Bio-based flexibilizer, epoxy adhesive and preparation method of bio-based flexibilizer and epoxy adhesive

Abstract

The invention relates to a bio-based toughening agent, an epoxy adhesive and a preparation method of the bio-based toughening agent. The bio-based toughening agent is obtained through a reaction of a polyurethane prepolymer and cardanol; the polyurethane prepolymer is obtained by reaction of castor oil and polyisocyanate; the molar ratio of an isocyanate group in the polyurethane prepolymer to a phenolic hydroxyl group in the cardanol is 1: (1-2); the molar ratio of hydroxyl groups in the castor oil to isocyanate groups in the polyisocyanate is 1: (1-3). The prepared toughening agent is applied to the epoxy adhesive, and the prepared epoxy adhesive has high peel strength and impact absorption capacity and good anti-aging capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and specifically relates to a bio-based toughening agent, an epoxy adhesive and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, the needs and requirements of related supporting industries are also constantly increasing. In terms of lightweighting of new energy vehicles, compared with traditional bolt connection and riveting processes, high-strength body structural adhesives can provide excellent bonding performance, replace or assist traditional connection processes, thereby achieving the goal of reducing weight and increasing efficiency.

[0003] Epoxy adhesives have a wide range of uses and are commonly used in the bonding of devices and components. They have high mechanical strength and good dielectric properties. In many industrial and daily use scenarios, epoxy adhesives are widely used for material bonding and repair. However, epoxy adhesives often exhibit the disadvantages of high brittleness and low peel strength, and cars are often in a vibrating environment and occasionally experience extreme collisions. The above-mentioned shortcomings of epoxy adhesives make it impossible to use them in the connection of automotive body structural parts. In order to expand the scope of application of epoxy adhesives in the energy vehicle industry, it is necessary to improve the peel strength and impact resistance of epoxy adhesives. Summary of the invention

[0004] Based on this, the object of the present invention is to improve the peel strength and impact resistance of epoxy adhesive.

[0005] In order to achieve the above-mentioned object of the invention, the present invention includes the following technical solutions.

[0006] In a first aspect, the present invention provides a bio-based toughening agent obtained by reacting a polyurethane prepolymer and cardanol;

[0007] The polyurethane prepolymer is obtained by reacting castor oil with polyisocyanate;

[0008] The molar ratio of the isocyanate group in the polyurethane prepolymer to the phenolic hydroxyl group in the cardanol is 1:1-2;

[0009] The molar ratio of the hydroxyl group in the castor oil to the isocyanate group in the polyisocyanate is 1:1-3.

[0010] In some of the embodiments, the molar ratio of the isocyanate groups in the polyurethane prepolymer to the phenolic hydroxyl groups in the cardanol is 1:1.1-1.5; the molar ratio of the hydroxyl groups in the castor oil to the isocyanate groups in the polyisocyanate is 1:1.2-2.5.

[0011] In some of the embodiments, the molar ratio of the isocyanate groups in the polyurethane prepolymer to the phenolic hydroxyl groups in the cardanol is 1:1.1-1.5; the molar ratio of the hydroxyl groups in the castor oil to the isocyanate groups in the polyisocyanate is 1:1.8-2.2.

[0012] In some of the embodiments, the molar ratio of the isocyanate groups in the polyurethane prepolymer to the phenolic hydroxyl groups in the cardanol is 1:1.2-1.3; the molar ratio of the hydroxyl groups in the castor oil to the isocyanate groups in the polyisocyanate is 1:1.8-2.2.

[0013] In some of the embodiments, the molar ratio of the isocyanate groups in the polyurethane prepolymer to the phenolic hydroxyl groups in the cardanol is 1:1.2; the molar ratio of the hydroxyl groups in the castor oil to the isocyanate groups in the polyisocyanate is 1:2.

[0014] In some embodiments, the polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0015] In a second aspect, the present invention provides a method for preparing the bio-based toughening agent, comprising the following steps:

[0016] (1) reacting the castor oil and polyisocyanate at a temperature of 60° C. to 100° C. for 2 to 8 hours to obtain the polyurethane prepolymer;

[0017] (2) reacting the polyurethane prepolymer and cardanol at a temperature of 50° C. to 80° C. for 2 to 8 hours to obtain the bio-based toughening agent.

[0018] In some embodiments, the method for preparing the bio-based toughening agent comprises the following steps:

[0019] (1) reacting the castor oil and polyisocyanate at a temperature of 70° C. to 80° C. for 5 to 7 hours to obtain the polyurethane prepolymer;

[0020] (2) reacting the polyurethane prepolymer and cardanol at a temperature of 55° C. to 65° C. for 4 to 6 hours to obtain the bio-based toughening agent.

[0021] In some embodiments, the reaction is carried out with or without the addition of a solvent; the solvent is selected from one or more of acetone, butanone, ethylene dichloride, ethyl acetate, and butyl acetate.

[0022] In some of the embodiments, the reaction is carried out under the condition of adding a solvent, and the step of removing the solvent is further included after the reaction of the polyurethane prepolymer and cardanol.

[0023] In some embodiments, the solvent is removed by vacuuming and stirring for 1-2 hours to remove the solvent.

[0024] In some embodiments, the vacuuming is performed to a vacuum degree of -0.08 MPa to -0.1 MPa.

[0025] In a third aspect, the present invention further provides an epoxy adhesive to which a toughening agent is added, and the toughening agent includes the bio-based toughening agent described in the present invention.

[0026] In some embodiments, the bio-based toughening agent accounts for 5-25% by weight in the epoxy adhesive.

[0027] In some embodiments, the bio-based toughening agent accounts for 10-20% by weight in the epoxy adhesive.

[0028] In some embodiments, the bio-based toughening agent accounts for 13-20% by weight in the epoxy adhesive.

[0029] In some embodiments, the bio-based toughening agent accounts for 15-20% by weight in the epoxy adhesive.

[0030] In some embodiments, the bio-based toughening agent accounts for 14-16% by weight in the epoxy adhesive.

[0031] In some of the embodiments, the epoxy adhesive is prepared from raw materials including the following components in parts by weight:

[0032]

[0033] In some embodiments, the epoxy adhesive is prepared from raw materials including the following components in parts by weight:

[0034]

[0035]

[0036] In some embodiments, the epoxy adhesive is prepared from raw materials including the following components in parts by weight:

[0037]

[0038] In some embodiments, the epoxy adhesive is prepared from raw materials including the following components in parts by weight:

[0039]

[0040] In some embodiments, the weight proportion of the universal toughening agent in the epoxy adhesive is 5-25%.

[0041] In some embodiments, the weight proportion of the universal toughening agent in the epoxy adhesive is 10-25%.

[0042] In some embodiments, the weight proportion of the universal toughening agent in the epoxy adhesive is 15-25%.

[0043] In some embodiments, the weight proportion of the universal toughening agent in the epoxy adhesive is 20-25%.

[0044] In some embodiments, the weight percentage of the universal toughening agent in the epoxy adhesive is 18-20%.

[0045] In some embodiments, the epoxy resin is one or more of a glycidyl ether epoxy resin and a glycidyl ester epoxy resin.

[0046] In some of the embodiments, the universal toughening agent is one or more of a CTBN toughening agent, a core-shell rubber, and a polyurethane-modified epoxy resin.

[0047] In some embodiments, the curing agent is one or more of imidazole, dicyandiamide, acid anhydride and pyridine.

[0048] In some embodiments, the accelerator is one or more of imidazole, pyridine and organic urea (eg, diuron, fenuron).

[0049] In a fourth aspect, the present invention also provides a method for preparing the epoxy adhesive, comprising the following steps: uniformly mixing the epoxy resin, bio-based toughening agent, universal toughening agent, curing agent and accelerator at a temperature of 50°C-70°C, and cooling to room temperature to obtain the epoxy adhesive.

[0050] The present invention has the following beneficial effects:

[0051] The invention adopts castor oil, polyisocyanate and cardanol as raw materials to react in a specific ratio to prepare a bio-based toughening agent. The toughening agent is applied to epoxy adhesives to significantly improve the peel strength and impact absorption capacity of the epoxy adhesives, and can overcome the defects of high brittleness and low peel strength of the epoxy adhesives, thereby improving the performance and reliability of the epoxy adhesives in various applications.

[0052] At the same time, the toughening agent prepared by the present invention contains unsaturated bonds, which can undergo addition reactions when free radicals are generated during thermal oxidative aging, thereby slowing down the aging phenomenon and improving the anti-aging ability of the epoxy adhesive.

[0053] In addition, the present invention uses castor oil and cardanol as bio-based raw materials, which has significant advantages in the use of renewable raw materials and the reduction of carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the infrared spectrum of the bio-based toughening agent prepared in Example 1. DETAILED DESCRIPTION

[0055] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0056] The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0057] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0058] In addition, as used in the present invention, the term "or" is an inclusive "or" symbol and is equivalent to the term "and / or", unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on other factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meanings of "a", "an", and "the" include plural referents. The meaning of "in..." includes "in..." and "on...".

[0059] In the following examples, the structural formula of castor oil is as follows:

[0060]

[0061] The structural formula of diphenylmethane diisocyanate is as follows:

[0062]

[0063] The structural formula of cardanol is as follows:

[0064]

[0065] Among them, n is 0, 1, 2, 3.

[0066] The reaction mechanism of castor oil, diphenylmethane diisocyanate and cardanol is as follows:

[0067]

[0068] The epoxy resin used in the following examples and comparative examples is bisphenol A glycidyl ether, the curing agent is dicyandiamide, and the accelerator is diuron.

[0069] The following are specific embodiments.

[0070] Example 1

[0071] This embodiment provides a bio-based toughening agent, an epoxy adhesive and a preparation method thereof.

[0072] (1) Prepare the bio-based toughening agent according to the following method:

[0073] Step 1: Weigh castor oil and diphenylmethane diisocyanate in a ratio of hydroxyl group to isocyanate group = 1:1.2 by molar ratio, and weigh 30% by mass of ethyl acetate (i.e., ethyl acetate accounts for 30% of the total mass, and castor oil + diphenylmethane diisocyanate accounts for 70% of the total mass).

[0074] Step 2: Add the above raw materials into a three-necked flask, reflux at a constant temperature of 75° C., and stir for 6 hours to obtain a polyurethane prepolymer.

[0075] Step 3: Weigh cardanol in a molar ratio of polyurethane prepolymer and isocyanate group: phenolic hydroxyl group = 1:1.5, add it to the three-necked flask in step 2, stir at 60°C for 4 hours, then evacuate to -0.1MPa, stir for 2 hours, recover the solvent, and obtain the bio-based toughening agent.

[0076] Its infrared spectrum is as follows Figure 1 Shown: 2250cm -1 The NCO infrared peak at 1560cm -1 、3500cm -1 The NH and OH peaks at 2900 cm -1 The infrared peak of CH at is enhanced, indicating that NCO reacts with phenolic hydroxyl group to generate the bio-based toughening agent.

[0077] (2) Prepare epoxy adhesive according to the raw material composition in Table 1 and the following method:

[0078] Table 1 Epoxy adhesive composition in Example 1

[0079]

[0080]

[0081] The preparation method of the epoxy adhesive is carried out according to the following steps: weigh each raw material according to the mass fraction of each raw material in Table 1, stir and mix them evenly at 60° C., and obtain the adhesive after cooling to room temperature.

[0082] Example 2

[0083] This embodiment provides a bio-based toughening agent, an epoxy adhesive and a preparation method thereof.

[0084] (1) Prepare the bio-based toughening agent according to the following method:

[0085] Step 1: Weigh castor oil and diphenylmethane diisocyanate in a ratio of hydroxyl group to isocyanate group = 1:2 by mole ratio, and weigh 30% by mass of ethyl acetate.

[0086] Step 2: Add the above raw materials into a three-necked flask, reflux at a constant temperature of 75° C., and stir for 6 hours to obtain a polyurethane prepolymer.

[0087] Step 3: Weigh cardanol in a molar ratio of polyurethane prepolymer and isocyanate group: phenolic hydroxyl group = 1:1.2, add it to the three-necked flask in step 2, stir at 60°C for 4 hours, then evacuate to -0.1MPa, stir for 2 hours, recover the solvent, and obtain the bio-based toughening agent.

[0088] (2) Prepare epoxy adhesive according to the raw material composition in Table 2 and the preparation method of Example 1.

[0089] Table 2 Adhesive components in Example 2

[0090] Raw material name Mass Epoxy resin 50 Bio-based toughening agents 15 CTBN toughening agent 25 Curing agent 9 Accelerator 1

[0091] Example 3

[0092] This embodiment provides a bio-based toughening agent, an epoxy adhesive and a preparation method thereof.

[0093] (1) Prepare the bio-based toughening agent according to the following method:

[0094] Step 1: Weigh castor oil and diphenylmethane diisocyanate in a ratio of hydroxyl group to isocyanate group = 1:2.5 by mole ratio, and weigh 30% by mass of ethyl acetate.

[0095] Step 2: Add the above raw materials into a three-necked flask, reflux at a constant temperature of 75° C., and stir for 6 hours to obtain a polyurethane prepolymer.

[0096] Step 3: Weigh the polyurethane prepolymer and cardanol in a ratio of isocyanate group to phenolic hydroxyl group = 1:1.1 by molar ratio, add them to the three-necked flask in step 2, stir for 4 hours at 60°C, then evacuate to -0.1MPa, stir for 2 hours, recover the solvent, and obtain the bio-based toughening agent.

[0097] (2) Prepare epoxy adhesive according to the raw material composition in Table 3 and the preparation method of Example 1.

[0098] Table 3 Adhesive components in Example 3

[0099] Raw material name Mass Epoxy resin 50 Bio-based toughening agents 15 CTBN toughening agent 25 Curing agent 9 Accelerator 1

[0100] Example 4

[0101] This embodiment provides an epoxy adhesive and a preparation method thereof.

[0102] The epoxy adhesive was prepared according to the raw material composition in Table 4 and the preparation method in Example 1.

[0103] Table 4 Adhesive components in Example 4

[0104] Raw material name Mass Epoxy resin 55 Bio-based toughening agents 10 CTBN toughening agent 25 Curing agent 9 Accelerator 1

[0105] Among them, the bio-based toughening agent is the same as that in Example 2.

[0106] Example 5

[0107] This embodiment provides an epoxy adhesive and a preparation method thereof.

[0108] The epoxy adhesive was prepared according to the raw material composition in Table 5 and the preparation method in Example 1.

[0109] Table 5 Adhesive components in Example 5

[0110] Raw material name Mass Epoxy resin 55 Bio-based toughening agents 15 CTBN toughening agent 20 Curing agent 9 Accelerator 1

[0111] Among them, the bio-based toughening agent is the same as that in Example 2.

[0112] Example 6

[0113] This embodiment provides an epoxy adhesive and a preparation method thereof.

[0114] The epoxy adhesive was prepared according to the raw material composition in Table 6 and the preparation method in Example 1.

[0115] Table 6 Adhesive components in Example 6

[0116] Raw material name Mass Epoxy resin 50 Bio-based toughening agents 20 CTBN toughening agent 20 Curing agent 9 Accelerator 1

[0117] Among them, the bio-based toughening agent is the same as that in Example 2.

[0118] Comparative Example 1

[0119] This comparative example provides an epoxy adhesive and a preparation method thereof, which is different from Example 2 in that no bio-based toughening agent is added, that is, CTBN toughening agent is used instead of the bio-based toughening agent.

[0120] The epoxy adhesive was prepared according to the raw material composition in Table 7 and the preparation method in Example 1.

[0121] Table 7 Adhesive components in Comparative Example 1

[0122] Raw material name Mass Epoxy resin 50 CTBN toughening agent 40 Curing agent 9 Accelerator 1

[0123] Comparative Example 2

[0124] This comparative example provides an epoxy adhesive and a preparation method thereof, which is different from Example 2 in that the polyurethane prepolymer and cardanol are not reacted but are directly added to the adhesive component.

[0125] The epoxy adhesive was prepared according to the raw material composition in Table 8 and the preparation method in Example 1.

[0126] Table 8 Adhesive components in Comparative Example 2

[0127] Raw material name Mass Epoxy resin 50 Polyurethane prepolymer 12 Cardanol 3 CTBN toughening agent 25 Curing agent 9 Accelerator 1

[0128] Wherein, the polyurethane prepolymer is the polyurethane prepolymer prepared in Example 2.

[0129] Comparative Example 3

[0130] This comparative example provides an epoxy adhesive and a preparation method thereof, which differs from Example 2 in that an equal amount of polyurethane prepolymer is used to replace the bio-based toughening agent.

[0131] The epoxy adhesive was prepared according to the raw material composition in Table 9 and the preparation method in Example 1.

[0132] Table 9 Adhesive components in Comparative Example 3

[0133]

[0134]

[0135] Wherein, the polyurethane prepolymer is the polyurethane prepolymer prepared in Example 2.

[0136] Comparative Example 4

[0137] This comparative example provides an epoxy adhesive and a preparation method thereof, which differs from Example 2 in that an equal amount of polyurethane prepolymer is used to replace the bio-based toughening agent.

[0138] The epoxy adhesive was prepared according to the raw material composition in Table 10 and the preparation method of Example 1.

[0139] Table 10 Adhesive components in Comparative Example 4

[0140] Raw material name Mass Epoxy resin 50 Polyurethane prepolymer 15 CTBN toughening agent 25 Curing agent 9 Accelerator 1

[0141] Wherein, the preparation method of polyurethane prepolymer is as follows:

[0142] Step 1: Weigh diphenylmethane diisocyanate and cardanol in a molar ratio of isocyanate group in diphenylmethane diisocyanate and cardanol to phenolic hydroxyl group in the ratio of 1:1.2, and weigh 30% by mass of ethyl acetate at the same time.

[0143] Step 2: Add the above raw materials into a three-necked flask, stir at 60°C for 4 hours, then evacuate to -0.1MPa, stir for 2 hours, recover the solvent, and obtain a polyurethane prepolymer.

[0144] The following performance tests were performed on the epoxy adhesives prepared in Examples 1-6 and Comparative Examples 1-4:

[0145] Shear strength: tested according to GB / T 7124 method.

[0146] Peel strength: tested according to GB / T 2791 method.

[0147] Tensile strength: tested according to GB / T 7124 method.

[0148] Impact toughness: tested according to GB / T 1043 method.

[0149] Aging test: After high and low temperature alternation (-40℃ for 2 hours, 95℃ for 2 hours), test according to the above method.

[0150] The test results are shown in Table 11.

[0151] Table 11 Performance test results of epoxy adhesive

[0152]

[0153] From the results in Table 1, it can be seen that the raw material ratios of the bio-based toughening agents prepared in Examples 1-3 are different, and the peel strength, impact resistance and other properties of the obtained epoxy adhesives are different. Among them, Example 2 is reacted at a molar ratio of hydroxyl group:isocyanate group in castor oil and diphenylmethane diisocyanate = 1:2, and at a molar ratio of isocyanate group:phenolic hydroxyl group in polyurethane prepolymer and cardanol = 1:1.2. The obtained bio-based toughening agent has the best reinforcing effect on the epoxy adhesive.

[0154] Compared with Example 2, Examples 4-6 changed the amount of bio-based toughening agent and CTBN toughening agent. It can be seen from the results in Table 1 that the amount of bio-based toughening agent and CTBN toughening agent has an impact on the peel strength and impact resistance of the obtained epoxy adhesive. The peel strength and impact resistance of the epoxy adhesive will increase with the increase of the amount of bio-based toughening agent (Example 5), but when the amount is too high, the performance improvement effect of the epoxy adhesive is limited or even decreased (Example 6); when the amount of CTBN added is too high, the various properties of the obtained epoxy adhesive will be significantly reduced (Example 4).

[0155] Compared with Example 2, Comparative Example 1 does not add a bio-based toughening agent, and the peel strength and impact resistance of the epoxy adhesive obtained are significantly lower than those of Example 2, indicating that the bio-based toughening agent of the present invention can significantly improve the comprehensive properties of the epoxy adhesive, such as the peel strength and impact resistance.

[0156] Comparative Example 2 Compared with Example 2, the polyurethane prepolymer and cardanol were not reacted and were directly added to the adhesive component. The peel strength and impact resistance of the obtained epoxy adhesive were lower than those of Example 2. Comparative Examples 3 and 4 respectively replaced the bio-based toughening agent in Example 2 with an equal amount of polyurethane prepolymer. The peel strength and impact resistance of the obtained epoxy adhesive were significantly lower than those of Example 2, indicating that the bio-based toughening agent prepared by the three-component reaction of castor oil, polyisocyanate and cardanol in the present invention can synergistically improve the peel strength and impact resistance of the epoxy adhesive.

[0157] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A bio-based toughening agent, characterized in that: Obtained by the reaction of polyurethane prepolymer and cardanol; The polyurethane prepolymer is obtained by reacting castor oil with polyisocyanate; The molar ratio of the isocyanate group in the polyurethane prepolymer to the phenolic hydroxyl group in the cardanol is 1:1-2; The molar ratio of the hydroxyl group in the castor oil to the isocyanate group in the polyisocyanate is 1:1-3.

2. The bio-based toughening agent according to claim 1, characterized in that The molar ratio of the isocyanate group in the polyurethane prepolymer to the phenolic hydroxyl group in the cardanol is 1:1.1-1.5; the molar ratio of the hydroxyl group in the castor oil to the isocyanate group in the polyisocyanate is 1:1.2-2.

5.

3. The bio-based toughening agent according to claim 2, characterized in that: The molar ratio of the isocyanate group in the polyurethane prepolymer to the phenolic hydroxyl group in the cardanol is 1:1.2-1.3; the molar ratio of the hydroxyl group in the castor oil to the isocyanate group in the polyisocyanate is 1:1.8-2.

2.

4. The bio-based toughening agent according to claim 3, characterized in that: The molar ratio of the isocyanate groups in the polyurethane prepolymer to the phenolic hydroxyl groups in the cardanol is 1:1.2; the molar ratio of the hydroxyl groups in the castor oil to the isocyanate groups in the polyisocyanate is 1:

2.

5. The bio-based toughening agent according to any one of claims 1 to 4, characterized in that The polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

6. A method for preparing the bio-based toughening agent according to any one of claims 1 to 5, characterized in that: The steps include: (1) reacting the castor oil and polyisocyanate at a temperature of 60° C. to 100° C. for 2 to 8 hours to obtain the polyurethane prepolymer; (2) reacting the polyurethane prepolymer and cardanol at a temperature of 50° C. to 80° C. for 2 to 8 hours to obtain the bio-based toughening agent.

7. An epoxy adhesive, characterized in that: A toughening agent is added thereto, and the toughening agent comprises the bio-based toughening agent according to any one of claims 1 to 5, and the weight proportion of the bio-based toughening agent in the epoxy adhesive is preferably 5-25%, more preferably 10-20%, more preferably 13-20%, and more preferably 14-16%.

8. The epoxy adhesive according to claim 7, characterized in that: The composition is prepared from the following raw materials in parts by weight: Preferably, the epoxy adhesive is prepared from raw materials including the following components in parts by weight: Preferably, the epoxy adhesive is prepared from raw materials including the following components in parts by weight: Preferably, the epoxy adhesive is prepared from raw materials including the following components in parts by weight:

9. The epoxy adhesive according to claim 8, characterized in that: The epoxy resin is one or more of a glycidyl ether epoxy resin and a glycidyl ester epoxy resin; and / or, The universal toughening agent is one or more of CTBN toughening agent, core-shell rubber, and polyurethane modified epoxy resin; and / or, The curing agent is one or more of imidazole, dicyandiamide, acid anhydride and pyridine; and / or, The accelerator is one or more of imidazole, pyridine and organic urea.

10. A method for preparing the epoxy adhesive according to claim 8 or 9, characterized in that: The method comprises the following steps: uniformly mixing the epoxy resin, bio-based toughening agent, universal toughening agent, curing agent and accelerator at a temperature of 50-70°C, and cooling the mixture to room temperature to obtain the epoxy adhesive.

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