Salt-tolerant copolymer based on modified polyacrylamide, preparation method and application

Abstract

The invention relates to the technical field of chemical synthesis, and discloses a salt-tolerant copolymer based on modified polyacrylamide as well as a preparation method and application thereof, and the preparation method comprises the following steps: pre-emulsification: dissolving acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, a fluorine-containing functional monomer, a silicon-containing crosslinking monomer and a structure adjusting monomer in deionized water, adding an emulsifier, and stirring to obtain a pre-emulsion; stirring and emulsifying for 20-40 minutes at the temperature of 40-50 DEG C at the speed of 800-1200r / min to obtain a pre-emulsion, initiating polymerization, and by setting a fluorine-containing functional monomer unit, when the copolymer is applied in a high-salinity environment, constructing a hydrophobic association effect among molecular chains and forming a dynamic physical cross-linked network aiming at environments with different salinity, so that the copolymer has a good application prospect. The structural stability of the copolymer under different mineralization degree conditions is guaranteed, meanwhile, the shielding effect of salt ions on molecular chain charges is converted into association driving force in real time, and the durability of the viscosity of a copolymer solution is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, specifically to salt-resistant copolymers based on modified polyacrylamide, their preparation methods, and applications. Background Technology

[0002] Synthesis refers to the process of transforming a relatively simple substance into a complex substance through a chemical reaction.

[0003] Modified polyacrylamide copolymers are important functional polymer materials with wide applications in oilfield development, wastewater treatment and other fields. This is one of the key characteristics of their molecular chains, which contain a variety of active groups. The amide groups can provide good water solubility and adsorption performance, while the sulfonic acid groups endow the polymer with the ability to resist salt ion interference. In order to improve the stability of the copolymer in a high-salt environment, it is usually necessary to introduce salt-resistant functional monomers for structural modification.

[0004] Currently, due to the presence of high concentrations of polyvalent metal ions in oilfield formation water and industrial wastewater, the synergistic effect of hydrophobic associating groups and crosslinking groups in the molecular chain cannot be controlled in real time when copolymers are synthesized under high temperature and high salinity conditions. This can lead to conformational shrinkage or phase separation of copolymer molecules, and there is a lack of effective online correction methods when abnormal molecular chain aggregation occurs.

[0005] Therefore, a salt-resistant copolymer based on modified polyacrylamide, its preparation method, and its application are proposed to solve the above problems. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a salt-resistant copolymer based on modified polyacrylamide, its preparation method, and its application, thus solving the problems mentioned in the background section.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a salt-resistant copolymer based on modified polyacrylamide, its preparation method, and its application, prepared by free radical copolymerization of the following monomer raw materials in parts by weight: Acrylamide 60-80 parts, 15-25 parts of 2-acrylamido-2-methylpropanesulfonic acid 3-8 parts of fluorinated functional monomers, Contains 2-6 parts of silicon crosslinking monomer. 1-4 parts of structure-regulating monomer; The fluorinated functional monomer is at least one of hexafluorobutyl methacrylate and dodecafluoroheptyl acrylate, the silicon-containing crosslinking monomer is γ-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane, and the structure-regulating monomer is diacetone acrylamide or N-hydroxymethylacrylamide.

[0009] Preferably, the mass ratio of the fluorinated functional monomer to the silicon-containing crosslinked monomer is (1.5-2.5):1, and the amount of the structure-modifying monomer added is 30-70% of the mass of the silicon-containing crosslinked monomer.

[0010] Preferably, it includes the following steps: Step 1: Pre-emulsification: Dissolve acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, fluorinated functional monomers, silicon-containing crosslinking monomers and structure-regulating monomers in deionized water, add emulsifier, and emulsify at 800-1200 r / min at 40-50℃ for 20-40 min to obtain a pre-emulsion; Step 2: Initiation of polymerization: Transfer the pre-emulsion to the reactor, purge with nitrogen to remove oxygen for 15-25 min, add the redox initiation system, and react at 50-70℃ for 3-6 h; Step 3: Post-treatment: After the reaction is complete, add chain transfer agent, continue to heat and mature for 1-2 hours, cool and adjust pH to 6-8, precipitate with acetone, wash and dry to obtain salt-resistant copolymer; The redox initiation system consists of ammonium persulfate and sodium bisulfite in a mass ratio of (1-1.5):1, with the amount added being 0.5-1.5% of the total mass of the monomers.

[0011] Preferably, the emulsifier in step one is a compound of hexadecyltrimethylammonium bromide and sorbitan monooleate, with a mass ratio of 1:(0.8-1.2), and the total amount of emulsifier is 1.5-3% of the total mass of monomers.

[0012] Preferably, the reaction process in step two adopts gradient temperature control: the first stage is 50-55℃ for 1-2 hours, the second stage is 60-65℃ for 1.5-3 hours, and the third stage is 68-70℃ for 0.5-1 hours.

[0013] Preferably, the chain transfer agent in step three is isopropanol or dodecyl mercaptan, and the amount added is 0.05-0.15% of the total mass of the monomers, and the chain transfer agent is added when the reaction conversion rate reaches 85-90%.

[0014] Preferably, the drying process in step three is freeze drying, specifically: the precipitated product is pre-frozen at -40°C to -30°C for 4-6 hours, and then dried at a vacuum of 10-50 Pa and a cold trap temperature of -55°C to -45°C for 24-48 hours.

[0015] Preferably, the salt-resistant copolymer is prepared into an aqueous solution with a concentration of 0.1-0.5 wt%, and an inorganic salt stabilizer is added. The inorganic salt stabilizer is a compound of sodium chloride and calcium chloride with a mass ratio of (3-5):1 and a total concentration of 5000-20000 mg / L.

[0016] Preferably, the salt-resistant copolymer is used in combination with polyaluminum chloride. The amount of salt-resistant copolymer added is 0.005-0.02% of the wastewater mass, and the amount of polyaluminum chloride added is 0.01-0.05% of the wastewater mass. After compounding, the mixture is first stirred rapidly at 200-400 r / min for 2-5 min, and then stirred slowly at 50-80 r / min for 10-20 min.

[0017] Preferably, the salt-resistant copolymer is subjected to plasma activation treatment before compounding. The treatment conditions are: nitrogen atmosphere, vacuum degree 1×10⁻²-1×10⁻³Pa, plasma power 300-500W, and treatment time 5-15min.

[0018] (III) Beneficial Effects

[0019] Compared with the prior art, the present invention provides a salt-resistant copolymer based on modified polyacrylamide, a preparation method, and applications, which have the following beneficial effects: 1. In this invention, by setting fluorine-containing functional monomer units, hydrophobic association between molecular chains is constructed when the copolymer is applied in a high-salt environment, and a dynamic physical cross-linking network is formed for different salinity environments. This ensures the structural stability of the copolymer under different mineralization conditions. At the same time, the shielding effect of salt ions on the charge of molecular chains is converted into association driving force in real time, which can resist the problem of molecular chain collapse caused by high concentration of salt ions in real time, ensure the durability of the viscosity of the copolymer solution, and further reduce the impact of salt sensitivity on the application effect.

[0020] 2. In this invention, by setting up a silicon-containing crosslinking control unit, during the synthesis of copolymers under high temperature and high salt conditions, the conformational change process of molecular chains is monitored, and the spatial distribution density of crosslinking groups is adjusted in real time. This allows the polymerization system to avoid disordered aggregation of molecular chains due to high temperature. Furthermore, when the conformation of molecular chains deviates from the preset trajectory, the spatial structure can be corrected in real time through the in-situ formed siloxane crosslinking network. This enables the copolymer molecular chains to quickly restore their ordered arrangement when abnormally aggregated, ensuring the precise controllability of the topological structure of the final product.

[0021] 3. In this invention, by setting a gradient salinity response unit, when the copolymer is applied to different salinity scenarios, the salt-tolerant functional domains partitioned in the molecular chain are activated, the salt ion concentration threshold of the external environment is identified in real time, and the extension mode of the molecular chain is automatically switched according to different salinity levels. This allows the same copolymer to adaptively match the differentiated needs of ultra-high salinity for oil displacement and low salinity for wastewater treatment, avoiding resource waste or effect failure due to performance redundancy or insufficiency, and further improving the performance adaptability and efficiency of the copolymer in cross-domain applications.

[0022] 4. In this invention, by setting a salinity sensing unit, when the copolymer comes into contact with media of different salinities, a preset ion response switch in the molecular chain is triggered to identify the salt ion concentration gradient of the external environment in real time. At the same time, the salinity signal is converted into a molecular chain conformation adjustment instruction, which can dynamically adjust the spatial arrangement ratio of hydrophobic association domains and hydrophilic groups, ensuring that the copolymer maintains a fully extended state in a low-salt environment and automatically shrinks into a dense network in a high-salt environment, further reducing the risk of performance fluctuations caused by sudden changes in salinity.

[0023] 5. In this invention, by setting up an energy optimization unit, the instantaneous heat energy released by the polymerization reaction is captured during the copolymer preparation process and fed back to the temperature gradient control system in real time. At the same time, the excess reaction heat is converted into driving energy for segmented temperature control. This can accurately match the different activation energy requirements of each polymerization stage, ensure the energy balance between the orderly growth of molecular chains in the low-temperature initiation stage and the network strengthening in the high-temperature crosslinking stage, and further reduce the phenomenon of molecular weight distribution broadening caused by ineffective heat dissipation. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0025] Example 1

[0026] Salt-resistant copolymers based on modified polyacrylamide, their preparation methods, and applications are described. These copolymers are prepared from the following monomer raw materials via free radical copolymerization: 60 parts acrylamide 15 parts of 2-acrylamido-2-methylpropanesulfonic acid Three parts of fluorinated functional monomers, Contains 2 parts of silicon crosslinking monomer, One part of the structure-regulating monomer; Among them, the fluorinated functional monomer is at least one of hexafluorobutyl methacrylate and dodecafluoroheptyl acrylate, the silicon-containing crosslinking monomer is γ-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane, and the structure-regulating monomer is diacetone acrylamide or N-hydroxymethylacrylamide. The mass ratio of fluorinated functional monomer to silicon-containing crosslinked monomer is 1.5:1, and the amount of structure-modifying monomer added is 30% of the mass of silicon-containing crosslinked monomer; The following steps are involved: Step 1: Pre-emulsification: Dissolve acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, fluorinated functional monomers, silicon-containing crosslinking monomers and structure-regulating monomers in deionized water, add emulsifier, and emulsify at 800 r / min for 20 min at 40℃ to obtain a pre-emulsion; Step 2: Initiation of polymerization: Transfer the pre-emulsion to the reactor, purge with nitrogen to remove oxygen for 15 min, add the redox initiation system, and react at 50°C for 3 h; Step 3: Post-treatment: After the reaction is complete, add chain transfer agent, continue to heat and mature for 1 hour, cool and adjust pH to 6, precipitate with acetone, wash and dry to obtain salt-resistant copolymer; The redox initiation system consists of ammonium persulfate and sodium bisulfite in a 1:1 mass ratio, with the amount added being 0.5% of the total monomer mass. In step one, the emulsifier is a compound of hexadecyltrimethylammonium bromide and sorbitan monooleate, with a mass ratio of 1:0.8, and the total amount of emulsifier is 1.5% of the total mass of the monomers. The reaction process in step two adopts gradient temperature control: the first stage is 50℃ for 1 hour, the second stage is 60℃ for 1.5 hours, and the third stage is 68℃ for 0.5 hours. In step three, the chain transfer agent is isopropanol or dodecyl mercaptan, and the amount added is 0.05% of the total mass of the monomers. The chain transfer agent is added when the reaction conversion rate reaches 85%. In step three, the drying process adopts freeze drying, specifically: the precipitated product is pre-frozen at -40℃ for 4 hours, and then dried at a vacuum of 10Pa and a cold trap temperature of -55℃ for 24 hours. The salt-resistant copolymer was prepared into an aqueous solution with a concentration of 0.1 wt%, and an inorganic salt stabilizer was added. The inorganic salt stabilizer was a compound of sodium chloride and calcium chloride with a mass ratio of 3:1 and a total concentration of 5000 mg / L. The salt-resistant copolymer was combined with polyaluminum chloride. The amount of salt-resistant copolymer added was 0.005% of the wastewater mass, and the amount of polyaluminum chloride added was 0.01% of the wastewater mass. After the mixture was combined, it was first stirred rapidly at 200 r / min for 2 min, and then stirred slowly at 50 r / min for 10 min. Before compounding, the salt-resistant copolymer was activated by plasma under the following conditions: nitrogen atmosphere, vacuum degree 1×10⁻², plasma power 300W, and treatment time 5min.

[0027] Example 2

[0028] Salt-resistant copolymers based on modified polyacrylamide, their preparation methods, and applications are described. These copolymers are prepared from the following monomer raw materials via free radical copolymerization: 70 parts acrylamide 20 parts of 2-acrylamido-2-methylpropanesulfonic acid 5 parts of fluorinated functional monomers, Contains 4 parts of silicon crosslinking monomer, Three parts of the structure-regulating monomer; Among them, the fluorinated functional monomer is at least one of hexafluorobutyl methacrylate and dodecafluoroheptyl acrylate, the silicon-containing crosslinking monomer is γ-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane, and the structure-regulating monomer is diacetone acrylamide or N-hydroxymethylacrylamide. The mass ratio of fluorinated functional monomer to silicon-containing crosslinked monomer is 2.0:1, and the amount of structure-modifying monomer added is 50% of the mass of silicon-containing crosslinked monomer; The following steps are involved: Step 1: Pre-emulsification: Dissolve acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, fluorinated functional monomers, silicon-containing crosslinking monomers and structure-regulating monomers in deionized water, add emulsifier, and emulsify at 1000 r / min for 30 min at 45℃ to obtain a pre-emulsion; Step 2: Initiation of polymerization: Transfer the pre-emulsion to the reactor, purge with nitrogen to remove oxygen for 20 min, add the redox initiation system, and react at 60℃ for 4 h; Step 3: Post-treatment: After the reaction is complete, add chain transfer agent, continue to heat and mature for 1.5 hours, cool and adjust pH to 7, precipitate with acetone, wash and dry to obtain salt-resistant copolymer; The redox initiation system consists of ammonium persulfate and sodium bisulfite in a mass ratio of 1.2:1, with the amount added being 1.0% of the total monomer mass. In step one, the emulsifier is a compound of hexadecyltrimethylammonium bromide and sorbitan monooleate, with a mass ratio of 1:1.0, and the total amount of emulsifier is 2% of the total mass of the monomers. The reaction process in step two adopts gradient temperature control: the first stage is 53℃ for 1.5h, the second stage is 62℃ for 2h, and the third stage is 69℃ for 0.7h. In step three, the chain transfer agent is isopropanol or dodecyl mercaptan, and the amount added is 0.10% of the total mass of the monomers. The chain transfer agent is added when the reaction conversion rate reaches 87%. In step three, the drying process adopts freeze drying, specifically: the precipitated product is pre-frozen at -35℃ for 5 hours, and then dried at a vacuum of 30Pa and a cold trap temperature of -50℃ for 36 hours. The salt-resistant copolymer was prepared into an aqueous solution with a concentration of 0.3 wt%, and an inorganic salt stabilizer was added. The inorganic salt stabilizer was a compound of sodium chloride and calcium chloride with a mass ratio of 4:1 and a total concentration of 10000 mg / L. The salt-resistant copolymer was used in combination with polyaluminum chloride. The amount of salt-resistant copolymer added was 0.01% of the wastewater mass, and the amount of polyaluminum chloride added was 0.03% of the wastewater mass. After compounding, the mixture was first stirred rapidly at 300 r / min for 4 min, and then stirred slowly at 60 r / min for 15 min. Before compounding, the salt-resistant copolymer was activated by plasma under the following conditions: nitrogen atmosphere, vacuum degree 1×10⁻²Pa, plasma power 400W, and treatment time 10min.

[0029] Example 3

[0030] Salt-resistant copolymers based on modified polyacrylamide, their preparation methods, and applications are described. These copolymers are prepared from the following monomer raw materials via free radical copolymerization: 80 parts of acrylamide 25 parts of 2-acrylamido-2-methylpropanesulfonic acid 8 parts of fluorinated functional monomers, Contains 6 parts of silicon crosslinking monomer, Four parts of structure-regulating monomer; Among them, the fluorinated functional monomer is at least one of hexafluorobutyl methacrylate and dodecafluoroheptyl acrylate, the silicon-containing crosslinking monomer is γ-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane, and the structure-regulating monomer is diacetone acrylamide or N-hydroxymethylacrylamide. The mass ratio of fluorinated functional monomer to silicon-containing crosslinked monomer is 2.5:1, and the amount of structure-modifying monomer added is 70% of the mass of silicon-containing crosslinked monomer; The following steps are involved: Step 1: Pre-emulsification: Dissolve acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, fluorinated functional monomers, silicon-containing crosslinking monomers and structure-regulating monomers in deionized water, add emulsifier, and emulsify at 1200 r / min for 40 min at 50℃ to obtain a pre-emulsion; Step 2: Initiation of polymerization: Transfer the pre-emulsion to the reactor, purge with nitrogen to remove oxygen for 25 min, add the redox initiation system, and react at 70℃ for 6 h; Step 3: Post-treatment: After the reaction is complete, add chain transfer agent, continue to heat and mature for 2 hours, cool and adjust pH to 8, precipitate with acetone, wash and dry to obtain salt-resistant copolymer; The redox initiation system consists of ammonium persulfate and sodium bisulfite in a mass ratio of 1.5:1, with the amount added being 1.5% of the total monomer mass. In step one, the emulsifier is a compound of hexadecyltrimethylammonium bromide and sorbitan monooleate, with a mass ratio of 1:1.2, and the total amount of emulsifier is 3% of the total mass of the monomers. In step two, the reaction process adopts gradient temperature control: the first stage is 55℃ for 2 hours, the second stage is 65℃ for 3 hours, and the third stage is 70℃ for 1 hour. In step three, the chain transfer agent is isopropanol or dodecyl mercaptan, and the amount added is 0.15% of the total mass of the monomers. The chain transfer agent is added when the reaction conversion rate reaches 90%. In step three, the drying process adopts freeze drying, specifically: the precipitated product is pre-frozen at -30℃ for 6 hours, and then dried at a vacuum of 50Pa and a cold trap temperature of -45℃ for 48 hours. The salt-resistant copolymer was prepared into an aqueous solution with a concentration of 0.5 wt%, and an inorganic salt stabilizer was added. The inorganic salt stabilizer was a compound of sodium chloride and calcium chloride with a mass ratio of 5:1 and a total concentration of 20000 mg / L. The salt-resistant copolymer was used in combination with polyaluminum chloride. The amount of salt-resistant copolymer added was 0.02% of the wastewater mass, and the amount of polyaluminum chloride added was 0.05% of the wastewater mass. After compounding, the mixture was first stirred rapidly at 400 r / min for 5 min, and then stirred slowly at 80 r / min for 20 min. Before compounding, the salt-resistant copolymer was activated by plasma under the following conditions: nitrogen atmosphere, vacuum degree 1×10⁻³Pa, plasma power 500W, and treatment time 15min.

[0031] Comparative Example 1: The difference between this comparative example and Example 1 is that no fluorinated functional monomers were added during the copolymerization reaction in this comparative example.

[0032] Comparative Example 2 differs from Example 2 in that no silicon-containing crosslinking monomer was added during the copolymerization reaction.

[0033] Comparative Example 3 differs from Example 3 in that it does not employ a gradient temperature control process.

[0034] Comparative Example 4 differs from Example 3 in that this comparative example was not subjected to plasma activation treatment before application.

[0035] The salt-resistant copolymers prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The test items and test methods are as follows: Salt resistance test: Prepare a 20000 mg / L mineralized salt solution, add the copolymer to form a 0.3 wt% solution, and use a rotational viscometer to measure the initial viscosity and the viscosity after 72 hours of aging, and calculate the viscosity retention rate; Flocculation performance test: The copolymer was added to simulated wastewater containing 5000 mg / L CaCl2, and after settling, the turbidity of the supernatant and the water content of the flocs were measured. Thermal stability test: The copolymer solution was placed in a 90℃ constant temperature chamber, and samples were taken every 24 hours to measure the intrinsic viscosity. The intrinsic viscosity decay rate was calculated over 7 days.

[0036] The test data of the salt-resistant copolymers in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0037] By comparing and analyzing the data in the table, it can be seen that the salt-resistant copolymers prepared using the methods in Examples 1-3 show improved performance compared to the copolymers prepared in Comparative Examples 1-4. This indicates that by incorporating fluorinated functional monomer units, when applying copolymers in high-salt environments, hydrophobic association between molecular chains is constructed, and a dynamic physical cross-linking network is formed for different salinity environments. This ensures the structural stability of the copolymer under different mineralization conditions. Simultaneously, the shielding effect of salt ions on molecular chain charges is converted into association driving force in real time, which can resist the molecular chain collapse problem caused by high concentrations of salt ions, ensuring the durability of the copolymer solution viscosity and further reducing the salt sensitivity effect. By incorporating a silicon-containing crosslinking control unit, the conformational changes of molecular chains are monitored during copolymer synthesis under high-temperature and high-salt conditions. The spatial distribution density of crosslinking groups is adjusted in real time, preventing disordered aggregation of molecular chains due to high temperatures. Furthermore, when the conformation deviates from the preset trajectory, the spatial structure is corrected in real time through an in-situ formed siloxane crosslinking network. This allows the copolymer molecular chains to quickly restore their ordered arrangement during abnormal aggregation, ensuring the precise controllability of the final product's topology. By setting a gradient salinity response unit, the zoned resistance within the molecular chains is activated when the copolymer is applied to different salinity scenarios. The salt functional domain identifies the salt ion concentration threshold of the external environment in real time and automatically switches the extension mode of the molecular chain according to different salinity levels. This allows the same copolymer to adaptively match the differentiated needs of ultra-high salinity in oil displacement and low salinity in wastewater treatment, avoiding resource waste or effect failure due to performance redundancy or insufficiency. This further improves the performance adaptability and efficiency of the copolymer in cross-domain applications. By setting a salinity sensing unit, when the copolymer comes into contact with media of different salinity, a preset ion response switch in the molecular chain is triggered to identify the salt ion concentration gradient of the external environment in real time. At the same time, the salinity signal is converted into a molecular chain conformation adjustment command, which can dynamically adjust the hydrophobic association. The spatial arrangement ratio of domains and hydrophilic groups ensures that the copolymer remains fully extended in a low-salt environment and automatically shrinks into a dense network in a high-salt environment, further reducing the risk of performance fluctuations caused by abrupt changes in salinity. By setting up an energy optimization unit, the instantaneous heat energy released by the polymerization reaction is captured during the copolymer preparation process and fed back to the temperature gradient control system in real time. At the same time, the excess reaction heat is converted into driving energy for segmented temperature control, which can accurately match the differences in activation energy requirements of each polymerization stage, ensuring the energy balance between the orderly growth of molecular chains in the low-temperature initiation stage and the network strengthening in the high-temperature crosslinking stage, and further reducing the widening of molecular weight distribution caused by ineffective heat dissipation.

[0038] By comparing and analyzing the relevant data in the table, it can be seen that the salt-resistant copolymer prepared by the present invention has stability, controllability and adaptability, which indicates that the salt-resistant copolymer and its preparation method have broad application prospects in the fields of oilfield flooding and industrial wastewater treatment.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0040] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A salt-resistant copolymer based on modified polyacrylamide, characterized in that: It is prepared by free radical copolymerization of the following monomer raw materials in parts by weight: Acrylamide 60-80 parts, 15-25 parts of 2-acrylamido-2-methylpropanesulfonic acid 3-8 parts of fluorinated functional monomers, Contains 2-6 parts of silicon crosslinking monomer. 1-4 parts of structure-regulating monomer; The fluorinated functional monomer is at least one of hexafluorobutyl methacrylate and dodecafluoroheptyl acrylate, the silicon-containing crosslinking monomer is γ-methacryloyloxypropyltrimethoxysilane or vinyltriethoxysilane, and the structure-regulating monomer is diacetone acrylamide or N-hydroxymethylacrylamide.

2. The salt-resistant copolymer based on modified polyacrylamide according to claim 1, characterized in that: The mass ratio of the fluorinated functional monomer to the silicon-containing crosslinked monomer is (1.5-2.5):1, and the amount of the structure-modifying monomer added is 30-70% of the mass of the silicon-containing crosslinked monomer.

3. The method for preparing the salt-resistant copolymer according to claim 1, characterized in that: The following steps are involved: Step 1: Pre-emulsification: Dissolve acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, fluorinated functional monomers, silicon-containing crosslinking monomers and structure-regulating monomers in deionized water, add emulsifier, and emulsify at 800-1200 r / min at 40-50℃ for 20-40 min to obtain a pre-emulsion; Step 2: Initiation of polymerization: Transfer the pre-emulsion to the reactor, purge with nitrogen to remove oxygen for 15-25 min, add the redox initiation system, and react at 50-70℃ for 3-6 h; Step 3: Post-treatment: After the reaction is complete, add chain transfer agent, continue to heat and mature for 1-2 hours, cool and adjust pH to 6-8, precipitate with acetone, wash and dry to obtain salt-resistant copolymer; The redox initiation system consists of ammonium persulfate and sodium bisulfite in a mass ratio of (1-1.5):1, with the amount added being 0.5-1.5% of the total mass of the monomers.

4. The method for preparing the salt-resistant copolymer according to claim 3, characterized in that: The emulsifier mentioned in step one is a compound of hexadecyltrimethylammonium bromide and sorbitan monooleate, with a mass ratio of 1:(0.8-1.2), and the total amount of emulsifier is 1.5-3% of the total mass of monomers.

5. The method for preparing the salt-resistant copolymer according to claim 3, characterized in that: In step two, the reaction process adopts gradient temperature control: the first stage is 50-55℃ for 1-2 hours, the second stage is 60-65℃ for 1.5-3 hours, and the third stage is 68-70℃ for 0.5-1 hours.

6. The method for preparing the salt-resistant copolymer according to claim 3, characterized in that: The chain transfer agent mentioned in step three is isopropanol or dodecyl mercaptan, and the amount added is 0.05-0.15% of the total mass of the monomers. The chain transfer agent is added when the reaction conversion rate reaches 85-90%.

7. The method for preparing the salt-resistant copolymer according to claim 3, characterized in that: In step three, the drying process adopts freeze drying, specifically: the precipitated product is pre-frozen at -40℃ to -30℃ for 4-6 hours, and then dried at a vacuum of 10-50Pa and a cold trap temperature of -55℃ to -45℃ for 24-48 hours.

8. The application of the salt-tolerant copolymer according to claim 1 in oilfield displacement agents, characterized in that: The salt-resistant copolymer was prepared into an aqueous solution with a concentration of 0.1-0.5 wt%, and an inorganic salt stabilizer was added. The inorganic salt stabilizer was a compound of sodium chloride and calcium chloride with a mass ratio of (3-5):1 and a total concentration of 5000-20000 mg / L.

9. The application of the salt-resistant copolymer according to claim 1 in industrial wastewater treatment, characterized in that: The salt-resistant copolymer is used in combination with polyaluminum chloride. The amount of salt-resistant copolymer added is 0.005-0.02% of the wastewater mass, and the amount of polyaluminum chloride added is 0.01-0.05% of the wastewater mass. After compounding, the mixture is first stirred rapidly at 200-400 r / min for 2-5 min, and then stirred slowly at 50-80 r / min for 10-20 min.

10. The application of the salt-resistant copolymer according to claim 9 in industrial wastewater treatment, characterized in that: The salt-resistant copolymer is subjected to plasma activation treatment before compounding. The treatment conditions are: nitrogen atmosphere, vacuum degree 1×10⁻²-1×10⁻³Pa, plasma power 300-500W, and treatment time 5-15min.

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