Toughening agent, toughened epoxy resin adhesive as well as preparation method and application of toughening agent and toughened epoxy resin adhesive

Abstract

The invention discloses a toughening agent, a toughened epoxy resin adhesive and a preparation method and application thereof. The toughening agent is obtained by carrying out esterification reaction on components including a phenolic compound containing a polyphenol skeleton and an anhydride compound containing a long-chain alkyl structure. The raw materials used by the toughening agent are bio-based molecules and have excellent renewability, the toughening agent is high in toughening efficiency, the impact strength of the epoxy resin adhesive can be effectively improved under the condition of low addition amount, and meanwhile, the bonding strength and the hydrothermal durability of the epoxy resin adhesive can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a toughening agent, a toughened epoxy resin adhesive, and a preparation method and application thereof. Background Art

[0002] Epoxy resin is a very important polymer material. Due to the three-dimensional network formed by thermal curing, it has excellent mechanical properties, and also has high transparency, low shrinkage and strong bonding properties. However, due to the highly cross-linked nature of epoxy resin itself, the cured product is relatively brittle and has poor impact resistance. In addition, for epoxy resin adhesives, during their service life, the bonded joints are often subjected to variable loads and harsh working environments. Therefore, strong interfacial bonding is very important to maintain the structural integrity of the bonded structure. Commonly used epoxy resin toughening agents tend to reduce the strength of the resin while improving the impact strength, and usually need to be added to about 10wt% to achieve a more stable toughening effect, without further strengthening the bonding performance. At the same time, the global principle and pursuit of sustainable development have led to people's growing interest in the use of bio-based sustainable raw materials in the synthesis of bio-based chemicals. Therefore, more and more research and inventions tend to be bio-based epoxy resin additives.

[0003] Therefore, based on the problems of high brittleness of epoxy resin and poor water resistance of joints, it is very necessary to synthesize a toughening agent that is compatible with the epoxy resin matrix and can comprehensively improve the toughness of the adhesive and the water durability of the bond. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a toughening agent, a toughened epoxy resin adhesive, and a preparation method and application thereof. The present invention utilizes economical reaction raw materials and a relatively simple synthesis process to prepare a bio-based toughening agent with a branched structure. The epoxy resin adhesive provided by the present invention adopts a bio-based toughening agent system, which has the advantage of being more environmentally friendly. In addition, due to the introduction of plant polyphenols, the bonding performance of the epoxy resin adhesive is greatly improved, and good bonding durability can be maintained in water; at the same time, the toughening agent has good compatibility in the epoxy resin matrix, has little effect on the curing and degassing process, and the adhesive has good transparency after curing; in terms of mechanical properties, the toughening agent of the present invention can greatly improve the impact strength without reducing the tensile strength of the epoxy resin.

[0005] One of the objectives of the present invention is to provide a toughening agent obtained by the esterification reaction of components including a phenolic compound containing a polyphenolic backbone and an acid anhydride compound containing a long-chain hydrocarbon structure. The toughening agent of the present invention is formed by the esterification reaction of phenolic hydroxyl groups and acid anhydride groups, and exists as a molecule with a rigid backbone and flexible multi-arm branches.

[0006] In a preferred embodiment of the present invention,

[0007] The phenolic compound containing a polyphenol skeleton is at least one of tannic acid, tea polyphenols, gallic acid, and ellagic acid, preferably at least one of tannic acid and tea polyphenols; and / or

[0008] The number of carbon atoms of the long-chain hydrocarbon structure in the acid anhydride compound containing a long-chain hydrocarbon structure is ≥6. Preferably, the acid anhydride compound containing a long-chain hydrocarbon structure is at least one of octenyl succinic anhydride, dodecenyl succinic anhydride, nonenyl succinic anhydride, decenyl succinic anhydride, and decyl succinic anhydride, and is preferably at least one of octenyl succinic anhydride and dodecenyl succinic anhydride.

[0009] In a preferred embodiment of the present invention,

[0010] The molar ratio of the acid compound containing a polyphenol skeleton to the acid anhydride compound containing a long-chain hydrocarbon structure is 1:(1-80), preferably 1:(1-50), and more preferably 1:(5-50); when the phenolic compound containing a polyphenol skeleton is tannic acid, the molar ratio of the tannic acid to the acid anhydride compound containing a long-chain hydrocarbon structure is preferably 1:(5-50), and more preferably 1:(25-50).

[0011] In a preferred embodiment of the present invention,

[0012] The conditions of the esterification reaction include: a temperature of 70-90° C., preferably 80-90° C.; and / or a time of 12-72 hours, preferably 24-48 hours; further, the esterification reaction temperature should not exceed 90° C., and an inert environment (such as nitrogen) should be maintained to avoid oxidation of the raw materials in the system; and / or,

[0013] The esterification reaction is carried out in a solvent; preferably, the solvent is at least one organic solvent, preferably at least one of dioxane, pyridine, and acetone; and / or, the amount of the solvent is 10-30 ml per 1 g of the acid anhydride compound containing a long-chain hydrocarbon structure.

[0014] Preferably, the preparation process of the toughening agent of the present invention comprises the following steps: mixing components including a phenolic compound containing a polyphenol skeleton and an acid anhydride compound containing a long-chain hydrocarbon structure, and subjecting the mixture to an esterification reaction, followed by rotary evaporation, washing, and drying to obtain the toughening agent.

[0015] A second object of the present invention is to provide a toughened epoxy resin adhesive comprising an epoxy resin, a curing agent and the toughening agent which is one of the objects of the present invention.

[0016] In a preferred embodiment of the present invention,

[0017] Based on 100 parts by weight of the epoxy resin, the curing agent is 5-50 parts by weight, and the toughening agent is 0.1-3 parts by weight; preferably, based on 100 parts by weight of the epoxy resin, the curing agent is 20-40 parts by weight, and the toughening agent is 0.2-2 parts by weight; more preferably, based on 100 parts by weight of the epoxy resin, the curing agent is 25-35 parts by weight, and the toughening agent is 0.5-1.5 parts by weight; further preferably, based on 100 parts by weight of the epoxy resin, the curing agent is 30-32 parts by weight, and the toughening agent is 0.66-1.31 parts by weight.

[0018] In a preferred embodiment of the present invention,

[0019] The epoxy resin is a conventional epoxy resin in the art, and in the present invention, preferably at least one of bisphenol A epoxy resin and bisphenol F epoxy resin; further, the epoxy equivalent of the epoxy resin is 0.45-0.55 mol / 100g; and / or,

[0020] The curing agent is a conventional curing agent in the art, and in the present invention, it is preferably at least one of aliphatic amine curing agents, aromatic amine curing agents, polyamide curing agents, and polyetheramine curing agents, and is preferably at least one of D230, D400, T403, and PACM curing agents.

[0021] The toughened epoxy resin adhesive of the present invention may also include any other conventional components in the art, such as inorganic fillers such as calcium carbonate and titanium oxide, as well as functional additives such as coupling agents, diluents, and catalysts. The amounts used are also conventional amounts, and those skilled in the art can add them according to actual conditions.

[0022] The third object of the present invention is to provide a method for preparing the toughened epoxy resin adhesive of the second object of the present invention, comprising the step of mixing components including the epoxy resin, the curing agent and the toughening agent.

[0023] In a preferred embodiment of the present invention,

[0024] After the components including the epoxy resin, curing agent and toughening agent are uniformly mixed, the method further comprises a step of vacuum degassing at 50-70° C. for 5-30 min.

[0025] A fourth object of the present invention is to provide an application of the toughened epoxy resin adhesive of the second object of the present invention or the toughened epoxy resin adhesive prepared by the preparation method of the third object of the present invention in construction, automobile, and aerospace products; preferably, the application conditions of the toughened epoxy resin adhesive include curing at a temperature of 80-100°C for 1-24 hours.

[0026] The beneficial effects of the present invention are as follows:

[0027] The present invention utilizes common and economical chemical raw materials such as tannic acid and octenylsuccinic anhydride to synthesize a toughening agent suitable for epoxy resin matrices. When added to epoxy resin, it can significantly improve impact resistance. The rigid bio-based skeleton and flexible branched arm structure can induce stress dispersion and energy absorption in the resin. The strong hydrogen bonding effect of the plant polyphenol structure can enhance the binding force of the resin to the bonding interface, thereby achieving better bonding and improving the bonding durability of the epoxy resin in a humid and hot environment. Excellent toughening and strong bonding effects can be achieved at a relatively low addition amount. Compared with the toughening agents of the prior art, the advantages of the present invention are that the raw materials used are bio-based molecules with excellent renewability; the toughening efficiency of the toughening agent is higher, and the impact strength can be improved at a low addition amount; and the bonding strength and hydrothermal durability of the epoxy resin adhesive can be simultaneously improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the infrared spectrum of the toughening agent synthesized in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to specific embodiments and the accompanying drawings. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0030] In the examples of the present invention, all the raw materials used are conventional commercially available raw materials.

[0031] Example 1

[0032] Preparation of toughening agent:

[0033] Tannic acid and octenylsuccinic anhydride were mixed in a pyridine solvent at a molar ratio of 1:25 (the amount of pyridine was 20 ml of pyridine for every 1 g of octenylsuccinic anhydride) at room temperature. Under nitrogen protection, the temperature was raised to 90°C and stirred for 36 hours. The solution was then rotary evaporated to obtain a viscous liquid crude product. The crude product was washed three times with petroleum ether and then washed three times with water. It was then dried in an oven at 80°C for 24 hours to obtain a brown viscous liquid TA-OSA1 (i.e., a toughening agent).

[0034] The infrared spectrum of the toughening agent obtained is as follows Figure 1 As shown: In the spectrum of tannic acid TA, 3400 cm -1 The larger broad band nearby is attributed to the phenolic OH groups, which originates from the hydrogen bonding interaction of the dense phenolic OH groups. -1The OH band in the region of 2500-3500 cm -1 A new carboxyl band appeared in the region at 1736 cm -1 The smaller absorption peak is attributed to the stretching vibration of the ester group C=O after the anhydride esterification. In addition, 2800-3000cm -1 The absorption peak at comes from the aliphatic CH vibration in octenylsuccinic anhydride OSA. Therefore, the successful preparation of TA-OSA1 can be proved.

[0035] Preparation of toughened epoxy resin adhesive:

[0036] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA1 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker and preheated with stirring at a speed of 500r / min on a hot plate at 60°C to increase its fluidity. Then, 0.33g of toughening agent TA-OSA1 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added and stirred to evenly disperse D230. Then, the mixture is transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0037] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0038] Example 2

[0039] Preparation of toughening agent (same as Example 1).

[0040] Preparation of toughened epoxy resin adhesive:

[0041] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA1 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker, stirred and preheated at a speed of 500r / min on a hot plate at 60°C to increase its fluidity, and then 0.66g of toughening agent TA-OSA1 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, stirred to evenly disperse D230, and then transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0042] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0043] Example 3

[0044] Preparation of toughening agent (same as Example 1).

[0045] Preparation of toughened epoxy resin adhesive:

[0046] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA1 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker, and preheated with stirring at a speed of 500r / min on a hot plate at 60°C to increase its fluidity. Then, 1.31g of toughening agent TA-OSA1 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, and stirred to evenly disperse D230. Then, the mixture is transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0047] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0048] Example 4

[0049] Preparation of toughening agent (same as Example 1).

[0050] Preparation of toughened epoxy resin adhesive:

[0051] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA1 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker, and preheated with stirring at a speed of 500r / min on a hot plate at 60°C to increase its fluidity, and then 1.97g of toughening agent TA-OSA1 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, and stirred to evenly disperse D230. Then, the mixture is transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0052] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0053] Example 5

[0054] Preparation of toughening agent:

[0055] Tannic acid and octenylsuccinic anhydride were mixed in a pyridine solvent at a molar ratio of 1:5 (the amount of pyridine was 20 ml of pyridine for every 1 g of octenylsuccinic anhydride) at room temperature. The mixture was heated to 90°C under nitrogen and stirred for 36 hours. The solution was then rotary evaporated to obtain a powdery crude product. The crude product was washed three times with petroleum ether and three times with water, and then dried in an oven at 80°C for 24 hours to obtain a brown powder TA-OSA2 (i.e., a toughening agent).

[0056] Preparation of toughened epoxy resin adhesive:

[0057] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA2 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker, and preheated with stirring at a speed of 500r / min on a hot plate at 60°C to increase its fluidity, and then 1.31g of toughening agent TA-OSA2 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, and stirred to evenly disperse D230, and then transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0058] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0059] Example 6

[0060] Preparation of toughening agent:

[0061] Tannic acid and octenylsuccinic anhydride were mixed in a pyridine solvent at a molar ratio of 1:10 (20 ml of pyridine was added for every 1 g of octenylsuccinic anhydride) at room temperature. The mixture was heated to 90°C under nitrogen and stirred for 36 hours. The solution was then rotary evaporated to obtain a powdery crude product. The crude product was washed three times with petroleum ether and three times with water, and then dried in an oven at 80°C for 24 hours to obtain a brown powder TA-OSA3 (i.e., a toughening agent).

[0062] Preparation of toughened epoxy resin adhesive:

[0063] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA3 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically: 100g of bisphenol A epoxy resin is placed in a beaker, and preheated with stirring at a speed of 500r / min on a hot plate at 60°C to increase its fluidity, and then 1.31g of toughening agent TA-OSA3 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, and stirred to evenly disperse D230, and then transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0064] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0065] Example 7

[0066] Preparation of toughening agent:

[0067] Tannic acid and octenylsuccinic anhydride were mixed in a pyridine solvent at a molar ratio of 1:50 (the amount of pyridine was 20 ml of pyridine for every 1 g of octenylsuccinic anhydride) at room temperature. The mixture was heated to 90°C under nitrogen and stirred for 36 hours. The solution was then rotary evaporated to obtain a viscous liquid crude product. The crude product was washed three times with petroleum ether and three times with water, and then dried in an oven at 80°C for 24 hours to obtain a brown viscous liquid TA-OSA4 (i.e., a toughening agent).

[0068] Preparation of toughened epoxy resin adhesive:

[0069] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-OSA4 are mixed, stirred evenly, and then vacuum degassing is performed. Specifically: 100g of bisphenol A epoxy resin is placed in a beaker, and preheated with stirring at a speed of 500r / min on a hot plate at 60°C to increase its fluidity, and then 1.31g of toughening agent TA-OSA4 is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, and stirred to evenly disperse D230, and then transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0070] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0071] Example 8

[0072] Preparation of toughening agent:

[0073] Tannic acid and dodecylsuccinic anhydride were mixed in a pyridine solvent at a molar ratio of 1:25 (the amount of pyridine was 20 ml of pyridine for every 1 g of dodecylsuccinic anhydride) at room temperature. The mixture was heated to 90° C. under nitrogen and stirred for 36 hours. The solution was then rotary evaporated to obtain a waxy crude product. The crude product was washed three times with petroleum ether and three times with water, and then dried in an oven at 80° C. for 24 hours. After cooling, a brown waxy solid TA-DDSA (i.e., a toughening agent) was obtained.

[0074] Preparation of toughened epoxy resin adhesive:

[0075] The base bisphenol A epoxy resin (DGEBA: E-51), curing agent polyetheramine (D230), and the above-mentioned toughening agent TA-DDSA are mixed and evenly stirred before vacuum degassing. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker and preheated at 500r / min on a 60°C hot plate to increase its fluidity. Then, 1.31g of toughening agent TA-DDSA is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added and stirred to evenly disperse D230. The mixture is then transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0076] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0077] Example 9

[0078] Preparation of toughening agent:

[0079] Tea polyphenols (TPP) and octenylsuccinic anhydride were mixed in a pyridine solvent at a molar ratio of 1:4 (the amount of pyridine was 20 ml of pyridine for every 1 g of octenylsuccinic anhydride) at room temperature. The mixture was heated to 90°C under nitrogen and stirred for 36 hours. The solution was then rotary evaporated to obtain a powdery crude product. The crude product was washed three times with petroleum ether and three times with water. The product was then dried in an oven at 80°C for 24 hours and cooled to obtain brown powder TPP-OSA (i.e., toughening agent).

[0080] Preparation of toughened epoxy resin adhesive:

[0081] The base bisphenol A epoxy resin (DGEBA: E-51), the curing agent polyetheramine (D230), and the above-mentioned toughening agent TPP-OSA are mixed, stirred evenly, and then vacuum degassing is performed. Specifically, 100g of bisphenol A epoxy resin is placed in a beaker, stirred and preheated at a speed of 500r / min on a hot plate at 60°C to increase its fluidity, and then 1.31g of toughening agent TPP-OSA is mixed with the epoxy resin. After the toughening agent is completely mixed, 31g of curing agent polyetheramine D230 is added, stirred to evenly disperse D230, and then transferred to a 60°C vacuum oven for vacuum degassing. Degassing is carried out at a pressure of -0.1MPa for 15 minutes to obtain a toughened epoxy resin adhesive.

[0082] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0083] Comparative Example 1

[0084] Preparation of epoxy resin adhesive:

[0085] The base bisphenol A epoxy resin (DGEBA: E-51) and the curing agent polyetheramine (D230) were mixed and evenly stirred before vacuum degassing. Specifically, 100g of bisphenol A epoxy resin was placed in a beaker and preheated on a 60°C hot plate at 500 rpm to increase its fluidity. 31g of the curing agent polyetheramine D230 was then added and stirred until the D230 was evenly dispersed. The mixture was then placed in a 60°C vacuum oven for vacuum degassing at a pressure of -0.1 MPa for 15 minutes to obtain an epoxy resin adhesive.

[0086] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0087] Comparative Example 2

[0088] Preparation of epoxy resin adhesive:

[0089] The base bisphenol A epoxy resin (DGEBA: E-51), curing agent polyetheramine (D230), tannic acid, and octenyl succinic anhydride were mixed and uniformly stirred before vacuum degassing. Specifically, 100g of bisphenol A epoxy resin was placed in a beaker and preheated at 500r / min on a 60°C hot plate to increase its fluidity. 0.32g of tannic acid and 0.99g of octenyl succinic anhydride were then mixed with the epoxy resin. After the mixture was uniformly mixed, 31g of curing agent polyetheramine D230 was added and stirred to evenly disperse the D230. The mixture was then transferred to a 60°C vacuum oven for vacuum degassing. Degassing was performed at a pressure of -0.1MPa for 15 minutes to obtain an epoxy resin adhesive.

[0090] During the test, the epoxy resin adhesive was poured into the mold corresponding to the test method, cured at 80°C for 4 hours, and the obtained epoxy cured product was subjected to relevant performance tests.

[0091] The conventional mechanical properties and tensile shear properties of the epoxy resin adhesive were tested according to the following standards. The results are shown in Table 1.

[0092] Izod impact strength: tested in accordance with GB / T1043.1-2018 standard, the impact energy is 2.7J;

[0093] Tensile strength: tested in accordance with GB / T1040.1-2018 standard, test speed is 5mm / min;

[0094] Shear strength: Adhesive shear test was conducted in accordance with GB / T 7124-2008 standard at a test speed of 2 mm / min.

[0095] Shear strength after hydrothermal aging: Adhesive shear test was conducted in accordance with GB / T 7124-2008 at a test speed of 2 mm / min. The tensile shear strength of the adhesive joint was tested after immersion in a 40°C water bath.

[0096] Table 1

[0097]

[0098] As can be seen from Example 3, Comparative Examples 1-2, and Table 1, the present invention adds a toughening agent obtained by esterifying a phenolic compound containing a polyphenol skeleton with an acid anhydride compound containing a long-chain hydrocarbon structure to an epoxy resin, which not only improves the bonding performance (shear strength) of the adhesive, but also significantly improves the impact strength of the epoxy resin adhesive while maintaining or even improving the tensile strength of the epoxy resin adhesive.

[0099] It can be seen from Examples 1-4 and Table 1 that the toughening agent of the present invention can effectively toughen the epoxy resin adhesive when added in a small amount. Based on 100 parts by weight of the epoxy resin, the amount of the toughening agent is preferably 0.1-3 parts by weight, more preferably 0.2-2 parts by weight, and further preferably 0.5-1.5 parts by weight. Within the above range, the comprehensive properties of the epoxy resin adhesive (including tensile strength, impact strength and bonding strength) can be maintained at a high level.

[0100] It can be seen from Examples 1-9 and Table 1 that the toughening agent of the present invention is applied to epoxy resin adhesives, can effectively improve the toughness and bonding properties of epoxy resin adhesives, and has excellent hydrothermal bonding stability.

[0101] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A toughening agent obtained by esterification reaction of components including a phenolic compound containing a polyphenol skeleton and an acid anhydride compound containing a long-chain hydrocarbon structure.

2. The toughening agent according to claim 1, wherein: The phenolic compound containing a polyphenol skeleton is at least one of tannic acid, tea polyphenols, gallic acid, and ellagic acid, preferably at least one of tannic acid and tea polyphenols; and / or The number of carbon atoms of the long-chain hydrocarbon structure in the acid anhydride compound containing a long-chain hydrocarbon structure is ≥6. Preferably, the acid anhydride compound containing a long-chain hydrocarbon structure is at least one of octenyl succinic anhydride, dodecenyl succinic anhydride, nonenyl succinic anhydride, decenyl succinic anhydride, and decyl succinic anhydride.

3. The toughening agent according to claim 1, characterized in that: The molar ratio of the acid compound containing a polyphenol skeleton to the acid anhydride compound containing a long-chain hydrocarbon structure is 1:(1-80), preferably 1:(1-50).

4. The toughening agent according to any one of claims 1 to 3, characterized in that: The conditions of the esterification reaction include: a temperature of 70-90° C., preferably 80-90° C.; and / or a time of 12-72 hours, preferably 24-48 hours; and / or, The esterification reaction is carried out in a solvent; preferably, the solvent is at least one organic solvent, preferably at least one of dioxane, pyridine, and acetone; and / or, the amount of the solvent is 10-30 ml per 1 g of the acid anhydride compound containing a long-chain hydrocarbon structure.

5. A toughened epoxy resin adhesive comprising an epoxy resin, a curing agent and the toughening agent according to any one of claims 1 to 4.

6. The toughened epoxy resin adhesive according to claim 5, characterized in that: Based on 100 parts by weight of the epoxy resin, the curing agent is 5-50 parts by weight, and the toughening agent is 0.1-3 parts by weight; preferably, based on 100 parts by weight of the epoxy resin, the curing agent is 20-40 parts by weight, and the toughening agent is 0.2-2 parts by weight; more preferably, based on 100 parts by weight of the epoxy resin, the curing agent is 25-35 parts by weight, and the toughening agent is 0.5-1.5 parts by weight.

7. The toughened epoxy resin adhesive according to claim 5, characterized in that: The epoxy resin is at least one of bisphenol A epoxy resin and bisphenol F epoxy resin; and / or The curing agent is selected from at least one of aliphatic amine curing agents, aromatic amine curing agents, polyamide curing agents, and polyetheramine curing agents.

8. A method for preparing the toughened epoxy resin adhesive according to any one of claims 5 to 7, comprising the step of mixing components including the epoxy resin, a curing agent and a toughening agent.

9. The preparation method according to claim 8, wherein: After the components including the epoxy resin, curing agent and toughening agent are uniformly mixed, the method further comprises a step of vacuum degassing at 50-70° C. for 5-30 min.

10. Use of the toughened epoxy resin adhesive according to any one of claims 5 to 7 or the toughened epoxy resin adhesive prepared by the preparation method according to any one of claims 8 to 9 in construction, automobile, and aerospace products; preferably, the application conditions of the toughened epoxy resin adhesive include curing at a temperature of 80-100° C. for 1-24 hours.

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