Polyimide with high adhesion and preparation method thereof

Abstract

The invention discloses polyimide with high adhesion and a preparation method thereof, the polyimide is prepared by polymerizing a diamine monomer and a dianhydride monomer, and the diamine monomer comprises furyl diamine. The high-adhesion polyimide is simple in preparation process, the monomers are easy to obtain, and the high-adhesion polyimide has excellent adhesion, outstanding heat resistance and good mechanical properties and can be applied to the fields of aerospace, ship industry, electronic packaging, high-temperature composite materials and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a polyimide with high adhesion and its preparation method. Background Technology

[0002] Polyimide possesses excellent mechanical properties, high heat resistance, and high insulation, making it a core material in high-end fields such as aerospace, defense, and electronics. However, the traditional polyimide monomer structure is mainly based on non-polar benzene ring structures, resulting in poor adhesion, particularly insufficient interfacial bonding with metals (such as copper foil), which makes it difficult to meet the application requirements of aerospace, shipbuilding, electronic packaging, and high-temperature composite materials. Furthermore, traditional polyimide monomers are mostly derived from non-renewable petroleum resources. With the advancement of carbon reduction and the increasing scarcity of fossil resources, the development of high-performance polymers based on renewable biomass resources has become a global frontier.

[0003] One of the most important applications of polyimide is as a substrate or insulating layer for flexible printed circuit boards and high-performance rigid copper-clad laminates. Its basic structure is a sandwich structure of "metal (typically copper foil) - polyimide adhesive - polyimide film" or similar. The main reasons why copper foil is difficult to bond are as follows:

[0004] 1. Physical incompatibility: Copper is a metal with high surface energy, rigidity, and a dense structure; polyimide is an organic polymer with lower surface energy and relative softness. The two are naturally not easily bonded together.

[0005] 2. Chemical inertness: Conventional benzene-based polyimides are chemically stable, non-polar overall, and have few surface-active functional groups. Their ability to form strong chemical bonds (covalent bonds and coordinate bonds) with copper surfaces is limited, and they mainly rely on relatively weak van der Waals forces.

[0006] 3. Significant difference in thermal expansion coefficients: Copper has a thermal expansion coefficient of approximately 17 ppm / ℃, while polyimide typically ranges from 30-50 ppm / ℃. The difference in their expansion and contraction rates during temperature changes generates significant shear stress at the interface, making them highly susceptible to delamination.

[0007] 4. Instability of copper surface: Copper is easily oxidized, and the strength of the oxide layer is much lower than that of pure copper. The interface often breaks down at the weaker oxide layer.

[0008] Furanyl compounds derived from lignocellulosic biomass are an important class of bio-based platform molecules. They contain unique rigid five-membered aromatic heterocycles, exhibiting rigidity similar to phenyl compounds, which provides a foundation for constructing polymer backbones with high thermal stability, high modulus, and high strength. Furthermore, the polar oxygen atoms in the furan ring can significantly enhance the polarity of the molecular chain, improving interfacial adhesion to substrates such as metals and ceramics through hydrogen bonding or coordination bonds, thus overcoming the adhesion bottleneck of traditional petroleum-based polyimides caused by the non-polar benzene ring. Summary of the Invention

[0009] Based on the above analysis, and addressing the shortcomings of existing polyimides in terms of adhesion and environmental friendliness, this invention provides a polyimide with high adhesion and its preparation method, thereby solving the problems of poor sustainability and insufficient adhesion performance in practical applications of existing polyimide products. The high-adhesion polyimide of this invention has a simple preparation process, readily available monomers, and exhibits excellent adhesion, flexibility, and good mechanical properties, making it suitable for applications such as flexible copper-clad laminates, chip packaging, and enameled wires.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] The present invention relates to a highly adhesive polyimide, which is produced by polymerizing a diamine monomer and a dianhydride monomer, wherein the diamine monomer includes furanyl diamine monomer and other diamine monomers.

[0012] The furanyldiamine monomer is selected from one or more of the compounds shown in the following structures:

[0013]

[0014] The other diamine monomers are selected from one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 1,4-bis(4-aminophenoxy)benzene.

[0015] The furanyl diamine monomer accounts for 1 mol% to 100 mol% of the total diamine monomer, preferably 5 mol% to 50 mol%.

[0016] The dianhydride monomer is selected from one or more compounds with the following structures:

[0017]

[0018] This invention discloses a method for preparing a highly adhesive polyimide. In an inert atmosphere, a diamine monomer is dissolved in a solvent, and a dianhydride monomer is gradually added at low temperature. The mixture undergoes polymerization and imidization reactions to obtain the highly adhesive polyimide. Specifically, the method includes the following steps:

[0019] Step 1: In an inert atmosphere, dissolve the diamine monomer in an organic solvent, add the dianhydride monomer in batches at -40℃ to 20℃, and stir the reaction for 8-12 hours. After the reaction is complete, a polyamic acid solution is obtained.

[0020] Step 2: The polyamic acid solution obtained in Step 1 is coated onto the substrate, and an imidization reaction is carried out by gradient heating to 350°C to obtain a highly adhesive polyimide.

[0021] The molar ratio of the diamine monomer to the dianhydride monomer is 1:0.95~1.05.

[0022] The organic solvent is any one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP), preferably N,N-dimethylacetamide (DMAc). More preferably, the water content of the solvent is controlled below 100 ppm.

[0023] The inert atmosphere is a nitrogen atmosphere.

[0024] Furthermore, while adding the dianhydride monomer in batches, the temperature of the reaction system is controlled between -40°C and 10°C, preferably between -20°C and 5°C.

[0025] In step 1, during the stirring reaction, the system temperature is controlled at -20~40℃, preferably -10~30℃.

[0026] The solid content of the polyamic acid solution obtained in step 1 is 10-25%, preferably 18-22%.

[0027] The gradient temperature program is set as follows: sequentially increase the temperature to 100℃ and hold for 0.5~2 h, 200℃ and hold for 0.5~2 h, 300℃ and hold for 0.5~2 h, and 350℃ and hold for 0.5~2 h.

[0028] This invention relates to the application of highly adhesive polyimide in the preparation of insulating adhesives for metal substrates.

[0029] The metal substrate includes copper.

[0030] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0031] This invention uses bio-based furan monomers as raw materials. By controlling the type and content of furanyl diamine monomers, a novel bio-based high polyimide is prepared, reducing dependence on fossil resources and improving its adhesion to metals (such as copper foil). This avoids the introduction of complex and expensive special monomers and overcomes the adhesion bottleneck of traditional phenyl polyimide, demonstrating important application value in fields such as flexible copper clad laminates, chip packaging, and enameled wires. Detailed Implementation

[0032] Except for furanyldiamine, all raw materials used in the examples were commercially available.

[0033] Furanyldiamine was prepared using the following method:

[0034] A1: Add furfurylamine (11.67 g, 120 mmol) to a three-necked flask. Slowly add 70 mL of hydrochloric acid aqueous solution in an ice-water bath. After the addition is complete, raise the reaction solution to room temperature, then add 4.90 mL of 37% formaldehyde solution to the reaction system. After the addition is complete, react at room temperature for 5 h. Adjust the pH of the reaction solution to > 10 with sodium hydroxide aqueous solution. The product is obtained by extraction, rotary evaporation, and vacuum distillation. A6 and A7 can be prepared by replacing formaldehyde with acetone and acetaldehyde, respectively, using the same method as A1.

[0035] A2: At 0 °C, di-tert-butyl dicarbonate (44.95 g, 1 eq) was dissolved in 110 mL of dichloromethane, and then furfurylamine (19.53 g, 200 mmol) was slowly added dropwise. After reacting overnight at room temperature, the reaction solution was washed successively with saturated sodium carbonate solution, saturated ammonium chloride solution and saturated brine. The organic phase was dried and rotary evaporated to obtain intermediate 1 of A2.

[0036] Anhydrous tetrahydrofuran (400 mL), N,N,N',N'-tetramethylethylenediamine (35 mL, 240 mmol), and A2 intermediate 1 (19.74 g, 100 mmol) were added to a three-necked flask under a nitrogen atmosphere. After adding n-butyllithium (1.6 M, 135 mL, 210 mmol) to the solution at -78 °C, the reaction mixture was allowed to react for 6 h. The solution was then brought to room temperature, and CuCl2 (20.45 g, 150 mmol) and CuCl (12.87 g, 130 mmol) were added. The reaction mixture was then refluxed overnight. Ethyl acetate was added to the reaction mixture, and the mixture was filtered. The organic phase was washed with saturated brine, and rotary evaporated to obtain A2 intermediate 2.

[0037] Intermediate 2 of A2 (19.74 g, 100 mmol) was added to a flask, followed by 35 mL of 1,4-dioxane hydrochloride solution. After stirring at room temperature for 12 h, the reaction mixture was diluted with diethyl ether. The mixture was filtered, and the resulting filter cake was washed with diethyl ether to obtain a solid. The solid was dissolved in water, and the solution was adjusted to pH > 10 with sodium hydroxide, followed by extraction with dichloromethane. The resulting organic phase was dried and rotary evaporated to obtain A2.

[0038] A3: Furan dicarboxaldehyde (1.24 g, 10 mmol), 0.6 g Raney Ni, and 150 mL tetrahydrofuran were added to a high-pressure reactor. After sealing, ammonia gas was introduced to 0.5 MPa, followed by hydrogen gas to 1.0 MPa, and the reaction was carried out at 140 °C for 5 hours. After the reaction was completed, the reaction solution was filtered, concentrated, and purified by passing through a short sintered glass column to obtain product A3.

[0039] By replacing furan dicarboxaldehyde with bis-(5-formylfurfuryl) ether, A4 can be prepared using the same method as A3.

[0040] A5: Combine 5-bromo-2-furfural (5.24 g, 30 mmol), sodium sulfide hydrate (4.04 g, 16.8 mmol), and 100 mL of deionized water at 95°C. o The reaction was carried out at C for 2 h. After the reaction was completed, the product A5 intermediate was obtained by filtration and drying.

[0041] Tert-butyl carbamate (14.06 g, 120 mmol) and A5 intermediate (4.44 g, 20 mmol) were dissolved in a mixed solvent of dichloromethane / acetonitrile. Triethylsilane (13.95 g, 120 mmol) and trifluoroacetic acid (9.12 g, 80 mmol) were added dropwise, and the reaction was carried out at room temperature for 18 h. The reaction solution was quenched with sodium bicarbonate aqueous solution and extracted with dichloromethane. The organic phase was dried and concentrated, and the resulting solid was transferred to a flask. 35 mL of 1,4-dioxane hydrochloride solution was added, and the mixture was stirred at room temperature for 12 h. After the reaction was complete, the solid was filtered off. The solid was dissolved in water, and the aqueous phase was adjusted to pH 10 with potassium hydroxide. Insoluble matter was removed by filtration. The filtrate was extracted with dichloromethane, and the organic phase was evaporated to dryness to obtain A5.

[0042] The technical solution of the present invention will be further analyzed and explained through specific embodiments below.

[0043] Example 1:

[0044] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), Al (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 2 h, 200 °C for 2 h, 300 °C for 2 h, and 350 °C for 0.5 h to obtain polyimide.

[0045] Example 2:

[0046] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), A2 (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 0.5 h, 200 °C for 0.5 h, 300 °C for 2 h, and 350 °C for 2 h to obtain polyimide.

[0047] Example 3:

[0048] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), A3 (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 1 h to obtain polyimide.

[0049] Example 4:

[0050] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), A4 (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1.5 h, 200 °C for 1.5 h, 300 °C for 1 h, and 350 °C for 1 h to obtain polyimide.

[0051] Example 5:

[0052] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), A5 (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0053] Example 6:

[0054] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), A6 (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1.5 h, and 350 °C for 0.5 h to obtain polyimide.

[0055] Example 7:

[0056] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (7 mmol), A7 (3 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B1 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0057] Example 8:

[0058] Under a nitrogen atmosphere, 4,4'-diaminodiphenylmethane (9 mmol), Al (1 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B2 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0059] Example 9:

[0060] Under a nitrogen atmosphere, p-phenylenediamine (9 mmol), A1 (1 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B3 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0061] Example 10:

[0062] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl sulfone (9 mmol), Al (1 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B4 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0063] Example 11:

[0064] At room temperature, 4,4'-diaminodiphenyl ether (9 mmol), Al (1 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B5 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0065] Example 12:

[0066] Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (3 mmol), Al (7 mmol), and anhydrous DMF (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B6 (10 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0067] Example 13:

[0068] Under a nitrogen atmosphere, 4,4'-diaminodiphenylmethane (6 mmol), Al (4 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B7 (10.05 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0069] Example 14:

[0070] Under a nitrogen atmosphere, 4,4'-diaminodiphenylmethane (8 mmol), Al (2 mmol), and anhydrous DMAc (20 mL) were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, dianhydride B8 (9.95 mmol) was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1.5 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0071] Comparative Example 1:

[0072] Under a nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether and 20 mL of anhydrous DMAc were added to a 50 mL three-necked flask, and the mixture was stirred at room temperature until the diamine monomer was completely dissolved. After cooling the reaction system to 0 °C, 10 mmol of dianhydride B5 was added in portions. After reacting overnight, a polyamic acid solution was obtained. The polyamic acid solution was subjected to imidization reactions at 100 °C for 1 h, 200 °C for 1 h, 300 °C for 1 h, and 350 °C for 0.5 h to obtain polyimide.

[0073] The obtained bio-based polyimide was tested, and the test results are shown in the table below:

[0074]

[0075] The peel strength test involves uniformly coating a polyamic acid solution onto a copper foil and sequentially imidizing it at 100℃ for 1 hour, 200℃ for 1 hour, 300℃ for 1 hour, and 350℃ for 0.5 hours to obtain a "copper foil-polyimide" test sample. The sample is then tested according to the IPC-TM-650 test method.

[0076] This invention effectively enhances the interfacial interaction between polyimide and copper foil by introducing a highly polar furan ring structure, thereby significantly improving its peel strength compared to traditional phenyl polyimide. This material possesses both excellent high-temperature stability and outstanding adhesive properties, making it an ideal matrix material for preparing high-performance high-temperature adhesives, with broad application prospects in aerospace, shipbuilding, electronic packaging, and high-temperature composite materials.

Claims

1. A method for preparing a polyimide with high adhesion, characterized in that: The highly adhesive polyimide is produced by polymerizing a diamine monomer and a dianhydride monomer, wherein the diamine monomer includes furanyl diamine monomer and other diamine monomers; The furanyldiamine monomer is selected from one or more of the compounds shown in the following structures: ； The other diamine monomers are selected from one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 1,4-bis(4-aminophenoxy)benzene.

2. The preparation method according to claim 1, characterized in that: The furanyl diamine monomer accounts for 5 mol% to 50 mol% of the total diamine monomer.

3. The preparation method according to claim 1, characterized in that: The dianhydride monomer is selected from one or more compounds with the following structures: 。 4. The preparation method according to claim 1, 2 or 3, characterized in that... Includes the following steps: Step 1: In an inert atmosphere, dissolve the diamine monomer in an organic solvent, and add the dianhydride monomer in batches at a temperature of -40°C to 20°C. Stir the reaction until the reaction is complete to obtain a polyamic acid solution with a solid content of 10-25%. Step 2: The polyamic acid solution obtained in Step 1 is coated onto the substrate, and an imidization reaction is carried out by gradient heating to 350°C to obtain a highly adhesive polyimide.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the diamine monomer to the dianhydride monomer is 1:0.95~1.

05.

6. The preparation method according to claim 4, characterized in that: The organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

7. The preparation method according to claim 4, characterized in that: The gradient temperature program is set as follows: sequentially increase the temperature to 100℃ and hold for 0.5~2 h, 200℃ and hold for 0.5~2 h, 300℃ and hold for 0.5~2 h, and 350℃ and hold for 0.5~2 h.

8. A polyimide with high adhesion, prepared according to any one of claims 1-7.

9. The use of the polyimide with high adhesion as described in claim 8 in the preparation of insulating adhesives for metal substrates.

10. The application according to claim 9, characterized in that: The metal substrate includes copper.

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