JPH0429197B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention can be used to melt snow and ice that has accumulated on the roofs of buildings, airplanes, automobiles, trains, etc., passageways near entrances and exits of houses, roads, runways of airports, etc. The present invention relates to a panel-shaped heater. <Prior Art> Conventionally, when removing accumulated snow, physical snow removal operations such as snow shoveling, snow melting using a fountain, etc. have been used. Additionally, attempts have been made to use panel heaters that use electricity, hot water, or the like. <Problems to be solved by the invention> However, the nichrome wire electric heaters and panel heaters using hot water, etc. that have been tried so far,
Although it is possible to melt snow, the required electricity and equipment costs are high, making it impractical. <Means for Solving the Problems> As a result of various studies on heaters with good thermal efficiency, the present invention is based on the use of a special heat-sensitive electrical resistance composition previously provided by the present inventor in JP-A-60-140692. Eventually, we discovered that this was possible, and we have now completed it. In other words, it is made of an organic compound containing multiple alkylene oxides as a unit structure in the molecule and fine carbon particles in the form of powder, fibers, and whiskers, and its electrical resistance changes rapidly with temperature changes between the electrically insulating sheets. It is characterized in that a heat-sensitive electrical resistance composition having the following properties is sealed together with an electrode, and this is covered with a rigid plate material such as a resin plate, a metal plate, or a wooden plate. Details of the conductive heat storage medium can be found in the above-mentioned JP-A-60
As detailed in No. 140692, the temperature change in conductivity δ is generally δ=δ. exp(−ΔE/kT)
It can be expressed as However, there are substances that comply with the above equation below a certain temperature, but exhibit a much larger resistance value than calculated using the above equation above a certain temperature. This property is called a "positive property." Conventionally, as an inorganic material having positive properties, barium titanate with a trace amount of rare earth element added has been used. On the other hand, carbon-
Paraffin-polyethylene systems are known. However, this composition has poor compatibility, and there are problems with mixing methods and changes in properties over time. Other carbon-polymer compositions have been used, but the positive properties are not as great. The heat-sensitive electrical resistance composition used in the present invention has a large positive property, and carbon is very easily dispersed in an organic compound containing a plurality of alkylene oxides as a unit structure in the molecule, and has a very large positive property. It is characterized by being stably obtained. Among them, polyethylene glycol (hereinafter referred to as
We focused on the fact that PEG (abbreviated as PEG) as the main component is particularly good, and that it is excellent as a heat storage medium because it is flame retardant and has low flammability.As a result of intensive research, we found that there are multiple We discovered that compounds containing alkylene oxide as a unit structure exhibit significantly superior properties compared to other organic compounds.
As mentioned above, it was provided as a heat-sensitive electrical resistance composition. Organic compounds containing a plurality of alkylene oxides as unit structures in their molecules exhibit excellent positive properties regardless of whether they are linear or cyclic. The specific compounds are illustrated below. Examples of linear compounds include polyoxyalkylenes, such as PEG and its high molecular weight polyethylene oxide, block copolymers of polyoxyethylene and polyoxypropylene (so-called Pluronic and Tetronic), polyoxy Examples include ethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, and polyoxyethylene sorbitan fatty acid ester. In addition to trioxane, cyclic compounds include various crown ethers, such as dibenzo-14-
Crown-4, 15-Crown-5, Benzo-15-
Crown-5, 18-Crown-6, Dibenzo-18
-crown-6, dicyclohexyl-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, dicyclohexyl-24-crown-8, tetrabenzo-24-crown-8,
There are many examples, such as Bejinzo-60 and Crown-20. The carbon to be mixed with the above-mentioned organic compounds containing multiple alkylene oxides as unit structures in the molecule is in the form of whiskers made of powder, fibers, or single crystals such as graphite, activated carbon, and amorphous carbon. It refers to fine carbon particles that can be mixed into the above-mentioned linear or cyclic polyether. A mixture of the two is extremely stable and uniformly mixed at any composition ratio, and does not undergo phase separation. There is a region where positive characteristics appear depending on the mixing ratio of carbon particles, usually 10% to 100% organic matter.
It is in the range of 80. When it is less than 10, the resistance is high and there is no conductivity, and when it is more than 80, the conductivity becomes large and it does not exhibit positive characteristics due to temperature changes. However, since the range in which positive characteristics appear varies greatly depending on the type of organic compound and the type of carbon fine particles, it is not limited to the above range. In this way, the mixing ratio of organic compounds and carbon fine particles is an important factor, and by changing the mixing ratio, the temperature range suitable for snow melting can be set, judging from the energization time, temperature rise, and change in resistance value. . For example, melting point
Graphite powder to 120 parts of PEG (#2000) at 49℃
Figure 5 shows the time and temperature changes when electricity is applied to systems containing 20, 40, 60, and 80 parts.
At 80 parts, the temperature does not rise, and at 80 parts, the temperature rises in a short time. It can be seen that it works well at 40 to 60 parts, and is stable at about 40°C at 40 parts, and stable at about 48°C at 60 parts. At the initial stage of energization, the electrical resistance is less than 500Ω.
The current value is about 1.5A, but when the PEG softens or melts, the resistance rises to 1900Ω, the current decreases to less than 0.1A, and the equilibrium temperature is reached. The pattern is shown in Figure 6. Even with the same PEG, #1540 has an internal temperature of 45°C and #6000 has an internal temperature of 55°C, and as the molecular weight increases, the temperature at which positive characteristics are exhibited rises. In this way, a heat storage medium mixed with 10 to 60 parts of graphite powder becomes a heat-sensitive electrical resistance composition that has a self-temperature regulating function that does not require a heater or thermostat. As mentioned above, PEG exhibits the most favorable properties, and even if a polyoxypropylene chain is connected to it, or even if the terminal group is substituted with an alkoxy group such as a hydroxyl group or a methoxy group, or an alkyl ester or an alkylamine, Shows positive characteristics. Such positive characteristics include a sharp increase in electrical resistance when electricity is applied at a temperature below the melting point of the organic compound medium. This is shown in Table 1.

[Table] In the present invention, a suitable one is selected from among the heat-sensitive electrical resistance compositions described above, the composition is appropriately prepared, and the composition is used as a positive characteristic temperature suitable for snow melting. For example, the relationship between the temperature and the electrical resistance value of a thermosensitive electrical resistance composition is measured using graphite carbon (hereinafter abbreviated as GC).
(28.5%) + PEG #6000 (35.7%) + PEG2000 (35.7
%) system (solid line) and GC (28%) + Pluronik F68 (72%) system (dashed line).
It is shown in Fig. 7. In the present invention, such a heat-sensitive electrical resistance composition is used as it is, or by impregnating and supporting a non-conductive sheet such as a thin woven fabric, non-woven fabric, or sponge sheet to form a planar heating element, and this is used as a sheet heating element. It was sealed with a sheet, electrodes were buried inside it at predetermined intervals, and the whole was covered with a rigid plate such as a resin plate, metal plate, or wooden plate. 〈Function〉 By using such a special heat-sensitive electrical resistance composition, when only the energizing equipment is installed, the self-temperature adjustment function works to maintain the temperature suitable for melting snow, efficiently converting electricity into heat. In order to melt snow efficiently, it is not necessary to raise the surface temperature of the panel heater to a high temperature, and as shown in Table 1, a positive characteristic temperature of 20 to 60°C is sufficient. In some cases, the temperature may be around 10°C. Since this is a low-temperature panel heater, power consumption is low, and since the composition exhibits positive characteristics, no temperature control device is required. Although the reason for the stable positive properties is still not fully clear, it is thought to be due to the change in dielectric constant caused by the interaction between the unpaired electrons of the oxygen atoms in the ether bonds in the alkylene oxides and the carbon particles. Embodiments of the present invention will be described in detail below with reference to the drawings. <Example 1> FIG. 1 is a partially cutaway perspective view of a panel heater for snow melting according to the present invention, and FIG.
FIG. FIG. 3 is a plan view of the internal planar heating element. As seen in these figures, this panel heater for snow melting has a structure in which the surface of a planar heating element 1 is covered with a resin plate 2. Alternatively, depending on the purpose of use, a rigid plate such as a metal plate may be used.
The planar heating element 1 is as described in detail above, and by appropriately selecting and using a heat-sensitive electrical resistance composition, the panel surface is made to have a temperature of 10 to 10, which is suitable for snow melting.
Can be heated to 40℃. In this example, the composition of heat-sensitive electrical resistance composition 3 was a mixture of 600 g of PEG (#6000) and 295 g of graphite powder. In the example shown in the figure, a planar heating element 1 with a length of 1000 mm, a width of 1700 mm, and a thickness of about 2.4 mm is made of two non-conductive sheets 4 made of polyester films 0.2 mm thick, and the outer periphery of is coated with FRP resin to a total thickness of 10 mm. The planar heating element 1 is elongated in the horizontal direction and has a width of 5 mm.
Divide into 5 equal parts with 2mm thick partition tape 5, about 150mm wide.
5 thin spaces with a length of about 1660 mm are provided, and sawtooth electrodes 6, 6 with a capacity of 10 A are arranged on both sides of each non-conductive partition tape 5, and the heat-sensitive electrical resistance composition is directly placed in the spaces 7a to 7e. 3 was filled to 240g. A 100V AC power source was connected to this snow melting panel heater, and the panel surface temperature was measured over time at an air temperature of -5°C. The results are shown in Table 2.

【table】

[Table] As is clear from Table 2, a current of 5A flows immediately after energization, but after 1 minute it becomes 2A, and after 5 to 10 minutes it reaches the almost equilibrium value of 1.5A. The temperature is also 30℃
Temperatures reach 40°C, and do not rise above 40°C. Since this temperature is the surface temperature, the inside temperature is approximately 55°C. When the temperature drops, the resistance value decreases, so the current increases, and the temperature returns to a constant level again, making it ideal as a panel heater for snow removal.
In this example, the surface temperature was measured at the center of the surface of the snow removal panel heater). <Example 2> PEG (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) #2000 and
A thermosensitive electrical resistance composition of 5:5:4 weight ratio of Pluronik F68 (average molecular weight 8000, manufactured by Asahi Denka Kogyo Co., Ltd.) and graphite carbon (manufactured by Yoneyama Pharmaceutical Co., Ltd.) was prepared, and Using the same planar heating element, we measured the temperature and current value after energizing 100V AC. After energization, the temperature rose and eventually maintained a constant temperature, and the current decreased accordingly, eventually reaching a constant value of 1.3 A and 36°C. Therefore, at both ends of the polypropylene glycol chain,
Even when Pluronic with a PEG-bonded structure is used, it can be used as a panel heater for snow removal by adjusting the saturation temperature to a thermally efficient range suitable for snow removal. The self-temperature-adjustable planar heating element 1 in which a heat-sensitive electrical resistance composition is enclosed by an insulating sheet has been covered with a resin plate, a resin-coated steel plate, or the like. However, in places where high loads are applied, such as runways and roads, the space of the non-grounding part 10 of the steel plate 9 of the high load receiving structure with intermittent grounding parts 8 as shown in FIG. If the planar heating element 1 is provided, it can be avoided from being destroyed by the load. <Effects of the Invention> The panel heater for snow removal of the present invention uses a heat-sensitive electrical resistance composition having the above-mentioned positive characteristics, and has a structure that has a self-temperature adjustment function, so a thermistor is not included in the device. It has a simple structure that does not require complicated parts for temperature control. Furthermore, since it is stable at low temperatures, it has good electricity-to-heat conversion efficiency, so the power consumption required for snow removal is low.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a panel heater for snow melting according to the present invention, and FIG.
FIG. FIG. 3 is a plan view of the internal heat-sensitive electrical resistance composition sheet. FIG. 4 is an enlarged sectional view of a main part of another embodiment. Figure 5 is a graph showing the relationship between energization time and temperature for heat-sensitive electrical resistance compositions with different mixing ratios of PEG and graphite powder, and Figure 6 is a graph showing the initial energization period when the graphite powder content in Figure 5 is 60 parts. 3 is a graph showing the relationship between time, temperature, and current value. FIG. 7 is a graph showing the relationship between temperature and electrical resistance of a heat-sensitive electrical resistance composition. DESCRIPTION OF SYMBOLS 1... Planar heating element, 2... Resin plate, 3... Heat-sensitive electrical resistance composition, 4... Non-conductive sheet, 6...
Electrodes, between 7a and 7e, 8... Grounding section, 9...
... Steel plate with high load bearing structure, 10 ... Non-grounding part.

Claims (1)

[Claims] 1 Between the electrical insulating sheets is an organic compound containing multiple alkylene oxides as a unit structure in the molecule, and fine carbon particles in the form of powders, fibers, and whiskers, and has the property of having electrical resistance that changes rapidly with temperature changes. 1. A panel heater for snow melting, in which a heat-sensitive electrical resistance composition having the composition is encapsulated together with an electrode, and this is covered with a rigid plate material such as a resin plate, a metal plate, or a wooden plate.