An epoxy resin reaction accelerator

Abstract

This invention discloses an epoxy resin reaction accelerator, belonging to the technical field of epoxy resin accelerators. First, by introducing rigid benzene rings and maleimide groups into the accelerator, not only is the crosslinking density and thermal stability of the material improved, but it also exhibits good dispersibility and compatibility with the epoxy resin matrix. Second, the imidazole group is modified to effectively reduce the reactivity of the imidazole structure with the epoxy groups in the epoxy resin, thus limiting the reaction of the single-component system at low temperatures while maintaining high reactivity at the reaction temperature. Therefore, the epoxy resin cured product prepared by the accelerator of this invention has high transparency and good heat resistance.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin accelerator technology, and more specifically to an epoxy resin reaction accelerator. Background Technology

[0002] In recent years, with the expansion of epoxy resin applications and the increase in demand, the requirements for epoxy resin products in industrial production have also been rising, especially the demand for single-component epoxy resin systems. Single-component epoxy resin systems are widely used in adhesives, coatings, and electronic packaging, but this also places higher demands on the system's stability, pot life, and heat resistance. In industrial production, ternary systems of epoxy resin, curing agent, and curing accelerator are required to not undergo cross-linking reactions at relatively low temperatures or room temperature and to be stably stored for a period of time. However, because some systems have curing agents with low epoxy open-opening activity or lacking active groups in their structure, the activation energy of the curing reaction is too high, resulting in a slow curing rate. This necessitates high temperatures to complete the reaction, or even prevents it from occurring altogether, wasting energy and increasing production risks.

[0003] Therefore, a heat-latent curing accelerator containing heat-resistant groups was 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 address the aforementioned technical problems, this invention provides an epoxy resin reaction accelerator.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An epoxy resin reaction accelerator has the following structural formula:

[0007]

[0008] The epoxy resin reaction accelerator is prepared by the following steps:

[0009] Step S1: Add 4-aminobenzoyl chloride to a flask containing tetrahydrofuran and stir evenly in an ice-water bath. Then, add triethylamine to the 2-methylimidazolium tetrahydrofuran solution, mix and stir evenly, and then add it dropwise to the flask using a separatory funnel. After the addition is complete, transfer the flask to a 40°C constant temperature oil bath and stir the reaction for 3-5 hours. After the reaction is complete, filter and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry at 50°C for 12 hours to obtain intermediate 1. The reaction process is as follows:

[0010]

[0011] In step S1, the active hydrogen on the pyrrolidone nitrogen in 2-methylimidazolium is replaced by nucleophilic substitution, and a strongly electronegative carbonyl group is introduced to form a conjugated structure with the benzene ring, which stabilizes the electrons and weakens the electron density cloud of the pyridine nitrogen on the imidazolium. This effectively reduces the reactivity of the imidazolium structure with the epoxy group in the epoxy resin, thereby limiting the reaction of the single-component system at low temperatures, while exhibiting high reactivity at the reaction temperature.

[0012] Furthermore, the ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazolium tetrahydrofuran solution, and triethylamine is 2.15-4.30 g : 20-40 mL : 20-40 mL : 2.78-5.56 mL. The 2-methylimidazolium tetrahydrofuran solution is prepared by mixing 2-methylimidazolium and tetrahydrofuran in a ratio of 1.61-3.28 g : 20-40 mL.

[0013] Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine to a three-necked flask. Then add dichloromethane and mix thoroughly. Next, add dicyclohexylcarbodiimide dichloromethane solution dropwise. After the addition is complete, continue stirring the reaction for 5-6 hours. Filter the reaction solution, wash the filtrate five times with deionized water, concentrate it in a rotary evaporator, and recrystallize to obtain intermediate 2, with the following structural formula:

[0014]

[0015] In step S2, the carboxyl group on pyromellitic acid reacts with the hydroxyl group on (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, thereby introducing maleic anhydride;

[0016] Furthermore, the ratio of the amounts of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic 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 ratio of 6.16-12.3 g : 90-180 mL.

[0017] Step S3: Under nitrogen atmosphere, intermediate 1 is placed in a flask, N,N-dimethylformamide is added and stirred for 30 min. Then, a mixed solution of intermediate 2 is added dropwise to the flask, and stirring is continued at room temperature for 24 h. After the reaction is complete, the above solution is poured into distilled water and allowed to stand for 30 min. After filtration and washing, it is dried under vacuum at 80 °C for 24 h to obtain product 1, with the following structural formula:

[0018]

[0019] Furthermore, the ratio of intermediate 1, N,N-dimethylformamide and intermediate 2 in the mixed solution 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 in a ratio of 0.012-0.036 mol: 80-160 mL.

[0020] Step S4: Add product 1, sodium acetate and acetic anhydride into the reactor and mix. Heat to 60°C and stir continuously for 2-4 hours. Then, rapidly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and vacuum dry at 80°C for 24 hours to obtain epoxy resin reaction accelerator.

[0021] In step S4, product 1 undergoes dehydration and ring closure under the action of acetic anhydride and sodium acetate, thereby introducing maleimide groups. This gives the cured material good light transmittance because the bismaleimide structure participates in the epoxy resin curing reaction and has good dispersibility in the epoxy resin matrix, exhibiting good compatibility with the matrix. Bismaleimide can also crosslink and polymerize with the curing agent, thereby increasing the crosslinking density of the material and improving its thermal stability. 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 interactions of the polymer material, thereby increasing the glass transition temperature of the polymer material.

[0022] Furthermore, the ratio of product 1, sodium acetate, and acetic anhydride is 0.01-0.03 mol: 0.16-0.5 g: 20-60 mL.

[0023] The beneficial effects of this invention are:

[0024] The present invention provides an epoxy resin reaction accelerator that has excellent stability at room temperature and exhibits high reactivity at the reaction temperature. Furthermore, the epoxy resin material prepared after the accelerator participates in the curing reaction has high transparency and good heat resistance.

[0025] By modifying the imidazole group through nucleophilic substitution, the active hydrogen on the pyrrolidium nitrogen in the imidazole is replaced, and a strongly electronegative carbonyl group is introduced to form a conjugated structure with the benzene ring, stabilizing electrons and reducing the electron density cloud of the pyridine nitrogen on the imidazole. This effectively reduces the reactivity of the imidazole structure with the epoxy groups in the epoxy resin, thus limiting the reaction of the single-component system at low temperatures, while allowing it to exhibit high reactivity at the reaction temperature.

[0026] The introduction of maleimide groups gives the cured material 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, as well as good compatibility with the matrix. Bismaleimide can also crosslink and polymerize with the curing agent, thereby increasing the crosslinking density of the material and improving its thermal stability. In addition, the introduction of benzene rings can also effectively improve the heat resistance of the material. This is because rigid benzene rings can increase the intermolecular interactions of polymer materials, thereby increasing the glass transition temperature of the polymer materials. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0028] An epoxy resin reaction accelerator, with the following structural formula:

[0029]

[0030] An epoxy resin reaction accelerator is prepared by the following steps:

[0031] Step S1: Add 4-aminobenzoyl chloride to a flask containing tetrahydrofuran and stir evenly under an ice-water bath. Then add triethylamine to the 2-methylimidazolium tetrahydrofuran solution, mix and stir evenly, and then add it dropwise to the flask using a separatory funnel. After the addition is complete, transfer the flask to a 40°C constant temperature oil bath and stir to react for 3 hours. After the reaction is complete, filter and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry at 50°C for 12 hours to obtain intermediate 1. The ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazolium tetrahydrofuran solution and triethylamine is 2.15 g: 20 mL: 20 mL: 2.78 mL. The 2-methylimidazolium tetrahydrofuran solution is prepared by mixing 2-methylimidazolium and tetrahydrofuran in a ratio of 1.61 g: 20 mL.

[0032] Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine to a three-necked flask, then add dichloromethane and mix thoroughly. Next, add dicyclohexylcarbodiimide dichloromethane solution dropwise. After the addition is complete, continue stirring for 5 hours, then filter the reaction solution. Wash the filtrate five times with deionized water, concentrate it in a rotary evaporator, and recrystallize to obtain intermediate 2. The ratio of the amounts of 9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, 4-dimethylaminopyridine, dichloromethane, and dicyclohexylcarbodiimide dichloromethane solution is 0.03 mol: 0.01 mol: 0.17 g: 140 mL: 90 mL. The dicyclohexylcarbodiimide dichloromethane solution is prepared by mixing dicyclohexylcarbodiimide and dichloromethane in a ratio of 6.16 g: 90 mL.

[0033] Step S3: Under nitrogen atmosphere, intermediate 1 is placed in a flask, N,N-dimethylformamide is added and stirred for 30 min. Then, intermediate 2 mixed solution is added dropwise to the flask and stirred continuously at room temperature for 24 h. After the reaction is complete, the above solution is poured into distilled water and allowed to stand for 30 min. After filtration and washing, it is vacuum dried at 80 °C for 24 h to obtain product 1. The ratio of intermediate 1, N,N-dimethylformamide and intermediate 2 mixed solution is 0.03 mol: 80 mL: 80 mL. Intermediate 2 mixed solution is prepared by mixing intermediate 2 and N,N-dimethylformamide at a ratio of 0.012 mol: 80 mL.

[0034] Step S4: Add product 1, sodium acetate and acetic anhydride to the reactor and mix. Heat to 60°C and stir continuously for 2 hours. Then, rapidly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and vacuum dry at 80°C for 24 hours to obtain epoxy resin reaction promoter. The ratio of product 1, sodium acetate and acetic anhydride is 0.01 mol: 0.16 g: 20 mL. Example

[0035] An epoxy resin reaction accelerator is prepared by the following steps:

[0036] Step S1: Add 4-aminobenzoyl chloride to a flask containing tetrahydrofuran and stir evenly under an ice-water bath. Then add triethylamine to the 2-methylimidazolium tetrahydrofuran solution, mix and stir evenly, and then add it dropwise to the flask using a separatory funnel. After the addition is complete, transfer the flask to a 40°C constant temperature oil bath and stir to react for 4 hours. After the reaction is complete, filter and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry at 50°C for 12 hours to obtain intermediate 1. The ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazolium tetrahydrofuran solution and triethylamine is 3.23 g: 30 mL: 30 mL: 4.17 mL. The 2-methylimidazolium tetrahydrofuran solution is prepared by mixing 2-methylimidazolium and tetrahydrofuran in a ratio of 2.46 g: 30 mL.

[0037] Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine to a three-necked flask, then add dichloromethane and mix thoroughly. Next, add dicyclohexylcarbodiimide dichloromethane solution dropwise. After the addition is complete, continue stirring for 5.5 hours, then filter the reaction solution. Wash the filtrate five times with deionized water, concentrate it in a rotary evaporator, and recrystallize to obtain intermediate 2, (9ci) The ratio of the amounts of ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, 4-dimethylaminopyridine, dichloromethane, and 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 ratio of 9.24 g: 135 mL.

[0038] Step S3: Under nitrogen atmosphere, intermediate 1 is placed in a flask, N,N-dimethylformamide is added and stirred for 30 min. Then, intermediate 2 mixed solution is added dropwise to the flask and stirred continuously at room temperature for 24 h. After the reaction is complete, the above solution is poured into distilled water and allowed to stand for 30 min. After filtration and washing, it is vacuum dried at 80 °C for 24 h to obtain product 1. The ratio of intermediate 1, N,N-dimethylformamide and intermediate 2 mixed solution is 0.045 mol: 120 mL: 120 mL. Intermediate 2 mixed solution is prepared by mixing intermediate 2 and N,N-dimethylformamide at a ratio of 0.024 mol: 120 mL.

[0039] Step S4: Add product 1, sodium acetate and acetic anhydride to the reactor and mix. Heat to 60°C and stir continuously for 3 hours. Then, rapidly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and vacuum dry at 80°C for 24 hours to obtain epoxy resin reaction promoter. The ratio of product 1, sodium acetate and acetic anhydride is 0.02mol:0.033g:40mL. Example

[0040] An epoxy resin reaction accelerator is prepared by the following steps:

[0041] Step S1: Add 4-aminobenzoyl chloride to a flask containing tetrahydrofuran and stir evenly under an ice-water bath. Then add triethylamine to the 2-methylimidazolium tetrahydrofuran solution, mix and stir evenly, and then add it dropwise to the flask using a separatory funnel. After the addition is complete, transfer the flask to a 40°C constant temperature oil bath and stir to react for 5 hours. After the reaction is complete, filter and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry at 50°C for 12 hours to obtain intermediate 1. The ratio of 4-aminobenzoyl chloride, tetrahydrofuran, 2-methylimidazolium tetrahydrofuran solution and triethylamine is 4.30 g: 40 mL: 40 mL: 5.56 mL. The 2-methylimidazolium tetrahydrofuran solution is prepared by mixing 2-methylimidazolium and tetrahydrofuran in a ratio of 3.28 g: 40 mL.

[0042] Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine to a three-necked flask, then add dichloromethane and mix thoroughly. Next, add dicyclohexylcarbodiimide dichloromethane solution dropwise. After the addition is complete, continue stirring for 6 hours, then filter the reaction solution. Wash the filtrate five times with deionized water, concentrate it in a rotary evaporator, and recrystallize to obtain intermediate 2, (9ci) The ratio of the amounts of ci)-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 in a ratio of 12.3 g: 180 mL.

[0043] Step S3: Under nitrogen atmosphere, intermediate 1 is placed in a flask, N,N-dimethylformamide is added and stirred for 30 min. Then, intermediate 2 mixed solution is added dropwise to the flask and stirred continuously at room temperature for 24 h. After the reaction is complete, the above solution is poured into distilled water and allowed to stand for 30 min. After filtration and washing, it is vacuum dried at 80 °C for 24 h to obtain product 1. The ratio of intermediate 1, N,N-dimethylformamide and intermediate 2 mixed solution is 0.06 mol: 160 mL: 160 mL. Intermediate 2 mixed solution is prepared by mixing intermediate 2 and N,N-dimethylformamide at a ratio of 0.036 mol: 160 mL.

[0044] Step S4: Add product 1, sodium acetate and acetic anhydride to the reactor and mix. Heat to 60°C and stir continuously for 4 hours. Then, rapidly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and vacuum dry at 80°C for 24 hours to obtain epoxy resin reaction accelerator. The ratio of product 1, sodium acetate and acetic anhydride is 0.03 mol: 0.5 g: 60 mL. Example

[0045] E44 epoxy resin, maleic anhydride, and the accelerator prepared in Example 1 were mixed in a mass ratio of 100:80:1.3, heated to 90°C and cured for 1 hour, then heated to 150°C and cured for another hour. After curing, the mold was removed and cooled to room temperature before the mold was opened and demolded to obtain the standard cured sample. Example

[0046] E44 epoxy resin, maleic anhydride, and the accelerator prepared in Example 2 were mixed in a mass ratio of 100:80:1.3, heated to 90°C for 1 hour, and then heated to 150°C for 1 hour. After curing, the mold was removed and cooled to room temperature. The mold was then opened and demolded to obtain the standard cured sample. Example

[0047] E44 epoxy resin, maleic anhydride, and the accelerator prepared in Example 3 were mixed in a mass ratio of 100:80:1.3, heated to 90°C and cured for 1 hour, then heated to 150°C and cured for another hour. After curing, the mold was removed and cooled to room temperature before the mold was opened and demolded to obtain the standard cured sample.

[0048] Comparative Example

[0049] E44 epoxy resin, maleic anhydride, and 2-ethyl-4-methylimidazole were mixed in a mass ratio of 100:80:1.3, heated to 90℃ for 1 hour, and then heated to 150℃ for 1 hour. After curing, the mold was removed and cooled to room temperature before demolding to obtain a standard cured sample.

[0050] The epoxy resin cured samples prepared in Examples 4-6 and the comparative examples were subjected to transmittance tests, heat resistance tests, and appearance inspections. Transmittance test: The transmittance of the cured samples at 800 nm was measured using a UV-Vis spectrophotometer. Heat resistance test: The cured epoxy resin was placed in an environment of 150°C for 30 hours, and then the samples were removed and their appearance observed. The test results are shown in Table 1.

[0051] Table 1

[0052]

[0053] As can be seen from Table 1, the epoxy resin samples prepared in the embodiments of the present invention have higher light transmittance, slower color change after heating, high transparency, and better heat resistance.

[0054] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described 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 in the claims, they should all fall within the protection scope of the present invention.

Claims

1. An epoxy resin reaction accelerator, characterized in that, Its structural formula is as follows: 。 2. The epoxy resin reaction accelerator according to claim 1, characterized in that, This epoxy resin reaction accelerator is prepared by the following steps: Step S1: Add 4-aminobenzoyl chloride to a flask containing tetrahydrofuran and stir evenly under an ice-water bath. Then add triethylamine to the 2-methylimidazolium tetrahydrofuran solution, mix and stir evenly, and then add it dropwise to the flask using a separatory funnel. After the addition is complete, transfer the flask to a 40°C constant temperature oil bath and stir to react for 3-5 hours. After the reaction is complete, filter and rotary evaporate the filtrate. Wash the obtained solid with deionized water, filter, and dry at 50°C for 12 hours to obtain intermediate 1. Step S2: Add (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic acid, and 4-dimethylaminopyridine to a three-necked flask, then add dichloromethane and mix thoroughly. Next, add dicyclohexylcarbodiimide dichloromethane solution dropwise. After the addition is complete, continue stirring the reaction for 5-6 hours, then filter the reaction solution. Wash the filtrate 5 times with deionized water, concentrate it in a rotary evaporator, and recrystallize to obtain intermediate 2. Step S3: Under nitrogen conditions, intermediate 1 is placed in a flask, N,N-dimethylformamide is added and stirred for 30 min. Then, intermediate 2 mixed solution is added dropwise to the flask and stirred continuously at room temperature for 24 h. After the reaction is completed, the above solution is poured into distilled water and allowed to stand for 30 min. After filtration and washing, it is dried under vacuum at 80 °C for 24 h to obtain product 1. Step S4: Add product 1, sodium acetate and acetic anhydride to the reactor and mix. Heat to 60°C and stir continuously for 2-4 hours. Then, rapidly cool the system to room temperature in an ice-water bath, filter, wash, recrystallize, and vacuum dry at 80°C for 24 hours to obtain the epoxy resin reaction accelerator.

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

4. The epoxy resin reaction accelerator according to claim 2, characterized in that, In step S2, the ratio of (9ci)-3-(hydroxymethyl)-4-methyl-2,5-furandione, trimesic 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 ratio of 6.16-12.3 g : 90-180 mL.

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

6. The epoxy resin reaction accelerator according to claim 1, characterized in that, In step S4, the 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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