Flame-retardant resin material and preparation method thereof

Abstract

The invention discloses a flame-retardant resin material and a preparation method, and belongs to the technical field of flame-retardant materials. The flame-retardant resin material comprises an epoxy resin prepolymer, an additive flame retardant, a reactive flame retardant, a flexibilizer, an accelerant and a curing agent. Through the synergistic effect of the additive flame retardant and the reactive flame retardant, the epoxy resin material has efficient flame retardance.

Description

Technical Field

[0001] The present application relates to the technical field of flame retardant materials, and in particular to a flame retardant resin material and a preparation method thereof. Background Art

[0002] Epoxy resins, with their excellent electrical insulation, mechanical properties, chemical stability, and adhesive properties, are widely used in flame-retardant materials. For example, they are often used as insulation in transformers, switchgear, cable accessories, and other equipment to ensure the safe and reliable operation of power equipment. During operation, power equipment can generate high temperatures and arcs due to faults such as overloads and short circuits, potentially causing fires and resulting in serious consequences such as equipment damage and casualties. Therefore, improving the flame-retardant properties of epoxy resins is crucial to ensuring the safety of power equipment.

[0003] Conventional flame retardants can be added to epoxy resins to improve their flame retardancy. Additive flame retardants, in particular, exhibit a strong flame retardant effect and are therefore commonly used in flame-retardant materials. However, these additive flame retardants are typically solid particles. When added to epoxy resins, differences in polarity and surface properties make it difficult for the flame retardant particles to disperse evenly within the epoxy resin matrix. Consequently, they tend to agglomerate, forming large particle aggregates. This results in insufficient interfacial bonding between the flame retardant and the epoxy resin matrix, allowing the flame retardant to easily migrate from the epoxy resin to the surface, resulting in a low flame retardant efficiency for the epoxy resin material. Summary of the Invention

[0004] The main purpose of this application is to provide a flame retardant resin material and a preparation method, aiming to solve the technical problem that conventional additive flame retardants have poor compatibility with epoxy resins, resulting in poor flame retardancy of epoxy resins.

[0005] To achieve the above objectives, the present application provides a flame retardant resin material, which includes: an epoxy resin prepolymer, an additive flame retardant, a reactive flame retardant, a toughening agent, an accelerator, and a curing agent.

[0006] Optionally, the molecular structures of the additive flame retardant and the reactive flame retardant include the same core structural unit.

[0007] Optionally, the flame retardant resin material comprises, in parts by weight: Epoxy resin prepolymer: 70~90 parts; Toughening agent: 6~12 parts; Curing agent: 10~90 parts; Accelerator: 1~5 parts; Additive flame retardant: 8~12 parts; Reactive flame retardant: 1~8 parts.

[0008] Optionally, the additive flame retardant includes at least one of a phosphate flame retardant, a phosphate ester flame retardant, a phosphonate flame retardant, a phosphite flame retardant and a phosphazene flame retardant; And / or, the reactive flame retardant includes at least one of a phosphate flame retardant, a phosphonate flame retardant, a phosphite flame retardant and a phosphazene flame retardant.

[0009] Optionally, the additive flame retardant includes at least one of hexaphenoxycyclotriphosphazene, hexaphenoxycyclotriphosphazene benzenesulfonic acid, hexaphenoxycyclotriphosphazene phenylnitrate, sodium hexaphenoxycyclotriphosphazene benzenesulfonate and potassium hexaphenoxycyclotriphosphazene benzenesulfonate.

[0010] Optionally, the reactive flame retardant includes: cyclotriphosphazene hexaepoxide and / or cyclotriphosphazene hexaglycol.

[0011] Optionally, the epoxy resin prepolymer includes at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin and alicyclic epoxy resin.

[0012] Optionally, the toughening agent includes at least one of dibenzoic anhydride, dialkyl chain anhydride, dialkoxy anhydride, liquid nitrile rubber and carboxyl-terminated liquid nitrile rubber.

[0013] Optionally, the curing agent includes at least one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, polyamine, dicyandiamide and phenolic resin.

[0014] Optionally, the accelerator includes at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, triethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

[0015] The present application also provides a method for preparing a flame retardant resin material, the method being used to prepare the flame retardant resin material, the method comprising the following steps: Provide additive flame retardants and reactive flame retardants; Blending the epoxy resin prepolymer, the additive flame retardant, the reactive flame retardant and the toughening agent to obtain a first mixture; An accelerator and a curing agent are mixed with the first mixture to prepare a flame retardant resin material.

[0016] This application discloses a flame-retardant resin material and preparation method. The flame-retardant resin material is prepared from an epoxy resin prepolymer, an additive flame retardant, a reactive flame retardant, a toughening agent, and a curing agent. The additive flame retardant is dispersed in a matrix and exerts its flame retardant properties during combustion by releasing non-combustible gases, forming a char layer that acts as a physical barrier, and capturing reactive free radicals (such as H and HO) generated by combustion. The reactive flame retardant chemically bonds to the epoxy resin backbone, acting as an effective compatibilizer between the additive flame retardant and the epoxy resin matrix, enhancing the interfacial adhesion between the additive flame retardant and the epoxy resin matrix, thereby ensuring a more uniform dispersion of the additive flame retardant within the matrix. Furthermore, during the combustion of the resin material, the reactive flame retardant provides chemical reaction sites that capture reactive free radicals, promote the formation of a dense char layer, and isolate heat and oxygen. The synergistic effect of the two flame retardants can be used to form a more effective physical barrier carbon layer and enhance the ability to capture active free radicals, inhibiting the chain propagation process during the combustion chain reaction of the epoxy resin material. Furthermore, the synergistic effect allows the flame retardants to be evenly dispersed in the epoxy resin matrix, more fully exerting their flame retardant effect, and avoiding the impact of flame retardancy caused by excessively high or low local concentrations. At the same time, good interfacial adhesion ensures that the two flame retardants can work better together during the combustion process, jointly exerting their flame retardant efficiency, significantly improving the flame retardant properties of the epoxy resin material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic flow chart of a method for preparing a flame retardant resin material according to an embodiment of the present application; Figure 2 Schematic diagram of the structure of the preparation method of the additive flame retardant involved in the embodiment of the present application; Figure 3 Schematic diagram of the structure of the method for preparing the reactive flame retardant involved in the embodiment of the present application.

[0018] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0020] In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0021] A first aspect of an embodiment of the present application provides a flame retardant resin material, comprising an epoxy resin prepolymer, an additive flame retardant, a reactive flame retardant, a toughening agent, an accelerator, and a curing agent.

[0022] In this embodiment, the additive flame retardant releases non-combustible gases through the synergistic flame retardant effect of the gas phase and the condensed phase, diluting oxygen and lowering the temperature during combustion while promoting the formation of a char layer, isolating heat and oxygen, and thus playing a flame retardant role. The reactive flame retardant forms covalent bonds with the resin matrix through a chemical reaction, becoming part of the material's molecular structure. Through molecular design, it catalyzes the dehydration and crosslinking between epoxy resin molecules at high temperatures to form a char layer, which plays a flame retardant role. The synergistic effect of the two is reflected in the dynamic coordination of the combustion process. The chemical modification of the resin matrix by the reactive flame retardant compensates for the interfacial defects caused by the physical blending of the additive flame retardant, allowing the material to maintain key mechanical parameters such as elongation at break and impact strength while improving the limiting oxygen index. Its flame retardant durability is also significantly enhanced due to the chemical bonding structure's inhibition of the migration of the flame retardant component, ultimately forming a composite material with both flame retardant properties and material mechanical properties. Furthermore, the epoxy resin prepolymer forms the matrix of the flame-retardant resin material, providing the material's essential mechanical support. The toughening agent, dispersed within the epoxy resin's rigid network, absorbs energy through deformation when subjected to external impact, thereby preventing crack propagation and improving the resin's toughness. The epoxy resin prepolymer molecules contain epoxy groups, with which the curing agent reacts chemically, initiating a crosslinking reaction. Furthermore, the accelerator reduces the activation energy required for the curing process, allowing the reaction to proceed more rapidly at lower temperatures or within a shorter timeframe, thus improving the efficiency of the curing reaction. The result is an epoxy resin material with both high flame retardancy and excellent mechanical properties.

[0023] In a feasible embodiment, the molecular structures of the additive flame retardant and the reactive flame retardant include the same core structural unit.

[0024] Alternatively, the core structural unit is the basic part of the molecular structure with specific chemical properties and functions, which determines some key characteristics of the molecule. For additive flame retardants and reactive flame retardants, the same core structural unit means that they have a part of the same chemical structure fragment in their molecular composition.

[0025] Alternatively, additive flame retardants may include hexaphenoxycyclotriphosphazene, hexaphenoxycyclotriphosphazene benzenesulfonic acid, hexaphenoxycyclotriphosphazene phenyl nitrate, sodium hexaphenoxycyclotriphosphazene benzenesulfonate, and potassium hexaphenoxycyclotriphosphazene benzenesulfonate. Reactive flame retardants may include cyclotriphosphazene hexaepoxide and cyclotriphosphazene hexadiol. Both additive and reactive flame retardants are prepared using hexachlorocyclotriphosphazene as a monomer. This core unit is a six-membered ring structure composed of alternating phosphorus (P) and nitrogen (N) atoms. These additive and reactive flame retardants are then produced by reacting other compounds based on this core unit.

[0026] Alternatively, additive and reactive flame retardants can be prepared based on hexachlorocyclotriphosphazene. These two flame retardants share the same core structural unit, resulting in more uniform dispersion within the resin matrix, stronger interfacial bonding, and improved compatibility with epoxy resins. This improves the flame retardancy of epoxy resin materials while minimizing negative impacts on other properties (such as mechanical and processing properties), thereby enhancing the overall performance of the material. Furthermore, the two flame retardants have similar phosphorus contents, resulting in higher concentrations of phosphorus-containing free radicals released during thermal decomposition, covering a wider temperature range and enhancing vapor-phase flame retardancy. Furthermore, the two flame retardants share the same core structural unit, similar raw materials, and some similar synthesis processes, simplifying the production process and reducing production costs.

[0027] In a feasible embodiment, the flame retardant resin material includes, by weight: Epoxy resin prepolymer: 70~90 parts; Toughening agent: 6~12 parts; Curing agent: 10~90 parts; Accelerator: 1~5 parts; Additive flame retardant: 8~12 parts; Reactive flame retardant: 1~8 parts.

[0028] Optionally, the flame retardant resin material includes 70 to 90 parts of epoxy resin prepolymer by weight, for example, the epoxy resin prepolymer is 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, etc.

[0029] Optionally, the epoxy resin prepolymer is the matrix of the flame-retardant resin material, providing the material with basic physical and chemical properties such as mechanical strength, adhesion, and chemical stability. The high proportion is because it forms a continuous network structure, encapsulating and fixing other components within it, ensuring the overall performance of the resin material. If the epoxy resin prepolymer is present in too few parts, an effective matrix structure cannot be formed, affecting the strength and stability of the material. If the epoxy resin prepolymer is present in too many parts, the content of other functional components is relatively reduced, resulting in insufficient flame retardancy and toughness. Therefore, when the epoxy resin prepolymer is present in 70-90 parts, it can ensure the strength and stability of the resin material without affecting its other properties such as flame retardancy and toughness.

[0030] Optionally, the flame retardant resin material includes 6 to 12 parts of toughening agent in parts by weight, for example, the toughening agent is 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, etc.

[0031] Optionally, a toughening agent improves the material's toughness and impact resistance, preventing brittle fracture during use. An appropriate amount of toughening agent can form a dispersed phase within the epoxy resin matrix, increasing the material's toughness by absorbing and dispersing energy. This can achieve a good toughening effect without significantly compromising other material properties (such as strength and flame retardancy).

[0032] Optionally, the flame retardant resin material includes 10 to 90 parts of curing agent in parts by weight, for example, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, etc. of curing agent.

[0033] Optionally, a curing agent is used to crosslink the epoxy resin prepolymer, forming a three-dimensional network structure that solidifies the material and fully cures the epoxy resin to achieve the desired hardness, strength, and chemical stability. Too little curing can result in incomplete curing and unstable material properties. Too much curing can lead to excessively rapid curing, making the molding process difficult to control, and thus affecting the toughness and other properties of the resin material. Therefore, a curing agent content of 10 to 90 parts per part allows the epoxy resin to cure at an appropriate rate without affecting other properties.

[0034] Optionally, the flame retardant resin material includes 1 to 5 parts of accelerator in parts by weight, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc. of the accelerator.

[0035] Optionally, an accelerator is used to initiate the curing reaction of the epoxy resin, reducing the activation energy of the reaction and accelerating the reaction speed and progress. Within a certain range, the more accelerator added, the more significant its promoting effect on the curing reaction. When the accelerator content is too low, its effect on reducing the reaction activation energy, initiating and accelerating the reaction is not significant, and the curing reaction speed is limited, which cannot effectively shorten the curing time. This may lead to low production efficiency and the product being in an uncured state for a long time, affecting product quality and subsequent processing. When the accelerator content is too high, the curing reaction speed is too fast, which may cause large internal stresses within the resin system. This may cause defects such as cracks and deformation in the cured material, reducing the material's mechanical properties, heat resistance, and flame retardancy. Therefore, when the accelerator content is 1 to 5 parts, it can effectively promote the curing reaction and improve production efficiency while enabling the flame-retardant resin material to obtain good overall properties, including mechanical properties, heat resistance, and flame retardancy, while taking into account cost factors, achieving an optimal balance between performance and cost.

[0036] Optionally, the flame retardant resin material includes 8 to 12 parts of additive flame retardant in parts by weight, for example, the additive flame retardant is 8 parts, 9 parts, 10 parts, 11 parts, or 12 parts.

[0037] Optionally, additive flame retardants exert their flame retardant properties by being physically dispersed within the matrix. An appropriate amount of additive flame retardant can release non-combustible gases during combustion, diluting oxygen and lowering the temperature, thus achieving a flame retardant effect. Additive flame retardants are physically dispersed within the matrix. Excessive amounts of additive flame retardants can lead to uneven dispersion and agglomeration, causing stress concentration in the material and reducing its strength and toughness. Furthermore, excessive amounts of additive flame retardants can increase the viscosity of the material, impairing its fluidity during processing and making it difficult to form. Furthermore, excessive amounts of additive flame retardants can affect its compatibility with other ingredients, such as the epoxy resin prepolymer and toughening agent, leading to delamination and phase separation, thereby reducing the overall performance of the material. Therefore, when the additive flame retardant content is 4 to 10 parts, the epoxy resin material can achieve flame retardant properties while avoiding significant uneven dispersion, increased viscosity, and agglomeration.

[0038] Optionally, the flame retardant resin material includes 1 to 8 parts of reactive flame retardant by weight, for example, the reactive flame retardant is 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, etc.

[0039] Alternatively, reactive flame retardants chemically bond to the epoxy resin backbone, promoting the formation of a dense carbon layer that isolates heat and oxygen. Because they chemically react with the epoxy resin, a small amount of reactive flame retardant can provide a good flame retardant effect. Controlling its proportion can prevent the introduction of excessive other groups from adversely affecting the mechanical and other properties of the material. Reactive flame retardants chemically bond to the epoxy resin backbone. Excessive reactive flame retardants will change the molecular structure and crosslink density of the epoxy resin, potentially increasing the hardness and reducing the toughness of the material, making the material more brittle and prone to cracking when subjected to external forces. Reactive flame retardants participate in the curing reaction of the epoxy resin. Excessive proportions of reactive flame retardants may affect the speed and extent of the curing reaction, resulting in excessively fast or slow curing, preventing the material from achieving the expected performance. For example, a curing rate that is too fast may increase internal stress and reduce the stability of the material; a curing rate that is too slow will extend the production cycle and reduce production efficiency. Furthermore, reactive flame retardants are generally relatively expensive, and increasing their proportion will significantly increase the material preparation cost. Therefore, when the reactive additive is 1 to 8 parts, the epoxy resin material can achieve flame retardant properties while increasing the compatibility of the additive flame retardant with the epoxy resin material without affecting other properties of the epoxy resin, such as toughness and hardness.

[0040] In a feasible embodiment, the additive flame retardant includes: at least one of a phosphate flame retardant, a phosphate ester flame retardant, a phosphonate flame retardant, a phosphite flame retardant, and a phosphazene flame retardant; And / or, the reactive flame retardant includes at least one of a phosphate flame retardant, a phosphonate flame retardant, a phosphite flame retardant and a phosphazene flame retardant.

[0041] Optionally, additive flame retardants release non-combustible gases to dilute oxygen and reduce temperature during combustion through the synergistic flame retardant effect of the gas phase and the condensed phase, while promoting the formation of a char layer to isolate heat and oxygen, thereby improving the flame retardant properties of the resin material.

[0042] Optionally, phosphate flame retardants decompose during combustion to produce phosphorus-containing free radicals, which react with highly active free radicals in the gas phase to interrupt the chain reaction. Further, the decomposition forms polyphosphoric acid, which promotes the dehydration and carbonization of the resin to form a char layer, which insulates heat and oxygen and inhibits combustion. Phosphate flame retardants can decompose at high temperatures to produce volatile phosphorus compounds, which dilute oxygen, capture free radicals and inhibit chain reactions. Further decomposition produces phosphoric acid and other substances that promote resin carbonization. They also have a carbonizing effect themselves, forming a char layer to isolate heat and oxygen. Phosphonic acid can also burn and decompose to produce small phosphorus-containing molecules, which react with free radicals in the gas phase to terminate the chain reaction. Phosphite flame retardants can resist oxidation and prevent accelerated decomposition of materials in the early stages of combustion. Further decomposition at high temperatures to produce phosphorous acid promotes the dehydration and carbonization of the resin material to form a char layer, and the volatile substances produced by decomposition dilute oxygen and capture free radicals in the gas phase, thereby playing a flame retardant role. Phosphazene flame retardants can decompose through combustion to produce volatile substances containing phosphorus and nitrogen, which further capture gas-phase free radicals, dilute oxygen and inhibit chain reactions, and form a stable char layer at high temperatures to isolate heat and oxygen and prevent combustion, thereby playing a flame retardant role.

[0043] Alternatively, reactive flame retardants form covalent bonds with the resin matrix (eg, polymer chains) through chemical reactions, becoming part of the material's molecular structure.

[0044] Alternatively, phosphate flame retardants contain reactive groups (e.g., hydroxyl, epoxy) that can react with functional groups (e.g., hydroxyl, carboxyl) of the resin material during resin synthesis or processing through esterification, ring-opening addition, and other reactions, thereby incorporating into the resin material. Phosphonate flame retardants contain PC bonds and can be incorporated into the resin material through copolymerization with resin monomers or grafting with polymer chains via reactive groups (e.g., vinyl, amino). Phosphite flame retardants can be incorporated into the resin material by cross-linking with reactive groups such as epoxy and thiol groups. Phosphazene flame retardants contain PN main-chain polymers with reactive side chains (e.g., hydroxyl, amino) that can be condensed or copolymerized with the resin. Furthermore, reactive flame retardants can also exert flame retardant effects through the same mechanisms as the additive flame retardants described above, such as gas-phase flame retardancy and condensed-phase carbonization.

[0045] In this example, the additive flame retardant achieves a comprehensive effect of highly effective flame suppression, fire delay, material structure protection, and environmental friendliness through multiple mechanisms, including vapor-phase flame retardancy, condensed-phase carbonization, and antioxidant protection. In addition to chemically bonding to the resin, reactive flame retardants also exert flame retardant effects through mechanisms like additive flame retardancy, such as vapor-phase flame retardancy and condensed-phase carbonization. This synergistic effect of multiple flame-retardant mechanisms makes the flame retardancy of epoxy resin materials even more significant.

[0046] In a feasible embodiment, the additive flame retardant includes at least one of hexaphenoxycyclotriphosphazene, hexaphenoxycyclotriphosphazene benzenesulfonic acid, hexaphenoxycyclotriphosphazene phenylnitrate, sodium hexaphenoxycyclotriphosphazene benzenesulfonate, and potassium hexaphenoxycyclotriphosphazene benzenesulfonate.

[0047] Optionally, polyphosphazene flame retardants have high reactivity, excellent thermal stability and better flame retardant performance, especially hexaphenoxycyclotriphosphazene.

[0048] Optionally, sodium hexaphenoxycyclotriphosphazene benzenesulfonate and potassium hexaphenoxycyclotriphosphazene benzenesulfonate are sodium or potassium salts, which have higher thermal stability than hexaphenoxycyclotriphosphazene benzenesulfonic acid. When the epoxy resin is heated, they can maintain a relatively stable structure at higher temperatures and will not decompose prematurely. Furthermore, the presence of ionic bonds enables them to form certain interactions with the epoxy resin molecules, such as electrostatic effects and hydrogen bonds, thereby more evenly dispersing in the epoxy resin matrix. They can also enhance interfacial bonding and promote the formation and stabilization of the char layer during combustion.

[0049] In a feasible embodiment, the reactive flame retardant includes: cyclotriphosphazene hexaepoxide and / or cyclotriphosphazene hexaglycol.

[0050] Alternatively, other compounds containing epoxy or hydroxyl groups can participate in the reaction to produce reactive flame retardants. In alkaline conditions, epoxy-containing compounds undergo ring-opening and substitution with the chlorine atoms in hexachlorocyclotriphosphazene, such as in glycidyl ethers. In alkaline solvents, hydroxyl-containing compounds undergo deprotonation, forming oxygen anions that attack the hexacyclic ring of cyclotriphosphazene, displacing the epoxy group to produce polyols, such as diols. The resulting reactive flame retardant contains phosphorus and nitrogen, allowing it to chemically bond with the resin material. It exhibits excellent dispersibility and stability, avoiding the migration and precipitation issues associated with additive flame retardants.

[0051] In this embodiment, the additive flame retardant exerts a flame retardant effect by being physically dispersed in the matrix. An appropriate amount of additive flame retardant can release non-combustible gas during combustion, dilute oxygen and reduce temperature, thereby achieving a flame retardant effect. On the one hand, the reactive flame retardant provides chemical reaction sites to play a flame retardant role. On the other hand, it acts as an effective compatibilizer between the additive flame retardant and the matrix, enhancing the interfacial adhesion between the additive flame retardant and the matrix, while making the additive flame retardant more evenly dispersed in the matrix. The two work synergistically to construct an effective physical barrier carbon layer and enhance the ability to capture active free radicals, thereby inhibiting the chain propagation process in the chain reaction of the resin material combustion. The flame retardant performance of the resin material can be significantly improved.

[0052] In a feasible embodiment, the epoxy resin prepolymer includes at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin and alicyclic epoxy resin.

[0053] Alternatively, an epoxy resin prepolymer refers to an oligomer with epoxy groups (-CH(O)CH-) at the end or side chains of the molecular chain. It is the main component of the epoxy resin system before curing. A certain number of epoxy groups remain in the prepolymer molecule, making it active for further polymerization reactions. Under the action of a curing agent, the epoxy resin prepolymer undergoes a cross-linking reaction, forming a three-dimensional network of polymer structures. This provides the fundamental mechanical properties of the entire material, imparting a certain strength and hardness. The epoxy resin prepolymer serves as a matrix in the flame-retardant resin material, allowing components such as the additive flame retardant, reactive flame retardant, toughening agent, and curing agent to be evenly dispersed and function. Furthermore, the epoxy resin prepolymer can synergistically interact with the additive and reactive flame retardants during combustion. At high temperatures, the epoxy resin prepolymer undergoes thermal decomposition, and the flame retardant decomposes to produce phosphorus-containing free radicals and substances such as phosphoric acid. These phosphorus-containing substances can promote the carbonization of epoxy resin prepolymers, forming a dense char layer that isolates oxygen and heat, thereby improving the material's flame retardancy. Reactive flame retardants contain active functional groups capable of reacting with epoxy groups, such as the epoxy and hydroxyl groups in cyclotriphosphazene hexaepoxy and cyclotriphosphazene hexadiol. These react chemically with the epoxy groups in epoxy resin prepolymers, introducing phosphorus into the epoxy resin's molecular structure. This makes the flame retardant more evenly distributed throughout the material, improving the durability and stability of the flame retardant effect.

[0054] In a feasible embodiment, the toughening agent includes at least one of dibenzoic anhydride, dialkyl chain anhydride, dialkoxy anhydride, liquid nitrile rubber and carboxyl-terminated liquid nitrile rubber.

[0055] Alternatively, toughening agents are functional additives used to mitigate the brittleness of epoxy resins and improve their impact strength and fracture toughness. Toughening agents interact with the resin matrix through physical or chemical means, mitigating their inherent brittleness while maintaining mechanical and thermal properties. Rubber-based toughening agents are uniformly dispersed in the epoxy resin matrix in the form of tiny particles. When the material is subjected to external forces, the rubber particles can induce crazing (microscopic cracks) and shear bands. The generation and propagation of crazing consumes significant energy, thus preventing further crack expansion. Simultaneously, the formation of shear bands absorbs and dissipates energy, improving the toughness of the material. Furthermore, rubber molecular chains are highly flexible, allowing them to entangle with other epoxy resin chains during the epoxy resin curing process. These flexible segments of the rubber chains can undergo significant deformation under stress, thereby increasing the material's deformability and toughness. Anhydride-based toughening agents participate in the epoxy resin curing reaction, but their relatively large molecular structure can hinder crosslinking between epoxy resin molecules to a certain extent, thereby reducing the crosslink density. A lower crosslink density gives the material's molecular chains more room to move, allowing them to deform more when subjected to stress, thereby improving the material's toughness. The molecular structure of anhydride toughening agents contains flexible groups that increase the distance between molecular chains, reduce intermolecular forces, and make the material softer and more resilient.

[0056] In a feasible embodiment, the curing agent includes at least one of anhydride, polyamine, dicyandiamide and phenolic resin.

[0057] Alternatively, a curing agent refers to a compound that chemically reacts with epoxy resin prepolymers (containing epoxy groups), transforming them from a liquid or thermoplastic state into a three-dimensional cross-linked network structure. This curing process imparts excellent mechanical properties, heat resistance, and chemical stability to epoxy resin materials. For example, in anhydride curing agents, the anhydride groups (-CO-O-CO-) in the anhydride molecules, under the influence of heat or a catalyst, undergo a ring-opening esterification reaction with the epoxy groups (-CH(O)CH-) in the epoxy resin molecules. The anhydride first ring-opens to form a carboxylic acid, which then reacts with the epoxy groups to form ester bonds, thus connecting the epoxy resin molecules and forming a cross-linked network structure. In polyamine curing agents, the polyamine molecules contain multiple active amine groups (-NH2 or -NHR). The hydrogen atoms on these amine groups are highly reactive and can undergo a ring-opening addition reaction with the epoxy groups in the epoxy resin molecules. As the reaction proceeds, the polyamine molecules continuously react with multiple epoxy resin molecules, ultimately forming a three-dimensional network structure. The reaction typically proceeds rapidly at room temperature or lower. Dicyandiamide curing agents are relatively stable at room temperature and have a long shelf life when mixed with epoxy resin, making them latent curing agents. When heated to a certain temperature, the cyano groups (-CN) in the dicyandiamide molecule react to form reactive intermediates, which react with the epoxy groups in the epoxy resin molecule, initiating the curing process. Epoxy resins cured with dicyandiamide exhibit excellent heat resistance and mechanical properties. Phenolic resin curing agents contain numerous phenolic hydroxyl groups (-OH). Under heating and the presence of a catalyst, the hydrogen atoms on these phenolic hydroxyl groups react with the epoxy groups in the epoxy resin molecule to form ether bonds and hydroxyl groups, linking the phenolic resin molecules and forming a cross-linked structure. Epoxy resins cured with phenolic resin exhibit high heat resistance, chemical resistance, and mechanical strength.

[0058] In a feasible embodiment, the accelerator includes at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, triethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

[0059] Optionally, accelerators can accelerate chemical reactions, shorten reaction times, and reduce curing conditions (such as temperature and curing agent content). In reactions such as resin curing, accelerators can significantly increase production efficiency and improve product performance. 2-Methylimidazole and 2-ethyl-4-methylimidazole have imidazole ring structures that interact with reactant molecules, promoting the reaction. Their molecules contain three ethyl groups and one nitrogen atom, which can activate curing agent molecules. 2,4,6-Tris(dimethylaminomethyl)phenol, containing phenolic hydroxyl groups and multiple dimethylaminomethyl groups, exhibits strong alkalinity and reactivity. Benzyldimethylamine, containing a benzyl group and two dimethylamino groups, exhibits moderate alkalinity and initiating activity.

[0060] In this embodiment, the additive flame retardant, through the synergistic flame retardant effects of the gas and condensed phases, releases non-combustible gases during combustion to dilute oxygen and lower the temperature, while also promoting the formation of a char layer, isolating heat and oxygen and thus providing a flame retardant effect. The reactive flame retardant, through a chemical reaction, forms covalent bonds with the resin matrix (e.g., polymer chains), becoming part of the material's molecular structure. Through molecular design, it catalyzes the dehydration and crosslinking of epoxy resin molecules at high temperatures, forming a char layer that also provides a flame retardant effect. The synergistic effect of the two is reflected in the dynamic coordination of the combustion process. The chemical modification of the resin matrix by the reactive flame retardant compensates for the interfacial defects caused by the physical blending of the additive flame retardant, resulting in an improved limiting oxygen index while maintaining key mechanical parameters such as elongation at break and impact strength. The flame retardant durability is also significantly enhanced due to the chemical bonding structure's suppression of the migration of the flame retardant component, ultimately forming a composite material that combines flame retardancy with mechanical properties. Furthermore, by dispersing the toughening agent within the rigid network of the epoxy resin, it can absorb energy through deformation when subjected to external impact, thereby preventing crack propagation and improving the toughness of the resin material. The epoxy resin prepolymer molecules contain epoxy groups, which the curing agent can chemically react with to initiate a crosslinking reaction. The active accelerator can accelerate the curing reaction, ultimately resulting in an epoxy resin material with high flame retardancy and excellent mechanical properties.

[0061] The present invention provides a method for preparing a flame retardant resin material. The method is used to prepare a flame retardant resin material, and the method comprises the following steps: Step S10, providing an additive flame retardant and a reactive flame retardant; In a feasible embodiment, the additive flame retardant and the reactive flame retardant can be purchased on the market or prepared.

[0062] Alternatively, phosphazene additive flame retardants can be prepared from raw materials. Figure 2 In the presence of sodium hydroxide solution, hexachlorocyclotriphosphazene is reacted with phenol to produce hexaphenoxycyclotriphosphazene; further, 50% sulfuric acid or nitric acid is used to carry out sulfonation and / or nitration of hexaphenoxycyclotriphosphazene to produce hexaphenoxycyclotriphosphazene benzenesulfonic acid and / or hexaphenoxycyclotriphosphazene phenylnitrate; further, hexaphenoxycyclotriphosphazene benzenesulfonic acid is subjected to a displacement reaction with sodium hydroxide and / or potassium hydroxide to produce novel sodium hexaphenoxycyclotriphosphazene benzenesulfonate and / or potassium hexaphenoxycyclotriphosphazene benzenesulfonate.

[0063] Alternatively, phosphazene reactive flame retardants can be prepared from raw materials. Figure 3In the presence of sodium hydroxide solution, hexachlorocyclotriphosphazene and 3-propylene oxide methanol undergo a substitution reaction to obtain cyclotriphosphazene hexaepoxy; further, in the presence of triethylamine, the reaction is heated to 70-100°C, and cyclotriphosphazene hexaepoxy and ethylene glycol undergo a displacement reaction to obtain cyclotriphosphazene hexadiol.

[0064] Step S20, blending the epoxy resin prepolymer, the additive flame retardant, the reactive flame retardant, and the toughening agent to obtain a first mixture; Alternatively, blending refers to the process of uniformly mixing different materials through the application of mechanical forces. Blending allows the epoxy resin prepolymer, additive flame retardant, reactive flame retardant, and toughening agent to be thoroughly mixed, ensuring uniform distribution of the components throughout the mixture. This ensures consistent material properties and avoids localized performance variations. The resulting homogeneous mixture is called the primary mixture. It serves as an intermediate product for subsequent processing and preparation of the final product.

[0065] Step S30: mixing the accelerator and the curing agent with the first mixture to prepare a flame retardant resin material.

[0066] Optionally, when the accelerator and curing agent are fully in contact with the epoxy resin prepolymer in the first mixture, the curing reaction begins. The addition of the accelerator allows the curing reaction to proceed uniformly throughout the system, resulting in uniform material properties. After the curing agent is added, the mixture can be poured into a mold and subjected to vacuum degassing and multi-step curing to produce a flame-retardant resin material.

[0067] This embodiment uses a combination of additive flame retardants and reactive flame retardants to prepare flame-retardant resin materials. Additive flame retardants can exert physical or chemical effects to inhibit combustion when the resin burns, and reactive flame retardants chemically bond to the resin molecular structure to make the flame retardant effect more durable and stable. The additive flame retardant and reactive flame retardant work synergistically to improve the flame retardant properties of the resin material from different levels and mechanisms, which is better than the effect of using a single flame retardant. Adding a toughening agent to the epoxy resin can improve the toughness and impact resistance of the resin material. Furthermore, in the preparation process of the flame-retardant resin material, a blending step is performed to uniformly mix the epoxy resin prepolymer, additive flame retardant, reactive flame retardant and toughening agent using mechanical force to obtain a first mixture, so that each component is evenly distributed in the mixture, avoiding the problem of local performance differences caused by uneven distribution of components. When the curing agent is subsequently added, the first mixture is already uniform, allowing for full contact between the curing agent and the epoxy resin prepolymer in the first mixture. Furthermore, the addition of the accelerator allows the curing reaction to proceed uniformly throughout the entire system. The resulting flame-retardant resin material exhibits uniform properties, ensuring the stability and reliability of product quality. Furthermore, by controlling the ratios of the various components, flame-retardant epoxy resin materials with excellent flame retardancy can be produced while maintaining low costs.

[0068] In order to make the details and operations of the above embodiments of the present application clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the flame-retardant resin material and preparation method of the embodiments of the present application, the above technical solutions are illustrated by multiple embodiments below.

[0069] Example 1 80 parts by weight of epoxy resin prepolymer, 8 parts of additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate), 1 part of reactive flame retardant (cyclotriphosphazene hexaepoxy), and 10 parts of toughening agent (dibenzoic anhydride) were added to a reaction container, blended, and stirred at room temperature until uniform to prepare a first mixture; Add 80 parts of curing agent (methyltetrahydrophthalic anhydride) and 1 part of accelerator (2-ethyl-4-methylimidazole) to the first mixture and continue stirring until uniform. Then, pour the mixed material into a pre-prepared mold and place the material in the mold into a vacuum device for degassing.

[0070] The mold was placed in an oven, set at 60°C and maintained for a period of time; the temperature was gradually increased to 100°C and maintained for a certain period of time; finally, the temperature was increased to 180°C and post-cured for a certain period of time to obtain a flame retardant resin material 1.

[0071] Example 2 The steps are the same as those in Example 1, except that 8 parts of an additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 5 parts of a reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame retardant resin material 2.

[0072] Example 3 The steps are the same as those in Example 1, except that 8 parts of an additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 8 parts of a reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame-retardant epoxy resin material 3.

[0073] Example 4 The steps are the same as those in Example 1, except that: 12 parts of additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 1 part of reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare flame retardant resin material 4.

[0074] Example 5 The steps are the same as those in Example 1, except that 12 parts of an additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 5 parts of a reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame retardant resin material 5.

[0075] Example 6 The steps are the same as those in Example 1, except that 12 parts of an additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 8 parts of a reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame retardant resin material 6.

[0076] Example 7 The steps are the same as those in Example 1, except that 10 parts of an additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 5 parts of a reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame retardant resin material 7.

[0077] Example 8 The steps are the same as those in Example 1, except that 10 parts of an additive flame retardant (sodium hexaphenoxy cyclotriphosphazene benzenesulfonate) and 5 parts of a reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame retardant resin material 8.

[0078] Comparative Example 1 The steps are the same as those in Example 1, except that: 12 parts of the additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 0 parts of the reactive flame retardant (cyclotriphosphazene hexaepoxy) are added to prepare a flame retardant resin material 9.

[0079] Comparative Example 2 The steps are the same as those in Example 1, except that: 0 parts of the additive flame retardant (hexaphenoxy cyclotriphosphazene phenyl nitrate) and 8 parts of the reactive flame retardant (cyclotriphosphazene hexaepoxy) are used to prepare a flame retardant resin material 10.

[0080] Comparative Example 3 The steps are the same as those in Example 1, except that 12 parts of a flame retardant (tetrabromobisphenol A) are added to prepare a flame retardant resin material 11 .

[0081] Comparative Example 4 The steps are the same as those in Example 1, except that no flame retardant is added to prepare the epoxy resin material 12.

[0082] Furthermore, in order to verify the progress of the embodiments of the present application, the following performance tests were conducted on each embodiment and comparative example: 1. Vertical burning test The vertical burning test is conducted in accordance with UL 94 (Tests for Flammability of Plastic Materials for Parts in Devices and Appliances).

[0083] 2. Tensile strength and flexural strength (1) The tensile strength of epoxy resin is tested according to GB / T 2567~2021 "Test method for properties of resin castings"; (2) The flexural strength of epoxy resin is tested according to GB / T 2567~2021 "Test method for properties of resin castings".

[0084] 3. Glass transition temperature Characterization was performed using DSC (Differential Scanning Calorimetry) data.

[0085] 4. Limiting Oxygen Index (LOI) The Limiting Oxygen Index (LOI) is tested in accordance with GB / T 2406.1~2008 "Plastics - Determination of Burning Behavior by Oxygen Index Method - Part 1: Guidelines" and GB / T 2406.2~2009 "Plastics - Determination of Burning Behavior by Oxygen Index Method - Part 2: Room Temperature Test".

[0086] The test results are shown in Table 1 below: Table 1

[0087] As shown in Table 1, Examples 1 to 8 are examples in which an additive flame retardant and a reactive flame retardant are added. As shown in Table 1, compared with Comparative Examples 1 to 4 in which only one flame retardant is added or no flame retardant is added, the examples 1 to 8 exhibit better flame retardancy, mechanical properties, higher glass transition temperature and limiting oxygen index, indicating that in the epoxy resin material, the synergistic effect of the additive flame retardant and the reactive flame retardant can effectively increase the compatibility of the flame retardant in the epoxy resin, thereby improving the flame retardancy and other properties of the prepared flame retardant resin material. The flame retardant grade of the flame retardant resin material prepared in the present application reaches V~0, and has good flame retardant properties; the limiting oxygen index (LOI) reaches 28~36%; compared with the flame retardant epoxy resin materials prepared in comparative examples 1~4, the limiting oxygen index is higher and the flame retardant properties are better; and the tensile strength and flexural strength of the flame retardant epoxy resin material reach above 80 MPa, and the elongation at break reaches above 50%, with excellent tensile strength; furthermore, the heat resistance of the flame retardant resin material is improved, and the glass transition temperature reaches above 145°C.

[0088] The above are only preferred embodiments of the present application and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of the present invention.

Claims

1. A flame retardant resin material, characterized in that: The flame retardant resin material comprises: epoxy resin prepolymer, additive flame retardant, reactive flame retardant, toughening agent, accelerator and curing agent.

2. The flame retardant resin material according to claim 1, wherein The molecular structures of the additive flame retardant and the reactive flame retardant include the same core structural unit.

3. The flame retardant resin material according to claim 1, wherein In parts by weight, the flame retardant resin material comprises: Epoxy resin prepolymer: 70~90 parts; Toughening agent: 6~12 parts; Curing agent: 10~90 parts; Accelerator: 1~5 parts; Additive flame retardant: 8~12 parts; Reactive flame retardant: 1~8 parts.

4. The flame retardant resin material according to claim 1, wherein The additive flame retardant includes: at least one of phosphate flame retardants, phosphate ester flame retardants, phosphonate flame retardants, phosphite flame retardants and phosphazene flame retardants; And / or, the reactive flame retardant includes at least one of a phosphate flame retardant, a phosphonate flame retardant, a phosphite flame retardant and a phosphazene flame retardant.

5. The flame retardant resin material according to claim 1, wherein The additive flame retardant comprises at least one of hexaphenoxy cyclotriphosphazene, hexaphenoxy cyclotriphosphazene benzenesulfonic acid, hexaphenoxy cyclotriphosphazene phenyl nitrate, hexaphenoxy cyclotriphosphazene benzenesulfonate sodium and hexaphenoxy cyclotriphosphazene benzenesulfonate potassium.

6. The flame retardant resin material according to claim 1, wherein The reactive flame retardant includes: cyclotriphosphazene hexaepoxide and / or cyclotriphosphazene hexaglycol.

7. The flame retardant resin material according to claim 1, wherein The epoxy resin prepolymer includes at least one of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin and alicyclic epoxy resin.

8. The flame retardant resin material according to claim 1, wherein The toughening agent comprises at least one of dibenzoic anhydride, dialkyl chain anhydride, dialkoxy anhydride, liquid nitrile rubber and carboxyl-terminated liquid nitrile rubber.

9. The flame retardant resin material according to claim 1, wherein The curing agent comprises at least one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, polyamine, dicyandiamide and phenolic resin; And / or, the accelerator includes at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, triethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and benzyldimethylamine.

10. A method for preparing a flame retardant resin material, characterized in that: The method is used to prepare the flame retardant resin material according to any one of claims 1 to 9, and the method comprises the following steps: Provide additive flame retardants and reactive flame retardants; Blending the epoxy resin prepolymer, the additive flame retardant, the reactive flame retardant and the toughening agent to obtain a first mixture; An accelerator and a curing agent are mixed with the first mixture to prepare a flame retardant resin material.

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