Flame-retardant epoxy resin composition, flame-retardant epoxy resin material, and preparation method and application thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses a flame-retardant epoxy resin composition, which comprises the following components based on the total amount of the composition: 30-40 wt% of epoxy resin, 20-40 wt% of a curing agent, 0.5-2 wt% of an accelerator, 20-30 wt% of a flame retardant, 1-10 wt% of a diluent, 1-5 wt% of a coupling agent and 0-1 wt% of a defoaming agent. The flame-retardant epoxy resin composition has the effects of high flame-retardant efficiency and good mechanical properties, can meet the highest-grade flame-retardant requirements in UL94 and other standard requirements, has excellent process performance in the processing of composite materials, and has an attractive appearance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant epoxy resin composition, flame-retardant epoxy resin material, its preparation method, and its application. Background Technology

[0002] Epoxy resin, as a major thermosetting resin, is widely used in various fields. Especially as a composite material resin matrix, epoxy resin has significant advantages. However, epoxy resin is one of the more flammable thermosetting resins; the oxygen index of ordinary epoxy resin is only about 19.8%, meaning it will continue to burn even after the ignition source is removed, increasing the risk of fire. Furthermore, the toxic fumes and gases produced during ablation can cause injury or death to people in the surrounding area. For applications of composite materials in transportation, construction, electronics, and other fields requiring flame retardancy, epoxy resin needs to be given flame-retardant properties through flame-retardant treatment.

[0003] The commonly used technical approach for preparing flame-retardant epoxy resins is to add flame retardants to the epoxy resin system. Flame retardants are generally divided into halogenated flame retardants and halogen-free flame retardants. Halogenated flame retardants have high flame retardant efficiency, but they are not environmentally friendly, so halogen-free flame retardants are currently more commonly used. Compared with halogenated flame retardants, halogen-free flame retardants have relatively lower flame retardant efficiency. To achieve a certain flame retardant effect, the amount of flame retardant needs to be increased. On the one hand, this will lead to an increase in the viscosity of the epoxy resin system, reducing the resin's processing performance; on the other hand, excessive use of flame retardants will adversely affect the resin's mechanical and thermodynamic properties. How to balance the flame retardant properties and mechanical properties of epoxy resin systems is one of the current research challenges.

[0004] Therefore, it is necessary to study a high-performance flame-retardant epoxy resin that has both high flame-retardant efficiency and excellent mechanical properties to meet the needs of various processing techniques. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem in existing technologies where excessive use of flame retardants leads to a decrease in the mechanical properties of epoxy resins. This invention provides a flame-retardant epoxy resin composition, a flame-retardant epoxy resin material, its preparation method, and its applications. This resin exhibits high flame-retardant efficiency and excellent mechanical properties, meeting the highest level of flame retardancy requirements in standards such as UL94. Furthermore, it demonstrates excellent processability during composite material processing, resulting in aesthetically pleasing finished products.

[0006] To achieve the above objectives, a first aspect of the present invention provides a flame-retardant epoxy resin composition, wherein, based on the total amount of the composition, the composition comprises the following components: 30-40 wt% epoxy resin, 20-40 wt% curing agent, 0.5-2 wt% accelerator, 20-30 wt% flame retardant, 1-10 wt% diluent, 1-5 wt% coupling agent, and 0-1 wt% defoamer.

[0007] A second aspect of this invention provides a method for preparing a flame-retardant epoxy resin material, comprising the following steps:

[0008] (1) Mix the epoxy resin and diluent evenly under the first stirring condition to obtain mixture I;

[0009] (2) Add flame retardant and defoamer to mixture I and mix evenly under the second stirring condition to obtain mixture II;

[0010] (3) Add coupling agent, curing agent and accelerator to mixture II, mix evenly under the third stirring condition, and cure to obtain flame retardant epoxy resin material.

[0011] A third aspect of the present invention provides a flame-retardant epoxy resin material prepared by the method described in the second aspect of the present invention, wherein the flame-retardant epoxy resin material has a limiting oxygen index of 25-35%, a viscosity of less than 1000 mPa·s at 25°C, a tensile property of 40-70 MPa, a tensile modulus of 2.5-3.4 GPa, a flexural property of 90-135 MPa, and a flexural modulus of 2.5-3 GPa.

[0012] The fourth aspect of the present invention provides an application of the flame-retardant epoxy resin material described in the third aspect of the present invention in carbon fiber composite materials.

[0013] Through the above technical solution, the present invention has the following beneficial effects:

[0014] (1) The flame-retardant epoxy resin composition provided by the present invention has high flame retardant efficiency, low flame retardant dosage, minimal impact on the viscosity of the epoxy resin system, and good resin processing performance.

[0015] (2) The flame-retardant epoxy resin composition provided by the present invention can improve the toughness of epoxy resin, while having little effect on tensile strength and flexural strength, ensuring that the resin system has high toughness and high strength mechanical properties, and is suitable for processes with high mechanical property requirements, such as winding molding.

[0016] (3) The flame-retardant epoxy resin composition provided by the present invention has good wettability to large tow carbon fibers. The hydroxyl and other groups in the resin react and combine with the surface groups of the large tow carbon fibers, which can give full play to the high strength characteristics of carbon fibers. The composite material of the present invention has high mechanical properties and high interlaminar shear strength. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of the present invention provides a flame-retardant epoxy resin composition, which, based on the total amount of the composition, comprises the following components: 30-40 wt% epoxy resin, 20-40 wt% curing agent, 0.5-2 wt% accelerator, 20-30 wt% flame retardant, 1-10 wt% diluent, 1-5 wt% coupling agent, and 0-1 wt% defoamer.

[0019] In this invention, by adding a coupling agent to the flame-retardant epoxy resin composition, the influence of the flame retardant on the viscosity of the epoxy resin system is reduced, thereby improving the flame-retardant efficiency of the flame-retardant epoxy resin composition while also possessing excellent mechanical properties, thus meeting the process requirements of subsequent composite material processing.

[0020] According to the present invention, the mass ratio of the coupling agent to the flame retardant is 1-5:20-30.

[0021] In this invention, the coupling agent in the epoxy resin system can improve the bonding performance between the epoxy resin and additional additives, enhance stability, help optimize the curing process of the epoxy resin, and improve the performance and durability of the final product.

[0022] Furthermore, the role of coupling agents in flame-retardant epoxy resin systems is mainly manifested in the following aspects: 1. Improving the dispersibility of flame retardants in epoxy resins and enhancing the flame-retardant effect. 2. Forming a good interfacial bond between epoxy resins and flame retardants, enhancing the compatibility among the three. 3. Helping flame retardants better exert their flame-retardant effect and improving the flame-retardant performance of epoxy resins. 4. Improving the processing and mechanical properties of epoxy resins. In summary, coupling agents play multiple roles in flame-retardant epoxy resin systems, including promoting compatibility, improving flame-retardant performance, and enhancing processing and mechanical properties.

[0023] Furthermore, the mass ratio of the coupling agent to the flame retardant is 1-2:24-28.

[0024] In this invention, the synergistic effect between the coupling agent and the flame retardant is optimal when the mass ratio between them satisfies the above-mentioned relationship.

[0025] According to the present invention, based on the total amount of the composition, the composition comprises the following components: 33-38 wt% epoxy resin, 28-35 wt% curing agent, 1-1.5 wt% accelerator, 25-28 wt% flame retardant, 4-6 wt% diluent, 2-3 wt% coupling agent, and 0.2-0.6 wt% defoamer.

[0026] According to the present invention, the epoxy resin is selected from at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidylamine epoxy resin, phenolic epoxy resin and mixed epoxy resin.

[0027] According to one embodiment of the present invention, the epoxy equivalent of the epoxy resin is 110-200 g / eq.

[0028] In this invention, the glycidyl ether epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

[0029] According to one embodiment of the present invention, the bisphenol A epoxy resin has an epoxy equivalent of 110-230 g / eq. and a viscosity of 1500-10000 mPa·s at 25°C.

[0030] According to one embodiment of the present invention, the bisphenol F epoxy resin has an epoxy equivalent of 170-190 g / eq.

[0031] The viscosity at 25℃ is 2000-5000 mPa·s.

[0032] According to one embodiment of the present invention, the bisphenol S epoxy resin has an epoxy equivalent of 180-200 g / eq.

[0033] The viscosity at 25℃ is 2000-3000 mPa·s.

[0034] In this invention, the mixed epoxy resin is an epoxy-based multifunctional epoxy resin, selected from at least one of 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester (TDE85), high-purity triglycidyl p-aminophenol MY0510, and 4,4′-diaminodiphenylmethane tetraglycidylamine (AG80).

[0035] In a specific embodiment of the present invention, the epoxy resin is selected from bisphenol A type liquid epoxy resin, trifunctional liquid epoxy resin glycidyl ether, and trifunctional liquid epoxy resin glycidylamine, with a mass ratio of 10-15:10-15:10-15.

[0036] In a specific embodiment of the present invention, the epoxy resin is selected from bisphenol F type liquid epoxy resin, trifunctional liquid epoxy resin glycidyl ether, and trifunctional liquid epoxy resin glycidylamine, with a mass ratio of 10-15:10-15:10-15.

[0037] In a specific embodiment of the present invention, the epoxy resin is selected from bisphenol A type liquid epoxy resin and trifunctional liquid epoxy resin glycidyl ether, with a mass ratio of 13-17:15-20.

[0038] According to the present invention, the curing agent is selected from acid anhydride curing agents and / or amine curing agents.

[0039] According to the present invention, the anhydride curing agent is selected from at least one of monofunctional anhydrides, difunctional anhydrides, and linear phenolic resins.

[0040] According to the present invention, the amine curing agent is at least one of diamines, aromatic amines, dicyandiamides, and organic hydrazides.

[0041] In this invention, the inventors, through extensive research, discovered that selecting anhydride-based curing agents yields better technical results. For this invention, anhydride-based curing agents have a better coupling effect than amine-based curing agents, which can better improve the dispersibility of flame retardants in epoxy resins and enhance the flame retardant effect. Furthermore, it can enhance the compatibility between epoxy resins and flame retardants, improving flame retardant performance. It helps flame retardants better exert their flame retardant function and improves the processing and mechanical properties of epoxy resins. It possesses excellent high-temperature resistance, aging resistance, and low shrinkage. Moreover, it is easy to use and has good process operability.

[0042] According to the present invention, the promoter is selected from at least one of tertiary amine salt complexes, imidazoles, and modified imidazoles.

[0043] In this invention, the accelerator may be diethyltetramethylimidazole.

[0044] According to the present invention, the diluent is selected from glycidyl ethers and / or glycidylamines.

[0045] According to the present invention, the defoamer is selected from at least one of tributyl phosphate, 2,4,7,9-tetramethyl-5-decyn-4,7-diol and BYKA530.

[0046] According to the present invention, the coupling agent is selected from phosphorus-nitrogen silane coupling agents as shown in structural formula (1).

[0047]

[0048] R1 is selected from C1-C5 alkylene groups, and R2 and R3 are each independently selected from C1-C5 alkoxy groups.

[0049] In this invention, the role of the phosphorus-nitrogen-silane coupling agent is to improve the dispersibility and stability of the mixture by adding flame-retardant elements, thereby enhancing the flame-retardant effect.

[0050] In this invention, the coupling agent shown in formula (1) is prepared in the laboratory by means of the following method: γ-aminopropyltriethoxysilane, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-ethanol 10-oxide (CAS No.: 63562-41-4), and anhydrous ethanol are mixed and reacted at 60-90℃ for 5-8 hours using microwave reflux to obtain a reaction mixture. Then, the reaction mixture is rotary evaporated at 50℃ for half an hour, and after removal, it is vacuum dried at 30℃ for 4 hours to obtain the phosphorus nitrogen silane coupling agent.

[0051] In a particularly preferred embodiment of the invention, the coupling agent is selected from phosphorus-nitrogen silane coupling agents as shown in structural formula (2).

[0052]

[0053] In this invention, the phosphorus-nitrogen-silane coupling agent is prepared in the laboratory. This phosphorus-nitrogen-silane coupling agent is a multifunctional additive that not only improves the organic-inorganic compatibility of composite materials and enhances their mechanical properties, but also significantly improves their flame retardancy. The phosphorus and nitrogen elements in its molecular structure can generate phosphoric acid at high temperatures, acting as a dehydrating agent. Simultaneously, the generated nitrogen gas can dilute oxygen, effectively inhibiting combustion and improving the toughness and thermal stability of the epoxy resin.

[0054] According to the present invention, the flame retardant comprises component A and component B, wherein component A is selected from at least one of phosphazene flame retardants, alkylphosphinates, phosphaphenanthrene flame retardants, phosphate ester flame retardants, phosphorus-containing ionic liquids, and phosphate flame retardants; and component B is selected from at least one of organosilicon compounds, metal oxides, metal hydroxides, and graphitic substances.

[0055] According to the present invention, component A is selected from at least one of polydiphenoxyphosphazene, hexaphenoxycyclotriphosphazene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, phosphaphenanthrene triazine compounds, DOPO ester compounds, triphenyl phosphate, resorcinol bis(diphenyl) phosphate, toluene diphenyl phosphate, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, ammonium polyphosphate, and melamine polyphosphate.

[0056] According to the present invention, component B is selected from at least one of antimony oxide, zinc borate, magnesium hydroxide, aluminum hydroxide, molybdenum oxide, ammonium molybdate, zirconium phosphate, polysiloxane, polysilazane, silicon dioxide, graphite, carbon nanotubes and graphene.

[0057] According to the present invention, the mass ratio of component A to component B is 80-20:99-1, preferably 60-40:10-2.

[0058] In this invention, components A and B in the flame retardant work synergistically. Building upon the typical function of coupling agents—"increasing system stability"—the addition of phosphorus and nitrogen (flame-retardant elements) increases the overall phosphorus and nitrogen content, thus contributing to the flame retardancy of the system. However, simply adding too much flame retardant can significantly impact the performance of the resin system, such as its mechanical properties, and also increase viscosity, negatively affecting the final product's performance. Therefore, the amount of flame retardant added is limited, and consequently, the content of flame-retardant elements in the system is also limited. Supplementing flame-retardant elements through phosphorus-nitrogen-silane coupling agents, thereby reducing the impact on the resin system's mechanical properties, is one way to introduce phosphorus and nitrogen. The resulting product possesses both good flame-retardant and mechanical properties.

[0059] A second aspect of this invention provides a method for preparing a flame-retardant epoxy resin material, comprising the following steps:

[0060] (1) Mix the epoxy resin and diluent evenly under the first stirring condition to obtain mixture I;

[0061] (2) Add flame retardant and defoamer to mixture I and mix evenly under the second stirring condition to obtain mixture II;

[0062] (3) Add coupling agent, curing agent and accelerator to mixture II, mix evenly under the third stirring condition, and cure to obtain flame retardant epoxy resin material.

[0063] In this invention, a preheating step of the mixing device is included before step (1).

[0064] In this invention, before step (3), the mixture II is further cooled to 30-50°C.

[0065] This invention involves stepwise mixing of epoxy resin, diluent, flame retardant, defoamer, coupling agent, curing agent, and accelerator to prepare a flame-retardant epoxy resin material. The preparation method is simple and easy to operate. The resulting flame-retardant epoxy resin material exhibits good wettability to large-tow carbon fibers, and the hydroxyl and other groups in the resin react and combine with the surface groups of the large-tow carbon fibers, fully utilizing the high strength properties of the carbon fibers.

[0066] In this invention, when epoxy resin, diluent, flame retardant, defoamer, coupling agent, curing agent and accelerator are added in the above proportions, the flame retardant epoxy resin material prepared has the best flame retardant performance and mechanical properties.

[0067] According to the present invention, the first stirring conditions include: a stirring temperature of 50-80°C and a stirring speed of 200-400 rpm.

[0068] According to the present invention, the second stirring conditions include: a stirring temperature of 80-200°C and a stirring speed of 200-500 rpm.

[0069] According to the present invention, the third stirring conditions include: a stirring temperature of 30-50°C and a stirring speed of 100-300 rpm.

[0070] According to the present invention, the curing conditions include: holding at 80-100°C for 60-120 min under normal pressure, then raising the temperature to 130-150°C and reacting for 90-180 min.

[0071] In a specific application of this invention, the prepared flame-retardant epoxy resin material can be wound and molded with large-tow carbon fibers to form a composite material. It exhibits good wettability to the large-tow carbon fibers, and the hydroxyl and other groups in the resin react and combine with the surface groups of the large-tow carbon fibers, fully utilizing the high strength characteristics of the carbon fibers. The composite material of this invention possesses high mechanical properties and high interlaminar shear strength. The large-tow carbon fibers can be 48K SCF35S large-tow carbon fibers.

[0072] The third aspect of the present invention provides a flame-retardant epoxy resin material prepared by the method described in the second aspect of the present invention, wherein the flame-retardant epoxy resin material has a viscosity of less than 1000 mPa·s at 25°C, a limiting oxygen index of 25-35%, a tensile property of 40-70 MPa, a tensile modulus of 2.5-3.4 GPa, a flexural property of 90-135 MPa, and a flexural modulus of 2.5-3 GPa.

[0073] The fourth aspect of the present invention provides an application of the flame-retardant epoxy resin material described in the third aspect of the present invention in epoxy resin composite materials.

[0074] The flame-retardant epoxy resin material provided by this invention has high flame-retardant efficiency and high toughness and strength mechanical properties, making it suitable for processes with high requirements for mechanical properties.

[0075] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples,

[0076] The mechanical properties of the resin castings were tested using a fully automated material testing machine.

[0077] The tensile properties of resin castings were tested in accordance with the national standard GB / T 2567.

[0078] The bending performance test of resin castings shall be conducted in accordance with the national standard GB / T 2570;

[0079] Viscosity was measured at 25°C using a rotational viscometer (BROCKFIELD DV-IIRo).

[0080] The resin's combustion performance was tested using an oxygen index tester and a horizontal / vertical combustion tester.

[0081] Oxygen index measurement shall be performed in accordance with national standard GB / T 2406;

[0082] Vertical burning measurements were performed in accordance with national standard GB / T 2408 (UL94).

[0083] The mechanical properties of the composite material Noir ring were tested using a universal testing machine.

[0084] The tensile properties of composite materials were measured in accordance with the national standard GB / T 3354.

[0085] The lamellar shear properties of composite materials were measured in accordance with the national standard GB / T 3357.

[0086] Coupling agent A: R1 is a C3 alkylene group, R2 is a C2 alkoxy group, and R3 is a C2 alkoxy group;

[0087] Coupling agent B: R1 is a C5 alkylene group, R2 is a C5 alkoxy group, and R3 is a C5 alkoxy group.

[0088] Unless otherwise specified, the bisphenol A epoxy resins used in the examples and comparative examples all have an epoxy equivalent of 200 g / eq. and a viscosity of 5000 mPa·s at 25°C. The bisphenol F epoxy resins all have an epoxy equivalent of 180 g / eq. and a viscosity of 3000 mPa·s at 25°C.

[0089] Diluent: Glycidylamine, purchased from Hubei Zhenzhengfeng New Materials Co., Ltd., brand name MF-2133, epoxy equivalent 105-118 g / eq., viscosity at 25℃ 50-150 mPa·s.

[0090] Glycidyl ether, polypropylene glycol diglycidyl ether, CAS No.: 26142-30-3.

[0091] KH550 was purchased from Klein (Shandong) Biotechnology Co., Ltd.

[0092] Example 1

[0093] The composition of the flame-retardant epoxy resin composition disclosed in this embodiment is as follows (by mass parts):

[0094] The composition includes 33% epoxy resin, 31% curing agent, 1% accelerator, 25% flame retardant, 7% diluent, 2.8% coupling agent, and 0.2% defoamer. (The mass ratio of coupling agent to flame retardant is 3.8:25.)

[0095] The first step is to weigh 15g of bisphenol A type liquid epoxy resin, 18g of trifunctional liquid epoxy resin glycidyl ether, and 7g of MF-2133 diluent, heat to 80℃, and mechanically stir until uniform to obtain epoxy resin matrix.

[0096] The second step involves weighing 20g of the compounded phosphorus-containing flame retardant hexaphenoxycyclotriphosphazene, 2g of 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide (total 22%), 1.5g of other flame retardants ammonium molybdate, 1.5g of polysilazane (total 3g), and 0.2g of defoamer 2,4,7,9-tetramethyl-5-decyn-4,7-diol. These are then added to the epoxy resin matrix, heated to 180°C to melt, and rapidly and mechanically stirred until homogeneous.

[0097] The third step is to cool the mixture obtained in the second step to below 50°C, add 2.8g of coupling agent A, 31g of curing agent methylnadic anhydride, and 1g of accelerator diethyltetramethylimidazolium, and mix quickly and evenly to obtain a flame-retardant epoxy resin composition.

[0098] The fourth step involves degassing the obtained flame-retardant epoxy resin composition under vacuum at 50°C and dividing it into two parts: one part is placed in a mold and heated to cure, forming a resin casting. The curing process of the epoxy resin is to keep it at 90°C for about 120 minutes until the resin gels, and then raise the temperature to 140°C and continue the reaction for 120 minutes; the other part is wound with SCF35S 48K large tow carbon fiber through a winding machine. The curing process of the composite material is: 90°C / 90min + 135°C / 180min.

[0099] Example 2

[0100] The composition of the flame-retardant epoxy resin composition disclosed in this embodiment is as follows (by mass parts):

[0101] The composition includes 35% epoxy resin, 31% curing agent, 1.5% accelerator, 20.5% flame retardant, 8% diluent, 3.8% coupling agent, and 0.2% defoamer. (The mass ratio of coupling agent to flame retardant is 3.8:20.5)

[0102] The first step is to weigh 17g of bisphenol A type liquid epoxy resin, 18g of trifunctional liquid epoxy resin glycidyl ether, and 8g of MF-2133 diluent, heat to 80℃, and mechanically stir until uniform to obtain epoxy resin matrix.

[0103] The second step involves weighing 18g of the compound phosphorus-containing flame retardant polydiphenoxyphosphazene, 1g of 1-butyl-3-methylimidazolium dibutyl phosphate salt (total 19g), 0.7g of other flame retardants zinc borate, 0.8g of carbon nanotubes (total 1.5g), and 0.2g of tributyl phosphate. This mixture is then combined with the epoxy resin matrix described above, heated to 130℃ to melt, and rapidly mechanically stirred until homogeneous.

[0104] The third step is to cool the mixture obtained in the second step to below 50°C, add 3.8g of coupling agent A, 31g of curing agent methylnadic anhydride, and 1.5g of accelerator diethyltetramethylimidazolium, and mix quickly and evenly to obtain a flame-retardant epoxy resin composition.

[0105] The fourth step involves degassing the obtained flame-retardant epoxy resin composition under vacuum at 50°C and dividing it into two parts: one part is placed in a mold and heated to cure, forming a resin casting. The curing process of the epoxy resin is to keep it at 100°C for about 120 minutes until the resin gels, and then raise the temperature to 140°C and continue the reaction for 180 minutes; the other part is wound with SCF35S 48 large tow carbon fiber and the curing process of the composite material is: 100°C / 90 minutes + 135°C / 240 minutes.

[0106] Example 3

[0107] The composition of the flame-retardant epoxy resin composition disclosed in this embodiment is as follows (by mass parts):

[0108] The composition includes 38% epoxy resin, 32% curing agent, 1% accelerator, 21.5% flame retardant, 3.6% diluent, 1.8% coupling agent, and 0.1% defoamer. (The mass ratio of coupling agent to flame retardant is 1.8:21.5)

[0109] The first step involves weighing 12g of bisphenol A type liquid epoxy resin, 13g of trifunctional liquid epoxy resin glycidyl ether, 13g of trifunctional liquid epoxy resin glycidylamine, and 3.6g of MF-2133 diluent. The mixture is heated to 80℃ and mechanically stirred until homogeneous to obtain the epoxy resin matrix.

[0110] The second step involves weighing 18g of the compounded phosphorus flame retardant polydiphenoxyphosphazene, 2g of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), a total of 20g, 1.5g of other flame retardants zirconium phosphate, and 0.1g of defoamer tributyl phosphate. These are then added to the epoxy resin matrix, heated to 130℃ to melt, and rapidly and mechanically stirred until homogeneous.

[0111] Third step: After the mixture obtained in the second step has cooled to below 50°C, weigh out 1.8g of coupling agent A, 32g of curing agent methylnadic anhydride, and 1g of accelerator diethyltetramethylimidazole, add them to the mixture, and quickly mix them evenly to obtain a flame-retardant epoxy resin composition.

[0112] The fourth step involves degassing the flame-retardant epoxy resin composition under vacuum at 50°C and dividing it into two parts: one part is placed in a mold and heated to cure, preparing a resin casting for characterization testing. The curing process of the epoxy resin is to keep it at 90°C for about 120 minutes until the resin gels, and then raise the temperature to 135°C and continue the reaction for 120 minutes; the other part is wound with SCF35S 48 large tow carbon fiber through a winding machine. The curing process of the composite material is: 90°C / 90 minutes + 130°C / 180 minutes.

[0113] Example 4

[0114] The composition of the flame-retardant epoxy resin composition disclosed in this embodiment is as follows (by mass parts):

[0115] The composition is as follows: epoxy resin 35%, curing agent 31%, accelerator 1%, flame retardant 23%, diluent 7.8%, coupling agent 2%, defoamer 0.2%. (The mass ratio of coupling agent to flame retardant is 2:23.)

[0116] The first step involves weighing 10g of bisphenol F type liquid epoxy resin, 13g of trifunctional liquid epoxy resin glycidyl ether, 12g of trifunctional liquid epoxy resin glycidylamine, and 7.8g of diluent polypropylene glycol diglycidyl ether. The mixture is heated to 80℃ and mechanically stirred until homogeneous to obtain the epoxy resin matrix.

[0117] The second step involves weighing 20g of the compound phosphorus-containing flame retardant phosphaphenanthrene triazine compound (TAD), 1.5g of 1-butyl-3-methylimidazolium dibutyl phosphate salt, totaling 21.5g, along with 1.5g of other flame retardants such as zinc borate and 0.2g of defoamer tributyl phosphate. These are then added to the epoxy resin matrix, heated to 180℃ to melt, and rapidly and mechanically stirred until homogeneous.

[0118] Third step: After the mixture obtained in the second step is cooled to below 50°C, weigh out 2g of coupling agent A, 31g of curing agent methyl nadic anhydride and 1g of accelerator diethyltetramethylimidazol, add them to the mixture, and quickly mix them evenly to obtain a flame-retardant epoxy resin composition.

[0119] The fourth step involves degassing the flame-retardant epoxy resin composition under vacuum at 50°C and dividing it into two parts: one part is placed in a mold and heated to cure, forming a resin casting. The curing process of the epoxy resin is to keep it at 90°C for about 120 minutes until the resin gels, and then raise the temperature to 140°C and continue the reaction for 120 minutes; the other part is wound with SCF35S 48K large tow carbon fiber using a winding machine. The curing process of the composite material is: 90°C / 90 minutes + 135°C / 180 minutes.

[0120] Example 5

[0121] The method is the same as in Example 1, except that 12g of bisphenol A type liquid epoxy resin and 20g of glycidylamine diluent are used, so that the epoxy resin content in the composition is 30% and the diluent content is 10%.

[0122] Example 6

[0123] The method is the same as in Example 1, except that the amount of coupling agent A is 5g, hexaphenoxycyclotriphosphazene 20g, 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide 2g, totaling 22%, and other flame retardant ammonium molybdate 0.8g.

[0124] Example 7

[0125] The method is the same as in Example 1, except that a commercially available phosphorus-containing flame retardant (Disflamoll DPK flame retardant purchased by Shanghai Guangbin Trading) is used.

[0126] Example 8

[0127] The method is the same as in Example 1, except that the coupling agent used is commercially available KH550.

[0128] Example 9

[0129] The method is the same as in Example 1, except that the flame retardant is a single hexaphenoxycyclotriphosphazene, and the amount used is 25g.

[0130] Comparative Example 1

[0131] The method is the same as in Example 1, except that no coupling agent is added.

[0132] Comparative Example 2

[0133] The method is the same as in Example 1, except that 20g of bisphenol A type liquid epoxy resin, 30g of trifunctional liquid epoxy resin glycidyl ether, 2g of diluent glycidylamine, 15g of flame retardant hexaphenoxycyclotriphosphazene, 0.2g of defoamer 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 8g of coupling agent A, 23g of curing agent methylnadic anhydride, and 1.8g of accelerator diethyltetramethylimidazole are used.

[0134] The resin castings prepared in the examples and comparative examples were subjected to mechanical property tests, and the carbon fiber composites were subjected to tensile and lamellar shear tests. The results are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] Table 1 (continued)

[0139]

[0140] Note: D1 and D2 represent Comparative Example 1 and Comparative Example 2, respectively.

[0141] As can be seen from the results in Table 1, the flame-retardant epoxy resin compositions prepared using Examples 1-4 of the present invention not only ensure flame-retardant performance but also exhibit good bonding with Shanghai Petrochemical SCF35S 48k large filament bundles, resulting in high-performance composite materials.

[0142] As can be seen from Examples 1 and 9, the flame retardant system using the present invention has higher flame retardant performance than commercially available flame retardant systems, and has less impact on the mechanical and thermodynamic properties of the resin system. It also has good compatibility with Shanghai Petrochemical SCF35S 48k large filament bundle, and the prepared composite material has high performance.

[0143] Comparing Example 1 and Comparative Example 1, it can be seen that the addition of coupling agent helps to further improve the flame retardant properties of the system, and has a positive impact on the mechanical properties, toughness and bonding with carbon fiber of the resin.

[0144] Compared with existing technologies, the flame retardant resin preparation process of this invention is simple, the system is stable, and the winding molding method has good processability, simple curing conditions, excellent mechanical properties of the product, good bonding with Shanghai Petrochemical SCF35S large filaments, and the prepared composite material has high mechanical properties.

[0145] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A flame-retardant epoxy resin composition, characterized in that, Based on the total amount of the composition, the composition comprises the following components: The composition includes 33-38 wt% epoxy resin, 28-35 wt% curing agent, 1-1.5 wt% accelerator, 25-28 wt% flame retardant, 4-6 wt% diluent, 2-3 wt% coupling agent, and 0.2-0.6 wt% defoamer. The mass ratio of the coupling agent to the flame retardant is 2-4:24-28; The coupling agent is selected from the phosphorus-nitrogen silane coupling agent shown in structural formula (1). Equation (1) R1 is selected from C2-C4 alkylene groups, and R2 and R3 are each independently selected from C2-C3 alkoxy groups.

2. The composition according to claim 1, characterized in that, The epoxy resin is selected from at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidylamine epoxy resin, phenolic epoxy resin, and mixed epoxy resin.

3. The composition according to claim 2, characterized in that, The glycidyl ether epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

4. The composition according to claim 1, characterized in that, The curing agent is selected from acid anhydride curing agents and / or amine curing agents.

5. The composition according to claim 4, characterized in that, The anhydride curing agent is selected from at least one of monofunctional anhydrides, difunctional anhydrides, and linear phenolic resins.

6. The composition according to claim 4, characterized in that, The amine curing agent is selected from at least one of diamines, aromatic amines, dicyandiamides, and organic hydrazides.

7. The composition according to claim 1, characterized in that, The accelerator is selected from at least one of tertiary amine salt complexes, imidazole, and modified imidazole.

8. The composition according to claim 1, characterized in that, The diluent is selected from glycidyl ether and / or glycidylamine.

9. The composition according to claim 1, characterized in that, The defoamer is selected from at least one of tributyl phosphate, 2,4,7,9-tetramethyl-5-decyn-4,7-diol and BYKA530.

10. The composition according to any one of claims 1-9, characterized in that, The flame retardant comprises component A and component B; Component A is selected from at least one of phosphazene flame retardants, alkyl phosphonates, phosphaphenanthrene flame retardants, phosphate ester flame retardants, phosphorus-containing ionic liquids, and phosphate flame retardants. Component B is selected from at least one of organosilicon compounds, metal oxides, metal hydroxides, and graphitic substances.

11. The composition according to claim 10, characterized in that, The mass ratio of component A to component B is 80-20:99-1.

12. The composition according to claim 10, characterized in that, Component A is selected from at least one of the following: polydiphenoxyphosphazene, hexaphenoxycyclotriphosphazene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, phosphaphenanthrene triazine compounds, DOPO esters, triphenyl phosphate, resorcinol bis(diphenyl) phosphate, toluene diphenyl phosphate, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, ammonium polyphosphate, and melamine polyphosphate.

13. The composition according to claim 10, characterized in that, Component B is selected from at least one of antimony oxide, zinc borate, magnesium hydroxide, aluminum hydroxide, molybdenum oxide, ammonium molybdate, zirconium phosphate, polysiloxane, polysilazane, silicon dioxide, graphite, carbon nanotubes, and graphene.

14. A method for preparing a flame-retardant epoxy resin material, characterized in that, Includes the following steps: (1) Mix the epoxy resin and diluent evenly under the first stirring condition to obtain mixture I; (2) Add the flame retardant and defoamer to mixture I and mix them evenly under the second stirring condition to obtain mixture II; (3) Add coupling agent, curing agent and accelerator to mixture II, mix evenly under the third stirring condition, and cure to obtain flame retardant epoxy resin material; The composition includes 33-38 wt% epoxy resin, 28-35 wt% curing agent, 1-1.5 wt% accelerator, 25-28 wt% flame retardant, 4-6 wt% diluent, 2-3 wt% coupling agent, and 0.2-0.6 wt% defoamer. The mass ratio of the coupling agent to the flame retardant is 2-4:24-28; The coupling agent is selected from the phosphorus-nitrogen silane coupling agent shown in structural formula (1). Equation (1) R1 is selected from C2-C4 alkylene groups, and R2 and R3 are each independently selected from C2-C3 alkoxy groups.

15. The method according to claim 14, characterized in that, The first stirring conditions include: a stirring temperature of 50-80℃ and a stirring speed of 200-400 rpm.

16. The method according to claim 14, characterized in that, The second stirring conditions include: a stirring temperature of 80-200℃ and a stirring speed of 200-500 rpm.

17. The method according to claim 14, characterized in that, The third stirring conditions include: a stirring temperature of 30-50℃ and a stirring speed of 100-300 rpm.

18. The method according to any one of claims 14-17, characterized in that, The curing conditions include: holding at 80-100℃ for 60-120 minutes under normal pressure, then raising the temperature to 130-150℃ and reacting for 90-180 minutes.

19. A flame-retardant epoxy resin material prepared by the method according to any one of claims 14-18, wherein the flame-retardant epoxy resin material has a viscosity of less than 1000 mPa·s at 25°C, a limiting oxygen index of 25-35%, tensile properties of 40-70 MPa, tensile modulus of 2.5-3.4 GPa, flexural properties of 90-135 MPa, and flexural modulus of 2.5-3 GPa.

20. The application of the flame-retardant epoxy resin material of claim 19 in carbon fiber composite materials.

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