JPH02139887A - Flat type heating element - Google Patents

Abstract

PURPOSE:To obtain a heating element having self temperature control quality and generating safe and soft warm heat by applying the constitution wherein a conductive resin composition having a mixture of the specified weight ratio of respectively specified thermoplastic resin and carbon black is thermocompression bonded onto a cloth-like support body. CONSTITUTION:A conductive resin composition is thermocompression bonded onto a cloth-like support body, thereby obtaining a flat type heating element. The conductive resin composition for thermocompression bonding is composed of a mixture of 100 weight parts of thermoplastic resin having a linear expansion coefficient equal to or more than 3.0X10<-4>K<-1> and 15 to 200 weight parts of carbon black having dibutyl phthalate oil absorption rate of 800m<2>/g or less. According to the aforesaid construction, it is possible to obtain a heating element having excellent heat resistance and self-temperature control quality, while generating highly safe and soft warm heat.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention (Field of Industrial Application) The present invention relates to a planar heating element, and more particularly, to a planar heating element having excellent heat resistance and self-temperature controllability.

(Prior Art) Generally, as a planar heating element, one using a metal heating element is well known, but when such a metal heating element is energized, the resistance value of the heating element decreases as it generates heat. The current increases, and as a result, the temperature of the heat generated becomes higher, which could lead to a disaster. Also, for that purpose,
This type of surface heating element using a metal heating element has the disadvantage that an expensive temperature control device must be used to ensure safety. Furthermore, if the temperature control device were to malfunction, there was a risk of serious accidents such as a fire occurring or being burned to death.

In addition, a sheet heating element that incorporates a linear heating element generates heat at the location where the linear heating element is present, so it may cause temperature unevenness in the sheet heating element or a sawtooth-like height difference in the control temperature. This tends to occur, and there are drawbacks such as the so-called warmth becoming hard and causing discomfort to the user.

(Problems to be Solved by the Invention) The present invention seeks to provide a planar heating element that is low cost, has self-temperature control, is highly safe, and provides soft warmth. .

<b) Structure of the Invention (Means for Solving the Problems) As a result of various studies conducted by the present inventors to eliminate the above-mentioned drawbacks of conventional planar heating elements, the present inventors have developed a method with a specific high coefficient of linear expansion. This objective was achieved by forming a heating element using a conductive resin in which carbon black having specific physical properties was blended with a thermoplastic resin in a specific proportion.

That is, the sheet heating element of the present invention has a linear expansion coefficient of 3.0X.
10-' for 100 parts by weight of the thermoplastic resin,
Dibutyl phthalate oil absorption is 1001n1/100
g or more and a specific surface area of 800 bo/g or less, the conductive resin composition is thermocompressed onto a cloth-like support. be.

The linear expansion coefficient of the thermoplastic resin described herein is at a temperature of 30
It refers to the average linear swelling rate at ~60°C.

The conductive resin composition of the present invention, which is thermocompressed onto a cloth-like support, acts as an electrical resistor and generates heat. Carbon black having specific physical properties is blended and kneaded in a specific blending ratio. The conductive resin composition that acts as this type of surface heating element has an electrical resistance of 10'Ω or less (the distance between the electrodes is 5'Ω or less).
cm5 electrode width is 5 cn+),
In addition, in order to impart self-temperature control to it, it is necessary to have a characteristic that the resistance value increases significantly as the temperature increases, that is, "pos it it t ve".
Temperature Coefficient
(Hereinafter, this will be abbreviated as rPTCJ) A high value of "", preferably 100° for a resistance value of 30°C
It is desirable that the resistance value of C be three times or more, and that the change in resistance value during that time increases linearly with temperature changes.

According to the research conducted by the present inventors, P in conductive thermoplastic resin containing carbon black as a conductive agent
The expression of TC is closely related to the coefficient of linear expansion of the thermoplastic resin used, and in order to obtain a conductive resin with sufficient self-temperature control, that is, a high PTC value, the linear expansion of the thermoplastic resin must be Rate 3. It was found that it is sufficient to increase the oxygen concentration to 10-4K-1 or more.

The coefficient of linear expansion used in the present invention is 3.0×10−
Examples of thermoplastic resins of 4K-1 or higher include urethane resins, ethylene-vinyl acetate copolymer resins, and the like.

A typical example of the urethane resin is a urethane resin obtained by reacting an alicyclic diisocyanate, a polyether glycol and/or a polyester glycol having a side chain, and a diamine as a chain extender. It will be done.

Examples of the alicyclic diisocyanate used in this case include isophorone diisocyanate, 1,4-cyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexyl diisocyanate, and isophorone diisocyanate is particularly preferred.

In addition, examples of the polyether glycol include polyethylene glycol, polypropylene glycol,
Examples include polytetramethylene ether glycol.

Examples of polyester glycols having side chains include dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, maleic acid, glucuric acid, and phthalic acid, and 1,2-propylene glycol and 1,2-butanediol. , 1,3-butanediol, 3-methyl-1,
5-pencundiol, neopentyl glycol, 3.
Examples include those obtained by polycondensation with glycols having an alkyl side chain, such as 3-dimethylolpenkune and 3,3-dimethylolhebutane. More specific examples include polypropylene adipate and polyneopentylene adipate. Furthermore, polylactone diols obtained by ring-opening polymerization of lactones having alkyl side chains such as β-methyl-δ-valerolactone and β-ethyl-δ-valerolactone can also be used.

Further, examples of the diamine as the chain extender include ethylene diamine, propylene diamine, hexamethylene diamine, isophorone diamine, hydrazine, piperazine, dicyclohexylmethane-4,4'-diamine, and the like.

To produce the urethane resin used in the present invention by reacting such alicyclic diisocyanate, polyether glycol and/or polyester glycol having a side chain, and diamine as a chain extender, a conventional method can be used. be able to.

For example, the above diisocyanate and polyol,
It may be produced using a two-step method in which a prepolymer is produced by reacting so that isocyanate groups are in excess, and then reacted with an amine as a chain extender, or it may be produced by reacting a diisocyanate, a polyol, and a chain extender all at once. It may also be manufactured using a one-step process.

In the production of the urethane resin, commonly used urethane reaction catalysts can be used, and examples of the urethane catalyst include commonly used tin-based, iron-based, tertiary amine-based catalysts, etc. Either can be used. Examples of the tin-based catalyst include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, and stannath octoate.

Examples of the iron-based catalyst include iron acetylacetonate and ferric chloride. Examples of the tertiary amine catalyst include triethylamine and triethylenediamine. Further, a reaction solvent may or may not be used, but it is desirable to use a solvent in order to obtain a more uniform resin solution.

Any reaction solvent may be used as long as it can dissolve each of the components to be reacted. Specific examples of the solvent include ketones such as 2-butanone, 4-methyl-2-pentanone, and cyclohexanone, ethyl acetate, toluene, and isopropanol.

The urethane resin used in the present invention usually has a molecular weight of 5,000 to 100,000, preferably 10,000.
~70,000 are used. If the molecular weight is too small, the heat resistance will be insufficient, and if the molecular weight is too small, the ethylene-vinyl acetate copolymer resin used in the present invention should have a coefficient of linear expansion that satisfies the above conditions. In addition, it is preferable to use a material that is rich in flexibility and elasticity and is resistant to softening at the practical temperature of a surface heating element, specifically, a material with a softening point of 100° C. or higher by the ring and ball method. The ethylene-vinyl acetate copolymer resin that satisfies these conditions is
For example, Evaflex 360, Evaflex 460, Evaflex 560
(All of the above are commercially available under the trade names of Mitsui Polychemical Co., Ltd.), so the present invention can be carried out using such commercially available resins.

If the coefficient of linear expansion of this type of thermoplastic resin used for manufacturing a sheet heating element is 3.0×10-', which is less than 1, the self-temperature controllability of the sheet heating element obtained is insufficient. Therefore, in the present invention, 3, OX 10-4
A thermoplastic resin having a coefficient of linear expansion of K-1 or higher is selected and used.

Further, carbon black is blended in order to impart conductivity to the resin composition, and in the present invention, the oil absorption amount of dibutyl phthalate is 100! d/100g or more and the specific surface area is 800m2/g or less, preferably 4
Select and use one with a value of 00rrf/g or less. , the dibutyl phthalate oil absorption of the carbon black used is 100+
If it is less than 1/100g, the dispersibility of carbon black becomes poor and a conductive network cannot be formed, making it impossible to obtain sufficient conductivity, and it does not generate heat even when energized, making it useless as a sheet heating element. - Furthermore, if the specific surface area of carbon black exceeds 800 m2/g, the PTC of the conductive thermoplastic resin composition becomes small, resulting in insufficient self-temperature control.

The carbon black that satisfies these conditions in the present invention is
For example, 63050B, #315 manufactured by Mitsubishi Kasei Corporation
0B and #3250B, #4500 and #5500 manufactured by Tokai Carbon Co., Ltd., and Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., etc., and the present invention can be carried out using such commercial products. can.

The surface heating element of the present invention contains 15 to 200 parts by weight of the above-mentioned carbon black, based on 100 parts by weight of the above-mentioned thermoplastic resin.
Preferably, a conductive resin composition containing 20 to 100 parts by weight is thermocompressed onto a fabric support.

The blending ratio of carbon black is determined depending on the desired conductivity, but if the blending ratio is too low, sufficient conductivity cannot be obtained, and if the blending ratio is too high, the viscosity of the resin composition becomes too high, making it difficult to coat the fabric support. Since effective pressure bonding cannot be achieved, the blending ratio is selected within the above-mentioned range.

In addition, as the cloth-like support, all those normally used in surface heating elements can be used.
In particular, cloth-like materials using cotton, Kevlar, polyimide fibers, etc. are preferred.

In the present invention, the thermoplastic resin and carbon black are blended by heating to a temperature of 130 to 250°C to melt the resin, using a mixing roll, a Banbury mixer, etc.
It is preferable to knead with carbon black using a shaft or twin-screw extrude brush co-kneader. At that time, in order to facilitate kneading and dispersion of carbon black, 8 agents such as 2-phytanone, 4-methyl-2-pentanone, cyclohexanone, and toluene may be used as viscosity modifiers (2). , carbon black can be blended at room temperature.

The thermoplastic resin composition mixed with a predetermined amount of carbon black and kneaded is then pressure-bonded to a cloth-like support.
082 using a roll or press at a temperature of 80°C.
It is desirable to form a sheet with a thickness of ~10° Omm, preferably 0.5 to 5 mm, and to thermally press the sheet onto one or both sides, preferably both sides, of a cloth-like support.

For the thermocompression bonding, spreading thermocompression bonding using a heating roll, thermocompression bonding using a hot press, etc. can be appropriately employed, but the method is not limited to these.

A thermoplastic resin composition containing carbon black can be prepared using a solvent as described above, but a sheet obtained from a thermoplastic resin composition prepared using a solvent cannot be prepared before thermocompression bonding. It is necessary to heat-press the sheet as a solvent-free sheet that completely removes the solvent. In addition, if the thickness of the sheet to be thermocompressed is too thick, the flexibility of the obtained surface heating element will be lost, so as mentioned above, the thickness of the sheet should be 0.2 to 10.0 m.
m, preferably 0.5 to 5 mm thick.

The heating temperature of the resin during thermocompression bonding varies depending on the type of resin, for example, in the case of urethane resin, it is 100 to 130.
°C, 12 in the case of ethylene-vinyl acetate copolymer resin
It is 0-150°C. The pressure during thermocompression bonding is such that the molten resin completely fills in the irregularities on the surface of the fabric support to obtain full-surface adhesion, that is, usually 0.1 to 2.0 kg/
crA, preferably 0.5-1.0 kg/ci
pressure is used. If the pressure is too high, the resin composition layer of the planar heating element becomes too thin, causing problems such as the cloth support being exposed on the surface and the resistance value becoming too high.

The surface heating element obtained as described above is preferably finished into a product by laminating both surfaces with an insulating polymer film for the purpose of preventing electrical leakage to the outside and water penetration. Examples of the laminate film include films of polyvinyl chloride, crosslinked polyethylene, polyimide, and the like.

(Examples, etc.) Below, Examples and Comparative Examples will be given and further detailed.
The invention is not limited to this example.

Examples 1 to 6 Comparative Examples 1 to 4 As shown in Table 1, various thermoplastic resins, various cars, 1
Various planar heating elements were manufactured in the following manner using resin compositions containing various proportions of run black.

That is, the ethylene-vinyl acetate copolymer resin is 120
Knead with carbon black using a 4-inch open roll heated to °C, and when thoroughly kneaded, set the slit width of the open roll to 1. Omm, and after passing through 10 times, 1. It was taken out as a sheet with a thickness of Q mm.

The polypropylene resin was kneaded in a B-type Banbury mixer heated to 180°C, transferred to a 6-inch open roll heated to 180°C, and taken out as a 1.0 tmh thick sheet.

Polycarbonate resin is PCM heated to 250°C.
-Kneaded using a 30 type twin screw extruder, 1. It was extruded as a sheet with a thickness of 0 mm.

The polyurethane resin is a resin composition containing 30% by weight of a mixed solvent of methyl ethyl ketone and impropatul, and is sufficiently kneaded with carbon black on an open roll at room temperature, with a slit width of 1.0 mm on the open roll. After 10 longitudinal passes, a 1.0 mm thick sheet was taken out and treated in a vacuum dryer at 100° C. for 24 hours to completely remove the remaining solvent.

Each of the carbon black-containing resin sheets obtained in the above manner was sandwiched between both sides of a cotton cloth support with a conductor woven into it as an electrode at both ends in a sandwich-like manner, and at the melting temperature of each resin, a weight of 0.8 kg/ It was press-molded under a load of cnt to form a planar heating element. The dimensions of the obtained surface heating elements were such that the distance between both electrodes was 5 cm, and the electrode width was 5 cm.

The physical properties of the heating elements obtained on each side were as shown in Table 1.

To measure the resistance value in this case, use a digital resistance meter TR-6856 manufactured by Takeda Riken Co., Ltd., and because the resistance value will not be stable until after the second temperature rise and fall, the third temperature rise value is used. did. Further, the PTC characteristic value at each temperature was expressed as a value obtained by dividing the resistance value at each temperature by the resistance value at 30°C.

In addition, the coefficient of linear expansion of thermoplastic resin can be measured using a thermomechanical analyzer T.
It was measured using MAIO (manufactured by Seiko Electronics Co., Ltd.) by the following method. In other words, a resin film with a thickness of about 311 ILB from which the solvent has been completely removed is cut into a resin film with a diameter of about 8 m.
Cut the sample into 100m long pieces, and heat the sample at 100°C before measurement.
After pretreatment for 30 minutes, measurements were performed using the following measurement conditions, and the average value of the measured values from 30°C to 60°C was calculated, which was taken as the linear expansion coefficient of the resin.

Measurement mode: Expansion/compression load: None Heating rate: 10°C/min Measuring temperature range: 30°C to 60°C Notes to Table 1 in the margin below: *l...Product name of Mitsui Polychemical Co., Ltd. Evaflex 560 *2...Mitsubishi Kasei Corporation 702*3...Mitsubishi Kasei Corporation 302*4...Mitsubishi Kasei Corporation 6002*5...Mitsubishi Kasei Corporation 4100Y*6
... Mitsubishi Kasei Corporation Product name Tubarex 70308 *7 ... All manufactured by Mitsubishi Kasei Corporation *8 ... Dibutyl tucrate oil absorption 1 According to the results in Table 1, the results obtained in each example It is obvious that the sheet heating element has excellent self-temperature controllability, as its PTC characteristic value increases as the temperature increases.

(C) Effects of the Invention The planar heating element of the present invention has excellent heat resistance, can be manufactured at low cost, has excellent self-temperature controllability, is highly safe, and can generate heat with a soft warmth.

Claims (1)

[Claims] (1) Dibutyl phthalate oil absorption is 100ml/100g or more and specific surface area is 800m^2/ for 100 parts by weight of thermoplastic resin with linear expansion coefficient of 3.0 x 10^-^4K^-^1 or more. Carbon black less than 15-20 g
1. A planar heating element characterized in that it is formed by thermocompression-bonding a conductive resin composition containing 0 parts by weight onto a cloth-like support.