JPH0684953B2 - Humidity sensor-element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a humidity sensor element made of a polymer in which a polymer compound having an electronic conductivity is nonuniformly distributed.

[Prior art and its problems]

The need to detect humidity is not only for making the living environment comfortable, but also has a wide range of applications including humidity detection in various measuring instruments. Therefore, research and development of such a sensor element for detecting humidity is also active. For example, one that detects a weak current flowing according to humidity by applying a voltage to the solid polymer electrolyte, specifically, one in which electrodes are adhered to both sides of a film-like material to which an ion exchange group is bonded, a ceramic solid electrolyte is used. They include those used, those using a solid electrolyte composed of polyethylene oxide and LiClO _4, and those utilizing mechanical changes such as expansion and contraction of substances due to humidity.
However, in consideration of recording or restraint of humidity in the equipment by such a humidity sensor element, it is preferable to detect the change of the humidity as an electric signal, and further apply a voltage to the humidity sensor element. It is highly desirable to be able to freely extract the electric signal without such an operation.

[Means for solving problems]

As a result of earnest research in view of the above problems, the present inventors have found that a polymer having a non-uniformly distributed polymer compound having electron conductivity is extremely effective as a humidity sensor element. Has been provided. That is, the present invention is a humidity sensor element composed of a polymer having an anion exchange group, in which a polymer compound having electron conductivity is non-uniformly distributed.

As the polymer compound having electron conductivity of the present invention, a conventionally known polymer compound having electron conductivity is used.
Specific examples of the polymer compound having electron conductivity include pyrrole and its derivatives, for example, N-alkylpyrroles such as N-methylpyrrole and 2-ethylpyrrole, and thiophene derivatives such as thiophene and 3-alkylthiophene. , Isothianaphthene and its derivatives, indole, azulene, furan, aniline, phenol, benzene, naphthalene, phenylenediamines and other derivatives, and polymers of acetylene monomer compounds. In particular, polymers such as pyrrole, indole, thiophene, aniline, furan, acetylene and their derivatives are preferable, and those whose monomers have good affinity with the polymer used as the substrate of the humidity sensor element in the present invention are preferable. It is appropriately selected and used.

Further, the polymer as the base material of the humidity sensor element of the present invention may be any one having an anion exchange group,
From the aspect of the production method described later, a hydrophilic polymer having an affinity for the monomer compound of the polymer compound having electron conductivity as described above (hereinafter, also simply referred to as a compound having electron conductivity) is preferable. As the polymer having an affinity for such a compound having electron conductivity, a polymer having a cation exchange group in addition to an anion exchange group, a polymer having a hydroxyl group, and the like are particularly preferably used. .

As the polymer (hereinafter, simply referred to as an ion exchanger) as a substrate having an anion exchange group, a conventionally known polymerization system such as a so-called styrene-divinylbenzene copolymer or a condensation polymer Anion-exchange group,
And optionally a cation exchange group together with an anion exchange group. As such an ion exchanger, a conventionally known homogeneous or heterogeneous ion exchanger can be used, and a hydrocarbon-based one, a fluorocarbon-based one, or a perfluorocarbon is used as a substrate of the ion exchanger. It is preferably used regardless of the type of system. Ion exchangers particularly suitable for the present invention are those of the dried ion exchange membrane.
The ion exchange group is not particularly limited as long as it has 0.1 to 15 milliequivalents of ion exchange groups bonded per gram, but an ion exchanger having only the anion exchange group and having the above exchange capacity is preferable. As the ion exchange group, there are conventionally known cation exchange groups such as sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphorous acid group, sulfonic acid ester group, phenolic hydroxyl group, thiol group and tertiary perfluoro group. Examples of the anion exchange group include alcohols and the like, and onium bases such as primary, secondary, and tertiary amines, quaternary ammonium, tertiary sulfonium, quaternary phosphonium, and cobalticinium. It should be noted that such an ion exchanger is not limited to having only one kind of ion exchange group bonded, and is effective when a plurality of kinds of ion exchange groups are bonded. Anion exchangers in which one or more secondary and tertiary amines and onium bases are mixed and bonded are suitable. Further, in addition to the anion exchange group, an ion exchanger having a carboxylic acid group and a sulfonic acid group bonded thereto, particularly an ion exchanger having a sulfonic acid group and a quaternary ammonium salt group bonded at the same time are also preferably used. To be Further, a membrane-shaped ion exchanger in which the distribution of ion-exchange groups differs with respect to the membrane cross section, for example, a membrane in which ion-exchange groups are densely present on one surface of the membrane and sparsely present on the other side, an ion-exchange membrane A membrane in which a thin layer having an electric charge opposite to that of the exchange group of the ion exchange membrane is present in the surface layer of is also effectively used. In addition, a porous ion-exchange membrane, that is, an anion-exchange group or, if desired, a porous membrane-like material in which an anion-exchange group and a cation-exchange group are bonded is extremely dependent on the purpose of use as a humidity sensor element. It is valid. In this case, the porosity and thickness of the membrane are appropriately selected depending on the purpose of use, but in general, a porosity of 95% and a thickness of 0.0001 to 1.0 cm are respectively suitable.

Specific examples of the above-mentioned polymer having a hydroxyl group include polyvinyl alcohol and its derivatives, a copolymer having a vinyl alcohol unit, such as a hydrolyzate of a copolymer of vinyl acetate and ethylene in the main chain. A polymer in which one or more hydroxyl groups are bonded, or a compound in which one or more hydroxyl groups are bonded to the main chain via an alkyl chain or an aromatic ring, for example, a polymer or copolymer of vinylphenols, Cellulose and its derivatives such as cellulose monoacetate and cellulose diacetate are preferably used.
Then, an anion exchange group may be introduced into these polymers by a conventional method.

The shape of the polymer body serving as the substrate is appropriately selected from film-like, sheet-like, film-like (hereinafter also referred to as film-like), fibrous, and intermediate thread depending on the intended use of the humidity sensor element. It Generally, a conventionally known membranous ion exchanger (anion exchange membrane) is simply adopted. Further, a membranous polymer having an asymmetric structure with respect to the membrane cross section, such as a reverse osmosis membrane and an ultrafiltration membrane, which are widely used as a separation membrane, can be preferably used.

In the present invention, as a mode in which the polymer compound having electron conductivity is non-uniformly distributed in the polymer of the substrate, the polymer compound having electron conductivity with respect to the cross section of the membranous polymer which is generally the substrate is It is a state in which the polymer compound has a non-uniform distribution in a layered state, in particular, a polymer compound having electron conductivity is present only on one side of the film polymer, and the state in which the polymer compound has little or no electron conductivity on the other side is most preferable. It is not limited to. That is, depending on the usage of the humidity sensor element, when the polymer compound having electron conductivity has a high concentration on both sides of the film-like substance and the central part of the film cross section is low, the central part of the film cross section is When the concentration of the polymer compound having electron conductivity is high and both surfaces are low, there are multiple shades of the polymer compound having electron conductivity in the cross section of the film, and the concentration of one surface of the film is high and the other surface is When the concentration is low, the concentration on both sides is low, or the concentration on both sides is high, it is effective, and a plurality of these film-like materials can be laminated and used. Further, when the fibrous polymer is used as the substrate, similarly, the concentration of the polymer compound having electron conductivity is high on one surface of the fiber, low on the other surface, and further by stacking them, It can be distributed non-uniformly. In addition, these film-like and fibrous polymer bodies showed an example in which they exist non-uniformly with respect to the cross section,
It is also preferable that the fibrous material and the filmy material are present non-uniformly in the length direction or the width direction. That is, one end of the fibrous material is rich in a polymer compound having electron conductivity, and the other end is not present at all or is present at a low concentration. Similarly, with respect to the film-like material, the concentration of the polymer compound having electron conductivity is high on one side, and the polymer compound is not present at all on the other side, or is present at a low concentration, or The concentration of the polymer compound on the two sides is high, but it is also suitable when the other side does not exist at all or at a low concentration. In particular, when these substrates are fibrous, a good humidity sensor element of the present invention can be obtained by stacking them in the same direction with respect to the concentration of the polymer compound having electron conductivity. Also, in the case of a film-shaped substrate, a humidity sensor element having improved sensitivity can be obtained by using a porous polymer. A particularly preferred embodiment of the substrate is a porous polymer having an anion-exchange group bonded in the form of a film and a polymer having an anion-exchange group bonded in the form of a fiber, which is a bundle of a plurality of fibers. . The humidity sensor element preferably has a surface area as large as possible and is in contact with the atmosphere, and any method therefor can be applied. For example, a polymer compound having non-uniform electron conductivity is allowed to exist in an ion exchange membrane of a substrate, and the polymer compound is cut into a short shape and then used in parallel.

The concentration of the polymer compound having electron conductivity distributed in the above-described polymer of the present invention is such that only the polymer compound having electron conductivity is present, and other compounds, that is, the polymer of the substrate is not present at all. This is the highest concentration, and when a component of the polymer is appropriately mixed therein, another inactive polymer or the like may be mixed in the polymer compound having electron conductivity. Further, in a polymer having no polymer having electron conductivity, the concentration of the polymer having electron conductivity can be adjusted to be present as necessary. The concentration (amount) of the electron-conducting polymer compound to be nonuniformly present in such a polymer can be indicated by the increase in weight of the polymer (basic). Thus, in the present invention, this weight gain rate is generally between 5 and 400
In the range of%, good results are shown as a humidity sensor element. That is, when the rate of increase in weight is less than 5%, the voltage detected by the humidity sensor element is extremely low, resulting in poor sensitivity. Also, if the weight increase rate is more than 400%, it is difficult to make the electron-conducting polymer compound non-uniformly present in the polymer of the substrate, and since it is distributed almost evenly, it is similar to the humidity sensor element. Since the electromotive force and the detected voltage are low, the sensitivity error is large.

In the method of manufacturing the humidity sensor element of the present invention, the following method is generally used in order to make the polymer compound having electron conductivity nonuniformly exist in the polymer body of the substrate.
For example, (1) a method in which a compound (monomer) having an electron conductivity is nonuniformly present in the polymer of the substrate and post-polymerization is performed (2) a compound having electron conductivity in the polymer of the substrate A method in which (monomer) is uniformly present and then polymerization is performed so that the polymer is present nonuniformly (3) A compound (monomer) having nonuniform electron conductivity in the base polymer (4) A method of laminating, coating, spraying, coating, and adsorbing a polymer compound having electron conductivity on the polymer of the substrate (5) After stacking, coating, spraying, coating and adsorbing a polymer compound having electron conductivity on the molecular body, the polymer and the polymer compound having electron conductivity at the surface layer are chemically stable ionic bonds. , Linked together by covalent bonds, coordinate bonds, etc. Method (6) After a polymer compound having electron conductivity is allowed to exist in the polymer of the substrate by the method (4), it is treated with an adhesive such as epoxy-amine, polyisocyanate and polyol. Alternatively, a method of polymerizing and adhering a vinyl monomer in the presence thereof (7) A method of non-uniformly polymerizing a compound having electron conductivity in a polymer by electrolytic oxidation or electrolytic reduction. The compound (monomer) which it has can also be used by mixing a copolymerizable monomer of a polymer compound which does not show electron conductivity. In addition, the polymer of the substrate is not limited to the case of using a film-form material having an ion-exchange group in advance, but a film-form material having a functional group that can be easily converted into an ion-exchange group has electron conductivity. The ion exchange group may be introduced after the compound is allowed to exist. For example, a method of introducing an anion exchange group by impregnating and polymerizing a compound having electron conductivity as described above into a polymer film having haloalkylstyrene bonded thereto, and then reacting with an amine to introduce an anion-exchange group.

Furthermore, the polymerization method is not limited to the above-mentioned polymerization by electrolytic oxidation or electrolytic reduction, but a method of polymerizing by radical ionization, anionic polymerization, cationic polymerization, or ionizing radiation such as α, β, γ-rays, X Conventionally known polymerization methods such as a method using rays, a method of polymerizing by UV irradiation, visible light in the presence or absence of a photosensitizer, a redox reaction, and an oxidative polymerization can be used without any limitation.

Further, in the present invention, it is necessary to impart a desired electron conductivity by allowing a dopant to be present together with the above-described polymer compound having electron conductivity.
As the doping method, a conventionally known method can be adopted without particular limitation. That is, a method of immersing the base polymer in a dopant solution, a method of electrochemically doping, a method of contacting with a vapor of a dopant, a method of blending and the like. Known dopants are widely used as dopants, and for example, ClO ₄ ⁻ , PF ₄ ⁻ , As
^{_{F 4 -, Cl -, F}} -, Br -, I -, FeCl 3, styrene sulfonic acid,
Polystyrene sulfonic acid, perfluorocarbon sulfonic acid, toluene sulfonic acid, benzene sulfonic acid, rose bengal, anthraquinone disulfate, tetra (sulfonyl) porphyrin, tetrasulfophthalcyanine, bathophenanthroline disulfate, bathophenanthroline, polyvinyl sulfate, PtCl ₄ ^2- , AuCl ₄ , PdCl ₄ ^2- , Fe (CN) ₆ ^3- , Ru
Known compounds such as O ₄ ⁻ and MnO ₄ can be used without any limitation, but halogen ions are generally preferable, and Cl ⁻ is particularly preferable. Further, the amount of the dopant present may be generally 0.001 or more by weight with respect to the polymer compound exhibiting electron conductivity.

〔The invention's effect〕

The humidity sensor element of the present invention is used as a humidity sensor after being set, and as a result of measuring the voltage with respect to relative humidity, a clear linear relationship is recognized between the two. Therefore, by detecting such a voltage, the bearing humidity can be easily obtained. In order to take out an electric potential as such a humidity sensor, an electrode is naturally required. Any metal having electrical conductivity can be used as the electrode without particular limitation. For example, copper, silver, platinum, iron, and more preferably a metal having electrical conductivity and anticorrosion property are preferable. Besides, a compound having electric conductivity such as carbon is used for both electrodes without any limitation. By using the humidity sensor element of the present invention, the voltage generated as the humidity sensor can be put into a voltmeter having a relatively high internal resistance for display, or can be digitally displayed after A / D conversion.

〔Example〕

Hereinafter, the humidity sensor element of the present invention will be specifically described, but the present invention is not limited to these examples.

Example 1 An anion exchange membrane (Neoceptor AM-1, manufactured by Tokuyama Soda Co., Ltd.) based on a styrene-divinylbenzene copolymer was made into a chloride ion type and then incorporated into a device capable of reacting only one side of the membrane, The film surface was contacted with a 3% aqueous solution of pyrrole for 24 hours. Then, a 5% aqueous ferric chloride solution was brought into contact with the film surface side in contact with the pyrrole solution for 4 hours to oxidatively polymerize the pyrrole impregnated in the film. The membrane was taken out of the apparatus, washed with water, immersed in 1N hydrochloric acid, washed with water, and air dried. The obtained film-like material was immersed and equilibrated in an aqueous Na ₂ WO ₄ solution, and then the cross section of the film was examined by an X-ray microanalyzer to examine the distribution of tungsten. The result is
As shown in FIG. 1, the state in which polypyrrole is non-uniformly distributed is confirmed from the difference in absorption intensity between the side where polypyrrole is present and the side where polypyrrole is not present in the film material. In addition,
The weight increase of the membrane was 70%.

Using the above film-like material as an element of a humidity sensor, press and tighten platinum plates on both sides, leave it in various atmospheres with different relative humidity, and set the potential on both sides of the film to an internal resistance of 1000
I read it with an MΩ digital voltmeter. As a result, as shown in FIG. 2, a direct relationship was recognized between the relative humidity and the voltage.

Example 2 Polychloromethylstyrene (molecular weight: about 7600) was dissolved in methylethylketone so that the concentration of methylstyrene became 20%, and this was cast on a platinum plate to give about 0.08 on the platinum plate.
A film with a thickness of mm was formed. Then, the above film plate was immersed in a solution of 0.3 mol of pyrrole in acetonitrile and 0.2 mol of tetraethylammonium perchlorate, which was used as an anode, and a platinum plate was also used as a cathode, and a current of 3 mA / cm ² was applied. Electrolyzed at density for 15 minutes. As a result, pyrrole was polymerized only in the vicinity of the platinum plate of the anode, and partially impregnated and polymerized on the surface of polychloromethylstyrene. Next, peel off this film from the platinum plate and remove N, N,
Acetone of N ', N'-tetramethylethylenediamine 20
% Solution and subjected to amination and simultaneous amination.

The treated film was dipped in 1N hydrochloric acid to form Cl ⁻ type, and then copper foil was pressed against both sides as a humidity sensor element to measure the electromotive force. The electromotive force was 520 mV at 60% relative humidity and 250 mV at 30% relative humidity, and there was a linear relationship between relative humidity and electromotive force.

In addition, a film of polychloromethylstyrene was formed on a platinum plate in the same manner as described above, and a film not impregnated with pyrrole and polymerized only by reacting it with N, N, N ', N'-tetramethylethylenediamine was used as a platinum film. The weight was measured from the plate and was compared with the weight of the treated film in which the above-mentioned pyrrole of the same area was non-uniformly dip-polymerized, and found to be 35%
An increase in weight was observed.

Example 3 A polyvinyl chloride fine powder was dissolved in tetrahydrofuran, cast on a glass plate coated with ITO, and dried to obtain a film having a thickness of about 0.08 mm on ITO. Using ITO coated with this polyvinyl chloride film as an anode, thiophene 0.5 mol / l and
_{(C 2 H 5) 4 NBF} 4 - 0.2 mol / l was immersed in solution obtained by dissolving in acetonitrile, as a cathode another platinum plate, KoTsuta electrolytic oxidation polymerization. As a result of electrolysis for 15 minutes at current density, polythiophene was formed only near the surface of ITO. Next, the film was peeled off from the ITO, and then immersed in an aqueous hydrazine solution and heated. When the film surface without polythiophene was observed in the infrared absorption spectrum, absorption indicating the presence of anion-exchange groups was observed.

When the anion exchange capacity was measured by a conventional method, it was 2.1 meq / g dry membrane. When a silver net was applied to both sides of this film thin film and the voltage between them was measured, it was found that there was a linear relationship between humidity and electromotive force. In addition,
The weight increase due to impregnation polymerization of polythiophene was measured by the same method as in Example 2 and was found to be 83%.

Example 4 Using an amphoteric ion-exchange membrane (Neoceptor CSV, manufactured by Tokuyama Soda Co., Ltd.) as a substrate, N-methylpyrrole (3%) and dispersed water were contacted with stirring for 24 hours for sufficient adsorption to the membrane. Then, this membrane was installed in a device capable of reacting only on one side of the membrane as in Example 1, and was contacted with a 10% aqueous solution of ferric nitrate for 4 hours on only one side of the membrane to polymerize N-methylpyrrole.
Further, this treated film was taken out, and as many pin poles as possible were opened on the entire surface of the film with a needle having a diameter of 0.01 mm.

Using the film-like material obtained above as a humidity sensor element, pressing a copper plate against both sides and measuring the voltage during this, a linear relationship was observed between the relative humidity and the electromotive force, and the response to changes in humidity was quick. It was

In addition, the weight increase of the film due to the polymerization of N-methylpyrrole
It was 152%.

Example 5 Polyethersulfone was chloromethylated by a conventional method to introduce a chloromethyl group to obtain a thin thread of 3 denier. Twenty-five of these yarns were bundled into a thread, which was then immersed in an aqueous trimethylamine solution to give an anion-exchangeable fiber. It had an ion exchange capacity of 0.95 meq / g dry yarn. Next, when one of the bundled yarns was dipped in a 20% solution of pyrrole in ethanol, pyrrole was impregnated into the bundled yarns by the capillary phenomenon. After standing for 24 hours, the pyrrole solution was removed, and a 10% aqueous solution of ferric chloride was placed instead, and one end of the yarn was immersed. Leave it for 5 hours,
The pyrrole in the bundled yarn was polymerized to form polypyrrole. This was thoroughly washed with water and further washed with ethanol to obtain an ion-exchangeable fiber in which polypyrrole was present from one end of the yarn toward the other end.

Using this fiber as a humidity sensor element, both ends were clipped with a gap of 5 mm. The voltage measured during this period is
A clear correlation was observed between relative humidity and electromotive force.

The weight increase of the fiber was measured and found to be 220%.

Example 6 Using a cellulose film (trade name, cellophane) having a thickness of 0.05 mm and a polyvinyl alcohol film and incorporating each in the same manner as in Example 1 into a device capable of reacting only one of them, aniline 1 was dispersed in 10 of water. The aqueous solution was contacted and stirred for 24 hours, and aniline was sufficiently adsorbed on each of the above films. Then, the liquid of aniline was extracted, and instead, a 10% aqueous solution of ammonium persulfate was filled and stirred,
It was left to stand for 4 hours for oxidative polymerization.

Each of the films obtained above was dipped in 1N hydrochloric acid, and then pressed with a platinum mesh as a humidity sensor element to measure the voltage with respect to relative humidity. As a result, relative humidity
At 60%, the electromotive force is 180 mV for polyvinyl alcohol film and 90 mV for cellulose film.
It was. Then, when the relative humidity was set to 32%, the electromotive force was approximately halved for each film.

The weight increase due to the polymerization of aniline in the film is
It was 48% for polyvinyl alcohol and 15% for cellulose film.

[Brief description of drawings]

FIG. 1 shows the results of analysis and confirmation by an X-ray microanalyzer of the distribution state of polypyrrole in the film material obtained in Example 1. FIG. 2 shows the relationship between measured relative humidity and electromotive force (voltage) using the humidity sensor manufactured in Example 1.

Claims (1)

[Claims] 1. A humidity sensor element comprising a polymer having an anion exchange group, in which a polymer compound having electronic conductivity is non-uniformly distributed.