A low viscosity toughened bismaleimide resin composition and a method for preparing the same

Abstract

The application provides a low-viscosity toughened bismaleimide resin composition and a preparation method thereof, and belongs to the technical field of bismaleimide resins. The resin composition comprises a bismaleimide resin, an allyl compound, a reactive thermoplastic toughening agent, an active diluent and an ionic liquid solubilizer. The ionic liquid solubilizer and the bismaleimide resin only have physical interaction and do not react chemically, thereby avoiding the generation of insoluble gels and eliminating the need for filtration. The reactive thermoplastic toughening agent is a polyarylether sulfone oligomer containing an allyl group at the end, which can be combined into the resin network in the form of a covalent bond, without being separated out or significantly reducing the heat resistance. The resin composition obtained in this way has the advantages of low viscosity, high toughness, high heat resistance and more than 180 days of room temperature storage stability.

Description

Technical Field

[0001] This invention relates to the field of bismaleimide resin technology, and in particular to a low-viscosity toughened bismaleimide resin composition and its preparation method. Background Technology

[0002] Bismaleimide resins are thermosetting polymers with excellent heat resistance, dielectric properties, and dimensional stability, finding wide application in aerospace structural components, electronic packaging substrates, and high-temperature composite materials. Their glass transition temperatures typically exceed 250°C, enabling them to maintain mechanical properties over extended periods at high temperatures, thus making them an important matrix material in the field of high-performance composite materials. In recent years, the increasing demands for high-speed aircraft and highly integrated electronic devices have placed higher requirements on the processing adaptability and mechanical properties of resin materials.

[0003] To address the issues of excessively high crosslinking density and inherent brittleness in bismaleimide resins, researchers have developed various modification methods. For example, copolymerizing bismaleimide with allyl compounds (such as diallylbisphenol A) can reduce the crosslinking density and improve toughness; introducing thermoplastic resins (such as polyethersulfone and polyetheretherketone) to form an interpenetrating network structure can effectively improve fracture toughness; to meet the low viscosity requirements of liquid molding processes such as resin transfer molding and pultrusion, reactive diluents are usually added or prepolymerization techniques are used to reduce melt viscosity. Thus, these methods alleviate the problems of insufficient toughness or excessively high viscosity to some extent.

[0004] However, existing modification methods have the following problems in practical applications: First, when using amines to improve resin solubility, insoluble crosslinking byproducts are often generated, necessitating the addition of a filtration step in the process. This can cause some effective components to be filtered out along with the gel, deviating the actual resin composition from the designed formulation. Furthermore, if filtration is incomplete, residual gel particles may become stress concentration points in the cured product, reducing the material's mechanical strength and fracture toughness, thus affecting the composite material's performance. Second, introducing thermoplastic toughening agents physically requires dissolution at temperatures above 140°C. After cooling, the toughening agent easily precipitates, causing white spots and uneven viscosity on the prepreg surface, reducing its layability. Third, while epoxy blending modification can reduce viscosity, it often comes at the cost of sacrificing the glass transition temperature, significantly reducing the heat resistance of the cured product.

[0005] Therefore, it is necessary to provide a bismaleimide resin composition with low viscosity, good toughness, storage stability and no significant decrease in heat resistance to solve the above-mentioned technical problems. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a low viscosity toughened bismaleimide resin composition and its preparation method. The resin composition achieves low viscosity, high toughness, high heat resistance and room temperature storage stability of more than 180 days without filtration and with a yield close to 100%.

[0007] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a low-viscosity toughened bismaleimide resin composition comprising the following components in parts by weight: 100 parts of bismaleimide resin, 30-80 parts of allyl compound, 10-40 parts of reactive thermoplastic toughening agent, 10-50 parts of reactive diluent, and 1-20 parts of ionic liquid solubilizer.

[0008] Preferably, the amount of the ionic liquid solubilizer added is 5 to 15 parts by weight, and the ionic liquid solubilizer is an imidazole-based ionic liquid.

[0009] Preferably, the imidazole ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium dicyandiamide, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate.

[0010] Preferably, the bismaleimide resin is selected from one or a combination of two of diphenylmethane-type bismaleimide and toluenediamine-type bismaleimide.

[0011] Preferably, the allyl compound is selected from at least one of 2,2'-diallylbisphenol A, diallylbisphenol S, and diallylphenol.

[0012] Preferably, the reactive diluent is selected from at least one of 2-allylphenol and 4-allyl anisole.

[0013] Preferably, the reactive thermoplastic toughening agent is a polyarylene ether sulfone oligomer with allyl end groups, having a number-average molecular weight of 1000-5000 and a number-average allyl functionality of 1.5-2.5.

[0014] Preferably, the composition further contains 0.5 to 5 parts by weight of a latent curing accelerator, wherein the latent curing accelerator is selected from at least one of microencapsulated imidazole and organic urea derivatives.

[0015] On the other hand, the present invention also provides a method for preparing the above-mentioned low-viscosity toughened bismaleimide resin composition, comprising the following steps: S1. Add bismaleimide resin, allyl compound, reactive diluent and ionic liquid solubilizer into the reaction vessel according to the ratio, heat to 80~120℃ under nitrogen atmosphere, stir until all materials are fully dissolved, and obtain a transparent premixed liquid. S2. Add a reactive thermoplastic toughening agent to the obtained transparent premixed liquid, maintain the temperature at 100~120℃ and stir for 20~60 minutes to obtain a homogeneous transparent mixture; S3. Allow the obtained homogeneous transparent mixture to cool naturally to room temperature to obtain the low-viscosity toughened bismaleimide resin composition.

[0016] Preferably, after obtaining the homogeneous transparent mixture in step S2 and before cooling in step S3, a latent curing accelerator is added. The specific process is as follows: the homogeneous transparent mixture is cooled to 60~80℃, the latent curing accelerator is added and stirred for 15~30 minutes to obtain a compound mixture, and then the low viscosity toughened bismaleimide resin composition is obtained by cooling in step S3.

[0017] Compared with the prior art, the present invention discloses at least the following technical effects: This invention uses ionic liquids instead of traditional amine solubilizing components, utilizing physical forces such as cation-π interactions and hydrogen bonds to uniformly dissolve bismaleimide resin. No chemical reactions occur during the entire process, thus avoiding the insoluble gel byproducts that are difficult to eliminate in amine-based methods. Filtration is unnecessary during preparation, the formulation composition is consistent with the final product, and the yield is close to 100%. It also eliminates the potential damage to mechanical properties caused by residual gel particles. Simultaneously, this invention uses polyarylene ether sulfone oligomers with allyl groups at the ends as toughening agents. During the curing stage, these oligomers undergo a copolymerization reaction with the double bonds of bismaleimide via allyl groups, permanently connecting to the resin network in a covalent manner. Unlike toughening agents used in ordinary physical blends, these do not precipitate upon cooling, causing surface defects and reduced viscosity in the prepreg. Furthermore, due to their high glass transition temperature, they do not significantly lower the overall heat resistance. The measured glass transition temperature of the cured material remains above 265℃, and the fracture toughness and elongation at break are significantly superior to existing modified materials. Furthermore, since the interaction between the ionic liquid and bismaleimide is a reversible physical bond rather than an irreversible chemical reaction, the resin can maintain a homogeneous and stable state for a long time at room temperature. In actual tests, after being stored at 25°C for more than 180 days, no precipitates were observed, and the viscosity and curing activity remained basically unchanged. Its storage stability is far superior to that of existing bismaleimide resin materials. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a flowchart illustrating the preparation method of a low-viscosity toughened bismaleimide resin composition according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the present invention provides a method for preparing a low-viscosity toughened bismaleimide resin composition, comprising the following steps: S1. Add bismaleimide resin, allyl compound, reactive diluent and ionic liquid solubilizer into the reaction vessel according to the ratio, heat to 80~120℃ under nitrogen atmosphere, and stir until all materials are fully dissolved to obtain a transparent premixed liquid.

[0023] Specifically, based on 100 parts by weight of bismaleimide resin, the amount of allyl compound is 30-80 parts by weight, the amount of reactive diluent is 10-50 parts by weight, and the amount of ionic liquid solubilizer is 1-20 parts by weight, more preferably 5-15 parts by weight. The bismaleimide resin is selected from at least one of diphenylmethane-type bismaleimide and toluenediamine-type bismaleimide, each molecule containing a maleimide group at both ends. After curing, it can form a three-dimensional network with high crosslinking density, giving the material excellent heat resistance. The allyl compound is selected from at least one of 2,2'-diallylbisphenol A, diallylbisphenol S, or diallylphenol. This type of compound can act as an reactive comonomer, subsequently combining with the double bonds of bismaleimide through Ene reaction or Michael addition reaction to reduce crosslinking density and improve toughness. Simultaneously, the hydroxyl and ether bonds contained in its molecule help improve the compatibility between the components.

[0024] The reactive diluent is selected from at least one of 2-allylphenol and 4-allyl anisole. These substances are in a low-viscosity liquid state at room temperature, which can significantly reduce the melt viscosity of the entire mixture, so that the final resin composition has good flowability, thereby meeting the requirements of injection viscosity for liquid molding processes such as resin transfer molding and pultrusion.

[0025] Ionic liquid solubilizer is the main component of this scheme. Imidazole-based ionic liquids are selected in this step, specifically at least one of 1-ethyl-3-methylimidazolium dicyandiamide, 1-butyl-3-methylimidazolium tetrafluoroborate, or 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. During heating and stirring at 80-120°C, the imidazole cations of the ionic liquid interact with the π-electron clouds of the aromatic rings in the bismaleimide molecule through cation-π interactions, while the anions form weak hydrogen bonds with the carbonyl oxygen of the bismaleimide. These two physical forces synergistically break down the original strong π-π stacking and hydrogen bond network between bismaleimide molecules, allowing the originally highly crystalline and difficult-to-dissolve bismaleimide resin to completely dissolve in the allyl compound and reactive diluent at a lower temperature, forming a transparent and homogeneous premix.

[0026] It should be noted that 1-butyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate are chemically stable and do not possess the ability to undergo nucleophilic addition or cross-linking reactions with the maleimide double bond. 1-ethyl-3-methylimidazolium dicyandiamide salt has extremely low reactivity under the low-temperature heating environment in this step, making chemical reaction difficult. Therefore, the overall dissolution process is primarily a purely physical mixing process, with virtually no covalent bond formation or breakage. Unlike existing technologies that use amine solubilizers such as ethylenediamine and cyclohexylamine, where amines can promote dissolution, their amino groups can undergo uncontrollable addition reactions with the double bond of bismaleimide, inevitably forming partially insoluble cross-linked gels. In this invention, no significant chemical reaction occurs during the dissolution stage, thus preventing the generation of any gel byproducts. Subsequent filtration steps are unnecessary, the actual composition of the resin composition is completely consistent with the feed formulation, the yield is close to 100%, and the risk of residual gel particles becoming stress concentration points leading to a decrease in mechanical properties is avoided.

[0027] S2. Add a reactive thermoplastic toughening agent to the obtained transparent premixed liquid, maintain the temperature at 100~120℃ and stir for 20~60 minutes to obtain a homogeneous transparent mixture.

[0028] Specifically, based on 100 parts by weight of bismaleimide resin, the amount of reactive thermoplastic toughening agent is 10-40 parts by weight. This reactive thermoplastic toughening agent is a polyarylene ether sulfone oligomer with allyl end groups, its number-average molecular weight controlled at 1000-5000, and its number-average allyl functionality at 1.5-2.5. This oligomer can be prepared by an epoxy ring-opening etherification reaction between commercially available hydroxyl-terminated polyether sulfone and allyl glycidyl ether under the action of a catalyst. Under stirring conditions of 100-120°C, due to the strong polarity of the ionic liquid added in the previous step, there is a strong interaction between it and the sulfone and ether oxygen atoms in the main chain of the polyarylene ether sulfone oligomer, which can effectively reduce the dissolution activation energy of the oligomer, allowing it to completely dissolve in the premix within the temperature range of this step without raising the temperature to 140-150°C. The lower operating temperature prevents premature thermal polymerization of the bismaleimide resin at this stage, thus ensuring the stability of the resin viscosity and the controllability of subsequent processes.

[0029] After complete dissolution, the terminal allyl polyarylene ether sulfone oligomer is uniformly dispersed in the resin mixture in the form of molecular chains. Since the curing temperature has not yet been reached, the allyl end groups and the double bonds of bismaleimide only maintain physical contact and no significant addition reaction occurs. Therefore, the entire system maintains a low viscosity and good flowability.

[0030] S3. Allow the obtained homogeneous transparent mixture to cool naturally to room temperature to obtain the low-viscosity toughened bismaleimide resin composition.

[0031] Specifically, during the natural cooling process, because the interaction between the ionic liquid and bismaleimide is a reversible physical interaction rather than an irreversible chemical combination, the ionic liquid remains uniformly distributed in the resin after the temperature decreases. Unlike some organic solvents, the bismaleimide will not recrystallize and precipitate due to a decrease in supersaturation. Simultaneously, the terminal allyl polyarylene ether sulfone oligomer dissolves in the system in the form of molecular chains without undergoing any phase transition. After cooling, it remains in a transparent and homogeneous state, avoiding the problem of micron-sized particles precipitating from physically blended thermoplastic resins due to decreasing solubility at temperature, as seen in existing technologies. Therefore, the resin composition obtained after cooling in this step requires no filtration or post-treatment and can be directly used for prepreg preparation or liquid molding processes.

[0032] In addition, after obtaining the homogeneous transparent mixture in step S2 and before cooling in step S3, a latent curing accelerator can be added as needed. The specific process is as follows: cool the homogeneous transparent mixture to 60-80°C, add the latent curing accelerator and stir for 15-30 minutes to obtain a compound mixture, and then perform the cooling treatment in step S3. The latent curing accelerator is selected from at least one of microcapsule-encapsulated imidazole or organic urea derivatives, and its dosage is 0.5-5 parts of the total mass of the resin composition. This type of accelerator remains inert at room temperature and will not trigger a cross-linking reaction between bismaleimide and allyl compounds; therefore, the resin composition can still be stored for a long time after its addition. When high-temperature curing is subsequently performed, the microcapsule wall material ruptures or the organic urea derivative decomposes, releasing active components that can catalyze the Ene reaction and the ring-opening polymerization reaction between epoxy groups and phenolic hydroxyl groups, thereby reducing the curing temperature or shortening the curing time.

[0033] Furthermore, the bismaleimide resin composition obtained by the above preparation method requires high-temperature curing to obtain the final mechanical properties and heat resistance. A stepped temperature-increasing curing process can be adopted: holding at 150℃ for 2 hours allows the system to undergo the initial Ene reaction to form a pre-crosslinked structure; then heating to 180℃ and holding for 2 hours promotes further addition of bismaleimide to allyl compounds and chemical incorporation of terminal allyl polyarylene ether sulfone oligomers; finally, heating to 220℃ and holding for 2 hours completes deep crosslinking, forming a uniform three-dimensional network. During this curing process, if the selected ionic liquid is 1-ethyl-3-methylimidazolium dicyandiamide salt, the dicyandiamide anion in the system can directly play a catalytic role in an environment above 150℃, accelerating the curing reaction without relying on thermal decomposition to generate active substances. Even without the addition of an additional catalyst, the resin can be completely cured. In this process, the terminal allyl polyarylene sulfone oligomer undergoes a copolymerization reaction between its terminal allyl group and the double bond of bismaleimide, and is permanently linked to the resin backbone in the form of covalent bonds, thus achieving chemical anchoring of the toughening segment and preventing migration or precipitation at any temperature.

[0034] Finally, experimental verification showed that the resin composition obtained by the above preparation method has a viscosity of less than 2000 mPa·s at room temperature and less than 500 mPa·s at 40°C, which can meet the injection requirements of liquid molding processes such as resin transfer molding and pultrusion. After being stored in a sealed container at 25°C for more than 180 days, the appearance remains uniform and transparent, without any precipitates, and the viscosity does not increase significantly. After curing according to the aforementioned step-curing process, the glass transition temperature is higher than 265°C, and the fracture toughness K0 is high. IC Greater than 1.6 MPa·m 1 / 2 The elongation at break is greater than 2.8%.

[0035] The above content will be further described below through specific implementation methods. It should be noted that all raw materials used in the examples are commercially available industrial-grade raw materials. The terminal allyl polyarylene ether sulfone oligomer was prepared in-house using the following method, which is an epoxy ring-opening etherification reaction: 100g each of hydroxyl-terminated polyarylene ether sulfones with number-average molecular weights of 1500, 2000, and 3000 (denoted as PES-OH-1500, PES-OH-2000, and PES-OH-3000, respectively) were dissolved in N-methylpyrrolidone. Allyl glycidyl ether was then added, maintaining the molar ratio of allyl glycidyl ether to hydroxyl groups in the system at 2:1. Triethylamine was added as a catalyst, and the reaction was carried out at a constant temperature of 80℃ for 12 hours. After the reaction, the reaction solution was poured into methanol to precipitate the product. The precipitate was then filtered, washed with alcohol, and vacuum dried to obtain oligomers of different specifications of terminal allyl polyarylene ether sulfones. The number-average allyl functionality of the products was determined by iodine titration, and the measured results were 2.2, 2.0, and 1.8, respectively.

[0036] All other raw materials used are commercially available industrial products, with the following specific specifications: diphenylmethane-type bismaleimide (BMI-1, purity ≥98%), toluene diamine-type bismaleimide (BMI-TDI, purity ≥98%), 2,2′-diallylbisphenol A (DABPA), diallylbisphenol S, 2-allylphenol, and 4-allyl anisole; the ionic liquids used are 1-ethyl-3-methylimidazolium dicyandiamide salt ([EMIm][N(CN)2]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][OTf]); the latent curing accelerators can be commercially available microcapsule-encapsulated imidazole or organic urea derivatives.

[0037] Example 1 This embodiment provides a low-viscosity toughened bismaleimide resin composition and its preparation method. By weight, the resin composition consists of: 100g of diphenylmethane-type bismaleimide resin, 40g of 2,2′-diallylbisphenol A, 20g of 2-allylphenol, 8g of 1-ethyl-3-methylimidazolium dicyandiamide salt, and 25g of terminal allyl polyarylene ether sulfone oligomer (number average molecular weight 2000, number average allyl functionality 2.0).

[0038] The preparation steps are as follows: Step 1: Add diphenylmethane-type bismaleimide resin, 2,2′-diallylbisphenol A, 2-allylphenol and 1-ethyl-3-methylimidazolium dicyandiamide salt to a three-necked flask according to the specified ratio. Under a nitrogen protective atmosphere, heat to 100°C and stir continuously for 30 minutes until all materials are fully dissolved to obtain a transparent red premixed liquid.

[0039] Step 2: Add terminal allyl polyarylene ether sulfone oligomer to the premix obtained in Step 1, maintain the temperature at 110°C, and continue stirring for 40 minutes to make the system completely homogeneous and transparent, thus obtaining a homogeneous mixture.

[0040] Step 3: Allow the homogeneous mixture obtained in Step 2 to cool naturally to room temperature without filtration to obtain a low-viscosity toughened bismaleimide resin composition with a yield of 99.8%.

[0041] Step 4: Pour the resin composition obtained in Step 3 into a preheated mold, place the mold in a forced-air drying oven, and perform heat curing according to a stepped heating process of 150℃ for 2 hours, 180℃ for 2 hours, and 220℃ for 2 hours. After cooling to room temperature, remove the resin sample.

[0042] Comparative Example 1 This comparative example refers to the method of Example 1 in CN118325332A, and provides a bismaleimide resin composition using amine solubilization. By weight, the components are: 100g of diphenylmethane-type bismaleimide resin, 43g of 2,2′-diallylbisphenol A, 43g of 2-allylphenol, 14.3g of cyclohexylamine, and 21.5g of oxazoline.

[0043] The preparation steps are as follows: Step 1: Add diphenylmethane-type bismaleimide resin, 2,2′-diallylbisphenol A, 2-allylphenol and cyclohexylamine to a three-necked flask, and stir for 15 minutes at 25°C under nitrogen protection to obtain a suspension in which the powder is uniformly dispersed.

[0044] Step 2: While stirring, raise the temperature to 60°C and continue stirring at 60°C for 30 minutes.

[0045] Step 3: Continue heating to 100℃ and stir for 30 minutes. At this point, the system will be a red solution.

[0046] Step 4: Add oxazoline to the solution obtained in Step 3, and continue stirring at 100°C for 20 minutes.

[0047] Step 5: While still hot, filter through a sieve to remove the insoluble gel generated by the amine side reaction. After cooling, the final product is obtained, with a yield of approximately 92% after filtration.

[0048] Step 6: Pour the final product into a preheated mold and perform heat curing according to a stepped curing process of holding at 140℃ for 2 hours, 160℃ for 2 hours, 200℃ for 2 hours, and 240℃ for 2 hours. After cooling, remove the resin sample.

[0049] Comparative Example 2 This comparative example refers to the method of Example 3 in CN119060536A, and provides a bismaleimide resin composition using an epoxy modifier combined with a physically blended thermoplastic resin. By weight, the components are: diallyl bisphenol A 25g, phenol 0.5g, diphenylmethane type bismaleimide resin 28g, toluene diamine type bismaleimide resin 30g, bisphenol F diglycidyl ether 12g, polyethersulfone toughening resin 5g, and triphenylphosphine 0.3g.

[0050] The preparation steps are as follows: Step 1: Add diallyl bisphenol A and phenol to a three-necked flask, heat to 125°C, and mix and stir for 30 minutes to obtain the first premix.

[0051] Step 2: Cool the first premix to 85°C, add the polyethersulfone toughened resin particles, and disperse for 25 minutes; then heat to 145°C and continuously mechanically stir for 25 minutes to completely dissolve the polyethersulfone, thus obtaining the second premix.

[0052] Step 3: Add toluene diamine-type bismaleimide resin and diphenylmethane-type bismaleimide resin to the second premix, and stir at 125°C for 25 minutes to obtain the third premix.

[0053] Step 4: Add bisphenol F diglycidyl ether to the third premix, control the temperature at 90°C, and mix and stir for 30 minutes; then cool to 75°C, add triphenylphosphine, stir for 30 minutes, and after cooling, obtain the modified bismaleimide resin composition, which does not require filtration and has a yield of 99%.

[0054] Step 5: Pour the above resin composition into a preheated mold and heat-cur it according to the curing process of holding at 150°C for 2 hours, 180°C for 2 hours, and 220°C for 2 hours. After cooling, take out the resin sample.

[0055] The performance of the finished products obtained in Example 1 and Comparative Examples 1 and 2 was tested. The results showed that the resin composition prepared in Example 1 had a viscosity of 1850 mPa·s at 25°C and 420 mPa·s at 40°C. After being stored in a sealed container at 25°C for 180 days, it remained transparent and homogeneous with no precipitates, and its viscosity was 1910 mPa·s. The glass transition temperature of the cured resin was 268°C, the tensile strength was 72 MPa, the elongation at break was 2.9%, and the fracture toughness K0 was [not specified]. IC 1.72 MPa·m 1 / 2 .

[0056] The resin composition prepared in Comparative Example 1 had a viscosity of 850 mPa·s at 40°C; trace precipitation began to appear after 90 days of storage at 25°C, and significant precipitation occurred after 120 days. The cured resin had a glass transition temperature of 265°C, a tensile strength of 62 MPa, an elongation at break of 1.8%, and a fracture toughness K0.05. IC Approximately 0.95 MPa·m 1 / 2 .

[0057] The resin composition prepared in Comparative Example 2 had a viscosity of 2.35 Pa·s (i.e., 2350 mPa·s) at 115°C, but no viscosity data was provided for 40°C. The resulting prepreg showed a significant decrease in viscosity after being stored at 25°C for 15 days, and white spots formed by the physical precipitation of common polyethersulfone appeared on the surface. The glass transition temperature of the cured resin was 220°C, and its fracture toughness K0 was [not specified]. IC 1.40 MPa·m 1 / 2 The elongation at break is 2.3%.

[0058] The performance test results above show that the low-viscosity toughened bismaleimide resin composition prepared by this invention has low viscosity, excellent storage stability, high heat resistance and excellent mechanical properties. Its viscosity is even lower at room temperature and medium and low temperature, making it suitable for various liquid molding processes. It does not release any components during long-term storage and its viscosity changes little. Compared with amine solubilization systems and physically blended modified resins, it not only has a higher glass transition temperature after curing, but also has superior mechanical properties such as tensile strength, elongation at break and fracture toughness. At the same time, no gel byproducts are generated during the preparation process, and no filtration is required, resulting in higher production efficiency and product yield. Overall, its comprehensive performance and industrial application value are significantly better than existing modified bismaleimide resins.

[0059] Example 2 This embodiment provides a low-viscosity toughened bismaleimide resin composition and its preparation method. By weight, the resin composition consists of: 80g of diphenylmethane-type bismaleimide resin, 20g of toluene diamine-type bismaleimide resin, 45g of diallyl bisphenol S, 15g of 4-allyl anisole, 10g of 1-butyl-3-methylimidazolium tetrafluoroborate, and 25g of terminal allyl polyarylene ether sulfone oligomer (number average molecular weight 3000, number average allyl functionality 1.8).

[0060] The preparation steps are as follows: Step 1: Add diphenylmethane-type bismaleimide resin, toluenediamine-type bismaleimide resin, diallyl bisphenol S, 4-allyl anisole, and 1-butyl-3-methylimidazolium tetrafluoroborate to a three-necked flask according to the specified ratio. Heat to 90°C under nitrogen protection and stir for 35 minutes until completely dissolved to obtain a transparent red premixed solution.

[0061] Step 2: Add terminal allyl polyarylene ether sulfone oligomer to the premix obtained in Step 1, maintain the temperature at 110°C, and continue stirring for 30 minutes to obtain a homogeneous and transparent mixture.

[0062] Step 3: Allow the homogeneous mixture obtained in Step 2 to cool naturally to room temperature without filtration to obtain a low-viscosity toughened bismaleimide resin composition with a yield of 99.6%.

[0063] Step 4: Perform heat curing according to the same step curing process as in Example 1 to obtain resin samples.

[0064] Performance testing showed that the resin composition prepared in this embodiment had a viscosity of 1920 mPa·s at 25°C and 460 mPa·s at 40°C; after 180 days of storage at 25°C, no precipitation occurred, and the viscosity remained at 1980 mPa·s. The cured resin had a glass transition temperature of 267°C, a tensile strength of 70 MPa, an elongation at break of 2.8%, and a fracture toughness of K0.05. IC 1.68 MPa·m 1 / 2 .

[0065] Example 3 This embodiment provides a low-viscosity toughened bismaleimide resin composition and its preparation method. By weight, the resin composition consists of: 100g of diphenylmethane-type bismaleimide resin, 60g of 2,2′-diallylbisphenol A, 30g of 2-allylphenol, 15g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 30g of terminal allyl polyarylene ether sulfone oligomer (number average molecular weight 1500, number average allyl functionality 2.2), and 2g of microcapsule-coated imidazole.

[0066] The preparation steps are as follows: Step 1: Add diphenylmethane-type bismaleimide resin, 2,2′-diallylbisphenol A, 2-allylphenol and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate to a three-necked flask according to the specified ratio, heat to 110°C under nitrogen protection, and stir for 25 minutes until completely dissolved to obtain a transparent premixed solution.

[0067] Step 2: Add terminal allyl polyarylene ether sulfone oligomer to the premix obtained in Step 1, maintain at 110°C and continue stirring for 45 minutes until the system is uniform and transparent, and obtain a homogeneous mixture.

[0068] Step 3: Cool the homogeneous mixture obtained in Step 2 to 70°C, add imidazole encapsulated in microcapsules, and stir for 20 minutes to obtain a compound mixture. The preferred temperature range for adding the mixture is 60~80°C.

[0069] Step 4: Allow the compound mixture obtained in Step 3 to cool naturally to room temperature without filtration to obtain a low-viscosity toughened bismaleimide resin composition with a yield of 99.7%.

[0070] Step 5: Pour the resin composition obtained in Step 4 into a preheated mold and heat-cur it according to a stepped heating process of 140℃ for 2 hours, 180℃ for 2 hours, and 220℃ for 2 hours. After cooling to room temperature, remove the resin sample.

[0071] Performance testing showed that the resin composition prepared in this embodiment had a viscosity of 1980 mPa·s at 25°C and 480 mPa·s at 40°C; after 180 days of storage at 25°C, no precipitation occurred, and the viscosity remained at 2040 mPa·s. The cured resin had a glass transition temperature of 266°C, a tensile strength of 71 MPa, an elongation at break of 3.1%, and a fracture toughness of K0. IC 1.78 MPa·m 1 / 2 .

[0072] Example 4 This embodiment provides a low-viscosity toughened bismaleimide resin composition and its preparation method. By weight, the resin composition consists of: 100g of diphenylmethane-type bismaleimide resin, 35g of diallyl bisphenol S, 15g of 2-allylphenol, 12g of 1-ethyl-3-methylimidazolium dicyandiamide salt, and 18g of terminal allyl polyarylene ether sulfone oligomer (number average molecular weight 4000, number average allyl functionality 1.6).

[0073] The preparation steps are as follows: Step 1: Add diphenylmethane-type bismaleimide resin, diallyl bisphenol S, 2-allyl phenol and 1-ethyl-3-methylimidazolium dicyandiamide salt to a three-necked flask according to the specified ratio. Heat to 120°C under nitrogen protection and stir for 30 minutes until completely dissolved to obtain a transparent red premixed solution.

[0074] Step 2: Add terminal allyl polyarylene ether sulfone oligomer to the premix obtained in Step 1, maintain the temperature at 120°C, and continue stirring for 30 minutes to obtain a homogeneous and transparent mixture.

[0075] Step 3: Allow the homogeneous mixture obtained in Step 2 to cool naturally to room temperature without filtration to obtain a low-viscosity toughened bismaleimide resin composition with a yield of 99.4%.

[0076] Step 4: Perform heat curing according to the same step curing process as in Example 1 to obtain resin samples.

[0077] Performance testing showed that the resin composition prepared in this embodiment had a viscosity of 1880 mPa·s at 25°C and 440 mPa·s at 40°C; after 180 days of storage at 25°C, no precipitation occurred, and the viscosity remained at 1950 mPa·s. The cured resin had a glass transition temperature of 265°C, a tensile strength of 68 MPa, an elongation at break of 2.8%, and a fracture toughness of K0. IC 1.65 MPa·m 1 / 2 .

[0078] Therefore, by using the above-mentioned low-viscosity toughened bismaleimide resin composition and its preparation method, the resin composition achieves low viscosity, high toughness, high heat resistance, and room temperature storage stability of over 180 days without the need for filtration and with a yield close to 100%.

[0079] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0080] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A low-viscosity toughened bismaleimide resin composition, characterized in that, It comprises the following components in parts by weight: 100 parts of bismaleimide resin, 30-80 parts of allyl compound, 10-40 parts of reactive thermoplastic toughening agent, 10-50 parts of reactive diluent, and 1-20 parts of ionic liquid solubilizer.

2. The low-viscosity toughened bismaleimide resin composition according to claim 1, characterized in that, The amount of the ionic liquid solubilizer added is 5 to 15 parts by weight, and the ionic liquid solubilizer is an imidazole ionic liquid.

3. The low-viscosity toughened bismaleimide resin composition according to claim 2, characterized in that, The imidazole ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium dicyandiamide, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate.

4. The low-viscosity toughened bismaleimide resin composition according to claim 1, characterized in that, The bismaleimide resin is selected from one or a combination of two of diphenylmethane-type bismaleimide and toluenediamine-type bismaleimide.

5. The low-viscosity toughened bismaleimide resin composition according to claim 1, characterized in that, The allyl compound is selected from at least one of 2,2'-diallylbisphenol A, diallylbisphenol S, and diallylphenol.

6. The low-viscosity toughened bismaleimide resin composition according to claim 1, characterized in that, The active diluent is selected from at least one of 2-allylphenol and 4-allyl anisole.

7. The low-viscosity toughened bismaleimide resin composition according to claim 1, characterized in that, The reactive thermoplastic toughening agent is a polyarylene ether sulfone oligomer with allyl end groups, having a number-average molecular weight of 1000-5000 and a number-average allyl functionality of 1.5-2.

5.

8. The low-viscosity toughened bismaleimide resin composition according to claim 1, characterized in that, The composition also contains 0.5 to 5 parts by weight of a latent curing accelerator, wherein the latent curing accelerator is selected from at least one of microencapsulated imidazole and organic urea derivatives.

9. A method for preparing a low-viscosity toughened bismaleimide resin composition according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Add bismaleimide resin, allyl compound, reactive diluent and ionic liquid solubilizer into the reaction vessel according to the ratio, heat to 80~120℃ under nitrogen atmosphere, stir until all materials are fully dissolved, and obtain a transparent premixed liquid. S2. Add a reactive thermoplastic toughening agent to the obtained transparent premix, maintain the temperature at 100~120℃ and stir for 20~60 minutes to obtain a homogeneous transparent mixture; S3. Allow the obtained homogeneous transparent mixture to cool naturally to room temperature to obtain the low-viscosity toughened bismaleimide resin composition.

10. The preparation method according to claim 9, characterized in that, After obtaining the homogeneous transparent mixture in step S2 and before cooling in step S3, a latent curing accelerator is added. The specific process is as follows: the homogeneous transparent mixture is cooled to 60~80℃, the latent curing accelerator is added and stirred for 15~30 minutes to obtain a compound mixture, and then the low viscosity toughened bismaleimide resin composition is obtained by cooling in step S3.

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