Benzoxazine monomers containing polymerizable double bonds, and cured resins and composite resins thereof

Abstract

The application discloses a benzoxazine monomer containing polymerizable double bonds, and a cured resin and a composite resin thereof, and relates to the technical field of resin synthesis. Under the protection of nitrogen, an aldehyde compound, furfurylamine, 2,2'-diallyl bisphenol A and an organic solvent are added into a reaction container, and then the mixture is reacted at 80-120 DEG C for 2-24 hours, and the 2,2'-diallyl bisphenol A-furfurylamine type benzoxazine monomer is obtained after post-treatment. The obtained benzoxazine monomer containing polymerizable double bonds is dissolved and then heat-cured to obtain a cured resin. The obtained benzoxazine monomer containing polymerizable double bonds is mixed and dissolved with polyphenyl ether and its modified products, and then heat-cured to obtain a benzoxazine / polyphenyl ether composite resin. The 2,2'-diallyl bisphenol A-furfurylamine type benzoxazine monomer is synthesized by using a relatively simple method, and then a 2,2'-diallyl bisphenol A-furfurylamine type benzoxazine / polyphenyl ether composite resin is obtained by blending and heat-curing. The composite resin has excellent thermal performance and high-frequency dielectric performance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to benzoxazine monomers containing polymerizable double bonds and their cured resins and composite resins. Background Technology

[0002] Printed circuit boards (PCBs) are crucial carriers for electronic components and the transmission of electrical signals. Their substrate, copper-clad laminate (CCL), is made by coating (or impregnating) fiberglass cloth with a polymer resin and then hot-pressing it with copper foil. The polymer matrix resin plays a vital role in the CCL's bonding strength, water absorption, chemical stability, dielectric properties, and thermal properties. With the widespread application of 5G technology and the research and development of 6G technology, the requirements for polymer matrix resins are becoming increasingly stringent. Currently, the less-than-ideal dielectric and thermal properties of polymer resins are the main obstacles limiting their application in ultra-high frequency (UHF) communication. Therefore, the design and preparation of polymer resins with both excellent dielectric properties (dielectric constant (k) < 3, dielectric loss (f) ≤ 0.008) and thermal properties (glass transition temperature ≥ 240℃) is a hot topic in the field of ultra-high frequency communication research (Industrial & Engineering Chemistry Research, 2022, https: / / doi.org / 10.1021 / acs.iecr.1c03846).

[0003] Polyphenylene ether (PPE) resin is an amorphous thermoplastic with excellent dielectric properties, high tensile and flexural strength, and low water absorption, making it a popular choice for applications in the electronics and communications field. However, high molecular weight PPE resins suffer from high melt viscosity and poor processability, limiting their practical applications. Furthermore, thermoplastic PPE resins used as matrix resins for printed circuit boards require thermosetting modification. Low molecular weight PPE oligomers (number average molecular weight < 4000) retain the advantages of high molecular weight PPE, such as excellent dielectric properties and low water absorption, while also offering superior advantages such as ease of processing, good solubility, and suitability for chemical modification. However, due to the reduced molecular weight, the thermal properties of PPE oligomers require further improvement. Studies have shown that introducing crosslinkable functional groups into polyphenylene ether oligomers can not only prepare thermosetting polyphenylene ether resins, but also improve their thermal properties accordingly (ACS Sustainable Chemistry & Engineering, 2018, 6(7): 9277-9282). However, to date, it is still difficult to prepare polyphenylene ether thermosetting resins with excellent comprehensive properties such as good processability, thermal properties and dielectric properties.

[0004] Benzoxazine is a class of oxygen-nitrogen heterocyclic intermediates synthesized from phenols, amines, and paraformaldehyde. It undergoes ring-opening polymerization under heating and / or catalysis, without the release of small molecules, producing a nitrogen-containing, phenolic resin-like network polymer, known as polybenzoxazine or benzoxazine resin (Polymer Chemistry, 1994, 32(6):1121-1129). As a novel thermosetting resin, benzoxazine resin possesses many unique properties such as good mechanical properties, high char residue, near-zero volume shrinkage / expansion during polymerization, low water absorption, and good chemical resistance. Especially at low crosslinking densities, it exhibits a high glass transition temperature due to abundant intramolecular and intermolecular hydrogen bonding. Furthermore, it possesses good dielectric properties, exhibiting a relatively low and stable k-value at high frequencies, thus making it a promising candidate for use as a matrix resin in copper-clad laminates. However, traditional benzoxazine resins typically have a k-value of 3.5 and an f-value of 0.02 at 1 GHz, which cannot adequately meet the requirements of the electronics and information industry for matrix resins.

[0005] Given the advantages of polyphenylene ether (PPE) and benzoxazine resins in terms of dielectric and thermal properties, the preparation of benzoxazine / PPE composite resins is a new method to obtain high-performance resins with excellent comprehensive properties such as low dielectric strength and high heat resistance. In 2018, Chen et al. first introduced benzoxazine functional groups into PPE resins (Polymers, 2018, 10(4): 411-425). Using low molecular weight (number average molecular weight of 1600) PPE oligomer SA90, namely phenol-terminated oligomer (2,6-dimethylphenylene oxide), as raw material, they carried out nucleophilic substitution with fluoronitrobenzene and then catalytic hydrogenation to prepare amino-terminated SA90 (APPO). Using APPO as the amine source, paraformaldehyde, phenol, or bisphenol A are used to prepare either a telechelic benzoxazine-functionalized polyphenylene ether prepolymer or a main-chain benzoxazine-functionalized polyphenylene ether prepolymer. Finally, through self-curing and epoxy resin curing, a thermosetting resin with a high glass transition temperature (218–225 °C) and good dielectric properties (k = 2.9, 1 GHz) can be obtained. However, its glass transition temperature (<240 °C) still falls short of the requirements for high-frequency, high-speed, and high-performance communication equipment. Furthermore, this preparation method is complex, requiring multiple chemical reactions such as nitration, amination, and benzoxazine functionalization. The steps are cumbersome, and numerous side reactions occur, making purification after chemical synthesis a significant challenge. Therefore, a simple and effective method is urgently needed to prepare benzoxazine / polyphenylene ether composite resins with both low dielectric properties and high heat resistance. Summary of the Invention

[0006] One objective of this invention is to provide a benzoxazine monomer containing polymerizable double bonds, a cured resin, and a method for preparing the same. The resulting cured resin exhibits excellent thermal and high-frequency dielectric properties, fully meeting the requirements of ultra-high frequency communication. Another objective of this invention is to provide a benzoxazine / polyphenylene ether composite resin that combines both thermal and high-frequency dielectric properties, and a method for preparing the same. The preparation method is simple and effective, and its performance meets the requirements of high-frequency, high-speed, and high-performance communication equipment.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] The benzoxazine monomer containing polymerizable double bonds has the following structural formula:

[0009]

[0010] The method for preparing the above-mentioned benzoxazine monomer containing polymerizable double bonds includes the following steps:

[0011] Under nitrogen protection, aldehyde compounds, furfurylamine, 2,2'-diallylbisphenol A, and organic solvents were added to the reaction vessel, and the reaction was carried out at 80-120°C for 2-24 hours. After post-treatment, 2,2'-diallylbisphenol A-furfurylamine type benzoxazine monomers were obtained.

[0012] According to the above scheme, the molar ratio of the aldehyde group, the amino group in furfurylamine, and the phenolic hydroxyl group in 2,2'-diallylbisphenol A in the aldehyde compound is 2:1:1.

[0013] According to the above scheme, the aldehyde compound is formaldehyde or paraformaldehyde.

[0014] According to the above scheme, the preparation is carried out by a single feeding method: aldehyde compounds, furfurylamine, and 2,2'-diallylbisphenol A are added to the reaction vessel at the same time, and then an organic solvent is added to dissolve them;

[0015] Alternatively, it can be prepared by adding the following ingredients in multiple steps: first, add the aldehyde compound and furfurylamine to the reaction vessel, add an organic solvent and stir thoroughly, then react at 80-120°C for 1-12 hours, and then add 2,2'-diallylbisphenol A and continue the reaction for 1-12 hours.

[0016] According to the above scheme, the organic solvent is one or any mixture of butanone, ethyl acetate, toluene, acetone, diethyl ether, N,N'-dimethylformamide, dioxane, chloroform, ethanol, methanol, and xylene.

[0017] According to the above scheme, the post-processing includes:

[0018] The reaction solution was poured into a methanol solution to obtain a suspension. After standing, the supernatant was removed to obtain a precipitate. The precipitate was dried and ground to obtain 2,2'-diallylbisphenol A-furfurylamine type benzoxazine monomer. The preferred methanol solution concentration was 30-85 wt%.

[0019] A 2,2'-diallylbisphenol A-furfurylamine type benzoxazine resin is obtained by dissolving the above-mentioned benzoxazine monomer containing polymerizable double bonds and then thermally curing it.

[0020] A benzoxazine / polyphenylene ether composite resin is a composite resin with a semi-interpenetrating network structure obtained by dissolving and blending the above-mentioned benzoxazine monomer containing polymerizable double bonds with high molecular weight polyphenylene ether or polyphenylene ether oligomer in a mass ratio of (10-1):(1-10) and then thermosetting.

[0021] A benzoxazine / polyphenylene ether composite resin is a composite resin with a fully interpenetrating network and a grafted interpenetrating network structure obtained by dissolving and blending a benzoxazine monomer containing polymerizable double bonds and a polyphenylene ether oligomer containing self-crosslinking functional groups in a double bond: crosslinking functional group molar ratio of (1-5): (5-1), adding a curing accelerator or crosslinking agent, and then thermosetting.

[0022] A resin varnish is composed of the above-mentioned benzoxazine monomer containing polymerizable double bonds and an organic solvent; or it uses a prepolymer of the above-mentioned benzoxazine / polyphenylene ether composite resin.

[0023] A prepreg body is composed of the above-mentioned resin varnish with the addition of inorganic fillers and / or flame retardants.

[0024] A laminate is formed by uniformly coating the aforementioned prepreg onto a nonwoven fabric.

[0025] A multilayer printed circuit board is made of copper foil and a copper foil-loaded laminate.

[0026] In this invention, a novel 2,2′-diallylbisphenol A-furfurylamine-type benzoxazine monomer was synthesized through molecular design and chemical synthesis. The selected phenolic source is 2,2′-diallylbisphenol A containing polymerizable double bonds. In addition to the ring-opening polymerization of the oxazine ring, crosslinking sites are increased, thereby improving the thermal properties of the cured resin. Simultaneously, the low-polarity CH bonds formed after polymerization reduce the resin's polarity, thus improving its dielectric properties. The selected amine source—furfurylamine—derives from renewable resources. Its furan ring can undergo a crosslinking reaction with the nitrogen atoms on the Mannich bridge formed after the oxazine ring opens, significantly enhancing the thermal properties. In particular, the multiple crosslinking reactions of the oxazine ring, double bonds, and furan ring increase the degree of crosslinking in the resin, reducing the concentration of polar functionality per unit volume. Furthermore, the low polarity of furfurylamine itself significantly reduces the polarity of the 2,2′-diallylbisphenol A-furfurylamine-type benzoxazine resin compared to ordinary benzoxazine resins, which also contributes to improved dielectric properties.

[0027] In composite resin systems constructed from 2,2′-diallylbisphenol A-furfurylamine-type benzoxazine monomers and high-molecular-weight polyphenylene ether (PPE), low-molecular-weight PPE oligomers, and their modifiers, a relatively dense network structure can be formed based on the multiple crosslinking reactions of the oxazine ring, double bonds, and furan rings in the novel benzoxazine monomer. The PPE molecular chains entwine and interpenetrate within the crosslinked network structure of the benzoxazine resin, forming a semi-interpenetrating network structure, thereby increasing the crosslinking density of the benzoxazine resin and contributing to the simultaneous improvement of the composite resin's thermal and dielectric properties. Simultaneously, the phenolic hydroxyl groups formed by ring-opening of the benzoxazine resin can form abundant intermolecular and intramolecular hydrogen bonds with the ether oxygen functional groups of PPE, which also improves the compatibility of the two and the thermal properties of the composite resin. Furthermore, the introduction of PPE, which possesses excellent dielectric properties, can significantly enhance the dielectric properties of the benzoxazine / PPE composite resin.

[0028] 2,2′-Diallylbisphenol A-furfurylamine-type benzoxazine monomers and polyphenylene ethers containing self-crosslinking functional groups (alkenyl, alkynyl, etc.) can form composite resin systems with fully interpenetrating and grafted interpenetrating network structures. The polyphenylene ether resin containing crosslinking functional groups can undergo self-polymerization during the polymerization and curing process of benzoxazine, forming a fully interpenetrating crosslinked network structure with the benzoxazine resin, thereby effectively improving the crosslinking density and high-temperature resistance of the composite resin. Furthermore, the regular structure and low polarity of the polyphenylene ether containing self-crosslinking functional groups can improve the dielectric properties of the entire composite resin system. In particular, the double bonds of the 2,2′-diallylbisphenol A-furfurylamine-type benzoxazine monomer can undergo chemical copolymerization with the double bond structure contained in the polyphenylene ether to form a grafted interpenetrating crosslinked network structure, effectively improving the compatibility of the two and the crosslinking density of the copolymer, thus improving the thermal properties. The low-polarity CH bonds formed after polymerization significantly reduce the polarity of the composite resin, further improving its dielectric properties. Furthermore, the hydrogen bonding between benzoxazine resin and polyphenylene ether resin can further enhance the thermal properties of the composite resin, thereby increasing its glass transition temperature.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] Based on the flexible molecular designability of benzoxazine, this invention prepares a novel 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer. The novel benzoxazine resin obtained by thermosetting has excellent thermal properties (glass transition temperature 307-310℃) and high-frequency dielectric properties (k value of 2.640-2.641 and f value of 0.00747-0.00756 at 10GHz), which can fully meet the requirements of ultra-high frequency communication.

[0031] In this invention, the 2,2′-diallylbisphenol A-furfurylamine-type benzoxazine monomer obtained is blended with high molecular weight polyphenylene ether, low molecular weight polyphenylene ether oligomers and their modifications, as well as polyphenylene ether oligomers containing self-crosslinking functional groups, and then thermosetting to prepare composite resins with semi-interpenetrating network, fully interpenetrating network, and grafted interpenetrating network structures. Based on the physical and chemical interactions between 2,2′-diallylbisphenol A-furfurylamine-type benzoxazine and polyphenylene ether, the prepared composite resins all exhibit excellent compatibility.

[0032] The curing temperature of 2,2′-diallylbisphenol A-furfurylamine type benzoxazine is relatively high (≥260℃), while polyphenylene ether resin can act as a catalyst for the ring-opening reaction of benzoxazine. Based on the hydrogen bonding between the oxazine ring and the ether oxygen functional groups of polyphenylene ether, the energy barrier for ring-opening of the oxazine ring can be effectively reduced, thereby lowering the curing temperature of the benzoxazine / polyphenylene ether composite resin (≤220℃), imparting good processing properties to the composite resin, improving polymerization efficiency, and reducing energy consumption.

[0033] The preparation process of this invention is simple, efficient, and easy to industrialize. A relatively simple method was used to synthesize 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer, which was then blended and cured by heat to obtain a 2,2′-diallylbisphenol A-furfurylamine type benzoxazine / polyphenylene ether composite resin. The composite resin exhibits excellent thermal properties (glass transition temperature 198–329℃) and high-frequency dielectric properties (k value 2.321–2.639 and f value 0.00415–0.00744 at 10 GHz). Furthermore, due to the long-chain structure of polyphenylene ether resin, the composite resin possesses flexibility, significantly improving the flexibility of the benzoxazine / polyphenylene ether composite resin.

[0034] Compared to polyphenylene ether resins containing benzoxazine structures reported in the literature, most composite resins exhibit higher glass transition temperatures (218–225 °C) and significantly lower dielectric constants (k = 2.9, 1 GHz). Furthermore, the dielectric loss of these composite resins fully meets the requirements for ultra-high frequency (UHF) communication (≤0.008). Therefore, most 2,2′-diallylbisphenol A-furfurylamine type benzoxazine / polyphenylene ether composite resins fully meet the requirements for UHF communication. Particularly noteworthy is the simple and efficient preparation method, which eliminates cumbersome chemical reactions and purification processes. Consequently, 2,2′-diallylbisphenol A-furfurylamine type benzoxazine / polyphenylene ether composite resins, possessing excellent comprehensive properties including good processing performance, thermal properties, and dielectric properties, have broad application prospects in emerging fields such as UHF communication. Attached Figure Description

[0035] Figure 1 FTIR spectra of 2,2′-diallylbisphenol A-furfurylamine benzoxazine (Df) and 2,2′-diallylbisphenol A-aniline benzoxazine (Da). Detailed Implementation

[0036] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0037] A specific embodiment provides a method for preparing a benzoxazine monomer containing polymerizable double bonds:

[0038] Under nitrogen protection, aldehyde compounds, furfurylamine, 2,2'-diallylbisphenol A, and organic solvents were added to the reaction vessel, and the reaction was carried out at 80-120°C for 2-24 hours. After post-treatment, 2,2'-diallylbisphenol A-furfurylamine type benzoxazine monomers were obtained.

[0039] Specifically, the molar ratio of the aldehyde group, the amino group in furfurylamine, and the phenolic hydroxyl group in 2,2'-diallylbisphenol A in the aldehyde compound is 2:1:1.

[0040] Specifically, the aldehyde compound is formaldehyde or paraformaldehyde.

[0041] Specifically, it can be prepared by a single-feed method: aldehyde compound, furfurylamine, and 2,2'-diallylbisphenol A are simultaneously added to the reaction vessel, and then an organic solvent is added to dissolve them; or it can be prepared by a stepwise multiple-feed method: first, aldehyde compound and furfurylamine are added to the reaction vessel, organic solvent is added and stirred thoroughly, and then the reaction is carried out at 80-120°C for 1-12 hours, and then 2,2'-diallylbisphenol A is added and the reaction is continued for 1-12 hours.

[0042] Specifically, the organic solvent is one or any mixture of butanone, ethyl acetate, toluene, acetone, diethyl ether, N,N'-dimethylformamide, dioxane, chloroform, ethanol, methanol, and xylene.

[0043] Specifically, the post-processing includes: pouring the reaction solution into a methanol solution to obtain a suspension, allowing it to stand, removing the supernatant to obtain a precipitate, drying the precipitate, and grinding it to obtain a 2,2'-diallylbisphenol A-furfurylamine type benzoxazine monomer; the preferred methanol solution concentration is 30-85 wt%.

[0044] A specific embodiment also provides a 2,2'-diallylbisphenol A-furfurylamine type benzoxazine resin, which is obtained by dissolving the above-mentioned benzoxazine monomer containing polymerizable double bonds and then thermosetting it.

[0045] The resulting cured resin has excellent thermal properties (glass transition temperature 307-310℃) and high-frequency dielectric properties (k value of 2.640-2.641 and f value of 0.00747-0.00756 at 10GHz), which fully meets the requirements of ultra-high frequency communication.

[0046] A specific embodiment also provides a benzoxazine / polyphenylene ether composite resin, which is a composite resin with a semi-interpenetrating network structure obtained by dissolving and blending the above-mentioned benzoxazine monomer containing polymerizable double bonds with high molecular weight polyphenylene ether (number average molecular weight > 4000) or polyphenylene ether oligomer (number average molecular weight < 4000) in a mass ratio of (10~1):(1~10).

[0047] A specific embodiment also provides a benzoxazine / polyphenylene ether composite resin, which is obtained by dissolving and blending the above-mentioned benzoxazine monomer containing polymerizable double bonds and polyphenylene ether oligomer (number average molecular weight <4000) containing self-crosslinking functional groups (alkenyl, alkynyl, etc.) in a molar ratio of double bond: crosslinking functional group = (1~5): (5~1), adding a curing accelerator or crosslinking agent, and then thermosetting to obtain a composite resin with a fully interpenetrating network and grafted interpenetrating network structure.

[0048] The resulting benzoxazine / polyphenylene ether composite resin exhibits excellent thermal properties (glass transition temperature 198–329 °C) and high-frequency dielectric properties (k value 2.321–2.639 and f value 0.00415–0.00744 at 10 GHz). Furthermore, the long-chain structure of polyphenylene ether resin imparts flexibility to the composite resin, significantly improving its overall flexibility.

[0049] A specific embodiment also provides a resin varnish composed of the above-mentioned benzoxazine monomer containing polymerizable double bonds and an organic solvent; or using the above-mentioned benzoxazine / polyphenylene ether composite resin prepolymer.

[0050] A specific embodiment also provides a pre-impregnated body, which is composed of the above-mentioned resin varnish with the addition of inorganic fillers and / or flame retardants.

[0051] A further embodiment provides a laminate, which is formed by uniformly coating the aforementioned prepreg onto a nonwoven fabric.

[0052] A further embodiment provides a multilayer printed circuit board, which is made of copper foil and the aforementioned laminate loaded with copper foil.

[0053] Comparative Example 1

[0054] Under nitrogen protection, 0.1 mol of 2,2′-diallylbisphenol A, 0.2 mol of aniline, and 0.4 mol of paraformaldehyde were added to a 250 mL four-necked flask equipped with a condenser, magnetic stirrer, and thermometer. The molar ratio of aldehyde, phenolic hydroxyl, and amino functional groups was 2:1:1. Then, 55 mL of butanone was added, and the mixture was heated to 80 °C for 24 hours. After the reaction, the reaction solution was poured into 100 mL of methanol solution (85 wt%) to obtain a suspension. After standing for 24 hours, the supernatant was removed to obtain a precipitate. The precipitate was then vacuum dried at 70 °C for 8 hours. Finally, the dried product was ground into a powder, which is the 2,2′-diallylbisphenol A-aniline type benzoxazine monomer. Its chemical structure is as follows:

[0055]

[0056] Comparative Example 2

[0057] The 2,2′-diallylbisphenol A-aniline benzoxazine monomer obtained in Comparative Example 1 was dissolved in xylene and placed in a vacuum oven. It was kept at 80°C for 24 hours and then cured at 280°C for 12 hours to obtain a thermosetting resin with a glass transition temperature of 242°C, a k of 3.247 and a f of 0.02150 at 10 GHz.

[0058] Comparative Example 3

[0059] The 2,2′-diallylbisphenol A-aniline benzoxazine monomer obtained in Comparative Example 1 was blended and dissolved with methacrylate-terminated low molecular weight polyphenylene ether in toluene solution. The molar ratio of the functional groups of the double bonds of the 2,2′-diallylbisphenol A-aniline benzoxazine monomer to the double bonds of the polyphenylene ether was 3:1. Di-tert-butylperoxide diisopropylbenzene was added as a curing accelerator for the modified polyphenylene ether oligomer, at a dosage of 2% of the mass of the polyphenylene ether. After ultrasonic stirring for 30 minutes, the mixture was placed in a vacuum oven and kept at 80°C for 24 hours, followed by curing at 240°C for 12 hours to obtain a benzoxazine / polyphenylene ether composite resin with a glass transition temperature of 200°C, a k of 2.972, and an f of 0.01770 at 10 GHz.

[0060] In this comparative example, the methacrylate-terminated low molecular weight polyphenylene ether has a number-average molecular weight of 2300, and its structural formula is as follows:

[0061]

[0062] Example 1

[0063] Under nitrogen protection, 0.1 mol of 2,2′-diallylbisphenol A, 0.2 mol of furfurylamine, and 0.4 mol of paraformaldehyde were added to a 250 mL four-necked flask equipped with a condenser, magnetic stirrer, and thermometer. The molar ratio of aldehyde, phenolic hydroxyl, and amino functional groups was 2:1:1. Then, 55 mL of butanone was added, and the mixture was heated to 80 °C for 24 hours. After the reaction was completed, the reaction solution was poured into 100 mL of methanol solution (30 wt%) to obtain a suspension. After standing for 24 hours, the supernatant was removed to obtain a precipitate. The precipitate was then vacuum dried at 70 °C for 12 hours. Finally, the dried product was ground to obtain a powder, which is the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer.

[0064] The products synthesized in Comparative Example 1 and Example 1 were characterized by Fourier Transmission Infrared (FTIR) spectroscopy. The FTIR characterization results are shown below. Figure 1 As shown, this invention demonstrates that the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine has been successfully synthesized.

[0065] The chemical structures of two benzoxazine monomers, 2,2′-diallylbisphenol A-furfurylamine type benzoxazine (Df) and 2,2′-diallylbisphenol A-aniline type benzoxazine (Da), were compared and analyzed. The two benzoxazine monomers were analyzed at 936 cm⁻¹. -1 Characteristic absorption peaks corresponding to the oxazine ring appeared at 1021 and 1230 cm⁻¹. -1 The characteristic absorption peaks of -CNC- and -COC- in the oxazine ring are at 1495 cm⁻¹. -1 The characteristic absorption peak of the trisubstituted benzene ring is at 1638 cm⁻¹. -1These are characteristic absorption peaks of the -C=C- bond in diallyl bisphenol A. In particular, the 2,2′-diallyl bisphenol A-furfurylamine type benzoxazine (Df) monomer shows characteristic absorption peaks at 1586 and 986 cm⁻¹. -1 Characteristic absorption peaks related to the furan ring appeared at [location missing]. These results demonstrate the successful synthesis of the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer.

[0066] Example 2

[0067] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 1 was dissolved in N,N'-dimethylformamide and then placed in a vacuum oven and cured at 260°C for 1 hour to obtain a thermosetting resin with a glass transition temperature of 310°C, a k of 2.641 and a f of 0.00756 at 10 GHz.

[0068] Example 3

[0069] Under nitrogen protection, 0.2 mol of furfurylamine and 0.4 mol of paraformaldehyde were added to a 250 mL four-necked flask equipped with a condenser, magnetic stirrer, and thermometer. 60 mL of xylene solvent was added, and the mixture was thoroughly mixed and heated to 120 °C for 1 hour. Then, 0.1 mol of 2,2′-diallylbisphenol A was added, and the reaction continued for another hour. The molar ratio of aldehyde, phenolic hydroxyl, and amino functional groups in the reaction system was 2:1:1. After the reaction, the reaction solution was poured into 100 mL of methanol solution (60 wt%) to obtain a suspension. The suspension was allowed to stand for 24 hours, and the supernatant was removed to obtain a precipitate. The precipitate was then vacuum-dried at 90 °C for 12 hours. Finally, the dried product was ground into a powder, which is the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer.

[0070] Example 4

[0071] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 3 was dissolved in toluene and placed in a vacuum oven and cured at 260°C for 1 hour to obtain a thermosetting resin with a glass transition temperature of 307°C, a k of 2.640 and a f of 0.00747 at 10 GHz.

[0072] Example 5

[0073] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 1 was blended and dissolved with methacrylate-terminated low molecular weight polyphenylene ether in toluene solvent. The molar ratio of the functional groups of the double bonds of the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer to the double bonds of the polyphenylene ether was 1:1. Di-tert-butylperoxide diisopropylbenzene was used as a curing accelerator for the polyphenylene ether, and the amount used was 2% of the mass of the polyphenylene ether. After ultrasonic stirring for 30 minutes, the mixture was placed in a vacuum oven and kept at 80°C for 24 hours, followed by curing at 200°C for 4 hours to obtain a benzoxazine / polyphenylene ether composite resin with a grafted interpenetrating network structure. Its glass transition temperature was 198°C, the dielectric constant at 10 GHz was 2.530, and the dielectric loss was 0.00615.

[0074] In this embodiment, the methacrylate-terminated low molecular weight polyphenylene ether has a number-average molecular weight of 2300, and its structural formula is as follows:

[0075]

[0076] Example 6

[0077] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 1 was blended and dissolved with methacrylate-terminated low molecular weight polyphenylene ether in toluene solvent. The molar ratio of the functional groups of the double bonds of the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer to the double bonds of the polyphenylene ether was 3:1. Di-tert-butylperoxide diisopropylbenzene was used as a curing accelerator for the polyphenylene ether, and the amount used was 2% of the mass of the polyphenylene ether. After ultrasonic stirring for 30 minutes, the mixture was placed in a vacuum oven and kept at 80°C for 24 hours, followed by curing at 220°C for 2 hours to obtain a benzoxazine / polyphenylene ether composite resin with a grafted interpenetrating network structure. Its glass transition temperature was 245°C, the dielectric constant at 10 GHz was 2.631, and the dielectric loss was 0.00717.

[0078] In this embodiment, the methacrylate-terminated low molecular weight polyphenylene ether has a number-average molecular weight of 2300, and its structural formula is as follows:

[0079]

[0080] Example 7

[0081] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 3 was blended and dissolved with methacrylate-terminated low molecular weight polyphenylene ether in xylene solvent. The molar ratio of the functional groups of the double bonds of the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer to the double bonds of the polyphenylene ether was 5:1. Triallyl isocyanurate was used as a crosslinking agent for the polyphenylene ether, and the amount used was 1% of the mass of the polyphenylene ether. After ultrasonic stirring for 30 minutes, the mixture was placed in a vacuum oven and kept at 80°C for 24 hours, followed by curing at 180°C for 8 hours to obtain a benzoxazine / polyphenylene ether composite resin with a grafted interpenetrating network structure. Its glass transition temperature was 307°C, the dielectric constant at 10 GHz was 2.639, and the dielectric loss was 0.00744.

[0082] In this embodiment, the methacrylate-terminated low molecular weight polyphenylene ether has a number-average molecular weight of 2300, and its structural formula is as follows:

[0083]

[0084] Example 8

[0085] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 1 was blended and dissolved with high molecular weight polyphenylene ether resin in a toluene / ethanol (5:1 v / v) mixed solvent, with the mass ratio of 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer to polyphenylene ether being 10:1. After ultrasonic stirring for 30 minutes, the mixture was placed in a vacuum oven and kept at 80°C for 24 hours, followed by curing at 200°C for 6 hours to obtain a benzoxazine / polyphenylene ether composite resin with a semi-interpenetrating network structure. Its glass transition temperature was 309°C, its dielectric constant at 10 GHz was 2.637, and its dielectric loss was 0.00740.

[0086] In this embodiment, the number-average molecular weight of the polyphenylene ether resin is 12000, and its structural formula is:

[0087]

[0088] Example 9

[0089] The 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer obtained in Example 3 was blended and dissolved with maleimide-terminated low molecular weight polyphenylene ether in an ethanol / toluene (2:1 v / v) mixed solvent. The molar ratio of the double bond of the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine monomer to the maleimide functional group of the polyphenylene ether was 1:5. Diisopropylbenzene peroxide was used as a curing accelerator for the polyphenylene ether, at a dosage of 2% of the polyphenylene ether mass. After ultrasonic stirring for 30 minutes, the mixture was placed in a vacuum oven and kept at 80°C for 24 hours, followed by curing at 160°C for 12 hours to obtain a benzoxazine / polyphenylene ether composite resin with a grafted interpenetrating network structure. Its glass transition temperature was 329°C, its dielectric constant at 10 GHz was 2.321, and its dielectric loss was 0.00415.

[0090] In this embodiment, the maleimide-terminated low molecular weight polyphenylene ether has a number-average molecular weight of 1700, and its structural formula is as follows:

[0091]

[0092] Example 10

[0093] 100 parts of the prepolymer of 2,2′-diallylbisphenol A-furfurylamine type benzoxazine / polyphenylene ether composite resin prepared in Example 9 (solid content 25 wt%, solvent: ethanol / toluene (2:1 v / v) mixed solvent) were added. Dicumyl peroxide and triallyl isocyanurate were added, each at 1% of the polyphenylene ether mass. Then, 80 parts of nano-silica (solid content 75 wt%, solvent: ethanol / toluene (2:1 v / v) mixed solvent) were added. The solution was ultrasonically mixed for 90 minutes at a power of 500 W, with a 5-minute pause after every 15 minutes of ultrasonication, to prepare a uniformly dispersed prepolymer solution of the nanocomposite resin. The prepolymer solution of the nanocomposite resin was then uniformly coated onto a nonwoven fabric (approximately 0.05 mm thick), air-dried at room temperature, and then pre-cured in a forced-air oven at a controlled temperature below 120°C to obtain a semi-cured sheet. Prepreg sheets of regular shape are cut, stacked into six layers, and coated with copper foil on one side. They are then placed in a hot press and pressed for 1.5 hours at a controlled processing temperature of 180℃ and a pressure of 10.0 MPa, with degassing every ten minutes. Finally, the resulting boards undergo processing methods such as hole drilling, metal plating, and etching to obtain copper-clad laminates.

[0094] The physical properties of the prepared copper-clad laminate were tested as follows. The copper foil peel strength was 1.8 N / mm, indicating that the 2,2′-diallylbisphenol A-furfurylamine type benzoxazine / polyphenylene ether composite resin has excellent adhesion. After etching the copper, the copper-clad laminate was cut into small pieces of a certain size and placed in a pressure cooker. After being boiled at 105 kPa, 121℃, and 360 minutes, a solder heat resistance test (PCT, solder bath 288℃) was conducted. No bubbling or delamination occurred after more than 5 minutes, demonstrating good water resistance to boiling. Thermomechanical analysis showed a coefficient of thermal expansion (CTE) of 33 ppm / ℃, indicating good dimensional stability. Dynamic thermomechanical analysis showed a glass transition temperature of 304℃, exhibiting excellent thermal properties. At a test frequency of 10 GHz, the dielectric constant and dielectric loss were 2.879 and 0.00459, respectively, indicating excellent ultra-high frequency dielectric properties of the copper-clad laminate.

[0095] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A benzoxazine / polyphenylene ether composite resin, characterized in that... A composite resin with a semi-interpenetrating network structure is obtained by dissolving and blending benzoxazine monomers containing polymerizable double bonds with high molecular weight polyphenylene ether at a mass ratio of (10-1):(1-10) and then thermosetting. The molecular structure of the benzoxazine monomer containing polymerizable double bonds is as follows: ； The benzoxazine monomer containing polymerizable double bonds is prepared by the following method: Under nitrogen protection, aldehyde compounds and furfurylamine were first added to the reaction vessel, and organic solvent was added and stirred thoroughly. The reaction was carried out at 80-120°C for 1-12 hours. Then, 2,2'-diallylbisphenol A was added and the reaction was continued for 1-12 hours. After post-treatment, 2,2'-diallylbisphenol A-furfurylamine type benzoxazine monomer was obtained. The high molecular weight polyphenylene ether has a number average molecular weight of 12000 and its structural formula is: 。 2. A benzoxazine / polyphenylene ether composite resin, characterized in that... A composite resin with a fully interpenetrating network and a grafted interpenetrating network structure is obtained by mixing a benzoxazine monomer containing polymerizable double bonds with a polyphenylene ether oligomer containing self-crosslinking functional groups in a double bond: crosslinking functional group (1-5): (5-1) molar ratio, adding a curing accelerator or crosslinking agent, dissolving and blending, and then thermosetting. The molecular structure of the benzoxazine monomer containing polymerizable double bonds is as follows: ； The benzoxazine monomer containing polymerizable double bonds is prepared by the following method: Under nitrogen protection, aldehyde compounds and furfurylamine were first added to the reaction vessel, and organic solvent was added and stirred thoroughly. The reaction was carried out at 80-120°C for 1-12 hours. Then, 2,2'-diallylbisphenol A was added and the reaction was continued for 1-12 hours. After post-treatment, 2,2'-diallylbisphenol A-furfurylamine type benzoxazine monomer was obtained. The polyphenylene ether oligomer containing self-crosslinking functional groups has a number-average molecular weight of 2300 and a structural formula as follows: 。 3. A resin varnish, characterized in that... The prepolymer of the benzoxazine / polyphenylene ether composite resin as described in claim 1 or 2 is used.

4. A pre-impregnated body, characterized in that... It is composed of the resin varnish of claim 3 with the addition of inorganic fillers and / or flame retardants.

5. A laminate, characterized in that... It is formed by uniformly coating the prepreg described in claim 4 onto a nonwoven fabric.

6. A multilayer printed circuit board, characterized in that... It is made of copper foil and a copper foil-loaded laminate as described in claim 5.

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