Branched polyacrylamide as well as preparation method and application thereof
By preparing branched polyacrylamide and utilizing the stable coordination bonds of thiol groups and nitrogen heterocycles, the thermal stability and shear resistance of polyacrylamide were improved, solving the problem of performance degradation of traditional products under high salt and shear conditions, and enabling its application in oil extraction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional linear polyacrylamide molecules tend to curl up in high-salt environments and break under shearing, affecting their performance and lifespan.
Branched monomers are prepared by efficient click reaction, and thiol-derived heat-resistant groups and rigid conjugated structures of nitrogen heterocycles are introduced to form stable coordination bonds, thereby enhancing the thermal stability and shear resistance of polyacrylamide.
Under high salt and shear conditions, branched polyacrylamide maintains good viscosity and performance stability, extends service life, and solves the performance degradation problem of traditional products.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of oilfield chemical additives and polymer polymerization technology, and particularly to a branched polyacrylamide, its preparation method and application. Background Technology
[0002] Polyacrylamide is an important water-soluble polymer with excellent flocculation, thickening, and drag-reducing properties, making it widely used in oil extraction, wastewater treatment, mining, and papermaking. However, traditional linear polyacrylamide has drawbacks in use, including the tendency for its molecular chains to coil in high-salt environments, leading to a decline in thickening and flocculation properties; and the tendency for its molecular chains to break under shear stress, affecting its performance and service life.
[0003] Therefore, there is an urgent need for a branched polyacrylamide, its preparation method, and its application. Summary of the Invention
[0004] This invention provides a branched polyacrylamide, its preparation method, and its application. The branched polyacrylamide prepared has both salt resistance, temperature stability, and shear mechanical properties, and has broad application prospects and technical value in the field of oil extraction.
[0005] The present invention provides a method for preparing branched polyacrylamide in a first aspect, comprising: (1) Reaction of polythiol compounds and vinyl monomers yields branched monomers; (2) Mix the amide-containing monomer, the sulfonic acid-containing monomer, the nitrogen-containing heterocyclic vinyl monomer, the branched monomer, deionized water and pH adjuster to obtain a mixed solution; (3) Nitrogen gas is introduced into the mixed solution, and then an initiator is added to initiate the polymerization reaction to obtain the branched polyacrylamide.
[0006] Preferably, in step (1): The polythiol compound is at least one of trimethylolpropane tris(3-mercaptopropionate) and pentaerythritol tetra(3-mercaptopropionate); The vinyl monomer is at least one of styrene, methyl methacrylate, or N-vinylpyrrolidone.
[0007] Preferably, in step (1): the molar ratio of the polythiol compound and the vinyl monomer is 1:1.
[0008] Preferably, step (1) includes: (11) The polythiol compound, the vinyl monomer and 2,2-dimethylolpropionic acid were added sequentially to the reaction vessel and mixed to obtain an initial mixed solution; (12) After purging nitrogen into the initial mixed solution, the reaction vessel is sealed and then subjected to ultraviolet light irradiation. After the irradiation ends, the solution is subjected to rotary evaporation and purification to obtain the branched monomer.
[0009] More preferably, the ultraviolet irradiation time is 1 to 2 hours.
[0010] More preferably, the ultraviolet wavelength used is 365nm.
[0011] More preferably, the molar ratio of 2,2-dimethylolpropionic acid to the polythiol compound is 0.01:1.
[0012] Preferably, in step (2): The amide-containing monomer is at least one selected from acrylamide, N-methylacrylamide, N-hydroxymethylacrylamide, and N-tert-butylacrylamide; The sulfonic acid-containing monomer is at least one of vinyl sulfonic acid, sodium vinyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonic acid, sodium methpropylene sulfonate, sodium allyl sulfonate, p-styrene sulfonic acid, and sodium p-styrene sulfonate.
[0013] More preferably, the sulfonic acid-containing monomer is sodium 2-acrylamide-2-methylpropanesulfonate or p-styrenesulfonic acid.
[0014] Preferably, in step (2): the nitrogen-containing heterocyclic vinyl monomer is at least one of N-vinylcaprolactam, N-vinylimidazole, 2-vinylpyridine and 4-vinylpyridine.
[0015] Preferably, the raw materials used to prepare the branched polyacrylamide are in the following weight proportions: 150-250 parts of the amide-containing monomer, 3-10 parts of the sulfonic acid-containing monomer, 5-10 parts of the nitrogen-containing heterocyclic vinyl monomer, 2-5 parts of the branched monomer, 714-836 parts of deionized water, 4-10 parts of pH adjuster, and 0.03-0.1 parts of initiator.
[0016] Preferably, in step (2): the pH adjuster is at least one of dilute sulfuric acid, dilute hydrochloric acid, acrylic acid, and sodium hydroxide aqueous solution.
[0017] More preferably, the pH of the mixed solution is 6.8 to 7.2.
[0018] Preferably, in step (3): The initiator includes azo initiators and redox initiators; The azo initiator is azobisisobutyronitrile; The redox initiator includes an oxidant and a reducing agent, wherein the oxidant is ammonium persulfate or benzoyl peroxide; and the reducing agent is ferrous sulfate or sodium bisulfite.
[0019] Preferably, in step (3), the nitrogen gas is introduced for 20 to 40 minutes.
[0020] Preferably, in step (3): after the addition of the initiator to initiate the polymerization reaction, the polymerization reaction is made to be exothermic and the temperature is raised until the temperature of the polymerization reaction reaches 30~70℃ and no longer rises, and then kept at the temperature for 3~6 hours to obtain the branched polyacrylamide.
[0021] Secondly, the present invention provides a branched polyacrylamide prepared by the preparation method of the first aspect described above.
[0022] Thirdly, the present invention provides an application of the branched polyacrylamide described in the second aspect above, using the branched polyacrylamide as an additive in the field of oil extraction.
[0023] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention achieves precise functional group grafting through the branched monomers prepared by efficient click reaction, stably combining thiol-derived heat-resistant groups (such as aromatic rings and heterocycles) with the alkenyl skeleton and introducing them into the polyacrylamide molecular chain, thus endowing polyacrylamide with excellent thermal stability; at the same time, the thiol group and metal ions (Ca) 2+ Mg 2+ The coordination of polyacrylamide can form an ion trapping effect, which can inhibit the damage of salt ions to the hydration layer of the molecular chain in a high-salt environment, thereby significantly improving the viscosity retention rate of the polyacrylamide solution and significantly improving the shear resistance of the copolymer.
[0024] (2) The branched polyacrylamide prepared by introducing a rigid conjugated structure of a nitrogen heterocycle in this invention not only significantly improves the thermal stability of the polyacrylamide molecular chain, but also effectively inhibits amide group hydrolysis and main chain breakage, thus extending the half-life. Simultaneously, the nitrogen atom in the nitrogen heterocycle can react with Ca... 2+ Mg 2+ When metal ions form stable coordination bonds, the branched polyacrylamide can still maintain good water solubility in highly mineralized salt solutions, solving the problems of salting out and flocculation that are common in traditional linear polyacrylamide products. This also gives the branched polyacrylamide good shear resistance; when subjected to shear, the molecular chains are not easily broken, maintaining the stability of its performance and extending its service life. Detailed Implementation
[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] This invention provides a method for preparing branched polyacrylamide, the method comprising: (1) Reaction of polythiol compounds and vinyl monomers yields branched monomers; (2) Mix the amide-containing monomer, the sulfonic acid-containing monomer, the nitrogen-containing heterocyclic vinyl monomer, the branched monomer, deionized water and pH adjuster to obtain a mixed solution; (3) Nitrogen gas is introduced into the mixed solution, and then an initiator is added to initiate the polymerization reaction to obtain branched polyacrylamide.
[0027] In this embodiment of the invention, the branched monomer prepared by efficient click reaction achieves precise functional group grafting, stably combining thiol-derived heat-resistant groups (such as aromatic rings and heterocycles) with the alkenyl skeleton and introducing them into the polyacrylamide molecular chain, endowing the polyacrylamide with excellent thermal stability; simultaneously, the thiol group and metal ions (Ca) 2+ Mg 2+ The coordination of polyacrylamide can form an ion trapping effect, which can inhibit the damage of salt ions to the hydration layer of the molecular chain in a high-salt environment, thereby significantly improving the viscosity retention rate of the polyacrylamide solution and significantly improving the shear resistance of the copolymer.
[0028] This invention prepares branched polyacrylamide by introducing a rigid conjugated structure of a nitrogen heterocycle. This not only significantly improves the thermal stability of the polyacrylamide molecular chain but also effectively inhibits amide group hydrolysis and main chain breakage, thus extending the half-life. Simultaneously, the nitrogen atom in the nitrogen heterocycle can react with Ca... 2+ Mg 2+ When metal ions form stable coordination bonds, the branched polyacrylamide can still maintain good water solubility in highly mineralized salt solutions, solving the problems of salting out and flocculation that are common in traditional linear polyacrylamide products. This also gives the branched polyacrylamide good shear resistance; when subjected to shear, the molecular chains are not easily broken, maintaining the stability of its performance and extending its service life.
[0029] In some preferred embodiments, the raw materials used to prepare branched polyacrylamide are in the following weight parts: 150-250 parts of amide-containing monomer (e.g., 150, 155, 160, 165, 170, 175, 180, 190, 200, 210, 220, 230, 240, or 250 parts), 3-10 parts of sulfonic acid-containing monomer (e.g., 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 parts), and 5-10 parts of nitrogen-containing heterocyclic vinyl monomer (e.g., 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 parts). 9.5 or 10 parts), 2 to 5 parts of branched monomer (e.g., 2, 2.5, 3, 3.5, 4, 4.5, or 5 parts), 714 to 836 parts of deionized water (e.g., 714, 720, 740, 750, 760, 780, 800, 810, 820, 830, or 836 parts), 4 to 10 parts of pH adjuster (e.g., 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 parts), and 0.03 to 0.1 parts of initiator (e.g., 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 parts).
[0030] In this invention, the viscosity and properties of branched polyacrylamide are controlled by adjusting the amounts of branched monomers, amide-containing monomers, sulfonic acid-containing monomers, and nitrogen-containing heterocyclic vinyl monomers, so as to ensure that it still has stable properties under high temperature and high salinity conditions.
[0031] In some preferred embodiments, in step (1): The polythiol compound is at least one of trimethylolpropane tris(3-mercaptopropionate) and pentaerythritol tetra(3-mercaptopropionate); The vinyl monomer is at least one of styrene, methyl methacrylate or N-vinylpyrrolidone.
[0032] It should be noted that pentaerythritol tetra(3-mercaptopropionate) is also known as pentaerythritol tetra(3-mercaptopropionic acid) ester.
[0033] It should be noted that at least one refers to a mixture of any one or more of them in any proportion.
[0034] In some preferred embodiments, in step (1), the molar ratio of the polythiol compound and the vinyl monomer is 1:1.
[0035] In some preferred embodiments, step (1) includes: (11) Add polythiol compound, vinyl monomer and 2,2-dimethylolpropionic acid to the reaction vessel in sequence and mix well to obtain an initial mixed solution; (12) After purging nitrogen into the initial mixed solution, the reaction vessel is sealed and then subjected to ultraviolet light. After the light irradiation ends, the product is subjected to rotary evaporation and purification to obtain the branched monomer.
[0036] In some preferred embodiments, the ultraviolet irradiation time is 1 to 2 hours (e.g., 1 hour, 1.5 hours or 2 hours).
[0037] In some preferred embodiments, the ultraviolet wavelength used is 365 nm.
[0038] In some preferred embodiments, the molar ratio of 2,2-dimethylolpropionic acid to the polythiol compound is 0.01:1.
[0039] Specifically, in a reaction flask, a polythiol compound, a vinyl monomer, and 2,2-dimethylolpropionic acid (DMPA) are added sequentially. If dilution is required, tetrahydrofuran (THF) can be added. Nitrogen gas is purged for 10 minutes to remove oxygen from the system, and the reaction flask is then sealed. The reaction flask is placed on a magnetic stirrer, 10-15 cm away from a 365 nm UV lamp, and irradiated at room temperature for 1-2 hours. After the reaction is complete, the solvent is removed by rotary evaporation to obtain the crude product. The crude product is then purified by petroleum ether / ethyl acetate, collected, and vacuum dried to obtain the branched monomer.
[0040] In some preferred embodiments, in step (2): The monomer containing the amide group is at least one of acrylamide, N-methylacrylamide, N-hydroxymethylacrylamide, and N-tert-butylacrylamide; The sulfonic acid-containing monomer is at least one of vinyl sulfonic acid, sodium vinyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonate, sodium methpropylene sulfonate, sodium allyl sulfonate, p-styrene sulfonic acid, and sodium p-styrene sulfonate.
[0041] In some preferred embodiments, in step (2): the sulfonic acid monomer is sodium 2-acrylamide-2-methylpropanesulfonate or p-styrenesulfonic acid.
[0042] In some preferred embodiments, in step (2): the nitrogen-containing heterocyclic vinyl monomer is at least one of N-vinylcaprolactam, N-vinylimidazole, 2-vinylpyridine and 4-vinylpyridine.
[0043] In some preferred embodiments, in step (2): the pH adjuster is at least one of dilute sulfuric acid, dilute hydrochloric acid, acrylic acid, and sodium hydroxide aqueous solution.
[0044] In some preferred embodiments, the pH of the mixed solution is 6.8 to 7.2.
[0045] Experiments have shown that adjusting the pH of the mixed solution to 6.8-7.2 not only avoids the acidity or alkalinity of the reaction medium from affecting the decomposition rate of the initiator and ensures the degree of polymerization of branched polyacrylamide, but also ensures that the reaction medium is neutral, making the preparation process more environmentally friendly.
[0046] In some preferred embodiments, in step (3): Initiators include azo initiators and redox initiators; The azo initiator is azobisisobutyronitrile; Redox initiators include oxidants and reductants. The oxidant is ammonium persulfate or benzoyl peroxide; the reductant is ferrous sulfate or sodium bisulfite.
[0047] In this invention, the composite initiator can increase the temperature of the reaction system by using the heat released from the polymerization reaction initiated by the redox initiator at low temperature. This causes the azo initiator to decompose and generate free radicals to continuously initiate the polymerization reaction, thereby reducing energy consumption while increasing the polymerization conversion rate and the molecular weight of the polymer.
[0048] In some preferred embodiments, in step (3): the nitrogen gas is introduced for 20 to 40 minutes (for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes).
[0049] In some preferred embodiments, in step (3): after adding an initiator to initiate the polymerization reaction, the polymerization reaction is made to be exothermic and the temperature is raised until the temperature of the polymerization reaction reaches 30~70℃ (for example, it can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or 70℃) and the temperature stops rising, and then the temperature is maintained for 3~6h (for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h) to obtain branched polyacrylamide.
[0050] In this invention, oxygen, as a polymerization inhibitor, can affect the polymerization reaction of branched polyacrylamide. Therefore, nitrogen gas needs to be introduced to remove oxygen in order to ensure that the polymerization reaction proceeds normally.
[0051] In this invention, since the reaction process is exothermic, in order to avoid the reaction rate from accelerating at higher temperatures, causing excessive heat release that is difficult to control and may result in overflow or even burns, the initiation temperature is limited to a lower temperature. In this way, the polymerization reaction can be completed by relying on the heat release of the reaction itself after initiation, and the temperature of the system at the end of the reaction is about 30~70°C.
[0052] In this invention, water is used as the reaction medium for the polymerization reaction, which not only reduces costs but also eliminates the environmental pollution caused by organic solvents. The preparation process is simple and requires no heating. Moreover, the reaction medium is in a neutral environment, making the preparation process environmentally friendly, pollution-free, energy-efficient, and producing non-toxic and non-corrosive products that do not generate secondary pollution, thus aligning with the development direction of green and environmentally friendly chemical additives.
[0053] The present invention also provides a branched polyacrylamide, which is prepared by any of the preparation methods described above.
[0054] The present invention also provides an application of branched polyacrylamide, using branched polyacrylamide as an additive in the field of oil extraction; preferably, using branched polyacrylamide as an oil displacement agent.
[0055] Unless otherwise specified, the raw materials used in this invention can be commercially available products or synthesized by existing methods; In this invention, the use of "and / or" between multiple technical features indicates that these technical features are connected by an "and / or" relationship, meaning that it can be any one of these technical features, or any combination of two or more of these technical features.
[0056] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.
[0057] In the following examples and comparative examples, the mass of polythiol compounds, vinyl monomers, amide-containing monomers, sulfonic acid-containing monomers, nitrogen-containing heterocyclic vinyl monomers, branched monomers, deionized water, pH adjusters, and initiators are expressed in parts by mass.
[0058] Preparation of branched monomer A: (11) In a reaction flask, add trimethylolpropane tris(3-mercaptopropionate) (1 mmol), styrene (1 mmol, in equimolar ratio with polythiol compound), and DMPA (0.01 mmol) in sequence and mix well to obtain an initial mixed solution; (12) Purge nitrogen into the initial mixed solution for 10 min to remove oxygen from the system and seal the reaction flask. Then place the reaction flask on a magnetic stirrer and irradiate the reaction at room temperature for 1 hour at a distance of 10 cm from the ultraviolet lamp (wavelength 365 nm). After the reaction is complete, remove the solvent by rotary evaporation to obtain the crude product. Purify the product with ethyl acetate, collect the target product, and dry it under vacuum to obtain branched monomer A.
[0059] Preparation of branched monomer B: (11) In a reaction flask, pentaerythritol tetra(3-mercaptopropionate) (1 mmol), styrene (1 mmol, in equimolar ratio with polythiol compound), and DMPA (0.01 mmol) were added sequentially and mixed to obtain an initial mixed solution; (12) Purge nitrogen into the initial mixed solution for 10 min to remove oxygen from the system and seal the reaction flask. Then place the reaction flask on a magnetic stirrer and irradiate it at room temperature for 1 hour at a distance of 10 cm from the UV lamp (wavelength 365 nm). After the reaction is complete, remove the solvent by rotary evaporation to obtain the crude product. Purify the target product by petroleum ether, collect it, and dry it under vacuum to obtain the branched monomer B.
[0060] Preparation of branched monomer C: (11) In the reaction flask, add pentaerythritol tetra(3-mercaptopropionate) (1 mmol), styrene (1 mmol, in equimolar ratio with polythiol compound), and DMPA (0.01 mmol) in sequence and mix well. Then add 5 mL of THF to obtain the initial mixed solution. (12) Purge nitrogen into the initial mixed solution for 10 min to remove oxygen from the system and seal the reaction flask. Then place the reaction flask on a magnetic stirrer and irradiate it at room temperature for 2 hours at a distance of 15 cm from the UV lamp (wavelength 365 nm). After the reaction is complete, remove the solvent by rotary evaporation to obtain the crude product. Purify the target product by petroleum ether, collect it, and dry it under vacuum to obtain the branched monomer C.
[0061] Example 1 A method for preparing branched polyacrylamide, comprising: 150 parts by weight of acrylamide, 3 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate, 5 parts by weight of N-vinylcaprolactam, 2 parts by weight of branched monomer A, and 835.97 parts by weight of deionized water were thoroughly mixed and added to a reactor. Then, 4 parts by weight of pH adjuster (dilute sulfuric acid or sodium hydroxide aqueous solution) were added to adjust the pH value to 6.8. After purging with nitrogen for 20 minutes, an initiator (0.01 parts by weight of ammonium persulfate and 0.02 parts by weight of azobisisobutyronitrile) was added to initiate the polymerization reaction. After the reaction temperature stopped rising, it was kept at the temperature for another 3 hours to obtain the target product. The target product was crushed, dried, and ground to obtain branched polyacrylamide.
[0062] Example 2 A method for preparing branched polyacrylamide, comprising: 250 parts by weight of acrylamide, 10 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate, 10 parts by weight of N-vinylcaprolactam, 5 parts by weight of branched monomer B, and 714.9 parts by weight of deionized water were thoroughly mixed and added to a reactor. Then, 8 parts by weight of pH adjuster (dilute sulfuric acid or sodium hydroxide aqueous solution) were added to adjust the pH value to 7.0. After purging with nitrogen for 25 minutes, an initiator (0.05 parts by weight of ammonium persulfate and 0.05 parts by weight of azobisisobutyronitrile) was added to initiate the polymerization reaction. After the reaction temperature stopped rising, it was kept at the temperature for another 3 hours to obtain the target product. The target product was crushed, dried, and ground to obtain branched polyacrylamide.
[0063] Example 3 A method for preparing branched polyacrylamide, comprising: 200 parts by weight of acrylamide, 6.5 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate, 7.5 parts by weight of N-vinylcaprolactam, 3.5 parts by weight of branched monomer A, and 775.45 parts by weight of deionized water were thoroughly mixed and added to a reactor. Then, 8 parts by weight of pH adjuster (dilute sulfuric acid or sodium hydroxide aqueous solution) were added to adjust the pH value to 7.1. After purging with nitrogen for 25 minutes, an initiator (0.03 parts by weight of ammonium persulfate and 0.02 parts by weight of azobisisobutyronitrile) was added to initiate the polymerization reaction. After the reaction temperature stopped rising, the temperature was maintained for another 6 hours to obtain the target product. The target product was crushed, dried, and ground to obtain branched polyacrylamide.
[0064] Example 4 A method for preparing branched polyacrylamide, comprising: 200 parts by weight of acrylamide, 6.5 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate, 7.5 parts by weight of N-vinylcaprolactam, 3.5 parts by weight of branched monomer C, and 775.45 parts by weight of deionized water were thoroughly mixed and added to a reactor. Then, 8 parts by weight of pH adjuster (dilute sulfuric acid or sodium hydroxide aqueous solution) were added to adjust the pH value to 7.1. After purging with nitrogen for 25 minutes, an initiator (0.03 parts by weight of ammonium persulfate and 0.02 parts by weight of azobisisobutyronitrile) was added to initiate the polymerization reaction. After the reaction temperature stopped rising, it was kept at the temperature for another 3 hours to obtain the target product. The target product was crushed, dried, and ground to obtain branched polyacrylamide.
[0065] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that branched monomer A was not added; Specifically, 150 parts by weight of acrylamide, 3 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate, 5 parts by weight of N-vinylcaprolactam, and 837.97 parts by weight of deionized water were thoroughly mixed and added to a reaction vessel. Then, 4 parts by weight of pH adjuster (dilute sulfuric acid or sodium hydroxide aqueous solution) were added to adjust the pH value to 6.8. After purging with nitrogen for 20 minutes, an initiator (0.01 parts by weight of ammonium persulfate and 0.02 parts by weight of azobisisobutyronitrile) was added to initiate the polymerization reaction. After the reaction temperature stopped rising, the temperature was maintained for another 3 hours to obtain the target product. The target product was crushed, dried, and ground to obtain polyacrylamide.
[0066] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that N-vinylcaprolactam was not added; Specifically, 150 parts by weight of acrylamide, 3 parts by weight of sodium 2-acrylamido-2-methylpropanesulfonate, 2 parts by weight of branched monomer A2, and 840.97 parts by weight of deionized water were thoroughly mixed and added to a reaction vessel. Then, 4 parts by weight of pH adjuster (dilute sulfuric acid or sodium hydroxide aqueous solution) were added to adjust the pH value to 6.8. After purging with nitrogen for 20 minutes, an initiator (0.01 parts by weight of ammonium persulfate and 0.02 parts by weight of azobisisobutyronitrile) was added to initiate the polymerization reaction. After the reaction temperature stopped rising, it was kept at the temperature for another 3 hours to obtain the target product. The target product was crushed, dried, and ground to obtain polyacrylamide.
[0067] The viscosity of the samples prepared in the examples and comparative examples was tested at different temperatures, and the results are shown in Table 1. Each sample was dissolved in a solution with a mineralization of 100,000 mg / L to prepare a 1500 ppm test solution, and then the viscosity was tested at 45℃, 55℃, 80℃, and 100℃. Specifically, the test solution was prepared as follows: First, accurately weigh (1 / S) g of sample (S is the solid content), accurate to 0.0001 g. Weigh (200-1 / S) g of mineralized water into a 500 mL beaker. Turn on the constant speed stirrer and slowly add the sample along the vortex wall at 400±20 rpm for 30 s. Then stir at a stirring rate of 700±20 rpm for 1 h to obtain a mother liquor concentration of 5000 mg / L. Then take 15.00 g of the mother liquor and add it to a 100 mL beaker, then add 35.00 g of mineralized water (mineralization degree of 100000 mg / L). Stir on a magnetic stirrer at a speed of 300±20 rpm for 15 min to obtain a test solution with a concentration of 1500 mg / L.
[0068] Table 1 As shown in Table 1, in Examples 1 to 4, the polymers with added branched monomers exhibited viscosities above 70 mPa·s under high mineralization conditions at 45°C; and viscosities above 65 mPa·s under high mineralization conditions at 100°C, with viscosity retention rates all above 87.83%. This indicates that the branched polyacrylamide prepared in this invention possesses properties such as salt resistance, temperature resistance, and shear resistance. Comparison of Example 1, Comparative Example 1, and Comparative Example 2 confirms that the absence of nitrogen-containing heterocyclic vinyl monomers or branched monomers leads to poor salt resistance, salt stability, and shear mechanical properties in the prepared polyacrylamide.
[0069] The parts of this invention not described in detail are techniques known to those skilled in the art.
[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing branched polyacrylamide, characterized in that, include: (1) Reaction of polythiol compounds and vinyl monomers yields branched monomers; (2) Mix the amide-containing monomer, the sulfonic acid-containing monomer, the nitrogen-containing heterocyclic vinyl monomer, the branched monomer, deionized water and pH adjuster to obtain a mixed solution; (3) Nitrogen gas is introduced into the mixed solution, and then an initiator is added to initiate the polymerization reaction to obtain the branched polyacrylamide.
2. The preparation method according to claim 1, characterized in that, In step (1): The polythiol compound is at least one of trimethylolpropane tris(3-mercaptopropionate) and pentaerythritol tetra(3-mercaptopropionate); The vinyl monomer is at least one of styrene, methyl methacrylate, or N-vinylpyrrolidone; and / or The molar ratio of the polythiol compound to the vinyl monomer is 1:
1.
3. The preparation method according to claim 1, characterized in that, Step (1) includes: (11) The polythiol compound, the vinyl monomer and 2,2-dimethylolpropionic acid are added sequentially to the reaction vessel and mixed to obtain an initial mixed solution; preferably, the molar ratio of 2,2-dimethylolpropionic acid to the polythiol compound is 0.01:1; (12) After introducing nitrogen into the initial mixed solution, the reaction vessel is sealed and then subjected to ultraviolet light irradiation. After the irradiation ends, only rotary evaporation and purification are performed to obtain the branched monomer. Preferably, the ultraviolet light irradiation time is 1-2 hours. More preferably, the ultraviolet wavelength used is 365 nm.
4. The preparation method according to claim 1, characterized in that, In step (2): The amide-containing monomer is at least one selected from acrylamide, N-methylacrylamide, N-hydroxymethylacrylamide, and N-tert-butylacrylamide; The sulfonic acid-containing monomer is at least one selected from vinyl sulfonic acid, sodium vinyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium 2-acrylamido-2-methylpropanesulfonic acid, sodium methylpropanesulfonate, sodium allyl sulfonate, p-styrene sulfonic acid, and sodium p-styrene sulfonate; preferably sodium 2-acrylamido-2-methylpropanesulfonic acid or p-styrene sulfonic acid; and / or, The nitrogen-containing heterocyclic vinyl monomer is at least one of N-vinylcaprolactam, N-vinylimidazole, 2-vinylpyridine, and 4-vinylpyridine.
5. The preparation method according to claim 1, characterized in that: The raw materials used to prepare the branched polyacrylamide are as follows by weight: 150-250 parts of the amide-containing monomer, 3-10 parts of the sulfonic acid-containing monomer, 5-10 parts of the nitrogen-containing heterocyclic vinyl monomer, 2-5 parts of the branched monomer, 714-836 parts of deionized water, 4-10 parts of pH adjuster, and 0.03-0.1 parts of initiator.
6. The preparation method according to claim 1, characterized in that, In step (2): The pH adjuster is at least one of dilute sulfuric acid, dilute hydrochloric acid, acrylic acid, and sodium hydroxide aqueous solution; preferably, the pH of the mixed solution is 6.8 to 7.
2.
7. The preparation method according to claim 1, characterized in that, In step (3): The initiator includes azo initiators and redox initiators; The azo initiator is azobisisobutyronitrile; The redox initiator includes an oxidant and a reducing agent, wherein the oxidant is ammonium persulfate or benzoyl peroxide; and the reducing agent is ferrous sulfate or sodium bisulfite.
8. The preparation method according to any one of claims 1 to 7, characterized in that, In step (3): The nitrogen gas introduction time is 20-40 minutes; and / or, After the initiator is added to initiate the polymerization reaction, the polymerization reaction is made to rise exothermically until the temperature of the polymerization reaction reaches 30~70℃ and no longer rises. Then, the temperature is maintained for 3~6 hours to obtain the branched polyacrylamide.
9. A branched polyacrylamide prepared by any one of the preparation methods described in claims 1 to 8.
10. An application of the branched polyacrylamide as described in claim 9, characterized in that, The branched polyacrylamide is used as an additive in the field of oil extraction.