A method for preparing high thermal conductivity graphite film material using recycled materials

Abstract

The present invention discloses a method for preparing a high-thermal-conductivity graphite film material using recycled materials. The method first attempts to crush damaged graphite material to produce regenerated graphite powder, then mixes asphalt with the regenerated graphite powder and fumed silica, and modulates the mixture with a solvent to obtain a mixture paste for use; then prepares a polyimide resin slurry, and disperses graphene therein; the polyimide resin slurry and the mixture paste are superimposed to obtain a composite film, and a continuous reciprocating roller pressing operation is used to reduce the thickness of the composite film. The polyimide resin in the composite film is then subjected to a high-temperature curing treatment to cause the polyimide resin to undergo a cross-linking reaction; and the composite film after the polyimide resin is cured is then sequentially carbonized and graphitized to obtain a finished heat-dissipating graphite film material. The method of the present invention can produce a carbon-based film heat-dissipating material with excellent physical properties, structural stability, and thermal conductivity using low-cost raw materials.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling damaged graphite raw materials, and in particular to a method for preparing a high-thermal-conductivity graphite film material by utilizing recycled materials. Background Art

[0002] With the rapid development of economic life, electronic instruments and equipment such as mobile phones, computers, and aerospace control systems are becoming lighter, smaller, and more compact. At the same time, their performance is constantly improving, and the heat dissipation problem is becoming more and more prominent. If the heat cannot be discharged in time, it will seriously affect the working stability and life of electronic components.

[0003] As a crucial component of thermal solutions, heat dissipation materials with lightweight and high thermal conductivity are in high demand. Film heat dissipation materials can effectively adapt to the size of miniaturized electronic devices and effectively transfer heat from them to the external environment, preventing heat accumulation from adversely affecting device performance. Furthermore, film heat dissipation materials possess excellent mechanical and processability, adapting to a variety of complex shapes and sizes. Through methods such as opening holes and shaping, they can improve fit with corresponding components and optimize their heat conduction paths after heating. This not only ensures the normal operation and performance of electronic devices, but also opens up new possibilities for product design and manufacturing.

[0004] High thermal conductivity polyimide film, as a type of carbon-based film heat dissipation material, is made from polyimide (PI) as a raw material and then carbonized and graphitized under pressure in an inert atmosphere. It has a low thermal expansion coefficient and good thermomechanical properties, and is the most promising heat dissipation material today. However, the existing technology for preparing high thermal conductivity polyimide film uses polyimide resin as the main raw material, and is usually synthesized using raw materials such as phthalic anhydride and paraphenylenediamine. It is impossible to use waste materials from other industries to improve the process. At the same time, there are generally problems such as high carbonization temperature and high energy consumption; long carbonization cycle; low carbonization rate of carbonized film, and the prepared carbonized film is brittle and easy to break.

[0005] Based on the above reasons, there is still room for improvement in the carbon-based film heat dissipation materials in the existing technology; it is necessary to further improve the existing process methods to obtain a low-cost carbon-based film heat dissipation material that is light in weight and has high thermal conductivity. Summary of the Invention

[0006] The technical problem solved by the present invention is to provide a method for preparing high thermal conductivity graphite film material using recycled materials, so as to solve the defects in the above technical background.

[0007] The technical problem solved by the present invention is achieved by adopting the following technical solutions:

[0008] A method for preparing a high thermal conductivity graphite film material using recycled materials, specifically comprising the following steps:

[0009] S1 selects damaged graphite blank fragments and damaged graphite parts as raw materials, and grinds the raw materials into recycled graphite powder with a particle size of less than 0.5mm through a crushing device and a grinding device in sequence;

[0010] S2: Asphalt with a softening point of 50-70°C is selected as a raw material, and the asphalt is mixed with recycled graphite powder and fumed silica and prepared with a solvent to obtain a mixture paste, wherein the amount of recycled graphite powder is 65-75wt%, the amount of fumed silica is 0.05-0.3wt%, and the balance is asphalt;

[0011] S3: preparing a polyimide resin, and then adding a solvent to the polyimide resin to form a polyimide resin slurry, adding 0.3 to 0.5 wt % of graphene to the solution, which accounts for the mass of the dianhydride component and the diamine component in the polyimide resin, and dispersing the graphene uniformly;

[0012] S4: applying the polyimide resin slurry obtained in step S3 to the surface of a hard substrate, drying part of the solvent after leveling, and obtaining a polyimide resin film in a stable adhesion state with a weight loss of 30-60%. The polyimide resin film and the hard substrate are regarded as a processing unit, and the mixture paste obtained in step S2 is evenly coated on the surface of the polyimide resin film of one processing unit. Then, another processing unit is placed on the surface of the mixture paste to laminate the polyimide resin film of the processing unit to the surface of the mixture paste.

[0013] S5: performing a continuous reciprocating rolling operation on the hard substrate surface of the processing units on both sides using a pressing roller, so that the thickness of the composite film structure of the polyimide resin film-mixture paste-polyimide resin film is reduced to 1 / 5 to 1 / 10 of the original thickness;

[0014] S6: The composite film structure obtained in step S5 is subjected to a high-temperature curing treatment of a polyimide resin to cause a cross-linking reaction of the polyimide resin; and then the composite film after the polyimide resin is cured is sequentially carbonized and graphitized to obtain a finished heat dissipation graphite film material.

[0015] As a further limitation, if there are pollutants or impurities on the damaged graphite blank fragments and damaged graphite parts, they can be ultrasonically cleaned with an organic solvent to clean off the pollutants and debris on the surface, and after cleaning, they can be vacuum dried and then crushed in a crusher.

[0016] As a further limitation, when performing the mixing operation in step S2, the asphalt is first melted in the asphalt melting tank, and at the same time, the regenerated graphite powder and the fumed silica are added to the kneading pot for dry mixing, and then the asphalt is added to the kneading pot for wet mixing, and after uniform mixing, the graphite mixture powder is obtained.

[0017] As a further limitation, the polyimide resin solution is obtained by polymerizing phthalic anhydride and phenylenediamine in a solvent at a molar ratio of 1:1;

[0018] The polymerization reaction is carried out in an argon atmosphere at 60-80° C. for 5-8 hours, and continuous stirring is maintained during the polymerization;

[0019] The solvent is dimethyl sulfoxide or N-methylpyrrolidone;

[0020] The total mass of phthalic anhydride and phenylenediamine in the polyimide resin solution is 10-30% of the mass of the solvent.

[0021] As a further limitation, the hard substrate is a tempered glass substrate.

[0022] As a further limitation, in step S4, the coating thickness of the mixture paste between the two layers of polyimide resin films is 1 / 2 to 3 / 2 times the sum of the thicknesses of the two layers of polyimide resin films; and the thickness difference between the two layers of polyimide resin films does not exceed 30% of the average thickness of the two layers of polyimide resin films.

[0023] As a further limitation, in step S6, when the high-temperature curing treatment of the polyimide resin is carried out, the temperature is raised to 90-120°C at a heating rate of 15-20°C / min, maintained for 45-60 minutes, and then the temperature is raised to 200°C at a heating rate of 30-50°C / min and maintained for 60-90 minutes, thereby completing the high-temperature curing of the polyimide resin.

[0024] As a further limitation, in step S6, the carbonization and graphitization treatment of the composite film is performed in an argon protective gas environment, the carbonization temperature is 900-1300°C, and the graphitization temperature is 2200-2800°C.

[0025] Beneficial effects: The method of the present invention for preparing high thermal conductivity graphite film materials using recycled materials is an improved process for the PI carbonization film forming process. It can use damaged graphite blank fragments and damaged graphite parts as raw materials to prepare high thermal conductivity carbon-based film heat dissipation materials. It uses a polyimide structure to sandwich the upper and lower surfaces of a mixture paste prepared with recycled graphite, and uses polyimide and the mixture paste to form a spatial bonding structure during the continuous reciprocating rolling operation, and generates structural traction at the interface layer position. This continuous reciprocating rolling operation can effectively avoid the generation of bubbles and internal pores in the polyimide during the curing and molding process, ensuring a dense structure and thus improving the mechanical strength.

[0026] The mixture paste between the polyimide structures can not only serve as a matrix to maintain the material shrinkage and dimensional stability of the graphite film, but also combine with graphene to prevent the occurrence of defects caused by chemical structure changes during the carbonization process of polyimide, thereby increasing the carbonization rate of polyimide. Furthermore, it increases the internal stress generated during the carbonization process of polyimide, reduces the brittleness of the carbonized film, makes it easier to prepare a complete large-area carbon film, and ensures that the carbon film has better material mechanical properties than traditional PI carbonized film. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solutions of the present invention and to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with specific embodiments.

[0028] This embodiment is only a part of the embodiments of the present invention, and represents all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention. It should be noted that the terms in the specification, claims and following embodiments of the present invention are used to distinguish similar objects. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed.

[0029] In the method for preparing a high thermal conductivity graphite film material using recycled materials in the embodiment, scrapped damaged graphite crucibles are used as raw materials. These graphite crucibles are waste graphite crucibles eliminated by polysilicon manufacturers. When scrapped, pollutants remain in the crucibles. Before processing, these graphite crucibles are first crushed by a crusher, and then placed in an ultrasonic cleaning machine and assisted by organic solvents to clean off surface pollutants and debris. After cleaning, they are vacuum dried and then ground into recycled graphite powder with a particle size of less than 0.5 mm using a grinding equipment.

[0030] 70 wt% of regenerated graphite powder and 0.15 wt% of fumed silica were added to a kneader for dry mixing. After 50 minutes of dry mixing, a dry mixture was obtained. Then, the remaining 29.85 wt% of asphalt was added. Wet mixing was performed, and solvent oil was added three times during the wet mixing process to dilute the materials to obtain a viscous mixture paste for later use.

[0031] Then, a polyimide resin slurry is prepared, and dimethyl sulfoxide is used as a solvent. Phthalic anhydride and phenylenediamine are added to the solvent in a molar ratio of 1:1. The total mass of phthalic anhydride and phenylenediamine in the polyimide resin solution is controlled to be 20% of the mass of the solvent for polymerization reaction. The polymerization reaction is carried out in an argon atmosphere at 60-80° C. The polymerization reaction treatment time is 6 hours, and during the polymerization, a plate and frame stirrer is used to maintain a stirring speed of 210 rad / min for continuous stirring. When there are 30 minutes left in the polymerization reaction, graphene accounting for 0.4 wt% of the mass of the dianhydride component and the diamine component in the polyimide resin is added, and stirring is continued. After the reaction is completed, the polyimide resin slurry is obtained.

[0032] A tempered glass substrate is used as a hard substrate. A polyimide resin slurry is applied to the surface of the hard substrate after cleaning and siliconizing the surface. After leveling, some of the solvent is dried to obtain a stably adhered polyimide resin film with a weight loss of 45%. The polyimide resin film and the hard substrate are combined as a processing unit. The prepared mixture paste is evenly applied to the surface of the polyimide resin film of one processing unit. Another processing unit is then placed on the surface of the mixture paste, with the polyimide resin film of the other processing unit adhered to the surface of the mixture paste. During the above process, the thickness ratio of the polyimide resin films is controlled to be 1:1, and the coating thickness of the mixture paste is the same as that of a single layer of polyimide resin film.

[0033] The laminated structure is then subjected to a continuous reciprocating rolling operation using rollers placed on both sides of the rigid substrates, reducing the thickness of the polyimide resin film-mixture paste-polyimide resin film composite structure to 1 / 10 of its original thickness. The rigid substrates are then removed, and the resulting composite structure undergoes a high-temperature curing treatment of the polyimide resin. The high-temperature curing treatment involves first increasing the temperature to 100°C at a rate of 20°C / min and holding for 50 minutes, then increasing the temperature to 200°C at a rate of 50°C / min and holding for 60 minutes, thereby completing the cross-linking reaction and curing of the polyimide resin.

[0034] Then, the composite film after curing the polyimide resin is successively carbonized and graphitized. The carbonization and graphitization treatments are carried out in an argon protective gas environment during high-temperature graphitization treatment. The carbonization temperature set in the carbonization furnace is 1200°C, and the treatment time is 180 minutes. The polyimide and the asphalt in the mixture paste are heat-treated, so that all or most of the non-carbon components in the polymer, such as hydrogen, oxygen, and nitrogen, are volatilized to obtain a cross-linked composite structure membrane. The graphite, asphalt carbonization structure, and polyimide carbonization structure in the composite structure membrane are mainly chaotic layer structures. If a carbonized membrane with good thermal conductivity is to be obtained, further graphitization treatment is required. At this time, the graphitization temperature set in the graphitization furnace is 2380°C for carbon graphitization treatment, and the treatment is 280 minutes to obtain a finished heat dissipation graphite film material.

[0035] The corresponding finished heat dissipation graphite film material has a high proportion of highly oriented carbon layer structure inside, and has high crystallinity, and has better thermal conductivity. Its thermal conductivity coefficient is 700~1200W / (mK), which is equivalent to 2 to 3 times that of traditional metal thermal conductive materials copper and 3 to 5 times that of aluminum; and the thermal conductivity coefficient gradually increases with the increase of temperature, and can reach a stable state of 1050±50W / (mK) at about 1600℃. At the same time, it has better temperature resistance and thermomechanical properties than metal thermal conductive film materials. The film material itself is soft and has good reprocessability, which is convenient for cutting and secondary processing. It can be bent and can also be coated with glue on the surface or compounded with other film materials. It can provide an optional thermal conductive material for the development of thin electronic products.

[0036] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high thermal conductivity graphite film using recycled materials, characterized in that: The specific steps include the following: S1 selects damaged graphite blank fragments and damaged graphite parts as raw materials, and grinds the raw materials into recycled graphite powder with a particle size of less than 0.5mm through a crushing device and a grinding device in sequence; S2 selects asphalt with a softening point of 50-70°C as raw material, mixes the asphalt with recycled graphite powder and fumed silica, and modulates the mixture with a solvent to obtain a mixture paste, wherein the amount of recycled graphite powder used is 65-75wt%, the amount of fumed silica used is 0.05-0.3wt%, and the balance is asphalt; S3 uses dimethyl sulfoxide or N-methylpyrrolidone as a solvent, adds phthalic anhydride and phenylenediamine to the solvent in a molar ratio of 1:1 to obtain a polyimide resin solution, controls the total mass of phthalic anhydride and phenylenediamine in the polyimide resin solution to be 10-30% of the mass of the solvent, and performs a polymerization reaction. The polymerization reaction is carried out in an argon atmosphere at 60-80° C. for 5-8 hours. Stirring is continued during the polymerization reaction. When there are 30 minutes left in the polymerization reaction, graphene is added in an amount of 0.3-0.5 wt % of the total mass of the dianhydride component and the diamine component in the polyimide resin. Stirring is continued and after the reaction is completed, a polyimide resin slurry is obtained. S4: applying the polyimide resin slurry obtained in step S3 to the surface of a hard substrate, drying part of the solvent after leveling, and obtaining a polyimide resin film in a stable adhesion state with a weight loss of 30-60%. The polyimide resin film and the hard substrate are used as a processing unit, and the mixture paste obtained in step S2 is evenly coated on the surface of the polyimide resin film of one processing unit. Then, another processing unit is placed on the surface of the mixture paste to laminate the polyimide resin film of the processing unit to the surface of the mixture paste. S5 uses a pressing roller to perform a continuous reciprocating rolling operation on the surface of the hard substrate of the processing units on both sides, so that the thickness of the composite film structure of the polyimide resin film-mixture paste-polyimide resin film is reduced to 1 / 5 to 1 / 10 of the original thickness; S6: The composite film structure obtained in step S5 is subjected to a high-temperature curing treatment of a polyimide resin to cause a cross-linking reaction of the polyimide resin; and then the composite film after the polyimide resin is cured is sequentially carbonized and graphitized to obtain a finished heat dissipation graphite film material.

2. The method for preparing a high thermal conductivity graphite film material using recycled materials according to claim 1, characterized in that: If there are pollutants or impurities on the damaged graphite blank fragments and damaged graphite parts, they can be ultrasonically cleaned with organic solvents to remove the pollutants and debris on the surface. After cleaning, they can be vacuum dried and then crushed in a crusher.

3. The method for preparing a high thermal conductivity graphite film material using recycled materials according to claim 1, characterized in that: During the mixing operation in step S2, the asphalt is first melted in an asphalt melting tank, and the regenerated graphite powder and fumed silica are added to a kneading pot for dry mixing. The asphalt is then added to the kneading pot for wet mixing, and the mixture is uniformly mixed to obtain a graphite mixture powder.

4. The method for preparing a high thermal conductivity graphite film material using recycled materials according to claim 1, characterized in that: The hard substrate is a tempered glass substrate.

5. The method for preparing a high thermal conductivity graphite film material using recycled materials according to claim 1, characterized in that: In step S4, the coating thickness of the mixture paste between the two polyimide resin films is 1 / 2 to 3 / 2 times the sum of the thicknesses of the two polyimide resin films; and the thickness difference between the two polyimide resin films does not exceed 30% of the average thickness of the two polyimide resin films.

6. The method for preparing a high thermal conductivity graphite film material using recycled materials according to claim 1, characterized in that: In step S6, when performing high-temperature curing treatment of the polyimide resin, the temperature is raised to 90-120°C at a heating rate of 15-20°C / min, maintained for 45-60 minutes, and then raised to 200°C at a heating rate of 30-50°C / min and maintained for 60-90 minutes, thereby completing the high-temperature curing of the polyimide resin.

7. The method for preparing a high thermal conductivity graphite film material using recycled materials according to claim 1, characterized in that: In step S6, the carbonization and graphitization of the composite film are performed in an argon protective gas environment, with the carbonization temperature being 900-1300°C and the graphitization temperature being 2200-2800°C.