Full-bio-based epoxy resin composite material based on cardanol modified boron nitride and preparation method of full-bio-based epoxy resin composite material

Abstract

The invention discloses a full-bio-based epoxy resin composite material based on cardanol modified boron nitride and a preparation method of the full-bio-based epoxy resin composite material. According to the phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant heat conduction agent and the phosphorus-containing cardanol-based flame-retardant curing agent grafted boron nitride flame-retardant heat conduction agent provided by the invention, the preparation process is based on a technology of combining molecular design, grafting modification and heat conduction and flame retardance, and hydroxylated boron nitride is grafted and modified by a cardanol-based flame-retardant epoxy monomer; and the flame-retardant and heat-conducting bio-based epoxy resin composite material is obtained by introducing the flame-retardant and heat-conducting bio-based epoxy resin into the epoxy resin, so that the defects of flammability and low heat conductivity of the epoxy resin are overcome, and the application range of the flame-retardant and heat-conducting bio-based

Description

Technical Field

[0001] The present invention relates to a fully bio-based epoxy resin composite material based on cardanol-modified boron nitride and a preparation method thereof, belonging to the technical field of chemical materials. Background Art

[0002] With the global deployment of 5G networks and the rapid development of technologies such as the Internet of Things and artificial intelligence, the demand for high-frequency, high-speed, and high-reliability printed circuit boards (PCBs) has skyrocketed. As the core carrier of electronic devices, PCB performance directly determines signal transmission efficiency, device stability, and energy management capabilities. Therefore, epoxy resin has become a key material in PCB manufacturing due to its low cost, easy processing, excellent electrical insulation, and chemical stability. However, the characteristics of 5G technology place higher demands on epoxy resin. High power density and miniaturized designs exacerbate the thermal management challenges of PCBs, creating an urgent need for epoxy resin composites that combine efficient thermal conductivity with flame retardancy and safety.

[0003] Among renewable biomass, cardanol is a natural product extracted from cashew nut shell liquid. Its chemical structure combines a benzene ring structure, a phenolic hydroxyl group, and a C15 linear chain with an unsaturated double bond. The benzene ring imparts rigidity to the material, while the long alkyl chain imparts toughness, giving cardanol its "hardness and flexibility" properties. This has become a research hotspot in the field of bio-based materials in recent years. Furthermore, the unsaturated double bonds and phenolic hydroxyl groups in cardanol's structure impart excellent reactivity, allowing it to be chemically modified to produce high-performance flame retardants. Currently, the application of cardanol in epoxy resins primarily involves using it as a modifier or additive to modify the epoxy resin, followed by its addition to the epoxy resin. However, the overall proportion of cardanol in epoxy resins is relatively small, hindering its full potential.

[0004] At the same time, boron nitride (BN) has become a promising candidate filler due to its excellent mechanical properties, superior thermal conductivity, low density, and chemical resistance. However, strong van der Waals forces between BN layers easily lead to agglomeration. Furthermore, its high surface chemical inertness limits its application. Currently, research on the use of boron nitride as a filler in epoxy resin modification has made some progress. However, current research focuses primarily on simply modifying boron nitride and then adding it directly to the epoxy resin system. For example, in patent CN116515244A, a phosphorus-nitrogen composite-modified epoxy resin and copper-clad laminate prepared therefrom, boron nitride is modified with lignin and then added directly to the epoxy resin as a flame retardant additive. In patent CN119708811A, a boron nitride-containing resin composition and its application, boron nitride is mixed with a sintering aid, sintered, and crushed to obtain the modified boron nitride, thereby increasing the boron nitride filling ratio in the resin.

[0005] At present, there is no report on how to prepare a fully bio-based epoxy resin composite material with added bio-based modified boron nitride. How to use cardanol to prepare a flame retardant and thermally conductive epoxy resin is crucial for the application of epoxy resin in PCBs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention introduces a phosphorus-containing cardanol-based flame-retardant epoxy monomer and a phosphorus-containing cardanol-based flame-retardant curing agent. Leveraging their unique chemical structure and reactivity, the present invention addresses the dispersibility and compatibility issues of boron nitride in epoxy resins, while also simplifying the process and reducing costs. The composite material prepared by the present invention not only exhibits excellent flame retardancy and thermal conductivity but also achieves environmental and sustainable development goals.

[0007] The present invention is achieved through the following technical solutions:

[0008] The first object of the present invention is to provide a method for preparing a fully bio-based epoxy resin composite material based on cardanol-modified boron nitride, comprising the following steps:

[0009] S1. Dissolve cardanol, an acid-binding agent, and a P-Cl compound in an organic solvent, react at 40-80°C, filter the reaction solution, partially purify the filtrate, wash with water, and dry to obtain a phosphorus-containing cardanol derivative;

[0010] S2. Dissolving a phosphorus-containing cardanol derivative and an epoxidizing agent in an organic solvent, reacting the mixture under ice bath, filtering the reaction solution, partially purifying the filtrate, washing the filtrate with water, and drying the filtrate to obtain a phosphorus-containing cardanol-based flame-retardant epoxy monomer;

[0011] S3, adding the phosphorus-containing cardanol derivative and the unsaturated dicarboxylic anhydride into the reactor in sequence and continuously stirring and mixing until uniform, reflux and condense at 160-200° C. under nitrogen or inert gas protection, dissolving the crude product in an organic solvent after the reaction, washing and purifying, collecting the organic phase and removing the solvent to obtain a phosphorus-containing cardanol-based curing agent;

[0012] S4, adding boron nitride powder to a solvent for ultrasonic dispersion, then adding 3-6 mol / L NaOH solution, reacting at 40-80°C, and drying after the reaction to obtain hydroxylated boron nitride;

[0013] S5. Evenly mix the phosphorus-containing cardanol-based flame-retardant epoxy monomer prepared in S2, the hydroxylated boron nitride prepared in S4, a catalyst, and an organic solvent in a reactor, react at 80-150° C., wash the resulting solid with water, and then dry it to obtain an epoxy monomer-grafted boron nitride flame-retardant thermal conductive agent;

[0014] S6. Add the phosphorus-containing cardanol-based flame retardant curing agent prepared in S3 and the hydroxylated boron nitride prepared in S4 to an organic solvent, and react at 40-80° C. under vigorous stirring. Wash the resulting solid with water and then dry it to obtain a curing agent-grafted boron nitride flame retardant thermal conductive agent.

[0015] S7. Dissolve the epoxy monomer grafted boron nitride flame retardant thermal conductive agent prepared in S5 or the curing agent grafted boron nitride flame retardant thermal conductive agent prepared in S6 in an organic solvent, disperse evenly, add it to a certain amount of phosphorus-containing cardanol-based flame retardant epoxy monomer prepared in S2, and then add a corresponding amount of phosphorus-containing cardanol-based flame retardant curing agent prepared in S3. After stirring and mixing evenly, cure at 90-130°C for 1-3 h, at 140-160°C for 1-3 h, and at 170-200°C for 1-3 h to obtain a fully bio-based epoxy resin composite material, wherein the epoxy monomer grafted boron nitride flame retardant thermal conductive agent or the curing agent grafted boron nitride flame retardant thermal conductive agent accounts for 20-35% of the total composite material mass; the molar ratio of the cardanol-containing epoxy monomer to the phosphorus-containing cardanol-based flame retardant curing agent is (1-2):1.

[0016] In one embodiment of the present invention, the organic solvent is one or a mixture of chloroform, dichloromethane, toluene, xylene, tetrahydrofuran.

[0017] In one embodiment of the present invention, the amount of the organic solvent used is 30-80% of the mass of the total reaction system.

[0018] In one embodiment of the present invention, the P-Cl compound in S1 is one or a mixture of diphenyl chlorophosphate, diphenylphosphinyl chloride, phenyl dichloride, phenylphosphonic acid dichloride, phosphorus oxychloride, phosphorus trichloride, hexachlorocyclotriphosphazene.

[0019] In one embodiment of the present invention, the molar ratio of cardanol, acid-binding agent and P-Cl compound in S1 is (1-6):(1-6):1.

[0020] In one embodiment of the present invention, the acid binding agent in S1 is one or a mixture of triethylamine, pyridine, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

[0021] In one embodiment of the present invention, the epoxidation oxidant in S2 is one or a mixture of m-chloroperbenzoic acid (m-CPBA), hydrogen peroxide, and peracetic acid.

[0022] In one embodiment of the present invention, the molar ratio of the phosphorus-containing cardanol derivative to the epoxidation oxidant in S2 is 1:(1-6).

[0023] In one embodiment of the present invention, the molar ratio of the phosphorus-containing cardanol derivative to the unsaturated dicarboxylic anhydride in S3 is 1:(1-3).

[0024] In one embodiment of the present invention, the unsaturated dicarboxylic anhydride in S3 is maleic anhydride, itaconic anhydride, citraconic anhydride or a mixture of several thereof.

[0025] In one embodiment of the present invention, the mass ratio of boron nitride to sodium hydroxide solution in S4 is 1:(1-5).

[0026] In one embodiment of the present invention, the solvent in step S4 is water, ethanol, acetone or a mixture of several thereof.

[0027] In one embodiment of the present invention, the mass ratio of the phosphorus-containing cardanol-based epoxy monomer to the hydroxylated boron nitride in S5 is (1-15):1.

[0028] In one embodiment of the present invention, the catalyst in S5 is one or a mixture of triethylamine, sodium hydroxide, boron trifluoride, and boron trifluoride ether.

[0029] In one embodiment of the present invention, the mass ratio of the phosphorus-containing cardanol-based flame retardant curing agent to the hydroxylated boron nitride in S6 is (1-15):1.

[0030] The second object of the present invention is to provide a fully bio-based epoxy resin composite material based on cardanol-modified boron nitride prepared by the method.

[0031] The third object of the present invention is to provide an application of the all-biobased epoxy resin composite material based on cardanol-modified boron nitride in the preparation of circuit boards.

[0032] Beneficial effects of the present invention:

[0033] The present invention utilizes a phosphorus-containing cardanol-based flame-retardant epoxy monomer or a phosphorus-containing cardanol-based flame-retardant curing agent to graft boron nitride to prepare a flame-retardant thermal conductive agent. The prepared flame-retardant thermal conductive agent is then synergistically prepared with a phosphorus-containing cardanol-based flame-retardant curing agent and a phosphorus-containing cardanol-based flame-retardant epoxy resin monomer to prepare an all-biobased epoxy resin composite material. Because the three components all use the renewable resource cardanol as a common raw material, molecular structure design and reasonable proportioning can achieve high compatibility between the components within the system, better addressing the problems of boron nitride's easy agglomeration and poor compatibility with epoxy resin. The all-biobased epoxy resin composite material prepared by the present invention has excellent flame retardancy and thermal conductivity, achieving a balanced flame retardancy and thermal conductivity. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific examples. These implementation cases are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims appended hereto.

[0035] Source of raw materials:

[0036] Cardanol was provided by Cardolite (Zhuhai, China): a pale yellow liquid composed of 41% triene, 36% diene, 20% monoene, and 3% saturated compounds. Epoxy resin (DGEBA, E-44) was provided by Hefei Jiangfeng Chemical Co., Ltd. Phenylphosphonium dichloride (98%), hexachlorocyclotriphosphazene (98%), diphenyl chlorophosphate (97%), 3-chloroperbenzoic acid (85%), and boron nitride (10 μm) were purchased from Aladdin Chemical Co., Ltd. (Shanghai, China). Phosphorus oxychloride, chloroform, dichloromethane, anhydrous sodium sulfate, triethylamine, and 4,4'-diaminodiphenylmethane (DDM) were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0037] Test method:

[0038] Limiting oxygen index (LOI): According to GB / T 2406.2-2009, samples (size: 100 mm × 6.5 mm × 3.2 mm) were tested on an HC-2 oxygen index analyzer (Jiangning, China).

[0039] Cone Calorimeter test: According to ISO 5660-1, the sample (size 100 mm × 100 mm × 4 mm) is placed in aluminum foil, and the thermal radiation flux is 50 kW / m 2 .

[0040] Thermal Conductivity: Thermal diffusivity (α) and specific heat (Cp) were measured using a laser flash analyzer (LFA 467 Nanoflash, NETZSCH, Germany). Density (ρ) was estimated by measuring the sample volume and mass. The sample's TC value was obtained using the typical equation: TC = α × Cp × ρ.

[0041] The technical solutions of the present invention are described in detail below with reference to specific embodiments. In the following embodiments, unless otherwise specified, the reagents, materials and equipment used can be purchased from commercial sources, or prepared by conventional methods, or are commonly used in the industry.

[0042] Example 1: Preparation of a fully bio-based epoxy resin composite material with epoxy monomer grafted boron nitride flame retardant thermal conductive agent as the modifier

[0043] (1) In a three-necked flask, 0.2 mol of cardanol, 0.2 mol of triethylamine, and 0.1 mol of phenylphosphonium dichloride were dissolved in 250 mL of chloroform and reacted at 70°C for 5 h. After the reaction, the temperature was cooled to room temperature, filtered, and the filtrate was partially purified, washed with water, and dried to obtain a phosphorus-containing cardanol derivative.

[0044] (2) In a three-necked flask, 0.05 mol of a phosphorus-containing cardanol derivative and 0.3 mol of 3-chloroperoxybenzoic acid were dissolved in 200 mL of dichloromethane and reacted under ice for 5 h. The filtrate was filtered, partially purified, washed with water, and dried to obtain a phosphorus-containing cardanol-based flame-retardant epoxy monomer.

[0045] (3) 0.1 mol of a phosphorus-containing cardanol derivative and 0.2 mol of maleic anhydride were added sequentially to a three-necked round-bottom flask and stirred continuously to mix thoroughly. The mixture was refluxed and condensed at 195 °C under a nitrogen atmosphere for 6 h. Finally, the mixture was cooled to room temperature, and the crude product was dissolved in an organic solvent, washed and purified. The organic phase was collected and dried over anhydrous sodium sulfate. Finally, the solvent was removed by rotary evaporation to obtain a phosphorus-containing cardanol-based curing agent.

[0046] (4) Take 5 g of boron nitride powder and add it to 50 mL of ethanol and ultrasonically disperse it for 10 min. Then add 100 mL of 5 mol / L NaOH solution and reflux it in an oil bath at 100 °C for 20 h. After cooling, filter and dry it to obtain hydroxylated boron nitride.

[0047] (5) 0.1 mol of phosphorus-containing cardanol-based flame-retardant epoxy monomer, 0.2 mol of hydroxylated boron nitride, 0.1 mol of boron trifluoride etherate and 100 mL of dichloromethane were mixed evenly in a reactor. The reaction temperature was 90 °C and the reaction time was 6 h. The obtained solid was washed with water and then dried to obtain an epoxy monomer-grafted boron nitride flame-retardant thermal conductive agent.

[0048] (6) The above-mentioned phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent accounting for 20%, 25%, 30% and 35% of the total mass of the composite material synthesized above was dissolved in dichloromethane, and after ultrasonic dispersion, it was added to a certain amount of phosphorus-containing cardanol-based flame-retardant epoxy monomer, and then a corresponding amount of phosphorus-containing cardanol-based flame-retardant curing agent was added, wherein the molar ratio of phosphorus-containing cardanol-based flame-retardant epoxy monomer to phosphorus-containing cardanol-based curing agent was 2:1. After stirring and mixing evenly, the mixture was cured at 90-130°C for 1-3h, at 140-160°C for 1-3h, and at 170-200°C for 1-3h to obtain a fully bio-based epoxy resin composite material with flame retardancy, thermal conductivity and toughening functions, which were respectively recorded as composite material-1, composite material-2, composite material-3 and composite material-4.

[0049] The obtained all-biobased epoxy resin composite material was subjected to performance testing, and the test results are as follows:

[0050] Table 1

[0051]

[0052] The results show:

[0053] As the addition amount of phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent continues to increase, the limiting oxygen index of the composite material also continues to rise. At the same time, the peak heat release rate (PHRR) and total heat release (THR) of the composite material gradually decrease. The decrease in PHRR and THR further indicates the improvement of the flame retardant properties of the composite material. However, when the addition amount of phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent reaches 30%, the limiting oxygen index of the composite material begins to decrease and the PHRR also increases when the phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent is continued to be added. Continuing to increase the addition amount of phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent has little effect on improving the flame retardant properties.

[0054] As the addition level of the phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent increases, the thermal conductivity of the composite material increases significantly. However, when the addition level reaches 30%, further addition of the phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent causes the thermal conductivity of the composite material to decrease. This is due to the fact that the addition of nanoparticles alters the phonon scattering and coupling within the material. At low nanoparticle concentrations, the interaction between the nanoparticles and the matrix enhances phonon scattering, reducing the phonon mean free path and thus increasing thermal conductivity. However, when the nanoparticle concentration exceeds a certain value, phonon scattering becomes more complex. Excessive nanoparticles cause phonons to encounter more scattering centers during transmission, further reducing the phonon mean free path and thus inhibiting the increase in thermal conductivity.

[0055] Therefore, it can be considered that when the addition amount of phosphorus-containing cardanol-based flame-retardant epoxy monomer grafted boron nitride flame-retardant thermal conductive agent reaches 30%, the comprehensive performance of the composite material is good.

[0056] Example 2: Preparation of a fully bio-based epoxy resin composite material with a curing agent grafted with boron nitride flame retardant and thermal conductive agent

[0057] (1) In a three-necked flask, 0.2 mol of cardanol, 0.2 mol of triethylamine, and 0.1 mol of phenylphosphonium dichloride were dissolved in 250 mL of chloroform and reacted at 70°C for 5 h. After the reaction, the temperature was cooled to room temperature, filtered, and the filtrate was partially purified, washed with water, and dried to obtain a phosphorus-containing cardanol derivative.

[0058] (2) In a three-necked flask, 0.05 mol of a phosphorus-containing cardanol derivative and 0.3 mol of 3-chloroperoxybenzoic acid were dissolved in 200 mL of dichloromethane and reacted under ice for 5 h. The filtrate was filtered, partially purified, washed with water, and dried to obtain a phosphorus-containing cardanol-based flame-retardant epoxy monomer.

[0059] (3) 0.1 mol of a phosphorus-containing cardanol derivative and 0.2 mol of maleic anhydride were added sequentially to a three-necked round-bottom flask and stirred continuously until uniformly mixed. The mixture was refluxed at 195 °C under a nitrogen atmosphere for 6 h. Finally, the mixture was cooled to room temperature. The crude product was dissolved in an organic solvent, washed and purified, and the organic phase was collected and dried over anhydrous sodium sulfate. Finally, the solvent was removed by rotary evaporation to obtain a phosphorus-containing cardanol-based curing agent.

[0060] (4) Take 5 g of boron nitride powder and add it to 50 mL of ethanol and ultrasonically disperse it for 10 min. Then add 100 mL of 5 mol / L NaOH solution and reflux it in an oil bath at 100 °C for 20 h. After cooling, filter and dry it to obtain hydroxylated boron nitride.

[0061] (5) 0.2 mol of hydroxylated boron nitride and 0.1 mol of phosphorus-containing cardanol-based flame retardant curing agent were placed in 100 mL of tetrahydrofuran and refluxed at 60 °C for 6 h under vigorous stirring. The obtained solid was washed with water and then dried to obtain a phosphorus-containing cardanol-based flame retardant curing agent grafted boron nitride flame retardant thermal conductive agent.

[0062] (6) The phosphorus-containing cardanol-based flame retardant curing agent grafted boron nitride flame retardant thermal conductive agent synthesized above, accounting for 20%, 25%, 30%, and 35% of the total mass of the composite material, was dissolved in dichloromethane and evenly dispersed by ultrasonication. Then, it was added to a certain amount of phosphorus-containing cardanol-based flame retardant epoxy monomer, and then a corresponding amount of phosphorus-containing cardanol-based flame retardant curing agent was added, wherein the molar ratio of phosphorus-containing cardanol-based flame retardant epoxy monomer to phosphorus-containing cardanol-based flame retardant curing agent was 4:1. After stirring and mixing evenly, the mixture was cured at 90-130 °C for 1-3 h, at 140-160 °C for 1-3 h, and at 170-200 °C for 1-3 h to obtain a fully bio-based epoxy resin composite material with flame retardancy, thermal conductivity, and toughening functions, which were respectively recorded as composite material-5, composite material-6, composite material-7, and composite material-8.

[0063] Example 3: Effect of Temperatures of Different Phosphorus-Containing Cardanol-Based Flame Retardant Curing Agents Grafted onto Hydroxylated Boron Nitride on the Preparation of Fully Bio-Based Epoxy Resin Composite Materials with Curing Agent Grafted onto Boron Nitride Flame Retardant Thermal Conductive Agent

[0064] Specific implementation method The preparation method of composite material-7 in which the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounts for 30% of the total mass of the composite material is the same as in Example 2, except that the temperature of 60°C for grafting hydroxylated boron nitride with the phosphorus-containing cardanol-based flame retardant curing agent in step (5) is adjusted to 40°C and 80°C, while other conditions remain unchanged. The fully bio-based epoxy resin composite materials in which the modifier is the curing agent grafted boron nitride flame retardant thermal conductive agent are prepared, and are respectively recorded as composite material-9 and composite material-10.

[0065] The performance of the all-biobased epoxy resin composite materials obtained in Example 2 and Example 3 was tested, and the test results are as follows:

[0066] Table 2

[0067]

[0068] The results show:

[0069] As the addition level of the phosphorus-containing cardanol-based flame retardant curing agent grafted with boron nitride flame retardant thermal conductor increases, the limiting oxygen index (LOI) of the composite material increases. Simultaneously, the peak heat release rate (PHRR) and total heat release (THR) of the composite material decrease. This decrease in PHRR and THR indicates improved flame retardancy, a finding consistent with the increasing LOI trend. Furthermore, the thermal conductivity of the composite material increases significantly with increasing addition level of the phosphorus-containing cardanol-based flame retardant curing agent grafted with boron nitride flame retardant thermal conductor. However, when the addition level reaches 30%, the thermal conductivity of the composite material begins to decrease with further addition of the phosphorus-containing cardanol-based flame retardant curing agent grafted with boron nitride flame retardant thermal conductor.

[0070] The flame retardant and thermal conductivity effects of the composite material containing a phosphorus-containing cardanol-based flame retardant curing agent grafted onto boron nitride are better than those of the composite material containing a phosphorus-containing cardanol-based flame retardant epoxy monomer grafted onto boron nitride. This is because the grafting rate of a phosphorus-containing cardanol-based flame retardant curing agent grafted onto hydroxylated boron nitride is greater than the grafting rate of a phosphorus-containing cardanol-based flame retardant epoxy monomer grafted onto hydroxylated boron nitride.

[0071] When the temperature for grafting phosphorus-containing cardanol-based flame-retardant epoxy monomer onto hydroxylated boron nitride is 40 ℃, the grafting of phosphorus-containing cardanol-based flame-retardant curing agent and boron nitride is less, and the compatibility of hydroxylated boron nitride in the epoxy system is poor, so the thermal conductivity decreases. When the temperature for grafting phosphorus-containing cardanol-based flame-retardant epoxy monomer onto hydroxylated boron nitride is 80 ℃, the reaction produces more by-products, resulting in a decrease in the yield of phosphorus-containing cardanol-based flame-retardant curing agent grafted onto boron nitride flame-retardant thermal conductive agent, so the thermal conductivity will decrease.

[0072] In summary, based on the balance between flame retardancy and thermal conductivity, the composite material 7 in Example 2 has the best overall performance.

[0073] Furthermore, based on the composite material-7 in Example 2 having the best overall performance, comparisons were made with other comparative examples.

[0074] Comparative Example 1: Curing agent modified boron nitride without hydroxyl groups

[0075] The epoxy resin composite material was prepared by preparing the composite material-7 in which the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material in Example 2, except that the curing agent was used to directly modify the boron nitride (the boron nitride did not need to be hydroxylated) instead of the curing agent-modified hydroxylated boron nitride, omitting step (4) and keeping other conditions unchanged.

[0076] Comparative Example 2: Direct addition of boron nitride

[0077] The epoxy resin composite material was prepared by specifically preparing the composite material-7 in which the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material in Example 2, except that boron nitride was used instead of the phosphorus-containing cardanol-based flame retardant curing agent grafted boron nitride flame retardant thermal conductive agent, omitting steps (4) and (5), and keeping other conditions unchanged.

[0078] Comparative Example 3: Using Alumina

[0079] The epoxy resin composite material was prepared by using the same method as in Example 2, wherein the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material, except that alumina was used instead of the phosphorus-containing cardanol-based flame retardant curing agent grafted boron nitride flame retardant thermal conductive agent, and steps (4) and (5) were omitted. Other conditions remained unchanged.

[0080] Comparative Example 4: Boron Nitride Modified with Eugenol-Based Curing Agent

[0081] The epoxy resin composite material was prepared by preparing the composite material-7 in which the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material in Example 2, except that eugenol was used instead of cardanol. Other conditions remained unchanged.

[0082] Comparative Example 5: Single-unit commercial use

[0083] The epoxy resin composite material was prepared by using the same method as in Example 2, wherein the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material, except that DGEBA was used instead of the phosphorus-containing cardanol-based epoxy monomer, step (2) was omitted, and other conditions remained unchanged.

[0084] Comparative Example 6: Commercial Curing Agent

[0085] The epoxy resin composite material was prepared in the same manner as in Example 2, wherein the curing agent-grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material, except that DDM was used instead of the phosphorus-containing cardanol-based curing agent. Other conditions remained unchanged.

[0086] Comparative Example 7: Both monomer and curing agent are commercially available

[0087] The epoxy resin composite material was prepared by specifically preparing the composite material-7 in which the curing agent grafted hydroxylated boron nitride flame retardant thermal conductive agent accounted for 30% of the total mass of the composite material in Example 2, except that DGEBA was used instead of the phosphorus-containing cardanol-based epoxy monomer and DDM was used instead of the phosphorus-containing cardanol-based curing agent, step (2) was omitted, and other conditions remained unchanged.

[0088] The epoxy resin composite materials obtained in Comparative Examples 1 to 8 were subjected to performance tests, and the test results are as follows:

[0089] Table 3

[0090]

[0091] The results show:

[0092] In Comparative Example 1, boron nitride that has not been hydroxylated is grafted onto the phosphorus-containing cardanol-based flame retardant curing agent, which reduces the grafting rate of the boron nitride onto the phosphorus-containing cardanol-based flame retardant curing agent and reduces the thermal conductivity of the composite material.

[0093] In Comparative Example 2, hydroxylated boron nitride that has not been grafted and modified is used, so its dispersibility in the epoxy matrix is ​​not as good as the dispersibility and compatibility of boron nitride grafted with a phosphorus-containing cardanol-based flame retardant curing agent, resulting in a decrease in the thermal conductivity of the composite material.

[0094] In Comparative Example 3, aluminum oxide was used instead of boron nitride grafted with a phosphorus-containing cardanol-based flame retardant curing agent. Since aluminum oxide is mostly spherical, its flame retardancy and thermal conductivity are poor. Boron nitride, on the other hand, has a layered structure. Furthermore, after being grafted with a phosphorus-containing cardanol-based flame retardant curing agent, boron nitride exhibits better dispersibility and compatibility in the epoxy system, resulting in improved flame retardancy and thermal conductivity.

[0095] In Comparative Example 4, eugenol was used instead of cardanol. Since eugenol has only one double bond and can only form one epoxy group, the crosslinking density of the eugenol derivative epoxy monomer after curing with the eugenol derivative curing agent is lower than the crosslinking density of the cardanol derivative epoxy monomer after curing with the cardanol derivative curing agent, resulting in reduced flame retardancy and thermal conductivity.

[0096] In Comparative Example 5, DGEBA was used instead of the phosphorus-containing cardanol-based flame-retardant epoxy monomer, and the flame retardant effect was poor, but the thermal conductivity was similar to that of the phosphorus-containing cardanol-based flame-retardant composite material.

[0097] In Comparative Example 6, DDM was used instead of the phosphorus-containing cardanol-based flame retardant curing agent, and the flame retardant effect was poor, but the thermal conductivity was not much different from that of the phosphorus-containing cardanol-based flame retardant composite material.

[0098] In Comparative Example 7, DGEBA and DDM were used simultaneously to replace the phosphorus-containing cardanol-based flame-retardant epoxy monomer and the phosphorus-containing cardanol-based flame-retardant curing agent. The flame retardant effect was poor, but the thermal conductivity was similar to that of the phosphorus-containing cardanol-based flame-retardant composite material.

[0099] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described in detail to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art, in combination with existing common knowledge, fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a fully bio-based epoxy resin composite material based on cardanol-modified boron nitride, comprising the following steps: S1, dissolving cardanol, an acid-binding agent, and a P-Cl compound in an organic solvent, reacting at 40-80° C., filtering the reaction solution, partially purifying the filtrate, washing with water, and drying to obtain a phosphorus-containing cardanol derivative; S2, dissolving the phosphorus-containing cardanol derivative and the epoxidation oxidant in an organic solvent, reacting under an ice bath, filtering the reaction solution, washing the filtrate with water, and drying to obtain a phosphorus-containing cardanol-based flame-retardant epoxy monomer; S3, adding the phosphorus-containing cardanol derivative and the unsaturated dicarboxylic anhydride to the reactor in sequence and continuously stirring and mixing them uniformly, reflux condensing at 160-200° C. under nitrogen or inert gas protection, dissolving the crude product in an organic solvent after the reaction, washing and purifying, collecting the organic phase and removing the solvent to obtain a phosphorus-containing cardanol-based curing agent; S4, taking boron nitride powder, adding it to a solvent and ultrasonically dispersing it, then adding 3-6 mol / L NaOH solution, reacting it at 40-80° C., and drying it after the reaction to obtain hydroxylated boron nitride; S5, uniformly mixing the phosphorus-containing cardanol-based flame-retardant epoxy monomer prepared in S2, the hydroxylated boron nitride prepared in S4, a catalyst, and an organic solvent in a reactor, reacting at 80-150° C., washing the resulting solid with water, and then drying it to obtain an epoxy monomer-grafted boron nitride flame-retardant thermal conductive agent; S6. Add the phosphorus-containing cardanol-based flame retardant curing agent prepared in S3 and the hydroxylated boron nitride prepared in S4 to an organic solvent, and react at 40-80° C. under vigorous stirring. Wash the solid obtained by the reaction with water and then dry it to obtain a curing agent-grafted boron nitride flame retardant thermal conductive agent; S7, dissolving the epoxy monomer grafted boron nitride flame retardant thermal conductive agent prepared in S5 or the curing agent grafted boron nitride flame retardant thermal conductive agent prepared in S6 in an organic solvent, and after uniform dispersion, adding it to a certain amount of phosphorus-containing cardanol-based flame retardant epoxy monomer prepared in S2, and then adding a corresponding amount of phosphorus-containing cardanol-based flame retardant curing agent prepared in S3, stirring and mixing evenly and volatilizing the solvent, and curing at 90-130°C for 1-3h, curing at 140-160°C for 1-3h, and curing at 170-200°C for 1-3h to obtain a fully bio-based epoxy resin composite material, wherein, The epoxy monomer grafted boron nitride flame retardant thermal conductive agent or the curing agent grafted boron nitride flame retardant thermal conductive agent accounts for 20-35% of the total composite material mass; the molar ratio of the cardanol-containing epoxy monomer to the phosphorus-containing cardanol-based flame retardant curing agent is (1-2):

1.

2. The preparation method according to claim 1, characterized in that The P-Cl compound in S1 is one or a mixture of diphenyl chlorophosphate, diphenylphosphinyl chloride, phenyl dichloride, phenyl phosphorus dichloride, phosphorus oxychloride, phosphorus trichloride, hexachlorocyclotriphosphazene.

3. The preparation method according to claim 1, characterized in that The acid binding agent in S1 is one or a mixture of triethylamine, pyridine, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

4. The preparation method according to claim 1, characterized in that The molar ratio of cardanol, acid-binding agent and P-Cl compound in S1 is (1-6):(1-6):

1.

5. The preparation method according to claim 1, characterized in that The epoxidation oxidant in S2 is one or a mixture of m-chloroperbenzoic acid, hydrogen peroxide, and peracetic acid.

6. The preparation method according to claim 1, characterized in that The unsaturated dicarboxylic anhydride in S3 is one or a mixture of maleic anhydride, itaconic anhydride and citraconic anhydride.

7. The preparation method according to claim 1, characterized in that The mass ratio of the phosphorus-containing cardanol-based epoxy monomer to the hydroxylated boron nitride in S5 is (1-15):1; the mass ratio of the phosphorus-containing cardanol-based flame retardant curing agent to the hydroxylated boron nitride in S6 is (1-15):

1.

8. The preparation method according to claim 1, characterized in that The catalyst in S5 is one or a mixture of triethylamine, sodium hydroxide, boron trifluoride, and boron trifluoride ether.

9. A fully bio-based epoxy resin composite material based on cardanol-modified boron nitride prepared by the method according to any one of claims 1 to 8.

10. Use of the all-biobased epoxy resin composite material based on cardanol-modified boron nitride according to claim 9 in the preparation of circuit boards.

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