A method for preparing a bismaleimide resin and a bismaleimide resin composition

Abstract

This application belongs to the field of composite material technology, and particularly relates to a method for preparing bismaleimide resin and a bismaleimide resin composition. In the prior art, intralayer toughening and interlayer toughening are independent and lack synergy, or require additional complex post-processing steps such as powder spreading and toughening film application, or the amount of toughening agent added is limited, resulting in insufficient toughening effect. This solution introduces intralayer toughening agents and interlayer toughening agents with different compatibility into the same bismaleimide resin prepolymer. By utilizing the difference in compatibility between the two toughening agents and the bismaleimide resin prepolymer, as well as the extrusion-enrichment effect in the hot-melt prepreg preparation process, the intralayer toughening agent is spontaneously retained in the matrix and the interlayer toughening agent migrates and enriches at the interlayer interface in a one-pot process, achieving a zonal distribution of intralayer toughening agent retained in the matrix and interlayer toughening agent migrating and enriching at the interlayer interface without additional steps, thus obtaining the synergistic effect of intralayer toughening and interlayer toughening simultaneously.

Description

Technical Field

[0001] This application belongs to the field of composite material technology, and particularly relates to a method for preparing bismaleimide resin and a bismaleimide resin composition. Background Technology

[0002] Bismaleimide resins are thermosetting resins with excellent heat resistance, radiation resistance, high mechanical strength, and good dielectric properties. They are widely used in high-end composite material fields such as aerospace, electronic packaging, and rail transportation. Compared with epoxy resins, bismaleimide resins have a higher glass transition temperature (typically above 250℃) and a long-term service temperature of around 200℃. Compared with polyimide, bismaleimide resins have a wider processing window and a lower curing temperature (typically 180-230℃), making them more suitable for hot-melt prepreg preparation processes.

[0003] However, the inherently high crosslinking density of bismaleimide resin makes it brittle after curing, with poor impact resistance and crack resistance. In particular, the interlaminar fracture toughness of the composite material often fails to meet the requirements of the main load-bearing structural components. Existing technologies struggle to simultaneously achieve the following objectives: maintaining the good hot-melt processability of bismaleimide resin, improving the interlaminar toughness of the composite material without significantly sacrificing heat resistance, and avoiding complex post-processing steps. Summary of the Invention

[0004] This application provides a method for preparing bismaleimide resin and a bismaleimide resin composition to solve the following technical problem: how to prepare bismaleimide resin with synergistic toughening between layers and with excellent hot-melt processability in a one-pot process.

[0005] In a first aspect, embodiments of this application provide a method for preparing bismaleimide resin, the method comprising: A mixture of bismaleimide monomers and an allyl compound are added to a reaction vessel at a certain mass ratio. The mixture is heated to a first temperature and then stirred at a first stirring speed for a first duration to obtain a bismaleimide resin prepolymer. The bismaleimide resin prepolymer is cooled to a second temperature; then an intralayer toughening agent and an interlayer toughening agent are added to the bismaleimide resin prepolymer, and the mixture is stirred at a second stirring speed for a second duration to uniformly disperse the intralayer toughening agent and the interlayer toughening agent in the bismaleimide resin prepolymer, thereby obtaining a bismaleimide resin prepolymer mixture. The bismaleimide resin prepolymer mixture is ground to achieve submicron-level uniform dispersion of the intralayer toughening agent and the interlayer toughening agent, thereby obtaining the bismaleimide resin finished product. The bismaleimide monomer mixture is composed of at least three of the following four components: diphenylmethane bismaleimide, N,N'-m-phenylene bismaleimide, 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and phenylmethane maleimide polymer. The allyl compound is one or more of diallyl bisphenol A, diallyl bisphenol S, diallyl diphenyl ether, allyl ether ketone resin, and allyl phenol epoxy resin; The in-layer toughening agent is one or more of polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone. The interlayer toughening agent is one or more of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole.

[0006] Optionally, the amount of the allyl compound added is 45%-90% of the total mass of the bismaleimide monomer mixture, the amount of the intralayer toughening agent added is 5%-20% of the total mass of the bismaleimide monomer mixture, and the amount of the interlayer toughening agent added is 1%-10% of the total mass of the bismaleimide monomer mixture.

[0007] Optionally, the mass proportions of each component in the bismaleimide monomer mixture are as follows: 20-60 parts of diphenylmethane bismaleimide, 10-40 parts of N,N'-m-phenylene bismaleimide, 5-30 parts of 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and 5-30 parts of phenylmethane maleimide polymer.

[0008] Optionally, the number average molecular weight of the polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone is 5000-50000 g / mol; The number average molecular weights of the polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole are 10,000-60,000 g / mol.

[0009] Optionally, the first temperature is 120-150℃, the first stirring speed is 300-1000rpm, and the first duration is 20-60min.

[0010] Optionally, the second temperature is 60-100℃, the second stirring speed is 300-1000rpm, and the second duration is 10-40min.

[0011] Optionally, the grinding is carried out using a three-roll grinding process, and the grinding is performed 3-5 times.

[0012] Optionally, the method further includes: The bismaleimide resin product is coated on release paper using a hot melt method, a PE film is laid on top of the coating, and the film is then wound up to obtain a bismaleimide resin film. The thickness of the bismaleimide resin film is 50-100μm, and the coating temperature is 75-95℃. The bismaleimide resin film is compounded with unidirectional fibers to obtain a bismaleimide resin / fiber prepreg. The temperature of the heating roller in the compounding process is 90-110℃, and the temperature of the cooling plate is 10-15℃. The bismaleimide resin / fiber prepreg is cut, laid up, and hot-pressed to form a bismaleimide resin / fiber composite laminate.

[0013] Optionally, the unidirectional fiber is carbon fiber.

[0014] Optionally, the finished bismaleimide resin has a melt viscosity of 5000-50000 mPa·s in the range of 60-80°C.

[0015] Optionally, the bismaleimide resin / fiber prepreg has a resin content of 32-36 wt% and is laid up in 20 layers.

[0016] In a second aspect, embodiments of this application provide a bismaleimide resin composition, prepared by the method described in any one of the first aspects, wherein the bismaleimide resin composition comprises: Bismaleimide resin prepolymer is formed by prepolymerization of a mixture of bismaleimide monomers and allyl compounds; An intralayer toughening agent is uniformly dispersed in the bismaleimide resin prepolymer, wherein the intralayer toughening agent is one or more of polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone. An interlayer toughening agent is dispersed in the bismaleimide resin prepolymer in the form of submicron particles and enriched in the interlayer interface region after curing. The interlayer toughening agent is one or more of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole.

[0017] Optionally, the intralayer toughening agent forms a semi-interpenetrating network structure or a microphase separation structure after curing; After curing, the interlayer toughening agent forms a high-toughness interface layer enriched with interlayer toughening agent between every two layers of prepreg.

[0018] The technical solution provided in this application has the following advantages compared with the prior art: A mixture of bismaleimide monomers and an allyl compound were added to a reaction vessel at a specific mass ratio. The mixture was heated to a first temperature and then stirred at a first stirring speed for a first duration to obtain a bismaleimide resin prepolymer. The combination of multiple bismaleimide monomers controlled the crosslinking density and melt viscosity of the prepolymer. The allyl compound acted as a diluent in the prepolymerization reaction, ensuring that the bismaleimide resin prepolymer maintained a suitable viscosity while exhibiting good hot-melt processability. The bismaleimide resin prepolymer was then cooled to a second temperature, and then an in-layer toughening agent and an interlayer toughening agent were added. The mixture was stirred at a second stirring speed for a second duration to ensure that the in-layer and interlayer toughening agents were uniformly dispersed within the bismaleimide resin prepolymer, resulting in a bismaleimide resin prepolymer mixture. The in-layer toughening agent exhibited good compatibility with the bismaleimide resin prepolymer and could be uniformly dispersed within the bismaleimide resin matrix. The interlayer toughening agent… The toughening agent has relatively poor compatibility with bismaleimide resin prepolymer. In the subsequent hot-melt prepreg preparation process, it can migrate to the interlayer interface by utilizing the extrusion effect. The bismaleimide resin prepolymer mixture is ground to achieve submicron-level uniform dispersion of the intralayer toughening agent and interlayer toughening agent, thus obtaining the finished bismaleimide resin. The strong shearing action of the three-roll mill causes the intralayer toughening agent and bismaleimide resin prepolymer to form a molecular or submicron-level mixture, and the interlayer toughening agent is forcibly dispersed into submicron-level particles. Thus, in a one-pot process, the uniform dispersion of the intralayer toughening agent in the bismaleimide resin matrix and the spontaneous enrichment of the interlayer toughening agent at the interlayer interface are achieved simultaneously. This results in the finished bismaleimide resin having both intralayer and interlayer toughening effects while maintaining excellent hot-melt processability, solving the technical problem of how to prepare bismaleimide resin with synergistic intralayer and interlayer toughening and excellent hot-melt processability in a one-pot process. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other related drawings can be derived from these drawings without creative effort.

[0021] Figure 1 Dynamic thermomechanical analysis loss factor-temperature curves of bismaleimide resin / fiber composite laminates of Comparative Example 1, Example 1, Example 2 and Example 3 provided for embodiments of this application; Figure 2 Scanning electron microscope image of the cured bismaleimide resin / fiber composite laminate provided in the embodiments of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within the range. For example, a range description of "1 to 6" or "1~6" covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms used herein, including "comprising" and other terms indicating "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or steps and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist alone or simultaneously; expressions such as "at least one," "more than one," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in the text, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used in this text can all be obtained through commercial purchase or prepared by existing methods.

[0024] In a first aspect, embodiments of this application provide a method for preparing bismaleimide resin, the method comprising: A mixture of bismaleimide monomers and an allyl compound are added to a reaction vessel at a certain mass ratio. The mixture is heated to a first temperature and then stirred at a first stirring speed for a first duration to obtain a bismaleimide resin prepolymer. The bismaleimide resin prepolymer is cooled to a second temperature; then an intralayer toughening agent and an interlayer toughening agent are added to the bismaleimide resin prepolymer, and the mixture is stirred at a second stirring speed for a second duration to uniformly disperse the intralayer toughening agent and the interlayer toughening agent in the bismaleimide resin prepolymer, thereby obtaining a bismaleimide resin prepolymer mixture. The bismaleimide resin prepolymer mixture is ground to achieve submicron-level uniform dispersion of the intralayer toughening agent and the interlayer toughening agent, thereby obtaining the bismaleimide resin finished product. The bismaleimide monomer mixture is composed of at least three of the following four components: diphenylmethane bismaleimide, N,N'-m-phenylene bismaleimide, 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and phenylmethane maleimide polymer.

[0025] Diphenylmethane bismaleimide

[0026] N,N'-m-phenylenebismaleimide

[0027] 2,2'-Bis[4-(4-butadieneimidephenoxy)phenyl]propane

[0028] Phenylmethane maleimide polymer The allyl compound is one or more of diallyl bisphenol A, diallyl bisphenol S, diallyl diphenyl ether, allyl ether ketone resin, and allyl phenol epoxy resin; The in-layer toughening agent is one or more of polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone. The interlayer toughening agent is one or more of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole.

[0029] In existing technologies, intralayer toughening and interlayer toughening are isolated from each other, or require additional complex post-processing steps such as powder spreading and toughening film application, or the amount of toughening agent added is limited, resulting in insufficient toughening effect. This solution introduces intralayer toughening agents and interlayer toughening agents with different compatibility into the same bismaleimide resin prepolymer. By utilizing the difference in compatibility between the two toughening agents and the bismaleimide resin prepolymer, as well as the extrusion-enrichment effect in the hot-melt prepreg preparation process, the intralayer toughening agent is spontaneously retained in the matrix and the interlayer toughening agent migrates and enriches at the interlayer interface in a one-pot process, achieving a synergistic effect of intralayer toughening and interlayer toughening without additional steps.

[0030] In some embodiments, the allyl compound is added at 45%-90% of the total mass of the bismaleimide monomer mixture, the intralayer toughening agent is added at 5%-20% of the total mass of the bismaleimide monomer mixture, and the interlayer toughening agent is added at 1%-10% of the total mass of the bismaleimide monomer mixture.

[0031] The allyl compound is added at 45%-90% of the total mass of the bismaleimide monomer mixture, the in-layer toughening agent is added at 5%-20% of the total mass of the bismaleimide monomer mixture, and the interlayer toughening agent is added at 1%-10% of the total mass of the bismaleimide monomer mixture. Within this addition range, the allyl compound acts as a diluent to sufficiently reduce the melt viscosity of the bismaleimide resin prepolymer, ensuring that the bismaleimide resin prepolymer maintains suitable hot-melt coating processability. Within this addition range, the in-layer toughening agent is uniformly dispersed within the bismaleimide resin matrix to form an effective toughening phase without causing... The viscosity of the resin system increases sharply. Within this addition range, the interlayer toughening agent is dispersed in the bismaleimide resin prepolymer in the form of submicron particles and migrates and accumulates at the interlayer interface during the subsequent hot-melt prepreg preparation process. This achieves both intralayer and interlayer toughening while ensuring the excellent hot-melt processability of the finished bismaleimide resin. Consequently, the finished bismaleimide resin can have both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability in a one-pot process, solving the technical problem of how to prepare bismaleimide resin with synergistic intralayer and interlayer toughening and excellent hot-melt processability in a one-pot process.

[0032] The amount of allyl compound added includes, but is not limited to, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90% of the total mass of the bismaleimide monomer mixture. The amount of intralayer toughening agent added includes, but is not limited to, 5%, 8%, 10%, 12%, 15%, 18%, and 20% of the total mass of the bismaleimide monomer mixture. The amount of interlayer toughening agent added includes, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10% of the total mass of the bismaleimide monomer mixture.

[0033] In some embodiments, the mass proportions of each component in the bismaleimide monomer mixture are as follows: 20-60 parts of diphenylmethane bismaleimide, 10-40 parts of N,N'-m-phenylene bismaleimide, 5-30 parts of 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and 5-30 parts of phenylmethane maleimide polymer.

[0034] The mass proportions of each component in the bismaleimide monomer mixture are as follows: 20-60 parts of diphenylmethane bismaleimide, 10-40 parts of N,N'-m-phenylene bismaleimide, 5-30 parts of 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and 5-30 parts of phenylmethane maleimide polymer. Diphenylmethane bismaleimide serves as the main bismaleimide monomer, providing the basic cross-linked network structure. N,N'-m-phenylene bismaleimide regulates the rigidity and heat resistance of the prepolymer, and 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane introduces a flexible ether bond structure to improve toughness. The phenylmethane maleimide polymer provides multifunctional crosslinking points to regulate the crosslinking density. The four bismaleimide monomers synergistically regulate the crosslinking density and melt viscosity of the bismaleimide resin prepolymer within a specific mass ratio range, enabling the bismaleimide resin prepolymer to maintain excellent hot-melt processability while possessing good curing reactivity. This provides a suitable matrix viscosity environment for the synergistic dispersion of intralayer and interlayer toughening agents in a one-pot process, thereby enabling the finished bismaleimide resin product to have both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability. This solves the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot-melt processability in a one-pot process.

[0035] Diphenylmethane bismaleimide: including but not limited to 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, etc. N,N'-m-phenylene bismaleimide: including but not limited to 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, etc. 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane: including but not limited to 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 25 parts, 30 parts, etc. Phenylmethane maleimide polymer: including but not limited to 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 25 parts, 30 parts, etc.

[0036] In some embodiments, the number average molecular weight of the polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone is 5000-50000 g / mol; The number average molecular weights of the polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole are 10,000-60,000 g / mol.

[0037] The number average molecular weights of polyethersulfone, polyarylene ethersulfone, polyarylene ether ketone, and polyphenylene sulfone are 5000-50000 g / mol; the number average molecular weights of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole are 10000-60000 g / mol. Intralayer toughening agents with a number average molecular weight range of 5000-50000 g / mol exhibit good compatibility with bismaleimide resin prepolymers and can form a molecular- or submicron-level uniform mixture with bismaleimide resin prepolymers under the strong shearing action of three-roll milling. After curing, they form a semi-interpenetrating network structure or a microphase-separated structure. Interlayer toughening agents with a number average molecular weight range of 10000- The compatibility with bismaleimide resin prepolymer is relatively poor in the number-average molecular weight range of 60,000 g / mol. Under the strong shearing action of three-roll milling, it is dispersed into submicron particles. During the subsequent hot-melt prepreg preparation process, it migrates to the interlayer interface through the extrusion effect. Thus, in the one-pot process, the intralayer toughening agent is retained inside the bismaleimide resin matrix to exert the intralayer toughening effect, while the interlayer toughening agent is enriched at the interlayer interface to exert the interlayer toughening effect. As a result, the finished bismaleimide resin has both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability. This solves the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot-melt processability in a one-pot process.

[0038] The number-average molecular weights of polyethersulfone, polyarylene ethersulfone, polyarylene ether ketone, and polyphenylsulfone include, but are not limited to, 5000 g / mol, 10000 g / mol, 15000 g / mol, 20000 g / mol, 25000 g / mol, 30000 g / mol, 35000 g / mol, 40000 g / mol, 45000 g / mol, and 50000 g / mol. The number-average molecular weights of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole include, but are not limited to, 10,000 g / mol, 15,000 g / mol, 20,000 g / mol, 25,000 g / mol, 30,000 g / mol, 35,000 g / mol, 40,000 g / mol, 45,000 g / mol, 50,000 g / mol, 55,000 g / mol, and 60,000 g / mol.

[0039] In some embodiments, the first temperature is 120-150°C, the first stirring speed is 300-1000 rpm, and the first duration is 20-60 min.

[0040] The first temperature is 120-150℃, the first stirring speed is 300-1000 rpm, and the first time is 20-60 min. At the first temperature of 120-150℃, the bismaleimide monomer mixture and allyl compound undergo a prepolymerization reaction to form a bismaleimide resin prepolymer with a suitable molecular weight. The first stirring speed of 300-1000 rpm ensures uniform mixing of the reactants and controls the prepolymerization rate. The first time of 20-60 min allows the prepolymerization reaction to proceed until the bismaleimide resin prepolymer reaches a suitable viscosity and reactivity. Thus, under the synergistic effect of the first temperature, first stirring speed, and first time, a bismaleimide resin prepolymer with suitable melt viscosity and good hot-melt processability is obtained. This allows the bismaleimide resin prepolymer to simultaneously carry the uniform dispersion of intralayer and interlayer toughening agents and maintain excellent hot-melt processability in subsequent one-pot processes. This solves the technical problem of how to prepare bismaleimide resin with synergistic intralayer and interlayer toughening and excellent hot-melt processability in a one-pot process.

[0041] First temperature: including but not limited to 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, etc. First stirring speed: including but not limited to 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, etc. First stirring time: including but not limited to 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.

[0042] In some embodiments, the second temperature is 60-100°C, the second stirring speed is 300-1000 rpm, and the second duration is 10-40 min.

[0043] The second temperature is 60-100℃, the second stirring speed is 300-1000 rpm, and the second duration is 10-40 min. The second temperature, within the range of 60-100℃, is lower than the first temperature, ensuring that the bismaleimide resin prepolymer remains in a suitable molten state when the intralayer and interlayer toughening agents are added, preventing further prepolymerization. The second stirring speed, within the range of 300-1000 rpm, ensures that the intralayer and interlayer toughening agents are initially and uniformly dispersed in the bismaleimide resin prepolymer. The second duration, within the range of 10-40 min, ensures the effective dispersion of the intralayer and interlayer toughening agents. The toughening agent is fully impregnated and dispersed in the bismaleimide resin prepolymer, thereby obtaining a bismaleimide resin prepolymer mixture with initially uniform dispersion of intralayer and interlayer toughening agents under the synergistic effect of the second temperature, the second stirring speed, and the second duration. This makes it easy to achieve submicron-level uniform dispersion of the bismaleimide resin prepolymer mixture in the subsequent grinding process, providing a uniform intermediate product for the one-pot preparation of bismaleimide resin products with both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability. This solves the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot-melt processability in a one-pot process.

[0044] Second temperature: including but not limited to 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, etc. Second stirring speed: including but not limited to 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, etc. Second duration: including but not limited to 10min, 15min, 20min, 25min, 30min, 35min, 40min, etc.

[0045] In some embodiments, the grinding is performed using a three-roll grinding process, and the grinding is performed 3-5 times.

[0046] The grinding process employs a three-roll milling technique, with 3-5 milling cycles. This technique utilizes strong shearing to achieve a molecular- or submicron-level uniform mixture between the intralayer toughening agent molecular chains and the bismaleimide resin prepolymer. This forces the interlayer toughening agent to disperse into submicron-level particles. The 3-5 milling cycles ensure sufficient submicron-level uniform dispersion of both intralayer and interlayer toughening agents within the bismaleimide resin prepolymer. This allows the intralayer toughening agent to be uniformly dispersed within the bismaleimide resin matrix and retained in the one-pot process, while the interlayer toughening agent is uniformly dispersed in the bismaleimide resin prepolymer as submicron-level particles. During subsequent hot-melt prepreg preparation, the interlayer toughening agent migrates and accumulates at the interlayer interface. Consequently, the finished bismaleimide resin exhibits both synergistic intralayer and interlayer toughening effects and excellent hot-melt processability, thus solving the technical problem of how to prepare bismaleimide resin with synergistic intralayer and interlayer toughening and excellent hot-melt processability in a one-pot process.

[0047] In some embodiments, the method further includes: The bismaleimide resin product is coated on release paper using a hot melt method, a PE film is laid on top of the coating, and the film is then wound up to obtain a bismaleimide resin film. The thickness of the bismaleimide resin film is 50-100μm, and the coating temperature is 75-95℃. The bismaleimide resin film is compounded with unidirectional fibers to obtain a bismaleimide resin / fiber prepreg. The temperature of the heating roller in the compounding process is 90-110℃, and the temperature of the cooling plate is 10-15℃. The bismaleimide resin / fiber prepreg is cut, laid up, and hot-pressed to form a bismaleimide resin / fiber composite laminate.

[0048] The bismaleimide resin product is coated onto release paper using a hot-melt method. A PE film is then laid on top of the coating, and the mixture is wound up to obtain a bismaleimide resin film with a thickness of 50-100 μm. The coating temperature is 75-95℃. The bismaleimide resin product has a suitable melt viscosity of 5000-50000 mPa·s within the coating temperature range of 75-95℃, allowing the bismaleimide resin product to form a uniform film with a thickness of 50-100 μm on the release paper. The PE film covers and protects the surface of the film. The bismaleimide resin film is then compounded with unidirectional fibers to obtain a bismaleimide resin / fiber prepreg. The temperature of the heating roller for compounding is 90-110℃, and the temperature of the cooling plate is 10-15℃. The heating roller temperature of 90-110℃ allows the bismaleimide resin film to melt and fully impregnate and bond with the unidirectional fibers, while the cooling plate temperature of 10-15℃ allows the bismaleimide resin / fiber prepreg to bond effectively. The rapid shaping of bismaleimide prepreg involves the extrusion of interlayer toughening agent particles towards the flow front or low-shear region and their migration towards the interlayer interface during the hot-melt prepreg preparation process. The bismaleimide resin / fiber prepreg is then cut, laid up, and hot-pressed to form a bismaleimide resin / fiber composite laminate. During the hot-pressing process after laying up multiple layers of bismaleimide resin / fiber prepreg, the bismaleimide monomers and allyl compounds undergo a cross-linking reaction to form a three-dimensional network structure. The interlayer toughening agent is expelled from the matrix phase and physically fixed in the interlayer interface region. This results in a high-toughness interface layer enriched with interlayer toughening agent formed between every two layers of bismaleimide resin / fiber prepreg in a one-pot process. Consequently, the bismaleimide resin / fiber composite laminate exhibits both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability, solving the technical problem of how to prepare bismaleimide resin with synergistic intralayer and interlayer toughening and excellent hot-melt processability in a one-pot process.

[0049] Thickness of bismaleimide resin film: including but not limited to 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, etc. Coating temperature: including but not limited to 75℃, 78℃, 80℃, 82℃, 85℃, 88℃, 90℃, 92℃, 95℃, etc. Heating roller temperature: including but not limited to 90℃, 92℃, 95℃, 98℃, 100℃, 102℃, 105℃, 108℃, 110℃, etc. Cooling plate temperature: including but not limited to 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, etc.

[0050] In some embodiments, the unidirectional fiber is carbon fiber.

[0051] Unidirectional fiber is carbon fiber; carbon fiber has high strength, high modulus and low density mechanical properties, which enable the bismaleimide resin / fiber prepreg formed by the composite of bismaleimide resin film and carbon fiber to have excellent load-bearing capacity. The carbon fiber surface and the bismaleimide resin prepolymer in the finished bismaleimide resin have good interfacial bonding, which allows the interlayer toughening agent to effectively migrate along the carbon fiber surface to the interlayer interface region during the hot melt prepreg preparation process. Thus, in the one-pot process, the bismaleimide resin / carbon fiber prepreg can maintain the excellent mechanical properties of carbon fiber while also having a synergistic toughening effect between the layers. In this way, the bismaleimide resin / fiber composite laminate has both a synergistic toughening effect between the layers and the layers and excellent hot melt processability, which solves the technical problem of how to prepare bismaleimide resin with synergistic toughening between the layers and the layers and excellent hot melt processability in a one-pot process.

[0052] In some embodiments, the finished bismaleimide resin has a melt viscosity of 5000-50000 mPa·s in the range of 60-80°C.

[0053] The finished bismaleimide resin has a melt viscosity of 5000-50000 mPa·s within the range of 60-80℃. The finished bismaleimide resin also exhibits a suitable melt viscosity of 5000-50000 mPa·s within the test temperature range of 60-80℃. This ensures that the finished bismaleimide resin possesses sufficient fluidity to form a uniform film on the release paper during the hot-melt coating process, while also possessing appropriate viscosity to guarantee good interlayer adhesion after the film is peeled from the release paper. Thus, in a one-pot process, the finished bismaleimide resin meets the requirements of hot-melt prepreg for resin fluidity and film coating properties. Furthermore, the finished bismaleimide resin exhibits both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability, solving the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot-melt processability in a one-pot process.

[0054] The melt viscosity of bismaleimide resin products in the range of 60-80℃ includes, but is not limited to, 5000 mPa·s, 10000 mPa·s, 15000 mPa·s, 20000 mPa·s, 25000 mPa·s, 30000 mPa·s, 35000 mPa·s, 40000 mPa·s, 45000 mPa·s, and 50000 mPa·s. The coating temperature of bismaleimide resin products in the range of 60-80℃ includes, but is not limited to, 60℃, 65℃, 70℃, 75℃, and 80℃.

[0055] In some embodiments, the bismaleimide resin / fiber prepreg has a resin content of 32-36 wt% and is laid up in 20 layers.

[0056] The bismaleimide resin / fiber prepreg contains 32-36 wt% resin and has 20 layers. The 32-36 wt% resin content in the prepreg allows for a suitable resin matrix layer thickness between the carbon fibers, providing sufficient space for the enrichment of interlayer toughening agents at the interlayer interface. The 20-layer layup ensures that the prepreg forms a bismaleimide resin / fiber composite laminate with sufficient thickness and mechanical properties during hot pressing. Thus, the synergistic effect of the 32-36 wt% resin content and the 20-layer layup results in a high-toughness interface layer enriched with interlayer toughening agents between every two layers of prepreg. This allows the bismaleimide resin / fiber composite laminate to possess both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability, solving the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot-melt processability in a one-pot process.

[0057] The resin content in bismaleimide resin / fiber prepreg includes, but is not limited to, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, etc.

[0058] In a second aspect, embodiments of this application provide a bismaleimide resin composition, prepared by the method described in any one of the first aspects, wherein the bismaleimide resin composition comprises: Bismaleimide resin prepolymer is formed by prepolymerization of a mixture of bismaleimide monomers and allyl compounds; An intralayer toughening agent is uniformly dispersed in the bismaleimide resin prepolymer, wherein the intralayer toughening agent is one or more of polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone. An interlayer toughening agent is dispersed in the bismaleimide resin prepolymer in the form of submicron particles and enriched in the interlayer interface region after curing. The interlayer toughening agent is one or more of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole.

[0059] The bismaleimide resin composition is formed by prepolymerizing a mixture of bismaleimide monomers and allyl compounds to form a bismaleimide resin prepolymer. Intralayer toughening agents are uniformly dispersed within the bismaleimide resin prepolymer, while interlayer toughening agents are dispersed in the bismaleimide resin prepolymer as submicron-sized particles and enriched in the interlayer interface region after curing. The bismaleimide resin prepolymer, formed by prepolymerizing various bismaleimide monomers and allyl compounds, possesses suitable melt viscosity and good hot-melt processability. The intralayer toughening agents are uniformly dispersed within the bismaleimide resin prepolymer and form a semi-interpenetrating network structure or microphase separation structure after curing. During cracking, the toughening agents work through plastic deformation, crack pinning, and... The bridging mechanism absorbs energy to achieve intralayer toughening. The interlayer toughening agent is dispersed in the bismaleimide resin prepolymer in the form of submicron particles and is enriched in the interlayer interface region after curing to form a high-toughness interface layer, which effectively inhibits the initiation of interlayer cracks. Thus, in the one-pot process, the bismaleimide resin composition can simultaneously have the uniform toughening of the intralayer toughening agent in the matrix and the enrichment toughening of the interlayer toughening agent at the interlayer interface. In this way, the bismaleimide resin composition has both intralayer and interlayer synergistic toughening effect and excellent hot melt processability, which solves the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot melt processability in one pot.

[0060] In some embodiments, the intralayer toughening agent forms a semi-interpenetrating network structure or a microphase separation structure after curing; After curing, the interlayer toughening agent forms a high-toughness interface layer enriched with interlayer toughening agent between every two layers of prepreg.

[0061] After curing, the intralayer toughening agent forms a semi-interpenetrating network structure or a microphase separation structure. The interlayer toughening agent, after curing, forms a high-toughness interface layer enriched with interlayer toughening agent between every two layers of prepreg. During curing, the intralayer toughening agent forms a semi-interpenetrating network structure or a microphase separation structure with the bismaleimide resin prepolymer. During cracking, it absorbs energy through plastic deformation, crack pinning, and bridging mechanisms, achieving uniform toughening of the bismaleimide resin matrix. During curing, the interlayer toughening agent is physically fixed to the interlayer interface region by the locking effect of the cross-linked network, forming a high-toughness interface layer between every two layers of prepreg. A high-toughness interface layer enriched with interlayer toughening agent is formed between the impregnating materials. This high-toughness interface layer has higher fracture toughness than the bismaleimide resin matrix and can effectively inhibit the initiation and propagation of interlayer cracks. Thus, in the one-pot process, the intralayer toughening agent inhibits crack initiation inside the bismaleimide resin matrix, and the interlayer toughening agent prevents cracking in the interlayer interface region. As a result, the bismaleimide resin composition has both intralayer and interlayer synergistic toughening effects and excellent hot-melt processability, solving the technical problem of how to prepare bismaleimide resin with intralayer and interlayer synergistic toughening and excellent hot-melt processability in a one-pot process.

[0062] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0063] Example 1 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 20 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0064] (2) Allyl compounds: 60 parts of diallyl bisphenol A.

[0065] (3) In-layer toughening agent: 12 parts of polyethersulfone (Mn≈20000).

[0066] (4) Interlayer toughening agent: None.

[0067] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 500 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0068] The bismaleimide resin prepolymer was cooled to 80°C; then an intralayer toughening agent was added to the bismaleimide resin prepolymer, and the mixture was stirred at a second stirring speed of 500 rpm for a second stirring time of 30 min to ensure that the intralayer toughening agent was uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0069] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with three milling cycles, to achieve submicron-level uniform dispersion of the toughening agent within the layer, thus obtaining the finished bismaleimide resin product.

[0070] Example 2 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 20 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0071] (2) Allyl compounds: Diallyl bisphenol A 65 parts.

[0072] (3) In-layer toughening agent: None.

[0073] (4) Interlayer toughening agent: 5 parts of polyimide (Mn≈30000).

[0074] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 500 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0075] The bismaleimide resin prepolymer was cooled to 100°C; then an interlayer toughening agent was added to the bismaleimide resin prepolymer, and the mixture was stirred at a second stirring speed of 500 rpm for a second duration of 20 min to ensure that the interlayer toughening agent was uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0076] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with four milling cycles, to achieve submicron-level uniform dispersion of the interlayer toughening agent, thus obtaining the finished bismaleimide resin product.

[0077] Example 3 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 40 parts of diphenylmethane bismaleimide, 40 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0078] (2) Allyl compounds: 60 parts of diallyl bisphenol A.

[0079] (3) In-layer toughening agent: 12 parts of polyethersulfone (Mn≈20000).

[0080] (4) Interlayer toughening agent: 5 parts of polyimide (Mn≈30000).

[0081] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to the reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 600 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0082] The bismaleimide resin prepolymer was cooled to 100°C. Then, an intralayer toughening agent and an interlayer toughening agent were added to the bismaleimide resin prepolymer. The mixture was stirred at a second stirring speed of 600 rpm for a second duration of 20 min to ensure that the intralayer toughening agent and the interlayer toughening agent were uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0083] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with five milling cycles, to achieve submicron-level uniform dispersion of the intralayer and interlayer toughening agents, thus obtaining the finished bismaleimide resin product.

[0084] Example 4 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 50 parts of diphenylmethane bismaleimide, 30 parts of N,N'-m-phenylene bismaleimide, 15 parts of 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and 5 parts of phenylmethane maleimide polymer.

[0085] (2) Allyl compounds: Diallyl bisphenol S 70 parts.

[0086] (3) In-layer toughening agent: 15 parts of polyarylether sulfone (Mn≈15000).

[0087] (4) Interlayer toughening agent: 8 parts of polyetherimide (Mn≈25000).

[0088] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 140°C and stirred at a first stirring speed of 600 rpm for a first stirring time of 40 min to obtain the bismaleimide resin prepolymer.

[0089] The bismaleimide resin prepolymer was cooled to 90°C. Then, an intralayer toughening agent and an interlayer toughening agent were added to the bismaleimide resin prepolymer. The mixture was stirred at a second stirring speed of 600 rpm for a second duration of 25 min to ensure that the intralayer toughening agent and the interlayer toughening agent were uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0090] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with three milling cycles, to achieve submicron-level uniform dispersion of the intralayer and interlayer toughening agents, thus obtaining the finished bismaleimide resin product.

[0091] Example 5 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 55 parts of diphenylmethane bismaleimide, 25 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0092] (2) Allyl compounds: 55 parts diallyl diphenyl ether.

[0093] (3) In-layer toughening agent: 10 parts of polyaryletherketone (Mn≈30000).

[0094] (4) Interlayer toughening agent: 6 parts of polyether ether ketone (Mn≈40000).

[0095] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 125°C and stirred at a first stirring speed of 400 rpm for a first stirring time of 35 min to obtain the bismaleimide resin prepolymer.

[0096] The bismaleimide resin prepolymer was cooled to 70°C. Then, an intralayer toughening agent and an interlayer toughening agent were added to the bismaleimide resin prepolymer. The mixture was stirred at a second stirring speed of 500 rpm for a second duration of 30 min to ensure that the intralayer toughening agent and the interlayer toughening agent were uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0097] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with four milling cycles, to achieve submicron-level uniform dispersion of the intralayer and interlayer toughening agents, thus obtaining the finished bismaleimide resin product.

[0098] Example 6 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 45 parts of diphenylmethane bismaleimide, 35 parts of N,N'-m-phenylene bismaleimide, 12 parts of 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and 8 parts of phenylmethane maleimide polymer.

[0099] (2) Allyl compounds: 80 parts of allyl ether ketone resin.

[0100] (3) In-layer toughening agent: 18 parts of polyphenylsulfone (Mn≈25000).

[0101] (4) Interlayer toughening agent: 4 parts of polyphenylene sulfide (Mn≈35000).

[0102] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 150°C and stirred at a first stirring speed of 800 rpm for 25 min to obtain the bismaleimide resin prepolymer.

[0103] The bismaleimide resin prepolymer was cooled to 85°C. Then, an intralayer toughening agent and an interlayer toughening agent were added to the bismaleimide resin prepolymer. The mixture was stirred at a second stirring speed of 800 rpm for a second duration of 15 min to ensure that the intralayer toughening agent and the interlayer toughening agent were uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0104] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with five milling cycles, to achieve submicron-level uniform dispersion of the intralayer and interlayer toughening agents, thus obtaining the finished bismaleimide resin product.

[0105] Example 7 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 30 parts of N,N'-m-phenylene bismaleimide, and 10 parts of 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane.

[0106] (2) Allyl compounds: 50 parts of allylphenol epoxy resin.

[0107] (3) In-layer toughening agent: 8 parts of polyethersulfone (Mn≈35000).

[0108] (4) Interlayer toughening agent: 7 parts of polyether ketone (Mn≈20000).

[0109] Preparation method: The bismaleimide monomer mixture and allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 135°C and stirred at a first stirring speed of 700 rpm for a first stirring time of 45 min to obtain the bismaleimide resin prepolymer.

[0110] The bismaleimide resin prepolymer was cooled to 75°C. Then, an intralayer toughening agent and an interlayer toughening agent were added to the bismaleimide resin prepolymer. The mixture was stirred at a second stirring speed of 700 rpm for a second duration of 20 min to ensure that the intralayer toughening agent and the interlayer toughening agent were uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0111] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with four milling cycles, to achieve submicron-level uniform dispersion of the intralayer and interlayer toughening agents, thus obtaining the finished bismaleimide resin product.

[0112] Comparative Example 1 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 20 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0113] (2) Allyl compounds: 60 parts of diallyl bisphenol A.

[0114] (3) In-layer toughening agent: None.

[0115] (4) Interlayer toughening agent: None.

[0116] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 500 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0117] Comparative Example 2 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 20 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0118] (2) Allyl compounds: 60 parts of diallyl bisphenol A.

[0119] (3) In-layer toughening agent: 25 parts of polyethersulfone (Mn≈20000).

[0120] (4) Interlayer toughening agent: None.

[0121] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 500 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0122] The bismaleimide resin prepolymer was cooled to 80°C; then an intralayer toughening agent was added to the bismaleimide resin prepolymer, and the mixture was stirred at a second stirring speed of 500 rpm for a second stirring time of 30 min to ensure that the intralayer toughening agent was uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0123] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with three milling cycles, to achieve submicron-level uniform dispersion of the toughening agent within the layer, thus obtaining the finished bismaleimide resin product.

[0124] Comparative Example 3 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 20 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0125] (2) Allyl compounds: 60 parts of diallyl bisphenol A.

[0126] (3) In-layer toughening agent: None.

[0127] (4) Interlayer toughening agent: 15 parts of polyimide (Mn≈30000).

[0128] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 500 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0129] The bismaleimide resin prepolymer was cooled to 100°C; then an interlayer toughening agent was added to the bismaleimide resin prepolymer, and the mixture was stirred at a second stirring speed of 500 rpm for a second duration of 20 min to ensure that the interlayer toughening agent was uniformly dispersed in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0130] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with four milling cycles, to achieve submicron-level uniform dispersion of the interlayer toughening agent, thus obtaining the finished bismaleimide resin product.

[0131] Comparative Example 4 Formula composition: (1) Mixture of bismaleimide monomers (total mass 100 parts): 60 parts of diphenylmethane bismaleimide, 20 parts of N,N'-m-phenylene bismaleimide, 10 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 10 parts of phenylmethane maleimide polymer.

[0132] (2) Allyl compounds: 60 parts of diallyl bisphenol A.

[0133] (3) In-layer toughening agent: 10 parts of carboxyl-terminated butadiene nitrile rubber.

[0134] (4) Interlayer toughening agent: None.

[0135] Preparation method: The bismaleimide monomer mixture and the allyl compound were added to a reaction vessel at a certain mass ratio. The mixture was heated to 130°C and stirred at a first stirring speed of 500 rpm for a first stirring time of 30 min to obtain the bismaleimide resin prepolymer.

[0136] The bismaleimide resin prepolymer was cooled to 80°C; then, carboxyl-terminated nitrile butadiene rubber was added to the bismaleimide resin prepolymer, and the mixture was stirred at a second stirring speed of 500 rpm for a second stirring time of 30 min to uniformly disperse the carboxyl-terminated nitrile butadiene rubber in the bismaleimide resin prepolymer, thus obtaining a bismaleimide resin prepolymer mixture.

[0137] The bismaleimide resin prepolymer mixture was milled using a three-roll milling process, with five milling cycles, to achieve submicron-level uniform dispersion of the carboxyl-terminated nitrile rubber, thus obtaining the finished bismaleimide resin product.

[0138] Experimental methods for evaluating results: 1. Method for testing interlaminar shear strength at room temperature: The test was conducted according to GB / T 1450.1-2005 "Test Method for Interlaminar Shear Strength of Fiber Reinforced Plastics". The test temperature was 23±2℃, the sample size was 25mm×6mm×2mm, the loading rate was 2mm / min, the maximum load at which the sample failed in interlaminar shear was recorded, and the interlaminar shear strength was calculated.

[0139] 2. Method for testing interlaminar shear strength at 220℃: The test was conducted according to GB / T 1450.1-2005 "Test Method for Interlaminar Shear Strength of Fiber Reinforced Plastics". The test temperature was 220±2℃. The specimen was kept at the test temperature for 10 min before the test. The specimen size was 25mm×6mm×2mm. The loading rate was 2mm / min. The maximum load at which the specimen failed in interlaminar shear was recorded, and the interlaminar shear strength was calculated.

[0140] 3. Glass transition temperature (Tg) test method: The test was conducted according to GB / T 19466.2-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 2: Determination of Glass Transition Temperature". The heating rate was 10℃ / min, and the atmosphere was nitrogen. The midpoint temperature of the glass transition on the DSC curve was recorded as the glass transition temperature (Tg).

[0141] 4. Evaluation method for hot melt coating: The bismaleimide resin product was coated onto release paper using a hot melt method. The coating temperature was controlled within the melt viscosity test temperature range of the bismaleimide resin product. The uniformity of the film surface was visually observed. The melt viscosity of the bismaleimide resin product at the coating temperature was measured using a rotational viscometer to evaluate the uniformity and viscosity suitability of the film.

[0142] Table 1. Results of Examples / Comparative Examples

[0143] Detailed explanation of the attached diagram: Figure 1 Dynamic thermomechanical analysis loss factor-temperature curves of bismaleimide resin / fiber composite laminates of Comparative Example 1, Example 1, Example 2 and Example 3 provided for embodiments of this application; from Figure 1It can be seen that: Comparative Example 1 is a pure bismaleimide resin system without the addition of intralayer and interlayer toughening agents, and its glass transition temperature is 280.24℃. The bismaleimide resin product of Example 1 contains polyethersulfone, and its glass transition temperature is 274.98℃. The glass transition temperature of Example 1 is lower than that of Comparative Example 1, indicating that the introduction of polyethersulfone has a slight effect on the heat resistance of the bismaleimide resin / fiber composite laminate. The bismaleimide resin product of Example 2 contains polyimide as an interlayer toughening agent, and its glass transition temperature is 281.02℃. The glass transition temperature of Example 2 is higher than that of Comparative Example 1, indicating that the interlayer toughening agent polyimide itself has extremely high heat resistance, and the introduction of the interlayer toughening agent polyimide improves the heat resistance of the bismaleimide resin / fiber composite laminate. In Example 3, the bismaleimide resin product contained both polyethersulfone and interlayer toughening agent polyimide. The glass transition temperature of Example 3 was 289.55°C. The glass transition temperature of Example 3 was higher than that of Comparative Example 1, indicating that under a specific ratio, the synergistic effect of polyethersulfone and interlayer toughening agent polyimide not only did not reduce the heat resistance of the bismaleimide resin / fiber composite laminate, but also improved the heat resistance of the bismaleimide resin / fiber composite laminate.

[0144] Figure 2 Scanning electron microscope image of the cured bismaleimide resin / fiber composite laminate provided in the embodiments of this application; from Figure 2 It can be seen that: Figure 2 The cured bismaleimide resin matrix exhibits a clear phase separation structure. Figure 2 The medium-dark continuous phase is the cross-linked network matrix after bismaleimide resin is cured, and the light-colored dispersed phase is toughening agent particles. The toughening agent particles are irregularly shaped and dispersed in the bismaleimide resin matrix, and the size of the toughening agent particles is in the submicron to micron range. Figure 2 The toughening agent particles have good interfacial bonding with the bismaleimide resin matrix. Figure 2 No obvious interfacial debonding or pore defects were observed between the toughening agent particles and the bismaleimide resin matrix. Figure 2 The toughening agent particles in the middle exhibit plastic deformation characteristics, indicating that during the cracking process, the toughening agent particles absorb energy through plastic deformation, crack pinning and bridging mechanisms, thereby achieving the toughening effect of the bismaleimide resin matrix. Figure 2 The microstructure shows that the intralayer toughening agent forms a semi-interpenetrating network structure or microphase separation structure inside the bismaleimide resin matrix, the intralayer toughening agent is uniformly distributed inside the bismaleimide resin matrix, and the interlayer toughening agent is enriched in the interlayer interface region to form a high-toughness interface layer.

[0145] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing bismaleimide resin, characterized in that, The method includes: A mixture of bismaleimide monomers and an allyl compound are added to a reaction vessel at a certain mass ratio. The mixture is heated to a first temperature and then stirred at a first stirring speed for a first duration to obtain a bismaleimide resin prepolymer. The bismaleimide resin prepolymer is cooled to a second temperature; then an intralayer toughening agent and an interlayer toughening agent are added to the bismaleimide resin prepolymer, and the mixture is stirred at a second stirring speed for a second duration to uniformly disperse the intralayer toughening agent and the interlayer toughening agent in the bismaleimide resin prepolymer, thereby obtaining a bismaleimide resin prepolymer mixture. The bismaleimide resin prepolymer mixture is ground to achieve submicron-level uniform dispersion of the intralayer toughening agent and the interlayer toughening agent, thereby obtaining the bismaleimide resin finished product. The bismaleimide monomer mixture is composed of at least three of the following four components: diphenylmethane bismaleimide, N,N'-m-phenylene bismaleimide, 2,2'-bis[4-(4-butadieneimide phenoxy)phenyl]propane, and phenylmethane maleimide polymer. The allyl compound is one or more of diallyl bisphenol A, diallyl bisphenol S, diallyl diphenyl ether, allyl ether ketone resin, and allyl phenol epoxy resin; The in-layer toughening agent is one or more of polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone. The interlayer toughening agent is one or more of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole.

2. The method for preparing bismaleimide resin according to claim 1, characterized in that, The amount of the allyl compound added is 45%-90% of the total mass of the bismaleimide monomer mixture, the amount of the intralayer toughening agent added is 5%-20% of the total mass of the bismaleimide monomer mixture, and the amount of the interlayer toughening agent added is 1%-10% of the total mass of the bismaleimide monomer mixture.

3. The method for preparing bismaleimide resin according to claim 1, characterized in that, The mass proportions of each component in the bismaleimide monomer mixture are as follows: 20-60 parts of diphenylmethane bismaleimide, 10-40 parts of N,N'-m-phenylene bismaleimide, 5-30 parts of 2,2'-bis[4-(4-cis-butadieneimide phenoxy)phenyl]propane, and 5-30 parts of phenylmethane maleimide polymer.

4. The method for preparing bismaleimide resin according to claims 1 to 3, characterized in that, The number average molecular weight of the polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone is 5000-50000 g / mol. The number average molecular weights of the polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole are 10,000-60,000 g / mol.

5. The method for preparing bismaleimide resin according to claim 1, characterized in that, The first temperature is 120-150℃, the first stirring speed is 300-1000rpm, and the first duration is 20-60min.

6. The method for preparing bismaleimide resin according to claim 1, characterized in that, The second temperature is 60-100℃, the second stirring speed is 300-1000rpm, and the second duration is 10-40min.

7. The method for preparing bismaleimide resin according to claim 1, characterized in that, The grinding process is carried out using a three-roll grinding process, and the grinding is performed 3-5 times.

8. The method for preparing bismaleimide resin according to claim 1, characterized in that, The method further includes: The bismaleimide resin product is coated on release paper using a hot melt method, a PE film is laid on top of the coating, and the film is then wound up to obtain a bismaleimide resin film. The thickness of the bismaleimide resin film is 50-100μm, and the coating temperature is 75-95℃. The bismaleimide resin film is compounded with unidirectional fibers to obtain a bismaleimide resin / fiber prepreg. The temperature of the heating roller in the compounding process is 90-110℃, and the temperature of the cooling plate is 10-15℃. The bismaleimide resin / fiber prepreg is cut, laid up, and hot-pressed to form a bismaleimide resin / fiber composite laminate.

9. The method for preparing bismaleimide resin according to claim 8, characterized in that, The unidirectional fiber is carbon fiber.

10. The method for preparing bismaleimide resin according to claim 1, characterized in that, The finished bismaleimide resin has a melt viscosity of 5000-50000 mPa·s in the range of 60-80℃.

11. The method for preparing bismaleimide resin according to claim 8 or 9, characterized in that, The bismaleimide resin / fiber prepreg has a resin content of 32-36 wt% and a layup of 20 layers.

12. A bismaleimide resin composition, characterized in that, The bismaleimide resin composition is prepared by the method according to any one of claims 1-11, and comprises: Bismaleimide resin prepolymer is formed by prepolymerization of a mixture of bismaleimide monomers and allyl compounds; An intralayer toughening agent is uniformly dispersed in the bismaleimide resin prepolymer, wherein the intralayer toughening agent is one or more of polyethersulfone, polyarylethersulfone, polyaryletherketone, and polyphenylsulfone. An interlayer toughening agent is dispersed in the bismaleimide resin prepolymer in the form of submicron particles and enriched in the interlayer interface region after curing. The interlayer toughening agent is one or more of polyetherimide, polyimide, polyetheretherketone, polyetherketoneketone, polyphenylene sulfide, and polyphenylene imidazole.

13. The bismaleimide resin composition according to claim 12, characterized in that, The intralayer toughening agent forms a semi-interpenetrating network structure or a microphase separation structure after curing. After curing, the interlayer toughening agent forms a high-toughness interface layer enriched with interlayer toughening agent between every two layers of prepreg.

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