Black insulating polyimide material and preparation method thereof

Abstract

The invention provides a black insulating polyimide material and a preparation method thereof, and particularly provides a polyamide acid solution which comprises a diamine monomer, a dianhydride monomer and a simple substance phosphorus-containing mixture, and the simple substance phosphorus-containing mixture is a mixture obtained by ball-milling simple substance phosphorus and boron nitride or porous silicon and a solvent. The black insulating polyimide material can be prepared from the polyamide acid solution, the influence of a carbon-based material on the insulating property of the polyimide material is avoided due to the adoption of the mixture containing the elemental phosphorus, and the elemental phosphorus material does not need to be added with a plasticizer and other materials. More importantly, the simple substance phosphorus and the boron nitride or the porous silicon can enable the polyimide to be black, meanwhile, the insulating property of the polyimide is improved, the heat-conducting property is improved, and the comprehensive performance of the black polyimide material is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of material modification, and in particular to a black insulating polyimide material and a preparation method thereof. Background Art

[0002] Polyimide materials have excellent mechanical properties, including resistance to thermal oxidation, heat resistance, radiation resistance, low-temperature properties, and chemical resistance. They are often used in a variety of applications, including aerospace-grade heat-resistant materials and electronic-grade insulation materials. Black polyimide is a high-performance polyimide material that is made black by adding black fillers (such as carbon black, black pigments, etc.) or chemically modifying the polyimide material. It retains the excellent properties of polyimide while meeting the requirements for color, optical properties, or conductivity in specific applications. As application requirements continue to change, black polyimide materials with insulating properties have become one of the important development directions of high-performance polymer materials. Chinese invention patent CN109880366A discloses a high-insulation-strength black polyimide composite film and its preparation method. The composite film is composed of a first black polyimide film layer and a second black polyimide film layer. The first black polyimide film layer contains 0.1-1% black colorant and 1-10% inorganic oxide particles, while the second black polyimide film layer contains 1-8% black colorant and 1-10% inorganic oxide particles. However, existing black insulating polyimide materials still primarily use black colorants, and the insulation performance of single-layer polyimide films needs to be further improved. Summary of the Invention

[0003] In response to the problems of the existing technology, the purpose of the present invention is to provide a black polyimide material with excellent insulating properties and a preparation method thereof, which utilizes micro-nano phosphorus to be compounded with boron nitride or porous silicon and combined with polyimide to form a black insulating polyimide material.

[0004] One aspect of the present invention provides a polyamic acid solution for preparing a black polyimide material, comprising:

[0005] a) diamine monomer;

[0006] b) dianhydride monomers;

[0007] c) a mixture containing elemental phosphorus, wherein the mixture containing elemental phosphorus is a mixture of elemental phosphorus and boron nitride or porous silicon after ball milling;

[0008] d) solvent.

[0009] Furthermore, the mass of the mixture containing elemental phosphorus is 0.1% to 10% of the mass of the components excluding the solvent.

[0010] Furthermore, the elemental phosphorus is black phosphorus, white phosphorus, red phosphorus or purple phosphorus.

[0011] Furthermore, the particle size of elemental phosphorus or elemental boron is 10 nanometers to 50 micrometers.

[0012] Furthermore, the boron nitride is hexagonal boron nitride or cubic boron nitride containing a graphite structure.

[0013] Furthermore, the porous silicon is one of a silicon molecular sieve having an MFI topology structure, a silicon molecular sieve having a BEA topology structure, and a silicon molecular sieve having a FAU topology structure.

[0014] Furthermore, the mass ratio of elemental phosphorus to boron nitride or porous silicon in the elemental phosphorus-containing mixture is 1:0.3-0.5.

[0015] Further, the diamine monomer is selected from 4,4'-oxydianiline, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 2,2'-diaminobiphenyl, 1,3-phenylenediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,2-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,5-bis(4-aminophenoxy)toluene, bis[4-(4-aminophenoxy)phenyl]ether, 4,4'-bis(aminooxy)diphenyl, and 2,2-bis[4(4-aminophenoxy)phenyl]propane.

[0016] Furthermore, the dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic anhydride (ODPA), difluorobiphenyl dianhydride (6FDA), triphenoylmethane tetracarboxylic anhydride (TPDA), biphenyltetracarboxylic dianhydride (BPDA), diphenylsulfone tetracarboxylic dianhydride (DSDA), 1,4-bis(3,4-dicarboxylic phenoxyphthalic anhydride) (HQDEA).

[0017] Furthermore, the solvent is one or a combination of two or more of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), γ-butyrolactam (GBL), and N,N-dimethylacetamide (DMAc).

[0018] Furthermore, the mass ratio of the diamine monomer to the dianhydride monomer is 1:1 to 1:1.15.

[0019] Furthermore, the polyamic acid solution does not contain a plasticizer.

[0020] Another aspect of the present invention provides a black polyimide prepared from the polyamic acid solution.

[0021] Furthermore, the black polyimide is in the form of a film, fiber, powder, particle or coating.

[0022] Furthermore, the light transmittance of the black polyimide is 0% to 10%.

[0023] Furthermore, the black polyimide has insulating properties.

[0024] Another aspect of the present invention provides a method for preparing the polyamic acid solution. The polyamic acid solution is obtained by uniformly mixing a diamine monomer, a dianhydride monomer, a mixture containing elemental phosphorus, and a solvent.

[0025] Further, it comprises the following steps:

[0026] S1) preparing a polyimide precursor solution by adding diamine and dianhydride monomers to a first organic solvent;

[0027] S2) adding a phosphorus-containing mixture to a second organic solvent for dispersion to form a dispersed solution; the phosphorus-containing mixture is a ball-milled mixture of phosphorus and boron nitride or porous silicon;

[0028] S3) mixing the polyimide precursor solution and the dispersion solution to form a polyamic acid solution.

[0029] Furthermore, the preparation method of the elemental phosphorus-containing mixture comprises ball milling and dispersing elemental phosphorus, boron nitride or porous silicon, and a third organic solvent in a mass ratio of 1:0.3-0.5:20-50.

[0030] Furthermore, the third organic solvent is isopropanol, n-propanol, methanol, ethanol, or butanol.

[0031] Furthermore, the first organic solvent and the second organic solvent are the same solvent and are selected from one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), γ-butyrolactam (GBL), and N,N-dimethylacetamide (DMAc).

[0032] Furthermore, the first organic solvent and the second organic solvent are different solvents, independently selected from one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) or γ-butyrolactam (GBL), and N,N-dimethylacetamide (DMAc).

[0033] Furthermore, the elemental phosphorus is black phosphorus, white phosphorus, red phosphorus or purple phosphorus.

[0034] Furthermore, the boron nitride is hexagonal boron nitride or cubic boron nitride containing a graphite structure.

[0035] Furthermore, the porous silicon is one of a silicon molecular sieve having an MFI topology structure, a silicon molecular sieve having a BEA topology structure, and a silicon molecular sieve having a FAU topology structure.

[0036] Furthermore, the rotation speed of the dispersion treatment in step S2 is 5000 rpm to 10000 rpm, and the treatment time is 5 to 60 minutes.

[0037] Another aspect of the present invention provides a method for preparing the black polyimide material, which comprises the following steps:

[0038] The polyamic acid solution is taken, formed, and then heated and cured to form a black polyimide material.

[0039] Furthermore, no plasticizer is added during the preparation of the black polyimide material.

[0040] Furthermore, the temperature for heating and curing is 300°C to 450°C.

[0041] Furthermore, the forming method is casting, coating, tableting, spinning, pulverization or injection molding.

[0042] Furthermore, the method of forming by spinning is to spin the polyamic acid solution by wet method or dry-wet method to obtain nascent fibers, and then dry them at 80°C to 120°C.

[0043] Furthermore, the powder or granular polyimide material is obtained by obtaining a polyimide film or fiber material and then crushing it.

[0044] Furthermore, the method further includes the step of mixing a leveling agent and an organic silane into the polyamic acid solution before molding.

[0045] Furthermore, the volume ratio of the polyamic acid solution, the leveling agent and the organosilane is 1:0.1-10:0.05-0.5.

[0046] Beneficial effects

[0047] Compared to existing technologies, the present invention provides a black polyimide material with excellent insulation properties. The use of a mixture containing elemental phosphorus eliminates the effects of carbon-based materials on the insulation properties of the polyimide material, and the elemental phosphorus material also eliminates the need for the addition of plasticizers or other materials. More importantly, the combination of elemental phosphorus and boron nitride or porous silicon gives the polyimide a black color, while also enhancing its insulation and thermal conductivity, significantly improving the overall performance of the black polyimide material. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 These are actual photos of polyimide films (the left side is a conventional polyimide film; the right side is the polyimide film of the present invention).

[0049] Figure 2 These are actual photos of polyimide fibers (the top one is conventional polyimide fiber; the bottom one is the polyimide fiber of the present invention).

[0050] Figure 3 This is the infrared spectrum of conventional polyimide film.

[0051] Figure 4 This is the infrared spectrum of the polyimide film of the present invention.

[0052] Figure 5 The invention discloses a black polyimide powder obtained by the method of the present invention. DETAILED DESCRIPTION

[0053] The content of the present invention is preferably described in detail below through specific examples. It should be noted that these examples are only used to illustrate the present invention and are not intended to limit the scope of the invention. In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. Below in conjunction with the examples, the features and performance of the present invention are preferably described in detail.

[0054] The present invention provides a black insulating polyimide material obtained by adding a phosphorus-containing mixture to a polyamic acid solution and then heating and forming the mixture. The phosphorus-containing mixture is a ball-milled mixture of phosphorus and boron nitride or porous silicon. The mass of the phosphorus-containing mixture accounts for 0.1% to 10% of the black polyimide material. The phosphorus is black phosphorus, white phosphorus, red phosphorus, or purple phosphorus. The boron nitride is hexagonal boron nitride or cubic boron nitride with a graphite structure. The porous silicon is a silicon molecular sieve with an MFI topology, a BEA topology, or a FAU topology. The resulting black polyimide material can be in various forms, such as a film, fiber, powder, granules, or coating.

[0055] The black insulating polyimide material is obtained by the following preparation method:

[0056] S01) adding diamine and dianhydride monomers into a first organic solvent to prepare a polyimide precursor solution;

[0057] In some specific embodiments, the diamine is 4,4'-oxydiphenylamine, 4,4'-diaminodiphenyl ether, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 2,2'-diaminobiphenyl, 1,3-phenylenediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,2-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,5-bis(4-aminophenoxy)toluene, bis[4-(4-aminophenoxy)] The dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic anhydride (ODPA), difluorobiphenyl dianhydride (6FDA), triphenoylmethane tetracarboxylic dianhydride (TPDA), biphenyltetracarboxylic dianhydride (BPDA), diphenylsulfonetetracarboxylic dianhydride (DSDA), 1,4-bis(3,4-dicarboxyphenoxyphthalic dianhydride) (HQDEA).

[0058] The molar ratio of the diamine and dianhydride monomers can be prepared using known ratios of diamine and dianhydride monomers in the art. In some specific embodiments, the molar ratio of the diamine and dianhydride monomers is 1:1 to 1:1.15. In some specific embodiments, the mass percentage of the polyimide precursor solution is 10% to 50%, for example, 10%, 20%, 30%, 40%, or 50%.

[0059] S02) adding a mixture containing elemental phosphorus into a second organic solvent for dispersion to form a dispersed solution; the mixture containing elemental phosphorus is a mixture of elemental phosphorus and boron nitride or porous silicon after ball milling.

[0060] The preparation method of the elemental phosphorus-containing mixture comprises the steps of ball milling, dispersing and mixing elemental phosphorus, boron nitride or porous silicon, and a third organic solvent in a mass ratio of 1:0.3-0.5:20-50.

[0061] The third organic solvent can be isopropanol, n-propanol, methanol, ethanol, or butanol.

[0062] In some specific embodiments, the mass of the elemental phosphorus-containing mixture is 0.1% to 10% of the total mass of all components excluding the solvent, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0063] In some specific embodiments, the first organic solvent and the second organic solvent are the same solvent and are selected from one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), γ-butyrolactam (GBL), and N,N-dimethylacetamide (DMAc).

[0064] In some specific embodiments, the first organic solvent and the second organic solvent are different solvents, independently selected from one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) or γ-butyrolactam (GBL), and N,N-dimethylacetamide (DMAc).

[0065] In some specific embodiments, the elemental phosphorus is black phosphorus, white phosphorus, red phosphorus or purple phosphorus.

[0066] In some specific embodiments, the boron nitride is hexagonal boron nitride or cubic boron nitride containing a graphite structure.

[0067] In some specific embodiments, the porous silicon is one of a silicon molecular sieve having an MFI topology structure, a silicon molecular sieve having a BEA topology structure, and a silicon molecular sieve having a FAU topology structure.

[0068] In some specific embodiments, the rotation speed of the dispersion treatment in step S2 is 5000 rpm to 10000 rpm, and the treatment time is 5 to 60 minutes.

[0069] S03) mixing the polyimide precursor solution and the dispersion solution to form a polyamic acid solution, which is then heated and cured after molding to form a black insulating polyimide material; the polyamic acid solution does not contain a plasticizer.

[0070] In some specific embodiments, the temperature for heating and curing in step S03) is 300°C to 450°C.

[0071] In some specific embodiments, the forming method in step S03) is casting, coating, sheeting, spinning or injection molding.

[0072] In the step S3), the method for forming by spinning is to spin the polyamic acid solution by wet spinning or dry-wet spinning to obtain nascent fibers, and then dry them at 80° C. to 120° C.

[0073] In some specific embodiments, the step S3) further comprises the step of mixing a leveling agent and an organosilane into the polyamic acid solution before molding; the volume ratio of the polyamic acid solution, the leveling agent and the organosilane is 1:0.1-10:0.05-0.5.

[0074] In some specific embodiments, the mass of the mixture containing elemental phosphorus is 0.1% to 10% of the black polyimide material, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0075] Example 1 Preparation method of black insulating polyimide film

[0076] S1) preparing a polyimide precursor solution by adding monomers 4,4'-oxydianiline and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA) to N,N-dimethylformamide (DMF);

[0077] S2) adding red phosphorus, hexagonal boron nitride containing graphite structure, isopropyl alcohol, and grinding balls into a ball mill and performing ball milling to obtain a mixture containing elemental phosphorus, wherein the mass ratio of red phosphorus, hexagonal boron nitride containing graphite structure, and isopropyl alcohol is 1:0.3:50, and the ball milling time is 1 hour;

[0078] The elemental phosphorus mixture was added to N-methylpyrrolidone (NMP) and dispersed at a speed of 5000 rpm to form a dispersed solution;

[0079] S3) mixing the above two solutions to form a polyamic acid solution, wherein the mass of the elemental phosphorus-containing mixture added is 5% of the total mass of the monomers 4,4'-oxydianiline, 3,3',4,4'-biphenyltetracarboxylic dianhydride and the elemental phosphorus-containing mixture; forming a film by casting, and curing at 300-450° C. to form a film.

[0080] Example 2 Preparation method of black insulating polyimide film

[0081] S1) preparing a polyimide precursor solution by adding monomers 4,4'-diaminodiphenyl ether and pyromellitic dianhydride to N,N-dimethylformamide (DMF);

[0082] S2) adding black phosphorus, silicon molecular sieve with MFI topology, isopropyl alcohol, and grinding balls into a ball mill and performing ball milling to obtain a mixture containing elemental phosphorus, wherein the mass ratio of black phosphorus, silicon molecular sieve with MFI topology, and isopropyl alcohol is 1:0.5:20, and the ball milling time is 6 hours;

[0083] The mixture containing elemental phosphorus was added to N,N-dimethylformamide (DMF) and dispersed at a speed of 10000 rpm to form a dispersed solution;

[0084] S3) mixing the two solutions to form a polyamic acid solution, wherein the mass of the elemental phosphorus mixture added is 0.5% of the total mass of 4,4'-diaminodiphenyl ether, pyromellitic dianhydride and the elemental phosphorus mixture; forming a film by casting, and curing at 300-450°C to form a film.

[0085] Example 3 Preparation method of black insulating polyimide fiber

[0086] S1) preparing a polyimide precursor solution by adding monomers 3,3'-diaminobenzidine and triphenylmethane tetraanhydride (TPDA) to N,N-dimethylformamide (DMF);

[0087] S2) adding purple phosphorus, cubic boron nitride containing graphite structure, isopropyl alcohol, and grinding balls into a ball mill and performing ball milling to obtain a mixture containing elemental phosphorus, wherein the mass ratio of purple phosphorus, cubic boron nitride containing graphite structure, and isopropyl alcohol is 1:0.3:20, and the ball milling time is 2 hours;

[0088] The elemental phosphorus mixture was added to N,N-dimethylformamide (DMF) and dispersed at a speed of 10000 rpm to form a dispersed solution;

[0089] S3) mixing the two solutions in a static mixer to form a polyamic acid solution, wherein the mass of the elemental phosphorus-containing mixture added is 1% of the total mass of 3,3'-diaminobenzidine, triphenylmethane tetracarboxylic anhydride (TPDA), and the elemental phosphorus-containing mixture; transporting the solution to a spinneret and spinning the solution using a wet process to obtain spun fibers;

[0090] S4) drying the as-spun fibers at 80° C., and then imidizing and curing the fibers at 300-450° C. to obtain black polyimide fibers.

[0091] Example 4 Preparation method of black insulating polyimide fiber

[0092] S1) preparing a polyimide precursor solution by adding monomers p-phenylenediamine and 4,4'-oxydiphthalic anhydride (ODPA) to N,N-dimethylformamide (DMF);

[0093] S2) adding black phosphorus, silicon molecular sieve with BEA topology structure, isopropyl alcohol, and grinding balls into a ball mill and performing ball milling to obtain a mixture containing elemental phosphorus, wherein the mass ratio of black phosphorus, silicon molecular sieve with BEA topology structure, and isopropyl alcohol is 1:0.5:50, and the ball milling time is 1 hour;

[0094] The mixture containing elemental phosphorus was added to N,N-dimethylformamide (DMF) and dispersed at a speed of 10000 rpm to form a dispersed solution;

[0095] S3) mixing the two solutions in a static mixer to form a polyamic acid solution, wherein the mass of the elemental phosphorus-containing mixture added is 8% of the total mass of p-phenylenediamine, 4,4'-oxybisphthalic anhydride, and the elemental phosphorus-containing mixture; transporting the solution to a spinneret and spinning the solution using a dry-wet process to obtain spun fibers;

[0096] S4) drying the as-spun fibers at 120° C., and then imidizing and curing the fibers at 300-450° C. to obtain black polyimide fibers.

[0097] Example 5 Preparation method of black insulating polyimide coating material

[0098] S1) preparing a polyimide precursor solution by adding 4,4'-diaminobiphenyl and pyromellitic dianhydride (PMDA) to N-methylpyrrolidone (NMP);

[0099] S2) adding red phosphorus, hexagonal boron nitride containing graphite structure, isopropyl alcohol, and grinding balls into a ball mill and performing ball milling to obtain a mixture containing elemental phosphorus, wherein the mass ratio of red phosphorus, hexagonal boron nitride containing graphite structure, and isopropyl alcohol is 1:0.3:30, and the ball milling time is 2 hours;

[0100] The elemental phosphorus mixture was added to N-methylpyrrolidone (NMP) and dispersed at a speed of 8000 rpm to form a dispersed solution;

[0101] S3) mixing the above two solutions to form a polyamic acid solution, wherein the mass of the added elemental phosphorus-containing mixture is 2% of the total mass of 4,4'-diaminobiphenyl, pyromellitic dianhydride and the elemental phosphorus-containing mixture; then adding 5 parts of an acrylic leveling agent and 0.05 parts of an organosilane, stirring at a stirring speed of 5000 rpm for 100 minutes, applying it to the surface of the material and curing it at 300-450°C for 3 hours.

[0102] Example 6 Preparation method of black insulating polyimide coating material

[0103] S1) preparing a polyimide precursor solution by adding 1,3-bis(4-aminophenoxy)benzene and biphenyltetracarboxylic dianhydride monomers to N-methylpyrrolidone (NMP);

[0104] S2) adding black phosphorus, silicon molecular sieve with BEA topology structure, isopropyl alcohol, and grinding balls into a ball mill and performing ball milling to obtain a mixture containing elemental phosphorus, wherein the mass ratio of black phosphorus, silicon molecular sieve with BEA topology structure, and isopropyl alcohol is 1:0.4:40, and the ball milling time is 3 hours;

[0105] The mixture containing elemental phosphorus was added to N,N-dimethylformamide (DMF) and dispersed at a speed of 10000 rpm to form a dispersed solution;

[0106] S3) The above two solutions are mixed to form a polyamic acid solution, wherein the mass of the elemental phosphorus-containing mixture added is 6% of the total mass of 1,3-bis(4-aminophenoxy)benzene, biphenyltetracarboxylic dianhydride and the elemental phosphorus-containing mixture; then 1 part of a leveling agent and 0.5 parts of an organosilane are added, and the mixture is stirred at a stirring speed of 8000 rpm for 20 minutes, applied to the surface of the material and cured at 300-450°C for 3 hours.

[0107] Example 7 Preparation Method of Black Insulating Polyimide Powder

[0108] The sample prepared in Example 4 was repeatedly ground by a jet mill, an ultrafine grinder, and the like to obtain black polyimide powder. Figure 5 .

[0109] Comparative Example

[0110] S1) preparing a polyimide precursor solution by adding monomers 4,4'-oxydianiline and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA) to N,N-dimethylformamide (DMF);

[0111] S2) forming a thin film by casting and curing at 300-450°C to form a film.

[0112] The infrared spectra of the films of Comparative Example 1 and Example 1 were tested by infrared spectroscopy. The test results are shown in Figure 3-4 , it can be found from the spectrum that the characteristic peak of imide structure in yellow polyimide is 1243cm -1 (COC), 1378cm -1 (CNC), the characteristic peak of the imine structure in the present invention is significantly shifted to 1252 cm -1 、1384cm -1 This indicates that the introduction of phosphorus changes the imide structure and increases the spectral absorption range, resulting in a black color. The light transmittance of the black polyimide obtained in the embodiment is 0% to 10%.

[0113] Observe the color of the materials of Examples 1-6 and see the test results. Figure 1-2 The dielectric strength of Examples 1-2 was tested, and when the thickness was 50 microns, the dielectric strength could reach 160 kV / mm, and the thermal conductivity could reach 0.8 W / m·K.

[0114] The present invention provides a black polyimide material with good insulating properties. The raw materials are easily available and the preparation process is simple. It shows significant advantages in terms of insulating properties and comprehensive performance. The product performance indicators reach the level of similar foreign products, and it has significant technological progress and economic and social benefits.

Claims

1. A polyamic acid solution for preparing a black polyimide material, characterized in that: It includes: a) diamine monomer; b) dianhydride monomer; c) a mixture containing elemental phosphorus, wherein the mixture containing elemental phosphorus is a mixture of elemental phosphorus and boron nitride or porous silicon after ball milling; d) solvent; The mass of the mixture containing elemental phosphorus is 0.1% to 10% of the mass of the components excluding the solvent.

2. The polyamic acid solution according to claim 1, wherein The elemental phosphorus is black phosphorus, white phosphorus, red phosphorus or purple phosphorus; Preferably, the particle size of elemental phosphorus or elemental boron is 10 nanometers to 50 micrometers.

3. The polyamic acid solution according to claim 1, wherein The boron nitride is hexagonal boron nitride or cubic boron nitride containing a graphite structure; Preferably, the porous silicon is one of a silicon molecular sieve having an MFI topology structure, a silicon molecular sieve having a BEA topology structure, and a silicon molecular sieve having a FAU topology structure.

4. The polyamic acid solution according to claim 1, characterized in that The mass ratio of elemental phosphorus to boron nitride or porous silicon in the elemental phosphorus-containing mixture is 1:0.3-0.

5.

5. The polyamic acid solution according to claim 1, characterized in that The diamine monomer is selected from 4,4'-oxydianiline, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 2,2'-diaminobiphenyl, 1,3-phenylenediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,2-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,5-bis(4-aminophenoxy)toluene, bis[4-(4-aminophenoxy)phenyl]ether, 4,4'-bis(aminooxy)diphenyl, and 2,2-bis[4(4-aminophenoxy)phenyl]propane; The dianhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic anhydride (ODPA), difluorobiphenyl dianhydride (6FDA), triphenoylmethane tetracarboxylic anhydride (TPDA), biphenyltetracarboxylic dianhydride (BPDA), diphenylsulfone tetracarboxylic dianhydride (DSDA), and 1,4-bis(3,4-dicarboxylic phenoxyphthalic anhydride) (HQDEA).

6. A black polyimide material prepared from the polyamic acid solution according to any one of claims 1 to 5; Preferably, the black polyimide material is in the form of a film, fiber, powder, granule or coating.

7. The method for preparing the polyamic acid solution according to any one of claims 1 to 5, characterized in that: The polyamic acid solution is obtained by uniformly mixing a diamine monomer, a dianhydride monomer, a mixture containing elemental phosphorus, and a solvent.

8. The preparation method according to claim 7, characterized in that It includes the following steps: S1) preparing a polyimide precursor solution by adding diamine and dianhydride monomers to a first organic solvent; S2) adding the elemental phosphorus mixture into a second organic solvent for dispersion to form a dispersed solution; the elemental phosphorus mixture is a mixture of elemental phosphorus and boron nitride or porous silicon after ball milling S3) mixing the polyimide precursor solution and the dispersion solution to form a polyamic acid solution; The first organic solvent and the second organic solvent are the same or different; Preferably, the preparation method of the elemental phosphorus-containing mixture comprises ball milling and dispersing elemental phosphorus, boron nitride or porous silicon, and a third organic solvent in a mass ratio of 1:0.3-0.5:20-50; Preferably, the third organic solvent is isopropanol, n-propanol, methanol, ethanol, or butanol.

9. The method for preparing the black polyimide material according to claim 6, characterized in that: It includes the following steps: Take the above polyamic acid solution, shape it, and heat and solidify it to form a black polyimide material; Preferably, no plasticizer is added during the preparation of the black polyimide material; Preferably, the temperature for heating and curing is 300°C to 450°C.

10. The preparation method according to claim 9, characterized in that The forming method is casting, coating, tableting, pulverization, spinning or injection molding; Preferably, the method of forming by spinning is to spin the polyamic acid solution by wet spinning or dry-wet spinning to obtain nascent fibers, and then drying at 80° C. to 120° C.; Preferably, the powder or granular polyimide material is formed by crushing the obtained polyimide film or fiber material; Preferably, the method further comprises mixing a leveling agent and an organosilane into the polyamic acid solution before molding; More preferably, the volume ratio of the polyamic acid solution, the leveling agent and the organosilane is 1:0.1-10:0.05-0.5.

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