Method for preparing polyvinyl alcohol hydrogel microparticles through emulsion crosslinking

Abstract

The invention provides a method for preparing polyvinyl alcohol hydrogel microparticles through emulsion crosslinking. The preparation method comprises the following steps: 1) dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol solution; 2) adding dialdehyde and an emulsifier into the polyvinyl alcohol solution, and uniformly mixing to obtain a water phase; 3) mixing the water phase and the oil phase, and emulsifying to obtain an emulsion; 4) adding a catalyst into the emulsion, and stirring to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles; and 5) carrying out solid-liquid separation on the reaction liquid containing the polyvinyl alcohol hydrogel microparticles to obtain precipitates which are the polyvinyl alcohol hydrogel microparticles.

Description

Technical Field

[0001] The invention relates to the field of oil and gas development, and in particular to a method for preparing polyvinyl alcohol hydrogel microparticles by emulsion cross-linking. Background Art

[0002] The Tahe Oilfield is a typical carbonate fracture-cavity high-temperature and high-salinity oil reservoir. The high water content problem of special oil fields such as high-temperature, high-salinity, fracture-cavity oil reservoirs is becoming increasingly prominent, and conventional deep profile adjustment and water plugging operations can no longer effectively solve the deep bypass problem.

[0003] The particle size of the plugging agent currently used is poorly matched to the size of the formation fracture, and there are problems of near-well accumulation and difficulty in plugging at the far end, with an overall efficiency of less than 35%. In addition, the plugging agents currently used are mainly flexible particles, polymer microspheres or pre-crosslinked bulk particles, of which the latter two are cross-linked polymers with acrylamide as the main monomer. This type of polymer plugging agent is easily hydrolyzed and degraded in high-temperature, high-mineralization water, and reacts with Ca 2+ Mg 2+ Coordination and complexation lead to coagulation, and the pre-crosslinked bulk particles are easily broken by extrusion, and will be completely degraded within a few days at high temperature (120°C), so they are not suitable for water plugging operations in high-temperature and high-salinity oil reservoirs. Although the rubber particles prepared from traditional rubber can resist high temperature and high mineralization, they have the disadvantages of difficult control of the compatibility of particles with formation pore throats, formation pollution, difficulty in reaching deep formations, and the rubber material is too hard and not easy to deform. Summary of the invention

[0004] One of the present inventions provides a method for preparing polyvinyl alcohol hydrogel microparticles, which comprises the following steps:

[0005] 1) dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol solution;

[0006] 2) adding dialdehyde and emulsifier to the polyvinyl alcohol solution, mixing evenly to obtain an aqueous phase;

[0007] 3) mixing the water phase and the oil phase, emulsifying, and obtaining an emulsion;

[0008] 4) adding a catalyst to the emulsion and stirring to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles;

[0009] 5) subjecting the reaction solution containing the polyvinyl alcohol hydrogel microparticles to solid-liquid separation, and obtaining the precipitate as the polyvinyl alcohol hydrogel microparticles.

[0010] In a specific embodiment, the degree of polymerization of the polyvinyl alcohol is 1700 to 2400.

[0011] In a specific embodiment, the alcoholysis degree of the polyvinyl alcohol is 88% to 99%.

[0012] In a specific embodiment, the dialdehyde is at least one of glyoxal, succinaldehyde, glutaraldehyde, terephthalaldehyde and isophthalaldehyde.

[0013] In a specific embodiment, the emulsifier is at least one of Tween, sodium dodecylbenzene sulfonate, Span, hexadecyltrimethylammonium bromide, sodium stearate and polyether silicone oil.

[0014] In a specific embodiment, the Tween is Tween 80 and / or Tween 60.

[0015] In one embodiment, the oil phase is alkane oil and / or chlorinated paraffin;

[0016] In a specific embodiment, the alkane oil is at least one of industrial white oil, naphthenic oil, diesel and kerosene.

[0017] In a specific embodiment, the viscosity of the alkane oil is 1 to 200 mPa·s, wherein the viscosity is the viscosity at 25°C.

[0018] In a specific embodiment, the chlorinated paraffin is chlorinated paraffin-42 and / or chlorinated paraffin-52.

[0019] In a specific embodiment, the catalyst is at least one of hydrogen chloride, sulfuric acid, phosphoric acid and p-toluenesulfonic acid.

[0020] In one specific embodiment, based on the total mass of the aqueous phase as 100%, the amount of the catalyst is 0.025% to 0.1%.

[0021] In one specific embodiment, in step 1), polyvinyl alcohol and an inorganic salt are dissolved in water to obtain a polyvinyl alcohol solution.

[0022] In a specific embodiment, the inorganic salt is at least one of chloride salt, bromide salt, iodide salt, sulfate salt, carbonate salt and nitrate salt.

[0023] In a specific embodiment, the inorganic salt is at least one of sodium chloride, potassium chloride, calcium chloride, sodium bromide, potassium bromide and sodium sulfate.

[0024] In a specific embodiment, based on the total mass of the aqueous phase being 100%, the concentration of the polyvinyl alcohol in the aqueous phase is 5% to 15%.

[0025] In a specific embodiment, the mass ratio of the water phase to the oil phase is 1:9 to 3:7.

[0026] In one embodiment, in step 4), the cross-linking reaction is carried out by stirring at 25 to 50° C. for 10 to 20 minutes to generate polyvinyl alcohol hydrogel microparticles.

[0027] Beneficial effects of the present invention:

[0028] (1) The present invention directly prepares microparticles from a solution state through in-situ crosslinking, without the need for secondary cutting and molding, making the preparation more convenient, and the microparticles do not adhere to each other;

[0029] (2) By adjusting the ratio of alkane oil and chlorinated paraffin and adding an emulsifier, the particle size of the polyvinyl alcohol hydrogel microparticles can be adjusted within the range of 0.1 to 5 mm, wherein the higher the content of chlorinated paraffin, the smaller the particle size.

[0030] (3) The flexibility of the polyvinyl alcohol hydrogel microparticles was controlled by adjusting the concentration of polyvinyl alcohol in the aqueous phase and the amount of dialdehyde. The storage modulus (1 Hz) of the polyvinyl alcohol hydrogel microparticles was adjustable within the range of 2728 to 12530 Pa, and the microparticles were able to pass through narrow channels by deformation and prevent reflux.

[0031] (4) The density of polyvinyl alcohol hydrogel is increased by adding inorganic salts, ranging from 0.99 to 1.15 g / cm 3 Adjustable.

[0032] (5) Solvent oil is easy to recycle, has low production costs, and can be promoted on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The following is a photograph showing the appearance of the polyvinyl alcohol hydrogel microparticles prepared in Example 1.

[0034] Figure 2 The following is a photograph showing the appearance of the polyvinyl alcohol hydrogel microparticles prepared in Example 2.

[0035] Figure 3 The following is a photograph showing the appearance of the polyvinyl alcohol hydrogel microparticles prepared in Example 3.

[0036] Figure 4 The following is a photograph showing the appearance of the polyvinyl alcohol hydrogel microparticles prepared in Example 4. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with examples, but the examples of the present invention are only exemplary descriptions, and the implementation manner does not constitute a limitation of the present invention under any circumstances.

[0038] Example 1

[0039] 1) Dissolve 20 g of polyvinyl alcohol 1799 (degree of polymerization: 1700, degree of alcoholysis: 99%) in 178 g of water to prepare a polyvinyl alcohol solution;

[0040] 2) adding 1 g of glutaraldehyde and 2 g of Tween 80 to the polyvinyl alcohol solution, mixing well to obtain an aqueous phase, wherein the concentration of the polyvinyl alcohol in the aqueous phase is 10%;

[0041] 3) adding 800 g of chlorinated paraffin-52 into the aqueous phase, and emulsifying with a homogenizer at a speed of 10000 r / min for 5 min to obtain an emulsion;

[0042] 4) adding 2 g of 10 wt% aqueous hydrochloric acid solution to the emulsion at a stirring speed of 700 r / min, and stirring at 25° C. for 20 min to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles; 5) centrifuging the reaction solution containing polyvinyl alcohol hydrogel microparticles at 5000 rpm for 5 min to separate the precipitate and obtain polyvinyl alcohol hydrogel microparticles.

[0043] Example 2

[0044] The 800 g of chlorinated paraffin-52 in Example 1 was replaced by 650 g of chlorinated paraffin-52 and 150 g of 5# industrial white oil, and the rest remained unchanged.

[0045] Example 3

[0046] The 800 g of chlorinated paraffin-52 in Example 1 was replaced by 473 g of chlorinated paraffin-52 and 327 g of 5# industrial white oil, and the rest remained unchanged.

[0047] Example 4

[0048] The 800 g of chlorinated paraffin-52 in Example 1 was replaced by 260 g of chlorinated paraffin-52 and 540 g of 5# industrial white oil, and the rest remained unchanged.

[0049] Example 5

[0050] The 800 g of chlorinated paraffin-52 in Example 1 was replaced by 800 g of 5# industrial white oil, and the rest remained unchanged.

[0051] Example 6

[0052] 1) 6 g of polyvinyl alcohol 2488 (degree of polymerization: 2400, degree of alcoholysis: 88%) was dissolved in 92 g of water to prepare a polyvinyl alcohol solution;

[0053] 2) adding 1 g of glutaraldehyde and 1 g of Tween 80 to the polyvinyl alcohol solution, mixing them evenly to obtain an aqueous phase, wherein the concentration of the polyvinyl alcohol in the aqueous phase is 6%;

[0054] 3) Add 900 g of 7# industrial white oil to the aqueous phase and emulsify for 5 min at a speed of 10000 r / min using a homogenizer to obtain an emulsion;

[0055] 4) adding 0.2 g phosphoric acid to the emulsion at a speed of 800 r / min, stirring at 35° C. for 20 min to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles; 5) centrifuging the reaction solution containing polyvinyl alcohol hydrogel microparticles at 6000 rpm for 15 min to separate and precipitate polyvinyl alcohol hydrogel microparticles.

[0056] Example 7

[0057] 1) dissolving 18 g of polyvinyl alcohol 2488 (degree of polymerization: 2400, degree of alcoholysis: 88%) in 276 g of water to prepare a polyvinyl alcohol solution;

[0058] 2) adding 3 g of glutaraldehyde and 3 g of Tween 80 to the polyvinyl alcohol solution, mixing them evenly to obtain an aqueous phase, wherein the concentration of the polyvinyl alcohol in the aqueous phase is 6%;

[0059] 3) Add 700 g of 7# industrial white oil to the aqueous phase and emulsify for 5 min at a speed of 10,000 r / min using a homogenizer to obtain an emulsion;

[0060] 4) adding 0.2 g of phosphoric acid to the emulsion at a rotation speed of 800 r / min, stirring at 35° C. for 20 min to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles;

[0061] 5) The reaction solution containing the polyvinyl alcohol hydrogel microparticles was centrifuged at 6000 rpm for 15 min to separate the precipitate and obtain the polyvinyl alcohol hydrogel microparticles.

[0062] Example 8

[0063] 1) 8 g of polyvinyl alcohol 1788 (degree of polymerization: 1700, degree of alcoholysis: 88%) was dissolved in 189 g of water to prepare a polyvinyl alcohol solution;

[0064] 2) adding 1 g of succinaldehyde and 2 g of Tween 60 to the polyvinyl alcohol solution, mixing well to obtain an aqueous phase, wherein the concentration of the polyvinyl alcohol in the aqueous phase is 4%;

[0065] 3) 250 g of 5# industrial white oil and 550 g of chlorinated paraffin-52 were mixed to prepare an oil phase;

[0066] 4) Then the water phase and the oil phase are mixed and emulsified at a speed of 15000 r / min for 10 min using a homogenizer to obtain an emulsion;

[0067] 5) adding 0.5 g of a 10 wt % sulfuric acid aqueous solution to the emulsion under stirring at a speed of 900 r / min, and stirring at 25° C. for 15 min to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles;

[0068] 6) The reaction solution containing polyvinyl alcohol hydrogel microparticles was centrifuged at 6000 rpm for 10 min to separate the precipitate and obtain polyvinyl alcohol hydrogel microparticles.

[0069] Example 9

[0070] 1) Dissolve 12 g of polyvinyl alcohol 1788 in 187 g of water to prepare a polyvinyl alcohol solution;

[0071] 2) to 6) are the same as in Example 7.

[0072] The concentration of polyvinyl alcohol in the water phase is 6%.

[0073] Example 10

[0074] 1) Dissolve 16 g of polyvinyl alcohol 1788 in 183 g of water to prepare a polyvinyl alcohol solution;

[0075] 2) to 6) are the same as in Example 7.

[0076] The concentration of polyvinyl alcohol in the water phase is 8%.

[0077] Embodiment 11

[0078] 1) Dissolve 20 g of polyvinyl alcohol 1788 in 177 g of water to prepare a polyvinyl alcohol solution;

[0079] 2) to 6) are the same as in Example 7.

[0080] The concentration of polyvinyl alcohol in the water phase is 10%.

[0081] Example 12

[0082] 1) Dissolve 24 g of polyvinyl alcohol 1788 in 173 g of water to prepare a polyvinyl alcohol solution;

[0083] 2) to 6) are the same as in Example 7.

[0084] The concentration of polyvinyl alcohol in the water phase is 12%.

[0085] Embodiment 13

[0086] 1) 30 g of polyvinyl alcohol 1799 (degree of polymerization: 1700, degree of alcoholysis: 99%), 10 g of calcium chloride, 15 g of potassium chloride and 5 g of sodium bromide were dissolved in 133 g of water to prepare a polyvinyl alcohol solution;

[0087] 2) adding 5 g of terephthalaldehyde and 2 g of sodium dodecylbenzene sulfonate to the polyvinyl alcohol solution, mixing them evenly to obtain an aqueous phase, wherein the concentration of the polyvinyl alcohol in the aqueous phase is 15%;

[0088] 3) 550 g of cyclohexane oil having a viscosity of 20 mPa·s at 25° C. and 250 g of chlorinated paraffin-42 are mixed to prepare an oil phase;

[0089] 4) Mix the water phase and the oil phase, and emulsify them with a homogenizer at a speed of 8000 r / min for 5 min to obtain an emulsion;

[0090] 5) adding 2 g of 10 wt % aqueous hydrochloric acid solution to the emulsion under stirring at 900 r / min, and stirring at 50° C. for 10 min to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles;

[0091] 6) The reaction solution containing polyvinyl alcohol hydrogel microparticles was centrifuged at 4000 rpm for 15 min to separate the precipitate and obtain polyvinyl alcohol hydrogel microparticles.

[0092] Embodiment 14

[0093] 1) 30 g of polyvinyl alcohol 1799 (degree of polymerization: 1700, degree of alcoholysis: 99%), 5 g of sodium sulfate and 10 g of potassium chloride were dissolved in 148 g of water to prepare a polyvinyl alcohol solution;

[0094] 2) to 6) are the same as in Example 12.

[0095] The concentration of polyvinyl alcohol in the water phase is 15%.

[0096] Embodiment 15

[0097] 1) 30 g of polyvinyl alcohol 1799 (degree of polymerization: 1700, degree of alcoholysis: 99%) and 5 g of potassium bromide were dissolved in 158 g of water to prepare a polyvinyl alcohol solution;

[0098] 2) to 6) are the same as in Example 12.

[0099] The concentration of polyvinyl alcohol in the water phase is 15%.

[0100] Example 16

[0101] 1) Dissolve 30 g of polyvinyl alcohol 1799 (degree of polymerization: 1700, degree of alcoholysis: 99%) in 163 g of water to prepare a polyvinyl alcohol solution;

[0102] 2) to 6) are the same as in Example 12.

[0103] The concentration of polyvinyl alcohol in the water phase is 15%.

[0104] Comparative Example 1

[0105] The glutaraldehyde in Example 1 was replaced by acetaldehyde, and the rest remained unchanged.

[0106] Comparative Example 2

[0107] 1) Dissolve 20 g of polyvinyl alcohol 1799 (degree of polymerization: 1700, degree of alcoholysis: 99%) in 177 g of water to prepare a polyvinyl alcohol solution with a concentration of 10%;

[0108] 2) Add 1 g of glutaraldehyde and 2 g of 10 wt % aqueous hydrochloric acid solution to the polyvinyl alcohol solution, mix well and let stand at 25° C. for 24 hours to obtain a PVA hydrogel.

[0109] 3) Add 50 g of PVA hydrogel and 500 g of water into a SC-8022 wall-breaking machine, break for 5 minutes, and filter to obtain PVA hydrogel particles.

[0110] The particle size of the polyvinyl alcohol hydrogel microparticles was observed and measured, and the particle size results are shown in Table 1. The polyvinyl alcohol hydrogel microparticles were left for a week, and 1 g of the particles were added to 10 g of deionized water to observe whether they could be completely dispersed.

[0111] Comparative Example 3

[0112] 1) to 4) are the same as in Example 7.

[0113] 5) adding 0.5 g of ionized water to the emulsion under stirring at a speed of 900 r / min, and stirring at 25° C. for 15 min to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles;

[0114] 6) Same as Example 7.

[0115] Comparative Example 4

[0116] 1) Same as Example 12.

[0117] 2) adding 5 g of terephthalaldehyde to the polyvinyl alcohol solution and mixing well to obtain an aqueous phase;

[0118] 3) to 6) are the same as in Example 12.

[0119] Test Example 1

[0120] The products prepared in Examples 1 to 16 and Comparative Examples 1 to 4 were observed immediately after preparation and the particle sizes were measured with a vernier caliper. Figures 1 to 4 The median particle size results of the products prepared in each embodiment and comparative example are shown in Table 1.

[0121] The products prepared in Examples 1 to 16 and Comparative Examples 1 to 4 were left for 7 days, 1 g of the products were added to 10 g of deionized water, and the dispersion state in the water was observed. See Table 1.

[0122] From the data in Table 1, it can be seen that Examples 1 to 6 can all obtain polyvinyl alcohol hydrogel particles of relatively uniform size, and after being placed for a period of time, the particles do not adhere to each other and have good storage properties. In Comparative Example 1, hydrogel particles cannot be obtained by simply replacing the dialdehyde with a monoaldehyde, indicating that dialdehyde is indispensable in the preparation process of polyvinyl alcohol hydrogel particles. Comparative Example 2 uses a traditional method to first crosslink PVA to obtain a hydrogel, and then obtain PVA hydrogel particles by a physical crushing method. The hydrogel particles obtained by this method have a wide particle size distribution, and after being placed for a period of time, they adhere to each other. According to the particle size results of Examples 1 to 5, hydrogel particles of different particle sizes can be obtained by changing the ratio of chlorinated paraffin and white oil. As the amount of chlorinated paraffin used increases, particles with smaller particle sizes can be prepared.

[0123] Table 1

[0124] Example Median particle size (mm) Dispersion state in water after 7 days Example 1 0.1±0.03 Complete dispersion, no sticking Example 2 0.3±0.1 Complete dispersion, no sticking Example 3 0.5±0.1 Complete dispersion, no sticking Example 4 1.5±0.5 Complete dispersion, no sticking Example 5 2.5±0.5 Complete dispersion, no sticking Example 6 5±1 Complete dispersion, no sticking Example 7 3.0±0.5 Complete dispersion, no sticking Example 8 0.3±0.1 Complete dispersion, no sticking Example 9 0.3±0.1 Complete dispersion, no sticking Example 10 0.4±0.1 Complete dispersion, no sticking Embodiment 11 0.5±0.2 Complete dispersion, no sticking Example 12 0.6±0.2 Complete dispersion, no sticking Embodiment 13 1.8±0.6 Complete dispersion, no sticking Embodiment 14 1.6±0.5 Complete dispersion, no sticking Embodiment 15 1.6±0.5 Complete dispersion, no sticking Example 16 1.4±0.5 Complete dispersion, no sticking Comparative Example 1 Not granulated Comparative Example 2 2.6±2.5 Stick together Comparative Example 3 Not granulated — Comparative Example 4 Not granulated —

[0125] Test Example 2

[0126] 10 g of the products prepared in Examples 1 to 16 and Comparative Examples 1 to 4, 1 g of the polyvinyl alcohol solution prepared in step 1) in Examples 1 to 16 and Comparative Examples 1 to 4 (the type and amount of polyvinyl alcohol correspond to the examples or comparative examples corresponding to the obtained products), 0.05 g of succinaldehyde and 0.02 g of a 10 wt % aqueous sulfuric acid solution were mixed uniformly and then placed in a The cylindrical mold was cured at 25°C for 24 hours to obtain a cylindrical sample, which was cut into a disc sample with a thickness of 2±0.5 mm using a cutter. The three rheological performance indicators of storage modulus, loss modulus and complex viscosity were tested using a HAAKE MARS 3 rheometer. The experimental conditions were 25°C, strain 1%, and frequency 1Hz. The results are shown in Table 2.

[0127] Table 2

[0128]

[0129] According to the results of Examples 7 to 11 in Table 2, by using the method provided by the present invention, the concentration of the polyvinyl alcohol solution in step 1) is adjusted to obtain hydrogel particles with different softness. In addition, in Comparative Example 3, based on Example 7, sulfuric acid is replaced with deionized water, and no hydrogel particles can be obtained, indicating that acid is a necessary component of the preparation method of the present invention.

[0130] Test Example 3

[0131] 5 g of the products prepared in Examples 1 to 16 and Comparative Examples 1 to 4 were added to a 25 mL volumetric flask and the volume was fixed to 25 mL. The volume of each product was calculated based on the volume of water added, and then the density of each product was calculated. The results are shown in Table 3.

[0132] Table 3

[0133] Example <![CDATA[Particle density (g / cm 3 )]]> Example 1 1.00 Example 2 0.99 Example 3 1.00 Example 4 1.00 Example 5 0.99 Example 6 1.01 Example 7 0.99 Example 8 1.00 Example 9 1.00 Example 10 1.00 Embodiment 11 1.01 Example 12 1.14 Embodiment 13 1.07 Embodiment 14 1.02 Embodiment 15 0.99 Comparative Example 1 — Comparative Example 2 0.99 Comparative Example 3 — Comparative Example 4 —

[0134] According to the results of Examples 7 to 11 in Table 3, by using the method provided by the present invention, adding inorganic salts to the polyvinyl alcohol solution in step 1) can increase the density of the polyvinyl alcohol hydrogel particles, and the density gradually increases with the increase in the amount added. In addition, in Comparative Example 4, based on Example 12, sodium dodecylbenzene sulfonate was removed, and no hydrogel particles could be obtained, indicating that the emulsifier is a necessary component of the preparation method of the present invention.

[0135] Although the present invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes may be made without departing from the true spirit and scope of the present invention. In addition, the subject matter, spirit and scope of the present invention may be varied to accommodate specific situations, materials, material combinations and methods. All of these changes are included within the scope of the claims of the present invention.

Claims

1. A method for preparing polyvinyl alcohol hydrogel microparticles, comprising the following steps: 1) dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol solution; 2) adding dialdehyde and emulsifier to the polyvinyl alcohol solution, mixing evenly to obtain an aqueous phase; 3) mixing the water phase and the oil phase, emulsifying, and obtaining an emulsion; 4) adding a catalyst to the emulsion and stirring to obtain a reaction solution containing polyvinyl alcohol hydrogel microparticles; 5) subjecting the reaction solution containing the polyvinyl alcohol hydrogel microparticles to solid-liquid separation, and obtaining the precipitate as the polyvinyl alcohol hydrogel microparticles.

2. The method according to claim 1, characterized in that The degree of polymerization of the polyvinyl alcohol is 1700 to 2400; Preferably, the alcoholysis degree of the polyvinyl alcohol is 88% to 99%.

3. The method according to claim 1, characterized in that The dialdehyde is at least one of glyoxal, succinaldehyde, glutaraldehyde, terephthalaldehyde and isophthalaldehyde.

4. The method according to claim 1, characterized in that: The emulsifier is at least one of Tween, sodium dodecylbenzene sulfonate, Span, hexadecyltrimethylammonium bromide, sodium stearate and polyether silicone oil; Preferably, the Tween is Tween 80 and / or Tween 60.

5. The method according to claim 1, characterized in that The oil phase is alkane oil and / or chlorinated paraffin; Preferably, the alkane oil is at least one of industrial white oil, naphthenic oil, diesel and kerosene; Preferably, the viscosity of the alkane oil is 1 to 200 mPa·s; Preferably, the chlorinated paraffin is chlorinated paraffin-42 and / or chlorinated paraffin-52.

6. The method according to claim 1, characterized in that The catalyst is at least one of hydrogen chloride, sulfuric acid, phosphoric acid and p-toluenesulfonic acid; Preferably, based on the total mass of the aqueous phase as 100%, the amount of the catalyst used is 0.025% to 0.1%.

7. The method according to claim 1, characterized in that In step 1), polyvinyl alcohol and an inorganic salt are dissolved in water to obtain a polyvinyl alcohol solution; Preferably, the inorganic salt is at least one of chloride, bromide, iodide, sulfate, carbonate and nitrate; Preferably, the inorganic salt is at least one of sodium chloride, potassium chloride, calcium chloride, sodium bromide, potassium bromide and sodium sulfate.

8. The method according to claim 1, characterized in that Taking the total mass of the water phase as 100%, the concentration of the polyvinyl alcohol in the water phase is 5% to 15%.

9. The method according to claim 1, characterized in that: The mass ratio of the water phase to the oil phase is 1:9 to 3:

7.

10. The method according to claim 1, characterized in that In step 4), a cross-linking reaction is carried out by stirring at 25 to 50° C. for 10 to 20 minutes to generate polyvinyl alcohol hydrogel microparticles.

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