Heating film and preparation method therefor, and heating tube and heating appliance

Abstract

Provided in the present disclosure are a heating film and a preparation method therefor, and a heating tube and a heating appliance. The heating film has a critical temperature; when the temperature of the heating film is lower than the critical temperature, the resistance of the heating film decreases as the temperature rises; and when the temperature of the heating film is higher than the critical temperature, the resistance of the heating film increases as the temperature rises.

Description

Heating diaphragm and preparation method thereof, heating tube and heating appliance

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims the benefit of priority to Chinese patent application No. 2023117932500, filed on December 22, 2023, and incorporates the entirety of the patent application herein. Technical Field

[0003] The present disclosure relates to the field of electrical appliance technology, and more specifically, to a heating diaphragm and a preparation method thereof, a heating tube, and a heating appliance. Background Art

[0004] Traditional electric ovens primarily heat the air inside the oven cavity, thereby heating the food, and directly heat the food surface through heat radiation. Currently, the heating components used in electric ovens, microwave ovens, steam ovens, and other heating appliances on the market mainly include metal heating tubes (maximum heating temperature range between 550-750°C), quartz heating tubes (heating wire temperature range between 660-800°C), halogen heating tubes (maximum heating temperature less than 1000°C), and carbon fiber heating tubes (maximum heating temperature less than 1000°C). However, these heating tubes have problems such as not heating quickly enough within the heating temperature range, not reaching a high enough temperature, or being prone to high-temperature melting during the heating process. This prolongs cooking time and makes it difficult to achieve a crispy exterior and tender interior for the food during the heating process, resulting in a poor user experience.

[0005] Summary of the Invention

[0006] The present disclosure aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present disclosure is to provide a heating diaphragm that has the advantage of self-limiting temperature, which can reduce the problem of melting caused by high temperature during the continuous increase of heating temperature.

[0007] In one aspect of the present disclosure, the present disclosure provides a heating diaphragm. According to an embodiment of the present disclosure, the heating diaphragm has a critical temperature, and when the temperature of the heating diaphragm is lower than the critical temperature, the resistance of the heating diaphragm decreases as the temperature increases; when the temperature of the heating diaphragm is higher than the critical temperature, the resistance of the heating diaphragm increases as the temperature increases. It can be seen that the heating diaphragm of the present disclosure has the characteristic of self-limiting temperature, specifically: in the initial stage of heating (that is, when the temperature of the heating diaphragm is lower than the critical temperature), the resistance of the heating diaphragm decreases as the temperature increases, and the current increases, so that the power of the heating diaphragm increases as the temperature increases, so at this stage, the heating diaphragm can heat up rapidly; when the heating temperature of the heating diaphragm reaches the critical temperature, the resistance of the heating diaphragm increases as the temperature increases, and the current decreases, so that the power of the heating diaphragm decreases as the temperature increases, so at this stage, the heating rate of the heating diaphragm begins to slow down. The self-limiting temperature characteristic of the above-mentioned heating diaphragm can, on the one hand, accelerate the heating rate of the temperature zone below the critical temperature, so that the heating diaphragm reaches the target temperature as soon as possible; on the other hand, when the temperature is higher than the critical temperature, it can reduce the melting problem caused by the continuous increase in heating temperature.

[0008] According to an embodiment of the present disclosure, when the temperature of the heating diaphragm is lower than the critical temperature, the heating rate of the heating diaphragm is a first heating rate; when the temperature of the heating diaphragm is higher than the critical temperature, the heating rate of the heating diaphragm is a second heating rate, wherein the first heating rate is higher than the second heating rate.

[0009] According to an embodiment of the present disclosure, the critical temperature value of the heating film is 50°C-500°C.

[0010] According to an embodiment of the present disclosure, the time for the heating film to reach the maximum heating temperature is 0.5s to 2s.

[0011] According to an embodiment of the present disclosure, the maximum heating temperature of the heating film is 500°C to 1700°C.

[0012] According to an embodiment of the present disclosure, the material of the heating film is graphite.

[0013] According to an embodiment of the present disclosure, the heating film is in a sheet shape.

[0014] According to an embodiment of the present disclosure, the heating film satisfies at least one of the following conditions: the thickness of the heating film is 0.04 mm to 2 mm; the density of the heating film is 0.6 g / cm 3 ~1.8g / cm 3 .

[0015] According to an embodiment of the present disclosure, the weight of the heating film with a length of 1 decimeter is 0.03 to 0.1 g.

[0016] According to the embodiment of the present disclosure, the thermal diffusion coefficient of the heating film is 50m 2 / s~450m 2 / s.

[0017] According to an embodiment of the present disclosure, the power of the heating film is 15W to 10000W.

[0018] According to an embodiment of the present disclosure, the heating film includes a plurality of heating units sequentially arranged along the length direction, and adjacent heating units are arranged at intervals and connected by connecting sections.

[0019] According to an embodiment of the present disclosure, each of the heating units is provided with a hollow hole.

[0020] In another aspect of the present disclosure, the present disclosure provides a method for preparing the aforementioned heating film. According to an embodiment of the present disclosure, the raw materials for preparing the heating film include natural graphite or graphene microsheets. Thus, the heating film prepared from natural graphite or graphene microsheets has the characteristic of self-limiting temperature. Specifically: in the initial stage of heating (i.e., when the temperature of the heating film is less than the critical temperature), the resistance of the heating film decreases with increasing temperature, and the current increases, so that the power of the heating film increases with increasing temperature, so in this stage, the heating film can heat up rapidly; when the heating temperature of the heating film reaches the critical temperature, the resistance of the heating film increases with increasing temperature, and the current decreases, so that the power of the heating film decreases with increasing temperature, so in this stage, the heating rate of the heating film begins to slow down. The above-mentioned self-limiting temperature characteristic of the heating film can enable the heating film to accelerate the heating rate of the temperature zone below the critical temperature on the one hand, so that the heating film reaches the target temperature as soon as possible, and on the other hand, when it is above the critical temperature, it can reduce the problem of melting caused by the continuous increase in heating temperature. In addition, the production cost can be effectively reduced by using natural graphite or graphene microsheets to prepare heating membranes. Natural graphite is graphite that exists in nature and does not need to be prepared, thereby reducing the preparation process and cost. The source of graphene microsheets is also relatively wide, which also helps to reduce the preparation cost of heating membranes.

[0021] According to an embodiment of the present disclosure, the method for preparing the aforementioned heating film includes: providing the natural graphite and processing it to obtain expandable graphite; expanding the expandable graphite to obtain expanded graphite; and rolling, performing a first heat treatment, and cutting the expanded graphite to obtain the heating film.

[0022] According to an embodiment of the present disclosure, the critical temperature of the heating film is 50-200°C.

[0023] According to an embodiment of the present disclosure, the method for preparing the aforementioned heating film includes: mixing and dispersing the graphene microsheets and additives evenly to obtain a dispersion; coating the dispersion to obtain a dispersion film; performing a second heat treatment on the dispersion film to obtain a carbon-based primary film; and calendering and cutting the carbon-based primary film to obtain the heating film.

[0024] According to an embodiment of the present disclosure, the critical temperature of the heating film is 150-500°C.

[0025] According to an embodiment of the present disclosure, the additive includes at least one of carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, polyacrylic acid and aqueous polyurethane, and the mass fraction of the additive is less than or equal to 5% based on the total mass of the dispersion.

[0026] In another aspect of the present disclosure, a heating pipe is provided. According to an embodiment of the present disclosure, the heating pipe includes the aforementioned heating diaphragm. As a result, the heating pipe has a relatively fast heating rate and a relatively high heating temperature, and also exhibits a self-limiting temperature characteristic. This allows the heating pipe to accelerate the heating rate in the temperature zone below the critical temperature, allowing the heating pipe to reach the target temperature as quickly as possible. Furthermore, when the temperature is above the critical temperature, the risk of fusing caused by the continued increase in heating temperature is reduced.

[0027] In another aspect of the present disclosure, a heating appliance is provided. According to an embodiment of the present disclosure, the heating appliance includes the aforementioned heating tube. As a result, the heating appliance heats up quickly, reaches a high temperature, and exhibits self-limiting temperature characteristics. This allows the heating appliance to heat up quickly, allowing it to reach the target temperature as quickly as possible, while also minimizing the risk of fusing during a continuous temperature increase.

[0028] According to an embodiment of the present disclosure, the heating appliance is an electric oven, a microwave oven, a steam oven, an electric kettle, an electric blanket, an electric fan heater, an electric heater, a bathroom heater, an electric ceramic stove or a disinfection cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present disclosure will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0030] FIG1 is a schematic diagram of heat radiation of a heating film disclosed in the present invention;

[0031] FIG2 is a schematic diagram of heat radiation of a heating pipe in the prior art;

[0032] FIG3 is a schematic structural diagram of a heating membrane in an embodiment of the present disclosure;

[0033] FIG4 is a schematic structural diagram of a heating film in other embodiments of the present disclosure;

[0034] FIG5 is a schematic structural diagram of a heating film in other embodiments of the present disclosure;

[0035] FIG6 is a schematic diagram of the structure of the heating pipe in some other embodiments of the present disclosure

[0036] FIG7 is a schematic structural diagram of a heating pipe in some other embodiments of the present disclosure;

[0037] FIG8 is a schematic structural diagram of a heating pipe in some other embodiments of the present disclosure;

[0038] FIG9 is a schematic structural diagram of a heating film in other embodiments of the present disclosure.

[0039] FIG10 is a schematic diagram of a curve showing the change in resistance of the heating film with temperature in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0040] The scheme of the present disclosure will be explained below in conjunction with the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present disclosure and should not be considered to limit the scope of the present disclosure. Where specific techniques or conditions are not specified in the examples, they are carried out according to the techniques or conditions described in the literature in this area or according to the product instructions. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0041] The present disclosure is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present disclosure in any way.

[0042] In one aspect of the present disclosure, the present disclosure provides a heating diaphragm. According to an embodiment of the present disclosure, the heating diaphragm has a critical temperature, and when the temperature of the heating diaphragm is lower than the critical temperature, the resistance of the heating diaphragm decreases as the temperature increases; when the temperature of the heating diaphragm is higher than the critical temperature, the resistance of the heating diaphragm increases as the temperature increases. It can be seen that the heating diaphragm of the present disclosure has the characteristic of self-limiting temperature, specifically: in the initial stage of heating (that is, when the temperature of the heating diaphragm is lower than the critical temperature), the resistance of the heating diaphragm decreases as the temperature increases, and the current increases, so that the power of the heating diaphragm increases as the temperature increases, so at this stage, the heating diaphragm can heat up rapidly; when the heating temperature of the heating diaphragm reaches the critical temperature, the resistance of the heating diaphragm increases as the temperature increases, and the current decreases, so that the power of the heating diaphragm decreases as the temperature increases, so at this stage, the heating rate of the heating diaphragm begins to slow down, and slowly gradually reaches the maximum heating temperature of the heating diaphragm. The self-limiting temperature characteristic of the above-mentioned heating diaphragm can, on the one hand, accelerate the heating rate of the temperature zone below the critical temperature, so that the heating diaphragm reaches the target temperature as soon as possible; on the other hand, when the temperature is higher than the critical temperature, it can reduce the melting problem caused by the continuous increase in the heating temperature, such as improving the reliability and stability of the heating diaphragm.

[0043] According to some embodiments of the present disclosure, when the temperature of the heating diaphragm is lower than the critical temperature, the heating rate of the heating diaphragm is a first heating rate, and when the temperature of the heating diaphragm is higher than the critical temperature, the heating rate of the heating diaphragm is a second heating rate, wherein the first heating rate is higher than the second heating rate. Thus, it can be seen that the heating diaphragm of the present disclosure has a first heating rate with a faster heating rate, which can accelerate the heating speed of the heating diaphragm, so that it reaches the critical temperature in a shorter time, and then continues to heat up at a relatively smaller second heating rate, thereby avoiding the problem of melting caused by the continuous increase in heating temperature, such as improving the reliability and stability of the heating diaphragm.

[0044] According to some embodiments of the present disclosure, the critical temperature value of the heating diaphragm is 50°C-500°C. For example, the critical temperature of the heating diaphragm can be 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 230°C, 250°C, 280°C, 300°C, 330°C, 350°C, 370°C, 400°C, 420°C, 450°C, 480°C, 500°C, etc. It can be seen that the heating diaphragm of the present disclosure can adjust the specific critical temperature value of the heating diaphragm within a wider range. If the heating temperature of the heating diaphragm is higher, a higher critical temperature value can be selected. If the heating temperature of the heating diaphragm is lower, a lower critical temperature value can be selected. In this way, the faster heating speed of the heating diaphragm and the problem of preventing melting can be better guaranteed at the same time.

[0045] In some embodiments, different heating diaphragms may have different critical temperature values. The specific size of the critical temperature value can be adjusted by adjusting factors such as the crystallinity, density, thickness, or carbon content of the heating diaphragm material. In some embodiments, the higher the crystallinity of the heating diaphragm, the lower its critical temperature; in other embodiments, the greater the density of the heating diaphragm, the lower its critical temperature; in still other embodiments, the greater the thickness of the heating diaphragm, the lower its critical temperature; in still other embodiments, the greater the carbon content of the heating diaphragm, the lower its critical temperature. Thus, in the present disclosure, the critical temperature value of the heating diaphragm can be adjusted by flexibly adjusting factors such as the density, crystallinity, or carbon content of the heating diaphragm.

[0046] According to some embodiments of the present disclosure, the time for the heating film to reach the maximum heating temperature is 0.5s to 2s, such as 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 1.1s, 1.2s, 1.3s, 1.4s, 1.5s, 1.6s, 1.7s, 1.8s, 1.9s, 2.0s, etc. It can be seen that the heating film of the present disclosure has a fast heating speed and can reach the maximum heating temperature in a shorter time, thereby greatly improving the heating efficiency of the heating film.

[0047] According to some embodiments of the present disclosure, the maximum heating temperature of the heating film is 500°C to 1700°C. For example, the maximum heating temperature of the heating film can be 500°C, 550°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, etc. It can be seen that the heating film of the present disclosure has a relatively high maximum heating temperature, even up to 1700°C, thereby meeting more application heating requirements of the heating film and obtaining heating films of various powers, such as ultra-low power heating films or ultra-high power heating films.

[0048] According to some embodiments of the present disclosure, the material of the heating diaphragm 10 is graphite. Therefore, graphite is used as the material of the carbon-based heating diaphragm. Referring to FIG1 , graphite is in a sheet-like structure, and the heating diaphragm 10 is also in a sheet-like structure. The extension plane of the sheet-like heating diaphragm 10 is basically consistent with the extension plane of the sheet-like graphite. When the heating diaphragm generates heat, the heat is mainly radiated along the vertical direction of the heating surface, with strong directivity and more concentrated radiated heat, thereby better improving the heating efficiency. Moreover, when the heating diaphragm using graphite as the material meets the above conditions, the heating diaphragm has a faster heating speed, a higher heating temperature, and a faster heating rate. In the current prior art, referring to FIG2 , the heat radiation of the heating tube 20 (such as a metal heating tube or a quartz tube) is evenly emitted in all directions, and the heat cannot be concentratedly emitted, which usually causes heat waste and reduces the heating efficiency.

[0049] According to some embodiments of the present disclosure, the weight of a heating film with a length of 1 decimeter is 0.03 to 0.1 g, such as 0.03 g, 0.04 g, 0.05 g, 0.06 g, 0.07 g, 0.08 g, 0.09 g, 0.1 g, etc. Thus, the heating film material of the present disclosure is graphite, which is relatively lightweight. This allows the heating film to have a relatively small weight, which is much smaller than the weight of heating tubes such as metal heating tubes or quartz tubes. This further contributes to the lightweight design of the heating film of the present disclosure, and further helps to obtain a relatively lightweight heating tube.

[0050] According to some embodiments of the present disclosure, the carbon content of the heating diaphragm is greater than or equal to 85%. This results in a higher carbon content, i.e., higher purity, which in turn facilitates obtaining a heating diaphragm with better performance. Furthermore, in the present disclosure, the critical temperature of the heating diaphragm can be adjusted by adjusting the carbon content to meet various adaptability requirements.

[0051] According to some embodiments of the present disclosure, the heating film satisfies at least one of the following conditions: the thickness of the heating film is 0.04 mm to 2 mm, for example, the thickness of the heating film is 0.04 mm, 0.06 mm, 0.08 mm, 0.1 mm, 0.2 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm, etc.; the density of the heating film is 0.6 g / cm 3 ~1.8g / cm 3 For example, the density of the heating film is 0.6g / cm 3 , 0.8g / cm 3 , 1.0g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm3 , 1.8g / cm 3 Etc. The heating film of the above density and thickness can meet the requirements of different power sizes for the heating film; moreover, the carbon-based heating film disclosed in the present invention has high manufacturability, that is, high production yield and long service life. In some specific embodiments of the present disclosure, the resistance characteristics of the carbon-based heating film (under constant density conditions) are: the resistance gradually decreases with increasing thickness; the greater the thickness, the closer the resistance is to 0, and the smaller the thickness, the greater the resistance. Based on this, in the present disclosure, the heating film can obtain the above-mentioned heating film of various different power sizes under the above-mentioned density and thickness conditions.

[0052] According to some embodiments of the present disclosure, the power of the heating diaphragm is 15W to 10000W, such as 15W, 20W, 40W, 50W, 70W, 100W, 150W, 300W, 500W, 800W, 1000W, 1500W, 3000W, 4500W, 5000W, 6000W, 7000W, 8000W, 9000W, 10000W, etc. Therefore, the heating diaphragm of the present disclosure can effectively realize a heating diaphragm with different powers over a large span, that is, it can realize an ultra-low power heating diaphragm, and it can also realize an ultra-high power heating diaphragm, meeting the power usage requirements of the heating diaphragm under various application conditions.

[0053] According to some embodiments of the present disclosure, the thermal diffusion coefficient of the heating film is 50m 2 / s~450m 2 / s, for example, 50m 2 / s、80m 2 / s、100m 2 / s、130m 2 / s、150m 2 / s、280m 2 / s、300m 2 / s、320m 2 / s、350m 2 / s、370m 2 / s、400m 2 / s, etc. The above thermal diffusion coefficient can transfer the heat of the heating diaphragm to the heating chamber at a more appropriate rate, so that the heat generated by the heating diaphragm is mainly concentrated on the object to be heated. In this way, a better heating rate can be guaranteed without causing the heat to be transferred out too quickly, resulting in a large heat loss. In addition, the above thermal diffusion coefficient also helps to extend the service life of the heating diaphragm and improve the manufacturability of the heating diaphragm.

[0054] In the embodiments of the present disclosure, the specific cutting shape of the heating film can be diversified. Those skilled in the art can flexibly design the cutting shape of the heating film according to the actual requirements of the resistance, power, etc. of the heating film. The following introduces some cutting shapes of the heating film based on some specific embodiments of the present disclosure:

[0055] In some embodiments of the present disclosure, referring to FIG3 , the heating film includes a plurality of heating units 01 arranged sequentially along the length direction, with adjacent heating units 01 spaced apart and connected by connecting sections 02 . Thus, the heating film of the present disclosure can be cut into a variety of different cut-out structures to meet different usage requirements. Specifically, in some embodiments of the present disclosure, referring to FIG3 , the outer peripheral wall of the heating unit is formed into an oblong or polygonal shape.

[0056] In some embodiments of the present disclosure, referring to (b), (c), and (i) in FIG3 , each heating unit 01 is provided with a hollow hole 03. Thus, the provision of the hollow hole can accelerate the heat dissipation rate of the heating membrane and accelerate the heating rate of the object to be heated.

[0057] In some embodiments of the present disclosure, referring to FIG4 , the heating diaphragm includes a first heating segment S1 and a second heating segment S2 adjacent to each other in the length direction, the first heating segment S1 includes a plurality of connected heating units 01, and the second heating segment S2 includes a plurality of adjacent heating units 10. The size of the heating unit 01 corresponding to the first heating segment S1 is smaller than the size of the heating unit 10 corresponding to the second heating segment S2. For example, in FIG4 (a), the length of the heating unit 01 corresponding to the first heating segment S1 is the same as the length of the heating unit 10 corresponding to the second heating segment S2, but the widths d1 and d2 of the two are different. For example, in FIG4 (b) and (c), the width of the heating unit 01 corresponding to the first heating segment S1 is the same as the width of the heating unit 10 corresponding to the second heating segment S2, but the lengths d1 and d2 of the two are different. This can achieve diversification of the heating diaphragm structure.

[0058] In some embodiments of the present disclosure, referring to FIG5 , the first heating segment S1 and the second heating segment S2 are staggered in the width direction of the heating diaphragm, thereby achieving a diversified structure of the heating diaphragm.

[0059] In some embodiments of the present disclosure, referring to (d), (e), (f), (h), (i), and (j) in FIG3 , the heating diaphragm includes a plurality of notches spaced apart along its length. This allows for a variety of heating diaphragm structures. Furthermore, in some embodiments of the present disclosure, referring to (i) in FIG3 , each notch is defined by separating a portion of the heating diaphragm from the rest and then bending it.

[0060] In some embodiments, as shown in FIG9 , the same heating film may include a plurality of different cut types, or include the same cut type with uneven density distribution.

[0061] In another aspect of the present disclosure, the present disclosure provides a method for preparing the aforementioned heating film. According to an embodiment of the present disclosure, the raw materials for preparing the heating film include natural graphite or graphene microsheets. Thus, the heating film prepared from natural graphite or graphene microsheets has the characteristic of self-limiting temperature. Specifically: in the initial stage of heating (i.e., when the temperature of the heating film is less than the critical temperature), the resistance of the heating film decreases with increasing temperature, and the current increases, so that the power of the heating film increases with increasing temperature, so in this stage, the heating film can heat up rapidly; when the heating temperature of the heating film reaches the critical temperature, the resistance of the heating film increases with increasing temperature, and the current decreases, so that the power of the heating film decreases with increasing temperature, so in this stage, the heating rate of the heating film begins to slow down. The above-mentioned self-limiting temperature characteristic of the heating film can enable the heating film to accelerate the heating rate of the temperature zone below the critical temperature on the one hand, so that the heating film reaches the target temperature as soon as possible, and on the other hand, when it is above the critical temperature, it can reduce the problem of melting caused by the continuous increase in heating temperature. In addition, the production cost can be effectively reduced by using natural graphite or graphene microsheets to prepare heating membranes. Natural graphite is graphite that exists in nature and does not need to be prepared, thereby reducing the preparation process and cost. The source of graphene microsheets is also relatively wide, which also helps to reduce the preparation cost of heating membranes.

[0062] The following describes in detail the method for preparing the heating film according to different preparation raw materials:

[0063] According to some embodiments of the present disclosure, a method for preparing the aforementioned heating film includes:

[0064] S110: providing natural graphite and processing the natural graphite to obtain expandable graphite.

[0065] In the present disclosure, natural graphite is used. Natural graphite ore has large reserves among the earth's minerals. At the same time, the carbon-based diaphragm material does not require high-temperature graphitization during the preparation process, does not need to be prepared by other processes, and can be produced continuously to reduce costs. Overall, the carbon-based diaphragm material has the advantages of a wide range of raw material sources, a simple preparation process, good product stability, and performance parameters that can be easily adjusted according to demand. It has huge advantages in reducing product costs, enhancing product reliability, and enriching product types. If artificial graphite is used, it is necessary to further set up a process flow for making artificial graphite, which will greatly increase the production cost and time of the heating diaphragm and reduce production efficiency; moreover, natural flake graphite can be further used. The graphite single-layer structure is a layered structure, which can make the graphite in the prepared heating diaphragm also have a layered structure, thereby improving the concentrated heating effect of the heating diaphragm.

[0066] S120: performing expansion treatment on the expandable graphite to obtain expanded graphite.

[0067] In some embodiments, upon entering the expansion furnace, expandable graphite experiences a transient high temperature, rapidly expanding to form graphite worms, also known as expanded graphite. This expansion process can achieve expansion multiples of 30 to 400 times. The expansion process occurs at a temperature of 850-1200°C and for a time of 0.7 to 1.3 seconds.

[0068] S130: The expanded graphite is rolled, subjected to a first heat treatment, and cut to obtain a heating film. The heating film is cut into a certain shape. The specific cutting shape can be seen in Figures 3, 4, and 5. The characteristics of the specific cutting shape are consistent with the requirements described above and will not be described in detail here.

[0069] In some embodiments, the critical temperature of the heating film prepared by using natural graphite is 50-200° C. Therefore, a heating film with a lower critical temperature can be prepared by the above method.

[0070] According to other embodiments of the present disclosure, a method for preparing the aforementioned heating film includes:

[0071] S210: The graphene microsheets and the additive are mixed and dispersed uniformly to obtain a dispersion.

[0072] In some embodiments, the planar size of the graphene microsheet is 1-100 μm and the specific surface area is 30-800 m 2 / g, the graphene microsheets required above are easy to disperse evenly.

[0073] In some embodiments, the additive includes at least one of carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, polyacrylic acid, and water-based polyurethane. The addition of the above additives can effectively increase the film-forming property of the graphene microsheets.

[0074] Furthermore, based on the total mass of the dispersion, the mass fraction of the additive is less than or equal to 5%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The amount of the additive is low and will not affect the good performance of the prepared heating film.

[0075] S220: Apply the dispersion to obtain a dispersion film.

[0076] In some embodiments, there are no special requirements for the specific coating method. Those skilled in the art can flexibly select an appropriate coating method according to actual needs, such as spin coating, spray coating, etc.

[0077] S230: performing a second heat treatment on the dispersion film to obtain a carbon-based primary film.

[0078] In this step, the graphene is deoxidized through a second heat treatment to produce a graphite material. The second heat treatment can be performed under vacuum or an inert atmosphere at a temperature of 1500-3000°C. This method can produce graphite with a high carbon content, for example, a carbon content exceeding 99%.

[0079] S240: The carbon-based primary film is rolled and cut to obtain the heating film. The heating film is cut into a certain shape. The specific cutting shape can be seen in Figures 3, 4 and 5. The characteristics of the specific cutting shape are consistent with the requirements described above and will not be described in detail here.

[0080] In some embodiments, the critical temperature of the heating film prepared from the graphene microsheet is 150-500° C. Therefore, a heating film with a higher critical temperature can be prepared by the above method.

[0081] According to the embodiments of the present disclosure, the above two process methods for preparing heating films are simple, the formula is adjustable, and heating films with different critical temperature values ​​can be obtained, which can meet various heating temperature requirements for heating films in turn.

[0082] In another aspect of the present disclosure, the present disclosure provides a heating tube. According to an embodiment of the present disclosure, the heating tube includes the heating film described above. As a result, the heating tube has a faster heating speed, a higher heating temperature, and a self-limiting temperature characteristic. On the one hand, the heating tube can accelerate the heating speed of the temperature zone below the critical temperature, so that the heating tube reaches the target temperature as soon as possible. On the other hand, when the temperature is higher than the critical temperature, the problem of melting caused by the continuous increase in the heating temperature can be reduced. It can be understood by those skilled in the art that the heating tube has all the features and advantages of the heating film described above, and no further details will be given here.

[0083] In some embodiments, referring to Figure 6 (the S area in the figure refers to a partial cross-sectional view of the sleeve), Figure 7 and Figure 8, the heating tube also includes a sleeve 10, and the heating membrane 20 is placed in the sleeve 10. Terminals 21 are provided at both ends of the heating membrane 20, wherein the sleeve can be a quartz glass tube or the like.

[0084] In another aspect of the present disclosure, a heating appliance is provided. According to an embodiment of the present disclosure, the heating appliance includes the aforementioned heating tube. As a result, the heating appliance heats up quickly, reaches a high temperature, and exhibits self-limiting temperature characteristics. This allows the heating appliance to heat up quickly, allowing it to reach the target temperature as quickly as possible, while also minimizing the risk of fusing during a continuous temperature increase.

[0085] According to an embodiment of the present disclosure, the heating appliance is an electric oven, a microwave oven, a steam oven, an electric kettle, an electric blanket, an electric fan heater, an electric heater, a bathroom heater, an electric ceramic stove or a disinfection cabinet.

[0086] Those skilled in the art will understand that, in addition to the above-mentioned heating tubes, the heating appliance also includes the necessary structures or components of the heating appliance. Taking the electric oven as an example, in addition to the above-mentioned heating tubes, it also includes the necessary structures or components such as the shell, heating space, base, and plug.

[0087] Example

[0088] Example 1

[0089] The heating film is made of natural graphite. The structural diagram of the heating film can be seen in Figure 3 (a). The density of the heating film is 1.5g / cm 3 The heating film has a thickness of 1mm, a length of 300mm, and a width of 8mm. The temperature, current, resistance, power, maximum heating temperature, and the time required to reach the maximum heating temperature of the heating film were tested at a voltage of 50V. The test results are shown in Table 1, and the resistance-temperature curve of the heating film can be seen in Figure 10. As can be seen from Figure 10 and Table 1, the critical temperature value of the heating film is 200℃.

[0090] Table 1

[0091] Example 2

[0092] The difference from Example 1 is that natural graphite is used to prepare the heating film. The structural schematic diagram of the heating film can be seen in Figure 3 (c). The heating film has a thickness of 0.7 mm, a length of 270 mm, and a width of 10 mm. The critical temperature, maximum heating temperature, and time required to reach the maximum heating temperature of the heating film at different densities were tested at a voltage of 50 V. The test results are shown in Table 2. As can be seen, as the density of the heating film increases, its critical temperature gradually decreases.

[0093] Table 2

[0094] Example 3

[0095] A heating film was fabricated using graphene. See Figure 3 (c) for a schematic diagram of the heating film structure. The heating film had a thickness of 0.2 mm, a length of 350 mm, and a width of 9.5 mm. The critical temperature, maximum heating temperature, and time required to reach the maximum heating temperature of the heating films with different carbon contents were tested at a voltage of 65 V. The test results are shown in Table 3. As can be seen, as the carbon content of the heating film increases, its critical temperature gradually decreases.

[0096] Table 3

[0097] Example 4

[0098] The difference from Example 1 is that natural graphite is used to prepare the heating film. The structural diagram of the heating film can be referred to (c) in Figure 3. The density of the heating film is 1.3g / cm 3 , length 420mm, width 10mm, test the critical temperature, maximum heating temperature and time required to reach the maximum heating temperature of the heating diaphragm at a voltage of 100V. The test results are shown in Table 4. It can be seen that as the thickness of the heating diaphragm increases, its critical temperature value gradually decreases.

[0099] Table 4

[0100] Example 5

[0101] The thickness of the present invention is 1.0 mm and the density is 1.2 g / cm 3 A heating film (cut as shown in (a) in Figure 3) was fabricated into a heating tube. The heating tube from Example 1 was then placed in the same oven (volume 10 L) as a halogen tube, a quartz tube, and a metal tube. All the heating tubes were tested at a power of 600 W. The time required for each heating tube to reach 200°C was measured. The test results are shown in Table 5. As can be seen from the data, the heating tube in Example 1 achieved a 48.6% higher heating rate than the quartz tube, a 46.6% higher heating rate than the metal tube, and a 31.7% higher heating rate than the halogen tube.

[0102] Table 5

[0103] Comparative Example 1

[0104] The maximum heating temperature of the quartz tube and the metal tube and the time to reach the maximum heating temperature were tested. The test results can be seen in Table 6.

[0105] Table 6

[0106] It can be seen from the above embodiments and comparative examples that the heating film of embodiment 1 of the present disclosure has a relatively high heating temperature and a rapid heating rate, and the heating film in the above embodiments does not suffer from the undesirable phenomenon of melting during the heating process.

[0107] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0108] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0109] Although the embodiments of the present disclosure have been shown and described above, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A heating film, wherein: The heating film has a critical temperature. When the temperature of the heating film is lower than the critical temperature, the resistance of the heating film decreases as the temperature increases; when the temperature of the heating film is higher than the critical temperature, the resistance of the heating film increases as the temperature increases.

2. The heating film according to claim 1, wherein: When the temperature of the heating diaphragm is lower than the critical temperature, the heating rate of the heating diaphragm is a first heating rate, and when the temperature of the heating diaphragm is higher than the critical temperature, the heating rate of the heating diaphragm is a second heating rate, wherein the first heating rate is higher than the second heating rate.

3. The heating film according to claim 1 or 2, wherein: The critical temperature value of the heating film is 50°C-500°C.

4. The heating film according to any one of claims 1 to 3, wherein: The time for the heating film to reach the highest heating temperature is 0.5s to 2s.

5. The heating film according to claim 4, wherein: The maximum heating temperature of the heating film is 500°C to 1700°C.

6. The heating film according to any one of claims 1 to 5, wherein: The material of the heating film is graphite.

7. The heating film according to any one of claims 1 to 6, wherein: The heating film is in sheet shape.

8. The heating film according to any one of claims 1 to 7, wherein: The heating film satisfies at least one of the following conditions: The thickness of the heating film is 0.04 mm to 2 mm; The density of the heating film is 0.6 g / cm 3 ~1.8g / cm 3 .

9. The heating film according to any one of claims 1 to 8, wherein: The weight of the heating film with a length of 1 decimeter is 0.03 to 0.1 g.

10. The heating film according to any one of claims 1 to 9, wherein: The thermal diffusion coefficient of the heating film is 50m 2 / s~450m 2 / s.

11. The heating film according to any one of claims 1 to 10, wherein: The power of the heating film is 15W-10000W.

12. The heating film according to any one of claims 1 to 11, wherein: The heating film comprises a plurality of heating units sequentially arranged along the length direction, and adjacent heating units are arranged at intervals and connected via a connecting section.

13. The heating film according to claim 12, wherein: Each of the heating units is provided with a hollow hole.

14. A method for preparing the heating film according to any one of claims 1 to 13, wherein: The raw materials for preparing the heating film include natural graphite or graphene microsheets.

15. The method according to claim 14, wherein: include: Providing the natural graphite, and treating it to obtain expandable graphite; Performing an expansion treatment on the expandable graphite to obtain expanded graphite; The expanded graphite is subjected to rolling, a first heat treatment, and cutting to obtain the heating film.

16. The method according to claim 14 or 15, wherein: The critical temperature of the heating film is 50-200°C.

17. The method according to any one of claims 14 to 16, wherein: include: Mixing and dispersing the graphene microsheets and additives uniformly to obtain a dispersion; Applying the dispersion to obtain a dispersion film; Performing a second heat treatment on the dispersion film to obtain a carbon-based primary film; The carbon-based primary film is rolled and cut to obtain the heating film.

18. The method according to any one of claims 14 to 17, wherein: The critical temperature of the heating film is 150-500°C.

19. The method according to claim 17 or 18, wherein: The additive comprises at least one of carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, polyacrylic acid and waterborne polyurethane, Based on the total mass of the dispersion, the mass fraction of the additive is less than or equal to 5% by mass.

20. A heat pipe, wherein: The invention comprises the heating film sheet according to any one of claims 1 to 13.

21. A heating appliance, wherein: Comprising the heating tube as claimed in claim 20.

22. The heating appliance according to claim 21, wherein: The heating appliance is an electric oven, a microwave oven, a steam oven, an electric kettle, an electric blanket, an electric fan, an electric heater, a bathroom heater, an electric ceramic stove or a disinfection cabinet.

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