A furan group-containing polyimide coating material, a method for preparing the same, and a coating layer

Abstract

The application discloses a kind of furan group-containing polyimide coating and its preparation method and coating, it belongs to the field of coating, wherein, polyimide coating is powder coating, including following raw materials: polyamide acid, resin and auxiliary agent;Polyamide acid is synthesized by condensation polymerization reaction of diamine monomer and aromatic dianhydride;Diamine monomer includes 2,7-bis (5-aminomethyl furan-2-yl) fluorene.The application can introduce furan ring and flexible segment by adding 2,7-bis (5-aminomethyl furan-2-yl) fluorene monomer as raw material, to reduce the softening temperature and curing start temperature of polyimide prepolymer, facilitate low-temperature forming processing, and significantly reduce the regularity of polymeric molecule, so that coating spraying adaptability is high, powder rate is high, adhesion is strong, matte is uniform and delicate, and is resistant to heat and humidity.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a furan-based polyimide coating, its preparation method, and the coating itself. Background Technology

[0002] Polyimide coatings are an important component of the modern coatings industry, possessing excellent mechanical properties, low-temperature resistance, dielectric properties, and radiation resistance, and are widely used in aerospace, microelectronics, nanotechnology, liquid crystals, separation membranes, and lasers. However, traditional polyimide coatings mostly use fully aromatic polyimides as raw materials, resulting in weak adhesion to the substrate after curing, and their heat resistance also needs improvement.

[0003] Therefore, developing a polyimide coating that possesses both excellent heat resistance and adhesive properties has become a pressing technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a furan-based polyimide coating, its preparation method, and the coating itself, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A furan-based polyimide coating, which is a powder coating, comprises the following raw materials: polyamic acid, resin and additives; wherein the polyamic acid is synthesized by polycondensation reaction of a diamine monomer and an aromatic dianhydride; wherein the diamine monomer includes 2,7-bis(5-aminomethylfuran-2-yl)fluorene.

[0007] Furthermore, the diamine monomer also includes p-phenylenediamine, wherein 2,7-bis(5-aminomethylfuran-2-yl)fluorene accounts for 10%-30% of the total amount of the diamine monomer.

[0008] Furthermore, the aromatic dianhydride is one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 4,4'-oxobisphthalic anhydride.

[0009] Furthermore, the total amount of polyamic acid and resin accounts for 80%-95% of the total mass of the raw materials, wherein the mass ratio of polyamic acid and resin is (1-3):1.

[0010] Furthermore, the resin is one or more of acrylic resin, epoxy resin, and polyester resin; the additives include one or more of curing agent, leveling agent, and degassing agent; the curing agent is TGIC or HAA; the leveling agent is any one of polysiloxane polyether, silicone compound, and fluorocarbon compound; and the degassing agent is benzoin or diphenoxypropanol.

[0011] Another object of the present invention is to provide a method for preparing the above-mentioned polyimide coating, which includes the following steps:

[0012] Polyamic acid, resin and additives are mixed and then crushed and sieved to obtain polyimide coatings.

[0013] Furthermore, the method for synthesizing the polyamic acid includes the following steps:

[0014] A diamine solution is prepared by dissolving the diamine monomer in an aprotic polar solvent.

[0015] Under a protective atmosphere, aromatic dianhydrides are added in batches to a diamine solution to carry out a polycondensation reaction, yielding a polyamic acid solution.

[0016] The polyamic acid solution was freeze-dried to remove the solvent, resulting in powdered polyamic acid.

[0017] Furthermore, the aprotic polar solvent is one or more of N,N'-dimethylacetamide, N,N'-dimethylformamide, and N-methylpyrrolidone; the reaction temperature of the polycondensation reaction is 10-30℃.

[0018] Another object of the present invention is to provide a coating which is formed by electrostatically spraying the above-mentioned polyimide coating onto a substrate and then curing it.

[0019] Furthermore, the curing is carried out in two stages: the first stage involves heating at 200-250℃ for 10-20 minutes, and the second stage involves heating at 300-350℃ for 20-40 minutes.

[0020] This invention provides a furan-based polyimide coating. By adding 2,7-bis(5-aminomethylfuran-2-yl)fluorene monomer as a raw material, furan rings and flexible segments can be introduced to lower the softening temperature and curing initiation temperature of the polyimide prepolymer, facilitating low-temperature molding and processing. It also significantly reduces the regularity of the polymer molecules, resulting in coatings with high sprayability, high powder application rate, strong adhesion, uniform and delicate matte finish, and resistance to damp heat. The polyimide coating prepared by this invention exhibits excellent heat resistance, showing no peeling or carbonization under prolonged baking at 300°C and above. Compared to traditional fully aromatic polyimide coatings, the furan-based polyimide coating provided by this invention demonstrates strong adhesion after imidization. Using internationally standard test tapes, the percentage of peeling area detected by the cross-cut adhesion test is as low as 1%. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the synthesis and thermal imidization route of polyamic acid provided in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] In one embodiment of the present invention, a furan-based polyimide coating is provided, which can be used as a powder coating. It comprises the following raw materials: polyamic acid, resin, and additives. The polyamic acid, resin, and additives are mixed, then pulverized and sieved (e.g., through a 150-200 mesh) to obtain the polyimide coating. The polyamic acid is synthesized by a polycondensation reaction of a diamine monomer and an aromatic dianhydride; the diamine monomer includes 2,7-bis(5-aminomethylfuran-2-yl)fluorene.

[0024] Preferably, the diamine monomer further includes p-phenylenediamine, wherein 2,7-bis(5-aminomethylfuran-2-yl)fluorene accounts for 10%-30% of the total molar amount of the diamine monomer. The aromatic dianhydride is one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4'-oxobisphthalic anhydride (ODPA). The total amount of polyamic acid and resin accounts for 80%-95% of the total mass of the raw materials, wherein the mass ratio of polyamic acid to resin is (1-3):1.

[0025] It should be noted that the curing temperature of polyimide is higher than that of the resin. The resin mentioned above can be one or more of acrylic resin, epoxy resin, and polyester resin; the additives mentioned above include one or more of curing agent, leveling agent, and degassing agent; wherein, the curing agent can be TGIC or HAA; the leveling agent can be any one of polysiloxane polyether, silicone compound, or fluorocarbon compound; the degassing agent can be benzoin or diphenoxypropanol. Each type of additive can be added according to the actual situation, and the amount added is not limited. For example, the amount of curing agent is 4%-15% of the total mass of the raw materials, the amount of leveling agent is 0.8%-4% of the total mass of the raw materials, and the amount of degassing agent is 0.2%-1% of the total mass of the raw materials.

[0026] like Figure 1 As shown, in another embodiment of the present invention, the method for synthesizing polyamic acid includes the following steps:

[0027] S1. Dissolve the diamine monomer in an aprotic polar solvent to prepare a diamine solution.

[0028] S2. Under a protective atmosphere (such as nitrogen), aromatic dianhydrides are added in batches to the diamine solution to carry out a polycondensation reaction to obtain a polyamic acid solution; the viscosity of the solution is adjusted to 20,000-100,000 mPa·s, with an interval of 1-2 hours between each addition; the reaction temperature of the polycondensation reaction is 10-30℃, the reaction time is 4-8 hours, and the solid content of the polyamic acid solution is controlled at 10%-20%.

[0029] S3. The polyamic acid solution is freeze-dried to remove the solvent, yielding powdered polyamic acid. Polyamic acid can be thermally imidized to obtain polyimide.

[0030] Preferably, one or more of the aprotic polar solvents N,N'-dimethylacetamide, N,N'-dimethylformamide, and N-methylpyrrolidone are used.

[0031] In this embodiment of the invention, the batch feeding method of diamine and anhydride makes the distribution of 2,7-bis(5-aminomethylfuran-2-yl)fluorene monomer on the polyimide chain segment more uniform, and makes the advantages brought by the above-mentioned 2,7-bis(5-aminomethylfuran-2-yl)fluorene more stable.

[0032] In another embodiment of the present invention, the general synthetic route for 2,7-bis(5-aminomethylfuran-2-yl)fluorene (abbreviated as FBF-BAMF) is as follows:

[0033] Suzuki coupling: 2,7-dibromofluorene + 5-formylfuran-2-boronic acid → 2,7-bis(5-formylfuran-2-yl)fluorene (dialdehyde intermediate);

[0034] Reductive amination: 2,7-bis(5-formylfuran-2-yl)fluorene + ammonium formate / ammonia + reducing agent → 2,7-bis(5-aminomethylfuran-2-yl)fluorene.

[0035] Specifically, the preparation method of 2,7-bis(5-aminomethylfuran-2-yl)fluorene is as follows:

[0036] Step 1, Suzuki Coupling – Preparation of the Dialdehyde Intermediate: First, weigh the following raw materials:

[0037] 2,7-Dibromofluorene: 1.79 g (0.005 mol, 1.0 eq)

[0038] 5-Formylfuran-2-boronic acid: 1.54 g (0.011 mol, 2.2 eq);

[0039] Pd(PPh3)4: 0.29g (0.00025mol, 5%);

[0040] Anhydrous K₂CO₃: 2.76 g (0.02 mol, 4 eq);

[0041] Solvent: Anhydrous THF / Toluene = 1:1, 50 mL in total;

[0042] Water: 10 mL (to dissolve potassium carbonate and prepare a K2CO3 aqueous solution);

[0043] Next, the three-necked flask was evacuated and nitrogen was replaced three times, with nitrogen protection throughout the process; 2,7-dibromofluorene, 5-formylfuran-2-boronic acid, and catalyst Pd(PPh3)4 were added, and dry solvent was injected; the mixture was stirred for 10 min, and then K2CO3 aqueous solution was injected; the mixture was refluxed at 75 °C for 24 h, and monitored by TLC (dichloromethane:n-hexane = 3:1); the mixture was cooled, separated, and the aqueous phase was extracted twice with ethyl acetate; the organic phases were combined, washed with saturated brine, and dried over anhydrous Na2SO4; the mixture was then subjected to rotary evaporation and silica gel column chromatography (eluent: DCM / hexane = 2:1) to obtain a yellow solid dialdehyde intermediate, with a yield of 70%-78%.

[0044] Step 2, reductive amination: First, weigh the following raw materials:

[0045] The dialdehyde intermediate obtained in the first step: 1.80 g (0.004 mol);

[0046] Ammonium formate: 3.0g (excess);

[0047] Deionized water: 5 mL;

[0048] Ethanol: 20 mL;

[0049] Toluene: 5 mL (azeotropic);

[0050] Next, under nitrogen protection, the dialdehyde intermediate was dissolved in ethanol / toluene, ammonium formate and water were added, and the mixture was slowly heated to 85°C and refluxed for 6-8 hours. TLC monitoring showed that the dialdehyde intermediate had completely disappeared. After cooling, the pH was adjusted to 9-10 with 20% NaOH. The mixture was extracted with ethyl acetate, washed with water, dried, and rotary evaporated. The crude product was recrystallized 1-2 times with ethanol / water and dried under vacuum at 60°C to obtain 2,7-bis(5-aminomethylfuran-2-yl)fluorene, which is a nearly white / pale yellow powder with a yield of 65%-75%.

[0051] In another embodiment of the present invention, a coating is also provided, which is formed by electrostatically spraying the above-mentioned polyimide coating onto a substrate and then curing it. The thickness of the electrostatically sprayed coating is controlled to be 60-80 μm. The curing is carried out in two stages: the first stage is heated at 200-250°C for 10-20 min, and the second stage is heated at 300-350°C for 20-40 min.

[0052] In this embodiment of the invention, by utilizing electrostatic spraying technology, powdered polyimide coating can be uniformly adsorbed onto the surface of the substrate workpiece. After curing, the coating is uniform and has good adsorption capacity. The coating utilization rate is as high as 90% or more, which can save coating. Moreover, the particle flow speed of electrostatic spraying is slow and the particle scattering is less, which can improve the working environment.

[0053] The following embodiments are examples of the present invention in practical applications, and are only illustrative and are not limited thereto.

[0054] Example 1: This example provides a method for preparing a furan-containing polyimide coating and a polyimide coating layer, specifically including the following steps:

[0055] S1. Add 18.3838 g (0.17 mol) of p-phenylenediamine and 10.6845 g (0.03 mol) of 2,7-bis(5-aminomethylfuran-2-yl)fluorene to the reaction flask, then add 325.58 g of N,N'-dimethylacetamide, and stir to dissolve under nitrogen protection.

[0056] S2. After complete dissolution, cool to -15℃ and add 59.43143 g (0.202 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the reaction flask in four batches. Then stir the reaction at this temperature for 5 hours, with each batch added 1 hour apart.

[0057] S3. After the reaction is complete and the time is reached, a viscous polyamic acid solution is obtained. The apparent viscosity of the solution is 28500 cps. The polyamic acid solution is placed in a freeze dryer for 18 hours to remove N,N'-dimethylacetamide, and the solvent-free powdered polyamic acid is obtained.

[0058] S4. Take 60g of solvent-removed polyamic acid, 30g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain polyimide coating as a powder coating for electrostatic spraying.

[0059] S5. Using an electrostatic spraying device, the above-mentioned polyimide coating is uniformly sprayed onto the iron plate, and the coating thickness is controlled to be 60μm. The electrostatically sprayed iron plate is placed in an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15min, and the second stage is 320℃ for 30min, finally obtaining the polyimide coating.

[0060] Example 2: This example provides a method for preparing a furan-containing polyimide coating and a polyimide coating layer, specifically including the following steps:

[0061] S1. Add 19.465 g (0.18 mol) of p-phenylenediamine and 7.123 g (0.02 mol) of 2,7-bis(5-aminomethylfuran-2-yl)fluorene to the reaction flask, then add 325.58 g of N,N'-dimethylacetamide, and stir to dissolve under nitrogen protection.

[0062] S2. After complete dissolution, cool to -15℃ and add 59.43143 g (0.202 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the reaction flask in four batches. Then stir the reaction at this temperature for 5 hours, with each batch added 1 hour apart.

[0063] S3. After the reaction is complete and the time is reached, a viscous polyamic acid solution is obtained. The apparent viscosity of the solution is 30500 cps. The polyamic acid solution is placed in a freeze dryer for 18 hours to remove N,N'-dimethylacetamide, and the solvent-free powdered polyamic acid is obtained.

[0064] S4. Take 60g of solvent-removed polyamic acid, 30g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain polyimide coating as a powder coating for electrostatic spraying.

[0065] S5. Using an electrostatic spraying device, the above-mentioned polyimide coating is uniformly sprayed onto the iron plate, and the coating thickness is controlled to be 60μm. The electrostatically sprayed iron plate is placed in an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15min, and the second stage is 320℃ for 30min, finally obtaining the polyimide coating.

[0066] Example 3: This example provides a method for preparing a furan-containing polyimide coating and a polyimide coating layer, specifically including the following steps:

[0067] S1. Add 17.3024 g (0.16 mol) of p-phenylenediamine and 14.246 g (0.04 mol) of 2,7-bis(5-aminomethylfuran-2-yl)fluorene to the reaction flask, then add 325.58 g of N,N'-dimethylacetamide, and stir to dissolve under nitrogen protection.

[0068] S2. After complete dissolution, cool to -15℃ and add 59.43143 g (0.202 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the reaction flask in four batches. Then stir the reaction at this temperature for 5 hours, with each batch added 1 hour apart.

[0069] S3. After the reaction is complete and the time is reached, a viscous polyamic acid solution is obtained. The apparent viscosity of the solution is 25000 cps. The polyamic acid solution is placed in a freeze dryer for 18 hours to remove N,N'-dimethylacetamide, and the solvent-free powdered polyamic acid is obtained.

[0070] S4. Take 60g of solvent-removed polyamic acid, 30g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain polyimide coating as a powder coating for electrostatic spraying.

[0071] S5. Using an electrostatic spraying device, the above-mentioned polyimide coating is uniformly sprayed onto the iron plate, and the coating thickness is controlled to be 60μm. The electrostatically sprayed iron plate is placed in an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15min, and the second stage is 320℃ for 30min, finally obtaining the polyimide coating.

[0072] Example 4: This example provides a method for preparing a furan-containing polyimide coating and a polyimide coating layer, specifically including the following steps:

[0073] S1. Add 16.221 g (0.15 mol) of p-phenylenediamine and 17.8075 g (0.05 mol) of 2,7-bis(5-aminomethylfuran-2-yl)fluorene to the reaction flask, then add 325.58 g of N,N'-dimethylacetamide, and stir to dissolve under nitrogen protection.

[0074] S2. After complete dissolution, cool to -15℃ and add 59.43143 g (0.202 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the reaction flask in four batches. Then stir the reaction at this temperature for 5 hours, with each batch added 1 hour apart.

[0075] S3. After the reaction is complete and the time is reached, a viscous polyamic acid solution is obtained. The apparent viscosity of the solution is 22500 cps. The polyamic acid solution is placed in a freeze dryer for 18 hours to remove N,N'-dimethylacetamide, and the solvent-free powdered polyamic acid is obtained.

[0076] S4. Take 60g of solvent-removed polyamic acid, 30g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain polyimide coating as a powder coating for electrostatic spraying.

[0077] S5. Using an electrostatic spraying device, the above-mentioned polyimide coating is uniformly sprayed onto the iron plate, and the coating thickness is controlled to be 60μm. The electrostatically sprayed iron plate is placed in an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15min, and the second stage is 320℃ for 30min, finally obtaining the polyimide coating.

[0078] Example 5: This example provides a method for preparing a furan-containing polyimide coating and a polyimide coating layer, specifically including the following steps:

[0079] S1. Add 15.1396 g (0.14 mol) of p-phenylenediamine and 21.369 g (0.06 mol) of 2,7-bis(5-aminomethylfuran-2-yl)fluorene to the reaction flask, then add 325.58 g of N,N'-dimethylacetamide, and stir to dissolve under nitrogen protection.

[0080] S2. After complete dissolution, cool to -15℃ and add 59.43143 g (0.202 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the reaction flask in four batches. Then stir the reaction at this temperature for 5 hours, with each batch added 1 hour apart.

[0081] S3. After the reaction is complete and the time is reached, a viscous polyamic acid solution is obtained. The apparent viscosity of the solution is 20,000 cps. The polyamic acid solution is placed in a freeze dryer for 18 hours to remove N,N'-dimethylacetamide, and the solvent-free powdered polyamic acid is obtained.

[0082] S4. Take 60g of solvent-removed polyamic acid, 30g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain polyimide coating as a powder coating for electrostatic spraying.

[0083] S5. Using an electrostatic spraying device, the above-mentioned polyimide coating is uniformly sprayed onto the iron plate, and the coating thickness is controlled to be 60μm. The electrostatically sprayed iron plate is placed in an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15min, and the second stage is 320℃ for 30min, finally obtaining the polyimide coating.

[0084] Comparative Example 1: This comparative example provides a method for preparing polyimide coatings and polyimide coating layers, specifically including the following steps:

[0085] S1. Add 21.628 g (0.20 mol) of p-phenylenediamine to the reaction flask, then add 325.58 g of N,N'-dimethylacetamide, and stir to dissolve under nitrogen protection.

[0086] S2. After complete dissolution, cool to -15℃ and add 59.43143 g (0.202 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the reaction flask in four batches. Then stir the reaction at this temperature for 5 hours, with each batch added 1 hour apart.

[0087] S3. After the reaction is complete and the time is reached, a viscous polyamic acid solution is obtained. The apparent viscosity of the solution is 31500 cps. The polyamic acid solution is placed in a freeze dryer for 18 hours to remove N,N'-dimethylacetamide, and the solvent-free powdered polyamic acid is obtained.

[0088] S4. Take 60g of solvent-removed polyamic acid, 30g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain polyimide coating as a powder coating for electrostatic spraying.

[0089] S5. Using an electrostatic spraying device, the above-mentioned polyimide coating is uniformly sprayed onto the iron plate, and the coating thickness is controlled to be 60μm. The electrostatically sprayed iron plate is placed in an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15min, and the second stage is 320℃ for 30min, finally obtaining the polyimide coating.

[0090] Comparative Example 2: This comparative example provides a method for preparing acrylic coatings and acrylic coating layers, specifically including the following steps:

[0091] S1. Take 90g of acrylic resin, 7g of TGIC, 2.5g of 486CFL leveling agent, and 0.5g of benzoin, mix them, and put them into a pulverizer to grind them. Then, sieve the pulverized fine powder through an 180-mesh inspection sieve to separate it into fine powder particles, and obtain acrylic coating as a powder coating for electrostatic spraying.

[0092] S5. Using an electrostatic spraying device, uniformly spray the above-mentioned acrylic coating onto the iron plate, controlling the coating thickness to be 60μm; place the electrostatically sprayed iron plate into an oven for high-temperature curing. The high-temperature curing is carried out in two stages: the first stage is 200℃ for 15 minutes, and the second stage is 320℃ for 30 minutes, finally obtaining the acrylic coating.

[0093] Performance testing: 1. The glass transition temperature (Tg) and 5% thermogravimetric temperature (Td) of the polyimide coatings and polyimide coatings prepared in Comparative Example 1 and Examples 1-5 were tested. 5% The performance tests for items such as coating peel strength were conducted, and the results are shown in Table 1 below:

[0094] Table 1

[0095]

[0096] II. High Temperature Test: The coatings obtained in Examples 1-5 and Comparative Examples 1-2 were placed in an oven for high-temperature baking at 250°C for one hour, 300°C for one hour, 350°C for one hour, and 400°C for one hour. The coating samples were observed every half hour. The results are shown in Table 2.

[0097] Table 2

[0098]

[0099] In Table 2, "-" indicates no shedding or carbonization; "+" indicates shedding or carbonization.

[0100] III. Coating Adhesion Test: The coating adhesion test was conducted using 3M 600 tape, an internationally standardized test tape. 3M 600 tape was applied to the coatings prepared in Examples 1-5 and Comparative Examples 1-2, pressed firmly, and then peeled off after 5 minutes. The percentage of coating area that peeled off was measured using the cross-cut adhesion test method. The calculation formula is as follows: Peeling area (%) = Area of ​​coating peeled off after test / Area of ​​tape adhered × 100%. The test results are shown in Table 3.

[0101] Table 3

[0102]

[0103] In summary, the furan-containing polyimide coating prepared in the embodiments of the present invention has good high temperature resistance, reaching above 400°C; and good adhesion strength, with the coating peeling area not exceeding 10% when the adhesion is tested with 3M 600 tape.

[0104] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification.

Claims

1. A polyimide coating containing furan groups, which is a powder coating, characterized in that, It includes the following raw materials: polyamic acid, resin and additives; the polyamic acid is synthesized by polycondensation reaction of diamine monomer and aromatic dianhydride; the diamine monomer includes 2,7-bis(5-aminomethylfuran-2-yl)fluorene.

2. The furan-containing polyimide coating according to claim 1, characterized in that, The diamine monomer also includes p-phenylenediamine, wherein 2,7-bis(5-aminomethylfuran-2-yl)fluorene accounts for 10%-30% of the total amount of the diamine monomer.

3. The furan-containing polyimide coating according to claim 1, characterized in that, The aromatic dianhydride is one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 4,4'-oxobisphthalic anhydride.

4. The furan-containing polyimide coating according to claim 1, characterized in that, The total amount of polyamic acid and resin accounts for 80%-95% of the total mass of the raw materials, wherein the mass ratio of polyamic acid and resin is (1-3):

1.

5. The furan-containing polyimide coating according to claim 1 or 4, characterized in that, The resin is one or more of acrylic resin, epoxy resin and polyester resin; the additives include one or more of curing agent, leveling agent and degassing agent; the curing agent is TGIC or HAA; the leveling agent is any one of polysiloxane polyether, silicone compound and fluorocarbon compound; the degassing agent is benzoin or diphenoxypropanol.

6. A method for preparing a polyimide coating as described in any one of claims 1-5, characterized in that, Includes the following steps: Polyamic acid, resin and additives are mixed and then crushed and sieved to obtain polyimide coatings.

7. The method for preparing the furan-containing polyimide coating according to claim 6, characterized in that, The method for synthesizing the polyamic acid includes the following steps: A diamine solution is prepared by dissolving the diamine monomer in an aprotic polar solvent. Under a protective atmosphere, aromatic dianhydrides are added in batches to a diamine solution to carry out a polycondensation reaction, yielding a polyamic acid solution. The polyamic acid solution was freeze-dried to remove the solvent, resulting in powdered polyamic acid.

8. The method for preparing the furan-containing polyimide coating according to claim 7, characterized in that, The aprotic polar solvent is one or more of N,N'-dimethylacetamide, N,N'-dimethylformamide, and N-methylpyrrolidone; the reaction temperature of the polycondensation reaction is 10-30℃.

9. A coating, characterized in that, The coating is formed by electrostatically spraying the polyimide coating of any one of claims 1-5 onto a substrate and then curing it.

10. The coating according to claim 9, characterized in that, The curing process is carried out in two stages: the first stage involves heating at 200-250℃ for 10-20 minutes, and the second stage involves heating at 300-350℃ for 20-40 minutes.

Images