Preparation method of salt-resistant polyacrylamide

Abstract

The present invention relates to the technical field of polymer preparation, and discloses a preparation method of salt-resistant polyacrylamide. An emulsifier and azobisisobutyronitrile are added to white oil to make them completely dispersed to obtain an oil phase; acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water are added to a reactor, and after complete dissolution, disodium ethylenediaminetetraacetate and N,N-dimethylformamide are continuously added, sodium hydroxide is added to adjust the pH, and then an initiator is added thereto to obtain an aqueous phase; the aqueous phase and the oil phase are added to a reaction kettle, nitrogen is introduced to remove oxygen, nitrogen is passed, and then modified nano-silica and an oxygen scavenger are added thereto, and after filtration, washing and drying, salt-resistant polyacrylamide is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer preparation, and specifically to a preparation method of salt-resistant polyacrylamide. Background Art

[0002] The hydrolysis of polyacrylamide can effectively increase the viscosity of aqueous solutions, improve the heterogeneity of oil layers, and enhance the recovery rate of crude oil. It is widely used as a polymer flooding agent in tertiary oil recovery. However, hydrolyzed polyacrylamide also has many defects, such as poor temperature resistance, salt resistance, and shear resistance. The development of temperature and salt-resistant polyacrylamide is of great practical significance for improving the technical level of tertiary oil recovery in oil fields. However, due to the flexible molecular chain of polyacrylamide, it shows a random coil conformation in aqueous solutions. In high-temperature and high-salinity brines, the molecular chain curls, resulting in a significant decrease in viscosity and a loss of the thickening effect of the polymer solution. Moreover, the flexible chain is prone to mechanical degradation, which greatly limits its application range and cannot well meet the requirements of high-temperature, high-salinity, and ultra-deep drilling oil recovery. For example, the literature "Synthesis and Properties of Temperature and Salt-Resistant Sulfonated Polyacrylamide" uses a redox initiator system composed of ammonium persulfate and sodium formaldehyde sulfoxylate and azobisisobutyramidine hydrochloride to initiate the copolymerization of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid to obtain salt-resistant polyacrylamide. Summary of the Invention

[0003] (1) Technical Problem to be Solved

[0004] In view of the deficiencies of the prior art, the present invention provides a preparation method of salt-resistant polyacrylamide.

[0005] (2) Technical Solution

[0006] To achieve the above object, the present invention provides the following technical solution: A preparation method of salt-resistant polyacrylamide, wherein the salt-resistant polyacrylamide comprises the following weight components: 80-100 parts of acrylamide, 30-40 parts of acrylic acid monomer grafted imidazole type, 5-7 parts of modified nano-silica, 60-80 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.4-0.7 parts of initiator, 0.04-0.8 parts of emulsifier, and 1-2 parts of deoxidizer.

[0007] Preferably, the preparation method of the salt-resistant polyacrylamide comprises the following steps:

[0008] (1) Add the emulsifier and 10-20 parts of azobisisobutyronitrile to white oil, stir for 20-30 min to completely disperse to obtain an oil phase;

[0009] (2) Add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water into a reactor. After complete dissolution, continue to add 20 - 40 parts of disodium ethylenediaminetetraacetate and 30 - 40 parts of N,N-dimethylformamide. Stir for 10 - 15 min, then add sodium hydroxide to adjust the pH to 6 - 7, and then add an initiator to obtain the aqueous phase;

[0010] (3) Add the aqueous phase and the oil phase into a reaction kettle. Stir for 10 - 20 min, then introduce nitrogen to remove oxygen. The nitrogen introduction time is 25 - 35 min. Then add modified nano-silica and an oxygen scavenger to it. The reaction temperature is 20 - 25 °C, and the reaction time is 2 - 3 h. Filter, wash, and dry to obtain salt-resistant polyacrylamide.

[0011] Preferably, the preparation method of the acrylic acid monomer grafted imidazole type is as follows: Add 3.61 - 3.63 g of allyl bromide, 7.41 - 7.46 g of anhydrous potassium carbonate, 0.02 - 0.04 g of hydroquinone, 6.6 - 6.7 g of N,N-dimethylformamide, and the imidazole type monomer into a reactor. The reaction temperature is 70 - 80 °C, then introduce nitrogen and react for 20 - 24 h. Cool to room temperature, and carry out vacuum distillation, separation, and purification to obtain the acrylic acid monomer grafted imidazole type.

[0012] Preferably, the emulsifier is sorbitan oleate, polyoxyethylene sorbitan monooleate; the oxygen scavenger is any one or several of sodium sulfite, iron hydroxide, ascorbic acid, hydrazine, dimethyl ketoxime, and sodium dithiotetroxide.

[0013] Preferably, the imidazole type monomer in (2) is:

[0014]

[0015] any one of them.

[0016] Preferably, the preparation method of the imidazole type monomer in (2) is as follows: Add diglycerol borate, ethylenediamine, and xylene into a reactor. Protect with nitrogen, the reaction temperature is 90 - 100 °C, and the reaction time is 6 - 8 h to obtain a crude product. Carry out vacuum distillation, washing, and drying to obtain the imidazole type monomer.

[0017] Preferably, the preparation method of the modified nano-silica in (3) is:

[0018] (1) Activate 1 - 2 g of nano - silica in a vacuum oven at 140 - 150 °C for 10 - 12 h. Then add 39 - 46.8 g of cyclohexane, ultrasonically disperse for 15 - 20 min, pour it into a reactor, add 1.5 - 2 g of 3 - aminopropyltriethoxysilane and introduce nitrogen for protection. Stir for 20 - 30 min, adjust the pH to 5 - 6, raise the temperature to 70 - 80 °C, and stir for another 22 - 24 h. Then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A;

[0019] (2) Disperse 0.5 - 1 g of product A into 43.6 - 52.32 g of toluene solution, add 0.123 - 0.125 g of anhydrous potassium carbonate, ultrasonically bath at ice - bath temperature for 20 - 30 min, then add 0.5 - 1 ml of acryloyl chloride, react at 60 - 80 °C for 12 - 13 h, wash with toluene and dry to obtain modified nano - silica.

[0020] Preferably, the mass ratio of the nano - silica, cyclohexane, and 3 - aminopropyltriethoxysilane is 1:23.4 - 39:1 - 1.5.

[0021] Preferably, the initiator is any one or several of potassium persulfate, azobisisobutyronitrile, ammonium persulfate, lauroyl peroxide, tert - butyl hydroperoxide, and cumene hydroperoxide.

[0022] (III) Beneficial technical effects

[0023] In the present invention, an oil phase is obtained by adding an emulsifier and azobisisobutyronitrile to white oil; an aqueous phase is further obtained by adding acrylamide, 2 - acrylamido - 2 - methylpropanesulfonic acid, acrylic acid monomer - grafted imidazole type, and deionized water to a reactor. The aqueous phase and the oil phase are added to a reaction kettle, nitrogen is introduced to remove oxygen, nitrogen is passed through, and then modified nano - silica and an oxygen scavenger are added thereto. After filtration, washing, and drying, a salt - resistant polyacrylamide is obtained. In the present invention, imidazole groups are added to the polymer, which has a salt - resistant effect. At the same time, the ring of the imidazole group has a rigid effect, improving the stability of polyacrylamide and avoiding entanglement, aggregation, and tortuosity of molecular chains. The side chain of the present invention also contains sulfonic acid groups, which are insensitive to divalent ions, facilitating the improvement of salt - resistance ability. The modified silica in the side chain also improves the temperature - resistance performance and fluidity of polyacrylamide. Introducing sulfonic acid groups, amino groups, and strongly hydrophilic groups into the polyamide molecule is beneficial to improving the viscosity - increasing performance and drag - reducing performance of polyacrylamide. Description of the drawings

[0024] Figure 1 It is a reaction route diagram of modified nano - silica.

[0025] Figure 2 It is a preparation route diagram of imidazole - type monomer.

[0026] Figure 3 It is the preparation route diagram of salt - resistant polyacrylamide. Specific implementation method

[0027] Example 1

[0028] A preparation method of salt - resistant polyacrylamide, the salt - resistant polyacrylamide comprises the following weight components: 80 parts of acrylamide, 30 parts of acrylic acid monomer grafted imidazole type, 5 parts of modified nano - silica, 60 parts of 2 - acrylamido - 2 - methylpropanesulfonic acid, 0.4 part of initiator, 0.04 part of emulsifier, 1 part of deoxidizer;

[0029] The emulsifier is sorbitan oleate, polyethylene glycol sorbitan monooleate; the deoxidizer is sodium sulfite, iron hydroxide, ascorbic acid;

[0030] The initiator is potassium persulfate, azobisisobutyronitrile, ammonium persulfate;

[0031] (1) Add 3.61 g of allyl bromide, 7.41 g of anhydrous potassium carbonate, 0.02 g of hydroquinone, 6.6 g of N,N - dimethylformamide, and imidazole - type monomer into a reactor, the reaction temperature is 70 °C, then introduce nitrogen and react for 20 h, cool to room temperature, carry out vacuum distillation and separation and purification to obtain acrylic acid monomer grafted imidazole type;

[0032] (2) Activate 1 g of nano - silica in a vacuum oven at 140 °C for 10 h, add 39 g of cyclohexane to it, ultrasonically disperse for 15 min, pour it into a reactor, add 1.5 g of 3 - aminopropyltriethoxysilane to it and introduce nitrogen for protection, stir for 20 min, adjust the pH to 5, raise the temperature to 70 °C, stir for another 22 h, then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A;

[0033] (3) Disperse 0.5 g of product A into 43.6 g of toluene solution, add 0.123 g of anhydrous potassium carbonate, ultrasonically bath in ice for 20 min, then add 0.5 ml of acryloyl chloride, the reaction temperature is 60 °C, the reaction time is 12 h, wash with toluene and dry to obtain modified nano - silica;

[0034] (4) Add the emulsifier and 10 parts of azobisisobutyronitrile into white oil, stir for 20 min to make it completely dispersed to obtain the oil phase;

[0035] (5) Add acrylamide, 2 - acrylamido - 2 - methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water into a reactor, after complete dissolution, continue to add 20 parts of disodium ethylenediaminetetraacetate and 30 parts of N,N - dimethylformamide, stir for 10 min, then add sodium hydroxide to adjust the pH to 6, and then add the initiator to obtain the water phase;

[0036] (6) Add the aqueous phase and the oil phase into the reactor, stir for 10 min, then introduce nitrogen to remove oxygen for 25 min. Then add modified nano-silica and deoxidizer to it. The reaction temperature is 20 °C and the reaction time is 2 h. Filter, wash and dry to obtain salt-resistant polyacrylamide.

[0037] Example 2

[0038] A preparation method of salt-resistant polyacrylamide, and the salt-resistant polyacrylamide comprises the following weight components: 100 parts of acrylamide, 40 parts of acrylic acid monomer grafted imidazole type, 7 parts of modified nano-silica, 80 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.7 part of initiator, 0.8 part of emulsifier, 2 parts of deoxidizer;

[0039] The emulsifier is sorbitan oleate; the deoxidizer is sodium sulfite, hydrazine, dimethyl ketoxime, sodium dithiotetroxide;

[0040] The initiator is potassium persulfate, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide;

[0041] (1) Add 3.63 g of allyl bromide, 7.46 g of anhydrous potassium carbonate, 0.04 g of hydroquinone, 6.7 g of N,N-dimethylformamide and imidazole monomer into the reactor. The reaction temperature is 80 °C, then introduce nitrogen and react for 24 h. Cool to room temperature, carry out vacuum distillation and separation and purification to obtain acrylic acid monomer grafted imidazole type;

[0042] (2) Activate 2 g of nano-silica in a vacuum oven at 150 °C for 12 h. Then add 46.8 g of cyclohexane to it, ultrasonically disperse for 20 min, pour it into the reactor, add 2 g of 3-aminopropyltriethoxysilane to it and introduce nitrogen for protection, stir for 30 min, adjust the pH to 6, raise the temperature to 80 °C, stir for another 24 h, then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A;

[0043] (3) Disperse 1 g of product A into 52.32 g of toluene solution, add 0.125 g of anhydrous potassium carbonate, carry out ice bath ultrasonic treatment for 30 min, then add 1 ml of acryloyl chloride, the reaction temperature is 80 °C, the reaction time is 13 h, wash with toluene and dry to obtain modified nano-silica;

[0044] (4) Add the emulsifier and 20 parts of azobisisobutyronitrile into white oil, stir for 30 min to make it completely dispersed to obtain the oil phase;

[0045] (5) Add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water into a reactor. After complete dissolution, continue to add 40 parts of disodium ethylenediaminetetraacetate and 40 parts of N,N-dimethylformamide. After stirring for 15 min, add sodium hydroxide to adjust the pH to 7, and then add an initiator to obtain the aqueous phase;

[0046] (6) Add the aqueous phase and the oil phase into a reaction kettle. After stirring for 20 min, introduce nitrogen to remove oxygen. The nitrogen introduction time is 35 min. Then add modified nano-silica and an oxygen scavenger to it. The reaction temperature is 25 °C and the reaction time is 3 h. Filter, wash and dry to obtain salt-resistant polyacrylamide.

[0047] Example 3

[0048] A preparation method of salt-resistant polyacrylamide, the salt-resistant polyacrylamide includes the following weight components: 90 parts of acrylamide, 35 parts of acrylic acid monomer grafted imidazole type, 6 parts of modified nano-silica, 70 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.55 parts of initiator, 0.42 parts of emulsifier, 1.5 parts of oxygen scavenger;

[0049] The emulsifier is polyoxyethylene sorbitan monooleate; the oxygen scavenger is ascorbic acid, hydrazine, dimethyl ketoxime, sodium dithiotetroxide;

[0050] The initiator is ammonium persulfate, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide;

[0051] (1) Add 3.62 g of allyl bromide, 7.3 g of anhydrous potassium carbonate, 0.03 g of hydroquinone, 6.65 g of N,N-dimethylformamide, and imidazole type monomer into a reactor. The reaction temperature is 75 °C, and then introduce nitrogen to react for 22 h. Cool to room temperature, and carry out vacuum distillation and separation and purification to obtain acrylic acid monomer grafted imidazole type;

[0052] (2) Activate 1.5 g of nano-silica in a vacuum oven at 145 °C for 11 h. Then add 42.9 g of cyclohexane to it, ultrasonically disperse for 17.5 min, pour it into a reactor, add 2.25 g of 3-aminopropyltriethoxysilane and introduce nitrogen protection, stir for 25 min, adjust the pH to 5.5, heat up to 75 °C, stir for another 23 h, then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A;

[0053] (3) Disperse 0.75 g of product A into 47.96 g of toluene solution, add 0.124 g of anhydrous potassium carbonate, ultrasonically bath in ice for 25 min, then add 0.75 ml of acryloyl chloride, the reaction temperature is 70 °C, the reaction time is 12.5 h, wash with toluene and dry to obtain modified nano-silica;

[0054] (4) Add the emulsifier and 15 parts of azobisisobutyronitrile to white oil, stir for 25 min to completely disperse them to obtain the oil phase;

[0055] (5) Add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water to the reactor. After complete dissolution, continue to add 30 parts of disodium ethylenediaminetetraacetate and 35 parts of N,N-dimethylformamide. After stirring for 12.5 min, add sodium hydroxide to adjust the pH to 6.5, and then add the initiator to obtain the water phase;

[0056] (6) Add the water phase and the oil phase to the reaction kettle, stir for 15 min, then introduce nitrogen to remove oxygen for 30 min. Then add modified nano-silica and deoxidizer to it. The reaction temperature is 22.5 °C and the reaction time is 2.5 h. Filter, wash and dry to obtain salt-resistant polyacrylamide.

[0057] Example 4

[0058] A preparation method of salt-resistant polyacrylamide, wherein the salt-resistant polyacrylamide comprises the following weight components: 90 parts of acrylamide, 35 parts of acrylic acid monomer grafted imidazole type, 6 parts of modified nano-silica, 70 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.55 part of initiator, 0.42 part of emulsifier, 1.5 parts of deoxidizer;

[0059] The emulsifier is polyoxyethylene sorbitan monooleate; the deoxidizer is ascorbic acid, hydrazine, dimethyl ketoxime, sodium dithiotetroxide;

[0060] The initiator is ammonium persulfate, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide;

[0061] (1) Add 3.63 g of allyl bromide, 7.46 g of anhydrous potassium carbonate, 0.04 g of hydroquinone, 6.7 g of N,N-dimethylformamide, and imidazole type monomer to the reactor. The reaction temperature is 80 °C, then introduce nitrogen and react for 24 h. Cool to room temperature, carry out vacuum distillation, separation and purification to obtain acrylic acid monomer grafted imidazole type;

[0062] (2) Activate 2 g of nano-silica in a vacuum oven at 150 °C for 12 h, add 46.8 g of cyclohexane to it, ultrasonically disperse for 20 min, pour it into the reactor, add 2 g of 3-aminopropyltriethoxysilane to it and introduce nitrogen for protection, stir for 30 min, adjust the pH to 6, raise the temperature to 80 °C, stir for another 24 h, then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A;

[0063] (3) Disperse 1 g of product A into 52.32 g of toluene solution, add 0.125 g of anhydrous potassium carbonate, ultrasonicate in an ice bath for 30 min, then add 1 ml of acryloyl chloride, react at 80 °C for 13 h, wash with toluene and dry to obtain modified nano-silica;

[0064] (4) Add emulsifier and 10 - 20 parts of azobisisobutyronitrile to white oil, stir for 20 - 30 min to make it completely dispersed to obtain the oil phase;

[0065] (5) Add acrylamide, 2 - acrylamido - 2 - methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water to the reactor. After complete dissolution, continue to add 20 parts of disodium ethylenediaminetetraacetate and 30 parts of N,N - dimethylformamide, stir for 10 min, then add sodium hydroxide to adjust the pH to 6, and then add initiator to obtain the aqueous phase;

[0066] (6) Add the aqueous phase and the oil phase to the reaction kettle, stir for 10 min, then pass nitrogen to remove oxygen for 25 min, then add modified nano - silica and deoxidizer to it, react at 20 °C for 2 h, filter, wash and dry to obtain salt - resistant polyacrylamide.

[0067] Example 5

[0068] A preparation method of salt - resistant polyacrylamide, the salt - resistant polyacrylamide comprises the following weight components: 100 parts of acrylamide, 40 parts of acrylic acid monomer grafted imidazole type, 7 parts of modified nano - silica, 80 parts of 2 - acrylamido - 2 - methylpropanesulfonic acid, 0.7 part of initiator, 0.8 part of emulsifier, 2 parts of deoxidizer;

[0069] The emulsifier is sorbitan oleate; the deoxidizer is sodium sulfite, hydrazine, dimethyl ketoxime, sodium dithiotetroxide;

[0070] The initiator is potassium persulfate, lauroyl peroxide, tert - butyl hydroperoxide, cumene hydroperoxide;

[0071] (1) Add 3.61 g of allyl bromide, 7.41 g of anhydrous potassium carbonate, 0.02 g of hydroquinone, 6.6 g of N,N - dimethylformamide and imidazole - type monomer to the reactor, react at 70 °C, then pass nitrogen and react for 20 h, cool to room temperature, carry out vacuum distillation and separation and purification to obtain acrylic acid monomer grafted imidazole type;

[0072] (2) Activate 1 g of nano-silica in a vacuum oven at 140 °C for 10 h. Then add 39 g of cyclohexane to it, ultrasonically disperse for 15 min, pour it into a reactor, add 1.5 g of 3-aminopropyltriethoxysilane and introduce nitrogen for protection, stir for 20 min, adjust the pH to 5, raise the temperature to 70 °C, stir for another 22 h, then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A;

[0073] (3) Add the emulsifier and 10 - 20 parts of azobisisobutyronitrile to white oil, stir for 20 - 30 min to make it completely dispersed to obtain the oil phase;

[0074] (4) Disperse 0.5 g of product A into 43.6 g of toluene solution, add 0.123 g of anhydrous potassium carbonate, ultrasonically disperse in an ice bath for 20 min, then add 0.5 ml of acryloyl chloride, react at 60 °C for 12 h, wash with toluene and dry to obtain modified nano-silica;

[0075] (5) Add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water to the reactor. After complete dissolution, continue to add 30 parts of disodium ethylenediaminetetraacetate and 35 parts of N,N-dimethylformamide. Stir for 12.5 min and then add sodium hydroxide to adjust the pH to 6.5, and then add the initiator to obtain the aqueous phase;

[0076] (6) Add the aqueous phase and the oil phase to the reaction kettle, stir for 15 min and then introduce nitrogen to remove oxygen for 30 min. Then add the modified nano-silica and the deoxidizer to it. The reaction temperature is 22.5 °C and the reaction time is 2.5 h. Filter, wash and dry to obtain salt-resistant polyacrylamide.

[0077] Comparative Example 1

[0078] A preparation method of salt-resistant polyacrylamide, wherein the salt-resistant polyacrylamide comprises the following weight components: 80 parts of acrylamide, 0.4 part of initiator, 0.04 part of emulsifier, 1 part of deoxidizer;

[0079] The emulsifier is sorbitan oleate and polyoxyethylene sorbitan monooleate; the deoxidizer is sodium sulfite, iron hydroxide, ascorbic acid;

[0080] (1) Add the emulsifier and 15 parts of azobisisobutyronitrile to white oil, stir for 25 min to make it completely dispersed to obtain the oil phase;

[0081] (2) Add acrylamide and deionized water to the reactor. After complete dissolution, continue to add 30 parts of disodium ethylenediaminetetraacetate and 35 parts of N,N-dimethylformamide. Stir for 12.5 min and then add sodium hydroxide to adjust the pH to 6.5, and then add the initiator to obtain the aqueous phase;

[0082] (3) Add the aqueous phase and the oil phase into the reaction kettle, stir for 10 min, then introduce nitrogen to remove oxygen for 25 min. Then add the deoxidizer thereto. The reaction temperature is 20 °C and the reaction time is 2 h. Filter, wash, and dry to obtain the salt-resistant polyacrylamide.

[0083] Test the apparent viscosity and insoluble matter of the polyacrylamide according to Q / SH1020. High temperature resistance test: Prepare the polyacrylamide prepared in Examples 1-5 and Comparative Example 1 into a polymer aqueous solution with a concentration of 0.3 g / L, and measure its apparent viscosity W at 25 °C with a Brookfield viscometer. 1 Heat it in a water bath at 80 °C for 10 h, and measure the apparent viscosity W after heating. 2 And calculate the viscosity retention rate according to the formula 100% × W 2 / W 1 The same applies to 100 °C.

[0084] Salt resistance test: Prepare the polyacrylamide prepared in Examples 1-5 and Comparative Example 1 into a polymer aqueous solution with a concentration of 0.3 g / L, and measure its apparent viscosity W at 25 °C with a Brookfield viscometer. 3 Then add 1.5 g of anhydrous manganese chloride and 1.0 g of anhydrous calcium chloride to 300 mL of the polymer aqueous solution, stir and dissolve it, and let it be treated in a calcium and manganese solution with a concentration of 3000 mg / L for 10 h, and then measure the apparent viscosity W after treatment. 4 And calculate the viscosity retention rate according to the formula 100% × W 4 / W 3 Calculate the viscosity retention rate.

[0085] The experimental results are shown in Table 1:

[0086] Table 1

[0087]

[0088]

[0089] Modify the polyacrylamide by introducing sulfonic acid groups, imidazole groups, and nano-silica. The apparent viscosity of the polyacrylamide reaches 128.2 - 136.5 mPa, the high-temperature viscosity retention rate reaches 81.1 - 89.5%, the salt-resistant viscosity retention rate reaches 85.3 - 87.2%, and the insoluble matter reaches 0.018 - 0.029%.

[0090] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, according to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A preparation method of a salt-resistant polyacrylamide, characterized in that: The salt-resistant polyacrylamide comprises the following components by weight: 80-100 parts of acrylamide, 30-40 parts of acrylic acid monomer grafted imidazole type, 5-7 parts of modified nano-silica, 60-80 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.4-0.7 parts of initiator, 0.04-0.8 parts of emulsifier, 1-2 parts of deoxidizer; The preparation method of the salt-resistant polyacrylamide comprises the following steps: (1) Add the emulsifier and 10-20 parts of azobisisobutyronitrile to white oil, stir for 20-30 min to make it completely dispersed to obtain the oil phase; (2) Add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid monomer grafted imidazole type and deionized water to the reactor. After complete dissolution, continue to add 20-40 parts of disodium ethylenediaminetetraacetate and 30-40 parts of N,N-dimethylformamide. Stir for 10-15 min and then add sodium hydroxide to adjust the pH to 6-7. Then add the initiator to obtain the water phase; (3) Add the water phase and the oil phase to the reaction kettle, stir for 10-20 min and then pass nitrogen to remove oxygen. The nitrogen passing time is 25-35 min. Then add modified nano-silica and deoxidizer to it. The reaction temperature is 20-25 °C and the reaction time is 2-3 h. Filter, wash and dry to obtain the salt-resistant polyacrylamide; The preparation method of the acrylic acid monomer grafted imidazole type is: Add 3.61-3.63 g of allyl bromide, 7.41-7.46 g of anhydrous potassium carbonate, 0.02-0.04 g of hydroquinone, 6.6-6.7 g of N,N-dimethylformamide, and imidazole type monomer to the reactor. The reaction temperature is 70-80 °C, then pass nitrogen and react for 20-24 h. Cool to room temperature, carry out vacuum distillation and separation and purification to obtain the acrylic acid monomer grafted imidazole type; The imidazole type monomer in (2) is: any one of; The preparation method of the modified nano-silica in (3) is: (1) Activate 1-2 g of nano-silica in a vacuum oven at 140-150 °C for 10-12 h. Then add 39-46.8 g of cyclohexane to it, ultrasonically disperse for 15-20 min, pour it into the reactor, add 1.5-2 g of 3-aminopropyltriethoxysilane to it and pass nitrogen to protect it. Stir for 20-30 min, adjust the pH to 5-6, heat up to 70-80 °C, and then stir for 22-24 h. Then separate by centrifuge, wash with absolute ethanol, filter and dry to obtain product A; (2) Disperse 0.5-1 g of product A into 43.6-52.32 g of toluene solution, add 0.123-0.125 g of anhydrous potassium carbonate, carry out ice bath ultrasonic for 20-30 min, then add 0.5-1 ml of acryloyl chloride. The reaction temperature is 60-80 °C and the reaction time is 12-13 h. Wash with toluene and dry to obtain the modified nano-silica.

2. The preparation method of the salt-resistant polyacrylamide according to claim 1, characterized in that: The emulsifier is sorbitan oleate and polyoxyethylene sorbitan monooleate; the deoxidizer is any one or several of sodium sulfite, iron hydroxide, ascorbic acid, hydrazine, dimethyl ketoxime, and sodium dithionate.

3. The preparation method of the salt-resistant polyacrylamide according to claim 1, characterized in that: The preparation method of the imidazole monomer in (2) is as follows: Add diglycerol borate, diethylenetriamine, and xylene into a reactor, introduce nitrogen for protection, the reaction temperature is 90-100 °C, and the reaction time is 6-8 h to obtain a crude product, which is subjected to vacuum distillation, washing, and drying to obtain the imidazole monomer.

4. The preparation method of the salt-resistant polyacrylamide according to claim 1, characterized in that: The mass ratio of the nano-silica, cyclohexane, and 3-aminopropyltriethoxysilane is 1:23.4-39:1-1.

5.

5. The preparation method of the salt-resistant polyacrylamide according to claim 1, characterized in that: The initiator is any one or several of potassium persulfate, azobisisobutyronitrile, ammonium persulfate, lauroyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide.

Images