JPH0617185U - Moisture resistant sheet heating element - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a moisture-resistant planar heating element having a stable material structure that does not cause phenomena such as moisture infiltration and delamination during a long-term use process. [Structure] The sheet heating element 1 has a laminated coating structure in which upper and lower surfaces are integrally covered with an FRP layer 2 having an aluminum foil 3 sandwiched therebetween. It is preferable to form a large number of small holes having a diameter of 2 to 10 mm on the entire surface of the aluminum foil 3 so that the area ratio is 30% or less.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a moisture-resistant sheet-like heating element that is guaranteed to be used stably for a long period of time.

[0002]

[Prior art]

 Conventionally, as a heater for snow melting or underwater which requires a high degree of moisture resistance, a heater having a structure in which a planar heat-resistant element is covered with a laminated FRP of rubber or resin matrix and glass fiber cloth has been developed. .

Of these, the structure covered with rubber requires a thick coating layer in consideration of the reinforcement of the planar heating element, and thus has a drawback of high weight. On the other hand, the structure covered with the laminated FRP can be formed as a lightweight thin coating layer because the FRP itself has excellent strength. However, since the coating of the laminated FRP is difficult to be resistant to moisture, the resistance of the heating element gradually increases due to moisture absorption, or swelling or delamination occurs between the heating element and the FRP layer during long-term use. There are difficulties.

[0004]

[Problems to be solved by the device]

 The reason why the coating of the FRP layer becomes a problem in terms of moisture resistance is that the matrix resin has some water absorbency. For example, the epoxy resin / glass fiber cloth FRP layer exhibits water absorption of 0.5 to 1.0%, and the phenol resin / paper FRP layer exhibits water absorption of 0.1 to 0.2%. It gradually causes water to pass through during use.

The present invention has been made in order to solve the above-mentioned problems caused by the conventional laminated FRP coating structure, and its purpose is to prevent phenomena such as moisture infiltration and delamination during long-term use. Another object of the present invention is to provide a moisture resistant sheet heating element having a stable material structure.

[0006]

[Means for Solving the Problems]

 The moisture-resistant planar heating element according to the present invention for achieving the above object has a laminated coating structure in which the upper and lower surfaces of the planar heating element are integrally encapsulated by FRM layers sandwiching aluminum foil. This is a structural feature.

FIG. 1 is a cross-sectional view illustrating a moisture-resistant planar heating element of the present invention, where 1 is a planar heating element and 2 is a state in which an aluminum foil 3 is sandwiched between the upper and lower surfaces of the planar heating element 1. The FRP layer is integrally encapsulated in.

There are no particular restrictions on the material composition of the planar heating element 1 that serves as the heating base material of the present invention, but there is no limitation to the alumina short fiber and graphite powder as described in JP-A-1-143180. A heat generating sheet made by adding a binder to make a paper sheet is preferably used in a structure in which it is sandwiched and integrated between the ceramic sheet layers.

The FRP layer 2 integrally encapsulating the sheet heating element 1 is formed by applying a matrix resin liquid such as epoxy resin or phenol resin to a reinforcing fiber cloth such as glass fiber, silica fiber or silica-alumina fiber. Alternatively, it is configured by laminating a plurality of impregnated FRPs.

The aluminum foil 3 is sandwiched between the upper and lower FRP layers 2 and functions to prevent a situation where moisture permeates the FRP layer 2 and adversely affects the planar heating element 1. Becomes The aluminum foil 3 may be an unprocessed aluminum foil as it is, or as shown in the drawing, an innumerable small holes may be provided on the foil surface and then intervened. When small holes are provided on the foil surface, the upper and lower FRP layers are directly bonded through the holes, which is effective in improving the adhesiveness. Regarding the size of the small holes to be formed, if the diameter is less than 2 mm, the adhesive effect is not sufficiently achieved, and if it exceeds 10 mm, the moisture resistance function deteriorates. Set to. However, if the area ratio of the small holes exceeds 30%, the strength of the material will increase, but it will not be possible to sufficiently prevent the permeation of water. Therefore, it is preferable to form the small holes so that the area ratio is 30% or less. Such small holes can be easily formed by a punching device that is designed in advance to satisfy the above conditions.

As shown in FIG. 2, the sheet heating element having the above structure has a plurality of semi-cured FRP prepregs 4, an aluminum foil 3, a plurality of FRP prepregs 4, and a metal electrode portion 5 at a side end portion. The sheet heating element 1 installed, a plurality of FRP prepregs 4, an aluminum foil 3, and a plurality of FRP prepregs 4 were filled in a mold in this order, and pressure was applied from the upper and lower surfaces to mold and mold, followed by heat curing. It is manufactured in the process of integrating them. At this time, if necessary, an epoxy resin adhesive is interposed between the layers to strengthen the bonding force.

[0012]

[Action]

 According to the moisture-resistant planar heating element of the present invention, the aluminum foil sandwiched in the laminated FRP layer functions to effectively prevent the permeation of moisture, and the adverse effect of moisture on the planar heating element is adversely affected. Are effectively erased. In this case, if an aluminum foil with numerous small holes with a diameter of 2 to 10 mm is formed on the entire surface so that the area ratio is 30% or less, the strength characteristics of the material and the delamination resistance can be improved. it can.

Through such an action, even if it is used for a long period of time, the resistance of the sheet heating element does not change due to the infiltration of moisture, and the delamination and swelling phenomenon due to repeated heat generation do not occur, and it is a strong and lightweight material. It is possible to provide a moisture-resistant sheet-shaped heating element having excellent stability.

[0014]

【Example】

 Hereinafter, the present invention will be described based on embodiments.

[Preparation of Moisture-Resistant Sheet Heating Element] 1 kg of epoxy resin [“EP-4100” manufactured by Asahi Denka Kogyo Co., Ltd.] was mixed with 600 g of a curing agent [“EH-520” manufactured by Asahi Denka Kogyo Co., Ltd.] The resin solution obtained by adding 800 g of acetone was further applied to a glass fiber cloth 300 mm in length and width and 0.2 mm in thickness [“Glasslon cloth” manufactured by Asahi Fiber Glass Co., Ltd.], and air-dried to give a semi-cured prepreg. It was made. As shown in FIG. 2, the above-mentioned three prepregs, aluminum foil, two prepregs, sheet heating elements, two prepregs, aluminum foil, and three prepregs were sequentially stacked on the molding die in the vertical direction. It heat-cured while pressing and the planar heating element shown in FIG. 1 was obtained. The pressing pressure was 10 kg / cm ² , and the heat curing was a two-step treatment at 120 ° C. for 2 hours and 140 ° C. for 30 minutes.

For the planar heating element, a ceramic sheet heating element having a structure in which alumina short fibers and graphite powder are made into paper with a pulp binder and then sandwiched between alumina sheet layers [“MONAHEAT” manufactured by Tokai Carbon Co., Ltd.] The resistance was 100 Ω], and the unprocessed aluminum foil and the aluminum foil having a thickness of 10 μm punched to have different area ratios with small holes of 5 mm in diameter were used. In addition, for comparison, a planar heating element having a structure in which aluminum foil was not sandwiched was manufactured according to the above steps.

[Evaluation of Properties] Each of the sheet heating elements described above was immersed in water for a certain period of time, and the state of resistance change of the sheet heating element due to moisture absorption over time was measured and investigated. In addition, the bending strength of the sheet heating element was measured in order to evaluate the interlayer adhesive strength of the FRP layer. The results are shown in Table 1 in comparison.

[0018]

[Table 1]

From the results shown in Table 1, in the planar heating element in which the FRP layer was sandwiched by aluminum foils without forming small holes, the variation with time of resistance was extremely small, and sufficient moisture resistance was exhibited. On the other hand, it was confirmed that the strength characteristics deteriorate. On the other hand, in the structure in which the aluminum foils having the small hole area ratio of 30% or less were sandwiched, the resistance change with time due to immersion in water was small, and practical bending strength was imparted. With the structure in which the aluminum foil is not sandwiched and the structure in which the aluminum foil with a small pore area of 40% is sandwiched, the resistance to moisture change is so poor that the resistance changes significantly when immersed in water, making it impossible to use in water.

[0020]

[Effect of device]

 As described above, according to the present invention, it is possible to provide a lightweight, integrally-covered, moisture-resistant planar heating element that exhibits sufficient stability for a long period of time in water or a humid atmosphere. Therefore, it is extremely useful as a heater member for snow melting or underwater use, for example.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a moisture resistant sheet heating element according to the present invention.

FIG. 2 is a perspective explanatory view showing a state in which moisture-resistant planar heating elements are laminated and assembled.

[Explanation of symbols]

 1 Sheet heating element 2 FRP layer 3 Aluminum foil 4 FRP prepreg 5 Metal electrode part

Claims (2)

[Scope of utility model registration request] 1. A moisture-resistant planar heating element having a laminated coating structure in which the upper and lower surfaces of the planar heating element are integrally covered with FRP layers sandwiching aluminum foil. 2. The moisture-resistant planar heating element according to claim 1, wherein an aluminum foil having an innumerable number of small holes having a diameter of 2 to 10 mm formed so that the area ratio is 30% or less is used.