JP3000416B2 - Polymer thermosensitive body and thermosensitive element using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a polymer thermosensor is generally disposed between a pair of winding electrodes and used as a flexible linear temperature sensor or a heat-sensitive heater. Examples of the polymer thermosensitive material include nylon 12 and modified polyamide 11 (ATO-CHI) disclosed in JP-A-55-100693.
A polyamide composition such as “Rilsan N nylon” (trade name, manufactured by MIE) is used, and its temperature change such as capacitance, resistance, or impedance is used to perform the function of a temperature sensor.

Further, Japanese Patent Publication No. Sho 60-48081 discloses a polyamide composition containing a phosphite as a thermal degradation improving agent, and Japanese Patent Application Laid-Open No. Sho 64-30203 discloses a copper deactivator and a phenolic antioxidant. Examples of added ion conductive thermosensitive compositions are disclosed.

[0004]

Nylon 12 is excellent in that it has low hygroscopicity, but it is difficult to use it as a temperature sensor because of its large fluctuation in temperature sensitivity due to humidity. Further, in the modified polyamide 11 described in JP-A-55-100693, since the temperature dependence of impedance is small, the temperature detection sensitivity is low and the heat resistance stability is poor. Therefore, in order to improve humidity resistance and temperature sensitivity, Japanese Patent Publication No. 3-50401 is used.
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-260, a composition containing an aldehyde polycondensate of a phenolic compound has been proposed.

[0005] However, these have problems such as low temperature dependence of impedance and insufficient thermal stability over a long period of time.

Further, when used as a temperature sensor for an electric heater or the like, a half-wave electric field may be applied to the thermosensitive body at a high temperature (100 to 120 ° C.) due to restrictions on its control circuit.

[0007] When a half-wave electric field is applied to the above thermosensitive body composition, since it is an ion-conductive substance, it undergoes severe polarization, causing a large change in impedance with time, and has a problem in practical use. .

The present invention solves the above-mentioned conventional problems, has a large temperature dependency of impedance, has excellent thermal stability, and has a temperature detecting function that is stable even when a half-wave current is applied for a long time. It is an object of the present invention to provide a polymer thermosensor and a thermosensor using the polymer thermosensor.

[0009]

In order to achieve the above object, the polymer thermosensor of the present invention comprises at least 0.1 to 20 parts by weight of cadmium iodide per 100 parts by weight of polyamide, and further comprises hindered phenol or naphthylamine. And a polyamide composition blended with at least one selected from the group consisting of: Further, the thermosensitive element of the present invention is configured by disposing the polymer thermosensitive body between a pair of electrodes.

[0010]

In general, a polymer thermosensor is disposed between a pair of copper or copper alloy winding electrodes and is used as a flexible linear temperature sensor or thermal heater. The heat stability of these temperature sensors and heat-sensitive heaters is determined by the stability of the polymer thermosensor itself and the surface condition of the winding electrode.

When the polyamide composition of the present invention is used,
The cadmium iodide in the polymer thermosensor significantly enhances the temperature dependence of the impedance due to the ion carrier properties of the cadmium iodide, and forms a cadmium complex with an amide group to increase the current-carrying stability.

Further, the antioxidant property of hindered phenol or naphthylamine makes it thermally stable.

As in the present invention, the combination of cadmium chloride and hindered phenol or naphthylamine is not excluded from each other even if the actions overlap, but has a synergistic action when added. Therefore, it is considered that the thermal stability of the polymer thermosensitive body is improved, and the thermal stability as a temperature sensor or a thermosensitive heater is remarkably increased.

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

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a polymer thermosensor and a thermosensor using the same according to an embodiment of the present invention will be described with reference to the drawings. In the present example, as the polyamide, nylon 12, nylon 12-nylon 40 copolymer, N-alkyl-substituted polyamide 11, polyetheramide, or dimer acid-containing polyamide was selected as the polyamide having low hygroscopicity. They were used in combination in proportions. Cadmium iodide having high thermal stability was used as a conductivity-imparting agent (sensitizer) for increasing the temperature dependence of the impedance of these polymers.

As an antioxidant hindered phenol that enhances antioxidant properties and thermal stability, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-
Hydroxyphenyl) propionate (molecular weight 586.
8), pentaerythrityl-tetrakis [3- (3,5
-Di-tert-butyl-4-hydroxyphenyl) propionate (molecular weight 1177.7), N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-)
Hydroxynamamide) (molecular weight 637.0) or 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy]-
1,1-dimethylethyl {-2,4,8,10-tetraoxaspiro [5,5] undecane (molecular weight 741) was selected, and phenyl-α-naphthylamine (molecular weight 404) and the like were selected as naphthylamine.

Further, in the case of adding an aldehyde polycondensate of a phenol compound, an octyl oxybenzoate-formaldehyde polycondensate having good compatibility with polyamide was selected.

A sample is prepared by mixing these components, kneading them with an extruder, and then using a hot press to obtain a sample of about 70 mm × 70 mm and a thickness of 1 mm.
And a silver-coated surface electrode was provided on both sides of the sheet. The temperature dependence of the impedance was represented by the thermistor B constant at 40 ° C. to 80 ° C. The thermal stability is the initial impedance at 100 ° C.
It was expressed as the temperature difference (ΔT _z ) from the impedance after 100 hours of half-wave conduction at 100 ° C. for 1,000 hours. Note that 40
The thermistor B constant at a temperature between 80 ° C. and 80 ° C. was calculated based on the results of measuring the impedance Z _{40 at} 40 ° C. and the impedance Z ₈₀ at 80 ° C.

Table 1 shows the contents and results of Examples 1 to 8 and Comparative Examples 1 and 2 showing the composition and properties of these polymer thermosensors.

[0020]

[Table 1]

Cadmium iodide is used as a sensitizer in this embodiment, which contributes to the improvement of the thermistor B constant. Cadmium iodide is optimally blended in an amount of 0.1 to 20 parts by weight with respect to 100 parts by weight of polyamide.
If the amount is less than 0.1 part by weight, no improvement in the thermistor B constant is observed, and if the amount is more than 20 parts by weight, the mechanical properties of the polyamide deteriorate, which is not preferable. It is considered that by mixing cadmium iodide, a cadmium complex is formed at the amide group in the polyamide, the movement of cadmium ions is appropriately suppressed with respect to half-wave conduction, and extreme polarization is unlikely to occur.

Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] or pentaerythrityl-tetrakis as a hindered phenol used as an antioxidant [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate], or N,
N'-hexamethylenebis (3,5-di-t-butyl-
4-hydroxy-hydroxynamamide), or 3,
9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,
1-dimethylethyl {-2,4,8,10-tetraoxaspiro [5,5] undecane and naphthylamine contribute to the improvement of heat resistance.

The combination of these antioxidants exhibits a further synergistic effect. In addition, aldehyde polycondensates of phenolic compounds include p-oxybenzoic acid octyl ester-aldehyde polycondensate and p-oxybenzoic acid isostearyl ester-formaldehyde polycondensate, which are excellent in compatibility and moisture resistance. However, in addition to the p-oxybenzoic acid alkyl ester, an aldehyde polycondensate such as p-dodecylphenol, p-chlorophenol, and nonyl p-oxybenzoate may be used. These aldehyde polycondensates are blended in an amount of 5 to 30 parts by weight based on 100 parts by weight of the polyamide. If the amount is less than 5 parts by weight, the effect is low. If the amount is more than 30 parts by weight, the properties of the composition are significantly impaired.

For evaluation of the thermosensitive element, nylon 12 (1
00 parts by weight), cadmium iodide (1.0 parts by weight),
N, N'-hexamethylenebis (3,5-t-butyl-
Pellets of a polyamide composition comprising 4-hydroxy-hydroxyn namamide (0.5 parts by weight) were prepared, and the pellets were used to prepare a temperature-sensitive element as shown in FIG. 1, that is, a temperature detection line.

The temperature-sensitive element is composed of a 1,500 denier polyester core yarn 2 wound with a 0.5% silver-containing copper electrode wire 1 and a polyamide sensed wire wound with a 0.5% silver-containing copper electrode wire 3. It is covered with a warm layer 4 and further covered with a polyester separation layer 5 and a vinyl chloride jacket 6. That is, a thermosensitive element is formed by disposing a polymer thermosensitive element between a pair of electrodes.

The thermistor B constant of this thermosensitive element was, for comparison, a thermistor B constant of 3,500 (K) of the prototype of Comparative Example 1 shown in Table 1 in which the polyamide thermosensitive layer 4 was formed only with nylon 12. The value was 9,300 (K), which is about three times as large as that, and the device exhibited a durability of 1,500 hours or more under continuous 100 V half-wave conduction at 120 ° C., which was performed as a heat resistance life test.

[0027]

As is apparent from the above description, according to the polymer thermosensitive body of the present invention and the thermosensitive element using the same,
The combined use of cadmium iodide and further hindered phenol or naphthylamine can improve the thermistor B constant and make the long-term mechanical strength and electrical properties synergistically stable even at high temperatures, making it useful for many practical applications. Reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view of a thermosensitive element using a polymer thermosensitive element according to one embodiment of the present invention.

[Explanation of symbols]

 1,3 electrode wire 2 polyester core yarn 4 polyamide thermosensitive layer (polymer thermosensitive body) 5 polyester separation layer 6 vinyl chloride jacket

Claims (6)

(57) [Claims] 1. A thermosensitive polymer having a polyamide composition comprising 100 parts by weight of polyamide and at least 0.1 to 20 parts by weight of cadmium iodide and at least one selected from hindered phenol and naphthylamine. body. 2. The method according to claim 1, wherein the hindered phenol is triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] or pentaerythrityl-tetrakis [3- (3,5 -Ji-
t-butyl-4-hydroxyphenyl) propionate], or N, N'-hexamethylenebis (3,5-
Di-tert-butyl-4-hydroxy-hydroxynamamide) or 3,9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1, 1-dimethylethyl} -2,4,8,
The polymer thermosensor according to claim 1, which is at least one selected from 10-tetraoxaspiro [5,5] undecane. 3. The polymer thermosensor according to claim 1, wherein the naphthylamine is at least one selected from phenyl-α-naphthylamine and N′N-di-β-naphthyl-p-phenylenediamine. . 4. The polymer thermosensor according to claim 1, wherein the polyamide composition contains a polycondensate of oxybenzoic acid ester and formaldehyde. 5. The polyamide according to any one of the following (a) to (f):
2. The at least one member selected from the group consisting of:
5. The polymer thermosensor according to any one of items 1 to 4. (A) polyundecanamide (b) polydodecanamide (c) straight chain saturated hydrocarbon C ₁₂ polyamide containing more and copolymers thereof (d) polyundecanamide or N- alkyl-substituted polyamide copolymer polydodecanamide (E) Polyetheramide copolymer of polyundecaneamide or polydodecaneamide (f) Polyamide containing dimer acid 6. A thermosensitive polymer having a polyamide composition comprising 100 parts by weight of polyamide and at least 0.1 to 20 parts by weight of cadmium iodide and at least one selected from hindered phenol and naphthylamine. Is disposed between a pair of electrodes.