JPH0369153B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a polymer-based self-polymer which is stable even under high voltage and is added with a polymeric substance that swells to a polyoxyalkylene-carbon particle mixed system. This invention relates to a temperature regulating heating element.

<Prior art> A mixture of an organic compound containing a plurality of alkylene oxides as a unit structure in its molecule and fine carbon particles in the form of powder, fibers, whiskers, etc. is prepared by adjusting the mixing ratio within an appropriate range. If so, it will have good properties as a so-called positive characteristic heat-sensitive electrical resistance composition, which has the property that its electrical resistance changes suddenly with respect to temperature changes. Among them, polyoxyalkylene and its derivatives are practically suitable substances because they can be supplied in large quantities at low cost, and they have been found to have excellent positive properties, and have already been published in Japanese Patent Application Laid-Open No.
This was proposed in No. 140692. In addition, the polymer-based self-temperature-regulating heating element with positive characteristics also acts as a temperature fuse on the temperature sensor itself, and is safe and eliminates the need to install a separate temperature sensor or temperature fuse inside the heating element. Focusing on the fact that it can be used as an economical thermal storage heating device, we developed a planar heating element that is suitable for base materials such as floor heating equipment in buildings, heating carpets, and heating pine for agricultural production such as brooding, brooding, and seedling raising. It was proposed in Kaisho 60-158586.

<Problems to be solved by the invention> However, subsequent research revealed that the applied voltage was 100V.
Even if the heating element operates stably,
It was discovered that when the voltage reached 200V, it became extremely unstable, making it virtually unusable, and various studies were conducted to find out the reasons for this and ways to solve it.

<Means for Solving the Problems> The present invention solves the above problems, and by adding a swelling polymeric substance to a polyoxyalkylene-carbon fines mixture system, it can withstand overvoltage. They discovered that it can be used as a heating element that operates extremely stably, and have now completed it.

The polyoxyalkylenes used in the present invention include, for example, linear compounds such as polyoxyalkylenes, such as polyethylene glycol and its high molecular weight polyethylene oxide, and block copolymers of polyoxyethylene and polyoxypropylene (so-called Pluronic, Tetronic), polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene sorbitan fatty acid ester, and the like. Among them, polyethylene glycol exhibits the most favorable properties. What these all have in common is that multiple alkylene oxides present in the molecule seem to play an important role in the dispersion of carbon particles.

The carbon fine particles to be mixed with the polyoxyalkylenes are in the form of graphite powder, activated carbon powder, amorphous carbon powder, carbon fiber fragments, single crystal whiskers, and the like.

Mixed systems of polyoxyalkylenes and fine carbon particles have positive characteristics depending on their mixing ratio, and usually the mixture of fine carbon particles is in the range of 10 to 80 parts (weight ratio) to 100 parts of polyoxyalkylenes. be.
If it is less than 10, the resistance will be high and there will be no conductivity, and if it is more than 80, the conductivity will be so high that it will not exhibit positive characteristics due to temperature changes. However, since the range in which positive characteristics are exhibited varies greatly depending on the type of polyoxyalkylene and the type of carbon fine particles, it is not limited to the above range. For example, the time-temperature characteristics of polyethylene glycol-graphite powder systems with different mixing ratios are shown in Figure 1, and the appearance of positive characteristics when the graphite powder is 33% is shown in Figure 2. In addition, the positive characteristic curve for other polyoxyalkylenes is the third
It is a diagram.

Such positive characteristics are obtained when a voltage of 100 V AC is applied between the electrodes, but when the voltage is increased, for example, under 200 V AC, even with a 30% carbon mixture system that is stable at 100 V, the As shown in Figure 4, the stability of the positive characteristics collapses and the graphite powder becomes overheated, similar to the region where the graphite powder is 40% or more as shown in Figure 1. The reason for this is not fully understood, but it is thought that the heating element between the electrodes changes from planar heat generation to linear heat generation under high voltage, resulting in a kind of short circuit and an overcurrent state. Therefore, we thought that it would be better to add a substance that suppresses the movement of such fine carbon particles and creates a network that fixes the planarly dispersed state, and after various studies, we found the following: This is the effect of adding a polymeric substance that swells to the polyoxyalkylene-carbon fines mixed system.

Swelling polymeric substances include water-soluble or water-swellable synthetic or natural polymers and derivatives thereof. Examples of water-soluble or water-swellable synthetic polymers include polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamide, polyacrylic acid, or a mixture of two or more of them, such as acrylamide-acrylic acid-methyl methacrylate terpolymer. be. In addition, examples of water-soluble or water-swellable natural polymers or derivatives thereof include starch,
Examples include one or a mixture of two or more of soluble starch, cellulose, methylcellulose, carboxymethylcellulose, agar, casein, gelatin, and the like. Among these, polyvinylpyrrolidone is completely soluble in polyoxyalkylenes and has an extremely large stabilizing effect on heating elements, and as shown in the examples below, it shows a remarkable effect even when added at only 0.3%. .

Generally, the stabilizing effect of these water-soluble or water-swellable polymeric substances becomes noticeable when the amount added is in the range of 0.01 to 10 parts per 100 parts of the polyoxyalkylene-carbon fines mixture.

Hereinafter, the configuration and effects of the present invention will be specifically explained with reference to Examples. The polyvinylpyrrolidone of Example 1 is completely compatible, but the other polymeric substances of Example 2 and later only swell even when mixed and heated in powder form. However, since extremely stable positive characteristics were obtained in both cases under high voltage, it is thought that the swollen material partially dissolves and stable positive characteristics are obtained.

Example 1 Mixture of polyethylene glycol (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., hereinafter the same #6000), polyethylene glycol (same #2000), graphite carbon (manufactured by Yoneyama Pharmaceutical Co., Ltd., the same hereinafter) in a weight ratio of 5:5:4 Heat generating element 1 obtained by heating and melting 0.3 parts of polyvinylpyrrolidone (manufactured by Hanui Chemical Co., Ltd., reagent grade 1) per 100 parts and stirring,
As shown in Figures 6 and 7, a non-conductive sheet 3 (300 x 80 x 0.16 mm) made of a polyester sheet with a fiber layer 2 on the inside is poured between two sheets, and copper foil tape electrodes are placed on both sides. I got 4.
The total thickness was 0.25 mm. A temperature sensor 5 is attached to this surface, and the temperature-time curve of the heating element when AC voltages of 100V and 200V are applied is shown in Figure 4.
and shown in B. At 100V, it stabilized at approximately 44.5℃, and at 200V, it exhibited stable self-temperature regulation at approximately 53℃.

As a comparative example, a heating element obtained by removing polyvinylpyrrolidone from the above mixture is shown by dotted lines C and D in FIG.

As is clear from the comparison between these Examples and Comparative Examples, there is not much change at a voltage of 100V, but when the voltage increases to 200V, the positive characteristics completely disappear and the product becomes unusable.

Example 2 100 mg of carboxymethyl cellulose (hereinafter referred to as CMC) (manufactured by Hanui Chemical Co., Ltd.) was added to 100 g of polyethylene glycol, placed in a mortar, thoroughly stirred with a pestle, heated and melted, and 39 g of graphite carbon was added. Mixed. This composition (carbon 28%, CMC 0.07%) was processed into the same planar heating element as in Example 1, energized at 200 VAC, and the temperature measured at each time after the start of energization.
Shown in the figure. This composition also exhibited a self-temperature regulating function as in Example 1, reaching a constant temperature of 59°C.

Example 3 100 mg of cellulose powder (manufactured by Hanui Chemicals Co., Ltd.) was added to 100 g of polyethylene glycol (#6000), stirred and mixed thoroughly with a mortar and pestle in the same manner as in Example 2, and after heating and melting, 39 g of graphite carbon was added.
A planar heating element similar to that in Example 1 was prepared by mixing the above, and a current of 200 VAC was applied, and the temperature at each time was measured, and the results are shown in FIG. This sample also reached a constant temperature of 59° C. as in Example 2.

Example 4 100 g of polyethylene glycol (#6000) and 100 g of agar powder (first class (EP) manufactured by Hani Chemical Co., Ltd.)
After stirring and mixing thoroughly with a mortar and pestle in the same manner as in Examples 2 and 3, the mixture was heated and melted, and 39 g of graphite carbon was mixed therein to produce a planar heating element similar to Examples 1 to 3. After energization, the temperature at each time was measured and shown in FIG. It can be seen that this composition also has a constant temperature at 59°C.

Example 5 100 mg of soluble starch (manufactured by Merck & Co., Ltd., analytical reagent) in 100 g of polyethylene glycol (#6000)
After stirring and mixing thoroughly with a mortar and pestle in the same manner as in Examples 2 to 4, the mixture was heated and melted, and 39 g of graphite carbon was mixed therein to produce a sheet heating element similar to that in Examples 1 to 4. , 200 VAC was applied, and the temperature at each time was measured and shown in FIG. In this composition as well, the temperature remained constant at 59°C.

Example 6 Polyethylene glycol (#6000) 3 to 100g
Example 2~ Similar to Example 5, the mixture was thoroughly stirred and mixed with a mortar and pestle, and then heated and melted to produce a sheet heating element in the same manner as in Examples 1 to 5.
A current of 200 VAC was applied, and the temperature at each time was measured and shown in FIG. Also in this composition
A constant temperature of 59°C was obtained.

Example 7 100g of polyethylene glycol (#6000) and polyvinyl alcohol (manufactured by Hanui Chemical Co., Ltd.,
Polymerization degree 500, saponification degree 86.5-89%) 100mg was added, stirred and mixed thoroughly with a mortar and pestle in the same manner as Examples 2-6, heated and melted, and 39g of graphite carbon was mixed. The same planar heating element as
Figure 5 shows the temperature at each time after AC200V was applied. The constant temperature reached by this composition was also 59°C.

Example 8 100g of polyethylene glycol (#6000) and polyvinyl alcohol (manufactured by Hanui Chemical Co., Ltd.,
Add 100 mg of polymerization degree 2500, saponification degree 99-100%,
As in Examples 2 to 7, the mixture was thoroughly stirred and mixed with a mortar and pestle, and after heating and melting, 39 g of graphite carbon was mixed to produce the same planar heating element as in Examples 1 to 7.
200VAC was applied. The results of measuring the temperature at each time are shown in FIG. The constant temperature reached was 59°C.

Example 9 100 g of polyethylene glycol (#6000) and casein (manufactured by Hanui Chemical Co., Ltd., reagent special grade)
Add 100 mg, stir and mix thoroughly with a mortar and pestle as in Examples 2 to 8, heat and melt, mix with 39 g of graphite carbon, and prepare a sheet heating element in the same manner as in Examples 1 to 8. The temperature at each time after 200 VAC was applied is shown in FIG. The constant temperature reached by this composition was 59°C.

<Effects of the Invention> As is clear from the above results, the polymer self-temperature-regulating heating element made of the composition of the present invention has the following effects:
Stable positive characteristics can be obtained even when a voltage of 200V is applied.
As a result, the building's floor heating equipment, heating carpets,
It has now become possible to supply a highly safe product as a sheet heating element for use in a variety of other applications.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between energization time and temperature for heating elements with different mixing ratios of polyethylene glycol and graphite powder, and Figure 2 shows the positive characteristics when graphite powder is 33% in Figure 1. The graph and FIG. 3 are graphs showing the positive characteristics of various polyoxyalkylene-graphite powder mixture heating elements. FIG. 4 is a graph showing the relationship between current application time and temperature showing the effect of adding polyvinylpyrrolidone, and FIG. 5 is a graph corresponding to FIG. 4 showing the effect of adding various other polymers. In addition, Fig. 6 and Fig. 7 show sheet heating elements.
FIG. 6 is a plan view, and FIG. 7 is an enlarged cross-sectional view taken along line AA in FIG. 6.

Claims (1)

[Claims] 1. Polyoxyalkylene-carbon fine particle mixed system
1. A polymer self-temperature-regulating heating element, characterized in that 0.01 to 10 parts of a water-soluble or water-swellable organic polymer substance is added to 100 parts. 2. The self-temperature of a polymer according to claim 1, wherein the water-soluble or water-swellable organic polymer substance is one or a mixture of two or more of polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamide, polyacrylic acid, etc. Adjustable heating element. 3 Water-soluble or water-swellable organic polymer substances include natural polymers such as starch, cellulose, methyl cellulose,
Carboxymethyl cellulose, agar, casein,
The polymeric self-temperature-regulating heating element according to claim 1, which is one or a mixture of two or more of gelatin and the like.