JPS6251186A - Self-temperature controlling type heat generating body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention exhibits a property (hereinafter referred to as PTC property) in which the temperature coefficient of resistance of a heating element rapidly increases in the positive direction when a specific temperature range is reached. This invention relates to a self-temperature-controlled heating element.

[Conventional technology]

It has been well known that heating elements made of crystalline polymer as a matrix and kneaded with conductive filaments such as carbon black or graphite to form a desired shape have PTC characteristics at temperatures near the melting point of the matrix. A conformal PTC characteristic curve is shown in curve (al) in FIG. 2. In FIG. 2, the vertical axis is the resistance value (KΩ) expressed in ohms.

The horizontal axis is temperature ('C) expressed in degrees. The resistance value of the heating element increases gradually below the melting point of the matrix, but increases rapidly as it approaches the melting point of the matrix.

Therefore, by utilizing this property, it is possible to form a self-temperature-controlled token heating element that generates heat within a temperature range that does not exceed the melting point of the matrix.

However, the resistance value of the two heating elements reaches a peak approximately at the melting point and gradually decreases at temperatures above that point. Therefore.

If the temperature of the heating element exceeds this peak temperature for some reason, the self-temperature control function is lost, and there is a risk that the current will increase and cause burnout.

In JP-A-58-71584, by using a crystalline thermoplastic polymer containing a cellulose resin as a matrix, the peak value of the resistance value is increased as shown in the curve (bl) in Figure 2, and Improvements have been made so that this peak temperature cannot be exceeded during use.

Furthermore, in JP-A-55-6745, by using a composition of two or more types of crystalline polymers in the matrix,
As shown in curve (C) in Figure 2, the resistance value has multiple peaks, and even if the temperature of the heating element exceeds the first peak temperature for some reason, safety is ensured by controlling the temperature at the second peak. did.

As mentioned above, a crystalline polymer is used as a matrix.

The PTC characteristic exhibited by a heating element made by kneading conductive filler such as carbon black or graphite and molding it into a desired shape is due to the volume expansion that occurs as the crystalline polymer melts.
This is because the distance between the conductive fillers dispersed therein is expanded and the contact resistance increases rapidly.

[Problem that the invention seeks to solve]

In conventional self-temperature control keepsake heating elements like the one above.

When the melting point is exceeded, the resistance value decreases, but this is due to the fluidity of the matrix.If the matrix resin is three-dimensionally crosslinked by electron beam irradiation to suppress the fluidity, the resistance value does not decrease. However, on the other hand, there was a problem in that the PTC characteristics deteriorated.

This invention was made to solve this problem, and the resistance value increases rapidly in a specific temperature range, and even if the temperature exceeds that temperature, the resistance value does not actually decrease, so that it cannot be used for a long period of time. Another object of the present invention is to obtain a highly reliable self-temperature-controlled keepsake heating element with little change in characteristics.

[Means for solving problems]

The self-temperature-controlled keepsake heating element of this invention has a softening temperature of 200°C.
The above thermoplastic polymer is used as a matrix, and a petroleum resin having a melting point of 50°C to 150°C.

It contains a conductive filler and an antioxidant.

[Effect]

Since petroleum resins with a melting point of 50°C to 150°C have a sharper melting point than crystalline polymers, the resistance value of the molded heating element increases rapidly near the melting point of the petroleum resin, which has a low melting point. Furthermore, since Ma) IJ Lux, which has a high softening temperature even above its melting point, is used, the matrix does not soften in practice and does not exhibit fluidity.

Therefore, practically no decrease in resistance value occurs. Also.

Addition of an antioxidant suppresses a decrease in the molecular weight of the matrix, and almost no change in properties occurs even during long-term use, resulting in a highly reliable self-temperature-controlling keepsake heating element.

As the thermoplastic polymer having a softening temperature of 200°C or higher, at least one of polyester, polycarbonate, polyamide, cellulose fiber resin, fluororesin, etc. is used. In addition.

If the softening temperature is 200° C. or higher, it is considered that it will not soften in practice within the operating temperature range considering the use of organic materials.

As a petroleum resin with a melting point of so'c to 150°C.

Products with a melting point in the temperature range of 70°C to 120°C are commercially available.1 For example, Finton 13-170 with a melting point of 70°C
(Product name 9 manufactured by Nippon Zeon), Hiretsu T-100X (Product name, Mitsui Petrochemical Co., Ltd.) with a melting point of 100°C, and Toho Petrosin #120 (Product name, Toho Petroleum Resin Co., Ltd.) with a melting point of 120°C. At least one of these is used.

There are other imported products, but their melting points are in the same temperature range.

As the conductive filler, for example, at least one of carbon black, graphite, carbon fiber, etc. is used, and the blending amount is 10 to 40% by weight of the thermoplastic polymer containing petroleum resin with a melting point of 50°C to 150°C. It is preferable to choose from the range of .

As the antioxidant, at least one of penzimidazoles, hindered phenols, triazine derivatives, phenol sulfides, etc. is used,
In particular, 2-mercaptobenzimidazole is preferably used. Note that the addition of an antioxidant suppresses lowering of the molecular weight due to oxidation of IJ lux, and therefore also suppresses a decrease in the softening temperature, contributing to improved reliability.

The present invention will be specifically explained below with reference to Examples.

Example 1 50 parts by weight of polycarbonate with a softening temperature of 220°C (manufactured by Mitsubishi Gas Chemical, trade name Niepiron E2000), 100 parts by weight of Kraton B-170 with a melting point of 70°C, 45 parts by weight of furnace carbon black, and 2-mercaptobenzimidazole. 4 parts by weight was put into a Pan Bali mixer and kneaded.

It was formed into a sheet with a thickness of 1 xx, a width of 10 mm, and a length of 1 G+1)7F+ using a heated triple roll. Next, a self-temperature-controlled photothermal body according to an embodiment of the present invention was fabricated by providing electrodes with a width of 1 mm at both ends and insulating and protecting both sides with a polyethylene terephthalate film.

Example 2 A self-temperature-controlled heating device according to another example of the present invention was produced in the same manner as in Example 1, using Hiretsu T-100X having a melting point of 100° C. instead of Kraton B-170.

Example 3 A self-temperature-controlled photothermal body according to another example of the present invention was produced in the same manner as in Example 1, using Toho Petrosine #120 having a melting point of 120° C. instead of Kraton B-170.

FIG. 1 is a resistance-temperature characteristic diagram showing the change in resistance of the self-temperature-controlled photothermal element according to the temperature measured after the self-temperature-controlled photothermal element obtained in the above example was placed in an electric oven at each temperature. , the vertical axis is the resistance value (KΩ) expressed in ohms, and the horizontal axis is the temperature (° C.) expressed in degrees. In the figure, (d)
- (el and (fl indicate the characteristics of Examples 1.2 and 3, respectively).

As is clear from Figure 1, in the self-temperature-controlled photothermal element of the present invention, the resistance value increases rapidly near the melting point of petroleum resin, which has a melting point of 50°C to 150°C, and even when the melting point is exceeded, the resistance value increases rapidly. The coefficient remained positive.

The embodiments of the present invention can be put to practical use by, for example, extrusion molding into a film or injection molding into a specific shape.

〔Effect of the invention〕

As explained above, this invention uses a matrix made of a thermoplastic polymer with a softening temperature of 200°C or higher, which contains a petroleum resin conductive filler with a melting point of 50°C to 150°C and an antioxidant. As a result, the resistance value increases rapidly in a specific temperature range, and the resistance value does not actually decrease even after that temperature is exceeded. Highly reliable self-temperature control with excellent characteristics that do not change much even after long-term use. A shaped photothermal body can be obtained. Furthermore, it can be applied to a wide range of applications by molding it into any desired shape, such as a planar shape.

[Brief explanation of drawings]

FIG. 1 is a resistance temperature characteristic diagram of an embodiment of the present invention. FIG. 2 is a resistance temperature characteristic diagram of a conventional self-temperature-controlled photothermal element. In the figure, (a) shows the characteristics of a general self-temperature-controlled photothermal body using a crystalline polymer as a matrix. tbl is the characteristic of a matrix using a thermoplastic resin composition containing a cellulose resin, (C) is the characteristic of a matrix using a composition of multiple crystalline polymers,
(di, (el and [fl) are characteristics of embodiments of this invention.

Claims (4)

[Claims] (1) A self-temperature-controlling heating element having a thermoplastic polymer matrix having a softening temperature of 200°C or higher and containing a petroleum resin conductive filler and an antioxidant having a melting point of 50°C to 150°C. (2) The self-temperature-controlled heating element according to claim 1, wherein the antioxidant is at least one of 2-mercaptobenzimidazole, a high molecular weight hindered phenol, a triazine derivative, and a dialkylphenol sulfide. (3) The self-temperature-controlled heating element according to claim 1 or 2, wherein the conductive filler is at least one of carbon black, graphite, and carbon fiber. (4) The self-temperature control type according to any one of claims 1 to 3, wherein the thermoplastic polymer is at least one of polyester, polycarbonate, polyamide, cellulose resin, and fluororesin. heating element.