Lightweight glass fiber reinforced fire-retardant fireproof tank box and preparation method thereof

Abstract

The application discloses a light-weight glass fiber reinforced fire-retardant fireproof tank box and a preparation method thereof, and belongs to the technical field of fireproof tank boxes. The tank box is prepared from a boron-modified phenolic resin with a boron-oxygen six-membered ring structure by chemical bonding as a matrix, modified glass fiber cloth with a diamino DOPO fire-retardant structure grafted by Schiff base reaction on the surface, and components such as a curing agent and a synergistic fire retardant. In the preparation, the boron-modified phenolic resin and the diamino DOPO fire-retardant intermediate are first synthesized, then the glass fiber surface is modified through oxygen plasma activation, silane coupling and two-step Schiff base reaction, and finally the tank box is formed by segmental temperature rising mold curing after being impregnated with glue solution. The tank box has the characteristics of high fire resistance limit, excellent mechanical retention and light weight and low smoke, can effectively block the glass fiber candle core effect, and is suitable for cable fire protection in power, data center and other scenes.

Description

Technical Field

[0001] This invention relates to the technical field of fireproof slot boxes, and in particular to a lightweight glass fiber reinforced flame-retardant fireproof slot box and its preparation method. Background Technology

[0002] With the rapid development of power transmission, data centers, and rail transportation, the scale of cable laying continues to expand. Fire-resistant cable trays, as crucial passive fire protection components, play a vital role in fire separation, preventing the spread of flames, and protecting the safe operation of internal cables. Their fire resistance, mechanical reliability, and installation compatibility directly impact the fire safety of power systems. In recent years, the industry has continuously raised the performance requirements for fire-resistant cable trays, demanding not only compliance with relevant fire resistance standards but also lightweight, weather-resistant, low-smoke, and non-toxic properties. However, existing mainstream fire-resistant cable tray technologies all have varying degrees of performance shortcomings, making them unsuitable for the needs of high-level fire protection scenarios.

[0003] Currently, fireproof cable trays on the market are mainly divided into two categories: inorganic materials and organic fiberglass reinforced materials. Inorganic fireproof cable trays are mostly made of magnesium oxychloride cement, magnesium chloride, or silicate substrates, which have the advantages of good non-combustibility and low raw material cost. However, they generally have the problems of heavy weight and high brittleness, and are prone to cracking during transportation and installation. They also have poor water and weather resistance, and are prone to efflorescence and frost in humid environments, which can corrode the internal cables and shorten their service life. At the same time, inorganic cable trays are difficult to cut and splice on site, resulting in low installation efficiency, and cannot meet the lightweight application requirements of large-span cable trays and complex laying scenarios.

[0004] Organic fiberglass reinforced fireproof slots use unsaturated polyester resin, ordinary phenolic resin, etc. as the matrix, reinforced with fiberglass cloth. They have advantages such as light weight, high mechanical strength, corrosion resistance, and easy processing and molding. However, their flame-retardant and fire-resistant properties have obvious shortcomings. Although ordinary phenolic resin has a certain degree of self-extinguishing properties, the char layer formed at high temperatures is loose and porous, and easily powders and falls off, failing to form a continuous and effective heat insulation barrier layer, resulting in a generally low fire resistance limit. At the same time, the two-phase interface between the fiberglass and the resin matrix is ​​a weak area for combustion. At high temperatures, the resin shrinks and easily debonds from the fiberglass, producing a significant "wick effect." Flames and heat can quickly penetrate into the material along the fiberglass interface, further shortening the fire resistance time. In severe cases, it can lead to the collapse of the slot structure and loss of fire protection.

[0005] To improve the flame-retardant and fire-resistant properties of organic fiberglass troughs, the industry's conventional approach is to add large amounts of inorganic flame-retardant fillers such as aluminum hydroxide and magnesium hydroxide to the resin matrix, relying on the endothermic decomposition and dilution effects of the fillers to increase the oxygen index. However, this approach has significant problems: to achieve the ideal flame-retardant effect, the amount of filler added is usually high, which significantly increases the material density and greatly increases the weight of the trough. At the same time, the compatibility between inorganic fillers and the resin matrix is ​​limited, and high filler content will deteriorate the mechanical properties of the matrix, increase the brittleness of the material, and exacerbate the risk of interface cracking and char layer detachment at high temperatures. In addition, the combustion of fillers will generate a large number of inorganic aerosol particles, significantly increasing the smoke density of the material, reducing visibility in fire scenarios, and hindering personnel escape and rescue operations. The industry has also tried chemical modification approaches, such as boron modification of phenolic resin to improve the char-forming properties of the matrix, or surface flame-retardant coating of glass fiber to improve interfacial performance. However, single modification has performance bottlenecks: boron modification can only optimize the char-forming quality of the resin matrix itself and cannot solve the wicking effect at the glass fiber interface; the physical flame-retardant coating on the glass fiber surface has poor adhesion and is prone to peeling and failure under long-term use or humid and hot conditions, and cannot form chemical bonds with the resin matrix. Interfacial debonding will still occur at high temperatures, making it difficult to achieve a leapfrog improvement in fire resistance.

[0006] In summary, existing glass fiber reinforced resin-based fireproof troughs have consistently struggled to overcome the technical dilemma of mutual constraints between flame retardant performance, mechanical strength, and material density. They cannot simultaneously achieve high fire resistance limits, high mechanical strength retention rates, and low smoke and non-toxicity while maintaining low weight, thus failing to meet the actual needs of high-level fire protection in power systems. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a lightweight glass fiber reinforced flame-retardant fireproof slot box and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a lightweight glass fiber reinforced flame-retardant fireproof slot box, comprising the following components by weight: boron modified phenolic resin: 40-55 parts, modified glass fiber cloth: 30-40 parts, curing agent: 3-6 parts, curing accelerator: 0.5-2 parts, synergistic flame retardant: 2-5 parts, processing aid: 1-3 parts.

[0009] Preferably, the boron-modified phenolic resin is synthesized in two steps from phenol, formaldehyde aqueous solution and boric acid, wherein boron is chemically bonded to the main chain of the phenolic resin molecule in a boron-oxygen six-membered ring structure.

[0010] Preferably, the modified glass fiber cloth is prepared by first grafting the surface of the alkali-free glass fiber cloth with silane coupling agent KH-550, then reacting it with terephthalaldehyde through a Schiff base reaction to make the surface contain aldehyde functional groups, and finally reacting it with the diamino DOPO flame retardant intermediate through a Schiff base reaction.

[0011] Preferably, the molecular structure of the diaminoDOPO flame-retardant intermediate is as follows: .

[0012] Preferably, the curing agent is hexamethylenetetramine.

[0013] Preferably, the curing accelerator is magnesium oxide or zinc oxide.

[0014] Preferably, the synergistic flame retardant is organically modified montmorillonite with a layer spacing ≥2.5 nm.

[0015] Preferably, the processing aid is zinc stearate.

[0016] Furthermore, the present invention also provides a method for preparing a lightweight glass fiber reinforced flame-retardant fireproof slot box, comprising the following steps: (1) Phenol and formaldehyde are added to a reaction apparatus equipped with a stirrer, thermometer and condenser. After stirring evenly, sodium hydroxide is added, the temperature is raised to 55-65℃, and the reaction is carried out for 1-2 hours to complete the first stage reaction. Then, the product is dehydrated under reduced pressure. In the second stage, boric acid is added to the dehydrated reaction vessel, the temperature is raised to 85-95℃, and the reaction is carried out for 1-2 hours to complete the second stage reaction. Then, the product is dehydrated under reduced pressure again. The reactants are poured out while hot, cooled to room temperature, and then dried under vacuum to obtain boron-modified phenolic resin. The chemical reaction is shown in the following diagram: ; In the first stage, under alkaline catalysis, phenol and formaldehyde react to generate ortho- or para-substituted hydroxymethylated products. At this temperature, the generated hydroxymethyl groups undergo mild dehydration condensation with hydrogen on the phenol ring, forming a small number of methylene bridges. This gradually forms a low-molecular-weight linear / branched methyl phenolic oligomer. In the second stage, after the addition of boric acid, electron-deficient boron atoms coordinate with ortho- and benzylic hydroxyl groups on the phenolic molecule, accompanied by a dehydration reaction, forming a stable six-membered boron-oxygen heterocycle structure. Boron is chemically bonded to the phenolic resin molecule backbone. In this stage, the temperature increase simultaneously promotes the condensation reaction, further increasing the resin molecular weight. However, the overall structure remains in a low-crosslinking methyl prepolymer state, retaining sufficient free hydroxymethyl groups for subsequent curing and crosslinking. (2) Under nitrogen protection, DOPO and 4,4'-diaminobenzophenone were added to the reaction vessel and heated to 180-200℃ with stirring. The reaction was carried out for 2-4 hours. After the reaction was completed, the system was cooled to 100℃, toluene was added to the flask, and the precipitate was dispersed by stirring. The precipitate was filtered while hot, and the filter cake was washed three times with toluene. The filter cake was recrystallized in tetrahydrofuran, and the solid was collected after filtration and dried to obtain the diaminoDOPO flame retardant intermediate. The chemical reaction equation is as follows: ; This reaction is a nucleophilic addition reaction of phosphorus-hydrogen bonds to carbonyl groups. In the high-temperature molten state, the PH bond in the DOPO molecule breaks, and the phosphorus atom forms a stable CP covalent bond with the carbonyl carbon. Since 4,4'-diaminobenzophenone contains only one carbonyl reaction site, two DOPO molecules will symmetrically add to the same carbonyl carbon. The aromatic primary amino groups on the benzene rings at both ends of the molecule do not participate in the reaction and are thus preserved intact, providing reaction sites for subsequent Schiff base grafting. (3) Clean, alkali-free glass fibers are placed in an oxygen plasma treatment instrument for oxygen plasma treatment to obtain activated glass fiber cloth; prepare an ethanol-water solution of silane coupling agent KH550, adjust the pH to 4.0-4.5 with glacial acetic acid, stir and pre-hydrolyze at room temperature for 20-40 min, completely immerse the activated glass fiber cloth in the ethanol-water solution of silane coupling agent KH550, heat to 50-70℃, shake and react for 2-3 h, remove, ultrasonically clean with ethanol 3 times, and dry to obtain surface-aminated glass fiber cloth; the chemical reaction is shown below: ; Oxygen plasma treatment etches the glass fiber surface with high-energy particles, introducing a large number of active silanol groups and polar groups while etching the rough surface, thereby enhancing surface reactivity. KH-550 undergoes pre-hydrolysis in a weakly acidic water-alcohol system, where ethoxy groups are replaced by hydroxyl groups to generate silanol intermediates with multiple silanol groups. After immersing the activated glass fiber in the solution, the silanol silanol undergoes a dehydration condensation reaction with the silanol groups on the glass fiber surface, forming stable Si-O-Si covalent bonds. This anchors the silane molecules to the glass fiber surface, while the amino groups at the other end of the molecule are exposed, completing the amylation modification of the glass fiber surface. (4) Prepare a terephthalaldehyde ethanol solution, completely immerse the surface-aminated glass fiber cloth in the terephthalaldehyde ethanol solution, adjust the pH of the system to 5.0-6.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 50-60℃, shake and react for 3-5 hours, remove, ultrasonically clean with ethanol 3 times, and dry to obtain surface-terminated aldehyde-based glass fiber cloth; the chemical reaction is shown below: ; This step is a typical Schiff base condensation reaction. Under weakly acidic catalytic conditions, one aldehyde group in the terephthalaldehyde molecule is protonated and activated. The primary amino group on the glass fiber surface acts as a nucleophile to attack the activated aldehyde carbon, undergoing nucleophilic addition and dehydration reactions in sequence to generate a product containing an imine bond (C=N). This covalently attaches terephthalaldehyde to the glass fiber surface. In the reaction system, terephthalaldehyde is in large excess, and kinetically, single-molecule single-end grafting preferentially occurs. This effectively avoids bridging side reactions where one aldehyde molecule is simultaneously attached to two surface amino groups, ensuring that the aldehyde group at the other end of the molecule is exposed to the outside. The 4A molecular sieve added to the system can adsorb the water molecules generated in the reaction, promoting the reversible Schiff base reaction in the forward direction and increasing the surface grafting rate. (5) Prepare a bisaminoDOPO flame retardant intermediate ethanol / tetrahydrofuran solution, completely immerse the surface-terminated aldehyde-modified glass fiber cloth in the bisaminoDOPO flame retardant intermediate ethanol / tetrahydrofuran solution, adjust the pH of the system to 5.0-6.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 60-70℃, shake and react for 2-4 hours, remove, ultrasonically clean with ethanol 3 times, and dry to obtain modified glass fiber cloth; the chemical reaction is shown below: ; This step is also a Schiff base condensation reaction. Under weakly acidic conditions, the aldehyde groups exposed on the glass fiber surface are protonated and activated. An aromatic primary amino group in the diamino DOPO flame retardant intermediate molecule attacks the aldehyde group, forming an imine bond through nucleophilic addition and dehydration. This covalently grafts the phosphorus-nitrogen flame retardant structure onto the glass fiber surface. Since the diamino DOPO intermediate is in excess relative to the surface aldehyde groups in the reaction system, each aldehyde group only reacts with one side of the amino group of a diamine molecule. The aromatic primary amino group at the other end of the molecule is retained outward and can participate in the crosslinking reaction in the subsequent resin curing stage to achieve covalent bonding between the glass fiber and the resin matrix. (6) After crushing the boron-modified phenolic resin, add anhydrous ethanol to dissolve it and prepare a resin solution. Add curing agent, curing accelerator, synergistic flame retardant and processing aid in sequence, stir for 20-40 minutes to obtain impregnation solution. Completely immerse the modified glass fiber cloth in the impregnation solution. After fully wetting, take it out and pre-dry it in an oven for 10-15 minutes to obtain prepreg. Cut the prepreg according to the design and lay it in the mold of the slot box. Send it into the flat vulcanizing machine and cure it by segmented heating and pressure. After curing, cool it down to below 60°C, demold the product, trim the edges and remove burrs to obtain a lightweight glass fiber reinforced flame retardant fireproof slot box.

[0017] Preferably, the formaldehyde in (1) is an aqueous solution with a volume fraction of 37-40%.

[0018] Preferably, the molar ratio of phenol, formaldehyde and boric acid in (1) is 1:1.3-1.5:0.3-0.5.

[0019] Preferably, the amount of sodium hydroxide used in (1) is 2-5% of the mass of phenol.

[0020] Preferably, in (2), the molar ratio of DOPO and 4,4'-diaminobenzophenone is 4-6:1.

[0021] Preferably, the oxygen plasma treatment in (3) has a power of 160-200W, an oxygen flow rate of 10-30mL / min, and a treatment time of 3-5min.

[0022] Preferably, the concentration of the ethanol aqueous solution of the silane coupling agent KH550 in (3) is 2-5 wt%, and the volume ratio of ethanol to water is 9:1.

[0023] Preferably, the concentration of the terephthalaldehyde ethanol solution in (4) is 0.2-0.5 mol / L.

[0024] Preferably, the concentration of the ethanol / tetrahydrofuran solution of the diaminoDOPO flame retardant intermediate in (5) is 0.2-0.4 mol / L, and the volume ratio of ethanol to tetrahydrofuran is 1:1-3.

[0025] Preferably, the solid content of the resin solution in (6) is 50-60%.

[0026] Preferably, the temperature of the oven in (6) is 80-90℃.

[0027] Preferably, the segmented heating and pressurization process in (6) is as follows: in the first stage, the temperature is raised to 120-130℃, the pressure is applied to 8-10MPa, and the temperature and pressure are maintained for 15-20 minutes; in the second stage, the temperature is raised to 160-170℃, the pressure is increased to 12-15MPa, and the temperature and pressure are maintained for 25-30 minutes.

[0028] Preferably, the working mechanism of the lightweight glass fiber reinforced flame-retardant fireproof slot box of the present invention is explained as follows: The flame-retardant effect of the lightweight glass fiber reinforced flame-retardant fireproof slot box of this invention originates from the intrinsic char-forming and heat-insulating properties of boron-modified phenolic resin. After phenol and formaldehyde undergo hydroxymethylation and mild condensation to form a methyl phenolic prepolymer, boric acid, through coordination dehydration reactions with ortho-phenolic hydroxyl and benzyl hydroxyl groups, is incorporated into the resin molecular chain via a boron-oxygen six-membered ring structure, becoming part of a three-dimensional cross-linked network after curing. During high-temperature combustion, boron gradually transforms into a molten borate glass phase as the resin degrades. On one hand, this phase catalyzes the aromatization reaction of the phenolic backbone, promoting rapid char formation, increasing the high-temperature char residue rate, and reducing the release of combustible small molecules and combustion heat. On the other hand, the molten glassy substance fills the pores and microcracks within the char layer, forming a continuous and dense barrier layer that prevents external oxygen from diffusing into the material and simultaneously blocks external heat transfer into the slot box, slowing down the rate of internal temperature rise. Compared with ordinary phenolic resins, the chemically bonded boron structure significantly improves the thermal stability and thermal shock resistance of the carbon layer, preventing the carbon layer from rapidly pulverizing and falling off at high temperatures.

[0029] The phosphorus-nitrogen flame-retardant interface layer on the modified glass fiber surface plays a dual role in interface flame retardancy and interface reinforcement. After grafting with a silane coupling agent and undergoing a two-step Schiff base reaction, the DOPO diamino flame-retardant structure of the alkali-free glass fiber is covalently anchored on the glass fiber surface, allowing phosphorus and nitrogen elements to be precisely enriched at the interface between the glass fiber and the resin, which is precisely the weak point in the combustion of glass fiber-reinforced flame-retardant materials. At high temperatures, the DOPO phosphorus-phenanthroline structure at the interface preferentially decomposes, releasing phosphorus-containing active free radicals, which can quench the chain reaction in gas-phase combustion and inhibit flame propagation. At the same time, the phosphorus decomposition products can catalyze the premature carbonization of the resin matrix near the interface, forming a tightly wrapped phosphorus-nitrogen carbon layer on the glass fiber surface, fundamentally blocking the "wick effect" of the glass fiber and preventing the glass fiber from acting as a heat conduction and ignition channel to guide the flame into the interior of the material. Meanwhile, the aromatic primary amino groups retained on the outer side of the diamino DOPO molecule can undergo dehydration condensation with the free hydroxymethyl groups of boron phenolic resin during the molding and curing process to form methylene bridges. This allows the glass fiber and the resin matrix to achieve chemical bonding through covalent bonds, replacing the physical entanglement and hydrogen bonding in traditional modification. This eliminates interfacial defects at the molecular level, avoids interfacial debonding and cracking caused by resin shrinkage at high temperatures, and blocks the path of flame and high-temperature flue gas penetration along the interface. It also improves the interfacial bonding strength and high-temperature mechanical retention of the composite material.

[0030] The boron phase in the matrix and the phosphorus-nitrogen phase at the interface can form a synergistic flame-retardant effect through spatial partitioning, resulting in a performance improvement far exceeding the linear superposition of single modifications. In this system, boron is mainly distributed in the resin bulk phase, responsible for constructing the overall heat-insulating char layer framework; phosphorus-nitrogen is concentrated in the glass fiber-resin interface phase, responsible for sealing weak combustion areas and inhibiting interface failure. During high-temperature degradation, the borate glass phase generated in the matrix phase has a certain melt fluidity, which can penetrate and fill the microcracks in the phosphorus-nitrogen char layer at the interface, fusing with the phosphorus-nitrogen char layer to form a crack-free, high-strength boron-phosphorus-nitrogen composite ceramicized char layer. This composite char layer combines the rapid char formation characteristics of the phosphorus-nitrogen char layer with the dense barrier properties of the borate glass phase, resulting in a lower thermal conductivity and stronger resistance to flame penetration. At the same time, boron and phosphorus-nitrogen can produce a synergistic catalytic char formation effect in the condensed phase, further improving the graphitization degree and residual char content of the char layer, jointly extending the fire resistance limit of the tank.

[0031] Organo-montmorillonite exhibits excellent compatibility with phenolic resin, allowing it to be exfoliated and dispersed into nanosheet structures within the matrix. This extends the diffusion path of combustible gases and heat, acting as a physical barrier. Simultaneously, the nanosheets serve as an inorganic framework, enhancing the mechanical strength of the char layer and reducing cracking and spalling under thermal shock. Glass fiber, as a continuous reinforcing phase, combined with the strong bonding of interfacial covalent bonds, ensures that even after partial resin degradation at high temperatures, the tank maintains its overall structural integrity, preventing breakage, collapse, or other failure modes, thus continuously providing fire protection for the internal facilities.

[0032] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention incorporates boron into the phenolic resin molecular backbone through chemical bonding, while simultaneously constructing a phosphorus-nitrogen type flame-retardant interface layer on the glass fiber surface. These two elements create a spatially partitioned, synergistic flame-retardant effect. At high temperatures, the matrix borate glass phase and the interface phosphorus-nitrogen carbon layer can interpenetrate and fuse to form a dense composite ceramicized carbon layer. This not only improves the carbonization rate of the matrix and the thermal stability of the carbon layer but also blocks the wicking effect of the glass fiber, significantly extending the fire resistance limit of the slot. The flame-retardant performance far exceeds that of single modification schemes, achieving a high level of fire protection without relying on highly filled inorganic flame retardants.

[0033] 2. This invention grafts a flame-retardant intermediate with active amino groups onto the surface of glass fiber through a two-step Schiff base reaction. During the curing process, it can form covalent bonds with the free hydroxymethyl groups of phenolic resin, eliminating interfacial defects between glass fiber and resin, effectively improving interfacial bonding strength and load transfer efficiency, significantly improving the room temperature mechanical properties of the slot box, while avoiding interfacial debonding and cracking caused by resin shrinkage at high temperatures, greatly improving the high temperature mechanical retention rate, and ensuring the structural integrity of the slot box in fire scenarios.

[0034] 3. This invention achieves both flame retardancy and reinforcement through chemical modification, eliminating the need for large amounts of inorganic flame retardant fillers. The material's weight is comparable to that of ordinary glass fiber reinforced phenolic systems, effectively reducing installation load and transportation costs, and adapting to the laying requirements of large-span cable trays. At the same time, the flame retardant mechanism, which is mainly based on condensed phases, reduces the release of combustible small molecules and smoke, lowers the density of combustion smoke and the amount of toxic smoke generated, and improves the safety of escape and rescue in fire scenarios, meeting the low-smoke and non-toxic requirements for fire prevention in power engineering.

[0035] 4. The boron-modified phenolic resin synthesized in this invention has mild and controllable reaction conditions; the glass fiber surface modification adopts a liquid-phase impregnation reaction, the process parameters are easy to control, the grafting uniformity is good, no special complex equipment is required, it can be well integrated with the existing compression molding process, the production process has low energy consumption and low pollutant emissions, and the prepared slot box products have good performance uniformity, making them suitable for large-scale industrial production and engineering promotion and application. Attached Figure Description

[0036] Figure 1 The image shows the 1H NMR spectrum of the bisaminoDOPO flame-retardant intermediate prepared in Example 2 of this invention. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Example 1: A specific preparation method of a lightweight glass fiber reinforced flame-retardant fireproof slot box, comprising the following steps: (1) Add 2 mol of phenol and 2.6 mol of formaldehyde (37% formaldehyde aqueous solution by volume) to a reaction apparatus equipped with a stirrer, thermometer and condenser. After stirring evenly, add sodium hydroxide at 2% of the mass of phenol, heat to 55°C and react for 1 h to complete the first stage reaction. Then dehydrate under reduced pressure. In the second stage, add 0.6 mol of boric acid to the dehydrated reaction vessel, heat to 85°C and react for 1 h to complete the second stage reaction. Then dehydrate under reduced pressure again, pour out the reactants while hot, cool to room temperature and dry under vacuum to obtain boron-modified phenolic resin. (2) Under nitrogen protection, 0.4 mol DOPO and 0.1 mol 4,4'-diaminobenzophenone were added to the reaction vessel, and the temperature was raised to 180°C with stirring. The reaction was carried out for 2 hours. After the reaction was completed, the system was cooled to 100°C, toluene was added to the flask, and the precipitate was filtered while hot after stirring and dispersion. The filter cake was washed repeatedly with toluene 3 times. The filter cake was recrystallized in tetrahydrofuran, and the solid was collected after filtration and dried to obtain the bisaminoDOPO flame retardant intermediate. (3) Clean alkali-free glass fiber is placed in an oxygen plasma treatment instrument for oxygen plasma treatment. The treatment power is 160W, the oxygen flow rate is 10mL / min, and the treatment time is 3min to obtain activated glass fiber cloth. Prepare an ethanol aqueous solution of 2% by mass of silane coupling agent KH550, with a volume ratio of ethanol to water of 9:1. Adjust the pH to 4.0 with glacial acetic acid. Stir and pre-hydrolyze at room temperature for 20min. Immerse the activated glass fiber cloth completely in the ethanol aqueous solution of silane coupling agent KH550, heat to 50℃, and shake for 2h. Take out the glass fiber cloth, ultrasonically clean it with ethanol 3 times, and dry it to obtain surface aminated glass fiber cloth. (4) Prepare a 0.2 mol / L terephthalaldehyde ethanol solution, completely immerse the surface aminated glass fiber cloth in the terephthalaldehyde ethanol solution, adjust the pH of the system to 5.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 50℃, shake and react for 3 hours, take it out, ultrasonically clean it with ethanol 3 times, and dry it to obtain the surface end aldehyde-modified glass fiber cloth; (5) Prepare a 0.2 mol / L ethanol / tetrahydrofuran solution of the DOPO flame retardant intermediate, with a volume ratio of ethanol to tetrahydrofuran of 1:1. Completely immerse the surface-terminated aldehyde-based glass fiber cloth in the ethanol / tetrahydrofuran solution of the DOPO flame retardant intermediate, adjust the pH of the system to 5.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 60℃, shake and react for 2 hours, remove, ultrasonically clean with ethanol 3 times, and dry to obtain the modified glass fiber cloth. (6) Take 40 parts of boron-modified phenolic resin, crush it, add anhydrous ethanol to dissolve it, and prepare a resin solution with a solid content of 50%; add 3 parts of hexamethylenetetramine, 0.5 parts of magnesium oxide, 2 parts of organic modified montmorillonite, and 1 part of zinc stearate in sequence, stir for 20 minutes to obtain impregnation solution; completely immerse 30 parts of modified glass fiber cloth in impregnation solution, after fully wetting, take it out and pre-dry it in an 80℃ oven for 10 minutes to obtain prepreg; cut the prepreg into 200mm×100mm sheets according to the design, and lay 6 layers in the tank. In the box forming mold, the mold cavity corresponds to a groove box sample with a forming length of 200mm, a width of 100mm, a side height of 50mm, and a wall thickness of 4mm. It is sent into a flat vulcanizing machine and cured using a segmented heating and pressurizing process: the first stage heats up to 120℃, applies a pressure of 8MPa, and holds the temperature and pressure for 15min; the second stage heats up to 160℃, increases the pressure to 12MPa, and holds the temperature and pressure for 25min; after curing, the temperature is cooled down to below 60℃, the product is demolded and removed, the edges are trimmed and deburred, and a lightweight glass fiber reinforced flame-retardant fireproof groove box is obtained.

[0039] Example 2: A specific preparation method of a lightweight glass fiber reinforced flame-retardant fireproof slot box, comprising the following steps: (1) Add 2 mol of phenol and 2.8 mol of formaldehyde (38% formaldehyde aqueous solution by volume) to a reaction apparatus equipped with a stirrer, thermometer and condenser. After stirring evenly, add sodium hydroxide at 3% of the mass of phenol, heat to 60°C and react for 1.5 h to complete the first stage reaction. Then dehydrate under reduced pressure. In the second stage, add 0.8 mol of boric acid to the dehydrated reaction vessel, heat to 90°C and react for 1.5 h to complete the second stage reaction. Then dehydrate under reduced pressure again, pour out the reactants while hot, cool to room temperature and dry under vacuum to obtain boron-modified phenolic resin. (2) Under nitrogen protection, 0.5 mol DOPO and 0.1 mol 4,4'-diaminobenzophenone were added to the reaction vessel and heated to 190°C with stirring. The reaction was carried out for 3 hours. After the reaction was completed, the system was cooled to 100°C. Toluene was added to the flask and stirred to disperse the precipitate. The precipitate was filtered while hot. The filter cake was washed three times with toluene. The filter cake was recrystallized in tetrahydrofuran. The solid was collected after filtration and dried to obtain the bisaminoDOPO flame retardant intermediate. (3) Clean alkali-free glass fiber is placed in an oxygen plasma treatment instrument for oxygen plasma treatment. The treatment power is 180W, the oxygen flow rate is 20mL / min, and the treatment time is 4min to obtain activated glass fiber cloth. Prepare an ethanol aqueous solution of 4% by mass of silane coupling agent KH550, with a volume ratio of ethanol to water of 9:1. Adjust the pH to 4.2 with glacial acetic acid. Stir and pre-hydrolyze at room temperature for 30min. Completely immerse the activated glass fiber cloth in the ethanol aqueous solution of silane coupling agent KH550, heat to 60℃, and shake for 2.5h. Take out the glass fiber cloth, ultrasonically clean it with ethanol 3 times, and dry it to obtain surface-aminated glass fiber cloth. (4) Prepare a 0.35 mol / L terephthalaldehyde ethanol solution, completely immerse the surface aminated glass fiber cloth in the terephthalaldehyde ethanol solution, adjust the pH of the system to 5.5 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 55℃, shake and react for 4 hours, take it out, ultrasonically clean it with ethanol 3 times, and dry it to obtain the surface aldehyde-terminated glass fiber cloth. (5) Prepare a 0.3 mol / L ethanol / tetrahydrofuran solution of the DOPO flame retardant intermediate, with a volume ratio of ethanol to tetrahydrofuran of 2:1. Immerse the surface-terminated aldehyde-based glass fiber cloth completely in the ethanol / tetrahydrofuran solution of the DOPO flame retardant intermediate, adjust the pH of the system to 5.5 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 65℃, shake and react for 3 hours, take it out, ultrasonically clean it 3 times with ethanol, and dry it to obtain the modified glass fiber cloth. (6) Take 48 parts of boron-modified phenolic resin, pulverize it, add anhydrous ethanol to dissolve it, and prepare a resin solution with a solid content of 55%; add 4.5 parts of hexamethylenetetramine, 1.25 parts of magnesium oxide, 3.5 parts of organic modified montmorillonite, and 2 parts of zinc stearate in sequence, stir for 30 minutes to obtain an impregnation solution; completely immerse 35 parts of modified glass fiber cloth in the impregnation solution, and after full immersion, take it out and pre-dry it in an 85℃ oven for 12 minutes to obtain a prepreg; cut the prepreg into 200mm×100mm sheets according to the design, and lay them out in a total of 6 The sample is placed in a mold for forming a slot box. The mold cavity corresponds to a slot box sample with a forming length of 200mm, a width of 100mm, a side height of 50mm, and a wall thickness of 4mm. The sample is then fed into a flat vulcanizing machine and cured using a segmented heating and pressurizing process: the first stage involves heating to 125℃, applying a pressure of 9MPa, and holding the temperature and pressure for 18min; the second stage involves heating to 165℃, increasing the pressure to 13MPa, and holding the temperature and pressure for 28min; after curing, the temperature is lowered to below 60℃, the sample is demolded and removed, and the edges are trimmed and deburred to obtain a lightweight glass fiber reinforced flame-retardant fireproof slot box.

[0040] Example 3: A specific preparation method of a lightweight glass fiber reinforced flame-retardant fireproof slot box, comprising the following steps: (1) Add 2 mol of phenol and 3.0 mol of formaldehyde (40% formaldehyde aqueous solution by volume) to a reaction apparatus equipped with a stirrer, thermometer and condenser. After stirring evenly, add sodium hydroxide at 5% of the mass of phenol, heat to 65°C and react for 2 hours to complete the first stage reaction. Then dehydrate under reduced pressure. In the second stage, add 1.0 mol of boric acid to the dehydrated reaction vessel, heat to 95°C and react for 2 hours to complete the second stage reaction. Then dehydrate under reduced pressure again, pour out the reactants while hot, cool to room temperature and dry under vacuum to obtain boron-modified phenolic resin. (2) Under nitrogen protection, 0.6 mol DOPO and 0.1 mol 4,4'-diaminobenzophenone were added to the reaction vessel and heated to 200°C with stirring. The reaction was carried out for 4 hours. After the reaction was completed, the system was cooled to 100°C. Toluene was added to the flask and stirred to disperse the precipitate. The precipitate was filtered while hot. The filter cake was washed three times with toluene. The filter cake was recrystallized in tetrahydrofuran. The solid was collected after filtration and dried to obtain the bisaminoDOPO flame retardant intermediate. (3) Clean alkali-free glass fiber is placed in an oxygen plasma treatment instrument for oxygen plasma treatment. The treatment power is 200W, the oxygen flow rate is 30mL / min, and the treatment time is 5min to obtain activated glass fiber cloth. Prepare an ethanol aqueous solution of 5% by mass of silane coupling agent KH550, with a volume ratio of ethanol to water of 9:1. Adjust the pH to 4.5 with glacial acetic acid. Stir and pre-hydrolyze at room temperature for 40min. Immerse the activated glass fiber cloth completely in the ethanol aqueous solution of silane coupling agent KH550, heat to 70℃, and shake for 3h. Take out the glass fiber cloth, ultrasonically clean it with ethanol 3 times, and dry it to obtain surface aminated glass fiber cloth. (4) Prepare a 0.5 mol / L terephthalaldehyde ethanol solution, completely immerse the surface aminated glass fiber cloth in the terephthalaldehyde ethanol solution, adjust the pH of the system to 6.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 60℃, shake and react for 5 h, take it out, ultrasonically clean it with ethanol 3 times, and dry it to obtain the surface end aldehyde-modified glass fiber cloth; (5) Prepare a 0.4 mol / L ethanol / tetrahydrofuran solution of the bisaminoDOPO flame retardant intermediate, with a volume ratio of ethanol to tetrahydrofuran of 3:1. Completely immerse the surface-terminated aldehyde-based glass fiber cloth in the ethanol / tetrahydrofuran solution of the bisaminoDOPO flame retardant intermediate, adjust the pH of the system to 6.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 70℃, shake and react for 4 hours, remove, ultrasonically clean with ethanol 3 times, and dry to obtain the modified glass fiber cloth; (6) Take 55 parts of boron-modified phenolic resin, pulverize it, add anhydrous ethanol to dissolve it, and prepare a resin solution with a solid content of 60%; add 6 parts of hexamethylenetetramine and 2 parts of... Mix 1 part zinc oxide, 5 parts organic modified montmorillonite, and 3 parts zinc stearate, and stir for 40 minutes to obtain an impregnation solution. Completely immerse 40 parts modified glass fiber cloth in the impregnation solution, and after thorough wetting, remove and pre-dry in a 90℃ oven for 15 minutes to obtain a prepreg. Cut the prepreg into 200mm×100mm sheets according to the design, and lay 6 layers in a slot box forming mold. The mold cavity corresponds to a slot box sample with a forming length of 200mm, a width of 100mm, a side height of 50mm, and a wall thickness of 4mm. Feed the sample into a flat vulcanizing machine and cure using a segmented heating and pressurizing process: the first stage heats to 130℃, applies a pressure of 10MPa, and holds for 20 minutes; the second stage heats to 170℃, increases the pressure to 15MPa, and holds for 30 minutes; after curing, cool to below 60℃, demold, remove the product, trim and deburr, and obtain a lightweight glass fiber reinforced flame-retardant fireproof slot box.

[0041] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that boric acid is not added in step (1) to prepare phenolic resin, and then steps (2)-(5) are omitted. The boron-modified phenolic resin in step (6) is replaced with phenolic resin, and the modified glass fiber cloth is replaced with ordinary glass fiber cloth.

[0042] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that steps (2)-(5) are omitted, and the modified glass fiber cloth in step (6) is replaced with ordinary glass fiber cloth.

[0043] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that boric acid is not added in step (1) to prepare phenolic resin, and then the boron-modified phenolic resin in step (6) is replaced with phenolic resin.

[0044] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that 4,4'-diaminobenzophenone in step (2) is replaced with 4-aminobenzophenone to prepare a monoamino DOPO flame retardant intermediate.

[0045] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that boric acid is not added in step (1), phenolic resin is prepared, and then aluminum hydroxide is physically added as the main flame retardant using ordinary glass fiber cloth. The specific preparation method is as follows: (1) Add 2 mol of phenol and 2.8 mol of formaldehyde (38% formaldehyde aqueous solution by volume) to a reaction apparatus equipped with a stirrer, thermometer and condenser. After stirring evenly, add sodium hydroxide at 3% of the mass of phenol, heat to 60°C and react for 1.5 h to complete the first stage reaction. Then dehydrate under reduced pressure. In the second stage, heat to 90°C and react for 1.5 h to complete the second stage reaction. Then dehydrate under reduced pressure again. Pour off the reactants while hot, cool to room temperature and dry under vacuum to obtain phenolic resin. (2) Take clean, unmodified, alkali-free glass fiber cloth for later use; (3) Take 49 parts of phenolic resin, crush it, add anhydrous ethanol to dissolve it, and prepare a resin solution with a solid content of 55%; add 4.5 parts of hexamethylenetetramine, 1.25 parts of magnesium oxide, 30 parts of aluminum hydroxide, and 2 parts of zinc stearate in sequence, stir for 30 minutes to obtain an impregnation solution; completely immerse 35 parts of ordinary glass fiber cloth in the impregnation solution, and after full immersion, take it out and pre-dry it in an 85℃ oven for 12 minutes to obtain a prepreg; cut the prepreg into 200mm×100mm sheets according to the design, and lay them out in a total of 6 The sample is placed in a mold for forming a slot box. The mold cavity corresponds to a slot box sample with a forming length of 200mm, a width of 100mm, a side height of 50mm, and a wall thickness of 4mm. The sample is then fed into a flat vulcanizing machine and cured using a segmented heating and pressurizing process: In the first stage, the temperature is raised to 125℃ and the pressure is applied to 9MPa, and the temperature and pressure are maintained for 18 minutes; in the second stage, the temperature is raised to 165℃ and the pressure is increased to 13MPa, and the temperature and pressure are maintained for 28 minutes; after curing, the temperature is lowered to below 60℃, the sample is demolded and removed, and the edges are trimmed and deburred to obtain a fireproof slot box.

[0046] Performance testing: The following performance tests were conducted on the fireproof slotted box samples prepared in Examples 1-3 and Comparative Examples 1-5: 1. Limiting Oxygen Index Test: In accordance with the requirements of GB / T 2406.2-2009 Test Method for Burning Performance of Plastics, the groove box materials of each embodiment and comparative example were processed into standard specimens with dimensions of 120mm×6.5mm×3mm. Five parallel specimens were prepared for each group. The test was conducted using an oxygen index meter under normal temperature and pressure. The oxygen concentration in the oxygen-nitrogen mixture was gradually adjusted, and the minimum oxygen volume fraction required for the specimen to maintain stable combustion was recorded. The average value of the five test results was taken as the final oxygen index value. 2. Combustion growth rate index and total heat release within 600 seconds test: Combustion heat release performance was tested using a cone calorimeter according to ISO 5660 standard. The sample size was 100mm×100mm×3mm, with 3 parallel samples per group. The heat radiation flux during the test was set to 50kW / m². 2 By analyzing the heat release rate curve, the combustion growth rate index and the total heat release within 600 seconds were extracted respectively. 3. Fire resistance limit test: In accordance with the requirements of the relevant fire resistance test methods in GB 29416-2012, a complete tank sample with a specification of 200mm×100mm×50mm was used for fire resistance performance testing. The tank was placed horizontally in a small fire resistance test furnace, and a temperature sensor was placed at the center point inside the tank. Flames were applied to the fire-exposed surface according to the standard temperature rise curve, and the temperature change of the unexposed surface of the tank was continuously recorded. The time when the average temperature of the unexposed surface reached 180℃ or the main body of the tank collapsed or developed penetrating cracks was taken as the fire resistance limit time. 4. Bending strength and high-temperature mechanical retention rate test: According to GB / T 1449-2005 Test method for bending properties of fiber reinforced plastics, the material was processed into standard bending specimens. The room temperature bending strength was tested using a universal testing machine in three-point bending mode. The test span was set to 48 mm and the loading rate was 2 mm / min. Another batch of specimens was placed in a 200℃ constant temperature oven for 30 min for heat treatment. After removal, the same bending test was performed immediately. The ratio of high-temperature bending strength to room temperature bending strength was calculated to obtain the mechanical retention rate. 5. Apparent density test: According to GB / T 1033.1-2008 standard for determination of density of non-foamed plastics, the apparent density of each sample was tested by immersion method. Three parallel samples with regular size were prepared for each group. The dry weight and the suspended weight after immersion of the sample were weighed and the density value was calculated. The average value of the three groups was taken as the final density data. 6. Smoke density rating test: The test was conducted according to GB / T 8627-2007 Test method for smoke density of building materials during combustion or decomposition. The sample size was 75mm×75mm×3mm, and three parallel samples were tested in each group. The open flame combustion mode was used in the smoke density test chamber. The maximum light attenuation value during the test was recorded and the smoke density rating was calculated. The experimental results are shown in Table 1.

[0047] Table 1 Performance Test Results

[0048] Data Analysis: From the perspectives of limiting oxygen index and heat release performance, the flame retardant level of the fireproof slotted box material prepared in the embodiments of the present invention is significantly better than that of the control groups, fully demonstrating the synergistic effect of boron-modified phenolic matrix, phosphorus-nitrogen interface flame retardant layer and organomontmorillonite. The limiting oxygen index of Comparative Example 1 is only 31.3%, which is at the basic flame-retardant level; Comparative Example 2, which only uses boron-modified phenolic matrix, and Comparative Example 3, which only performs phosphorus-nitrogen modification of glass fiber interface, have oxygen indices increased to 42.7% and 36.9%, respectively, indicating that single modification methods can improve the flame retardancy of materials, but the contribution of matrix boron modification to the overall flame retardancy is greater; Comparative Example 4, which uses monoamino DOPO modification, has both boron matrix and interface phosphorus-nitrogen structure, but because it cannot form complete interface covalent crosslinking, the flame retardant improvement effect is weaker than that of the fully modified examples, with an oxygen index of 44.8%; Comparative Example 5, which uses traditional aluminum hydroxide physical filler, has an oxygen index of only 38.3%, with limited improvement. The limiting oxygen index of the three embodiments of the present invention all exceeded 50%, with the best reaching 55.6%, which is far higher than the industry's conventional access requirements. The improvement is far greater than the linear superposition of single modification. The corresponding combustion growth rate index and the total heat release within 600s also decreased significantly. This indicates that the system plays a dual role in gas phase quenching and condensed phase char formation, which can both suppress the initial spread of the flame and reduce the heat release throughout the combustion process.

[0049] The fire resistance test results further verified the long-term heat insulation capability of the composite ceramicized carbon layer. The fire resistance of all embodiments of the present invention consistently reached over 90 minutes, meeting the performance requirements of F1-level fireproof slot boxes. The fire resistance of blank comparative example 1 was only 32.7 minutes. At high temperatures, the resin degraded rapidly and the glass fiber interface was prone to debonding, allowing flame and heat to penetrate rapidly along the interface. Comparative example 2, which was modified only by boron, relied on the carbon layer formed by the borate glass phase, and its fire resistance increased to 61.2 minutes. Comparative example 3, which was modified only by the interface, had a fire resistance of only 46.3 minutes due to the lack of intrinsic flame retardant ability in the matrix. Although comparative example 4 combined two modification paths, the interface bonding was insufficient, and the carbon layer was prone to cracking. Its fire resistance was 68.5 minutes, which still did not meet the high-level fire resistance requirements. Comparative example 5, filled with traditional aluminum hydroxide, relied only on the heat absorption effect of the inorganic filler to delay the temperature rise and could not form a continuous and dense barrier carbon layer. Its fire resistance was 52.7 minutes, which was inferior to the boron-modified system. In this embodiment of the invention, a glassy carbon layer formed by the boron phase in the matrix builds a heat insulation framework, and an interfacial phosphorus-nitrogen carbon layer blocks the fire transmission path of the glass fiber. The two penetrate and fuse with each other to form a crack-free boron-phosphorus-nitrogen composite ceramic carbon layer. Combined with nano-montmorillonite, the mechanical strength of the carbon layer is improved. At the same time, the interfacial covalent bonds prevent the resin and glass fiber from debonding and cracking at high temperatures. This blocks the transfer of heat and flame from multiple dimensions. Therefore, the fire resistance limit is improved by more than 40% compared with the optimal single modification scheme, and the long-term heat insulation performance is outstanding.

[0050] In terms of mechanical properties, this solution simultaneously optimizes mechanical strength and high-temperature stability while improving flame retardancy, unlike the traditional filler solution where flame retardancy and mechanical properties are mutually exclusive. Regarding room-temperature flexural strength, Comparative Example 3, which only underwent interface covalent modification, showed significantly higher strength than Comparative Example 2, which only underwent boron matrix modification. This indicates that the chemical bonding between glass fiber and resin has a more significant effect on load transfer and macroscopic strength improvement. Comparative Example 4, lacking crosslinking sites on the resin side, experienced decreased interfacial bonding, resulting in lower flexural strength than Comparative Example 3. In Comparative Example 5, the large amount of aluminum hydroxide filler disrupted the continuity of the resin matrix, increasing matrix brittleness, and resulting in the lowest room-temperature flexural strength among all groups. The difference in high-temperature mechanical retention rate is even more pronounced. The high-temperature mechanical retention rate of this invention can reach over 64%, with the best approaching 77%. On one hand, boron modification improves the thermal stability of the resin matrix itself; on the other hand, the interfacial covalent bonds can resist the interfacial stress generated by resin shrinkage at high temperatures, preventing debonding failure and allowing the glass fiber to continue its reinforcing role. In contrast, traditional filler systems are more prone to interfacial defects at high temperatures, resulting in a mechanical retention rate of less than 40% and poor high-temperature structural reliability.

[0051] Apparent density and smoke density tests demonstrate the comprehensive advantages of this invention: lightweight and low smoke. The apparent density of embodiments of this invention is between 1.58 and 1.66 g / cm³. 3 The apparent density of the material was roughly the same as that of the blank ordinary glass fiber phenolic system, indicating that the entire chemical modification scheme did not increase the material's weight, and maintained its lightweight characteristics while significantly improving its flame retardant and fire-resistant properties. In contrast, the high-filler system of Comparative Example 5 showed an apparent density of 1.98 g / cm³. 3 This would significantly increase the installation load on the cable tray, which is detrimental to engineering applications. Regarding smoke density levels, the smoke densities in the embodiments of this invention are all below 60, belonging to the low-to-medium smoke level. The synergistic catalytic char formation of boron-phosphorus-nitrogen fixes more combustible components in the condensed phase carbon layer, reducing the release of smoke and toxic small molecules. In contrast, Comparative Example 5 produces a large number of inorganic aerosol particles during combustion, coupled with resin decomposition smoke, resulting in a smoke density level as high as 85. This leads to poor visibility and escape safety in fire environments. The low-smoke characteristics of this solution better meet the fire safety requirements of power engineering.

[0052] 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 lightweight glass fiber reinforced flame-retardant fireproof slot box, characterized in that, It includes the following components by weight: boron-modified phenolic resin: 40-55 parts, modified glass fiber cloth: 30-40 parts, curing agent: 3-6 parts, curing accelerator: 0.5-2 parts, synergistic flame retardant: 2-5 parts, processing aid: 1-3 parts; The boron-modified phenolic resin is synthesized in two steps from phenol, formaldehyde aqueous solution and boric acid, wherein boron element is chemically bonded to the main chain of phenolic resin molecule in a boron-oxygen six-membered ring structure. The modified glass fiber cloth is prepared by first grafting the surface of the alkali-free glass fiber cloth with silane coupling agent KH-550, then reacting it with terephthalaldehyde through a Schiff base reaction to make the surface contain aldehyde functional groups, and finally reacting it with the bisaminoDOPO flame retardant intermediate through a Schiff base reaction. The molecular structure of the diaminoDOPO flame-retardant intermediate is as follows: 。 2. The lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 1, characterized in that, The curing agent is hexamethylenetetramine; the curing accelerator is magnesium oxide or zinc oxide; the synergistic flame retardant is organically modified montmorillonite with a layer spacing ≥2.5nm; and the processing aid is zinc stearate.

3. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Phenol and formaldehyde are added to a reaction apparatus equipped with a stirrer, thermometer and condenser. After stirring evenly, sodium hydroxide is added and the temperature is raised to 55-65℃. The reaction is carried out for 1-2 hours to complete the first stage reaction. Then the reaction is dehydrated under reduced pressure. In the second stage, boric acid is added to the dehydrated reaction vessel and the temperature is raised to 85-95℃. The reaction is carried out for 1-2 hours to complete the second stage reaction. Then the reaction is dehydrated under reduced pressure again. The reactants are poured out while hot and cooled to room temperature. The product is then dried under vacuum to obtain boron-modified phenolic resin. (2) Under nitrogen protection, DOPO and 4,4'-diaminobenzophenone were added to the reaction vessel and heated to 180-200℃ with stirring. The reaction was carried out for 2-4 hours. After the reaction was completed, the system was cooled to 100℃. Toluene was added to the flask and stirred to disperse the precipitate. The precipitate was filtered while hot. The filter cake was washed three times with toluene. The filter cake was recrystallized in tetrahydrofuran. The solid was collected after filtration and dried to obtain the bisaminoDOPO flame retardant intermediate. (3) Clean alkali-free glass fiber is placed in an oxygen plasma treatment instrument and subjected to oxygen plasma treatment to obtain activated glass fiber cloth; prepare an ethanol aqueous solution of silane coupling agent KH550, adjust the pH to 4.0-4.5 with glacial acetic acid, stir and pre-hydrolyze at room temperature for 20-40 min, completely immerse the activated glass fiber cloth in the ethanol aqueous solution of silane coupling agent KH550, heat to 50-70℃, shake and react for 2-3 h, take it out, ultrasonically clean it with ethanol 3 times, and dry it to obtain surface aminated glass fiber cloth; (4) Prepare a terephthalaldehyde ethanol solution, immerse the surface aminated glass fiber cloth completely in the terephthalaldehyde ethanol solution, adjust the pH of the system to 5.0-6.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 50-60℃, shake and react for 3-5 hours, take it out, ultrasonically clean it with ethanol 3 times, and dry it to obtain the surface aldehyde-terminated glass fiber cloth. (5) Prepare a bisaminoDOPO flame retardant intermediate ethanol / tetrahydrofuran solution, completely immerse the surface-terminated aldehyde-modified glass fiber cloth in the bisaminoDOPO flame retardant intermediate ethanol / tetrahydrofuran solution, adjust the pH of the system to 5.0-6.0 with glacial acetic acid, add 4A molecular sieve as a dehydrating agent, heat to 60-70℃, shake and react for 2-4 hours, take it out, ultrasonically clean it 3 times with ethanol, and dry it to obtain the modified glass fiber cloth; (6) After crushing the boron-modified phenolic resin, add anhydrous ethanol to dissolve it and prepare a resin solution. Add curing agent, curing accelerator, synergistic flame retardant and processing aid in sequence, stir for 20-40 minutes to obtain impregnation solution. Completely immerse the modified glass fiber cloth in the impregnation solution. After fully wetting, take it out and pre-dry it in an oven for 10-15 minutes to obtain prepreg. Cut the prepreg according to the design and lay it in the mold of the slot box. Send it into the flat vulcanizing machine and cure it by segmented heating and pressure. After curing, cool it down to below 60°C, demold the product, trim the edges and remove burrs to obtain a lightweight glass fiber reinforced flame retardant fireproof slot box.

4. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, In (1), formaldehyde is an aqueous solution with a volume fraction of 37-40%; the molar ratio of phenol, formaldehyde and boric acid is 1:1.3-1.5:0.3-0.5; and the amount of sodium hydroxide is 2-5% of the mass of phenol.

5. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, In (2), the molar ratio of DOPO and 4,4'-diaminobenzophenone is 4-6:

1.

6. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, The oxygen plasma treatment in (3) has a power of 160-200W, an oxygen flow rate of 10-30mL / min, and a treatment time of 3-5min.

7. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, The concentration of the ethanol aqueous solution of the silane coupling agent KH550 in (3) is 2-5wt%, and the volume ratio of ethanol to water is 9:

1.

8. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, The concentration of the terephthalaldehyde ethanol solution in (4) is 0.2-0.5 mol / L.

9. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, The concentration of the ethanol / tetrahydrofuran solution of the diaminoDOPO flame retardant intermediate in (5) is 0.2-0.4 mol / L, and the volume ratio of ethanol to tetrahydrofuran is 1:1-3.

10. The method for preparing the lightweight glass fiber reinforced flame-retardant fireproof slot box according to claim 3, characterized in that, The solid content of the resin solution in (6) is 50-60%; the temperature of the oven is 80-90℃; the segmented heating and pressurization process is as follows: in the first stage, the temperature is raised to 120-130℃, the pressure is applied to 8-10MPa, and the temperature and pressure are maintained for 15-20min; in the second stage, the temperature is raised to 160-170℃, the pressure is increased to 12-15MPa, and the temperature and pressure are maintained for 25-30min.

Images