High-elongation UV-heat dual-curing adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of adhesives, and particularly relates to a high-elongation UV-thermal dual-curing adhesive and a preparation method thereof.The high-elongation UV-thermal dual-curing adhesive is prepared from, by weight, 20-50 parts of alicyclic epoxy resin; 10 to 25 parts of thiol modified alicyclic epoxy resin; 10 to 25 parts of oxetane; 10 to 30 parts of a toughening agent; 10 to 20 parts of filler; 2-5 parts of a thixotropic agent; 0.5 to 5 parts of a thermal initiator; and 0.5 to 5 parts of a photoinitiator. According to the preparation method provided by the invention, the design of a cation system is adopted, and a thiol structure is introduced into a macromolecular structure of alicyclic epoxy through molecular structure design, so that the finally obtained UV-thermal dual-curing adhesive not only has low shrinkage rate, but also has high elongation, excellent tensile strength and drop resistance; the method can be widely applied to the fields of 3C electronic products, vehicle-mounted electronics and the like.

Description

Technical Field

[0001] This invention specifically relates to a high elongation UV-thermal dual-curing adhesive and its preparation method, belonging to the field of adhesive technology. Background Technology

[0002] As people's living standards continue to improve, they have higher requirements for various electronic and electrical products such as smartphones and electric vehicles. Consequently, manufacturers are increasingly demanding higher standards for adhesives used in these products. Ultraviolet (UV) curing, due to its fast curing speed, environmental friendliness, and solvent-free operation, is widely used in the production of various electronic products. However, in practical applications, the use of UV adhesives is limited by issues such as opaque or partially opaque materials, thick adhesive layers, and colored coatings. To overcome these problems, dual-curing systems have emerged in recent years. The UV-thermal dual-curing system is the most researched, with acrylate systems being the most widely used. However, the free radical polymerization of acrylates is easily affected by oxygen inhibition, and the cured product has a large shrinkage rate, which limits its application in precision applications such as camera modules. Cationic epoxy UV-thermal dual-curing systems are not affected by oxygen inhibition and have a smaller curing shrinkage rate, but their cured products lack toughness and have poor drop performance, severely limiting their application range in electronic products.

[0003] Therefore, it is of great significance to develop a UV-thermal dual-curing adhesive that is not affected by oxygen inhibition, has low shrinkage after curing, excellent toughness of the cured product, and excellent drop performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high elongation UV-thermal dual-curing adhesive and its preparation method. This method employs a cationic system design, and through molecular structure design, introduces a thiol structure into the macromolecular structure of an alicyclic epoxy. The resulting UV-thermal dual-curing adhesive not only has low shrinkage but also high elongation, excellent tensile strength, and drop resistance.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A high elongation UV-thermal dual-curing adhesive, which, by weight, comprises: 20-50 parts of alicyclic epoxy resin; 10-25 parts of thiol-modified alicyclic epoxy resin; 10-25 parts of oxetane; 10-30 parts of toughening agent; 10-20 parts of filler; 2-5 parts of thixotropic agent; 0.5-5 parts of thermal initiator; and 0.5-5 parts of photoinitiator.

[0006] Furthermore, the weight ratio of thiol-modified alicyclic epoxy resin, alicyclic epoxy resin, oxetane, and toughening agent is 1:(1~5):(0.5~1.5):(0.5~3).

[0007] Furthermore, the alicyclic epoxy resin is a compound having an alicyclic structure and epoxy groups within the molecule, preferably at least one of TTA21 and TTA26.

[0008] Furthermore, the oxetane is a compound containing an oxetane structure, preferably at least one of OXT-121, OXT-221, and OXT-101.

[0009] Furthermore, the toughening agent is a rubber polymer, preferably at least one of MBS and SBS; more preferably at least one of XT100, M701, M711, D1116, D1118, and D1155.

[0010] Furthermore, the filler is silica powder.

[0011] Furthermore, the thixotropic agent is fumed silica.

[0012] Furthermore, the thermal initiator is a blocked cationic thermal initiator, preferably at least one of CTI-100, CTI-200, and CTI-300.

[0013] Furthermore, the photoinitiator is a triarylsulfonium salt, preferably at least one of Uyracure-160 and Doublecure 1176.

[0014] Furthermore, the thiol-modified alicyclic epoxy resin was prepared according to the following steps: S1. Add the thiol, solvent, and photoinitiator to the reaction flask and stir until completely dissolved; S2. Under nitrogen protection and 365nm ultraviolet light irradiation, vinyl epoxy compound is slowly added dropwise while stirring. After the addition is complete and the reaction is finished, thiol-modified alicyclic epoxy resin is obtained.

[0015] Furthermore, in the preparation process of thiol-modified alicyclic epoxy resin, the molar ratio of thiol, vinyl epoxy compound and photoinitiator is 1:(1~4):(0.005~0.05).

[0016] Furthermore, in the preparation process of thiol-modified alicyclic epoxy resin, the reaction temperature is 20~30℃ and the reaction time is 1~3 hours.

[0017] Furthermore, the structural formula of thiols is shown below: , Where n is any integer from 1 to 4, and R is at least one of hydrogen, methyl, ethyl, propyl, butyl, and mercaptopropionic acid.

[0018] Furthermore, the thiol is preferably either pentaerythritol tetrakis(3-mercaptopropionic acid) or trimethylolpropane tri(3-mercaptopropionic acid) ester.

[0019] Furthermore, the vinyl epoxy compound is either 4-vinylepoxycyclohexane or oxetane methacrylate.

[0020] Furthermore, in step S1, the solvent is at least one of tetrahydrofuran, toluene, and dichloromethane, preferably tetrahydrofuran.

[0021] Furthermore, in step S1, the photoinitiator is Irgacure 651.

[0022] This invention also discloses a method for preparing a high elongation UV-thermal dual-curing adhesive, the preparation method comprising the following steps: (1) Under yellow light throughout the process, weigh alicyclic epoxy resin, thiol-modified alicyclic epoxy resin, oxetane, toughening agent, thermal initiator, and photoinitiator, and put them into a stirrer and stir for 1-2 hours until they are mixed evenly. (2) Under yellow light throughout the process, weigh the filler and thixotropic agent, put them into the stirrer, vacuum, stir for 1~2 hours, mix evenly, and you will get the high elongation UV-thermal dual curing adhesive.

[0023] Furthermore, in step (1), the temperature is controlled at 20~30℃.

[0024] Furthermore, in step (2), the temperature is controlled at 20~30℃.

[0025] Furthermore, in step (2), the vacuum is evacuated to below -0.08 MPa.

[0026] The high elongation UV-thermal dual-curing adhesive prepared by this invention can be widely used in the 3C electronics and automotive electronics industries.

[0027] The beneficial effects of this invention are: The high elongation UV-thermal dual-curing adhesive provided by this invention adopts a cationic system design. Through molecular structure design, a thiol structure is introduced into the macromolecular structure of alicyclic epoxy, which works together with the other components to obtain a UV-thermal dual-curing adhesive that not only has low shrinkage but also high elongation, excellent tensile strength and drop resistance. It can be widely used in the 3C electronics and automotive electronics industries. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0030] The components used in the embodiments and comparative examples of this invention are only for better explaining the technology of this invention and are not intended to limit the technology of this invention. The raw materials involved in the specific embodiments of this invention are as follows: Alicyclic epoxy resins are compounds with an alicyclic structure and epoxy groups within the molecule, preferably at least one of TTA 21 and TTA 26 from Taitel New Materials.

[0031] Oxycyclic butane is a compound containing an oxycyclic butane structure, preferably at least one of OXT-121, OXT-221, and OXT-101 synthesized by Toa Synthetic in Japan.

[0032] The toughening agent is a rubber polymer, preferably at least one of methyl methacrylate-butadiene-styrene terpolymer (MBS) and styrene-butadiene-styrene block copolymer (SBS); more preferably at least one of Arkema's XT100, Kaneka's M701 and M711, and Kraton's D1116, D1118 and D1155.

[0033] Specifically, the filler is silica powder.

[0034] Specifically, the thixotropic agent is fumed silica.

[0035] Specifically, the thermal initiator is a blocked cationic thermal initiator, preferably at least one of CTI-100, CTI-200, and CTI-300 from Yuyang Technology.

[0036] Specifically, the photoinitiator is a triarylsulfonium salt, preferably at least one of Uyracure-160 and Doublecure1176 from UYANG Technology.

[0037] This invention provides a high elongation UV-thermal dual-curing adhesive, comprising, by weight: 20-50 parts alicyclic epoxy resin; 10-25 parts thiol-modified alicyclic epoxy resin; 10-25 parts oxetane; 10-30 parts toughening agent; 10-20 parts filler; 2-5 parts thixotropic agent; 0.5-5 parts thermal initiator; and 0.5-5 parts photoinitiator.

[0038] Specifically, the weight ratio of thiol-modified alicyclic epoxy resin, alicyclic epoxy resin, oxetane, and toughening agent is 1:(1~5):(0.5~1.5):(0.5~3).

[0039] Specifically, the thiol-modified alicyclic epoxy resin is prepared according to the following steps: S1. Add the thiol, solvent, and photoinitiator Irgacure 651 to the reaction flask and stir until completely dissolved; S2. Under nitrogen protection and 365nm ultraviolet light irradiation, vinyl epoxy compound is slowly added dropwise while stirring. After the addition is complete and the reaction is finished, thiol-modified alicyclic epoxy resin is obtained.

[0040] More specifically, the synthetic route for preparing thiol-modified alicyclic epoxy resin is as follows: , Where n is any integer from 1 to 4, R is at least one of hydrogen, methyl, ethyl, propyl, butyl, and mercaptopropionic acid; and R1 is any one of epoxycyclohexyl or methylpropionic acid oxobutane ester.

[0041] Specifically, in the preparation process of thiol-modified alicyclic epoxy resin, the molar ratio of thiol, vinyl epoxy compound and photoinitiator is 1:(1~4):(0.005~0.05).

[0042] Specifically, in the preparation process of thiol-modified alicyclic epoxy resin, the reaction temperature is 20~30℃ and the reaction time is 1~3 hours.

[0043] Specifically, in step S1, the thiol structure is shown below: , Where n is any integer from 1 to 4, and R is at least one of methyl, ethyl, propyl, butyl, and mercaptopropionic acid groups.

[0044] More specifically, the thiol is preferably either pentaerythritol tetrakis(3-mercaptopropionic acid) ester or trimethylolpropane tri(3-mercaptopropionic acid) ester; wherein, the structural formula of pentaerythritol tetrakis(3-mercaptopropionic acid) ester is as follows: , The structural formula of trimethylolpropane tris(3-mercaptopropionic acid) ester is as follows: .

[0045] Specifically, the vinyl epoxy compound is either 4-vinylepoxycyclohexane or oxetane methacrylate; wherein, the structural formula of 4-vinylepoxycyclohexane is as follows: , The structural formula of oxetane methacrylate is as follows: .

[0046] Specifically, in step S1, the solvent is at least one of tetrahydrofuran, toluene, and dichloromethane, preferably tetrahydrofuran.

[0047] This invention also provides a method for preparing a high elongation UV-thermal dual-curing adhesive, the preparation method comprising the following steps: (1) Under yellow light throughout the process, weigh alicyclic epoxy resin, thiol-modified alicyclic epoxy resin, oxetane, toughening agent, thermal initiator and photoinitiator, put them into a high-speed planetary mixer and stir for 1-2 hours, with the temperature controlled at 20-30℃, and mix evenly. (2) Under yellow light throughout the process, weigh the filler and thixotropic agent, put them into a high-speed planetary mixer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1~2 hours, mix evenly, and obtain high elongation UV-thermal dual-curing adhesive.

[0048] The stirrers mentioned in the embodiments and comparative examples of this invention are all high-speed planetary stirrers, but this does not limit the technology of this invention, as long as the preparation conditions of the high elongation UV-thermal dual-curing adhesive provided by this invention can be achieved.

[0049] Example 1 Thiol-modified alicyclic epoxy resins were prepared according to the following steps, and the synthetic route is as follows: S1. Add 48.8g of pentaerythritol tetrakis(3-mercaptopropionic acid), 200mL of tetrahydrofuran solvent, and 1.28g of photoinitiator Irgacure 651 to a 500mL three-necked flask and stir until completely dissolved. S2. Under nitrogen protection and 365nm ultraviolet light irradiation, 50.6g of 4-vinylepoxycyclohexane was slowly added dropwise while stirring. After the addition was completed, the reaction was continued at 20~30℃ for 2h. After the reaction was completed, the mixture was concentrated by rotary evaporation to obtain thiol-modified alicyclic epoxy resin.

[0050] The preparation of a high elongation UV-thermal dual-curing adhesive includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 10g of thiol-modified alicyclic epoxy resin prepared in Example 1, 15g of oxetane OXT-121, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0051] Example 2 The thiol-modified alicyclic epoxy resin was prepared using the same method as in Example 1.

[0052] The preparation of a high elongation UV-thermal dual-curing adhesive includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 20g of thiol-modified alicyclic epoxy resin prepared in Example 1, 15g of oxetane OXT-221, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0053] Example 3 Thiol-modified alicyclic epoxy resins were prepared according to the following steps, and the synthetic route is as follows: S1. Add 39.8g of trimethylolpropane tris(3-mercaptopropionic acid), 200mL of tetrahydrofuran solvent and 1.28g of photoinitiator Irgacure 651 to a 500mL three-necked flask and stir until completely dissolved. S2. Under nitrogen protection and 365nm ultraviolet light irradiation, 37.9g ​​of 4-vinylepoxycyclohexane was slowly added dropwise while stirring. After the addition was completed, the reaction was continued at 20~30℃ for 2h. After the reaction was completed, the mixture was concentrated by rotary evaporation to obtain thiol-modified alicyclic epoxy resin.

[0054] The preparation of a high elongation UV-thermal dual-curing adhesive includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 20g of thiol-modified alicyclic epoxy resin prepared in Example 3, 15g of oxetane OXT-221, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0055] Example 4 Thiol-modified alicyclic epoxy resins were prepared according to the following steps, and the synthetic route is as follows: S1. Add 39.8g of trimethylolpropane tris(3-mercaptopropionic acid), 200mL of tetrahydrofuran solvent and 1.28g of photoinitiator Irgacure 651 to a 500mL three-necked flask and stir until completely dissolved. S2. Under nitrogen protection and 365nm ultraviolet light irradiation, 55.27g of oxybutane methacrylate was slowly added dropwise while stirring. After the addition was completed, the reaction was continued at 20~30℃ for 2h. After the reaction was completed, the mixture was concentrated by rotary evaporation to obtain thiol-modified alicyclic epoxy resin.

[0056] The preparation of a high elongation UV-thermal dual-curing adhesive includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 20g of thiol-modified alicyclic epoxy resin prepared in Example 4, 15g of oxetane OXT-221, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0057] Example 5 The thiol-modified alicyclic epoxy resin was prepared using the same method as in Example 1.

[0058] The preparation of a high elongation UV-thermal dual-curing adhesive includes the following steps: (1) Under yellow light throughout the process, weigh 25g of alicyclic epoxy resin TTA 21, 20g of thiol-modified alicyclic epoxy resin prepared in Example 1, 20g of oxetane OXT-221, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0059] Example 6 The thiol-modified alicyclic epoxy resin was prepared using the same method as in Example 1.

[0060] The preparation of a high elongation UV-thermal dual-curing adhesive includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 20g of thiol-modified alicyclic epoxy resin prepared in Example 1, 15g of oxetane OXT-221, 10g of toughening agent XT100, 3g of thermal initiator CTI-100, and 2.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0061] Comparative Example 1 The preparation of the high elongation UV-thermal dual-curing adhesive in this comparative example uses the same method as in Example 1, except that the thiol-modified alicyclic epoxy resin prepared in this invention is not used. The process includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 15g of oxetane OXT-221, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0062] Comparative Example 2 The preparation of the high elongation UV-thermal dual-curing adhesive in this comparative example uses the same method as in Example 1, except that 5g of the thiol-modified alicyclic epoxy resin prepared in Example 1 is added, and the process includes the following steps: (1) Under yellow light throughout the process, weigh 30g of alicyclic epoxy resin TTA 21, 5g of thiol-modified alicyclic epoxy resin prepared in Example 1, 15g of oxetane OXT-221, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0063] Comparative Example 3 The thiol-modified alicyclic epoxy resin was prepared using the same method as in Example 1, except that in step S2, 50.6 g of 4-vinylepoxycyclohexane was directly added to the reaction system.

[0064] The high elongation UV-thermal dual-curing adhesive was prepared using the same method as in Example 1, except that the added thiol-modified alicyclic epoxy resin was prepared using the method described in Comparative Example 4.

[0065] Comparative Example 4 The preparation of the high elongation UV-thermal dual-curing adhesive follows the same method as in Example 1, except that 20g of alicyclic epoxy resin TTA 21 and 25g of thiol-modified alicyclic epoxy resin are added. The weight ratio of thiol-modified alicyclic epoxy resin, alicyclic epoxy resin, oxetane, and toughening agent is 1:0.8:0.6:0.4. The specific steps include: (1) Under yellow light throughout the process, weigh 20g of alicyclic epoxy resin TTA 21, 25g of thiol-modified alicyclic epoxy resin prepared in Example 1, 15g of oxetane OXT-121, 10g of toughening agent XT100, 2g of thermal initiator CTI-100, and 1.5g of photoinitiator Doublecure 1176, and put them into a high-speed planetary stirrer and stir for 1 hour, with the temperature controlled at 20~30℃, until they are mixed evenly; (2) Under yellow light throughout the process, weigh 20g of silicon micro powder and 3g of fumed silica, put them into a high-speed planetary stirrer, control the temperature at 20~30℃, evacuate to below -0.08MPa, stir for 1.5h, mix evenly, and obtain high elongation UV-thermal dual curing adhesive.

[0066] Comparative Example 5 The preparation of high elongation UV-thermal dual-curing adhesive was carried out using the same method as in Example 1, except that the temperature was controlled at 40°C in step (1).

[0067] The examples and comparative examples were coated into dumbbell-shaped molds made according to GB / T 1040, cured for 5 seconds with a 1000mw UV lamp at 365nm, then cured in an oven at 80℃ for 60 minutes. After cooling to room temperature, the samples were tested according to GB / T 1040. The tensile shear strength was tested according to the standard (GB / T2792-2014). The drop performance test was conducted: 50 drops from a height of 1.8m to determine whether cracking occurred. The test data are shown in Table 1 below: Table 1 Mechanical property tests of high elongation UV-thermal dual-curing adhesives in the examples and comparative examples Based on the data in Table 1, the test data from the examples show that the high elongation UV-thermal dual-curing adhesive provided by this invention adopts a cationic system design. Through molecular structure design, a thiol structure is introduced into the macromolecular structure of the alicyclic epoxy, interacting with other components to result in a UV-thermal dual-curing adhesive that not only has low shrinkage but also high elongation, excellent tensile strength, and drop resistance. This superior performance makes it widely applicable in the 3C electronics and automotive electronics industries. In Examples 1 and 2, increasing the content of the thiol-modified alicyclic epoxy resin increases the elongation at break due to the increase in thiol chain segments, while also increasing functionality and tensile strength. In Example 3, a trifunctional thiol was used to prepare the thiol-modified alicyclic epoxy resin, reducing resin functionality and thus lowering crosslinking density. The elongation was higher than in Example 2, but the tensile strength was lower. In Example 5, compared to Example 2, the content of the alicyclic epoxy resin was lower, while the content of oxetane was higher, resulting in an improved elongation. The increased content of thermal initiator and photoinitiator in Example 6 results in a faster curing speed under the same curing conditions, leading to a higher crosslinking density, which in turn reduces elongation and increases tensile strength.

[0068] Based on the data in Table 1, a comparison between Comparative Example 1 and Example 1 shows that Comparative Example 1, which did not use thiol-modified alicyclic epoxy resin, had a very low elongation and could not pass the drop test. This is because it has poor toughness and insufficient impact resistance.

[0069] Based on the data in Table 1, a comparison between Comparative Example 2 and Example 1 shows that the content of thiol-modified alicyclic epoxy resin used in Comparative Example 2 was insufficient. Therefore, although the elongation was improved, it still failed the drop test. This is because its toughness is poor and its impact resistance is insufficient.

[0070] Based on the data in Table 1, a comparison between Comparative Example 3 and Example 1 shows that in the preparation process of the thiol-modified alicyclic epoxy resin used in Comparative Example 3, 50.6 g of 4-vinylepoxycyclohexane was directly added to the reaction system in step S2. When this thiol-modified alicyclic epoxy resin was applied to the preparation of a high-elongation UV-thermal dual-curing adhesive, the elongation and flexibility of the final UV-thermal dual-curing adhesive decreased after curing. This is because, in the preparation process of the thiol-modified alicyclic epoxy resin, the direct addition of 4-vinylepoxycyclohexane to the reaction system in step S2 resulted in an excessively high initial concentration of 4-vinylepoxycyclohexane in the reaction system, leading to the generation of byproducts. This resulted in insufficient purity of the final thiol-modified alicyclic epoxy resin, thus affecting the performance of the UV-thermal dual-curing adhesive.

[0071] Based on the data in Table 1, a comparison between Comparative Example 4 and Example 1 shows that the weight ratio of thiol-modified alicyclic epoxy resin, alicyclic epoxy resin, oxetane, and toughening agent in Comparative Example 5 is 1:0.8:0.6:0.4, which is outside the required ratio range of this invention. This results in lower performance of the UV-thermal dual-curing adhesive compared to Comparative Example 1. This is because the components have a certain synergistic effect, which ultimately leads to the excellent performance of the UV-thermal dual-curing adhesive. Although the amounts of each component are within the required range of this invention, when the ratio between the components is outside the required range, the interaction between the components is affected, thus impacting the performance of the UV-thermal dual-curing adhesive.

[0072] Based on the data in Table 1, a comparison between Comparative Example 5 and Example 1 shows that in Comparative Example 6, the temperature in step (1) of preparing the high elongation UV-thermal dual-curing adhesive was controlled at 40°C, resulting in a decrease in elongation and insufficient flexibility after curing. This is because excessively high temperatures during the synthesis of the modified resin can lead to side reactions, resulting in insufficient purity of the final thiol-modified alicyclic epoxy resin, which in turn affects the performance of the UV-thermal dual-curing adhesive.

[0073] 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 exhaustively listed. 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.

[0074] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A high elongation UV-thermal dual-curing adhesive, characterized in that, The adhesive comprises, by weight, 20-50 parts of alicyclic epoxy resin; 10-25 parts of thiol-modified alicyclic epoxy resin; 10-25 parts of oxetane; 10-30 parts toughening agent; 10-20 parts of filler; 2-5 parts of thixotropic agent; 0.5 to 5 parts of thermal initiator; Photoinitiator 0.5 to 5 parts.

2. The high elongation UV-thermal dual-curing adhesive according to claim 1, characterized in that, The weight ratio of the thiol-modified alicyclic epoxy resin, the alicyclic epoxy resin, the oxetane, and the toughening agent is 1:(1~5):(0.5~1.5):(0.5~3).

3. The high elongation UV-thermal dual-curing adhesive according to claim 1, characterized in that, The thiol-modified alicyclic epoxy resin was prepared according to the following steps: S1. Add the thiol, solvent, and photoinitiator to the reaction flask and stir until completely dissolved; S2. Under nitrogen protection and 365nm ultraviolet light irradiation, vinyl epoxy compound is slowly added dropwise while stirring. After the addition is complete and the reaction is finished, thiol-modified alicyclic epoxy resin is obtained.

4. The high elongation UV-thermal dual-curing adhesive according to claim 3, characterized in that, The molar ratio of the thiol, the vinyl epoxy compound, and the photoinitiator is 1:(1~4):(0.005~0.05).

5. The high elongation UV-thermal dual-curing adhesive according to claim 3, characterized in that, The reaction temperature is 20~30℃, and the reaction time is 1~3 hours.

6. The high elongation UV-thermal dual-curing adhesive according to claim 3, characterized in that, The structural formula of the thiol is shown below: ， Where n is any integer from 1 to 4, and R is at least one of hydrogen, methyl, ethyl, propyl, butyl, and mercaptopropionic acid.

7. The high elongation UV-thermal dual-curing adhesive according to claim 6, characterized in that, The thiol is either pentaerythritol tetrakis(3-mercaptopropionic acid) ester or trimethylolpropane tri(3-mercaptopropionic acid) ester.

8. The high elongation UV-thermal dual-curing adhesive according to claim 3, characterized in that, The vinyl epoxy compound is either 4-vinylepoxycyclohexane or oxetane methacrylate.

9. The high elongation UV-thermal dual-curing adhesive according to claim 1, characterized in that, The alicyclic epoxy resin is a compound with an alicyclic structure and epoxy groups within its molecule; The oxetane is a compound containing an oxetane structure; The toughening agent is a rubber-based polymer; The filler is silica powder; The thixotropic agent is fumed silica; The thermal initiator is a closed-type cationic thermal initiator; The photoinitiator is a triarylthionium salt.

10. A method for preparing a high elongation UV-thermal dual-curing adhesive according to any one of claims 1-9, characterized in that, The preparation method includes the following steps: (1) Under yellow light throughout the process, weigh alicyclic epoxy resin, thiol-modified alicyclic epoxy resin, oxetane, toughening agent, thermal initiator, and photoinitiator, put them into a stirrer and stir until they are evenly mixed. (2) Under yellow light throughout the process, weigh the filler and thixotropic agent, put them into the stirrer, stir and mix evenly to obtain high elongation UV-thermal dual curing adhesive.

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