Photo-thermal dual-curing bi-component sulfydryl epoxy adhesive and preparation method thereof

Abstract

The invention belongs to the field of epoxy adhesives, and relates to a photo-thermal dual-curing bi-component sulfydryl epoxy adhesive and a preparation method thereof. The bi-component sulfydryl epoxy adhesive contains a component A and a component B, the component A contains 100-120 parts of sulfydryl modified epoxy resin, 10-30 parts of an epoxy diluent containing double bonds, 0.5-3 parts of a photoinitiator and 1-5 parts of a latent thermal accelerator, and the component B contains 80-120 parts of epoxy resin, 4-8 parts of a latent curing agent, 20-60 parts of filler and 5-15 parts of a toughening agent. The sulfydryl modified epoxy resin has a structure as shown in Figure 1. The photo-thermal dual-curing bi-component sulfydryl epoxy adhesive provided by the invention can be rapidly and preliminarily cured in a low-temperature environment (5 DEG C), the construction efficiency is improved, a cross-linked network after secondary curing is tighter, and the shear strength, the tensile strength and the elongation at break are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin adhesive preparation technology, specifically to a mercapto-modified epoxy resin adhesive that can be rapidly cured at low temperature or room temperature and is stable in storage, and its preparation method. Background Technology

[0002] Epoxy resins possess excellent comprehensive mechanical properties, high adhesive strength, low shrinkage, and good stability, making them widely used in machinery, electronics, electrical engineering, aerospace, and coatings industries as a matrix for coatings, adhesives, composite resins, and electronic packaging materials. However, traditional epoxy resin adhesives experience a rapid decrease in curing rate at low temperatures, sometimes even failing to cure, severely impacting construction efficiency in winter or low-temperature environments. While using strong accelerators can improve the low-temperature curing rate, it significantly shortens the adhesive's shelf life, causing considerable inconvenience in production and application. Existing technologies struggle to simultaneously meet the conflicting demands of "rapid curing" and "long-term storage at room temperature." Summary of the Invention

[0003] Based on the above analysis, the purpose of this invention is to provide a method for preparing a photo-thermal dual-curing mercapto epoxy resin adhesive. This adhesive does not require a high-temperature environment during application and only needs brief UV irradiation for initial curing, greatly improving production efficiency and convenience. It ingeniously combines the "photo-triggered thiol-ene reaction" with the "thermal-triggered epoxy-mercapto / amine reaction," creatively utilizing the complementarity of the two reaction mechanisms to achieve precise control of the curing process. Rapid shaping is achieved through photocuring, solving the problem of slow initial reaction at low temperatures; while the thermal curing stage ensures the high strength and heat resistance of the final product.

[0004] This invention provides a low-temperature, rapid-curing, photo-thermal dual-curing mercapto epoxy resin adhesive, comprising component A and component B. Component A contains 100-120 parts of mercapto-modified epoxy resin, 10-30 parts of epoxy diluent containing double bonds, 0.5-3 parts of photoinitiator, and 1-5 parts of latent thermal accelerator. Component B contains 80-120 parts of epoxy resin, 4-8 parts of latent curing agent, 20-60 parts of filler, and 5-15 parts of toughening agent.

[0005] The structure of the mercapto-epoxy resin is as follows: R1 is -R 11 -SH or -O-CO-R 12 -SH, R 11 R 12 Each is an alkylene group that is independently C1-C6, and n is an integer greater than or equal to 1.

[0006] Preferably, the preparation method of the mercapto-modified epoxy resin includes the following steps: weighing 20-40 parts of bisphenol A type epoxy resin and 150-200 parts of solvent, adding them to a reaction vessel, and stirring at room temperature for 30-50 min; then adding 8-15 parts of thiol compound and 0.2-0.5 parts of catalyst, heating to 60-80℃, and reacting for 3-5 h; heating to 90-105℃, and distilling under reduced pressure at -0.1 MPa for 1-2 h, the system changes from turbid to clear liquid, thus obtaining the mercapto-modified epoxy resin.

[0007] Preferably, the solvent is at least one of anhydrous ethanol, isopropanol, or toluene.

[0008] Preferably, the catalyst is at least one of triethylamine, triphenylphosphine, bis(dimethylaminoethyl) ether, or 2-ethyl-4-methylimidazole.

[0009] Preferably, the thiol compound is at least one of 1,1-propanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,6-hexanedithiol, 1,2-ethanedithiol, 2,3-dimercapto-1-propanol (2-mercaptoacetate), and 2,3-dimercapto-1-propanol (3-mercaptoacetate).

[0010] Preferably, the mass ratio of the thiol compound to the bisphenol A type epoxy resin is (20-60):(6-20); and the mass ratio of the bisphenol A type epoxy resin to the organic solvent is (20-60):(80-160).

[0011] Preferably, the mass mixing ratio of component A and component B is 1:(1-1.3).

[0012] Preferably, the epoxy diluent containing double bonds is allyl glycidyl ether (AGE) or glycidyl acrylate (GAA).

[0013] Preferably, the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 1-hydroxycyclohexylphenyl ketone.

[0014] Preferably, the latent heat accelerator is at least one or more of EP-500, SH-A100, SH-A150, UR-300 or EMI-24.

[0015] Preferably, the epoxy resin is at least one or more of bisphenol A type epoxy resins E-51, E-44, E-42, E-54, and E-35.

[0016] Preferably, the latent curing agent is at least one or more of dicyandiamide, 2-methylimidazole, 2-phenylimidazole, diaminodiphenyl sulfone, diaminodiphenylmethane, and m-phenylenediamine.

[0017] Preferably, the filler is at least one of calcium carbonate, aluminum hydroxide, calcium silicate, carbon black, alumina, calcium carbonate, or silica powder.

[0018] Preferably, the toughening agent is at least one or more of carboxyl-terminated nitrile rubber, polysulfide rubber, polyether, polyimide, and nano-calcium carbonate.

[0019] Compared with the prior art, the present invention has the following beneficial effects: the key to the present invention lies in having Figure 1 The thiol-modified epoxy resin with the structure shown, combined with photoinitiators, latent curing agents, latent thermal accelerators, fillers, and toughening agents, results in a two-component thiol-modified epoxy adhesive that can achieve rapid curing at low temperatures (5°C), improving construction efficiency. After secondary thermal curing, the crosslinking density increases, giving the adhesive superior mechanical properties. The reasons for this are speculated to be: firstly, the introduction of a photo-triggered thiol-olefin click chemistry reaction as the first curing stage allows the thiol-modified epoxy resin and the epoxy diluent containing double bonds to react within tens of seconds under UV irradiation and the action of a photoinitiator. The reaction rate is minimally affected by ambient temperature, solving the problem of slow initial reaction at low temperatures; secondly, the photo-thermal dual curing allows for sufficient chain extension and crosslinking of the numerous epoxy groups in the system, forming a dense and stable three-dimensional network. This co-curing crosslinking structure improves the mechanical properties, heat resistance, and durability of the cured product without significantly sacrificing the epoxy resin's stiffness. Attached Figure Description

[0020] Figure 1 The structure of the mercapto epoxy resin described in this invention is shown below. Detailed Implementation

[0021] The present invention can be better understood from the following embodiments. However, the descriptions of the embodiments are for illustrative purposes only and should not, and will not, limit the invention as described in detail in the claims.

[0022] Example 1: This example illustrates the preparation of a two-component epoxy adhesive.

[0023] Weigh 20 parts by weight of bisphenol A type epoxy resin E-51 and 180 parts by weight of toluene, add them to a reaction vessel equipped with a thermometer, a stirrer and a condenser, purge with N2, stir and heat to 40℃, keep at this temperature for 40 min; slowly add 8 parts by weight of 1,6-hexanedithiol and 0.3 parts by weight of triethylamine, heat to 80℃, react for 3 h and then heat to 90℃, and distill under reduced pressure at -0.1 MPa until the system is completely transparent and clear, thus obtaining the mercapto-modified epoxy resin.

[0024] 100 parts by weight of mercapto-modified epoxy resin, 10 parts by weight of allyl glycidyl ether, 1 part by weight of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2 parts by weight of latent thermal accelerator EP-500 were added to a double planetary reactor and stirred at room temperature for 2 hours. After defoaming by vacuuming for 1 hour, component A was obtained.

[0025] 90 parts by weight of bisphenol A type epoxy resin E-51, 4 parts by weight of dicyandiamide, 25 parts by weight of calcium carbonate, and 8 parts by weight of carboxyl-terminated butadiene nitrile rubber were added to a double planetary reactor and stirred at room temperature for 2 hours. After vacuuming for 1 hour to remove bubbles, component B was obtained.

[0026] The mercapto-modified epoxy resin adhesive can be obtained by mixing component A and component B in a mass ratio of 1:1.

[0027] Example 2: This example illustrates the preparation of a two-component epoxy adhesive.

[0028] Weigh 20 parts by weight of bisphenol A type epoxy resin E-44 and 180 parts by weight of isopropanol, add them to a reaction vessel equipped with a thermometer, a stirrer and a condenser, purge with N2, stir and heat to 40℃, keep at this temperature for 40 min; slowly add 5 parts by weight of 1,1-propanedithiol and 0.2 parts by weight of triphenylphosphine, heat to 60℃, react for 3 h and then heat to 95℃, and distill under reduced pressure at -0.1 MPa until the system is completely transparent and clear, thus obtaining the mercapto-modified epoxy resin.

[0029] 100 parts by weight of mercapto-modified epoxy resin, 15 parts by weight of glycidyl acrylate, 1 part by weight of 1-hydroxycyclohexyl phenyl ketone, and 2 parts by weight of latent thermal accelerator SH-A100 were added to a double planetary reactor and stirred at room temperature for 2 hours. After degassing by vacuuming for 1 hour, component A was obtained.

[0030] 90 parts by weight of bisphenol A type epoxy resin E-44, 4 parts by weight of dicyandiamide, 25 parts by weight of aluminum hydroxide, and 8 parts by weight of polysulfide rubber were added to a double planetary reactor. The mixture was stirred at room temperature for 2 hours and then vacuumed for 1 hour to remove bubbles, thus obtaining component B.

[0031] The mercapto-modified epoxy resin adhesive can be obtained by mixing component A and component B in a mass ratio of 1:1.

[0032] Example 3: This example illustrates the preparation of a two-component epoxy adhesive.

[0033] Weigh 20 parts by weight of bisphenol A type epoxy resin E-44 and 200 parts by weight of toluene, add them to a reaction vessel equipped with a thermometer, a stirrer and a condenser, purge with N2, stir and heat to 40℃, keep at this temperature for 40 min; slowly add 7 parts by weight of 1,2-ethylenedithiol and 0.2 parts by weight of triphenylphosphine, heat to 85℃, react for 3 h and then heat to 105℃, and distill under reduced pressure at -0.1 MPa until the system is completely transparent and clear, thus obtaining the mercapto-modified epoxy resin.

[0034] 100 parts by weight of mercapto-modified epoxy resin, 15 parts by weight of glycidyl acrylate, 1 part by weight of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2 parts by weight of latent thermal accelerator SH-A100 were added to a double planetary reactor and stirred at room temperature for 2 hours. After defoaming by vacuuming for 1 hour, component A was obtained.

[0035] 110 parts by weight of bisphenol A type epoxy resin E-44, 4 parts by weight of dicyandiamide, 25 parts by weight of silica powder, and 8 parts by weight of polysulfide rubber were added to a double planetary reactor and stirred at room temperature for 2 hours. After vacuuming for 1 hour to remove bubbles, component B was obtained.

[0036] The mercapto-modified epoxy resin adhesive can be obtained by mixing component A and component B in a mass ratio of 1:1.

[0037] Comparative Example 1: Commercially available two-component epoxy adhesive Loctite E-20HP.

[0038] Examples 1-3 were cured using a dual photo-thermal curing method, while Comparative Example 1 was cured using thermal curing. Specific curing conditions: Photocuring: 365nm / 395nm UV lamp, 1500mW / cm² 2 10s; thermosetting: 80℃ / 60min.

[0039] Shear strength test: The test was conducted according to the method in standard GB / T7124-2008. The epoxy adhesives obtained in the above examples and comparative examples were used to prepare PC-to-PC shear sheets with an overlap area of ​​25.4mm*12.7mm and an adhesive layer thickness of 0.2mm.

[0040] Tensile strength test: The test was conducted according to the method in standard ASTM D638. After the epoxy adhesives obtained in the above examples and comparative examples were cured, they were cut into standard dumbbell-shaped specimens and tensile tests were performed using a universal testing machine with a loading speed of 10 mm / min.

[0041]

[0042] As can be seen from the table above, the photo-thermal dual-curing two-component thiol epoxy adhesive provided by this invention can achieve preliminary curing at low temperatures, improving construction efficiency. After secondary thermal curing, its crosslinking density increases, giving the adhesive superior mechanical properties. A comparison of Examples 1-3 with Comparative Example 1 shows that in the photo-thermal dual-curing two-component thiol epoxy adhesive provided by this invention, the thiol-modified epoxy resin and photoinitiator work synergistically, allowing the adhesive layer to achieve preliminary curing under ultraviolet irradiation at low temperatures, forming a three-dimensional crosslinking network. Further thermal curing results in a denser crosslinking network, giving the adhesive both excellent low-temperature curing characteristics and superior final mechanical properties.

[0043] The present invention has been described in detail above with reference to specific examples; however, these descriptions do not constitute a limitation on the scope of the invention. It should be understood that various modifications, improvements, and substitutions can be made to the technical solutions and specific embodiments of the present invention without departing from the scope and spirit of the invention, and all such modifications, improvements, and substitutions should fall within the protection scope of the appended claims.

Claims

1. A photo-thermal dual-curing two-component mercapto epoxy adhesive, characterized in that, By weight, the mercapto epoxy adhesive comprises the following components: component A contains 100-120 parts mercapto modified epoxy resin, 10-30 parts epoxy diluent containing double bonds, 0.5-3 parts photoinitiator, and 1-5 parts latent thermal accelerator; component B contains 80-120 parts epoxy resin, 4-8 parts latent curing agent, 20-60 parts filler, and 5-15 parts toughening agent.

2. The structure of the mercapto epoxy resin is as follows: ， R1 is -R 11 -SH or -O-CO-R 12 -SH, R 11 R 12 Each is an independent C1-C6 alkylene group, where n is an integer greater than or equal to 1; The preparation method includes the following steps, by weight: weigh 20-40 parts of bisphenol A type epoxy resin and 150-200 parts of solvent, add them to a reaction vessel, and stir at room temperature for 30-50 min; then add 8-15 parts of thiol compound and 0.2-0.5 parts of catalyst, heat to 60-80℃ and react for 3-5 h; heat to 90-105℃ and distill under reduced pressure at -0.1 MPa for 1-2 h, and the system changes from turbid to clear liquid to obtain mercapto-modified epoxy resin; The solvent is at least one of anhydrous ethanol, isopropanol, or toluene; The catalyst is at least one of triethylamine, triphenylphosphine, bis(dimethylaminoethyl) ether, or 2-ethyl-4-methylimidazole; The thiol compound is at least one of 1,1-propanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,6-hexanedithiol, 1,2-ethanedithiol, 2,3-dimercapto-1-propanol (2-mercaptoacetate), and 2,3-dimercapto-1-propanol (3-mercaptoacetate). The mass ratio of the thiol compound to the bisphenol A type epoxy resin is (20 ~ 60): (6 ~ 20); the mass ratio of the bisphenol A type epoxy resin to the organic solvent is (20 ~ 60): (80 ~ 160).

3. The mercapto epoxy adhesive according to claim 1, characterized in that, The preferred mass mixing ratio of component A and component B is 1:(1 ~ 1.3).

4. The mercapto epoxy adhesive according to claim 1, characterized in that, The epoxy diluent containing double bonds is at least one of allyl glycidyl ether (AGE) or glycidyl methacrylate (GMA).

5. The mercapto epoxy adhesive according to claim 1, characterized in that, The photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 1-hydroxycyclohexylphenyl ketone.

6. The mercapto epoxy adhesive according to claim 1, characterized in that, The latent heat accelerator is at least one or more of EP-500, SH-A100, SH-A150, UR-300 or EMI-24.

7. The mercapto epoxy adhesive according to claim 1, characterized in that, The epoxy resin is at least one or more of bisphenol A type epoxy resins E-51, E-44, E-42, E-54, and E-35.

8. The mercapto epoxy adhesive according to claim 1, characterized in that, The latent curing agent is at least one or more of dicyandiamide, 2-methylimidazole, 2-phenylimidazole, diaminodiphenyl sulfone, diaminodiphenylmethane, and m-phenylenediamine.

9. The mercapto epoxy adhesive according to claim 1, characterized in that, The filler is at least one of calcium carbonate, aluminum hydroxide, calcium silicate, carbon black, aluminum oxide, calcium carbonate, or silica powder.

10. The mercapto epoxy adhesive according to claim 1, characterized in that, The toughening agent is at least one of carboxyl-terminated nitrile butadiene rubber, polysulfide rubber, polyether, polyimide, and nano-calcium carbonate.

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