Degradable hard polyimide foam material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a degradable hard polyimide foam material and a preparation method thereof. According to the foam material, degradable dianhydride containing degradable chain segments (such as ester bonds, amido bonds, anhydride bonds, acetal bonds and the like) serves as a main raw material, and the degradable hard polyimide foam material is prepared through a one-step method. A controllable degradation unit is introduced into a molecular chain of a hard polyimide foam material, and foaming process parameters are optimized, so that the environmental problem that traditional polyimide foam is difficult to degrade is successfully solved, and meanwhile, the inherent excellent performance of the hard polyimide foam material is reserved. The foam material can be controllably degraded in a natural environment, meets the harsh requirements in the fields of aerospace, electronics, transportation, environment-friendly packaging, biomedical treatment and the like, and conforms to the environment-friendly concept of sustainable development at the same time.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically a biodegradable rigid polyimide foam material and its preparation method. Background Technology

[0002] Polyimide is a polymer with excellent comprehensive properties. When used as a matrix to prepare foam materials, it retains many of the advantages of the bulk material, such as self-flame retardancy, resistance to high and low temperatures, corrosion resistance, radiation resistance, low thermal conductivity, resistance to chemical solvents, and good dielectric properties. Furthermore, the unique cell structure of foam materials endows them with properties such as shock absorption and damping, thermal insulation, and sound absorption and noise reduction. Therefore, polyimide foam is widely used in high-end fields such as aerospace (thermal and sound insulation layers, core materials), shipbuilding (fireproof and thermal insulation), transportation (sandwich materials), electronics and electrical appliances (insulation encapsulation), and precision instruments (vibration damping).

[0003] Polyimide foam can be classified into flexible and rigid foams according to its hardness. Flexible open-cell polyimide foam is lightweight and can be processed into various sizes and shapes, but its mechanical properties are poor, making it difficult to use as a structural foam. Furthermore, its low closed-cell ratio results in poor moisture barrier properties, making it unsuitable for protecting internal components. Rigid polyimide foam, on the other hand, possesses advantages such as high specific strength, high specific modulus, high temperature resistance, high closed-cell ratio, and dimensional stability. It is commonly used as a structural foam, such as in helicopter blades, missile housings, and relay frames. Depending on the manufacturing process, the main methods for preparing rigid polyimide foam include two-step and one-step methods. The two-step method involves prepolymerizing the monomers at low temperature in a solvent to form a precursor solution, then drying it into a precursor powder, and finally imidizing it through heating or chemical methods, simultaneously foaming to form polyimide foam. The one-step method involves foaming in a single reaction without the precursor product. The two-step method offers high closed-cell ratio and a wide density adjustment range, but it requires sophisticated processes, involves complex foaming procedures, and incurs high costs. Conversely, the one-step method is simple, has a short cycle time, is easy to operate, produces uniform pore size, and exhibits stable performance, but it cannot yield high-density products, and its mechanical properties cannot reach their optimal levels. Therefore, employing a one-step method to prepare low-cost, simple, and mechanically superior rigid polyimide foam materials has significant practical implications.

[0004] Polyimide foam molecules consist of stable imide and aromatic rings in their main chain, exhibiting high chemical bond energy and a dense structure. This results in extremely strong chemical and biological inertness, making them difficult to degrade in natural environments due to harsh degradation conditions. With the widespread use of polyimide foam materials, environmental pollution and resource waste have become increasingly prominent, contradicting the current global advocacy for green, circular, and sustainable development. Currently, adding large amounts of biodegradable fillers (starch, cellulose, etc.) or physically blending biodegradable polymers to polyimide is one method to improve its degradability, but this often affects the core high performance characteristics of polyimide foam (such as temperature resistance and strength).

[0005] Chinese patent CN115417989A discloses a method for preparing a biodegradable, high-heat-resistant polyimide material. This method primarily synthesizes a substance containing acetal and pyridine structures (diamine 3,9-bis[4-(5-amino-2-pyridinoxy)pyridyl]-2,4,6,10-hexaoxy-spiro(5,5)undecane), which is then used to modify polyimide to prepare a degradable polyimide film. The polyimide film prepared by this invention can degrade under acidic conditions. The introduction of the pyridine structure effectively avoids the poor heat resistance drawbacks caused by the acetal structure. However, the preparation cost is high, and the complexity is significant, making it unsuitable for low-cost, large-scale production.

[0006] Chinese patent CN116284777A discloses a biodegradable, heat-resistant, and environmentally friendly material and its preparation method. This method uses pentaerythritol, p-hydroxybenzaldehyde, cyclohexane, and p-toluenesulfonic acid to synthesize a crude product, which is then purified by adding bisphenol, anhydrous potassium carbonate, and dimethylformamide. Subsequently, it reacts with diphenyl iodide chloride synthesized from nitrobenzaldehyde, benzoyl, and amine acetate to synthesize the biodegradable, heat-resistant, and environmentally friendly polyimide material. This material exhibits good comprehensive properties and can be completely degraded under relatively mild conditions, breaking down bulk polyimide into small fragments. The degradation cost is low, and it maintains its original mechanical properties, allowing for large-scale application and greater environmental friendliness. However, this invention also suffers from a long preparation cycle, indirectly increasing time costs. Furthermore, the specification only mentions heat resistance and degradability, without assessing the impact on its mechanical properties, thus presenting certain limitations.

[0007] In summary, introducing biodegradable units into the main chain of polyimide materials through chemical methods is an effective approach to balancing degradability and high performance. However, this method suffers from problems such as long development cycles, high costs, and difficulty in balancing mechanical properties and degradability. Furthermore, research on preparing biodegradable polyimide foams is limited. Therefore, preparing a biodegradable polyimide foam material with simple processing and excellent mechanical properties is currently a key research direction. Summary of the Invention

[0008] To address the aforementioned technical problems in the prior art, this invention provides a biodegradable rigid polyimide foam material and its preparation method. Specifically, this is achieved through the following technical solution: A method for preparing a biodegradable rigid polyimide foam material specifically includes the following steps: (1) Prepare precursor A by mixing biodegradable dianhydride, low molecular weight alcohol and surfactant I; prepare precursor B by mixing catalyst and foaming agent; (2) Thoroughly mix precursor A and precursor B to obtain foamed white material; (3) Mix isocyanate and surfactant II thoroughly to obtain foaming black material; (4) Mix the foamed white material and the foamed black material in proportion and stir them. Pour the mixture into a mold, let it stand, and then microwave it for curing. Then place the cured sample in an oven to solidify and shape it to obtain the foam material.

[0009] Furthermore, the biodegradable dianhydride is any one or more of the following, mixed in any proportion: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, N,N'-bis(3,4-dicarboxybenzoyl)p-phenylenediamine dianhydride, 4,4'-bis(3,4-dicarboxybenzoamide)biphenyl dianhydride, 3,3,4,4'-benzophenone tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, and hydrogenated biphenyltetracarboxylic dianhydride.

[0010] Furthermore, the low molecular weight alcohol is any one or more of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, glycerol, isobutanol, 1,4-butanediol, neopentyl glycol, and isopentyl glycol mixed in any proportion.

[0011] Furthermore, the surfactant I or surfactant II is any one or more of L-550, AK-6602, DC-190, DC-193, Silbyk-9210, L6988, LK-221, DC-5103, Silbyk-TP3796, JY-6404, JYS-2000, Niax L-6900, L6920, AK-8807, M-8803, M-8872, and M-6698LV, mixed in any proportion.

[0012] Furthermore, the catalyst is any one or more of heptamethyltrisiloxane, triethylenediamine, dibutyltin dilaurate, 1,1,3,3-tetramethyldisiloxane, platinum vinylsiloxane, diethanolamine, triethanolamine, nickel dialkyldithiocarbamate, acetophenone, tetramethylalkylenediamine, cerium carboxylate, benzophenone, potassium oleate, and dibutyltin diacetate, mixed in any proportion.

[0013] Furthermore, the foaming agent is any one or more of the following physical or chemical foaming agents, mixed in any proportion: methanol, ethanol, water, acetone, 2-butoxyethanol, N,N'-dimethylformamide, carbamide, monomethylurea, dimethyl ether, HFC-134a, HCFC-141-B, cyclopentane, n-pentane, ammonium bicarbonate, ammonium carbonate, etc.

[0014] Furthermore, the isocyanate is any one or more of 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate (TDI), toluene diisocyanate, terephthalimethylene diisocyanate, polyphenyl polymethylene polyisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and methylcyclohexyl diisocyanate, mixed in any proportion.

[0015] Furthermore, in step (4), the foamed white material and the foamed black material are mixed in a mass ratio of 1:(0.4-2.5).

[0016] Furthermore, the mixing is carried out using mechanical stirring at a speed of 120-1500 r / min for a duration of 10-240 min.

[0017] Furthermore, in step (4), the microwave curing parameters are set to a frequency of 100-915Hz and a duration of 10-300min; the oven curing parameters are set to a temperature of 180-300℃ and a duration of 60-360min.

[0018] A biodegradable rigid polyimide foam material is prepared by the above method.

[0019] Compared with the prior art, the technical effects of this invention are reflected in: This invention introduces biodegradable groups into the polyimide backbone, enabling the polyimide foam to degrade under specific environmental conditions through chain segment breakage. This solves the environmental problem of the inability of traditional polyimide foams to degrade. The degradation rate can be altered by controlling the type, content, and distribution of the biodegradable units. The surfactant used in this invention can change the interfacial tension of the substances, allowing acid anhydrides to form well-dispersed solutions with low molecular weight alcohols, avoiding the health hazards and environmental pollution caused by the volatilization of traditional organic reagents. The preparation method used in this invention is based on a mature one-step polyimide foaming process, which is simple to operate, has a clear process route, and has the potential for industrial production. Furthermore, the biodegradable rigid polyimide foam prepared by this method possesses both biodegradable and environmentally friendly properties and the excellent performance of rigid foam, making it highly promising for applications in aerospace, electronics, transportation, environmentally friendly packaging, and biomedicine. Detailed Implementation

[0020] The technical solution of the present invention will be further defined below with reference to specific embodiments, but the scope of protection is not limited to the description made.

[0021] Example 1 (1) 75 parts of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 20 parts of methanol, 15 parts of ethanol and 20 parts of AK-6602 were mixed to prepare precursor A. The stirring speed was 500 r / min and the mixture was stirred for 60 min. 3 parts of triethanolamine, 1.5 parts of triethylenediamine, 1.7 parts of HCFC-141-B and 3.8 parts of water were mixed to prepare precursor B. The stirring speed was 900 r / min and the mixture was stirred for 30 min.

[0022] (2) Mix precursor A and precursor B thoroughly to obtain foamed white material. Stir at 900 r / min for 30 min.

[0023] (3) Mix 50 parts toluene diisocyanate, 50 parts terephthalic diisocyanate, 10 parts AK-8807 and 15 parts JYS-2000 thoroughly to obtain foamed black material. Stir at 100 r / min for 30 min.

[0024] (4) Mix the foamed white material and foamed black material in a ratio of 1:0.68 at a stirring speed of 2000r / min for 10s, pour the mixture into a mold, let it stand for 20min, and then place it in a microwave oven at a frequency of 500hz for 15min to cure. Then place the cured sample in an oven at 200℃ for 180min to obtain the foam material.

[0025] Example 2 (1) 70 parts of 3,3,4,4,-benzophenone tetracarboxylic dianhydride, 30 parts of propanol, 8 parts of Silbyk-9210 and 7 parts of Silbyk-TP3796 were mixed to prepare precursor A, and the stirring speed was 400 r / min for 52 min; 1.5 parts of dibutyltin diacetate, 1.5 parts of dibutyltin dilaurate, 2 parts of HFC-134a and 4 parts of water were mixed to prepare precursor B, and the stirring speed was 800 r / min for 20 min.

[0026] (2) Mix precursor A and precursor B thoroughly to obtain foamed white material. Stir at 800 r / min for 20 min.

[0027] (3) Mix 35 parts of 4,4'-diphenylmethane diisocyanate, 35 parts of terephthalic dimethyl diisocyanate and 10 parts of NiaxL-6900 thoroughly to obtain foamed black material. Stir at 100 r / min for 60 min.

[0028] (4) Mix the foamed white material and foamed black material in a ratio of 1:0.61 at a stirring speed of 1800 r / min for 18s, pour the mixture into a mold, let it stand for 22 min, and then place it in a microwave oven at a frequency of 550 Hz for 20 min to cure. Then place the cured sample in an oven at 210 ℃ for 150 min to obtain the foam material.

[0029] Example 3 (1) 35 parts of 3,3,4,4,-benzophenone tetracarboxylic dianhydride, 35 parts of cyclobutane tetracarboxylic dianhydride, 15 parts of methanol, 15 parts of ethanol, 8 parts of DC-193 and 8 parts of DC-5103 were mixed to prepare precursor A, and the stirring speed was 619 r / min for 45 min; 1.5 parts of triethanolamine and 5.2 parts of water were mixed to prepare precursor B, and the stirring speed was 750 r / min for 25 min.

[0030] (2) Mix precursor A and precursor B thoroughly to obtain foamed white material. Stir at 900 r / min for 24 min.

[0031] (3) Mix 70 parts of diphenylmethane diisocyanate and 10 parts of Silbyk-TP3796 thoroughly to obtain foamed black material. Stir at 200 r / min for 45 min.

[0032] (4) Mix the foamed white material and foamed black material in a ratio of 1:0.66 at a stirring speed of 1750 r / min for 21 seconds, pour the mixture into a mold, let it stand for 25 minutes, and then place it in a microwave oven at a frequency of 500 Hz for 30 minutes to cure. Then place the cured sample in an oven at 180 ℃ for 210 minutes to obtain the foam material.

[0033] Example 4 (1) 30 parts of pyromellitic dianhydride, 55 parts of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 25 parts of ethanol, 25 parts of butanol, 8 parts of Silbyk-9210 and 16 parts of JY-6404 were mixed to prepare precursor A. The stirring speed was 800 r / min and the mixture was stirred for 60 min. 3 parts of dibutyltin diacetate, 1.5 parts of dibutyltin dilaurate, 1.5 parts of heptamethyltrisiloxane, 0.6 parts of HFC-134a, 0.3 parts of HCFC-141-B and 5 parts of water were mixed to prepare precursor B. The stirring speed was 800 r / min and the mixture was stirred for 20 min.

[0034] (2) Mix precursor A and precursor B thoroughly to obtain foamed white material. Stir at 1000 r / min for 40 min.

[0035] (3) Mix 60 parts toluene diisocyanate, 35 parts terephthalic diisocyanate and 20 parts L-550 thoroughly to obtain foamed black material. Stir at 100 r / min for 60 min.

[0036] (4) Mix the foamed white material and foamed black material in a ratio of 1:0.63 at a stirring speed of 2000r / min for 15s, pour the mixture into a mold, let it stand for 30min, and then place it in a microwave oven at a frequency of 600Hz for 20min to cure. Then place the cured sample in an oven at 200℃ for 240min to obtain the foam material.

[0037] The main properties of the polyimide foam prepared according to the above embodiments are shown in Table 1 below: Table 1

[0038] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing a biodegradable rigid polyimide foam material, characterized in that, Specifically, the steps include the following: (1) Prepare precursor A by mixing biodegradable dianhydride, low molecular weight alcohol and surfactant I; prepare precursor B by mixing catalyst and foaming agent; (2) Thoroughly mix precursor A and precursor B to obtain foamed white material; (3) Mix isocyanate and surfactant II thoroughly to obtain foaming black material; (4) Mix the foamed white material and the foamed black material in proportion and stir them. Pour the mixture into a mold, let it stand, and then microwave it for curing. Then place the cured sample in an oven to solidify and shape it to obtain the foam material.

2. The preparation method according to claim 1, characterized in that, The biodegradable dihydric anhydride is any one or more of the following, mixed in any proportion: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, N,N'-bis(3,4-dicarboxybenzoyl)p-phenylenediamine dianhydride, 4,4'-bis(3,4-dicarboxybenzoamide)biphenyl dianhydride, 3,3,4,4'-benzophenone tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, and hydrogenated biphenyltetracarboxylic dianhydride.

3. The preparation method according to claim 1, characterized in that, The low molecular weight alcohol is any one or more of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, glycerol, isobutanol, 1,4-butanediol, neopentyl glycol, and isopentyl glycol, mixed in any proportion.

4. The preparation method according to claim 1, characterized in that, The surfactant I or surfactant II is any one or more of L-550, AK-6602, DC-190, DC-193, Silbyk-9210, L6988, LK-221, DC-5103, Silbyk-TP3796, JY-6404, JYS-2000, Niax L-6900, L6920, AK-8807, M-8803, M-8872, and M-6698LV, mixed in any proportion.

5. The preparation method according to claim 1, characterized in that, The catalyst is any one or more of heptamethyltrisiloxane, triethylenediamine, dibutyltin dilaurate, 1,1,3,3-tetramethyldisiloxane, platinum vinylsiloxane, diethanolamine, triethanolamine, nickel dialkyldithiocarbamate, acetophenone, tetramethylalkylene diamine, cerium carboxylate, benzophenone, potassium oleate, and dibutyltin diacetate, mixed in any proportion.

6. The preparation method according to claim 1, characterized in that, The foaming agent is any one or more of the following physical or chemical foaming agents, mixed in any proportion: methanol, ethanol, water, acetone, 2-butoxyethanol, N,N'-dimethylformamide, carbamide, monomethylurea, dimethyl ether, HFC-134a, HCFC-141-B, cyclopentane, n-pentane, ammonium bicarbonate, ammonium carbonate, etc.

7. The preparation method according to claim 1, characterized in that, The isocyanate is any one or more of 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, terephthalimethylene diisocyanate, polyphenyl polymethylene polyisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and methylcyclohexyl diisocyanate, mixed in any proportion.

8. The preparation method according to claim 1, characterized in that, In step (4), the foamed white material and the foamed black material are mixed in a mass ratio of 1:(0.4-2.5).

9. The preparation method according to claim 1, characterized in that, The mixing process employs mechanical stirring at a speed of 120-1500 r / min for a duration of 10-240 min.

10. A biodegradable rigid polyimide foam material, characterized in that, It is prepared by the method described in any one of claims 1-9.

Images