A high molecular weight zwitterionic polyacrylamide emulsion and its preparation method

Abstract

This invention belongs to the field of tertiary oil recovery technology, specifically relating to an ultra-high molecular weight zwitterionic polyacrylamide emulsion and its preparation method. The preparation method comprises the following steps: acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, allyl naphthalene, 1-allyl-3-methylimidazolium p-toluenesulfonate, Tween 80, and a buffer salt are added sequentially to a reaction vessel to form an emulsion; a portion of the emulsion is transferred to a first high-level tank, and 2-acrylamido-2-methylpropanesulfonic acid and 1-allyl-3-methylimidazolium p-toluenesulfonate are added again, and the mixture is stirred until homogeneous; the emulsion in the reaction vessel is heated, an initiator is added to a second high-level tank and uniformly dripped into the reaction vessel, and the liquid in the first high-level tank is uniformly dripped into the reaction vessel, and the reaction yields the product of this invention. This invention features readily available raw materials, a simple synthesis process, no byproducts, safety and environmental friendliness, high surface viscosity, and high shear resistance.

Description

Technical Field

[0001] This invention belongs to the field of tertiary oil recovery technology, and relates to a high molecular weight polymer and its preparation method, particularly to an ultra-high molecular weight zwitterionic polyacrylamide emulsion and its preparation method. Background Technology

[0002] Polyacrylamide (PAM) is a water-soluble polymer with amide groups in its molecular structure. It can be easily modified into various branched or network structures through grafting or cross-linking. PAM molecules can be infused with various ionic groups to achieve specific properties. It is widely used in various fields such as chemical engineering, metallurgy, geology, coal mining, petroleum, papermaking, and water treatment, earning it the title of "auxiliary agent for all industries," with the largest usage in oilfield development.

[0003] Polymer flooding involves adding a certain amount of high-molecular-weight polyacrylamide to the injected water to increase its viscosity, improve the oil-water mobility ratio, and increase the seepage resistance of the injected water. This increases the water absorption of low-permeability or low-water-flooded layers, expands the contact area of ​​the injected water on the oil layer plane and the water-flooded thickness in the oil layer longitudinally, and then expands the swept volume to displace the crude oil that was not utilized during waterflooding, thereby achieving the goal of improving oil recovery.

[0004] As the relative molecular mass of PAM increases, the viscosity reduction rate of the system decreases, and high-concentration, ultra-high molecular weight polymer systems exhibit better shear resistance. With increasing PAM concentration and relative molecular mass, the oil displacement effect of the system improves; therefore, high-concentration, ultra-high molecular weight polymer systems are a good choice for achieving high oil recovery.

[0005] CN 104910321 B discloses a ternary copolymer cationic polyacrylamide. The preparation of this product includes the preparation of the cationic monomer E-AM, the preparation of a monomer aqueous solution, and the ternary copolymerization of AM, E-AM, and DAC. The ternary copolymer cationic polyacrylamide provided by this invention effectively combines the high polymerization activity and good flocculation effect of E-AM monomer with the ease of preparing high molecular weight copolymers from DAC. Compared with existing common flocculants, this invention has high cationicity and high molecular weight, while exhibiting excellent flocculation performance. Actual test results show that it also possesses high solubility, making it suitable for use as a flocculant in wastewater treatment. However, this product is cationic and used as a coagulant aid in wastewater treatment, while polyacrylamide has a large market application in oil displacement. This product is not suitable for oil extraction, thus limiting its application scope. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a supermolecular-weight zwitterionic polyacrylamide emulsion and its preparation method. This invention features readily available raw materials, a simple synthesis process, no byproducts, safety and environmental friendliness, high surface viscosity, and high shear resistance.

[0007] To achieve the above objectives, one objective of this invention discloses an amphoteric polyacrylamide emulsion, the molecular structural formula of which is as follows:

[0008]

[0009] Where a = 50000 - 300000;

[0010] b = 10000 - 50000;

[0011] c = 5000 - 30000;

[0012] d = 10000 - 50000.

[0013] Preferably, the viscosity-average molecular weight of the zwitterionic polyacrylamide emulsion is 20,000,000-30,000,000.

[0014] Another objective of this invention is to disclose a method for preparing the above-mentioned zwitterionic polyacrylamide emulsion, the specific steps of which are as follows:

[0015] (1) Purge the reactor and pipeline with nitrogen for 5-8 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, allyl naphthalene, 1-allyl-3-methylimidazolium p-toluenesulfonate, Tween 80, buffer salt, and deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0016] (2) Transfer 50-80% of the weight of the above emulsion to the first high-level tank, add 2-acrylamido-2-methylpropanesulfonic acid and 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank again, stir evenly, adjust the pH to 7-8 with 1mol / L sodium hydroxide, add deionized water to the reaction vessel again, and stir evenly.

[0017] (3) Continue stirring the emulsion in the reactor and raise the temperature to 40-45℃. Add the initiator to the second high-level tank and add it to the reactor at a uniform rate. After 15-20 minutes, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 2-10 minutes. The total addition time of the initiator in the second high-level tank is controlled at 40-60 minutes. After the addition is completed, stir and raise the temperature of the reactor to 70-73℃ and continue stirring for 60-80 minutes.

[0018] (4) Cool down to 40-45℃ and adjust the pH to 7-8 with 1mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion of the present invention.

[0019] Preferably, in step (1), the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid, allyl naphthalene, 1-allyl-3-methylimidazolium p-toluenesulfonate to acrylamide is 0.02-0.1:0.05-0.2:0.02-0.1:1.

[0020] Preferably, in step (1), the weight ratio of Tween80, buffer salt, deionized water and acrylamide is 0.02-0.04:0.01-0.02:2.5-3:1.

[0021] Preferably, in step (1), the buffer salt is one of disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate.

[0022] Preferably, in step (2), the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid, 1-allyl-3-methylimidazolium p-toluenesulfonate to acrylamide is 0.05-0.2:0.05-0.2:1.

[0023] Preferably, in step (2), the weight ratio of deionized water to acrylamide is 1-1.5:1.

[0024] Preferably, in step (3), the initiator is a mixed solution of one of potassium persulfate, ammonium persulfate, and sodium persulfate with one of sodium bisulfite, sodium sulfite, and sodium thiosulfate, wherein the concentration of persulfate is 10 wt%, the concentration of sodium bisulfite, sodium sulfite, or sodium thiosulfate is 5 wt%, and the weight ratio of initiator to acrylamide is 0.2-0.5:1.

[0025] The reaction equation for the synthesis of the zwitterionic polyacrylamide emulsion of the present invention is as follows:

[0026]

[0027]

[0028] This invention provides an ultra-high molecular weight zwitterionic polyacrylamide emulsion, the main component of which is a quaternary polymer with acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, allyl naphthalene, and 1-allyl-3-methylimidazolium p-toluenesulfonate as monomers. Acrylamide is the main monomer, and the anionic surfactant 2-acrylamido-2-methylpropanesulfonic acid is introduced into the molecule to enhance the oil displacement performance of the product; the zwitterionic surfactant 1-allyl-3-methylimidazolium p-toluenesulfonate is introduced to enhance both the oil displacement performance and the acid and alkali resistance of the product; the allyl naphthalene monomer is introduced to significantly improve the shear resistance of the product; and the Tween80 nonionic surfactant is added during the synthesis process, which can increase the ability to emulsify and displace crude oil, and also improve the polymerization quality and molecular weight of the product, thereby increasing the viscosity of the product.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The zwitterionic polyacrylamide emulsion synthesis of the present invention is a one-pot method, the raw materials are readily available, the synthesis process is simple, there are no by-products, and it is safe and environmentally friendly.

[0031] (2) The zwitterionic polyacrylamide emulsion of the present invention has the characteristic of high surface viscosity, with a surface viscosity greater than 100 mPa·s;

[0032] (3) The zwitterionic polyacrylamide emulsion of the present invention has the characteristics of high shear resistance and viscosity retention rate greater than 90%. Detailed Implementation

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] The technical solution of the invention will be further explained below with reference to specific embodiments.

[0035] Example 1

[0036] (1) Purge the reactor and pipeline with nitrogen for 5 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.04 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.4 mol allyl naphthalene, 0.2 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 2.84 g Tween 80, 1.42 g disodium hydrogen phosphate, and 426 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0037] (2) Transfer 50% of the weight of the above emulsion to the first high-level tank, add 0.1 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.4 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 142 g of deionized water to the reaction vessel, and stir evenly.

[0038] (3) Continue stirring the emulsion in the reactor and raise the temperature to 40°C. Add 28.4g of initiator to the second high-level tank. The initiator is 10wt% sodium persulfate and 5wt% sodium sulfite. Add it to the reactor at a uniform rate. After 15min, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 2min. The total addition time of the initiator in the second high-level tank is controlled at 40min. After the addition is completed, stir and raise the temperature of the reactor to 70°C and continue stirring for 60min.

[0039] (4) Cool down to 40°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion A of the present invention.

[0040] Example 2

[0041] (1) Purge the reactor and pipeline with nitrogen for 8 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.2 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.35 mol allyl naphthalene, 0.04 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 3.17 g Tween 80, 1.77 g disodium hydrogen phosphate, and 410 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0042] (2) Transfer 55% of the weight of the above emulsion to the first high-level tank, add 0.4 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.1 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 160 g of deionized water to the reaction vessel, and stir evenly.

[0043] (3) Continue stirring the emulsion in the reactor and raise the temperature to 42°C. Add 35.4g of initiator to the second high-level tank. The initiator is 10wt% sodium persulfate and 5wt% sodium bisulfite. Add it to the reactor at a uniform rate. After 20min, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 7min. The total addition time of the initiator in the second high-level tank is controlled at 47min. After the addition is completed, stir and raise the temperature of the reactor to 71°C and continue stirring for 65min.

[0044] (4) Cool down to 42°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion B of the present invention.

[0045] Example 3

[0046] (1) Purge the reactor and pipeline with nitrogen for 6 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.07 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.25 mol allyl naphthalene, 0.17 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 3.88 g Tween 80, 1.82 g dipotassium hydrogen phosphate, and 403 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0047] (2) Transfer 60% of the weight of the above emulsion to the first high-level tank, add 0.17 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.35 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 177 g of deionized water to the reaction vessel, and stir evenly.

[0048] (3) Continue stirring the emulsion in the reactor and raise the temperature to 45°C. Add 41.4g of initiator to the second high-level tank. The initiator is 10wt% potassium persulfate and 5wt% sodium sulfite. Add it to the reactor at a uniform rate. After 16min, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 6min. The total addition time of the initiator in the second high-level tank is controlled to be 50min. After the addition is completed, stir and raise the temperature of the reactor to 72°C and continue stirring for 70min.

[0049] (4) Cool down to 41°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion C of the present invention.

[0050] Example 4

[0051] (1) Purge the reactor and pipeline with nitrogen for 7 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.17 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.2 mol allyl naphthalene, 0.07 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 4.11 g Tween 80, 2.14 g dipotassium hydrogen phosphate, and 376 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0052] (2) Transfer 65% of the weight of the above emulsion to the first high-level tank, add 0.35 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.17 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 189 g of deionized water to the reaction vessel, and stir evenly.

[0053] (3) Continue stirring the emulsion in the reactor and raise the temperature to 43°C. Add 51.7g of initiator to the second high-level tank. The initiator is 10wt% sodium persulfate and 5wt% sodium thiosulfate. Add it to the reactor at a uniform rate. After 18 minutes, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 7 minutes. The total addition time of the initiator in the second high-level tank is controlled at 60 minutes. After the addition is completed, stir and raise the temperature of the reactor to 73°C and continue stirring for 75 minutes.

[0054] (4) Cool down to 43°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion D of the present invention.

[0055] Example 5

[0056] (1) Purge the reactor and pipeline with nitrogen for 6 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.1 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.17 mol allyl naphthalene, 0.15 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 4.75 g Tween 80, 2.44 g diammonium hydrogen phosphate, and 370 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0057] (2) Transfer 58% of the weight of the above emulsion to the first high-level tank, add 0.2 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.3 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 198 g of deionized water to the reaction vessel, and stir evenly.

[0058] (3) Continue stirring the emulsion in the reactor and raise the temperature to 42°C. Add 57.5g of initiator to the second high-level tank. The initiator is 10wt% ammonium persulfate and 5wt% sodium sulfite. Add it to the reactor at a uniform rate. After 17min, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 10min. The total addition time of the initiator in the second high-level tank is controlled to be 50min. After the addition is completed, stir and raise the temperature of the reactor to 70°C and continue stirring for 80min.

[0059] (4) Cool down to 40°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion E of the present invention.

[0060] Example 6

[0061] (1) Purge the reactor and pipeline with nitrogen for 8 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.15 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.14 mol allyl naphthalene, 0.1 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 5.21 g Tween 80, 2.67 g diammonium hydrogen phosphate, and 364 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0062] (2) Transfer 80% of the weight of the above emulsion to the first high-level tank, add 0.3 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.2 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 204 g of deionized water to the reaction vessel, and stir evenly.

[0063] (3) Continue stirring the emulsion in the reactor and raise the temperature to 44°C. Add 62.3g of initiator to the second high-level tank. The initiator is 10wt% ammonium persulfate and 5wt% sodium bisulfite. Add it to the reactor at a uniform rate. After 16min, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 6min. The total addition time of the initiator in the second high-level tank is controlled at 55min. After the addition is completed, stir and raise the temperature of the reactor to 72°C and continue stirring for 70min.

[0064] (4) Cool down to 42°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion F of the present invention.

[0065] Example 7

[0066] (1) Purge the reactor and pipeline with nitrogen for 5 minutes. During the later synthesis process, nitrogen is slowly introduced to keep the entire system as isolated from air as possible. Add 2 mol acrylamide, 0.12 mol 2-acrylamido-2-methylpropanesulfonic acid, 0.1 mol allyl naphthalene, 0.12 mol 1-allyl-3-methylimidazolium p-toluenesulfonate, 5.68 g Tween 80, 2.84 g diammonium hydrogen phosphate, and 350 g deionized water to the reactor in sequence. Start stirring and adjust the pH to 7-8 with 1 mol / L sodium hydroxide until all raw materials become a uniform emulsion.

[0067] (2) Transfer 58% of the weight of the above emulsion to the first high-level tank, add 0.25 mol of 2-acrylamido-2-methylpropanesulfonic acid and 0.25 mol of 1-allyl-3-methylimidazolium p-toluenesulfonate to the first high-level tank, stir evenly, adjust the pH to 7-8 with 1 mol / L sodium hydroxide, add 213 g of deionized water to the reaction vessel, and stir evenly.

[0068] (3) Continue stirring the emulsion in the reactor and raise the temperature to 41°C. Add 71g of initiator to the second high-level tank. The initiator is 10wt% ammonium persulfate and 5wt% sodium sulfite. Add it to the reactor at a uniform rate. After 17min, add the liquid in the first high-level tank to the reactor at a uniform rate. Control the initiator in the second high-level tank to be added later than the liquid in the first high-level tank. The lag time is 8min. The total addition time of the initiator in the second high-level tank is controlled at 45min. After the addition is completed, stir and raise the temperature of the reactor to 73°C and continue stirring for 80min.

[0069] (4) Cool down to 45°C and adjust the pH to 7-8 with 1 mol / L sodium hydroxide solution to obtain the zwitterionic polyacrylamide emulsion G of the present invention.

[0070] Test Example 1: Viscosity-average molecular weight and apparent viscosity test

[0071] Molecular weight testing was performed according to GB17514-2008 "Polyacrylamide for Water Treatment Agents", and apparent viscosity testing was performed according to Q / SH1020 1572-2022 "Polyacrylamide for Oil Displacement". A comparison sample, No. 3 PAM from Gansu Qingyang PAM Oilfield Displacement Agent Co., Ltd., was used. The test results are shown in Table 1.

[0072] As can be seen from Table 1, the viscosity-average molecular weights of the zwitterionic polyacrylamide emulsions A, B, C, D, E, F, and G of this invention are greater than 20 million, reaching a maximum of 29.5 million, while the viscosity-average molecular weight of product #3 is 12 million, which is significantly lower than that of this invention. The apparent viscosity of the zwitterionic polyacrylamide emulsions A, B, C, D, E, F, and G of this invention is greater than 100 mPa·s, reaching a maximum of 142 mPa·s, while the apparent viscosity of product #3 is 60 mPa·s, which is significantly lower than that of this invention.

[0073] Test Example 2 Shear Resistance Evaluation

[0074] The shear resistance evaluation was based on "Q / SH1020 1572-2022 Polyacrylamide for Oil Displacement", with PAM No. 3 from Gansu Qingyang PAM Oilfield Displacement Agent Co., Ltd. used as a comparative sample. The test results are shown in Table 1.

[0075] Table 1. Molecular weight, apparent viscosity, and test results

[0076] sample Viscosity-average molecular weight, 10,000 Apparent viscosity, mPa·s Shear viscosity retention, % A 2050 102 93.8 B 2260 108 93.2 C 2440 118 92.7 D 2500 122 92.5 E 2680 128 91.9 F 2840 136 91.4 G 2950 142 90.5 3# 1200 60 86.8

[0077] As can be seen from Table 1, the shear viscosity retention rates of the zwitterionic polyacrylamide emulsions A, B, C, D, E, F, and G of this invention are greater than 90%, with the highest reaching 93.8%, while the shear viscosity retention rate of product #3 is 86.8%, which is significantly lower than that of this invention.

[0078] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the preparation of an ultra-high molecular weight zwitterionic polyacrylamide emulsion, characterized in that, The specific steps of the preparation method are as follows: (1) The reaction kettle and pipeline are purged with nitrogen for 5-8 minutes, and nitrogen is slowly introduced during the later synthesis process to keep the whole system isolated from air as much as possible. Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, allylnaphthalene, 1-allyl-3-methylimidazolium p-toluenesulfonate, tween80, buffer salt and deionized water are sequentially added to the reaction kettle, stirring is started, and 1 mol / L sodium hydroxide is used to adjust the pH to 7-8 until all raw materials become a uniform emulsion. The molar ratio of 2-acrylamido-2-methylpropanesulfonic acid, allylnaphthalene, 1-allyl-3-methylimidazolium p-toluenesulfonate and acrylamide is 0.02-0.1:0.05-0.2:0.02-0.1:1, and the weight ratio of tween80, buffer salt, deionized water and acrylamide is 0.02-0.04:0.01-0.02:2.5-3:

1. (2) 50-80% of the above emulsion is transferred to the first high tank, 2-acrylamido-2-methylpropanesulfonic acid and 1-allyl-3-methylimidazolium p-toluenesulfonate are added again in the first high tank, stirring is uniform, 1 mol / L sodium hydroxide is used to adjust the pH to 7-8, deionized water is added again in the reaction kettle, and stirring is uniform. The molar ratio of 2-acrylamido-2-methylpropanesulfonic acid, 1-allyl-3-methylimidazolium p-toluenesulfonate and acrylamide is 0.05-0.2:0.05-0.2:1, and the weight ratio of deionized water and acrylamide is 1-1.5:

1. (3) The emulsion in the reaction kettle continues to be stirred, and the temperature is raised to 40-45℃. The initiator is added to the second high tank and is added to the reaction kettle at a constant speed. After 15-20 minutes, the liquid in the first high tank is added to the reaction kettle at a constant speed. The initiator in the second high tank is added after the liquid in the first high tank is added completely, and the lag time is 2-10 minutes. The total addition time of the initiator in the second high tank is controlled to be 40-60 minutes. After the addition is completed, the reaction kettle is stirred and the temperature is raised to 70-73℃. Stirring is continued for 60-80 minutes. (4) The temperature is lowered to 40-45℃, 1 mol / L sodium hydroxide solution is used to adjust the pH to 7-8, and the zwitterionic polyacrylamide emulsion is obtained. The viscosity average molecular weight of the zwitterionic polyacrylamide emulsion is 20,000,000-30,000,000.

2. The process for preparing an ultra-high molecular weight zwitterionic polyacrylamide emulsion according to claim 1, characterized in that, In step (1), the buffer salt is one of disodium hydrogen phosphate, dipotassium hydrogen phosphate and diammonium hydrogen phosphate.

3. The method for preparing an ultra-high molecular weight zwitterionic polyacrylamide emulsion according to claim 1, characterized in that, In step (3), the initiator is a mixed solution of one of potassium persulfate, ammonium persulfate and sodium persulfate and one of sodium bisulfite, sodium sulfite and sodium thiosulfate. The concentration of the persulfate salt is 10 wt%, the concentration of sodium bisulfite, sodium sulfite or sodium thiosulfate is 5 wt%, and the weight ratio of the initiator to acrylamide is 0.2-0.5:

1.

4. An ultra-high molecular weight zwitterionic polyacrylamide emulsion characterized in that, The molecular structure formula of the zwitterionic polyacrylamide emulsion is as follows: wherein a=50,000-300,000. b＝10000-50000； c＝5000-30000； d＝10000-50000。

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