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

Abstract

The invention provides a colorless transparent high-temperature-resistant polyimide material and a preparation method thereof. The colorless transparent high-temperature-resistant polyimide material is prepared from diamine and aromatic dianhydride, the diamine comprises a first diamine compound, and the first diamine compound has a nitrogen-containing aromatic heterocyclic structure and an adamantane structure. The high-performance transparent polyimide (CPI) film is prepared through molecular multi-level synchronous design, a series of diamines containing nitrogen-containing heteroaromatic rings and adamantane structures are synthesized, firstly, the rigidity and linearity of molecular chains are improved through introduction of the nitrogen-containing heteroaromatic rings, and the film is endowed with excellent heat resistance; secondly, an adamantane structure is introduced to inhibit the charge transfer (CT) effect in PI molecular chains and between the molecular chains, and the optical performance of the film is improved. The advantages of all monomers are synthesized through copolymerization, the comprehensive performance of the film is regulated and controlled, and the obtained high-performance CPI film has wide application prospects in the fields of flexible electronics and spacecraft thermal management.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a colorless, transparent, high-temperature resistant polyimide material and a preparation method thereof. Background Art

[0002] Flexible displays are gradually developing towards lightweight, ultra-thin, and fully bendable, and the demand for organic polymer films with high transparency and high temperature resistance is becoming increasingly strong. The glass transition temperature (T g ) is relatively low (<200°C) and cannot meet the processing temperature requirements of flexible display devices. Polyimide (PI) has become the preferred material for flexible display substrates and cover plates due to its excellent high and low temperature resistance and dimensional stability. Traditional aromatic polyimide films have brownish-yellow or even reddish-brown optical properties and have low light transmittance in the visible light range (400-780nm) (light transmittance at 500nm is <40%), which limits its application in flexible display and other fields. Therefore, while maintaining the excellent heat resistance of PI, improving its transparency has become a research hotspot in related fields. Summary of the Invention

[0003] The object of the present invention is to provide a colorless, transparent, high-temperature resistant polyimide material and a preparation method thereof. The polyimide material prepared by the present invention has both excellent heat resistance and optical transmittance.

[0004] The present invention provides a colorless, transparent, high-temperature resistant polyimide material, which is prepared from diamine and aromatic dianhydride;

[0005] The diamine includes a first diamine compound having a nitrogen-containing aromatic heterocyclic structure and an adamantane structure.

[0006] Preferably, the first diamine compound has one or more structures shown in Formula I-1 to Formula I-4:

[0007]

[0008] Preferably, the molar ratio of the diamine compound to the aromatic dianhydride is 0.9:1 to 1:0.9. Preferably, the aromatic dianhydride has one or more of the following structures:

[0009]

[0010] The present invention provides a method for preparing the colorless, transparent, high-temperature resistant polyimide material as described above, comprising the following steps:

[0011] A) diamine and aromatic dianhydride are stirred and polymerized in an organic solvent to obtain a polyamic acid solution;

[0012] B) mixing the polyamic acid solution, a catalyst and a dehydrating agent, and performing imidization to obtain a polyimide solution;

[0013] C) forming the polyimide solution and then curing it to obtain a colorless, transparent, and high-temperature resistant polyimide material.

[0014] Preferably, the polymerization temperature in step A) is -5 to 30° C., and the polymerization time is 6 to 108 hours.

[0015] Preferably, after the imidization reaction in step B) is completed, the present invention adds a precipitant to the obtained imidization product to precipitate the polyimide, which is filtered and then dried to obtain a polyimide powder;

[0016] The polyimide powder is redissolved in an aprotic solvent to obtain a polyimide solution.

[0017] Preferably, the first diamine compound is prepared according to the following steps:

[0018] Mixing the compound represented by Formula II, the compound represented by Formula III, a reducing agent, and a water absorbent in a solvent, and reacting them under a protective atmosphere to obtain a first diamine compound;

[0019]

[0020] Wherein, R1 is a carboxylic acid group or an acyl chloride group, R2 is an amino group, a carboxylic acid group or an acyl chloride group; R3 is an amino group, a hydroxyl group or a hydrogen atom, R4 is an amino group, a hydroxyl group or a hydrogen atom, and R3 and R4 are not hydrogen atom at the same time.

[0021] Preferably, the molar ratio of the compound represented by formula II to the compound represented by formula III is 1.05:0.5 to 1:2.1;

[0022] The solvent comprises one or more of boric acid, polyphosphoric acid and concentrated sulfuric acid, and the mass of the solvent is 5 to 15 times the mass of the compound represented by formula III;

[0023] The reducing agent includes tin powder and / or stannous chloride, and the molar ratio of the reducing agent to the first diamine compound is (5-30):100;

[0024] The water absorbing agent includes phosphorus pentoxide, and the molar ratio of the water absorbing agent to the compound represented by formula II is (0.5-2):1.

[0025] Preferably, the reaction temperature for preparing the first diamine compound is 170 to 220° C., and the reaction time is 5 to 16 hours.

[0026] Traditional aromatic polyimide films (such as Kapton U-Varnish and other commercial products) exhibit optical properties ranging from yellow to dark brown. This intrinsic coloring property causes its light transmittance to be unable to meet the transparent substrate requirements of bottom-emitting OLEDs. Improving optical transparency while maintaining the inherent high temperature resistance and dimensional stability of polyimide has become a cutting-edge topic in the current international research field. From the perspective of molecular design, there is a significant mutual constraint between the thermal stability, dimensional stability and optical transparency of polyimide materials. The research in this application found that this performance contradiction stems from the fact that the conjugated structure of the aromatic molecular chain, while giving the material high thermal stability, also leads to enhanced charge transfer, thereby reducing light transmittance. As a result, there has been no public report on a polyimide molecular structure design scheme that can fully meet the substrate indicators of bottom-emitting OLED devices.

[0027] Based on this, the present invention provides a colorless, transparent, and high-temperature resistant polyimide material, which is prepared from diamine and aromatic dianhydride; the diamine includes a first diamine compound, and the first diamine compound has a nitrogen-containing aromatic heterocyclic structure and an adamantane structure. The present invention prepares a high-performance transparent polyimide (CPI) film through molecular multi-level synchronous design, and synthesizes a series of diamines containing nitrogen-containing aromatic heterocyclic and adamantane structures. First, the introduction of the nitrogen-containing aromatic heterocyclic structure increases the rigidity and linearity of the molecular chain, giving the film excellent heat resistance; secondly, the introduction of the adamantane structure inhibits the charge transfer (CT) effect within and between the PI molecular chains, thereby improving the optical properties of the film. By combining the advantages of each monomer through copolymerization reaction and regulating the comprehensive performance of the film, the high-performance CPI film obtained has broad application prospects in the fields of flexible electronics and spacecraft thermal management. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0029] Figure 1 This is the H-NMR spectrum of the diamine monomer prepared in Example 1 of the present invention;

[0030] Figure 2 DMA curves of the polyimide films prepared in Examples 2 to 6 of the present invention;

[0031] Figure 3 TMA curves of the polyimide films prepared in Examples 2 to 6 of the present invention;

[0032] Figure 4 The UV-visible light transmission curves of the polyimide films prepared in Examples 2 to 6 of the present invention;

[0033] Figure 5 Film patterns of a polyimide film prepared in Example 4 of the present invention (left picture) and a film in the prior art (right picture). DETAILED DESCRIPTION

[0034] The present invention provides a colorless, transparent, high-temperature resistant polyimide material, which is prepared from diamine and aromatic dianhydride;

[0035] The diamine includes a first diamine compound having a nitrogen-containing aromatic heterocyclic structure and an adamantane structure.

[0036] In the present invention, the first diamine compound has one or more structures shown in Formula I-1 to Formula I-4:

[0037]

[0038] In the present invention, the diamine further comprises a second diamine compound, and the second diamine compound comprises one or more structures represented by Formula IV-1 to Formula IV-5:

[0039]

[0040] Wherein, X is -O-, -S-, -SO2-, -CO- or -C(CF3)2-; Y is -O-, -S- or -N-.

[0041] In the present invention, when the diamine contains a second diamine compound, the molar ratio of the second diamine compound to the first diamine compound is preferably 1:10 to 10:1, more preferably 1:5 to 5:1, such as 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, preferably a range value with any of the above values ​​as the upper or lower limit.

[0042] In the present invention, the aromatic dianhydride has one or more of the following structures:

[0043]

[0044] In the present invention, the molar ratio of the diamine to the aromatic dianhydride is preferably 0.9:1 to 1:0.9, more preferably 1:1.

[0045] The present invention provides a method for preparing the colorless, transparent, high-temperature resistant polyimide material described above, comprising the following steps:

[0046] A) diamine and aromatic dianhydride are stirred and polymerized in an organic solvent to obtain a polyamic acid solution;

[0047] B) mixing the polyamic acid solution, a catalyst and a dehydrating agent, and performing imidization to obtain a polyimide solution;

[0048] C) forming the polyimide solution and then curing it to obtain a colorless, transparent, and high-temperature resistant polyimide material.

[0049] In the present invention, the types and amounts of the diamine and aromatic dianhydride are consistent with those described above, and the present invention will not elaborate on them here.

[0050] In the present invention, the first diamine compound is preferably prepared according to the following steps:

[0051] Mixing the compound represented by Formula II, the compound represented by Formula III, a reducing agent, and a water absorbent in a solvent, and reacting them under a protective atmosphere to obtain a first diamine compound;

[0052]

[0053] Wherein, R1 is a carboxylic acid group or an acyl chloride group, R2 is an amino group, a carboxylic acid group or an acyl chloride group; R3 is an amino group, a hydroxyl group or a hydrogen atom, R4 is an amino group, a hydroxyl group or a hydrogen atom, and R3 and R4 are not hydrogen atom at the same time.

[0054]

[0055] In the present invention, the compound represented by formula III preferably has the following structure:

[0056]

[0057] In the present invention, the molar ratio of the compound represented by formula II to the compound represented by formula III is preferably 1.05:0.5 to 1:2.1, more preferably 1:1 to 1:2, and most preferably 1:1.5 to 1:2.

[0058] In the present invention, the reducing agent preferably includes tin powder and stannous chloride, and the molar ratio of the reducing agent to the first diamine compound is preferably (5-30):100, more preferably (10-20):100, such as 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, preferably a range value with any of the above values ​​as the upper or lower limit.

[0059] In the present invention, the water absorbent is preferably phosphorus pentoxide (P2O5), and the molar ratio of the water absorbent to the compound represented by formula II is preferably (0.5-2):1, more preferably (1-1.5):1, such as 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, .5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, preferably a range value with any of the above values ​​as the upper or lower limit.

[0060] In the present invention, the solvent preferably includes one or more of boric acid, polyphosphoric acid and concentrated sulfuric acid, and the mass of the solvent is preferably 5 to 15 times the mass of the compound represented by Formula III, more preferably 8 to 12 times, such as 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times, 12 times, 13 times, 14 times, 15 times, preferably a range value with any of the above values ​​as the upper or lower limit.

[0061] In the present invention, the above reaction is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably nitrogen and / or argon.

[0062] After the first diamine compound is prepared, the diamine containing the first diamine compound and the aromatic dianhydride are preferably mixed in an organic solvent under a protective atmosphere to perform polymerization to obtain a polyamic acid solution.

[0063] In the present invention, the organic solvent is preferably an aprotic solvent, more preferably one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO).

[0064] In the present invention, the polymerization temperature is preferably -5 to 30°C, more preferably 0 to 25°C, such as -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, preferably a range value with any of the above values ​​as the upper or lower limit; the polymerization time is preferably 6 to 108 hours, more preferably 12 to 90 hours, such as 6 hours, 12 hours, 24 hours, 36 hours, 48 ​​hours, 60 hours, 72 hours, 84 hours, 96 hours, 108 hours, preferably a range value with any of the above values ​​as the upper or lower limit.

[0065] In the present invention, the solid content of the polyamic acid is preferably 5-30wt%, more preferably 10-25wt%, such as 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0066] After obtaining the polyamic acid solution, the present invention mixes it with a catalyst and a dehydrating agent to carry out an imidization reaction. After the reaction is completed, a precipitant is added to the reaction product to precipitate polyimide, which is filtered, crushed and dried to obtain polyimide powder. The polyimide powder is then redissolved in an aprotic solvent to obtain a polyimide solution.

[0067] In the present invention, the catalyst is preferably one or more of pyridine, triethylamine, p-pyrroline, lutidine, collidine and quinoline, and the molar ratio of the catalyst to the diamine is preferably (0.1-2):1, more preferably (0.5-1.5):1, such as 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1 .5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, preferably a range value with any of the above values ​​as the upper or lower limit; the dehydrating agent preferably includes one or more of acetic anhydride, trifluoroacetic anhydride and propionic anhydride, and the molar ratio of the dehydrating agent to the diamine is preferably (2-5):1, more preferably (3-4):1, such as 2:1, 2.5:1, 3:1, .5:1, 4:1, 4.5:1, 5:1, preferably a range value with any of the above values ​​as the upper or lower limit.

[0068] In the present invention, the temperature of the imidization reaction is preferably 0 to 50° C., more preferably 10 to 40° C., such as 0° C., 10° C., 20° C., 30° C., 40° C., 50° C., preferably a range value with any of the above values ​​as the upper or lower limit; the time of the imidization reaction is preferably 6 to 12 hours, more preferably 8 to 10 hours.

[0069] In the present invention, the precipitant is preferably methanol and / or ethanol.

[0070] In the present invention, the drying temperature is preferably 100-130° C., more preferably 110-120° C., and the drying time is preferably 20-30 hours, more preferably 24-28 hours.

[0071] In the present invention, the aprotic solvent used to redissolve the polyimide powder is preferably one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO).

[0072] In the present invention, the solid content of the polyimide solution is preferably 10-25wt%, more preferably 15-20wt%, such as 10wt%, 15wt%, 20wt%, 25wt%, preferably a range with any of the above values ​​as the upper or lower limit.

[0073] After obtaining the polyimide solution, the present invention shapes the polyimide solution. The shaping can adopt common methods in the field, such as cast film, casting, or spinning. Preferably, the present invention casts the polyimide solution into a film, and after drying and curing, a colorless, transparent, and high-temperature resistant polyimide film is prepared.

[0074] In the present invention, the drying is preferably carried out according to the following heating program:

[0075] The first stage: 60-100°C, 4-6 hours; the second stage: 130-160°C, 0.5-2 hours; the third stage: 220-260°C, 0.5-2 hours; the fourth stage: 280-320°C, 0.5-2 hours.

[0076] Preferably, the drying temperature rise program is as follows:

[0077] The first stage: 80-90°C, 5-5.5 hours; the second stage: 140-150°C, 1-1.5 hours; the third stage: 240-250°C, 1-1.5 hours; the fourth stage: 300-310°C, 1-1.5 hours.

[0078] In the present invention, the polyimide film can also be prepared by a one-step method, such as adding aromatic dianhydride and diamine to a phenolic solvent such as meta-cresol and meta-chlorophenol under an inert gas atmosphere, reacting at a temperature of 190-210°C for 6-72 hours to obtain a polyimide solution, and then obtaining a polyimide film through processes such as casting and drying.

[0079] The present invention provides a colorless, transparent, and high-temperature resistant polyimide material, which is prepared from diamine and aromatic dianhydride; the diamine includes a first diamine compound, and the first diamine compound has a nitrogen-containing aromatic heterocyclic structure and an adamantane structure. The present invention prepares a high-performance transparent polyimide (CPI) film through molecular multi-level synchronous design, and synthesizes a series of diamines containing nitrogen-containing aromatic heterocyclic and adamantane structures. First, the introduction of the nitrogen-containing aromatic heterocyclic structure increases the rigidity and linearity of the molecular chain, giving the film excellent heat resistance; secondly, the introduction of the adamantane structure inhibits the charge transfer (CT) effect within and between the PI molecular chains, thereby improving the optical properties of the film. By combining the advantages of each monomer through copolymerization reaction and regulating the comprehensive performance of the film, the high-performance CPI film obtained has broad application prospects in the fields of flexible electronics and spacecraft thermal management.

[0080] In order to further illustrate the present invention, a colorless, transparent, high-temperature resistant polyimide material and a preparation method thereof provided by the present invention are described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0081] Example 1

[0082] Polyphosphoric acid was heated to 60°C. Under nitrogen, polyphosphoric acid (1000g), 1,3-adamantanedicarboxylic acid (44.85g, 0.2mol), and stannous chloride dihydrate (0.02mol, 4.513g) were added to a 2L three-necked flask. 2,4-diaminophenol dihydrochloride (78.824g, 0.4mol) was then added in batches. After the additions were complete, the mixture was stirred for 3 hours until HCl gas evolution ceased. Phosphorus pentoxide (PO) (28.388g, 0.2mol) was then added and stirred for 0.5 hours. The temperature was slowly raised to 150°C, stirred for 3 hours, and then to 200°C for 10 hours. After the reaction was complete, the solution was cooled to room temperature. The pH of the solution was then adjusted to approximately 8-9 using saturated sodium carbonate solution. The solution was washed three times with water and then ethanol, filtered, and dried to obtain the crude diamine product, which was purified to obtain a white solid in a 77% yield.

[0083] The purified product was characterized by H NMR spectroscopy, and the results were as follows Figure 1 As shown: 1 H NMR (500MHz, DMSO-d6) δ = 7.30 (d, J = 8.6, 1H), 6.80 ( d, J = 2.2, 1H), 6.59 ( dd, J = 8.6, 2.3, 1H), 5.00 ( s, 2H) ,2.38(s,1H),2.26(p,J=3.0,1H),2.11(dd,J=12.9,3.0,2H),2.04(d,J=13.4,2H),1.81(d,J=3.2,1H).

[0084] The molecular structure (I-1) in this embodiment 1 is as follows:

[0085]

[0086] Example 2

[0087] Under nitrogen protection, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride 6FDA (3.554g, 0.008mol), the diamine of the structure shown in formula (III-1a) in Example 1 (3.204g, 0.008mol), and 27g of solvent N,N-dimethylacetamide were added to a three-necked flask equipped with a mechanical stirrer. The mixture was reacted at 0°C for 72h to obtain a colorless polyamic acid solution. Triethylamine (0.8g) and acetic anhydride (2.0g) were then added and stirred for 10h. The polyimide was transferred to methanol for precipitation, filtered, broken, and dried to obtain a polyimide powder. The polyimide powder was redissolved in N,N-dimethylacetamide solvent to a solid content of 15wt%. The polyimide solution was coated on a clean glass plate and the residual solvent was removed in an oven at 80°C / 5h, 150°C / 1h, 250°C / 1h, and 300°C / 1h.

[0088] Example 3

[0089] Under nitrogen, a three-necked flask equipped with a mechanical stirrer was charged with 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA) (1.793 g, 0.008 mol), the diamine represented by formula (III-1a) in Example 1 (3.204 g, 0.008 mol), and 20 g of N,N-dimethylacetamide (solvent). The mixture was reacted at 0°C for 72 hours to obtain a colorless polyamic acid solution. Triethylamine (0.8 g) and acetic anhydride (2.0 g) were then added, and stirring continued for 10 hours. The polyimide was transferred to methanol for precipitation, filtered, broken into pieces, and dried to obtain a polyimide powder. The polyimide powder was redissolved in N,N-dimethylacetamide (solvent) to a solids content of 15 wt%. The polyimide solution was coated on a clean glass plate and the residual solvent was removed in an oven at 80°C for 5 hours, 150°C for 1 hour, 250°C for 1 hour, and 300°C for 1 hour.

[0090] Example 4

[0091] Under nitrogen, a three-necked flask equipped with a mechanical stirrer was charged with cyclobutanetetracarboxylic dianhydride (CBDA) (1.569 g, 0.008 mol), the diamine represented by the structure of formula (III-1a) in Example 1 (3.204 g, 0.008 mol), and 19 g of N,N-dimethylacetamide (solvent). The mixture was reacted at 0°C for 72 hours to obtain a colorless polyamic acid solution. Triethylamine (0.8 g) and acetic anhydride (2.0 g) were then added, and stirring was continued for 10 hours. The polyimide was transferred to methanol for precipitation, filtered, broken into pieces, and dried to obtain a polyimide powder. The polyimide powder was redissolved in N,N-dimethylacetamide solvent to a solid content of 15 wt%. The polyimide solution was coated on a clean glass plate and the residual solvent was removed in an oven at 80°C for 5 hours, 150°C for 1 hour, 250°C for 1 hour, and 300°C for 1 hour.

[0092] Example 5

[0093] Under nitrogen, dimethylcyclobutanetetracarboxylic dianhydride (DMCBDA) (1.793 g, 0.008 mol), the diamine represented by formula (III-1a) in Example 1 (3.204 g, 0.008 mol), and 20 g of N,N-dimethylacetamide (solvent) were added to a three-necked flask equipped with a mechanical stirrer. The mixture was reacted at 0°C for 72 hours to obtain a colorless polyamic acid solution. Triethylamine (0.8 g) and acetic anhydride (2.0 g) were then added, and stirring was continued for 10 hours. The polyimide was transferred to methanol for precipitation, filtered, broken into pieces, and dried to obtain a polyimide powder. The polyimide powder was redissolved in N,N-dimethylacetamide solvent to a solid content of 15 wt%. The polyimide solution was coated on a clean glass plate and the residual solvent was removed in an oven at 80°C for 5 hours, 150°C for 1 hour, 250°C for 1 hour, and 300°C for 1 hour.

[0094] Example 6

[0095] Under nitrogen protection, dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride HBPDA (2.451g, 0.008mol), the diamine of the structure shown in formula (III-1a) in Example 1 (3.204g, 0.008mol), and 22g of N,N-dimethylacetamide solvent were added to a three-necked flask equipped with a mechanical stirrer. The mixture was reacted at 0°C for 72h to obtain a colorless polyamic acid solution. Triethylamine (0.8g) and acetic anhydride (2.0g) were then added and stirring continued for 10h. The polyimide was transferred to methanol for precipitation, filtered, broken, and dried to obtain a polyimide powder. The polyimide powder was redissolved in N,N-dimethylacetamide solvent to a solid content of 15wt%. The polyimide solution was coated on a clean glass plate and the residual solvent was removed in an oven at 80°C / 5h, 150°C / 1h, 250°C / 1h, and 300°C / 1h.

[0096] Example 7

[0097] Under nitrogen protection, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride (2.0g, 0.008mol), diamine of the structure shown in formula (III-1a) in Example 1 (3.204g, 0.008mol), and 21g of N,N-dimethylacetamide solvent were added to a three-necked flask equipped with a mechanical stirrer. The mixture was reacted at 0°C for 72h to obtain a colorless polyamic acid solution. Triethylamine (0.8g) and acetic anhydride (2.0g) were then added and stirred for 10h. The polyimide was transferred to methanol for precipitation, filtered, broken, and dried to obtain a polyimide powder. The polyimide powder was redissolved in N,N-dimethylacetamide solvent to a solid content of 15wt%. The polyimide solution was coated on a clean glass plate and the residual solvent was removed in an oven at 80°C / 5h, 150°C / 1h, 250°C / 1h, and 300°C / 1h.

[0098] The DMA curves of the CPI films prepared in Examples 2 to 6 are as follows: Figure 2 As shown; the TMA curve of the film is as Figure 3 As shown; the UV-visible light curve of the film is as shown Figure 4 The thermal and optical properties of the film are shown in Table 1. As can be seen from Table 1, the T g The temperature is 415℃ and the CTE value is as low as 34.7ppm·K -1 This indicates that the oxazole structure inhibits the thermal motion of the molecular chain, resulting in the film having better thermal properties and dimensional stability.

[0099] Table 1 Performance data of CPI films prepared in Examples 2 to 6

[0100]

[0101] a T g : T of the embodiment g Obtained through DMA testing;

[0102] b CTE: Example CTE values ​​were tested in the temperature range of 50-250°C;

[0103] c T 450 : Transmittance of the film at 450nm.

[0104] The transmittance of the film prepared in Example 4 at 450nm is 86%. The prepared polyimide film has excellent optical transparency. Figure 5 Left) and the film pattern of Example 9 in patent CN115716990A ( Figure 5 For comparison, Figure 5As shown, it can be seen that the introduction of the adamantane structure significantly improves the optical properties of the film compared to the aromatic ring, and has better optical transparency.

[0105] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A colorless, transparent, high-temperature resistant polyimide material prepared from diamine and aromatic dianhydride; The diamine includes a first diamine compound having a nitrogen-containing aromatic heterocyclic structure and an adamantane structure.

2. The colorless, transparent, high-temperature resistant polyimide material according to claim 1, characterized in that: The first diamine compound has one or more structures shown in Formula I-1 to Formula I-4:

3. The colorless, transparent, high-temperature resistant polyimide material according to claim 1, characterized in that: The molar ratio of the diamine compound to the aromatic dianhydride is 0.9:1 to 1:0.

9.

4. The colorless, transparent, high-temperature resistant polyimide material according to claim 1, characterized in that: The aromatic dianhydride has one or more of the following structures:

5. The method for preparing the colorless, transparent, high-temperature resistant polyimide material according to claim 1, comprising the following steps: A) diamine and aromatic dianhydride are stirred and polymerized in an organic solvent to obtain a polyamic acid solution; B) mixing the polyamic acid solution, a catalyst and a dehydrating agent, and performing imidization to obtain a polyimide solution; C) forming the polyimide solution and then curing it to obtain a colorless, transparent, and high-temperature resistant polyimide material.

6. The preparation method according to claim 5, characterized in that The polymerization temperature in step A) is -5 to 30° C., and the polymerization time is 6 to 108 hours.

7. The preparation method according to claim 5, characterized in that After the imidization reaction in step B) is completed, the present invention adds a precipitant to the obtained imidization product to precipitate polyimide 3, filters it and then dries it to obtain polyimide powder; The polyimide powder is redissolved in an aprotic solvent to obtain a polyimide solution.

8. The preparation method according to claim 5, characterized in that The first diamine compound is prepared according to the following steps: Mixing the compound represented by Formula II, the compound represented by Formula III, a reducing agent, and a water absorbent in a solvent, and reacting them under a protective atmosphere to obtain a first diamine compound; Wherein, R1 is a carboxylic acid group or an acyl chloride group, R2 is an amino group, a carboxylic acid group or an acyl chloride group; R3 is an amino group, a hydroxyl group or a hydrogen atom, R4 is an amino group, a hydroxyl group or a hydrogen atom, and R3 and R4 are not hydrogen atom at the same time.

9. The preparation method according to claim 8, characterized in that The molar ratio of the compound represented by formula II to the compound represented by formula III is 1.05:0.5 to 1:2.1; The solvent comprises one or more of boric acid, polyphosphoric acid and concentrated sulfuric acid, and the mass of the solvent is 5 to 15 times the mass of the compound represented by formula III; The reducing agent includes tin powder and / or stannous chloride, and the molar ratio of the reducing agent to the first diamine compound is (5-30):100; The water absorbing agent includes phosphorus pentoxide, and the molar ratio of the water absorbing agent to the compound represented by formula II is (0.5-2):

1.

10. The preparation method according to claim 8, characterized in that The reaction temperature for preparing the first diamine compound is 170 to 220° C., and the reaction time is 5 to 16 hours.

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