Free radical solution polymerization method, polymer and its use

Abstract

The present invention provides a free radical solution polymerization process, a polymer and its use. The polymerization process includes introducing micro-nano bubbles of gas B into an aqueous solution of a vinyl monomer, and initiating free radical solution polymerization of the vinyl monomer with free radicals generated after cavitation of the micro-nano bubbles to prepare a polymer. The micro-nano bubbles can generate free radicals by cavitation without external stimulation, and in the present invention, free radical solution polymerization of the vinyl monomer is initiated by cavitation of the micro-nano bubbles.

Description

Technical Field

[0001] The present invention relates to the field of free radical solution polymerization, and particularly relates to free radical solution polymerization processes, polymers, and their use.

Background Art

[0002] Free radical polymerization is an effective method for large-scale production of various vinyl polymers, and more than about 60% of vinyl polymers are produced by free radical polymerization. Free radical polymerization has the advantages of high polymerization or copolymerization activity for various vinyl monomers, mild polymerization conditions, few impurities in the polymerization system, low cost, and the ability to use environmentally friendly water as a reaction medium. An important stage of free radical polymerization is chain initiation, and the formation of primary free radicals, which is the first step of chain initiation, is the most important. Free radicals are generally generated in the polymerization system by photoinitiation, thermal initiation, initiation by irradiation with high-energy rays, addition of initiators, etc.

[0003] In the prior art, methods for initiating polymerization include photoinitiation, thermal initiation, initiation by irradiation with high-energy rays, redox initiation, etc. Here, one method may be used, or a plurality of methods may be combined and used. Examples of initiators used include azo initiators, redox initiators, photoinitiators, etc. However, the above-mentioned initiation methods all have the disadvantages of complicated operation and high energy consumption. Conventional initiators are limited by initiation efficiency and half-life and cannot be initiated at any temperature. In addition, conventional initiators have problems such as limited supply sources, high cost, toxicity, and low stability. Methods such as photoinitiation, thermal initiation, and initiation by irradiation with high-energy rays have the problem of high energy consumption.

[0004] Furthermore, in the manufacturing process, initiators are generally added in excess in order to keep the residual monomer content in the polymer low (e.g., less than 0.1% by weight). As a result, a trace amount of the initiator remains in the polymer product, leading to a decrease in the viscosity retention rate over time and poor long-term stability.

[0005] Furthermore, most acrylamide-based polymers are solid core dry powders obtained by free radical aqueous solution polymerization initiated by initiators. The manufacturing process generally includes steps such as polymerization, granulation (optionally hydrolysis), drying, grinding, sieving, etc. When water is present as a solvent during polymerization, the diffusion of the polymerization heat is promoted, so it is easy to control the polymerization reaction temperature. However, a large amount of thermal energy is required to evaporate most of the water in the drying procedure, and the drying procedure is too long, resulting in cross-linking between polymer chains and affecting the properties of the polymer.

[0006] It is known that porous polymers can be produced by adding foaming agents, etc. For example, Chinese Patent Application Publication No. 1542027 discloses the production of polyacrylamide using ammonium bicarbonate as a foaming agent. Chinese Patent Application Publication No. 105566539 discloses the production of polyacrylamide using ammonium bicarbonate as a foaming agent and N,N-dimethyldodecylamine oxide or N,N-diethyldodecylamine oxide as a foaming accelerator. The bubbles introduced in these prior arts are large in diameter (at the millimeter level), the bubbles are not uniformly distributed in the polymerization system, and do not have an obvious mass transfer function and heat transfer function. These introduced bubbles do not have a great impact on the polymer manufacturing process.

[0007] Therefore, there is a need for a free radical solution polymerization process that is easy to operate, consumes less energy, is easy and convenient to control, and can be widely applied. On the other hand, there is also a need for a polymer having a porous structure with low energy consumption in the post-treatment procedure, short dissolution time, low residual monomer content, and high viscosity retention rate over time.

Prior Art Documents

Patent Document

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

[0009] (Disclosure of the Invention) The present invention provides a free radical solution polymerization process, a polymer, and its use for solving one or more technical problems of the prior art.

[0010] Micro-nano bubbles generally refer to bubbles with a diameter of 50 μm or less. Microbubbles with a diameter of 1 μm or more are called microbubbles, and ultra-small bubbles with a diameter of less than 1 μm and more than 1 nm are called nano-bubbles. Compared with conventional coarse bubbles (with a diameter of more than 50 mm), micro-nano bubbles have a small diameter and a large effect of small size. The mass transfer characteristics, heat transfer characteristics, and interfacial characteristics of micro-nano bubbles are clearly different from those of conventional coarse bubbles. Micro-nano bubbles have a very small buoyancy in water (due to their small volume) compared with general bubbles, so they can stay in water for several minutes to several hours. In a solution, since micro-nano bubbles have a small diameter and a large curvature, the internal pressure of the bubbles increases due to the surface tension of water, and the gas in the bubbles is gradually compressed, and finally the bubbles burst. This process is called "cavitation". In the process of "cavitation", when micro-nano bubbles shrink, the charge density of the electric double layer increases rapidly, and when the bubbles burst, due to the dramatic change that the gas-liquid interface disappears, the energy accumulated by high-concentration positive and negative ions on the interface is released, and at this moment, a large amount of hydroxyl free radicals are generated by excitation.

[0011] The inventors have surprisingly found that by selecting an appropriate gas source to generate bubbles with a diameter in the micronanometer scale and introducing these bubbles into a vinyl monomer free radical solution polymerization system, a large amount of hydroxyl free radicals can be generated after the cavitation of the micronanometer bubbles in the system, and the free radical solution polymerization of the vinyl monomer can be initiated using these hydroxyl free radicals.

[0012] Therefore, micronanobubbles can be introduced into the free radical solution polymerization system, and the polymerization can be initiated by utilizing the "cavitation" effect of the micronanobubbles in the solution. Since free radicals can be generated and the free radical solution polymerization of vinyl monomers can be initiated without adding external stimuli or polymerization initiators, the free radical solution polymerization can be simplified and the energy consumption can be reduced.

[0013] In the process of the present invention, after introducing micronanogas bubbles, free radicals can be generated, and the free radical solution polymerization of vinyl monomers can be initiated without external stimuli, so the operation is simple and the energy consumption is low. The initiation of the free radical solution polymerization of the vinyl monomer using micronanobubbles is characterized by being easy to control, convenient, and widely applicable. Furthermore, in the process of the present invention, there is no need to add an initiator.

[0014] One aspect of the present invention is to provide a free radical solution polymerization process, which includes introducing micronanobubbles of gas B into an aqueous solution of a vinyl monomer, and initiating the free radical solution polymerization of the vinyl monomer by the free radicals generated after the cavitation of the micronanobubbles to prepare a polymer. In some embodiments, the free radical solution polymerization process further includes passing an inert gas A through the aqueous solution of the vinyl monomer to remove oxygen before introducing the micronanobubbles of gas B.

[0015] Another aspect of the present invention is After passing an inert gas A through an aqueous solution of a vinyl monomer to remove oxygen, introducing micro-nano bubbles of gas B, and initiating free radical solution polymerization of the vinyl monomer by free radicals generated after cavitation of the micro-nano bubbles to prepare a polymer. A free radical solution polymerization process comprising the above is provided.

[0016] According to some embodiments, the present invention (1) Passing an inert gas A through an aqueous solution of a vinyl monomer to remove oxygen, thereby obtaining an oxygen-removed aqueous solution of the vinyl monomer; (2) Introducing micro-nano bubbles of gas B into the oxygen-removed water to obtain oxygen-removed water containing the micro-nano bubbles; and (3) Mixing the oxygen-removed aqueous solution of the vinyl monomer obtained in step (1) with the oxygen-removed water containing the micro-nano bubbles obtained in (2), and initiating free radical solution polymerization of the vinyl monomer by free radicals generated after cavitation of the micro-nano bubbles to prepare a polymer. A free radical solution polymerization process comprising the above is provided.

[0017] Yet another aspect of the present invention relates to a polymer prepared by the free radical solution polymerization process of the present invention.

[0018] Yet another aspect of the present invention relates to an acrylamide-based polymer having a micro-nano porous structure, wherein the polymer has pores with a diameter of 0.05 μm to 2 μm, more preferably 0.1 μm to 1 μm, even more preferably 0.1 μm to 0.5 μm, and 0.080 to 1 cm 3 / g, preferably 0.090 to 0.80 cm 3 / g, even more preferably 0.090 to 0.50 cm 3It has a pore volume of / g, and the initiator content in the polymer is zero. In some embodiments, the acrylamide-based polymer having the micro-nanoporous structure has the following properties: water solubility with a dissolution time of less than 30 minutes; a viscosity average molecular weight of 300×10 4 ~3000×10 4 ; a weight content of residual monomer of less than 0.1%; and a viscosity retention rate over time (105 °C) of more than 90%, having at least one, preferably all of the properties.

[0019] Another aspect of the present invention relates to the use of the above polymer in oil layer recovery, preferably in high-temperature and high-salinity oil layer polymer flooding, offshore oil layer polymer flooding, heavy oil layer polymer flooding, and fracturing.

[0020] (Detailed Description) The present invention provides a free radical solution polymerization process in which free radical solution polymerization of vinyl monomers is initiated by free radicals generated after cavitation of micro-nanobubbles, preferably nanobubbles, to produce a polymer.

[0021] In the free radical solution polymerization process of the present invention, no free radical initiator is added, and free radicals are not generated by other means such as light, heat, radiation, etc. That is, in the free radical solution polymerization process of the present invention, the free radicals used to initiate the free radical solution polymerization of vinyl monomers are generated only by cavitation of micro-nanobubbles.

[0022] As will be understood by those skilled in the art, since no free radical initiator is spontaneously added during polymerization, the initiator content in the polymer obtained by the polymerization process of the present invention is zero.

[0023] One aspect of the present invention is to provide a free radical solution polymerization process, which includes introducing micro-nano bubbles of gas B into an aqueous solution of a vinyl monomer, and initiating free radical solution polymerization of the vinyl monomer by free radicals generated after cavitation of the micro-nano bubbles to prepare a polymer. Preferably, in the free radical solution polymerization process, before introducing the micro-nano bubbles of gas B, an inert gas A is passed through the aqueous solution of the vinyl monomer to remove oxygen.

[0024] In some embodiments, the aqueous solution of the vinyl monomer may have a weight concentration of the vinyl monomer of 10% - 55% or 10% - 50%, preferably 15% - 50%, more preferably 15% - 35%.

[0025] In the present invention, any water generally used in free radical solution polymerization can be used. For example, deionized water, distilled water, tap water, circulating water, recycled water, natural water, etc. can be used. Examples of natural water may include river water, lake water, sea water, rain water, etc.

[0026] In the present invention, the inert gas A is any inert gas that can remove oxygen from the aqueous solution. Removing oxygen from the monomer aqueous solution (also called oxygen removal or inactivation) before free radical solution polymerization is known in the art. Any inert gas generally known in the art that can be used for oxygen removal can be used. In some embodiments, the inert gas A may be at least one of nitrogen, argon, helium, neon, krypton, xenon, or any combination thereof.

[0027] In the present invention, the gas B can be any gas that can generate free radicals by cavitation of micro-nano bubbles. In some embodiments, the gas B may be at least one of nitrogen, argon, helium, neon, krypton, xenon, carbon dioxide, or any combination thereof.

[0028] The inert gas A and the gas B may be the same or different. The inert gas A and the gas B may be a single gas or a mixture of a plurality of gases.

[0029] In the present invention, the vinyl monomer refers to a monomer having one or more carbon-carbon double bonds and capable of free radical solution polymerization.

[0030] In some embodiments, the vinyl monomer may be selected from the group consisting of an anionic monomer, a salt of an anionic monomer, a nonionic monomer, a cationic monomer, and any combination thereof. For example, the vinyl monomer may be at least one or more of an anionic monomer, their salts such as alkali metal salts, alkaline earth metal salts, and ammonium salts, nonionic monomers, and cationic monomers, for example, 2, 3, 4, 5 or more.

[0031] According to some embodiments, the vinyl monomer is preferably an electron-deficient olefin, and more preferably an electron-deficient olefin containing at least one group selected from the group consisting of an amide group, a carboxyl group, an ester group, a phenyl group, a sulfonic acid group, and combinations thereof.

[0032] In some embodiments, the anionic monomer includes, or can be selected from, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, cinnamic acid, (E)-butenedioic acid, crotonic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acrylamidopropanesulfonic acid, 2-methacrylamidopropanesulfonic acid, vinylsulfonic acid, propenylsulfonic acid, styrenesulfonic acid, and any combination thereof.

[0033] The salt of the anionic monomer can be selected from the group consisting of alkali metal salts, alkaline earth metal salts, and ammonium salts. In some embodiments, the alkali metal salt can be selected from lithium salts, potassium salts, and sodium salts, and the alkaline earth metal salt can be selected from magnesium salts, calcium salts, strontium salts, and barium salts.

[0034] In some embodiments, the nonionic monomer can include at least one of acrylamide, methacrylamide, N-vinylpyrrolidone, N-ethylacrylamide, N-ethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and N,N-diisopropylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide, and N,N-diisopropylmethacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, N-vinylacetamide, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, vinyl acetate, vinyl propionate, N-[(4-aminosulfonyl)phenyl]acrylamide, and any combination thereof, or can be selected from the group consisting of them.

[0035] In some embodiments, the nonionic monomer contains a hydrophilic group. In some embodiments, the nonionic monomer containing a hydrophilic group includes, or can be selected from, acrylamide, methacrylamide, N-vinylpyrrolidone, N-ethylacrylamide, N-ethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and N,N-diisopropylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide, and N,N-diisopropylmethacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, N-vinylacetamide, N-[(4-aminosulfonyl)phenyl]acrylamide, and any combination thereof.

[0036] In some embodiments, the cationic monomer includes, or can be selected from, dimethylaminoethyl acrylate and its quaternary ammonium salt, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropyl acrylate and its quaternary ammonium salt, dimethylaminopropyl methacrylate and its quaternary ammonium salt, dimethylaminopropyl acrylamide and its quaternary ammonium salt, dimethylaminopropyl methacrylamide and its quaternary ammonium salt, and any combination thereof.

[0037] In one embodiment, the vinyl monomer may further include a hydrophobic monomer. The hydrophobic monomer may be used in an amount that does not affect the water solubility of the polymer. For example, the total weight of the hydrophobic monomer is 10% or less of the total weight of the vinyl monomer. The hydrophobic monomer includes, or may be selected from, N-hexylacrylamide, N-octylacrylamide, N-nonylacrylamide, N-dodecylacrylamide, N-tetradecylacrylamide, N-hexadecylacrylamide, N-octadecylacrylamide, N,N-dibutylacrylamide, N,N-dihexylacrylamide, N,N-dioctylacrylamide, N,N-didecylacrylamide, N,N-di(dodecyl)acrylamide, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, propyl acrylate, propyl methacrylate, vinyl acetate, vinyl propionate, and combinations thereof.

[0038] In some embodiments of the present invention, the vinyl monomer may be selected from the group consisting of acrylamide, methacrylamide, N,N-dimethylacrylamide, dimethylaminoethyl methacrylate, sodium acrylate, sodium crotonate, sodium 2-acrylamido-2-methylpropanesulfonate, methyl acrylate, N-vinylpyrrolidone, maleic anhydride, and N-[(4-aminosulfonyl)phenyl]acrylamide.

[0039] In some embodiments of the present invention, the vinyl monomer in the aqueous solution of the vinyl monomer contains acrylamide, preferably contains a major amount of acrylamide, and optionally contains one or more of the above vinyl monomers other than acrylamide. In some embodiments of the present invention, the vinyl monomer contains a major amount of acrylamide and one or more additional vinyl monomers selected from the group consisting of methacrylamide, N,N-dimethylacrylamide, dimethylaminoethyl methacrylate, sodium acrylate, sodium crotonate, sodium 2-acrylamido-2-methylpropanesulfonate, methyl acrylate, N-vinylpyrrolidone, maleic anhydride, and N-[(4-aminosulfonyl)phenyl]acrylamide. In the present invention, the major amount refers to at least 50% by weight, for example at least 60% by weight, based on the total amount of the vinyl monomer.

[0040] In the present invention, the gas B is introduced in the form of micro-nano bubbles into the aqueous solution of the vinyl monomer. The average diameter of the micro-nano bubbles of the gas B can be 20 nm to 1 μm, preferably 20 nm to 900 nm, more preferably 30 nm to 500 nm, still more preferably 40 nm to 400 nm, and even more preferably 50 nm to 200 nm.

[0041] In the present invention, the size of the micro-nano bubbles is measured by the dynamic light scattering method, and the Z-average value is used as the diameter of the bubbles.

[0042] Preferably, in the present invention, the micro-nano bubbles of the gas B are nano bubbles.

[0043] In some preferred embodiments of the present invention, the micro-nano bubbles of the gas B have an average diameter of 50 nm to 500 nm, more preferably 50 nm to 200 nm.

[0044] When the average diameter of the micro-nano bubbles is on the nano-scale, after the micro-nano bubbles are introduced into the aqueous solution of the vinyl monomer, cavitation begins to occur. Due to the cavitation of the micro-nano bubbles, a large amount of hydroxyl free radicals can be excited and generated. As a result, the free radical solution polymerization of the vinyl monomer is initiated.

[0045] In the present invention, there is no particular limitation on the method for generating micro-nano bubbles. The micro-nano bubbles can be generated using any method capable of generating micro-nano bubbles. For example, methods such as hydrodynamic cavitation, ultrasonic cavitation, pressure fluctuation, and electrolysis of water can be used to generate the micro-nano bubbles.

[0046] In some embodiments, the micro-nano bubbles can be generated using a model LF1500 micro-nano bubble generator manufactured by Shandong Micro-bubble Environmental Protection Equipment Co., LTD. The diameter of the bubbles can be controlled by a rotameter, pressure, and the generator. When the gas input of the micro-nano bubble generator is controlled at 10 - 200 mL / min and the inlet pressure is controlled at 0.2 - 1 MPa, the average diameter of the micro-nano bubbles can be controlled at 50 nm - 20 μm.

[0047] In some embodiments, the volume of the micro-nano bubble-containing solution or water obtained after the introduction of micro-nano bubbles increases. For example, the volume of the solution or water can increase by 0.5% - 4%, such as 0.6% - 3% after the introduction of the micro-nano bubbles.

[0048] In some embodiments, the concentration of hydroxyl free radicals in the polymerization system can be in the range of 0.05 - 0.5 μmol / L.

[0049] In the present invention, the concentration of hydroxyl free radicals is measured by methylene blue spectrophotometry.

[0050] In some preferred embodiments of the present invention, the pH of the aqueous solution of the vinyl monomer can be 4 to 9, preferably 4 to 6. For example, the pH can be adjusted by adding an acid or a base.

[0051] In the free radical solution polymerization process of the present invention, in some embodiments, the introduction of the micro-nano bubbles of gas B includes directly introducing the micro-nano bubbles of gas B into the oxygen-removed aqueous solution of the vinyl monomer.

[0052] In the free radical solution polymerization process of the present invention, in some embodiments, the introduction of the micro-nano bubbles of gas B includes introducing the micro-nano bubbles of gas B into oxygen-removed water to obtain oxygen-removed water containing the micro-nano bubbles, and mixing the oxygen-removed water containing the micro-nano bubbles with the oxygen-removed aqueous solution of the vinyl monomer. After mixing, an aqueous solution of the vinyl monomer containing micro-nano bubbles is obtained, and the free radical solution polymerization of the vinyl monomer is initiated by free radicals generated after the cavitation of the micro-nano bubbles, and a polymer is prepared. As will be understood by those skilled in the art, the aqueous solution of the vinyl monomer containing micro-nano bubbles obtained after mixing the oxygen-removed water containing micro-nano bubbles with the oxygen-removed aqueous solution of the vinyl monomer can have the above-mentioned weight concentration of the vinyl monomer.

[0053] In the free radical solution polymerization process of the present application, the initial polymerization reaction temperature can be -10°C to 40°C, preferably 0 to 25°C.

[0054] According to some embodiments, in the free radical solution polymerization process of the present invention, the polymerization reaction is an exothermic reaction.

[0055] The free radical solution polymerization process of the present invention can be carried out in any suitable reactor. In some embodiments, the free radical solution polymerization of the present invention is carried out in an adiabatic reactor.

[0056] In some embodiments of the present invention, the diameter of the bubbles of the inert gas A can be 1 mm to 10 mm. In some embodiments of the present invention, the time for passing the bubbles of the inert gas A can be 5 minutes to 60 minutes, preferably, the passing time can be 20 minutes to 40 minutes.

[0057] As is known to those skilled in the art, the purpose of passing the inert gas A is to remove oxygen. In some embodiments, by combining a general nitrogen gas cylinder and a pressure reducing valve with a flow meter and controlling the flow rate of the pressure reducing valve to 2 to 20 L / min, preferably 5 to 15 L / min, an inert gas A with bubble diameters of 1 mm to 10 mm can be provided.

[0058] In the present invention, a polymer is obtained after the free radical solution polymerization of the vinyl monomer is completed. Since the micro-nano bubbles can stay in water for a long time, in the free radical solution polymerization process of the present invention, micro-nano bubbles are present in the polymerization system during polymerization. Due to the presence of the micro-nano bubbles, after the polymerization is completed, a polymer in the form of a jelly containing bubbles is obtained.

[0059] The treatment of the polymer in the form of jelly is known in the art. For example, the treatment methods for jelly-like solids include granulating the jelly-like solid, hydrolyzing or not hydrolyzing it, oven drying it, pulverizing it, and sieving it, etc. The polymer in the form of a bubble-containing jelly of the present invention can also be treated by the same treatment methods.

[0060] In some embodiments, jelly-like solids of different types of polymers are produced, granulated if necessary, and then may be hydrolyzed and then dried in an oven, or may be directly dried in an oven without hydrolysis. After granulating the polymer to be hydrolyzed, a base is added and reacted at a certain temperature for a certain time to prepare a polymer having a certain degree of hydrolysis. The non-hydrolyzed polymer does not need to be hydrolyzed and is directly oven dried after granulation.

[0061] After treating the polymer in the form of a jelly containing bubbles, a polymer having a micro-nano porous structure is obtained. According to some embodiments, the polymer having the micro-nano porous structure can be a granular polymer or a powdered polymer.

[0062] According to some embodiments, the polymer having the micro-nano porous structure has pores with a diameter of 0.05 μm to 2 μm, more preferably 0.1 μm to 1 μm, and even more preferably 0.1 μm to 0.5 μm, and the pore volume is 0.080 to 1 cm 3 / g, preferably 0.090 to 0.80 cm 3 / g, and even more preferably 0.090 to 0.50 cm 3 / g. For example, the pore volume can be 0.080 cm 3 / g, 0.090 cm 3 / g, 0.10 cm 3 / g, 0.11 cm 3 / g, 0.12 cm 3 / g, 0.13 cm 3 / g, 0.14 cm 3 / g, 0.15 cm 3 / g, 0.20 cm 3 / g, 0.25 cm 3 / g, 0.30 cm 3 / g, 0.35 cm 3 / g, 0.40 cm 3 / g, 0.45 cm 3 / g, 0.50 cm 3 / g, 0.55 cm 3 / g, 0.60 cm 3 / g, 0.65 cm 3 / g, 0.70 cm 3 / g, 0.75 cm 3 / g, 0.80 cm 3 / g, 0.90 cm 3 / g, or 1 cm 3 / g.

[0063] In the present invention, 200 pores are randomly selected for diameter measurement, and the average value is used as the pore diameter. The pore volume is measured according to GB / T 21650.1-2008 "Pore Size Distribution and Porosity of Solid Materials by Mercury Porosimetry and Gas Adsorption Method - Part 1: Mercury Porosimetry".

[0064] In some embodiments of the present invention, after the temperature of the polymerization system rises by 0.5 to 1 °C, the introduction of micro-nano bubbles is stopped, and the reaction is continued for another 1 to 6 hours, preferably 2 to 5 hours.

[0065] The polymer obtained by the free radical solution polymerization process of the present invention has a desired molecular weight. The polymer obtained by the free radical solution polymerization process of the present invention has a viscosity average molecular weight of 300×10 4 ~3000×10 4 and may have.

[0066] The polymer obtained by the free radical solution polymerization process of the present invention is water-soluble and has a beneficial dissolution rate. Due to the presence of a porous structure in the polymer, the polymer obtained by the free radical solution polymerization process of the present invention may have water solubility with a dissolution time of less than 30 minutes.

[0067] The polymer obtained by the free radical solution polymerization process of the present invention has a low residual monomer content. The polymer obtained by the free radical solution polymerization process of the present invention may have a residual monomer content of less than 0.1% by weight.

[0068] Since the free radical solution polymerization process of the present invention does not use an initiator, there is no problem of initiator residue. Therefore, the polymer obtained by the free radical solution polymerization process of the present invention has a high viscosity retention rate over time and thus good long-term stability. The polymer obtained by the free radical solution polymerization process of the present invention may have a viscosity retention rate over time of more than 90% (105 °C).

[0069] In some embodiments, the polymer obtained by the free radical solution polymerization process of the present invention has the following properties: water solubility with a dissolution time of less than 30 minutes; a viscosity average molecular weight of 300×10 4 ~3000×10 4 ; a residual monomer content of less than 0.1 wt%; and a viscosity retention rate over time of more than 90%, and may have at least one, preferably all of these properties (at 105 °C).

[0070] Another aspect of the present invention is to provide a polymer prepared by the free radical solution polymerization process of the present invention. As will be understood by those skilled in the art, the polymer produced by the free radical solution polymerization process of the present invention has the properties described herein. For example, the initiator content in the polymer is zero.

[0071] According to some embodiments, the polymer produced by the free radical solution polymerization process of the present invention is a granular polymer or a powdered polymer having a micro-nano porous structure. According to some embodiments, the polymer produced by the free radical solution polymerization process of the present invention is a particle or powder having a micro-nano porous structure. According to some embodiments, the polymer having a micro-nano porous structure has pores with a diameter of 0.05 μm to 2 μm, more preferably 0.1 μm to 1 μm, even more preferably 0.1 μm to 0.5 μm, and the pore volume is 0.080 to 1 cm 3 / g, preferably 0.090 to 0.80 cm 3 / g, even more preferably 0.090 to 0.50 cm 3 / g. For example, the pore volume is 0.080 cm 3 / g, 0.090 cm 3 / g, 0.10 cm 3 / g, 0.11 cm 3 / g, 0.12 cm 3 / g, 0.13 cm 3 / g, 0.14 cm 3 / g, 0.15 cm 3 / g, 0.20 cm 3 / g, 0.25 cm 3 / g, 0.30 cm3 / g, 0.35 cm 3 / g, 0.40 cm 3 / g, 0.45 cm 3 / g, 0.50 cm 3 / g, 0.55 cm 3 / g, 0.60 cm 3 / g, 0.65 cm 3 / g, 0.70 cm 3 / g, 0.75 cm 3 / g, 0.80 cm 3 / g, 0.90 cm 3 / g, or 1 cm 3 / g and may be.

[0072] Another aspect of the present invention is to provide an acrylamide-based polymer having a micro-nano porous structure, wherein the polymer has pores with a diameter of 0.05 μm to 2 μm, more preferably 0.1 μm to 1 μm, and even more preferably 0.1 μm to 0.5 μm, and the pore volume is 0.080 to 1 cm 3 / g, preferably 0.090 to 0.80 cm 3 / g, even more preferably 0.090 to 0.50 cm 3 / g, and the initiator content in the polymer is zero. For example, the pore volume is 0.080 cm 3 / g, 0.090 cm 3 / g, 0.10 cm 3 / g, 0.11 cm 3 / g, 0.12 cm 3 / g, 0.13 cm 3 / g, 0.14 cm 3 / g, 0.15 cm 3 / g, 0.20 cm 3 / g, 0.25 cm 3 / g, 0.30 cm 3 / g, 0.35 cm 3 / g, 0.40 cm 3 / g, 0.45 cm 3 / g, 0.50 cm 3 / g, 0.55 cm 3 / g, 0.60 cm 3 / g, 0.65 cm 3 / g, 0.70 cm 3 / g, 0.75 cm3 / g, 0.80 cm 3 / g, 0.90 cm 3 / g, or 1 cm 3 / g may be possible.

[0073] In some embodiments, the acrylamide-based polymer having the micro-nanoporous structure has the following properties: water solubility with a dissolution time of less than 30 minutes; a viscosity average molecular weight of 300 × 10 4 ~3000 × 10 4 ; a weight content of residual monomer of less than 0.1%; and a viscosity retention rate over time of more than 90%, and has at least one, preferably all of the properties (at 105 °C).

[0074] The acrylamide-based polymer includes acrylamide, preferably a major amount of acrylamide, and optionally one or more of the above-mentioned vinyl monomers other than acrylamide.

[0075] A further aspect of the present invention is to provide for the use of the polymers of the present invention in industries such as oil recovery, water treatment, printing and dyeing, papermaking, and mineral processing.

[0076] Some embodiments of the present invention provide for the use of the polymers of the present invention in oil reservoir recovery, preferably in high-temperature and high-salinity oil reservoir polymer flooding, offshore oil reservoir polymer flooding, heavy oil reservoir polymer flooding, and fracturing. The polymers of the present invention can be used as thickeners for high-temperature and high-salinity oil reservoir polymer flooding, offshore oil reservoir polymer flooding, and heavy oil reservoir polymer flooding, or as thickeners and drag reducers for fracturing. The polymers of the present invention have a micro-nanoporous structure uniformly distributed on the inside and surface, and during the dissolution process of granular or powdered polymers, the polymer particles or powder come into contact with water and quickly penetrate and swell, thereby significantly shortening the dissolution time of the polymer.

[0077] As is known in the field of polymer flooding methods, the polymers for offshore oil reservoir polymer flooding methods are formulated using wastewater and have a short on-line aging time. Therefore, there is a need to develop a polymer for a fast-dissolving method suitable for offshore oil reservoir polymer flooding methods. The polymer of the present invention has an excellent dissolution rate and thus meets the fast-dissolving requirements of polymers for offshore oil reservoir polymer flooding methods.

[0078] The polymer of the present invention has a high viscosity retention rate over time and good long-term stability, and is therefore particularly suitable as a polymer for high-temperature and high-salinity oil reservoir polymer flooding methods or offshore oil reservoir polymer flooding methods.

[0079] In some embodiments, the present invention includes the following steps: A step of formulating one or more vinyl monomers in an aqueous solution having a weight concentration of 10 to 55%, preferably 15 to 50%; A step of controlling the initial polymerization temperature of the system to -10°C to 40°C, preferably 0°C to 25°C; A step of blowing general bubbles of an inert gas A having a diameter of 1 mm to 10 mm into the system for 5 to 60 minutes, preferably 20 to 40 minutes, to remove oxygen; then, A step of introducing micro-nano bubbles of a gas B having a diameter of 50 nm to 500 nm, preferably 50 nm to 200 nm, into the system; A step of continuing the reaction for 1 to 6 hours, preferably 2 to 5 hours, after the temperature of the system has risen by 0.5 to 1°C and the system has become viscous, and then stopping the introduction of the micro-nano bubbles; A step of subjecting the obtained jelly to procedures such as granulation, hydrolysis or non-hydrolysis, oven drying, pulverization, sieving, etc., to obtain a polymer having a molecular weight of 300×10 4 ~3000×10 4 ; including a method for initiating free radical solution polymerization of vinyl monomers, wherein the inert gas A is at least one selected from the group consisting of nitrogen, argon, helium, neon, krypton, xenon, and combinations thereof, The gas B is at least one selected from the group consisting of nitrogen, argon, helium, neon, krypton, xenon, carbon dioxide, and combinations thereof. The vinyl monomer is at least one selected from the group consisting of an anionic monomer and its alkali metal salts and its ammonium salts, a nonionic monomer, and a cationic monomer, preferably an electron-deficient olefin, more preferably an electron-deficient olefin containing at least one group selected from the group consisting of an amide group, a carboxyl group, an ester group, a phenyl group, a sulfonic acid group, and combinations thereof. Here, a small amount of a hydrophobic monomer may be further included on the condition that the water solubility of the polymer is not affected. The anionic monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic anhydride, cinnamic acid, fumaric acid, crotonic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, propenylsulfonic acid, styrenesulfonic acid, and combinations thereof. The alkali metal salt is at least one selected from the group consisting of lithium, potassium, or sodium metal salts. The nonionic monomer contains a hydrophilic group and is preferably at least one selected from the group consisting of acrylamide, methacrylamide, N-vinylpyrrolidone, N-ethylacrylamide, N,N-dimethylacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, N-vinylacetamide, and combinations thereof. The cationic monomer is at least one selected from the group consisting of dimethylaminoethyl acrylate and its quaternary ammonium salt, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropyl acrylamide and its quaternary ammonium salt, dimethylaminopropyl methacrylamide and its quaternary ammonium salt, and combinations thereof. The hydrophobic monomer is at least one selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, vinyl acetate, vinyl propionate, and combinations thereof.

[0080] In the present invention, free radical solution polymerization of vinyl monomers is initiated via micronano bubbles. Free radicals can be generated by the micronano bubbles without external stimuli. When the micronano bubbles shrink, the charge density of the electric double layer increases rapidly. When the bubbles burst, the energy accumulated by high-concentration positive and negative ions on the interface is released due to the dramatic change of the disappearance of the gas-liquid interface. At this moment, a large amount of hydroxyl free radicals are generated by excitation, and free radical solution polymerization of vinyl monomers is initiated.

[0081] The starting method using the micronano bubbles to initiate the free radical solution polymerization of vinyl monomers of the present invention has the characteristics of simple operation, low energy consumption, easy control, convenience, and wide applicability.

[0082] The present invention has the following advantages and effects regarding the starting range and polymer properties: it is not restricted by the starting efficiency and half-life of conventional initiators and can be started at any temperature; it can avoid problems such as the source, cost, toxicity, stability of conventional initiators, and the influence of residues of conventional initiators on the properties of the polymer; it can avoid the problem of energy consumption of conventional starting methods such as light, heat, and high-energy radiation irradiation. The inventors have surprisingly found that the polymerization process of the present invention can improve the stability of the obtained polymer over time in hot water while keeping the residual monomer content low.

[0083] On the other hand, in the present invention, due to the introduction of micro-nano bubbles, a porous structure (0.1 μm - 0.5 μm) is formed in the polymer dry powder after the drying of the jelly-like solid, and a polymer having a micro-nano porous structure is obtained. Therefore, the present invention further has the following advantages: (1) The introduced micro-nano bubbles have a small diameter and are uniformly distributed in the polymerization solution. Due to the small size effect of the micro-nano bubbles, high-efficiency heat transfer is enhanced, and fluctuations in jelly characteristics due to local polymerization overheating are reduced; (2) In the drying procedure, the specific surface area is significantly increased by the micro-nano bubbles on the jelly surface, high-efficiency heat transfer is enhanced, the drying time is shortened, and energy consumption is reduced; (3) Similarly, the cooling time of the jelly granules is also shortened, and the efficiency in subsequent grinding and sieving procedures is also improved; and (4) Due to the porous structure, it quickly penetrates and swells when contacting water, and as a result, the dissolution time of the polymer is significantly shortened.

Examples

[0084] Hereinafter, the present invention will be described in detail together with specific examples. It should be noted here that the following examples are for further explaining the present invention and should not be construed as a limitation on the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention are still included in the protection scope of the present invention.

[0085] The starting materials and reagents used in the examples and comparative examples are all common commercially available starting materials: Acrylamide was purchased from Dongying Baomo Environmental Engineering Co., Ltd.; Sodium 2-acrylamido-2-methylpropanesulfonate was purchased from Weifang Jinshi Environmental Protection Technology Co., Ltd.; 2,2’-Azobis(2-methylpropionamidine) dihydrochloride was purchased from Sigma-Aldrich; N,N-Dimethylacrylamide was purchased from Beijing RBL Chemicals Co., Ltd.; All other starting materials and reagents are commercially available.

[0086] In the present invention, the following tests are carried out: (1) The solid content, viscosity average molecular weight and residual monomer content of the polymer are measured according to the methods specified in the "Oil and Gas Industry Standard SY / T5862-2020 of the People's Republic of China". (2) Dissolution rate test: This test is carried out in simulated saline with a mineralization degree of 10,000 mg / L and a temperature of 40 °C. The specific method is as follows: 1) Step of putting 300 g of simulated physiological saline into a beaker and adding 2 or 3 drops of 1% sodium indigotindisulfonate; 2) Step of weighing 0.3 g of dry polymer powder; 3) Step of slowly adding the weighed dry polymer powder at a stirring speed of 500 revolutions per minute; 4) Observe the dissolution state at regular intervals. If the color distribution of the solution is uniform, the polymer is completely dissolved. Alternatively, if there are bright spots, continue to observe until the dissolution becomes uniform and then end the experiment. including. (3) Test of viscosity retention rate over time: In simulated physiological saline with a temperature of 105°C, a mineralization degree of 10,000 mg / L, calcium ion and magnesium ion contents of 500 mg / L, and an oxygen content of less than 0.5 mg / L, after allowing a 1500 mg / L polymer solution to stand for a certain number of days, measure its viscosity (using a Brookfield viscometer, 7.34 s -1 condition, using a 0# rotor), and calculate the viscosity retention rate over time as the ratio of the viscosity after a certain time to the initial viscosity. (4) Test of filtration coefficient: According to the method specified in SY / T 5862 - 2020, use a Gelman 2220 filter membrane holder, a 600 mL Millipore filter cartridge or a similar product, and conduct the test using simulated physiological saline with a mineralization degree of 10,000 mg / L and calcium and magnesium ion contents of 500 mg / L. (5) Micro - nano bubbles are generated using an LF1500 - type micro - nano bubble generator manufactured by Shandong Micro - bubble Environmental Protection Equipment Co., LTD. The size of the generated micro - nano bubbles is measured by the dynamic light scattering method at 25°C and 173 degrees using a laser particle size distribution measuring device Zetasizer Nano ZS manufactured by Malvern Panalytical. Take the obtained Z - average value as the diameter of the bubbles, repeat the measurement 3 times, and take the average value of the 3 measurement values as the average diameter of the micro - nano bubbles. (6) The concentration of hydroxyl free radicals is measured by the methylene blue spectrophotometric method. First, prepare a methylene blue standard solution, set the measurement wavelength to 660 nm, and measure the standard working curve between the methylene blue concentration and absorbance. Next, when adding a methylene blue solution to the water containing micro - nano bubbles, the hydroxyl free radicals in the water containing micro - nano bubbles react with methylene blue, causing a change in the color of the solution. Measure the change in absorbance and calculate the concentration of hydroxyl free radicals in the solution according to the standard curve of the methylene blue solution. After subjecting the surface of the porous polymer powder to gold plating treatment, the surface morphology of the porous polymer powder is observed using a scanning electron microscope (SEM) S-4800 (Hitachi, Japan). Using Photoshop software, 200 pores are randomly selected, their diameters are measured, and the average value is taken as the average pore diameter. The pore volume is measured using a model AutoPore IV 9500 fully automatic mercury porosimeter in accordance with the test method "Measurement of mercury porosimetry and pore size distribution and porosity of solid materials by gas adsorption method - Part 1: Measurement of mercury porosimetry" (GB / T 21650.1-2-2008).

[0087] Example 1 40 g of acrylamide, 5 g of sodium acrylate, and 5 g of sodium 2-acrylamido-2-methylpropanesulfonate were dissolved in 250 g of deionized water, the pH was adjusted to 4.0, the initial temperature was controlled at 5°C, nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen, and then nitrogen nanobubbles with an average diameter of 50 nm were introduced into the system (the inlet pressure was controlled at 0.8 MPa and the gas input amount was controlled at 10 mL / min). The volume of the system was increased by 1.0%, and when the hydroxyl free radical concentration was measured, it was 0.23 μmol / L. After the temperature of the system was raised by 0.5°C, the introduction of nanobubbles was stopped, but the reaction was continued for another 5 hours. After polymerization was completed, the obtained jelly-like solid was granulated, dried at 50°C until the solid content reached 89%, pulverized, and sieved to obtain a polymer of 20 to 80 mesh.

[0088] When the viscosity average molecular weight of the polymer was measured, it was 2320×10 4 It was as follows.

[0089] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105°C, pore volume, and average pore diameter of the dry powder sample of this polymer were measured to obtain the data in Table 1.

[0090] Example 2 Dissolve 50 g of acrylamide, 5 g of methacrylamide, and 3 g of sodium crotonate in 242 g of deionized water, adjust the pH to 6, control the initial temperature at 10 °C, pass nitrogen with a diameter of 1 mm to 10 mm through the system for 20 minutes to remove oxygen, and then introduce argon nanobubbles with an average diameter of 80 nm into the system (control the inlet pressure at 0.7 MPa and the gas input rate at 20 mL / min). Increase the volume of the system by 1.2% and measure the hydroxyl free radical concentration, which was found to be 0.25 μmol / L. After raising the temperature of the system by 1 °C, stop the introduction of nanobubbles, but continue the reaction for another 2 hours. After polymerization is completed, granulate the obtained jelly-like solid, dry it at 50 °C until the solid content reaches 89%, perform pulverization and sieving to obtain a polymer with a mesh size of 20 to 80.

[0091] The viscosity average molecular weight of the polymer was measured to be 1550×10 4 It was.

[0092] Measure the dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105 °C, pore volume, and average pore diameter of the dry powder sample of this polymer to obtain the data in Table 1.

[0093] Example 3 Dissolve 60 g of acrylamide, 13 g of N,N-dimethylacrylamide, 15 g of sodium 2-acrylamido-2-methylpropanesulfonate, and 2 g of methyl acrylate in 210 g of deionized water, adjust the pH to 5.0, control the initial temperature at 20 °C, pass nitrogen with a diameter of 1 mm to 10 mm through the system for 40 minutes to remove oxygen, and then introduce helium nanobubbles with an average diameter of 150 nm into the system (control the inlet pressure at 0.5 MPa and the gas input rate at 30 mL / min). Increase the volume of the system by 1.5% and measure the hydroxyl free radical concentration, which was found to be 0.21 μmol / L. After raising the temperature of the system by 0.8 °C, stop the introduction of nanobubbles, but continue the reaction for another 4 hours. After polymerization is completed, granulate the obtained jelly-like solid, dry it at 50 °C until the solid content reaches 89%, perform pulverization and sieving to obtain a polymer with a mesh size of 20 to 80.

[0094] The viscosity-average molecular weight of the polymer was measured to be 1010×10 4 .

[0095] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105°C, pore volume, and average pore diameter of the dry powder sample of this polymer were measured, and the data in Table 1 were obtained.

[0096] Example 4 60 g of acrylamide and 5 g of methacryloyloxyethyltrimethylammonium chloride were dissolved in 235 g of deionized water, the pH was adjusted to 6, the initial temperature was controlled at 20°C, nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen, and then nitrogen nanobubbles with an average diameter of 200 nm were introduced into the system (the inlet pressure was controlled at 0.3 MPa, and the gas input rate was controlled at 20 mL / min). The volume of the system was increased by 2.6%, and the hydroxyl free radical concentration was measured to be 0.18 μmol / L. After the temperature of the system was raised by 0.5°C, the introduction of micronano bubbles was stopped, but the reaction was continued for another 3 hours. After the polymerization was completed, the obtained jelly-like solid was granulated, dried at 50°C until the solid content reached 89%, pulverized and sieved to obtain a polymer of 20 - 80 mesh.

[0097] The viscosity-average molecular weight of the polymer was measured to be 510×10 4 .

[0098] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105°C, pore volume, and average pore diameter of the dry powder sample of this polymer were measured, and the data in Table 1 were obtained.

[0099] Example 5 82 g of acrylamide, 8 g of N-vinylpyrrolidone, and 4 g of maleic anhydride were dissolved in 200 g of deionized water. The pH was adjusted to 6.0, and the initial temperature was controlled at 25°C. Nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen, and then carbon dioxide micro-nanobubbles with an average diameter of 100 nm were introduced into the system (the inlet pressure was controlled at 0.5 MPa, and the gas input rate was controlled at 15 mL / min). The volume of the system was increased by 1.7%, and the hydroxyl free radical concentration was measured to be 0.19 μmol / L. After the temperature of the system was raised by 0.8°C to initiate polymerization, the introduction of micro-nanobubbles was stopped, but the reaction was continued for another 3 hours. After polymerization was completed, the jelly-like solid was taken out, granulated, 9.24 g of sodium hydroxide was added and mixed uniformly, a hydrolysis reaction was carried out at 80°C for 3 hours, and it was dried at 50°C until the solid content reached 89%, followed by grinding and sieving to obtain a polymer with a mesh size of 20 to 80.

[0100] The viscosity average molecular weight of the polymer was measured to be 1200×10 4 .

[0101] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105°C, pore volume, and average pore diameter of the dry powder sample of this polymer were measured to obtain the data in Table 1.

[0102] Example 6 50 g of acrylamide and 5 g of sodium acrylate were dissolved in 245 g of deionized water. The pH was adjusted to 6, and the initial temperature was controlled at 10°C. Nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen, and then argon nanobubbles with an average diameter of 80 nm were introduced into the system (the inlet pressure was controlled at 0.7 MPa, and the gas input rate was controlled at 20 mL / min). The volume of the system was increased by 1.4%, and the hydroxyl free radical concentration was measured to be 0.26 μmol / L. After the temperature of the system was raised by 1°C, the introduction of nanobubbles was stopped, but the reaction was continued for another 2 hours. After polymerization was completed, the obtained jelly-like solid was granulated and dried at 50°C until the solid content reached 89%, followed by grinding and sieving to obtain a polymer with a mesh size of 20 to 80.

[0103] The viscosity-average molecular weight of the polymer was measured and found to be 2180×10 4 .

[0104] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105°C, pore volume, and average pore diameter of the dry powder sample of this polymer were measured, and the data in Table 1 were obtained.

[0105] Example 7 (1) 45 g of acrylamide and 15 g of sodium 2-acrylamido-2-methylpropanesulfonate were dissolved in 70 g of deionized water, and nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen, obtaining an oxygen-removed monomer solution with a monomer concentration of 46.2%.

[0106] (2) 1 L of deionized water was added to a beaker, and nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen. Then, nitrogen nanobubbles with an average diameter of 80 nm were introduced into the system (the inlet pressure was controlled at 0.7 MPa, and the gas input rate was controlled at 20 mL / min), and circulated for 20 minutes to obtain oxygen-removed water containing micronano bubbles. The volume of the system was increased by 1.36%, and the concentration of hydroxyl free radicals was measured and found to be 0.24 μmol / L.

[0107] (3) 170 g of the oxygen-removed water containing micronano bubbles in (2) was taken out, mixed with the high-concentration oxygen-removed monomer solution in (1), stirred uniformly, the pH was adjusted to 6.0, the mixture was put into a polymerization reactor, the initial temperature was controlled at 8°C, and a polymerization reaction was carried out for another 5 hours. After the polymerization was completed, the obtained jelly-like solid was granulated, dried at 50°C until the solid content reached 89%, pulverized and sieved to obtain a polymer of 20 to 80 mesh.

[0108] The viscosity-average molecular weight of the polymer was measured and found to be 1950×10 4 .

[0109] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105 °C, pore volume, and average pore diameter of the polymer dry powder sample were measured to obtain the data in Table 1.

[0110] Example 8 (1) 40 g of acrylamide, 1.5 g of N-vinylpyrrolidone, and 9 g of sodium 2-acrylamido-2-methylpropanesulfonate were dissolved in 85 g of deionized water, and nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen.

[0111] (2) 1 L of deionized water was added to a beaker, and nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen. Then, nitrogen nanobubbles with an average diameter of 150 nm were introduced into the system (the inlet pressure was controlled at 0.5 MPa, and the gas input rate was controlled at 30 mL / min) and circulated for 15 minutes to obtain oxygen-removed water containing micro-nanobubbles. The volume of the system was increased by 1.6%, and the concentration of hydroxyl free radicals was measured to be 0.22 μmol / L.

[0112] (3) 164.5 g of the oxygen-removed water containing micro-nanobubbles obtained in (2) was taken out, mixed with the high-concentration oxygen-removed monomer solution obtained in (1), stirred uniformly, put into a polymerization reactor, the pH was adjusted to 6.0, the initial temperature was controlled at 5 °C, and a polymerization reaction was carried out for 5 hours. After the polymerization was completed, the obtained jelly-like solid was granulated, dried at 50 °C until the solid content reached 89%, pulverized and sieved to obtain a polymer with a mesh size of 20 to 80.

[0113] The viscosity average molecular weight of the polymer was measured to be 1790×10 4 It was.

[0114] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105 °C, pore volume, and average pore diameter of the polymer dry powder sample were measured to obtain the data in Table 1.

[0115] Example 9 The permeability is 600×10 -3 μm 2A selected rock core was vacuum-treated for at least 2 hours and saturated with simulated salt water (mineralization degree 10,000 mg / L, calcium ion and magnesium ion content 500 mg / L). Using crude oil with a viscosity of 30 mPa·s, the rock core was saturated at 105°C. Using simulated salt water, water-driving was performed at a displacement rate of 0.005 mL / min until the water content at the outlet of the rock core model reached at least 98%. The water-driving recovery rate was 31.2%. After excluding the waste liquid and dead volume, a 2000 mg / L aqueous solution of the polymer of Example 7 was injected at 2 PV, and displacement was performed at a rate of 0.005 mL / min. Next, the waste liquid and dead volume were excluded, and water-driving was performed at 0.005 mL / min until the water content reached at least 98%. The recovery rate after polymer injection was 50.5%, and the oil displacement efficiency increased by 19.3%.

[0116] Comparative Example 1 40 g of acrylamide, 5 g of sodium acrylate, and 5 g of sodium 2-acrylamido-2-methylpropanesulfonate were dissolved in 250 g of deionized water, and the pH was adjusted to 4.0. The initial temperature was controlled at 5°C, and nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen. Next, 2.5 g of an aqueous ammonium persulfate solution with a mass concentration of 0.2% and 3.0 g of an aqueous sodium bisulfite solution with a mass concentration of 0.3% were added. After raising the temperature of the system by 0.5°C, the nitrogen injection was stopped, and the reaction was continued for another 6 hours. After the polymerization was completed, the obtained jelly-like solid was granulated and dried at 50°C until the solid content reached 89%. Crushing and sieving were performed to obtain a polymer of 20 to 80 mesh.

[0117] When the viscosity average molecular weight of the polymer was measured, it was 2050×10 4 as follows.

[0118] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over time at 105°C for 30 days, pore volume, and average pore diameter of the polymer dry powder sample were measured to obtain the data in Table 1.

[0119] Comparative Example 2 50 g of acrylamide, 5 g of methacrylamide, and 3 g of sodium crotonate were dissolved in 242 g of deionized water, and the pH was adjusted to 6. The initial temperature was controlled at 10 °C, and nitrogen with a diameter of 1 mm to 10 mm was passed through the system for 20 minutes to remove oxygen. Next, 1.0 g of an aqueous solution of 2,2'-azobis(2-methylpropionamidine) dihydrochloride with a mass concentration of 0.25%, 1.3 g of an aqueous solution of sodium persulfate with a mass concentration of 0.2%, and 3.0 g of an aqueous solution of potassium bisulfite with a mass concentration of 0.3% were added. After raising the temperature of the system by 0.5 °C, the nitrogen blowing was stopped, and the reaction was continued for another 4 hours. After the polymerization was completed, the obtained jelly-like solid was granulated and dried at 60 °C until the solid content reached 89%. Grinding and sieving were performed to obtain a polymer of 20 to 80 mesh.

[0120] When the viscosity-average molecular weight of the polymer was measured, it was 1480×10 4 It was.

[0121] The dissolution time, filtration coefficient, residual monomer content, viscosity retention rate over 30 days at 105 °C, pore volume, and average pore diameter of the polymer dry powder sample were measured to obtain the data in Table 1.

[0122]

Table 1

[0123] From Examples 1 to 8, it can be seen that by introducing micro-nano bubbles with a gas bubble diameter of 50 nm to 200 nm into the polymerization system, all free radical polymerizations in the system can be initiated. The viscosity-average molecular weight of the prepared polymer is 520×10 4 ~2320×10 4Moreover, the content of the residual monomer can be controlled to the same level as that obtained by polymerization initiated by an initiator. This indicates that a large amount of hydroxyl free radicals are generated after the cavitation of micro-nano bubbles in the system, and these hydroxyl free radicals can initiate the free radical solution polymerization of vinyl monomers to obtain polymers. On the other hand, the viscosity retention rate over time at 105 °C of the polymers obtained in Examples 1 to 8 is significantly higher than that of the comparative examples over time. From this, it is demonstrated that in the initiation using micro-nano bubbles, since no conventional initiator is introduced, free radical decomposition caused by the residues of the initiator can be avoided.

[0124] Comparing Example 1 with Comparative Example 1 and Example 2 with Comparative Example 2, it can be seen that in both Example 1 and Example 2, polymers with the same molecular weight as those in Comparative Example 1 and Comparative Example 2 can be obtained, indicating that micro-nano bubble initiation can replace the conventional initiator and achieve the same polymerization effect as the conventional initiator. In addition, the polymers obtained in Example 1 and Example 2 form a porous structure due to the introduction of micro-nano bubbles, so the drying time and dissolution time are significantly shorter than those in Comparative Example 1 and Comparative Example 2, and the pore volume is significantly larger than that in Comparative Examples 1 to 2.

[0125] From the data of Examples 1 to 8, it can be seen that by introducing micro-nano bubbles into the system, a good polymerization effect can be obtained, and the conventional initiator for polymerization initiation can be replaced. Problems such as the source, cost, toxicity, and stability of conventional polymerization initiators, as well as the influence of conventional initiators on the properties of polymers, can be avoided, and problems such as the energy consumption of conventional initiation methods such as light, heat, and radiation can also be avoided. The free radical solution polymerization initiation method has the characteristics of simple operation, low energy consumption, easy control, convenience, and wide applicability.

[0126] As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, many simple modifications can be made to the technical solution of the present invention, and combinations of various technical features in any other appropriate manner are included. These simple modifications and combinations should also be regarded as the disclosure of the present invention, and all of them are included in the protection scope of the present invention.

[0127] The endpoints and any values disclosed in this specification are not limited to the exact ranges or values, and these ranges or values are understood to include values close to the relevant ranges or values. For numerical ranges, various endpoint values of different ranges, various endpoint values of different ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, and these new numerical ranges are regarded as specifically disclosed in this specification.

[0128] The reference to "one embodiment" or "some embodiments" in this specification means that the features, structures or characteristics described in connection with the embodiment are included in at least one embodiment. These features, structures or characteristics can be combined in any appropriate manner in one or more embodiments.

Claims

1. A free radical solution polymerization process, wherein the process comprises: introducing micro-nano bubbles of gas B into an aqueous solution of a vinyl monomer, and initiating the free radical solution polymerization of the vinyl monomer with free radicals generated after cavitation of the micro-nano bubbles to prepare a polymer. A free radical solution polymerization process, characterized by comprising the above.

2. The free radical solution polymerization process according to claim 1, characterized in that, before introducing the micro-nano bubbles of gas B, an inert gas A is passed through the aqueous solution of the vinyl monomer to remove oxygen.

3. The inert gas A is at least one selected from the group consisting of nitrogen, argon, helium, neon, krypton, xenon, and any combination thereof; and / or The diameter of the bubbles of the inert gas A is 1 mm to 10 mm, and the passing time is 5 minutes to 60 minutes, preferably 20 minutes to 40 minutes. The free radical solution polymerization process according to claim 2, characterized by the above.

4. The free radical solution polymerization process according to any one of claims 1 to 3, characterized in that the polymer is obtained in the form of a bubble-containing jelly.

5. The process further comprises treating the polymer in the form of a bubble-containing jelly to obtain a polymer having a micro-nano porous structure. Preferably, the treatment of the polymer in the form of a bubble-containing jelly includes granulating the obtained bubble-containing jelly, optionally hydrolyzing, drying, pulverizing, and optionally sieving. The free radical solution polymerization process according to claim 4.

6. The weight concentration of the aqueous solution of the vinyl monomer is 10% to 55%, preferably 15% to 35%; and / or The gas B is at least one selected from the group consisting of nitrogen, argon, helium, neon, krypton, xenon, carbon dioxide, and combinations thereof; and / or The vinyl monomer is at least one selected from the group consisting of an anionic monomer and its alkali metal salts, its alkaline earth metal salts, and its ammonium salts, a nonionic monomer, a cationic monomer, and combinations thereof; the vinyl monomer is preferably an electron-deficient olefin, more preferably an electron-deficient olefin containing at least one group selected from the group consisting of an amide group, a carboxyl group, an ester group, a phenyl group, a sulfonic acid group, and combinations thereof. The free radical solution polymerization process according to any one of claims 1 to 5, characterized in that

7. The anionic monomer contains at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, cinnamic acid, (E)-butenedioic acid, crotonic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acrylamidopropanesulfonic acid, 2-methacrylamidopropanesulfonic acid, vinylsulfonic acid, propenylsulfonic acid, styrenesulfonic acid, and combinations thereof; and / or The alkali metal salt is a lithium salt, a potassium salt or a sodium salt, and the alkaline earth metal salt is a magnesium salt, a calcium salt, a strontium salt or a barium salt; and / or The nonionic monomer contains a hydrophilic group. Preferably, the nonionic monomer is at least one selected from the group consisting of acrylamide, methacrylamide, N-vinylpyrrolidone, N-ethylacrylamide, N-ethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and N,N-diisopropylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide, and N,N-diisopropylmethacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, N-vinylacetamide, N-[(4-aminosulfonyl)phenyl]acrylamide, and combinations thereof; and / or The free radical solution polymerization process according to claim 5, wherein the cationic monomer comprises at least one selected from the group consisting of dimethylaminoethyl acrylate and its quaternary ammonium salt, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropyl acrylate and its quaternary ammonium salt, dimethylaminopropyl methacrylate and its quaternary ammonium salt, dimethylaminopropylacrylamide and its quaternary ammonium salt, dimethylaminopropylmethacrylamide and its quaternary ammonium salt, and combinations thereof.

8. The vinyl monomer further contains a hydrophobic monomer, wherein the total weight of the hydrophobic monomer is 10% or less of the total weight of the vinyl monomer; Preferably, the hydrophobic monomer includes at least one selected from the group consisting of N-hexylacrylamide, N-octylacrylamide, N-nonylacrylamide, N-dodecylacrylamide, N-tetradecylacrylamide, N-hexadecylacrylamide, N-octadecylacrylamide, N,N-dibutylacrylamide, N,N-dihexylacrylamide, N,N-dioctylacrylamide, N,N-didecylacrylamide, N,N-di(dodecyl)acrylamide, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, propyl acrylate, propyl methacrylate, vinyl acetate, vinyl propionate, and combinations thereof. The free radical solution polymerization process according to claim 6 or 7 is characterized by this.

9. The average diameter of the micro-nanobubbles of the gas B is 20 nm to 1 μm, preferably 20 nm to 900 nm, more preferably 30 nm to 500 nm, more preferably 40 nm to 400 nm, and even more preferably 50 nm to 200 nm. The free radical solution polymerization process according to any one of claims 1 to 8 is characterized by this.

10. The pH of the aqueous solution of the vinyl monomer is 4 to 9, preferably 4 to 6; and / or The initial polymerization reaction temperature is -10°C to 40°C, preferably 0 to 25°C; and / or The introduction of the micro-nanobubbles is stopped after the temperature of the system is raised by 0.5°C to 1°C, and the reaction is continued for 1 to 6 hours, preferably 2 to 5 hours. The free radical solution polymerization process according to any one of claims 1 to 9 is characterized by this.

11. The introduction of the micro-nanobubbles of the gas B includes directly introducing the micro-nanobubbles of the gas B into the aqueous solution of the vinyl monomer. Or The introduction of the micro-nano bubbles of the gas B includes introducing the micro-nano bubbles of the gas B into oxygen-removed water to obtain oxygen-removed water containing the micro-nano bubbles, and mixing the oxygen-removed water containing the micro-nano bubbles with an oxygen-removed aqueous solution of a vinyl monomer. The free radical solution polymerization process according to any one of claims 1 to 10 is characterized by this.

12. The free radical for initiating the free radical solution polymerization of the vinyl monomer is generated only by the cavitation of the micro-nano bubbles, and / or the initiator content in the polymer is zero. The free radical solution polymerization process according to any one of claims 1 to 11 is characterized by this.

13. The polymer having the micro-nano porous structure has pores with a diameter of 0.05 μm to 2 μm, more preferably 0.1 μm to 1 μm, and even more preferably 0.1 μm to 0.5 μm, and has a pore volume of 0.080 to 1 cm ３ / g, preferably 0.090 to 0.80 cm ３ / g, and even more preferably 0.090 to 0.50 cm ３ / g. The free radical solution polymerization process according to claim 5 is characterized by this.

14. The polymer has at least one, preferably all of the following characteristics: water solubility with a dissolution time of less than 30 minutes; a viscosity average molecular weight of 300×10 ４ to 3000×10 ４ ; a residual monomer content of less than 0.1% by weight; and a viscosity retention rate over time (105 °C) of more than 90%. The free radical solution polymerization process according to any one of claims 1 to 13 is characterized by this.

15. A polymer prepared by the free radical solution polymerization process according to any one of claims 1 to 14.

16. An acrylamide-based polymer having a micro-nanoporous structure, wherein the polymer has pores with a diameter of 0.05 μm to 2 μm, more preferably 0.1 μm to 1 μm, even more preferably 0.1 μm to 0.5 μm, and has a pore volume of 0.080 to 1 cm ３ / g, preferably 0.090 to 0.80 cm ３ / g, even more preferably 0.090 to 0.50 cm ３ / g, and the initiator content in the polymer is zero, an acrylamide-based polymer having a micro-nanoporous structure.

17. The polymer has the following properties: water solubility with a dissolution time of less than 30 minutes; a viscosity average molecular weight of 300×10 ４ to 3000×10 ４ ; a residual monomer content of less than 0.1% by weight; and a viscosity retention rate over time (105°C) of more than 90%. The acrylamide-based polymer having a micro-nanoporous structure according to claim 16, characterized by having at least one, preferably all of the above properties.

18. The polymer contains an acrylamide monomer and optionally one or more additional vinyl monomers. Preferably, the vinyl monomer is selected from the group consisting of anionic monomers and their alkali metal salts, alkaline earth metal salts, and ammonium salts, non-ionic monomers, cationic monomers, and combinations thereof; the vinyl monomer is preferably an electron-deficient olefin, more preferably an electron-deficient olefin containing at least one group selected from the group consisting of an amide group, a carboxyl group, an ester group, a phenyl group, a sulfonic acid group, and combinations thereof. The polymer according to claim 16 or 17.

19. The anionic monomer contains at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, cinnamic acid, (E)-butenedioic acid, crotonic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acrylamido-propanesulfonic acid, 2-methacrylamido-propanesulfonic acid, vinylsulfonic acid, propenylsulfonic acid, styrenesulfonic acid, and combinations thereof; and / or The alkali metal salt is a lithium salt, a potassium salt or a sodium salt, and the alkaline earth metal salt is a magnesium salt, a calcium salt, a strontium salt or a barium salt; and / or The nonionic monomer contains a hydrophilic group, and preferably, the nonionic monomer is selected from the group consisting of acrylamide, methacrylamide, N-vinylpyrrolidone, N-ethylacrylamide, N-ethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide and N,N-diisopropylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide and N,N-diisopropylmethacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, N-vinylacetamide, N-[(4-aminosulfonyl)phenyl]acrylamide, and combinations thereof; and / or The cationic monomer includes at least one selected from the group consisting of dimethylaminoethyl acrylate and its quaternary ammonium salt, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropyl acrylate and its quaternary ammonium salt, dimethylaminopropyl methacrylate and its quaternary ammonium salt, dimethylaminopropyl acrylamide and its quaternary ammonium salt, dimethylaminopropyl methacrylamide and its quaternary ammonium salt, and combinations thereof; Optionally, the vinyl monomer further includes a hydrophobic monomer, where the total weight of the hydrophobic monomer is 10% or less of the total weight of the vinyl monomer; The hydrophobic monomer includes at least one selected from the group consisting of N-hexylacrylamide, N-octylacrylamide, N-nonylacrylamide, N-dodecylacrylamide, N-tetradecylacrylamide, N-hexadecylacrylamide, N-octadecylacrylamide, N,N-dibutylacrylamide, N,N-dihexylacrylamide, N,N-dioctylacrylamide, N,N-didecylacrylamide, N,N-di(dodecyl)acrylamide, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, vinyl acetate, vinyl propionate, and combinations thereof, The polymer according to claim 18, characterized in that.

20. Use of the polymer according to claim 15 or the polymer according to any one of claims 16 to 19 in oil layer recovery, preferably high-temperature and high-salinity oil layer polymer flooding, offshore oil layer polymer flooding, heavy oil layer polymer flooding, and fracturing.

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