A method for polyimide high-efficiency acid and alkali-free green wet micro-degradation regeneration

Abstract

The application discloses a kind of polyimide efficient acid-base-free green wet micro-degradation regeneration method, belong to green circular economy field and light material synthesis technical field.The preparation method of the present application is: polyimide material, ring-opening agent and organic solvent are mixed in closed container to obtain polyamide acid homogeneous mixture liquid;The obtained polyamide acid homogeneous mixture liquid can be used as raw material and polyamide acid mixed hot pressing amination to prepare polyimide composite film.The application utilizes green wet degradation technology, and polyimide film is recovered.Due to existing recovery technology, acid-base wastewater is easily generated, and it is easy to cause huge energy consumption to be changed into monomer, compared with the present application, with simple and mild operation process, simple and easy recovery method, low cost and no acid-base wastewater is generated, with very high economic benefit, low energy consumption, less environmental pollution and high added value, realize the green regeneration of polyimide waste.

Description

Technical Field

[0001] This invention belongs to the fields of green circular economy and lightweight material synthesis technology, specifically relating to a method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide. Background Technology

[0002] Polyimide is a class of high-molecular polymers containing imide rings (-CO-NR-CO) in its main chain, and it is one of the best-performing organic polymer materials. It can be used for extended periods in a temperature range of -200 to 300°C, exhibiting excellent temperature resistance, chemical corrosion resistance, and electrical insulation. Due to its superior properties, polyimide is now widely used in various fields such as solar panels, photoresists, separation membranes, and liquid crystal displays. However, the large-scale use of polyimide has led to a continuous increase in waste resources, making its rational recycling a major concern.

[0003] Polyimide is mainly prepared from aromatic diamines and aromatic dianhydrides. However, the preparation processes of aromatic diamines and aromatic dianhydrides are complex and expensive. Therefore, recovering high-value-added polyamic acid from polyimide waste and conducting a secondary reaction to obtain polyimide films can reduce resource waste, avoid environmental pollution, and provide a new method for preparing synthetic polyimide films, achieving green recycling.

[0004] Chinese patent CN115057769 A discloses a method for recycling waste polyimide film. This method primarily involves converting waste polyimide film into monomers for polyimide film production—4,4'-diaminodiphenyl ether (ODA) and pyromellitic phthalic anhydride (PMDA)—under high-temperature and strongly alkaline conditions. This achieves the recycling of waste polyimide film and offers significant economic and environmental benefits. However, the high-temperature and strongly alkaline conditions place high demands on the equipment used, and the energy consumption for converting fully polymerized waste polyimide film into monomers is also high.

[0005] Chinese patent CN103553906 B discloses a method for recovering polyimide raw materials by hydrolyzing waste polyimide films with ammonia. The method mainly involves converting waste polyimide films into PMDA and ODA in an ammonia solution, with a purity of up to 99.5%. However, this reaction requires high pressure, and ammonia is highly volatile, which is not conducive to industrialization. Summary of the Invention

[0006] In view of the above-mentioned problems in the existing technology, the technical problem to be solved by the present invention is to provide a method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide. The recycling method of the present invention is simple and easy to implement, does not generate industrial acid and alkali wastewater, promotes the recycling and utilization of chemical raw materials, reduces production costs, and realizes the green regeneration of polyimide waste.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide includes the following steps: mixing polyimide material, ring-opening agent and organic solvent and reacting them in a closed container to obtain a homogeneous polyamic acid mixture; mixing the obtained homogeneous polyamic acid solution with polyamic acid raw material and carrying out a thermal imidization reaction to obtain a polyimide composite film.

[0009] This invention recovers high-value-added polyamic acid by selectively breaking imide bonds. The reaction process is as follows:

[0010]

[0011] This invention enables the controlled degradation of polyamic acid by controlling the mass ratio of ring-opening agent and organic solvent. The recycling method is simple and easy to implement, does not generate industrial acid or alkali wastewater, promotes the recycling of chemical raw materials, reduces production costs, and achieves green regeneration of polyimide waste.

[0012] Preferably, the polyimide material has the following structural formula:

[0013]

[0014] Ar1 includes the following structure:

[0015]

[0016] Ar2 includes the following structure:

[0017]

[0018] Preferably, the organic solvent is selected from any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, m-cresol, nitrobenzene, dimethyl sulfoxide, toluene, formamide, and acetamide. The organic solvent is used to improve the wettability of the degradation system with the polyimide material and to dissolve the degradation products. The organic solvent selected in this scheme has good swelling effect and reactivity for the degradation of polyimide materials.

[0019] Preferably, the ring-opening agent is selected from any one or more of tert-butanol, n-hexanol, propanol, cyclopentanol, 2-propanol, methanol, ethanol, water, benzyl alcohol, ethylene glycol, and glycerol. The ring-opening agent selected in this scheme has a good selective cleavage effect on the imide bond, and the mass ratio of the polyimide repeating unit to the ring-opening agent can be changed to control the generation of different reaction products.

[0020] Preferably, the mass ratio of the polyimide material to the organic solvent is 1:5~15, and the mass ratio of the polyimide material to the ring-opening agent is 1:0.1~10. When the mass ratio of the polyimide material to the organic solvent is too large, the organic solvent cannot fully swell the polyimide, which is not conducive to the ring-opening agent acting on the polyimide and reduces the ring-opening effect. When the mass ratio of the polyimide material to the organic solvent is too small, the amount of organic solvent used is large, the relative content of degradation products is low, and the economy is poor. When the mass ratio of the polyimide material to the ring-opening agent is too large, the ring-opening agent cannot exert its ring-opening effect, and the degradation reaction will basically not occur. When the mass ratio of the polyimide material to the ring-opening agent is too small, the excess of the ring-opening agent will cause the polyimide material to be completely degraded into monomers, and a polyamic acid solution cannot be obtained.

[0021] Preferably, the reaction temperature is 40~250℃, and the reaction time is 1~12 h. When the reaction temperature is below 40℃, the reaction will not occur, and when it is above 250℃, side reactions will occur. When the reaction time is less than 1 hour, the reaction is incomplete; when the reaction time is more than 12 hours, there is no significant improvement in the reaction effect, resulting in energy waste and prolonging the reaction cycle.

[0022] Preferably, the mass ratio of the polyamic acid and the homogeneous polyamic acid solution is 1:0.05~0.5; the mixing time is 1~12 h; and the mixing temperature is 25~80℃. This method prepares a polyamic acid solution by compounding two solutions, significantly reducing viscosity changes caused by the same degree of metering error, solving the problem of mass transfer difficulties, and greatly improving the uniformity of the polyamic acid solution. When the reaction temperature is below 25℃, the reaction will not occur, while above 80℃, side reactions will occur. When the reaction time is less than 1 h, the polycondensation reaction is incomplete; when the reaction time is more than 12 h, there is no significant improvement in the reaction effect.

[0023] Preferably, the high-temperature imidization temperature is 200~300℃, and the imidization time is 2~12h. When the imidization temperature is below 200℃ or the reaction time is less than 2h, the degree of imidization is insufficient; when the imidization temperature is above 300℃ or the reaction time is more than 12h, side reactions occur, but have no effect on the degree of imidization.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0025] 1. The present invention provides a method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide. The reaction process conditions are relatively mild, the recycling method is simple and easy to implement, no acid or alkali industrial wastewater is generated, the economic added value is high, and the huge energy consumption caused by the degradation and recycling of polyimide materials is avoided.

[0026] 2. This invention achieves controlled degradation of polyimide materials and recovers high-value-added polyamic acid by selectively breaking imide bonds.

[0027] 3. The preparation process is simple and low-cost, and the prepared polyimide composite film has excellent performance and can be widely used in fields such as electronic communications, aerospace and microelectronics. Attached Figure Description

[0028] Figure 1 A photograph of the actual product used to recover the polyamic acid solution;

[0029] Figure 2 Infrared spectrum of recycled polyimide film scrap;

[0030] Figure 3 This is a tensile stress-strain diagram of a polyimide composite film.

[0031] Figure 4 This is a thermal stability diagram of the polyimide composite film. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the raw materials used are all available from publicly available commercial sources.

[0033] The testing method used in the following embodiments is as follows:

[0034] Tensile strength: The tensile strength of the polyimide composite film material was tested according to GB 13022-91.

[0035] Young's modulus: The Young's modulus of composite film materials was determined according to ISO 527-2-2012.

[0036] Thermal decomposition temperature: The thermal decomposition temperature of the composite film material was determined according to GB / T 13464-2008.

[0037] Example 1

[0038] A method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide includes the following steps:

[0039] (1) 10 g of Kapton® HN polyimide film edge material (structural formula below) and 50 g of N,N-dimethylformamide and 1 g of tert-butanol as ring-opening agent were reacted in a closed container at 40 °C for 12 h to obtain a homogeneous polyamic acid mixture.

[0040] (2) Mix 100 g of polyamic acid solution and 5 g of polyamic acid homogeneous mixture at 25°C for 12 h, then stretch biaxially and imidize at 200°C in a high-temperature oven for 12 h to obtain polyimide composite film.

[0041]

[0042] The basic properties of the polyimide composite film obtained after testing are as follows:

[0043] Tensile strength: 23.2 MPa

[0044] Young's modulus: 8 GPa

[0045] Thermal decomposition temperature: 548 ℃

[0046] Figure 2 Infrared spectrum of recycled polyimide film scrap; by Figure 2 It can be seen that at 1778 cm⁻¹ in the infrared spectrum of PI -1 1717cm -1 Symmetric and asymmetric stretching vibration peaks of the carbonyl group appeared at 1373 cm⁻¹, respectively. -1 The presence of imine rings in the infrared spectrum indicates that the edge material of the polyimide film has undergone partial degradation.

[0047] Example 2

[0048] A method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide includes the following steps:

[0049] (1) 50 g of colorless transparent polyimide molding powder (structural formula as follows) and 750 g of dimethyl sulfoxide and 500 g of tert-butanol as ring-opening agents were reacted in a closed container at 250 °C for 1 h to obtain a homogeneous polyamic acid mixture.

[0050] (2) Mix 100 g of polyamic acid solution and 50 g of polyamic acid homogeneous mixture at 80°C for 1 h, then stretch biaxially and imidize at 300°C for 2 h in a high-temperature oven to obtain polyimide composite film.

[0051]

[0052] The basic properties of the prepared polyimide composite film are as follows:

[0053] Tensile strength: 17 MPa

[0054] Young's modulus: 7.3 GPa

[0055] Thermal decomposition temperature: 530 ℃

[0056] Figure 3 Tensile strain diagrams of Example 1, Example 2, and pure polyimide film materials; through Figure 3 It can be seen that, compared with pure polyimide film materials, the tensile properties of composite film materials after composite modification are slightly reduced, but the tensile strength can still be maintained above 15 MPa.

[0057] Example 3

[0058] A method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide includes the following steps:

[0059] (1) 1000 g of polyimide material (structural formula below) and 10000 g of N-methylpyrrolidone, and 5000 g of water as ring-opening agent were reacted in a closed container at 125 °C for 6 h to obtain a homogeneous polyamic acid mixture.

[0060] (2) Mix 100 g of polyamic acid solution and 25 g of polyamic acid homogeneous mixture at 40 °C for 4 h, then stretch biaxially and imidize at 250 °C for 8 h in a high-temperature oven to obtain polyimide composite film.

[0061]

[0062] The basic properties of the prepared polyimide composite film are as follows:

[0063] Tensile strength: 27.2 MPa

[0064] Young's modulus: 15.2 GPa

[0065] Thermal decomposition temperature: 550℃

[0066] Example 4

[0067] A method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide includes the following steps:

[0068] (1) 30 g of polyimide film (structural formula below) and 240 g of toluene and 240 g of glycerol as ring-opening agents were reacted in a closed container at 200 °C for 4 h at 3 MPa to obtain a homogeneous polyamic acid mixture.

[0069] (2) Mix 100 g of polyamic acid solution and 40 g of polyamic acid homogeneous mixture at 60 °C for 6 h, then stretch biaxially and imidize at 250 °C for 8 h in a high-temperature oven to obtain polyimide composite film.

[0070]

[0071] The basic properties of the prepared polyimide composite film are as follows:

[0072] Tensile strength: 28 MPa

[0073] Young's modulus: 10.3 GPa

[0074] Thermal decomposition temperature: 520℃

[0075] Figure 4 Thermal stability diagrams of pure polyimide film materials, Examples 1, 2, 3, and 4; (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 4 It can be seen that, compared with pure polyimide film materials, the thermal stability of composite polyimide films is slightly reduced, but the temperature at which 5% of the film decomposes is greater than 520 ℃, and the residual carbon content at 1000 ℃ is increased.

Claims

1. A method for the efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide, characterized in that, The process includes the following steps: mixing polyimide material, a ring-opening agent, and an organic solvent, and then reacting the mixture in a sealed container to obtain a homogeneous polyamic acid solution; mixing the obtained homogeneous polyamic acid solution with the polyamic acid raw material, and performing a thermal imidization reaction to obtain a polyimide composite film; the structural formula of the polyimide material is as follows: ； Ar1 is selected from one or more of the following structures: ； Ar2 is selected from one or more of the following structures: ； The organic solvent is selected from any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, m-cresol, nitrobenzene, dimethyl sulfoxide, toluene, formamide, and acetamide; the ring-opening agent is selected from any one or more of tert-butanol, n-hexanol, propanol, cyclopentanol, 1-propanol, methanol, ethanol, water, benzyl alcohol, ethylene glycol, and glycerol; the mass ratio of the polyimide material to the organic solvent is 1:5~15, and the mass ratio of the polyimide material to the ring-opening agent is 1:0.1~10; the reaction temperature is 40~250 °C, and the reaction time is 1~12 h; the pressure of the sealed container is 0~5 MPa.

2. The method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide according to claim 1, characterized in that, The mass ratio of the homogeneous polyamic acid solution to the polyamic acid mixture is 1:0.05~0.5, the mixing time is 1~12h, and the mixing temperature is 25~80℃.

3. The method for efficient, acid- and alkali-free, green wet micro-degradation and regeneration of polyimide according to claim 1, characterized in that, The thermal imidization temperature is 200~300℃, and the imidization time is 2~12h.

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