A method of initiating radical solution polymerization, polymers and applications

Abstract

The application provides a radical solution polymerization initiation method, a polymer and an application. The initiation method comprises the following steps: introducing inert gas A into an aqueally allyl monomer solution to remove oxygen, then introducing micro-nano bubbles of gas B, the micro-nano bubbles can initiate the radical solution polymerization of the allyl monomer after cavitation, and the polymer is obtained after treatment of the obtained colloid. The application initiates the radical solution polymerization of the allyl monomer through the micro-nano bubbles, the micro-nano bubbles can generate free radicals without external stimulation, the operation is simple, the energy consumption is low, and the application has the characteristics of convenience, controllability and wide application range.

Description

Technical Field

[0001] This invention relates to the field of free radical solution polymerization technology, and more specifically, to a method for initiating free radical solution polymerization, a polymer, and its applications. Background Technology

[0002] Free radical polymerization is an effective method for the large-scale production of various olefin polymers; approximately 60% of olefin polymers are produced through free radical polymerization. The advantages of free radicals include high polymerization and copolymerization activity with a variety of olefin monomers, mild polymerization conditions, the ability to contain small amounts of impurities in the polymerization system, and even the use of inexpensive and environmentally friendly water as the reaction medium. A crucial step in free radical polymerization is chain initiation, with the formation of primary free radicals in the first step being the most critical. Common methods for generating free radicals within the reaction system include using light, heat, radiation, or the addition of initiators.

[0003] Existing technologies for initiating polymerization include photoinitiation, thermal initiation, radiation initiation, and redox initiation. It can be a single method or a combination of several, using initiators such as azo initiators, redox initiators, and photoinitiators. However, all of these initiation methods suffer from drawbacks such as complex operation or high energy consumption. Furthermore, traditional initiators are limited by initiation efficiency and half-life, preventing initiation at arbitrary temperatures. The sources of traditional initiators are also limited, their costs are high, they are often toxic, and their stability is insufficient. Additionally, photo, thermal, and radiation initiation methods suffer from energy consumption issues.

[0004] Therefore, it is necessary to study an initiation method for free radical solution polymerization that is simple to operate, consumes less energy, is convenient and controllable, and has a wide range of applications. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the present invention provides a method for initiating free radical solution polymerization, a polymer, and its applications.

[0006] This invention selects a suitable gas source to generate bubbles with a diameter of micro-nano scale, and introduces them into an alkenyl monomer free radical solution polymerization system. After the micro-nano bubbles cavitate in the system, they generate a large number of hydroxyl radicals, which are used to initiate the alkenyl monomer free radical solution polymerization.

[0007] Micro- and nano-bubbles typically refer to bubbles with a diameter of less than 50 μm. Microbubbles with a diameter greater than 1 μm are called microbubbles, while ultramicrobubbles with a diameter less than 1 μm but greater than 1 nm are further called nanobubbles. Compared to traditional large bubbles (coarse bubbles, diameter > 50 mm) and small bubbles (fine bubbles, diameter < 5 mm), micro- and nano-bubbles have smaller diameters and a more significant small-size effect, resulting in significantly different mass and heat transfer characteristics and interfacial properties. Due to their small size, micro- and nano-bubbles experience far less buoyancy in water than ordinary bubbles, allowing them to remain submerged for minutes or even hours. The formation, growth, and collapse of micro- and nano-bubbles in solution is called cavitation. During cavitation, as micro- and nano-bubbles contract, the charge density of the electric double layer increases rapidly. When the bubble collapses, the drastic change of the disappearance of the gas-liquid interface releases the energy stored in the high concentration of positive and negative ions at the interface, which can then generate a large number of hydroxyl radicals.

[0008] Therefore, by combining the "cavitation" effect of micro and nano bubbles in solution, it can be introduced into the initiation method of free radical solution polymerization. Free radicals can be generated without external stimulation to initiate the free radical solution polymerization of alkenyl monomers, which can simplify free radical solution polymerization and reduce energy consumption.

[0009] This invention introduces micro-nano bubbles that can generate free radicals without external stimulation, initiating free radical solution polymerization of alkenyl monomers. The operation is simple and energy consumption is low. Using micro-nano bubbles as an initiation method for free radical solution polymerization of alkenyl monomers is convenient, controllable, and has a wide range of applications.

[0010] One objective of this invention is to provide a method for initiating free radical solution polymerization, comprising:

[0011] Inert gas A is introduced into an aqueous solution of alkenyl monomers to remove oxygen, followed by the introduction of micro- and nano-bubbles of gas B. The cavitation of the micro- and nano-bubbles triggers free radical solution polymerization of the alkenyl monomers. The resulting colloid is then treated to obtain the polymer.

[0012] In a preferred embodiment of the present invention,

[0013] The mass concentration of the alkenyl monomer aqueous solution is 10% to 50%; preferably 15% to 35%.

[0014] The inert gas A is at least one of nitrogen, argon, and helium;

[0015] The gas B is at least one of nitrogen, argon, helium, and carbon dioxide;

[0016] Inert gas A and gas B can be the same or different; inert gas A and gas B can be one of the above gases or a mixture of the above gases.

[0017] The alkenyl monomer is at least one of anionic monomers and their alkali metal or ammonium salts, nonionic monomers, and cationic monomers; such as two, three, or more.

[0018] In a preferred embodiment of the present invention,

[0019] The anionic monomer is at least one selected from acrylic acid, methacrylic acid, maleic anhydride, cinnamic acid, fumaric acid, crotonic acid, aconitic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, propane sulfonic acid, and styrene sulfonic acid; and / or,

[0020] The alkali metal salt is a lithium, potassium, or sodium metal salt; and / or,

[0021] The nonionic monomer contains a hydrophilic group; preferably at least one of acrylamide, methacrylamide, N-vinylpyrrolidone, N-substituted acrylamide, N,N-dimethylacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxy polyethylene glycol methacrylate, methoxy polyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, and N-vinylacetamide; and / or,

[0022] The cationic monomer is at least one of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide and its quaternary ammonium salt, and diallyl dimethylammonium chloride.

[0023] In a preferred embodiment of the present invention,

[0024] The alkenyl monomer also includes at least one of acrylate and hydrophobic monomer; the acrylate and hydrophobic monomer are used in small amounts without affecting the water solubility of the polymer, and the total mass of the acrylate and hydrophobic monomer does not exceed 10% of the total mass of the alkenyl monomer.

[0025] The acrylate is at least one of methacrylate, ethyl methacrylate, and butyl methacrylate; the hydrophobic monomer is at least one of vinyl acetate and vinyl propionate.

[0026] In a preferred embodiment of the present invention,

[0027] The average diameter of the gas B micro-nano bubbles is 50 nanometers to 500 nanometers; preferably 50 nanometers to 200 nanometers.

[0028] When micro- and nanobubbles have an average diameter of 50 to 500 nanometers, cavitation begins when they are introduced into an aqueous solution of alkenyl monomers. The formation, growth, and collapse of micro- and nanobubbles in the alkenyl monomer aqueous solution is called "cavitation." This is because micro- and nanobubbles are small in size and experience far less buoyancy in water than ordinary bubbles, allowing them to remain in water for several minutes or even hours. During cavitation, as the micro- and nanobubbles contract, the charge density of the double layer increases rapidly. When the bubbles burst, the drastic change of the disappearance of the gas-liquid interface releases the energy stored in the high concentration of positive and negative ions at the interface. This can stimulate the generation of a large number of hydroxyl radicals, thereby initiating the free radical solution polymerization of alkenyl monomers.

[0029] Preferably, the present invention uses the LF1500 micro-nano bubble generator produced by Shandong Microbubble Environmental Protection Equipment Co., Ltd. to introduce micro-nano bubbles. The diameter of the bubbles is controlled by a rotor flow meter, pressure and generator. When the air intake 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 to be 50 nanometers to 20 micrometers.

[0030] In a preferred embodiment of the present invention,

[0031] The pH value of the aqueous solution of the alkenyl monomer is 4-9; preferably 4-6.

[0032] The initial reaction temperature is -10℃ to 40℃; preferably 0℃ to 25℃.

[0033] Polymerization is an exothermic reaction and takes place in an adiabatic reactor;

[0034] The diameter of the inert gas A bubble is 1 mm to 10 mm; the introduction time is 5 min to 60 min; preferably 20 min to 40 min;

[0035] The purpose of introducing inert gas A is to remove oxygen. A regular nitrogen cylinder is used with a pressure reducing valve equipped with a flow meter. The flow rate of the pressure reducing valve is controlled at 2 to 20 L / min, preferably 5 to 15 L / min, which can provide inert gas A with a bubble diameter of 1 mm to 10 mm.

[0036] The colloid processing method involves granulating, hydrolyzing or not hydrolyzing, drying, pulverizing, and sieving the obtained colloid.

[0037] The colloids of different types of polymers obtained can be granulated and then hydrolyzed or dried directly without hydrolysis, depending on the requirements. For polymers that need to be hydrolyzed, after granulation, alkali is added and reacted at a certain temperature for a period of time to prepare polymers with a certain degree of hydrolysis. For non-hydrolyzed polymers, hydrolysis is not required and they are directly dried after granulation.

[0038] In a preferred embodiment of the present invention,

[0039] After the system temperature rises by 0.5℃ to 1℃, the introduction of micro-nano bubbles is stopped, and the reaction continues for 1 hour to 6 hours; preferably 2 hours to 5 hours.

[0040] A second objective of this invention is to provide a polymer obtained by a free radical solution polymerization initiation method.

[0041] The third objective of this invention is to provide an application of the polymer obtained by this invention in oil reservoir development, preferably in polymer flooding of high-temperature and high-salinity oil reservoirs, polymer flooding of offshore oil reservoirs, water flooding of heavy oil reservoirs, and fracturing; it can be used as a thickener for polymer flooding of high-temperature and high-salinity oil reservoirs, polymer flooding of offshore oil reservoirs, and water flooding of heavy oil reservoirs, or as a thickener and drag reducer for fracturing.

[0042] The present invention can specifically adopt the following technical solutions:

[0043] An initiation method for free radical solution polymerization of alkenyl monomers, comprising the following steps:

[0044] One or more alkenyl monomers are weighed and prepared into an aqueous solution with a molar concentration of 10% to 50%, preferably 15% to 35%. The pH of the aqueous solution is adjusted to 4 to 9, preferably 4 to 6. The system temperature is controlled at -10℃ to 40℃, preferably 0 to 25℃. Ordinary inert gas A with a diameter of 1 mm to 10 mm is introduced into the system for 5 min to 60 min, preferably 20 min to 40 min, to remove oxygen. Then, micro-nano bubbles with a diameter of 50 nm to 500 nm, preferably 50 nm to 200 nm, are introduced into the system. The system temperature is increased by 0.5℃ to 1℃. After the system becomes viscous, the introduction of micro-nano bubbles is stopped, and the reaction continues for 1 to 6 hours, preferably 2 hours to 5 hours. The obtained colloid is subjected to granulation, hydrolysis or non-hydrolysis, drying, pulverization, sieving and other processes to obtain a polymer with a molecular weight of 3 million to 30 million.

[0045] Inert gas A is at least one of nitrogen, argon, and helium;

[0046] Gas B is at least one of nitrogen, argon, helium, and carbon dioxide;

[0047] The alkenyl monomer is at least one of anionic monomers and their alkali metal or ammonium salts, nonionic monomers, and cationic monomers; it may also include at least one of acrylates and hydrophobic monomers without affecting the water solubility of the polymer.

[0048] The anionic monomer is at least one of acrylic acid, methacrylic acid, maleic anhydride, cinnamic acid, fumaric acid, crotonic acid, aconitic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, propane sulfonic acid, and styrene sulfonic acid.

[0049] The alkali metal salt is at least one of lithium, potassium or sodium metal salts;

[0050] The nonionic monomer contains a hydrophilic group; preferably at least one of acrylamide, methacrylamide, N-vinylpyrrolidone, N-substituted acrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxy polyethylene glycol methacrylate, methoxy polyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, and N-vinylacetamide.

[0051] The cationic monomer is at least one of dimethylaminoethyl acrylate and its quaternary ammonium salt, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropylacrylamide and its quaternary ammonium salt, dimethylaminopropylmethacrylamide and its quaternary ammonium salt, and diallyl dimethylammonium chloride.

[0052] The acrylate is at least one of methacrylate, ethyl methacrylate, and butyl methacrylate;

[0053] The hydrophobic monomer is at least one of vinyl acetate and vinyl propionate.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0055] This invention utilizes micro-nano bubbles to initiate free radical solution polymerization of alkenyl monomers. Micro-nano bubbles can generate free radicals without external stimulation. When the micro-nano bubbles contract, the charge density of the double layer increases rapidly. When the bubbles rupture, the drastic change of the disappearance of the gas-liquid interface releases the energy stored in the high concentration of positive and negative ions on the interface. At this time, a large number of hydroxyl radicals can be generated, which can initiate free radical solution polymerization of alkenyl monomers.

[0056] The present invention provides a simple, energy-efficient, convenient, controllable, and widely applicable method for initiating free radical solution polymerization of alkenyl monomers using micro-nano bubbles.

[0057] The present invention has the following advantages and effects in terms of initiation range and polymer properties: it is not limited by the initiation efficiency and half-life of traditional initiators, and can be initiated at any temperature; it avoids the problems of source, cost, toxicity, stability and impact on polymer properties of traditional initiators; and it avoids the energy consumption problems of conventional initiation methods such as light, heat and radiation. Detailed Implementation

[0058] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0059] The raw materials used in the examples and comparative examples were all commercially available.

[0060] Acrylamide was purchased from Dongying Baomo Environmental Engineering Co., Ltd.

[0061] Sodium 2-acrylamido-2-methylpropanesulfonate was purchased from Weifang Jinshi Environmental Protection Technology Co., Ltd.

[0062] 2,2-Azobisisobutyramidine hydrochloride was purchased from Sigma-Aldrich.

[0063] N,N-Dimethylacrylamide was purchased from Beijing Ruibolong Technology Development Co., Ltd.

[0064] Unless otherwise specified, all other reagents can be obtained commercially.

[0065] Test method:

[0066] Molecular weight determination: Refer to Q / HNYJ 307-2007 "Detailed Rules for Testing the Intrinsic Viscosity of Polyacrylamide".

[0067] Example 1

[0068] This embodiment illustrates a method for initiating free radical solution polymerization of alkenyl monomers.

[0069] 40g acrylamide, 5g sodium acrylate, and 5g sodium 2-acrylamido-2-methylpropanesulfonate were dissolved in 250g deionized water, and the pH was adjusted to 4.0. The initial temperature was controlled at 5℃. Nitrogen gas with a diameter of 1mm to 10mm was introduced into the system for 20 minutes to remove oxygen. Then, nitrogen nanobubbles with an average diameter of 50 nanometers were introduced into the system (the inlet pressure was controlled at 0.8MPa and the gas flow rate was controlled at 10mL / min). The system temperature was increased by 0.5℃, and the introduction of nanobubbles was stopped. The reaction continued for 5 hours. After polymerization, the resulting colloid was granulated, dried at 50℃ until the solid content reached more than 89%, and then pulverized and sieved to obtain a polymer of 20-80 mesh.

[0070] The molecular weight of the polymer was measured to be 23.2 million.

[0071] Example 2

[0072] This embodiment illustrates a method for initiating free radical solution polymerization of alkenyl monomers.

[0073] 50g acrylamide, 5g methacrylamide, 3g sodium crotonate, and 3g vinyl acetate were dissolved in 239g deionized water, and the pH was adjusted to 6. The initial temperature was controlled at 10℃. Nitrogen gas with a diameter of 1mm to 10mm was introduced into the system for 20 minutes to remove oxygen. Then, argon nanobubbles with an average diameter of 80 nm (inlet pressure controlled at 0.7MPa, inlet flow rate controlled at 20mL / min) were introduced into the system. The system temperature was increased by 1℃, and the introduction of nanobubbles was stopped. The reaction continued for 2 hours. After polymerization, the resulting colloid was granulated, dried at 50℃ until the solid content reached above 89%, and then pulverized and sieved to obtain a polymer of 20-80 mesh. The molecular weight of the polymer was measured to be 13.5 million.

[0074] Example 3

[0075] This embodiment illustrates a method for initiating free radical solution polymerization of alkenyl monomers.

[0076] 60g of acrylamide, 13g of N,N-dimethylacrylamide, 15g of sodium 2-acrylamido-2-methylpropanesulfonate, and 2g of methacrylate were dissolved in 210g of deionized water, and the pH was adjusted to 5.0. The initial temperature was controlled at 20℃. Nitrogen gas with a diameter of 1mm to 10mm was introduced into the system for 40 minutes to remove oxygen. Then, helium nanobubbles with an average diameter of 150 nm (inlet pressure controlled at 0.5MPa, inlet flow rate controlled at 30mL / min) were introduced into the system. The system temperature was increased by 0.8℃, the introduction of nanobubbles was stopped, and the reaction continued for 4 hours. After polymerization, the resulting colloid was granulated, dried at 50℃ until the solid content reached above 89%, and then pulverized and sieved to obtain a polymer of 20-80 mesh. The molecular weight of the polymer was measured to be 10.1 million.

[0077] Example 4

[0078] This embodiment illustrates a method for initiating free radical solution polymerization of alkenyl monomers.

[0079] 60g of acrylamide and 5g of diallyldimethylammonium chloride were dissolved in 235g of deionized water, and the pH was adjusted to 6. The initial temperature was controlled at 20℃. Nitrogen gas with a diameter of 1mm to 10mm was introduced into the system for 20 minutes to remove oxygen. Then, nitrogen microbubbles with an average diameter of 200 nm (inlet pressure controlled at 0.3MPa, gas flow rate controlled at 20mL / min) were introduced into the system. The system temperature was increased by 0.5℃ to initiate polymerization. After that, the introduction of microbubbles was stopped, and the reaction continued for 3 hours. After polymerization, the resulting colloid was granulated, dried at 50℃ until the solid content reached above 89%, and then pulverized and sieved to obtain a polymer of 20-80 mesh. The molecular weight of the polymer was measured to be 5.2 million.

[0080] Example 5

[0081] This embodiment illustrates a method for initiating free radical solution polymerization of alkenyl monomers.

[0082] 82g of acrylamide, 8g of N-vinylpyrrolidone, and 4g of maleic anhydride were dissolved in 200g of deionized water, and the pH was adjusted to 6.0. The initial temperature was controlled at 25℃, and nitrogen gas was bubbled into the system for 20min to remove oxygen. Then, carbon dioxide micro-nano bubbles with an average diameter of 100 nm were introduced into the system (inlet pressure controlled at 0.5MPa, gas flow rate controlled at 15mL / min). The system temperature was increased by 0.8℃ to initiate polymerization. After that, the introduction of micro-nano bubbles was stopped, and the reaction continued for 3 hours. After polymerization, the colloid was removed, granulated, and 9.24g of sodium hydroxide granules were added and mixed evenly. Hydrolysis was carried out at 80℃ for 3 hours. The reaction was continued at 50℃ until the solid content reached more than 89%. The polymer was then pulverized and sieved to obtain a 20-80 mesh polymer. The molecular weight of the polymer was measured to be 12 million.

[0083] Example 6

[0084] This embodiment illustrates a method for initiating free radical solution polymerization of alkenyl monomers.

[0085] 50g of acrylamide and 5g of sodium acrylate were dissolved in 245g of deionized water, and the pH was adjusted to 6. The initial temperature was controlled at 10℃. Nitrogen gas (1mm-10mm diameter) was introduced into the system for 20 minutes to remove oxygen. Then, argon nanobubbles with an average diameter of 80nm were introduced into the system (inlet pressure controlled at 0.7MPa, inlet flow rate controlled at 20mL / min). The system temperature was increased by 1℃, and the introduction of nanobubbles was stopped. The reaction continued for 2 hours. After polymerization, the resulting colloid was granulated, dried at 50℃ until the solid content reached over 89%, and then pulverized and sieved to obtain a 20-80 mesh polymer. The molecular weight of the polymer was measured to be 21.8 million.

[0086] Comparative Example 1

[0087] Comparative Example 1 is compared with Example 1;

[0088] 40g acrylamide, 5g sodium acrylate, and 5g sodium 2-acrylamido-2-methylpropanesulfonate were dissolved in 250g deionized water, and the pH was adjusted to 4.0. The initial temperature was controlled at 5℃. Nitrogen gas with a diameter of 1mm to 10mm was introduced into the system for 20 minutes to remove oxygen. Then, 2.5g of 0.2% ammonium persulfate aqueous solution and 3.0g of 0.3% sodium bisulfite aqueous solution were added. After the system temperature rose by 0.5℃, nitrogen blowing was stopped, and the reaction continued for 6 hours. After polymerization, the resulting colloid was granulated, dried at 50℃ until the solid content reached 89%, and then pulverized and sieved to obtain a polymer of 20-80 mesh.

[0089] The molecular weight of the polymer was measured to be 20.5 million.

[0090] Comparative Example 2

[0091] Comparative Example 2 is compared with Example 2;

[0092] 50g acrylamide, 5g methacrylamide, 3g sodium crotonate, and 3g vinyl acetate were dissolved in 239g deionized water, and the pH was adjusted to 6. The initial temperature was controlled at 10℃. Nitrogen gas with a diameter of 1mm to 10mm was pumped into the system for 20 minutes to remove oxygen. Then, 1.0g of azobisisobutyramidine hydrochloride aqueous solution (0.25% by mass), 1.5g of sodium persulfate aqueous solution (0.2% by mass), and 4.0g of potassium bisulfite aqueous solution (0.3% by mass) were added to the system. After the system temperature rose by 0.5℃, the nitrogen pumping was stopped, and the reaction continued for 4 hours. After polymerization, the resulting colloid was granulated, dried at 60℃ until the solid content reached 89%, and then pulverized and sieved to obtain a polymer of 20-80 mesh.

[0093] The molecular weight of the polymer was measured to be 12.8 million.

[0094] As demonstrated in Examples 1-6, introducing micro- and nano-bubbles with diameters ranging from 50 nm to 200 nm into the polymerization system can initiate free radical polymerization, resulting in polymers with molecular weights ranging from 5 million to 25 million. This proves that after cavitation in the system, micro- and nano-bubbles generate a large number of hydroxyl radicals, which can initiate free radical solution polymerization of alkenyl monomers to obtain polymers.

[0095] Compared with Comparative Example 1, Example 2 was compared with Comparative Example 2. Both Examples 1 and 2 can produce polymers with similar molecular weights to Comparative Examples 1 and 2, proving that micro-nano bubble initiation can replace traditional initiators and achieve polymerization effects similar to those of traditional initiators.

[0096] The data from Examples 1-6 illustrate that introducing micro- and nano-bubbles into the system can achieve better polymerization results and can replace traditional initiators for initiating polymerization. This avoids the problems of traditional initiators, such as source, cost, toxicity, stability, and impact on polymer properties. It also avoids the energy consumption problems of conventional initiation methods such as light, heat, and radiation. It is a simple, low-energy-consumption initiation method for free radical solution polymerization, and has the characteristics of being convenient, controllable, and widely applicable.

Claims

1. A method for initiating free radical solution polymerization, characterized in that... The method includes: An inert gas A is introduced into an aqueous solution of an alkenyl monomer to remove oxygen, followed by the introduction of micro-nano bubbles of gas B. After cavitation of the micro-nano bubbles, free radical solution polymerization of the alkenyl monomer is initiated. The resulting colloid is then treated to obtain a polymer. The gas B is at least one of nitrogen, argon, helium, and carbon dioxide. The average diameter of the micro-nano bubbles of gas B is 50 nanometers to 500 nanometers. The mass concentration of the alkenyl monomer aqueous solution is 10%~50%; The alkenyl monomer is at least one of anionic monomers and their alkali metal salts or ammonium salts, nonionic monomers, and cationic monomers. The pH value of the alkenyl monomer aqueous solution is 4 to 9; the initial reaction temperature is -10℃ to 40℃; after the system temperature rises by 0.5℃ to 1℃, the introduction of micro-nano bubbles is stopped, and the reaction continues for 1 to 6 hours.

2. The method for initiating free radical solution polymerization as described in claim 1, characterized in that: The mass concentration of the alkenyl monomer aqueous solution is 15%~35%; and / or, The inert gas A is at least one of nitrogen, argon, and helium.

3. The method for initiating free radical solution polymerization as described in claim 1, characterized in that: The anionic monomer is at least one selected from acrylic acid, methacrylic acid, maleic anhydride, cinnamic acid, fumaric acid, crotonic acid, aconitic acid, 2-methacrylamidoethanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, propane sulfonic acid, and styrene sulfonic acid; and / or, The alkali metal salt is a lithium, potassium, or sodium metal salt; and / or, The nonionic monomer is at least one selected from acrylamide, methacrylamide, N-vinylpyrrolidone, N-substituted acrylamide, N,N-dimethylacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, methoxy polyethylene glycol methacrylate, methoxy polyethylene glycol acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, and N-vinylacetamide; and / or, The cationic monomer is at least one of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide and its quaternary ammonium salt, and diallyl dimethylammonium chloride.

4. The method for initiating free radical solution polymerization as described in claim 1, characterized in that: The alkenyl monomer further includes at least one of acrylate and hydrophobic monomer; the total mass of acrylate and hydrophobic monomer does not exceed 10% of the total mass of alkenyl monomer; The acrylate is at least one of methacrylate, ethyl methacrylate, and butyl methacrylate; the hydrophobic monomer is at least one of vinyl acetate and vinyl propionate.

5. The method for initiating free radical solution polymerization as described in claim 1, characterized in that: The average diameter of the gas B micro-nano bubbles is 50 nanometers to 200 nanometers.

6. The method for initiating free radical solution polymerization as described in claim 1, characterized in that: The pH value of the aqueous solution of the alkenyl monomer is 4-6; and / or, The initial reaction temperature is 0℃~25℃; and / or, The diameter of the inert gas A bubbles is 1 mm to 10 mm; the introduction time is 5 min to 60 min.

7. The method for initiating free radical solution polymerization as described in claim 6, characterized in that: The inert gas A bubbles are introduced over a period of 20 to 40 minutes.

8. The method for initiating free radical solution polymerization as described in claim 1, characterized in that: After the system temperature is increased by 0.5℃~1℃, the introduction of micro / nano bubbles is stopped, and the reaction continues for 2 to 5 hours; and / or, The colloid processing method involves granulating, hydrolyzing or not hydrolyzing, drying, pulverizing, and sieving the obtained colloid.

9. A polymer prepared by the initiation method of free radical solution polymerization according to any one of claims 1 to 8.

10. The application of the polymer as described in claim 9 in oil reservoir development.

11. The application of the polymer as described in claim 10 in oil reservoir development, characterized in that: Applications in polymer flooding in high-temperature and high-salinity reservoirs, polymer flooding in offshore reservoirs, water flooding in heavy oil reservoirs, and hydraulic fracturing.