A PTFE multilayer composite membrane and its preparation method

Abstract

This invention relates to the field of multilayer composite membrane technology, specifically to a PTFE multilayer composite membrane and its preparation method: S1: Raw material preparation, the PTFE membrane consists of three layers, namely two outer layers and an inner layer, with the inner layer sandwiched between the two outer layers. In this invention, the stretching process generates numerous wrinkles on the PTFE membrane surface, creating tiny pores. Subsequent treatment with a sodium naphthalene solution generates free radicals on the PTFE membrane surface, enabling the PTFE membrane to effectively adhere to and bond with the fibrous material contained in the second coating. This ensures the fibrous material is firmly attached to the PTFE membrane surface, improving the bonding strength of the multilayer PTFE membrane. The PTFE membrane with the attached fiber layer is sandwiched between the two outer layers, achieving the goal of improving the strength performance of the PTFE multilayer composite membrane.

Description

Technical Field

[0001] This invention relates to the field of multilayer composite membrane technology, specifically to a PTFE multilayer composite membrane and its preparation method. Background Technology

[0002] PTFE membrane is a polymer material made of tetrafluoroethylene. PTFE membrane has extremely high stability and can withstand most strong acids, strong alkalis and strong oxidants. It also has a low coefficient of friction and is non-stick. In industry, it is used for chemical pipeline linings, electronic insulation layers, etc. In daily life, it is used for non-stick cookware coatings, outdoor clothing and medical catheter coatings, and many other applications.

[0003] In existing technologies, the bonding performance of multilayer PTFE membranes is poor during the preparation of PTFE multilayer composite membranes, which affects the strength performance of the PTFE multilayer composite membrane. Therefore, this invention provides a PTFE multilayer composite membrane and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a PTFE multilayer composite membrane and its preparation method. The PTFE multilayer composite membrane prepared by this invention not only has good tensile strength properties, but also excellent elongation at break properties, effectively improving the performance of the PTFE multilayer composite membrane.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a PTFE multilayer composite film, comprising the following steps:

[0007] S1: Raw material preparation, the PTFE membrane is divided into three layers, the three-layer PTFE membrane is divided into two outer layers and an inner layer, the inner layer is placed between the two outer layers when stacked, the thickness of the two outer layers is 0.08-0.12mm, and the thickness of the inner layer is 0.12-0.14mm;

[0008] S3: The inner membrane undergoes a stretching process;

[0009] S4: The inner membrane after stretching is modified to obtain a modified inner membrane;

[0010] S5: Preparation of the first coating material, wherein the first coating material is used to coat the surfaces of the two outer film layers;

[0011] S6: Preparation of the second coating material, wherein the second coating material is used to coat the surface of the modified inner layer film;

[0012] S7: Pressing process, the two coated outer films and the coated inner film are pressed together to obtain a PTFE multilayer composite film.

[0013] Further, the method for stretching the inner layer film is as follows: the inner layer film is sent into a drying oven, the oven is set to 120-130℃ for 12-16 minutes for heating treatment, the heated inner layer film is fixed in the clamp position of the biaxial stretching machine, the stretching speed is set to 1-3 mm / s, the stretching ratio is 1.2-1.6 times, and after stretching to the required position, it is held for 8-12 seconds. After a single stretching is completed, it is sent into the drying oven to continue the above heating steps. The heating and stretching steps are repeated 3-5 times to complete the stretching treatment of the inner layer film.

[0014] Further, the modification treatment method for the inner layer membrane after stretching is as follows: the inner layer membrane is immersed in sodium naphthalene solution for 4-6 minutes, and after immersion, it is placed in a draining frame and left to stand for 1-3 hours. Then, it is placed in a lamp box, and the surface of the inner layer membrane is irradiated with ultraviolet lamp for 40-50 minutes. Halfway through the irradiation time, the inner layer membrane is turned over. After the irradiation treatment is completed, the inner layer membrane is rinsed with acetone. After rinsing, it is placed in an oven and dried at 50-70℃ for 20-30 minutes to complete the modification treatment of the inner layer membrane and obtain the modified inner layer membrane.

[0015] Furthermore, the concentration of the sodium naphthalene solution is 0.4–0.6 mol / L.

[0016] Furthermore, the wavelength of the ultraviolet lamp is 200–300 nm, and the irradiation intensity is 20–40 mW / cm². 2 .

[0017] Furthermore, the first coating material is a mixture of waterborne polyurethane emulsion and hydroxyethyl cellulose, wherein the mass of the hydroxyethyl cellulose is 4 to 6% of the mass of the waterborne polyurethane emulsion.

[0018] Furthermore, the coating process of the first coating material is as follows: the outer film is immersed in the first coating material for 2 to 4 hours, and after immersion, it is placed in an oven and dried at 40 to 50 degrees Celsius for 20 to 30 minutes to complete the coating process of the outer film.

[0019] Further, the second coating material is selected as a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, wherein the mass ratio of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive is 1:(0.6~0.8):(0.6~0.8):(0.1~0.3). The coating treatment method of the second coating material is as follows: the second coating material is uniformly coated on the surface of the modified inner layer film, and after coating, vacuum drying treatment is performed at a temperature of 50~60℃, a vacuum degree of 0.07~0.09MPa, and a treatment time of 1~3h to complete the coating treatment of the second coating material.

[0020] Furthermore, the pressing process is as follows: two outer films that have completed the coating process and a modified inner film that has completed the coating process are stacked together, and the stacked material is pressed together. The pressure is set to 0.8-1.2 MPa, and the heating temperature on both sides is 340-360°C. After pressing, the material is allowed to cool down to obtain a PTFE multilayer composite film.

[0021] Secondly, the present invention also provides a PTFE multilayer composite membrane, which is prepared by a method for preparing PTFE multilayer composite membranes.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. In this invention, during the preparation of the PTFE multilayer composite membrane, the inner membrane is pre-stretched and modified. The stretching process generates numerous wrinkles on the PTFE membrane surface and creates tiny pores. Subsequent treatment with sodium naphthalene solution generates free radicals on the PTFE membrane surface, enabling the PTFE membrane to effectively adhere to and bond with the fibrous material contained in the second coating. This ensures the fibrous material is firmly attached to the PTFE membrane surface, improving the bonding strength of the multilayer PTFE membrane. The PTFE membrane with the attached fiber layer is sandwiched between the two outer membranes, achieving the goal of improving the strength performance of the PTFE multilayer composite membrane.

[0024] 2. In this invention, by treating the PTFE membrane with ultraviolet light, the ultraviolet light can cause the molecular chains on the surface of the PTFE membrane to undergo photochemical reactions. The photochemical reactions generate free radicals and active sites of unsaturated bonds. These active sites can react with the active components in the second coating material, thereby improving the bonding performance between the second coating material and the PTFE membrane and enhancing the strength of the PTFE membrane.

[0025] 3. In this invention, the combined use of glass fiber, aramid fiber, epoxy resin, and polyurethane adhesive in the second coating material provides excellent insulation and chemical corrosion resistance for the glass fiber, and outstanding tensile and impact resistance for the aramid fiber. The combined use of these two materials effectively improves the strength of the PTFE membrane. At the same time, the epoxy resin and polyurethane adhesive produce good bonding properties, allowing the fiber layer to bond better with the PTFE membrane. When the PTFE multilayer composite membrane is subjected to tension during use, the fiber structure can bear the tensile force and prevent crack propagation, thereby improving the tensile properties and tensile strength at break of the composite membrane. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] S1: Raw material preparation, the PTFE membrane is divided into three layers, the three-layer PTFE membrane is divided into two outer layers and an inner layer, the inner layer is placed between the two outer layers when stacked, the thickness of the two outer layers is 0.08mm, and the thickness of the inner layer is 0.12mm;

[0029] S3: The inner membrane undergoes a stretching process;

[0030] S4: The inner membrane after stretching is modified to obtain a modified inner membrane;

[0031] S5: Preparation of the first coating material, wherein the first coating material is used to coat the surfaces of the two outer film layers;

[0032] S6: Preparation of the second coating material, wherein the second coating material is used to coat the surface of the modified inner layer film;

[0033] S7: Pressing process, the two coated outer films and the coated inner film are pressed together to obtain a PTFE multilayer composite film.

[0034] The method for stretching the inner layer membrane is as follows: the inner layer membrane is sent into a drying oven, the oven is set to 120℃ for 12 minutes, the heated inner layer membrane is fixed in the clamp position of the biaxial stretching machine, the stretching speed is set to 1 mm / s, the stretching ratio is 1.2 times, and it is held for 8 seconds after stretching. After a single stretching is completed, it is sent into the drying oven to continue the above heating steps. The heating and stretching steps are repeated 3 times to complete the stretching treatment of the inner layer membrane.

[0035] The modification treatment method for the inner layer membrane after stretching is as follows: The inner layer membrane is immersed in sodium naphthalene solution for 4 minutes. After immersion, it is placed in a draining frame and left to stand for 1 hour. Then, it is placed in a lamp box and the surface of the inner layer membrane is irradiated with ultraviolet lamp for 40 minutes. Halfway through the irradiation time, the inner layer membrane is turned over. After the irradiation treatment is completed, the inner layer membrane is rinsed with acetone. After rinsing, it is placed in an oven and dried at 50°C for 20 minutes to complete the modification treatment of the inner layer membrane and obtain the modified inner layer membrane.

[0036] The concentration of the sodium naphthalene solution is 0.4 mol / L.

[0037] The ultraviolet lamp has a wavelength of 200nm and an irradiation intensity of 20mW / cm². 2 .

[0038] The first coating material is a mixture of waterborne polyurethane emulsion and hydroxyethyl cellulose, wherein the mass of hydroxyethyl cellulose is 4% of the mass of the waterborne polyurethane emulsion.

[0039] The coating process of the first coating material is as follows: the outer film is immersed in the first coating material for 2 hours, and after immersion, it is placed in an oven and dried at 40°C for 20 minutes to complete the coating process of the outer film.

[0040] The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, wherein the mass ratio of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive is 1:(0.6):(0.6):(0.1). The coating treatment method of the second coating material is as follows: the second coating material is uniformly coated on the surface of the modified inner layer film, and after coating, vacuum drying treatment is performed at a temperature of 50°C, a vacuum degree of 0.07MPa and a treatment time of 1 hour to complete the coating treatment of the second coating material.

[0041] The pressing process is as follows: two outer films that have completed the coating process and a modified inner film that has completed the coating process are stacked together, and the stacked material is pressed together. The pressure is set to 0.8 MPa, and the heating temperature on both sides is 340°C. After pressing, the material is allowed to cool down to obtain a PTFE multilayer composite film.

[0042] Example 2:

[0043] S1: Raw material preparation, the PTFE membrane is divided into three layers, the three-layer PTFE membrane is divided into two outer layers and an inner layer, the inner layer is placed between the two outer layers when stacked, the thickness of the two outer layers is 0.1mm, and the thickness of the inner layer is 0.13mm;

[0044] S3: The inner membrane undergoes a stretching process;

[0045] S4: The inner membrane after stretching is modified to obtain a modified inner membrane;

[0046] S5: Preparation of the first coating material, wherein the first coating material is used to coat the surfaces of the two outer film layers;

[0047] S6: Preparation of the second coating material, wherein the second coating material is used to coat the surface of the modified inner layer film;

[0048] S7: Pressing process, the two coated outer films and the coated inner film are pressed together to obtain a PTFE multilayer composite film.

[0049] The method for stretching the inner layer membrane is as follows: the inner layer membrane is sent into a drying oven, which is set to 125°C for 14 minutes. After heating, the inner layer membrane is fixed in the clamp position of the biaxial stretching machine. The stretching speed is set to 2 mm / s and the stretching ratio is 1.4 times. After stretching to the desired position, it is held for 10 seconds. After a single stretching is completed, the membrane is sent back into the drying oven to continue the above heating steps. The heating and stretching steps are repeated 4 times to complete the stretching treatment of the inner layer membrane.

[0050] The modification treatment method for the inner layer membrane after stretching is as follows: The inner layer membrane is immersed in sodium naphthalene solution for 5 minutes. After immersion, it is placed in a draining frame and left to stand for 2 hours. Then, it is placed in a lamp box and the surface of the inner layer membrane is irradiated with ultraviolet lamp for 45 minutes. Halfway through the irradiation time, the inner layer membrane is turned over. After the irradiation treatment is completed, the inner layer membrane is rinsed with acetone. After rinsing, it is placed in an oven and dried at 60°C for 25 minutes to complete the modification treatment of the inner layer membrane and obtain the modified inner layer membrane.

[0051] The concentration of the sodium naphthalene solution is 0.5 mol / L.

[0052] The ultraviolet lamp has a wavelength of 250nm and an irradiation intensity of 30mW / cm². 2 .

[0053] The first coating material is a mixture of waterborne polyurethane emulsion and hydroxyethyl cellulose, wherein the mass of hydroxyethyl cellulose is 5% of the mass of the waterborne polyurethane emulsion.

[0054] The coating process of the first coating material is as follows: the outer film is immersed in the first coating material for 3 hours, and after immersion, it is placed in an oven and dried at 45°C for 25 minutes to complete the coating process of the outer film.

[0055] The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin, and polyurethane adhesive, wherein the mass ratio of glass fiber, aramid fiber, epoxy resin, and polyurethane adhesive is 1:1.

[0056] (0.7): (0.7): (0.2), the coating treatment method of the second coating material is as follows: the second coating material is uniformly coated on the surface of the modified inner layer film, and after coating, vacuum drying treatment is performed at a temperature of 55°C, a vacuum degree of 0.08MPa, and a treatment time of 5h to complete the coating treatment of the second coating material.

[0057] The pressing process is as follows: two outer films that have completed the coating process and a modified inner film that has completed the coating process are stacked together, and the stacked material is pressed together. The pressure is set to 1 MPa, and the heating temperature on both sides is 350°C. After pressing, the material is allowed to cool down to obtain a PTFE multilayer composite film.

[0058] Example 3:

[0059] S1: Raw material preparation, the PTFE membrane is divided into three layers, the three-layer PTFE membrane is divided into two outer layers and an inner layer, the inner layer is placed between the two outer layers when stacked, the thickness of the two outer layers is 0.12mm, and the thickness of the inner layer is 0.14mm;

[0060] S3: The inner membrane undergoes a stretching process;

[0061] S4: The inner membrane after stretching is modified to obtain a modified inner membrane;

[0062] S5: Preparation of the first coating material, wherein the first coating material is used to coat the surfaces of the two outer film layers;

[0063] S6: Preparation of the second coating material, wherein the second coating material is used to coat the surface of the modified inner layer film;

[0064] S7: Pressing process, the two coated outer films and the coated inner film are pressed together to obtain a PTFE multilayer composite film.

[0065] The method for stretching the inner layer membrane is as follows: the inner layer membrane is sent into a drying oven, which is set to 130°C for 16 minutes. After heating, the inner layer membrane is fixed in the clamp position of the biaxial stretching machine. The stretching speed is set to 3 mm / s and the stretching ratio is 1.6 times. After stretching to the desired position, it is held for 12 seconds. After a single stretching is completed, the membrane is sent back into the drying oven to continue the above heating steps. The heating and stretching steps are repeated 5 times to complete the stretching treatment of the inner layer membrane.

[0066] The modification treatment method for the inner layer membrane after stretching is as follows: The inner layer membrane is immersed in sodium naphthalene solution for 6 minutes. After immersion, it is placed in a draining frame and left to stand for 3 hours. Then, it is placed in a lamp box and the surface of the inner layer membrane is irradiated with ultraviolet lamp for 50 minutes. Halfway through the irradiation time, the inner layer membrane is turned over. After the irradiation treatment is completed, the inner layer membrane is rinsed with acetone. After rinsing, it is placed in an oven and dried at 70°C for 30 minutes to complete the modification treatment of the inner layer membrane and obtain the modified inner layer membrane.

[0067] The concentration of the sodium naphthalene solution is 0.6 mol / L.

[0068] The ultraviolet lamp has a wavelength of 300nm and an irradiation intensity of 40mW / cm². 2 .

[0069] The first coating material is a mixture of waterborne polyurethane emulsion and hydroxyethyl cellulose, wherein the mass of hydroxyethyl cellulose is 6% of the mass of the waterborne polyurethane emulsion.

[0070] The coating process of the first coating material is as follows: the outer film is immersed in the first coating material for 4 hours, and after immersion, it is placed in an oven and dried at 50°C for 30 minutes to complete the coating process of the outer film.

[0071] The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, wherein the mass ratio of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive is 1:(0.8):(0.8):(0.3). The coating treatment method of the second coating material is as follows: the second coating material is uniformly coated on the surface of the modified inner layer film, and after coating, vacuum drying treatment is performed at a temperature of 60°C, a vacuum degree of 0.09MPa and a treatment time of 3h to complete the coating treatment of the second coating material.

[0072] The pressing process is as follows: two outer films that have completed the coating process and a modified inner film that has completed the coating process are stacked together, and the stacked material is pressed together. The pressure is set to 1.2 MPa, and the heating temperature on both sides is 360°C. After pressing, the material is allowed to cool down to obtain a PTFE multilayer composite film.

[0073] Comparative Example 1: The difference between this comparative example and Example 1 is that the inner membrane was not stretched in this comparative example.

[0074] Comparative Example 2 differs from Example 1 in that the inner membrane was not modified in this comparative example.

[0075] Comparative Example 3 differs from Example 1 in that it does not include the first coating material or the coating process of the first coating material.

[0076] Comparative Example 4 differs from Example 1 in that it does not include the second coating material or the coating process of the second coating material.

[0077] Performance testing: The PTFE multilayer composite membranes prepared in Examples 1, 2, 3, 1, 2, 3, and 4 were subjected to performance testing. The test data are recorded in the table below:

[0078]

[0079] In the performance test, the PTFE multilayer composite films prepared in Examples 1, 2, 3, 1, 2, 3 and 4 were all cut into test samples with a length of 300 mm and a width of 80 mm. The samples were clamped in a tensile testing machine, and the tensile strength and elongation at break were tested in the transverse and longitudinal directions, respectively. The tensile speed of the tensile testing machine was 2 mm / s.

[0080] The transverse tensile strength data of the PTFE multilayer composite membranes prepared in Examples 1, 2, 3, 1, 2, 3, and 4 are 75.3 MPa, 75.8 MPa, 75.2 MPa, 61.5 MPa, 62.7 MPa, 59.6 MPa, and 64.7 MPa, respectively.

[0081] The longitudinal tensile strength data of the PTFE multilayer composite membranes prepared in Examples 1, 2, 3, 1, 2, 3 and 4 are 72.4 MPa, 73.1 MPa, 72.6 MPa, 59.3 MPa, 61.5 MPa, 51.5 MPa and 60.5 MPa, respectively.

[0082] The transverse elongation at break of the PTFE multilayer composite membranes prepared in Examples 1, 2, 3, 1, 2, 3, and 4 were 233.5%, 234.6%, 232.8%, 163.3%, 164.6%, 152.2%, and 166.7%, respectively.

[0083] The longitudinal elongation at break of the PTFE multilayer composite membranes prepared in Examples 1, 2, 3, 1, 2, 3, and 4 were 256.1%, 258.7%, 256.4%, 182.5%, 183.4%, 177.6%, and 171.1%, respectively.

[0084] It is evident that the tensile strength and elongation at break of the PTFE multilayer composite membranes prepared in Comparative Examples 1, 2, 3, and 4 are all lower than those in Examples 1, 2, and 3. This indicates that during the preparation of the PTFE multilayer composite membrane, the pre-stretching and modification treatment of the inner membrane generates numerous wrinkles and micropores on the PTFE membrane surface. Subsequent treatment with sodium naphthalene solution generates free radicals on the PTFE membrane surface, enabling the PTFE membrane to effectively adhere to and bond with the fibrous material contained in the second coating. This allows the fibrous material to firmly adhere to the PTFE membrane surface, and the PTFE membrane with the attached fiber layer is sandwiched between the two outer membranes, thus achieving the goal of improving the strength performance of the PTFE multilayer composite membrane.

[0085] By comparing and analyzing the relevant data in the table, it can be seen that the PTFE multilayer composite film prepared by this invention not only has good tensile strength properties but also excellent elongation at break properties. This indicates that the PTFE multilayer composite film and its preparation method provided by this invention have broader market prospects and are more suitable for widespread application.

[0086] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0087] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a PTFE multilayer composite membrane, characterized in that: Includes the following steps: S1: Raw material preparation, the PTFE membrane is divided into three layers, the three-layer PTFE membrane is divided into two outer layers and an inner layer, the inner layer is placed between the two outer layers when stacked, the thickness of the two outer layers is 0.08-0.12mm, and the thickness of the inner layer is 0.12-0.14mm; S3: The inner membrane undergoes a stretching process; S4: The inner membrane after stretching is modified to obtain a modified inner membrane; S5: Preparation of the first coating material, wherein the first coating material is used to coat the surfaces of the two outer film layers; S6: Preparation of the second coating material, wherein the second coating material is used to coat the surface of the modified inner layer film; S7: Pressing process, the two coated outer films and the coated inner film are pressed together to obtain a PTFE multilayer composite film; The method for stretching the inner layer film is as follows: the inner layer film is sent into a drying oven, the oven is set to 120-130℃ for 12-16 minutes, the heated inner layer film is fixed in the clamp position of the biaxial stretching machine, the stretching speed is set to 1-3 mm / s, the stretching ratio is 1.2-1.6 times, and after stretching to the desired position, it is held for 8-12 seconds. After a single stretching is completed, it is sent into the drying oven to continue the above heating steps. The heating and stretching steps are repeated 3-5 times to complete the stretching treatment of the inner layer film. The modification treatment method for the inner layer membrane after stretching is as follows: The inner layer membrane is immersed in sodium naphthalene solution for 4-6 minutes. After immersion, it is placed in a draining frame and left to stand for 1-3 hours. Then, it is placed in a lamp box and the surface of the inner layer membrane is irradiated with ultraviolet lamp for 40-50 minutes. Halfway through the irradiation time, the inner layer membrane is turned over. After the irradiation treatment is completed, the inner layer membrane is rinsed with acetone. After rinsing, it is placed in an oven and dried at 50-70℃ for 20-30 minutes to complete the modification treatment of the inner layer membrane and obtain the modified inner layer membrane. The first coating material is a mixture of waterborne polyurethane emulsion and hydroxyethyl cellulose, wherein the mass of hydroxyethyl cellulose is 4-6% of the mass of the waterborne polyurethane emulsion; The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, wherein the mass ratio of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive is 1:(0.6~0.8):(0.6~0.8):(0.1~0.3).

2. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that, The concentration of the sodium naphthalene solution is 0.4–0.6 mol / L.

3. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that, The ultraviolet lamp has a wavelength of 200–300 nm and an irradiation intensity of 20–40 nm. .

4. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that, The coating process of the first coating material is as follows: the outer film is immersed in the first coating material for 2 to 4 hours, and after immersion, it is placed in an oven and dried at 40 to 50 degrees Celsius for 20 to 30 minutes to complete the coating process of the outer film.

5. The method for preparing a PTFE multilayer composite membrane according to claim 1, characterized in that, The coating process for the second coating material is as follows: the second coating material is uniformly coated on the surface of the modified inner layer film, and then vacuum drying is performed at a temperature of 50-60℃, a vacuum degree of 0.07-0.09MPa, and a processing time of 1-3h to complete the coating process of the second coating material.

6. The method for preparing a PTFE multilayer composite membrane according to claim 1, characterized in that, The pressing process is as follows: two outer films that have completed the coating process and a modified inner film that has completed the coating process are stacked together, and the stacked material is pressed together. The pressure is set to 0.8 to 1.2 MPa, and the heating temperature on both sides is 340 to 360°C. After pressing, the material is allowed to cool down to obtain a PTFE multilayer composite film.

7. A PTFE multilayer composite membrane, characterized in that, It is prepared by the method for preparing PTFE multilayer composite membrane according to any one of claims 1 to 6.

Images