Graphene-based linear heating body and preparation method of graphene electrothermal film

Abstract

The invention provides a preparation method of a graphene-based linear heating element and a graphene electrothermal film, and relates to the field of graphene electrothermal films, nanocellulose and a conductive filler are uniformly dispersed in water to prepare a spinning solution, and a linear heating element material is prepared by a wet spinning process; a plurality of graphene-based linear heating bodies are combined into one strand, then the strand is directionally coiled on a lower surface packaging material according to a preset pattern and fixed, copper electrodes are bonded to the two ends of the strand respectively, then packaging forming is conducted through an upper surface packaging material, and the graphene electrothermal film is obtained; according to the invention, the graphene is prepared into the linear heating body material, and the linear heating body material replaces the existing thin-film heating body material to be applied to the graphene electrothermal film product, so that the use requirements under the application conditions of low power supply power but large graphene electrothermal film area requirement and the like can be met; the heating areas are uniformly distributed, the heating area proportion is larger, and the heating experience effect of a user is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of graphene electric heating films, and in particular to a graphene base-line heating element and a preparation method of the graphene electric heating film. Background Art

[0002] Graphene is a two-dimensional carbon atom crystal with a single atom thickness. It is considered to be the basic structural unit of fullerene, carbon nanotubes (CNT) and graphite. In 2004, Ceim et al. used the tape bonding method to peel off a small amount of single-layer graphene from a highly crystalline graphite block, and studied its electrical properties. They found that its conductivity is 1.6 times that of silver, making it the best conductive material known in the world. In recent years, taking advantage of the ultra-high conductivity of graphene, the industry has continuously researched and developed new graphene electric heating films. In the prior art, the preparation method of graphene electric heating film generally uses a hot pressing method or a conductive adhesive bonding method to electrically connect the heating element material to the electrode, and then the upper and lower surfaces are encapsulated and formed with fabric or polymer film.

[0003] At present, the heating element materials used in the graphene electric heating films that have appeared on the market are all graphene conductive films. Considering the operability of production, the width of the graphene conductive film cutting must be at least 8mm. If the width of the conductive film is less than 8mm, it is difficult for workers to position it on the electrode because the film is too thin, and the operation is difficult, which affects production efficiency and product yield.

[0004] When the power supply provided by the customer is low but the area requirement of the graphene heating film is large, considering the heating experience effect, the entire heating area of ​​the heating film will be designed into multiple strip heating areas. Because the width of the graphene conductive film can only be cut into 8mm at the minimum, it is difficult to distribute the evenly distributed strip heating areas all over the membrane, resulting in the problem of local heat and local coldness, which greatly affects the user's heating experience. Summary of the invention

[0005] In view of the above-mentioned problems existing in the prior art, the present invention provides a method for preparing a graphene-based linear heating element and a graphene electric heating film, wherein the existing thin-film heating element material is replaced with a graphene-based linear heating element material, and the linear heating element material is coiled on the entire membrane to further form a graphene electric heating film, so that the heating area is more evenly distributed and the heating area accounts for a larger proportion.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] On the one hand, the present invention provides a method for preparing a graphene-based linear heating element, which is characterized in that nanocellulose and a conductive filler are uniformly dispersed in water to prepare a spinning solution, and a wet spinning process is adopted to obtain a linear heating element material.

[0008] The process of preparing the spinning solution is as follows: the nanocellulose and deionized water are ultrasonically mixed and dispersed at an ultrasonic frequency of 50 to 100 KHz for a dispersion time of 10 to 60 minutes; then a conductive filler is added thereto and ultrasonic dispersion is continued for 30 to 120 minutes to obtain a uniformly dispersed spinning solution.

[0009] Furthermore, the diameter of the linear heating element material is 100 to 300 μm. If the diameter of the linear heating element material is less than 100 μm, the material is too thin, resulting in low mechanical strength and easy breakage; if the diameter of the linear heating element material is greater than 300 μm, the diameter will be uneven when the syringe is extruded.

[0010] Furthermore, the conductive filler is graphene powder; or, the conductive filler is a mixed powder of graphene and carbon nanotubes or a mixed powder of graphene and conductive carbon black, or, the conductive filler is a mixed powder of graphene, carbon nanotubes and conductive carbon black.

[0011] Furthermore, the graphene powder is a single-layer or multi-layer graphene microsheet with a sheet diameter of 0.5-6 μm, a thickness of 1-10 nm, and a specific surface area of ​​20-200 m 2 / g, the conductivity is 8×10 4 -2×10 5 S / m; the nanocellulose comes from various plants such as wood, bamboo, cotton, hemp, straw, wheat straw, reed, pulp, etc., and its diameter and length are both within 100 nanometers.

[0012] Furthermore, the mass proportion of the nanocellulose in the spinning solution is 3-7.5%. The content of nanocellulose will affect the strength of the linear heating element material. If the content of nanocellulose is less than 3%, the viscosity of the spinning solution will be low and the fluidity will be high. During injection molding, the linear heating element material will be too thin and the strength will be too low, which will easily break. If the content of nanocellulose is higher than 7.5%, the viscosity of the spinning solution will be high and the fluidity will be too low. During injection molding, the spinning solution will block the syringe, and the internal bubbles will be difficult to discharge. After molding, the linear heating element material will have a large number of pores.

[0013] Furthermore, the mass proportion of the conductive filler in the spinning solution is 3-15%. The content of the conductive filler will affect the conductivity of the linear heating element material. If the content of the conductive filler is higher than 15%, it will be difficult to disperse the conductive filler evenly, resulting in too many particles in the linear heating element material, which will make the linear heating element material very easy to break; if the content of the conductive filler is lower than 3%, the resistance of the linear heating element material will be too high, which is not suitable for the application of electric heating film.

[0014] Furthermore, the wet spinning process is: adding the spinning solution into a syringe, and then squeezing the spinning solution in the syringe into a spinning bath to obtain a linear heating element material. The spinning bath uses a mixed solution of alcohol and water, wherein the alcohol content is 75-90%.

[0015] The principle of preparing linear heating element materials by wet spinning: when the spinning solution enters the spinning bath, the alcohol in the spinning bath replaces the water in the linear heating element material, removes the moisture in the material, and causes the material to shrink, causing it to solidify into shape.

[0016] On the other hand, the present invention provides a method for preparing a graphene electric heating film, that is, applying the above-mentioned graphene base-shaped heating element to the preparation of the graphene electric heating film, characterized in that the graphene base-shaped heating element prepared by the above-mentioned preparation method is used, multiple graphene base-shaped heating elements are combined into a strand, and then they are directionally coiled and fixed on the lower surface packaging material according to a pre-designed pattern, copper electrodes are respectively bonded to the two ends of the strand of graphene base-shaped heating element, and then they are packaged and formed with the upper surface packaging material to obtain the graphene electric heating film.

[0017] Furthermore, the graphene-based shaped heating element is fixed to the lower surface packaging material by bonding with an adhesive, which may be one of an acrylate adhesive, an epoxy resin adhesive, a polyurethane adhesive, or a polyvinyl acetate adhesive.

[0018] Furthermore, the packaging material may be a fabric or a polymer film.

[0019] Furthermore, the fabric can be one of cotton, linen, wool, woolen cloth, silk, polyester, acrylic fiber, spandex, nylon or non-woven fabric, and the polymer film can be one of polyimide film or polyester film.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention changes the structure of graphene conductive film used in the prior art as the heating element material, and creatively makes graphene into a linear heating element material, and replaces the existing film-shaped heating element material in the graphene heating film product, which can solve the use requirements in application scenarios such as "the power supply power is low but the area requirement of the graphene heating film is large". At this time, the linear heating element material is coiled on the entire diaphragm, the heating area is evenly distributed and the heating area accounts for a larger proportion, which greatly improves the user's heating experience.

[0022] 2. The present invention creatively adopts a wet spinning process to prepare a graphene-based linear heating element material. Specifically, conductive fillers such as graphene are dispersed together with nanocellulose in water to form a spinning solution, and the amount of graphene and nanocellulose is controlled so that wet spinning can be successfully completed. The water in a specific spinning bath solution is replaced to obtain a linear heating element material. The preparation method is simple and easy, and meets the application requirements of graphene-based linear heating element materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a design diagram of a graphene electric heating film according to Example 1 of the present invention;

[0024] Figure 2 This is a design diagram of a graphene electric heating film according to Example 2 of the present invention;

[0025] Figure 3 This is a design diagram of a graphene electric heating film according to Example 3 of the present invention;

[0026] Figure 4 This is a design diagram of a graphene electric heating film according to Comparative Example 1 of the present invention;

[0027] Figure 5 This is a design diagram of a graphene electric heating film according to Comparative Example 2 of the present invention;

[0028] Figure 6 This is a design diagram of a graphene electric heating film according to Comparative Example 3 of the present invention;

[0029] In the figure: 1. Copper electrode (positive), 2. Copper electrode (negative), 3. Linear heating element material, 4. Graphene conductive film. DETAILED DESCRIPTION

[0030] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0031] Example 1

[0032] The customer put forward the following requirements for the graphene heating film: power supply voltage 5V, power not exceeding 2W, heating temperature 55℃, and external dimensions 130mm*120mm.

[0033] S1. Ultrasonic mixing and dispersion of nanocellulose and deionized water at an ultrasonic frequency of 50 KHz for 10 min; then graphene powder is added thereto and ultrasonic dispersion is continued for 40 min to obtain a uniformly dispersed mixture as a spinning solution, wherein the mass proportion of nanocellulose and graphene powder in the spinning solution is 3% each.

[0034] S2. Wet spinning: Add the spinning solution into a syringe, and then squeeze the spinning solution in the syringe into a spinning bath to obtain a linear heating element material with a diameter of 100 μm and a resistance of 20 Ω / m; the spinning bath uses a mixed solution of alcohol and water, in which the alcohol content is 90%.

[0035] S3. Combine two linear heating element materials, each with a length of 1.4 m, into one strand, and then use epoxy resin adhesive to bond them according to a pre-designed pattern and wind them on a nylon cloth with a size of 130*120 mm.

[0036] S4. Copper electrodes are bonded to both ends of the linear heating element material with conductive silver glue, and the copper electrodes are used to weld the power supply wires; then, nylon cloth with a size of 130*120mm is used for packaging and molding to obtain a graphene electric heating film.

[0037] Example 2

[0038] The customer put forward the following requirements for the graphene heating film: power supply voltage 5V, power not exceeding 5W, heating temperature 65℃, and external dimensions 320mm*50mm.

[0039] S1. Ultrasonic mixing and dispersion of nanocellulose and deionized water at an ultrasonic frequency of 80 KHz for 30 min; then graphene powder is added thereto and ultrasonic dispersion is continued for 60 min to obtain a uniformly dispersed mixture as a spinning solution, wherein the mass proportions of nanocellulose and graphene powder in the spinning solution are 5% and 8%, respectively.

[0040] S2. Wet spinning: Add the spinning solution into a syringe, and then squeeze the spinning solution in the syringe into a spinning bath to obtain a linear heating element material with a diameter of 200 μm and a resistance of 13.2 Ω / m; the spinning bath uses a mixed solution of alcohol and water, in which the alcohol content is 85%.

[0041] S3. Combine three linear heating element materials with a length of 1.25 m each into one strand, and then use polyurethane adhesive to bond them according to a pre-designed pattern and wind them on a polyimide film with a size of 320*50 mm.

[0042] S4. Copper electrodes are bonded to both ends of the linear heating element material with conductive silver glue, and the copper electrodes are used to weld the power supply wires; then, a polyimide film with a size of 320*50mm is used for packaging and molding to obtain a graphene electric heating film.

[0043] Example 3

[0044] The customer put forward the following requirements for the graphene heating film: power supply voltage 5V, power not exceeding 10W, heating temperature 50℃, and external dimensions 245mm*220mm.

[0045] S1. Ultrasonic mixing and dispersion of nanocellulose and deionized water, with an ultrasonic frequency of 100 KHz and a dispersion time of 40 min; then graphene powder is added thereto and ultrasonic dispersion is continued for 120 min to obtain a uniformly dispersed mixture as a spinning solution, wherein the mass proportions of nanocellulose and graphene powder in the spinning solution are 7.5% and 15%, respectively.

[0046] S2. Add the spinning solution into the syringe, and then squeeze the spinning solution in the syringe into the spinning bath to obtain a linear heating element material with a diameter of 300 μm and a resistance of 9 Ω / m; the spinning bath uses a mixed solution of alcohol and water, in which the alcohol content is 75%.

[0047] S3. Combine 10 linear heating element materials with a length of 3.15 m each into a strand, and then use acrylic adhesive to bond them in a directional manner and wind them on a non-woven fabric with a size of 245*220 mm according to a pre-designed pattern.

[0048] S4. Copper electrodes are bonded to both ends of the linear heating element material with conductive silver glue, and the copper electrodes are used to weld the power supply wires; then, a non-woven fabric with a size of 245*220mm is used for packaging and molding to obtain a graphene electric heating film.

[0049] Example 4

[0050] The preparation method of this embodiment is basically the same as that of Embodiment 1, except that the graphene powder in step S1 is replaced by a mixed powder of graphene and carbon nanotubes, and the mass ratio of graphene to carbon nanotubes is 1:0.5; and step S2 obtains a linear heating element material with a diameter of 100 μm and a resistance of 22 Ω / m.

[0051] Example 5

[0052] The preparation method of this embodiment is basically the same as that of Embodiment 1, except that the graphene powder in step S1 is replaced by a mixed powder of graphene and conductive carbon black, and the mass ratio of graphene to conductive carbon black is 1:0.5; and step S2 obtains a linear heating element material with a diameter of 100 μm and a resistance of 20.8 Ω / m.

[0053] Example 6

[0054] The preparation method of this embodiment is basically the same as that of Embodiment 1, except that the graphene powder in step S1 is replaced with a mixed powder of graphene, carbon nanotubes and conductive carbon black, and the mass ratio of graphene, carbon nanotubes and conductive carbon black is 1:0.25:0.25; and step S2 obtains a linear heating element material with a diameter of 100 μm, and its resistance is 21.2 Ω / m.

[0055] Comparative Example 1

[0056] The graphene electric heating film was prepared according to the requirements of the customer in Example 1: the graphene conductive film with a resistance of 7Ω / sq ​​was cut into strips with a width of 8mm; the four conductive films were electrically connected to the copper electrodes by bonding with conductive adhesive, and the distance between the positive and negative electrodes was 60mm; then the upper and lower surfaces were packaged with nylon cloth with a size of 130*120mm.

[0057] Comparative Example 2

[0058] The graphene electric heating film was prepared according to the requirements of the customer in Example 2: the graphene conductive film with a resistance of 60Ω / sq was cut into strips with a width of 15mm; 5 conductive films were electrically connected to the copper electrodes by hot pressing, and the distance between the positive and negative electrodes was 19mm; then the upper and lower surfaces were encapsulated with a polyimide film with a size of 320*50mm.

[0059] Comparative Example 3

[0060] The graphene electric heating film was prepared according to the requirements of the customer in Example 3: the graphene conductive film with a resistance of 6Ω / sq was cut into strips with a width of 15mm; 5 conductive films were electrically connected to the copper electrodes by bonding with conductive adhesive, and the distance between the positive and negative electrodes was 60mm; then the upper and lower surfaces were packaged with non-woven fabrics with a size of 245*220mm.

[0061] Comparative Example 4

[0062] The method for preparing the graphene-based linear heating element in this comparative example is basically the same as that in Example 1, except that the mass proportion of nanocellulose in the spinning solution is 8.5%. As a result, the spinning solution prepared in step S1 has high viscosity and low fluidity. During the injection molding process in step S2, the spinning solution often blocks the syringe, and the obtained linear heating element material has a large number of pores inside, resulting in extremely uneven material resistance, so it is not suitable for the production of electric heating film.

[0063] Comparative Example 5

[0064] The method for preparing the graphene-based linear heating element in this comparative example is basically the same as that in Example 1, except that the mass proportion of nanocellulose in the spinning solution is 2%. As a result, the diameter of the linear heating element material obtained in step S2 is only 55 μm, the material is too thin, the strength is too low, and it is very easy to break during the process of taking, winding or using the electric heating film, so it is not suitable for the production of electric heating film.

[0065] Comparative Example 6

[0066] The method for preparing the graphene-based linear heating element in this comparative example is basically the same as that in Example 1, except that the mass proportion of graphene powder in the spinning solution is 16%. As a result, the graphene powder in the spinning solution prepared in step S1 is difficult to disperse evenly and agglomerates into particles. A large number of particles appear in the linear heating element material prepared in step S2. The particles make the material extremely easy to break and also make the material resistance extremely uneven, so it is not suitable for the production of electric heating film.

[0067] Comparative Example 7

[0068] The method for preparing the graphene-based linear heating element in this comparative example is basically the same as that in Example 1, except that the mass proportion of graphene powder in the spinning solution is 2%. As a result, the resistance of the linear heating element material obtained in step S2 reaches 31.5Ω / m, which is too high and is not suitable for the application of electric heating film.

[0069] Comparative Example 8

[0070] The method for preparing the graphene-based linear heating element in this comparative example is basically the same as that in Example 1, except that the spinning bath used is a conventional spinning bath in the existing wet spinning process, that is, the spinning bath is a mixed solution of sulfuric acid, sodium sulfate and water, wherein the sodium sulfate is 260 g / L and the sulfuric acid is 80 g / L. As a result, the graphene-based linear heating element cannot be coagulated in the spinning bath, that is, the wet spinning cannot be successfully performed.

[0071] test

[0072] Test method: Connect the graphene electric heating films of Examples 1 to 3 and Comparative Examples 1 to 3 to a 5V DC regulated power supply, record the power of each electric heating film, and reach a steady state of heating after 10 minutes of power on. Use an infrared thermal imager to detect the temperature of the electric heating film, and use a ruler to measure and calculate the ratio of the heating area of ​​the electric heating film to the total area of ​​the film. Among them, in the electric heating industry, the area surrounded by the linear heating element material is taken as the heating area, and the area covered by the strip heating element material, i.e., the graphene conductive film, is taken as the heating area.

[0073] Table 1

[0074]

[0075] It can be seen from the data in Table 1 that when the power supply voltage, power upper limit, temperature and external dimensions of the graphene electric heating film are the same, the electric heating film made of linear heating element material has a much higher heating area than the electric heating film made of graphene conductive film. Therefore, when the power supply power provided by the customer is low but the area requirement of the graphene electric heating film is large, the linear heating element material can be used to replace the thin film heating element material of the existing technology, namely the graphene conductive film. The linear heating element material is coiled on the entire diaphragm, the heating area is evenly distributed and the heating area accounts for a larger proportion, which greatly improves the user's heating experience.

[0076] From the data comparison of Example 1 and Examples 4 to 6, it can be seen that the conductive filler using graphene powder, a mixed powder of graphene and carbon nanotubes, a mixed powder of graphene and conductive carbon black, or a mixed powder of graphene, carbon nanotubes and conductive carbon black will have a certain impact on the power and temperature of the electric heating film, but will not affect other properties.

[0077] It can be seen from the comparison between Example 1 and Comparative Example 8 that the conventional wet spinning process, i.e., a conventional mixed solution of sulfuric acid, sodium sulfate and water as a spinning bath, cannot successfully achieve wet spinning of the spinning solution. This solution uses a specific alcohol aqueous solution as a spinning bath, and successfully achieves the preparation of a graphene-based linear heating element using a wet method.

Claims

1. A method for preparing a graphene-based heating element, characterized in that: Nanocellulose and conductive filler are uniformly dispersed in water to prepare a spinning solution, and a wet spinning process is adopted to obtain a linear heating element material.

2. The method for preparing the graphene-based linear heating element according to claim 1, characterized in that: The diameter of the linear heating element material is 100-300 μm.

3. The method for preparing the graphene-based linear heating element according to claim 1, characterized in that: The conductive filler is graphene powder.

4. The method for preparing the graphene-based linear heating element according to claim 1, characterized in that: The conductive filler is a mixed powder of graphene and carbon nanotubes, or a mixed powder of graphene and conductive carbon black, or a mixed powder of graphene, carbon nanotubes and conductive carbon black.

5. The method for preparing the graphene-based linear heating element according to claim 3, characterized in that: The graphene powder is a single-layer or multi-layer graphene microsheet with a sheet diameter of 0.5-6 μm, a thickness of 1-10 nm, and a specific surface area of ​​20-200 m 2 / g, the conductivity is 8×10 4 -2×10 5 S / m.

6. The method for preparing the graphene-based linear heating element according to claim 1, characterized in that: The mass proportion of the nanocellulose in the spinning solution is 3-7.5%.

7. The method for preparing the graphene-based linear heating element according to claim 6, characterized in that: The conductive filler accounts for 3-15% by weight in the spinning solution.

8. The method for preparing the graphene-based linear heating element according to claim 1, characterized in that: In the wet spinning process, the spinning bath uses a mixed solution of alcohol and water, wherein the alcohol content is 75-90%.

9. A method for preparing a graphene electric heating film, characterized in that: A graphene base linear heating element is prepared by the preparation method as described in any one of claims 1 to 8, and multiple graphene base linear heating elements are combined into a strand, which is then directionally coiled and fixed on a lower surface packaging material according to a pre-designed pattern, copper electrodes are respectively bonded to both ends of the strand of graphene base linear heating element, and then packaged and formed with an upper surface packaging material to obtain a graphene electric heating film.

10. The method for preparing the graphene electric heating film according to claim 9, characterized in that: The graphene-based linear heating element is fixed to the lower surface packaging material by adhesive bonding.

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