JPS5920986A - Panel heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a planar heating element, and more particularly to a planar heating element in which the amount of current automatically decreases when the temperature rises.

A planar heating element is a flat heating element base made of a conductive material and a non-conductive material, provided with electrodes for conducting electricity, and subjected to insulation treatment.When electricity is applied to this element, it generates Joule heat and generates heat. It emits infrared rays from its body surface. Due to its simplicity and safety, in recent years it has been used for a wide range of applications, including floor heating in cold regions, snow melting on roofs, agricultural hotbeds, greenhouses, and heating for general homes.

Hitherto, known bases for planar heating elements include glass cloth coated with a resin containing carbon, a blend of carbon and synthetic resin, and etched metal foil. Among these, those made of a blend of carbon particles and synthetic resin are simple to manufacture and have a structure, and are excellent in electrical insulation, moisture resistance, chemical resistance, etc. Such a planar heating element containing carbon particles has the property of a kind of thermal semiconductor, in which when the temperature rises to a certain extent due to the application of electricity, the flow of current is automatically stopped and the temperature is maintained at a constant level. In other words, □At low temperatures, the contact area of carbon, which is a conductor, is large, and current flows and generates heat. However, when the temperature rises due to heat generation, synthetic resins, such as polyvinyl chloride,
Since it has twice the coefficient of thermal expansion, the contact area of the carbon particles dispersed in the resin becomes smaller, and the current that flows also becomes smaller.

As the temperature rises further, the carbon particles become completely non-contact, current flow stops, and the temperature begins to drop. When the temperature drops to a certain temperature, the carbon particles in the resin come into contact again, a current flows and heat is generated, and this operation is repeated to automatically maintain a predetermined constant temperature.

However, the above-mentioned planar heating element made of a simple blend of carbon and resin has problems such as abnormally high temperatures in some parts and poor dimensional stability in handling.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a planar heating element that has an extremely small temperature distribution width and good dimensional stability.

In order to achieve the above object, the present invention provides a planar heating element in which a pair of linear electrodes are provided along both ends of a sheet made of a polymeric material blended with carbon particles. It is characterized in that a conductive linear object is provided substantially parallel to the electrode.

In the present invention, it is preferable that the sheet made of the polymeric material is an integrated synthetic resin sheet and fabric. Examples of the integration method include impregnating or coating a fabric with a resin containing carbon particles, or laminating a sheet of a blend of carbon particles and a synthetic resin onto a fabric. When using a synthetic resin sheet integrated with a fabric, it is preferable that the conductive linear object is provided by being inserted through the fabric.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a plan view of a planar heating element showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II-II.

This heating element 1 consists of a fabric 2 impregnated with a synthetic resin blended with carbon particles and formed into a sheet, a pair of electrodes 3A and 3B provided at both ends of the fabric 20, and a gap between the electrodes. It consists of a plurality of conductive linear objects 4 provided substantially in parallel with the electrodes, and a synthetic resin sheet 5 that insulates both lower surfaces of the heating element.

The synthetic resin used in the present invention may be any resin that has sufficient insulation and heat resistance to be used as a planar heating element, such as polyvinyl chloride resin, fluororesin, polyethylene resin, polypropylene resin, polyamide resin, Examples include polyester resins, epoxy resins, and polyimide resins. Among these, thermoplastic resins such as polyvinyl chloride resins, polyethylene resins, and polypropylene resins are preferably used. In addition, as carbon particles,
Carbon black having an average particle size of 2 to 100 μm, preferably about 2 to 5° Alμ, is preferably used. The amount of carbon particles to be added to 100 parts by weight of the synthetic resin of the planar heating element is preferably 50 to 120 parts by weight.

A known dispersant can be added to stabilize the carbon particles in the resin. Examples of such dispersants include mineral fibrous materials such as asbestos, sepiolite, apulgite, varicorskite, wollastonite, and tobermorite.

The fibrous materials of these minerals have excellent dispersion and adsorption properties, and due to this action, the carbon powder particles are dispersed and stabilized together with the fibrous materials in the synthetic resin. The amount of added mineral fibrous material to the synthetic resin is 0.05 to 1.
0% by weight, particularly preferably 0.5 to 7%.

In addition, mineral fibrous materials with a fiber length of 5 mm or less are
It is preferably used because blending does not take much time and a planar heating element with the desired performance can be obtained. In addition, even if it exceeds 5, it may be used as long as it can be sufficiently blended with the synthetic resin.

Furthermore, among the mineral fibrous materials that are useful for dispersing carbon powder into synthetic resins, those with good dispersibility are
The higher the wet volume value defined below, the better the effect. The wet volume is the volume of 1g of mineral fibrous material Ftl, 000ml (inner diameter 63.5m, 104 scale) placed in a graduated cylinder, and water at a temperature of 20°C and pH 6 to 7 added to bring the total volume to 1. 000m?
After binding and thoroughly mixing by shaking several times, the mixture was allowed to stand for 2 hours in a room at 20°C, and the volume of the settled fibrous material was measured.

For example, if there is a fibrous material that has settled to the 100 ml scale, the wet volume of that fibrous material is 100 ml.
Define as 1. In the present invention, fibrous materials having a wet volume of 100 or more are preferable because they are bulky and dispersed. The fibrous material that is dispersed in such a bulky manner only needs to be separated into thin fiber bundles or single fibers, and is not directly related to the type of fiber. Furthermore, the longer the fiber length, the higher the wet volume, but long fiber lengths require consideration in blending as described above. For this reason, among mineral fibrous materials, those that can be dispersed into thin fiber bundles or single fibers without shortening the fiber length are preferable, and in this respect, asbestos, especially chrysotile asbestos, is preferable. .

Among asbestos that can easily increase the wet volume, commercially available asbestos has a wet volume of 200 m1.
There are few of the above, and therefore it is generally desirable to use commercially available asbestos by wet defibration or dry defibration using known techniques to increase the wet volume. In particular, asbestos with a fiber length of 1 m or less and a wet volume of j00+nJ or more, and more preferably 300 m1 or more, is easy to disperse because of its short fiber length, and it adsorbs carbon particles and improves its uniform dispersibility. Since it becomes even higher, it becomes suitable for the present invention.

The fabric used in the present invention is preferably a knitted fabric or a nonwoven fabric, particularly a mesh-like knitted fabric, but a sheet-like porous body can also be used. Fiber materials include natural fibers such as cellulose and wool, regenerated fibers such as rayon, semi-synthetic fibers such as acetate, organic synthetic fibers (preferably polyester fibers) such as polyacrylonitrile, polyester, and polyamide, and glass fibers. Inorganic fibers such as

The basis weight (weight per unit area) of these fabrics is 30 to 5.
001/i is appropriate.

In order to provide the linear electrodes 3A and 3B along both ends of the fabric, one or more copper wires with a diameter of 0.1 to 5 mx are inserted or placed and fixed in parallel through the fabric. Bye. Instead of the plurality of copper wires described above, a flat linear object (for example, a mesh electrode) or the like may be used.

The conductive linear object 4 provided substantially in parallel between the linear electrodes 3A and 3B is, for example, a conductive material including copper wire, carbon black, metal particles, etc. with a diameter of about o, oi to 0.5 beads. Examples include fibers. These trees can be used singly or in combination.

In order to insert the conductive linear objects into the fabric, for example, these linear objects can be twisted with fibers, knitted and woven, mixed into every few fibers, or embedded in a non-woven fabric. can be given. These linear objects may be arranged so that they are substantially parallel to both ends of the electrode, for example, as shown in (a) in Figure 3.
Various arrangements as shown in ~(c) can be mentioned. The installation interval of such conductive linear objects may be within a range where uniform conductivity can be obtained, and 1 to 10 CIIL is usually appropriate.

In order to manufacture the planar heating element of the present invention, for example, a fabric having electrodes at both ends and tetraelectric wires at appropriate intervals between the electrodes is prepared in advance, and a synthetic resin containing carbon particles is added to the fabric. After impregnating the heating element with carbon particles or laminating a synthetic resin sheet containing carbon particles, both sides of the heating element may be insulated and coated with synthetic resin.

When a voltage is applied to the electrodes at both ends of the planar heating element obtained as described above, current flows between the carbon particles and generates heat. However, at this time, the conductive wire inserted between the electrodes of the fabric plays the role of a kind of station, which makes the current density uniform over the entire surface of the sheet heating element, preventing the occurrence of localized abnormal high temperatures. Prevented. This conductive wire is uniformly inserted through the fabric, and the fabric itself is in close contact with the synthetic resin layer containing carbon particles, so that the current can be made even more uniform. Furthermore, since the fabric is composed of fibers, it has great dimensional stability and is much less deformable than conventional sheets only.

As described above, according to the present invention, by providing conductive wires in parallel at appropriate intervals between the electrodes at both ends of a sheet made of a polymeric material containing carbon particles, the current density over the entire surface of the heating element is made uniform. It is possible to prevent uneven temperature distribution or local abnormal high temperatures, and improve dimensional stability.

Hereinafter, specific examples of the present invention will be described.

Example 1 A woven fabric with a warp of 10 wood/am and a weft of 7 wood/am was prepared using 210 denier/4 filament polyester fiber. At this time, connect 5 copper wires with a diameter of 0.3 mm to each end.
This was pressed through to form an electrode, and a conductive linear material was made between both ends by using polyester fibers in which copper wires with a diameter of 0.1 mm were twisted in the warp at intervals of 4 m.

Carbon black: polyvinyl chloride, 7:
The planar heating element of the present invention was manufactured by laminating 10 sheets with a thickness of 1 to 1, and laminating 0.7 m polyvinyl chloride sheets on both sides for insulation coating.

This sheet heating element 5 n? Lay it on the floor, occupying 1 floor area @
When electricity was applied by applying AC 100V between both electrodes under a load of 70 kg, the heat generation temperature remained uniform at 60° C. at all locations even after 1500 hours of electricity application. Also, the temperature and dimensions of the 500-fold bent convex edge remained unchanged.

Example 2 Fabric weight 1 using 0.1 denier 5-yel polyacrylic fiber
00 // / n? Two webs were manufactured using the papermaking method. Three copper wires with a diameter of 0.5 mm are placed on each end of one web, and wires with a diameter of 0.2 mm are placed between them at intervals of 6 CrrL.
After placing the same copper wire, another web was placed on top of it, and the two layers of web were intertwined and integrated in a columnar flow.

On the other hand, 1g of 7D clickil asbestos from Canada per 11g of water.
and anionic surfactants o and iy were added and stirred for 24 hours at room temperature with air blowing to obtain a suspension of asbestos (fiber length 5 or less, fiber bundle pore diameter 25 μm) with a wet volume of 800+++ l. Ta.

After this suspension was diluted 10 times with urine, acetylene black 51-■ (manufactured by Nippon Carbon Co., Ltd., specific surface area approximately 100 crn/11, particle size 2-3 mm) 7011 was added and mixed. At this point, aggregates of carbon black adsorbed to asbestos begin to form. The mixed solution containing this aggregate is centrifuged to separate the solids, and the solids are separated by 50%
Dry at a temperature of ~60°C.

The obtained dry solid was pulverized, 100 g of polyvinyl chloride powder was added thereto, blended for 10 minutes, 40 g of plasticizer was added, and the mixture was rolled to a thickness of 1.0 my with a calender roll.
It was molded into a sheet of n.

The 1fr U-shaped heating element of the present invention was manufactured by laminating the above-mentioned borosalt hibinyl sheet onto the integrated fabric. When AClooV was applied to the electrodes of this planar heating element to energize it, the temperature remained constant at 60°C at all locations even after 2000 hours of electricity.

Furthermore, the 500-cycle curved convex ridge did not change to the above value.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a planar heating element showing one embodiment of the present invention, FIG. 2 is a sectional view taken along line II-u, and FIG.
Figures (A), (B), (C), . . . are diagrams showing various shapes of conductive linear objects used in the present invention, respectively. The explanation of the symbols is as follows. 1... Planar heating element, 2... Synthetic resin sheet, 3A. 3B... Electrode, 4... Conductive linear object, 5... Insulating coating. Agent Patent Attorney Takeshi Kawakita 111 Figure 2rlJ

Claims (2)

[Claims] (1) In a planar heating element in which a pair of linear electrodes are provided over both ends of a sheet made of a polymeric material blended with carbon particles, the electrodes are arranged substantially parallel to each other with an interval between the electrodes. A planar heating element characterized in that a conductive linear object is provided on the surface of the heating element. (2) The sheet made of the polymeric material is formed by integrating a fabric and a synthetic resin sheet, and the conductive linear object is inserted through the fabric. The planar heating element described in .