A crystalline polyimide / polyimide composite material, its preparation method and application

Abstract

This invention discloses a crystalline polyimide / polyimide composite material, its preparation method, and its applications. The method involves first uniformly mixing phenylhexacarboxylic acid trihydride with a diamine monomer, followed by a solid-phase reaction under argon atmosphere protection. After the reaction, the product is immersed in a polar solvent to obtain crystalline polyimide. Then, the crystalline polyimide is added to an organic solution of polyamic acid, subjected to ultrasonic treatment in an ice-water bath, and subsequently thermosetting to obtain the crystalline polyimide / polyimide composite material. The crystalline polyimide in this composite material has a layered two-dimensional COF structure, giving it relatively high thermal conductivity, heat resistance, and high-temperature mechanical properties. Introducing the crystalline polyimide into the polyamic acid solution utilizes the special interfacial compatibility between the amino groups in the crystalline polyimide and the anhydrides in the polyamic acid to react, solving the problem of difficult processing and effectively expanding its application range.

Description

Technical Field

[0001] This invention belongs to the field of composite material development technology, and relates to a crystalline polyimide / polyimide composite material, its preparation method, and its application. Background Technology

[0002] Polyimide (PI) is a special engineering material whose main molecular chain contains imide rings. Due to the strong intermolecular association forces and the imide rings in its structure, it possesses excellent chemical resistance, radiation resistance, low dielectric loss, and electrical insulation properties. Therefore, it has broad application prospects in electronic applications in aerospace, medical, and automotive industries. However, with the popularization of smart devices and the Internet, electronic products are increasingly demanding high speed, high frequency, miniaturization, and integration. Consequently, the dielectric, thermal conductivity, and insulation properties of electronic components are facing challenges.

[0003] The traditional polyimide molecular structure, due to its aromatic rings and imide bonds, has lower thermal conductivity than metals or traditional thermally conductive materials, making it unsuitable for the rapid heat dissipation requirements of electronic devices. Although the thermal conductivity can be improved by adding inorganic fillers with good thermal conductivity, uneven dispersion often leads to increased dielectric loss and decreased mechanical strength. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a crystalline polyimide / polyimide composite material, its preparation method, and its application. This solves the technical problem in the prior art where uneven dispersion of thermally conductive fillers leads to increased dielectric loss and decreased mechanical strength of polyimide when thermally conductive fillers are added. At the same time, this invention also solves the technical problem that crystalline polyimide has poor solubility and meltability, making it difficult to process and apply, thus affecting its application.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a crystalline polyimide / polyimide composite material includes the following steps:

[0007] S1: After uniformly mixing benzohexacarboxylic acid trianic anhydride and diamine monomer, a solid-phase reaction was carried out under argon atmosphere protection. After the reaction was completed, the product was immersed in a polar solvent to obtain a crystalline polyimide with a two-dimensional COF structure.

[0008] S2: The crystalline polyimide is added to an organic solution of polyamic acid, and ultrasonically treated in an ice-water bath to uniformly disperse the crystalline polyimide in the organic solution of polyamic acid. After thermosetting, the crystalline polyimide / polyimide composite material is obtained.

[0009] Preferably, in step S1, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenediphenylamine, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

[0010] Preferably, in step S1, the reaction temperature of the solid-phase reaction is 240–280°C, and the reaction time is 6–10 h.

[0011] Preferably, in step S1, the polar solvent is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

[0012] Preferably, the molar ratio of the benzohexacarboxylic trianic anhydride to the diamine monomer is (0.8-1):(0.82-1.02).

[0013] Preferably, the average pore size of the crystalline polyimide is 1–4 nm.

[0014] Preferably, in step S2, the ratio of the crystalline polyimide to the polyamic acid organic solution is (0.03-0.833):(10-50) by mass, and the solid content of the polyamic acid organic solution is 10%-20%.

[0015] Preferably, in step S2, the thermosetting process is as follows: a programmed gradient temperature increase is performed within the range of 150 to 300°C, with each temperature being treated for 1 to 2 hours.

[0016] A crystalline polyimide / polyimide composite material is prepared by the above method; the crystalline polyimide / polyimide composite material has an initial thermal weight loss temperature ≥510℃ in air atmosphere, a thermal conductivity ≥1.2W / (m·K), and a dielectric loss ≤0.002.

[0017] The above-mentioned application of a crystalline polyimide / polyimide composite material in electronic components.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] This invention discloses a method for preparing crystalline polyimide / polyimide composite materials. First, benzohexacarboxylic acid trianic anhydride with a symmetrical structure is used as a dianhydride monomer, which undergoes a solid-state dehydration condensation reaction with a diamine. In this process, monomers with highly symmetrical structures participate in the reaction. These monomers have a tendency to crystallize, which is beneficial for forming a highly ordered structure. By controlling the degree of polymerization, the molecular weight of the polymer can be adjusted. A higher molecular weight helps to improve the crystallinity of the polymer. Introducing a crystalline structure into traditional polyimide can significantly improve its heat resistance and high-temperature mechanical properties. This step utilizes a solid-state reaction to promote the reaction. This method has the advantages of being environmentally friendly, simple, safe, and low-cost. Next, the product is immersed in a polar solvent to effectively remove unreacted monomers, resulting in crystalline polyimide. The crystalline polyimide has a two-dimensional COF structure. Two-dimensional COFs have a unique periodic layered structure, large conjugated planes, and π-π stacking between layers, which gives it a relatively high thermal conductivity, effectively improving the heat dissipation problem of electronic devices. Then, the obtained crystalline polyimide is added to an organic solution of polyamic acid as a filler. After ultrasonic homogenization, it is subjected to thermosetting to obtain a crystalline polyimide / polyimide composite material. This process utilizes the special interfacial compatibility between the amino groups in the crystalline polyimide and the anhydrides in the polyamic acid to achieve uniform dispersion of the crystalline polyimide in the organic solution of polyamic acid. After thermosetting, the crystalline polyimide / polyimide composite material is obtained, which effectively improves the processability of crystalline polyimide and also retains the excellent dielectric properties of polyimide. The crystalline polyimide / polyimide composite material in this invention has an initial thermal weight loss temperature ≥510℃ in air atmosphere, a thermal conductivity ≥1.2W / (m·K), a dielectric loss ≤0.002, and a dielectric constant of 3±0.54.

[0020] Furthermore, another inventive point of this invention is that in step S1, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenediphenylamine, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene. Firstly, the preferred diamine can effectively control the degree of polymerization in the reaction with the tricarboxylic acid anhydride. The degree of polymerization controls the crystallinity and morphology of the resulting product; that is, the preferred diamine can effectively undergo dehydration condensation with the tricarboxylic acid anhydride to form a stable imine link. COFs, which are polyimide crystallinity optimizations achieved by selecting appropriate diamine monomers or combinations thereof, can form highly ordered crystalline structures, thereby improving the heat resistance and high-temperature mechanical properties of the material. In addition, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene contain phenoxy functional groups, which not only help to enhance intermolecular interactions but may also endow the material with better solubility, higher dielectric constant, or lower dielectric loss.

[0021] Furthermore, another inventive point of this invention is that in step S1, the reaction temperature of the solid-state reaction is 240–280°C, and the reaction time is 6–10 h. First, solid-state reactions typically require higher temperatures to overcome the energy barriers between reactants and promote the breaking and recombination of chemical bonds. Setting the reaction temperature in the range of 240–280°C ensures that the reactant molecules obtain sufficient energy, thereby accelerating the reaction. Such a temperature setting is neither too high, leading to an increase in side reactions or product decomposition, nor too low, leading to an excessively slow reaction rate. This temperature allows the diamine monomer in step S1 to fully react with phenylhexacarboxylic acid trianic anhydride, resulting in a crystal phase transformation, which helps to obtain high-quality crystalline polyimide products. In addition, a longer reaction time helps to ensure sufficient contact and reaction between reactants. In solid-state reactions, reactant molecules need time to diffuse, contact, and undergo chemical reactions. By setting a sufficient reaction time, it can be ensured that the reactants are converted into products as completely as possible, improving the purity and yield of the products. More importantly, the temperature and time of solid-state reactions have a significant impact on the structure of the products. Under appropriate temperature and time conditions, reactant molecules can arrange and combine in an orderly manner to form products with specific structures and properties. By precisely controlling the reaction temperature and time, key parameters such as the crystallinity and molecular weight distribution of the products can be adjusted, thereby optimizing the product's performance. Furthermore, higher reaction temperatures and longer reaction times help remove impurities and unreacted substances from the reaction system. In solid-state reactions, unreacted monomers or oligomers can affect the product's performance. By increasing the reaction temperature and extending the reaction time, these impurities and unreacted substances can be further reacted or decomposed, thereby improving the purity and quality of the product. Under appropriate reaction conditions, highly ordered crystalline structures can be formed, thereby improving key properties of the material such as heat resistance, mechanical strength, and chemical stability.

[0022] Furthermore, another inventive aspect of this invention is that in step S1, the polar solvent is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide. First, these polar solvents have good solubility for polyimide and its precursors. After the solid-phase reaction is completed, the product contains unreacted monomers, oligomers, or impurities. Immersing these products in these polar solvents can effectively dissolve and remove these impurities, thereby improving the purity and quality of the product.

[0023] Furthermore, another inventive aspect of this invention is that the molar ratio of the phenylhexacarboxylic trihydric anhydride to the diamine monomer is (0.8–1):(0.82–1.02). First, by precisely controlling the molar ratio of the reactants, it can be ensured that the reactants react in a manner close to stoichiometry, thereby improving reaction efficiency. This ratio setting helps to reduce unreacted monomer residues and improve the purity and yield of the product. Second, within this ratio range, the phenylhexacarboxylic trihydric anhydride and the diamine monomer can react fully to form ordered polyimide segments. This ordered structure is conducive to the formation and growth of crystals, thereby improving the crystallinity of the crystalline polyimide. High crystallinity means that the material has better thermal stability, mechanical strength, and chemical stability. In addition, an appropriate reactant ratio helps to control the phase transformation during the reaction process. If the reactant ratio is inappropriate, it may lead to the appearance of multiple crystal phases or disordered structures in the product, thereby affecting the performance of the material. By setting a reasonable molar ratio, such unfavorable phase transformations can be prevented, ensuring that the product has a uniform and stable crystal phase structure. Meanwhile, the interfacial compatibility between crystalline polyimide and polyamic acid is crucial to the performance of composite materials. By optimizing the reactant ratio, the surface properties and structure of crystalline polyimide can be controlled, thereby enhancing its interfacial compatibility with other materials. This improved compatibility helps the composite material to be uniformly dispersed and stably bonded during the preparation process.

[0024] Furthermore, another inventive aspect of this invention is that the average pore size of the crystalline polyimide is 1–4 nm. Firstly, the nanoscale pore size provides a short and direct transport path for ions, reducing ion obstruction and scattering during transport within the material, thereby significantly improving the material's ionic conductivity. This is of great significance for applications requiring rapid ion transport, such as batteries, supercapacitors, and ion sensors. Secondly, in electrochemical energy storage devices, such as lithium-ion and sodium-ion batteries, rapid ion transport within the electrode material is a key factor in improving energy storage and conversion efficiency. The nanoporous structure of the crystalline polyimide helps achieve this goal, thereby improving battery performance and cycle stability. In addition, the nanoporous structure not only promotes rapid ion transport but may also positively influence the kinetics of electrochemical reactions. It may provide more reactive sites and shorten the diffusion distance between reactants and products, thereby accelerating the rate of electrochemical reactions. Furthermore, the nanoporous structure helps stabilize the material's crystal structure, reducing structural changes or damage that may occur during charging, discharging, or use. This stability is crucial for extending the material's lifespan and improving device reliability.

[0025] Furthermore, another inventive aspect of this invention is that in step S2, the ratio of the crystalline polyimide to the polyamic acid organic solution, by mass parts, is (0.03–0.83):(10–50), and the solid content of the polyamic acid organic solution is 10–20%. Firstly, by precisely controlling the ratio of crystalline polyimide to polyamic acid, it can be ensured that the crystalline polyimide is uniformly dispersed in the polyamic acid solution. This uniform dispersion helps reduce or eliminate agglomeration and precipitation, resulting in more stable performance of the composite material during subsequent processing and use. The uniformly dispersed crystalline polyimide can interact more effectively with the polyamic acid, forming a denser and more stable composite material structure. This structure helps improve the mechanical strength, thermal stability, and chemical stability of the composite material, thereby meeting a wider range of application needs. Additionally, the appropriate solid content and ratio setting gives the composite solution good flow properties. This flowability helps achieve uniform coating, injection molding, or extrusion operations during processing, improving production efficiency and product quality. At the same time, good stability also reduces fluctuations and changes that may occur during processing. Moreover, uniformly dispersed crystalline polyimide and polyamic acid can form a stronger interfacial bond. This bond helps to transfer stress and load in the composite material, improving the overall strength and durability of the material. At the same time, it also helps to reduce defects and cracks at the interface, improving the reliability of the material.

[0026] Furthermore, another inventive aspect of this invention is that in step S2, the thermosetting process involves a programmed gradient temperature increase within the range of 150–300°C, with each temperature lasting 1–2 hours. Firstly, the programmed gradient temperature increase allows for more precise control of the material's curing process. Different temperature stages correspond to different physical and chemical changes within the material, such as solvent evaporation, chain segment movement, and cross-linking reactions. By gradually increasing the temperature, these changes can be ensured to occur gradually at suitable temperatures, thereby optimizing the curing effect and improving the material's performance. Rapid heating may lead to large temperature gradients and thermal stress within the material, causing problems such as deformation and cracking. The programmed gradient temperature increase, however, slows down the rate of temperature change, resulting in a more uniform temperature distribution within the material, reducing stress concentration, and improving the material's stability and durability.

[0027] Furthermore, this invention also discloses a crystalline polyimide / polyimide composite material prepared by the above method. In this composite material, the crystalline polyimide is a layered two-dimensional COFs structure. This structure of polyimide has a unique periodic layered structure, large conjugated planes, and π-π stacking effect between layers, which gives it a relatively high thermal conductivity. At the same time, the crystalline polyimide has better heat resistance and high-temperature mechanical properties. Although the stable COFs conjugated structure has the characteristics of being difficult to melt and dissolve, making it difficult to further process and limiting its wide application in the electronics field, this invention introduces the crystalline polyimide into the N,N-dimethylformamide (DMF) solution of polyamic acid. By utilizing the special interfacial compatibility between the amino group in the crystalline polyimide and the anhydride in the polyamic acid, the problem of its difficult processing can be solved, effectively expanding its application range. The crystalline polyimide / polyimide composite material described in this invention has an initial thermogravimetric temperature (TGF-β) ≥ 510℃ in air, a thermal conductivity ≥ 1.2 W / (m·K), and a dielectric loss ≤ 0.002. The TGF-β refers to the temperature at which the material's weight begins to decrease significantly during heating. Thermal conductivity is a physical quantity that measures a material's ability to conduct heat; it describes the efficiency of heat transfer under a given temperature difference. Assuming a thermal conductivity of 0.4 W / (m·K), it means that under steady-state heat transfer conditions, the material transfers 0.4 watts per unit area per unit time. Dielectric loss refers to the phenomenon where a dielectric material heats up due to the consumption of some electrical energy in an alternating electric field. Lower dielectric loss indicates better insulation performance, which helps maintain the efficiency and stability of the equipment. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The XRD patterns of the composite materials prepared in Examples 1(a) and 2(b) of the present invention are shown.

[0030] Figure 2 Thermogravimetric analysis results of the composite materials obtained in Examples 1 and 2 of this invention are shown.

[0031] Figure 3 This is a TEM image of the morphology of the crystalline polyimide obtained in Example 1 of the present invention. Detailed Implementation

[0032] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0033] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0034] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0035] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0036] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0037] This invention provides a method for preparing crystalline polyimide / polyimide composite materials, specifically including the following steps:

[0038] (1) Preparation of crystalline polyimide

[0039] First, by mass, 0.8–1 part of phenylhexacarboxylic trianic anhydride and 0.82–1.02 parts of diamine monomer are ground and mixed evenly. The mixture is then reacted at 240–280°C for 6–10 hours under an argon atmosphere. After the reaction is complete and the mixture is allowed to cool naturally to room temperature, the product is crude crystalline polyimide. The product is then stirred in 30–60 parts of a polar solvent for 24 hours and filtered to remove unreacted monomers. Next, it is washed and purified multiple times with 50–200 parts of deionized water. Finally, it is dried under vacuum at 80°C for 8 hours to obtain imine-linked crystalline polyimide.

[0040] The diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenediphenylamine, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene;

[0041] The polar solvent is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide;

[0042] The crystalline polyimide has a two-dimensional COF structure with a pore size of 1–4.05 nm.

[0043] The “two-dimensional COFs structure” mentioned in the article refers to a two-dimensional planar network framework structure formed by organic small molecule structural units linked by covalent bonds.

[0044] (2) Preparation of crystalline polyimide / polyimide composite materials

[0045] First, by weight, 0.03–0.83 parts of crystalline polyimide are added to 10–50 parts of an organic solution of polyamic acid, wherein the solid content of the organic solution of polyamic acid is 10%–20%. The mixture is stirred and dispersed in an ice-water bath for 1–2 hours until uniformly dispersed. Then, it is transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid is cured by casting. The curing process involves reacting at 150°C for 1 hour, at 180°C for 1 hour, and at 300°C for 1 hour. This yields a crystalline polyimide / polyimide composite board. The organic solution of polyamic acid can be a DMF solution of polyamic acid.

[0046] The above-mentioned preparation process of polyamic acid is as follows: under ice-water bath conditions, 2 parts of 4,4-diaminodiphenyl ether are uniformly dispersed in 25 parts of N,N-dimethylformamide, and then 2.18 parts of pyromellitic anhydride are slowly added to the above solution over 1 hour. After the addition is complete, the reaction is carried out for 6 hours to prepare a polyamic acid solution.

[0047] This invention discloses a method for preparing crystalline polyimide / polyimide composite materials. The method utilizes a dehydration condensation reaction between symmetrically structured phenylhexacarboxylic acid trianic anhydride and a diamine to synthesize crystalline polyimide. The obtained crystalline polyimide is then added as a filler to a DMF solution of polyamic acid, transferred to a mold, and prepared as a crystalline polyimide / polyimide composite board by casting under a specific curing process. The resulting composite material exhibits excellent high-temperature resistance, good thermal conductivity, low dielectric loss, and stable dielectric constant. Introducing a crystalline structure into traditional polyimide significantly improves its heat resistance, corrosion resistance, and high-temperature mechanical properties. Furthermore, the unique periodic layered structure, highly conjugated planes, and π-π stacking between layers of two-dimensional COFs result in a relatively high thermal conductivity, effectively improving heat dissipation in electronic devices. The preparation of composite materials by utilizing the unique interfacial compatibility between the amino groups in crystalline polyimides and the anhydrides in polyamic acids improves the processability of crystalline polyimides in applications while retaining the excellent dielectric properties of polyimides. Furthermore, the preparation method described in this invention has advantages such as simplicity, ease of control, low cost of reactants, and wide applicability in the electronics field, making it suitable for industrial production. The crystalline polyimide / polyimide composite material prepared by this invention has an initial thermal weight loss temperature ≥510℃ in air, a thermal conductivity ≥1.2W / (m·K), a dielectric loss ≤0.002, and a dielectric constant of 3±0.54. In contrast, the pure polyimide material, without the addition of crystalline polyimide as a filler, exhibits an initial thermal weight loss temperature ≥370℃ in air when the curing process is the same. The thermal conductivity is ≥0.4W / (m·K), the dielectric loss is ≤0.007, and the dielectric constant is 3±0.54. Therefore, this composite material possesses excellent high-temperature resistance, good thermal conductivity, low dielectric loss, and stable dielectric constant.

[0048] This invention modifies the chemical structure of polyimide to impart crystallinity, resulting in a two-dimensional COFs polyimide with a covalent organic framework (COFs) structure. This polyimide exhibits a unique periodic layered structure, large conjugated planes, and π-π stacking between layers, giving it a relatively high thermal conductivity. Simultaneously, the crystalline polyimide possesses superior heat resistance and high-temperature mechanical properties. While the stable conjugated structure of COFs is difficult to melt and dissolve, hindering further processing and limiting its widespread application in the electronics field, this invention introduces crystalline polyimide into an N,N-dimethylformamide (DMF) solution of polyamic acid. Utilizing the unique interfacial compatibility between the amino groups in the crystalline polyimide and the anhydrides in the polyamic acid, the processing difficulties are overcome, effectively expanding its application range.

[0049] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0050] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0051] Example 1

[0052] 1) Preparation of crystalline polyimide

[0053] First, 0.8 parts of phenylhexacarboxylic acid trianic anhydride and 0.82 parts of p-phenylenediamine were ground and mixed evenly, and then reacted at 240°C for 6 hours under an argon atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 30 parts of dimethyl sulfoxide for 24 hours and then filtered to remove unreacted monomers. Next, it was washed and purified multiple times with 50 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain imine-linked crystalline polyimide with a pore size of 2.42 nm.

[0054] 2) Preparation of crystalline polyimide / polyimide composite materials

[0055] First, 0.03 parts of the crystalline polyimide were added to 10 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 1 hour. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0056] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 515℃, the thermal conductivity was 1.2W / (m·K), the dielectric loss was 0.002, and the dielectric constant was 3.2.

[0057] Example 2

[0058] 1) Preparation of crystalline polyimide

[0059] First, 1 part of phenylhexacarboxylic acid trianic anhydride and 1.02 parts of diaminodiphenyl ether were ground and mixed evenly, and then reacted at 280°C for 10 h under an argon atmosphere. After the reaction was completed, the product was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 60 parts of N-methylpyrrolidone for 24 h and then filtered to remove unreacted monomers. Then, it was washed and purified multiple times with 200 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 h to obtain imine-linked crystalline polyimide with a pore size of 3.85 nm.

[0060] 2) Preparation of crystalline polyimide / polyimide composite materials

[0061] First, 0.833 parts of the crystalline polyimide were added to 50 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 2 hours. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0062] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 552℃, the thermal conductivity was 1.35W / (m·K), the dielectric loss was 0.001, and the dielectric constant was 3.02.

[0063] Example 3

[0064] 1) Preparation of crystalline polyimide

[0065] First, 0.85 parts of phenylhexacarboxylic acid trianic anhydride and 0.87 parts of m-phenylenediamine were ground and mixed evenly, and then reacted at 255°C for 8 hours under an argon atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 50 parts of N-methylpyrrolidone for 24 hours and then filtered to remove unreacted monomers. Next, it was washed and purified multiple times with 80 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain imine-linked crystalline polyimide with a pore size of 3.33 nm.

[0066] 2) Preparation of crystalline polyimide / polyimide composite materials

[0067] First, 0.05 parts of the crystalline polyimide were added to 15 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 1.5 hours. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0068] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 525℃, the thermal conductivity was 1.25W / (m·K), the dielectric loss was 0.001, and the dielectric constant was 3.45.

[0069] Example 4

[0070] 1) Preparation of crystalline polyimide

[0071] First, 0.9 parts of phenylhexacarboxylic acid trianic anhydride and 0.92 parts of 1,3-bis(4'-aminophenoxy)benzene were ground and mixed evenly, and then reacted at 250°C for 8 hours under an argon atmosphere. After the reaction was completed, the product was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 40 parts of N,N-dimethylacetamide for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified multiple times with 120 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain imine-linked crystalline polyimide with a pore size of 2.65 nm.

[0072] 2) Preparation of crystalline polyimide / polyimide composite materials

[0073] First, 0.65 parts of the crystalline polyimide were added to 38 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 2 hours. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0074] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 530℃, the thermal conductivity was 1.6W / (m·K), the dielectric loss was 0.001, and the dielectric constant was 3.5.

[0075] Example 5

[0076] 1) Preparation of crystalline polyimide

[0077] First, 0.8 parts of phenylhexacarboxylic acid trianic anhydride and 0.82 parts of 1,4-bis(4-aminophenoxy)benzene were ground and mixed evenly, and then reacted at 275°C for 10 h under an argon atmosphere. After the reaction was completed, the product was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 30 parts of dimethyl sulfoxide for 24 h and then filtered to remove unreacted monomers. Then, it was washed and purified multiple times with 60 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 h to obtain imine-linked crystalline polyimide with a pore size of 1.68 nm.

[0078] 2) Preparation of crystalline polyimide / polyimide composite materials

[0079] First, 0.03 parts of the crystalline polyimide were added to 10 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 1 hour. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0080] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 532℃, the thermal conductivity was 1.47W / (m·K), the dielectric loss was 0.002, and the dielectric constant was 3.12.

[0081] Example 6

[0082] 1) Preparation of crystalline polyimide

[0083] First, 0.88 parts of phenylhexacarboxylic acid trianic anhydride and 0.9 parts of 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane were ground and mixed evenly, and then reacted at 260°C for 6 hours under an argon atmosphere. After the reaction was completed, the product was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 40 parts of N,N-dimethylacetamide for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified multiple times with 100 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain imine-linked crystalline polyimide with a pore size of 1.33 nm.

[0084] 2) Preparation of crystalline polyimide / polyimide composite materials

[0085] First, 0.06 parts of the crystalline polyimide were added to 18 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 1 hour. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0086] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 522℃, the thermal conductivity was 1.5W / (m·K), the dielectric loss was 0.002, and the dielectric constant was 2.9.

[0087] Example 7

[0088] 1) Preparation of crystalline polyimide

[0089] First, 0.9 parts of phenylhexacarboxylic acid trianic anhydride and 0.92 parts of 4,4'-methylenediphenylamine were ground and mixed evenly, and then reacted at 265°C for 6 hours under an argon atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product was stirred in 50 parts of N,N-dimethylacetamide for 24 hours and then filtered to remove unreacted monomers. Next, it was washed and purified multiple times with 140 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain imine-linked crystalline polyimide with a pore size of 2.38 nm.

[0090] 2) Preparation of crystalline polyimide / polyimide composite materials

[0091] First, 0.7 parts of the crystalline polyimide were added to 42 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 1.5 hours until uniformly dispersed. Then, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0092] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 530℃, the thermal conductivity was 1.35W / (m·K), the dielectric loss was 0.001, and the dielectric constant was 2.88.

[0093] Example 8

[0094] 1) Preparation of crystalline polyimide

[0095] First, 0.95 parts of phenylhexacarboxylic acid trianic anhydride and 0.97 parts of 1,3-di(4'-aminophenoxy)benzene were ground and mixed evenly, and then reacted at 280℃ for 10 h under an argon atmosphere. After the reaction was completed, the product was allowed to cool naturally to room temperature, and the product was crude crystalline polyimide. The product obtained from the reaction was stirred in 60 parts of N-methylpyrrolidone for 24 h and then filtered to remove unreacted monomers. Then, it was washed and purified multiple times with 200 parts of deionized water. Finally, it was dried under vacuum at 80℃ for 8 h to obtain imine-linked crystalline polyimide with a pore size of 3.89 nm. 2) Preparation of crystalline polyimide / polyimide composite material

[0096] First, 0.05 parts of the crystalline polyimide were added to 15 parts of a DMF solution of polyamic acid. The mixture was stirred and dispersed in an ice-water bath for 1.5 hours. After uniform dispersion, the solution was transferred to a mold, and the composite solution of crystalline polyimide / polyamic acid was cured by casting. The curing temperatures were 150℃ for 1 hour, 180℃ for 1 hour, and 300℃ for 1 hour. This yielded a crystalline polyimide / polyimide composite board.

[0097] The properties of the obtained crystalline polyimide / polyimide composite material were tested. The results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 525℃, the thermal conductivity was 1.55W / (m·K), the dielectric loss was 0.002, and the dielectric constant was 2.8.

[0098] Figure 1 The figures show the XRD patterns of the composite materials prepared in Examples 1 and 2 of this invention. As can be seen from the figures, the XRD patterns measured in Examples 1 and 2 both show sharp diffraction peaks. It can be concluded that the polyimide prepared in this patent is crystalline and the crystal structure is relatively ordered. The crystal integrity is high, the molecular arrangement inside the crystal is relatively fixed, and the crystallinity of the crystal is also high.

[0099] Figure 2 The figures show the thermogravimetric analysis (TGA) results of the composite materials prepared in Examples 1 and 2 of this invention. As can be seen from the figures, the initial TGA of the crystalline polyimide / polyimide composite material in Example 1 is 515°C in air, and the initial TGA of the crystalline polyimide / polyimide composite material in Example 2 is 552°C in air. Therefore, the composite materials prepared in this application have excellent high-temperature resistance.

[0100] Figure 3 The image shows a TEM image of the morphology of the crystalline polyimide obtained in Example 1 of this invention. As can be seen from the image, the crystalline polyimide in Example 1 has a dense multilayered sheet structure.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a crystalline polyimide / polyimide composite material, characterized in that, Includes the following steps: S1: After uniformly mixing benzohexacarboxylic acid trianic anhydride and diamine monomer, a solid-phase reaction was carried out under argon atmosphere protection. After the reaction was completed, the product was immersed in a polar solvent to obtain a crystalline polyimide with a two-dimensional COF structure. S2: The crystalline polyimide is added to an organic solution of polyamic acid, and ultrasonically treated in an ice-water bath to uniformly disperse the crystalline polyimide in the organic solution of polyamic acid. After thermosetting, the crystalline polyimide / polyimide composite material is obtained. In step S1, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenediphenylamine, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene; In step S1, the reaction temperature of the solid-phase reaction is 240~280℃, and the reaction time is 6~10 h; The molar ratio of the benzohexacarboxylic acid trianic anhydride to the diamine monomer is (0.8~1):(0.82~1.02); The average pore size of the crystalline polyimide is 1~4 nm; In step S2, the ratio of the crystalline polyimide to the polyamic acid organic solution is (0.03~0.833):(10~50) by mass, and the solid content of the polyamic acid organic solution is 10%~20%. In step S2, the thermosetting process is as follows: a programmed gradient temperature increase is performed within the range of 150~300℃, and each temperature is treated for 1~2 hours.

2. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that, In step S1, the polar solvent is one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

3. A crystalline polyimide / polyimide composite material, characterized in that, The crystalline polyimide / polyimide composite material is prepared by the method described in any one of claims 1 to 2; the initial thermal weight loss temperature in air is ≥510℃, the thermal conductivity is ≥1.2 W / (m·K), and the dielectric loss is ≤0.

002.

4. The application of the crystalline polyimide / polyimide composite material as described in claim 3 in electronic components.

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