Halogen-free flame-retardant wave-transparent bismaleimide resin, prepreg and preparation method thereof

Abstract

The invention relates to the technical field of resin-based composite materials, in particular to halogen-free flame-retardant wave-transparent bismaleimide resin, prepreg and a preparation method thereof. The halogen-free flame-retardant wave-transparent bismaleimide resin comprises the following components in parts by weight: 100 parts of bismaleimide resin monomer; 30-60 parts of flame-retardant temperature-resistant epoxy resin; 70 to 130 parts of an allyl compound; 15-30 parts of a curing agent; 20 to 100 parts of a flame retardant; and 10-40 parts of a toughening agent. The halogen-free flame-retardant wave-transparent bismaleimide resin prepreg comprises halogen-free flame-retardant wave-transparent bismaleimide resin, and the mass ratio of the halogen-free flame-retardant wave-transparent bismaleimide resin is 30-60%. The halogen-free flame-retardant wave-transparent bismaleimide resin, the prepreg and the preparation method of the halogen-free flame-retardant wave-transparent bismaleimide resin and the prepreg aim at solving the problem that the bismaleimide resin is difficult to have good low dielectricity and high flame retardance at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of resin-based composite materials, and in particular to a halogen-free flame-retardant wave-transmitting bismaleimide resin, a prepreg and a preparation method thereof. Background Art

[0002] Resin-based composites offer advantages such as high specific strength, high specific modulus, strong designability, and ease of integral molding, making them widely used in aerospace, transportation, energy, and communications. Bismaleimide (BMI), a bifunctional compound with maleimide as the active end group, can be copolymerized with a variety of compounds to produce tough, heat-resistant resins. Its backbone contains aromatic and nitrogen heterocyclic rings, endowing these resins with excellent properties such as high-temperature resistance, heat and humidity resistance, radiation resistance, high insulation, friction resistance, flame retardancy, excellent mechanical properties, and dimensional stability. These resins are used in defense, aerospace, electronics, and other fields. BMI resin composites prepared with BMI as a matrix are widely used as wave-transmitting materials in structures such as radomes and smart skins.

[0003] In recent years, researchers have conducted research on the wave transmission performance or flame retardant performance of BMA, but existing wave-transmitting BMA resin composite materials usually do not comprehensively consider the flame retardant performance of the material (such as invention patent CN117986864A), or the flame retardant performance is relatively low (such as invention patent CN117327286A, the flame retardant grade can reach V-0 level but is unstable, and the material heat release rate is greater than 350W), or contain halogens that are harmful to the human body, such as fluorine and bromine. Conversely, BMA resin composite materials for flame retardancy also do not comprehensively consider the wave transmission performance of the material, and the flame retardant performance is relatively low (such as invention patent CN117866013A, which only contains limiting oxygen index and decomposition temperature, and no performance characterization such as heat release rate).

[0004] Therefore, the inventors provide a halogen-free flame-retardant wave-transmitting bismaleimide resin, a prepreg and a preparation method thereof. Summary of the Invention

[0005] (1) Technical problems to be solved The embodiments of the present invention provide a halogen-free flame-retardant wave-transmitting bismaleimide resin, a prepreg and a preparation method thereof, which solve the technical problem that bismaleimide resin is difficult to achieve both good low dielectric properties and high flame retardancy.

[0006] (2) Technical solution The first aspect of the present invention provides a halogen-free flame-retardant wave-transmitting bismaleimide resin, which comprises the following components in parts by weight: 100 parts of bismaleimide resin monomer; 30-60 parts of flame retardant and heat resistant epoxy resin; 70-130 parts of allyl compound; 15-30 parts of curing agent; 20-100 parts of flame retardant; 10 to 40 parts of toughening agent.

[0007] Furthermore, the bismaleimide resin monomer is diphenylmethane bismaleimide.

[0008] Furthermore, the heat-resistant and flame-retardant epoxy resin includes at least one of a biphenyl epoxy resin and a phenolic epoxy resin.

[0009] Furthermore, the allyl compound is at least one of a monoallyl compound, diallyl bisphenol A, and allyl phenol formaldehyde.

[0010] Furthermore, the curing agent is 4,4'-diaminodiphenyl sulfone.

[0011] Furthermore, the toughening agent is at least one of thermoplastic polyimide, thermoplastic polyaryletherketone, thermoplastic polyether, thermoplastic polyimide modified product, thermoplastic polyaryletherketone modified product, and thermoplastic polyether modified product.

[0012] A second aspect of the present invention provides a halogen-free flame retardant and wave-transmitting bismaleimide resin prepreg, comprising the above-mentioned halogen-free flame retardant and wave-transmitting bismaleimide resin, with the mass proportion of the resin being 30 to 60%.

[0013] Furthermore, the thickness of a single layer of solidification is 0.01 to 0.45 mm.

[0014] A third aspect of the present invention provides a method for preparing the above-mentioned halogen-free flame-retardant and wave-transmitting bismaleimide resin prepreg, comprising the following steps: The heat-resistant flame-retardant epoxy and the allyl compound are prepolymerized, and then the bismaleimide resin monomer, curing agent, flame retardant and toughening agent are added and fully mixed and dispersed to obtain a halogen-free flame-retardant wave-transmitting bismaleimide resin; The halogen-free flame-retardant bismaleimide resin is made into a film and compounded with continuous fibers or fabrics to prepare a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg.

[0015] Furthermore, the halogen-free flame-retardant bismaleimide resin is made into a film and compounded with continuous fibers or fabrics to prepare a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg, specifically: According to the resin content requirements and the surface density of the fiber reinforcement material, the halogen-free flame-retardant and wave-transmitting bismaleimide resin is made into a film on a film machine, and is compounded with the continuous fiber or fabric on a prepreg machine to make the halogen-free flame-retardant and wave-transmitting bismaleimide resin prepreg.

[0016] (3) Beneficial effects In summary, the present invention adopts a flame-retardant and heat-resistant epoxy resin with a high carbon content, copolymerizes it with an allyl compound, blends it with a bismaleimide monomer, and adds an appropriate amount of additive flame retardant and toughening agent. While improving the flame retardant properties of the material, it minimizes the impact on the low dielectric wave transmission properties of the material itself. The halogen-free flame-retardant and wave-transmitting bismaleimide resin prepreg has excellent low dielectric properties and temperature resistance, which can meet the use requirements of wave-transmitting materials in medium and high temperature environments; at the same time, it has excellent flame retardant properties, the combustion performance reaches V0 level, and the peak heat release rate of the composite material is greatly reduced, which meets the use requirements of cabin materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 The present invention provides a flow chart of a method for preparing a halogen-free, flame-retardant, and wave-transmitting bismaleimide resin prepreg. DETAILED DESCRIPTION

[0019] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments.

[0020] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] On the one hand, an embodiment of the present invention provides a halogen-free, flame-retardant, wave-transmitting bismaleimide resin, which may include the following components, in parts by weight: 100 parts of bismaleimide resin monomer; 30 to 60 parts of flame-retardant and heat-resistant epoxy resin; 70 to 130 parts of allyl compound; 15 to 30 parts of curing agent; 20 to 100 parts of flame retardant; and 10 to 40 parts of toughening agent.

[0022] In the above embodiment, traditional bismaleimide resins offer excellent low-dielectric wave transmission performance (dielectric constant of 2.8-3.2), heat resistance, and mechanical properties, but their inherent flame retardancy is poor. The addition of traditional halogen-free flame retardant additives creates interfacial effects that increase the dielectric constant of the material, thereby reducing its wave transmission performance. Alternatively, a low-dielectric reactive flame-retardant resin can be introduced. Among reactive resins, phenolic resins offer excellent flame retardancy and heat resistance, but their high dielectric constant (4.5-5) makes them difficult to directly apply to the preparation of low-dielectric wave-transmitting materials. Conventional epoxy resins have a low dielectric constant (3.0-3.4), but their inherent flame retardancy and low temperature resistance make them difficult to directly apply to the preparation of flame-retardant materials. Highly heat-resistant flame-retardant epoxy resins (biphenyl-type epoxies and phenolic-type epoxies) have high charring efficiency during combustion, which facilitates the formation of a char layer during combustion, insulating against flames, high temperatures, and combustible gases, thereby enhancing flame retardancy. However, due to the high rigidity of these resins, they are hard and brittle when used directly, requiring the addition of more flexible allyl compounds to ensure proper use. Therefore, the purpose of this application is to leverage the advantages of BMA resins, which offer low dielectric constant and high heat resistance, and reactive resins, which offer high flame retardancy. This approach overcomes the difficulty of achieving both low dielectric constant and high flame retardancy, and improves the flame retardancy of BMA resin composites while maintaining their wave transmission and temperature resistance.

[0023] Among them, the flame retardant is a nitrogen-based or phosphorus-based halogen-free flame retardant, the allyl compound is at least one of monoallyl compound, diallyl bisphenol A, and allyl phenolic formaldehyde, and the toughening agent is at least one of thermoplastic polyimide, thermoplastic polyaryletherketone, thermoplastic polyether, thermoplastic polyimide modified product, thermoplastic polyaryletherketone modified product, and thermoplastic polyether modified product.

[0024] Taking into account both heat resistance, flame retardancy, and material toughness, a heat-resistant epoxy and allyl compound are blended in a ratio of approximately 1:1 (1.5-2.5), with the ratio adjusted based on the specific material. To ensure the inherent performance of the BMA resin, the BMA resin monomer typically accounts for 35%-50% of the combined total of the three components (BMA resin monomer, flame-retardant and heat-resistant epoxy, and allyl compound), but this is not a mandatory requirement. The curing agent is added based on the number of reactive groups in the specific material. Flame retardants are added based on flame retardancy requirements, but excessive additions can degrade mechanical properties, so their inclusion rate typically does not exceed 30% of the total resin content. The toughening agent dosage varies depending on the specific material, typically ranging from 5%-20% of the combined total of the three components (BMA resin monomer, flame-retardant and heat-resistant epoxy, and allyl compound).

[0025] As an optional embodiment, the bismaleimide resin monomer is diphenylmethane bismaleimide. It should be noted that diphenylmethane bismaleimide has the highest heat resistance in the system and has a certain degree of flexibility. Other monomers can also be used, but the heat resistance and toughness are not as good as this monomer.

[0026] As an optional embodiment, the heat-resistant and flame-retardant epoxy resin includes at least one of a biphenyl epoxy resin and a phenolic epoxy resin. Specifically, all aromatic epoxies exhibit heat-resistant and flame-retardant properties. The two selected in this embodiment are the least rigid and highest carbon-content aromatic epoxies. Others, such as naphthalene epoxy resins and triazine epoxy resins, also exhibit good heat-resistant and flame-retardant properties. However, their molecular chains are too rigid, severely impacting the toughness of the final material. The addition of more flexible materials to enhance toughness would, in turn, reduce the flame-retardant effect of the final material, and therefore are not selected.

[0027] As an optional embodiment, the curing agent is 4,4'-diaminodiphenyl sulfone. The curing agent selected in this embodiment is an aromatic amine curing agent, which can take into account the heat resistance and mechanical properties after curing and the processability during the curing process. Other curing agents such as fatty amine curing agents and imidazole curing agents do not have high heat resistance after curing. Moreover, among the aromatic amine curing agents, the selected curing agent (4,4'-diaminodiphenyl sulfone) is significantly higher than other similar curing agents after curing. Anhydride curing agents are easy to absorb moisture (especially the interface between the fiber and the resin selected in this application is poor and is more susceptible to moisture absorption, so it needs to be avoided. If carbon fiber is used, it can be ignored, but carbon fiber will seriously affect the dielectric properties of the material).

[0028] On the other hand, an embodiment of the present invention further provides a halogen-free, flame-retardant, and wave-transmitting bismaleimide resin prepreg, which may include a halogen-free, flame-retardant, and wave-transmitting bismaleimide resin, with the mass proportion of the resin being 30 to 60%. The single-layer cured thickness is 0.01 to 0.45 mm. The use requirements of the prepreg are that if the resin content is too low, it will be difficult for the resin to impregnate the reinforcing material (fibers and fabrics such as quartz fiber and glass fiber), and if the resin content is too high, it will affect the mechanical properties and single-layer thickness of the material after curing. The resin content needs to be designed according to actual use requirements, but it must not be less than 30%. Based on many years of experience in the use of prepregs, the range of 30 to 60% can cover most use requirements. In addition, the single-layer cured thickness is calculated based on the resin content and the resin and fiber density.

[0029] Figure 1 This is a flow chart of a method for preparing a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg provided by an embodiment of the present invention, see Figure 1 , the method may include the following steps: S100, prepolymerizing the heat-resistant flame-retardant epoxy and the allyl compound, then adding bismaleimide resin monomer, curing agent, flame retardant, and toughening agent to fully mix and disperse to obtain a halogen-free flame-retardant wave-transmitting bismaleimide resin.

[0030] Specifically, in step S100, the bismaleimide resin monomer is diphenylmethane bismaleimide, the bismaleimide resin monomer is diphenylmethane bismaleimide, the heat-resistant flame-retardant epoxy is a mixture of one or more of biphenyl epoxy and phenolic epoxy, the allyl compound is a mixture of one or more of monoallyl compound, diallyl bisphenol A, and allyl phenolic, the curing agent is 4,4'-diaminodiphenyl sulfone, and the toughening agent is a mixture of one or more of thermoplastic polyimide, thermoplastic polyaryletherketone, thermoplastic polyether and its modified products.

[0031] S200, preparing a halogen-free flame-retardant bismaleimide resin into a film, and compounding the film with continuous fibers or fabrics to prepare a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg.

[0032] Specifically, in step S200, a halogen-free, flame-retardant, and wave-transmitting BMA resin is formed into a film on a laminating machine according to the required resin content and the surface density of the fiber reinforcement material. This film is then composited with continuous fibers or fabrics on a prepreg machine to produce a halogen-free, flame-retardant, and wave-transmitting BMA resin prepreg. The continuous fibers or fabrics may be quartz fibers, glass fibers, aramid fibers, or other organic fibers and fabrics thereof.

[0033] Example 1 A method for preparing a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg comprises the following steps: (1) Add 800g of allyl bisphenol A into the reactor and heat it to 70°C; (2) adding 400 g of biphenyl epoxy resin into the reactor and performing melt prepolymerization with allyl bisphenol A in (1); (3) The mixture was transferred into a grinder, and 1200 g of bismaleimide resin monomer powder, 200 g of thermoplastic polyimide powder, 200 g of 4,4'-diaminodiphenyl sulfone and 800 g of ammonium polyphosphate were added and stirred and blended to obtain a halogen-free flame retardant and wave-transmitting bismaleimide resin; (4) The prepared halogen-free flame-retardant and wave-transmitting bismaleimide resin was used as the matrix resin, and a resin film was made at 90°C on a film laminating machine by a hot melt method. The quartz fiber and the matrix resin were compounded on a prepreg machine to prepare a halogen-free flame-retardant and wave-transmitting bismaleimide resin prepreg.

[0034] The composite material made from the above prepreg has a flame retardant performance of V0 level, a glass transition temperature of 220℃, and a heat release rate of 55kw / m 2 , the dielectric constant is 3.49.

[0035] Example 2 A method for preparing a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg comprises the following steps: (1) Add 800g of diallyl bisphenol A into the reactor and heat it to 120°C; (2) Add 200 g of polyaryletherketone into the reactor and melt the allyl bisphenol A in (1); (3) Cool to 80°C, add 600g of phenolic epoxy, and melt prepolymerize; (4) Add 600g of ammonium polyphosphate and 200g of melamine urate and stir to mix; (5) The mixture was transferred into a grinder, and 1000 g of bismaleimide resin monomer powder and 300 g of 4,4'-diaminodiphenyl sulfone were added and stirred and blended to obtain a halogen-free flame retardant and wave-transmitting bismaleimide resin; (6) The prepared halogen-free flame retardant and wave-transmitting bismaleimide resin was used as the matrix resin, and a resin film was made at 90°C on a film laminating machine by a hot melt method. The glass fiber fabric was compounded with the matrix resin on a prepreg machine to prepare a halogen-free flame retardant and wave-transmitting bismaleimide resin prepreg.

[0036] The composite material made from the above prepreg has a flame retardant performance of V0 level, a glass transition temperature of 230℃, and a heat release rate of 48kw / m 2 , the dielectric constant is 3.75.

[0037] Example 3 A method for preparing a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg comprises the following steps: (1) Add 1000g of diallyl bisphenol A into the reactor and heat it to 120°C; (2) Add 100 g of polyaryletherketone into the reactor and melt the diallylbisphenol A in (1); (3) Cool to 80°C, add 500g of biphenyl epoxy, and melt prepolymerize; (4) Add 600g of ammonium polyphosphate and 200g of melamine urate and stir to mix; (5) The mixture was transferred into a grinder, and 1500 g of bismaleimide resin monomer powder and 250 g of 4,4'-diaminodiphenyl sulfone were added and stirred and blended to obtain a halogen-free flame retardant and wave-transmitting bismaleimide resin; (6) The prepared halogen-free flame retardant and wave-transmitting bismaleimide resin was used as the matrix resin, and a resin film was made at 90°C on a film laminating machine by a hot melt method. The quartz fiber fabric was compounded with the matrix resin on a prepreg machine to prepare a halogen-free flame retardant and wave-transmitting bismaleimide resin prepreg.

[0038] The composite material made from the above prepreg has a flame retardant performance of V0 level, a glass transition temperature of 220℃, and a heat release rate of 46kw / m2 , the dielectric constant is 3.53.

[0039] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.

[0040] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A halogen-free flame-retardant wave-transmitting bismaleimide resin, characterized in that: In parts by weight, it comprises the following components: 100 parts of bismaleimide resin monomer; 30-60 parts of flame retardant and heat resistant epoxy resin; 70-130 parts of allyl compound; 15-30 parts of curing agent; 20-100 parts of flame retardant; 10 to 40 parts of toughening agent.

2. The halogen-free flame-retardant wave-transmitting bismaleimide resin according to claim 1, characterized in that: The bismaleimide resin monomer is diphenylmethane bismaleimide.

3. The halogen-free flame-retardant wave-transmitting bismaleimide resin according to claim 1, characterized in that: The heat-resistant and flame-retardant epoxy resin includes at least one of a biphenyl epoxy resin and a phenolic epoxy resin.

4. The halogen-free flame-retardant wave-transmitting bismaleimide resin according to claim 1, characterized in that: The allyl compound is at least one of monoallyl compound, diallyl bisphenol A and allyl phenol formaldehyde.

5. The halogen-free flame-retardant wave-transmitting bismaleimide resin according to claim 1, characterized in that: The curing agent is 4,4'-diaminodiphenyl sulfone.

6. The halogen-free flame-retardant wave-transmitting bismaleimide resin according to claim 1, characterized in that: The toughening agent is at least one of thermoplastic polyimide, thermoplastic polyaryletherketone, thermoplastic polyether, thermoplastic polyimide modified product, thermoplastic polyaryletherketone modified product, and thermoplastic polyether modified product.

7. A halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg, characterized in that: The invention comprises the halogen-free flame-retardant wave-transmitting bismaleimide resin according to any one of claims 1 to 6, wherein the mass proportion of the resin is 30 to 60%.

8. The halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg according to claim 7, characterized in that: The thickness of a single layer of curing is 0.01 to 0.45 mm.

9. A method for preparing the halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg according to claim 7, characterized in that: The method comprises the following steps: The heat-resistant flame-retardant epoxy and the allyl compound are prepolymerized, and then the bismaleimide resin monomer, curing agent, flame retardant and toughening agent are added and fully mixed and dispersed to obtain a halogen-free flame-retardant wave-transmitting bismaleimide resin; The halogen-free flame-retardant bismaleimide resin is made into a film and compounded with continuous fibers or fabrics to prepare a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg.

10. The method for preparing the halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg according to claim 9, characterized in that: The halogen-free flame-retardant bismaleimide resin is made into a film and compounded with continuous fibers or fabrics to prepare a halogen-free flame-retardant wave-transmitting bismaleimide resin prepreg, specifically: According to the resin content requirements and the surface density of the fiber reinforcement material, the halogen-free flame-retardant and wave-transmitting bismaleimide resin is made into a film on a film machine, and is compounded with the continuous fiber or fabric on a prepreg machine to make the halogen-free flame-retardant and wave-transmitting bismaleimide resin prepreg.

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