JPS6251187A - 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] [Industrial Application Field] This invention relates to a self-heating element that 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 temperature-controlled heating element.

[Conventional technology]

It is well known that heating elements made of crystalline polymer as a matrix and kneaded with conductive fillers such as carbon black or graphite to form a desired shape have PTC characteristics at temperatures near the melting point of the matrix. There is. A typical PTCfi+ curve is shown in curve (a) of FIG. In FIG. 2, the vertical axis is the resistance value (0Ω) expressed in ohms, and the horizontal axis is the temperature ('C) expressed in degrees. The resistance value of the heating element increases gradually below the melting point of the IJ lux, 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 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, it will not lose its self-temperature control function, and there is a risk that the heat flow will increase, leading to burnout.

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

In addition, Japanese Patent Application Laid-Open No. 55-6745 discloses (Ma) IJ socks by using a composition of two or more types of crystalline polymers, so that the resistance value has multiple peaks as shown in curve (c) in FIG. Even if the temperature of the heating element exceeds the first peak temperature for some reason, υ safety is ensured by controlling the temperature at the second peak.

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

The PTC characteristic exhibited by a heating element made by kneading conductive fillers 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, and the conductivity dispersed within it. This is due to the fact that the gap between the fillers is expanded and the contact resistance increases rapidly.

[Problem that the invention seeks to solve]

In conventional self-temperature-controlled heating elements such as those mentioned above.

When the melting point is exceeded, the resistance value decreases, but this is due to the fact that the matrix exhibits fluidity.If the matrix resin is three-dimensionally crosslinked by electron beam irradiation, etc. to suppress the fluidity, the resistance value decreases. 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 heating element with excellent characteristics that undergo little change. “ [Means for solving the problem] The self-temperature-controlled heating element of the present invention has a softening temperature of 200
℃ or higher thermoplastic polymer is made into an IJ sock, which contains microcrystalline wax, a conductive filler, and an antioxidant.

[Effect]

Since microcrystalline wax has a sharper melting point than crystalline polymers, the resistance value of the molded heating element increases rapidly near the melting point of microcrystalline wax. Further, since a matrix having a high softening temperature even above the melting point is used, the matrix does not soften in practice and does not exhibit fluidity, and therefore, in practice, no decrease in resistance value occurs. In addition, the addition of an antioxidant suppresses a decrease in the molecular weight of the matrix, resulting in almost no change in properties even after long-term use, resulting in a highly reliable self-temperature-controlled heating element.

〔Example〕

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. Note that 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 an organic material.

Microcrystalline wax has a melting point of 70~
Products with a temperature range of 100°C are commercially available.

For example, Seratsuta 104 (product name 2 manufactured by Nippon Oil Refining Co., Ltd.) has a melting point of 76°C, Hl-Mic4080 (product name 2, manufactured by Nippon Oil Refining Co., Ltd.) has a melting point of 84°C,
Product name: 9 Nippon'N#4) and Hl with a melting point of 96°C
- At least one type of Mic2095 (trade name 2 manufactured by Nippon Seikon Co., Ltd.) 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 selected from the range of 10 to 40% by weight of the thermoplastic polymer containing microcrystalline wax. desirable.

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

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

Example 1 50 parts by weight of polycarbonate having a softening temperature of 220° C. (Mitsubishi Gas Chemical Exhibition, trade name: Nipiron B2000).

100 parts by weight of Seratsuta 104 having a melting point of 76°C, 45 parts by weight of furnace carbon black, and 4 parts by weight of 2-mercaptobenzimidazole were put into a Pan Bali mixer, kneaded, and kneaded using three heated rolls to a thickness of 111°C. Width 1
It was formed into a sheet of 0 clIL and 10 degrees long. Next, electrodes having a width of 1 cIrL were provided at both ends, and both sides were insulated and protected with a polyethylene terephthalate film, thereby producing a self-temperature-controlled heating element according to an embodiment of the present invention.

Example 2 Hl-Mic10 with a melting point of 84°C was used as a substitute for Seratuta 104.
A self-temperature-controlled heating element according to another example of the present invention was manufactured in the same manner as in Example 1 using No. 80.

Example 3 Hi-Mi with a melting point of 96° C. was used as a substitute for the Seratuta 104.
In the same manner as in Example 1, a self-temperature-controlled heating element according to another example of the present invention was manufactured using C.c.2095.

Figure 1 is a resistance-temperature characteristic diagram showing the resistance value change of the self-temperature-controlled heating element obtained in the above example according to the measured temperature after the self-temperature-controlled heating element was placed in an electrical open circuit at each temperature. Yes, the vertical axis is the resistance value (KΩ) expressed in ohms,
The horizontal axis is temperature ('C) expressed in degrees. In the figure,
(d), (8) and (f) show the characteristics of Examples 1, 2 and 3, respectively.

As is clear from Figure 1, the resistance value of the self-temperature-controlled heating element of the present invention increases rapidly near the melting point of the microcrystalline wax, and the temperature coefficient of resistance maintains a positive value even beyond the melting point. did.

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

[Effects of the Invention] As described above, the present invention has a softening temperature of 200°C.
The above thermoplastic polymer is used as a matrix.

By using this material containing microcrystalline wax, conductive filler, and antioxidant, the resistance value increases rapidly in a specific temperature range, and the resistance value does not actually decrease even after that temperature. Therefore, it is possible to obtain a highly reliable self-temperature-controlled heating element that exhibits excellent characteristics with little change even after long-term use. Moreover, it can be applied to a wide range of applications by molding it into an arbitrary 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 heating element. In the figure, (a) shows the characteristics of a general self-temperature-controlled heating element using a crystalline polymer as a matrix. (b) 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;
(d), (e) and (f) are characteristics of embodiments of the invention.

Claims (4)

[Claims] (1) A thermoplastic polymer with a softening temperature of 200°C or higher is used as a matrix, and microcrystalline wax,
Self-temperature-controlled heating element containing conductive filler and antioxidant. (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.