JPH0696843A - Temperature self-control conductive composition, temperature self-control surface heating element and temperature self-control pipe heater - Google Patents

Abstract

PURPOSE:To provide a temperature self-control heating element of high perfor mance by mixing a specific ratio of spherical of specific average grain size or expansion graphite power, with a varnish-like mixture containing a thermo plastic resin and carbon black. CONSTITUTION:Spherical carbon of average grain size of 2-30mum or expansion graphite power of average diameter of no more than 5000mum, is mixed with a varnish-like mixture containing a thermoplastic resin and carbon black, and a conductive composition is provided. A miximg ratio of both components is 5-95 weight parts for spherical carbon to 100 weight parts of the varnish-like mixture. Silver electrodes 4 for supplying power to a heating element are provided on an insulated substrate 3 consisting of a film and a non-woven fabric and the like, at two points, and the heating element 5 consisting of conductive composition is formed thereof by screen printing or spraying, and a surface heating element body is formed. A temperature self-control heating element body of high performance, which has excellent uniform heating characteristic as well as wide temperature control range, is thus provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature self-controlling conductive composition, a temperature self-controlling sheet heating element, and a temperature self-controlling pipe heater. More specifically, the present invention provides
A heat-generating element having a temperature self-controlling property, in particular, a conductive composition useful for producing a light and thin planar heating element having an arbitrary shape and rich flexibility, and temperature self-controlling obtained using the conductive composition The present invention relates to a flexible sheet heating element and a pipe-shaped heater capable of controlling temperature.

[0002]

2. Description of the Related Art Conventionally, as a lightweight and thin heating element, a composite of a metal wire, a metal foil, etc. and a resin has been generally known. However, since most of them cannot control the temperature by themselves, a thermostat, a fuse, etc. , It was necessary to use it together with the electrical resistor in the wiring.

Therefore, in recent years, attention has been paid to a heat-generating element capable of self-controlling the temperature which does not require the above-mentioned additional element. When such a heat-generating element exceeds a specific temperature, the resistance sharply increases and the temperature rises. A heating element has been developed in which a base is coated with a conductive composition whose self-control is performed. As such a conductive composition, a composition of carbon black and a resin has been conventionally known (for example, Japanese Patent Publication No. 61-
35223, JP-A-60-257091,
JP-A-61-39475).

However, carbon black originally has a property that it is difficult to disperse in a resin, and therefore the conventionally known conductive composition has a limit in reducing the resistance value and is usually used as a base of a heating element. Film,
Adhesion to non-woven fabric, foil, etc. was not sufficient. In particular, the resin that can be used to obtain a thin heating element using the above conventional conductive composition is extremely limited, and the width of the temperature range that can be controlled is considerably limited. In addition, the above-mentioned conventionally known conductive compositions also have the disadvantages that the temperature self-control region is limited to the low temperature region and that hysteresis due to heat cycle cannot be sufficiently eliminated.

Further, JP-A-61-181859 and JP-A-61-181860 disclose a conductive composition comprising a resin, carbon black and graphite. However, conventionally used graphite is natural graphite or artificial graphite, and they have a scaly shape, a needle shape, a plate shape, or the like, which is far from a spherical shape. In such a conventional conductive composition, there is a disadvantage that the graphite is apt to be non-uniformly dispersed, and when a planar heating element is used, the heat generation is non-uniform and lacks stability, and the heating element is easily separated from the base. It was

Further, a conventionally known heating element having temperature self-controlling property has a low rated temperature of about 30 to 120 ° C.,
In addition, since the temperature rising time to reach the holding temperature is as slow as 5 to 30 minutes, the application is generally limited to snow melting, anti-fog, floor heating and the like. Further, in the conventionally known heating element, the temperature distribution on the entire surface has a difference of 5 to 20 ° C., and the uniform heating property is poor. Further, the conventionally known heating element is limited to a film having a thickness of 0.5 mm or more and a rubber sheet having a thickness of several mm or more, such as a thin sheet and a pipe. No variant was obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and is not limited by the type of the thermoplastic resin, and can be easily printed on the base by a simple method such as printing. It is an object of the present invention to provide a conductive composition capable of easily forming a uniform thin film (planar heating element) and obtaining a high-performance heating element with extremely little hysteresis due to heat cycle. Further, according to the present invention, it is possible to easily obtain a heat-generating element having various self-controlling temperatures over a wide temperature range of 30 to 250 ° C., which is excellent in soaking property and has a short reaching time to the holding temperature. It is an object of the present invention to provide a conductive composition capable of obtaining a heating element.

The present invention further provides a thin sheet-shaped temperature self-controlling sheet heating element having the above-mentioned various characteristics,
It is another object of the present invention to provide a pipe-shaped heater having a pipe-shaped temperature self-controlling heating element that has been difficult to obtain conventionally.

[0009]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have found that spherical carbon and / or expanded graphite powder having a specific shape is converted into a varnish-like mixture containing a thermoplastic resin and carbon black. The inventors have found that a conductive composition that solves the above problems can be obtained by mixing, and have reached the present invention.

That is, the temperature self-controlling conductive composition of the present invention comprises (A) at least one selected from spherical carbon having an average particle diameter of 2 to 30 μm and expanded graphite powder having an average diameter of 5000 μm or less, and (B) a thermoplastic resin. A varnish-like mixture containing a resin and carbon black is contained at a ratio of 5 to 95 parts by weight of the component (A) with respect to 100 parts by weight of the component (B).

First, the temperature self-controlling conductive composition of the present invention will be described in detail below.

The spherical carbon according to the present invention is completely different in shape and size from conventionally used carbon black or so-called artificial graphite, and in the present invention, among them, the average particle diameter is 2 to 30 μm. Preferably 5-10
Use the one with μm. If the average particle size is less than 2 μm, it is extremely difficult to industrially manufacture, and if the average particle size is more than 30 μm, the conductive composition cannot be smoothly coated on the base or the like, which is inconvenient.

Such spherical carbon is different from the above-mentioned artificial graphite in the manufacturing method, and is mainly obtained by any of the following methods.

That is, (a) a method of carbonizing a spherical infusible phenol resin by heat treatment at 1500 to 2200 ° C., and (b) carbonization by carbon fine powder and / or heating on the surface of the spherical infusible phenol resin. The method of carbonizing by heating at 1500 to 2200 ° C. after coating the material to be coated, or (c) the material which acts as a binder and is carbonized by heating is preferably 5
This is a method of mixing 0 to 130% by weight of carbon fine powder, granulating, and then heat-treating at 1500 to 2200 ° C. to carbonize, and the method (b) is particularly preferable. Spherical carbon is obtained according to the conditions in each of the above methods.

The non-melting phenolic resin is a phenolic resin which does not melt even at the heat treatment temperature, and is, for example, Unitex C type Univex C type or UA.
Type phenol resin or Bell Pearl R type phenol resin manufactured by Kanebo Co., Ltd. is preferred. The carbon fine powder has an average particle size of 12
It is preferably about 40 to 40 nm, and examples thereof include carbon black. As the material carbonized by the above heating, a synthetic resin carbonized at the heat treatment temperature (for example, a meltable phenolic resin such as Univex S type or N type phenol resin manufactured by Unitika Ltd., Bellpearl S type phenol resin manufactured by Kanebo Ltd.) ), Or pitches that are carbonized at the above heat treatment temperature are preferred.

The carbonization treatment in each of the above methods is usually performed in a non-oxidizing atmosphere. In addition, as the coating method in the above method (b), a method of adhering carbon fine powder to the resin surface by a mechanochemical method, or a resin surface that is carbonized by the above heating alone or as a mixture with carbon fine powder The method of coating with is preferable.

The expanded graphite powder according to the present invention is also completely different from carbon black and so-called artificial graphite which have been conventionally used. In the present invention, among them, the average diameter is 5000 μm or less, preferably 2 to 5000 μm. Use one. Even if an average particle size of less than 2 μm is used, a heating element having sufficient temperature self-control performance and good reproducibility tends to be unobtainable. On the other hand, if an average particle size of more than 5000 μm is used, a conductive composition is obtained. However, it is not possible to coat the base and the like smoothly. Further, in the present invention, it is preferable to use expanded graphite having a C-axis direction expansion coefficient of at least 50 times or more. C-axis expansion rate is 50
This is because the conductive composition obtained by using less than twice the amount tends to be unable to smoothly coat the base or the like.

Such expanded graphite powder is mainly obtained by the following method. That is, natural graphite, quiche graphite, graphite having a layered crystal structure such as pyrolytic graphite is sulfuric acid,
It is immersed in a strong oxidizing agent such as nitric acid or chloric acid to form an intercalation compound, washed with water if necessary, and then heated (preferably 1000 ° C. or higher) in a non-oxidizing atmosphere. Then, the obtained expanded graphite is pulverized and sized as necessary to obtain expanded graphite powder having an average diameter of 5000 μm or less.

In the present invention, any one of the above-mentioned spherical carbon or expanded graphite powder may be used, or they may be used in combination (hereinafter,
(It is called component (A)).

The varnish-like mixture (hereinafter referred to as the component (B)) contained in the conductive composition of the present invention together with the component (A) contains a thermoplastic resin and carbon black.

Various kinds of thermoplastic resins can be used, for example, polycarbosilane, silicon resin,
At least one selected from a bismaleimide-triazine resin, a polyurethane resin and a polyester resin is preferred, and a mixture of polycarbosilane and a silicone resin or a silicone resin is particularly preferred.

The polycarbosilane usable in the present invention preferably has a molecular weight (MN) of 500 to 5,000. If the molecular weight is less than 500, the viscosity is low and kneading and three-roll kneading tend to be difficult, and there is a possibility that problems such as gas generation during curing may occur. On the other hand, when the molecular weight is more than 5,000, the viscosity is high, and it tends to be difficult to dissolve in a solvent to make varnish difficult, and the film forming property is poor even if varnishing is possible. Such polycarbosilane is preferably used by mixing with a silicon resin, and the content of polycarbosilane in the mixed resin is 70 to 90 wt%.
Is preferred. The content of polycarbosilane is 7
If it is less than 0 wt%, it tends to change over time or be difficult to use at a temperature of 180 ° C or higher, while 90 wt%
This is because if it exceeds%, the printability, adhesion and flexibility tend to be poor.

As carbon black which is an essential component of the varnish mixture according to the present invention, it is preferable to use furnace black or acetylene black having a well-developed structure because the electrical resistance value can be reduced with a small addition amount.

Further, a solvent may be optionally added to the varnish mixture according to the present invention. For example, Diana Solvent No. 2 (manufactured by Idemitsu Kosan Co., Ltd.), paraffinic solvent, carbitol acetate, dimethylformamide and γ
At least one selected from -butyl lactone is preferably used.

In the electroconductive composition of the present invention, sufficient dispersibility can be obtained only with the above components, but a dispersant such as a metallic soap or a nonionic surfactant may be optionally added to further improve the dispersibility. May be added to.

The varnish mixture used in the present invention contains 90 to 99% by weight of the above-mentioned thermoplastic resin (when the solvent is contained, the total amount of the thermoplastic resin and the solvent), the above-mentioned carbon black (containing the dispersant. In this case, the total amount of carbon black and dispersant) is preferably 1 to 10% by weight. In the varnish-like mixture, if the carbon black is higher than the above range, the dispersion tends to be insufficient, whereas if it is less than the above range, the effect of the present invention tends not to be exhibited.

In the conductive composition of the present invention, the component (A) is added in an amount of 5 to 100 parts by weight of the component (B).
The content must be 95 parts by weight, preferably 5 to 92 parts by weight. When the content of the component (A) is less than 5 parts by weight,
It is not possible to obtain a desired resistance value as a planar heating element, and it is not possible to obtain a uniform heating element. On the other hand, when the content of the component (A) exceeds 95 parts by weight, not only the component (A) does not disperse uniformly, but the adhesion to the base decreases,
The heating element is easily peeled off.

The conductive composition of the present invention can be obtained by appropriately mixing the above-mentioned components (A) and (B) in the compounding amounts within the above range, and the mixing method at that time is preferably a roll kneading method.

In the conductive composition of the present invention, its specific resistance and self-controllable temperature are set by appropriately selecting the composition within the scope of the present invention. For example, the specific resistance value can be adjusted by increasing or decreasing the content of carbon black or spherical carbon. Further, by changing the type and content of the thermoplastic resin and the solvent, the temperature at which the resistance value rapidly increases, that is, the temperature at which the resin around the conductive member partially melts and interrupts conduction between the conductive members, Can be adjusted. However, in the conductive composition of the present invention, whichever composition is adopted, the adhesion of the conductive composition to the base is maintained at a high level.

By appropriately molding the above-mentioned electrically conductive composition of the present invention, various temperature self-controlling heating elements, preferably planar heating elements, can be easily obtained. Less than,
The temperature-controlled surface heating element of the present invention will be described.

That is, the temperature self-controlling sheet heating element of the present invention is obtained by heat-treating a sheet obtained by molding the above-mentioned conductive composition of the present invention into a sheet.

The method for molding the conductive composition into a planar shape is not particularly limited. For example, a method by screen printing (80 to 325 mesh), a method of appropriately diluting with a solvent and spraying, or a method of coating with a bar coater is used. Can be molded into a shape. Further, when the conductive composition is formed into a sheet, it is usually formed as a coating on a base such as a film or a non-woven fabric. The above heat treatment cures / stabilizes the conductive composition, preferably at 130 to 250 ° C. for 1 hour.
Perform for 0 to 90 minutes. The shape and thickness of the sheet heating element of the present invention are not particularly limited, but a thickness of 5 to 100 μm is preferable.

Practically, the heating element can be obtained by providing the planar heating element with at least two electrodes for power supply connection before or after the heat treatment. As a method for forming the electrodes, there are a printing method using a silver resin ink and a method of attaching a metal foil tape via an anisotropic conductive adhesive. Further, in the field where moisture resistance is required, it is also possible to overcoat the above heating element with a silicone rubber or fluororubber ink having both water repellency and insulation.

Further, since the sheet heating element obtained by using the above-mentioned conductive composition of the present invention is excellent in moldability and adhesion to various substrates, it has been difficult to obtain a pipe-shaped sheet. It becomes possible to easily obtain a temperature self-controlling heating element having an arbitrary shape such as. Hereinafter, the pipe-shaped heater of the present invention having a pipe-shaped temperature self-controlling heating element will be described.

That is, the temperature-controlled pipe-shaped heater of the present invention is a pipe-shaped insulating base material, and the conductive composition of the present invention is heat-treated on a pipe-shaped insulating base material. It is characterized in that it is provided with a heating element obtained in this way and an electrode for energizing the heating element.

The pipe-shaped insulating base material is not particularly limited, and examples thereof include a metal pipe having a size suitable for the application, the surface of which is subjected to an insulation treatment, and quartz glass.

Further, as the above-mentioned electrode, a commercially available silver paste or the like can be used.
As a silver electrode paste corresponding to a high temperature region of ° C, a paste using a ladder type silicone oligomer as a matrix and silver powder as a filler is preferable. In the case of such a silver electrode paste, the silver powder in the paste is preferably 75 to 90 wt%. This is because if the silver powder is less than 75 wt%, the adhesion and conductivity tend to be poor, while if it exceeds 90 wt%, it tends to be difficult to form a paste.

Further, in the pipe-shaped heater of the present invention, a protective film made of a film-shaped insulating material may be further provided on the heating element. By providing the protective film having high thermal conductivity and excellent slidability, it is possible to protect the heat generating portion, improve the moisture resistance and the slidability. As a method of forming such a protective film, a method of overcoating the surface of the heater portion by covering with a heat-shrinkable fluororesin tube having an inner diameter larger by about 10% than the outer diameter of the pipe-shaped heater to heat-shrink is preferable. Alternatively, the protective film may be formed by coating the matrix with a ladder-type silicone oligomer and the filler with a paste using boron nitride. The boron nitride in the paste is effective in improving the sliding property and heat conductivity of the protective film, and the amount is preferably 5 to 10% by weight.

[0039]

EXAMPLES The present invention will be described more specifically below based on examples and comparative examples.

Example 1 The following composition: -Bismaleimide-triazine resin (BT2170) 27.9 wt% [Mitsubishi Gas Chemical Co., Ltd.]-Carbon black (acetylene black) 4.8 wt% [Electrochemical industry ( Co., Ltd.]-Dispersant (NP-2: manufactured by Nikko Chemicals Co., Ltd.) 2.2% by weight-Carbitol acetate 65.1% by weight was prepared as a varnish mixture. The above varnish mixture 10
Expanded graphite powder (average diameter 4500μ
m, manufactured by Nippon Carbon Co., Ltd.), and kneaded with a planetary mixer, and further passed through a triple roll to obtain a conductive composition.

The obtained conductive composition was applied onto a polyimide film using a SUS100 mesh screen for 20 minutes.
Screen print on a size of 0x100mm, 150 ℃
When heat-treated for 30 minutes, a very smooth sheet heating element (thickness 38 μm) was obtained. Then, electrodes were printed with silver paste on both ends of the planar heating element to obtain heating elements.
The resistance of both ends of the obtained heating element at room temperature was 220Ω.

Next, when a voltage of 100 V was applied to the above heating element, heat was generated and after 20 seconds, the temperature became 210 ° C., and thereafter, the temperature became constant at 210 ° C. ± 4 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. afterwards,
The power was turned off once and the heating element was cooled to room temperature. Furthermore, the above-mentioned heating element was repeatedly used 100 times under the same conditions, but no peeling of the heating element occurred, and there was no change in the temperature at which it was in a steady state.

Example 2 The following composition: -Bismaleimide-triazine resin (BT2170) 28.0% by weight-Carbon black (acetylene black) 4.6% by weight-Dispersant (metal soap) 2.2% by weight-Acetic acid A varnish-like mixture of 65.2% by weight carbitol was prepared. On the other hand, the surface of a spherical infusible phenol resin was coated with carbon black by a mechanochemical method, and then carbonized at 2000 ° C. to obtain spherical carbon having an average particle size of 10 μm. Then, to 100 parts by weight of the varnish-like mixture, 16 parts by weight of the spherical carbon and 6.0 parts by weight of the same expanded graphite powder as in Example 1 were added, and the mixture was kneaded with a planetary mixer, and further four times on a three-roll mill. To obtain a conductive composition.

The conductive composition thus obtained was applied onto a polyimide film using a SUS200 mesh screen.
Screen-printed on a size of 0x100mm, 170 ℃
When heat-treated for 30 minutes, a very smooth sheet heating element (film thickness 14 μm) was obtained. Then, electrodes were printed with silver paste on both ends of the planar heating element to obtain heating elements.
The resistance of both ends of the obtained heating element at room temperature was 300Ω.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, it generated heat and reached 130 ° C. 20 seconds later, and thereafter, the temperature became constant at 130 ° C. ± 2 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. afterwards,
The power was turned off once and the heating element was cooled to room temperature. Furthermore, the above-mentioned heating element was repeatedly used 100 times under the same conditions, but no peeling of the heating element occurred, and there was no change in the temperature at which it was in a steady state.

Example 3 The following composition: Silicon resin (TSE-3221: manufactured by Toshiba Silicone Co., Ltd.) 91.0% by weight Carbon black (Furnace Black MA-8) 9.0% by weight [Mitsubishi Kasei )] Was prepared. The above varnish mixture 10
45 parts by weight of spherical carbon similar to that in Example 2 was added to 0 parts by weight, kneaded with a planetary mixer, and passed through a triple roll to obtain a conductive composition.

The obtained conductive composition was diluted with the same amount of xylene and a spray gun was used to form a 100 × 100 mm size coating on the polyarylate resin film (thickness 75 μm). When heat-treated for a minute, a very smooth sheet heating element (film thickness 10 μm) was obtained. Then, electrodes were printed with silver paste on both ends of the planar heating element and heat-treated at 150 ° C. for 30 minutes to obtain a heating element. The resistance of both ends of the obtained heating element at room temperature was 425.
It was Ω.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, it generated heat and reached 87 ° C. after 30 seconds, and thereafter the temperature became constant at 87 ° ± 5 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. Then, the power supply was once turned off and the heating element was cooled to room temperature. Furthermore, the above-mentioned heating element was repeatedly used 100 times under the same conditions, but no peeling of the heating element occurred, and there was no change in the temperature at which it was in a steady state.

Example 4 The following composition: -Polyurethane resin (Takenate B-7013) 79.3% by weight [Takeda Pharmaceutical Co., Ltd.]-Carbon black (acetylene black) 4.1% by weight-γ-butyl lactone A 16.6 wt.% Varnish mixture was prepared. On the other hand, the surface of a spherical infusible phenol resin was coated with molten pitch, and then carbonized at 2000 ° C. to obtain spherical carbon having an average particle diameter of 10 μm. Then, 75 parts by weight of the spherical carbon was added to 100 parts by weight of the varnish-like mixture, kneaded by a planetary mixer, and further passed through a triple roll to obtain a conductive composition.

The conductive composition thus obtained was screen-printed on a polyarylate resin film (thickness: 100 μm) to a size of 100 × 100 mm using a SUS200 mesh screen and heat-treated at 150 ° C. for 15 minutes. A smooth planar heating element (film thickness 12 μm) was obtained. Then, electrodes were printed with silver paste on both ends of the planar heating element to obtain heating elements. The resistance of both ends of the obtained heating element at room temperature was 180Ω.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, it generated heat and reached 65 ° C. after 30 seconds, and thereafter the temperature became constant at 65 ° C. ± 10 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. Then, the power supply was once turned off and the heating element was cooled to room temperature. further,
The heating element was repeatedly used 100 times under the same conditions, but no peeling of the heating element occurred, and no change was observed in the temperature at which the heating element was in a steady state.

Example 5 The following composition: a varnish mixture of 63.2% by weight of polyester resin, 2.3% by weight of carbon black (furnace black MA-8) and 34.5% by weight of DMF was prepared. On the other hand, the spherical infusible phenol resin was carbonized at 2000 ° C. to obtain spherical carbon having an average particle size of 5 μm. And the above-mentioned varnish mixture 10
15 parts by weight of the spherical carbon is added to 0 parts by weight,
The mixture was kneaded with a planetary mixer and passed through a triple roll to obtain a conductive composition.

The conductive composition thus obtained was screen-printed on a polyarylate resin film (thickness: 100 μm) to a size of 100 × 100 mm using a SUS200 mesh screen and heat-treated at 120 ° C. for 30 minutes. A smooth planar heating element (film thickness 14 μm) was obtained. Then, electrodes were printed with silver paste on both ends of the planar heating element to obtain heating elements. The resistance of both ends of the obtained heating element at room temperature was 580Ω.

Next, when a voltage of 100 V was applied to the above heating element, it generated heat and reached 45 ° C. 50 seconds later, and thereafter, the temperature became constant at 45 ° C. ± 8 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. Then, the power supply was once turned off and the heating element was cooled to room temperature. Furthermore, the above-mentioned heating element was repeatedly used 100 times under the same conditions, but no peeling of the heating element occurred, and there was no change in the temperature at which it was in a steady state.

Example 6 The following composition: Silicon resin (Q1-4010) 91.0% by weight [Toray Dow Corning Co., Ltd.] Carbon black (acetylene black) 9.0% by weight varnish mixture Prepared. On the other hand, carbon black (acetylene black) and pitch are mixed in equal weights, granulated and then carbonized at 1800 ° C. to give an average particle size of 12 μm.
m spherical carbon was obtained. Then, to 100 parts by weight of the varnish-like mixture, 60 parts by weight of the spherical carbon and 6.7 parts by weight of expanded graphite powder having an average diameter of 1000 μm were added, kneaded with a planetary mixer, and further passed through a three-roll to conduct electricity. A composition was obtained.

The resulting electrically conductive composition was applied to an aramid nonwoven fabric (thickness: 130) using a SUS200 mesh screen.
[mu] m: manufactured by DuPont Co., Ltd., screen-printed in a size of 100 * 100 mm and heat-treated at 150 [deg.] C. for 15 minutes to obtain a very smooth sheet heating element (film thickness 15 [mu] m). Then, electrodes were printed with silver paste on both ends of the planar heating element to obtain heating elements. The resistance of both ends of the obtained heating element at room temperature was 350Ω.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, it generated heat and reached 100 ° C. after 30 seconds, and thereafter the temperature became constant at 100 ° C. ± 5 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. afterwards,
The power was turned off once and the heating element was cooled to room temperature. Furthermore, the above-mentioned heating element was repeatedly used 100 times under the same conditions, but no peeling of the heating element occurred, and there was no change in the temperature at which it was in a steady state.

Example 7 The following composition: a varnish mixture of silicon resin (TSE-3221: manufactured by Toshiba Silicone Co., Ltd.) 91.0 wt% carbon black (acetylene black) 9.0 wt% was prepared. The above varnish mixture 10
11 parts by weight of expanded graphite powder having an average diameter of 1000 μm was added to 0 parts by weight, and the mixture was kneaded by a planetary mixer and passed through a triple roll to obtain a conductive composition.

The conductive composition thus obtained was screen-printed on a polyarylate resin film (thickness: 100 μm) to a size of 200 × 100 mm using a SUS200 mesh screen and heat-treated at 150 ° C. for 30 minutes. A smooth planar heating element (film thickness 15 μm) was obtained. Then, electrodes were printed with silver paste on both ends of the planar heating element to obtain heating elements. The resistance of both ends of the obtained heating element at room temperature was 210Ω.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, it generated heat and reached 145 ° C. after 20 seconds, and thereafter the temperature became constant at 145 ° C. ± 2 ° C. The voltage was applied as it was for 50 hours, but there was no particular change. afterwards,
The power was turned off once and the heating element was cooled to room temperature.

The relationship between the temperature from the heat generation to the cooling and the element resistance value (total resistance value) was measured, and the result is shown in FIG. In FIG. 1, the solid line (1) is the resistance increase curve when the temperature rises, and the broken line (2) is the resistance decrease curve when the temperature falls. As is clear from FIG. 1, the resistance of the heating element of the present example sharply increased from around 120 ° C., and the temperature was self-controlled. In addition, the hysteresis when the temperature rises and when the temperature falls is very small, and the total resistance at room temperature was almost the same before and after energization.

Further, the heating element is heated under the same conditions for 100
After repeated use, no exfoliation of the heating element occurred and no change was observed in the temperature at which the heating element reached a steady state.

Comparative Example 1 A heating element was obtained in the same manner as in Example 1 except that the amount of expanded graphite powder added was 4.0 parts by weight with respect to 100 parts by weight of the varnish mixture.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, heat was generated and the temperature reached 80 ° C. 120 seconds later. When the voltage was continuously applied for 50 hours, the temperature was kept substantially constant. However, when the power source was once turned off to cool the heating element to room temperature and then the above voltage was applied again, the temperature did not rise so much that the temperature was only 35 ° C. even after 5 minutes, and it could not be repeatedly used thereafter.

Comparative Example 2 A heating element was obtained in the same manner as in Example 4 except that the amount of spherical carbon added was 100 parts by weight with respect to 100 parts by weight of the varnish mixture.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, heat was generated and the temperature reached 70 ° C. 20 seconds later, but after that, the temperature gradually increased and the heating element was thermally deformed, so it continued. I can no longer use it.

Comparative Example 3 The following composition: -Polyurethane resin (Takenate B-7013) 80.0% by weight-Carbon black (Ketjenblack EC600JD) 20.0% by weight A varnish mixture was prepared and kneaded to conduct electricity. A sex composition was obtained. Then, Example 4 was repeated except that this conductive composition was used.
A heating element was obtained in the same manner as in.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, it generated heat and reached 80 ° C. 40 seconds later, but the temperature of the heating surface locally rose, and after about 1 hour, the heating element turned off. Since the part began to melt, it could not be used continuously, and the power had to be turned off.

Comparative Example 4 20 parts by weight of artificial graphite (ground powder: average diameter 12 μm) was added to 100 parts by weight of the varnish mixture of Comparative Example 3,
The mixture was kneaded with a planetary mixer and passed through a triple roll to obtain a conductive composition. Then, a heating element was obtained in the same manner as in Example 4 except that this conductive composition was used.

Next, when a voltage of 100 V was applied to the above heating element, a large amount of local heat was generated, and there was a variation of 30 to 80 ° C. on the surface even after 120 seconds. It is considered that this is because uniform heat generation could not be obtained due to uneven distribution of graphite and variation in film thickness.

Comparative Example 5 A heating element was obtained in the same manner as in Example 4 except that spherical carbon having an average particle size of 50 μm was used.

Next, when a voltage of 100 V was applied to the above-mentioned heating element, heat was generated and reached 65 ° C. after 30 seconds, and thereafter, the temperature became constant at 65 ° C. ± 15 ° C., but the film thickness became uneven. Cracking and delamination of the film, which was attributed to it, occurred after about 10 hours and became unusable.

Comparative Example 6 An electrically conductive composition was prepared in the same manner as in Example 1 except that expanded graphite powder having an average diameter of 8000 μm was used.
Familiarity with the varnish mixture was poor and a homogeneous composition could not be obtained.

Example 8 The following composition: Polycarbosilane (average molecular weight 800) 52.6% by weight [Nippon Carbon Co., Ltd.] Silicon resin (Q1-4010) 13.1% by weight [Toray Dow Corning] Manufactured by Co., Ltd.-Carbon black (acetylene black) 7.8 wt% [Denki Kagaku Kogyo Co., Ltd.]-Solvent (Diana Solvent No. 2) 26.5 wt% [Idemitsu Kosan Co., Ltd.] Varnish A mixture was prepared. The above varnish mixture 10
Expanded graphite powder (average diameter 4500μ
m, FL-GA: manufactured by Nippon Carbon Co., Ltd. 11.8 parts by weight and spherical carbon (average particle size 10 μm, MC-10).
20: 78.7 parts by weight of Nippon Carbon Co., Ltd. was added,
Knead with a planetary mixer, and then roll on three rolls.
A conductive composition was obtained over time.

On the other hand, the following composition: Silicon resin (GR-908: Showa Denko KK) 9.0 wt% Silver powder (TCG7: Tokuriki Kagaku Kenkyusho) 35.7 wt% Silver powder (E20: E20: A mixture of 15.3 wt% and solvent (ethyl carbitol acetate) 40.0 wt% was prepared. This mixture was kneaded with a planetary mixer and passed through a triple roll for 30 minutes to obtain a silver electrode paste.

Next, the obtained conductive composition was treated with SUS20.
Screen print on a polyimide film to a size of 200 x 50 mm using a 0 mesh screen.
When heat-treated at 0 ° C. for 30 minutes, a very smooth sheet heating element (film thickness 30 μm) was obtained. Then, a comb-shaped electrode (distance between electrodes: 14 mm) was printed on the planar heating element using the above silver paste to obtain a heating element. The resistance of both ends of the obtained heating element at room temperature was 19Ω.

Next, when a voltage of 60 V was applied to the above-mentioned heating element, it generated heat and after 20 seconds the temperature became 190 ° C. After that, the temperature became constant at 190 ° C. ± 3 ° C. When the voltage is further increased to 80V, the temperature becomes constant at 215 ° C ± 3 ° C and 10
Even if the voltage was increased to 0 V, 215 ° C. ± 3 ° C. did not change, and it was confirmed that the temperature was well controlled. Further, the energization was continued for 100 hours with the voltage of 60 V applied to the heating element, but there was no particular change in the holding temperature and its variation. After that, the power was once turned off, left for 5 minutes, and then energized again for 5 minutes. This operation was repeated 50 times, but no exfoliation of the heating element occurred, and there was no change in performance such as temperature rising time or holding temperature. I couldn't see it.

Example 9 Instead of the silicone resin (GR-908), the silicone resin (GR-
100: An aluminum pipe whose surface was treated with alumina using a silver electrode paste obtained in the same manner as in Example 8 except that Showa Denko KK was used (wall thickness 1 mm, outer diameter 12 mmφ × 35).
0 mmL) was printed on the outer peripheral surface, and the comb-shaped electrodes (interelectrode distance 2.7 mm) shown in FIG. 2 were formed as electrodes for power supply connection.

Then, a conductive composition similar to that used in Example 8 was diluted with 150 parts by weight of a volatile solvent (Diana Solvent No. 2) per 100 parts by weight of the composition, and a spray gun was used. 2 on the outer peripheral surface of the pipe using
As shown in Fig.3, form a coating with a length of 300 mm and
When heat-treated for 30 minutes, a pipe-shaped heater having a planar heating element (film thickness 30 μm) formed in a pipe shape with a smooth surface was obtained. The resistance of both ends of the obtained heating element at room temperature was 31Ω. Moreover, it was confirmed that the resistance change of the heating element with respect to the environmental temperature change was positive and that the heating element had temperature self-controllability.

When a voltage of 100 V AC was applied to the heating element, it generated heat and reached 213 ° C. in 3 minutes, and thereafter 213
The temperature became constant at ℃ ± 1 ℃. Further, the temperature distribution on the surface of the heating element was kept within the range of 213 ° C. ± 1 ° C. over the entire surface, and the heating characteristics were stable with no change even when electricity was continuously applied for 120 hours.

Example 10 The following composition: Silicon resin (Q1-4010) 59.2% by weight Silicon resin (TSE-3221: manufactured by Toshiba Silicone Co., Ltd.) 39.5% by weight Carbon black (acetylene black) A 1.3% by weight varnish mixture was prepared. The above varnish mixture 10
Expanded graphite powder (average diameter 4500μ
m, FL-GA) 2.0 parts by weight and spherical carbon (average particle size 10 μm, MC-1020) 62.5 parts by weight were added, and the mixture was kneaded with a planetary mixer and further passed through a three-roll for 2 hours to be conductive. A composition was obtained.

Then, a polyester silver paste (XA-
527: Fujikura Kasei Co., Ltd. aluminum pipe whose surface is treated with alumina (wall thickness 1 mm, outer diameter 12 mmφ × 260 m)
(mL) was printed on the outer peripheral surface, and the comb-shaped electrodes (interelectrode distance 2.7 mm) shown in FIG. 2 were formed as electrodes for power supply connection.

Further, the conductive composition obtained above was diluted with 200 parts by weight of a volatile solvent (Diana Solvent No. 2) per 100 parts by weight of the composition, and the above pipe was used by using a curved surface printing machine. As shown in FIG. 2, a coating film having a length of 220 mm was formed on the outer peripheral surface of and was heat-treated at 150 ° C. for 30 minutes to have a planar heating element (thickness 30 μm) formed in a pipe shape with a smooth surface. A pipe heater was obtained. The resistance of both ends of the obtained heating element at room temperature is 20Ω.
Met. Moreover, it was confirmed that the resistance change of the heating element with respect to the environmental temperature change was positive and that the heating element had temperature self-controllability.

When a voltage of AC100V was applied to the heating element, it generated heat and reached 121 ° C. after 3 minutes.
The temperature became constant at ℃ ± 1 ℃. In addition, the temperature distribution on the surface of the heating element was entirely within the range of 121 ° C ± 4 ° C.

Next, as shown in FIG. 3, the entire surface of the heating element is covered with a fluororesin tube (thickness: 0.3 mm, inner diameter: 13 m).
mφ × 230 mmL, GF tube: Gunze Co., Ltd.)
When heat-treated at 100 ° C. for 10 minutes, the heating portion was overcoated due to shrinkage of the fluororesin tube, and a pipe-shaped heater having a protective film with excellent slidability was obtained. In FIG. 3, the thickness is enlarged in order to illustrate the thickness. AC10 for the above heating element
When a voltage of 0 V was applied, the characteristics of the heating element did not change at all, and peeling of the heating element and protective film did not occur.

Reference Example 1 Composition below: -Polyimide resin (CT-4150) 18.1% by weight [manufactured by Toshiba Chemical Co., Ltd.]-Carbon black (acetylene black) 1.5% by weight-Solvent (N-methyl-2-pyrrolidone) ) A varnish mixture of 80.4% by weight was prepared. The above varnish mixture 10
Expanded graphite powder (average diameter 4500μ
m, FL-GA) 2.2 parts by weight and spherical carbon (average particle size 10 μm, MC-1020) 14.5 parts by weight were added, and the mixture was kneaded with a planetary mixer and further passed through a three-roll for 2 hours to be conductive. A composition was obtained.

Then, a pipe-shaped heater having a planar heating element molded into a pipe shape was obtained in the same manner as in Example 9 except that this conductive composition was used.

When a voltage of AC 100 V was applied to this heating element, it generated heat and reached 212 ° C. after 3 minutes.
The temperature becomes constant at ℃ ± 1 ℃, and the temperature distribution on the surface of the heating element is 2
It fell within the range of 12 ° C ± 1 ° C. However, the temperature coefficient of this heating element was negative, and there was no self-control performance.

Reference Example 2 An electrode for connecting a power source was used as a urethane silver paste (DD-15).
50: A pipe-shaped heater having a sheet-shaped heating element molded into a pipe was obtained in the same manner as in Example 9 except that the heater was manufactured using Kyoto Elex Co., Ltd.

When a voltage of 100 V AC was applied to this heating element, it generated heat and had the same heating characteristics as in Example 9. However, when the voltage was continuously applied for 100 hours, the electrode part turned light brown and a local temperature rise occurred.
Shortly after that, a short circuit occurred and the exothermic temperature dropped.

Reference Example 3 Composition as follows: 40% by weight of bismaleimide-triazine resin (BT-2170) [manufactured by Mitsubishi Gas Chemical Co., Inc.] 60% by weight of xylene-ethylmethylketone (MEK) mixed solvent Varnish form A mixture was prepared. A pipe-shaped heater was obtained in the same manner as in Example 10 except that a protective film for the heating element was formed by forming a coating film of the above varnish-like mixture on the heating portion using a spray gun. However, the protective film peeled off after curing.

As is clear from the results of each of the above examples, the conductive composition of the present invention was obtained in spite of using a general resin which was conventionally difficult to use in combination with carbon black. All of the above-mentioned sheet heating elements have excellent covering power for the base, and are conductive below a certain temperature, but have extremely high electrical resistance above a certain temperature (having positive resistance to temperature), It had excellent temperature self-control performance. Further, the above-mentioned sheet heating element of the present invention has a heat resistance hysteresis property and is stable even after repeated use. Such good performance is due to the fact that both the component (A) component carbon black and the component (B) component carbon black are uniformly dispersed in the thin film, and a uniform resistance distribution is maintained, and their conductivity and (B ) It is considered that this is achieved by a good combination with the plasticity of the component resins depending on the temperature.

The heating element of the present invention obtained by using the above-mentioned conductive composition of the present invention has a uniform temperature distribution of about 20.
The holding temperature was reached in less than a second, and the holding temperature could be freely designed within a wide range of 30 ° C to 250 ° C. Further, the heating element of the present invention has good adhesion to the substrate, and a heating element of any shape such as a thin film self-controlling pipe-shaped heating element having the above-mentioned excellent properties could be produced.

On the other hand, the planar heating element of each comparative example obtained by using the conductive composition outside the scope of the present invention, temperature control performance, adhesion to the base, stability of control temperature (reproducibility). ) Was inferior in at least one of the points.

[0095]

As described above, when the conductive composition of the present invention is used, a strong and uniform thin film (planar heating element) is formed on the base without being limited by the kind of the thermoplastic resin. It is possible to obtain a high-performance temperature self-controlling heating element which can be easily formed and has extremely low hysteresis and good reproducibility. In addition, the conductive composition of the present invention has various self-controlling temperatures over a very wide temperature range of 30 to 250 ° C. by appropriately selecting the composition and the like within the range of the present invention. It is possible to easily obtain a heating element, and in particular, it is possible to obtain a planar heating element with excellent durability and reproducibility even if the heating element has a high self-control temperature, which was relatively difficult to obtain in the past. It becomes possible.

Further, since the planar heating element of the present invention is excellent in soaking property, has a short time to reach the holding temperature, and has a wide controllable temperature range as described above, it is not suitable for the planar heating element of the present invention. It has many uses. And, by using the conductive composition of the present invention, it is possible to easily obtain a planar heating element having excellent adhesion to a substrate and moldability. Therefore, the present invention has a temperature self-controlling property for OA equipment parts, for example. A pipe-shaped heater or the like can be easily obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a temperature from heat generation to cooling and an element resistance value (total resistance value) of a heating element according to an embodiment of the present invention.

FIG. 2 is a perspective view of an embodiment of a temperature-controlled pipe heater according to the present invention.

FIG. 3 is a partial vertical cross-sectional view of one embodiment of the temperature-controlled pipe heater of the present invention.

[Explanation of symbols]

1: curve of resistance increase when temperature rises, 2: curve of resistance decrease when temperature falls, 3: insulating pipe, 4: silver electrode, 5: heating element, 6: protective film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01C 7/00 J H05B 3/20 305 3/42 7913-3K

Claims (11)

[Claims] (A) at least one selected from spherical carbon having an average particle diameter of 2 to 30 μm and expanded graphite powder having an average diameter of 5000 μm or less, and (B) a varnish mixture containing a thermoplastic resin and carbon black. ,
A temperature self-controlling conductive composition, characterized in that the component (A) is contained in an amount of 5 to 95 parts by weight with respect to 100 parts by weight of the component (B). 2. The spherical carbon is (b) a spherical infusible phenol resin carbonized at 1500 to 2200 ° C., (b) a fine carbon powder and / or a spherical surface-coated material which is carbonized by heating. At least one selected from carbonized non-melting phenol resin at 1500 to 2200 ° C., and (c) spherical molded product of a mixture of carbon fine powder and a material carbonized by heating, carbonized at 1500 to 2200 ° C. The electrically conductive composition according to claim 1, wherein the electrically conductive composition is present. The conductive material according to claim 1 or 2, wherein the thermoplastic resin is at least one selected from polycarbosilane, silicon resin, bismaleimide-triazine resin, polyurethane resin and polyester resin. Sex composition. 04. The electrically conductive composition according to claim 1, wherein the thermoplastic resin is a mixture of polycarbosilane and a silicon resin, or a silicon resin. . 05. The varnish mixture comprises 90 to 99% by weight of the thermoplastic resin and 1 to 1 of the carbon black.
The electrically conductive composition according to claim 1, wherein the electrically conductive composition is contained in an amount of 0% by weight. 6. The electrically conductive composition according to claim 1, wherein the varnish-like mixture further contains a solvent and / or a dispersant. 7. The conductive composition according to claim 6, wherein the solvent is at least one selected from paraffinic solvents, carbitol acetate, dimethylformamide, and γ-butyl lactone. 8. The varnish-like mixture according to claim 6, wherein the thermoplastic resin and the solvent are contained in an amount of 90 to 99% by weight, and the carbon black and the dispersant are contained in an amount of 1 to 10% by weight. Conductive composition of. 09. Any one of claims 1 to 8
A planar heating element having a temperature self-controlling property, which is obtained by heat-treating a sheet obtained by molding the electroconductive composition according to the item 1. 10. A pipe-shaped insulating base material, and a sheet-shaped molding of the conductive composition according to claim 1 heat-treated on the pipe-shaped insulating base material. A temperature-controlled pipe-shaped heater comprising: the heating element obtained in this way; and an electrode for energizing the heating element. 11. The temperature self-controlling pipe-shaped heater, further comprising a protective film made of a film-shaped insulating material on the heating element.