A flame-retardant and odorless nano-phenolic board

Abstract

This invention discloses a flame-retardant and odorless nano-phenolic board, belonging to the field of phenolic board technology. First, this invention utilizes boron phenolic resin generated by the reaction of p-hydroxyhexanone, formaldehyde, and 3-methoxy-4-methylphenylboronic acid. This resin forms a stable and dense boron carbide layer at high temperatures, achieving heat resistance and high flame retardancy. Next, an epoxy structure is introduced into the boron phenolic resin, generating a highly polymeric network structure within the matrix, improving the board's compressive strength and flame retardancy. Then, melamine and polyacrylonitrile are spun into carbon fibers through ultrasonic-magnetic field-assisted microfluidic spinning and double heating, indirectly reinforcing the foam board. Microwave radiation is then used to create a mechanical bond between the fibers and the resin. Finally, silica is electrostatically sprayed onto both sides of the board, further enhancing its flame retardant effect. The phenolic board prepared by this invention exhibits flame retardancy and compressive strength.

Description

Technical Field

[0001] This invention relates to the field of phenolic board technology, specifically to a flame-retardant and odorless nano-phenolic board. Background Technology

[0002] With the continuous research and development of polymer materials, traditional building materials used daily are gradually being replaced by polymer materials. Among them, polymer foam materials, due to the large number of micron-sized gas pores distributed within their structure, possess excellent properties such as lightweight, shock absorption, and thermal insulation. Currently, with the rapid development of industries such as aerospace, transportation, and construction, the demand for foam materials in terms of high compressive strength, high thermal insulation, and flame resistance is increasing daily. However, the performance of traditional foam materials is insufficient to meet these requirements, thus necessitating the modification and optimization of polymer foam materials. Phenolic resins, due to their highly cross-linked structure, endow materials with excellent heat resistance and chemical resistance, ensuring mechanical strength and dimensional stability of workpieces. They also retain their excellent flame retardancy, making them widely used in various engineering fields, including daily production, military, and aerospace. They are mainly used in casting, friction materials, heat-resistant materials, adhesives, and substrate coatings. However, when phenolic resins are made into foam materials, although they can work for a long time at 150°C and have flame-retardant and self-extinguishing properties when burned, they also have disadvantages such as low strength and smoldering, which affect their application. Therefore, it is particularly important to invent a new type of phenolic foam material. Summary of the Invention

[0003] The purpose of this invention is to provide a flame-retardant and odorless nano-phenolic board and its preparation method, so as to solve the problems existing in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a flame-retardant and odorless nano-phenolic board, wherein the flame-retardant and odorless nano-phenolic board is made by modifying phenolic foam board and carbon fiber, and then electrostatically spraying silica.

[0005] Furthermore, the modified phenolic foam board is prepared by reacting boron phenolic resin, which is obtained by reacting p-hydroxyhexanone, formaldehyde, and 3-methoxy-4-methylphenylboronic acid, with epichlorohydrin.

[0006] Furthermore, the carbon fiber is prepared from polyacrylonitrile through steps such as ultrasonic-magnetic field assisted microfluidic spinning and dual heating.

[0007] Furthermore, a method for preparing a flame-retardant and odorless nano-phenolic board includes the following preparation steps:

[0008] (1) Mix 37wt% formaldehyde aqueous solution and p-hydroxyhexanone at a mass ratio of 13:17~17:25, stir evenly, add 2~3 times the mass of p-hydroxyhexanone in 30wt% sodium hydroxide aqueous solution, heat to 55~70℃, stir at 70~100rpm for 1.5~3h, cool to 40~50℃, add 1~1.5 times the mass of p-hydroxyhexanone in 3-methoxy-4-methylphenylboronic acid and 0.4~0.6 times the mass of p-hydroxyhexanone in methanol, heat to 65~75℃, react for 2~3h, cool again to 40~50℃, add 45wt% sodium hydroxide aqueous solution until the solution pH is 8~9, 3 Distilled at 5-40℃ and 800-1000Pa for 1-3 hours, then formic acid was added until the solution pH was 6.5-7. Epichlorohydrin (1.5-3 times the mass of p-hydroxyhexanone) and tetrabutylammonium bromide (0.02-0.04 times the mass of p-hydroxyhexanone) were added. The temperature was raised to 75-85℃. Sodium hydroxide (0.25-0.35 times the mass of p-hydroxyhexanone) was added in 4 portions over 60-90 minutes. The reaction was continued for 2.5-4 hours. The mixture was filtered, and the solid was washed 3-5 times with deionized water at 50℃. Distilled at 10-20℃ and 800-1000Pa for 1-3 hours to obtain modified phenolic resin.

[0009] (2) Place the modified phenolic resin in an oil bath at 80°C and stir at 30-60 rpm for 0.5-1.5 h. Add Tween-80 and n-pentane and stir at 70-100 rpm for 20-40 min. Add 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid and continue stirring for 1-3 min. Pour into a mold and let stand for 60-80 min. Demold and cure at 50-80°C for 8-12 h. Then, microwave irradiate to obtain the modified phenolic foam board.

[0010] (3) Melamine and N,N-dimethylformamide at 60℃ are mixed at a mass ratio of 0.5:20~1:23 and stirred at 70~100rpm for 1.5~3h. Then, polyacrylonitrile with a molecular weight of 81000 is added at 4~8 times the mass of melamine and stirred for 10~14h to obtain spinning solution. Then, ultrasonic-magnetic field assisted microfluidic spinning is performed and dried at 65~75℃ for 10~14h to obtain spun fibers.

[0011] (4) The spun fibers are heated twice and cooled, and then covered on the modified phenolic foam board to obtain carbon fiber composite modified phenolic foam board.

[0012] (5) Electrostatically spray the silica precursor liquid onto both sides of the carbon fiber composite modified phenolic foam board. The spraying process parameters are: voltage 15~25kV, receiving distance 10~20cm, flow rate 3mL / h, drying at 40~60℃ for 4~6h to obtain flame-retardant and odorless nano phenolic board.

[0013] Furthermore, the microwave radiation source in step (2) is a 2400~2500MHz continuous wave with an output power of 50~70W and a duration of 1.5~3min.

[0014] Furthermore, the mass ratio of the modified phenolic resin, Tween-80, n-pentane, 40wt% sulfuric acid aqueous solution, and p-toluenesulfonic acid in step (2) is 35:4:8:20:20~45:8:16:30:30.

[0015] Furthermore, the process parameters for ultrasonic-magnetic field assisted microfluidic spinning in step (3) are as follows: extrusion pump feed rate 0.3 mL / h, receiving device rotary motor speed 400 r / min, stepper translation motor frequency 6000 Hz, ultrasonic frequency 21 kHz, vibration power 1000 W, vibration time 80 min, and magnetic field strength 0.3 T.

[0016] Furthermore, the conditions for the dual heating described in step (4) are as follows: the first heating time is 1~2h and the temperature is 1250~1350℃; the second heating time is 1~3min and the temperature is 150~200℃, the wave source is 2400~2500MHz continuous wave and the output power is 80~100W.

[0017] Furthermore, the preparation method of the silica precursor liquid in step (5) is as follows: tetraethyl orthosilicate, acetone, and 1wt% aqueous acetic acid solution are mixed in a mass ratio of 3:0.8:1.5~5:1.2:2.5.

[0018] Furthermore, the electrostatic spraying in step (5) is carried out in a nitric acid solution with a concentration of 10 mol / L at a temperature of 50~60℃.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] The board material of this invention is made by combining modified phenolic foam board with carbon fiber and then electrostatically spraying microcapsule flame retardant to achieve flame retardant and pressure resistant effects.

[0021] First, boron phenolic resin is generated by reacting p-hydroxyhexanone, formaldehyde, and 3-methoxy-4-methylphenylboronic acid. The boron element in this resin can block easily oxidized phenolic hydroxyl groups at high temperatures, causing it to crosslink and form a boron-oxy-boron bond structure. This reduces the distance between benzene rings, significantly improving the system's thermal properties. Furthermore, it can capture free phenolic hydroxyl groups, adhering to the matrix surface to form a stable and dense boron carbide layer, effectively isolating the resin from air. Even in the later stages of weight loss, it maintains a high char rate, thus achieving heat resistance and high flame retardancy. Next, the hydroxyl groups of p-hydroxyhexanone are cycloetherified, introducing an epoxy structure to produce a highly crosslinked polymeric network structure. Combined with a large number of benzene rings, this enhances the resin's mechanical strength, achieving compressive strength and improving the flame retardant properties of the board.

[0022] Secondly, melamine and polyacrylonitrile are spun into nanofiber membranes using ultrasonic-magnetic field-assisted microfluidic spinning. Ultrasonic vibration enhances the peristalsis of molecular chains in the spinning solution, thereby untangling them and reducing interaction forces. The magnetic field further aligns the molecular chains, increasing the fiber's orderliness and thus improving its strength, indirectly enhancing the compressive strength of the foam board. Double heating then carbonizes the fibers, further strengthening the matrix's compressive strength. Next, microwave radiation is used to increase the roughness of the carbon fiber membrane and the matrix, creating an uneven, textured structure that mechanically interlocks the fibers with the resin. Silica is then electrostatically sprayed onto both sides of the board. One side fills the foam pores, while the other side, during electrostatic spraying, is placed in an acidic water mist environment, stimulating the release of oxygen-containing groups from silica and carbon fibers. This allows the silica microcapsule flame retardant to graft onto the carbon fibers via hydrogen bonding, further enhancing the board's flame retardant effect and effectively preventing the smoldering of boron phenolic resin. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The test methods for various indicators of the flame-retardant and odorless nano-phenolic boards prepared in the following embodiments are as follows:

[0025] Compressive strength: Take examples and comparative examples of the same size and conduct compressive strength tests in accordance with GB / T5486.

[0026] Thermal insulation: Take the same size examples and comparative examples and test the thermal conductivity according to GB / T10294.

[0027] Flame retardancy: Examples and comparative examples of the same size were taken and subjected to UL94 horizontal and vertical burning tests according to GB / T2408 and GB / T2406.2 standards, and the LOI of the materials was tested.

[0028] Example 1

[0029] (1) Mix 37wt% formaldehyde aqueous solution and p-hydroxyhexanone at a mass ratio of 13:17, stir evenly, add 30wt% sodium hydroxide aqueous solution with a mass of 2 times that of p-hydroxyhexanone, heat to 55℃, stir at 70rpm for 1.5h, cool to 40℃, add 3-methoxy-4-methylphenylboronic acid with a mass of 1 times that of p-hydroxyhexanone and methanol with a mass of 0.4 times that of p-hydroxyhexanone, heat to 65℃, react for 2h, cool to 40℃ again, add 45wt% sodium hydroxide aqueous solution until the solution pH is [missing value]. 8. Distill at 35℃ and 800Pa for 1 hour, then add formic acid until the solution pH is 6.5, add epichlorohydrin at 1.5 times the mass of p-hydroxyhexanone and tetrabutylammonium bromide at 0.02 times the mass of p-hydroxyhexanone, heat to 75℃, and add sodium hydroxide at 0.25 times the mass of p-hydroxyhexanone in 4 portions within 60 minutes of reaction, continue the reaction for 2.5 hours, filter, take the solid, wash 3 times with deionized water at 50℃, and distill at 10℃ and 800Pa for 1 hour to obtain modified phenolic resin;

[0030] (2) The modified phenolic resin was placed in an oil bath at 80°C and stirred at 30 rpm for 0.5 h. Tween-80 and n-pentane were added and stirred at 70 rpm for 20 min. 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid were added and stirred for 1 min. The mixture was poured into a mold, allowed to stand for 60 min, demolded, and cured at 50°C for 8 h. Then it was subjected to microwave radiation with a wave source of 2400 MHz continuous wave and an output power of 50 W for 1.5 min to obtain the modified phenolic foam board. The mass ratio of the modified phenolic resin, Tween-80, n-pentane, 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid was 35:4:8:20:20.

[0031] (3) Melamine and N,N-dimethylformamide at 60℃ are mixed at a mass ratio of 0.5:20 and stirred at 70~100rpm for 1.5h. Polyacrylonitrile with a molecular weight of 81000 is added at 4 times the mass of melamine and stirred for another 10h to obtain spinning solution. Then, ultrasonic-magnetic field assisted microfluidic spinning is performed. The spinning process parameters are: extrusion pump feed rate 0.3mL / h, receiving device rotary motor speed 400r / min, stepper translation motor frequency 6000Hz, ultrasonic frequency 21kHz, vibration power 1000W, vibration time 80min, magnetic field strength 0.3T, and dried at 65℃ for 10h to obtain spun fibers.

[0032] (4) The spun fibers are heated twice; the first heating time is 1h and the temperature is 1250℃; the second heating time is 1min and the temperature is 150℃. The microwave radiation source is a 2400MHz continuous wave with an output power of 80W. After cooling, it is covered on the modified phenolic foam board to obtain carbon fiber composite modified phenolic foam board.

[0033] (5) Tetraethyl orthosilicate, acetone, and 1wt% acetic acid aqueous solution were mixed in a mass ratio of 3:0.8:1.5 to obtain a silica precursor solution. In a nitric acid solution with a concentration of 10mol / L, the silica precursor solution was electrostatically sprayed onto both sides of the carbon fiber composite modified phenolic foam board at 50℃. The spraying process parameters were: voltage 15kV, receiving distance 10cm, flow rate 3mL / h, and drying at 40℃ for 4h to obtain flame-retardant and odorless nano phenolic board.

[0034] Example 2

[0035] (1) Mix 37wt% formaldehyde aqueous solution and p-hydroxyhexanone at a mass ratio of 15:21, stir evenly, add 2.5 times the mass of p-hydroxyhexanone in 30wt% sodium hydroxide aqueous solution, heat to 62℃, stir at 85rpm for 2.5h, cool to 45℃, add 1.3 times the mass of p-hydroxyhexanone in 3-methoxy-4-methylphenylboronic acid and 0.5 times the mass of p-hydroxyhexanone in methanol, heat to 70℃, react for 2.5h, cool to 45℃ again, add 45wt% sodium hydroxide aqueous solution to the solution pH. The solution was distilled at 38°C and 900 Pa for 2 hours with a pH of 8.5. Formic acid was then added until the pH of the solution reached 6.8. Epichlorohydrin (2.3 times the mass of p-hydroxyhexanone) and tetrabutylammonium bromide (0.03 times the mass of p-hydroxyhexanone) were added. The temperature was raised to 80°C. Sodium hydroxide (0.3 times the mass of p-hydroxyhexanone) was added in four portions over 85 minutes of the reaction. The reaction was continued for 3.5 hours. The solution was filtered, and the solid was washed four times with deionized water at 50°C. The solution was then distilled at 15°C and 900 Pa for 1.5 hours to obtain the modified phenolic resin.

[0036] (2) The modified phenolic resin was placed in an oil bath at 80°C and stirred at 45 rpm for 1 h. Tween-80 and n-pentane were added and stirred at 85 rpm for 30 min. 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid were added and stirred for another 2 min. The mixture was poured into a mold, allowed to stand for 70 min, demolded, and cured at 65°C for 10 h. Then it was subjected to microwave radiation with a wave source of 2450 MHz continuous wave and an output power of 60 W for 2.5 min to obtain the modified phenolic foam board. The mass ratio of the modified phenolic resin, Tween-80, n-pentane, 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid was 40:6:12:25:25.

[0037] (3) Melamine and N,N-dimethylformamide at 60℃ were mixed at a mass ratio of 0.75:21.5 and stirred at 85 rpm for 2.5 h. Polyacrylonitrile with a molecular weight of 81000 was added at 6 times the mass of melamine and stirred for 12 h to obtain spinning solution. Then, ultrasonic-magnetic field assisted microfluidic spinning was performed. The spinning process parameters were: extrusion pump feed rate 0.3 mL / h, receiving device rotary motor speed 400 r / min, stepper translation motor frequency 6000 Hz, ultrasonic frequency 21 kHz, vibration power 1000 W, vibration time 80 min, magnetic field strength 0.3 T, and dried at 70℃ for 12 h to obtain spun fibers.

[0038] (4) The spun fibers are heated twice; the first heating time is 1.5h and the temperature is 1300℃; the second heating time is 1.5min and the temperature is 175℃. The microwave radiation source is a 2450MHz continuous wave with an output power of 90W. After cooling, it is covered on the modified phenolic foam board to obtain carbon fiber composite modified phenolic foam board.

[0039] (5) Tetraethyl orthosilicate, acetone and 1wt% acetic acid aqueous solution are mixed in a mass ratio of 4:1:2 to obtain silica precursor solution; in the environment of 10mol / L nitric acid solution, the silica precursor solution is electrostatically sprayed on both sides of carbon fiber composite modified phenolic foam board at 55℃. The spraying process parameters are: voltage 20kV, receiving distance 15cm, flow rate 3mL / h, and drying at 50℃ for 5h to obtain flame-retardant and odorless nano phenolic board.

[0040] Example 3

[0041] (1) Mix 37wt% formaldehyde aqueous solution and p-hydroxyhexanone at a mass ratio of 17:25, stir evenly, add 30wt% sodium hydroxide aqueous solution (3 times the mass of p-hydroxyhexanone), heat to 70℃, stir at 100rpm for 3h, cool to 50℃, add 1.5 times the mass of 3-methoxy-4-methylphenylboronic acid and 0.6 times the mass of p-hydroxyhexanone methanol, heat to 75℃, react for 3h, cool to 50℃ again, and add 45wt% sodium hydroxide aqueous solution to the solution. Distilled at pH 9, 40℃ and 1000Pa for 3 hours, then formic acid was added until the solution pH was 7. Epichlorohydrin (3 times the mass of p-hydroxyhexanone) and tetrabutylammonium bromide (0.04 times the mass of p-hydroxyhexanone) were added. The temperature was raised to 85℃, and sodium hydroxide (0.35 times the mass of p-hydroxyhexanone) was added in 4 portions over 90 minutes. The reaction was continued for 4 hours. The mixture was filtered, and the solid was washed 5 times with deionized water at 50℃. Distilled at 20℃ and 1000Pa for 3 hours to obtain modified phenolic resin.

[0042] (2) The modified phenolic resin was placed in an oil bath at 80°C and stirred at 60 rpm for 1.5 h. Tween-80 and n-pentane were added and stirred at 100 rpm for 40 min. 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid were added and stirred for another 3 min. The mixture was poured into a mold, allowed to stand for 80 min, demolded, and cured at 80°C for 12 h. Then it was subjected to microwave radiation with a wave source of 2500 MHz continuous wave and an output power of 70 W for 3 min to obtain the modified phenolic foam board. The mass ratio of the modified phenolic resin, Tween-80, n-pentane, 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid was 45:8:16:30:30.

[0043] (3) Melamine and N,N-dimethylformamide at 60℃ were mixed at a mass ratio of 1:23 and stirred at 100 rpm for 3 h. Polyacrylonitrile with a molecular weight of 81,000 was added at 8 times the mass of melamine and stirred for 14 h to obtain spinning solution. Then, ultrasonic-magnetic field assisted microfluidic spinning was performed. The spinning process parameters were: extrusion pump feed rate 0.3 mL / h, receiving device rotary motor speed 400 r / min, stepper translation motor frequency 6000 Hz, ultrasonic frequency 21 kHz, vibration power 1000 W, vibration time 80 min, magnetic field strength 0.3 T, and dried at 75℃ for 14 h to obtain spun fibers.

[0044] (4) The spun fibers are heated twice; the first heating time is 2 hours and the temperature is 1350℃; the second heating time is 3 minutes and the temperature is 200℃. The microwave radiation source is a 2500MHz continuous wave with an output power of 100W. After cooling, it is covered on the modified phenolic foam board to obtain carbon fiber composite modified phenolic foam board.

[0045] (5) Tetraethyl orthosilicate, acetone, and 1wt% acetic acid aqueous solution were mixed in a mass ratio of 5:1.2:2.5 to obtain a silica precursor solution. In a nitric acid solution with a concentration of 10mol / L, the silica precursor solution was electrostatically sprayed onto both sides of the carbon fiber composite modified phenolic foam board at 60℃. The spraying process parameters were: voltage 25kV, receiving distance 20cm, flow rate 3mL / h, and drying at 60℃ for 6h to obtain flame-retardant and odorless nano phenolic board.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 2 lies in step (1). Step (1) is changed as follows: 37wt% formaldehyde aqueous solution and p-hydroxyhexanone are mixed at a mass ratio of 15:21 and stirred evenly. Then, 2.5 times the mass of p-hydroxyhexanone in 30wt% sodium hydroxide aqueous solution is added. The mixture is heated to 62℃ and stirred at 85rpm for 2.5h. The temperature is then lowered to 45℃, and 0.5 times the mass of p-hydroxyhexanone in methanol is added. The temperature is then raised to 70℃ and reacted for 2.5h. The temperature is then lowered again to 45℃, and 45wt% sodium hydroxide aqueous solution is added until the solution pH is 8.5. The solution was distilled at 38°C and 900 Pa for 2 hours, then formic acid was added until the pH of the solution was 6.8. Epichlorohydrin (2.3 times the mass of p-hydroxyhexanone) and tetrabutylammonium bromide (0.03 times the mass of p-hydroxyhexanone) were added. The temperature was raised to 80°C, and sodium hydroxide (0.3 times the mass of p-hydroxyhexanone) was added in four portions over 85 minutes. The reaction was continued for 3.5 hours. The solution was filtered, and the solid was washed four times with deionized water at 50°C. The solution was then distilled at 15°C and 900 Pa for 1.5 hours to obtain the modified phenolic resin. The remaining steps were the same as in Example 2.

[0048] Comparative Example 2

[0049] The difference between Comparative Example 2 and Example 2 lies in step (1). Step (1) is changed as follows: 37wt% formaldehyde aqueous solution and p-hydroxyhexanone are mixed at a mass ratio of 15:21 and stirred evenly. Then, 30wt% sodium hydroxide aqueous solution with a mass of 2.5 times that of p-hydroxyhexanone is added. The mixture is heated to 62°C and stirred at 85 rpm for 2.5 h. The mixture is then cooled to 45°C and 3-methoxy-4-methylphenylboronic acid with a mass of 1.3 times that of p-hydroxyhexanone is added. The mixture is heated to 70°C and reacted for 2.5 h. The mixture is then cooled to 45°C again and 45wt% sodium hydroxide aqueous solution is added until the solution pH is 8.5. The mixture is then distilled at 38°C and 900 Pa for 2 h to obtain modified phenolic resin. The remaining steps are the same as in Example 2.

[0050] Comparative Example 3

[0051] The difference between Comparative Example 3 and Example 2 is that steps (3) and (4) are omitted; the remaining steps are the same as in Example 2.

[0052] Comparative Example 4

[0053] The difference between Comparative Example 4 and Example 2 is that step (5) is omitted; the remaining steps are the same as in Example 2.

[0054] Comparative Example 5

[0055] The difference between Comparative Example 5 and Example 2 is that steps (3), (4) and (5) are omitted. Step (1) is changed to: 37wt% formaldehyde aqueous solution and p-hydroxyphenylhexanone are mixed at a mass ratio of 15:21 and stirred evenly. Then, 30wt% sodium hydroxide aqueous solution with a mass of 2.5 times that of p-hydroxyphenylhexanone is added. The mixture is heated to 62°C, stirred at 85 rpm for 2.5 h, cooled to 45°C, and distilled at 38°C and 900 Pa for 2 h to obtain phenolic resin. The remaining steps are the same as in Example 2.

[0056] Example of effect

[0057] Table 1 below shows the performance analysis results of the flame-retardant and odorless nano-phenolic boards produced using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0058] Table 1

[0059]

[0060] A comparison of the test data from the examples and comparative examples reveals that the boron phenolic resin generated by reacting p-hydroxyhexanone, formaldehyde, and 3-methoxy-4-methylphenylboronic acid can block easily oxidized phenolic hydroxyl groups under high-temperature conditions, forming a stable and dense boron carbide layer on the matrix surface, thus isolating it from air and achieving heat resistance and high flame retardancy. Furthermore, introducing an epoxy structure into the boron phenolic resin creates a polymeric network structure, enhancing the resin's mechanical strength. Carbon fibers produced using melamine and polyacrylonitrile through ultrasonic-magnetic field-assisted microfluidic spinning and dual heating can indirectly enhance the compressive strength of the foam board. Microwave radiation further improves the roughness of the carbon fiber film and the matrix, creating a mechanical bond between the fiber and the resin. Finally, electrostatic spraying of silica onto both sides of the board enhances its flame retardant effect.

[0061] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A fire-resistant, tasteless, nanophenol-formaldehyde plate, characterized in that, The flame-retardant and odorless nano-phenolic board is prepared by modifying phenolic foam board and composite carbon fiber, followed by electrostatic spraying of silica; the preparation method of the flame-retardant and odorless nano-phenolic board includes the following preparation steps: (1) Mix 37wt% formaldehyde aqueous solution and p-hydroxyhexanone at a mass ratio of 15:21, stir evenly, add 2.5 times the mass of p-hydroxyhexanone in 30wt% sodium hydroxide aqueous solution, heat to 62℃, stir at 85rpm for 2.5h, cool to 45℃, add 1.3 times the mass of p-hydroxyhexanone in 3-methoxy-4-methylphenylboronic acid and 0.5 times the mass of p-hydroxyhexanone in methanol, heat to 70℃, react for 2.5h, cool to 45℃ again, add 45wt% sodium hydroxide aqueous solution to the solution pH. The solution was distilled at 38°C and 900 Pa for 2 hours with a pH of 8.

5. Formic acid was then added until the pH of the solution reached 6.

8. Epichlorohydrin (2.3 times the mass of p-hydroxyhexanone) and tetrabutylammonium bromide (0.03 times the mass of p-hydroxyhexanone) were added. The temperature was raised to 80°C. Sodium hydroxide (0.3 times the mass of p-hydroxyhexanone) was added in four portions over 85 minutes of the reaction. The reaction was continued for 3.5 hours. The solution was filtered, and the solid was washed four times with deionized water at 50°C. The solution was then distilled at 15°C and 900 Pa for 1.5 hours to obtain the modified phenolic resin. (2) The modified phenolic resin was placed in an oil bath at 80°C and stirred at 45 rpm for 1 h. Tween-80 and n-pentane were added and stirred at 85 rpm for 30 min. 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid were added and stirred for another 2 min. The mixture was poured into a mold, allowed to stand for 70 min, demolded, and cured at 65°C for 10 h. Then it was subjected to microwave radiation with a wave source of 2450 MHz continuous wave and an output power of 60 W for 2.5 min to obtain the modified phenolic foam board. The mass ratio of the modified phenolic resin, Tween-80, n-pentane, 40 wt% sulfuric acid aqueous solution and p-toluenesulfonic acid was 40:6:12:25:

25. (3) Melamine and N,N-dimethylformamide at 60℃ were mixed at a mass ratio of 0.75:21.5 and stirred at 85 rpm for 2.5 h. Polyacrylonitrile with a molecular weight of 81000 was added at 6 times the mass of melamine and stirred for 12 h to obtain spinning solution. Then, ultrasonic-magnetic field assisted microfluidic spinning was performed. The spinning process parameters were: extrusion pump feed rate 0.3 mL / h, receiving device rotary motor speed 400 r / min, stepper translation motor frequency 6000 Hz, ultrasonic frequency 21 kHz, vibration power 1000 W, vibration time 80 min, magnetic field strength 0.3 T, and dried at 70℃ for 12 h to obtain spun fibers. (4) The spun fibers are heated twice; the first heating time is 1.5h and the temperature is 1300℃; the second heating time is 1.5min and the temperature is 175℃. The microwave radiation source is a 2450MHz continuous wave with an output power of 90W. After cooling, it is covered on the modified phenolic foam board to obtain carbon fiber composite modified phenolic foam board. (5) tetraethyl orthosilicate, acetone, 1wt% acetic acid aqueous solution are mixed according to the mass ratio of 4:1:2 to obtain a silica precursor solution; the silica precursor solution is electrostatically sprayed on both sides of the carbon fiber composite modified phenolic foam board in a 10mol / L nitric acid solution environment at 55℃, the spraying process parameters are: voltage 20kV, receiving distance 15cm, flow rate 3mL / h, and the obtained product is dried at 50℃ for 5h to obtain a non-smelly nano-phenolic board with fire resistance.

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