JP2004219407A - Method of measuring gas permeability and apparatus for measuring gas permeability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure gas permeability, without being affected by the presence of gases which are abundant in the natural world. <P>SOLUTION: A low-pressure chamber 135 of a transmission cell 110, separated by a test piece 100, is evacuated, and an isotope gas<SP>17</SP>O<SB>2</SB>, having a mass number different from measured oxygen<SP>16</SP>O<SB>2</SB>, and hardly existing in the natural world and having an identical chemical properties is introduced into a high-pressure chamber 140. The isotope gas<SP>17</SP>O<SB>2</SB>, passing through the test piece 100, is detected by a detector 160 comprising a mass spectrometer. The permeability of oxygen<SP>16</SP>O<SB>2</SB>to be measured is measured. There is no influence by the oxygen<SP>16</SP>O<SB>2</SB>remaining in the transmission cell 110 and adsorbed to the test piece 100. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a gas permeability measuring method for measuring gas permeability of, for example, a plastic film, sheet, processed paper, and the like, and a gas permeability measuring device used for the method.

  2. Description of the Related Art Conventionally, when selecting materials used for various applications such as packaging, agricultural use, and electric materials, the transmittance of gases such as oxygen and water vapor is measured.

  For example, in the case of packaging materials, the magnitude of the oxygen permeability directly affects the oxidation and color tone of the components of the object to be packaged with the packaging material, changes in fragrance, etc., and is important in maintaining quality. Therefore, in selecting a packaging material, the permeability of a gas such as oxygen is measured.

  In order to measure the transmittance (permeability) of a gas such as oxygen or water vapor to a plastic film or sheet, a gas permeability test method JIS K 7126 and a water vapor permeability test method JIS K 7129 are generally used.

  FIG. 3 is a schematic configuration diagram of a gas permeability measuring device according to JIS K 7126 (see Non-Patent Document 1).

  In the figure, reference numeral 110 denotes a permeation cell as a test container on which the test piece 100 is mounted and through which gas permeates the test piece 100; 160 ', a pressure detector for detecting a pressure change caused by the permeated gas; 155, a permeation cell 110 , A test gas cylinder, 150 ′ a vacuum pump, and 122 to 125, stop valves.

  The test piece 100 is placed on the filter paper 105 and set so as to be sandwiched between the upper cell 110a and the lower cell 110b of the permeation cell 110. A high-pressure chamber 140 is formed on the upper side and a low-pressure chamber 135 is formed on the lower side.

  First, the vacuum pump 116 is operated, and the low pressure chamber 135 of the permeation cell 110 is evacuated first, and then the high pressure chamber 140 is evacuated. Next, the evacuation of the low-pressure chamber 135 is stopped to maintain the vacuum.

Next, a test gas is introduced into the high pressure chamber 140 of the permeation cell 110 at about 1 atm. At this time, the pressure in the high-pressure chamber 140 is recorded. The pressure in the low-pressure chamber 135 starts to increase, and transmission is confirmed. The gas permeability or the gas permeability coefficient is calculated from the slope of the linear portion of the transmission curve according to a predetermined calculation formula.
"Japanese Industrial Standard JIS K 7126 Gas Permeability Test Method for Plastic Films and Sheets", Japan Standards Association, 1998.

  However, according to such a conventional gas permeability measuring method, for example, when measuring the permeability of a gas that is present in a large amount in the natural world such as oxygen or water vapor gas, the gas in the low-pressure chamber 135 is converted to the test piece 100. It is difficult to distinguish whether the gas permeated the gas, the gas remaining in the permeation cell 110 or the like, or the gas adsorbed on the test piece 100. ,There is a limit.

  In particular, it is difficult to measure the gas permeability of a specimen having extremely low gas permeability, such as a vacuum heat insulating material or a sealing film for an organic EL display.

  The present invention has been made in view of the above points, and has a gas permeability measuring method and a gas permeability measuring method capable of measuring a gas permeability without being substantially affected by a gas existing in nature. It is intended to provide a device.

  The present invention is configured as follows to achieve the above object.

  That is, the gas permeability measuring method of the present invention is a method for measuring the gas permeability of a test piece, and the gas whose transmittance is to be measured in one of two spaces separated by the test piece. Is to introduce an isotope gas having a different mass number, detect the isotope gas that has passed through the test piece and reached the other space, and measure the transmittance of the gas to be measured.

  Here, the test piece may be in the form of a film, sheet, or film.

  According to the present invention, the gas to be measured hardly exists in nature having a different mass number, and furthermore, an isotope gas having the same chemical properties as the gas to be measured is used. Can be detected as a gas that has passed through, and can be detected without being affected by the gas that is present in a large amount in the natural world. The transmittance of the gas to be measured can be measured without being affected by the gas.

  In one embodiment of the present invention, the other space is evacuated, and the amount of the isotope gas is detected by a mass spectrometer.

  According to this embodiment, the isotope gas that has passed through the test piece and reached the other space in the vacuum can be detected with high accuracy using the mass spectrometer based on the mass number.

In another embodiment of the present invention, the gas to be measured is oxygen ¹⁶ O ₂ , and the isotope gas is at least one of ¹⁷ O ₂ and ¹⁸ O ₂ .

According to this embodiment, at least one gas of ¹⁷ O ₂ and ¹⁸ O ₂ , which hardly exists in nature and whose chemical properties are the same as the oxygen ¹⁶ O ₂ to be measured, is used as the isotope gas. This isotope gas can be separated from the oxygen ¹⁶ O ₂ as a gas permeating the test piece and detected without being affected by the same, whereby the oxygen ¹⁶ O ₂ remaining in the permeation cell or the like or the test piece can be detected. The transmittance can be measured without being affected by the oxygen ¹⁶ O ₂ adsorbed on the substrate.

  In still another embodiment of the present invention, the gas to be measured is water vapor, and the isotope gas is heavy water vapor.

  According to this embodiment, the vapor of heavy water which hardly exists in nature and whose chemical property is the same as the water vapor to be measured is used as the isotope gas, so that this isotope gas is separated from the water vapor. It is possible to detect and measure the water vapor transmittance without being affected by the influence.

  In a preferred embodiment of the present invention, the two spaces are formed in the test container by mounting the test piece on the test container, and the test container on which the test piece is mounted is pre-high vacuum. Is to be exhausted.

Here, high vacuum means that the degree of vacuum is higher than 10 ^-1 Pa, for example, and preferably about 10 ^-4 Pa.

  According to this embodiment, since the test container in which the test piece is mounted in advance and the two spaces are formed is evacuated to a high vacuum, high sensitivity is eliminated by eliminating the influence of the gas remaining or adsorbed on the test piece or the test container. Can measure the gas permeability.

  The gas permeability measuring device of the present invention is a device for measuring the gas permeability of a test piece, a test vessel having two spaces separated by the test piece, and a test container having two spaces separated by the test piece. An isotope gas supply source that supplies an isotope gas having a different mass number from the gas whose transmittance is to be measured in one space, and the isotope that has passed through the test piece and reached the other space of the test container. A mass spectrometer for detecting gas.

  According to the present invention, the isotope gas, which hardly exists in nature and has the same chemical properties as the gas to be measured, can be detected as a gas that has passed through the test piece. The gas can be detected without being affected by the gas that is present in a large amount in the natural world, so that the measurement can be performed without being affected by the gas remaining in the transmission cell or the gas adsorbed on the test piece. The transmittance of the gas to be measured can be measured.

  As described above, according to the present invention, a test piece is transmitted using an isotope gas having almost no chemical properties and having the same chemical properties, and the transmittance is measured by detecting the isotope gas. Therefore, the gas transmittance can be accurately measured without being affected by the gas which is present in the natural world and which remains in the test container such as the transmission cell or the gas adsorbed on the test piece.

  In particular, by evacuating the transmission cell and the test piece to high vacuum in advance, the amount of adsorbed gas can be reduced, and the gas transmittance can be measured more accurately.

  Since gas permeability can be measured with high precision in this way, gas permeability is significantly higher than conventional films such as vacuum insulation materials used in refrigerators and sealing materials and films for organic EL displays. Even with a low gas permeability, the gas permeability can be easily measured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a gas permeability measuring device used for carrying out a gas permeability measuring method according to a first embodiment of the present invention. I do.

The gas permeability measuring apparatus according to this embodiment includes a permeation cell 110 as a test container in which a sheet-like test piece 100 such as a plastic film is set, and oxygen atoms having a mass number of 16 as a gas to be measured. A gas cylinder 150 as an isotope gas supply source filled with an isotope gas ¹⁷ O ₂ composed of oxygen atoms having a mass number of 17 different from oxygen ¹⁶ O ₂ and permeating the isotope gas from the gas cylinder 150 The test gas introducing device 155 to be introduced into the cell 110, the vacuum pumps 115 and 116 for roughing and high vacuum for evacuating the permeation cell 110, the vacuum gauge 145 for measuring the degree of vacuum, and the test piece 100 A detector 160 for detecting the transmitted isotope gas, and a required valve provided with stop valves 120 to 124 and 126 and a leak valve 128 They are connected by a pipe 165.

  In the gas permeability measuring method according to this embodiment, a sheet-like test piece 100 such as a plastic film is placed on a filter paper 105, and the periphery thereof is surrounded by an upper cell 110a and a lower cell 110b of the permeation cell 110. Set as if sandwiched. A vacuum sealing mechanism (not shown) such as an O-ring is provided in a portion of the transmission cell 110 that sandwiches the test piece 100 and around the test piece 100. In this state, an upper high-pressure chamber 140 and a lower low-pressure chamber 135, which are two spaces partitioned by the test piece 100, are formed in the transmission cell 110.

Next, with the valves 120 to 124, 126, and 128 closed in advance, the roughing vacuum pump 115 is operated, the stop valves 120 and 123 are opened, and the low-pressure chamber 135 on the filter paper 105 side of the transmission cell 110 is exhausted. Thereafter, the stop valve 122 is opened, and the high-pressure chamber 140 in the space of the transmission cell 110 on the opposite side of the test piece 100 is exhausted. In order to further create a high vacuum state, the stop valve 120 is closed, the high vacuum pump 116 is operated, the stop valve 121 is opened, and the low pressure chamber 135 and the high pressure chamber 140 are evacuated to, for example, a vacuum degree of about 10 ⁻⁴ Pa or less. Evacuate until it becomes The degree of vacuum is measured by a vacuum gauge 145. Note that as another embodiment of the present invention, the evacuation to a high vacuum state may be omitted.

Next, the stop valve 122 is closed, the stop valve 124 is opened from the gas cylinder 150 filled with the isotope gas ¹⁷ O _{2 of} oxygen ¹⁶ O ₂ to be measured, the flow rate of the gas is adjusted by the test gas introducing device 155, and the permeation is performed. The isotope gas is introduced so that the pressure in the high-pressure chamber 140 of the cell 110 becomes 1 atm. The stop valve 126 is opened simultaneously with the introduction of the isotope gas, and the amount of the isotope gas that has passed through the test piece 100 is measured by the detector 160.

  As the detector 160, a mass spectrometer is used to detect the mass number of the transmitted isotope gas, and to measure a change in a detected value before and after the introduction of the isotope gas. The gas permeability is calculated from this change amount.

  The calculation of the gas permeability is performed, for example, as follows. That is, since the detection value of the detector 160, which is a mass spectrometer, is output as an ion current value, it is necessary to convert this to a transmittance. For this reason, the transmittance of the same test piece is measured by the conventional method standardized in the above-mentioned JIS, while the transmittance is measured by the method according to the present embodiment, and based on the relationship between the two, this embodiment is used. A conversion coefficient and a conversion formula for converting the measured value into the transmittance are calculated in advance.

The detection value of the detector 160 is converted into the transmittance using the conversion formula or the like obtained in advance in this way, and the transmittance is used as the transmittance of oxygen ¹⁶ O ₂ .

As described above, the transmittance is measured using the isotope gas ¹⁷ O ₂ which has the same chemical properties as the oxygen ¹⁶ O ₂ to be measured and hardly exists in the natural world. Thus, the oxygen transmittance can be measured without being affected by the oxygen ¹⁶ O ₂ adsorbed on the test piece 100.

In particular, by evacuating the low-pressure chamber 135 and the high-pressure chamber 140 of the permeation cell 110 to high vacuum in advance, the amount of oxygen ¹⁶ O ₂ remaining or adsorbed on the permeation cell 110 or the test piece 100 can be reduced. Thus, the transmittance of oxygen ¹⁶ O ₂ can be measured more accurately.

In this embodiment, although ¹⁷ O ₂ is used as an isotope gas, as another embodiment of the present invention, an isotope gas ¹⁸ O ₂ having an oxygen atom having a mass number of 18 may be used. Alternatively, an isotope gas in which both gases ¹⁷ O ₂ and ¹⁸ O ₂ are mixed may be used.

(Embodiment 2)
FIG. 2 is a schematic configuration diagram of a gas permeability measuring device used for carrying out the gas permeability measuring method according to the second embodiment of the present invention, and the portions corresponding to FIG. Attach. This embodiment will be described by applying the present invention to the measurement of water vapor transmittance.

In gas permeability measuring apparatus of this embodiment, in place of the gas cylinder 150 and the test gas inlet 155 of the first embodiment described above, the mass number 18 steam H ₂ O to be measured, mass mass number different A steam generator 200 for generating steam of heavy water D ₂ O which is an isotope gas of Formula 20 is provided.

  Further, in this embodiment, the lower side of the test piece 100 is the high-pressure chamber 140 and the upper side is the low-pressure chamber 135, which is upside down from FIG. 1 of the first embodiment. This is because when the high-pressure chamber 140 is maintained at a humidity close to the saturated vapor pressure, the dewed water does not collect on the test piece 100 but returns to the steam generator 200.

  In the gas permeability measuring method according to the present embodiment, the filter paper 105 is placed on the test piece 100, and the periphery thereof is set so as to be sandwiched between the upper cell 110a and the lower cell 110b of the transmission cell 110. A vacuum sealing mechanism (not shown) such as an O-ring is provided around the portion of the transmission cell 110 that sandwiches the test piece 100 and around the test piece 100 as in the first embodiment.

Next, with the valves 120 to 123 and 126 to 128 closed in advance, the roughing vacuum pump 115 is operated, the stop valves 120 and 122 are opened, the low-pressure chamber 135 is evacuated, and then the stop valve 123 is opened. The high pressure chamber 140 is evacuated. In order to further create a high vacuum state, the stop valve 120 is closed, the high vacuum pump 116 is operated, and the stop valve 121 is opened to evacuate the low-pressure chamber 135 and the high-pressure chamber 140 to, for example, 10 ^-4 Pa or less. Evacuate until The degree of vacuum is measured by a vacuum gauge 145.

The heavy water D ₂ O was charged into the steam generator 200, keep the steam in heavy water D ₂ O which is an isotope gas is saturated vapor pressure. Next, at the same time when the stop valve 127 is opened, the stop valve 126 is opened, and the detector 160 measures the amount of steam of the heavy water D ₂ O that has passed through the test piece 100.

Since the inside of the permeation cell 110 is evacuated to a high vacuum before exposing the test piece 100 to the vapor, the moisture adsorbed on the permeation cell 110 and the test piece 100 can be made sufficiently small, and Since the amount of heavy water D ₂ O contained in the water is small enough to be ignored, when the detector 160 detects heavy water D ₂ O having a mass number of 20, it is below the detection limit.

After evacuating to a high vacuum in this manner, steam of heavy water D ₂ O is introduced into the high-pressure chamber 140. From the start of the introduction, the detector 160 detects heavy water D ₂ O having a mass number of 20, and from the change in the detected value before and after the introduction, the permeated water content is calculated from the conversion formula in the same manner as in the first embodiment.

As described above, since the test piece 100 is permeated using the vapor of the heavy water D ₂ O which hardly exists in the natural world and evacuated to a high vacuum as described above, only the permeated heavy water D ₂ O is detected. As a result, the transmittance can be measured without being left in the transmission cell 110 or affected by the water vapor adsorbed on the test piece 100.

(Other embodiments)
Although the above embodiment has been described by applying to the measurement of the transmittance of oxygen and water vapor, the present invention is applicable to the measurement of the transmittance of another gas, for example, a gas such as carbon monoxide, carbon dioxide, or methane. In this case, for example, an isotope gas containing deuterium ² H having a mass number of 2 or carbon ¹³ C having a mass number of 13 may be used.

  INDUSTRIAL APPLICABILITY The present invention is useful for measuring the gas permeability of a test product having extremely low gas permeability, such as a plastic film or a sheet, particularly, a vacuum heat insulating material or a sealing film for an organic EL display.

FIG. 1 is a schematic configuration diagram of a gas permeability measuring device according to Embodiment 1 of the present invention. It is a schematic structure figure of a gas permeability measuring device concerning Embodiment 2 of the present invention. It is a schematic structure figure of a conventional example.

Explanation of reference numerals

100 test piece 110 transmission cell (test container)
115 Vacuum pump for roughing 116 High vacuum pump 135 Low pressure chamber 140 High pressure chamber 150 Gas cylinder 155 Test gas introducer 160 Detector 200 Steam generator

Claims (6)

A method for measuring the gas permeability of a test piece,
An isotope gas having a different mass number from the gas whose transmittance is to be measured was introduced into one of the two spaces separated by the test piece, and the gas passed through the test piece to reach the other space. A gas permeability measuring method, comprising: detecting the isotope gas and measuring the permeability of the gas to be measured.   The method according to claim 1, wherein the other space is evacuated, and the amount of the isotope gas is detected by a mass spectrometer. _3. The method according to claim 1, wherein the gas to be measured is oxygen ¹⁶ O ₂ , and the isotope gas is at least one of ¹⁷ O ₂ and ¹⁸ O ₂ .   3. The method according to claim 1, wherein the gas to be measured is water vapor, and the isotope gas is heavy water vapor.   The two spaces are formed in the test container by mounting the test piece in a test container, and the test container in which the test piece is mounted is evacuated to a high vacuum in advance. The gas permeability measurement method according to any one of the above. An apparatus for measuring the gas permeability of a test piece,
A test container having two spaces separated by the test piece, and an isotope for supplying an isotope gas having a different mass number from a gas whose transmittance is to be measured in one of the two spaces of the test container. A gas permeability measuring device, comprising: a body gas supply source; and a mass spectrometer that detects the isotope gas that has passed through the test piece and reached the other space of the test container.

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