Modified epoxidized soybean oil, epoxy resin adhesive and its preparation method

Abstract

This invention discloses a modified epoxidized soybean oil, an epoxy resin adhesive, and their preparation method. The modified epoxidized soybean oil is obtained by reacting a cyclodextrin-epoxidized soybean oil inclusion complex with citric acid. The cyclodextrin-epoxidized soybean oil inclusion complex is obtained by reacting cyclodextrin with epoxidized soybean oil. The epoxy resin adhesive is prepared from bisphenol A type epoxy resin, modified epoxidized soybean oil, an anhydride curing agent, and a curing accelerator. This invention, by adding modified epoxidized soybean oil to the epoxy resin adhesive, results in improved tensile strength, elongation at break, impact strength, and low-temperature impact strength, demonstrating a significant toughening effect.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and more specifically, this invention relates to a modified epoxidized soybean oil, an epoxy resin adhesive, and a method for preparing the same. Background Technology

[0002] Epoxy resin adhesives are widely used in electronic device sealing, structural component bonding, coatings, and composite materials due to their excellent mechanical properties, electrical insulation, adhesion, and chemical stability. However, because epoxy resin adhesives have high cohesive strength and rigidity after curing, they are hard and brittle, and have poor resistance to aging, impact, and high and low temperatures, which seriously affects their service life and operating environment.

[0003] To address the aforementioned problems with epoxy resin adhesives, toughening agents are often introduced. In recent years, biomass raw materials, represented by epoxidized soybean oil, have attracted attention from academia and industry due to their low cost, wide availability, simple processing, environmental friendliness, high transparency, and good chemical and thermal stability. They have become important toughening modifiers for thermosetting resins. Introducing epoxidized soybean oil into epoxy resins allows its flexible long branches to be grafted onto the epoxy resin adhesive via epoxy groups, which can improve the fracture toughness of rigid resin adhesives to some extent. However, its toughening effect on epoxy resin adhesives is still not ideal. Summary of the Invention

[0004] Therefore, the purpose of this invention is to improve the toughness of epoxy resin adhesive and enhance its impact resistance.

[0005] The specific technical solutions for achieving the above-mentioned objectives are as follows.

[0006] In a first aspect, the present invention provides a modified epoxidized soybean oil, which is obtained by reacting a cyclodextrin-epoxidized soybean oil inclusion complex with citric acid, wherein the cyclodextrin-epoxidized soybean oil inclusion complex is obtained by reacting cyclodextrin with epoxidized soybean oil.

[0007] A second aspect of the present invention provides a method for preparing the above-mentioned modified epoxidized soybean oil, comprising the following steps:

[0008] (1) Cyclodextrin and epoxidized soybean oil were stirred and reacted at 65℃~75℃ for 0.5h~1.5h to obtain cyclodextrin-epoxidized soybean oil inclusion complex;

[0009] (2) The cyclodextrin-epoxidized soybean oil inclusion complex and citric acid were reacted at 65℃~75℃ for 2h~4h;

[0010] (3) Add N,N-dimethylbenzylamine (BDMA) and react under vacuum at 75℃~85℃ for 0.5h~1.5h to obtain the product.

[0011] A third aspect of the present invention provides an epoxy resin adhesive, which is prepared from the following raw materials in parts by weight:

[0012]

[0013] In a fourth aspect, the present invention provides a method for preparing the above-mentioned epoxy resin adhesive, comprising the following steps: mixing bisphenol A type epoxy resin, modified epoxy soybean oil, an anhydride curing agent, and a curing accelerator; stirring under vacuum at a dispersion rate of 200 rpm to 300 rpm for 5 min to 20 min at 25°C to 35°C; and curing at 95°C to 105°C for 2.5 h to 3.5 h to obtain the adhesive.

[0014] This invention first prepares a modified epoxidized soybean oil using cyclodextrin, citric acid, and epoxidized soybean oil in a specific molar ratio as reactants. Then, by adding this modified epoxidized soybean oil to an epoxy resin system, a high-toughness epoxy resin adhesive is prepared. On one hand, the hydrophilic outer end and hydrophobic inner end properties of cyclodextrin, along with the carboxyl groups introduced by citric acid, synergistically improve the compatibility of epoxidized soybean oil in the epoxy resin system. This allows the flexible long branches in the modified epoxidized soybean oil to effectively reduce the brittleness of the epoxy resin, enhance its fracture toughness, and give it higher mechanical properties and ductility. On the other hand, cyclodextrin forms polyrotaxane in the modified epoxidized soybean oil. During curing, the hydroxyl groups on the cyclodextrin can graft onto the epoxy resin crosslinking network, forming a slip ring crosslinking network structure. This structure allows cyclodextrin molecules to slide and rotate on the chain segments. When subjected to external stress, the sliding and rotating of the slip rings can drive the activity of the slip ring polymer network, thereby achieving energy dissipation and further toughening the epoxy resin adhesive. Therefore, the modified epoxidized soybean oil obtained by synergistic modification of epoxidized soybean oil with cyclodextrin and citric acid can significantly improve the toughness of epoxy resin adhesive. Compared with epoxy resin adhesive prepared using unmodified epoxidized soybean oil, the epoxy resin adhesive prepared using the modified epoxidized soybean oil of the present invention has significantly improved elongation at break, impact strength and impact strength.

[0015] The modified epoxidized soybean oil formulation involved in this invention incorporates cyclodextrin. Its functions are twofold: firstly, it utilizes the hydrophilic outer end and hydrophobic inner end of cyclodextrin to increase the solubility of epoxidized soybean oil in highly polar systems; secondly, during the cross-linking and curing process, the hydroxyl groups on the cyclodextrin can graft onto the epoxy resin cross-linking network, forming a slip ring cross-linking network, thus increasing the degree of cross-linking and imparting higher fracture toughness to the cross-linking network. The cross-linking of organic acids with epoxidized soybean oil introduces carboxyl groups to increase the polarity of the epoxidized soybean oil and also thickens it, further improving the compatibility between epoxidized soybean oil and epoxy resin. The high-toughness epoxy resin adhesive prepared with modified epoxidized soybean oil benefits from the free carboxyl and hydroxyl groups in the modified epoxidized soybean oil, which promote the curing of the epoxy resin. Cyclodextrin forms mechanically interlocked structures such as rotaxanes and hydroxyl groups within the polymer network, enhancing the gelation and mechanical strength of the bulk. Furthermore, the sliding and rotation of cyclodextrin molecules on the chain segments drives the activity of the slip ring polymer network, giving it a unique stress absorption and release mechanism, achieving the toughening purpose.

[0016] Furthermore, the slip ring crosslinking network formed by the grafting of hydroxyl groups from cyclodextrin into the epoxy resin crosslinking network during the crosslinking curing process can increase the crosslinking density of the epoxy resin. The mechanically interlocking structures such as rotaxanes and hydroxyl groups formed by cyclodextrin within the polymer network can also enhance the gelation of the epoxy resin matrix. The free carboxyl and hydroxyl groups introduced into the modified epoxidized soybean oil promote the curing of the epoxy resin. Under the synergistic effect of these factors, the modified epoxidized soybean oil of this invention can significantly improve the mechanical strength of the resulting epoxy resin matrix. Compared with epoxy resin matrix prepared using unmodified epoxidized soybean oil, the tensile strength of the epoxy resin matrix prepared using the modified epoxidized soybean oil of this invention is also significantly improved.

[0017] The raw materials used in this invention to prepare modified epoxidized soybean oil are all biomass materials, which are low in cost, high in yield, and environmentally friendly. The preparation process is simple, pollution-free, and has a high yield. Attached Figure Description

[0018] Figure 1 The infrared absorption (FTIR) spectra of epoxidized soybean oil, CD1-ESO10-CA30 prepared in Example 1, CD2-ESO10-CA30 prepared in Example 2, CD5-ESO10-CA30 prepared in Example 3, CD1-ESO10-CA60 prepared in Example 4, CD2-ESO10-CA60 prepared in Example 5, and CD5-ESO10-CA60 prepared in Example 6. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more complete description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0021] In some embodiments of the present invention, a modified epoxidized soybean oil is disclosed, which is obtained by reacting a cyclodextrin-epoxidized soybean oil inclusion complex with citric acid, wherein the cyclodextrin-epoxidized soybean oil inclusion complex is obtained by reacting cyclodextrin with epoxidized soybean oil.

[0022] In some of these embodiments, the cyclodextrin is β-cyclodextrin.

[0023] In some embodiments, the molar ratio of cyclodextrin, epoxidized soybean oil and citric acid is 0.1-0.5:1:3-9, preferably 0.1-0.5:1:3-6, and more preferably 0.2-0.5:1:3-6.

[0024] In other embodiments of the present invention, a method for preparing the above-mentioned modified epoxidized soybean oil is disclosed, comprising the following steps:

[0025] (1) Cyclodextrin and epoxidized soybean oil were reacted at 65℃~75℃ for 0.5h~1.5h to obtain cyclodextrin-epoxidized soybean oil inclusion complex;

[0026] (2) The cyclodextrin-epoxidized soybean oil inclusion complex and citric acid were reacted at 65℃~75℃ for 2h~4h;

[0027] (3) Add N,N-dimethylbenzylamine (BDMA) and react under vacuum at 75℃~85℃ for 0.5h~1.5h to obtain the product.

[0028] In some embodiments, the reactions in steps (1) and (2) are carried out in the presence of water.

[0029] In some embodiments, the ratio of water to cyclodextrin in step (1) is 1 mL: 2 g to 12 g.

[0030] In some embodiments, the ratio of water to cyclodextrin in step (1) is 1 mL: 2.26 g to 11.3 g.

[0031] In some embodiments, the ratio of water to citric acid in step (2) is 1 mL: 3 g to 8 g.

[0032] In some embodiments, the ratio of water to citric acid in step (2) is 1 mL: 3.84 g to 7.68 g.

[0033] In some embodiments, the preparation method of the modified epoxidized soybean oil includes the following steps:

[0034] (1) Cyclodextrin and water were stirred evenly at 65℃~75℃, and then epoxidized soybean oil was added. The mixture was reacted at 65℃~75℃ for 0.5h~1.5h to remove water and obtain cyclodextrin-epoxidized soybean oil inclusion complex.

[0035] (2) The cyclodextrin-epoxidized soybean oil inclusion complex, water and citric acid are reacted at 65℃~75℃ for 2h~4h to remove water;

[0036] (3) Add N,N-dimethylbenzylamine and react under vacuum at 75℃~85℃ for 0.5h~1.5h to obtain the product.

[0037] In some embodiments, the temperature of the reaction in step (1) is 68°C to 72°C, more preferably 69°C to 71°C; and / or the reaction time is 0.8h to 1.2h, more preferably 0.9h to 1.1h.

[0038] In some embodiments, the temperature of the reaction in step (2) is 68°C to 72°C, more preferably 69°C to 71°C; and / or the reaction time is 2.5h to 3.5h, more preferably 2.8h to 3.2h.

[0039] In some embodiments, the temperature of the reaction in step (3) is 78°C to 82°C, more preferably 79°C to 81°C.

[0040] In some embodiments, the reaction time in step (3) is 0.8h to 1.2h.

[0041] In some embodiments, the reaction time in step (3) is 0.9 h to 1.1 h;

[0042] In some embodiments, the vacuum degree of the vacuum in step (3) is -0.08MPa to -0.10MPa.

[0043] In some embodiments, the vacuum degree of the vacuum in step (3) is -0.085MPa to -0.095MPa.

[0044] In other embodiments of the present invention, the application of the above-mentioned modified epoxidized soybean oil as a toughening agent in the preparation of epoxy resin adhesives is disclosed.

[0045] In other embodiments of the present invention, an epoxy resin adhesive is disclosed, which is prepared from the following raw materials in parts by weight:

[0046]

[0047] In some embodiments, the epoxy resin adhesive is prepared from the following raw materials in parts by weight:

[0048]

[0049]

[0050] In some embodiments, the epoxy resin adhesive is prepared from the following raw materials in parts by weight:

[0051]

[0052] In some embodiments, the bisphenol A type epoxy resin is one or more of E51, E54, and E44, preferably E51.

[0053] In some embodiments, the anhydride curing agent is one or more of methyltetrahydrophthalic anhydride, maleic anhydride, and phthalic anhydride, preferably methyltetrahydrophthalic anhydride.

[0054] In some embodiments, the curing accelerator is one or more of dimethylbenzylamine, dodecyl ammonium bromide, and DMP-30, preferably DMP-30.

[0055] In other embodiments of the present invention, a method for preparing the above-mentioned epoxy resin adhesive is disclosed, comprising the following steps: mixing bisphenol A type epoxy resin, modified epoxy soybean oil, acid anhydride curing agent, and curing accelerator; stirring under vacuum at a dispersion rate of 200 rpm to 300 rpm for 5 min to 20 min at 25°C to 35°C; and then curing at 95°C to 105°C for 2.5 h to 3.5 h.

[0056] In some embodiments, the vacuum degree is -0.08MPa to -0.10MPa, more preferably -0.085MPa to -0.095MPa.

[0057] Unless otherwise specified, all examples were conducted under standard experimental conditions or according to the conditions recommended in the manufacturer's instructions. The sources of the epoxidized soybean oil, β-cyclodextrin, citric acid, N,N-dimethylbenzylamine, bisphenol A epoxy resin, curing agent, and curing accelerator described in this invention are not particularly limited; commercially available products well-known to those skilled in the art can be used. All raw materials used in the following examples of this invention are commercially available products.

[0058] In the following examples, modified epoxidized soybean oil was prepared using epoxidized soybean oil, β-cyclodextrin, and citric acid as reactants. The reaction process and principle are as follows:

[0059]

[0060] First, epoxidized soybean oil and β-cyclodextrin react to form an inclusion complex of epoxidized soybean oil encapsulated by β-cyclodextrin. This inclusion complex then undergoes a stepwise reaction with citric acid. The carboxyl groups in the citric acid first undergo a ring-opening cross-linking reaction with the epoxy groups in the epoxidized soybean oil molecules to form a cross-linked network. Then, under the action of N,N-dimethylbenzylamine, the carboxyl groups in the citric acid can further undergo an esterification reaction with the hydroxyl groups on the β-cyclodextrin, thereby grafting more citric acid onto the inclusion complex, resulting in a higher concentration of carboxyl groups. A schematic diagram of the resulting modified epoxidized soybean oil is shown below:

[0061]

[0062] Wherein, R1 represents a group containing epoxidized soybean oil residues and citric acid residues formed by cross-linking an epoxidized soybean oil molecule with another epoxidized soybean oil molecule through citric acid, and R2 represents a group grafted onto cyclodextrin by citric acid through an esterification reaction.

[0063] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] Example 1: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0065] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0066] Weigh 11.3 g (10 mmol) of β-cyclodextrin into a 250 mL round-bottom flask, add 5 mL of deionized water, stir at 70 °C for 15 min, add 100 g (100 mmol) of epoxidized soybean oil, stir at 70 °C for 1 h, and obtain a white emulsion. Remove water by vacuum distillation and dry under vacuum to obtain the cyclodextrin-epoxidized soybean oil inclusion complex CD1-ESO10.

[0067] 2. Preparation of modified epoxidized soybean oil

[0068] 57.6 g (300 mmol) of citric acid was weighed into a 250 mL round-bottom flask, and 15 mL of deionized water and 111.3 g of cyclodextrin-epoxidized soybean oil CD1-ESO10 were added. The reaction was carried out at 70 °C for 3 h. Water was removed by vacuum distillation. 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA) was added, and the reaction was carried out at 80 °C for 1 h under a vacuum of -0.09 MPa. After the reaction, excess citric acid was washed away with water, and the mixture was dried under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil CD1-ESO10-CA30.

[0069] The modified epoxidized soybean oil prepared by the preparation is added to the epoxy resin system to prepare an epoxy resin adhesive, including the following steps:

[0070] 40g of bisphenol A type epoxy resin E51, 10g of modified epoxy soybean oil CD1-ESO10-CA30, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0071] Example 2: Preparation of modified epoxy soybean oil and epoxy resin adhesive

[0072] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0073] Weigh 22.6 g (20 mmol) of β-cyclodextrin into a 250 mL round-bottom flask, add 5 mL of deionized water, stir at 70 °C for 15 min, add 100 g (100 mmol) of epoxidized soybean oil, stir at 70 °C for 1 h, and obtain a white emulsion. Remove water by vacuum distillation and dry under vacuum to obtain the cyclodextrin-epoxidized soybean oil inclusion complex CD2-ESO10.

[0074] 2. Preparation of modified epoxidized soybean oil

[0075] 57.6 g (300 mmol) of citric acid was weighed into a 250 mL round-bottom flask, and 15 mL of deionized water and 122.6 g of cyclodextrin-epoxidized soybean oil CD2-ESO10 were added. The reaction was carried out at 70 °C for 3 h. Water was removed by vacuum distillation. 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA) was added, and the reaction was carried out at 80 °C for 1 h under a vacuum of -0.09 MPa. After the reaction was completed, excess citric acid was washed away with water, and the mixture was dried under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil CD2-ESO10-CA30.

[0076] 3. Preparation of epoxy resin adhesive

[0077] 40g of bisphenol A type epoxy resin E51, 10g of modified epoxy soybean oil CD2-ESO10-CA30, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0078] Example 3: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0079] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0080] Weigh 56.5 g (50 mmol) of β-cyclodextrin into a 250 mL round-bottom flask, add 5 mL of deionized water, stir at 70 °C for 15 min, add 100 g (100 mmol) of epoxidized soybean oil, stir at 70 °C for 1 h, and obtain a white emulsion. Remove water by vacuum distillation and dry under vacuum to obtain the cyclodextrin-epoxidized soybean oil inclusion complex CD5-ESO10.

[0081] 2. Preparation of modified epoxidized soybean oil

[0082] Weigh 57.6 g (300 mmol) of citric acid into a 250 mL round-bottom flask, add 15 mL of deionized water and 156.5 g of cyclodextrin-epoxidized soybean oil CD5-ESO10, and react at 70 °C for 3 h. Remove water by vacuum distillation. Add 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA), and react at -0.09 MPa at 80 °C for 1 h. After the reaction, wash away excess citric acid with water, and dry under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil CD5-ESO10-CA30.

[0083] 3. Preparation of epoxy resin adhesive

[0084] 40g of bisphenol A type epoxy resin E51, 10g of modified epoxy soybean oil CD5-ESO10-CA30, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0085] Example 4: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0086] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0087] Weigh 11.3 g (10 mmol) of β-cyclodextrin into a 250 mL round-bottom flask, add 5 mL of deionized water, stir at 70 °C for 15 min, add 100 g (100 mmol) of epoxidized soybean oil, stir at 70 °C for 1 h, and obtain a white emulsion. Remove water by vacuum distillation and dry under vacuum to obtain the cyclodextrin-epoxidized soybean oil inclusion complex CD1-ESO10.

[0088] 2. Preparation of modified epoxidized soybean oil

[0089] 115.2 g (600 mmol) of citric acid was weighed into a 250 mL round-bottom flask, and 15 mL of deionized water and 111.3 g of cyclodextrin-epoxidized soybean oil CD1-ESO10 were added. The reaction was carried out at 70 °C for 3 h. Water was removed by vacuum distillation. 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA) was added, and the reaction was carried out at 80 °C for 1 h under a vacuum of -0.09 MPa. After the reaction was completed, excess citric acid was washed away with water, and the mixture was dried under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil CD1-ESO10-CA60.

[0090] 3. Preparation of epoxy resin adhesive

[0091] 40g of bisphenol A type epoxy resin E51, 10g of modified epoxy soybean oil CD1-ESO10-CA60, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0092] Example 5: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0093] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0094] Weigh 22.6 g (20 mmol) of β-cyclodextrin into a 250 mL round-bottom flask, add 5 mL of deionized water, stir at 70 °C for 15 min, add 100 g (100 mmol) of epoxidized soybean oil, stir at 70 °C for 1 h, and obtain a white emulsion. Remove water by vacuum distillation and dry under vacuum to obtain the cyclodextrin-epoxidized soybean oil inclusion complex CD2-ESO10.

[0095] 2. Preparation of modified epoxidized soybean oil

[0096] 115.2 g (600 mmol) of citric acid was weighed into a 250 mL round-bottom flask, and 15 mL of deionized water and 122.6 g of cyclodextrin-epoxidized soybean oil CD2-ESO10 were added. The reaction was carried out at 70 °C for 3 h. Water was removed by vacuum distillation. 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA) was added, and the reaction was carried out at 80 °C for 1 h under a vacuum of -0.09 MPa. After the reaction was completed, excess citric acid was washed away with water, and the mixture was dried under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil CD2-ESO10-CA60.

[0097] 3. Preparation of epoxy resin adhesive

[0098] 40g of bisphenol A type epoxy resin E51, 10g of modified epoxy soybean oil CD2-ESO10-CA60, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0099] Example 6: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0100] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0101] Weigh 56.5 g (50 mmol) of β-cyclodextrin into a 250 mL round-bottom flask, add 5 mL of deionized water, stir at 70 °C for 15 min, add 100 g (100 mmol) of epoxidized soybean oil, stir at 70 °C for 1 h, and obtain a white emulsion. Remove water by vacuum distillation and dry under vacuum to obtain the cyclodextrin-epoxidized soybean oil inclusion complex CD5-ESO10.

[0102] 2. Preparation of modified epoxidized soybean oil

[0103] 115.2 g (600 mmol) of citric acid was weighed into a 250 mL round-bottom flask, and 15 mL of deionized water and 156.5 g of cyclodextrin-epoxidized soybean oil CD5-ESO10 were added. The reaction was carried out at 70 °C for 3 h. Water was removed by vacuum distillation. 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA) was added, and the reaction was carried out at 80 °C for 1 h under a vacuum of -0.09 MPa. After the reaction was completed, excess citric acid was washed away with water, and the mixture was dried under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil CD5-ESO10-CA60.

[0104] 3. Preparation of epoxy resin adhesive

[0105] 40g of bisphenol A type epoxy resin E51, 10g of modified epoxy soybean oil CD5-ESO10-CA60, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0106] Example 7: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0107] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0108] Same as Example 1.

[0109] 2. Preparation of modified epoxidized soybean oil

[0110] Same as Example 1.

[0111] 3. Preparation of epoxy resin adhesive

[0112] 35g of bisphenol A type epoxy resin E51, 15g of modified epoxy soybean oil CD1-ESO10-CA30, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0113] Example 8: Preparation of modified epoxidized soybean oil and epoxy resin adhesive

[0114] 1. Synthesis of cyclodextrin-epoxidized soybean oil inclusion complex

[0115] Same as Example 1.

[0116] 2. Preparation of modified epoxidized soybean oil

[0117] Same as Example 1.

[0118] 3. Preparation of epoxy resin adhesive

[0119] 40g of bisphenol A type epoxy resin E51, 15g of modified epoxy soybean oil CD1-ESO10-CA30, 44.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0120] Comparative Example 1: Preparation of Epoxy Resin Adhesive

[0121] 50g of bisphenol A type epoxy resin E51, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0122] Comparative Example 2: Preparation of Epoxy Resin Adhesive

[0123] 55g of bisphenol A type epoxy resin E51, 44.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0124] Preparation of epoxy resin adhesive in Comparative Example 3

[0125] 40g of bisphenol A type epoxy resin E51, 10g of epoxidized soybean oil, 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0126] Comparative Example 4: Preparation of Epoxy Resin Adhesive

[0127] 45g of bisphenol A type epoxy resin E51, 10g of epoxidized soybean oil, 44.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0128] Comparative Example 5

[0129] 40g of bisphenol A type epoxy resin E51, 10g of cyclodextrin-epoxy soybean oil inclusion complex (prepared by the same method as in Example 1), 49.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0130] Comparative Example 6

[0131] 1. Preparation of modified epoxidized soybean oil

[0132] 57.6 g (300 mmol) of citric acid was weighed into a 250 mL round-bottom flask, and 15 mL of deionized water and 100 g (100 mmol) of epoxidized soybean oil were added. The reaction was carried out at 70 °C for 3 h. Water was removed by vacuum distillation. 0.675 g (5 mmol) of N,N-dimethylbenzylamine (BDMA) was added, and the reaction was carried out at 80 °C for 1 h under a vacuum of -0.09 MPa. After the reaction was completed, excess citric acid was washed away with water, and the mixture was dried under vacuum at 40 °C for 24 h to obtain modified epoxidized soybean oil ESO10-CA30.

[0133] 2. Preparation of epoxy resin adhesive

[0134] 40g of bisphenol A type epoxy resin E51, 15g of modified epoxy soybean oil ESO10-CA30, 44.5g of methyltetrahydrophthalic anhydride, and 0.5g of DMP-30 were mixed in a sample container and stirred at 200rpm for 15min under a vacuum of -0.09MPa at 30℃ in a high-speed disperser. After uniform mixing, the mixture was coated into a polytetrafluoroethylene mold and cured at 100℃ for 3h to obtain the final product.

[0135] Figure 1 The Fourier Transform Infrared (FTIR) spectra of unmodified epoxidized soybean oil, CD1-ESO10-CA30 prepared in Example 1, CD2-ESO10-CA30 prepared in Example 2, CD5-ESO10-CA30 prepared in Example 3, CD1-ESO10-CA60 prepared in Example 4, CD2-ESO10-CA60 prepared in Example 5, and CD5-ESO10-CA60 prepared in Example 6. Figure 1 It can be seen that as the citric acid content in modified epoxidized soybean oil increases, the 1740cm... -1 The ester peak at 1460 cm⁻¹ gradually broadens into a shoulder peak. -1 The CH bending vibration peak also gradually changed from a sharp peak to a basal peak, indicating that the epoxy groups in epoxidized soybean oil undergo ring-opening under the action of citric acid, increasing the degree of polymerization of the system. (1025 cm⁻¹) -1 The peak intensity gradually increases, which is due to the hydroxyl groups generated by the ring-opening of epoxidized soybean oil and the hydroxyl groups of cyclodextrin.

[0136] Table 1 shows the component selection and proportions for the examples and comparative examples. The epoxy resin adhesives for each example and comparative example were subjected to the following performance tests (curing conditions: 80℃, 6h):

[0137] 1. Tensile strength and elongation at break: GB / T 528-2009, Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0138] 2. Impact strength: GB / T 2567-2008, Test method for performance of resin castings.

[0139] The test results are shown in Table 2.

[0140] Table 1

[0141]

[0142] Note: The parts by weight are the components used in Table 1. In Comparative Example 5, a represents cyclodextrin-epoxidized soybean oil inclusion complex (CD1-ESO10), and in Comparative Example 6, b represents citric acid-modified epoxidized soybean oil (ESO10-CA30).

[0143] Table 2

[0144]

[0145]

[0146] As shown in Table 2, compared with epoxy resin adhesives prepared without epoxidized soybean oil (Comparative Examples 1-2), epoxy resin adhesives prepared with epoxidized soybean oil (Comparative Examples 3-4) showed improvements in tensile strength, elongation at break, and impact strength at both room temperature and low temperature. Compared with epoxy resin adhesives prepared with unmodified epoxidized soybean oil (Comparative Examples 3-4), epoxy resin adhesives prepared with cyclodextrin-modified epoxidized soybean oil (Comparative Example 5) showed no significant improvement in mechanical properties, while epoxy resin adhesives prepared with citric acid-modified epoxidized soybean oil (Comparative Example 6) showed improvements in both mechanical and tensile properties. Epoxy resin adhesives prepared with the modified epoxidized soybean oil of this invention exhibited significantly better tensile strength, elongation at break, impact strength, and low-temperature impact strength (Examples 1-8), indicating that the synergistic modification of epoxidized soybean oil by cyclodextrin and citric acid significantly toughens the epoxy resin adhesive and also significantly improves its mechanical and tensile properties.

[0147] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A modified epoxidized soybean oil, characterized in that, The preparation method of the modified epoxidized soybean oil includes the following steps: (1) Cyclodextrin and epoxidized soybean oil were reacted at 65℃~75℃ for 0.5 h~1.5 h to obtain cyclodextrin-epoxidized soybean oil inclusion complex; (2) The cyclodextrin-epoxidized soybean oil inclusion complex and citric acid were reacted at 65℃~75℃ for 2 h~4 h; (3) Add N,N-dimethylbenzylamine and react under vacuum at 75℃~85℃ for 0.5 h~1.5 h to obtain the product; The molar ratio of cyclodextrin, epoxidized soybean oil and citric acid is 0.1~0.5:1:3~9.

2. The modified epoxidized soybean oil according to claim 1, characterized in that, The cyclodextrin is β-cyclodextrin.

3. The modified epoxidized soybean oil according to claim 1, characterized in that, The molar ratio of cyclodextrin, epoxidized soybean oil and citric acid is 0.1~0.5:1:3~6.

4. The modified epoxidized soybean oil according to claim 3, characterized in that, The molar ratio of cyclodextrin, epoxidized soybean oil and citric acid is 0.2~0.5:1:3~6.

5. A method for preparing modified epoxidized soybean oil according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Cyclodextrin and epoxidized soybean oil were reacted at 65℃~75℃ for 0.5 h~1.5 h to obtain cyclodextrin-epoxidized soybean oil inclusion complex; (2) The cyclodextrin-epoxidized soybean oil inclusion complex and citric acid were reacted at 65℃~75℃ for 2 h~4 h; (3) Add N,N-dimethylbenzylamine and react under vacuum at 75℃~85℃ for 0.5 h~1.5 h to obtain the product.

6. The method for preparing modified epoxidized soybean oil according to claim 5, characterized in that, The reactions in steps (1) and (2) are carried out in the presence of water; in step (1), the ratio of water to cyclodextrin is 1 mL: 2 g to 12 g; in step (2), the ratio of water to citric acid is 1 mL: 3 g to 8 g.

7. The method for preparing modified epoxidized soybean oil according to claim 6, characterized in that, In step (1), the ratio of water to cyclodextrin is 1 mL: 2.26 g~11.3 g, and in step (2), the ratio of water to citric acid is 1 mL: 3.84 g~7.68 g.

8. The method for preparing modified epoxidized soybean oil according to claim 5, characterized in that, Includes the following steps: (1) Stir cyclodextrin and water at 65℃~75℃ until homogeneous, then add epoxidized soybean oil and react at 65℃~75℃ for 0.5 h~1.5 h to remove water and obtain cyclodextrin-epoxidized soybean oil inclusion complex. (2) The cyclodextrin-epoxidized soybean oil inclusion complex, water and citric acid were reacted at 65℃~75℃ for 2 h~4 h to remove water; (3) Add N,N-dimethylbenzylamine and react under vacuum at 75℃~85℃ for 0.5 h~1.5 h to obtain the product.

9. The method for preparing modified epoxidized soybean oil according to claim 8, characterized in that, The reaction temperature in step (1) is 68℃~72℃; the reaction time is 0.8 h~1.2 h; And / or, the temperature of the reaction in step (2) is 68℃~72℃; the reaction time is 2.5 h~3.5 h; And / or, the temperature of the reaction in step (3) is 78℃~82℃; the reaction time is 0.8 h~1.2 h; And / or, the vacuum degree of the vacuum in step (3) is -0.08 MPa to -0.10 MPa.

10. The method for preparing modified epoxidized soybean oil according to claim 9, characterized in that, The reaction temperature in step (1) is 69℃~71℃; the reaction time is 0.9 h~1.1 h; And / or, the temperature of the reaction in step (2) is 69℃~71℃; the reaction time is 2.8 h~3.2 h; And / or, the temperature of the reaction in step (3) is 79℃~81℃; the reaction time is 0.9 h~1.1 h; And / or, the vacuum degree of the vacuum in step (3) is -0.085 MPa to -0.095 MPa.

11. The use of the modified epoxidized soybean oil according to any one of claims 1 to 4 as a toughening agent in the preparation of epoxy resin adhesives.

12. An epoxy resin adhesive, characterized in that, It is prepared from the following raw materials in parts by weight: 30-55 parts of bisphenol A type epoxy resin 5 to 15 parts of the modified epoxidized soybean oil according to any one of claims 1 to 4 30-55 parts of anhydride curing agent Curing accelerator: 0.1 to 1 part.

13. The epoxy resin adhesive according to claim 12, characterized in that, It is prepared from the following raw materials in parts by weight: 35-45 parts of bisphenol A type epoxy resin 8 to 15 parts of the modified epoxidized soybean oil according to any one of claims 1 to 4 40-50 parts of anhydride curing agent Curing accelerator: 0.2 to 0.8 parts.

14. The epoxy resin adhesive according to claim 13, characterized in that, It is prepared from the following raw materials in parts by weight: 35-40 parts of bisphenol A type epoxy resin 10 to 15 parts of the modified epoxidized soybean oil according to any one of claims 1 to 4 40-50 parts of anhydride curing agent Curing accelerator: 0.4 to 0.6 parts.

15. The epoxy resin adhesive according to any one of claims 12 to 14, characterized in that, The bisphenol A type epoxy resin is one or more of E51, E54, and E44; And / or, the anhydride curing agent is one or more of methyltetrahydrophthalic anhydride, maleic anhydride, and phthalic anhydride; And / or, the curing accelerator is one or more of dimethylbenzylamine, dodecyl ammonium bromide, and DMP-30.

16. The epoxy resin adhesive according to claim 15, characterized in that, The bisphenol A type epoxy resin is E51; the acid anhydride curing agent is methyltetrahydrophthalic anhydride; and the curing accelerator is DMP-30.

17. A method for preparing an epoxy resin adhesive according to any one of claims 12-16, characterized in that, Includes the following steps: Bisphenol A type epoxy resin, modified epoxy soybean oil, acid anhydride curing agent, and curing accelerator are mixed and stirred under vacuum at a dispersion rate of 200 rpm to 300 rpm for 5 min to 20 min at 25 ℃ to 35 ℃. Then, the mixture is cured at 95 ℃ to 105 ℃ for 2.5 h to 3.5 h to obtain the final product.

Images