Microcapsule type curing agent as well as preparation method and application thereof

Abstract

The invention discloses a microcapsule type curing agent as well as a preparation method and application thereof, and belongs to the technical field of epoxy resin curing. The microcapsule type curing agent comprises a microcapsule shell and a microcapsule core, the microcapsule core is an imidazole curing agent, and the microcapsule shell is obtained by a thiol-ene click reaction of an allyl compound and a thiol compound. According to the present invention, the sulfydryl-alkene click reaction has characteristics of high selectivity and high efficiency, such that the allyl compound and the sulfydryl compound can rapidly form the cross-linked shell layer during the reaction so as to rapidly coat the imidazole curing agent so as to improve the coating rate; moreover, the allyl compound and the sulfhydryl compound react to form a compact three-dimensional network, so that the strength and compactness of the microcapsule shell are improved, and the dispersion stability of the curing agent in the epoxy resin and the final curing performance are improved.

Description

Technical Field

[0001] This application relates to the field of epoxy resin curing technology, and in particular to a microcapsule-type curing agent, its preparation method, and its application. Background Technology

[0002] Epoxy resin adhesives are widely used in the encapsulation, filling, and bonding of electronic components, semiconductors, and integrated circuits due to their excellent bonding strength, electrical insulation properties, chemical resistance, and mechanical strength. Epoxy resin adhesives are available in two types: two-component and one-component. One-component epoxy resin adhesives premix epoxy resin with a latent curing agent, eliminating the need for weighing and mixing before application. This greatly simplifies the production process and improves production efficiency and product consistency.

[0003] To improve the storage stability of latent curing agents, microencapsulation technology is typically used, where the curing agent is encapsulated with a polymer to isolate it from the epoxy resin. When curing is required, certain conditions are applied to rupture the microcapsule shell, releasing the curing agent and initiating a curing reaction between the curing agent and the epoxy resin.

[0004] However, microcapsule-type curing agents in related technologies have problems such as low encapsulation rate and insufficient strength and density of microcapsule shells, which affect their dispersion stability and final curing performance in epoxy resins. Summary of the Invention

[0005] This application provides a microencapsulated curing agent, its preparation method, and its application, which can improve the dispersion stability and final curing performance of the curing agent in epoxy resin. The technical solution is as follows: On the one hand, a microcapsule-type curing agent is provided, the microcapsule-type curing agent comprising: a microcapsule shell and a microcapsule core; The microcapsule core is an imidazole curing agent, and the microcapsule shell is obtained by a mercapto-alkene click reaction of an allyl compound and a mercapto compound.

[0006] In one possible implementation, the allyl compound is a trifunctional allyl compound.

[0007] In another possible implementation, the trifunctional allyl compound is selected from at least one of triallyl isocyanurate, triallyl cyanurate, and triallyl phosphate.

[0008] In another possible implementation, the thiol compound is a trifunctional thiol compound.

[0009] In another possible implementation, the trifunctional thiol compound is selected from at least one of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate and trimethylolpropane tris(3-mercaptopropionate).

[0010] In another possible implementation, the imidazole curing agent is selected from 2 Methylimidazole, 1-benzyl-2-methylimidazole, 2 Phenylidene and 2 Ethyl 4 At least one of methylimidazoles.

[0011] In another possible implementation, the mass ratio of the allyl compound to the mercapto compound is 1:(1~3).

[0012] In another possible implementation, the particle size of the microencapsulated curing agent is less than 30 μm.

[0013] On the other hand, this application provides a method for preparing a microcapsule-type curing agent, wherein the microcapsule-type curing agent is as described in any of the above claims, and the preparation method includes: An oil phase mixture is obtained by mixing an imidazole curing agent, a photoinitiator, an allyl compound, and a mercapto compound. The emulsifier is dissolved in water to obtain an aqueous phase; The oil phase mixture is added to the aqueous phase, and after mixing, an oil-in-water emulsion is obtained. Under ultraviolet light irradiation, a mercapto-olefin click reaction is initiated. After washing and drying, the microcapsule-type curing agent is obtained.

[0014] In one possible implementation, the mass ratio of the oil phase mixture to the water phase is 1:(10~20).

[0015] In another possible implementation, the photoinitiator has a mass fraction of 1% to 6% in the oil phase mixture; The imidazole curing agent has a mass fraction of 50% to 70% in the oil phase mixture.

[0016] In another possible implementation, the photoinitiator is selected from benzoin dimethyl ether, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and 2 hydroxyl 2 At least one of methylphenylacetone.

[0017] On the other hand, this application provides an epoxy resin adhesive, which comprises the following components in parts by weight: 70-80 parts epoxy resin, 5-10 parts reactive diluent, 0.5-3 parts silane coupling agent, 15-20 parts microencapsulated curing agent, and 5-20 parts filler; The microcapsule-type curing agent is as described in any of the above.

[0018] In one possible implementation, the reactive diluent is a monofunctional reactive diluent.

[0019] In another possible implementation, the monofunctional active diluent is selected from at least one of p-tert-butylphenyl glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, and alkyl glycidyl ether.

[0020] In another possible implementation, the epoxy resin is selected from at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin; The silane coupling agent is selected from at least one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; The filler is selected from at least one of titanium dioxide, aluminum hydroxide, kaolin, calcium carbonate powder and silica powder, and the particle size D50 of the filler is less than 10 μm.

[0021] On the other hand, this application provides a method for preparing an epoxy resin adhesive, wherein the epoxy resin adhesive is as described in any of the above claims, and the preparation method includes: The epoxy resin, silane coupling agent, microencapsulated curing agent and filler are mixed evenly to obtain a mixture. An active diluent is added to the mixture, and after mixing evenly, an epoxy resin adhesive is obtained.

[0022] This application provides a microencapsulated curing agent in which an allyl compound and a thiol compound form a microcapsule shell through a thiol-alkene click reaction, encapsulating an imidazole curing agent within. Due to the high selectivity and efficiency of the thiol-alkene click reaction, the allyl compound and thiol compound can rapidly form a cross-linked shell, quickly encapsulating the imidazole curing agent and thus improving the encapsulation rate. Furthermore, the reaction of the allyl compound and the thiol compound can form a dense three-dimensional network, which helps to improve the strength and density of the microcapsule shell, thereby improving the dispersion stability of the curing agent in epoxy resin and the final curing performance. Attached Figure Description

[0023] Figure 1 This is a flowchart of a method for preparing a microcapsule-type curing agent provided in an embodiment of this application; Figure 2This is a schematic diagram illustrating the preparation of a microcapsule-type curing agent according to an embodiment of this application; Figure 3 This is a flowchart of a method for preparing an epoxy resin adhesive provided in an embodiment of this application. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In view of the problems of low encapsulation rate and insufficient strength and density of microcapsule shells in related technologies, this application provides a microcapsule-type curing agent that can solve the problems of low encapsulation rate and insufficient strength and density of microcapsule shells.

[0026] The microcapsule-type curing agent provided in this application includes: a microcapsule shell and a microcapsule core; The microcapsule core is an imidazole curing agent, and the microcapsule shell is obtained by a mercapto-alkene click reaction of an allyl compound and a mercapto compound.

[0027] This application provides a microencapsulated curing agent in which an allyl compound and a thiol compound form a microcapsule shell through a thiol-alkene click reaction, encapsulating an imidazole curing agent within. Due to the high selectivity and efficiency of the thiol-alkene click reaction, the allyl compound and thiol compound can rapidly form a cross-linked shell, quickly encapsulating the imidazole curing agent and thus improving the encapsulation rate. Furthermore, the reaction of the allyl compound and the thiol compound can form a dense three-dimensional network, which helps to improve the strength and density of the microcapsule shell, thereby improving the dispersion stability of the curing agent in epoxy resin and the final curing performance.

[0028] In addition, since the microcapsule shell formed by the reaction of allyl compounds and mercapto compounds encapsulates the imidazole curing agent, the microcapsule curing agent has excellent storage stability and can be stored for a long time at room temperature. This effectively prevents the imidazole curing agent from reacting prematurely at room temperature, overcoming the disadvantages of traditional imidazole curing agents that easily form gels or solids at room temperature after being mixed with epoxy resins, resulting in a short pot life.

[0029] In some examples, the allyl compound is a trifunctional allyl compound.

[0030] Compared to monofunctional and difunctional allyl compounds, trifunctional allyl compounds offer more reaction sites. Their reaction with thiol compounds forms a three-dimensional cross-linked network, which helps improve the strength and density of the microcapsule shell, prevents premature leakage of imidazole curing agents, and ensures storage stability. Furthermore, the microcapsule shell formed by the reaction of trifunctional allyl compounds and thiol compounds has a higher glass transition temperature, which contributes to improving the stability of microencapsulated curing agents in epoxy resins.

[0031] Optionally, the trifunctional allyl compound is selected from at least one of triallyl isocyanurate, triallyl cyanurate, and triallyl phosphate.

[0032] Triallyl isocyanurate, triallyl cyanurate, and triallyl phosphate contain three allyl groups, providing more reaction sites. Their reaction with thiol compounds forms a three-dimensional cross-linked network, which helps improve the strength and density of the microcapsule shell, prevents premature leakage of imidazole curing agents, and ensures storage stability. Furthermore, the microcapsule shells formed by the reaction of triallyl isocyanurate, triallyl cyanurate, and triallyl phosphate with thiol compounds have a high glass transition temperature, which helps improve the stability of microcapsule-type curing agents in epoxy resins.

[0033] In some examples, the thiol compound is a trifunctional thiol compound.

[0034] The functional matching between trifunctional thiol compounds and trifunctional allyl compounds can form a good three-dimensional cross-linked network, which helps to improve the encapsulation rate and the strength and density of the microcapsule shell, thereby improving the dispersion stability of the curing agent in epoxy resin and the final curing performance.

[0035] Optionally, the trifunctional thiol compound is selected from at least one of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate and trimethylolpropane tris(3-mercaptopropionate).

[0036] Tris[2-(3-mercaptopropoxy)ethyl]isocyanurate and trimethylolpropane tris(3-mercaptopropionate) contain three thiol groups, which can provide more reaction sites. They can react with trifunctional allyl compounds to form a good three-dimensional cross-linked network, which helps to improve the encapsulation rate and the strength and density of the microcapsule shell, thereby improving the dispersion stability of the curing agent in epoxy resin and the final curing performance.

[0037] In some examples, imidazole curing agents are selected from 2 Methylimidazole, 1-benzyl-2-methylimidazole, 2 Phenylidene and 2 Ethyl 4 At least one of methylimidazoles.

[0038] The imidazole curing agents mentioned above have high reactivity and readily undergo curing reactions with epoxy resins.

[0039] In some examples, the mass ratio of allyl compound to mercapto compound is 1:(1~3).

[0040] For example, the mass ratio of allyl compound to mercapto compound can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.

[0041] In the embodiments of this application, by setting the mass ratio of allyl compound to mercapto compound, the complete reaction of allyl compound can be ensured, forming a dense three-dimensional cross-linked network, improving the strength and density of the microcapsule shell, and avoiding the impact of unreacted allyl compound residue on storage stability. Furthermore, an appropriate excess of mercapto compound can accelerate the reaction rate, forming the microcapsule shell more quickly, reducing the diffusion time of the imidazole curing agent into the aqueous phase, and improving the encapsulation rate.

[0042] In some examples, the particle size of the microencapsulated curing agent is less than 30 μm.

[0043] In the embodiments of this application, the particle size of the microencapsulated curing agent is less than 30 μm, which helps to improve the dispersion stability of the microencapsulated curing agent in epoxy resin.

[0044] On the other hand, embodiments of this application provide a method for preparing a microcapsule-type curing agent, see [link to relevant documentation]. Figure 1 The preparation method includes: Step 101: Mix the imidazole curing agent, photoinitiator, allyl compound and thiol compound to obtain an oil phase mixture.

[0045] The photoinitiator has a mass fraction of 1% to 6% in the oil phase mixture, and the imidazole curing agent has a mass fraction of 50% to 70% in the oil phase mixture.

[0046] For example, the mass fraction of the photoinitiator in the oil phase mixture can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, etc. The mass fraction of the imidazole curing agent in the oil phase mixture can be 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, etc.

[0047] In this embodiment, by setting the mass fraction of the photoinitiator in the oil phase mixture, the reaction between the allyl compound and the mercapto compound can be fully initiated, avoiding incomplete reaction. By setting the mass fraction of the imidazole curing agent in the oil phase mixture, the content of the microcapsule core can be increased, ensuring curing activity, and the amount of microcapsule-type curing agent used in the epoxy resin can be reduced, allowing the epoxy resin system to maintain a suitable viscosity.

[0048] Based on the mass fractions of the photoinitiator and imidazole curing agent, the sum of the mass fractions of allyl and mercapto compounds can be calculated, which is 24%~49%. The mass ratio of allyl to mercapto compounds is 1:(1~3). Therefore, based on the sum of the mass fractions of allyl and mercapto compounds and their mass ratio, the mass fractions of allyl and mercapto compounds in the oil phase mixture can be calculated separately. The specific calculation process will not be elaborated here.

[0049] In some examples, the photoinitiator is selected from benzoin dimethyl ether, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), and 2 hydroxyl 2 At least one of methylphenylacetone.

[0050] The aforementioned photoinitiator can initiate a mercapto-alkene click reaction between allyl compounds and mercapto compounds under ultraviolet light irradiation.

[0051] Step 102: Add the emulsifier to water to dissolve it, and obtain the aqueous phase.

[0052] In some examples, the emulsifier is selected from at least one of PVA (polyvinyl alcohol), PEG (polyethylene glycol), and gelatin.

[0053] The mass fraction of the emulsifier in the aqueous phase can be set and changed as needed, and there is no specific limitation thereto. For example, the mass fraction of the emulsifier in the aqueous phase can be 1% to 3%. Exemplary examples include 1%, 1.5%, 2%, 2.5%, 3%, etc. Optionally, the mass fraction of the emulsifier in the aqueous phase can be 2%.

[0054] Step 103: Add the oil phase mixture to the aqueous phase, and after mixing, an oil-in-water emulsion is obtained. Under ultraviolet light irradiation, a mercapto-olefin click reaction is initiated. After washing and drying, a microcapsule-type curing agent is obtained.

[0055] The mass ratio of the oil phase mixture to the water phase is 1:(10~20).

[0056] For example, the mass ratio of the oil phase mixture to the water phase can be 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, or 1:20.

[0057] In this embodiment, the emulsifier has an emulsifying and dispersing effect. After the aqueous phase obtained by dissolving the emulsifier is mixed with the above-mentioned oil phase mixture, the emulsifier can disperse the oil phase in the aqueous phase. Furthermore, the emulsifier can be adsorbed at the oil-water interface, providing a stable reaction interface and ensuring that the allyl compound and the thiol compound react fully. At the same time, by setting the mass ratio of the oil phase mixture to the aqueous phase, the oil phase can be fully dispersed in the aqueous phase, improving the transmittance of ultraviolet light and ensuring that the thiol compound and the allyl compound can react fully under ultraviolet light irradiation.

[0058] In this step, after adding the oil phase mixture to the aqueous phase according to the above mass ratio, it is thoroughly stirred and dispersed at a certain temperature to obtain an oil-in-water emulsion.

[0059] The stirring temperature, stirring rate, and stirring time can all be set and changed as needed. For example, the stirring temperature can be 55℃~65℃, the stirring rate can be 5000r / min~10000r / min, and the stirring time can be 5min~30min.

[0060] For example, the stirring temperature can be 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, etc. The stirring rate can be 5000 r / min, 6000 r / min, 7000 r / min, 8000 r / min, 9000 r / min, 10000 r / min, etc. The stirring time can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0061] By setting the stirring temperature, stirring rate, and stirring time, the oil phase mixture and the water phase can be fully mixed, which is beneficial to the full dispersion of the oil phase mixture, thereby obtaining an oil-in-water emulsion.

[0062] After obtaining the oil-in-water emulsion, the emulsion was irradiated with ultraviolet light to initiate a mercapto-olefin click reaction. The reaction time was less than 30 minutes. After the reaction time was reached, the emulsion was washed multiple times with distilled water and then dried at room temperature to obtain a microcapsule-type curing agent, which is a pale yellow solid powder.

[0063] The reaction time can be 10 min, 12 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, etc.

[0064] By setting the wavelength of ultraviolet light and the reaction time, the thiol compound and the allyl compound can react fully, resulting in microcapsule shells with high strength and density.

[0065] See Figure 2 , Figure 2 This is a schematic diagram for preparing a microcapsule-type curing agent.

[0066] It should be noted that the preparation process of microcapsule-type curing agents in related technologies is complex, involving multiple steps of reaction, strict pH control, or the use of large amounts of organic solvents, resulting in high production costs and high energy consumption, making it difficult to achieve large-scale industrial production.

[0067] This application uses a mercapto-olefin click reaction to prepare microcapsule-type curing agents. By mixing imidazole curing agents, photoinitiators, allyl compounds and mercapto compounds, and performing simple steps such as stirring, emulsification and ultraviolet light initiation reaction, the preparation process is greatly simplified, production costs are reduced, production efficiency is improved, and the disadvantages of traditional preparation methods, such as complex processes, high costs and high energy consumption, are overcome.

[0068] Furthermore, this application achieves high efficiency and high yield under mild conditions through mercapto-olefin click reaction, and is insensitive to oxygen or water, providing a new approach for the preparation of high-performance microcapsule-type curing agents.

[0069] On the other hand, embodiments of this application provide an epoxy resin adhesive comprising the following components in parts by weight: 70-80 parts epoxy resin, 5-10 parts reactive diluent, 0.5-3 parts silane coupling agent, 15-20 parts microencapsulated curing agent, and 5-20 parts filler.

[0070] Among them, the microcapsule curing agent is the microcapsule curing agent mentioned above.

[0071] For example, the mass fractions of epoxy resin can be 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, etc. The mass fractions of reactive diluent can be 5, 6, 7, 8, 9, 10, etc. The mass fractions of silane coupling agent can be 0.5, 1, 1.5, 2, 2.5, 3, etc. The mass fractions of microencapsulated curing agent can be 15, 16, 17, 18, 19, 20, etc. The mass fractions of filler can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc.

[0072] In related technologies, the addition amount of microencapsulated curing agents in epoxy resin adhesives is relatively large, resulting in slow curing speed, significant viscosity increase, and poor viscosity stability, making it difficult to meet the requirements for rapid curing. However, as can be seen from the formulation of the aforementioned epoxy resin adhesives, the microencapsulated curing agent provided in this application embodiment is added in a smaller amount. Although the amount of microencapsulated curing agent added is small, its curing speed, viscosity, and viscosity stability are moderate, thus still meeting the requirements for rapid curing.

[0073] Furthermore, in related technologies, epoxy resin adhesives rely on the dissolution temperature of solid curing agents to achieve latency, requiring high curing temperatures (typically above 150°C), resulting in high energy consumption and potential damage to heat-sensitive components. In contrast, the microcapsule-type curing agent provided in this application can cure at around 90°C, significantly reducing energy consumption and avoiding damage to heat-sensitive components.

[0074] Furthermore, as can be seen from the above, the microcapsule-type curing agent provided in this application embodiment can be directly used in epoxy resin adhesives without the need for additional curing agents, which simplifies the formulation design, improves product consistency, and is suitable for the needs of modern automated production.

[0075] In some examples, the reactive diluent is a monofunctional reactive diluent.

[0076] Compared to monofunctional reactive diluents, multifunctional reactive diluents have multiple epoxy groups. These epoxy groups participate in the construction of the epoxy crosslinking network, leading to a rapid increase in the molecular weight and a surge in viscosity, thus affecting storage stability. Monofunctional reactive diluents, on the other hand, only act as chain terminators and do not participate in the construction of the epoxy crosslinking network. Therefore, they have less impact on viscosity and are beneficial for long-term product storage.

[0077] Optionally, the monofunctional active diluent is selected from at least one of p-tert-butylphenyl glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, and alkyl glycidyl ether.

[0078] The aforementioned monofunctional reactive diluents only act as chain terminators and do not participate in the construction of the epoxy crosslinking network. Therefore, they have little impact on viscosity and are beneficial for long-term product storage.

[0079] In some examples, the epoxy resin is selected from at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0080] The silane coupling agent is selected from at least one of γ-glycidoxypropyltrimethoxysilane (KH560), γ-glycidoxypropyltriethoxysilane (KH561), and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (A186).

[0081] The filler is selected from at least one of titanium dioxide, aluminum hydroxide, kaolin, calcium carbonate powder and silica powder, and the particle size D50 of the filler is less than 10 μm.

[0082] Bisphenol A and bisphenol F epoxy resins have moderate viscosity, which ensures uniform dispersion of the microcapsule-type curing agent and has high reactivity, meeting the requirements for rapid curing.

[0083] The aforementioned silane coupling agent can enhance the adhesion between the filler and the resin interface and improve the bonding strength.

[0084] Adding the above-mentioned fillers to epoxy resin adhesives can control the viscosity and thixotropy of the adhesives, while also enhancing their mechanical strength. Furthermore, the smaller particle size (D50) of the fillers helps them to disperse uniformly in the epoxy resin adhesives, preventing agglomeration or sedimentation.

[0085] On the other hand, embodiments of this application provide a method for preparing an epoxy resin adhesive, see [link to relevant documentation]. Figure 3 The preparation method includes: Step 301: Mix the epoxy resin, silane coupling agent, microencapsulated curing agent and filler evenly to obtain a mixture.

[0086] In this step, epoxy resin, silane coupling agent, microencapsulated curing agent and filler can be added to a planetary vacuum mixer according to the mass proportions of each component. Then, the mixture is vacuum stirred at a speed of 500 rpm to 1200 rpm for 2 min to 5 min to ensure that the components are mixed evenly, thereby obtaining a mixture.

[0087] For example, the rotation speed can be 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, etc. The stirring time can be 2 min, 3 min, 4 min, 5 min, etc.

[0088] Step 302: Add reactive diluent to the mixture and mix well to obtain epoxy resin adhesive.

[0089] Add an active diluent to the mixture, and then continue to stir under vacuum at a speed of 500 rpm to 1200 rpm for 2 min to 5 min. After mixing evenly, an epoxy resin adhesive is obtained.

[0090] In step 2, the rotation speed and stirring time can be the same as or different from those in step 1; no specific restrictions are imposed.

[0091] The specific embodiments of this application will be described in more detail below. While specific embodiments of this application are described below, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0092] Synthesis example 1 Synthesis Example 1 provides a microencapsulated curing agent, the preparation method of which is as follows: 60g of imidazole curing agent 2-ethyl-4-methylimidazolium, 2g of photoinitiator TPO, 20g of triallyl isocyanurate, and 20g of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate were mixed to obtain an oil phase mixture.

[0093] A 2wt% PVA aqueous solution was prepared as the aqueous phase. 10g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 15min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0094] Synthesis example 2 70g of imidazole curing agent 2-ethyl-4-methylimidazol and 2g of photoinitiator 2 hydroxyl 2 Methylphenylacetone, 15g triallyl cyanurate, and 15g trimethylolpropane tris(3-mercaptopropionate) were mixed to obtain an oil phase mixture.

[0095] A 3wt% PVA aqueous solution was prepared as the aqueous phase. 6g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 20min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0096] Synthesis example 3 Add 50g of imidazole curing agent 1-benzyl-2-methylimidazol and 3g of photoinitiator 2 hydroxyl 2 Methylphenylacetone, 25g triallyl phosphate, and 25g tris[2-(3-mercaptopropoxy)ethyl]isocyanurate were mixed to obtain an oil phase mixture.

[0097] A 3wt% PVA aqueous solution was prepared as the aqueous phase. 5g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 15min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0098] Comparative Synthesis Example 1 60g of imidazole curing agent 2 Ethyl 4 Methylimidazole, 2g of photoinitiator TPO, 30g of triallyl isocyanurate, and 10g of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate were mixed to obtain an oil phase mixture.

[0099] A 2wt% PVA aqueous solution was prepared as the aqueous phase. 10g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 15min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0100] Comparative Synthesis Example 2 60g of imidazole curing agent 2 Ethyl 4 Methylimidazole, 2g of photoinitiator TPO, 20g of diallyl malonate diethyl ester, and 20g of di(3-mercaptopropionic acid) ethylene glycol were mixed to obtain an oil phase mixture.

[0101] A 2wt% PVA aqueous solution was prepared as the aqueous phase. 10g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 15min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0102] Comparative Synthesis Example 3 80g of imidazole curing agent 2 Ethyl 4 Methylimidazole, 2g of photoinitiator TPO, 10g of triallyl isocyanurate, and 10g of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate were mixed to obtain an oil phase mixture.

[0103] A 2wt% PVA aqueous solution was prepared as the aqueous phase. 10g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 15min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0104] Comparative Synthesis Example 4 40g of imidazole curing agent 2 Ethyl 4 Methylimidazole, 2g of photoinitiator TPO, 30g of triallyl isocyanurate, and 30g of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate were mixed to obtain an oil phase mixture.

[0105] A 2wt% PVA aqueous solution was prepared as the aqueous phase. 10g of the oil phase mixture was added to 100g of the aqueous phase, and the mixture was stirred and dispersed at 60℃ and 700rpm for 10min to obtain an oil-in-water emulsion. A mercapto-olefin click reaction was initiated under 356nm ultraviolet light irradiation. After reacting for 15min, the reaction product was washed three times with distilled water and dried at room temperature to obtain a microcapsule-type curing agent.

[0106] Example 1 Example 1 provides an epoxy resin adhesive, the preparation method of which is as follows: 70g of bisphenol F epoxy resin, 2g of silane coupling agent KH560, 15g of the microcapsule curing agent prepared in Synthesis Example 1, and 10g of 6000-mesh kaolin were added to a planetary vacuum mixer. The mixture was stirred under vacuum at 800 rpm for 2 minutes until homogeneous. Then, 5g of reactive diluent p-tert-butylphenyl glycidyl ether was added, and the mixture was stirred under vacuum at 800 rpm for another 2 minutes until homogeneous to obtain the epoxy resin adhesive.

[0107] Example 2 Example 2 provides an epoxy resin adhesive, the preparation method of which is as follows: 75g of bisphenol A epoxy resin, 3g of silane coupling agent KH560, 15g of the microcapsule curing agent prepared in Synthesis Example 1, and 15g of 6000-mesh kaolin were added to a planetary vacuum mixer. The mixture was stirred under vacuum at 800 rpm for 2 minutes until homogeneous. Then, 7g of reactive diluent p-tert-butylphenyl glycidyl ether was added, and the mixture was stirred under vacuum at 800 rpm for 2 minutes until homogeneous to obtain the epoxy resin adhesive.

[0108] Example 3 Example 3 provides an epoxy resin adhesive, the preparation method of which is as follows: Add 70g of bisphenol F epoxy resin, 2g of silane coupling agent KH560, 20g of the microcapsule curing agent prepared in Synthesis Example 2, and 5g of calcium carbonate powder to a planetary vacuum mixer. Vacuum mix at 800 rpm for 2 minutes, scrape the material with a scraper, and then vacuum mix at 800 rpm for another 2 minutes. After mixing evenly, add 5g of reactive diluent phenyl glycidyl ether and continue vacuum mixing at 800 rpm for 3 minutes. After mixing evenly, epoxy resin adhesive is obtained.

[0109] Example 4 Example 4 provides an epoxy resin adhesive, the preparation method of which is as follows: Add 70g of bisphenol F epoxy resin, 2g of silane coupling agent KH560, 20g of the microcapsule curing agent prepared in Synthesis Example 3, and 5g of calcium carbonate powder to a planetary vacuum mixer. Vacuum mix at 800 rpm for 2 minutes, scrape the material with a scraper, and then vacuum mix at 800 rpm for another 2 minutes. After mixing evenly, add 5g of reactive diluent phenyl glycidyl ether and continue vacuum mixing at 800 rpm for 3 minutes. After mixing evenly, epoxy resin adhesive is obtained.

[0110] Comparative Example 1 Comparative Example 1 provides an epoxy resin adhesive that differs from Example 1 in that the reactive diluent used is a bifunctional reactive diluent, neopentyl glycol diglycidyl ether. The remaining components and amounts are the same as in Example 1, and will not be repeated here.

[0111] Comparative Example 2 Comparative Example 2 provides an epoxy resin adhesive that differs from Example 1 in that it directly adds an imidazole curing agent, 2-ethyl-4-methylimidazolium, instead of a microcapsule-type curing agent. The remaining components and amounts are the same as in Example 1, and will not be repeated here.

[0112] Comparative Example 3 Comparative Example 3 provides an epoxy resin adhesive that differs from Example 1 in that it uses the microcapsule-type curing agent prepared in Comparative Synthesis Example 1. The remaining components and amounts are the same as in Example 1, and will not be described again here.

[0113] Comparative Example 4 Comparative Example 4 provides an epoxy resin adhesive that differs from Example 1 in that it uses the microcapsule-type curing agent prepared in Comparative Synthesis Example 2. The remaining components and amounts are the same as in Example 1, and will not be repeated here.

[0114] Comparative Example 5 Comparative Example 5 provides an epoxy resin adhesive that differs from Example 1 in that it uses the microcapsule-type curing agent prepared in Comparative Synthesis Example 3. The remaining components and amounts are the same as in Example 1, and will not be described again here.

[0115] Comparative Example 6 Comparative Example 6 provides an epoxy resin adhesive that differs from Example 1 in that it uses the microcapsule-type curing agent prepared in Comparative Synthesis Example 4. The remaining components and amounts are the same as in Example 1, and will not be repeated here.

[0116] Test case This application conducted the following performance tests on the epoxy resin adhesives prepared in Examples 1-4 and Comparative Examples 1-6, testing the viscosity, curing performance, glass transition temperature, push-pull force, viscosity stability, and storage stability of the final products. The test methods are as follows: 1. Viscosity According to ASTM D2393 test method, the test was conducted using a rotational viscometer at 25°C, and the unit is cps.

[0117] 2. Curing performance Differential scanning calorimetry (DSC) was used to test and obtain the DSC curing curve. The curing time at a constant temperature of 90℃ was recorded in minutes.

[0118] 3. Glass transition temperature (Tg) Samples were prepared by curing at 90℃ in a forced-air oven for 60 min and tested using thermomechanical analysis (TMA), including compression testing. The heating range was -20℃ to 200℃, with a heating rate of 5℃ / min. The pre-stress was 0.05N. Two heating-cooling cycles were performed, and the second heating curve was used. The unit is ℃.

[0119] 4. Push and pull force Apply epoxy resin adhesive between PET and (5×5mm) glass, cure at 90°C for 60 minutes, and measure the push-pull force according to ASTM D1002 test method, in kg.

[0120] 5. Viscosity stability The epoxy resin adhesive was sealed in a 30mL syringe and left at room temperature (25℃). The viscosity was tested every hour, and the time it took for the viscosity to increase to 50% was measured. The longest test was conducted in 12 hours. The unit is hours. Growth rate = (measured viscosity - initial viscosity) 100% of initial viscosity.

[0121] 6. Storage stability Seal the epoxy resin adhesive in standard packaging (such as aluminum foil bags or plastic syringes) to ensure airtightness and eliminate the influence of moisture. Place the sealed sample in a low-temperature freezer or constant-temperature refrigerator maintained at -40℃±2℃, and take samples once a week. The packaging must be left to stand in a closed, dry environment at 25℃±2℃ for at least 2 hours to allow the sample temperature to equilibrate with the environment. Determine the various properties of the sample after equilibration using the same methods as for viscosity and push-pull force tests. When the viscosity change rate is less than 30% and the push-pull force retention rate is greater than 95%, the storage stability is considered qualified.

[0122] The test results are shown in Table 1.

[0123]

[0124] A comparison of Example 1 and Comparative Example 1 shows that bifunctional reactive diluents are not suitable for single-component epoxy resin adhesive systems. Compared to monofunctional reactive diluents, the viscosity stability decreased sharply from 12 hours to 4 hours after adding the bifunctional reactive diluent. This is because the bifunctional reactive diluent (neopentyl glycol diglycidyl ether) contains two epoxy groups, which participate in the construction of the epoxy crosslinking network. Even a small amount of reaction leads to a rapid increase in the molecular weight of the system and a surge in viscosity, resulting in poor storage stability. Monofunctional reactive diluents, on the other hand, only act as chain terminators and do not participate in the construction of the epoxy crosslinking network. Therefore, they have less impact on viscosity and can be stored for a long time. This demonstrates that for single-component epoxy resin adhesive systems, the use of multifunctional reactive diluents must be avoided or used with caution during formulation design, otherwise, storage stability will be severely compromised. The epoxy resin adhesive of this application uses a monofunctional reactive diluent, which is an important basis for achieving long-term storage.

[0125] A comparison of Example 1 and Comparative Example 2 demonstrates the necessity of microencapsulation. In Comparative Example 2, the time required for the viscosity to increase to 50% by directly adding an imidazole curing agent to the epoxy resin adhesive was less than 1 hour, indicating that the epoxy resin adhesive cannot be used as a single-component system. This is because imidazole curing agents possess certain solubility and reactivity in epoxy resin at room temperature. When directly added to the epoxy resin adhesive, the imidazole molecules disperse in the resin, freely colliding with the epoxy groups and initiating a slow curing reaction until gelation. This illustrates that microencapsulation is a necessary means to achieve the latency of imidazole curing agents. This application successfully "dormantizes" the active component through physical barrier, solving the technical problem of "short shelf life" in long-term storage in the field.

[0126] A comparison of Example 1 and Comparative Example 3 shows that the ratio of allyl compound to mercapto compound directly affects the compactness of the microcapsule shell. In Comparative Example 3, the mass ratio of allyl compound to mercapto compound is 3:1, which is outside the scope of protection of this application. This results in incomplete cross-linking of the allyl compound and mercapto compound, leading to insufficient mechanical strength of the formed microcapsule shell. The microcapsule shell is prone to rupture during storage or under shear force, and the imidazole curing agent in the core will slowly diffuse and seep out, causing it to react prematurely with the epoxy resin.

[0127] A comparison of Example 1 and Comparative Example 4 reveals that the functionality of the allyl and mercapto compounds directly affects the density of the microcapsule shell. In Comparative Example 4, both the allyl and mercapto compounds were bifunctional raw materials, while in Example 1, both were trifunctional. Compared to trifunctional raw materials, the product prepared using bifunctional raw materials exhibited significantly reduced viscosity stability, lower push-pull force, and shorter storage time. This is because the microcapsule shell formed by the crosslinking of bifunctional raw materials is not dense enough, allowing the imidazole curing agent in the core to slowly diffuse and seep out, leading to premature reaction with the epoxy resin.

[0128] Comparing Example 1, Comparative Example 5, and Comparative Example 6, it can be seen that the wall thickness of the microcapsule shell directly affects the curing time, push-pull force, and storage stability of the epoxy resin adhesive. In Comparative Example 5, the mass of allyl compound and mercapto compound is relatively small, resulting in a thinner microcapsule shell with insufficient density, leading to insufficient mechanical strength. It is prone to breakage during storage or under shear force, and the imidazole curing agent in the core will slowly diffuse out, causing it to react prematurely with the epoxy resin. In Comparative Example 6, the mass of allyl compound and mercapto compound is relatively large, resulting in a thicker microcapsule shell with excellent storage stability. However, the following problems exist: (1) The thicker microcapsule shell hinders the release of the imidazole curing agent in the core at high temperatures, resulting in a longer curing time; (2) The modulus of the cured product is significantly reduced, and the product becomes soft. The microcapsule shell is an organic polymer, and organic polymers themselves have a low modulus. A large amount of low-modulus wall material is mixed into the epoxy crosslinking network as an "impurity" or "plasticizer," which destroys the integrity of the network structure and leads to a decrease in overall mechanical properties.

[0129] In summary, the microcapsule-type curing agent provided in this application achieves optimal wall thickness balance of the microcapsule shell by controlling the type, amount and reaction conditions of each component. This ensures storage stability at room temperature and enables effective release of imidazole curing agent at curing temperature without affecting the mechanical properties of the final product.

[0130] The above description is only for the purpose of enabling those skilled in the art to understand the technical solution of this application, and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A microcapsule-type curing agent, characterized in that, The microcapsule-type curing agent includes: a microcapsule shell and a microcapsule core; The microcapsule core is an imidazole curing agent, and the microcapsule shell is obtained by a mercapto-alkene click reaction of an allyl compound and a mercapto compound.

2. The microencapsulated curing agent according to claim 1, characterized in that, The allyl compound is a trifunctional allyl compound.

3. The microencapsulated curing agent according to claim 2, characterized in that, The trifunctional allyl compound is selected from at least one of triallyl isocyanurate, triallyl cyanurate, and triallyl phosphate.

4. The microencapsulated curing agent according to claim 1, characterized in that, The thiol compound is a trifunctional thiol compound.

5. The microencapsulated curing agent according to claim 4, characterized in that, The trifunctional thiol compound is selected from at least one of tris[2-(3-mercaptopropoxy)ethyl]isocyanurate and trimethylolpropane tris(3-mercaptopropionate).

6. The microencapsulated curing agent according to claim 1, characterized in that, The imidazole curing agent is selected from 2 Methylimidazole, 1-benzyl-2-methylimidazole, 2 Phenylidene and 2 Ethyl 4 At least one of methylimidazoles.

7. The microencapsulated curing agent according to claim 1, characterized in that, The mass ratio of the allyl compound to the mercapto compound is 1:(1~3).

8. The microencapsulated curing agent according to claim 1, characterized in that, The microcapsule-type curing agent has a particle size of less than 30 μm.

9. A method for preparing a microcapsule-type curing agent, characterized in that, The microcapsule-type curing agent is as described in any one of claims 1 to 8, and the preparation method comprises: An oil phase mixture is obtained by mixing an imidazole curing agent, a photoinitiator, an allyl compound, and a mercapto compound. The emulsifier is dissolved in water to obtain an aqueous phase; The oil phase mixture is added to the aqueous phase, and after mixing, an oil-in-water emulsion is obtained. Under ultraviolet light irradiation, a mercapto-olefin click reaction is initiated. After washing and drying, the microcapsule-type curing agent is obtained.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the oil phase mixture to the water phase is 1:(10~20).

11. The preparation method according to claim 9, characterized in that, The photoinitiator has a mass fraction of 1% to 6% in the oil phase mixture; The imidazole curing agent has a mass fraction of 50% to 70% in the oil phase mixture.

12. The preparation method according to claim 9 or 11, characterized in that, The photoinitiator is selected from benzoin dimethyl ether, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and 2 hydroxyl 2 At least one of methylphenylacetone.

13. An epoxy resin adhesive, characterized in that, The epoxy resin adhesive comprises the following components in parts by weight: 70-80 parts epoxy resin, 5-10 parts reactive diluent, 0.5-3 parts silane coupling agent, 15-20 parts microencapsulated curing agent, and 5-20 parts filler; The microencapsulated curing agent is as described in any one of claims 1 to 8.

14. The epoxy resin adhesive according to claim 13, characterized in that, The reactive diluent is a monofunctional reactive diluent.

15. The epoxy resin adhesive according to claim 14, characterized in that, The monofunctional reactive diluent is selected from at least one of p-tert-butylphenyl glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, and alkyl glycidyl ether.

16. The epoxy resin adhesive according to claim 13, characterized in that, The epoxy resin is selected from at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin; The silane coupling agent is selected from at least one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; The filler is selected from at least one of titanium dioxide, aluminum hydroxide, kaolin, calcium carbonate powder and silica powder, and the particle size D50 of the filler is less than 10 μm.

17. A method for preparing an epoxy resin adhesive, characterized in that, The epoxy resin adhesive is as described in any one of claims 13 to 16, and the preparation method comprises: The epoxy resin, silane coupling agent, microencapsulated curing agent and filler are mixed evenly to obtain a mixture. An active diluent is added to the mixture, and after mixing evenly, an epoxy resin adhesive is obtained.

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