A dopamine derivative-modified hydrophobically associating polymer and its preparation method

Abstract

The present invention relates to a dopamine derivative modified hydrophobically associating polymer and a preparation method thereof. The preparation method includes steps such as the preparation of dopamine derivative monomers, the preparation of a monomer mixed aqueous solution, the synthesis of a polymer sol, and the preparation of polymer powder. The dopamine derivative modified hydrophobically associating polymer synthesized in the present invention has a larger hydrodynamic size and a higher molecular weight. The apparent viscosity of its solution is greatly improved, and the polymer has excellent temperature and salt resistance properties. The hydrophobically associating polymer has good water solubility and can be quickly dissolved in water. It also has excellent corrosion inhibition performance and can delay the corrosion problem of internal pipelines during the actual oilfield exploitation process.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional polymers. More specifically, the present invention relates to a dopamine derivative-modified hydrophobically associating polymer, and also relates to a preparation method of the dopamine derivative-modified hydrophobically associating polymer.

Background Art

[0002] With the recovery of the international economy and the continuous development of the scientific and technological level, the demand for oil by major factories is increasing day by day. During the oilfield exploitation process, the recovery rates of primary oil recovery and secondary oil recovery are very low (<40%), and there is still a large amount of crude oil mixed in the formation that cannot be completely exploited, resulting in a waste of resources. Therefore, the tertiary oil recovery of oilfields occupies an important economic and strategic position.

[0003] Currently, the most commonly used enhanced oil recovery method is polymer flooding, which can increase the viscosity of the displacement fluid, reduce the mobility ratio of the oil-water two-phase, and enhance the oil recovery ability; however, the currently most commonly used partially hydrolyzed polyacrylamide (HPAM) and its derivatives have major defects such as poor temperature and salt tolerance. Especially in a high-salt environment, the polymer molecular chain will quickly bend and curl, causing a significant reduction in the apparent viscosity of the produced fluid and losing the oil-carrying ability. Therefore, traditional HPAM cannot meet the current high-temperature and high-salt reservoir recovery environment, and its hydrophobic modification must be carried out to enhance its key properties such as temperature and salt tolerance.

[0004] Hydrophobically associating polyacrylamide (HAPAM) generally refers to a water-soluble polymer formed by introducing a small amount of hydrophobic groups (<2 mol%) into a hydrophilic polymer macromolecular chain. When the solution concentration exceeds the critical association concentration (CAC), the hydrophobic groups tend to associate intermolecularly, and reversible dynamic physical crosslinking networks are easily formed between the macromolecular chains and have ductility. The hydrodynamic size increases, and the apparent viscosity of the solution increases significantly.

[0005] Therefore, aiming at the technical defects existing in the prior art, on the basis of summarizing the prior art, through a large number of experimental studies and analysis and summary, the inventor of the present invention finally completed the present invention.

Summary of the Invention

[0006] [Technical Problems to be Solved]

[0007] The object of the present invention is to provide a dopamine derivative-modified hydrophobically associating polymer.

[0008] Another object of the present invention is to provide a preparation method of the dopamine derivative-modified hydrophobically associating polymer.

[0009] [Technical Solutions]

[0010] The present invention is achieved by the following technical solutions.

[0011] The present invention relates to a dopamine derivative-modified hydrophobically associating polymer.

[0012] The hydrophobically associating polymer has the following chemical structural formula (I):

[0013]

[0014] In the formula:

[0015] R1 represents H, CH2OH or (CH2)2OH;

[0016] R2 represents H, CH3, CH2CH3, CH2COOH or O(CH2)2COOH;

[0017] R3 represents CH3, CH2CH3, (CH2) 11 CH3, (CH2) 15 CH3 or (CH2) 17 CH3;

[0018] R4 represents H, CH2(CH3)2N + (CH2) 11 CH3, CH2(CH3)2N + (CH2) 15 CH3 or CH2(CH3)2N + (CH2) 17 CH3;

[0019] m = 49.8 - 95.0 mol%, n = 2 - 25 mol%, p = 3 - 20 mol%, q = 0 - 5 mol%, x = 0 - 0.2 mol%.

[0020] According to a preferred embodiment of the present invention, in formula (I), m = 60 - 78 mol%, n = 16 - 22 mol%, p = 6 - 18 mol%, q = 0.2 - 2.0 mol%, x = 0.02 - 0.12 mol%.

[0021] The present invention also relates to a preparation method of the hydrophobically associating polymer.

[0022] The preparation steps of the preparation method are as follows:

[0023] A. Preparation of dopamine derivative monomer

[0024] Mix dopamine hydrochloride and N-hydroxymethylacrylamide evenly at a molar ratio of 1:3 - 6. Then, add absolute ethanol according to a weight ratio of dopamine derivative to absolute ethanol of 1:4 - 10, stir and dissolve at room temperature. Next, slowly dropwise add a catalyst under nitrogen protection according to a weight ratio of dopamine derivative to catalyst of 1:0.5 - 2.0, mix evenly, heat to a temperature of 30 - 65 °C, and react at this temperature for 48 - 120 h. Then, cool the temperature to room temperature, filter by suction, and repeatedly wash the separated solid matter with absolute ethanol until the pH of the filtrate > 6.8. Let the washed solid matter recrystallize in absolute ethanol at room temperature, filter and separate. The collected crystal is the dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide, which has the following chemical structural formula (II):

[0025]

[0026] B. Preparation of monomer mixed aqueous solution

[0027] In a reaction vessel, mix acrylamide monomer, acrylic acid monomer, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, allyl quaternary ammonium salt cationic monomer and the above dopamine derivative monomer evenly in deionized water at a molar ratio of 60 - 78:6 - 22:6 - 18:0.2 - 2.0:0.02 - 0.12. Adjust the pH of the obtained monomer mixture solution to 6 - 8 using a sodium hydroxide aqueous solution with a concentration of 1.6 - 2.4 M. Thus, a monomer mixed aqueous solution with a total monomer content of 10 - 30% by weight is obtained;

[0028] C. Synthesis of polymer sol

[0029] Introduce nitrogen into the monomer mixed aqueous solution obtained in step B for 25 - 35 min. Meanwhile, add an initiator accounting for 0.05 - 0.5% of the total weight of the monomer mixture, add a magnetic stir bar, and seal the reaction vessel. The reaction vessel reacts in a constant temperature water bath electromagnetic stirrer under the conditions of a magnetic stir bar rotation speed of 100 - 600 r / min and a temperature of 50 - 70 °C for 0.5 - 3.0 h, filter and separate to obtain a light yellow polymer sol;

[0030] D. Preparation of polymer powder

[0031] Cool the polymer sol obtained in step C to room temperature, cut it into pieces, repeatedly wash it with absolute ethanol until no white substance precipitates on the surface. Then, transfer it to a constant temperature vacuum drying oven and dry it at a temperature of 55 - 65 °C for 24 - 48 h, pulverize it, sieve it, and the undersize part collected is the hydrophobic associating polymer powder.

[0032] According to another preferred embodiment of the present invention, in step A, the catalyst is sulfuric acid or aluminum chloride, the concentration of sulfuric acid is 15.0 - 18.4 M; the particle size of aluminum chloride is 4 - 20 mesh.

[0033] According to another preferred embodiment of the present invention, in step B, the acrylamide monomer is one or more acrylamide monomers selected from acrylamide, N - hydroxymethyl acrylamide or N - hydroxyethyl acrylamide.

[0034] According to another preferred embodiment of the present invention, in step B, the acrylic acid monomer is one or more acrylic acid monomers selected from acrylic acid, methacrylic acid, itaconic acid or β - carboxyethyl acrylate.

[0035] According to another preferred embodiment of the present invention, in step B, the allyl quaternary ammonium salt cationic monomer is one or more allyl quaternary ammonium salt cationic monomers selected from trimethylallylammonium chloride, dodecyldimethylallylammonium chloride, hexadecyldimethylallylammonium chloride, octadecyldimethylallylammonium chloride, triethylallylammonium bromide or methacryloyloxyethyltrimethylammonium chloride.

[0036] According to another preferred embodiment of the present invention, in step C, the initiator is one or more initiators selected from sodium persulfate, ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride or 2,2 - azobis(2 - methylpropylimid) dihydrochloride.

[0037] According to another preferred embodiment of the present invention, in step D, the mesh of the sieve used is 40 - 80 mesh.

[0038] The present invention also relates to a dopamine derivative - modified hydrophobically associating polymer prepared by the said preparation method. The apparent viscosity of an aqueous solution with a mass concentration of 5 g / L of the dopamine derivative - modified hydrophobically associating polymer is 570 mPa·s or more, its apparent viscosity in an aqueous sodium chloride solution with a mass concentration of 20 g / L is 590 mPa·s or more, and the viscosity retention rate is 87.62% or more; its apparent viscosity in an aqueous calcium chloride solution with a mass concentration of 10 g / L is 342 mPa·s or more, and the viscosity retention rate is 33.4% or more.

[0039] The present invention will be described in more detail below.

[0040] The present invention relates to a dopamine derivative - modified hydrophobically associating polymer.

[0041] The said hydrophobically associating polymer has the following chemical structural formula (I):

[0042]

[0043] In the formula:

[0044] R1 represents H, CH2OH or (CH2)2OH;

[0045] R2 represents H, CH3, CH2CH3, CH2COOH or O(CH2)2COOH;

[0046] R3 represents CH3, CH2CH3, (CH2) 11 CH3, (CH2) 15 CH3 or (CH2) 17 CH3;

[0047] R4 represents H, CH2(CH3)2N + (CH2) 11 CH3, CH2(CH3)2N + (CH2) 15 CH3 or CH2(CH3)2N + (CH2) 17 CH3;

[0048] m = 49.8 - 95.0 mol%, n = 2 - 25 mol%, p = 3 - 20 mol%, q = 0 - 5 mol%, x = 0 - 0.2 mol%.

[0049] Preferably, in formula (I), m = 60 - 78 mol%, n = 16 - 22 mol%, p = 6 - 18 mol%, q = 0.2 - 2.0 mol%, x = 0.02 - 0.12 mol%.

[0050] The dopamine derivative modified hydrophobically associating polymer of the present invention uses acrylamide monomer and acrylic acid monomer as the polymer main chain, ensuring that the polymer can have excellent water solubility to meet the actual use requirements, and it is also easy to graft other functional water-soluble monomers. For example, a sulfonic acid group insensitive to salt is introduced into the polymer side chain, improving the salt resistance of the hydrophobically associating polymer.

[0051] The dopamine derivative modified hydrophobically associating polymer of the present invention is grafted with an allyl quaternary ammonium salt cationic monomer, which is an amphiphilic hydrophobic monomer with both oil solubility and water solubility. Compared with traditional acrylate hydrophobic monomers, it can directly participate in the free radical polymerization reaction in aqueous solution, thus avoiding the defects of reduced solution viscosity and product purity caused by introducing co-solvents or surfactants. Moreover, the long-chain hydrophobic groups can greatly increase the apparent viscosity of the polymer solution through intermolecular hydrophobic association, so it has excellent temperature and salt resistance. Therefore, this type of monomer is an excellent choice to simplify the synthesis process of hydrophobically associating polymers and improve their performance.

[0052] The dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide in the dopamine derivative modified hydrophobically associating polymer of the present invention is a cross-linking monomer with excellent water solubility and multi-functionality, which can increase the hydrodynamic size and molecular weight of the polymer, form a stable three-dimensional network structure, and greatly improve the apparent viscosity of the polymer solution.

[0053] The present invention also relates to a preparation method of the hydrophobically associating polymer.

[0054] The preparation steps of the preparation method are as follows:

[0055] A. Preparation of dopamine derivative monomer

[0056] Mix dopamine hydrochloride and N-methylolacrylamide evenly according to a molar ratio of 1:3-6, then add absolute ethanol according to a weight ratio of dopamine derivative to absolute ethanol of 1:4-10, stir and dissolve at room temperature, then slowly dropwise add a catalyst according to a weight ratio of dopamine derivative to catalyst of 1:0.5-2.0 under nitrogen protection, mix evenly, heat to a temperature of 30-65 °C, and react at this temperature for 48-120 h. Then cool the temperature to room temperature, filter by suction, and repeatedly wash the separated solid with absolute ethanol until the pH of the filtrate > 6.8. Let the washed solid recrystallize in absolute ethanol at room temperature, filter and separate, and the collected crystals are the dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide (DAAM);

[0057] The basic principle of its preparation is to utilize the Friedel-Crafts reaction, starting from the structure of dopamine hydrochloride and reacting with N-methylolacrylamide to make it have an acrylamide double bond structure, which can react with double bond functional monomers such as acrylamide in subsequent reactions to generate polymer high molecular chains.

[0058] In this step, the molar ratio of dopamine hydrochloride to N-methylolacrylamide is 1:3-6. If the molar ratio of dopamine hydrochloride to N-methylolacrylamide is greater than 1:3, a disubstituted by-product will be generated; if the molar ratio of dopamine hydrochloride to N-methylolacrylamide is less than 1:6, a large amount of N-methylolacrylamide will be wasted. Therefore, the molar ratio of dopamine hydrochloride to N-methylolacrylamide of 1:3-6 is reasonable, and preferably 1:3.5-5.5;

[0059] The weight ratio of dopamine derivative to absolute ethanol is 1:4 to 10. If the weight ratio of dopamine derivative to absolute ethanol is greater than 1:4, all monomers cannot be dissolved or raw material monomers will precipitate during the reaction process; if the weight ratio of dopamine derivative to absolute ethanol is less than 1:10, the reaction rate will be reduced and the yield will be decreased; therefore, the weight ratio of dopamine derivative to absolute ethanol being 1:4 to 10 is advisable, and preferably 1:6 to 8;

[0060] The catalyst used in the present invention is sulfuric acid or aluminum chloride, the concentration of sulfuric acid is 15.0 to 18.4 M; the particle size of aluminum chloride is 4 to 20 mesh. The weight ratio of dopamine derivative to catalyst is 1:0.5 to 2.0. If the weight ratio of dopamine derivative to catalyst is greater than 1:0.5, the reaction rate will be significantly reduced and disubstituted by-products will be generated; if the weight ratio of dopamine derivative to catalyst is less than 1:2.0, the reaction rate will be too fast, the system will generate a large amount of heat, resulting in a decrease in yield and affecting the subsequent number of washing times; therefore, the weight ratio of dopamine derivative to catalyst being 1:0.5 to 2.0 is appropriate, and preferably 1:0.8 to 1.6;

[0061] According to the present invention, dopamine hydrochloride and N-hydroxymethylacrylamide react in absolute ethanol under the condition of a temperature of 30 to 65 °C for 48 to 120 h, and the solid is recrystallized in absolute ethanol at room temperature.

[0062] When the reaction time is within the above range, if the reaction temperature is lower than 30 °C, the reaction cannot proceed; if the reaction temperature is higher than 65 °C, the product structure will be damaged; therefore, the reaction temperature of 30 to 65 °C is appropriate; when the reaction temperature is within the above range, if the reaction time is shorter than 48 h, the reaction is incomplete; if the reaction time is longer than 120 h, the reaction cycle will be increased, resulting in waste of resources; therefore, the reaction time of 48 to 120 h is suitable;

[0063] The separated solid is washed repeatedly with absolute ethanol until the pH of the filtrate > 6.8, and its main purpose is to wash away the catalyst, improve the product purity and maintain the best activity.

[0064] The purpose of recrystallizing the reaction product in absolute ethanol is to improve the product purity and remove all possible by-products and unreacted monomers.

[0065] It is determined by detection using infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and carbon spectrum analysis methods that the obtained crystal is dopamine-derived monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide, which has the following chemical structural formula (II):

[0066]

[0067] The dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide obtained here not only has excellent water solubility, but also each monomer molecule has 3 C=C double bonds and can be used as a chemical cross-linking agent.

[0068] The dopamine hydrochloride, N-methylolacrylamide, and catalyst used in the present invention are all products sold on the current market. For example, the dopamine hydrochloride sold by Aladdin Biochemical Technology Co., Ltd. under the trade name dopamine hydrochloride, and the N-methylolacrylamide sold by Aladdin Biochemical Technology Co., Ltd. under the trade name N-methylolacrylamide.

[0069] B. Preparation of the monomer mixed aqueous solution

[0070] In a reaction vessel, acrylamide monomer, acrylic acid monomer, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, allyl quaternary ammonium salt cationic monomer and the above dopamine derivative monomer are mixed uniformly in deionized water according to a molar ratio of 60-78:6-22:6-18:0.2-2.0:0.02-0.12. The obtained monomer mixture solution is adjusted to a pH of 6-8 with an aqueous sodium hydroxide solution having a concentration of 1.6-2.4 M, and thus a monomer mixed aqueous solution with a total monomer content of 10-30% by weight is obtained;

[0071] In the present invention, the acrylamide monomer is one or more acrylamide monomers selected from acrylamide, N-methylolacrylamide or N-hydroxyethylacrylamide. The role of the acrylamide monomer in the preparation of the hydrophobically associating polymer is that it constitutes the main chain skeleton of the hydrophobically associating polymer and enables the aqueous solution of the hydrophobically associating polymer to maintain a high apparent viscosity and water solubility. The acrylamide monomers used in the present invention are all products sold on the current market. For example, the product sold by Jiangxi Changjiu Agrochemical Co., Ltd. under the trade name acrylamide.

[0072] The acrylic acid monomer is one or more acrylic acid monomers selected from acrylic acid, methacrylic acid, itaconic acid or β-carboxyethyl acrylate. The role of the acrylic acid monomer in the preparation of the hydrophobically associating polymer is to further increase the apparent viscosity of the hydrophobically associating polymer solution, form the main chain of the partially hydrolyzed polyacrylamide molecule, and improve the temperature resistance of the hydrophobically associating polymer. The acrylic acid monomers used in the present invention are all products sold on the current market. For example, the product sold by Aladdin Biochemical Technology Co., Ltd. under the trade name acrylic acid.

[0073] The role of the sodium 2-acrylamido-2-methylpropanesulfonate in preparing the hydrophobically associating polymer is to improve the salt tolerance of the hydrophobically associating polymer by introducing a sulfonic acid group insensitive to salts. The sodium 2-acrylamido-2-methylpropanesulfonate used in the present invention is a product currently sold on the market, for example, the product sold by Shanghai Titan Scientific Co., Ltd. under the trade name sodium 2-acrylamido-2-methylpropanesulfonate.

[0074] The allyl quaternary ammonium salt cationic monomer is one or more allyl quaternary ammonium salt cationic monomers selected from trimethylallyl ammonium chloride, dodecyl dimethylallyl ammonium chloride, cetyl dimethylallyl ammonium chloride, octadecyl dimethylallyl ammonium chloride, triethylallyl ammonium bromide or methacryloyloxyethyl trimethyl ammonium chloride. The allyl quaternary ammonium salt cationic monomer has both oil-soluble and water-soluble amphiphilic hydrophobic monomers. Compared with acrylate hydrophobic monomers, the allyl quaternary ammonium salt cationic monomer can directly participate in the free radical polymerization reaction in an aqueous solution without adding a cosolvent or surfactant, thus avoiding the defects of reducing the solution viscosity and product purity caused by them, and greatly simplifying the synthesis process. The allyl quaternary ammonium salt cationic monomers used in the present invention are all products currently sold on the market, for example, the product sold by Zhangjiagang City Renda Chemical Co., Ltd. under the trade name cetyl dimethylallyl ammonium chloride.

[0075] According to the present invention, the molar ratio of acrylamide monomer, acrylic acid monomer, sodium 2-acrylamido-2-methylpropanesulfonate, allyl quaternary ammonium salt cationic monomer to dopamine derivative monomer is 60-78:6-22:6-18:0.2-2.0:0.02-0.12.

[0076] According to the present invention, when the amounts of acrylic acid monomer, sodium 2-acrylamido-2-methylpropanesulfonate, allyl quaternary ammonium salt cationic monomer and dopamine derivative monomer are within the above ranges, if the amount of acrylamide monomer is less than 60, the apparent viscosity of the product will decrease significantly; if the amount of acrylamide monomer is higher than 78, the salt tolerance of the product will be poor; therefore, it is reasonable that the amount of acrylamide monomer is 60-78, and preferably 64-72;

[0077] When the amounts of acrylamide monomer, sodium 2-acrylamido-2-methylpropanesulfonate, allyl quaternary ammonium salt cationic monomer and dopamine derivative monomer are within the above ranges, if the amount of acrylic acid monomer is less than 6, the temperature resistance and salt tolerance of the product will be poor; if the amount of acrylic acid monomer is higher than 22, the apparent viscosity of the product will decrease; therefore, it is advisable that the amount of acrylic acid monomer is 6-22, and preferably 9-18;

[0078] When the dosages of acrylamide monomer, acrylic acid monomer, allyl quaternary ammonium salt cationic monomer and dopamine derivative monomer are within the described ranges, if the dosage of sodium 2-acrylamido-2-methylpropanesulfonate is less than 6, the salt tolerance of the product is poor; if the dosage of sodium 2-acrylamido-2-methylpropanesulfonate is higher than 18, the apparent viscosity of the product decreases significantly; therefore, it is appropriate that the dosage of sodium 2-acrylamido-2-methylpropanesulfonate is 6-18, preferably 8-15;

[0079] When the dosages of acrylamide monomer, acrylic acid monomer, sodium 2-acrylamido-2-methylpropanesulfonate and dopamine derivative monomer are within the described ranges, if the dosage of allyl quaternary ammonium salt cationic monomer is less than 0.2, the salt tolerance of the product decreases significantly; if the dosage of allyl quaternary ammonium salt cationic monomer is higher than 2.0, the product is prone to form intramolecular hydrophobic association, and both the apparent viscosity and salt tolerance decrease significantly; therefore, it is suitable that the dosage of allyl quaternary ammonium salt cationic monomer is 0.2-2.0, preferably 0.5-1.6;

[0080] When the dosages of acrylamide monomer, acrylic acid monomer, sodium 2-acrylamido-2-methylpropanesulfonate and allyl quaternary ammonium salt cationic monomer are within the described ranges, if the dosage of dopamine derivative monomer is less than 0.02, the various properties of the product cannot be effectively improved; if the dosage of dopamine derivative monomer is higher than 0.12, the product will form an insoluble gel and completely lose its salt tolerance; therefore, it is appropriate that the dosage of dopamine derivative monomer is 0.02-0.12, preferably 0.05-0.09;

[0081] Preferably, the molar ratio of acrylamide monomer, acrylic acid monomer, sodium 2-acrylamido-2-methylpropanesulfonate, allyl quaternary ammonium salt cationic monomer and dopamine derivative monomer is 64-72:9-18:8-15:0.5-1.6:0.05-0.09.

[0082] In this step, the obtained monomer mixture solution is adjusted to a pH of 6-8 with an aqueous sodium hydroxide solution having a concentration of 1.6-2.4 M, aiming to improve the conversion rate of the product and make the product have the best performance.

[0083] In the present invention, the total monomer content of the monomer mixed aqueous solution is 10 to 30% by weight; if the total monomer content of the monomer mixed aqueous solution is less than 10%, the solution cannot form a gel block, and the viscosity of the obtained monomer mixed aqueous solution is greatly reduced; if the total monomer content of the monomer mixed aqueous solution is higher than 30%, these monomers are crosslinked excessively, resulting in a significant decrease in the water solubility of the monomer mixed aqueous solution, and even loss of water solubility, which cannot meet the requirements of the preparation method of the present invention. Therefore, it is feasible that the total monomer content of the monomer mixed aqueous solution is 10 to 30%, preferably 20 to 25%.

[0084] C. Synthesis of polymer sol

[0085] Nitrogen is introduced into the monomer mixed aqueous solution obtained in step B for 25 to 35 minutes. Meanwhile, an initiator accounting for 0.05 to 0.5% of the total weight of the monomer mixture is added, a magnetic stirrer bar is added, and the reaction vessel is sealed; the reaction vessel reacts in a constant temperature water bath electromagnetic stirrer under the conditions of a magnetic stirrer bar rotation speed of 100 to 600 r / min and a temperature of 50 to 70 °C for 0.5 to 3.0 hours, and then is filtered and separated to obtain a light yellow polymer sol;

[0086] In this step, the main function of introducing nitrogen into the monomer mixed aqueous solution for 25 to 35 minutes is to remove the oxygen contained in the monomer mixed aqueous solution, thereby avoiding the side effect that oxygen terminates the free radical chain growth process of the azo initiator in advance during the reaction process, resulting in a significant reduction in the polymer molecular weight and a significant decrease in the solution viscosity.

[0087] According to the present invention, the initiator is one or more initiators selected from sodium persulfate, ammonium persulfate, potassium persulfate, azodiisobutyramidine hydrochloride or 2,2 - azobis(2 - methylpropionamidine) dihydrochloride. The initiators used in the present invention are all water - soluble initiators, which can be quickly dissolved in water and initiate the reaction, and they are all products sold on the current market, such as the product sold by Aladdin Biochemical Technology Co., Ltd. under the trade name of 2,2 - azobis(2 - methylpropionamidine) dihydrochloride.

[0088] In the present invention, the initiator dosage is 0.05 to 0.5% of the total weight of the monomer mixture. If the initiator dosage is less than 0.05%, the polymerization reaction rate will be significantly reduced, or the polymerization reaction will not proceed completely, or even the polymerization reaction cannot be initiated; if the initiator dosage is higher than 0.5%, the molecular weight of the synthesized polymer will be significantly reduced, and the viscosity of the monomer mixed aqueous solution will also be significantly reduced, which cannot meet the requirements of the polymerization reaction.

[0089] According to the present invention, the monomer mixed aqueous solution and the initiator react for 0.5 to 3.0 hours under the conditions of a magnetic stirrer bar rotation speed of 100 to 600 r / min and a temperature of 50 to 70 °C.

[0090] In this step, when the reaction temperature and reaction time are within the specified ranges, if the magnetic stirrer speed is lower than 100 r / min, the monomers will not be evenly mixed, and the product is likely to form insoluble gels; if the magnetic stirrer speed is higher than 600 r / min, the monomer conversion rate will be reduced or even the reaction cannot be initiated; therefore, a magnetic stirrer speed of 100 - 600 r / min is appropriate;

[0091] When the magnetic stirrer speed and reaction time are within the specified ranges, if the reaction temperature is lower than 50 °C, these monomers cannot be polymerized; if the reaction temperature is higher than 70 °C, the initiation rate is too fast, and the molecular weight of the resulting polymer molecules is greatly reduced, and the solution viscosity also decreases significantly, so the requirements for subsequent steps cannot be met; therefore, a reaction temperature of 50 - 70 °C is reasonable;

[0092] When the reaction temperature and magnetic stirrer speed are within the specified ranges, if the reaction time is shorter than 0.5 h, the reaction is incomplete or even the reaction cannot be initiated; if the reaction time is longer than 3.0 h, the reaction has already been completed, which will only increase the reaction cycle and ineffective reaction time; therefore, a reaction time of 0.5 - 3.0 h is appropriate;

[0093] D. Preparation of polymer powder

[0094] Cool the polymer sol obtained in step C to room temperature, cut it into pieces, wash it repeatedly with absolute ethanol until no white substances precipitate on the surface, then transfer it to a constant-temperature vacuum drying oven and dry it at a temperature of 55 - 65 °C for 24 - 48 h, crush it, sieve it, and the fraction collected under the sieve is the hydrophobic associative polymer powder described above.

[0095] In this step, the main function of repeatedly washing the cut polymer sol with absolute ethanol is to wash away the reaction monomers present on the surface and inside the polymer sol.

[0096] The washed polymer sol is dried at a temperature of 55 - 65 °C for 24 - 48 h. When the drying time is within the specified range, if the drying temperature is lower than 55 °C, the moisture cannot be completely removed; if the drying temperature is higher than 65 °C, the polymer molecular structure will be damaged; therefore, a drying temperature of 55 - 65 °C is appropriate; when the drying temperature is within the specified range, if the drying time is shorter than 24 h, the moisture cannot be completely removed; if the drying time is longer than 48 h, the reaction cycle will be increased and the production efficiency will be reduced; therefore, a drying time of 24 - 48 h is appropriate.

[0097] The sieve used in the present invention is a sieve commonly used in this technical field, and its mesh size is 40 - 80 meshes.

[0098] The present invention also relates to a dopamine derivative-modified hydrophobically associating polymer prepared by the above preparation method. The apparent viscosity of an aqueous solution of the dopamine derivative-modified hydrophobically associating polymer with a mass concentration of 5 g / L is above 570 mPa·s, its apparent viscosity in an aqueous solution of sodium chloride with a mass concentration of 20 g / L is above 590 mPa·s, and the viscosity retention rate is above 87.62%; its apparent viscosity in an aqueous solution of calcium chloride with a mass concentration of 10 g / L is above 342 mPa·s, and the viscosity retention rate is above 33.4%.

[0099] For the dopamine derivative-modified hydrophobically associating polymer powder prepared in the present invention, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analysis, apparent viscosity, dissolution rate, corrosion rate and corrosion inhibition efficiency were measured. The measurement results can be seen in the specific embodiments section below.

[0100] The measurement methods adopted in the present invention will be described in detail below.

[0101] (1) Infrared spectroscopy measurement:

[0102] The product prepared in the present invention and spectroscopic pure KBr were ground and pressed into tablets respectively. The infrared spectrum with a wave number of 400 - 4000 cm -1 was measured using an Avatar-380 Fourier transform infrared spectrometer produced by Thermo nicolet Corporation under conventional measurement conditions.

[0103] Specifically, the infrared spectroscopy measurement results of DAAM and HAPAMC 16 D1 in Example 1 and HAPAMC 16 in Comparative Example 1 are listed in the appendix Figure 1 .

[0104] Determined according to the GB / T 6040 - 2019 standard, the stretching vibration peak at 3533 cm -1 in the infrared spectrum of DAAM belongs to the stretching vibration peak of -NH; the stretching vibration peak at 3371 cm -1 belongs to the stretching vibration peak of -OH; the stretching vibration peak at 1658 cm -1 belongs to the stretching vibration peak of -C=O; the -C=C- bending vibration peaks at 1545 cm -1 , 1499 cm -1 , and 1455 cm -1 belong to the benzene ring skeleton.

[0105] The stretching vibration peak at 3440 cm 16 in the infrared spectrum of HAPAMC -1 D1 belongs to the stretching vibration peak of -NH; the stretching vibration peaks at 2938 cm -1 and 2834 cm -1The stretching vibration peaks of -CH3 and -CH2 in the hydrophobic monomer cetyl, and 1452 cm -1 、1377 cm -1 are the bending vibration peaks of -CH3 and -CH2; 1662 cm -1 is the stretching vibration peak of -C=O-; 1040 cm -1 is the stretching vibration peak of the sulfonic acid group S=O; 774 cm -1 is the bending vibration peak of the benzene ring C-H.

[0106] HAPAMC 16 In the infrared spectrum at 3422 cm -1 is the stretching vibration peak of -NH; 2934 cm -1 、2850 cm -1 are the stretching vibration peaks of -CH3 and -CH2 in the hydrophobic monomer cetyl, 1443 cm -1 、1383 cm -1 are the bending vibration peaks of -CH3 and -CH2; 1665 cm -1 is the stretching vibration peak of -C=O-; 1037 cm -1 is the stretching vibration peak of the sulfonic acid group S=O;

[0107] (2) Nuclear magnetic resonance spectrum determination:

[0108] The product prepared in the present invention was dissolved in deuterium (D2O) and transferred to a nuclear magnetic resonance tube. Tetramethylsilane (TMS) was added as an internal standard, and its nuclear magnetic resonance hydrogen spectrum was measured using an AvanceⅢ 600 MHz nuclear magnetic resonance spectrometer sold by Bruker International under conventional measurement conditions.

[0109] Specifically, the nuclear magnetic resonance hydrogen spectra of DAAM and HAPAMC 16 D1 prepared in Example 1 and HAPAMC 16 prepared in Comparative Example 1 are listed in the appendix Figure 2 .

[0110] Determined according to the NMR system standard 2.0, in the nuclear magnetic resonance hydrogen spectrum and carbon spectrum of DAAM, δ = 9.63 and 9.51 are the chemical shifts of the phenolic hydroxyl -OH hydrogen of the benzene ring; δ = 8.99, 8.70 and 8.34 are the chemical shifts of the imino -NH hydrogen respectively; δ = 8.05 is the chemical shift of the protonated amino -NH3 + hydrogen; δ = 6.31, 6.14 and 5.63 are the chemical shifts of the saturated -CH=CH2 hydrogen respectively; δ = 4.37 is the chemical shift of -CH2-N hydrogen; δ = 3.45 is -CH2-N+ Chemical shift of hydrogen; δ = 3.06 is the chemical shift of -CH2- hydrogen. δ = 166.2 is the chemical shift of C=O carbon; δ = 145.2 and 144.4 are the chemical shifts of benzene ring C-OH carbon; δ = 132.0 and 131.1 are the chemical shifts of benzene ring unsaturated -C=C- carbon; near δ = 126.4 and 125.7 are the chemical shifts of saturated -C=C- carbon; δ = 145.2 and 144.4 are the chemical shifts of C-OH carbon; δ = 56.5 is -C-NH3 + Chemical shift of carbon; δ = 37.9 and 35.7 are the chemical shifts of -C-N- carbon; δ = 18.9 is the chemical shift of -C-C- carbon.

[0111] In HAPAMC 16 In the 1H NMR spectrum of D1, δ = 4.69 is the chemical shift of -NH2 hydrogen in AM; δ = 2.12 is the chemical shift of -CH-COO- hydrogen in AA; δ = 3.57 is the chemical shift of -CH2-S hydrogen in AMPS; δ = 1.43 is the chemical shift of -CH3 hydrogen in AMPS; δ = 3.34 is 16 the chemical shift of -NH2+- hydrogen in DMAAC; δ = 1.10 is 16 the chemical shift of long-chain -CH2- hydrogen in DMAAC; δ = 7.85 is -NH3 + the chemical shift of hydrogen.

[0112] In HAPAMC 16 In the 1H NMR spectrum of, δ = 4.70 is the chemical shift of -NH2 hydrogen in AM; δ = 2.10 is the chemical shift of -CH-COO- hydrogen in AA; δ = 3.56 is the chemical shift of -CH2-S hydrogen in AMPS; δ = 1.40 is the chemical shift of -CH3 hydrogen in AMPS; δ = 3.33 is 16 the chemical shift of -NH2 + - hydrogen in DMAAC; δ = 1.09 is 16 the chemical shift of long-chain -CH2- hydrogen in DMAAC.

[0113] (3) Thermogravimetric analysis:

[0114] The products prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention were subjected to TG and DTG analysis using a STA449 thermogravimetric analyzer sold by NETZSCH Company under the conditions of nitrogen as the protective gas - purge gas, a heating rate of 10 °C / min, and a temperature range of 30-800 °C. The thermal analysis results are listed in the appendix Figure 3 .

[0115] Appendix Figure 3It is clear that the change trends of their thermogravimetric TG curves are basically the same, with HAPAMC 16 Take D5 as an example: (1) 30-195℃: The polymer loses weight slowly by about 9.68%, which is mainly attributed to the fact that the hydrophilic groups of the polymer (such as -NH2) easily absorb moisture from the air. Some solvents are not volatilized during the drying process of the product, and moisture from the air is absorbed during the granulation and storage process. Therefore, this temperature range is mainly caused by the slow evaporation of water vapor, which leads to slow weight loss. In the DTG curve, the absolute value of this section is small and the trend is gentle. (2) 195-302℃: The slope of the TG curve increases, and the weight loss of the polymer accelerates, with a weight loss of about 6.01%. This is because the polymer undergoes an imidization reaction, that is, every two amide groups in the molecular chain remove an amine molecule and simultaneously generate a new imide group, resulting in mass loss. Among them, the slope of point A in the TG curve is the largest and the weight loss is the fastest, indicating that the temperature at which the imidization reaction is most likely to occur is 263.53℃. (3) 302-412℃: The polymer loses weight fastest and loses the most weight, about 31.82%. At this time, the imide group continues to thermally decompose, and the polymer molecular skeleton gradually breaks into small molecules and loses through thermal degradation, resulting in a large loss of mass. The weight loss rate reaches a peak at 375.29℃. (4) 412-750℃: The weight loss is only 8.17%, mainly due to the weight loss of the residue after the polymer is carbonized. After 539.45℃, the absolute value of dw (thermal weight loss derivative) gradually approaches 0, and the thermal weight loss of the polymer is basically over, with a total weight loss of about 55.68%.

[0116] It can also be seen from the TG curve that the higher the DAAM content, the less weight loss the polymer has and the stronger thermal stability. This is mainly because the molecular chemical cross-linking forms a more stable three-dimensional network structure, and the polymer skeleton is more extended and strong. It can also be seen from the DTG curve that in the second and third stages of thermal weight loss, the weight loss peak rate is lower, so the polymer has better temperature resistance and can play a better role in the field of enhanced oil recovery.

[0117] (4) Determination of apparent viscosity:

[0118] The product prepared in the present invention was weighed and dissolved in 100 mL of deionized water, and a magnet was added. The product was magnetically stirred for 5 h at room temperature to completely dissolve the product, and a product solution with a concentration of 0.1 to 6 g / L was obtained. The apparent viscosity of the solution was measured using a DV-I rotational viscometer sold by Brookfield under the conditions of a constant temperature of 30°C, a No. 5 rotor, and a rotation speed of 100 r / min. The apparent viscosity results are listed in the attached Figure 4 .

[0119] The relationship between the apparent viscosity and solution concentration of the products obtained in Examples 1-5 and Comparative Examples 1-2 is shown in the attached Figure 4. Due to the introduction of a small amount of hydrophobic groups in the polymer molecular chain, it exhibits hydrophobic association characteristics. In the present invention, the critical aggregation concentration should be understood as the concentration of the polymer solution at which the apparent viscosity of the polymer solution increases sharply. When the concentration is less than the critical aggregation concentration (CAC), the probability of intermolecular collision is small. In order to avoid water molecules, the hydrophobic groups cause the molecular chain to bend and curl inward, showing intra-molecular association, reducing the hydrodynamic size. Therefore, the increase in the apparent viscosity of the polymer solution is small at low concentrations; when its concentration gradually increases and exceeds the CAC, the probability of intermolecular collision increases. At this time, intermolecular association plays a dominant role, and a dynamic three-dimensional physical cross-linked network is gradually formed through hydrogen bonding, and the apparent viscosity of the solution increases significantly. And DAAM can cause chemical cross-linking of the polymer to form a more stable and more extended three-dimensional network structure, and the hydrophobic association characteristics are further enhanced. Therefore, the increase in solution viscosity is greater, where HAPAMC 16 D5 has an apparent concentration of 1024 mPa·s at 5 g·L -1 .

[0120] (5) Determination of viscosity retention rate:

[0121] Prepare the product solution obtained in the present invention with a concentration of 5 g / L according to the above method. Heat it from the specified temperature T1 to different temperatures T2 in a constant temperature water bath. Measure the apparent viscosity of the solution according to the above method, and calculate the viscosity retention rate according to the formula η2 / η1.

[0122] The relationship between the apparent viscosity and temperature of the polymers (5 g·L -1 ) prepared in Examples 1-5 and Comparative Examples 1-2 is shown in the appendix Figure 5。As the temperature rises, the apparent viscosity of the polymer solution decreases, conforming to Arrhenius' law. The increase in temperature enhances the thermal motion of molecules, weakening the intermolecular hydrophobic association and hydrogen bonding. Among them, HPAM only has hydrogen bonding, so its temperature resistance is the worst. When approaching room temperature (25 °C), the apparent viscosity shows a slight upward trend or remains basically flat with the increase in temperature. This is attributed to the fact that hydrophobic association is an endothermic entropy-increasing process. A slight increase in temperature enhances the intermolecular hydrophobic association performance, manifested as a slight thickening phenomenon. Therefore, the apparent viscosity of the solution slightly increases between 20 °C and 30 °C. As the temperature continues to rise, the thermal motion of molecules enhances and gradually weakens the hydrophobic association. The dynamic physical cross-linked three-dimensional network is destroyed, and the hydrodynamic size decreases. Therefore, the apparent viscosity of the solution continues to decrease. DAAM can enable intermolecular chemical cross-linking to form a very stable network structure. Even when the hydrogen bonding and hydrophobic association are weakened, its hydrodynamic size can still be maintained within a certain temperature range. Therefore, the polymer HAPAMC16D5 exhibits very good temperature resistance. When the temperature is 90 °C, the apparent viscosity of the solution with a concentration of 5 g·L -1 can reach 573 mPa·s, and the retention rate is 55.96%. This result is also consistent with TGA.

[0123] Viscosity retention rate: Pipette 100 mL of NaCl solutions with different weight concentrations, add 0.5 g of the product prepared by the present invention, dissolve to obtain a stable homogeneous solution containing NaCl, and measure the apparent viscosity of the solution according to the above method, and calculate the viscosity retention rate.

[0124] Measure the apparent viscosity and calculate the viscosity retention rate of the homogeneous solution containing CaCl2 in the same manner.

[0125] The relationship between the apparent viscosity and salt concentration of the polymers prepared in Examples 1-5 and Comparative Examples 1-2 (5 g·L -1 ) is shown in the appendix Figure 6 . As the salt concentrations of NaCl and CaCl2 increase, the viscosity of HPAM rapidly decreases until it has no viscosity. Since there is only electrostatic repulsion between its molecules, the ions in the solution enhance the repulsion between polymer ions, and the molecular chain shrinks and bends. Thus, the apparent viscosity of the solution rapidly decreases. For Na + : The viscosity of the hydrophobic associating polymer shows a trend of first increasing and then gently decreasing. When Na +When the concentration is low, its viscosity increases, showing an anti-polyelectrolyte effect. At this time, the hydrophobic association force far exceeds the influence of electrostatic repulsion. Moreover, NaCl increases the polarity of the solvent. In order to avoid water molecules, the hydrophobic groups strengthen the intermolecular hydrophobic association, and the molecular aggregation increases the hydrodynamic size, resulting in an increase in the apparent viscosity of the solution. However, as the NaCl concentration continues to increase, the electrostatic repulsion gradually increases and weakens the hydrophobic association, and the dynamic network structure of physical cross-linking is gradually destroyed, and the viscosity begins to decrease; DAAM causes chemical cross-linking of the polymer to form a more stable and larger molecular configuration, and the hydrophobic association is enhanced, and the viscosity increases greatly at low salinity; but due to the increase in the molecular weight of the polymer with the increase of DAAM, the hydrophobic groups are more widely distributed. Therefore, when the salinity continues to increase, due to the electrostatic repulsion, the molecular chain bends and contracts inward, and the hydrophobic groups on the same molecular chain approach each other and tend to form intramolecular association. Therefore, the solution viscosity decreases significantly, which also proves that the dosage of DAAM should be limited to within 0.01% to effectively play the salt tolerance performance.

[0126] For Ca 2+ : Due to the higher ionic strength of divalent metal salts, the electrostatic repulsion plays a stronger role and weakens the hydrophobic association very much. Therefore, when the Ca 2+ concentration is greater than 2 g·L -1 , the solution viscosity begins to decrease significantly. HAPAMC16D3 exhibits the best salt tolerance performance. At a temperature of 25 °C, the apparent viscosities of the polymer solution with a concentration of 5 g·L -1 in 20 g·L -1 NaCl and 10 g·L -1 CaCl2 solutions can reach 722 and 463 mPa·s respectively, and the retention rates are 87.62% and 56.19% respectively, showing very excellent salt tolerance performance.

[0127] (6) Dissolution rate: Accurately weigh 0.04 ± 0.001 g of the hydrophobic associating polymer powder of the present invention according to the national standard GB / T 12005.8-1989, dissolve it in 100 mL of distilled water, and use the DDSJ-308F conductivity meter sold by Shanghai Leici Co., Ltd. to measure the dissolution rate of the polymer at a temperature of 30 °C.

[0128] The water solubility of the polymer is also one of the important indicators affecting the oil displacement efficiency. Since ionic polymers will ionize to produce ions and counterions after dissolving in water, and the conductivity of its solution increases with the increase of its dissolution amount, the conductivity method is used to measure the polymer dissolution rate.

[0129] The change of the solubility of the polymers prepared in Examples 1-5 and Comparative Examples 1-2 with time is shown in the appendix Figure 7 . As Figure 7As shown in the figure, the conductivity of the polymer increases rapidly at first, then slows down and remains stable as time goes by. HPAM only has hydrophilic -NH2 groups and can be dissolved quickly, with a dissolution time of only 7 minutes. However, due to the introduction of hydrophobic groups in other polymers and the low concentration of the polymer solution (<CAC), the hydrophobic groups tend to aggregate within the molecules to avoid water, hindering the diffusion and dissolution of the molecules from the bulk to the solution. 16 The dissolution time is 10 minutes. On the one hand, the polymer containing DAAM increases its molecular weight and hydrodynamic size due to chemical cross-linking, which is not conducive to the swelling and dissolution of polymer molecules. On the other hand, it has a larger specific surface area and a loose and porous network structure, which is conducive to the rapid penetration of water molecules into the polymer and accelerates dissolution, which makes up for the disadvantage to a certain extent. Therefore, HAPAMC 16 The dissolution time of D5 increased to 17 min, but it still met the requirements for use in the polymer-driven tertiary oil recovery process.

[0130] (7) Corrosion rate V and corrosion inhibition efficiency IE:

[0131] In a wide-mouth bottle, a 1 mol / L hydrochloric acid aqueous solution corrosive medium and different weights of the product prepared by the present invention are added, and the products are fully dissolved under stirring with a magnetic stirrer to obtain a product solution with a weight concentration of 1 to 5 g / L, and a hydrochloric acid aqueous solution without a polymer product is used as a control group;

[0132] A 50 mm × 10 mm × 3 mm Q235 steel bar sold by Shandong Shengxin Technology Co., Ltd. was polished with 800, 1000, 1200, and 2000 grit sandpaper, cleaned with ethanol and dried, and weighed and recorded as W1.

[0133] The steel bars were hung in a wide-mouth bottle with a thin rope to ensure that the steel bars did not touch the bottle wall but were in full contact with the hydrochloric acid solution. The wide-mouth bottle was placed in a constant temperature water bath at 30°C for 72 hours. The steel bars were then taken out and placed in a rust removal solution consisting of concentrated hydrochloric acid, distilled water and hexamethylenetetramine in a weight ratio of 50:50:1. The steel bars were ultrasonically treated for 5 minutes using an Elma Select ultrasonic device sold by Elma, Germany, at an ultrasonic frequency of 40kHz and an ultrasonic power of 60W to remove the corrosion on the surface of the steel bars. The steel bars were rinsed with ethanol, dried, and weighed as W2. The corrosion rate V and the corrosion inhibition efficiency IE were calculated according to the following formulas (1) and (2):

[0134] V = (W1 - W2) / (S × t) (1)

[0135] Where:

[0136] V represents the corrosion rate, mg·cm-2 ·h -1 ;

[0137] W1 represents the weight of the steel bar before corrosion, mg;

[0138] W2 represents the weight of the steel bar after corrosion, mg;

[0139] S represents the surface area of the steel bar, cm 2 ;

[0140] t is the immersion time, h;

[0141] IE(%) = (V0 - V) / V0 × 100% (2)

[0142] In the formula:

[0143] IE is the corrosion inhibition efficiency of the polymer, %;

[0144] V0 represents the corrosion rate without polymer, mg˙cm -2 ·h -1 ;

[0145] V represents the corrosion rate with added polymer, mg˙cm -2 ·h -1 ;

[0146] W1 represents the weight of the steel bar before corrosion, mg;

[0147] W2 represents the weight of the steel bar after corrosion, mg.

[0148] During the oilfield exploitation process, internal corrosion of pipelines is also an important factor affecting oil production efficiency and maintenance costs. Polyacrylamide contains abundant amino and carboxyl groups. The lone pair electrons of amino nitrogen atoms and the double bonds of carboxyl oxygen atoms can both form coordination bonds with iron ions, forming a stable adsorption film on the surface of carbon steel, reducing the corrosion of Cl -1 on metal pipelines. As an excellent corrosion inhibitor, it can effectively reduce pipeline maintenance costs while increasing oil recovery rate.

[0149] The corrosion inhibition efficiencies of the polymers prepared in Examples 1-5 and Comparative Examples 1-2 varying with concentration are shown in the appendix Figure 8 . As the polymer concentration increases, the corrosion inhibition efficiency shows a trend of first increasing and then remaining stable. As the polymer concentration rises, the number of polymer molecules adsorbed on the surface of the steel bar increases, gradually forming a dense adsorption film, and the thickness of the film layer also increases accordingly. When the surface adsorption reaches saturation, the adsorption and desorption reach a dynamic equilibrium, and the corrosion inhibition efficiency approaches the maximum value. Among them, HAPAMC 16 The concentration at which the saturated adsorption amount on the surface of the steel bar is reached is about 4 g·L -1(>CAC); The intermolecular hydrophobic association increases the hydrodynamic size, makes the coating on the Q235 steel sheet more compact, hinders charge transfer, and thus plays a good protective role. The corrosion inhibition performance can reach up to 94.23%; while the polymer formed by adding DAAM has a more extended network structure and larger molecular size, and the protective film shows better stability and durability, and its corrosion inhibition efficiency can reach 99.02%. Therefore, the polymer HAPAMC 16 D can effectively delay pipeline corrosion.

[0150] [Beneficial effects]

[0151] The beneficial technical effects of the present invention are: compared with the prior art,

[0152] All monomers used in the present invention have good water solubility. Therefore, the hydrophobic associating polymer can be synthesized only through a homogeneous free radical copolymerization reaction. The synthesis process is simple and the raw materials are easy to obtain; the dopamine hydrochloride-derived monomer synthesized in the present invention is a new type of cross-linking monomer, which has both excellent water solubility and high functionality, and only a very low dosage is required to greatly increase the apparent viscosity of the aqueous solution of the hydrophobic associating polymer. The allyl quaternary ammonium salt cationic monomer used in the present invention is an amphiphilic functional monomer with both hydrophobic and hydrophilic groups. Compared with the commonly used acrylate, the hydrophobic group can be introduced into the side chain of the polymer molecule without adding an organic co-solvent or surfactant, avoiding the defects that the organic co-solvent greatly reduces the apparent viscosity of the polymer solution and the surfactant reduces the product purity.

[0153] The dopamine derivative-modified hydrophobic associating polymer synthesized in the present invention has a larger hydrodynamic size and a higher molecular weight, its solution apparent viscosity is greatly increased, and the polymer has excellent temperature and salt resistance properties. The hydrophobic associating polymer has good water solubility, can be quickly dissolved in water, and also has excellent corrosion inhibition performance, and can delay the internal pipeline corrosion problem in the actual oilfield exploitation process.

Description of the drawings

[0154] Figure 1 is the infrared spectrum of DAAM prepared in Example 1, the hydrophobic associating polymers prepared in Comparative Example 1 and Example 1;

[0155] Figure 2 is the 1H NMR, 13C NMR spectra of DAAM prepared in Example 1 and the 1H NMR spectra of the hydrophobic associating polymers prepared in Comparative Example 1 and Example 1;

[0156] Figure 3 is the thermogravimetric TG curve and DTG curve of the polymers in Examples 1-5 and Comparative Examples 1-2.

[0157] Figure 4It is a graph showing the relationship between the apparent viscosity and concentration of the polymer solutions in Examples 1-5 and Comparative Examples 1-2.

[0158] Figure 5 It is a graph showing the relationship between the apparent viscosity and temperature of the polymer solutions in Examples 1-5 and Comparative Examples 1-2.

[0159] Figure 6 It is a graph showing the relationship between the apparent viscosity of the polymer solutions in Examples 1-5 and Comparative Examples 1-2 and the concentrations of NaCl and CaCl2.

[0160] Figure 7 It is a graph of the dissolution rate of the polymer powders in Examples 1-5 and Comparative Examples 1-2 (refer to GB / T12005.8-1989).

[0161] Figure 8 It is a graph showing the relationship between the corrosion inhibition efficiency of the polymers in Examples 1-5 and Comparative Examples 1-2 and the solution concentration.

Detailed Implementation Modes

[0162] The present invention can be better understood through the following examples.

[0163] Example 1: Preparation of the dopamine derivative-modified hydrophobically associating polymer of the present invention

[0164] The implementation steps of this example are as follows:

[0165] A. Preparation of the dopamine derivative monomer

[0166] Mix dopamine hydrochloride and N-hydroxymethylacrylamide evenly at a molar ratio of 1:3.8. Then, add absolute ethanol at a weight ratio of dopamine derivative to absolute ethanol of 1:6, stir and dissolve at room temperature. Next, slowly add the catalyst under nitrogen protection at a weight ratio of dopamine derivative to 18.4M sulfuric acid catalyst of 1:0.5, mix evenly, heat to 65°C, and react at this temperature for 48h. Then, cool the temperature to room temperature, filter by suction, and repeatedly wash the separated solid with absolute ethanol until the pH of the filtrate is 6.9. Let the washed solid recrystallize in absolute ethanol at room temperature, filter and separate. Detect according to the analysis method described in the specification of this application, and the collected crystals are the dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide (DAAM);

[0167] B. Preparation of the monomer mixed aqueous solution

[0168] In a reaction vessel, acrylamide, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, the allyl quaternary ammonium salt cationic monomer of cetyl dimethyl allyl ammonium chloride and the above-mentioned dopamine derivative monomer were mixed uniformly in deionized water according to a molar ratio of 68:18:12:0.2:0.12. The obtained monomer mixture solution was adjusted to a pH of 7.0 with an aqueous sodium hydroxide solution having a concentration of 1.8 M, and thus a monomer mixed aqueous solution with a total monomer content of 21% by weight was obtained;

[0169] C, Synthesis of polymer sol

[0170] Nitrogen was introduced into the monomer mixed aqueous solution obtained in step B for 30 min. Meanwhile, 0.31% of sodium persulfate initiator based on the total weight of the monomer mixture was added, a magnetic stirrer bar was added, and the reaction vessel was sealed; the reaction vessel was reacted in a constant temperature water bath electromagnetic stirrer under the conditions of a magnetic stirrer bar rotation speed of 300 r / min and a temperature of 65 °C for 1.2 h, and then filtered and separated to obtain a light yellow polymer (HAPAMC 16 D1) sol;

[0171] D, Preparation of polymer powder

[0172] The polymer sol obtained in step C was cooled to room temperature, cut into pieces, repeatedly washed with absolute ethanol until no white substances were precipitated on the surface, and then transferred to a constant temperature vacuum drying oven and dried at a temperature of 60 °C for 36 h, pulverized, sieved, and the fraction passing through the sieve collected was the hydrophobic associating polymer (HAPAMC 16 D1) powder.

[0173] The infrared spectra of the DAAM and the hydrophobic associating polymer prepared in this example are listed in the appendix Figure 1 ; the proton nuclear magnetic resonance spectrum and carbon spectrum of DAAM and the proton nuclear magnetic resonance spectrum of the hydrophobic associating polymer are listed in the appendix Figure 2 ;

[0174] The TG and DTG, apparent viscosity vs. concentration, apparent viscosity vs. NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency vs. solution concentration of the hydrophobic associating polymer prepared in this example are respectively listed in the appendix Figures 3 - 8 ;

[0175] Example 2: Preparation of dopamine derivative modified hydrophobic associating polymer of the present invention

[0176] The implementation steps of this example are as follows:

[0177] A, Preparation of dopamine derivative monomer

[0178] Mix dopamine hydrochloride and N-hydroxymethylacrylamide evenly at a molar ratio of 1:3.0. Then, add absolute ethanol at a weight ratio of dopamine derivative to absolute ethanol of 1:4, stir and dissolve at room temperature. Next, slowly add a catalyst under nitrogen protection at a weight ratio of dopamine derivative to 15.0 M sulfuric acid catalyst of 1:0.9, mix evenly, heat to 30 °C, and react at this temperature for 120 h. Then, cool the temperature to room temperature, filter by suction, and repeatedly wash the separated solid matter with absolute ethanol until the pH of the filtrate is 7.0. Let the washed solid matter recrystallize in absolute ethanol at room temperature, filter and separate, and detect according to the analysis method described in the specification of this application. The collected crystal is the dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide (DAAM);

[0179] B. Preparation of monomer mixed aqueous solution

[0180] In a reaction vessel, mix N-hydroxymethylacrylamide, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, trimethylallylammonium chloride allyl quaternary ammonium salt cationic monomer and the above-mentioned dopamine derivative monomer evenly in deionized water at a molar ratio of 73:22:15:0.6:0.04. Adjust the pH of the obtained monomer mixture solution to 6.0 with a 1.6 M sodium hydroxide aqueous solution, and thus obtain a monomer mixed aqueous solution with a total monomer content of 25% by weight;

[0181] C. Synthesis of polymer sol

[0182] Pass nitrogen into the monomer mixed aqueous solution obtained in step B for 35 min. At the same time, add an initiator of 2,2'-azobis(2-methylpropionamidine) dihydrochloride at 0.05% based on the total weight of the monomer mixture, add a magnetic stir bar, and seal the reaction vessel; React the reaction vessel in a constant temperature water bath electromagnetic stirrer at a magnetic stir bar rotation speed of 100 r / min and a temperature of 70 °C for 0.5 h, filter and separate to obtain a light yellow polymer (HAPAMC 16 D2) sol;

[0183] D. Preparation of polymer powder

[0184] Cool the polymer sol obtained in step C to room temperature, cut it into pieces, repeatedly wash it with absolute ethanol until no white substance precipitates on the surface, then transfer it to a constant temperature vacuum drying oven and dry it at 55 °C for 48 h, crush it, sieve it, and the fraction passing through the sieve collected is the hydrophobic associating polymer (HAPAMC 16 D2) powder.

[0185] The measurement results of TG, DTG, apparent viscosity vs. concentration, apparent viscosity vs. NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency vs. solution concentration of the hydrophobically associating polymer prepared in this example are listed in the appendix Figures 3 - 8 as follows.

[0186] Example 3: Preparation of dopamine derivative-modified hydrophobically associating polymer of the present invention

[0187] The implementation steps of this example are as follows:

[0188] A. Preparation of dopamine derivative monomer

[0189] Mix dopamine hydrochloride and N-hydroxymethylacrylamide evenly at a molar ratio of 1:6.0. Then add absolute ethanol at a weight ratio of dopamine derivative to absolute ethanol of 1:8, stir and dissolve at room temperature. Then, under nitrogen protection, slowly add a catalyst at a weight ratio of dopamine derivative to aluminum chloride catalyst with a particle size of 4-20 mesh of 1:1.2, mix evenly, heat to a temperature of 48 °C, and react at this temperature for 84 h. Then cool the temperature to room temperature, filter, and repeatedly wash the separated solid with absolute ethanol until the pH of the filtrate is 7.1. Let the washed solid recrystallize in absolute ethanol at room temperature, filter and separate. Detect according to the analysis method described in the specification of this application. The collected crystal is dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide (DAAM);

[0190] B. Preparation of monomer mixed aqueous solution

[0191] In a reaction vessel, N-hydroxyethylacrylamide, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, dodecyl dimethyl allyl ammonium chloride allyl quaternary ammonium salt cationic monomer and the above dopamine derivative monomer are mixed evenly in deionized water at a molar ratio of 60:6:18:1.0:0.08. The obtained monomer mixture solution is adjusted to a pH of 8.0 with a 2.4 M aqueous sodium hydroxide solution, and thus a monomer mixed aqueous solution with a total monomer content of 10% by weight is obtained;

[0192] C. Synthesis of polymer sol

[0193] Introduce nitrogen into the monomer mixed aqueous solution obtained in step B for 25 min. At the same time, add an ammonium persulfate initiator at 0.42% by the total weight of the monomer mixture, add a magnetic stirrer, and seal the reaction vessel; the reaction vessel reacts in a constant temperature water bath electromagnetic stirrer under the conditions of a magnetic stirrer speed of 600 r / min and a temperature of 50 °C for 3.0 h, filter and separate to obtain a light yellow polymer (HAPAMC16D3) sol;

[0194] D. Preparation of polymer powder

[0195] Cool the polymer sol obtained in step C to room temperature, cut it into pieces, wash it repeatedly with absolute ethanol until no white substances precipitate on the surface, then transfer it to a constant-temperature vacuum drying oven and dry it at 62 °C for 30 h, pulverize it, sieve it, and the undersize fraction collected is the powder of the hydrophobic associating polymer (HAPAMC16D3).

[0196] The TG, DTG, apparent viscosity vs. concentration, apparent viscosity vs. NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency vs. solution concentration of the hydrophobic associating polymer prepared in this example are listed in the appendix Figures 3 - 8 below.

[0197] Example 4: Preparation of dopamine derivative-modified hydrophobic associating polymer of the present invention

[0198] The implementation steps of this example are as follows:

[0199] A. Preparation of dopamine derivative monomer

[0200] Mix dopamine hydrochloride and N-hydroxymethylacrylamide evenly at a molar ratio of 1:4.6, then add absolute ethanol according to a weight ratio of dopamine derivative to absolute ethanol of 1:10, stir and dissolve at room temperature, then slowly add the catalyst under nitrogen protection according to a weight ratio of dopamine derivative to 18.4 M sulfuric acid catalyst of 1:2.0, mix evenly, heat to 38 °C, and react at this temperature for 102 h. Then cool its temperature to room temperature, filter by suction, wash the separated solid matter repeatedly with absolute ethanol until the pH of the filtrate is 6.9, let the washed solid matter recrystallize in absolute ethanol at room temperature, filter and separate, and detect according to the analysis method described in the specification of this application. The collected crystals are the dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide (DAAM);

[0201] B. Preparation of monomer mixed aqueous solution

[0202] In a reaction vessel, acrylamide, β-carboxyethyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, allyl quaternary ammonium salt cationic monomer of triethylallyl ammonium bromide and the above dopamine derivative monomer are mixed evenly in deionized water at a molar ratio of 64:10:6:1.4:0.02. The obtained monomer mixture solution is adjusted to a pH of 6.5 with a 2.0 M sodium hydroxide aqueous solution, and thus a monomer mixed aqueous solution with a total monomer content of 16% by weight is obtained;

[0203] C. Synthesis of polymer sol

[0204] Nitrogen was introduced into the monomer mixed aqueous solution obtained in step B for 30 min. Meanwhile, potassium persulfate initiator accounting for 0.18% of the total weight of the monomer mixture was added, a magnetic stir bar was added, and the reaction vessel was sealed. The reaction vessel was reacted in a constant temperature water bath electromagnetic stirrer under the conditions of a magnetic stir bar rotation speed of 400 r / min and a temperature of 60 °C for 1.8 h, followed by filtration and separation to obtain a light yellow polymer (HAPAMC16D4) sol;

[0205] D. Preparation of polymer powder

[0206] The polymer sol obtained in step C was cooled to room temperature, cut into pieces, repeatedly washed with absolute ethanol until no white substances precipitated on the surface, and then transferred to a constant temperature vacuum drying oven and dried at 65 °C for 24 h, crushed, sieved, and the fraction passing through the sieve was the hydrophobic associating polymer (HAPAMC16D4) powder.

[0207] The TG and DTG, apparent viscosity and concentration, apparent viscosity and NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency and solution concentration of the hydrophobic associating polymer prepared in this example were respectively listed in the appendix Figures 3 - 8 as follows.

[0208] Example 5: Preparation of dopamine derivative modified hydrophobic associating polymer of the present invention

[0209] The implementation steps of this example are as follows:

[0210] A. Preparation of dopamine derivative monomer

[0211] Dopamine hydrochloride and N-hydroxymethylacrylamide were mixed evenly at a molar ratio of 1:5.2. Then, absolute ethanol was added according to the weight ratio of dopamine derivative to absolute ethanol of 1:9, stirred and dissolved at room temperature, and then the catalyst was slowly added dropwise under nitrogen protection according to the weight ratio of dopamine derivative to 15.0 M sulfuric acid catalyst of 1:1.6, mixed evenly, heated to 56 °C, and reacted at this temperature for 66 h. Then, the temperature was lowered to room temperature, filtered by suction, and the separated solid was repeatedly washed with absolute ethanol until the pH of the filtrate was 7.0. The washed solid was recrystallized in absolute ethanol at room temperature, filtered and separated, and detected by the analysis method described in the specification of this application. The collected crystals were dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide (DAAM);

[0212] B. Preparation of monomer mixed aqueous solution

[0213] In a reaction vessel, N-hydroxymethylacrylamide, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, octadecyl dimethyl allyl ammonium chloride allyl quaternary ammonium salt cationic monomer and the above dopamine derivative monomer were mixed uniformly in deionized water according to a molar ratio of 78:14:9:2.0:0.10. The obtained monomer mixture solution was adjusted to pH 7.5 with an aqueous sodium hydroxide solution having a concentration of 2.2 M, and thus a monomer mixed aqueous solution with a total monomer content of 30% by weight was obtained;

[0214] C. Synthesis of polymer sol

[0215] Nitrogen was introduced into the monomer mixed aqueous solution obtained in step B for 35 min. At the same time, 2,2'-azobis(2-methylpropylimid) dihydrochloride initiator at 0.5% based on the total weight of the monomer mixture was added, a magnetic stirrer was added, and the reaction vessel was sealed; the reaction vessel was reacted in a constant temperature water bath electromagnetic stirrer at a magnetic stirrer speed of 200 r / min and a temperature of 55 °C for 2.4 h, and then filtered and separated to obtain a light yellow polymer (HAPAMC16D5) sol;

[0216] D. Preparation of polymer powder

[0217] The polymer sol obtained in step C was cooled to room temperature, cut into pieces, washed repeatedly with absolute ethanol until no white substance precipitated on the surface, then transferred to a constant temperature vacuum drying oven and dried at 60 °C for 42 h, pulverized, sieved, and the fraction passing through the sieve collected was the hydrophobic associating polymer (HAPAMC16D2) powder.

[0218] The TG and DTG, apparent viscosity and concentration, apparent viscosity and NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency and solution concentration of the hydrophobic associating polymer prepared in this example were measured and the results were listed in the appendix Figures 3 - 8 below.

[0219] Comparative Example 1: Preparation of partially hydrolyzed polyacrylamide (HPAM)

[0220] The implementation steps of this comparative example are as follows:

[0221] A. Preparation of monomer mixed aqueous solution

[0222] In a reaction vessel, acrylamide, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid sodium salt were mixed uniformly in deionized water according to a molar ratio of 68:18:12. The obtained monomer mixture solution was adjusted to pH 7.0 with an aqueous sodium hydroxide solution having a concentration of 1.8 M, and thus a monomer mixed aqueous solution with a total monomer content of 25% by weight was obtained;

[0223] B. Synthesis of polymer sol

[0224] Nitrogen was introduced into the monomer mixed aqueous solution obtained in step A for 30 min. At the same time, 0.31% of sodium persulfate initiator based on the total weight of the monomer mixture was added, a magnetic stir bar was added, and the reaction vessel was sealed. The reaction vessel was reacted in a constant temperature water bath electromagnetic stirrer at a magnetic stir bar rotation speed of 300 r / min and a temperature of 65 °C for 1.2 h, and then filtered and separated to obtain a white polymer (HPAM) sol;

[0225] C. Preparation of polymer powder

[0226] The polymer sol obtained in step B was cooled to room temperature, cut into pieces, washed repeatedly with absolute ethanol, then transferred to a constant temperature vacuum drying oven and dried at 60 °C for 24 h, pulverized, sieved, and the fraction passing through the sieve was the polymer (HPAM) powder.

[0227] The infrared spectrum of the polymer (HPAM) prepared in this comparative example is listed in the appendix Figure 1 below.

[0228] The measurement results of TG, DTG, apparent viscosity vs. concentration, apparent viscosity vs. NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency vs. solution concentration of the polymer prepared in this comparative example are respectively listed in the appendix Figures 3 - 8 below.

[0229] Comparative Example 2: Hydrophobically associating polymer HAPAMC 16 Preparation

[0230] The implementation steps of this comparative example are as follows:

[0231] A. Preparation of monomer mixed aqueous solution

[0232] In a reaction vessel, acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, and hexadecyl dimethyl allyl ammonium chloride allyl quaternary ammonium salt cationic monomer were mixed evenly in deionized water according to a molar ratio of 68:18:12:0.2. The pH of the obtained monomer mixture solution was adjusted to 7.0 using a 1.8 M aqueous sodium hydroxide solution, and thus a monomer mixed aqueous solution with a total monomer content of 25% by weight was obtained;

[0233] C. Synthesis of polymer sol

[0234] Nitrogen was introduced into the monomer mixed aqueous solution obtained in step B for 30 min. At the same time, 0.31% of sodium persulfate initiator based on the total weight of the monomer mixture was added, a magnetic stir bar was added, and the reaction vessel was sealed. The reaction vessel was reacted in a constant temperature water bath electromagnetic stirrer at a magnetic stir bar rotation speed of 300 r / min and a temperature of 65 °C for 1.2 h, and then filtered and separated to obtain a light yellow polymer (HAPAMC 16) Sol;

[0235] D. Preparation of polymer powder

[0236] Cool the polymer sol obtained in step C to room temperature, cut it into pieces, wash it repeatedly with absolute ethanol until no white substances precipitate on the surface, then transfer it to a constant-temperature vacuum drying oven and dry it at 60 °C for 36 h, crush it, sieve it, and the fraction collected under the sieve is the hydrophobic associating polymer (HAPAMC 16 ) powder.

[0237] The measurement results of TG and DTG, apparent viscosity vs. concentration, apparent viscosity vs. NaCl and CaCl2 concentrations, dissolution rate, and corrosion inhibition efficiency vs. solution concentration of the polymer prepared in this comparative example are listed in the appendix Figures 3 - 8 respectively.

Claims

1. A dopamine derivative-modified hydrophobically associating polymer, characterized in that The described hydrophobic associating polymer has the following chemical structural formula (I): （I） In the formula: R1 represents H, CH2OH or (CH2)2OH; R2 represents H, CH3, CH2CH3, CH2COOH or O(CH2)2COOH; R3 represents (CH2) 11 CH3, (CH2) 15 CH3 or (CH2) 17 CH3; R4 represents H, CH2(CH3)2N + (CH2) 11 CH3, CH2(CH3)2N + (CH2) 15 CH3 or CH2(CH3)2N + (CH2) 17 CH3; m = 49.8 - 95.0 mol%, n = 2 - 25 mol%, p = 3 - 20 mol%, q = 0 - 5 mol% and q is not 0 mol%, x = 0 - 0.2 mol%.

2. The hydrophobically associating polymer according to claim 1, wherein In formula (I), m = 60 - 78 mol%, n = 16 - 22 mol%, p = 6 - 18 mol%, q = 0.2 - 2.0 mol%, x = 0.02 - 0.12 mol%.

3. The preparation method of the hydrophobically associating polymer according to claim 1 or 2, characterized in that The preparation steps of the described preparation method are as follows: A. Preparation of dopamine derivative monomer Mix dopamine hydrochloride and N-hydroxymethylacrylamide evenly according to a molar ratio of 1:3 - 6. Then, add absolute ethanol according to a weight ratio of dopamine derivative to absolute ethanol of 1:4 - 10, stir and dissolve at room temperature. Next, slowly add a catalyst under nitrogen protection according to a weight ratio of dopamine derivative to catalyst of 1:0.5 - 2.0, mix evenly, heat to a temperature of 30 - 65 °C, and react at this temperature for 48 - 120 h. Then, lower the temperature to room temperature, filter, and repeatedly wash the separated solid with absolute ethanol until the pH of the filtrate > 6.

8. Let the washed solid recrystallize in absolute ethanol at room temperature, filter and separate. The collected crystals are the dopamine derivative monomer N-[2,4-bis-(acrylaminomethyl)-3-(2-aminoethyl)-5,6-dihydroxybenzyl]-acrylamide, which has the following chemical structural formula (II): (II) B. Preparation of monomer mixed aqueous solution In a reaction vessel, acrylamide monomer, acrylic acid monomer, 2-acrylamido-2-methylpropanesulfonic acid sodium salt, allyl quaternary ammonium salt cationic monomer and the above dopamine derivative monomer are mixed evenly in deionized water according to a molar ratio of 60 - 78:6 - 22:6 - 18:0.2 - 2.0:0.02 - 0.

12. The obtained monomer mixture solution is adjusted to a pH of 6 - 8 with a sodium hydroxide aqueous solution with a concentration of 1.6 - 2.4 M, and thus a monomer mixed aqueous solution with a total monomer content of 10 - 30% by weight is obtained; C. Synthesis of polymer sol Introduce nitrogen into the monomer mixed aqueous solution obtained in step B for 25 - 35 min. At the same time, add an initiator accounting for 0.05 - 0.5% of the total weight of the monomer mixture, add a magnetic stirrer, and seal the reaction vessel; the reaction vessel reacts in a constant temperature water bath electromagnetic stirrer under the conditions of a magnetic stirrer speed of 100 - 600 r / min and a temperature of 50 - 70 °C for 0.5 - 3.0 h, filter and separate to obtain a light yellow polymer sol; D. Preparation of polymer powder Cool the polymer sol obtained in step C to room temperature, cut it into pieces, repeatedly wash it with absolute ethanol until no white substance precipitates on the surface. Then, transfer it to a constant temperature vacuum drying oven and dry it at a temperature of 55 - 65 °C for 24 - 48 h, pulverize it, sieve it, and the undersize part collected is the hydrophobic associating polymer powder.

4. The preparation method according to claim 3, wherein In step A, the catalyst is sulfuric acid or aluminum chloride, with the sulfuric acid concentration being 15.0 - 18.4 M; the particle size of the aluminum chloride is 4 - 20 mesh.

5. The preparation method according to claim 3, characterized in that In step B, the acrylamide monomer is one or more acrylamide monomers selected from acrylamide, N - hydroxymethylacrylamide, or N - hydroxyethylacrylamide.

6. The preparation method according to claim 3, characterized in that In step B, the acrylic acid monomer is one or more acrylic acid monomers selected from acrylic acid, methacrylic acid, itaconic acid, or β - carboxyethyl acrylate.

7. The preparation method according to claim 3, wherein In step B, the allyl quaternary ammonium salt cationic monomer is one or more allyl quaternary ammonium salt cationic monomers selected from dodecyl dimethyl allyl ammonium chloride, cetyl dimethyl allyl ammonium chloride, or octadecyl dimethyl allyl ammonium chloride.

8. The preparation method according to claim 3, characterized in that In step C, the initiator is one or more initiators selected from sodium persulfate, ammonium persulfate, potassium persulfate, azodiisobutyramidine hydrochloride, or 2,2 - azobis(2 - methylpropylimid) dihydrochloride.

9. The preparation method according to claim 3, wherein In step D, the mesh size of the sieve used is 40 - 80 mesh.

10. A dopamine derivative-modified hydrophobically associating polymer prepared by the preparation method according to any one of claims 3-9, characterized in that The apparent viscosity of its aqueous solution with a mass concentration of 5 g / L is 570 mPa·s or more, its apparent viscosity in an aqueous sodium chloride solution with a mass concentration of 20 g / L is 590 mPa·s or more, and the viscosity retention rate is 87.62% or more; its apparent viscosity in an aqueous calcium chloride solution with a mass concentration of 10 g / L is 342 mPa·s or more, and the viscosity retention rate is 33.4% or more.

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