JPH02230684A - Planar heat generator - Google Patents

Abstract

PURPOSE:To reduce a secular change in resistance so as to attain a stable temperature-conductivity property by providing a stable resistant heat generating element having an excellent flexibility and a temperature self-controlling function in a low temperature region lower than about 100 deg.C and not requiring for special provision of a temperature detecting mechanism and a safety fuse for preventing overheating. CONSTITUTION:A planar heat generator is such constituted that a fabric base material is coated with a temperature sensing element or a resistant heat generating element having a temperature self-controlling property and incorporating a low-order substance mainly made of a crosslinked high polymer and a linear high polymer into a graphite or a carbon black. The element is prepared by incorporating a monomer of the crosslinked high polymer and powder of the linear high polymer compound as the low-order substance or liquid polymer and a low molecular weight organic compound into the conductive graphite or carbon black, applying or immersing a liquid, which is blended and polymerized in an organic solvent, in a base material where a copper foil wire is woven in a cotton fabric of twin-yarn #20 at intervals of 1mm, followed by reactively drying.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a self-temperature control function in a low temperature region of about 100"C or less, and has a separate compound conical incomplete temperature detection mechanism and an overheat prevention mechanism. The present invention relates to a sheet heating element equipped with a novel resistance heating element that is safe, flexible, and convenient to use without requiring a safety fuse.

[Conventional technology]

Conventionally, conductive resins or semiconductive resins are formed by blending thermosetting resins or thermoplastic resins with conductive substances such as graphite, carbon black, or metal powder, and the excellent properties of these organic materials are utilized. It is widely used as an electronic component or a heating element.

However, their fatal drawback is that they lack stability and are unreliable. In particular, changes over time after long-term use could not be avoided.

[Problem to be solved by the invention]

For example, it has stable temperature-conductivity characteristics in the low temperature range of about 100°C or less, has no change in electrical resistance value over time even after repeated heating and cooling, and has positive characteristics in specific temperature detection and specific temperature ranges. Has a self-temperature control function with large changes,
There is a need to develop a resistance heating element with excellent stability.

[Means to solve the problem]

As a result of intensive studies to achieve the above-mentioned problems, the present inventor has discovered that graphite or carbon black has a solid covalent bond in a two-dimensional typical six-membered ring network planar shape as a heating element of a self-temperature control planar heating element. The bonding force between plane layers is relatively loose and slips easily, but it has a considerable adsorption force and swells and degenerates between planes, and in secondary planes it is insulating as a so-called conjugated covalent bond. However, we focused on the fact that the interlayer plane exhibits conductivity similar to that of metal due to the presence of so-called π electron clouds, and we expanded the distance between the eyebrows by adsorbing a derivative with strong adsorption properties between the graphite or carbon black's eyebrows. At the same time, a crystalline low molecular weight organic compound is infiltrated between the upper and lower inorganic layers to replace part or all of the adsorbed derivative, or to be directly adsorbed to the inorganic layer to form a crosslink, and change the length of the crosslinked molecule. The inventors have discovered that the conductive resistance between layers can be freely controlled by this method, and have completed the present invention.

That is, the planar heating element of the present invention is a thermostatic element or a resistance heating element having self-temperature control properties, which is made by combining graphite or carbon black with a low-dimensional material mainly consisting of a cross-linked polymer and a linear polymer. It is characterized by being made by coating a cloth-like base material.

The sheet heating element according to the present invention is made by blending conductive graphite or carbon black with a cross-linked polymer, fine powder or liquid polymer of a linear polymer compound, which is a low-dimensional substance, and a low molecular weight organic compound. It is produced by applying or impregnating the blended and polymerized liquid in an organic solvent onto a base material in which copper foil wire is woven into a 1:20 cotton woven fabric with a double thread and one crane gap weaving, and then drying by reaction. be able to.

The base material of the above-mentioned sheet heating element is not limited to cotton woven fabric, but may also be organic or inorganic, and may have different characteristics such as plate, film, linear, woven, non-woven fabric, dense, porous, etc. No question. Any material may be used as long as it does not impair the self-temperature control conductive properties.

In the present invention, examples of graphite or carbon black include natural or artificial graphite, furnace black, acetylene black, etc., and the particle size is 1μ or less, especially 0.1μ.
It is preferable to use a material less than μ.

As the crosslinked polymer, heptanomers of thermosetting resins forming a three-dimensional network structure, such as epoxy resins, melamine resins, polyurethane resins, silicone resins, and their modified resins, are preferably used.

Examples of the linear polymer compound include polyethylone, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, olefin polymers such as polypropylene, and ionomaresin, and preferred are crystalline fine powders. It is polyethylene.

Typical examples of low molecular weight organic compounds include linear alkane hydrocarbons having 20 or more carbon atoms and fatty acids thereof.

Examples of organic solvents or reaction inducers include aromatic hydrocarbons such as benzene, toluene, and xylene, n-butanol, and n-butanol.
-Alcohols such as brobanol, aliphatic glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, alicyclic diols such as cyclopentane-1,2-diol, phenols such as hydro-coquinone, methyl ethyl ketone, etc. Examples include ketones and tetrahydrofuran.

In manufacturing the resistance heating element of the present invention, which is a planar heating element having self-temperature control characteristics, the above-mentioned related substances are mixed for 100 parts of a conductive high-dimensional material consisting of graphite and a crosslinked polymer.
It is appropriate that the graphite content be in the range of 10 to 60 parts, and the crosslinked polymer content be in the range of 40 to 90 parts.

If the amount of the crosslinked polymer exceeds 90 parts, the conductivity will deteriorate. In addition, if it is less than 40 parts, that is, even if the graphite exceeds 60 parts, the effect of increasing the amount is poor, and the basic conductivity at room temperature of the graphite or carbon blank composition varies depending on the type and amount, but specific temperature detection and self-temperature control characteristics may be uniformly determined. Furthermore, when a crosslinked polymer is grafted with carbon black, it becomes a matrix of a conductive substance, so the basic conductivity differs from case to case, but it can be uniformly determined.

In order to stabilize the conductivity, it is recommended that the linear (chain) polymer compound be added in an amount of 5 to 100 parts per 100 parts of N, which is the combined amount of the crosslinked polymer and graphite. good. When it exceeds 100 parts, the conductivity is extremely reduced and exceeds a practical range.

Low molecular weight organic compounds, such as the above hydrocarbons, have a molecular weight of 3 to 30
The range of If it exceeds 30 parts, the toughness of the product will decrease, and if it is less than 3 parts, the properties will be less effective. A minimum amount of 25 parts or more of the organic solvent is required, but the amount can be increased as desired depending on the need for dilution.

[Effect]

The element of the planar heating element with self-temperature control characteristics of the present invention is
In the process of sequentially mixing with the above ingredients, a crosslinked polymer 10nomer is first grafted onto graphite, and a linear polymer compound is mixed with the 7nomer to form a graphite. During the heat treatment process, this polymer is twisted and blended simultaneously with the polymerization reaction of the crosslinked polymer. This can be determined from the homogeneity of the device product. It also plays an extremely important role in providing flexibility to device products and stabilizing their properties in relation to the three-dimensionalization and degree of polymerization of cross-linked polymers. In this way, linear polymer compounds provide flexibility and entropic rigidity to three-dimensional network compounds, which tend to be hard.
It gives flexibility at low temperatures, prevents it from becoming loose at high temperatures, and stabilizes the entire system by providing tightness.

The low-molecular-weight organic compound appears to penetrate between the graphite layers directly or in cooperation with a reaction inducer, or to expand the graphite layers, and to strongly adsorb to the graphite layer 6 to form a glabellar compound.

This indicates that the sheet heating element with self-temperature control properties of the present invention can be repeatedly heated to high temperatures (at temperatures much higher than the melting point of low molecular weight organic compounds, e.g. 13°C for formulations with a melting point of 65°C).
This is supported by experimental results showing that it can withstand temperatures up to 0°C and its properties hardly change.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Note that parts of each component described in the following description represent M parts.

Example 1 Formulation of self-temperature-controlled conductive paint> Carbon black (average particle size 0.1 μm or less) 45 parts Alkyd melamine resin monomer 55 parts n-baraffin (fine powder with average particle size 5 μm or less) 25 parts High molecular weight polyethylene (Powder with average particle size of 15μ or less) 25 parts toluene
45 part MEK
25 parts n-butanol
Preparation of 30 parts of self-temperature control planar heating element specimen>
Thickness: 1 msi x 761 l x 26 as a sample for resistivity measurement
The above mixture was applied to a thickness of about 20 μm by roll ironing onto a commercially available slide glass of H. After drying at room temperature, the coating film was
．． It was cut leaving a width of Om. In addition, as test specimens for temperature-resistance characteristics and other characteristics tests, a copper foil conductor was embedded in a 20# double-thread cotton thread 111L square-woven cotton fabric, and the electrode width was 60 meters x 23 wires in length. A piece of base material was impregnated with the above-mentioned mixed solution and coated with two rolls made of silicone rubber (hardness: 50, pressing force: 1 kgf), and then dried at room temperature to form a test piece. Characteristic tests and results> The mixed solution obtained by the above formulation is a black juice-like liquid,
This was applied onto each of the above-mentioned wiping strip substrates and reacted with far infrared rays at an irradiation temperature of 155° C. for XIO minutes, resulting in a coated film with no cracks on the surface.

The specific resistance value of the glass base specimen is 8.5×10Ω at 25℃
It was 11. In addition, a voltage was applied to the sample element made of a cotton cloth base while keeping the top and bottom of the element surface warm with alumina wool. The element electrical resistance value immediately before voltage application is 13. The resistance value was OKΩ and the element surface temperature was 25°C, but when ACIOOV was applied, the resistance value increased proportionally to 16.8KΩ as the temperature rose. The temperature is 62
The temperature reached °C and was maintained at this temperature for more than 8000 hours, with no further increase in temperature.

After that, when twice the power, ie, 141vAC, was applied to the same test piece, the temperature of the heat generated remained at 75°C for a long time, and there was no further increase in temperature. The measured resistance of the element at this temperature had increased to 23.4KΩ. Further, when the voltage application to the sample element was cut off and the temperature returned to room temperature of 25.0°C, the resistance of the element completely returned to 13.0 KΩ. This was repeated 12 times and the result was exactly the same as above, so f! It has been certified.

FIG. 1 is a graph showing the relationship between the element surface temperature and the resistance value when the voltage applied to the sample element obtained in this example is changed.

FIG. 2 is a graph similarly showing the temperature increase characteristics, with the horizontal axis representing time (minutes) and the vertical axis representing temperature ("C").

Example 2 <Self-temperature control? Blend of Il conductive coating> Carbon black (average particle size 0.1μ or less) 30 parts Acrylic-epoxy resin monomer 70 parts Ionomaresin 35 parts N-baraffin (powder with average particle size 5μ or less) 15 parts 35 parts 15 parts 15 parts 25 parts Xylene MEK n-butanol Dia7ton alcohol (Preparation of sheet heating element specimen and property test) A sheet heating element was prepared in the same manner as in Example 1 using the above formulation. The specific resistance of the specimen was 1.9 x 10Ω-1 at 25°C. Moreover, the temperature increase characteristics are shown in FIG. The stability of acrylic-epoxy resin increases as the degree of polymerization of the three-dimensional structure increases, but as a one-sided heating element, it is extremely brittle, which is a major drawback in practical use. This drawback is compensated for by ionic bonding ionomare resin.

Ionomare resin is a thermoplastic elastomer that provides flexibility while maintaining stability to the entire device system, especially at low temperatures near room temperature. It has very good compatibility with acrylic-epoxy monomers and blends well. [Effects of the Invention] As explained above, according to the present invention, the resistance value shows very little change over time even after repeated use, has stable temperature-conductivity characteristics, and has no risk of local overheating. 4. Surface with various stages of self-temperature sensing and control functions as a level sensor. A shaped heating element can be provided.

In addition, the resistance heating element of this planar heating element is flexible and highly elastic even when the temperature rises, and has the properties of a flexible elastomer with appropriate rigidity, and can be processed into various shapes and has various manufacturing methods. It can be manufactured easily and at low cost, and is expected to have a wide range of applications.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between element surface temperature and resistance value when the applied voltage of the planar heating element obtained in Example 1 is changed. Figure 2 is a graph showing the temperature rise characteristics of the same as above. , FIG. 3 is a graph showing the temperature rise characteristics of the planar heating element similarly obtained in Example 2. Figure 1

Claims (1)

[Claims] A cloth-like base material is coated with a temperature-sensitive element or resistance heating element that has self-temperature control characteristics, which is made by combining graphite or carbon black with a low-dimensional material mainly consisting of a cross-linked polymer and a linear polymer. A sheet heating element characterized by: