Method for manufacturing carbon fiber-based surface heater having uniform heating characteristics, and surface heater manufactured thereby

Abstract

The present invention provides a method for manufacturing a planar heating element and a planar heating element manufactured thereby, comprising the steps of: preparing a nonwoven film by mixing and molding carbon fibers and heat-resistant polymer fibers; preparing a coating solution by mixing conductive ceramic powder into a polymer solution; applying the coating solution to the nonwoven film; and drying and heat-pressing the nonwoven film coated with the coating solution. The planar heating element not only has excellent heating efficiency but also possesses uniform heating characteristics throughout the entire heating element.

Description

Technology Field

[0001] The present invention relates to a carbon fiber-based heating element manufacturing technology, and more specifically, to a carbon fiber-based planar heating element manufacturing technology with improved heating efficiency and uniform heating characteristics. Background Technology

[0002] Conventional carbon fiber heating heaters are primarily manufactured by using short carbon fibers, a thickener and binder resin for even dispersion in water, filtering the mixture to produce a carbon fiber nonwoven fabric, and then drying and pressing it.

[0003] Conventional heating elements are primarily manufactured using a high content of carbon fiber, and deformation of the binder resin occurs when heating at high temperatures, leading to continuous deformation of the heating element. This results in changes in the resistance value of the heating element and can consequently lead to a degradation of the heating element's performance.

[0004] Meanwhile, conventional carbon fiber-based heating elements have the disadvantage of significantly reduced heating uniformity because they use short carbon fibers, so the binder resin is mixed only in a part of the carbon fiber. Prior art literature

[0005] Korean Registered Patent No. 10-1028843 (2011.04.05) (Carbon fiber planar heating element and method of manufacturing the same) The problem to be solved

[0006] The present invention is an invention sought to overcome the disadvantages of conventional carbon fiber-based heating elements as described above, and aims to provide a method for manufacturing a carbon fiber-based planar heating element capable of exhibiting not only heating efficiency but also uniform heating characteristics across the entire surface of the heating element.

[0007] In addition, the present invention aims to provide a carbon fiber-based planar heating element manufactured by the above-described manufacturing method, which minimizes changes in resistance by minimizing shape deformation at high temperatures and further possesses uniform heating characteristics. means of solving the problem

[0009] A method for manufacturing a carbon fiber-based planar heating element according to one embodiment of the present invention comprises the steps of: preparing a nonwoven film by mixing and molding carbon fibers and heat-resistant polymer fibers; preparing a coating solution by mixing conductive ceramic powder into a polymer solution; applying the coating solution to the nonwoven film; and drying and heat-pressing the nonwoven film coated with the coating solution.

[0010] The above heat-resistant polymer fiber may be composed of a polymer having a glass transition temperature of 140°C or higher.

[0011] The heat-resistant polymer fiber may include at least one polymer fiber among polycarbonate fiber or polyamide fiber.

[0012] The above coating solution may include a colliccarbonate solution as a polymer solution and may include alumina powder or basalt heat-treated powder, which is obtained by heat-treating basalt and then cooling it to powder, as a conductive ceramic powder.

[0013] The step of preparing the above nonwoven film may include: a step of mixing and dispersing carbon fibers and heat-resistant polymer fibers by introducing them into an aqueous solution containing a thickener; a step of preparing a nonwoven fabric by placing them in a molding die, filtering, and drying; and a step of heat-pressing the molded and dried nonwoven fabric.

[0014] A carbon fiber-based planar heating element according to one embodiment of the present invention comprises: a nonwoven fabric on a film comprising carbon fibers and polymer fibers; and a coating layer formed by coating the nonwoven fabric on the film with a coating solution comprising a polymer and conductive ceramic powder.

[0015] The above polymer fiber comprises at least one of polycarbonate fibers or polyamide fibers, and the above ceramic powder may comprise alumina or basalt heat-treated powder obtained by heat-treating basalt and then cooling it to powder. Effects of the invention

[0016] According to the method for manufacturing a carbon fiber-based planar heating element according to the present invention, a carbon fiber-based planar heating element can be manufactured that exhibits not only heating efficiency but also uniform heating characteristics across the entire surface of the heating element.

[0017] The manufactured carbon fiber-based planar heating element does not undergo a change in resistance value due to thermal deformation even in a heating environment of 130°C or higher, so it can provide a stable carbon heater even in a high-temperature environment. Brief explanation of the drawing

[0019] FIG. 1 is a flowchart conceptually illustrating a method for manufacturing a carbon fiber-based planar heating element according to one embodiment of the present invention. Figure 2 is a flowchart conceptually explaining a method for manufacturing heat-treated powder derived from basalt included in a coating solution. Figure 3 is a photograph showing the heating characteristics of a carbon fiber-based planar heating element according to one embodiment of the present invention. Specific details for implementing the invention

[0020] Hereinafter, a method for manufacturing a carbon fiber-based planar heating element according to an embodiment of the present invention and a planar heating element manufactured thereby will be described in detail with reference to the attached drawings. However, the following descriptions are exemplary descriptions intended to explain the embodied aspects of the technical concept of the present invention, and the technical concept of the present invention is not limited by the following descriptions. The technical concept of the present invention can only be interpreted and limited by the claims set forth below.

[0021] FIG. 1 is a flowchart conceptually illustrating a method for manufacturing a carbon fiber-based planar heating element according to one embodiment of the present invention.

[0022] Referring to FIG. 1, a method for manufacturing a carbon fiber-based planar heating element (S100) includes a nonwoven film preparation step (S110), a coating solution preparation step (S120), a coating step (S130), and a drying and heat pressing step (S140).

[0023] In this embodiment, the nonwoven film preparation step (S110) comprises: a step of mixing and dispersing carbon fibers and heat-resistant polymer fibers by introducing them into an aqueous solution containing a thickener; a step of preparing a nonwoven fabric by placing them in a molding die, filtering, and drying; and a step of heat-pressing the molded and dried nonwoven fabric.

[0024] It is preferable to use the heat-resistant polymer fiber in an amount of 20 to 50 weight percent relative to the total weight of the fiber. The heat-resistant polymer fiber is composed of a polymer having a glass transition temperature of 140°C or higher. Polycarbonate fibers or polyamide fibers may be used as the heat-resistant polymer fiber, and the fibers may be used alone or in combination.

[0025] Meanwhile, the carbon fibers and heat-resistant polymer fibers used have a length of approximately several millimeters. In addition, xanthan gum, etc., can be used as the thickener.

[0026] In the above coating solution preparation step (S120), a coating solution is prepared by mixing ceramic powder into a polymer solution. In this embodiment, for the polymer, for example, a solution in which polycarbonate is dissolved in acetone is used. As the ceramic powder mixed into the polymer solution, alumina powder or heat-treated basalt powder may be used.

[0027] The following describes the method for manufacturing heat-treated basalt powder.

[0028] Figure 2 is a flowchart conceptually explaining a method for manufacturing heat-treated powder derived from basalt included in a coating solution.

[0029] Referring to FIG. 2, in order to perform the method (S200) for manufacturing heat-treated powder derived from basalt, a basalt preparation and washing step (S210) is first performed to prepare and wash basalt. The basalt sample is a commercially available sample, and there are no specific restrictions on its shape. However, it is preferable not to purchase a basalt sample in powdered form to control the particle size in the subsequent crushing step. Washing is a measure to preemptively remove impurities present on the surface of the basalt so that they cannot act as factors that change the temperature in the subsequent melting step. Methods such as those utilizing differences in specific gravity may be used for removing the impurities.

[0030] After the basalt is washed and dried, a basalt crushing step (S220) is performed. Through the crushing step (S3220), crushed basalt is prepared, and it is desirable that the crushing be carried out so that the average particle size of the crushed material particles is maintained at approximately 0.01 mm to 0.05 mm. For melting efficiency, it is advantageous to crush the basalt more finely, but if the average particle size of the crushed particles is less than 0.01 mm, melting occurs too rapidly, making it difficult to achieve the full characteristics due to abnormal heat treatment. In the basalt crushing step (S220), foreign substances contained within the basalt and crushed are separated by various methods. This is because foreign substances can cause abnormal melting temperature in the melting step (S230) described later.

[0031] When the crushed basalt is prepared, a low-temperature melting step (S230) is performed to heat and melt the crushed basalt. The crushed basalt must be melted in a relatively low-temperature environment of 800 to 1000°C, rather than at a temperature of 1400°C or higher, which is the normal complete melting temperature, and by melting at the above temperature, the physical properties required as exothermic particles can be achieved. Meanwhile, during the process of performing the melting step (S230), sulfur or an acidic solution may be added.

[0032] When the low-temperature melting step (S230) is completed, a cooling step (S240) for cooling the molten material is performed. The cooling is carried out sufficiently at room temperature. When the cooling step (S240) is completed, a pulverization step (S250) for pulverizing the cooled molten material is performed, thereby preparing a basalt-derived heat-treated powder according to one embodiment of the present invention.

[0033] The above basalt-derived heat-treated powder may be variably configured such that the composition of the heat-treated powder has the following composition, depending on detailed melting temperature conditions or whether additives are added. Test results (Korea Institute of Materials Science) confirmed that the heat-treated powder contains 100 parts by weight of SiO2; 25 to 32 parts by weight of Al2O3; 18 to 22 parts by weight of CaO; 18 to 22 parts by weight of MgO; 18 to 22 parts by weight of Fe2O3; and metallic components such as Ti, Y, La, Ce, and Nd.

[0034] Table 1 below is a table illustrating the composition of the heat-treated powder above.

[0035] SiO2 Al2O3 CaO MgO Fe2O3 Ti Y La Ca Nd bal 15.33 10.19 10.07 10.18 1.19 0.0043 0.0095 0.0131 0.0071

[0036] Once the coating solution is prepared as described above, a coating step (S130) is performed to apply the coating solution to the prepared nonwoven film. The method of application can be varied; for example, a method of evenly applying the coating solution to the nonwoven film can be used.

[0037] When the coating step (S130) is completed, the drying and heat pressing step (S140) is performed. A coating layer is formed on the nonwoven film by drying the coated coating solution. Subsequently, a planar heating element can be manufactured through heat pressing. The heat pressing is performed by applying pressure with a hot press heated to 240°C to 260°C.

[0038] A carbon fiber-based planar heating element manufactured by the above method comprises, consequently, a nonwoven fabric on a film comprising carbon fibers and polymer fibers; and a coating layer formed by coating the nonwoven fabric on the film with a coating solution comprising polymer and conductive ceramic powder.

[0039] The following describes in detail the manufacturing method of a carbon fiber-based planar heating element.

[0040] [Example]

[0041] Example 1

[0042] 1.5g of carbon fiber with a length of 3mm and polycarbonate fiber with a length of 3mm were placed in 3L of an aqueous solution containing xanthan gum, a thickening agent, and mixed and dispersed using a mechanical stirrer for 10 minutes. The mixture was then placed into a 20cm x 20cm mold, filtered, dried, and then compressed using a hot press at room temperature. Additionally, 10g of polycarbonate was dissolved in 50g of acetone, and 40g of alumina powder was mixed into the solution to create a solution. A portion of this mixed solution was evenly applied to a carbon fiber-polycarbonate fiber nonwoven film prepared by the above method, dried, placed into a hot press, and pressed with a hot press heated to 250℃ to produce a planar heating element.

[0043] Comparative Example 1

[0044] 2g of carbon fiber with a length of 3mm was placed in 3L of a 5% aqueous solution of PVA containing xanthan gum, a thickening agent, and mixed and dispersed for 10 minutes using a mechanical stirrer. The mixture was then placed into a 20cm x 20cm mold, filtered, dried, and then compressed using a hot press to produce a carbon fiber heating element.

[0045] [Evaluation of Heat Generation Characteristics]

[0046] Figure 3 is a photograph showing the heating characteristics of a carbon fiber-based planar heating element according to one embodiment of the present invention.

[0047] Referring to FIG. 3, it can be seen that the planar heating element manufactured in Example 1 exhibits significantly more uniform heating characteristics compared to the planar heating element manufactured in Comparative Example 1.

Claims

Claim 1 A method for manufacturing a carbon fiber-based planar heating element, comprising the steps of: preparing a nonwoven film by mixing and molding carbon fibers and heat-resistant polymer fibers; preparing a coating solution by mixing conductive ceramic powder into a polymer solution; applying the coating solution to the nonwoven film; and drying and heat-pressing the nonwoven film coated with the coating solution, wherein the coating solution comprises a polycarbonate solution as the polymer solution and alumina powder or basalt heat-treated powder obtained by heat-treating basalt and then cooling it to powder as the conductive ceramic powder. Claim 2 A method for manufacturing a carbon fiber-based planar heating element, characterized in that, in claim 1, the heat-resistant polymer fiber is composed of a polymer having a glass transition temperature of 140°C or higher. Claim 3 A method for manufacturing a carbon fiber-based planar heating element according to claim 1, characterized in that the heat-resistant polymer fiber comprises at least one polymer fiber among polycarbonate fiber or polyamide fiber. Claim 4 delete Claim 5 A method for manufacturing a carbon fiber-based planar heating element according to claim 1, wherein the step of preparing the nonwoven film comprises: a step of mixing and dispersing carbon fibers and heat-resistant polymer fibers in an aqueous solution containing a thickener; a step of preparing a nonwoven fabric by placing them in a molding die, filtering, and drying; and a step of heat-pressing the molded and dried nonwoven fabric. Claim 6 A nonwoven fabric in the form of a film comprising carbon fibers and polymer fibers; and a coating layer formed by coating the nonwoven fabric in the form of a film with a coating solution comprising polymer and conductive ceramic powder, wherein the polymer fibers comprise at most one of polycarbonate fibers or polyamide fibers, and the ceramic powder comprises alumina or basalt heat-treated powder obtained by heat-treating basalt and then cooling it to powder. Claim 7 delete

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