A cardanol-based epoxy resin containing a fatty amine and having basic properties and mechanical strength, and a method for preparing the same

Abstract

The application discloses a cardanol-based epoxy resin with a fatty amine, and a preparation method thereof, and belongs to the field of flame-retardant technology.The preparation method comprises the following steps: introducing an aldehyde group on a benzene ring of cardanol, and then reacting with a diamine to form an epoxy resin precursor; and fully mixing and reacting an epoxy chloropropane, a phase transfer catalyst and an alkaline substance to obtain a cardanol-based epoxy resin with flame retardation and mechanical enhancement; the problems of the traditional bisphenol A type epoxy resin, such as non-renewable raw materials, brittleness caused by a molecular structure, flammability, and the fact that flame-retardant performance and mechanical performance cannot be considered together, are solved; the epoxy resin is prepared by using the widely-sourced and low-cost biomass cardanol as a raw material, combining the flexibility of a fatty chain and the rigidity of an aromatic hydrocarbon, improving the flame-retardant efficiency of a matrix and the mechanical performance of the epoxy resin at the same time in a Schiff base structure; and the cured epoxy resin system has excellent thermal stability, flame retardation and mechanical performance, and has an excellent popularization and application prospect.

Description

Technical Field

[0001] This invention relates to the field of flame retardant polymer materials, specifically to a cashew nut shell resin containing aliphatic amines and its mechanically enhanced flame retardant epoxy resin and its preparation method. Background Technology

[0002] Thermosetting epoxy resins are three-dimensional network polymers formed by crosslinking epoxy monomers or oligomers with a curing agent. Their unique characteristics lie in their insolubility and infusibility. This material exhibits excellent thermodynamic properties, outstanding chemical resistance, and superior dimensional stability, thus finding wide application in aerospace, coatings, high-performance composite materials, and electronic encapsulants, among other fields. Currently, over 90% of epoxy resins globally are composed of bisphenol A diglycidyl ether, synthesized from bisphenol A and epichlorohydrin. Bisphenol A is a compound derived from non-renewable petroleum resources. Its overexploitation and use not only exacerbate the energy crisis but also pose a potential threat to human health. Given these health, energy, and environmental considerations, the research field is actively exploring and developing suitable biomass raw materials to effectively replace petroleum-based bisphenol A. This research direction not only aligns with the concept of sustainable development but also opens up new paths for the future development of the epoxy resin industry.

[0003] Bio-based epoxy resins, as innovative synthetic materials, demonstrate significant green, environmentally friendly, and renewable characteristics by partially or completely replacing traditional resin components with renewable raw materials, showing great potential in production and daily life applications. This material can serve as an ideal alternative to traditional petroleum-based plastics and coatings, effectively alleviating the crisis of petroleum resource shortages and significantly reducing environmental pollution. Cashew nut shell extract, derived from natural cashew nut shell liquid, is widely available and readily accessible. As a unique alkylphenol, it has broad practical value in the preparation of thermosetting polymers, thus being regarded as a valuable source of bio-monomers. Existing technologies also include cashew nut shell derivatives for toughening and flame-retardant epoxy resins, effectively improving the flame retardancy and mechanical properties of epoxy resins. Invention patent CN114524927A reports the application of cashew nut shell bio-based polyols in flexible packaging adhesives, effectively solving the problem of solvent-free ink dissolution. Invention patent CN114920989A reports a method for applying cashew nut shell extract to rubber, which can effectively improve the performance of rubber products during rubber compounding. There are also bio-based toughening agents containing rigid-flexible structures that have been disclosed and used in epoxy resins. By utilizing the toughness of the aliphatic chains in the molecular structure, the toughness of epoxy resins can be improved to a certain extent. However, this also leads to lower mechanical properties due to changes in the steric hindrance of the epoxy resin itself, and increases the complexity and economic cost of its preparation process.

[0004] Therefore, there is an urgent need for an epoxy resin system that possesses excellent mechanical properties, biodegradability, and flame retardancy, while being simple to prepare, low in cost, and easy to mass-produce industrially. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a cashew nut shell resin containing aliphatic amines with mechanically enhanced flame-retardant properties and its preparation method, belonging to the field of flame-retardant technology. The preparation method includes: introducing an aldehyde group onto the benzene ring of cashew nut shell resin and reacting it with a diamine to form an epoxy resin precursor; thoroughly mixing and reacting the epoxy resin precursor, epichlorohydrin, a phase transfer catalyst, and an alkaline substance to obtain a cashew nut shell resin with both basic flame-retardant and mechanically enhanced properties. This invention solves the problems of non-renewable raw materials, high brittleness due to molecular structure, flammability, and the inability to simultaneously achieve flame-retardant and mechanical properties in traditional bisphenol A type epoxy resins. Using widely available and low-cost biomass cashew nut shell resin as raw material, and combining the flexibility of aliphatic chains with the rigidity of aromatic hydrocarbons, the invention improves the matrix flame-retardant efficiency while enhancing its mechanical properties through a Schiff base structure. The cured epoxy resin system exhibits excellent thermal stability, flame retardancy, and mechanical properties, and has excellent prospects for widespread application.

[0006] To achieve the above technical effects, the following technical solution is adopted:

[0007] A cashew nut phenol-containing, mechanically reinforced, flame-retardant epoxy resin with basic characteristics of aliphatic amines, has the following molecular structural formula:

[0008]

[0009] Wherein, R is an aliphatic linear chain and its derivatives with 4 to 12 carbon atoms.

[0010] A method for preparing a cashew nut shell resin containing aliphatic amines and characterized by mechanical strength and flame retardancy includes: step S1, cashew nut shell resin aldehyde formation; step S2, introduction of a Schiff base structure; and step S3, epoxidation. Specifically:

[0011] Step S1: Cashew nut shell powder, surfactant, and tin tetrachloride are thoroughly mixed in an organic solvent at room temperature; then paraformaldehyde is added, and after stirring for 30 minutes, the mixture is reacted in a reaction vessel under nitrogen protection; the mixture is purified to obtain aldehyde-modified cashew nut shell powder; the molecular structure of the aldehyde-modified cashew nut shell powder is as follows:

[0012]

[0013] Step S2: The aldehyde-modified cashew nut shell powder obtained in step S1 is thoroughly mixed with diamine in an organic solvent and reacted in a reaction vessel under nitrogen protection. After purification, a cashew nut shell powder-based epoxy resin precursor containing a Schiff base structure is obtained. The molecular structure of the epoxy resin precursor is shown below:

[0014]

[0015] Step S3: Epichlorohydrin, the epoxy resin precursor obtained in Step S2, the phase transfer catalyst, and the alkaline substance are thoroughly mixed and reacted in a reaction vessel under nitrogen protection. After purification, cashew nut shell phenol-reinforced mechanically enhanced flame-retardant epoxy resin is obtained. The molecular structure of the cashew nut shell phenol-reinforced mechanically enhanced flame-retardant epoxy resin is shown below:

[0016]

[0017] Wherein, R is an aliphatic linear chain and its derivatives with 4 to 12 carbon atoms.

[0018] Furthermore, in step S1, the molar ratio of cashew phenol, surfactant, tin tetrachloride, paraformaldehyde, and organic solvent is (0.8–1.2):(0.08–0.15):(0.08–0.12):(1.2–1.8):(2.0–3.0); the reaction temperature in step S1 is 80–100°C, and the reaction time is 8–9 hours.

[0019] Furthermore, the surfactant includes one or more combinations of benzyltriethylammonium chloride and tetrabutylammonium bromide (TBAB); the organic solvent includes one or more combinations of amines, alcohols, aromatic hydrocarbons, and dimethyl sulfoxide; the amine includes triethylamine; the alcohol includes ethanol; and the aromatic hydrocarbon includes toluene, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0020] Furthermore, in step S2, the molar ratio of aldehyde-modified cashew phenol, diamine, and organic solvent is (0.8–1.2):(0.3–0.6):(2.0–3.0); the reaction temperature in step S2 is 70–90°C, and the reaction time is 5–6 hours; the diamine is an aliphatic linear diamine with 4 to 12 carbon atoms or its derivatives.

[0021] Furthermore, the organic solvent is one or more combinations of alcohols, aromatic hydrocarbons, ketones, and ethers; the alcohols include ethanol; the aromatic hydrocarbons are one or more combinations of N,N-dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide; the ketones include acetone; and the ethers include petroleum ether and tetrahydrofuran.

[0022] Furthermore, in step S3, the molar ratio of epoxy resin precursor, epichlorohydrin, phase transfer catalyst, and alkaline substance is (0.8-1.2):(15-25):(0.08-0.15):(1.5-2.5); the reaction temperature in step S3 is 70-90℃, and the reaction time is 5-8 hours.

[0023] Furthermore, the phase transfer catalyst comprises one or more combinations of quaternary ammonium salts, polyethers, and quaternary phosphine salts; the quaternary ammonium salts are one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bisulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, or tetradecyltrimethylammonium chloride; the polyethers are chain-like polyethylene glycol; the quaternary phosphine salts are one or more of tetraphenylphosphine chloride, triphenylphosphine, and their derivatives; the alkaline substance is an aqueous solution of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate; and the concentration of the alkaline substance is 10 mol / L.

[0024] Furthermore, in steps S2 and S3, the purification process includes separation and drying steps:

[0025] The separation step specifically involves: extracting the mixture after the reaction with ethyl acetate and distilled water multiple times in sequence until the upper organic liquid is clear;

[0026] The drying step specifically involves using a desiccant and a vacuum drying oven to dry the organic liquid in sequence, in order to remove moisture and organic impurities from the organic liquid.

[0027] Furthermore, the desiccant is one or more combinations of sodium sulfate, sodium carbonate, potassium carbonate, calcium chloride, calcium sulfate, and calcium oxide, and the drying temperature in the vacuum drying oven is 50-80℃.

[0028] The beneficial effects of this invention are as follows:

[0029] 1) This invention provides a cashew nut shell resin containing aliphatic amines and its preparation method. Through molecular structure design and a simple synthesis process, it utilizes the structural stability advantage of cashew nut shell resin's C15 unsaturated flexible aliphatic chain. Simultaneously, a Schiff base structure is introduced by incorporating a benzene ring containing a rigid aromatic hydrocarbon structure and its derivatives. The C15 unsaturated aliphatic chain imparts flexibility to the resin matrix, while the π-π structure formed by the aromatic hydrocarbon structure and the Schiff base imparts rigidity, achieving a balance between rigidity and flexibility. Furthermore, the self-crosslinking of the Schiff base structure at high temperatures endows the resin matrix with excellent flame-retardant properties. This method can enhance the mechanical properties of the resin matrix while improving its flame-retardant performance. The advantages of this design concept include readily available and renewable raw materials, overcoming the drawback of traditional flame-retardant reinforcement methods that cannot simultaneously improve flame-retardant performance and mechanical properties.

[0030] 2) This invention provides a flame-retardant epoxy resin containing aliphatic amine cashew phenol and its preparation method. Cashew phenol, an aromatic compound derived from lignin (cashew shell oil) that can be produced on a large scale, is used as raw material to solve the problems of flammability and brittleness of thermosetting epoxy resins, while alleviating the problems of environmental pollution, excessive consumption and excessive emission of carbides in the process of fossil resource conversion.

[0031] 3) This invention provides a cashew phenol-based flame-retardant epoxy resin containing fatty amines and its preparation method. Through molecular structure design, it solves the problems of non-renewable raw materials, flammability, and high brittleness of traditional epoxy resins from the source.

[0032] 4) This invention provides a cashew phenol-based flame-retardant epoxy resin containing fatty amines and its preparation method. It is highly operable, well controllable, economically cost-effective, easy to implement, and has good prospects for widespread use, which is conducive to large-scale industrial production.

[0033] This invention solves the problems of traditional bisphenol A type epoxy resins, such as non-renewable raw materials, high brittleness due to molecular structure, flammability, and the inability to simultaneously achieve flame retardant and mechanical properties. It uses widely available and inexpensive biomass cashew phenol as a raw material, combining the flexibility of aliphatic chains with the rigidity of aromatic hydrocarbons, and improves both the flame retardant efficiency of the matrix and its mechanical properties through a Schiff base structure. The cured epoxy resin system exhibits excellent thermal stability, flame retardancy, and mechanical properties. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 The molecular structural formula of the aldehyde-containing substance in the embodiments of the present invention is shown below;

[0036] Figure 2 The molecular structural formula of the epoxy resin precursor material in the embodiments of the present invention is shown below;

[0037] Figure 3 The molecular structural formula of the cashew nut phenol-containing mechanically enhanced flame-retardant epoxy resin containing fatty amines is shown in the embodiment of the present invention.

[0038] Figure 4 This is a flowchart of the preparation method steps in an embodiment of the present invention;

[0039] Figure 5 The infrared spectrum of the cashew phenolic epoxy resin containing 1,6-hexanediamine prepared in Example 1 of this invention.

[0040] Figure 6 The infrared spectrum of the cashew phenolic epoxy resin containing 1,5-pentanediamine prepared in Example 2 of the present invention.

[0041] Figure 7 This is a comparison chart of the heat release rate curves of the embodiments and comparative examples of the present invention;

[0042] Figure 8 This is a comparison chart of the total heat release curves of the embodiments and comparative examples of the present invention;

[0043] Figure 9 This is a comparison chart of the smoke production rate curves of the embodiments and comparative examples of the present invention;

[0044] Figure 10 This is a comparison chart of the total smoke production curves of the embodiments and comparative examples of the present invention. Detailed Implementation

[0045] 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.

[0046] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0048] Please see Figures 1-8 This invention provides a technical solution: a cashew nut shell phenol-based mechanically reinforced flame-retardant epoxy resin, which has the following molecular structure: Figure 3 As shown.

[0049] On the other hand, a method for preparing the cashew nut phenol-based mechanically enhanced flame-retardant epoxy resin containing fatty amines is provided, the preparation process as follows: Figure 4 As shown, it specifically includes:

[0050] In the first stage, cashew nut shellac, a surfactant, and tin tetrachloride were thoroughly mixed in an organic solvent at room temperature. Then, paraformaldehyde was added, and the mixture was stirred for 30 minutes, followed by low-speed stirring at 80-100°C for 8-9 hours. The mixture was purified to obtain an aldehyde-modified cashew nut shellac oil. It possesses the following properties: Figure 1 The molecular structural formula shown;

[0051] In the second stage, the aldehyde-modified cashew phenol and diamine are thoroughly mixed in an organic solvent and reacted in a reaction vessel at 70-90°C under nitrogen protection for 5-6 hours. After purification, a cashew phenol-based epoxy resin precursor containing a Schiff base structure is obtained, which has the following properties: Figure 2 The molecular structural formula shown;

[0052] In the third stage, the above-mentioned epoxy resin precursor, epichlorohydrin, phase transfer catalyst, and alkaline substance are thoroughly mixed and reacted in a reaction vessel at 70-90℃ under nitrogen protection for 5-8 hours. After purification, a cardamom-based flame-retardant and mechanically reinforced epoxy resin is obtained, which has the following properties: Figure 3 The molecular structure shown is shown.

[0053] Furthermore, the mass ratios of cashew phenol, surfactant, tin tetrachloride, paraformaldehyde, and organic solvent are as follows: (0.8–1.2): (0.08–0.15): (0.08–0.12): (1.2–1.8): (2.0–3.0).

[0054] Furthermore, the mass ratio of the aldehyde-modified cashew phenol, diamine, and organic solvent is (0.8–1.2):(0.3–0.6):(2.0–3.0).

[0055] Furthermore, the mass ratio of epoxy resin precursor, epichlorohydrin, phase transfer catalyst, and alkaline substance is (0.8-1.2):(15-25):(0.08-0.15):(1.5-2.5).

[0056] Furthermore, the purification process involves separating and drying the reacted mixture system.

[0057] In the separation step, the mixture after the separation reaction is extracted and separated multiple times with ethyl acetate and distilled water until the upper organic liquid is clear.

[0058] Furthermore, in the drying step, a desiccant and a vacuum drying oven are used sequentially to dry the organic liquid, in order to remove moisture and organic impurities from the organic liquid.

[0059] Furthermore, the desiccant is one or more combinations of sodium sulfate, sodium carbonate, potassium carbonate, calcium chloride, calcium sulfate, and calcium oxide.

[0060] Furthermore, the drying temperature in the vacuum drying oven is 50-80℃.

[0061] Furthermore, the surfactants include, but are not limited to, one or more combinations of benzyltriethylammonium chloride and tetrabutylammonium bromide.

[0062] Furthermore, the organic solvents include, but are not limited to, one or more combinations of amines, alcohols, aromatic hydrocarbons, and dimethyl sulfoxide.

[0063] Furthermore, the amine organic solvent is triethylamine; the alcohol organic solvent is ethanol; the aromatic hydrocarbon organic solvent is toluene, N,N-dimethylacetamide, and N-methylpyrrolidone; the ketone organic solvent is acetone; and the ether organic solvent is petroleum ether and tetrahydrofuran.

[0064] Furthermore, the phase transfer catalyst is one or more combinations of quaternary ammonium salts, polyethers, and quaternary phosphine salts; the quaternary ammonium salt phase transfer catalyst is benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, or tetradecyltrimethylammonium chloride; the polyether phase transfer catalyst is chain polyethylene glycol; and the quaternary phosphine salt phase transfer catalyst is tetraphenylphosphine chloride, triphenylphosphine, and their derivatives.

[0065] Furthermore, the alkaline substance is one or more aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate with a concentration of 10 mol / L.

[0066] Example 1

[0067] Triethylamine (0.55 mL, 0.004 mol), tin tetrachloride (IV) (0.261 g, 0.001 mol), and benzyltriethylammonium chloride (TEBA) (0.001 mol) were added to a solution of hydrogenated cashew phenol (3.04 g, 0.01 mol) in toluene (20 mL). The reaction mixture was stirred at room temperature under N2 for 30 minutes, then paraformaldehyde (0.66 g, 0.02 mol) was added, and finally the reaction mixture was stirred at 100 °C for 8 hours. After the reaction was completed, the reactants were cooled to room temperature, then poured into water and acidified with hydrochloric acid to pH 2. The aqueous layer was then extracted with ethyl acetate. The organic layer was dried over anhydrous sodium sulfate, filtered, and concentrated to dryness to obtain an aldehyde-containing substance with the following structural formula:

[0068]

[0069] The 13.28 g of aldehyde-containing substance and 3.27 g of 1,6-hexanediamine obtained above were uniformly mixed in a four-necked flask, and nitrogen gas was purged for 10 minutes. Then, 500 ml of DMAC was added, and the mixture was heated to 80 °C under nitrogen protection and reacted for 5 hours. The mixture was then poured into distilled water (while stirring slowly for a long time). After distillation and precipitation, the mixture was allowed to stand overnight and filtered to obtain the organic compound. Finally, the compound was dried in a vacuum drying oven at 80 °C for 24 hours to remove moisture, yielding an epoxy resin precursor with the following structural formula:

[0070]

[0071] The 3.22g epoxy resin precursor, 92.52g epichlorohydrin, and 3.22g tetrabutylammonium bromide obtained above were then uniformly mixed and placed in a 500ml flask. Under nitrogen protection, the mixture was heated to 80℃ and reacted for 3 hours. Then, 30ml of sodium hydroxide solution (10mol / L) was slowly added dropwise. The mixture was extracted and separated several times with ethyl acetate and distilled water until the upper organic liquid was clear. The organic layer was dried with sodium sulfate and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain 2.67g of oily, brownish-red cashew phenolic epoxy resin with the following structural formula:

[0072]

[0073] The infrared spectrum of the cashew phenol-based epoxy resin is as follows: Figure 5 As shown; by Figure 5 It can be seen that an absorption peak (1640 cm⁻¹) of the Schiff base structure appears. -1 3281cm -1 The absorption peaks of the epoxide group and epoxy group (925 cm⁻¹) -1 This indicates that cashew phenol-based epoxy resin containing 1,6-hexanediamine was successfully prepared.

[0074] Example 2

[0075] Triethylamine (0.55 mL, 0.004 mol), tin tetrachloride (IV) (0.261 g, 0.001 mol), and tetrabutylammonium bromide (TBAB) (0.001 mol) were added to a solution of hydrogenated cashew phenol (3.04 g, 0.01 mol) in toluene (20 mL). The reaction mixture was stirred at room temperature under N2 for 30 minutes, then paraformaldehyde (0.66 g, 0.02 mol) was added, and finally the reaction mixture was stirred at 100 °C for 8 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, then poured into water and acidified with hydrochloric acid to pH 2. The aqueous layer was then extracted with ethyl acetate. The organic layer was dried over anhydrous sodium sulfate, filtered, and concentrated to dryness to give an aldehyde-containing substance with the following structural formula:

[0076]

[0077] The 13.28 g of aldehyde-containing substance and 3.44 g of 1,5-pentanediamine obtained above were uniformly mixed in a four-necked flask, and nitrogen gas was purged for 10 minutes. Then, 500 ml of DMAC was added, and the mixture was heated to 80 °C under nitrogen protection and reacted for 5 hours. The mixture was then poured into distilled water (while stirring slowly for a long time). After distillation and precipitation, the mixture was allowed to stand overnight and filtered to obtain the organic compound. Finally, the compound was dried in a vacuum drying oven at 80 °C for 24 hours to remove moisture, yielding an epoxy resin precursor with the following structural formula:

[0078]

[0079] The 3.46g epoxy resin precursor, 92.52g epichlorohydrin, and 3.22g tetrabutylammonium bromide obtained above were then uniformly mixed and placed in a 500ml flask. Under nitrogen protection, the mixture was heated to 80℃ and reacted for 3 hours. Then, 30ml of sodium hydroxide solution (10mol / L) was slowly added dropwise. The mixture was extracted and separated several times with ethyl acetate and distilled water until the upper organic liquid was clear. The organic layer was dried with sodium sulfate and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain 2.83g of oily, brownish-red cashew phenolic epoxy resin with the following structural formula:

[0080]

[0081] The infrared spectrum of the cashew phenol-based epoxy resin, as shown below. Figure 6 As shown, an absorption peak (1641 cm⁻¹) of the Schiff base structure appears. -1 3275cm -1 The absorption peaks of the epoxide group and epoxy group (927 cm⁻¹) -1 This indicates that cashew phenol-based epoxy resin containing 1,5-pentanediamine was successfully prepared.

[0082] Comparative example:

[0083] 100g of E51 epoxy resin was mixed evenly with 25.28g of 4,4'-diaminodiphenylmethane (DDM). The mixture was first pre-cured at 80℃ for 1 hour, then cured at 120℃ for 2 hours and 150℃ for 2 hours to obtain the cured epoxy compound. According to standard ASTM D3801-20, the UL-94 test result for this cured compound was negative. A cone calorimeter was used at 35kW / m³. 2 The flame retardant properties of E51 epoxy resin were tested under radiation intensity. Figure 7 According to the data from the a and b tables, the peak heat release rate, total heat release, peak smoke production rate, and total smoke production of E51 epoxy resin are 703.5 kW / m³.2 84.742 MJ / m 2 0.206m 2 / s and 29.04m 2 These results indicate that E51 epoxy resin is prone to combustion, and generates a large amount of heat and toxic fumes during combustion.

[0084] Example 3

[0085] 100g of cashew phenol-based epoxy resin containing 1,6-hexanediamine synthesized in Example 1 was mixed evenly with 16.42g of 4,4'-diaminodiphenylmethane (DDM). The mixture was first pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and 150°C for 2 hours to obtain the cured epoxy. The flame retardancy of this cured product reached UL-94V0 level, as measured by standard ASTM D3801-20. A cone calorimeter was used at 35kW / m³. 2 The flame retardant properties of cashew phenol-based epoxy resin containing 1,6-hexanediamine were tested under radiation intensity. Figures 7-10 It can be seen that, compared with E51 epoxy resin, the peak heat release rate of cashew phenol-based epoxy resin containing 1,6-hexanediamine decreased by 55.1%, the total heat release decreased by 48.9%, the peak smoke production rate decreased by 16.5%, and the total smoke production decreased by 37.9%. This indicates that cashew phenol-based epoxy resin containing 1,6-hexanediamine has superior flame retardant properties.

[0086] Example 4

[0087] 100g of cashew phenol-based epoxy resin containing 1,5-pentanediamine synthesized in Example 2 was mixed evenly with 17.42g of 4,4'-diaminodiphenylmethane (DDM). The mixture was first pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and 150°C for 2 hours to obtain the cured epoxy. According to standard ASTM D3801-20, the flame retardancy of this cured product reached the UL-94V0 level. A cone calorimeter was used at 35kW / m³. 2 The flame retardant properties of cashew phenol-based epoxy resin containing 1,5-pentanediamine were tested under radiation intensity. Figures 7-10 It can be seen that, compared with E51 epoxy resin, the peak heat release rate of cashew phenol-based epoxy resin containing 1,5-pentanediamine decreased by 52.6%, the total heat release decreased by 45.1%, the peak smoke production rate decreased by 13.1%, and the total smoke production decreased by 31.1%. This indicates that cashew phenol-based epoxy resin containing 1,5-pentanediamine has excellent flame retardant properties.

[0088] Example 5

[0089] 100g of the cashew nut shell epoxy resin containing 1,6-hexanediamine synthesized in Example 1 was mixed evenly with 16.42g of 4,4'-diaminodiphenylmethane (DDM). The mixture was first pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and 150°C for 2 hours to obtain the cured epoxy. Table 1 shows that compared to E51 epoxy resin, the cashew nut shell epoxy resin containing 1,6-hexanediamine exhibited a 7.2% increase in tensile strength and a 593% increase in elongation at break, indicating that it possesses superior mechanical properties.

[0090] Table 1 Comparison of Mechanical Properties

[0091]

[0092] In summary, this invention discloses a cashew nut shell resin containing aliphatic amines and its mechanically enhanced flame-retardant epoxy resin and its preparation method. Addressing the shortcomings of traditional epoxy resins, such as non-renewable, flammable, brittle, and poorly biodegradable raw materials, this invention uses cashew nut shell resin, an aromatic compound derived from lignin and capable of large-scale production, as a raw material. Leveraging the structural stability advantage of cashew nut shell resin's C15 unsaturated flexible aliphatic chain, a Schiff base structure is introduced simultaneously with a benzene ring containing a rigid aromatic hydrocarbon structure and its derivatives. The C15 unsaturated aliphatic chain imparts flexibility to the resin matrix, while the π-π structure formed by the aromatic hydrocarbon structure and the Schiff base imparts rigidity, achieving a balance between rigidity and flexibility. Furthermore, the self-crosslinking of the Schiff base structure at high temperatures endows the resin matrix with excellent flame-retardant properties. The cured epoxy resin system exhibits excellent flame-retardant, toughness, and biodegradability. Moreover, its preparation method is highly operable, controllable, and easy to implement, facilitating large-scale industrial production.

[0093] Therefore, those skilled in the art will recognize that although embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A cashew nut phenol-based mechanically reinforced flame-retardant epoxy resin containing fatty amines, characterized in that, The molecular structure of the flame-retardant epoxy resin is: ； Wherein, R is an aliphatic straight chain and its derivatives with 4 to 12 carbon atoms; The preparation method of the cashew nut shell resin containing aliphatic amines with basic mechanical properties and flame retardant properties includes: step S1 is cashew nut shell aldehyde formation, step S2 is introducing a Schiff base structure, and step S3 is epoxidation; specifically: Step S1: Hydrogenated cashew nut shell powder, surfactant, and tin tetrachloride are thoroughly mixed in an organic solvent at room temperature; then paraformaldehyde is added, and after stirring for 30 min, the mixture is reacted in a reaction vessel under nitrogen protection; the mixture is purified to obtain aldehyde-modified cashew nut shell powder; the molecular structure of the aldehyde-modified cashew nut shell powder is as follows: ； Step S2: The aldehyde-modified cashew nut shell powder obtained in step S1 is thoroughly mixed with diamine in an organic solvent and reacted in a reaction vessel under nitrogen protection. After purification, a cashew nut shell powder-based epoxy resin precursor containing a Schiff base structure is obtained. The molecular structure of the epoxy resin precursor is shown below: ； Step S3: The epichlorohydrin, the epoxy resin precursor obtained in step S2, the phase transfer catalyst and the alkaline substance are thoroughly mixed and reacted in a reaction vessel under nitrogen protection. After purification, the cashew phenol-based mechanically enhanced flame-retardant epoxy resin is obtained.

2. The cashew nut shell resin containing fatty amines with basic mechanical properties of flame retardant as described in claim 1, characterized in that, In step S1, the molar ratio of hydrogenated cashew nut shellac, surfactant, tin tetrachloride, paraformaldehyde, and organic solvent is 0.8~1.2:0.08~0.15:0.08~0.12:1.2~1.8:2.0~3.0; the reaction temperature in step S1 is 80-100℃, and the reaction time is 8-9 hours.

3. The cashew nut shell resin containing fatty amines with basic mechanical properties that is mechanically reinforced and flame-retardant as described in claim 2, characterized in that, The surfactant includes one or more combinations of benzyltriethylammonium chloride (TEBA) and tetrabutylammonium bromide (TBAB); the organic solvent in step S1 is toluene and triethylamine.

4. The cashew nut shell resin containing fatty amines with basic mechanical properties that is mechanically reinforced and flame-retardant as described in claim 1, characterized in that, In step S2, the molar ratio of aldehyde-modified cashew phenol, diamine, and organic solvent is 0.8~1.2:0.3~0.6:2.0~3.0; the reaction temperature in step S2 is 70-90℃, and the reaction time is 5-6 hours; the diamine is an aliphatic straight-chain diamine with 4 to 12 carbon atoms and its derivatives.

5. The cashew nut shell resin containing fatty amines with basic mechanical properties that is mechanically reinforced and flame-retardant as described in claim 4, characterized in that, The organic solvent in step S2 is N,N-dimethylacetamide (DMAC).

6. The cashew nut shell resin containing fatty amines with basic mechanical properties of flame retardant as described in claim 1, characterized in that, In step S3, the molar ratio of epoxy resin precursor, epichlorohydrin, phase transfer catalyst, and alkaline substance is 0.8~1.2:15~25:0.08~0.15:1.5~2.5; the reaction temperature in step S3 is 70-90℃, and the reaction time is 5-8 hours.

7. The cashew nut shell resin containing fatty amines with basic mechanical properties of flame retardant as described in claim 6, characterized in that, The phase transfer catalyst comprises one or more combinations of quaternary ammonium salts, polyethers, and quaternary phosphine salts; the quaternary ammonium salts are one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bisulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, or tetradecyltrimethylammonium chloride; the polyethers are chain polyethylene glycol; the quaternary phosphine salts are one or more of tetraphenylphosphine chloride, triphenylphosphine, and their derivatives; the alkaline substance is an aqueous solution of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate; the concentration of the alkaline substance is 10 mol / L.

8. The cashew nut shell resin containing aliphatic amines with basic mechanical properties that is mechanically reinforced and flame-retardant as described in claim 1, characterized in that, In steps S2 and S3, the purification process includes separation and drying steps: The separation step specifically involves: extracting the mixture after the reaction with ethyl acetate and distilled water multiple times in sequence until the upper organic liquid is clear; The drying step specifically involves using a desiccant and a vacuum drying oven to dry the organic liquid in sequence, in order to remove moisture and organic impurities from the organic liquid.

9. The cashew nut shell resin containing fatty amines with basic mechanical properties of flame retardant as described in claim 8, characterized in that, The desiccant is one or more of sodium sulfate, sodium carbonate, potassium carbonate, calcium chloride, calcium sulfate, and calcium oxide, and the drying temperature is 50-80℃.

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