Aliphatic amine-containing cardanol basic intrinsic mechanical enhanced flame-retardant epoxy resin and preparation method thereof

Abstract

The invention discloses cardanol basic characteristic mechanical enhanced flame-retardant epoxy resin containing aliphatic amine and a preparation method of the cardanol basic characteristic mechanical enhanced flame-retardant epoxy resin, and belongs to the technical field of flame retardance. The preparation method comprises the following steps: introducing an aldehyde group on a benzene ring of cardanol, and reacting with diamine to form an epoxy resin precursor substance; the preparation method comprises the following steps: fully mixing an epoxy resin precursor substance, epoxy chloropropane, a phase transfer catalyst and an alkaline substance for reaction to obtain cardanol basic intrinsic flame-retardant and mechanically-reinforced epoxy resin; the problems that raw materials of traditional bisphenol A type epoxy resin are non-renewable, the brittleness is large due to the molecular structure, flammability is caused, and the flame retardant property and the mechanical property cannot be considered at the same time are solved, biomass cardanol which is wide in source and low in cost is used as the raw material, and flexibility of an aliphatic chain and rigidity of aromatic hydrocarbon are combined; the Schiff base structure improves the flame-retardant efficiency of the matrix and also improves the mechanical properties of the matrix; the cured epoxy resin system has excellent thermal stability, flame retardance and mechanical properties, and has excellent popularization and application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant polymer materials, and in particular to a cardanol-based mechanically enhanced flame retardant epoxy resin containing a fatty amine and a preparation method thereof. Background Art

[0002] Thermosetting epoxy resin is a three-dimensional network polymer formed by crosslinking epoxy monomers or oligomers with curing agents. Its uniqueness lies in its insolubility and infusibility. This material exhibits excellent thermodynamic properties, outstanding chemical resistance and excellent dimensional stability, and is therefore widely used in many fields such as aerospace, coatings, high-performance composite materials and electronic encapsulants. At present, more than 90% of epoxy resins worldwide are composed of bisphenol A diglycidyl ether synthesized from bisphenol A and epichlorohydrin. Among them, bisphenol A is a compound derived from non-renewable petroleum resources. Its excessive exploitation and use will not only aggravate the energy crisis, but also pose a potential threat to human health. In view of the above-mentioned health, energy and environmental considerations, the current scientific research field is actively committed to exploring and developing suitable biomass raw materials in order to achieve an effective replacement for petroleum-based bisphenol A. This research direction not only conforms to the concept of sustainable development, but also opens up a new path for the future development of the epoxy resin industry.

[0003] Bio-based epoxy resin, as an innovative synthetic material, partially or completely replaces traditional resin components with renewable raw materials, demonstrating the significant characteristics of green, environmental protection and renewable, and has great potential in production and life applications. This material can be used as an ideal substitute for traditional petroleum-based plastics and coatings, effectively alleviate the crisis of oil resource shortage, and significantly reduce the degree of environmental pollution. Cardanol comes from natural cashew shell liquid, which is widely available and easy to obtain. As a unique alkylphenol, it has broad practical value in the preparation of thermosetting polymers and is therefore regarded as a valuable source of bio-monomers. There are also cardanol-based derivatives in the prior art to toughen flame-retardant epoxy resins, which can effectively improve the flame retardancy and mechanical properties of epoxy resins. Invention patent CN114524927A reports the application of a cardanol bio-based polyol in flexible packaging adhesives, which effectively solves the problem of solvent-free ink dissolution. Invention patent CN114920989A reports a method for applying cardanol to rubber, which can effectively improve the performance of rubber products in rubber mixing. There are also bio-based toughening agents with rigid-flexible structures that have been disclosed. They are used in epoxy resins. By utilizing the toughness of the fatty chains in the molecular structure, the toughness of the epoxy resin can be improved to a certain extent. However, since the steric hindrance of the epoxy resin itself is changed, the mechanical properties are low and the complexity and economic cost of the preparation process are increased.

[0004] Therefore, there is an urgent need for an epoxy resin system that has excellent mechanical properties, biodegradability and flame retardancy, and is simple to prepare, low in cost, and easy to industrialize and mass produce. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art, and to provide a cardanol-based mechanically enhanced flame-retardant epoxy resin containing a fatty amine and a preparation method thereof, which belongs to the field of flame retardant technology; the preparation method comprises: introducing an aldehyde group on the benzene ring of cardanol and reacting with a diamine to form an epoxy resin precursor; fully mixing the epoxy resin precursor, epichlorohydrin, a phase transfer catalyst and an alkaline substance to react, so as to obtain a cardanol-based flame-retardant and mechanically enhanced epoxy resin; the problems of non-renewable raw materials, high brittleness and flammability caused by the molecular structure of the traditional bisphenol A type epoxy resin, and the inability to take both flame retardant and mechanical properties into consideration are solved, and the widely available and low-cost biomass cardanol is used as the raw material, combined with the flexibility of the fatty chain and the rigidity of the aromatic hydrocarbon, while the Schiff base structure improves the flame retardant efficiency of the matrix and improves its mechanical properties; the cured epoxy resin system has excellent thermal stability, flame retardant and mechanical properties, and has an excellent prospect for promotion and application.

[0006] In order to achieve the above technical effects, the following technical solutions are adopted:

[0007] A cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amines, the molecular structure of which is:

[0008]

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

[0010] A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing a fatty amine, comprising: step S1 is cardanol aldehyde radicalization, step S2 is introducing a Schiff base structure, and step S3 is epoxidation; specifically,

[0011] Step S1: fully mix cardanol, surfactant and tin tetrachloride in an organic solvent at room temperature; then add paraformaldehyde, stir for 30 minutes, and react in a reaction container under nitrogen protection; the mixture is purified to obtain formaldehyde-modified cardanol; the molecular structure of the formaldehyde-modified cardanol is as follows:

[0012]

[0013] Step S2: The formaldehyde-modified cardanol obtained in step S1 is fully mixed with diamine in an organic solvent, reacted in a reaction container under nitrogen protection, and a cardanol-based epoxy resin precursor containing a Schiff base structure is obtained after purification. The molecular structure of the epoxy resin precursor is shown below:

[0014]

[0015] Step S3: Epichlorohydrin, the epoxy resin precursor obtained in step S2, a phase transfer catalyst and an alkaline substance are fully mixed and reacted in a reaction container under nitrogen protection, and the cardanol basic characteristics mechanically enhanced flame retardant epoxy resin is obtained after purification. The molecular structure formula of the cardanol basic characteristics mechanically enhanced flame retardant epoxy resin is as follows:

[0016]

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

[0018] Furthermore, in the step S1, the molar ratio of cardanol, 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 the 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 amines include triethylamine; the alcohols include ethanol; the aromatic hydrocarbons include toluene, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0020] Furthermore, in the step S2, the molar ratio of the formaldehyded cardanol, diamine and organic solvent is (0.8-1.2): (0.3-0.6): (2.0-3.0); the reaction temperature in the step S2 is 70-90°C, and the reaction time is 5-6 hours; the diamine is an aliphatic straight-chain diamine having 4 to 12 carbon atoms and 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 the 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° C., and the reaction time is 5-8 hours.

[0023] Furthermore, the phase transfer catalyst includes one or more combinations of quaternary ammonium salts, polyethers, and quaternary phosphonium salts; the quaternary ammonium salts are one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, or tetradecyltrimethylammonium chloride; the polyethers are chain polyethylene glycols; the quaternary phosphonium salts are one or more of tetraphenylphosphine chloride, triphenylphosphine, and derivatives thereof; the alkaline substance is one or more aqueous solutions 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 step S2 and step S3, the purification process includes separation and drying steps:

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

[0026] The drying step specifically includes: using a desiccant and a vacuum drying oven to dry the organic liquid in sequence, so as to remove moisture and organic impurities in 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°C.

[0028] The beneficial effects of the present invention are:

[0029] 1) The present invention provides a flame-retardant epoxy resin based on cardanol containing fatty amines and a preparation method thereof. Through molecular structure design and simple synthesis process, the structural stability advantage of cardanol itself containing C15 unsaturated flexible fatty chains is utilized, and a Schiff base structure is introduced while introducing a benzene ring containing a rigid aromatic hydrocarbon structure and its derivative compounds. The C15 unsaturated fatty chain gives flexibility to the resin matrix, and the π-π structure formed by the aromatic hydrocarbon structure and the Schiff base gives rigidity to the resin matrix, thereby achieving the purpose of combining rigidity and flexibility. In addition, the self-crosslinking of the Schiff base structure at high temperature gives the resin matrix excellent flame retardant properties. This method can enhance the mechanical properties of the resin matrix while improving the flame retardant properties of the resin matrix. The advantages of this design concept include that the raw materials are easily available and renewable, which solves the disadvantage that traditional flame retardant enhancement methods cannot take into account both the improvement of flame retardant properties and mechanical properties;

[0030] 2) The present invention provides a flame-retardant epoxy resin containing cardanol as a basic characteristic of fatty amine and a preparation method thereof, which uses cardanol, an aromatic compound derived from lignin (cashew nut shell oil) that can be mass-produced, as a raw material to solve the problems of flammability and brittleness of thermosetting epoxy resins, while alleviating environmental pollution, excessive consumption and excessive carbonized material emissions during the conversion of fossil resources;

[0031] 3) The present invention provides a flame-retardant epoxy resin containing cardanol basic characteristics of fatty amine and a preparation method thereof, which solves the problems of non-renewable raw materials, flammability, and high brittleness of traditional epoxy resins from the source through molecular structure design;

[0032] 4) The present invention provides a flame-retardant epoxy resin containing cardanol and a preparation method thereof, which has strong operability, good controllability, low economic cost, easy implementation, good prospects for promotion and use, and is conducive to industrial large-scale production;

[0033] The present invention solves the problems of non-renewable raw materials, high brittleness and flammability caused by molecular structure, and inability to balance flame retardancy and mechanical properties of traditional bisphenol A epoxy resin. It uses cardanol, a biomass with a wide source and low cost, as raw materials, combines the flexibility of aliphatic chains and the rigidity of aromatic hydrocarbons, improves the flame retardancy efficiency of the matrix while improving its mechanical properties through the Schiff base structure. The cured epoxy resin system has excellent thermal stability, flame retardancy and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings in the following description are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0035] Figure 1 is the molecular structural formula of the aldehyde-containing substance in the embodiment of the present invention;

[0036] Figure 2 is the molecular structure formula of the epoxy resin precursor material of the embodiment of the present invention;

[0037] Figure 3 is the molecular structure formula of the cardanol basic characteristics mechanically enhanced flame retardant epoxy resin containing fatty amine in the embodiment of the present invention;

[0038] Figure 4 This is a flow chart of the steps of the preparation method according to an embodiment of the present invention;

[0039] Figure 5 The infrared spectrum of the cardanol-based epoxy resin containing 1,6-hexanediamine prepared in Example 1 of the present invention;

[0040] Figure 6 This is the infrared spectrum of the cardanol-based epoxy resin containing 1,5-pentanediamine prepared in Example 2 of the present invention;

[0041] Figure 7 A comparison diagram of heat release rate curves of the embodiment of the present invention and the comparative example;

[0042] Figure 8 A comparison diagram of total heat release curves of the embodiment of the present invention and the comparative example;

[0043] Fig. 9 It is a comparison diagram of smoke production rate curves of the embodiment of the present invention and the comparative example;

[0044] Fig.10 It is a comparison chart of total smoke production curves of the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

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

[0048] See also Figure 1-Figure 8 The present invention provides a technical solution: a cardanol basic mechanically enhanced flame retardant epoxy resin having a molecular structure such as Figure 3 shown.

[0049] On the other hand, a method for preparing the cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine is provided. The preparation process is as follows: Figure 4 As shown, specifically including:

[0050] In the first stage, cardanol, surfactant and tin tetrachloride are fully mixed in an organic solvent at room temperature. Then, polyformaldehyde is added, stirred for 30 minutes, and then stirred at a low speed at 80-100°C for 8-9 hours. The mixture is purified to obtain a formaldehyde cardanol oily substance. It has the following characteristics: Figure 1 The molecular structure shown;

[0051] In the second stage, the above-mentioned formaldehyde-modified cardanol and diamine are fully mixed in an organic solvent, reacted in a reaction container at 70-90° C. and under nitrogen protection for 5-6 hours, and after purification, a cardanol-based epoxy resin precursor containing a Schiff base structure is obtained, which has the following characteristics: Figure 2 The molecular structure shown;

[0052] In the third stage, the epoxy resin precursor, epichlorohydrin, phase transfer catalyst and alkaline substance are fully mixed, reacted in a reaction vessel at 70-90° C. under nitrogen protection for 5-8 hours, and then purified to obtain a flame retardant and mechanically enhanced epoxy resin with cardanol basic characteristics, which has the following characteristics: Figure 3 The molecular structure is shown.

[0053] Furthermore, the masses of cardanol, surfactant, tin tetrachloride, paraformaldehyde and organic solvent are in the molar mass ratio of (0.8-1.2):(0.08-0.15):(0.08-0.12):(1.2-1.8):(2.0-3.0).

[0054] Furthermore, the masses of the formaldehyde-modified cardanol, diamine and organic solvent are in a molar mass ratio of (0.8-1.2):(0.3-0.6):(2.0-3.0).

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

[0056] Furthermore, the purification process is to separate and dry the mixture system after the reaction.

[0057] In the separation step, ethyl acetate and distilled water are used to extract and separate the reaction mixture multiple times in sequence until the upper organic liquid is clear.

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

[0061] Furthermore, the surfactant includes, but is not limited to, one or more combinations of benzyltriethylammonium chloride and tetrabutylammonium bromide.

[0062] Furthermore, the organic solvent includes, but is 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, 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 phosphonium 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; the quaternary phosphonium salt phase transfer catalyst is tetraphenylphosphine chloride, triphenylphosphine and its 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) and tin(IV) chloride (0.261 g, 0.001 mol) were added to a solution of hydrogenated cardanol (3.04 g, 0.01 mol) in toluene (20 mL), and benzyltriethylammonium chloride TEBA (0.001 mol). The reaction mixture was heated at room temperature under N 2 The mixture was stirred at 100°C for 30 minutes, then paraformaldehyde (0.66 g, 0.02 mol) was added, and the reaction mixture was stirred at 100°C for 8 hours. After the reaction was completed, the reactant was cooled to room temperature, then poured into water and acidified to pH = 2 with hydrochloric acid, and then the aqueous layer was extracted with ethyl acetate. The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated to dryness to obtain an aldehyde-containing substance having the following structural formula:

[0068]

[0069] The 13.28g aldehyde-containing substance obtained above and 3.27g 1,6-hexanediamine were uniformly mixed and placed in a four-necked flask, and then nitrogen was introduced for 10 minutes, followed by the addition of 500ml of DMAC, and the temperature was raised to 80°C under nitrogen protection, and the reaction was performed for 5 hours. The mixed liquid was then poured into distilled water (stirring while pouring, slowly pouring, and stirring for a long time), and the organic matter was obtained after distilled water precipitation, overnight standing, and suction filtration. Finally, the organic matter was dried in a vacuum drying oven at 80°C for 24 hours to remove moisture, and an epoxy resin precursor substance was obtained, which has the following structural formula:

[0070]

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

[0072]

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

[0074] Example 2

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

[0076]

[0077] The 13.28 aldehyde-containing substance obtained above and 3.44 g 1,5-pentanediamine were uniformly mixed and placed in a four-necked flask, and then nitrogen was introduced for 10 minutes, followed by the addition of 500 ml of DMAC, and the temperature was raised to 80°C under nitrogen protection, and the reaction was performed for 5 hours. The mixed liquid was then poured into distilled water (stirring while pouring, slowly pouring, and stirring for a long time), and the organic matter was obtained after distilled water precipitation, overnight standing, and suction filtration. Finally, the organic matter was dried in a vacuum drying oven at 80°C for 24 hours to remove moisture, and an epoxy resin precursor substance was obtained, which has the following structural formula:

[0078]

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

[0080]

[0081] The infrared spectrum of the cardanol-based epoxy resin is as follows: Figure 6 As shown in the figure, the absorption peak of Schiff base structure (1641cm -1 , 3275cm -1 ) and the absorption peak of epoxy group (927cm -1 ), which indicates that the cardanol-based epoxy resin containing 1,5-pentanediamine was successfully prepared.

[0082] Comparative Example:

[0083] 100g E51 epoxy resin was mixed with 25.28g 4,4'-diaminodiphenylmethane (DDM) and pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and 150°C for 2 hours to obtain an epoxy cured product. The UL-94 test of this cured product was not rated according to ASTM D3801-20. The calorimeter was used to measure the calorimetry of the cured product at 35kW / m 2 The flame retardant properties of E51 epoxy resin were tested under radiation intensity. Figure 7It can be seen from ad that the peak heat release rate, total heat release, peak smoke generation rate and total smoke generation of E51 epoxy resin are 703.5kW / m 2 、84.742MJ / m 2 、0.206m 2 / s and 29.04m 2 ,These results show that E51 epoxy resin is easy to burn, and a large amount of heat and toxic and harmful smoke are generated during the combustion process.

[0084] Example 3

[0085] 100 g of the cardanol-based epoxy resin containing 1,6-hexanediamine synthesized in Example 1 was mixed evenly with 16.42 g of 4,4'-diaminodiphenylmethane (DDM), and firstly pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and at 150°C for 2 hours to obtain an epoxy cured product. According to the standard ASTM D3801-20, the flame retardant performance of the cured product reached the UL-94V0 level. The flame retardant performance of the cured product was measured by a cone calorimeter at 35 kW / m 2 The flame retardant properties of cardanol-based epoxy resin containing 1,6-hexanediamine were tested under radiation intensity. Figure 7-Figure 10 It can be seen that compared with E51 epoxy resin, the peak heat release rate of cardanol-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%, which indicates that the cardanol-based epoxy resin containing 1,6-hexanediamine has better flame retardant properties.

[0086] Example 4

[0087] 100 g of the cardanol-based epoxy resin containing 1,5-pentanediamine synthesized in Example 2 was mixed with 17.42 g of 4,4'-diaminodiphenylmethane (DDM) and pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and 150°C for 2 hours to obtain an epoxy cured product. According to the standard ASTM D3801-20 test, the flame retardant performance of the cured product reached the UL-94V0 level. The flame retardant performance of the cured product was measured by a cone calorimeter at 35 kW / m 2 The flame retardancy of cardanol-based epoxy resin containing 1,5-pentanediamine was tested under radiation intensity. Figure 7-Figure 10 It can be seen that compared with E51 epoxy resin, the peak heat release rate of cardanol-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%, which indicates that the cardanol-based epoxy resin containing 1,5-pentanediamine has excellent flame retardant properties.

[0088] Example 5

[0089] 100 g of the cardanol-based epoxy resin containing 1,6-hexanediamine synthesized in Example 1 was mixed evenly with 16.42 g of 4,4'-diaminodiphenylmethane (DDM), and firstly pre-cured at 80°C for 1 hour, then cured at 120°C for 2 hours and 150°C for 2 hours to obtain an epoxy cured product. As shown in Table 1, compared with the E51 epoxy resin, the cardanol-based epoxy resin containing 1,6-hexanediamine has a tensile strength increased by 7.2% and an elongation at break increased by 593%, which indicates that the cardanol-based epoxy resin containing 1,6-hexanediamine has better mechanical properties.

[0090] Table 1 Comparison of mechanical properties

[0091]

[0092] In summary, the present invention discloses a mechanically enhanced flame-retardant epoxy resin containing cardanol containing fatty amines and a preparation method thereof. The present invention takes the non-renewable, flammable, brittle, and poorly degradable raw materials of traditional epoxy resins as starting points, and uses the lignin-derived aromatic compound cardanol that can be mass-produced as raw materials. The structural stability advantage of cardanol itself containing C15 unsaturated flexible fatty chains is utilized. While introducing benzene rings containing rigid aromatic hydrocarbon structures and derivative compounds thereof, a Schiff base structure is introduced. The C15 unsaturated fatty chain gives flexibility to the resin matrix, and the π-π structure formed by the aromatic hydrocarbon structure and the Schiff base gives rigidity to the resin matrix, achieving the purpose of both rigidity and flexibility. In addition, the self-crosslinking of the Schiff base structure at high temperature gives the resin matrix excellent flame retardant properties. The cured epoxy resin system has excellent flame retardant properties, toughness, and degradable properties. At the same time, its preparation method is highly operable, controllable, easy to implement, and conducive to industrial large-scale production.

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

Claims

1. A cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amines, characterized in that: The flame retardant epoxy resin molecular structure formula is: Wherein, R is an aliphatic straight chain having 4 to 12 carbon atoms and its derivatives.

2. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amines, characterized in that: The preparation method comprises: step S1 is aldehyde-forming of cardanol, step S2 is introducing Schiff base structure, and step S3 is epoxidation; specifically: Step S1: fully mix cardanol, surfactant and tin tetrachloride in an organic solvent at room temperature; then add paraformaldehyde, stir for 30 minutes, and react in a reaction container under nitrogen protection; the mixture is purified to obtain formaldehyde-modified cardanol; the molecular structure of the formaldehyde-modified cardanol is as follows: Step S2: The formaldehyde-modified cardanol obtained in step S1 is fully mixed with diamine in an organic solvent, reacted in a reaction container under nitrogen protection, and a cardanol-based epoxy resin precursor containing a Schiff base structure is obtained after purification. The molecular structure of the epoxy resin precursor is shown below: Step S3: Epichlorohydrin, the epoxy resin precursor obtained in step S2, a phase transfer catalyst and an alkaline substance are fully mixed and reacted in a reaction container under nitrogen protection, and the cardanol basic characteristics mechanically enhanced flame retardant epoxy resin is obtained after purification. The molecular structure formula of the cardanol basic characteristics mechanically enhanced flame retardant epoxy resin is as follows: Wherein, R is an aliphatic straight chain having 4 to 12 carbon atoms and its derivatives.

3. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 1, characterized in that: In the step S1, the molar ratio of cardanol, 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 the step S1 is 80-100° C., and the reaction time is 8-9 hours.

4. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 3, characterized in that: The surfactant includes one or more combinations of benzyltriethylammonium chloride TEBA and tetrabutylammonium bromide TBAB; the organic solvent includes one or more combinations of amines, alcohols, aromatic hydrocarbons and dimethyl sulfoxide; the amines include triethylamine; the alcohols include ethanol; the aromatic hydrocarbons include toluene, N,N-dimethylacetamide DMAC and N-methylpyrrolidone NMP.

5. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 1, characterized in that: In the step S2, the molar ratio of the formaldehyded cardanol, diamine and organic solvent is 0.8-1.2:0.3-0.6:2.0-3.0; the reaction temperature in the step S2 is 70-90°C, and the reaction time is 5-6 hours; the diamine is an aliphatic straight-chain diamine having 4 to 12 carbon atoms and its derivatives.

6. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 5, characterized in that: 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 DMAC, N-methylpyrrolidone NMP, and N,N-dimethylformamide DMF; the ketones include acetone; and the ethers include petroleum ether and tetrahydrofuran.

7. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 1, characterized in that: In the step S3, the molar ratio of the 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 the step S3 is 70-90°C, and the reaction time is 5-8 hours.

8. The method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 6, characterized in that: The phase transfer catalyst comprises one or more combinations of quaternary ammonium salts, polyethers, and quaternary phosphonium salts; the quaternary ammonium salts are one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, or tetradecyltrimethylammonium chloride; the polyethers are chain polyethylene glycols; the quaternary phosphonium salts are one or more of tetraphenylphosphine chloride, triphenylphosphine, and derivatives thereof; the alkaline substance is one or more aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate; and the concentration of the alkaline substance is 10 mol / L.

9. A method for preparing a cardanol-based mechanically enhanced flame-retardant epoxy resin containing fatty amine as claimed in claim 1, characterized in that: In step S2 and step S3, the purification process includes separation and drying steps: The separation step specifically comprises: extracting and separating the reaction mixture using ethyl acetate and distilled water in sequence for multiple times until the upper organic liquid is clear; The drying step specifically includes: using a desiccant and a vacuum drying oven to dry the organic liquid in sequence, so as to remove moisture and organic impurities in the organic liquid.

10. A method for preparing a cardanol-based mechanically reinforced flame-retardant epoxy resin containing fatty amine as claimed in claim 9, characterized in that: 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 is 50-80°C.

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