JPH07142209A - Temperature-sensitive polymer material and temperature sensor - Google Patents

Abstract

PURPOSE:To obtain a temperature-sensitive polymer material having a stable temperature detecting function even when the material is subjected to half-wave conduction for a long period by using a polyamide composition composed of polyamide containing specific amounts of a cadmium iodide and phosphite compound. CONSTITUTION:A temperature-sensitive polymer material 4 is prepared by using a polyamide composition, which comprises 100 pts.wt. of polyamide, 0.1-20 pts.wt. of cadmium iodide, and phosphite compound containing 3 to 20wt.% phosphorus and having a molecular weight of 200 to 5,000. A temperature- sensitive element using the material is constituted by interposing the temperature-sensitive polymer material 4 between paired electrodes 1 and 3. Therefore, the reliability of the element can be improved, because the thermistor constant can be improved and, even at a high temperature, the mechanical strength and electrical characteristics of the element can be improved in a multiplied state. Moreover, the temperature detecting sensitivity and heat resistance of the element are also improved.

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.

Further, in JP-B-60-48081, a polyamide composition in which a phosphite is added as a heat deterioration improving agent, and in JP-A-64-30203, a copper deactivator and a phenolic antioxidant are used. Examples of added ion conductive heat sensitive compositions are disclosed.

[0004]

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. In addition, when used as a temperature sensor for an electric heating tool or the like, 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 the 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, and has a high temperature dependence of impedance, excellent thermal stability, and a high temperature detection function that is stable even for long-term half-wave energization. An object is to provide a molecular temperature sensor and a temperature sensor using this polymer temperature sensor.

[0007]

In order to achieve the above object, the polymer temperature sensor of the present invention comprises 100 parts by weight of polyamide,
A polyamide composition comprising at least 0.1 to 20 parts by weight of cadmium iodide and a phosphite compound having a phosphorus concentration of 3 to 20% by weight and a molecular weight of 200 to 5,000, Further, the temperature-sensitive element of the present invention is configured by disposing the polymer temperature-sensitive body between a pair of electrodes.

[0008]

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 ion carrier property of cadmium iodide in the polymer thermosensitizer markedly increases the temperature dependence of impedance and makes it thermally stable. Moreover, such as tetraphenyl dipropylene glycol diphosphite, tetraphenyl tetra (tridecyl) pentaerythritol tetraphosphite and hydrogenated bisphenol A / pentaerythritol phosphite polymer, diphosphite or tetraphosphite having a high molecular weight and a high phosphorus concentration or Due to the effects of the antioxidant and reducing rust preventive properties of the phosphite-based polymer, the thermal deterioration is remarkably synergistically suppressed. If the phosphorus concentration is low, this effect is low, and if it is too high, it is not practical. A phosphorus concentration of 3 to 20% by weight is effective, but a phosphorus concentration of 5 to 15% by weight is most preferable.

If the molecular weight is low, it easily volatilizes at high temperature,
The sustainability of the effect is poor. Further, if it exceeds 5,000, dispersion becomes difficult, and therefore, it is preferably 300 to 3,500.
Is practical.

In the present invention, the combination of cadmium iodide and the phosphite compound is not excluded from each other even if the actions overlap, but has a synergistic effect by being added. Therefore, it is considered that the thermal stability of the polymer temperature sensitive body is improved, and the heat resistance stability of the temperature sensor or the heat sensitive heater is significantly increased.

Further, by blending an aldehyde polycondensate of a phenol compound, a strong anti-moisture absorption effect can be imparted. Phenolic compounds have good compatibility with polyamides and coordinate with hydrogen bonding sites instead of water molecules in polyamides to reduce hygroscopicity and reduce fluctuations in temperature-sensitive characteristics due to humidity. Further, the action on the amide group also has the effect of increasing the temperature sensitivity.

[0013]

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.

As the polyamide in this embodiment, nylon 12 having a low hygroscopic property and nylon 12-nylon 4 are used.
0 copolymer, N-alkyl-substituted polyamide 11, polyether amide, or polyamide containing dimer acid was selected and used alone or in combination at a fixed ratio.
As a conductivity-imparting agent (sensitizer) for increasing the temperature dependence of impedance of these polymers, an iodine metal compound such as cadmium iodide having high thermal stability is suitable. Further, as an antioxidant that enhances the antioxidant property and the reduction rust preventive action by synergizing with the above-mentioned cadmium iodide, tetraphenyl dipropylene glycol diphosphite (molecular weight 566, phosphorus concentration 10. 9% by weight), tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite (molecular weight 1,424, phosphorus concentration 8.7% by weight), or hydrogenated bisphenol A.
Pentaerythritol phosphite (molecular weight 2,500
To 3,100 and a phosphorus concentration of 13.8% by weight). The composition ratio of these phosphite compounds was 1 part by weight for all the additives with respect to 100 parts by weight of polyamide. In the example in which the aldehyde polycondensate of the phenol compound was added, an oxybenzoic acid octyl ester-formaldehyde polycondensate having good compatibility with polyamide was selected.

The sample was blended with these, kneaded by an extruder, and then heated by a press to about 70 mm × 70 mm, thickness 1 mm.
Was formed into a sheet and the electrodes coated with silver were provided on both sides of the sheet. The temperature dependence of impedance is represented by the thermistor B constant at 40 ° C to 80 ° C. The heat resistance is 100% at the initial impedance and 100
It was expressed as a temperature difference (ΔT _z ) from the impedance after conducting a half-wave current of 100 V at 1,000 ° C. for 1,000 hours. 40
The thermistor B constant at ℃ to 80 ℃ was calculated based on the results of measuring the impedance Z _{40 at 40} ℃ and the impedance Z ₈₀ at 80 ℃.

Table 1 shows the contents and results of Examples 1 to 6 and Comparative Examples 1 to 4 showing the compositions and characteristics of the above-mentioned polymeric thermosensitive materials.

[0017]

[Table 1]

Cadmium iodide as the sensitizer in this example contributes to the improvement of temperature sensitivity and heat resistance. Cadmium iodide to be blended is 100 parts by weight of polyamide,
0.1 to 20 parts by weight is optimum, and if it is less than 0.1 parts by weight, the thermistor B constant is not improved, and if it is added in excess of 20 parts by weight, mechanical properties of polyamide are deteriorated, which is not preferable. .

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

As the phosphite ester compound as an antioxidant, tetraphenyldipropylene glycol phosphite and tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite, which have a high molecular weight, excellent nonvolatility, and an appropriate phosphorus concentration, can be used. Fight or hydrogenated bisphenol A / pentaerythritol phosphite polymer is used, which contributes to improvement of heat resistance stability and rust prevention action. These combinations have a further synergistic effect.

Further, as the aldehyde polycondensate of the phenolic compound, p-oxybenzoic acid octyl ester-aldehyde polycondensate and p-oxybenzoic acid isostearyl ester-formaldehyde polycondensate are compatible and moisture resistant. However, aldehyde polycondensates such as p-dodecylphenol, p-chlorophenol, and p-oxybenzoic acid nonyl ester may be used in addition to p-oxybenzoic acid alkyl ester. These aldehyde polycondensates are blended in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of polyamide. If it is less than 5 parts by weight, the effect is low, and if it is more than 30 parts by weight, the properties of the composition are significantly impaired.

Nylon 12 (10
0 part by weight), cadmium iodide (1 part by weight), and tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite (1 part by weight) to prepare a pellet of a polyamide composition, which is shown in FIG. Such a temperature sensitive element, that is, a temperature detection line was created.

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 feeling wound with 0.5% silver-containing copper electrode wire 3. It is coated with a warm layer 4, and the periphery thereof is further coated with a polyester separation layer 5 and a 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 shows 8,200 (K), which is 2.3 times higher, and 1,500 against continuous 100 V energization at 120 ° C conducted as a heat resistance life test.
It showed durability over time.

[0024]

As is apparent from the above description, according to the polymer temperature sensor of the present invention and the temperature sensor using the same,
The combined use of cadmium iodide and a phosphite compound having an appropriate molecular weight and phosphorus concentration provides a synergistically stable mechanical strength and electrical properties over a long period of time even at an improved thermistor B constant and at high temperature. As a matter of fact, it can improve the reliability of many practical applications. Further, a polymer temperature sensitive body having high temperature detection sensitivity and good heat resistance can be obtained.

[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 (5)

[Claims] 1. 100 parts by weight of polyamide, at least 0.1 to 20 parts by weight of cadmium iodide, a phosphorus concentration of 3 to 20% by weight and a molecular weight of 200 to 5,0.
A polymeric thermosensitizer having a polyamide composition blended with a phosphite compound of No. 00. 2. The phosphite compound is selected from tetraphenyl dipropylene glycol diphosphite, tetraphenyl tetra (tridecyl) pentaerythritol tetraphosphite, or hydrogenated bisphenol A / pentaerythritol phosphite polymer. The polymer thermosensitizer according to claim 1, which is at least one kind. 3. The polyamide composition comprises an oxybenzoic acid ester / formaldehyde polycondensate.
Alternatively, the polymer temperature sensor according to item 2. 4. The polyamide comprises the following (a) to (f):
2. At least one selected from the group consisting of:
4. The polymeric temperature sensor according to any one of 1 to 3. (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 5. 100 parts by weight of polyamide, at least 0.1 to 20 parts by weight of cadmium iodide, a phosphorus concentration of 3 to 20% by weight and a molecular weight of 200 to 5,0.
A thermosensitive element in which a polymeric thermosensitizer having a polyamide composition containing 00 of a phosphite compound is disposed between a pair of electrodes.