A comb-shaped high-molecular terpolymer and a preparation process thereof

Abstract

This invention relates to the field of water-soluble polymer materials technology, and discloses a comb-shaped ternary polymer and its preparation process. The polyacrylamide is polymerized from a backbone monomer, anionic monomer, comb-shaped macromolecular monomer, and optional functional reinforcing monomers under the action of a redox and azo-based composite initiation system. The preparation process includes solution preparation and neutralization, deoxygenation and temperature control, adiabatic polymerization, and post-treatment steps, employing a control strategy combining low-temperature initiation and adiabatic temperature rise polymerization. This invention effectively overcomes the defects of traditional linear polymers—low viscosity retention and poor shear resistance—in high-temperature and high-salt environments by introducing comb-shaped side chains to create a steric hindrance effect. The resulting product possesses ultra-high molecular weight, low water-insoluble content, and excellent solubility, exhibiting excellent salt-resistant thickening advantages and mechanical stability, meeting the oil displacement requirements of harsh reservoir environments.

Description

Technical Field

[0001] This invention relates to the field of water-soluble polymer materials technology, and in particular to a comb-type ternary polymer and its preparation process. Background Technology

[0002] Polyacrylamide-based ternary polymers are important water-soluble polymer materials with wide applications in oilfield tertiary oil recovery, water treatment, and papermaking. In oilfield polymer flooding processes, acrylamide is typically used as the matrix, with anionic monomers and other functional monomers copolymerized to form ternary polymers. This increases the viscosity of the aqueous phase and improves the water-oil mobility ratio, thereby enhancing oil recovery.

[0003] As oilfield development enters its mid-to-late stages, reservoir environments exhibit high temperatures and high salinity. Existing polyacrylamide-based ternary polymers mostly possess linear molecular structures, and their thickening mechanism relies on the electrostatic repulsion generated by negatively charged side groups on the molecular chain, allowing the chain to remain extended in aqueous solution to achieve a larger hydrodynamic volume. However, when facing highly salinized formation water, the numerous metal cations in the fluid compress the electric double layer on the polymer chain surface, generating a charge shielding effect. This effect significantly weakens the electrostatic repulsion between polymer side groups, causing the linear molecular chain to rapidly contract from its extended state and coil into a coil shape. Macroscopically, this manifests as a significant decrease in the apparent viscosity of the polymer solution and a substantial reduction in its thickening ability.

[0004] Meanwhile, in industrial applications, increasing the polymer molecular weight is typically used to compensate for viscosity loss. However, linear ultra-high molecular weight ternary polymers experience high-intensity mechanical shear flow fields during high-speed pumping, pipeline throttling, and injection into near-wellbore areas via surface distribution systems. Due to the insufficient rigidity of the linear molecular backbone, excessive stretching easily occurs in strong shear flow fields. When the traction force generated by the fluid exceeds the bond energy of the polymer's carbon-carbon backbone, the polymer backbone undergoes irreversible mechanical fracture and degradation, resulting in a permanent loss of solution viscosity and a decrease in the polymer's sweep susceptibility control in deep formations.

[0005] Furthermore, existing ternary polymer synthesis processes struggle to simultaneously achieve ultra-high molecular weight and excellent solubility. Introducing specific structural monomers to improve temperature and salt resistance often leads to decreased polymer water solubility and prolonged dissolution time. Conventional polymerization processes, in pursuit of ultra-high molecular weight, are highly susceptible to cross-linking side reactions, resulting in a large amount of water-insoluble matter and poorly soluble micelles. These insoluble substances not only reduce the effective concentration of the polymer solution but also easily cause physical blockage of porous media during injection into formations. Therefore, current technologies require a novel polymer and its corresponding synthesis process that can maintain viscosity stability in high-salt environments, possess high shear resistance, and exhibit excellent solubility. Summary of the Invention

[0006] The purpose of this invention is to provide a comb-type ternary polymer and its preparation process, which solves the problems of existing linear polyacrylamide failing due to electrostatic repulsion under high mineralization and high temperature environments, resulting in a significant decrease in thickening ability, and the easy chain scission degradation under strong mechanical shearing, leading to low viscosity retention.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a comb-shaped ternary polymer, which adopts the following technical solution:

[0009] A comb-shaped ternary polymer is polymerized from monomer raw materials comprising the following mass percentages under the action of an initiation system: backbone monomer: 65.0%-85.0%; anionic monomer: 10.0%-25.0%; comb-shaped macromolecular monomer: 2.0%-10.0%; functional reinforcing monomer: 0%-10.0%; the sum of the mass percentages of each monomer raw material is 100%; the initiation system includes an oxidant, a reducing agent and an azo initiator.

[0010] By employing the above technical solution, this invention utilizes a preset monomer ratio to construct an ultra-high molecular weight polymer with a comb-like topology. Its mechanism of action is as follows:

[0011] First, the backbone monomers (such as acrylamide) constitute the main chain of the polymer, providing the basic degree of polymerization and water solubility. Second, the introduced comb-shaped macromonomers are grafted onto the main chain during polymerization, forming a comb-shaped structure with long side chains. This special topology generates a steric hindrance effect at the microscopic level. In high-mineralization (high-salt) environments, even if the electrostatic repulsion of anionic groups (such as carboxyl groups) on the main chain is weakened due to the compression of the electric double layer, the rigid long side chain steric hindrance can still physically support the main chain to remain extended, thereby maintaining a large hydrodynamic volume and exhibiting excellent salt-resistant thickening properties. At the same time, this dense side chain structure can encapsulate the main chain, absorbing shear energy through side chain deformation when the fluid is subjected to high-intensity mechanical shear (such as through pumps or sieves), and preventing the main chain from being stretched to its fracture limit, thereby improving the polymer's resistance to shear degradation. Third, the use of a composite initiation system achieves a combination of low-temperature initiation and high-temperature curing, ensuring the formation of high molecular weight (long main chain) and low residual monomer content.

[0012] Preferably, the specific components of each monomer raw material are as follows: the backbone monomer is acrylamide; the anionic monomer is acrylic acid or sodium salt of acrylic acid; the comb-type macromolecular monomer is polyethylene glycol monomethacrylate or isopentenyl alcohol polyoxyethylene ether; and the functional enhancement monomer is 2-acrylamido-2-methylpropanesulfonic acid or N-vinylpyrrolidone.

[0013] By employing the above technical solutions, polyethylene glycol monomethacrylate or isopentenyl alcohol polyoxyethylene ether, as the side chain source, exhibits excellent hydrophilicity and flexibility, forming a thick hydration layer in water, further enhancing salt resistance. If functional reinforcing monomers such as 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are introduced, the sulfonic acid groups it contains exhibit stronger resistance to calcium and magnesium ions than the carboxylic acid groups, and the large side group structure increases the rigidity of the main chain, thereby further improving the polymer's temperature resistance and resistance to divalent ions.

[0014] Preferably, the amount of each component added in the initiation system is based on the total mass of the monomer raw materials: the oxidant is ammonium persulfate or potassium persulfate, and the amount added is 0.005%-0.020%; the reducing agent is sodium bisulfite, sodium metabisulfite or urea, and the amount added is 0.005%-0.020%; the azo initiator is azobisisobutyramidine hydrochloride or azobisisobutyronitrile, and the amount added is 0.010%-0.030%.

[0015] By adopting the above technical solution, extremely low concentrations of redox initiators can generate a small number of free radicals at low temperatures, initiating chain growth reactions, which is conducive to the formation of ultra-long molecular chains; while azo initiators decompose as the system temperature rises in the middle and later stages of the reaction, replenishing free radicals, ensuring high conversion rate, and avoiding the problems of explosive polymerization or incomplete reaction caused by a single initiation system.

[0016] Preferably, the monomer raw material also contains additives, including metal chelating agents and chain transfer agents; the metal chelating agent is disodium ethylenediaminetetraacetate, and the amount added is 0.01%-0.03% of the total mass of the monomer raw material; the chain transfer agent is sodium formate or sodium hypophosphite, and the amount added is 0.001%-0.01% of the total mass of the monomer raw material.

[0017] By adopting the above technical solution, disodium ethylenediaminetetraacetate can shield metal ion impurities in water, preventing them from causing abnormal decomposition of the initiator or cross-linking; the addition of trace chain transfer agents (sodium formate or sodium hypophosphite) can inhibit the occurrence of gelation (cross-linking) reaction, regulate molecular weight distribution, improve the water solubility of the product, and reduce the generation of fish eyes and water-insoluble matter.

[0018] Secondly, the present invention provides a preparation process for a comb-shaped ternary polymer, employing the following technical solution:

[0019] A preparation process for a comb-shaped ternary polymer, applied to the above-mentioned comb-shaped ternary polymer, includes the following steps:

[0020] S1. Solution preparation and neutralization: Dissolve the backbone monomer, comb-type macromonomer, and functional enhancement monomer in water, add anionic monomer and adjust the pH value, add auxiliary agent, and mix evenly to obtain an aqueous solution of polymeric monomer.

[0021] S2. Deoxygenation and Temperature Control: Place the aqueous solution of the monomer in a sealed container, introduce inert gas to deoxygenate, and lower the solution temperature to the initiation temperature.

[0022] S3. Polymerization reaction: Add an initiation system to the solution after step S2 to initiate the polymerization reaction. The reaction is carried out under adiabatic conditions until the system temperature rises to the highest point and then is kept warm for aging.

[0023] S4. Post-processing: The matured colloid is granulated, dried, and pulverized to obtain comb-type polymeric polyacrylamide.

[0024] By adopting the above technical solution, this process employs a low-temperature initiation and adiabatic polymerization control strategy, and its reaction mechanism and process advantages are as follows:

[0025] The first stage (initiation period): In step S2, the system is cooled to the initiation temperature and oxygen is strictly removed. After adding the redox initiator in step S3, free radicals are slowly generated at low temperature. At this time, the system viscosity is low, the free radical concentration is low, and the probability of bimolecular termination is small, which is conducive to the rapid addition of monomer molecules to the active chain, forming extremely long primary molecular chains. This is the key to obtaining ultra-high molecular weight molecules.

[0026] The second stage (growth phase): The reaction takes place under adiabatic conditions, and the exothermic polymerization causes the system temperature to rise naturally. As the temperature rises, the molecular chains continue to grow, and the comb-shaped macromonomers copolymerize into the main chain through their terminal double bonds. The adiabatic temperature rise process avoids thermal degradation caused by external heat sources, while automatically accelerating the reaction using the heat of reaction.

[0027] The third stage (conversion period): When the temperature rises to a certain level (e.g., above 40-50℃), the azo initiator begins to decompose and release free radicals, which take over the redox system to continue initiating the polymerization of the remaining monomers. This mechanism ensures that the reaction rate can still be maintained even when the monomer concentration decreases in the later stages of the reaction, minimizing the residual monomer content.

[0028] The fourth stage (curing period): After the system reaches the highest temperature, it is kept at this temperature to relax the molecular chain structure and further complete the conversion of trace monomers, finally obtaining a comb-shaped polymer colloid with a uniform structure.

[0029] Preferably, in step S1, the total mass concentration of monomer raw materials in the monomer aqueous solution is controlled at 20.0%-35.0%; the pH value is adjusted to 6.5-7.5, and the adjusting agent used is sodium hydroxide aqueous solution.

[0030] By adopting the above technical solution and controlling the monomer concentration between 20.0% and 35.0%, it is ensured that the exothermic polymerization energy can push the system to a sufficiently high ripening temperature, while avoiding excessively vigorous polymerization or cross-linking due to excessive concentration. A neutral pH environment is beneficial in preventing the hydrolysis of acrylamide groups (generating too many carboxylate groups, leading to decreased salt tolerance) or imidization (leading to insoluble cross-linking).

[0031] Preferably, in step S2, the inert gas is nitrogen, the deoxygenation time is 30-60 minutes, and the mass concentration of dissolved oxygen in the solution is controlled at 0.01 mg / L-0.20 mg / L; the initiation temperature is controlled between 5.0℃ and 10.0℃.

[0032] By adopting the above technical solution, the dissolved oxygen content is strictly controlled to be below 0.20 mg / L, eliminating the consumption of free radicals by oxygen as a polymerization inhibitor and eliminating the initiation period. The low-temperature starting conditions of 5.0℃-10.0℃ can minimize the initial free radical concentration, inhibit the chain termination reaction, and thus significantly increase the average molecular weight of the product.

[0033] Preferably, in step S3, the order of adding the initiation system is as follows: first add the oxidant solution, then add the azo initiator solution, and finally add the reducing agent solution; after adding the initiation system, stir rapidly for 30-60 seconds, then stop stirring and seal the reaction system.

[0034] By adopting the above technical solution, the preset feeding sequence avoids instantaneous boiling due to excessively high local concentrations of oxidant and reductant. The reductant is added last as a trigger, initiating the redox reaction immediately upon addition. After rapid stirring, the mixture is immediately allowed to stand to prevent shear forces from cutting off the forming primary long chains and to prevent air from being reintroduced.

[0035] Preferably, in step S3, the polymerization reaction under adiabatic conditions causes the system temperature to rise naturally to 85℃-98℃; the curing time is 2.0-4.0 hours.

[0036] By adopting the above technical solution, the endpoint temperature is pushed up to 85℃-98℃ using the heat of polymerization. This temperature range not only ensures that the monomer conversion rate is close to 100%, but also allows for heat treatment of the colloid, reducing branch entanglement and improving solubility.

[0037] Preferably, in step S4, the drying temperature is controlled at 75℃-90℃, the drying time is 60-120 minutes, and the moisture content of the final product is controlled at 8.0%-10.0%.

[0038] By adopting the above technical solution, drying at 75℃-90℃ can prevent the polymer from undergoing thermal degradation or cross-linking (such as imidization), while retaining an appropriate amount of moisture (8.0%-10.0%) helps maintain the solubility of polymer particles and prevents keratinization and insolubility caused by excessive drying.

[0039] In summary, the present invention has at least one of the following beneficial technical effects:

[0040] 1. The comb-shaped ternary polymer of this invention exhibits excellent salt-resistant thickening properties. By introducing comb-shaped macromonomers (such as polyethylene glycol monomethacrylate), a high-density long side-chain structure is constructed on the side of the polymer backbone. This comb-shaped topology can generate a significant steric hindrance effect. In a high-saltification brine environment, even if the electrostatic repulsion of anionic groups on the backbone is weakened due to double-layer compression, the rigid side-chain steric hindrance can still physically support the backbone to remain extended, preventing excessive coiling and contraction of the molecular chains, thereby maintaining a large hydrodynamic volume of the polymer and improving its viscosity retention rate in saline environments.

[0041] 2. The comb-shaped ternary polymer of this invention exhibits excellent shear mechanical stability. Unlike traditional linear polymers, which are easily stretched and broken in high-speed shear flow fields, the comb-shaped structure of this invention increases the rigidity of the molecular chains and intramolecular friction. When subjected to strong mechanical shearing forces such as those encountered during oilfield polymer injection pumping or orifice throttling, the dense side chains effectively disperse shear stress, preventing the main chain from being stretched to its fracture limit. This significantly reduces viscosity loss due to chain breakage, ensuring the viscosity stability of the polymer solution during injection into the formation.

[0042] 3. The preparation process provided by this invention achieves a balance between ultra-high molecular weight and excellent solubility. This process employs a control strategy combining low-temperature initiation and adiabatic polymerization, coupled with a composite initiation system of redox and azo compounds. The low-temperature initiation condition effectively reduces the free radical concentration, promoting the growth of long molecular chains and increasing the molecular weight of the product; while the adiabatic temperature rise process, combined with the relay effect of medium- and high-temperature initiators, ensures a high monomer conversion rate. Furthermore, the pre-set formulation and process control effectively suppress cross-linking side reactions, resulting in a final product with extremely low water-insoluble content and rapid dissolution, solving the technical problem of conventional high molecular weight polymers easily producing poorly soluble substances. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to embodiments and comparative examples.

[0044] This invention provides a comb-shaped ternary polymer and its preparation process.

[0045] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0046] Polyethylene glycol monomethacrylate, CAS No.: 26915-72-0, corresponding number average molecular weight is approximately 1000;

[0047] Isoprene alcohol polyoxyethylene ether, CAS No.: 134467-31-3, corresponding number average molecular weight is approximately 2400.

[0048] Examples 1-4:

[0049] Example 1:

[0050] This embodiment provides a comb-type polymeric polyacrylamide, including the following steps:

[0051] (1) Add 748g of deionized water to the mixing tank, start stirring, and add 195.0g of acrylamide and 12.5g of polyethylene glycol monomethacrylate (Mn=1000) in sequence, stirring until completely dissolved; then add 42.5g of acrylic acid, and slowly add 30% sodium hydroxide solution under cooling conditions to adjust the pH of the system to 7.0. At this time, the total mass concentration of monomers is about 25.0%.

[0052] (2) Add 0.05g of disodium ethylenediaminetetraacetate, a metal chelating agent, and 0.01g of sodium formate, a chain transfer agent, to the solution, and continue stirring for 15 minutes to mix them evenly;

[0053] (3) Transfer the mixed solution to an insulated polymerization reactor, continuously introduce nitrogen gas with a purity of 99.99% into the bottom of the reactor for bubbling deoxygenation at a rate of 300 L / h and a deoxygenation time of 40 minutes. At the same time, turn on the jacket cooling water to lower the temperature of the reaction system and stabilize it at 5.0℃.

[0054] (4) Under nitrogen protection and rapid stirring, add ammonium persulfate aqueous solution (containing 0.025 g of ammonium persulfate), azobisisobutyramidine hydrochloride aqueous solution (containing 0.035 g of V50) and sodium bisulfite aqueous solution (containing 0.025 g of sodium bisulfite) in sequence. After stirring for 30 seconds, stop stirring immediately and turn off the nitrogen gas. Seal the polymerization reactor.

[0055] (5) The reaction was carried out under adiabatic conditions. The system temperature naturally rose to the highest point of 92°C within 90 minutes. It was then kept at the highest temperature for 3 hours to obtain a transparent elastic colloid.

[0056] (6) Take out the colloid, cut it into particles with a diameter of 3-5 mm by a granulator, place it in a fluidized bed dryer and dry it at 80°C for 90 minutes, then crush it by a pulverizer and pass it through a 20-mesh sieve to obtain comb-type high molecular weight polyacrylamide powder.

[0057] Example 2:

[0058] This embodiment provides a comb-type polymeric polyacrylamide, including the following steps:

[0059] (1) Add 730g of deionized water to the mixing tank, start stirring, and add 175.0g of acrylamide, 25.0g of 2-acrylamido-2-methylpropanesulfonic acid, and 12.5g of isopentenyl alcohol polyoxyethylene ether (Mn=2400) in sequence, and stir to dissolve; add 37.5g of acrylic acid, and add 30% sodium hydroxide solution dropwise to adjust the pH value to 7.0. At this time, the total mass concentration of monomers is about 25.0%.

[0060] (2) Add 0.06 g of disodium ethylenediaminetetraacetate and 0.008 g of sodium formate to the solution and stir until homogeneous;

[0061] (3) Transfer the solution to an insulated autoclave, purge with nitrogen for 45 minutes to remove oxygen, and simultaneously cool to 6.0℃;

[0062] (4) Add potassium persulfate aqueous solution (containing 0.030 g potassium persulfate), azobisisobutyramidine hydrochloride aqueous solution (containing 0.040 g V50) and urea aqueous solution (containing 0.030 g urea) in sequence, stir quickly to mix, and then seal the polymerization reactor;

[0063] (5) The adiabatic reaction is heated to the highest point of 95°C and kept warm for 4 hours to obtain a colloid;

[0064] (6) The colloid is granulated, dried in a forced-air dryer at 85°C for 2 hours, pulverized and sieved to obtain heat-resistant reinforced comb-type polymeric polyacrylamide powder.

[0065] Example 3:

[0066] This embodiment provides a comb-type polymeric polyacrylamide, including the following steps:

[0067] (1) Add 690g of deionized water to the mixing tank, start stirring, add 255.0g of acrylamide and 9.0g of polyethylene glycol monomethacrylate (Mn=1000), dissolve, add 36.0g of acrylic acid, and adjust the pH to 7.2 with liquid alkali. At this time, the total mass concentration of monomers is about 30.0%;

[0068] (2) Add 0.08g of disodium ethylenediaminetetraacetate and 0.015g of sodium formate, and mix well;

[0069] (3) Transfer to the polymerization reactor, purge with nitrogen for 35 minutes to remove oxygen, and cool to 8.0℃;

[0070] (4) Add 0.045g of ammonium persulfate, 0.060g of V50, and 0.045g of sodium bisulfite (all prepared as solutions before addition), mix well, and then seal.

[0071] (5) The adiabatic reaction is heated to 98°C and kept warm for 3 hours;

[0072] (6) The colloid is granulated, dried at 75°C for 120 minutes, pulverized and sieved to obtain the finished product.

[0073] Example 4:

[0074] This embodiment provides a comb-type polymeric polyacrylamide, including the following steps:

[0075] (1) Add 790g of deionized water to the mixing tank, start stirring, add 144.0g of acrylamide and 16.0g of isopentenyl alcohol polyoxyethylene ether (Mn=2400), dissolve, add 40.0g of acrylic acid, adjust the pH to 6.8 with liquid alkali, at which point the total mass concentration of monomers is about 20.0%;

[0076] (2) Add 0.04 g of disodium ethylenediaminetetraacetate and 0.005 g of sodium formate, and mix well;

[0077] (3) Transfer to the polymerization reactor, purge with nitrogen to remove oxygen for 30 minutes, and control the system temperature at 10.0℃;

[0078] (4) Add 0.020g of ammonium persulfate, 0.030g of V50 and 0.020g of sodium bisulfite (all prepared as solutions before addition), mix well and seal;

[0079] (5) The adiabatic reaction is heated to 86°C and kept warm for 2.5 hours;

[0080] (6) The colloid is granulated, dried at 80°C for 100 minutes, pulverized and sieved to obtain the finished product.

[0081] Comparative Examples 1-4:

[0082] Comparative Example 1: Compared with Example 1, the difference is that polyethylene glycol monomethacrylate is not added, and this part is replaced with an equal mass of acrylamide, that is, the monomer composition is 207.5g of acrylamide and 42.5g of acrylic acid, and a common linear polyacrylamide is constructed. All other aspects are the same.

[0083] Comparative Example 2: Compared with Example 1, the difference is that methyl methacrylate was used instead of polyethylene glycol monomethacrylate in equal mass, and a hydrophobic modified polyacrylamide without long side chain structure was constructed. All other aspects are the same.

[0084] Comparative Example 3: Compared with Example 1, the difference is that the initiation temperature in the polymerization process was adjusted to 45°C, and the adiabatic polymerization method was not used. Instead, a 45°C constant temperature water bath was used for the polymerization reaction. All other aspects are the same.

[0085] Comparative Example 4: Compared with Example 1, the difference is that acrylic acid was not added, and this part was replaced with an equal mass of acrylamide to construct a nonionic comb-type polyacrylamide. All other aspects are the same.

[0086] Test Examples 1-4:

[0087] Test Example 1: Basic Test of Physicochemical Properties

[0088] This test case aims to determine the basic physicochemical properties of the polymers prepared in Examples 1-4 and Comparative Examples 1-4, in order to verify the stability of the preparation process and the basic characteristics of the products.

[0089] Test method:

[0090] Appearance: Place the dried polymer powder in a colorimetric tube and observe its color, particle state, and flowability under natural light by visual inspection.

[0091] Solid content determination: Performed according to GB / T12005.2-1989 "Determination of Solid Content of Polyacrylamide". Accurately weigh approximately 1.0 g of sample and dry it in a constant temperature drying oven at 120±2℃ until constant weight. Calculate the solid content based on the mass change before and after drying.

[0092] Molecular weight determination: According to GB / T12005.1-1989 "Determination of intrinsic viscosity of polyacrylamide", the intrinsic viscosity of the polymer in 1 mol / L sodium chloride solution was determined using an Ubbelohde viscometer at 30℃. The molecular weight was then converted to viscosity-average molecular weight using the Mark-Houwink equation. .

[0093] Dissolution time determination: Weigh a certain amount of polymer powder and prepare an aqueous solution with a mass concentration of 0.1%. Dissolve the polymer powder at 25℃ and a stirring speed of 400 r / min. Measure the conductivity of the solution every 5 minutes. Record the time required when the conductivity value remains constant in three consecutive measurements and no insoluble gel particles (fish eyes) are visually observed in the solution.

[0094] (5) The determination of water-insoluble matter is based on GB / T12005.6-1989 standard. The dissolved polymer solution is filtered through a standard sieve with a pore size of 180μm, washed, dried and weighed, and the mass fraction of water-insoluble matter is calculated.

[0095] Test results:

[0096] Table 1. Summary of physicochemical properties of products from each embodiment and comparative example

[0097] Group Appearance Solid content (%) <![CDATA[Viscosity-average molecular weight (10 4 )]]> Dissolution time (min) Water-insoluble matter (%) Example 1 White granules 89.2 1945 42 0.08 Example 2 White granules 88.7 2120 46 0.11 Example 3 White granules 90.1 1880 44 0.15 Example 4 White granules 89.5 1760 39 0.05 Comparative Example 1 White granules 89.4 1910 68 0.10 Comparative Example 2 Slightly yellow granules 88.9 1450 75 0.85 Comparative Example 3 White powder 90.3 860 35 0.06 Comparative Example 4 White granules 89.0 1620 82 0.25

[0098] Results analysis:

[0099] Based on the data in Table 1 and the technical mechanism of this invention, the analysis is as follows:

[0100] Relationship between molecular weight and polymerization process: Examples 1-4 and Comparative Example 1 all employed a low-temperature composite initiation and adiabatic polymerization process, resulting in products with molecular weights consistently above 17 million. In contrast, Comparative Example 3 used a 45°C constant-temperature water bath polymerization process. Due to the excessively rapid initiation rate, the free radical termination reaction intensified, limiting chain growth, and its molecular weight dropped significantly to 8.6 million. This confirms that the low-temperature initiation and adiabatic heating process described in this invention plays a decisive role in obtaining high molecular weight polymers.

[0101] Effect of comb-like structure on solubility: Under the premise of similar molecular weight (approximately 19 million), the solubility time of Example 1 (42 min) was lower than that of Comparative Example 1 (68 min). This is because the polyethylene glycol monomethacrylate side chain introduced in Example 1 contains a large number of hydrophilic ether bonds, which enhances the permeability of water molecules; at the same time, the steric hindrance effect of the comb-like side chain weakens the physical entanglement between polymer molecular chains, promoting the swelling and dispersion of particles in water.

[0102] The effect of monomer selection on product uniformity: Comparative Example 2 used the short-chain hydrophobic monomer methyl methacrylate instead of the comb-type monomer, resulting in a water-insoluble content as high as 0.85% and a prolonged dissolution time. This is because the hydrophobic groups are unevenly distributed in the aqueous polymerization system, easily leading to microphase separation or local cross-linking. In contrast, the PEGMA or TPEG monomers selected in this invention have excellent water solubility, ensuring the uniformity of the copolymerization reaction and the high solubility of the product.

[0103] The role of anionic groups: In Comparative Example 4, the acrylic acid component was missing, and its dissolution time was extended to 82 minutes. This indicates that the electrostatic repulsion generated by the carboxylate ions introduced by the acrylic acid structural unit, combined with the steric hindrance effect of the comb-shaped side chains, is a key factor in achieving rapid dissolution of high molecular weight polymers.

[0104] In summary, this invention successfully prepared comb-type polyacrylamide with high molecular weight, low water insoluble matter, and excellent solubility through a preset monomer ratio and low-temperature adiabatic polymerization process.

[0105] Test Example 2: Salt Tolerance Thickening Performance Test

[0106] This test case aims to examine the apparent viscosity changes of the polymers prepared in each embodiment and comparative example in deionized water and high-mineralization brine environments, in order to verify the resistance of the comb-like molecular structure to the salt ion shielding effect and the thickening stability.

[0107] Experimental methods:

[0108] Preparation of experimental solutions:

[0109] Deionized water solution: Accurately weigh the polymer powder samples prepared in each example and comparative example, and prepare a polymer solution with a mass concentration of 2000 mg / L using deionized water. Stir at 300 r / min for 120 minutes at 25°C to ensure complete dissolution.

[0110] Simulated brine solution: A high-mineralization brine solution was prepared to simulate the formation water environment of the oil reservoir, with a total mineralization set at 30,000 mg / L. The brine components were: sodium chloride (NaCl) 27.0 g / L, anhydrous calcium chloride (CaCl2) 2.0 g / L, and magnesium chloride hexahydrate (MgCl2·6H2O) 1.0 g / L. The polymer powder was dissolved using this simulated brine solution to prepare a polymer brine solution with a mass concentration of 2000 mg / L, under the same dissolution conditions as above.

[0111] Viscosity measurement:

[0112] The measurements were performed using a Brookfield DV-II+Pro rotational viscometer. A UL low viscosity adapter was selected, the test temperature was controlled at 25±0.5℃, and the shear rate was set to 7.34 s. -1 (Rotation speed 6 r / min). The apparent viscosity of each group of samples in deionized water was measured respectively. ) and apparent viscosity in simulated salt water ( The reading is taken after the torque has stabilized.

[0113] Data Calculation: The viscosity retention rate is calculated according to the following formula to quantify salt resistance:

[0114] ;

[0115] Test results:

[0116] Table 2. Viscosity measurement data of each embodiment and comparative example under different media environments.

[0117] Group Deionized water viscosity (mPa·s) Simulated salt water viscosity (mPa·s) Viscosity retention rate (%) Example 1 142.3 118.5 83.3 Example 2 165.7 146.2 88.2 Example 3 138.4 112.1 81.0 Example 4 121.9 98.6 80.9 Comparative Example 1 139.5 44.8 32.1 Comparative Example 2 88.4 41.2 46.6 Comparative Example 3 41.6 17.9 43.0 Comparative Example 4 26.2 22.4 85.5*

[0118] *Note: Due to the lack of ionic groups, the initial viscosity of the sample in Comparative Example 4 was too low, and it did not have the thickening effect required for practical applications. Therefore, its retention rate value is not representative.

[0119] Results analysis:

[0120] Based on the data in Table 2 and combined with the analysis of the polymer's physicochemical mechanism, the following is an analysis:

[0121] Verification of the steric hindrance effect of the comb-shaped structure: Examples 1 to 4 all maintained a viscosity retention rate of over 80% in highly saline solutions, higher than the 32.1% of Comparative Example 1 (linear structure). Ordinary linear polyacrylamide (Comparative Example 1) achieves higher viscosity in deionized water primarily due to the electrostatic repulsion between the negative charges of acrylate groups, allowing the molecular chains to extend; however, in solutions containing high concentrations of Na... + Ca 2+ In salt water, the electric double layer is compressed, electrostatic repulsion fails, causing the molecular chains to coil and shrink rapidly, resulting in a decrease in hydrodynamic volume and a sharp drop in viscosity. In contrast, the polyethylene glycol side chains (PEGMA / TPEG) introduced in this embodiment of the invention construct a high-density steric hindrance around the molecular backbone. This rigid steric hindrance persists even in a strong electrolyte environment, physically supporting the backbone to maintain a relatively extended conformation, thereby maintaining a higher hydrodynamic volume and solution viscosity.

[0122] Synergistic effect of side chain length and sulfonic acid groups: Example 2 used long-chain TPEG and introduced AMPS monomer, and its brine viscosity (146.2 mPa·s) and retention rate (88.2%) were the highest among all groups. Long-chain TPEG provides a larger radius of gyration and stronger steric support than short-chain PEGMA; at the same time, the sulfonic acid groups in the AMPS structure are much less sensitive to calcium and magnesium ions than the carboxylic acid groups in acrylic acid. The synergistic effect of the two improves the thickening stability of the polymer in complex ionic environments.

[0123] Relationship between solubility and thickening ability: Comparative Example 2 uses the short-chain hydrophobic monomer MMA, and its absolute viscosity in salt water is only 41.2 mPa·s. This is because the hydrophobic monomer cannot form an effective solubilization layer and lacks the spatial support of long side chains, which leads to excessive shrinkage or even precipitation of the molecular chain due to hydrophobic association in salt water, thus failing to exert an effective thickening effect.

[0124] In summary, the comb-type polyacrylamide of this invention overcomes the poor salt resistance of traditional linear polymers through a side-chain steric hindrance mechanism, demonstrating the effectiveness of the technical solution in salt-resistant thickening.

[0125] Test Example 3: Temperature Aging Resistance Test

[0126] This test case aims to simulate a high-temperature reservoir environment and examine the viscosity retention of polymer solutions prepared in each embodiment and comparative example under prolonged high-temperature thermal action, in order to evaluate the thermal stability of their molecular structure.

[0127] Experimental methods:

[0128] Preparation of aging samples:

[0129] The simulated saline polymer solutions (polymer concentration 2000 mg / L, mineralization 30,000 mg / L) prepared in Test Example 2 were selected as test samples. The solutions were placed into stainless steel sealed aging containers, filling them to 2 / 3 of their volume. High-purity nitrogen gas was continuously introduced into the containers for 10 minutes to displace the air at the top of the liquid surface. The sealing caps were then tightened to prevent oxygen intrusion during aging, which could lead to oxidative degradation and interfere with the thermal stability test.

[0130] High-temperature aging treatment:

[0131] Place the sealed aging tank in a constant-temperature roller oven and set the temperature to 90°C. Keep it at this constant temperature for 168 hours (7 days) under static conditions.

[0132] Viscosity measurement after aging:

[0133] After aging, remove the aging tank and allow it to cool naturally to 25°C at room temperature. Open the sealed cap and observe whether the solution shows any stratification, precipitation, or turbidity. Use the same test conditions as in Test Example 2 (Brookfield DV-II+Pro viscometer, UL adapter, 25°C, shear rate 7.34s). -1 ) Determine the apparent viscosity of the solution after aging ( ).

[0134] The high-temperature viscosity retention rate is calculated using the following formula:

[0135] ;

[0136] in, The viscosity of the simulated salt water solution measured before aging (i.e., in Test Example 2) data).

[0137] Test results:

[0138] Table 3. Viscosity changes of each embodiment and comparative example after aging at 90°C for 168 hours.

[0139] Group Initial viscosity (mPa·s) Viscosity after aging (mPa·s) High-temperature viscosity retention rate (%) Example 1 118.5 102.1 86.2 Example 2 146.2 137.9 94.3 Example 3 112.1 93.5 83.4 Example 4 98.6 82.4 83.6 Comparative Example 1 44.8 15.3 34.2 Comparative Example 2 41.2 21.7 52.7 Comparative Example 3 17.9 7.4 41.3 Comparative Example 4 22.4 18.1 80.8*

[0140] *Note: Comparative Example 4 does not contain ionic groups, so its initial viscosity is extremely low and the change in value before and after aging is small. Although the calculated retention rate is high, the absolute viscosity has no practical application value.

[0141] Results analysis:

[0142] Based on the data in Table 3 and the analysis of the polymer thermal degradation mechanism, the following is a summary:

[0143] Spatial shielding and thermal stabilization effects of the side chain: The high-temperature viscosity retention rates of Examples 1 to 4 were all maintained above 83%, which was superior to Comparative Example 1 (34.2%). Under high-temperature conditions, the amide groups on the polyacrylamide backbone are prone to hydrolysis to generate carboxylate ions. If the carboxylate ion density is too high, it easily reacts with Ca in water. 2+ Mg 2+ Cross-linking and precipitation occur, leading to viscosity loss; at the same time, the main carbon backbone is also at risk of thermal breakage. The dense comb-shaped side chains (PEGMA / TPEG) introduced in this invention spatially encapsulate the main chain, effectively hindering the attack of water molecules and free radicals on the sensitive groups of the main chain, delaying the hydrolysis and chain breakage process, and thus exhibiting excellent thermal stability on a macroscopic scale.

[0144] The temperature resistance enhancement mechanism of AMPS monomers: Example 2 exhibits the best temperature resistance performance, with a retention rate as high as 94.3%. This is because this example introduces AMPS monomers into the comb-like structure. The sulfonic acid groups in the AMPS molecule have extremely high thermal stability and hydrolysis resistance, and their large side group structure further increases the rigidity of the molecular chain (increasing the glass transition temperature), restricting the thermal motion of molecular chain segments at high temperatures, thereby maximizing the maintenance of the polymer's hydrodynamic volume.

[0145] The relationship between molecular weight and anti-aging properties: Comparative Example 3 used a traditional high-temperature initiation process. Due to its low initial molecular weight (shorter chain length), its molecular chains were more easily degraded to below the critical entangled molecular weight during high-temperature aging, resulting in a viscosity of only 7.4 mPa·s after aging, almost completely losing its thickening ability. This demonstrates the necessity of obtaining ultra-high molecular weight using a low-temperature adiabatic polymerization process in this invention to ensure the final temperature resistance of the product.

[0146] In summary, this invention improves the structural stability of polymers in high-temperature and high-salt environments by utilizing the spatial protection effect of comb-shaped side chains and the introduction of functional monomers.

[0147] Test Example 4: Shear Resistance Test

[0148] This test case aims to simulate the mechanical stability of polymer solutions during injection in oilfields under conditions of high-speed pumping, pipeline turbulence, and perforation shearing, and to examine the degree of damage to the polymer molecular chain structure and viscosity retention capacity caused by strong mechanical shearing.

[0149] Experimental methods:

[0150] For sample preparation, the simulated saline polymer solutions (mass concentration 2000 mg / L, mineralization 30,000 mg / L) prepared in Test Example 2 were selected as the reference test solutions. All samples were ensured to be kept at a constant temperature of 25°C before testing.

[0151] Mechanical shearing was performed according to APIRP 63, "Recommended Procedures for the Evaluation of Polymers Used in Enhanced Oil Production Operations." 500 mL of the polymer solution to be tested was placed in a glass of a standard WaringBlender. The stirrer speed was set to 3500 rpm (simulating the high-intensity shear field near the wellbore), and the continuous shearing time was set to 20 seconds.

[0152] Post-shear viscosity measurement: After shearing, the solution was allowed to stand for 30 minutes to eliminate air bubbles generated by high-speed stirring. Viscosity was measured under the same conditions as before shearing (25°C, Brookfield DV-II+Pro viscometer, UL adapter, shear rate 7.34 s). -1 ) Determine the apparent viscosity of the solution after shearing ( ).

[0153] Data Calculation: The shear resistance coefficient (viscosity retention rate) is calculated using the following formula; a higher value indicates better shear resistance.

[0154] ;

[0155] in, The viscosity of the simulated salt solution measured in Test Example 2.

[0156] Test results:

[0157] Table 4. Viscosity stability test data of each embodiment and comparative example under high-speed shear conditions

[0158] Group Initial viscosity (mPa·s) Viscosity after shearing (mPa·s) Shear strength (%) Example 1 118.5 98.4 83.0 Example 2 146.2 125.7 86.0 Example 3 112.1 91.3 81.4 Example 4 98.6 81.0 82.2 Comparative Example 1 44.8 21.7 48.4 Comparative Example 2 41.2 25.9 62.9 Comparative Example 3 17.9 15.5 86.6* Comparative Example 4 22.4 19.2 85.7*

[0159] *Note: Comparative Example 3 has an inflated retention rate due to its extremely low initial molecular weight, short molecular chain length, and minimal impact from shear force; Comparative Example 4 has data that is not of practical reference value due to its excessively low initial viscosity.

[0160] Results analysis:

[0161] Based on the data in Table 4 and combined with the analysis of polymer rheology and mechanical degradation mechanisms, the following is an analysis:

[0162] Influence of molecular topology on shear resistance: In samples with similarly high molecular weights (>17 million), the shear resistance coefficients of Examples 1 to 4 remained stable above 81%, while that of Comparative Example 1 (linear structure) was only 48.4%. In high-speed turbulent flow, the flexible backbone of linear polyacrylamide is easily stretched by the tensile flow field, leading to chain breakage and degradation when the fluid traction force exceeds the carbon-carbon bond energy, resulting in irreversible viscosity loss. The comb-shaped polymer prepared in this invention, due to the high-density grafting of side chains (PEGMA / TPEG), increases the rigidity and diameter of the molecular chain, making it less prone to excessive deformation and full extension in the flow field. This rigid molecular conformation effectively disperses shear stress, thereby reducing the probability of backbone breakage.

[0163] Balancing Effective Viscosity and Shear Stability: Comparative Example 3 showed a high retention rate of 86.6%, but this was attributed to the short-chain effect caused by its low molecular weight. Short-chain molecules experience less tensile force in a shear field and are less prone to breakage, but their absolute viscosity (15.5 mPa·s) is far below the threshold required for effective oil displacement. In contrast, Example 2 not only maintained a high absolute viscosity of 125.7 mPa·s but also possessed a high shear retention rate of 86.0%, demonstrating that the introduction of long side chains and rigid AMPS groups can genuinely improve the mechanical stability of polymeric materials without sacrificing molecular weight.

[0164] Inhibition of degradation by side chain steric hindrance: The shear resistance coefficient of Example 2 is better than that of Example 1, indicating that as the side chain length increases (from PEGMA to TPEG), the steric hindrance and intramolecular friction provided by the side chain further increase, which hinders the slippage and deentanglement of the main chain under shear action, making the polymer network structure more stable under strong mechanical action.

[0165] In summary, the comb-type polyacrylamide of this invention effectively overcomes the defect of poor shear resistance of traditional high molecular weight polymers by changing the molecular topology, and can meet the requirements of high-intensity injection processes in oil fields.

Claims

1. A comb-shaped ternary polymer, characterized in that, It is polymerized from monomer raw materials containing the following mass percentages under the action of an initiation system: Skeletal monomers: 65.0%-85.0%; Anionic monomers: 10.0%-25.0%; Comb-shaped macromonomers: 2.0%-10.0%; Enhanced functional monomers: 0%-10.0%; The sum of the mass percentages of all the monomer raw materials is 100%; The initiation system includes an oxidant, a reducing agent, and an azo initiator.

2. The comb-shaped ternary polymer according to claim 1, characterized in that, The specific components of each of the monomer raw materials are as follows: The skeleton monomer is acrylamide; The anionic monomer is acrylic acid or a sodium salt of acrylic acid; The comb-shaped macromonomer is polyethylene glycol monomethacrylate or isopentenyl alcohol polyoxyethylene ether. The functional enhancement monomer is 2-acrylamido-2-methylpropanesulfonic acid or N-vinylpyrrolidone.

3. The comb-shaped ternary polymer according to claim 1, characterized in that, The amount of each component added in the initiation system is based on the total mass of the monomer raw materials: The oxidant is ammonium persulfate or potassium persulfate, and the addition amount is 0.005%-0.020%. The reducing agent is sodium bisulfite, sodium metabisulfite, or urea, and the amount added is 0.005%-0.020%. The azo initiator is azobisisobutyramidine hydrochloride or azobisisobutyronitrile, and the addition amount is 0.010%-0.030%.

4. The comb-shaped ternary polymer according to claim 1, characterized in that, The monomer raw material also contains additives, including metal chelating agents and chain transfer agents; The metal chelating agent is disodium ethylenediaminetetraacetate, and the amount added is 0.01%-0.03% of the total mass of the monomer raw materials; The chain transfer agent is sodium formate or sodium hypophosphite, and the amount added is 0.001%-0.01% of the total mass of the monomer raw materials.

5. A preparation process for a comb-shaped ternary polymer, characterized in that, The application of a comb-type polymeric polyacrylamide according to any one of claims 1-4 includes the following steps: S1. Solution preparation and neutralization: Dissolve the backbone monomer, comb-type macromonomer, and functional enhancement monomer in water, add anionic monomer and adjust the pH value, add auxiliary agent, and mix evenly to obtain an aqueous solution of polymeric monomer. S2. Deoxygenation and Temperature Control: Place the aqueous solution of the monomer in a sealed container, introduce inert gas to deoxygenate, and lower the solution temperature to the initiation temperature. S3. Polymerization reaction: Add an initiation system to the solution after step S2 to initiate the polymerization reaction. The reaction is carried out under adiabatic conditions until the system temperature rises to the highest point and then is kept warm for aging. S4. Post-processing: The matured colloid is granulated, dried, and pulverized to obtain the comb-shaped polymeric polyacrylamide.

6. The preparation process of a comb-shaped ternary polymer according to claim 5, characterized in that, In step S1, the total mass concentration of monomer raw materials in the aqueous solution of the polymer monomer is controlled at 20.0%-35.0%; the pH value is adjusted to 6.5-7.5, and the adjusting agent used is an aqueous solution of sodium hydroxide.

7. The preparation process of a comb-shaped ternary polymer according to claim 5, characterized in that, In step S2, the inert gas is nitrogen, the deoxygenation time is 30-60 minutes, and the mass concentration of dissolved oxygen in the solution is controlled to be 0.01 mg / L-0.20 mg / L; The initiation temperature is controlled between 5.0℃ and 10.0℃.

8. The preparation process of a comb-shaped ternary polymer according to claim 5, characterized in that, In step S3, the order in which the initiation system is added is as follows: First add the oxidizing agent solution, then add the azo initiator solution, and finally add the reducing agent solution; After adding the initiation system, stir rapidly for 30-60 seconds, then stop stirring and seal the reaction system.

9. The preparation process of a comb-shaped ternary polymer according to claim 5, characterized in that, In step S3, the polymerization reaction under adiabatic conditions causes the system temperature to rise naturally to 85℃-98℃; The heat preservation and curing time is 2.0-4.0 hours.

10. The preparation process of a comb-shaped ternary polymer according to claim 5, characterized in that, In step S4, the drying temperature is controlled at 75℃-90℃, the drying time is 60-120 minutes, and the moisture content of the final product is controlled at 8.0%-10.0%.