JPS5832382A - Self-temperature controllable heater - 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] The present invention relates to a self-temperature control heater.

Conventionally, self-temperature control heaters with positive temperature coefficient characteristics (hereinafter referred to as p'rc characteristics) based on polyolefins have been made using base resins such as low-density polyethylene, high-density polyethylene, and ethylene copolymers, as well as graphite and other materials. A system to which a conductivity imparting material such as carbon black is added is used.

However, in the case of low-medium construction method high-density polyethylene base,
The rise in PTO characteristics at high temperatures is large, but the P'RA characteristics at low temperatures are nearly flat, so the operating temperature becomes high, and because the difference between the crystal melting point and the operating temperature is small, the exothermic temperature locally exceeds the melting point. This is a concern. In that case, the resistance value changes as the conductivity imparting material moves in the matrix, and as the resistance value decreases, it tends to generate more heat, and there is a risk that it will eventually catch fire.

On the other hand, high-pressure low-density polyethylene has relatively good low-temperature PTC properties, but its melting point is as low as 100 to 110°C, so the operating temperature cannot be set very high. In this respect, ethylene copolymer has an even lower melting point, so
The operating temperature tends to be low.

Therefore, if it is possible to obtain a product with an operating temperature close to that of low-medium method high-density polyethylene, polyolefin-based PTO
Therefore, the purpose of the present invention is to provide a self-temperature control heater that solves the problems of the prior art described above and has improved PTO characteristics.

That is, the gist of the present invention is that linear low-density polyethylene is used as a pace resin for a self-temperature-controlling heater.

Here, the above-mentioned linear low-density polyethylene refers to the following.

It is a polymer produced by copolymerizing a higher α-olefin monomer with ethylene, and refers to low-density polyethylene polymerized using a medium-low pressure method.

The density is comparable to conventional low density polyethylene, but the molecules are linear like medium to high density polyethylene. Conventional low density polyethylene has many long chain branches, whereas linear low density polyethylene is characterized by having many short chain branches.

In addition to using this polymer alone, an ethylene copolymer or the like may be used in combination to improve other properties.

Further, the conductivity-imparting material includes carbon black, graphite, carbon black grafted with an organic polymer, metal powder, and the like.

Other stabilizers, lubricants, flame retardants, crosslinking aids, antioxidants,
There is no problem even if it contains a dispersant or the like.

These compositions are uniformly kneaded using a Panbury mixer, rolls, kneader, etc., and then pelletized using an extruder.

After this material is extruded and coated onto the electrode, crosslinking treatment is performed using electron beam irradiation, organic peroxide, or the like.

Example 1 Linear low-density polyethylene (density 0.92, threading = '0.
3) 1-00 parts by weight, Vulcan 0.2 parts by weight was kneaded in a panburi mixer until uniform, formed into a sheet with a roll, and then formed into a pellet.

Next, as shown in Fig. 1, two conductors 1 made by twisting 19 tin-plated wires with an outer diameter of 0.20 wm (distance between the conductors 5 m
) The above mixture was extrusion coated on top of the sample to a thickness of 2 layers. Next, thermoplastic elastomer TPR5190 was applied to a thickness of 0.
Extrusion coating 3 was applied to a thickness of 2 m and irradiated with an electron beam of 20 Mraa. The F T , 0 characteristics of the resistor are shown in 7 in Figure 6.
Shown below.

Example 2 Linear low density polyethylene (density 0.92, M = 0.3
) 100 parts by weight, graphite xs-2,5 (Lonza) 40 parts by weight, trimethylolpantrimethacrylate 2 parts by weight, 4,4'-thiobis-(6-tert-butyl-3-methylphenol) 0 A composition containing 0.2 parts by weight of zinc stearate and 0.2 parts by weight of zinc stearate was prepared under the same conditions as in Example 1. The PTC characteristics of the resistor are shown at 8 in FIG.

Example 3 The procedure was the same as in Example 1 except that 90 parts by weight of linear low-density polyethylene and 10 parts by weight of ethylene-propylene rubber were used instead of 100 parts by weight of linear low-density polyethylene.

Comparative Example 1 Instead of 100 parts by weight of the linear low density polyethylene of Example 1, high-pressure low density polyethylene (density 0.92M = 0.00 parts by weight) was used.
3) 100 parts by weight was used. Other ingredients and manufacturing method are the same as in Example 1.

Comparative Example 2 Instead of 100 parts by weight of the linear low density polyethylene of Example 1, medium-low construction method high density polyethylene (density 0.95, M construction =
0.3) 100 parts by weight was used. Other ingredients and manufacturing method are the same as in Example 1.

The results of the above Examples and Comparative Examples are shown in Table 1.

Table 1 Test method (1) Heat generation temperature: Attach a thermocouple on the resistor and read the heat generation temperature when a father current voltage of 100 V is applied between the resistor electrodes.

(2) Volume resistivity: The resistance value was read using a Wheatstone bridge and converted to volume resistivity.

For PTC characteristics, the resistance value was measured in a state where the material was heated to a predetermined temperature in a constant temperature bath.

(6) Charge cycle: 100 AC voltage between the electrodes of the resistor
(2) is charged for 1 hour and then stopped for 10 minutes.

The process was repeated with each cycle taken as one cycle. The exothermic temperature and volume resistivity were measured after 100 cycles and 1000 cycles.

As explained above, by using linear low-density polyethylene, the present invention has PTC characteristics at low temperatures close to those of high-pressure process low-density polyethylene, and at high temperatures close to those of low-medium process high-density polyethylene, so the PTO characteristics are sharp over the entire temperature range. become. This results in sharper switching and significantly increased reliability. This PTO property is related to the specific volume-temperature property of the polymer and is unique to linear low density polyethylene.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an embodiment of the self-temperature control heater of the present invention, and Figure 2 is a cross-sectional view showing the specific volumes of the linear low-density polyethylene of the present invention, conventional high-pressure process low-density polyethylene, and low-pressure process high-density polyethylene. A characteristic diagram showing temperature characteristics, FIG. 3 shows the P of the composition based on linear low density polyethylene of the present invention.
FIG. 2 is a characteristic diagram showing TC characteristics in comparison with conventional polyethylene. 1: Conductor (electrode), 2: Resistor, 6: Insulator, 4: Characteristic curve of linear low-density polyethylene, 5: Characteristic curve of high-pressure method low-density polyethylene, 6: Characteristic curve of medium-low method high-density polyethylene , 7: Characteristic curve of Example 1, 8: Characteristic curve of Example 2, 9: Characteristic curve of Comparative Example 1, 10: Characteristic curve of Comparative Example 2.

Claims (1)

[Claims] 1. A self-temperature-controlling heater characterized in that a mixture of linear low-density polyethylene and a conductivity imparting material is provided on electrodes arranged at predetermined intervals, and is cross-linked after being heated.