PTFE multilayer composite film and preparation method thereof

Abstract

The invention relates to the technical field of multi-layer composite membranes, in particular to a PTFE multi-layer composite membrane and a preparation method thereof, and the preparation method comprises the following steps: S1, raw material preparation: the PTFE membrane is divided into three layers, the three layers of PTFE membranes are divided into two outer layer membranes and an inner layer membrane, and the inner layer membrane is located between the two outer layer membranes during stacking; according to the method, a large number of wrinkles can be generated on the surface of the PTFE membrane through stretching treatment, meanwhile, tiny pores can be generated on the surface of the PTFE membrane, free radicals are generated on the surface of the PTFE membrane through subsequent sodium-naphthalene solution treatment, the PTFE membrane can be effectively attached and combined with fiber substances contained in a second coating material, the fiber substances are stably attached to the surface of the PTFE membrane, and therefore the PTFE membrane can be effectively attached to the surface of the PTFE membrane. And the PTFE film attached with the fiber layer is clamped between the two outer-layer films, so that the purpose of improving the strength performance of the PTFE multi-layer composite film is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of multilayer composite membranes, in particular to a PTFE multilayer composite membrane and a preparation method thereof. Background Art

[0002] PTFE membrane is a polymer material formed by the polymerization of tetrafluoroethylene. PTFE membrane is extremely stable and can withstand most strong acids, strong alkalis and strong oxidants. It has a low surface friction coefficient and is non-sticky. It is used in industry for chemical pipeline linings, electronic insulation layers, etc. In daily life, it is used for non-stick pan coatings, outdoor clothing, medical catheter coatings and many other aspects.

[0003] In the prior art, in the preparation of PTFE multilayer composite membranes, the bonding performance of the multilayer PTFE membranes is poor, which affects the strength performance of the PTFE multilayer composite membranes. Based on this, the present invention provides a PTFE multilayer composite membrane and a preparation method. Summary of the invention

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

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a PTFE multilayer composite membrane, 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 membranes and an inner membrane, the inner membrane is located between the two outer membranes when superimposed, the thickness of the two outer membranes is 0.08-0.12 mm, and the thickness of the inner membrane is 0.12-0.14 mm;

[0008] S3: The inner layer film is stretched;

[0009] S4: performing a modification treatment on the inner layer film after the stretching treatment to obtain a modified inner layer film;

[0010] S5: preparing a first coating material, wherein the first coating material is applied to the surfaces of the two outer films;

[0011] S6: preparing a second coating material, wherein the second coating material is applied to the surface of the modified inner layer film;

[0012] S7: Lamination treatment: two outer layer films that have been coated and an inner layer film that has been coated are laminated to obtain a PTFE multilayer composite film.

[0013] Furthermore, the method for stretching the inner layer film is as follows: the inner layer film is sent to a drying oven, the oven is set at 120-130°C for heating treatment 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 the film is held for 8-12 seconds after being stretched into place. After a single stretching is completed, the film is sent to the oven to continue the above-mentioned heating steps. The heating and stretching steps are repeated 3-5 times to complete the stretching treatment of the inner layer film.

[0014] Furthermore, the modification method of the inner layer film that has completed the stretching treatment is: the inner layer film is immersed in a sodium naphthalene solution for 4 to 6 minutes, and then placed in a drain frame for 1 to 3 hours, and then sent to a light box. The light box uses an ultraviolet lamp to irradiate the surface of the inner layer film for 40 to 50 minutes. When the time is halfway, the inner layer film is turned over. After the irradiation treatment is completed, the inner layer film is rinsed with acetone, and then placed in an oven. The oven is set at 50 to 70°C for drying for 20 to 30 minutes to complete the modification treatment of the inner layer film and obtain a modified inner layer film.

[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 200-300nm, and the irradiation intensity is 20-40mW / cm 2 .

[0017] Furthermore, the first coating material is a mixture of water-based polyurethane emulsion and hydroxyethyl cellulose, and the mass of the hydroxyethyl cellulose is 4-6% of the mass of the water-based polyurethane emulsion.

[0018] Furthermore, the coating treatment method of the first coating material is: the outer layer film is immersed in the first coating material for 2 to 4 hours, and then placed in an oven at 40 to 50° C. for drying for 20 to 30 minutes to complete the coating treatment of the outer layer film.

[0019] Furthermore, the second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, and the mass ratio of the 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: uniformly apply the second coating material on the surface of the modified inner layer film, and perform vacuum drying treatment after coating, the temperature is 50-60°C, the vacuum degree is 0.07-0.09MPa, and the treatment time is 1-3h to complete the coating treatment of the second coating material.

[0020] Furthermore, the lamination method is as follows: two outer layer membranes that have been coated and a modified inner layer membrane that has been coated are stacked, the stacked product is subjected to lamination, the pressure is set to 0.8-1.2 MPa, the heating temperature of both sides is 340-360°C, and after lamination is completed, cooling is waited to obtain a PTFE multilayer composite membrane.

[0021] In a second aspect, the present invention further provides a PTFE multi-layer composite membrane, which is prepared by the preparation method of the PTFE multi-layer composite membrane.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In the present invention, during the preparation process of the PTFE multilayer composite membrane, the inner layer membrane is pre-stretched and modified, and the stretching treatment will cause a large number of wrinkles to be generated on the surface of the PTFE membrane, and at the same time, tiny pores can be generated on the surface of the PTFE membrane. After the subsequent sodium naphthalene solution treatment, free radicals are generated on the surface of the PTFE membrane, so that the PTFE membrane can effectively adhere to and combine with the fiber material contained in the second coating material, so that the fiber material is firmly attached to the surface of the PTFE membrane, thereby improving the bonding strength of the multilayer PTFE membrane. The PTFE membrane attached with the fiber layer is sandwiched between the two outer membranes, thereby achieving the purpose of improving the strength performance of the PTFE multilayer composite membrane.

[0024] 2. In the present invention, by subjecting the PTFE membrane to ultraviolet irradiation treatment, ultraviolet irradiation can cause a photochemical reaction in the molecular chains on the surface of the PTFE membrane. The photochemical reaction produces active sites of free radicals and unsaturated bonds. The active sites can react with the active ingredients in the second coating material, thereby improving the bonding performance between the second coating material and the PTFE membrane and enhancing the strength enhancement effect on the PTFE membrane.

[0025] 3. In the present invention, through the combined use of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive in the second coating material, the glass fiber has good insulation and chemical corrosion resistance, and the aramid fiber has excellent tensile and impact resistance. The combined use of the two can effectively improve the strength performance of the PTFE membrane. At the same time, the use of epoxy resin and polyurethane adhesive produces better bonding performance, which can make the fiber layer and the PTFE membrane better bonded together. When the PTFE multi-layer composite membrane is stretched during use, the fiber structure can be used to bear the tension and prevent the expansion of cracks, thereby improving the tensile properties and elongation at break performance of the composite membrane. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1:

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

[0029] S3: The inner layer film is stretched;

[0030] S4: performing a modification treatment on the inner layer film after the stretching treatment to obtain a modified inner layer film;

[0031] S5: preparing a first coating material, wherein the first coating material is applied to the surfaces of the two outer films;

[0032] S6: preparing a second coating material, wherein the second coating material is applied to the surface of the modified inner layer film;

[0033] S7: Lamination treatment: two outer layer films that have been coated and an inner layer film that has been coated are laminated to obtain a PTFE multilayer composite film.

[0034] The method for stretching the inner layer film is as follows: the inner layer film is sent to a drying oven, the oven is set to 120°C for heating treatment for 12 minutes, the heated inner layer film is fixed in the clamp position of the biaxial stretching machine, the stretching speed is set to 1mm / s, the stretching ratio is 1.2 times, and it is held for 8s after being stretched into place. After a single stretching is completed, it is sent to the 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 film.

[0035] The modification method of the inner layer film that has completed the stretching treatment is as follows: the inner layer film is immersed in a sodium naphthalene solution for 4 minutes, and then placed in a drain frame for 1 hour, and then sent to a light box. The light box uses an ultraviolet lamp to irradiate the surface of the inner layer film for 40 minutes. When the time is halfway, the inner layer film is turned over. After the irradiation treatment is completed, the inner layer film is rinsed with acetone, and then placed in an oven. The oven is set at 50°C for drying for 20 minutes to complete the modification treatment of the inner layer film and obtain a modified inner layer film.

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

[0037] The wavelength of the ultraviolet lamp is 200nm, and the irradiation intensity is 20mW / cm 2 .

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

[0039] The coating treatment method of the first coating material is: the outer layer film is immersed in the first coating material for 2 hours, and then placed in an oven after immersion, and the oven is set at 40° C. for drying for 20 minutes to complete the coating treatment of the outer layer film.

[0040] The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, and the mass ratio of the glass fiber, aramid fiber, epoxy resin and polyurethane adhesive is 1:(0.6):(0.6):(0.1). The coating method of the second coating material is: evenly apply the second coating material on the surface of the modified inner layer film, and perform vacuum drying after coating, the temperature is 50°C, the vacuum degree is 0.07MPa, the processing time is 1h, and the coating treatment of the second coating material is completed.

[0041] The lamination method is as follows: two outer layer films that have been coated are superimposed on the modified inner layer film that has been coated, and the superimposed materials are subjected to lamination. The pressure is set to 0.8 MPa, and the heating temperature of both sides is 340° C. After the lamination is completed, cooling is waited to obtain a PTFE multilayer composite film.

[0042] Embodiment 2:

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

[0044] S3: The inner layer film is stretched;

[0045] S4: performing a modification treatment on the inner layer film after the stretching treatment to obtain a modified inner layer film;

[0046] S5: preparing a first coating material, wherein the first coating material is applied to the surfaces of the two outer films;

[0047] S6: preparing a second coating material, wherein the second coating material is applied to the surface of the modified inner layer film;

[0048] S7: Lamination treatment: two outer layer films that have been coated and an inner layer film that has been coated are laminated to obtain a PTFE multilayer composite film.

[0049] The method for stretching the inner layer film is as follows: the inner layer film is sent to a drying oven, the oven is set at 125°C for heating treatment for 14 minutes, the heated inner layer film is fixed in the clamp position of the biaxial stretching machine, the stretching speed is set to 2mm / s, the stretching ratio is 1.4 times, and it is held for 10s after being stretched into place. After a single stretching is completed, it is sent to the 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 film.

[0050] The modification method of the inner layer film that has completed the stretching treatment is as follows: the inner layer film is immersed in a sodium naphthalene solution for 5 minutes, placed in a drain frame for 2 hours, and then sent to a light box. The light box uses an ultraviolet lamp to irradiate the surface of the inner layer film for 45 minutes. When the time is halfway, the inner layer film is turned over. After the irradiation treatment is completed, the inner layer film is rinsed with acetone, and then placed in an oven. The oven is set at 60°C for drying for 25 minutes to complete the modification treatment of the inner layer film and obtain a modified inner layer film.

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

[0052] The wavelength of the ultraviolet lamp is 250nm and the irradiation intensity is 30mW / cm 2 .

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

[0054] The coating treatment method of the first coating material is: the outer layer film is immersed in the first coating material for 3 hours, and then placed in an oven at 45° C. for 25 minutes to complete the coating treatment of the outer layer film.

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

[0056] (0.7): (0.7): (0.2), the coating treatment method of the second coating material is: evenly coat the second coating material on the surface of the modified inner layer film, and perform vacuum drying treatment after coating, the temperature is 55°C, the vacuum degree is 0.08MPa, the treatment time is 5h, and the coating treatment of the second coating material is completed.

[0057] The lamination method is as follows: two outer layer films that have been coated are superimposed on the modified inner layer film that has been coated, and the superimposed materials are subjected to lamination. The pressure is set to 1 MPa, and the heating temperature of both sides is 350° C. After the lamination is completed, cooling is waited to obtain a PTFE multilayer composite film.

[0058] Embodiment three:

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

[0060] S3: The inner layer film is stretched;

[0061] S4: performing a modification treatment on the inner layer film after the stretching treatment to obtain a modified inner layer film;

[0062] S5: preparing a first coating material, wherein the first coating material is applied to the surfaces of the two outer films;

[0063] S6: preparing a second coating material, wherein the second coating material is applied to the surface of the modified inner layer film;

[0064] S7: Lamination treatment: two outer layer films that have been coated and an inner layer film that has been coated are laminated to obtain a PTFE multilayer composite film.

[0065] The method for stretching the inner layer film is as follows: the inner layer film is sent to a drying oven, the oven is set to 130°C for heating treatment for 16 minutes, the heated inner layer film is fixed in the clamp position of the biaxial stretching machine, the stretching speed is set to 3mm / s, the stretching ratio is 1.6 times, and it is held for 12s after being stretched into place. After a single stretching is completed, it is sent to the 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 film.

[0066] The modification method of the inner layer film that has completed the stretching treatment is as follows: the inner layer film is immersed in a sodium naphthalene solution for 6 minutes, and then placed in a drain frame for 3 hours, and then sent to a light box. The light box uses an ultraviolet lamp to irradiate the surface of the inner layer film for 50 minutes. When the time is halfway, the inner layer film is turned over. After the irradiation treatment is completed, the inner layer film is rinsed with acetone, and then placed in an oven. The oven is set at 70°C for drying for 30 minutes to complete the modification treatment of the inner layer film and obtain a modified inner layer film.

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

[0068] The wavelength of the ultraviolet lamp is 300nm and the irradiation intensity is 40mW / cm 2 .

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

[0070] The coating treatment method of the first coating material is: the outer layer film is immersed in the first coating material for 4 hours, and then placed in an oven after immersion, and the oven is set at 50° C. for drying for 30 minutes to complete the coating treatment of the outer layer film.

[0071] The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, and the mass ratio of the glass fiber, aramid fiber, epoxy resin and polyurethane adhesive is 1:(0.8):(0.8):(0.3). The coating method of the second coating material is: evenly coat the second coating material on the surface of the modified inner layer membrane, and perform vacuum drying after coating, the temperature is 60°C, the vacuum degree is 0.09MPa, the processing time is 3h, and the coating treatment of the second coating material is completed.

[0072] The lamination method is as follows: two outer layer films that have been coated are superimposed on the modified inner layer film that has been coated, and the superimposed materials are subjected to lamination. The pressure is set to 1.2 MPa, and the heating temperature of both sides is 360° C. After the lamination is completed, cooling is waited to obtain a PTFE multilayer composite film.

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

[0074] Comparative Example 2: The difference between this comparative example and Example 1 is that: in this comparative example, the inner layer film is not modified.

[0075] Comparative Example 3: The difference between this comparative example and Example 1 is that this comparative example does not contain the first coating material and the coating treatment step of the first coating material.

[0076] Comparative Example 4: The difference between this comparative example and Example 1 is that this comparative example does not contain the second coating material and the coating treatment step of the second coating material.

[0077] Performance test: The PTFE multilayer composite membranes prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were subjected to performance tests, and the test data obtained are recorded in the following table:

[0078]

[0079] In the performance test, the PTFE multilayer composite films prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 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 stretching speed of the tensile testing machine was 2 mm / s.

[0080] Among them, the transverse tensile strength data of the PTFE multilayer composite membranes prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 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 Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 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 data of the PTFE multilayer composite films prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are 233.5%, 234.6%, 232.8%, 163.3%, 164.6%, 152.2% and 166.7%, respectively;

[0083] The longitudinal elongation at break data of the PTFE multilayer composite films prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are 256.1%, 258.7%, 256.4%, 182.5%, 183.4%, 177.6% and 171.1%, respectively.

[0084] It can be seen that the tensile strength performance and elongation at break performance of the PTFE multilayer composite membranes prepared in Comparative Examples 1, 2, 3 and 4 are lower than those in Examples 1, 2 and 3; this indicates that: in the preparation process of the PTFE multilayer composite membrane, through the pre-stretching and modification treatment of the inner layer membrane, the stretching treatment will cause a large number of wrinkles to be generated on the surface of the PTFE membrane, and at the same time, tiny pores can be generated on the surface of the PTFE membrane. After the subsequent treatment with sodium naphthalene solution, free radicals are generated on the surface of the PTFE membrane, so that the PTFE membrane can effectively adhere to and combine with the fiber material contained in the second coating material, so that the fiber material is firmly attached to the surface of the PTFE membrane, and the PTFE membrane with the fiber layer attached is sandwiched between the two outer membranes, thereby achieving the purpose 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 the present invention not only has good tensile strength performance, but also has excellent elongation at break performance. This shows that the PTFE multilayer composite film and preparation method provided by the present invention have a broader market prospect and are more suitable for promotion.

[0086] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0087] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present 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: The following steps are involved: S1: raw material preparation, the PTFE membrane is divided into three layers, the three-layer PTFE membrane is divided into two outer membranes and an inner membrane, the inner membrane is located between the two outer membranes when superimposed, the thickness of the two outer membranes is 0.08-0.12 mm, and the thickness of the inner membrane is 0.12-0.14 mm; S3: The inner layer film is stretched; S4: performing a modification treatment on the inner layer film after the stretching treatment to obtain a modified inner layer film; S5: preparing a first coating material, wherein the first coating material is applied to the surfaces of the two outer films; S6: preparing a second coating material, wherein the second coating material is applied to the surface of the modified inner layer film; S7: Lamination treatment: two outer layer films that have been coated and an inner layer film that has been coated are laminated to obtain a PTFE multilayer composite film.

2. The method for preparing a PTFE multilayer composite membrane according to claim 1, wherein The method for stretching the inner layer film is as follows: the inner layer film is sent to a drying oven, the oven is set at 120-130°C for heating treatment 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 the film is held for 8-12 seconds after being stretched into place. After a single stretching is completed, the inner layer film is sent to the 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.

3. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that: The modification method of the inner layer film that has completed the stretching treatment is as follows: the inner layer film is immersed in a sodium naphthalene solution for 4 to 6 minutes, and then placed in a drain frame for 1 to 3 hours, and then sent to a light box. The light box uses an ultraviolet lamp to irradiate the surface of the inner layer film for 40 to 50 minutes. When the time is halfway, the inner layer film is turned over. After the irradiation treatment is completed, the inner layer film is rinsed with acetone, and then placed in an oven. The oven is set at 50 to 70°C for drying for 20 to 30 minutes to complete the modification treatment of the inner layer film and obtain a modified inner layer film.

4. The method for preparing the PTFE multilayer composite membrane according to claim 3, characterized in that: The concentration of the sodium naphthalene solution is 0.4-0.6 mol / L.

5. The method for preparing the PTFE multilayer composite membrane according to claim 3, characterized in that: The wavelength of the ultraviolet lamp is 200-300nm, and the irradiation intensity is 20-40mW / cm 2 .

6. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that: The first coating material is a mixture of water-based polyurethane emulsion and hydroxyethyl cellulose, and the mass of the hydroxyethyl cellulose is 4-6% of the mass of the water-based polyurethane emulsion.

7. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that: The coating treatment method of the first coating material is: the outer layer film is immersed in the first coating material for 2 to 4 hours, and then placed in an oven at 40 to 50° C. for drying for 20 to 30 minutes to complete the coating treatment of the outer layer film.

8. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that: The second coating material is a mixture of glass fiber, aramid fiber, epoxy resin and polyurethane adhesive, and the mass ratio of the 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 method of the second coating material is: evenly apply the second coating material on the surface of the modified inner layer film, and perform vacuum drying after coating, the temperature is 50-60°C, the vacuum degree is 0.07-0.09MPa, and the processing time is 1-3h to complete the coating treatment of the second coating material.

9. The method for preparing the PTFE multilayer composite membrane according to claim 1, characterized in that: The lamination method is as follows: two outer layer films that have been coated are superimposed on the modified inner layer film that has been coated, and the superimposed materials are subjected to lamination. The pressure is set to 0.8-1.2 MPa, and the heating temperature of both sides is 340-360° C. After lamination is completed, cooling is waited to obtain a PTFE multilayer composite film.

10. A PTFE multilayer composite membrane, characterized in that: The PTFE multilayer composite membrane is prepared by the preparation method of any one of claims 1 to 9.

Images