Crystalline polyimide / polyimide composite material as well as preparation method and application thereof

Abstract

The invention discloses a crystalline polyimide / polyimide composite material as well as a preparation method and application thereof, the method comprises the following steps: firstly, uniformly mixing benzenehexanoic acid trianhydride and a diamine monomer, then carrying out solid-phase reaction under the protection of argon atmosphere, and after the reaction is finished, putting a product into a polar solvent for soaking treatment to prepare crystalline polyimide; then adding the crystalline polyimide into an organic solution of polyamide acid, carrying out ultrasonic treatment in an ice-water bath, and then carrying out thermocuring to prepare the crystalline polyimide / polyimide composite material. Crystalline polyimide in the composite material is of a layered two-dimensional COFs structure, so that the composite material has relatively high heat conductivity coefficient, heat resistance and high-temperature mechanical property, the crystalline polyimide is introduced into a polyamide acid solution, and a reaction is performed by utilizing the special interface compatibility of amino in the crystalline polyimide and anhydride in polyamide acid, so that the composite material is obtained. And the problem of difficulty in processing can be solved, and the application range is effectively expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material development, and relates to a crystalline polyimide / polyimide composite material and a preparation method and application thereof. Background Art

[0002] Polyimide (PI) is a special engineering material with an imide ring in the main chain of the molecule. Due to the imide ring in its structure and the strong intermolecular bonding force, it has good chemical corrosion resistance, radiation resistance, low dielectric loss, electrical insulation and other properties. Therefore, it has broad application prospects in electronic applications in the fields of aerospace, medical and automotive industries. However, with the popularization of smart devices and the Internet, electronic products have an increasing demand for high speed, high frequency, miniaturization and integration, so the dielectric properties, thermal conductivity and insulation properties of electronic components are also facing challenges.

[0003] The thermal conductivity of traditional polyimide molecules is inferior to that of metals or traditional thermal conductive materials due to their aromatic ring and imide bond structure, making them unable to meet the needs of rapid heat dissipation in electronic devices. Although the thermal conductivity of polyimide can be improved by adding inorganic fillers with good thermal conductivity to polyimide, the uneven dispersion often leads to increased dielectric loss and decreased mechanical strength. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a crystalline polyimide / polyimide composite material and a preparation method and application thereof, thereby solving the technical problem in the prior art that when adding thermal conductive fillers to polyimide, the thermal conductive fillers are unevenly dispersed, resulting in increased dielectric loss and decreased mechanical strength of the polyimide. At the same time, the present invention also solves the technical problem that the solubility and meltability of the crystalline polyimide are poor, making it difficult to process and apply, which affects its application.

[0005] The present invention is achieved through the following technical solutions:

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

[0007] S1: After uniformly mixing mellitic acid trianhydride and diamine monomer, a solid phase reaction is carried out under the protection of argon atmosphere. After the reaction is completed, the product is immersed in a polar solvent to obtain a crystalline polyimide with a two-dimensional COFs structure;

[0008] S2: adding the crystalline polyimide to an organic solution of polyamic acid, subjecting the solution to ultrasonic treatment in an ice-water bath to uniformly disperse the crystalline polyimide in the organic solution of polyamic acid, and subjecting the solution to thermal curing to obtain the crystalline polyimide / polyimide composite material.

[0009] Preferably, in step S1, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenedianiline, 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 mellitic acid trianhydride to the diamine monomer is (0.8-1):(0.82-1.02).

[0013] Preferably, the average pore diameter of the crystalline polyimide is 1 to 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 thermal curing process is: performing a programmed gradient temperature increase treatment within a 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 of ≥510°C in air atmosphere, a thermal conductivity of ≥1.2W / (m·K), and a dielectric loss of ≤0.002.

[0017] Application of the above-mentioned crystalline polyimide / polyimide composite material in electronic components.

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

[0019] The invention discloses a preparation method of a crystalline polyimide / polyimide composite material. In the method, firstly, mellitic acid trianhydride with a symmetrical structure is used as a dianhydride monomer, and the dianhydride monomer and a diamine are subjected to a solid phase dehydration condensation reaction. In the process, monomers with a highly symmetrical structure are used to participate in the reaction. Such monomers have a tendency to crystallize, which is conducive to forming a highly ordered structure. By controlling the degree of polymerization, the molecular weight of the polymer can be adjusted. A higher molecular weight is conducive to improving the crystallinity of the polymer. Introducing a crystalline structure into a traditional polyimide can significantly improve its heat resistance and high-temperature mechanical properties. In this step, a solid phase reaction is used to promote the reaction. The method has the advantages of being environmentally friendly, simple in process, safe and low in cost. Then, the product is immersed in a polar solvent for treatment, and unreacted monomers can be effectively removed to obtain a crystalline polyimide. The crystalline polyimide is a two-dimensional COFs structure. The two-dimensional COFs has a unique periodic layered structure, a large conjugated plane and a π-π stacking effect between layers, which makes it have a relatively high thermal conductivity and can effectively improve the heat dissipation problem of its electronic devices; then the obtained crystalline polyimide is added to an organic solution of polyamic acid in the form of a filler, and after ultrasonic homogenization, a thermal curing treatment is performed to obtain a crystalline polyimide / polyimide composite material. This process utilizes the special interface compatibility of the amino group in the crystalline polyimide and the acid anhydride in the polyamic acid to react, thereby achieving uniform dispersion of the crystalline polyimide in the organic solution of polyamic acid. After thermal curing, a crystalline polyimide / polyimide composite material is obtained, which effectively improves the processability of the crystalline polyimide while having the excellent dielectric properties of the polyimide. The crystalline polyimide / polyimide composite material of the present invention has an initial thermal weight loss temperature of ≥510°C in air atmosphere, a thermal conductivity of ≥1.2W / (m·K), a dielectric loss of ≤0.002, and a dielectric constant of 3±0.54.

[0020] Furthermore, another inventive point of the present invention is that in step S1, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenedianiline, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene and 1,4-bis(4-aminophenoxy)benzene. First, the preferred diamine can effectively control the degree of polymerization of the reaction with the ternary acid anhydride, and the crystallinity and morphology of the generated product can be controlled by the degree of polymerization, that is, the preferred diamine can effectively undergo a dehydration condensation reaction with the ternary acid anhydride to form a stable imine connection. COFs, that is, by selecting suitable diamine monomers or their combinations, certain properties of the crystallinity of polyimide can be optimized in a targeted manner to form a highly ordered crystalline structure, 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, etc., contain functional groups such as phenoxy groups, which not only help to enhance the interaction between molecules, but also may give the material better solubility, higher dielectric constant or lower dielectric loss, etc.

[0021] Furthermore, another inventive point of the present invention is that in step S1, the reaction temperature of the solid phase reaction is 240-280°C, and the reaction time is 6-10h. First, solid phase reactions usually require higher temperatures to overcome the energy barriers between reactants and promote the breaking and recombination of chemical bonds. Setting the reaction temperature within the range of 240-280°C can ensure that the reactant molecules obtain sufficient energy, thereby accelerating the reaction. Such a temperature setting will neither be too high to increase side reactions or product decomposition, nor too low to cause a slow reaction rate. The temperature can allow the diamine monomer in step S1 to fully react with mellitic acid trianhydride to undergo a crystal phase transition, thereby helping to obtain a high-quality crystalline polyimide product. In addition, a longer reaction time helps to ensure sufficient contact and reaction between the reactants. In a solid phase reaction, the reactant molecules need time to diffuse, contact and undergo a chemical reaction. By setting a sufficient reaction time, it can be ensured that the reactants are converted into products as completely as possible, thereby improving the purity and yield of the products. More importantly, the temperature and time of the solid-phase reaction have an important influence on the structure of the product. Under appropriate temperature and time conditions, the reactant molecules can be arranged and combined 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 product can be regulated, thereby optimizing the performance of the product. Moreover, higher reaction temperatures and longer reaction times help to remove impurities and unreacted products in the reaction system. In solid-phase reactions, unreacted monomers or oligomers can affect the performance of the product. By increasing the reaction temperature and extending the reaction time, these impurities and unreacted products can be further reacted or decomposed, thereby improving the purity and quality of the product. Under appropriate reaction conditions, a highly ordered crystalline structure can be formed, thereby improving the key properties of the material such as heat resistance, mechanical strength, and chemical stability.

[0022] Furthermore, another inventive point of the present 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 incompletely reacted 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] Further, another inventive point of the present invention is that the molar ratio of mellitic acid trianhydride to diamine monomer is (0.8-1): (0.82-1.02). First, by accurately controlling the molar ratio of the reactants, it is possible to ensure that the reactants react in a manner close to the stoichiometric ratio, thereby improving the reaction efficiency. This ratio setting helps to reduce the unreacted monomer residue and improve the purity and yield of the product. Secondly, within this ratio range, mellitic acid trianhydride and diamine monomer can fully react to form an ordered polyimide segment. This ordered structure is conducive to the formation and growth of crystals, thereby improving the crystallinity of crystalline polyimide. High crystallinity means that the material has better thermal stability, mechanical strength and chemical stability. In addition, the appropriate reactant ratio helps to control the crystal phase transition during the reaction. If the reactant ratio is inappropriate, multiple crystal phases or disordered structures may appear in the product, thereby affecting the performance of the material. By setting a reasonable molar ratio, this unfavorable crystal phase transition can be prevented, ensuring that the product has a uniform and stable crystal phase structure. At the same time, the interfacial compatibility between crystalline polyimide and polyamic acid is crucial to the performance of the composite material. By optimizing the ratio of reactants, the surface properties and structure of crystalline polyimide can be regulated, thereby enhancing its interfacial compatibility with other materials. This improved compatibility helps the uniform dispersion and stable bonding of the composite material during the preparation process.

[0024] Furthermore, another inventive point of the present invention is that the average pore size of the crystalline polyimide is 1 to 4 nm. First, the nanoscale pore size provides a short and direct transmission path for ions, reduces the obstruction and scattering of ions when they are transmitted inside the material, and thus significantly improves the ionic conductivity of the material, which is of great significance for application scenarios that require rapid ion transmission, such as batteries, supercapacitors, and ion sensors. In addition, in electrochemical energy storage devices, such as lithium-ion batteries and sodium-ion batteries, the rapid transmission of ions in electrode materials is one of the key factors in improving energy storage and conversion efficiency. The nanopore structure of crystalline polyimide helps to achieve this goal, thereby improving the performance and cycle stability of the battery. In addition, the nanopore structure not only promotes the rapid transmission of ions, but also may have a positive effect on the kinetics of the electrochemical reaction. It may provide more reactive sites, shorten the diffusion distance between reactants and products, and thus accelerate the rate of the electrochemical reaction. In addition, the nanopore structure helps to stabilize the crystal structure of the material and reduce structural changes or damage that may occur during charging, discharging, or use. This stability is essential for extending the service life of the material and improving the reliability of the device.

[0025] Further, another invention point of the present invention is that in step S2, in terms of mass fraction, the ratio of the crystalline polyimide to the polyamic acid organic solution is (0.03-0.83): (10-50), the solid content of the organic solution of the polyamic acid is 10-20%, first, by accurately controlling the ratio of the crystalline polyimide to the polyamic acid, it is possible to ensure that the crystalline polyimide is uniformly dispersed in the polyamic acid solution, and this uniform dispersion helps to reduce or eliminate agglomeration and precipitation phenomena, so that the composite material has more stable performance during subsequent processing and use, and the uniformly dispersed crystalline polyimide can interact with the polyamic acid more effectively to form a more compact and stable composite material structure, which helps to improve the mechanical strength, thermal stability, chemical stability and other properties of the composite material, thereby meeting a wider range of application requirements. In addition, appropriate solid content and ratio settings make the composite solution have good flow properties, and this flowability helps to achieve uniform coating, injection molding or extrusion operations during processing, improve production efficiency and product quality, and at the same time, good stability also reduces the fluctuations and changes that may occur during processing. Moreover, a stronger interfacial bonding force can be formed between the uniformly dispersed crystalline polyimide and polyamic acid, which helps to transfer stress and load in the composite material, improve the overall strength and durability of the material, and at the same time, it also helps to reduce defects and cracks at the interface and improve the reliability of the material.

[0026] Furthermore, another inventive point of the present invention is that in step S2, the thermal curing process is: program gradient heating treatment within 150-300°C, and treatment at each temperature for 1-2 hours. First, program gradient heating can more accurately control the curing process of the material. Different temperature stages correspond to different physical and chemical changes inside the material, such as solvent volatilization, chain segment movement, cross-linking reaction, etc. By gradually heating up, it can be ensured that these changes are gradually carried out at a suitable temperature, thereby optimizing the curing effect and improving the performance of the material. Rapid heating may cause a large temperature gradient and thermal stress inside the material, which in turn causes deformation, cracking and other problems of the material, while program gradient heating can slow down the speed of temperature change, make the temperature distribution inside the material more uniform, reduce stress concentration, and improve the stability and durability of the material.

[0027] In addition, the present invention also discloses a crystalline polyimide / polyimide composite material prepared by the above method, in which the crystalline polyimide in the composite material is a layered two-dimensional COFs structure, and the polyimide of the structure has a unique periodic layered structure, a large conjugated plane and a π-π stacking effect between layers, which makes it have a relatively high thermal conductivity. At the same time, the crystalline polyimide has more excellent heat resistance and high-temperature mechanical properties. Although the stable COFs conjugated structure has the characteristics of being difficult to melt and dissolve, it is difficult to further process, which limits its wide application in the electronic field. In the present invention, the crystalline polyimide is introduced into the N,N-dimethylformamide (DMF) solution of polyamic acid, and the amino group in the crystalline polyimide is reacted with the special interface compatibility of the acid anhydride in the polyamic acid, which can solve the problem of its difficult processing and effectively expand its application range. The crystalline polyimide / polyimide composite material described in the present invention has an initial thermal weight loss temperature of ≥510°C in an air atmosphere, a thermal conductivity of ≥1.2W / (m·K), and a dielectric loss of ≤0.002. The thermal weight loss temperature of the crystalline polyimide / polyimide composite material refers to the temperature at which the weight of the material begins to decrease significantly during the heating process. Thermal conductivity is a physical quantity that measures the thermal conductivity of a material. It describes the efficiency of the material in transferring heat under a certain temperature difference. Assuming that the thermal conductivity is 0.4W / (m·K), it means that under stable heat transfer conditions, the heat transferred through a unit area per unit time is 0.4 watts per meter Kelvin. Dielectric loss refers to the phenomenon that in an alternating electric field, the dielectric generates heat due to the consumption of part of the electrical energy. The smaller the dielectric loss, the better the performance of the insulating material, which helps to maintain the efficiency and stability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 XRD spectra of the composite materials prepared in Example 1(a) and Example 2(b) of the present invention;

[0030] Figure 2 This is a thermal gravimetric test diagram of the composite material prepared in Example 1 and Example 2 of the present invention;

[0031] Figure 3 This is a TEM image of the crystalline polyimide prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

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

[0034] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0035] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0036] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0037] The present invention provides a method for preparing a crystalline polyimide / polyimide composite material, which specifically comprises the following steps:

[0038] (1) Preparation of crystalline polyimide

[0039] First, by weight, 0.8 to 1 parts of mellitic acid trianhydride and 0.82 to 1.02 parts of diamine monomer are ground and mixed evenly, and then reacted at 240 to 280°C for 6 to 10 hours under argon atmosphere. After the reaction is completed and the temperature is naturally cooled to room temperature, the product is a crude crystalline polyimide. The product obtained by the reaction is stirred in 30 to 60 parts of a polar solvent for 24 hours and then filtered to remove unreacted monomers. Then, it is washed and purified with 50 to 200 parts of deionized water for multiple times. Finally, it is dried at 80°C under vacuum for 8 hours to obtain an imide-linked crystalline polyimide.

[0040] Wherein, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenedianiline, 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 is a two-dimensional COFs structure with a pore size of 1 to 4.05 nm.

[0043] The "two-dimensional COFs structure" in this article is 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 composites

[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%, and the mixture is stirred and dispersed for 1-2 hours under an ice-water bath. After being uniformly dispersed, the mixture is transferred to a mold, and the crystalline polyimide / polyamic acid organic solution composite solution is solidified by a casting method, wherein the solidification process is to react at 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. That is, a crystalline polyimide / polyimide composite sheet is obtained. The organic solution of polyamic acid can be a DMF solution of polyamic acid.

[0046] The preparation process of the above-mentioned polyamic acid is to uniformly disperse 2 parts of 4,4-diaminodiphenyl ether in 25 parts of N,N-dimethylformamide under ice water bath conditions, and then slowly add 2.18 parts of pyromellitic anhydride to the above solution within 1 hour, react for 6 hours after adding, and prepare a polyamic acid solution.

[0047] The invention discloses a method for preparing a crystalline polyimide / polyimide composite material. The method uses symmetrically structured mellitic acid trianhydride and diamine to carry out dehydration condensation reaction to synthesize crystalline polyimide, and the obtained crystalline polyimide is added to a DMF solution of polyamic acid in the form of a filler, transferred to a mold, and a crystalline polyimide / polyimide composite sheet is prepared by a casting method under a certain curing process. The prepared composite material has the characteristics of excellent high temperature resistance, good thermal conductivity, low dielectric loss and stable dielectric constant, wherein the introduction of a crystalline structure into a traditional polyimide can significantly improve its heat resistance, corrosion resistance and high temperature mechanical properties. At the same time, two-dimensional COFs have a unique periodic layered structure, a large conjugated plane and a π-π stacking effect between layers, which makes it have a relatively high thermal conductivity, which can effectively improve the heat dissipation problem of electronic devices. The composite material is prepared by utilizing the special interface compatibility of the amino group in the crystalline polyimide and the anhydride in the polyamic acid, thereby improving the processability of the crystalline polyimide in the application and combining the excellent dielectric properties of the polyimide. The preparation method of the present invention has the advantages of being simple and easy to control, having a low-cost reaction monomer, and being widely applicable to the electronic field, and is suitable for industrial production. The crystalline polyimide / polyimide composite material prepared by the present invention has an initial thermal weight loss temperature of ≥510°C in an air atmosphere, a thermal conductivity of ≥1.2W / (m·K), a dielectric loss of ≤0.002, and a dielectric constant of 3±0.54. The pure polyimide material does not add crystalline polyimide as a filler. When the curing process is the same as above, it is tested that the pure polyimide material has an initial thermal weight loss temperature of ≥370°C in an air atmosphere, a thermal conductivity of ≥0.4W / (m·K), a dielectric loss of ≤0.007, and a dielectric constant of 3±0.54. It can be seen that the composite material has the characteristics of excellent high temperature resistance, good thermal conductivity, low dielectric loss, stable dielectric constant and the like.

[0048] The present invention modifies the chemical structure of polyimide itself and imparts crystallinity to it, thereby obtaining a two-dimensional COFs polyimide having a covalent organic framework (COFs) structure. The polyimide of this structure has a unique periodic layered structure, a large conjugated plane, and a π-π stacking effect between layers, which makes it have a relatively high thermal conductivity. At the same time, the crystalline polyimide has more excellent heat resistance and high-temperature mechanical properties. Although the stable COFs conjugated structure has the characteristics of being difficult to melt and dissolve, it is difficult to further process, which limits its wide application in the field of electronics. In the present invention, the crystalline polyimide is introduced into the N,N-dimethylformamide (DMF) solution of polyamic acid, and the amino group in the crystalline polyimide is reacted with the special interface compatibility of the acid anhydride in the polyamic acid, which can solve the problem of its difficult processing and effectively expand its application range.

[0049] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0050] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0051] Example 1

[0052] 1) Preparation of crystalline polyimide

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

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

[0055] First, add 0.03 parts of the above crystalline polyimide to 10 parts of DMF solution of polyamic acid, stir and disperse for 1 hour under ice water bath conditions, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, with the curing temperature of 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0056] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 515°C, 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 mellitic acid trianhydride and 1.02 parts of diaminodiphenyl ether were ground and mixed evenly, and then reacted at 280°C for 10 hours under argon atmosphere. After the reaction was completed and the temperature naturally dropped to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction was stirred in 60 parts of N-methylpyrrolidone for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified with 200 parts of deionized water for multiple times. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 3.85nm.

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

[0061] First, add the above 0.833 parts of crystalline polyimide to 50 parts of DMF solution of polyamic acid, stir and disperse for 2 hours under ice water bath, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, and the curing temperature is 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0062] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 552°C, 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 mellitic acid trianhydride and 0.87 parts of m-phenylenediamine were ground and mixed evenly, and then reacted at 255°C for 8 hours under argon atmosphere. After the reaction was completed and the temperature naturally dropped to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction was stirred in 50 parts of N-methylpyrrolidone for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified several times with 80 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 3.33nm.

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

[0067] First, add 0.05 parts of the above crystalline polyimide to 15 parts of DMF solution of polyamic acid, stir and disperse for 1.5 hours under ice water bath conditions, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, with the solidification temperature of 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0068] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 525°C, 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 mellitic acid trianhydride and 0.92 parts of 1,3-di(4'-aminophenoxy)benzene were ground and mixed evenly, and then reacted at 250°C for 8 hours under argon atmosphere. After the reaction was completed and the temperature naturally dropped to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction 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 with 120 parts of deionized water for multiple times. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 2.65nm.

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

[0073] First, add the above 0.65 parts of crystalline polyimide to 38 parts of DMF solution of polyamic acid, stir and disperse for 2 hours under ice water bath, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, and the curing temperature is 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0074] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 530°C, 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 mellitic acid trianhydride and 0.82 parts of 1,4-bis(4-aminophenoxy)benzene were ground and mixed evenly, and then reacted at 275°C for 10 hours under argon atmosphere. After the reaction was completed and the temperature naturally dropped to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction was stirred in 30 parts of dimethyl sulfoxide for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified several times with 60 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 1.68nm.

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

[0079] First, add 0.03 parts of the above crystalline polyimide to 10 parts of DMF solution of polyamic acid, stir and disperse for 1 hour under ice water bath conditions, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, with the curing temperature of 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0080] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 532°C, 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 mellitic acid trianhydride 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 argon atmosphere. After the reaction was completed and the temperature naturally dropped to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction 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 with 100 parts of deionized water for multiple times. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 1.33nm.

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

[0085] First, add 0.06 parts of the above crystalline polyimide to 18 parts of DMF solution of polyamic acid, stir and disperse for 1 hour under ice water bath conditions, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, with the solidification temperature of 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0086] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 522°C, 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 mellitic acid trianhydride and 0.92 parts of 4,4'-methylenedianiline were ground and mixed evenly, and then reacted at 265°C for 6 hours under argon atmosphere. After the reaction was completed and the temperature naturally dropped to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction was stirred in 50 parts of N,N-dimethylacetamide for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified with 140 parts of deionized water for multiple times. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 2.38nm.

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

[0091] First, add the above 0.7 parts of crystalline polyimide to 42 parts of DMF solution of polyamic acid, stir and disperse for 1.5 hours under ice water bath, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, and the curing temperature is 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0092] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 530°C, 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 mellitic acid trianhydride and 0.97 parts of 1,3-di(4'-aminophenoxy)benzene were ground and mixed evenly, and then reacted at 280°C for 10 hours under argon atmosphere. After the reaction was completed and naturally cooled to room temperature, the product was a crude crystalline polyimide. The product obtained by the reaction was stirred in 60 parts of N-methylpyrrolidone for 24 hours and then filtered to remove unreacted monomers. Then, it was washed and purified several times with 200 parts of deionized water. Finally, it was dried under vacuum at 80°C for 8 hours to obtain an imide-linked crystalline polyimide with a pore size of 3.89 nm. 2) Preparation of crystalline polyimide / polyimide composite materials

[0096] First, add 0.05 parts of the above crystalline polyimide to 15 parts of DMF solution of polyamic acid, stir and disperse for 1.5 hours under ice water bath conditions, transfer to a mold after uniform dispersion, and solidify the composite solution of crystalline polyimide / polyamic acid DMF solution by casting, with the solidification temperature of 150°C for 1 hour, 180°C for 1 hour, and 300°C for 1 hour. Thus, a crystalline polyimide / polyimide composite sheet is obtained.

[0097] The properties of the obtained crystalline polyimide / polyimide composite material were tested, and the results showed that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere was 525°C, 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 XRD spectra of the composite materials prepared in Example 1 and Example 2 of the present invention are as shown in the figure. As can be seen from the figure, the XRD spectra measured in Example 1 and Example 2 both show sharp diffraction peaks. It can be concluded that the polyimide prepared in this patent is crystalline and the structural arrangement of the crystal is relatively orderly, the integrity of the crystal is high, the molecular arrangement inside the crystal is relatively fixed, and the crystallinity of the crystal is also high.

[0099] Figure 2 This is a thermal weight loss test diagram of the composite materials prepared in Example 1 and Example 2 of the present invention. It can be seen from the figure that the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material of Example 1 in an air atmosphere is 515°C, and the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material of Example 2 in an air atmosphere is 552°C. Therefore, the composite material prepared in the present application has excellent high temperature resistance.

[0100] Figure 3 This is a TEM image of the crystalline polyimide prepared in Example 1 of the present invention. As can be seen from the image, the crystalline polyimide in Example 1 presents a dense multi-layered sheet structure.

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as 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 solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a crystalline polyimide / polyimide composite material, characterized in that: The following steps are involved: S1: After uniformly mixing mellitic acid trianhydride and diamine monomer, a solid phase reaction is carried out under the protection of argon atmosphere. After the reaction is completed, the product is immersed in a polar solvent to obtain a crystalline polyimide with a two-dimensional COFs structure; S2: adding the crystalline polyimide to an organic solution of polyamic acid, subjecting the solution to ultrasonic treatment in an ice-water bath to uniformly disperse the crystalline polyimide in the organic solution of polyamic acid, and subjecting the solution to thermal curing to obtain the crystalline polyimide / polyimide composite material.

2. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that: In step S1, the diamine monomer is one or more of diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 4,4'-methylenedianiline, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4'-aminophenoxy)benzene and 1,4-bis(4-aminophenoxy)benzene.

3. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that: In step S1, the reaction temperature of the solid phase reaction is 240-280° C., and the reaction time is 6-10 hours.

4. 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.

5. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that: The molar ratio of the mellitic acid trianhydride to the diamine monomer is (0.8-1):(0.82-1.02).

6. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that: The average pore diameter of the crystalline polyimide is 1 to 4 nm.

7. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that: 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%.

8. The method for preparing a crystalline polyimide / polyimide composite material according to claim 1, characterized in that: In step S2, the thermal curing process is: performing a programmed gradient temperature increase treatment within a range of 150 to 300° C., and treating at each temperature for 1 to 2 hours.

9. 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 8; the initial thermal weight loss temperature of the crystalline polyimide / polyimide composite material in air atmosphere is ≥510°C, the thermal conductivity is ≥1.2W / (m·K), and the dielectric loss is ≤0.

002.

10. Use of the crystalline polyimide / polyimide composite material as claimed in claim 9 in electronic components.

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