High-adhesion polyimide resin material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a high-adhesion polyimide resin material and a preparation method thereof, and the high-adhesion polyimide resin material is prepared from a polyimide precursor and a surface modified inorganic filler; wherein a dynamic disulfide bond network constructed by a thioctic acid modified diamine monomer enables the material to achieve a scratch repair rate of 88% or above within 12 h after being heated at 60 DEG C, the service life is remarkably prolonged, and the material is endowed with an ultraviolet absorption rate of 90% or above through the synergistic effect of triazine ring dianhydride and thioctic acid; according to the present invention, the silane coupling agent modified filler enables the damp-heat resistance time to break through 2800h, and is nearly doubled compared with the traditional material, the heat conductivity coefficient of 0.60-0.65 W / mK is achieved through the compound filler system and the dynamic cross-linking structure, the high adhesion of 7.1 N / cm is maintained, the high-end electronic packaging requirement is met, and the wide application prospect is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a high-adhesion polyimide resin material and a preparation method thereof. Background Art

[0002] Polyimide resin material is a type of aromatic heterocyclic polymer containing imide groups on the main chain. It has outstanding heat resistance, mechanical properties and insulation properties and is widely used in many fields. However, the application scenarios of polyimide resin materials such as insulating coatings and composite material matrices determine that it must form a stable bond with the contact interface (metal conductors and reinforcing fibers, etc.). The specific reasons are as follows: When used as an insulating coating for wires, it needs to be tightly bonded to metal conductors such as copper, otherwise it is easy to peel and fall off under high temperature, humidity or mechanical vibration, resulting in insulation failure; when used as a matrix for carbon fiber reinforced composite materials (CF / PI), the fibers need to be "bonded" into a whole. The interfacial adhesion directly affects the mechanical properties of the composite material. If the adhesion is insufficient, key indicators such as interlaminar shear strength and bending strength will drop significantly, and even the fibers and the matrix may peel off when subjected to force.

[0003] In the existing technology, the adhesion between the polyimide resin material and the substrate interface is mainly enhanced by improving the resin melt fluidity, enhancing the wettability, strengthening the interfacial chemical action, and adjusting the material structure.

[0004] However, while existing technologies can improve adhesion, they still have the following limitations: (1) The problem of balancing mechanical properties, that is, high adhesion may be achieved at the expense of some toughness, which is related to the decrease in molecular chain flexibility caused by the increase in resin cross-linking density (enhanced adhesion); (2) Increased processing costs and process complexity: To improve adhesion, it is necessary to precisely control the molecular weight of the prepolymer, optimize the fiber surface treatment, or adopt a special curing process. These measures will increase the difficulty of raw material matching and the production cycle, and increase manufacturing costs; (3) Some means of improving adhesion may affect the heat resistance of the material; (4) Limited application scenarios: High-adhesion polyimide often relies on the adaptive design of specific interfaces (such as carbon fiber, copper conductor), and it is difficult to take into account the needs of multiple scenarios.

[0005] Therefore, according to the above-mentioned related technologies, it is urgent to develop a high-adhesion polyimide resin material and a preparation method thereof. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to propose a high-adhesion polyimide resin material and a preparation method thereof. By optimizing the monomer ratio, modifying the surface of inorganic fillers, multi-scale composite and gradient curing process control, the interfacial bonding strength between the material and the conductor is synergistically improved, and the material is given multifunctional properties such as self-healing and UV blocking.

[0007] Based on the above objectives, the present invention provides a high-adhesion polyimide resin material and a preparation method thereof.

[0008] A high-adhesion polyimide resin material is prepared from a polyimide precursor and a surface-modified inorganic filler; The polyimide precursor is prepared from a diamine monomer and a dianhydride monomer; The surface-modified inorganic filler is a composite system of nano-silicon dioxide and boron nitride nano-sheets treated with a silane coupling agent.

[0009] Preferably, the preparation process of the polyimide precursor is as follows: Step A1. Raw material preparation: preparing diamine monomer, dianhydride monomer, solvent and additive; Step A2 monomer dissolution: In a nitrogen-protected three-necked flask, add the diamine monomer, pour in the solvent, and mechanically stir at 200 rpm at 25-30 ° C for 30-40 min until the diamine monomer is completely dissolved to ensure the uniformity of subsequent polymerization to obtain solution A2; Step A3 polymerization reaction: The diamine monomer and the dianhydride monomer are added to the solution A2 in a molar ratio of 1:0.98-1.02, the solvent is added to adjust the solid content of the system to 25-35wt%, the temperature is raised to 35-55 ° C, and stirring is continued for 5-7h to form a polyamic acid prepolymer solution; Step A4 chemical imidization: acetic anhydride and triethylamine were added to the polyimide solution and stirred at 35-40 ° C for 24 hours. After the reaction, the solution was light yellow and transparent with no obvious precipitation to obtain a reaction solution A4; Step A5. Purification and drying: Pour the reaction solution A4 into 3 times the volume of ethanol to precipitate a flocculent precipitate. After standing for 1 hour, filter it and wash the precipitate three times with ethanol to remove unreacted monomers. Vacuum dry it at 80°C for 24 hours and then at 200°C for 4 hours to obtain a polyimide precursor powder.

[0010] Preferably, the diamine monomer in step A1 is diaminodiphenyl ether (ODA), phenylenediamine (PPD), or lipoic acid-modified diamine monomer, wherein the ether bond of ODA imparts flexibility, PPD enhances polar interactions, and lipoic acid-modified diamine achieves self-repair through dynamic disulfide bonds.

[0011] Preferably, the molar ratio of diaminodiphenyl ether, phenylenediamine and lipoic acid-modified diamine monomer in the diamine monomer in step A1 is 60-80:10-20:10-20.

[0012] Preferably, the preparation process of the lipoic acid modified diamine monomer is as follows: Step A101. Prepare raw materials: lipoic acid, ethylenediamine, carbonyldiimidazole, anhydrous chloroform, saturated brine, NaOH aqueous solution and anhydrous sodium sulfate; Step A102. Lipoic acid activation: To a 250 mL three-necked flask under argon, add lipoic acid and anhydrous chloroform, stir at room temperature until dissolved, add CDI, and activate at room temperature for 30 minutes to form a reactive imidazoline intermediate and enhance the reactivity of the carboxyl group. Argon is used to prevent oxidation. The molar ratio of CDI to lipoic acid is equimolar to ensure mono-activation, to obtain reaction solution A102. Step A103. Condensation reaction: Place the reaction solution A102 in an ice-water bath at 0-4°C and slowly add a solution of ethylenediamine in anhydrous chloroform dropwise. After the addition is complete, remove the water bath and stir at room temperature for 12-16 hours to ensure that the amide bond is fully formed. Follow with thin-layer chromatography using a 4:1 volume ratio of chloroform and methanol as the developing solvent to separate lipoic acid from the product. Step A104. The reaction solution was washed sequentially with saturated brine and 5% aqueous NaOH to remove unreacted CDI and ethylenediamine. The organic phase was dried over anhydrous sodium sulfate for 2 h, filtered, and the chloroform was evaporated to dryness under reduced pressure to obtain a pale yellow oily crude product. Finally, the product was purified by column chromatography (using a gradient elution of chloroform:methanol = 10:1 → 5:1). The target fractions were collected and dried under vacuum to obtain a white solid product, thereby obtaining the lipoic acid-modified diamine monomer.

[0013] The purity of the lipoic acid in step A101 is ≥99%, and the CAS number of the lipoic acid is 1077-28-7, which is used to provide disulfide bonds and carboxyl groups. The purity of the ethylenediamine in step A101 is ≥99%, which is used to provide free amino groups. The carbonyldiimidazole in step A101 serves as a carboxyl group activator, and the anhydrous chloroform in step A101 is used as a solvent.

[0014] Preferably, the usage ratio of lipoic acid, anhydrous chloroform, and CDI in step A102 is 2-2.2 g:50-55 mL:1.5-1.8 g.

[0015] Preferably, the mass ratio of ethylenediamine to lipoic acid in step A103 is 1:2.

[0016] Preferably, in step A103, the volume ratio of the reaction solution A102 to the anhydrous chloroform solution of ethylenediamine is 50-55:20-22.

[0017] Preferably, the washing times with saturated brine in step A104 are 3 times, 50 mL each time, and the washing times with NaOH solution are 2 times, 50 mL each time.

[0018] Preferably, the dianhydride monomer in step A1 is biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), or triazine cyclic dianhydride, wherein BPDA improves hydrolysis resistance, PMDA enhances reaction activity, and triazine cyclic dianhydride expands performance through ultraviolet absorption function.

[0019] Preferably, the molar ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and triazine ring dianhydride in the dianhydride monomer in step A1 is 50-70:20-30:10-20.

[0020] Preferably, the solvent in step A2 is a mixture of N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 15-25:75-85.

[0021] Preferably, the auxiliary agent in step A1 includes a dehydrating agent and a catalyst, the dehydrating agent is acetic anhydride, and the catalyst is triethylamine.

[0022] Preferably, the amount of acetic anhydride used in step A4 is 1.2 times the molar number of the amic acid group, wherein the molar ratio of triethylamine to acetic anhydride is 1:1.2.

[0023] Preferably, the preparation process of the surface-modified inorganic filler is as follows: Step B1. Raw material preparation: prepare inorganic filler, modifier and dispersion medium.

[0024] Step B2 filler dispersion: 100g of dispersion medium was added to a 500mL three-necked flask, an inorganic filler was added, mechanical stirring was started at a speed of 200-300rpm, and ultrasonic dispersion was performed at a power of 300W for 40 minutes to form a uniform suspension to avoid agglomeration; Step B3. Surface modification reaction: Add a modifier to the suspension, raise the temperature to 65-85°C under nitrogen protection, and stir for 2.5-3.5 hours. During the reaction, the silane coupling agent hydrolyzes to form silanol groups, which react with the hydroxyl groups on the surface of the inorganic filler to graft active groups onto the surface of the inorganic filler to obtain reaction solution B3; Step B4. Post-treatment: After the reaction is completed, the reaction solution B3 is cooled to room temperature and directly used as an inorganic filler dispersion to avoid secondary agglomeration caused by drying.

[0025] Preferably, the inorganic filler in step B1 is a mixture of nano-silicon dioxide and boron nitride nanosheets in a mass ratio of 7-9:1-3, wherein the particle size of the nano-silicon dioxide is 20-50 nm, the thickness of the boron nitride nanosheets is 5-10 nm, and the lateral size is 1-2 μm, wherein the nano-silicon dioxide is used to enhance mechanical anchoring and the boron nitride constructs a thermal conductive path.

[0026] Preferably, the modifiers in step B1 are γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560), and the amount of the modifiers used is 8%-15% of the total mass of the filler.

[0027] Preferably, the dispersion medium in step B1 is DMAc, and the mass ratio of the dispersion medium to the inorganic filler is 100:20-35. The dispersion medium is compatible with the solvent for preparing the polyimide precursor, thus avoiding subsequent miscibility problems.

[0028] A method for preparing a high-adhesion polyimide resin material comprises the following steps: Step S1. Composite dispersion: Under nitrogen protection, the prepared inorganic filler dispersion was dropped into the polyimide precursor powder, and mechanically stirred at 30°C at a speed of 300 rpm for 4 h; Step S2. A planetary ball mill was used to disperse the mixture at a speed of 300 rpm for 30 min to further break up the agglomerates and ensure that the filler was evenly dispersed in the matrix, so that the final solid content was 40 wt % and the viscosity was 5000-8000 mPa·s to obtain a composite resin solution; Step S3. Gradient curing: The composite resin solution is applied to the surface of the copper conductor by dip coating, with the wet film thickness controlled at 110 μm. The first, second, and third stage curing are then performed, and the mixture is finally cooled to room temperature to obtain an insulating film with a thickness of 70 μm, i.e., a high-adhesion polyimide resin material.

[0029] Preferably, the mass ratio of the inorganic filler dispersion to the polyimide precursor in step S1 is 3:10.

[0030] Preferably, the curing temperature of the first stage curing in step S3 is 130-150° C., and the curing time is 2 hours.

[0031] Preferably, the curing temperature of the second stage curing in step S3 is 280-300° C., and the curing time is 3 hours.

[0032] Preferably, the curing temperature of the third stage curing in step S3 is 320-340° C., and the curing time is 2 hours.

[0033] Beneficial effects of the present invention: 1. Dynamic repair and long life: The dynamic disulfide bond network constructed by the lipoic acid-modified diamine monomer provided by the present invention enables the material to achieve a scratch repair rate of more than 88% within 12 hours when heated at 60°C, significantly extending the service life.

[0034] 2. Multi-dimensional protection performance: The synergistic effect of triazine cyclic dianhydride and lipoic acid provided by this invention gives the material a UV absorption rate of over 90%. The filler modified with a silane coupling agent extends the moisture and heat resistance time to over 2800 hours, nearly double that of traditional materials.

[0035] 3. High-performance integrated design: This invention achieves a thermal conductivity of 0.60-0.65W / m·K through a composite filler system (nano-silica + boron nitride) and a dynamic cross-linking structure, while maintaining a high adhesion of 7.1N / cm, meeting the requirements of high-end electronic packaging. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0037] Example 1: A method for preparing a high-adhesion polyimide resin material, comprising the following steps: S1. Prepare raw materials: Prepare lipoic acid (purity ≥99%), ethylenediamine (purity ≥99%), carbonyldiimidazole, anhydrous chloroform, saturated brine, aqueous NaOH solution, and anhydrous sodium sulfate. The CAS number of lipoic acid is 1077-28-7. S2. Lipoic acid activation: In a 250-mL three-necked flask under argon, add 2 g of lipoic acid and 50 mL of anhydrous chloroform. Add 1.5 g of CDI and activate at room temperature for 30 min to form a reactive imidazoline intermediate and enhance the reactivity of the carboxyl group. Argon protection is used to prevent oxidation. The molar ratio of CDI to lipoic acid is equimolar to ensure single activation, yielding reaction solution A102. S3. Condensation reaction: Place 50 mL of reaction solution A102 in a 0°C ice-water bath and slowly add dropwise 20 mL of anhydrous chloroform solution of ethylenediamine (in a mass ratio of 1:2 to lipoic acid). Stir at room temperature until dissolved. After the addition is complete, remove from the water bath and stir at room temperature for 12 h to ensure sufficient formation of the amide bond. Perform thin-layer chromatography (TLC) using a 4:1 volume ratio of chloroform and methanol as the developing solvent to separate lipoic acid from the product. S4. The reaction solution was washed three times with saturated brine (50 mL each time) and twice with 5% NaOH aqueous solution (50 mL each time) to remove unreacted CDI and ethylenediamine. The organic phase was dried over anhydrous sodium sulfate for 2 h, filtered, and evaporated to dryness under reduced pressure to obtain a pale yellow oily crude product. The crude product was then purified by column chromatography using a gradient elution ratio of chloroform to methanol (10:1 → 5:1). The target fractions were collected and dried under vacuum to obtain a white solid product (thioctic acid-ethylenediamine monosubstituted product, yield 75-80%). This product was a thioctic acid-modified diamine monomer. The structure was verified as follows: 1HNMR (300 MHz, CDCl3): δ 6.13 (s, 1H, amide H), 3.54 (m, 2H, CH2CH2NH2), 3.29 (t, 2H, CH2CONH), 2.79 (t, 2H, dithiolane CH2), 1.6-1.2 ppm (multiplet, aliphatic chain H); MS (ESI+): m / z 262.1 [M+H]+ (theoretical value 261.3, confirming amide bond formation); S5. Raw material preparation: preparing diaminodiphenyl ether (ODA), phenylenediamine (PPD), and lipoic acid-modified diamine monomers as diamine monomers; preparing biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and triazine ring dianhydride as dianhydride monomers; mixing N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 15:75 to obtain a solvent; preparing a dehydrating agent and a catalyst as auxiliary agents, wherein the dehydrating agent is acetic anhydride and the catalyst is triethylamine; wherein the molar ratio of diaminodiphenyl ether, phenylenediamine, and lipoic acid-modified diamine monomer in the diamine monomer is 60:10:10, and wherein the molar ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and triazine ring dianhydride in the dianhydride monomer is 50:20:10; S6. Monomer Dissolution: In a nitrogen-protected three-necked flask, add diamine monomer and solvent. Stir mechanically at 200 rpm at 25°C for 30 min until the diamine monomer is completely dissolved to ensure uniformity in subsequent polymerization. Solution A2 is obtained, wherein the solvent is a mixture of N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 15:75. S7 polymerization reaction: The diamine monomer and the dianhydride monomer were added to the solution A2 in a molar ratio of 1:0.98, the solvent was added to adjust the solid content of the system to 25wt%, the temperature was raised to 35 ° C, and stirring was continued for 5h to form a polyamic acid prepolymer solution; S8. Chemical imidization: Acetic anhydride and triethylamine were added to the polyimide solution and stirred at 35 ° C for 24 h. After the reaction, the solution was light yellow and transparent with no obvious precipitation to obtain a reaction solution A4, wherein the amount of acetic anhydride was 1.2 times the molar number of amic acid groups, and the molar ratio of triethylamine to acetic anhydride was 1:1.2; S9. Purification and drying: The reaction solution A4 was poured into 3 volumes of ethanol to precipitate a flocculent precipitate. After standing for 1 hour, the precipitate was filtered and washed with ethanol three times to remove unreacted monomers. The precipitate was vacuum dried at 80 ° C for 24 hours and then vacuum dried at 200 ° C for 4 hours to obtain a polyimide precursor powder. S10. Raw material preparation: Prepare an inorganic filler, a modifier, and a dispersion medium, wherein the inorganic filler is a mixture of nano-silica and boron nitride nanosheets in a mass ratio of 7:1, wherein the nano-silica has a particle size of 20-50 nm, wherein the boron nitride nanosheets have a thickness of 5-10 nm, and a lateral size of 1-2 μm, wherein the modifier is any one of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560), and the amount of the modifier is 8% of the total mass of the filler, wherein the dispersion medium is DMAc, and the mass ratio of the dispersion medium to the inorganic filler is 100:20; S11 filler dispersion: 100g of dispersion medium was added to a 500mL three-necked flask, an inorganic filler was added, mechanical stirring was started at a speed of 200rpm, and ultrasonic dispersion was performed at a power of 300W for 40 minutes to form a uniform suspension to avoid agglomeration; S12. Surface modification reaction: A modifier was added to the suspension, and the temperature was raised to 65°C under nitrogen protection and stirred for 2.5 h. During the reaction, the silane coupling agent was hydrolyzed to form silanol groups, which condensed with the hydroxyl groups on the surface of the inorganic filler to graft active groups onto the surface of the inorganic filler, thereby obtaining reaction solution B3. S13 post-treatment: After the reaction is completed, the reaction solution B3 is cooled to room temperature and directly used as an inorganic filler dispersion to avoid secondary agglomeration caused by drying; S14. Composite dispersion: Under nitrogen protection, the prepared inorganic filler dispersion was dropwise added to the polyimide precursor powder and mechanically stirred at 300 rpm and 30°C for 4 h. The mass ratio of the inorganic filler dispersion to the polyimide precursor was 3:10. S15. A planetary ball mill was used to disperse the mixture at 300 rpm for 30 min to further break up agglomerates and ensure that the filler was evenly dispersed in the matrix, resulting in a final solid content of 40 wt % and a viscosity of 5000 mPa·s to obtain a composite resin solution. S16. Gradient curing: The composite resin solution is applied to the surface of the copper conductor by a dip coating method, and the wet film thickness is controlled to be 110 μm. Then, the first stage curing, the second stage curing and the third stage curing are carried out, and finally the material is cooled to room temperature to obtain an insulating film with a thickness of 70 μm, i.e., a high-adhesion polyimide resin material. The curing temperature of the first stage curing is 130°C, and the curing time is 2 hours. The curing temperature of the second stage curing is 280°C, and the curing time is 3 hours. The curing temperature of the third stage curing is 320°C, and the curing time is 2 hours.

[0038] Example 2: A method for preparing a high-adhesion polyimide resin material, comprising the following steps: S1. Prepare raw materials: Prepare lipoic acid (purity ≥99%), ethylenediamine (purity ≥99%), carbonyldiimidazole, anhydrous chloroform, saturated brine, aqueous NaOH solution, and anhydrous sodium sulfate. The CAS number of lipoic acid is 1077-28-7. S2. Lipoic acid activation: In a 250-mL three-necked flask under argon, add 2.1 g of lipoic acid and 52 mL of anhydrous chloroform. Add 1.65 g of CDI and activate at room temperature for 30 min to form a reactive imidazoline intermediate and enhance the reactivity of the carboxyl group. Argon protection is used to prevent oxidation. An equimolar ratio of CDI to lipoic acid ensures mono-activation, yielding reaction solution A102. S3. Condensation reaction: Place 53 mL of reaction solution A102 in a 2°C ice-water bath and slowly add dropwise 21 mL of anhydrous chloroform solution of ethylenediamine (in a 1:2 mass ratio of ethylenediamine to lipoic acid) at room temperature until dissolved. After the addition is complete, remove from the water bath and stir at room temperature for 14 h to ensure full formation of the amide bond. Perform thin-layer chromatography (TLC) using a 4:1 volume ratio of chloroform and methanol as the developing solvent to separate the lipoic acid from the product. S4. The reaction mixture was washed three times with saturated brine (50 mL each time) and twice with 5% aqueous NaOH (50 mL each time) to remove unreacted CDI and ethylenediamine. The organic phase was dried over anhydrous sodium sulfate for 2 h, filtered, and evaporated to dryness under reduced pressure to obtain a pale yellow oily crude product. The crude product was then purified by column chromatography using a gradient elution ratio of chloroform to methanol (10:1 → 5:1). The target fractions were collected and dried under vacuum to obtain a white solid product (lipoic acid-ethylenediamine monosubstituted product, yield 75-80%), thus obtaining a lipoic acid-modified diamine monomer. S5. Raw material preparation: preparing diaminodiphenyl ether (ODA), phenylenediamine (PPD), and lipoic acid-modified diamine monomers as diamine monomers; preparing biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and triazine ring dianhydride as dianhydride monomers; mixing N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 20:80 to obtain a solvent; preparing a dehydrating agent and a catalyst as auxiliary agents, wherein the dehydrating agent is acetic anhydride and the catalyst is triethylamine; wherein the molar ratio of diaminodiphenyl ether, phenylenediamine, and lipoic acid-modified diamine monomer in the diamine monomer is 70:15:15, and wherein the molar ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and triazine ring dianhydride in the dianhydride monomer is 60:25:15; S6. Monomer Dissolution: In a nitrogen-protected three-necked flask, add the diamine monomer and the solvent. Stir mechanically at 200 rpm at 27°C for 35 min until the diamine monomer is completely dissolved to ensure uniformity in subsequent polymerization. Solution A2 is obtained. The solvent is a mixture of N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 20:80. S7 polymerization reaction: The diamine monomer and the dianhydride monomer were added to the solution A2 in a molar ratio of 1:1, the solvent was added to adjust the solid content of the system to 30wt%, the temperature was raised to 45 ° C, and stirring was continued for 6h to form a polyamic acid prepolymer solution; S8. Chemical imidization: Acetic anhydride and triethylamine were added to the polyimide solution and stirred at 37°C for 24 h. After the reaction, the solution was light yellow and transparent with no obvious precipitation to obtain reaction solution A4, wherein the amount of acetic anhydride was 1.2 times the molar number of amic acid groups, and the molar ratio of triethylamine to acetic anhydride was 1:1.2; S9. Purification and drying: The reaction solution A4 was poured into 3 volumes of ethanol to precipitate a flocculent precipitate. After standing for 1 hour, the precipitate was filtered and washed with ethanol three times to remove unreacted monomers. The precipitate was vacuum dried at 80 ° C for 24 hours and then vacuum dried at 200 ° C for 4 hours to obtain a polyimide precursor powder. S10. Raw material preparation: Prepare an inorganic filler, a modifier, and a dispersion medium, wherein the inorganic filler is a mixture of nano-silica and boron nitride nanosheets in a mass ratio of 8:2, wherein the nano-silica has a particle size of 20-50 nm, wherein the boron nitride nanosheets have a thickness of 5-10 nm, and a lateral size of 1-2 μm, wherein the modifier is any one of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560), and the amount of the modifier is 11% of the total mass of the filler, wherein the dispersion medium is DMAc, and the mass ratio of the dispersion medium to the inorganic filler is 100:27; S11 filler dispersion: 100g of dispersion medium was added to a 500mL three-necked flask, an inorganic filler was added, mechanical stirring was started at a speed of 250rpm, and ultrasonic dispersion was performed at a power of 300W for 40 minutes to form a uniform suspension to avoid agglomeration; S12. Surface modification reaction: A modifier was added to the suspension, and the temperature was raised to 75°C under nitrogen protection and stirred for 3 h. During the reaction, the silane coupling agent was hydrolyzed to form silanol groups, which condensed with the hydroxyl groups on the surface of the inorganic filler to graft active groups onto the surface of the inorganic filler, thereby obtaining reaction solution B3. S13 post-treatment: After the reaction is completed, the reaction solution B3 is cooled to room temperature and directly used as an inorganic filler dispersion to avoid secondary agglomeration caused by drying; S14. Composite dispersion: Under nitrogen protection, the prepared inorganic filler dispersion was dropwise added to the polyimide precursor powder and mechanically stirred at 300 rpm and 30°C for 4 h. The mass ratio of the inorganic filler dispersion to the polyimide precursor was 3:10. S15. A planetary ball mill was used to disperse the mixture at 300 rpm for 30 min to further break up agglomerates and ensure that the filler was evenly dispersed in the matrix, resulting in a final solid content of 40 wt % and a viscosity of 6500 mPa·s to obtain a composite resin solution. S16. Gradient curing: The composite resin solution is applied to the surface of the copper conductor by a dip coating method, and the wet film thickness is controlled to be 110 μm. Then, the first stage curing, the second stage curing and the third stage curing are carried out, and finally the material is cooled to room temperature to obtain an insulating film with a thickness of 70 μm, i.e., a high-adhesion polyimide resin material. The curing temperature of the first stage curing is 140°C, and the curing time is 2 hours. The curing temperature of the second stage curing is 290°C, and the curing time is 3 hours. The curing temperature of the third stage curing is 330°C, and the curing time is 2 hours.

[0039] Example 3: A method for preparing a high-adhesion polyimide resin material, comprising the following steps: S1. Prepare raw materials: Prepare lipoic acid (purity ≥99%), ethylenediamine (purity ≥99%), carbonyldiimidazole, anhydrous chloroform, saturated brine, aqueous NaOH solution, and anhydrous sodium sulfate. The CAS number of lipoic acid is 1077-28-7. S2. Lipoic acid activation: In a 250-mL three-necked flask under argon, add 2.2 g of lipoic acid and 55 mL of anhydrous chloroform. Add 1.8 g of CDI and activate at room temperature for 30 min to form a reactive imidazoline intermediate and enhance the reactivity of the carboxyl group. Argon is used to prevent oxidation. An equimolar ratio of CDI to lipoic acid ensures mono-activation, yielding reaction solution A102. S3. Condensation reaction: Place 55 mL of reaction solution A102 in a 4°C ice-water bath and slowly add dropwise 22 mL of anhydrous chloroform solution of ethylenediamine (in a 1:2 mass ratio of ethylenediamine to lipoic acid) at room temperature until dissolved. After the addition is complete, remove from the water bath and stir at room temperature for 16 h to ensure sufficient formation of the amide bond. Perform thin-layer chromatography (TLC) using a 4:1 volume ratio of chloroform and methanol as the developing solvent to separate the lipoic acid from the product. S4. The reaction mixture was washed three times with saturated brine (50 mL each time) and twice with 5% aqueous NaOH (50 mL each time) to remove unreacted CDI and ethylenediamine. The organic phase was dried over anhydrous sodium sulfate for 2 h, filtered, and evaporated to dryness under reduced pressure to obtain a pale yellow oily crude product. The crude product was then purified by column chromatography using a gradient elution ratio of chloroform to methanol (10:1 → 5:1). The target fractions were collected and dried under vacuum to obtain a white solid product (lipoic acid-ethylenediamine monosubstituted product, yield 75-80%), thus obtaining a lipoic acid-modified diamine monomer. S5. Raw material preparation: preparing diaminodiphenyl ether (ODA), phenylenediamine (PPD), and lipoic acid-modified diamine monomers as diamine monomers; preparing biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and triazine ring dianhydride as dianhydride monomers; mixing N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 25:85 to obtain a solvent; preparing a dehydrating agent and a catalyst as auxiliary agents, wherein the dehydrating agent is acetic anhydride and the catalyst is triethylamine; wherein the molar ratio of diaminodiphenyl ether, phenylenediamine, and lipoic acid-modified diamine monomer in the diamine monomer is 80:20:20, and wherein the molar ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and triazine ring dianhydride in the dianhydride monomer is 70:30:20; S6. Monomer Dissolution: In a nitrogen-protected three-necked flask, add diamine monomer and solvent. Stir mechanically at 200 rpm and 30°C for 40 min until the diamine monomer is completely dissolved to ensure uniformity in subsequent polymerization. Solution A2 is obtained, wherein the solvent is a mixture of N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc) in a mass ratio of 25:85. S7 polymerization reaction: The diamine monomer and the dianhydride monomer were added to the solution A2 in a molar ratio of 1:1.02, the solvent was added to adjust the solid content of the system to 35wt%, the temperature was raised to 55 ° C, and stirring was continued for 7h to form a polyamic acid prepolymer solution; S8. Chemical imidization: Acetic anhydride and triethylamine were added to the polyimide solution and stirred at 40 ° C for 24 h. After the reaction, the solution was light yellow and transparent with no obvious precipitation to obtain a reaction solution A4, wherein the amount of acetic anhydride was 1.2 times the molar number of amic acid groups, and the molar ratio of triethylamine to acetic anhydride was 1:1.2; S9. Purification and drying: The reaction solution A4 was poured into 3 volumes of ethanol to precipitate a flocculent precipitate. After standing for 1 hour, the precipitate was filtered and washed with ethanol three times to remove unreacted monomers. The precipitate was vacuum dried at 80 ° C for 24 hours and then vacuum dried at 200 ° C for 4 hours to obtain a polyimide precursor powder. S10. Raw material preparation: Prepare an inorganic filler, a modifier, and a dispersion medium, wherein the inorganic filler is a mixture of nano-silica and boron nitride nanosheets in a mass ratio of 9:3, wherein the nano-silica has a particle size of 20-50 nm, wherein the boron nitride nanosheets have a thickness of 5-10 nm, and a lateral size of 1-2 μm, wherein the modifier is any one of γ-aminopropyltriethoxysilane (KH550) and γ-glycidoxypropyltrimethoxysilane (KH560), and the amount of the modifier is 15% of the total mass of the filler, wherein the dispersion medium is DMAc, and the mass ratio of the dispersion medium to the inorganic filler is 100:35; S11 filler dispersion: 100g of dispersion medium was added to a 500mL three-necked flask, an inorganic filler was added, mechanical stirring was started at a speed of 300rpm, and ultrasonic dispersion was performed at a power of 300W for 40 minutes to form a uniform suspension to avoid agglomeration; S12. Surface modification reaction: A modifier was added to the suspension, and the temperature was raised to 85°C under nitrogen protection and stirred for 3.5 h. During the reaction, the silane coupling agent was hydrolyzed to form silanol groups, which condensed with the hydroxyl groups on the surface of the inorganic filler to graft active groups onto the surface of the inorganic filler, thereby obtaining reaction solution B3. S13 post-treatment: After the reaction is completed, the reaction solution B3 is cooled to room temperature and directly used as an inorganic filler dispersion to avoid secondary agglomeration caused by drying; S14. Composite dispersion: Under nitrogen protection, the prepared inorganic filler dispersion was dropwise added to the polyimide precursor powder and mechanically stirred at 300 rpm and 30°C for 4 h. The mass ratio of the inorganic filler dispersion to the polyimide precursor was 3:10. S15. A planetary ball mill was used to disperse the mixture at 300 rpm for 30 min to further break up agglomerates and ensure that the filler was evenly dispersed in the matrix, resulting in a final solid content of 40 wt % and a viscosity of 8000 mPa·s to obtain a composite resin solution. S16. Gradient curing: The composite resin solution is applied to the surface of the copper conductor by a dip coating method, and the wet film thickness is controlled to be 110 μm. Then, the first stage curing, the second stage curing and the third stage curing are carried out, and finally the material is cooled to room temperature to obtain an insulating film with a thickness of 70 μm, i.e., a high-adhesion polyimide resin material. The curing temperature of the first stage curing is 150°C, and the curing time is 2 hours. The curing temperature of the second stage curing is 300°C, and the curing time is 3 hours. The curing temperature of the third stage curing is 340°C, and the curing time is 2 hours.

[0040] Comparative Example 1: No lipoic acid-modified diamine monomer was added (lack of self-repair and dynamic bond-enhanced adhesion mechanism): Preparation method: Compared with Example 2, only the diamine monomer composition was adjusted to "diaminodiphenyl ether (ODA): phenylenediamine (PPD) = 85:15" (the lipoic acid-modified diamine monomer was deleted), and the remaining steps (including the dianhydride monomer ratio, filler modification, curing process, etc.) were consistent with Example 2.

[0041] Comparative Example 2: No triazine cyclic dianhydride added (lack of UV blocking and hydrogen bond enhancement mechanism): Preparation method: Compared with Example 2, only the dianhydride monomer composition was adjusted to "biphenyltetracarboxylic dianhydride (BPDA): pyromellitic dianhydride (PMDA) = 75:25" (triazine ring dianhydride was deleted), and the remaining steps were consistent with Example 2.

[0042] Comparative Example 3: Using unmodified inorganic filler (lack of interfacial chemical bonding): Preparation method: Compared with Example 2, only the "surface-modified inorganic filler" is replaced by the "nano-silica and boron nitride composite system not treated with a silane coupling agent" (mass ratio 8:2), and the remaining steps are consistent with Example 2.

[0043] Comparative Example 4: Single temperature curing (lack of gradient curing stress control): Preparation method: Compared with Example 2, only the curing process was adjusted to "290°C constant temperature curing for 7h" (instead of gradient curing), and the remaining steps were consistent with Example 2.

[0044] Comparative Example 5: Using a single inorganic filler (lacking multi-scale composite reinforcement): Preparation method: Compared with Example 2, only the inorganic filler is replaced by "single nano-silica" (the amount used is the same as the total mass of the composite filler in Example 2), and the remaining steps are consistent with Example 2.

[0045] Performance testing: Adhesion test: Refer to ASTM D3359 standard, use the cross-hatch method with a tensile tester to test the peel force between the insulation film and the copper conductor, unit N / cm (test environment: 23°C, 50% relative humidity).

[0046] Self-healing performance test: A scratch with a depth of 5 μm was made on the surface of the film with a blade. After heating at 60°C for 12 hours, the scratch repair rate was observed under an optical microscope (repaired area / initial scratch area × 100%).

[0047] UV barrier test: A UV-visible spectrophotometer (model UV-2600) was used to test the UV absorbance in the 300-400nm band (test sample: film thickness 70μm).

[0048] Moisture and heat resistance test: Place the sample in a humidity and heat chamber at 155°C and 95% RH, regularly observe whether the film is cracking or falling off, and record the longest time without obvious defects (unit: h).

[0049] Surge resistance test: Use Changzhou Willyue Electric's sine wave generator to conduct Vt test at 1500Vp, 100kHz, and 155℃, and record the time (unit: h) during which the insulation is not damaged.

[0050] Thermal conductivity test: The thermal conductivity (unit: W / m·K) at 25°C was measured using the laser flash method (Model LFA467).

[0051] The results are shown in Tables 1 and 3 below: Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-5 Table 2 Performance test results of Examples 1-3 and Comparative Examples 1-5 Table 3 Performance test results of Examples 1-3 and Comparative Examples 1-5 Data Analysis: (1) Adhesion and interface bonding mechanism The adhesion of Examples 1-3 (6.2-7.1 N / cm) was significantly higher than that of Comparative Example 1 (4.2 N / cm) and Comparative Example 3 (3.8 N / cm). The key reason is the introduction of lipoic acid-modified diamine monomers. During the curing process, the disulfide bonds in the lipoic acid molecules chemically adsorb to the copper conductor surface. Simultaneously, its carboxylic acid groups undergo a polycondensation reaction with the matrix resin, forming a "molecular bridge" structure that significantly enhances interfacial bonding. Comparative Example 1, which omitted this monomer and relied solely on physical adsorption, exhibited a 47.6% decrease in adhesion. Comparative Example 3 used unmodified filler, resulting in significant voids between the filler and the matrix, increasing interfacial thermal resistance and further weakening adhesion.

[0052] 2. Dynamic chemical basis of self-healing properties The self-repair rates of Examples 1-3 (88-92%) were much higher than those of Comparative Example 1 (<10%). This is due to the introduction of dynamic disulfide bonds into the backbone of the lipoic acid-modified diamine monomer. When the material is scratched, the broken disulfide radicals recombine upon heating at 60°C or react with adjacent thiol groups, leading to molecular chain reconstruction. Comparative Example 1 lacks a dynamic crosslinking network and is unable to self-repair after breakage. Notably, Comparative Example 2 (without the addition of triazine cyclic dianhydride) still achieved a self-repair rate of 91%, indicating that triazine cyclic dianhydride primarily affects UV absorption and has no direct effect on the self-repair mechanism.

[0053] (III) Synergistic effect of UV blocking performance The UV absorbance of Examples 1-3 (89-91%) is similar to that of Comparative Examples 1, 3, 4, and 5 (around 90%), but significantly higher than that of Comparative Example 2 (<30%). This indicates that triazine cyclic dianhydride is the core component for UV absorption, and the triazine ring structure in its molecule absorbs UV light in the 300-400nm band through π-π conjugation. Comparative Example 2 omitted this component, resulting in a loss of UV absorption capacity. In contrast, in the Examples and other Comparative Examples, the benzene ring structure of the lipoic acid-modified diamine monomer forms a synergistic absorption effect with the triazine ring, further enhancing UV blocking performance.

[0054] (IV) Moisture and heat resistance and chemical stability The wet heat resistance time (2800-3000 hours) of Examples 1-3 increased by 86.7%-100% compared to Comparative Example 1 (1500 hours) and Comparative Example 3 (1800 hours). This is attributed to the interface optimization achieved by the silane coupling agent-modified filler. The alkoxy groups of the silane coupling agent hydrolyze and form Si-O-Si bonds with the hydroxyl groups on the surfaces of the nano-silica and boron nitride. Simultaneously, the organic groups react with the resin matrix to form a dense interfacial transition layer, effectively preventing water penetration. The unmodified filler in Comparative Example 3 has a large number of hydrophilic hydroxyl groups on its surface, which allows water molecules to easily enter the material through capillary action, leading to resin hydrolysis and filler shedding.

[0055] (V) Dynamic-rigidity balance of surge resistance The surge resistance of Examples 1-3 (>280 hours) significantly outperforms that of Comparative Example 3 (>180 hours) and Comparative Example 5 (>250 hours). This is primarily due to the synergistic effect of the dynamic disulfide bonds and the rigid triazine ring structure. The dynamic disulfide bonds undergo reversible breakage and recombination under the localized high temperatures generated by the surge, dissipating some of the energy. The rigid triazine ring structure, on the other hand, limits excessive molecular chain slippage, maintaining the overall structural stability of the material. Comparative Example 3 lacks a dynamic network, preventing effective energy dissipation and leading to rapid breakdown of the insulation layer.

[0056] (VI) Filler design logic for thermal conductivity Example 2 achieved the highest thermal conductivity (0.65 W / m・K) due to its use of an 8:2 nano-silica / boron nitride composite system, and the silane coupling agent modification resulted in uniform dispersion of the boron nitride nanosheets, forming a continuous thermal conductivity path. Comparative Example 5, using only nano-silica, failed to establish an efficient thermal network, resulting in a 56.9% decrease in thermal conductivity (0.28 W / m・K) compared to Example 2. Comparative Example 3, using unmodified filler, exhibited severe boron nitride agglomeration, resulting in a thermal conductivity (0.32 W / m・K) still lower than that of Example 1, demonstrating the crucial role of interfacial modification in thermal conductivity.

[0057] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0058] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-adhesion polyimide resin material, characterized in that: It is prepared from polyimide precursor and surface-modified inorganic filler; The polyimide precursor is prepared from a diamine monomer and a dianhydride monomer; The surface-modified inorganic filler is a composite system of nano-silicon dioxide and boron nitride nano-sheets treated with a silane coupling agent.

2. The high-adhesion polyimide resin material according to claim 1, characterized in that: The preparation process of the polyimide precursor is as follows: Step A1. Raw material preparation: preparing diamine monomer, dianhydride monomer, solvent and additive; Step A2 monomer dissolution: In a nitrogen-protected three-necked flask, add the diamine monomer, pour the solvent, and mechanically stir at 25-30 ° C at 200 rpm for 30-40min until the diamine monomer is completely dissolved to obtain a solution A2; Step A3 polymerization reaction: The diamine monomer and the dianhydride monomer are added to the solution A2, the solvent is added to adjust the solid content of the system to 25-35wt%, the temperature is raised to 35-55 ° C, and stirring is continued for 5-7h to form a polyamic acid prepolymer solution; Step A4 chemical imidization: acetic anhydride and triethylamine were added to the polyamic acid prepolymer solution and stirred at 35-40 ° C for 24 h. After the reaction, the solution was light yellow and transparent to obtain a reaction solution A4; Step A5. Purification and drying: Pour the reaction solution A4 into ethanol to precipitate a flocculent precipitate. After standing for 1 hour, filter it and wash the precipitate three times with ethanol to remove unreacted monomers. Vacuum dry it at 80°C for 24 hours and then at 200°C for 4 hours to obtain a polyimide precursor powder.

3. The high-adhesion polyimide resin material according to claim 2, characterized in that: In step A1, the diamine monomer is diaminodiphenyl ether, phenylenediamine, or lipoic acid-modified diamine monomer; The dianhydride monomer in step A1 is biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, or triazine ring dianhydride.

4. The high-adhesion polyimide resin material according to claim 2, characterized in that: The molar ratio of diaminodiphenyl ether, phenylenediamine and lipoic acid-modified diamine monomer in the diamine monomer in step A1 is 60-80:10-20:10-20; The molar ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and triazine ring dianhydride in the dianhydride monomer in step A1 is 50-70:20-30:10-20.

5. The high-adhesion polyimide resin material according to claim 2, characterized in that: The solvent in step A2 is a mixture of N-methylpyrrolidone and dimethylacetamide in a mass ratio of 15-25:75-85; The auxiliary agent in step A1 includes a dehydrating agent and a catalyst, the dehydrating agent is acetic anhydride, and the catalyst is triethylamine.

6. The high-adhesion polyimide resin material according to claim 2, characterized in that: The molar ratio of the diamine monomer to the dianhydride monomer in step A3 is 1:0.98-1.02; The amount of acetic anhydride used in step A4 is 1.2 times the molar number of the amic acid group, wherein the molar ratio of triethylamine to acetic anhydride is 1:1.2; The volume ratio of the reaction solution A4 and ethanol in step A5 is 1:

3.

7. The high-adhesion polyimide resin material according to claim 1, characterized in that: The preparation process of the surface modified inorganic filler is as follows: Step B1. Raw material preparation: preparing inorganic filler, modifier and dispersion medium; Step B2 filler dispersion: Add a dispersion medium to a three-necked flask, add an inorganic filler, start mechanical stirring at a speed of 200-300rpm, and use ultrasonic dispersion at a power of 300W for 40 minutes to form a uniform suspension to avoid agglomeration; Step B3. Surface modification reaction: Add a modifier to the suspension, raise the temperature to 65-85°C under nitrogen protection, and stir for 2.5-3.5 hours. During the reaction, the silane coupling agent hydrolyzes to form silanol groups, which react with the hydroxyl groups on the surface of the inorganic filler to graft active groups onto the surface of the inorganic filler to obtain reaction solution B3; Step B4. Post-treatment: After the reaction is completed, the reaction solution B3 is cooled to room temperature and directly used as an inorganic filler dispersion.

8. The high-adhesion polyimide resin material according to claim 7, characterized in that: The inorganic filler in step B1 is a mixture of nano-silicon dioxide and boron nitride nanosheets in a mass ratio of 7-9:1-3, wherein the particle size of the nano-silicon dioxide is 20-50 nm, and the thickness of the boron nitride nanosheets is 5-10 nm and the lateral size is 1-2 μm; The modifiers in step B1 are γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane, and the amount of the modifiers is 8%-15% of the total mass of the filler; The dispersion medium in step B1 is dimethylacetamide, and the mass ratio of the dispersion medium to the inorganic filler is 100:20-35.

9. A method for preparing a high-adhesion polyimide resin material, characterized in that: The following steps are involved: Step S1. Composite dispersion: Under nitrogen protection, the prepared inorganic filler dispersion was dropped into the polyimide precursor powder, and mechanically stirred at 30°C at a speed of 300 rpm for 4 h; Step S2. A planetary ball mill was used to disperse the mixture at a speed of 300 rpm for 30 min, so that the final solid content was 40 wt % and the viscosity was 5000-8000 mPa·s to obtain a composite resin solution; Step S3. Gradient curing: The composite resin solution is applied to the surface of the copper conductor by dip coating, with the wet film thickness controlled at 110 μm. The first, second, and third stage curing are then performed, and the mixture is finally cooled to room temperature to obtain an insulating film with a thickness of 70 μm, i.e., a high-adhesion polyimide resin material.

10. The method for preparing a high-adhesion polyimide resin material according to claim 9, wherein: The mass ratio of the inorganic filler dispersion to the polyimide precursor in step S1 is 3:10; The curing temperature of the first stage curing in step S3 is 130-150°C and the curing time is 2 hours; The curing temperature of the second stage curing in step S3 is 280-300°C and the curing time is 3 hours; The curing temperature of the third stage curing in step S3 is 320-340° C., and the curing time is 2 hours.

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