Polyimide composite film and preparation method therefor

Abstract

The present application discloses a polyimide composite film and a preparation method therefor. The polyimide composite film comprises a polyimide base film and a polymer coating; the polyimide base film is a polyimide fiber film; the polyimide fiber film comprises a plurality of polyimide fibers which are arranged in a stacked and crossed mode; the surface of the polyimide fibers is coated with the polymer coating; and junctions are formed at the intersections of the polyimide fibers, so that the crossed polyimide fibers are connected by means of the junctions to form a net structure.

Description

Polyimide composite film and preparation method thereof

[0001] The present application claims priority to Chinese Patent Application No. 202410463135.5, filed on April 17, 2024, the contents of which are incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of polymer films, in particular to a polyimide composite film and a preparation method thereof. BACKGROUND

[0003] The electrospun polyimide fiber film is an extremely fine fiber film with a size of microns to nanometers prepared by an electrospinning process. The main body of the electrospun polyimide fiber film is composed of a large number of fibers stacked, there are a large number of pores between the fibers, and each fiber is independent of each other, resulting in weak cohesion in the film and poor tear resistance, which can easily cause the film to delaminate during use.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. TECHNICAL PROBLEM

[0005] The main purpose of the present application is to provide a polyimide composite film and a preparation method thereof, aiming to solve the problem of film delamination of the current polyimide fiber film during use. TECHNICAL SOLUTION

[0006] To achieve the purpose of the present application, the present application provides a polyimide composite film, which comprises a polyimide base film and a polymer coating. The polyimide base film is a polyimide fiber film, which comprises a plurality of polyimide fibers stacked and cross arranged. The polymer coating is coated on the surface of the polyimide fibers, and a node is formed at the intersection of the polyimide fibers, so that the intersecting polyimide fibers are connected through the node and form a network structure.

[0007] In an embodiment, the material of the polymer coating is an olefin polymer.

[0008] In an embodiment, the olefin polymer is at least one of polyethylene, polypropylene, polystyrene, polymethylstyrene, polychloroprene, and chlorinated polyvinyl chloride.

[0009] In an embodiment, the weight ratio of the olefin polymer to the polyimide base film is (0.1-30):100.

[0010] The present application also provides a preparation method of the polyimide composite film as described above, which comprises the following steps:

[0011] Step S1, providing a polyimide fiber film and a polymer material;

[0012] Step S2, coating the polymer material in the form of a polymer coating on the surface of the polyimide fibers in the polyimide fiber film, and making the polymer coating form nodes at the intersections of the polyimide fibers to connect the intersecting polyimide fibers and form a network structure, to obtain the polyimide composite film.

[0013] In an embodiment, step S2 comprises:

[0014] Coating the olefin-based polymer material in the form of a coating on the surface of the polyimide fibers in the polyimide fiber film by using a soaking method or a spraying method, to obtain the polyimide composite film.

[0015] In an embodiment, step S2 comprises:

[0016] Step S21, dispersing the olefin-based polymer in an organic solvent to obtain a polymer solution after stirring and mixing;

[0017] Step S22, passing the polyimide fiber film through the polymer solution at a preset rate, and after drying, obtaining the polyimide composite film.

[0018] In an embodiment, in step S21, the concentration of the olefin-based polymer ranges from 0.5 to 10 wt%; and / or, the organic solvent is at least one of toluene, cyclohexane, and ethanol.

[0019] In an embodiment, in step S22, the preset rate is 0.4-0.6 m / min.

[0020] In an embodiment, in step S22, the drying is performed by using a drying oven, and the drying temperature ranges from 70 to 90°C. Advantages

[0021] The polyimide composite film provided by the present application comprises a polyimide-based film and a polymer coating. The polyimide-based film is a polyimide fiber film, which comprises a plurality of polyimide fibers arranged in a stacked and intersecting manner. The polymer coating is coated on the surface of the polyimide fibers, and forms nodes at the intersections of the polyimide fibers, so that the intersecting polyimide fibers are connected through the nodes and form a network structure. Since the polyimide fibers in the polyimide composite film are connected through the nodes and form a complex network structure, the cohesion, tear resistance, and tensile strength of the polyimide composite film can be improved, that is, the mechanical strength of the polyimide composite film is high, thereby effectively ensuring that the polyimide composite film is not prone to delamination during use. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0023] Fig. 1 is an electron microscope schematic diagram of the polyimide composite film provided by the present application;

[0024] Fig. 2 is an electron microscope schematic diagram of the polyimide fiber film in the polyimide composite film provided by the present application;

[0025] Fig. 3 is a schematic diagram of an embodiment of the preparation process of the polyimide composite film provided by the present application.

[0026] Explanation of reference numerals:

[0027] 100, polyimide fiber film; 200, polyimide composite film; 300, unwinding device; 400, polymer solution tank; 500, drying furnace; 600, winding device.

[0028] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. Embodiment of the present application

[0029] It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased in the market. In addition, the meaning of "and / or" appearing in the full text includes three parallel solutions. For example, "A and / or B" includes A solution, or B solution, or A and B solution. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it. When the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection claimed by the present application. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without any creative effort are within the scope of protection of the present application.

[0031] In order to solve the problem of film delamination of polyimide fiber film in the use process, the present application provides a polyimide composite film with high mechanical strength.

[0032] As shown in FIG. 1 and FIG. 2, in an embodiment of the present application, the polyimide composite film comprises a polyimide base film and a polymer coating layer, the polyimide base film is a polyimide fiber film, the polyimide fiber film comprises a plurality of polyimide fibers stacked and crossed, the polymer coating layer is coated on the surface of the polyimide fibers, and the nodes are formed at the intersections of the polyimide fibers, so that the intersecting polyimide fibers are connected through the nodes and form a network structure.

[0033] In the embodiment of the present application, the polyimide fiber film can be an electrospun polyimide fiber film, the main body of the film is composed of a large number of polyimide fibers stacked, there are a large number of pores between the polyimide fibers, and each polyimide fiber is independent of each other, that is, the polyimide fiber film is a porous and breathable film, the surface of the polyimide fiber is coated with a polymer coating layer, and the material of the polymer coating layer is not limited, as long as it can form nodes at the intersections of the polyimide fibers, and the intersecting polyimide fibers are connected through the nodes and form a network structure, while ensuring that the polyimide fiber film has good air permeability, all of which are within the protection scope of the present application.

[0034] It should be noted that the polyimide fiber film is a porous and breathable film, wherein the polymer coating layer only contacts and forms nodes at the intersections of the polyimide fibers through physical action, and there is no chemical interaction between the polymer coating layers.

[0035] Since the polyimide fibers in the polyimide composite film are connected through the nodes and form a complex network structure, the cohesion, tear resistance (i.e. vertical tensile strength) and tensile strength of the polyimide composite film can be improved, that is, the mechanical strength of the polyimide composite film is high, thereby effectively ensuring that the polyimide composite film is not prone to delamination during use.

[0036] In an embodiment of the present application, the material of the polymer coating layer is an olefin polymer, and the use of the olefin polymer can effectively fill the space between the intersecting polyimide fibers and form nodes at the intersections, and the complex network structure formed thereby has high tear resistance, thereby more effectively ensuring that the polyimide composite film is not prone to delamination during use.

[0037] In an optional embodiment of the present application, the olefin polymer is at least one of polyethylene, polypropylene, polystyrene, polymethylstyrene, polychloroprene, and chlorinated polyvinyl chloride.

[0038] In an embodiment of the present application, the weight ratio of the olefin polymer to the polyimide-based film is (0.1-30):100, such as 0.1:100, 0.5:100, 1:100, 10:100, 20:100, 30:100, and any interval value between any two endpoint values. With the above weight ratio, the mechanical strength of the polyimide composite film can be effectively improved, and at the same time, the good air permeability of the polyimide composite film can be ensured. If the weight ratio of the two is less than 0.1:100, the amount of the olefin polymer coated on the surface of the electrospun polyimide fiber film is small, and even the nodes at the intersections of the polyimide fibers cannot be effectively formed, and thus the complex network structure cannot be formed, and the mechanical strength cannot be significantly improved. If the weight ratio of the two is greater than 30:100, although the mechanical strength is improved, the air permeability of the polyimide composite film is poor due to the partial blockage of the pores of the polyimide composite film.

[0039] The present application also provides a preparation method of the polyimide composite film as described above, which comprises the following steps:

[0040] Step S1, providing a polyimide fiber film and a polymer material.

[0041] In a specific embodiment of the present application, the polyimide fiber film is an electrospun polyimide fiber film, and the polymer material is an olefin polymer, which can be at least one of polyethylene, polypropylene, polystyrene, polymethylstyrene, polychloroprene, and chlorinated polyvinyl chloride.

[0042] Step S2, coating the polymer material in the form of a polymer coating on the surface of the polyimide fibers in the polyimide fiber film, and allowing the polymer coating to form nodes at the intersections of the polyimide fibers to connect the intersecting polyimide fibers and form a network structure, to obtain the polyimide composite film.

[0043] In a specific embodiment of the present application, the olefin polymer material is coated on the surface of the polyimide fibers in the polyimide fiber film in the form of a coating by using a soaking method or a spraying method, to obtain the polyimide composite film.

[0044] The soaking method specifically comprises: dispersing the olefin polymer material into an organic solvent to obtain a polymer solution, soaking the polyimide fiber film in the polymer solution, coating the polymer material on the surface of the polyimide fibers in the polyimide fiber film after soaking, and forming nodes at the intersections of the polyimide fibers to connect the intersecting polyimide fibers and form a network structure, and then drying to obtain the polyimide composite film. The specific operation conditions are not limited, as long as the weight ratio of the olefin polymer material to the polyimide fiber film in the polyimide composite film satisfies (0.1-30):100, which is within the scope of the present application.

[0045] The spraying method is specifically: the olefin polymer material is atomized, and then sprayed onto the surface of the polyimide fibers in the polyimide fiber film, and nodes are formed at the intersections of the polyimide fibers to connect the intersecting polyimide fibers and form a network structure, thereby obtaining the polyimide composite film. The specific operation conditions are not limited, as long as the weight ratio of the polyimide composite film polymer material to the polyimide fiber film satisfies (0.1-30):100, which is within the scope of the present application.

[0046] In the specific embodiments of the present application, step S2 comprises:

[0047] Step S21: dispersing the olefin polymer in an organic solvent, and obtaining a polymer solution after stirring and mixing.

[0048] Specifically, the olefin polymer is at least one of polyethylene, polypropylene, polystyrene, polymethylstyrene, polychloroprene, and chlorinated polyvinyl chloride, and the organic solvent is at least one of toluene, cyclohexane, and ethanol. It should be noted that the selection principle of the solvent is that the solvent can dissolve the olefin polymer, but cannot dissolve the polyimide fiber film.

[0049] When preparing the polymer solution, the concentration of the polymer solution should be reasonably controlled. In an embodiment, the concentration of the olefin polymer is controlled in the range of 0.5-10wt%, such as 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%, and any interval value between any two endpoint values. The use of the olefin polymer in the above concentration range can not only improve the mechanical strength of the polyimide composite film, but also ensure good air permeability of the polyimide composite film. If the concentration of the olefin polymer material is less than 0.5wt%, the amount of the olefin polymer coated on the surface of the electrospun polyimide fiber film is small, and even cannot effectively form nodes at the intersections of the polyimide fiber film, thereby failing to form a complex network structure, and the mechanical strength of the polyimide composite film cannot be significantly improved. If the concentration of the olefin polymer material is greater than 10wt%, although the mechanical strength of the polyimide composite film is improved, most of the pores of the polyimide composite film are blocked, and the air permeability of the polyimide composite film is poor.

[0050] Step S22: passing the polyimide fiber film through the polymer solution at a predetermined rate, and obtaining a polyimide composite film after drying.

[0051] Specifically, referring to FIG. 3, the polymer solution tank 400 containing the polymer solution and the drying furnace 500 are sequentially and spacedly arranged between the unwinding device 300 of the electrospun polyimide fiber membrane 100 roll stock and the winding device 600, the advancing speed of the electrospun polyimide fiber membrane 100 is controlled, the electrospun polyimide fiber membrane 100 passes through the polymer solution at a preset speed, and then passes through the 5-m-long drying furnace for drying operation, the drying temperature can be selected as 70-90°C (such as 70°C, 75°C, 80°C, 85°C, 90°C, and interval values between any two endpoint values), and the roll stock of the polyimide composite membrane 200 can be obtained by winding at the winding device 600. The unwinding device 300 and the winding device 600 generally include unwinding rollers and winding rollers, and the specific structural arrangement can refer to the prior art, which will not be repeated here. It should be noted that the polymer solution tank 400 is provided with a plurality of spaced guide members (such as guide rollers) to enable the guided electrospun polyimide fiber membrane 100 roll stock to be immersed in the polymer solution tank 400 and contacted with the polymer solution, thereby facilitating the olefin polymer material to be coated on the surface of the polyimide fiber.

[0052] The advancing speed of the electrospun polyimide fiber membrane affects the immersion time of the electrospun polyimide fiber membrane in the polymer solution, and further affects the polymer content coated on the surface of the polyimide fiber and the mechanical strength of the polyimide composite membrane. In an embodiment, the advancing speed (i.e., the preset speed) of the electrospun polyimide fiber membrane 100 is 0.4-0.6 m / min (such as 0.4 m / min, 0.5 m / min, 0.6 m / min, and interval values between any two endpoint values). If the advancing speed is greater than 0.6 m / min, the immersion time of the electrospun polyimide fiber membrane in the polymer solution is short, and the drying time is short, the amount of olefin polymer coated on the surface of the electrospun polyimide fiber membrane is small, and even the nodes cannot be effectively formed at the intersections of the polyimide fiber membrane, and thus the complex network structure cannot be formed, and the mechanical strength of the polyimide composite membrane is not obviously improved. If the advancing speed is less than 0.4 m / min, the immersion time of the electrospun polyimide fiber membrane in the polymer solution is long, and the amount of olefin polymer coated on the surface of the electrospun polyimide fiber membrane is large, which causes most of the pores of the polyimide composite membrane to be blocked, and the air permeability of the polyimide composite membrane is poor.

[0053] The polyimide composite membrane and the preparation method thereof will be described in detail through specific embodiments. It should be noted that the polyimide fiber membranes used in the following examples and comparative examples are the same batch of electrospun polyimide fiber membranes, and their properties are basically the same.

[0054] Example 1

[0055] The polyimide composite film of the present embodiment is prepared by the following steps:

[0056] (1) At room temperature, polystyrene is dissolved in toluene solvent, stirred for 0.5 h to fully dissolve, to obtain a polymer solution, and the concentration of polystyrene in the polymer solution is 3 wt%.

[0057] (2) The roll stock of the electrospun polyimide fiber film is placed on the unwinding device as shown in Figure 3, and the electrospun polyimide fiber film is controlled to pass through the polymer solution in the polymer solution tank at a forward rate of 0.5 m / min, and the drying operation is carried out at 80°C in the drying oven to form a polymer coating by volatilizing the solvent, and then the roll stock of the polyimide composite film is obtained by winding through the winding device.

[0058] Example 2

[0059] The difference between the present embodiment and Example 1 is only that the concentration of polystyrene is 4 wt%, and the other operations are the same as those in Example 1.

[0060] Example 3

[0061] The difference between the present embodiment and Example 1 is only that the concentration of polystyrene is 5 wt%, and the other operations are the same as those in Example 1.

[0062] Example 4

[0063] The difference between the present embodiment and Example 1 is only that the concentration of polystyrene is 0.5 wt%, and the other operations are the same as those in Example 1.

[0064] Example 5

[0065] The difference between the present embodiment and Example 1 is only that the concentration of polystyrene is 10 wt%, and the other operations are the same as those in Example 1.

[0066] Example 6

[0067] The difference between the present embodiment and Example 1 is only that the electrospun polyimide fiber film passes through the polymer solution at a forward rate of 0.4 m / min, and the other operations are the same as those in Example 1.

[0068] Example 7

[0069] The difference between the present embodiment and Example 1 is only that the electrospun polyimide fiber film passes through the polymer solution at a forward rate of 0.6 m / min, and the other operations are the same as those in Example 1.

[0070] Comparative Example 1

[0071] The difference between the present comparative example and Example 1 is only that the concentration of polystyrene is 0.1 wt%, and the other operations are the same as those in Example 1.

[0072] Comparative Example 2

[0073] The present comparative example differs from Example 1 in that the concentration of polystyrene is 12 wt%, and other operations are the same as Example 1.

[0074] Comparative Example 3

[0075] The present comparative example differs from Example 1 in that the electrospun polyimide fiber membrane passes through the polymer solution at a forward rate of 1 m / min, and other operations are the same as Example 1. Other operations are the same as Example 1.

[0076] Comparative Example 4

[0077] The present comparative example differs from Example 1 in that the electrospun polyimide fiber membrane passes through the polymer solution at a forward rate of 0.1 m / min, and other operations are the same as Example 1. Other operations are the same as Example 1.

[0078] The polyimide composite membranes obtained in Examples 1-7 and Comparative Examples 1-4 were tested for performance, and the base membrane electrospun polyimide fiber membrane was also tested for performance, and the performance test results are shown in Table 1.

[0079] Table 1 Performance data of electrospun polyimide fiber membrane, polyimide composite membranes obtained in Examples 1-7 and Comparative Examples 1-4.

[0080] Polystyrene content, wt% Surface mass, g / m² Tear resistance, MPa Tensile strength, MPa Air permeability (7KPa, 2x2cm), ml / min Electrospun polyimide fiber membrane 0 5.3 0.5 30 300 Example 1 14.6 5.8 1.3 352 52 Example 2 16.8 6.2 1.6 362 40 Example 3 17.8 6.4 1.7 537 23 1 Example 4 5.1 5.5 0.7 337 3 Example 5 26.4 7.4 2.4 403 2 Example 6 15.9 6.1 2 364 4 Example 7 14.2 5.5 0.8 326 1 Comparative Example 1 0.6 5.3 0.5 323 00 Comparative Example 2 308.1 3.6 400 Comparative Example 3 6.6 5.5 0.7 347 0 Comparative Example 4 287.6 2.8 381 0

[0081] Note: The tear resistance in Table 1 is the tensile strength in the vertical direction.

[0082] As can be seen from the performance data in Table 1, compared with the original electrospun polyimide fiber membrane, the polyimide composite membranes of Examples 1-5 and Examples 6-7 have good tear strength, tensile strength and air permeability by adjusting the concentration of the olefin polymer (polystyrene) and the advancing rate of the electrospun polyimide fiber membrane, respectively.

[0083] As can be seen from the comparison of Comparative Example 1, Example 1 and the original electrospun polyimide fiber membrane, the tear strength and tensile strength of the polyimide composite membrane are not substantially improved when the concentration of the olefin polymer (polystyrene) is too small.

[0084] As can be seen from the comparison of Comparative Example 2, Example 1 and the original electrospun polyimide fiber membrane, the tear strength and tensile strength of the polyimide composite membrane are greatly improved when the concentration of the olefin polymer (polystyrene) is too large, but the air permeability of the polyimide composite membrane is poor, and the air permeation amount is reduced to zero.

[0085] As can be seen from the comparison of Comparative Example 3, Example 1 and the original electrospun polyimide fiber membrane, when the advancing rate of the electrospun polyimide fiber membrane is too large, the soaking time of the electrospun polyimide fiber membrane in the polymer solution is relatively short, and the drying time is also relatively short, so the tear strength and tensile strength of the polyimide composite membrane are reduced compared with Example 1.

[0086] As can be seen from the comparison of Comparative Example 4, Example 1 and the original electrospun polyimide fiber membrane, when the advancing rate of the electrospun polyimide fiber membrane is too small, the soaking time of the electrospun polyimide fiber membrane in the polymer solution is relatively long, so the amount of polystyrene polymer coated on the surface of the polyimide fiber is relatively large, although the tear strength and tensile strength of the polyimide composite membrane are improved, the air permeability of the polyimide composite membrane is poor.

[0087] It should be noted that in this paper, the term "including", "containing" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or system. Without more limitations, the element defined by the statement "including a…" does not exclude the presence of other identical elements in the process, method, article or system including the element.

[0088] The above is only an optional embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent article or equivalent process transformation using the content of the present application specification, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A polyimide composite film, wherein, The polyimide composite film comprises a polyimide base film and a polymer coating layer, the polyimide base film is a polyimide fiber film, the polyimide fiber film comprises a plurality of polyimide fibers stacked and cross arranged, the polymer coating layer is coated on the surface of the polyimide fibers, and the polymer coating layer forms nodes at the intersections of the polyimide fibers, so that the intersecting polyimide fibers are connected through the nodes and form a network structure.

2. The polyimide composite film of claim 1, wherein, The material of the polymer coating layer is an olefin polymer.

3. The polyimide composite film of claim 2, wherein, The olefin polymer is at least one of polyethylene, polypropylene, polystyrene, polymethylstyrene, polychloroprene, and chlorinated polyvinyl chloride.

4. The polyimide composite film of claim 2, wherein, The weight ratio of the olefin polymer to the polyimide base film is (0.1-30):

100.

5. A method for producing the polyimide composite film according to any one of claims 1 to 4, wherein, The preparation method comprises the following steps: Step S1, providing a polyimide fiber film and a polymer material; Step S2, coating the polymer material in the form of a polymer coating layer on the surface of the polyimide fibers in the polyimide fiber film, and making the polymer coating layer form nodes at the intersections of the polyimide fibers to connect the intersecting polyimide fibers and form a network structure, to obtain the polyimide composite film.

6. The method for preparing a polyimide composite film according to claim 5, wherein, Step S2 comprises: The olefin polymer material is coated on the surface of the polyimide fibers in the polyimide fiber film in the form of a coating layer by using a soaking method or a spraying method, to obtain the polyimide composite film.

7. The method for preparing a polyimide composite film according to claim 6, wherein, Step S2 comprises: Step S21, dispersing the olefin polymer in an organic solvent, and obtaining a polymer solution after stirring and mixing; Step S22, passing the polyimide fiber film through the polymer solution at a preset speed, and obtaining the polyimide composite film after drying.

8. The method for preparing a polyimide composite film according to claim 7, wherein, In step S21, the concentration of the olefin polymer ranges from 0.5wt% to 10wt%; and / or The organic solvent is at least one of toluene, cyclohexane, and ethanol.

9. The method of producing a polyimide composite film according to claim 7, wherein, In step S22, the preset speed ranges from 0.4m / min to 0.6m / min.

10. The method for preparing a polyimide composite film according to claim 7, wherein, In step S22, the drying is performed by using a drying furnace, and the drying temperature ranges from 70℃ to 90℃.

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