JPH02129885A - Self-temperature controllable heater - Google Patents

Abstract

PURPOSE:To obtain a self-temperature controllable heater, by providing electrodes in a heating body having its positive temperature coefficient, prepared through the process of dispersing and mixing tetracyanoquinodimethane and a nonionic activator or an anionic activator respectively into a high molecular compound or a composite high molecular compound, such as a plastic, etc., and adding carbon black, etc., to the resultant composition. CONSTITUTION:The resistance value of a heating body 1 is suitably set in accordance with the amount of carbon black being added, and yet its mixture ratio is kept small with the density of conductive carriers set to a low level, while the specific amount of tetracyanoquinodimethane functioning as an acceptor and the specific amount of a nonionic activator or an anionic activator functioning as a donor are respectively used to form a charge-transfer complex, and then the mobility of the conductive carriers is heightened accordingly as the heating body 1 becomes higher in temperature. The addition amount of the nonionic activator or the anionic activator is adjusted to set the mobility of the conductive carriers so that a characteristic which increases in resistance with the rise of temperature in the heating body 1 is adjusted. Electrode conductors 4 are respectively provided to be unified with the heating body 1. The heating body 1 keeps softness as well a flexibility, so that it is formed into a desired cross section for being permitted to quickly cover a water pipe 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a self-temperature control heater whose output can be adjusted according to ambient temperature or heat dissipation conditions.

[Problems to be solved by conventional techniques and inventions] Generally,
Heaters that use the coil resistance of high-resistance wires called nichrome wires or low-resistance wires can be used as long as the supplied voltage is constant.
Since power continues to be consumed in proportion to the voltage, there is a large waste of energy.

Furthermore, when it is necessary to maintain a constant temperature, it is necessary to provide a temperature regulator.

On the other hand, self-temperature control heaters utilize a heating element that has a PTC characteristic in which the resistance increases as the temperature of the heating element rises, and when the temperature reaches a preset temperature, the resistance of the heating element increases. It has a self-control function such that current stops flowing, limits output, and maintains a constant temperature.

The PTC characteristic is a positive temperature coefficient (positive thermistor), and as shown in FIG. 8, it refers to the function of a resistance element whose resistance increases as the temperature rises and has the function of gradually limiting the current. A heater that uses the resistance element as a heating element is a "self-temperature control heater."

Since the self-temperature control heater freely adjusts its output according to the ambient temperature or heat radiation conditions, it automatically adjusts its temperature even without an overoutput prevention device. Therefore, the overlapping portions due to bending or the like, or the overlapping portions such as double wrapping or cross-over of the tape heater, are extremely convenient because the heat generation amount can be adjusted by the self-temperature control function.

Conventional self-temperature control heaters use a resistor made of a highly crystalline polymer compound as a base material, mixed with a large amount of conductive material such as carbon black, graphite, or metal powder, as a heating element. The current was adjusted by changes in the volume expansion of the conductive particles and the rise and fall of the tunnel conduction effect of the conductive particles. Its operating principle is as follows.

(a) At room temperature, conductivity is obtained by electrons passing through the overlapping portions of conductive particles dispersed in the polymer base material due to the tunnel conduction effect.

(It) Since the conductive polymer mixture is a resistor, it generates heat when energized.

(c) When the temperature rises, the polymer base material expands and the overlapping conductive particles are spaced apart, so the resistance gradually increases and current no longer flows. When no current flows (when the temperature decreases, the polymer base material contracts, and the conductive particles approach each other, current begins to flow. By repeating this operation, a constant temperature is maintained. In other words, the heating element The amount of heat proportional to the temperature of the element itself is radiated, and the amount of heat generated and the amount of heat radiation reach a parallel temperature at which they are balanced.

In FIG. 10, a cross-sectional view of a conventional self-temperature control heater a is shown, and b is a heating element composed of a base material made of a polymer compound mixed with carbon black, graphite, etc.;
c and c are electrode conductors integrally provided on both side edges of the heating element, and d is an insulator covering these.

=4 However, the above conventional self-temperature control heater has the following drawbacks.

(a) In conductive carbon black, the strutures are destroyed by shearing during processing, so the resistance value tends to change significantly depending on processing conditions.

(U) Graphite does not have a striated structure, so it is less affected by processing. However, since the particles of graphite are larger than carbon black, there is a risk of electrical breakdown during energization.Furthermore, graphite has lower conductivity than carbon black, so it is necessary to mix it in large quantities, which causes heat generation. The body becomes hard and brittle, making it unsuitable for applications that require flexibility. Moreover, it is brittle and cannot be formed into a thin film.

(c) As the amount of conductive material mixed in increases, the difference in thermal expansion between the polymer base material and the conductive material such as graphite increases, so the gradient of resistance value/temperature characteristics tends to decrease.
Self-temperature regulation function decreases.

(=) With conventional products, when electricity is applied, a high-temperature area is likely to occur due to localized abnormal heat in the heating element, and once a high-temperature area occurs, it spreads and the temperature rises further. , eventually reaching the melting point of the heating element and causing a heat peak,
Accidents caused by fire often occurred. The cause of the occurrence of such localized high-temperature areas is thought to be due to poor dispersion of conductive substances such as carbon black and graphite mixed into the polymer base material, ie, local resistance imbalance of the heating element. 50 to 100 per 100 parts by weight of polymer base material
Conventional products contain a large amount of conductive material (parts by weight), making it difficult to completely disperse the material.

As shown in FIG. 9, this heat peak occurs when a high-temperature area e occurs in a part of the heating element, and the current that should normally flow through the high-temperature area e out of the current flowing between the electrode conductors c and c is generated. , avoids and detours around the high-temperature part e where the resistance has increased, so
As the current density around the area increases and the temperature rises rapidly, the high temperature area expands. In the figure, a portion f where parallel lines are close together indicates such a detour current. The frequency of heat peak occurrence increases as the distance between the electrodes c and c increases.

That is, it is known that when the distance between the electrodes exceeds about 100 mm, a heat peak occurs in a short time after the start of current application. Therefore, conventionally the distance between the electrodes was 100 m.
A self-temperature-controlling heating element with a temperature of m or more was not obtained.

(f) Conventional self-temperature control heaters generally deteriorate quickly over time and lack long-term stability. Although the cause is not clear, it can be inferred as follows. That is, when a large amount of conductive material is mixed, spatial gaps are generated due to poor dispersion of the conductive material and imbalance in the coefficient of thermal expansion between the polymer base material and the conductive material. Alternatively, bubbles may be generated due to moisture absorption or other chemical changes, and an increase in contact resistance may generate microscopic sparks at the interface, destroying the polymer composition or destroying the electrode.

As mentioned above, since it is not possible to increase the distance between the electrodes, various problems arise in terms of use. For example, when used to prevent freezing of water pipes, etc. A self-temperature control heater a formed into a tape shape
It was very troublesome as it had to be wound spirally.

An object of the present invention is to provide a self-temperature control heater that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, in the self-temperature-controlling heater of the present invention, tetracyanoquinodimethane as an acceptor and tetracyanoquinodimethane as a donor are added to a base material of a polymer compound or a composite polymer compound made of plastic or the like. An electrode comprising a heating element having a positive temperature coefficient characteristic formed by dispersing and mixing a nonionic active material or an anionic active material and adding a conductive additive such as carbon black, and further integrated with the heating element. It is equipped with a conductor.

In addition, on base materials made of polymer compounds such as plastics,
While dispersing and mixing 2.5 to 10 parts by weight of tetracyanoquinodimethane to 100 parts by weight of the base material,
~3 parts by weight of nonionic active material is dispersed and mixed, and 5~
It is equipped with a heating element constructed by adding 20 parts by weight of a conductive additive such as carbon black, and further provided with an electrode conductor integrated with the heating element.

The heating element has a substantially annular cross section with a discontinuous portion at one location, and electrode conductors are provided on both side edges of the heating element integrally with the heating element.

Further, the shape of the heating element may be rectangular or oblong in cross section, and electrode conductors may be provided at both side edges of the heating element integrally with the heating element.

The heating element may be formed into a flat plate, and in this case, electrode conductors can be provided on both side edges of the heating element integrally with the heating element.

The heating element may be formed to have a substantially annular cross section; in this case,
One electrode conductor is provided on the center side in the cross section of the heating element, and the other electrode conductor is provided on the outer diameter side in the cross section of the heating element so as to be integrated with the heating element.

[Function] The concentration of the conductive carrier is determined by the amount of conductive material such as carbon black added as a conductive aid, and by increasing or decreasing the amount added, the resistance value of the heating element can be set to an appropriate value. I can do it. The mixing ratio of carbon blank, etc., which is a conductive substance, is set to be low, that is, the concentration of the conductive carrier is set low, and in addition, in order to function as a heating element, tetracyanoquinodimethane and a nonionic active material or an anionic active material are set. is dispersed and mixed in a heating element to increase the mobility of conductive carriers. That is, a charge transfer complex is formed by tetracyanoquinodimethane as an acceptor and a nonionic active material or an anionic active material as a toner, and the mobility of the conductive carrier is increased as the temperature of the heating element increases. It is something. On the other hand, by adjusting the amount of nonionic active material or anionic active material added as a donor, the mobility of the conductive carrier can be set appropriately, and the strength of the PTC characteristic, in which the resistance increases as the temperature of the heating element increases, can be adjusted. You can.

Since electron transfer is carried out by a charge transfer complex with metallic properties, there is no heat peak caused by poor dispersion of carbon black, etc., and it is possible to reduce the amount of conductive material added. , the distance between the electrode conductors can be set large. Therefore, it is possible to make the overall shape planar, and if the overall shape is formed to have a substantially annular cross section with a discontinuous portion at one place,
To cover the outer circumferential surface of the pipe, it is possible to quickly install the pipe by expanding the discontinuous portion without having to wind it spirally many times.

[Example] An example will be described with reference to the drawings. Fig. 1 shows a case where the self-temperature control heater 3 according to the present invention is formed into a substantially cylindrical shape, and 9 is provided in the longitudinal direction. This is a fitting opening 6. Reference numeral 1 denotes a heating element, and the heating element 1 has a substantially annular cross section with a discontinuous portion 2 at one location. Reference numeral 44 denotes an electrode conductor, and the electrode body 4.4 is provided on both side edges 5, 5 of the heating element 1 integrally with the heating element 1. The surface of the heating element 1 is covered with an insulator 7.

Thus, the heating element 1 is made by dispersing and mixing tetracyanoquinodimethane (hereinafter referred to as "TCNQ") as an acceptor and a nonionic active material as a donor in a base material of a polymer compound made of plastic or the like, and It is composed by adding a conductive additive such as carbon black, and its composition ratio is 100 parts by weight of the base material, the ratio of TCNQ is 3 parts by weight, and the ratio of the nonionic active material is 1 part by weight. , the ratio of carbon black as a conductive aid to 8 parts by weight,
Similarly, the ratio of graphite as a conductive aid is set at 8 parts by weight.

In the present invention, in order to increase the conductivity of a polymer compound, a method of increasing the mobility of conductive carriers is adopted, and TCNQ, an organometallic semiconductor, is used as a charge transfer complex. Further, the polymer compound used as the base material is an insulator. An insulator is a dielectric material, and when an electric field is applied to it, a polarization phenomenon occurs and it becomes a dielectric conductor. Furthermore, ionic conductivity becomes dominant due to the activity of ionic impurities contained in the polymer. As the temperature rises, thermionic activity becomes more active, and the resistance value gradually decreases, resulting in a so-called NTC (negative thermistor) phenomenon. Therefore, it is important to select a polymer compound used for the base material that has a particularly low dipole efficiency.

Next, the experimental method and its results will be explained.

Experimentally, the invention began with the fact that when TCNQ was doped alone into a base material made of a polymer compound, a PTC reaction as shown in FIG. 4 occurred. TCNQ is a highly effective acceptor, and it is thought that by doping this acceptor, holes are generated and the PTC characteristic is exhibited. Therefore, the experiment started by mixing TCNQ alone into a polymer base material, and then added 1 part by weight of TCNQ to 100 parts by weight of polyolefin as a base material to form heating element 1 for the experiment. , from now on, the third
The linear heater shown in the figure was created and designated as Sample 8. In FIG. 3, the heating element 1 is formed to have a substantially circular cross section, and
One electrode conductor 4 is provided on the center side (inner diameter side) in the cross section of the heating element 1, and the other electrode conductor 4 is provided on the outer diameter side of the heating element 1, so that it is integrated with the heating element 1. be. Reference numeral 7 denotes an insulator that covers the outer peripheral surface of the electrode conductor 4 on the outer diameter side.

In the resistance test, the above sample 8 is placed in a thermostatic oven and the change in resistance value (impedance) is measured while gradually raising the temperature from 20°C.
The resistance value at 0°C was 7000 KΩ.

Next, when the amount of TCNQ added was increased to 3 parts by weight,
As shown by straight line B in Figure 4, the resistance value at 20°C is 2.
000 KΩ. However, in order for the heating element 1 of the sample 8 to function as a heater, the resistance value at 20°C must be 10 OKΩ or less. For this purpose, it becomes necessary to add at least 10 parts by weight of TCNQ. However, TCNQ is extremely expensive,
Due to the high cost, it cannot be used in large quantities.

Experiment I After trial and error, such as using various active materials and conductive substances in combination with TCNQ, we were able to break through the above wall by setting the following ratio.

Base material (polyolefin): Old: 100 parts by weight Acceptor (TCNQ): 3
Parts by weight Donor (nonionic active material): Old... 1 part by weight Conductive additive (carbon black): 8 parts by weight Conductive additive (Graphai: Former: 8 parts by weight) The heating element 1 based on the ratio was formed into a linear heater shown in FIG. 3 in the same manner as in Experiment 1 to form sample 8, and the resistance value due to temperature change was measured, as shown in C in FIG. 4.
The resistance value at 20°C was 20Ω.

The roles of various materials in this case are as follows.

TCNQ as an acceptor generates holes and converts PTC
Provide direction to The nonionic active material as a donor is
Since it generates free electrons or excites thermal ions to generate N (negative) type ion conduction, the strength of the PTC characteristic can be adjusted by adjusting the amount added. In other words, as shown in FIG. 7, at the desired set temperature T'C, P (positive) and N
Find the equilibrium point with (negative). The conductivity aids carbon black and graphite adjust the concentration of conductive carriers. That is, the resistance value of the heating element 1 is adjusted by increasing or decreasing the amount added. Importantly, using 10 to 20 parts by weight of carbon black and graphite other than TCNQ does not provide conductivity to function as a heating element. The mobility of the conductive carriers is increased by adding a very small amount of TCNQ as a nasal spray.

The composition ratio of each component of the heating element 1 is set as follows based on the results of numerous subsequent experiments. That is, 10
0 parts by weight of the base material, TCNQ in 2.5 to 10 parts by weight, nonionic active material as a donor in 0 to 3 parts by weight,
Good results can be obtained even if the carbon black as a conductive aid is set at 5 to 20 parts by weight and the graphite as a conductive aid is set at 0 to 20 parts by weight. .

In the above experiments, polyolefin polymers such as polyethylene and polypropylene were used as the base material, but other plastics, rubbers, or composite polymer compounds may also be used. TcNQ was used as the acceptor and a nonionic active material was used as the donor, which constitutes the charge transfer complex.
It is also preferable to use an anionic active material instead of a nonionic active material.

Regarding the conductive additive that determines the concentration of the conductive carrier, it is desirable to use both carbon black and graphite, but carbon black alone may also be used.
It is also preferable to use metal powder or the like instead of these.

By forming the fitting opening 9 at one location in the circumferential direction as shown in FIG. 1, the overall shape of the self-temperature-controllable heater 3 according to the present invention can be changed to a water tap as shown in FIG. It can be elastically attached to piping 10 such as a pipe with a single touch to cover the outer periphery, and can be removed with a single touch. As for the overall shape, as shown in Figure 5,
There is no problem even if the cross section is formed into a substantially elongated oval shape. in this case,
The heating element 1 is formed to have a substantially oblong cross section, and electrode conductors 4, 4 are provided integrally with the heating element 1 at both side edges 5, 5 of the heating element 1. Of course, the heating element 1 may have other shapes such as a rectangular cross section.

As for the shape of the heating element 1, it is preferable to have a flat plate shape as shown in FIG. Although not shown, it may be in the form of a tape.

Alternatively, it may be formed into the shape shown in FIG. 3 used in the experiment, for example.

The self-temperature control heater according to the present invention can be used for industrial purposes such as keeping pipes and tanks warm or preventing freezing, heating equipment or keeping them warm, and for agricultural purposes such as nursery beds, keeping livestock warm, greenhouses, and fermentation and brewing. It can be used for defrosting purposes such as heating, preventing freezing of water pipes and distribution pipes, floor heating, hot carpets, foot warmers, anchors, toilet bowls, and keeping warm beds, etc. for household purposes.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

■ TCNQ, an organometallic charge transfer complex, is used as a conductive carrier.
Since carbon black or graphite is used, the amount of mixing of carbon black or graphite can be extremely small. Therefore, the heating element 1 has flexibility and flexibility. Furthermore, since it does not become hard or brittle, it can be formed into a thin film. Due to its high flexibility, it can be applied to various uses that have not been used before, and it is also easy to manufacture.

(2) Since the amount of a conductive additive such as carbon black, which is a conductive substance, is added, there is no adverse effect due to a large difference in thermal expansion between the base material and the conductive substance. Furthermore, there is no risk of microscopic sparks occurring at the interface. Therefore, it has long-term stability, has improved reliability, and is safe.

(2) Conventionally, if the distance between the electrode conductors 4.4 exceeds 100 mm, a heat peak will always occur, so a wide planar self-temperature control heater has not existed. In the present invention, since the amount of the conductive substance added is small and a charge transfer complex having metallic properties is used for electron transfer, there is no risk of heat peaks occurring due to poor dispersion as in the conventional method. . Therefore, since the overall shape can be made into a wide planar shape or other wide shapes, the applications can be expanded to a greater extent than in the past.

■ By forming the overall shape into a substantially annular cross section with a fitting opening 9 in the longitudinal direction, as shown in Fig. 2,
It is possible to coat piping 10 such as a water pipe easily and quickly. In addition, since it can be formed into other shapes as desired, it can be used for various purposes other than conventional ones such as industrial and household use.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional perspective view of one embodiment of a self-temperature control heater according to the present invention, FIG. 2 is an explanatory diagram of how to use it, FIG. A characteristic diagram showing the experimental results, FIG. 5 is an enlarged cross-sectional view showing a modified example, FIG. 6 is an enlarged perspective view showing another example, and FIG. 7 is an explanatory diagram for setting the equilibrium point of PTC intensity. . FIG. 8 is a PTC characteristic diagram, FIG. 9 is an explanatory diagram showing the occurrence of heat peaks, FIG. 10 is an enlarged cross-sectional view showing a conventional example, and FIG. 11 is an explanatory diagram of usage. DESCRIPTION OF SYMBOLS 1... Heating element, 2... Discontinuous part, 4... Electrode conductor, 5... Side edge part.

Claims (1)

[Scope of Claims] 1. Tetracyanoquinodimethane as an acceptor and a nonionic active material or an anionic active material as a donor are dispersed and mixed in a base material of a polymer compound or a composite polymer compound made of plastic or the like, and It is characterized by comprising a heating element 1 having a positive temperature coefficient characteristic constructed by adding a conductive additive such as carbon black, and further comprising electrode conductors 4, 4 integrally provided with the heating element 1. Self-temperature control heater. 2. On a base material made of a polymer compound such as plastic, 1
Tetracyanoquinodimethane is dispersed and mixed at a ratio of 2.5 to 10 parts by weight to the base material of 0 to 0.0 parts by weight.
3 parts by weight of nonionic active material is dispersed and mixed, and 5 to 2 parts by weight of
Self-temperature control characterized by comprising a heating element 1 configured by adding 0 parts by weight of a conductive aid such as carbon black, and further comprising electrode conductors 4, 4 integrally provided with the heating element 1. heater. 3. The heating element 1 is formed to have a substantially annular cross section with a discontinuous portion 2 at one place, and electrode conductors 4, 4 are integrated with the heating element 1 at both side edges 5, 5 of the heating element 1. 2. The self-temperature control heater according to claim 1, further comprising: a self-temperature control heater; 4. The heating element 1 is formed to have a rectangular or oblong cross section, and the electrode conductors 4, 4 are provided on both side edges 5, 5 of the heating element 1 integrally with the heating element 1. Claim 1
Self-temperature control heater described. 5. The heating element 1 is formed into a flat plate shape, and the electrode conductors 4, 4
2. A self-temperature control heater according to claim 1, wherein said heating element is integrally formed with said heating element on both side edges 5, 5 of said heating element. 6. The heating element 1 is formed to have a substantially circular cross section, and one electrode conductor 4 is provided on the center side in the cross section of the heating element 1, and the other electrode conductor 4 is provided approximately in the cross section of the heating element 1. 2. The self-temperature control heater according to claim 1, wherein the heater is provided on the outer diameter side of the heater and is integrated with the heating element.