A method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier

Abstract

The invention discloses a preparation method of a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier, wherein tannic acid solution and epichlorohydrin are added to dimethylamine for reaction to obtain a tannic acid system; or gallic acid and epichlorohydrin are added to dimethylamine for reaction to obtain a gallic acid system; a bromine-containing end-capping agent is added to the tannic acid system or a bromine-containing end-capping agent is added to the gallic acid system, and the reaction is carried out at 55-70°C for 3-4h to obtain a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier. The present invention obtains an oligomeric quaternary ammonium salt demulsifier modified by natural polyphenols by adding a bromine-containing end-capping agent to the tannic acid system or a bromine-containing end-capping agent to the gallic acid system, because the demulsifier has a high reactivity due to the presence of hydroxyl and aromatic functional groups in tannic acid and gallic acid, the effect between π-π stacking and asphaltene promotes demulsification, and the surface of the oil-water emulsion carries a negative charge, which can neutralize the interfacial charge and reduce the repulsive force between the emulsions.

Description

Technical Field

[0001] The invention belongs to the field of synthetic materials for oilfield chemicals and relates to a method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier. Background Art

[0002] As natural polyphenols, tannic acid, anthocyanin, gallic acid and cardanol are widely found in many plants, such as oak, tea, unripe fruits and Chinese walnuts. The presence of polyphenol structure increases the number of contact points and the occupied interface area, and promotes the interaction between demulsifier and asphaltene. This structure ensures that the demulsifier molecules extend multiple times to water droplets and multiple benzene rings, improving the affinity with asphaltene in the oil-water film.

[0003] The synthesis route of oligomeric quaternary ammonium salts is simple and the conditions are mild. Compared with traditional polyether and polyamine demulsifiers that need to be synthesized under high temperature and high pressure conditions, the synthesis of oligomeric quaternary ammonium salts only requires a low temperature of 60°C and can initiate polymerization reactions under normal pressure. It has a moderate molecular weight and good stability, avoiding the shortcomings of high-temperature operations.

[0004] In oil production, complex crude oil emulsions such as W / O, O / W or multiple emulsions are produced, causing pipeline scaling and corrosion, reducing production efficiency, and even causing production disasters. Driven by environmental issues, bioeconomic growth, and the demand for green chemicals and energy security, research on complex emulsion demulsification is still not enough. Summary of the invention

[0005] In order to solve the demulsification problem of aged oil by using an efficient and green demulsifier, the present invention aims to provide a method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier comprises the following steps:

[0008] 1) adding tannic acid solution and epichlorohydrin to dimethylamine for reaction to obtain a tannic acid system; or

[0009] Gallic acid and epichlorohydrin are added to dimethylamine for reaction to obtain a gallic acid system;

[0010] 2) Adding the bromine-containing end-capping agent to the tannic acid system or adding the bromine-containing end-capping agent to the gallic acid system, and then reacting at 55-70° C. for 3-4 hours, and rotary evaporating to obtain a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier.

[0011] Further, tannic acid solution and epichlorohydrin are simultaneously added dropwise into dimethylamine; gallic acid and epichlorohydrin are simultaneously added dropwise into dimethylamine.

[0012] Furthermore, the molar ratio of epichlorohydrin, dimethylamine and tannic acid is 1:(1-1.2):(0.04-0.08).

[0013] Furthermore, the molar ratio of epichlorohydrin, dimethylamine and gallic acid is 1:(1-1.2):(0.04-0.08).

[0014] Further, tannic acid solution and epichlorohydrin are added to dimethylamine, and the reaction temperature is 55-70° C. and the reaction time is 6-8 hours.

[0015] Further, gallic acid and epichlorohydrin are added to dimethylamine, and the reaction temperature is 55-70° C. and the reaction time is 6-8 hours.

[0016] Furthermore, the amount of the bromine-containing end-capping agent is 4-5 times the amount of the dimethylamine substance.

[0017] Furthermore, the bromine-containing end-capping agent is hexyl bromide, ethyl bromide, octane bromide, dodecane bromide or benzyl bromide.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention constructs an oligomeric quaternary ammonium salt demulsifier modified by natural polyphenols by adding a bromine-containing end-capping agent to a tannic acid system or adding a bromine-containing end-capping agent to a gallic acid system. Since the demulsifier has a high reactivity due to the presence of hydroxyl groups and aromatic functional groups in tannic acid and gallic acid, the π-π stacking and the action between asphaltene promote demulsification. In addition, the oligomeric quaternary ammonium salt carries a positive charge, and the surface of the oil-water emulsion carries a negative charge, which can neutralize the interfacial charge and reduce the repulsive force between the emulsions. The cationic oligomeric quaternary ammonium salt modified by tannic acid and gallic acid relies on the positive charge neutralization mechanism to realize the destabilization flocculation of oil droplets during the demulsification and dehydration process, and the oil droplets coalesce to form large oil droplets, and the oil-water two phases are separated. At the same time, the coalescence demulsification between the oil droplets lags behind the flocculation of the oil droplets, and the hindering effect of polymers in sewage can be effectively overcome. The present invention has simple synthesis steps and mild conditions, and has potential application prospects in terms of practicality, greenness, high efficiency and difficulty in synthesizing demulsifiers, and is expected to be applied to large-scale production in oil fields.

[0020] Furthermore, the present invention adopts different bromoalkanes, i.e., hexyl bromide, ethyl bromide, octane bromide or dodecane bromide for end-capping, because the oily long chain makes the molecule more amphiphilic and wettable at the oil-water interface, and the alkyl chains of different lengths have different hydrophobic effects, which conforms to the size effect, and in the demulsification process, the polyphenol is used to break the π-π stacking of asphaltene at the oil-water interface, and when the quaternary ammonium salt ions neutralize the negative charge in the crude oil, the alkyl chain of the bromoalkanes and the benzene ring of benzyl bromide can better promote the polyphenol to break the rigid film of asphaltene, soften the film, and better aggregate the water droplets, thereby achieving a better effect of oil-water separation.

[0021] Furthermore, in the present invention, the reaction temperature of adding tannic acid solution and epichlorohydrin to dimethylamine should not exceed 70°C, which affects the molecular viscosity. Too high molecular viscosity affects the demulsification efficiency. The temperature is less than 55°C, the degree of polymerization is too low and affects the shedding of the Cl atom of epichlorohydrin. The reaction time should not exceed 8 hours. After adding the bromine-containing capping agent, the reaction time should not exceed 4 hours. If the time is too long, the viscosity and cross-linking degree are too high, which affects the molecular weight and demulsification efficiency. If the time is too short, the reaction is incomplete, which may lead to reaction failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the synthesis mechanism, technical scheme and application effect of the present invention clearer, the present invention provides the following drawings:

[0023] Figure 1 The synthesis mechanism of the tannic acid-modified oligomeric quaternary ammonium salt DMD of the present invention;

[0024] Figure 2 The synthesis mechanism of the gallic acid-modified oligomeric quaternary ammonium salt MMD of the present invention;

[0025] Figure 3 The NMR spectrum of the DMD4 demulsifier prepared by the present invention;

[0026] Figure 4 The NMR comparison spectra of DMD4 and its intermediate demulsifier prepared by the present invention;

[0027] Figure 5 This is the FT-IR comparison chart of MMD4 and raw material gallic acid;

[0028] Figure 6 The demulsification effect diagram of the demulsifier prepared by the present invention; wherein, (a) is the demulsification effect of MD1, MD2, MD3, MD4, MD5 and MD6, (b) is the oil-water emulsion before adding the demulsifier, the oil-water separation emulsion with the oligomeric quaternary ammonium salt demulsifier DMD4 modified by tannic acid, and the oil-water separation emulsion with the oligomeric quaternary ammonium salt demulsifier MMD4 modified by gallic acid. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0030] The method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier of the present invention comprises the following steps:

[0031] 1) Pour dimethylamine into a three-necked flask, dissolve tannic acid in distilled water to obtain a tannic acid solution, pour the tannic acid solution and epichlorohydrin into two constant pressure dropping funnels respectively, and simultaneously add the tannic acid solution and epichlorohydrin dropwise into the three-necked flask, react at 55-70° C. for 6-8 hours, and obtain a tannic acid system;

[0032] The molar ratio of epichlorohydrin, dimethylamine and tannic acid of polyphenols is 1:(1-1.2):(0.04-0.08).

[0033] Or 1) pour dimethylamine into a three-necked flask, dissolve gallic acid in distilled water to obtain a gallic acid solution, pour the gallic acid solution and epichlorohydrin into two constant pressure dropping funnels respectively, and simultaneously add the gallic acid solution and epichlorohydrin dropwise into the three-necked flask, react at 55-70° C. for 6-8 hours, and obtain a gallic acid system.

[0034] The molar ratio of epichlorohydrin, dimethylamine and gallic acid is 1:(1-1.2):(0.04-0.08).

[0035] The molecular weight of tannic acid is 1701.20, and the molecular weight of gallic acid is 188.14.

[0036] 2) Add the end-capping agent to the tannic acid system or the gallic acid system, continue to react for 3-4 hours under the conditions of heating in a water bath at 55-70° C. and stirring, and then perform rotary evaporation at 0.09 MPa and 75° C. to obtain a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier. The amount of the end-capping agent is 4-5 times the amount of the dimethylamine substance; the end-capping agent is hexyl bromide, ethyl bromide, octyl bromide, dodecane bromide or benzyl bromide.

[0037] When the end-capping agent is added to the tannic acid system, the natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier DMD1 is prepared when the end-capping agent is ethyl bromide, and the structural formula is:

[0038]

[0039] When the end-capping agent is added to the tannic acid system, the natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier DMD2 is prepared when the end-capping agent is benzyl bromide, and the structural formula is

[0040]

[0041] When the capping agent is added to the tannic acid system, the natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier DMD3 is prepared when the capping agent is octane bromide, and the structural formula is

[0042]

[0043] When the end-capping agent is added to the tannic acid system, the natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier DMD4 is prepared when the end-capping agent is bromhexane, and the structural formula is

[0044]

[0045] The end-capping agent is added to the tannic acid system. When the end-capping agent is dodecane bromide, the prepared natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier is DMD5, and the structural formula is

[0046]

[0047] The end-capping agent is added to the gallic acid system. When the end-capping agent is ethyl bromide, the prepared natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier is MMD1, and the structural formula is

[0048]

[0049] When the end-capping agent is added to the gallic acid system, the natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier MMD2 is prepared when the end-capping agent is benzyl bromide, and the structural formula is

[0050]

[0051] When the capping agent is added to the gallic acid system, the natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier MMD3 is prepared when the capping agent is octane bromide, and the structural formula is

[0052]

[0053] The capping agent is added to the gallic acid system. The natural polyphenol modified oligomeric quaternary ammonium salt demulsifier prepared by the capping agent is bromohexane, which is MMD4, and has the structural formula

[0054]

[0055] The capping agent is added to the gallic acid system. When the capping agent is dodecane bromide, the prepared natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier is MMD5, and the structural formula is

[0056]

[0057] The reaction mechanism of the present invention is:

[0058] 1) Preparation route and mechanism of tannic acid modified oligomeric quaternary ammonium salt DMD Figure 1As shown, the reaction is a nucleophilic addition reaction. The lone pair of electrons of the N atom of dimethylamine attacks the CO bond of epichlorohydrin, causing the CO ring to open, resulting in the chlorine end of intermediate 1 attacking the hydroxyl group of tannic acid. Finally, the bromine atom of bromohexane falls off, and the generated negative carbon ion attacks the active hydrogen connected to the N atom of intermediate 2 to generate tannic acid-modified oligomeric quaternary ammonium salt DMD.

[0059] 2) The preparation mechanism of gallic acid modified oligomeric quaternary ammonium salt MMD is as follows Figure 2 As shown, the reaction is a nucleophilic addition reaction. The lone pair of electrons of the N atom of dimethylamine attacks the CO bond of epichlorohydrin, causing the CO ring to open, resulting in the chlorine end of intermediate 1 attacking the hydroxyl group of gallic acid. Finally, the bromine atom of bromohexane falls off, and the generated negative carbon ion attacks the active hydrogen connected to the N atom of intermediate 2 to generate gallic acid-modified oligomeric quaternary ammonium salt MMD.

[0060] Example 1

[0061] The first step, one-pot method: 6.3 mL (0.05 mol) of dimethylamine aqueous solution, 3.9 mL (0.05 mol) of epichlorohydrin, and 0.6805 g of tannic acid were dissolved in 5 mL of deionized water, and reacted at 60 ° C with stirring for 8 h to obtain an uncapped intermediate.

[0062] In the second step, the intermediate was capped, 28.1 mL of bromohexane was added to the uncapped intermediate, and the mixture was stirred in a water bath at 60°C and gently refluxed for 3 h. The reaction product was rotary evaporated at 80°C and 0.09 MPa for 3 h to obtain DMD4 as a light reddish brown paste solid.

[0063] Example 2

[0064] The same as Example 1, except that the end-capping agent is 0.2 mol ethyl bromide, and DMD1 (brown-yellow transparent viscous liquid) is obtained.

[0065] Example 3

[0066] The same as Example 1, except that the end-capping agent is 0.2 mol of benzyl bromide, and DMD2 (red transparent viscous liquid) is obtained.

[0067] Example 4

[0068] The same as Example 1, except that the end-capping agent is 0.2 mol of bromooctane, and DMD3 (reddish brown viscous paste solid) is obtained.

[0069] Example 5

[0070] The same as Example 1, except that the end-capping agent is 0.2 mol of dodecane bromide, to obtain DMD5 (yellow-brown viscous paste solid).

[0071] Example 6

[0072] The first step, one-pot method: 6.3 mL (0.05 mol) of dimethylamine aqueous solution, 3.9 mL (0.05 mol) of epichlorohydrin, and 0.075 g of gallic acid were dissolved in 1 mL of deionized water, and reacted at 60 ° C with stirring for 8 h to obtain an uncapped intermediate.

[0073] In the second step, 28.1 mL of bromohexane was added to the uncapped intermediate, and the mixture was stirred in a water bath at 60°C and gently refluxed for 3 h. The reaction product was rotary evaporated at 75°C and 0.09 MPa for 3 h to obtain MMD4 as a green-brown viscous liquid.

[0074] Example 7

[0075] The same as Example 6, except that the end-capping agent is 0.2 mol ethyl bromide, and MMD1 (green-brown transparent viscous liquid) is obtained.

[0076] Example 8

[0077] The same as Example 6, except that the end-capping agent is 0.2 mol of benzyl bromide, and MMD2 (yellow-green transparent viscous liquid) is obtained.

[0078] Example 9

[0079] The same as Example 6, except that the end-capping agent is 0.2 mol of bromooctane, and MMD3 (green-brown viscous liquid) is obtained.

[0080] Example 10

[0081] The same as Example 6, except that the end-capping agent is 0.2 mol of dodecane bromide, to obtain DMD5 (chloro brown viscous paste solid).

[0082] Embodiment 11

[0083] In the first step, 0.06 mol of dimethylamine aqueous solution, 0.05 mol of epichlorohydrin, and 0.002 mol of tannic acid were dissolved in 5 mL of deionized water, and reacted at 55° C. with stirring for 8 h to obtain an uncapped intermediate.

[0084] In the second step, the intermediate is capped, and hexyl bromide is added to the uncapped intermediate, and the mixture is stirred in a water bath at 55°C and gently refluxed for 4 hours. The reaction product is rotary evaporated at 80°C and 0.09 MPa for 3 hours to obtain DMD4 as a light reddish brown paste solid. The amount of hexyl bromide used is 4 times the amount of dimethylamine.

[0085] Example 12

[0086] In the first step, 0.055 mol of dimethylamine aqueous solution, 0.05 mol of epichlorohydrin, and 0.004 mol of tannic acid were dissolved in 5 mL of deionized water, and reacted at 70° C. with stirring for 6 hours to obtain an uncapped intermediate.

[0087] In the second step, the intermediate is capped, and hexyl bromide is added to the uncapped intermediate, and the mixture is stirred in a water bath at 70°C and gently refluxed for 3 hours. The reaction product is rotary evaporated at 80°C and 0.09 MPa for 3 hours to obtain DMD4 as a light reddish brown paste solid. The amount of hexyl bromide used is 5 times the amount of dimethylamine substance.

[0088] Embodiment 13

[0089] In the first step, 0.05 mol of dimethylamine aqueous solution, 0.05 mol of epichlorohydrin, and 0.002 mol of gallic acid were dissolved in 1 mL of deionized water and reacted at 70° C. with stirring for 6 h to obtain an uncapped intermediate.

[0090] In the second step, 28.1 mL of bromohexane was added to the uncapped intermediate, and the mixture was stirred in a water bath at 55°C and gently refluxed for 4 h. The reaction product was rotary evaporated at 75°C and 0.09 MPa for 3 h to obtain MMD4 as a green-brown viscous liquid.

[0091] Embodiment 14

[0092] In the first step, 0.06 mol of dimethylamine aqueous solution, 0.05 mol of epichlorohydrin, and 0.004 mol of gallic acid were dissolved in 1 mL of deionized water and reacted at 55° C. with stirring for 8 h to obtain an uncapped intermediate.

[0093] In the second step, 28.1 mL of bromohexane was added to the uncapped intermediate, and the mixture was stirred in a water bath at 70°C and gently refluxed for 3 h. The reaction product was rotary evaporated at 75°C and 0.09 MPa for 3 h to obtain MMD4 as a green-brown viscous liquid.

[0094] Test Example 1 Material Structure Characterization

[0095] Testing conditions:

[0096] 1) Using a Nicolet infrared spectrometer and a thin film method, MMD4 is directly applied on a salt sheet and measured using a total reflection system or a reflection system with an alkali halide lens. Raw gallic acid is tested using the potassium bromide tablet method.

[0097] 2) DMD4 was dissolved in deuterated DMSO and precipitated on a Bruker 400M 1 H NMR ( 1 H NMR) detection.

[0098] from Figure 5 It can be seen that at 1134cm -1 It is an obvious stretching vibration peak of quaternary ammonium salt, which is the stretching vibration peak of alkyl CH bond. Compared with the raw material gallic acid, at 1134cm -1 and 1470cm -1 It is the characteristic peak of quaternary ammonium salt, 2866cm -1 and 2913cm -1 ,3200cm -1 -3400cm -1 It is -OH, and it is preliminarily judged that the synthesis of the gallic acid-modified oligomeric quaternary ammonium salt MMD is successful.

[0099] Table 1 FT-IR identification of MMD

[0100]

[0101] Figure 3 is the NMR spectrum of DMD4, 1 H NMR (400MHz, DMSO) δ6.84,4.98,4.66,4.50,4.17,3.60,,3.45,1.72,1.26,0.85.

[0102] Table 2 1HNMR assignment of tannic acid modified oligomeric quaternary ammonium salt DMD

[0103]

[0104] from Figure 4 It can be seen that the uncapped intermediate is compared with the modified oligomeric quaternary ammonium salt DMD capped with bromohexane, and the molecular formulas match, which further determines that the modification is successful.

[0105] Demulsification and dehydration rate effects of test examples 6 to 10:

[0106] Test conditions: 2000ppm demulsifier was added to the aged oil emulsion with a water content of 66.8% at 55℃ water bath, and the dehydration rate within 1h was tested. MD oligomeric quaternary ammonium salt without tannic acid and gallic acid was demulsified with DMD4 and MMD4 under the same conditions, and the demulsification effect is shown in Table 3.

[0107] Table 3 Demulsification effect of polyphenol-modified MD series oligomeric quaternary ammonium salt demulsifiers in aged oil emulsions

[0108]

[0109] The structural formula of MD1 in Table 3 is:

[0110]

[0111] The structural formula of MD2 is:

[0112]

[0113] The structural formula of MD3 is:

[0114]

[0115] The MD4 structure is:

[0116]

[0117] The MD5 structure is:

[0118]

[0119] The MD6 structure is:

[0120]

[0121] As can be seen from Table 3, the prepared polyphenol-modified oligomeric quaternary ammonium salt demulsifier has a good effect in the application of aged oil demulsification. Under the conditions of 70°C and 2000ppm, the dehydration rate of DMD4 in 1h reaches 95.67%, and the dehydration rate of MMD4 in 1h reaches 98.02% under the conditions of 70°C and 2000ppm. The demulsification effect of the two demulsifiers is obvious compared with the MD series demulsifier.

[0122] from Figure 6 It can be seen that Figure 6 In (a), from left to right, the demulsification effects of MD1, MD2, MD3, MD4, MD5 and MD6 are shown. Figure 6 In (b), from left to right, the first is the oil-water emulsion before adding demulsifier, the second is the oil-water separation emulsion with the addition of tannic acid-modified oligomeric quaternary ammonium salt demulsifier DMD4, and the third is the oil-water separation emulsion with the addition of gallic acid-modified oligomeric quaternary ammonium salt demulsifier MMD4. It can be seen that under the conditions of 70°C, 1h, and 2000ppm, the prepared polyphenol-modified oligomeric quaternary ammonium salt demulsifier has a good effect in the application of aged oil demulsification, a high dehydration rate, a neat interface, and clear water quality, and has better performance than the MD series demulsifiers.

[0123] Finally, it is noted that although the invention has been described in detail through the above preferred examples, various changes can be made in details and forms without departing from the scope defined in the claims of the present invention.

Claims

1. A method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier, characterized in that: The following steps are involved: 1) adding tannic acid solution and epichlorohydrin to dimethylamine to react, thereby obtaining a tannic acid system; or Gallic acid and epichlorohydrin are added to dimethylamine for reaction to obtain a gallic acid system; 2) adding a bromine-containing end-capping agent to a tannic acid system or adding a bromine-containing end-capping agent to a gallic acid system, and then reacting at 55-70° C. for 3-4 hours, and rotary evaporating to obtain a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier; The amount of bromine-containing capping agent used is 4-5 times the amount of dimethylamine substance; The bromine-containing blocking agent is hexyl bromide, ethyl bromide, octane bromide, dodecane bromide or benzyl bromide.

2. The method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier according to claim 1, characterized in that: Tannic acid solution and epichlorohydrin are added dropwise to dimethylamine at the same time; gallic acid and epichlorohydrin are added dropwise to dimethylamine at the same time.

3. The method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier according to claim 1, characterized in that: The molar ratio of epichlorohydrin, dimethylamine and tannic acid is 1:(1-1.2):(0.04-0.08).

4. The method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier according to claim 1, characterized in that: The molar ratio of epichlorohydrin, dimethylamine and gallic acid is 1:(1-1.2):(0.04-0.08).

5. The method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier according to claim 1, characterized in that: Add tannic acid solution and epichlorohydrin to dimethylamine, the reaction temperature is 55-70°C, and the reaction time is 6-8 hours.

6. The method for preparing a natural polyphenol-modified oligomeric quaternary ammonium salt demulsifier according to claim 1, characterized in that: Gallic acid and epichlorohydrin are added to dimethylamine, and the reaction temperature is 55-70°C and the reaction time is 6-8 hours.

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