Flexible far-infrared self-temperature-limiting composite electric heating material

Abstract

The invention discloses a flexible far infrared temperature self-limiting composite electric heating material, which comprises a flexible base material and far infrared temperature self-limiting conductive slurry coated on the flexible base material, the far-infrared self-temperature-limiting conductive slurry is prepared by mixing a far-infrared self-temperature-limiting conductive mixture, conductive polymer resin and a dispersing agent into purified water to form a solution, and heating and homogenizing the solution. The flexible far-infrared self-temperature-limiting composite electric heating material disclosed by the invention is wide in application range, low in production cost and high in heat transfer efficiency, is an advanced energy-saving material, and is free of hard texture, good in flexibility and resistant to folding; and the self-temperature-limiting function is achieved, and harm to the human body due to overheating can be avoided in the using process.

Description

Technical Field

[0001] This invention relates to a composite electrothermal material, specifically a flexible far-infrared self-limiting temperature composite electrothermal material. Background Technology

[0002] Far-infrared electric heating technology emerged in the mid-20th century. It utilizes radiative heat transfer and transmits energy via electromagnetic waves, making it a key energy-saving technology that is being promoted. When the wavelength of far-infrared rays matches the absorption wavelength of the object being heated, the object absorbs a large amount of far-infrared rays. At this time, the molecules and atoms inside the object resonate and generate strong vibrations, causing the temperature of the object to rise, thus achieving the purpose of heating.

[0003] With the improvement of people's living standards, the application scenarios of far-infrared technology have been further expanded, and it is widely used in infrared physiotherapy, building heating, food drying, sterilization, wearable devices, automotive heating, and home appliances. Especially in the fields of infrared physiotherapy, wearable devices, automotive heating, and home appliances, the flexibility of the heating element is highly demanding. Currently, the membrane materials using thermoplastic polymers mainly have the following problems: 1) uneven heating, large temperature differences, and poor user experience; 2) poor flexibility and impact resistance; 3) short lifespan, generally not exceeding 30,000 hours. Furthermore, current far-infrared heating materials require additional temperature control during operation. However, if the temperature sensor deviates or more than two heating areas are present, the temperature will become excessively high, not only affecting the user experience but also potentially causing burns due to excessive heat buildup.

[0004] Chinese Patent Publication No. CN111462941A discloses a carbon nanotube composite flexible conductive film and its method. The carbon nanotube composite flexible conductive film comprises: at least two carbon nanotube layers; and a composite material layer disposed between adjacent carbon nanotube layers, wherein the composite material layer comprises metal nanowires and graphene oxide. The resulting carbon nanotube composite flexible conductive film has a sheet resistance of 1-50 ohm / sq, and its sheet resistance change rate is less than 8%. This solution addresses the flexibility issue of heating materials, but its manufacturing process is complex, resulting in poor stability of the prepared flexible conductive film. More importantly, its conductive pathways utilize metal nanowires and graphene oxide, with graphene oxide particle sizes ranging from 1 to 100 micrometers. These conductive pathways rely on tightly packed graphene particles, and during use, rubbing, bending, or applying heavy pressure to different areas can cause graphene oxide to detach, damaging the conductive pathways and affecting heating. Furthermore, under prolonged heating conditions, the number of contacts between graphene oxide particles in the conductive pathways decreases, leading to increased resistance. This can result in either failing to reach the normal operating temperature or, in severe cases, "loose connections" in the conductive pathways, generating electrical sparks that can break down the flexible conductive film, creating safety hazards.

[0005] In view of the above problems, the present invention discloses a flexible far-infrared self-regulating composite electrothermal material. It has the technical features described below to solve the existing problems. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a flexible far-infrared self-limiting temperature composite electrothermal material, the entire surface of which is a heating surface, with uniform heating, small surface temperature difference, good softness and toughness, and self-limiting temperature protection function. When applied to wearable devices, it has no obvious hard feel and no sound. Its heat is mainly radiated in the form of far-infrared rays, which has a physiotherapy effect.

[0007] The flexible far-infrared self-regulating composite electrothermal material of the present invention is achieved through the following technical solution:

[0008] A flexible far-infrared self-regulating composite electrothermal material, wherein: the electrothermal material comprises: a flexible matrix material and a far-infrared self-regulating conductive paste coated on the flexible matrix material, wherein the far-infrared self-regulating conductive paste is obtained by mixing a far-infrared self-regulating conductive mixture, a conductive polymer resin and a dispersant into pure water to form a solution, which is then heated and homogenized.

[0009] The aforementioned flexible far-infrared self-limiting temperature composite electrothermal material, wherein the flexible substrate material is selected from either fabric or flexible film, wherein the fabric is selected from either glass fiber fabric, polyester fiber fabric, polyamide fiber fabric, polyvinyl alcohol acetal fiber fabric, polypropylene fiber fabric, polyvinyl chloride fiber or polyurethane fiber, and the flexible film is selected from either polyimide film, polyethylene terephthalate film, polyethylene film, polypropylene film, polycarbonate film or polyvinylidene fluoride film.

[0010] In the aforementioned flexible far-infrared self-regulating composite electrothermal material, the fabric has a fixed weight of 20-60 g / m³. 2 The thickness of the flexible film is 15-100 μm.

[0011] In the aforementioned flexible far-infrared self-regulating composite electrothermal material, the mass percentages of the far-infrared self-regulating conductive mixture, conductive polymer resin, and dispersant in the far-infrared self-regulating conductive slurry are as follows: far-infrared self-regulating conductive mixture 75%-90%, conductive polymer resin 7%-14%, and dispersant 1%-3%.

[0012] The aforementioned flexible far-infrared self-regulating composite electrothermal material comprises, wherein, the far-infrared self-regulating conductive mixture is added to a pure aqueous solution containing a dispersant at a constant temperature of 40-85°C, and homogenized for 15-30 minutes to form a far-infrared self-regulating conductive mixture solution; the far-infrared self-regulating conductive mixture solution is then heated to 50-90°C and kept at a constant temperature; conductive polymer resin is added, and homogenized for 30-60 minutes to form a far-infrared self-regulating conductive slurry; the concentration of the far-infrared self-regulating conductive slurry is 45%-75%.

[0013] The aforementioned flexible far-infrared self-regulating composite electric heating material, wherein the far-infrared self-regulating conductive mixture is formed by air-jet pulverization and mixing of far-infrared conductive mixture and self-regulating polymer at a mass percentage of 90%-95%: 5%-10%.

[0014] The aforementioned flexible far-infrared self-limiting temperature composite electrothermal material is wherein the far-infrared conductive mixed material is composed of 55%-75% carbon fiber, 10%-20% graphite, 14%-22% conductive carbon black, and 1%-3% graphene by mass percentage through airflow pulverization.

[0015] In the aforementioned flexible far-infrared self-limiting temperature composite electrothermal material, the carbon fiber is chopped carbon fiber, which is composed of polyacrylonitrile carbon fibers with lengths of 0.5mm, 1mm and 2mm, and the mass percentage of the chopped carbon fibers with lengths of 0.5mm, 1mm and 2mm is 40%-60%: 30%-40%: 10%-20%.

[0016] The aforementioned flexible far-infrared self-regulating composite electrothermal material, wherein the self-regulating polymer is one or a combination of polyethylene glycol, polypropylene, polyethylene, and polyvinylidene fluoride, and the self-regulating polymer is in powder form with a particle size of 10-25 μm.

[0017] In the aforementioned flexible far-infrared self-limiting temperature composite electrothermal material, the graphite is artificial graphite or natural graphite with a particle size of 10-30 μm, and the conductive carbon black has a particle size of 2-20 μm.

[0018] In the aforementioned flexible far-infrared self-limiting temperature composite electrothermal material, the graphene is graphene oxide.

[0019] In the aforementioned flexible far-infrared self-limiting temperature composite electrothermal material, the conductive polymer resin is one of waterborne polyurethane resin, waterborne acrylic resin, waterborne epoxy resin, or waterborne polyester resin.

[0020] In the aforementioned flexible far-infrared self-limiting temperature composite electrothermal material, the dispersant is one or a combination of sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

[0021] In the aforementioned flexible far-infrared self-regulating composite electrothermal material, the far-infrared self-regulating conductive paste is uniformly coated onto a flexible substrate material using a coating machine. The far-infrared self-regulating conductive paste is coated 2-3 times onto the flexible substrate material, with each coating weighing 5-20 g / m³. 2 After each coating is completed, drying is carried out using a heated roller with a rotation speed of 1-4 m / min and a drying temperature of 70-110℃.

[0022] The flexible far-infrared self-limiting temperature composite electrothermal material of this invention, due to the adoption of the above-mentioned solution, has the following advantages and positive effects compared with the prior art:

[0023] 1) The flexible far-infrared self-limiting temperature composite electrothermal material of the present invention has a wide range of applications and can be widely used in heating fields such as wearable devices, clothing, home furnishings, chairs, decorative walls, physiotherapy equipment, automobiles, and special equipment. It has low production costs and broad application prospects.

[0024] 2) The flexible far-infrared self-limiting temperature composite electrothermal material of the present invention has a wide applicable voltage range and can be designed within the AC / DC range of 3.85-220V according to actual needs, which can meet the needs of most application scenarios.

[0025] 3) The flexible far-infrared self-limiting temperature composite electrothermal material of the present invention has a heating surface on the entire surface, and the heat transfer is mainly through far-infrared radiation. The electrothermal conversion efficiency can reach 99%, and the electro-thermal radiation conversion efficiency can reach 50%. It has high heat transfer efficiency and is an advanced energy-saving material, saving at least 25% energy compared with existing materials.

[0026] 4) The flexible far-infrared self-limiting temperature composite electric heating material of the present invention has no hard texture, good softness, and is resistant to folding;

[0027] 5) The heating element of the flexible far-infrared self-limiting composite electrothermal material of this invention is a conductive network constructed from short-cut carbon fibers. Its conductive pathways are physically structured using short carbon fibers, exhibiting structural stability. Testing by the National Infrared Center has shown that its service life can reach over 100,000 hours. During use, it will not experience graphene oxide shedding due to rubbing, bending, or heavy pressure on different areas, thus preventing damage to the conductive pathways and affecting heating. Nor will it suffer from increased resistance due to a reduction in the number of contacts in the conductive pathways, leading to "loose connections" and electrical sparks that could damage the flexible conductive film and create safety hazards.

[0028] 6) The flexible far-infrared self-regulating composite electric heating material of the present invention has a self-regulating function, which can avoid harm to the human body due to overheating during use, and is also energy-saving and environmentally friendly.

[0029] A new type of material. Specific Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] A flexible far-infrared self-regulating composite electrothermal material, comprising: a flexible substrate material and a far-infrared self-regulating conductive slurry coated on the flexible substrate material, wherein the far-infrared self-regulating conductive slurry is obtained by mixing a far-infrared self-regulating conductive mixture, a conductive polymer resin and a dispersant into pure water to form a solution, which is then heated and homogenized.

[0032] The flexible substrate material is selected from either fabric or flexible film. The fabric is selected from either glass fiber fabric, polyester fiber fabric, polyamide fiber fabric, polyvinyl alcohol acetal fiber fabric, polypropylene fiber fabric, polyvinyl chloride fiber or polyurethane fiber. The flexible film is selected from either polyimide film, polyethylene terephthalate film, polyethylene film, polypropylene film, polycarbonate film or polyvinylidene fluoride film.

[0033] The fabric has a fixed weight of 20-60 g / m². 2 The thickness of the flexible film is 15-100 μm. The mass percentages of the far-infrared self-regulating conductive mixture, conductive polymer resin, and dispersant in the far-infrared self-regulating conductive slurry are: far-infrared self-regulating conductive mixture 75%-90%, conductive polymer resin 7%-14%, and dispersant 1%-3%. The far-infrared self-regulating conductive mixture is added to a pure aqueous solution containing the dispersant at a constant temperature of 40-85°C, and homogenized for 15-30 minutes to form a far-infrared self-regulating conductive mixture solution. This solution is then heated to 50-90°C and held at that temperature. After adding the conductive polymer resin, it is homogenized for 30-60 minutes to form the far-infrared self-regulating conductive slurry, with a concentration of 45%-75%.

[0034] The far-infrared self-regulating conductive mixture is made by air-jet pulverizing and mixing far-infrared conductive mixture material and self-regulating polymer at a mass percentage of 90%-95%: 5%-10%.

[0035] The far-infrared conductive composite material is composed of 55%-75% carbon fiber, 10%-20% graphite, 14%-22% conductive carbon black, and 1%-3% graphene by mass percentage, which are mixed by air-jet milling.

[0036] The carbon fiber is short-cut carbon fiber, composed of polyacrylonitrile-based carbon fibers with lengths of 0.5mm, 1mm, and 2mm, with a mass percentage of 40%-60%, 30%-40%, and 10%-20% for each length. The conductive path of the flexible far-infrared self-regulating composite electrothermal material conforms to the "conductive channel" theory. The 2mm short-cut carbon fibers in the flexible far-infrared self-regulating composite electrothermal material directly contact to form the main conductive network. The 1mm and 0.5mm short-cut carbon fibers supplement the main conductive network formed by the direct contact of the 2mm short-cut carbon fibers, forming a tight main conductive network composed of short-cut carbon fibers. The main conductive network is built by the direct contact of the short-cut carbon fibers, resulting in a stable network structure and preventing problems such as a decrease in the number of contacts due to continuous heating.

[0037] The self-regulating polymer is one or a combination of polyethylene glycol, polypropylene, polyethylene, and polyvinylidene fluoride. The self-regulating polymer is in powder form with a particle size of 10-25 μm. The flexible far-infrared self-regulating composite electrothermal material utilizes the "tunneling effect" of the self-regulating polymer composite conductive channels: conductivity is formed by a conductive network, but not through direct contact between conductive particles; rather, it is caused by the migration of electrons between conductive particles due to thermal vibration. The tunneling effect only occurs between very close filler aggregates; there is no conductive behavior between aggregates with large gaps. The tunneling effect assumes a close relationship between conductivity and temperature; thermal excitation voltage increases conductivity. Initially, conductive particles form conductive chains in the polymer. As the temperature rises, the polymer matrix expands. Due to the different expansion rates of the matrix and the conductive chains, the conductive chains are gradually separated, increasing resistance. At the melting point, the polymer volume suddenly increases, the conductive chains are destroyed, and the resistance also suddenly increases, i.e., the composite system exhibits the PTC phenomenon. Therefore, flexible far-infrared self-regulating composite electrothermal materials achieve self-regulating purpose by adjusting the number of contacts and the size of gaps between particles of short-cut carbon fiber and graphene mixture through the volume expansion of the self-regulating polymer.

[0038] In far-infrared conductive composite materials, the graphite used is artificial or natural graphite with a particle size of 10-30 μm, the conductive carbon black has a particle size of 2-20 μm, and the graphene is graphene oxide. The combination of graphite, conductive carbon black, and graphene in flexible far-infrared self-limiting composite electrothermal materials conforms to the "conductive channel" theory—conductivity only occurs when a complete, continuous conductive network is formed, i.e., when the gaps between conductive particles are very small. For a dense main channel conductive network composed of chopped carbon fibers, the main factors affecting its conductivity σ include the number of contacts, contact resistance, and gap size. Therefore, by supplementing the dense main channel conductive network composed of chopped carbon fibers with graphite, conductive carbon black, and graphene, the gaps in the main channel conductive network are filled, maximizing the number of contacts and the gap size of the conductive network channels, thereby improving conductivity.

[0039] The conductive polymer resin in the far-infrared self-regulating conductive slurry is one of waterborne polyurethane resin, waterborne acrylic resin, waterborne epoxy resin, or waterborne polyester resin. The dispersant is one or a combination of sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

[0040] In the production of far-infrared self-regulating conductive materials, a far-infrared self-regulating conductive slurry is uniformly coated onto a flexible substrate material using a coating machine. The far-infrared self-regulating conductive slurry is coated onto the flexible substrate material 2-3 times, with each coating weighing 5-20 g / m³. 2 After each coating is completed, drying is carried out using a heated roller with a rotation speed of 1-4 m / min and a drying temperature of 70-110℃.

[0041] The optimal method involves multiple coatings of the far-infrared self-regulating conductive paste onto the flexible substrate material. This avoids the uneven coating caused by a single coating and prevents issues such as the absence of far-infrared self-regulating conductive paste after the air bubbles generated on the flexible substrate material during the coating process are dried. This ensures that the far-infrared self-regulating conductive paste is evenly distributed on the flexible substrate material, guaranteeing uniform surface temperature, small surface temperature difference, and complete conductive pathways during the operation of the far-infrared self-regulating composite electrothermal material.

[0042] The flexible far-infrared self-limiting temperature composite electrothermal material of the present invention has a wide range of applications, low production cost, safety, high efficiency, energy saving and environmental protection.

[0043] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating orientation or positional relationships are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0044] Furthermore, 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0045] In summary, the above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A flexible far-infrared self-regulating composite electrothermal material, characterized in that: The electrothermal material includes: a flexible substrate material and a far-infrared self-regulating conductive paste coated on the flexible substrate material. The far-infrared self-regulating conductive paste is obtained by mixing a far-infrared self-regulating conductive mixture, a conductive polymer resin and a dispersant into pure water to form a solution, which is then heated and homogenized.

2. The flexible far-infrared self-regulating composite electrothermal material according to claim 1, characterized in that, The flexible substrate material is selected from either fabric or flexible film. The fabric is selected from either glass fiber fabric, polyester fiber fabric, polyamide fiber fabric, polyvinyl alcohol acetal fiber fabric, polypropylene fiber fabric, polyvinyl chloride fiber, or polyurethane fiber. The flexible film is selected from either polyimide film, polyethylene terephthalate film, polyethylene film, polypropylene film, polycarbonate film, or polyvinylidene fluoride film.

3. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 2, characterized in that, The fabric has a fixed weight of 20-60 g / m². 2 The thickness of the flexible film is 15-100 μm.

4. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 1, characterized in that, The mass percentages of the far-infrared self-regulating conductive mixture, conductive polymer resin, and dispersant in the far-infrared self-regulating conductive slurry are as follows: far-infrared self-regulating conductive mixture 75%-90%, conductive polymer resin 7%-14%, and dispersant 1%-3%.

5. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 4, characterized in that, The far-infrared self-regulating conductive mixture is added to a pure aqueous solution containing a dispersant at a constant temperature of 40-85℃. After homogenization for 15-30 minutes, a far-infrared self-regulating conductive mixture solution is formed. The far-infrared self-regulating conductive mixture solution is then heated to 50-90℃ and kept at a constant temperature. After adding a conductive polymer resin, it is homogenized for 30-60 minutes to form a far-infrared self-regulating conductive slurry. The concentration of the far-infrared self-regulating conductive slurry is 45%-75%.

6. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 5, characterized in that, The far-infrared self-regulating conductive mixture is made by air-jet pulverizing and mixing far-infrared conductive mixture material and self-regulating polymer at a mass percentage of 90%-95%: 5%-10%.

7. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 6, characterized in that, The far-infrared conductive composite material is composed of 55%-75% carbon fiber, 10%-20% graphite, 14%-22% conductive carbon black, and 1%-3% graphene by mass percentage, which are mixed by air-jet milling.

8. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 7, characterized in that, The carbon fiber is chopped carbon fiber, which is composed of polyacrylonitrile carbon fibers with lengths of 0.5 mm, 1 mm and 2 mm, and the mass percentage of the chopped carbon fibers with lengths of 0.5 mm, 1 mm and 2 mm is 40%-60%: 30%-40%: 10%-20%.

9. A flexible far-infrared self-regulating composite electrothermal material according to claim 6, characterized in that, The self-regulating polymer is one or a combination of polyethylene glycol, polypropylene, polyethylene, and polyvinylidene fluoride. The self-regulating polymer is in powder form with a particle size of 10-25 μm.

10. A flexible far-infrared self-regulating composite electrothermal material according to claim 7, characterized in that, The graphite used is artificial graphite or natural graphite with a particle size of 10-30 μm, and the conductive carbon black has a particle size of 2-20 μm.

11. The flexible far-infrared self-regulating composite electrothermal material according to claim 7, characterized in that, The graphene mentioned is graphene oxide.

12. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 4, characterized in that, The conductive polymer resin is one of waterborne polyurethane resin, waterborne acrylic resin, waterborne epoxy resin, or waterborne polyester resin.

13. The flexible far-infrared self-limiting temperature composite electrothermal material according to claim 4, characterized in that, The dispersant is one or a combination of sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate.

14. The flexible far-infrared self-regulating composite electrothermal material according to claim 5, characterized in that, The far-infrared self-regulating conductive paste is uniformly coated onto a flexible substrate material using a coating machine. The far-infrared self-regulating conductive paste is coated 2-3 times onto the flexible substrate material, with each coating weighing 5-20 g / m³. 2 After each coating is completed, drying is carried out using a heated roller with a rotation speed of 1-4 m / min and a drying temperature of 70-110℃.