Imidazolyl polyether ester compound, preparation method and application thereof, and epoxy adhesive

Abstract

The application belongs to the field of organic synthesis and polymer materials, and relates to an imidazole-based polyether ester compound, a preparation method and application thereof, and an epoxy adhesive. The epoxy adhesive contains an epoxy resin and a curing agent, and the curing agent is an imidazole-based polyether ester compound with a structure shown in formula (I). The key of the application is that the imidazole-based polyether ester compound with the structure shown in formula (I) is used as the curing agent of the epoxy adhesive. The imidazole-based polyether ester compound contains an imidazole group, a polyether segment and an ester group, and the ester group is located between the imidazole group and the polyether segment. The tail of the polyether segment is connected with a C5 alkyl group. The specific structure can not only retain the catalytic activity of the imidazole group, but also significantly improve the impact strength of the cured product of the epoxy adhesive. Formula (I).

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis and polymer materials, specifically relating to an imidazole polyether ester compound, its preparation method and application, and epoxy adhesives. Background Technology

[0002] Epoxy adhesives are widely used in aerospace, automotive, electronics, construction, and machinery manufacturing industries due to their excellent bonding and electrical insulation properties. In aerospace, epoxy adhesives are used for bonding structural components of aircraft and rockets, bonding layered composite material structures, and sealing and potting electronic equipment to prevent the effects of moisture, dust, and vibration, thus improving equipment reliability and lifespan. In the automotive industry, epoxy adhesives are used for bonding body panels such as doors, hoods, and trunk lids; bonding and sealing components such as engines and transmissions; and fixing interior trim such as carpets, headliners, and seats. In electronics, epoxy adhesives are used for encapsulating electronic components such as integrated circuits, transistors, and diodes; fixing components and laminating circuit boards; and for insulating and sealing electronic equipment such as transformers, capacitors, and inductors. In the construction industry, epoxy adhesives can be used to bond building materials such as stone, glass, and metal; to repair and reinforce cracks in concrete structures; and to waterproof and seal parts of buildings such as roofs, basements, and bathrooms. In the machinery manufacturing industry, epoxy adhesives can be used to bond and repair mechanical parts such as gears, bearings, and shafts; to repair and manufacture molds; and to create wear-resistant coatings for mechanical equipment.

[0003] Epoxy adhesives typically contain epoxy resin, a curing agent, and optional additives (such as fillers, accelerators, antioxidants, coupling agents, etc.). The curing agent reacts chemically with the epoxy resin, transforming its linear structure into a network structure. Imidazole compounds, due to the presence of nitrogen-containing heterocycles in their molecules, possess excellent nucleophilicity and catalytic activity, making them a commonly used curing agent for epoxy adhesives. For example, dimethylimidazole is often used as a latent curing agent for epoxy resins, enabling rapid curing at medium temperatures and imparting high thermal stability to the cured product. However, traditional imidazole compounds still have several shortcomings. First, small-molecule imidazole compounds have poor compatibility with epoxy resins, easily leading to phase separation in the cured product, thus affecting its mechanical strength. Second, the uneven dispersion of small-molecule imidazole compounds in the epoxy resin matrix, with excessively high local concentrations, can cause differences in curing rates, leading to internal stress concentration and reducing the impact strength of the cured product. These defects limit the application of imidazole epoxy adhesives in high-end fields (such as electronic packaging and composite materials). Summary of the Invention

[0004] The primary objective of this invention is to overcome the shortcomings of existing imidazole-based epoxy adhesives in terms of poor impact resistance, and to provide a new imidazole-based polyether ester compound. Using this imidazole-based polyether ester compound as a curing agent for epoxy adhesives can improve the impact resistance of the cured product.

[0005] A second objective of this invention is to provide a method for preparing the above-mentioned imidazole epoxy adhesive.

[0006] A third objective of this invention is to provide the application of the above-mentioned imidazole polyether ester compound in epoxy adhesives.

[0007] A fourth objective of this invention is to provide an epoxy adhesive using the aforementioned imidazole polyether ester compound as a curing agent.

[0008] The imidazole polyether ester compound provided by this invention has the structure shown in formula (Ⅰ): Equation (I) In formula (Ⅰ), R1 and R2 are each independently H or C1~C5 alkyl groups, and n is an integer from 3 to 30.

[0009] The method for preparing the imidazole-based polyether ester compound provided by the present invention includes the following steps: S1. The polyethylene glycol shown in formula (II) and n-pentanol shown in formula (III) are subjected to an etherification reaction in the presence of catalyst I and solvent I to obtain intermediate product S1; S2. Under inert gas protection, the intermediate product of S1 and the acrylic acid shown in formula (Ⅳ) are subjected to esterification reaction in the presence of catalyst II, solvent II and polymerization inhibitor to obtain the intermediate product of S2; S3. The intermediate product of S2 and the imidazole compound shown in formula (V) are subjected to an addition reaction in the presence of catalyst III and solvent III to obtain an imidazole polyether ester compound; Formula (II), Formula (Ⅲ), Equation (Ⅳ), Formula (V), In equation (II), n is an integer from 3 to 30; In formula (V), R1 and R2 are each independently H or C1~C5 alkyl groups, and n is an integer from 3 to 30.

[0010] The epoxy adhesive provided by the present invention contains epoxy resin and a curing agent, wherein the curing agent is the above-mentioned imidazole polyether ester compound.

[0011] The key to this invention lies in using an imidazole-based polyether ester compound with formula (I) as a curing agent for epoxy adhesives. This imidazole-based polyether ester compound simultaneously contains an imidazole group, a polyether segment, and an ester group, with the ester group located between the imidazole group and the polyether segment. Furthermore, the polyether segment is tail-bonded with a C5 alkyl group. This specific structure not only retains the catalytic activity of the imidazole group but also significantly improves the impact strength of the cured epoxy adhesive. In addition, the preparation method of the imidazole-based polyether ester compound provided by this invention requires only three reaction steps to efficiently obtain the compound, which is beneficial for improving the overall yield. Detailed Implementation

[0012] The imidazole polyether ester compound provided by this invention has the structure shown in formula (Ⅰ): Equation (I) In formula (I), R1 and R2 are each independently H or a C1-C5 alkyl group, preferably a C1-C3 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. n is an integer from 3 to 30, specifically an integer such as 3, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, etc.

[0013] The method for preparing the imidazole-based polyether ester compound provided by the present invention includes the following steps: S1. The polyethylene glycol shown in formula (II) and n-pentanol shown in formula (III) are subjected to an etherification reaction in the presence of catalyst I and solvent I to obtain intermediate product S1; S2. Under inert gas protection, the intermediate product of S1 and the acrylic acid shown in formula (Ⅳ) are subjected to esterification reaction in the presence of catalyst II, solvent II and polymerization inhibitor to obtain the intermediate product of S2; S3. The intermediate product of S2 and the imidazole compound shown in formula (V) are subjected to an addition reaction in the presence of catalyst III and solvent III to obtain an imidazole polyether ester compound; Formula (II), Formula (Ⅲ), Equation (Ⅳ), Formula (V), In equation (II), n is an integer from 3 to 30; In formula (V), R1 and R2 are each independently H or C1~C5 alkyl groups, and n is an integer from 3 to 30.

[0014] The reaction equation for the preparation process of the imidazole-based polyether ester compound provided by this invention is as follows:

[0015] In the preparation process of the above-mentioned imidazole-based polyether ester compound, the etherification reaction step S1 is not particularly limited. Polyethylene glycol, n-pentanol, catalyst I, and solvent I can be mixed in any order before the etherification reaction. In a preferred embodiment, the etherification reaction step includes dissolving polyethylene glycol and catalyst I in solvent I, slowly adding n-pentanol dropwise, and after the addition is complete, heating to the etherification temperature for reflux reaction. After the reaction is complete, the crude product is sequentially cooled to room temperature, washed, dried, and solvent removed to obtain the intermediate product S1. The dropping rate of n-pentanol is preferably controlled within a dropping time of 30-60 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any value between them. The washing method preferably includes washing with saturated sodium bicarbonate (NaHCO3) solution until neutral, followed by washing with water 1-3 times. The drying method preferably uses anhydrous magnesium sulfate (MgSO4). The solvent removal method is preferably vacuum distillation.

[0016] In the preparation process of the above-mentioned imidazole polyether ester compound, the esterification reaction step S2 is not particularly limited. The intermediate product S1, acrylic acid, catalyst II, solvent II, and polymerization inhibitor can be mixed in any order and then subjected to the esterification reaction. In a preferred embodiment, the esterification reaction step includes dissolving the intermediate product S1, catalyst II, and polymerization inhibitor in solvent II under an inert gas protection, slowly adding acrylic acid dropwise, and after the addition is complete, slowly raising the temperature to the esterification temperature to carry out the esterification reaction. After the reaction is complete, the crude product is cooled to room temperature, washed, dried, and the solvent is removed to obtain the intermediate product S2. The dropping rate of the acrylic acid is preferably controlled within a dropping time of 30-60 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any value between them. The washing method preferably includes washing with a saturated sodium bicarbonate (NaHCO3) solution until neutral, and then washing with water 1-3 times. The drying method preferably uses anhydrous magnesium sulfate (MgSO4). The preferred method for removing the solvent is vacuum distillation.

[0017] In the preparation of the above-mentioned imidazole-based polyether ester compound, the addition reaction step in step S3 is not particularly limited. The S2 intermediate product, imidazole compound, catalyst III, and solvent III can be mixed in any order and then subjected to esterification. In a preferred embodiment, the addition reaction step includes dissolving the S2 intermediate product and catalyst III in solvent III, slowly adding the imidazole compound dropwise, heating to the addition temperature after the addition is complete, and cooling the crude product to room temperature, washing, drying, and removing the solvent to obtain the imidazole-based polyether ester compound. The dropping rate of the imidazole compound is preferably controlled within a dropping time of 20-50 min, such as 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, or any value between them. The washing method preferably includes washing with saturated sodium chloride (NaCl) solution until neutral, followed by washing with water 1-3 times. The drying method preferably uses anhydrous magnesium sulfate (MgSO4). The solvent removal method is preferably vacuum distillation.

[0018] In the preparation of the above imidazole polyether ester compound, the molar ratio of n-pentanol to polyethylene glycol is preferably (1~1.2):1, specifically it can be 1:1, 1.02:1, 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, 1.2:1 or any value between them.

[0019] In the preparation of the above imidazole polyether ester compound, the molar ratio of acrylic acid to polyethylene glycol is preferably (1.4~1.6):1, specifically it can be 1.4:1, 1.42:1, 1.45:1, 1.48:1, 1.5:1, 1.52:1, 1.55:1, 1.58:1, 1.6:1 or any value between them.

[0020] In the preparation of the above imidazole-based polyether ester compound, the molar ratio of the imidazole compound to polyethylene glycol is preferably (0.7~0.9):1, specifically 0.7:1, 0.72:1, 0.75:1, 0.78:1, 0.8:1, 0.82:1, 0.85:1, 0.88:1, 0.9:1 or any value between them.

[0021] In the preparation of the above-mentioned imidazole polyether ester compound, the etherification reaction conditions preferably include a temperature of 120℃~160℃, specifically 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃ or any value between them; and a time of 8h~12h, specifically 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h or any value between them.

[0022] In the preparation of the above-mentioned imidazole polyether ester compound, the esterification reaction conditions preferably include a temperature of 80℃~100℃, specifically 80℃, 85℃, 90℃, 95℃, 100℃ or any value between them; and a time of 8h~24h, specifically 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or any value between them.

[0023] In the preparation of the above-mentioned imidazole polyether ester compound, the conditions for the addition reaction preferably include a temperature of 60℃~80℃, specifically 60℃, 65℃, 70℃, 75℃, 80℃ or any value between them; and a time of 6h~12h, specifically 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h or any value between them.

[0024] In the preparation of the above-mentioned imidazole-based polyether ester compounds, solvents I, II, and III can all be inert liquid reaction media commonly used in the art, specifically hydrocarbon solvents, ether solvents, esterification solvents, ketone solvents, etc. In a preferred embodiment, solvent I is preferably toluene, solvent II is toluene and / or xylene, and solvent III is selected from at least one of tetrahydrofuran, dichloromethane, and N,N-dimethylformamide (DMF). In this case, the solvents can achieve a gentle compatibility with the reactants, allowing the reaction process to proceed smoothly and further improving the yield. The terms "I," "II," and "III" are merely used to distinguish the solvents used in different positions for ease of description and are not particularly limiting.

[0025] In the preparation of the above-mentioned imidazole polyether ester compound, catalyst I can be any existing substance capable of promoting the dehydration condensation of alcohol compounds, without particular limitation, but preferably p-benzenesulfonic acid. Catalyst II can be any existing substance capable of promoting the esterification of alcohol compounds with carboxylic acids, without particular limitation, but preferably aluminum trichloride. Catalyst III can be any existing substance capable of promoting the addition reaction of carbon-carbon unsaturated double bonds with amino groups, without particular limitation, but preferably at least one of triethylamine, potassium carbonate, and sodium carbonate. The terms "I", "II", and "III" are merely used to distinguish the catalysts used in different positions for ease of description and are not particularly limiting.

[0026] In the preparation of the above-mentioned imidazole-based polyether ester compound, the polymerization inhibitor can be any existing substance capable of preventing polymerization, such as phenolic polymerization inhibitors, quinone polymerization inhibitors, etc. Examples of phenolic polymerization inhibitors include hydroquinone and tert-butylcatechol. Examples of quinone polymerization inhibitors include p-benzoquinone and tetrachlorobenzoquinone.

[0027] The present invention also provides the application of the above-mentioned imidazole polyether ester compounds in epoxy adhesives.

[0028] The present invention also provides an epoxy adhesive containing epoxy resin and a curing agent, wherein the curing agent is the above-mentioned imidazole polyether ester compound.

[0029] The present invention will be described in detail below through embodiments.

[0030] The present invention will be further described below with reference to the embodiments.

[0031] In the following test and comparative test examples, the epoxy resin (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate): 2021P, purchased from Daicel, Japan, CAS No. 2386-87-0; the SBS thermoelastic resin was purchased from Kraton, grade D1155; and the carbon black was purchased from Mitsubishi Chemical Corporation, grade 705.

[0032] Example 1: Imidazole-based polyether ester compounds and their preparation methods S1. In a three-necked flask, hexaethylene glycol (n=4, 28.2 g, 0.1 mol), p-toluenesulfonic acid (0.17 g, 1%), and toluene (50 mL) were added. A water separator and a reflux condenser were installed. Under inert gas protection, n-pentanol (10.6 g, 0.12 mol) was slowly added dropwise. After the addition was complete, the temperature was raised to 120 °C and the mixture was stirred and refluxed for 8 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the S1 intermediate product.

[0033] S2. Under inert gas protection, the intermediate product of S1 (35.2 g, 0.1 mol) was dissolved in toluene (50 mL) and stirred until homogeneous. Hydroquinone (0.049 g, 0.3% of acrylic acid) and aluminum trichloride (0.2 g, 1.5%) were added and stirred until homogeneous. Acrylic acid (10.8 g, 0.15 mol) was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 80 °C and the reaction was stirred for 10 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the intermediate product of S2.

[0034] S3. The intermediate product of S2 (40.6 g, 0.1 mol) was dissolved in tetrahydrofuran (50 mL) with stirring. Triethylamine (1 g, 10%) was added and stirred until homogeneous. Dimethylimidazole (7.69 g, 0.08 mol) was slowly added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 8 h. After the reaction was completed, the resulting product was cooled to room temperature, washed twice with saturated NaCl solution, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and distilled under reduced pressure to obtain a pale yellow viscous liquid product, which was the imidazole-based polyether ester compound (denoted as MM-01), with a yield of 88%.

[0035] The NMR data and characteristic data of the imidazole polyether ester compound are as follows: 1 H NMR (400 MHz, DMSO-d6) δ 6.80 (s, 1H), 4.54 (t, J = 7.6 Hz, 2H), 4.20 (t, J = 6.1 Hz, 2H), 3.72 -3.56 (m, 10H), 3.37 (t, J = 6.1 Hz, 2H), 2.80 (t, J = 7.7 Hz, 2H), 2.42 (s, 3H), 2.19 (s, 3H), 1.57 - 1.45 (m, 2H), 1.44 - 1.26 (m, 4H), 0.94 - 0.85 (m, 3H). The NMR results show that this imidazole polyether ester compound has the structure shown in formula (Ⅰ).

[0036] Example 2: Imidazole-based polyether ester compounds and their preparation methods S1. In a three-necked flask, hexaethylene glycol (n=4, 28.2 g, 0.1 mol), p-toluenesulfonic acid (0.17 g, 1%), and toluene (50 mL) were added. A water separator and a reflux condenser were installed. Under inert gas protection, n-pentanol (8.8 g, 0.1 mol) was slowly added dropwise. After the addition was complete, the temperature was raised to 160 °C and the mixture was stirred and refluxed for 10 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the S1 intermediate product.

[0037] S2. Under inert gas protection, the intermediate product of S1 (35.2 g, 0.1 mol) was dissolved in toluene (50 mL) and stirred until homogeneous. Hydroquinone (0.049 g, 0.3% of acrylic acid) and aluminum trichloride (0.2 g, 1.5%) were added and stirred until homogeneous. Acrylic acid (10.5 g, 0.16 mol) was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 90 °C and the reaction was stirred for 24 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the intermediate product of S2.

[0038] S3. The intermediate product of S2 (40.6 g, 0.1 mol) was dissolved in dichloromethane (50 mL) with stirring. K2CO3 (1.38 g, 10%) was added and stirred until homogeneous. Dimethylimidazole (6.73 g, 0.07 mol) was slowly added dropwise. After the addition was complete, the mixture was heated to 80 °C and stirred for 6 h. After the reaction was completed, the resulting product was cooled to room temperature, washed twice with saturated NaCl solution, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and distilled under reduced pressure to obtain a pale yellow viscous liquid product, which was the imidazole-based polyether ester compound (denoted as MM-02), with a yield of 80%.

[0039] The NMR data and characteristic data of the imidazole polyether ester compound are as follows: 1 H NMR (400 MHz, DMSO-d6) δ 6.80 (s, 1H), 4.54 (t, J = 7.6 Hz, 2H), 4.20 (t, J = 6.1 Hz, 2H), 3.72 -3.56 (m, 10H), 3.37 (t, J = 6.1 Hz, 2H), 2.80 (t, J= 7.7 Hz, 2H), 2.42 (s, 3H), 2.19 (s, 3H), 1.57 - 1.45 (m, 2H), 1.44 - 1.26 (m, 4H), 0.94 - 0.85 (m, 3H). The NMR results show that this imidazole polyether ester compound has the structure shown in formula (Ⅰ).

[0040] Example 3: Imidazole-based polyether ester compounds and their preparation methods S1. In a three-necked flask, hexaethylene glycol (n=4, 28.2 g, 0.1 mol), p-toluenesulfonic acid (0.17 g, 1%), and toluene (50 mL) were added. A water separator and a reflux condenser were installed. Under inert gas protection, n-pentanol (9.7 g, 0.11 mol) was slowly added dropwise. After the addition was complete, the temperature was raised to 140 °C and the mixture was stirred and refluxed for 12 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the S1 intermediate product.

[0041] S2. Under inert gas protection, the intermediate product of S1 (35.2 g, 0.1 mol) was dissolved in xylene (50 mL) and stirred until homogeneous. Hydroquinone (0.049 g, 0.3% of acrylic acid) and aluminum trichloride (0.2 g, 1.5%) were added and stirred until homogeneous. Acrylic acid (10.1 g, 0.14 mol) was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 100 °C and the reaction was stirred for 8 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, and then washed twice with water. The organic phase was dried with anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the intermediate product of S2.

[0042] S3. The intermediate product of S2 (40.6 g, 0.1 mol) was dissolved in N,N-dimethylformamide (50 mL) with stirring. Triethylamine (1 g, 10%) was added and stirred until homogeneous. Dimethylimidazole (8.65 g, 0.09 mol) was slowly added dropwise. After the addition was complete, the mixture was heated to 70 °C and stirred for 10 h. After the reaction was completed, the resulting product was cooled to room temperature, washed twice with saturated NaCl solution, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and distilled under reduced pressure to obtain a pale yellow viscous liquid product, which was the imidazole-based polyether ester compound (denoted as MM-03), with a yield of 79%.

[0043] The NMR data and characteristic data of the imidazole polyether ester compound are as follows: 1H NMR (400 MHz, DMSO-d6) δ 6.80 (s, 1H), 4.54 (t, J = 7.6 Hz, 2H), 4.20 (t, J = 6.1 Hz, 2H), 3.72 -3.56 (m, 10H), 3.37 (t, J = 6.1 Hz, 2H), 2.80 (t, J = 7.7 Hz, 2H), 2.42 (s, 3H), 2.19 (s, 3H), 1.57 - 1.45 (m, 2H), 1.44 - 1.26 (m, 4H), 0.94 - 0.85 (m, 3H). The NMR results show that this imidazole polyether ester compound has the structure shown in formula (Ⅰ).

[0044] Example 4: Imidazole-based polyether ester compounds and their preparation methods The imidazole-based polyether ester compound was prepared according to the method of Example 1, except that hexaethylene glycol was replaced with the same molar amount of polyethylene glycol (n is 5~30, number average molecular weight is 1000), and the other conditions were the same as in Example 1, to obtain the imidazole-based polyether ester compound, denoted as MM-04.

[0045] Comparative Example 1: Reference Imidazole Compound and its Preparation Method The imidazole compound was prepared according to the method of Example 1, except that in step S1, n-pentanol was replaced with the same molar amount of methanol, and the other conditions were the same as in Example 1, to obtain the reference imidazole compound, denoted as DMM-01.

[0046] Comparative Example 2: Reference Imidazole Compound and its Preparation Method The imidazole compound was prepared according to the method in Example 1, except that step S1 was omitted, and instead, hexaethylene glycol was reacted directly with acrylic acid. The specific steps are as follows: S1. Under an inert gas atmosphere, hexaethylene glycol (n=4, 28.2 g, 0.1 mol) was dissolved in toluene (50 mL) and stirred until homogeneous. Hydroquinone (0.049 g, 0.3% of acrylic acid) and aluminum trichloride (0.2 g, 1.5%) were added and stirred until homogeneous. Acrylic acid (10.8 g, 0.15 mol) was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 80 °C and the reaction was stirred for 10 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the intermediate product.

[0047] S2. The intermediate product (40.6 g, 0.1 mol) was dissolved in tetrahydrofuran (50 mL) with stirring. Triethylamine (1 g, 10%) was added and stirred until homogeneous. Dimethylimidazole (7.69 g, 0.08 mol) was slowly added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 8 h. After the reaction was complete, the resulting product was cooled to room temperature, washed twice with saturated NaCl solution, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and distilled under reduced pressure to obtain a pale yellow viscous liquid product, which was the reference imidazole polyether ester compound, denoted as DMM-02.

[0048] Comparative Example 3: Reference Imidazole Compound and its Preparation Method The imidazole compound was prepared according to the method in Example 1, except that acrylic acid was replaced with allyl bromide in the reaction. The specific steps are as follows: S1. In a three-necked flask, hexaethylene glycol (n=4, 28.2 g, 0.1 mol), p-toluenesulfonic acid (0.17 g, 1%), and toluene (50 mL) were added. A water separator and a reflux condenser were installed. Under inert gas protection, n-pentanol (10.6 g, 0.12 mol) was slowly added dropwise. After the addition was complete, the temperature was raised to 120 °C and the mixture was stirred and refluxed for 8 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting reaction product was washed with saturated NaHCO3 solution until neutral, then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the S1 intermediate product.

[0049] S2. Under inert gas protection, the intermediate product of S1 (35.2 g, 0.1 mol) was dissolved in dichloromethane (50 mL) and stirred until homogeneous. Potassium carbonate (1.38 g, 10%) was added and stirred until homogeneous. Allyl bromide (15.45 g, 0.15 mol) was slowly added dropwise at room temperature, and the reaction was stirred for 10 h. After the reaction was completed, the resulting reaction product was washed with saturated NaHCO3 solution until neutral, then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and then distilled under reduced pressure to obtain the intermediate product of S2.

[0050] S3. The intermediate product of S2 (40.6 g, 0.1 mol) was dissolved in tetrahydrofuran (50 mL) with stirring. Triethylamine (1 g, 10%) was added and stirred until homogeneous. Dimethylimidazole (7.69 g, 0.08 mol) was slowly added dropwise. After the addition was complete, the mixture was heated to 60 °C and stirred for 8 h. After the reaction was completed, the resulting product was cooled to room temperature, washed twice with saturated NaCl solution, and then washed twice with water. The organic phase was dried over anhydrous MgSO4, filtered, and distilled under reduced pressure to obtain a pale yellow viscous liquid product, which was the reference imidazole compound, denoted as DMM-03.

[0051] Test case According to the weight proportions, epoxy resin, curing agent, SBS thermoelastic resin, carbon black, and γ-epoxypropoxypropyltrimethoxysiloxane were stirred in a dual planetary hybrid stirring tank for 30 minutes, followed by a 15-minute wall scraping treatment. After vacuum degassing, the mixture was discharged to obtain the epoxy resin composition. The mass ratio of epoxy resin, SBS thermoelastic resin, carbon black, and γ-epoxypropoxypropyltrimethoxysiloxane was 100:45:2.3:11.4, and the molar ratio of epoxy groups in the epoxy resin to imidazole groups in the curing agent was 1:1. The curing agents were the imidazole polyether ester compounds obtained in the above examples, the reference imidazole polyether ester compounds obtained in the comparative examples, and dimethylimidazole.

[0052] The epoxy resin composition was heat-cured in an 80℃ oven for 50 min. After the cured product was made into standard samples, the elongation at break was tested using a tensile testing machine according to the method disclosed in GB T 1040.3-2006. The tensile speed was controlled at 50 mm / min. The results are shown in Table 1.

[0053] Table 1

[0054] As can be seen from the results of the above embodiments, the total yield of imidazole polyether ester compounds prepared by the method provided by the present invention can reach more than 79%.

[0055] The results of the above test examples and comparative test examples show that when the imidazole polyether ester compound provided by the present invention is used as the curing agent of epoxy adhesive, the elongation at break of the cured epoxy adhesive can reach more than 6.5%, that is, it can significantly improve the impact strength of the cured epoxy adhesive.

[0056] 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. An imidazole-based polyether ester compound, characterized in that, The imidazole-based polyether ester compound has the structure shown in formula (Ⅰ): Equation (I) In formula (Ⅰ), R1 and R2 are each independently H or C1~C5 alkyl groups, and n is an integer from 3 to 30.

2. The imidazole-based polyether ester compound according to claim 1, characterized in that, R1 and R2 are each independently a C1 to C3 alkyl group.

3. The method for preparing the imidazole-based polyether ester compound according to claim 1 or 2, characterized in that, The method includes the following steps: S1. The polyethylene glycol shown in formula (II) and n-pentanol shown in formula (III) are subjected to an etherification reaction in the presence of catalyst I and solvent I to obtain intermediate product S1; S2. Under inert gas protection, the intermediate product of S1 and the acrylic acid shown in formula (Ⅳ) are subjected to esterification reaction in the presence of catalyst II, solvent II and polymerization inhibitor to obtain the intermediate product of S2; S3. The intermediate product of S2 and the imidazole compound shown in formula (V) are subjected to an addition reaction in the presence of catalyst III and solvent III to obtain an imidazole polyether ester compound; Formula (II), Formula (Ⅲ), Equation (Ⅳ), Formula (V), In equation (II), n is an integer from 3 to 30; In formula (V), R1 and R2 are each independently H or C1~C5 alkyl groups, and n is an integer from 3 to 30.

4. The method for preparing the imidazole-based polyether ester compound according to claim 3, characterized in that, In step S1, the etherification reaction includes dissolving polyethylene glycol and catalyst I in solvent I, slowly adding n-pentanol dropwise, and after the addition is complete, heating to the etherification temperature for reflux reaction. After the reaction is complete, the crude product is cooled to room temperature, washed, dried and solvent removed to obtain intermediate product S1.

5. The method for preparing the imidazole-based polyether ester compound according to claim 3, characterized in that, In step S2, the esterification reaction includes dissolving the S1 intermediate product, catalyst II, and polymerization inhibitor in solvent II under inert gas protection, slowly adding acrylic acid dropwise, and then slowly heating to the esterification temperature to carry out the esterification reaction. After the reaction is complete, the crude product is cooled to room temperature, washed, dried, and the solvent is removed to obtain the S2 intermediate product.

6. The method for preparing the imidazole-based polyether ester compound according to claim 3, characterized in that, In step S3, the addition reaction includes dissolving the intermediate product of S2 and catalyst III in solvent III, slowly adding an imidazole compound dropwise, heating to the addition temperature after the addition is complete, and cooling the crude product to room temperature, washing, drying and removing the solvent to obtain an imidazole polyether ester compound.

7. The method for preparing the imidazole-based polyether ester compound according to any one of claims 3 to 6, characterized in that, The molar ratio of n-pentanol to polyethylene glycol is (1~1.2):1; the molar ratio of acrylic acid to polyethylene glycol is (1.4~1.6):1; and the molar ratio of imidazole compound to polyethylene glycol is (0.7~0.9):

1.

8. The method for preparing the imidazole-based polyether ester compound according to any one of claims 3 to 6, characterized in that, The conditions for the etherification reaction include a temperature of 120℃~160℃ and a time of 8h~12h; the conditions for the esterification reaction include a temperature of 80℃~100℃ and a time of 8h~24h; and the conditions for the addition reaction include a temperature of 60℃~80℃ and a time of 6h~12h.

9. The use of the imidazole polyether ester compound of claim 1 or 2 in epoxy adhesives.

10. An epoxy adhesive, wherein the epoxy adhesive contains an epoxy resin and a curing agent, characterized in that, The curing agent is the imidazole polyether ester compound as described in claim 1 or 2.

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