Heat-conducting and wave-absorbing silicone sheet and preparation method thereof

Abstract

The present invention discloses a thermally conductive wave-absorbing silicone sheet and a preparation method thereof, and relates to the technical field of preparation of multifunctional composite materials. The thermally conductive wave-absorbing silicone sheet comprises the following components: thermally conductive powder, wave-absorbing powder, silicon dioxide and reinforcing powder. The thermally conductive wave-absorbing silicone sheet proposed in the present invention can accurately adjust the overall electromagnetic parameters of the thermally conductive wave-absorbing silicone sheet by using SiO2 powder in combination with wave-absorbing powder, thereby further regulating the impedance matching characteristics of the thermally conductive wave-absorbing silicone sheet, and finally achieving the excellent electromagnetic wave absorption capacity of the product. In addition, the use of thermally conductive powder makes the thermally conductive wave-absorbing silicone sheet have the characteristics of high thermal conductivity. The thermally conductive wave-absorbing silicone sheet proposed in the present invention can be made into a single-layer tablet, which simplifies the preparation process, and the thermally conductive wave-absorbing silicone sheet has excellent thermal conductive wave-absorbing effect.

Description

Technical Field

[0001] The invention relates to the technical field of multifunctional composite material preparation, and in particular to a heat-conducting and wave-absorbing silicone sheet and a preparation method thereof. Background Art

[0002] In the era of the Internet of Everything, the intelligentization, integration, and thinness of electronic devices are the general trend. However, with the iterative development of electronic devices, the heat dissipation problems between devices and between components inside devices, as well as electromagnetic interference and pollution problems are becoming increasingly prominent. Therefore, multifunctional thermal conductive and wave absorbing materials with excellent performance have been born under the urgent needs of the market.

[0003] At present, the thermal conductive wave absorbing industry provides a variety of solutions for the research and development of related products. Patent CN114197242A discloses a sandwich structure thermal conductive wave absorbing material with a thermal conductive layer, a wave absorbing layer and a filter paper layer superimposed on each other. This structure uses different components of each layer to independently play their respective advantages in order to achieve certain thermal conductive and wave absorbing performance. The sandwich structure increases the processing difficulty of the product and increases the loss rate of the product manufacturing process, which is not conducive to the cost control of the production enterprise. For example, patent CN 114525036A discloses a wave absorbing thermal conductive gasket filled with h-BN and rGO prepared by liquid nitrogen directional freezing and liquid silicone rubber casting. The preparation process involves liquid nitrogen cooling, raw material casting and other processes. The processing process is complicated and the required production equipment is expensive.

[0004] In summary, both of the above solutions have disadvantages, such as poor thermal conductivity and wave absorption effects, and complicated preparation processes. Summary of the invention

[0005] The main purpose of the present invention is to provide a heat-conducting and wave-absorbing silicone sheet and a preparation method thereof, aiming to provide a heat-conducting and wave-absorbing silicone sheet with good heat-conducting and wave-absorbing effect and easy preparation.

[0006] To achieve the above object, the present invention provides a heat-conducting and wave-absorbing silicone sheet, comprising the following components:

[0007] Thermal conductive powder, microwave absorbing powder, silica and reinforcing powder.

[0008] Optionally, the thermally conductive powder includes at least one of SiC, Al2O3, AlN, diamond and BN.

[0009] Optionally, the absorbing powder includes at least one of FeSiAl, FeAl, FeNi, carbonyl iron, Fe3O4 and FeSiCr.

[0010] Optionally, the reinforcing powder includes at least one of ZnO, wollastonite and white carbon black.

[0011] Optionally, the particle size of the thermally conductive powder is 30 to 80 μm; and / or,

[0012] The particle size of the wave-absorbing powder is 2 to 15 μm; and / or,

[0013] The particle size of the silicon dioxide is 3 to 20 μm; and / or,

[0014] The particle size of the reinforcing powder is 2 to 6 μm.

[0015] Optionally, in the thermally conductive and wave-absorbing silicone sheet, the mass fractions of each component are:

[0016] 30-60 parts of thermal conductive powder, 40-100 parts of wave absorbing powder, 20-50 parts of silicon dioxide and 10-30 parts of reinforcing powder.

[0017] The present invention further provides a method for preparing the thermally conductive and wave-absorbing silicone sheet as described above, comprising the following steps:

[0018] S10, mixing the thermal conductive powder, the microwave absorbing powder, the silicon dioxide and the reinforcing powder uniformly to obtain a mixed powder;

[0019] S20, adding vinyl silicone oil, hydrogen-containing silicone oil and a coupling agent to the mixed powder, mixing evenly, heating and cooling in vacuum to obtain a first intermediate;

[0020] S30, adding a catalyst and an additive to the first intermediate, mixing evenly, and maintaining the pressure at -0.09 to -0.1 MPa for 20 to 60 min to obtain a second intermediate;

[0021] S40, rolling the second intermediate into tablets, and then heating and curing the tablets to obtain heat-conducting and wave-absorbing silicone sheets.

[0022] Optionally, in step S20,

[0023] The viscosity of the vinyl silicone oil is 20 to 450 mPa.s; and / or,

[0024] The hydrogen content of the hydrogen-containing silicone oil is 0.07% to 0.5%; and / or,

[0025] The coupling agent includes at least one of vinyl trimethoxy silane, (2-mercaptopropyl) trimethoxy silane, n-decyl trimethoxy silane and isopropyl dioleyl titanate; and / or,

[0026] In the thermally conductive and absorbing silicone sheet, the mass fractions of the components are 30-60 parts of thermally conductive powder, 40-100 parts of absorbing powder, 20-50 parts of silicon dioxide and 10-30 parts of reinforcing powder, and the added amounts of the vinyl silicone oil, hydrogen-containing silicone oil and coupling agent are 4-12 parts of vinyl silicone oil, 0.2-1 parts of hydrogen-containing silicone oil and 0.02-0.4 parts of coupling agent; and / or,

[0027] The heating temperature is 100-180° C.; and / or,

[0028] The heating time is 10 to 50 minutes.

[0029] Optionally, in step S30,

[0030] The catalyst comprises at least one of a chloroplatinic acid-isopropanol catalyst, a chloroplatinic acid-diethylpolysiloxane complex catalyst, a copper-cuprous oxide-cupric oxide ternary copper-based catalyst, and a cerium oxide-cupric oxide composite catalyst; and / or,

[0031] The additive comprises at least one of a leveling agent, a defoaming agent and a release agent; and / or,

[0032] In the thermally conductive and wave-absorbing silicone sheet, the mass proportions of the components are 30-60 parts of thermally conductive powder, 40-100 parts of wave-absorbing powder, 20-50 parts of silicon dioxide and 10-30 parts of reinforcing powder, and the added amounts of the catalyst and additives are 0.02-0.35 parts of catalyst and 0.001-2 parts of additives.

[0033] Optionally, in step S40,

[0034] The thickness of the tablet is 0.1 to 5 mm; and / or,

[0035] The heating temperature is 120-160° C.; and / or,

[0036] The curing time is 5 to 60 minutes.

[0037] The thermally conductive wave-absorbing silicone sheet proposed in the present invention can accurately adjust the overall electromagnetic parameters of the thermally conductive wave-absorbing silicone sheet by using SiO2 powder in combination with wave-absorbing powder, thereby further regulating the impedance matching characteristics of the thermally conductive wave-absorbing silicone sheet, and finally achieving the excellent electromagnetic wave absorption capacity of the product. In addition, the use of thermally conductive powder makes the thermally conductive wave-absorbing silicone sheet have high thermal conductivity characteristics. The thermally conductive wave-absorbing silicone sheet proposed in the present invention can be made into a single-layer tablet, simplifying the preparation process, and the thermally conductive wave-absorbing silicone sheet has excellent thermal conductive wave-absorbing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 The present invention is a schematic flow chart of an embodiment of a method for preparing a heat-conducting and wave-absorbing silicone sheet.

[0040] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0042] It should be noted that, in the embodiments, those without specifying specific conditions are carried out according to normal conditions or conditions recommended by the manufacturer. Those without specifying the manufacturer of reagents or instruments used are conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes, and "A and / or B" is taken as an example, including schemes A, B, or A and B that meet the same time. In addition, the technical schemes between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in the field to achieve. When the combination of the technical schemes is contradictory or cannot be achieved, it should be considered that the combination of such technical schemes does not exist, and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work, all belong to the scope of protection of the present invention.

[0043] At present, the thermal conductive wave absorbing industry provides a variety of solutions for the research and development of related products. Patent CN 114197242A discloses a sandwich structure thermal conductive wave absorbing material with a thermal conductive layer, a wave absorbing layer and a filter paper layer superimposed. This structure uses different components of each layer to independently play their respective advantages in order to achieve certain thermal conductive and wave absorbing performance. The sandwich structure increases the processing difficulty of the product and increases the loss rate of the product manufacturing process, which is not conducive to the cost control of the production enterprise. For example, patent CN 114525036 A discloses a wave absorbing thermal conductive gasket filled with h-BN and rGO prepared by liquid nitrogen directional freezing and liquid silicone rubber casting. The preparation process involves liquid nitrogen cooling, raw material casting and other processes. The processing process is complicated and the required production equipment is expensive. In summary, the above two solutions have disadvantages, the thermal conductive wave absorbing effect is not good, and the preparation process is complicated.

[0044] In view of this, the present invention proposes a heat-conducting and wave-absorbing silicone sheet and a preparation method thereof, aiming to provide a heat-conducting and wave-absorbing silicone sheet that has good heat-conducting and wave-absorbing effects and is easy to prepare.

[0045] The heat-conducting and wave-absorbing silicone sheet proposed by the present invention comprises the following components:

[0046] Thermal conductive powder, microwave absorbing powder, silica and reinforcing powder.

[0047] The thermally conductive wave-absorbing silicone sheet proposed in the present invention can accurately adjust the overall electromagnetic parameters of the thermally conductive wave-absorbing silicone sheet by using SiO2 powder in combination with wave-absorbing powder, thereby further regulating the impedance matching characteristics of the thermally conductive wave-absorbing silicone sheet, and finally achieving the excellent electromagnetic wave absorption capacity of the product. In addition, the use of thermally conductive powder makes the thermally conductive wave-absorbing silicone sheet have high thermal conductivity characteristics. The thermally conductive wave-absorbing silicone sheet proposed in the present invention can be made into a single-layer tablet, simplifying the preparation process, and the thermally conductive wave-absorbing silicone sheet has excellent thermal conductive wave-absorbing effect.

[0048] The present invention does not limit the types of thermal conductive powder, wave absorbing powder and reinforcing powder. Preferably, in an embodiment of the present invention, the thermal conductive powder includes at least one of SiC, Al2O3, AlN, diamond and BN. Using at least one of the above substances can effectively improve the thermal conductive wave absorbing effect.

[0049] Preferably, the absorbing powder includes at least one of FeSiAl, FeAl, FeNi, carbonyl iron, Fe3O4 and FeSiCr. Using at least one of the above substances can effectively improve the thermal conductive absorbing effect.

[0050] The reinforcing powder includes at least one of ZnO, wollastonite and white carbon black. Using at least one of the above substances can effectively improve the thermal conductive and wave absorbing effect. In addition, it can also improve the strength and stability of the thermal conductive and wave absorbing silicone sheet.

[0051] The present invention does not limit the particle size of each component. Preferably, in the embodiment of the present invention, the particle size of the thermally conductive powder is 30-80 μm; the particle size of the absorbing powder is 2-15 μm; the particle size of the silicon dioxide is 3-20 μm; and the particle size of the reinforcing powder is 2-6 μm. In this way, by fully mixing and matching powders of different types and particle sizes, a single-layer preparation process of a multifunctional thermally conductive and absorbing silicone sheet is realized. Large-particle-size thermally conductive powder is used in combination with small-particle-size absorbing powder and SiO2 powder to achieve high thermal conductivity (≥5W / (m·K)) of the absorbing thermally conductive silicone sheet while having excellent absorbing performance, which can meet the relevant performance requirements of the current market environment for thermally conductive and absorbing sheets.

[0052] The large-particle thermal conductive powder ensures the high thermal conductivity and strong insulation of the final product, while the small-particle SiO2 with different proportions combined with the absorbing powder can reduce the overall dielectric constant of the product while ensuring the magnetic loss in the 5.85-26.5GHz band, adjust the impedance matching characteristics, and further optimize the entry and attenuation of electromagnetic waves.

[0053] It can be understood that the above-mentioned particle size restrictions of each component may satisfy only one of them or may satisfy both of them. In a preferred embodiment of the present invention, the above-mentioned particle sizes are satisfied simultaneously, so that the thermal conductive and wave absorbing silicone sheet has a better thermal conductive and wave absorbing effect.

[0054] The present invention does not limit the mass fraction of each component in the thermal conductive wave absorbing silicone sheet. Preferably, the mass fraction of each component in the thermal conductive wave absorbing silicone sheet is: 30-60 parts of thermal conductive powder, 40-100 parts of wave absorbing powder, 20-50 parts of silicon dioxide and 10-30 parts of reinforcing powder. Under the above ratio, the thermal conductive wave absorbing effect can be effectively improved.

[0055] The present invention further proposes a method for preparing the thermally conductive and wave-absorbing silicone sheet as described above. Figure 1 The method for preparing the heat-conducting and wave-absorbing silicone sheet proposed by the present invention comprises the following steps:

[0056] S10, uniformly mixing the thermal conductive powder, the microwave absorbing powder, the silicon dioxide and the reinforcing powder to obtain a mixed powder.

[0057] In this step, the components are mixed. In an embodiment of the present invention, the above components are mixed evenly by a three-dimensional motion mixer to prevent the components from agglomerating, segregating, bonding and other defects during mixing into the organic silica gel matrix, which may reduce the performance stability of the final product.

[0058] S20, adding vinyl silicone oil, hydrogen-containing silicone oil and a coupling agent to the mixed powder, mixing evenly, heating in vacuum and cooling to obtain a first intermediate.

[0059] In this step, vinyl silicone oil, hydrogen silicone oil and coupling agent are added to the mixed powder to make the components tightly combined. In an embodiment of the present invention, this step is carried out in a planetary vacuum mixer / screw extruder kneader. The purpose of heating is to defoam. Preferably, the heating temperature is 100-180°C; the heating time is 10-50min. Under the above conditions, the defoaming effect is better.

[0060] Preferably, the viscosity of the vinyl silicone oil is 20 to 450 mPa.s. Under the above viscosity, sufficient powder filling amount can be ensured while preventing powder deposition during the preparation process, so that the thermal conductive and wave-absorbing silicone sheet has good stability and each component is not easy to foam; the hydrogen content of the hydrogen-containing silicone oil is 0.07% to 0.5%. With the above hydrogen content, the thermal conductive and wave-absorbing silicone sheet has good stability and each component is not easy to foam.

[0061] The present invention does not limit the type of coupling agent. Preferably, in an embodiment of the present invention, the coupling agent includes at least one of vinyltrimethoxysilane, (2-mercaptopropyl)trimethoxysilane, n-decyltrimethoxysilane and isopropyl dioleyl titanate. The use of the above coupling agent can better combine the components and improve the stability of the thermally conductive and wave-absorbing silicone sheet.

[0062] The present invention does not impose any restriction on the amount of vinyl silicone oil, hydrogen-containing silicone oil and coupling agent added. Preferably, the mass fractions of each component are 30-60 parts of thermal conductive powder, 40-100 parts of absorbing powder, 20-50 parts of silica and 10-30 parts of reinforcing powder. The amount of vinyl silicone oil, hydrogen-containing silicone oil and coupling agent added is 4-12 parts of vinyl silicone oil, 0.2-1 part of hydrogen-containing silicone oil and 0.02-0.4 part of coupling agent. Under the above ratio, the thermal conductive and absorbing effects can be effectively improved.

[0063] S30, adding a catalyst and an additive to the first intermediate, mixing evenly, and maintaining the pressure at -0.09 to -0.1 MPa for 20 to 60 minutes to obtain a second intermediate.

[0064] In this step, each component undergoes a cross-linking reaction, and the reaction can be carried out in a vacuum box to prevent the components from being oxidized by air and to further eliminate the foam in the first intermediate. Preferably, the catalyst includes at least one of a chloroplatinic acid-isopropanol catalyst, a chloroplatinic acid-diethylpolysiloxane complex catalyst, a copper-cuprous oxide-cupric oxide ternary copper-based catalyst, and a cerium oxide-cupric oxide composite catalyst. The use of the above catalysts has a good catalytic reaction effect.

[0065] Preferably, the additive includes at least one of a leveling agent, a defoaming agent and a release agent. The leveling agent can eliminate the surface tension gradient difference on the coating surface and prevent the generation of shrinkage holes and ripples. The defoaming agent can further reduce the surface tension, inhibit the generation of foam or eliminate the generated foam; the release agent is an interface coating used on the surfaces of two objects that are easy to adhere to each other, which can make the surface of the object easy to detach, smooth and clean.

[0066] The amount of catalyst and additive added is not limited in the present invention. Preferably, in the thermal conductive wave absorbing silicone sheet, the mass fractions of each component are 30-60 parts of thermal conductive powder, 40-100 parts of wave absorbing powder, 20-50 parts of silicon dioxide and 10-30 parts of reinforcing powder, and the amount of catalyst and additive added is 0.02-0.35 parts of catalyst and 0.001-2 parts of additive. Under the above ratio, the thermal conductive wave absorbing effect can be effectively improved.

[0067] S40, rolling the second intermediate into tablets, and then heating and curing the tablets to obtain heat-conducting and wave-absorbing silicone sheets.

[0068] In this step, the second intermediate is calendered and heated to be cured to form a thermally conductive and wave-absorbing silicone sheet. Preferably, the thickness of the sheet is 0.1 to 5 mm. Under the above thickness, the obtained thermally conductive and wave-absorbing silicone sheet has good performance in all aspects.

[0069] Preferably, the heating temperature is 120-160° C. and the curing time is 5-60 min. Under the above heating and curing conditions, the obtained thermally conductive and wave-absorbing silicone sheet has excellent thermally conductive and wave-absorbing effects.

[0070] The preparation method of the heat-conductive and wave-absorbing silicone sheet proposed in the present invention realizes a single-layer preparation process of the multifunctional heat-conductive and wave-absorbing silicone sheet by fully mixing and matching powders of different types and particle sizes. Compared with the multi-layer structure, it greatly simplifies the processing and manufacturing process of the product, reduces the product loss rate in the production process, and realizes the preparation of low-cost, high-performance multifunctional organic silicone sheets, which can be further promoted to mass production.

[0071] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0072] Example 1

[0073] (1) Weigh 30 parts of SiC with a particle size of 40 μm, 40 parts of FeNi with a particle size of 3 μm, 20 parts of SiO2 with a particle size of 3 μm, and 10 parts of wollastonite with a particle size of 2 μm, and mix the above powders evenly in a three-dimensional motion mixer to obtain a mixed powder;

[0074] (2) 4 parts of vinyl silicone oil with a viscosity of 100 mPa.s, 0.2 parts of hydrogen-containing silicone oil with a hydrogen content of 0.07 wt% and 0.02 parts of a coupling agent (vinyl trimethoxy silane) are mixed into the mixed powder prepared in step (1), and then the mixture is fully mixed in a planetary vacuum mixer / screw extruder kneader and placed in a vacuum heating furnace at 100° C. for 10 minutes for preliminary heating and defoaming treatment to obtain a first intermediate;

[0075] (3) The first intermediate obtained in (2) is allowed to stand at room temperature, and after cooling to room temperature, 0.02 parts of catalyst (chloroplatinic acid-isopropanol catalyst, chloroplatinic acid-diethyl polysiloxane complex catalyst) and 0.001 parts of additive (leveling agent) are added to the first intermediate. After uniform mixing, the obtained mixture is placed in a vacuum box, maintained at -0.09 MPa for 20 minutes, and subjected to secondary defoaming treatment to obtain a second intermediate;

[0076] (4) After the secondary defoaming is completed, the second intermediate obtained in step (3) is subjected to a two-roll calender to prepare a tablet with a thickness of 0.5 mm, and then heated and cured at 120° C. for 5 min to obtain a thermally conductive and wave-absorbing silicone sheet.

[0077] In this embodiment, the filling ratio of SiO2 to thermal conductive powder and microwave absorbing powder is 2:3:4.

[0078] Example 2

[0079] (1) Weighing 30 parts of AlN with a particle size of 65 μm, 50 parts of carbonyl Fe powder with a particle size of 8 μm, 40 parts of SiO2 with a particle size of 10 μm, and 16 parts of ZnO with a particle size of 4 μm, and mixing the above powders uniformly in a three-dimensional motion mixer to obtain a mixed powder;

[0080] (2) 7 parts of vinyl silicone oil with a viscosity of 250 mPa.s, 0.5 parts of hydrogen-containing silicone oil with a hydrogen content of 0.18 wt% and 0.23 parts of a coupling agent ((2-mercaptopropyl)trimethoxysilane, n-decyltrimethoxysilane, isopropyl dioleyloxy titanate) are mixed into the mixed powder prepared in step (1), and then the mixture is fully mixed in a planetary vacuum mixer / screw extruder kneader and placed in a vacuum heating furnace at 135° C. for 25 minutes for preliminary heating and defoaming treatment to obtain a first intermediate;

[0081] (3) The first intermediate obtained in step (2) was allowed to stand at room temperature, and after cooling to room temperature, 0.13 parts of catalyst (copper-cuprous oxide-copper oxide ternary copper-based catalyst, cerium oxide-copper oxide composite catalyst) and 0.08 parts of additives (leveling agent, defoaming agent, release agent) were added to the first intermediate. After uniform mixing, the resulting mixture was placed in a vacuum box, maintained at -0.095 MPa for 35 minutes, and subjected to secondary defoaming treatment to obtain a second intermediate;

[0082] (4) After the secondary defoaming is completed, the mixture obtained in step (3) is subjected to a two-roll calender to prepare a tablet with a thickness of 2.5 mm, and then heated and cured at 140° C. for 18 min to obtain a thermally conductive and wave-absorbing silicone sheet.

[0083] In this embodiment, the filling ratio of SiO2 to thermal conductive powder and microwave absorbing powder is 4:3:5.

[0084] Example 3

[0085] (1) Weigh 60 parts of diamond with a particle size of 75 μm, 40 parts of FeSiAl with a particle size of 14 μm, 45 parts of SiO2 with a particle size of 18 μm, and 25 parts of ZnO with a particle size of 6 μm, and mix the above powders evenly in a three-dimensional motion mixer to obtain a mixed powder;

[0086] (2) 12 parts of vinyl silicone oil with a viscosity of 300 mPa.s, 1 part of hydrogen-containing silicone oil with a hydrogen content of 0.5 wt% and 0.4 parts of a coupling agent (isopropyl dioleyl titanate) are mixed into the mixed powder prepared in step (1), and then the mixture is fully mixed in a planetary vacuum mixer / screw extruder kneader and placed in a vacuum heating furnace at 180° C. for 45 minutes for preliminary heating and defoaming treatment to obtain a first intermediate;

[0087] (3) The first intermediate obtained in step (2) was allowed to stand at room temperature, and after cooling to room temperature, 0.34 parts of a catalyst (cerium oxide-copper oxide composite catalyst) and 1.5 parts of an additive (release agent) were added to the first intermediate. After uniform mixing, the resulting mixture was placed in a vacuum box at -0.1 MPa for 60 minutes for secondary defoaming treatment to obtain a second intermediate;

[0088] (4) After the secondary defoaming is completed, the second intermediate obtained in step 3 is subjected to a two-roll calender to prepare a tablet with a thickness of 5 mm, and then heated and cured at 150° C. for 45 min to obtain a thermally conductive and wave-absorbing silicone sheet.

[0089] In this embodiment, the filling ratio of SiO2 to thermal conductive powder and microwave absorbing powder is 9:12:8.

[0090] Example 4

[0091] (1) Weigh 45 parts of a mixture of Al2O3 and BN with a particle size of 30 μm, 100 parts of a mixture of Fe3O4 and FeSiCr with a particle size of 2 μm, 50 parts of SiO2 with a particle size of 20 μm, and 30 parts of a mixture of ZnO, wollastonite, and white carbon black with a particle size of 5 μm, and mix the above powders evenly in a three-dimensional motion mixer to obtain a mixed powder;

[0092] (2) 8 parts of vinyl silicone oil with a viscosity of 20 mPa.s, 0.6 parts of hydrogen-containing silicone oil with a hydrogen content of 0.25 wt% and 4 parts of a coupling agent (vinyl trimethoxy silane) are mixed into the mixed powder prepared in step (1), and then fully mixed in a planetary vacuum mixer / screw extruder kneader and placed in a vacuum heating furnace at 140° C. for 50 minutes for preliminary heating and defoaming treatment to obtain a first intermediate;

[0093] (3) The first intermediate obtained in (2) was allowed to stand at room temperature, and after cooling to room temperature, 0.35 parts of a catalyst (cerium oxide-copper oxide composite catalyst) and 2 parts of an additive (defoaming agent) were added to the first intermediate. After uniform mixing, the resulting mixture was placed in a vacuum box at -0.09 MPa for 40 minutes for secondary defoaming treatment to obtain a second intermediate;

[0094] (4) After the secondary defoaming is completed, the second intermediate obtained in step (3) is subjected to a two-roll calender to prepare a tablet with a thickness of 0.1 mm, and then heated and cured at 160° C. for 5 min to obtain a thermally conductive and wave-absorbing silicone sheet.

[0095] In this embodiment, the filling ratio of SiO2 to thermal conductive powder and microwave absorbing powder is 5:4.5:10.

[0096] Example 5

[0097] (1) Weigh 50 parts of AlN with a particle size of 80 μm, 70 parts of FeAl powder with a particle size of 15 μm, 35 parts of SiO2 with a particle size of 12 μm, and 20 parts of ZnO with a particle size of 3 μm, and mix the above powders evenly in a three-dimensional motion mixer to obtain a mixed powder;

[0098] (2) 10 parts of vinyl silicone oil with a viscosity of 450 mPa.s, 0.8 parts of hydrogen-containing silicone oil with a hydrogen content of 0.3 wt% and 2 parts of coupling agent (n-decyltrimethoxysilane, isopropyl dioleyl titanate) are mixed into the mixed powder prepared in step (1), and then the mixture is fully mixed in a planetary vacuum mixer / screw extruder kneader and placed in a vacuum heating furnace at 160° C. for 30 minutes for preliminary heating and defoaming treatment to obtain a first intermediate;

[0099] (3) The first intermediate obtained in step (2) is allowed to stand at room temperature, and after cooling to room temperature, 0.2 parts of catalyst (copper-cuprous oxide-copper oxide ternary copper-based catalyst, cerium oxide-copper oxide composite catalyst) and 1 part of additive (leveling agent, defoaming agent) are added to the first intermediate. After uniform mixing, the resulting mixture is placed in a vacuum box, maintained at -0.09 MPa for 50 minutes, and subjected to secondary defoaming treatment to obtain a second intermediate;

[0100] (4) After the secondary defoaming is completed, the mixture obtained in step (3) is subjected to a two-roll calender to prepare a tablet with a thickness of 2.6 mm, and then heated and cured at 130° C. for 60 min to obtain a thermally conductive and wave-absorbing silicone sheet.

[0101] In this embodiment, the filling ratio of SiO2 to thermal conductive powder and microwave absorbing powder is 3.5:8:7.

[0102] Comparative Example 1

[0103] Except that SiO2 is not added in step (1), the rest of the preparation method and conditions are the same as those in Example 1.

[0104] Comparative Example 2

[0105] Except that the amount of SiO2 added in step (1) is 70 parts, the rest of the preparation method and conditions are the same as those in Example 1.

[0106] Comparative Example 3

[0107] Except that the particle size of SiO2 in step (1) is 36 μm and the particle size of the thermal conductive powder is 15 μm, the rest of the preparation method and conditions are the same as those in Example 1.

[0108] The thermally conductive and wave-absorbing silicone sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were taken to test their thermal conductivity, and the wave-absorbing performance was further tested using a waveguide method. The test results are shown in Table 1:

[0109] Table 1 Thermal conductivity and wave absorption performance test of thermal conductive and wave absorbing silicone sheet

[0110]

[0111] From the data comparison of the embodiments and the comparative examples in Table 1, it can be seen that the thermally conductive and wave-absorbing silicone sheets prepared in Examples 1 to 5 have strong thermal conductivity, a wide effective absorption bandwidth, and good electromagnetic wave absorption capacity. The thermal conductivity and wave-absorbing properties are significantly better than those of Comparative Example 1 in which no SiO2 is added under the same conditions, Comparative Example 2 in which the SiO2 addition amount is not within the range, and Comparative Example 3 in which the SiO2 particle size is not within the range, indicating that the addition of SiO2, its addition amount and particle size have a great influence on its thermal conductivity and wave-absorbing effects.

[0112] In summary, the thermally conductive wave-absorbing silicone sheet prepared in the embodiment of the present invention can accurately adjust the overall electromagnetic parameters of the thermally conductive wave-absorbing silicone sheet by using SiO2 powder in combination with wave-absorbing powder, thereby further adjusting the impedance matching characteristics of the thermally conductive wave-absorbing silicone sheet, and finally achieving the excellent electromagnetic wave absorption capacity of the product. In addition, the use of thermally conductive powder makes the thermally conductive wave-absorbing silicone sheet have the characteristics of high thermal conductivity.

[0113] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A thermally conductive and wave-absorbing silicone sheet, characterized in that: Includes the following components: Thermal conductive powder, microwave absorbing powder, silica and reinforcing powder; Among them, the mass fractions of each component in the thermally conductive and wave-absorbing silicone sheet are: 30~60 parts of thermal conductive powder, 40~100 parts of microwave absorbing powder, 20~50 parts of silicon dioxide and 10~30 parts of reinforcing powder; The particle size of the thermal conductive powder is 30-80 μm, the particle size of the wave absorbing powder is 2-15 μm, the particle size of the silicon dioxide is 3-20 μm, and the particle size of the reinforcing powder is 2-6 μm.

2. The heat-conducting and wave-absorbing silicone sheet according to claim 1, characterized in that: The thermally conductive powder includes at least one of SiC, Al2O3, AlN, diamond and BN.

3. The heat-conducting and wave-absorbing silicone sheet according to claim 1, characterized in that: The absorbing powder includes at least one of FeSiAl, FeAl, FeNi, carbonyl iron, Fe3O4 and FeSiCr.

4. The heat-conducting and wave-absorbing silicone sheet according to claim 1, characterized in that: The reinforcing powder includes at least one of ZnO, wollastonite and white carbon black.

5. A method for preparing a heat-conducting and wave-absorbing silicone sheet according to any one of claims 1 to 4, characterized in that: The following steps are involved: S10, mixing the thermal conductive powder, the microwave absorbing powder, the silicon dioxide and the reinforcing powder uniformly to obtain a mixed powder; S20, adding vinyl silicone oil, hydrogen-containing silicone oil and a coupling agent to the mixed powder, mixing evenly, heating and cooling in vacuum to obtain a first intermediate; S30, adding a catalyst and an additive to the first intermediate, mixing evenly, and maintaining the pressure at -0.09 to -0.1 MPa for 20 to 60 min to obtain a second intermediate, wherein the additive comprises at least one of a leveling agent, a defoaming agent, and a release agent; S40, rolling the second intermediate into tablets, and then heating and curing the tablets to obtain heat-conducting and wave-absorbing silicone sheets.

6. The method for preparing the heat-conducting and wave-absorbing silicone sheet according to claim 5, characterized in that: In step S20, The viscosity of the vinyl silicone oil is 20-450 mPa.s; and / or, The hydrogen content of the hydrogen-containing silicone oil is 0.07% to 0.5% by mass; and / or, The coupling agent includes at least one of vinyl trimethoxy silane, (2-mercaptopropyl) trimethoxy silane, n-decyl trimethoxy silane and isopropyl dioleyl titanate; and / or, In the thermally conductive and wave-absorbing silicone sheet, the vinyl silicone oil, hydrogen-containing silicone oil and coupling agent are added in an amount of, by mass, 4 to 12 parts of vinyl silicone oil, 0.2 to 1 part of hydrogen-containing silicone oil and 0.02 to 0.4 parts of coupling agent; and / or, The heating temperature is 100-180°C; and / or, The heating time is 10~50min.

7. The method for preparing the heat-conducting and wave-absorbing silicone sheet according to claim 5, characterized in that: In step S30, The catalyst comprises at least one of a chloroplatinic acid-isopropanol catalyst, a chloroplatinic acid-diethylpolysiloxane complex catalyst, a copper-cuprous oxide-cupric oxide ternary copper-based catalyst, and a cerium oxide-cupric oxide composite catalyst; and / or, In the thermally conductive and wave-absorbing silicone sheet, the catalyst and the additive are added in amounts of 0.02-0.35 parts by mass of the catalyst and 0.001-2 parts by mass of the additive.

8. The method for preparing the heat-conducting and wave-absorbing silicone sheet according to claim 5, characterized in that: In step S40, The thickness of the tablet is 0.1 to 5 mm; and / or, The heating temperature is 120-160°C; and / or, The curing time is 5~60min.

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