JPS6326338B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method and apparatus for measuring membrane permeability of acidic and basic gases. Various types of plastic films have been known in the past, but it is often necessary to measure the permeability of acidic gases and basic gases with respect to such films. Currently, gas permeability measurements for such films are performed by dividing a chamber into two using the film to be measured as a diaphragm, filling one compartment A with gas and evacuating the other compartment B, and then passing the diaphragm through the chamber. This is done by detecting the amount of gas moving from section A to section B as the pressure increase value in section B. However, such a measurement method has disadvantages such as not being able to measure gas dissolved in the liquid, requiring a large apparatus, and complicating the measurement operation. The present invention is different from such conventional methods in that an aqueous solution of a salt corresponding to an acidic gas or a basic gas is contained in a container having an opening and equipped with hydrogen ion concentration detection means inside. At the same time, the opening is covered and sealed with a membrane to be measured, and this membrane is brought into contact with a liquid or gas containing an acidic gas or a basic gas, and the gas that permeates through the membrane is caused by the contact with an aqueous solution contained in a container. membrane permeability of acidic and basic gases, characterized in that the change in hydrogen ion concentration that occurs at that time is detected by a hydrogen ion concentration detection means, and this is related to the membrane permeability of the target gas. It provides a measurement method. The present invention has the advantage that the gas permeability of a film in gas and liquid can be measured, and that the apparatus is simple and the measurement operation is easy. Next, the present invention will be explained with reference to the drawings. Reference numeral 1 denotes a container, which is usually cylindrical in shape and has an open bottom. Reference numeral 3 denotes a hydrogen ion concentration detection means (composite hydrogen ion electrode), which protrudes into the interior of the container through the upper wall of the container. Reference numeral 4 denotes a membrane to be measured, which covers and seals the opening of the container 1 via an O-ring 6, and a membrane support that is screwed (or fitted) onto the peripheral wall of the container 1. It is supported and fixed by a tool 5. 2 is an aqueous solution of a salt corresponding to the acidic or basic gas contained in the container. 7 is a stirrer (magnetic stirrer), which rotates according to the rotation of the rotating magnet 15;
Stir the aqueous solution in container 1. 9 is an electric wire connected to a display device that displays the hydrogen ion concentration as voltage or PH. 10 is an aquarium, inside which there is liquid (water) 1
6 is contained in the liquid, and the above-mentioned measurement container 1 is contained in this liquid.
is installed. Further, a gas introduction tube 12 having a porous glass ball 13 for ejecting gas at its tip is introduced into this liquid. 14 is a partition plate and 11 is a thermometer. A stirrer 8 is rotated by a rotating magnet 15 to stir the liquid in the tank 10. To measure the gas permeability of a membrane according to the invention,
A target gas is ejected into the liquid 16 through the gas introduction pipe 12 and the porous glass ball 13 without the container 1 being placed in the liquid, thereby dissolving the gas at a certain concentration. Next, a film 4 is added to the liquid in which this gas is dissolved.
A measuring container 1 supported by the measuring container 1 is installed. When the measurement container 1 is placed in the liquid in this way, the gas dissolved in the liquid passes through the membrane 4 and enters the container, where it reacts with the aqueous solution 2 in the container and increases the amount of gas that permeated. Generates hydrogen ions. The amount of generated hydrogen ions is detected by the hydrogen ion concentration detection means 3, and this detected amount is displayed by a hydrogen ion concentration display device (PH meter or voltmeter, not shown). The amount of change in the hydrogen ion concentration in the aqueous solution in the measurement container 1 corresponds to the amount of gas permeated through the membrane, and the amount of gas permeated through the membrane is related to the area, thickness, and measurement time of the applied membrane. The gas permeability of the target membrane can be determined by The principle of gas permeability measurement according to the present invention will be explained in more detail as follows. Now, taking as an example the case where carbon dioxide gas (CO ₂ ) is used as the target gas, the carbon dioxide gas that permeates through the membrane and enters the container reacts with the aqueous solution inside the container to generate hydrogen ions. . CO ₂ +H ₂ OHCO ₃ ^- +H ⁺ (1) This equilibrium reaction shifts to the right according to the amount of permeated gas, and the hydrogen ion concentration in the aqueous solution in the container increases. The hydrogen ion concentration in this case is expressed by the following formula. [H ⁺ ] = K [CO ₂ ] / [HCO ₃ ^- ] (2) On the other hand, a salt corresponding to the target gas, in this case sodium hydrogen carbonate (NaHCO ₃ ), is dissolved in the aqueous solution inside the container. Next, an equilibrium reaction occurs. NaHCO ₃ Na ⁺ +HCO ₃ ⁻ (3) Therefore, a buffering effect occurs regarding hydrogen carbonate ions (HCO ₃ ⁻ ), and the concentration of hydrogen carbonate ions in the aqueous solution in the container is maintained approximately constant. As a result, the above formula (2) can be expressed as follows. [H ⁺ ] = K [CO ₂ ] / [HCO ₃ ^- ] = K' [CO ₂ ] (4) Then, the hydrogen ion concentration in the aqueous solution in the container is detected as the electrode voltage by the hydrogen ion concentration detection means. . E=E ⁰ −klog[H ⁺ ] =E ⁰ −klogK′−klog[CO ₂ ] =E ⁰ ′−klog[CO ₂ ] (5) (In the formula, k is the Nernst coefficient = RT/ZF) Next , gas membrane permeability (membrane permeability coefficient) P (cm ² (STP)·cm/cm ² .sec·cmHg) is expressed by the following equation under the above measurement conditions. (where E(t ₁ ), E(t ₂ ), E(0) and E(∞)
are the electrode voltages corresponding to the hydrogen ion concentrations at measurement times t ₁ , t ₂ , 0, and ∞, respectively, α is the carbon dioxide solubility coefficient, V is the volume of the aqueous solution in container 1, and L is the volume of the membrane (film). Thickness and A are the area of the film, and t ₁ and t ₂ each indicate the measurement time. ) As can be seen from this equation, the gas membrane permeability P
teeth,

It can be determined from the slope of the equation by plotting it against the measurement time t. Gases that can be applied in the present invention are acidic or basic gases, and specific examples of such gases include carbon dioxide gas, ammonia gas (NH ₃ ), sulfur dioxide gas (SO ₂ ), and nitrogen dioxide gas. (NO ₂ ), diethylamine gas (C ₂ H ₅ NHC ₂ H ₅ )
Examples include. Moreover, the following combinations can be mentioned as salts corresponding to acidic gases or basic gases used in the present invention. CO ₂ ...NaHCO ₃ , KHCO ₃ NH ₃ ...NH ₄ Cl SO ₂ ...NaHSO ₃ NO ₂ ...NaNO ₂ C ₂ H ₅ NHC ₂ H ₅ ... (C ₂ H ₅ ) ₂ NH ₂ Cl Also measured To give a specific example of a membrane as a target,
polystyrene, polyethylene, polypropylene,
polytetrafluoroethylene, polyvinyl chloride,
Examples include nylon, polyethylene terephthalate, cellulose acetate, cellophane, ethylene/vinyl acetate copolymer, and acrylic polymer. When carrying out the present invention, the stirrer 7 in the measurement container 1 is not necessarily required and its use can be omitted, but its use is advantageous in obtaining quick and accurate measurements. In addition, as the hydrogen ion concentration detection means 3, in addition to a composite hydrogen ion electrode,
It is possible to use an ordinary PH meter in which a hydrogen ion electrode and a target ion electrode are installed separately. Furthermore, the stirrers 7 and 8 are not limited to magnetic stirrers.
A device supported by a rotating shaft rotated by a normal motor can be used. Next, the present invention will be explained in more detail with reference to Examples. Example A measuring device having the structure shown in the drawings was used. In this case, the container 1 is cylindrical with internal dimensions of 1.65 cm in diameter and 2 cm in height.
Composite hydrogen ion electrode (approximately 1 cm in diameter) passed through the vessel wall.
The one with the inserted and installed was used. In addition, as the internal liquid 2 of this container, a 0.01 molar NaHCO ₃ aqueous solution is used.
Accommodates 3.6cc and magnetic stirrer 7,
The opening of the container was covered and sealed with a membrane 4 via an O-ring, and supported and fixed by a tightening support 5 screwed onto the peripheral wall of the container 1. This membrane body (thickness 0.01 mm to 1 mm, area 2.14 cm ² ) 4
and a composite hydrogen ion electrode 3, inside the
As shown in the drawing, the measurement container 1 containing the NaHCO ₃ aqueous solution and the magnetic stirrer 7 is connected to a carbon dioxide aqueous solution (CO ₂ concentration 100%, temperature 20℃), and the magnetic stirrer 7 is
and 8 while rotating the composite hydrogen ion electrode 3.
The electromotive force was measured. This measurement was performed on various films, and based on the measured values obtained, formula (6)
The carbon dioxide membrane permeability P (cm ² (STP) cm/cm ²
．． sec・cmHg) was calculated as follows. Membrane type Carbon dioxide permeability P×10 ¹⁰ Polystyrene 10 Polyethylene (low density) 16 Polypropylene 9.5 Polyvinyl chloride 1.7 Nylon 6 0.83 As is clear from the above measurement principle, the present invention
It can be applied to the measurement of the permeability of acidic or basic gases through various membranes, and in the case of the present invention, unlike conventional methods, it is possible to measure not only membranes in a dry state but also membranes in a wet state. It has the advantage of being able to measure gas permeability against

[Brief explanation of the drawing]

The drawing is an explanatory diagram of an apparatus system for carrying out the present invention. DESCRIPTION OF SYMBOLS 1... Measuring container, 2... Aqueous solution, 3... Hydrogen ion concentration detection means, 4... Membrane, 5... Membrane supporter, 6... O-ring, 7, 8... Magnetic stirrer, 9... Electric wire, 10... Tank, 11 ...Thermometer, 12...Gas introduction pipe, 13...Porous glass ball, 14...Partition plate, 1
5...Rotating magnet, 16...Water.

Claims (1)

[Claims] 1. An aqueous solution of a salt corresponding to an acidic gas or a basic gas is contained in a container having an opening and a hydrogen ion concentration detection means therein, and the opening is used as a measurement target. The membrane is covered and sealed with a membrane, and this membrane is brought into contact with a liquid or gas containing an acidic gas or a basic gas, and the gas that permeates through the membrane is caused to react with the aqueous solution contained in the container. A method for measuring membrane permeability of acidic and basic gases, characterized in that a change in hydrogen ion concentration is detected by a hydrogen ion concentration detection means, and this is correlated with membrane permeability of a target gas. 2. The method according to claim 1, wherein a stirrer is installed in the aqueous solution in the container to stir the aqueous solution. 3. A container to contain an aqueous solution of a salt corresponding to a basic gas or an acidic gas, which has an opening and is equipped with a hydrogen ion concentration detection means inside, and is screwed or fitted into the opening of the container, and the measurement is carried out. 1. A membrane permeability measurement device for acidic and basic gases, comprising a membrane supporter for covering and supporting a target membrane in the opening of the container.