A method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg

Abstract

This invention relates to the field of carbon fiber prepreg technology and discloses a method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg. First, a dihydroxy intermediate is prepared by reacting aldehyde-modified polyethylene glycol monomethyl ether with 2,2-bis(4-hydroxy-3-aminophenyl)propane via a Schiff base reaction. This intermediate is then reacted with spirocyclic pentaerythritol diphosphate diacyl chloride to obtain a flame-retardant emulsifier integrating a hydrophilic polyether chain, a compatible bisphenol A structural unit, and a highly efficient spirocyclic phosphate flame-retardant group. This emulsifier itself has a high limiting oxygen index, exhibiting excellent inherent flame retardancy. Next, the emulsifier is mixed with epoxy resin and a stable water-in-oil flame-retardant sizing agent is prepared through a homogenization emulsification process. Finally, the carbon fiber is impregnated, coated, and dried. The resulting carbon fiber prepreg has advantages such as uniform sizing, good stability, strong interfacial bonding, and high tensile strength.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber prepreg technology, specifically to a method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg. Background Technology

[0002] Carbon fiber prepreg is an advanced composite material intermediate formed by impregnation and curing of carbon fiber as reinforcement and resin matrix (such as epoxy resin) as binder. Due to its excellent properties such as high specific strength, high specific modulus, fatigue resistance, and strong designability, it is widely used in high-end technology fields such as aerospace, rail transportation, wind power generation, and sporting goods. However, traditional epoxy resin sizing agents for carbon fiber have poor flame retardancy and are highly flammable under fire or high-temperature conditions, releasing large amounts of heat and toxic fumes. This is detrimental to improving the flame retardant properties of carbon fiber prepreg and carbon fiber composites, severely limiting their application in certain fields with stringent flame retardant requirements (such as civil aviation, high-speed train interiors, and building reinforcement).

[0003] Currently, the mainstream technology for improving the flame retardant properties of epoxy resins relies on physically blended flame retardants, such as halogenated and phosphorus-based compounds. Although this method is relatively simple in terms of process, it has two significant inherent drawbacks: First, the blended flame retardant lacks strong chemical bonds with the resin matrix, resulting in poor interfacial compatibility and a tendency for phase separation and flame retardant migration and precipitation. This not only causes the flame retardant performance to decay over time but also severely damages the key mechanical properties of the composite material, especially the interfacial bond strength and tensile strength between the fiber and the resin. Second, during the preparation of water-based sizing agents, the various components in the physically blended system (such as resin, flame retardant, and emulsifier) ​​are difficult to form a stable synergistic effect, easily leading to poor emulsion stability and high surface tension, ultimately causing uneven sizing of carbon fibers and affecting the final quality of the prepreg. Summary of the Invention

[0004] (a) Technical problems to be solved:

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg, which solves the problems of poor flame retardancy and low sizing rate of carbon fiber prepreg.

[0006] (II) Technical Solution:

[0007] A method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg, comprising the following steps:

[0008] Step (1): Add aldehyde-modified polyethylene glycol monomethyl ether, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and ethanol to a flask equipped with a reflux condenser. Heat and stir the reaction mixture, then distill under reduced pressure until a precipitate forms. Filter, wash with petroleum ether, and dry to obtain the Schiff base dihydroxy intermediate. The preparation reaction formula is: .

[0009] Step (2): Under a nitrogen atmosphere, spirocyclic pentaerythritol diphosphate dichlorophosphate, Schiff base dihydroxy intermediate, and triethylamine were added to tetrahydrofuran. The mixture was heated and stirred to react, filtered, washed with an aqueous ethanol solution, filtered again, and dried to obtain the emulsifier. The preparation reaction formula is:

[0010] .

[0011] Step (3): Add emulsifier and epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizing emulsifier, and perform homogenization emulsification to obtain flame retardant sizing agent.

[0012] Step (4): Pour the flame-retardant sizing agent into the sizing tank, add distilled water to dilute it, immerse the carbon fiber in the diluted sizing agent, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, dry it, and obtain flame-retardant and fire-resistant epoxy resin carbon fiber prepreg.

[0013] Furthermore, the ratio of aldehyde-modified polyethylene glycol monomethyl ether, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and ethanol is (1550-1710) g: 100 g: (15-20) L.

[0014] Furthermore, in step (1), the heating temperature is 75-80℃, the reaction time is 8-10h, and reflux is used during the reaction.

[0015] Furthermore, the ratio of tetrahydrofuran, spirocyclic pentaerythritol diphosphate diacyl chloride, Schiff base dihydroxy intermediate, and triethylamine is (10-12) L: 100 g: (1440-1580) g: (200-220) g.

[0016] Furthermore, in step (2), the heating temperature is 20-60℃ and the reaction time is 10-16h.

[0017] Furthermore, the ratio of emulsifier to epoxy resin is (10-25) g: 100 g.

[0018] Furthermore, the specific steps of homogenization emulsification are as follows: adjust the speed of the homogenizer emulsifier to a first rotation speed of 8000-10000 r / min, add distilled water dropwise to the emulsifier-resin system for dispersion; then increase the rotation speed to a second rotation speed of 12000-15000 r / min for emulsification, so that the resin system changes from an oil-in-water state to a water-in-oil state.

[0019] Furthermore, in step (4), the soaking time is 40-60s and the drying temperature is 100-120℃.

[0020] (III) Beneficial technical effects:

[0021] This invention involves reacting aldehyde-modified polyethylene glycol monomethyl ether with 2,2-bis(4-hydroxy-3-aminophenyl)propane via a Schiff base reaction to obtain a Schiff base dihydroxy intermediate. This intermediate is then reacted with spirocyclic pentaerythritol diphosphate dichlorophosphate to yield an emulsifier, thereby introducing spirocyclic phosphate groups into the emulsifier and imparting flame-retardant properties. Subsequently, the emulsifier is mixed with epoxy resin, and homogenization emulsification transforms the resin system from an oil-in-water state to an oil-in-water state, yielding a flame-retardant sizing agent. Finally, the sizing agent is used to treat carbon fibers, followed by soaking, scraping, and drying to obtain a flame-retardant and fire-resistant epoxy resin carbon fiber prepreg.

[0022] The emulsifier used in the flame-retardant and fire-resistant epoxy resin carbon fiber prepreg of the present invention integrates hydrophilic polyether chains, bisphenol A structures similar to epoxy resin structures, and highly efficient spirocyclic phosphate flame-retardant groups through chemical grafting. The hydrophilic polyether chains in the emulsifier significantly reduce the surface tension of water, allowing the sizing agent emulsion to easily wet and completely coat each carbon fiber filament, forming a stable and uniform "oil-in-water" emulsion in water. This ensures stable dispersion of the epoxy resin, laying a solid foundation for subsequent uniform sizing and achieving low surface tension for high sizing rates and excellent long-term stability. The bisphenol A structure of the emulsifier has good compatibility with the epoxy resin, forming a double diffusion effect that greatly enhances interfacial adhesion. The sizing agent also effectively protects and increases the oxygen-containing polar functional groups on the carbon fiber surface. These functional groups can chemically react with the epoxy resin during impregnation and curing to generate stronger covalent bonds, thereby achieving higher tensile strength. The introduction of a spirocyclic pentaerythritol diphosphate structure into the epoxy resin sizing agent significantly improves the limiting oxygen index and flame retardant properties of the sizing agent, which is beneficial for improving the flame retardancy of carbon fiber prepregs and their composites. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Aldehyde-modified polyethylene glycol monomethyl ether was prepared according to the method described in my master's thesis, "Study on Polyethylene Glycol Monomethyl Ether Modified Chitosan and Carboxymethyl Chitosan". The structural formula is as follows: .

[0025] Spirocyclic pentaerythritol diphosphate diacyl chloride was prepared according to the method described in the journal *Polymer Materials Science and Engineering*, 2020, 36(11):64-68, in the literature "Synthesis of Spirocyclic Phosphorus-Nitrogen Synergistic Reaction Flame Retardant and Its Application in Epoxy Resins". The structural formula is as follows: .

[0026] The epoxy resin described below is bisphenol A type epoxy resin E44, purchased from Langfang Fucheng Anticorrosion Materials Co., Ltd.

[0027] Example 1:

[0028] Step (1): Add 124g of aldehyde-modified polyethylene glycol monomethyl ether, 8g of 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 2L of ethanol to a flask equipped with a reflux condenser. Heat to 80°C, stir and react for 8 hours, distill under reduced pressure until the precipitate is formed, filter, wash with petroleum ether, and dry to obtain the Schiff base dihydroxy intermediate.

[0029] Step (2): In a nitrogen atmosphere, add 10g of spirocyclic pentaerythritol diphosphate dichlorophosphate, 152g of Schiff base dihydroxy intermediate, and 22g of triethylamine to 1L of tetrahydrofuran. Stir at 20°C for 5h, then heat to 50°C and stir for 8h. Filter, wash with 90% ethanol aqueous solution and filter again, dry to obtain emulsifier.

[0030] Step (3): Add 0.1 kg of emulsifier and 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 8000 r / min, add 3 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 15000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the flame retardant sizing agent.

[0031] Step (4): Pour the flame-retardant sizing agent into the sizing tank, add 40L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 40s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 120℃ to obtain flame-retardant and fire-resistant epoxy resin carbon fiber prepreg.

[0032] Example 2:

[0033] Step (1): Add 130g of aldehyde-modified polyethylene glycol monomethyl ether, 8g of 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 1.6L of ethanol to a flask equipped with a reflux condenser. Heat to 80°C and stir for 10 hours. Distill under reduced pressure until the precipitate is formed. Filter, wash with petroleum ether, and dry to obtain the Schiff base dihydroxy intermediate.

[0034] Step (2): In a nitrogen atmosphere, add 10g of spirocyclic pentaerythritol diphosphate dichlorophosphate, 144g of Schiff base dihydroxy intermediate, and 20g of triethylamine to 1.2L of tetrahydrofuran. Stir at 20°C for 3h, then heat to 60°C and stir for 10h. Filter, wash with 90% ethanol aqueous solution and filter again, dry to obtain emulsifier.

[0035] Step (3): Add 0.15 kg of emulsifier and 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 9000 r / min, add 4 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 12000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the flame retardant sizing agent.

[0036] Step (4): Pour the flame-retardant sizing agent into the sizing tank, add 45L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 60s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 110℃ to obtain flame-retardant and fire-resistant epoxy resin carbon fiber prepreg.

[0037] Example 3:

[0038] Step (1): Add 136g of aldehyde-modified polyethylene glycol monomethyl ether, 8g of 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 1.5L of ethanol to a flask equipped with a reflux condenser. Heat to 75°C, stir and react for 10h, distill under reduced pressure until the precipitate is formed, filter, wash with petroleum ether, and dry to obtain the Schiff base dihydroxy intermediate.

[0039] Step (2): In a nitrogen atmosphere, add 10g of spirocyclic pentaerythritol diphosphate dichlorophosphate, 158g of Schiff base dihydroxy intermediate, and 22g of triethylamine to 1L of tetrahydrofuran. Stir at 20°C for 6h, then heat to 50°C and stir for 10h. Filter, wash with 90% ethanol aqueous solution and filter again, dry to obtain emulsifier.

[0040] Step (3): Add 0.2 kg of emulsifier and 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 10000 r / min, add 3 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 13000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the flame retardant sizing agent.

[0041] Step (4): Pour the flame-retardant sizing agent into the sizing tank, add 40L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 50s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 100℃ to obtain flame-retardant and fire-resistant epoxy resin carbon fiber prepreg.

[0042] Example 4:

[0043] Step (1): Add 136g of aldehyde-modified polyethylene glycol monomethyl ether, 8g of 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 2L of ethanol to a flask equipped with a reflux condenser. Heat to 75°C, stir and react for 8 hours, distill under reduced pressure until the precipitate is formed, filter, wash with petroleum ether, and dry to obtain the Schiff base dihydroxy intermediate.

[0044] Step (2): In a nitrogen atmosphere, add 10g of spirocyclic pentaerythritol diphosphate dichlorophosphate, 148g of Schiff base dihydroxy intermediate, and 21g of triethylamine to 1.2L of tetrahydrofuran. Stir at 20°C for 3h, then heat to 60°C and stir for 7h. Filter, wash with 90% ethanol aqueous solution and filter again, dry to obtain emulsifier.

[0045] Step (3): Add 0.25 kg of emulsifier and 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 8000 r / min, add 4 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 12000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the flame retardant sizing agent.

[0046] Step (4): Pour the flame-retardant sizing agent into the sizing tank, add 45L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 40s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 120℃ to obtain flame-retardant and fire-resistant epoxy resin carbon fiber prepreg.

[0047] Comparative Example 1: The difference between this comparative example and Example 1 is that no emulsifier is added.

[0048] Step (1): Add 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 8000 r / min, add 3 L of distilled water to the resin system for dispersion; then increase the speed to 15000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the sizing agent.

[0049] Step (2): Pour the sizing agent into the sizing tank, add 40L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 40s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 120℃ to obtain carbon fiber prepreg.

[0050] Comparative Example 2: The difference between this comparative example and Example 1 is that the Schiff base dihydroxy intermediate is used as an emulsifier.

[0051] Step (1): Add 124g of aldehyde-modified polyethylene glycol monomethyl ether, 8g of 2,2-bis(4-hydroxy-3-aminophenyl)propane, and 2L of ethanol to a flask equipped with a reflux condenser. Heat to 80°C, stir and react for 8 hours, distill under reduced pressure until the precipitate is formed, filter, wash with petroleum ether, and dry to obtain Schiff base dihydroxy intermediate emulsifier.

[0052] Step (2): Add 0.1 kg Schiff base dihydroxy intermediate emulsifier and 1 kg epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 8000 r / min, add 3 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 15000 r / min for emulsification, so that the resin system changes from the oil-in-water state to the water-in-oil state, and obtain the sizing agent.

[0053] Step (3): Pour the sizing agent into the sizing tank, add 40L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 40s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 120℃ to obtain carbon fiber prepreg.

[0054] Comparative Example 3: The difference between this comparative example and Example 1 is that serinel (CAS No.: 534-03-2) is used instead of 2,2-bis(4-hydroxy-3-aminophenyl)propane.

[0055] Step (1): Add 124g of aldehyde-modified polyethylene glycol monomethyl ether, 8g of serinel, and 2L of ethanol to a flask equipped with a reflux condenser. Heat to 80°C, stir for 8 hours, distill under reduced pressure, wash with petroleum ether, and dry to obtain a Schiff base dihydroxy intermediate with the following structural formula: .

[0056] Step (2): In a nitrogen atmosphere, add 10g of spirocyclic pentaerythritol diphosphate dichlorophosphate, 152g of Schiff base dihydroxy intermediate, and 22g of triethylamine to 1L of tetrahydrofuran. Stir at 20°C for 5h, then heat to 50°C and stir for 8h. Filter, wash with 90% ethanol aqueous solution and filter again, dry to obtain emulsifier.

[0057] Step (3): Add 0.1 kg of emulsifier and 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 8000 r / min, add 3 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 15000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the sizing agent.

[0058] Step (4): Pour the sizing agent into the sizing tank, add 40L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 40s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 120℃ to obtain carbon fiber prepreg.

[0059] Comparative Example 4: The difference between this comparative example and Example 1 is that bisphenol A (CAS No.: 80-05-7) is polymerized with spirocyclic pentaerythritol diphosphate diacyl chloride.

[0060] Step (1): In a nitrogen atmosphere, add 10g of spirocyclic pentaerythritol diphosphate dichlorophosphate, 152g of bisphenol A, and 22g of triethylamine to 1L of tetrahydrofuran. Stir at 20°C for 5h, then heat to 50°C and stir for 8h. Filter, wash with 90% ethanol aqueous solution and filter again, dry to obtain emulsifier.

[0061] Step (2): Add 0.1 kg of emulsifier and 1 kg of epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizer, adjust the speed of the homogenizer to 8000 r / min, add 3 L of distilled water to the emulsifier-resin system for dispersion; then increase the speed to 15000 r / min for emulsification, so that the resin system changes from the state of water in oil to the state of oil in water, and obtain the sizing agent.

[0062] Step (3): Pour the sizing agent into the sizing tank, add 40L of distilled water for dilution, immerse the carbon fiber in the diluted sizing agent for 40s, take out the carbon fiber, mechanically scrape off the excess sizing agent adhering to the surface of the carbon fiber with a scraper, and dry at 120℃ to obtain carbon fiber prepreg.

[0063] The surface tension of the sizing agent emulsion was determined by the hanging drop method using an automatic interfacial tensiometer, with the temperature controlled at (25±0.1)℃.

[0064] Add an appropriate amount of deionized water to the sizing agent to prepare an emulsion with a concentration of 3wt%. Let it stand at room temperature for 14 days and observe whether there are phenomena such as layering, precipitation and demulsification in the sizing agent to evaluate the stability of the sizing agent.

[0065] The carbon fiber prepreg was vacuum dried in an oven at 100℃ for 12 hours, then weighed and marked as m1. Next, the carbon fiber prepreg was placed in a Soxhlet extractor containing an acetone-ethanol (volume ratio 1:1) mixture for washing and desizing. The oil bath temperature was set to 80℃, and the reflux washing was performed for 3 hours at a reflux rate of 12 minutes per cycle. After desizing, the desizing carbon fiber was dried again in an oven at 100℃ for 12 hours, then weighed again and marked as m0. The sizing rate is calculated as (m1 - m0) / m0 × 100%, where m1 is the mass of the carbon fiber before desizing, and m0 is the mass of the carbon fiber after desizing.

[0066] The tensile strength of carbon fiber specimens was tested according to the method of GB / T 3362-2017.

[0067] Pour 300 mL of sizing agent into the mold, add 9.7 g of ethylenediamine curing agent, heat to 130 °C, and heat cure for 6 h to prepare a cured sample. Test the limiting oxygen index of the sample according to the method of GB / T 2406.1-2008.

[0068] Table 1 Performance Tests of Sizing Agent and Carbon Fiber Prepreg

[0069]

[0070] The emulsifier used in the flame-retardant and fire-resistant epoxy resin carbon fiber prepregs of Examples 1-4 integrates hydrophilic polyether chains, bisphenol A structures similar to epoxy resin structures, and highly efficient spirocyclic phosphate flame-retardant groups through chemical grafting. The hydrophilic polyether chains in the emulsifier significantly reduce the surface tension of water, allowing the sizing agent emulsion to easily wet and completely coat each carbon fiber filament, forming a stable and uniform "oil-in-water" emulsion in water. This ensures that the epoxy resin can be stably dispersed within it, laying a solid foundation for subsequent uniform sizing and achieving low surface tension and excellent long-term stability. The bisphenol A structure of the emulsifier has good compatibility with the epoxy resin, forming a double diffusion effect that greatly enhances interfacial adhesion. The sizing agent can also effectively protect and increase the oxygen-containing polar functional groups on the carbon fiber surface. These functional groups can chemically react with the epoxy resin during impregnation and curing to generate stronger covalent bonds, thereby achieving higher tensile strength. The introduction of a spirocyclic pentaerythritol diphosphate structure into the epoxy resin sizing agent significantly improves the limiting oxygen index and flame retardant properties of the sizing agent, which is beneficial for improving the flame retardancy of carbon fiber prepregs and their composites.

[0071] Comparative Example 1 is carbon fiber prepreg without emulsifier. The epoxy resin cannot form a stable "oil-in-water" emulsion in water, resulting in extremely high surface tension of the system, which cannot effectively wet and adhere to the carbon fiber. This ultimately leads to extremely low sizing rate and poor interfacial adhesion, and the tensile strength of the carbon fiber prepreg is significantly reduced.

[0072] Comparative Example 2 used Schiff base dihydroxy intermediate as emulsifier. Due to the absence of the key spirocyclic phosphate flame-retardant group in its molecule, the limiting oxygen index of the epoxy resin sizing agent was significantly reduced, resulting in poor flame-retardant performance.

[0073] Comparative Example 3 used serine instead of 2,2-bis(4-hydroxy-3-aminophenyl)propane to prepare an emulsifier. The lack of bisphenol A structure resulted in poor compatibility with epoxy resin, which led to decreased emulsion stability and reduced sizing rate, resulting in lower tensile strength.

[0074] Comparative Example 4 prepared an emulsifier by polymerizing bisphenol A with spirocyclic pentaerythritol diphosphate diacyl chloride. Its molecule lacks a hydrophilic polyether long chain, which cannot reduce the surface tension of water and cannot be used as an emulsifier. As a result, it cannot form a stable sizing agent, the emulsion has poor stability and high surface tension, resulting in an extremely low sizing rate.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a flame-retardant and fire-resistant epoxy resin carbon fiber prepreg, characterized in that, The preparation method includes the following steps: S1. Add emulsifier and epoxy resin to the container, heat and stir evenly, place the container at the bottom of the homogenizing emulsifier, and perform homogenization emulsification to obtain flame retardant sizing agent. S2. Pour the flame-retardant sizing agent into the sizing tank, add distilled water to dilute it, immerse the carbon fiber in the diluted sizing agent, take out the carbon fiber, mechanically scrape off the excess sizing agent on the surface of the carbon fiber with a scraper, dry it, and obtain flame-retardant and fire-resistant epoxy resin carbon fiber prepreg. The preparation method of the emulsifier includes the following steps: Step (1): Add aldehyde-modified polyethylene glycol monomethyl ether, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and ethanol to a flask equipped with a reflux condenser. Heat and stir the reaction, distill under reduced pressure until the precipitate is formed, filter, wash with petroleum ether, and dry to obtain Schiff base dihydroxy intermediate. Step (2): In a nitrogen atmosphere, add spirocyclic pentaerythritol diphosphate dichloride, Schiff base dihydroxy intermediate, and triethylamine to tetrahydrofuran, heat and stir to react, filter, wash with ethanol aqueous solution and filter again, dry to obtain emulsifier. The ratio of aldehyde-modified polyethylene glycol monomethyl ether, 2,2-bis(4-hydroxy-3-aminophenyl)propane, and ethanol is (1550-1710) g: 100 g: (15-20) L; The ratio of tetrahydrofuran, spirocyclic pentaerythritol diphosphate diacyl chloride, Schiff base dihydroxy intermediate, and triethylamine is (10-12) L: 100 g: (1440-1580) g: (200-220) g.

2. The method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg according to claim 1, characterized in that, The ratio of the emulsifier to the epoxy resin is (10-25) g: 100 g.

3. The method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg according to claim 1, characterized in that, The specific steps of the homogenization emulsification are as follows: the speed of the homogenization emulsifier is adjusted to a first rotation speed of 8000-10000 r / min, and distilled water is added dropwise to the emulsifier-resin system for dispersion; then the rotation speed is increased to a second rotation speed of 12000-15000 r / min for emulsification, so that the resin system changes from an oil-in-water state to a water-in-oil state.

4. The method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg according to claim 1, characterized in that, The soaking time in S2 is 40-60 seconds, and the drying temperature is 100-120℃.

5. The method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg according to claim 1, characterized in that, In step (1), the heating temperature is 75-80℃, the reaction time is 8-10h, and reflux is used during the reaction.

6. The method for preparing flame-retardant and fire-resistant epoxy resin carbon fiber prepreg according to claim 1, characterized in that, In step (2), the heating temperature is 20-60℃ and the reaction time is 10-16h.

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