JPH0658822A - Thermosensor - Google Patents

Abstract

PURPOSE:To obtain a thermosensor and a medium having switching property by making electric conductivity of the medium differ remarkably before and after a phase transition temperature of an electrolyte phase. CONSTITUTION:A medium of a temperature sensor is made up of an electrolyte and a support and as electric conductivity of the electrolyte changes significantly before and after a phase transition, the medium is preferably an electrolytic liquid containing a metal salt or polyether with excellent ion conductivity. The metal salt herein used, for example, is LiClO4, LiAlCl4 or LiBF4 and a solvent herein used, for example, is propylene carbonate, ethylene carbonate. gamma-butyrolacton. The phase transition temperature can be controlled optionally by mixing more than one different substance. A support herein used, for example, is polystyrene, polypropylene or polyisobuten. High polymer fine particles of these substances are 0.01-500mum in the diameter and a surfactant may be used for stabilizing the particles. The medium is so stable to allow the changing of the conductivity thereof significantly with better moldability thereby enabling utilization of the medium as switching element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor which can be used as a temperature control element, has good switching characteristics, is inexpensive and has excellent mechanical strength.

[0002]

2. Description of the Related Art Contact type temperature sensors include a thermistor that uses resistance change due to temperature and a thermocouple that uses the Seebeck effect. However, since a minute change in current value or voltage value is detected, a minute change amount is detected. When it is used as a detection circuit, an amplification circuit, or a control element, a switching circuit for ON-OFF operation is required. Therefore, there has been a demand for a medium whose current value and voltage value change rapidly at an arbitrary temperature. It was known that the temperature dependence of ionic conductivity had non-linearity before and after the phase transition, but there was no case where it was used positively for a sensor or the like. this is,
With respect to solid electrolytes, ionic conductors are mainly studied for increasing ionic conductivity, and therefore efforts have been made to bring the ionic conductivity of solids closer to that of liquids. Also, with respect to liquid electrolytes, research has been mainly conducted on a support / packaging method for preventing the generation of dendrites or eliminating liquid leakage, and the main objective was to widen the temperature range of high ionic conductivity. Also, in liquid electrolytes, there has been little research on the structure in which the ion conduction path and the support are separated.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a temperature sensor having a switching characteristic sufficient to be applied to a temperature control element and the like, and a medium thereof. To do.

[0004]

The present invention will be summarized as follows. A first invention of the present invention relates to a temperature sensor,
A temperature sensor comprising a medium composed of an ionic electrolyte and its support is characterized in that the electrical conductivity of the medium is significantly different before and after the phase transition temperature of the electrolyte phase. A second invention of the present invention is that, in the medium constituting the temperature sensor of the first invention, the electrolyte is water containing a metal salt, a polar solvent, a polyether, or a mixture thereof, and the support is a polymer. It is characterized by being a matrix.

The present inventors have been conducting research on ion-conducting substances, but by impregnating a polymer matrix with an electrolytic solution,
It has been clarified that high ionic conductivity can be obtained. By investigating the temperature characteristics of these electric conductivities, it was found that the electric conductivity greatly changes when the electrolytic solution phase changes from the solid phase to the liquid phase. It can be used for a temperature sensor by utilizing this large change in electrical conductivity.

The medium of this temperature sensor is composed of an electrolyte and a support. Any electrolyte may be used as long as its electric conductivity largely changes before and after the phase transition, and an electrolytic solution containing a metal salt and a polyether having excellent ionic conductivity are preferable. The metal salt used here may be any salt as long as it dissociates into ions, but for example, as a lithium salt,
LiClO ₄ , LiAlCl ₄ , LiBF ₄ , LiPF
₆ : LiAsF ₆ , LiNbF ₆ , LiSCN, LiC
1, Li (CF ₃ SO ₃ ), Li (C ₆ H ₅ SO ₃ ), etc. and mixtures thereof.

In addition, polar solvents such as propylene carbonate, ethylene carbonate, γ-butyrolactone, dimethyl carbonate, dimethylsulfoxide, acetonitrile, sulfolane, dimethylformamide, dimethylacetamide, 1,2-diethoxyethane, 1,2- Aprotic solvents such as ethoxymethoxyethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane and methyl acetate, water, and polyethers such as polyoxymethylene, polyoxyethylene, polyoxypropylene and polyoxyisoprene. There is. An electrolyte can be obtained by using these substances alone or as a mixture and incorporating the above-mentioned metal salt.

Since the phase transition temperature of the electrolyte phase differs depending on the substance, it is possible to induce the phase transition at any temperature by selecting an appropriate substance. In addition, 2 having different phase transition temperatures
By mixing two or more kinds of substances, it is possible to freely control the phase transition temperature of each pure substance. For example, in the combination of ethylene carbonate and propylene carbonate, 3
The phase change temperature can be set between 6 and −49 ° C., and the phase change temperature can be set between −42 and −130 ° C. by the combination of γ-butyrolactone and 1,2-ethoxymethoxyethane.

As the support, a polymer matrix is preferable, and a polymer emulsion which can be molded on a sheet using polymer particles can be used. The component of the polymer fine particles may be a general-purpose and inexpensive one, for example, polystyrene, polypropylene, polyisobutene, polybutadiene, polyisoprene, poly (α-methylstyrene), polybutyl methacrylate, polybutyl acrylate, poly (2-hexyl acrylate). ), Polybutyl phthalate, polyvinyl butyl ether, polyvinyl butyral, polyvinyl formal, polydimethyl siloxane, polydiphenyl siloxane, polymethylphenyl siloxane, and other low polar polymers, polyacrylonitrile,
Poly (vinylidene fluoride), polyoxyethylene, polyoxypropylene, polyvinyl chloride, polymethyl methacrylate, polymethyl acrylate, polymethacrylic acid (and metal salts), polyacrylic acid (and metal salts), polyvinyl alcohol, polychlorination There are polar polymers such as vinylidene, polyethyleneimine, polymethacrylonitrile and polyvinyl acetate, and copolymers thereof. Also,
The fine particles may be used not only alone but also as a mixture. Particles having a diameter of 0.01 μm to 500 μm are preferably used.

A stabilizer may be used for stabilizing the polymer fine particles, and a surfactant is preferably used for this. Examples of the surfactant include fatty acid metal salts, alkylbenzenesulfonic acid metal salts, alkylsulfate metal salts, dioctylsulfosuccinic acid metal salts, polyoxyethylene nonylphenyl ethers, polyoxyethylene stearic acid esters, polyoxyethylene sorbitan monolauric acid esters. , Polyoxyethylene, polyoxyethylene-polyoxypropylene copolymer, polyether modified silicone oil, and the like.

In order to stabilize the polymer fine particles, an ionic dissociative group may be incorporated into the polymer component by a covalent bond.
Examples of the ion dissociative group in this case include a carboxyl group, a hydroxyl group, a sulfone group, an ammonium group, and metal salt substituents thereof.

The medium is prepared by concentrating the polymer emulsion and, when the solid content concentration reaches 50% or more, forming the film on the film with a film applicator and heating or drying under reduced pressure to remove volatile components, There are a method of impregnating an electrolytic solution containing a metal salt and a polyether, a method of obtaining a sheet by drying a polymer emulsion to which a metal salt and a polyether are added, and then impregnating the electrolytic solution.

As another method for producing a medium, an electrolysis solution containing a metal salt or polyether and a cross-linking agent are added to the polar polymer as described above to form a sol, and then ultraviolet rays, radiation or heat is applied. There is also a method of forming a gel.

[0014]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 As a polymer fine particle dispersion containing a surfactant and a self-crosslinking component, 10 g of styrene-butadiene latex (trade name Nipol LX 432A made by Nippon Zeon) was taken and heated at 95 ° C. to obtain a solid content. After drying to 70% by weight, it was stretched into a sheet with a film applicator having a coating thickness of 100 μm. This was dried at 100 ° C. for 1 hour. 1 more
A polymer matrix film was obtained by drying at 10 ° C. and 0.1 Torr for 20 hours. 1 lithium perchlorate
The polymer matrix film was immersed in mol / l dissolved ethylene carbonate at 60 ° C. for 24 hours to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 2 Ethylene carbonate / propylene carbonate mixed solvent in which 1 mol / l of lithium perchlorate was dissolved (volume ratio 80 /
A polymer matrix prepared in the same manner as in Example 1 was immersed in 20) to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 3 Ethylene carbonate / propylene carbonate mixed solvent in which 1 mol / l of lithium perchlorate was dissolved (volume ratio 60 /
40) was immersed in a polymer matrix prepared in the same manner as in Example 1 to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 4 Ethylene carbonate / propylene carbonate mixed solvent in which 1 mol / l of lithium perchlorate was dissolved (volume ratio 40 /
A polymer matrix prepared in the same manner as in Example 1 was immersed in 60) to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 5 Ethylene carbonate / propylene carbonate mixed solvent in which 1 mol / l of lithium perchlorate was dissolved (volume ratio 20 /
The polymer matrix prepared in the same manner as in Example 1 was immersed in 80) to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 6 A polymer matrix prepared in the same manner as in Example 1 was immersed in propylene carbonate in which 1 mol / l of lithium perchlorate was dissolved to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 7 A polymer matrix prepared in the same manner as in Example 1 was immersed in 1,2-ethoxymethoxyethane in which 1 mol / l of lithium perchlorate was dissolved to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 8 A polymer matrix prepared in the same manner as in Example 1 was immersed in a 1,2-ethoxymethoxyethane / propylene carbonate mixed solvent (volume ratio 50/50) in which 1 mol / l of lithium perchlorate was dissolved. The medium was obtained. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 9 As a polymer fine particle dispersion containing a surfactant and a self-crosslinking component, 10 g of styrene-butadiene latex (trade name Nipol LX 432A, manufactured by Nippon Zeon Co., Ltd.) was taken, and the molecular weight was 6
000 polyoxyethylene (1 g) and lithium perchlorate (0.11 g) were added, followed by heating at 95 ° C. and drying until the solid content became 70% by weight, and then drawing into a sheet with a film applicator having a coating thickness of 100 μm. extended. This is 10
It was dried at 0 ° C. for 1 hour. 2 at 110 ° C and 0.1 Torr
The medium was obtained by drying for 0 hours. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

Example 10 Ethylene carbonate / polyoxyethylene mixture in which 1 mol / l lithium perchlorate was dissolved (weight ratio 50/50)
A polymer matrix prepared in the same manner as in Example 1 was dipped in to obtain a medium. An electrode was attached to this medium, and the temperature dependence of the electrical conductivity was examined. As a result, the electrical conductivity changed significantly before and after the phase transition.

The temperature dependence of the electric conductivity of Examples 1 to 10 is shown by the temperature (° C, horizontal axis) and the electric conductivity (S / cm, vertical axis).
It is shown in FIG. As is clear from FIG. 1, the electrical conductivity changes significantly before and after the phase transition.

[0026]

As is apparent from the above description, according to the present invention, the electric conductivity of the medium can be largely changed before and after the phase transition of the electrolyte and can be provided to the medium of the temperature sensor. This medium has good moldability, mechanical strength, and can be manufactured at low cost, so that it can be suitably used as a temperature sensor. Further, since the conductivity can be largely changed, it can be used as a switching element.

[Brief description of drawings]

FIG. 1 is a diagram showing temperature dependence of electric conductivity of ten examples of the present invention.

Claims (2)

[Claims] 1. A temperature sensor comprising a medium composed of an ionic electrolyte and a support thereof, wherein the electrical conductivity of the medium is significantly different before and after the phase transition temperature of the electrolyte phase. . 2. The temperature sensor according to claim 1, wherein the support comprises a polymer matrix, and the electrolyte comprises water containing a metal salt, a polar solvent, a polyether, or a mixture thereof.