JPH07142208A - Temperature-sensitive polymer material and temperature sensor - Google Patents

Abstract

PURPOSE:To provide a temperature-sensitive polymer material used for flexible temperature sensors or temperature-sensitive heaters for electric heating appa ratuses, etc., having an excellent heat-sensitive characteristic and thermal stabil ity and a temperature-sensitive element using the heat-sensitive body. CONSTITUTION:A temperature-sensitive polymer material is composed of a polyamide composition, which comprises 100 pts.wt. of polyamide and 0.1-20 pts.wt. of cadmium iodide, and has a temperature detecting property and thermal conduction stability. In addition, a heat-sensitive element using this heat-sensitive polymer material is constituted by interposing the heat-sensitive polymer material 4 between paired electrode wires 1 and 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymeric temperature sensor used for a flexible temperature sensor such as an electric heating tool and a temperature sensitive heater, and a temperature sensitive element using the same.

[0002]

2. Description of the Related Art Conventionally, a polymer temperature sensor is generally arranged between a pair of winding electrodes and used as a flexible linear temperature sensor or a heat sensitive heater. Examples of the polymer temperature sensitive material include nylon 12 and modified polyamide 11 (ATO-CHI) disclosed in JP-A-55-100693.
A polyamide composition such as a product manufactured by MIE Co., Ltd. under the trade name of “Rilsan N nylon”) is used, and its temperature change such as capacitance, resistance value or impedance is used to fulfill the function of a temperature sensor. Furthermore, Japanese Examined Japanese Patent Sho 60-4808
No. 1 discloses a polyamide composition to which a phosphite ester is added as a thermal deterioration improving agent, and JP-A No. 64-30203 discloses an ion conductive heat-sensitive composition containing a copper deactivator and a phenolic antioxidant. Examples of are disclosed.

[0003]

Nylon 12 is excellent in that it has a low moisture absorption rate, but it is difficult to put it into practical use as a temperature sensor, because its temperature-sensitive characteristics vary greatly depending on humidity. Further, in the modified polyamide 11 described in JP-A-55-100693, the temperature dependence of impedance is small, so that the temperature detection sensitivity is low and the heat stability is poor. Therefore, in order to improve the humidity resistance and the temperature sensitivity, Japanese Patent Publication No. 3-50401
As disclosed in the publication, a composition containing an aldehyde polycondensate of a phenolic compound is proposed.
However, these all have problems that the temperature dependence of impedance is low and the thermal stability for a long period of time is insufficient.

When used as a temperature sensor for an electric warming tool, a half-wave electric field may be applied to the temperature sensitive body at a high temperature (100 to 120 ° C.) due to restrictions on its control circuit. When a half-wave electric field is applied to the above-mentioned temperature sensitive composition, it is an ion conductive material, so that it causes severe polarization and causes a large change in impedance over time, which is a problem in practical use.

The present invention solves the above-mentioned problems of the prior art, has a large temperature dependence of impedance, is excellent in thermal stability, and has a high temperature detection function which is stable even for half-wave energization for a long period of time. An object is to provide a molecular temperature sensor and a temperature sensor using this polymer temperature sensor.

[0006]

In order to achieve the above object, the polymer thermosensitizer of the present invention comprises a polyamide composition in which 100 parts by weight of polyamide is mixed with 0.1 to 20 parts by weight of cadmium iodide. Further, the temperature-sensitive element of the present invention is configured by disposing the polymer temperature-sensitive body between a pair of electrodes.

[0007]

In general, the polymer temperature sensor is disposed between a pair of copper or copper alloy winding electrodes and is used as a flexible linear temperature sensor or a heat sensitive heater. The heat resistance stability of these temperature sensors and heat sensitive heaters is determined by the stability of the polymer temperature sensor itself and the surface condition of the winding electrode. When the polyamide composition of the present invention is used, the temperature dependence of the impedance is remarkably enhanced by the ion carrier property of cadmium iodide in the polymer thermosensitizer, and a cadmium complex is formed in the amide group, and half-wave current is applied. Increase stability against.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polymer temperature sensor and a temperature sensor using the same according to an embodiment of the present invention will be described below with reference to the drawings. In this embodiment, as the polyamide, nylon 12 having a low hygroscopic property, nylon 12-nylon 40 copolymer, N-alkyl-substituted polyamide 11, polyether amide, or dimer acid-containing polyamide is selected, and these are used alone or at a certain level. Used in combination in proportion. Cadmium iodide (cadmium iodide anhydrate) having high thermal stability was used as a conductivity-imparting agent (sensitizer) for increasing the temperature dependence of impedance of these polymers.

The samples were blended with each other, kneaded by an extruder, and then, as shown in FIG.
It was formed by forming a sheet having a size of 70 mm and a thickness of 1 mm, and providing silver-coated surface electrodes on both surfaces thereof. The temperature dependence of the impedance of the prepared sheet piece was represented by the thermistor B constant at 40 ° C to 80 ° C. The heat resistance stability was expressed by the temperature difference (ΔT _z ) between the initial impedance of this sheet piece at 100 ° C. and the impedance after 100 V half-wave energization at 100 ° C. for 1,000 hours. The thermistor B constant at 40 ° C to 80 ° C is 40.
It was calculated based on the results of measuring the impedance Z ₄₀ at 80 ° C and the impedance Z ₈₀ at 80 ° C.

Table 1 shows the contents and results of Examples 1 to 5 and Comparative Examples 1 and 2 showing the compositions and characteristics of the above-mentioned polymer thermosensitive materials.

[0011]

[Table 1]

Cadmium iodide is used as the sensitizer in this embodiment and contributes to the improvement of the thermistor B constant. The optimum content of cadmium iodide was 0.1 to 20 parts by weight based on 100 parts by weight of polyamide.
If it is less than 0.1 part by weight, the thermistor B constant is not improved, and if it is blended in more than 20 parts by weight, the mechanical properties of the polyamide are deteriorated, which is not preferable.

It is considered that, by blending cadmium iodide, a cadmium complex is formed in the amide group of the polyamide, the migration of cadmium ions is appropriately suppressed in response to half-wave current, and extreme polarization is unlikely to occur.

Nylon 12 (10
0 parts by weight) and a pellet of a polyamide composition containing cadmium iodide (1.0 parts by weight) were prepared, and the pellet was used to prepare a temperature sensitive element, that is, a temperature detection line as shown in FIG. The structure of this temperature sensitive element is as follows: 1,500 denier polyester core yarn 2 wound with 0.5% silver-containing copper electrode wire 1 and polyamide temperature sensitive layer 4 wound with 0.5% silver-containing copper electrode wire 3. And the periphery thereof is further covered with a polyester separation layer 5 and a heat resistant vinyl chloride jacket 6. That is, the temperature sensor is constructed by disposing the polymer temperature sensor between the pair of electrodes. The thermistor B constant of this temperature sensitive element is approximately the same as the thermistor B constant of 3,500 (K) of the prototype of Comparative Example 1 shown in Table 1 in which the polyamide temperature sensitive layer 4 is formed of only nylon 12 for comparison. It doubled to 7,500 (K), and showed durability of 2,000 hours or more against continuous 100 V half-wave energization at 120 ° C. performed as a heat resistance life test.

[0015]

As is apparent from the above description, according to the polymer temperature sensor of the present invention and the temperature sensor using the same,
By blending cadmium iodide with polyamide,
Even when the thermistor B constant is improved and the temperature is high, it contributes to the long-term stability of the electrical characteristics, and the reliability of many practical applications can be improved.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a temperature-sensitive element using a polymer temperature sensor according to an embodiment of the present invention.

[Explanation of symbols]

 1,3 Electrode wire 2 Polyester core yarn 4 Polyamide temperature sensitive layer (polymer temperature sensitive body) 5 Polyester separation layer 6 Vinyl chloride jacket

Claims (4)

[Claims] 1. A polymer temperature sensor having a polyamide composition in which 100 parts by weight of polyamide is mixed with at least 0.1 to 20 parts by weight of cadmium iodide. 2. The polymer thermosensitive material according to claim 1, wherein the polyamide composition contains an oxybenzoic acid ester / formaldehyde polycondensate. 3. The polyamide comprises the following (a) to (f):
2. At least one selected from the group consisting of:
Alternatively, the polymer temperature sensor according to item 2. (A) Polyundecane amide (b) Polydodecanamide (c) Polyamide containing linear saturated hydrocarbon C ₁₂ or more and copolymer thereof (d) Polyundecane amide or N-alkyl substituted polyamide copolymer of polydodecane amide (E) Polyundecanamide or Polydodecanamide Polyetheramide Copolymer (f) Dimer Acid-Containing Polyamide 4. A temperature-sensitive element comprising a polymer temperature sensor made of a polyamide composition in which 100 parts by weight of polyamide is mixed with at least 0.1 to 20 parts by weight of cadmium iodide between a pair of electrodes.