Intrinsic flame-retardant low-dielectric epoxy resin and preparation method thereof

Abstract

The invention relates to an intrinsic flame-retardant low-dielectric epoxy resin. The molecular structure of the epoxy resin comprises a) a biphenyl group, and at least one of b) a polyphenylene oxide (PPO) group, c) a polyether sulfone (PES) group or d) a polyamide imide (PAI) group. The preparation method comprises the following steps: dissolving biphenyl epoxy resin in a solvent, adding a polymer with an active group, adding independently or in a certain proportion in a combined manner, fully dissolving, adding a catalyst, heating, and carrying out solution polymerization; and after the reaction is finished, supplementing the solvent to prepare the solvent type modified epoxy resin. The obtained product can improve the limit oxygen index of the epoxy resin, reduce the dielectric constant Dk and the dielectric loss factor Df, realize a greener and more environment-friendly flame-retardant target, and better adapt to the performance requirements of high-end electronic products on high-speed transmission and low loss of electric signals.

Description

Technical Field

[0001] This invention relates to the field of modified synthesis and manufacturing of epoxy resins, specifically to an intrinsically flame-retardant low-dielectric epoxy resin and its preparation method. Background Technology

[0002] Epoxy resin is a general term for polymers containing two or more epoxy groups in their molecular structure. Due to the high reactivity of epoxy groups, it can undergo ring-opening reactions with various compounds containing active hydrogen, thereby curing and cross-linking to form a network structure. Therefore, epoxy resin is a typical thermosetting polymer synthetic material. After curing, epoxy resin exhibits excellent adhesive strength, mechanical strength, creep resistance, fatigue resistance, heat resistance, and insulation properties, demonstrating superior overall performance. It has been widely used in the manufacture of adhesives, anti-corrosion coatings, copper-clad laminates, electrical insulation materials, and composite materials.

[0003] It is particularly noteworthy that the copper clad laminate (CCL) industry consumes a massive amount of epoxy resin, the vast majority of which is flame-retardant epoxy resin. Data released by the Copper Clad Laminate Industry Association in 2025 shows that in 2024, the Chinese CCL industry consumed approximately 800,000 tons of epoxy resin; of which flame-retardant epoxy resin accounted for about 70%. With the rapid development of emerging technologies such as 5G communication, artificial intelligence, cloud computing, and big data storage, the demand for high-performance electronic materials is growing rapidly, such as substrate materials with faster signal transmission rates and lower signal transmission losses. At the same time, downstream PCB customers are placing more stringent requirements on the flame-retardant and dielectric properties of CCLs, such as adopting more environmentally friendly flame-retardant solutions, lower dielectric constants (Dk), and dielectric loss factors (Df). As one of the three major raw materials in CCL manufacturing, epoxy resin plays a decisive role in the flame-retardant and dielectric properties of CCLs. Therefore, improving the flame-retardant and dielectric properties of epoxy resin will be a research hotspot in the future development of epoxy resin.

[0004] Since most epoxy resins have a limiting oxygen index (LOI) between 19% and 20%, such as the most common basic epoxy resin E51 with an OX of 19.8%, they fall into the category of flammable materials. When burned, they produce large amounts of dense smoke and molten dripping, posing a significant fire hazard. Current industry-standard flame retardant solutions primarily involve introducing bromine or phosphorus elements into the epoxy resin's molecular structure to impart flame retardant properties. However, both bromine and phosphorus produce environmentally harmful substances during combustion, such as hydrogen bromide, dioxins, phosphoric acid, and metaphosphoric acid, which damage the air, ozone layer, and aquatic environment. Currently, some developed countries and economies have proposed greener, more environmentally friendly, and more efficient flame retardant concepts, with halogen-free and phosphorus-free flame retardants becoming a new development trend.

[0005] Epoxy resins contain a large number of hydroxyl groups in their molecular structure, resulting in high polarity. This leads to high dielectric constant (Dk), dielectric loss factor (Df), and water absorption, which cannot meet the performance requirements of high-end electronic materials for low dielectric constant and low dielectric loss factor. Currently, the industry mainly uses epoxy resins and curing agents with special structures to reduce the dielectric properties of cured epoxy products, such as dicyclopentadienol-type epoxy resins, reactive ester curing agents, and styrene-maleic anhydride copolymer curing agents. Although these solutions can reduce the dielectric constant and dielectric loss factor, they cannot improve the flame retardant properties of epoxy resins. Phosphorus or bromine elements still need to be introduced into the formulation system for flame retardancy. However, bromine and phosphorus further degrade the dielectric properties of epoxy resins, making flame retardancy and dielectric properties a difficult-to-resolve contradiction.

[0006] Therefore, there is an urgent need to find a solution that can simultaneously improve the dielectric and flame retardant properties of epoxy resin in order to meet the new performance requirements of resin raw materials for high-end copper clad laminate products.

[0007] Regarding the technical problem to be solved by this invention, there are currently some existing technologies. Existing technology one relates to a low-dielectric, bromine-containing flame-retardant epoxy resin formulation system: It typically uses high-bromine-content epoxy resin (bromine content 46-50%) or bromine-containing flame retardants (such as tetrabromobisphenol A, decabromodiphenyl ethane) blended into the formulation to provide flame-retardant properties. Simultaneously, it uses dicyclopentadienol-type epoxy resin and reactive ester curing agents in the formulation to reduce the dielectric constant and dielectric loss factor of the cured system. The disadvantages of the aforementioned prior art one are: 1) Bromine-based flame retardants: When cured products burn, they release toxic halogenated gases and produce carcinogenic substances such as dioxins, posing a threat to the environment and human health. With increasingly stringent environmental regulations, the use of bromine-containing flame retardants is facing growing restrictions. The United States, the European Union, South Korea, and Japan have all imposed strict limits on the halogen content in electronic products. For example, halogens and decabromodiphenyl ethane are key targets in RoHS and REACH testing. Bromine is highly polar, which is detrimental to reducing the dielectric constant Dk and dielectric loss factor Df of epoxy resins. 2) Dicyclopentadienol-type epoxy resins possess a unique alicyclic structure, which reduces the polarity and water absorption rate of the epoxy resin, thereby lowering its dielectric constant and dielectric loss factor. When reactive ester curing agents react with epoxy resins, they do not produce secondary hydroxyl groups, thus reducing the overall polarity of the cured product. However, this approach has very limited improvement on dielectric properties and cannot significantly improve the dielectric properties and dielectric loss factor of the cured system. Furthermore, reactive ester curing agents have low reactivity, making complete curing difficult. The curing process also results in the formation of numerous ester bonds, leading to poor alkali resistance, water resistance, and adhesion of the cured product, making it impossible to achieve a balance of various performance indicators. Existing technology two involves a low-dielectric, phosphorus-based flame-retardant epoxy resin formulation system: typically using a combination of dicyclopentadienol-type epoxy resin and a DOPO-modified PN curing agent (phosphorus content approximately 9.5%), or blending phosphorus-based flame retardants (such as phosphate esters or phosphazene flame retardants) into the dicyclopentadienol-type epoxy resin to provide flame-retardant properties. Simultaneously, reactive ester curing agents are used to reduce the dielectric constant and dielectric loss factor of the cured system. The disadvantage of existing technology two is that although phosphorus-based flame retardants are currently the mainstream halogen-free flame retardant solutions and pose less harm to human health and the environment compared to halogen flame retardants, the cured product still produces phosphoric acid-like substances during combustion, potentially harming the aquatic environment. Furthermore, phosphorus-based flame retardants lead to a significant increase in the water absorption rate of the cured product. Since the dielectric constant of water, Dk, is approximately 70, significantly higher than that of epoxy resin itself (approximately 4.0-4.5), the increased water absorption rate will result in a significant increase in both the dielectric constant and the dielectric loss factor. Additionally, the adhesion of phosphorus-based flame-retardant epoxy resin to copper foil decreases significantly, making it difficult for the resulting copper-clad laminate to meet the copper foil peel strength requirements. Existing technology three involves a low-dielectric, nitrogen-based flame-retardant epoxy resin formulation system: nitrogen-based flame retardancy is a potential solution for halogen-free and phosphorus-free flame retardancy, but it is currently in the exploratory stage and not yet mature. A more feasible solution is to use nitrogen-containing benzoxazine resin or amino resin as the curing agent for the epoxy resin, and also to mix a portion of nitrogen-containing flame retardant into the formulation to achieve the flame retardant requirements.Because nitrogen's flame-retardant efficiency is far lower than that of bromine and phosphorus, a nitrogen content of over 20% is required in the formulation to achieve the same flame-retardant rating. Using only benzoxazine or amino resins as curing agents cannot achieve such a high nitrogen content; therefore, nitrogen-containing flame retardants must be blended into the epoxy resin. Commonly available nitrogen-containing flame retardants are primarily melamine cyanurate (MCA). When this flame retardant is blended into epoxy resin, it causes a rapid increase in viscosity and turbidity, indicating poor compatibility. Furthermore, these nitrogen-containing resins and flame retardants do not significantly improve the dielectric constant and loss factor of epoxy resin; some even lead to dielectric degradation. The potential tertiary amine structure in nitrogen-containing compounds can catalyze the curing process of epoxy resin, resulting in significant deterioration of formulation stability and shelf life. Summary of the Invention

[0008] In view of the above problems, the present invention proposes a synthesis scheme for an intrinsically flame-retardant low-dielectric epoxy resin.

[0009] Intrinsic flame retardancy refers to the enhancement of the char residue of epoxy resin during combustion through unique molecular structure design. A high char residue typically means that the material can form more carbides at high temperatures. These carbides act as heat and oxygen barriers during combustion, thus slowing or preventing flame propagation and improving the material's flame retardant properties. A high char residue makes the epoxy resin itself self-extinguishing (limiting oxygen index: 22-27%) or non-flammable (limiting oxygen index > 27%), eliminating the need for halogens, phosphorus, or nitrogen elements for flame retardancy, achieving a more environmentally friendly, efficient, and pure flame retardant effect.

[0010] Low dielectric constant is achieved by grafting epoxy resin with reactive polymers that possess inherent flame retardancy and low dielectric constant, thereby altering the epoxy resin's molecular structure. This reduces the dielectric constant (Dk) and dielectric loss factor (Df) while retaining some of the excellent properties of epoxy resin itself, such as high reactivity, high heat resistance, high adhesion, good processability, and processability. This approach can simultaneously improve the flame retardancy and dielectric properties of epoxy resin, meeting the performance requirements of some high-end electronic materials, and can be widely used, especially in the manufacturing of copper-clad laminates.

[0011] Specifically, the present invention relates to an intrinsically flame-retardant low-dielectric epoxy resin, wherein the molecular structure of the epoxy resin, in addition to the epoxy group, also includes a) a biphenyl group and at least one selected from b) a polyphenylene ether (PPO) group, c) a polyether sulfone (PES) group or d) a polyamide imide (PAI) group.

[0012] a) Biphenyl group: ; b) Polyphenylene oxide (PPO) groups: Where n≥2, preferably n is 5-50; or Where m, n = 0–25, and m + n ≥ 1; Y is a linear (e.g., 1–20 C atoms), branched, or cyclic hydrocarbon group with 20 or fewer carbon atoms; c) Polyethersulfone (PES) groups: Where n≥2, preferably n is 5-100; d) Polyamide-imide (PAI) groups: ; The intrinsically flame-retardant low-dielectric epoxy resin described above preferably contains, in addition to epoxy groups, a) a) biphenyl groups and at least one b) polyphenylene oxide (PPO) group in its molecular structure.

[0013] More preferably, the intrinsically flame-retardant low-dielectric epoxy resin described above further comprises at least one of the polyether sulfone (PES) group shown in c) or the polyamide imide (PAI) group shown in d).

[0014] In molecular structure design, the intrinsic flame retardancy and low dielectric properties of epoxy resin can be achieved simultaneously through the combination of these chemical groups.

[0015] As described above, intrinsically flame-retardant low-dielectric epoxy resins contain biphenyl structures as their main raw material. Besides the biphenyl structure in its molecular backbone, this type of epoxy resin, due to differences in substituents and softening points, has a limiting oxygen index of approximately 22-25%, classifying it as a self-extinguishing material.

[0016] The raw materials used to modify epoxy resins have the following characteristics: 1) They have low dielectric properties, which can reduce the dielectric constant Dk and dielectric loss factor Df of the main epoxy resin; 2) They have a limiting oxygen index greater than 27%, which can improve the flame retardant properties of the main epoxy resin; 3) They have active groups that can undergo ring-opening reactions with epoxy groups, such as phenolic hydroxyl and carboxyl groups, which can copolymerize with the main epoxy resin to form a uniform copolymer without phase separation.

[0017] The preparation method of intrinsically flame-retardant low-dielectric epoxy resin includes the following steps: a certain mass of biphenyl-type epoxy resin is dissolved in a solvent, and a polymer with active groups and low dielectric and flame-retardant properties is added (flame retardancy is defined as a limiting oxygen index ≥27, classifying it as a flame-retardant material; low dielectric properties are defined as a dielectric constant Dk ≤3.2@10GHz. Polymers with active groups and low dielectric and flame-retardant properties include hydroxyl-terminated polyphenylene ether, hydroxyl-terminated polyethersulfone, and carboxyl-terminated polyamide-imide, etc.), added individually or in a certain proportion. After complete dissolution, a catalyst is added, the temperature is raised, and solution polymerization is carried out. After the reaction is completed, solvent is added to prepare a solvent-based modified epoxy resin.

[0018] The main chain structures of polyphenylene ether and polyethersulfone exhibit high symmetry and rigidity, while the main chain structure of polyamide imide consists of large planar aromatic heterocyclic structures. These structures make the dipole moment of the material less prone to significant polarization, thus resulting in a low dielectric constant Dk. Furthermore, the abundance of aromatic or heterocyclic structures in these polymers endows them with natural flame-retardant properties.

[0019] Furthermore, the softening point of the above-mentioned biphenyl-type epoxy resin is 50-90℃, preferably 53-75℃.

[0020] Furthermore, polymers with active groups and low dielectric and flame-retardant properties can be monophenol hydroxy polyphenylene ether, bisphenol hydroxy polyphenylene ether, terminal phenol hydroxy polyether sulfone, and terminal carboxyl polyamide imide.

[0021] Furthermore, the catalyst can be an imidazole, quaternary ammonium salt, or quaternary phosphonium salt compound; preferably a quaternary ammonium salt compound; more preferably tetramethylammonium chloride.

[0022] Furthermore, the solvent can be benzene, toluene, xylene, ethylbenzene, chlorobenzene, dichlorobenzene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, N-methyl-2-pyrrolidone, or dimethylacetamide; preferably toluene, N-methyl-2-pyrrolidone, or dimethylacetamide.

[0023] Specifically, the preparation method of the intrinsically flame-retardant low-dielectric epoxy resin as described above includes the following steps: Biphenyl-type epoxy resin and a certain amount of solvent are added to a reactor. Nitrogen gas is turned on to purge the air out of the reactor. Stirring is started, and the temperature is raised to 60-70°C. The mixture is stirred and dissolved thoroughly. After dissolution, an appropriate amount of polymer with active groups is added to the reactor. The temperature is raised to 115-125°C (e.g., 120°C), and the mixture is stirred thoroughly. After the particles are completely dissolved, the catalyst is added, and the temperature is raised to 145-155°C (e.g., 150°C) for polymerization. During the reaction, samples are taken to test the epoxy equivalent, and the reaction progress is judged based on the change in epoxy equivalent. After 5-6 hours of reaction, the reaction is terminated. The temperature is lowered to 138-142°C (e.g., 140°C), and solvent is added dropwise to dilute to the set solid content (preferably 40-60 wt%, more preferably 50 wt%). The material in the reactor is cooled to 45-55°C (e.g., 50°C), the solid content is tested, and the solvent is added again before being poured out and stored.

[0024] The solvent mass is preferably 0.5-1 times the mass of the biphenyl epoxy resin; the amount of polymer with active groups added is preferably 0.2-0.6 times the mass of the biphenyl epoxy resin; and the amount of catalyst added is preferably 100-1000 ppm of the mass of the biphenyl epoxy resin.

[0025] The raw materials used in the preparation method of the present invention are not limited to specific products of a certain company. For example, the biphenyl epoxy resin used can be KSE-3060H from Korea's Gukdu Chemical. The chemical structure of KSE-3060H is as follows: The softening point is 70℃. In addition, similar products from other companies can be used, such as: NC-3000 / NC-3000H from Nippon Kayaku Co., Ltd., YX-4000 from Mitsubishi Chemical Corporation, SQXN-322 / SQXN-323 / SQXN-324 from Shandong Shengquan New Material Co., Ltd., BPNE-3501 series from Jiashengde (Ningxia) New Material Technology Co., Ltd., TER-260 / 260H from Tongyu New Material (Guangdong) Co., Ltd., and epoxy resins with similar chemical structures. That is, raw materials with active groups and low dielectric and flame-retardant properties are not limited to the few used in the examples.

[0026] The present invention also relates to the application of the intrinsically flame-retardant low-dielectric epoxy resin or the intrinsically flame-retardant low-dielectric epoxy resin obtained by the method described above in the field of copper clad laminate manufacturing.

[0027] As described above, this application is obtained using conditions including a phenolic curing agent and a catalyst (e.g., triphenylphosphine).

[0028] The method for preparing the intrinsically flame-retardant low-dielectric epoxy resin of the present invention has the following advantages over the prior art: 1) The epoxy resin obtained by this invention has flame retardancy itself and does not require the use of halogen, phosphorus or nitrogen elements for flame retardancy. It is more green and environmentally friendly and more efficient. The performance of the resin after curing is more balanced, avoiding the introduction of other flame retardant elements that would cause some properties of the epoxy resin to deteriorate.

[0029] 2) The low dielectric groups introduced into the epoxy resin molecular structure can significantly reduce the dielectric constant Dk and dielectric loss factor Df of the epoxy resin, which can meet the low dielectric performance requirements of the resin raw materials for current high-end copper clad laminate products, so as to adapt to the rapidly developing emerging electronic information industry.

[0030] In summary, the product obtained by this invention can simultaneously improve the flame retardant and dielectric properties of epoxy resin, increase the limiting oxygen index of epoxy resin, reduce the dielectric constant Dk and dielectric loss factor Df, avoid the use of bromine and phosphorus elements that have potential harm to the ecological environment, achieve a more green and environmentally friendly flame retardant goal, and better meet the performance requirements of high-end electronic products for high-speed transmission and low loss of electrical signals. It can be widely used in the field of high-end copper clad laminate manufacturing. Detailed Implementation

[0031] To facilitate understanding of the present invention, various exemplary embodiments of the present invention are now described in detail. This detailed description should not be regarded as a specific limitation of the present invention, but should be understood as a more detailed description of certain aspects, features and embodiments of the present invention.

[0032] Among the following grades, KSE-3060H contains the above-mentioned structure a) biphenyl group; SA-120 and SA-90 contain the above-mentioned structure b) polyphenylene ether group; Veradel 3600RP contains the above-mentioned structure c) polyether sulfone group; Torlon AI30 contains the above-mentioned structure d) polyamide imide (PAI) group.

[0033] Example 1: Add 350g of biphenyl-type epoxy resin (brand name: KSE-3060H, manufacturer: Korea Gukdu Chemical) and 250g of toluene (industrial grade) to the reactor. Purge the reactor with nitrogen to displace the air. Start stirring and heat to 60-70℃, stirring thoroughly to dissolve. After dissolution, add 100g of monophenol hydroxy polyphenylene ether (brand name: SA-120, manufacturer: Sabic) and 50g of bisphenol hydroxy polyphenylene ether (brand name: SA-90, manufacturer: Sabic) to the reactor. Continue heating to 120℃ and stir thoroughly to mix. After the particles are completely dissolved, add 0.15g of tetramethylammonium chloride (TMAC) catalyst and continue heating to 150℃ to carry out polymerization. Nitrogen gas is continuously introduced during the reaction, and samples are taken every 1.5 hours to test the epoxy equivalent. The reaction progress is judged based on the change in epoxy equivalent. The reaction was terminated after 5 hours, and the temperature was lowered to 140°C. 250 g of toluene (industrial grade) was added dropwise, and the mixture was stirred thoroughly to dilute it. The material in the reactor was then cooled to about 50°C, and a sample was taken to test the solid content. Solvent was added to achieve the set solid content of 50%, and then the sample was poured out and stored to obtain sample A.

[0034] Example 2: 350g of biphenyl-type epoxy resin (brand: KSE-3060H, manufacturer: Gukdu Chemical, South Korea), 150g of toluene (industrial grade), and 150g of dimethylacetamide (DMAC) were added to a reactor. Nitrogen gas was used to purge the reactor and displace the air. Stirring was started, and the temperature was raised to 60-70℃, stirring thoroughly until dissolved. After dissolution, 75g of monophenolic hydroxyl polyphenylene ether (brand: SA-120, manufacturer: Sabic) and 75g of hydroxyl-terminated polyethersulfone (brand: Veradel 3600RP, manufacturer: SOLVAY) were added to the reactor. The temperature was raised to 120℃, and the mixture was stirred thoroughly until the particles were completely dissolved. Then, 0.15g of tetramethylammonium chloride (TMAC) catalyst was added, and the temperature was raised to 150℃ for polymerization. Nitrogen gas was continuously introduced during the reaction, and samples were taken every 1.5 hours to test the epoxy equivalent. The reaction progress was determined based on the changes in epoxy equivalent. The reaction was terminated after 6.5 hours, and the temperature was lowered to 140°C. 200 g of dimethylacetamide (DMAC) (industrial grade) was added dropwise, and the mixture was stirred thoroughly to dilute it. The material in the reactor was then cooled to approximately 50°C, and a sample was taken to test the solid content. Solvent was added to achieve the set solid content of 50%, and the sample was then poured out and stored to obtain sample B.

[0035] Example 3: 350g of biphenyl-type epoxy resin (brand: KSE-3060H, manufacturer: Korea Gukdu Chemical), 150g of toluene (industrial grade), and 150g of N-methyl-2-pyrrolidone (NMP) were added to a reactor. Nitrogen gas was used to purge the reactor and displace the air. Stirring was started, and the temperature was raised to 60-70℃, stirring thoroughly until dissolved. After dissolution, 75g of monophenolic hydroxyl polyphenylene ether (brand: SA-120, manufacturer: Sabic) and 75g of carboxyl-terminated polyamide imide (brand: TorlonAI30, manufacturer: SOLVAY) were added to the reactor. The temperature was raised to 120℃, and the mixture was stirred thoroughly until the particles were completely dissolved. Then, 0.15g of tetramethylammonium chloride (TMAC) catalyst was added, and the temperature was raised to 150℃ for polymerization. Nitrogen gas was continuously introduced during the reaction, and samples were taken every 1.5 hours to test the epoxy equivalent. The reaction progress was determined based on the change in epoxy equivalent. The reaction was terminated after 6.5 hours, and the temperature was lowered to 140°C. 200 g of N-methyl-2-pyrrolidone (NMP) (industrial grade) was added dropwise, and the mixture was stirred thoroughly to dilute it. The material in the reactor was then cooled to about 50°C, and a sample was taken to test the solid content. Solvent was added to achieve the set solid content of 50%, and then the sample was poured out and stored to obtain sample C.

[0036] During the reaction, infrared spectra were taken and tested. By comparing the spectra, it was found that the active groups hydroxyl and carboxyl groups in the active polymer raw material gradually decreased until they disappeared. This indicates that these active groups and the epoxy groups in the epoxy resin underwent a copolymerization reaction, resulting in a modified epoxy resin with a novel structure.

[0037] Comparative Example 1: Unmodified biphenyl-type epoxy resin, 100% solid content (brand: KSE-3060H, manufacturer: Korea Gukdu Chemical Co., Ltd.) Comparative Example 2: Dicyclopentadienol type epoxy resin, 100% solid content (brand name: KDCP-130, manufacturer: Korea Gukdu Chemical Co., Ltd.) Comparative Example 3: Conventional solid epoxy resin, 100% solid content (brand name: YD-011S, manufacturer: Gukdu Chemical Co., Ltd., South Korea) Performance testing: 1) Flame retardant performance test: The limit oxygen index is compared with that of the test examples and comparative samples; Test method: The test is conducted in accordance with the standard of ASTM D2863.

[0038] In the examples, the solvent-containing samples were pre-dried under the following conditions: 230°C for 120 min. The test results are shown in Table 1.

[0039] Table 1. Flame retardant performance test results of Examples 1-3 and Comparative Examples 1-3

[0040] 2) Dielectric property testing Examples 1-3 and Comparative Examples 1-3 used the same phenolic curing agent, PF-8020, manufactured by Shandong Shengquan New Material Co., Ltd. The epoxy equivalent and phenolic hydroxyl equivalent were compounded at a 1:1 ratio. Triphenylphosphine (TPP) was used as the catalyst, added at 1000 ppm of the epoxy resin solids. Butanone was added to adjust the solids content to 60%. The mixture was thoroughly stirred for 2 hours, and then the prepared adhesive was poured into a mold at a fixed mass for curing. The curing conditions were 200°C for 2 hours + 230°C for 1 hour. After curing, the mold was demolded, and the dielectric constant Dk and dielectric loss factor Df were tested.

[0041] Test method: IEC-61189-2-721 (SPDR), pure resin test, without fillers and reinforcing materials. Test results are shown in Table 2.

[0042] Table 2. Dielectric property test results of Examples 1-3 and Comparative Examples 1-3

[0043] The comparative analysis of the oxygen index test data above shows that in Examples 1-3, the modified epoxy resins exhibited significantly higher oxygen indices compared to Comparative Examples 1-3, all exceeding 27%, thus falling within the category of flame-retardant materials. This demonstrates that these modification methods can effectively improve the flame-retardant properties of epoxy resins.

[0044] The comparative analysis of the test data of dielectric constant Dk and dielectric loss factor Df in Examples 1-3 shows that both dielectric constant Dk and dielectric loss factor Df are significantly lower than those in Comparative Examples 1-3. This indicates that the modified epoxy resin can further improve the dielectric properties of copper clad laminates compared to the unmodified epoxy resin, and is better suited to the performance requirements of high-end electronic products for high-speed transmission and low loss of electrical signals. It is expected to be widely used in the field of high-end copper clad laminate manufacturing.

[0045] Based on the above data, this invention can simultaneously improve the flame retardant and dielectric properties of epoxy resin, avoid the use of bromine and phosphorus elements that have potential harm to the ecological environment, and achieve a more green and environmentally friendly flame retardant goal.

[0046] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An inherently flame retardant low dielectric epoxy resin characterized by: The molecular structure of the epoxy resin comprises a biphenyl group shown in a), and at least one of the following groups selected from b), c) or d): a) Biphenyl group: ； b) Polyphenylene oxide (PPO) group: wherein n > 2; or ; wherein m, n = 0 - 25, and m + n > 1 ; Y is a linear, branched, or cyclic hydrocarbyl group having 20 or fewer carbon atoms; c) Polyether sulfone (PES) group: ; wherein n > 2; d) Polyamide-imide (PAI) group: 。 2. The intrinsically flame retardant low dielectric epoxy resin according to claim 1, wherein, The molecular structure of the epoxy resin comprises a biphenyl group shown in a), and at least one of the polyphenylene oxide group shown in b).

3. The intrinsic flame-retardant low-dielectric epoxy resin of claim 2, further characterized in that the molecular structure of the epoxy resin further comprises at least one of the polyether sulfone group shown in c) or the polyamide-imide group shown in d).

4. The method for preparing an intrinsic flame-retardant low dielectric epoxy resin according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: a certain amount of biphenyl type epoxy resin is dissolved in a solvent, a polymer with active groups and low dielectric and flame-retardant properties is added alone or in combination according to a certain proportion, a catalyst is added after sufficient dissolution, the temperature is raised and solution polymerization is carried out; after the reaction is completed, solvent is added to prepare a solvent type modified epoxy resin.

5. The method for preparing an intrinsically flame-retardant low-dielectric epoxy resin as described in claim 4, characterized in that, The polymer with active groups and low dielectric and flame-retardant properties comprises at least one of monophenol hydroxyl polyphenylene oxide, bisphenol hydroxyl polyphenylene oxide, terminal phenol hydroxyl polyether sulfone, and terminal carboxyl polyamide-imide.

6. The method for preparing an intrinsically flame-retardant low-dielectric epoxy resin as described in claim 4 or 5, characterized in that, The softening point of the biphenyl type epoxy resin is 50-90℃.

7. The method for preparing an intrinsically flame-retardant low-dielectric epoxy resin as described in claim 4 or 5, characterized in that, The catalyst is an imidazole, a quaternary ammonium salt, a quaternary phosphonium salt compound; preferably a quaternary ammonium salt compound; more preferably tetramethylammonium chloride.

8. The method for preparing an intrinsically flame-retardant low-dielectric epoxy resin as described in claim 4 or 5, characterized in that, The solvent is at least one of benzene, toluene, xylene, ethylbenzene, chlorobenzene, dichlorobenzene, butanone, methyl isobutyl ketone, cyclohexanone, N-methyl-2-pyrrolidone, and dimethylacetamide.

9. The preparation method of the intrinsic flame-retardant low-dielectric epoxy resin of claim 4 or 5, further characterized in that the preparation method comprises the following steps: The biphenyl type epoxy resin and a certain amount of solvent are put into a reaction kettle, nitrogen is blown to replace the air in the reaction kettle, stirring is started, and then the temperature is raised to 60-70℃ for sufficient stirring and dissolution; after dissolution is completed, an appropriate amount of polymer with active groups is added to the reaction kettle, the temperature is continuously raised to 115-125℃, and the mixture is fully stirred and mixed; after the particulate matter is completely dissolved, a catalyst is added, the temperature is continuously raised to 145-155℃ for polymerization, and the reaction process is tested by sampling during the reaction; after 5-6 hours of reaction, the reaction is terminated, the temperature is lowered to 138-142℃, solvent is added dropwise to dilute to a set solid content, the material in the reaction kettle is cooled to 45-55℃, the solid content is tested, and solvent is added after which the product is poured out and stored.

10. Use of the intrinsic flame-retardant low-dielectric epoxy resin of any one of claims 1-3 or the intrinsic flame-retardant low-dielectric epoxy resin obtained by the preparation method of any one of claims 4-9 in the field of manufacturing copper-clad plates.

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