Pressure-resistant thermal expansion microcapsule and preparation method thereof

Abstract

The application relates to the technical field of thermal expansion microcapsules, in particular to a pressure-resistant thermal expansion microcapsule and a preparation method thereof, which comprises the following steps: 1) mixing a dispersion medium, an inorganic salt, a dispersion stabilizer and a dispersion stabilizing aid to obtain an aqueous phase; 2) mixing monomers, an initiator, a crosslinking agent and a foaming agent to obtain an oil phase; 3) uniformly stirring the oil phase and the aqueous phase to obtain a suspension; and 4) filtering and drying the pressure-resistant thermal expansion microcapsule obtained by polymerizing the suspension under an inert atmosphere at 40-80 DEG C and under a pressure of 0.01-1 MPa for 10-25 hours.

Description

Technical Field

[0001] This invention relates to the field of thermal expansion microcapsule technology, and more particularly to a pressure-resistant thermal expansion microcapsule and its preparation method. Background Technology

[0002] Emulsion explosives, with their excellent explosive properties and water resistance, are the most widely used type of industrial explosives in my country. Sensitization is a crucial and technically challenging aspect of emulsion explosive production. The theoretical basis for emulsion explosive sensitization is the hot spot theory. Chemical foaming sensitization or physical sensitization methods can adjust the density of emulsion explosives and improve their initiation sensitivity. Chemical sensitization is inexpensive, requires small dosages, and has good sensitization effects. However, it also has drawbacks such as numerous influencing factors, complex operation, easy aggregation and escape of sensitized bubbles, relatively low storage stability, and significant pressure desensitization. Currently, my country's high-temperature rapid chemical foaming technology for emulsion explosives exhibits poor solidification performance and limited controllability. Physical sensitization typically involves adding hollow glass microspheres or expanded perlite particles to a latex matrix, utilizing the adiabatic compression of gas within the cavities to form "hot spots" for sensitization. Considering cost, expanded perlite is often used as a sensitizer in China, which is relatively low in cost. However, it has the following disadvantages: (1) Perlite powder has a rough surface with sharp edges and poor compressive strength, making it easy to break; (2) Expanded perlite has strong oleophilicity, large pores and open pores. During the production and storage of emulsion explosives, a certain amount of high-temperature latex matrix will be absorbed into the body, blocking the pores; (3) Perlite is used in large quantities as a sensitizer for emulsion explosives, accounting for about 3 to 5% of the total mass, which leads to a reduction in the quality and power of emulsion explosives.

[0003] Therefore, the development direction of emulsion explosive sensitization technology is high-temperature sensitization. Using the pressure-resistant thermal expansion microcapsules in this invention as sensitizers, they have good elasticity and can withstand large pressure. After heating, their volume can rapidly expand to dozens of times their own size without rupturing. For emulsion explosives, they have excellent sensitization performance and require only 0.4% of the amount used, making them a good high-temperature sensitizer for emulsion explosives. Summary of the Invention

[0004] The purpose of this invention is to provide a pressure-resistant thermally expandable microcapsule and its preparation method, so as to overcome the defects of the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides a pressure-resistant, thermally expandable microcapsule, characterized by comprising the following steps:

[0006] (1) Mix the dispersion medium, inorganic salt, dispersion stabilizer and dispersion stabilizing aid to obtain an aqueous phase;

[0007] (2) Mix the monomer, initiator, crosslinking agent and foaming agent to obtain the oil phase;

[0008] (3) Stir the oil phase and the aqueous phase evenly to obtain a suspension;

[0009] (4) The obtained suspension is subjected to polymerization reaction in an inert atmosphere (including one or more of nitrogen or argon) at 40-80°C and 0.01-1MPa for 10-25 hours, then filtered and dried to obtain pressure-resistant thermal expansion microcapsules.

[0010] Furthermore, in step (1), the inorganic salt is one or more of sodium chloride, sodium nitrate, sodium nitrite, potassium chloride, magnesium chloride, calcium chloride, calcium nitrate, and magnesium nitrate, preferably sodium nitrite;

[0011] Furthermore, in step (1), the dispersing stabilizer is one or more of the following: salts of magnesium, manganese, calcium, sodium and zinc, metal oxides and metal hydroxides, preferably sodium hydroxide;

[0012] Furthermore, in step (1), the dispersion stabilizing agent is one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, calcium phosphate, and barium sulfate, preferably polyvinyl alcohol;

[0013] Furthermore, in step (2), the monomer is one or more of acrylonitrile monomers, ethylene monomers, acrylate monomers, acrylamide monomers, and fluorinated acrylate monomers;

[0014] Furthermore, in step (2), the acrylonitrile monomer is one or more of acrylonitrile and methacrylonitrile, preferably acrylonitrile; the ethylene monomer is one or more of vinylidene chloride and trifluoroethylene, preferably trifluoroethylene; the acrylate monomer is one or two of methyl methacrylate, ethyl methacrylate, and butyl methacrylate, preferably one or two of methyl methacrylate and ethyl methacrylate; the acrylamide monomer is one or more of acrylamide, methacrylamide, N-ethylacrylamide, and N,N-dimethylacrylamide, preferably methacrylamide; and the fluorinated acrylate monomer is methyl 2-fluoroacrylate.

[0015] Furthermore, the monomer described in step (2) comprises the following components in parts by weight:

[0016]

[0017] Further, in step (2), the initiator is one or more of 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylpentanonitrile), 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), diisopropyl peroxide, disec-butyl peroxide, di(2-ethylhexyl) peroxide, lauroyl peroxide, benzoyl peroxide and other diacyl peroxides, and ditert-butyl peroxide, preferably 2,2'-azobisisobutyronitrile.

[0018] Further, in step (2), the crosslinking agent is one or more of divinylbenzene, divinylnaphthalene, neopentyl glycol benzoate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane benzoate, 2-butyl-2-ethyl-1,3-propanediol dipropionate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, and allyl methacrylate, preferably one or two of ethylene glycol di(meth)acrylate or 1,6-hexanediol di(meth)acrylate.

[0019] Furthermore, in step (2), the foaming agent is one or more of isobutane, isopentane, isohexane, isoheptane, isooctane, isononane, isododecane, isotridecane, isotetradecane, isopentadecanane, isohexadecanane, isohexadecanane, isohexadecanane, isooctadecane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cyclododecane, and petroleum ether, preferably one or two of isopentane and isobutane.

[0020] Furthermore, based on the total weight of the monomer, it comprises the following weight fractions:

[0021]

[0022] Furthermore, in step (4), the preferred polymerization temperature is 45-70°C, the preferred pressure is 0.1-1 MPa, and the preferred polymerization time is 12-24 hours.

[0023] The average particle size of the thermally expandable microcapsules of the present invention is not particularly limited, but the preferred lower limit is 5 μm, and the preferred upper limit is 50 μm. When the particle size is less than 5 μm, the bubbles formed after foaming at the foaming temperature are too small, resulting in a low expansion ratio. When the particle size is greater than 50 μm, the bubbles formed after foaming at the foaming temperature are too large, leading to problems in strength and toughness. The more preferred lower limit for the above-mentioned average particle size is 10 μm, and the more preferred upper limit is 45 μm.

[0024] The maximum foaming temperature (T) of the thermal expansion microcapsules of the present invention max There are no particular limitations, but the preferred range is 120–180°C. When the maximum foaming temperature is below 120°C, the heat resistance of the thermally expanded microcapsules decreases, and they are prone to shrinkage and rupture at high temperatures, resulting in poor foaming stability.

[0025] The pressure-resistant, thermally expandable microcapsules obtained in this invention have a core-shell structure, using a low-boiling-point hydrocarbon as a foaming agent and a thermoplastic polymer as the outer shell. They exhibit excellent pressure resistance; the microcapsules expand easily and then readily return to their original volume after pressure release, allowing them to withstand multiple pressurization / depressurization cycles without rupture. This is crucial not only for the use of microcapsules in shock-absorbing materials but also for the extraction of microcapsules, either alone or in various mixtures. Therefore, the pressure-resistant, thermally expandable microcapsules of this invention are highly suitable for use as sensitizers in emulsion explosives. Detailed Implementation

[0026] The following examples illustrate the specific implementation steps of the present invention in detail. These examples should not be construed as limiting the scope of the present invention.

[0027] The main raw materials used in the examples are as follows:

[0028] Monomers: Acrylonitrile, trifluoroethylene, methyl methacrylate, methacrylamide, methyl methacrylate, 2-fluoroacrylate, N-ethylacrylamide

[0029] Foaming agents: isopentane, isobutane

[0030] Crosslinking agents: 1,6-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate

[0031] Dispersing stabilizers: sodium hydroxide, magnesium hydroxide

[0032] Dispersing and stabilizing agents: polyvinyl alcohol, polyvinylpyrrolidone

[0033] Initiator: 2,2'-azobisisobutyronitrile

[0034] The following methods and instruments were used to analyze all thermally expanded microcapsules in the examples:

[0035] The average particle size was measured using a nanolaser particle size analyzer from Zetasizer Nano.

[0036] The foaming properties of the microcapsules were tested using a Mettler TMA841 micrometer, with a heating rate of 5 °C / min and a load of 0.06 N. start It is the temperature at which expansion begins, T max It is the temperature at which maximum expansion is achieved. At Tmax At that time, an additional pressure of 0.06 N was applied, and the average particle size was measured again using a Zetasizer Nano nanolaser particle size analyzer.

[0037] Example 1

[0038] (1) Mix 500g water, 18g sodium hydroxide, 10g polyvinyl alcohol and 30g sodium nitrite evenly to obtain an aqueous phase;

[0039] (2) Mix 40g acrylonitrile, 10g trifluoroethylene, 20g methyl methacrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, 6g 1,6-hexanediol di(meth)acrylate and 30g isopentane to obtain the oil phase;

[0040] (3) Stir the oil phase and the aqueous phase evenly to obtain a suspension;

[0041] (4) The obtained suspension was subjected to polymerization reaction at 50°C and 0.5 MPa under an inert atmosphere (nitrogen in this case) for 15 hours. After filtration and drying, pressure-resistant thermally expandable microcapsules were obtained. The microcapsules have a core-shell structure, with the outer shell being a thermoplastic polymer material and the interior being a foaming agent. The outer shell thickness is 2-10 micrometers.

[0042] Example 2

[0043] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (1), 500g of water, 18g of magnesium hydroxide, 10g of polyvinyl alcohol and 30g of sodium nitrite were mixed evenly to obtain an aqueous phase.

[0044] Example 3

[0045] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (1), 500g of water, 18g of sodium hydroxide, 10g of polyvinylpyrrolidone and 30g of sodium nitrite were mixed evenly to obtain an aqueous phase.

[0046] Example 4

[0047] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, the same below), except that in step (1), 500g of water, 18g of magnesium hydroxide, 10g of polyvinyl alcohol and 30g of magnesium nitrate were mixed evenly to obtain an aqueous phase.

[0048] Example 5

[0049] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (2), 40g of methacrylonitrile, 10g of trifluoroethylene, 20g of ethyl methacrylate, 20g of methacrylamide, 10g of methyl 2-fluoroacrylate, 5g of 2,2'-azobisisobutyronitrile, 6g of 1,6-hexanediol di(meth)acrylate and 30g of isopentane were mixed to obtain an oil phase.

[0050] Example 6

[0051] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (2), 40g of methacrylonitrile, 10g of trifluoroethylene, 20g of methyl methacrylate, 20g of methacrylamide, 10g of methyl 2-fluoroacrylate, 5g of 2,2'-azobisisobutyronitrile, 6g of 1,6-hexanediol di(meth)acrylate and 30g of isopentane were mixed to obtain an oil phase.

[0052] Example 7

[0053] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (2), 40g of methacrylonitrile, 10g of trifluoroethylene, 20g of ethyl methacrylate, 20g of N-ethylacrylamide, 10g of methyl 2-fluoroacrylate, 5g of 2,2'-azobisisobutyronitrile, 6g of 1,6-hexanediol di(meth)acrylate and 30g of isopentane were mixed to obtain an oil phase.

[0054] Example 8

[0055] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (2), 40g of methacrylonitrile, 10g of trifluoroethylene, 20g of ethyl methacrylate, 20g of methacrylamide, 10g of methyl 2-fluoroacrylate, 5g of 2,2'-azobis(2,4-dimethylpentanonitrile), 6g of 1,6-hexanediol di(meth)acrylate and 30g of isopentane were mixed to obtain an oil phase.

[0056] Example 9

[0057] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (2), 40g of methacrylonitrile, 10g of trifluoroethylene, 20g of ethyl methacrylate, 20g of methacrylamide, 10g of methyl 2-fluoroacrylate, 5g of 2,2'-azobisisobutyronitrile, 6g of diethylene glycol di(meth)acrylate and 30g of isopentane were mixed to obtain an oil phase.

[0058] Example 10

[0059] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, hereinafter the same), except that in step (2), 40g of methacrylonitrile, 10g of trifluoroethylene, 20g of ethyl methacrylate, 20g of methacrylamide, 10g of methyl 2-fluoroacrylate, 5g of 2,2'-azobisisobutyronitrile, 6g of 1,6-hexanediol di(meth)acrylate, 20g of isopentane and 10g of isobutane were mixed to obtain an oil phase.

[0060] Example 11

[0061] Thermally expandable microcapsules were prepared according to the method of Example 1 (the process and conditions were the same as in Example 1, the same below), except that in step (4), the obtained suspension was subjected to polymerization reaction at 60°C and 0.5MPa pressure under an inert atmosphere for 12 hours, and then filtered and dried to obtain pressure-resistant thermally expandable microcapsules.

[0062] The above embodiments are some implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and are included within the protection scope of the present invention.

[0063] Comparative Example 1

[0064] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (1), 500g of water, 10g of polyvinyl alcohol and 30g of sodium nitrite were mixed evenly to obtain an aqueous phase.

[0065] Comparative Example 2

[0066] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (1), 500g of water, 18g of sodium hydroxide, 10g of barium oxalate and 30g of sodium nitrite were mixed evenly to obtain an aqueous phase.

[0067] Comparative Example 3

[0068] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (2), 40g fumaric acid, 10g trifluoroethylene, 20g methyl methacrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, 6g 1,6-hexanediol di(meth)acrylate and 30g isopentane were mixed to obtain an oil phase.

[0069] Comparative Example 4

[0070] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (2), 40g acrylonitrile, 10g trifluoroethylene, 20g butyl acrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, 6g 1,6-hexanediol di(meth)acrylate and 30g isopentane were mixed to obtain an oil phase.

[0071] Comparative Example 5

[0072] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (2), 20g acrylonitrile, 10g trifluoroethylene, 20g methyl methacrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, 6g 1,6-hexanediol di(meth)acrylate and 30g isopentane were mixed to obtain an oil phase.

[0073] Comparative Example 6

[0074] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (2), 40g acrylonitrile, 10g trifluoroethylene, 20g methyl methacrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, and 30g isopentane were mixed to obtain an oil phase.

[0075] Comparative Example 7

[0076] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (2), 40g acrylonitrile, 10g trifluoroethylene, 20g butyl acrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, and 6g 1,6-hexanediol di(meth)acrylate were mixed to obtain an oil phase.

[0077] Comparative Example 8

[0078] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (2), 40g acrylonitrile, 10g trifluoroethylene, 20g butyl acrylate, 20g methacrylamide, 10g methyl 2-fluoroacrylate, 5g 2,2'-azobisisobutyronitrile, 6g 1,6-hexanediol di(meth)acrylate and 10g isopentane were mixed to obtain an oil phase.

[0079] Comparative Example 9

[0080] Thermally expandable microcapsules were prepared according to the method of Example 1, except that in step (4), the obtained suspension was subjected to polymerization reaction at 80°C and 0.5 MPa under an inert atmosphere for 15 hours, and then filtered and dried to obtain pressure-resistant thermally expandable microcapsules.

[0081] The results of comparing the examples and comparative examples are shown in Tables 1 and 2 below:

[0082] Table 1

[0083]

[0084]

[0085] Table 2

[0086]

[0087] Compared with the comparative examples, the examples show better pressure resistance and good foaming performance. Compared with Example 1, Example 2 reduced the amount of dispersant stabilizer; Example 3 changed the type of dispersant, using a non-optimal dispersant, resulting in uneven dispersion during polymerization and a slight decrease in pressure resistance and foaming performance; Example 4 changed the type of inorganic salt, lowering the initial foaming temperature and slightly decreasing the foaming performance; Examples 5, 6, and 7 changed the type of monomer, resulting in a slight decrease in the shell strength of the thermally expanded microcapsules and slightly poorer pressure resistance; Example 8 changed the type of initiator, resulting in a smaller particle size of the thermally expanded microcapsules; Example 9 changed the type of crosslinking agent, resulting in a decrease in the strength of the polymer shell and a decrease in pressure resistance; Example 10 changed the type of foaming agent, lowering the initial foaming temperature; Example 11 changed the polymerization temperature and time, also obtaining thermally expanded microcapsules with good pressure resistance.

[0088] From the comparative examples, Comparative Example 1 removed the dispersant stabilizer, and Comparative Example 2 changed the type of dispersant stabilizer, resulting in uneven dispersion and reduced pressure resistance during polymerization. Comparative Examples 3 and 4 changed the monomer types, using non-preferred monomers, leading to poorer pressure resistance in the resulting microcapsules, which even ruptured under pressure. Comparative Example 5 reduced the amount of nitrile monomers, which was not the preferred amount, resulting in reduced strength of the polymer shell and significantly reduced pressure resistance. Comparative Example 6 removed the crosslinking agent, resulting in poor rigidity of the polymer shell and poor pressure resistance. Comparative Example 7 did not add a foaming agent, and Comparative Example 8 reduced the amount of foaming agent, which was not the preferred amount, resulting in no foaming or very poor foaming performance. Comparative Example 9 changed the polymerization temperature and time, which were not the preferred temperature and time, resulting in low microcapsule formation rate and poor pressure resistance and foaming performance.

[0089] The pressure-resistant thermally expandable microcapsules described in this invention can be used as sensitizers for emulsion explosives. The unfoamed pressure-resistant thermally expandable microcapsules obtained in Example 1 were mixed with Mobil 32# machine oil at a mass ratio of 1:0.3 and then heated at 180°C for 5 minutes to foam. 5 kg of emulsion matrix (temperature 85–90°C) produced by the high-temperature sensitization production line of Jiangsu Maoheng Chemical Co., Ltd. was added, along with 20 g of the foamed microcapsules. The mixture was then mixed and sensitized in a mixer to obtain an emulsion explosive. The explosive performance was tested, showing a detonation velocity of 5000–5200 m / s, a sympathetic detonation distance of 7 cm, and a brute force of 18.2 mm.

Claims

1. A method for preparing pressure-resistant thermally expandable microcapsules, characterized in that, Includes the following steps: (1) Mix the dispersion medium, inorganic salt, dispersion stabilizer, and dispersion stabilizing aid to obtain an aqueous phase; (2) Mix the monomer, initiator, crosslinking agent and foaming agent to obtain the oil phase; (3) Stir the oil phase and the aqueous phase evenly to obtain a suspension; (4) After the obtained suspension is subjected to polymerization reaction at 40~80℃ and 0.01~1MPa under an inert atmosphere for 10~25 hours, it is filtered and dried to obtain pressure-resistant thermal expansion microcapsules; The monomer mentioned in step (2) comprises the following components in parts by weight: 30-90 parts of acrylonitrile monomers 10-30 parts of ethylene monomers 10-60 parts of acrylate monomers 20-50 parts of acrylamide monomers 10-20 parts of fluorinated acrylate monomers, In step (2), the acrylonitrile monomer is one or more of acrylonitrile and methacrylonitrile; the ethylene monomer is one or more of vinylidene chloride and trifluoroethylene; the acrylate monomer is one or two of methyl methacrylate, ethyl methacrylate, and butyl methacrylate; the acrylamide monomer is one or more of acrylamide, methacrylamide, N-ethylacrylamide, and N,N-dimethylacrylamide; and the fluorinated acrylate monomer is methyl 2-fluoroacrylate.

2. The method for preparing pressure-resistant thermally expandable microcapsules according to claim 1, characterized in that, The thermally expandable microcapsule comprises a thermoplastic shell and a foaming agent encapsulated within the thermoplastic shell.

3. The method for preparing pressure-resistant thermally expandable microcapsules according to claim 1, characterized in that, In step (1), the dispersion medium is water. In step (1), the inorganic salt is one or more of sodium chloride, sodium nitrate, sodium nitrite, potassium chloride, magnesium chloride, calcium chloride, calcium nitrate, and magnesium nitrate. In step (1), the dispersant stabilizer is one or more of the following: salts of magnesium, manganese, calcium, sodium and zinc, metal oxides and metal hydroxides; In step (1), the dispersion stabilizing agent is one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, calcium phosphate, and barium sulfate.

4. The method for preparing pressure-resistant thermally expandable microcapsules according to claim 1, characterized in that, In step (2), the initiator is one or more of the following: 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylpentanonitrile), 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), diisopropyl peroxide, disec-butyl peroxide, di(2-ethylhexyl) peroxide, lauroyl peroxide, benzoyl peroxide, and ditert-butyl peroxide; In step (2), the crosslinking agent is one or more of the following: divinylbenzene, divinylnaphthalene, neopentyl glycol benzoate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane benzoate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, and allyl methacrylate. In step (2), the foaming agent is one or more of the following: isobutane, isopentane, isohexane, isoheptane, isooctane, isononane, isododecane, isotridecane, isotetradecane, isopentadecadecane, isohexadecadecane, isohexadecadecane, isohexadecadecane, isohexadecadecane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cyclododecane, and petroleum ether.

5. The method for preparing pressure-resistant thermally expandable microcapsules according to claim 1, characterized in that, Based on the total weight of the monomers as 1 part, the other materials in the suspension consist of the following weight fractions: 20-200 parts of inorganic salts Crosslinking agent 0.01~10 parts Initiator 0.01~10 parts 10-60 parts of foaming agent Dispersant stabilizer 0.1~20 parts Dispersant stabilizer 0.1~20 parts Water 100-1000 parts.

6. The pressure-resistant thermal expansion microcapsules prepared by the method of any one of claims 1-5.

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