A method for preparing an epoxy resin

Abstract

This invention discloses a method for preparing epoxy resin, comprising the following steps: uniformly mixing a toughening agent and a curing agent to obtain a compound, wherein the curing agent is methylhexahydrophthalic anhydride and the toughening agent is ZIF-8; preheating bisphenol A type epoxy resin E51 at 60-80℃ for 15-20 min to obtain a pretreated epoxy resin; mixing the pretreated epoxy resin with the compound at 60-80℃; adding a defoamer and an accelerator under stirring; reacting at a constant temperature of 60-80℃ for 5-8 min to obtain a mixture; vacuum degassing the mixture, curing, and demolding to obtain the epoxy resin. The preparation method of this invention utilizes the synergistic effect of 2,4,6-tris(dimethylaminomethyl)phenol and ZIF-8 to toughen the epoxy resin, resulting in an epoxy resin with excellent mechanical properties, with an impact strength reaching up to 28.24 KJ / m². 2 .

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin technology, and specifically relates to a method for preparing epoxy resin. Background Technology

[0002] Epoxy resin (EP) is a high-molecular-weight polymer that forms a highly cross-linked physical structure during curing. Its excellent mechanical strength, heat resistance, and chemical stability make it widely used in the matrix of advanced composite materials. However, while the high cross-linking density endows epoxy resin with excellent mechanical properties, it also restricts the movement of molecular chains, leading to significant internal stress after curing. This results in marked brittleness and poor impact resistance. Therefore, the modification of epoxy resin has become a key research focus. Although the brittleness of epoxy resin has become a critical bottleneck for its application expansion, existing modification schemes still face many challenges in practical applications, and an ideal solution that balances performance and practicality has not yet been found.

[0003] Currently, epoxy resins face two major challenges: first, there is an irreconcilable contradiction between toughening modification and epoxy resin stability; second, the regulation process of toughening systems is complex and its effects are limited. Specifically, adding toughening materials to epoxy resin systems often leads to poor thermal stability; simultaneously, the toughening effect of a single toughening material on epoxy resin is limited, while multi-toughening systems require the introduction of multiple types of toughening agents, and there are complex interactions between different types of toughening agents. The complex interaction mechanisms have not yet been fully elucidated, making it difficult to fully realize the synergistic toughening effect and hindering precise regulation of epoxy resins. Furthermore, nano- or micro-scale toughening agents are prone to aggregation in the epoxy resin matrix, which also leads to a significant reduction in toughening effect. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing epoxy resin, wherein the epoxy resin prepared by this method is synergistically toughened by a toughening agent (ZIF-8) and an accelerator.

[0005] The objective of this invention is achieved through the following technical solution.

[0006] A method for preparing an epoxy resin includes the following steps:

[0007] Step 1: Mix the toughening agent and the curing agent evenly to obtain a compound, wherein, by mass parts, the ratio of the toughening agent to the curing agent is (0.08~0.12):80, the curing agent is methyl hexahydrophthalic anhydride (MeHHPA), and the toughening agent is ZIF-8;

[0008] In step 1, the toughening agent is first dried and then mixed evenly with the curing agent. The drying temperature is 110~120℃ and the drying time is 8~12h.

[0009] Step 2: Preheat bisphenol A type epoxy resin E51 at 60~80℃ for 15~20min to obtain pretreated epoxy resin. Mix the pretreated epoxy resin with the compound at 60~80℃, and then add defoamer and accelerator under stirring. React at 60~80℃ for 5~8min to obtain a mixture. The ratio of bisphenol A type epoxy resin E51, compound, defoamer and accelerator by mass is 100:(80~80.1):(0.8~1.2):(0.8~1.2). The accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

[0010] In step 2, the defoamer is a polyether-modified polysiloxane oily defoamer.

[0011] In step 2, the stirring speed is 8000~10000 r / min.

[0012] Step 3: Vacuum degassing, curing, and demolding of the mixture to obtain epoxy resin.

[0013] In step 3, vacuum degassing is performed at 60~80℃.

[0014] In step 3, the curing process includes: maintaining the temperature at 110-120°C for 3-4 hours and then allowing it to cool naturally to room temperature.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. The preparation method of this invention utilizes the synergistic effect of 2,4,6-tris(dimethylaminomethyl)phenol and ZIF-8 to toughen epoxy resin, resulting in epoxy resin with excellent mechanical properties, and its impact strength can reach up to 28.24 KJ / m. 2 .

[0017] 2. This invention uses 2,4,6-tris(dimethylaminomethyl)phenol as an accelerator, which can accelerate the curing reaction, increase the crosslinking density, form a more uniform epoxy network, and balance toughness. Its alkalinity improves the dispersion uniformity of the toughening agent (ZIF-8) in bisphenol A type epoxy resin E51, effectively inhibits the occurrence of agglomeration, further optimizes interfacial bonding, and improves toughening strength. This invention enhances the interfacial strength of bisphenol A type epoxy resin E51 by combining the amino groups in the accelerator with the metal nodes Zn in the toughening agent.

[0018] 3. The toughening agent used in the preparation method of the present invention has good chemical stability, is environmentally friendly, simple to obtain, and economical and efficient. Attached Figure Description

[0019] Figure 1 The image shows a 500x magnified SEM image of the impact fracture cross section of the epoxy resin in Comparative Example 1.

[0020] Figure 2 The image is a 2000x magnified SEM image of the impact fracture cross section of the epoxy resin in Comparative Example 1.

[0021] Figure 3 This is a 500x magnified SEM image of the impact fracture cross section of the epoxy resin obtained in Example 2.

[0022] Figure 4 This is a 2000x magnified SEM image of the impact fracture cross section of the epoxy resin obtained in Example 2.

[0023] Figure 5 The impact properties of the epoxy resins obtained in Examples 1-5 and Comparative Examples 1-3;

[0024] Figure 6 The images show the DSC analysis results of the epoxy resin obtained in Example 2 and the epoxy resin in Comparative Example 1. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] The sources of raw materials involved in the following embodiments:

[0027] ZIF-8 was purchased from Shanghai Aladdin Technology Co., Ltd. (Zn content: 28~30wt%).

[0028] 2,4,6-Tris(dimethylaminomethyl)phenol was purchased from Shanghai Aladdin Technology Co., Ltd. (analytical grade);

[0029] Methylhexahydrophthalic anhydride (MeHHPA) was purchased from Runxiang Chemical Co., Ltd. in Changzhou, China (industrial grade).

[0030] The polyether-modified polysiloxane oily defoamer was purchased from Dongguan Haoyouduo New Materials Co., Ltd., China (model KS-603, industrial grade).

[0031] The sources of the instruments involved in the following embodiments:

[0032] The high-speed homogenizer (HR-500 model) was purchased from Shanghai Huxi Industrial Co., Ltd.

[0033] The vacuum drying oven (model DZF-6021) was purchased from Shanghai Yiheng Scientific Instruments Co., Ltd.

[0034] The digital display cantilever beam-simply supported beam combined impact testing machine (model ST-XJL-50) was purchased from Xiamen EST Instrument Co., Ltd.

[0035] Examples 1-5

[0036] A method for preparing an epoxy resin includes the following steps:

[0037] Step 1: Dry the toughening agent at 120℃ for 12 hours, then mix the curing agent and the dried toughening agent, stir at 8000 r / min for 3 minutes using a high-speed homogenizer, and then ultrasonically disperse for 3 minutes to obtain the compound. The ratio of toughening agent to curing agent by mass is X. X in different embodiments is shown in Table 1. The curing agent is methyl hexahydrophthalic anhydride (MeHHPA), and the toughening agent is ZIF-8 (powder).

[0038] Step 2: Preheat bisphenol A type epoxy resin E51 (purchased from DOW Company, USA, industrial grade, epoxy equivalent of 180-200 g / eq, model DER331 resin) in an 80℃ water bath for 20 min to obtain pretreated epoxy resin. Mix the pretreated epoxy resin with the compound (the temperature of the compound is 70±1℃), and stir at 8000 r / min for 5 min with a high-speed homogenizer until uniform. Then, add defoamer and accelerator under stirring conditions, and react at a constant temperature of 80℃ in a water bath for 5 min. After the reaction is completed, a mixture is obtained. The ratio of bisphenol A type epoxy resin E51, compound, defoamer and accelerator by mass is Y. Y for different embodiments is shown in Table 1. The defoamer is a polyether modified polysiloxane oily defoamer, and the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

[0039] Step 3: Place the mixture in a vacuum drying oven at 80°C for vacuum degassing. After vacuum degassing, the defoamed mixture is obtained. The defoamed mixture is poured into a polytetrafluoroethylene mold and kept at 120°C for 3 hours. After naturally cooling to room temperature, the mixture is demolded to obtain epoxy resin.

[0040] Table 1

[0041]

[0042] Comparative Example 1

[0043] A method for preparing epoxy resin involves preheating bisphenol A type epoxy resin E51 (purchased from Dow Chemical Company, USA, industrial grade, epoxy equivalent of 180-200 g / eq, model DER331 resin) in a water bath at 80°C for 20 min to obtain pretreated epoxy resin. The pretreated epoxy resin is then mixed with a curing agent (curing agent temperature 70±1°C) and stirred at 8000 r / min for 5 min using a high-speed homogenizer until homogeneous. The mixture is then placed in a vacuum drying oven at 80°C for vacuum degassing. After vacuum degassing, a defoamed mixture is obtained. The defoamed mixture is then poured into a polytetrafluoroethylene mold and kept at 120°C for 3 h. After natural cooling to room temperature, the mixture is demolded to obtain epoxy resin. The curing agent is methyl hexahydrophthalic anhydride (MeHHPA), and the ratio of bisphenol A type epoxy resin E51 to curing agent is 100:80 by mass.

[0044] Comparative Example 2

[0045] A method for preparing an epoxy resin is basically the same as in Example 2, except that: toughening agent ZIF-8 (powder) is not added in this comparative example, and the ratio of bisphenol A type epoxy resin E51, curing agent, defoamer and accelerator by mass parts is 100:80.1:1:1.

[0046] Comparative Example 3

[0047] A method for preparing an epoxy resin is basically the same as that in Example 2, except that no accelerator is added in this comparative example.

[0048] Impact performance tests were conducted on the epoxy resins obtained in Examples 1-5 and Comparative Examples 1-3. The specific conditions for the impact performance tests were as follows: at room temperature, the clamps (simple beam impact clamps) of the digital display cantilever beam-simple beam combined impact testing machine were used to fix both ends of the test specimen (the dimensions of the test specimen were 80mm long, 10mm wide, and 4mm thick; the support distance of the simple beams in the simple beam impact clamp was 60mm). The pendulum of the digital display cantilever beam-simple beam combined impact testing machine was positioned relative to the center of the test specimen, with the pendulum's trajectory forming a 150° angle with the vertical direction (i.e., a pendulum swing angle of 150° and an impact energy of 5J). The center of the test specimen was then impacted to obtain the impact strength. The results of the impact strength are shown in Table 2 and... Figure 5 As shown. The test specimens are one of the epoxy resins obtained in Examples 1-5 and Comparative Examples 1-3.

[0049] Depend on Figure 5 As shown in Table 2, the epoxy resin obtained in Example 2 has the highest impact strength, reaching 28.24 KJ / m. 2 This represents a 579% improvement compared to Comparative Example 1. This demonstrates that the epoxy resin obtained in Example 2 possesses excellent impact resistance.

[0050] Table 2

[0051]

[0052] The impact fracture morphology of the epoxy resin obtained in Example 2 and the epoxy resin obtained in Comparative Example 1 was tested using scanning electron microscopy (SEM). Figures 1-4 As shown. Among them, Figure 1 The image shows the morphology of the epoxy resin obtained in Comparative Example 1 at 500x magnification. Figure 2 The morphology of the epoxy resin obtained in Comparative Example 1 is magnified 2000 times. Figure 3 The image shows the morphology of the epoxy resin obtained in Example 2, magnified 500 times. Figure 4 The image shows the morphology of the epoxy resin obtained in Example 2 magnified 2000 times.

[0053] Depend on Figure 1 and Figure 2 It can be seen that the impact fracture section of the epoxy resin obtained in Comparative Example 1 exhibits a smooth and flat morphology with almost no river-like striations and fewer crack bifurcations, showing brittle fracture and low toughness.

[0054] Depend on Figure 3 and Figure 4 It can be seen that the impact fracture cross section of the epoxy resin obtained in Example 2, which was synergistically toughened by the toughening agent and the accelerator, is rough and uneven, exhibiting numerous river-like streaks and spherical voids. This indicates that the epoxy resin obtained in Example 2 exhibits ductile fracture with high toughness. This is because the imidazole groups on the surface of the toughening agent initiate epoxy curing, resulting in covalent bonding between the toughening agent and the matrix of bisphenol A type epoxy resin E51, thereby improving its strength. In addition, due to the high specific surface area of ​​the toughening agent, the contact interface between it and the bisphenol A type epoxy resin E51 is large, resulting in high interfacial bonding strength and effective resistance to plastic deformation.

[0055] DSC (Differential Scanning Calorimetry) analysis was performed on the epoxy resin obtained in Example 2 and the epoxy resin obtained in Comparative Example 1 to obtain the change in heat flow rate with temperature. The results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the glass transition temperature (Tg) of the epoxy resin obtained in Comparative Example 1 is 102.3℃. Compared with Comparative Example 1, the glass transition temperature (Tg) of the epoxy resin obtained in Example 2 (101.6℃) is only reduced by 0.7℃, but its impact strength is significantly improved. This indicates that the introduction of the compound did not reduce the rigidity of the resin matrix backbone, and the polymer chain crosslinking network after the curing reaction was not destroyed. It only weakened the intermolecular forces and improved the chain segment mobility, thus achieving toughening and a slight decrease in Tg.

[0056] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing an epoxy resin, characterized in that, The preparation method for toughening epoxy resin using the synergistic effect of 2,4,6-tris(dimethylaminomethyl)phenol and ZIF-8 includes the following steps: Step 1: Mix the toughening agent and the curing agent evenly to obtain a compound, wherein, by mass parts, the ratio of the toughening agent to the curing agent is (0.08~0.12):80, the curing agent is methyl hexahydrophthalic anhydride, and the toughening agent is ZIF-8; Step 2: Preheat bisphenol A type epoxy resin E51 at 60~80℃ for 15~20min to obtain pretreated epoxy resin. Mix the pretreated epoxy resin with the compound at 60~80℃, and then add defoamer and accelerator under stirring. React at 60~80℃ for 5~8min to obtain a mixture. The ratio of bisphenol A type epoxy resin E51, compound, defoamer and accelerator by mass is 100:(80~80.1):(0.8~1.2):(0.8~1.2). The accelerator is 2,4,6-tris(dimethylaminomethyl)phenol. Step 3: Vacuum degassing, curing, and demolding of the mixture to obtain epoxy resin.

2. The preparation method according to claim 1, characterized in that, In step 1, the toughening agent is first dried and then mixed evenly with the curing agent. The drying temperature is 110~120℃ and the drying time is 8~12h.

3. The preparation method according to claim 1, characterized in that, In step 2, the defoamer is a polyether-modified polysiloxane oily defoamer.

4. The preparation method according to claim 1, characterized in that, In step 2, the stirring speed is 8000~10000 r / min.

5. The preparation method according to claim 1, characterized in that, In step 3, vacuum degassing is performed at 60~80℃.

6. The preparation method according to claim 1, characterized in that, In step 3, the curing process includes: maintaining the temperature at 110-120°C for 3-4 hours and then allowing it to cool naturally to room temperature.

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