Self-assembled emulsified core-shell polymer microspheres, preparation method and application thereof

Abstract

The present application relates to a kind of self-assembly emulsified core-shell polymer microspheres and its preparation method and application, mainly solve the problems existing in prior art when preparing core-shell polymer microspheres, process is more complex, the problems such as core-shell structure is difficult to guarantee especially microsphere emulsion stability is poor.The present application by using a kind of self-assembly emulsified core-shell polymer microspheres, by weight parts, by the following components comprising reaction system in the presence of composite initiator is prepared by step reaction: 20~50 weight parts of oil phase;1~20 weight parts of composite emulsifier system;20~50 weight parts of polymer monomer technical scheme, preferably solve the problem, the polymer microsphere product prepared can be stored for a long time, with distinct core-shell structure, can be used in oilfield enhanced recovery in field application.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of self-assembly emulsification core-shell polymer microspheres and its preparation method and application. BACKGROUND

[0002] Polymer microspheres with initial particle size of nanometer micron level play a unique effect in deep profile control operation of oil field compared with other profile control agents, which can enter the deep formation, slowly expand and aggregate during migration, and effectively plug the pore throat by adsorption, bridging and other effects. Such polymer microspheres are generally polymerized by inverse emulsion method. According to the subdivision of microsphere particle size, the process is different, among which, nanometer level (initial particle size is about 100 nanometers) generally adopts inverse microemulsion polymerization, in order to achieve thermodynamic stability, the content of emulsifier is generally more than 10%; while micro level (initial particle size is 1-100 microns) generally adopts inverse (micro) suspension polymerization, although the content of emulsifier is lower, but the product stability is poor, generally several days or even hours will cause microsphere sedimentation and stratification; the microspheres with particle size between the above two generally adopt inverse (fine) emulsion polymerization, in order to improve the stability of the product, the polymerization system often needs to be homogenized before reaction. In order to improve the performance and price ratio of profile control agent and the profile control effect, in addition to improving the effective solid content of microsphere emulsion, the microspheres can also be designed into core-shell structure from homogeneous structure, the core-shell two parts have different electrical properties, after a certain time of high temperature aging, partial hydrolysis or degradation, the microspheres can attract each other to form larger aggregates, greatly improving the plugging efficiency of profile control.

[0003] Since the polymer microspheres for profile control generally use water-soluble monomers for polymerization, in order to obtain core-shell structure, generally a two-step method is used: first, mix the oil phase, emulsifier and water phase containing core monomers uniformly, initiate polymerization to obtain the core part of the microspheres, then add the water phase containing shell monomers, mix uniformly and initiate polymerization to complete the shell coating reaction, to obtain core-shell microspheres. However, since both water phases contain water-soluble monomers, mutual solubility or interpenetration is easy to occur, and it is difficult to obtain a clear core-shell structure; in addition, due to the increase of water phase monomer content in the second step, the content of emulsifier in the system is reduced, which will greatly affect the firmness of the emulsifier layer during further reaction, and will also affect the core-shell structure and the stability of the product.

[0004] It is well known that surfactants play a very important role as emulsifiers in emulsion polymerization, mainly manifested as: before polymerization, dispersing and solubilizing monomers to form a relatively stable monomer emulsion, providing a place for monomer polymerization, stabilizing latex particles after polymerization to prevent coagulation, forming a stable polymer microsphere emulsion with a certain solid content and viscosity, and having a great influence on the polymerization behavior of monomers in the emulsion, latex particle size and distribution, and latex particle properties. Conventional emulsifiers are usually attached to the surface of polymer microsphere particles in a physical adsorption manner, and are easily affected by the external environment and desorbed and migrated. In order to overcome the shortcomings of conventional emulsifiers, researchers at home and abroad have developed many new types of emulsifiers, such as low-foaming surfactants, high-molecular-weight surfactants, easily-decomposable surfactants, and polymerizable surfactants. Among them, the polymerizable emulsifier has a functional group that can participate in free radical polymerization reaction in its molecular structure in addition to hydrophilic and lipophilic groups. Because of its polymerization activity, its reactive functional group can participate in emulsion polymerization reaction and be bonded to the surface of the polymer particle in a covalent bond manner to play an internal emulsification role, instead of relying on physical adsorption, making the desorption of the surfactant more difficult, and thus it is also called reactive surfactant or surfactant monomer. This kind of polymerizable emulsifier is actually an amphiphilic monomer containing a polymerizable double bond, containing a hydrophobic (lipophilic) carbon chain on one part and a hydrophilic group on the other part, which can be anionic, cationic or non-ionic. So far, people have used this kind of surfactant more in the preparation of water-in-oil type coating emulsion products, which can improve the water resistance of the polymer film, and less in the preparation of water-in-oil type polymer products such as microspheres for oil fields, and the structure is simple. For example, CN112661903A adds methacrylate as a polymerizable surfactant to replace part of the traditional small-molecule emulsifier, but the emulsifier content is still as high as 5% or more, and the system also contains 1-2% of an alcohol or salt stabilizer. A wide-distribution micron-level homogeneous microsphere with an effective solid content of less than 28% is prepared, which does not show obvious superiority in product performance indicators compared with general reverse emulsion or reverse suspension polymerization. SUMMARY

[0005] Based on extensive and in-depth research on the synthesis principle, structure characterization and properties of core-shell polymer microspheres, the inventors obtained self-assembled emulsified core-shell polymer microspheres by introducing a polymerizable surfactant monomer to participate in the reverse emulsion step-by-step polymerization.

[0006] Specifically, the present application relates to the following aspects:

[0007] 1. A self-assembled emulsified core-shell polymer microsphere, wherein the polymer microsphere is prepared by reacting a mixture comprising the following components:

[0008] a) 20-50 parts by weight of an oil phase; preferably 25-40 parts by weight;

[0009] b) 1-20 parts by weight of a complex emulsifier system; preferably 1-10 parts by weight;

[0010] c) 20-50 parts by weight of a polymerizable monomer; preferably 25-40 parts by weight;

[0011] d) 0.01-2.0 parts by weight of a crosslinking agent; preferably 0.1-1.0 parts by weight;

[0012] e) 0.001-1 parts by weight of an initiator; preferably 0.005-0.5 parts by weight;

[0013] f) the rest is water;

[0014] wherein the initiator comprises:

[0015] 1) an oxidizing agent, the weight of which is 0.01-1.0% of the weight of the polymerizable monomer; preferably 0.02-0.5%;

[0016] 2) a reducing agent, the weight of which is 0.02-2.0% of the weight of the polymerizable monomer; preferably 0.05-1.0%;

[0017] 3) an azo initiator, the weight of which is 0-5% of the weight of the polymerizable monomer; preferably 0.1-2.0%.

[0018] 2. The self-assembled emulsified core-shell polymer microspheres according to any of the preceding or subsequent aspects, wherein the oil phase is selected from at least one of aliphatic hydrocarbons and aromatic hydrocarbons.

[0019] The aliphatic hydrocarbons are selected from at least one of technical white oil and solvent oil; preferably at least one of No. 3 white oil, No. 5 white oil, No. 7 white oil, No. 120 solvent oil and No. 200 solvent oil; the aromatic hydrocarbons are selected from at least one of benzene, toluene and xylene, preferably xylene; the amount is 20-50%, preferably 25-40%, of the entire reaction system.

[0020] 3. The self-assembled emulsified core-shell polymer microspheres according to any of the preceding or subsequent aspects, wherein the complex emulsifier system is a combination of a non-ionic emulsifier and a long carbon chain polymerizable surfactant monomer, the long carbon chain polymerizable surfactant monomer accounting for 0.5-20%, preferably 1-10%, of the entire emulsifier system. The hydrophilic-lipophilic balance value HLB of the complex emulsifier system is between 3 and 9, preferably between 4 and 7.

[0021] 4. The self-assembled emulsified core-shell polymer microspheres according to any one of the preceding or following aspects, wherein the non-ionic emulsifier system comprises a lipophilic surfactant and a hydrophilic surfactant; wherein the lipophilic surfactant is a sorbitan fatty acid ester, preferably at least one of Span 85, Span 80, Span 65 and Span 60; and the hydrophilic surfactant is an alkyl phenol polyoxyethylene ether, a fatty alcohol polyoxyethylene ether or a polyoxyethylene sorbitan fatty acid ester, preferably at least one of the AEO series of fatty alcohol polyoxyethylene ether, the isomeric alcohol series (oxirane addition number greater than 5) and Tween 85, Tween 80, Tween 60, Tween 40, Tween 20 of polyoxyethylene sorbitan fatty acid ester.

[0022] 5. The self-assembled emulsified core-shell polymer microspheres according to any one of the preceding or following aspects, wherein the long carbon chain polymerizable surfactant monomer is selected from a hydrophobic monomer having a lipophilic chain of not less than 8 carbon atoms, such as an anionic 2-acrylamido sodium alkyl sulfonate, a polyol sodium maleate, a maleic anhydride derivative and the like, a cationic allyl alkyl (dimethyl) ammonium chloride, a methacryloyloxyethyl alkyl dimethyl ammonium bromide, a 2-acrylamidoethyl N-alkyl dimethyl ammonium bromide and the like, a non-ionic N-alkyl acrylamide twin-tail hydrophobic monomer such as N,N-dialkyl acrylamide, a polymerizable surfactant composed of a plurality of hydrophobic butylene oxide units and hydrophilic ethylene oxide units and the like.

[0023] The long carbon chain polymerizable surfactant monomer is added to the reaction system and mixed thoroughly before the end of the nucleation and the shell reaction of the polymer microspheres using the inverse emulsion method.

[0024] 6. The self-assembled emulsified core-shell polymer microspheres according to any one of the preceding or following aspects, wherein the polymerizable monomer is at least one selected from the group consisting of a non-ionic water-soluble monomer, an anionic monomer and a cationic monomer.

[0025] The non-ionic water-soluble monomer is at least one selected from the group consisting of acrylamide, methyl (or ethyl) acrylamide, t-butyl acrylamide and the like.

[0026] The anionic monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, itaconic acid, maleic acid, fumaric acid or a salt thereof and the like.

[0027] The cationic monomer is at least one selected from the group consisting of dimethyldiallyl ammonium chloride, acryloyloxyethyltrimethyl ammonium chloride, methacryloyloxyethyltrimethyl ammonium chloride and 2-acrylamido-2-methylpropyltrimethyl ammonium chloride.

[0028] 7. The self-assembled emulsified core-shell polymer microspheres according to any of the preceding or following aspects, wherein the crosslinking agent is at least one selected from the group consisting of methylene bisacrylamide, divinylbenzene, polyethylene glycol diacrylate and pentaerythritol triacrylate.

[0029] 8. The self-assembled emulsified core-shell polymer microspheres according to any of the preceding or following aspects, wherein the oxidizing agent is at least one selected from the group consisting of potassium persulfate, sodium persulfate, ammonium persulfate and benzoyl peroxide.

[0030] The reducing agent is at least one selected from the group consisting of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, sodium thiosulfate and ferrous chloride.

[0031] The azo initiator is at least one selected from the group consisting of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (V044), azobis isobutylamidine hydrochloride (V50), azobis isobutyronitrile (AIBN) and azobis isohexyl nitrile (ABVN).

[0032] 9. The self-assembled emulsified core-shell polymer microspheres according to any of the preceding or following aspects, wherein the self-assembled emulsified core-shell polymer microspheres further comprise a complexing agent, the weight of which is 0.01-0.5% of the weight of the polymerizable monomers, preferably 0.05-0.2%; the complexing agent is at least one selected from the group consisting of disodium ethylenediaminetetraacetate and sodium diethylenetriaminepentaacetate.

[0033] 10. A method for preparing self-assembled emulsified core-shell polymer microspheres, comprising the following steps:

[0034] ① mixing the oil phase and the nonionic emulsifier in the complex emulsifier system and the oil-soluble azo initiator uniformly to form a continuous phase;

[0035] mixing the polymerizable monomers, the crosslinking agent, the optional complexing agent, the water-soluble azo initiator and water required for preparing the core and shell of the microspheres respectively to form water phase I and water phase II; wherein the mass ratio of the water phase I to the water phase II is 1:9-9:1, and the water phase I and the water phase II contain part of the polymerizable monomers with different structures or electrical properties;

[0036] configuring an aqueous oxidizing agent solution and an aqueous reducing agent solution respectively, the concentration of the aqueous oxidizing agent solution and the aqueous reducing agent solution being 1-50 wt%, preferably 5-30 wt%;

[0037] ②The continuous phase and the water phase I are sequentially put into a reaction kettle and mixed uniformly to obtain a mixture A; the temperature in the reaction kettle is controlled at 10-30℃, oxygen is removed by nitrogen, then an oxidant aqueous solution is added and stirred uniformly, and then a reducing agent aqueous solution is continuously added to initiate polymerization; after the polymerization temperature reaches the highest temperature, the reaction is maintained for 1 hour to obtain the core part of the polymer microspheres;

[0038] The polymerization system is cooled to 20-30℃, the long carbon chain polymerizable surfactant monomer is added and stirred for several minutes, then the water phase II is added and stirred uniformly, oxygen is removed by nitrogen, and the oxidant and the reducing agent are sequentially added, and after the polymerization temperature reaches the highest temperature, the reaction is maintained for 1 hour to complete the shell coating reaction, thereby obtaining the core-shell polymer microspheres.

[0039] The oil-soluble azo initiator is used to prepare the nanoscale core-shell microspheres, and the water-soluble azo initiator is used to prepare the sub-micron and micron scale core-shell microspheres.

[0040] 11. The self-assembled emulsified core-shell polymer microspheres prepared by the method according to any one of the preceding aspects, and the use of the self-assembled emulsified core-shell polymer microspheres in the tertiary oil recovery of oil fields.

[0041] Technical effects

[0042] The self-assembled emulsified core-shell polymer microspheres and the preparation method thereof disclosed by the application introduce the long carbon chain polymerizable surfactant monomer, and after the core-shell polymer microspheres are prepared by the step-by-step polymerization, the long carbon chain polymerizable surfactant monomer is added and mixed fully, the monomer is arranged on the surface of the core of the polymer microspheres, the lipophilic end of the monomer points to the continuous phase, the structural stability and the steric hindrance of the emulsifier layer are increased, the shell water phase that is added subsequently is not easy to enter the generated microsphere core, and the active groups contained in the hydrophilic end of the monomer will participate in the copolymerization of the shell water phase monomer, which is equivalent to providing many riveting points on the surface of the microsphere core for the subsequent shell coating reaction. After the shell coating reaction is completed, the microspheres with clear core and shell are obtained. In this way, even if the content of the emulsifier is not increased, the shell coating reaction of the microspheres can be stably carried out, and the effective solid content of the product is further increased. Compared with the general polymerizable surfactant, the self-assembled emulsified core-shell polymer microspheres play a different effect. The self-assembled emulsified core-shell polymer microspheres can be directly used or compounded with other oil field chemicals for the field application of deep profile control, oil displacement and the like in the tertiary oil recovery of high temperature and high salt, medium-high permeability oil reservoirs.

[0043] The self-assembled emulsified core-shell polymer microspheres prepared by the preparation process have an initial particle size of 100nm-10um, and the product is stable and does not separate at room temperature for a long period of time. After being prepared into a microsphere profile control agent with oilfield site water and injected into a stratum, the profile control agent still has good swelling performance and plugging performance after long-term aging under high temperature and high salinity, and good technical effects are achieved.

[0044] The application will be further described below through specific examples. DETAILED DESCRIPTION

[0045] The specific embodiments of the application are described in detail below, but it should be pointed out that the protection scope of the application is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0046] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the definition in this specification prevails.

[0047] When the specification derives materials, substances, methods, steps, devices or components, etc. with the word head "known to those skilled in the art", "prior art" or similar terms, the objects derived by the word head cover those commonly used in the art at the time of the application, but also include those not commonly used at present, but will be recognized as suitable for similar purposes in the art.

[0048] In the context of the specification, the extractable solid content, initial particle size and plugging rate of polyacrylamide microsphere emulsion are tested according to the determination method of Q / SH3375 134-2019 Enterprise Standard of Shanghai Research Institute of Petrochemical Corporation of China Petroleum and Chemical Corporation "Temperature-resistant and salt-resistant polymer microsphere profile control agent", and the microsphere emulsion is refined.

[0049] In the context of the specification, the compound names and abbreviations mentioned are shown in the following table:

[0050]

[0051]

[0052] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless it is not in accordance with the conventional understanding of those skilled in the art when based on weight.

[0053]

Example 1

[0054] In a reaction kettle, 1000g of No. 7 white oil, 180g of Span 80, 12g of Tween 60, and 0.1g of AIBN were first added and stirred until uniformly mixed; in a beaker, 530g of water, 10g of t-butyl acrylamide, 400g of acrylamide, 12g of maleic acid, 100g of dimethyl diallyl ammonium chloride (60%), 0.5g of disodium ethylenediaminetetraacetate, 2.5g of methylene bisacrylamide were added and stirred to dissolve uniformly as the water phase I; in another beaker, 410g of water, 28g of 2-acrylamido-2-methylsulfonic acid sodium, 510g of acrylamide, 0.5g of disodium ethylenediaminetetraacetate, 1.0g of methylene bisacrylamide were added and stirred to dissolve uniformly as the water phase II; ammonium persulfate and sodium bisulfite were separately prepared into 20% aqueous solution for standby. The water phase I was added to the reaction kettle, continuously stirred at 500 rpm, the temperature in the kettle was controlled at 20°C, and nitrogen was used to remove oxygen for 0.5h, then 5g of ammonium persulfate aqueous solution was added dropwise and stirred for 10min until uniform, then 7g of sodium bisulfite aqueous solution was added to initiate polymerization, the temperature quickly rose to 85°C after a few minutes, and the reaction was continued for 1h to obtain a transparent self-assembled emulsion core-shell polymer microsphere core; the temperature in the kettle was reduced to below 30°C, 0.2g of AIBN and 2.5g of sodium tetradecyl alcohol maleate were added and stirred uniformly, then the water phase II was added to the formed core emulsion, stirred and deoxygenated with nitrogen for 0.5h, 10g of oxidant aqueous solution was added dropwise and stirred for 10min until uniform, then 12g of reducing agent aqueous solution was added to initiate polymerization, the temperature quickly rose to 78°C after a few minutes, and the reaction was continued for 1h to obtain a transparent self-assembled emulsion core-shell polymer microsphere, which could be stored stably for more than one year.

[0055] According to material calculation, the content of nonionic emulsifier in the entire reaction system is 6.0%, which is about half of the content of emulsifier in the preparation of nanometer microspheres by general reverse microemulsion method.

[0056] According to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Co., Ltd. Shanghai Research Institute of Petroleum Chemical Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", the core and the final product of the core-shell microsphere were tested for the content of precipitable solids, which were 21.5% and 31.9% respectively, and the initial particle size tests were 92nm and 116nm respectively; in addition, the core and shell emulsion of the microsphere were refined into refined dry powder according to the method in the above standard, and Zeta potential test was carried out, the potential of the core and shell of the microsphere was 29.4mV and-3.6mV respectively. The above data show that the electrical properties of the raw monomers are basically consistent, a cationic core and an anionic shell are obtained, and the increase in particle size also indicates that the shell reaction is completed.

[0057] The microsphere emulsion was prepared into 0.3% concentration with total mineralization 200000mg / L brine, aged at 95℃ for 30 days, and evaluated for plugging rate with 300mD sand filling tube according to the above standard method, and the plugging rate was 86%.

[0058] [Example 2]

[0059] In a reaction kettle, 1000g of No. 5 white oil, 120g of Span 65, 40g of Tween 80, and 0.1g of ABVN were first added and stirred until mixed uniformly; in a beaker, 510g of water, 15g of N-vinyl pyrrolidone, 380g of acrylamide, 12g of acrylic acid, 80g of methacryloyloxyethyl trimethylammonium chloride (80%), 0.5g of disodium ethylenediaminetetraacetate, and 2.5g of methylene bisacrylamide were added and stirred until dissolved uniformly as water phase I; in another beaker, 410g of water, 38g of 2-acrylamido-2-methylsulfonic acid sodium, 500g of acrylamide, 0.5g of disodium ethylenediaminetetraacetate, and 1.0g of methylene bisacrylamide were added and stirred until dissolved uniformly as water phase II; ammonium persulfate and sodium bisulfite were separately prepared into 20% aqueous solution for standby. Water phase I was added into the reaction kettle, and the stirring was continued at 500rpm, the temperature in the reaction kettle was controlled at 20℃, and nitrogen was blown to remove oxygen for 0.5h, then 5.5g of ammonium persulfate aqueous solution was added dropwise and stirred for 10min until uniform, then 8g of sodium bisulfite aqueous solution was added dropwise to initiate polymerization, and the temperature quickly rose to 83℃ after a few minutes, and the reaction was continued for 1h to obtain a transparent self-assembled emulsion core-shell polymer microsphere core; the temperature in the kettle was lowered to below 30℃, 0.2g of ABVN and 3.2g of maleic anhydride dodecanol propyl sulfonic acid sodium were added and stirred until uniform, then water phase II was added into the formed core emulsion, and the stirring was continued with nitrogen blowing to remove oxygen for 0.5h, then 10g of oxidant aqueous solution was added dropwise and stirred for 10min until uniform, then 12g of reducing agent aqueous solution was added dropwise to initiate polymerization, and the temperature quickly rose to 81℃ after a few minutes, and the reaction was continued for 1h to obtain a transparent self-assembled emulsion core-shell polymer microsphere, which could be stored for more than one year.

[0060] According to material calculation, the nonionic emulsifier accounted for 5.1% of the entire reaction system, which was reduced by about half compared with the emulsifier content in the general reverse microemulsion method for preparing nanometer microspheres.

[0061] The core and the final product of the core-shell microspheres were tested for precipitable solid content according to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Corporation Shanghai Petrochemical Research Institute Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", which were 21.8% and 32.4%, respectively. The initial particle size tests were 156 nm and 182 nm, respectively. In addition, the core and shell emulsion of the microspheres were refined into dry powder according to the method in the above standard, and Zeta potential test was performed, respectively. The potential of the core and shell of the microspheres was 28.6 mV and -4.2 mV, respectively. The above data show that the electrical properties of the raw monomers are basically consistent, and the core with cationic electrical properties and the shell with anionic electrical properties are obtained. The increase in particle size also indicates that the shell formation reaction is completed.

[0062] The microsphere emulsion was prepared into a 0.3% concentration with a total salinity of 200,000 mg / L brine, aged at 95°C for 30 days, and evaluated for plugging rate using a 500 mD sand filling tube according to the above standard method. The plugging rate was measured to be 89%.

[0063]

Example 3

[0064] In the reaction kettle, 1000g of No. 3 white oil, 100g of Span80, and 15g of AEO7 were first added and stirred until they were uniformly mixed. In a beaker, 500g of water, 12g of methacrylamide, 380g of acrylamide, 12g of itaconic acid, 80g of acryloyloxyethyl trimethyl ammonium chloride (80%), 0.6g of sodium diethylenetriamine pentaacetate, 2.5g of methylene bisacrylamide, and 0.1g of V044 were added and stirred until they were uniformly dissolved as water phase I. In another beaker, 410g of water, 30g of sodium acrylate, 8g of sodium styrene sulfonate, 500g of acrylamide, 0.6g of sodium diethylenetriamine pentaacetate, 1.0g of divinylbenzene, and 0.2g of V044 were added and stirred until they were uniformly dissolved as water phase II. A 20% aqueous solution of potassium persulfate and sodium bisulfite was prepared for use. Water phase I was added to the reaction kettle, which was continuously stirred at 500 rpm, and the temperature in the reaction kettle was controlled at 20°C. Nitrogen was used to remove oxygen for 0.5h, then 4.5g of potassium persulfate aqueous solution was added dropwise and stirred for 10 min until it was uniformly mixed. Then, 6.8g of sodium bisulfite aqueous solution was added dropwise to initiate polymerization. After a few minutes, the temperature quickly rose to 81°C, and the reaction was continued for 1 hour to obtain a milky white self-assembled emulsion core-shell polymer microsphere core. The temperature in the kettle was reduced to below 30°C, 2.8g of N,N-dioctyl acrylamide was added and stirred until it was uniformly mixed. Then, water phase II was added to the formed core emulsion, which was stirred and deoxygenated with nitrogen for 0.5h. Then, 9g of potassium persulfate aqueous solution was added dropwise and stirred for 10 min until it was uniformly mixed. Then, 11g of sodium bisulfite aqueous solution was added dropwise to initiate polymerization. After a few minutes, the temperature quickly rose to 79°C, and the reaction was continued for 1 hour to obtain a milky white self-assembled emulsion core-shell polymer microsphere, which could be stored stably for more than half a year.

[0065] From the material calculation, the nonionic emulsifier accounts for 3.8% of the entire reaction system, which is about half of the emulsifier content in the general reverse emulsion method for preparing sub-micron microspheres.

[0066] According to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Industry Co., Ltd. Shanghai Petroleum Chemical Industry Research Institute Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", the core and the final product of the core-shell microsphere were tested for the content of precipitable solids, which were 21.7% and 32.6% respectively, and the initial particle size test was 463 nm and 526 nm respectively; in addition, the core and shell emulsion of the microsphere were refined into refined dry powder according to the method in the above standard, and Zeta potential test was carried out, the potential of the core and shell of the microsphere was 30.5 mV and -6.2 mV respectively. The above data show that the electrical properties of the monomers basically coincide, the core with cationic electrical properties and the shell with anionic electrical properties are obtained, and the increase of the particle size also indicates that the shell reaction is completed.

[0067] The microsphere emulsion was prepared into a concentration of 0.3% with a total salinity of 200,000 mg / L brine, aged at 95°C for 30 days, and the plugging rate was evaluated by the above standard method with a 1000 mD sand filling pipe, and the plugging rate was measured to be 87%.

[0068]

Example 4

[0069] In a reaction kettle, 1000 g of 200# solvent oil, 82 g of Span60, and 8 g of AEO9 were first added and stirred until uniformly mixed; in a beaker, 530 g of water, 400 g of acrylamide, 12 g of maleic acid, 120 g of dimethyl diallyl ammonium chloride (60%), 0.5 g of disodium ethylenediaminetetraacetate, 2.5 g of methylene bisacrylamide, and 0.15 g of V50 were added and stirred until uniformly dissolved as the water phase I; in another beaker, 410 g of water, 18 g of sodium styrene sulfonate, 520 g of acrylamide, 0.5 g of disodium ethylenediaminetetraacetate, 1.0 g of methylene bisacrylamide, and 0.25 g of V50 were added and stirred until uniformly dissolved as the water phase II; ammonium persulfate and sodium bisulfite were respectively configured into 20% aqueous solution for standby. The water phase I was added into the reaction kettle, and the stirring was continuously carried out at 500 rpm, the temperature in the reaction kettle was controlled at 20°C, and the oxygen was removed by nitrogen for 0.5 h, then 5 g of ammonium persulfate aqueous solution was dropped and stirred for 10 min until uniformly, then 7 g of sodium bisulfite aqueous solution was dropped to initiate polymerization, and the temperature was rapidly increased to 89°C after a few minutes, and the reaction was continuously carried out for 1 h to obtain the core part of the self-assembled emulsion core-shell polymer microspheres in milky white; the temperature in the kettle was reduced to below 30°C, 1.8 g of acrylamidopropyl lauryldimethyl ammonium bromide was added and stirred until uniformly, the water phase II was added into the core emulsion which had been formed, the stirring was carried out and the oxygen was removed by nitrogen for 0.5 h, then 9 g of ammonium persulfate aqueous solution was dropped and stirred for 10 min until uniformly, then 11 g of sodium bisulfite aqueous solution was dropped to initiate polymerization, and the temperature was rapidly increased to 73°C after a few minutes, and the reaction was continuously carried out for 1 h to obtain the self-assembled emulsion core-shell polymer microspheres in milky white, which could be stored for more than half a year.

[0070] According to the material calculation, the content of nonionic emulsifier in the entire reaction system was 2.9%, which was reduced by about half compared with the content of emulsifier in the preparation of sub-micron microspheres by general inverse emulsion method.

[0071] According to the determination method of Q / SH3375 134-2019 Enterprise Standard of Shanghai Research Institute of Petrochemical Co., Ltd. for "Temperature-resistant and salt-resistant polymer microsphere profile control agent", the extractable solid content test of the core and the final product of the core-shell microspheres was carried out, which was 23.1% and 33.4% respectively, and the initial particle size test was 1.12 μm and 1.37 μm respectively; in addition, the core and shell emulsion of the microspheres were refined into dry powder according to the method in the above standard, and Zeta potential test was carried out, the potential of the core and shell of the microspheres was 27.6 mV and -2.9 mV respectively. The above data show that the electrical properties of the raw materials are basically consistent, the core with cationic electrical property and the shell with anionic electrical property are obtained, and the increase of particle size also indicates that the shell reaction is completed.

[0072] The microsphere emulsion was prepared into 0.3% concentration with total mineralization 200000mg / L brine, aged at 95℃ for 30 days, and evaluated for plugging rate with 1500mD sand filling tube according to the above standard method, and the plugging rate was 91%.

[0073] [Example 5]

[0074] In a reaction kettle, 1050g of No. 120 solvent oil, 50g of Span 65, and 18g of TO12 were first added and stirred until mixed uniformly; in a beaker, 530g of water, 10g of N-vinyl pyrrolidone, 390g of acrylamide, 10g of methacrylic acid, 80g of methacryloyloxyethyl trimethyl ammonium chloride (80%), 0.5g of disodium ethylenediaminetetraacetate, 2.5g of methylene bisacrylamide, and 0.15g of V50 were added and stirred until dissolved uniformly as water phase I; in another beaker, 400g of water, 60g of 2-acrylamido-2-methylsulfonic acid sodium, 450g of acrylamide, 0.5g of disodium ethylenediaminetetraacetate, 1.0g of methylene bisacrylamide, and 0.25g of V50 were added and stirred until dissolved uniformly as water phase II; ammonium persulfate and sodium bisulfite were separately prepared into 20% aqueous solution for standby. Water phase I was added into the reaction kettle, and the stirring was continued at 500rpm, the temperature in the reaction kettle was controlled at 20℃, and nitrogen was blown to remove oxygen for 0.5h, then 5g of ammonium persulfate aqueous solution was added dropwise and stirred for 10min until uniform, and then 7g of sodium bisulfite aqueous solution was added to initiate polymerization, and the temperature quickly rose to 89℃ after a few minutes, and the reaction was continued for 1h, and a semi-transparent self-assembled emulsified core-shell polymer microsphere core was obtained; the temperature in the kettle was lowered below 30℃, 1.2g of dimethyloctadecylallyl ammonium chloride was added and stirred until uniform, water phase II was added into the formed core emulsion, and nitrogen was blown to remove oxygen for 0.5h, 9g of ammonium persulfate aqueous solution was added dropwise and stirred for 10min until uniform, and then 11g of sodium bisulfite aqueous solution was added to initiate polymerization, and the temperature quickly rose to 73℃ after a few minutes, and the reaction was continued for 1h, and a semi-transparent self-assembled emulsified core-shell polymer microsphere was obtained, which could be stored stably for more than one month.

[0075] According to material calculation, the nonionic emulsifier accounted for 2.2% of the entire reaction system, which was reduced by about half compared with the emulsifier content in the general reverse phase micro-suspension method for preparing microspheres.

[0076] The core and final product of the core-shell microspheres were tested for precipitable solid content according to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Corporation Shanghai Petrochemical Research Institute Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", which were 22.1% and 32.3%, respectively. The initial particle size tests were 2.35 μm and 2.69 μm, respectively. In addition, the core and shell emulsion of the microspheres were refined into dry powder according to the method in the above standard, and Zeta potential test was performed, respectively. The potential of the core and shell of the microspheres was 29.6 mV and -5.8 mV, respectively. The above data show that the electrical properties of the raw monomers are basically consistent, and the core with cationic electrical properties and the shell with anionic electrical properties are obtained. The increase in particle size also indicates that the shell formation reaction is completed.

[0077] The microsphere emulsion was prepared into a 0.3% concentration with a total salinity of 200,000 mg / L brine, aged at 95°C for 30 days, and evaluated for plugging rate using a 2000 mD sand filling tube according to the above standard method. The plugging rate was measured to be 93%.

[0078]

Example 6

[0079] In the reaction kettle, 1100 g of No. 120 solvent oil, 30 g of Span 85, and 10 g of TO15 were first added and stirred until uniformly mixed. In a beaker, 530 g of water, 10 g of ethyl acrylamide, 390 g of acrylamide, 10 g of itaconic acid, 85 g of acryloyloxyethyl trimethyl ammonium chloride (80%), 0.5 g of disodium ethylenediaminetetraacetate, 2.5 g of methylene bisacrylamide, and 0.15 g of V50 were added and stirred until dissolved uniformly as water phase I. In another beaker, 400 g of water, 32 g of sodium styrene sulfonate, 480 g of acrylamide, 0.5 g of disodium ethylenediaminetetraacetate, 1.0 g of methylene bisacrylamide, and 0.25 g of V50 were added and stirred until dissolved uniformly as water phase II. Ammonium persulfate and sodium bisulfite were separately prepared into 20% aqueous solutions for standby use. Water phase I was added to the reaction kettle, and the stirring was continued at 500 rpm. The temperature in the reaction kettle was controlled at 20°C, and nitrogen was introduced to remove oxygen for 0.5 h. Then, 5 g of ammonium persulfate aqueous solution was added dropwise, and the stirring was continued for 10 min until uniform. Then, 7 g of sodium bisulfite aqueous solution was added dropwise to initiate polymerization. After a few minutes, the temperature rapidly rose to 89°C, and the reaction was continued for 1 h to obtain a semi-transparent self-assembled emulsified core-shell polymer microsphere core portion. The temperature in the kettle was reduced to below 30°C, and 1.1 g of dodecyl sulfopropyl sodium maleate was added and stirred until uniform. Water phase II was added to the formed core emulsion, and the stirring was continued with nitrogen introduction to remove oxygen for 0.5 h. Then, 9 g of ammonium persulfate aqueous solution was added dropwise, and the stirring was continued for 10 min until uniform. Then, 11 g of sodium bisulfite aqueous solution was added dropwise to initiate polymerization. After a few minutes, the temperature rapidly rose to 73°C, and the reaction was continued for 1 h to obtain a semi-transparent self-assembled emulsified core-shell polymer microsphere, which could be stored stably for more than one month.

[0080] From the material calculation, the nonionic emulsifier accounts for 1.3% of the entire reaction system, which is about half of the emulsifier content in the general reverse micro-suspension method for preparing micron microspheres.

[0081] According to the determination method of Q / SH3375 134-2019, the enterprise standard of Shanghai Research Institute of Petrochemical Co., Ltd. for temperature-resistant and salt-resistant polymer microsphere profile control agent, the extractable solid content of the core and the final product of the core-shell microsphere was tested, which was 22.0% and 32.1% respectively, and the initial particle size test was 5.86 μm and 6.32 μm respectively; in addition, the core and shell emulsion of the microsphere were refined into dry powder according to the method in the above standard, and the Zeta potential test was carried out, the potential of the core and shell of the microsphere was 28.3 mV and-8.2 mV respectively. The above data shows that the electrical properties of the monomers basically coincide, the core with cationic electrical properties and the shell with anionic electrical properties are obtained, and the increase of particle size also shows that the shell reaction is completed.

[0082] The microsphere emulsion was prepared into a concentration of 0.3% with a total salinity of 200000 mg / L brine, aged at 95°C for 30 days, and the plugging rate was evaluated by the above standard method with a 5000 mD sand filling pipe, and the plugging rate was measured to be 88%.

[0083]

Comparative Example 1

[0084] The same as example 1, first add 1000g No.7 white oil, 180g Span80, 12g Tween60, 0.1g AIBN in the reaction kettle, stirring until mixed evenly; add 530g water, 10g tert-butyl acrylamide, 400g acrylamide, 12g maleic acid, 100g dimethyl diallyl ammonium chloride (60%), 0.5g disodium ethylenediaminetetraacetate, 2.5g methylene bisacrylamide in a beaker, stirring to dissolve evenly as water phase I; add 410g water, 28g 2-acrylamido-2-methylsulfonic acid sodium, 510g acrylamide, 0.5g disodium ethylenediaminetetraacetate, 1.0g methylene bisacrylamide in another beaker, stirring to dissolve evenly as water phase II; prepare 20% aqueous solution of ammonium persulfate and sodium bisulfite separately for standby. Add water phase I into the reaction kettle, continuously stirring at 500 rpm, control the temperature in the reaction kettle at 20℃, deoxidize for 0.5h by nitrogen, then drop 5g ammonium persulfate aqueous solution, stirring for 10min until uniform, then drop 7g sodium bisulfite aqueous solution to initiate polymerization, the temperature rises rapidly to 88℃ after a few minutes, continue to react for 1h, get nearly transparent polymer microspheres core part; reduce the temperature in the kettle to below 30℃, add 0.2g AIBN, stirring until uniform, then add water phase II into the formed core emulsion, stirring and deoxidizing for 0.5h by nitrogen, drop 10g ammonium persulfate aqueous solution, stirring for 10min until uniform, then drop 12g sodium bisulfite aqueous solution to initiate polymerization, the temperature rises rapidly to 81℃ after a few minutes, continue to react for 1h, get nearly transparent polymer microspheres. But gel particles appear in both steps of reaction under naked eye.

[0085] From the comparison between comparative example 1 and example 1, it can be seen that when the nonionic emulsifier still accounts for 6.0% of the entire reaction system, the long carbon chain polymerizable surfactant monomer is removed, and gel particles appear during the encapsulation polymerization process, indicating that the system stability is poor.

[0086] According to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Co., Ltd. Shanghai Research Institute of Petroleum Chemical Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", the initial particle size is composed of a bimodal distribution of about 100nm and 1μm, the core and shell emulsion of the microspheres are refined into dry powder according to the method in the above standard, and the Zeta potential test is carried out, the potential of the core and shell of the microspheres is 28.7mV and 15.6mV respectively. The above data show that not only the particle size of the microspheres becomes larger and wider, but also interpenetration is formed between the core and shell, resulting in partial neutralization of the anionic charge of the shell by the cationic charge of the core.

[0087] The microsphere emulsion was prepared into 0.3% concentration with total salinity 200000 mg / L brine, aged at 95℃ for 30 days, and evaluated for plugging rate by filling sand pipe with 300 mD according to the above standard method. The plugging rate was measured to be 32%.

[0088] [Comparative Example 2]

[0089] The same as Example 3, 1000g of No. 3 white oil, 100g of Span80, 15g of AEO7 were first added to the reaction kettle and stirred until mixed evenly; 500g of water, 12g of methacrylamide, 380g of acrylamide, 12g of itaconic acid, 80g of acryloyloxyethyl trimethyl ammonium chloride (80%), 0.6g of sodium diethylenetriamine pentaacetate, 2.5g of methylene bisacrylamide, and 0.1g of V044 were added to a beaker and stirred to dissolve evenly as water phase I; 410g of water, 30g of sodium acrylate, 508g of acrylamide, 0.6g of sodium diethylenetriamine pentaacetate, 1.0g of divinylbenzene, and 0.2g of V044 were added to another beaker and stirred to dissolve evenly as water phase II; potassium persulfate and sodium bisulfite were separately prepared into 20% aqueous solution for standby. Water phase I was added to the reaction kettle and continuously stirred at 500 rpm, the temperature in the reaction kettle was controlled at 20℃, and nitrogen was blown to remove oxygen for 0.5h, then 4.5g of potassium persulfate aqueous solution was dropped in and stirred for 10min until uniform, then 6.8g of sodium bisulfite aqueous solution was dropped in to initiate polymerization, the temperature quickly rose to 84℃ after a few minutes, and the reaction continued for 1h to obtain a milky white polymer microsphere core portion; the temperature in the kettle was lowered below 30℃, and water phase II was added to the formed core emulsion, stirred, and nitrogen was blown to remove oxygen for 0.5h, then 9g of potassium persulfate aqueous solution was dropped in and stirred for 10min until uniform, then 11g of sodium bisulfite aqueous solution was dropped in to initiate polymerization, the temperature quickly rose to 81℃ after a few minutes, and the reaction continued for 1h to obtain a milky white polymer microsphere. However, gel particles appeared in the shell reaction which could be seen by naked eye.

[0090] As can be seen from the comparison between Comparative Example 2 and Example 3, when the non-ionic emulsifier still accounts for 3.8% of the entire reaction system, the polymerizable surfactant monomer in the water phase is removed, and gel particles appear in the shell polymerization process, indicating that the system stability is poor.

[0091] According to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Corporation Shanghai Research Institute of Petroleum Chemical Corporation Enterprise Standard “Temperature-resistant and salt-resistant polymer microsphere profile control agent”, the initial particle size is composed of bimodal peaks of hundreds of nanometers and several microns; in addition, the core and shell emulsions of the microspheres were refined into dry powders according to the method in the above standard, and Zeta potential test was performed, the potential of the microsphere core and shell was 28.5mV and 17.2mV respectively. The above data show that not only the microsphere particle size is larger and wider, but also interpenetration is formed between the core and shell.

[0092] The microsphere emulsion was prepared into 0.3% concentration with total salinity 200000 mg / L brine, aged at 95°C for 30 days, and evaluated for plugging rate with 1000 mD sand filling tube according to the above standard method, and the plugging rate was measured to be 26%.

[0093]

Comparative Example 3

[0094] The same as Example 5, except that the long carbon chain polymerizable monomer dimethyl octadecyl allyl ammonium chloride was replaced by the short carbon chain hydrophobic monomer styrene sodium sulfonate, and as a result, visible gel particles appeared in the process of encapsulation, indicating that the short carbon chain hydrophobic monomer did not play a stabilizing role when the subsequent water phase was added.

[0095] According to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Industry Co., Ltd. Shanghai Research Institute of Petroleum Chemical Industry Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", the initial particle size was composed of bimodal peaks of several microns and tens of microns; in addition, the core and shell emulsions of the microspheres were refined into refined dry powder according to the method in the above standard, and Zeta potential test was performed, and the potentials of the core and shell of the microspheres were 29.5 mV and 12.6 mV respectively. The above data show that not only the particle size of the microspheres becomes larger and wider, but also interpenetration is formed between the core and shell.

[0096] The microsphere emulsion was prepared into 0.3% concentration with total salinity 200000 mg / L brine, aged at 95°C for 30 days, and evaluated for plugging rate with 2000 mD sand filling tube according to the above standard method, and the plugging rate was measured to be 47%.

[0097]

Comparative Example 4

[0098] The same as Example 6, except that the long carbon chain polymerizable monomer dimethyl octadecyl allyl ammonium chloride was replaced by the short carbon chain hydrophobic monomer styrene sodium sulfonate, and as a result, visible gel particles appeared in the process of encapsulation, indicating that the short carbon chain hydrophobic monomer did not play a stabilizing role when the subsequent water phase was added.

[0099] According to the determination method of Q / SH3375 134-2019 China Petroleum Chemical Industry Co., Ltd. Shanghai Research Institute of Petroleum Chemical Industry Enterprise Standard "Temperature-resistant and salt-resistant polymer microsphere profile control agent", the initial particle size was composed of bimodal peaks of several microns and tens of microns; in addition, the core and shell emulsions of the microspheres were refined into refined dry powder according to the method in the above standard, and Zeta potential test was performed, and the potentials of the core and shell of the microspheres were 29.5 mV and 12.6 mV respectively. The above data show that not only the particle size of the microspheres becomes larger and wider, but also interpenetration is formed between the core and shell.

[0100] The microsphere emulsion was prepared into 0.3% concentration with total mineralization 200000 mg / L brine, aged at 95°C for 30 days, and evaluated for plugging rate by the above-mentioned standard method using 5000 mD sand pack tube, and the plugging rate was measured to be 43%.

[0101] The evaluation results are summarized in Table 1.

[0102] Table 1 Properties of self-emulsifying core-shell polymer microspheres prepared by adding long carbon chain polymerizable surfactant monomer

[0103]

[0104] As shown in Table 1, the self-assembled emulsifying core-shell polymer microspheres prepared by the example scheme have excellent product stability and plugging performance under high temperature and high salt conditions. The comparative examples only use traditional nonionic surfactants, or add short carbon chain hydrophobic monomers or ordinary polymerizable surfactants, and the stability of the coating polymerization process is poor, with gel particles. The prepared microspheres have wide particle size distribution, and the potential test results show that the core-shell structure is not distinct and is severely interpenetrated, so the plugging effect is poor under the same conditions.

Claims

1. A self-assembled emulsified core-shell polymer microsphere, said polymer microsphere is prepared by reaction of a mixture comprising: a) 20-50 parts by weight of an oil phase; b) 1-20 parts by weight of a composite emulsifier system; c) 20-50 parts by weight of a polymerizable monomer; d) 0.01-2.0 parts by weight of a crosslinking agent; e) 0.001-1 parts by weight of an initiator; f) the rest is water; wherein said oil phase is selected from at least one of aliphatic hydrocarbons, aromatic hydrocarbons; said aliphatic hydrocarbons are selected from at least one of white oil and solvent oil; said aromatic hydrocarbons are selected from at least one of benzene, toluene and xylene; the amount is 20-50% of the entire reaction system; said polymerizable monomer is selected from at least one of non-ionic water-soluble monomer, anionic monomer and cationic monomer; said non-ionic water-soluble monomer is selected from at least one of acrylamide, methacrylamide, tert-butyl acrylamide; said anionic monomer is selected from at least one of acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, itaconic acid, maleic acid, fumaric acid or its salts; said cationic monomer is selected from at least one of dimethyl diallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride; said initiator includes: 1) an oxidizing agent, the weight of which is 0.01-1.0% of the weight of said polymerizable monomer; 2) a reducing agent, the weight of which is 0.02-2.0% of the weight of said polymerizable monomer; 3) an azo initiator, the weight of which is 0-5% of the weight of said polymerizable monomer; said composite emulsifier system is a combination of non-ionic emulsifier and long carbon chain polymerizable surfactant monomer, the amount of polymerizable surfactant monomer is 0.5-20% of the entire emulsifier system; said non-ionic emulsifier includes lipophilic surfactant and hydrophilic surfactant; wherein said lipophilic surfactant is sorbitan fatty acid ester; said hydrophilic surfactant is alkyl phenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether or polyoxyethylene sorbitan fatty acid ester; said long carbon chain polymerizable surfactant monomer is selected from hydrophobic monomer containing lipophilic chain with not less than 8 carbon atoms; said long carbon chain polymerizable surfactant monomer is selected from anionic 2-acrylamido N-alkyl sulfonic acid sodium, polyol sodium maleate, maleic anhydride derivative, cationic allyl alkyl (dimethyl) ammonium chloride, methacryloyloxyethyl alkyl dimethyl ammonium bromide, 2-acrylamidoethyl N-alkyl dimethyl ammonium bromide, non-ionic N-alkyl acrylamide, twin tail hydrophobic monomer N, N-dialkyl acrylamide, polymerizable surfactant composed of multiple hydrophobic butylene oxide units and hydrophilic ethylene oxide units; said core-shell polymer microsphere is prepared by stepwise polymerization, wherein said long carbon chain polymerizable surfactant monomer is added after the completion of the nucleation reaction.

2. The self-assembled emulsification core-shell type polymer microspheres according to claim 1, characterized by, said polymer microsphere is prepared by reaction of a mixture comprising: a) 25-40 parts by weight of an oil phase; b) 1-10 parts by weight of a composite emulsifier system; c) 25-40 parts by weight of a polymerizable monomer; d) 0.1-1.0 parts by weight of a crosslinking agent; e) 0.005-0.5 parts by weight of an initiator; f) the rest is water; wherein the initiator comprises: 1) an oxidizing agent, the weight of which is 0.02-0.5% of the weight of the polymerizable monomer; 2) a reducing agent, the weight of which is 0.05-1.0% of the weight of the polymerizable monomer; 3) an azo initiator, the weight of which is 0.1-2.0% of the weight of the polymerizable monomer.

3. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The aliphatic hydrocarbon is selected from at least one of white oil No. 3, white oil No. 5, white oil No. 7, 120# solvent oil and 200# solvent oil.

4. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The amount of the aromatic hydrocarbon accounts for 20-50% of the entire reaction system.

5. The self-assembled emulsification core-shell type polymer microspheres according to claim 4, characterized by, The amount of the aromatic hydrocarbon accounts for 25-40% of the entire reaction system.

6. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The polymerizable surface active monomer accounts for 1-10% of the entire emulsifier system; the hydrophilic-lipophilic balance value HLB of the composite emulsifier system is between 3 and 9.

7. The self-assembled emulsification core-shell type polymer microspheres according to claim 6, characterized by, The hydrophilic-lipophilic balance value HLB of the composite emulsifier system is between 4 and 7.

8. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The lipophilic surfactant is at least one of Span 85, Span 80, Span 65 and Span 60; the hydrophilic surfactant is at least one of the AEO series in fatty alcohol polyoxyethylene ether, the isomeric alcohol series and Tween 85, Tween 80, Tween 60, Tween 40, Tween 20 in polyoxyethylene sorbitan fatty acid ester.

9. The self-assembled emulsification core-shell type polymer microspheres according to claim 8, characterized by, In the hydrophilic surfactant, the adduct number of ethylene oxide in the isomeric alcohol series is greater than 5.

10. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The crosslinking agent is at least one selected from the group consisting of methylene bisacrylamide, divinylbenzene, polyethylene glycol diacrylate and pentaerythritol triacrylate.

11. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The oxidizing agent is at least one selected from the group consisting of potassium persulfate, sodium persulfate, ammonium persulfate and benzoyl peroxide; The reducing agent is at least one selected from the group consisting of sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, sodium thiosulfate and ferrous chloride; The azo initiator is at least one selected from the group consisting of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, azobis isobutylamidine hydrochloride, azobis isobutyronitrile and azobis isoheptyl nitrile.

12. The self-assembled emulsification core-shell type polymer microsphere according to claim 1, characterized by, The self-assembled emulsion core-shell polymer microspheres further comprise a complexing agent, the weight of which is 0.01-0.5% of the weight of the polymerizable monomer; the complexing agent is at least one selected from the group consisting of disodium ethylenediaminetetraacetate and sodium diethylenetriaminepentaacetate.

13. The self-assembled emulsification core-shell type polymer microspheres according to claim 12, characterized by, The weight of the complexing agent is 0.05-0.2% of the weight of the polymerizable monomer.

14. The preparation method of the self-assembled emulsion core-shell polymer microspheres according to any one of claims 1-13, comprising the following steps: ①Mixing the oil phase and the non-ionic emulsifier in the composite emulsifier system and the oil-soluble azo initiator uniformly to form a continuous phase; Mixing the polymerizable monomer, the crosslinking agent, the optional complexing agent, the water-soluble azo initiator and water required for preparing the core part and the shell part of the microspheres uniformly to form water phase I and water phase II; the mass ratio of the water phase I to the water phase II is 1:9-9:1; respectively configure oxidant aqueous solution and reducing agent aqueous solution; ②The continuous phase, the aqueous phase I is mixed in the reaction kettle in turn to obtain mixture A; the temperature in the reaction kettle is controlled at 10-30 DEG C, nitrogen is passed to remove oxygen, then the oxidant aqueous solution is added and stirred uniformly, the reducing agent aqueous solution is continuously added to initiate polymerization, after the polymerization temperature reaches the highest temperature, the reaction is preserved for 1 hour, the core part of polymer microspheres is obtained; ③The polymerization system is cooled to 20-30 DEG C, the long carbon chain polymerizable surfactant monomer is added and stirred for several minutes, then the aqueous phase II is added and stirred uniformly, nitrogen is passed to remove oxygen, the oxidant and the reducing agent are added in turn, after the polymerization temperature reaches the highest temperature, the reaction is preserved for 1 hour, the coating reaction is completed, the core-shell polymer microspheres are obtained.

15. The self-assembled emulsified core-shell polymer microspheres according to any one of claims 1-13, and the application of the self-assembled emulsified core-shell polymer microspheres prepared by the preparation method of claim 14 in the tertiary oil recovery of oil field.

Images