A single-component epoxy adhesive with a long open period at room temperature and rapid curing at medium temperature.

Abstract

This invention discloses a single-component epoxy adhesive and its preparation method, comprising, by weight: 50-60 parts epoxy resin, 20-30 parts acetyl thioester, 10-20 parts microcapsules, 2-6.5 parts interface trigger source inhibitory composition, and 0.2-0.6 parts antioxidant. The microcapsules consist of a polyurethane wall material with a thioester bond density of 0.5-2.0 mmol / g and a crosslinking degree of 10-30% encapsulating a quaternary phosphonium salt core material. The interface trigger source inhibitory composition is a compound of hydrophobic fumed silica, reactive fluorosilicone additives, and 3A molecular sieves. This invention achieves simultaneous activation at 60-80℃, an open period of ≥48 hours at room temperature, complete curing at 60-80℃ for 20-60 minutes, a shear strength ≥16 MPa, and a storage period of ≥90 days at 40℃ / 80%RH through a triple mechanism of "wall material as curing agent," synergistic interface inhibition, and chemical latency of acetyl thioester combined with physical isolation by microcapsules, thus solving the problem of "surface dryness but internal non-drying."

Description

Technical Field

[0001] This invention relates to the field of epoxy resin adhesive technology, specifically to a single-component epoxy adhesive with a long open period at room temperature and rapid curing at medium temperature, and its preparation method. It is particularly suitable for applications with stringent requirements for open period and curing speed, such as electronic component potting, structural bonding, and automated coating. Background Technology

[0002] Epoxy-thiol curing systems are widely used in electronic component potting, structural bonding, UV-thermal dual-curing coatings, and composite materials due to their advantages such as low-temperature rapid curing, low shrinkage, high bond strength, and low toxicity. To achieve single-component formulation and storage stability, the industry commonly uses latent curing agents compounded with epoxy-thiol systems. Typical examples include moisture-latent ketimine / aldehyde imines, blocked imidazoles, microencapsulated agents, and boron trifluoride-amine complexes.

[0003] However, existing epoxy-thiol latent curing systems have serious technical defects in practical applications: when the system is placed in the air at room temperature, the surface is very easy to form a skin and cure quickly, while the inside remains liquid, resulting in an abnormal curing phenomenon of "dry on the surface but not dry inside". Specifically, the open construction period is extremely short, with the surface forming a skin in only 3 to 12 hours, which cannot meet the construction window requirement of ≥24 hours; (2) the inside cannot cure normally after skinning, resulting in insufficient bonding strength and sealing failure; (3) the skinning phenomenon is significantly affected by the environment and has poor stability; (4) conventional adjustment methods (reducing the amount of accelerator, changing the latent curing agent, etc.) cannot take into account both the two major properties of "anti-skinning" and "rapid curing".

[0004] The root cause of the aforementioned technical defects lies primarily in the following common technical bottlenecks in existing technologies:

[0005] Firstly, the wall materials of microcapsules are all inert polymer materials, serving only a physical isolation function and not participating in the curing reaction. For example, Chinese patent CN104893635A discloses a single-component epoxy microcapsule pre-coating adhesive, whose wall material is an inert material such as urea-formaldehyde resin or polyurethane, used only to coat the epoxy resin. After curing, the wall material becomes a "defect point" in the system, not only reducing the crosslinking density but also affecting the mechanical properties and durability of the cured product due to its inert residue. This "wall material inertization" design is a common approach in existing technologies, resulting in the wall material being unable to contribute active groups to the curing reaction.

[0006] Secondly, there is a lack of synergistic suppression design targeting the gas-liquid interface triggering source. Although existing technologies attempt to add single components such as hydrophobic fumed silica and molecular sieves to adsorb moisture, they do not suppress the diffusion of moisture, CO2, and oxygen to the adhesive interface from a multi-factor synergistic perspective. This leads to the adhesive surface being easily "triggered" at room temperature, forming a gradient effect of preferential surface curing, while the interior remains liquid due to the lack of activation of the catalyst or curing agent, which is the direct cause of the "surface dry, interior not dry" phenomenon.

[0007] Third, the design of the latent curing system fails to achieve a balance between "long open period at room temperature" and "fast curing at medium temperature." Existing technologies typically employ a "gradient activation" design, where the curing agent or accelerator is released sequentially at different temperature windows. However, mismatched temperature windows often lead to premature release of thiols without a catalyst, or premature release of the catalyst without thiols, resulting in side reactions or uneven curing. Furthermore, existing technologies often use tertiary amines as accelerators, which are highly active at room temperature and easily deactivated by CO2, further exacerbating the risk of surface skin formation.

[0008] Therefore, developing a single-component epoxy-thiol adhesive that can achieve both an ultra-long open period at room temperature (≥48 hours) and rapid complete curing at medium temperature (60-80℃ / 20-60 minutes), with the wall material itself participating in the curing reaction and leaving no inert residue, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] This invention addresses the technical shortcomings of existing epoxy-thiol latent curing systems, such as rapid skinning at room temperature, short open periods, and surface-dry but internally incomplete curing. It provides a single-component epoxy adhesive with a long open period at room temperature and rapid curing at medium temperature, along with its preparation method. This invention utilizes a five-in-one compound design of "highly stable latent curing agent + moisture / CO2 shielding agent + composite thiol curing agent + medium-temperature controllable catalysis + surface inert modification" to achieve no skinning after ≥48 hours of open placement at room temperature, complete curing at medium temperature in a short time, and no surface-dry but internally incomplete curing phenomenon.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] In a first aspect, the present invention provides a single-component epoxy adhesive with a long open period at room temperature and rapid curing at medium temperature, characterized in that, by weight, it comprises the following components: 50-60 parts epoxy resin, 20-30 parts acetyl thioester, 10-20 parts microcapsules, 2-6.5 parts interface trigger source inhibitory composition, and 0.2-0.6 parts antioxidant.

[0012] The microcapsules consist of a quaternary phosphonium salt core material encapsulated by a polyurethane wall material containing sulfur ester bonds, and a diluent is also added to the core material.

[0013] The single-component epoxy adhesive provided by this invention constructs a five-in-one functional system of "highly stable latent curing agent + moisture barrier agent + composite thiol curing agent + medium-temperature controllable catalysis + surface inert modification" through the synergistic compounding of epoxy resin, acetyl thioester, microcapsules, interface trigger source inhibitory composition, antioxidant, and optional auxiliary catalyst. Among them, acetyl thioester, as a free latent curing agent, maintains chemical inertness at room temperature, ensuring an ultra-long open period for the adhesive; the thioester-containing polyurethane wall material of the microcapsules has both physical isolation and curing functions, releasing primary thiols upon dissociation at medium temperature, which together with the thiols dissociated from acetyl thioester constitute the composite thiol curing agent, while simultaneously releasing the quaternary phosphonium salt core material to catalyze the reaction; the interface trigger source inhibitory composition inhibits the diffusion of moisture and CO2 to the adhesive interface from the source, preventing premature skinning; and the antioxidant further optimizes storage stability. Each component operates independently and without interference at room temperature, but is simultaneously activated and reacts synergistically at medium temperature, thus achieving a balance between "long open period at room temperature (≥48 hours) and rapid curing at medium temperature (60-80℃ / 20-60 minutes)".

[0014] In this invention, the epoxy resin is in the form of 50 to 60 parts by weight, for example, 50 parts, 50.5 parts, 51 parts, 51.5 parts, 52 parts, 52.5 parts, 53 parts, 53.5 parts, 54 parts, 54.5 parts, 55 parts, 55.5 parts, 56 parts, 56.5 parts, 57 parts, 57.5 parts, 58 parts, 58.5 parts, 59 parts, 59.5 parts, or 60 parts, etc.

[0015] In this invention, the weight parts of acetyl thioester are 20 to 30 parts, for example, 20 parts, 20.5 parts, 21 parts, 21.5 parts, 22 parts, 22.5 parts, 23 parts, 23.5 parts, 24 parts, 24.5 parts, 25 parts, 25.5 parts, 26 parts, 26.5 parts, 27 parts, 27.5 parts, 28 parts, 28.5 parts, 29 parts, 29.5 parts, or 30 parts, etc.

[0016] In this invention, the weight of the microcapsules is 10 to 20 parts, for example, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts, or 20 parts, etc.

[0017] In this invention, the weight percentage of the interface trigger source suppression composition is 2 to 6.5 parts, for example, it can be 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4 parts, 4.2 parts, 4.5 parts, 4.8 parts, 5 parts, 5.2 parts, 5.5 parts, 5.8 parts, 6 parts, 6.2 parts, or 6.5 parts, etc.

[0018] In this invention, the antioxidant is present in parts by weight of 0.2 to 0.6, for example, 0.2 parts, 0.22 parts, 0.25 parts, 0.28 parts, 0.30 parts, 0.32 parts, 0.35 parts, 0.38 parts, 0.40 parts, 0.42 parts, 0.45 parts, 0.48 parts, 0.50 parts, 0.52 parts, 0.55 parts, 0.58 parts, or 0.6 parts, etc.

[0019] As a preferred embodiment of the present invention, the average particle size of the microcapsules is 5-20 μm, the particle size distribution range D ≤ 1.5, and the mass ratio of the core material to the wall material is 1:(2-3).

[0020] Preferably, after the microcapsules are stored at 40°C and 80% relative humidity for 90 days, the core material leakage rate is ≤5%.

[0021] This invention reveals that the average particle size of microcapsules directly affects their dispersion stability and rupture behavior in adhesives. Too small a particle size leads to an excessively large specific surface area, increasing the risk of core material leakage during storage; too large a particle size results in easy sedimentation and uneven distribution within the adhesive layer, affecting curing uniformity. A particle size distribution span D ≤ 1.5 ensures uniform microcapsule size, preventing premature rupture of small capsules and delayed rupture of large capsules, thus guaranteeing "synchronous activation" at medium temperatures. The core-to-wall material mass ratio represents the optimal range balancing the mechanical strength of the wall material and the effective content of the core material. Too thin a wall material leads to premature leakage, while too thick a wall material results in insufficient core material and inadequate catalyst release. A core material leakage rate ≤ 5% (stored at 40℃ and 80%RH for 90 days) is a key indicator for evaluating the isolation performance of microcapsules. An excessively high leakage rate will cause premature catalyst release at room temperature, leading to surface crusting and compromising the system's latency.

[0022] In this invention, the average particle size of the microcapsules is 5 to 20 μm, for example, it can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm or 20 μm, etc.

[0023] In this invention, the mass ratio of the core material to the wall material is 1:(2-3), for example, it can be 1:2.0, 1:2.05, 1:2.10, 1:2.15, 1:2.20, 1:2.25, 1:2.30, 1:2.35, 1:2.40, 1:2.45, 1:2.50, 1:2.55, 1:2.60, 1:2.65, 1:2.70, 1:2.75, 1:2.80, 1:2.85, 1:2.90, 1:2.95, or 1:3.0, etc.

[0024] As a preferred embodiment of the present invention, the polyurethane wall material containing sulfide bonds has a sulfide bond density of 0.5–2.0 mmol / g, a crosslinking degree of 10–30%, and a wall material thickness of 3–10 μm.

[0025] Researchers discovered that the density of thioester bonds determines the amount of primary thiols released after the wall material dissociates at medium temperatures. If the density is too low, the thiols contributed by the wall material dissociation are insufficient to completely cure the epoxy resin, leading to insufficient internal crosslinking density and decreased strength. If the density is too high, the wall material becomes more brittle, easily breaking at room temperature and shortening the open period. The degree of crosslinking affects the mechanical strength and cracking temperature of the wall material. Too low a crosslinking level makes the wall material prone to leakage, while too high a level makes it difficult to crack at medium temperatures, hindering the release of the core material. A wall material thickness of 3–10 μm is the preferred range to ensure effective isolation of the core material during storage and rapid cracking at medium temperatures. A number-average molecular weight of 5000–20000 and a molecular weight distribution of 1.5–2.5 ensure that the wall material has appropriate film-forming properties, mechanical strength, and thermal dissociation behavior, which is beneficial for the formation of a complete and dense shell during microencapsulation.

[0026] In this invention, the thioester bond density of the polyurethane wall material containing thioester bonds is 0.5–2.0 mmol / g, for example, it can be 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, or 2.00 mmol / g, etc.

[0027] In this invention, the degree of crosslinking of the polyurethane wall material containing sulfide bonds is 10-30%, for example, it can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, or 30%, etc.

[0028] In this invention, the thickness of the polyurethane wall material containing sulfide bonds is 3 to 10 μm, for example, it can be 3.0 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5.0 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6.0 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7.0 μm, 7.2 μm, 7.5 μm, 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9.0 μm, or 10 μm, etc.

[0029] As a preferred embodiment of the present invention, the number-average molecular weight of the polyurethane wall material containing sulfide bonds is 5,000 to 20,000, and the molecular weight distribution is 1.5 to 2.5.

[0030] Soft segments (polyethylene glycol, polypropylene glycol) impart flexibility to wall materials and influence their glass transition temperature (Tg) and cracking temperature. A soft segment molecular weight of 1000–2000 and a content of 30–60% can control the Tg of the wall material at 40–70℃, ensuring that the wall material softens and cracks at intermediate temperatures of 60–80℃. Hard segments (diisocyanates) provide rigidity and strength to the wall material; sufficient hard segment content ensures adequate mechanical strength at room temperature, preventing core material leakage. Chain extenders containing thioester bonds are key components for introducing thioester bonds. They contain both thioester bonds and active hydrogen (-OH, -NH2, -SH), covalently linking the thioester bonds to the main chain of the wall material through the reaction of active hydrogen with the -NCO at the end of the prepolymer. A certain amount of chain extender ensures that the thioester bond density in the wall material reaches 0.5–2.0 mmol / g without excessive cross-linking leading to embrittlement. The preferred chain extenders of this invention all simultaneously meet the structural requirements of thioester bonds and active hydrogen, which can efficiently introduce thioester bonds into the wall material, and the primary thiols released after dissociation can effectively participate in the curing reaction.

[0031] In this invention, the number average molecular weight of the polyurethane wall material containing sulfide bonds is 5,000 to 20,000, for example, it can be 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, 10,000, 10,500, 11,000, 11,500, 12,000, 12,500, 13,000, 13,500, 14,000, 14,500, 15,000, 15,500, 16,000, 16,500, 17,000, 17,500, 18,000, 18,500, 19,000, 19,500, or 20,000, etc.

[0032] In this invention, the molecular weight distribution of the polyurethane wall material containing sulfide bonds is 1.5 to 2.5, for example, it can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5, etc.

[0033] As a preferred embodiment of the present invention, the polyurethane wall material containing sulfur ester bonds is composed of soft segments, hard segments, and a chain extender containing sulfur ester bonds, wherein:

[0034] The soft segments are selected from one or more of polyethylene glycol and polypropylene glycol, with a number average molecular weight of 1000 to 2000, and the content of soft segments accounts for 30% to 60% of the total mass of the wall material.

[0035] The hard segments are selected from one or more of isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate, and the content of hard segments accounts for 20-40% of the total mass of the wall material.

[0036] The chain extender containing thioester bonds is a compound containing thioester bonds (-C(=O)-S-) and active hydrogen. Its molecular structure contains at least one -C(=O)-S- group and at least one active hydrogen group selected from hydroxyl, amino or mercapto groups. The chain extender content accounts for 10 to 30% of the total mass of the wall material.

[0037] Preferably, the chain extender containing a thioester bond is selected from one or more of the following: 1,3-propanedithiol monoacetyl thioester, ethylene glycol bis(thioethyl mercaptoacetate), trimethylolpropane trithioethyl mercaptoacetate, pentaerythritol tetrathioethyl mercaptoacetate, S-acetyl-2-mercapto-1,3-propanediol, S-acetyl-cysteine, S-acetyl-mercaptopentaerythritol, and S-acetyl-cysteine.

[0038] The dissociation temperature of 55–90℃, especially 60–80℃, ensures the stability of acetyl thioesters at room temperature and rapid dissociation within the medium-temperature curing window, synchronizing with wall material cracking and quaternary phosphonate activation. The mercapto equivalent of 50–80 g / eq matches the epoxy equivalent of epoxy resin (170–220 g / eq), ensuring the curing reaction proceeds stoichiometrically and with complete crosslinking. The dissociation temperature of 1,3-propanedithiol diacetyl thioester and its analogues (2-methyl-substituted, 3-oxa-substituted) matches the curing window, and the resulting dithiol is a primary thiol with high reactivity, facilitating rapid curing. Targeted screening of acetyl thioester structures avoids the problem of a sharp drop in open period caused by using common primary thiols (which react with epoxy resin at room temperature), and is crucial for ensuring chemical latency.

[0039] In this invention, the number-average molecular weight of the soft segments is 1000 to 2000, for example, it can be 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950 or 2000, etc.

[0040] In this invention, the soft segment content accounts for 30% to 60% of the total mass of the wall material, for example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%, etc.

[0041] In this invention, the content of hard segments accounts for 20-40% of the total mass of the wall material, for example, it can be 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, 35%, 35.5%, 36%, 36.5%, 37%, 37.5%, 38%, 38.5%, 39%, 39.5%, or 40%, etc.

[0042] In this invention, the chain extender content accounts for 10-30% of the total mass of the wall material, for example, it can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, or 30%, etc.

[0043] As a preferred embodiment of the present invention, the dissociation temperature of acetyl thioester is 55-90°C, and the amount of mercapto equivalents released after dissociation is 50-80 g / eq.

[0044] Preferably, the acetyl thioester is selected from one or more of 1,3-propanedithiol diacetyl thioester, 2-methyl-1,3-propanedithiol diacetyl thioester, and 3-oxa-1,5-pentanedithiol diacetyl thioester.

[0045] Preferably, the acetyl thioester is 1,3-propanedithiol diacetyl thioester, with a dissociation temperature of 60–80°C.

[0046] In this invention, the dissociation temperature of acetyl thioester is 55-90℃, for example, it can be 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 85℃, 88℃ or 90℃, etc.

[0047] Preferably, the quaternary phosphonium salt core material is selected from one or more of tetraphenylphosphonium bromide, ethyltriphenylphosphonium bromide, and tetrabutylphosphonium bromide.

[0048] Preferably, the diluent is selected from one or more of benzoate and phthalate.

[0049] Quaternary phosphorus salt (R4P) + X -As an accelerator for the epoxy-thiol reaction, quaternary phosphonium salts possess unique advantages not found in tertiary amine accelerators: ① Activity latency: Quaternary phosphonium salts have a stable ion-pair structure at room temperature and extremely low catalytic activity, preventing the epoxy-thiol reaction and thus ensuring the stability of the adhesive during room temperature storage; ② CO2 inertness: Tertiary amine accelerators readily react with CO2 in the air to form carbamates and become inactive, while quaternary phosphonium salts, as phosphonium salts, have their positive charge centers shielded by four organic groups, preventing them from reacting with CO2 and maintaining their catalytic activity over long-term storage; ③ Thermal activation characteristics: The ion-pair dissociation temperatures of tetrabutylphosphonium bromide and ethyltriphenylphosphonium bromide are approximately 60-80℃, perfectly matching the dissociation temperature of acetyl thioesters and the cracking temperature of wall materials, enabling "synchronous activation"; tetraphenylphosphonium bromide exhibits higher thermal stability (decomposition temperature >350℃), making it suitable for applications requiring a higher curing window.

[0050] The present invention preferably uses tetrabutylphosphonium bromide, ethyltriphenylphosphonium bromide, and tetraphenylphosphonium bromide because: tetrabutylphosphonium bromide (melting point 100-103℃) exhibits the most complete ion pair dissociation and best catalytic activity within a 60-80℃ temperature window; ethyltriphenylphosphonium bromide (melting point 230-235℃) combines high thermal stability with a moderate activation temperature; and tetraphenylphosphonium bromide (melting point 295-300℃) has the highest thermal stability, making it suitable for applications requiring a higher curing temperature window. The activation temperatures of the three quaternary phosphonium salts match the 60-80℃ medium-temperature curing window of the present invention, ensuring rapid release of active species at medium temperatures to catalyze the thiol-epoxy reaction.

[0051] The purpose of adding diluents (dibutyl phthalate, benzoate, etc.) to the core material is to: ① promote diffusion after release: When quaternary phosphonium salts are coated by the wall material, if the core material is a pure solid and the wall material cracks at medium temperature, it is difficult to disperse rapidly throughout the reaction system after release, easily leading to excessively high local catalytic concentrations and uneven curing. The addition of diluents allows the core material melt to diffuse rapidly in the adhesive after release, promoting uniform distribution of quaternary phosphonium salts; ② adjust the melt viscosity of the core material: Diluents reduce the viscosity of the quaternary phosphonium salt melt, which is beneficial for emulsification during microencapsulation and ensures uniform distribution of the core material in the oil droplets. The amount of diluent used is 10-30% of the mass of the quaternary phosphonium salt. Below 10%, the diffusion-promoting effect is not significant; above 30%, it may dilute the catalytic activity of the quaternary phosphonium salt and affect the medium-temperature curing speed.

[0052] The combination of quaternary phosphonium salt and diluent forms a synergistic mechanism of "physical isolation + latent activity" with the polyurethane wall material containing thioester bonds: at room temperature, the quaternary phosphonium salt is completely encapsulated by the wall material, and the diluent is sealed inside the microcapsule. Neither comes into contact with the epoxy resin and acetyl thioester, ensuring the ultra-long storage stability of the adhesive; at medium temperature, the wall material dissociates and breaks down, and the quaternary phosphonium salt-diluent molten liquid is rapidly released and diffuses. The quaternary phosphonium salt ion pairs rapidly dissociate in the epoxy resin, generating active tertiary phosphine species, which efficiently catalyze the thiol-epoxy reaction. This avoids the technical defects of tertiary amine accelerators being easily deactivated by CO2 and prone to surface skinning at room temperature, and is one of the key links in achieving the unity of "long open period at room temperature" and "rapid curing at medium temperature".

[0053] As a preferred embodiment of the present invention, the interface trigger source suppression composition comprises the following components by weight: 0.9 to 2.5 parts of hydrophobic fumed silica, 0.1 to 0.5 parts of reactive fluorosilicone additive, and 1.0 to 3.5 parts of 3A molecular sieve;

[0054] Preferably, the hydrophobic fumed silica is selected from one or more of AEROSIL R972, AEROSIL R974, AEROSIL R202, and CAB-O-SIL TS-610;

[0055] Preferably, the reactive fluorosilicone additive is selected from one or more of the following: SiFast SF-334, FS-7140, IOTA FT12, and A28.

[0056] Preferably, the particle size of the 3A molecular sieve is ≤10um, and it is activated at 150-200℃ for 2 hours before use, with a moisture content of ≤0.2% after activation.

[0057] The interface trigger source suppression composition of this invention is a compound of hydrophobic fumed silica, reactive fluorosilicone additive, and 3A molecular sieve. These three components work synergistically to provide physical barrier, low-energy interface shielding, and chemical adsorption: the hydrophobic fumed silica forms a dense physical barrier layer on the surface of the adhesive, effectively blocking moisture penetration; the reactive fluorosilicone additive, after pre-hydrolysis, chemically bonds to the silica surface, forming an interface layer with extremely low surface energy (10-20 mN / m), simultaneously inhibiting the diffusion of water vapor and CO2; the 3A molecular sieve further reduces the water activity around the interface by selectively adsorbing residual moisture. All three components are indispensable: reducing or eliminating any component will lead to a sharp drop in the open period and a surge in the core material leakage rate. This composition fundamentally cuts off the diffusion of "trigger sources" such as moisture and CO2 to the reaction interface, which is one of the core guarantees for achieving an open period of ≥48 hours at room temperature in this invention.

[0058] In this invention, the amount of hydrophobic fumed silica is 0.9 to 2.5 parts, for example, it can be 0.9 parts, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, or 2.5 parts, etc.

[0059] In this invention, the reactive fluorosilicone additive is used in amounts of 0.1 to 0.5 parts, for example, 0.10 parts, 0.12 parts, 0.15 parts, 0.18 parts, 0.20 parts, 0.22 parts, 0.25 parts, 0.28 parts, 0.30 parts, 0.32 parts, 0.35 parts, 0.38 parts, 0.40 parts, 0.42 parts, 0.45 parts, 0.48 parts, or 0.50 parts.

[0060] In this invention, the 3A molecular sieve is 1.0 to 3.5 parts, for example, it can be 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, 3.0 parts, 3.1 parts, 3.2 parts, 3.3 parts, 3.4 parts, or 3.5 parts, etc.

[0061] As a preferred embodiment of the present invention, the epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, glycidylamine type epoxy resin, alicyclic epoxy resin, multifunctional epoxy resin, and polyether modified epoxy resin.

[0062] Preferably, the epoxy equivalent of the epoxy resin is 170-220 g / eq.

[0063] The epoxy resin used in this invention can be of various types, including bisphenol A, bisphenol F, and phenolic epoxy, and the epoxy equivalent is limited to 170-220 g / eq. This is because the epoxy equivalent matches the mercapto equivalent of acetyl thioester (50-80 g / eq) and the thiol equivalent contributed by the wall material dissociation, ensuring that the curing reaction proceeds according to stoichiometry. If the epoxy equivalent is too low, there is an excess of epoxy groups, resulting in incomplete curing, insufficient crosslinking density, and decreased mechanical properties. If the epoxy equivalent is too high, there is an insufficient number of epoxy groups, leading to increased system viscosity, difficulty in microcapsule dispersion, and reduced heat resistance after curing. Bisphenol A type epoxy resin (such as E-51, EEW≈190) and its compound with bisphenol F type exhibit the best overall performance in terms of viscosity, reactivity, and mechanical properties, and are therefore the preferred main resin of this invention.

[0064] In this invention, the epoxy equivalent of the epoxy resin is 170-220 g / eq, for example, it can be 170 g / eq, 175 g / eq, 180 g / eq, 185 g / eq, 190 g / eq, 195 g / eq, 200 g / eq, 205 g / eq, 210 g / eq, 215 g / eq or 220 g / eq, etc.

[0065] Preferably, the antioxidant is selected from one or more of triphenylphosphine, triphenyl phosphite, Irganox 1010, and Irganox 1076.

[0066] Preferably, the antioxidant is triphenylphosphine.

[0067] In the system of this invention, the primary thiol generated after the dissociation of acetyl thioester is easily oxidized to disulfide by oxygen, resulting in a reduction of effective thiol groups and incomplete curing. Triphenylphosphine possesses both antioxidant and weak catalytic effects, capturing free radicals at room temperature to prevent thiol oxidation. Simultaneously, the lone pair electrons on its phosphorus atom form a synergistic catalytic effect with the quaternary phosphonium salt at intermediate temperatures, improving curing efficiency. At lower dosages, insufficient antioxidant activity leads to decreased storage stability; at higher dosages, excessive antioxidant may slightly interfere with the curing reaction, resulting in a decrease in tensile strength. Therefore, 0.2-0.6 parts is the optimal range for balancing storage stability and curing performance.

[0068] Preferably, the adhesive further comprises 0 to 0.5 parts of an auxiliary catalyst.

[0069] Preferably, the auxiliary catalyst is selected from one or more of zinc acetylacetonate, aluminum acetylacetonate, and cobalt acetylacetonate.

[0070] Preferably, the auxiliary catalyst is zinc acetylacetonate.

[0071] In this invention, the auxiliary catalyst further optimizes the curing temperature window. Zinc acetylacetonate exhibits good thermal latency and is compatible with epoxy resins and thioesters at room temperature without initiating a reaction. At intermediate temperatures, its coordination structure changes, and zinc ions, acting as Lewis acids, can activate epoxy groups, forming a dual-catalytic system of "main catalyst + co-catalyst" with quaternary phosphonium salts. This reduces the peak curing temperature by 10-15°C while maintaining the curing rate and crosslinking density. Appropriate dosage can effectively reduce the curing temperature without affecting the open period and storage stability; lower dosages have little effect, while higher dosages decrease storage stability. Therefore, this dosage range achieves the optimal balance between curing temperature and storage stability.

[0072] In this invention, the auxiliary catalyst is 0 to 0.5 parts, for example, it can be 0 parts, 0.02 parts, 0.05 parts, 0.08 parts, 0.10 parts, 0.12 parts, 0.15 parts, 0.18 parts, 0.20 parts, 0.22 parts, 0.25 parts, 0.28 parts, 0.30 parts, 0.32 parts, 0.35 parts, 0.38 parts, 0.40 parts, 0.42 parts, 0.45 parts, 0.48 parts, or 0.50 parts, etc.

[0073] Secondly, the present invention provides a method for preparing the above-mentioned microcapsules, comprising the following steps:

[0074] S1: Add the soft segment and hard segment to the reactor at a molar ratio of hydroxyl to isocyanate group of 1:(2-3), and react at 60-80℃ for 2-4 hours under nitrogen protection to obtain the terminal isocyanate group prepolymer. Control the -NCO content of the prepolymer to be 5-10%. Add a chain extender containing sulfur ester bond to the prepolymer and continue the reaction for 1-2 hours until the -NCO content is stable.

[0075] S2: Mix the quaternary phosphonium salt and diluent at a mass ratio of 1:(0.1~0.3), heat to 50~80℃ to melt, stir evenly to obtain the core material melt;

[0076] S3: Add the core material melt obtained in step S2 to an aqueous solution containing protective colloid; emulsify under high-speed shearing at 8000-12000 rpm for 5-15 minutes to form an oil-in-water emulsion, and control the oil droplet size to be 5-20 μm;

[0077] S4: Slowly add the prepolymer obtained in step S1 to the emulsion in step S3, control the adding time to 30 to 60 minutes, and maintain the shear speed at 5000 to 8000 rpm, so that the prepolymer is adsorbed on the surface of the oil droplets.

[0078] S5: Add crosslinking agent and polyamine curing agent to the system, heat to 40-60℃, react for 3-6 hours to cure the wall material;

[0079] S6: After the reaction is complete, cool to room temperature, filter, wash with deionized water 3 to 5 times, and vacuum dry at 40 to 60°C for 12 to 24 hours to obtain microcapsule powder.

[0080] In this invention, the quaternary phosphonium salt and the diluent are in a mass ratio of 1:(0.1 to 0.3), for example, it can be 1:0.10, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.20, 1:0.21, 1:0.22, 1:0.23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29 or 1:0.3, etc.

[0081] In this invention, the oil droplet size is 5–20 μm, for example, it can be 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12.0 μm, 12.5 μm, 13.0 μm, 13.5 μm, 14.0 μm, 14.5 μm, 15.0 μm, 15.5 μm, 16.0 μm, 16.5 μm, 17.0 μm, 17.5 μm, 18.0 μm, 18.5 μm, 19.0 μm, 19.5 μm, or 20 μm, etc.

[0082] As a preferred embodiment of the present invention, the number-average molecular weight of the prepolymer in step S1 is 2000-5000, and the molecular weight distribution is 1.2-1.8.

[0083] Preferably, the protective colloid in step S3 is selected from one or more of polyvinyl alcohol, gelatin, and gum arabic, and its concentration in the aqueous solution is 1-5%.

[0084] Preferably, the protective colloid is polyvinyl alcohol with a degree of alcoholysis of 80-90% and a degree of polymerization of 500-2000.

[0085] Preferably, in step S3, the mass ratio of the aqueous phase to the oil phase in the oil-in-water emulsion is (2-5):1.

[0086] Preferably, in step S4, the dropping rate of the prepolymer is 1 to 5 mL / min, and the temperature of the reaction system is maintained at 30 to 50°C during the dropping process.

[0087] Preferably, in step S5, the crosslinking agent is selected from one or more of trimethylolpropane, glycerol, and pentaerythritol, and the amount added is 5 to 15% of the mass of the prepolymer.

[0088] Preferably, in step S5, the polyamine curing agent is selected from one or more of ethylenediamine, diethylenetriamine, and triethylenetetramine, and the amount added is 1% to 5% of the prepolymer mass.

[0089] Preferably, the vacuum degree of vacuum drying in step S6 is -0.09 to -0.095 MPa, and the moisture content of the microcapsules after drying is ≤0.5%.

[0090] In this invention, the number average molecular weight of the prepolymer is 2000 to 5000, for example, it can be 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900 or 5000, etc.

[0091] In this invention, the molecular weight distribution of the prepolymer is 1.2 to 1.8, for example, it can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 1.8.

[0092] In this invention, the amount of crosslinking agent added is 5-15% of the mass of the prepolymer, for example, it can be 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, 10.2%, 10.5%, 10.8%, 11%, 11.2%, 11.5%, 11.8%, 12%, 12.2%, 12.5%, 12.8%, 13%, 13.2%, 13.5%, 13.8%, 14%, 14.2%, 14.5%, 14.8%, or 15%, etc.

[0093] In this invention, the amount of polyamine curing agent added is 1% to 5% of the prepolymer mass, for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, or 5%, etc.

[0094] Thirdly, the present invention provides a method for preparing an adhesive, comprising the following steps:

[0095] The epoxy resin, acetyl thioester, microcapsules, interface trigger source inhibitory composition, antioxidant and optional auxiliary catalyst are mixed evenly according to the above ratio to obtain a one-component epoxy adhesive.

[0096] Compared with the prior art, the present invention has the following beneficial effects:

[0097] (1) Significantly prolongs the open period at room temperature: The interface trigger source inhibition composition (hydrophobic silica + reactive fluorosilicone additive + molecular sieve) synergistically inhibits the diffusion of moisture and oxygen to the interface of the adhesive. Combined with the activity regulation of composite thiol and the controllable catalysis at medium temperature, the adhesive can be left open in the air at room temperature for ≥48 hours without forming a skin, which is far greater than the 3-12 hours of the existing technology.

[0098] (2) Medium-temperature rapid complete curing: The dissociation temperature of acetyl thioester, the cracking temperature of wall material and the activation temperature of quaternary phosphonium salt are all designed in the range of 60 to 80℃ to achieve "synchronous activation". After heating to 60 to 80℃, it can be completely cured in 20 to 60 minutes. There is no phenomenon of surface drying but internal drying. The curing is uniform and the bonding strength is high.

[0099] (3) Excellent storage stability: The microcapsule wall material contains thioester bonds, which physically isolate the core material at room temperature; acetyl thioester is inert at room temperature; the interface composition provides effective protection; after 90 days of accelerated aging at 40℃ and 80%RH, the viscosity growth rate is <50%, and the temperature change of the curing exothermic peak is ≤5℃.

[0100] (4) High component utilization: The sulfur ester polyurethane wall material has both isolation and curing functions. It releases primary thiols to participate in the reaction at medium temperature, leaving no inert residue and high crosslinking density. After curing, the tensile shear strength is ≥16MPa, the elongation at break is ≥200%, and the Tg is ≥80℃. Detailed Implementation

[0101] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0102] To fully and clearly explain the implementation process, information on some raw materials is disclosed as follows:

[0103] Bisphenol A type epoxy resin: grade E-51, epoxy equivalent 190 g / eq, provided by Sinopec Baling Petrochemical Company;

[0104] Polypropylene glycol: Grade PPG-1000, number average molecular weight 1000, provided by Shandong Lanxing Dongda Chemical Co., Ltd.

[0105] Isophorone diisocyanate (IPDI): purity ≥99.5%, provided by Wanhua Chemical Group Co., Ltd.

[0106] Ethylene glycol bis(thioethyl mercaptoacetate): analytical grade, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0107] Tetrabutylphosphonium bromide: 98% purity, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0108] Dibutyl phthalate: analytical grade, provided by Sinopharm Chemical Reagent Co., Ltd.;

[0109] Polyvinyl alcohol: Grade 1788, degree of alcoholysis 88%, degree of polymerization 1700, provided by Shanghai Maclean Biochemical Technology Co., Ltd.

[0110] Trimethylolpropane: Industrial grade, supplied by Baichuan Chemical Co., Ltd.;

[0111] Ethylenediamine: analytical grade, provided by Sinopharm Chemical Reagent Co., Ltd.;

[0112] 1,3-Propanedithiol diacetyl thioester: analytical grade, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0113] Hydrophobic fumed silica: Grade AEROSIL R972, supplied by Evonik Industries;

[0114] Reactive fluorosilicone additive: SiFast SF-334, provided by Standard & Poor's Technology Co., Ltd.

[0115] 3A molecular sieve: spherical, supplied by Shanghai Jiuzhou Chemical Co., Ltd.

[0116] Triphenylphosphine: analytical grade, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0117] Zinc acetylacetone: 98% purity, provided by Shanghai Maclean Biochemical Technology Co., Ltd.

[0118] Ethylene glycol bis(thioethyl mercaptoacetate): analytical grade, provided by Shanghai Aladdin Biochemical Technology Co., Ltd.

[0119] Preparation Example 1: Preparation of Microcapsule A1

[0120] (1) Preparation of prepolymer: 100 parts of polypropylene glycol (PPG-1000, number average molecular weight 1000) and 50 parts of isophorone diisocyanate (IPDI) were added to a reactor and reacted at 70°C for 2 hours under nitrogen protection to obtain a prepolymer with terminal isocyanate groups. The -NCO content of the prepolymer was controlled to be 8.5%. 30 parts of ethylene glycol bis(thioethyl mercaptoacetate) were added, and the reaction was continued for 1.5 hours until the -NCO content stabilized. The number average molecular weight of the obtained prepolymer was 3500, and the molecular weight distribution was 1.5.

[0121] (2) Core material preparation: 67.8 parts of tetrabutylphosphonium bromide and 13.5 parts of dibutyl phthalate are mixed at a mass ratio of 1:0.2, heated to 60°C to melt, and stirred evenly to obtain core material melt.

[0122] (3) Emulsification: The core material melt obtained in step (2) is added to an aqueous solution containing 2% polyvinyl alcohol (degree of alcoholysis 88%, degree of polymerization 1500), and emulsified for 10 minutes under high-speed shear at 10000 rpm to form an oil-in-water emulsion. The oil droplet size is controlled to be 10 μm, and the mass ratio of water phase to oil phase is 3:1.

[0123] (4) Wall material adsorption: The prepolymer obtained in step (1) is slowly added dropwise to the emulsion in step (3) at a rate of 2 mL / min. During the dropwise addition, the temperature of the reaction system is kept at 40℃, the dropwise addition time is controlled at 45 minutes, and the shear speed is kept at 6000 rpm so that the prepolymer is adsorbed on the surface of the oil droplets.

[0124] (5) Interface polymerization and curing: Add trimethylolpropane (10% of the prepolymer mass, i.e. 18 parts) and ethylenediamine (3% of the prepolymer mass, i.e. 5.4 parts) to the system, heat to 45°C and react for 2.5 hours, then heat to 55°C and react for 2 hours to cure the wall material.

[0125] (6) Post-processing: After the reaction is completed, cool to room temperature, filter, wash 4 times with deionized water, and dry under vacuum at 50°C for 18 hours (vacuum degree -0.092 MPa) to obtain microcapsule powder.

[0126] The obtained microcapsules had an average particle size of 12 μm, a particle size distribution span D=1.2, a core-to-wall material mass ratio of 1:2.5, a wall material thickness of 5 μm, a thioester bond density of 1.2 mmol / g, a crosslinking degree of 18%, and a moisture content of 0.3%. The wall material had a number-average molecular weight of 8500 and a molecular weight distribution of 1.8. The wall material contained 49.2% soft segments, 24.6% hard segments, and 14.8% chain extenders containing thioester bonds.

[0127] Preparation Example 2: Preparation of Microcapsule A2

[0128] The method is the same as that used in Preparation Example 1, except that:

[0129] In step (1), the amount of ethylene glycol bis(thioethyl mercaptoacetate) used is adjusted to 22 parts;

[0130] In step (5), the amount of trimethylolpropane is adjusted to 4.8% (i.e. 7.92 parts) of the prepolymer mass, and the amount of ethylenediamine is adjusted to 1.2% (i.e. 1.98 parts) of the prepolymer mass.

[0131] The resulting microcapsules had a thioester bond density of 0.5 mmol / g in the wall material, a crosslinking degree of 10%, and a glass transition temperature (Tg) of 40℃. Other parameters were the same as in Preparation Example 1.

[0132] Preparation Example 3: Preparation of Microcapsule A3

[0133] The method is the same as that used in Preparation Example 1, except that:

[0134] In step (1), the amount of ethylene glycol bis(thioethyl mercaptoacetate) used is adjusted to 48 parts;

[0135] In step (5), the amount of trimethylolpropane is adjusted to 15% of the prepolymer mass (i.e., 29.7 parts), the amount of ethylenediamine is adjusted to 5% of the prepolymer mass (i.e., 9.9 parts), and the post-curing temperature is adjusted to 60℃.

[0136] The resulting microcapsules had a thioester bond density of 2.0 mmol / g in the wall material, a crosslinking degree of 30%, and a glass transition temperature (Tg) of 70℃. Other parameters were the same as in Preparation Example 1.

[0137] Preparation Example 4: Preparation of Microcapsule A4

[0138] The method is the same as that used in Preparation Example 1, except that:

[0139] In step (1), the amount of ethylene glycol bis(thioethyl mercaptoacetate) used is adjusted to 9.5 parts;

[0140] In step (5), the amount of trimethylolpropane is adjusted to 6% of the prepolymer mass (i.e., 9.57 parts), the amount of ethylenediamine is adjusted to 1.5% of the prepolymer mass (i.e., 2.39 parts), and the curing temperature is adjusted to 40℃-50℃.

[0141] The resulting microcapsules had a thioester bond density of 0.4 mmol / g in the wall material, a crosslinking degree of 8%, and a Tg of 35℃. Other parameters were the same as in Preparation Example 1.

[0142] Preparation Example 5: Preparation of Microcapsules A5

[0143] The method is the same as that used in Preparation Example 1, except that:

[0144] In step (1), the amount of ethylene glycol bis(thioethyl mercaptoacetate) used is adjusted to 55 parts;

[0145] In step (5), the amount of trimethylolpropane is adjusted to 18% of the prepolymer mass (i.e., 36.9 parts), the amount of ethylenediamine is adjusted to 6% of the prepolymer mass (i.e., 12.3 parts), and the curing temperature is adjusted to 50℃-65℃.

[0146] The resulting microcapsules had a thioester bond density of 2.2 mmol / g in the wall material, a crosslinking degree of 33%, and a Tg of 75℃. Other parameters were the same as in Preparation Example 1.

[0147] Preparation Example 6: Preparation of Microcapsules A6

[0148] (1) Core material preparation: Same as in preparation example 1, 67.8 parts of tetrabutylphosphonium bromide and 13.5 parts of dibutyl phthalate were mixed at a mass ratio of 1:0.2, heated to 60°C to melt, and stirred evenly to obtain core material melt.

[0149] (2) Preparation of oil phase: Mix 80 parts of isophorone diisocyanate (IPDI) (as isocyanate monomer of polyurea wall material) with the above core material melt and stir evenly to form the oil phase.

[0150] (3) Emulsification: The oil phase obtained in step (2) is added to an aqueous solution containing 2% polyvinyl alcohol (degree of alcoholysis 88%, degree of polymerization 1500) and emulsified for 10 minutes under high-speed shear at 10000 rpm to form an oil-in-water emulsion. The oil droplet size is controlled to be 10 μm and the mass ratio of water phase to oil phase is 3:1.

[0151] (4) Interface polymerization and wall material curing: Add ethylenediamine (accounting for 15% of the total mass of the oil phase, i.e., about 22.2 parts) to the system as a chain extender and curing agent, heat to 45°C and react for 2.5 hours, then heat to 55°C and react for 2 hours to cure the polyurea wall material.

[0152] (5) Post-processing: After the reaction is completed, cool to room temperature, filter, wash 4 times with deionized water, and dry under vacuum at 50°C for 18 hours (vacuum degree -0.092 MPa) to obtain microcapsule powder.

[0153] The resulting microcapsules had an average particle size of 12 μm, a particle size distribution span of D=1.2, a core-to-wall material mass ratio of 1:2.5, a wall material thickness of 5 μm, and a moisture content of 0.3%. The wall material was an inert polyurea, free of thioester bonds, with a crosslinking degree of approximately 25% and a glass transition temperature (Tg) of approximately 55°C.

[0154] Example 1

[0155] 1. Pretreatment of the interface trigger source suppression composition

[0156] Dissolve 0.3 parts of SF-334 reactive fluorosilicone additive in a 90 / 10 ethanol / water mixture, adjust the pH to 4.5, stir for 30 minutes for pre-hydrolysis, mix with 1.7 parts of AEROSIL R972, and dry at 80°C for 2 hours to chemically bond fluorosilane to the silica surface; activate 2.25 parts of 3A molecular sieve at 180°C for 2 hours and grind to a particle size ≤10 μm.

[0157] 2. Preparation of adhesives

[0158] Weigh the following components based on a total weight of 100 parts: 55 parts of bisphenol A type epoxy resin (E-51, epoxy equivalent 190 g / eq), 25 parts of 1,3-propanedithiol diacetyl thioester, 15 parts of microcapsule A1, 4.25 parts of interface trigger source inhibition composition (AEROSIL R97 21.7 parts + SF-334 0.3 parts + activated 3A molecular sieve 2.25 parts, totaling 4.25 parts), 0.4 parts of triphenylphosphine, and 0.35 parts of zinc acetylacetone.

[0159] The epoxy resin and the interface trigger source inhibition composition were dispersed at 2000 rpm for 20 minutes (vacuum degassing); 1,3-propanedithiol diacetyl thioester, triphenylphosphine, and zinc acetylacetone were added and dispersed evenly by low-speed stirring; finally, the microcapsules were added and stirred at 500 rpm for 10 minutes to obtain the adhesive.

[0160] Example 2

[0161] The difference from Example 1 is that the weight of bisphenol A type epoxy resin (E-51, epoxy equivalent 190 g / eq) is changed to 50 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0162] Example 3

[0163] The difference from Example 1 is that the weight parts of bisphenol A type epoxy resin (E-51, epoxy equivalent 190 g / eq) are changed to 60 parts, and the weight parts of other components are reduced proportionally, while the total weight remains unchanged at 100 parts.

[0164] Example 4

[0165] The difference from Example 1 is that the weight of ethylene glycol bis(thioethyl mercaptoacetate) is changed to 20 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0166] Example 5

[0167] The difference from Example 1 is that the weight of ethylene glycol bis(thioethyl mercaptoacetate) is changed to 30 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0168] Example 6

[0169] The difference from Example 1 is that the weight of microcapsule A1 is changed to 10 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0170] Example 7

[0171] The difference from Example 1 is that the weight of microcapsule A1 is changed to 20 parts, while the weight of other components is reduced proportionally, and the total weight remains unchanged at 100 parts.

[0172] Example 8

[0173] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (0.9 parts of AEROSIL R972 + 0.1 parts of SF-334 + 1.0 part of activated 3A molecular sieve) is changed to 2 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0174] Example 9

[0175] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (2.5 parts of AEROSIL R972 + 0.5 parts of SF-334 + 3.5 parts of activated 3A molecular sieve) is changed to 6.5 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0176] Example 10

[0177] The difference from Example 1 is that the weight of triphenylphosphine is changed to 0.2 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0178] Example 11

[0179] The difference from Example 1 is that the weight of triphenylphosphine is changed to 0.6 parts, while the weight of other components is reduced proportionally, and the total weight remains unchanged at 100 parts.

[0180] Example 12

[0181] The difference from Example 1 is that zinc acetylacetone is not added, while the weight proportions of other components remain unchanged.

[0182] Example 13

[0183] The difference from Example 1 is that the weight of zinc acetylacetone is changed to 0.5 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0184] Example 14

[0185] The difference from Example 1 is that only microcapsule A2 is used instead of microcapsule A1, while the types and weight parts of other components remain unchanged, and the total amount remains unchanged at 100 parts by weight.

[0186] Example 15

[0187] The difference from Example 1 is that only microcapsule A3 is used instead of microcapsule A1, while the types and weight parts of other components remain unchanged, and the total amount remains unchanged at 100 parts by weight.

[0188] Comparative Example 1

[0189] The difference from Example 1 is that the weight parts of bisphenol A type epoxy resin (E-51, epoxy equivalent 190 g / eq) are changed to 49 parts, while the weight parts of other components are increased proportionally, and the total weight remains unchanged at 100 parts.

[0190] Comparative Example 2

[0191] The difference from Example 1 is that the weight parts of bisphenol A type epoxy resin (E-51, epoxy equivalent 190 g / eq) are changed to 61 parts, and the weight parts of other components are reduced proportionally, while the total weight remains unchanged at 100 parts.

[0192] Comparative Example 3

[0193] The difference from Example 1 is that the weight of ethylene glycol bis(thioethyl mercaptoacetate) is changed to 19.5 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0194] Comparative Example 4

[0195] The difference from Example 1 is that the weight of ethylene glycol bis(thioethyl mercaptoacetate) is changed to 31 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0196] Comparative Example 5

[0197] The difference from Example 1 is that the weight of microcapsule A1 is changed to 9.5 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0198] Comparative Example 6

[0199] The difference from Example 1 is that the weight of microcapsule A1 is changed to 21 parts, while the weight of other components is reduced proportionally, and the total weight remains unchanged at 100 parts.

[0200] Comparative Example 7

[0201] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (0.7 parts of AEROSIL R972 + 0.1 parts of SF-334 + 1.0 part of activated 3A molecular sieve) is changed to 1.8 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0202] Comparative Example 8

[0203] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (0.9 parts of AEROSIL R972 + 0.1 parts of SF-334 + 0.8 parts of activated 3A molecular sieve) is changed to 1.8 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0204] Comparative Example 9

[0205] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (0.75 parts of AEROSIL R972 + 0.05 parts of SF-334 + 1.0 part of activated 3A molecular sieve) is changed to 1.8 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0206] Comparative Example 10

[0207] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (2.8 parts of AEROSIL R972 + 0.5 parts of SF-334 + 3.5 parts of activated 3A molecular sieve) is changed to 6.8 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0208] Comparative Example 11

[0209] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (2.5 parts of AEROSIL R972 + 0.8 parts of SF-334 + 3.5 parts of activated 3A molecular sieve) is changed to 6.8 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0210] Comparative Example 12

[0211] The difference from Example 1 is that the weight of the interface trigger source inhibition composition (2.5 parts of AEROSIL R972 + 0.5 parts of SF-334 + 3.8 parts of activated 3A molecular sieve) is changed to 6.8 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0212] Comparative Example 13

[0213] The difference from Example 1 is that the weight of triphenylphosphine is changed to 0.18 parts, while the weight of other components is increased proportionally, and the total weight remains unchanged at 100 parts.

[0214] Comparative Example 14

[0215] The difference from Example 1 is that the weight of triphenylphosphine is changed to 0.63 parts, while the weight of other components is reduced proportionally, and the total weight remains unchanged at 100 parts.

[0216] Comparative Example 15

[0217] The difference from Example 1 is that the weight of zinc acetylacetone is changed to 0.55 parts, and the weight of other components is reduced proportionally, while the total weight remains unchanged at 100 parts.

[0218] Comparative Example 16

[0219] The difference from Example 1 is that only microcapsule A4 is used instead of microcapsule A1, while the types and weight parts of other components remain unchanged, and the total amount remains unchanged at 100 parts by weight.

[0220] Comparative Example 17

[0221] The difference from Example 1 is that only microcapsule A5 is used instead of microcapsule A1, while the types and weight parts of other components remain unchanged, and the total amount remains unchanged at 100 parts by weight.

[0222] Comparative Example 18

[0223] The difference from Example 1 is that only microcapsule A6 is used instead of microcapsule A1, while the types and weight parts of other components remain unchanged, and the total amount remains unchanged at 100 parts by weight.

[0224] Comparative Example 19

[0225] The difference from Example 1 is that only trimethylolpropane tris(3-mercaptopropionate) is used instead of 1,3-propanedithiol diacetyl thioester, while the types and weight parts of other components remain unchanged, and the total amount remains unchanged at 100 parts by weight.

[0226] Test items and methods

[0227] (1) Open period at room temperature (skinning time): At 23±2℃ and RH50±5%, the adhesive was applied to the glass plate (2mm thick). Every 2 hours, the surface was touched with a wooden spatula and the time when it no longer adhered was recorded.

[0228] (2) Medium temperature curing rate: DSC test, heating rate 10℃ / min, record peak temperature (T_peak).

[0229] (3) Consistency between surface drying and internal drying: Inject the adhesive into the mold (φ50mm×10mm), cure at 70℃ for 30 minutes, and then cut it open to observe the cross section.

[0230] (4) Storage stability: After sealing, place in a constant temperature and humidity chamber at 40℃ and 80%RH and measure the viscosity doubling time.

[0231] (5) Tensile shear strength: Tested according to GB / T 7124-2008, with aluminum sheets overlapping and cured at 70℃ for 1 hour.

[0232] (6) Core material leakage rate: The content of quaternary phosphonium salts released was determined by HPLC after the microcapsules were stored at 40℃ and 80%RH for 90 days.

[0233] Test Results

[0234] The test results of Examples 1-15 are shown in Table 1, and the test results of Comparative Examples 1-19 are shown in Table 2.

[0235] Table 1 Performance test results of Examples 1-15

[0236] Table 1

[0237]

[0238] Table 2 Performance test results of Comparative Examples 1-19

[0239]

[0240] By comparing the systems of the embodiments with those of the comparative examples, the following clear conclusions can be drawn:

[0241] (1) Wall material curing agent promotes curing

[0242] Example 1 was fully cured, with a tensile strength of 18.5 MPa and a Tg of 85℃; Comparative Example 16 was not fully cured; Comparative Example 17 had an open period of only 5 hours; Comparative Example 18 was not fully cured, with a strength of only 10.2 MPa and a Tg of 60℃; Examples 14-15 were all fully cured, with performance slightly lower than Example 1, demonstrating that a thioester bond density of 0.5–2.0 mmol / g is the key range for achieving "wall material as curing agent". The wall material has both physical isolation and curing functions, and releases primary thiols upon dissociation at medium temperature, significantly increasing the crosslinking density.

[0243] (2) Synergistic effect of interface trigger source inhibition composition

[0244] Example 1: Open period > 72 h, leakage rate 3.2%; Comparative Example 7: Open period 8 h, leakage rate 18.3%; Comparative Example 8: Open period 6 h, leakage rate 20.1%; Comparative Example 9: Open period 5 h, leakage rate 22.5%. The synergistic inhibition of moisture and CO2 diffusion to the interface by the three components of hydrophobic fumed silica, reactive fluorosilicone additive, and molecular sieve is the key to extending the open period and improving storage stability.

[0245] (3) Synergistic protection of the triple latent mechanism

[0246] Firstly, in Comparative Example 19, ordinary primary thiol was used instead of acetylthioester. The open period was only 6 hours and the storage stability was 20 days, proving that the chemical latency of acetylthioester is the basis for its stability at room temperature.

[0247] Second: In Comparative Example 5, the amount of microcapsules added was insufficient, the core material leakage rate was 15.8%, the open period was 6 hours, and the internal liquid state was observed after curing at 70℃, proving that physical isolation by microcapsules is indispensable.

[0248] Thirdly: In Comparative Example 13, the amount of antioxidant added was insufficient, and the storage stability decreased to 50 days, but the open period was still 12 hours, proving that the activity latency of quaternary phosphonium salts is better than that of tertiary amines.

[0249] The three latency mechanisms work together, and none of them can be omitted, to jointly ensure the stability of ultra-long-term storage at room temperature.

[0250] (4) Curing advantages of simultaneous activation of temperature window

[0251] In Example 1, the acetyl thioester dissociation temperature was 72°C, the wall material cracking temperature was approximately 70°C, and the quaternary phosphonium salt activation temperature was approximately 70°C. These three temperatures overlapped, resulting in complete curing at 70°C for 30 minutes. In Comparative Example 3, the wall material dissociation temperature rose to 85°C, resulting in surface dryness but internal incomplete drying. In Comparative Example 5, the quaternary phosphonium salt leaked prematurely, leaving the interior liquid. In Comparative Example 6, the open period was only 4 hours. The simultaneous design of these three temperatures within a 60-80°C window is the fundamental guarantee for achieving "instantaneous triggering and concentrated reaction."

[0252] (5) Screening of acetyl thioesters and matching of mercapto equivalents

[0253] Example 1, with a dissociation temperature of 60-80℃ and a mercapto equivalent of 54 g / eq, showed good matching with an epoxy equivalent of 190 g / eq, resulting in optimal performance. Examples 2 and 3 showed slight shifts in dissociation windows, leading to a slight decrease in performance. Comparative Example 19 used common primary thiols, reacting at room temperature with an open period of only 6 hours, demonstrating that targeted screening of acetyl thioesters is key to ensuring chemical latency and temperature window matching.

[0254] (6) Regulatory effect of co-catalysts and antioxidants

[0255] Using 0.2-0.5 parts of zinc acetylacetonate can reduce the curing temperature by 10-15℃ (Example 12: 85℃ → Example 1: 78℃ → Example 13: 75℃), but more than 0.5 parts (Comparative Example 15) result in decreased storage stability. Using 0.2-0.6 parts of triphenylphosphine ensures storage stability of ≥80 days, less than 0.2 parts (Comparative Example 13) reduces it to 50 days, and more than 0.6 parts (Comparative Example 14) results in decreased tensile strength.

[0256] (7) Boundary effect of component dosage

[0257] Within the range of 50-60 parts epoxy resin, 20-30 parts acetyl thioester, 10-20 parts microcapsules, 2-6.5 parts interface composition, 0.2-0.6 parts antioxidant, and 0.2-0.5 parts auxiliary catalyst, an open period of ≥48 h, complete curing, and tensile strength of ≥16.5 MPa can be achieved. Beyond the range, significant performance degradation occurs, demonstrating the rationality of the scope of the claims.

[0258] (8) Optimal ratio for overall performance

[0259] Example 1 exhibits the best overall performance: open period at room temperature >72 h, complete curing at 70℃ / 30 min, storage stability >90 d, tensile strength 18.5 MPa, Tg 85℃, and core material leakage rate 3.2%, all falling within the scope of the claims, demonstrating the feasibility and advancement of the present invention.

[0260] In summary, this invention, through the use of sulfur-containing polyurethane wall material microcapsules, interface trigger source inhibition composition, triple latency mechanism, simultaneous activation at temperature windows, and directional screening of acetyl thioesters, successfully achieves the unification of "long open period at room temperature and rapid curing at medium temperature," solving the problem of "surface dry but not internally dry" in existing technologies. The components work synergistically, demonstrating outstanding substantive features and significant progress.

[0261] Industrial applicability

[0262] The single-component epoxy adhesive of this invention can be widely used in fields such as electronic component potting, structural bonding, automated coating, photovoltaic module encapsulation, automotive electronics, and 5G communication modules. It is particularly suitable for automated production lines with stringent requirements for open period and curing speed, and can significantly improve production efficiency, reduce material waste, and ensure product reliability.

[0263] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0264] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A one-component epoxy adhesive with a long open period at room temperature and rapid curing at medium temperature, characterized in that, Based on parts by weight, it comprises the following components: 50-60 parts epoxy resin, 20-30 parts acetyl thioester, 10-20 parts microcapsules, 2-6.5 parts interface trigger source inhibitory composition, and 0.2-0.6 parts antioxidant; The microcapsules consist of a quaternary phosphonium salt core material encapsulated by a polyurethane wall material containing sulfur ester bonds, and the core material also contains a diluent.

2. The adhesive according to claim 1, characterized in that, The average particle size of the microcapsules is 5-20 μm, the particle size distribution range D ≤ 1.5, and the mass ratio of the core material to the wall material is 1:(2-3). Preferably, after the microcapsules are stored at 40°C and 80% relative humidity for 90 days, the core material leakage rate is ≤5%.

3. The adhesive according to claim 1, characterized in that, The polyurethane wall material containing sulfur ester bonds has a sulfur ester bond density of 0.5–2.0 mmol / g, a crosslinking degree of 10–30%, and a wall material thickness of 3–10 μm.

4. The adhesive according to claim 1, characterized in that, The number-average molecular weight of the polyurethane wall material containing sulfur ester bonds is 5,000 to 20,000, and the molecular weight distribution is 1.5 to 2.

5.

5. The adhesive according to claim 1, characterized in that, The sulfur-containing ester bond polyurethane wall material is composed of soft segments, hard segments, and a chain extender containing sulfur ester bonds, wherein: The soft segments are selected from one or more of polyethylene glycol and polypropylene glycol, with a number average molecular weight of 1000-2000, and the content of the soft segments accounts for 30-60% of the total mass of the wall material; The hard segment is selected from one or more of isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate, and the content of the hard segment accounts for 20% to 40% of the total mass of the wall material; The chain extender containing thioester bonds is a compound containing thioester bonds (-C(=O)-S-) and active hydrogen, and its molecular structure contains at least one -C(=O)-S- group and at least one active hydrogen group selected from hydroxyl, amino or mercapto groups. The chain extender accounts for 10-30% of the total mass of the wall material. Preferably, the chain extender containing the sulfur ester bond is selected from one or more of 1,3-propanedithiol monoacetyl thioester, ethylene glycol bis(thioethyl mercaptoacetate), trimethylolpropane trithioethyl mercaptoacetate, pentaerythritol tetrathioethyl mercaptoacetate, S-acetyl-2-mercapto-1,3-propanediol, S-acetyl-cysteine, S-acetyl-mercaptopentaerythritol, and S-acetyl-cysteine.

6. The adhesive according to claim 1, characterized in that, The acetyl thioester has a dissociation temperature of 55–90°C and releases 50–80 g / eq of mercapto equivalents after dissociation. Preferably, the acetyl thioester is selected from one or more of 1,3-propanedithiol diacetyl thioester, 2-methyl-1,3-propanedithiol diacetyl thioester, and 3-oxa-1,5-pentanedithiol diacetyl thioester. Preferably, the acetyl thioester is 1,3-propanedithiol diacetyl thioester, with a dissociation temperature of 60–80°C; Preferably, the quaternary phosphonium salt core material is selected from one or more of tetraphenylphosphonium bromide, ethyltriphenylphosphonium bromide, and tetrabutylphosphonium bromide; Preferably, the diluent is selected from one or more of benzoate and phthalate.

7. The adhesive according to claim 1, characterized in that, The interface trigger source suppression composition comprises, by weight, the following components: 0.9 to 2.5 parts of hydrophobic fumed silica, 0.1 to 0.5 parts of reactive fluorosilicone additive, and 1.0 to 3.5 parts of 3A molecular sieve; Preferably, the hydrophobic fumed silica is selected from one or more of AEROSIL R972, AEROSIL R974, AEROSIL R202, and CAB-O-SIL TS-610; Preferably, the reactive fluorosilicone additive is selected from one or more of SiFast SF-334, FS-7140, IOTA FT12, and A28. Preferably, the 3A molecular sieve has a particle size ≤10μm and is activated at 150-200℃ for 2 hours before use, with a moisture content ≤0.2% after activation.

8. The adhesive according to claim 1, characterized in that, The epoxy resin is selected from one or more of the following: bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, glycidylamine type epoxy resin, alicyclic epoxy resin, multifunctional epoxy resin, and polyether modified epoxy resin. Preferably, the epoxy equivalent of the epoxy resin is 170-220 g / eq; Preferably, the antioxidant is selected from one or more of triphenylphosphine, triphenyl phosphite, Irganox 1010, and Irganox 1076; Preferably, the antioxidant is triphenylphosphine; Preferably, the adhesive further comprises 0 to 0.5 parts of an auxiliary catalyst; Preferably, the auxiliary catalyst is selected from one or more of zinc acetylacetonate, aluminum acetylacetonate, and cobalt acetylacetonate; Preferably, the auxiliary catalyst is zinc acetylacetonate.

9. A method for preparing the microcapsules according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Add the soft segment and hard segment to the reactor at a molar ratio of hydroxyl to isocyanate group of 1:(2-3), and react at 60-80℃ for 2-4 hours under nitrogen protection to obtain the terminal isocyanate group prepolymer. Control the -NCO content of the prepolymer to be 5-10%. Add a chain extender containing sulfur ester bond to the prepolymer and continue the reaction for 1-2 hours until the -NCO content is stable. S2: Mix the quaternary phosphonium salt and diluent at a mass ratio of 1:(0.1~0.3), heat to 50~80℃ to melt, and stir evenly to obtain a core material melt; S3: Add the core material melt obtained in step S2 to an aqueous solution containing protective colloid; emulsify under high-speed shearing at 8000-12000 rpm for 5-15 minutes to form an oil-in-water emulsion, and control the oil droplet size to be 5-20 μm; S4: Slowly add the prepolymer obtained in step S1 to the emulsion in step S3, control the adding time to 30 to 60 minutes, and maintain the shear speed at 5000 to 8000 rpm, so that the prepolymer is adsorbed on the surface of the oil droplets. S5: Add crosslinking agent and polyamine curing agent to the system, heat to 40-60℃, react for 3-6 hours to cure the wall material; S6: After the reaction is complete, cool to room temperature, filter, wash with deionized water 3 to 5 times, and vacuum dry at 40 to 60°C for 12 to 24 hours to obtain microcapsule powder.

10. The preparation method according to claim 9, characterized in that, The number-average molecular weight of the prepolymer in step S1 is 2000-5000, and the molecular weight distribution is 1.2-1.

8. Preferably, the protective colloid in step S3 is selected from one or more of polyvinyl alcohol, gelatin, and gum arabic, and its concentration in the aqueous solution is 1-5%. Preferably, the protective colloid is polyvinyl alcohol with a degree of alcoholysis of 80-90% and a degree of polymerization of 500-2000; Preferably, the mass ratio of the aqueous phase to the oil phase in the oil-in-water emulsion in step S3 is (2-5):1; Preferably, the dropping rate of the prepolymer in step S4 is 1 to 5 mL / min, and the temperature of the reaction system is maintained at 30 to 50°C during the dropping process; Preferably, the crosslinking agent in step S5 is selected from one or more of trimethylolpropane, glycerol, and pentaerythritol, and the amount added is 5-15% of the mass of the prepolymer. Preferably, the polyamine curing agent in step S5 is selected from one or more of ethylenediamine, diethylenetriamine, and triethylenetetramine, and the amount added is 1% to 5% of the mass of the prepolymer. Preferably, the vacuum degree of the vacuum drying in step S6 is -0.09 to -0.095 MPa, and the moisture content of the microcapsules after drying is ≤0.5%.

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