A flexible hectorite / polyurethane composite film and preparation method thereof

Abstract

The invention discloses a flexible hectorite / polyurethane composite film and a preparation method thereof, belonging to the technical field of composite material preparation, the method uses fly ash as raw material, utilizes alkali molten acid treatment to depolymerize into fly ash geopolymer, and then utilizes solid-phase system and freeze-drying technology to prepare fly ash-based hectorite; finally, using fly ash-based hectorite as filler, a flexible hectorite / polyurethane composite film is prepared by a scraping process. The inventive method has the characteristics of low cost and high efficiency, which can not only help fly ash reduction and high value, but also provide new ideas for the development of electronic components.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and particularly relates to a flexible hectorite / polyurethane composite film and a preparation method thereof. Background Art

[0002] With the rapid development of flexible electronics in recent years, the demand for high-performance flexible materials has been growing. Flexible composite films, due to their excellent mechanical flexibility, chemical stability, and customizability, have shown great potential for application in sensing electronics (such as flexible sensors and wearable devices). Polyurethane (PU)-based composite films, in particular, have become a research hotspot due to their excellent film-forming properties and elasticity.

[0003] However, the existing technology still has the following limitations. For example, traditional polyurethane composite films often use carbon-based materials or dielectric materials as fillers to enhance their relevant properties. However, the fillers used in the existing technology are easy to agglomerate, and their dispersibility and composite efficiency in polyurethane are poor, which will cause the prepared composite film to be non-uniform in mechanical and chemical properties. Secondly, the current preparation methods of polyurethane-based composite films mostly rely on high temperature and high pressure or long-term solvent volatilization, resulting in low production efficiency, high energy consumption, and insufficient control accuracy of film thickness, which affects its application scenarios in electronic devices. Thirdly, the preparation of some fillers relies on high-purity raw materials or complex synthesis processes, which is costly and difficult to meet the needs of green manufacturing. Summary of the Invention

[0004] To address the problems existing in the prior art for preparing flexible composite membranes, the present invention provides a flexible hectorite / polyurethane composite membrane and its preparation method. Using geopolymer formed by depolymerizing fly ash as raw material, the fly ash-based hectorite is prepared using an environmentally friendly preparation process. This hectorite can form a homogeneous gel in water, which facilitates composite with polyurethane and improves the mechanical properties of the composite membrane. Furthermore, thanks to the relatively abundant lithium ions in the hectorite, the resulting composite membrane facilitates charge transfer, facilitating its application as an electronic component.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a flexible hectorite / polyurethane composite film comprises the following steps:

[0007] S1. Mix thermoplastic polyurethane elastomer (TPU-60), N,N-dimethylformamide solution, and functional filler aqueous solution in a mass-to-volume ratio of 1-4 g:20 ml:0.01-2 g. Place the mixture on a hot plate with a magnetic stirring function and use a stirring bar to dissolve the thermoplastic polyurethane elastomer in the N,N-dimethylformamide solution to form a mixed solution A. Dissolution conditions are: magnetic stirring rate 300-1500 rpm / min, stirring time 2-4 h, and hot plate temperature 60-80°C.

[0008] S2. Use a coating machine to apply the mixed solution A onto a glass plate, then leave the glass plate stationary on the coating machine for 0.5-1 hour, and use the temperature of the coating machine to solidify the composite film; the coating conditions of the coating machine are: coating rate of 30-90 mm / s, coating machine temperature of 50-70° C., and coating length of 200-400 mm;

[0009] S3. Transfer the glass plate with the composite film to a drying oven at 70-80°C and dry it for 1-2 hours before taking it out.

[0010] S4. The glass plate with the composite film is transferred to a drying oven at 70-80° C. for continuous aging for 8-12 hours. After the aging is completed, the film on the glass plate is peeled off to obtain a flexible hectorite / polyurethane composite film.

[0011] Furthermore, in step S1, the mass fraction of the N,N-dimethylformamide solution is 99.9%, and the functional filler aqueous solution is a 2% aqueous solution prepared by dissolving the functional filler in deionized water.

[0012] Furthermore, in step S1, the functional filler is fly ash-based hectorite, and its preparation method is as follows:

[0013] A1. The lithium source, magnesium source and fly ash-based mineral polymer were mixed in a molar ratio of 1.0:3.0:1.7-3.0 and stirred thoroughly. The resulting mixture was designated as mixture I.

[0014] A2. The mixture Ⅰ was transferred to a polytetrafluoroethylene-lined hydrothermal reactor tank, and 3-5 ml of ammonia solution was added to the bottom of the polytetrafluoroethylene-lined hydrothermal reactor tank;

[0015] A3. Place the loaded polytetrafluoroethylene-lined tank into a stainless steel reactor, place it in a constant temperature oven, and react at a temperature of 110-200°C for 24-72h.

[0016] A4. After the reaction is complete, remove the polytetrafluoroethylene-lined tank from the hydrothermal reactor, centrifuge and wash the solid product until neutral, transfer the solid product with deionized water, and freeze-dry the resulting material. The resulting solid powder is fly ash-based hectorite.

[0017] Furthermore, in step A1, the lithium source is one of lithium fluoride, lithium carbonate, and lithium hydroxide monohydrate, or a mixture of two of them; the magnesium source is one of magnesium chloride, magnesium carbonate, and magnesium hydroxide, or a mixture of two of them.

[0018] Furthermore, in step A2, the mass concentration of the ammonia water used is 25%; the mixture I and the ammonia solution are separated by a polytetrafluoroethylene mesh, that is, during the reaction, only the alkaline vapor formed by the heating of the ammonia water serves as the reaction medium.

[0019] Furthermore, in step A4, the freeze-drying conditions are: freezing temperature -80°C, and freeze-drying time is 1-3 days.

[0020] Furthermore, in step A1, the fly ash-based mineral polymer is prepared by the following method, specifically comprising:

[0021] C1. Mixing sodium hydroxide and fly ash in a mass ratio of 1:1.4, calcining in a muffle furnace at 720-900° C. for 2-4 hours, or calcining in a microwave muffle furnace at 720-900° C. for 0.5-1 hour; after calcination, removing from the muffle furnace, grinding into powder, and sieving through an 80-mesh sieve to obtain an alkali-fused powder;

[0022] C2. Filter the alkali molten powder with deionized water until it is neutral, and dry it in an oven at 90°C for 12 hours to obtain a neutral alkali molten powder;

[0023] C3. The neutral alkali molten powder and the acid solution are loaded into a microwave digestion tank according to a certain solid-liquid ratio, wherein the mass volume ratio of the alkali molten powder to the acid solution is in the range of 1:2.5-5 g / ml;

[0024] C4. Place the microwave digestion vessel prepared in step C3 into a microwave digestion instrument and irradiate at a certain temperature according to specific irradiation conditions, specifically, an irradiation temperature of 150-200° C. and 30-60 irradiation cycles;

[0025] C5. Take out the microwave digestion tank after microwave irradiation, filter the solid product until it is neutral, and place it in a constant temperature oven at 80-90°C to dry for 12 hours. The obtained solid powder is the fly ash-based mineral polymer.

[0026] Furthermore, in step C3, the acid solution is hydrochloric acid with a concentration of 2-4 mol / L;

[0027] In step C3, the fly ash and the acid solution are isolated by a polytetrafluoroethylene mesh, that is, during the microwave irradiation process, only the acid solution is heated to form acidic steam as the reaction medium.

[0028] Furthermore, in step C4, the irradiation cycle is specifically each cycle of 200W irradiation for 10s, 230W irradiation for 10s, 270W irradiation for 10s, 330W irradiation for 10s, 350W irradiation for 10s, and rest for 10s.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] 1. In terms of synthetic raw materials, the present invention uses fly ash as the synthetic raw material for hectorite, providing a practical method for green high value and reduction of fly ash, which also provides a green preparation method for the green preparation of hectorite.

[0031] 2. The fly ash-based mineral polymer is prepared using a composite process combining a solid-phase method and microwave progressive irradiation. This allows low-concentration acid to function as a high-concentration acid, effectively improving its efficiency. It also enables multiple recycling by adding small amounts of acid. Furthermore, the acid can contain a large amount of high-value elements, such as aluminum, present in fly ash. The alkali melting of fly ash can be treated not only in a muffle furnace but also in a microwave muffle furnace, providing multiple solutions for industrial production.

[0032] 3. During the microwave acid leaching process, the fly ash powder after alkali melting is directly irradiated with microwaves. Due to the differences in the microwave response of chemical bonds between different elements, direct activation is achieved, resulting in consistent activation and rupture of chemical bonds. These ruptured chemical bonds can better bind firmly and uniformly to the magnetic particles through chemical interactions. This also allows Al2O3, Fe2O3, and other components to be separated from the acid vapor, facilitating the separation of fly ash components.

[0033] 4. Using fly ash-based hectorite as a filler allows it to form a homogeneous gel in water, facilitating efficient composite bonding with polyurethane. Furthermore, the relatively abundant lithium ions in fly ash-based hectorite facilitate charge transfer, facilitating its application as an electronic component. Coating methods can also be used for industrial mass production of polyurethane composite films. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0035] Figure 1 The SEM image of fly ash is shown in the implementation case 1;

[0036] Figure 2 For implementation case 1, the XRD pattern of fly ash is shown;

[0037] Figure 3 The XRD pattern of fly ash-based mineral polymer is shown in implementation case 1;

[0038] Figure 4 The SEM image of fly ash-based mineral polymer is shown in implementation case 1;

[0039] Figure 5 This is the XRD pattern of fly ash-based hectorite for implementation case 1;

[0040] Figure 6 This is a physical picture of the flexible hectorite / polyurethane composite membrane in implementation case 1;

[0041] Figure 7 The XRD comparison diagram of implementation case 1 and the one without added filler (fly ash-based hectorite);

[0042] according to Figure 1 , Figure 2 , Figure 3 and Figure 4 The comparison can clearly confirm that the fly ash has been completely deagglomerated, its spherical morphology has been completely broken into irregular blocks, and its crystal structure has been transformed into an amorphous state. Figure 5 The XRD pattern of the synthetic product is shown in Figure 2, from which it can be determined that the material is hectorite. Figure 7 As can be seen from the figure, both the filler- and unfilled samples exhibit an amorphous state, indicating that the filler is evenly dispersed in the polyurethane without agglomeration. The diffraction peak decreases slightly due to the addition of filler, but the overall trend is essentially the same as that of the unfilled sample. DETAILED DESCRIPTION

[0043] In order to clearly and completely describe the technical solution and specific working process of the present invention, the specific implementation methods of the present invention are as follows in conjunction with the accompanying drawings:

[0044] Example 1

[0045] This embodiment provides a method for preparing a flexible hectorite / polyurethane composite film, and the specific steps are as follows:

[0046] S1. Mix thermoplastic polyurethane elastomer (TPU-60), N,N-dimethylformamide solution, and functional filler in a ratio of 4 g TPU-60: 20 ml functional filler aqueous solution (2% by mass) to form mixed solution A. Place the mixture on a hot plate equipped with a magnetic stirrer and use a stirring bar to dissolve the TPU-60 in the N,N-dimethylformamide solution to form mixed solution A. Dissolution conditions are: magnetic stirring rate 1500 rpm / min, stirring time 2 h, and hot plate temperature 80°C.

[0047] S2. Use a coating machine to apply mixed solution A to a glass plate. Then, leave the glass plate stationary on the coating machine for 0.5 hours while the coating machine heat cures the composite film. The coating conditions are: coating rate of 30 mm / s, temperature of 70°C, and coating length of 400 mm.

[0048] S3. Transfer the glass plate with the composite film to a drying oven at 80°C and dry it for 1 hour before taking it out.

[0049] S4. The glass plate with the composite film is transferred to a drying oven at 70° C. for continuous aging for 12 hours. After the aging is completed, the film on the glass plate is peeled off to obtain a flexible hectorite / polyurethane composite film.

[0050] In this embodiment, the mass fraction of N,N-dimethylformamide is 99.9%. The functional filler aqueous solution is a 2% aqueous solution prepared by dissolving the functional filler in deionized water.

[0051] Wherein, the functional filler is fly ash-based hectorite, and its preparation method is as follows:

[0052] A1. The lithium source, magnesium source, fly ash-based mineral polymer were mixed in a molar ratio of 1.0:3.0:1.7 and stirred thoroughly. The resulting mixture was designated as mixture Ⅰ.

[0053] A2. Transfer the above mixture Ⅰ to a 100 ml polytetrafluoroethylene-lined hydrothermal reactor tank and add 3 ml of ammonia solution to the bottom of the polytetrafluoroethylene-lined hydrothermal reactor tank;

[0054] A3. The polytetrafluoroethylene-lined tank in step A2 was loaded into a stainless steel reactor and placed in a constant temperature oven at a temperature of 110°C for 72h.

[0055] A4. After the reaction is complete, remove the polytetrafluoroethylene-lined tank from the hydrothermal reactor, centrifuge and wash the solid product until neutral, transfer it with deionized water, and freeze-dry the resulting solid powder, which is fly ash-based hectorite.

[0056] In this embodiment, in step A1, the lithium source is lithium fluoride; and the magnesium source is magnesium hydroxide.

[0057] In this embodiment, in step A2, the mass concentration of the ammonia water used is 25%; the mixture I and the ammonia solution are separated by a polytetrafluoroethylene mesh, that is, during the reaction process, only the alkaline vapor formed by the heating of the ammonia water serves as the reaction medium.

[0058] In this embodiment, in step A4, the freeze-drying conditions are: freezing temperature -80°C, and freeze-drying time is 1 day.

[0059] In this embodiment, the preparation process of the fly ash-based mineral polymer in step S1 is as follows:

[0060] C1. Sodium hydroxide and fly ash were mixed in a mass ratio of 1:1.4 and calcined in a muffle furnace at 720° C. for 4 h. After calcination, the mixture was removed from the muffle furnace, ground into powder, and sieved through an 80-mesh sieve to obtain an alkali-fused powder.

[0061] C2. Filter the alkali molten powder with deionized water until it is neutral, and dry it in an oven at 90°C for 12 hours to obtain a neutral alkali molten powder;

[0062] C3. Load the neutral alkali molten powder and acid solution into a microwave digestion tank at a certain solid-liquid ratio, with the ratio range of alkali molten powder: acid solution = 1:2.5 g / ml;

[0063] C4, placing the microwave digestion vessel prepared in step C3 into a microwave digestion instrument, and irradiating the solution at a certain temperature according to specific irradiation conditions, specifically, an irradiation temperature of 150° C. and 60 irradiation cycles;

[0064] C5. Take out the microwave digestion tank after microwave irradiation, filter the solid product until it is neutral, and place it in a constant temperature oven at 90°C to dry for 12 hours. The obtained solid powder is the fly ash-based mineral polymer.

[0065] In this embodiment, in step C3, the acid solution used is hydrochloric acid with a concentration of 2 mol / L;

[0066] In step C3, the fly ash and the acid solution are isolated by a polytetrafluoroethylene mesh, that is, during the microwave irradiation process, only the acid solution is heated to form acidic steam as the reaction medium.

[0067] In step C4, the irradiation cycle mentioned is specifically each cycle of 200W irradiation for 10s, 230W irradiation for 10s, 270W irradiation for 10s, 330W irradiation for 10s, 350W irradiation for 10s, and rest for 10s.

[0068] Example 2 is otherwise identical to Example 1, except that in step S1, the thermoplastic polyurethane elastomer (TPU-60): N,N-dimethylformamide solution: functional filler aqueous solution (2% by mass) is prepared in a ratio of 1 g: 20 ml: 0.01 g. Dissolution conditions are: magnetic stirring rate 300 rpm / min, stirring time 4 hours, hot plate temperature 60°C. In step S2, mixed solution A is applied to a glass plate using a coater. The glass plate is then left stationary on the coater for 1 hour while the heat of the coater cures the composite film. The coating conditions are: coating rate 90 mm / s, coater temperature 50°C, coating length 200 mm. In step S3, the glass plate with the composite film is transferred to a 70°C drying oven and dried for 2 hours before removal. In step S4, the glass plate with the composite film is transferred to a drying oven at 80° C. and aged for 8 hours. After the aging is completed, the film on the glass plate is peeled off to obtain a flexible hectorite / polyurethane composite film.

[0069] The rest of Example 3 is the same as Example 1, except that, in step A1, the lithium source, magnesium source, and fly ash-based mineral polymer are used in a molar ratio of 1.0:3.0:3.0; in step A2, 5 ml of ammonia solution is added to the bottom of the polytetrafluoroethylene hydrothermal reaction lined kettle; and in step A3, the reaction is carried out in a constant temperature oven at 200° C. for 24 h.

[0070] The rest of Example 4 is the same as Example 1, except that in step A1, the lithium source is lithium hydroxide monohydrate, the magnesium source is magnesium chloride, and in step A4, the freeze-drying conditions are: freezing temperature -80°C, and freeze-drying time is 3 days.

[0071] Example 5 was otherwise identical to Example 1, except that in step C1, the sodium hydroxide and fly ash were mixed and calcined in a muffle furnace at 900°C for 2 hours. In step C3, the ratio of alkali-molten powder to acid solution was 1:5 g / ml, and the hydrochloric acid solution used had a concentration of 4 mol / L. In step 4, the irradiation temperature was 200°C, and the irradiation cycle was 30.

[0072] The rest of Example 6 is the same as Example 1, except that in step C1, sodium hydroxide and fly ash are mixed and calcined in a microwave muffle furnace at 900° C. for 0.5 h.

[0073] The rest of Example 7 is the same as Example 1, except that in step C1, sodium hydroxide and fly ash are mixed and calcined in a microwave muffle furnace at 720° C. for 1 hour.

[0074] Mechanical properties testing

[0075] Mechanical properties include tensile strength and elongation at break, which were tested using an electronic universal strength testing machine. Each sample was measured 5 times and the average value was taken.

[0076] Dielectric constant and dielectric loss test

[0077] The frequency-dependent dielectric properties of the film were tested using a precision impedance analyzer. The film was cut into 20mm diameter specimens and placed on a holder. The thickness was read and entered into the machine. The test environment was room temperature and the test frequency range was 0.1-10 7 Hz.

[0078] Table 1 shows the mechanical properties test results and dielectric properties of samples from implementation cases 1-7 and samples without fillers.

[0079] Example Tensile strength (MPa) Elongation at break (%) Dielectric constant (1kHz) Dielectric loss (1kHz) TPU-60 (no filler added) 42.78 840 4.44 0.0158 Example 1 45.96 1057 7.60 0.0564 Example 2 43.81 871 10.80 0.056 Example 3 45.82 1154 9.43 0.0875 Example 4 46.62 1065 11.70 0.0732 Example 5 47.83 1032 10.89 0.0772 Example 6 45.24 1120 11.42 0.0684 Example 7 45.46 1085 11.56 0.0754

[0080] As shown in Table 1, the flexible hectorite / polyurethane composite films prepared in each example exhibit excellent mechanical properties. This is due to the addition of fillers, which alters the microphase environment of the polyurethane, thereby enhancing the mechanical strength and electrochemical response of the polyurethane composite films. Furthermore, the resourceful utilization of fly ash to prepare hectorite not only reduces raw material costs but also achieves high-value conversion of industrial solid waste, aligning with the concept of sustainable development.

[0081] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0082] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0083] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a flexible hectorite / polyurethane composite film, characterized in that: The specific steps include: S1. Mix a thermoplastic polyurethane elastomer, an N,N-dimethylformamide solution, and an aqueous solution of a functional filler in a mass-to-volume ratio of 1-4 g:20 ml:0.01-2 g. Place the mixture on a hot plate with a magnetic stirring function, and use a stirring bar to dissolve the thermoplastic polyurethane elastomer in the N,N-dimethylformamide solution to form a mixed solution A. The dissolution conditions are: a magnetic stirring rate of 300-1500 rpm / min, a stirring time of 2-4 h, and a hot plate temperature of 60-80°C. S2. Use a coating machine to apply the mixed solution A onto a glass plate, then leave the glass plate stationary on the coating machine for 0.5-1 hour, and use the temperature of the coating machine to solidify the composite film; the coating conditions of the coating machine are: coating rate of 30-90 mm / s, coating machine temperature of 50-70° C., and coating length of 200-400 mm; S3. Transfer the glass plate with the composite film to a drying oven at 70-80°C and dry it for 1-2 hours before taking it out. S4, transferring the glass plate with the composite film to a drying oven at 70-80°C for continuous aging for 8-12 hours. After aging is completed, peeling off the film on the glass plate to obtain a flexible hectorite / polyurethane composite film; The functional filler is fly ash-based hectorite, and its preparation method is as follows: A1. The lithium source, magnesium source and fly ash-based mineral polymer were mixed in a molar ratio of 1.0:3.0:1.7-3.0 and stirred thoroughly. The resulting mixture was designated as mixture I. A2. Transfer the above mixture I to a polytetrafluoroethylene-lined hydrothermal reactor. Add 3-5 ml of ammonia solution to the bottom of the polytetrafluoroethylene-lined reactor. Mixture I and the ammonia solution are separated by a polytetrafluoroethylene mesh. During the reaction, only the alkaline vapor formed by the heated ammonia solution serves as the reaction medium. A3. Place the loaded polytetrafluoroethylene-lined tank into a stainless steel reactor, place it in a constant temperature oven, and react at a temperature of 110-200°C for 24-72h. A4. After the reaction is complete, remove the polytetrafluoroethylene-lined tank from the hydrothermal reactor, centrifuge and wash the solid product until neutral, transfer the solid product with deionized water, and freeze-dry the resulting material. The resulting solid powder is fly ash-based hectorite.

2. The method for preparing a flexible hectorite / polyurethane composite film according to claim 1, wherein: In step S1, the mass fraction of the N,N-dimethylformamide solution is 99.9%, and the functional filler aqueous solution is a 2% aqueous solution prepared by dissolving the functional filler in deionized water.

3. The method for preparing a flexible hectorite / polyurethane composite film according to claim 1, wherein: In step A1, the lithium source is one of lithium fluoride, lithium carbonate, and lithium hydroxide monohydrate, or a mixture of two of them; the magnesium source is one of magnesium chloride, magnesium carbonate, and magnesium hydroxide, or a mixture of two of them.

4. The method for preparing a flexible hectorite / polyurethane composite film according to claim 1, wherein: In step A2, the mass concentration of the ammonia water used is 25%.

5. The method for preparing a flexible hectorite / polyurethane composite film according to claim 3, wherein: In step A4, the freeze-drying conditions are: freezing temperature -80°C, and freeze-drying time is 1-3 days.

6. The method for preparing a flexible hectorite / polyurethane composite film according to claim 1, wherein: In step A1, the fly ash-based mineral polymer is prepared by the following method, specifically comprising: C1. Mixing sodium hydroxide and fly ash in a mass ratio of 1:1.4, calcining in a muffle furnace at 720-900° C. for 2-4 hours, or calcining in a microwave muffle furnace at 720-900° C. for 0.5-1 hour; after calcination, removing from the muffle furnace, grinding into powder, and sieving through an 80-mesh sieve to obtain an alkali-fused powder; C2. Filter the alkali molten powder with deionized water until it is neutral, and dry it in an oven at 90°C for 12 hours to obtain a neutral alkali molten powder; C3. The neutral alkali molten powder and the acid solution are loaded into a microwave digestion tank according to a certain solid-liquid ratio, wherein the mass volume ratio of the alkali molten powder to the acid solution ranges from 1:2.5 to 5 g / ml; C4, placing the microwave digestion vessel prepared in step C3 into a microwave digestion instrument, and irradiating the solution at a certain temperature according to specific irradiation conditions, specifically, an irradiation temperature of 150-200° C. and 30-60 irradiation cycles; C5. Take out the microwave digestion tank after microwave irradiation, filter the solid product until it is neutral, and place it in a constant temperature oven at 80-90°C to dry for 12 hours. The obtained solid powder is the fly ash-based mineral polymer.

7. The method for preparing a flexible hectorite / polyurethane composite film according to claim 6, wherein: In step C3, the acid solution is hydrochloric acid with a concentration of 2-4 mol / L; In step C3, the fly ash and the acid solution are isolated by a polytetrafluoroethylene mesh, that is, during the microwave irradiation process, only the acid solution is heated to form acidic steam as the reaction medium.

8. The method for preparing a flexible hectorite / polyurethane composite film according to claim 6, wherein: In step C4, the irradiation cycle is specifically each cycle of 200W irradiation for 10s, 230W irradiation for 10s, 270W irradiation for 10s, 330W irradiation for 10s, 350W irradiation for 10s, and rest for 10s.

9. A flexible hectorite / polyurethane composite film, characterized in that: The method is prepared by any one of claims 1 to 8.

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