Heat-conducting silica gel composition and preparation method thereof

Abstract

The invention provides a heat-conducting silica gel composition and a preparation method thereof. The heat-conducting silica gel composition comprises a heat-conducting composite filler premix, a silane coupling agent and hydrogen-containing silicone oil, wherein the heat-conducting composite filler powder is sequentially provided with a surface layer, a middle layer and a core layer from the surface to the inside; the surface layer hardness < middle layer < core layer; the surface layer is connected to the middle layer and is first heat-conducting filler powder; the middle layer is connected to the core layer and comprises second heat-conducting filler powder; the core layer is third heat-conducting filler powder; the particle size of the heat-conducting composite filler powder is not more than 50 microns; the second heat-conducting filler powder is greater than the first heat-conducting filler powder in particle size and less than the third heat-conducting filler powder; the weight ratio of the first heat conducting filler powder to the second heat conducting filler powder to the third heat conducting filler powder is (100-400): (400-800): (1200-2000); the weight ratio of the heat-conducting composite filler premix to the silane coupling agent to the hydrogen-containing silicone oil is 2100: (10-16): (5-11). The heat-conducting silica gel composition disclosed by the invention has high heat conductivity, low abrasion and low oil outlet performance, is suitable for steel mesh printing, and is particularly suitable for being used in a high-temperature hot oil soaking environment.

Description

Technical Field

[0001] The invention belongs to the technical field of thermally conductive organic silicone gel, and relates to a composition of thermally conductive organic silicone gel prepared from a thermally conductive composite filler premix and a preparation method thereof. Technical Background

[0002] In the production of domestic mining machines, heat dissipation adhesive is usually applied between the electronic chip and the radiator to improve the heat dissipation effect. For example, the Chinese utility model patent with patent number CN202011561903.9 provides a silicone gel composition. By preparing a modified base polymer, the thermal conductivity of the composition is significantly improved. The thermal conductivity coefficient can reach 1.53-5.67W / m×K, which meets the needs of some heat dissipation applications. However, in order to improve the thermal conductivity coefficient, a large amount of large-particle thermal conductive fillers are added, which leads to increased wear on the product and printing and coating tools. For example, adding high thermal conductivity powders such as diamond can achieve the purpose of improving the thermal conductivity coefficient, but the diamond particles are large and hard, and it is easy to cause wear on the surface of the product during printing. In addition, the industry will also use thermal oil immersion to improve the heat dissipation effect, but silicone gel is prone to oil loss and shedding in the environment of long-term immersion and flushing of high-temperature thermal oil.

[0003] Wear damage can be reduced by improving the structure of thermally conductive fillers. For example, the Chinese utility model patent with patent number CN202311706754.4 provides a thermally conductive silicone composition and its cured product and application. By setting a shell layer with a lower hardness on the surface of the thermally conductive filler, the Mohs hardness of the shell layer is generally ≤7, which reduces the wear on the dispensing equipment. However, for more demanding use conditions and more sophisticated products, such as steel mesh printed chip products, the steel mesh printing will not only wear the printing equipment, but more importantly, the application products, especially the chips, and this wear prevention effect is still insufficient; in addition, the steel mesh printing process is more demanding on the use environment of the powder than the dispensing process. For example, the glue material will be printed repeatedly during printing. At this time, the shell layer on the surface of the composite filler powder will fall off, and the exposed high hardness inner layer will also cause the anti-wear failure, which will aggravate the wear.

[0004] Therefore, there is an urgent need for a thermally conductive silicone gel composition that has good and stable wear reduction effect and oil resistance on the basis of high thermal conductivity, and is suitable for use in an environment of repeated immersion and soaking in high-temperature hot oil. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides:

[0006] A thermally conductive silicone gel composition comprises a thermally conductive composite filler premix, a silane coupling agent, and hydrogen-containing silicone oil; wherein:

[0007] The thermally conductive composite filler premix comprises a mixed vinyl silicone oil and a thermally conductive composite filler powder; the thermally conductive composite filler powder comprises a surface layer, an intermediate layer and a core layer arranged in sequence from the surface to the inside; the hardness of the surface layer is less than the hardness of the intermediate layer and less than the hardness of the core layer; the surface layer is connected to the intermediate layer and is a first thermally conductive filler powder; the intermediate layer is connected to the core layer and comprises a second thermally conductive filler powder; the core layer is a third thermally conductive filler powder; the particle size of the thermally conductive composite filler powder is ≤50 μm; the particle size of the first thermally conductive filler powder is less than the particle size of the second thermally conductive filler powder and less than the particle size of the third thermally conductive filler powder; the weight ratio of the first thermally conductive filler powder, the second thermally conductive filler powder and the third thermally conductive filler powder is 100-400:400-800:1200-2000;

[0008] The weight ratio of the thermal conductive composite filler premix to the silane coupling agent and the hydrogen-containing silicone oil is 2100:10-16:5-11.

[0009] Furthermore: the vinyl silicone oil in the thermally conductive composite filler premix is ​​long-chain alkyl polyether modified vinyl silicone oil, and the weight ratio of the third thermally conductive filler powder to the long-chain alkyl polyether modified vinyl silicone oil is 1500:75-125.

[0010] Furthermore: the hydrogen-containing silicone oil includes terminal hydrogen-containing silicone oil and side hydrogen-containing silicone oil, the weight ratio of the thermal conductive composite filler premix to the terminal hydrogen-containing silicone oil is 2100:2-5, and the weight ratio of the thermal conductive composite filler premix to the side hydrogen-containing silicone oil is 2100:3-6; the viscosity range of the thermal conductive silicone gel composition is 10000-150000cps.

[0011] Furthermore: the hardness of the first thermally conductive filler powder is ≤ the hardness of the second thermally conductive filler powder < the hardness of the third thermally conductive filler powder; the particle size range of the first thermally conductive filler powder is 0.01-1μm, the particle size range of the second thermally conductive filler powder is 1-4μm, and the particle size range of the third thermally conductive filler powder is 5-50μm.

[0012] Furthermore: the particle size ratio of the first thermally conductive filler powder and the second thermally conductive filler powder is 0.05-0.1:3, and the particle size ratio of the second thermally conductive filler powder and the third thermally conductive filler powder is 3:20-30; the shape of the first thermally conductive filler powder is spherical or nearly spherical, and the shape of the third thermally conductive filler powder is spherical or nearly spherical.

[0013] Furthermore, the thermal conductivity of the first thermally conductive filler powder is less than the thermal conductivity of the third thermally conductive filler powder and the second thermally conductive filler powder; and the thermal conductivity range of the core layer is ≥30 W / m·K.

[0014] Furthermore: the connection method between the surface layer and the middle layer is molecular chain entanglement, and the connection method between the middle layer and the core layer is chemical bond connection; the first, second and third thermal conductive filler surfaces are respectively provided with the first, second and third connecting layers, the surface layer is connected to the middle layer through the first connecting layer and the second connecting layer, and the middle layer is connected to the core layer through the third connecting layer; the first connecting layer is a long-chain borate ester, stearic acid modified layer, the second connecting layer is a long-chain aluminate, stearic acid modified layer, and the third connecting layer is a silane modified layer.

[0015] The above-mentioned thermally conductive silicone gel composition comprises two components A and B; the component A comprises a thermally conductive composite filler premix and a silane coupling agent, and the component B comprises a thermally conductive composite filler premix and hydrogen-containing silicone oil; wherein: the weight ratio of the thermally conductive composite filler premix to the silane coupling agent in the component A is 1060:10-16; the weight ratio of the thermally conductive composite filler premix to the hydrogen-containing silicone oil in the component B is 1040:5-11.

[0016] A method for preparing the above-mentioned thermally conductive silicone gel composition, comprising S1. preparing a first thermally conductive filler powder, a second thermally conductive filler powder, and a third thermally conductive filler powder, S2. preparing a thermally conductive composite filler premix, and S3. preparing components A and B of the thermally conductive silicone gel composition; characterized in that:

[0017] The S1. comprises: S11. modifying the first thermally conductive filler to obtain a first thermally conductive filler powder, S12. modifying the second thermally conductive filler to obtain a second thermally conductive filler powder, S13. modifying the third thermally conductive filler to obtain a third thermally conductive filler powder;

[0018] The S2. comprises: S21. mixing a third thermally conductive filler powder, a vinyl silicone oil dispersant, and a second thermally conductive filler powder to form a primary composite filler mixture, S22. mixing the primary composite filler mixture and the first thermally conductive filler powder to form a thermally conductive composite filler premix; the primary filler modified mixture comprises a pre-composite filler, the pre-composite filler is a two-layer structure, comprising an inner layer and an outer layer connected, the outer layer is the second thermally conductive filler powder, and the inner layer is the third thermally conductive filler powder;

[0019] The S3. comprises: taking a thermally conductive composite filler premix, adding a silane coupling agent, and stirring until a uniform component A is obtained; taking a thermally conductive composite filler premix, adding hydrogenated silicone oil, and then adding a silane coupling agent, and stirring until a uniform component B is obtained.

[0020] Further: the S11. includes using long-chain borate and stearic acid to modify the first thermally conductive filler to obtain a first thermally conductive filler powder, S12. includes using long-chain aluminate and stearic acid to modify the second thermally conductive filler to obtain a second thermally conductive filler powder, S13. includes using silane KH570 to modify the third thermally conductive filler to obtain a third thermally conductive filler powder; the S21. includes S211. mixing the third thermally conductive filler and vinyl silicone oil dispersant, S212. adding and mixing the second thermally conductive filler to form a primary filler modified mixture.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The thermally conductive silicone gel composition and the preparation method thereof provided by the present invention improve the filler structure, composition formula and preparation process, have a good wear reduction effect, are suitable for the steel screen printing process with repeated rubbing, and the preparation method is simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the thermally conductive composite filler powder of the present invention;

[0024] Figure 2 It is a schematic diagram of the formation process of the thermal conductive composite filler powder of the present invention.

[0025] Explanation of symbols

[0026] 1 The first thermal conductive filler powder 2 Second thermal conductive filler powder 3 Third thermal conductive filler powder 23 Pre-compounded fillers 123 Thermally conductive composite filler powder DETAILED DESCRIPTION

[0027] Example

[0028] The embodiment of the present invention provides: a thermally conductive silicone gel composition, such as Figure 1 As shown, it includes a thermal conductive composite filler premix, a silane coupling agent, and hydrogen-containing silicone oil; wherein:

[0029] The thermally conductive composite filler premix comprises a mixed vinyl silicone oil and a thermally conductive composite filler powder 123; the thermally conductive composite filler powder comprises a surface layer, an intermediate layer and a core layer arranged in sequence from the surface to the inside; the hardness of the surface layer is less than the hardness of the intermediate layer and less than the hardness of the core layer; the surface layer is connected to the intermediate layer and is a first thermally conductive filler powder 1; the intermediate layer is connected to the core layer and comprises a second thermally conductive filler powder 2; the core layer is a third thermally conductive filler powder 3; the particle size of the thermally conductive composite filler powder 123 is ≤50μm; the particle size of the first thermally conductive filler powder 1 is less than the particle size of the second thermally conductive filler powder 2 and less than the particle size of the third thermally conductive filler powder 3; the weight ratio of the first thermally conductive filler powder 1, the second thermally conductive filler powder 2 and the third thermally conductive filler powder 3 is 100-400:400-800:1200-2000;

[0030] The weight ratio of the thermal conductive composite filler premix to the silane coupling agent and the hydrogen-containing silicone oil is 2100:10-16:5-11.

[0031] It should be noted that the steel screen printing process is different from other dispensing machines or coating processes. It requires the use of a mesh steel screen for printing. It is usually suitable for precision products such as electronic chips or products with fixed requirements for printed shapes. The particle size of the thermal conductive filler powder should not exceed 50μm. Otherwise, the particle size is too large, the dispersion effect of the filler will be poor, which will lead to poor thermal conductivity and increased wear of the thermal conductive composite filler powder. The composite filler powder used in the silicone gel composition of the present invention is a multi-layer composite structure with a small particle size, which can play a good shielding role for the core layer. Among them, the hardness of the surface layer and the middle layer are both less than that of the core layer. In the process of coating or printing the thermal conductive adhesive, the filler surface is relatively soft, which can reduce the damage to the coating tool or product. Even in repeated friction and collision or for chip products that are not wear-resistant, when the surface layer is rubbed off, the middle layer can still play a good role in reducing wear. In addition, the detached surface layer can flow better with the adhesive material during the printing process due to smaller particles and lower hardness, and can reduce the damage to the composite structure caused by collision with the composite filler powder; in addition, in order to enable the core layer of the thermally conductive composite filler powder to provide core support for the composite structure to obtain a stable thermal conductive path, in the present invention, the weight of the third thermally conductive filler powder should be at least greater than the sum of the first thermally conductive filler powder and the second thermally conductive filler powder. So far, when preparing the composite structure, the second thermally conductive filler powder and the first thermally conductive filler powder can be connected to the third thermally conductive filler powder in sequence to form the middle layer and the surface layer in sequence, which is conducive to the formation of the thermally conductive composite filler.

[0032] It should also be noted that in the prior art, thermal conductive fillers are usually added in powder form. However, in order to obtain a high thermal conductivity effect, it is usually necessary to increase the amount of filler added, which makes the mixing process more difficult and increases the wear of the stirring equipment. The present invention adds the filler in the form of a liquid premix. Compared with the prior art, while reducing the powder heating and drying processes, it avoids the fall-off of the filler on the surface of the composite filler powder caused by multiple stirring, which affects the effect of reducing wear.

[0033] Further: the vinyl silicone oil in the thermally conductive composite filler premix is ​​a long-chain alkyl polyether modified vinyl silicone oil, and the weight ratio of the third thermally conductive filler powder to the long-chain alkyl polyether modified vinyl silicone oil is 1500:75-125. The present invention adopts a long-chain alkyl polyether modified vinyl silicone oil, which improves the dispersion of the filler in the silicone gel composition while achieving good oil resistance. The long-chain structure in its molecule can improve the dispersion effect of the third thermally conductive filler and thus improve the forming of the thermally conductive composite filler, and can also improve the dispersion effect of the composite filler in the composition. The ether bond in its molecular structure can improve the oil resistance of the silicone gel, so that the silicone gel can still maintain a low oil yield under long-term high-temperature hot oil immersion, and is particularly suitable for situations where heat dissipation with thermal oil is required.

[0034] Furthermore: the hydrogen-containing silicone oil includes terminal hydrogen-containing silicone oil and side hydrogen-containing silicone oil, the weight ratio of the thermal conductive composite filler premix to the terminal hydrogen-containing silicone oil is 2100:2-5, and the weight ratio of the thermal conductive composite filler premix to the side hydrogen-containing silicone oil is 2100:3-6; the viscosity range of the thermal conductive silicone gel composition is 10000-150000cps, and the curing temperature of the gel composition is ≥80°C. Specifically, the terminal hydrogen-containing silicone oil is a hydrogen-containing silicone oil with silicon and hydrogen at both ends of the molecular chain for silicon hydrogen addition reaction known in the art, with a viscosity range of 20-100CPS and a silicon hydrogen content of 0.03-1.5% in the molecule; preferably, the terminal hydrogen-containing silicone oil is TH01, and the silicon hydrogen content is 1.0%. Specifically, the side hydrogen-containing silicone oil is a hydrogen-containing silicone oil in the middle of the molecular chain for silane addition reaction known in the art, with a viscosity range of 20-100 CPS and a silane-hydrogen content of 0.03-1.5% in the molecule; preferably, the side hydrogen-containing silicone oil is TH36, with a viscosity of 50-100 CPS and a silane-hydrogen content of 0.36%. Specifically, the silane coupling agent is a silane coupling agent known in the art, with a viscosity of 200 CPS, and examples thereof include one or more of KH-560, KH-570, KH-792, A-1160, A-171, COSMP200, COS2287, Silquest A-1871, and Silquest A-187. In addition, the thermally conductive silicone gel composition may also be added with catalysts, inhibitors, and color pastes according to actual needs, with the catalyst weight range being 1-3 parts, the inhibitor weight range being 0.1-0.5 parts, the viscosity being 20-50 CPS, and the color paste weight range being 2-4 parts. Specifically, the catalyst is a platinum catalyst known in the art for promoting hydrosilylation reaction, selected from platinum or platinum compounds, and examples thereof include platinum catalysts such as single substance platinum, platinum black, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds; preferably, the platinum catalyst is platinum. Specifically, the inhibitor is a known inhibitor in the art for inhibiting the hydrosilylation reaction at room temperature and extending the shelf life, and examples thereof include acetylenic alcohols (e.g., ethynylmethyldecylmethanol, 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol) and other acetylenic compounds, tributylamine, tetramethylethylenediamine, benzotriazole and other nitrogen compounds, triphenylphosphine and other organic phosphorus compounds, oxime compounds, organic chlorine compounds, etc.; preferably, the inhibitor is 1-ethynyl-1-cyclohexanol. Specifically, the color paste is a known color paste, which is prepared by premixing vinyl silicone oil and dye, and is used to change the color of the composition.

[0035] Further: the hardness of the first thermally conductive filler powder ≤ the hardness of the second thermally conductive filler powder < the hardness of the third thermally conductive filler powder; the particle size of the first thermally conductive filler powder ≤ 1μm, the particle size of the second thermally conductive filler powder ≤ 4μm, and the particle size of the third thermally conductive filler powder ≤ 50μm. Specifically, the Mohs hardness range of the surface layer is 3-5, the Mohs hardness range of the middle layer filler is 5-7, and the Mohs hardness range of the core layer thermally conductive filler is 8-10. In the present invention, since the core layer of the thermally conductive composite filler needs to provide a core for the composite structure to support the attachment and connection of the middle layer and the surface layer, its surface hardness should not be less than the second and first thermally conductive fillers. At this point, it is helpful to avoid the negative situation of deformation of the multi-layer structure due to force of the composite filler during printing.

[0036] Furthermore: the particle size range of the first thermally conductive filler powder is 0.01-1 μm, the particle size range of the second thermally conductive filler powder is 1-4 μm, and the particle size range of the third thermally conductive filler powder is 5-50 μm.

[0037] Furthermore: the particle size ratio of the first thermally conductive filler powder and the second thermally conductive filler powder is 0.05-0.1:3, and the particle size ratio of the second thermally conductive filler powder and the third thermally conductive filler powder is 3:20-30; the shape of the first thermally conductive filler powder is spherical or nearly spherical, and the shape of the third thermally conductive filler powder is spherical or nearly spherical. Preferably, the particle size of the first thermally conductive filler powder is 0.1μm, the particle size of the second thermally conductive filler powder is 3μm, and the particle size of the third thermally conductive filler powder is 30μm. In the present invention, in order to meet the low wear effect, the particle size of the third thermally conductive filler as the core in the composite filler should be larger than the second thermally conductive filler and much larger than the third thermally conductive filler. At this time, when each layer of the composite structure is formed layer by layer, it is easier to obtain more attachments to ensure the covering and shielding effect of the other layers on the core layer. In addition, the higher the sphericity of the thermally conductive filler powder in the core layer and the surface layer, the smaller its surface energy, the better the surface fluidity of the ball, and the better the connection effect with the other two layers.

[0038] Furthermore: the thermal conductivity of the first thermally conductive filler powder is less than the thermal conductivity of the third thermally conductive filler powder and the second thermally conductive filler powder; the thermal conductivity range of the core layer is ≥30W / m·K. Specifically, the first, second and third thermally conductive fillers are selected from common insulating thermally conductive filler powders in the field, wherein the first thermally conductive filler is selected from zinc oxide with a thermal conductivity of 30W / m·K, the second thermally conductive filler is selected from hexagonal boron nitride with a thermal conductivity of 180W / m·K, and the third thermally conductive filler is selected from one or a combination of aluminum nitride, α-alumina and diamond powder. Preferably, the third thermally conductive filler is aluminum nitride with a thermal conductivity of 320W / m·K. The core layer of the thermally conductive composite filler used in the gel composition of the present invention plays a major role in thermal conductivity, followed by the middle layer and finally the surface layer. The thermal conductivity gradually decreases from the inside to the outside, and the resulting thermal conduction path is more orderly, which is conducive to heat transfer.

[0039] Furthermore: the connection mode between the surface layer and the middle layer is molecular chain entanglement, and the connection mode between the middle layer and the core layer is chemical bond connection; the first, second and third thermal conductive filler surfaces are respectively provided with the first, second and third connection layers, the surface layer is connected to the middle layer through the first connection layer and the second connection layer, and the middle layer is connected to the core layer through the third connection layer; the first connection layer is a long-chain borate ester and stearic acid modified layer, the second connection layer is a long-chain aluminate ester and stearic acid modified layer, and the third connection layer is a silane modified layer. The thermal conductive composite filler used in the gel composition of the present invention, when the core layer is connected to the middle layer, the silane coupling agent of the third connection layer provides hydroxyl groups to react with the hydroxyl groups on the surface of the second thermal conductive filler after hydrolysis to form a chemical bond connection, the chemical bond connection strength is relatively large, and can provide a stable connection for the connection between the core layer and the middle layer, when the surface layer is connected to the middle layer, the long-chain aluminate ester of the second connection layer and the long-chain borate ester of the first connection layer are entangled to form an entangled connection, the entangled connection strength is relatively small and the connection distance is longer. Preferably, the silane modified layer includes silane coupling agent KH560.

[0040] The above-mentioned thermally conductive silicone gel composition comprises two components A and B; the component A comprises a thermally conductive composite filler premix and a silane coupling agent, and the component B comprises a thermally conductive composite filler premix and a hydrogen-containing silicone oil; wherein: the weight ratio of the thermally conductive composite filler premix to the silane coupling agent in the component A is 1060:10-16; the weight ratio of the thermally conductive composite filler premix to the hydrogen-containing silicone oil in the component B is 1040:5-11. The present invention also provides a two-component silicone gel composition, which is divided into two components for configuration, transportation and storage, which not only makes the configuration and use of the composition more flexible, but also avoids premature curing reaction during transportation and storage.

[0041] A method for preparing the above-mentioned thermally conductive silicone gel composition, comprising S1. preparing a first thermally conductive filler powder, a second thermally conductive filler powder, and a third thermally conductive filler powder, S2. preparing a thermally conductive composite filler premix, and S3. preparing components A and B of the thermally conductive silicone gel composition; characterized in that:

[0042] The S1. comprises: S11. modifying the first thermally conductive filler to obtain a first thermally conductive filler powder, S12. modifying the second thermally conductive filler to obtain a second thermally conductive filler powder, S13. modifying the third thermally conductive filler to obtain a third thermally conductive filler powder;

[0043] S2. Figure 2 As shown, it includes: S21. Mixing a third thermally conductive filler powder, a vinyl silicone oil dispersant, and a second thermally conductive filler powder to form a primary composite filler mixture, S22. Mixing the primary composite filler mixture and the first thermally conductive filler powder to form a thermally conductive composite filler premix; the primary composite filler mixture includes a pre-composite filler, and the pre-composite filler is a two-layer structure, including an inner layer and an outer layer connected, the outer layer is the second thermally conductive filler powder, and the inner layer is the third thermally conductive filler powder;

[0044] The S3. comprises: taking a thermally conductive composite filler premix, adding a silane coupling agent, and stirring until a uniform component A is obtained; taking a thermally conductive composite filler premix, adding hydrogenated silicone oil, and then adding a silane coupling agent, and stirring until a uniform component B is obtained.

[0045] Further: S11. is to obtain the first thermally conductive filler powder by modifying the first thermally conductive filler with a long-chain borate coupling agent and stearic acid, S12. is to obtain the second thermally conductive filler powder by modifying the second thermally conductive filler with a long-chain aluminate coupling agent and stearic acid, and S13. is to obtain the third thermally conductive filler powder by modifying the third thermally conductive filler with a silane coupling agent. Specifically, S11. includes: pre-drying the first thermally conductive filler under heating conditions to remove free water until the water content in the first thermally conductive filler is ≤0.1%; then, placing 100 parts by weight of the first thermally conductive filler in a kneader, adding 3-5 parts by weight of distearoyloxyisopropyl borate, and kneading at a temperature of 110-120°C; then, adding 0.5-1 parts by weight of stearic acid, and continuing to knead under heating conditions; finally, drying under heating conditions until the water content of the first thermally conductive filler is ≤0.1%, and obtaining the first thermally conductive filler powder. Specifically, the S12. includes: pre-drying the second thermally conductive filler under heating conditions to remove free moisture until the moisture content of the second thermally conductive powder is ≤0.1%; then, placing 100 parts by weight of the second thermally conductive filler in a kneader, adding 1-3 parts by weight of aluminate DL-411, and kneading under heating conditions; then, adding 0.5-0.8 parts by weight of stearic acid, and continuing to knead under heating conditions; finally, drying under heating conditions until the moisture content of the first thermally conductive filler is ≤0.1%, thereby obtaining a second thermally conductive filler powder. Specifically, the S13. comprises: mixing 15-20 parts by weight of silane KH560, 5-10 parts by weight of distilled water, and 70-80 parts by weight of anhydrous ethanol to carry out a hydrolysis reaction; then, after the reaction, placing 100 parts by weight of the third thermally conductive filler in a closed box with a blower to fully lift it, and then spraying it for hydrolysis, and the hydrolyzed silane is evenly sprayed on the surface of the third thermally conductive filler; then, drying it under heating conditions, and when the moisture content of the third thermally conductive powder is ≤0.1%, a modified third thermally conductive filler powder is obtained. The present invention uses borate, aluminate, and silane to modify the first thermally conductive powder, the second thermally conductive powder, and the third thermally conductive powder, respectively, which can improve the dispersion, adhesion, and connection effects between thermally conductive powders of different types and particle sizes.

[0046] Furthermore: the S21. includes S211. mixing the third thermally conductive filler and the vinyl silicone oil dispersant, and S212. adding and mixing the second thermally conductive filler to form a primary filler modified mixture. Specifically, the S211. includes: at room temperature, taking 1500 parts by weight of the third thermally conductive filler powder, adding 100 parts by weight of long-chain alkyl polyether vinyl silicone oil, dispersing for 5-8 minutes under the condition of a high-speed disperser speed of 500-800, and stopping the dispersion. Specifically, S212. includes: adding 400 parts by weight of the second thermally conductive filler powder, placing the stirring cup in an ultrasonic instrument at the same time, adjusting the speed of the high-speed disperser to 1500-2000, after dispersing for 5-8 minutes, turning on the ultrasonic instrument, continuing to disperse for 10-15 minutes, turning off the ultrasonic instrument, stopping the dispersion, and obtaining a primary composite filler mixture. The present invention uses long-chain alkyl polyether vinyl silicone oil as a dispersant to enable the third thermally conductive filler powder to obtain a good dispersion effect.

[0047] Further: S22. includes: adding 100 parts by weight of a first thermally conductive filler powder to the primary filler modified mixture; then, adjusting the speed of the high-speed disperser to 1000-1500, dispersing for 5-8 minutes, turning on the ultrasonic instrument, continuing to disperse for 10-15 minutes, turning off the ultrasonic instrument, stopping the dispersion, and obtaining a thermally conductive composite filler premix.

[0048] Further: S3. includes: taking 1060 parts by weight of a thermally conductive composite filler premix, adding 1-3 parts by weight of a platinum catalyst, adding 0.1-0.5 parts by weight of an inhibitor, stirring evenly, adding 5-8 parts by weight of a silane coupling agent polyethylene glycol trimethoxysilyl propyl ether, and continuing to stir until component A is evenly obtained; then, taking 1040 parts by weight of a thermally conductive composite filler premix, adding 2-5 parts by weight of end hydrogenated silicone oil, 3-6 parts by weight of side hydrogenated silicone oil, and 2-4 parts by weight of a color paste, stirring evenly, adding 5-8 parts by weight of a silane coupling agent polyethylene glycol trimethoxysilyl propyl ether, and continuing to stir until component B is evenly obtained.

[0049] Example 1

[0050] S11.: pre-drying the first thermally conductive filler BN under heating conditions to remove free water until the water content of the first thermally conductive filler is ≤0.1%; then, placing 100 parts by weight of the first thermally conductive filler in a kneader, adding 3 parts by weight of distearoyloxyisopropyl borate, and kneading at a temperature of 110° C.; then, adding 0.5 parts by weight of stearic acid, and continuing to knead under heating conditions; finally, drying under heating conditions until the water content of the first thermally conductive filler is ≤0.1%, thereby obtaining a first thermally conductive filler powder;

[0051] S12.: pre-drying the second thermally conductive filler ZnO under heating conditions to remove free water until the moisture content of the second thermally conductive powder is ≤0.1%; then, placing 100 parts by weight of the second thermally conductive filler in a kneader, adding 1 part by weight of aluminate DL-411, and kneading under heating conditions; then, adding 0.5 parts by weight of stearic acid, and continuing to knead under heating conditions; finally, drying under heating conditions until the moisture content of the second thermally conductive filler is ≤0.1%, thereby obtaining a second thermally conductive filler powder;

[0052] S13.: 15 parts by weight of silane KH560, 5 parts by weight of distilled water, and 70 parts by weight of anhydrous ethanol are mixed to perform a hydrolysis reaction; then, after the reaction, 100 parts by weight of the third thermally conductive filler is placed in a closed box with a blower to be fully lifted, and then sprayed for hydrolysis, and the hydrolyzed silane is evenly sprayed onto the surface of the third thermally conductive filler; then, drying is performed under heating conditions, and the moisture content of the third thermally conductive powder is ≤0.1%, to obtain a modified third thermally conductive filler powder;

[0053] S21. Take 1500 parts by weight of the third thermally conductive filler powder Al2O3, add 100 parts by weight of vinyl silicone oil, disperse for 5 min at a high-speed disperser speed of 500, and stop dispersing; add 400 parts by weight of the second thermally conductive filler powder, and place the stirring cup in an ultrasonic instrument, adjust the speed of the high-speed disperser to 1500, disperse for 5 min, turn on the ultrasonic instrument, continue to disperse for 10 min, turn off the ultrasonic instrument, stop dispersing, and obtain a primary composite filler mixture;

[0054] S22. Add 100 parts by weight of the first thermally conductive filler powder to the primary filler modified mixture; then, adjust the speed of the high-speed disperser to 1000, disperse for 5 minutes, turn on the ultrasonic instrument, continue to disperse for 10 minutes, turn off the ultrasonic instrument, stop dispersing, and obtain a thermally conductive composite filler premix. Parameters are shown in Table 1.

[0055] S3.: Take 1060 parts by weight of the thermal conductive composite filler premix, add 3 parts by weight of platinum catalyst, add 0.5 parts by weight of inhibitor, stir evenly, add 8 parts by weight of silane coupling agent polyethylene glycol trimethoxysilyl propyl ether, continue stirring until uniform, and obtain component A; then, take 1040 parts by weight of the thermal conductive composite filler premix, add 5 parts by weight of end hydrogenated silicone oil, 6 parts by weight of side hydrogenated silicone oil, 4 parts by weight of color paste, stir evenly, add 8 parts by weight of silane coupling agent polyethylene glycol trimethoxysilyl propyl ether, continue stirring until uniform, and obtain component B. Parameters are shown in Table 2.

[0056] Comparative Example 1#

[0057] The difference between comparative example 1# and embodiment 1 is that the thermally conductive composite filler of embodiment 1 is formed by the third, second and first thermally conductive fillers, while comparative example 1# is formed only by the third and second thermally conductive fillers; parameters are shown in Table 1.

[0058] Comparative Example 2#

[0059] The difference between Comparative Example 2# and Example 1 is that the weight of the first thermal conductive filler in Example 1 is 100 parts, while the weight of Comparative Example 2# is 50 parts. Parameters are shown in Table 1.

[0060] Example 2

[0061] The difference between Example 2 and Example 1 is that the weight of the first thermal conductive filler in Example 1 is 100 parts, while the weight of the first thermal conductive filler in Example 2 is 200 parts. Parameters are shown in Table 1.

[0062] Embodiment 3-4

[0063] The difference between Example 3-4 and Example 1 is that the radius of the second thermally conductive filler in Example 1 is 1 μm, while that in Example 2 is 2 μm and that in Example 3 is 3 μm. Parameters are shown in Table 1.

[0064] Example 5

[0065] The difference between Example 5 and Example 1 is that the radius of the first thermal conductive filler in Example 1 is 0.1 μm, while that in Example 5 is 0.5 μm. Parameters are shown in Table 1.

[0066] Test example:

[0067] The compositions of each embodiment and comparative example A and B were mixed evenly to obtain a silicone gel mixture, and the wear performance was tested; then, the silicone gel mixture was heated and cured, and the thermal conductivity was tested. The specific test method is as follows:

[0068] (1) Wear test

[0069] The silicone gel mixture was placed on an aluminum alloy plate and scraped back and forth 10 times using a scraping plate. The aluminum alloy plate was rinsed clean and the mass before and after scraping was tested. The wear amount was calculated in units of weight loss percentage. The results are shown in Table 1.

[0070] (2) Thermal conductivity test

[0071] The silicone gel mixture was injected into the mold using the ASTM D 5470 heat flow steady-state method and cured at 130 ° C for 30 minutes to obtain a test sample of 26 mm × 26 mm and 3 mm thickness. The thermal conductivity of the sample at room temperature was then measured in W / m·k. The results are shown in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] It can be seen from the parameters and results of the embodiments and comparative examples in Table 1 that the thermal conductivity of the silicone gel prepared by using the thermally conductive composite filler premix of the present invention is not less than 4.1 W / m·K, showing excellent thermal conductivity and meeting the application requirements of chip-type electronic products. In addition, the present invention also:

[0076] (1) Adding thermal conductive fillers in the form of premixes can reduce the friction and shedding of the surface layer of the composite filler powder during the addition and dispersion process, thereby affecting the wear effect during use;

[0077] (1)(2) Low and stable wear. From the wear test results of Comparative Example 1# and Comparative Example 2# and Examples 1-5, it can be seen that the wear amount is less after adding the first thermally conductive filler to the thermally conductive composite filler. In addition, the wear amount is relatively stable and fluctuates only within a small range.

[0078] Embodiment 6-8

[0079] The difference between Examples 6-8 is that the dispersant in the thermally conductive composite filler premix of Example 1 is long-chain alkyl polyether modified vinyl silicone oil, while the dispersant in Examples 6-8 is long-chain alkyl polyether modified vinyl silicone oil. The parameters are shown in Table 2.

[0080] Examples 9-10

[0081] The difference between Example 9-10 and Example 6 is that the coupling agent polyethylene glycol trimethoxysilyl propyl ether in the silicone gel composition of Example 6 is 6 parts by weight, while that in Examples 9-10 is 5 and 7 parts by weight respectively. The parameters are shown in Table 2.

[0082] The compositions of each embodiment and comparative example A and B were mixed evenly to obtain a silicone gel mixture, and the viscosity was tested; then, the silicone gel mixture was heated and cured, and the oil resistance was tested. The specific test method is as follows:

[0083] (1) Viscosity test

[0084] Referring to ASTM D1084, the silicone gel mixture was placed in a disposable cup and placed at 23±2℃ for 30 minutes. The viscosity of the sample was then tested. The results are shown in Table 2.

[0085] (2) Oil resistance test

[0086] The silicone gel mixture was cured at 130°C for 30 min to obtain a cured block, which was cut into small cubes of 1±0.1 mm×1±0.1 mm×1±0.1 mm. The small cubes were then placed in thermal oil and immersed in an oven at 100°C for an immersion test. After 1000 h, the small cubes were taken out to test their size, quality, and appearance. At the same time, it was observed whether the thermal oil had any color bubbles. The unit was weight loss percentage. The results are shown in Table 2.

[0087] Table 2

[0088]

[0089]

[0090] It can be seen from the parameters and results of the embodiments and comparative examples in Table 2 that the thermally conductive silicone gel composition of the present invention not only meets the viscosity requirement for steel screen printing, that is, the viscosity is between 80,000-150,000 cps, but also has the following characteristics:

[0091] (1) Oil resistance: From the oil resistance test results of Comparative Examples 6-8, it can be seen that the use of an appropriate amount of long-chain alkyl polyether-modified vinyl silicone oil as a dispersant and polyethylene glycol trimethoxysilyl propyl ether as a coupling agent can improve the oil yield of silicone gel, and even in a long-term immersion environment of high-temperature thermal oil, the oil yield is still kept low;

[0092] In summary, the viscosity of the silicone gel composition of the present invention is between 80,000 and 150,000 cps, the gel particle size is ≤55 μm, and the thermal conductivity of the cured product is >4.0 W / mk. It is very suitable for situations where a steel screen printing process is required and it needs to be used in a high-temperature hot oil repeated dipping or soaking environment.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Those skilled in the art should understand that the technical solution of the present invention can be deduced or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A thermally conductive silicone gel composition, comprising a thermally conductive composite filler premix, a silane coupling agent, and hydrogen-containing silicone oil; characterized in that: The thermally conductive composite filler premix comprises a mixed vinyl silicone oil and a thermally conductive composite filler powder; the thermally conductive composite filler powder comprises a surface layer, an intermediate layer and a core layer arranged in sequence from the surface to the inside; the hardness of the surface layer is less than the hardness of the intermediate layer and less than the hardness of the core layer; the surface layer is connected to the intermediate layer and is a first thermally conductive filler powder; The intermediate layer is connected to the core layer and includes a second thermally conductive filler powder; the core layer is a third thermally conductive filler powder; the particle size of the thermally conductive composite filler powder is ≤50 μm; the particle size of the first thermally conductive filler powder is less than the particle size of the second thermally conductive filler powder and less than the particle size of the third thermally conductive filler powder; The weight ratio of the first thermally conductive filler powder, the second thermally conductive filler powder, and the third thermally conductive filler powder is 100-400: 400-800: 1200-2000; The weight ratio of the thermal conductive composite filler premix to the silane coupling agent and the hydrogen-containing silicone oil is 2100:10-16:5-11.

2. The thermally conductive silicone gel composition according to claim 1, wherein: The vinyl silicone oil in the thermally conductive composite filler premix is ​​long-chain alkyl polyether modified vinyl silicone oil, and the weight ratio of the third thermally conductive filler powder to the long-chain alkyl polyether modified vinyl silicone oil is 1500:75-125.

3. The thermally conductive silicone gel composition according to claim 2, wherein: The hydrogen-containing silicone oil includes terminal hydrogen-containing silicone oil and side hydrogen-containing silicone oil. The weight ratio of the thermal conductive composite filler premix to the terminal hydrogen-containing silicone oil is 2100:2-5, and the weight ratio of the thermal conductive composite filler premix to the side hydrogen-containing silicone oil is 2100:3-6. The viscosity range of the thermal conductive silicone gel composition is 10000-150000cps.

4. The thermally conductive composite filler premix according to any one of claims 1 to 3, characterized in that: The hardness of the first thermally conductive filler powder is ≤ the hardness of the second thermally conductive filler powder < the hardness of the third thermally conductive filler powder; the particle size range of the first thermally conductive filler powder is 0.01-1μm, the particle size range of the second thermally conductive filler powder is 1-4μm, and the particle size range of the third thermally conductive filler powder is 5-50μm.

5. The thermally conductive composite filler premix according to claim 4, characterized in that: The particle size ratio of the first thermally conductive filler powder and the second thermally conductive filler powder is 0.05-0.1:3, and the particle size ratio of the second thermally conductive filler powder and the third thermally conductive filler powder is 3:20-30; the shape of the first thermally conductive filler powder is spherical or nearly spherical, and the shape of the third thermally conductive filler powder is spherical or nearly spherical.

6. The thermally conductive composite filler premix according to claim 5, characterized in that: The thermal conductivity of the first thermally conductive filler powder is less than the thermal conductivity of the third thermally conductive filler powder and the second thermally conductive filler powder; and the thermal conductivity of the core layer is in the range of ≥30 W / m·K.

7. The thermally conductive composite filler premix based on silicone gel according to any one of claims 1 to 3, characterized in that: The surface layer and the middle layer are connected by molecular chain entanglement, and the middle layer and the core layer are connected by chemical bond connection; the surfaces of the first, second and third thermal conductive fillers are respectively provided with the first, second and third connecting layers, the surface layer is connected to the middle layer through the first connecting layer and the second connecting layer, and the middle layer is connected to the core layer through the third connecting layer; the first connecting layer is a long-chain borate ester and stearic acid modified layer, the second connecting layer is a long-chain aluminate ester and stearic acid modified layer, and the third connecting layer is a silane modified layer.

8. An organic silicone gel composition as claimed in claim 1, comprising two components A and B; the component A comprises a thermal conductive composite filler premix and a silane coupling agent, and the component B comprises a thermal conductive composite filler premix and hydrogen-containing silicone oil; characterized in that: The weight ratio of the thermal conductive composite filler premix to the silane coupling agent in component A is 1060:10-16; the weight ratio of the thermal conductive composite filler premix to the hydrogen-containing silicone oil in component B is 1040:5-11.

9. A method for preparing a thermally conductive silicone gel two-component composition as claimed in claim 8, comprising S1. preparing a first thermally conductive filler powder, a second thermally conductive filler powder, and a third thermally conductive filler powder, S2. preparing a thermally conductive composite filler premix, and S3. preparing components A and B of the thermally conductive silicone gel composition; characterized in that: The S1. comprises: S11. modifying the first thermally conductive filler to obtain a first thermally conductive filler powder, S12. modifying the second thermally conductive filler to obtain a second thermally conductive filler powder, S13. modifying the third thermally conductive filler to obtain a third thermally conductive filler powder; The S2. comprises: S21. mixing a third thermally conductive filler powder, a vinyl silicone oil dispersant, and a second thermally conductive filler powder to form a primary composite filler mixture, S22. mixing the primary composite filler mixture and the first thermally conductive filler powder to form a thermally conductive composite filler premix; the primary filler modified mixture comprises a pre-composite filler, the pre-composite filler is a two-layer structure, comprising an inner layer and an outer layer connected, the outer layer is the second thermally conductive filler powder, and the inner layer is the third thermally conductive filler powder; The S3. comprises: taking a thermally conductive composite filler premix, adding a silane coupling agent, and stirring until a uniform component A is obtained; taking a thermally conductive composite filler premix, adding hydrogenated silicone oil, and then adding a silane coupling agent, and stirring until a uniform component B is obtained.

10. The method for preparing the thermally conductive silicone gel composition according to claim 9, characterized in that: The S11. includes using long-chain borate and stearic acid to modify the first thermally conductive filler to obtain a first thermally conductive filler powder, S12. includes using long-chain aluminate and stearic acid to modify the second thermally conductive filler to obtain a second thermally conductive filler powder, S13. includes using silane KH570 to modify the third thermally conductive filler to obtain a third thermally conductive filler powder; the S21. includes S211. mixing the third thermally conductive filler and vinyl silicone oil dispersant, and S212. adding and mixing the second thermally conductive filler to form a primary filler modified mixture.

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