High-viscosity instant polyacrylamide for oil field and preparation method thereof

Abstract

The invention relates to the field of high polymer materials, in particular to high-viscosity instant polyacrylamide for an oil field and a preparation method of the high-viscosity instant polyacrylamide for the oil field, and aims to solve the problem that the application of the traditional polyacrylamide in a complex oil field environment is limited due to the defects that the viscosity of the traditional polyacrylamide is sharply reduced and the temperature resistance and the salt resistance are poor in formation water with relatively high mineralization degree. Carboxyl and sodium sulfonate groups are introduced into the molecular structure of the high-viscosity instant polyacrylamide for the oil field, so that the interaction force among polymer molecules is enhanced, the viscosity of the polymer is improved, and meanwhile, the high-viscosity instant polyacrylamide for the oil field has excellent dissolving property and can be quickly dissolved in water; and sodium sulfonate groups and a large number of C-F bonds improve the thermal stability and salt tolerance of the polymer, so that the polymer can still maintain higher viscosity in a high-temperature and high-salt environment.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, and in particular to high-viscosity and fast-dissolving oilfield polyacrylamide and a preparation method thereof. Background Art

[0002] As an important synthetic polymer material, polyacrylamide is widely used in water treatment, oilfield development, pulp, textile and other fields. In oilfield development, polyacrylamide has become an important oil displacement agent for improving oil recovery due to its high viscosity and good rheological properties. However, traditional polyacrylamide has problems such as a sharp drop in viscosity and poor temperature and salt resistance in formation water with high mineralization, which limits its application in complex oilfield environments. Therefore, the development of a high-viscosity, fast-dissolving oilfield polyacrylamide and its preparation method has important theoretical significance and industrial practical value, which can maintain high viscosity for a long time under high temperature and high mineralization formation conditions. Summary of the invention

[0003] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide a high-viscosity and fast-dissolving oilfield polyacrylamide and a preparation method thereof, which solves the problem that traditional polyacrylamide has the disadvantages of a sharp drop in viscosity and poor temperature and salt resistance in formation water with high mineralization, which limits its application in complex oilfield environments.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] The preparation method of high-viscosity instant oilfield polyacrylamide comprises the following steps:

[0006] Step S1: Add ferric chloride, 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and anhydrous tetrahydrofuran to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir and react for 20-30 minutes at a temperature of 25-30° C. and a stirring rate of 300-400 r / min, then add N-chlorosuccinimide and 3,5-xylenol and continue stirring and reacting for 10-15 hours under the condition of heating to 60-65° C. After the reaction, cool the reaction product to room temperature, then add it to distilled water, then extract with ethyl acetate 2-3 times, combine the extracts and wash with sodium thiosulfate solution and saturated saline solution 2-3 times in sequence, then dry with anhydrous magnesium sulfate, then vacuum filter, rotary evaporate the filtrate to remove the solvent, and then recrystallize with n-hexane to obtain intermediate 1;

[0007] Step S2: adding intermediate 1, concentrated nitric acid and deionized water to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stirring the reaction at a temperature of 170-180° C. and a stirring rate of 300-400 r / min for 8-10 hours, cooling the reaction product to room temperature after the reaction, and then adjusting the pH to 7.5-8.5 with sodium hydroxide solution, and then continuing to stir for 1-1.5 hours, and then vacuum filtering the reaction product, adjusting the filtrate to a pH of 4-5 with hydrochloric acid solution, and then vacuum filtering, placing the filter cake in a vacuum drying oven, and drying it at a temperature of 50-55° C. for 2-3 hours to obtain intermediate 2;

[0008] Step S3: Add intermediate 2, heptafluorobutanol, p-toluenesulfonic acid and N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, introduce nitrogen protection, stir and react for 5-10 minutes at a temperature of 25-30° C. and a stirring rate of 300-400 r / min, then heat to 80-90° C. and continue stirring and reacting for 3-5 hours. After the reaction is completed, cool the reaction product to room temperature, and then remove the solvent by rotary evaporation to obtain intermediate 3;

[0009] Step S4: adding intermediate 3, anhydrous potassium carbonate and tetrahydrofuran to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stirring the reaction for 15-25 minutes at a temperature of 0-5°C and a stirring rate of 300-400r / min, then adding acryloyl chloride dropwise while stirring, controlling the dropping rate to 1-2 drops / s, and heating to 60-65°C after the dropwise addition is completed, and stirring the reaction for 2-4 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain intermediate 4;

[0010] Step S5: adding the intermediate 4 and the sodium sulfite solution to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introducing nitrogen protection, stirring the reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 20-30 min, then heating to 120-140° C. and continuing to stir the reaction for 6-8 h. After the reaction is completed, the reaction product is cooled to room temperature, then the solvent is removed by rotary evaporation, and then recrystallized with anhydrous ethanol to obtain a modified monomer;

[0011] Step S6: Add acrylamide, acrylic acid, modified monomer, emulsifier and deionized water into a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 15-25 minutes at a temperature of 0-5°C and a stirring rate of 300-400r / min, then add the initiator solution dropwise while stirring, and control the dropping rate to 1-2 drops / s. After the addition is completed, the temperature is raised to 60-65°C and the stirring reaction is continued for 2-4 hours. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0012] As a further scheme of the present invention: the dosage ratio of the ferric chloride, 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide, anhydrous tetrahydrofuran, N-chlorosuccinimide and 3,5-dimethylphenol in step S1 is 0.05-0.1 g: 0.3-0.5 g: 30-40 mL: 11-13 mmol: 10 mmol.

[0013] As a further solution of the present invention: the molar concentration of the sodium thiosulfate solution in step S1 is 1-1.5 mol / L.

[0014] As a further solution of the present invention: the usage ratio of the intermediate 1, concentrated nitric acid and deionized water in step S2 is 2g:10-12mL:20-25mL.

[0015] As a further solution of the present invention: the mass fraction of the concentrated nitric acid in step S2 is 65-68%, the mass fraction of the sodium hydroxide solution is 20-25%, and the mass fraction of the hydrochloric acid solution is 15-20%.

[0016] As a further scheme of the present invention: the usage ratio of the intermediate 2, heptafluorobutanol, p-toluenesulfonic acid and N,N-dimethylformamide in step S3 is 10 mmol: 22-25 mmol: 0.01-0.05 g: 50-60 mL.

[0017] As a further solution of the present invention: the usage ratio of the intermediate 3, anhydrous potassium carbonate, tetrahydrofuran and acryloyl chloride in step S4 is 10 mmol: 15-20 mmol: 50-60 mL: 11-13 mmol.

[0018] As a further solution of the present invention: the usage ratio of the intermediate 4 and the sodium sulfite solution in step S5 is 2 g: 25-30 mL.

[0019] As a further embodiment of the present invention: the mass fraction of the sodium sulfite solution in step S5 is 35-40%.

[0020] As a further solution of the present invention: the usage ratio of acrylamide, acrylic acid, modified monomer, emulsifier, deionized water and initiator solution in step S6 is 40-50g:18-24g:2.5-11.5g:0.5-0.9g:80-100mL:10-15mL.

[0021] As a further solution of the present invention: the emulsifier in step S6 is a mixture of emulsifier span-80 and emulsifier tx-10 in a mass ratio of 1:1.

[0022] As a further solution of the present invention: the initiator solution in step S6 is an ammonium persulfate solution with a mass fraction of 2-3%.

[0023] As a further solution of the present invention: high-viscosity and fast-soluble oilfield polyacrylamide is prepared according to the preparation method of high-viscosity and fast-soluble oilfield polyacrylamide.

[0024] Beneficial effects of the present invention:

[0025] The high-viscosity instant oilfield polyacrylamide and the preparation method thereof are as follows: N-chlorosuccinimide and 3,5-xylenol are reacted, 3,5-xylenol is chlorinated by N-chlorosuccinimide, and a chlorine atom is introduced into carbon No. 4 of the benzene ring of 3,5-xylenol to obtain an intermediate 1; then the intermediate 1 is reacted with concentrated nitric acid, the concentrated nitric acid oxidizes the intermediate 1, and the methyl group on the intermediate 1 is oxidized into a carboxyl group to obtain an intermediate 2; then the intermediate 2 is reacted with heptafluorobutanol, the carboxyl group on the intermediate 2 reacts with the alcoholic hydroxyl group on the heptafluorobutanol, a large number of CF bonds are introduced, and an intermediate 3 is obtained; then the intermediate 3 is reacted with acryloyl chloride, the phenolic hydroxyl group on the intermediate 3 reacts with the acyl chloride group on the acryloyl chloride, and an olefinic group is introduced. , intermediate 4 is obtained, and then intermediate 4 and sodium sulfite solution are reacted, the chlorine atoms on intermediate 4 react with sodium sulfite, and the chlorine atoms are replaced by sodium sulfonate groups to obtain modified monomers, and finally acrylamide, acrylic acid, and modified monomer comonomers are used for emulsion polymerization to form a polymer to obtain high-viscosity instant oilfield polyacrylamide; the molecular structure of the high-viscosity instant oilfield polyacrylamide is enhanced by introducing carboxyl groups and sodium sulfonate groups, thereby enhancing the interaction force between polymer molecules and improving the viscosity of the polymer, while making it have excellent solubility and can be quickly dissolved in water, and the sodium sulfonate groups and a large number of CF bonds improve the thermal stability and salt resistance of the polymer, so that it can still maintain a high viscosity in a high temperature and high salt environment. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1:

[0028] This embodiment is a method for preparing a high-viscosity, fast-dissolving oilfield polyacrylamide, comprising the following steps:

[0029] Step S1: 0.05 g of ferric chloride, 0.3 g of 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and 30 mL of anhydrous tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 25° C. and a stirring rate of 300 r / min for 20 min. Then, 11 mmol of N-chlorosuccinimide and 10 mmol of 3,5-xylenol were added and the temperature was raised to 60° C. and the stirring reaction was continued for 10 h. After the reaction was completed, the reaction product was cooled to room temperature and then added to distilled water. The mixture was extracted with ethyl acetate twice, and the extracts were combined and washed with a sodium thiosulfate solution with a molar concentration of 1 mol / L and a saturated saline solution twice, and then dried with anhydrous magnesium sulfate, and then vacuum filtered. The filtrate was rotary evaporated to remove the solvent, and then recrystallized with n-hexane to obtain intermediate 1;

[0030] Step S2: 2 g of intermediate 1, 10 mL of 65% concentrated nitric acid and 20 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for 8 h at a temperature of 170 ° C and a stirring rate of 300 r / min. After the reaction, the reaction product was cooled to room temperature, and then adjusted to pH 7.5 with a 20% sodium hydroxide solution, and then continued to stir for 1 h. After that, the reaction product was vacuum filtered, and the filtrate was adjusted to pH 4 with a 15% hydrochloric acid solution, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at a temperature of 50 ° C for 2 h to obtain intermediate 2;

[0031] Step S3: 10 mmol of intermediate 2, 22 mmol of heptafluorobutanol, 0.01 g of p-toluenesulfonic acid and 50 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 300 r / min for 5 min, and then the temperature was raised to 80° C. and the stirring reaction was continued for 3 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 3;

[0032] Step S4: 10 mmol of intermediate 3, 15 mmol of anhydrous potassium carbonate and 50 mL of tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction at a temperature of 0°C and a stirring rate of 300 r / min for 15 min, and then 11 mmol of acryloyl chloride was added dropwise while stirring, and the dropping rate was controlled to be 1 drop / s. After the addition was completed, the temperature was raised to 60°C and the stirring reaction was continued for 2 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0033] Step S5: 2 g of intermediate 4 and 25 mL of a 35% sodium sulfite solution were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 300 r / min for 20 min, and then the mixture was heated to 120° C. and stirred for 6 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation, and then recrystallized from anhydrous ethanol to obtain a modified monomer;

[0034] Step S6: 40g acrylamide, 18g acrylic acid, 2.5g modified monomer, 0.5g emulsifier span-80 and emulsifier tx-10 mixed in a mass ratio of 1:1 and 80mL deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction for 15min at a temperature of 0°C and a stirring rate of 300r / min, and then 10mL of 2% ammonium persulfate solution is added dropwise while stirring, and the dropping rate is controlled to be 1 drop / s. After the addition is completed, the temperature is raised to 60°C and the stirring reaction is continued for 2h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0035] Embodiment 2:

[0036] This embodiment is a method for preparing a high-viscosity, fast-dissolving oilfield polyacrylamide, comprising the following steps:

[0037] Step S1: 0.08 g of ferric chloride, 0.4 g of 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and 35 mL of anhydrous tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 28° C. and a stirring rate of 350 r / min for 25 min. Then, 12 mmol of N-chlorosuccinimide and 10 mmol of 3,5-xylenol were added and the temperature was raised to 62° C. and the stirring reaction was continued for 12 h. After the reaction was completed, the reaction product was cooled to room temperature and then added to distilled water. The mixture was extracted with ethyl acetate twice, and the extracts were combined and washed with a sodium thiosulfate solution having a molar concentration of 1.2 mol / L and a saturated saline solution twice, and then dried with anhydrous magnesium sulfate, and then vacuum filtered. The filtrate was rotary evaporated to remove the solvent, and then recrystallized with n-hexane to obtain intermediate 1;

[0038] Step S2: 2 g of intermediate 1, 11 mL of 67% concentrated nitric acid and 22 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for 9 hours at a temperature of 175° C. and a stirring rate of 350 r / min. After the reaction, the reaction product was cooled to room temperature, and then adjusted to pH 8.0 with a 22% sodium hydroxide solution, and then continued to stir for 1.2 hours. The reaction product was then vacuum filtered, and the filtrate was adjusted to pH 4.5 with a 18% hydrochloric acid solution, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at a temperature of 52° C. for 2.5 hours to obtain intermediate 2;

[0039] Step S3: 10 mmol of intermediate 2, 24 mmol of heptafluorobutanol, 0.03 g of p-toluenesulfonic acid and 55 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 28° C. and a stirring rate of 350 r / min for 8 min, and then the mixture was heated to 85° C. and stirred for 4 h. After the reaction, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 3;

[0040] Step S4: 10 mmol of intermediate 3, 18 mmol of anhydrous potassium carbonate and 55 mL of tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction at a temperature of 3°C and a stirring rate of 350 r / min for 20 min, and then 12 mmol of acryloyl chloride was added dropwise while stirring, and the dropping rate was controlled to be 1 drop / s. After the addition was completed, the temperature was raised to 62°C and the stirring reaction was continued for 3 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0041] Step S5: 2 g of intermediate 4 and 28 mL of a 38% sodium sulfite solution were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 28° C. and a stirring rate of 350 r / min for 25 min, and then the mixture was heated to 130° C. and stirred for 7 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation, and then recrystallized from anhydrous ethanol to obtain a modified monomer;

[0042] Step S6: 45g acrylamide, 21g acrylic acid, 7g modified monomer, 0.7g emulsifier span-80 and emulsifier tx-10 mixed in a mass ratio of 1:1 and 90mL deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction for 20min at a temperature of 3°C and a stirring rate of 350r / min, and then 12mL of 2.5% ammonium persulfate solution is added dropwise while stirring, and the dropping rate is controlled to 2 drops / s. After the addition is completed, the temperature is raised to 62°C and the stirring reaction is continued for 3h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0043] Embodiment 3:

[0044] This embodiment is a method for preparing a high-viscosity, fast-dissolving oilfield polyacrylamide, comprising the following steps:

[0045] Step S1: 0.1 g of ferric chloride, 0.5 g of 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and 40 mL of anhydrous tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 30° C. and a stirring rate of 400 r / min for 30 min. Then, 13 mmol of N-chlorosuccinimide and 10 mmol of 3,5-xylenol were added and the temperature was raised to 65° C. and the stirring reaction was continued for 15 h. After the reaction was completed, the reaction product was cooled to room temperature and then added to distilled water. The mixture was extracted with ethyl acetate for 3 times. The extracts were combined and washed with a sodium thiosulfate solution having a molar concentration of 1.5 mol / L and a saturated saline solution for 3 times, and then dried with anhydrous magnesium sulfate. The mixture was vacuum filtered, and the filtrate was rotary evaporated to remove the solvent. The filtrate was recrystallized with n-hexane to obtain an intermediate 1.

[0046] Step S2: 2 g of intermediate 1, 12 mL of 68% concentrated nitric acid and 25 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for 10 h at a temperature of 180 ° C and a stirring rate of 400 r / min. After the reaction, the reaction product was cooled to room temperature, and then adjusted to pH 8.5 with a 25% sodium hydroxide solution, and then continued to stir for 1.5 h. The reaction product was then vacuum filtered, and the filtrate was adjusted to pH 5 with a 20% hydrochloric acid solution, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at a temperature of 55 ° C for 3 h to obtain intermediate 2;

[0047] Step S3: 10 mmol of intermediate 2, 25 mmol of heptafluorobutanol, 0.05 g of p-toluenesulfonic acid and 60 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 10 min, and then the temperature was raised to 90° C. and the stirring reaction was continued for 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 3;

[0048] Step S4: 10 mmol of intermediate 3, 20 mmol of anhydrous potassium carbonate and 60 mL of tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction at a temperature of 5° C. and a stirring rate of 400 r / min for 25 min, and then 13 mmol of acryloyl chloride was added dropwise while stirring, and the dropping rate was controlled to be 2 drops / s. After the addition was completed, the temperature was raised to 65° C. and the stirring reaction was continued for 4 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0049] Step S5: 2 g of intermediate 4 and 30 mL of a 40% sodium sulfite solution were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 140° C. and stirred for 8 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation, and then recrystallized from anhydrous ethanol to obtain a modified monomer;

[0050] Step S6: 50g acrylamide, 24g acrylic acid, 11.5g modified monomer, 0.9g emulsifier span-80 and emulsifier tx-10 mixed in a mass ratio of 1:1 and 100mL deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction for 25min at a temperature of 5°C and a stirring rate of 400r / min, and then 15mL of 3% ammonium persulfate solution is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the dropwise addition is completed, the temperature is raised to 65°C and the stirring reaction is continued for 4h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0051] Comparative Example 1:

[0052] This comparative example is a method for preparing a high-viscosity, fast-dissolving oilfield polyacrylamide, comprising the following steps:

[0053] 50g acrylamide, 0.9g emulsifier span-80 and emulsifier tx-10 mixed in a mass ratio of 1:1 and 100mL deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for 25min at a temperature of 5°C and a stirring rate of 400r / min. Then, 15mL of 3% ammonium persulfate solution was added dropwise while stirring, and the dropping rate was controlled to 2 drops / s. After the addition was completed, the temperature was raised to 65°C and the stirring reaction was continued for 4h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0054] Comparative Example 2:

[0055] This comparative example is a method for preparing a high-viscosity, fast-dissolving oilfield polyacrylamide, comprising the following steps:

[0056] 50g acrylamide, 24g acrylic acid, 0.9g emulsifier span-80 and emulsifier tx-10 mixed in a mass ratio of 1:1 and 100mL deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction for 25min at a temperature of 5°C and a stirring rate of 400r / min. Then, 15mL of 3% ammonium persulfate solution was added dropwise while stirring, and the dropping rate was controlled to 2 drops / s. After the addition was completed, the temperature was raised to 65°C and the stirring reaction was continued for 4h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0057] Comparative Example 3:

[0058] This comparative example is a method for preparing a high-viscosity, fast-dissolving oilfield polyacrylamide, comprising the following steps:

[0059] Step S1: 0.1 g of ferric chloride, 0.5 g of 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and 40 mL of anhydrous tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 30° C. and a stirring rate of 400 r / min for 30 min. Then, 13 mmol of N-chlorosuccinimide and 10 mmol of 3,5-xylenol were added and the temperature was raised to 65° C. and the stirring reaction was continued for 15 h. After the reaction was completed, the reaction product was cooled to room temperature and then added to distilled water. The mixture was extracted with ethyl acetate for 3 times. The extracts were combined and washed with a sodium thiosulfate solution having a molar concentration of 1.5 mol / L and a saturated saline solution for 3 times, and then dried with anhydrous magnesium sulfate. The mixture was vacuum filtered, and the filtrate was rotary evaporated to remove the solvent. The filtrate was recrystallized with n-hexane to obtain an intermediate 1.

[0060] Step S2: 2 g of intermediate 1, 12 mL of 68% concentrated nitric acid and 25 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for 10 h at a temperature of 180 ° C and a stirring rate of 400 r / min. After the reaction, the reaction product was cooled to room temperature, and then adjusted to pH 8.5 with a 25% sodium hydroxide solution, and then continued to stir for 1.5 h. The reaction product was then vacuum filtered, and the filtrate was adjusted to pH 5 with a 20% hydrochloric acid solution, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at a temperature of 55 ° C for 3 h to obtain intermediate 2;

[0061] Step S3: 10 mmol of intermediate 2, 25 mmol of heptafluorobutanol, 0.05 g of p-toluenesulfonic acid and 60 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 10 min, and then the temperature was raised to 90° C. and the stirring reaction was continued for 5 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 3;

[0062] Step S4: 10 mmol of intermediate 3, 20 mmol of anhydrous potassium carbonate and 60 mL of tetrahydrofuran were added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction at a temperature of 5° C. and a stirring rate of 400 r / min for 25 min, and then 13 mmol of acryloyl chloride was added dropwise while stirring, and the dropping rate was controlled to be 2 drops / s. After the addition was completed, the temperature was raised to 65° C. and the stirring reaction was continued for 4 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 4;

[0063] Step S5: 2 g of intermediate 4 and 30 mL of a 40% sodium sulfite solution were added to a three-necked flask equipped with a stirrer, a thermometer and a gas guide tube, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 140° C. and stirred for 8 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation, and then recrystallized from anhydrous ethanol to obtain a modified monomer;

[0064] Step S6: 50g acrylamide, 11.5g modified monomer, 0.9g emulsifier span-80 and emulsifier tx-10 mixed in a mass ratio of 1:1 and 100mL deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stirred for reaction for 25min at a temperature of 5°C and a stirring rate of 400r / min, and then 15mL of 3% ammonium persulfate solution is added dropwise while stirring, and the dropping rate is controlled to be 2 drops / s. After the addition is completed, the temperature is raised to 65°C and the stirring reaction is continued for 4h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain high-viscosity instant oilfield polyacrylamide.

[0065] The high-viscosity, instant-soluble oilfield polyacrylamide of Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing under the conditions of 60° C. and a salinity of 20,000 mg / L. The test results are shown in the following table:

[0066] sample Apparent viscosity, mPa·s Dissolution time, min Viscosity retention rate after standing at 90℃ for 7 days, % Example 1 35.1 36 85.3 Example 2 36.8 33 88.7 Example 3 38.3 31 90.5 Comparative Example 1 21.7 77 28.4 Comparative Example 2 32.4 56 37.5 Comparative Example 3 30.5 44 82.9

[0067] Referring to the data in the above table, according to the comparison between Examples 1-3 and Comparative Examples 1-3, it can be known that the addition of acrylic acid, modified monomers and acrylamide for copolymerization can effectively improve the viscosity and high temperature resistance of oilfield polyacrylamide, and the dissolution rate is greatly improved.

[0068] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0069] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing high-viscosity instant oilfield polyacrylamide, characterized in that: The following steps are involved: Step S1: stirring ferric chloride, 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and anhydrous tetrahydrofuran for reaction, then adding N-chlorosuccinimide and 3,5-xylenol and continuing stirring for reaction, cooling the reaction product after the reaction, then adding it into distilled water, then extracting, combining the extracts and washing with sodium thiosulfate solution and saturated saline solution in sequence, then drying, then vacuum filtering, rotary evaporating the filtrate, and then recrystallizing to obtain intermediate 1; Step S2: stirring the intermediate 1, concentrated nitric acid and deionized water for reaction, cooling the reaction product after the reaction, adjusting the pH with a sodium hydroxide solution, and continuing stirring, vacuum filtering the reaction product, adjusting the pH of the filtrate with a hydrochloric acid solution, vacuum filtering, and drying the filter cake to obtain the intermediate 2; Step S3: stirring the intermediate 2, heptafluorobutanol, p-toluenesulfonic acid and N,N-dimethylformamide for reaction, cooling the reaction product after the reaction is completed, and then rotary evaporating to obtain the intermediate 3; Step S4: stirring the intermediate 3, anhydrous potassium carbonate and tetrahydrofuran for reaction, then adding acryloyl chloride dropwise while stirring, and continuing to stir the reaction after the addition is complete. After the reaction is complete, the reaction product is cooled and then rotary evaporated to obtain the intermediate 4; Step S5: stirring the intermediate 4 and the sodium sulfite solution to react, cooling the reaction product after the reaction is completed, then rotary evaporating, and then recrystallizing to obtain a modified monomer; Step S6: acrylamide, acrylic acid, modified monomer, emulsifier and deionized water are stirred for reaction, and then the initiator solution is added dropwise while stirring. After the addition is completed, the stirring reaction is continued. After the reaction is completed, the reaction product is cooled and then rotary evaporated to obtain high-viscosity instant oilfield polyacrylamide.

2. The method for preparing the high-viscosity and fast-dissolving oilfield polyacrylamide according to claim 1, characterized in that: The amount ratio of the ferric chloride, 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide, anhydrous tetrahydrofuran, N-chlorosuccinimide and 3,5-dimethylphenol in step S1 is 0.05-0.1g: 0.3-0.5g: 30-40mL: 11-13mmol: 10mmol; the molar concentration of the sodium thiosulfate solution in step S1 is 1-1.5mol / L.

3. The method for preparing the high-viscosity and fast-dissolving oilfield polyacrylamide according to claim 1, characterized in that: The usage ratio of the intermediate 1, concentrated nitric acid and deionized water in step S2 is 2g:10-12mL:20-25mL; the mass fraction of the concentrated nitric acid in step S2 is 65-68%, the mass fraction of the sodium hydroxide solution is 20-25%, and the mass fraction of the hydrochloric acid solution is 15-20%.

4. The method for preparing the high-viscosity and fast-dissolving oilfield polyacrylamide according to claim 1, characterized in that: The usage ratio of the intermediate 2, heptafluorobutanol, p-toluenesulfonic acid and N,N-dimethylformamide in step S3 is 10 mmol: 22-25 mmol: 0.01-0.05 g: 50-60 mL.

5. The method for preparing high-viscosity and fast-dissolving oilfield polyacrylamide according to claim 1, characterized in that: The usage ratio of the intermediate 3, anhydrous potassium carbonate, tetrahydrofuran and acryloyl chloride in step S4 is 10 mmol: 15-20 mmol: 50-60 mL: 11-13 mmol.

6. The method for preparing high-viscosity and fast-dissolving oilfield polyacrylamide according to claim 1, characterized in that: The usage ratio of the intermediate 4 and the sodium sulfite solution in step S5 is 2 g: 25-30 mL; the mass fraction of the sodium sulfite solution in step S5 is 35-40%.

7. The method for preparing high-viscosity and fast-dissolving oilfield polyacrylamide according to claim 1, characterized in that: The usage ratio of acrylamide, acrylic acid, modified monomer, emulsifier, deionized water and initiator solution in step S6 is 40-50g:18-24g:2.5-11.5g:0.5-0.9g:80-100mL:10-15mL; the emulsifier in step S6 is a mixture of emulsifier span-80 and emulsifier tx-10 in a mass ratio of 1:1; the initiator solution in step S6 is an ammonium persulfate solution with a mass fraction of 2-3%.

8. High-viscosity, fast-dissolving oilfield polyacrylamide, characterized in that: The high-viscosity and fast-soluble oilfield polyacrylamide is prepared according to the preparation method of the high-viscosity and fast-soluble oilfield polyacrylamide according to any one of claims 1-7.