A low-volatile oil-free film thermally conductive gel and preparation method thereof

Abstract

The present application discloses a low-volatile oil-free film thermally conductive gel and a preparation method thereof, and relates to the field of thermally conductive gel. The low-volatile oil-free film thermally conductive gel is composed of the following raw materials in weight percentage: 3-14% pre-treated resin, 85-96% thermally conductive filler and 0.05-1% coupling agent; each weight portion of pre-treated resin is composed of the following raw materials in weight percentage: 93-97% vinyl silicone oil, 2-6% hydrogen-containing silicone oil, 0.1-1% catalyst and 0.2-0.4% inhibitor; wherein, the pre-treatment method of the pre-treated resin is: according to the ratio, vinyl silicone oil, hydrogen-containing silicone oil, and inhibitor are put into a container and dispersed evenly, and then the catalyst is added, and the mixture is continuously stirred at 140-155°C and vacuum conditions for 6.5-8h, and at the same time, the top temperature of the container is maintained at 23-25°C. The thermally conductive gel in the present application has low volatile small molecule substances, which effectively reduces the appearance of oil film.

Description

Technical Field

[0001] The invention relates to the field of thermal conductive gel, in particular to a low-volatile oil-free film thermal conductive gel and a preparation method thereof. Background Art

[0002] Thermally conductive gels are mainly used in areas such as chip heat dissipation, mobile phone processor heat dissipation and automotive electronics heat conduction, while low-volatile thermally conductive gels are suitable for heat dissipation application environments that require high-performance filters, optical cameras and LED lights without condensation or fog.

[0003] Low-volatile thermal conductive gel mainly refers to silicone oil products with a small molecule content of ΣD3-D10 or ΣD3-D20 less than 100ppm. This type of volatile small molecule ring body cannot participate in the cross-linking and curing of the thermal conductive gel because it does not contain reactive functional groups. In the subsequent use process, this type of volatile small molecules will gradually be released, which will manifest as an oil film on the surface of the product. The produced oil film will adhere to the surface of the device or lens, resulting in a decrease in the light transmittance of the optical equipment, and in severe cases, it will also corrode the transparent substrate.

[0004] Although the small molecule content in the low-volatile thermal conductive gel has been controlled to less than 100 ppm, a small amount of oil film will still appear on the product surface in actual applications. For this reason, the applicant has conducted further research to improve the situation of oil film appearing on the surface of the thermal conductive gel product. Summary of the invention

[0005] In order to improve the situation where oil film appears on the surface of thermally conductive gel products, the present application provides a low-volatile oil-film-free thermally conductive gel and a preparation method thereof.

[0006] In a first aspect, the present application provides a low-volatile oil-free film thermally conductive gel, which adopts the following technical solution:

[0007] A low-volatile oil-free film thermally conductive gel, composed of the following raw materials in weight percentage: 3-14% pre-treated resin, 85-96% thermally conductive filler and 0.05-1% coupling agent;

[0008] Each weight portion of pre-treated resin is composed of the following raw materials in weight percentage: 93-97% vinyl silicone oil, 2-6% hydrogen-containing silicone oil, 0.1-1% catalyst and 0.2-0.4% inhibitor;

[0009] The pretreatment method of the pretreated resin is as follows: according to the ratio, vinyl silicone oil, hydrogenated silicone oil and inhibitor are put into a container and dispersed evenly, then a catalyst is added, and stirring is continued for 6.5-8h at 140-155°C and vacuum conditions, and at the same time, the top temperature of the container is maintained at 23-25°C.

[0010] By adopting the above technical scheme, the vinyl group in the vinyl silicone oil and the silicon hydrogen in the hydrogen-containing silicone oil can react under the action of a catalyst to achieve cross-linking. The viscosity of the vinyl silicone oil and the hydrogen-containing silicone oil in the present application is less than 1000cps, so that weak cross-linking can occur after mixing. The viscosity after cross-linking is 1000-4000cps. The prepared pretreated resin has a low degree of cross-linking and is in a fluid state, which is convenient for subsequent mixing with thermally conductive fillers and coupling agents. The thermally conductive fillers contact each other in the thermally conductive gel system to form an effective thermally conductive path, thereby giving the thermally conductive gel high thermal conductivity.

[0011] During the cross-linking process of vinyl silicone oil and hydrogen-containing silicone oil, there will be some uncross-linked small molecules or additional small molecules will be generated due to cross-linking. These small molecules will form an oil film after being released. The present application prepares the thermal conductive gel under heating conditions and controls the temperature of the top of the container at the same time. During the stirring process, the small molecules will evaporate due to vacuum and high temperature. When encountering the top of the container with a lower temperature, the small molecules will be adsorbed and condensed on the top of the container, thereby removing the uncross-linked small molecules in the thermal conductive gel, thereby reducing the occurrence of oil film in the later stage.

[0012] In a specific embodiment, the ΣD3-D10 of the vinyl silicone oil and the hydrogen-containing silicone oil are both less than 100 ppm.

[0013] By adopting the above technical solution, the content of small molecules in silicone oil can be reduced, thereby reducing the occurrence of oil film in the later stage.

[0014] In a specific embodiment, the thermal conductive filler includes large particle size powder, medium particle size powder and small particle size powder in a mass ratio of (10-15):(5-6):1.

[0015] By adopting the above technical solution, medium-sized powders and small-sized powders can be filled between large-sized powders, and small-sized powders can be filled between medium-sized powders, so that the powders can achieve effective contact, thereby promoting the formation of heat-conducting pathways and ensuring that the thermally conductive gel has excellent thermal conductivity.

[0016] In a specific embodiment, the large-particle powder has a particle size of 40-120 um, the medium-particle powder has a particle size of 5-20 um, and the small-particle powder has a particle size of 0.5-1.5 um.

[0017] By adopting the above technical solution, effective contact between powders can be promoted, ensuring the formation of a heat conduction path.

[0018] In a specific embodiment, the coupling agent is a macromolecular long-chain silane coupling agent.

[0019] In a specific embodiment, the macromolecular long-chain silane coupling agent is dodecyltrimethoxysilane, hexadecyltrimethoxysilane or trimethoxy-terminated polydimethylsiloxane.

[0020] By adopting the above technical scheme, the coupling agent can connect silicone oil and thermal conductive filler in the thermal conductive gel system, so that the thermal conductive gel has better wettability. The large molecular long chain coupling agent has higher stability and strong coating property, which can reduce the volatilization of small molecular substances, thereby further reducing the appearance of oil film.

[0021] In a second aspect, the present application provides a method for preparing a low-volatile oil-free film thermally conductive gel, using the following technical solution:

[0022] A method for preparing a low-volatile oil-free film thermally conductive gel comprises the following steps:

[0023] S1. Resin pretreatment: according to the ratio, vinyl silicone oil, hydrogen silicone oil and inhibitor are put into a container and dispersed evenly, then the catalyst is added, and the mixture is stirred continuously for 6.5-8h at 140-155°C and vacuum conditions, and at the same time, the top temperature of the container is maintained at 23-25°C, and the pretreated resin is obtained after the mixture is finished;

[0024] S2. Raw material mixing: Add the thermal conductive filler and coupling agent into the pre-treated resin and mix them evenly to obtain a low-volatile oil-free film thermal conductive gel.

[0025] By adopting the above technical solution, under heating and vacuum conditions, small molecules will evaporate from the mixture, and the relatively low temperature at the top of the container is conducive to the adsorption and condensation of small molecules, thereby achieving the removal of small molecules and reducing the appearance of oil film when the thermal conductive gel is used.

[0026] In a specific possible implementation scheme, in step S2, the coupling agent and the pretreated resin are mixed to form a primary mixture, and then the small particle size powder is first added to the primary mixture and stirred at 20-30r / min for 20-30min; then the large particle size powder is added and stirred at 20-30r / min for 20-30min; finally, the medium particle size powder is added and stirred at 20-30r / min for 15-20min.

[0027] By adopting the above technical solution, small-particle powder is difficult to disperse in the mixture. By adding small-particle powder in advance, the mixture can be pre-wetted with small-particle powder, and then large-particle powder is added. The large-particle powder is used to rub and collide with the undispersed small-particle powder, so as to achieve a better dispersion effect. The medium-particle powder has a better dispersion effect than the first two. Finally, the medium-particle powder is added to quickly achieve the expected dispersion effect.

[0028] In addition, the vinyl silicone oil and hydrogen silicone oil in the pre-treated resin are only weakly cross-linked. After adding the thermal conductive filler and stirring, the shear force generated can easily break the cross-linked long chains, causing mechanical degradation, which will lead to the generation of small molecules. By controlling the stirring speed to 20-30r / min, the interruption of the pre-cross-linked long chains due to excessively high rotation speed is reduced, and the additional generation of small molecules is reduced.

[0029] In a specific implementation scheme, in step S2, after the pretreated resin, thermal conductive filler and coupling agent are mixed, the mixture is heated to 140-155°C and stirred at 5-6 r / min for 3.5-4.5 hours under vacuum conditions. At the same time, the top temperature of the container is maintained at 23-25°C. After completion, a low-volatile oil-free film thermal conductive gel is obtained.

[0030] By adopting the above technical solution, during the mixing process of the pre-treated resin and the thermal conductive filler, due to shear and friction, the small molecules that have not been removed inside the mixture will be exposed. At this time, the small molecules are removed, which can further reduce the occurrence of oil film in the thermal conductive gel during the later use.

[0031] In summary, the present application includes at least one of the following beneficial technical effects:

[0032] 1. The present application utilizes heating and vacuuming to promote the volatilization of small molecules in the thermal conductive gel system under a certain shear force, and utilizes the top of the container with a lower temperature to make the small molecules adhere and condense, thereby achieving the effect of removing small molecules and effectively reducing the appearance of oil film during the use of the product.

[0033] 2. The present application reduces the possibility of long chains of pre-crosslinked silicone oil being broken by controlling the stirring speed, thereby reducing the additional production of small molecules and reducing the appearance of oil film in the later stage to a certain extent.

[0034] 3. The present application can effectively reduce the amount of small molecules in the thermal conductive gel by pretreating the resin, heating and stirring the mixture after mixing the raw materials, and low-temperature treatment on the top of the container, thereby reducing the situation in which the thermal conductive gel produces small molecules and forms an oil film during later use. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the structure of the container for mixing raw materials in this application.

[0036] Figure 2 It is a cross-sectional view of a container for mixing raw materials in the present application.

[0037] Description of reference numerals:

[0038] 1. Kettle body; 11. Inner barrel; 12. Outer barrel; 13. Oil inlet pipe; 14. Oil outlet pipe; 15. Heating wire; 2. Kettle cover; 21. Motor; 22. Stirring rod; 23. Stirring paddle; 24. Condensation plate; 25. Water supply pipe; 26. Water outlet pipe; 27. Observation window. DETAILED DESCRIPTION

[0039] The following is combined with Figure 1-2 The present application is further described in detail with reference to the accompanying drawings and embodiments.

[0040] Preparation Example of Pretreated Resin

[0041] Preparation Example 1

[0042] Accurately weigh 930g of vinyl silicone oil, 60g of hydrogenated silicone oil, and 4g of inhibitor, stir at a speed of 10r / min for 10min, then add 6g of catalyst to the container, stir at a speed of 10r / min, and evacuate to a vacuum degree of less than 90kpa, heat the container to 140°C, and control the temperature of the top of the container to 23°C, continue stirring for 6.5h, and obtain the pretreated resin after the end. Among them, the ΣD3-D10 of vinyl silicone oil and hydrogenated silicone oil are both less than 100ppm, the model of vinyl silicone oil is Andisil VS 500CV; the model of hydrogenated silicone oil is Andisil XL 18LV; the catalyst is a platinum catalyst, model pt-1000, and the inhibitor is methyl butynol.

[0043] The container used in this preparation example is Figure 1 and Figure 2 As shown, the container includes a kettle body 1 and a kettle cover 2. The kettle body 1 includes an inner barrel 11 and an outer barrel 12 arranged outside the inner barrel 11. A cavity for containing oil is formed between the inner barrel 11 and the outer barrel 12. The outer barrel 12 is connected with an oil inlet pipe 13 and an oil outlet pipe 14, and a heating wire 15 is arranged between the outer barrel 12 and the inner barrel 11. The inner barrel 11 can be heated by an oil bath so that the temperature of the inner barrel 11 reaches 140°C.

[0044] A motor 21 is installed on the kettle cover 2, and the output shaft of the motor 21 is connected to a stirring rod 22. The stirring rod 22 passes through the kettle cover 2 and can extend into the inner barrel 11. A stirring paddle 23 is installed on the stirring rod 22 to stir the raw materials. A condensation plate 24 is installed in the kettle cover 2, and a space for accommodating cold water is formed between the condensation plate 24 and the kettle cover 2. The kettle cover 2 is connected with a water supply pipe 25 and a water outlet pipe 26. The temperature of the condensation plate 24 can be controlled at 23°C by adding cold water, so that the volatilized small molecular substances can condense on the condensation plate 24 when encountering the condensation plate 24. An observation window 27 is installed on the kettle cover 2 for the staff to observe the situation inside the kettle body 1. The staff can observe the condensation plate 24 through the observation window 27. When there is a lot of condensate on the condensation plate 24, the kettle cover 2 can be opened, and the condensation plate 24 can be wiped with a cleaning cloth dipped in ethanol, so as to clean the condensate on the condensation plate 24 and reduce the possibility of contaminating the mixture when the condensate accumulates too much.

[0045] In this preparation example, the ΣD3-D10 of the vinyl silicone oil and the hydrogen silicone oil is less than 100 ppm, so during the treatment process, less small molecular weight is volatilized, and the small molecules will not condense on the condensation plate 24 in large quantities and drip into the mixture, and only a thin mist oil film will be formed. In this preparation example, the condensation plate 24 is cleaned once every hour to facilitate the small molecules to contact the condensation plate 24 and achieve condensation.

[0046] Preparation Example 2

[0047] Accurately weigh 966g of vinyl silicone oil, 20g of hydrogenated silicone oil, and 4g of inhibitor, stir at a speed of 10r / min for 10min, then add 10g of catalyst into the container, stir at a speed of 10r / min, and evacuate the vacuum to less than 90kPa, heat the container to 150℃, and control the temperature on the top of the container to 25℃, continue stirring for 8h, and then obtain the pretreated resin.

[0048] The container used in this preparation example is the same as that in Preparation Example 1.

[0049] Preparation Example 3

[0050] Accurately weigh 970g of vinyl silicone oil, 27g of hydrogenated silicone oil, and 2g of inhibitor, stir at a speed of 10r / min for 10min, then add 1g of catalyst to the container, stir at a speed of 10r / min, and evacuate the vacuum to less than 90kPa, heat the container to 155℃, and control the temperature at the top of the container to 25℃, continue stirring for 7h, and then obtain the pretreated resin.

[0051] The container used in this preparation example is the same as that in Preparation Example 1.

[0052] Preparation Example 4

[0053] Accurately weigh 950g of vinyl silicone oil, 46g of hydrogenated silicone oil, and 3g of inhibitor, stir at a speed of 10r / min for 10min, then add 1g of catalyst to the container, stir at a speed of 10r / min, and evacuate the vacuum to less than 90kPa, heat the container to 155℃, and control the temperature at the top of the container to 25℃, continue stirring for 7h, and then obtain the pretreated resin.

[0054] The container used in this preparation example is the same as that in Preparation Example 1.

[0055] Example

[0056] Example 1

[0057] A low-volatile oil-free film thermally conductive gel comprises 100 g of pretreated resin, 900 g of thermally conductive filler and 10 g of coupling agent. The pretreated resin is the pretreated resin prepared in the pretreated resin preparation example 1, the thermally conductive filler is a large and medium particle size powder, specifically 600 g of aluminum oxide with a particle size of 70 μm and 300 g of aluminum oxide with a particle size of 10 μm, and the coupling agent is a macromolecular long-chain coupling agent, specifically dodecyltrimethoxysilane.

[0058] The preparation method of low-volatile oil-free film thermally conductive gel is as follows:

[0059] The above raw materials were accurately weighed, mixed, and stirred continuously at a speed of 20 r / min for 1 hour to obtain a low-volatile oil-free film thermal conductive gel.

[0060] Example 2-Example 4

[0061] The difference between Examples 2 to 4 and Example 1 is only the different raw material dosages, as shown in Table 1.

[0062] Table 1 Raw material composition of thermally conductive gel in Examples 1 to 4

[0063]

[0064]

[0065] Example 5

[0066] The only difference between this embodiment and embodiment 1 is that the pretreatment resin is the pretreatment resin prepared in the pretreatment resin preparation example 2.

[0067] Example 6

[0068] The only difference between this embodiment and embodiment 1 is that the pretreatment resin is the pretreatment resin prepared in the pretreatment resin preparation example 3.

[0069] Example 7

[0070] The only difference between this embodiment and embodiment 1 is that the pretreatment resin is the pretreatment resin prepared in the pretreatment resin preparation example 4.

[0071] In order to verify the beneficial effects of the pre-treated resin, Comparative Example 1 was set up.

[0072] Comparative Example 1

[0073] The only difference between this comparative example and Example 2 is that the preparation method of the pretreated resin is: accurately weigh 930g of vinyl silicone oil, 60g of hydrogenated silicone oil, and 4g of inhibitor, stir at a speed of 10r / min for 10min, then add 6g of catalyst into the container, and continue stirring at a speed of 10r / min for 6.5h, after which the pretreated resin is obtained.

[0074] Examples 1 to 7 and Comparative Example 1 were tested using the following test methods:

[0075] E1. Fill the sample into a 30CC EFD tube and perform vacuum extraction to remove bubbles;

[0076] E2. Use a dispensing machine to spread the sample on the bottom of a 300ml beaker with a sample height of 2mm. Then place the beaker on a heating platform and cover the beaker with a glass sheet. Heat to 125°C. After heating for 72 hours, observe whether there is an oil film or condensate on the glass sheet.

[0077] Table 2 Test results of Example 1-Example 7 and Comparative Example 1

[0078]

[0079]

[0080] It can be seen from Table 2 that, compared with Comparative Example 1, the thermally conductive gels in Examples 1 to 7 have no oil film and only a small amount of condensate, indicating that the present application pre-treats the resin to remove most of the uncross-linked small molecules in the thermally conductive gel, thereby reducing the occurrence of an oil film when the thermally conductive gel is used.

[0081] Example 8-Example 10

[0082] The only difference between Examples 8 to 10 and Example 1 is that the composition and particle size of the thermal conductive filler are different, as shown in Table 3. The large particle size powder, the medium particle size powder and the small particle size powder are all aluminum oxide.

[0083] Table 3 Composition and particle size of thermal conductive fillers in Examples 8 to 10

[0084]

[0085] In order to verify the influence of the composition and particle size of the thermally conductive filler on the thermally conductive gel, the aforementioned test method was used to test Example 1, Example 8-Example 10, and the thermal conductivity of the thermally conductive gel was tested in accordance with ASTM D5470-2006.

[0086] Table 4 Test results of Example 1, Example 8-Example 11

[0087] project Observations Thermal conductivity (W / m·k) Example 1 No oil film ring, a small amount of condensate 5.37 Example 8 No oil film ring, a small amount of condensate 8.39 Example 9 No oil film ring, a small amount of condensate 8.43 Example 10 No oil film ring, a small amount of condensate 8.40

[0088] Referring to Table 4, compared with Example 1, the thermally conductive gel obtained by compounding powders of different particle sizes in Examples 8 to 10 has a better thermal conductivity effect. It is analyzed that when a single small-particle powder is used, the powder is wrapped by silicone oil and it is difficult to form an effective thermal conduction path. When a single medium-particle powder is used, an effective thermal conduction path can be formed between the powders, but there is a certain contact thermal resistance between them. The large-particle powder is easy to contact each other due to its large particle size, and can form an effective thermal conduction path. At the same time, there are more gaps between the large-particle powders, and the medium-particle powder and the small-particle powder can fill in the gaps, which helps to promote the formation of the thermal conduction path. Therefore, compared with Example 1 using only medium-particle powder, Examples 8 to 10 using powders of different particle sizes for compounding show better thermal conduction effects.

[0089] Embodiment 11

[0090] The only difference between this embodiment and embodiment 1 is that the coupling agent is hexadecyltrimethoxysilane.

[0091] Example 12

[0092] The only difference between this embodiment and embodiment 1 is that the coupling agent is trimethoxy-terminated polydimethylsiloxane.

[0093] Example 13

[0094] The only difference between this embodiment and embodiment 1 is that a small molecule coupling agent is selected as the coupling agent, specifically 3-aminopropyltriethoxysilane.

[0095] Embodiment 14

[0096] The difference between this embodiment and embodiment 1 is that a low-volatile oil-free film thermally conductive gel comprises 60 g of pre-treated resin, 939.9 g of thermally conductive filler and 0.1 g of coupling agent.

[0097] Embodiment 15

[0098] The difference between this embodiment and embodiment 1 is that a low-volatile oil-free film thermally conductive gel comprises 60 g of pre-treated resin, 920 g of thermally conductive filler and 20 g of coupling agent.

[0099] In order to verify the influence of the coupling agent, the above method was used to test Example 1 and Example 11-Example 15. After testing, compared with Example 1 and Example 11-Example 13, no oil film ring appeared, but Example 13 showed more condensate. It shows that the small molecule coupling agent has a weak coating property on small molecule substances, making it easy for small molecule substances to evaporate from the thermal conductive gel system, thereby forming more condensate. When the macromolecular coupling agent dodecyltrimethoxysilane, hexadecyltrimethoxysilane or trimethoxy-terminated polydimethylsiloxane is selected, the methoxy group will condense with the trace amount of moisture and hydroxyl groups on the surface of alumina, remove alcohol, and graft on the surface of alumina, wherein the long chain of the coupling agent faces outward and can be entangled and locked with the small molecule, thereby effectively coating the small molecule substance and reducing the volatilization of the small molecule substance.

[0100] An oil film ring appeared in Example 14, and condensate appeared in Example 15. Analysis showed that the coupling agent dosage was too low and failed to well cover the small molecules in the system, making the small molecules easily volatilize and forming an oil film ring. When the coupling agent dosage was too high, the coupling agent not combined with the powder was in a free state in the system. When the thermal conductive gel was heated, the coupling agent with a lower boiling point volatilized from the thermal conductive gel to form a condensate. Adding the coupling agent within the range disclosed in this application can well reduce the adverse effects of the coupling agent.

[0101] Example 16

[0102] The difference between this embodiment and embodiment 8 is that the preparation method of the low-volatile oil-free film thermally conductive gel is:

[0103] S1. Accurately weigh the pre-treated resin, thermal conductive filler and coupling agent;

[0104] S2. First, mix the pretreated resin and the coupling agent, stir at 20r / min for 10min to make a primary mixture, then add the small-particle powder into the primary mixture, stir at 20r / min for 20min; then add the large-particle powder, stir at 20r / min for 20min; finally, add the medium-particle powder, stir at 20r / min for 15min to obtain a low-volatile oil-free film thermal conductive gel.

[0105] Embodiment 17

[0106] The only difference between this embodiment and embodiment 16 is that the preparation method of the low-volatile oil-free film thermally conductive gel is:

[0107] S1. Accurately weigh the pre-treated resin, thermal conductive filler and coupling agent;

[0108] S2. First, mix the pretreated resin and the coupling agent, stir at 30r / min for 5min to make a primary mixture, then add the small-particle powder into the primary mixture, stir at 30r / min for 30min; then add the large-particle powder, stir at 30r / min for 30min; finally, add the medium-particle powder, stir at 30r / min for 20min to obtain a low-volatile oil-free film thermal conductive gel.

[0109] Embodiment 18

[0110] The only difference between this embodiment and embodiment 16 is that in step S2, the pretreated resin and the coupling agent are first mixed, stirred at 100 r / min for 10 minutes to form a primary mixture, and then the small-particle powder is added to the primary mixture and stirred at 100 r / min for 20 minutes; then the large-particle powder is added and stirred at 100 r / min for 20 minutes; finally, the medium-particle powder is added and stirred at 100 r / min for 15 minutes to obtain a low-volatile oil-free film thermal conductive gel.

[0111] The above scheme was used to test Example 16-Example 18, and the test results are shown in Table 5.

[0112] Table 5 Test results of Example 1, Example 16-Example 18

[0113]

[0114] Referring to Table 5, compared with Example 8, the thermally conductive gels in Examples 16 and 17 volatilize less condensate, indicating that by adjusting the order of adding thermally conductive fillers and using large-particle powders to rub and collide with small-particle powders, a better dispersion effect can be achieved, which helps to form more heat conduction pathways, thereby ensuring that the thermally conductive gel has an excellent thermal conductivity.

[0115] In combination with Example 16, Example 17 and Example 18, the thermally conductive gel in Example 18 volatilizes more small molecules, indicating that too high a rotation speed may interrupt the pre-cross-linked resin, thereby causing the generation of small molecules, and more small molecules will volatilize during subsequent use.

[0116] Embodiment 19

[0117] The difference between this embodiment and embodiment 16 is that the preparation method of the low-volatile oil-free film thermally conductive gel is:

[0118] S1. Accurately weigh the pre-treated resin, thermal conductive filler and coupling agent;

[0119] S2. First, mix the pretreated resin and the coupling agent, stir at 20r / min for 10min to make a primary mixture, then add the small-particle powder to the primary mixture, stir at 20r / min for 20min; then add the large-particle powder, stir at 20r / min for 20min; finally, add the medium-particle powder, stir at 20r / min for 15min;

[0120] S3. Heat the mixture in S2 to 140°C, and evacuate the mixture to a vacuum degree of less than 90 kPa. Stir continuously at 5 r / min for 3.5 hours. Meanwhile, keep the top temperature of the container at 23°C. After completion, a low-volatile oil-free film thermal conductive gel is obtained.

[0121] Embodiment 20

[0122] The difference between this embodiment and embodiment 16 is that the preparation method of the low-volatile oil-free film thermally conductive gel is:

[0123] S1. Accurately weigh the pre-treated resin, thermal conductive filler and coupling agent;

[0124] S2. First, mix the pretreated resin and the coupling agent, stir at 20r / min for 10min to make a primary mixture, then add the small-particle powder to the primary mixture, stir at 20r / min for 20min; then add the large-particle powder, stir at 20r / min for 20min; finally, add the medium-particle powder, stir at 20r / min for 15min;

[0125] S3. Heat the mixture in S2 to 150°C, and evacuate the mixture to a vacuum degree of less than 90 kPa. Stir continuously at 6 r / min for 4 hours. Meanwhile, keep the top temperature of the container at 24°C. After completion, a low-volatile oil-free film thermal conductive gel is obtained.

[0126] Embodiment 21

[0127] The difference between this embodiment and embodiment 16 is that the preparation method of the low-volatile oil-free film thermally conductive gel is:

[0128] S1. Accurately weigh the pre-treated resin, thermal conductive filler and coupling agent;

[0129] S2. First, mix the pretreated resin and the coupling agent, stir at 20r / min for 10min to make a primary mixture, then add the small-particle powder to the primary mixture, stir at 20r / min for 20min; then add the large-particle powder, stir at 20r / min for 20min; then add the medium-particle powder, stir at 20r / min for 15min;

[0130] S3. Heat the mixture in S2 to 155°C, and evacuate the mixture to a vacuum degree of less than 90 kPa. Stir continuously at 5 r / min for 4.5 hours. Meanwhile, keep the top temperature of the container at 25°C. After completion, a low-volatile oil-free film thermal conductive gel is obtained.

[0131] The thermally conductive gels in Example 19, Example 20 and Example 21 were tested using the aforementioned method. The test results are shown in Table 6.

[0132] Table 6 Test results of Example 16, Example 17-Example 19

[0133] project Observations Example 16 No oil film ring, a small amount of condensate Embodiment 19 No oil film and condensation Embodiment 20 No oil film and condensation Embodiment 21 No oil film and condensation

[0134] Referring to Table 6, it can be seen that after the pretreatment resin, thermal conductive filler and coupling agent are mixed, the small molecule substances are removed, which can further reduce the appearance of oil film and condensate. Analysis shows that during the mixing process, long-term shearing and friction will expose the small molecule substances that have not been completely removed in the mixture. At this time, removing the small molecule substances can better reduce the appearance of oil film in the thermal conductive gel.

[0135] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low-volatile oil-free film thermally conductive gel, characterized in that: It is composed of the following raw materials in weight percentage: 3-14% pre-treated resin, 85-96% thermal conductive filler and 0.05-1% coupling agent; Each weight portion of pre-treated resin is composed of the following raw materials in weight percentage: 93-97% vinyl silicone oil, 2-6% hydrogen-containing silicone oil, 0.1-1% catalyst and 0.2-0.4% inhibitor; The pretreatment method of the pretreated resin is as follows: according to the ratio, vinyl silicone oil, hydrogen silicone oil and inhibitor are put into a container and dispersed evenly, and then a catalyst is added, and the mixture is stirred continuously for 6.5-8 hours at 140-155° C. and vacuum conditions, and at the same time, the top temperature of the container is maintained at 23-25° C.; The thermal conductive filler comprises a large-particle powder, a medium-particle powder and a small-particle powder in a mass ratio of (10-15): (5-6): 1, wherein the large-particle powder has a particle size of 40-120 μm, the medium-particle powder has a particle size of 5-20 μm, and the small-particle powder has a particle size of 0.5-1.5 μm; The coupling agent is a macromolecular long-chain silane coupling agent; The macromolecular long-chain silane coupling agent is dodecyltrimethoxysilane, hexadecyltrimethoxysilane or trimethoxy-terminated polydimethylsiloxane; The preparation method of the low-volatile oil-free film thermally conductive gel comprises the following steps: S1. Resin pretreatment: according to the ratio, vinyl silicone oil, hydrogen silicone oil and inhibitor are put into a container and dispersed evenly, then the catalyst is added, and the mixture is stirred continuously for 6.5-8h at 140-155°C and vacuum conditions, and at the same time, the top temperature of the container is maintained at 23-25°C, and the pretreated resin is obtained after the mixture is finished; S2, raw material mixing: adding thermal conductive filler and coupling agent into pre-treated resin, and mixing well to obtain low-volatile oil-free film thermal conductive gel; In step S2, the coupling agent and the pretreated resin are mixed to form a primary mixture, and then the small-particle powder is first added to the primary mixture and stirred at 20-30 r / min for 20-30 min; then the large-particle powder is added and stirred at 20-30 r / min for 20-30 min; finally, the medium-particle powder is added and stirred at 20-30 r / min for 15-20 min.

2. The low-volatile oil-free film thermally conductive gel according to claim 1, characterized in that: The ΣD3-D10 of the vinyl silicone oil and the hydrogen-containing silicone oil are both less than 100 ppm.

3. A method for preparing a low-volatile oil-free film thermally conductive gel according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Resin pretreatment: according to the ratio, vinyl silicone oil, hydrogen silicone oil and inhibitor are put into a container and dispersed evenly, then the catalyst is added, and the mixture is stirred continuously for 6.5-8h at 140-155°C and vacuum conditions, and at the same time, the top temperature of the container is maintained at 23-25°C, and the pretreated resin is obtained after the mixture is finished; S2, raw material mixing: adding thermal conductive filler and coupling agent into pre-treated resin, and mixing well to obtain low-volatile oil-free film thermal conductive gel; In step S2, the coupling agent and the pre-treated resin are mixed to form a primary mixture, and then the small-particle powder is first added to the primary mixture and stirred at 20-30 r / min for 20-30 min; then the large-particle powder is added and stirred at 20-30 r / min for 20-30 min; Finally, add medium-sized powder and stir at 20-30r / min for 15-20min.

4. The method for preparing a low-volatile oil-free film thermally conductive gel according to claim 3, characterized in that: In step S2, after the pretreated resin, thermal conductive filler and coupling agent are mixed, the mixture is heated to 140-155°C and stirred at 5-6r / min for 3.5-4.5h under vacuum conditions. At the same time, the top temperature of the container is maintained at 23-25°C. After completion, a low-volatile oil-free film thermal conductive gel is obtained.

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