Methods for recycling coated glass films containing glass core cloth and fluoropolymer coatings

Abstract

This invention relates to a method for selectively dissolving a coated glass membrane comprising a glass core cloth and at least one layer of fluoropolymer coating. The method includes the following steps: providing fragments of the coated glass membrane; immersing the fragments in an alkaline solution with a pH greater than or equal to 10; heating the alkaline solution to a temperature above 50°C to dissolve the glass core cloth of the fragments; and performing solid / liquid separation to recover the fluoropolymer coating.

Description

Technical Field

[0001] This invention relates to the technical field of coated glass membrane recycling. More specifically, this invention relates to a method for selectively dissolving a coated glass membrane comprising a glass core cloth and at least one layer of fluoropolymer coating. Background Technology

[0002] As environmental pollution has become a major problem, industries have been seeking innovative solutions to reduce or recycle waste generated from their activities. More specifically, the glass fiber industry loses millions of tons of glass waste due to the complexities of glass recycling. Glass fibers used to process into glass fiber mats are typically coated with resin (cured or uncured) or fluoropolymers. Several methods exist for removing resin coatings from glass fibers. For example, US 7,934,393 B2 describes a method for removing resin coatings that involves immersing the fibers in an aqueous fluid within a hydrothermal reactor and applying high temperature and pressure.

[0003] Fluoropolymer coatings, such as polytetrafluoroethylene (PTFE), are frequently used due to their inert and hardness properties. Some apparatuses for processing PTFE by irradiation and grinding are known, such as the apparatus disclosed in EP 1 137 657 B2. However, these apparatuses are bulky and energy-intensive. Furthermore, they are not designed for processing materials coated with PTFE.

[0004] Therefore, the applicant has discovered a method that can efficiently separate the fluoropolymer coating of a coated glass film from the glass core cloth without requiring high energy consumption.

[0005] One of the objectives of this invention is to separate fluoropolymers from glass fibers so that the fluoropolymer portion of the composite material can be utilized by existing fluoropolymer recycling technologies. Summary of the Invention

[0006] This invention relates to a method for selectively dissolving a coated glass film, the coated glass film comprising a glass core cloth and at least one layer of fluoropolymer coating, the method comprising the following steps: - Provide fragments of the coated glass film; - Immerse the fragments in an alkaline solution with a pH greater than or equal to 10; - Heat the alkaline solution to a temperature above 50°C to dissolve the glass core cloth fragments; - Perform solid / liquid separation to recover the fluoropolymer coating.

[0007] In this invention, "coated glass film" may be referred to as "glass film", "coated film" or "film". Similarly, glass core cloth may be referred to as "glass cloth", "core cloth" or "cloth".

[0008] In this invention, "selective dissolution" means that only the glass core cloth is dissolved, while one or more layers of the fluoropolymer coating are not dissolved.

[0009] The term "dissolved" refers to the glass core cloth dissolving in an alkaline solution solvent, i.e., changing from a solid to a liquid state. This means that at least 45 wt% of the glass core cloth is dissolved relative to the total mass of the glass core cloth contained in the coated glass film prior to selective dissolution.

[0010] The term "completely dissolved" means that more than 99 wt% of the glass core cloth contained in the coated glass film is dissolved relative to the total mass of the glass core cloth contained before selective dissolution.

[0011] Coated glass film

[0012] The coated glass film can be taken from roofing membrane materials of a stretched structure or conveyor belt, and cut into fragments.

[0013] The purpose of this step is to allow the cut surface of the coated glass film to be touched by the alkaline solution.

[0014] Preferably, the coated glass film is cut into fragments using any suitable tool. The means and methods used to cut the film are not limited.

[0015] The geometry of the fragments should facilitate the alkaline solution reaching the entire glass fiber core in the shortest possible time. Advantageously, the fragments of the coated glass film comprise at least two glass core points in contact with the alkaline solution, the distance between the two points being advantageously less than 5 cm.

[0016] According to the present invention, the areal density of the coated glass film is between 100 g / m³. 2 Up to 2000 g / m 2 Between, preferably between 150 g / m 2 Up to 1800 g / m 2 between.

[0017] Glass core cloth

[0018] The glass core cloth can be woven fabric, nonwoven fabric, mesh, or at least one yarn.

[0019] According to the present invention, the areal density of the glass core cloth is between 50 g / m². 2 Up to 1200 g / m 2 Between, preferably between 75g / m 2 Up to 1000 g / m 2 Between, more preferably between 100 g / m 2 Up to 800 g / m 2 between.

[0020] In one specific embodiment, the glass core cloth comprises at least one glass fiber, the glass fiber comprising: - 40 wt% to 76 wt% SiO2, - Total 10 wt% to 25 wt% Na2O and K2O, - Total 10 wt% to 16 wt% CaO and MgO, - 0 to 18 wt% B2O, - 0 to 5 wt% Al2O3, Based on the total weight of the glass fibers.

[0021] In addition, the glass fiber may also contain P2O5, Fe2O3, SrO, Li2O and F, preferably up to 10 wt% based on the total weight of the glass fiber.

[0022] In one specific embodiment, the glass fiber comprises: - 66 wt% to 73 wt% SiO2, - A total of 12 wt% to 17 wt% Na2O and K2O, - A total of 13 wt% to 16 wt% CaO and MgO, - 2 wt% to 3 wt% of B2O3, - 0 to 0.3 wt% Al2O3, The total weight of the glass fibers is used as a reference.

[0023] In addition, the glass fiber may also contain P2O5, Fe2O3, SrO, Li2O and F, preferably up to 10 wt% based on the total weight of the glass fiber.

[0024] In another embodiment, the glass fiber comprises: - 40 wt% to 66 wt% SiO2, - A total of 17 wt% to 25 wt% Na2O and K2O, - A total of 10 wt% to 13 wt% CaO and MgO, - 3 wt% to 18 wt% B2O3, - 0.3 wt% to 5 wt% Al2O3.

[0025] In addition, the glass fiber may also contain P2O5, Fe2O3, SrO, Li2O and F, preferably up to 10 wt% based on the total weight of the glass fiber.

[0026] In one specific embodiment, the glass core cloth comprises at least one type of glass fiber, said type of glass fiber comprising: - 49 wt% to 69 wt% SiO2, - 16 wt% to 26 wt% Al2O3, - 15 wt% to 16 wt% MgO, - 0 to 6 wt% CaO; - Total 0 to 6 wt% of B2O3, Li2O, Na2O, Y2O3 and La2O3, - Total 0 to 6 wt% of K2O, SrO, TiO2, ZrO2 and Fe2O3, Based on the total weight of the glass fiber of the aforementioned type.

[0027] According to the present invention, the glass fiber may be a first type of glass fiber (GF1), a second type of glass fiber (GF2), or a type C glass derived from glass wool insulation board fiber.

[0028] The glass core cloth may contain more than one type of glass fiber, such as GF1 and C-type glass from glass wool insulation board fibers.

[0029] Preferably, the glass core cloth does not contain E glass fiber.

[0030] According to the present invention, the nominal monofilament diameter of the glass fiber may be between 2 µm and 20 µm, preferably between 3 µm and 17 µm.

[0031] Preferably, the Young's modulus (E) of the glass fiber is between 60 GPa and 100 GPa.

[0032] Preferably, the tensile strength of the glass fiber is between 3000 MPa and 4500 MPa.

[0033] Fluoropolymer coating

[0034] According to the invention, the coated glass film may comprise at least one layer of fluoropolymer coating. Advantageously, it may comprise multiple layers of fluoropolymer coating. Typically, it may comprise up to 10 layers, but may comprise more layers if necessary to achieve the specific technical performance required for the intended use of the coated glass film.

[0035] When the coated glass film contains more than one layer of fluoropolymer coating, each layer may have the same polymer composition or different polymer compositions.

[0036] Advantageously, the coated glass film comprises at least two layers of fluoropolymer coating, both of which have the same polymer composition.

[0037] As an alternative, the coated glass film comprises at least two layers of fluoropolymer coating, each of the two layers comprising a different fluoropolymer.

[0038] When the glass core cloth is at least one yarn, each yarn is covered with at least one layer of fluoropolymer coating.

[0039] The at least one fluoropolymer coating preferably comprises at least one fluoropolymer selected from the following substances: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoroalkoxy polymer (PFA), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and mixtures thereof.

[0040] Advantageously, the fluoropolymer is polytetrafluoroethylene.

[0041] In other embodiments, the at least one fluoropolymer coating layer comprises different fluoropolymers. For example, each layer may comprise a combination of at least two different fluoropolymers.

[0042] For example, the at least one fluoropolymer coating may comprise PTFE and FEP, or PTFE and PFA, or PVDF and PVF, or PVDF and PTFE, or FEP and PFA. Preferred mixtures are PTFE and PFA, or PTFE and FEP, PFA and FEP, or PTFE, FEP and PFA.

[0043] Advantageously, the fluoropolymer coating cannot be dissolved under the conditions of the method described in this invention.

[0044] alkaline solution

[0045] Fragments of the coated glass film are immersed in an alkaline solution with a pH greater than or equal to 10. The pH can be 11, 12, 13, or even 14. Preferably, the pH is equal to or greater than 12.

[0046] Preferably, the alkaline solution is a Brønsted alkaline solution selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and ammonia.

[0047] In a preferred embodiment, the alkaline solution is an aqueous solution of sodium hydroxide with a pH greater than or equal to 12.

[0048] Advantageously, the alkaline solution is heated to a temperature above 50°C, preferably above 70°C, to dissolve the glass core cloth of the fragments of the coated glass film.

[0049] Preferably, the temperature is between 70°C and 125°C. Advantageously, the temperature is 105°C or 110°C.

[0050] Preferably, the step of heating the alkaline solution is performed at a temperature higher than 10°C. 5 The test was conducted under a pressure of Pa.

[0051] In some embodiments, the undissolved coated glass film fragments are washed with an aqueous solution and then immersed in an alkaline solution to improve the dissolution effect.

[0052] Preferably, the dissolution is carried out in multiple steps. For example, the membrane can be dissolved by immersing it in an alkaline solution for 1 to 10 hours, followed by heating in distilled water for 1 to 2 hours. Afterward, the membrane can be immersed in an alkaline solution again for 1 to 10 hours. These steps can be repeated several times.

[0053] Advantageously, the fragments of the coated glass film completely dissolved after 55 hours.

[0054] In some embodiments, the alkaline solution may be heated in an autoclave.

[0055] In a specific embodiment, the alkaline solution is stirred to accelerate dissolution.

[0056] solid / liquid separation

[0057] Once at least 90 wt% of the glass core cloth has dissolved, solid / liquid separation is performed to recover the fluoropolymer coating. This solid / liquid separation can be filtration or centrifugation. For example, it can be vacuum filtration, tangential flow filtration, ultrafiltration, but is not limited to these techniques.

[0058] Preferably, the fluoropolymer coating recovered by the solid / liquid separation is washed with an aqueous solution to remove residual alkaline solution.

[0059] In some embodiments, the fluoropolymer coating can be washed multiple times. Attached Figure Description

[0060]

Figure 1

[0061] Example

[0062] Materials used in the examples: The embodiments are prepared using the following glass fibers: - Type I glass fiber (GF1), with a nominal monofilament diameter of 17 µm; - Type II glass fiber (GF2), with a nominal monofilament diameter of 9 µm; - The C-type glass from the glass wool insulation board "TW-1 040" is supplied by SUPERGLASS DÄMMSTOFFE in Germany. Its glass fibers contain up to 7% organic binder resin and less than 18% (by weight) of oxides of sodium, potassium, calcium, magnesium and barium. - E-glass fiber with a nominal monofilament diameter of 4 µm, supplied by AGY; - E glass fiber with a nominal monofilament diameter of 6 µm, supplied by VETROTEX.

[0063]

[0064] Table 1: Comparison of chemical composition of GF1, GF2 and E glass fibers

[0065] Example 1 (Invention Example): A PTFE coated film containing GF2 glass fiber was heated in NaOH at pH=14.

[0066] GF2 glass fibers are woven into a plain-weave glass fabric. The areal density of the glass fibers is approximately 310 g / m². 2 The glass fabric was then coated on an industrial coating production line using a multilayer commercially available aqueous PTFE dispersion until the areal density of the coated glass film reached approximately 600 g / m². 2 After each coating layer, the fabric is dried and the PTFE is sintered. The resulting coated fabric (15 kg in weight) is then mechanically shredded in an industrial blade shredder until the resulting fragments are less than 10 mm in diameter. During the shredding process, 13% of the material is lost. This is mainly due to the generation of fine glass fibers, which are released into the atmosphere and subsequently removed by the ventilation system.

[0067] Take 3.84 g of the obtained fragment sample and heat it in a sodium hydroxide aqueous solution (20% NaOH) at pH 14 for 6 hours at a temperature of approximately 110°C ± 10°C. After 6 hours, boil the fragment in deionized water. Dry the sample at 120°C for 6 hours and weigh it. This 18-hour cycle was repeated 8 times. The sample was weighed at 18 h, 36 h, 54 h, 72 h, 90 h, 108 h, 126 h, and 144 h, corresponding to pH 14 exposure times of 6 h, 12 h, 18 h, 24 h, 30 h, 36 h, 42 h, and 48 h, respectively.

[0068] Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. The weight loss of the coating film, including a 13% weight loss of the glass fabric, was also determined. The results are listed in Table 2.

[0069]

[0070] Table 2: Weight loss of glass fabric after 48 hours of exposure.

[0071] Example 2 (Invention Example): A PTFE coated film containing GF1 glass fiber was heated in NaOH at pH=14.

[0072] GF1 is woven into a plain-weave glass fabric. The areal density of the glass fibers is approximately 940 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the coated fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1690 g / m³. 2 Cut a circular fragment with a diameter of approximately 3.6 cm from the coating film.

[0073] The fragment was heated in NaOH at pH 14 for 52 h at a temperature of approximately 110°C ± 10°C. The remaining mass of the coating film and the base fabric was determined at 8 h, 16 h, 24 h, 32 h, 40 h, and 52 h. The sample was dried at 120°C for 1 h before mass measurement. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 52 hours, 44.7% of the base fabric was dissolved. The results are listed in Table 3.

[0074]

[0075] Table 3: Weight loss of glass fabric after 52 hours of exposure.

[0076] Example 3 (Invention Example): A PTFE coated film containing GF1 was heated in NaOH at pH=14.

[0077] GF1 was woven into a plain weave glass fabric with an areal density of approximately 940 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1690 g / m³. 2 Use scissors to manually cut the coated film into smaller pieces measuring 3–8 mm.

[0078] The fragments were heated in NaOH at pH 14 for a total of 25 h at a temperature of approximately 110°C ± 10°C. After each 5-hour boiling period in NaOH at pH 14, the sample was heated in distilled water for 1 hour. After each cycle of "5 hours of heating at pH 14 followed by 1 hour of heating in water," the sample was dried at 120°C for 1 hour and weighed. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 25 hours, 58.2% of the base fabric was dissolved. The results are listed in Table 4.

[0079]

[0080] Table 4: Weight loss of glass fabric after 25 hours of exposure.

[0081] Example 4 (Comparative Example): PTFE coated film containing GF1 was heated in sulfuric acid (H2SO4) at pH=1.

[0082] GF1 was woven into a plain weave glass fabric with an areal density of approximately 940 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the coated fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1690 g / m³. 2 Cut a circular fragment with a diameter of approximately 3.6 cm from the coating film.

[0083] The fragment was heated in sulfuric acid at pH 1 for 18 h at a temperature of approximately 110°C ± 10°C. Mass was measured at 6 h, 12 h, and 18 h. The sample was dried at 120°C for 1 h before mass measurement. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 18 hours, only 0.4% of the base fabric was dissolved. The results are listed in Table 5.

[0084]

[0085] Table 5: Weight loss of glass fabric after 18 hours of exposure.

[0086] Example 5 (Comparative Example): A PTFE coated film made of GF1 was heated in sulfuric acid at pH=1.

[0087] GF1 was woven into a plain weave glass fabric with an areal density of approximately 940 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the coated fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1690 g / m³. 2 Use scissors to manually cut the coated film into smaller pieces measuring 3–8 mm.

[0088] The fragments were heated in sulfuric acid at pH 1 for 18 h at a temperature of approximately 110°C ± 10°C. Mass was measured at 6 h, 12 h, and 18 h. The samples were dried at 120°C for 1 h before mass measurement. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 18 hours, only 0.6% of the base fabric was dissolved. The results are listed in Table 6.

[0089]

[0090] Table 6: Weight loss of glass fabric after 18 hours of exposure.

[0091] Example 6 (Comparative Example): PTFE-coated fabric containing GF1 was heated in hydrochloric acid (HCl) at pH=1.

[0092] GF1 was woven into a plain weave glass fabric with an areal density of approximately 940 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the coated fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1690 g / m³. 2 Cut a circular fragment with a diameter of approximately 3.6 cm from the coating film.

[0093] The fragment was heated in hydrochloric acid at pH 1 for 18 h at a temperature of approximately 110°C ± 10°C. Mass was measured at 6 h, 12 h, and 18 h. The sample was dried at 120°C for 1 h before mass measurement. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 18 hours, only 0.3% of the base fabric was dissolved. The results are listed in Table 7.

[0094]

[0095] Table 7: Weight loss of glass fabric after 18 hours of exposure.

[0096] Example 7 (Comparative Example): A PTFE coated film made of GF1 was heated in HCl at pH=1.

[0097] GF1 was woven into a plain weave glass fabric with an areal density of approximately 940 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the coated fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1690 g / m³. 2 Use scissors to manually cut the coated fabric into smaller pieces measuring 3–8 mm.

[0098] The fragments were heated in hydrochloric acid at pH 1 for 18 h at a temperature of approximately 110°C ± 10°C. Mass was measured at 6 h, 12 h, and 18 h. The samples were dried at 120°C for 1 h before mass measurement. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 18 hours, only 0.5% of the base fabric was dissolved. The results are listed in Table 8.

[0099]

[0100] Table 8: Weight loss of glass fabric after 18 hours of exposure.

[0101] Example 8 (Comparative Example): A PTFE-coated film made of E glass was heated in NaOH at pH=14.

[0102] E-glass fibers are woven into a plain weave glass fabric with an areal density of approximately 480 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1140 g / m³. 2Cut a circular fragment with a diameter of approximately 3.6 cm from the coating film.

[0103] The fragment was heated in NaOH at pH 14 for a total of 12 h at a temperature of approximately 110°C ± 10°C. At 6 h and 12 h, the fragment was dried at 120°C for 1 h and weighed. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 12 h, the amount of dissolved base fabric could not be determined. The results are listed in Table 9.

[0104]

[0105] Table 9: Weight loss of glass fabric after 12 hours of exposure.

[0106] Example 9 (Comparative Example): A PTFE-coated film made of E glass was heated in NaOH at pH=14.

[0107] E-glass fibers are woven into a plain weave glass fabric with an areal density of approximately 480 g / m². 2 The glass fabric was then coated with a multilayer PTFE dispersion, wherein after each layer was coated, the fabric was dried and the PTFE was sintered until the areal density of the coated glass film reached approximately 1140 g / m³. 2 Use scissors to manually cut the coated film into smaller pieces measuring 3–8 mm.

[0108] The fragment was heated in NaOH at pH 14 for a total of 12 h at a temperature of approximately 110°C ± 10°C. At 6 h and 12 h, the sample was dried at 120°C for 1 h and weighed. Weight loss was calculated relative to the total weight of the coating film and relative to the weight of the glass fabric. After 12 h, the amount of dissolved base fabric could not be determined. The results are listed in Table 10.

[0109]

[0110] Table 10: Weight loss of glass fabric after 12 hours of exposure.

[0111] In conclusion, only the coated glass film fragments (i.e., the fragments according to the invention) immersed in an alkaline solution with a pH of at least 10 were dissolved by more than 40%.

Claims

1. A method for selectively dissolving a coated glass film, the coated glass film comprising a glass core cloth and at least one layer of a fluoropolymer coating, the method comprising the following steps: - Provide fragments of the coated glass film; - Immerse the fragments in an alkaline solution with a pH greater than or equal to 10; - Heat the alkaline solution to a temperature above 50°C to dissolve the glass core cloth fragments; - Perform solid / liquid separation to recover the fluoropolymer coating.

2. The method according to claim 1, characterized in that, The fragment of the coated glass film contains at least two glass core points that are in contact with the alkaline solution, and the distance between the two points is less than 5 cm.

3. The method according to claim 1 or 2, characterized in that, The glass core cloth comprises at least one glass fiber, and based on the total weight of the glass fibers, the glass fibers contain: - 40 wt% to 76 wt% SiO2, - Total 10 wt% to 25 wt% Na2O and K2O, - Total 10 wt% to 16 wt% CaO and MgO, - 0 to 18 wt% B2O, - 0 to 5 wt% Al2O3.

4. The method according to claim 1 or 2, characterized in that, The glass core cloth comprises at least one glass fiber, and based on the total weight of the glass fibers, the glass fibers contain: - 49 wt% to 69 wt% SiO2, - 16 wt% to 26 wt% Al2O3, - 15 wt% to 16 wt% MgO, - 0 to 6 wt% CaO; - Total 0 to 6 wt% of B2O3, Li2O, Na2O, Y2O3 and La2O3, - Total 0 to 6 wt% of K2O, SrO, TiO2, ZrO2 and Fe2O3.

5. The method according to any one of the preceding claims, characterized in that, The glass core cloth is woven fabric, nonwoven fabric, mesh, or at least one yarn.

6. The method according to any one of the preceding claims, characterized in that, The at least one fluoropolymer coating comprises at least one fluoropolymer selected from the following: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoroalkoxy polymer (PFA), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and mixtures thereof.

7. The method according to claim 6, characterized in that, The fluoropolymer is polytetrafluoroethylene.

8. The method according to any one of the preceding claims, characterized in that, The coated glass film comprises at least two layers of fluoropolymer coating, wherein the two layers have the same polymer composition.

9. The method according to any one of the preceding claims, characterized in that, The coated glass film comprises at least two layers of fluoropolymer coating, each of which contains a different fluoropolymer.

10. The method according to any one of the preceding claims, characterized in that, The alkaline solution is selected from the following Brønsted alkaline solutions: alkali metal hydroxides, alkaline earth metal hydroxides, and ammonia.

11. The method according to any one of the preceding claims, characterized in that, The alkaline solution is an aqueous sodium hydroxide solution with a pH greater than or equal to 12.

12. The method according to any one of the preceding claims, characterized in that, The step of heating the alkaline solution is above 10 5 The test was conducted under a pressure of Pa.

13. The method according to any one of the preceding claims, characterized in that, Solid / liquid separation is achieved through filtration or centrifugation.

14. The method according to any one of the preceding claims, characterized in that, The fluoropolymer coating recovered from solid / liquid separation is washed with an aqueous solution.

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