JPH07183078A - Self-temperature controlling, current-carrying heating element - Google Patents

Abstract

PURPOSE:To provide a self-temperature controlling, current-carrying heating element having a good temperature distribution with a heating temperature of 150 deg.C or higher and therefore a long load life by composing a resistor chiefly of a composition wherein an electrically conducting material is dispersed in an organic high polymer of a specific characteristic. CONSTITUTION:In a current-carrying heating element which is heated by application of voltage to a resistor composed chiefly of a composition wherein an electricaly conducting material is dispersed in an organic high polymer, the organic high polymer is made from polyether ketone (PEEK) and a resin whose melt viscosity is 10<-3>-10<4> poise at a temperature of 380 deg.C and at a shear rate of 10<2>s<-1>. Polyphenylene sulfide(PPS), polyether imide, or polyether sulfone is used as such a resin. The electrically conducting material added to the organic polymer is carbon black, graphite, or preferably MnZn ferrite. The conducting material is kneaded and dispersed by 50vol.% in the organic high polymer (PEEK/PPS=6/4) to form a pressboard, and electrodes are bonded to both sides of the pressboard and voltages are applied to the electrodes for heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element which is useful as a heat collecting device and a general heating device.

[0002]

2. Description of the Related Art A heater having a self-temperature control characteristic is
In a resistor in which a conductive material is kneaded and dispersed in an organic polymer, the organic polymer thermally expands due to temperature and spreads the distance between the conductive materials, raising the resistance of the entire system and stopping heat generation and cooling when it cools. However, it is a heater that constantly generates heat at a predetermined temperature by utilizing the characteristic of generating heat again.

Therefore, it has a very useful characteristic that the temperature can be set without applying a control function even when a voltage is applied,
It also has the useful property that there is no danger of overheating because the resistance rises and heat generation is stopped.

At present, crosslinked polyolefins and crosslinked fluororesins are often used as organic polymers.

[0005]

However, the conventional method is 150 ° C.
The composition corresponding to the above heat generation has not been studied, and since the self-temperature control function is exhibited at the thermal change point of the resin due to the characteristics of the heat generating element, the strength of the heat generating element is lowered and a supporting material is required. There is a problem that there is.

Further, the conventional energization heating element has a problem that when it is repeatedly used, the air comes into contact with the exposed portion of the heating element to cause oxidative deterioration of the organic polymer in the heating element.

[0007]

Means for Solving the Problems The present invention is to solve the above problems, and its gist is to apply a voltage to a resistor whose main component is a composition in which a conductive material is dispersed in an organic polymer. In an electric heating element for generating heat, the organic polymer of the electric heating element is polyetheretherketone and a temperature of 380 ° C.,
Melt viscosity at a shear rate of 10 ² sec ^-1 is 10 ³ to 1
0 in the self temperature control energization heater, characterized in that it is formed from a resin which is a ⁴ poise.

The present invention will be described in detail below.

The self-temperature controlling electric heating element of the present invention is mainly composed of a composition in which a conductive material is dispersed in an organic polymer, and the organic polymer is a resin having a high melting temperature and a crystalline resin. It comprises polyether ether ketone (hereinafter referred to as PEEK) and a resin having a melt viscosity of 10 ³ to 10 ⁴ poise at a temperature of 380 ° C. and a shear rate of 10 ² sec ^-1 .

The processing temperature of PEEK is about 380 to 400 ° C.
However, if the other resin has the above characteristics,
It can be uniformly mixed with PEEK and melt-molded.
Further, in the obtained electric heating element, the other resin is softened or crystal-melted at a temperature lower than that of PEEK, and the exothermic temperature becomes low, so that it is necessary to be within the above melt viscosity range.

Examples of such a resin include polyphenylene sulfide (hereinafter referred to as PPS), polyetherimide (hereinafter referred to as PEI) or polyether sulfone (hereinafter referred to as PES), and particularly, amorphous resin PES, PEI is more preferable because it can impart the shape retention strength of the heater itself without changing the characteristics due to heat.

The ratio of other resin in PEEK is 30-80.
Volume% is preferred.

If the resin having the melt viscosity is 30% by volume or less, the thermal expansion of the resin does not have a force to spread the distance of the conductive material, and eventually the thermal expansion of the high melting point resin controls the temperature, which is not preferable. If it is 80% by volume or more, it becomes difficult to maintain the shape in practical use, so the above range is preferable.

The conductive material added to the organic polymer may be carbon black graphite or the like, but especially MnZ.
n-ferrite is preferable in terms of heat resistance and resistance uniformity. The ratio of MnZn ferrite in the organic polymer is in the range of 30 to 70% by volume, particularly 40 to 60% by volume based on the total amount of the organic polymer and MnZn ferrite. In this way, the resin composition is kneaded and dispersed by a known means, molded by a known molding technique such as extrusion molding and press molding, and a copper foil is stretched on both sides to obtain the resin composition. The self-temperature-controlled energization heating element thus obtained is heated by heat-sealing the end face exposed in the air with the same material as the organic polymer material in the energization heating element and sealing the exposed part. It is preferable because deterioration can be prevented and load life can be improved. Further, it is preferable to apply a far-infrared paint on the outer surface because the energy efficiency is improved, and especially for radiant heating.

FIG. 1 is a diagram showing a DSC curve when PEEK is added with the resin having the specific melt viscosity.

A heating element consisting only of PEEK is about 250 ° C.
Although the temperature is self-controlled by, the resistance of PEEK and a resin having a specific melt viscosity, such as PPS, kneaded and dispersed with a conductive material, causes melting of PPS crystals at about 210 ° C, which causes thermal expansion and conductivity. The distance between the materials is expanded and a positive temperature characteristic is expressed (see FIG. 1). When a resistor utilizing this characteristic is heated, a heating element capable of self-controlling the temperature at about 210 to 230 ° C. can be produced.

Although the heat generation temperature near 210 ° C. can be obtained only with PPS, the strength of the resistor at 210 ° C. is small and it causes a practical problem. Therefore, PEEK can provide strength.

It has been found that the self-temperature control expression point of the crystalline resin corresponds to the initial melting temperature of the crystal, and that the initial melting temperature of this crystal changes depending on its thermal history. That is, it indicates that the crystalline state changes depending on the thermal history.

Therefore, in order to actually perform stable self-temperature control, if the expression is performed with a crystalline resin such as PPS, the PES that does not change due to the heat history is accompanied by the phenomenon of the above-mentioned change in the temperature of the heating element over time, which is not practical. , PE
It has been found that it is preferable to express self-temperature control with an amorphous resin such as I.

[0020]

EXAMPLES The present invention will be described in more detail based on the following examples. Example 1 A conductive material (MnZn ferrite) was used as an organic polymer (PEEK).
/ PPS = 6/4), which was kneaded and dispersed in 50% by volume, was used as a press plate having a size of 30 mm × 40 mm × 1 mm (thickness), and copper foil was attached to both surfaces thereof to prepare a test piece.

FIG. 2 shows a time-dependent change in heat generation temperature when a continuous energization test was performed by applying a voltage of 100 V in the thickness direction by using this test piece and the apparatus shown in FIG. Example 2 A conductive material (MnZn ferrite) was used as an organic polymer (PEEK).
/ PEI = 6/4), which was kneaded and dispersed in 50% by volume, was used as a press plate having the same size as in Example 1, and a copper foil was attached to both surfaces thereof to prepare a test piece.

FIG. 2 shows the change over time in the heat generation temperature when this test piece was subjected to the continuous energization test in the same manner as in Example 1. Example 3 A conductive material (MnZn ferrite) was used as an organic polymer (PEEK).
/ PES = 6/4) was kneaded and dispersed in a volume of 50% by volume to make a press plate having the same size as in Example 1, and a copper foil was attached to both surfaces thereof to prepare a test piece.

FIG. 2 shows the changes over time in the heat generation temperature when this test piece was subjected to the continuous energization test in the same manner as in Example 1.

In the PPS of Example 1 in which the low melting point resin which actually exhibits self-temperature control is a crystalline resin, the heat generation temperature gradually rises as shown in FIG. On the other hand, the PEI of Example 2 and the PES of Example 3 in which the low melting point resin is an amorphous resin does not show the increase in the exothermic temperature with time.

Therefore, it can be seen that PES and PEI show better results than PPS. Example 4 An organic polymer material (PEEK / PEI = 6/4) using MnZn ferrite as a conductive material has a volume resistivity of 1
A pipe having a thickness of 1 mm was made of a composition filled with 50% by volume so as to be 0 ³ to 10 ⁵ Ωcm, and a nickel-plated product was used as the electrode 2 as shown in FIG. 4, and a PEEK / PEI cap (sealing material 3 ), And the exposed portion of the heating element was sealed by ultrasonic welding. The load life was significantly improved compared to the case where the exposed part was not sealed. Example 5 An organic polymer material (PEEK / PES = 6/4) using MnZn ferrite as a conductive material has a volume resistivity of 1
A 1 mm plate was made of a composition filled with 50% by volume so as to be 0 ³ to 10 ⁵ Ωcm, and a nickel foil (18 μm was used as an electrode.
The surface to which the m) had been pasted was coated with a far-infrared paint (SHOWEXCEL manufactured by Showa Densen). This one was capable of radiant heating equivalent to the one with a heating element temperature higher by about 50 ° C., and had excellent energy efficiency.

[0026]

EFFECTS OF THE INVENTION According to the present invention, by using a specific composition, it is possible to prepare a self-temperature control heater having a heat generation temperature of 150 ° C. or higher and a good temperature distribution, and the range of use of the self-temperature control heater is expanded. .

Further, by sealing the end surface of the self-temperature control heating element exposed in the air, the load life can be greatly improved without peeling off the sealing material.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a DSC curve of a heating element in which 50 vol% of MnZn ferrite is kneaded and dispersed in polyetheretherketone / resin having a specific melting temperature = 6/4.

FIG. 2 is a diagram showing a time-dependent change in heat generation temperature when a continuous energization test of the heating elements of Examples 1 to 3 is performed.

FIG. 3 is a schematic diagram of a test method of an energization test.

FIG. 4 is a view showing a shape of a heat-exposed-body-exposed-portion-sealed product formed by ultrasonic fusion of a pipe-shaped heat generating element.

[Explanation of symbols] 1 heating element 2 electrode 3 sealing material

Claims (6)

[Claims] 1. A current-carrying heating element for applying a voltage to a resistor having a composition comprising a conductive material dispersed in an organic polymer as a main component to generate heat, wherein the organic polymer of the current-generating heating element is polyetheretherketone. And temperature 380 ° C, shear rate 10 ²
A self-temperature-controlled energization heating element, which is formed from a resin having a melt viscosity of 10 ³ to 10 ⁴ poise at sec ⁻¹ . 2. The self-temperature-controlled electric heating element according to claim 1, wherein the resin having the melt viscosity according to claim 1 is polyphenylene sulfide. 3. The self-temperature-controlled energization heating element according to claim 1, wherein the resin having the melt viscosity according to claim 1 is an amorphous resin. 4. The self-temperature-controlled energization heating element according to claim 3, wherein the resin according to claim 3 is polyetherimide or polyether sulfone. 5. The heat made of the same material as the organic polymer material according to claim 1, the end surface of the self-temperature controlling energization heating element according to claim 1 exposed in the air. A self-temperature-controlled energization heating element characterized by being sealed with a fusion material. 6. The self-temperature-controlled energization heating element according to claim 1, wherein a far-infrared paint is applied to the outer surface of the energization heating element.