Colorless transparent high-temperature-resistant polyimide and preparation method thereof

Abstract

The application discloses a colorless transparent high-temperature-resistant polyimide and a preparation method thereof, and belongs to the technical field of polyimide preparation. The preparation method of the colorless transparent high-temperature-resistant polyimide comprises the following steps: step one, under a nitrogen environment, a new type of diamine monomer is added to an organic solvent and stirred and dissolved to obtain a diamine solution; step two, a new type of dianhydride monomer is added to the diamine solution and stirred and reacted to obtain a polyamide acid solution; step three, a catalyst is added to the polyamide acid solution, the mixture is uniformly stirred, an external electric field is applied, and an imidization reaction is carried out by heating; after the reaction is completed, the mixture is cooled, poured into a precipitant, filtered, washed, and vacuum dried to obtain the colorless transparent high-temperature-resistant polyimide. The polyimide prepared by the method has excellent high-temperature resistance and high transparency.

Description

Technical Field

[0001] This invention belongs to the field of polyimide preparation technology, specifically relating to colorless, transparent, high-temperature resistant polyimide and its preparation method. Background Technology

[0002] Polyimide (CPI), as a high-performance polymer material, possesses excellent high-temperature resistance, mechanical properties, and chemical stability, and is widely used in electronics, aerospace, and display industries. Especially in high-end display fields such as Micro-OLED, the requirements for the material's optical properties, high-temperature resistance, and dimensional stability are extremely high.

[0003] Traditional polyimides generally suffer from a high yellowness index, which seriously affects the performance of high-end display applications. At the same time, the birefringence phenomenon is obvious, which leads to changes in the polarization state of light and reduces the display quality. Furthermore, some existing transparent polyimides have a significantly reduced light transmittance and are prone to yellowing at temperatures above 300°C, which cannot meet the requirements of optical components in high-temperature scenarios.

[0004] Current industry research struggles to simultaneously achieve a yellowness index below 2.0, light transmittance above 90%, and resistance to temperatures above 300℃, while also lacking effective molecular chain modulation technology to reduce birefringence, making it difficult to meet the stringent requirements of high-end displays. Therefore, developing polyimide materials that combine colorless transparency, high temperature resistance, yellowing resistance, and low birefringence to fill the technological gap in high-temperature optical applications has become an urgent technical challenge. Summary of the Invention

[0005] The purpose of this invention is to provide a colorless, transparent, high-temperature resistant polyimide and its preparation method, in order to solve the technical problems of poor transparency and high-temperature resistance of polyimides in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a colorless, transparent, high-temperature resistant polyimide, which is composed of the following components by weight: 40-60 parts of a novel diamine monomer, 40-60 parts of a novel dianhydride monomer, 100-200 parts of an organic solvent, and 1-2 parts of a catalyst.

[0007] Preferably, the method for preparing the novel diamine monomer includes the following steps: Q1: Under nitrogen atmosphere, 9H-fluorene-9-methylamine, 4-fluoronitrobenzene, triethylamine and dimethyl sulfoxide were added to a container, heated and stirred to react. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized to obtain product 1. Under nitrogen atmosphere, product 1, 2-bromo-9,9'-spirodifluorene, copper powder, potassium carbonate, 18-crown ether-6 and o-dichlorobenzene were added to a container, heated and stirred to react, filtered, distilled under reduced pressure, and recrystallized to obtain product 2. Q2: Add product 2, 1,4-dioxane and Pd / C to a container, heat to reflux, add hydrazine hydrate, continue the reaction, filter, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain product 3; under a nitrogen atmosphere, add product 3, 4-fluoronitrobenzene, cesium fluoride and dimethyl sulfoxide to a container, heat and stir the reaction, cool, add to ethanol, precipitate solid, recrystallize to obtain product 4; Q3: Add products 4, 1,4-dioxane and Pd / C to a container, heat to reflux, add hydrazine hydrate, continue the reaction, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

[0008] In the above process, the synthetic reaction formula for the novel diamine monomer is as follows:

[0009] The mass spectrometry analysis results for product 1 were: m / z: 316.12 (100.0%), 317.12 (22.4%), 318.13 (2.7%); for product 2: m / z: 630.23 (100.0%), 631.23 (49.5%), 632.24 (11.8%), 633.24 (2.0%); for product 3: m / z: 600.26 (100.0%), 601.26 (49.0%), 602.26 (11.9%), 603.27 (1.8%); and for product 4: m / z: 842.29 (100.0%), 843.29 (63.3%), 844.30. (19.0%), 845.30 (4.3%), 844.29 (1.7%); The mass spectrometry analysis results of the novel diamine monomer are: m / z: 782.34 (100.0%), 783.34 (63.1%), 784.35 (19.0%), 785.35 (3.8%).

[0010] Preferably, in Q1, the molar ratio of 9H-fluorene-9-methylamine, 4-fluoronitrobenzene, triethylamine, and dimethyl sulfoxide is (38.38-42.54) g : (32.23-38.61) g : (31.12-33.46) : (250-290) mL. The mixture is heated to 80-90℃ and stirred for 36-48 h, then recrystallized with ethanol and N,N-dimethylformamide; the product is 1,2-bromo-9,9-methylamine. The ratio of '-spirodifluorene, copper powder, potassium carbonate, 18-crown ether-6 and o-dichlorobenzene was (6.02-6.43) g : (8.82-9.23) g : (5.34-5.98) g : (12.28-13.04) g : (2.88-3.11) g : (45-52) mL. The mixture was heated to 160-165℃ and stirred for 15-20 h. The mixture was then recrystallized with ethanol and N,N-dimethylacetamide.

[0011] Preferably, in Q2, the ratio of product 2, 1,4-dioxane, Pd / C, and hydrazine hydrate is (8.82-9.13) g : (75-85) mL : (0.92-1.05) g : (9.89-10.36) g, and the mixture is heated to 60-75℃ and reacted for 4-6 h; the ratio of product 3, 4-fluoronitrobenzene, cesium fluoride, and dimethyl sulfoxide is (5.68-6.31) g : (3.22-3.65) g : (4.02-4.43) g : (35-45) mL, and the mixture is heated to 120-140℃ and stirred for 18-20 h, and then recrystallized with acetic acid and N,N-dimethylformamide.

[0012] Preferably, in Q3, the ratio of product 4, 1,4-dioxane, Pd / C and hydrazine hydrate is (6.28-6.88) g : (45-55) mL : (1.56-2.12) g : (9.46-10.27) g, and the mixture is heated to 60-70℃ and the reaction continues for 20-24 h.

[0013] Preferably, the method for preparing the novel dianhydride monomer includes the following steps: S1: 2,7-Dichloro-9-fluorenone and phenol were added to a container containing o-xylene. After heating and stirring, the mixture was cooled, filtered, washed, and recrystallized to obtain solid a. 4-Nitrophthalonitrile and dimethyl sulfoxide were added to a container. After stirring and mixing, solid a and potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere. After the reaction was completed, the mixture was added to ice water, filtered, purified, and recrystallized to obtain crystal b. S2: Add crystal b, potassium hydroxide, anhydrous ethanol and distilled water to a container in sequence, heat and stir to react, filter while hot, add the filtrate to distilled water, adjust the pH, filter, wash and dry to obtain solid c; S3: Add solid c and glacial acetic acid to a container, heat and stir to dissolve, then add acetic anhydride, heat under reflux to react, cool, filter, and recrystallize to obtain a novel dianhydride monomer.

[0014] In the above process, the synthesis reaction formula for the novel dianhydride monomer is as follows:

[0015] The mass spectrometry analysis results for solid a are: m / z: 364.11 (100.0%), 365.11 (27.2%), 366.12 (3.6%); the mass spectrometry analysis results for crystal b are: m / z: 616.15 (100.0%), 617.16 (44.7%), 618.16 (10.4%), 619.16 (1.8%), 617.15 (1.5%); the mass spectrometry analysis results for solid c are: m / z: 692.13 (100.0%), 693.14 (45.0%), 694.14 (12.2%), 695.14 (2.4%); the mass spectrometry analysis results for the novel dianhydride monomer are: m / z: 656.11 (100.0%), 657.11. (44.7%), 658.12 (9.8%), 659.12 (2.2%), 658.11 (1.8%).

[0016] Preferably, in S1, the ratio of 2,7-dichloro-9-fluorenone, phenol, and o-xylene is (18.88-20.06) g : (31.12-34.68) g : (76-88) mL, the mixture is heated to 120-130℃ and stirred for 10-12 h, washed with dichloromethane, and recrystallized with acetone; the ratio of 4-nitrophthalonitrile, dimethyl sulfoxide, solid a, and potassium carbonate is (3.12-3.81) g : (25-35) mL : (3.56-4.06) g : (4.02-4.26) g, the mixture is reacted at room temperature for 20-24 h, and recrystallized in acetonitrile using a 2:1 volume ratio of dichloromethane and petroleum ether as the eluent.

[0017] Preferably, in step S2, the ratio of crystal b, potassium hydroxide, anhydrous ethanol, and distilled water is (6.12-6.44) g : (5.12-5.98) g : (50-55) mL : (45-55) mL. The mixture is heated to 100-104℃ and stirred for 40-50 h. The pH is adjusted to 1-2 with 1 mol / L hydrochloric acid, and the mixture is washed with distilled water. In step S3, the ratio of solid c, glacial acetic acid, and acetic anhydride is (6.88-7.24) g : (45-55) mL : (20-30) mL. The mixture is heated to 120-130℃ and refluxed for 4-6 h. Recrystallization is then carried out in acetic anhydride.

[0018] Preferably, the preparation method of the colorless, transparent, high-temperature resistant polyimide includes the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to an organic solvent and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution, stir and react to obtain a polyamic acid solution; Step 3: Add the catalyst to the polyamic acid solution, stir evenly, apply an external electric field, and heat to carry out the imidization reaction. After the reaction is completed, cool, pour into a precipitant for precipitation, filter, wash, and vacuum dry to obtain colorless, transparent, high-temperature resistant polyimide.

[0019] Preferably, in step one, the organic solvent is composed of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; in step two, the stirring reaction temperature is 0-30℃, and the time is 4-12h; in step three, the catalyst is composed of one or more of triethylamine, pyridine, and imidazole, an external electric field is applied to assist molecular chain orientation, the electric field strength is 1-10kV / cm, the heating rate is 1-5℃ / min, the temperature is raised to 150-250℃ and held for 2-6h, and the precipitant is composed of one or more of ethanol, methanol, and deionized water, and vacuum dried at 100-150℃ for 8-12h.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In the process of preparing polyimide, the present invention uses novel diamine monomers and novel dianhydride monomers as raw materials, so that the obtained polyimide has excellent solubility, thermal stability and high transparency.

[0021] 2. This invention uses the novel diamine monomer obtained as a raw material for polyimide, which can give it excellent solubility, high optical transparency, and high thermal stability. The fluorene and spirodifluorene structures contained in the novel diamine monomer have a large volume, non-coplanar, and rigid backbone, which can effectively disrupt the close packing of polymer molecular chains, increase the free volume between chains, and weaken the formation of charge-transfer complexes, thereby reducing the absorption of polyimide in the visible light region, improving transparency, and reducing yellowing. At the same time, the large volume side groups hinder the regular arrangement of molecular chains, making it easier for solvent molecules to penetrate, giving the material good solubility in common organic solvents and facilitating processing. Meanwhile, the rigid spirocyclic structure restricts chain segment movement, increases the glass transition temperature and thermal decomposition temperature, and enhances heat resistance.

[0022] 3. This invention applies the novel dianhydride monomer obtained to the preparation process of polyimide, which can not only effectively improve its optical transparency and thermal stability, but also improve its solubility and processing performance. The fluorene group contained in the novel dianhydride monomer has a large steric hindrance, which can effectively destroy the conjugation of the polyimide molecular backbone and inhibit the formation of intramolecular and intermolecular charge transfer complexes, thereby significantly reducing the absorption of polyimide in the visible light region and making it exhibit good transparency. The flexible ether bond contained therein further increases the flexibility of the molecular chain, reduces the close packing between chains, and synergistically improves the light transmittance. At the same time, the non-coplanar structure of the fluorene skeleton and its large volume hinder the close packing of polymer molecular chains, increase the free volume, and enable polyimide to dissolve in organic solvents while maintaining excellent heat resistance, thus improving its processing performance. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: This example discloses a novel method for preparing a diamine monomer, comprising the following steps: Q1: Under nitrogen atmosphere, 40.42 g of 9H-fluorene-9-methylamine, 35.42 g of 4-fluoronitrobenzene, 32.24 g of triethylamine and 270 mL of dimethyl sulfoxide were added to a container, heated to 85 °C and stirred for 48 h. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized with ethanol and N,N-dimethylformamide to obtain product 1. Under nitrogen atmosphere, 6.22 g of product 1, 9.02 g of 2-bromo-9,9'-spirodifluorene, 5.62 g of copper powder, 12.67 g of potassium carbonate, 2.99 g of 18-crown ether-6 and 47 mL of o-dichlorobenzene were added to a container, heated to 160 °C and stirred for 20 h. After filtration, the mixture was distilled under reduced pressure and recrystallized with ethanol and N,N-dimethylacetamide to obtain product 2. Q2: 8.94 g of product 2, 80 mL of 1,4-dioxane and 0.98 g of Pd / C were added to a container, heated to 65 °C under reflux, and then 10.02 g of hydrazine hydrate was added. The reaction was continued for 6 h, filtered, concentrated by vacuum distillation, and cooled under a nitrogen atmosphere to obtain product 3. Under a nitrogen atmosphere, 5.94 g of product 3, 3.44 g of 4-fluoronitrobenzene, 4.22 g of cesium fluoride and 40 mL of dimethyl sulfoxide were added to a container, heated to 130 °C and stirred for 20 h. After cooling, the mixture was added to ethanol, and a solid precipitated. The solid was recrystallized with acetic acid and N,N-dimethylformamide to obtain product 4. Q3: Add 6.58g of product 4, 50mL of 1,4-dioxane and 1.84g of Pd / C to a container, heat to 65℃ and reflux, then add 9.86g of hydrazine hydrate, continue the reaction for 24h, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

[0025] This embodiment discloses a novel method for preparing dianhydride monomers, including the following steps: S1: 19.74 g of 2,7-dichloro-9-fluorenone and 32.38 g of phenol were added to a container containing 84 mL of o-xylene. The mixture was heated to 125 °C and stirred for 12 h. After cooling, the mixture was filtered, washed with dichloromethane, and recrystallized with acetone to obtain solid a. 3.42 g of 4-nitrophthalonitrile and 30 mL of dimethyl sulfoxide were added to a container. After stirring and mixing, 3.86 g of solid a and 4.14 g of potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere for 24 h. After the reaction was completed, the mixture was added to ice water, filtered, and purified using a 2:1 (v / v) mixture of dichloromethane and petroleum ether as eluent. The mixture was then recrystallized in acetonitrile to obtain crystal b. S2: 6.28g of crystal b, 5.58g of potassium hydroxide, 53mL of anhydrous ethanol and 50mL of distilled water were added to a container in sequence. The mixture was heated to 100℃ and stirred for 48h. The mixture was then filtered while hot. The filtrate was added to distilled water and the pH was adjusted to 1.6 with 1mol / L hydrochloric acid. The mixture was then filtered, washed with distilled water, and dried to obtain solid c. S3: Add 7.02g of solid c and 50mL of glacial acetic acid to a container, heat and stir to dissolve, then add 25mL of acetic anhydride, heat to 125℃ and reflux for 6h, cool, filter, and recrystallize in acetic anhydride to obtain a novel dianhydride monomer.

[0026] This embodiment discloses a colorless, transparent, high-temperature resistant polyimide, which is composed of the following components by weight: 50 parts of a novel diamine monomer, 50 parts of a novel dianhydride monomer, 150 parts of N,N-dimethylformamide, and 1.5 parts of triethylamine.

[0027] This embodiment discloses a method for preparing colorless, transparent, high-temperature resistant polyimide, including the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to N,N-dimethylformamide and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution and stir at 27°C for 8 hours to obtain a polyamic acid solution; Step 3: Add triethylamine to the polyamic acid solution, stir evenly, and then apply an external electric field to assist in molecular chain orientation (place the polyamic acid solution between two electrodes with a distance of 3 cm between the electrodes, and the direction of the electric field is parallel to the film surface). The electric field strength is 6 kV / cm. Initiate the imidization reaction by heating at a rate of 3 °C / min. Heat to 180 °C and hold for 6 h. After the reaction is complete, cool, pour into ethanol for precipitation, filter, wash, and vacuum dry at 120 °C for 12 h to obtain colorless, transparent, high-temperature resistant polyimide.

[0028] Example 2: This example discloses a novel method for preparing a diamine monomer, comprising the following steps: Q1: Under nitrogen atmosphere, 38.38 g of 9H-fluorene-9-methylamine, 32.23 g of 4-fluoronitrobenzene, 31.12 g of triethylamine, and 290 mL of dimethyl sulfoxide were added to a container, heated to 85 °C, and stirred for 48 h. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized with ethanol and N,N-dimethylformamide to obtain product 1. Under nitrogen atmosphere, 6.02 g of product 1, 8.82 g of 2-bromo-9,9'-spirodifluorene, 5.98 g of copper powder, 12.28 g of potassium carbonate, 2.88 g of 18-crown ether-6, and 45 mL of o-dichlorobenzene were added to a container, heated to 160 °C, and stirred for 20 h. After filtration and vacuum distillation, the product was recrystallized with ethanol and N,N-dimethylacetamide to obtain product 2. Q2: 8.82 g of product 2, 85 mL of 1,4-dioxane and 0.92 g of Pd / C were added to a container, heated to 65 °C under reflux, and then 9.89 g of hydrazine hydrate was added. The reaction was continued for 6 h, filtered, concentrated by vacuum distillation, and cooled under a nitrogen atmosphere to obtain product 3. Under a nitrogen atmosphere, 5.68 g of product 3, 3.22 g of 4-fluoronitrobenzene, 4.03 g of cesium fluoride and 35 mL of dimethyl sulfoxide were added to a container, heated to 130 °C and stirred for 20 h. After cooling, the mixture was added to ethanol, and a solid precipitated. The solid was recrystallized with acetic acid and N,N-dimethylformamide to obtain product 4. Q3: Add 6.28g of product 4, 45mL of 1,4-dioxane and 1.56g of Pd / C to a container, heat to 65℃ and reflux, then add 9.46g of hydrazine hydrate, continue the reaction for 24h, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

[0029] This embodiment discloses a novel method for preparing dianhydride monomers, including the following steps: S1: 18.88 g of 2,7-dichloro-9-fluorenone and 31.12 g of phenol were added to a container containing 76 mL of o-xylene. The mixture was heated to 125 °C and stirred for 12 h. After cooling, the mixture was filtered, washed with dichloromethane, and recrystallized with acetone to obtain solid a. 3.12 g of 4-nitrophthalonitrile and 35 mL of dimethyl sulfoxide were added to a container. After stirring and mixing, 3.56 g of solid a and 4.26 g of potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere for 24 h. After the reaction was completed, the mixture was added to ice water, filtered, and purified using a 2:1 (v / v) mixture of dichloromethane and petroleum ether as eluent. The purified crystals were then recrystallized in acetonitrile to obtain crystal b. S2: 6.12g of crystal b, 5.12g of potassium hydroxide, 50mL of anhydrous ethanol and 55mL of distilled water were added to a container in sequence. The mixture was heated to 100℃ and stirred for 48h. The mixture was then filtered while hot. The filtrate was added to distilled water and the pH was adjusted to 1.6 with 1mol / L hydrochloric acid. The mixture was then filtered, washed with distilled water, and dried to obtain solid c. S3: Add 6.88g of solid c and 45mL of glacial acetic acid to a container, heat and stir to dissolve, then add 20mL of acetic anhydride, heat to 125℃ and reflux for 6h, cool, filter, and recrystallize in acetic anhydride to obtain a novel dianhydride monomer.

[0030] This embodiment discloses a colorless, transparent, high-temperature resistant polyimide, which is composed of the following components by weight: 40 parts of a novel diamine monomer, 60 parts of a novel dianhydride monomer, 200 parts of N,N-dimethylacetamide, and 2 parts of pyridine.

[0031] This embodiment discloses a method for preparing colorless, transparent, high-temperature resistant polyimide, including the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to N,N-dimethylacetamide and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution and stir at 25°C for 8 hours to obtain a polyamic acid solution; Step 3: Add pyridine to the polyamic acid solution, stir evenly, and then apply an external electric field to assist in molecular chain orientation (place the polyamic acid solution between two electrodes with an electrode spacing of 3 cm and the electric field direction parallel to the film surface). The electric field strength is 4 kV / cm. Initiate the imidization reaction by heating at a rate of 3 °C / min. Heat to 180 °C and hold for 6 h. After the reaction is complete, cool, pour into ethanol for precipitation, filter, wash, and vacuum dry at 120 °C for 12 h to obtain colorless, transparent, high-temperature resistant polyimide.

[0032] Example 3: This example discloses a novel method for preparing a diamine monomer, comprising the following steps: Q1: Under nitrogen atmosphere, 42.54 g of 9H-fluorene-9-methylamine, 38.61 g of 4-fluoronitrobenzene, 33.46 g of triethylamine and 250 mL of dimethyl sulfoxide were added to a container, heated to 85 °C and stirred for 48 h. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized with ethanol and N,N-dimethylformamide to obtain product 1. Under nitrogen atmosphere, 6.43 g of product 1, 9.23 g of 2-bromo-9,9'-spirodifluorene, 5.34 g of copper powder, 13.04 g of potassium carbonate, 3.11 g of 18-crown ether-6 and 52 mL of o-dichlorobenzene were added to a container, heated to 160 °C and stirred for 20 h. After filtration, the mixture was distilled under reduced pressure and recrystallized with ethanol and N,N-dimethylacetamide to obtain product 2. Q2: 9.13g of product 2, 75mL of 1,4-dioxane and 1.05g of Pd / C were added to a container, heated to 65℃ and refluxed, then 10.36g of hydrazine hydrate was added, and the reaction was continued for 6h. After filtration, the product was concentrated by vacuum distillation and cooled under a nitrogen atmosphere to obtain product 3. Under a nitrogen atmosphere, 6.31g of product 3, 3.65g of 4-fluoronitrobenzene, 4.43g of cesium fluoride and 45mL of dimethyl sulfoxide were added to a container, heated to 130℃ and stirred for 20h, then cooled and added to ethanol. The solid precipitated and recrystallized with acetic acid and N,N-dimethylformamide to obtain product 4. Q3: Add 6.88g of product 4, 55mL of 1,4-dioxane and 2.12g of Pd / C to a container, heat to 65℃ and reflux, then add 10.27g of hydrazine hydrate, continue the reaction for 24h, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

[0033] This embodiment discloses a novel method for preparing dianhydride monomers, including the following steps: S1: 20.06 g of 2,7-dichloro-9-fluorenone and 34.68 g of phenol were added to a container containing 88 mL of o-xylene. The mixture was heated to 125 °C and stirred for 12 h. After cooling, the mixture was filtered, washed with dichloromethane, and recrystallized with acetone to obtain solid a. 3.81 g of 4-nitrophthalonitrile and 25 mL of dimethyl sulfoxide were added to a container. After stirring and mixing, 4.06 g of solid a and 4.02 g of potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere for 24 h. After the reaction was completed, the mixture was added to ice water, filtered, and purified using a 2:1 (v / v) mixture of dichloromethane and petroleum ether as eluent. The mixture was then recrystallized in acetonitrile to obtain crystal b. S2: 6.44g of crystal b, 5.98g of potassium hydroxide, 55mL of anhydrous ethanol and 45mL of distilled water were added to a container in sequence. The mixture was heated to 100℃ and stirred for 48h. The mixture was then filtered while hot. The filtrate was added to distilled water and the pH was adjusted to 1.6 with 1mol / L hydrochloric acid. The mixture was then filtered, washed with distilled water, and dried to obtain solid c. S3: Add 7.24g of solid c and 55mL of glacial acetic acid to a container, heat and stir to dissolve, then add 30mL of acetic anhydride, heat to 125℃ and reflux for 6h, cool, filter, and recrystallize in acetic anhydride to obtain a novel dianhydride monomer.

[0034] This embodiment discloses a colorless, transparent, high-temperature resistant polyimide, which is composed of the following components by weight: 60 parts of a novel diamine monomer, 40 parts of a novel dianhydride monomer, 100 parts of N-methylpyrrolidone, and 1 part of imidazole.

[0035] This embodiment discloses a method for preparing colorless, transparent, high-temperature resistant polyimide, including the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to N-methylpyrrolidone and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution and stir at 27°C for 8 hours to obtain a polyamic acid solution; Step 3: Add imidazole to the polyamic acid solution, stir evenly, and then apply an external electric field to assist in molecular chain orientation (place the polyamic acid solution between two electrodes with a distance of 3 cm between the electrodes, and the direction of the electric field is parallel to the film surface). The electric field strength is 3 kV / cm. The imidization reaction is carried out by heating at a rate of 3 °C / min. The temperature is raised to 180 °C and held for 6 h. After the reaction is completed, the mixture is cooled, poured into ethanol for precipitation, filtered, washed, and vacuum dried at 120 °C for 12 h to obtain colorless, transparent, high-temperature resistant polyimide.

[0036] Example 4: This example discloses a novel method for preparing a diamine monomer, comprising the following steps: Q1: Under nitrogen atmosphere, 39.62 g of 9H-fluorene-9-methylamine, 33.96 g of 4-fluoronitrobenzene, 31.96 g of triethylamine, and 260 mL of dimethyl sulfoxide were added to a container, heated to 85 °C, and stirred for 48 h. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized with ethanol and N,N-dimethylformamide to obtain product 1. Under nitrogen atmosphere, 6.12 g of product 1, 8.96 g of 2-bromo-9,9'-spirodifluorene, 5.79 g of copper powder, 12.46 g of potassium carbonate, 2.92 g of 18-crown ether-6, and 46 mL of o-dichlorobenzene were added to a container, heated to 160 °C, and stirred for 20 h. After filtration and vacuum distillation, the product was recrystallized with ethanol and N,N-dimethylacetamide to obtain product 2. Q2: 8.91g of product 2, 78mL of 1,4-dioxane and 0.95g of Pd / C were added to a container, heated to 65℃ and refluxed, then 9.93g of hydrazine hydrate was added, and the reaction was continued for 6h. After filtration, the product was concentrated by vacuum distillation and cooled under a nitrogen atmosphere to obtain product 3. Under a nitrogen atmosphere, 5.82g of product 3, 3.37g of 4-fluoronitrobenzene, 4.16g of cesium fluoride and 42mL of dimethyl sulfoxide were added to a container, heated to 130℃ and stirred for 20h, then cooled and added to ethanol. The solid precipitated and recrystallized with acetic acid and N,N-dimethylformamide to obtain product 4. Q3: Add 6.37g of product 4, 48mL of 1,4-dioxane and 1.78g of Pd / C to a container, heat to 65℃ and reflux, then add 9.66g of hydrazine hydrate, continue the reaction for 24h, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

[0037] This embodiment discloses a novel method for preparing dianhydride monomers, including the following steps: S1: 19.23 g of 2,7-dichloro-9-fluorenone and 32.12 g of phenol were added to a container containing 80 mL of o-xylene. The mixture was heated to 125 °C and stirred for 12 h. After cooling, the mixture was filtered, washed with dichloromethane, and recrystallized with acetone to obtain solid a. 3.28 g of 4-nitrophthalonitrile and 28 mL of dimethyl sulfoxide were added to a container. After stirring and mixing, 3.68 g of solid a and 4.21 g of potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere for 24 h. After the reaction was completed, the mixture was added to ice water, filtered, and purified using a 2:1 (v / v) mixture of dichloromethane and petroleum ether as eluent. The mixture was then recrystallized in acetonitrile to obtain crystal b. S2: 6.21g of crystal b, 5.36g of potassium hydroxide, 51mL of anhydrous ethanol and 48mL of distilled water were added to a container in sequence. The mixture was heated to 100℃ and stirred for 48h. The mixture was then filtered while hot. The filtrate was added to distilled water and the pH was adjusted to 1.6 with 1mol / L hydrochloric acid. The mixture was then filtered, washed with distilled water, and dried to obtain solid c. S3: Add 6.96g of solid c and 48mL of glacial acetic acid to a container, heat and stir to dissolve, then add 28mL of acetic anhydride, heat to 125℃ and reflux for 6h, cool, filter, and recrystallize in acetic anhydride to obtain a novel dianhydride monomer.

[0038] This embodiment discloses a colorless, transparent, high-temperature resistant polyimide, which is composed of the following components by weight: 55 parts of a novel diamine monomer, 45 parts of a novel dianhydride monomer, 120 parts of dimethyl sulfoxide, and 1.2 parts of triethylamine.

[0039] This embodiment discloses a method for preparing colorless, transparent, high-temperature resistant polyimide, including the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to dimethyl sulfoxide and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution and stir at 27°C for 8 hours to obtain a polyamic acid solution; Step 3: Add triethylamine to the polyamic acid solution, stir evenly, and then apply an external electric field to assist in molecular chain orientation (place the polyamic acid solution between two electrodes with a distance of 3 cm between the electrodes, and the direction of the electric field is parallel to the film surface). The electric field strength is 7 kV / cm. The imidization reaction is carried out by heating at a rate of 3 °C / min. The temperature is raised to 180 °C and held for 6 h. After the reaction is completed, the mixture is cooled, poured into ethanol for precipitation, filtered, washed, and vacuum dried at 120 °C for 12 h to obtain colorless, transparent, high-temperature resistant polyimide.

[0040] Example 5: This example discloses a novel method for preparing a diamine monomer, comprising the following steps: Q1: Under nitrogen atmosphere, 41.76 g of 9H-fluorene-9-methylamine, 37.12 g of 4-fluoronitrobenzene, 32.89 g of triethylamine and 280 mL of dimethyl sulfoxide were added to a container, heated to 85 °C and stirred for 48 h. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized with ethanol and N,N-dimethylformamide to obtain product 1. Under nitrogen atmosphere, 6.33 g of product 1, 9.17 g of 2-bromo-9,9'-spirodifluorene, 5.41 g of copper powder, 12.97 g of potassium carbonate, 3.04 g of 18-crown ether-6 and 50 mL of o-dichlorobenzene were added to a container, heated to 160 °C and stirred for 20 h. After filtration, the mixture was distilled under reduced pressure and recrystallized with ethanol and N,N-dimethylacetamide to obtain product 2. Q2: 9.06 g of product 2, 82 mL of 1,4-dioxane and 1.03 g of Pd / C were added to a container, heated to 65 °C under reflux, and then 10.21 g of hydrazine hydrate was added. The reaction was continued for 6 h, filtered, concentrated by vacuum distillation, and cooled under a nitrogen atmosphere to obtain product 3. Under a nitrogen atmosphere, 6.15 g of product 3, 3.56 g of 4-fluoronitrobenzene, 4.37 g of cesium fluoride and 38 mL of dimethyl sulfoxide were added to a container, heated to 130 °C and stirred for 20 h. After cooling, the mixture was added to ethanol, and a solid precipitated. The solid was recrystallized with acetic acid and N,N-dimethylformamide to obtain product 4. Q3: Add 6.68g of product 4, 52mL of 1,4-dioxane and 2.06g of Pd / C to a container, heat to 65℃ and reflux, then add 10.07g of hydrazine hydrate, continue the reaction for 24h, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

[0041] This embodiment discloses a novel method for preparing dianhydride monomers, including the following steps: S1: 19.97 g of 2,7-dichloro-9-fluorenone and 33.96 g of phenol were added to a container containing 86 mL of o-xylene. The mixture was heated to 125 °C and stirred for 12 h. After cooling, the mixture was filtered, washed with dichloromethane, and recrystallized with acetone to obtain solid a. 3.66 g of 4-nitrophthalonitrile and 32 mL of dimethyl sulfoxide were added to a container. After stirring and mixing, 3.95 g of solid a and 4.11 g of potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere for 24 h. After the reaction was completed, the mixture was added to ice water, filtered, and purified using a 2:1 (v / v) mixture of dichloromethane and petroleum ether as eluent. The mixture was then recrystallized in acetonitrile to obtain crystal b. S2: 6.37g of crystal b, 5.76g of potassium hydroxide, 54mL of anhydrous ethanol and 52mL of distilled water were added to a container in sequence. The mixture was heated to 100℃ and stirred for 48h. The mixture was then filtered while hot. The filtrate was added to distilled water and the pH was adjusted to 1.6 with 1mol / L hydrochloric acid. The mixture was then filtered, washed with distilled water, and dried to obtain solid c. S3: Add 7.13g of solid c and 52mL of glacial acetic acid to a container, heat and stir to dissolve, then add 22mL of acetic anhydride, heat to 125℃ and reflux for 6h, cool, filter, and recrystallize in acetic anhydride to obtain a novel dianhydride monomer.

[0042] This embodiment discloses a colorless, transparent, high-temperature resistant polyimide, which is composed of the following components by weight: 45 parts of a novel diamine monomer, 55 parts of a novel dianhydride monomer, 180 parts of N-methylpyrrolidone, and 1.8 parts of pyridine.

[0043] This embodiment discloses a method for preparing colorless, transparent, high-temperature resistant polyimide, including the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to N-methylpyrrolidone and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution and stir at 27°C for 8 hours to obtain a polyamic acid solution; Step 3: Add pyridine to the polyamic acid solution, stir evenly, and then apply an external electric field to assist in molecular chain orientation (place the polyamic acid solution between two electrodes with an electrode spacing of 3 cm and the electric field direction parallel to the film surface). The electric field strength is 8 kV / cm. Initiate the imidization reaction by heating at a rate of 3 °C / min. Heat to 180 °C and hold for 6 h. After the reaction is complete, cool, pour into ethanol for precipitation, filter, wash, and vacuum dry at 120 °C for 12 h to obtain colorless, transparent, high-temperature resistant polyimide.

[0044] Comparative Example 1: Compared with Example 1, Comparative Example 1 used m-phenylenediamine instead of the novel diamine monomer in the preparation of colorless transparent high-temperature resistant polyimide, while other conditions remained unchanged.

[0045] Comparative Example 2: Compared with Example 1, Comparative Example 2 used pyromellitic dianhydride instead of the novel dianhydride monomer in the preparation of colorless transparent high-temperature resistant polyimide, while other conditions remained unchanged.

[0046] Performance testing: The polyimides prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests. The glass transition temperature was tested according to GB / T19466.2-2004, the transmittance according to GB / T 2410-2008, and the yellow index according to HG / T 3862-2006. 0.1 g of sample was added to 5 mL of N,N-dimethylformamide, tetrahydrofuran, and N-methylpyrrolidone, respectively. After stirring at 45°C for 2 h, the dissolution was observed. If the sample completely dissolved to form a clear homogeneous solution, it was considered soluble; if it partially dissolved and some residue remained, it was considered partially soluble; if it was essentially insoluble and the sample remained unchanged, it was considered insoluble. The test results are shown in Table 1.

[0047] As shown in Table 1, the test results indicate that polyimides with excellent solubility, high transparency, and high heat resistance can be prepared using the methods described in Examples 1-5. A comparison between Comparative Example 1 and Examples 1-5 reveals that the use of novel diamine monomers can effectively improve the solubility, transparency, and heat resistance of polyimides; a comparison between Comparative Example 2 and Examples 1-5 reveals that the use of novel dianhydride monomers can effectively improve the solubility, transparency, and heat resistance of polyimides.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0049] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A colorless, transparent, high-temperature resistant polyimide, characterized in that, It consists of the following components by weight: 40-60 parts of novel diamine monomer, 40-60 parts of novel dianhydride monomer, 100-200 parts of organic solvent and 1-2 parts of catalyst.

2. The colorless, transparent, high-temperature resistant polyimide according to claim 1, characterized in that, The method for preparing the novel diamine monomer, Includes the following steps: Q1: Under nitrogen atmosphere, 9H-fluorene-9-methylamine, 4-fluoronitrobenzene, triethylamine and dimethyl sulfoxide were added to a container, heated and stirred to react. After the reaction was completed, the container was placed in an ice-water bath, filtered, and recrystallized to obtain product 1. Under nitrogen atmosphere, product 1, 2-bromo-9,9'-spirodifluorene, copper powder, potassium carbonate, 18-crown ether-6 and o-dichlorobenzene were added to a container, heated and stirred to react, filtered, distilled under reduced pressure, and recrystallized to obtain product 2. Q2: Add product 2, 1,4-dioxane and Pd / C to a container, heat to reflux, add hydrazine hydrate, continue the reaction, filter, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain product 3; under a nitrogen atmosphere, add product 3, 4-fluoronitrobenzene, cesium fluoride and dimethyl sulfoxide to a container, heat and stir the reaction, cool, add to ethanol, precipitate solid, recrystallize to obtain product 4; Q3: Add products 4, 1,4-dioxane and Pd / C to a container, heat to reflux, add hydrazine hydrate, continue the reaction, filter while hot, concentrate by vacuum distillation, and cool under a nitrogen atmosphere to obtain a novel diamine monomer.

3. The colorless, transparent, high-temperature resistant polyimide according to claim 2, characterized in that, In Q1, the ratio of 9H-fluorene-9-methylamine, 4-fluoronitrobenzene, triethylamine, and dimethyl sulfoxide is (38.38-42.54) g : (32.23-38.61) g : (31.12-33.46) : (250-290) mL; the ratio of product 1, 2-bromo-9,9'-spirodifluorene, copper powder, potassium carbonate, 18-crown ether-6, and o-dichlorobenzene is (6.02-6.43) g : (8.82-9.23) g : (5.34-5.98) g : (12.28-13.04) g : (2.88-3.11) g : (45-52) mL.

4. The colorless, transparent, high-temperature resistant polyimide according to claim 2, characterized in that, In Q2, the ratio of the amounts of product 2, 1,4-dioxane, Pd / C and hydrazine hydrate is (8.82-9.13) g : (75-85) mL : (0.92-1.05) g : (9.89-10.36) g; the ratio of the amounts of product 3,4-fluoronitrobenzene, cesium fluoride and dimethyl sulfoxide is (5.68-6.31) g : (3.22-3.65) g : (4.02-4.43) g : (35-45) mL.

5. The colorless, transparent, high-temperature resistant polyimide according to claim 2, characterized in that, In Q3, the ratio of the amounts of product 4, 1,4-dioxane, Pd / C and hydrazine hydrate is (6.28-6.88) g : (45-55) mL : (1.56-2.12) g : (9.46-10.27) g.

6. The colorless, transparent, high-temperature resistant polyimide according to claim 1, characterized in that, The method for preparing the novel dianhydride monomer includes the following steps: S1: 2,7-Dichloro-9-fluorenone and phenol were added to a container containing o-xylene. After heating and stirring, the mixture was cooled, filtered, washed, and recrystallized to obtain solid a. 4-Nitrophthalonitrile and dimethyl sulfoxide were added to a container. After stirring and mixing, solid a and potassium carbonate were added. The mixture was reacted at room temperature under nitrogen atmosphere. After the reaction was completed, the mixture was added to ice water, filtered, purified, and recrystallized to obtain crystal b. S2: Add crystal b, potassium hydroxide, anhydrous ethanol and distilled water to a container in sequence, heat and stir to react, filter while hot, add the filtrate to distilled water, adjust the pH, filter, wash and dry to obtain solid c; S3: Add solid c and glacial acetic acid to a container, heat and stir to dissolve, then add acetic anhydride, heat under reflux to react, cool, filter, and recrystallize to obtain a novel dianhydride monomer.

7. The colorless, transparent, high-temperature resistant polyimide according to claim 6, characterized in that, In S1, the ratio of 2,7-dichloro-9-fluorenone, phenol, and o-xylene is (18.88-20.06) g : (31.12-34.68) g : (76-88) mL; the ratio of 4-nitrophthalonitrile, dimethyl sulfoxide, solid a, and potassium carbonate is (3.12-3.81) g : (25-35) mL : (3.56-4.06) g : (4.02-4.26) g.

8. The colorless, transparent, high-temperature resistant polyimide according to claim 6, characterized in that, In S2, the ratio of crystal b, potassium hydroxide, anhydrous ethanol, and distilled water is (6.12-6.44) g : (5.12-5.98) g : (50-55) mL : (45-55) mL; in S3, the ratio of solid c, glacial acetic acid, and acetic anhydride is (6.88-7.24) g : (45-55) mL : (20-30) mL.

9. The method for preparing colorless, transparent, high-temperature resistant polyimide according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Under nitrogen atmosphere, the novel diamine monomer is added to an organic solvent and stirred to dissolve, thus obtaining a diamine solution; Step 2: Add the novel dianhydride monomer to the diamine solution, stir and react to obtain a polyamic acid solution; Step 3: Add the catalyst to the polyamic acid solution, stir evenly, apply an external electric field, and heat to carry out the imidization reaction. After the reaction is completed, cool, pour into a precipitant for precipitation, filter, wash, and vacuum dry to obtain colorless, transparent, high-temperature resistant polyimide.

10. The method for preparing colorless, transparent, high-temperature resistant polyimide according to claim 9, characterized in that, In step one, the organic solvent is composed of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; in step two, the stirring reaction temperature is 0-30℃, and the time is 4-12h; in step three, the catalyst is composed of one or more of triethylamine, pyridine, and imidazole, an external electric field is applied to assist molecular chain orientation, the electric field strength is 1-10kV / cm, the heating rate is 1-5℃ / min, the temperature is raised to 150-250℃ and held for 2-6h, and the precipitant is composed of one or more of ethanol, methanol, and deionized water.

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