Preparation method of environment-friendly graphene heating film as well as product and application of environment-friendly graphene heating film

Abstract

The invention belongs to the technical field of heating films, and particularly relates to a preparation method of an environment-friendly graphene heating film, a corresponding film material and wearable equipment. The preparation method is used for preparing the graphene heating film comprising a substrate layer, a graphene heating layer, a conductive layer, an electrode current-carrying strip, a heat storage slow release layer and a protective layer, the substrate material is prepared from regenerated degradable cellulose, and the protective layer is prepared from chitosan or other analogues. The graphene heating layer and the conductive layer are patterned on the substrate layer through an intaglio printing technology, and the electrode current-carrying strip, the heat storage slow release layer and the protective layer are compounded with other materials through a hot pressing technology. The graphene heating film prepared by the invention is better in degradability and is more environment-friendly; the product has higher flexibility and durability, the texture is close to that of a fabric, and the user experience can be improved. The preparation process is low in raw material cost, suitable for flow line production, beneficial to cost reduction and higher in commercial value.

Description

Technical Field

[0001] The present invention belongs to the technical field of heating films, and specifically relates to a method for preparing an environmentally friendly graphene heating film, and corresponding film materials and wearable devices. Background Art

[0002] Graphene is a two-dimensional nanomaterial with a hexagonal honeycomb lattice structure formed by carbon atoms through sp2 hybrid orbitals and only one layer of carbon atoms thick. The unique structure of graphene gives it many excellent properties, such as high theoretical specific surface area (2630m2 / g), ultra-high electron mobility (~200000cm2 / vs), high thermal conductivity (5000W / mK), high Young's modulus (1.0TPa) and high transmittance (about 97.7%). With its structural and performance advantages, graphene has great application prospects in energy storage and conversion devices, nanoelectronic devices, multifunctional sensors, flexible wearable electronics, electromagnetic shielding, and anti-corrosion. In view of the flexibility and conductive properties of graphene, a conductive ink is prepared by adding graphene slurry to ink, and further prepared into a flexible graphene heating layer by ink spraying and drying, and made into a graphene heating element, which has the characteristics of fast production process, material saving, and low cost.

[0003] With people's pursuit of environmental protection, it is urgent to improve the preparation materials of traditional heaters, find more economical and environmentally friendly alternative materials, and develop new green heating systems. At present, the commonly used substrate materials in the preparation of graphene heating films are mostly non-degradable polymer materials, such as PET, PI, Acrylic, etc., and the protective layer is mostly a thinner material of the same material. The substrate and protective layer composed of polymers not only do not meet the requirements of environmentally friendly development, but also limit the flexibility, bending resistance and service life of the heating film to a certain extent, limiting the practical application of the product. Therefore, how to improve the preparation process of graphene heating film to make it environmentally friendly, with good flexibility and long-term stability is very important for expanding the function and adaptability of graphene heating film. Summary of the invention

[0004] In order to solve the problems of existing graphene heating films such as non-degradability, insufficient flexibility and bending resistance, and poor long-term stability, the present invention provides a method for preparing an environmentally friendly graphene heating film, and its products and applications.

[0005] The technical solution provided by the present invention is as follows:

[0006] A method for preparing an environmentally friendly graphene heating film comprises the following steps:

[0007] S1: chitosan powder is mixed with a thickener, a cross-linking agent and a plasticizer in proportion and dissolved in a solvent to obtain a chitosan solution; the chitosan solution is evenly coated in a mold and cured to obtain a chitosan film.

[0008] S2: Prepare graphene ink, use fabric made of recycled biodegradable fibers as the base material, print the conductive ink onto the base material through gravure printing, and then heat and dry it at a constant temperature of 130°C, and cool it back on the wheel to form a patterned heating layer on the base material.

[0009] S3: Prepare silver paste material, and print the silver paste onto the base material through gravure printing process, and then heat and dry it at a constant temperature of 160°C, and then return the wheel to cool, so as to form a patterned conductive layer on the base material.

[0010] S4: Prepare the electrode current-carrying bar cut into a specified shape, place the electrode current-carrying bar at a specified position on the base material, and combine and solidify the electrode current-carrying bar with the base material through a hot pressing process. The electrode current-carrying bar forms an electrical connection with the heating layer through the conductive layer.

[0011] S5: Prepare nanofibers and / or fiber composite materials as heat storage slow-release materials, and evenly stack them on the surface of a base material comprising a heating layer, a conductive layer, and an electrode current-carrying strip; then combine and solidify the heat storage slow-release material with the base material through a hot pressing process to form a heat storage slow-release layer.

[0012] S6: placing chitosan films on both sides of the base material forming the heat storage slow-release layer or on one side close to the heat storage slow-release layer, and then combining and curing the chitosan film with the base material having the heat storage slow-release layer through a hot pressing process to form a protective layer.

[0013] The obtained composite film material with a protective layer is an environmentally friendly graphene heating film. According to the number of layers of the chitosan film, the prepared products are divided into two types: single-sided coating and double-sided coating.

[0014] As a further improvement of the present invention, in step S1, the solvent is acetic acid or ethanol.

[0015] and / or

[0016] The chitosan solution is cured by heating or chemical cross-linking.

[0017] As a further improvement of the present invention, in step S2, the preparation method of graphene ink is as follows: graphene powder, nanographite, conductive carbon black, conductive resin and dispersant are fully mixed in a specified ratio to obtain graphene ink.

[0018] As a further improvement of the present invention, in step S2, the regenerated degradable fiber used as the base material includes triacetate fiber, viscose fiber, tencel fiber or cupro fiber.

[0019] Wherein, the preparation method of viscose fiber type substrate is as follows:

[0020] The cellulosic raw material is soaked in an alkaline solution to remove impurities and non-cellulosic components.

[0021] The alkali-treated cellulose raw material is soaked in a viscose solution to form viscose fiber.

[0022] The viscose fiber is soaked in a solvent to remove excess viscose and solvent, and then filtered and washed.

[0023] The washed fiber material is formed into fibers by spinning or spraying, and then stretched and shaped by rotating centrifugal force or air flow.

[0024] Finally, the shaped fibers are subjected to heat treatment or chemical cross-linking, and the regenerated degradable fibers after curing are spun to produce the desired fabric.

[0025] As a further improvement of the present invention, the cellulose raw material is cotton, hemp, bamboo, straw, bark or other natural fiber materials.

[0026] and / or

[0027] The alkaline solution is sodium hydroxide solution.

[0028] and / or

[0029] The solvent for soaking the viscose fiber is a ketone or aldehyde solvent.

[0030] As a further improvement of the present invention, in steps S2 and S3, graphene ink and silver paste are printed onto the base material by a roll-to-roll printer; during the printing process, the graphene ink or silver paste is filled into the grooves in the gravure printing roller, and during the printing process, the material in the grooves contacts the base material and is then transferred to the base material.

[0031] As a further improvement of the present invention, in step S5, the electrode current-carrying strip is a nickel-plated copper electrode.

[0032] and / or

[0033] In steps S1 and S6, the chitosan powder used to prepare the protective film is replaced by chitosan derivatives, chitosan analogs and other polysaccharide materials.

[0034] The present invention also includes an environmentally friendly graphene heating film, which is prepared by the preparation method of the environmentally friendly graphene heating film as described above, and includes: a base layer made of recycled degradable fibers; an electrode current-carrying strip located on the base layer and a patterned graphene heating layer and a conductive layer; a heat storage slow-release layer covering the electrode current-carrying strip, the heating layer and the conductive layer; and a chitosan protective layer covering only the heat storage slow-release layer or simultaneously covering the heat storage slow-release layer and below the base layer.

[0035] The present invention also includes an application of an environmentally friendly graphene heating film, in which a single-sided film-coated product prepared by the preparation method of the environmentally friendly graphene heating film as mentioned above is used as a fabric for preparing self-heating clothing or accessories; or a double-sided film-coated product is used as an interlayer material in a self-heating wearable device.

[0036] The present invention also includes a self-heating wearable device, which includes the aforementioned environmentally friendly graphene heating film and a power supply module electrically connected to the electrode current-carrying strips in the environmentally friendly graphene heating film.

[0037] The technical solution provided by the present invention has the following beneficial effects:

[0038] The various raw materials used in the environmentally friendly flexible graphene heating film provided by the present invention are cheap and easy to obtain, which can reduce the production cost of the product. The product preparation process adopts a roll-to-roll gravure printing process, flow drying, return wheel cooling and hot pressing composite integrated production line, which can realize large-scale commercial production.

[0039] Among them, the flexible graphene heating film uses green and environmentally friendly recycled degradable cellulose as the base and chitosan film as the protective layer. The product is easier to degrade, making it environmentally friendly and antibacterial.

[0040] After the material is improved, the environmentally friendly flexible graphene heating film provided by the present invention greatly improves the flexibility and durability of the graphene heating film, and has a texture similar to fabric. It can be widely used in various functional clothing, accessories and wearable devices, and can improve user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a flow chart of the steps of the method for preparing the environmentally friendly graphene heating film provided in Example 1 of the present invention.

[0042] Figure 2 This is a schematic structural diagram of the single-sided coated graphene heating film provided in Example 2 of the present invention.

[0043] Figure 3 This is a schematic structural diagram of the double-sided coated graphene heating film provided in Example 2 of the present invention.

[0044] The markings in the figure are:

[0045] 1. Protective layer; 2. Heat storage and slow-release layer; 3. Electrode current-carrying strip; 4. Conductive layer; 5. Heating layer; 6. Base layer. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0047] Example 1

[0048] This embodiment provides a method for preparing an environmentally friendly graphene heating film, which is used to prepare a graphene heating film including a base layer, a graphene heating layer, a conductive layer, an electrode current-carrying strip, a heat storage slow-release layer and a protective layer, wherein the base material is made of recycled degradable cellulose, and the protective layer is made of chitosan or other similar materials. Specifically, Figure 1 As shown, the preparation method mentioned in this embodiment includes the following steps:

[0049] S1: chitosan powder is mixed with a thickener, a cross-linking agent and a plasticizer in proportion and dissolved in a solvent to obtain a chitosan solution; the chitosan solution is evenly coated in a mold and cured to obtain a chitosan film.

[0050] The chitosan film in this embodiment is used to make a protective layer on the surface of the graphene heating film, and the protective layer can be wear-resistant, skin-friendly, and has a certain waterproof performance. Based on the same requirements, in other embodiments, the chitosan film can also be made of chitosan derivatives (such as: N-acetyl chitosan (N-acetyl chitosan) and chitosan acid (such as: chitosan sulfate, etc.), chitosan analogs (such as: chitosanase and chitosanase-like substances, etc.), other polysaccharide materials (for example, alginate, galactomannan and xylan, etc.).

[0051] When preparing chitosan film, the present embodiment will dissolve chitosan powder in a suitable solvent, such as acetic acid, ethanol, etc., to form a chitosan solution. The concentration of the solution can be adjusted as needed. In addition, the chitosan solution is also mixed with other additives, such as thickeners, cross-linking agents, plasticizers, etc., to improve the performance and processing properties of the film.

[0052] Then use a stirrer to stir the mixture evenly to ensure that the components in the solution are evenly dispersed. Pour the mixed solution into a flat or round mold, and then use a scraper or scraper or oscillate to evenly apply the solution on the surface of the mold. At this time, the thickness of the coated solution can be adjusted according to the required film thickness. Place the coated chitosan solution in a well-ventilated environment and let it dry naturally. You can also use an oven or other drying equipment to accelerate the drying process. After ensuring that the film is completely dry, remove the film. During the preparation process of the chitosan film, the chitosan film needs to be cured and cross-linked to improve its mechanical properties and stability. Common curing methods include heat treatment, chemical cross-linking, etc.

[0053] S2: Prepare graphene ink, use fabric made of recycled biodegradable fibers as the base material, print the conductive ink onto the base material through gravure printing, and then heat and dry it at a constant temperature of 130°C, and cool it back on the wheel to form a patterned heating layer on the base material.

[0054] In this embodiment, the preparation method of graphene ink is as follows: graphene powder, nanographite, conductive carbon black, conductive resin and dispersant are fully mixed in a specified ratio to obtain graphene ink. In practical applications, by adjusting the ratio of each component, the graphene ink required for the graphene heating film that meets the specific power requirements can be prepared.

[0055] In the solution of this embodiment, the base material is a fabric, and is made of recycled degradable fibers. The recycled degradable fibers used in the base material include triacetate fibers, viscose fibers, tencel fibers or cuprammonia fibers, etc. Taking viscose fibers as an example, the preparation method of the base material in this embodiment is as follows:

[0056] First, cellulose raw materials such as cotton, hemp, bamboo, trees, shrubs, straw, and bark are soaked in an alkaline solution to remove impurities and non-cellulose components. The alkaline solution can be a sodium hydroxide solution.

[0057] Then, the cellulose raw material treated with alkali is immersed in a viscose solution, which is usually composed of an adhesive and a solvent. The viscose solution in this embodiment uses a textile adhesive solution or a viscose cellulose solution. After the cellulose raw material contacts the viscose solution, the cellulose surface will absorb the adhesive, thereby generating a viscose-formed cellulose raw material.

[0058] Next, the viscose-treated cellulose raw material is soaked in a solvent, such as an alcohol or ketone solvent, to remove excess viscose and solvent. The solvent-treated cellulose raw material is then filtered and washed to remove residual solvent and impurities.

[0059] Finally, the washed cellulose raw material is spun or sprayed to form fibers. The fibers can be stretched and shaped by the centrifugal force of rotation or airflow. The formed fibers are cured, such as heat treatment or chemical cross-linking, to enhance the mechanical properties and stability of the fibers. The cured fibers are used for weaving, and the resulting fabric is the desired base material.

[0060] This embodiment adopts a printing process to prepare the required heating layer, which can not only greatly improve the production efficiency, but also can carry out complex patterning of the heating layer on the base material as needed to meet the diverse market needs and support users to customize the heating layer pattern. Specifically, the heating layer preparation process in this embodiment is as follows:

[0061] Prepare the substrate material made of recycled biodegradable cellulose and graphene ink to be printed. Make sure the surface of the substrate material is clean and flat, and remove any obvious dust or impurities. Use the gravure production process to etch the pattern or text to be printed on the gravure printing roller. The gravure printing roller can be made of metal or polymer material, and the surface of the printing roller has grooves with a specific pattern. Apply the graphene ink on the gravure. During the coating process, tools such as scrapers or rollers can be used to ensure that the ink evenly fills all the grooves in the printing roller. Next, pass the substrate material through the printing unit in the roll-to-roll printer. In the printing unit, the graphene ink in the gravure contacts the surface of the substrate material, and the ink is transferred from the grooves to the substrate material. Finally, after drying and curing, the patterned ink can be firmly attached to the surface of the substrate material.

[0062] In the solution of this embodiment, the graphene ink is heated and dried at a constant temperature of 130°C, and then subjected to recirculation cooling. Recirculation cooling utilizes the heat transfer characteristics of the heat medium, circulates the heat medium to the equipment or system that needs to be cooled, and then recirculates the cooled heat medium back into the cooling device to achieve heat transfer and cooling effects.

[0063] S3: Prepare silver paste material, and print the silver paste onto the base material through gravure printing process, and then heat and dry it at a constant temperature of 160°C, and then return the wheel to cool, so as to form a patterned conductive layer on the base material.

[0064] The silver paste material is a viscous slurry composed of a mechanical mixture of high-purity metallic silver particles, adhesives, solvents, and additives; this embodiment uses the silver paste material to prepare a conductive layer located between the electrode current-carrying bar and the heating layer, thereby achieving a stable electrical connection between the electrode current-carrying bar and the patterned conductive layer.

[0065] The conductive layer in this embodiment is prepared by the same printing process as the heating layer, so the printing process of the conductive layer is not described in detail in this embodiment. During the curing process of the conductive layer, there is a difference in the curing temperature of the silver paste material and the graphene ink. The curing temperature of the silver paste material is higher than that of the graphene ink, which is about 160°C.

[0066] S4: Prepare the electrode current-carrying bar cut into a specified shape, place the electrode current-carrying bar at a specified position on the base material, and combine and solidify the electrode current-carrying bar with the base material through a hot pressing process. The electrode current-carrying bar forms an electrical connection with the heating layer through the conductive layer.

[0067] The electrode current-carrying bar in this embodiment adopts a copper electrode with nickel plating on the surface. The electrode current-carrying bar is used to connect the power supply, and then the graphene heating layer converts the electrical energy into heat energy and releases it outward. In this embodiment, the electrode current-carrying bar is cut into the required shape and size. The shape of the electrode current-carrying bar matches the shape of the conductive layer printed in the previous step. Each electrode current-carrying bar is stacked to the position of the corresponding conductive layer and completely covers the conductive layer. The stacked material is placed in a hot pressing mold, and then the mold is placed in a preheated hot press. According to the characteristics and requirements of the material, appropriate temperature and pressure are applied and maintained for a certain time. During the hot pressing process, heat and pressure will combine the electrode material with the substrate. After the hot pressing is completed, the mold is removed from the hot press to allow the material to cool and solidify. This helps to ensure that the electrode material is firmly bonded to the substrate and form a stable electrode structure.

[0068] S5: Prepare nanofibers and / or fiber composite materials as heat storage slow-release materials, and evenly stack them on the surface of a base material comprising a heating layer, a conductive layer, and an electrode current-carrying strip; then combine and solidify the heat storage slow-release material with the base material through a hot pressing process to form a heat storage slow-release layer.

[0069] In this embodiment, the heat storage slow-release layer has the function of accumulating heat and releasing it slowly, which plays a role in maintaining the constant heat generation of the graphene heating layer. During the processing, the flexible substrate and the heat storage slow-release layer are stacked. Ensure that the heat storage slow-release layer is in close contact with the substrate. The stacked material is placed in a hot pressing mold, and then the mold is placed in a preheated hot press. According to the characteristics and requirements of the material, appropriate temperature and pressure are applied and maintained for a certain time. During the hot pressing process, heat and pressure will combine the heat storage slow-release material with the substrate. After the hot pressing is completed, the mold is removed from the hot press to allow the material to cool and solidify. This helps to ensure that the hot pressing slow-release layer is firmly bonded to the substrate.

[0070] S6: placing chitosan films on both sides of the base material forming the heat storage slow-release layer or on one side close to the heat storage slow-release layer, and then combining and curing the chitosan film with the base material having the heat storage slow-release layer through a hot pressing process to form a protective layer.

[0071] The obtained composite film material with a protective layer is an environmentally friendly graphene heating film. According to the number of layers of the chitosan film, the prepared products are divided into two types: single-sided coating and double-sided coating.

[0072] In a more optimized solution of this embodiment, an antibacterial agent may be added to the renewable cellulose, or the final produced base material may be subjected to a specific surface treatment so that the graphene heating film using the base material has antibacterial properties.

[0073] Example 2

[0074] Based on the scheme of this embodiment 1, this embodiment provides an environmentally friendly graphene heating film, and the functional film material is prepared by the preparation method of the environmentally friendly graphene heating film in embodiment 1. The environmentally friendly graphene heating film provided in this embodiment is divided into two typical structures: single-sided film type and double-sided film type.

[0075] like Figure 2 As shown, the single-sided coated graphene heating film includes a base layer 6, an electrode current-carrying bar 3, a heating layer 5, a conductive layer 4, a heat storage slow-release layer 2 and a protective layer 1. Among them, the base layer 6 is made of recycled degradable fibers; the base layer 6 serves as an attachment layer for each functional layer thereon. The heating layer 5 is located on the base layer 6 and is solidified by graphene ink. The heating layer 5 is prepared by a printing process, so that various complex patterns required can be formed. The electrode current-carrying bar 3 is compounded with the base material by a hot pressing process and is electrically connected to the patterned heating layer 5. The electrode current-carrying bar 3 serves as an input electrode when the heating layer 5 is connected to the power supply by wire. The conductive layer 4 is printed with a silver paste material, and the silver paste material is located between the electrode current-carrying bar 3 and the heating layer 5, thereby ensuring a stable electrical connection between the two. The heat storage slow-release layer 2 is made of nanofibers or fiber composite materials that can absorb and store heat. In this embodiment, the above-mentioned materials are covered on the electrode current-carrying bar 3, the heating layer 5 and the conductive layer 4, and then a heat storage slow-release layer 2 covering the heating layer 5 is formed by a hot pressing process. The heat absorption and heat storage performance of the heat storage slow-release layer 2 can, on the one hand, prevent local overheating of the product when the heating layer 5 is powered on, and on the other hand, enable the product to maintain a high temperature state for a long time after the heating layer 5 is powered off. Finally, the single-sided coated graphene heating film also includes a chitosan protective layer 1 covering the heat storage slow-release layer 2.

[0076] The double-sided coated graphene heating film includes a base layer 6, an electrode current carrying strip 3, a heating layer 5, a conductive layer 4, a heat storage slow release layer 2 and a protective layer 1. Figure 3 As shown, compared with the single-sided film-coated product, the double-sided film-coated product has a chitosan protective layer 1 disposed above the heat storage sustained-release layer 2 and below the base layer 6 .

[0077] In actual application, the look and feel of single-sided coated products are similar to textile fabrics, so they can be used to make self-heating clothing or accessories, such as scarves and heating vests. Double-sided coated products have better durability and longer service life, and can withstand more severe use environments, so they are used as interlayer materials in various self-heating wearable devices.

[0078] Compared with various existing graphene heating films, the base material and protective layer 1 material of the graphene heating film of this embodiment have good degradability, which can solve the environmental pollution problem of traditional products. This new environmentally friendly graphene heating film also has better flexibility, bending resistance and stability, and the material is closer to fiber fabrics, thus expanding the function and application range of graphene heating films.

[0079] In addition, the regenerated degradable cellulose fabric and chitosan film used in the product of this embodiment have antibacterial properties with graphite. As environmentally friendly materials, the regenerated degradable cellulose fabric and chitosan film are coupled with the antibacterial properties of graphene, which greatly enhances the antibacterial properties of the graphene heating film and makes up for the defect that the base and protective film of the common graphene heating film have no antibacterial properties.

[0080] At the same time, by selecting environmentally friendly regenerated degradable cellulose fabric and chitosan film as the substrate and protective layer 1 respectively, the flexibility and wear resistance of the fabric can be effectively utilized, providing a feasible solution for the subsequent use of the graphene heating film for wearable heating fabrics. The graphene heating film proposed in this invention has more excellent antibacterial properties for wearable fabrics, which can better meet people's needs for healthy living. For example, the environmentally friendly graphene heating film provided in this embodiment can be used to make various self-heating cushions, clothing, and various emerging wearable devices.

[0081] The raw material cost of the product provided in this embodiment is low, and the preparation process is very suitable for large-scale industrial production using assembly line equipment, which helps to further reduce production costs and has broad commercial prospects.

[0082] Example 3

[0083] The present embodiment provides a self-heating wearable device, which includes an environmentally friendly graphene heating film as in Example 1, and a power supply module electrically connected to the electrode current-carrying strip in the environmentally friendly graphene heating film. In practical applications, the power supply module is used to provide power to the graphene heating film, and the graphene heating film is used to convert electrical energy into thermal energy and output it continuously and stably. Since the graphene heating film used in the self-heating wearable device in this embodiment has the characteristics of being soft and skin-friendly, it can significantly improve the user experience while ensuring the self-heating function of the product.

[0084] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing an environmentally friendly graphene heating film, characterized in that: It includes the following steps: S1: mixing chitosan powder with a thickener, a cross-linking agent, and a plasticizer in proportion and dissolving them in a solvent to obtain a chitosan solution; uniformly coating the chitosan solution in a mold and performing a curing treatment to obtain a chitosan film; S2: preparing graphene ink, using a fabric made of recycled biodegradable fibers as a base material, printing the conductive ink onto the base material through a gravure printing process, and then heating and drying at a constant temperature of 130°C, and cooling the back wheel, thereby forming a patterned heating layer on the base material; S3: preparing silver paste material, and printing the silver paste onto the base material through gravure printing process, and then heating and drying at a constant temperature of 160°C, and then cooling the wheel, thereby forming a patterned conductive layer on the base material; S4: preparing an electrode current-carrying bar cut into a specified shape, placing the electrode current-carrying bar at a specified position on the base material, and combining and curing the electrode current-carrying bar with the base material through a hot pressing process; the electrode current-carrying bar is electrically connected to the heat-generating layer through the conductive layer; S5: preparing nanofibers and / or fiber composite materials as heat storage slow-release materials, and evenly stacking them on the surface of a base material including a heating layer, a conductive layer, and an electrode current-carrying strip; and then combining and curing the heat storage slow-release material with the base material through a hot pressing process to form a heat storage slow-release layer; S6: placing chitosan films on both sides of the base material forming the heat storage slow-release layer or on one side close to the heat storage slow-release layer, and then combining and curing the chitosan film with the base material having the heat storage slow-release layer through a hot pressing process to form a protective layer; The obtained composite film material with a protective layer is an environmentally friendly graphene heating film. According to the number of layers of the chitosan film, the prepared products are divided into two types: single-sided coating and double-sided coating.

2. The method for preparing the environmentally friendly graphene heating film according to claim 1, characterized in that: In step S1, the solvent is acetic acid or ethanol; and / or The chitosan solution is solidified by heating or chemical cross-linking.

3. The method for preparing the environmentally friendly graphene heating film according to claim 1, characterized in that: In step S2, the preparation method of the graphene ink is as follows: graphene powder, nanographite, conductive carbon black, conductive resin and dispersant are fully mixed according to a specified ratio to obtain graphene ink.

4. The method for preparing the environmentally friendly graphene heating film according to claim 1, characterized in that: In step S2, the regenerated biodegradable fiber used as the base material includes triacetate fiber, viscose fiber, tencel fiber or cuprammonium fiber; The preparation method of the viscose fiber type base material is as follows: Soaking the cellulosic raw material in an alkaline solution to remove impurities and non-cellulosic components; The cellulose raw material treated with alkali is soaked in a viscose solution to form viscose fibers; Soak the viscose fiber in a solvent to remove excess viscose and solvent, then filter and wash; The washed fiber material is formed into fibers by spinning or spraying, and then stretched and shaped by rotating centrifugal force or air flow; Finally, the shaped fibers are subjected to heat treatment or chemical cross-linking, and the regenerated degradable fibers after curing are spun to produce the desired fabric.

5. The method for preparing the environmentally friendly graphene heating film according to claim 4, characterized in that: The cellulose raw material is cotton, hemp, bamboo, straw, bark or other natural fiber materials; and / or The alkaline solution is a sodium hydroxide solution; and / or The solvent for soaking the viscose fiber is a ketone or aldehyde solvent.

6. The method for preparing the environmentally friendly graphene heating film according to claim 1, characterized in that: In steps S2 and S3, graphene ink and silver paste are printed onto the substrate material through a roll-to-roll printer; during the printing process, the graphene ink or silver paste is filled into the grooves in the gravure printing roller, and during the printing process, the material in the grooves contacts the substrate material and is then transferred to the substrate material.

7. The method for preparing the environmentally friendly graphene heating film according to claim 1, characterized in that: In step S5, the electrode current-carrying bar is a nickel-plated copper electrode; and / or In steps S1 and S6, the chitosan powder used to prepare the protective film is replaced by chitosan derivatives, chitosan analogs and other polysaccharide materials.

8. An environmentally friendly graphene heating film, characterized in that: It is prepared by the preparation method of the environmentally friendly graphene heating film as described in any one of claims 1 to 7, and includes: a base layer made of recycled degradable fibers; an electrode current-carrying strip and a patterned graphene heating layer and a conductive layer located on the base layer; a heat storage slow-release layer covering the electrode current-carrying strip, the heating layer and the conductive layer; and a chitosan protective layer covering only the heat storage slow-release layer or simultaneously covering the heat storage slow-release layer and the base layer.

9. An application of an environmentally friendly graphene heating film, characterized in that: A single-sided coated product prepared by the preparation method of the environmentally friendly graphene heating film as described in any one of claims 1 to 7 is used as a fabric for preparing self-heating clothing or accessories; or a double-sided coated product is used as an interlayer material in a self-heating wearable device.

10. A self-heating wearable device, characterized in that: It comprises the environmentally friendly graphene heating film as claimed in claim 8, and a power supply module electrically connected to the electrode current-carrying strips in the environmentally friendly graphene heating film.

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