High-temperature-resistant low-dielectric benzoxazine-epoxy resin copolymer and preparation method thereof

Abstract

The invention provides a high-temperature-resistant low-dielectric benzoxazine-epoxy resin copolymer and a preparation method thereof, and relates to the technical field of high-performance polymer materials. The method comprises the following steps: S1, synthesizing a methylamine type benzoxazine monomer by taking a methylamine aqueous solution, a phenol source and a formaldehyde aqueous solution as raw materials, S2, blending the methylamine type benzoxazine monomer and epoxy resin by adopting a blending method to obtain a blend, and S3, carrying out gradient heating on the blend, and carrying out a copolymerization reaction to obtain the high-temperature-resistant and low-dielectric benzoxazine-epoxy resin copolymer. The methylamine nitrogen source with the shortest aliphatic chain is used for constructing benzoxazine, the benzoxazine and the multifunctional epoxy resin are subjected to ring opening to form a low-polarity three-dimensional network, fluorine-containing / phosphorus-containing or inorganic filler is not depended on, high heat resistance and low dielectric property are achieved, the impact strength is improved by more than or equal to 30%, and the service life is prolonged. The defects that an existing aromatic amine type benzoxazine-epoxy copolymer system is large in brittleness and limited in toughness improvement are overcome.

Description

Technical Field

[0001] This invention relates to the field of high-performance polymer materials technology, and more specifically, to a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer and its preparation method. Background Technology

[0002] In the field of high-frequency electronic devices and integrated circuit packaging, as signal frequencies continue to increase, the dielectric properties of materials have a significant impact on the quality and speed of signal transmission. Although traditional epoxy resin-based composite materials have good mechanical and processing properties, their high dielectric constant leads to increased signal transmission loss in high-frequency applications. Furthermore, their brittleness makes them prone to microcrack propagation under high-temperature and vibration environments, becoming a bottleneck restricting their service life and failing to meet the development needs of modern high-frequency electronic technology.

[0003] The ring-opening polymerization of benzoxazine resins has advantages such as zero volume shrinkage, high heat resistance and low water absorption, and is widely used for epoxy modification. However, existing technologies mostly use aromatic amine-type benzoxazine with bisphenol A epoxy copolymerization, but the aromatic amine-type benzoxazine-epoxy copolymerization system has the defects of high brittleness and limited toughness improvement. As early as 1994, Ishida H. team (Polymer, 1994, 36(16): 3151-3158) first synthesized monocyclic methylamine-type benzoxazine by bisphenol A, methylamine and formaldehyde solution method, and pointed out that its aliphatic segment can improve the impact strength by about 25% compared with aniline type. However, this work only focused on monomer synthesis and DSC kinetics, and did not involve copolymerization with epoxy resin, nor did it provide 1 MHz dielectric-toughness synergistic data. Subsequently, methylamine-type benzoxazine has been mostly used as a toughening agent, and systematic research has been conducted on its blending and copolymerization with other resins, as well as its high heat resistance and low dielectric properties. However, there has been little research on how to overcome the defects of aromatic amine-type benzoxazine-epoxy copolymer systems, such as high brittleness.

[0004] Chinese patent CN101831073A is the first to use methylamine-bisphenol A phenolic benzoxazine in halogen-free laminates, with T after pure resin curing. g ≈160 ℃, peel strength 1.5 N·mm -1 It has UL-94 V-0 rating, but it does not provide data on dielectric properties and impact toughness. Its performance remains at the level of heat resistance and flame retardancy of a single resin. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer and its preparation method. This copolymer uses the shortest aliphatic chain methylamine nitrogen source to construct benzoxazine, which co-ring-opens with a multifunctional epoxy resin to form a low-polarity three-dimensional network. It is independent of fluorine / phosphorus-containing or inorganic fillers and achieves D-copolymerization at 1 MHz. k ≤3.0, T gWith a temperature of ≥250℃, while maintaining high heat resistance, the impact strength is increased by ≥30%, thus overcoming the defects of existing aromatic amine-type benzoxazine-epoxy copolymer systems, which are brittle and have limited toughness improvement. This provides a pure resin solution with high heat resistance and low dielectric properties for high-frequency copper clad laminates, chip packaging, and radomes.

[0006] The technical problem solved by this invention is achieved by the following technical solution.

[0007] On one hand, embodiments of this application provide a method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, comprising the following steps: S1: Using aqueous methylamine solution, phenol source and aqueous formaldehyde solution (or paraformaldehyde) as raw materials, and according to the functional group ratio of amine: aldehyde: phenol = 1.1~1.5:2~2.5:1, methylamine type benzoxazine monomer is synthesized; S2: By weight, methylamine-type benzoxazine monomer and epoxy resin are blended in a ratio of 1-5:1-5 to obtain a blend. S3: The blend is copolymerized under a gradient heating condition of 80-220℃ to obtain a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer.

[0008] In some embodiments of the present invention, step S1 further includes adding toluene and / or dioxane to maintain the solid content. After the raw materials are mixed, they are reacted at 60-90°C for 3-12 hours. After the reaction is completed, the mixture is washed and separated to obtain a methylamine-type benzoxazine monomer.

[0009] Furthermore, the phenol source is any one or more of phenol, p-cresol, o-cresol, m-cresol, tert-butylphenol, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxydiphenyl ether, resorcinol, hydroquinone, catechol, 2,7-dihydroxynaphthalene, bisphenol fluorene, phenolphthalein, o-allylphenol, p-allylphenol, p-hydroxybenzyl alcohol, p-hydroxyacetophenone, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, p-hydroxyanisole, 1,1,1-tris(4-hydroxyphenyl)ethane, tris(4-hydroxyphenyl)methane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, and tetra(4-hydroxyphenyl)adamantane.

[0010] In some embodiments of the present invention, in step S2, the epoxy resin is any one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin and glycidylamine epoxy resin.

[0011] Furthermore, it also includes a curing agent for epoxy resins, the curing agent containing at least two active functional groups capable of ring-opening reaction with epoxy groups, the active functional groups being selected from any one of 1)-3): 1) Primary amines, secondary amines, and amide amines; 2) Acid anhydrides, carboxylic acids, and carboxylic acid hydrazides; 3) Phenolic hydroxyl group, thiol group, isocyanate group.

[0012] Furthermore, the blending method can be any one of melt blending, solution blending, mechanical blending, and in-situ polymerization blending.

[0013] Further, the melt blending step is as follows: heating the methylamine type benzoxazine monomer to 80-120℃, then adding the epoxy resin monomer, and mechanically stirring for 0.5-2 hours to obtain a homogeneous blend.

[0014] Further, the solution blending step is as follows: by weight, select 6-10 parts of methylamine-type benzoxazine monomer, 60-70 parts of epoxy resin and 34-32 parts of organic solvent, mix them and then magnetically stir at 30-80℃ for 0.5-2 hours to obtain a homogeneous blend; wherein, the organic solvent is any one or more of acetone, butanone, chloroform, toluene, xylene, dioxane, tetrahydrofuran, and N,N-dimethylformamide.

[0015] In some embodiments of the present invention, step S3 includes injecting the blend into a mold, removing the organic solvent by vacuuming at 80-130°C, and then holding it at 100-220°C for 2 hours at each temperature to carry out a gradient temperature copolymerization reaction.

[0016] On the other hand, embodiments of this application provide a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, which is prepared by the above-described preparation method.

[0017] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: 1. The benzoxazine-epoxy resin copolymer network of the present invention has a rigid aromatic heterocycle as the main chain, and the polar group density is lower than that of traditional amine-cured epoxy, resulting in weakened orientation polarization. The use of methylamine to replace traditional aromatic amine reduces the π electron density, decreases the number of hydroxyl groups, and lowers the intrinsic dielectric constant. At the same time, the crosslinking density is high and the free volume is small, which inhibits ion migration and thus results in low dielectric loss. 2. This invention utilizes a benzoxazine monomer structure formed by the Mannich condensation reaction of methylamine, phenol, and formaldehyde aqueous solution, followed by a thermally initiated ring-opening polymerization reaction to form a three-dimensional cross-linked network structure. No small molecule release is observed, and the abundance of aromatic rings increases the rigidity of the molecular chains. After copolymerization with epoxy, the number of cross-linking points increases, the spacing shortens, chain segment movement is restricted, and the cross-linking density rises. Staged curing allows for the formation of a T... g >250 ℃, heat resistance is generally higher than that of existing epoxy resins on the market; 3. This invention effectively improves the impact toughness of materials by introducing methylamine-type benzoxazine monomers. The methylamine structure introduces flexible segments, while the phenolic hydroxyl groups generated by ring opening synergistically crosslink with epoxy to form a uniform network. In addition, the energy consumption of hydrogen bonding "sacrifice" and the good interfacial compatibility result in stress dispersion and crack propagation inhibition, thereby improving the toughness of the blended methylamine-type benzoxazine with epoxy. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a comparison graph of broadband dielectric curves of the copolymers obtained in Example 1 and Comparative Example 1 of the present invention; Figure 2 This is a comparison graph showing the breakdown voltages of the copolymers obtained in Examples 2-4 and Comparative Example 2 of the present invention; Figure 3 This is a comparison diagram of DMA of the copolymers obtained in Examples 2-4 and Comparative Example 2 of the present invention; Figure 4 This is a comparison graph of broadband dielectric curves of the copolymers obtained in Examples 2-4 and Comparative Example 2 of the present invention; Figure 5 This is a comparison diagram of the impact toughness of the copolymers obtained in Example 5 and Comparative Example 3 of the present invention; Figure 6 This is a comparison graph of the broadband dielectric curves of the copolymers obtained in Example 6 and Comparative Example 4 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0022] Example 1 This embodiment provides a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, which is prepared by the following method: S1: Using aqueous methylamine, phenol, and aqueous formaldehyde (or paraformaldehyde) as raw materials, mix them in a molar ratio of 1:1:2, then add toluene as a solvent to maintain the solid content of the reaction system at 70%. React at 80℃ for 12 hours. After the reaction, wash with 1M NaOH aqueous solution (1 wt% of the reaction system mass), and then wash 2-3 times until the pH of the aqueous phase reaches 7. Remove the remaining solvent under vacuum to obtain the methylamine-type benzoxazine monomer. The chemical formula of the methylamine-type benzoxazine monomer is shown in Formula I.

[0023] Formula I; S2: By weight, select 50 parts of methylamine type benzoxazine monomer and 100 parts of bisphenol A type epoxy resin, mix them, heat to 100℃, and mechanically stir for 20 minutes to obtain a homogeneous blend. S3: Inject the blend into a mold, vacuum at 100°C for 2 hours to remove the solvent, and then sequentially raise the temperature to 140°C and hold for 2 hours, 160°C and hold for 2 hours, 180°C and hold for 2 hours, and 200°C and hold for 2 hours to obtain the benzoxazine-(bisphenol A type) epoxy resin copolymer.

[0024] Example 2 This embodiment provides a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, which is prepared by the following method: S1: Using methylamine aqueous solution, bisphenol A, and formaldehyde aqueous solution (or paraformaldehyde) as raw materials, mix them in a molar ratio of 2:1:4, and then add toluene as a solvent to maintain the solid content of the reaction system at 60%. Then react at 90℃ for 11 hours. After the reaction is completed, wash with 1M NaOH aqueous solution (1wt% of the mass of the reaction system), and then wash with water 2-3 times until the pH of the aqueous phase is 7. Remove the remaining solvent under vacuum to obtain the methylamine type benzoxazine monomer; the chemical formula of the methylamine type benzoxazine monomer is shown in Formula II:

[0025] Formula II; S2: By weight, select 100 parts of methylamine-type benzoxazine monomer and 50 parts of alicyclic epoxy resin (such as UVR6110), mix them, heat to 80°C, and mechanically stir for 30 minutes to obtain a homogeneous blend. S3: Inject the blend into a mold, vacuum at 120°C for 2 hours to remove the solvent, and then sequentially heat to 140°C for 2 hours, 160°C for 2 hours, 180°C for 2 hours, 200°C for 2 hours, and 220°C for 2 hours to obtain the benzoxazine-(alicyclic) epoxy resin copolymer.

[0026] Example 3 This embodiment is basically the same as Embodiment 2, with the only difference being: In step S2, 50 parts of methylamine-type benzoxazine monomer and 50 parts of alicyclic epoxy resin are selected for copolymerization.

[0027] Example 4 This embodiment is basically the same as Embodiment 2, with the only difference being: In step S2, 50 parts of methylamine-type benzoxazine monomer and 100 parts of alicyclic epoxy resin are selected for copolymerization.

[0028] Example 5 This embodiment provides a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, which is prepared by the following method: S1: Using methylamine aqueous solution, cashew phenol, and formaldehyde aqueous solution (or paraformaldehyde) as raw materials, mix them in a molar ratio of 1.2:1:2, and then add toluene as a solvent to maintain the solid content of the reaction system at 70%. Then react at 60℃ for 10 h. After the reaction is completed, wash with 1M NaOH aqueous solution accounting for 1wt% of the mass of the reaction system, and then wash with water 2-3 times to separate the layers until the pH of the aqueous phase is 7. Remove the remaining solvent under vacuum to obtain the methylamine type benzoxazine monomer; the chemical formula of the methylamine type benzoxazine monomer is shown in Formula III:

[0029] Formula III; S2: At room temperature, select 8 parts by weight of solid methylamine benzoxazine monomer, 66 parts of glycidyl amine epoxy resin (such as AG80 epoxy resin), and 28 parts of curing agent DDM, and add 20-50 parts of acetone as solvent. After mixing, heat to 40°C and mechanically stir for 30 minutes to obtain a homogeneous blend. S3: Inject the blend into a mold, vacuum at 100℃ for 2 hours to remove the solvent, and then sequentially heat to 140℃ for 2 hours, 160℃ for 2 hours, 180℃ for 2 hours, 200℃ for 2 hours, and 220℃ for 2 hours to obtain the benzoxazine-(glycidylamine) epoxy resin copolymer.

[0030] Example 6 This embodiment provides a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, which is prepared by the following method: S1: Using methylamine aqueous solution, pyrogallol A, and formaldehyde aqueous solution (or paraformaldehyde) as raw materials, mix them in a molar ratio of 3:1:6, and then add toluene as a solvent to maintain the solid content of the reaction system at 50%. Then react at 75℃ for 8 hours. After the reaction is completed, wash with 1M NaOH aqueous solution (1wt% of the mass of the reaction system), and then wash with water 2-3 times until the pH of the aqueous phase is 7. Remove the remaining solvent under vacuum to obtain the methylamine type benzoxazine monomer; the chemical formula of the methylamine type benzoxazine monomer is shown in Formula IV:

[0031] Formula IV; Select 100 parts of methylamine-type benzoxazine monomer and 50 parts of aromatic epoxy resin E44, mix them, heat to 80℃, and mechanically stir for 30 minutes to obtain a homogeneous blend. S3: Inject the blend into a mold, vacuum at 120°C for 2 hours to remove the solvent, and then sequentially raise the temperature to 140°C and hold for 2 hours, 160°C and hold for 2 hours, 180°C and hold for 2 hours, 200°C and hold for 2 hours, and 220°C and hold for 2 hours to obtain the benzoxazine-(aromatic) epoxy resin copolymer.

[0032] Compare with Example 1 This comparative example serves as a comparison with Example 1, and the operational steps are basically the same as those in Example 1, with the only difference being: In step S2, instead of using methylamine-type benzoxazine monomer, 25 parts of traditional curing agent DDM and 100 parts of bisphenol A type epoxy resin are copolymerized.

[0033] The same applies to step S3; after heating and copolymerization, epoxy resin / DDM copolymer is obtained.

[0034] Then, the dielectric properties of the epoxy resin / DDM copolymer and the benzoxazine-(bisphenol A type) epoxy resin copolymer prepared in Example 1 were tested, and the experimental results are as follows: Figure 1 As shown, the dielectric constant of the benzoxazine-(bisphenol A type) epoxy resin copolymer is consistent throughout the 10⁻¹⁰ kJ / L. 2 -10 7 The frequency response was consistently lower than that of the DDM system in the Hz range, and there was no obvious relaxation peak. This indicates that the rigid heterocyclic structure of benzoxazine restricts the segment orientation polarization on the one hand, and reduces the carrier migration probability on the other hand. This synergistically weakens the interfacial polarization and dipole loss, giving the material lower energy dissipation and better frequency stability, and exhibiting good low dielectric properties.

[0035] Compare with Example 2 This comparative example serves as a comparison with Example 2, and the operational steps are basically the same as those in Example 2, with the only difference being: In step S2, instead of using methylamine-type benzoxazine monomer, 120 parts of the traditional curing agent methylhexahydrophthalic anhydride and 100 parts of alicyclic epoxy resin are copolymerized.

[0036] The same applies to step S3; after heating and copolymerization, an epoxy resin / methylhexahydrophthalic anhydride copolymer is obtained.

[0037] Then, the epoxy resin / methylhexahydrophthalic anhydride copolymer and the benzoxazine-(alicyclic) epoxy resin copolymer prepared in Examples 2-4 were compared and verified, including tests on voltage breakdown strength, loss factor (DMA) and dielectric properties. The experimental results are as follows: Figure 2 - Figure 4 As shown, where: Depend on Figure 2 It can be seen that the breakdown voltage of epoxy resin-traditional curing agent has reached a high value of 58.8 kV / mm² for epoxy resin. -1 After introducing methylamine-type benzoxazine monomers, the breakdown voltage showed a trend of first increasing and then decreasing with the increase of the mixing ratio of methylamine-type benzoxazine monomers. Analysis suggests that insufficient curing and crosslinking may lead to a decrease in breakdown strength in the system with a small amount of methylamine-type benzoxazine monomers (2:1). The system with an equal amount of methylamine-type benzoxazine monomers (1:1) showed a peak value of 58.6 kV / mm. -1 The performance is comparable to that of epoxy-conventional curing agents; however, in systems with excess methylamine-type benzoxazine monomers (1:2), the breakdown value drops to 55 kV mm due to the decrease in crosslinking density. -1 .

[0038] Depend on Figure 3 It can be seen that as the mixing ratio of methylamine-type benzoxazine monomers increases, the glass transition temperature T... g The temperature also increased from 209.0℃ to 271.9℃, indicating that the rigid aromatic rings in the methylamine-type benzoxazine monomer were effectively anchored to the network, inhibiting chain segment slippage. Analysis suggests that the higher the content of the methylamine-type benzoxazine monomer, the more rigid aromatic rings there are overall, making the chain segments more difficult to move, less likely to soften and transform into a rubbery state, and thus exhibiting better heat resistance.

[0039] Depend on Figure 4 It can be seen that as the mixing ratio of methylamine-type benzoxazine monomers increases, at 10 2 -10 7 Within the Hz range, the dielectric constant is lowest in the system of small amounts of methylamine-type benzoxazine monomers (2:1).

[0040] Compare with Example 3 This comparative example serves as a comparison with Example 3, and the operational steps are basically the same as those in Example 3, with the only difference being: In step S2, methylamine-type benzoxazine monomers are not used; instead, 66 parts of glycidylamine epoxy resin (such as AG80 type epoxy resin) and 28 parts of curing agent DDM are used.

[0041] The same applies to step S3; after heating and copolymerization, epoxy resin / DDM copolymer is obtained.

[0042] Then, the epoxy resin / DDM copolymer and the benzoxazine-(glycidylamine) epoxy resin copolymer prepared in Example 3 were subjected to impact toughness tests, and the test results are as follows: Figure 5 As shown, the impact strength of the system with added methylamine-type benzoxazine monomer reaches 27.55 kJ·m. -2 It is much higher than the 16.53 kJ·m⁻¹ of the unadded value. -2 The toughening effect was approximately 66%, indicating that the methylamine-type benzoxazine monomer has a significant effect on improving toughness. Therefore, the addition of the methylamine-type benzoxazine monomer effectively enhances the impact resistance of the material.

[0043] Compare with Example 4 This comparative example serves as a comparison with Example 6, and the operational steps are basically the same as those in Example 6, with the only difference being: In step S2, instead of using methylamine-type benzoxazine monomer, 25 parts of traditional curing agent DDM and 100 parts of aromatic E44 type epoxy resin are copolymerized.

[0044] The same applies to step S3; after heating and copolymerization, epoxy resin / DDM copolymer is obtained.

[0045] Then, the dielectric properties of the epoxy resin / DDM copolymer and the benzoxazine-(aromatic) epoxy resin copolymer prepared in Example 6 were tested, and the experimental results are as follows: Figure 6 As shown. Studies have shown that the copolymer of pyrogallol A type benzoxazine and E44 epoxy resin at 10 2 -10 7 The dielectric constant remains consistently lower than that of the DDM system within the Hz frequency band, and there is no significant relaxation peak. This indicates that the rigid heterocyclic structure of the methylamine-type benzoxazine monomer not only restricts the orientation polarization of the chain segments, but also further confines the molecular chain motion and reduces the free volume through branched topology. This synergistically suppresses carrier migration and interface polarization, weakens dipole losses, achieves low energy dissipation and excellent frequency stability, and endows the material with outstanding low dielectric properties.

[0046] In summary, the embodiments of the present invention provide a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer and its preparation method. The benzoxazine-epoxy resin copolymer network of the present invention has COC and CNC rigid aromatic heterocycles as the main chain, and the polar group density is lower than that of traditional amine-cured epoxy resins, resulting in weakened orientation polarization. By replacing traditional aromatic amines with methylamine, the π electron density decreases, the number of hydroxyl groups decreases, and the intrinsic dielectric constant decreases. At the same time, the crosslinking density is high and the free volume is small, which inhibits ion migration, thus resulting in low dielectric loss. This invention generates a Mannich bridging structure by cyclizing a methylamine-type benzoxazine monomer, which increases the rigidity of the molecular chain. After copolymerization with epoxy, the crosslinking point spacing is shortened and the chain segment movement is restricted. Through staged curing, the Tg can be greater than 250 °C, and the heat resistance is generally higher than that of existing epoxy resins on the market. This invention effectively improves the impact toughness of materials by introducing methylamine-type benzoxazine monomers.

[0047] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, characterized in that, Includes the following steps: S1: Using aqueous methylamine, phenol source and aqueous formaldehyde as raw materials, methylamine-type benzoxazine monomers were synthesized according to the functional group ratio of amine: aldehyde: phenol = 1~1.5:2~2.5:

1. S2: The methylamine-type benzoxazine monomer and epoxy resin are blended in a ratio of 1-5:1-5 by a blending method to obtain a blend. S3: The blend is subjected to a copolymerization reaction under a gradient heating condition of 80-220℃ to obtain a high-temperature resistant and low-dielectric benzoxazine-epoxy resin copolymer.

2. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 1, characterized in that, Step S1 also includes adding toluene and / or dioxane to maintain the solid content. After mixing the raw materials, the mixture is reacted at 60-90°C for 3-12 hours. After the reaction is completed, the mixture is washed and separated to obtain the methylamine type benzoxazine monomer.

3. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 2, characterized in that, The phenol source is any one or more of phenol, p-cresol, o-cresol, m-cresol, tert-butylphenol, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxydiphenyl ether, resorcinol, hydroquinone, catechol, 2,7-dihydroxynaphthalene, bisphenol fluorene, phenolphthalein, o-allylphenol, p-allylphenol, p-hydroxybenzyl alcohol, p-hydroxyacetophenone, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, p-hydroxyanisole, 1,1,1-tris(4-hydroxyphenyl)ethane, tris(4-hydroxyphenyl)methane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, and tetra(4-hydroxyphenyl)adamantane.

4. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 1, characterized in that, In step S2, the epoxy resin is any one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin and glycidylamine epoxy resin.

5. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 4, characterized in that, It also includes a curing agent for the epoxy resin, the curing agent containing at least two active functional groups capable of ring-opening reaction with epoxy groups, the active functional groups being selected from any one of 1)-3): 1) Primary amines, secondary amines, and amide amines; 2) Acid anhydrides, carboxylic acids, and carboxylic acid hydrazides; 3) Phenolic hydroxyl group, thiol group, isocyanate group.

6. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 4, characterized in that, The blending method can be either melt blending or solution blending.

7. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 6, characterized in that, The melt blending step is as follows: heating the methylamine type benzoxazine monomer to 80-120℃, then adding the epoxy resin monomer, and mechanically stirring for 0.5-2 hours to obtain a homogeneous blend.

8. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 6, characterized in that, The solution blending step is as follows: by weight, select 6-10 parts of the methylamine-type benzoxazine monomer, 60-70 parts of the epoxy resin and 34-32 parts of the organic solvent, mix them and then magnetically stir at 30-80℃ for 0.5-2 hours to obtain a homogeneous blend; wherein, the organic solvent is any one or more of acetone, butanone, chloroform, toluene, xylene, dioxane, tetrahydrofuran, and N,N-dimethylformamide.

9. The method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer according to claim 1, characterized in that, Step S3 includes injecting the blend into a mold, removing the organic solvent by vacuuming at 80-130°C, and then holding it at 100-220°C for 2 hours at each temperature to carry out a gradient temperature copolymerization reaction.

10. A high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer, characterized in that, It is prepared by the method for preparing a high-temperature resistant, low-dielectric benzoxazine-epoxy resin copolymer as described in any one of claims 1-9.

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