A method for preparing and reprocessing high-temperature-resistant benzoxazine resin-based can based on si-o-ph bond metathesis reaction

Abstract

The application relates to a high-temperature-resistant benzoxazine resin-based CANs preparation and reprocessing method based on Si-O-Ph bond metathesis reaction. A dynamic Si-O-Ph bond is generated by reacting siloxy (Si-O-R) with phenolic hydroxyl (Ph-OH), Ph-OH is controlled to participate in forming the Si-O-Ph bond, and finally a high-temperature-resistant dynamic covalent adaptive network (CANs) based on Si-O-Ph bond metathesis reaction is obtained. The application has low raw material cost, simple operation steps, realizes the reprocessing of thermosetting resin, and improves the heat resistance and dielectric properties of the thermosetting resin through additional crosslinking of the Si-O-Ph bond and consumption of the Ph-OH polar group.

Description

Technical Field

[0001] This invention relates to a method for preparing and reprocessing high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction, belonging to the field of reprocessable, high-temperature resistant and low-dielectric thermosetting resins. Background Technology

[0002] Thermosetting polymers possess a three-dimensional cross-linked network, endowing them with high-temperature resistance, dimensional stability, solvent resistance, and electrical insulation, making them widely used in aerospace, electronic shipbuilding, and automotive manufacturing. However, traditional thermosetting polymers, due to their permanent cross-linked structure, become insoluble and infusible once processed, and cannot be reprocessed. Damaged thermosetting polymer waste can only be disposed of through incineration or landfill, leading to serious resource waste and environmental pollution. In recent years, introducing dynamic covalent bonds into thermosetting polymers to construct dynamic covalent adaptive networks (CANs) has become a feasible approach to address these issues. Under the influence of external stimuli (light, heat, pH, or pressure), the cross-linked structure of CANs undergoes a dissociation process involving bond breakage followed by bond formation, or an association process where bond formation and breakage occur simultaneously, thereby rearranging its topological structure and enabling it to be reprocessed like thermoplastic polymers. Generally, dynamic covalent bonds such as ester bonds, disulfide bonds, acylhydrazone bonds, and carbamate bonds are introduced into thermosetting polymers to impart this reprocessing capability. However, these dynamic covalent bonds can usually be exchanged at relatively low temperatures, which greatly limits their heat resistance.

[0003] Chinese patent CN 108546272 A discloses a Si-O-Ph organic-inorganic hybrid crosslinked polybenzoxazine, a polybenzoxazine monomer, and a method for preparing the same. Specifically, the polybenzoxazine is obtained by subjecting the benzoxazine monomer to two-stage thermosetting. Due to the increased crosslinking density caused by the Si-O-Ph organic-inorganic hybrid bonds, the heat resistance of the polybenzoxazine is significantly improved compared to ordinary polybenzoxazine. However, the presence of free hydroxyl groups in this patent causes oxidation of the prepared polybenzoxazine resin during reprocessing, thus affecting its heat resistance and reprocessability.

[0004] In conclusion, the preparation of thermosetting resins with high heat resistance and reprocessability remains an urgent problem to be solved. Summary of the Invention

[0005] To overcome the aforementioned technical barriers, this invention provides a method for preparing and reprocessing a thermosetting resin with high heat resistance and reprocessability. By utilizing a stepwise heating and curing process to react Ph-OH with silanoxy groups to form Si-O-Ph bonds, and by controlling the curing conditions to ensure that all Ph-OH participates in the formation of Si-O-Ph bonds, the influence of oxidation on the resin's thermal properties during subsequent hot pressing is avoided. This results in the preparation of a high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis. In this invention, the construction of CANs is simple and easy, the preparation cost is low, and the reprocessing conditions are simple and easy to operate.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction includes the following steps: curing a siloxane-containing benzoxazine monomer to react silaneoxy groups (Si-OR) with phenolic hydroxyl groups (Ph-OH) to generate dynamic Si-O-Ph bonds, ultimately obtaining high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction.

[0008] The curing process described above ensures that all Ph-OH polar groups participate in the Si-O-Ph bond, preventing damage to thermal properties and reprocessability caused by oxidation of free hydroxyl groups during reprocessing or reactions with the polymer crosslinking network. The resulting Si-O-Ph bonds further increase the crosslinking density of the benzoxazine resin. Combined with the elimination of the polar Ph-OH groups, both of these factors endow high-temperature benzoxazine resin-based CANs (Conductive Acids) based on the Si-O-Ph bond metathesis reaction with excellent dielectric properties.

[0009] Furthermore, the siloxane-containing benzoxazine monomer is a monocyclic, bicyclic, or polycyclic siloxane-containing benzoxazine monomer.

[0010] The structure of the monocyclic siloxane benzoxazine monomer is shown in formula (I):

[0011]

[0012] Wherein, R1 is H, CH3, CH2CH3, C9H 19 C(CH3)3, sec-C5H 11 sec-C8H 17 iso-C9H 19 iso-C8H 17 iso-C 12 H 25 One of F, Cl, Br, and I;

[0013] R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

[0014] The structure of the bicyclic siloxane benzoxazine monomer is shown in formula (II):

[0015]

[0016] Among them, R2 is one of C(CH3)2, CCH3CH2CH3, CHCH3, CHCH2CH3, C(CH2CH3)2, CCH3CH(CH3)2, CCH3CH=CH2, CCH3C(CH3)3, C[CH(CH3)2]2, CH2, O, O=S=O, C=O, -OC=O;

[0017] R is one of OCH3, OCH2CH3, and OCH2CH2CH3;

[0018] The structure of the polycyclic siloxane benzoxazine monomer is shown in formula (III):

[0019]

[0020] Wherein, R3 is CCH3, CCH2CH3, One of them;

[0021] R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

[0022] The structure of the high-temperature resistant benzoxazine resin-based CANs obtained by the monocyclic siloxane benzoxazine monomer based on the Si-O-Ph bond metathesis reaction is shown in formula (IV):

[0023]

[0024] Wherein, R1 is H, CH3, CH2CH3, C9H 19 C(CH3)3, sec-C5H 11 sec-C8H 17 iso-C9H 19 iso-C8H 17 iso-C 12 H 25 One of F, Cl, Br, and I;

[0025] R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

[0026] The structure of high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction was obtained using a bicyclic silane-containing benzoxazine monomer, as shown in formula (V):

[0027]

[0028] Among them, R2 is one of C(CH3)2, CCH3CH2CH3, CHCH3, CHCH2CH3, C(CH2CH3)2, CCH3CH(CH3)2, CCH3CH=CH2, CCH3C(CH3)3, C[CH(CH3)2]2, CH2, O, O=S=O, C=O, -OC=O;

[0029] R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

[0030] The structure of high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction was obtained using polycyclic silane-containing benzoxazine monomers, as shown in formula (VI):

[0031]

[0032] Wherein, R3 is CCH3, CCH2CH3, One of them;

[0033] R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

[0034] The high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction were further optimized under the following gradient temperature curing conditions: Curing endpoint temperature: 250–400℃, total curing time: 24–48 h, curing temperature gradient: 5–20℃, heating rate: 5–20℃ / min, nitrogen flow rate: 20–50 mL / min.

[0035] Preferably, the curing endpoint temperature is 250–340°C.

[0036] Preferably, the residence time for each temperature gradient is 1 to 4 hours.

[0037] The gradient heating causes benzoxazine to open its ring and release phenolic hydroxyl groups; as the temperature increases, the released Ph-OH participates in the formation of dynamic Si-O-Ph bonds.

[0038] The present invention also provides a reprocessing method for high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction. The specific steps include: mechanically grinding the high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction into powder, and then reprocessing them into complete resin samples by hot pressing.

[0039] The high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction are further processed under the following conditions: the high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction are ground to 100-400 mesh; the hot-pressing temperature is 230-300℃, preferably 230-270℃; the pressure is 15-30MPa; and the hot-pressing time is 2.5-4h.

[0040] The high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction are reprocessed 1 to 2 times.

[0041] like Figure 17 The diagram shows the preparation and reprocessing flow of high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. As can be seen from the diagram, the preparation and reprocessing flow is as follows: First, a silaneoxy group (Si-OR) compound and a phenolic hydroxyl group (Ph-OH) are cured to generate a complete sample of high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction; then, after being pulverized into powder, it is hot-pressed to form a remolded complete sample of high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0042] The reprocessing mechanism of high-temperature benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction is as follows: Figure 18 As shown in the figure, after being stimulated by hot pressing, the Si-O-Ph bond undergoes a metathesis reaction to form a new Si-O-Ph bond, which is macroscopically manifested as the resin powder being reshaped into a complete resin sample.

[0043] The high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction, their preparation method, and their reprocessing method can be applied to the resin field.

[0044] The present invention has the following significant advantages:

[0045] 1. This invention is the first to propose that by controlling the curing conditions, all Ph-OH polar groups can participate in the Si-O-Ph bond, thus avoiding the damage to the resin's thermal properties and reprocessability caused by the oxidation of free hydroxyl groups during reprocessing and their reaction with the polymer crosslinking network.

[0046] 2. The method for preparing high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction provided by the present invention eliminates the polar group Ph-OH, and at the same time, it synergistically increases the crosslinking density of benzoxazine resin with Si-O-Ph bond, thereby improving the dielectric properties of benzoxazine resin.

[0047] 3. This invention is the first to discover the metathesis reaction between dynamic Si-O-Ph bonds in benzoxazine resins, a discovery that endows thermosetting resins with reprocessability. Simultaneously, the introduction of dynamic Si-O-Ph bonds does not adversely affect the heat resistance of thermosetting resins; on the contrary, the additional crosslinking effect of Si-O-Ph bonds gives thermosetting resins excellent heat resistance. The bond energy of the Si-O bond (422.5 kJ / mol) is much higher than that of the CC (347 kJ / mol) and CN (305 kJ / mol) bonds in ordinary benzoxazine resins, giving thermosetting resins excellent resistance to thermal oxidation.

[0048] 4. This method has a wide range of applications in preparing high-temperature resistant CANs based on Si-O-Ph bond metathesis reaction. It can be used in other thermosetting resin systems, including but not limited to benzoxazine resin systems. This method is simple, easy to implement, has low preparation cost, and easy-to-operate curing and reprocessing conditions.

[0049] 5. Based on the metathesis reaction of Si-O-Ph bonds, thermosetting resins can be reprocessed. The reprocessing does not require the participation of a catalyst, thus avoiding the adverse effects of catalyst oxidation, degradation, precipitation and long-term failure on thermosetting resins. Attached Figure Description

[0050] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0051] Figure 1 The images show the DSC diagrams of the high-temperature resistant monocyclic silicon-containing benzoxazine resin-based CANs before and after curing based on the Si-O-Ph bond metathesis reaction in Example 1.

[0052] Figure 2 The following are FT-IR spectra of high-temperature resistant monocyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction during different curing processes in Example 1;

[0053] Figure 3 This is a DMA diagram of high-temperature resistant monocyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction for different reprocessing times in Example 1;

[0054] Figure 4 The TGA curves of high-temperature resistant monocyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction in Example 1 under nitrogen (a) and air (b) atmospheres with different reprocessing times;

[0055] Figure 5The following are FT-IR spectra of high-temperature resistant monocyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction at different reprocessing times in Example 1;

[0056] Figure 6 The images show physical samples of high-temperature resistant monocyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction at different reprocessing times in Example 1.

[0057] Figure 7 The dielectric constants of the high-temperature resistant monocyclic silicon-containing benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction in Example 1 at different frequencies;

[0058] Figure 8 These are images of the high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction in Example 1 before and after treatment at 50°C for 24 hours in different solvents;

[0059] Figure 9 The images show the DSC diagrams of the high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction before and after curing in Example 2.

[0060] Figure 10 The FT-IR spectrum of the high-temperature resistant bicyclic benzoxazine resin-based CANs curing process based on the Si-O-Ph bond metathesis reaction in Example 2 is shown below.

[0061] Figure 11 This is the DMA diagram of high-temperature resistant bicyclic silane-containing benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction in Example 2;

[0062] Figure 12 The TGA curves of high-temperature resistant bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction in nitrogen (a) and air (b) atmospheres are shown in Example 2.

[0063] Figure 13 The following are FT-IR spectra of high-temperature resistant bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction at different reprocessing times in Example 2;

[0064] Figure 14 The images shown are of high-temperature resistant bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction under different processing times in Example 2.

[0065] Figure 15 The dielectric constants of the high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction in Example 2 at different frequencies;

[0066] Figure 16 Images of high-temperature resistant bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction in different solvents before and after treatment at 50°C for 24 hours;

[0067] Figure 17 This is a flowchart illustrating the preparation and reprocessing of high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0068] Figure 18 A diagram illustrating the reprocessing mechanism of high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction;

[0069] Figure 19 DMA curves of the same sample of bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis at different heat treatment temperatures. Detailed Implementation

[0070] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0071] Example 1

[0072] 3,4-Dihydro-3-[3-(triethoxysilyl)propyl]-2H-1,3-benzoxazine (P-mtes) was placed in a self-made aluminum foil box and heated from 120℃ to 280℃ in 20℃ increments at a heating rate of 10℃ / min. Within the temperature range of 120–160℃, each temperature gradient was held for 2 hours, and within the temperature range of 180–280℃, each temperature gradient was held for 4 hours. Nitrogen gas was maintained at a flow rate of 20 mL / min, and the mixture was cured under a nitrogen atmosphere for 30 hours to obtain high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0073] The reprocessing conditions are as follows: High-temperature benzoxazine-based CANs based on the Si-O-Ph bond metathesis reaction are mechanically crushed and ground, then passed through a 60-mesh sieve to obtain resin powder of the appropriate particle size. The hot-pressing temperature is 230℃, the pressure is 15MPa, and the hot-pressing time is 2.5h. The same reprocessing conditions are applied twice.

[0074] The 3,4-dihydro-3-[3-(triethoxysilyl)propyl]-2H-1,3-benzoxazine monomer (P-mtes) is synthesized from phenol and 3-aminopropyltriethoxysilane.

[0075] The chemical formula of the high-temperature resistant benzoxazine resin-based CANs (Poly(P-mtes)) based on the Si-O-Ph bond metathesis reaction is:

[0076]

[0077] To further optimize the curing and reprocessing process, the following experiments were conducted in this embodiment:

[0078] The FT-IR spectra of P-mtes resin samples obtained by thermosetting at different temperatures during the curing process are shown below. Figure 2 As shown. The reprocessing times were set to 0, 1, and 2 times respectively. The reprocessing conditions were as follows: high-temperature benzoxazine-based CANs based on the Si-O-Ph bond metathesis reaction were mechanically crushed and ground, passed through a 60-mesh sieve to obtain resin powder of the corresponding particle size; the hot-pressing temperature was 230℃, the pressure was 15MPa, and the hot-pressing time was 2.5h. Resin samples were obtained. The DAM image, TGA image, FT-IR image, and physical image of the resin samples are shown below. Figure 3 , 4 As shown in Figures 5 and 6.

[0079] To test the solvent resistance of the high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction, the resin was treated at 50°C for 24 h in toluene, acetone, chloroform, tetrahydrofuran, anhydrous ethanol, and water, respectively. The results after treatment are as follows: Figure 8 As shown.

[0080] like Figure 1 The figure shows the DSC diagrams of silane-containing monocyclic benzoxazine monomers and high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. From curve (a) in the figure, it can be seen that the curing initiation temperature T of P-mtes is... i The peak curing temperature is 242℃, T. p The curing temperature is 262.9℃, and the curing termination temperature T is... f The temperature was 277.5℃. As can be seen from curve (b) in the figure, no curing peak appeared after curing at 280℃, indicating that a fully cured monocyclic silicone benzoxazine resin-based CANs was obtained.

[0081] like Figure 2 The image shows the FT-IR spectra of siloxane-containing monocyclic benzoxazine monomers at different curing temperatures. At 240℃, the characteristic infrared peak corresponding to the oxazine ring disappears, and the intensity of the characteristic peak of Ph-OH reaches its maximum. At 280℃, the intensity of the characteristic infrared peak corresponding to the Si-O-Ph bond reaches its maximum, and the characteristic peak of Ph-OH disappears. This indicates that curing to 280℃ yields monocyclic siloxane-containing benzoxazine resin-based CANs with the highest Si-O-Ph bond content and no Ph-OH.

[0082] like Figure 3The figure shows the DMA (Digital Metathesis) curves of the original and reprocessed samples of high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. Detailed data are shown in Table 1. As can be seen from the figure, the T0 of the original monocyclic silicon-containing benzoxazine resin-based CANs sample was determined by the energy dissipation modulus (G″) and tanδ curves. g The results showed excellent heat resistance at 327℃ and 341℃ respectively. The heat resistance of the monocyclic silicone benzoxazine resin-based CANs was maximized after two reprocessing processes.

[0083] like Figure 4 The image shows the TGA images of the original and reprocessed samples of high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. Detailed data are shown in Table 1. Specifically, the TGA values ​​of the monocyclic silicon-containing benzoxazine resin-based CANs under nitrogen atmosphere are... d5 T d10 and Y 800 The values ​​were 390℃, 437℃, and 63.8%, respectively. In air, they were 375℃, 453℃, and 23.1%. The thermo-oxidative stability of monocyclic silane-containing benzoxazine resin-based CANs was maximized after two reprocessing steps.

[0084] like Figure 5 The figure shows the FT-IR spectra of the original and reprocessed samples of high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. As can be seen from the figure, the intensity of the infrared characteristic peak of the Si-O-Ph bond decreases with the increase of the number of processing times, indicating that the number of Si-O-Ph bonds decreases with the increase of the number of reprocessing times.

[0085] like Figure 6 The image shown is a reprocessing image of high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. It can be seen that the resin powder, after being hot-pressed, can be healed into a complete whole.

[0086] like Figure 7 The figure shows the dielectric constants of high-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction at different frequencies. Detailed data are shown in Table 1. As can be seen from the figure, the dielectric constant gradually decreases with increasing test frequency, reaching 2.9 at 10MHz.

[0087] like Figure 8 The figure shows the solvent resistance of high-temperature resistant monocyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction in toluene, acetone, chloroform, tetrahydrofuran, anhydrous ethanol, and water. After treatment at 50℃ for 24 h, the resin did not swell or dissolve, indicating that the high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction have excellent solvent resistance.

[0088] Example 2

[0089] 6,6′-(1-methylethylidene)bis[3,4-dihydro-3-[3-(triethoxysilyl)propyl]-2H-1,3-benzoxazine was placed in a self-made aluminum foil box and heated from 140℃ to 280℃ in 20℃ increments at a heating rate of 5℃ / min. Each temperature gradient was maintained for 4 hours within the 140–280℃ temperature range. Nitrogen gas was maintained at a flow rate of 10 mL / min, and the mixture was cured under a nitrogen atmosphere for 32 hours. This yielded high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0090] The reprocessing conditions are as follows: High-temperature benzoxazine-based CANs based on the Si-O-Ph bond metathesis reaction are mechanically crushed and ground, then passed through a 100-mesh sieve to obtain resin powder of the appropriate particle size. The hot-pressing temperature is 260℃, the pressure is 20MPa, and the hot-pressing time is 3.5h. The same reprocessing conditions are applied twice.

[0091] The 6,6′-(1-methylethylidene)bis[3,4-dihydro-3-[3-(triethoxysilyl)propyl]-2H-1,3-benzoxazine monomer (BA-mtes) is synthesized from bisphenol-A and 3-aminopropyltriethoxysilane.

[0092] The chemical formula of the high-temperature resistant bisbenzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction is:

[0093]

[0094] To further optimize the curing and reprocessing process, the following experiments were conducted in this embodiment:

[0095] The FT-IR spectra of BA-mtes resin samples obtained by thermosetting at different temperatures during the curing process are shown below. Figure 10 As shown. The reprocessing times were set to 0, 1, and 2 times respectively. The reprocessing conditions were as follows: High-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction were mechanically crushed and ground, passed through a 100-mesh sieve to obtain resin powder of the corresponding particle size; the hot-pressing temperature was 260℃, the pressure was 20MPa, and the hot-pressing time was 3.5h. Resin samples were obtained. The DAM image, TGA image, FT-IR image, and physical image of the resin samples are shown below. Figure 11 , 12 As shown in Figures 13 and 14.

[0096] To test the solvent resistance of the high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction, the resin was treated at 50°C for 24 h in toluene, acetone, chloroform, tetrahydrofuran, anhydrous ethanol, and water, respectively. The results after treatment are as follows: Figure 16 As shown.

[0097] like Figure 9 The figure shows the DSC diagrams of silane-containing bicyclic benzoxazine monomers and high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction. From curve (a) in the figure, it can be seen that the curing initiation temperature T of BA-mtes is... i The peak curing temperature is 249.5℃, T. p The curing temperature is 269.98℃, and the curing termination temperature T is... f The temperature was 293.3℃. As can be seen from curve (b) in the figure, no curing peak appeared after curing at 280℃, indicating that the fully cured bicyclic silicone benzoxazine resin-based CANs were obtained.

[0098] like Figure 10 The image shows the FT-IR spectra of the silane-containing bicyclic benzoxazine monomer at different curing temperatures. At 240℃, the characteristic infrared peak corresponding to the oxazine ring disappears, and the intensity of the characteristic peak of Ph-OH reaches its maximum. At 280℃, the intensity of the characteristic infrared peak corresponding to the Si-O-Ph bond reaches its maximum, and the characteristic peak of Ph-OH disappears. This indicates that curing to 280℃ yields bicyclic silane-containing benzoxazine resin-based CANs with the highest Si-O-Ph bond content and no Ph-OH.

[0099] like Figure 11 The figure shows the DMA (Dielectric Dynamics) curves of the original and reprocessed samples of high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. Detailed data are shown in Table 1. As can be seen from the figure, the T0 of the original monocyclic silicon-containing benzoxazine resin-based CANs sample was determined by the energy dissipation modulus (G″) and tanδ curves. g The temperatures reached 386℃ and well above 400℃, respectively, demonstrating excellent heat resistance. The heat resistance of the bicyclic silicone benzoxazine resin-based CANs was maximized after two reprocessing steps.

[0100] like Figure 12 The image shows the TGA images of the original and reprocessed samples of high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. Detailed data are shown in Table 1. Specifically, the TGA values ​​of monocyclic silicon-containing benzoxazine resin-based CANs under nitrogen atmosphere are shown. d5 T d10 and Y 800The values ​​were 393℃, 448℃, and 51.2%, respectively. In air, they were 426℃, 453℃, and 53.5%. The thermo-oxidative stability of the bicyclic silane-containing benzoxazine resin-based CANs was maximized after two reprocessing steps.

[0101] like Figure 13 The figure shows the FT-IR spectra of the original and reprocessed samples of high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. As can be seen from the figure, the intensity of the infrared characteristic peak of the Si-O-Ph bond decreases with the increase of the number of processing times, indicating that the number of Si-O-Ph bonds decreases with the increase of the number of reprocessing times.

[0102] like Figure 14 The image shown is a reprocessing image of high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. It can be seen that the resin powder can be healed into a complete whole after hot pressing.

[0103] like Figure 15 The figure shows the dielectric constants of high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction at different frequencies. Detailed data are shown in Table 1. As can be seen from the figure, the dielectric constant gradually decreases with increasing test frequency, reaching 2.59 at 10MHz.

[0104] like Figure 16 The figure shows the solvent resistance of high-temperature resistant bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction in toluene, acetone, chloroform, tetrahydrofuran, anhydrous ethanol, and water. After treatment at 50℃ for 24 h, the resin did not swell or dissolve, indicating that the high-temperature resistant bicyclic benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction have excellent solvent resistance.

[0105] Example 3

[0106] 6,6′,6″-ethylenediamine[3,4-dihydro-3-[3-(triethoxysilyl)propyl]-2H-1,3-benzoxazine monomer was placed in a self-made aluminum foil box and heated from 160℃ to 340℃ in 10℃ increments at a heating rate of 20℃ / min. Within the temperature range of 160–220℃, each temperature gradient was held for 3 hours, and within the temperature range of 230–340℃, each temperature gradient was held for 2 hours. Nitrogen gas flow was maintained at 30 mL / min, and the mixture was cured under a nitrogen atmosphere for 45 hours. This yielded high-temperature resistant polycyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0107] The reprocessing conditions are as follows: High-temperature benzoxazine-based CANs based on the Si-O-Ph bond metathesis reaction are mechanically crushed and ground, then passed through a 200-mesh sieve to obtain resin powder of the appropriate particle size. The hot-pressing temperature is 280℃, the pressure is 35MPa, and the hot-pressing time is 5h. The same reprocessing conditions are applied twice.

[0108] Example 4

[0109] 3-[3-(diethoxymethylsilyl)propyl]-3,4-dihydro-2H-1,3-benzoxazine monomer was placed in a self-made aluminum foil box and heated from 180℃ to 360℃ in 20℃ increments at a heating rate of 15℃ / min. The temperature was maintained for 4 hours at each gradient between 180℃ and 240℃, 2.5 hours at each gradient between 260℃ and 300℃, and 1.5 hours at each gradient between 320℃ and 360℃, with a nitrogen flow rate of 60 mL / min. Curing was carried out under a nitrogen atmosphere for 28 hours. High-temperature resistant monocyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction were obtained. The same reprocessing conditions were then applied twice.

[0110] The reprocessing conditions are as follows: the high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction are mechanically crushed and ground through a 300-mesh sieve to obtain resin powder of the corresponding particle size. The hot pressing temperature is 220℃, the pressure is 10MPa, and the hot pressing time is 2h.

[0111] Example 5

[0112] 6,6′-(1-Methylethylidene)bis[3-[3-(diethoxymethylsilyl)propyl]-3,4-dihydro-2H-1,3-benzoxazine monomer was placed in a self-made aluminum foil box and heated from 200℃ to 400℃ in 10℃ increments at a heating rate of 5℃ / min. Within the 200–300℃ temperature range, each temperature gradient was held for 2 hours; within the 310–400℃ temperature range, each temperature gradient was held for 1 hour. Nitrogen gas flow was maintained at 80 mL / min, and the mixture was cured under a nitrogen atmosphere for 32 hours. This yielded high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0113] The reprocessing conditions are as follows: High-temperature benzoxazine-based CANs based on the Si-O-Ph bond metathesis reaction are mechanically crushed and ground, then passed through a 400-mesh sieve to obtain resin powder of the appropriate particle size. The hot-pressing temperature is 280℃, the pressure is 25MPa, and the hot-pressing time is 4h. The same reprocessing conditions are applied twice.

[0114] Example 6

[0115] 6,6′-(1-methylethylidene)bis[3,4-dihydro-3-[3-(triethoxysilane)propyl]-2H-1,3-benzoxazine was placed in a self-made aluminum foil box and heated from 140℃ to 350℃ in 10℃ increments at a heating rate of 5℃ / min. Each temperature gradient was maintained for 1.5 h within the 140–350℃ range, with a nitrogen flow rate of 10 mL / min. The mixture was cured under a nitrogen atmosphere for 33 h. This yielded high-temperature resistant bicyclic benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction.

[0116] Figure 19 The images show the DMA diagrams of the original sample, the sample heat-treated at 350°C, and the sample heat-treated at 350°C followed by heat treatment at 400°C, based on the Si-O-Ph bond metathesis reaction of high-temperature resistant bicyclic benzoxazine resin-based CANs in Example 6. It can be seen that after heat treatment, the heat resistance of the Si-O-Ph bond metathesis reaction-based high-temperature resistant bicyclic benzoxazine resin-based CANs becomes even better.

[0117] Table 1 Thermal properties of resin-based CANs in Examples 1 and 2

[0118]

Claims

1. A method for preparing high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction, characterized in that, The specific steps include: The siloxane-containing benzoxazine monomer is cured to allow the silanoxy group to react with the phenolic hydroxyl group to generate dynamic Si-O-Ph bonds, ultimately obtaining high-temperature benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction. The curing process is a gradient temperature curing method; The curing endpoint temperature is 280~400°C. o C; Total curing time: 24~48 h; Curing temperature gradient: 5~20 o C; Heating rate: 5~20 o C / min; residence time for each temperature gradient is 1~4 h; the curing process is carried out under a nitrogen atmosphere, and the nitrogen flow rate is 20~50 mL / min; The siloxane-containing benzoxazine monomer is a monocyclic, bicyclic, or polycyclic siloxane-containing benzoxazine monomer; The structure of the monocyclic siloxane benzoxazine monomer is shown in formula (I): （I）， Wherein, R1 is H, CH3, CH2CH3, C9H 19 C(CH3)3, sec-C5H 11 sec-C8H 17 iso-C9H 19 iso-C8H 17 iso-C 12 H 25 One of F, Cl, Br, and I; R is one of OCH3, OCH2CH3, and OCH2CH2CH3; The structure of the bicyclic siloxane benzoxazine monomer is shown in formula (II): (II) Wherein, R2 is one of C(CH3)2, CCH3CH2CH3, CHCH3, CHCH2CH3, C(CH2CH3)2, CCH3CH(CH3)2, CCH3CH=CH2, CCH3C(CH3)3, C[CH(CH3)2]2, CH2, O, O=S=O, C=O, -OC=O; R is one of OCH3, OCH2CH3, and OCH2CH2CH3; The structure of the polycyclic siloxane benzoxazine monomer is shown in formula (III): (III) Wherein, R3 is CCH3, CCH2CH3, , One of them; R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

2. The method for preparing high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction according to claim 1, characterized in that, The curing endpoint temperature is 280~340℃. o C.

3. The method for preparing high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction according to claim 1, characterized in that, The structure of the high-temperature resistant benzoxazine resin-based CANs obtained by the monocyclic siloxane benzoxazine monomer based on the Si-O-Ph bond metathesis reaction is shown in formula (IV): (IV) Wherein, R1 is H, CH3, CH2CH3, C9H 19 C(CH3)3, sec-C5H 11 sec-C8H 17 iso-C9H 19 iso-C8H 17 iso-C 12 H 25 One of F, Cl, Br, and I; R is one of OCH3, OCH2CH3, and OCH2CH2CH3; The structure of high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction was obtained using a bicyclic silane-containing benzoxazine monomer, as shown in formula (V): （V）， Wherein, R2 is one of C(CH3)2, CCH3CH2CH3, CHCH3, CHCH2CH3, C(CH2CH3)2, CCH3CH(CH3)2, CCH3CH=CH2, CCH3C(CH3)3, C[CH(CH3)2]2, CH2, O, O=S=O, C=O, -OC=O; R is one of OCH3, OCH2CH3, and OCH2CH2CH3; The structure of high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction was obtained using polycyclic silane-containing benzoxazine monomers, as shown in formula (VI): (VI); Wherein, R3 is CCH3, CCH2CH3, , One of them; R is one of OCH3, OCH2CH3, and OCH2CH2CH3.

4. A reprocessing method for high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction, characterized in that, The specific steps are as follows: The high-temperature resistant benzoxazine resin-based CANs based on the Si-O-Ph bond metathesis reaction prepared by the method described in any one of claims 1-3 are mechanically ground into powder and then processed into complete resin samples by hot pressing and co-stimulation.

5. The reprocessing method for high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction according to claim 4, characterized in that, The specific steps are as follows: The grinding particle size is 100~400 mesh, and the hot pressing temperature is 230~300℃. o C. Pressure is 15~30 MPa, hot pressing time is 2.5~4h.

6. The reprocessing method for high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction according to claim 5, characterized in that, The hot pressing temperature is 230~270 ℃.

7. The reprocessing method for high-temperature resistant benzoxazine resin-based CANs based on Si-O-Ph bond metathesis reaction according to claim 5, characterized in that, The specific steps are as follows: the reprocessing is carried out 1 to 2 times.

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