Polyimide precursor and preparation method thereof, fully-crosslinked polyimide ink and preparation method thereof, and polyimide material

Abstract

The invention discloses a polyimide precursor and a preparation method thereof, fully-crosslinked polyimide ink and a preparation method thereof, and a polyimide material, the preparation method of the polyimide precursor comprises the following steps: introducing a photosensitive group into a molecular structure of a dianhydride compound, and carrying out a chlorination reaction to obtain an intermediate; and reacting the intermediate with a diamine compound to obtain the photosensitive polyimide precursor. The polyimide material provided by the invention can effectively solve the problems of structural collapse and deformation of a product caused by volume shrinkage after ultraviolet curing and thermal amidation treatment during 3D printing.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, specifically to a polyimide precursor and its preparation method, a fully cross-linked polyimide ink and its preparation method, and polyimide materials. Background Technology

[0002] 3D printing is a rapid prototyping technology that does not require specific molds. It can effectively reduce labor costs, shorten product delivery time, and is beneficial for meeting the customized or personalized needs of complex structures. However, it is difficult to achieve a balance between processing and performance in the polymer materials currently used for 3D printing. High-temperature resistant polymers often exhibit problems such as fragility, poor solubility, and poor melting, making them difficult to process, while easily processed polymers often fail to meet performance specifications.

[0003] Polyimide molecules contain numerous imide groups and rigid nitrogen-containing five-membered heterocycles, which collectively enhance the bond energy of the main chain and intermolecular forces. Therefore, polyimide exhibits excellent mechanical properties, high heat resistance, and thermal stability, as well as excellent chemical resistance and UV radiation resistance. Currently, many 3D printing methods based on photosensitive polyimide synthesize polyimide by grafting acrylic groups, then formulate the polyimide with solvents, diluents, and photoinitiators to form an ink, followed by photocuring and 3D printing. However, this method suffers from severe volume shrinkage after UV curing and heat treatment, resulting in products with structural collapse and deformation. Therefore, developing low-shrinkage, high-precision, and high-structural-fidelity 3D printing polyimide materials is urgently needed. Summary of the Invention

[0004] The purpose of this application is to provide a 3D printing polyimide material with low shrinkage, high precision and high structural fidelity, which can effectively solve the problem of volume shrinkage during 3D printing due to UV curing and heat treatment, which leads to structural collapse and deformation of the product.

[0005] To achieve the above objectives, the technical solution of this application provides a polyimide precursor having the following general structural formula:

[0006]

[0007] Wherein, Ar1 is an aromatic group having two benzene rings; Ar2 is an aromatic group having 2 to 4 benzene rings; and the weight-average molecular weight of the polyimide precursor is 6000 to 30000.

[0008] In some embodiments of this application, Ar1 is selected from the following groups:

[0009]

[0010] Ar2 is selected from the following groups:

[0011]

[0012] The technical solution of this application also provides a method for preparing the above-mentioned polyimide precursor, comprising: introducing a photosensitive group into the molecular structure of a dianhydride compound, followed by a chlorination reaction to obtain an intermediate; and reacting the intermediate with a diamine compound to obtain the photosensitive polyimide precursor.

[0013] In some embodiments of this application, the method of introducing the photosensitive group into the molecular structure of the dianhydride compound includes reacting the dianhydride compound and the compound containing the photosensitive group in a molar ratio of 1:(1.0 to 1.25).

[0014] In some embodiments of this application, the dianhydride compound is selected from at least one of the following compounds:

[0015]

[0016] The compound with the photosensitive group is selected from at least one of 2-hydroxyethyl methacrylate, hydroxyethyl acrylate, methacrylate, and 2-(dimethylamino)ethyl methacrylate.

[0017] In some embodiments of this application, the diamine compound is selected from at least one of the following compounds:

[0018]

[0019] The present application also provides a fully crosslinked polyimide ink, comprising the following components by weight percentage: 30% to 50% of the aforementioned polyimide precursor; 40% to 60% of the crosslinkable solvent; 2.5% to 7.5% of the crosslinking agent; and 1.5% to 3% of the photoinitiator.

[0020] In some embodiments of this application, the crosslinkable solvent includes at least one of: N-methoxymethyl-2-methyl-2-acrylamide, N-(N-butoxymethyl)acrylamide, N-methylmethacrylamide, N-(N-butoxymethyl)acrylamide, phenyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, GAMMA-butyrolactone-3-yl isobutylene ester, N,N-dimethylacrylamide, and 2-methylenebutyrolactone.

[0021] In some embodiments of this application, the crosslinking agent includes at least one of tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol diacrylate, and polyethylene glycol diacrylate.

[0022] In some embodiments of this application, the photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]acetone-1-(O-acetyloxime).

[0023] The present application also provides a method for preparing the above-mentioned fully crosslinked polyimide ink, comprising: mixing the polyimide precursor, crosslinkable solvent, crosslinking agent and photoinitiator evenly to obtain the fully crosslinked polyimide ink.

[0024] The technical solution of this application also provides a polyimide material, which is prepared by ultraviolet curing and thermal imidization of the above-mentioned fully cross-linked polyimide ink.

[0025] The technical solution of this application uses a polyimide precursor, a crosslinkable solvent, a crosslinking agent, and a photoinitiator to compose a fully crosslinked polyimide ink. All components participate in the polymerization reaction, fundamentally solving the shrinkage problem and ensuring the stability of the product structure. At the same time, the composite material formed by the aliphatic polyacrylamide polymerized by the crosslinkable solvent and the aromatic polyimide exhibits good structural identity and there is no obvious two-phase separation. Attached Figure Description

[0026] The following accompanying drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals denote similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting and exemplary, and the drawings are for illustrative purposes only and are not intended to limit the scope of this application. Other embodiments may similarly fulfill the inventive intent of this application. It should be understood that the drawings are not drawn to scale. Wherein:

[0027] Figure 1 This is a photograph of the 3D printed product of Embodiment 1 of this application;

[0028] Figure 2 The above are the hydrogen nuclear magnetic resonance spectra of HEMA, ODPA-HEMA, and PSPAE in Example 1 of this application.

[0029] Figure 3 This is a SEM test image of the 3D printed product of Embodiment 1 of this application;

[0030] Figure 4 These are mechanical property test diagrams of the 3D printed product and the final product of Embodiment 1 of this application;

[0031] Figure 5The images show dynamic thermomechanical analysis test results of the 3D printed product, the final product, and the poly(NN) dimethacrylamide of Comparative Example 1 of this application.

[0032] Figure 6 Thermogravimetric analysis (TGA) results are shown for the 3D printed product of Example 1 of this application, the final product, and the poly(NN) dimethacrylamide of Comparative Example 1. Detailed Implementation

[0033] The following description provides specific application scenarios and requirements for this application, intended to enable those skilled in the art to make and use the content of this application. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0034] The inventors' research into current 3D printing methods revealed that severe volume shrinkage after polymerization and heat treatment during 3D printing, leading to structural collapse and deformation, is caused by the fact that current photosensitive polyimide 3D printing methods consume large amounts of organic solvents to dissolve the polyimide. Since these organic solvents are non-photosensitive molecules that do not participate in the polymerization reaction, they overflow from the system during heat treatment, resulting in severe volume shrinkage and structural collapse. If acrylic reactive monomers such as methyl methacrylate are used, polyimide does not have good solubility in them. While vinyl monomers such as 1-vinyl-2-pyrrolidone can dissolve polyimide, they cannot fully participate in polymerization due to the difference in activity between vinyl and acrylic groups, and ultimately still leave the system, leading to volume shrinkage and structural collapse.

[0035] Based on this, the present application provides a polyimide precursor and a fully crosslinked 3D printing polyimide ink system based on the polyimide precursor. All components in the system participate in the polymerization reaction, thereby fundamentally solving the shrinkage problem and ensuring the stability of the structure.

[0036] This application provides a polyimide precursor having the following general structural formula:

[0037]

[0038] Wherein, Ar1 is an aromatic group having two benzene rings; Ar2 is an aromatic group having 2 to 4 benzene rings; and the weight-average molecular weight of the polyimide precursor is 6000 to 30000.

[0039] In the above general structural formula, ether bonds (-O-) and carbonyl groups (-CO-) can reduce the interaction between molecular chains, increase the flexibility of molecular chains, and facilitate the entry of solvent molecules into the polymer network, thereby improving the solubility of polyimide precursors.

[0040] In some preferred embodiments, Ar1 is selected from the following groups:

[0041]

[0042] In some preferred embodiments, Ar2 is selected from the following groups:

[0043]

[0044]

[0045] In some specific embodiments, Ar2 is selected from the following groups:

[0046]

[0047] This application also provides a method for preparing the above-mentioned polyimide precursor, including the following steps:

[0048] Step S1: Introduce a photosensitive group into the molecular structure of a dianhydride compound, followed by a chlorination reaction to obtain an intermediate;

[0049] Step S2: React the intermediate and the diamine compound to obtain the photosensitive polyimide precursor.

[0050] In step S1, the method of introducing a photosensitive group into the molecular structure of the dianhydride compound can be to chemically react the dianhydride compound with a compound containing a photosensitive group, thereby grafting the photosensitive group onto the molecular chain of the dianhydride compound. Preferably, the molar ratio of the dianhydride compound to the compound containing the photosensitive group is 1:(1.0 to 1.25).

[0051] In some preferred embodiments, the dianhydride compound is selected from at least one of the following compounds:

[0052]

[0053] In some preferred embodiments, the compound with the photosensitive group is selected from at least one of 2-hydroxyethyl methacrylate, hydroxyethyl acrylate, methacrylate, and 2-(dimethylamino)ethyl methacrylate.

[0054] In some specific embodiments, the method for chemically reacting the dianhydride compound with a compound bearing a photosensitive group includes: dissolving the compound bearing the photosensitive group in a solvent to form a mixed system; simultaneously stirring, heating, and introducing an inert gas into the mixed system, while adding the dianhydride compound during this process; after the addition of the dianhydride compound, stirring is continued for a first time, the introduction of the inert gas is stopped, and the reaction continues for a second time under the protection of the inert gas to obtain the reaction product (hereinafter referred to as the intermediate product) of the dianhydride compound and the compound bearing the photosensitive group. The reaction temperature can be room temperature (e.g., 25°C), the first time can be 0.5 hours to 2 hours, and the second time can be 8 hours to 24 hours.

[0055] In this embodiment, the chlorination reaction refers to the reaction between the intermediate product and the chlorination reagent. Preferably, the chlorination reagent is sulfoxide. In some embodiments, the chlorination reagent can be added dropwise to a system including the intermediate product, and the intermediate can be obtained after a third reaction time. The molar ratio of the dianhydride compound and the intermediate product to the chlorination reagent can be 1:(1.0 to 1.25), the reaction conditions for the chlorination reaction can be an ice-water bath at 0°C, and the third reaction time can be 4 to 6 hours.

[0056] In some preferred embodiments, 2-hydroxyethyl methacrylate (HEMA) is selected as the compound with the photosensitive group, dimethylacetamide (DMAc) is used as the solvent, ODPA is used as the dianhydride compound, and sulfoxide chloride is used as the chlorinating agent to prepare 4,4-oxybenzoic anhydride chloride (ODPA-HEMA-Cl). The preparation reaction formula is as follows:

[0057]

[0058] In step S2, the diamine compound is preferably at least one of the following compounds:

[0059]

[0060] In some embodiments, during step S2, the diamine compound and the base are added dropwise to the intermediate, wherein the base can neutralize the acidic substances in the system, which is beneficial to the polymerization of the intermediate and the diamine compound. The reaction is carried out under an inert gas atmosphere for a third time to obtain the photosensitive polyimide precursor. The reaction temperature can be room temperature, and the third time can be 12 to 16 hours.

[0061] In some preferred embodiments, ODA is selected as the diamine compound and triethylamine is selected as the base substance to prepare ODPA-ODA-HEMA polyamide ester (PSPAE). The preparation reaction formula is as follows:

[0062]

[0063] The molar ratio of the intermediate to the diamine compound can be 1:(1.0 to 1.25).

[0064] In the embodiments of this application, the weight-average molecular weight of the photosensitive polyimide precursor can be adjusted by regulating the molar ratio of the dianhydride compound and the diamine compound. In some preferred embodiments, the molar ratio of the dianhydride compound and the diamine compound is 1:(1.0 to 1.25) to achieve a suitable weight-average molecular weight for the photosensitive polyimide precursor.

[0065] In this embodiment, the weight-average molecular weight of the photosensitive polyimide precursor is 6000-20000. If the weight-average molecular weight of the photosensitive polyimide precursor is too low, it will result in poor device toughness; if the weight-average molecular weight of the photosensitive polyimide precursor is too high, it will result in poor solubility, excessive viscosity when formulated into 3D printing ink, and low solid content.

[0066] In some embodiments, after the intermediate and diamine compound have reacted, the product is further post-processed, which includes: precipitating the product in a thin stream in a mixed solution of water and methanol (volume ratio, for example, 1:1) to obtain a precipitate; crushing the precipitate, rinsing it with deionized water and filtering it; and drying the filter material under vacuum to obtain a pure photosensitive polyimide precursor.

[0067] This application also provides a fully crosslinked polyimide ink, comprising the aforementioned polyimide precursor, a crosslinkable solvent, a crosslinking agent, and a photoinitiator. The crosslinkable solvent can both dissolve the polyimide precursor and participate in the UV curing reaction. When using the fully crosslinked polyimide ink of this application for 3D printing, all components participate in the polymerization reaction. Therefore, during UV curing and thermal imidization, there are no volatile components, effectively solving the problems of volume shrinkage and structural collapse.

[0068] In some preferred embodiments, the crosslinkable solvent includes at least one selected from: N-methoxymethyl-2-methyl-2-acrylamide, N-(N-butoxymethyl)acrylamide, N-methylmethacrylamide, N-(N-butoxymethyl)acrylamide, phenyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, GAMMA-butyrolactone-3-yl isobutylene ester, N,N-dimethylacrylamide, and 2-methylenebutyrolactone. The polymer of the polyimide precursor is an aromatic polyimide, and the polymer of the crosslinkable solvent is an aliphatic polyacrylamide. The composite material formed by the two exhibits good structural integrity and does not show significant phase separation.

[0069] In the components of the fully crosslinked polyimide ink, a higher solid content in the polyimide precursor results in better heat resistance and mechanical properties of the device; however, the ink viscosity also increases, potentially leading to printing failure. Conversely, a lower solid content in the polyimide precursor results in poorer heat resistance and mechanical properties of the device, while decreasing ink viscosity, which is beneficial for printing. A higher content of the crosslinkable solvent results in lower ink viscosity, which is more conducive to printing, but also decreases mechanical properties. In the embodiments of this application, the weight percentages of each component are: polyimide precursor 20%–60%, crosslinkable solvent 40%–60%, crosslinking agent 2.5%–7.5%, and photoinitiator 1.5%–3%. This achieves a balance between the device's heat resistance, mechanical properties, and processing performance.

[0070] The preparation method of the fully crosslinked polyimide ink includes: mixing the polyimide precursor, crosslinkable solvent, crosslinking agent and photoinitiator evenly to obtain the fully crosslinked polyimide ink.

[0071] In some embodiments, the preparation method of the fully crosslinked polyimide ink includes: first mixing the polyimide precursor, crosslinkable solvent, crosslinking agent and photoinitiator in a spin coater at a speed of 1500 rpm for 5 minutes, and then mixing at a speed of 1000 rpm for 5 minutes to obtain a uniform gelatin liquid without visible particles and precipitates, which is the fully crosslinked polyimide ink.

[0072] This application also provides a polyimide material, which is prepared by ultraviolet curing and thermal imidization of the above-mentioned fully crosslinked polyimide ink.

[0073] In some specific embodiments, the preparation method of the polyimide material includes: placing the fully cross-linked polyimide ink on the roll of a digital light processing (DLP) device, setting printing parameters with the help of a computer, and performing 3D printing to complete the ultraviolet curing process. Then, the molded product is separated by a scraper, and residual ink on the surface of the molded product is cleaned with a mixed solution of N,N-dimethylformamide (DMF) and ethanol. The molded product is then placed in a curing chamber for secondary curing with 405nm UV light. Finally, the product after secondary curing is placed in an oven for thermal imidization treatment.

[0074] Example 1

[0075] (1) Preparation of polyimide precursor

[0076] 268.33 g (3.08 mol) of DMAc and 53.0979 g (0.408 mol) of HEMA were added to a three-necked flask. Stirring was started, and 62.0420 g (0.2 mol) of ODPA was added in batches during heating, eventually stabilizing at 55 °C. These components were stirred under a nitrogen atmosphere for 1 hour. After the nitrogen atmosphere was closed, the reaction continued under a nitrogen atmosphere for 12 hours to obtain ODPA-HEMA. Then, the mixture was cooled to room temperature. 59.4850 g (0.5 mol) of thionyl chloride was added dropwise to a three-necked flask wrapped in an ice-water bath using a constant-pressure funnel. The reaction was continued at room temperature for 4 hours to prepare ODPA-HEMA-Cl.

[0077] 40.4760 g (0.4 mol) of triethylamine and 40.0473 g (0.2 mol) of ODA were added to a washed and dried 2 L three-necked flask. Under ice-water bath conditions, ODPA-HEMA-Cl was added dropwise to the flask, and the reaction continued for 6 hours under nitrogen protection to obtain ODPA-ODA-HEMA polyamide ester (PSPAE) (Mw = 16400). PSPAE was precipitated in a 1:1 water-methanol mixture by a thin stream. Larger particles were crushed to obtain a yellow powder, which was repeatedly washed with deionized water, filtered to remove moisture, and then vacuum dried in a freeze dryer for 7 days to obtain pure PSPAE.

[0078] (2) Preparation of fully crosslinked polyimide ink

[0079] 30g of PSPAE, 60g of N,N-dimethylacrylamide, 6g of tetraethylene glycol diacrylate, 1.5g of polyethylene glycol diacrylate (Mw=1000) and 2.5g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819) were mixed evenly to obtain fully crosslinked polyimide ink.

[0080] (3) Preparation of polyimide materials

[0081] 3D printing process:

[0082] Fully crosslinked polyimide ink was placed on the reel of a digital light processing (DLP) device, and printing parameters were set with the aid of a computer. During layer-by-layer printing, the exposure time for the bottom layer was 60 seconds, and there were five bottom layers, each 50 μm thick, with an exposure time of 6 seconds per layer. After printing, the molded product was separated using a squeegee, and residual ink on the surface was cleaned with DMF and ethanol. It was then placed in a curing chamber for secondary curing with 405 nm UV light to obtain the 3D printed product. See product image. Figure 1 .

[0083] Thermal imidization treatment:

[0084] The 3D printed product undergoes thermal imidization in an oven to obtain the final product. The heating program is as follows: hold at 25°C for 1 hour, hold at 50°C for 1 hour, increase to 100°C and hold for 1 hour, increase to 150°C and hold for 2 hours, increase to 200°C and hold for 2 hours, increase to 250°C and hold for 2 hours, and increase to 300°C and hold for 2 hours.

[0085] The HEMA, ODPA-HEMA, and PSPAE of this embodiment were subjected to proton nuclear magnetic resonance (NMR) spectroscopy. Figure 2 The following are the proton NMR spectra. The NMR data for HEMA and PSPAE are as follows: ¹H NMR (600 MHz, DMSO-d6, δ), HEMA: 6.06 (s, 1H), 5.68 (s, 1H), 4.83 (s, 1H), 4.10 (s, 2H), 3.61 (s, 2H), 1.89 (s, 3H); ¹H NMR (600 MHz, DMSO-d6, δ), PSPAE: 6.02 (d, J = 31.32 Hz, 1H), 5.62 (d, J = 29.22 Hz, 1H), 4.46 (s, 1H), 4.29 (s, 1H), 1.83 (d, J = 26.28 Hz, 3H).

[0086] The NMR data above show that the hydroxyl absorption peak disappears after HEMA is grafted with polyamide ester. The chemical environment of the adjacent methylene group changes from the adjacent hydroxyl group to an ether bond, with a chemical shift of 3.61 ppm to 4.46 ppm. Therefore, photosensitive modified polyimide can be successfully prepared by the chloride method.

[0087] SEM testing was performed on the 3D printed product, with test conditions including an accelerating voltage of 10kV, a magnification of 100x, and a scale size of 1mm. For example... Figure 3As shown, the dense structure between the fracture layers indicates good interlayer bonding in DLP printing, with no serious defects. The good regularity of the fractures indicates that there are no voids or breaks that occur during separation between the crosslinkable solvent and the polyimide.

[0088] Mechanical properties of 3D printed products and the final products obtained through thermoimidization were tested using a universal tensile testing machine (SUST, Zhuhai). The tensile specimens were 75mm in diameter and dumbbell-shaped, with a tensile rate of 5mm / min. Test results are shown in Table 1 and... Figure 4 As shown, 3D printed products exhibit high toughness, i.e., high elongation at break and low elastic modulus. After thermal imidization, the photosensitive polyamide ester forms aromatic conjugated amide bonds, resulting in excellent high strength properties in the final product, i.e., high elastic modulus, low elongation at break and higher tensile strength.

[0089] Table 1. Mechanical property test results of Example 1

[0090]

[0091] Comparative Example 1

[0092] N,N-dimethylacrylamide was dissolved in 2.5 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819) to obtain an N,N-dimethylacrylamide solution, which was then cured with 405 nm UV light to obtain poly(N,N-dimethylacrylamide).

[0093] The 3D printed product of Example 1, the final product after thermal imidization, and the poly(N-N) dimethacrylamide of Comparative Example 1 were tested using a dynamic thermomechanical analyzer (TA Instruments, Q800 series, USA). The temperature was increased to 320°C at a rate of 5°C / min, and the frequency was 1Hz. The test results are as follows: Figure 5 As shown, compared to poly(N-N) dimethacrylamide, the glass transition temperature of 3D printed products and the final product is increased.

[0094] The 3D printed product of Example 1, the final product obtained from thermal imidization, and the poly(NN) dimethacrylamide of Comparative Example 1 were tested using a thermogravimetric analyzer (TA Instruments, Discovery 550, USA). The product was heated to 800°C at a heating rate of 20°C / min under a nitrogen atmosphere. The test results are as follows: Figure 6 As shown. Due to the small amount of uncrosslinked photosensitive groups in the 3D printed product, there is a slight thermogravimetric peak (less than 5% of the specific gravity) between 200℃ and 280℃, while the T of the final product after thermal imidization treatment... d 5 Greater than 390℃.

[0095] Example 2

[0096] The preparation process of the polyimide precursor and the fully crosslinked polyimide ink is the same as in Example 1.

[0097] Preparation of polyimide materials

[0098] 3D printing process:

[0099] The fully crosslinked polyimide ink was placed in the tray of the digital light processing (DLP) equipment, and the printing parameters were set with the aid of a computer. During the layer-by-layer printing process, the exposure time for the bottom layer was 45 seconds, and there were three bottom layers, each with a thickness of 20 μm and an exposure time of 5 seconds. After printing, the molded product was separated using a squeegee, and any residual ink on the surface of the molded product was cleaned with DMF and ethanol.

[0100] The method of thermal imidization is the same as in Example 1.

[0101] Example 3

[0102] (1) Preparation of polyimide precursor

[0103] 268.33 g (3.08 mol) of DMAc and 53.0979 g (0.408 mol) of HEMA were added to a three-necked flask. Stirring was started, and 62.0420 g (0.2 mol) of ODPA was added in portions during heating. These components were stirred for 1 hour under a nitrogen atmosphere. After the nitrogen atmosphere was closed, the reaction continued for 12 hours under a nitrogen atmosphere to obtain ODPA-HEMA. The mixture was then cooled to room temperature. 59.4850 g (0.5 mol) of thionyl chloride was added dropwise to a three-necked flask wrapped in an ice-water bath using a constant-pressure funnel. The reaction was continued at room temperature for 4 hours to prepare ODPA-HEMA-Cl.

[0104] 40.4760 g (0.4 mol) of triethylamine and 41.0484 g (0.205 mol) of ODA were added to a washed and dried 2 L three-necked flask. Under ice-water bath conditions, ODPA-HEMA-Cl was added dropwise to the flask, and the reaction continued for 6 hours under nitrogen protection to obtain ODPA-ODA-HEMA polyamide ester (PSPAE). PSPAE was precipitated in a 1:1 water-methanol mixture as a thin stream. Larger particles were crushed to obtain a yellow powder, which was repeatedly washed with deionized water, filtered to remove moisture, and then vacuum dried in a freeze dryer for 7 days to obtain pure PSPAE.

[0105] (2) Preparation of fully crosslinked polyimide ink

[0106] 40g of PSPAE, 50g of N,N-dimethylacrylamide, 4.5g of (specific crosslinking agent name for tetraethylene glycol diacrylate), 3g of polyethylene glycol diacrylate (Mw=1000), and 2.5g of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) were mixed evenly to obtain fully crosslinked polyimide ink.

[0107] (3) The preparation method of polyimide material is the same as in Example 2.

[0108] Example 4

[0109] (1) Preparation of polyimide precursor

[0110] 213.4450 g (2.45 mol) of DMAc and 26.6791 g (0.205 mol) of HEMA were added to a three-necked flask. Stirring was started, and 44.4240 g (0.1 mol) of 6FDA was added in portions during heating. These components were stirred under a nitrogen atmosphere for 1 hour. After the nitrogen atmosphere was closed, the reaction was continued under a nitrogen atmosphere for 12 hours to obtain ODPA-HEMA. The mixture was then cooled to room temperature. 29.7425 g (0.25 mol) of thionyl chloride was added dropwise to a three-necked flask wrapped in an ice-water bath using a constant-pressure funnel. The reaction was continued at room temperature for 4 hours to prepare ODPA-HEMA-Cl.

[0111] 20.238 g (0.20 mol) of triethylamine and 20.5242 g (0.1025 mol) of ODA were added to a washed and dried 2 L three-necked flask. Under ice-water bath conditions, ODPA-HEMA-Cl was added dropwise to the flask, and the reaction continued for 6 hours under nitrogen protection to obtain ODPA-ODA-HEMA polyamide ester (PSPAE). PSPAE was precipitated in a 1:1 water-methanol mixture as a thin stream. Larger particles were crushed to obtain a yellow powder, which was repeatedly washed with deionized water, filtered to remove moisture, and then vacuum dried in a freeze dryer for 7 days to obtain pure PSPAE.

[0112] (2) Preparation of fully crosslinked polyimide ink

[0113] 40g of PSPAE, 50g of N,N-dimethylacrylamide, 6g of (tetraethylene glycol dimethacrylate), 1g of polyethylene glycol diacrylate (Mw=1200) and 3g of (phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) were mixed evenly to obtain a fully crosslinked polyimide ink.

[0114] (3) The preparation method of polyimide material is the same as in Example 2.

[0115] The height shrinkage rate of the 3D printed products from Examples 2-4 was measured at different temperatures during the thermoimidization process using vernier calipers. Measurements were taken at least three times at different locations, and the average value was recorded. The shrinkage rate (a%) of height, width, and length can all be calculated using the following formula: A 打印 It can refer to the target print height, target print length, or target print width; correspondingly, A 实际 This can refer to the actual measured height, actual measured length, or actual measured width. The test results are shown in Table 2. During the programmed temperature rise of the thermal imidization treatment, the shrinkage rates of each structure were small, indicating that the shape had high fidelity and there was no severe volume shrinkage.

[0116] Table 2. Shrinkage test results of Examples 2-4

[0117]

[0118]

[0119] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A polyimide precursor, characterized in that, It has the following general structural formula: Wherein, Ar1 is an aromatic group having two benzene rings; Ar2 is an aromatic group having 2 to 4 benzene rings; and the weight-average molecular weight of the polyimide precursor is 6000 to 30000.

2. The polyimide precursor according to claim 1, characterized in that, Ar1 is selected from the following groups: Ar2 is selected from the following groups:

3. A method for preparing the polyimide precursor as described in claim 1 or 2, characterized in that, include: A photosensitive group is introduced into the molecular structure of a dianhydride compound, followed by a chlorination reaction to obtain an intermediate. The intermediate and the diamine compound are reacted to obtain the photosensitive polyimide precursor.

4. The method for preparing the polyimide precursor according to claim 3, characterized in that, The method for introducing the photosensitive group into the molecular structure of the dianhydride compound includes reacting the dianhydride compound and the compound containing the photosensitive group in a molar ratio of 1:(1.0 to 1.25).

5. The method for preparing the polyimide precursor according to claim 4, characterized in that, The dianhydride compound is selected from at least one of the following compounds: The compound with the photosensitive group is selected from at least one of 2-hydroxyethyl methacrylate, hydroxyethyl acrylate, methacrylate, and 2-(dimethylamino)ethyl methacrylate.

6. The method for preparing the polyimide precursor according to any one of claims 3 to 5, characterized in that, The diamine compound is selected from at least one of the following compounds:

7. A fully crosslinked polyimide ink, characterized in that, Includes the following components by weight percentage:

8. The fully crosslinked polyimide ink according to claim 7, characterized in that, The crosslinkable solvent includes at least one of the following: N-methoxymethyl-2-methyl-2-acrylamide, N-(N-butoxymethyl)acrylamide, N-methylmethacrylamide, N-(N-butoxymethyl)acrylamide, phenyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, GAMMA-butyrolactone-3-yl isobutylene ester, N,N-dimethylacrylamide, and 2-methylenebutyrolactone.

9. The fully crosslinked polyimide ink according to claim 7, characterized in that, The photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]acetone-1-(O-acetyloxime).

10. The fully crosslinked polyimide ink according to claim 7, characterized in that, The crosslinking agent includes at least one of tetraethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate.

11. A method for preparing a fully crosslinked polyimide ink as described in any one of claims 7 to 10, characterized in that, include: The polyimide precursor, crosslinkable solvent, crosslinking agent, and photoinitiator are mixed evenly to obtain the fully crosslinked polyimide ink.

12. A polyimide material, characterized in that, The fully crosslinked polyimide ink according to any one of claims 7 to 10 is prepared by UV curing and thermal imidization.

Images