JP2610474B2 - Planar heating element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention [Industrial Application Field] The present invention relates to a sheet heating element and a method for producing the same, and more particularly, has a self-temperature control function and an overheating prevention function and is used repeatedly. The present invention relates to a sheet-like heating element in which a change in electric resistance due to the above is suppressed and a method for manufacturing the same.

[Prior Art] Conventionally, this type of planar heating element has a temperature coefficient of electric resistance obtained by dispersing conductive particles (for example, carbon black or metal particles) in a crystalline polymer compound. It has been proposed to form a positive heating layer, and (ii) to control the temperature of a bimetal or the like to a heating layer formed by dispersing conductive particles (for example, carbon black or metal particles) in an elastomer. One incorporating a member has also been proposed.

[Problems to be Solved] However, in the conventional planar heating element, when the (i) heating layer having a positive temperature coefficient of electric resistance is formed by the crystalline polymer compound, the crystalline polymer compound serving as a matrix is heated. As it becomes easier to expand and flow with the increase in the number of repeated use, there is a disadvantage that the chain of the conductive particles in the crystalline polymer compound as the matrix is gradually broken and the electric resistance is gradually increased, and Due to its high hardness, it is not easy to bend or fold, and it is difficult to bend and place it in a place with a small radius of curvature, and it requires a large space for storage. i
i) When a heat generating layer is formed by an elastomer, it is necessary to incorporate a temperature control member such as a bimetal, so that there is a drawback that the number of parts increases, and even if it is flexible, it is bent to a place with a small radius of curvature. There is a disadvantage that it is difficult to dispose it in a state and a large space is required for storage.

In order to eliminate these drawbacks, the present invention provides a sheet-like heating device having a self-temperature control function and an overheating prevention function, having high strength and flexibility, and having a sufficiently suppressed change in electric resistance even in repeated use. It is intended to provide a body and a method for producing the same.

(2) Configuration of the Invention [Means for Solving the Problems] The means for solving the problems provided by the present invention is as follows: "In a planar heating element in which electrodes are arranged on a heating layer,
The heat generating layer comprises: (a) a PTC composition comprising: a first polymer compound having a carboxyl group in a side chain; and conductive particles dispersed in the first polymer compound. (B) a second polymer compound disposed around the PTC region and having an unsaturated bond in at least one of a main chain and a side chain; and A conductive elastomer region comprising a conductive elastomer composition containing other conductive particles dispersed with respect to the polymer compound of (c), and (c) a carboxyl group having a large number of carboxyl groups relative to the carboxyl group of the first polymer compound. And a unsaturated carboxylic acid which is cross-linked through a valent metal and whose unsaturated bond is cross-linked to the unsaturated bond of the second polymer compound through sulfur. Planar heating element ".

Another solution to the problems provided by the present invention is: (a) a first method for preparing a PTC composition by dispersing at least conductive particles in a crystalline polymer compound having a carboxyl group in a side chain; (B) a second step of dissolving the PTC composition in a solvent to form a PTC composition solution; and (c) dropping the PTC composition solution into a poor solvent to precipitate the PTC particles. And (d) dispersing the PTC particles in a solvent together with a polyvalent metal salt and an unsaturated carboxylic acid, so that the carboxyl group of the first polymer compound is converted into a unsaturated carboxylic acid by a polyvalent metal. A fourth step of cross-linking a carboxyl group in the acid, and (e) applying at least another conductive particle to the second polymer compound having an unsaturated bond in at least one of a main chain and a side chain. A fifth step of dissolving the dispersed conductive elastomer composition in a solvent to form a conductive elastomer solution; and (f) changing the unsaturated carboxyl group to the conductive elastomer solution by the polyvalent metal. By dispersing the PTC particles cross-linked to the carboxyl group in the acid and then drying, the unsaturated bond in the unsaturated carboxylic acid is converted into sulfur to the unsaturated bond in the second polymer compound. A sixth step of forming PTC elastomer particles cross-linked through the method; and (g) pressing the PTC elastomer particles under pressure to form a conductive elastomer around the PTC region where the temperature coefficient of electrical resistance is positive. Seventh forming the heating layer in which the regions are arranged
And (h) an eighth step of arranging an electrode on the heat generating layer. "

[Function] The sheet heating element according to the present invention is characterized in that the heating layer comprises (a) a first polymer compound having a carboxyl group in a side chain and conductive particles dispersed in the first polymer compound. A PTC region comprising a PTC composition in which the carboxyl group is bonded to a carboxyl group in an unsaturated carboxylic acid by a polyvalent metal, wherein a temperature coefficient of electric resistance is positive; A second polymer compound disposed around the PTC region and having an unsaturated bond bonded to an unsaturated bond in the unsaturated carboxylic acid via sulfur, and dispersed in the second polymer compound; (I) self-temperature control function and overheating without additional temperature control members such as bimetals, since the conductive elastomer region is made of a conductive elastomer composition containing other conductive particles. Achieve prevention function In addition to the action of (ii) securing flexibility, and thus enabling installation in a place with a small radius of curvature, and at the same time reducing the space for storage, and (iii) the liquidity during repeated use It acts to prevent the increase and sufficiently suppress the change in the electric resistance.

Further, the method for producing a sheet heating element according to the present invention comprises dissolving a PTC composition in which at least conductive particles are dispersed in a first polymer compound having a carboxyl group in a side chain in a solvent, and dissolving the PTC composition in a solvent. The PTC composition solution was dropped into a poor solvent and allowed to settle to form PTC particles.
By dispersing the TC particles in a solvent together with a polyvalent metal salt and an unsaturated carboxylic acid, the carboxyl group of the first polymer compound is cross-linked to the carboxyl group in the unsaturated carboxylic acid by a polyvalent metal, Then, a conductive elastomer compound prepared by dissolving a conductive elastomer compound in which at least a plurality of conductive particles are dispersed in a second polymer compound having an unsaturated bond in at least one of a main chain and a side chain in a solvent. PTC against solution
The particles are dispersed and the unsaturated bonds in the unsaturated carboxylic acid are cross-linked to the unsaturated bonds in the second polymer compound via sulfur to form PTC elastomer particles. Since the heat generating layer is formed by pressure molding, in addition to the functions (i) to (iii), the function (iv) facilitates the work of stabilizing the heat generating layer.

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

FIG. 1 is an enlarged cross-sectional view along an II line showing an embodiment of a sheet heating element according to the present invention.

FIG. 2 is an enlarged sectional view showing the fine structure of the embodiment shown in FIG.

 FIG. 2 is a plan view of the embodiment of FIG.

First, the configuration and operation of an embodiment of a sheet heating element according to the present invention will be described in detail with reference to FIGS.

10 is a planar heating element according to the present invention, a heating layer 11 having a self-temperature control function and an overheating prevention function, and electrodes 12, 13 disposed separately from the heating layer 11
And

The heat generating layer 11 is composed of a first polymer compound having a carboxyl group in a side chain (preferably a crystalline polymer compound; hereinafter, mainly described in this case) and a main polymer mixed with the first polymer compound. And a second polymer compound having an unsaturated bond in at least one of the side chains (preferably an elastomer; this case will be mainly described below)
And an appropriate conductive material which can be dispersed in the first and second polymer compounds, respectively, and a terminal carboxyl group via an appropriate polyvalent metal (for example, calcium).
And a unsaturated carboxylic acid which is cross-linked to the carboxyl group of the polymer compound and whose unsaturated bond is cross-linked to the unsaturated bond of the second polymer compound through sulfur.

The first polymer compound exhibits PTC characteristics (that is, characteristics in which the temperature coefficient of electric resistance is positive) when an appropriate conductive material is dispersed. In other words, the first polymer compound and an appropriate conductive material form a composition exhibiting PTC characteristics, that is, a PTC composition, and are included in the heating layer 11 of the sheet heating element 10 according to the present invention. It functions as PTC area 11A, and as a result, has a self-temperature control function and an overheat prevention function.

The second polymer compound shows conductivity when an appropriate conductive material is dispersed. In other words, the second
The high molecular compound and a suitable conductive material form a conductive elastomer composition, and the sheet heating element according to the present invention is
It functions as a conductive elastomer region 11B in the ten heat generating layers 11 and ensures flexibility.

As apparent from the above, the polyvalent metal, sulfur and unsaturated carboxylic acid sequentially form a cross-link between the carboxyl group of the first polymer compound and the unsaturated bond of the second polymer compound. The cross-linking agent functions as a cross-linking agent, and prevents the sheet heating element 10 according to the present invention from deteriorating and increasing fluidity when repeatedly used, thereby preventing changes in electric resistance and the like.

The surface heating element 10 according to the present invention is provided with an insulating layer (for example, an insulating polymer film layer such as a vinyl chloride sheet) 14 as a surface layer, if necessary. May be. That is, the insulating layer 14 is disposed on the outer surfaces of the heat generating layer 11 and the electrodes 12, 13 in order to avoid direct contact with peripheral members.
Since there is no electric shock risk when it is not necessary to consider the contact with the peripheral members, also the voltage applied to the sheet heating element 10 according to the present invention is low in some applications of the planar heat generating element 10 according to the present invention, this May be removed.

Electrodes 12 and 13 are DC or AC power supply (not shown)
Can be connected to.

Thus, the sheet heating element 10 according to the present invention includes electrodes 12, 13
When an appropriate voltage is applied in between, a current flows through the heat generating layer 11 to generate heat. While the temperature is low, the thermal expansion of the PTC region 11A hardly occurs, the chain of conductive particles is sufficiently maintained, the electric resistance is maintained low, and a large current flows through the heat generating layer 11, so that the heat generating layer 11 with time elapses. The calorific value of 11 increases, and the temperature of the planar heating element 10 according to the present invention increases.

When the temperature rises, the thermal expansion of the PTC region 11A increases, and the chain of the conductive particles is gradually broken, the electrical resistance increases, and the current is limited. For this reason, the calorific value of the heating layer 11 decreases, and the temperature of the planar heating element 10 according to the present invention decreases.

When the temperature decreases, the thermal expansion of the PTC region 11A decreases, the chain of the conductive particles is restored, and the electric resistance decreases,
The current increases. As a result, the amount of heat generated by the heating layer 11 increases,
The temperature of the sheet heating element 10 according to the present invention rises again.

By repeating the above operation, the sheet heating element 10 according to the present invention calms down to a temperature at which the calorific value matches the heat radiation amount, and exhibits a self-temperature adjusting function and an overheating preventing function.

In the sheet heating element 10 according to the present invention, the carboxyl group in the side chain of the polymer compound contained in the PTC composition was contained in the conductive elastomer composition by the polyvalent metal, the unsaturated carboxylic acid and the sulfur. Since the unsaturated bond of the polymer compound is cross-linked as described above, the structure of the matrix is prevented from changing even if the voltage application is repeated, and the fluidity and electric resistance of the heat generating layer 11 are reduced. Is suppressed from changing.

Further, in the planar heating element 10 according to the present invention, the PTC composition and the conductive elastomer composition are mixed with each other, and the conductive elastomer region is disposed around the PTC region (in other words, the PTC region is formed within the conductive elastomer region). Since they are dispersed in the form of islands), flexibility is ensured, and they can be arranged in a location having a small radius of curvature without difficulty.

Next, an embodiment of a method for manufacturing a sheet heating element according to the present invention will be described in detail with reference to FIG. 1 to FIG.

(Preparation of Conductive Elastomer Composition) The conductive elastomer composition is obtained by adjusting (i) electric resistance to a polymer compound having an unsaturated bond in at least one of a main chain and a side chain by adjusting electric resistance. (Ii) a rubber compounding agent (ie, a vulcanizing agent as an essential component and a reinforcing filler, a plasticizer, and a vulcanization accelerator as an optional component); , A vulcanization regulator, a processing aid, an antioxidant, a flame retardant, etc.) by means of a kneading machine (for example, an open roll), and dispersion-mixing.

Although any desired elastomer can be used, a material that is not deteriorated by air oxidation is preferable in consideration of the fact that the planar heating element 10 according to the present invention is often used in air. That is, those not containing much unsaturated bonds, for example, (i) ethylene propylene rubber,
At least one of rubbers such as acrylonitrile butadiene rubber, acrylic rubber, silicone rubber, fluoro rubber, butyl rubber, chlorinated polyethylene, or (ii) polyvinyl chloride containing a plasticizer such as DOP, dioctyl phthalate, or a resin family It is preferable to use at least one of resins such as polyamide.

At least one of a particulate material and a fibrous material may be used as the conductive material.

Particulate materials include (i) ketchen black, acetylene black, ECF carbon black, and sterling.
V, at least one material selected from carbon black materials such as graphite or carbon fiber, or (ii) nickel powder, copper powder, gold powder, silver powder, aluminum powder, brass powder, metal-coated mica powder, It is preferable to use at least one material selected from metal-based materials such as glass powder coated with metal. The addition amount of carbon black material is 10
It is preferably 5 to 50 parts by weight with respect to 0 parts by weight, and the addition amount of the metal material is 10 to 100 parts by weight of the elastomer.
~ 90 parts by weight are preferred. If desired, a carbon black-based material and a metal-based material may be used in combination with each other. In this case, the amount of each addition is appropriately selected according to the requirements for the weight and conductivity of the sheet heating element 10 according to the present invention.

As the fibrous material, carbon fiber, metal-coated polymer fiber, metal-coated glass fiber or metal fiber (for example, aluminum fiber, brass fiber, nickel fiber) and the like are preferable. The addition amount of the fibrous material is preferably 10 to 90 parts by weight based on 100 parts by weight of the elastomer.

Examples of reinforcing fillers include white carbon,
It is preferable to use at least one of precipitated calcium carbonate, fine powdered mica, short fibers of synthetic fibers (for example, nylon or Tetron), whiskers and hard clay.

As the vulcanizing agent, it is preferable to use, for example, sulfur or peroxide. Here, as the peroxide, at least one of dicumyl peroxide, tert-butylcumyl peroxide and 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane is used. Preferred and optionally ethylene dimethacrylate,
At least one of trimethylolpropane trimethacrylate and a polyaryl compound (for example, triaryl isocyanurate) may be used in combination.

When sulfur is used as the vulcanization accelerator, benzothiazoles (for example, 2-mercaptobenzothiazole), dithiocarbamine hydrochlorides and thiurams (for example, tetramethylthiuram monosulfide) when sulfur is used as the vulcanizing agent.
It is preferable to use at least one of the above. It is preferable to add a vulcanization accelerator (for example, zinc white) together with the vulcanization accelerator because the vulcanization accelerator functions sufficiently.

As the antioxidant, for example, at least one of N, N'-diphenyl-P-phenylenediamine, P-isopropoxydiphenylamine and N, N'-di-O-tolylethylenediamine is preferably used. is there.

Flame retardants work together with anti-aging agents to ensure product life and safety. As the flame retardant, organophosphorus compounds (for example, tricresyl phosphate,
At least one of diphenylcresyl phosphate, trioctyl phosphate, triphenyl phosphate, tris (chloroethyl) phosphate, and the like, and an organic halogen compound (for example, hexabromobiphenyl, pentabromochlorocyclohexane or tris- ( At least one of 2,3-dibromopropyl-1) -isocyanurate and the like; a metal oxide (for example, antimony oxide); and a metal hydroxide (for example, aluminum hydroxide or zinc borate). It is preferred to use at least one selected from the group consisting of at least one).

If stearic acid is used as a processing aid,
It is suitable.

(Preparation of PTC composition) The PTC composition is, for example, 10 ^-2 to 10 ³ Ωcm with respect to a polymer compound having a carboxyl group in a side chain and functioning as a matrix resin (for example, a crystalline polymer compound).
It is prepared by dispersing conductive particles so as to exhibit a degree of conductivity. That is, the PTC composition is prepared by charging a polymer compound having a carboxyl group in a side chain (for example, a crystalline polymer compound) and appropriate conductive particles into a kneader (for example, an open roll or a kneader) and adding the compound to the side chain. It is prepared by kneading while heating to the softening point of a polymer compound having a carboxyl group (for example, a crystalline polymer compound).

As the crystalline polymer compound, ethylene acryl having a melting point of as low as 103 ° C. and having a carboxyl group in a side chain and capable of bonding to a carboxyl group existing at the terminal of an unsaturated carboxylic acid via a polyvalent metal (eg, calcium). Acid copolymers are preferred.

The conductive particles include carbon black (furnace carbon black, channel carbon black,
It is preferable to use at least one of thermal carbon black, acetylene carbon black, Stirling V, Ketchen black, etc.), graphite powder, carbon fiber, metal fiber or metal powder. The amount of the conductive particles to be added may be appropriately selected as desired, but is preferably from 10 to 85 parts by weight based on 100 parts by weight of the polymer compound (crystalline polymer compound).

(Dissolution of PTC composition) The PTC composition is dissolved by stirring in an appropriate solvent,
This is a TC composition solution.

PTC composition solution, the dropping operation in the subsequent particle forming step is performed by a dropping funnel and the like, and in order to shorten the time required for the dropping operation, the viscosity is about 100 to 1000 cp, so that the viscosity is about 10 to 1000 cp or less. Is preferable.

(Particulation of PTC composition) The PTC composition solution is converted into PTC particles by dropping into a suitable poor solvent (eg, toluene) using a dropping funnel or the like and stirring to precipitate as fine particles. You.

The stirring speed of the poor solvent is appropriately adjusted so that the PTC particles have a size of 1 to 100 μm. Here, the grounds that the PTC particles are 1 to 100 μm are as follows: (i) If it is less than 1 μm, it becomes difficult to handle in the subsequent step, and (ii) if it exceeds 100 μm, the surface area becomes too small compared to the volume, The subsequent reaction with the polyvalent metal takes a great deal of time to reach the interior of the PTC particles.

(Cross-Link Formation in PTC Particles) PTC particles are dispersed in an appropriate solvent together with a polyvalent metal salt and an unsaturated carboxylic acid, and are stirred while heating.
Here, the amount of the carboxyl group present at the terminal of the unsaturated carboxylic acid is preferably equal to or more than the amount of the carboxyl group present in the side chain of the polymer compound (for example, a crystalline polymer compound) in the PTC particles. . Also, the amount of the polyvalent metal in the polyvalent metal salt is preferably equal to or more than the amount of the carboxyl group present in the side chain of the polymer compound (for example, a crystalline polymer compound) in the PTC particles.

As a result, a cross-link is formed between the carboxyl group in the side chain of the polymer compound (for example, a crystalline polymer compound) in the PTC particles and the carboxyl group at the end of the unsaturated carboxylic acid via a polyvalent metal. So, the PTC particles are
Be stabilized.

The PTC particles are then washed with water and with toluene to remove excess polyvalent metal salts.

(Dissolution of Conductive Elastomer Composition) The conductive elastomer composition is dissolved by being appropriately stirred in a solvent (for example, toluene) to form a conductive elastomer solution.

The conductive elastomer solution has a viscosity of 10,000 cp to efficiently perform stirring in the subsequent PTC particle dispersion step.
It is preferable that the concentration be 20% by weight or less so that

(Dispersion and Precipitation of PTC Particles) PTC particles cross-linked with an unsaturated carboxylic acid via a polyvalent metal are thoroughly stirred after being dispersed in a conductive elastomer solution. The conductive elastomer solution in which the PTC particles are dispersed and sufficiently stirred is dropped using a dropping funnel or the like onto an appropriate poor solvent being stirred, and precipitated as fine particles, whereby particles having an appropriate particle size are obtained. It is said.

Thereby, PTC elastomer particles, that is, PTC particles around which the conductive elastomer composition is arranged are produced.

(Preparation of PTC composition sheet) After casting and drying PTC elastomer particles,
By performing pressure molding while heating, a cross-linking bond is formed between the unsaturated bond of the unsaturated carboxylic acid and the unsaturated bond of the polymer compound in the conductive elastomer composition via sulfur, and the PTC composition It is a sheet.

Therefore, the PTC composition sheet microscopically has a conductive elastomer region disposed around the PTC region (in other words, the PTC region is dispersed in the conductive elastomer region in an island shape), and The carboxyl group in the side chain of the high molecular compound (for example, a crystalline high molecular compound) is cross-linked to the carboxyl group at the terminal of the unsaturated carboxylic acid via a polyvalent metal, and Since the saturated bond is cross-linked via sulfur to the unsaturated bond in the polymer compound in the conductive elastomer region, PT
Even if the C region thermally expands, it does not fluidize and is stabilized. For this reason, the PTC composition sheet is suppressed from changing its electrical resistance even when voltage is repeatedly applied.

(Arrangement of Electrodes) The PTC composition sheet is cut into an appropriate size if desired, and is used as a heat generating layer body. Electrodes 12 and 13 are disposed on the surface of the heat generating layer body by using an appropriate conductive adhesive or by vulcanization bonding or pressure bonding to form a heat generating layer 11 (see FIGS. 1 and 3). ).

Thereby, the sheet heating element 10 according to the present invention is formed.

Here, the electrodes 12 and 13 are preferably formed of a metal plate such as copper, brass, stainless steel, or aluminum, a metal foil, a metal rod, a metal thread, a metal twisted thread, or a metal net. When it is necessary to ensure the flexibility of the heating element 10, the heating element 10 is preferably formed of a metal wire or a metal foil.

(Disposition of Insulating Layer) In the planar heating element 10 according to the present invention, the heating layer
An insulating layer 14 may be provided on the outer surfaces of the electrodes 11 and the electrodes 12 and 13.

In addition, an embodiment of the sheet heating element and the method of manufacturing the same according to the present invention will be described with specific numerical values and the like for better understanding.

(Example 1) Only 80 parts by weight of Stirling V as conductive particles were mixed with 100 parts by weight of an ethylene acrylic acid copolymer as a crystalline polymer compound, and kneaded with an open roll heated to 80 to 100 ° C. Thereafter, a sheet having a thickness of 300 μm was formed and finally cut into small pieces of 3 mm × 3 mm to prepare a PTC composition.

The PTC composition was dissolved in decalin heated to 80 to 100 ° C. to give a PTC composition solution having a concentration of 5% by weight.

The PTC composition solution was dropped into about 10 times the amount of toluene being stirred to form PTC particles. PTC particles are dried after being passed, the particle size is 1 to 100 μm
And it was.

The PTC particle powder is dispersed by 100 g in a mixed solvent 1 of water and ethyl alcohol, and then 3 g of calcium hydroxide as a polyvalent metal salt and 15 g of linoleic acid as an unsaturated carboxylic acid are added. Stirred for 4 hours. As a result, the PTC particles were stabilized by the cross-linking of the carboxyl group present in the side chain of the ethylene acrylic acid copolymer contained therein to the carboxyl group present at the terminal of linoleic acid by calcium ions.

The PTC particles stabilized with calcium ions were washed with water and then with toluene.

PTC particles stabilized with calcium ions are dispersed in a conductive elastomer solution, that is, a toluene solution of a conductive elastomer compound, and then precipitated by dripping against methyl alcohol, separately washed with water and dried. , Around which a conductive elastomer compound is placed,
PTC elastomer particles. Here, the conductive elastomer solution is composed of 100 parts by weight of NBR, that is, acrylonitrile butadiene rubber, 30 parts by weight of Ketjen Black EC, and 5 parts by weight.
Parts by weight of zinc white, 1.5 parts by weight of stearic acid, 1.5 parts by weight of tetramethylthiuram monosulfide, 0.5 parts by weight of tetrathiuram disulfide, and 2 parts by weight of sulfur are dispersed and mixed in a kneader. The prepared conductive elastomer composition was prepared by dissolving 45 g of the prepared conductive elastomer composition in an appropriate amount of 10 wt% toluene.

The PTC elastomer particles are heated to a temperature of 180 ° C. for 6 minutes and pressed to form a conductive elastomer region around the PTC region at a thickness of 300 μm and a length of 10 cm × 1 cm.
It was a 1 cm PTC composition sheet. At this time, in the PTC elastomer particles, a cross-link was formed between the unsaturated bond in the acrylonitrile butadiene rubber and the unsaturated bond in the linoleic acid via sulfur.

The PTC composition sheet has a large tensile strength at break T _B of 130 kg / cm ² and a sufficient strength, and an elongation at break E _{B of} 10
It was as large as 0% and had sufficient flexibility.

Further, the PTC composition sheet was directly used as a heat generating layer body, and a copper foil having a width of 5 mm was adhered to both side edges as electrodes to obtain a sheet heat generating body according to the present invention.

The sheet heating element according to the present invention created as described above,
The electrical resistance R ₂₀ at room temperature (that is, 20 ° C.) of the heating layer and the electrical resistance R _{80 at} 80 ° C. were measured, and R ₈₀ / R ₂₀ between them was calculated as a resistance change rate. 13 and had a sufficient temperature control function.

Further, the sheet heating element according to the present invention prepared as described above applies a test voltage of 80 ° C. between the electrodes, that is, the heating layer, by alternately repeating a 5-minute conduction period and a 5-minute interruption period. Heated to temperature. The test voltage application time
Even after 100 hours, the change in the electrical resistance between the electrodes is 1
% And was substantially negligible.

(Example 2) A conductive elastomer solution was prepared by mixing 100 parts by weight of ethylene propylene rubber, 30 parts by weight of Ketjen Black EC, and 5 parts by weight.
Parts by weight of zinc white, 1.5 parts by weight of stearic acid, 1.5 parts by weight of tetramethylthiuram monosulfide, 0.5 parts by weight of tetrathiuram disulfide, and 2 parts by weight of sulfur are dispersed and mixed in a kneader. Example 1 was repeated except that the prepared conductive elastomer composition was prepared by dissolving only 45 g to 10% by weight in toluene.

The PTC composition sheet has a large tensile strength at break T _B of 160 kg / cm ² and has sufficient strength, and an elongation at break E _{B of} 12
It was as large as 0% and had sufficient flexibility.

The resistance change rate R ₈₀ / R ₂₀ of the sheet heating element according to the present invention is 1
5, which was sufficient for the self-temperature control function.

The sheet heating element according to the present invention was heated to a temperature of 80 ° C. by applying a test voltage alternately repeating a 5-minute conduction period and a 5-minute interruption period between the electrodes, that is, the heating layer. . Even if the test voltage is applied for 100 hours,
The change in the electrical resistance between the electrodes was less than 1% and was substantially negligible.

(Example 3) A conductive elastomer solution was prepared by mixing 100 parts by weight of ethylene propylene rubber, 30 parts by weight of Ketjen Black EC, and 5 parts by weight.
Parts by weight of zinc white, 1.5 parts by weight of stearic acid, 1.5 parts by weight of tetramethylthiuram monosulfide, 0.5 parts by weight of tetrathiuram disulfide, and 2 parts by weight of sulfur are dispersed and mixed in a kneader. Example 1 was repeated except that the prepared conductive elastomer composition was prepared by dissolving only 25 g to 10% by weight in toluene.

The PTC composition sheet has a sufficient tensile strength at break tensile strength T _B of 150 kg / cm ² and an elongation at break E _{B of} 75
% And sufficient flexibility.

The resistance change rate R ₈₀ / R ₂₀ of the sheet heating element according to the present invention is 2
7, which had a sufficient self-temperature control function.

The sheet heating element according to the present invention was heated to a temperature of 80 ° C. by applying a test voltage alternately repeating a 5-minute conduction period and a 5-minute interruption period between the electrodes, that is, the heating layer. . Even if the test voltage is applied for 100 hours,
The change in the electric resistance between the electrodes was less than 1% and was substantially negligible.

(Example 4) 100 parts by weight of ethylene propylene rubber, 30 parts by weight of Ketjen Black EC,
Parts by weight of zinc white, 1.5 parts by weight of stearic acid, 1.5 parts by weight of tetramethylthiuram monosulfide, 0.5 parts by weight of tetrathiuram disulfide, and 2 parts by weight of sulfur are dispersed and mixed in a kneader. Example 1 was repeated, except that the prepared conductive elastomer composition was prepared by dissolving only 70 g to 10% by weight in toluene.

The PTC composition sheet has a large tensile strength at break T _B of 180 kg / cm ² and a sufficient strength, and an elongation at break E _{B of} 18
It was as large as 0% and had sufficient flexibility.

The resistance change rate R ₈₀ / R ₂₀ of the sheet heating element according to the present invention,
6, which was sufficient for a self-temperature control function.

The sheet heating element according to the present invention was heated to a temperature of 80 ° C. by applying a test voltage alternately repeating a 5-minute conduction period and a 5-minute interruption period between the electrodes, that is, the heating layer. . Even if the test voltage is applied for 100 hours,
The change in the electric resistance between the electrodes was less than 1% and was substantially negligible.

(Comparative Example 1) Only 80 parts by weight of Stirling V as conductive particles was blended with 100 parts by weight of an ethylene acrylic acid copolymer as a crystalline polymer compound, and heated with an open roll heated to 80 to 100 ° C. The mixture was kneaded, then formed into a sheet having a thickness of 300 μm, and finally cut into small pieces of 3 mm × 3 mm to prepare a PTC composition.

The PTC composition was dissolved in decalin heated to 80 to 100 ° C. to give a PTC composition solution having a concentration of 5% by weight.

The PTC composition solution was dropped into about 10 times the amount of toluene being stirred to form PTC particles. PTC particles are dried after being passed, the particle size is 1 to 100 μm
And it was.

PTC particles are dispersed only in 100 g of a conductive elastomer solution, that is, a toluene solution of a conductive elastomer compound, and then dropped and precipitated in methyl alcohol.
Separately, by washing with water and drying, a conductive elastomer compound was placed around the resultant, and PTC elastomer particles were obtained. Here, the conductive elastomer solution is 100 parts by weight of NBR.
That is, acrylonitrile butadiene rubber, 30 parts by weight of Ketjen Black EC, 5 parts by weight of zinc white, 1.5 parts by weight
Parts by weight of stearic acid, 1.5 parts by weight of tetramethylthiuram monosulfide, 0.5 parts by weight of tetrathiuram disulfide, and 2 parts by weight of a conductive elastomer composition prepared by dispersing and mixing each other with a kneader. ,
It was prepared by dissolving only 45 g in a suitable amount of toluene so as to be 10% by weight.

The PTC elastomer particles are heated to a temperature of 180 ° C. for 6 minutes and pressed to form a conductive elastomer region around the PTC region at a thickness of 300 μm and a length of 10 cm × 1 cm.
It was a 1 cm PTC composition sheet.

The PTC composition sheet has a large tensile strength at break T _B of 130 kg / cm ² and has sufficient strength, and an elongation at break E _{B of} 11
It was as large as 0% and had sufficient flexibility.

Further, the PTC composition sheet was directly used as a heating layer body, and a copper foil having a width of 5 mm was adhered as an electrode to both side edges thereof to form a sheet heating element.

The sheet heating element prepared as described above has an electric resistance value at room temperature (that is, 20 ° C.) between the electrodes and, consequently, of the heating layer.
R ₂₀ and the electrical resistance value R _{80 at} 80 ° C. were measured, respectively, and the ratio R ₈₀ / R ₂₀ between them was calculated as the rate of change in resistance. As a result, the ratio was 14, which was sufficient for self-temperature control.

The planar heating element prepared as described above is heated to a temperature of 80 ° C. by applying a test voltage that alternately repeats a 5-minute conduction period and a 5-minute interruption period between the electrodes, that is, the heating layer. Was. When the test voltage was applied for 100 hours, the change in the electrical resistance between the electrodes was -8%, which was not substantially negligible.

(Comparative Example 2) Only 80 parts by weight of Stirling V as conductive particles were mixed with 100 parts by weight of an ethylene acrylic acid copolymer as a crystalline polymer compound, and kneaded with an open roll heated to 80 to 100 ° C. Thereafter, a sheet having a thickness of 300 μm was formed and finally cut into small pieces of 3 mm × 3 mm to prepare a PTC composition.

The PTC composition was dissolved in decalin heated to 80 to 100 ° C. to give a PTC composition solution having a concentration of 5% by weight.

The PTC composition solution was dropped into about 10 times the amount of toluene being stirred to form PTC particles. PTC particles are dried after being passed, the particle size is 1 to 100 μm
And it was.

PTC particles are dispersed in a 100 g conductive elastomer solution in a toluene solution of a conductive elastomer compound, then dropped into methyl alcohol to precipitate, separately washed with water and dried to form a conductive elastomer compound around. Was placed and made into PTC elastomer particles. Here, the conductive elastomer solution is composed of 100 parts by weight of ethylene propylene rubber, 30 parts by weight of Ketjen Black EC,
5 parts by weight of zinc white, 1.5 parts by weight of stearic acid, 1.5 parts by weight
Parts by weight of tetramethylthiuram monosulfide and 0.5 parts by weight
A conductive elastomer composition prepared by dispersing and mixing parts by weight of tetrathiuram disulfide and 2 parts by weight of sulfur with a kneader is prepared by dissolving only 45 g in an appropriate amount of toluene so as to be 10% by weight. Was done.

The PTC elastomer particles are heated to a temperature of 180 ° C. for 6 minutes and pressed to form a conductive elastomer region around the PTC region at a thickness of 300 μm and a length of 10 cm × 1 cm.
It was a 1 cm PTC composition sheet.

The PTC composition sheet has a tensile strength at break T _B of 150 kg / cm ^{2, which} is large enough and has an elongation at break E _{B of} 12
It had a large enough flexibility of 5%.

Further, the PTC composition sheet was directly used as a heating layer body, and a copper foil having a width of 5 mm was adhered as an electrode to both side edges thereof to form a sheet heating element.

The sheet heating element prepared as described above has an electric resistance value at room temperature (that is, 20 ° C.) between the electrodes and, consequently, of the heating layer.
R ₂₀ and the electric resistance value R _{80 at} 80 ° C. were measured, respectively, and the ratio R ₈₀ / R ₂₀ between them was calculated as the rate of change in resistance. As a result, it was 14, which was sufficient for the self-temperature control function.

The planar heating element prepared as described above is heated to a temperature of 80 ° C. by applying a test voltage that alternately repeats a 5-minute conduction period and a 5-minute interruption period between the electrodes, that is, the heating layer. Was. When the test voltage was applied for 100 hours, the change in the electrical resistance between the electrodes was -7%, which was not substantially negligible.

As is clear from comparison between Examples 1 to 4 and Comparative Examples 1 and 2, in the sheet heating element according to the present invention, the carboxyl group in the polymer compound in the PTC region and the polymer compound in the conductive elastomer region Since the unsaturated bond of was sequentially cross-linked via a polyvalent metal, an unsaturated carboxylic acid and sulfur, the flexibility and the self-temperature control function can be maintained,
At the same time, a function of suppressing an increase in the fluidity of the matrix due to repeated application of a voltage could be secured.

(3) Effects of the Invention As is clear from the above, the sheet heating element according to the present invention is a sheet heating element in which electrodes are arranged on the heating layer, and in particular, the heating layer has the following characteristics. A) a PTC composition including a first polymer compound having a carboxyl group in a side chain and conductive particles dispersed in the first polymer compound, wherein the temperature coefficient of electric resistance is positive. A PTC region, (b) a second polymer compound which is arranged around the PTC region and has an unsaturated bond in at least one of a main chain and a side chain, and (C) a carboxyl group cross-linked to a carboxyl group of the first polymer compound through a polyvalent metal, the conductive elastomer region comprising a conductive elastomer composition containing other dispersed conductive particles; And the unsaturated bond is And the unsaturated carboxylic acid cross-linked to the unsaturated bond of the second polymer compound. (I) The self-temperature control function can be performed without additionally providing a temperature control member such as a bimetal. In addition, it has the effect of achieving the function of preventing overheating, and (ii) has the effect of securing flexibility and, consequently, allowing it to be installed in a place with a small radius of curvature, and at the same time reducing the space for storage. And (iii) has the effect of preventing an increase in fluidity during repeated use and sufficiently suppressing a change in electric resistance.

Further, the method for producing a sheet heating element according to the present invention comprises: (a) a first step of preparing a PTC composition by dispersing at least conductive particles in a crystalline polymer compound having a carboxyl group in a side chain. (B) a second step of dissolving the PTC composition in a solvent to form a PTC composition solution; and (c) dropping the PTC composition solution in a poor solvent to precipitate the PTC particles. A third step, (d) dispersing the PTC particles in a solvent together with a polyvalent metal salt and an unsaturated carboxylic acid, so that the carboxyl group of the first polymer compound is converted into the unsaturated carboxylic acid by a polyvalent metal. And (e) dispersing at least other conductive particles in the second polymer compound having an unsaturated bond in at least one of the main chain and the side chain. A fifth step of preparing a conductive elastomer solution by dissolving the conductive elastomer composition in a solvent; and (f) changing the carboxyl group of the conductive elastomer solution to the unsaturated carboxylic acid by the polyvalent metal. The PTC particles cross-linked to the carboxyl groups in the dispersion are dispersed and then dried, whereby the unsaturated bonds in the unsaturated carboxylic acid are converted to the unsaturated bonds in the second polymer compound via sulfur. And (g) pressing the PTC elastomer particles under pressure to form a conductive elastomer region around the PTC region having a positive temperature coefficient of electrical resistance. 7th forming the heat generating layer in which is disposed
And (h) an eighth step of disposing electrodes on the heat generating layer. In addition to the effects (i) to (iii), (iv) work for stabilizing the heat generating layer This has the effect of making it easier.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a sheet heating element according to the present invention.
FIG. 2 is an enlarged sectional view showing the fine structure of the embodiment of FIG. 1, and FIG. 3 is a plan view of the embodiment of FIG. 10 Planar heating element 11 Heat generating layer 11A PTC area 11B Conductive elastomer area 12, 13 Electrode 14 Insulating layer

Claims (2)

(57) [Claims] 1. A planar heating element in which electrodes are disposed on a heating layer, wherein the heating layer comprises: (a) a first polymer compound having a carboxyl group in a side chain; A PTC region comprising a PTC composition containing conductive particles dispersed with respect to a polymer compound, and having a positive temperature coefficient of electric resistance; and (b) being disposed around the PTC region, comprising a main chain. And a second polymer compound having an unsaturated bond in at least one of the side chains, and another conductive particle dispersed in the second polymer compound. And (c) a carboxyl group is cross-linked to the carboxyl group of the first polymer compound through a polyvalent metal, and an unsaturated bond is bonded to the carboxyl group of the second polymer compound through sulfur. Unsaturated cross-linked to saturated bonds A planar heating element, characterized by containing a carboxylic acid. (A) a first compound having a carboxyl group in a side chain;
A first step of preparing a PTC composition by dispersing at least conductive particles in the polymer compound of (b), and (b) a second step of preparing a PTC composition solution by dissolving the PTC composition in a solvent. (C) a third step of dropping the PTC composition solution into a poor solvent and causing the PTC particles to precipitate to form PTC particles; and (d) converting the PTC particles into a solvent together with a polyvalent metal salt and an unsaturated carboxylic acid. A fourth step of crosslinking the carboxyl group of the first polymer compound to the carboxyl group in the unsaturated carboxylic acid with a polyvalent metal by dispersing; and (e) forming a main chain and a side chain. Dissolving in a solvent a conductive elastomer composition in which at least one other conductive particle is dispersed in a second polymer compound having an unsaturated bond on at least one side to form a conductive elastomer solution; And (f) dispersing the PTC particles in which the carboxyl group is cross-linked to the carboxyl group in the unsaturated carboxylic acid by the polyvalent metal in the conductive elastomer solution, followed by drying. A sixth step of producing PTC elastomer particles in which the unsaturated bond in the unsaturated carboxylic acid is cross-linked via sulfur to the unsaturated bond in the second polymer compound; (g) Forming a heating layer in which a conductive elastomer region is arranged around a PTC region having a positive temperature coefficient of electrical resistance by pressure molding PTC elastomer particles.
And (h) an eighth step of arranging an electrode on the heat-generating layer.