Preparation method of graphene heat-conducting film with high heat conductivity

Abstract

The invention belongs to the field of heat-conducting materials, and particularly relates to a preparation method of a high-heat-conductivity graphene heat-conducting film. Through combination of various graphene materials (such as mechanically stripped graphene and reduced graphene oxide), a carbon-containing material is adopted as a dispersoid, so that the content of bound water and hydrogen bonds is reduced, and the production efficiency is improved; and meanwhile, the three-roller machine is used for dispersing to realize mutual lap joint of the graphene materials, so that the internal arrangement of the film materials is more uniform and compact, and the heat conductivity of the heat-conducting film is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive materials, specifically relating to a method for preparing a high thermal conductivity graphene thermally conductive film. Background Technology

[0002] Graphene is a two-dimensional nanomaterial composed of a single atomic layer. It has extremely high thermal conductivity, excellent mechanical properties, and good electrical properties. The theoretical thermal conductivity of single-layer graphene can reach 5300 W / m·K, which is higher than that of single-walled carbon nanotubes (3500 W / m·K) and multi-walled carbon nanotubes (3000 W / m·K). It is the material with the highest thermal conductivity known to date. It is also one of the materials with the highest strength known. At the same time, it also has good toughness and can be bent. The theoretical Young's modulus of graphene reaches 1.0 TPa, and its inherent tensile strength is 130 GPa.

[0003] Graphene thermally conductive films are prepared by stacking monolayers of graphene sheets. The existing main preparation process involves dispersing, homogenizing, coating, cutting, carbonizing, graphitizing, and calendering graphene oxide (GO). However, the existing technical route has many drawbacks:

[0004] ① The initial raw material is graphene oxide, which has many defects. The reduction and repair during the graphitization stage can only partially repair it. Currently, the highest thermal conductivity can only be 2000W / m·k (70 micrometers thick), but the graphitization temperature needs to reach 3150℃, which is more than twice the cost of graphitization temperature of 2900℃, making it unfavorable for mass production. ② The functional groups such as -OH and -COOH contained in graphene oxide easily form hydrogen bonds with H2O, which slows down the evaporation of bound water and limits the coating drying rate. ③ Due to the high viscosity, the slurry solid content is generally <8%, so the coating film cannot be thicker. Thick films need to be laminated, which increases the interlayer thermal resistance and makes delamination easy. ④ During the high-temperature process, the functional groups of GO raw materials are removed and a large amount of gas (such as CO and CO2) is released. The accumulation of gas leads to film expansion, an increase in structural defects, and a serious reduction in thermal conductivity. ⑤ During the carbonization and graphitization process, the film material expands to 5-10 times its original size. The production process can only cut the film into pieces and cannot roll it up to the next, resulting in low production efficiency. ⑥ To obtain products with higher thermal conductivity, graphitization repair usually requires higher temperatures, reaching 3150℃, which is close to the upper limit of the graphitization furnace's operating temperature of 3200℃. This results in huge equipment wear and tear, huge energy consumption, and doubled costs. ⑦ The yield rate is less than 90%, mainly because the raw material GO has too many impurities. A large amount of dust is generated during the graphitization process, which adheres to the surface of the film and causes a large number of defective products.

[0005] As the heat generation power of future electronic products increases, products with higher thermal conductivity and lower cost are required. How to further improve the thermal conductivity of graphene thermal conductive films has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a high thermal conductivity graphene thermal conductive film. By combining various graphene materials and using carbon-containing materials as the dispersant, the content of bound water and hydrogen bonds is reduced, thereby improving production efficiency. Simultaneously, a three-roll mill is used to disperse the graphene materials, enabling them to overlap and making the internal arrangement of the film more uniform and compact, thus significantly improving the thermal conductivity of the thermal conductive film.

[0007] The present invention adopts the following technical solution: A method for preparing a high thermal conductivity graphene thermal conductive film includes the following steps: (1) Weigh the thermal conductive material, dispersion and solvent according to the mass ratio of 1:0.01~0.5:1~3 and stir them evenly in a disperser, and then homogenize them with a homogenizer to obtain a slurry; (2) Grind the homogenized slurry 2 to 4 times using a three-roll mill, then defoam it using a defoamer, coat the defoamed slurry into a film with a thickness of 1000 to 5000 μm, dry it and then roll it up. (3) Place the roll material in an oven and treat it at a low temperature of 50-180℃ to crosslink the dispersion with the hydroxyl and / or carboxyl groups on the surface of the thermally conductive material (esterification and / or amidation). (4) Place the low-temperature treated roll material into a carbonization furnace and carbonize it at 800~1200℃. After the carbonization is completed, place it into a graphitization furnace and graphitize it at 2500~3000℃. After natural cooling, take out the film material, roll it with rollers, and package and cut the finished product for output. The thermally conductive material is selected from at least two of mechanically exfoliated graphene, reduced graphene oxide, CVD-grown graphene, graphene oxide, and carbon nanotubes; the dispersion is selected from one or more of sodium alginate, acrylic resin, coal tar, pitch-based, dianhydride, diamine, and acrylonitrile; and the solvent is selected from one or more of deionized water, ethanol, methanol, NMP, and DMF.

[0008] Preferably, the thermally conductive material is selected from at least two of mechanically exfoliated graphene, reduced graphene oxide, CVD-grown graphene, graphene oxide, and carbon nanotubes, with each thermally conductive material accounting for 10% to 80% of the total mass of the thermally conductive material.

[0009] Preferably, the solvent is mainly composed of deionized water, which accounts for 60% to 100% of the total mass of the solvent.

[0010] Preferably, the dispersant has a stirring speed of 1000~5000 rpm and a stirring time of 0.5~2h.

[0011] Preferably, the homogenizer is used to homogenize 2 to 3 times under conditions of 50 to 100 MPa.

[0012] Preferably, during grinding with a three-roll mill, the speed ratio of the front, middle and rear rollers is 1:3:9, and the roller gap is adjusted to 1~30μm.

[0013] Preferably, the defoamer operates at a speed of 2000~4000 rpm, a vacuum degree of 50~150 MPa, and a defoaming time of 2~5 min.

[0014] Preferably, the density of the film material after roll forming reaches 2.0~2.2 g / cm³. 3 .

[0015] The present invention also provides a graphene thermally conductive film prepared by the above preparation method.

[0016] The present invention also provides a thermally conductive pad prepared using the graphene thermally conductive film.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. This invention uses mechanically exfoliated graphene and reduced graphene oxide, etc. Compared with pure graphene oxide, the thermally conductive material contains fewer functional groups, less bound water and hydrogen bonds, has a faster drying rate, higher coating efficiency, and can improve production efficiency by more than 20%.

[0018] 2. The present invention uses carbon-containing materials as the dispersion medium to disperse the thermal conductive material. The slurry viscosity is relatively low, which can increase the solid content and thus form a film material with a higher thickness. Moreover, the dispersion medium can also form a carbon skeleton after carbonization and graphitization treatment.

[0019] 3. By combining various thermally conductive materials, the graphene oxide content is reduced, the impurity content is reduced, less dust and impurities are generated during the heat treatment stage, and the product yield is higher; during the heat treatment process, less gas is released from the removal of graphene oxide functional groups, the film material has less expansion rate and structural defects, and the thermal conductivity is higher; the thermal conductivity is more than 20% higher than that of using graphene oxide thermal conductive film alone.

[0020] 4. Using a three-roll mill to disperse and overlap various graphene materials makes the internal arrangement of the film more uniform and compact, significantly improving the thermal conductivity of the thermal conductive film.

[0021] 5. The membrane material contains less resin and graphene oxide, requiring lower temperatures and holding times for carbonization and graphitization, resulting in reduced energy consumption and lower costs; the membrane material has a low expansion rate (graphene oxide, as a raw material, will expand to 5-10 times its original thickness), allowing for roll-to-roll production and improving production efficiency. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described in the following description are merely illustrative examples of specific implementations of this invention and are intended to explain the invention, but do not constitute a limitation thereof.

[0023] The endpoints of the ranges and any values ​​disclosed herein are not limited to the exact ranges or values, which should be understood to include those close to them.

[0024] Example 1 Weigh 1.70 kg of mechanically exfoliated graphene, 0.90 kg of reduced graphene oxide, 0.40 kg of graphene oxide (GO), 0.10 kg of sodium alginate, 0.10 kg of dianhydride, 0.10 kg of diamine, 4.00 kg of deionized water, 0.60 kg of ethanol, and NMP. 0.20 kg of the mixture was placed in a double planetary disperser and stirred at 3000 rpm for 60 minutes. The slurry was then removed and placed in a homogenizer and homogenized twice at 80 MPa. The homogenized slurry was then ground twice in a three-roll mill with the roller gap adjusted to 1 micrometer. The slurry after three-roll milling was then placed in a defoamer at 3500 rpm and a vacuum of 100 MPa for 3 minutes to defoam. The defoamed slurry was then coated into films using a comma coater with coating thicknesses of 1000 μm, 2000 μm, and 5000 μm. After drying at a temperature gradient of 30℃-100℃, the film was wound up and placed in an oven for low-temperature treatment at 50-180℃. The low-temperature treated film was then placed in a carbonization furnace for carbonization at 800-1200℃. After carbonization, the film was placed in a graphitization furnace for graphitization at 2900℃. After natural cooling, the membrane material is removed and compacted using a roller mill to achieve a density of 2.1 g / cm³. 3 After compaction, the corresponding thicknesses were 20μm, 40μm, and 100μm, with measured thermal conductivity of 1967W / m·k, 1893W / m·k, and 1771W / m·k, respectively. Because roll-to-roll processing is used, subsequent thickness testing no longer requires manual measurement with a thickness gauge; instead, an online laser thickness gauge can be used, improving overall efficiency by 30%.

[0025] Example 2 Weigh out 1.70 kg of CVD-grown graphene, 0.90 kg of reduced graphene oxide, 0.40 kg of graphene oxide (GO), 0.10 kg of acrylic resin, 0.10 kg of coal tar, 0.10 kg of pitch-based material, 4.00 kg of deionized water, 0.60 kg of ethanol, and 0.20 kg of DMF. Place all materials into a double planetary disperser and stir at 3000 rpm for 60 minutes. Then, remove the slurry and homogenize it twice at 80 MPa. Next, grind the homogenized slurry twice in a three-roll mill, adjusting the roller gap to 1 micrometer. Finally, place the three-roll milled slurry into a defoamer. At 3500 rpm and a vacuum of 100 MPa, the defoamed slurry was defoamed for 3 minutes and then coated onto films using a comma coater to achieve thicknesses of 1000 μm, 2000 μm, and 5000 μm. After drying in a temperature gradient of 30℃-100℃, the film was wound up and placed in an oven for low-temperature treatment at 50-180℃. The low-temperature treated film was then placed in a carbonization furnace for carbonization at 800-1200℃, followed by graphitization at 2900℃. After natural cooling, the film was removed and compacted using a roller mill to achieve a density of 2.1 g / cm³. 3 After compaction, the corresponding thicknesses were 20μm, 40μm, and 100μm, with measured thermal conductivity of 1987W / m·K, 1906W / m·K, and 1803W / m·K, respectively. Because roll-to-roll processing is used, subsequent thickness testing no longer requires manual measurement with a thickness gauge; instead, an online laser thickness gauge can be used, improving overall efficiency by 30%.

[0026] Example 3 Weigh 0.60 kg of mechanically exfoliated graphene, 1.20 kg of CVD-grown graphene, 0.80 kg of reduced graphene oxide, 0.40 kg of graphene oxide (GO), 0.10 kg of acrylic resin, 0.10 kg of coal tar, 0.10 kg of acrylonitrile, 4.00 kg of deionized water, 0.60 kg of ethanol, and DMF. 0.20 kg of the mixture was placed in a double planetary disperser and stirred at 3000 rpm for 60 minutes. The slurry was then removed and placed in a homogenizer and homogenized twice at 80 MPa. The homogenized slurry was then ground twice in a three-roll mill with the roller gap adjusted to 1 micrometer. The slurry after three-roll milling was then placed in a defoamer at 3500 rpm and a vacuum of 100 MPa for 3 minutes to defoam. The defoamed slurry was then coated into films using a comma coater with coating thicknesses of 1000 μm, 2000 μm, and 5000 μm. After drying at a temperature gradient of 30℃-100℃, the film was wound up and placed in an oven for low-temperature treatment at 50-180℃. The low-temperature treated film was then placed in a carbonization furnace for carbonization at 800-1200℃. After carbonization, the film was placed in a graphitization furnace for graphitization at 2900℃. After natural cooling, the membrane material is removed and compacted using a roller mill to achieve a density of 2.1 g / cm³. 3 After compaction, the corresponding thicknesses were 20μm, 40μm, and 100μm, with measured thermal conductivity of 1975W / m·k, 1893W / m·k, and 1785W / m·k, respectively. Because roll-to-roll processing is used, subsequent thickness testing no longer requires manual measurement with a thickness gauge; instead, an online laser thickness gauge can be used, improving overall efficiency by 30%.

[0027] Comparative Example 1 Weigh 6.38 kg of graphene oxide (GO) filter cake and place it into a double planetary disperser. Weigh 0.36 kg of ammonia water and 4.43 kg of deionized water, and add them to the double planetary disperser. Stir at 3000 rpm for 60 minutes. Then, remove the slurry and place it into a homogenizer. Homogenize twice at 80 MPa. Grind the homogenized slurry twice in a three-roll mill, adjusting the roller gap to 1 micrometer. Place the three-roll milled slurry into a defoamer at 3500 rpm. The slurry was defoamed for 3 minutes at a pressure of 100 MPa. Then, it was coated onto films using a comma-type coating machine to achieve thicknesses of 1000 μm, 2000 μm, and 5000 μm. After drying in a temperature gradient of 30℃-100℃, the films were cut into sheets and placed in an oven for low-temperature treatment at 50-180℃. The low-temperature treated sheets were then placed in a carbonization furnace for carbonization at 800-1200℃, followed by graphitization at 2900℃. After natural cooling, the films were removed and compacted using a flat press to achieve a density of 2.1 g / cm³. 3After compaction, the corresponding thicknesses were 10μm, 20μm, and 50μm, and the measured thermal conductivityes were 1749W / m·k, 1706W / m·k, and 1668W / m·k, respectively.

[0028] Comparative Example 2 Weigh 6.38 kg of graphene oxide (GO) filter cake and place it in a double planetary disperser. Weigh 0.36 kg of ammonia water and 4.43 kg of deionized water and place them in the double planetary disperser. Stir at 3000 rpm for 60 min. Then, remove the slurry and place it in a homogenizer. Homogenize twice at 80 MPa. Place it in a defoamer at 3500 rpm and a vacuum of 100 MPa for 3 min to defoam. Coat the dispersed slurry into films using a comma coater with coating thicknesses of 1000 μm, 2000 μm, and 5000 μm. After drying in a temperature gradient of 30℃-100℃, cut the films into sheets. Place the sheets in an oven and treat them at a low temperature of 50-180℃. Place the low-temperature treated sheets in a carbonization furnace and carbonize them at 800-1200℃. After carbonization, place them in a graphitization furnace and graphitize them at 2900℃. After natural cooling, the membrane material is removed and compacted using a flatbed press to achieve a density of 2.1 g / cm³. 3 After compaction, the corresponding thicknesses were 10μm, 20μm, and 50μm, and the measured thermal conductivityes were 1517W / m·k, 1483W / m·k, and 1451W / m·k, respectively.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the content of the present invention. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in the present invention and all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity graphene thermal conductive film, characterized in that, Includes the following steps: (1) Weigh the thermal conductive material, dispersion and solvent according to the mass ratio of 1:0.01~0.5:1~3 and stir them evenly in a disperser, and then homogenize them with a homogenizer to obtain a slurry; (2) Grind the homogenized slurry 2 to 4 times using a three-roll mill, then defoam it using a defoamer, coat the defoamed slurry into a film with a thickness of 1000 to 5000 μm, dry it and then roll it up. (3) Place the roll material in an oven and treat it at a low temperature of 50-180℃ to allow the dispersion to crosslink with the hydroxyl and / or carboxyl groups on the surface of the thermally conductive material. (4) Place the low-temperature treated roll material into a carbonization furnace and carbonize it at 800~1200℃. After the carbonization is completed, place it into a graphitization furnace and graphitize it at 2500~3000℃. After natural cooling, take out the film material, roll it with rollers, and package and cut the finished product for output. The thermally conductive material is selected from at least two of mechanically exfoliated graphene, reduced graphene oxide, CVD-grown graphene, graphene oxide, and carbon nanotubes; the dispersion is selected from one or more of sodium alginate, acrylic resin, coal tar, pitch-based, dianhydride, diamine, and acrylonitrile; and the solvent is selected from one or more of deionized water, ethanol, methanol, NMP, and DMF.

2. The preparation method according to claim 1, characterized in that, The thermally conductive material is selected from at least two of mechanically exfoliated graphene, reduced graphene oxide, CVD-grown graphene, graphene oxide, and carbon nanotubes, with each thermally conductive material accounting for 10% to 80% of the total mass of the thermally conductive material.

3. The preparation method according to claim 1, characterized in that, The solvent is mainly composed of deionized water, which accounts for 60% to 100% of the total mass of the solvent.

4. The preparation method according to claim 1, characterized in that, The dispersant has a stirring speed of 1000~5000 rpm and a stirring time of 0.5~2 hours.

5. The preparation method according to claim 1, characterized in that, The homogenizer is used to homogenize 2 to 3 times under conditions of 50 to 110 MPa.

6. The preparation method according to claim 1, characterized in that, When grinding with a three-roll mill, the speed ratio of the front, middle and rear rollers is 1:3:9, and the roller gap is adjusted to 1~30μm.

7. The preparation method according to claim 1, characterized in that, The defoamer operates at a speed of 2000~4000rpm, a vacuum of 50~150MPa, and a defoaming time of 2~5min.

8. The preparation method according to claim 1, characterized in that, The density of the film material after roll forming reaches 2.0~2.2 g / cm³. 3 .

9. A high thermal conductivity graphene thermal conductive film, characterized in that, Prepared using the preparation method described in any one of claims 1-8.

10. A thermally conductive pad, characterized in that, It is prepared using the high thermal conductivity graphene thermal conductive film of claim 9.