Preparation method of low-temperature-resistant water-in-water emulsion

Abstract

The invention relates to the technical field of water-soluble polymers, in particular to a preparation method of a low-temperature-resistant water-in-water emulsion, which comprises the following steps: mixing acrylamide, an anionic monomer, a hydrophobic monomer, a dispersing agent, a chain transfer agent and water, adjusting the pH value, mixing with a stabilizer, introducing nitrogen, sequentially adding an oxidizing agent and a reducing agent to initiate a polymerization reaction, and cooling to obtain the low-temperature-resistant water-in-water emulsion. Quickly adjusting the stirring speed when the viscosity of the mixed system is increased, always keeping vortex at the center of the liquid level in the reaction process, and adjusting the stirring speed to continue the reaction after the polymerization system forms emulsion drops; and when the temperature of the polymerization system begins to reduce, adding an excessive amount of a reducing agent into the reaction system to continue the reaction, and obtaining the low-temperature-resistant water-in-water emulsion after the reaction is finished. The emulsion has the advantages of low apparent viscosity, high dissolution speed, small environmental damage, low temperature resistance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of water-soluble polymers, and more specifically, to a method for preparing a water-in-water emulsion with low-temperature resistance. Background Art

[0002] An emulsion is a colloidal system composed of two thermodynamically incompatible phases, where the dispersed phase exists in the form of droplets in the other phase, and the droplet structure is maintained by a stabilizer. It has various functions such as thickening, flocculation, drag reduction, defoaming, lubrication, and emulsification, and is widely used in the fields of oil fields, papermaking, coatings, and water treatment. Traditional emulsions are mainly oil-in-water and water-in-oil emulsions, which often contain a large amount of surfactants and oil-phase solvents, causing great pollution to the environment during production and use.

[0003] With the continuous in-depth research on aqueous polymers, the current research direction of emulsions has further focused on new, efficient, low-pollution, and low-cost green products. As a safe and effective product, the water-in-water emulsion can effectively solve the environmental pollution problems brought by traditional oil-water emulsions and has broad application prospects.

[0004] However, in practical applications, the water-in-water emulsion is limited due to problems such as high apparent viscosity, poor stability, and low active content. In response to the above problems, scientists and engineers have carried out a series of research and explorations and achieved certain results. For example, the relative stability of the emulsion is improved by particle stabilization and continuous-phase gel stabilization methods. In recent years, it has been found that polymers can also stabilize water-in-water emulsions. Xu Junying et al. synthesized an anionic surfactant as a stabilizer by monomer copolymerization, and the prepared polymer emulsion has good stability (CN 104774289 B A method for preparing a "water-in-water" type hydrophobically associating polyacrylamide emulsion). Rong Minjie et al. synthesized a water-in-water type cationic polyacrylamide emulsion, and its effective content reached 40-43%. When used as a papermaking retention aid, the dosage is reduced by 28-41% compared with conventional cationic polyacrylamide (CN108690171 B A water-in-water type cationic polyacrylamide emulsion, its preparation method and application).

[0005] Up to now, the research on the stability of water-in-water emulsions mainly focuses on the synthesis of various polymer stabilizers, but there are few reports on the stability of water-in-water emulsions under low-temperature conditions. Therefore, it is urgent to develop a water-in-water emulsion with low cost, simple preparation method, and long-term stable storage at low temperature, so as to solve the problem of limited application of water-in-water emulsions in terms of time and space. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a low-temperature resistant water-in-water emulsion. Different from the current research on conventional cationic and anionic polymer stabilizers, the present invention uses polyvinyl alcohol rich in hydroxyl groups as a stabilizer. The hydroxyl groups in the polyvinyl alcohol molecular chain have strong polarity and are easily adsorbed on the surface of emulsion droplets to form a protective film. The adsorbed polyvinyl alcohol molecules form a physical barrier between the droplets through the extended flexible chain segments, which can effectively avoid particle collision or aggregation caused by the weakened Brownian motion at low temperatures. The hydrogen bond network formed between polyvinyl alcohol molecules and with water molecules will be enhanced at low temperatures, reducing the freezing point of the solution and inhibiting the phase separation caused by freezing. This method has the advantages of simple operation, safety, pollution-free, and stable storage at low temperatures.

[0007] In order to achieve the above object, a method for preparing a low-temperature resistant water-in-water emulsion according to the present invention is characterized by comprising the following steps: (1) Mix acrylamide, an anionic monomer, a hydrophobic monomer, a dispersant, a chain transfer agent and water, and adjust the pH value to 6.5 - 7; (2) Mix the mixed system obtained in step (1) with a stabilizer, set the stirring speed to 500 - 800 rpm, and stir for 5 min; (3) Pass nitrogen into the mixed system in step (2) for 30 min, and then sequentially add an oxidant and a reductant to initiate a polymerization reaction, and set the stirring speed to 300 - 500 rpm; (4) When the viscosity of the mixed system increases, quickly adjust the stirring speed to 500 - 1500 rpm, always keep a vortex in the center of the liquid surface during the reaction process, and maintain the reaction temperature below 55 °C for 1 h; (5) Under the action of high shear, the polymerization reaction gradually transitions from aqueous solution polymerization to quasi-emulsion polymerization, reduce the stirring speed to 300 - 800 rpm, and continue the reaction for 10 - 30 min; (6) Aging: When the temperature of the polymerization system begins to decrease, add an excessive amount of reductant to the reaction system and continue the reaction for 20 - 30 min, set the stirring speed to 300 - 500 rpm, and the low-temperature resistant water-in-water emulsion of the present invention can be obtained after the reaction ends.

[0008] In the present invention, in step (1), acrylamide, an anionic monomer, a hydrophobic monomer, a dispersant, a chain transfer agent and water are mixed, and stirring is to accelerate the dissolution of the monomers in water; The preferred method for step (l) includes: the acrylamide, anionic monomer and hydrophobic monomer are 15 wt% - 20 wt% of the total mass of the reaction system; the molar ratio of acrylamide, anionic monomer and hydrophobic monomer is (60 - 90):(9 - 39):(1 - 5); The anionic monomer is one or more of acrylic acid, methacrylic acid, vinylsulfonic acid, vinylphosphonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and is further preferably 2-acrylamido-2-methylpropanesulfonic acid; The hydrophobic monomer is one or more of methyl acrylate, butyl acrylate, glycidyl methacrylate, isobutyl methacrylate, and is further preferably methyl acrylate; The dispersant is one or more of sodium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, and is further preferably ammonium sulfate; The dispersant accounts for 15 wt%-18 wt% of the total mass of the reaction system; The selection of the dispersant mainly considers two aspects: one is that it can effectively play the salting-out effect, that is, it can quickly and effectively make the polymer continuously precipitate and reduce the high viscosity generated during the polymerization process; the other is that the dispersant is required to have a high solubility and cannot interfere with the dissolution of the monomer.

[0009] The chain transfer agent is one or more of sodium formate, isopropanol, mercaptoethanol, and is further preferably sodium formate; The chain transfer agent is 0.05 wt%-0.5 wt% of the total mass of the monomer.

[0010] In the present invention, step (2): Mix and stir the mixed system obtained in step (1) with a stabilizer, and set the stirring speed to 500-800 rpm; Rapid stirring can accelerate the dissolution and dispersion of the stabilizer and effectively avoid the instability of the product composition and performance caused by uneven dispersion of the dispersant; The method of step (2) is preferably: The stabilizer is one or more of polyethylene glycol 20000, polyvinylpyrrolidone, polyvinyl alcohol, hydroxypropyl methylcellulose, and is further preferably polyvinyl alcohol; The stabilizer accounts for 3 wt%-7 wt% of the total mass of the reaction system.

[0011] In the present invention, step (3): Add an initiator to the mixed system in step (2) to initiate a polymerization reaction, and set the stirring speed to 300-500 rpm; The method of step (3) is preferably: In the redox initiation system, the oxidant is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, potassium bromate; In the redox initiation system, the reducing agent is one or more of sodium bisulfite, sodium metabisulfite, ferrous sulfate; It is further preferably the ammonium persulfate / sodium metabisulfite redox system; The initiator is 0.1 wt%-0.5 wt% of the total mass of the monomer.

[0012] In the present invention, step (4): When the viscosity of the mixed system increases, quickly adjust the stirring speed to 500-1500 rpm, and always keep a vortex in the center of the liquid surface during the reaction process; The method of step (4) preferably includes: after the polymerization reaction occurs and when the viscosity of the system increases or the rod climbing phenomenon appears, immediately adjust the stirring speed to 800 - 1500 rpm.

[0013] In the present invention, step (5): after the polymerization system forms emulsion droplets, adjust the stirring speed to 300 - 500 rpm. The function of stirring is to disperse the materials and accelerate the mass transfer efficiency. After the formation of emulsion droplets, since the active free radicals are wrapped inside the emulsion droplets, the polymerization reaction transfers to the inside of the emulsion droplets, and the function of stirring is to promote the diffusion of monomers into the emulsion droplets.

[0014] The preparation method of the low-temperature water-in-water emulsion provided by the present invention has the following beneficial effects: (1) The preparation method of the present invention is simple, the product has a low apparent viscosity, a fast dissolution rate, and little environmental pollution.

[0015] (2) The present invention uses polyvinyl alcohol as a stabilizer. By utilizing the strong polar hydroxyl groups and the extended flexible chain segments in its molecular chain, and by adsorbing on the surface of the emulsion droplets and forming a physical barrier between the droplets, it can effectively avoid particle collision or aggregation caused by the weakening of Brownian motion at low temperatures and maintain the stability of the emulsion. In addition, the hydrogen bond network formed between polyvinyl alcohol molecules and with water molecules will be enhanced at low temperatures, reducing the freezing point of the solution and inhibiting phase separation caused by freezing, enabling stable storage for more than 6 months at a relatively low temperature.

[0016] (3) The water-in-water emulsion prepared by the present invention introduces a trace amount of hydrophobic monomers, which increases the viscosity-average relative molecular weight of the polymer emulsion, effectively increases the dilution viscosity of the emulsion, and at the same time reduces the affinity between the polymer molecules and the reservoir, and can be used as a thickening agent or drag reducer for fracturing. Specific Embodiments

[0017] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments include but are not limited to this. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] Example 1: (1) Mix 56.8 g of acrylamide, 28.5 g of 2-acrylamido-2-methylpropanesulfonic acid, 4.7 g of methyl acrylate, 78 g of ammonium sulfate and 0.2 g of sodium formate and dissolve them in 172 g of deionized water, and adjust the pH value to 6.8 with NaOH; (2) Then mix the mixed solution with 110 g of polyvinyl alcohol solution (18.7 g of polyvinyl alcohol), and stir at a speed of 500 rpm for 5 min; (3) Then, nitrogen gas was introduced into the mixed system and stirred at a speed of 500 rpm for 30 min. The temperature of the system was controlled at about 25 °C. Then, the stirring speed was reduced to 300 rpm, 100 mg of ammonium persulfate as the oxidant was added, and a 5.0 g / L sodium metabisulfite solution was slowly added dropwise at a rate of 1 mL / h; (4) When the viscosity of the system increased, the rotation speed was adjusted to 1000 rpm. There was always a vortex in the center of the liquid surface of the reaction system, and the reaction was maintained at a temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changed from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system began to decrease. The stirring speed was adjusted to 450 rpm and the reaction continued for 30 min; (6) When the temperature of the polymerization system began to drop, the stirring speed was reduced to 300 rpm, and the reducing agent sodium metabisulfite was added to continue the reaction for 30 min. After the polymerization reaction was completed, the low-temperature water-in-water emulsion of the present invention could be obtained.

[0019] Example 2: (1) 68 g of acrylamide, 19.4 g of 2-acrylamido-2-methylpropanesulfonic acid, 2.6 g of methyl acrylate, 70 g of ammonium sulfate and 0.2 g of sodium formate were mixed and dissolved in 170 g of deionized water, and the pH value was adjusted to 6.8 with NaOH; (2) Then, the mixed solution was mixed with 120 g of polyvinyl alcohol solution (24 g of polyvinyl alcohol) and stirred at a speed of 500 rpm for 5 min; (3) Then, nitrogen gas was introduced into the mixed system and stirred at a speed of 500 rpm for 30 min. The temperature of the system was controlled at about 25 °C. Then, the stirring speed was reduced to 300 rpm, 200 mg of ammonium persulfate as the oxidant was added, and a 10 g / L sodium metabisulfite solution was slowly added dropwise at a rate of 1 mL / h; (4) When the viscosity of the system increased, the rotation speed was adjusted to 1000 rpm. There was always a vortex in the center of the liquid surface of the reaction system, and the reaction was maintained at a temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changed from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system began to decrease. The stirring speed was adjusted to 450 rpm and the reaction continued for 30 min; (6) When the temperature of the polymerization system began to drop, the stirring speed was reduced to 300 rpm, and the reducing agent sodium metabisulfite was added to continue the reaction for 30 min. After the polymerization reaction was completed, the low-temperature water-in-water emulsion of the present invention could be obtained.

[0020] Example 3: (1) Dissolve 68 g of acrylamide, 19.4 g of 2-acrylamido-2-methylpropanesulfonic acid, 2.6 g of methyl acrylate, 80 g of ammonium sulfate and 0.2 g of sodium formate in 170 g of deionized water, and adjust the pH value to 6.8 with NaOH; (2) Then mix the mixed solution with 110 g of polyvinyl alcohol solution (18 g of polyvinyl alcohol), and stir at 500 rpm for 5 min; (3) Then introduce nitrogen into the mixed system and stir at 500 rpm for 30 min, control the system temperature at about 25 °C, then reduce the stirring speed to 300 rpm, add 200 mg of ammonium persulfate as an oxidant and slowly dropwise add 10 g / L of sodium metabisulfite solution at a rate of 1 mL / h; (4) When the viscosity of the system increases, adjust the rotation speed to 800 rpm, always keep a vortex at the center of the liquid surface of the reaction system and maintain the system temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changes from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system begins to decrease, adjust the stirring speed to 450 rpm and continue the reaction for 30 min; (6) When the temperature of the polymerization system begins to drop, reduce the stirring speed to 300 rpm, add sodium metabisulfite as a reducing agent and continue the reaction for 30 min. After the polymerization reaction is completed, the low-temperature water-in-water emulsion of the present invention can be obtained.

[0021] Example 4: (1) Dissolve 68 g of acrylamide, 19.4 g of 2-acrylamido-2-methylpropanesulfonic acid, 2.6 g of methyl acrylate, 80 g of ammonium sulfate and 0.2 g of sodium formate in 170 g of deionized water, and adjust the pH value to 6.8 with NaOH; (2) Then mix the mixed solution with 120 g of polyvinyl alcohol solution (24 g of polyvinyl alcohol), and stir at 500 rpm for 5 min; (3) Then introduce nitrogen into the mixed system and stir at 500 rpm for 30 min, control the system temperature at about 25 °C, then reduce the stirring speed to 300 rpm, add 200 mg of ammonium persulfate as an oxidant and slowly dropwise add 10 g / L of sodium metabisulfite solution at a rate of 1 mL / h; (4) When the viscosity of the system increases, adjust the rotation speed to 1000 rpm, always keep a vortex at the center of the liquid surface of the reaction system and maintain the system temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changes from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system begins to decrease, adjust the stirring speed to 450 rpm and continue the reaction for 30 min; (6) When the temperature of the polymerization system starts to drop, reduce the stirring speed to 300 rpm, add sodium metabisulfite as the reducing agent and continue the reaction for 30 min. After the polymerization reaction is completed, the low-temperature-resistant water-in-water emulsion of the present invention can be obtained.

[0022] Example 5: (1) Dissolve 50 g of acrylamide, 38.3 g of 2-acrylamido-2-methylpropanesulfonic acid, 1.7 g of methyl acrylate, 80 g of ammonium sulfate and 0.2 g of sodium formate in 190 g of deionized water, and adjust the pH value to 6.8 with NaOH; (2) Then mix the mixed solution with 90 g of polyvinyl alcohol solution (16.2 g of polyvinyl alcohol), and stir at 500 rpm for 5 min; (3) Then introduce nitrogen into the mixed system and stir at 500 rpm for 30 min, control the system temperature at about 25 °C, then reduce the stirring speed to 300 rpm, add 300 mg of ammonium persulfate as the oxidizing agent and slowly dropwise add an 8 g / L sodium metabisulfite solution at a rate of 2 mL / h; (4) When the viscosity of the system increases, adjust the rotation speed to 1000 rpm, always keep a vortex at the center of the liquid surface of the reaction system and maintain the system temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changes from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system starts to decrease, adjust the stirring speed to 450 rpm and continue the reaction for 30 min; (6) When the temperature of the polymerization system starts to drop, reduce the stirring speed to 300 rpm, add sodium metabisulfite as the reducing agent and continue the reaction for 30 min. After the polymerization reaction is completed, the low-temperature-resistant water-in-water emulsion of the present invention can be obtained.

[0023] Comparative Example 1: (1) Dissolve 50 g of acrylamide, 38.3 g of 2-acrylamido-2-methylpropanesulfonic acid, 1.7 g of methyl acrylate, 80 g of ammonium sulfate and 0.2 g of sodium formate in 190 g of deionized water, and adjust the pH value to 6.8 with NaOH; (2) Then mix the mixed solution with 120 g of sodium dodecyl sulfate solution (24 g of sodium dodecyl sulfate), and stir at 500 rpm for 5 min; (3) Then introduce nitrogen into the mixed system and stir at 500 rpm for 30 min, control the system temperature at about 25 °C, then reduce the stirring speed to 300 rpm, add 300 mg of ammonium persulfate as the oxidizing agent and slowly dropwise add an 8 g / L sodium metabisulfite solution at a rate of 2 mL / h; (4) When the viscosity of the system increases, adjust the rotation speed to 1000 rpm, and always keep a vortex at the center of the liquid surface of the reaction system and maintain the system temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changes from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system begins to decrease. Adjust the stirring speed to 450 rpm and continue the reaction for 30 min; (6) When the temperature of the polymerization system begins to drop, reduce the stirring speed to 300 rpm, add the reducing agent sodium metabisulfite and continue the reaction for 30 min. After the polymerization reaction is completed, an emulsion can be obtained.

[0024] Comparative Example 2: (1) Dissolve 68 g of acrylamide, 19.4 g of 2-acrylamido-2-methylpropanesulfonic acid, 2.6 g of methyl acrylate, 80 g of ammonium sulfate and 0.2 g of sodium formate in 170 g of deionized water, and adjust the pH value to 6.8 with NaOH; (2) Then mix the mixed solution with 120 g of sodium dodecyl sulfate solution (24 g of sodium dodecyl sulfate) and stir at 500 rpm for 5 min; (3) Then introduce nitrogen into the mixed system and stir at 500 rpm for 30 min, control the system temperature at about 25 °C, then reduce the stirring speed to 300 rpm, add 200 mg of the oxidant ammonium persulfate and slowly dropwise add a 10 g / L sodium metabisulfite solution at a rate of 1 mL / h; (4) When the viscosity of the system increases, adjust the rotation speed to 1000 rpm, and always keep a vortex at the center of the liquid surface of the reaction system and maintain the system temperature below 55 °C for 1 h; (5) When the polymerization reaction gradually changes from aqueous solution polymerization to quasi-emulsion polymerization to form emulsion droplets, the viscosity of the system begins to decrease. Adjust the stirring speed to 450 rpm and continue the reaction for 30 min; (6) When the temperature of the polymerization system begins to drop, reduce the stirring speed to 300 rpm, add the reducing agent sodium metabisulfite and continue the reaction for 30 min. After the polymerization reaction is completed, an emulsion can be obtained.

[0025] In order to further prove the technical effects of the present invention, the various indicators of the examples will now be evaluated.

[0026] Test the viscosity, shear stability, sand-carrying rate, and salt tolerance of the product according to the standard Q / JRF135-2021 "Polymer Thickening Agent JRYLZG for Fracturing". The test results are shown in Table 1.

[0027]

[0028] Table 1 shows the test results. For the water-in-water emulsions using different stabilizers, except for the apparent viscosity, there are obvious differences in the test data, and there are no significant differences in other indicators. The reason for this phenomenon is that the viscosity and relative movement resistance of the dispersed droplets formed by the stabilizer used in the present invention are small, and the apparent viscosity is correspondingly low.

[0029] Stability test: Referring to GB / T1603-2001 (Determination method for the stability of pesticide emulsions), the samples of the examples and comparative examples were respectively transferred to the test vessels, and subjected to static stability and freeze-thaw stability test treatments. The upper-layer emulsion after the corresponding treatment was diluted into a 1wt% aqueous solution, and the viscosity was measured with a six-speed rotary viscometer. The viscosity of the solution is related to the polymer content, and the stability of the emulsion was measured by the change in viscosity; the test results are shown in Table 2.

[0030]

[0031] The dispersed droplet size formed by the stabilizer used in the present invention is smaller than that of other conventional stabilizers, the specific surface area is larger, the surface energy is higher, and the mutual repulsion between droplets is stronger, making it difficult for the droplets to collide and coalesce, so it is also more stable. In addition, due to the multi-hydroxy structure of the stabilizer itself, the emulsion still maintains good stability at a lower temperature, is less affected by temperature during the freeze-thaw experiment, and exhibits good low-temperature resistance.

Claims

1. A method for preparing a low-temperature resistant water-in-water emulsion, characterized in that: It includes the following steps: (1) Mix acrylamide, an anionic monomer, a hydrophobic monomer, a dispersant, a chain transfer agent and water, and adjust the pH value to 6.5 - 7; (2) Mix the mixed system obtained in step (1) with a stabilizer, set the stirring speed at 500 - 800 rpm, and stir for 5 min; (3) Pass nitrogen into the mixed system in step (2) for 30 min, then sequentially add an oxidant and a reductant to initiate the polymerization reaction, and set the stirring speed at 300 - 500 rpm; (4) When the viscosity of the mixed system increases, quickly adjust the stirring speed to 500 - 1500 rpm, always keep a vortex at the center of the liquid surface during the reaction, and maintain the reaction temperature below 55°C for 1 h; (5) Under high - shear action, the polymerization reaction gradually transitions from aqueous solution polymerization to quasi - emulsion polymerization, reduce the stirring speed to 300 - 800 rpm, and continue the reaction for 10 - 30 min; (6) Aging: When the temperature of the polymerization system begins to decrease, add an excessive amount of reductant to the reaction system and continue the reaction for 20 - 30 min, set the stirring speed at 300 - 500 rpm, and the low - temperature water - in - water emulsion of the present invention can be obtained after the reaction ends.

2. The method for preparing the low-temperature resistant water-in-water emulsion according to claim 1, characterized in that, The acrylamide, anionic monomer and hydrophobic monomer are 15 wt% - 20 wt% of the total mass of the reaction system; the molar ratio of acrylamide, anionic monomer and hydrophobic monomer is (60 - 90):(9 - 39):(1 - 5).

3. The method for preparing a low-temperature resistant water-in-water emulsion according to claim 1 or 2, characterized in that, The anionic monomer is one or more of acrylic acid, methacrylic acid, vinylsulfonic acid, vinylphosphonic acid, p - styrenesulfonic acid, 2 - acrylamido - 2 - methylpropanesulfonic acid, and is further preferably 2 - acrylamido - 2 - methylpropanesulfonic acid; the hydrophobic monomer is one or more of methyl acrylate, butyl acrylate, glycidyl methacrylate, isobutyl methacrylate, and is further preferably methyl acrylate.

4. The method for preparing a low-temperature resistant water-in-water emulsion according to claim 1, characterized in that, The dispersant is one or more of sodium chloride, sodium sulfate, potassium sulfate, ammonium sulfate; it is further preferably ammonium sulfate; the dispersant is 15 wt% - 20 wt% of the total mass of the reaction system.

5. The method for preparing a low-temperature resistant water-in-water emulsion according to claim 1, characterized in that, The stabilizer is one or more of polyethylene glycol 20000, polyvinylpyrrolidone, polyvinyl alcohol, hydroxypropyl methylcellulose; it is further preferably polyvinyl alcohol; the stabilizer is 3 wt% - 7 wt% of the total mass of the reaction system.

6. The method for preparing a low-temperature resistant water-in-water emulsion according to claim 1, wherein, In the redox initiation system, the oxidant is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, potassium bromate; the reductant in the redox initiation system is one or more of sodium bisulfite, sodium metabisulfite, ferrous sulfate; it is further preferably the ammonium persulfate / sodium metabisulfite redox system; the initiator is 0.1 wt% - 0.5 wt% of the total mass of the monomers.

7. The method for preparing a low-temperature resistant water-in-water emulsion according to claim 1, wherein The chain transfer agent is one or more of sodium formate, isopropyl alcohol, mercaptoethanol, and is further preferably sodium formate; the chain transfer agent is 0.05 wt% - 0.5 wt% of the total mass of the monomers.

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