A temperature- and salt-resistant polyacrylamide and its preparation method

Abstract

This application relates to a temperature- and salt-resistant polyacrylamide and its preparation method, belonging to the field of polymer materials. The raw materials for preparation include the following components in parts by weight: 80-100 parts acrylamide, 46-72 parts a composite ionic composition, 3.5-5.5 parts a hydrophobic associating monomer, 2-4 parts an emulsifier, 0.05-0.15 parts an initiation system, 15-25 parts a hydrolysate, and a pH adjuster; the composite ionic composition includes 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and dodecyl dimethyl benzyl ammonium chloride. The preparation method includes the following steps: adding acrylamide, the composite ionic composition, and the hydrophobic associating monomer to water, adding an emulsifier, adjusting the pH to neutral with a pH adjuster, stirring to dissolve and deoxygenating, adding the initiation system under a protective atmosphere, stirring and reacting to obtain a polymer colloid, granulating, adding a hydrolysate, hydrolyzing, drying, and pulverizing to obtain the temperature- and salt-resistant polyacrylamide. This application has the effect of improving the salt resistance and temperature resistance of polyacrylamide.

Description

Technical Field

[0001] This application relates to the field of polymer materials, and in particular to a heat- and salt-resistant polyacrylamide and its preparation method. Background Technology

[0002] Polyacrylamide, as an important water-soluble polymer material, has wide applications in oil extraction, wastewater treatment, papermaking, and mining and metallurgy. With the continuous expansion of its applications, especially in oil and gas field development and other complex environments involving high temperatures and high salinity, higher demands are being placed on the temperature and salt resistance of polyacrylamide. Therefore, improving the performance stability of polyacrylamide under extreme conditions has become a key research focus in this field.

[0003] In existing technologies, the following methods are commonly used to improve the temperature and salt resistance of polyacrylamide: First, optimize the polymerization process, including controlling parameters such as polymerization temperature, pressure, and initiator system to control the molecular weight and molecular weight distribution of the polymer; second, introduce functional additives, such as inorganic minerals and small organic molecules, to enhance the structural stability of the polymer through physical or chemical actions; and third, carry out chemical modification, such as introducing salt-resistant functional groups (e.g., sulfonic acid groups) or temperature-resistant structural units into the molecular chain to improve its tolerance to harsh environments.

[0004] However, the aforementioned existing technologies still have significant shortcomings. Traditional polyacrylamide molecules are prone to hydrolysis, breakage, or aggregation under high temperature and high salinity conditions, leading to a significant decrease in solution viscosity and making it difficult to simultaneously achieve good temperature and salt resistance. Especially in extreme environments with high concentrations of calcium and magnesium ions, the performance degradation of existing materials is even more severe, making it difficult to meet the long-term stability requirements of practical engineering applications. Therefore, developing a polyacrylamide with both excellent temperature and salt resistance, and establishing a corresponding preparation method, has significant application value and practical significance. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a heat- and salt-resistant polyacrylamide and its preparation method.

[0006] This application provides a temperature- and salt-resistant polyacrylamide and its preparation method, which adopts the following technical solution: In a first aspect, this application provides a temperature- and salt-resistant polyacrylamide, employing the following technical solution: A heat- and salt-resistant polyacrylamide is prepared from raw materials comprising the following components in parts by weight: 80-100 parts of acrylamide 46-72 parts of composite ionic composition 3.5-5.5 parts of hydrophobic associating monomer 2-4 parts emulsifier Initiating system: 0.05-0.15 parts 15-25 parts of hydrolysate pH adjuster; The composite ionic composition includes 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and dodecyl dimethyl benzyl ammonium chloride.

[0007] The sulfonate groups introduced by 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate in the composite ionic composition form a strong hydration layer on the molecular chain, effectively resisting the compression of the chain structure by salt ions. At the same time, the benzene ring structure of sodium p-styrenesulfonate and the benzyl group in dodecyl dimethyl benzyl ammonium chloride produce a π-π stacking effect, which enhances the rigidity of the molecular chain and inhibits the violent movement of chain segments at high temperatures. The quaternary ammonium salt cation provided by dodecyl dimethyl benzyl ammonium chloride forms an ion pair network with the above two anionic monomers, generating an anti-polyelectrolyte effect in salt solutions, allowing the molecular chain to maintain its extended configuration in a high-mineralization environment. The physical crosslinking network constructed by the hydrophobic associating monomers forms a synergistic stable structure with the ion pair network, further improving the structural integrity of the polymer in high-temperature and high-salt environments, and comprehensively improving the temperature resistance and salt resistance.

[0008] Preferably, the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and dodecyl dimethyl benzyl ammonium chloride is 1:(0.3-0.4):2.2.

[0009] At the aforementioned mass ratio, 2-acrylamido-2-methylpropanesulfonic acid and the sulfonate groups provided by sodium p-styrenesulfonate form a charge balance with the quaternary ammonium salt groups of dodecyl dimethyl benzyl ammonium chloride in terms of molar amount. This allows the polymer molecular chains to exhibit an anti-polyelectrolyte effect in a high-salt environment with a net charge approaching zero. The introduction of salt ions actually promotes the stretching of the molecular chains and improves the salt resistance. At the same time, the benzene ring structure of sodium p-styrenesulfonate and the benzyl groups of dodecyl dimethyl benzyl ammonium chloride form an effective π-π stacking interaction at this ratio. Together with the hydrophobic association of the dodecyl long chain, they construct a rigid framework and physical cross-linking network for the molecular chains, suppressing the coiling and hydrolysis side reactions of the molecular chains under high-temperature conditions and improving the temperature resistance.

[0010] Preferably, the hydrophobic associating monomer comprises N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate.

[0011] The rigid benzene ring side groups of N-phenylacrylamide introduce rigid nodes into the molecular chain, which inhibit the coiling and movement of the molecular chain at high temperatures through steric hindrance, thus improving temperature resistance. The polyoxyethylene ether segments of alkylphenol polyoxyethylene ether acrylate form a nonionic hydrophilic layer, maintaining a stable hydration structure in salt solutions and resisting the compression of the molecular chain by electrolytes, thereby improving salt resistance. At the same time, the hydrophobic groups of both form a reversible physical cross-linked network in water. The strong hydrophobic association of N-phenylacrylamide provides the network framework, while the polyoxyethylene ether segments of alkylphenol polyoxyethylene ether acrylate regulate the association strength and enhance steric stability. The rigid-flexible synergistic hydrophobic association network further improves the structural stability of the polymer in high-temperature and high-salt environments.

[0012] Preferably, the mass ratio of N-phenylacrylamide to alkylphenol polyoxyethylene ether acrylate is 1:(0.8-1.2).

[0013] At the aforementioned mass ratio, the rigid benzene ring side group of N-phenylacrylamide and the hydrophilic polyoxyethylene ether segment of alkylphenol polyoxyethylene ether acrylate form a rigid-flexible synergistic hydrophobic association network. N-phenylacrylamide constructs physical cross-linking nodes through strong hydrophobic interactions, inhibiting the coiling and segment movement of molecular chains at high temperatures, thus improving temperature resistance. The polyoxyethylene ether segment of alkylphenol polyoxyethylene ether acrylate forms a stable hydration layer in salt solutions, resisting the compression of molecular chains by electrolytes. At the same time, its hydrophobic groups moderately regulate the association strength, avoiding the problem of excessive association that may be caused by a single rigid hydrophobic monomer. This allows the polymer to obtain a stable physical cross-linking structure while maintaining good solubility, comprehensively improving both temperature and salt resistance.

[0014] Preferably, the raw materials further include a crosslinking agent, prepared using the following steps: Nano-silica was dispersed in ethanol, and vinyl isocyanate, γ-glycidyl etheroxypropyltrimethoxysilane and dibutyltin dilaurate were added. The mixture was heated and stirred under a protective atmosphere. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the crosslinking agent.

[0015] Introducing polymerizable double bonds into the surface of nano-silica using vinyl isocyanate allows these bonds to covalently embed into the polyacrylamide molecular chain network during polymerization, forming chemical bonding nodes with nanoparticles as crosslinking centers. This inhibits the relative slippage and dissociation of molecular chains at high temperatures, thus improving temperature resistance. γ-glycidyl etheroxypropyltrimethoxysilane introduces epoxy groups into the surface of nano-silica. These epoxy groups can undergo ring-opening reactions with amino groups in the system during post-polymerization treatment or use, constructing a secondary crosslinking network. Simultaneously, the rigid core of the nano-silica itself provides thermal resistance, further restricting the movement of molecular chains at high temperatures. The synergistic effect of these two types of functional groups enables the nanoparticles and polymer matrix to form a strong interfacial bond, enhancing the crosslinking network density and improving the conformational stability of the molecular chains in salt solutions, thereby simultaneously improving both temperature and salt resistance.

[0016] Preferably, the amount of crosslinking agent added is 1-3 parts.

[0017] The above-mentioned addition range allows the crosslinking agent to form a suitable crosslinking density in the polymer system. The vinyl groups introduced on the surface of the crosslinking agent participate in the polymerization reaction to form chemical bonding nodes. After the rigid core of nano-silica is embedded in the molecular chain network, it inhibits the movement of molecular chains at high temperatures through the thermal resistance effect. At the same time, the presence of crosslinking points restricts the excessive coiling of chain segments in salt solutions, thus improving the temperature resistance. The epoxy groups introduced on the surface of the crosslinking agent undergo ring-opening reactions with amino groups in the system to form a secondary crosslinking network. At this addition amount, the crosslinking network forms an interpenetrating structure with the hydrophobic association network of the polymer backbone. The crosslinking points are evenly distributed, and the conformational stability of the molecular chains in salt solutions is enhanced, thus improving the salt resistance.

[0018] Preferably, the mass ratio of the nano-silica, vinyl isocyanate and γ-glycidyl etheroxypropyltrimethoxysilane is 1:(0.45-0.55):0.6.

[0019] At the aforementioned mass ratio, vinyl isocyanate and γ-glycidoxypropyltrimethoxysilane form a bifunctional modified layer on the surface of nano-silica. The isocyanate groups of vinyl isocyanate react with the silanol groups on the surface of nano-silica to introduce polymerizable double bonds. The proportion ensures that the double bond grafting density is sufficient to form chemical crosslinking points centered on nanoparticles during polymerization. At this ratio, γ-glycidoxypropyltrimethoxysilane provides sufficient epoxy groups, which not only firmly anchor to the surface of nanoparticles through its silane structure, but also reserve secondary crosslinking sites for subsequent epoxy-amino ring-opening reactions. The synergistic ratio of the two types of functional groups enables the formation of a uniform bifunctional interface layer on the surface of nano-silica, avoiding insufficient crosslinking or weak interfacial bonding caused by single modification. After embedding into the polymer network, the physical thermal resistance effect of the rigid nano core and the chemical stabilizing effect of the double crosslinking mechanism work together to improve the polymer's structural retention ability at high temperatures and conformational stability in salt solutions, thereby simultaneously improving temperature resistance and salt resistance.

[0020] Preferably, the emulsifier includes sorbitan monooleate and polyoxyethylene sorbitan monooleate.

[0021] Preferably, the initiation system comprises ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride.

[0022] Secondly, this application provides a method for preparing temperature- and salt-resistant polyacrylamide, using the following technical solution: A method for preparing temperature- and salt-resistant polyacrylamide includes the following steps: Acrylamide, a complex ionic composition, and a hydrophobic associating monomer are added to water, an emulsifier is added, and the pH is adjusted to neutral with a pH adjuster. After stirring to dissolve and removing oxygen, an initiation system is added under a protective atmosphere. After stirring and reacting, a polymer colloid is obtained. After granulation, a hydrolyzing agent is added. After hydrolysis, the product is dried and pulverized to obtain polyacrylamide for temperature and salt resistance.

[0023] In summary, this application includes at least one of the following beneficial technical effects: 1. The sulfonate groups introduced by 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate in the composite ionic composition form a strong hydration layer on the molecular chain, effectively resisting the compression of the chain structure by salt ions. At the same time, the benzene ring structure of sodium p-styrenesulfonate and the benzyl group in dodecyl dimethyl benzyl ammonium chloride produce a π-π stacking effect, which enhances the rigidity of the molecular chain and inhibits the violent movement of chain segments at high temperatures. The quaternary ammonium salt cation provided by dodecyl dimethyl benzyl ammonium chloride forms an ion pair network with the above two anionic monomers, generating an anti-polyelectrolyte effect in salt solution, so that the molecular chain maintains its extended configuration in a high-mineralization environment. The physical cross-linking network constructed by the hydrophobic associating monomers forms a synergistic stable structure with the ion pair network, further improving the structural integrity of the polymer in a high-temperature and high-salt environment, and comprehensively improving the temperature resistance and salt resistance.

[0024] 2. The rigid side groups of the benzene ring in N-phenylacrylamide introduce rigid nodes into the molecular chain, which inhibit the coiling and movement of the molecular chain at high temperatures through steric hindrance, thus improving the temperature resistance. The polyoxyethylene ether segments of alkylphenol polyoxyethylene ether acrylate form a nonionic hydrophilic layer, which maintains a stable hydration structure in salt solutions, resists the compression of the molecular chain by electrolytes, and improves the salt resistance. At the same time, the hydrophobic groups of both form a reversible physical cross-linking network in water. The strong hydrophobic association of N-phenylacrylamide provides the network framework, while the polyoxyethylene ether segments of alkylphenol polyoxyethylene ether acrylate regulate the association strength and enhance the steric stabilization effect. The rigid-flexible synergistic hydrophobic association network further improves the structural stability of the polymer in high-temperature and high-salt environments.

[0025] 3. By introducing polymerizable double bonds onto the surface of nano-silica using vinyl isocyanate, these bonds are covalently embedded into the polyacrylamide molecular chain network during polymerization, forming chemical bonding nodes with nanoparticles as crosslinking centers. This inhibits the relative slippage and dissociation of molecular chains at high temperatures, thus improving temperature resistance. γ-glycidyl etheroxypropyltrimethoxysilane introduces epoxy groups onto the surface of nano-silica. These epoxy groups can undergo ring-opening reactions with amino groups in the system during post-polymerization treatment or use, constructing a secondary crosslinking network. Simultaneously, the rigid core of the nano-silica itself provides thermal resistance, further restricting the movement of molecular chains at high temperatures. The synergistic effect of these two types of functional groups enables the nanoparticles and polymer matrix to form a strong interfacial bond, enhancing the crosslinking network density and improving the conformational stability of the molecular chains in salt solutions, thereby simultaneously improving both temperature and salt resistance. Detailed Implementation

[0026] This application discloses a temperature- and salt-resistant polyacrylamide and its preparation method. Unless otherwise specified, all raw materials used in this application are commercially available. The following examples provide further detailed description of this application: Raw material specifications: Acrylamide (CAS No.: 79-06-1), 2-acrylamido-2-methylpropanesulfonic acid (CAS No.: 15214-89-8), sodium p-styrenesulfonate (CAS No.: 2695-37-6), dodecyl dimethyl benzyl ammonium chloride (CAS No.: 139-07-1), N-phenylacrylamide (CAS No.: 2210-25-4), alkylphenol polyoxyethylene ether acrylate (CAS No.: 50974-47-5), purchased from Qingdao Renas Polymer Materials Co., Ltd.; Span-80 and Tween-80 purchased from Haian Petrochemical Plant, Jiangsu Province; persulfate. Ammonium (CAS No.: 7727-54-0), sodium bisulfite (CAS No.: 7631-90-5), and azobisisobutyramidine hydrochloride V-50 were purchased from Jinan Junhe Pharmaceutical Co., Ltd., sodium carbonate (CAS No.: 497-19-8), sodium hydroxide (CAS No.: 1310-73-2), nano silica were purchased from Hubei Huifu Nanomaterials Co., Ltd., vinyl isocyanate (CAS No.: 3555-94-0), γ-glycidoxypropyltrimethoxysilane (CAS No.: 2530-83-8), and dibutyltin dilaurate (CAS No.: 77-58-7). Example 1

[0027] Preparation of temperature- and salt-resistant polyacrylamide Weigh out 80 parts of acrylamide, 46 parts of the composite ionic composition, 3.5 parts of the hydrophobic associating monomer, 2 parts of emulsifier, 0.05 parts of the initiation system, 15 parts of the hydrolysate, and the pH adjuster. The composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.3:2.2. The hydrophobic associating monomer consists of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:0.8. The emulsifier consists of sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 5:1. The initiation system consists of ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride (V-50) in a mass ratio of 2:1:1. The hydrolysate is sodium carbonate, and the pH adjuster is sodium hydroxide.

[0028] Acrylamide, a composite ionic composition, and a hydrophobic associating monomer were added to deionized water (30% solid content). An emulsifier was added, and the pH was adjusted to 7.0 with a pH adjuster. The mixture was stirred at 200 rpm to dissolve the polymer, and then high-purity nitrogen was introduced to remove oxygen for 30 minutes. Under a nitrogen protective atmosphere, an initiation system was added, and the polymerization reaction was initiated at 10°C for 4 hours. The temperature was then raised to 40°C and reacted for 2 hours to obtain a polymer colloid. After granulation, a hydrolyzing agent was added, and the mixture was hydrolyzed at 90°C for 2 hours. After drying and pulverizing, polyacrylamide for temperature and salt resistance was obtained. Example 2

[0029] Weigh out 100 parts of acrylamide, 72 parts of the composite ionic composition, 5.5 parts of the hydrophobic associating monomer, 4 parts of emulsifier, 0.15 parts of the initiation system, 25 parts of the hydrolysate, and the pH adjuster. The composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.4:2.2. The hydrophobic associating monomer consists of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:1.2. The emulsifier consists of sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 5:1. The initiation system consists of ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride (V-50) in a mass ratio of 2:1:1. The hydrolysate is sodium carbonate, and the pH adjuster is sodium hydroxide.

[0030] Acrylamide, a composite ionic composition, and a hydrophobic associating monomer were added to deionized water (30% solid content). An emulsifier was added, and the pH was adjusted to 7.0 with a pH adjuster. The mixture was stirred at 200 rpm to dissolve the polymer, and then high-purity nitrogen was introduced to remove oxygen for 30 minutes. Under a nitrogen protective atmosphere, an initiation system was added, and the polymerization reaction was initiated at 10°C for 4 hours. The temperature was then raised to 40°C and reacted for 2 hours to obtain a polymer colloid. After granulation, a hydrolyzing agent was added, and the mixture was hydrolyzed at 90°C for 2 hours. After drying and pulverizing, polyacrylamide for temperature and salt resistance was obtained. Example 3

[0031] Weigh out 90 parts of acrylamide, 59 parts of the composite ionic composition, 4.5 parts of the hydrophobic associating monomer, 3 parts of emulsifier, 0.1 parts of the initiation system, 20 parts of the hydrolysate, and the pH adjuster. The composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.35:2.2. The hydrophobic associating monomer consists of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:1. The emulsifier consists of sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 5:1. The initiation system consists of ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride (V-50) in a mass ratio of 2:1:1. The hydrolysate is sodium carbonate, and the pH adjuster is sodium hydroxide.

[0032] Acrylamide, a composite ionic composition, and a hydrophobic associating monomer were added to deionized water (30% solid content). An emulsifier was added, and the pH was adjusted to 7.0 with a pH adjuster. The mixture was stirred at 200 rpm to dissolve the polymer, and then high-purity nitrogen was introduced to remove oxygen for 30 minutes. Under a nitrogen protective atmosphere, an initiation system was added, and the polymerization reaction was initiated at 10°C for 4 hours. The temperature was then raised to 40°C and reacted for 2 hours to obtain a polymer colloid. After granulation, a hydrolyzing agent was added, and the mixture was hydrolyzed at 90°C for 2 hours. After drying and pulverizing, polyacrylamide for temperature and salt resistance was obtained. Example 4

[0033] Example 4 is based on Example 3. The only difference between Example 4 and Example 3 is that in Example 4, the composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.2:2.2. Example 5

[0034] Example 5 is based on Example 3. The only difference between Example 5 and Example 3 is that in Example 5, the composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.5:2.2. Example 6

[0035] Example 6 is based on Example 3. The only difference between Example 6 and Example 3 is that in Example 6, the hydrophobic associating monomer is composed of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:0.5. Example 7

[0036] Example 7 is based on Example 3. The only difference between Example 7 and Example 3 is that in Example 7, the hydrophobic associating monomer is composed of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:1.5. Example 8

[0037] Example 8 is based on Example 3. The only difference between Example 8 and Example 3 is that the hydrophobic associating monomer in Example 8 is N-phenylacrylamide. Example 9

[0038] Example 9 is based on Example 3. The only difference between Example 9 and Example 3 is that the hydrophobic associating monomer in Example 9 is alkylphenol polyoxyethylene ether acrylate. Example 10

[0039] Example 10 is based on Example 3. The only difference between Example 10 and Example 3 is that the raw materials prepared in Example 10 also include 1 part of crosslinking agent.

[0040] Preparation of crosslinking agent The mass ratio of nano silica, vinyl isocyanate and γ-glycidyl etheroxypropyltrimethoxysilane is 1:0.45:0.6, the amount of dibutyltin dilaurate accounts for 0.5% of the nano silica, and the particle size of the nano silica is 50-100 nm.

[0041] Nano-silica was ultrasonically dispersed in anhydrous ethanol (solid content 10%), and vinyl isocyanate, γ-glycidyl etheroxypropyltrimethoxysilane and dibutyltin dilaurate were added sequentially. The mixture was heated to 65°C under nitrogen protection and stirred at 200 rpm for 10 h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 50°C for 12 h to obtain the crosslinking agent.

[0042] Preparation of temperature- and salt-resistant polyacrylamide Weigh out 90 parts of acrylamide, 59 parts of the composite ionic composition, 4.5 parts of the hydrophobic associating monomer, 3 parts of emulsifier, 0.1 parts of the initiation system, 20 parts of hydrolysate, 1 part of crosslinking agent, and pH adjuster. The composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.35:2.2. The hydrophobic associating monomer consists of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:1. The emulsifier consists of sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 5:1. The initiation system consists of ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride (V-50) in a mass ratio of 2:1:1. The hydrolysate is sodium carbonate, and the pH adjuster is sodium hydroxide.

[0043] Acrylamide, a composite ionic composition, and a hydrophobic associating monomer were added to deionized water (30% solids content). An emulsifier was added, and the pH was adjusted to 7.0 with a pH adjuster. The mixture was stirred at 200 rpm to dissolve the polymer, and then high-purity nitrogen was introduced to remove oxygen for 30 min. Under a nitrogen protective atmosphere, a crosslinking agent was added, and the mixture was stirred at 200 rpm for 10 min. An initiation system was added, and the polymerization reaction was initiated at 10 °C for 4 h. The temperature was then raised to 40 °C and reacted for 2 h to obtain a polymer colloid. After granulation, a hydrolyzing agent was added, and the mixture was hydrolyzed at 90 °C for 2 h. After drying and pulverizing, polyacrylamide for temperature and salt resistance was obtained. Example 11

[0044] Example 11 is based on Example 3. The only difference between Example 11 and Example 3 is that the raw materials prepared in Example 11 also include 3 parts of crosslinking agent.

[0045] Preparation of crosslinking agent The mass ratio of nano silica, vinyl isocyanate and γ-glycidyl etheroxypropyltrimethoxysilane is 1:0.55:0.6, the amount of dibutyltin dilaurate accounts for 0.5% of the nano silica, and the particle size of the nano silica is 50-100 nm.

[0046] Nano-silica was ultrasonically dispersed in anhydrous ethanol (solid content 10%), and vinyl isocyanate, γ-glycidyl etheroxypropyltrimethoxysilane and dibutyltin dilaurate were added sequentially. The mixture was heated to 65°C under nitrogen protection and stirred at 200 rpm for 10 h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 50°C for 12 h to obtain the crosslinking agent.

[0047] Preparation of temperature- and salt-resistant polyacrylamide Weigh out 90 parts of acrylamide, 59 parts of the composite ionic composition, 4.5 parts of the hydrophobic associating monomer, 3 parts of emulsifier, 0.1 parts of the initiation system, 20 parts of hydrolysate, 3 parts of crosslinking agent, and pH adjuster. The composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.35:2.2. The hydrophobic associating monomer consists of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:1. The emulsifier consists of sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 5:1. The initiation system consists of ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride (V-50) in a mass ratio of 2:1:1. The hydrolysate is sodium carbonate, and the pH adjuster is sodium hydroxide.

[0048] Acrylamide, a composite ionic composition, and a hydrophobic associating monomer were added to deionized water (30% solids content). An emulsifier was added, and the pH was adjusted to 7.0 with a pH adjuster. The mixture was stirred at 200 rpm to dissolve the polymer, and then high-purity nitrogen was introduced to remove oxygen for 30 min. Under a nitrogen protective atmosphere, a crosslinking agent was added, and the mixture was stirred at 200 rpm for 10 min. An initiation system was added, and the polymerization reaction was initiated at 10 °C for 4 h. The temperature was then raised to 40 °C and reacted for 2 h to obtain a polymer colloid. After granulation, a hydrolyzing agent was added, and the mixture was hydrolyzed at 90 °C for 2 h. After drying and pulverizing, polyacrylamide for temperature and salt resistance was obtained. Example 12

[0049] Example 12 is based on Example 3. The only difference between Example 12 and Example 3 is that the raw materials prepared in Example 12 also include 2 parts of crosslinking agent.

[0050] Preparation of crosslinking agent The mass ratio of nano silica, vinyl isocyanate and γ-glycidyl etheroxypropyltrimethoxysilane is 1:0.5:0.6, the amount of dibutyltin dilaurate accounts for 0.5% of the nano silica, and the particle size of the nano silica is 50-100 nm.

[0051] Nano-silica was ultrasonically dispersed in anhydrous ethanol (solid content 10%), and vinyl isocyanate, γ-glycidyl etheroxypropyltrimethoxysilane and dibutyltin dilaurate were added sequentially. The mixture was heated to 65°C under nitrogen protection and stirred at 200 rpm for 10 h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 50°C for 12 h to obtain the crosslinking agent.

[0052] Preparation of temperature- and salt-resistant polyacrylamide Weigh out 90 parts of acrylamide, 59 parts of the composite ionic composition, 4.5 parts of the hydrophobic associating monomer, 3 parts of emulsifier, 0.1 parts of the initiation system, 20 parts of hydrolysate, 2 parts of crosslinking agent, and pH adjuster. The composite ionic composition consists of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1:0.35:2.2. The hydrophobic associating monomer consists of N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate in a mass ratio of 1:1. The emulsifier consists of sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 5:1. The initiation system consists of ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride (V-50) in a mass ratio of 2:1:1. The hydrolysate is sodium carbonate, and the pH adjuster is sodium hydroxide.

[0053] Acrylamide, a composite ionic composition, and a hydrophobic associating monomer were added to deionized water (30% solids content). An emulsifier was added, and the pH was adjusted to 7.0 with a pH adjuster. The mixture was stirred at 200 rpm to dissolve the polymer, and then high-purity nitrogen was introduced to remove oxygen for 30 min. Under a nitrogen protective atmosphere, a crosslinking agent was added, and the mixture was stirred at 200 rpm for 10 min. An initiation system was added, and the polymerization reaction was initiated at 10 °C for 4 h. The temperature was then raised to 40 °C and reacted for 2 h to obtain a polymer colloid. After granulation, a hydrolyzing agent was added, and the mixture was hydrolyzed at 90 °C for 2 h. After drying and pulverizing, polyacrylamide for temperature and salt resistance was obtained. Example 13

[0054] Example 13 is based on Example 12. The only difference between Example 13 and Example 12 is that in Example 13, the mass ratio of nano silica, vinyl isocyanate and γ-glycidoxypropyltrimethoxysilane when preparing the crosslinking agent is 1:0.35:0.6. Example 14

[0055] Example 14 is based on Example 12. The only difference between Example 14 and Example 12 is that in Example 14, the mass ratio of nano silica, vinyl isocyanate and γ-glycidoxypropyltrimethoxysilane is 1:0.65:0.6 when preparing the crosslinking agent. Example 15

[0056] Example 15 is based on Example 12. The only difference between Example 15 and Example 12 is that the amount of crosslinking agent added in Example 15 is 0.5 parts. Example 16

[0057] Example 16 is based on Example 12. The only difference between Example 16 and Example 12 is that the amount of crosslinking agent added in Example 16 is 5 parts. Example 17

[0058] Example 17 is based on Example 12. The only difference between Example 17 and Example 12 is that γ-glycidoxypropyltrimethoxysilane is not added when preparing the crosslinking agent in Example 17.

[0059] Preparation of crosslinking agent The mass ratio of nano-silica to vinyl isocyanate is 1:0.5, the amount of dibutyltin dilaurate is 0.5% of the nano-silica, and the particle size of the nano-silica is 50-100nm.

[0060] Nano-silica was ultrasonically dispersed in anhydrous ethanol (solid content 10%), and vinyl isocyanate and dibutyltin dilaurate were added sequentially. The mixture was heated to 65°C under nitrogen protection and stirred at 200 rpm for 10 h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 50°C for 12 h to obtain the crosslinking agent.

[0061] Comparative Example 1 Comparative Example 1 is based on Example 3. The only difference between Comparative Example 1 and Example 3 is that the composite ionic composition in Comparative Example 1 consists of 2-acrylamido-2-methylpropanesulfonic acid and dodecyl dimethyl benzyl ammonium chloride in a mass ratio of 1.35:2.2.

[0062] Comparative Example 2 Comparative Example 2 is based on Example 3. The only difference between Comparative Example 2 and Example 3 is that the composite ionic composition in Comparative Example 2 consists of 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrenesulfonate in a mass ratio of 1:0.35.

[0063] Comparative Example 3 Comparative Example 3 is based on Example 3, except that the composite ionic composition in Comparative Example 3 is replaced with an equal mass of 2-acrylamido-2-methylpropanesulfonic acid. Performance testing experiment

[0064] The standard used was ASTM D2196-20, "Standard Test Method for Determination of Rheological Properties of Non-Newtonian Materials by Rotational Viscometer". The sample was prepared into a 0.5% (w / w) polymer aqueous solution. Steady-state measurement was performed for 300 s at 25°C and a shear rate of 7.34 s⁻¹, and the initial apparent viscosity was recorded. The sample was then transferred to a high-temperature aging bottle, sealed with nitrogen, and cured in a constant-temperature drying oven at 85°C for 60 days. After cooling to 25°C, the apparent viscosity after aging was measured, and the ratio of the aged apparent viscosity to the initial apparent viscosity was recorded as the viscosity retention rate after aging. Alternatively, the sample was dissolved in 50000 mg / L NaCl brine to prepare a 0.5% (w / w) polymer aqueous solution. Steady-state measurement was performed for 300 s at 25°C and a shear rate of 7.34 s⁻¹, and the apparent viscosity in the brine was measured. The ratio of the apparent viscosity in the brine to the initial apparent viscosity was recorded as the brine viscosity retention rate.

[0065] Table 1. Test results of viscosity, temperature resistance, and salt resistance. Test results Apparent viscosity (mPa·s) Viscosity retention rate after aging (%) Brine viscosity retention rate (%) Example 1 128 80.9 85.4 Example 2 135 80.3 84.8 Example 3 132 81.5 86.1 Example 4 124 78.5 79.2 Example 5 138 79.8 83.5 Example 6 125 81.8 84.6 Example 7 134 80.0 86.3 Example 8 112 83.2 75.8 Example 9 120 72.5 87.4 Example 10 138 84.5 88.2 Example 11 145 86.3 89.8 Example 12 151 87.2 90.5 Example 13 141 84.1 88.0 Example 14 140 84.3 87.5 Example 15 136 83.5 87.6 Example 16 125 82.0 86.8 Example 17 138 82.5 86.3 Comparative Example 1 118 74.5 70.3 Comparative Example 2 125 78.2 73.5 Comparative Example 3 108 68.5 62.0 As shown in Table 1, the apparent viscosity of Examples 1-3 is above 128 mPa·s, the viscosity retention rate after aging is above 80.3%, and the viscosity retention rate in brine is above 84.8%, thus demonstrating that the polyacrylamide prepared in this application has good temperature resistance and salt resistance.

[0066] As shown in Table 1, the only difference between Examples 4 and 5 and Example 3 is that the limited ratio of the composite ionic composition was changed in Examples 4 and 5. Too high or too low a ratio will affect the synergistic effect between the components and the balance of performance.

[0067] As shown in Table 1, the difference between Examples 6-9 and Example 3 is only that: in Examples 6 and 7, the limited ratio of hydrophobic associating monomers was changed, and the ratio of rigid and flexible monomers would affect the balance of performance; in Examples 8 and 9, only one monomer was used, lacking the synergistic effect of compounding, and the balance of performance was further disrupted.

[0068] As shown in Table 1, the difference between Examples 10-17 and Example 3 is only that: in Examples 10-12, a limited amount of crosslinking agent was added to form a chemical crosslinking-physical reinforcement dual network structure, which improved the performance of polyacrylamide; in Examples 13 and 14, the synthesis ratio of the crosslinking agent was changed, affecting the balance of performance; in Examples 15 and 16, too little addition would lead to insufficient crosslinking, and too much addition would lead to a decrease in solubility; in Example 17, γ-glycidoxypropyltrimethoxysilane was not added when preparing the crosslinking agent, which lacked epoxy group interface reinforcement and secondary crosslinking function, resulting in a decrease in the performance improvement effect.

[0069] As shown in Table 1, the only difference between Comparative Examples 1-3 and Example 3 is that: Comparative Example 1 lacks the rigidity of the benzene ring and the synergistic effect of disulfonic acid, resulting in a decrease in both temperature and salt resistance; Comparative Example 2 lacks cationic monomers, has no ion-pair network, and no anti-polyelectrolyte effect, resulting in a decrease in performance; and Comparative Example 3 uses only 2-acrylamido-2-methylpropanesulfonic acid, further deteriorating its performance.

[0070] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. An anti-temperature and anti-salt polyacrylamide, characterized in that: The raw materials for preparation include the following components in parts by weight: 80-100 parts of acrylamide 46-72 parts of composite ionic composition 3.5-5.5 parts of hydrophobic associating monomer 2-4 parts emulsifier Initiating system: 0.05-0.15 parts 15-25 parts of hydrolysate pH adjuster; The composite ionic composition includes 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and dodecyl dimethyl benzyl ammonium chloride.

2. The temperature and salt resistant polyacrylamide according to claim 1, characterized by: The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, and dodecyl dimethyl benzyl ammonium chloride is 1:(0.3-0.4):2.

2.

3. The temperature and salt resistant polyacrylamide according to claim 1, characterized by: The hydrophobic associating monomers include N-phenylacrylamide and alkylphenol polyoxyethylene ether acrylate.

4. The temperature and salt resistant polyacrylamide according to claim 3, characterized by: The mass ratio of N-phenylacrylamide to alkylphenol polyoxyethylene ether acrylate is 1:(0.8-1.2).

5. The temperature- and salt-resistant polyacrylamide according to claim 1, characterized in that: The raw materials used in the preparation also include a crosslinking agent, which is prepared using the following steps: Nano-silica was dispersed in ethanol, and vinyl isocyanate, γ-glycidyl etheroxypropyltrimethoxysilane and dibutyltin dilaurate were added. The mixture was heated and stirred under a protective atmosphere. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the crosslinking agent.

6. The temperature- and salt-resistant polyacrylamide according to claim 5, characterized in that: The amount of crosslinking agent added is 1-3 parts.

7. The temperature- and salt-resistant polyacrylamide according to claim 6, characterized in that: The mass ratio of the nano-silica, vinyl isocyanate and γ-glycidyl etheroxypropyltrimethoxysilane is 1:(0.45-0.55):0.

6.

8. The temperature- and salt-resistant polyacrylamide according to claim 1, characterized in that: The emulsifiers include sorbitan monooleate and polyoxyethylene sorbitan monooleate.

9. The temperature- and salt-resistant polyacrylamide according to claim 1, characterized in that: The initiation system includes ammonium persulfate, sodium bisulfite, and azobisisobutyramidine hydrochloride.

10. A method for preparing temperature- and salt-resistant polyacrylamide as described in any one of claims 1-9, characterized in that: Includes the following steps: Acrylamide, a complex ionic composition, and a hydrophobic associating monomer are added to water, an emulsifier is added, and the pH is adjusted to neutral with a pH adjuster. After stirring to dissolve and removing oxygen, an initiation system is added under a protective atmosphere. After stirring and reacting, a polymer colloid is obtained. After granulation, a hydrolyzing agent is added. After hydrolysis, the product is dried and pulverized to obtain polyacrylamide for temperature and salt resistance.