Flexible organic silicon heat-conducting composition and preparation method thereof

Abstract

The invention discloses a flexible organic silicon heat-conducting composition and a preparation method thereof, and relates to the technical field of heat-conducting materials. The flexible organic silicon heat-conducting composition comprises a core heat-conducting composition, an insulating layer and an isolating layer from inside to outside, the core heat-conducting composition is prepared from the following components in percentage by mass: 5 to 30 percent of organic silicon base polymer, 0.2 to 5 percent of organic silicon cross-linking agent, 1 to 8 percent of organic silicon chain extender, 60 to 95 percent of heat-conducting filler, 0.1 to 1.2 percent of powder dispersing agent, 0.02 to 0.2 percent of catalyst, 0.02 to 0.1 percent of retarder and 0.4 to 6 percent of toughening agent; the insulating layer is prepared from the following components in percentage by mass: 85 to 95 percent of organic silicon base polymer, 0.2 to 8 percent of organic silicon cross-linking agent, 1 to 10 percent of organic silicon chain extender, 0.1 to 0.5 percent of dewatering agent, 0.05 to 0.15 percent of catalyst, 0.02 to 0.1 percent of retarder and 1 to 15 percent of flexibilizer; the isolating layer comprises the following components in percentage by mass: 95-99% of metal oxide and 1-5% of a powder dispersing agent. According to the present invention, the 1-8 W / mk level heat conduction gap filling material has advantages of ultralow oil permeation rate, high electrical insulation strength, wide gap filling range and flexible application mode.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal conductive materials, and in particular to a flexible organic silicon thermal conductive composition and a preparation method thereof. Background Art

[0002] In today's era of explosive information development, the demand for electronic equipment is growing exponentially, and thermal conductive filling materials for thermal interfaces are essential key materials in the assembly of electronic equipment. Thermal conductive filling materials play an important role in quickly transferring heat from the heating end to the heat dissipation end in the thermal interface, ensuring that the temperature of electronic components is controlled at a reasonable level designed to avoid the situation where the electronic components cannot operate normally due to excessively high temperatures and the service life of electronic equipment is drastically reduced due to long-term excessively high temperatures.

[0003] In the field of thermal interface filling materials, the earlier materials include thermal grease and thermal gasket. Thermal grease is only suitable for filling very thin and small gaps and cannot be used as an insulating material. The oil leakage problem is more prominent. Oil leakage will contaminate other electronic components. The long-term temperature resistance is insufficient and the application scenarios are limited. Thermal gaskets are generally used in applications with larger gaps, which have a certain insulation capacity (3-10kv / mm). When used, they are cut into sheets, and the upper and lower surfaces of the gaskets are protected by release films. The release films are manually removed during assembly, and the gaskets are manually aligned and assembled to the specified position. Thermal gaskets supplement some thermal filling application scenarios that thermal grease cannot meet, but this application has certain compressibility requirements for thermal gaskets. Therefore, thermal gaskets will be designed as a flexible material, so that the overall cross-linking degree of the material is not high, and there will still be a certain risk of oil leakage during the application process. At the same time, thermal gaskets rely on manual operation and gradually cannot meet the requirements of modern intelligent and automated production methods. In addition to the above two thermal interface thermal filling materials, a new form of thermal filling material has emerged in recent years: thermal silicone gel. Thermally conductive silicone gel can be dispensed automatically to meet the requirements of efficient production operations, but its degree of cross-linking is lower and oil leakage also occurs. It cannot be used as an insulating material because its manual dispensing is difficult and has poor consistency, and it does not meet the requirements of small-batch manual operations.

[0004] Therefore, a new type of thermally conductive filling material is designed and prepared, which can meet the needs of both automated production operations and small-batch manual operations. It can effectively avoid the risk of oil leakage in application and meet the insulation requirements of high voltage resistance. It can meet the needs of both performance and process in current and future industrial intelligent manufacturing. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a flexible silicone thermal conductive composition and a preparation method thereof. The flexible silicone thermal conductive composition of the present invention can be adapted to both mechanical automation and manual operation, and has ultra-high insulation performance, temperature resistance reliability, and ultra-low oil permeability.

[0006] The present invention provides the following technical solutions:

[0007] A flexible silicone thermally conductive composition, characterized in that it comprises, from inside to outside, a core thermally conductive composition, an insulating layer and an isolation layer;

[0008] The core thermal conductive composition comprises the following components in mass fraction: 5-30% of organic silicon base polymer, 0.2-5% of organic silicon crosslinking agent, 1-8% of organic silicon chain extender, 60-95% of thermal conductive filler, 0.1-1.2% of powder dispersant, 0.02-0.2% of catalyst, 0.02-0.1% of retarder, and 0.5-6% of toughening agent;

[0009] The insulating layer comprises the following components in mass fraction: 85-95% of organic silicon base polymer, 0.2-8% of organic silicon crosslinking agent, 1-10% of organic silicon chain extender, 0.1-0.5% of dehydrating agent, 0.05-0.15% of catalyst, 0.02-0.1% of retarder, and 0.4-15% of toughening agent;

[0010] The isolation layer comprises the following components in mass fraction: 95-99% of metal oxide and 1-5% of powder dispersant.

[0011] Preferably, the core thermal conductive composition further comprises a colorant with a mass fraction of 0.05-0.3%.

[0012] Furthermore, the mass ratio of the core thermal conductive composition, the insulating layer and the isolation layer is 100:(0.1-2):(0.05-0.9).

[0013] Furthermore, the hydrogen content of the organosilicon crosslinking agent is 0.05-1.1%, and the molecular structure is shown in the following formula (1):

[0014]

[0015] Wherein R1, R2, and R4 are one or a combination of methyl and hydrogen, but not methyl at the same time; R3 is one of methyl and phenyl; n=150-3000, m=300-1500.

[0016] Furthermore, the molecular structure of the organosilicon chain extender is as shown in the following formula (2):

[0017]

[0018] Wherein n1=5-600; x=1-18.

[0019] Furthermore, the organic silicon base polymer is selected from at least one of single-end vinyl polydimethylsiloxane, double-end vinyl polydimethylsiloxane, single-end vinyl polymethylphenyl siloxane, double-end vinyl polymethylphenyl siloxane, branched vinyl polydimethylsiloxane, and vinyl methyl silicone resin (VMQ silicone resin).

[0020] Preferably, in the thermal conductive composition, when the silicone base polymer is selected from at least one of single-end vinyl polydimethylsiloxane, double-end vinyl polydimethylsiloxane, single-end vinyl polymethylphenyl siloxane and double-end vinyl polymethylphenyl siloxane, its vinyl content is 0.05-3% and its kinematic viscosity is 40-20000 cst; when the silicone base polymer is branched vinyl polydimethylsiloxane, its kinematic viscosity is 200-50000 cst and its vinyl content is 3-9%; when the silicone base polymer is VMQ silicone resin, the ratio (MQ ratio) of monofunctional siloxy units (M units for short) to tetrafunctional siloxy units (Q units for short) in the VMQ silicone resin is (0.5-0.85):1, and the vinyl content of MQ is 0.05-1.8%.

[0021] Preferably, in the insulating layer, the kinematic viscosity of the silicone base polymer is 1000-150000 cst, and when the silicone base polymer is selected from at least one of single-end vinyl polydimethylsiloxane, double-end vinyl polydimethylsiloxane, single-end vinyl polymethylphenyl siloxane and double-end vinyl polymethylphenyl siloxane, its vinyl content is 0.02-1.2%; when the silicone base polymer is a branched vinyl polydimethylsiloxane, its vinyl content is 3-9%; when the silicone base polymer is a VMQ silicone resin, the MQ ratio in the VMQ silicone resin is (0.5-0.85):1, and the vinyl content of MQ is 0.05-1.8%.

[0022] Furthermore, the thermally conductive filler comprises a large-medium particle size filler and a small-medium particle size filler in a mass ratio of (1-5):1, the medium particle size of the large-medium particle size filler is 30μm-200μm, and the medium particle size of the small-medium particle size is 0.1μm-15μm; the large-medium particle size filler is selected from at least one of ceramic alumina, aluminum hydroxide, diamond, aluminum nitride, boron nitride and magnesium oxide; the small-medium particle size filler comprises at least one of ceramic alumina, zinc oxide, silicon nitride and aluminum nitride.

[0023] Furthermore, the appearance of the thermal conductive filler is a combination of two or more of flake, prism, ellipsoid or quasi-spherical shapes.

[0024] Furthermore, the molecular formula of the powder dispersant is R—Si(OR)3, wherein R is a C8-C16 straight-chain alkyl group.

[0025] Furthermore, the catalyst is a platinum coordination catalyst, and the molecular structure is shown in the following formula (3):

[0026]

[0027] The concentration of the platinum coordination catalyst is 200ppm-9000ppm.

[0028] Furthermore, the molecular formula of the retarder is [CH3(CH2=CH)SiO] n2 , where n2=4-8, purity ≥96%.

[0029] Furthermore, the colorant is an organic colorant or an inorganic colorant, and the color is not limited.

[0030] Furthermore, the toughening agent is selected from at least one of white carbon black, a base material mainly composed of white carbon black, and methyl silicone resin (MQ silicone resin).

[0031] Furthermore, the molecular structural formula of the water removal agent is CH2=CHSi(R5)3, wherein R5 is a methoxy group or an ethoxy group.

[0032] Furthermore, the metal oxide is selected from at least one of aluminum oxide, zinc oxide and silicon dioxide, and the median particle size of the metal oxide is 0.05 μm-1 μm.

[0033] The present application also provides a method for preparing the above-mentioned flexible silicone thermally conductive composition, comprising the following steps:

[0034] S1: Preparation of core thermal conductive composition premix: Mix the organosilicon base polymer, organosilicon crosslinker, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler according to the ratio in the core thermal conductive composition and stir for 15-80 minutes, add the catalyst according to the ratio, and continue stirring for 5-60 minutes until uniform, to obtain the core thermal conductive composition premix; the stirring speed is 20-200 rpm;

[0035] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 100-160°C according to the ratio in the insulating layer, stir at a speed of 10-100rpm for 10-60min to obtain a dried silicone base polymer, cool the temperature to below 30°C, mix with the silicone crosslinker, silicone chain extender, water dispenser and retarder according to the ratio, stir at a speed of 10-100rpm for 7-60min, then add the catalyst according to the ratio, continue stirring for 3-30min to mix evenly, and obtain the insulating layer premix;

[0036] S3: isolation layer premix; heat the metal oxide and powder dispersant to 60-80°C according to the ratio in the isolation layer, stir at a speed of 300-1500 rpm for 3-40 minutes to make it uniform, and obtain an isolation layer premix;

[0037] S4: pre-curing the core thermal conductive composition premix at a temperature of 50-70° C., extruding it through an extrusion port diameter of 5-80 mm at an extrusion speed of 15-90 g / min to form microspheres, and then heating it to completely cure it to obtain core thermal conductive composition microspheres;

[0038] S5: spraying the insulating layer premix uniformly on the core thermal conductive composition microspheres, heating to solidify them, and obtaining insulating thermal conductive microspheres;

[0039] S6: The isolation layer premix is ​​blown into a space through airflow to keep its concentration at 50-1600g / m 3 The insulating thermally conductive microspheres are passed through the above space so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0040] Through the above scheme design, the present invention has the following effects:

[0041] The flexible silicone thermally conductive composition of the present invention has an ultra-low oil permeability rate and a higher electrical insulation strength among thermally conductive gap filling materials at the 1-8W / mk level compared to other thermally conductive materials, and has a wider range of gap filling, which can meet the needs of both automated production operations and small-batch manual operations, and has a more flexible application method. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1This is a schematic diagram of the flexible silicone thermally conductive composition provided by the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0046] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0047] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0048] Example 1

[0049] A flexible silicone thermally conductive composition, specifically Figure 1 As shown, from inside to outside, it includes a core thermal conductive composition, an insulating layer and a separation layer;

[0050] The core thermal conductive composition includes the following components by mass fraction: 15% of organic silicon base polymer, 2.2% of organic silicon crosslinking agent, 3.8% of organic silicon chain extender, 76.6% of thermal conductive filler, 0.55% of powder dispersant, 0.12% of catalyst, 0.05% of retarder, 0.18% of colorant, and 1.5% of toughening agent;

[0051] The insulating layer includes the following components by mass fraction: 90% of organic silicon base polymer, 3% of organic silicon cross-linking agent, 6% of organic silicon chain extender, 0.2% of dehydrating agent, 0.08% of catalyst, 0.03% of retarder, and 0.69% of toughening agent;

[0052] The isolation layer comprises the following components in mass fractions: 98% of metal oxide and 2% of powder dispersant.

[0053] Specifically, the silicone base polymer in the core thermal conductive composition is a dual-end vinyl polydimethylsiloxane with a vinyl content of 0.14% and a viscosity of 10000 cst; the silicone base polymer in the insulating layer is a dual-end vinyl polydimethylsiloxane with a vinyl content of 0.138% and a viscosity of 5000 cst.

[0054] Specifically, the molecular structure of the organosilicon crosslinking agent in the core thermal conductive composition is as shown in formula (1), wherein R1, R2, and R4 are hydrogen groups, and R3 is a methyl group; n=2000, m=900; the molecular structure of the organosilicon crosslinking agent in the insulating layer is as shown in formula (1), wherein R1 and R2 are hydrogen groups, and R3 and R4 are methyl groups; n=300, m=500.

[0055]

[0056] Specifically, the molecular structure of the organosilicon chain extender in the core thermal conductive composition is shown in formula (2), wherein n1=120, x=10; the molecular structure of the organosilicon chain extender in the insulating layer is shown in formula (2), wherein n1=210, x=10.

[0057]

[0058] The molecular formula of the powder dispersant is R—Si(OR)3, wherein R is a C12 straight-chain alkyl group.

[0059] The molecular formula of retarder is [CH3(CH2=CH)SiO]4.

[0060] The toughening agent in the core thermal conductive composition is white carbon black; the toughening agent in the insulating layer is MQ silicone resin.

[0061] The colorant is an organic colorant.

[0062] The thermal conductive filler is quasi-spherical aluminum oxide with a medium particle size of 75 μm and prismatic zinc oxide with a medium particle size of 0.9 μm, wherein the mass percentage of the aluminum oxide is 60% and the mass percentage of the zinc oxide is 16.6%.

[0063] The molecular structure of the catalyst is shown in formula (3). The catalyst concentration in the core thermal conductive composition is 1500 ppm; the catalyst concentration in the insulating layer is 5000 ppm.

[0064]

[0065] The molecular structure formula of the water removal agent is CH2=CHSi(CH3O)3.

[0066] The metal oxide is aluminum oxide with a median particle size of 0.8 μm.

[0067] A method for preparing the above-mentioned flexible silicone thermally conductive composition comprises the following steps:

[0068] S1: Preparation of core thermal conductive composition premix: put the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler into a planetary stirring reactor according to the proportion in the core thermal conductive composition, mix and stir for 30 minutes, add the catalyst according to the proportion, continue stirring for 20 minutes until uniform, and obtain the core thermal conductive composition premix; the stirring speed is 120rpm;

[0069] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 110°C according to the ratio in the insulating layer, stir at 30 rpm for 40 min to obtain a dried silicone base polymer, cool the temperature to below 30°C, stir with the silicone crosslinker, silicone chain extender, water dispenser and retarder at 40 rpm for 10 min, add the catalyst, continue stirring for 10 min to mix evenly, and obtain an insulating layer premix;

[0070] S3: isolation layer premix; the metal oxide and powder dispersant are heated to 68°C according to the ratio in the isolation layer, and stirred at a speed of 800 rpm for 12 minutes to make them uniformly stirred to obtain an isolation layer premix;

[0071] S4: The core thermal conductive composition premix is ​​heated and pre-cured at a temperature of 58° C., and extruded through an extrusion port diameter of 32 mm at an extrusion speed of 280 g / min to form pellets, and then conveyed to a heating tunnel furnace by rolling at a speed of 3.5 m / min and heated to 125° C. to completely cure the premix, thereby obtaining core thermal conductive composition microspheres;

[0072] S5: spraying the insulating layer premix uniformly on the core thermal conductive composition microspheres at a spraying speed of 25 g / min, and then conveying them to a second-stage heating tunnel furnace at a speed of 4 m / min by rolling, heating them to 130° C. to completely cure them, thereby obtaining insulating thermal conductive microspheres;

[0073] S6: The premix of the isolation layer is blown into a nearly closed tunnel space by airflow to keep its concentration at 800g / m 3 The insulating thermally conductive microspheres are passed through the above space at a conveying speed of 6 m / min, so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0074] Example 2

[0075] A flexible silicone thermally conductive composition, comprising, from inside to outside, a core thermally conductive composition, an insulating layer and an isolation layer;

[0076] The core thermal conductive composition includes the following components by mass fraction: 5% of organic silicon base polymer, 0.2% of organic silicon crosslinking agent, 1.0% of organic silicon chain extender, 93% of thermal conductive filler, 0.15% of powder dispersant, 0.06% of catalyst, 0.03% of retarder, 0.06% of colorant, and 0.50% of toughening agent;

[0077] The insulating layer includes the following components by mass fraction: 92% of organic silicon base polymer, 1.6% of organic silicon cross-linking agent, 5% of organic silicon chain extender, 0.3% of water scavenger, 0.09% of catalyst, 0.04% of retarder, and 0.97% of toughening agent;

[0078] The isolation layer includes the following components in mass fractions: 96% of metal oxide and 4% of powder dispersant.

[0079] Specifically, the silicone base polymer in the core thermal conductive composition is a single-end vinyl polydimethylsiloxane with a vinyl content of 1.21% and a viscosity of 110 cst, and a branched vinyl polydimethylsiloxane with a vinyl content of 9% and a viscosity of 300 cst; the silicone base polymer in the insulating layer is a single-end vinyl polymethylphenyl siloxane with a vinyl content of 0.138% and a viscosity of 10000 cst, and a double-end vinyl polymethylphenyl siloxane with a vinyl content of 0.115% and a viscosity of 15000 cst.

[0080] Specifically, the molecular structure of the organosilicon crosslinking agent in the core thermal conductive composition is as shown in formula (1), wherein R2 is a hydrogen group, R1, R3, and R4 are methyl groups; n=260, m=400; the molecular structure of the organosilicon crosslinking agent in the insulating layer is as shown in formula (1), wherein R2 is a hydrogen group, R1 and R4 are methyl groups, and R3 is a phenyl group; n=300, m=500.

[0081] Specifically, the molecular structure of the organosilicon chain extender in the core thermal conductive composition is shown in formula (2), wherein n1=60, x=12; the molecular structure of the organosilicon chain extender in the insulating layer is shown in formula (2), wherein n1=30, x=4.

[0082] The molecular formula of the powder dispersant is R—Si(OR) 3 , wherein R in the core thermal conductive composition is a C16 straight-chain alkyl group, and R in the isolation layer is a C8 straight-chain alkyl group.

[0083] The molecular formula of the retarder in the core thermal conductive composition is [CH3(CH2=CH)SiO]6, and the molecular formula of the retarder in the insulating layer is [CH3(CH2=CH)SiO]4.

[0084] The toughening agent is a base material mainly composed of white carbon black.

[0085] The colorant is an organic colorant.

[0086] The thermal conductive filler is quasi-spherical aluminum nitride with a medium particle size of 120 μm and prismatic ceramic aluminum oxide with a medium particle size of 2 μm, wherein the mass percentage of the aluminum nitride is 58% and the mass percentage of the ceramic aluminum oxide is 35%.

[0087] The molecular structure of the catalyst is shown in formula (3). The catalyst concentration in the core thermal conductive composition is 6000 ppm; the catalyst concentration in the insulating layer is 2000 ppm.

[0088] The molecular structural formula of the water removal agent is CH2=CHSi(C2H5O)3.

[0089] The metal oxide is zinc oxide with a median particle size of 0.2 μm.

[0090] A method for preparing the above-mentioned flexible silicone thermally conductive composition comprises the following steps:

[0091] S1: Preparation of core thermal conductive composition premix: put the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler into a planetary stirring reactor according to the proportion in the core thermal conductive composition, mix and stir for 50 minutes, add the catalyst according to the proportion, continue stirring for 50 minutes until uniform, and obtain the core thermal conductive composition premix; the stirring speed is 60rpm;

[0092] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 150°C according to the ratio in the insulating layer, stir at 70 rpm for 50 min to obtain a dried silicone base polymer, cool the temperature to below 30°C, stir with the silicone crosslinker, silicone chain extender, water dispenser and retarder at 80 rpm for 20 min, add the catalyst, continue stirring for 10 min to mix evenly, and obtain an insulating layer premix;

[0093] S3: isolation layer premix; the metal oxide and powder dispersant are heated to 75°C according to the ratio in the isolation layer, and stirred at a speed of 1200 rpm for 5 minutes to make them uniform, to obtain an isolation layer premix;

[0094] S4: The core thermal conductive composition premix is ​​heated and pre-cured at a temperature of 65° C., and extruded through an extrusion port diameter of 15 mm at an extrusion speed of 120 g / min to form microspheres, and then conveyed to a heating tunnel furnace by rolling at a speed of 0.6 m / min and heated to 140° C. to completely cure the microspheres, thereby obtaining core thermal conductive composition microspheres;

[0095] S5: The insulating layer premix is ​​uniformly sprayed on the core thermal conductive composition microspheres at a spraying speed of 10 g / min, and then conveyed to a second-stage heating tunnel furnace by rolling at a speed of 0.9 m / min and heated to 110° C. to completely cure it, thereby obtaining insulating thermal conductive microspheres;

[0096] S6: The isolation layer premix is ​​blown into a nearly closed tunnel space by airflow to keep its concentration at 60g / m 3 The insulating thermally conductive microspheres are passed through the above space at a conveying speed of 2 m / min, so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0097] Example 3

[0098] A flexible silicone thermally conductive composition, comprising, from inside to outside, a core thermally conductive composition, an insulating layer and an isolation layer;

[0099] The core thermal conductive composition includes the following components by mass fraction: 30% of organic silicon base polymer, 4.8% of organic silicon crosslinking agent, 3.6% of organic silicon chain extender, 60% of thermal conductive filler, 0.1% of powder dispersant, 0.2% of catalyst, 0.02% of retarder, and 1.28% of toughening agent;

[0100] The insulating layer includes the following components by mass fraction: 85% of organic silicon base polymer, 0.2% of organic silicon cross-linking agent, 1.3% of organic silicon chain extender, 0.3% of dehydrating agent, 0.15% of catalyst, 0.05% of retarder, and 13% of toughening agent;

[0101] The isolation layer comprises the following components in mass fractions: 99% of metal oxide and 1% of powder dispersant.

[0102] Specifically, the silicone base polymer in the core thermal conductive composition is a branched vinyl polydimethylsiloxane with a vinyl content of 3% and a viscosity of 50,000 cst and a VMQ silicone resin with a vinyl content of 1.8% and an MQ ratio of 0.5:1; the silicone base polymer in the insulating layer is a single-end vinyl polydimethylsiloxane with a vinyl content of 0.08% and a viscosity of 20,000 cst.

[0103] Specifically, the molecular structure of the organosilicon crosslinking agent in the core thermal conductive composition is as shown in formula (1), wherein R4 is a hydrogen group, R3 is a phenyl group, R1 and R4 are methyl groups; n=3000, m=300; the molecular structure of the organosilicon crosslinking agent in the insulating layer is as shown in formula (1), wherein R1 is a hydrogen group, R2, R3 and R4 are methyl groups; n=500, m=700.

[0104] Specifically, the molecular structure of the organosilicon chain extender in the core thermal conductive composition is shown in formula (2), wherein n1=5, x=18; the molecular structure of the organosilicon chain extender in the insulating layer is shown in formula (2), wherein n1=300, x=10.

[0105] The molecular formula of the powder dispersant is R—Si(OR) 3 , wherein R in the core thermal conductive composition is a C8 straight-chain alkyl group, and R in the isolation layer is a C10 straight-chain alkyl group.

[0106] The molecular formula of the retarder in the core thermal conductive composition is [CH3(CH2=CH)SiO]8, and the molecular formula of the retarder in the insulating layer is [CH3(CH2=CH)SiO]5.

[0107] The toughening agent is white carbon black.

[0108] The thermal conductive filler is prismatic aluminum nitride with a medium particle size of 130 μm, flaky ceramic alumina with a medium particle size of 30 μm, and quasi-spherical aluminum nitride with a medium particle size of 0.1 μm, wherein the mass percentage of prismatic aluminum nitride is 30%, the mass percentage of flaky ceramic alumina is 20%, and the mass percentage of quasi-spherical aluminum nitride is 10%.

[0109] The molecular structure of the catalyst is shown in formula (3). The catalyst concentration in the core thermal conductive composition is 200 ppm; the catalyst concentration in the insulating layer is 500 ppm.

[0110] The molecular structural formula of the water removal agent is CH2=CHSi(C2H5O)3.

[0111] The metal oxide includes 29% by mass of aluminum oxide, 20% by mass of zinc oxide and 50% by mass of silicon dioxide, wherein the median particle size of the aluminum oxide is 0.05 μm, the median particle size of the zinc oxide is 0.5 μm, and the median particle size of the silicon dioxide is 1 μm.

[0112] A method for preparing the above-mentioned flexible silicone thermally conductive composition comprises the following steps:

[0113] S1: Preparation of core thermal conductive composition premix: Put the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler into a planetary stirring reactor according to the proportion in the core thermal conductive composition, mix and stir for 60 minutes, add the catalyst according to the proportion, continue stirring for 60 minutes until uniform, and obtain the core thermal conductive composition premix; the stirring speed is 20rpm;

[0114] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 120°C according to the ratio in the insulating layer, stir at a speed of 10 rpm for 60 minutes to obtain a dried silicone base polymer, cool the temperature to below 30°C, stir with the silicone cross-linking agent, silicone chain extender, water dispenser and retarder at a speed of 60 rpm for 30 minutes, add the catalyst, continue stirring for 10 minutes to mix evenly, and obtain an insulating layer premix;

[0115] S3: isolation layer premix; the metal oxide and powder dispersant are heated to 60°C according to the ratio in the isolation layer, and stirred at a speed of 1500 rpm for 3 minutes to make them uniformly stirred to obtain an isolation layer premix;

[0116] S4: The core thermal conductive composition premix is ​​heated and pre-cured at a temperature of 50° C., and extruded through an extrusion port diameter of 5 mm at an extrusion speed of 15 g / min to form pellets, and then conveyed to a heating tunnel furnace by rolling at a speed of 0.1 m / min and heated to 120° C. to completely cure the premix, thereby obtaining core thermal conductive composition microspheres;

[0117] S5: spraying the insulating layer premix uniformly on the core thermal conductive composition microspheres at a spraying speed of 0.5 g / min, and then conveying them to a second-stage heating tunnel furnace by rolling at a speed of 5.5 m / min and heating them to 100° C. to completely cure them, thereby obtaining insulating thermal conductive microspheres;

[0118] S6: The isolation layer premix is ​​blown into a nearly closed tunnel space by airflow to keep its concentration at 1600g / m 3 The insulating thermally conductive microspheres are passed through the above space at a conveying speed of 20 m / min, so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0119] Example 4

[0120] A flexible silicone thermally conductive composition, comprising, from inside to outside, a core thermally conductive composition, an insulating layer and an isolation layer;

[0121] The core thermal conductive composition includes the following components by mass fraction: 18% of organic silicon base polymer, 5% of organic silicon crosslinking agent, 8% of organic silicon chain extender, 65% of thermal conductive filler, 0.5% of powder dispersant, 0.1% of catalyst, 0.05% of retarder, 0.05% of colorant, and 3.3% of toughening agent;

[0122] The insulating layer includes the following components by mass fraction: 95% of organic silicon base polymer, 1.43% of organic silicon cross-linking agent, 3% of organic silicon chain extender, 0.1% of water scavenger, 0.05% of catalyst, 0.02% of retarder, and 0.4% of toughening agent;

[0123] The isolation layer comprises the following components in mass fractions: 98% of metal oxide and 2% of powder dispersant.

[0124] Specifically, the silicone base polymer in the core thermal conductive composition is a single-end vinyl polymethylphenyl siloxane with a vinyl content of 0.05% and a viscosity of 20,000 cst, and a double-end vinyl polymethylphenyl siloxane with a vinyl content of 3% and a viscosity of 1,000 cst; the silicone base polymer in the insulating layer is a double-end vinyl polydimethylsiloxane with a vinyl content of 1.2% and a viscosity of 150,000 cst, and a double-end vinyl polydimethylsiloxane with a vinyl content of 0.02% and a viscosity of 20,000 cst.

[0125] Specifically, the molecular structure of the organosilicon crosslinking agent in the core thermal conductive composition is as shown in formula (1), wherein R1 and R4 are hydrogen groups, R2 and R3 are methyl groups; n=2500, m=600; the molecular structure of the organosilicon crosslinking agent in the insulating layer is as shown in formula (1), wherein R2 and R4 are hydrogen groups, R1 is methyl group, and R3 is phenyl group; n=1000, m=1500.

[0126] Specifically, the molecular structure of the organosilicon chain extender in the core thermal conductive composition is shown in formula (2), wherein n1=600, x=1; the molecular structure of the organosilicon chain extender in the insulating layer is shown in formula (2), wherein n1=260, x=9.

[0127] The molecular formula of the powder dispersant is R—Si(OR) 3 , wherein R in the core thermal conductive composition is a C11 straight-chain alkyl group, and R in the isolation layer is a C12 straight-chain alkyl group.

[0128] The molecular formula of the retarder in the core thermal conductive composition is [CH3(CH2=CH)SiO]4, and the molecular formula of the retarder in the insulating layer is [CH3(CH2=CH)SiO]4.

[0129] The toughening agent in the core heat-conducting composition is MQ silicone resin, and the toughening agent in the isolation layer is a base material mainly composed of white carbon black.

[0130] The colorant is an inorganic colorant.

[0131] The thermal conductive filler is prismatic boron nitride with a medium particle size of 160 μm, diamond with a medium particle size of 50 μm and ellipsoidal silicon nitride with a medium particle size of 0.5 μm, wherein the mass percentage of boron nitride is 40%, the mass percentage of diamond is 10%, and the mass percentage of silicon nitride is 15%.

[0132] The molecular structure of the catalyst is shown in formula (3). The catalyst concentration in the core thermal conductive composition is 9000 ppm; the catalyst concentration in the insulating layer is 3000 ppm.

[0133] The molecular structure formula of the water removal agent is CH2=CHSi(CH3O)3.

[0134] The metal oxides are aluminum oxide and zinc oxide with a medium particle size of 0.6 μm, wherein the mass percentage of aluminum oxide is 52% and the mass percentage of zinc oxide is 46%.

[0135] A method for preparing the above-mentioned flexible silicone thermally conductive composition comprises the following steps:

[0136] S1: Preparation of core thermal conductive composition premix: put the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler into a planetary stirring reactor according to the proportion in the core thermal conductive composition, mix and stir for 60 minutes, add the catalyst according to the proportion, continue stirring for 40 minutes until uniform, and obtain the core thermal conductive composition premix; the stirring speed is 100 rpm;

[0137] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 100°C according to the ratio in the insulating layer, stir at 60 rpm for 30 min to obtain a dried silicone base polymer, cool the temperature to below 30°C, stir with the silicone crosslinker, silicone chain extender, water dispenser and retarder at 100 rpm for 7 min, add the catalyst, continue stirring for 3 min to mix evenly, and obtain an insulating layer premix;

[0138] S3: isolation layer premix; the metal oxide and powder dispersant are heated to 70°C according to the ratio in the isolation layer, and stirred at a speed of 600 rpm for 20 minutes to make them uniform, to obtain an isolation layer premix;

[0139] S4: The core thermal conductive composition premix is ​​heated and pre-cured at a temperature of 67° C., and extruded through an extrusion port diameter of 30 mm at an extrusion speed of 30 g / min to form pellets, and then conveyed to a heating tunnel furnace by rolling at a speed of 6.5 m / min and heated to 150° C. to completely cure the premix, thereby obtaining core thermal conductive composition microspheres;

[0140] S5: The insulating layer premix is ​​uniformly sprayed on the core thermal conductive composition microspheres at a spraying speed of 30 g / min, and then transported to a second-stage heating tunnel furnace by rolling at a speed of 0.1 m / min and heated to 120° C. to completely cure the premix, thereby obtaining insulating thermal conductive microspheres;

[0141] S6: The isolation layer premix is ​​blown into a nearly closed tunnel space by airflow to keep its concentration at 1000g / m 3The insulating thermally conductive microspheres are passed through the above space at a conveying speed of 12 m / min, so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0142] Example 5

[0143] A flexible silicone thermally conductive composition, comprising, from inside to outside, a core thermally conductive composition, an insulating layer and an isolation layer;

[0144] The core thermal conductive composition includes the following components by mass fraction: 12% of organic silicon base polymer, 3.6% of organic silicon crosslinking agent, 1.18% of organic silicon chain extender, 80% of thermal conductive filler, 1.2% of powder dispersant, 0.02% of catalyst, 0.1% of retarder, 0.3% of colorant, and 1.6% of toughening agent;

[0145] The insulating layer includes the following components by mass fraction: 88% of organic silicon base polymer, 8% of organic silicon cross-linking agent, 1% of organic silicon chain extender, 0.5% of water scavenger, 0.1% of catalyst, 0.1% of retarder, and 2.3% of toughening agent;

[0146] The isolation layer comprises the following components in mass fractions: 97% of metal oxide and 3% of powder dispersant.

[0147] Specifically, the silicone base polymer in the core thermal conductive composition is a double-ended vinyl polydimethylsiloxane with a vinyl content of 0.87% and a viscosity of 1500 cst and a branched vinyl polydimethylsiloxane with a vinyl content of 6.78% and a viscosity of 200 cst; the silicone base polymer in the insulating layer is a branched vinyl polydimethylsiloxane with a vinyl content of 5.66% and a viscosity of 30000 cst.

[0148] Specifically, the molecular structure of the organosilicon crosslinking agent in the core thermal conductive composition is as shown in formula (1), wherein R3 is a phenyl group, R1, R3, and R4 are hydrogen groups; n=200, m=1200; the molecular structure of the organosilicon crosslinking agent in the insulating layer is as shown in formula (1), wherein R1 and R2 are hydrogen groups, R3 and R4 are methyl groups; n=150, m=600.

[0149] Specifically, the molecular structure of the organosilicon chain extender in the core thermal conductive composition is shown in formula (2), wherein n1=80, x=16; the molecular structure of the organosilicon chain extender in the insulating layer is shown in formula (2), wherein n1=10, x=6.

[0150] The molecular formula of the powder dispersant is R—Si(OR) 3 , wherein R in the core thermal conductive composition is a C9 straight-chain alkyl group, and R in the isolation layer is a C8 straight-chain alkyl group.

[0151] The molecular formula of the retarder in the core thermal conductive composition is [CH3(CH2=CH)SiO]8, and the molecular formula of the retarder in the insulating layer is [CH3(CH2=CH)SiO]6.

[0152] The toughening agent in the core thermal conductive composition is a base material mainly composed of white carbon black; the toughening agent in the insulating layer is white carbon black.

[0153] The colorant is an organic colorant.

[0154] The thermally conductive fillers are ellipsoidal aluminum hydroxide, boron nitride and magnesium oxide with a medium particle size of 200 μm, and quasi-spherical zinc oxide and silicon nitride with a medium particle size of 15 μm, wherein the mass percentage of aluminum hydroxide is 20%, the mass percentage of boron nitride is 10%, the mass percentage of magnesium oxide is 10%, the mass percentage of zinc oxide is 20%, and the mass percentage of silicon nitride is 20%.

[0155] The molecular structure of the catalyst is shown in formula (3). The catalyst concentration in the core thermal conductive composition is 3000 ppm; the catalyst concentration in the insulating layer is 800 ppm.

[0156] The molecular structure formula of the water removal agent is CH2=CHSi(CH3O)3.

[0157] The metal oxide is silicon dioxide with a median particle size of 0.5 μm.

[0158] A method for preparing the above-mentioned flexible silicone thermally conductive composition comprises the following steps:

[0159] S1: Preparation of core thermal conductive composition premix: Put the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler into a planetary stirring reactor according to the proportion of the core thermal conductive composition, mix and stir for 15 minutes, add the catalyst according to the proportion, continue stirring for 5 minutes until uniform, and obtain the core thermal conductive composition premix; the stirring speed is 200 rpm;

[0160] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 120°C according to the ratio in the insulating layer, stir at 80 rpm for 10 min to obtain a dried silicone base polymer, cool the temperature to below 30°C, stir with the silicone crosslinker, silicone chain extender, water dispenser and retarder at 50 rpm for 12 min, add the catalyst, continue stirring for 8 min to mix evenly, and obtain an insulating layer premix;

[0161] S3: isolation layer premix; the metal oxide and powder dispersant are heated to 80°C according to the ratio in the isolation layer, and stirred at a speed of 300 rpm for 40 minutes to make them uniformly stirred to obtain an isolation layer premix;

[0162] S4: pre-curing the core thermal conductive composition premix at 60° C., extruding it through an extrusion port diameter of 25 mm at an extrusion speed of 200 g / min to form a ball, and then conveying it to a heating tunnel furnace by rolling at a speed of 5 m / min and heating it to 100° C. to completely cure it, thereby obtaining core thermal conductive composition microspheres;

[0163] S5: spraying the insulating layer premix uniformly on the core thermal conductive composition microspheres at a spraying speed of 10 g / min, and then conveying them to a second-stage heating tunnel furnace by rolling at a speed of 2 m / min and heating them to 150° C. to completely cure them, thereby obtaining insulating thermal conductive microspheres;

[0164] S6: The isolation layer premix is ​​blown into a nearly closed tunnel space by airflow to keep its concentration at 50g / m 3 The insulating thermally conductive microspheres are passed through the above space at a conveying speed of 1 m / min, so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0165] Example 6

[0166] A flexible silicone thermally conductive composition, comprising, from inside to outside, a core thermally conductive composition, an insulating layer and an isolation layer;

[0167] The core thermal conductive composition includes the following components by mass fraction: 22% of organic silicon base polymer, 2.1% of organic silicon crosslinking agent, 2.8% of organic silicon chain extender, 66% of thermal conductive filler, 0.6% of powder dispersant, 0.15% of catalyst, 0.08% of retarder, 0.27% of colorant, and 6% of toughening agent;

[0168] The insulating layer includes the following components by mass fraction: 90% of organic silicon base polymer, 0.2% of organic silicon cross-linking agent, 4% of organic silicon chain extender, 0.4% of water scavenger, 0.14% of catalyst, 0.06% of retarder, and 5.2% of toughening agent;

[0169] The isolation layer comprises the following components in mass fractions: 95% of metal oxide and 5% of powder dispersant.

[0170] Specifically, the organic silicon base polymer in the core thermal conductive composition is 1% VMQ silicone resin with an MQ ratio of 0.85:1; the organic silicon base polymer in the insulating layer is VMQ silicone resin with a vinyl content of 0.85% and an MQ ratio of 0.8:1.

[0171] Specifically, the molecular structure of the organosilicon crosslinking agent in the core thermal conductive composition is as shown in formula (1), wherein R1, R2, and R4 are hydrogen groups, and R3 is a methyl group; n=1600, m=1000; the molecular structure of the organosilicon crosslinking agent in the insulating layer is as shown in formula (1), wherein R1 and R2 are hydrogen groups, and R3 and R4 are methyl groups; n=200, m=360.

[0172] Specifically, the molecular structure of the organosilicon chain extender in the core thermal conductive composition is shown in formula (2), wherein n1=400, x=15; the molecular structure of the organosilicon chain extender in the insulating layer is shown in formula (2), wherein n1=200, x=2.

[0173] The molecular formula of the powder dispersant is R—Si(OR) 3 , wherein R in the core thermal conductive composition is a C15 straight-chain alkyl group, and R in the isolation layer is a C16 straight-chain alkyl group.

[0174] The molecular formula of the retarder in the core thermal conductive composition is [CH3(CH2=CH)SiO]6, and the molecular formula of the retarder in the insulating layer is [CH3(CH2=CH)SiO]6.

[0175] The toughening agent in the core thermal conductive composition is white carbon black, and the toughening agent in the isolation layer is MQ silicone resin.

[0176] The colorant is an organic colorant.

[0177] The thermal conductive filler is quasi-spherical ceramic alumina with a medium particle size of 80 μm and prismatic ceramic alumina with a medium particle size of 0.6 μm, wherein the mass percentage of aluminum nitride is 48% and the mass percentage of ceramic alumina is 18%.

[0178] The molecular structure of the catalyst is shown in formula (3). The catalyst concentration in the core thermal conductive composition is 6000 ppm; the catalyst concentration in the insulating layer is 1000 ppm.

[0179] The molecular structure formula of the water removal agent is CH2=CHSi(CH3O)3.

[0180] The metal oxide is aluminum oxide with a median particle size of 0.8 μm.

[0181] A method for preparing the above-mentioned flexible silicone thermally conductive composition comprises the following steps:

[0182] S1: Preparation of core thermal conductive composition premix: put the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant and thermal conductive filler into a planetary stirring reactor according to the proportion in the core thermal conductive composition, mix and stir for 40 minutes, add the catalyst according to the proportion, continue stirring for 20 minutes until uniform, and obtain the core thermal conductive composition premix; the stirring speed is 180 rpm;

[0183] S2: Preparation of insulating layer premix: vacuum heat the silicone base polymer to 160°C according to the ratio in the insulating layer, stir at 100 rpm for 12 minutes to obtain a dried silicone base polymer, cool the temperature to below 30°C, stir with the silicone crosslinker, silicone chain extender, water dispenser and retarder at 10 rpm for 40 minutes, add the catalyst, continue stirring for 20 minutes to mix evenly, and obtain an insulating layer premix;

[0184] S3: isolation layer premix; the metal oxide and powder dispersant are heated to 60°C according to the ratio in the isolation layer, and stirred at a speed of 1000 rpm for 8 minutes to make them uniformly stirred to obtain an isolation layer premix;

[0185] S4: The core thermal conductive composition premix is ​​heated and pre-cured at a temperature of 70° C., and extruded through an extrusion port diameter of 80 mm at an extrusion speed of 900 g / min to form pellets, and then conveyed to a heating tunnel furnace by rolling at a speed of 10 m / min and heated to 130° C. to completely cure the premix, thereby obtaining core thermal conductive composition microspheres;

[0186] S5: The insulating layer premix is ​​uniformly sprayed on the core thermal conductive composition microspheres at a spraying speed of 50 g / min, and then conveyed to a second-stage heating tunnel furnace by rolling at a speed of 10 m / min and heated to 125° C. to completely cure it, thereby obtaining insulating thermal conductive microspheres;

[0187] S6: The isolation layer premix is ​​blown into a nearly closed tunnel space by airflow to keep its concentration at 500g / m 3 The insulating thermally conductive microspheres are passed through the above space at a conveying speed of 10 m / min, so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

[0188] The thermal conductivity, oil permeability, electrical insulation strength, filling gap and application mode of the flexible silicone thermally conductive compositions of Examples 1-6 were tested. The test results are shown in Table 1 below.

[0189] Table 1 Performance test results of Examples 1-6

[0190]

[0191] Comparative Examples 1-3 are set as follows based on Example 1:

[0192] Comparative Example 1

[0193] The difference from Example 1 is that the steps related to the spherical insulating layer and the raw material components related thereto are missing.

[0194] Comparative Example 2

[0195] The difference from Example 1 is that the steps related to the spherical isolation layer and the raw material components related thereto are missing.

[0196] Comparative Example 3

[0197] The difference from Example 1 is that in the molecular structure of the organosilicon crosslinking agent, R1, R2 and R4 are all methyl groups.

[0198] Comparative Example 4

[0199] The difference from Example 1 is that in the preparation of thermally conductive microspheres - the ball-forming step, the pre-curing heating temperature is 40° C.; the full curing heating temperature is 80° C. and the conveying speed is 16 m / min.

[0200] Comparative Example 5

[0201] The difference from Example 1 is that in the step of preparing the thermally conductive microspheres and insulating layer, the spraying speed is 0.2 g / min and the heating temperature is 60°C.

[0202] Comparative Example 6

[0203] The difference from Example 1 is that the concentration of the coating isolation layer in the thermal conductive microsphere preparation-isolation layer step is 20g / m 3 , the conveying speed is 30m / min.

[0204] Select commercially available products 1-4 as follows:

[0205] Commercially available products 1

[0206] A commercially available thermal conductive pad with a thermal conductivity of 1.0 W / mk was selected.

[0207] Commercially available product 2

[0208] A commercially available thermal conductive pad with a thermal conductivity of 8W / mk was selected.

[0209] Commercially available product 3

[0210] Select commercially available thermal grease with a thermal conductivity of 1.0 W / mk.

[0211] Commercially available products 4

[0212] A commercially available thermally conductive silicone gel with a thermal conductivity of 1.0 W / mk was selected.

[0213] The thermal conductivity, oil permeability, electrical insulation strength, filling gap and application mode of the flexible silicone thermal conductive compositions of Comparative Examples 1-6 and commercially available products 1-4 were tested and compared with the data of Example 1. The test results are shown in Table 2 below.

[0214] Table 2 Effect test results of Example 1, Comparative Examples 1-6 and Commercially Available Products 1-4

[0215]

[0216] As can be seen from Table 2, when there is no insulating layer, there is no dense silicone thin layer to wrap the core thermal conductive composition, and the core thermal conductive composition needs to maintain a flexible state, resulting in a low degree of cross-linking. The uncross-linked silicone oil inside is easy to migrate out, and the cage-like support structure is also lost, which has different degrees of influence on the oil permeability, electrical insulation strength and filling gap of the flexible silicone thermal conductive composition. The application method can only be manual application. When there is no isolation layer, the stickiness of the insulating layer surface makes it difficult to separate it from the material of the tooling fixture, so that the flexible silicone thermal conductive composition can only be used manually and cannot meet the needs of automated production operations.

[0217] By comparing the adhesive of the present application with commercially available products, it can be clearly seen that the flexible silicone thermally conductive gel of the present application has an ultra-low oil permeability rate and ultra-high electrical insulation strength compared with other materials in the 1-8W / mk level thermal conductive gap filling material, and the filling gap range is wider, which can meet the needs of automated production operations as well as the requirements of small-batch manual operations, and the application method is more flexible.

[0218] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A flexible silicone thermally conductive composition, characterized in that: From the inside to the outside, it includes a core thermally conductive composition, an insulating layer and a separation layer; The core thermal conductive composition comprises the following components in mass fraction: 5-30% of organic silicon base polymer, 0.2-5% of organic silicon crosslinking agent, 1-8% of organic silicon chain extender, 60-93% of thermal conductive filler, 0.1-1.2% of powder dispersant, 0.02-0.2% of catalyst, 0.02-0.1% of retarder, and 0.5-6% of toughening agent; The insulating layer comprises the following components in mass fraction: 85-95% of organic silicon base polymer, 0.2-8% of organic silicon crosslinking agent, 1-10% of organic silicon chain extender, 0.1-0.5% of dehydrating agent, 0.05-0.15% of catalyst, 0.02-0.1% of retarder, and 0.4-15% of toughening agent; The isolation layer comprises the following components in mass fraction: 95-99% of metal oxide and 1-5% of powder dispersant.

2. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The mass ratio of the core thermal conductive composition, the insulating layer and the isolation layer is 100:(0.1-2):(0.05-0.9).

3. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The hydrogen content of the organosilicon crosslinking agent is 0.05-1.1%, and the molecular structure is shown in formula (1): Wherein R1, R2, and R4 are one or a combination of methyl and hydrogen, but not methyl at the same time; R3 is one of methyl and phenyl; n=150-3000, m=300-1500.

4. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The molecular structure of the organosilicon chain extender is shown in formula (2): Wherein n1=5-600; x=1-18.

5. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The organic silicon base polymer is selected from at least one of single-end vinyl polydimethylsiloxane, double-end vinyl polydimethylsiloxane, single-end vinyl polymethylphenylsiloxane, double-end vinyl polymethylphenylsiloxane, branched vinyl polydimethylsiloxane and vinyl methyl silicone resin.

6. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The molecular formula of the powder dispersant is R—Si(OR)3, wherein R is a C8-C16 straight-chain alkyl group.

7. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The catalyst is a platinum coordination catalyst, and the molecular structure is shown in formula (3). The concentration of the platinum coordination catalyst is 200ppm-9000ppm.

8. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The molecular formula of the retarder is [CH3(CH2=CH)SiO] n2 , where n2=4-8.

9. The flexible silicone thermally conductive composition according to claim 1, characterized in that: The molecular structural formula of the dehydrating agent is CH2=CHSi(R5)3, wherein R5 is a methoxy group or an ethoxy group.

10. The method for preparing the flexible silicone thermally conductive composition according to any one of claims 1 to 9, comprising the following steps: S1: Preparation of core thermal conductive composition premix: mixing and stirring the organosilicon base polymer, organosilicon crosslinking agent, organosilicon chain extender, powder dispersant, retarder, toughening agent, colorant, and thermal conductive filler according to the proportion in the core thermal conductive composition, adding a catalyst according to the proportion, and continuing to stir until uniform to obtain the core thermal conductive composition premix; S2: Preparation of insulating layer premix: vacuum heating and stirring the organosilicon base polymer according to the ratio in the insulating layer to obtain a dried organosilicon base polymer, cooling the temperature to below 30° C., mixing and stirring with an organosilicon crosslinker, an organosilicon chain extender, a water dispenser and a retarder according to the ratio, adding a catalyst according to the ratio, and continuing to stir until the mixture is uniform to obtain an insulating layer premix; S3: isolation layer premix; heating and stirring the metal oxide and powder dispersant according to the ratio in the isolation layer to obtain an isolation layer premix; S4: pre-curing the spherical thermal conductive composition premix by heating at a temperature of 50-70° C., extruding it through an extrusion port diameter of 5-80 mm to form a ball, and then heating it to completely cure it to obtain a core thermal conductive composition microsphere; S5: spraying the insulating layer premix uniformly on the core thermal conductive composition microspheres, heating to solidify them, and obtaining insulating thermal conductive microspheres; S6: The isolation layer premix is ​​blown into a space through airflow to keep its concentration at 50-1600g / m 3 The insulating thermally conductive microspheres are passed through the above space so that the surface of the microspheres is evenly coated with the isolation layer premix to obtain a flexible silicone thermally conductive composition.

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