Anti-aging low-oil-permeability heat-conducting gasket and preparation method thereof

Abstract

The invention relates to the technical field of heat-conducting materials, in particular to an anti-aging low-oil-permeability heat-conducting gasket and a preparation method thereof. The aging-resistant low-oil-permeability heat-conducting gasket is prepared from the following components in parts by mass: 9 to 12 parts of vinyl silicone oil, 2.5 to 3.2 parts of hydrogen-containing silicone oil, 0.03 to 0.06 part of a catalyst, 1.2 to 2.2 parts of a hyperbranched modifier, 0.05 to 0.08 part of a flatting agent, 0.01 to 0.03 part of an inhibitor and 95 to 105 parts of modified heat-conducting filler, the modified heat-conducting filler comprises epoxy modified boron nitride, modified spherical aluminum oxide and zinc oxide. The problems that silicone oil molecules of a heat-conducting gasket are easy to separate out, oil leakage is caused, the heat-conducting gasket is insufficient in thermo-oxidative aging resistance, and the service life of an electronic product is affected are solved, the low-oil-leakage aging-resistant heat-conducting gasket is prepared, the requirements of instruments and equipment with higher precision for a thermal interface material are met, and the service life of the electronic product is prolonged.

Description

Technical Field

[0001] This application belongs to the field of thermal conductive materials technology, specifically relating to an aging-resistant, low-oil-permeability thermal conductive pad and its preparation method. Background Technology

[0002] In recent years, with the rapid development of the 3C industry, 3C products have emerged in an endless stream. Computers, mobile phones, and other electronic components require high-frequency, high-speed, large-capacity storage, and high-speed signal transmission capabilities, which leads to a significant increase in the heat flux density of these components. Excessive heat can easily cause aging of electronic components, reducing chip lifespan and reliability. Furthermore, the performance of chips degrades as ambient temperature rises due to the rapid increase in heat generation. Therefore, chip cooling and heat dissipation have always been crucial issues restricting the stability and reliability of high-performance chips. Thermal pads are widely used thermal gap pad materials, favored compared to other thermal greases due to their more flexible thickness selection range, excellent dimensional stability, and material flexibility and compressibility.

[0003] Currently, thermal pads primarily use silicone oil as the thermally conductive matrix. The operating environment of thermal pads typically involves a certain amount of pressure. During alternating hot and cold cycles, the pressure causes short-chain silicone oil molecules in the thermal pad to gradually precipitate, contaminating components and reducing the pad's anti-aging performance. This phenomenon of silicone oil precipitation in thermal pads is called compression leakage. Once this problem occurs, it not only contaminates equipment and makes cleaning difficult, but the leaked silicone oil can also easily cause short circuits in components. Surrounding impurities and particles may be adsorbed or adhered to the leaked oil, posing a potential threat to the operation and lifespan of the equipment. Therefore, compression leakage is used as a standard for judging the quality of a thermal pad. Simultaneously, thermal pads also suffer from thermal aging, resulting in unstable performance and poor heat resistance. Therefore, there is an urgent need for a thermal pad material that can effectively reduce leakage and ensure anti-aging performance under high-temperature environments. Summary of the Invention

[0004] To address the problem that silicone oil molecules easily precipitate and have poor aging resistance in thermal pads under high-temperature compression conditions, this application provides an aging-resistant, low-oil-permeability thermal pad and its preparation method.

[0005] In a first aspect, this application provides a thermally conductive pad that is resistant to aging and has low oil permeability, employing the following technical solution: A thermally conductive pad with low oil permeability and resistance to aging comprises the following components in parts by weight: 9-12 parts vinyl silicone oil, 2.5-3.2 parts hydrogen-containing silicone oil, 0.03-0.06 parts catalyst, 1.2-2.2 parts hyperbranched modifier, 0.05-0.08 parts leveling agent, 0.01-0.03 parts inhibitor, and 95-105 parts modified thermally conductive filler; wherein the modified thermally conductive filler comprises epoxy-modified boron nitride, modified spherical alumina, and zinc oxide.

[0006] Even with the aforementioned technical solution, a small number of unreacted, free short-chain silicone oil molecules still exist in the network system formed by the crosslinking of vinyl silicone oil and hydrogen-containing silicone oil. The precipitation of these free silicone oil molecules can cause oil seepage in the gasket and reduce its aging resistance. To address this, the inventors enhanced the toughness of the gasket compound by adding hyperbranched polyester resin. The hyperbranched polyester resin contains a large number of active groups such as hydroxyl and carboxyl groups, which can combine with free short-chain silicone oil molecules, further preventing silicone oil leakage and significantly enhancing the aging resistance of the thermal pad. Furthermore, the addition of thermally conductive fillers further improves the hardness and thermal conductivity of the thermal pad. By using a mixture of boron nitride, spherical alumina, and zinc oxide with different shapes and microstructures, the thermal conductivity of the thermal pad is improved. Firstly, the surface of the boron nitride is epoxy-modified, which prevents its agglomeration and helps form a three-dimensional thermally conductive network. Secondly, the addition of modified spherical alumina introduces active functional groups that can combine with the hyperbranched polyester resin and epoxy-modified boron nitride, further enhancing the interfacial bonding force between the filler and the organic phase, reducing interfacial thermal resistance, and lowering the friction between adjacent powder particles. Based on this, the addition of zinc oxide with good particle size uniformity ensures the miscibility of the filler and the silicone oil compound. This prevents the system viscosity from rising rapidly and ensures a high thermal conductivity. On the other hand, modified boron nitride easily adheres to hyperbranched polyurethane, further improving the compatibility between the thermally conductive filler and the silicone oil system, enhancing the overall stability and density of the thermally conductive pad, preventing oil leakage, and enabling rapid heat conduction through the hyperbranched polyester resin, further improving the thermal conductivity of the thermally conductive pad.

[0007] In one specific implementation scheme, the hyperbranching modifier is a hyperbranched polyester resin, and its preparation method includes the following steps: adding diisopropanolamine and ethylene glycol diglycidyl ether to water, stirring and heating to 75-85℃, reacting for 1-2 hours, distilling under reduced pressure to obtain the branching modifier, dissolving the branching modifier in water, and then sequentially adding dodecylbenzenesulfonic acid and succinic anhydride, stirring and refluxing at 200-220℃ for 15-18 hours to obtain the branched polyester resin; Acrylic acid was added to an ethanol solution of dimethyl sulfoxide and stirred, followed by the addition of acetyl hydroquinone. The mixture was reacted at room temperature for 3-6 hours. After evaporation and crystallization, the product was added to the above-mentioned branched polyester resin and dissolved in a methanol solution of azobisisobutyronitrile at a temperature of 60-75°C. After stirring evenly, the mixture was heated to 90-120°C and refluxed for 3-5 hours. The hyperbranched polyester resin was obtained by filtration.

[0008] By employing the above technical solution and preparing hyperbranched polyester resin, the hyperbranched polyester resin possesses abundant phenolic hydroxyl groups. The ortho or meta positions of the phenolic hydroxyl groups contain carbonyl groups, which form intramolecular hydrogen bonds with the ortho carbonyl groups, enhancing the material's impact resistance and endowing the hyperbranched polyester resin with anti-aging properties. This results in excellent anti-aging performance for the thermally conductive adhesive. Furthermore, the branched polyester resin forms a hyperbranched dendritic structure in different directions, with each branch containing ether bonds, significantly enhancing the toughness of the thermally conductive pad. Simultaneously, the hyperbranched polyester resin contains a large number of carboxyl groups, which can react with the epoxy groups on the thermally conductive filler, increasing the thermal conductivity pathway of the filler and ensuring the integrity of the thermally conductive pad, preventing oil leakage.

[0009] In one specific implementation scheme, the mass ratio of the epoxy-modified boron nitride, the modified spherical alumina, and the zinc oxide is (3-5):(5-11):1.

[0010] The method for preparing the modified spherical alumina includes: dispersing spherical alumina in toluene, adding 3-aminopropyltriethoxysilane, reacting at 70-80℃ for 5-8h, dispersing the resulting aminated alumina in DMF, adding 3-hydroxyphenylphosphopropionic acid, EDC / NHS, and reacting at 50-60℃ for 10-12h to obtain the modified spherical alumina.

[0011] By employing the above technical solution, a grafting reaction is carried out between epoxy-modified hexagonal boron carbide and hyperbranched polyester resin in a certain mass ratio, allowing the epoxy-modified boron carbide to be fully dispersed in the system, forming a thermally conductive pathway. The addition of modified spherical alumina allows its surface-active functional groups to form stable crosslinks with the carboxyl groups of the hyperbranched polyester resin and the epoxy groups of the epoxy-modified boron nitride. This not only enhances the interfacial bonding strength between the filler and the matrix, reducing interfacial thermal resistance to ensure high thermal conductivity, but also reduces interparticle friction due to the spherical structure, preventing viscosity increases and avoiding porosity in the bottom compound during calendering, effectively ensuring the quality and calendering stability of the thermal pad. Simultaneously, the phenolic hydroxyl and phosphoryl groups introduced onto the surface of the modified spherical alumina serve as highly efficient antioxidant functional groups, significantly improving overall anti-aging performance. The addition of zinc oxide with good particle size uniformity ensures the miscibility of the filler and silicone oil compound. Therefore, this application discloses a certain mass ratio of epoxy-modified boron nitride, modified spherical alumina, and zinc oxide, which can achieve comparable thermal conductivity and ensure the mechanical properties of the thermal pad.

[0012] In one specific implementation scheme, the preparation method of the epoxy-modified boron nitride includes dispersing hexagonal boron nitride in an aqueous sodium hydroxide solution, reacting at an ambient temperature of 110-120℃ for 7-11 hours, then cooling at the ambient temperature, centrifuging, washing and drying to obtain hydroxyl-modified boron nitride; taking hydroxyl-modified boron nitride and epichlorohydrin, adding them to a mixed solution of sodium hydroxide and ethanol at a temperature of 75-80℃, stirring for 2-3 hours, cooling at the ambient temperature, centrifuging, washing and drying to obtain epoxy-modified boron nitride.

[0013] In one specific embodiment, the catalyst is a platinum-based catalyst selected from one or more of chloroplatinic acid, platinum tetrachloride, platinum and carbonyl complexes, and alcohol-modified chloroplatinic acid.

[0014] In one specific implementation, the hydrogen-containing silicone oil has a hydrogen content of 0.1-0.21%.

[0015] By adopting the above technical solution, the hydrogen content of the hydrogen-containing silicone oil is adjusted to allow it to react fully with the vinyl silicone oil, thereby reducing the free short-chain silicone oil molecules in the gasket compound, reducing the precipitation of silicone oil molecules to a certain extent, regulating the degree of cross-linking of the compound, and forming a thermally conductive gasket with low oil permeability and stable thermal conductivity.

[0016] Secondly, this application provides a method for preparing an aging-resistant and low-oil-permeability thermal pad, employing the following technical solution: A method for preparing an aging-resistant, low-oil-permeability thermal pad includes the following steps: After mixing vinyl silicone oil and hydrogen-containing silicone oil in proportion, add inhibitor and stir at 50-60 r / min for 10-20 min. Then add hyperbranching modifier and stir at 100-110 r / min for 10-20 min. After standing for 45-60 min, add modified thermally conductive filler and stir at 150-180 r / min for 45-60 min. Then add catalyst and leveling agent and continue stirring for 10-20 min. After vacuuming, obtain thermally conductive material. Calender and cure the thermally conductive material to obtain thermally conductive pad.

[0017] The curing conditions are as follows: curing at a temperature of 120-150℃ for 20-30 minutes.

[0018] By adopting the above technical solution, the hyperbranched modifier is first mixed into the organosilicon network system, and then the modified thermally conductive filler is added. Vacuuming is used to reduce the interfacial thermal resistance, improve the interfacial compatibility between the thermally conductive filler and the organosilicon resin system, and increase the degree of crosslinking with the hyperbranched modifier, thereby improving the thermal conductivity, preventing oil seepage, and making the thermal pad have aging resistance.

[0019] In summary, this application has the following beneficial effects: 1. By adding hyperbranched polyester resin, the toughness of the gasket material is enhanced. Hyperbranched polyester resin contains a large number of active groups such as hydroxyl and carboxyl groups, which can combine with free short-chain silicone oil molecules to prevent silicone oil leakage and significantly enhance the aging resistance of the thermal pad. Furthermore, the addition of thermally conductive fillers further improves the hardness and thermal conductivity of the thermal pad. The use of a mixture of boron nitride, spherical alumina, and zinc oxide with different shapes and microstructures improves the thermal conductivity of the thermal pad and enhances the compatibility between the thermally conductive filler and the silicone oil system, thereby improving the overall stability of the thermal pad and preventing oil leakage. Moreover, the hyperbranched polyester resin enables rapid heat conduction, further improving the thermal conductivity of the thermal pad.

[0020] 2. Hyperbranched polyester resin has abundant phenolic hydroxyl groups, and carbonyl groups are present at the ortho or meta positions of the phenolic hydroxyl groups. The ortho carbonyl groups and phenolic hydroxyl groups can form intramolecular hydrogen bonds, thereby enhancing the toughness and impact resistance of the material. This endows hyperbranched polyester resin with anti-aging properties, making the thermally conductive adhesive material have excellent anti-aging properties. At the same time, hyperbranched polyester resin contains a large number of carboxyl groups, which can react with the epoxy groups on the thermally conductive filler to further increase the thermal conductivity pathway of the thermally conductive filler and improve its thermal conductivity.

[0021] 3. A grafting reaction of epoxy-modified hexagonal boron carbide with the dendritic structure of hyperbranched polyester resin at a certain mass ratio ensures that the epoxy-modified boron carbide is fully dispersed in the system, forming thermally conductive pathways. This avoids insufficient epoxy-modified boron carbide content, which would reduce the thermal conductivity of the thermal pad. The addition of modified spherical alumina improves the crosslinking with the hyperbranched polyester resin while maintaining a high thermal conductivity, reducing interparticle friction, and preventing viscosity increases. This effectively ensures the quality and calendering stability of the thermal pad. The addition of zinc oxide with good particle size uniformity ensures the miscibility of the filler and silicone oil compound. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the embodiments.

[0023] raw material Some of the raw materials used in the preparation examples and embodiments: Vinyl silicone oil, model BG-208, has a viscosity of 500 mPa·s at 25℃; hydrogen-containing silicone oil, model BG-204; chloroplatinic acid, product number: boren026; platinum tetrachloride, purchased from Tianjin Maisco Chemical Co., Ltd.; leveling agent: H421 leveling agent; inhibitor: 1-ethynylcyclohexanol; hexagonal boron nitride (5-7μm), product number: Q / TY·J08.34-2022, purchased from Tianyuan Aviation Materials; spherical alumina (1μm), purchased from Shanghai Naio Nanotechnology Co., Ltd.; zinc oxide (30nm), product number: XH-ZnO; diisopropanolamine, purchased from Shanghai Kangtuo Chemical Co., Ltd.; ethylene glycol diglycidyl ether, purchased from Guangzhou Ruishi Biotechnology Co., Ltd.; dimethyl sulfoxide in ethanol, with a mass fraction of 5%; azobisisobutyronitrile in methanol, with a mass fraction of 8%.

[0024] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products.

[0025] Preparation Example 1 Diisopropanolamine and ethylene glycol diglycidyl ether in a mass ratio of 2:1 were added to 6 times the volume of water, stirred, and heated to 85°C for 1 hour. The mixture was then distilled under reduced pressure to obtain a branching modifier. 10 g of the branching modifier was dissolved in 100 ml of water, followed by the addition of 0.8 g of dodecylbenzenesulfonic acid and 2 g of succinic anhydride. The mixture was stirred and refluxed at 220°C for 15 hours to obtain a branched polyester resin. 8 g of acrylic acid was added to 80 ml of dimethyl sulfoxide in ethanol solution and stirred. Then, 6 g of acetylhydroquinone was added and reacted at room temperature for 6 hours. After evaporation and crystallization, the product was added to the above branched polyester resin and dissolved in 10 ml of azobisisobutyronitrile in methanol solution at 60°C. After stirring evenly, the mixture was heated to 120°C and refluxed for 3 hours. The mixture was then filtered to obtain a hyperbranched polyester resin.

[0026] Preparation Example 2 Diisopropanolamine and ethylene glycol diglycidyl ether in a mass ratio of 2:1 were added to 6 times the volume of water, stirred and heated to 85°C, reacted for 1 hour, and then distilled under reduced pressure to obtain a branching modifier. 10 g of the branching modifier was dissolved in 100 ml of water, and then 0.8 g of dodecylbenzenesulfonic acid and 2 g of succinic anhydride were added in sequence. The mixture was stirred and refluxed at 220°C for 15 hours to obtain a branched polyester resin.

[0027] Preparation Example 3 Diisopropanolamine and ethylene glycol diglycidyl ether in a mass ratio of 2:1 were added to 6 times the volume of water, stirred, and heated to 85°C for 1 hour. The mixture was then distilled under reduced pressure to obtain a branching modifier. 10 g of the branching modifier was dissolved in 100 ml of water, followed by the addition of 0.8 g of dodecylbenzenesulfonic acid and 2 g of succinic anhydride. The mixture was stirred and refluxed at 220°C for 15 hours to obtain a branched polyester resin. This resin was then dissolved in 10 ml of azobisisobutyronitrile methanol solution at 60°C, stirred until homogeneous, and then refluxed at 120°C for 3 hours. The resin was then filtered to obtain a hyperbranched polyester resin.

[0028] Preparation Example 4 20g of hexagonal boron nitride was dispersed in 200ml of sodium hydroxide aqueous solution and reacted at 110℃ for 11h. After cooling at room temperature, centrifugation, washing with water, and drying at 60℃, hydroxyl-modified boron nitride was obtained. 8g of hydroxyl-modified boron nitride and 11g of epichlorohydrin were added to a mixed solution of 50ml of sodium hydroxide and 150ml of ethanol at 75℃, stirred for 3h, cooled at room temperature, centrifuged, washed with water, and dried at 60℃, to obtain epoxy-modified boron nitride.

[0029] Preparation Example 5 20g of hexagonal boron nitride was dispersed in 200ml of sodium hydroxide aqueous solution and reacted at an ambient temperature of 120℃ for 7h. After cooling at room temperature, centrifugation, washing with water, and drying at 60℃, hydroxyl-modified boron nitride was obtained. 8g of hydroxyl-modified boron nitride and 11g of epichlorohydrin were added to a mixed solution of 50ml of sodium hydroxide and 150ml of ethanol at 80℃. The mixture was stirred for 2h, cooled at room temperature, centrifuged, washed with water, and dried at 60℃, to obtain epoxy-modified boron nitride.

[0030] Preparation Example 6 20g of hexagonal boron nitride was dispersed in 200ml of sodium hydroxide aqueous solution and reacted at an ambient temperature of 120℃ for 7h. After cooling, centrifugation, washing with water, and drying at 60℃, hydroxyl-modified boron nitride was obtained.

[0031] Preparation Example 7 Modified spherical alumina: 10g of spherical alumina was dispersed in 50ml of toluene, 1g of 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 80℃ for 6h. After centrifugation and washing, aminated alumina was obtained. 10g of aminated alumina was dispersed in 40ml of DMF, 1.8g of 3-hydroxyphenylphosphonopropionic acid, 0.92g of EDC, and 0.35g of NHS were added. The mixture was reacted at 60℃ for 12h, and after centrifugation and washing, modified spherical alumina was obtained.

[0032] Example 1 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 90g of vinyl silicone oil, 32g of hydrogen-containing silicone oil, 0.3g of catalyst, 12g of hyperbranched modifier prepared in Preparation Example 1, 0.5g of leveling agent, 0.3g of inhibitor, and 105g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.1%; and the catalyst is platinum tetrachloride.

[0033] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 50 r / min for 20 min. Then, hyperbranched modifier is added and stirred at 100 r / min for 20 min. After standing for 45 min, modified thermally conductive filler is added and stirred at 180 r / min for 45 min. Catalyst and leveling agent are added and stirred continuously for 20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 150℃ for 30 min to obtain a 2.5 mm thick thermally conductive pad.

[0034] Example 2 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 120g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.3g of catalyst, 22g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.1g of inhibitor, and 95g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is platinum tetrachloride.

[0035] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 150℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0036] Example 3 An aging-resistant, low-oil-permeability thermally conductive pad comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0037] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0038] Example 4 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 5:11:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0039] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0040] Example 5 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 1:7:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0041] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0042] Example 6 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 5:3:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0043] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0044] Example 7 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 2, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0045] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0046] Example 8 An aging-resistant, low-oil-permeability thermally conductive pad comprises the following components: 110g vinyl silicone oil, 25g hydrogen-containing silicone oil, 0.5g catalyst, 18g hyperbranched modifier prepared in Preparation Example 3, 0.8g leveling agent, 0.2g inhibitor, and 100g modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0047] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0048] Example 9 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 5, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0049] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0050] Example 10 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 6, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0051] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0052] Example 11 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.1%; and the catalyst is chloroplatinic acid.

[0053] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0054] Example 12 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 1%; and the catalyst is chloroplatinic acid.

[0055] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0056] Comparative Example 1 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4, modified spherical alumina prepared in Preparation Example 7, and zinc oxide prepared in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0057] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. After adding inhibitor, the mixture is stirred at 60 r / min for 10 min. Then, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Finally, catalyst and leveling agent are added and stirred for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0058] Comparative Example 2 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride prepared in Preparation Example 4 and modified spherical alumina prepared in Preparation Example 7; the mass ratio of epoxy-modified boron nitride to spherical alumina is 3:6; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0059] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0060] Comparative Example 3 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride and zinc oxide prepared in Preparation Example 4; the mass ratio of epoxy-modified boron nitride to zinc oxide is 8:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0061] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0062] Comparative Example 4 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is modified spherical alumina and zinc oxide prepared in Preparation Example 7 at a mass ratio of 8:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0063] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0064] Comparative Example 5 A thermally conductive pad with low oil permeability and resistance to aging comprises the following components: 110g of vinyl silicone oil, 25g of hydrogen-containing silicone oil, 0.5g of catalyst, 18g of hyperbranched modifier prepared in Preparation Example 1, 0.8g of leveling agent, 0.2g of inhibitor, and 100g of modified thermally conductive filler; wherein the modified thermally conductive filler is epoxy-modified boron nitride, spherical alumina, and zinc oxide prepared in Preparation Example 4 in a mass ratio of 3:5:1; the hydrogen-containing silicone oil has a hydrogen content of 0.21%; and the catalyst is chloroplatinic acid.

[0065] According to the formula, vinyl silicone oil and hydrogen-containing silicone oil are mixed in proportion. Inhibitor is added and stirred at 60 r / min for 10 min. Then, hyperbranched modifier is added and stirred at 110 r / min for 10 min. After standing for 60 min, modified thermally conductive filler is added and stirred at 150 r / min for 45-60 min. Catalyst and leveling agent are added and stirred continuously for 10-20 min. Vacuum is then applied to obtain thermally conductive material. The thermally conductive material is calendered and cured at 120℃ for 20 min to obtain a 2.5 mm thick thermally conductive pad.

[0066] Performance testing The performance of the thermal pads prepared in Examples 1-12 and Comparative Examples 1-5 was tested using the following methods: a. Thermal conductivity test: Tested according to ASTM D5470 standard; b. Hardness test: Tested according to ASTM D2240 standard; c. Tensile strength test: Refer to GB / T1040.4-2006; d. Oil seepage and aging resistance test: A certain amount of thermal pads was weighed in a glass dish and placed in a desiccator at room temperature for 3 months. After that, the oil seeping from the surface was removed. The thermal pads were then placed at 150℃ for 1000 hours and the oil seeping from the surface was removed. Oil seepage rate = weight loss of thermal pad / original weight of thermal pad × 100%; Performance is shown in Table 1: Table 1 Performance Test Results As shown in Table 1, comparing Examples 3-6 and Comparative Examples 3-5, the thermal conductivity, hardness, tensile strength, oil seepage, and aging resistance of the thermal pad prepared in Example 3 are all superior to those of Examples 5-6 and Comparative Examples 3-5. This indicates that a certain mass ratio of epoxy-modified hexagonal boron carbide grafting reaction with the dendritic structure of hyperbranched polyester resin forms a thermally conductive pathway, avoiding insufficient epoxy-modified boron carbide content, which would reduce the thermal conductivity of the thermal pad. The addition of modified spherical alumina introduces anti-aging groups and improves crosslinking, ensuring a high thermal conductivity of the system. Furthermore, the spherical shape reduces interparticle friction, improving the quality and calendering stability of the thermal pad. Zinc oxide ensures the miscibility of the filler and silicone oil compound. However, while introducing anti-aging groups improves crosslinking, direct doping of spherical alumina reduces aging resistance, causing the hardness to gradually increase with aging time, while elasticity decreases, brittleness increases, and cracking becomes more likely.

[0067] Comparing Examples 3 and 9-10, it can be seen that the thermal conductivity, hardness, tensile strength, oil seepage reduction, and aging resistance of the thermally conductive pad prepared in Example 3 are better than those in Example 10. It is believed that the branched polyester resin forms a hyperbranched dendritic structure in different directions, and the ether bonds on each branch chain greatly enhance the toughness of the thermally conductive pad. At the same time, the hyperbranched polyester resin contains a large number of carboxyl groups, which can react with the epoxy groups on the thermally conductive filler to further increase the thermal conductivity pathway of the thermally conductive filler, and also ensure the integrity of the overall thermally conductive pad and prevent oil seepage from occurring.

[0068] Comparing Examples 3, 7-8, and 1-2, it can be seen that the thermal conductivity, hardness, tensile strength, oil seepage, and aging resistance of the thermal pad prepared in Example 3 are better than those of Example 8 and 1-2. It is believed that by adding hyperbranched polyester resin, the toughness of the pad material is enhanced, and the hyperbranched polyester resin contains a large number of active groups such as hydroxyl and carboxyl groups, which can combine with free short-chain silicone oil molecules, thereby further preventing silicone oil seepage and significantly enhancing the aging resistance of the thermal pad.

[0069] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A thermally conductive pad with low oil permeability and resistance to aging, characterized in that: The raw materials include the following components in parts by weight: 9-12 parts vinyl silicone oil, 2.5-3.2 parts hydrogen-containing silicone oil, 0.03-0.06 parts catalyst, 1.2-2.2 parts hyperbranching modifier, 0.05-0.08 parts leveling agent, 0.01-0.03 parts inhibitor, and 95-105 parts modified thermally conductive filler; wherein the modified thermally conductive filler includes epoxy-modified boron nitride, modified spherical alumina, and zinc oxide.

2. The aging-resistant, low-oil-permeability thermal pad according to claim 1, characterized in that: The hyperbranched modifier is a hyperbranched polyester resin, and its preparation method includes the following steps: adding diisopropanolamine and ethylene glycol diglycidyl ether to water, stirring and heating to 75-85℃, reacting for 1-2 hours, distilling under reduced pressure to obtain the branched modifier, dissolving the branched modifier in water, and then adding dodecylbenzenesulfonic acid and succinic anhydride in sequence, stirring and refluxing at 200-220℃ for 15-18 hours to obtain the branched polyester resin; Acrylic acid was added to an ethanol solution of dimethyl sulfoxide and stirred, followed by the addition of acetyl hydroquinone. The mixture was reacted at room temperature for 3-6 hours. After evaporation and crystallization, the product was added to the above-mentioned branched polyester resin and dissolved in a methanol solution of azobisisobutyronitrile at a temperature of 60-75°C. After stirring evenly, the mixture was heated to 90-120°C and refluxed for 3-5 hours. The hyperbranched polyester resin was obtained by filtration.

3. The aging-resistant, low-oil-permeability thermal pad according to claim 1, characterized in that: The mass ratio of the epoxy-modified boron nitride, modified spherical alumina, and zinc oxide is (3-5):(5-11):

1.

4. The aging-resistant, low-oil-permeability thermal pad according to claim 1, characterized in that: The preparation method of the epoxy-modified boron nitride includes dispersing hexagonal boron nitride in an aqueous sodium hydroxide solution, reacting at an ambient temperature of 110-120℃ for 7-11 hours, cooling at ambient temperature, centrifuging, washing and drying to obtain hydroxyl-modified boron nitride; taking hydroxyl-modified boron nitride and epichlorohydrin, adding them to a mixed solution of sodium hydroxide and ethanol at a temperature of 75-80℃, stirring for 2-3 hours, cooling at ambient temperature, centrifuging, washing and drying to obtain epoxy-modified boron nitride.

5. The aging-resistant, low-oil-permeability thermal pad according to claim 1, characterized in that: The catalyst is a platinum-based catalyst, selected from one or more of chloroplatinic acid, platinum tetrachloride, platinum and carbonyl complexes, and alcohol-modified chloroplatinic acid.

6. The aging-resistant, low-oil-permeability thermal pad according to claim 1, characterized in that: The hydrogen-containing silicone oil has a hydrogen content of 0.1-0.21%.

7. The method for preparing the aging-resistant, low-oil-permeability thermal pad according to any one of claims 1-6, characterized in that, Includes the following steps: After mixing vinyl silicone oil and hydrogen-containing silicone oil in proportion, add inhibitor and stir at 50-60 r / min for 10-20 min. Then add hyperbranching modifier and stir at 100-110 r / min for 10-20 min. After standing for 45-60 min, add modified thermally conductive filler and stir at 150-180 r / min for 45-60 min. Then add catalyst and leveling agent and continue stirring for 10-20 min. After vacuuming, obtain thermally conductive material. Calender and cure the thermally conductive material to obtain thermally conductive pad.

8. The method for preparing the aging-resistant, low-oil-permeability thermal pad according to claim 7, characterized in that: The curing conditions are as follows: curing at a temperature of 120-150℃ for 20-30 minutes.

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