High-performance recoverable fluoropolyimide plastic as well as preparation method and recovery method thereof

Abstract

The invention discloses high-performance recoverable fluoropolyimide plastic as well as a preparation method and a recovery method thereof, and belongs to the technical field of recoverable plastic. According to the invention, the bifunctional aldehyde and the bifunctional hydrazide monomer are subjected to polycondensation to prepare the plastic, so that the molding processing of the plastic becomes convenient, and the gelation problem caused by crosslinking of a polyfunctional system is avoided. The prepared high-performance recyclable fluoropolyimide plastic has excellent mechanical properties and toughness, good optical properties, outstanding chemical stability and thermal properties, and unique selective solubility, so that the fluoropolyimide plastic has the performance of recycling and reprocessing, and has wide application.

Description

Technical Field

[0001] The present invention relates to the technical field of recyclable plastics, and particularly relates to a high-performance recyclable fluoropolyimide plastic, a preparation method thereof, and a recycling method thereof. Background Art

[0002] Plastics have become an indispensable and important material in human production and life. However, their non-degradability has led to plastic waste being everywhere. The sustainable recycling of plastics is an effective way to solve such a dilemma. Closed-loop recycling is a process of depolymerizing polymers to form repeating units or monomers and then re-polymerizing them to form the same material as the original polymer. The key to realizing closed-loop recycling is to introduce dynamic covalent bonds into the polymer system. The imine bond is a type of dynamic covalent bond formed based on the condensation reaction between an aldehyde group and an amino group. Due to the efficient reaction between the aldehyde group and the amino group and the mild depolymerization conditions of the imine bond without the need for a catalyst, it is often used to prepare recyclable polymers. However, imine-based polymers have problems such as low mechanical strength, poor toughness, insufficient water resistance, low thermal performance, and poor transparency, which greatly limit the application of imine-based polymers. To solve the above problems, existing research usually introduces polyfunctional aldehydes or amino compounds as dynamic covalent crosslinking points, but this makes the preparation process of polymer plastics cumbersome, not convenient for large-scale production, and the solution to the above problems is also limited, and it cannot achieve a comprehensive improvement in comprehensive performance. Therefore, how to develop high-performance recyclable polymer plastics has important social and economic value, but it is still extremely difficult.

[0003] As a high-performance plastic, polyimide has been widely used in the fields of electronics and electricity, aerospace, and microelectronics due to its excellent thermal performance, mechanical properties, and chemical stability. However, traditional polyimides, such as the most widely used Kapton film, exhibit the characteristics of being insoluble and infusible, making their recycling and reprocessing extremely difficult. Therefore, it is imperative to develop new high-performance polyimides using sustainable strategies. However, there are huge challenges in achieving the sustainability of polyimide while maintaining its high performance. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a high-performance recyclable fluoropolyimide plastic, a preparation method thereof, and a recycling method thereof. The prepared high-performance fluoropolyimide plastic has excellent transparency, water stability, high mechanical strength and toughness, and at the same time, the recycling and reprocessing of plastics can be realized.

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

[0006] The present invention provides a high-performance recyclable fluoropolyimide plastic, which is prepared by condensing fluoroimide dialdehyde and isophthaloyl hydrazide, and its structural general formula is:

[0007]

[0008] In the above general structural formula, R can be any one of the following structures:

[0009]

[0010] The present invention also provides a preparation method of a high-performance recyclable fluoropolyimide plastic, and the preparation steps include:

[0011] 1) Synthesize fluoroimide dialdehyde;

[0012] 2) Dissolve fluoroimide dialdehyde and isophthaloyl hydrazide in an organic solvent, react at 80 - 140 °C for 12 - 24 h, then fluoroimide dialdehyde and isophthaloyl hydrazide condense to obtain a fluoropolyimide plastic solution, and after molding, the organic solvent is removed by drying to obtain the fluoropolyimide plastic.

[0013] Optionally, step 1) includes:

[0014] 1.1) React a fluorinated diamine monomer with trimellitic anhydride to obtain fluoroimide diacid;

[0015] 1.2) React fluoroimide diacid with thionyl chloride to obtain fluoroimide dichloride;

[0016] 1.3) React fluoroimide dichloride with p-hydroxybenzaldehyde to obtain fluoroimide dialdehyde.

[0017] Furthermore, the steps of step 1 are:

[0018] 1.1) Select a fluorinated diamine monomer and trimellitic anhydride, heat and stir under reflux in acetic acid, after stirring under reflux for 10 - 24 hours, pour the reaction solution into ethanol or methanol to obtain a precipitate, filter and wash with ethanol, and then dry in vacuum to obtain fluoroimide diacid; the molar ratio range of the fluorinated diamine monomer to trimellitic anhydride is 1:2 - 3;

[0019] 1.2) Mix fluoroimide diacid and thionyl chloride, stir at 60 - 80 °C under a nitrogen atmosphere, after reacting for 5 - 24 hours, rotary evaporate to remove the excess thionyl chloride to obtain fluoroimide dichloride;

[0020] 1.3) Dissolve fluoroimide dichloride and p-hydroxybenzaldehyde in dichloromethane or tetrahydrofuran, add triethylamine, and stir at 0 °C - 25 °C for 6 - 24 hours; drop the reaction solution into methanol or ethanol, filter and collect the precipitate, and dry in vacuum to obtain fluoroimide dialdehyde; the molar ratio range of fluoroimide dichloride to p-hydroxybenzaldehyde is 1:3 - 5, and the molar ratio range of fluoroimide dichloride to triethylamine is 1:3 - 5.

[0021] The synthetic route of fluoroimide dialdehyde is shown as follows, where the R structure of the fluorinated diamine monomer is the same as the above R:

[0022]

[0023] Optionally, the molar ratio of the fluoroimide dialdehyde to isophthaloyl hydrazide is 1:1 - 1.05, more preferably 1:1.

[0024] Optionally, the organic solvent can be one or more of N,N - dimethylformamide, N,N - dimethylacetamide, dimethyl sulfoxide, and N - methylpyrrolidone.

[0025] Optionally, the fluoroimide dialdehyde and isophthaloyl hydrazide are dissolved in an organic solvent to form a solution with a solid content of 5% - 20%.

[0026] Optionally, the forming includes coating into a film or forming with a mold, etc.

[0027] The reaction formula for synthesizing the high - performance recyclable fluoropolyimide plastic is as follows:

[0028]

[0029] The present invention also provides a method for recycling a high - performance recyclable fluoropolyimide plastic. By the method of dissolving and re - processing the plastic, the high - performance recyclable fluoropolyimide plastic is dissolved in an organic solvent, which can be one or more of N,N - dimethylformamide, N,N - dimethylacetamide, dimethyl sulfoxide, and N - methylpyrrolidone. The solution is re - formed and dried to remove the organic solvent to obtain the fluoropolyimide plastic again.

[0030] The present invention also provides another method for recycling a high - performance recyclable fluoropolyimide plastic. By the method of depolymerizing and recycling the plastic, the high - performance recyclable fluoropolyimide plastic is dissolved in a first solvent to depolymerize and dissolve the plastic to obtain a homogeneous solution; the above solution is added to a second solvent for precipitation, and then a third solvent is added for neutralization; finally, centrifugal drying is carried out to obtain a raw material mixture of fluoroimide dialdehyde and isophthaloyl hydrazide. This mixture can be directly re - condensed to prepare a fluoropolyimide resin. The first solvent is anhydrous DMAc or anhydrous DMF, the second solvent is an aqueous hydrochloric acid solution, and the third solvent is tetrahydrofuran.

[0031] The diamine used in the present invention is isophthaloyl hydrazide. When it reacts with dialdehyde to form a Schiff base structure, the amide group is retained, which can form hydrogen bonds between polyimide chains. In addition, π - π interactions can be formed between fluoroimide dialdehydes, which can also enhance the intermolecular interaction. The introduction of fluorine elements can enhance hydrophobicity and transparency.

[0032] The beneficial effects of the present invention are as follows:

[0033] The high-performance recyclable fluoropolyimide plastic prepared by the present invention has excellent mechanical properties and toughness, good optical properties, outstanding chemical stability and thermal properties, and unique selective solubility, enabling the fluoropolyimide plastic to have two recyclable methods. The present invention only involves two monomers, dialdehyde and diamine, and does not involve 3-functional group and multi-functional group polymerization monomers, avoiding the problem of gelation during the polymerization process, enabling the entire polymerization process to be in a solution state, with mild polymerization conditions and simple polymerization and processing and forming processes.

[0034] Other features and beneficial effects of the present invention will be described in the subsequent specification, and some will be obvious from the specification or understood by implementing the present invention. Brief Description of the Drawings

[0035] Figure 1 1H NMR spectrum and 13C NMR spectrum of fluoroimide dialdehyde 2 in Example 2;

[0036] Figure 2 Infrared spectra of fluoroimide dialdehyde 2, isophthalohydrazide, and fluoropolyimide plastic 2 in Example 2;

[0037] Figure 3 UV-visible light transmittance diagram of fluoropolyimide plastic 1 in Example 1;

[0038] Figure 4 Differential scanning calorimetry curve of fluoropolyimide plastic 3 in Example 3;

[0039] Figure 5 Stress-strain curves of fluoropolyimide plastic 4 before and after being soaked in water for 24 h in Example 4;

[0040] Figure 6 Comparison diagrams of fluoropolyimide plastic 5 before and after being soaked in various solvents for 24 h in Example 5;

[0041] Figure 7 Schematic diagram of the recycling method 1 of fluoropolyimide plastic in Example 7;

[0042] Figure 8 Schematic diagram of the recycling method 2 of fluoropolyimide plastic in Example 8. Detailed Embodiments

[0043] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] Synthesis of fluoroimide dialdehyde:

[0046] Dissolve 2,2-bis(4-aminophenyl)hexafluoropropane (20 mmol) and trimellitic anhydride (20 mmol) in 120 mL of acetic acid, and reflux the reaction at 115 °C for 24 h. After the reaction cools to room temperature, precipitate with ethanol, collect the white precipitate, filter by suction, wash it repeatedly with ethanol three times, and finally dry it in a vacuum oven at 150 °C for 24 h. Fluoroimide diacid 1 is prepared.

[0047] Disperse fluoroimide diacid 1 (8 g) in 20 mL of thionyl chloride, place it at 80 °C, and after reacting for 16 h, remove thionyl chloride by rotary evaporation to obtain a yellow precipitate, fluoroimide dichloride 1.

[0048] Dissolve fluoroimide dichloride 1 (10 mmol) and p-hydroxybenzaldehyde (30 mmol) in 80 mL of tetrahydrofuran and 20 mL of dichloromethane, stir at room temperature, and simultaneously add triethylamine (30 mmol). After reacting at room temperature for 12 h, drop the reaction solution into ethanol, filter by suction to collect the precipitate, wash it with ethanol three times, and finally dry it in a vacuum oven at 80 °C for 24 h. Fluoroimide dialdehyde 1 is prepared.

[0049] Preparation method of high-performance recyclable fluoropolyimide plastic:

[0050] Dissolve fluoroimide dialdehyde 1 (0.5 mmol) and isophthaloyl hydrazide (0.5 mmol) in 10 mL of anhydrous DMAc, place it in an oil bath at 80 °C and react for 12 h, at 100 °C for 1 h; at 120 °C for 1 h; at 140 °C for 1 h. After the reaction is completed, pour the reaction solution into a mold and dry it at 80 °C for 24 hours to obtain fluoroimide plastic 1.

[0051] Example 2

[0052] Synthesis of fluoroimide dialdehyde:

[0053] Dissolve 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (20 mmol) and trimellitic anhydride (20 mmol) in 120 mL of acetic acid, and reflux the reaction at 115 °C for 24 h. After the reaction cools to room temperature, precipitate with ethanol, collect the white precipitate, filter by suction, wash it repeatedly with ethanol three times, and finally dry it in a vacuum oven at 150 °C for 24 h. Fluoroimide diacid 2 is prepared.

[0054] Disperse fluoroimide diacid 2 (8 g) in 25 mL of thionyl chloride, place it at 80 °C, and after reacting for 12 h, remove thionyl chloride by rotary evaporation to obtain a yellow precipitate, fluoroimide dichloride 2.

[0055] Dissolve fluoroimide dichloride 2 (10 mmol) and p-hydroxybenzaldehyde (30 mmol) in 100 mL of dichloromethane, stir at room temperature, and simultaneously add triethylamine (30 mmol). After reacting at room temperature for 12 h, drop the reaction solution into ethanol, filter by suction to collect the precipitate, wash it with ethanol three times, and finally dry it under vacuum in an oven at 80 °C for 24 h. Fluoroimide dialdehyde 2 is prepared.

[0056] Figure 1 1H NMR spectrum and 13C NMR spectrum of fluoroimide dialdehyde 2. It can be seen from the figure that the NMR peaks correspond one by one without impurity peaks, indicating the high purity of fluoroimide dialdehyde 2.

[0057] Preparation method of high-performance recyclable fluoropolyimide plastics:

[0058] Dissolve fluoroimide dialdehyde 2 (0.5 mmol) and isophthaloyl hydrazide (0.5 mmol) in 10 mL of anhydrous DMAc, place it in an oil bath at 80 °C and react for 12 h, at 100 °C for 1 h, at 120 °C for 1 h, at 140 °C for 1 h. After the reaction is completed, pour the reaction solution into a mold, dry it at 80 °C for 24 hours, and dry it at 140 °C for 1 h to obtain fluoroimide plastic 2.

[0059] Example 3

[0060] Synthesis of fluoroimide dialdehyde:

[0061] Dissolve N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(4-aminobenzamide) (20 mmol) and trimellitic anhydride (20 mmol) in 120 mL of acetic acid, and reflux and react at 115 °C for 24 h. After the reaction cools to room temperature, precipitate with ethanol, collect the white precipitate, filter by suction, wash it repeatedly with ethanol three times, and finally dry it under vacuum in an oven at 150 °C for 24 h. Fluoroimide diacid 3 is prepared.

[0062] Take fluoroimide diacid 3 (8 g), disperse it with 20 mL of thionyl chloride, place it at 75 °C, after reacting for 16 h, rotary evaporate to remove thionyl chloride to obtain a yellow precipitate, fluoroimide dichloride 3.

[0063] Dissolve fluoroimide dichloride 3 (10 mmol) and p-hydroxybenzaldehyde (25 mmol) in 100 mL of dichloromethane, stir at room temperature, and simultaneously add triethylamine (25 mmol). After reacting at room temperature for 12 h, drop the reaction solution into ethanol, filter by suction to collect the precipitate, wash it with ethanol three times, and finally dry it under vacuum in an oven at 80 °C for 24 h. Fluoroimide dialdehyde 3 is prepared.

[0064] Preparation method of high-performance recyclable fluoropolyimide plastics:

[0065] Dissolve fluoroimide dialdehyde 3 (0.5 mmol) and isophthalic dihydrazide (0.5 mmol) in 10 mL of anhydrous DMF, place it in an oil bath at 80 °C and react for 12 h, at 100 °C for 1 h; at 120 °C for 1 h; at 140 °C for 1 h. After the reaction is completed, pour the reaction solution into a mold, dry it at 80 °C for 24 hours, and dry it at 140 °C for 1 h to obtain fluoroimide plastic 3.

[0066] Example 4

[0067] Synthesis of fluoroimide dialdehyde:

[0068] Dissolve 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (20 mmol) and trimellitic anhydride (20 mmol) in 120 mL of acetic acid and reflux at 115 °C for 24 h. After the reaction cools to room temperature, precipitate with ethanol, collect the white precipitate, filter by suction, wash it repeatedly with ethanol 3 times, and finally dry it in a vacuum oven at 150 °C for 24 h. Fluoroimide diacid 4 is prepared.

[0069] Disperse fluoroimide diacid 4 (8 g) with 15 mL of thionyl chloride, place it at 80 °C, after reacting for 10 h, rotate and evaporate to remove thionyl chloride to obtain a yellow precipitate, fluoroimide dichloride 4.

[0070] Dissolve fluoroimide dichloride 4 (10 mmol) and p-hydroxybenzaldehyde (30 mmol) in 100 mL of tetrahydrofuran, stir at room temperature, and simultaneously add triethylamine (30 mmol). After reacting at room temperature for 12 h, drop the reaction solution into ethanol, filter by suction to collect the precipitate, wash it with ethanol 3 times, and finally dry it in a vacuum oven at 80 °C for 24 h. Fluoroimide dialdehyde 4 is prepared.

[0071] Preparation method of high-performance recyclable fluoropolyimide plastic:

[0072] Dissolve fluoroimide dialdehyde 4 (0.5 mmol) and isophthalic dihydrazide (0.5 mmol) in 10 mL of anhydrous DMAc, place it in an oil bath at 80 °C and react for 12 h, at 100 °C for 1.5 h; at 120 °C for 1.5 h; at 140 °C for 1 h. After the reaction is completed, pour the reaction solution into a mold, dry it at 80 °C for 24 hours, and dry it at 140 °C for 1 h to obtain fluoroimide plastic 4.

[0073] Example 5

[0074] Synthesis of fluoroimide dialdehyde:

[0075] Dissolve 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (20 mmol) and trimellitic anhydride (20 mmol) in 120 mL of acetic acid, and reflux the reaction at 115 °C for 24 h. After the reaction cools to room temperature, precipitate with ethanol, collect the white precipitate, filter by suction, wash it repeatedly with ethanol three times, and finally dry it under vacuum in an oven at 150 °C for 24 h. Fluoroimide diacid 5 is prepared.

[0076] Disperse fluoroimide diacid 5 (7 g) in 20 mL of thionyl chloride, place it at 80 °C, and after reacting for 16 h, rotary evaporate to remove thionyl chloride to obtain a yellow precipitate, fluoroimide dichloride 5.

[0077] Dissolve fluoroimide dichloride 5 (10 mmol) and p-hydroxybenzaldehyde (30 mmol) in 100 mL of dichloromethane, stir at room temperature, and simultaneously add triethylamine (30 mmol). After reacting at room temperature for 12 h, drop the reaction solution into ethanol, filter by suction to collect the precipitate, wash it with ethanol three times, and finally dry it under vacuum in an oven at 80 °C for 24 h. Fluoroimide dialdehyde 5 is prepared.

[0078] Preparation method of high-performance recyclable fluoropolyimide plastic:

[0079] Dissolve fluoroimide dialdehyde 5 (0.5 mmol) and isophthaloyl hydrazide (0.5 mmol) in 5 mL of anhydrous DMAc, place it in an oil bath at 80 °C and react for 12 h, at 100 °C for 1.5 h; at 120 °C for 1.5 h; at 140 °C for 1 h. After the reaction is completed, pour the reaction solution into a mold, dry it at 80 °C for 24 hours, and dry it at 140 °C for 1 h to obtain fluoroimide plastic 5.

[0080] Example 6

[0081] Synthesis of fluoroimide dialdehyde:

[0082] Dissolve 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (20 mmol) and trimellitic anhydride (20 mmol) in 120 mL of acetic acid, and reflux the reaction at 115 °C for 24 h. After the reaction cools to room temperature, precipitate with ethanol, collect the white precipitate, filter by suction, wash it repeatedly with ethanol three times, and finally dry it under vacuum in an oven at 150 °C for 24 h. Fluoroimide diacid 6 is prepared.

[0083] Take fluoroimide diacid 6 (8 g) and disperse it in 30 mL of thionyl chloride, place it at 80 °C, and after reacting for 16 h, rotary evaporate to remove thionyl chloride to obtain a yellow precipitate, fluoroimide dichloride 6.

[0084] Dissolve fluoroimide dichloride 6 (10 mmol) and p-hydroxybenzaldehyde (30 mmol) in 20 mL of dichloromethane and 80 mL of tetrahydrofuran, stir at room temperature, and simultaneously add triethylamine (30 mmol). After reacting at room temperature for 12 h, drop the reaction solution into ethanol, filter with suction to collect the precipitate, wash it three times with ethanol, and finally dry it in a vacuum oven at 80 °C for 24 h. Fluoroimide dialdehyde 6 is prepared.

[0085] Preparation method of high-performance recyclable fluoropolyimide plastics:

[0086] Dissolve fluoroimide dialdehyde 6 (0.6 mmol) and isophthaloyl hydrazide (0.5 mmol) in 10 mL of anhydrous DMAc, place it in an oil bath at 80 °C and react for 12 h, at 100 °C for 1.5 h, at 120 °C for 1.5 h, and at 140 °C for 1 h. After the reaction is completed, pour the reaction solution into a mold, dry it at 80 °C for 24 hours, and dry it at 140 °C for 1 h to obtain fluoroimide plastic 6.

[0087] Figure 2 Infrared spectra of fluoroimide dialdehyde 2, isophthaloyl hydrazide, and fluoropolyimide plastic 2 in Example 2. As can be seen from the figure, the characteristic peak of the C=N double bond appears in the PI-CHO / IPDA infrared spectrum.

[0088] Figure 3 Ultraviolet-visible light transmittance diagram of fluoropolyimide plastic 1 in Example 1. As can be seen from the figure, its transmittance to ultraviolet light is 0, its transmittance to visible light is high, and the transmittance at 550 nm is 84%.

[0089] Figure 4 Differential scanning calorimetry curve of fluoropolyimide plastic 3 in Example 3. As can be seen from the figure, its glass transition temperature is 198 °C.

[0090] Figure 5 Stress-strain curves of fluoropolyimide plastic 4 in Example 4 before and after soaking in water for 24 h. As can be seen from the figure, its tensile strength is 94.7 MPa. After soaking in deionized water for 24 h, its tensile strength remains basically unchanged.

[0091] Figure 6 Comparison diagram of fluoropolyimide plastic 5 in Example 5 before and after soaking in various solvents for 24 h. As can be seen from the figure, after soaking in common organic solvents (ethanol, acetonitrile, dichloromethane, tetrahydrofuran) for 24 h, the film does not dissolve, while it completely dissolves in DMF and DMSO solvents, showing unique selective solubility.

[0092] The tensile properties of the film were tested according to GB / T 1040.3-2006 of the national standard on a universal testing machine, and no less than five groups of test samples were taken and averaged.

[0093] The transmittance of the thin film was measured by an ultraviolet-visible spectrometer, and the transmittance of the thin film with a thickness of about 50 μm at 550 nm.

[0094] The glass transition temperature (Tg) was measured by a differential scanning calorimeter (DSC). The sample was heated from 100 - 250 °C at a heating rate of 10 °C / min under a nitrogen stream.

[0095] Table 1 Mechanical properties, optical properties and thermal properties of the fluoropolyimide plastics prepared in Examples 1 - 6

[0096]

[0097]

[0098] It can be seen from the data in Table 1 that the prepared thin films have the following advantages:

[0099] (1) Excellent mechanical properties and toughness: The high-performance recyclable fluoropolyimide plastic prepared in the present invention has a tensile strength greater than 100 MPa, a modulus between 2.4 - 3 GPa, and an elongation at break greater than 20%, showing outstanding mechanical properties;

[0100] (2) Good optical properties: The high-performance recyclable fluoropolyimide plastic prepared in the present invention has a transmittance between 82% - 85% at 550 nm and a transmittance of 0% at 400 nm, showing good light transmittance and ultraviolet shielding properties;

[0101] (3) Outstanding thermal properties: The high-performance recyclable fluoropolyimide plastic prepared in the present invention has a glass transition temperature (Tg) between 180 - 200 °C.

[0102] Example 7

[0103] Recycling method 1 of fluoropolyimide plastic: Refer to Figure 7 , weigh 2 (0.5 g) of the fluoropolyimide plastic prepared in Example 2 in 10 mL of anhydrous DMAc, place it at room temperature for 24 h to obtain a transparent mucus, pour it into a mold, and dry it at 80 °C for 24 hours. The polyimide plastic was re-prepared.

[0104] Example 8

[0105] Recycling method 2 of fluoropolyimide plastic: Refer to Figure 8, Weigh 1 (0.5 g) of the fluorinated polyimide plastic prepared in Example 1 in 10 mL of anhydrous DMAc, place it at room temperature for 24 h to obtain a transparent mucus, then add 1 M hydrochloric acid aqueous solution to obtain a polyimide depolymerization solution, drop the depolymerization solution into tetrahydrofuran, collect the precipitate and dry it to obtain a depolymerized monomer mixture. This mixture can be directly re-condensed to prepare a fluorinated polyimide resin.

[0106] The fluorinated polyimide plastic of the present invention introduces hydrazone bonds into the polymer chain through the reaction of aldehyde groups and hydrazides, increasing the hydrogen bond interaction between polymer chains. The prepared fluorinated polyimide plastic not only has high tensile strength but also exhibits high toughness. At the same time, the hydrazone bond enables the prepared fluorinated imide plastic to have reprocessing performance. The presence of the fluoroimide structure makes the prepared fluoroimide plastic have good optical properties, thermal properties, water resistance and solvent resistance. It can be applied to fields such as engineering plastics.

[0107] The above embodiments are only used to further illustrate a high-performance recyclable fluorinated polyimide plastic and its preparation method and recycling method of the present invention, but the present invention is not limited to the embodiments. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention all fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-performance recyclable fluorinated polyimide plastic, characterized in that: The fluorinated polyimide plastic is prepared by condensing fluorinated imide dialdehyde and isophthalic acid hydrazide, and its general structural formula is: Wherein, R is any one of the following structures:

2. A method for preparing the high-performance recyclable fluorinated polyimide plastic according to claim 1, characterized in that: The following steps are involved: 1) Synthesis of fluoroimide dialdehyde; 2) dissolving fluoroimide dialdehyde and isophthalic acid hydrazide in an organic solvent, reacting at 80-140° C. for 12-24 hours, condensing fluoroimide dialdehyde and isophthalic acid hydrazide to obtain a fluorinated polyimide plastic solution, and drying and removing the organic solvent after molding to obtain the fluorinated polyimide plastic.

3. The method for preparing high-performance recyclable fluorinated polyimide plastic according to claim 2, characterized in that: Step 1) includes: 1.1) reacting a fluorinated diamine monomer with trimellitic anhydride to obtain fluoroimide diacid; 1.2) reacting fluoroimide diacid with thionyl chloride to obtain fluoroimide dichloride; 1.3) Fluoroimide dichloride is reacted with p-hydroxybenzaldehyde to obtain fluoroimide dialdehyde.

4. The method for preparing high-performance recyclable fluorinated polyimide plastic according to claim 3, characterized in that: Step 1) includes: 1.1) heating the fluorinated diamine monomer and trimellitic anhydride in acetic acid with stirring and reflux, stirring and reflux for 10-24 hours, pouring the reaction solution into ethanol or methanol to obtain a precipitate, washing and vacuum drying to obtain the fluoroimide diacid; 1.2) mixing the fluoroimide diacid with thionyl chloride, reacting at 60-80° C. under a nitrogen atmosphere for 5-24 hours, and removing excess thionyl chloride to obtain the fluoroimide dichloride; 1.3) Dissolve the fluoroimide dichloride and p-hydroxybenzaldehyde in dichloromethane or tetrahydrofuran, add triethylamine, stir at 0°C-25°C for 6-24 hours, add the reaction solution dropwise into methanol or ethanol, collect the precipitate by filtration, and vacuum dry to obtain the fluoroimide dialdehyde.

5. The method for preparing high-performance recyclable fluorinated polyimide plastic according to claim 2, characterized in that: The molar ratio of the fluoroimide dialdehyde to isophthalic acid hydrazide is 1:1-1.

05.

6. The method for preparing high-performance recyclable fluorinated polyimide plastic according to claim 2, characterized in that: The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone.

7. The method for preparing high-performance recyclable fluorinated polyimide plastic according to claim 2, characterized in that: In step 2), the reaction adopts programmed temperature rise, including 60°C-80°C / 6-12h, 100°C-110°C / 1.5-2h, 120°C-130°C / 1.5-2h, 140°C-160°C / 1-2h.

8. A method for recycling high-performance recyclable fluorinated polyimide plastic according to claim 1, characterized in that: The fluorinated polyimide plastic is dissolved in an organic solvent; the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone.

9. A method for recycling high-performance recyclable fluorinated polyimide plastic according to claim 1, characterized in that: The fluoropolyimide plastic is dissolved in a first solvent to depolymerize and dissolve the plastic to obtain a uniform solution; the solution is added to a second solvent for precipitation, and then a third solvent is added for neutralization, and centrifugation and drying are performed to obtain a raw material mixture of fluoroimide dialdehyde and isophthalic acid hydrazide.

10. The method for recycling high-performance recyclable fluorinated polyimide plastic according to claim 9, characterized in that: The first solvent is anhydrous DMAc or anhydrous DMF, the second solvent is aqueous hydrogen chloride solution, and the third solvent is tetrahydrofuran.

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