JPH02118443A - Acidic gas detecting element - Google Patents

Abstract

PURPOSE:To miniaturize the device and to make measurement continuously with ease and accuracy by providing porous metal electrodes to a graft copolymer. CONSTITUTION:A porous polyethylene film which is a porous film having acid resistance and water resistance and a monomer having a dimenthyl amino group, such as dimethylaminoethyl methacrylate or dimethylaminoethyl acrylate, are graft-polymerized, by which the porous graft copolymer 1 having several 10mu to several 100mu thickness is formed. The porous metal electrodes 2, 2 are formed by vapor deposition on both surface of the polymer 1, by which the detecting element A is constituted. Such element A has the excellent acid resistance and water resistance, is free from the degradation in performance and deformation by adsorption of acidic gases and moisture and stays stable over a long period of time. The device is, therefore, miniaturized and the continuous measurement is made with ease and accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an acidic gas detection element that utilizes impedance that changes depending on the amount of acidity in the atmosphere.

BACKGROUND ART Conventionally, a gas chromatograph has been used to measure the concentration of acidic gases such as acetic acid vapor and hydrogen chloride present in the atmosphere.

<Problems to be Solved by the Invention> However, although the measurement accuracy of the above-mentioned chromatograph is good, the apparatus is large, the measurement operation takes time, continuous measurement is impossible, and it is expensive.

Therefore, the present invention aims to eliminate the drawbacks of the above-mentioned conventional examples and provide a sensing element that is small, easy to use, and capable of continuous and accurate measurement.

Means for solving the problems〉 A porous metal electrode is provided on a graft copolymer obtained by graft polymerizing a porous polymer film having acid resistance and water resistance and a monomer having 7 methylamino groups in the side chain. It becomes.

Effect> A part of the acetic acid adsorbed on the detection element is separated into ions, becomes conductive through ion conduction, and the impedance decreases to detect acidic gas.

<Example> Hereinafter, the present invention will be explained in detail using examples shown in the drawings. Porous polyethylene wA (high bore = Asahi Kasei Corporation), which is an acid-resistant and water-resistant porous polymer film, and nomethylaminoethyl A porous graft copolymer 1 having a thickness of several 10 μm to several 100 μm is formed by graft polymerizing a monomer having a dimethylamine/group such as methacrylate or trimethylaminoethyl acrylate, and porous metal is coated on both sides of this polymer. ? 4 pole 2
The acidic gas detection element A is constructed by forming .degree.2 by vapor deposition.

Next, to determine the performance of the human detection element A configured as described above, first of all, as a preparation, a picture electrode for the gas detection element obtained by graft polymerizing the high-bore membrane and dimethylamino-7-ethyl methacrylate was used. Second, lead wires are connected using silver paste or by sandwiching them between stems having spring-like pressure terminals, and the impedance between the two electrodes is quantitatively measured in response to changes in gas concentration.

And the volume is 6.6 [N] to keep the temperature constant.
The gas detection element A was housed and held in a stainless steel container, and air with controlled humidity (relative humidity 40%) was fed into the container at a rate of 10 [l/+*inl, using a microsyringe. and acetic acid at 100°200,
..., by changing the amount in steps of 10μi1 up to 500 [μm] and injecting additionally, the acetic acid vapor concentration in the container is changed (increased), and the acetic acid vapor concentration between electrodes 2 and 2 of the element A is changed (increased). Figure 2 shows the change in impedance over time when an alternating current of 1 KHz is passed through it. The figure shows time (minutes) in the horizontal direction and impedance [Ω] in the vertical direction.
is displayed as a logarithmic value, and a? bfeldte each indicates the amount of acetic acid injected.

As above, stainless steel! i! When acetic acid is injected into the container, the acetic acid is vaporized and adsorbed by the graft copolymer 1 of the gas sensing element A, and a portion of the acetic acid is dissociated into ions to lower the impedance. The impedance changes depending on the concentration of acetic acid vapor in the atmosphere, and at the same time as the concentration decreases and the acetic acid vapor disappears, the impedance value returns to the state before acetic acid injection, and reproducibility is maintained.

In addition, when the reciprocal of the minimum value of each impedance in the characteristics shown in Fig. 2 is plotted against the amount of acetic acid injected, the third
It will look like the figure.

Therefore, from the characteristics shown in FIG. 3 above, the following empirical formula can be obtained, where the impedance is 21, the vinegar a concentration in the atmosphere is A, the relative humidity is P, and K is a constant.

1/Z=KAX10' As is clear from the correlation shown by the experimental formula, the acetic acid concentration in the atmosphere can also be determined by simultaneously measuring the relative humidity from the impedance value. Furthermore, Z
, A, and P, the impedance reduction of gas sensing element A is not affected by humidity when the acetic acid vapor concentration is zero, but depends on humidity in an atmosphere where acetic acid vapor is present, and moreover, when the humidity is high. This shows that it is quite significant.

<Effects of the Invention> The gas sensing element of the present invention as described above has excellent acid resistance and water resistance, and maintains stability over a long period of time without deterioration or deformation of performance due to adsorption of acidic bus or moisture.

Furthermore, since it has a sandwich structure, dust in the atmosphere is unlikely to enter the porous walls, resulting in stable sensitivity.

Furthermore, since a porous film is used as the backbone polymer, it has many advantages such as easy diffusion, adsorption, and detachment of the bus, fast response speed to acidic gas, and excellent reproducibility. This invention has significant effects unique to the present invention.

[Brief explanation of the drawing]

tpJ1 is a side view of the gas detection element of the present invention, FIG. 2 is a time vs. impedance characteristic diagram of the same element, and FIG. 3 is an acetic acid injection amount vs. reverse immunity characteristic diagram of the same element. 1... Graft copolymer, 2.2... Electrode A... acidic human detection element

Claims (1)

[Claims] 1. An acidic product characterized by having a porous metal electrode provided on a graft copolymer obtained by graft polymerizing a porous polymer film having acid resistance and water resistance and a monomer having a dimethylamino group in its side chain. Gas detection element.