Silicon-containing bifunctional epoxy compound, preparation method and application thereof, and epoxy adhesive

Abstract

The invention belongs to the field of adhesives, and particularly relates to a silicon-containing bifunctional epoxy compound, a preparation method and application thereof and an epoxy adhesive. The silicon-containing bifunctional epoxy compound has a structure as shown in a formula (1). In the research process, the inventor surprisingly finds that the long-term toughness and heat resistance of the epoxy adhesive can be effectively improved by using the silicon-containing bifunctional epoxy compound with the structure as shown in the formula (1) as the curing agent of the epoxy adhesive.

Description

Technical Field

[0001] This invention belongs to the field of adhesives, specifically relating to a silicon-containing bifunctional epoxy compound, its preparation method and application, and epoxy adhesives. Background Technology

[0002] Epoxy adhesives primarily contain epoxy resin and a curing agent. In addition to epoxy resin and curing agent, they may also contain auxiliary materials such as toughening agents, diluents, accelerators, and coupling agents. Epoxy adhesives are renowned for their excellent bonding properties and are often referred to as "all-purpose glue" or "super glue." They are currently widely used for bonding various materials such as metals, plastics, and glass, and have extensive applications in the automotive, electronics, and aerospace industries, making them highly sought after in the market.

[0003] While traditional epoxy adhesives possess good bonding strength, they suffer from poor heat resistance. Furthermore, the rigid molecular chains of epoxy resins lack the flexibility and extensibility of rubber, making it difficult to absorb and disperse energy through molecular chain slippage and rearrangement under stress. Simultaneously, the increased crosslinking density during curing restricts the movement of molecular chains, further weakening toughness. This makes epoxy resins more prone to brittle fracture under external impact or deformation, resulting in high brittleness and poor fatigue resistance after curing, and a tendency to crack over long-term use. To address this deficiency, existing technologies typically increase the toughness of epoxy adhesives by adding rubber particles. However, while this toughening method improves initial toughness, it easily leads to phase separation and stress concentration, resulting in a significant decline in long-term performance, especially after exposure to high temperatures. Therefore, there is an urgent need to develop an epoxy adhesive system that combines long-term toughness with heat resistance. Summary of the Invention

[0004] The primary objective of this invention is to provide a silicon-containing difunctional epoxy compound that can effectively improve the long-term toughness and heat resistance of epoxy adhesives.

[0005] A second objective of this invention is to provide a method for preparing the aforementioned silicon-containing difunctional epoxy compound.

[0006] A third objective of this invention is to provide the application of the aforementioned silicon-containing difunctional epoxy compounds in adhesives.

[0007] A fourth objective of this invention is to provide an epoxy adhesive.

[0008] The silicon-containing bifunctional epoxy compound provided by this invention has the structure shown in formula (1):

[0009]

[0010] In formula (1), R1, R2, R3, R4, R5, R6, R7 and R8 are independently H or C1-C5 alkyl groups, R1 R 2 R 3 and R 4 Each is an H or C1-C5 alkyl group, which can be independently formed.

[0011] The method for preparing silicon-containing bifunctional epoxy compounds provided by this invention includes the following steps:

[0012] S1. The p-hydroxystyrene compound shown in formula (2) is subjected to a substitution reaction with the epoxy compound shown in formula (3) to obtain a product containing an intermediate;

[0013] S2. The product containing the intermediate is subjected to an addition reaction with the cyclosiloxane compound shown in formula (4) to obtain the product containing a silicon-bifunctional epoxy compound;

[0014]

[0015] In formula (2), R1, R2, R3 and R4 are independently H or C1 to C5 alkyl groups;

[0016] In equation (3), X is a halogen;

[0017] In equation (4), R 1 R 2 R 3 and R 4 Each is an H or C1-C5 alkyl group, which can be independently formed.

[0018] The epoxy adhesive provided by the present invention includes epoxy resin and curing agent, wherein the curing agent is the above-mentioned silicon-containing difunctional epoxy compound.

[0019] The inventors of this invention have conducted in-depth and extensive research on epoxy adhesives, attempting to adjust them from the perspectives of modifying the epoxy resin itself, the type and amount of toughening agents, etc., but have failed to significantly improve the long-term toughness and heat resistance of epoxy adhesives. During the research process, the inventors of this invention were surprised to discover that using a silicon-containing bifunctional epoxy compound with the structure shown in formula (1) as a curing agent for epoxy adhesives can effectively improve the long-term toughness and heat resistance of epoxy adhesives. It is speculated that this is because the compound itself contains an aromatic ring structure and a relatively long chain arm span; the aromatic ring structure can increase the heat resistance of the compound, and the relatively long chain arm span can increase the toughness of the compound.

[0020] Furthermore, this invention uses p-hydroxystyrene compounds, epoxides, and cyclosiloxanes as starting materials. These materials all possess high reactivity and good structural stability. Substituting the p-hydroxystyrene compounds with the epoxides followed by hydrolysis with the cyclosiloxanes ensures full reactivity and guarantees reaction stability. Only two steps are needed to efficiently obtain silicon-containing bifunctional epoxides, which is beneficial for improving the overall yield. In addition, the preparation system for silicon-containing bifunctional epoxides provided by this invention is simple, easy to operate, and uses mild reaction conditions; the entire reaction system is economical and efficient. Detailed Implementation

[0021] The silicon-containing bifunctional epoxy compound provided by this invention has the structure shown in formula (1):

[0022]

[0023] In formula (1), R1, R2, R3, R4, R5, R6, R7 and R8 are independently H or C1-C5 alkyl groups, R 1 R 2 R 3 and R 4 Each of the alkyl groups is independently H or a C1-C5 alkyl group. Examples of the C1-C5 alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, or neopentyl. Preferably, R1, R2, R3, R4, R5, R6, R7, and R8 are all H, and R... 1 R 2 R 3 and R 4 All are C1 to C3 alkyl groups.

[0024] The method for preparing silicon-containing bifunctional epoxy compounds provided by this invention includes the following steps:

[0025] S1. A substitution reaction is carried out between a p-hydroxystyrene compound and an epoxy compound to obtain a product containing an intermediate;

[0026] S2. The product containing the intermediate is subjected to an addition reaction with a cyclosiloxane compound to obtain a product containing a silicon-bifunctional epoxy compound.

[0027] In this invention, the p-hydroxystyrene compound has the structure shown in formula (2):

[0028]

[0029] In formula (2), R1, R2, R3 and R4 are independently H or C1-C5 alkyl groups, preferably H or C1-C3 alkyl groups. Specifically, from the perspective of the availability of raw materials, the p-hydroxystyrene can be selected from the compounds shown in formulas (2-1) to (2-4), wherein R' is a C1-C5 alkyl group, preferably a C1-C3 alkyl group.

[0030] In this invention, the epoxy compound has the structure shown in formula (3):

[0031]

[0032] In formula (3), X is a halogen, specifically fluorine, chlorine, bromine, or iodine, preferably chlorine or bromine. That is, the epoxy compound is preferably epichlorohydrin and / or epibromopropane.

[0033] In this invention, the cyclosiloxane compound has the structure shown in formula (4):

[0034]

[0035] In equation (4), R 1 R 2 R 3 and R 4 Each alkyl group is independently H or C1 to C5, preferably C1 to C3. From the perspective of raw material availability, the cyclosiloxane compound can be selected from compounds represented by formulas (4-1) to (4-9).

[0036] The specific reaction equation for the preparation method of the silicon-containing bifunctional epoxy compound provided by this invention is as follows:

[0037]

[0038] In this invention, in step S1, the molar ratio of the p-hydroxystyrene compound to the epoxide compound is preferably 1:(1-3), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any value between them. The substitution reaction generally needs to be carried out in the presence of a base. The base may include at least one of sodium hydroxide, potassium hydroxide, and ammonia. The molar ratio of the base to the p-hydroxystyrene compound is preferably 1:(0.8-1.1), such as 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, or any value between them. The substitution reaction is not particularly limited in method, as long as it enables the substitution reaction between the p-hydroxystyrene compound and the epoxide compound. For example, the p-hydroxystyrene compound can be dissolved in an organic solvent first, and then the epoxide compound and a base can be added for the substitution reaction; the epoxide compound can be dissolved in an organic solvent first, and then the p-hydroxystyrene compound and a base can be added for the substitution reaction; the p-hydroxystyrene compound and a base can be dissolved in an organic solvent first, and then the epoxide compound can be added for the substitution reaction; or the epoxide compound and a base can be dissolved in an organic solvent first, and then the p-hydroxystyrene compound can be added for the substitution reaction. In a preferred embodiment, the substitution reaction steps include dissolving the p-hydroxystyrene compound in an organic solvent under an inert gas atmosphere, controlling the temperature of the resulting mixture to the substitution reaction temperature, adding an alkaline solution and an epoxide compound for the reaction, removing the solvent after the reaction is complete, washing the crude product with water and drying it to obtain a product containing an intermediate.

[0039] In this invention, in step S2, the molar ratio of the cyclosiloxane compound to the intermediate is preferably (1.5–2.5):1, such as 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, or any value between them. The addition reaction is generally carried out in the presence of a catalyst. The catalyst is particularly preferably a platinum catalyst. The amount of the catalyst is preferably 0.1–0.5% of the mass of the cyclosiloxane compound, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between them. The addition reaction method is not particularly limited, as long as it enables the intermediate-containing product to undergo an addition reaction with the cyclosiloxane compound. For example, the intermediate-containing product can be dissolved in an organic solvent first, and then the cyclosiloxane compound and catalyst can be added for the addition reaction; the cyclosiloxane compound can be dissolved in an organic solvent first, and then the intermediate-containing product and catalyst can be added for the addition reaction; the intermediate-containing product and catalyst can be dissolved in an organic solvent first, and then the cyclosiloxane compound can be added for the addition reaction; or the cyclosiloxane compound and catalyst can be dissolved in an organic solvent first, and then the intermediate-containing product can be added for the addition reaction. In a preferred embodiment, the addition reaction step includes dissolving the cyclosiloxane compound in an organic solvent, controlling the temperature of the resulting mixture to the addition reaction temperature under inert gas protection and stirring, adding the intermediate-containing product and catalyst for the reaction, filtering out the catalyst and removing the solvent after the reaction is complete to obtain the product of a silicon-containing bifunctional epoxy compound.

[0040] In this invention, the conditions for the substitution reaction preferably include a temperature of -40°C to 10°C, such as -40°C, -35°C, -38°C, -30°C, -20°C, -10°C, 0°C, 7°C, 10°C or any value between them; and a time of 8 to 24 hours, such as 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 24 hours or any value between them.

[0041] In this invention, the conditions for the addition reaction preferably include a temperature of 50°C to 100°C, such as 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, 98°C, 100°C, or any value between them; and a time of 12 to 48 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 48 ​​hours, or any value between them.

[0042] The preferred method for preparing the silicon-containing bifunctional epoxy compound provided by the present invention further includes purifying the product containing the intermediate before the addition reaction. The purification method includes washing the product containing the intermediate with water until neutral, extracting it with n-hexane, drying the resulting organic phase with anhydrous sodium sulfate, and then removing the solvent by vacuum distillation.

[0043] The present invention also provides the application of the above-mentioned silicon-containing bifunctional epoxy compounds in adhesives.

[0044] The present invention also provides an epoxy adhesive comprising an epoxy resin and a curing agent, wherein the curing agent is the aforementioned silicon-containing difunctional epoxy compound.

[0045] The present invention will be further described below with reference to the embodiments.

[0046] In the following examples and comparative examples, the platinum catalyst was purchased from Neutron Star Chemical Company, and its brand name was PC-42.

[0047] In the following examples and comparative examples, the bisphenol A type epoxy resin was EPICLON EXA-850CRP from DIC Corporation, with an epoxy equivalent of 170-175 g / eq; 1,4-cyclohexanediethanol diglycidyl ether was CDMDG from Showa Denko Corporation, with an epoxy equivalent of 135 g / eq; 3-epoxypropoxypropyltrimethoxysilane was KBM-403 from Shin-Etsu Chemical Co., Ltd.; and fumed silica was AEROSIL R202 from Evonik Corporation.

[0048] Preparation Example 1

[0049] S1. 7.22 g (60.1 mmol, 1 eq) of p-hydroxystyrene was dissolved in 10 mL of ethanol in a 250 mL reaction flask. The temperature was controlled at 0 °C under stirring. Then, a mixture of 3.12 g (78 mmol, 1.3 eq) of dissolved sodium hydroxide and 50 mL of ethanol was added. Finally, 14.1 mL (180 mmol, 3 eq) of epichlorohydrin was added dropwise to the reaction flask. After the addition was completed, the mixture was moved to room temperature and stirred for 30 min. After reacting for 16 h, the solvent was recovered by vacuum distillation. The product was then extracted with n-hexane and washed with pure water. This washing process was repeated 3 times. The organic phase was dried with anhydrous magnesium sulfate, and after vacuum distillation, it was recrystallized with n-hexane to obtain a white solid intermediate product.

[0050] S2. 70 g (291.4 mmol, 1.85 eq) of tetramethylcyclotetrasiloxane and 70 mL of toluene were added sequentially to a 250 mL three-necked flask, purged with nitrogen, and the temperature was slowly raised to 80 °C. 25.6 g (158 mmol, 1 eq) of the intermediate product obtained in step S1 was dissolved in 20 mL of toluene, and 0.15 g (0.25%) of platinum catalyst was added. The mixture was stirred until homogeneous. When the temperature of the reaction solution reached 80 °C, the catalyst was added dropwise. After reacting for 24 h, the mixture was cooled to room temperature, filtered to remove the catalyst, and then the solvent was recovered by vacuum distillation to obtain a colorless silicon-containing bifunctional epoxy compound, denoted as Si-EP1.

[0051] The overall yield of the two-step reaction is 75%.

[0052] The silicon-containing bifunctional epoxy compound was subjected to NMR analysis, and the results are as follows: (400MHz, CDCl3)δ 7.33(d, J=8.6Hz, 4H), 6.87(d, J=10.0Hz, 4H), 4.19-3.96(m, 4H), 3.52(s, J=3.1Hz, 2H), 3.05-2.98(m, 2H), 2.65-2.34(m, 8H), 0.96(t, J=3.5Hz, 4H), 0.19-0.12(m, 12H). Therefore, the silicon-containing bifunctional epoxy compound has the structure shown in formula (1).

[0053] Preparation Example 2

[0054] S1. 7.22 g (60.1 mmol, 1 eq) of p-hydroxystyrene was dissolved in 10 mL of ethanol in a 250 mL reaction flask. The temperature was controlled at -40 °C under stirring. Then, a mixture of 3.12 g (78 mmol, 1.3 eq) of dissolved sodium hydroxide and 50 mL of ethanol was added. Finally, 25 g (180 mmol, 3 eq) of epichlorohydrin was added dropwise to the reaction flask. After the addition was completed, the mixture was moved to room temperature and stirred for 30 min. After reacting for 24 h, the solvent was recovered by vacuum distillation. The product was then extracted with n-hexane and washed with pure water. This washing process was repeated 3 times. The organic phase was dried with anhydrous magnesium sulfate, and after vacuum distillation, it was recrystallized with n-hexane to obtain a white solid intermediate product.

[0055] S2. 70 g (291.4 mmol, 1.85 eq) of tetramethylcyclotetrasiloxane and 70 mL of toluene were added sequentially to a 250 mL three-necked flask, purged with nitrogen, and the temperature was slowly raised to 50 °C. 25.6 g (158 mmol, 1 eq) of the intermediate product obtained in step S1 was dissolved in 20 mL of toluene, and 0.15 g (0.25%) of platinum catalyst was added. The mixture was stirred until homogeneous. When the temperature of the reaction solution reached 50 °C, the catalyst was added dropwise. After reacting for 48 h, the mixture was cooled to room temperature, filtered to remove the catalyst, and then the solvent was recovered by vacuum distillation to obtain a colorless silicon-containing bifunctional epoxy compound, denoted as Si-EP2.

[0056] The overall yield of the two-step reaction was 73%.

[0057] The silicon-containing bifunctional epoxy compound was subjected to NMR analysis, and the results are as follows: (400MHz, CDCl3)δ 7.33(d, J=8.6Hz, 4H), 6.87(d, J=10.0Hz, 4H), 4.19-3.96(m, 4H), 3.52(s, J=3.1Hz, 2H), 3.05-2.98(m, 2H), 2.65-2.34(m, 8H), 0.96(t, J=3.5Hz, 4H), 0.19-0.12(m, 12H). Therefore, the silicon-containing bifunctional epoxy compound has the structure shown in formula (1).

[0058] Preparation Example 3

[0059] S1. 7.22 g (60.1 mmol, 1 eq) of p-hydroxystyrene was dissolved in 10 mL of ethanol in a 250 mL reaction flask. The temperature was controlled at -20 °C under stirring. Then, a mixture of 3.12 g (78 mmol, 1.3 eq) of dissolved sodium hydroxide and 50 mL of ethanol was added. Finally, 25 g (180 mmol, 3 eq) of epichlorohydrin was added dropwise to the reaction flask. After the addition was completed, the mixture was moved to room temperature and stirred for 30 min. After reacting for 16 h, the solvent was recovered by vacuum distillation. The product was then extracted with n-hexane and washed with pure water. This washing process was repeated 3 times. The organic phase was dried with anhydrous magnesium sulfate, and after vacuum distillation, it was recrystallized with n-hexane to obtain a white solid intermediate product.

[0060] S2. 70 g (291.4 mmol, 1.85 eq) of tetramethylcyclotetrasiloxane and 70 mL of toluene were added sequentially to a 250 mL three-necked flask, purged with nitrogen, and the temperature was slowly raised to 90 °C. 25.6 g (158 mmol, 1 eq) of the intermediate product obtained in step S1 was dissolved in 20 mL of toluene, and 0.15 g (0.25%) of platinum catalyst was added. The mixture was stirred until homogeneous. When the temperature of the reaction solution reached 90 °C, the catalyst was added dropwise. After reacting for 24 h, the mixture was cooled to room temperature, filtered to remove the catalyst, and then the solvent was recovered by vacuum distillation to obtain a colorless silicon-containing bifunctional epoxy compound, denoted as Si-EP3.

[0061] The overall yield of the two-step reaction was 78%.

[0062] The silicon-containing bifunctional epoxy compound was subjected to NMR analysis, and the results are as follows: (400MHz, CDCl3)δ 7.33(d, J=8.6Hz, 4H), 6.87(d, J=10.0Hz, 4H), 4.19-3.96(m, 4H), 3.52(s, J=3.1Hz, 2H), 3.05-2.98(m, 2H), 2.65-2.34(m, 8H), 0.96(t, J=3.5Hz, 4H), 0.19-0.12(m, 12H). Therefore, the silicon-containing bifunctional epoxy compound has the structure shown in formula (1).

[0063] Preparation Example 4

[0064] S1. 7.22 g (60.1 mmol, 1 eq) of p-hydroxystyrene was dissolved in 10 mL of ethanol in a 250 mL reaction flask. The temperature was controlled at 0 °C under stirring. Then, a mixture of 3.12 g (78 mmol, 1.3 eq) of dissolved sodium hydroxide and 50 mL of ethanol was added. Finally, 25 g (180 mmol, 3 eq) of epichlorohydrin was added dropwise to the reaction flask. After the addition was completed, the mixture was moved to room temperature and stirred for 30 min. After reacting for 16 h, the solvent was recovered by vacuum distillation. The product was then extracted with n-hexane and washed with pure water. This washing process was repeated 3 times. The organic phase was dried with anhydrous magnesium sulfate, and after vacuum distillation, it was recrystallized with n-hexane to obtain a white solid intermediate product.

[0065] S2. 70 g (291.4 mmol, 1.85 eq) of tetramethylcyclotetrasiloxane and 70 mL of toluene were added sequentially to a 250 mL three-necked flask, purged with nitrogen, and the temperature was slowly raised to 90 °C. 25.6 g (158 mmol, 1 eq) of the intermediate product obtained in step S1 was dissolved in 20 mL of toluene, and 0.15 g (0.25%) of platinum catalyst was added. The mixture was stirred until homogeneous. When the temperature of the reaction solution reached 90 °C, the catalyst was added dropwise. After reacting for 48 h, the mixture was cooled to room temperature, filtered to remove the catalyst, and then the solvent was recovered by vacuum distillation to obtain a colorless silicon-containing bifunctional epoxy compound, denoted as Si-EP4.

[0066] The overall yield of the two-step reaction was 78%.

[0067] The silicon-containing bifunctional epoxy compound was subjected to NMR analysis, and the results are as follows: (400MHz, CDCl3)δ 7.33(d, J=8.6Hz, 4H), 6.87(d, J=10.0Hz, 4H), 4.19-3.96(m, 4H), 3.52(s, J=3.1Hz, 2H), 3.05-2.98(m, 2H), 2.65-2.34(m, 8H), 0.96(t, J=3.5Hz, 4H), 0.19-0.12(m, 12H). Therefore, the silicon-containing bifunctional epoxy compound has the structure shown in formula (1).

[0068] Preparation Example 5

[0069] S1. 7.22 g (60.1 mmol, 1 eq) of p-hydroxystyrene was dissolved in 10 mL of ethanol in a 250 mL reaction flask. The temperature was controlled at 0 °C under stirring. Then, a mixture of 4.37 g (78 mmol, 1.3 eq) of dissolved potassium hydroxide and 50 mL of ethanol was added. Finally, 25 g (180 mmol, 3 eq) of epichlorohydrin was added dropwise to the reaction flask. After the addition was completed, the mixture was moved to room temperature and stirred for 30 min. After reacting for 16 h, the solvent was recovered by vacuum distillation. The product was then extracted with n-hexane and washed with pure water. This washing process was repeated 3 times. The organic phase was dried with anhydrous magnesium sulfate, and after vacuum distillation, it was recrystallized with n-hexane to obtain a white solid intermediate product.

[0070] S2. 70 g (291.4 mmol, 1.85 eq) of tetramethylcyclotetrasiloxane and 70 mL of toluene were added sequentially to a 250 mL three-necked flask, purged with nitrogen, and the temperature was slowly raised to 90 °C. 25.6 g (158 mmol, 1 eq) of the intermediate product obtained in step S1 was dissolved in 20 mL of toluene, and 0.15 g (0.25%) of platinum catalyst was added. The mixture was stirred until homogeneous. When the temperature of the reaction solution reached 90 °C, the catalyst was added dropwise. After reacting for 48 h, the mixture was cooled to room temperature, filtered to remove the catalyst, and then the solvent was recovered by vacuum distillation to obtain a colorless silicon-containing bifunctional epoxy compound, denoted as Si-EP5.

[0071] The overall yield of the two-step reaction is 75%.

[0072] The silicon-containing bifunctional epoxy compound was subjected to NMR analysis, and the results are as follows: (400MHz, CDCl3)δ 7.33(d, J=8.6Hz, 4H), 6.87(d, J=10.0Hz, 4H), 4.19-3.96(m, 4H), 3.52(s, J=3.1Hz, 2H), 3.05-2.98(m, 2H), 2.65-2.34(m, 8H), 0.96(t, J=3.5Hz, 4H), 0.19-0.12(m, 12H). Therefore, the silicon-containing bifunctional epoxy compound has the structure shown in formula (1).

[0073] Preparation Example 6

[0074] S1. 7.22 g (60.1 mmol, 1 eq) of p-hydroxystyrene was dissolved in 10 mL of ethanol in a 250 mL reaction flask. The temperature was controlled at 0 °C under stirring. Then, a mixture of 3.12 g (78 mmol, 1.3 eq) of dissolved sodium hydroxide and 50 mL of ethanol was added. Finally, 14.1 mL (180 mmol, 3 eq) of epichlorohydrin was added dropwise to the reaction flask. After the addition was completed, the mixture was moved to room temperature and stirred for 30 min. After reacting for 8 h, the solvent was recovered by vacuum distillation. The product was then extracted with n-hexane and washed with pure water. This washing process was repeated 3 times. The organic phase was dried with anhydrous magnesium sulfate, and after vacuum distillation, it was recrystallized with n-hexane to obtain a white solid intermediate product.

[0075] S2. 70 g (291.4 mmol, 1.85 eq) of tetramethylcyclotetrasiloxane and 70 mL of toluene were added sequentially to a 250 mL three-necked flask, purged with nitrogen, and the temperature was slowly raised to 80 °C. 25.6 g (158 mmol, 1 eq) of the intermediate product obtained in step S1 was dissolved in 20 mL of toluene, and 0.15 g (0.25%) of platinum catalyst was added. The mixture was stirred until homogeneous. When the temperature of the reaction solution reached 80 °C, the catalyst was added dropwise. After reacting for 24 h, the mixture was cooled to room temperature, filtered to remove the catalyst, and then the solvent was recovered by vacuum distillation to obtain a colorless silicon-containing bifunctional epoxy compound, denoted as Si-EP6.

[0076] The overall yield of the two-step reaction is 70%.

[0077] The silicon-containing bifunctional epoxy compound was subjected to NMR analysis, and the results are as follows: (400MHz, CDCl3)δ 7.33(d, J=8.6Hz, 4H), 6.87(d, J=10.0Hz, 4H), 4.19-3.96(m, 4H), 3.52(s, J=3.1Hz, 2H), 3.05-2.98(m, 2H), 2.65-2.34(m, 8H), 0.96(t, J=3.5Hz, 4H), 0.19-0.12(m, 12H). Therefore, the silicon-containing bifunctional epoxy compound has the structure shown in formula (1).

[0078] Comparative Preparation Example 1

[0079] A silicon-containing bifunctional epoxy compound was prepared according to the method of Preparation Example 1, except that tetramethylcyclotetrasiloxane was replaced with the same molar amount of 1,2-bis(mercaptomethyl)disilane (HS-CH2-SiH2-CH2-SH), and the other conditions were the same as in Preparation Example 1, to obtain a silicon-containing bifunctional epoxy compound, denoted as DSi-EP1.

[0080] Example 1

[0081] By weight, 50 parts of bisphenol A type epoxy resin, 5 parts of silicon-containing bifunctional epoxy compound (Si-EP1), 3 parts of 3-epoxypropoxypropyltrimethoxysilane, and 5 parts of fumed silica were added to a planetary mixer and stirred for 15 minutes at room temperature. Then, the mixture was dispersed for 30 minutes at room temperature using a three-roll mill. The mixture was then discharged and packaged to obtain the epoxy resin composition.

[0082] Example 2

[0083] By weight, 50 parts of 1,4-cyclohexanediethanol diglycidyl ether, 5 parts of silicon-containing bifunctional epoxy compound (Si-EP2), 1 part of 3-epoxypropoxypropyltrimethoxysilane, and 2 parts of fumed silica were added to a planetary mixer and stirred for 20 minutes at room temperature. Then, the mixture was dispersed for 20 minutes at room temperature using a three-roll mill. The mixture was then discharged and packaged to obtain the epoxy resin composition.

[0084] Example 3

[0085] By weight, 50 parts of 1,4-cyclohexanediethanol diglycidyl ether, 5 parts of silicon-containing bifunctional epoxy compound (Si-EP3), 5 parts of 3-epoxypropoxypropyltrimethoxysilane, and 2 parts of fumed silica were added to a planetary mixer and stirred for 30 minutes at room temperature. Then, the mixture was dispersed for 15 minutes at room temperature using a three-roll mill. The mixture was then discharged and packaged to obtain the epoxy resin composition.

[0086] Example 4

[0087] An epoxy resin composition was prepared according to the method of Example 1, except that the silicon-containing bifunctional epoxy compound (Si-EP1) obtained from Preparation Example 1 was replaced with the same molar amount of the silicon-containing bifunctional epoxy compound (Si-EP4) obtained from Preparation Example 4, and the other conditions were the same as in Example 1, to obtain the epoxy resin composition.

[0088] Example 5

[0089] An epoxy resin composition was prepared according to the method of Example 1, except that the silicon-containing bifunctional epoxy compound (Si-EP1) obtained from Preparation Example 1 was replaced with the same molar amount of the silicon-containing bifunctional epoxy compound (Si-EP5) obtained from Preparation Example 5, and the other conditions were the same as in Example 1, to obtain the epoxy resin composition.

[0090] Example 6

[0091] An epoxy resin composition was prepared according to the method of Example 1, except that the silicon-containing bifunctional epoxy compound (Si-EP1) obtained from Preparation Example 1 was replaced with the same molar amount of the silicon-containing bifunctional epoxy compound (Si-EP6) obtained from Preparation Example 6, and the other conditions were the same as in Example 1, to obtain the epoxy resin composition.

[0092] Comparative Example 1

[0093] An epoxy resin composition was prepared according to the method of Example 1, except that the silicon-containing bifunctional epoxy compound (Si-EP1) obtained from Preparation Example 1 was replaced with the same molar amount of the silicon-containing bifunctional epoxy compound (DSi-EP1) obtained from Comparative Preparation Example 1, and the other conditions were the same as in Example 1, to obtain a reference epoxy resin composition.

[0094] Test case

[0095] (1) Heat Resistance: The epoxy resin compositions obtained in the above embodiments and the reference epoxy resin composition obtained in the comparative example were coated on stainless steel sheets, and then overlapped and pressed with tempered glass sheets with an overlap area of ​​20mm × 3mm and an adhesive layer thickness of 0.1mm. After heat curing in a 60℃ oven for 60min, the two sheets were pulled apart in opposite directions using a universal testing machine, and the peel force was tested at an ambient temperature of 85℃. The measured force value was the initial adhesive strength. After curing, the samples were treated under heating and humidification conditions of 85℃ / 85%RH / 240h, and the peel force was tested again at an ambient temperature of 85℃. The measured force value was the heat-resistant adhesive strength. Adhesive strength reduction Δ = (initial adhesive strength - heat-resistant adhesive strength) / initial adhesive strength × 100%. The smaller the adhesive strength reduction Δ, the better the heat resistance; conversely, the larger the reduction, the worse the heat resistance. The results are shown in Table 1.

[0096] (2) Long-term toughness: The epoxy resin compositions obtained in the above embodiments and the reference epoxy resin composition obtained in the comparative example were prepared into samples according to the method specified in GB / T6328-2021 and subjected to impact performance testing to obtain the initial impact strength. After the epoxy resin compositions obtained in the above embodiments and the reference epoxy resin composition obtained in the comparative example were prepared into samples, they were aged at 60°C for 6 months, and then subjected to impact performance testing according to the method specified in GB / T6328-2021 to obtain the aged impact strength. Toughness reduction Δ = (initial impact strength - aged impact strength) / initial impact strength × 100%. The smaller the toughness reduction Δ, the better the long-term toughness, and vice versa. The results are shown in Table 1.

[0097] Table 1

[0098]

[0099] As can be seen from the results in Table 1, the epoxy adhesive obtained by using the silicon-containing difunctional epoxy compound provided by the present invention as a curing agent not only has excellent heat resistance, but also has good long-term toughness after being subjected to high temperature. That is, it has both good heat resistance and long-term toughness, and has broad application prospects.

[0100] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A silicon-containing difunctional epoxy compound, characterized in that, The silicon-containing bifunctional epoxy compound has the structure shown in formula (1): In formula (1), R1, R2, R3, R4, R5, R6, R7 and R8 are independently H or C1-C5 alkyl groups, R 1 R 2 R 3 and R 4 Each is an H or C1-C5 alkyl group, which can be independently formed.

2. The silicon-containing difunctional epoxy compound according to claim 1, characterized in that, In equation (1), R1, R2, R3, R4, R5, R6, R7, and R8 are all H, and R 1 R 2 R 3 and R 4 All are C1 to C3 alkyl groups.

3. The method for preparing the silicon-containing difunctional epoxy compound according to claim 1 or 2, characterized in that, The method includes the following steps: S1. The p-hydroxystyrene compound shown in formula (2) is subjected to a substitution reaction with the epoxy compound shown in formula (3) to obtain a product containing an intermediate; S2. The product containing the intermediate is subjected to an addition reaction with the cyclosiloxane compound shown in formula (4) to obtain the product containing a silicon-bifunctional epoxy compound; In formula (2), R1, R2, R3 and R4 are independently H or C1 to C5 alkyl groups; In equation (3), X is a halogen; In equation (4), R 1 R 2 R 3 and R 4 Each is an H or C1-C5 alkyl group, which can be independently formed.

4. The method for preparing the silicon-containing difunctional epoxy compound according to claim 3, characterized in that, In step S1, the substitution reaction includes dissolving a p-hydroxystyrene compound in an organic solvent under an inert gas atmosphere, controlling the temperature of the resulting mixture to the substitution reaction temperature, adding an alkaline solution and an epoxy compound to react, removing the solvent after the reaction is complete, washing the crude product with water and drying it to obtain a product containing an intermediate.

5. The method for preparing the silicon-containing difunctional epoxy compound according to claim 3, characterized in that, In step S2, the addition reaction includes dissolving the cyclosiloxane compound in an organic solvent, controlling the temperature of the resulting mixture to the addition reaction temperature under inert gas protection and stirring, adding the product containing the intermediate and the catalyst to react, filtering out the catalyst and removing the solvent after the reaction is complete, and obtaining the product containing a silicon-bifunctional epoxy compound.

6. The method for preparing the silicon-containing difunctional epoxy compound according to claim 3, characterized in that, The conditions for the substitution reaction include a temperature of -40℃ to 10℃ and a time of 8 to 24 hours.

7. The method for preparing the silicon-containing difunctional epoxy compound according to claim 3, characterized in that, The conditions for the addition reaction include a temperature of 50℃ to 100℃ and a time of 12 to 48 hours.

8. The method for preparing the silicon-containing difunctional epoxy compound according to claim 3, characterized in that, The method also includes purifying the intermediate-containing product before the addition reaction. The purification method includes washing the intermediate-containing product with water until neutral, extracting it with n-hexane, drying the resulting organic phase with anhydrous sodium sulfate, and then removing the solvent by vacuum distillation.

9. The use of the silicon-containing bifunctional epoxy compound of claim 1 or 2 in adhesives.

10. An epoxy adhesive, characterized in that, The epoxy adhesive comprises epoxy resin and a curing agent, wherein the curing agent is the silicon-containing difunctional epoxy compound as described in claim 1 or 2.

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