JP2542233B2 - 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, as a planar heating element of this type, (i) conductive particles (for example, carbon black or metal particles) are added to a crystalline polymer compound having a positive temperature coefficient of electric resistance. It has been proposed to form a heat generating layer by dispersing them, and (ii) adjust the temperature of a bimetal or the like for the heat generating layer formed by dispersing conductive particles (for example, carbon black or metal particles) in the elastomer. Those that incorporate members have been proposed.

[Problems to be Solved] However, in the conventional sheet heating element, (i) when the heating layer is formed of a crystalline polymer compound having a positive temperature coefficient of electric resistance, the crystal structure changes with heating. Therefore, there is a drawback that the electric resistance changes as the number of times of repeated use increases, and because the hardness is large, it is not easy to bend or fold, and it is necessary to bend it to a place with a small radius of curvature. However, it has a drawback that it requires a large space for storage, and in addition (ii) when the heat generating layer is formed by an elastomer, it is necessary to incorporate a temperature adjusting member such as bimetal, so the number of parts increases. However, it has a drawback that even if it is flexible, it is difficult to arrange it in a curved state in a place having a small radius of curvature, 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 Problem] The means for solving the problem provided by the present invention is, “In a planar heating element in which an electrode is provided for the heating layer, the heating layer is (A) A PCT composition in which conductive particles are dispersed in a crystalline polymer compound having a positive temperature coefficient of electric resistance and a carboxyl group in a side chain, and the carboxyl groups are bound to each other by a polyvalent metal. And (b) a conductive elastomer arranged around the PTC particles.

Another means for solving the problems provided by the present invention is, “(a) a first step of dispersing conductive particles in a crystalline polymer compound having a carboxyl group in a side chain to prepare a PTC composition. And (b) a second step in which the PTC composition is dissolved in a solvent to prepare a PTC composition solution, and (c) the PTC composition solution is dropped into a poor solvent and precipitated to prepare PTC particles. A third step, and (d) a fourth step in which the PTC particles are dispersed in a solution of a polyvalent metal salt to bond the carboxyl groups of the side chains of the crystalline polymer compound to each other by a polyvalent metal, (E) a fifth step of dissolving a conductive elastomer in which other conductive particles are dispersed in the elastomer in a solvent to prepare a conductive elastomer solution, and (f) the above-mentioned polyvalent resin for the conductive elastomer solution. Bound by metal A sixth step of forming PTC elastomer particles by dispersing PTC particles and then drying, (g) a seventh step of forming a heat-generating layer by pressure molding the PTC elastomer particles, and (h) An eighth step of disposing electrodes on the heat generating layer, and a method for manufacturing a planar heat generating element ”.

[Function] In the sheet heating element of the present invention, in the heating layer, conductive particles are dispersed in (a) a crystalline polymer compound having a positive temperature coefficient of electric resistance and a carboxyl group in a side chain, PTC in which the carboxyl groups are bound to each other by a polyvalent metal
Since it comprises PTC particles composed of the composition and (b) a conductive elastomer disposed around the PTC particles,
(I) In addition to the effect of achieving a self-temperature control function and an overheat prevention function without additionally disposing a temperature control member such as a bimetal, (ii) ensuring flexibility, and consequently disposing in a place having a small radius of curvature. In addition, it has a function of reducing the space for storage, and (iii) a function of sufficiently suppressing a change in electric resistance during repeated use.

Further, the method for producing a planar heating element according to the present invention is a method in which conductive particles are dispersed in a crystalline polymer compound having a carboxyl group in a side chain and the PTC composition is dissolved in a solvent to form a PTC composition.
A TC composition solution is prepared, and the PTC composition solution is added dropwise to a poor solvent to cause precipitation to form PTC particles, and the PTC particles are dispersed in a solution of a polyvalent metal salt to form the crystalline polymer compound. Carry out polyvalent metal binding of carboxyl groups to the side chains, and then disperse PTC particles in a conductive elastomer solution created by dissolving the conductive elastomer in which other conductive particles are dispersed in the elastomer in a solvent. Since the PTC elastomer particles are prepared by forming the PTC elastomer particles by pressure molding to form the heat generating layer, in addition to the above (i) to (iii) actions, (iv) stabilizing the heat generating layer is performed. It acts to facilitate.

[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. 3 is a plan view of the embodiment shown in 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.

Reference numeral 10 denotes a planar heating element according to the present invention, which has a heating layer 11 having a self-temperature control function and an overheat prevention function, and the heating layer.
Electrodes 12 and 13 are arranged apart from each other with respect to 11.

The heating layer 11 includes PTC particles (that is, particles of a polymer conductive material composition having a positive temperature coefficient of electric resistance) 11A having a self-temperature control function and an overheat prevention function, and PTC particles 11A.
And a conductive elastomer 11B for ensuring flexibility. PTC particles 11A
The conductive particles are dispersed in a crystalline polymer compound having a positive temperature coefficient of electric resistance and a carboxyl group on the side chain, a composition in which the carboxyl groups are bound to each other by a polyvalent metal (hereinafter, "PTC composition"). Conductive elastomer 11B
Has a conductive material dispersed in a rubber compounding agent. The ratio of the PTC particles 11A to the conductive elastomer 11B is a weight ratio in order to satisfy the requirements for the self-temperature control function and the overheat prevention function and the flexibility at the same time.
It is preferably 70 to 90:10 to 30.

An insulating layer (for example, an insulating polymer film layer such as a vinyl chloride sheet) 14 is provided as a surface layer on the sheet heating element 10 , but this may be removed depending on the application. That is, on the surfaces of the heat generating layer 11 and the electrodes 12 and 13, the insulating layer 14 is provided to avoid direct contact with peripheral members.
However, it is not necessary to consider contact with peripheral members depending on the application of the sheet heating element 10 , and the sheet heating element 10 is also provided.
There is no risk of electric shock when the voltage applied to is low, so 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 electric resistance of the PTC particles 11A is small and a large current flows in the heat generating layer 11, so that the heat generation amount of the heat generating layer 11A increases with the passage of time, and the temperature of the sheet heating element 10 according to the present invention rises. .

When the temperature rises, the electrical resistance of PTC particles 11A increases,
Limit the current. Therefore, the heat generation amount of the heat generation layer 11A is reduced, and the temperature of the sheet heating element 10 according to the present invention is lowered.

When the temperature decreases, the electrical resistance of PTC particles 11A decreases,
The current increases. Therefore, the heat generation amount of the heat generation layer 11A increases, and 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 exhibits the self-temperature control function and the overheat prevention function.

Further, in the sheet heating element 10 according to the present invention, since the Carboxyl groups in the side chains of the crystalline polymer compound contained in the PTC particles 11A are bound to each other by the polyvalent metal, even if the voltage application is repeated. The change in the structure is suppressed, and thus the change in the electric resistance of the heat generating layer 11 is suppressed.

Further, in the sheet heating element 10 according to the present invention, the flexibility is ensured by the conductive elastomer 11B arranged around the PTC particles 11A, and it can be arranged without difficulty by bending to a place having a small radius of curvature. .

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
(I) a conductive material for adjusting electric resistance to appropriately set the calorific value and thus the exothermic temperature, and (ii) a rubber compounding agent (that is, a vulcanizing agent as an essential component and a reinforcing filler as an optional component). , Plasticizer, vulcanization accelerator, vulcanization regulator,
A processing aid, an antioxidant, a flame retardant, and the like) are kneaded by a kneader (for example, a roll) and dispersed and mixed to prepare.

The elastomer is preferably one that is not deteriorated by air oxidation because the sheet heating element 10 of the present invention is often used in the air. That is, those containing not much unsaturated groups, for example (i) ethylene propylene rubber,
At least one of rubbers such as acrylic rubber, silicone rubber, fluorine rubber, butyl rubber, chlorinated polyethylene, or (ii) polyvinyl chloride containing a plasticizer such as DOP, dioctyl phthalate, resin such as resin group polyamide It is preferred to use at least one of the classes.

A particulate material or a fibrous material may be adopted as the conductive material.

As the particulate material, (i) at least one material selected from carbon black materials such as Ketchen black, acetylene black, ECF carbon black, graphite or carbon fiber, or (i
i) Nickel powder, copper powder, silver powder, gold powder, aluminum powder,
It is preferable to use at least one material selected from metal-based materials such as brass powder, metal-coated mica powder, and metal-coated glass powder. The amount of carbon black material added is preferably 5 to 50 parts by weight per 100 parts by weight of elastomer, and the amount of metal material added is 10 to 90 parts by weight per 100 parts by weight of elastomer. preferable. If desired, a carbon black material and a metal material may be used in combination with each other. In this case, the addition amount of each is appropriately selected according to the requirements for the weight and conductivity of the sheet heating element 10 of 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.

As the vulcanization accelerator, when sulfur is used as the vulcanizing agent, a benzothiazole agent (for example, 2-mercaptobenzothiazole), dithiocarbamine arithmetic salts and thiurams (for example, tetramethylthiuram monosulfide).
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, it is preferable to use at least one of N, N'-diphenyl-P-phenylenediamine, P-isopropoxydiphenylamine, and N, N'-di-0-tolylethylenediamine. is there.

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

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

(Preparation of PTC composition) A PTC composition (that is, a polymer conductive material composition having a positive temperature coefficient of electric resistance) is, for example, 10 ^-2 to 10 ^{3 relative} to a crystalline polymer compound functioning as a matrix resin.
It is prepared by dispersing conductive particles so as to exhibit conductivity of about Ωcm. That is, the PTC composition is
The crystalline polymer compound and the conductive particles are put into a kneading machine (for example, an open roll or a kneader) and kneaded while being heated to the softening point of the crystalline polymer compound.

As the crystalline polymer compound, an ethylene acrylic acid copolymer having a melting point as low as 103 ° C. and having a carboxyl group in the side chain and capable of binding the carboxyl groups to each other via a polyvalent metal is preferable.

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, Ketchen black, etc.), graphite powder, carbon fiber, metal fiber or metal powder. The amount of the conductive particles added may be appropriately selected as desired, but is preferably 10 to 70 parts by weight relative to 100 parts by weight of the crystalline polymer compound.

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

The PTC composition solution has a viscosity of about 100 to 1000 cp so that the dropping operation in the subsequent particles or the step is performed with a dropping funnel and the time required for the dropping operation is shortened to 10% by weight or less. It is preferable that the concentration is set to.

(Particulation of PTC composition) The PTC composition solution is dropped into a poor solvent under stirring using a dropping funnel or the like to be precipitated as fine particles to obtain PTC particles.

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.

(Reaction between PTC particles and polyvalent metal) PTC particles are dispersed in a polyvalent metal salt solution (for example, an aqueous solution of polyvalent metal) and stirred while heating.

As a result, the carboxyl group in the side chain of the ethylene-acrylic acid copolymer reacts with the polyvalent metal, and the PTC particles are stabilized.

(Dissolution of Conductive Elastomer Composition) The conductive elastomer composition is appropriately stirred and dissolved in a solvent to obtain a conductive elastomer solution.

It is preferable that the conductive elastomer solution has a concentration of 20% by weight or less so that the viscosity is 10000 cp or less in order to disperse the subsequent PTC particles and efficiently perform stirring.

(Dispersion and Drying of PTC Particles) The PTC particles reacted with the polyvalent metal are dispersed in the conductive elastomer solution and then stirred. PTC particles are thoroughly stirred and then (i) cast and dry, or
Alternatively, (ii) a precipitation treatment is performed, and then excess and then dried.

As a result, PTC elastomer particles, that is, PTC particles around which the conductive elastomer is arranged, are produced.

(Preparation of PTC composition sheet) PTC elastomer particles can be formed into PTC
It is a composition sheet.

(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 provided on the surface of the heat generating layer body by using an appropriate conductive adhesive, or by vulcanization adhesion or pressure bonding to form the heat generating layer 11 (see FIGS. 1 to 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 twisted metal thread, or a metal mesh, and particularly the surface shape of the present invention. When it is necessary to ensure the flexibility of the heating element 10 , it 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 insulating layer 1 is formed on the surfaces of the conductive elastomer layer 11 and the electrodes 12 and 13 as desired.
4 may be provided.

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) 15 parts by weight of Ketjen Black EC as conductive particles was mixed with 100 parts by weight of ethylene acrylic acid copolymer as a crystalline polymer compound, and the mixture was heated by an open roller heated to 80 to 100 ° C. Knead and then thickness 300μm
As a sheet of the above, a PTC composition was prepared by finally cutting it into small pieces of 3 mm × 3 mm.

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.

The PTC particles are dissolved in an aqueous solution of calcium hydroxide containing an excess amount of calcium ions as compared with the amount necessary to bond the carboxyl groups in the ethylene acrylic acid copolymer contained in the PTC particles to each other after being passed. And maintained at a temperature of 80-100 ° C. for 5 hours. As a result, the PTC particles were sufficiently dispersed in the aqueous solution of calcium hydroxide, and the carboxyl groups in the ethylene acrylic acid copolymer contained therein were reacted with calcium ions to be bound and stabilized.

2 PTC particles stabilized by calcium ions
The dispersion was dispersed in a 0% by weight conductive elastomer solution, sufficiently stirred, and then separated, washed with water and dried to dispose the conductive elastomer in the periphery to obtain PTC elastomer particles. The conductive elastomer solution is 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, and 1.5 parts by weight of tetramethyl thiuram. It was prepared by dispersing and mixing monosulfide, 0.5 parts by weight of tetrathiuram disulfide and 2 parts by weight of sulfur with a kneader and then dissolving them in a solvent.

PTC elastomer particles are heated to 180 ° C for 5 minutes and pressure molded to give a thickness of 300 μm and length 11 cm x width 11 c.
m PTC composition sheet.

The PTC composition sheet was directly used as a heat generating layer body, and copper foil having a width of 5 mm was bonded as an electrode to both side edge portions thereof.

The sheet heating element according to the present invention created as described above,
The electric resistance value between the electrodes, that is, the heat generating layer was 58Ω at room temperature of 20 ° C.

In addition, the planar heating element according to the present invention produced as described above has a 5 minute energization period between electrodes
A voltage was applied that alternated with a cut-off period of 1 minute.
Even if the voltage was applied for 10 hours, the electrical resistance between the electrodes did not change.

Comparative Example The above example was repeated except that the step of treating the PTC particles with the aqueous calcium hydroxide solution was omitted.

The sheet-like heating element thus produced had an electrical resistance value of 55Ω between the electrodes, that is, between the heating layers at room temperature of 20 ° C.

Further, the electric resistance value between the electrodes of the planar heating element, that is, the heating layer, is only -6% when the voltage application time in which the energization period of 5 minutes and the interruption period of 5 minutes are alternately repeated becomes 10 hours. It was changing.

(3) Effects of the Invention As is apparent from the above, the planar heating element according to the present invention is a planar heating element in which electrodes are arranged on the heating layer, and particularly ) A PTC composition in which conductive particles are dispersed in a crystalline polymer compound having a carboxyl group in a side chain having a positive temperature coefficient of electric resistance, and the carboxyl groups are bound to each other by a polyvalent metal. Since the PTC particles and (b) the conductive elastomer arranged around the PTC particles are included, (i) the self-temperature control function and the self-temperature control function can be obtained without additionally disposing a temperature control member such as a bimetal. It has the effect of achieving an overheat prevention function, and (ii) it has the effect of ensuring flexibility and allowing it to be installed in a place with a small radius of curvature, and at the same time reducing the space for storage. Also (iii) repeated use It has the effect of sufficiently suppressing a change in electrical resistance Saishi.

Further, the method for producing a planar heating element according to the present invention comprises (a) a first step of dispersing conductive particles in a crystalline polymer compound having a carboxyl group in a side chain to prepare a PTC composition, (B) a second step of dissolving the PTC composition in a solvent to prepare a PTC composition solution; (c) a third step of dropping the PTC composition solution into a poor solvent and precipitating it to form PTC particles And (d) a fourth step in which the PTC particles are dispersed in a solution of a polyvalent metal salt to bond the carboxyl groups of the side chains of the crystalline polymer compound to each other by a polyvalent metal, ) A fifth step of dissolving the conductive elastomer in which other conductive particles are dispersed in the elastomer in a solvent to prepare a conductive elastomer solution, and (f) adding the polyvalent metal to the conductive elastomer solution. Combined PTC grain Is dispersed and dried to form PTC elastomer particles, and (g) a seventh step of forming the heat generating layer by pressure-molding the PTC elastomer particles, and (h) the heat generation. The eighth step of arranging electrodes on the layers is provided. Therefore, in addition to the effects (i) to (iii), (iv) the effect of facilitating the work of stabilizing the heat generating layer is provided.

[Brief description of 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 …… Sheet heating element 11 …… Heating layer 11A …… PTC particles 11B …… Conductive elastomer 12, 13 …… Electrode 14 …… Insulation layer

Claims (2)

(57) [Claims] 1. A planar heating element in which an electrode is provided for a heating layer, wherein the heating layer comprises (a) a crystalline polymer having a positive temperature coefficient of electric resistance and a carboxyl group in a side chain. Conductive particles are dispersed in the compound, PTC particles composed of a PCT composition in which the carboxyl groups are bound to each other by a polyvalent metal, and (b) a conductive elastomer arranged around the PTC particles. A planar heating element characterized by containing. 2. A first step (a) of preparing a PTC composition by dispersing conductive particles in a crystalline polymer compound having a carboxyl group in a side chain, and (b) a solvent of the PTC composition. A second step of preparing the PTC composition solution by dissolving the PTC composition solution in a solvent, and (c) a third step of preparing PTC particles by dropping the PTC composition solution into a poor solvent and precipitating the solution. A fourth step in which the carboxyl groups of the side chains of the crystalline polymer compound are bound to each other by a polyvalent metal by dispersing the particles in a solution of a polyvalent metal salt; and (e) another conductive particle for the elastomer. A fifth step of dissolving a conductive elastomer in which the above is dispersed in a solvent to prepare a conductive elastomer solution, and (f) after dispersing the PTC particles bound by the polyvalent metal into the conductive elastomer solution. To dry A sixth step of producing PTC elastomer particles, (g) a seventh step of forming a heat-generating layer by pressure molding the PTC elastomer particles, and (h) arranging electrodes on the heat-generating layer. An eighth step of providing, and a method of manufacturing a planar heating element, comprising: