A method for synthesizing a high-temperature-resistant epoxy resin

Abstract

The application provides a synthesis method of a high-temperature-resistant epoxy resin, which is prepared from an allyl phenolic compound, first, a flexible silicon-oxygen bond is introduced between aromatic rings by using the polycondensation reaction between the allyl phenolic compound and silane, then a tetra-functional epoxy resin is obtained by the chemical reaction between epoxy chloropropane and the phenolic hydroxyl group, and finally, a phosphorus-modified epoxy resin is obtained based on the ring-opening addition reaction between DOPO and the epoxy resin. The application uses a molecular design method to prepare an epoxy resin system, and the technology process is simple, and industrial production can be realized; after the prepared resin is cured by using DDS, the glass transition temperature is greater than 240 DEG C, the carbon residue rate is greater than 60% under 800 DEG C in an inert atmosphere, the bending strength is greater than 120 MPa, and the highest level V-0 level of vertical combustion test is reached; the excellent performance can further expand the application range, and has a wide application prospect in the fields of aerospace, electronic packaging and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for synthesizing a high-temperature resistant epoxy resin. Background Technology

[0002] Epoxy resin is a high-performance thermosetting resin with wide applications in aerospace, shipbuilding, automotive, and electronic packaging. Over the past two decades, to further expand the application areas of epoxy resin, many scholars both domestically and internationally have focused on the design and synthesis of various high-performance epoxy resins, especially high-temperature resistant resins. For example, 4,4'-diaminodiphenylmethane type epoxy resin typically has a glass transition temperature as high as 230-280℃, significantly higher than traditional bisphenol A type epoxy resin. Therefore, this system has been widely used in some high-temperature applications. However, to date, most high-temperature resistant epoxy resins have very high epoxy functionality, resulting in a high crosslinking density in the cured resin system, leading to high brittleness and poor impact resistance, which limits the use of these resins in many fields.

[0003] Researchers have explored several highly effective methods to improve the processing performance of resins. Qi et al. started with the design of the molecular backbone structure, reacting the phenolic hydroxyl groups in the magnolol structure with epichlorohydrin to epoxidize the allyl double bonds, ultimately obtaining a novel tetratube-energy epoxy resin. While improving the inherent biphenyl structure of the resin has been shown to facilitate the formation of a pyrolysis-resistant char layer during combustion, thus improving the system's heat resistance, this biphenyl structure also increases the resin's rigidity, further reducing its toughness. Furthermore, while increasing the proportion of aromatic structures improves the resin's high-temperature resistance, it has a relatively small impact on improving its flame retardant properties.

[0004] Teng et al. introduced the rigid flame retardant DOPO into epoxy-terminated hyperbranched polymers through chemical grafting. At the same time, they adjusted the physical topology and molecular chemical structure of the hyperbranched polymers and designed and synthesized a series of flame-retardant hyperbranched polymers, obtaining a series of high-toughness and flame-retardant epoxy resins. However, the glass transition temperature of the obtained epoxy resins was only about 200℃, which was difficult to meet the requirements of some special working conditions.

[0005] Therefore, developing intrinsically flame-retardant, high-temperature resistant, and high-toughness epoxy resins by adjusting the structure of the resin matrix from a multidimensional composite perspective and starting from molecular structure design still presents a significant technical challenge. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of current technology by providing a high-temperature resistant epoxy resin and its synthesis method, specifically an epoxy resin with intrinsic flame retardancy, high glass transition temperature, and high toughness, and its preparation method.

[0007] This resin originates from allylphenol compounds. First, flexible silicon-oxygen bonds are introduced between aromatic rings through the condensation reaction between allylphenols and silanes. Then, a tetrafunctional epoxy resin is obtained through the chemical reaction between epichlorohydrin and phenolic hydroxyl groups. Finally, a phosphorus-modified epoxy resin is obtained based on the ring-opening addition reaction of DOPO with the epoxy resin. This resin is a trifunctional resin system, with multiple aromatic ring structures linked by flexible silicon-oxygen bonds. It also contains a planar rigid structure of phosphorus-phenanthrene as a suspension chain, which improves the toughness and thermal stability of the molecular structure. The introduction of phosphorus allows it to produce phosphate compounds during combustion, increasing the resin's carbonization rate and capturing combustion free radicals such as oxygen and hydrogen, further contributing to flame retardancy and high-temperature resistance.

[0008] This invention provides a high-temperature resistant epoxy resin having the following structure:

[0009]

[0010] Another aspect of the present invention provides a method for preparing a high-temperature resistant epoxy resin, the method comprising the following steps: (1) mixing an alkenylphenol compound, silane, and solvent for reaction and post-treatment to obtain reaction intermediate 1; (2) mixing reaction intermediate 1, epichlorohydrin, and catalyst for reaction, adding an alkaline aqueous solution to continue the reaction.

[0011] The mixture was filtered, washed, dried, filtered again, and then rotary evaporated to obtain reaction intermediate 2.

[0012] (3) The reaction intermediate 2 is mixed with the phosphorus-containing reactant and reacted to obtain a high-temperature resistant epoxy resin.

[0013] (4) Mix the epoxy resin obtained in step (3) with the curing agent, degas under vacuum, pour into the mold, and cure to obtain the cured product.

[0014] Another aspect of the present invention provides an application of a high-temperature resistant epoxy resin, which is used to manufacture engine compartment covers, blades, or wall panels via an RTM process.

[0015] The beneficial effects of the high-temperature resistant epoxy resin provided by this invention are as follows:

[0016] This invention utilizes molecular design to prepare an epoxy resin system. This technology is simple and can be industrialized. The prepared resin, after curing with DDS, has a glass transition temperature greater than 240℃, a carbon residue rate greater than 60% at 800℃ under an inert atmosphere, and a flexural strength greater than 120MPa, achieving the highest level V-0 rating in vertical combustion testing. Its excellent properties will further expand its application range and have broad application prospects in aerospace, electronic packaging and other fields. Attached Figure Description

[0017] Figure 1 The image shows the 1H NMR spectrum of the high-temperature resistant epoxy resin prepared in this invention.

[0018] Figure 2 The image shows the 13C NMR spectrum of the high-temperature resistant epoxy resin prepared in this invention.

[0019] Figure 3 The TanδVs temperature curve of the resin prepared in Example 3 of this invention is shown. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to specific embodiments and comparative examples.

[0021] This invention discloses a high-temperature resistant epoxy resin, which is a bio-based epoxy resin having the following structure:

[0022]

[0023] The method for preparing the high-temperature resistant epoxy resin of the present invention comprises the following specific steps:

[0024] (1) Mix alkenylphenol compounds, silanes and solvents, react and post-process them to obtain reaction intermediate 1;

[0025] (2) Mix reaction intermediate 1, epichlorohydrin and catalyst, react, add alkaline aqueous solution to continue the reaction, filter, wash, dry, filter, and rotary evaporate to obtain reaction intermediate 2.

[0026] (3) The reaction intermediate 2 is mixed with the phosphorus-containing reactant and reacted to obtain a high-temperature resistant epoxy resin.

[0027] (4) Mix the epoxy resin obtained in step (3) with the curing agent, degas under vacuum, pour into the mold, and cure to obtain the cured product.

[0028] The present invention provides a specific method in which, in step (1), the alkenylphenol compound is an alkenyl pyrogallol compound, preferably stilbene; the silane is a chlorosilane, preferably dichlorodimethylsilane; the solvent is an aromatic solvent, preferably toluene; and the post-treatment is distillation, preferably vacuum distillation.

[0029] The present invention provides a specific method in which, in step (1), the molar ratio of phenolic compound to silane is 4:1, the reaction temperature is 30-50℃, the reaction time is 1-4h, and the reaction environment is an inert environment.

[0030] The present invention provides a specific method in which, in step (2), the catalyst is an aromatic amine compound, preferably 3-methylbenzylamine; the alkaline aqueous solution is an aqueous solution of sodium salt, preferably an aqueous solution of sodium hydroxide; the washing is with deionized water; and the drying is with anhydrous magnesium sulfate.

[0031] The present invention provides a specific method in which, in step (2), the amount of intermediate 1 is 50-150 mmol, the specific amount of epichlorohydrin in the present invention is 300-500 ml, the amount of catalyst is 5-8.5 mmol, the reaction temperature is 80-120℃, the reaction time is 3-6 hours, the mass fraction of sodium hydroxide solution is 30-50 wt%, the specific amount of sodium hydroxide in the present invention is 10-25 g, and the subsequent reaction time is 1-3 hours; the pH value after washing with deionized water is 6.5-7, and the specific amount of anhydrous magnesium sulfate in the present invention is 20-40 g.

[0032] The present invention provides a specific method in which, in step (3), the amount of reaction intermediate 2 is 50-150 mmol; the temperature is 100-130℃; the phosphorus-containing reactant is DOPO, the amount of which is preferably 50-180 mmol; the temperature is raised to 150-180℃; and the reaction is carried out for 5-10 hours.

[0033] This invention provides a specific method in which, in step (4), the curing agent is an aromatic amine curing agent, specifically DDS, with a mass ratio of epoxy resin to DDS of 10:3, or DETDA, with a mass ratio of epoxy resin to curing agent DETDA of 10:22.5. The curing procedure of this invention is 130℃ for 2 hours; 150℃ for 3 hours; and 180℃ for 3 hours.

[0034] The following provides a specific implementation process for obtaining high-temperature resistant epoxy resin.

[0035] Example 1

[0036] In a 250ml three-necked flask, 4.56g of stilbene triol, 1.3g of dimethyldichlorosilane, and 50ml of toluene were added sequentially. The mixture was magnetically stirred until a homogeneous solution was formed. Nitrogen gas was introduced, and the temperature was raised to 35℃ with continuous stirring for 2 hours. The solvent was removed by vacuum distillation to obtain reaction intermediate 1. 51.2g of intermediate 1 was dissolved in 350ml of epichlorohydrin, and 0.6g of 3-methylbenzylamine was added. Nitrogen gas was introduced, and the temperature was raised to 120℃ with vigorous stirring. After reacting for 5 hours, the mixture was cooled to room temperature, and 20g of 40wt% sodium hydroxide aqueous solution was added. The reaction was continued for 2 hours, filtered, and the filtrate was washed with deionized water and separated using a separatory funnel until the pH of the filtrate was 6.5. 30g of anhydrous magnesium sulfate was added and dried for 2 hours. The filtrate was filtered again, and unreacted substances were removed by rotary evaporation to obtain reaction intermediate 2. Under a nitrogen atmosphere, 170.1g of reaction intermediate 2 was heated to 110℃, and 64.8g of... DOPO was heated to 160℃ and reacted for 8 hours to obtain a high-temperature resistant, flame-retardant epoxy resin. The obtained epoxy resin was uniformly mixed with curing agent DDS at a mass ratio of 10:3. After uniform mixing and vacuum degassing, the resin was poured into a mold and cured at 130℃ for 2 hours; 150℃ for 3 hours; and 180℃ for 3 hours (this curing process is continuous). The properties of the cured system are as follows: char residue of 63.5% at 800℃ under N2 atmosphere; glass transition temperature of 252℃; flexural strength of 135MPa; and flame retardancy rating of V-0, the highest level for vertical burning.

[0037] Example 2

[0038] In a 500ml three-necked flask, 13.68g of stilbene triol, 3.9g of dimethyldichlorosilane, and 150ml of toluene were added sequentially. The mixture was magnetically stirred until a homogeneous solution was formed. Nitrogen gas was introduced, and the mixture was heated to 50℃ and stirred continuously for 2 hours. The solvent was removed by vacuum distillation to obtain reaction intermediate 1. 51.2g of intermediate 1 was dissolved in 350ml of epichlorohydrin, and 0.6g of 3-methylbenzylamine was added. Nitrogen gas was introduced, and the mixture was heated to 120℃ with vigorous stirring. After reacting for 5 hours, the mixture was cooled to room temperature, and 20g of 40wt% sodium hydroxide aqueous solution was added. The reaction was continued for 2 hours, filtered, and the filtrate was washed with deionized water and separated using a separatory funnel until the pH of the filtrate was 6.5. 30g of anhydrous magnesium sulfate was added and dried for 2 hours. The filtrate was filtered again, and unreacted substances were removed by rotary evaporation to obtain reaction intermediate 2. Under a nitrogen atmosphere, 170.1g of reaction intermediate 2 was heated to 110℃, and 64.8g of... DOPO was heated to 160℃ and reacted for 8 hours to obtain a high-temperature resistant, flame-retardant epoxy resin. The obtained epoxy resin was uniformly mixed with curing agent DETDA at a mass ratio of 10:22.5. After uniform mixing and vacuum degassing, the resin was poured into a mold and cured at 130℃ for 2 hours; 150℃ for 3 hours; and 180℃ for 3 hours. The properties of the cured system are as follows: char residue of 61.5% at 800℃ under N2 atmosphere; glass transition temperature of 242℃; flexural strength of 156MPa; and flame retardancy rating of V-0, the highest level for vertical burning.

[0039] Example 3

[0040] In a 500ml three-necked flask, 13.68g of stilbene triol, 3.9g of dimethyldichlorosilane, and 150ml of toluene were added sequentially. The mixture was magnetically stirred until a homogeneous solution was formed. Nitrogen gas was introduced, and the mixture was heated to 50℃ and stirred continuously for 5 hours. The solvent was removed by vacuum distillation to obtain reaction intermediate 1. 51.2g of intermediate 1 was dissolved in 280ml of epichlorohydrin, and 0.8g of 3-methylbenzylamine was added. Nitrogen gas was introduced, and the mixture was heated to 120℃ with vigorous stirring. After reacting for 5 hours, the mixture was cooled to room temperature, and 20g of 40wt% sodium hydroxide aqueous solution was added. The reaction was continued for 1.5 hours. The mixture was filtered, and the filtrate was washed with deionized water and separated using a separatory funnel until the pH of the filtrate was 6.5. 30g of anhydrous magnesium sulfate was added, and the mixture was dried for 2 hours. The mixture was filtered again, and unreacted substances were removed by rotary evaporation to obtain reaction intermediate 2. Under a nitrogen atmosphere, 170.1g of reaction intermediate 2 was heated to 120℃, and 64.8g of... DOPO was heated to 190℃ and reacted for 8 hours to obtain a high-temperature resistant, flame-retardant epoxy resin. The obtained epoxy resin was uniformly mixed with curing agent DETDA at a mass ratio of 10:22.5. After uniform mixing and vacuum degassing, the resin was poured into a mold and cured at 130℃ for 2 hours; 150℃ for 3 hours; and 180℃ for 3 hours. The properties of the cured system are as follows: char residue of 61.5% at 800℃ under N2 atmosphere; glass transition temperature of 269℃; flexural strength of 126MPa; and flame retardancy rating of V-0, the highest level for vertical burning.

[0041] The epoxy resin of this invention possesses a high glass transition temperature, flame retardancy, and toughness, and can be used to prepare various structural components using RTM, filament winding, or hand lay-up processes, satisfying a wide range of applications. Specifically, the epoxy resin of this invention can be used via RTM to prepare canopies, blades, or panels for unmanned aerial vehicles (UAVs), exhibiting excellent high-temperature resistance, structural stability, and weight reduction.

Claims

1. A high-temperature resistant epoxy resin, characterized in that, This high-temperature resistant epoxy resin is prepared by the following method: Step (1) involves mixing stilbene, dimethyldichlorosilane and toluene for reaction and post-treatment to obtain reaction intermediate 1; Step (2) Mix reaction intermediate 1, epichlorohydrin and 3-methylbenzylamine, react them, add sodium hydroxide aqueous solution to continue the reaction, filter, wash, dry, filter, and rotary evaporate to obtain reaction intermediate 2; Step (3) The reaction intermediate 2 is mixed with DOPO and reacted to obtain a high-temperature resistant epoxy resin.

2. A method for preparing a high-temperature resistant epoxy resin, characterized in that, The preparation method involves the following steps: Step (1) involves mixing stilbene, dimethyldichlorosilane and toluene for reaction and post-treatment to obtain reaction intermediate 1; Step (2) Mix reaction intermediate 1, epichlorohydrin and 3-methylbenzylamine, react them, add sodium hydroxide aqueous solution to continue the reaction, filter, wash, dry, filter, and rotary evaporate to obtain reaction intermediate 2; Step (3) The reaction intermediate 2 is mixed with DOPO and reacted to obtain a high-temperature resistant epoxy resin; Step (4) Mix the epoxy resin obtained in step (3) with the curing agent, degas under vacuum, pour into the mold, and cure to obtain the cured product.

3. The preparation method according to claim 2, characterized in that: In step (1), the post-processing is vacuum distillation.

4. The preparation method according to claim 2, characterized in that: In step (1), the molar ratio of stilbene to dimethyldichlorosilane is 4:1, and the reaction temperature is 30-50°C. o C; reaction time is 1-4 hours; reaction environment is inert.

5. The preparation method according to claim 2, characterized in that: In step (2), the amount of reaction intermediate 1 is 50-150 mmol, the amount of 3-methylbenzylamine is 5-8.5 mmol, and the reaction temperature is 80-120 °C. o C, the reaction time is 3-6 hours, the mass fraction of sodium hydroxide solution is 30-50 wt%, and the subsequent reaction time is 1-3 hours; the pH value after washing with deionized water is 6.5-7.

6. The preparation method according to claim 2, characterized in that: In step (3), the amount of reaction intermediate 2 is 50-150 mmol; the temperature is 100-130°C. o C; The specific dosage of DOPO is 50-180 mmol, heated to 150-180 °C. o C, reaction time 5-10 hours.

7. The preparation method according to claim 2, characterized in that: In step (4), the curing agent is DDS or DETDA, the mass ratio of epoxy resin to DDS is 10:3, and the mass ratio of epoxy resin to curing agent DETDA is 10:22.

5.

8. The preparation method according to claim 2, characterized in that: In step (4), the curing process is 130. o C, 2h; 150 o C, 3h and 180 o C 3h.

9. An application based on the high-temperature resistant epoxy resin according to claim 1, characterized in that, High-temperature resistant epoxy resin is used to manufacture nacelle covers, propellers, or wall panels through the RTM process.

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