A kind of graphene thermal conductive silicone grease and its preparation method and application

Abstract

The present invention relates to the field of thermal interface materials and discloses a graphene thermal grease, a preparation method thereof, and an application thereof. The preparation method of the present invention comprises: (1) in the presence of a protective gas and microwaves, expanding and reducing graphene oxide to obtain microwave-reduced graphene oxide; and in the presence of a solvent, contacting and reacting a compounded spherical alumina with a silane coupling agent to obtain modified spherical alumina; and (2) mixing and reacting silicone oil with the microwave-reduced graphene oxide and the modified spherical alumina under stirring to obtain the graphene thermal grease. The graphene thermal grease prepared by the method provided by the present invention has a high thermal conductivity coefficient and good stability, and is suitable for preparing composite materials with relatively high thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the field of thermal interface thermal conductive materials, and in particular to a graphene thermal conductive silicone grease and a preparation method and application thereof. Background Art

[0002] As a thermal conductive and heat dissipation interface material, thermal grease has poor thermal conductivity of the base silicone oil. Therefore, thermal grease mainly relies on the good thermal conductivity of thermal conductive fillers to improve its own thermal conductivity.

[0003] At present, the most commonly used thermal conductive fillers on the market are copper, aluminum, aluminum oxide, aluminum nitride, and silicon carbide, with thermal conductivities of 398, 247, 40, 320, and 270 W / (m·K), respectively. When the above fillers are used to fill the interface thermal conductive material at room temperature, the filler filling volume is larger when the thermal conductivity of the system reaches 1-5 W / (m·K). The thermal conductive fillers are used to fill the thermal conductive silicone grease matrix with the same volume fraction or mass fraction. The higher the thermal conductivity, the better the thermal conductivity of the composite material.

[0004] Therefore, the use of fillers with higher thermal conductivity can prepare composite materials with higher thermal conductivity, and less filler can be used to achieve the same thermal conductivity effect.

[0005] Graphene is a two-dimensional carbon nanomaterial composed of carbon atoms arranged in a hexagonal honeycomb lattice using sp2 hybrid orbitals. Compared to other carbon materials, single-layer graphene has a thermal conductivity of up to 5300 W / (m·K). It possesses advantages such as ultra-high carrier mobility, excellent thermal conductivity, high specific surface area, and high flexibility. These advantages give graphene excellent and unique optical, electrical, thermal, and mechanical properties.

[0006] Therefore, by using graphene as a new type of thermal conductive filler to fill into the thermal grease matrix, high thermal conductivity graphene thermal grease can be prepared, and its thermal conductivity is far superior to that of thermal grease prepared with other traditional fillers.

[0007] CN107488349A discloses a thermally conductive silicone grease modified with a binary additive of graphene and aluminum oxide. The thermally conductive silicone grease comprises the following raw materials by weight: 2-50 parts silicone oil and 50-98 parts additive; the additive is prepared from the following raw materials by weight: 50-60 parts aluminum oxide and 1-1.2 parts graphene. The thermally conductive silicone grease obtained using this prior art has low thermal conductivity, is prone to stratification and oil separation, and has poor stability.

[0008] CN105400201A discloses a spherical alumina / graphene composite thermal grease. Specifically, the disclosed composite thermal grease comprises: 10-40 parts silicone oil, 60-80 parts modified spherical alumina / corundum / graphene composite thermally conductive filler, 3%-8% silane coupling agent, 0.1%-1% cross-linking agent, and 0.1-1 part antioxidant. This prior art thermally conductive filler filling ratio is low, and the resulting thermal grease has a low thermal conductivity. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems of poor thermal conductivity and poor stability of thermal conductive silicone grease in the prior art.

[0010] In order to achieve the above object, the first aspect of the present invention provides a method for preparing graphene thermal grease, the method comprising:

[0011] (1) in the presence of a protective gas and microwaves, the graphene oxide is expanded and reduced to obtain microwave-reduced graphene oxide; and

[0012] In the presence of a solvent, the compounded spherical alumina is contacted with a silane coupling agent to react to obtain modified spherical alumina;

[0013] (2) mixing the silicone oil with the microwave-reduced graphene oxide and the modified spherical alumina under stirring to obtain the graphene thermal grease;

[0014] In step (1), during the puffing reduction, the microwave conditions at least meet the following requirements: microwave output frequency is 1.5 GHz to 3.0 GHz, and temperature is 800° C. to 1100° C.;

[0015] In step (1), in the contact reaction, the compounded spherical alumina contains at least two spherical aluminas M with different particle size distributions D50, and the particle size distribution D50 of the spherical aluminas M is 2 μm-45 μm;

[0016] In step (2), the viscosity of the silicone oil at 25° C. is 100 cs-1000 cs; the weight ratio of the silicone oil, the microwave-reduced graphene oxide, and the modified spherical alumina is 1:9-30:70-92.

[0017] Preferably, in step (1), during the puffing reduction, the microwave conditions at least meet the following requirements: microwave output frequency is 2.5 GHz-3.0 GHz, and temperature is 850° C.-950° C.

[0018] More preferably, in step (1), during the puffing and reduction, the puffing and reduction time is 15-25s.

[0019] Preferably, in step (1), in the contact reaction, the compounded spherical alumina contains two spherical aluminas M with different particle size distributions D50, and the particle size distribution D50 of the spherical aluminas M is 5 μm-40 μm.

[0020] According to a preferred specific embodiment, in step (1), in the contact reaction, the compounded spherical alumina contains a first spherical alumina with a particle size distribution D50 of 20 μm-40 μm and a second spherical alumina with a particle size distribution D50 of 5 μm-15 μm, and the weight ratio of the first spherical alumina to the second spherical alumina is 3-5:1.

[0021] Preferably, in step (1), in the contact reaction, the weight ratio of the compounded spherical alumina to the silane coupling agent is 100:0.5-2.

[0022] Preferably, in step (1), in the contact reaction, the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane.

[0023] Preferably, in step (1), during the contact reaction, the solvent is ethanol and / or water.

[0024] Preferably, in step (1), in the contact reaction, the initial pH value of the contact reaction system is 3.5-5.5.

[0025] Preferably, in the contact reaction, the contact reaction is carried out under ultrasonic conditions, and the power of the ultrasound is 200-300W.

[0026] The second aspect of the present invention provides graphene thermal grease prepared by the method described in the first aspect.

[0027] The third aspect of the present invention provides the use of the graphene thermal grease described in the second aspect in the field of thermal interface thermal conductive materials.

[0028] The graphene thermal grease provided by the present invention has a high thermal conductivity coefficient. After being baked at a high temperature of 150°C for 1000 hours, the thermal grease will not crack, oil precipitate or powder, and can be widely used in the field of thermal interface thermal conductive materials. DETAILED DESCRIPTION

[0029] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0030] As mentioned above, the first aspect of the present invention provides a method for preparing graphene thermal grease, the method comprising:

[0031] (1) in the presence of a protective gas and microwaves, the graphene oxide is expanded and reduced to obtain microwave-reduced graphene oxide; and

[0032] In the presence of a solvent, the compounded spherical alumina is contacted with a silane coupling agent to react to obtain modified spherical alumina;

[0033] (2) mixing the silicone oil with the microwave-reduced graphene oxide and the modified spherical alumina under stirring to obtain the graphene thermal grease;

[0034] In step (1), during the puffing reduction, the microwave conditions at least meet the following requirements: microwave output frequency is 1.5 GHz to 3.0 GHz, and temperature is 800° C. to 1100° C.;

[0035] In step (1), in the contact reaction, the compounded spherical alumina contains at least two spherical aluminas M with different particle size distributions D50, and the particle size distribution D50 of the spherical aluminas M is 2 μm-45 μm;

[0036] In step (2), the viscosity of the silicone oil at 25° C. is 100 cs-1000 cs; the weight ratio of the silicone oil, the microwave-reduced graphene oxide, and the modified spherical alumina is 1:9-30:70-92.

[0037] Preferably, in step (1), during the puffing reduction, the microwave conditions at least meet the following requirements: microwave output frequency is 2.5 GHz-3.0 GHz, and temperature is 850° C.-950° C.

[0038] Preferably, in step (1), during the puffing and reduction, the puffing and reduction time is 15-25s.

[0039] According to a preferred embodiment, in step (1), the preparation process of the graphene oxide comprises: mixing graphite powder (average particle size not greater than 20 μm) and sodium nitrate under circulating cooling water at a temperature below 5° C., adding concentrated sulfuric acid under stirring and ultrasound (ultrasonic power of 200-300 W), reacting for 20-40 minutes, adding potassium permanganate, continuing the reaction for 40-70 minutes, raising the circulating water temperature to 35-45° C., continuing the reaction for 4.5-5.5 hours, adding water with a temperature not higher than 10° C., and raising the circulating water temperature to 90-100° C., continuing the reaction for 50-70 minutes, and then lowering the circulating water temperature to 15-25° C., so that the entire reaction temperature is lowered to room temperature; adding hydrogen peroxide to remove unreacted potassium permanganate, and then centrifuging the reaction mixture to remove the supernatant, and then repeatedly washing the mixture with hydrochloric acid and water until neutral, and drying and crushing the obtained product to obtain the graphene oxide.

[0040] More preferably, in step (1), during the preparation of graphene oxide, the weight ratio of the graphite powder, the sodium nitrate and the potassium permanganate is 1:0.4-0.7:0.3-0.6.

[0041] Preferably, the amount of concentrated sulfuric acid used is 45-55 mL per gram of the graphite powder.

[0042] More preferably, the amount of water having a temperature not higher than 10° C. is 90-110 mL per gram of the graphite powder.

[0043] Preferably, in step (1), the protective gas is nitrogen.

[0044] Preferably, in step (1), during the contact reaction, the compounded spherical alumina contains two spherical aluminas M having different particle size distributions D50, and the particle size distribution D50 of the spherical aluminas M is 5 μm-40 μm. The inventors have found that under this preferred embodiment, the thermal conductivity of the graphene thermal grease provided by the present invention is higher.

[0045] According to a preferred embodiment, in step (1), during the contact reaction, the compounded spherical alumina contains a first spherical alumina having a particle size distribution D50 of 20 μm to 40 μm and a second spherical alumina having a particle size distribution D50 of 5 μm to 15 μm, and the weight ratio of the first spherical alumina to the second spherical alumina is 3-5:1. Under this preferred embodiment, the inventors have found that the graphene thermal grease prepared by the method of the present invention has a higher thermal conductivity.

[0046] Preferably, in step (1), in the contact reaction, the weight ratio of the compounded spherical alumina to the silane coupling agent is 100:0.5-2. The inventors have found that under this preferred embodiment, the graphene thermal grease prepared by the method of the present invention has a higher thermal conductivity and better stability.

[0047] More preferably, in step (1), in the contact reaction, the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane.

[0048] Preferably, in step (1), in the contact reaction, the solvent is ethanol and / or water.

[0049] More preferably, in step (1), in the contact reaction, the solvent is ethanol and water.

[0050] According to a preferred embodiment, in step (1), the volume ratio of ethanol to water in the solvent is 18-20:1.

[0051] Preferably, in step (1), in the contact reaction, the initial pH value of the contact reaction system is 3.5-5.5.

[0052] More preferably, the initial pH value of the contact reaction system is adjusted by adding acid.

[0053] Preferably, the acid is acetic acid.

[0054] According to a preferred embodiment, in step (1), the contact reaction step includes:

[0055] S1: Prepare a solvent by mixing ethanol and water in a volume ratio of 18-20:1, adjust the pH value to 3.5-5.5 with acetic acid, and dissolve the silane coupling agent in the solvent to prepare a silane coupling agent diluent;

[0056] S2: The compounded spherical alumina is mixed with the silane coupling agent dilution solution, stirred, and ultrasonically dispersed, and then filtered to remove the solvent, and dried at 80-120° C. to obtain modified spherical alumina.

[0057] More preferably, in step (1), in the contact reaction, the ultrasonic conditions of the contact reaction include: power of 200-300W.

[0058] Further preferably, in step (1), during the contact reaction, the stirring conditions of the contact reaction include: a stirring speed of 300-400 rpm and a time of 20-40 min.

[0059] According to a preferred embodiment, in step (2), the mixing reaction step includes: placing the silicone oil in a stirrer, adding the modified spherical alumina to the silicone oil, and then adding the microwave-reduced graphene oxide, stirring evenly to obtain graphene thermal grease.

[0060] Preferably, in step (2), the mixing reaction conditions include: a stirring speed of 2000-4000 rpm and a temperature of 20-40°C.

[0061] More preferably, in step (2), the mixing reaction conditions include: a stirring speed of 2800-3200 rpm and a temperature of 20-25°C.

[0062] Preferably, the method of the present invention further comprises, in step (2), subjecting the graphene thermal grease obtained by the mixing reaction to a degassing treatment, wherein the degassing treatment is preferably a vacuum degassing treatment.

[0063] More preferably, the vacuum degassing conditions include: time is 1-5h.

[0064] Preferably, in the present invention, the agitator is a planetary agitator.

[0065] As mentioned above, the second aspect of the present invention provides graphene thermal grease prepared by the method described in the first aspect.

[0066] As mentioned above, the third aspect of the present invention provides the application of the graphene thermal grease described in the second aspect in the field of thermal interface thermal conductive materials.

[0067] The present invention will be described in detail below through examples.

[0068] In the following examples, unless otherwise specified, the experimental instruments, reagents, and raw materials involved are all commercially available, and the reagents are all analytically pure products.

[0069] In the present invention, unless otherwise specified, the room temperature refers to 25±2°C.

[0070] Raw materials and reagents

[0071] Graphite powder: average particle size 18 μm, Qingdao Yanhai Carbon Materials Co., Ltd.

[0072] The concentration of concentrated sulfuric acid used below is 98wt%;

[0073] Spherical alumina I: particle size distribution D50 is 40 μm, Ya'an Baitu High-tech Materials Co., Ltd.

[0074] Spherical alumina II: particle size distribution D50 is 30 μm, Ya'an Baitu High-tech Materials Co., Ltd.

[0075] Spherical alumina III: particle size distribution D50 is 20 μm, Ya'an Baitu High-tech Materials Co., Ltd.

[0076] Spherical alumina IV: particle size distribution D50 is 10 μm, Ya'an Baitu High-tech Materials Co., Ltd.

[0077] Spherical alumina V: particle size distribution D50 is 5 μm, Ya'an Baitu High-tech Materials Co., Ltd.

[0078] Silane coupling agent I: 3-(methacryloyloxy)propyltrimethoxysilane;

[0079] Silane coupling agent II: 3-(2,3-epoxypropoxy)propyltrimethoxysilane;

[0080] Silane coupling agent III: 3-aminopropyltriethoxysilane;

[0081] Silicone oil: dimethyl silicone oil I, viscosity 500 cs at 25°C, Dow Corning;

[0082] Silicone oil: dimethyl silicone oil II, viscosity 1000 cs at 25°C, Dow Corning;

[0083] Silicone oil: Dimethyl silicone oil III, viscosity 1500 cs at 25°C, Dow Corning.

[0084] instrument

[0085] High-temperature microwave oven: model HY-PH12010, Hunan Huaye Microwave Technology Co., Ltd.

[0086] Planetary mixer: Model TXJ-1, Taiyi (Shanghai) Industrial Co., Ltd.

[0087] In the following examples, the performance testing methods involved are as follows:

[0088] Thermal conductivity is tested according to ATSM D5470 standard.

[0089] In the following examples, anhydrous ethanol and water were mixed in a volume ratio of 19:1 to form a solvent, the volume of the solvent was 20 mL, and the pH value of the solvent system was adjusted to 4.0 by adding acetic acid.

[0090] In the following examples, unless otherwise specified, A represents the first spherical alumina, B represents the second spherical alumina, C represents microwave-reduced graphene oxide, D represents silicone oil, and E represents modified spherical alumina.

[0091] Preparation Example 1

[0092] Under circulating cooling water at a temperature of 4°C, 10g of graphite powder and 5.9g of sodium nitrate were mixed, and 500mL of concentrated sulfuric acid was added under stirring and ultrasound (ultrasonic power of 150W). After reacting for 30min, 4g of potassium permanganate was added, and the reaction was continued for 1h. The circulating water temperature was raised to 40°C, and after continuing the reaction for 5h, 1000mL of water at a temperature of 8°C was added, and the circulating water temperature was raised to 95°C. The reaction was continued for 1h, and then the circulating water temperature was lowered to 20°C, and the entire reaction temperature was lowered to room temperature; hydrogen peroxide was added to remove unreacted potassium permanganate, and then the reaction mixture was centrifuged to remove the supernatant, and then the mixture was repeatedly washed with 30wt% hydrochloric acid and water until neutral, and the obtained product was dried and crushed to obtain graphene oxide.

[0093] Example 1

[0094] This example is used to illustrate that the graphene thermal grease of the present invention is prepared according to the formula and process parameters in Table 1 and the method described below.

[0095] The method for preparing graphene thermal grease comprises the following steps:

[0096] (1) Setting the temperature of a high-temperature microwave oven (microwave output frequency of 2.5 GHz), introducing nitrogen, adding the graphene oxide obtained in the preparation example into the high-temperature microwave oven, and blowing out with nitrogen after expansion and reduction to obtain microwave-reduced graphene oxide;

[0097] (2) mixing two spherical aluminas of different particle sizes according to a weight ratio to obtain a compounded spherical alumina;

[0098] (3) Anhydrous ethanol and water were mixed in a volume ratio of 19:1 to form 20 mL of a solvent, acetic acid was added, the pH value of the system was adjusted to 4.0, a silane coupling agent was dissolved in the solvent, and the compounded spherical alumina was added to the solvent, and the reaction was carried out under stirring and ultrasound, and then the solvent was removed by filtration, and the mixture was dried at 100° C. to obtain modified spherical alumina;

[0099] The amount of the composite spherical alumina is 300g;

[0100] (4) Silicone oil was placed in a planetary stirrer, the modified spherical alumina was added to the silicone oil, and then the microwave-reduced graphene oxide was added, stirred and dispersed until uniform, and then kept under vacuum for 3 hours to obtain graphene thermal grease S1;

[0101] The amount of the silicone oil used is 30g.

[0102] Unless otherwise specified, the remaining examples were carried out using a process similar to that of Example 1, except that the formulations and process parameters used in each example were different. For details, see Table 1 (Note: the parameters not listed in Table 1 are the same as the corresponding parameters in Example 1).

[0103] Table 1

[0104]

[0105]

[0106] Comparative Example 1

[0107] This comparative example was carried out in a similar manner to Example 1, except that in step (1), the set temperature of the high-temperature microwave oven in this comparative example was 200°C.

[0108] The rest are the same as in Example 1.

[0109] Graphene thermal conductive silicone grease DS1 was prepared.

[0110] Comparative Example 2

[0111] This comparative example was carried out in a similar manner to Example 1, except that only spherical alumina of one particle size was used in this comparative example. Specifically, the method was as follows:

[0112] (1) preparing microwave-reduced graphene oxide by the same operation as step (1) in Example 1;

[0113] (2) The same operation as step (3) in Example 1 was performed, except that the same weight of spherical alumina I was used to replace the compounded spherical alumina in Example 1; the remaining operations were the same as those in Example 1;

[0114] (3) Graphene thermal conductive silicone grease SD2 was prepared by the same operation as step (4) in Example 1.

[0115] Comparative Example 3

[0116] This comparative example was carried out in a manner similar to that of Example 1, except that, in step (4), the weight ratio of microwave-reduced graphene oxide, dimethyl silicone oil I, and modified spherical alumina in this comparative example was 1:10:100, and the amount of dimethyl silicone oil I was the same as that in Example 1.

[0117] The rest are the same as in Example 1.

[0118] Graphene thermal conductive silicone grease DS3 was prepared.

[0119] Comparative Example 4

[0120] This comparative example was carried out in a similar manner to that of Example 1, except that, in step (4), the same weight of dimethyl silicone oil III was used in this comparative example to replace the dimethyl silicone oil I in Example 1.

[0121] The rest are the same as in Example 1.

[0122] Graphene thermal conductive silicone grease DS4 was prepared.

[0123] Test Case

[0124] The performance of the graphene thermal grease obtained in each embodiment and comparative example was measured using the aforementioned test method. The specific results are shown in Table 2.

[0125] Table 2

[0126]

[0127] Table 2 (Continued)

[0128]

[0129] It can be seen from the results in Table 2 that the graphene thermal grease prepared by the method of the present invention has a high thermal conductivity. After baking at 150° C. for 1000 h, the thermal grease does not crack, oil precipitate, or powder, and has good stability.

[0130] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing graphene thermal grease, characterized in that: The method includes: (1) in the presence of a protective gas and microwaves, the graphene oxide is expanded and reduced to obtain microwave-reduced graphene oxide; and In the presence of a solvent, the compounded spherical alumina is contacted with a silane coupling agent to react to obtain modified spherical alumina; (2) mixing the silicone oil with the microwave-reduced graphene oxide and the modified spherical alumina under stirring to obtain the graphene thermal grease; In step (1), during the puffing reduction, the microwave conditions at least meet the following requirements: microwave output frequency is 1.5 GHz to 3.0 GHz, and temperature is 800° C. to 1100° C.; In step (1), in the contact reaction, the compounded spherical alumina contains a first spherical alumina having a particle size distribution D50 of 20 μm to 40 μm and a second spherical alumina having a particle size distribution D50 of 5 μm to 15 μm, and the weight ratio of the first spherical alumina to the second spherical alumina is 3-5:1; In step (2), the viscosity of the silicone oil at 25° C. is 100 cs-1000 cs; the weight ratio of the microwave-reduced graphene oxide, the silicone oil, and the modified spherical alumina is 1:9-30:70-92.

2. The method according to claim 1, characterized in that In step (1), during the expansion reduction, the microwave conditions at least meet the following requirements: microwave output frequency is 2.5 GHz-3.0 GHz, and temperature is 850° C.-950° C.

3. The method according to claim 1, characterized in that In step (1), during the puffing and reduction, the puffing and reduction time is 15-25s.

4. The method according to claim 1, wherein In step (1), in the contact reaction, the weight ratio of the compounded spherical alumina to the silane coupling agent is 100:0.5-2.

5. The method according to claim 1 or 2, characterized in that In step (1), in the contact reaction, the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane; And / or, in step (1), in the contact reaction, the solvent is ethanol and / or water.

6. The method according to claim 1 or 2, characterized in that In step (1), in the contact reaction, the initial pH value of the contact reaction system is 3.5-5.5; And / or, in the contact reaction, the contact reaction is carried out under ultrasonic conditions, and the power of the ultrasound is 200-300W.

7. The graphene thermal grease prepared by the method according to any one of claims 1 to 6.

8. Use of the graphene thermal grease according to claim 7 in thermal interface thermal conductive materials.

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