A zinc oxide-spherical alumina composite micropowder, its preparation method and application, a thermal conductive gasket, and a thermally conductive polymer material

Abstract

The present invention provides a zinc oxide-spherical alumina composite micro-powder, a preparation method and application thereof, a thermal conductive gasket, and a thermally conductive polymer material, which relate to the technical field of thermal conductive fillers. In the present invention, zinc oxide, alumina and a silane coupling agent are mixed, melted and spheroidized, and then cooled and solidified to form a dense zinc oxide shell on the surface of the spherical alumina, thereby obtaining the zinc oxide-spherical alumina composite micro-powder. The preparation method provided by the present invention has a uniform thickness of the zinc oxide shell layer and uniform coating of the spherical alumina core. The zinc oxide-spherical alumina composite micro-powder has a very high sphericity, a high bonding strength between the zinc oxide shell layer and the spherical alumina core, and the zinc oxide shell layer is not easily detached, and the composite micro-powder has excellent thermal conductivity. Moreover, the zinc oxide shell layer has good compatibility with the polymer material and is easy to achieve high-content filling in the polymer material, solving the problem of poor filling performance of the existing alumina, and can effectively improve the thermal conductivity of the polymer material.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal conductive fillers, and particularly relates to a zinc oxide-spherical alumina composite micropowder, a preparation method and application thereof, a thermal conductive gasket, and a thermally conductive polymer material. Background Art

[0002] With the continuous development of electronic products towards the direction of multi-functionality and miniaturization, more and more heat is generated during the use of electronic products. If the generated heat cannot be conducted out and dissipated in time, the accumulated heat will cause the temperature of electronic components to continuously rise, seriously affecting the working efficiency and service life of electronic products, and even causing safety accidents. To solve the problem of heat conduction in electronic products, thermal interface materials are widely used between heat-generating electronic components and heat sinks, which can effectively improve the heat conduction efficiency and conduct the heat generated by electronic components to the heat sink in time and dissipate it. Currently, the main thermal interface materials are filled thermal composite materials, that is, thermal conductive fillers are added to polymer materials such as rubber and plastic to obtain thermal composite materials with high thermal conductivity.

[0003] Thermal conductive fillers must reach a certain addition ratio in the thermal conductive composite material to form effective thermal conduction network chains, so as to obtain high thermal conductivity. However, a high content of thermal conductive fillers will have a negative impact on the mechanical properties, processing and forming properties, etc. of the polymer material itself. Therefore, the properties of the thermal conductive fillers themselves will greatly affect the comprehensive properties of the thermal conductive composite material. Currently, alumina is widely used in thermal interface materials due to its rich resources and low price. However, the intrinsic thermal conductivity of alumina is relatively low (about 30 W / m·K), and a high filling amount is required to obtain a higher thermal conductivity. Due to the poor compatibility between ordinary irregularly shaped alumina and polymer materials, a large amount of addition will seriously affect the mechanical strength and processing performance of polymer materials. The thermal conductivity of zinc oxide is 60-70 W / m·K, which is more than twice that of alumina. Moreover, zinc oxide is a thixotropic filler with good compatibility with polymer materials. When added to polymer materials, it shows a shear-thinning state, which can effectively improve the processing and forming properties of polymer materials, especially silicone resin, when a high content of thermal conductive fillers is added. However, the currently used zinc oxide particles are basically in the sub-micron size range. Due to their small particle size and large specific surface area, zinc oxide particles are prone to agglomeration, and there are problems with difficult dispersion when used alone.

[0004] Chinese Patent CN118027709A discloses a preparation method of alumina filler. Alumina, zinc oxide and an alcohol solution of silane coupling agent are ground in a horizontal dry ball mill, so that zinc oxide extends on the surface of spherical alumina or spherical-like alumina and undergoes solid-phase coating. However, in the above preparation method, the mixing of zinc oxide and alumina is a simple physical mixing. The zinc oxide coating layer in the prepared alumina filler is uneven, and the bonding strength between the zinc oxide coating layer and alumina is weak. When high-speed stirring and mixing are carried out, the zinc oxide coating layer is likely to fall off, affecting the thermal conductivity of the alumina filler. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a zinc oxide-spherical alumina composite micro-powder, its preparation method and application, a thermal conductive gasket, and a thermally conductive polymer material. The zinc oxide-spherical alumina composite micro-powder prepared by the present invention has a core-shell structure, the thickness of the zinc oxide shell layer is uniform, and the bonding strength with the spherical alumina core is high, and the zinc oxide-spherical alumina composite micro-powder has excellent thermal conductivity.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of a zinc oxide-spherical alumina composite micro-powder, including the following steps: mixing zinc oxide, alumina and a silane coupling agent, performing melting spheroidization and then cooling and solidifying to form a dense zinc oxide shell on the surface of spherical alumina, thereby obtaining the zinc oxide-spherical alumina composite micro-powder.

[0008] Preferably, the mass of the zinc oxide accounts for 5-10% of the total mass of the zinc oxide and alumina;

[0009] The particle size of the zinc oxide is 0.6-1.5 μm;

[0010] The particle size of the alumina is 6-170 μm.

[0011] Preferably, the silane coupling agent includes one or more of octyltriethoxysilane, n-decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, and octadecyltrimethoxysilane;

[0012] The mass of the silane coupling agent accounts for 0.2-1% of the total mass of the zinc oxide and alumina.

[0013] Preferably, the mixing time is 10-30 min; the mixing includes high-speed stirring and mixing, and the stirring frequency of the high-speed stirring and mixing is 10-20 Hz;

[0014] The temperature of the melting spheroidization is 2000-2300 °C.

[0015] The present invention provides a zinc oxide-spherical alumina composite micro-powder prepared by the preparation method described in the above technical solution, which has a core-shell structure and includes a spherical alumina core and a zinc oxide shell layer.

[0016] Preferably, the thickness of the zinc oxide shell layer is 0.6 to 1.5 μm;

[0017] The particle size of the spherical alumina core is 5 to 150 μm.

[0018] The present invention also provides an application of the zinc oxide-spherical alumina composite micro-powder described in the above technical solution as a filler.

[0019] The present invention also provides a thermal conductive gasket. Calculated by mass parts, the preparation raw materials include: 100 parts of vinyl silicone oil, 5 to 15 parts of hydrogen-containing silicone oil, 0.5 to 1.5 parts of platinum catalyst, 0.05 to 0.15 parts of inhibitor, and 1000 to 3000 parts of thermal conductive filler; the thermal conductive filler includes the zinc oxide-spherical alumina composite micro-powder described in the above technical solution.

[0020] The present invention also provides a thermal conductive polymer material, and the preparation raw materials include a polymer material and the zinc oxide-spherical alumina composite micro-powder described in the above technical solution.

[0021] Preferably, the polymer material includes one or more of polypropylene, polyamide, polyurethane, epoxy resin, and silicone rubber.

[0022] The present invention provides a preparation method of zinc oxide-spherical alumina composite micro-powder, which includes the following steps: mixing zinc oxide, alumina, and a silane coupling agent, performing melting spheroidization and then cooling and solidifying to form a dense zinc oxide shell on the surface of the spherical alumina, thereby obtaining the zinc oxide-spherical alumina composite micro-powder. The present invention uses the high-temperature melting method to spheroidize the material particles. Zinc oxide with a lower melting point will first melt and accumulate on the surface of the alumina particles, and alumina with a higher melting point continues to melt and rapidly cools and solidifies on the surface of the dense spherical alumina core to form a dense zinc oxide shell layer. The thickness of the zinc oxide shell layer is uniform and the coating of the spherical alumina core is uniform. The prepared zinc oxide-spherical alumina composite micro-powder with a core-shell structure has a very high sphericity, a high bonding strength between the zinc oxide shell layer and the spherical alumina core, the zinc oxide shell layer is not easy to fall off, and has excellent thermal conductivity. Moreover, the zinc oxide shell layer has good compatibility with the polymer material and is easy to achieve high-content filling in the polymer material, which can solve the problem of poor filling performance of existing alumina and effectively improve the thermal conductivity of the polymer material. Moreover, the method of spheroidizing particles by the high-temperature melting method adopted by the present invention has a simple process and convenient operation, and is suitable for industrial batch production.

[0023] The zinc oxide-spherical alumina composite micropowder prepared by the present invention has a tightly bonded zinc oxide shell and a spherical alumina core, and the zinc oxide shell is not easily detached. The zinc oxide-spherical alumina high thermal conductivity composite micropowder particles are in regular spherical shapes, have good thermal conductivity, and the zinc oxide shell with a high thermal conductivity coefficient has good compatibility with polymer materials. The zinc oxide-spherical alumina composite micropowder can be added in high contents as a thermal conductive filler in polymer materials. When added to polymer materials such as polypropylene (PP), polyamide (PA), polyurethane (PU), epoxy resin, and silicone rubber (especially addition-cured liquid silicone rubber), a thermal conductive composite material with high thermal conductivity and excellent processing and forming properties can be obtained. Description of the Drawings

[0024] Figure 1 SEM image of angular alumina used in Example 2;

[0025] Figure 2 SEM image of the zinc oxide-alumina mixed material prepared in Example 2;

[0026] Figure 3 SEM image of the zinc oxide-spherical alumina composite micropowder with a core-shell structure prepared in Example 2;

[0027] Figure 4 SEM image of the polished cross-section of the zinc oxide-spherical alumina composite micropowder with a core-shell structure prepared in Example 2;

[0028] Figure 5 SEM image of the polished cross-section of the zinc oxide-spherical alumina composite micropowder with a core-shell structure prepared in Example 1. Detailed Embodiments

[0029] The present invention provides a method for preparing a zinc oxide-spherical alumina composite micropowder, which includes the following steps: mixing zinc oxide, alumina, and a silane coupling agent, performing melt spheroidization and then cooling and solidifying to form a dense zinc oxide shell on the surface of the spherical alumina, thereby obtaining the zinc oxide-spherical alumina composite micropowder.

[0030] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0031] In the present invention, the particle size of the zinc oxide is preferably 0.6 to 1.5 μm, and in specific embodiments, it may be 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm. In the present invention, the mass of the zinc oxide preferably accounts for 5 to 10% of the total mass of the zinc oxide and aluminum oxide, and in specific embodiments, it may be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%. The present invention can achieve precise control of the thickness of the zinc oxide shell layer by adjusting the ratio of zinc oxide and aluminum oxide. The present invention can achieve precise control of the particle size of the zinc oxide-spherical aluminum oxide composite micropowder by adjusting the particle sizes of zinc oxide and aluminum oxide.

[0032] In the present invention, the particle size of the aluminum oxide is preferably 6 to 170 μm, and in specific embodiments, it may be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm or 170 μm; the aluminum oxide preferably includes angular aluminum oxide.

[0033] In the present invention, the silane coupling agent preferably includes one or more of octyltriethoxysilane, n-decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane and octadecyltrimethoxysilane. In the present invention, the mass of the silane coupling agent preferably accounts for 0.2 to 1% of the total mass of the zinc oxide and aluminum oxide, and in specific embodiments, it may be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0034] In the present invention, the mixing time is preferably 10 to 30 min, and in specific embodiments, it may be 10 min, 15 min, 20 min, 25 min or 30 min; the mixing preferably includes high-speed stirring mixing, and the stirring frequency of the high-speed stirring mixing is preferably 10 to 20 Hz, and in specific embodiments, it may be 10 Hz, 11 Hz, 12 Hz, 13 Hz, 14 Hz, 15 Hz, 16 Hz, 17 Hz, 18 Hz, 19 Hz or 20 Hz.

[0035] In the present invention, the temperature of the melting spheroidization is preferably 2000 - 2300°C, and in specific embodiments, it can be 2000°C, 2050°C, 2100°C, 2150°C, 2200°C, 2250°C or 2300°C. In the present invention, during the melting spheroidization process, zinc oxide with a lower melting point will first melt and accumulate on the surface of alumina particles, and alumina with a higher melting point continues to melt. Then, the material particles are rapidly cooled, enabling the particles to retain the spherical state when the particles melt into a liquid, thereby obtaining zinc oxide - spherical alumina composite micropowders with a core - shell structure in which the surface is a dense zinc oxide shell layer and the interior is a dense spherical alumina core.

[0036] In the present invention, the cooling and solidification method preferably includes air cooling, and the cooling rate is preferably 400 - 600°C / s. In specific embodiments, it can be 400°C / s, 450°C / s, 500°C / s or 550°C / s.

[0037] After completing the cooling and solidification, the present invention preferably further includes: screening or classifying the particles obtained by cooling to obtain zinc oxide - spherical alumina composite micropowders.

[0038] The present invention also provides zinc oxide - spherical alumina composite micropowders prepared by the preparation method described in the above technical solution, which have a core - shell structure and include a spherical alumina core and a zinc oxide shell layer.

[0039] In the present invention, the thickness of the zinc oxide shell layer is preferably 0.6 - 1.5μm, and in specific embodiments, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm. In the present invention, the particle size of the spherical alumina core is preferably 5 - 150μm, and in specific embodiments, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm.

[0040] The present invention also provides the application of the zinc oxide - spherical alumina composite micropowders described in the above technical solution as fillers.

[0041] In the present invention, the zinc oxide - spherical alumina composite micropowders are preferably used as fillers for polymer materials. The polymer materials preferably include one or more of polypropylene (PP), polyamide (PA), polyurethane (PU), epoxy resin and silicone rubber; the silicone rubber preferably includes addition - type liquid silicone rubber.

[0042] In the present invention, the addition amount of the zinc oxide-spherical alumina composite micro-powder in the polymer material is preferably 30-97 wt%, and in specific embodiments, it can be 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt% or 97%.

[0043] For the zinc oxide-spherical alumina composite micro-powder prepared by the present invention, the zinc oxide shell layer is tightly combined with the spherical alumina core, the zinc oxide shell layer is not easily peeled off, the zinc oxide-spherical alumina high thermal conductivity composite micro-powder particles are in regular spherical shapes, with good thermal conductivity, and the zinc oxide shell layer with a high thermal conductivity coefficient has good compatibility with the polymer material. The zinc oxide-spherical alumina composite micro-powder can be added in a high content in the polymer material as a thermal conductivity filler. When added to polymer materials such as polypropylene (PP), polyamide (PA), polyurethane (PU), epoxy resin, silicone rubber (especially addition-cured liquid silicone rubber), etc., a thermal conductivity composite material with high thermal conductivity and excellent processing and molding properties can be obtained.

[0044] The present invention also provides a thermal conductivity gasket. By mass, the preparation raw materials include: 100 parts of vinyl silicone oil, 5-15 parts of hydrogen-containing silicone oil, 0.5-1.5 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, and 1000-3000 parts of thermal conductivity filler; the thermal conductivity filler includes the zinc oxide-spherical alumina composite micro-powder described in the above technical solution.

[0045] By mass, the preparation raw materials of the thermal conductivity gasket include 100 parts of vinyl silicone oil.

[0046] By the mass of the vinyl silicone oil, the preparation raw materials of the thermal conductivity gasket include 5-15 parts of hydrogen-containing silicone oil, and in specific embodiments, it can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or 15 parts.

[0047] By the mass of the vinyl silicone oil, the preparation raw materials of the thermal conductivity gasket include 0.5-1.5 parts of platinum catalyst, and in specific embodiments, it can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts or 1.5 parts.

[0048] By the mass of the vinyl silicone oil, the preparation raw materials of the thermal conductivity gasket include 0.05-0.15 parts of inhibitor, and in specific embodiments, it can be 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.10 parts, 0.11 parts, 0.12 parts, 0.13 parts, 0.14 parts or 0.15 parts.

[0049] Based on the parts by mass of the vinyl silicone oil, the raw materials for preparing the thermal conductive gasket include 1000 - 3000 parts of a thermal conductive filler, which can be 1000 parts, 1500 parts, 2000 parts, 2500 parts or 3000 parts in specific embodiments.

[0050] In the present invention, the preparation method of the thermal conductive gasket preferably includes the following steps: mixing the raw materials for preparation, pressing into a sheet and curing to obtain the thermal conductive gasket. In the present invention, the thickness of the thermal conductive gasket is preferably 0.5 - 5 mm, which can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm in specific embodiments. In the present invention, the curing temperature is preferably 80 - 150 °C, which can be 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C or 150 °C in specific embodiments; the curing time is preferably 10 - 30 min, which can be 10 min, 15 min, 20 min, 25 min or 30 min in specific embodiments.

[0051] The present invention also provides a thermal conductive polymer material, the raw materials for preparation including a polymer material and the zinc oxide - spherical alumina composite micropowder described in the above technical solution.

[0052] In the present invention, the polymer material preferably includes one or more of polypropylene (PP), polyamide (PA), polyurethane (PU), epoxy resin and silicone rubber; the silicone rubber preferably includes addition - type liquid silicone rubber. In the present invention, the content of the zinc oxide - spherical alumina composite micropowder in the polymer material is preferably 30 - 97 wt%, which can be 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt% or 97% in specific embodiments.

[0053] The present invention has no special limitation on the preparation method of the thermal conductive polymer material, and the preparation methods of the thermal conductive polymer materials well - known to those skilled in the art can be adopted.

[0054] To further illustrate the present invention, the following examples are used to describe in detail the zinc oxide - spherical alumina composite micropowder provided by the present invention, its preparation method and application, the thermal conductive gasket, and the thermal conductive polymer material, but they should not be construed as limiting the protection scope of the present invention.

[0055] Example 1

[0056] S1: Put zinc oxide with a particle size of 0.6 μm and angular alumina with a particle size of 6 μm into a high-speed mixer, add octyltriethoxysilane, start the high-speed mixer, and stir and mix for 30 min under the condition that the stirring frequency is 20 Hz to obtain a zinc oxide-alumina mixed material. Among them, the mass of zinc oxide accounts for 5% of the total mass of zinc oxide and angular alumina, and the mass of octyltriethoxysilane is 0.2% of the total mass of zinc oxide and angular alumina.

[0057] S2: Use the method of high-temperature melting to spheroidize the particles of the zinc oxide-alumina mixed material and then cool and solidify to obtain zinc oxide-spherical alumina composite micropowders with a core-shell structure. Among them, the temperature during high-temperature melting is 2000 °C, the thickness of the zinc oxide shell layer is 0.6 μm, and the particle size of the spherical alumina core is 5 μm.

[0058] S3: Classify the zinc oxide-spherical alumina composite micropowders with a core-shell structure obtained in S2 to obtain zinc oxide-spherical alumina composite micropowders with the required particle size distribution.

[0059] Example 2

[0060] S1: Put zinc oxide with a particle size of 1 μm and angular alumina with a particle size of 80 μm into a high-speed mixer, add dodecyltrimethoxysilane, start the high-speed mixer, and stir and mix for 20 min under the condition that the stirring frequency is 15 Hz to obtain a zinc oxide-alumina mixed material. Among them, the mass of zinc oxide accounts for 8% of the total mass of zinc oxide and angular alumina, and the mass of dodecyltrimethoxysilane is 0.3% of the total mass of zinc oxide and angular alumina.

[0061] S2: Use the method of high-temperature melting to spheroidize the particles of the zinc oxide-alumina mixed material and then cool and solidify to obtain zinc oxide-spherical alumina composite micropowders with a core-shell structure. Among them, the temperature during high-temperature melting is 2200 °C, the thickness of the zinc oxide shell layer is 1.3 μm, and the particle size of the spherical alumina core is 70 μm.

[0062] S3: Classify the zinc oxide-spherical alumina composite micropowders with a core-shell structure obtained in S2 to obtain zinc oxide-spherical alumina composite micropowders with the required particle size distribution.

[0063] Example 3

[0064] S1: Put zinc oxide with a particle size of 1.5 μm and angular alumina with a particle size of 170 μm into a high-speed mixer, add cetyltrimethoxysilane, start the high-speed mixer, and stir and mix for 10 min under the condition that the stirring frequency is 10 Hz to obtain a zinc oxide-alumina mixed material. Among them, the mass of zinc oxide accounts for 10% of the total mass of zinc oxide and angular alumina, and the mass of cetyltrimethoxysilane is 0.5% of the total mass of zinc oxide and angular alumina.

[0065] S2: The zinc oxide-aluminum oxide mixed material is spheroidized by high-temperature melting and then cooled and solidified to obtain zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure. Among them, the temperature during high-temperature melting is 2300 °C, the thickness of the zinc oxide shell layer is 1.5 μm, and the particle size of the spherical aluminum oxide core is 150 μm.

[0066] S3: The zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure obtained in S2 is subjected to screening treatment to obtain zinc oxide-spherical aluminum oxide composite micro-powder with a required particle size distribution.

[0067] The cross-sections of the angular aluminum oxide, the zinc oxide-aluminum oxide mixed materials prepared in Examples 1 to 3, the zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure, and the high thermal conductivity zinc oxide-spherical aluminum oxide composite micro-powder after polishing are observed for their micro-morphologies using a scanning electron microscope (SEM).

[0068] Figure 1 SEM image of the angular aluminum oxide used in Example 2. It can be seen from this figure that the morphology of the angular aluminum oxide is irregular, and there are many defects such as pores on the surface.

[0069] Figure 2 SEM image of the zinc oxide-aluminum oxide mixed material prepared in Example 2. It can be seen from this figure that small-sized zinc oxide particles are filled into the pore defects on the surface of the angular aluminum oxide, and the overall morphology of the particles is still irregular.

[0070] Figure 3 SEM image of the zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure prepared in Example 2. Figure 4 SEM image of the polished cross-section of the zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure prepared in Example 2. Figure 5 SEM image of the polished cross-section of the zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure prepared in Example 1. It can be seen from the SEM image that the zinc oxide-spherical aluminum oxide composite micro-powder with a core-shell structure prepared by the present invention has a regular morphology, a very high sphericity, and the zinc oxide shell layer and the spherical aluminum oxide core are tightly combined and not easy to fall off. In addition, the thickness of the zinc oxide shell layer can be accurately controlled by adjusting the ratio of zinc oxide to angular aluminum oxide.

[0071] Example 4

[0072] The zinc oxide-spherical alumina composite micropowders prepared in Examples 1 to 3 were used as heat-conducting fillers, and were mixed evenly with vinyl silicone oil (40 cst), hydrogen-containing silicone oil, platinum catalyst (platinum trichloride propylene), and inhibitor (ethynylcyclohexanol) according to the ratios in Table 1. The mixed material was processed into a sample sheet with a thickness of 2 mm using a tablet press. The formed sample sheet was placed in an electrothermal blast drying oven and cured at 130 °C for 20 min to obtain a heat-conducting gasket.

[0073] Comparative Example 1

[0074] The difference from Example 4 is only that: the heat-conducting fillers are spherical alumina with a particle size of 150 μm, spherical alumina with a particle size of 70 μm, and spherical alumina with a particle size of 5 μm. The total addition amount of the heat-conducting fillers is 2400 parts by mass. At this time, the mixing performance of the rubber compound is good, and it can be normally processed and formed into a heat-conducting gasket.

[0075] Comparative Example 2

[0076] The difference from Example 4 is only that: the heat-conducting fillers are 5 μm modified alumina A prepared in Example 1 of CN118027709A, 20 μm modified alumina B prepared in Example 2 of CN118027709A, 70 μm modified alumina C prepared in Example 3 of CN118027709A, and 2 μm quasi-spherical alumina used in Example 7 of CN118027709A. The total addition amount of the heat-conducting fillers is 1500 parts by mass. At this time, the mixing performance of the rubber compound is good, and it can be normally processed and formed into a heat-conducting gasket.

[0077] Comparative Example 3

[0078] The difference from Example 4 is only that: the heat-conducting fillers are spherical alumina with a particle size of 150 μm, spherical alumina with a particle size of 70 μm, and spherical alumina with a particle size of 5 μm. The total addition amount of the heat-conducting fillers is 3000 parts by mass. At this time, the mixing performance of the rubber compound is extremely poor. It cannot be processed and formed into a heat-conducting gasket.

[0079] Comparative Example 4

[0080] The difference from Example 4 is only that: the heat-conducting fillers are 5 μm modified alumina A prepared in Example 1 of CN118027709A, 20 μm modified alumina B prepared in Example 2 of CN118027709A, 70 μm modified alumina C prepared in Example 3 of CN118027709A, and 2 μm quasi-spherical alumina used in Example 7 of CN118027709A. The total addition amount of the heat-conducting fillers is 3000 parts by mass. At this time, the mixing performance of the rubber compound is extremely poor. It cannot be processed and formed into a heat-conducting gasket.

[0081] Referring to ASTM D5470 standard, a thermal conductivity tester was used to test the thermal conductivity of the thermal conductive gaskets prepared in Example 4 and Comparative Examples 1-2. The results are shown in Table 1.

[0082] Table 1 Raw material ratios (parts by mass) and thermal conductivities of the thermal conductive gaskets in Example 4 and Comparative Examples 1-4

[0083]

[0084]

[0085] As can be seen from Table 1, compared with the comparative examples, when using the zinc oxide-spherical alumina composite micro-powder with a core-shell structure prepared by the present invention to prepare the thermal conductive gasket, the total addition amount of the zinc oxide-spherical alumina highly thermal conductive composite micro-powder is significantly increased, reaching 3000 parts, and the thermal conductivity of the thermal conductive gasket is also significantly increased, reaching 8.47 W / m·K, which is 32.1% higher than the thermal conductivity of the gasket prepared with ordinary spherical alumina.

[0086] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing zinc oxide-spherical alumina composite micropowder, characterized in that, It includes the following steps: Mix zinc oxide, aluminum oxide and silane coupling agent, carry out melting spheroidization and then cool and solidify to form a dense zinc oxide shell on the surface of spherical aluminum oxide, obtaining zinc oxide-spherical aluminum oxide composite micropowder; The mass of the zinc oxide accounts for 5-10% of the total mass of the zinc oxide and the aluminum oxide; The particle size of the zinc oxide is 0.6-1.5 μm; The particle size of the aluminum oxide is 6-170 μm; The mixing time is 10-30 min; the mixing includes high-speed stirring mixing, and the stirring frequency of the high-speed stirring mixing is 10-20 Hz; The temperature of the melting spheroidization is 2000-2300 °C.

2. The preparation method according to claim 1, characterized in that, The silane coupling agent includes one or more of octyltriethoxysilane, n-decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane and octadecyltrimethoxysilane; The mass of the silane coupling agent accounts for 0.2-1% of the total mass of the zinc oxide and the aluminum oxide.

3. The zinc oxide-spherical aluminum oxide composite micropowder prepared by the preparation method according to any one of claims 1-2 has a core-shell structure, including a spherical aluminum oxide core and a zinc oxide shell layer.

4. The zinc oxide-spherical alumina composite fine powder according to claim 3, characterized in that, The thickness of the zinc oxide shell layer is 0.6-1.5 μm; The particle size of the spherical aluminum oxide core is 5-150 μm.

5. Application of the zinc oxide-spherical aluminum oxide composite micropowder according to claim 3 or 4 as a filler.

6. A thermal conductive gasket, the preparation raw materials of which include, by mass parts: 100 parts of vinyl silicone oil, 5-15 parts of hydrogen-containing silicone oil, 0.5-1.5 parts of platinum catalyst, 0.05-0.15 parts of inhibitor, 1000-3000 parts of heat-conducting filler; the heat-conducting filler includes the zinc oxide-spherical aluminum oxide composite micropowder according to claim 3 or 4.

7. A heat-conducting polymer material, the preparation raw materials of which include a polymer material and the zinc oxide-spherical aluminum oxide composite micropowder according to claim 3 or 4.

8. The thermally conductive polymer material according to claim 7, wherein, The polymer material includes one or more of polypropylene, polyamide, polyurethane, epoxy resin and silicone rubber.

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