Bio-based halogen-free flame-retardant toughening type 3C electronic epoxy prepreg and preparation method thereof

Abstract

The invention relates to a bio-based halogen-free flame-retardant toughening type 3C electronic epoxy prepreg and a preparation method thereof, and belongs to the technical field of polymer composite materials. Along with the improvement of environmental awareness, the demand of the market on the environment-friendly bio-based epoxy prepreg is increased, especially in the 3C electronic field. The invention aims at solving the problems of flammability and insufficient toughness of the existing bio-based epoxy prepreg, and improving the safety and environmental protection property of electronic products. The epoxy prepreg is composed of bio-based halogen-free flame-retardant toughening epoxy resin, a latent curing agent, an accelerant and a reinforcing material. The preparation method comprises the following steps: a) carrying out aldehyde-amine condensation reaction on bio-based vanillin and aliphatic polyamine to generate polyphenol containing a Schiff base structure; b) grafting a flame retardant to a polyphenol side group position by using an organic flame retardant and a catalyst to obtain an epoxy resin synthesis precursor; c) synthesizing bio-based halogen-free flame-retardant toughening epoxy resin through epoxidation reaction; and d) impregnating the reinforcing material by a hot melting method, and rolling and rolling to obtain the prepreg. The epoxy prepreg provided by the invention has the following advantages: by adopting a bio-based raw material, the dependence on petroleum resources is reduced, and the carbon footprint is reduced; through molecular-level toughening modification, the impact toughness of the material is improved; halogen-free flame-retardant elements are introduced, intrinsic flame retardance is achieved, and environmental pollution and health risks are avoided. Compared with the prior art, the prepreg disclosed by the invention has the advantages that the impact toughness and the flame retardant property are remarkably improved while excellent heat resistance is maintained, and the prepreg has important practical significance and market prospects.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a method for preparing a bio-based halogen-free flame-retardant toughened epoxy resin and its 3C electronic prepreg. Background Technology

[0002] With increasing environmental awareness and the implementation of relevant regulations, the market demand for bio-based epoxy prepregs is growing. Especially in the 3C electronics field, the application of these materials imbues products with environmentally friendly attributes. Bio-based epoxy resins and their prepregs, as materials prepared using renewable resources such as crops and trees as raw materials, are gaining attention due to their environmental friendliness. The development of bio-based materials not only helps reduce dependence on petroleum resources but also reduces the environmental impact of products during production and use. Compared with traditional petroleum-based materials, bio-based materials have advantages such as wide distribution, diverse sources, and low carbon emissions.

[0003] In the 3C electronics field, the application of bio-based epoxy prepregs is hampered by issues such as flammability and low toughness. Therefore, developing a novel bio-based halogen-free flame-retardant and toughened epoxy prepreg is of great significance for improving the safety and environmental friendliness of electronic products. The development of this material will help improve the overall performance of 3C electronic products, driving the industry towards a greener and more environmentally friendly direction, and has significant practical implications and broad market prospects.

[0004] This patent achieves molecular-level toughening modification by introducing flexible structural units through modification of bio-based precursors. Compared to conventional bio-based resin blending for toughening modification, this method avoids the problem of poor compatibility between the toughening agent and the matrix resin. In particular, this patent achieves intrinsic flame retardancy in bio-based epoxy resins by introducing halogen-free flame-retardant elements into the polymer structure through molecular modification, avoiding problems such as precipitation and decreased mechanical properties caused by the introduction of filler-type flame retardants. Summary of the Invention

[0005] To address the problems of flammability, insufficient toughness, and potential environmental impact of existing epoxy prepregs for 3C electronics, this invention provides a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics and its preparation method. This invention utilizes bio-based raw materials as the main component, introducing flexible structural units and halogen-free flame-retardant elements through molecular modification, achieving intrinsic flame retardancy and toughening effects while maintaining excellent heat resistance.

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

[0007] A bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics is composed of 100 parts of bio-based halogen-free flame-retardant and toughened epoxy resin, 3-15 parts of latent curing agent, 0-5 parts of accelerator, and 70-150 parts of reinforcing material.

[0008] A method for preparing a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics, the method comprising the following steps:

[0009] a. By utilizing the aldehyde-amine condensation reaction of bio-based vanillin and aliphatic polyamines in a specific solvent, polyphenols with a Schiff base structure as the core of a flexible aliphatic chain are generated.

[0010] b. Using organic flame retardants containing secondary amino, phosphorus-hydrogen bonds, or silicon-hydrogen bonds, and with the participation of a catalyst, based on their nucleophilic addition reaction with imine bonds, the organic flame retardant molecules are grafted onto the side group positions of polyphenols containing Schiff base structures to obtain bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursors.

[0011] c. Based on the epoxidation reaction of the precursor for the synthesis of bio-based halogen-free flame-retardant and toughened epoxy resin, a bio-based halogen-free flame-retardant and toughened epoxy resin is synthesized with the participation of epichlorohydrin and a phase transfer catalyst. After blending with a latent curing agent and an accelerator, a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics is obtained.

[0012] d. Based on the hot melt method, a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics is uniformly impregnated onto a reinforcing material, and then rolled and wound to obtain a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics.

[0013] Preferably, the specific scheme of step a is as follows: dissolve bio-based vanillin and aliphatic polyamine in specific solvents respectively, and then, under the conditions of reflux and nitrogen protection, add the aliphatic polyamine solution dropwise to the bio-based vanillin solution, maintain room temperature to 100°C, and react for 0.5 to 6 hours to obtain a polyphenol solution system with a flexible aliphatic chain as the core containing a Schiff base structure.

[0014] Preferably, the aliphatic polyamine in step a includes one or more of ethylenediamine, pentaethylenediamine, hexamethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, triethylenetetramine, tetraethylenepentamine, N,N'-bis(3-aminopropyl)ethylenediamine, and N,N'-bis(2-aminoethyl)-1,3-propanediamine.

[0015] Preferably, the molar ratio of bio-based vanillin to aliphatic polyamine in step a is (0.5-4):1.

[0016] Preferably, the specific solvent in step a is one or more of water or organic solvents such as hydrocarbons, alcohols, esters, ethers, and ketones.

[0017] Preferably, the specific scheme of step b is as follows: under reflux and nitrogen protection conditions, an organic flame retardant containing secondary amino groups, phosphorus hydrogen bonds or silicon hydrogen bonds is gradually added to a polyphenol solution system with a flexible aliphatic chain as the core containing a Schiff base structure, a catalyst is added, and the reaction is kept at room temperature to 120°C for 0.5 to 6 hours. After removing the solvent by rotary evaporation, a bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor is obtained.

[0018] Preferably, the organic flame retardant containing secondary amine, phosphorus-hydrogen bond, or silicon-hydrogen bond groups described in step b should have at least one NH, Si-H, or PH bond in its molecular structure, as shown in the figure below:

[0019]

[0020] Preferably, the catalyst in step b is a Lewis acid catalyst, and the amount added is 0.5 to 5% of the mass percentage of the organic flame retardant.

[0021] Preferably, step c is as follows: Under reflux conditions, the bio-based halogen-free flame-retardant and toughened epoxy resin precursor is stirred evenly with epichlorohydrin, followed by the addition of a phase transfer catalyst. The reaction is carried out at 60–120°C for 0.5–4 h. Subsequently, 10–50 wt% alkali solution is added dropwise at room temperature to 100°C, and the reaction is maintained at this temperature for 0.5–6 h. The system is washed multiple times with water until pH≈7, and excess epichlorohydrin and water are removed by rotary evaporation to obtain the bio-based halogen-free flame-retardant and toughened epoxy resin. 100 parts of the bio-based halogen-free flame-retardant and toughened epoxy resin are then added to a latent curing agent and an accelerator at 60–100°C to obtain a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics.

[0022] Preferably, the phase transfer catalyst in step c is a quaternary ammonium salt or quaternary phosphonium salt catalyst, and the amount added is 2 to 10% of the mass percentage of the precursor for the synthesis of bio-based halogen-free flame-retardant and toughened epoxy resin.

[0023] Preferably, the molar ratio of the bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor to epichlorohydrin in step c should be 1:(2-20).

[0024] Preferably, the latent curing agent in step c is one or more of succinic acid hydrazide, adipic acid hydrazide, dicyandiamide, imidazole, 2-methylimidazolium, 2-ethyl-4-methylimidazolium, maleic anhydride, and phthalic anhydride, and the amount added is 3 to 15 parts. The accelerator mentioned in step c is one or more of the following: carbonyl diimidazole, aluminum acetylacetonate, o-methylbenzidine, N-(2-hydroxyphenyl)-N',N'-dimethylurea, N-(2-hydroxy-4-nitrobenzene)-N',N'-dimethylurea, N-(5-chloro-2-hydroxyphenyl)-N',N'-dimethylurea, N-(4-chlorophenyl)-N',N'-dimethylurea, N-(4-chloro-2-hydroxyphenyl)-N',N'-dimethylurea, 3-phenyl-1,1-dimethylurea, and 3-(4-chlorophenyl)-1,1-dimethylurea, and is added in an amount of 0 to 5 parts.

[0025] Preferably, the viscosity range of the bio-based halogen-free flame-retardant toughened epoxy resin for 3C electronics described in step c should be 7000–40000 mPa·s at 70°C.

[0026] Preferably, step d involves heating a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics to a molten state, ensuring complete melting and good fluidity. Subsequently, the molten epoxy resin is uniformly coated or impregnated onto the surface of the reinforcing material laid on release paper, ensuring the resin fully penetrates and is evenly distributed throughout the reinforcing material. The resin-impregnated reinforcing material is then compacted using a roller press to ensure a tight bond between the resin and the reinforcing material. Finally, the surface of the prepreg after roller pressing is coated, wound, and cooled to obtain a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics.

[0027] Preferably, the reinforcing material in step d is one or more of the following: glass fiber mat, electronic-grade glass fiber cloth, unidirectional glass fiber cloth, plain weave carbon fiber cloth, twill weave carbon fiber cloth, satin weave carbon fiber cloth, unidirectional carbon fiber cloth, carbon fiber mat, plain weave basalt fiber cloth, twill weave basalt fiber cloth, satin weave basalt fiber cloth, unidirectional basalt fiber cloth, and basalt fiber mat, with the reinforcing material comprising 70 to 150 parts.

[0028] Beneficial effects: Compared with the prior art, the bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics, its preparation method, and its application have the following significant effects:

[0029] (1) This invention uses bio-based vanillin as a raw material, which is derived from renewable resources, reducing dependence on petroleum resources and significantly reducing the carbon footprint of 3C electronic products.

[0030] (2) By introducing flexible structural units, toughening modification of bio-based epoxy resin for 3C electronics at the molecular level is achieved, avoiding the problem of poor compatibility between traditional toughening agents and matrix resins. The composite board of a bio-based halogen-free flame-retardant toughened epoxy prepreg for 3C electronics in this invention has an impact strength of 44 kJ / m after curing. 2 This significantly improves the impact toughness of the material;

[0031] (2) By introducing halogen-free flame-retardant elements through molecular modification, the intrinsic flame retardancy of bio-based epoxy resin and its composite materials for 3C electronics is realized. In this invention, a bio-based halogen-free flame-retardant toughened epoxy prepreg for 3C electronics achieved the V-0 flame retardant level in the UL 94 test, while avoiding the environmental pollution and health risks of traditional halogen flame retardants. Attached Figure Description

[0032] Figure 1 The images show the FTIR spectra of the bio-based vanillin used in Example 1, the bio-based halogen-free flame-retardant and toughened epoxy resin synthesis precursor prepared therefrom, and the bio-based halogen-free flame-retardant and toughened epoxy resin. Detailed Implementation

[0033] To better understand the present invention, the following embodiments further illustrate the content of the present invention. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1:

[0035] a. Dissolve 304g of bio-based vanillin and 60g of ethylenediamine in 200mL of ethanol. Under reflux and nitrogen protection, slowly add the ethylenediamine solution dropwise to the vanillin solution, maintain the temperature at 80℃, and react for 4 hours to obtain a polyphenol solution system containing a Schiff base structure.

[0036] b. Under reflux and nitrogen protection conditions, 312 g of guanidine aminosulfonate was dissolved in water and gradually added to a polyphenol solution system containing a Schiff base structure, along with 5 g of zinc sulfate catalyst. The reaction was maintained at 90 °C for 3 hours, and the solvent was removed by rotary evaporation to obtain 614 g of bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor, with a yield of 91%.

[0037] c. Under reflux conditions, 200g of the bio-based halogen-free flame-retardant and toughened epoxy resin precursor was stirred evenly with 300mL of epichlorohydrin, followed by the addition of 10g of tetrabutylammonium bromide phase transfer catalyst. The reaction was carried out at 80℃ for 2 hours, followed by the dropwise addition of 100mL of 10wt% sodium hydroxide solution at 60℃, and the reaction was maintained at this temperature for 4 hours. After multiple water washings until pH≈7, excess epichlorohydrin and water were removed by rotary evaporation to obtain a brown bio-based halogen-free flame-retardant and toughened epoxy resin. 100g of the bio-based halogen-free flame-retardant and toughened epoxy resin was then mixed with 15g of dicyandiamide and 5g of N-(2-hydroxyphenyl)-N',N'-dimethylurea at 80℃ to obtain a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics, with a viscosity of 16000mPa·s at 70℃.

[0038] d. The bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics is heated to 70°C to ensure complete melting and good fluidity. Subsequently, the molten epoxy resin is uniformly coated or impregnated onto the surface of electronic-grade glass fiber cloth laid on release paper, ensuring that the resin fully penetrates and is evenly distributed throughout the reinforcing material. The resin-impregnated electronic-grade glass fiber cloth is compacted using a roller press to ensure a tight bond between the resin and the reinforcing material. Finally, the prepreg after roller pressing is surface-coated, wound up, and cooled to obtain a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics.

[0039] Example 2:

[0040] a. Dissolve 304g of bio-based vanillin and 102g of pentanediamine in 250mL of isopropanol. Under reflux and nitrogen protection, slowly add the pentanediamine solution dropwise to the vanillin solution, maintain the temperature at 90℃, and react for 3 hours to obtain a polyphenol solution system containing a Schiff base structure.

[0041] b. Under reflux and nitrogen protection conditions, 276 g of diethyl phosphite was gradually added to a polyphenol solution containing a Schiff base structure, along with 6 g of aluminum chloride catalyst. The reaction was maintained at 100 °C for 2 hours, and the solvent was removed by rotary evaporation to obtain 582 g of bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor, with a yield of 85%.

[0042] c. Under reflux conditions, 200g of the bio-based halogen-free flame-retardant and toughened epoxy resin precursor was stirred evenly with 300mL of epichlorohydrin, followed by the addition of 12g of tetrabutylammonium bromide phase transfer catalyst. The reaction was carried out at 90℃ for 2 hours, followed by the dropwise addition of 120mL of 10wt% potassium hydroxide solution at 70℃, and the reaction was maintained at this temperature for 3 hours. After multiple water washings until pH≈7, excess epichlorohydrin and water were removed by rotary evaporation to obtain a deep yellow bio-based halogen-free flame-retardant and toughened epoxy resin. 100g of the bio-based halogen-free flame-retardant and toughened epoxy resin was mixed with 12g of dicyandiamide and 4g of N-(4-chloro-2-hydroxybenzene)-N',N'-dimethylurea at 80℃ to obtain a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics, with a viscosity of 11700mPa·s at 70℃.

[0043] d. The bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics is heated to 70°C to ensure complete melting and good fluidity. Subsequently, the molten epoxy resin is uniformly coated or impregnated onto the surface of electronic-grade glass fiber cloth laid on release paper, ensuring that the resin fully penetrates and is evenly distributed throughout the reinforcing material. The resin-impregnated electronic-grade glass fiber cloth is compacted using a roller press to ensure a tight bond between the resin and the reinforcing material. Finally, the prepreg after roller pressing is surface-coated, wound up, and cooled to obtain a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics.

[0044] Comparative Example 1:

[0045] a. Compared to Example 3, this comparative example uses a diamine (4,4'-diaminodiphenyl disulfide) synthesized resin with an aromatic ring structure as the core, rather than an aliphatic chain structure. 304g of bio-based vanillin and 252g of 4,4'-diaminodiphenyl disulfide were dissolved in 250mL of acetone. Under reflux and nitrogen protection, the 4,4'-diaminodiphenyl disulfide solution was slowly added dropwise to the vanillin solution. The temperature was maintained at 50°C, and the reaction was carried out for 5 hours to obtain a polyphenol solution system containing a Schiff base structure with an aromatic hydrocarbon structure as the core.

[0046] b. Under reflux and nitrogen protection conditions, 396 g of diphenylmethylsilane was gradually added to a solution system of a Schiff base-containing polyphenol with an aromatic hydrocarbon core, along with 4 g of zinc chloride catalyst. The reaction was maintained at 80 °C for 2 hours, and the solvent was removed by rotary evaporation to obtain 631 g of a bio-based halogen-free flame-retardant and toughened epoxy resin precursor with an aromatic hydrocarbon core, with a yield of 66%.

[0047] c. Under reflux conditions, 200g of a bio-based halogen-free flame-retardant and toughened epoxy resin precursor with an aromatic hydrocarbon core was stirred evenly with 300mL of epichlorohydrin, followed by the addition of 8g of butyltriphenylphosphine chloride phase transfer catalyst. The reaction was carried out at 70℃ for 2 hours, followed by the dropwise addition of 80mL of 30wt% sodium hydroxide solution at 60℃, and the reaction was maintained at this temperature for 3 hours. After multiple water washings until pH≈7, excess epichlorohydrin and water were removed by rotary evaporation to obtain a deep yellow bio-based halogen-free flame-retardant and toughened epoxy resin with an aromatic hydrocarbon core. 100g of the bio-based halogen-free flame-retardant and toughened epoxy resin with an aromatic hydrocarbon core was added to 15g of dicyandiamide and 3g of N-(2-hydroxyphenyl)-N',N'-dimethylurea at 80℃ and mixed evenly to obtain a bio-based halogen-free flame-retardant and toughened epoxy resin for 3C electronics, with a viscosity of 33600mPa·s at 70℃.

[0048] d. A bio-based halogen-free flame-retardant and toughened epoxy resin with an aromatic hydrocarbon structure as its core is heated to 80°C to ensure complete melting and good fluidity. Subsequently, the molten epoxy resin is uniformly coated or impregnated onto the surface of electronic-grade glass fiber cloth laid on release paper, ensuring that the resin can fully penetrate and be evenly distributed throughout the reinforcing material. The resin-impregnated electronic-grade glass fiber cloth is compacted using a roller press to ensure a tight bond between the resin and the reinforcing material. Finally, the prepreg after roller pressing is surface-coated, wound up, and cooled to obtain a bio-based halogen-free flame-retardant and toughened epoxy prepreg for 3C electronics with an aromatic hydrocarbon structure as its core.

[0049] Comparative Example 2:

[0050] Commercial E51 epoxy resin and E20 epoxy resin were mixed at a ratio of 50:50, and 10 parts of DOPO flame retardant were added. The mixture was thoroughly mixed at 80°C. Then, 15g of dicyandiamide and 3g of dichlorophenyl dimethylurea were added at 80°C and mixed thoroughly to obtain petroleum-based epoxy resin. The prepreg preparation process was the same as in the example.

[0051] The prepregs from Examples 1-2 and Comparative Examples 1-2 were cut to the required sizes and laid layer by layer in a mold preheated to 140°C, ensuring each layer was aligned and flat, for a total of 8 layers. After laying, breathable material was placed and covered with release paper and PE film, and a vacuum pump was connected to remove air bubbles. The mold was placed in a hot press, and a pressure of 3 MPa was applied, maintaining a temperature of 140°C for 1 hour for curing. After curing, the mixture was allowed to cool naturally to room temperature, the composite board was removed, and the edges were trimmed, completing the hot-pressing of the electronic fiberglass cloth composite board.

[0052] The electronic fiberglass cloth composite boards prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to impact toughness and flame retardancy tests. The impact toughness of the present invention was tested according to GB / T 1451-2005 "Test Method for Impact Toughness of Fiber Reinforced Plastics by Simply Supported Beam". The UL-94 rating of the present invention was tested using the vertical method according to GB / T 2408-2008 "Determination of Burning Performance of Plastics by Horizontal and Vertical Methods". The test results are detailed in Table 1.

[0053] Table 1. Impact toughness and flame retardant properties of the electronic fiberglass cloth composite panels prepared in Examples 1-2 and Comparative Examples 1-2.

[0054] sample Impact toughness Flame retardant properties Example 1 <![CDATA[38kJ / m 2 ]]> V0 Example 2 <![CDATA[44kJ / m 2 ]]> V0 Comparative Example 1 <![CDATA[27kJ / m 2 ]]> V0 Comparative Example 2 <![CDATA[33kJ / m 2 ]]> V1

[0055] According to the test results:

[0056] (1) Compared with the epoxy prepreg synthesized and prepared by using diamine with aromatic ring as the molecular core in Comparative Example 1, the impact toughness of Examples 1-2 is increased by 41% and 62%, respectively. This is because the bio-based halogen-free flame-retardant toughened epoxy resin for 3C electronics synthesized in Examples 1-2 has a flexible structural unit as the molecular core. The polymer molecular chain has both hard segments (cross-linked structure) and soft segments (flexible chain segment enrichment region), which helps to reduce the stress concentration points generated when the material is subjected to force and improve the impact strength and fracture toughness of the material.

[0057] (2) Compared with Comparative Example 2, the flame retardant performance of Examples 1-2 was significantly improved, achieving a flame retardant effect of V-0 level. In addition, since no additive flame retardant was used in Examples 1 and 2, there was no flame retardant precipitation, and the impact on the appearance of the prepreg was small.

[0058] Figure 1 The images show the FTIR spectra of the bio-based vanillin used in Example 1, the bio-based halogen-free flame-retardant and toughened epoxy resin synthesis precursor prepared therefrom, and the bio-based halogen-free flame-retardant and toughened epoxy resin.

Claims

1. A bio-based halogen-free flame-retardant toughened epoxy prepreg for 3C electronics, characterized in that, Consists of the following components: Bio-based halogen-free flame-retardant toughened epoxy resin 100 parts; Latent curing agent 3-15 parts; Accelerator 0-5 parts; Reinforcing material 70-150 parts.

2. The method of producing a bio-based halogen-free flame-retardant toughened epoxy prepreg for 3C electronics according to claim 1, characterized in that, Comprise the following steps: a. Bio-based vanillin and aliphatic polyamine are respectively dissolved in a specific solvent, then the aliphatic polyamine solution is added dropwise into the bio-based vanillin solution under the conditions of condensation reflux and nitrogen protection, and reacted at room temperature-100℃ for 0.5-6h to obtain a polyphenol solution system containing Schiff base structure with flexible aliphatic chain as the core. b. Under the conditions of condensation reflux and nitrogen protection, an organic flame retardant containing secondary amino groups, phosphorus-hydrogen bonds or silicon-hydrogen bonds and other groups is gradually added to the polyphenol solution system containing Schiff base structure with flexible aliphatic chain as the core, a catalyst is added, and reacted at room temperature-120℃ for 0.5-6h, and then the solvent is removed by rotary evaporation to obtain a bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor. c. Under the conditions of condensation reflux, the bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor is stirred uniformly with epichlorohydrin, then a phase transfer catalyst is added. Reacted at 60-120℃ for 0.5-4h. Then 10-50wt% lye is added dropwise at room temperature-100℃, and reacted for 0.5-6h. The system is washed with water several times until pH≈7, and then the excess epichlorohydrin and water are removed by rotary evaporation to obtain a bio-based halogen-free flame-retardant toughened epoxy resin. 100 parts of bio-based halogen-free flame-retardant toughened epoxy resin is added with latent curing agent and accelerator at 60-100℃ to obtain a bio-based halogen-free flame-retardant toughened epoxy resin for 3C electronics; d. A bio-based halogen-free flame-retardant toughened epoxy resin for 3C electronics is heated to a molten state to ensure that it is completely melted and has good fluidity. Then, the molten epoxy resin is uniformly coated or impregnated on the surface of the reinforcing material laid on the release paper to ensure that the resin can fully penetrate and uniformly distribute in each part of the reinforcing material. The reinforcing material after impregnating the resin is compacted by rolling equipment to ensure that the resin and the reinforcing material are closely combined. Finally, the surface of the prepreg after rolling is coated, wound and cooled to obtain a bio-based halogen-free flame-retardant toughened epoxy prepreg for 3C electronics.

3. The method of claim 2, wherein, The aliphatic polyamine in step a includes one or more of ethylenediamine, pentanediamine, hexanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, triethylenetetramine, tetraethylenepentamine, N,N'-bis(3-aminopropyl)ethylenediamine, and N,N'-bis(2-aminoethyl)-1,3-propanediamine.

4. The preparation method according to claim 2, characterized in that, The molar ratio of bio-based vanillin to aliphatic polyamine in step a is (0.5-4):

1.

5. The preparation method according to claim 2, characterized in that, The specific solvent in step a is one or more of water or hydrocarbons, alcohols, esters, ethers, ketones, and other organic solvents.

6. The preparation method according to claim 2, characterized in that, The organic flame retardant containing secondary amino groups, phosphorus-hydrogen bonds or silicon-hydrogen bonds and other groups in step b should have at least one N-H, Si-H or P-H bond in its molecular structure, and its general formula is as follows:

7. The preparation method according to claim 2, characterized in that, The catalyst in step b is a Lewis acid catalyst, and the amount added is 0.5-5% of the mass percentage of the organic flame retardant.

8. The preparation method according to claim 2, characterized in that, The molar ratio of the bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor to the epichlorohydrin in step c should be 1:(2-20). The phase transfer catalyst is a quaternary ammonium salt or quaternary phosphonium salt catalyst, and the amount added is 2-10% of the mass percentage of the bio-based halogen-free flame-retardant toughened epoxy resin synthesis precursor.

9. The preparation method according to claim 2, characterized in that, The latent curing agent in step c is one or more of succinic acid hydrazide, adipic acid dihydrazide, dicyandiamide, imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, maleic anhydride, and phthalic anhydride, and the amount added is 3-15 parts.

10. The method of claim 2, wherein, The accelerator in step c is one or more of carbonyl diimidazole, aluminum acetylacetone, o-methylbenzene di-guanidine, N-(2-hydroxyphenyl)-N',N'-dimethylurea, N-(2-hydroxy-4-nitrophenyl)-N',N'-dimethylurea, N-(5-chloro-2-hydroxyphenyl)-N',N'-dimethylurea, N-(4-chlorophenyl)-N',N'-dimethylurea, N-(4-chloro-2-hydroxyphenyl)-N',N'-dimethylurea, 3-phenyl-1,1-dimethylurea, and 3-(4-chlorophenyl)-1,1-dimethylurea, and the amount added is 0-5 parts.

11. The method of claim 2, wherein, The viscosity of the bio-based halogen-free flame-retardant toughened epoxy resin for 3C electronics in step c at 70°C should be in the range of 7000-40000 mPa·s.

12. The method of claim 2, wherein, The reinforcing material in step d is one or more of glass fiber mat, electronic-grade glass fiber cloth, unidirectional glass fiber cloth, plain carbon fiber cloth, twill carbon fiber cloth, satin carbon fiber cloth, unidirectional carbon fiber cloth, carbon fiber mat, plain basalt fiber cloth, twill basalt fiber cloth, satin basalt fiber cloth, unidirectional basalt fiber cloth, and basalt fiber mat, and the amount of reinforcing material is 70-150 parts.

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