JPS6161244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a flexible polymer comprising a composition containing both semiconductor particles and conductor particles in a polymer matrix, which brings out the thermistor properties of the semiconductor particles. The present invention relates to temperature-sensitive body materials.

Conventionally, inorganic sintered materials have been the mainstream as thermistor materials, but none of these materials have flexibility, and for applications that require excellent flexibility, polymer materials using polymer sensitizers have been used. A warm body is used.

Polymer thermosensitive bodies are broadly classified into the following two types. 1st
This is an attempt to impart conductivity by adding an ionic surfactant or using an ion exchange resin. There are many examples of these in the past, but since they utilize the conductivity of ion carriers, when a DC electric field is applied, the carriers move to the electrodes and decrease, resulting in a decrease in specific resistance. It has the fatal flaw of causing an increase in
Therefore, only an AC circuit can be used as the temperature detection circuit.

The second type is an electron-conducting polymer temperature sensitive body, which has three types of configurations: a, b, and c.

(a) A polymer thermosensitive material in which electronically conductive thermistor powder such as metal oxide or organic semiconductor is blended into a polymer matrix. Generally, these materials do not exhibit conductivity unless 30 to 50 weight percent of thermistor powder is mixed into the matrix, and the combination of such a large amount significantly impairs flexibility and loses the advantage of using polymeric materials. .

(b) A thermosensitive body using a high molecular weight polymer having electronic conductivity, as shown in Japanese Patent Publication No. 10150/1982 and Japanese Patent Application Laid-open No. 61698/1983.

(c) Carbon black or graphite and 7, as seen in JP-A-51-22092;
A polymer thermosensitive material in which a charge transfer type organic semiconductor having 7,8,8-tetracyanoquinodimethane as an electron acceptor is mixed into a polymer matrix to impart electrical conductivity through electron conduction.

In the above, since the configuration of c is similar to the configuration in the present invention, this will be described in more detail. As seen in Japanese Patent Application Laid-Open No. 51-22092, the temperature sensitive body accepts electrons with carbon black or graphite of 20% by weight or less and 7,7,8,8-tetracyanoquinodimethane of 1 to 15% by weight. The thermistor B constant has been shown to change depending on the blending ratio of the organic semiconductor material. This means that the thermistor properties of the organic semiconductor material are not sufficiently obtained, and the disadvantage that the thermistor B constant varies depending on the manufacturing conditions when manufacturing the temperature sensor cannot be avoided, which is a practical difficulty. remains.

The present invention provides a novel polymer thermosensitive material that overcomes the drawbacks of these materials, and its features will be described below.

It is widely practiced to disperse conductor particles in a polymer matrix and use it as a conductive material. Since the thermal expansion coefficient of these materials is generally smaller than that of a polymer matrix, contact between particles is prevented by increasing the temperature, resulting in a positive temperature coefficient, and they are generally used as self-temperature control heaters. However, if semiconductor particles are further mixed into the particles, they will penetrate between the conductor particles and, microscopically, form a series circuit between the conductor particles and the semiconductor particles. Here, semiconductor particles are a general term for organic semiconductors and inorganic oxide semiconductors having a negative temperature coefficient of resistance, and conductor particles are a general term for carbon black, graphite, metal powder, and the like. Semiconductor particles generally have a resistivity value several orders of magnitude larger than that of conductor particles, so in such a composition, the conductor particles simply function as electrodes inside the material, and the resistance-temperature characteristics of the polymer composition are Defined solely by the semiconductor particles, the material will exhibit thermistor properties.

The temperature sensitive body of the present invention has the above configuration, and the volume ratio of the conductor particles to the semiconductor particles is 0.25 to 4.0.
It has been found that a temperature sensitive body with excellent characteristics can be obtained in the case of the above method, leading to the present invention. Under such a configuration, the thermistor B constant of the temperature sensitive body matches that of the semiconductor particles. This is one of the major features of the present invention, and allows the total mixing ratio of conductor particles and semiconductor particles to be changed while keeping the volume ratio of conductor particles and semiconductor particles mixed in the matrix within the above range. Therefore, it is meant to provide a temperature sensing element whose specific resistance value can be arbitrarily changed while keeping the thermistor B constant constant. Moreover, a temperature sensitive body having a composition in this range exhibits extremely stable electrical characteristics.

Here, I would like to add some additional information about the properties of conductor particles and semiconductor particles. That is, the variety in the type, particle size, and particle shape of both particles has a great influence on the electrical properties of the polymer thermosensitive material. For example, if carbon fibers are used as the conductor particles or those having an acicular structure are used as the semiconductor particles, it is possible to reduce the total blending amount of both particles. This is advantageous in providing flexibility and good processability to the temperature sensitive material. However, this does not cause a large change in the blending ratio of both particles, and a temperature sensitive body having the most desirable electrical characteristics is obtained when the volume ratio of both particles is in the range of 0.25 to 4.0.

Generally, in inorganic sintered body thermistors, when the resistance value is changed, the thermistor B constant also changes, but the one of the present invention shows a big difference from this.
In other words, even if the resistance value changes, thermistor B
The fact that the constant does not change gives the present thermosensitive material great utility, and makes it easy to connect it to electronic control circuits, making it a major industrial feature.

Here, when the conductor particles are carbon black or graphite, they have a reinforcing effect on the polymer material, which is advantageous in that they impart great flexibility to the thermosensitive material. . Furthermore, when the semiconductor particles are organic semiconductors,
Because of their good affinity for the polymer matrix, they are finely dispersed in the matrix, and by closely intercalating between the conductor particles, they contribute to the realization of a stable structure and stabilize the resistance of the thermosensor. Furthermore, if this is a 7,7,8,8-tetracyanoquinodimethane (hereinafter abbreviated as TCNQ) salt that uses a metal or a compound containing a nitrogen atom as an electron donor, the material itself has excellent stability. , shows even better results in terms of heat resistance. For example, alkali metals, alkaline earth metals,
Examples include copper, zinc and iron, metal complex ions, onium ions, and quaternary ammonium ions. In particular, when sodium, potassium, or copper is used as an electron donor, an ionic radical salt is obtained that is so stable that it does not decompose for a long time even when heated to about 200°C, and when these are used, particularly excellent results can be obtained. bring. That is, the above carbon black or graphite is selected as the conductor particle, TCNQ salt with sodium, potassium or copper as an electron donor is selected as the semiconductor particle, and polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, etc. are selected as the polymer matrix. If you use a thermoplastic polymer composition of
An excellent thermistor material can be obtained simply by mixing these and kneading them at the melting temperature of the matrix composition.

The details of the present invention will be further explained below with reference to Examples.

Example 1 For 700 g of polypropylene, the specific resistance at room temperature is 3 × 10 ⁶ Ω・cm and 0.003 Ω・cm, respectively.
potassium TCNQ and potassium graphite
A total of 300 g of TCNQ and graphite were added at different blending ratios, thoroughly mixed, and then kneaded for 20 minutes using a heated roll at 190°C. The obtained sample was 190
Press molded at ℃, 50Kg weight/ ^cm2 , 10cm x 10
Create a test piece of cm x 1 mm and have a diameter of 5 mm on both sides.
Colloidal carbon was coated in a circular shape of cm to form a sheet for electrical specific measurements.

Measure the DC resistance and impedance at 60Hz by varying the temperature, calculate the volume specific resistance and volume specific impedance at each temperature, and calculate the volume specific resistance and volume specific impedance at 30℃.
I read the thermistor B constant between and 60℃ from the graph.

The volume specific resistance and volume specific impedance at 60℃ are ρ and Z _SP , and potassium
Potassium relative to the total amount of TCNQ and graphite
The relationship between ρ and Z _SP with respect to P is shown in FIG. 1, where P is the blending ratio (volume percentage) of TCNQ.
Furthermore, the relationship between Bρ and B _Z with respect to P is shown in FIG. Here, Bρ and B _Z respectively indicate the values of the thermistor B constant determined from the temperature change of volume resistivity and volume resistivity.

In Figure 1, an inflection point is seen near P = 60 (%), and P = 20 to 80 (%), that is, the volume ratio of graphite to potassium TCNQ is 0.25 to 4.0.
It is shown that the specific resistance does not change significantly within the range of . Also in Figure 2, B in the range of P = 20 to 80
It can be seen that both B and _Z are constant, and compositions with blending ratios in this range give good results.

Example 2 To 650 g of vinylidene fluoride resin, a total of 350 g of sodium TCNQ and channel black, each having a specific resistance of 10 ⁵ Ω・cm and 0.1 Ω・cm at room temperature, were added as in Example 1, and the same procedure as in Example 1 was carried out. A test piece was created by the operation. A direct current electric field of DC100V/mm was applied to this sample at 120°C for 300°C.
The DC resistance was measured before and after the electric field was applied at 60°C. FIG. 3 shows the relationship between the resistance ratio after and before application of an electric field with respect to P, where P is the mixing ratio (volume percentage) of sodium TCNQ to the total amount of sodium TCNQ and channel black.

From Figure 3, P = 20~80, that is, the volume ratio of channel black and sodium TCNQ is 0.25~4.0.
It can be seen that compositions within this range are stable compositions that exhibit a constant resistance value.

As can be seen from Examples 1 and 2, it was confirmed that thermosensitive compositions in which the blending amount of conductor particles and semiconductor particles was in the range of 0.25 to 4.0 in terms of volume ratio showed good results. The flexibility and processability of the composition were examined. That is, the above composition was finely chopped into pellets and then tubed using a wire making extruder to obtain a linear composition. It was confirmed that the resulting linear composition had sufficient flexibility and bendability.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the amount of potassium TCNQ blended and the volume specific impedance of the thermosensor in a polymer thermosensor containing potassium TCNQ and graphite.
Figure 3 shows the relationship between the amount of TCNQ blended and the thermistor B constant of the thermosensor. FIG. 3 is a diagram showing the relationship with the resistance ratio of a temperature sensitive body.

Claims (1)

[Scope of Claims] 1. A polymeric temperature sensitive body made of a polymeric composition in which conductive particles and semiconductor particles having thermistor characteristics are dispersed in a polymeric matrix, and for detecting changes in electrical resistance or impedance due to temperature. , the volume ratio of the conductor particles and the semiconductor particles is
A polymer thermosensitive body characterized by having a temperature of 0.25 to 4.0. 2. The polymer temperature sensitive body according to claim 1, wherein the conductor is carbon black or graphite. 3. The polymer temperature sensitive body according to claim 1 or 2, wherein the semiconductor is a metal oxide or an organic semiconductor. 4. The polymer thermosensitive material according to claim 3, wherein the organic semiconductor is a 7,7,8,8-tetracyanoquinodimethane salt in which a metal or a compound containing a nitrogen atom is used as an electron donor. 5. The polymer temperature sensitive body according to claim 4, wherein the metal atom is sodium, potassium, or copper.