JP3126428B2 - Method for producing organic sheet heating element having positive temperature coefficient - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive temperature coefficient (PTC).
The present invention relates to a method for producing a sheet heating element having PTC, and more particularly to a method for producing a sheet heating element having PTC having a stable resistance value by a coating method with high efficiency.

[0002]

2. Description of the Related Art An organic planar heating element having a PTC (hereinafter also referred to as an organic PTC planar heater) is composed of a crystalline polymer, a conductive substance, a crosslinking agent and other additives (antioxidant). The composition is obtained by applying a material composition consisting of an agent, a stabilizer, a cross-linking aid, a surfactant, a flame retardant, a lubricant, etc.) to a substrate. When the temperature is lowered, conversely, when the temperature is lowered, the current increases to raise the temperature, that is, it has a self-temperature control function, and is used for various electric devices such as electric blankets and carpets.

[0003] As an organic heating element having PTC, a heating wire of a cable type (manufactured by extrusion) is generally commercially available. Not in a state. The reason for this is that when a wide sheet is made by the calendar sheeting method or extrusion method, the resistance value varies abnormally due to the mechanical stress during material processing and how heat is applied (temperature and time), resulting in uniform heat generation. This is because it is difficult to obtain a heater material having high performance.

[0004] Therefore, in order to stabilize the resistance value, extremely strict control of the manufacturing conditions is necessary, and there is a problem that it is difficult to mass-produce, and the cost becomes high in addition to technical difficulties.

[0005] In addition, a coating method in which a material composition solution is coated on a substrate, that is, a method in which the material composition is dissolved in a solvent and applied to the substrate, has been known in the past. However, although it is relatively easy to produce small piece samples on a laboratory scale by this method, it has been found that mass production by this method has the following problems and is not suitable for industrial production.

[0006] 1) A material composition solution is coated on a substrate (such as a fabric) to a thickness of 0.1 to
Since it is coated and dried continuously to about 0.5 mm, if it is applied thinly, it is applied and dried several times, so that the number of steps increases. 2) When the substrate is impregnated with the material composition solution, if the concentration is high, wrinkles are likely to be generated on the surface during cooling, and if the concentration is low, pinholes are formed, and a predetermined resistance value is not obtained. 3) In the coating or spray coating method, wrinkles and cracks are unavoidable on the surface. In these, since the material composition contains a crystalline polymer as an essential component, when dissolved in a solvent and coated, it is dried and then shrunk upon cooling. This is considered to be due to the fact that the formation is delayed and the crystal structure becomes uneven.

Further, in the calendering method or the extrusion method, when the material composition receives a mechanical stress, the resistance value increases, and depending on the degree of the stress (kneading time, warming time with a roll, sheeting time, etc.). 1 order to 2
The resistance is of the order of magnitude higher, and the effects of temperature (kneading temperature, roll temperature, summer / winter temperature difference, etc.) are also added.

An object of the present invention is to provide an economical method of manufacturing an organic PTC planar heater having a stable resistance value and capable of mass production.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies with the aim of solving the above-mentioned problems, and as a result, have found that a composition for producing a heating element having a PTC containing a crystalline polymer and a conductive substance is used as a base material. After impregnation, it was found that the above-mentioned problems could be solved all at once by applying treatments such as applying a composition for producing a heating element having PTC, and by cross-linking, thereby completing the present invention.

That is, the present invention relates to a method for producing a heating element having a PTC containing a crystalline polymer and a conductive substance, wherein the composition is impregnated into a substrate, and then a composition having the same composition or a different composition as the composition for producing a heating element is used. The present invention relates to a method for producing an organic PTC planar heater, which comprises treating with a composition for producing a heating element and crosslinking the composition.

As the material composition containing the crystalline polymer and the conductive substance in the present invention, those known in the art are appropriately selected and used. Examples of the crystalline polymer include polyolefins such as polyethylene and polypropylene, ethylene ethyl acrylate (EEA),
Ethylene-ethyl methacrylate, ethylene-tetrafluoroethylene, ethylene copolymers such as ethylene-vinyl acetate, polyvinylidene fluoride, chlorinated polyethylene, polybutene-1, polyester, and the like alone or in combination are exemplified. Further, ethylene-propylene rubber, chlorosulfonated polyethylene rubber, fluorine rubber, silicon rubber or the like may be added for the purpose of imparting flexibility.

As the conductive substance, carbon black,
Graphite, metal powder, known per se such as carbon black grafted organic polymer,
These may be used alone or in combination of two or more. These particle sizes are usually 0.5 to 150 μm, preferably 1 to 150 μm.
100 μm.

In order to further enhance the PTC characteristics, a pigment having good thermal conductivity, such as MgO, boron nitrite, barium titanate, etc., may be added.

These compositions may be used in the form of a solution (particularly in the impregnation step). Examples of the solvent include hydrocarbons such as benzene, halogenobenzene, toluene, xylene, methyl ethyl ketone and acetone, and ketones. , Tetrahydrofuran, tricrene and the like.

In the present invention, the mixing ratio of the crystalline polymer and the conductive substance is from 30 to 30 parts by weight per 100 parts by weight of the former.
It is 120 parts by weight, preferably 50 to 90 parts by weight.

The material composition of the present invention is preferably subjected to irradiation crosslinking (for example, electron beam irradiation crosslinking, gamma ray irradiation crosslinking) as described later, in which case a crosslinking accelerator such as triallyl isocyanurate (TAIC) is used. , Triallyl cyanurate (TAC), ethylene glycol dimethacrylate, trimethylpropane trimellitate, paraquinone dioxime, N, N'-metaphenylenebismaleimide, and the like. The compounding ratio of the crosslinking aid is based on 100 parts by weight of the crystalline polymer.
It is 0.5 to 5 parts by weight, preferably 0.7 to 2 parts by weight.

Further, the material composition of the present invention can be chemically crosslinked as described later, and dicumyl peroxide (DPO), 1,1-di-tert-butylperoxy-3 is used as a crosslinking agent at that time. , 3,5-trimethyl-cyclohexane, 2,5-dimethyl-2,5-di-tert-butylperoxyhexene, 1,3-bis-t-butyl-peroxyisopropylbenzene, etc .; Can be blended. The mixing ratio of the crosslinking agent is 0.5 to 100 parts by weight of the crystalline polymer.
5 parts by weight, preferably 1 to 2 parts by weight, and the compounding ratio of the crosslinking aid is 0.1 to 100 parts by weight of the crystalline polymer.
It is 5 to 5 parts by weight, preferably 0.7 to 2 parts by weight.

When the above-mentioned material composition is prepared as a solution by adding a solvent, its concentration is usually 5 to 40%, preferably 15 to 30%. It is desirable to heat. In this solution, the polymer is usually dissolved, but the fine particles of the conductive substance are in a dispersed state.

The substrate is capable of impregnating the above-mentioned solution, and woven fabric, non-woven fabric, mat-like material and the like are preferably used. Its materials include, for example, natural or synthetic fibers,
Glass, ceramic or the like is used.

In the present invention, the above-mentioned material composition is preferably impregnated into a substrate in the form of a solution, dried, and then dried again to obtain the material composition (even if it has the same composition as described above or a different composition). (May be applied) and then dried and cross-linked.

The impregnation step may be performed by any means.
For example, this is performed using an apparatus as shown in FIG. FIG.
In the figure, 1 is a heating and pressurizing pot, in which the material composition 2 is filled. 3 is a roller, 4 is a roll, and 5 is a substrate. The temperature of the material composition (i.e., the impregnation temperature) is 60 to 110C, preferably 70 to 9C.
0 ° C., and the immersion time is 3 to 300 seconds, preferably 5 to 1 second.
20 seconds. The traveling speed of the substrate is 0.2 m / min to 1
0 m / min is preferred. The viscosity of the material composition in the treatment is usually 10 to 1000 poise, preferably 30 to 500 poise at 80 ° C. The impregnation treatment is performed once or plural times, for example, once or twice. After impregnation, it is usually subjected to a drying step. Drying temperature is 20 ~
80 ° C., preferably 30-70 ° C., drying time 3-30
0 seconds, preferably 5 to 120 seconds is appropriate. In addition, you may dry under reduced pressure as needed.

After impregnation and drying, the material is treated again with the material composition. Here, the treatment refers to a treatment of coating a heating element manufacturing composition having PCT on the impregnated base material such as coating, spraying, and dipping. Specifically, the treatment is performed by brush coating, a doctor knife coating device, a sprayer, or the like. The temperature conditions at that time are almost the same as those of the impregnation process. This processing is performed once or plural times, for example, 1 to 3 times. The case using the doctor knife coating device will be described. In FIG. 2, 6 is a heating vessel,
3 'is a roller. The material composition 2 ′ is supplied onto the substrate 5 by the doctor knife 7. The solution viscosity of the material composition in the treatment is usually 10 to 2000 at 80 ° C.
Poise, preferably 100 to 1000 poise. The temperature of the material composition (ie, the coating temperature) is 60-
The temperature is 110 ° C, preferably 70 to 90 ° C. The traveling speed of the substrate is preferably from 0.2 m / min to 10 m / min.

After the treatment, drying is usually performed under the same conditions as described above to remove the solvent, and then crosslinking is performed. The crosslinking is preferably irradiation crosslinking. This is because, after the coating treatment, it is preferable not to give a heat history until the completion of crosslinking. Irradiation crosslinking is performed by electron beam, gamma ray (for example, cobalt 60).
Etc.). Irradiation is performed by means known per se, for example, high-speed scanning of a spot beam, curtain-shaped beam, or the like. Irradiation may be performed on only one side, but is usually performed on both sides. The irradiation dose is usually 1 to 10 megarads per side, preferably 3 to 1 megarads.
It is 0 megarats each, 1 to 20 megarads on the front and back, preferably 3 to 10 megarats. The crosslinking temperature in chemical crosslinking is usually from 130 to 180 ° C., preferably from 140 to 180 ° C.
To 160 ° C., and the crosslinking time is usually 30 minutes to 2 hours, preferably 30 minutes to 90 minutes.

In practicing the present invention, it is preferable to keep the concentration constant because the solvent evaporates during heating and the concentration changes. Therefore, it is preferable to perform the treatment in a sealed container. As described above, the method of the present invention is characterized in that a so-called two-stage coating process is required, in which a substrate is first impregnated with a material composition, dried and then coated with the same composition again. At this time, the content of the material composition by the impregnation is 20 to 120 g / m ² , preferably 30 to 120 g / m ² .
A to 100 g / m ^2, the amount of deposition by a second time processing 60~300g / m ^2, preferably 120～250G /
m ² .

[0025]

According to the method of the present invention, an organic PTC sheet heater having a stable resistance value at the original resistance level of the material can be obtained because no mechanical stress is applied during material processing. And an economical manufacturing method suitable for mass production is provided.

[0026]

Examples and comparative examples will be described below with reference to examples and comparative examples. Examples 1 to 3 Under the conditions described in Table 1, the cotton cloth substrate was impregnated with the material composition solution shown in Table 1 using the apparatus shown in FIG. The organic PTC planar heater was manufactured by coating using the apparatus shown in Table 1 and crosslinking under the conditions shown in Table 1.

Comparative Example 1 An organic PTC planar heater was manufactured in the same manner as in Example 1 except that the impregnation step was omitted under the conditions shown in Table 1.

Test Example 1 The organic PTC planar heaters manufactured in Examples and Comparative Examples were cut out into a sheet having a length of 200 mm (distance between electrodes) and a width of 100 mm, and a resistance value temperature characteristic test was performed with a tester. Are shown in Table 1.

[0029]

[Table 1]

[Brief description of the drawings]

FIG. 1 is an example of an apparatus used for impregnating a substrate with a composition for producing a heating element.

FIG. 2 is an embodiment of an apparatus used when a heating element manufacturing composition is further applied to a base material impregnated with the heating element manufacturing composition.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating pressure cooker 2 Composition for heating element production for impregnation 2 Composition for heating element production for coating 3 '4 Roll 4 Squeezing roll 5 Base material 6 Heating vessel 7 Doctor knife

Continuation of the front page (56) References JP-A-1-264189 (JP, A) JP-A-3-43986 (JP, A) JP-A-63-257197 (JP, A) JP-A-63-307683 (JP) JP-A-2-230684 (JP, A) JP-A-3-225788 (JP, A) JP-B-63-14825 (JP, B2) JP-B-63-14826 (JP, B2) 60-52553 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 3/20-3/38 H05B 3/14

Claims (1)

(57) [Claims] 1. After a base material is impregnated with a heating element-producing composition containing a crystalline polymer and a conductive substance and having a positive temperature coefficient, the composition is the same as or different from the heating element-producing composition. Coating with heating element manufacturing composition
A method for producing an organic sheet heating element having a positive temperature coefficient, wherein the heating step is followed by crosslinking.