A segmentable curing one-component silicone thermal bonding adhesive as well as a preparation method and application thereof

Abstract

The application belongs to the technical field of organic silicone adhesive, and discloses a single-component organic silicone hot bonding adhesive capable of being cured in segments, and a preparation method and application thereof. The preparation method is as follows: first, end-vinyl silicone oil, hexamethyl disilazane and fumed white carbon black are mixed, kneaded and ground to obtain a first base material; then, methyl MQ silicone resin, methyl-vinyl silicone rubber, hydrogen-containing silicone oil, inhibitor and diluent are mixed and dispersed to obtain a second base material; finally, tackifier and latent platinum catalyst are added. The single-component organic silicone hot bonding adhesive prepared by the application forms a hot bonding adhesive prepreg after initial curing, and has extremely low peeling force at normal temperature, is easy to peel off from a release film during use, and the adhesive surface is still flat and undamaged when the adhesive surface is pressed against the bonding surface. After the prepreg is hot-pressed during use, the cross-linking is complete, the bonding with the base material is tight, the peeling force is high, and the high strength required for long-term use can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of silicone adhesive technology, specifically relating to a single-component silicone thermal adhesive that can be cured in stages, its preparation method, and its application. Background Technology

[0002] Thermal adhesives are a type of special adhesive with the characteristics of "room temperature inertness and hot-press activation". At room temperature, the molecular chains are in a stable state with no significant adhesive force, enabling safe storage and transportation as well as precise coating. Under heating and pressurization, the system triggers a cross-linking reaction or molecular chain diffusion, quickly forming strong adhesion (high peel strength) to conventional substrates such as metals, plastics, ceramics, and polymer films, meeting structural bonding requirements.

[0003] Silicone thermal adhesives, with their unique molecular structure advantages, have become a core choice in high-end fields: the siloxane (Si-O-Si) main chain bond energy is as high as 444kJ / mol, giving the material an ultra-wide temperature range of -60~220℃ (short-term tolerance to welding temperatures of 260℃), while also possessing excellent resistance to UV aging, chemical stability (resistance to machine oil, acids, alkalis, and organic solvents), and electrical insulation. This makes them indispensable in fields such as electronic packaging, aerospace (high-temperature wire harness fixing), and high-temperature labels. Especially in the cutting-edge manufacturing of solid-state batteries, they can achieve precise bonding of copper foil double-sided PI film and separator, effectively avoiding the risk of battery short circuits by resisting electrolyte corrosion and suppressing interface shrinkage during thermal runaway, thus becoming a key material for improving the safety and cycle stability of solid-state batteries.

[0004] However, traditional silicone thermal adhesives have long faced technical bottlenecks: two- or multi-component systems require on-site mixing of curing agents (such as crosslinking agents and catalysts), which not only leads to performance fluctuations due to mixing ratio errors, but also results in a shelf life of less than 3 months due to the tendency of the curing agent and the main agent to react prematurely. Furthermore, the construction process is cumbersome and difficult to adapt to large-scale industrial production. While single-component systems simplify the operation process, they mostly rely on a single curing mechanism (condensation or addition type), which cannot balance the core contradiction between "remote construction" and "high strength requirements": condensation type systems release small molecule byproducts such as methanol and water during curing, which can easily form bubbles, corrode sensitive substrates, and have limited final bond strength (shear strength ≤ 1.5 MPa); although traditional addition type systems have no byproducts and a curing shrinkage rate ≤ 0.1%, the single temperature triggering mechanism means that coating and bonding must be carried out continuously. If the coating needs to be transported to a different location or bonding is delayed, the adhesive is prone to premature curing or tack reduction due to environmental temperature fluctuations. On the other hand, reducing the curing activity to adapt to storage and transportation will lead to incomplete crosslinking during bonding, making it impossible to achieve the high strength required for long-term use.

[0005] Therefore, developing a single-component silicone thermal adhesive that can be cured in sections and has high peel strength after hot pressing is of great significance for its industrial application in high-end industries. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a segmentally curable single-component silicone thermal adhesive, its preparation method, and its application. The prepreg formed after the initial curing of the single-component silicone thermal adhesive provided by this invention has extremely low peel strength (≤10g) at room temperature, making it easy to peel from the release film during use. Even when the adhesive surfaces are pressed together, the adhesive surface remains smooth and undamaged. During use, after hot pressing the prepreg, complete cross-linking occurs, resulting in a tight bond with the substrate and high peel strength, achieving the high strength required for long-term use.

[0007] This invention provides a method for preparing a segmented curable single-component silicone thermal adhesive.

[0008] Specifically, a method for preparing a segmented curable single-component silicone thermal adhesive includes the following steps: (1) Mix vinyl-terminated silicone oil, hexamethyldisilazane and fumed silica, knead and grind to obtain the first base material; (2) The first base material is mixed and dispersed with methyl MQ silicone resin, methyl vinyl silicone rubber, hydrogen-containing silicone oil, inhibitor, and diluent to obtain the second base material; (3) Add tackifier and latent platinum catalyst to the second base material, stir and mix to obtain a one-component organosilicon thermal adhesive; The inhibitor includes a first inhibitor and a second inhibitor. The first inhibitor is selected from at least one of propynyl alcohol, 2-methyl-3-butyn-2-ol, and 3-methyl-1-pentyn-3-ol. The second inhibitor is selected from at least one of ethynylcyclohexanol, 3,7,11-trimethyldodecyn-3-ol, divinyl maleate, and tetramethyltetravinylcyclotetrasiloxane. The mass ratio of the first inhibitor to the second inhibitor is (1-3):1. The tackifier is a random copolymer polydimethyl-methylvinylsiloxane modified with an epoxy silane coupling agent.

[0009] In some embodiments of the present invention, the mass ratio of the first inhibitor to the second inhibitor is (1.2-2.5):1. By strictly controlling the mass ratio and dosage of the first inhibitor and the second inhibitor, the present invention can ensure that the silicone layer achieves the ideal gelation rate or curing degree during pre-pressing preparation of the prepreg and final hot-pressing curing, effectively guaranteeing the initial tack performance and the subsequent crosslinking strength.

[0010] In some embodiments of the present invention, the epoxy silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, such as KH-560, Z-6040 (Dow Corning), KBE-403 (Shin-Etsu), GF-96 (Wacker), and A-187 (Momentive).

[0011] In some embodiments of the present invention, the random copolymer polydimethyl-methylvinylsiloxane is a linear polysiloxane polymer formed by random copolymerization of dimethylsiloxane units (-Me2SiO-) and methylvinylsiloxane units (-MeViSiO-).

[0012] In some embodiments of the present invention, the preparation method of the epoxy-silane coupling agent modified random copolymer polydimethyl-methylvinylsiloxane is as follows: S1. After mixing and dispersing dimethyldimethoxysilane and methylvinyldimethoxysilane, an alkali metal hydroxide was added; water was then added dropwise to the system, and the system temperature was adjusted to carry out a segmented heat preservation reaction; finally, the random copolymer polydimethyl-methylvinylsiloxane was obtained by separation and purification. S2. Mix the epoxy silane coupling agent with the organotin catalyst, then add random copolymer polydimethyl-methylvinylsiloxane dropwise, adjust the system temperature to carry out a second staged heat preservation reaction, and obtain epoxy silane coupling agent modified random copolymer polydimethyl-methylvinylsiloxane.

[0013] In some embodiments of the present invention, in step S1, the mass ratio of dimethyldimethoxysilane to methylvinyldimethoxysilane is (1.5-3):1.

[0014] In some embodiments of the present invention, in step S1, the process of the single-stage heat preservation reaction is to keep the reaction at 45-55°C for 1-3 hours, and then keep the reaction at 65-75°C for 1-3 hours.

[0015] In some embodiments of the present invention, in step S2, the secondary segmented heat preservation reaction process is as follows: heat preservation reaction at 45-55℃ for 0.5-1.5h, then heat preservation reaction at 75-85℃ for 1-3h, and finally heat preservation reaction at 95-110℃ for 1-3h.

[0016] In some embodiments of the present invention, the mass ratio of the terminal vinyl silicone oil to the hexamethyldisilazane and the fumed silica in step (1) is 100:(8-15):(40-60); preferably, the mass ratio of the terminal vinyl silicone oil to the hexamethyldisilazane and the fumed silica in step (1) is 100:(10-15):(45-55).

[0017] In some embodiments of the present invention, the viscosity of the end vinyl silicone oil in step (1) is 10000-50000 mPa·s.

[0018] In some embodiments of the present invention, water, preferably distilled water or deionized water, is added in step (1) when preparing the first base material. The mass ratio of the water to the terminal vinyl silicone oil is (0.5-2):100.

[0019] In some embodiments of the present invention, the process of obtaining the first base material in step (1) is as follows: the first end-vinyl silicone oil is mixed with the hexamethyldisilazane and the water, and then the fumed silica is added in batches, and the temperature is controlled below 85°C for cold kneading; then, vacuum kneading is performed under the conditions of -0.08-0.1 MPa and 150-180°C; finally, the second end-vinyl silicone oil is added, and vacuum kneading is continued until the end, and then ground to obtain the first base material. The first end-vinyl silicone oil and the second end-vinyl silicone oil constitute the end-vinyl silicone oil; the mass ratio of the first end-vinyl silicone oil to the second end-vinyl silicone oil is (5-12):1; preferably (7-10):1.

[0020] In some embodiments of the present invention, the process of obtaining the first base material in step (1) is as follows: the first end vinyl silicone oil is mixed with the hexamethyldisilazane and the water for 5-30 minutes, and then the fumed silica is added in batches. The temperature is controlled below 80°C and cold kneading is performed for 1-3 hours; then vacuum kneading is performed at -0.08-0.1 MPa and 150-170°C for 1-3 hours; finally, the second end vinyl silicone oil is added, and vacuum kneading is continued for 10-40 minutes until the end, and then the mixture is ground to obtain the first base material.

[0021] In some embodiments of the present invention, the mass ratio of the first base material to the methyl MQ silicone resin, the methyl vinyl silicone rubber, the inhibitor, and the diluent in step (2) is (1-3):(1-3):(1-2):(0.003-0.015):(5-20); preferably, the mass ratio of the first base material to the methyl MQ silicone resin, the methyl vinyl silicone rubber, the inhibitor, and the diluent in step (2) is (1.5-2):(1-2):(1-2):(0.003-0.010):(5-15).

[0022] In some embodiments of the present invention, the molecular weight of the methyl vinyl silicone rubber (110 raw rubber) in step (2) is 500,000 to 700,000, and the vinyl content is 0.03wt% to 0.06wt%.

[0023] In some embodiments of the present invention, the hydrogen-containing silicone oil in step (2) may be Momentive 484 / Dow 1107 / Shin-Etsu KF99. The mass ratio of the hydrogen-containing silicone oil to the first base material is (0.02-0.3):(1-3); preferably, the mass ratio of the hydrogen-containing silicone oil to the first base material is (0.03-0.2):(1-3).

[0024] In some embodiments of the present invention, during the preparation of the second base material in step (2), the temperature is controlled to not exceed 45°C; preferably, during the preparation of the second base material in step (2), the temperature is controlled to not exceed 40°C.

[0025] In some embodiments of the present invention, the solid content of the second base material in step (2) is 30%-45%; preferably, the solid content of the second base material in step (2) is 30%-40%, such as 32%-38%.

[0026] In some embodiments of the present invention, the amount of the thickener added in step (3) is 1.0%-2.5% of the mass of the solids in the second base material, and the amount of the latent platinum catalyst added is 1‰-12‰ of the mass of the solids in the second base material; preferably, the amount of the thickener added in step (3) is 1.5%-2.5% of the mass of the solids in the second base material, and the amount of the latent platinum catalyst added is 2‰-10‰ of the mass of the solids in the second base material.

[0027] In some embodiments of the present invention, the stirring and mixing process described in step (3) is carried out in a vacuum centrifugal stirring cup, and the stirring and mixing is carried out for 1-10 minutes at a speed of 650-1000 revolutions per minute and 400-600 rotations per minute.

[0028] The present invention also provides a single-component silicone thermal adhesive that can be cured in stages.

[0029] Specifically, a single-component silicone thermal adhesive that can be cured in stages is prepared by the above-described method.

[0030] The present invention also provides a heat-bonded adhesive semi-cured sheet.

[0031] Specifically, a heat-bonded adhesive semi-cured sheet is prepared by coating and initial curing of the above-mentioned single-component silicone heat-bonded adhesive, wherein the initial curing temperature is 130-145℃ and the time is 100-180s.

[0032] In some embodiments of the present invention, the initial curing temperature is 135-145°C and the time is 120-150 seconds.

[0033] The present invention also provides a method for using the above-mentioned one-component silicone thermal adhesive.

[0034] Specifically, the method of using the above-mentioned one-component silicone thermal adhesive includes the following steps: The above-mentioned single-component silicone thermal adhesive is applied to a base film. After initial curing, a release film is applied to the side away from the base film to form a thermal adhesive semi-cured sheet. When in use, the release film is removed, the adhesive side of the thermal adhesive semi-cured sheet is adhered to the substrate, and hot-pressed to complete the bonding and curing.

[0035] In some embodiments of the present invention, the initial curing temperature is 130-145°C and the time is 100-180s; preferably, the initial curing temperature is 135-145°C and the time is 120-150s.

[0036] In some embodiments of the present invention, the hot pressing temperature is 150-180°C, the pressure is 0.5-0.8 MPa, and the time is 150-300 s.

[0037] The core logic of segmented curing technology is to construct a multi-stage temperature-responsive curing path through formulation design. This involves using curing systems with different activation temperatures to divide the curing process into two precisely controllable stages: the first stage is pre-curing (coating pre-curing stage), where partial cross-linking is triggered at medium to low temperatures to form a semi-cured sheet, which can be safely rolled up and transported over long distances, meeting the requirements for coating and bonding in different locations; the second stage is final curing (bonding stage), where deep cross-linking is activated under high temperature and pressure, increasing the cross-linking degree of the system to ≥95%, forming a three-dimensional dense network, ultimately achieving high-strength, high-heat-resistant, and long-lasting stable bonding. Currently, the difficulty in achieving segmented curing of single-component silicone thermal adhesives lies in the difficulty of controlling the degree of cross-linking in the first stage, resulting in poor storage stability of the prepared semi-cured sheet, and simultaneously, incomplete cross-linking in the second stage, making it difficult to achieve high-strength bonding and low peel strength. This invention optimizes the formulation of silicone thermal adhesives, using specific low-boiling-point and high-boiling-point inhibitors and controlling their dosage ratio to perfectly complement a latent platinum catalyst, achieving controllable segmented curing. Simultaneously, the use of random copolymer polydimethyl-methylvinylsiloxane modified with epoxy silane coupling agent as a tackifier enables the silicone hot-press adhesive to have both excellent initial tack and stability, and to ensure the crosslinking strength and peel force after final hot pressing.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses vinyl-terminated polysiloxane, hexamethyldisilazane, and fumed silica as raw materials to prepare the first base material, then combines it with methyl MQ resin and other materials to adjust the viscosity, selects specific tackifiers to enhance interfacial bonding, and employs a latent platinum catalyst and inhibitor to construct a single-component system. By using specific inhibitors in combination with latent platinum catalysts and tackifiers, and controlling the curing temperature, segmental crosslinking is achieved, resulting in an organosilicon thermal adhesive with excellent initial tack and later strength. The prepreg formed after initial curing of the single-component organosilicon thermal adhesive provided by this invention has extremely low peel strength (≤10g) at room temperature, making it easy to peel from the release film during use. Even when the adhesive surfaces are pressed together, the adhesive surface remains flat and undamaged. The prepreg is easy to store, transport, and subsequently heat-press, making it simple and convenient to use. When the prepreg is heat-pressed during use, the crosslinking is complete, the bond with the substrate is tight, the peel strength is high, and it can achieve the high strength required for long-term use. Attached Figure Description

[0039] Figure 1 This is a test diagram of the peel force of the single-component silicone thermal adhesive prepared in Example 2 of the present invention after hot pressing. Detailed Implementation

[0040] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0041] The instruments or equipment used in the following examples and comparative examples include: a kneader (Jinyinghe 10L); a differential scanning calorimeter (DSC, Q2000, TA); a tensile testing machine (CMT6104, Meters Industrial); a constant temperature oven (DHG-9070, Shanghai Yiheng); and a high-speed disperser testing machine (Biaogeda). Other raw materials, reagents, or apparatus, unless otherwise specified, are available from conventional commercial sources or can be obtained by existing known methods.

[0042] Example 1: Preparation of Toughener This embodiment provides a method for preparing random copolymer polydimethyl-methylvinylsiloxane modified with tackifier epoxy silane coupling agent, as detailed below: S1. Add 240g of dimethyldimethoxysilane and 120g of methylvinyldimethoxysilane, stir at 200 rpm, and heat to 50°C in an oil-sealed pan to form a white, transparent solution. Then heat to 50°C and begin adding potassium hydroxide solution (4.8g water, 0.18g potassium hydroxide). After stirring, the solution slowly turns white and turbid. Then add distilled water. During the addition process, the temperature will rise, reaching a maximum of 62°C. The white and turbid solution becomes clear. After cooling, the solution turns white and turbid again. After the temperature stabilizes at 50°C, maintain the temperature for 2 hours. After 2 hours, heat the oil-sealed pan to 73°C and maintain the temperature for 2 hours. After the reaction is complete, add 115.2g of distilled water and stir for 15 minutes. Separate the lower layer using a separatory funnel. The product is in the lower layer, and the upper layer is waste liquid. Wash the product three times with 180g of distilled water. The product is in the upper layer, and the lower layer is waste liquid. Wash with water until the aqueous layer is neutral (pH=7), and the solution is a white and turbid liquid. 230g of crude product was obtained and poured into a rotary evaporator flask for vacuum distillation. The oil bath was set at 72℃, the rotation speed at 50 rpm, and the vacuum pressure at -0.01 MPa. 131.5g of white transparent product (random copolymer polydimethyl-methylvinylsiloxane) was obtained, with a viscosity of 12 mPa·s (25℃) and a moisture content of 0.21%.

[0043] S2. Add 57.6 g of r-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) and 0.024 g of stannous octoate to the reaction flask, stir, and heat the oil-sealed pan to 50°C. Apply vacuum to reduce the pressure in the reaction flask to a negative pressure (-0.08 MPa), and add 90 g of the product from the first step dropwise, controlling the addition over 1 hour. After the addition is complete, maintain the temperature at 50°C and react for 1 hour; then heat the oil-sealed pan to 80°C and maintain the temperature for 2 hours; then heat the oil-sealed pan to 100°C and maintain the temperature for 2 hours. Finally, break the vacuum, cool, continue stirring, and discharge the product to obtain 115 g of a white, transparent product. The viscosity was measured to be 13 mPa·s (25°C).

[0044] Example 2 This embodiment provides a method for preparing a segmented curable single-component silicone thermal adhesive, including the following steps: (1) Preparation of the first base material: 2700g of vinyl-terminated silicone oil (viscosity 10000mPa) In a 10-liter kneader, 370g of hexamethyldisilazane (Qiangsheng) and 29.6g of distilled water were kneaded for 10 minutes. Cold water was circulated through the kneader. Then, 1480g of fumed silica T30 / QS-30 was added to the kneader in batches. After the silica was absorbed, the fumed silica that had risen from the inner cavity was scraped into the clump of material using a spatula. Cold kneading was performed for 2 hours, with the temperature controlled not to exceed 80℃. After cold kneading, the electric heating was turned on, and the vacuum pump was turned on. The vacuum degree was -0.08 to -0.1MPa. The mixture was heated to 160℃ and vacuum kneaded for 2.5 hours. Then, 300g of vinyl-terminated silicone oil was added to the kneader and kneaded again for 20 minutes while maintaining a vacuum. After cooling, the material was discharged and ground twice using a three-roll mill for later use.

[0045] (2) Preparation of the second base material: Place 260g of industrial-grade xylene into a 2L straight-body mixing tank. Using a high-speed disperser with a 6cm diameter dispersion disc, disperse 35g of methyl vinyl silicone rubber (110 raw rubber, molecular weight 600,000, vinyl content 0.05wt%) and 50g of the first base material into the xylene in batches at 1600rpm. Control the temperature to not exceed 40℃, and if necessary, use ambient temperature tap water to control the temperature of the mixing tank. After one hour of dispersion, add 40g of methyl MQ resin (Shandong Dayi), stir at 1000rpm for 5 minutes, then clean the dispersion tank and the mixing paddle; stir for another 5 minutes. Stop the machine and add 2.8g of hydrogen-containing silicone oil (Momentive 484) and 0.25g of inhibitors (0.15g of 2-methyl-3-butyn-2-ol and 0.1g of ethynylcyclohexanol). After stirring at 1000 rpm for 5 minutes, filter the base adhesive through a 300-mesh stainless steel mesh by natural downward flow (without pressure). After filtration, place it at 105°C for 2 hours and then measure the solid content. Then adjust the solid content to 35% with xylene.

[0046] (3) Preparation of one-component silicone thermal adhesive: Add 50g of the second base material (35% solid content), 0.26g (1.5% of the solid content) of the tackifier prepared in Example 1, and 0.12g of the latent platinum catalyst (Silicone New Materials PT-2500-DZ-5, 7‰ of the solid content) to a 500mL vacuum centrifuge. Stir for 4 minutes at 800 rpm (revolutional speed) and 600 rpm (rotational speed) until the mixture is homogeneous and free of bubbles. The slurry should be uniform, without stratification or visible particles, to obtain a one-component silicone thermal adhesive.

[0047] Experimental Example In step (3), the influence of the type and amount of functional additives on the performance of the one-component silicone thermal adhesive was investigated. A silane-based anchoring and reinforcing agent (anchoring agent 297) was selected as the functional additive and compared with the tackifier prepared in Example 1 of this invention. The types and amounts of functional additives are shown in Table 1. Except for the differences in the types and amounts of functional additives, the other raw materials and preparation methods are the same as in Example 2.

[0048] Table 1

[0049] Coating and film formation: The single-component silicone thermal adhesives provided in experimental groups S1-1 to S1-6 and S2-1 to S2-12 were used for coating and film formation. The 50μm thick PI base film was fixed on the stage of the automatic coating test machine. A stainless steel frame film forming device with a 200μm gap was selected, and the coating speed was set to 10mm / s (a single speed was fixed for each experimental batch to avoid speed fluctuations affecting the uniformity of the coating). The film was coated at a uniform speed along the length of the base film to form a wet film.

[0050] Preparation of heat-bonded adhesive semi-cured sheets: The above wet film is subjected to initial curing treatment. Specifically, the coated PI base film is immediately transferred to a constant temperature forced-air drying oven, and the curing temperature is set to 140℃ and the curing time is 135s (using an intelligent temperature control system, with temperature fluctuations of ±2℃). After curing, the film is naturally cooled to room temperature, and the dry film thickness is measured in different areas of the sample (5 measuring points are randomly selected) using a digital display thin film thickness gauge (accuracy 0.1μm). Qualified samples with a dry film thickness of 28-32μm are selected. Finally, air bubbles are removed by using a glue roller and a release film (fluorosilicone release film) is applied to obtain the heat-bonded adhesive semi-cured sheet.

[0051] Hot pressing: The prepreg of the hot-pressed adhesive is hot-pressed and a peel force test is performed. Specifically, a flatbed embossing machine (heated on both sides) is used, with the cylinder adjusted to 0.6-0.8 MPa, the hot pressing temperature at 180℃, and the hot pressing time at 220 seconds. The release film (fluorosilicone release film) on the prepreg is removed, and the adhesive surface is bonded to the copper foil (30μm) surface, ensuring a uniform and bubble-free bonding surface. The film is then placed in a hot press for hot pressing. The composite film is cut into 10mm wide strips with an effective length ≥15cm, and five strips are taken from the middle section. The peel force is measured using a tensile tester (GB / T 2790-1995), and the average peel force is recorded.

[0052] Table 2. Peel force test results

[0053] As shown in Table 2, the tackifier provided in Example 1 of this invention can significantly improve the peel strength of silicone thermal adhesives. The effects are excellent when the addition amount is between 1.0% and 2.5%, and considering both cost and effectiveness, the addition amount of 1.5% to 2.0% is optimal. Experiments in groups S1-1 to S1-6 show that when using silane-based anchoring reinforcing agents, even with an addition amount of 1.6%, the effect is significantly less than that of the tackifier provided in Example 1.

[0054] Example 3 This embodiment provides a method for preparing a segmented curable single-component silicone thermal adhesive, including the following steps: (1) Preparation of the first base material: 2700g of vinyl-terminated silicone oil (viscosity 10000mPa) In a 10-liter kneader, mix 300g of hexamethyldisilazane (Qiangsheng) and 25g of distilled water for 10 minutes. Run cold water through the kneader. Then, add 1600g of fumed silica T30 / QS-30 in batches to the kneader. After the silica has absorbed the powder, scrape the fumed silica that has risen from the inner cavity into the clump of material using a spatula. Knead for 2 hours, controlling the temperature to not exceed 80℃. After cold kneading, turn on the electric heater and vacuum pump, maintaining a vacuum of -0.08 to -0.1MPa, and knead at 160℃ for 2.5 hours. Then, add 300g of vinyl-terminated silicone oil to the kneader and knead again for 20 minutes while maintaining a vacuum. After cooling, discharge the material and grind it twice using a three-roll mill for later use.

[0055] (2) Preparation of the second base material: Place 250g of industrial-grade xylene into a 2L straight-body mixing tank. Using a high-speed disperser with a 6cm diameter dispersion disc, disperse 40g of methyl vinyl silicone rubber (110 raw rubber, molecular weight 600,000, vinyl content 0.05wt%) and 55g of the first base material into the xylene in batches at 1600rpm. Control the temperature to not exceed 40℃; if necessary, use ambient temperature tap water to maintain the temperature of the mixing tank. After one hour of dispersion, add 35g of methyl MQ resin (Shandong Dayi), stir at 1000rpm for 5 minutes, then clean the dispersion tank and the mixing impeller; stir for another 5 minutes. Stop the machine and add 2.0g of hydrogen-containing silicone oil (Momentive 484) and 0.30g of inhibitor (0.09g of 2-methyl-3-butyn-2-ol and 0.06g of ethynylcyclohexanol). After stirring at 1000 rpm for 5 minutes, filter the base adhesive through a 300-mesh stainless steel mesh by natural downward flow (without pressure). After filtration, place it at 105°C for 2 hours and then measure the solid content. Then adjust the solid content to 35% with xylene.

[0056] (3) Preparation of one-component silicone thermal adhesive: Add 50g of the second base material (35% solid content), 0.28g (1.6% of the solid content) of the tackifier prepared in Example 1, and 0.10g of the latent platinum catalyst (Silicone New Materials PT-2500-DZ-5, 6‰ of the solid content) to a 500mL vacuum centrifuge mixing cup. Stir for 4 minutes at 800 rpm (revolutional speed) and 600 rpm (rotational speed) until the mixture is homogeneous and free of bubbles. The slurry should be uniform, without stratification or visible particles, to obtain a one-component silicone thermal adhesive.

[0057] Example 4 The difference between this embodiment and Example 2 is that, in step (2) when preparing the second base material, the inhibitor is 0.18g of 3-methyl-1-pentyn-3-ol and 0.12g of tetramethyltetravinylcyclotetrasiloxane; in step (3) when preparing the one-component silicone thermal adhesive, 0.28g (accounting for 1.6% of the solid content) of the tackifier prepared in Example 1 is used. The remaining raw materials and preparation methods are the same as in Example 2.

[0058] Example 5 The difference between this embodiment and Example 2 is that, in step (2) when preparing the second base material, the inhibitor is 0.18g of 2-methyl-3-butyn-2-ol and 0.07g of ethynylcyclohexanol. In step (3) when preparing the one-component silicone thermal adhesive, 0.28g (accounting for 1.6% of the solid content) of the tackifier prepared in Example 1 is used. The remaining raw materials and preparation methods are the same as in Example 2.

[0059] Comparative Example 1 The difference between this comparative example and Example 2 is that, in step (2) when preparing the second base material, the inhibitor is 0.25g of 2-methyl-3-butyn-2-ol, and ethynylcyclohexanol is not added. In step (3) when preparing the one-component silicone thermal adhesive, 0.28g (accounting for 1.6% of the solid content) of the tackifier prepared in Example 1 is used. The remaining raw materials and preparation methods are the same as in Example 2.

[0060] Comparative Example 2 The difference between this comparative example and Example 2 is that, in step (2) when preparing the second base material, the inhibitor is 0.25g of ethynylcyclohexanol, and 2-methyl-3-butyn-2-ol is not added. In step (3) when preparing the one-component silicone thermal adhesive, 0.28g (accounting for 1.6% of the solid content) of the tackifier prepared in Example 1 is used. The remaining raw materials and preparation methods are the same as in Example 2.

[0061] Comparative Example 3 The difference between this comparative example and Example 2 is that, in step (2) when preparing the second base material, the inhibitor is 0.04 g of 2-methyl-3-butyn-2-ol and 0.21 g of ethynylcyclohexanol. In step (3) when preparing the one-component silicone thermal adhesive, 0.28 g (accounting for 1.6% of the solid content) of the tackifier prepared in Example 1 is used. The remaining raw materials and preparation methods are the same as in Example 2.

[0062] Comparative Example 4 The difference between this comparative example and Example 2 is that, in step (3) when preparing the one-component silicone thermal adhesive, 0.28 g (1.6% of the solid content) of the random copolymer polydimethyl-methylvinylsiloxane prepared in Example 1 was used instead of the tackifier prepared in Example 1. The remaining raw materials and preparation methods are the same as in Example 2.

[0063] The performance of the single-component silicone thermal adhesives prepared in groups S2-7, Examples 3-5 and Comparative Examples 1-4 in the experimental cases was tested.

[0064] First, the prepreg of the heat-bonded adhesive was prepared and the final heat-pressed according to the methods described in the previous experimental examples. Then, the stability of the prepreg was tested, as follows: (1) The prepared heat-bonded adhesive semi-cured sheet is covered with a release film (fluorosilicone release film). To ensure that the bonding and positioning with the copper foil substrate can meet the requirements after the release film is removed, the heat-bonded adhesive semi-cured sheet needs to be able to easily remove the release film, and even if the release film falls off during storage or transportation, the heat-bonded adhesive semi-cured sheets in contact will not stick together, affecting the quality of the adhesive surface and the convenience of construction. Therefore, the following test was conducted on the heat-bonded adhesive semi-cured sheet: two heat-bonded adhesive semi-cured sheets with the release film removed were placed side by side, pressed together with a film-applying rubber roller for 10 minutes, and then peeled off. It is required that it is easy to peel off, and the adhesive surface is flat and undamaged after peeling. The test results are shown in Table 3.

[0065] Table 3

[0066] As shown in Table 3, the prepreg of the heat-bonding adhesive provided in this embodiment of the invention has a high degree of surface smoothness; the release film on the prepreg is not easily detached during storage; and after bonding, the adhesive surface is smooth and undamaged. The prepreg of the heat-bonding adhesive provided in this embodiment of the invention is easy to store, transport, and subsequently heat-bond, and is simple and convenient to use. The prepreg of the heat-bonding adhesive prepared in the comparative example is significantly less effective than that of the embodiment.

[0067] (2) Storage stability test The prepared heat-bonded adhesive semi-cured sheet was cut into A4-sized films, sealed in aluminum foil bags, and placed in a 25°C constant temperature cabinet. The peel strength was monitored after placement (a whole sheet was taken, cut into 10mm wide strips, and the middle 5 strips were tested, and the average value was taken), for a total of 12 weeks. The peel strength of groups S2-7 was tested once a week, and the peel strength of the other groups was tested after 0, 4, 8, and 12 weeks. The test results are shown in Tables 4 and 5.

[0068] Table 4 Test results for groups S2-7

[0069] As shown in Table 4, the heat-bonded adhesive semi-cured sheets prepared in groups S2-7 have strong peel strength and are stable during storage. After 12 weeks of storage, their peel strength is still greater than 1015 gf.

[0070] Table 5

[0071] Table 5 shows that the prepreg prepared using the single-component silicone thermal adhesive provided in the embodiments of the present invention exhibits strong storage stability. After 12 weeks of storage, it still maintains high peel strength after final hot pressing. Comparative Example 1 used only the first inhibitor (low-boiling-point inhibitor), which completely evaporated during the preparation of the "prepreg," resulting in near-complete curing of the adhesive system at this stage, forming a cured sheet. Therefore, the peel strength between the adhesive and the substrate significantly decreased during final hot pressing. Comparative Example 2 used only the second inhibitor (high-boiling-point inhibitor), achieving high peel strength, even slightly better than Example 2; however, its high viscosity led to misalignment, making storage, transportation, and construction inconvenient. Comparative Example 3 used a ratio of the first and second inhibitors that is outside the scope of this invention. While excessive use of the second inhibitor resulted in excellent peel strength, it also caused excessive viscosity, leading to misalignment of the prepreg and inconvenience in storage, transportation, and construction. Comparative Example 4 used random copolymer polydimethyl-methylvinylsiloxane instead of the tackifier prepared in Example 1, and the resulting adhesive had a low peel strength of only 756 gf.

[0072] As can be seen from the above embodiments and experimental examples, the single-component silicone thermal adhesive provided by the present invention can meet the requirements of controllable segmented curing. The prepreg prepared using it has excellent stability and is not prone to premature curing or tack reduction due to changes in storage or transportation environment. This silicone thermal adhesive is easy to process, and the prepreg prepared from it has strong storage stability, making it suitable for storage and transportation and easy for subsequent secondary processing. Moreover, it achieves complete cross-linking and high peel strength during final thermal curing, meeting the high strength required for long-term use.

[0073] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a one-component silicone thermal adhesive, characterized in that, Includes the following steps: (1) Mix vinyl-terminated silicone oil, hexamethyldisilazane and fumed silica, knead and grind to obtain the first base material; (2) The first base material is mixed and dispersed with methyl MQ silicone resin, methyl vinyl silicone rubber, hydrogen-containing silicone oil, inhibitor, and diluent to obtain the second base material; (3) Add tackifier and latent platinum catalyst to the second base material, stir and mix to obtain a one-component organosilicon thermal adhesive; The inhibitor in step (2) includes a first inhibitor and a second inhibitor. The first inhibitor is selected from at least one of propynyl alcohol, 2-methyl-3-butyn-2-ol, and 3-methyl-1-pentyn-3-ol. The second inhibitor is selected from at least one of ethynylcyclohexanol, 3,7,11-trimethyldodecyn-3-ol, divinyl maleate, and tetramethyltetravinylcyclotetrasiloxane. The mass ratio of the first inhibitor to the second inhibitor is (1-3):

1. The tackifier is a random copolymer polydimethyl-methylvinylsiloxane modified with an epoxy silane coupling agent. The amount of thickener added in step (3) is 1.0%-2.5% of the mass of the solids in the second base material.

2. The preparation method according to claim 1, characterized in that, The epoxy silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

3. The preparation method according to claim 1 or 2, characterized in that, The preparation method of the random copolymer polydimethyl-methylvinylsiloxane modified by the epoxy-based silane coupling agent is as follows: S1. After mixing and dispersing dimethyldimethoxysilane and methylvinyldimethoxysilane, an alkali metal hydroxide was added; water was then added dropwise to the system, and the system temperature was adjusted to carry out a segmented heat preservation reaction; finally, the random copolymer polydimethyl-methylvinylsiloxane was obtained by separation and purification. S2. Mix the epoxy silane coupling agent with the organotin catalyst, then add random copolymer polydimethyl-methylvinylsiloxane dropwise, adjust the system temperature to carry out a second staged heat preservation reaction, and obtain epoxy silane coupling agent modified random copolymer polydimethyl-methylvinylsiloxane.

4. The preparation method according to claim 3, characterized in that, In step S1, the mass ratio of dimethyldimethoxysilane to methylvinyldimethoxysilane is (1.5-3):1; the first stage of the heat preservation reaction is carried out at 45-55℃ for 1-3 hours, and then at 65-75℃ for 1-3 hours; in step S2, the second stage of the heat preservation reaction is carried out at 45-55℃ for 0.5-1.5 hours, then at 75-85℃ for 1-3 hours, and finally at 95-110℃ for 1-3 hours.

5. The preparation method according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the terminal vinyl silicone oil to the hexamethyldisilazane and the fumed silica is 100:(8-15):(40-60).

6. The preparation method according to claim 1 or 2, characterized in that, In step (2), the mass ratio of the first base material to the methyl MQ silicone resin, the methyl vinyl silicone rubber, the inhibitor, and the diluent is (1-3):(1-3):(1-2):(0.003-0.015):(5-20); and / or, the mass ratio of the hydrogen-containing silicone oil to the first base material in step (2) is (0.02-0.3):(1-3); and / or, the solid content of the second base material in step (2) is 30%-45%.

7. The preparation method according to claim 1 or 2, characterized in that, The amount of the latent platinum catalyst added is 1‰-12‰ of the mass of the solids in the second base material.

8. A one-component silicone thermal adhesive, characterized in that, It is prepared by any one of claims 1-7.

9. A heat-bonded adhesive semi-cured sheet, characterized in that, The adhesive is prepared by coating and initial curing of the single-component silicone thermal adhesive as described in claim 8; the initial curing temperature is 130-145℃ and the time is 100-180s.

10. The method of using the single-component silicone thermal adhesive according to claim 8, characterized in that, Includes the following steps: A single-component silicone thermal adhesive is applied to a base film. After initial curing, a release film is applied to the side away from the base film to form a thermal adhesive semi-cured sheet. When in use, the release film is removed, and the adhesive side of the thermal adhesive semi-cured sheet is adhered to the substrate and hot-pressed to complete the bonding and curing.

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