WO1999044391A1

WO1999044391A1 - Heating unit

Info

Publication number: WO1999044391A1
Application number: PCT/JP1999/000877
Authority: WO
Inventors: Eiichi Shitamori; Tsuyoshi Yamamoto
Original assignee: Idemitsu Kosan Co., Ltd.
Priority date: 1998-02-27
Filing date: 1999-02-25
Publication date: 1999-09-02

Abstract

A heating unit formed by coating metal core wires (l) with heating layers (A)(2) having positive temperature coefficient characteristics, and coating outer circumferential surfaces of these heating layers with a heating layer (Bl)(3) the positive temperature coefficient characteristics of which are different from those of the heating layers (A), or a heating layer (B2)(3) not having the positive temperature characteristics, a distance between the metal core wires (l) being set to within 5 mm, a volume ratio of the metal core wires (l) to these two layers of coating (2, 3) being set to 5-90 %. A heating unit, wherein conductive heating layers (X) are further formed between the metal core wires (l) and heating layers (A) so that a thermal expansion coefficient of the conductive heating layers has a value between that of a thermal expansion coefficient of the metal core wires and that of a thermal expansion coefficient of the heating layers (A). This heating unit is capable of reducing a load on an apparatus power source by reducing a rush current at a current application starting time, minimizing a decrease in the performance of the heating unit, and controlling the resistance temperature characteristics of a heating section easily, and, moreover, has a structure resistant to the use thereof in a high environmental temperature.

Description

Specification

Heating element

Technical field

The present invention relates to a planar or linear heater used as a heater for heating electric equipment, electronic equipment, mechanical parts, or the like, a heater for preventing dew condensation on a mirror or the like, a heater for preventing freezing of a water supply and drainage facility, and the like. Heating element.

Background art

Conventionally, various heaters formed by using nichrome wires and exothermic substances have been used as heaters for heating electrical equipment, electronic equipment, and mechanical parts, heaters for preventing condensation such as mirrors, and heaters for preventing freezing of plumbing equipment. Heating elements of various forms have been used.

In the case of using this -chrome wire, a control circuit for power supply is required to control the heat generation temperature, so a heat generating substance that can control the heat generation temperature without using such a control circuit was used. Heating elements are used in various fields. As such a heat generating substance, a substance having a positive temperature coefficient characteristic (hereinafter referred to as a PTC characteristic) in which the value of a specific resistance increases with an increase in temperature is used. As the substance having the PTC characteristic, for example, a heat generating composition in which a crystalline thermoplastic resin and conductive particles are mixed at a specific ratio is used.

In such a heat-generating composition, heat generation can be performed without using a power supply control circuit by variously selecting the type, the mixing ratio, and the like of the crystalline thermoplastic resin and the conductive particles that are constituents thereof. The temperature can be adjusted. Further, the form of the heating element formed by molding the heat generating composition is formed so as to conform to the form of a member requiring heating. Therefore, when the area of a member requiring heating is large, a planar heating element corresponding to the area is used. By the way, this planar heating element When it is installed in a device or an electronic device, it is necessary to incorporate a heat equalizing plate, which causes a problem that the volume of the entire device is increased. For this reason, when incorporated into these devices, particularly devices intended for miniaturization, a heating element having a planar or linear shape is suitable.

Conventionally known linear heating elements having P τ C characteristics have at least two metal core wires used as electrodes built in the center at a slight interval, and the outer circumference of this metal core wire is The heat-generating composition is coated, and its outer periphery is insulated and coated. By the way, in the linear heating element having such a configuration, the heat-generating composition having the PTC characteristic generally has a low electric resistance value in a low temperature range of about 0 to room temperature, and a high temperature range beyond room temperature. Since the resistance-temperature characteristics show that the electrical resistance value rises sharply when the temperature reaches this point, when the heating element incorporated in a device in a low-temperature region that requires heating starts energizing for heating, A large inrush current occurs. Therefore, there has been a problem that the performance of the heating element is deteriorated when the electric shock and the thermal shock are repeatedly received. In addition, the inconvenience of having to select the type of thermoplastic resin and conductive particles and their combination ratio so that the resistance temperature characteristics required for each application can be obtained for various applications. There was also the problem that there was.

Furthermore, in a heating element in which the temperature region exhibiting PTC characteristics is in a relatively low temperature region of, for example, 40 to 70 ° C, an environment in which the temperature may rise to about 150 ° C may occur. Then, there was a problem that it could not be used in such a case because of the possibility of heat damage.

The present invention reduces the inrush current at the start of energization in the conventional heating element, reduces the power supply load on the device, and reduces the deterioration in the performance of the heating element due to electric shock and thermal shock. Enables stable use over a wide range To provide a heating element having a structure capable of easily controlling the resistance temperature characteristics of the heating section, capable of controlling the temperature in a low temperature range, and enduring use at a high environmental temperature. It is intended for. Disclosure of the invention

The present inventors, as a linear heating element using a heat-generating composition having PTC characteristics, the configuration of the heat-generating portion is changed to a layer composed of a plurality of heat-generating compositions having different PTC characteristics, or a PTC characteristic. A layer composed of a heat-generating composition having no heat-generating composition and a heat-generating composition having no PTc characteristics.The distance between the metal core wires used as electrodes is set to a specific value. It has been found that the above-mentioned object can be achieved by configuring the ratio to be in a specific range, and the present invention has been completed based on such findings.

That is, the gist of the present invention is as follows.

1-A linear heating element in which a plurality of metal core wires arranged parallel to each other are coated with a heating composition containing at least a thermoplastic resin and conductive particles to form a heating section. A heating layer (A) made of a heating composition having a positive temperature coefficient characteristic is used as a coating layer near at least the metal core wire serving as an electrode of the metal core wire, and an outer peripheral portion of the heating layer (A) is used. The heating layer has a positive temperature coefficient characteristic as a coating layer of the heating layer, but in a temperature range in which the rising ratio of the resistance in the resistance temperature characteristic is equal to or lower than the temperature indicating the maximum rising ratio of the heating composition of the heating layer (A). It has a positive temperature coefficient characteristic that is lower than the rising ratio of the exothermic composition of (A) or that the temperature at which the resistance starts to rise in the resistance temperature characteristic is higher than the temperature at which the exothermic composition of the heating layer (A) starts to rise. From the exothermic composition That the heating layer (B l), or the heating layer made of no resin a positive temperature coefficient characteristic (B 2) with use, the spacing between the mutual metal core is within 5 mm, and the both of the metal core A heating element characterized in that the volume ratio to the coating layer is 5 to 90%.

2. When the heat-generating composition of the heat-generating layer (B 1) is in a temperature range in which the rising ratio of the resistance in the resistance-temperature characteristic is equal to or lower than the temperature indicating the maximum rising magnification of the heat-generating composition of the heat-generating layer (A), The heating magnification of the exothermic composition of (A) is 0.5 times or less, or the temperature at which the resistance starts to rise in the resistance temperature characteristic is lower than the temperature at which the heating composition of the heating layer (A) starts to rise. The heating element according to 1 above, which has a positive temperature coefficient characteristic higher by 5 ° C or more.

3. The exothermic composition of the exothermic layer (A) is a exothermic composition comprising a crystalline thermoplastic resin and conductive particles, and the exothermic composition of the exothermic layer (B 1) is a crystalline thermoplastic resin. 3. The heating element according to the above 1 or 2, which is a heating composition comprising conductive particles.

4. The heat-generating composition of the heat-generating layer (A) is a heat-generating composition comprising a crystalline thermoplastic resin and conductive particles, and the heat-generating composition of the heat-generating layer (B 1) comprises a thermoplastic resin and a silicone. 3. The heating element according to the above 1 or 2, which is a heating composition comprising a resin and conductive particles.

5. The heat generating composition of the heat generating layer (A) is a heat generating composition comprising a crystalline thermoplastic resin and conductive particles, and the heat generating composition of the heat generating layer (B 2) is a silicone resin and conductive particles. 2. The heating element according to 1 above, which is a heating composition comprising:

6. The heat generating composition of the heat generating layer (A) is a heat generating composition comprising a thermoplastic resin, a silicone resin, and conductive particles, and the resin of the heat generating layer (B 2) is a silicon resin and a conductive resin. 2. The heating element according to the above 1, wherein the heating element is a heating composition composed of conductive particles.

7. The conductive particles are made of carbon particles having a particle size of 10 to 200 mm. The heating element according to any one of 1 to 6, which is a rack particle.

8. Coating the outer peripheral surface of the heating element with a polyethylene terephthalate film, a polyethylene film, a polypropylene film, or an electrically insulating exterior material selected from a laminating film having an aluminum sheet attached to these films. The heating element according to any one of 1 to 7 above.

9. The cross-sectional shape of the heating element is rectangular, the short side is 0.1 to 1 mm, the long side is 1 to 7 mm, and the number of metal core wires is 2 to 10 The heating element according to any one of 1 to 8 above.

10. A lead wire is taken out from at least two metal core wires as electrodes of the heating element, and a connection terminal is provided at an end of the lead wire. Heating element.

1 1. The heating element according to the above item 3, wherein the MI of the crystalline thermoplastic resin is 0.1 or more.

1 2. The heating element according to the above item 4, wherein the M I of the crystalline thermoplastic resin, the thermoplastic resin and the silicone resin is 0.1 or more.

1 3. The heating element according to 1 above, wherein the shape of the metal core wire is rectangular, trapezoidal, or foil-like.

1 4. The heating element according to the above item 8, wherein the electrically insulating exterior material is coated by co-extrusion, and the resin of the electrically insulating exterior material has Ml of 0.1 or more.

1 5. An additional conductive and heat generating layer (X) is provided between the metal core and the heat generating layer (A), and the coefficient of thermal expansion of the conductive and heat generating layer (X) depends on the coefficient of thermal expansion of the metal core and the heat generating layer (A). The heating element according to the above item 1, wherein the heating element has a value between the coefficients of thermal expansion.

1 6. The heating element according to the item 15, wherein the conductive and heat generating layer (X) is a composition comprising a crystalline thermoplastic resin and conductive particles. 17. The heating element according to the item 15, wherein the heating element according to the item 15 includes an electrically insulating exterior material instead of the heat generation layers (B1) and (B2).

1 8. The heating element according to 15 above, wherein an outer peripheral surface of the heating element is coated with an electrically insulating exterior material.

1 9. Both the heating layer (A) and the conductive and heating layer (X) are both layers or one of them is the coating layer of the metal core wire, and the metal core wire with the coating layer is spirally arranged. 16. The heating element according to 15 above, which is characterized by:

20. The molding temperature used for molding the heat-generating layer (A), conductive / heat-generating layer (X), heat-generating layer (B1) or heat-generating layer (B2) and, if necessary, co-extrusion of the insulating resin is determined by the resin used. The method for molding a heating element according to the item 15 or 18, wherein the temperature is higher by at least 20 ° C than the maximum melting point.

2 1. In forming the heating element, the heating layer (A), conductive layer / heating layer (X), heating layer (B 1) or heating layer (B 2), and if necessary, co-extrusion molding of the insulating material. 20. The method for molding a heating element according to the item 20, wherein the extrusion speed during the heating is 5 m / min. Or more.

BRIEF DESCRIPTION OF THE FIGURES

1 to 4 are cross-sectional views of an example of the heating element of the present invention.

[Explanation of symbols]

1: Metal core wire

2: Heating layer (A)

3: Heating layer (B 1) or (B 2)

4: Conductive, heating layer (X)

5: Electrically insulating exterior

BEST MODE FOR CARRYING OUT THE INVENTION

The heating element of the present invention is obtained by coating a plurality of metal core wires arranged in parallel with each other with a heating composition containing at least a thermoplastic resin and conductive particles. Thus, a heat generating portion is formed. A heating layer (A) made of a heating composition having a positive temperature coefficient characteristic is disposed as a coating layer at least in the vicinity of the metal core wire serving as an electrode among the metal core wires, and the heating layer (A) It has a positive temperature coefficient characteristic as a coating layer on the outer peripheral portion, but in the temperature range where the rise ratio of the resistance in the resistance temperature characteristic is equal to or lower than the temperature indicating the maximum rise ratio of the exothermic composition of the exothermic layer (A). Positive temperature coefficient that is lower than the rising magnification of the exothermic composition of A) or that the temperature at which the resistance starts to rise in the resistance temperature characteristic is higher than the temperature at which the heating composition of the heating layer (A) starts to rise. A heat generating layer (B 1) made of a heat generating composition having characteristics or a heat generating layer (B 2) made of a heat generating composition having no positive temperature coefficient characteristics is provided.

As the metal core wire in the heating element of the present invention, a highly conductive metal used in a conventional heating element, for example, a metal wire of copper, a copper alloy, gold, silver, nickel, aluminum or the like is suitably used. The metal core wire may be a single wire, or may be in the form of a stranded wire or a net wire. The cross-sectional shape of the metal core wire is not particularly limited, but any shape such as a circle, an ellipse, a rectangle, and a foil can be used. In particular, those having a rectangular cross-sectional shape are preferable, and the short shape is preferably 0.035 to 0.1 mm and the long diameter is preferably 0.3 to 1.2 mm. The types include single wire, stranded wire, mesh wire, etc., and tin plating is mentioned as the coating material.

Further, it is preferable that the thermoplastic resin used for the heating layer (A) in the heating element of the present invention includes a crystalline thermoplastic resin. Examples of such a crystalline thermoplastic resin include a polyolefin resin and its copolymer resin, a vinyl acetate resin, a polyamide resin, a polyacetal resin, a thermoplastic polyester resin, a gen polymer, and a polyphenylene oxide resin. , Nonyl resin, polysulfone resin etc. No.

Examples of the polyolefin resin include polyethylenes such as high-density polyethylene, medium- and low-density polyethylene, and linear low-density polyethylene; polypropylenes such as asotactic polypropylene and syndiotactic polypropylene; Polybutene-11 and poly (4-methylpentene-1) resin.

Examples of the polyolefin copolymer include ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethylenol acrylate copolymer, and ethylene-ethylene copolymer. Ethylene acrylate copolymers such as methyl acrylate copolymers, copolymers of olefins and vinyl compounds such as ethylene-vinyl monochloride copolymers, fluorine-containing ethylene polymers, These modifications can also be used. Examples of the above-mentioned butyl acetate resin include butyl acetate resin, polyvinyl acetate acetal, and polybutyl butyral.

Examples of the polyamide resin include Nylon 6, Nylon 8, Nylon 11, Nylon 66, and Nylon 610.

As the polyacetal resin, a homopolymer may be used, or a copolymer may be used.

Examples of the thermoplastic polyester resin include polyethylene terephthalate and polybutylene terephthalate.

As the above-mentioned gen-based polymer, gen-based polymers such as trans-1,3-polyisoprene and syndiotactic 1,2-polybutadiene and copolymers thereof can be used.

Among these crystalline thermoplastic resins, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene monobutyl copolymer, ethylene-ethylene acrylate copolymer, and other olefin-based copolymers. Polymers and trans-1,4-polyisoprene are preferred.

These crystalline thermoplastic resins may be used alone or in a mixture of two or more.

Examples of the resin used for the heating layer (B 1) include the thermoplastic resin.

Further, examples of the resin for the heat generating layer (B 2) include a silicone resin, a thermosetting resin, and an amorphous thermoplastic resin.

Next, examples of the conductive particles used in the thermoplastic resin component include particles such as carbon black particles and graphite particles, and powders such as metal powder and metal oxide powder. And fibrous materials such as carbon fiber. Among them, granular materials such as carbon black particles and graphite particles, and particularly carbon black particles are preferred. These conductive particles may be used alone or in a combination of two or more.

As the particle size of these conductive particles, those having an average particle size of 10 to 200 micron are used, and those having an average particle size of 15 to 100 micron are more preferable. When the conductive particles are fibrous, the aspect ratio is usually from 1 to 100, preferably from 1 to 100.

Next, in preparing the exothermic composition, the thermoplastic resin and the conductive particles are mixed at a specific mixing ratio, and are melt-kneaded by a kneader or an extruder. In the melt-kneading step, it is preferable to add a cross-linking agent to cross-link the thermoplastic resin, since the PTC property of the obtained exothermic composition is improved.

The compounding ratio of the crystalline resin and the conductive particles is usually 10 to 80: 90 to 20, preferably 55 to 75: 45 to 25 by weight. You. If the mixing ratio of the conductive particles is less than this range, the specific resistance of the heat-generating composition will be reduced. When the resistance value is too large, heat generation may be insufficient, and when the mixing ratio of the conductive particles is larger than this range, the PTC characteristics of the heat generating composition may not be sufficiently exhibited.

As the cross-linking agent, an organic peroxide, a sulfur compound, an oxime, a nitroso compound, an amine compound, a polyamine compound, or the like is appropriately selected and used depending on the type of the thermoplastic resin. Can be. For example, in the case of a polyolefin-based resin, an organic peroxide is preferably used. These organic peroxides include, for example, benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl cumylno. Tert-Butylhydroperoxide, 2,5-dimethyl-1,2,5-di (tert-butylpropyl) hexine-1,3,1,1-bis (tert-butylperoxyisopropylate) Benzene, 1,1-bis (tert-butylpyroxy) -13,3,5-trimethylcyclohexane, n-butyl-14,4-bis (tert-butylperoxy) norrelate, 2,2- Bis (tert-butylperoxy) butane, tert-butylperoxybenzene and the like can be mentioned. Of these, 2,5-dimethyl-1,2,5-di (tert-butylperoxy) hexine-13 is preferred. These organic peroxides may be used alone or, if necessary, may be added with a cross-linking aid such as triallyl cyanurate divinylbenzene, triarylsocyanurate, or the like. .

The use ratio of these organic peroxides is usually 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the thermoplastic resin. If this ratio is less than 0.01 part by weight, the crosslinking of the thermoplastic resin becomes insufficient, and the PTC characteristics may not be sufficiently exhibited, or the resistance in a high temperature range may be reduced. If the amount exceeds 5 parts by weight, crosslinking The degree of conversion may be too high, resulting in reduced moldability or reduced PTC properties.

Next, the heat-generating composition is coated on at least two metal core wires to be used as electrodes. When coating the core with resin, the co-extrusion molding temperature at the time of coating the outer layer is in the range of 20 to 200 ° C higher than the resin maximum melting point (MP), preferably 50 to 110 ° C. Between C. Here, the resin maximum melting point temperature may have many melting points in the case of resin blend / copolymerization, etc., and refers to the melting point at the maximum temperature in this case. If the maximum melting point of the resin is below 20 ° C, the resin will not melt sufficiently and stable production and production will not be possible.

The linear velocity for co-extrusion is 5 to 350 m / min., Preferably 70 to 200 m / min. In this case, the exothermic composition and the metal core are co-extruded by holding the two metal cores in parallel in the die of the extruder for the exothermic composition and keeping the distance between the metal cores at a constant interval of 5 mm or less. By molding, coating treatment can be performed efficiently. The heat-generating composition used here is prepared by first coating the heat-generating composition used to form the heat-generating layer (A), and then forming the heat-generating layer (B1) or (B2) on the heat-generating composition. The exothermic composition for forming the exothermic layer (A) and the exothermic composition for forming the exothermic layer (B 1) or (B 2) may be extruded from respective extruders. In the molding die, the exothermic composition for forming the exothermic layer (A) is in contact with the metal core wire, and the exothermic composition for forming the exothermic layer (B 1) or (B 2) is outside. They may be co-extruded together with.

Next, two examples of the heating element of the present invention obtained as described above will be described.

The first example will be described with reference to FIG. Figure 1 shows the cross section of the heating element, In the figure, reference numeral 1 denotes a metal core wire, 2 denotes a heating layer (A), and 3 denotes a heating layer (B 1) or (B 2). The cross-sectional shape of the heating element is not particularly limited, but a rectangular shape is convenient for taking out a terminal for connection with a lead wire. In the case of a heating element to be incorporated into equipment intended for miniaturization, the practicality is high if the short side of this cross section is about 0.1 to 1 mm and the long side is about 1 to 7 mm. . In other words, if the dimensions are smaller than this, the wiring operation is not easy, and if the dimensions are larger than this, the flexibility is poor and it is not easy to incorporate into the equipment, and the equipment becomes large. is there.

Further, since the metal core wire 1 is used as an electrode, at least two metal core wires are required, but the metal core wire 1 may be 2 to 10 wires. In this case, the number of metal core wires 1 may be set to, for example, three, and the remaining metal core wire not used for the electrode may be used as a heat conductor for soaking. Alternatively, four metal core wires 1 may be used, two of which may be used as an anode and the other two may be used as a cathode. When the number of the metal core wires 1 is increased and the diameter is reduced in this manner, a heating element having more flexibility can be obtained.

The second example is described in FIG. The shape of the heating element is not particularly limited. However, in a case where the heating element is drawn while meandering on a flat surface, a shape close to a circle is preferable, and flexibility is required. In such an application, as shown in Fig. 4, the core wire coated with the necessary coating layer is twisted in a spiral shape to improve the addability, and the shape of the outer coating resin is circular. In this case, the temperature is further improved, and the application of the heating element is facilitated.

This metal core wire 1 is embedded in the heat generating composition such that the distance between the metal core wires 1 is within 5 mm, preferably 0.05 to 3 mm. If this interval exceeds 5 mm, local heating is likely to occur.

Next, in the vicinity of the metal core 1, the heat generating layer (A) 2 is formed, and the heat generating layer (A) 2 is formed by covering the outer peripheral surface with the heat generating layer (B 1) or (B 2) 3. Here, the heating layer (B 1) or (B

2) The exothermic composition used in (3) has a PTC characteristic in which the rise ratio of the resistance is less than the temperature indicating the maximum rise ratio of the resistance of the exothermic composition of the exothermic layer (A) 2; A) The exothermic composition is used in which the types and blending ratios of the thermoplastic resin and the conductive particles are adjusted so as to be lower than the rising magnification of the resistance of the exothermic composition of 2, preferably 0.5 times or less. In this case, instead of the above, the heating layer (B 1) or (B 2)

The temperature at which the resistance of the exothermic composition used in 3 starts to rise in the resistance temperature characteristics is higher than the temperature at which the resistance of the exothermic composition of the exothermic layer (A) 2 starts to rise, preferably 5 ° C or more. A heat-generating composition may be used in which the types and the mixing ratios of the thermoplastic resin and the conductive particles are adjusted so that Here, the rise ratio of the resistance value in the PTC characteristic is the maximum value of the resistance value when the resistance value of the heat-generating composition at the time of temperature rise is plotted, with the horizontal axis representing the temperature and the vertical axis representing the resistance value. Is the magnification for the minimum value of. The temperature at which the resistance value starts to rise in the resistance temperature characteristics is a temperature at which the resistance value of the exothermic composition at room temperature (23 ° C.) is twice as high as the resistance value.

As described above, the heat generating portion of the heat generating element is constituted by a combination of the two heat generating layers (A) 2 and (B 1) or (B 2) 3 having different PTC characteristics, so that one type is used alone. Inrush current at the start of energization can be greatly reduced as compared with a conventional heating element composed of a heating layer composed of only the heating composition described above, and damage to the heating element due to the inrush current is reduced. The life of the heating element can be extended.

In addition, this heat generating part is made of two kinds of heat generating layers (A) 2 having different PTC characteristics and a type of thermoplastic resin or conductive particles used for (B 1) or (B 2) 3. By changing the types and their proportions, and the thickness of both heating layers, it is possible to easily form a heat generating part with new PTC characteristics synthesized from the P τ C characteristics of both heating layers. This makes it easier to design products that meet a variety of required characteristics.

Further, as the exothermic composition of the exothermic layer (A) 2, an exothermic composition of the exothermic layer (B 1) having a temperature range of 40 to 70 ° C. in which the PTC characteristic appears is used. If a heater with a heat resistance of 150 ° C is used, the obtained heating element may be applied to a part where the environmental temperature may rise to about 150 ° C. Can be used without fear of thermal damage. When coating these heat generating layers (A) 2, (B l), and (B 2) 3 on the metal core wire 1, the heat generating layers (A) 2, (B 1), (B2) The thickness of each of these layers is adjusted so that the volume ratio to 3 is 5 to 90%, preferably 10 to 70%. If the volume ratio is less than 5%, local heating is likely to occur, and if the value exceeds 90%, a sufficient amount of heat cannot be obtained. A conductive layer (X) (4) is further provided between the metal core 1 and the heat generating layer (A), and the coefficient of thermal expansion of the conductive and heat generating layer (X) is equal to the coefficient of thermal expansion of the metal core 1 and the heat generation. By setting the thermal expansion coefficient to a value between the thermal expansion coefficients of the layer (A), the long-term durability when used at a temperature around the melting point of the heat generating layer (A) is improved, and a high voltage is applied. A heating element having improved long-term durability performance can be obtained. Fig. 3 shows a cross-sectional view of one example. Here, the conductive heating layer (X) is a composition comprising the above-mentioned crystalline thermoplastic resin and conductive particles. Each metal core 1, heat generating layer (A) and conductive and heat generating layer (X) have a coefficient of thermal expansion: heat generating layer (A)> conductive and heat generating layer (X)> core 1

In consideration of the required heat generation characteristics, select the heat generation layer (A) and the conductive and heat generation layer (X) so that the order is as follows. The preferred range of the coefficient of thermal expansion is as follows Is appropriately selected from the range.

Conductivity · Coefficient of thermal expansion of heat generating layer (X): 0.8 to 30 X 10 E-5 / ° C Thermal expansion of metal core wire: 1.4 to 2.0 X 10 E-5 / ° C

Thermal expansion coefficient of heat generating layer (A): 0.8 to 30 X 10E_5 / ° C

The addition of the conductive and heat generating layer (X) improves the long-term durability when used at a heat generating temperature near the melting point of the heat generating layer (A), and also improves the long-term durability at a high voltage. When the conductive layer and the heat generating layer (X) are not added, there is no problem in long-term durability if the heat generating temperature is lower than the melting point of the heat generating layer (A). In addition, there is no problem even if the heat generation temperature near the melting point temperature is short.

The problem of long-term durability as referred to here means a phenomenon in which the resistance value of the heating element increases due to actual use over several months or a thermal cycle test, and the calorific value decreases. It has been found that the main cause of this phenomenon is an increase in the contact resistance between the core wire and the heating layer. Therefore, in order to be applicable to the use near the melting point temperature of the heating layer (A), the conductive and heating layer (X) was added to prevent the contact resistance between the core wire and the heating layer from increasing. That is, by adding the conductive and heat generating layer (X), it is possible to prevent an increase in contact resistance between the core wire and the heat generating layer, and to widen a usable heat generating temperature range and a range of allowable applied voltage. In order to form each heat generating layer (A), conductive and heat generating layer (X), and heat generating layer B1, each layer may be formed individually or each layer may be formed simultaneously.

If the heating element is required to have flexibility or flexibility, coat each layer as necessary and knit the coated core wires spirally with each other. And an outer covering layer may be provided.

At one end of the metal core wire 1 in the heating element body manufactured as described above, a lead wire is connected to the exposed metal core wire 1 by exfoliating the heating layers 2 and 3 partially. Attach the connection terminal to the end of the wire, And be able to connect.

Next, this heating element is provided with an exterior material for electrical insulation to further extend the service life of the heating element and to reduce damage due to external force. An outer insulating material is coated on the outer peripheral surface of the heat generating portion by coextrusion. At this time, the resin of the electrically insulating exterior material is a polyolefin resin or the like, and the resin preferably has a melt index (Ml) of 0.1 g / lOmin or more. If M l is small, the co-extrusion of the coating resin cannot be performed cleanly, resulting in poor productivity. Examples of the electric insulating material include a high-density polyethylene film, a linear low-density polyethylene film, a low-density polyethylene finolem, a polyethylene phthalate film, a polypropylene film, and an aluminum sheet on these films. What is composed of a laminated film to which is attached is suitably used. The preferred ranges of Ml here are 0.03 to 13 for high density polyethylene, 1.2 to 9 for linear low density polyethylene, 1 to 40 for low density polyethylene and 0 to 4 for polyethylene phthalate. The Ml of each resin was measured in accordance with JISK7210 for high-density polyethylene and linear-low-density polyethylene, JISK6760 for low-density polyethylene, and ASTM D1238 for polyethylene phthalate.

【Example】

Next, the present invention will be described specifically with reference to examples.

(Example 1)

As a crystalline thermoplastic resin for producing a heat-generating composition for the heat-generating layer (A), an ethylene-ethyl acrylate copolymer [; Nippon Tunica Co., Ltd .: DPDJ 618: MI = 1.5, MP = 95 ° C] Using 60 parts by weight, the conductive particles used were carbon black with an average particle size of 43 millimicrons [Mitsubishi Chemical Corporation: Diamond Black E] 40 parts by weight were used. further, 0.1 weight of ethylene-ethylene acrylate copolymer as a crosslinking agent. 2,5_Dimethyl-2,5-di (tert-butylbutyloxy) hexine- ₁ in an amount equivalent to / ₀ [Nippon Oil & Fats Co., Ltd .: Parhexin 25B; 1 minute half-life temperature 193 ° C].

Next, these raw materials are supplied to an extruder, melt-kneaded at 200 ° C., extruded into a strand at a discharge rate of 5 kgZhr, and cut to obtain a pellet of the resin composition. Was. The pellet of the resin composition was fed to a single-screw extruder having an inner diameter of 25 mm and crosslinked at 260 ° C and 50 rpm with a shear energy of 0 and Oekw'hrZkg. Was done.

In addition, as a heat generating composition for the heat generating layer (B 1), high density polyethylene is used.

[Idemitsu Petrochemical Co .; Idemitsu Polyethylene 44 OM: MI = 1.0, MP = 135 ° C] 55 parts by weight, 45 parts by weight of the same carbon black as above, and 0.1 part by weight of the same crosslinking agent as above An exothermic composition obtained by melting and kneading these at 230 ° C. was used.

Next, the melt-kneaded product of the resin composition for the exothermic composition (A) was introduced into a supply port of a die for coating and molding a metal core wire, and was coated and formed. Next, two extruded molded articles of the exothermic composition (A) were arranged in a metal core wire coating molding die in parallel with each other so that the distance between the metal core wires was 0.54 mm, and introduced into the die. Then, a melt-kneaded product of the resin composition for the heat generating layer (B 1) is introduced from the resin supply port of the die, and the heat generating composition

A molded product in which two layers of (A) and the exothermic composition (B 1) were laminated was obtained. A copper wire having a diameter of 0.26 mm was used as the metal core wire.

The cross-sectional shape of the linear heating element obtained in this way is shown in Fig. 1, and it is a rectangle with two corners partially cut away, with a short side of 0.8 mm and a long side. 1.4 mm. And on the surface of copper wire 1, A heat generating layer (A) 2 having a thickness of 0.15 mm made of the above resin composition was formed. The volume ratio of the heat generating element to the two coating layers 2 and 3 of the copper wire 1 was 13%. Met.

Next, this linear heating element was cut to a length of 16 O mm, and one of the cut ends was extended 10 mm from its end, and the coating layers 2 and 3 were peeled off to expose the copper wire 1. Then, a lead wire was soldered to each of the two copper wires 1. Thereafter, the entire heating element was covered with a polyethylene terephthalate film except for the two lead wires, and the upper and lower surfaces were heat-laminated to provide an electrical insulation exterior.

The exothermic composition for the exothermic layer (A) and exothermic composition for the exothermic layer (B1) of the exothermic element obtained here were separately prepared separately for each of the exothermic compositions. measurements showed that the rise starting temperature of the electric resistance of the heat-generating composition for the heating layer (a) is the 4 3 ° C, the rising ratio of electrical resistance is 1 0 ⁷ times, while the heating layer (B 1) rising start temperature of the electric resistance of the heating compositions for is 5 5 ° C, the rising ratio of electrical resistance was 1 0 ⁸ times. Accordingly, it was confirmed that the rising start temperature of the heat generating composition of the heat generating layer (B 1) was higher by 12 ° C. than the rising start temperature of the heat generating composition of the heat generating layer (A). . When the electrical resistance of the heating element was measured, it was 8 Ω. As a result of measurement of a PTC characteristics of the heating elements, starting temperature Ri rising electric resistance value is 3 8 ° C, the rising ratio of electrical resistance was 1 0 ⁸ times.

Next, when a power supply wiring from a power supply is connected to the lead wire terminal of this heating element and a voltage of 6 volts is applied between both electrodes, the inrush current value at the start of energization becomes 0. The current was 75 amperes, and the current value during the subsequent stable heating was 0.6 amperes. In addition, the heating element was cooled to 150 ° C. After receiving the heat history in a bun, the outer shape was observed, and there was no change in the shape. When the PTC characteristics were measured again, there was no effect of the heat history.

(Example 2)

As the heat generating composition for the heat generating layer (A), the same heat generating composition as the heat generating layer (A) of Example 1 was used. As the exothermic composition for the exothermic layer (B1), 54 parts by weight of a high-density polyethylene (manufactured by Idemitsu Petrochemical Co .; Idemitsu Polyethylene 440 M) and a silicone resin [manufactured by Dow Corning Toray Co., Ltd .: SE6758] was added in an amount of 10 parts by weight, the same carbon black particles as in Example 1 were used in an amount of 36 parts by weight, and 2,5-dimethyl-1,2,5-di (tert-butylpyroxy) was used as a crosslinking agent. Hexin-13 was used in an amount of 0.1 part by weight, and an exothermic composition obtained by melt-kneading these was used. The heating element was manufactured in the same manner as in Example 1.

With respect to the heat-generating composition for the heat-generating layer (A) and the heat-generating composition for the heat-generating layer (B 1), the PTC characteristics were separately measured for both heat-generating compositions separately. As a result, the temperature at which the electrical resistance of the heat generating composition for the heat generating layer (A) started to rise was 43. Is C, rising ratio of electrical resistance is 1 0 ⁷ times, while rising start temperature of electrical resistance of the heat-generating composition for the heating layer (B 1) is located at 6 0 ° C , rising ratio of electrical resistance was 1 0 ⁷ times. Therefore, it was confirmed that the rising start temperature of the heat generating composition of the heat generating layer (B 1) was 17 ° C. higher than the rising start temperature of the heat generating composition of the heat generating layer (A).

When the electric resistance of the heating element was measured, it was 6 Ω. As a result of measurement of a PTC characteristics of the heating elements, starting temperature Ri rising electric resistance value is 4 5 ° C, the rising ratio of electrical resistance was 1 0 ⁷ times. Next, when the power supply wiring from the power supply is connected to the lead wire terminal of this heating element and a voltage of 6 volts is applied between both electrodes, the inrush current value at the start of energization is 1. The current value was 1 ampere, and the current value when the temperature was stabilized was 0.8 amperes. Furthermore, after placing this heating element in a 150 ° C oven and receiving heat history, the outer shape was observed.The shape did not change. When the PTC characteristics were measured again, the heat history There was no sound.

(Example 3)

As the heat generating composition for the heat generating layer (A), the same heat generating composition as the heat generating layer (A) of Example 1 was used. As a heat-generating composition for the heat-generating layer (B2), a conductive silicone resin [manufactured by Toray Dow Co., Ltd .: SE67558] was used. The heating element was manufactured in the same manner as in Example 1.

Regarding the exothermic composition for the exothermic layer (A) and exothermic composition for the exothermic layer (B 2) of the heating elements obtained here, the PTC characteristics were measured separately for both exothermic compositions. , rising start temperature of the electric resistance of the heat-generating composition for the heating layer (a) is the 4 3 ° C, a 1 0 ⁷ times the rising ratio of electrical resistance, while the heat generating layer (B The exothermic composition for 2) did not show PTC properties.

When the electrical resistance of this heating element was measured, it was 5.2 Ω. As a result of measurement of a PTC characteristic of the heating element, the rise start temperature of the electric resistance value is 4 3. 7 ° C, the rising ratio of electrical resistance was 1 0 ⁷ times.

Next, when the power supply wiring from the power supply is connected to the lead wire terminal of this heating element and a voltage of 6 volts is applied between both electrodes, the inrush current value at the start of energization is 1. The current value was 1 ampere, and the current value during the subsequent stable heating was 0.6 amperes. In addition, heat the heating element in an oven at 150 ° C. After receiving the thermal history in the tub, the external shape was observed and there was no change in the shape. When the PTC characteristics were measured again, there was no effect of the thermal history.

(Example 4)

As the heat-generating composition for the heat-generating layer (A), 48 parts by weight of the same ethylene-ethyl acrylate copolymer as in Example 1, 20 parts by weight of the same silicone resin as in Example 2, 32 parts by weight of the same carbon black particles as in Example 1 and 0.1 part by weight of 2,5-dimethyl-2,5-di (tert-butyloxy) hexine-13 as a crosslinking agent were used and melted. The exothermic composition obtained by kneading was used. In addition, the same conductive silicone resin as in Example 3 was used as the heat generating composition for the heat generating layer (B 2). The heating element was manufactured in the same manner as in Example 1. The heat-generating composition for the heat-generating layer (A) and the heat-generating composition for the heat-generating layer (B2) of the heating element obtained here were measured separately for the heat-generating compositions. , emitting thermal layer rising start temperature of the electric resistance of the heat-generating composition for (a) is 4 6 ° C, a rise ratio of the electric resistance value of 1 0 ⁷ times, while the heating layer (B 2) The exothermic composition did not show PTC properties.

When the electric resistance of the heating element was measured, it was 4 Ω. As a result of measurement of a PTC characteristics of the heating elements, starting temperature Ri rising electric resistance value is 4 7 ° C, the rising ratio of electrical resistance was 1 0 ⁶ times.

Next, when the power supply wiring from the power supply is connected to the lead wire terminal of this heating element and a voltage of 6 volts is applied between both electrodes, the inrush current value at the start of energization is 1. The current was 5 amperes, and the current value during the subsequent stable heating was 0.8 amperes. Furthermore, after placing this heating element in a 150 ° C oven and receiving heat history, the external shape was observed. However, when the P τ C characteristics were measured again, there was no effect due to this heat history.

[Example 5]

The heat generating layer (A) was the same as in Example 1, and the heat generating layer (B 1) used was the same as Example 1 except for 65 parts by weight of polyethylene and 35 parts by weight of CB. As shown in FIG. 1 (attached), a heating layer (A) was coated on the core wire in the same manner as in Example 1, two wires were arranged in parallel, and the heating layer (B 1) was co-extruded to obtain a heating element. The obtained heating element was cut into a length of 100 mm, lead wires were connected to core wires at both ends, and DC 12 V was applied between the electrodes. The resistance value was 5 ohms, the calorific value was 3 W, and the exothermic temperature was 45 ° C. Also 1

There was no significant change in shape after receiving a thermal history of 50 ° C. The change rate results before and after the heat history at 150 ° C are shown below.

• Width deformation rate: within 2% of soil

• Length deformation rate: within ± 5%

[Example 6]

The heat generating layer (A) was the same as in Example 1, and the heat generating layer (B 1) used was the same as Example 1 except for 65 parts by weight of polyethylene and 35 parts by weight of CB. The heating layer (A) was coated on the core wire in the same manner as in Example 1, and 21 wires were arranged in parallel, and the heating layer (B 1) was co-extruded to obtain a heating element. The obtained heating element was cut into a length of 13 O mm, lead wires were connected to the core wires at both ends, and DC 30 V was applied between the electrodes. The resistance value is 35 ohms and the calorific value is 3.

The heat generation temperature was 6 W, and the exothermic temperature was 53 ° C. In addition, there was no significant change in the shape even after receiving a heat history of 150 ° C. Rate of change before and after the heat history at 150 ° C The results are shown below.

• Width deformation ratio: within ± 2%

• Length deformation rate: within ± 5% [Example 7]

Polyethylene as a crystalline thermoplastic resin for the conductive and heat generating layer (X) [Idemitsu Petrochemical; Idemitsu Polyethylene 130 J: MI = 11, MP = 134 ° C] 57 parts by weight, CB [ Mitsubishi Chemical Corporation: Diamond Black E] 43 parts by weight were used. A cross-linking agent [Nippon Oil & Fat Co .: Perhexin 25 B] was used.

Next, these raw materials are supplied to an extruder, melt-kneaded at 200 ° C, extruded in a strand shape at a discharge rate of 5 kgZhr, and cut to obtain a pellet of a resin composition. Was. A pellet of this resin composition was fed to a single screw extruder having an inner diameter of 25 mm, and the resin composition was crosslinked at 260 ° C. and 50 rpm at a shear energy of 0.06 kw * hr Zkg. Was carried out.

Next, the melt-kneaded product of the exothermic composition was introduced into a supply port of a die for coating a metal core wire, and the metal core wire was coated with a conductive and heat generating layer (X). The thickness was 0.1 mm. The heat generating layer (X) is 57 parts by weight of polyethylene and 43 parts by weight of CB, and the heat generating layers (A) and (B 1) are the same as in Example 1. Conductive on the core wire as in Example 1. Heating layer (X) Heating layer

(A) was coated, two were arranged in parallel, and the heat generating layer (B 1) was co-extruded to obtain a heat generating body. The heating layer (A) was coated with a metal core wire at a molding temperature of 200 ° C and a linear velocity of 150 m / min. The coating of the heating layer (B1) was formed at a molding temperature of 220 ° C and a linear velocity of 100 m / min. Here, the thermal expansion coefficients of the heat generating layer (A), the conductive layer, the heat generating layer (X) and the core wire are “33 × 10E_5”, “25 × 10E-5” and “1”, respectively. 4 X 10E-5 ”, which satisfies the relationship of coefficient of thermal expansion: heat generating layer (A)> conductive and heat generating layer (X)> core wire. The selected heating element was cut into a length of 130 mm, lead wires were connected to the core wires at both ends, and DC 30 V was applied between the electrodes. The resistance value is 30 ohms and the calorific value is 4.1 W The exothermic temperature was 70 ° C. In addition, there was no significant change in shape even after receiving a thermal history of 150 ° C. The results of the rate of change before and after the heat history at 150 ° C are shown below.

• Width deformation rate: Sat 2. Within / ₀

• Length deformation rate: within ± 5%

In addition, stable heat generation characteristics were exhibited even in long-term tests of three months or more with AC 100 V applied, and durability at high voltages was confirmed. The results are shown below.

① Change in resistance value for 3 months long: within 30 Ω ± 5%

(2) Change in calorific value over a three-month period: within 7 W ± 10%

[Example 8]

As a crystalline thermoplastic resin for producing the heat-generating composition for the heat-generating layer (A), an ethylene-ethyl acrylate copolymer [; Nippon Tunica Co., Ltd .: DPDJ 6182: MI = 1.5, MP = 95 ° C] 60 parts by weight, and the conductive particles used were carbon black with an average particle size of 43 Milimicron [Diamond Black E] manufactured by Mitsubishi Chemical Corporation. 0 parts by weight were used. Further, as a cross-linking agent, 2,5-dimethyl-2,5-di (tert-butylbutyloxy) hexyne-1 in an amount equivalent to 0.5% by weight based on the ethylene-ethyl acrylate copolymer is used. Nippon Oil & Fats Co., Ltd .: Bar Hexin 25B; 1 minute half-life temperature 1933 ° C] was used.

Next, these raw materials were fed to an extruder, melt-kneaded at 200 ° C, extruded into a strand at a discharge rate of 5 kg Zhr, and cut to obtain a pellet of a resin composition. . The pellets of this resin composition were fed to a single-screw extruder having an inner diameter of 25 mm, and the resin composition was crosslinked at 260 ° C and 50 rpm at a shear energy of 0.06 kw'hr Zkg. Was carried out. In addition, as a heat generating composition for the heat generating layer (B 1), high density polyethylene is used.

[Idemitsu Petrochemical Co .; Idemitsu Polyethylene 440M: MI = 1.0] 55 parts by weight, 45 parts by weight of the same carbon black as described above, and 0.1 part by weight of the same crosslinking agent as described above were used. The exothermic composition obtained by melting and kneading at 230 ° C. was used.

Next, the melt-kneaded product of the resin composition for the exothermic composition (A) was introduced into a supply port of a die for coating and molding a metal core wire, and was coated and formed. Next, two extruded molded articles of the exothermic composition (A) were arranged in a metal core wire coating molding die in parallel with each other so that the distance between the metal core wires was 0.54 mm, and introduced into the die. Then, a melt-kneaded product of the resin composition for the heat generating layer (B 1) is introduced from the resin supply port of the die, and the heat generating composition is placed on the metal core wire.

The cross-sectional shape of the linear heating element obtained in this way is shown in Fig. 1, and it is a rectangle with two corners partially cut away, with a short side of 0.8 mm and a long side. Was 1.4 mm. On the surface of the copper wire 1, a heating layer (A) 2 having a thickness of 0.15 mm made of the above resin composition was formed. And the volume ratio to 3 was 13%. Next, the linear heating element was introduced into a supply port of a die for forming an outer cover (electric insulating layer), and formed into a cover. The coating thickness was 0.1 mm, and the coating resin used was low-density polyethylene [Idemitsu Petrochemical Co., Ltd .; Idemitsu polyethylene 534 G]. The molding conditions were melting at 200 ° C. and co-extrusion at a linear velocity of 100 m / min.

The exothermic composition for the exothermic layer (A) and exothermic composition for the exothermic layer (B1) of the exothermic element obtained here were separately prepared separately for each of the exothermic compositions. As a result of the measurement, the exothermic composition for the exothermic layer (A) A rising start temperature 4 3 ° C in the electric resistance of the object, the rising ratio of electrical resistance is 1 0 ⁷ times, while the heating layer (B 1) an electric resistance value of the heating composition for rising start temperature is 5 5 ° C, the rising ratio of electrical resistance was 1 0 ⁸ times. Accordingly, it was confirmed that the rising start temperature of the heat generating composition of the heat generating layer (B 1) was higher by 12 ° C. than the rising start temperature of the heat generating composition of the heat generating layer (A). . When the electrical resistance of the heating element was measured, it was 8 Ω. As a result of measurement of a PTC characteristics of the heating elements, starting temperature Ri rising electric resistance value is 3 8 ° C, the rising ratio of electrical resistance was 1 0 ⁸ times.

Next, when a power supply wiring from a power supply is connected to the terminal of the lead wire of the heating element and a voltage of 6 volts is applied between both electrodes, the inrush current value at the start of energization becomes 0. The current was 75 amperes, and the current value during the subsequent stable heating was 0.6 amperes. Furthermore, after placing this heating element in a 150 ° C oven and receiving heat history, the external shape was observed.The shape did not change, and the PTC characteristics were measured again. There was no effect from history.

(Example 9)

Polyethylene as the crystalline thermoplastic resin of the conductive and heat generating layer (X) [Idemitsu Petrochemical Co., Ltd .; Idemitsu Polyethylene 130 J: I = 11, MP = 1334 ° C] 57 parts by weight, CB [Mitsubishi Chemical Corporation: Diamond Black E] 43 parts by weight were used. A crosslinking agent [Nippon Oil & Fat Co .: Perhexin 25 B] was used.

Next, these raw materials were supplied to an extruder, melt-kneaded at 200 ° C, extruded into a strand at a discharge rate of 5 kg / hr, and cut to obtain a pellet of a resin composition. . A pellet of this resin composition was fed to a single-screw extruder having an inner diameter of 25 mm and subjected to shear energy at 260 ° C. and 50 rpm. The resin composition was crosslinked at 0.06 kw'hr Zkg.

The heat generating layers (A) and (B 1) are manufactured in the same manner as the heat generating layer (A) in Example 1, but the ratio of the resin to the carbon black is 70 parts by weight and 30 parts by weight. It was made. The outer cover molding resin is the same as in Example 8.

Next, the melt-kneaded product of the exothermic composition was introduced into a supply port of a die for coating a metal core wire, and the metal core wire was coated with a conductive and heat generating layer (X). The thickness was 0.1 mm. As in Example 1, the core wire is coated with a conductive and heat-generating layer (X) and then with a heat-generating layer (A). Then, as shown in FIG. (B 1) was co-extruded to obtain a heating element. The heating layer (A) was coated with a metal core wire at a molding temperature of 200 ° C and a linear velocity of 150 mZmin. Also the heating layer

The coating molding of (B1) was performed at a molding temperature of 220 ° C and a linear velocity of 100 m / min. Here, the thermal expansion coefficients of the heat generating layer (, the conductive layer, the heat generating layer (X), and the core wire are “33 X 10 E_5”, “25 X 10 E_5”, and “1.4,” respectively. X10E_5 ”, which satisfies the relationship of coefficient of thermal expansion: heat generating layer (A)> conductive layer 'heat generating layer (X)> core wire. Next, as shown in Fig. 4, exterior coating molding Was performed in the same manner as in Example 8.

The selected heating element was cut into a length of 13 O mm, lead wires were connected to the core wires at both ends, and AC 100 V was applied between the electrodes. The resistance was 152 ohms, the heat generation was 3.2 W, and the heat generation temperature was 64 ° C. Also, there was no big change in shape after being subjected to heat history 1 1 0 ^D C. The results of the rate of change before and after the 11 o ° c heat history are shown below.

• Width deformation ratio: within ± 2%

• Length deformation rate: within ± 5% In addition, stable heat generation characteristics were exhibited even in long-term tests of three months or more with AC 100 V applied, and durability at high voltages was confirmed. The results are shown below.

① Change in resistance value for 3 months long: Within 15 22 Ω ± 7%

(2) Change in calorific value over a long period of three months: within 3.2W ± 12%

(Comparative Example 1)

The same heat-generating composition as in Example 1 was supplied to the dice while passing the same two copper wires parallel to each other with a spacing of 0.54 mm to the die, and a single heat-generating layer was formed. Was molded by coating.

When the electrical resistance of this heating element was measured, it was 1.4 Ω. Also, as a result of measuring the PTC characteristics of this heating element, the temperature at which the electrical resistance started to rise was 38 ° C.

Next, when a power supply wiring from a power supply is connected to the terminal of the lead wire of this heating element and a voltage of 6 volts is applied between both electrodes, the inrush current value at the start of energization becomes 4.2 The current value when the temperature stabilization was stable was 0.7 amperes. Furthermore, after placing the heating element in an oven at 150 ° C and receiving heat history, the external shape was observed. The shape change was large, and reuse was difficult.

Industrial applicability

The heating element according to the present invention has a small rush current at the time of starting energization in a temperature range as low as about room temperature, and can reduce the load on the power supply of the apparatus and can suppress the performance deterioration of the heating element due to electric shock and thermal shock. Therefore, it can be used stably for a long period of time. In addition, it has an excellent effect that the resistance temperature characteristics of the heat generating portion can be easily controlled, the temperature can be controlled in a low temperature range, and the device can withstand use at a high environmental temperature.

Claims

The scope of the claims

1. A linear heating element in which a heating portion is formed by coating a plurality of metal core wires arranged in parallel with each other with a heating composition containing at least a thermoplastic resin and conductive particles. A heating layer (A) made of a heating composition having a positive temperature coefficient characteristic is used as a coating layer near at least the metal core wire serving as an electrode of the metal core wire, and an outer peripheral portion of the heating layer (A) is used. It has a positive temperature coefficient characteristic as a coating layer of the heat generating layer, but in a temperature range in which the rise ratio of the resistance in the resistance temperature characteristic is equal to or lower than the temperature indicating the maximum rise ratio of the heat generating composition of the heat generating layer (A). It has a positive temperature coefficient characteristic that is lower than the rising ratio of the exothermic composition of (A) or that the temperature at which the resistance starts to rise in the resistance temperature characteristic is higher than the temperature at which the exothermic composition of the heating layer (A) starts to rise. Composed of exothermic composition A heat layer (Bl) or a heat layer (B2) made of a resin having no positive temperature coefficient characteristic is used, the distance between the metal core wires is set to within 5 mm, and the metal core wire is covered with the above-mentioned two layers. A heating element characterized in that the volume ratio to the layer is 5 to 90%.

2. When the heat-generating composition of the heat-generating layer (B 1) is in a temperature range in which the rising ratio of the resistance in the resistance-temperature characteristic is equal to or lower than the temperature indicating the maximum rising magnification of the heat-generating composition of the heat-generating layer (A), The heating magnification of the exothermic composition of (A) is 0.5 times or less, or the temperature at which the resistance starts to rise in the resistance temperature characteristic is lower than the temperature at which the heating composition of the heating layer (A) starts to rise. The heating element according to claim 1, which has a positive temperature coefficient characteristic higher by 5 ° C or more.

3. The exothermic composition of the exothermic layer (A) is a exothermic composition comprising a crystalline thermoplastic resin and conductive particles, and the exothermic composition of the exothermic layer (B 1) is a crystalline thermoplastic resin. An exothermic composition comprising conductive particles, Heating element according to 1 or 2.

4. The heat generating composition of the heat generating layer (A) is a heat generating composition comprising a crystalline thermoplastic resin and conductive particles, and the heat generating composition of the heat generating layer (B 1) is a thermoplastic resin and a silicone. 3. The heating element according to claim 1, which is a heating composition comprising a resin and conductive particles.

5. The heat generating composition of the heat generating layer (A) is a heat generating composition comprising a crystalline thermoplastic resin and conductive particles, and the heat generating composition of the heat generating layer (B 2) is a silicone resin and conductive particles. The heating element according to claim 1, which is a heating composition comprising:

6. The heat generating composition of the heat generating layer (A) is a heat generating composition comprising a thermoplastic resin, a silicone resin and conductive particles, and the resin of the heat generating layer (B 2) is a silicon resin and a conductive resin. The heating element according to claim 1, wherein the heating element is a heat-generating composition comprising conductive particles.

7. The heating element according to any one of claims 1 to 6, wherein the conductive particles are carbon black particles having a particle size of 10 to 200 millimicrons.

8. The outer peripheral surface of the heating element is covered with an electrically insulating exterior material selected from a polyethylene terephthalate film, a polyethylene film, a polypropylene film, or a laminate film in which an aluminum sheet is attached to these films. The heating element according to any one of claims 1 to 7, comprising:

9. The cross-sectional shape of the heating element is rectangular, the short side is 0.1 to 1 mm, the long side is 1 to 7 mm, and the number of metal core wires is 2 to 10 The heating element according to any one of claims 1 to 8.

10. The lead according to any one of claims 1 to 9, wherein a lead wire is taken out from at least two metal core wires serving as electrodes of the heating element, and a connection terminal is provided at an end of the lead wire. Heating element as described.

1 1. The heating element according to claim 3, wherein M I of the crystalline thermoplastic resin is 0.1 or more.

1 2. The heating element according to claim 4, wherein M I of the crystalline thermoplastic resin, the thermoplastic resin, and the silicone resin is 0.1 or more.

1 3. The heating element according to claim 1, wherein the shape of the metal core wire is a rectangle, a trapezoid, or a foil.

1 4. The heating element according to claim 8, wherein the electrically insulating exterior material is coated by co-extrusion, and the resin of the electrically insulating exterior material has Ml of 0.1 or more.

1 5. A conductive / heat generating layer (X) is further provided between the metal core and the heat generating layer (A), and the thermal expansion coefficient of the conductive / heat generating layer (X) is determined by the coefficient of thermal expansion of the metal core and the heat generating layer (A). 2. The heat generating element according to claim 1, wherein the heat expansion coefficient is a value between the coefficients of thermal expansion.

16. The heating element according to claim 15, wherein the conductive and heat generating layer (X) is a composition comprising a crystalline thermoplastic resin and conductive particles.

17. The heating element according to claim 15, wherein the heating element according to claim 15 has an electrically insulating exterior material instead of the heating layers (B1) and (B2).

18. The heating element according to claim 15, wherein an outer peripheral surface of the heating element is coated with an electrically insulating exterior material.

1 9. Both the heat generating layer (A) and the conductive and heat generating layer (X) are both layers or one of them is the coating layer of the metal core wire, and the metal core wire provided with the coating layer is spirally arranged. The heating element according to claim 15, characterized in that:

20. The molding temperature for molding the heat-generating layer (A), the conductive / heat-generating layer (X) and the heat-generating layer (B1) or the heat-generating layer (B2) and, if necessary, the co-extrusion molding of the insulating material is determined by the resin used. The method for molding a heating element according to claim 15 or 18, wherein the temperature is higher than the maximum melting point by 20 ° C or more.

2 1. Heating layer (A), Conductive / heating layer (X) 20. The extrusion speed when forming the heat generating layer (B 1) or the heat generating layer (B 2) and the electrically insulating external material by co-extrusion if necessary is 5 m / min. Or more. Heating element molding method.