Epoxy resin reaction accelerator

Abstract

The invention discloses an epoxy resin reaction accelerator, and belongs to the technical field of epoxy resin accelerators. Firstly, a rigid benzene ring and a maleimide group are introduced into an accelerant, so that the crosslinking density of the material is improved, the thermal stability of the material is improved, and the material has relatively good dispersity in an epoxy resin matrix and relatively good compatibility with the matrix; and secondly, the imidazole group is modified, so that the reaction activity of the imidazole structure and the epoxy group in the epoxy resin is effectively reduced, the reaction of the single-component system is limited at low temperature, and the single-component system can show high reaction activity at reaction temperature. Therefore, the cured epoxy resin prepared from the accelerator is high in transparency and good in heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resin accelerators, and particularly relates to an epoxy resin reaction accelerator. Background Art

[0002] In recent years, with the expansion of the application fields of epoxy resins and the increase in demand, the requirements for epoxy resin products in industrial production have also been increasing day by day, especially for the increasing demand for single-component epoxy resin systems. Single-component epoxy resin systems have broad applications in adhesives, coatings, electronic packaging, etc. However, at the same time, higher requirements are put forward for the stability, pot life, and heat resistance of the systems. In the ternary system of epoxy resin, curing agent, and curing accelerator actually used in industrial production, it is required that no cross-linking reaction occurs at relatively low temperatures or room temperature, and it can be stably stored for a period of time. However, because the epoxy-opening activity of the curing agent is low in some systems, or there are no active groups in the structure of the curing agent, the activation energy of the curing reaction is too high, and the curing reaction rate is too slow. The reaction must be completed at high temperatures, or even the reaction cannot occur, which not only wastes energy but also increases production risks.

[0003] Therefore, a heat-latent curing accelerator containing heat-resistant groups is developed to solve the above problems. The added curing accelerator can not only reduce the reaction activation energy, shorten the reaction time, and increase the curing reaction rate, but also improve the heat resistance of the system. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides an epoxy resin reaction accelerator.

[0005] The object of the present invention can be achieved by the following technical solutions: An epoxy resin reaction accelerator has the following structural formula:

[0006] The epoxy resin reaction accelerator is prepared through the following steps: Step S1: Add 4-aminobenzoyl chloride into a flask containing tetrahydrofuran, and stir evenly in an ice-water bath. Then add triethylamine to the 2-methylimidazole tetrahydrofuran solution, mix and stir evenly, and dropwise add it to the flask with a separatory funnel. After the dropping is completed, transfer the flask to a 40°C constant-temperature oil bath and stir for reaction for 3 - 5 h. After the reaction ends, filter, and rotary evaporate the filtrate. The obtained solid is washed with deionized water, filtered, and dried at 50°C for 12 h to obtain Intermediate 1. The reaction process is as follows:

[0007] In step S1, a nucleophilic substitution method is used to replace the active hydrogen on the pyrrole nitrogen in 2-methylimidazole and introduce a strongly electronegative carbonyl group, which forms a conjugated structure with the benzene ring, stabilizes electrons, weakens the electron density cloud of the pyridine nitrogen on imidazole, effectively reduces the reactivity of the imidazole structure with the epoxy group in the epoxy resin, and further limits the reaction of the one-component system at low temperatures, while showing high reactivity at the reaction temperature; Furthermore, the dosage ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazole tetrahydrofuran solution, and triethylamine is 2.15 - 4.30 g : 20 - 40 mL : 20 - 40 mL : 2.78 - 5.56 mL. The 2-methylimidazole tetrahydrofuran solution is prepared by mixing 2-methylimidazole and tetrahydrofuran in a dosage ratio of 1.61 - 3.28 g : 20 - 40 mL.

[0008] Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine into a three-necked flask, then add dichloromethane and stir evenly. Then, dropwise add a dichloromethane solution of dicyclohexylcarbodiimide. After the addition is complete, continuously stir and react for 5 - 6 h, then filter the reaction solution. The filtrate is washed 5 times with deionized water and then concentrated, recrystallized in a rotary evaporator to obtain intermediate 2, and the structural formula is as follows:

[0009] In step S2, the carboxyl group on trimesic acid reacts with the hydroxyl group on (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, thereby introducing maleic anhydride; Furthermore, the dosage ratio of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, 4-dimethylaminopyridine, dichloromethane, and dichloromethane solution of dicyclohexylcarbodiimide is 0.03 - 0.06 mol : 0.01 - 0.02 mol : 0.17 - 0.33 g : 140 - 280 mL : 90 - 180 mL. The dichloromethane solution of dicyclohexylcarbodiimide is prepared by mixing dicyclohexylcarbodiimide and dichloromethane in a dosage ratio of 6.16 - 12.3 g : 90 - 180 mL.

[0010] Step S3: Under nitrogen conditions, put intermediate 1 into a flask, pour in N,N-dimethylformamide and stir for 30 min. Then, dropwise add a mixed solution of intermediate 2 into the flask and continuously stir at room temperature for 24 h. After the reaction is completed, pour the above solution into distilled water, let it stand for 30 min, then filter, wash, and vacuum dry at 80 °C for 24 h to obtain product 1, and the structural formula is as follows:

[0011] Further, the dosage ratio of intermediate 1, N,N-dimethylformamide, and the mixed solution of intermediate 2 is 0.03 - 0.06 mol : 80 - 160 mL : 80 - 160 mL. The mixed solution of intermediate 2 is prepared by mixing intermediate 2 and N,N-dimethylformamide according to a dosage ratio of 0.012 - 0.036 mol : 80 - 160 mL.

[0012] Step S4: Add product 1, sodium acetate, and acetic anhydride into a reactor, mix them, and heat up to 60 °C and continuously stir for 2 - 4 h. Then quickly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and place it in a vacuum dryer at 80 °C for 24 h to obtain the epoxy resin reaction promoter. In step S4, product 1 undergoes dehydration and ring closure under the action of acetic anhydride and sodium acetate, thereby introducing a maleimide group. This makes the cured material have good light transmittance because the bismaleimide structure participates in the epoxy resin curing reaction and has good dispersibility in the epoxy resin matrix and good compatibility with the matrix. Bismaleimide can also crosslink and polymerize with the curing agent, thereby increasing the crosslinking density of the material and enhancing the thermal stability of the material. In addition, the introduction of the benzene ring can also effectively improve the heat resistance of the material because the rigid benzene ring can increase the intermolecular interaction of the polymer material, thereby increasing the glass transition temperature of the polymer material. Further, the dosage ratio of product 1, sodium acetate, and acetic anhydride is 0.01 - 0.03 mol : 0.16 - 0.5 g : 20 - 60 mL.

[0013] Advantages of the present invention: An epoxy resin reaction promoter provided by the present invention has excellent stability at room temperature, exhibits high reaction activity at the reaction temperature, and the epoxy resin material prepared after its participation in the curing reaction has high transparency and good heat resistance.

[0014] The imidazole group is modified by nucleophilic substitution. The active hydrogen on the pyrrole nitrogen in imidazole is substituted, and a strongly electronegative carbonyl group is introduced, forming a conjugated structure with the benzene ring, stabilizing electrons, weakening the electron density cloud of the pyridine nitrogen on imidazole, effectively reducing the reaction activity of the imidazole structure with the epoxy group in the epoxy resin, and further restricting the reaction of the single-component system at low temperature, while it can exhibit high reaction activity at the reaction temperature.

[0015] The introduction of maleimide groups endows the cured material with good light transmittance. This is because the bismaleimide structure participates in the epoxy resin curing reaction and has good dispersibility in the epoxy resin matrix, showing good compatibility with the matrix. Bismaleimide can also crosslink and polymerize with the curing agent, thereby increasing the crosslink density of the material and enhancing its thermal stability. In addition, the introduction of benzene rings can effectively improve the heat resistance of the material because the rigid benzene rings can increase the intermolecular interactions of the polymer material, thus raising the glass transition temperature of the polymer material. Detailed implementation mode

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. Embodiment

[0017] An epoxy resin reaction accelerator has the following structural formula:

[0018] An epoxy resin reaction accelerator is prepared through the following steps: Step S1: Add 4-aminobenzoyl chloride into a flask containing tetrahydrofuran, and stir evenly in an ice-water bath. Then add triethylamine to the 2-methylimidazole tetrahydrofuran solution, mix and stir evenly, and then dropwise add the mixture to the flask with a separatory funnel. After the addition is completed, transfer the flask to a 40°C constant temperature oil bath and stir for 3 h. After the reaction ends, filter, and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry it at 50°C for 12 h to obtain Intermediate 1. The dosage ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazole tetrahydrofuran solution, and triethylamine is 2.15 g: 20 mL: 20 mL: 2.78 mL. The 2-methylimidazole tetrahydrofuran solution is prepared by mixing 2-methylimidazole and tetrahydrofuran in a dosage ratio of 1.61 g: 20 mL. Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine into a three-necked flask. Then add dichloromethane and stir evenly. Next, dropwise add a solution of dicyclohexylcarbodiimide in dichloromethane. After the addition is complete, continue stirring and reacting for 5 h, then filter the reaction solution. Wash the filtrate 5 times with deionized water, concentrate it in a rotary evaporator, and perform recrystallization to obtain Intermediate 2. The dosage ratio of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, 4-dimethylaminopyridine, dichloromethane, and the solution of dicyclohexylcarbodiimide in dichloromethane is 0.03 mol: 0.01 mol: 0.17 g: 140 mL: 90 mL. The solution of dicyclohexylcarbodiimide in dichloromethane is prepared by mixing dicyclohexylcarbodiimide and dichloromethane according to a dosage ratio of 6.16 g: 90 mL; Step S3: Under nitrogen conditions, put Intermediate 1 into a flask, pour in N,N-dimethylformamide and stir for 30 min. Then dropwise add a mixed solution of Intermediate 2 to the flask and continuously stir at room temperature for 24 h. After the reaction is completed, pour the above solution into distilled water and let it stand for 30 min, then filter, wash, and vacuum dry at 80 °C for 24 h to obtain Product 1. The dosage ratio of Intermediate 1, N,N-dimethylformamide, and the mixed solution of Intermediate 2 is 0.03 mol: 80 mL: 80 mL. The mixed solution of Intermediate 2 is prepared by mixing Intermediate 2 and N,N-dimethylformamide according to a dosage ratio of 0.012 mol: 80 mL; Step S4: Add Product 1, sodium acetate, and acetic anhydride into a reactor and mix them. Then heat up to 60 °C and continuously stir for 2 h. Then quickly cool the system to room temperature in an ice-water bath, filter, wash, perform recrystallization, and place it in a vacuum dryer at 80 °C for 24 h to obtain the epoxy resin reaction promoter. The dosage ratio of Product 1, sodium acetate, and acetic anhydride is 0.01 mol: 0.16 g: 20 mL. Example

[0019] An epoxy resin reaction promoter is prepared by the following steps: Step S1: Add 4-aminobenzoyl chloride into a flask containing tetrahydrofuran, and stir evenly in an ice-water bath. Then add triethylamine to the 2-methylimidazole tetrahydrofuran solution, mix and stir evenly, and gradually add it dropwise to the flask using a separatory funnel. After the addition is complete, transfer the flask to a constant-temperature oil bath at 40 °C and stir for 4 h. After the reaction is completed, filter, and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry at 50 °C for 12 h to obtain Intermediate 1. The dosage ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazole tetrahydrofuran solution, and triethylamine is 3.23 g: 30 mL: 30 mL: 4.17 mL. The 2-methylimidazole tetrahydrofuran solution is prepared by mixing 2-methylimidazole and tetrahydrofuran in a dosage ratio of 2.46 g: 30 mL; Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine into a three-necked flask, then add dichloromethane and mix and stir evenly. Then gradually add a solution of dicyclohexylcarbodiimide in dichloromethane dropwise. After the addition is complete, continue to stir and react for 5.5 h, then filter the reaction solution. Wash the filtrate 5 times with deionized water and concentrate it in a rotary evaporator, and perform recrystallization to obtain Intermediate 2. The dosage ratio of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, 4-dimethylaminopyridine, dichloromethane, and the dicyclohexylcarbodiimide dichloromethane solution is 0.045 mol: 0.015 mol: 0.25 g: 210 mL: 135 mL. The dicyclohexylcarbodiimide dichloromethane solution is prepared by mixing dicyclohexylcarbodiimide and dichloromethane in a dosage ratio of 9.24 g: 135 mL; Step S3: Under nitrogen conditions, put Intermediate 1 into a flask, pour in N,N-dimethylformamide and stir for 30 min. Then add a mixed solution of Intermediate 2 dropwise to the flask and continuously stir at room temperature for 24 h. After the reaction is completed, pour the above solution into distilled water, let it stand for 30 min, then filter, wash, and vacuum dry at 80 °C for 24 h to obtain Product 1. The dosage ratio of Intermediate 1, N,N-dimethylformamide, and the mixed solution of Intermediate 2 is 0.045 mol: 120 mL: 120 mL. The mixed solution of Intermediate 2 is prepared by mixing Intermediate 2 and N,N-dimethylformamide in a dosage ratio of 0.024 mol: 120 mL; Step S4: Add Product 1, sodium acetate, and acetic anhydride into a reactor, mix them, and raise the temperature to 60 °C and continuously stir for 3 h. Then quickly cool the system to room temperature in an ice-water bath, filter, wash, perform recrystallization, and place it in a vacuum dryer at 80 °C for 24 h to obtain an epoxy resin reaction accelerator. The dosage ratio of Product 1, sodium acetate, and acetic anhydride is 0.02 mol: 0.033 g: 40 mL. Example

[0020] An epoxy resin reaction promoter is prepared by the following steps: Step S1: Add 4-aminobenzoyl chloride into a flask containing tetrahydrofuran, stir evenly under an ice-water bath, then add triethylamine to the 2-methylimidazole tetrahydrofuran solution, mix and stir evenly, and then dropwise add it to the flask with a separating funnel. After the dropping is completed, transfer the flask to a 40°C constant-temperature oil bath and stir for reaction for 5 h. After the reaction is completed, filter, and rotary evaporate the filtrate. The obtained solid is washed with deionized water, filtered, and dried at 50°C for 12 h to obtain Intermediate 1. The dosage ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazole tetrahydrofuran solution, and triethylamine is 4.30 g: 40 mL: 40 mL: 5.56 mL. The 2-methylimidazole tetrahydrofuran solution is prepared by mixing 2-methylimidazole and tetrahydrofuran according to a dosage ratio of 3.28 g: 40 mL; Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine into a three-necked flask, then add dichloromethane and mix and stir evenly. Then dropwise add the dicyclohexylcarbodiimide dichloromethane solution. After the dropping is completed, continuously stir and react for 6 h, then filter the reaction solution. The filtrate is washed 5 times with deionized water and then concentrated and recrystallized in a rotary evaporator to obtain Intermediate 2. The dosage ratio of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, 4-dimethylaminopyridine, dichloromethane, and dicyclohexylcarbodiimide dichloromethane solution is 0.06 mol: 0.02 mol: 0.33 g: 280 mL: 180 mL. The dicyclohexylcarbodiimide dichloromethane solution is prepared by mixing dicyclohexylcarbodiimide and dichloromethane according to a dosage ratio of 12.3 g: 180 mL; Step S3: Under nitrogen conditions, put Intermediate 1 into a flask, pour in N,N-dimethylformamide and stir for 30 min. Then dropwise add the Intermediate 2 mixed solution to the flask and continuously stir at room temperature for 24 h. After the reaction is completed, pour the above solution into distilled water and let it stand for 30 min, then filter, wash, and vacuum dry at 80°C for 24 h to obtain Product 1. The dosage ratio of Intermediate 1, N,N-dimethylformamide, and the Intermediate 2 mixed solution is 0.06 mol: 160 mL: 160 mL. The Intermediate 2 mixed solution is prepared by mixing Intermediate 2 and N,N-dimethylformamide according to a dosage ratio of 0.036 mol: 160 mL; Step S4: Add Product 1, sodium acetate, and acetic anhydride into a reactor and mix, and heat up to 60°C and continuously stir for 4 h. Then quickly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and place it in a vacuum dryer at 80°C for 24 h to obtain the epoxy resin reaction promoter. The dosage ratio of Product 1, sodium acetate, and acetic anhydride is 0.03 mol: 0.5 g: 60 mL. Example

[0021] Mix E44 epoxy resin, maleic anhydride, and the accelerator prepared in Example 1 in a mass ratio of 100:80:1.3, heat to 90 °C for curing for 1 h, then heat to 150 °C for curing for 1 h. After the curing is completed, take out the mold, cool it to room temperature, open the mold and demold to obtain a standard cured sample bar. Example

[0022] Mix E44 epoxy resin, maleic anhydride, and the accelerator prepared in Example 2 in a mass ratio of 100:80:1.3, heat to 90 °C for curing for 1 h, then heat to 150 °C for curing for 1 h. After the curing is completed, take out the mold, cool it to room temperature, open the mold and demold to obtain a standard cured sample bar. Example

[0023] Mix E44 epoxy resin, maleic anhydride, and the accelerator prepared in Example 3 in a mass ratio of 100:80:1.3, heat to 90 °C for curing for 1 h, then heat to 150 °C for curing for 1 h. After the curing is completed, take out the mold, cool it to room temperature, open the mold and demold to obtain a standard cured sample bar.

[0024] Comparative Example Mix E44 epoxy resin, maleic anhydride, and 2-ethyl-4-methylimidazole in a mass ratio of 100:80:1.3, heat to 90 °C for curing for 1 h, then heat to 150 °C for curing for 1 h. After the curing is completed, take out the mold, cool it to room temperature, open the mold and demold to obtain a standard cured sample bar.

[0025] Perform light transmittance test, heat resistance test, and appearance inspection on the epoxy resin cured sample bars prepared in Examples 4-6 and the comparative example. Light transmittance test: Use a UV-visible spectrophotometer to test the light transmittance of the cured sample bar at 800 nm; Heat resistance test: Place the cured epoxy resin in an environment of 150 °C, take it out after 30 hours, and observe the appearance of the sample. The test results are shown in Table 1: Table 1

[0026] As can be seen from Table 1, the epoxy resin sample bars prepared in the examples of the present invention have higher light transmittance, slow color change of the sample bars after heating, high transparency, and better heat resistance.

[0027] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. An epoxy resin reaction promoter, characterized in that, Its structural formula is as follows:

2. An epoxy resin reaction promoter according to claim 1, characterized in that, The preparation of this epoxy resin reaction promoter includes the following steps: Step S1: Add 4-aminobenzoyl chloride into a flask containing tetrahydrofuran, and stir evenly under an ice-water bath. Then add triethylamine to the 2-methylimidazole tetrahydrofuran solution, mix and stir evenly, and dropwise add the mixture to the flask with a separatory funnel. After the addition is completed, transfer the flask to a constant temperature oil bath at 40 °C and stir for reaction for 3-5 h. After the reaction is completed, filter, and rotary evaporate the filtrate. The obtained solid is washed with deionized water, filtered, and dried at 50 °C for 12 h to obtain Intermediate 1. Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimellitic acid, and 4-dimethylaminopyridine into a three-necked flask, then add dichloromethane and mix and stir evenly. Then dropwise add the dicyclohexylcarbodiimide dichloromethane solution. After the addition is completed, continue to stir and react for 5-6 h, then filter the reaction solution. The filtrate is washed 5 times with deionized water and then concentrated in a rotary evaporator and recrystallized to obtain Intermediate 2. Step S3: Under nitrogen conditions, put Intermediate 1 into a flask, pour in N,N-dimethylformamide and stir for 30 min. Then dropwise add the Intermediate 2 mixed solution to the flask and continuously stir at room temperature for 24 h. After the reaction is completed, pour the above solution into distilled water and let it stand for 30 min, then filter, wash, and vacuum dry at 80 °C for 24 h to obtain Product 1. Step S4: Add Product 1, sodium acetate, and acetic anhydride into a reactor and mix, and heat up to 60 °C and continuously stir for 2-4 h. Then quickly cool the system to room temperature in an ice-water bath, filter, wash, and recrystallize, and place it in a vacuum dryer at 80 °C for 24 h to obtain the epoxy resin reaction promoter.

3. An epoxy resin reaction promoter according to claim 2, characterized in that, In Step S1, the dosage ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazole tetrahydrofuran solution, and triethylamine is 2.15-4.30 g: 20-40 mL: 20-40 mL: 2.78-5.56 mL. The 2-methylimidazole tetrahydrofuran solution is prepared by mixing 2-methylimidazole and tetrahydrofuran in a dosage ratio of 1.61-3.28 g: 20-40 mL.

4. An epoxy resin reaction promoter according to claim 2, characterized in that, In Step S2, the dosage ratio of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimellitic acid, 4-dimethylaminopyridine, dichloromethane, and dicyclohexylcarbodiimide dichloromethane solution is 0.03-0.06 mol: 0.01-0.02 mol: 0.17-0.33 g: 140-280 mL: 90-180 mL. The dicyclohexylcarbodiimide dichloromethane solution is prepared by mixing dicyclohexylcarbodiimide and dichloromethane in a dosage ratio of 6.16-12.3 g: 90-180 mL.

5. An epoxy resin reaction promoter according to claim 2, characterized in that, In Step S3, the dosage ratio of Intermediate 1, N,N-dimethylformamide, and Intermediate 2 mixed solution is 0.03-0.06 mol: 80-160 mL: 80-160 mL. The Intermediate 2 mixed solution is prepared by mixing Intermediate 2 and N,N-dimethylformamide in a dosage ratio of 0.012-0.036 mol: 80-160 mL.

6. The epoxy resin reaction promoter according to claim 1, characterized in that, In step S4, the dosage ratio of product 1, sodium acetate and acetic anhydride is 0.01 - 0.03 mol: 0.16 - 0.5 g: 20 - 60 mL.

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