Copolymer emulsions, methods of making and using the same

Abstract

The present application relates to the field of polymer synthesis, and discloses a copolymer emulsion, a preparation method and application thereof. The copolymer emulsion comprises a copolymer hydrogel, an organic solvent, an oil-soluble emulsifier and a water-soluble emulsifier, the average particle size of the copolymer hydrogel is 100-600 nm, the copolymer hydrogel comprises structural unit A, structural unit B and structural unit C, the copolymer emulsion has the characteristics of miniemulsion, is obtained by inverse emulsion polymerization of monomers, and the purity of monomer A is less than 99%; the copolymer emulsion can improve the flowability of crude oil when used for oil exploitation, thereby improving the recovery rate of crude oil.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis, and more specifically to a copolymer emulsion, its preparation method, and its application. Background Technology

[0002] With the advancement of the petroleum industry and the increasing difficulty of oil extraction, the requirements for the temperature and salt resistance of water-soluble polymers in oilfields are becoming increasingly stringent. The viscosity of ordinary partially hydrolyzed polyacrylamide aqueous solutions decreases sharply with increasing formation salinity and temperature, making it difficult to meet the requirements of oil production and fracturing operations. Copolymerizing temperature- and salt-resistant monomers with acrylamide (AM) monomers is an effective way to improve the temperature and salt resistance of polyacrylamide. Among them, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is an anionic temperature- and salt-resistant monomer that has been extensively studied in recent years. Its structural formula contains sulfonic acid groups insensitive to calcium and magnesium ions, shielded amide groups, and unsaturated double bonds, giving it excellent comprehensive properties.

[0003] Although copolymerization of AMPS and AM can significantly improve the temperature and salt resistance of polyacrylamide, as the AMPS content in the copolymer increases, on the one hand, the molecular weight of the copolymer is difficult to increase, affecting the thickening performance; on the other hand, the price of AMPS is higher than that of AM, leading to a significant increase in the cost of the copolymer. This is because, during the industrial production of AMPS, impurities such as N-tert-butylacrylamide easily remain in the product, resulting in lower molecular weight and lower product quality in later polymerization stages. Current technologies often require traditional methods such as washing or recrystallization to remove these impurities, which are cumbersome, increase material and energy consumption, generate a large amount of waste, have limited impurity removal effects, and significantly increase the production cost of AMPS monomers.

[0004] With the large-scale development of shale oil and gas resources, the demand for fracturing technology and supporting fast-dissolving fracturing fluids is increasing. Traditional polyacrylamide powder products, when used in oil and gas fields, require preparation trucks to arrive on-site in advance for preparation. The powder needs a long time to fully swell in the storage tank, resulting in long construction cycles and high preparation intensity, which can no longer meet the needs of large-scale fracturing in shale oil and gas wells. Emulsion-type polyacrylamide products can rapidly demulsify, dissolve, and thicken upon contact with water, with a fast dissolution rate, generally dissolving completely within minutes. This allows for continuous mixing of fracturing fluids, improving work efficiency. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a copolymer emulsion, its preparation method and application. The copolymer emulsion has the characteristics of a fine emulsion and is obtained by monomer through reverse emulsion polymerization. When used in oil extraction, it can improve the fluidity of crude oil, thereby improving the recovery rate of crude oil.

[0006] To achieve the above objectives, a first aspect of the present invention provides a copolymer emulsion, the copolymer emulsion comprising a copolymer hydrogel, an organic solvent, an oil-soluble emulsifier, and a water-soluble emulsifier;

[0007] The average particle size of the copolymer hydrogel is 100-600 nm;

[0008] The copolymer forming the copolymer hydrogel comprises structural unit A, structural unit B, and structural unit C, wherein structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3).

[0009]

[0010]

[0011] Among them, R1, R2, R3 and R4 are each independently H or methyl.

[0012] A second aspect of the present invention provides a method for preparing a copolymer emulsion, wherein the method includes:

[0013] S1. Mix the comonomer, chelating agent, first water-soluble initiator with deionized water, add soluble sodium compound to adjust pH, and form an aqueous phase; the comonomer includes monomer A, monomer B and monomer C;

[0014] S2. Mix the aqueous phase with an organic solvent to obtain an oil-water mixture;

[0015] S3. Add an oil-soluble emulsifier, a water-soluble emulsifier, and an oil-soluble initiator to the oil-water mixture to emulsify and form a water-in-oil emulsion;

[0016] S4. A second water-soluble initiator is added to the water-in-oil emulsion to carry out a polymerization reaction, thereby obtaining a copolymer emulsion containing a copolymer hydrogel;

[0017] The average particle size of the copolymer hydrogel is 100-600 nm;

[0018] The monomer A has the structure shown in formula (4), the monomer B has the structure shown in formula (5), and the monomer C has the structure shown in formula (6).

[0019]

[0020]

[0021] R1', R2', R3', and R4' are each independently H or methyl;

[0022] The purity of monomer A is <99%.

[0023] The third aspect of the present invention provides the application of the copolymer emulsion provided in the first aspect of the present invention or the copolymer emulsion prepared by the preparation method provided in the second aspect of the present invention in the field of polymers for oil fields.

[0024] Through the above technical solution, the present invention has the following beneficial effects:

[0025] (1) The copolymer emulsion provided by the present invention has the characteristics of a fine emulsion. The copolymer hydrogel has a small size, high molecular weight, fast dissolution rate, and excellent system stability and temperature and shear resistance. The copolymer that forms the copolymer hydrogel contains sulfonic acid groups that are insensitive to calcium and magnesium ions, shielded amide groups and unsaturated double bonds, which makes the copolymer emulsion have excellent temperature and salt resistance.

[0026] (2) The preparation method provided by the present invention is simple to operate, has mild reaction conditions, moderate polymerization rate, and high system stability. It can be produced on conventional reverse emulsion polymerization equipment. The monomers used are inexpensive and the amount of composite emulsifier used is moderate, which has the advantage of raw material cost.

[0027] (3) The copolymer emulsion provided by the present invention has excellent temperature and salt resistance, ensuring its stability during use. Using the copolymer emulsion in oilfield extraction can effectively improve the fluidity of crude oil and further improve the recovery rate of crude oil. Detailed Implementation

[0028] 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.

[0029] The first aspect of the present invention provides a copolymer emulsion, the copolymer emulsion comprising a copolymer hydrogel, an organic solvent, an oil-soluble emulsifier, and a water-soluble emulsifier;

[0030] The average particle size of the copolymer hydrogel is 100-600 nm;

[0031] The copolymer forming the copolymer hydrogel comprises structural unit A, structural unit B, and structural unit C, wherein structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3).

[0032]

[0033] Among them, R1, R2, R3 and R4 are each independently H or methyl.

[0034] In this invention, the copolymer emulsion exhibits the characteristics of a fine emulsion, possessing advantages such as small hydrogel size, high molecular weight, rapid dissolution, good system stability, and excellent temperature and shear resistance. The aforementioned structural units form a copolymer hydrogel structure during polymerization. Water molecules reside within the network structure formed by the copolymer molecular chains. Structural unit A introduces macromolecular branches into the copolymer molecular chains, increasing the copolymer's thermal stability. The sulfonic acid groups within this unit increase the copolymer's water solubility and hydration capacity, enhancing its salt resistance. Structural unit C introduces crosslinkable carboxylate groups into the copolymer molecular chains, increasing the copolymer's water solubility and system viscosity.

[0035] According to the present invention, based on 100 parts by weight of copolymer emulsion, the content of copolymer hydrogel is 50-75 parts by weight, the content of organic solvent is 20-45 parts by weight, the content of oil-soluble emulsifier is 1-4.5 parts by weight, and the content of water-soluble emulsifier is 0.2-1.5 parts by weight.

[0036] In this invention, copolymer emulsions with component contents within the above-mentioned ranges exhibit better stability and temperature and shear resistance.

[0037] Furthermore, based on 100 parts by weight of copolymer emulsion, the content of copolymer hydrogel is 60-75 parts by weight, the content of organic solvent is 20-40 parts by weight, the content of oil-soluble emulsifier is 3-4 parts by weight, and the content of water-soluble emulsifier is 0.2-1 parts by weight.

[0038] Furthermore, the average particle size of the copolymer hydrogel is 100-500 nm.

[0039] According to the present invention, the organic solvent is a mixture of at least one of white oil, kerosene and cyclohexane and an alkyl ester of an organic acid.

[0040] According to the present invention, the viscosity-average molecular weight of the copolymer is 12 million g / mol to 18 million g / mol.

[0041] According to the present invention, based on the total mass of the copolymer, the content of structural unit A is 10-50 wt%, the content of structural unit B is 25-85 wt%, and the content of structural unit C is 5-25 wt%.

[0042] In this invention, copolymers with the content of each structural unit within the above range have advantages such as high molecular weight and small size of copolymer hydrogels, resulting in better stability of the emulsion system.

[0043] Furthermore, based on the total mass of the copolymer, the content of structural unit A is 15-40 wt%, the content of structural unit B is 40-80 wt%, and the content of structural unit C is 5-20 wt%.

[0044] A second aspect of the present invention provides a method for preparing a copolymer emulsion, wherein the method includes:

[0045] S1. Mix the comonomer, chelating agent, first water-soluble initiator with deionized water, add soluble sodium compound to adjust pH, and form an aqueous phase; the comonomer includes monomer A, monomer B and monomer C;

[0046] S2. Mix the aqueous phase with an organic solvent to obtain an oil-water mixture;

[0047] S3. Add an oil-soluble emulsifier, a water-soluble emulsifier, and an oil-soluble initiator to the oil-water mixture to emulsify and form a water-in-oil emulsion;

[0048] S4. A second water-soluble initiator is added to the water-in-oil emulsion to carry out a polymerization reaction, thereby obtaining a copolymer emulsion containing a copolymer hydrogel;

[0049] The average particle size of the copolymer hydrogel is 100-600 nm;

[0050] The monomer A has the structure shown in formula (4), the monomer B has the structure shown in formula (5), and the monomer C has the structure shown in formula (6).

[0051]

[0052] R1', R2', R3', and R4' are each independently H or methyl;

[0053] The purity of monomer A is <99%.

[0054] In this invention, using monomer A with a purity within the above-mentioned range can yield a copolymer emulsion with fine emulsion characteristics. Furthermore, it can effectively reduce production costs, meet the economic requirements of the production process, and has high practicality.

[0055] Furthermore, the purity of monomer A is ≥85%.

[0056] Furthermore, the main impurity in monomer A is N-tert-butylacrylamide.

[0057] According to the present invention, in step S1, based on the total mass of the comonomers, the content of monomer A is 10-50 wt%, the content of monomer B is 25-85 wt%, and the content of monomer C is 5-25 wt%.

[0058] In this invention, when the amount of each monomer is within the above range, the reaction system exhibits high stability.

[0059] Furthermore, based on the total mass of the comonomers, the content of monomer A is 15-40 wt%, the content of monomer B is 40-80 wt%, and the content of monomer C is 5-20 wt%.

[0060] According to the present invention, in step S1, based on the total mass of the aqueous phase, the amount of the comonomer is 40wt%-50wt%, the amount of the chelating agent is 0.01-0.1wt%, and the amount of the first water-soluble initiator is 0.0001-0.2wt%.

[0061] Furthermore, based on the total mass of the aqueous phase, the amount of the comonomer is 45wt%-50wt%, the amount of the chelating agent is 0.01-0.05wt%, and the amount of the first water-soluble initiator is 0.005-0.2wt%.

[0062] According to the present invention, the chelating agent is an aminocarboxylic acid chelating agent.

[0063] Further, the chelating agent is at least one selected from ethylenediaminetetraacetic acid, hypotriacetic acid, diethylenetriaminepentaacetic acid, N-hydroxyethylethylaminetriacetic acid, and ethylene glycol-bis-(2-aminoethyl ether)tetraacetic acid.

[0064] According to the present invention, in step S1, the pH value of the aqueous phase is 5-7.

[0065] In this invention, the polymerization reaction needs to be carried out within the above-mentioned pH range. By adjusting the pH of the aqueous phase, the stability of the sodium sulfonate structure in copolymer structural unit A and the sodium acrylate structure in structural unit C in the emulsion can be guaranteed.

[0066] According to the present invention, step S1 may include: mixing monomer A with deionized water, adjusting the pH value to a first pH, then adding monomer B, monomer C, chelating agent, and a first water-soluble initiator, adjusting the pH value to a second pH, and forming an aqueous phase.

[0067] In this invention, adjusting the pH value to the first pH value allows monomer A to be converted into sodium acrylate structure first, reducing the exothermic reaction system. Then, the pH value is adjusted to the pH value required for the polymerization reaction, thereby improving the conversion rate and stability of the polymerization reaction.

[0068] According to the present invention, pH adjustment can be performed using an aqueous sodium hydroxide solution in step S1.

[0069] Furthermore, the first pH is 5-6.5, and the second pH is 5-6.5.

[0070] According to the present invention, the mixing process of the aqueous phase and the organic solvent is carried out using conventional operations in the field, which can ensure that the aqueous phase and the organic solvent are in full contact.

[0071] According to the present invention, in step S2, the mass ratio of the aqueous phase to the organic solvent is 1-3:1.

[0072] According to the present invention, the organic solvent comprises at least one of white oil, kerosene and cyclohexane and a mixture of alkyl esters of organic acids.

[0073] In this invention, the organic solvent can selectively transfer impurities in monomer A into the organic solvent, avoiding the influence of impurities on the polymerization process in the aqueous phase. Furthermore, the viscosity-average molecular weight of the copolymer can be controlled within a suitable range.

[0074] Furthermore, the organic acid alkyl ester accounts for 1-5 wt% of the total mass of the organic solvent.

[0075] Furthermore, the organic acid alkyl ester is selected from ethyl acetate and / or butyl acetate.

[0076] According to the present invention, in step S3, the total amount of oil-soluble emulsifier to water-soluble emulsifier is 0.015-0.05:1 in mass ratio to the oil-water mixture, and the mass ratio of oil-soluble emulsifier to water-soluble emulsifier is 3-15:1.

[0077] According to the present invention, the oil-soluble emulsifier is at least one of Span65, Span80, Span83 and Span85.

[0078] According to the present invention, the water-soluble emulsifier is at least one of OP-10, Tween80 and Tween85.

[0079] According to the present invention, in step S3, the oil-soluble initiator accounts for 0.001%-0.05 wt% of the total mass of the oil-water mixture.

[0080] Further, in step S3, the oil-soluble initiator accounts for 0.02-0.05 wt% of the total mass of the oil-water mixture.

[0081] According to the present invention, the oil-soluble initiator is an organic peroxide;

[0082] And / or, the oil-soluble initiator is an azo compound;

[0083] And / or, the oil-soluble initiator has the structure shown in formula (7);

[0084]

[0085] Where n and m are each an independent integer from 1 to 12;

[0086] R4, R5, R6 and R7 are each independently a C1-C6 straight-chain alkyl group or a C3-C6 branched alkyl group.

[0087] In this invention, the oil-soluble initiator has a highly efficient initiation effect, which improves the reaction rate.

[0088] Further, the organic peroxide is at least one selected from benzoyl peroxide, dicumyl peroxide, ditert-butyl peroxide, dodecyl peroxide, tert-butyl peroxide, diisopropyl peroxide, and dicyclohexyl peroxide.

[0089] Furthermore, the azo compound is azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0090] Furthermore, where n and m are each an independent integer from 1 to 6;

[0091] R4, R5, R6 and R7 are each independently a C1-C4 straight-chain alkyl group or a C3-C4 branched alkyl group.

[0092] In one specific embodiment of the present invention, the oil-soluble initiator has the structure shown in formula (7), wherein n = m = 2, and R4, R5, R6 and R7 are methyl groups.

[0093] According to the present invention, the first water-soluble initiator is a reducing initiator, and the second water-soluble initiator is an oxidizing initiator.

[0094] According to the present invention, the mass ratio of the first water-soluble initiator to the second water-soluble initiator is 0.5-2:1.

[0095] In this invention, the polymerization rate of the water-soluble initiator is controllable and moderate within the above-mentioned range.

[0096] Furthermore, the mass ratio of the first water-soluble initiator to the second water-soluble initiator is 0.8-1.5:1.

[0097] According to the present invention, the first water-soluble initiator is a reducing initiator, and the second water-soluble initiator is an oxidizing initiator.

[0098] Furthermore, the first water-soluble initiator is sodium sulfite and / or sodium bisulfite.

[0099] Furthermore, the second water-soluble initiator is ammonium persulfate and / or potassium persulfate.

[0100] According to the present invention, the process of emulsifying to form a water-in-oil emulsion is carried out using conventional operations in the field, which can form a stable water-in-oil emulsion.

[0101] According to the present invention, the polymerization reaction conditions include: cooling the water-in-oil emulsion to a first reaction temperature, adding a second water-soluble initiator, and controlling the water-in-oil emulsion to undergo a polymerization reaction at a second reaction temperature;

[0102] The first reaction temperature is 5-25℃, the second reaction temperature does not exceed 50℃, and the polymerization reaction time at the second reaction temperature is 2-6h.

[0103] Furthermore, the polymerization reaction conditions include: a first reaction temperature of 5-15°C, a second reaction temperature of 30-40°C, and a polymerization reaction time of 2-4 hours at the second reaction temperature.

[0104] The third aspect of the present invention provides the application of the copolymer emulsion provided in the first aspect of the present invention or the copolymer emulsion prepared by the preparation method provided in the second aspect of the present invention in the field of polymers for oil fields.

[0105] The present invention will be described in detail below through embodiments. It should be understood that the following embodiments are only used to further explain and illustrate the content of the present invention, and are not intended to limit the present invention.

[0106] In the following embodiments,

[0107] The method for testing the average particle size of copolymer hydrogels is as follows: after diluting the copolymer emulsion to a mass fraction of 0.01%, the average particle size of the copolymer hydrogel is determined using a nanoparticle size and potential analyzer.

[0108] The viscosity-average molecular weight of the copolymer forming the copolymer hydrogel is determined by washing a certain amount of emulsion with methanol and isopropanol in a volume ratio of 1:1 and drying it thoroughly at 105°C to obtain the dried copolymer. The copolymer is then tested and analyzed in accordance with the technical requirements for polymers used in oil displacement (SYT5862-2020) to obtain the viscosity-average molecular weight of the copolymer.

[0109] The temperature and shear resistance of the copolymer were tested and analyzed in accordance with the technical requirements of water-based fracturing fluids in SY / T 7627-2021. A high-temperature rheometer was used to test the copolymer emulsion at 180℃ for 100 seconds. -1 The viscosity change during shearing for 120 minutes under certain conditions is analyzed. If the viscosity remains at a stable value, it indicates that the copolymer emulsion has good temperature and shear resistance.

[0110] In the following embodiments,

[0111] Monomer A has the structure shown in formula (4) and purities of 98.5%, 95.2% and 88.6%, respectively.

[0112] Monomer B has the structure shown in formula (5), where R1' and R2' are H.

[0113] The monomer C has the structure shown in formula (6), where R3' and R4' are H.

[0114] The oil-soluble initiator has the structure shown in formula (7), where n = m = 2, and R4, R5, R6 and R7 are methyl groups.

[0115] Unless otherwise specified, all reagents and materials used in the following examples were purchased from reputable chemical reagent suppliers and were of analytical purity.

[0116] Example 1

[0117] (1) Mix 60g of monomer A with a purity of 95.2% and 60g of water evenly, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the first time, then add 60g of monomer B and 60g of 50wt% monomer C aqueous solution, then add 0.12g of disodium ethylenediaminetetraacetate and 0.027g of sodium bisulfite, add sodium hydroxide aqueous solution to adjust the pH value to 6.5 for the second time, and finally use deionized water to measure to 300g to form an aqueous phase.

[0118] (2) Take 2.4g of ethyl acetate and 117.6g of white oil and mix them thoroughly with the water phase to obtain an oil-water mixture.

[0119] (3) Add 13.37g of Span80, 1.03g of Tween80 and 0.13g of 1,4-diphenylaminocarbamate bis(2-dimethylaminoethanol) ester to the above oil-water mixture, stir evenly, and emulsify to form a water-in-oil emulsion.

[0120] (4) The water-in-oil emulsion is cooled from room temperature to 15°C, and after being deoxygenated by passing N2 through it, 3g of 1wt% potassium persulfate aqueous solution is slowly added dropwise to allow the water-in-oil emulsion to undergo polymerization. The temperature is raised to 35°C and the reaction system is kept at 35°C for 2 hours before the reaction is stopped.

[0121] (5) A copolymer emulsion was obtained. The average particle size of the copolymer hydrogel was 340 nm, and the viscosity-average molecular weight of the copolymer was 16.5 million g / mol. The emulsion was subjected to a reaction at 180 °C for 100 s. -1 The viscosity remained at 55 mPa·s after shearing for 120 min under the specified conditions.

[0122] Example 2

[0123] (1) Mix 15g of monomer A with a purity of 95.2% and 15g of water evenly, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the first time, then add 123g of monomer B, 24g of 50wt% monomer C aqueous solution, then add 0.15g of disodium ethylenediaminetetraacetate and 0.036g of sodium bisulfite, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the second time, and finally use deionized water to measure to 300g to form an aqueous phase.

[0124] (2) Take 3.75g of ethyl acetate and 121.25g of white oil and mix them thoroughly with the water phase to obtain an oil-water mixture.

[0125] (3) Add 14.90g of Span85, 1.35g of Tween85 and 0.21g of 1,4-diphenylaminocarbamate bis(2-dimethylaminoethanol) ester to the above oil-water mixture, stir evenly, and emulsify to form a water-in-oil emulsion.

[0126] (4) The water-in-oil emulsion was cooled from room temperature to 15°C, and after being deoxygenated by passing N2 through it, 3.96g of 1wt% potassium persulfate aqueous solution was slowly added dropwise to allow the water-in-oil emulsion to undergo polymerization. The temperature was raised to 35°C and the reaction system was kept at 35°C for 2 hours before the reaction was stopped.

[0127] (5) A copolymer emulsion was obtained. The average particle size of the copolymer hydrogel was 420 nm, and the viscosity-average molecular weight of the copolymer was 17.3 million g / mol. The emulsion was subjected to a temperature of 180 °C and a curing time of 100 s. -1 The viscosity remained at 53 mPa·s after shearing for 120 min under the specified conditions.

[0128] Example 3

[0129] (1) Mix 15g of monomer A with a purity of 95.2% and 15g of water evenly, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the first time, then add 123g of monomer B, 24g of 50wt% monomer C aqueous solution, then add 0.15g of disodium ethylenediaminetetraacetate and 0.036g of sodium bisulfite, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the second time, and finally use deionized water to measure to 300g to form an aqueous phase.

[0130] (2) Take 3.75g of ethyl acetate and 121.25g of kerosene and mix them thoroughly with the water phase to obtain an oil-water mixture.

[0131] (3) Add 14.90g of Span83, 1.35g of OP-10 and 0.21g of 1,4-diphenylaminocarbamate bis(2-dimethylaminoethanol) ester to the above oil-water mixture, stir evenly, and emulsify to form a water-in-oil emulsion.

[0132] (4) The water-in-oil emulsion was cooled from room temperature to 15°C, and after being deoxygenated by passing N2 through it, 3.96g of 1wt% potassium persulfate aqueous solution was slowly added dropwise to allow the water-in-oil emulsion to undergo polymerization. The temperature was raised to 35°C and the reaction system was kept at 35°C for 2 hours before the reaction was stopped.

[0133] (5) A copolymer emulsion was obtained. The average particle size of the copolymer hydrogel was 390 nm, and the viscosity-average molecular weight of the copolymer was 16.2 million g / mol. The emulsion was subjected to a temperature of 180 °C and a curing time of 100 s. -1 The viscosity remained at 49 mPa·s after shearing for 120 min under the specified conditions.

[0134] Example 4

[0135] (1) Mix 75g of monomer A with a purity of 95.2% and 75g of water evenly, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the first time, then add 37.5g of monomer B and 75g of 50wt% monomer C aqueous solution, then add 0.132g of disodium ethylenediaminetetraacetate and 0.03g of sodium bisulfite to dissolve completely, add sodium hydroxide aqueous solution to adjust the pH value to 6 for the second time, and finally use deionized water to measure to 300g to form an aqueous phase.

[0136] (2) Take 3.75g of ethyl acetate and 121.25g of white oil and mix them thoroughly with the water phase to obtain an oil-water mixture.

[0137] (3) Add 14.9g of Span80, 1.35g of Tween80 and 0.21g of 1,4-diphenylaminocarbamate bis(2-dimethylaminoethanol) ester to the above oil-water mixture, stir evenly, and emulsify to form a water-in-oil emulsion.

[0138] (4) The water-in-oil emulsion was cooled from room temperature to 15°C, and after being deoxygenated by passing N2 through it, 3.3g of 1wt% potassium persulfate aqueous solution was slowly added dropwise to allow the water-in-oil emulsion to undergo polymerization. The temperature was raised to 35°C and the reaction system was kept at 35°C for 2 hours before the reaction was stopped.

[0139] (5) A copolymer emulsion was obtained. The average particle size of the copolymer hydrogel was 210 nm, and the viscosity-average molecular weight of the copolymer was 15.8 million g / mol. The emulsion was subjected to a temperature of 180 °C and a curing time of 100 s. -1 The viscosity remained at 52 mPa·s after shearing for 120 min under the specified conditions.

[0140] Example 5

[0141] The copolymer emulsion was prepared according to the method of Example 1, except that bis(2-dimethylaminoethanol) 1,4-diphenylcarbamate was replaced with the same mass of azobisisobutyronitrile.

[0142] The copolymer emulsion was obtained, the average particle size of the copolymer hydrogel was 420 nm, and the viscosity-average molecular weight of the copolymer was 14.3 million g / mol. The copolymer was subjected to a reaction at 180 °C for 100 s. -1 The viscosity remained at 46 mPa·s after shearing for 120 min under the specified conditions.

[0143] Example 6

[0144] The copolymer emulsion was prepared according to the method of Example 1, except that ethyl acetate was replaced with the same mass of butyl acetate.

[0145] The copolymer emulsion was obtained, and the average particle size of the copolymer hydrogel was 300 nm, the viscosity-average molecular weight was 15.6 million g / mol, and it was subjected to a test at 180 °C for 100 s. -1 The viscosity remained at 53 mPa·s after shearing for 120 min under the specified conditions.

[0146] Example 7

[0147] The copolymer emulsion was prepared according to the method of Example 1, except that the amount of bis(2-dimethylaminoethanol) 1,4-diphenylaminocarbamate was 0.5 g.

[0148] The copolymer emulsion was obtained, and the copolymer hydrogel had an average particle size of 580 nm and a viscosity-average molecular weight of 14.8 million g / mol. It was subjected to a reaction at 180 °C for 100 s. -1 The viscosity remained at 52 mPa·s after shearing for 120 min under the specified conditions.

[0149] Example 8

[0150] The copolymer emulsion was prepared according to the method of Example 1, except that the purity of monomer A was 98.5%.

[0151] The copolymer emulsion was obtained, and the average particle size of the copolymer hydrogel was 390 nm, the viscosity-average molecular weight was 16.6 million g / mol, and it was subjected to a test at 180 °C for 100 s. -1 The viscosity remained at 55 mPa·s after shearing for 120 min under the specified conditions.

[0152] Example 9

[0153] The copolymer emulsion was prepared according to the method of Example 1, except that the purity of monomer A was 88.6%.

[0154] The copolymer emulsion was obtained, and the average particle size of the copolymer hydrogel was 220 nm, the viscosity-average molecular weight was 14.2 million g / mol, and it was subjected to a test at 180 °C for 100 s. -1 The viscosity remained at 49 mPa·s after shearing for 120 min under the specified conditions.

[0155] Comparative Example 1

[0156] The copolymer emulsion was prepared according to the method of Example 1, except that monomer A was replaced with monomer B of the same mass.

[0157] The copolymer emulsion was obtained, the average particle size of the copolymer hydrogel was 920 nm, and the viscosity-average molecular weight of the copolymer was 18.8 million g / mol. The copolymer was subjected to a reaction at 180 °C for 100 s. -1 The viscosity remained at 34 mPa·s after shearing for 120 min under the specified conditions.

[0158] Comparative Example 2

[0159] The copolymer emulsion was prepared according to the method of Example 1, except that monomer A was replaced with the same mass of purified product with a purity of 99.7%.

[0162] The copolymer emulsion was obtained, the average particle size of the copolymer hydrogel was 920 nm, and the viscosity-average molecular weight of the copolymer was 13.5 million g / mol. The copolymer was subjected to a reaction at 180 °C for 100 s. -1 The viscosity remained at 32 mPa·s after shearing for 120 min under the specified conditions.

[0163] The copolymer emulsion prepared by this invention has the characteristics of a fine emulsion, the copolymer hydrogel has a high viscosity-average molecular weight, and the copolymer emulsion has excellent temperature and shear resistance.

[0164] 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 copolymer emulsion, characterized in that, The copolymer emulsion comprises a copolymer hydrogel, an organic solvent, an oil-soluble emulsifier, and a water-soluble emulsifier; The average particle size of the copolymer hydrogel is 100-600 nm; The copolymer forming the copolymer hydrogel comprises structural unit A, structural unit B, and structural unit C, wherein structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), and structural unit C has the structure shown in formula (3). Among them, R1, R2, R3 and R4 are each independently H or methyl.

2. The copolymer emulsion according to claim 1, wherein, Based on 100 parts by weight of copolymer emulsion, the copolymer hydrogel content is 50-75 parts by weight, the organic solvent content is 20-45 parts by weight, the oil-soluble emulsifier content is 1-4.5 parts by weight, and the water-soluble emulsifier content is 0.2-1.5 parts by weight.

3. The copolymer emulsion according to claim 1 or 2, wherein, The average particle size of the copolymer hydrogel is 100-500 nm.

4. The copolymer emulsion according to claim 1 or 2, wherein, The organic solvent is a mixture of at least one of white oil, kerosene and cyclohexane and an alkyl ester of an organic acid.

5. The copolymer emulsion according to claim 1 or 2, wherein, The copolymer has a viscosity-average molecular weight of 12 million g / mol to 18 million g / mol.

6. The copolymer emulsion according to claim 1 or 2, wherein, Based on the total mass of the copolymer, the content of structural unit A is 10-50 wt%, preferably 15-40 wt%, the content of structural unit B is 25-85 wt%, preferably 40-80 wt%, and the content of structural unit C is 5-25 wt%, preferably 5-20 wt%.

7. A method for preparing a copolymer emulsion, wherein, The method includes: S1. Mix the comonomer, chelating agent, first water-soluble initiator with deionized water, add soluble sodium compound to adjust pH, and form an aqueous phase; the comonomer includes monomer A, monomer B and monomer C; S2. Mix the aqueous phase with an organic solvent to obtain an oil-water mixture; S3. Add an oil-soluble emulsifier, a water-soluble emulsifier, and an oil-soluble initiator to the oil-water mixture to emulsify and form a water-in-oil emulsion; S4. A second water-soluble initiator is added to the water-in-oil emulsion to carry out a polymerization reaction, thereby obtaining a copolymer emulsion containing a copolymer hydrogel; The average particle size of the copolymer hydrogel is 100-600 nm; The monomer A has the structure shown in formula (4), the monomer B has the structure shown in formula (5), and the monomer C has the structure shown in formula (6). R1', R2', R3', and R4' are each independently H or methyl; The purity of monomer A is <99%.

8. The preparation method according to claim 7, wherein, The purity of monomer A is ≥85%.

9. The preparation method according to claim 7 or 8, wherein, In step S1, based on the total mass of the comonomers, the content of monomer A is 10-50 wt%, preferably 15-40 wt%; the content of monomer B is 25-85 wt%, preferably 40-80 wt%; and the content of monomer C is 5-25 wt%, preferably 5-20 wt%. Preferably, based on the total mass of the aqueous phase, the amount of the comonomer is 40wt%-50wt%, the amount of the chelating agent is 0.01-0.1wt%, and the amount of the first water-soluble initiator is 0.0001-0.2wt%. Preferably, the pH value of the aqueous phase is 5-7.

10. The preparation method according to claim 7 or 8, wherein, In step S2, the mass ratio of the aqueous phase to the organic solvent is 1-3:1; Preferably, the organic solvent comprises at least one of white oil, kerosene, and cyclohexane, and a mixture of alkyl esters of organic acids; Preferably, the organic acid alkyl ester accounts for 1-5 wt% of the total mass of the organic solvent; Preferably, the organic acid alkyl ester is selected from ethyl acetate and / or butyl acetate.

11. The preparation method according to claim 7 or 8, wherein, In step S3, the total amount of oil-soluble emulsifier to water-soluble emulsifier in the oil-water mixture is 0.015-0.05:1, and the mass ratio of oil-soluble emulsifier to water-soluble emulsifier is 3-15:

1. Preferably, in step S3, the oil-soluble initiator accounts for 0.001%-0.05 wt% of the total mass of the oil-water mixture, more preferably 0.02-0.05 wt%.

12. The preparation method according to claim 7 or 8, wherein, The oil-soluble initiator is an organic peroxide; And / or, the oil-soluble initiator is an azo compound; And / or, the oil-soluble initiator has the structure shown in formula (7); Where n and m are each an independent integer from 1 to 12; R4, R5, R6 and R7 are each independently a C1-C6 straight-chain alkyl group or a C3-C6 branched alkyl group.

13. The preparation method according to claim 7 or 8, wherein, In step S4, the mass ratio of the first water-soluble initiator to the second water-soluble initiator is 0.5-2:

1.

14. The preparation method according to claim 7 or 8, wherein, The polymerization reaction conditions include: The water-in-oil emulsion is cooled to the first reaction temperature, and a second water-soluble initiator is added. The water-in-oil emulsion is then controlled to undergo polymerization at the second reaction temperature. Preferably, the first reaction temperature is 5-25℃, more preferably 5-15℃, the second reaction temperature does not exceed 50℃, more preferably 30-40℃, and the polymerization reaction time at the second reaction temperature is 2-6h, more preferably 2-4h.

15. The application of a copolymer emulsion according to any one of claims 1-6 or a copolymer emulsion prepared by any one of claims 7-14 in the field of polymers for oil fields.

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