Additive for improving salt tolerance stability of polyacrylamide emulsion and preparation method thereof

Abstract

This invention discloses an additive for improving the salt stability of polyacrylamide emulsions and its preparation method, relating to the field of stabilizing agents for polyacrylamide emulsions. The additive is obtained by copolymerizing N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate in a specific ratio. Adding this additive during the production of polyacrylamide emulsions can effectively improve their high-salt stability.

Description

Technical Field

[0001] This invention relates to the field of additives for stabilizing polyacrylamide emulsions, and in particular to an additive for improving the salt resistance of polyacrylamide emulsions and its preparation method. Background Technology

[0002] Polyacrylamide-based water-soluble polymers are widely used in various industrial fields, such as water treatment and offshore oil production, due to their excellent water solubility and thickening properties.

[0003] Currently, polyacrylamide exists in two forms: solid powder and liquid polyacrylamide emulsion. Both solid powder and liquid polyacrylamide emulsions are prepared using water and diluted with seawater when used for offshore oilfield enhanced oil recovery. Compared to solid powder polyacrylamide, liquid polyacrylamide emulsions have the advantage of faster dissolution time and are widely used in offshore oilfield enhanced oil recovery.

[0004] However, seawater is highly saline, and the viscosity of liquid polyacrylamide emulsion tends to decrease rapidly in a high-salt environment. Therefore, diluted polyacrylamide emulsion needs to be used promptly. Otherwise, if the polyacrylamide emulsion diluted with seawater is stored for a long time, its viscosity will decrease rapidly, which will greatly reduce the crude oil recovery rate.

[0005] Therefore, providing an additive that can improve the stability of polyacrylamide emulsions in high-salt environments is of great research significance. Summary of the Invention

[0006] To address the issue of rapid viscosity decline in polyacrylamide emulsions under high-salt conditions, this application provides an additive for improving the salt resistance stability of polyacrylamide emulsions and its preparation method.

[0007] This application provides an additive for improving the salt resistance of polyacrylamide emulsions, comprising the following raw materials in parts by weight: Monomer: 10-20 parts Initiator: 0.1-0.3 parts Emulsifier: 0.5-1 part Chain transfer agent: 0.03-0.06 parts Solvent: 100 parts The monomers include N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate, wherein the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is (0.5-1):1:(0.5-1).

[0008] When an additive, prepared by copolymerizing N-vinyl-2-pyrrolidone, vinyl-terminated silicone oil, and dimethylaminoethyl methacrylate in a specific ratio, is added to the comonomer of polyacrylamide to prepare a polyacrylamide emulsion, the polyacrylamide emulsion exhibits good viscosity stability under high salt conditions. This indicates that adding the additive of this application to the polyacrylamide emulsion can effectively improve its stability under high salt conditions. The inventors believe the reason for this is that the additive segments are embedded in the long chain of polyacrylamide. The polyacrylamide segments are structurally stable under high salt conditions and are not prone to curling or chain breakage, thus giving the polyacrylamide emulsion excellent viscosity stability.

[0009] Optionally, the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil and dimethylaminoethyl methacrylate is (0.6-0.8):1:(0.7-0.9).

[0010] When the weight ratio of N-vinyl-2-pyrrolidone, vinyl-terminated silicone oil and dimethylaminoethyl methacrylate is in the range of (0.6-0.8):1:(0.7-0.9), the additive can further improve the viscosity stability of polyacrylamide emulsion under high salt conditions, and at the same time, it is also beneficial to effectively improve the storage stability of the additive itself.

[0011] Optionally, the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is 0.7:1:0.8.

[0012] When the weight ratio of N-vinyl-2-pyrrolidone, vinyl-terminated silicone oil and dimethylaminoethyl methacrylate is 0.7:1:0.8, the additive can further improve the viscosity stability of polyacrylamide emulsion under high salt conditions.

[0013] Optionally, the viscosity of the end-vinyl silicone oil is 5000-60000.

[0014] When the viscosity of the vinyl-terminated silicone oil is 5000-60000, the additive exhibits good storage stability.

[0015] Optionally, the viscosity of the end-vinyl silicone oil is 20,000-40,000.

[0016] When the viscosity of the vinyl-terminated silicone oil is 20,000-40,000, the storage stability of the additive can be further improved. At the same time, the additive prepared by using the vinyl-terminated silicone oil in this viscosity range with N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate can further improve the viscosity stability of polyacrylamide emulsion under high salt conditions.

[0017] Optionally, the emulsifier includes isotretinoin polyoxyethylene ether and sodium fatty alcohol polyoxyethylene ether sulfate, wherein the weight ratio of isotretinoin polyoxyethylene ether to sodium fatty alcohol polyoxyethylene ether sulfate is 1:(3-4).

[0018] The emulsifier is a combination of isotridecyl alcohol polyoxyethylene ether and sodium fatty alcohol polyoxyethylene ether sulfate in a specific ratio, which can further improve the storage stability of the additive.

[0019] Optionally, the chain transfer agent is selected from at least one of isopropanol, mercaptopropionic acid, mercaptoethanol, mercaptoacetic acid, n-butanethiol, and tert-butanethiol.

[0020] Isopropanol, mercaptopropionic acid, mercaptoethanol, mercaptoacetic acid, n-butanethiol, and tert-butanethiol are all water-soluble chain transfer agents, which are beneficial to the continued progress of the reaction.

[0021] Optionally, the initiator is selected from at least one of water-soluble azo initiators and persulfate initiators.

[0022] The water-soluble azo initiator is selected from at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylammonium valerate, and azobisisopropylimidazoline.

[0023] The persulfate initiator is selected from at least one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0024] Secondly, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion provided in this application adopts the following technical solution: A method for preparing an additive to improve the salt resistance stability of polyacrylamide emulsions includes the following steps: According to the formula, N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate are added to 60-70% of the total mass of the solvent and stirred evenly to obtain a mixed monomer solution. Add the emulsifier to 10-20% of the total mass of the solvent and stir until homogeneous to obtain an emulsifier solution; Add the initiator to the remaining solvent and stir until homogeneous to obtain the initiator solution; Vinyl-terminated silicone oil, emulsifier solution, and chain transfer agent are added to a mixed monomer solution and stirred until homogeneous. Under nitrogen protection, an initiator solution is added dropwise, and the reaction system temperature is controlled at 30-65℃. The reaction is carried out for 2-3 hours to obtain an additive that improves the salt resistance stability of polyacrylamide emulsion.

[0025] The additives prepared using the above method can effectively reduce the residual amount of monomers.

[0026] Optionally, the reaction system temperature can be controlled at 50-55℃, and the reaction time can be 2-3 hours.

[0027] Controlling the reaction system temperature at 50-55℃ can further improve the high-salt stability of the additive on the polyacrylamide emulsion.

[0028] In summary, the technical solution of this application has at least the following beneficial effects: 1. The additive in this application is prepared by copolymerization of three monomers in a specific ratio: N-vinyl-2-pyrrolidone, vinyl-terminated silicone oil, and dimethylaminoethyl methacrylate. In the process of synthesizing polyacrylamide emulsion, the addition of the additive in this application can effectively improve the structural stability of polyacrylamide segments under high salt conditions, which is beneficial to improving the high salt stability of polyacrylamide emulsion.

[0029] 2. The additives in this application have good storage stability and can be stored for more than 2 years, which helps to reduce the waste of resources. Detailed Implementation

[0030] The following detailed explanation of this application is based on specific experiments. Example

[0031]

Example 1

[0032] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion includes the following steps: N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate are added to 65 kg of water according to the ratio, and stirred evenly to obtain a mixed monomer solution. Add isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate to 15 kg of water according to the ratio, stir evenly to obtain an emulsifier solution; Add ammonium persulfate to 20 kg of water and stir until homogeneous to obtain an initiator solution; Vinyl-terminated silicone oil, emulsifier solution, and n-butanethiol were added to a mixed monomer solution and stirred until homogeneous. Then, under nitrogen protection, an initiator solution was added dropwise. The reaction system temperature was controlled at 30°C, and the reaction was carried out for 2.5 hours to obtain an additive that improves the salt resistance stability of polyacrylamide emulsion.

[0033]

Example 2

[0034] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0035]

Example 3

[0036] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0037]

Example 4

[0038] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0039]

Example 5

[0040] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0041]

Example 6

[0042] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0043]

Example 7

[0044] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0045]

Example 8

[0046] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0047]

Example 9

[0048] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0049]

Example 10

[0050] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0051]

Example 11

[0052] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0053]

Example 12

[0054] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0055]

Example 13

[0056] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion is the same as that in Example [1].

[0057] Example

[14] An additive for improving the salt resistance stability of polyacrylamide emulsions, comprising the following raw materials: Monomer: 15 kg, comprising N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate, with a weight ratio of 0.7:1:0.8; wherein the molecular weight of the terminal vinyl silicone oil is 40,000. Initiator: 0.2 kg, ammonium persulfate is preferred; Emulsifier: 0.75 kg, including isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate, with a weight ratio of isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate of 1:4; Chain transfer agent: 0.045 kg, n-Butyl mercaptan is selected; Solvent: 100kg, water is preferred.

[0058] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion includes the following steps: N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate are added to 65 kg of water according to the ratio, and stirred evenly to obtain a mixed monomer solution. Add isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate to 15 kg of water according to the ratio, stir evenly to obtain an emulsifier solution; Add ammonium persulfate to 20 kg of water and stir until homogeneous to obtain an initiator solution; Vinyl-terminated silicone oil, emulsifier solution, and n-butanethiol were added to a mixed monomer solution and stirred until homogeneous. Then, under nitrogen protection, an initiator solution was added dropwise. The reaction system temperature was controlled at 50°C, and the reaction was carried out for 2.5 hours to obtain an additive that improves the salt resistance stability of polyacrylamide emulsion.

[0059] Example

[15] An additive for improving the salt resistance stability of polyacrylamide emulsions, comprising the following raw materials: Monomer: 15 kg, comprising N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate, with a weight ratio of 0.7:1:0.8; wherein the molecular weight of the terminal vinyl silicone oil is 40,000. Initiator: 0.2 kg, ammonium persulfate is preferred; Emulsifier: 0.75 kg, including isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate, with a weight ratio of isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate of 1:4; Chain transfer agent: 0.045 kg, n-Butyl mercaptan is selected; Solvent: 100kg, water is preferred.

[0060] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion includes the following steps: N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate are added to 65 kg of water according to the ratio, and stirred evenly to obtain a mixed monomer solution. Add isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate to 15 kg of water according to the ratio, stir evenly to obtain an emulsifier solution; Add ammonium persulfate to 20 kg of water and stir until homogeneous to obtain an initiator solution; Vinyl-terminated silicone oil, emulsifier solution, and n-butanethiol were added to a mixed monomer solution and stirred until homogeneous. Then, under nitrogen protection, an initiator solution was added dropwise. The reaction system temperature was controlled at 55°C, and the reaction was carried out for 2.5 hours to obtain an additive that improves the salt resistance stability of polyacrylamide emulsion.

[0061] Example

[16] An additive for improving the salt resistance stability of polyacrylamide emulsions, comprising the following raw materials: Monomer: 15 kg, comprising N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate, with a weight ratio of 0.7:1:0.8; wherein the molecular weight of the terminal vinyl silicone oil is 40,000. Initiator: 0.2 kg, ammonium persulfate is preferred; Emulsifier: 0.75 kg, including isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate, with a weight ratio of isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate of 1:4; Chain transfer agent: 0.045 kg, n-Butyl mercaptan is selected; Solvent: 100kg, water is preferred.

[0062] In this embodiment, the preparation method of the additive for improving the salt resistance stability of polyacrylamide emulsion includes the following steps: N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate are added to 65 kg of water according to the ratio, and stirred evenly to obtain a mixed monomer solution. Add isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate to 15 kg of water according to the ratio, stir evenly to obtain an emulsifier solution; Add ammonium persulfate to 20 kg of water and stir until homogeneous to obtain an initiator solution; Vinyl-terminated silicone oil, emulsifier solution, and n-butanethiol were added to a mixed monomer solution and stirred until homogeneous. Then, under nitrogen protection, an initiator solution was added dropwise. The reaction system temperature was controlled at 60°C, and the reaction was carried out for 2.5 hours to obtain an additive that improves the salt resistance stability of polyacrylamide emulsion.

[0063] Comparative Example Comparative Example 1 An additive for improving the salt resistance of polyacrylamide emulsions differs from Example 1 in that the monomer composition is different.

[0064] In this comparative example, the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is 1:0.5:1.

[0065] Comparative Example 2 An additive for improving the salt resistance of polyacrylamide emulsions differs from Example 1 in that the monomer composition is different.

[0066] In this comparative example, the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is 0.5:1:2.

[0067] Comparative Example 3 An additive for improving the salt resistance of polyacrylamide emulsions differs from Example 1 in that the monomer composition is different.

[0068] In this comparative example, N-vinyl-2-pyrrolidone was replaced with an equal amount of dimethylaminoethyl methacrylate.

[0069] Comparative Example 4 An additive for improving the salt resistance of polyacrylamide emulsions differs from Example 1 in that the monomer composition is different.

[0070] In this comparative example, dimethylaminoethyl methacrylate was replaced with an equal amount of N-vinyl-2-pyrrolidone.

[0071] Comparative Example 5 An additive for improving the salt resistance of polyacrylamide emulsions differs from Example 1 in that the monomer composition is different.

[0072] In this comparative example, the vinyl-terminated silicone oil was replaced with an equal amount of amino-terminated silicone oil.

[0073] Comparative Example 6 An additive for improving the salt resistance of polyacrylamide emulsions differs from Example 1 in that the monomer composition is different.

[0074] In this comparative example, the monomers include N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate, with a weight ratio of 0.5:1 between N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate.

[0075] Performance testing Preparation of polyacrylamide emulsion samples: Add 6 kg of Span80 and 1.6 kg of OP-10 to 50 kg of white oil and stir until homogeneous to obtain premix A; Add 8 kg of acrylamide, 1 kg of dimethyl diallyl ammonium chloride, 0.2 kg of N,N'-methylenebisacrylamide, 5 kg of additives and 0.05 kg of n-butanethiol to 30 kg of water, stir until completely dissolved, adjust the pH to neutral, and add 1 kg of 0.5% ammonium persulfate aqueous solution to obtain premix B. After mixing premix A and premix B evenly, the mixture was stirred under nitrogen for 30 minutes, then 0.5 kg of 0.5% sodium bisulfite aqueous solution was added, the mixture was heated to 60°C and reacted for 2 hours, and then cooled to room temperature to obtain polyacrylamide emulsion.

[0076] The additives used were those prepared in Examples 1-16 and Comparative Examples 1-6, respectively, to obtain polyacrylamide emulsions prepared with different additives.

[0077] 1. Salt stability of polyacrylamide emulsion: 20g of polyacrylamide emulsion was dispersed in 100mL of saline solution I to prepare a polyacrylamide emulsion dispersion. The dispersion was then allowed to stand at 25℃ for 90 days. The viscosity of the polyacrylamide emulsion dispersion was tested immediately after preparation, after 30 days of standing, and after 90 days of standing, and the results are recorded in Table 1 below. Saline solution I was prepared as follows: 7.39g of anhydrous calcium chloride, 5.58g of magnesium chloride hexahydrate, and 112.87g of sodium chloride were sequentially added to 4874.16g of distilled water and stirred until homogeneous, transparent, and free of precipitate to obtain saline solution I. The total mineralization of saline solution I was 20000mg / L.

[0078] 2. Storage stability of polyacrylamide emulsions: The stability was determined according to section 4.10 of GB / T 20623-2006. Two test speeds were used: 2500 r / min, 5000 r / min, and 8000 r / min. Whether stratification or flocculent matter appeared was recorded and shown in Table 2 below. The higher the rotation speed that the polyacrylamide emulsion can withstand, the better its stability under the same storage conditions.

[0079] Table 1 Based on Example 1 and Comparative Examples 1-6, and the data in Table 1, it can be seen that when an additive is prepared by using a specific ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate, the additive can effectively improve the high salt resistance stability of polyacrylamide emulsions.

[0080] Based on Examples 2 and 4-10 and the data in Table 1, it can be seen that the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate affects the high salt stability of the additive on polyacrylamide emulsion. Specifically, when the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is in the range of (0.6-0.8):1:(0.7-0.9), the high salt stability of the additive on the polyacrylamide emulsion can be further improved.

[0081] Based on Examples 7 and 11-13 and the data in Table 1, it can be seen that the viscosity of the vinyl-terminated silicone oil affects the high-salt stability effect of the additive on the polyacrylamide emulsion. Specifically, when the viscosity of the vinyl-terminated silicone oil is in the range of 20,000-40,000, it can further effectively improve the high-salt stability effect of the additive on the polyacrylamide emulsion.

[0082] Based on Examples 12 and 14-16 and the data in Table 1, it can be seen that the temperature control of the reaction system affects the high salt stability of the additive on the polyacrylamide emulsion during the preparation of the additive. Among them, the additive obtained by controlling the temperature of the reaction system at 50-55℃ has a better high salt stability effect on the polyacrylamide emulsion.

[0083] Table 2 Based on Examples 2 and 4-10 and the data in Table 1, it can be seen that the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate affects the storage stability of the additive. In particular, when the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is in the range of (0.6-0.8):1:(0.7-0.9), the storage stability of the additive can be further improved.

[0084] Based on Examples 7 and 11-13 and the data in Table 1, it can be seen that the viscosity of the vinyl-terminated silicone oil affects the storage stability of the additive. Specifically, the viscosity of the vinyl-terminated silicone oil in the range of 20,000-40,000 can further and effectively improve the storage stability of the additive.

[0085] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An additive for improving the salt resistance stability of polyacrylamide emulsions, characterized in that, Including the following parts by weight of raw materials: Monomer: 10-20 parts Initiator: 0.1-0.3 parts Emulsifier: 0.5-1 part Chain transfer agent: 0.03-0.06 parts Solvent: 100 parts The monomers include N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate, wherein the weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is (0.5-1):1:(0.5-1). The molecular weight of the terminal vinyl silicone oil is 5000-60000.

2. The additive for improving the salt resistance of polyacrylamide emulsions according to claim 1, characterized in that: The weight ratio of N-vinyl-2-pyrrolidone, vinyl-terminated silicone oil, and dimethylaminoethyl methacrylate is (0.6-0.8):1:(0.7-0.9).

3. The additive for improving the salt resistance stability of polyacrylamide emulsions according to claim 2, characterized in that: The weight ratio of N-vinyl-2-pyrrolidone, terminal vinyl silicone oil, and dimethylaminoethyl methacrylate is 0.7:1:0.

8.

4. The additive for improving the salt resistance stability of polyacrylamide emulsions according to claim 1, characterized in that: The molecular weight of the terminal vinyl silicone oil is 20,000-40,000.

5. An additive for improving the salt resistance stability of polyacrylamide emulsions according to any one of claims 1-4, characterized in that: The emulsifier comprises isotretinoin polyoxyethylene ether and sodium fatty alcohol polyoxyethylene ether sulfate, wherein the weight ratio of isotretinoin polyoxyethylene ether to sodium fatty alcohol polyoxyethylene ether sulfate is 1:(3-4).

6. An additive for improving the salt resistance stability of polyacrylamide emulsions according to any one of claims 1-4, characterized in that: The chain transfer agent is selected from at least one of isopropanol, mercaptopropionic acid, mercaptoethanol, mercaptoacetic acid, n-butanethiol, and tert-butanethiol.

7. An additive for improving the salt resistance stability of polyacrylamide emulsions according to any one of claims 1-4, characterized in that: The initiator is selected from at least one of water-soluble azo initiators and persulfate initiators.

8. A method for preparing an additive for improving the salt resistance of polyacrylamide emulsions according to any one of claims 1-7, characterized in that: Includes the following steps: According to the formula, N-vinyl-2-pyrrolidone and dimethylaminoethyl methacrylate are added to 60-70% of the total mass of the solvent and stirred evenly to obtain a mixed monomer solution. Add the emulsifier to 10-20% of the total mass of the solvent and stir until homogeneous to obtain an emulsifier solution; Add the initiator to the remaining solvent and stir until homogeneous to obtain an initiator solution; Vinyl-terminated silicone oil, emulsifier solution, and chain transfer agent are added to a mixed monomer solution and stirred until homogeneous. Under nitrogen protection, an initiator solution is added dropwise, and the reaction system temperature is controlled at 30-65℃. The reaction is carried out for 2-3 hours to obtain an additive that improves the salt resistance stability of polyacrylamide emulsion.

9. The method for preparing an additive to improve the salt resistance of polyacrylamide emulsion according to claim 8, characterized in that: The temperature of the reaction system is controlled at 50-55℃, and the reaction is carried out for 2-3 hours.

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