the mass of the phosphate ester.

[0012] The hydrocarbon group in the N-alkyl-N-allylamine refers to R1, which is selected from C1 to C 18 Hydrocarbon group.

[0013] The phosphate ester refers to one of dimethyl phosphite, diethyl phosphite, dipropyl phosphite, ethyl methyl phosphite, methyl methyl hypophosphite, ethyl methyl hypophosphite, methyl propyl hypophosphite, ethyl methyl hypophosphite, ethyl propyl hypophosphite, propyl methyl hypophosphite, propyl ethyl hypophosphite, and propyl propyl hypophosphite.

[0014] In order to effectively reduce the preparation cost of the glycidyl-containing α-(unsaturated ammonium) alkylphosphonic acid inner salt and ensure the total yield of the reaction product, the aldehyde or ketone is preferably a variety of commercially available industrial products. That is, when R4 and R5 in reaction formula-1 are both selected from H, the aldehyde is one of formaldehyde aqueous solution, triformaldehyde, and polyformaldehyde with a mass percentage concentration of 30-68%; or when one of R4 and R5 in reaction formula-1 is selected from H, the other is selected from C1-C 12 When the aldehyde is a hydrocarbon group, the aldehyde is preferably selected from acetaldehyde, acrolein, furfural, phenylacetaldehyde, cinnamaldehyde, or substituted or unsubstituted benzaldehyde; or when R4 and R5 in reaction formula-1 are both C1~C 12 The hydrocarbon group, the ketone is preferably selected from one of acetone, butanone, cyclohexanone, or substituted or unsubstituted acetophenone.

[0015] The solvent is selected from one or more of water, acetic acid, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, and 1,4-dioxane.

[0016] Step 2: Preparation of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester

[0017] An organic solvent and the α-(N-alkyl-N-allylamino)alkylphosphonate prepared in step 1 are weighed into a reactor, the temperature of the materials in the reactor is controlled to 20-60° C., trimethylsilyl bromide is slowly added, and the mixture is stirred for 12-48 hours to complete the substitution reaction, and then the unreacted trimethylsilyl bromide and organic solvent are recovered by distillation; the organic solvent and epichlorohydrin are further added to the reactor, the temperature of the materials in the reactor is increased to 20-90° C., and the mixture is stirred for 12-48 hours to complete the quaternization reaction, and the organic solvent and unreacted epichlorohydrin are recovered by vacuum rotary evaporation. The residue in the reactor is separated and purified to obtain α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester. Reaction Formula 2 expresses the substitution reaction between the α-(N-alkyl-N-allylamino)alkylphosphonate and trimethylsilyl bromide, and the quaternization reaction between the α-(N-alkyl-N-allylamino)alkylphosphonate and epichlorohydrin:

[0018]

[0019] Wherein R1 in reaction formula-2 is selected from C1~C18 Hydrocarbon group, R2 is selected from C1-C3 alkoxy, trimethylsilyl, or C1-C3 alkyl, R3 is selected from C1-C3 alkyl, R4 and R5 are selected from H, or C1-C 12 Hydrocarbon group.

[0020] The amount of trimethylsilyl bromide used is 1 to 5 times the mass of α-(N-alkyl-N-allylamino)alkylphosphonate, the amount of epichlorohydrin used is 1 to 5 times the mass of α-(N-alkyl-N-allylamino)alkylphosphonate, and the amount of the organic solvent used is 1 to 5 times the mass of α-(N-alkyl-N-allylamino)alkylphosphonate.

[0021] The organic solvent refers to one or more of dichloromethane, chloroform, 1,2-dichloroethane, tetrahydrofuran, 1,4-dioxane, acetone, acetonitrile, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

[0022] Step 3: Preparation of α-(unsaturated ammonium)alkylphosphonic acid inner salt

[0023] At room temperature, an alcohol solvent, α-(N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester prepared in step 2, a basic ion exchange resin and deionized water are added to a reactor. The temperature of the materials in the reactor is controlled to 20-90° C. and stirred for 2-8 hours to complete the hydrolysis reaction. After separating and removing the ion exchange resin, the mother liquor is concentrated by vacuum rotary evaporation. Then, an alcohol solvent is added to the reactor to recrystallize the residual material in the reactor. The crystals are collected and dried to obtain the glycidyl-containing α-(unsaturated ammonium)alkylphosphonic acid inner salt. The α-(unsaturated ammonium)alkylphosphonic acid inner salt has a chemical structure represented by the general formula (I):

[0024]

[0025] Wherein R1 in the general formula (I) is selected from C1 to C 18 Hydrocarbon group, R2 is selected from hydroxyl, or C1~C3 alkyl; R4, R5 are selected from H, or C1~C 12 Hydrocarbon group.

[0026] Reaction formula 3 expresses the process of preparing the α-(unsaturated ammonium) alkylphosphonic acid inner salt by hydrolysis of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium) alkylphosphonic acid (trimethylsilyl) ester:

[0027]

[0028] Wherein R1 in reaction formula-3 is selected from C1~C 18Hydrocarbon group, R2 is selected from trimethylsilyloxy, hydroxyl, or C1~C3 alkyl, R4 and R5 are selected from H, or C1~C 12 Hydrocarbon group.

[0029] The alkaline ion exchange resin refers to the D301 series macroporous tertiary amine styrene anion exchange resin.

[0030] The alcohol solvent refers to one or more of methanol, ethanol, propanol and butanol.

[0031] The amount of the alkaline ion exchange resin used is 0.2 to 2.0 times the mass of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester, the amount of deionized water used is 0.1 to 1.5 times the mass of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester, and the amount of the alcohol solvent used is 0.5 to 5 times the mass of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester.

[0032] The present invention provides an α-(unsaturated ammonium) hydrocarbylphosphonic acid inner salt having the following beneficial effects:

[0033] ① The methods for preparing the α-(unsaturated ammonium)alkylphosphonic acid inner salts of the present invention all utilize classic organic chemical reactions, resulting in simple preparation methods, high product yields in each step, safe and efficient process, and simple product separation and purification technology. The required raw materials are all industrial products, are readily available, and have low preparation costs.

[0034] ② The polymer material modified with the α-(unsaturated ammonium) hydrocarbon phosphonic acid inner salt of the present invention has functions and characteristics with high chemical stability in acidic or alkaline water environment.

[0035] ③ The α-(unsaturated ammonium) hydrocarbon phosphonic acid inner salt of the present invention is an α-(unsaturated ammonium) hydrocarbon phosphonic acid betaine, which can be used as a zwitterionic olefin monomer to carry out zwitterionic grafting modification on the surface of polymer materials; it can also be mixed into the copolymerization of acrylate, acrylonitrile or other olefin monomers to prepare zwitterionic polymers; it can also utilize the ring-opening reaction of its glycidyl group to carry out grafting modification on polymer materials such as starch, cellulose, polyurethane, polyamide, etc. containing hydroxyl or amino groups in the structure, and at the same time, the ammonium phosphonate type betaine is endowed with zwitterionic, hydrophilic, antibacterial, antifouling and other functions of the modified polymer material.

[0036] ④ The α-(unsaturated ammonium) hydrocarbon phosphonic acid inner salt of the present invention has a scientific structural design, comprehensive functions, optimized technology and superior performance. DETAILED DESCRIPTION

[0037] The preparation method of the α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt of the present invention is further illustrated by the following examples, the purpose of which is to provide a better understanding of the present invention.

[0038] Example 1 Preparation of α-(unsaturated ammonium)methylphosphonic acid inner salt-(1)

[0039] Step 1, preparation of diethyl α-(N,N-diallylamino)methylphosphonate

[0040] 30 g of deionized water, 30 g of diallylamine, 30 g of a 38% formaldehyde solution, and 40 g of diethyl phosphite were weighed into a reactor and stirred for 2 hours. The temperature of the materials in the reactor was raised to 50-55° C., and the reaction was stirred for 6 hours. Water and unreacted diallylamine were evaporated under reduced pressure. Analysis of the residue revealed a weight of 76.3 g, a diethyl α-(N,N-diallylamino)methylphosphonate content of 90.3%, and a calculated yield of diethyl α-(N,N-diallylamino)methylphosphonate of 96.3%.

[0041] Step 2: Preparation of bis(trimethylsilyl) α-(N-glycidyl-N,N-diallylammonium)methylphosphonate

[0042] 85 g of dichloromethane was added to the reactor to completely dissolve 50 g of α-(N,N-diallylamino)methylphosphonic acid diethyl ester, 130.5 g of trimethylsilyl bromide was slowly added to the reactor at room temperature, and the reaction was stirred for 12 hours. The temperature of the material in the reactor was increased to 45-50° C., and the reaction was stirred for another 12 hours. The dichloromethane and unreacted trimethylsilyl bromide were then evaporated off, and 108 g of epichlorohydrin and 25 g of dichloromethane were added to the reactor to dissolve the residue. The temperature of the material in the reactor was maintained at 50-55° C. and the reaction was stirred for 48 hours to complete the quaternization reaction. The dichloromethane and excess epichlorohydrin were then removed by rotary evaporation. 135 g of tert-butanol was added to the reactor, and the residue in the reactor was recrystallized and dried to constant weight to obtain α-(chloro-N-glycidyl-N,N-diallylammonium)methylphosphonic acid di(trimethylsilyl) ester.

[0043] Step 3: Preparation of α-(N-glycidyl-N,N-diallylammonium)methylphosphonic acid inner salt

[0044] At room temperature, 120 g of ethanol, 40 g of α-(N-glycidyl-N,N-diallylammonium)methylphosphonic acid di(trimethylsilyl) ester obtained in step 2, and 55 g of D301 weakly basic ion exchange resin were added to a reactor, 12 g of deionized water was gradually added, and the mixture was stirred and hydrolyzed for 4 hours. After removing the ion exchange resin, the mother liquor was cooled to -20 to -10°C and allowed to stand for 4 hours, and then filtered to obtain a solid product. The solid product was soaked and washed with tert-butyl alcohol, and then placed in a vacuum drying oven and dried to constant weight to obtain 20.3 g of product, namely α-(N-glycidyl-N,N-diallylammonium)methylphosphonic acid-(1). The product yield was 87.8% based on diethyl phosphite, and the melting point was 121.5°C (thermal decomposition). The elemental analysis of the product was: C 48.03%, H 7.17%, N 5.66%, which was consistent with the molecular formula C 10 H 18 The calculated values ​​of NO4P are C 48.58%, H 7.34%, and N 5.67%, which are consistent with the results of the previous analysis. The infrared spectrum data of the product (KBr pellet): 3351 cm -1 is the characteristic absorption peak of OH, 3027cm -1 Characteristic absorption peaks of C=CH, 2934, 2872 cm -1 The characteristic absorption peaks of methyl group are 1642 and 1438 cm -1 It is the characteristic absorption peak of C=C, 1357cm -1 The characteristic absorption peak of CN is 1254 cm -1 Characteristic absorption peaks of P=O double bond, 1126, 1043, 996 cm -1 The characteristic absorption peaks of COC and PO are at 1 H-NMR (D2O, δ): 2.36 (d, 2H), 3.16 (m, 1H), 3.24~3.93 (m, 8H), 4.90~5.05 (m, 2H), 5.73~5.86ppm

[0045] (m, 4H). Based on this, it is confirmed that the α-(N-glycidyl-N,N-diallylammonium)methylphosphonic acid-(1) product has the structural characteristics of the α-(N-glycidyl-N,N-diallylammonium)methylphosphonic acid inner salt of formula (1):

[0046]

[0047] Example 2 Preparation of α-(unsaturated ammonium)methylphosphonic acid betaine-(2)

[0048] According to the preparation method and steps of Example 1, the diallylamine was replaced with N-benzyl-N-allylamine to obtain α-(unsaturated ammonium)methylphosphonic acid inner salt-(2). Structural analysis and characterization showed that the product yield was 72.3% based on diethyl phosphite, and the melting point was 125.5°C (thermal decomposition). The elemental analysis of the product was: C 56.01%, H 6.33%, N 4.66%, which was consistent with the molecular formula C 14 H 20 The calculated values ​​of NO4P are C 56.56%, H 6.78%, and N 4.71%, which are consistent with the above-mentioned α-(unsaturated ammonium)methylphosphonic acid inner salt-(2). Infrared spectrum data (KBr pellet): 3347 cm -1 is the characteristic absorption peak of OH, 3032cm -1 Characteristic absorption peaks of C=CH, 2932 and 2872 cm -1 Characteristic absorption peaks of methylene, 1647 and 1437 cm -1 It is the characteristic absorption peak of C=C, 1358cm -1 It is the characteristic absorption peak of CN, 1259cm -1 Characteristic absorption peaks of P=O double bond, 1123, 1038, 989 cm -1 The characteristic absorption peaks of COC and PO are at 1 H-NMR (CD3OD, δ): 2.38 (d, 2H), 3.16 (m, 1H), 3.42-3.94 (m, 8H), 4.97 (m, 1H), 5.65 (m, 2H), 7.05 (m, 5H), 7.95 (s, 1H), which confirmed that the α-(unsaturated ammonium)methylphosphonic acid inner salt-(2) has the structural characteristics of α-(N-glycidyl-N-benzyl-N-allylammonium)methylphosphonic acid inner salt, see formula (2):

[0049]

[0050] Example 3 Preparation of α-(unsaturated ammonium)methylphosphonic acid-(3)

[0051] According to the preparation method and steps of Example 1, the diallylamine was replaced with N-benzyl-N-allylamine, and the diethyl phosphite was replaced with methyl ethyl phosphinate to obtain α-(unsaturated ammonium) methylphosphonic acid inner salt-(3). Structural analysis and characterization showed that the product yield was 75.1% based on methyl ethyl phosphinate, and the melting point was 118.5°C (thermal decomposition). The elemental analysis of the product was: C 59.86%, H 7.48%, N 4.72%, which was consistent with the molecular formula C 15 H 22The calculated values ​​of NO3P are C 61.01%, H 7.51%, and N 4.74%, which are consistent with the above-mentioned α-(unsaturated ammonium)alkylphosphonic acid inner salt-(3). Infrared spectrum data (KBr pellet): 3454 cm -1 is the characteristic absorption peak of OH, 3034 cm -1 Characteristic absorption peaks of C=CH, 2938, 2872 cm -1 Characteristic absorption peaks of methyl and methylene, 1648 and 1438 cm -1 is the characteristic absorption peak of C=C, 1366cm -1 is the characteristic absorption peak of CN, 1256cm -1 Characteristic absorption peaks of P=O double bond, 1132, 1044, 994 cm -1 The characteristic absorption peaks of COC and PO are at 1 H-NMR (CD3OD, δ): 1.03 (s, 3H), 2.36 (d, 2H), 3.14 (m, 1H), 3.46-3.97 (m, 8H), 4.96 (m, 1H), 5.66 (m, 2H), 7.06 (m, 5H). This confirms that the α-(unsaturated ammonium)alkylphosphonic acid inner salt (3) has the structural characteristics of an α-(N-glycidyl-N-benzyl-N-allylammonium)methylmethylphosphinic acid inner salt, see formula (3):

[0052]

[0053] Example 4 Preparation of α-(unsaturated ammonium)ethylphosphonic acid-(4)

[0054] According to the preparation method and steps of Example 1, the diallylamine is replaced with N-benzyl-N-allylamine, the formaldehyde solution is replaced with freshly distilled acetaldehyde, and the diethyl phosphite is replaced with methyl ethyl phosphinate to obtain α-(unsaturated ammonium)ethyl methylphosphinate inner salt-(4). Structural analysis and characterization show that the product yield is 75.1% based on methyl ethyl phosphinate, and the melting point is 103.5°C (thermal decomposition). The elemental analysis of the product is: C 62.06%, H 7.81%, N 4.52%, which is consistent with the molecular formula C 16 H 24 The calculated values ​​of NO3P are C 62.12%, H 7.82%, and N 4.53%, which are consistent with the above-mentioned α-(unsaturated ammonium)ethylmethylphosphinic acid inner salt-(4). Infrared spectrum data (KBr pellet): 3454 cm -1 is the characteristic absorption peak of OH, 3034 cm -1 Characteristic absorption peaks of C=CH, 2939, 2873 cm -1 Characteristic absorption peaks of methyl and methylene, 1648 and 1438 cm-1 is the characteristic absorption peak of C=C, 1366cm -1 is the characteristic absorption peak of CN, 1256cm -1 Characteristic absorption peaks of P=O double bond, 1132, 1044, 994 cm -1 The characteristic absorption peaks of COC and PO are at 1 H-NMR (CD3OD, δ): 1.02 (d, 3H), 1.08 (s, 3H), 2.77 (m, 1H), 3.14 (m, 1H), 3.46-3.97 (m, 8H), 4.96 (m, 1H), 5.66 (m, 2H), 7.06 (m, 5H). Based on this, it was confirmed that the α-(unsaturated ammonium)ethylmethylphosphonic acid inner salt (4) has the structural characteristics of α-(N-glycidyl-N-benzyl-N-allylammonium)ethylmethylphosphinic acid inner salt, see formula (4):

[0055]

[0056] Example 5 Characteristics of α-(unsaturated ammonium)alkylphosphonic acid inner salts

[0057] At a constant temperature of 25±0.5°C, the α-(unsaturated ammonium)alkylphosphonic acid inner salts of Examples 1-4 were gradually added to 10 g of deionized water and stirred for 2 hours to dissolve until saturation was achieved. The solubility of the α-(unsaturated ammonium)alkylphosphonic acid inner salts of Examples 1-4 in water was observed. The results are shown in Table 1.

[0058] Table 1 Characteristics of α-(unsaturated ammonium)methylphosphonic acid betaine

[0059]

Claims

1. A method for preparing an α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt, characterized in that: The following preparation steps are used: Step 1, preparation of α-(N-alkyl-N-allylamino)alkylphosphonate A solvent, N-alkyl-N-allylamine, aldehyde or ketone, and phosphate are weighed in sequence and added to a reaction kettle. After stirring at room temperature for 2 hours, the temperature of the materials in the reaction kettle is increased to 50-110° C., and the materials are stirred for 4-40 hours to complete the Mannich reaction. The solvent and water, as well as unreacted N-alkyl-N-allylamine and phosphate are recovered by negative pressure distillation. The high-boiling point substances remaining in the reaction kettle are separated and purified to obtain α-(N-alkyl-N-allylamino)alkylphosphonate. Reaction formula 1 expresses the process of preparing α-(N-alkyl-N-allylamino)alkylphosphonates via the Mannich reaction using N-alkyl-N-allylamine, aldehyde or ketone, and phosphate as raw materials: Wherein R1 in reaction formula-1 is selected from C1~C 18 Hydrocarbon group, R2 is selected from C1~C3 alkoxy, or C1~C3 alkyl, R3 is selected from C1~C3 alkyl, R4, R5 are selected from H, or C1~C 12 hydrocarbon group; The hydrocarbon group in the N-alkyl-N-allylamine refers to R1, which is selected from C1 to C 18 hydrocarbon group; The phosphate ester refers to one of dimethyl phosphite, diethyl phosphite, dipropyl phosphite, ethyl methyl phosphite, methyl methyl phosphite, ethyl methyl phosphite, methyl propyl phosphite, ethyl methyl phosphite, ethyl ethyl phosphite, ethyl propyl phosphite, propyl methyl phosphite, propyl ethyl phosphite, and propyl propyl phosphite; The aldehyde or ketone refers to: when R4 and R5 in reaction formula 1 are both H, the aldehyde is selected from a formaldehyde aqueous solution, trioxymethylene, or polyformaldehyde with a mass percentage concentration of 30-68%; or when one of R4 and R5 in reaction formula 1 is H, the other is selected from C1-C 18 When the aldehyde is a hydrocarbon group, the aldehyde is preferably selected from acetaldehyde, acrolein, furfural, phenylacetaldehyde, cinnamaldehyde, or substituted or unsubstituted benzaldehyde; or when R4 and R5 in reaction formula-1 are both C1~C 12 A hydrocarbon group, wherein the ketone is preferably selected from one of acetone, butanone, cyclohexanone, or substituted or unsubstituted acetophenone; The amount of the N-alkyl-N-allylamine is 1.0 to 2.0 times the molar amount of the phosphate, the amount of the aldehyde or ketone is 1.0 to 2.0 times the molar amount of the phosphate, and the amount of the solvent is 0.5 to 5.0 times the mass of the phosphate; Step 2: Preparation of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester An organic solvent and the α-(N-alkyl-N-allylamino)alkylphosphonate prepared in step 1 are weighed into a reactor, the temperature of the materials in the reactor is controlled to 20-60° C., trimethylsilyl bromide is slowly added, and the mixture is stirred for 12-48 hours to complete the substitution reaction, and then the unreacted trimethylsilyl bromide and organic solvent are recovered by distillation; an organic solvent and epichlorohydrin are further added to the reactor, the temperature of the materials in the reactor is increased to 20-90° C., and the mixture is stirred for 12-48 hours to complete the quaternization reaction, the organic solvent and unreacted epichlorohydrin are recovered by vacuum rotary evaporation, and the residue in the reactor is separated and purified to obtain α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester; Reaction formula 2 expresses the substitution reaction between α-(N-alkyl-N-allylamino)alkylphosphonate and trimethylsilyl bromide, and the quaternization reaction between α-(N-alkyl-N-allylamino)alkylphosphonate and epichlorohydrin: Wherein R1 in reaction formula-2 is selected from C1~C 18 Hydrocarbon group, R2 is selected from C1-C3 alkoxy, trimethylsilyl, or C1-C3 alkyl, R3 is selected from C1-C3 alkyl, R4 and R5 are selected from H, or C1-C 12 hydrocarbon group; The organic solvent refers to one or more of dichloromethane, chloroform, 1,2-dichloroethane, tetrahydrofuran, 1,4-dioxane, acetone, acetonitrile, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide; The amount of trimethylsilyl bromide used is 1 to 5 times the mass of 2-(N-alkyl-N-allylamino)alkylphosphonate, the amount of epichlorohydrin used is 1 to 5 times the mass of 2-(N-alkyl-N-allylamino)alkylphosphonate, and the amount of the organic solvent used is 1 to 5 times the mass of 2-(N-alkyl-N-allylamino)methylphosphonate; Step 3: Preparation of α-(unsaturated ammonium)alkylphosphonic acid inner salt At room temperature, an alcohol solvent, α-(N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester prepared in step 2, a basic ion exchange resin and deionized water are added to a reactor. The temperature of the materials in the reactor is controlled to 20-90° C. and stirred for 2-8 hours to complete the hydrolysis reaction. The mother liquor after separation and removal of the ion exchange resin is concentrated by vacuum rotary evaporation. After no water flows out, an alcohol solvent is added to the reactor to recrystallize the residual material in the reactor. The crystals are collected and dried to obtain the α-(unsaturated ammonium)alkylphosphonic acid inner salt having the chemical structure shown in the general formula (I): Wherein R1 in the general formula (I) is selected from C1 to C 18 Hydrocarbon group, R2 is selected from hydroxyl, or C1~C3 alkyl, R4, R5 are selected from H, or C1~C 12 hydrocarbon group; Reaction formula 3 expresses the hydrolysis reaction process of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester: Wherein R1 in reaction formula-3 is selected from C1~C 18 Hydrocarbon group, R2 is selected from trimethylsilyloxy, hydroxyl, or C1~C3 alkyl, R4 and R5 are selected from H, or C1~C 12 hydrocarbon group; The amount of the alkaline ion exchange resin used is 0.2 to 2.0 times the mass of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester, the amount of deionized water used is 0.1 to 1.5 times the mass of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester, and the amount of the alcohol solvent used is 0.5 to 5 times the mass of α-(chlorinated N-glycidyl-N-alkyl-N-allylammonium)alkylphosphonic acid (trimethylsilyl) ester.

2. The method for preparing an α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt according to claim 1, characterized in that The solvent is selected from one or more of water, acetic acid, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, tetrahydrofuran, and 1,4-dioxane.

3. The method for preparing an α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt according to claim 1, characterized in that The organic solvent refers to one or more of dichloromethane, chloroform, 1,2-dichloroethane, tetrahydrofuran, 1,4-dioxane, acetone, acetonitrile, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

4. The method for preparing an α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt according to claim 1, characterized in that The alkaline ion exchange resin refers to the D301 series macroporous tertiary amine styrene anion exchange resin.

5. The method for preparing an α-(unsaturated ammonium)hydrocarbylphosphonic acid inner salt according to claim 1, characterized in that The alcohol solvent refers to one or more of methanol, ethanol, propanol and butanol.

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