A process for the preparation of a multifunctional imide alicyclic epoxy resin

Abstract

The application belongs to the technical field of functional polymer synthesis, and particularly relates to a preparation method of a multifunctional imide alicyclic epoxy resin. The multifunctional imide alicyclic epoxy resin is obtained by subjecting an imide monomer containing an N-H structure to a Michael addition reaction on an acrylate, and then being subjected to cationic photocuring and thermal curing to form a multifunctional imide alicyclic epoxy resin film. The multifunctional imide alicyclic epoxy resin prepared by the method has an epoxy group at the end, can be rapidly cured by ultraviolet light through a cationic reaction mechanism, and can also be directly heated and cured with an acid anhydride or a phenol curing agent, so that the process flow is simple and efficient. Meanwhile, the introduction of the alicyclic structure improves the comprehensive performance of the cured film, so that the cured resin has high transparency, excellent heat resistance, good weather resistance and excellent electrical performance, and can be used in the fields of LCD liquid crystal cell packaging, IC carrier board solder resist ink, LED display packaging and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer synthesis technology, specifically relating to a method for preparing a polyfunctional imide cycloaliphatic epoxy resin. Background Technology

[0002] In recent years, epoxy resins, with their high optical transparency, good mechanical properties, and low curing shrinkage, have become increasingly popular in optoelectronic and flexible display applications. However, traditional aromatic encapsulation materials and solder resists are no longer sufficient to meet current requirements due to limitations in improving water and oxygen barrier properties, coefficient of thermal expansion, and resistance to yellowing. In contrast, multifunctional imide cycloaliphatic epoxy resins possess both excellent mechanical strength and optical transparency, making them widely applicable in electrical, electronic, optical materials, and other advanced materials fields.

[0003] Studies have shown that the conversion of dianhydride monomers into diimide monomers via imidization is a simple reaction, and cyanuric acid and barbituric acid are inexpensive and readily available, possessing imide structures and NH groups, making them suitable as direct reaction raw materials. Simultaneously, through Michael addition technology, the carbon-carbon double bond of acrylate reacts with the NH groups on the imide rings of diimide, cyanuric acid, or barbituric acid, introducing the terminal epoxy groups of alicyclic epoxy acrylate monomers into the polymer backbone. This endows the polymer with properties that can be effectively cured with various curing agents such as acid anhydrides, phenols, amines, and cationic curing agents, ultimately yielding a cured material with high Tg, high heat resistance, yellowing resistance, and low CTE light. This multifunctional cured material, besides meeting the requirements of IC substrate solder resist inks, can also be applied in perovskite solar cells, novel displays, and other fields. For example, Chinese invention patent CN 116554518A reports a method for preparing acrylated polyimide, which utilizes the Michael addition reaction of imide monomers with polyacrylates to obtain acrylated polyimide. However, although the double bonds of the acrylate intermediate obtained by this method can be cured by free radical photopolymerization, oxygen has a significant inhibitory effect on free radical curing, which affects the degree of curing and results in poor overall performance of the cured resin. Therefore, it is necessary to develop a new method for preparing polyfunctional imide cycloaliphatic epoxy resins to improve the curing properties and enhance their overall performance. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a method for preparing a novel multifunctional imide alicyclic epoxy resin. By introducing epoxy groups at the ends, it can be directly subjected to cationic photocuring and thermal curing. This method is simple, energy-efficient, and low-cost. Furthermore, the introduction of the alicyclic structure improves the transparency and rigidity of the cured film, thereby enhancing the overall performance of the cured resin.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The first aspect of this invention provides a method for preparing a polyfunctional imide alicyclic epoxy resin, the method comprising the following steps:

[0007] S1. An imide alicyclic epoxy resin is synthesized by dissolving a diimide monomer containing an NH structure and an alicyclic epoxy acrylate monomer in a solvent, adding a catalyst, and then undergoing a Michael addition reaction between the NH of the imide and the double bond of the acrylate.

[0008] The NH-containing diimide monomers include NH-containing diimide monomers obtained by an anhydride-efficient imidization method, as well as imide monomers that inherently contain an NH structure. The method for preparing NH-containing diimide monomers by the anhydride-efficient imidization method involves dissolving a tetracarboxylic acid dianhydride monomer and an imidization raw material in a solvent, performing a high-temperature imidization reaction, and collecting the precipitate to obtain the NH-containing diimide. Imide monomers that inherently contain an NH structure include cyanuric acid and barbituric acid.

[0009] S2. The imide cycloaliphatic epoxy resin obtained in S1 is subjected to cationic photocuring and acid anhydride curing, respectively, to prepare a multifunctional imide cycloaliphatic epoxy resin film.

[0010] The multifunctional imide alicyclic epoxy resin obtained in this invention is a resin with two or more alicyclic epoxy groups at the molecular end. It is prepared by Michael addition of the NH group of the imide in diimide, cyanuric acid, or barbituric acid to the double bond of acrylate. The alicyclic epoxy groups at the molecular end are shown below:

[0011]

[0012] This invention first reacts dianhydride with imidizing raw materials (ammonium acetate, urea, etc.) to efficiently convert dianhydride into diimide. This step is simple and rapid. Then, the NH groups of the imides in diimide, cyanuric acid, and barbituric acid are used to perform Michael addition reactions on the double bonds of acrylate. Finally, cationic photocuring and anhydride curing are performed respectively. In other words, this invention utilizes the Michael addition reaction of NH-containing imide monomers with acrylate to obtain a multifunctional imide alicyclic epoxy resin, which is then cationic photocured and thermocured to form a multifunctional imide alicyclic epoxy resin film. The preparation method of this invention is simple, energy-efficient, and low-cost. Introducing epoxy groups at the polymer ends allows for direct cationic photocuring and thermocuring.

[0013] Preferably, in S1, the alicyclic epoxy acrylate monomer is 7-oxabicyclo[4.1.0]hept-3-ylmethacrylate.

[0014] Preferably, in S1, the catalyst comprises 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0015] Preferably, in S1, the Michael addition reaction is carried out at a temperature of 75°C to 95°C for 8 to 10 hours.

[0016] Preferably, in S1, the specific structural formula of the tetracarboxylic acid dianhydride monomer is as follows, wherein X is an organic group:

[0017]

[0018] Preferably, in S1, the tetracarboxylic dianhydride monomer is selected from at least one of 4,4'-biphenyl ether dianhydride, 4,4′-(hexafluoroisopropene) phthalic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, bisphenol A type diether dianhydride, 3,4′-oxophthalic anhydride, 2,3,3′,4′-biphenyltetracarboxylic dianhydride, and dicyclohexyl-3,4,3′,4′-tetracarboxylic dianhydride.

[0019] Preferably, in S1, the imidizing raw material is selected from at least one of urea, ammonium acetate, and formamide.

[0020] More preferably, in S1, when the imidizing raw material is urea or ammonium acetate, the ratio of the imidizing raw material to the tetracarboxylic acid dianhydride monomer is 4-6:1; when formamide is used as the imidizing raw material, no solvent is required, and the dianhydride monomer is directly dissolved in the formamide solvent.

[0021] Preferably, in S1, the high-temperature imidization reaction is carried out by heating and stirring at 140-150°C for 3-4 hours.

[0022] Preferably, in the cationic photocuring described in S2, the photoinitiator used is bis(4-tert-butylphenyl)iodonium hexafluorophosphate, the photosensitizer is 9,10-dibutoxyanthracene, and the UV light intensity is 30–40 mw / cm². 2 The illumination time is 10-20 min; the amount of photoinitiator is 4-6 wt% of imide cycloaliphatic epoxy resin, and the amount of photosensitizer is 0.05-0.2 wt% of imide cycloaliphatic epoxy resin.

[0023] More preferably, in S2, the amount of photoinitiator is 5 wt% of the imide cycloaliphatic epoxy resin, and the amount of photosensitizer is 0.1 wt% of the imide cycloaliphatic epoxy resin. If the prepolymer is viscous, a small amount of 1,4-dioxane can be added to improve viscosity and solubility. Then, it is mixed evenly under ultrasonication to eliminate air bubbles in the photocurable resin. Then, it is poured into an aluminum foil mold or a polytetrafluoroethylene mold for curing. After being exposed to light, it is placed in a vacuum oven and slowly heated from 90°C to 150°C and kept at that temperature for 24 hours.

[0024] Preferably, in the anhydride curing process described in S2, the curing agent used is methylhexahydrophthalic anhydride (MHHPA), and the accelerator is N,N-dimethylbenzylamine (DMBA); the mass percentage of the imide alicyclic epoxy resin, curing agent, and accelerator is 50-60%: 40-50%: 0.05-0.2%; the curing reaction is first carried out at 70-90°C for 1-3 hours, and then at 160-180°C for 10-15 hours.

[0025] More preferably, in S2, the mass percentages of the imide cycloaliphatic epoxy resin, curing agent, and accelerator are 52.6%:47.3%:0.1%. The mixture is stirred evenly at room temperature to fully mix the curing agent and epoxy resin, resulting in an epoxy / anhydride curing system. This system is then placed in a vacuum oven and reacted at 80°C for 2 hours, followed by a reaction at 170°C for 12 hours.

[0026] Preferably, in S1, the solvent used to prepare the diimide monomer containing the NH structure is selected from at least one of glacial acetic acid, N'N-dimethylformamide, and N'N-dimethylacetamide.

[0027] Preferably, in S1, the solvent used in the Michael addition reaction includes, but is not limited to, N'N-dimethylformamide.

[0028] The second aspect of the present invention provides a multifunctional imide cycloaliphatic epoxy resin prepared by the preparation method described in the first aspect.

[0029] The third aspect of this invention provides the application of the polyfunctional imide cycloaliphatic epoxy resin described in the second aspect in the field of optoelectronic devices.

[0030] The multifunctional imide cycloaliphatic epoxy resin film prepared by the method of this invention has both excellent mechanical strength and optical transparency, and can be used in LCD liquid crystal cell packaging, IC substrate solder resist ink, LED display packaging and other fields, providing a new method for the application and development of flexible display film materials.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] This invention discloses a method for preparing a multifunctional imide alicyclic epoxy resin. First, a diimide containing an NH structure is obtained using an acid anhydride high-efficiency imidization method, or various NH-containing imide monomers such as cyanuric acid and barbituric acid are directly selected. Then, the NH groups of the imide undergo a Michael addition reaction with the acrylate double bonds to obtain the multifunctional imide alicyclic epoxy resin. Finally, the imide resin is subjected to cationic photocuring and thermal curing sequentially to obtain a multifunctional imide alicyclic epoxy resin film. The multifunctional imide alicyclic epoxy resin prepared by this method has epoxy groups at the ends, allowing for rapid UV curing via a cationic reaction mechanism, or direct heating curing with acid anhydrides or phenolic curing agents. The process is simple and efficient. Simultaneously, the introduction of the alicyclic structure improves the overall performance of the cured film, resulting in high transparency, excellent heat resistance, good weather resistance, and excellent electrical properties. It can be used in LCD cell packaging, IC substrate solder resist inks, LED display packaging, and other fields. Attached Figure Description

[0033] Figure 1 The 1H NMR spectrum of the product OHYE+DI-1 prepared in Example 1 ( 1 H-NMR).

[0034] Figure 2 The image shows the Fourier Transform Infrared (FT-IR) spectrum of the product OHYE+DI-1 prepared in Example 1.

[0035] Figure 3 The mass spectrometry (MS) spectrum of the product OHYE+DI-1 prepared in Example 1 is shown.

[0036] Figure 4 The 1H NMR spectrum of the product OHYE+DI-2 prepared in Example 2 ( 1 H-NMR).

[0037] Figure 5 The image shows the Fourier Transform Infrared (FT-IR) spectrum of the product OHYE+DI-2 prepared in Example 2.

[0038] Figure 6 The mass spectrometry (MS) spectrum of the product OHYE+DI-2 prepared in Example 2 is shown.

[0039] Figure 7 The 1H NMR spectrum of the product OHYE+BA prepared in Example 3 (… 1 H-NMR).

[0040] Figure 8 The image shows the Fourier Transform Infrared (FT-IR) spectrum of the product OHYE+BA prepared in Example 3.

[0041] Figure 9 The mass spectrometry (MS) spectrum of the product OHYE+BA prepared in Example 3 is shown.

[0042] Figure 10 The 1H NMR spectrum of the product OHYE+CNA prepared in Example 4 ( 1 H-NMR).

[0043] Figure 11 The image shows the Fourier Transform Infrared (FT-IR) spectrum of the product OHYE+CNA prepared in Example 4.

[0044] Figure 12 The mass spectrometry (MS) spectrum of the product OHYE+CNA prepared in Example 4 is shown.

[0045] Figure 13 The images show the appearance of the cured films prepared in Examples 1-4. Detailed Implementation

[0046] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0048] Example 1: Preparation of polyfunctional imide cycloaliphatic epoxy resin

[0049] The specific preparation method includes the following steps:

[0050] (1) Diimides with NH groups were obtained by dianhydride high-efficiency imidization.

[0051] 8.88 g (0.02 mol) of 4,4′-(hexafluoroisopropene) phthalic anhydride and 6.06 g (0.1 mol) of urea were added to a three-necked flask equipped with a reflux condenser, thermometer, mechanical stirrer, and continuous nitrogen purging. 250 mL of glacial acetic acid was added as solvent. The mixture was then heated and refluxed at 150 °C for 4 hours to obtain a diimide solution. After cooling to room temperature, the solution was added dropwise to deionized water until a white solid precipitated. The precipitate was then filtered and washed 2–3 times with deionized water. After vacuum drying for 24 hours, a white diimide, named DI-1, was obtained with a yield of 90%.

[0052] The DI-1 prepared in this step was analyzed by 1H NMR, IR absorption, and mass spectrometry. The 1H NMR signal peaks of DI-1 were found to be: chemical shifts of 11.61 ppm (2H, -NH-), 8.00 ppm (2H, aromatic -CH-), 7.83 ppm (2H, aromatic -CH-), and 7.65 ppm (2H, aromatic -CH-) in 400 MHz DMSO-d6 solvent; the characteristic peaks of the IR absorption spectrum of DI-1 were: 3280 cm⁻¹... -1 (NH stretching vibration), 3068cm -1 (Unsaturated CH stretching vibration), 1781, 1708 cm -1 (C=O asymmetric and symmetric stretching vibrations); the relative molecular mass of DI-1 is 442.04.

[0053] (2) Michael addition reaction of diimide to acrylate double bond

[0054] DI-1 (1.105 g, 0.0025 mol) was dissolved in 50 mL of DMF. 7-oxabicyclo[4.1.0]hept-3-yl methacrylate (0.91 g, 0.005 mol) and catalyst DBU (1 mL) were added sequentially. The mixture was stirred in an oil bath at 75 °C for 10 h to obtain an alicyclic epoxy resin solution. The resulting solution was then azeotropically mixed with water (at a 1:1 volume ratio) and the solvent DMF was removed by rotary evaporation. The solution was then dissolved in dichloromethane (adding dichloromethane until the product was completely dissolved). The solution was washed three times with a 1 mol / L dilute hydrochloric acid solution and once with a saturated sodium chloride solution. The dichloromethane was then removed by rotary evaporation. The product was placed in an oven and vacuum-dried at 40 °C for 8 h to obtain a relatively pure, pale yellow viscous product, which is the polyfunctional imide alicyclic epoxy resin OHYE-DI-1. The structural formula of OHYE-DI-1 is shown below:

[0055]

[0056] The product was analyzed by 1H NMR spectroscopy, infrared absorption spectroscopy, and mass spectrometry. The 1H NMR signal peaks of OHYE-DI-1 are shown below. Figure 1 As shown, the chemical shifts in the 400 MHz 1H NMR spectrum of DMSO-d6 solvent are 8.09 ppm (2H, aromatic -CH-), 7.88 ppm (2H, aromatic -CH-), 7.70 ppm (2H, aromatic -CH-), 3.86 ppm (4H, -CH2-O-), 3.49 ppm (4H, O=C-CH2-), 3.28 ppm (4H, -CH2-N-), 3.06 ppm (4H, epoxy -CH-), and 1.22–1.94 ppm (14H, alicyclic -CH-, -CH2-). The infrared absorption spectrum of OHYE-DI-1 is shown below. Figure 2 As shown, the original 3280cm -1 The characteristic absorption peak of -NH- disappears at 784 cm⁻¹. -1 744cm -1 A characteristic absorption peak of alicyclic epoxy appears at [location]. The mass spectrum of OHYE-DI-1 is as follows: Figure 3 As shown, the relative molecular mass is 806.23.

[0057] (3) Preparation of photocurable films

[0058] The prepared OHYE-DI-1 (0.4 g) was mixed with 5 wt% cationic photoinitiator bis(4-tert-butylphenyl)iodonium hexafluorophosphate (0.02 g) and 0.1 wt% photosensitizer 9,10-dibutoxyanthracene (0.0004 g). Then, 0.2 mL of 1,4-dioxane was added to improve the viscosity of the prepolymer solution. After ultrasonic dissolution at 55 °C, the solution was poured into an aluminum foil mold (5 cm × 5 cm) and placed on a constant-temperature heating stage at 95 °C for 15 min. Subsequently, the solution was subjected to light intensity of 38 mW / cm². 2 Expose the film to a mercury lamp point light source for 15 minutes, then place it in a vacuum oven and slowly increase the temperature stepwise from 90℃ to 150℃ at a rate of 20℃ / h, and keep it at that temperature for 24 hours to obtain a multifunctional imide cycloaliphatic epoxy resin film.

[0059] Infrared spectroscopy was performed on the polyimide film using an ATR module. Analysis of the infrared spectrum of the UV-cured film revealed that the epoxy prepolymer, after UV curing, had a 744 cm⁻¹ diameter. -1 The characteristic absorption peaks of the nearby epoxy have completely disappeared, and the prepolymer has changed from a resin state to a cured film state, indicating that the curing is complete.

[0060] (4) Preparation of thermosetting film

[0061] The prepared OHYE-DI-1 (0.4 g, 53.3 wt%) was mixed with the anhydride curing agent methyl hexahydrophthalic anhydride (0.35 g, 46.6 wt%) and the accelerator N,N-dimethylbenzylamine (0.00075 g, 0.1 wt%). The mixture was then stirred evenly at room temperature and ultrasonically dissolved evenly at 55 °C to obtain an epoxy / anhydride curing system. The curing system was then placed in a vacuum oven and reacted at 80 °C for 2 h, followed by a reaction at 170 °C for 12 h. After the reaction, a polyfunctional imide alicyclic epoxy resin film was obtained.

[0062] Example 2: Preparation of polyfunctional imide cycloaliphatic epoxy resin

[0063] The specific preparation method includes the following steps:

[0064] (1) Diimides with NH groups were obtained by dianhydride high-efficiency imidization.

[0065] 6.12 g (0.02 mol) of dicyclohexyl-3,4,3′,4′-tetracarboxylic acid dianhydride and 7.708 g (0.1 mol) of ammonium acetate were added to a three-necked flask equipped with a reflux condenser, thermometer, mechanical stirrer, and continuous nitrogen purging. 250 mL of glacial acetic acid solvent was added, and the mixture was heated and stirred under reflux at 150 °C for 4 hours to obtain a diimide solution. After cooling to room temperature, the solution was added dropwise to deionized water until a precipitate formed. The precipitate was washed 2-3 times with deionized water, filtered, and then dried under vacuum for 24 hours to obtain a white diimide, named DI-2, with a yield of 88%.

[0066] The DI-2 prepared in this step was analyzed by 1H NMR, IR absorption, and mass spectrometry. The 1H NMR signal peaks of DI-2 were as follows: chemical shifts in the 400 MHz 1H NMR spectrum of DMSO-d6 solvent were 10.89 ppm (2H, -NH-), 2.94 ppm (2H, O=C-CH-), 2.72 ppm (2H, O=C-CH-), 1.91 ppm (4H, alicyclic -CH2-), 1.51 ppm (4H, alicyclic -CH2-), 1.17 ppm (2H, alicyclic -CH-), and 0.87 ppm (4H, alicyclic -CH2-); the characteristic peak of the IR absorption spectrum of DI-2 was 3134 cm⁻¹. -1 (NH stretching vibration), 3061cm -1 (Unsaturated CH stretching vibration), 1765, 1697 cm -1 (C=O asymmetric and symmetric stretching vibrations); the relative molecular mass of DI-2 is 304.14.

[0067] (2) Michael addition reaction of diimide to acrylate double bond

[0068] DI-2 (0.76 g, 0.0025 mol) was dissolved in 50 mL of DMF. 7-oxabicyclo[4.1.0]hept-3-yl methacrylate (0.91 g, 0.005 mol) and catalyst DBU (1 mL) were added sequentially. The mixture was then stirred in an oil bath at 75 °C for 10 h to obtain an alicyclic epoxy resin solution. The resulting solution was then azeotropically mixed with water (at a 1:1 volume ratio) and the solvent DMF was removed by rotary evaporation. The solution was then dissolved in dichloromethane (adding dichloromethane until the product was completely dissolved), washed three times with a 1 mol / L dilute hydrochloric acid solution, and once with a saturated sodium chloride solution. The dichloromethane was then removed by rotary evaporation. The product was then placed in an oven and vacuum-dried at 40 °C for 8 h to obtain a relatively pure, pale yellow viscous product, which is the polyfunctional imide alicyclic epoxy resin OHYE-DI-2. The structural formula of OHYE-DI-2 is shown below:

[0069]

[0070] The product was analyzed by 1H NMR spectroscopy, infrared absorption spectroscopy, and mass spectrometry. The 1H NMR signal peaks of OHYE-DI-2 are shown below. Figure 4 As shown: the chemical shifts in the 400 MHz 1H NMR spectrum of DMSO-d6 solvent are 3.78 ppm, 3.60 ppm (4H, -CH2-O-), 3.26 ppm (4H, -CH2-N-), 3.09 ppm (4H, epoxy-CH-), 2.57 ppm (4H, -CH-C=ON-), 2.40 ppm (4H, O=C-CH2-), and 0.85–2.00 ppm (28H, alicyclic-CH-, -CH2-). The infrared absorption spectrum of OHYE-DI-2 is shown below. Figure 5 As shown, the original was 3134cm. -1 The characteristic absorption peak of -NH- disappears at 786 cm⁻¹. -1 750cm -1 A characteristic absorption peak of alicyclic epoxy appears at [location]. The mass spectrum of OHYE-DI-2 is as follows: Figure 6 As shown, the relative molecular mass is 668.33.

[0071] (3) Preparation of photocurable films

[0072] The prepared OHYE-DI-2 (0.4 g) was mixed with 5 wt% cationic photoinitiator bis(4-tert-butylphenyl)iodonium hexafluorophosphate (0.02 g) and 0.1 wt% photosensitizer 9,10-dibutoxyanthracene (0.0004 g). Then, 0.2 mL of 1,4-dioxane was added to improve the viscosity of the prepolymer solution. After ultrasonic dissolution at 55 °C, the solution was poured into an aluminum foil mold (5 cm × 5 cm) and placed on a 95 °C constant temperature heating stage for 15 min. Subsequently, the solution was subjected to light intensity of 38 mW / cm². 2 Expose the film to a mercury lamp point light source for 15 minutes, then place it in a vacuum oven and slowly increase the temperature stepwise from 90℃ to 150℃ at a rate of 20℃ / h, and keep it at that temperature for 24 hours to obtain a multifunctional imide cycloaliphatic epoxy resin film.

[0073] Infrared spectroscopy was performed on the polyimide film using an ATR module. Analysis of the infrared spectrum of the UV-cured film revealed that the epoxy prepolymer, after UV curing, had a 750cm² thickness. -1 The characteristic absorption peaks of epoxy in the vicinity have basically disappeared, and the prepolymer has changed from a resin state to a cured film state, with a curing degree of 95%.

[0074] (4) Preparation of thermosetting film

[0075] The prepared OHYE-DI-2 (0.4 g, 53.3 wt%) was mixed with the anhydride curing agent methyl hexahydrophthalic anhydride (0.35 g, 46.6 wt%) and the accelerator N,N-dimethylbenzylamine (0.00075 g, 0.1 wt%). The mixture was then stirred evenly at room temperature and ultrasonically dissolved evenly at 55 °C to obtain an epoxy / anhydride curing system. The curing system was then placed in a vacuum oven and reacted at 80 °C for 2 h, and then reacted at 170 °C for 12 h to obtain a polyfunctional imide alicyclic epoxy resin film.

[0076] Example 3: Preparation of polyfunctional imide cycloaliphatic epoxy resin

[0077] The specific preparation method includes the following steps:

[0078] (1) Michael addition reaction of barbituric acid to the double bond of acrylate

[0079] Barbituric acid (1.28 g, 0.01 mol) was dissolved in 50 mL of DMF. 7-oxabicyclo[4.1.0]hept-3-yl methacrylate (5.47 g, 0.03 mol) and catalyst DBU (1 mL) were added sequentially. The mixture was stirred in an oil bath at 75 °C for 10 h to obtain an alicyclic epoxy resin solution. The resulting solution was then azeotropically mixed with water (at a 1:1 volume ratio) and the solvent DMF was removed by rotary evaporation. The solution was then dissolved in dichloromethane (adding dichloromethane until the product was completely dissolved). The solution was washed three times with a 1 mol / L dilute hydrochloric acid solution and once with a saturated sodium chloride solution. Dichloromethane was then removed by rotary evaporation. The product was placed in an oven and vacuum-dried at 40 °C for 8 h to obtain a relatively pure, pale yellow viscous product, which is the polyfunctional imide alicyclic epoxy resin OHYE-BA. The structural formula of OHYE-BA is shown below:

[0080]

[0081] The product was analyzed by 1H NMR spectroscopy, infrared absorption spectroscopy, and mass spectrometry. The 1H NMR signal peaks of OHYE-BA are shown below. Figure 7 As shown: the chemical shifts in the 400 MHz 1H NMR spectrum of DMSO-d6 solvent are 3.80 ppm (6H, -CH2-O-), 3.42–3.49 ppm (1H, O=C-CH-), 3.42–3.49 ppm (4H, -CH2-N-), 3.08 ppm (6H, epoxy-CH-), 2.51 ppm (6H, -CH2-), 2.00–2.13 ppm (3H, alicyclic-CH-), and 1.06–1.68 ppm (18H, alicyclic-CH2-). The infrared absorption spectrum of OHYE-BA is as follows. Figure 8 As shown, the original height was 3187cm. -1 The characteristic absorption peak of -NH- disappears at 786 cm⁻¹. -1 752cm -1 A characteristic absorption peak of alicyclic epoxy appears at [location]. The mass spectrum of OHYE-BA is as follows: Figure 9 As shown, the relative molecular mass is 674.74.

[0082] (2) Preparation of photocurable films

[0083] The prepared OHYE-BA (0.4 g) was mixed with 5 wt% cationic photoinitiator bis(4-tert-butylphenyl)iodonium hexafluorophosphate (0.02 g) and 0.1 wt% photosensitizer 9,10-dibutoxyanthracene (0.0004 g). Then, 0.2 mL of 1,4-dioxane was added to improve the viscosity of the prepolymer solution. After ultrasonic dissolution at 55 °C, the solution was poured into an aluminum foil mold (5 cm × 5 cm) and placed on a 95 °C constant temperature heating stage for 15 min. Subsequently, the mixture was subjected to light intensity of 38 mW / cm².2 Expose the film to a mercury lamp point light source for 15 minutes, then place it in a vacuum oven and slowly increase the temperature stepwise from 90℃ to 150℃ at a rate of 20℃ / h, and keep it at that temperature for 24 hours to obtain a polyfunctional imide cycloaliphatic epoxy resin film.

[0084] Infrared spectroscopy was performed on the epoxy resin film using an ATR module. Analysis of the infrared spectrum of the UV-cured film revealed that the epoxy prepolymer, after UV curing, had a peak density of 752 cm⁻¹. -1 The characteristic absorption peaks of epoxy in the vicinity have basically disappeared, and the prepolymer has changed from a resin state to a cured film state, with a curing degree of 90%.

[0085] (3) Preparation of thermosetting film

[0086] The prepared OHYE-BA (0.4 g, 53.3 wt%) was mixed with the anhydride curing agent methyl hexahydrophthalic anhydride (0.35 g, 46.6 wt%) and the accelerator N,N-dimethylbenzylamine (0.00075 g, 0.1 wt%). The mixture was stirred evenly at room temperature and then ultrasonically dissolved at 55 °C to obtain an epoxy / anhydride curing system. The curing system was then placed in a vacuum oven and reacted at 80 °C for 2 h, and then reacted at 170 °C for 12 h to obtain a polyfunctional imide alicyclic epoxy resin film.

[0087] Example 4: Preparation of polyfunctional imide cycloaliphatic epoxy resin

[0088] The specific preparation method includes the following steps:

[0089] (1) Michael addition reaction of cyanuric acid to the double bond of acrylate

[0090] Cyanuric acid (1.29 g, 0.01 mol) was dissolved in 50 mL of DMF. 7-oxabicyclo[4.1.0]hept-3-yl methacrylate (5.47 g, 0.03 mol) and catalyst DBU (1 mL) were added sequentially. The mixture was stirred in an oil bath at 95 °C for 10 h to obtain an alicyclic epoxy resin solution. The resulting solution was then azeotropically mixed with water (at a 1:1 volume ratio) and the solvent DMF was removed by rotary evaporation. The solution was then dissolved in dichloromethane (adding dichloromethane until the product was completely dissolved), washed three times with a 1 mol / L dilute hydrochloric acid solution, and once with a saturated sodium chloride solution. The dichloromethane was then removed by rotary evaporation. The product was then placed in an oven and vacuum-dried at 40 °C for 8 h to obtain a relatively pure, pale yellow viscous product, which is the polyfunctional imide alicyclic epoxy resin OHYE-CNA. The structural formula of OHYE-CNA is shown below:

[0091]

[0092] The product was analyzed by 1H NMR spectroscopy, infrared absorption spectroscopy, and mass spectrometry. The 1H NMR signal peaks of OHYE-CNA are shown below. Figure 10 As shown: the chemical shifts in the 400 MHz 1H NMR spectrum of DMSO-d6 solvent are 3.90 ppm (6H, -CH2-O-), 3.49 ppm (6H, -CH2-N-), 3.08 ppm (6H, epoxy-CH-), 2.60 ppm (6H, -CH2-), 2.00 ppm (3H, alicyclic-CH-), and 1.00–1.68 ppm (18H, alicyclic-CH2-). The infrared absorption spectrum of OHYE-CNA is shown below. Figure 11 As shown, the original 3200cm -1 The characteristic absorption peak of -NH- disappears at 784 cm⁻¹. -1 761cm -1 A characteristic absorption peak of alicyclic epoxy appears at [location]. The mass spectrum of OHYE-CNA is as follows: Figure 12 As shown, the relative molecular mass is 675.30.

[0093] (2) Preparation of photocurable films

[0094] The prepared OHYE-CNA (0.4 g) was mixed with 5 wt% cationic photoinitiator bis(4-tert-butylphenyl)iodonium hexafluorophosphate (0.02 g) and 0.1 wt% photosensitizer 9,10-dibutoxyanthracene (0.0004 g). Then, 0.2 mL of 1,4-dioxane was added to improve the viscosity of the prepolymer solution. After ultrasonic dissolution at 55 °C, the solution was poured into an aluminum foil mold (5 cm × 5 cm) and placed on a 95 °C constant temperature heating stage for 15 min. Subsequently, the solution was subjected to light intensity of 38 mW / cm². 2 Expose the film to a mercury lamp point light source for 15 minutes, then place it in a vacuum oven and slowly increase the temperature stepwise from 90℃ to 150℃ at a rate of 20℃ / h, and keep it at that temperature for 24 hours to obtain a multifunctional imide cycloaliphatic epoxy resin film.

[0095] Infrared spectroscopy was performed on the epoxy resin film using an ATR module. Analysis of the infrared spectrum of the UV-cured film revealed that the epoxy prepolymer, after UV curing, had a peak density of 784 cm⁻¹. -1 Most of the characteristic absorption peaks of the nearby epoxy disappeared, and the prepolymer changed from a resin state to a cured film state, with a curing degree of 85%.

[0096] (3) Preparation of thermosetting film

[0097] The prepared OHYE-CNA (0.4 g, 53.3 wt%) was mixed with the anhydride curing agent methyl hexahydrophthalic anhydride (0.35 g, 46.6 wt%) and the accelerator N,N-dimethylbenzylamine (0.00075 g, 0.1 wt%). The mixture was stirred evenly at room temperature and then ultrasonically dissolved at 55 °C to obtain an epoxy / anhydride curing system. The curing system was then placed in a vacuum oven and reacted at 80 °C for 2 h, and then reacted at 170 °C for 12 h to obtain a polyfunctional imide alicyclic epoxy resin film.

[0098] Comparative Example 1: Preparation of Acrylate-modified Cyanoboric Acid Resin

[0099] The specific preparation method includes the following steps:

[0100] (1) Michael addition reaction of cyanuric acid to the double bond of acrylate

[0101] 1.29 g (0.01 mol) of cyanuric acid was dissolved in 50 mL of DMF, and 7.2 g (0.032 mol) of 1,6-hexanediol diacrylate and 0.38 g (0.0025 mol) of DBU were added sequentially. The mixture was heated to 75 °C and reacted for 8 h to obtain an acrylated cyanuric acid solution. The resulting solution was then azeotropically mixed with water (at a 1:1 volume ratio) and the solvent DMF was removed by rotary evaporation. The solution was then dissolved in dichloromethane (adding dichloromethane until the product was completely dissolved). The dissolved product was first acid-washed 2–3 times with a 1 mol / L dilute hydrochloric acid aqueous solution, and then washed 1–2 times with a methanol aqueous solution (methanol:water = 1:1). The organic phase was then filtered, and the dichloromethane was removed by rotary evaporation. Finally, the product was vacuum-dried at 40 °C for 8 h to obtain a yellow viscous acrylated cyanuric acid resin HDDA-CNA. The structural formula of HDDA-CNA is shown below:

[0102]

[0103] The product was analyzed by 1H NMR, IR absorption, and mass spectrometry. The 1H NMR signals of HDDA-CNA were as follows: chemical shifts in the 400 MHz NMR spectrum of DMSO-d6 solvent were 5.93–6.30 ppm (9H, -C=H-), 4.10 ppm (6H, -CH2-N-), 4.05 ppm (6H, -CH2-O-), 2.59 ppm (6H, -CH2-C=O-), 1.62 ppm (6H, -CH2-), and 1.33 ppm (6H, -CH2-). The IR absorption spectrum of HDDA-CNA was: [insert value here]. -1 The characteristic absorption peak of -NH- disappears at 810 cm⁻¹. -1 1619cm -1A characteristic absorption peak of a carbon-carbon double bond appears at [location missing]. The relative molecular mass of HDDA-CAN is 807.4.

[0104] (2) Preparation of photocurable films

[0105] The prepared HDDA-CAN (0.4 g) was mixed with 0.5 wt% photoinitiator Ir 184 (0.002 g), and after being ultrasonically dissolved and homogenized at 55 °C, it was poured into an aluminum foil mold (5 cm × 5 cm), and then heated at 38 mW / cm². 2 Acrylate-esterified cyanuric acid resin film was obtained by curing under UV light intensity for 60 seconds.

[0106] Experimental Example: Comparative Analysis of Cured Films from Different Resins

[0107] (1) Thermogravimetric analysis and hardness analysis

[0108] Table 1 shows the temperatures (T0, T0) at which the multifunctional imide cycloaliphatic epoxy resin films prepared by cationic photocuring in Examples 1, 2, 3, and 4 lose 5% of their thermal weight (T0). d5 The hardness of the OHYE+DI-1, OHYE+DI-2, OHYE+BA, and OHYE+CAN cured films is higher than that of the comparative example 1. This may be because the OHYE+DI-1, OHYE+DI-2, OHYE+BA, and OHYE+CAN products introduce alicyclic structures, resulting in greater steric hindrance and increased rigidity. In contrast, the HDDA+CNA product has a chain structure, with the cured film containing more alkane side groups and flexible groups, making the molecular chain more flexible. Therefore, the OHYE+DI-1, OHYE+DI-2, OHYE+BA, and OHYE+CAN cured films exhibit better heat resistance than the HDDA+CNA cured film. Hardness is related to the degree of cross-linking of the cured film. More functional groups and a higher degree of cross-linking result in a more compact structure and thus higher hardness. The presence of alicyclic structures in the molecules of the OHYE+DI-1, OHYE+DI-2, OHYE+BA, and OHYE+CAN cured films imparts good rigidity, thus increasing strength and resulting in higher hardness. Therefore, the proposed method for synthesizing imide alicyclic epoxy resin films via the Michael addition reaction of imide NH to acrylate double bonds is feasible. This implementation method has good prospects for industrialization.

[0109] Table 1 Properties of Cured Films with Different Resins

[0110] Example <![CDATA[T d5 (℃)]]> Cured film hardness Example 1 220.6 It is hard and will not tear even with considerable force. Example 2 227.1 It is hard and will not tear even with considerable force. Example 3 226.0 It is hard and will not tear even with considerable force. Example 4 223.3 It is hard and will not tear even with considerable force. Comparative Example 1 202.5 It's so soft that it will tear if you try to tear it by hand.

[0111] (2) Appearance of the cured film

[0112] Figure 13The images shown are of the appearance of the cured films prepared in the examples. Images a and d represent the cationic photocured OHYE+DI-1, OHYE+DI-2, OHYE+BA, and OHYE+CAN obtained in Examples 1-4, respectively. Images eh represent the thermocured OHYE+DI-1, OHYE+DI-2, OHYE+BA, and OHYE+CAN obtained in Examples 1-4, respectively. The photocured films exhibit good flexibility, a pale yellow color, and good light transmittance; the thermocured films have higher overall hardness, stronger wear resistance, and higher transparency.

[0113] (3) Pencil hardness and thermal stability test

[0114] The performance of the thermosetting films prepared in Examples 1-4 was tested using the following methods: (1) Pencil hardness was tested according to GB / T6739—2006; (2) TG test was performed using Netzsch's TG 209F1. Thermogravimetric analyzer was used to test the thermal stability of the thermosetting film. The heating rate was 10℃ / min, and the temperature range was 25~800℃.

[0115] Test results: The pencil hardness of these thermosetting films is around 5H, which is very high; the temperature at which the thermosetting films lose 10% of their weight in a nitrogen atmosphere is greater than 245℃, which shows good heat resistance.

[0116] In summary, this invention discloses a novel method for preparing a multifunctional imide cycloaliphatic epoxy resin. First, a diimide with an NH structure is obtained using an acid anhydride-efficient imidization method, or various NH-containing imide monomers such as cyanuric acid and barbituric acid are directly selected. Then, the NH groups of the imide undergo a Michael addition reaction with the acrylate double bonds to obtain the multifunctional imide cycloaliphatic epoxy resin. Finally, the imide resin is subjected to cationic photocuring and thermocuring sequentially to obtain a multifunctional imide cycloaliphatic epoxy resin film. This film exhibits excellent mechanical strength and optical transparency, making it suitable for applications such as LCD liquid crystal cell encapsulation, IC substrate solder resist inks, and LED display encapsulation. Furthermore, the processing technology is simple and low-cost, providing a new method for the application and development of flexible display film materials.

[0117] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A process for the preparation of a multifunctional imide alicyclic epoxy resin, characterized by, The method comprises the following steps: S1, dissolving the imide monomer with N-H structure or cyanuric acid and alicyclic epoxy acrylate monomer in a solvent, and adding a catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene, then synthesizing the imide alicyclic epoxy resin through Michael addition reaction between the N-H of the imide and the acrylate double bond; the temperature of the Michael addition reaction is 75-95 DEG C, and the reaction time is 8-10 h; The alicyclic epoxy acrylate monomer is 7-oxabicyclo[4.1.0]hept-3-yl methacrylate; the imide monomer with N-H structure includes the imide monomer with N-H structure obtained by using anhydride efficient imidization method, and the imide monomer containing N-H structure itself; wherein the method for preparing the imide monomer with N-H structure by using the anhydride efficient imidization method is that: dissolving tetracarboxylic dianhydride monomer and imidization raw material in a solvent, collecting the precipitate after high-temperature imidization reaction, and obtaining the imide with N-H structure; the imide monomer containing N-H structure itself is barbituric acid; S2, respectively performing cationic photocuring and anhydride curing on the imide alicyclic epoxy resin obtained in S1, and preparing a multifunctional imide alicyclic epoxy resin film.

2. The method for preparing a polyfunctional imide cycloaliphatic epoxy resin according to claim 1, characterized in that, In S1, the tetracarboxylic dianhydride monomer is selected from at least one of 4,4'-diphenyl ether dianhydride, 4,4'-hexafluoroisopropylidene diphthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, bisphenol A type diether dianhydride, 3,4'-oxydiphthalic anhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride, and dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride.

3. The method for preparing a polyfunctional imide cycloaliphatic epoxy resin according to claim 1, characterized in that, In S1, the imidization raw material is selected from at least one of urea, ammonium acetate, and formamide.

4. The method for preparing a polyfunctional imide cycloaliphatic epoxy resin according to claim 1, characterized in that, In S1, the high-temperature imidization reaction is heating and stirring reaction at 140-150 DEG C for 3-4 hours.

5. The method for preparing a polyfunctional imide cycloaliphatic epoxy resin according to claim 1, characterized in that, In the cationic photocuring of S2, the used photoinitiator is bis(4-tert-butylphenyl) iodonium hexafluorophosphate, the photosensitizer is 9,10-dibutoxyanthracene, the UV light intensity is 30-40 mw / cm 2 , the illumination time is 10-20 min; the amount of the photoinitiator is 4-6 wt% of the imide alicyclic epoxy resin, and the amount of the photosensitizer is 0.05-0.2 wt% of the imide alicyclic epoxy resin.

6. The method for preparing a polyfunctional imide cycloaliphatic epoxy resin according to claim 1, characterized in that, In the anhydride curing of S2, the curing agent used is methyl hexahydrophthalic anhydride, the accelerator is N,N-dimethylbenzylamine; the mass percentage of the imide alicyclic epoxy resin, the curing agent and the accelerator is 50-60%:40-50%:0.05-0.2%; the curing reaction is first reacting at 70-90 DEG C for 1-3 h, and then reacting at 160-180 DEG C for 10-15 h.

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