Method for producing polyimide composite film and polyimide composite film

Abstract

The application provides a polyimide composite film preparation method and a polyimide composite film. The polyimide composite film preparation method comprises the following steps: providing a first polyamic acid capable of forming a thermoplastic polyimide, wherein the first polyamic acid is terminated by a carbonylimidazole group; providing a second polyamic acid capable of forming a non-thermoplastic polyimide, wherein the second polyamic acid is terminated by an anhydride group; co-extruding and cyclizing the first polyamic acid and the second polyamic acid to obtain a polyimide composite film, wherein the polyimide composite film has amide groups generated by the reaction between the carbonylimidazole group and carboxyl groups in the second polyamic acid.

Description

Technical Field

[0001] This application relates to the field of polyimide film technology, and in particular to a method for preparing a polyimide composite film and the polyimide composite film. Background Technology

[0002] The three-layer polyimide film used in two-layer FPC (Flexible Printed Circuit) is a three-layer composite film with thermoplastic polyimide structure on both sides of a non-thermoplastic polyimide film. Due to insufficient interlayer adhesion, it is prone to interlayer peeling, bubbling and other phenomena, which leads to a decrease in the yield of FPC products. Summary of the Invention

[0003] This application provides a method for preparing a polyimide composite film and the polyimide composite film itself, in order to solve the problem of insufficient interlayer adhesion in three-layer composite films.

[0004] This application provides a method for preparing a polyimide composite film, comprising the following steps: providing a first polyamic acid capable of forming a thermoplastic polyimide, the first polyamic acid being capped with a carbonyl imidazole; providing a second polyamic acid capable of forming a non-thermoplastic polyimide, the second polyamic acid being capped with an anhydride group; co-extruded and cyclized the first polyamic acid and the second polyamic acid to obtain a polyimide composite film, wherein the polyimide composite film has an amide group generated by the reaction of the carbonyl imidazole with the carboxyl group in the second polyamic acid.

[0005] In one possible implementation, the thermoplastic polyimide is obtained by dehydration and cyclization of a carbonyl imidazole-terminated first polyamic acid. The preparation method of the carbonyl imidazole-terminated first polyamic acid includes: adding a first aromatic dianhydride, a first aromatic diamine, and N-formamide imidazole to a first polar solvent and condensing them at a first temperature.

[0006] In one possible implementation, the method for preparing the N-formamide imidazole includes: adding the first aromatic diamine and the diimidazole carbonyl group to a second polar solvent and stirring at a second temperature.

[0007] In one possible implementation, the first aromatic dianhydride includes, but is not limited to, one or more combinations of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, and 3,4,3',4'-triphenyl diether dianhydride.

[0008] The first aromatic diamine includes, but is not limited to, one or more combinations of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 1,3-bis(3-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

[0009] In one possible implementation, the molar ratio of the first aromatic diamine to the diimidazole carbonyl (CDI) is 1:1; the molar ratio of the first aromatic dianhydride to the sum of the aromatic diamine and the N-formamide imidazole is (0.98 to 1):1; and the molar ratio of the N-formamide imidazole to the first aromatic dianhydride is (0.001 to 0.009):1.

[0010] In one possible implementation, the non-thermoplastic polyimide is obtained by dehydration and cyclization of an anhydride-terminated second polyamic acid. The preparation method of the anhydride-terminated second polyamic acid includes: adding a second aromatic dianhydride and a second aromatic diamine to a third polar solvent and condensing them at a third temperature.

[0011] In one possible embodiment, the second aromatic dianhydride includes, but is not limited to, one or more of the following: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,4,3',4'-triphenyl diether dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]malonium, and 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride;

[0012] The second aromatic diamine includes, but is not limited to, one or more combinations of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 1,3-bis(3-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

[0013] In one possible implementation, the molar ratio of the second aromatic dianhydride to the second aromatic diamine is 1:(0.991 to 0.999).

[0014] This application also provides a polyimide composite film, which is prepared using the above-described method for preparing polyimide composite films.

[0015] In one possible implementation, the polyimide composite film includes a non-thermoplastic polyimide film and two thermoplastic polyimide films, with the two thermoplastic polyimide films respectively connected to opposite sides of the non-thermoplastic polyimide film.

[0016] The method for preparing the polyimide composite film of this application involves co-extruding and cyclizing a first polyamic acid that can form thermoplastic polyimide and a second polyamic acid that can form non-thermoplastic polyimide. During the extrusion molding of the polyimide composite film, the carbonyl imidazole in the first polyamic acid that can form thermoplastic polyimide reacts with the carboxyl group in the second polyamic acid that can form non-thermoplastic polyimide to generate amide groups. The amide groups can improve interlayer adhesion, resulting in a polyimide composite film with high peel strength. Furthermore, the amide bonds have high thermal stability, preventing decomposition and loss of function during high-temperature pressing. Simultaneously, by controlling the amount of carbonyl imidazole and the number of amide bonds, the interlayer adhesion is maximized without affecting the resin processing performance and the performance of the finished film. Moreover, this polyimide composite film does not require the addition of fillers to improve interlayer adhesion, has small interlayer differences, and a low coefficient of thermal expansion, which can be utilized in subsequent processes. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow for preparing the polyimide composite film of this application in one embodiment.

[0018] Figure 2 This is a schematic diagram of the structure of the polyimide composite film of this application in one embodiment.

[0019] Explanation of key component symbols: 100, preparation method of polyimide composite film; 200, polyimide composite film; 10, non-thermoplastic polyimide film; 20, thermoplastic polyimide film.

[0020] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0021] The following description will refer to the accompanying drawings to provide a more complete picture of the present application. The drawings illustrate exemplary embodiments of the present application. However, the present application may be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided to make the present application thorough and complete, and to fully convey the scope of the present application to those skilled in the art. Similar reference numerals denote the same or similar components.

[0022] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to limit the application. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to also include the plural forms. Furthermore, when used herein, “comprising” and / or “including” and / or “having,” integers, steps, operations, components, and / or components, but does not exclude the presence or addition of one or more other features, regions, integers, steps, operations, components, and / or groups thereof.

[0023] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Furthermore, unless expressly defined herein, terms such as those defined in a general dictionary should be interpreted as having the same meaning as they have in the relevant art and in the content of this application, and will not be interpreted as having an idealized or overly formal meaning.

[0024] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0025] like Figure 1 and Figure 2 As shown, this embodiment provides a method 100 for preparing a polyimide composite film, including the following steps:

[0026] S1. A first polyamic acid capable of forming a thermoplastic polyimide is provided, the first polyamic acid being capped with a carbonyl imidazole;

[0027] S2, providing a second polyamic acid capable of forming a non-thermoplastic polyimide, the second polyamic acid being anhydride-terminated;

[0028] S3. Co-extrude and cyclize a first polyamic acid that can form a thermoplastic polyimide and a second polyamic acid that can form a non-thermoplastic polyimide to obtain a polyimide composite film 200. The polyimide composite film 200 has amide groups generated by the reaction of carbonyl imidazole and the carboxyl group in the second polyamic acid.

[0029] Thus, the preparation method 100 of the polyimide composite film of this application involves co-extruding and cyclizing a first polyamic acid that can form a thermoplastic polyimide and a second polyamic acid that can form a non-thermoplastic polyimide. During the extrusion molding of the polyimide composite film 200, the carbonyl imidazole in the first polyamic acid reacts with the carboxyl group in the second polyamic acid to generate amide groups. The amide groups can improve interlayer adhesion, resulting in a polyimide composite film 200 with high peel strength. Furthermore, the amide bonds have high thermal stability, preventing decomposition and loss of function during high-temperature pressing. Simultaneously, by controlling the amount of carbonyl imidazole and the number of amide bonds, the interlayer adhesion of the polyimide composite film 200 is maximized without affecting the resin processing performance and the performance of the finished film. Moreover, the polyimide composite film 200 does not require the addition of fillers to improve interlayer adhesion, has small interlayer differences, and a low coefficient of thermal expansion, which can be utilized in subsequent processes.

[0030] In step S1, the above-mentioned thermoplastic polyimide is obtained by dehydration and cyclization of a carbonyl imidazole-terminated first polyamic acid. The preparation method of the carbonyl imidazole-terminated first polyamic acid includes: adding a first aromatic dianhydride, a first aromatic diamine, and N-formamide imidazole to a first polar solvent, and condensing them at a first temperature.

[0031] In this embodiment, the first polar solvent is any one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP), which can ensure that the added first aromatic dianhydride, first aromatic diamine, and N-formamide imidazole are fully dissolved.

[0032] In this embodiment, the first aromatic dianhydride, the first aromatic diamine, and N-formamide imidazole, after being added to the first polar solvent, need to undergo condensation at a low temperature. The first temperature range is 5°C to -5°C.

[0033] Understandably, the specific values ​​for the first temperature can be 5℃, 4℃, 3℃, 2℃, 1℃, 0℃, -1℃, -2℃, -3℃, -4℃, -5℃, etc.

[0034] Furthermore, the first aromatic dianhydride includes, but is not limited to, one or more combinations of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-diphenyl ether dianhydride (ODPA), and 3,4,3',4'-triphenyl diether dianhydride (HQDPA).

[0035] In this embodiment, the first aromatic dianhydride is one or a combination of two of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).

[0036] Furthermore, the first aromatic diamine includes, but is not limited to, one or more combinations of 4,4'-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), p-phenylenediamine (PDA), 4,4'-diaminodiphenylmethane (MDA), 2,2-bis(4-aminophenyl)propane (IDPA), 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), and 1,4-bis(4-aminophenoxy)benzene (1,4,4-APB).

[0037] In this embodiment, the first aromatic diamine is one or a combination of two of 4,4'-diaminodiphenyl ether (ODA) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

[0038] Furthermore, the preparation method of N-formamide imidazole includes: adding a first aromatic diamine and a diimidazole carbonyl group (CDI) to a second polar solvent and stirring at a second temperature.

[0039] In this embodiment, the first aromatic diamine is any one of the above-mentioned 4,4'-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), p-phenylenediamine (PDA), 4,4'-diaminodiphenylmethane (MDA), 2,2-bis(4-aminophenyl)propane (IDPA), 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), and 1,4-bis(4-aminophenoxy)benzene (1,4,4-APB). The first aromatic diamine and diimidazole carbonyl (CDI) are added to a second polar solvent, and after stirring at a low temperature, the two react to obtain N-formamide imidazole.

[0040] In this embodiment, the second polar solvent is any one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP).

[0041] In this embodiment, the temperature range of the second temperature is 0°C to -10°C.

[0042] Understandably, the specific values ​​for the second temperature can be 0℃, -1℃, -2℃, -3℃, -4℃, -5℃, -6℃, -7℃, -8℃, -9℃, -10℃, etc.

[0043] In this embodiment, the molar ratio of the first aromatic diamine to the diimidazolium carbonyl group (CDI) is 1:1, which ensures complete conversion of the diamine while preventing the consumption of the generated N-formamide imidazole. Furthermore, the chemical reaction formula between the first aromatic diamine and the diimidazolium carbonyl group (CDI) is as follows:

[0044] .

[0045] Furthermore, the molar ratio of the first aromatic dianhydride to the sum of the aromatic diamine and N-formamide imidazole is (0.98 to 1):1 to achieve carbonyl imidazole end-capping.

[0046] Understandably, the molar ratio of the first aromatic dianhydride to the sum of the aromatic diamine and N-formamide imidazole can be 0.980:1, 0.981:1, 0.982:1, 0.983:1, 0.984:1, 0.985:1, 0.986:1, 0.987:1, 0.988:1, 0.989:1, 0.990:1, 0.991:1, 0.992:1, 0.993:1, 0.994:1, 0.995:1, 0.996:1, 0.997:1, 0.998:1, 0.999:1, or 1.000:1.

[0047] In this embodiment, the molar ratio of the first aromatic dianhydride to the sum of the aromatic diamine and N-formamide imidazole is 0.995:1, which can achieve carbonyl imidazole end-capping while obtaining a larger polyamic acid molecular weight.

[0048] Furthermore, the molar ratio of N-formamide imidazole to the first aromatic dianhydride is (0.001 to 0.009):1. If there is too little N-formamide imidazole, the number of amide bonds formed between the layers is too small, resulting in low interlayer adhesion. If there is too much N-formamide imidazole, it leads to polyamic acid chain capping and a low molecular weight.

[0049] Understandably, the molar ratio of N-formamide imidazole to the first aromatic dianhydride can be 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, or 0.009:1.

[0050] In this embodiment, the molar ratio of N-formamide imidazole to the first aromatic dianhydride is (0.002 to 0.006):1.

[0051] Understandably, the molar ratio of N-formamide imidazole to the first aromatic dianhydride can be 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, etc.

[0052] In step S2, the above-mentioned non-thermoplastic polyimide is obtained by dehydration and cyclization of an anhydride-terminated second polyamic acid. The preparation method of the anhydride-terminated second polyamic acid includes: adding a second aromatic dianhydride and a second aromatic diamine to a third polar solvent, and condensing them at a third temperature.

[0053] In this embodiment, the third polar solvent is any one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP), which can ensure that the added second aromatic dianhydride and second aromatic diamine are fully dissolved.

[0054] In this embodiment, after adding the second aromatic dianhydride and the second aromatic diamine to the third polar solvent, polyamic acid is obtained by condensation at room temperature or after heating. The third temperature range is 30°C to 40°C.

[0055] Understandably, the specific values ​​for the third temperature can be 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc.

[0056] Furthermore, the second aromatic dianhydride includes, but is not limited to, one or more combinations of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,4,3',4'-triphenyl diether dianhydride (HQDPA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]malonium (BPADA), and 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride (PDPA).

[0057] In this embodiment, the second aromatic dianhydride is one or a combination of two of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).

[0058] Furthermore, the second aromatic diamine includes, but is not limited to, one or more combinations of 4,4'-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), p-phenylenediamine (PDA), 4,4'-diaminodiphenylmethane (MDA), 2,2-bis(4-aminophenyl)propane (IDPA), 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), and 1,4-bis(4-aminophenoxy)benzene (1,4,4-APB).

[0059] In this embodiment, the second aromatic diamine is one or a combination of two or more of 4,4'-diaminodiphenyl ether (ODA) and p-phenylenediamine (PDA).

[0060] Furthermore, the molar ratio of the second aromatic dianhydride to the second aromatic diamine is 1:(0.991 to 0.999) to achieve anhydride end-capping.

[0061] Understandably, the molar ratio of the second aromatic dianhydride to the second aromatic diamine can be 1:0.991, 1:0.992, 1:0.993, 1:0.994, 1:0.995, 1:0.996, 1:0.997, 1:0.998, 1:0.999, etc.

[0062] In this embodiment, the molar ratio of the second aromatic dianhydride to the second aromatic diamine is 1:(0.992 to 0.996).

[0063] Understandably, the molar ratio of the second aromatic dianhydride to the second aromatic diamine can be 1:0.992, 1:0.993, 1:0.994, 1:0.995, 1:0.996, etc.

[0064] In step S3, a first polyamic acid that can form a thermoplastic polyimide and a second polyamic acid that can form a non-thermoplastic polyimide are co-extruded and cyclized to obtain a polyimide composite film 200, which has amide groups generated by the reaction of carbonyl imidazole and carboxyl groups.

[0065] In this embodiment, the polyimide composite film 200 is a three-layer composite film, including a non-thermoplastic polyimide film 10 and two thermoplastic polyimide films 20, with the two thermoplastic polyimide films 20 respectively connected to opposite sides of the non-thermoplastic polyimide film 10.

[0066] Thermoplastic polyimide and non-thermoplastic polyimide are produced using a three-layer co-extrusion method with chemical imidization as the cyclization method, incorporating a dehydrating agent and a catalyst during processing. The dehydrating agent is specifically designed for the dehydration and cyclization of polyamic acid, and acetic anhydride can be used. The catalyst is an aliphatic or aromatic tertiary amine capable of catalyzing the dehydration and cyclization of polyamic acid, and isoquinoline can be selected. The dehydrating agent and catalyst used for thermoplastic and non-thermoplastic polyimide can be the same or different.

[0067] Furthermore, after each layer of thermoplastic polyimide and non-thermoplastic polyimide is uniformly mixed with a dehydrating agent and a catalyst, it is cast onto a support through an extrusion die. Under heating conditions, cyclization is achieved, and the carbonyl imidazole of the thermoplastic polyimide and the uncyclized carboxyl groups of the non-thermoplastic polyimide react to form amides. The specific chemical reaction formula is shown below:

[0068] .

[0069] In this embodiment, the thickness of the polyimide composite film 200 can be adjusted as needed. The thickness of the non-thermoplastic polyimide film 10 ranges from 12 μm to 100 μm, and the thickness of the thermoplastic polyimide film 20 ranges from 2 μm to 12 μm.

[0070] Understandably, the thickness of the non-thermoplastic polyimide film 10 can be 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 5 4μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm, 61μm, 62μm, 63μm, 64μm, 65μm, 66μm, 67μm, 68μm, 69μm, 70μm, 71μm, 72μm, 73μm, 74μm, 75μm, 76μm, 77μm , 78μm, 79μm, 80μm, 81μm, 82μm, 83μm, 84μm, 85μm, 86μm, 87μm, 88μm, 89μm m, 90μm, 91μm, 92μm, 93μm, 94μm, 95μm, 96μm, 97μm, 98μm, 99μm, 100μm, etc.

[0071] Understandably, the thickness of the thermoplastic polyimide film 20 can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, etc.

[0072] like Figure 1 and Figure 2 As shown, this embodiment also provides a polyimide composite film 200, which is prepared using the above-described polyimide composite film preparation method 100.

[0073] The polyimide composite film 200 is prepared by the above-described method 100. During the preparation process, carbonyl imidazole reacts with amino groups to form carbonyl imidazole-terminated polyamic acid in the thermoplastic layer. Subsequently, it reacts with the carboxyl groups in the anhydride-terminated non-thermoplastic layer to generate amide. Due to the presence of amide groups, the interlayer adhesion of the polyimide composite film 200 is effectively improved, thereby obtaining a polyimide composite film 200 with high peel strength. There is no need to add different types of fillers to the non-thermoplastic layer and the thermoplastic layer. The interlayer difference of the polyimide composite film 200 is small, resulting in a small coefficient of thermal expansion, which is beneficial to the subsequent processes.

[0074] Furthermore, during the preparation process, by controlling the amount of carbonyl imidazole and the number of amide bonds, the interlayer adhesion of the polyimide composite film 200 can be maximized without affecting the resin processing performance and the performance of the finished film. Simultaneously, carbonyl imidazole exhibits high reactivity, and the generated imidazole promotes imidization.

[0075] Example 1

[0076] To obtain an N-formamide imidazole solution: DMF (6.2 g) and CDI (0.3 g) were added to a dry reaction vessel filled with nitrogen at -5 °C. After stirring until all solids dissolved, BAPP (0.8 g) was added in batches and the reaction was stirred for 0.5 h to obtain an N-formamide imidazole solution in situ. The molar ratio of CDI to BAPP was 1:1.

[0077] To obtain the thermoplastic layer solution: At -5℃, DMF (4000.0 g) and BAPP (411.7 g) were added to a dry reactor filled with nitrogen. After stirring and dissolving, BPDA (294.2 g) was added, and the reaction was stirred for 3 h. Then, an N-formamide imidazole solution was added to the above solution, and the reaction was stirred for 1 h to obtain a thermoplastic polyamic acid solution containing carbonyl imidazole end groups. At -5℃, isoquinoline (471.3 g) and acetic anhydride (942.7 g) were added to the thermoplastic polyamic acid solution. After mixing thoroughly and degassing, the thermoplastic layer solution was obtained. The molar ratio of N-formamide imidazole to BPDA was 0.002:1, the molar ratio of BPDA to the sum of BAPP and N-formamide imidazole was 0.995:1, and the mass ratio of the sum of N-formamide imidazole, BPDA, and BAPP to DMF:isoquinoline:acetic anhydride was 15:85:10:20.

[0078] Anhydride-terminated non-thermoplastic layer solution was obtained: DMF (1666.8 g) and ODA (198.6 g) were added to a dry reactor filled with nitrogen at 35 °C. After stirring and dissolving, PMDA (218.1 g) was added, and the reaction was stirred for 3 h to obtain anhydride-terminated non-thermoplastic polyamic acid. Isoquinoline (208.4 g) and acetic anhydride (416.7 g) were added to the non-thermoplastic polyamic acid solution at -5 °C. After mixing thoroughly and degassing, a non-thermoplastic layer solution was obtained. The molar ratio of PMDA to ODA was 1:0.992, and the mass ratio of the sum of PMDA and ODA to DMF:isoquinoline:acetic anhydride was 20:80:10:20.

[0079] Film formation: The thermoplastic layer solution, non-thermoplastic layer solution and thermoplastic layer solution are co-extruded onto a steel strip, heated at 150℃ for 150s to remove solvent, and then sequentially passed through temperature zones of 200℃, 250℃, 300℃ and 350℃ for imidization to obtain a composite polyimide film with a thickness of 30μm, wherein the thickness of the upper and lower thermoplastic polyimide layers is 2.5μm and the thickness of the non-thermoplastic polyimide layer is 25μm.

[0080] Example 2

[0081] The only difference between this example and Example 1 is that the molar ratio of N-formamide imidazole to BPDA in the thermoplastic layer solution is 0.004:1. The amount of BPDA added is the same as in Example 1.

[0082] Example 3

[0083] The only difference between this example and Example 1 is that the molar ratio of N-formamide imidazole to BPDA in the thermoplastic layer solution is 0.006:1. The amount of BPDA added is the same as in Example 1.

[0084] Example 4

[0085] The only difference between this example and Example 1 is that the molar ratio of N-formamide imidazole to BPDA in the thermoplastic layer solution is 0.001:1. The amount of BPDA added is the same as in Example 1.

[0086] Example 5

[0087] The only difference between this example and Example 1 is that the molar ratio of N-formamide imidazole to BPDA in the thermoplastic layer solution is 0.010:1. The amount of BPDA added is the same as in Example 1.

[0088] Example 6

[0089] The only difference between this example and Example 1 is that the molar ratio of N-formamide imidazole to BPDA in the thermoplastic layer solution is 0.020:1. The amount of BPDA added is the same as in Example 1.

[0090] Comparative Example 1

[0091] The difference between this and Example 1 lies only in the acquisition of the thermoplastic layer solution: At 35°C, DMF (4005.0 g) and BAPP (412.6 g) were added to a dry reactor filled with nitrogen, stirred until dissolved, and then BPDA (294.2 g) was added. The mixture was stirred and reacted for 3 hours to obtain a thermoplastic polyamic acid solution. At -5°C, isoquinoline (471.2 g) and acetic anhydride (942.3 g) were added to the thermoplastic polyamic acid solution, mixed thoroughly, and degassed to obtain the thermoplastic layer solution. The molar ratio of BPDA to BAPP was 0.995:1, and the mass ratio of the sum of BPDA and BAPP to DMF to isoquinoline to acetic anhydride was 15:85:10:20.

[0092] Comparative Example 2

[0093] The only difference between this example and Example 1 is that the molar ratio of PMDA to ODA in the non-thermoplastic layer solution is 0.990:1. Specifically, PMDA is (215.9 g) and ODA is (200.2 g).

[0094] Comparative Example 3

[0095] The only difference between this example and Example 2 is that the molar ratio of PMDA to ODA in the non-thermoplastic layer solution is 0.990:1. Specifically, PMDA is (215.9 g) and ODA is (200.2 g).

[0096] Comparative Example 4

[0097] The only difference between this and Example 3 is that the molar ratio of PMDA:ODA in the non-thermoplastic layer solution is 0.990:1. Specifically, PMDA is (215.9 g) and ODA is (200.2 g).

[0098] The performance of the polyimide composite films 200 obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was tested. The peel strength of the polyimide composite films 200 was tested according to the method in IPC-TM-650-2.4.8, and the coefficient of thermal expansion was tested according to the relevant provisions of Method A in ISO 11359-1:2014. The test results are shown in Table 1:

[0099] Table 1

[0100]

[0101] According to the data in Table 1, under the same preparation process as Comparative Example 1, Examples 1-3 and Comparative Example 1 utilize the reaction of carbonyl imidazole with carboxyl groups to generate amide groups, which can effectively increase the adhesion between the thermoplastic and non-thermoplastic layers, thereby significantly improving the peel strength. According to Examples 1-6, the peel strength initially increases and then decreases with increasing N-formamide imidazole dosage. When the N-formamide imidazole dosage is less than 0.002, the number of interlayer amide bonds is insufficient, resulting in weak adhesion. When the N-formamide imidazole dosage is greater than 0.006, there are too many interlayer amide bonds, significantly affecting the cyclization or crosslinking degree of the non-thermoplastic layer. During high-temperature pressing, the molecular entanglement between layers decreases, leading to a significant reduction in peel strength. Furthermore, according to Examples 1 and Comparative Example 2, Examples 2 and Comparative Example 3, and Examples 3 and Comparative Example 4, the adhesion strength of interlayer urea groups is lower than that of amide groups, possibly due to the partial decomposition and loss of function of the urea groups during high-temperature pressing. Meanwhile, as can be seen from Examples 1-6 and Comparative Example 1, the presence of interlayer amide groups can reduce the coefficient of thermal expansion to a certain extent.

[0102] The specific embodiments of this application have been described above with reference to the accompanying drawings. However, those skilled in the art will understand that various changes and substitutions can be made to the specific embodiments of this application without departing from the scope of this application. All such changes and substitutions fall within the scope defined by this application.

Claims

1. A method for producing a polyimide composite film, characterized by, The method comprises the following steps: a first polyamic acid capable of forming a thermoplastic polyimide is provided, the first polyamic acid is terminated by a carbonylimidazole; the thermoplastic polyimide is obtained by dehydration and cyclization of the first polyamic acid terminated by a carbonylimidazole, and a preparation method of the first polyamic acid terminated by a carbonylimidazole comprises: adding a first aromatic dianhydride, a first aromatic diamine and N-formamidimidazole into a first polar solvent and condensing under a first temperature environment, a preparation method of the N-formamidimidazole comprises: adding the first aromatic diamine and diimidazole carbonyl into a second polar solvent and stirring under a second temperature environment; a molar ratio of the first aromatic diamine to the diimidazole carbonyl is 1:1; a molar ratio of the first aromatic dianhydride to a sum of the aromatic diamine and the N-formamidimidazole is (0.98 to 1):1; a molar ratio of the N-formamidimidazole to the first aromatic dianhydride is (0.001 to 0.009):1; a second polyamic acid capable of forming a non-thermoplastic polyimide is provided, the second polyamic acid is terminated by an anhydride group; the non-thermoplastic polyimide is obtained by dehydration and cyclization of the second polyamic acid terminated by an anhydride group, and a preparation method of the second polyamic acid terminated by an anhydride group comprises: adding a second aromatic dianhydride and a second aromatic diamine into a third polar solvent and condensing under a third temperature environment; a molar ratio of the second aromatic dianhydride to the second aromatic diamine is 1:(0.991 to 0.999); the first polyamic acid and the second polyamic acid are co-extruded and cyclized to obtain a polyimide composite film, the polyimide composite film has amide groups generated by reaction of the carbonylimidazole and carboxyl in the second polyamic acid.

2. The method for preparing a polyimide composite film according to claim 1, wherein The first aromatic dianhydride comprises one or a combination of two or more of pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride and 3,4,3',4'-triphenyl ether dianhydride; The first aromatic diamine comprises one or a combination of two or more of 4,4'-oxydianiline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane and 1,3-bis(3-aminophenoxy)benzene.

3. The method for preparing a polyimide composite film according to claim 1, wherein The second aromatic dianhydride comprises one or a combination of two or more of pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 3,4,3',4'-triphenyl ether dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedioic dianhydride and 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride. The second aromatic diamine comprises one or a combination of two or more of 4,4'-oxydianiline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane and 1,3-bis(3-aminophenoxy)benzene.

4. A polyimide composite film, characterized by, The polyimide composite film is prepared by the method according to any one of claims 1 to 3.

5. The polyimide composite film according to claim 4, wherein The polyimide composite film comprises a non-thermoplastic polyimide film and two thermoplastic polyimide films, and the two thermoplastic polyimide films are respectively connected to the opposite sides of the non-thermoplastic polyimide film.

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