Heat-conducting composite filler premix and preparation method thereof

Abstract

The invention provides a heat-conducting composite filler premix and a preparation method thereof. The heat-conducting composite filler premix comprises vinyl silicone oil and heat-conducting composite filler powder which are mixed, the heat-conducting composite filler powder comprises a surface layer, a middle layer and a core layer which are sequentially arranged from the surface to the inside, the hardness of the surface layer is more than the hardness of the middle layer and less than the hardness of the core layer; wherein 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 made of third heat-conducting filler powder; the particle size of the heat-conducting composite filler powder is less than or equal to 50 microns; the second heat-conducting filler powder is greater than the first heat-conducting filler powder 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). Compared with filler in the prior art, the heat-conducting composite filler premix disclosed by the invention is convenient to use and prepare heat-conducting silica gel, is high in anti-wear reliability and is suitable for a steel mesh printing process with repeated rubbing.

Description

Technical Field

[0001] The invention belongs to the technical field of thermally conductive organic silicone gel, and relates to an insulating thermally conductive composite filler premix for preparing thermally conductive organic silicone gel 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, the addition of 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.

[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 an easy-to-use thermally conductive composite filler premix that has good wear reduction effect and good reliability, and can be suitable for products with repeated friction, high precision and soft surface. Summary of the invention

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

[0006] A thermally conductive composite filler premix, comprising 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; wherein:

[0007] The surface layer is connected to the middle layer and is a first thermally conductive filler powder; the middle 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;

[0008] 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;

[0009] 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.

[0010] Furthermore: the weight ratio of the third thermally conductive filler powder to the vinyl silicone oil is 1500:75-125.

[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 of the first thermally conductive filler powder is ≤1μm, the particle size of the second thermally conductive filler powder is ≤4μm, and the particle size of the third thermally conductive filler powder is ≤50μm.

[0012] Furthermore: 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; 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.

[0013] Furthermore: 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.

[0014] 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.

[0015] Furthermore: the connection mode between the surface layer and the middle layer includes molecular chain entanglement, and the connection mode between the middle layer and the core layer includes chemical bond connection.

[0016] Furthermore: a first connecting layer is provided on the surface of the first thermally conductive filler powder, a second connecting layer is provided on the surface of the second thermally conductive filler powder, and a third connecting layer is provided on the surface of the third thermally conductive filler powder. The first and second connecting layers are intertwined to achieve molecular chain entanglement, and the second and third connecting layers react to achieve chemical bond connection.

[0017] A method for preparing the above-mentioned thermally conductive composite filler premix comprises S1. preparing a first thermally conductive filler powder, a second thermally conductive filler powder, and a third thermally conductive filler powder, and S2. preparing a thermally conductive composite filler premix; wherein:

[0018] 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;

[0019] 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 composite filler 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;

[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 heat-conductive composite filler premix and the preparation method thereof provided by the present invention improve the filler structure and the preparation process, have a good wear reduction effect, and are suitable for the steel screen printing process with repeated rubbing. 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]

[0027] DETAILED DESCRIPTION

[0028] Example

[0029] This embodiment provides: a thermally conductive composite filler premix, such as Figure 1 As shown, it includes mixed vinyl silicone oil and thermally conductive composite filler powder 123; the thermally conductive composite filler powder 123 includes a surface layer, an intermediate layer and a core layer arranged in sequence from the surface to the inside; wherein:

[0030] The surface layer is connected to the middle layer and is composed of a first thermally conductive filler powder 1; the middle layer is connected to the core layer and includes a second thermally conductive filler powder 2; the core layer is composed of a third thermally conductive filler powder 3;

[0031] The particle size of the thermally conductive composite filler powder 123 is ≤50 μm; 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;

[0032] 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.

[0033] 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 and the dispersion effect of the filler will deteriorate, which will lead to poor thermal conductivity.

[0034] The composite filler powder of this embodiment is a multi-layer composite structure, which can play a good shielding effect on the core layer. Among them, the hardness of the surface layer and the middle layer are both smaller than that of the core layer. In the process of coating or printing thermal conductive adhesive, the filler surface is softer and can reduce damage to coating tools or products. 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 has small particles and low hardness, so it can better flow with the adhesive during the printing process to avoid collision with the composite filler powder and cause damage to the composite structure.

[0035] 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, 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. At this point, 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 an intermediate layer and a surface layer in sequence. Of course, the above weight range provided in this embodiment can achieve better results.

[0036] Further: the weight ratio of the third thermally conductive filler powder to the vinyl silicone oil is 1500:75-125. Specifically, the vinyl silicone oil is a vinyl silicone oil commonly used as a dispersant in the art. Preferably, in the dispersion of the present invention, the vinyl silicone oil is a long-chain alkyl polyether vinyl silicone oil. The better the filler dispersion effect in the thermally conductive composite filler premix, the better the thermal conductivity of the product after adding the silicone gel. The modified vinyl silicone oil can improve the efficiency of forming the composite thermally conductive filler powder and improve the dispersion effect of the premix.

[0037] 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. 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. Preferably, the Mohs hardness of the surface layer is 4, the Mohs hardness of the middle layer is 6, and the Mohs hardness of the core layer is 9. 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, the composite structure will not be deformed due to force during printing.

[0038] Furthermore: the particle size of the first thermally conductive filler powder is ≤1 μm, the particle size of the second thermally conductive filler powder is ≤4 μm, and the particle size of the third thermally conductive filler powder is ≤50 μm.

[0039] Furthermore: 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; 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. 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 order to meet the composite structure required for the wear effect, the particle size of the third thermally conductive filler as the core 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 other layers on the core layer.

[0040] Furthermore: 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. Specifically, the shape of the second thermally conductive filler powder is hexagonal. 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 sphere, and the better the connection effect with the other two layers.

[0041] 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. Specifically, the thermal conductivity of the core layer is in the range of ≥30W / m·K. The core layer plays a major role in the thermal conductivity of the composite filler powder, followed by the middle layer, and the surface layer mainly plays a role in reducing wear. In addition, when the surface layer falls off during the printing process, the thermal conductivity of the outer and inner layers of the thermally conductive filler in the new composite structure is higher as a whole, and the thermal conductivity is better.

[0042] Furthermore: the first thermally conductive filler, the second thermally conductive filler, and the third thermally conductive filler are selected from common insulating thermally conductive filler powders in the art. Specifically, 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, aluminum oxide, and α diamond powder. Preferably, the third thermally conductive filler is aluminum nitride with a thermal conductivity of 320W / (m·K).

[0043] Furthermore: the connection mode between the surface layer and the middle layer includes molecular chain entanglement, and the connection mode between the middle layer and the core layer includes chemical bond connection.

[0044] Furthermore: the surfaces of the first thermally conductive filler, the second thermally conductive filler and the third thermally conductive filler 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 second connecting layer and the third connecting layer.

[0045] Furthermore: the first thermally conductive filler surface connection layer includes a long-chain borate and a stearic acid modified layer, the second thermally conductive filler surface connection layer includes a long-chain aluminate and a stearic acid modified layer, and the third thermally conductive filler surface connection layer includes a silane modified layer. Specifically, the silane includes the silane coupling agent KH560. When the core layer is connected to the middle layer, the silane coupling agent KH560 on the surface of the core layer provides hydroxyl groups to react with the hydroxyl groups on the surface of the middle layer to form a chemical bond connection. When the surface layer is connected to the middle layer, the long-chain aluminate on the surface of the middle layer and the long-chain borate on the surface of the surface layer are entangled to form an entangled connection. The chemical bond connection strength is relatively large, which can provide a stable connection between the core layer and the middle layer. The entangled connection strength is relatively small and the connection distance is longer, which satisfies the requirement that the outermost layer of the composite structure is the surface layer and can fall off earlier than the middle layer during the force friction process.

[0046] This embodiment also provides: a method for preparing the above-mentioned thermally conductive composite filler premix, 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; wherein:

[0047] 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;

[0048] S2. Figure 2 As shown, it includes: S21. Mixing a third thermally conductive filler powder 3, a vinyl silicone oil dispersant, and a second thermally conductive filler powder 2 to form a primary composite filler mixture, S22. Mixing the primary composite filler mixture and the first thermally conductive filler powder 1 to form a thermally conductive composite filler premix; the primary composite filler mixture includes a pre-composite filler 23, and the pre-composite filler 23 is a two-layer structure, including a connected inner layer and an outer layer, the outer layer is the second thermally conductive filler powder, and the inner layer is the third thermally conductive filler powder.

[0049] 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.

[0050] 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 composite filler mixture. Specifically, the S211. includes: taking 1500 parts by weight of the third thermally conductive filler powder at room temperature, 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, 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.

[0051] Specifically: S22. includes: adding 100 parts by weight of a first thermally conductive filler powder to the primary composite filler mixture; then, adjusting the speed of the high-speed disperser to 1000-1500, dispersing for 5-8 minutes, turning on an ultrasonic instrument, continuing to disperse for 10-15 minutes, turning off the ultrasonic instrument, stopping dispersion, and obtaining a thermally conductive composite filler premix.

[0052] Example 1

[0053] S11.: pre-drying the first thermally conductive filler 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;

[0054] S12.: pre-drying the second thermally conductive filler under heating conditions to remove free water until the water 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 water content of the second thermally conductive filler is ≤0.1%, thereby obtaining a second thermally conductive filler powder;

[0055] 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;

[0056] S21. Take 1500 parts by weight of the third thermally conductive filler powder, 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 filler modified mixture;

[0057] 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.

[0058] Comparative Example 1#

[0059] The difference between Comparative Example 1# and Example 1 is that the thermally conductive composite filler premix of Example 1 includes the third, second and first thermally conductive fillers, while Comparative Example 1# only includes the third and second thermally conductive fillers; parameters are shown in Table 1.

[0060] Comparative Example 2#

[0061] 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.

[0062] Example 2

[0063] 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.

[0064] Embodiment 3-4

[0065] 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, that in Example 2 is 2 μm, and that in Example 3 is 3 μm. Parameters are shown in Table 1.

[0066] Example 5

[0067] 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.

[0068] Test example:

[0069] 2100 parts by weight of the thermally conductive composite filler premix of each embodiment and comparative example, 16 parts by weight of silane coupling agent, 11 parts by weight of hydrogen-containing silicone oil and other additives were prepared into a thermally conductive silicone gel composition, and the wear performance was tested; then, the thermally conductive silicone gel composition was heated and cured, and the thermal conductivity was tested. The specific test method is as follows:

[0070] (1) Wear test

[0071] The thermal conductive gel composition is placed on an aluminum alloy plate, and is scraped back and forth 10 times using a scraping plate. The aluminum alloy plate is rinsed clean, and the mass before and after scraping is tested to calculate the wear amount, which is expressed as a percentage of weight loss.

[0072] (2) Thermal conductivity test

[0073] The ASTM D 5470 heat flow steady state method was used. The sample preparation method was as follows: the thermally conductive gel composition was injected into the mold, and was cured at 130°C for 30 minutes to obtain a test sample of 26 mm × 26 mm and a thickness of 1, 2, and 3 mm. The thermal conductivity of the sample at room temperature was then tested in W / m·k. The results are shown in Table 1.

[0074] Table 1

[0075]

[0076] From the parameters and results of the embodiments and comparative examples in Table 1, it can be seen that the thermal conductivity of the gel composition prepared by using the thermally conductive composite filler premix of the present invention is not less than 4.1 W / m·K, and can even reach 4.5 W / m·K, showing a more excellent thermal conductivity, meeting the common thermal conductivity requirements in the application field of silicone gel electronic products. In addition, compared with the prior art, it also:

[0077] (1) The preparation process is optimized. Compared with the prior art in which the powder is directly added, the present invention adopts a premixed form to avoid the surface layer of the thermal conductive powder being rubbed off during the addition and dispersion process;

[0078] (2) Low wear. From the wear test results of Comparative Example 1# and Comparative Example 2# and Examples 1-5, it can be seen that when the thermally conductive composite filler premix is ​​added with the first thermally conductive filler to form the thermally conductive composite filler and the thermally conductive composite filler premix of the present invention, the wear rate can be as low as 0.1 and fluctuates only within a relatively narrow wear range, and the wear is reduced and the wear degree is relatively stable.

[0079] (3) Low wear and excellent thermal conductivity. From the wear test results of Comparative Example 1 and Examples 1-5, it can be seen that the particle sizes of the first thermally conductive filler and the second thermally conductive filler have an impact on the wear performance. When the particle sizes of the first and second thermally conductive fillers are 0.1 and 3 μm, respectively, the wear is low and the thermal conductivity is excellent.

[0080] 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 composite filler premix, comprising 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; characterized in that: The surface layer is connected to the middle 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.

2. The thermally conductive composite filler premix according to claim 1, characterized in that: The weight ratio of the third thermally conductive filler powder to the vinyl silicone oil is 1500:75-125.

3. The thermally conductive composite filler premix according to claim 1 or 2, characterized in that: The hardness of the first thermally conductive filler powder is ≤ the hardness of the second thermally conductive filler powder and < the hardness of the third thermally conductive filler powder; the particle size of the first thermally conductive filler powder is ≤1 μm, the particle size of the second thermally conductive filler powder is ≤4 μm, and the particle size of the third thermally conductive filler powder is ≤50 μm.

4. The thermally conductive composite filler premix according to claim 3, wherein: 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; the particle size ratio of the first thermally conductive filler powder to the second thermally conductive filler powder is 0.05-0.1:3, and the particle size ratio of the second thermally conductive filler powder to the third thermally conductive filler powder is 3:20-30.

5. The thermally conductive composite filler premix according to claim 4, characterized in that: The first thermally conductive filler powder is spherical or nearly spherical in shape, and the third thermally conductive filler powder is spherical or nearly spherical in shape.

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.

7. The thermally conductive composite filler premix according to claim 1 or 2, characterized in that: The connection mode between the surface layer and the middle layer includes molecular chain entanglement, and the connection mode between the middle layer and the core layer includes chemical bond connection.

8. The thermally conductive composite filler premix based on silicone gel according to claim 7, characterized in that: A first connecting layer is arranged on the surface of the first thermally conductive filler powder, a second connecting layer is arranged on the surface of the second thermally conductive filler powder, and a third connecting layer is arranged on the surface of the third thermally conductive filler powder. The first and second connecting layers are intertwined to achieve molecular chain entanglement, and the second and third connecting layers react to achieve chemical bond connection.

9. A method for preparing a thermally conductive composite filler premix as claimed in claim 1, 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; 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. 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 a connected inner layer and an outer layer, the outer layer is the second thermally conductive filler powder, and the inner layer is the third thermally conductive filler powder.

10. The method for preparing the thermally conductive composite filler premix 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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