JPH04329337A - Measuring method for gas permeability of film - Google Patents

Abstract

PURPOSE:To measure the gas permeability of a plastic film under the atmospheric pressure. CONSTITUTION:A container 1 is covered with a film 3 to form a sealed chamber 4 while valves 8, 9 are closed. The composition of the gas in the sealed chamber 4 is the same as that of the atmosphere. The valves 8, 9 are opened, a single gas, e.g. nitrogen, is fed to the sealed chamber 4 from a gas source 6. The valve 9 is opened at this time, and the sealed chamber 4 is kept at the atmospheric pressure. When the gas is fed to the sealed chamber 4 to some degree, the valves 8, 9 are closed. The composition of the gas in the sealed chamber 4 differs from that of the atmosphere. A measuring instrument 14 is operated, the gas of the sealed chamber 4 is circulated, its concentration is measured with the measuring instrument 14, and the gas permeability of a film 3 is calculated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for measuring gas permeability in plastic film materials such as Teflon and polypropylene.

0002

[Prior Art] As a device for measuring the gas permeability of a plastic film, there is a device for measuring the selective permeability of a high-pressure mixed gas in a film sample (Japanese Patent Publication No. 2-62013),
and “Gas permeability measuring device” (Utility Model Application Publication No. 2-50668
) can be mentioned.

In the former method, the supply chamber and the permeation chamber are separated by attaching a film sample, and a safety valve is installed in the permeation chamber to prevent abnormal pressure rise, so that even if the mixed gas supply pressure is high, it is possible to maintain accuracy and safety. This is the device that made this measurement possible. The latter uses a differential pressure gauge to detect the differential pressure between the sample gas and the atmosphere, and uses a signal from a microcomputer that feeds back a differential pressure signal to move the piston head via a motor, increasing the pressure in the chamber and separating the high-pressure side and the low-pressure side. This device is designed to maintain a constant pressure difference between the two sides at all times and improve the measurement accuracy of gas permeability.

0004

[Problem to be Solved by the Invention] However, in all of the above conventional examples, a pressure difference is created before and after the film sample to measure the gas permeability, so if the film sample is thin, measurement is difficult. It is. In order to prevent the sample from deforming, there is a method of reinforcing it with a perforated plate, but in this case, the permeation area of the sample tends to be inaccurate, and measurement errors are likely to occur.

[0005] In view of the current situation, the inventor of the present application has conducted extensive research and found that if the composition of the gas in a sealed chamber covered with a sample is different from that of the atmosphere, and the concentration of the composition in the sealed chamber is measured over time, They focused on the fact that the gas permeability of a sample can be measured without applying a pressure difference before and after the sample, and completed the present invention.

That is, in the present invention, a sealed chamber is formed by covering a container with a film sample whose gas permeability is to be measured, and a part of the gas in the chamber is replaced with another gas, thereby creating a composition different from that of the atmosphere. This is a method for measuring the gas permeability of a film, which is characterized in that the composition of the gas in the sealed chamber is measured over time, and the gas permeability of the sample is measured.

[0007]

[Means for Solving the Problems] The present invention will be described in detail below with reference to the accompanying drawings. First, in FIG. 1, reference numeral 1 denotes a cylindrical container with an opening 2 at the top.The opening 2 is covered with a sample for measuring gas permeability, that is, a film 3, and a sealed chamber 4
to form. The area of this opening 2 becomes the gas permeation area.

Two communication ports are bored in the wall of the container 1, one of which is a gas introduction port 5 connected to a gas source 6 to be supplied to the sealed chamber 4. . The gas source acts to make the composition of the gas to be measured in the closed container 4 different from that of the atmosphere. For example, when measuring the permeability of oxygen, nitrogen, or water vapor, nitrogen can be used as the gas source because it is easy to handle, but when measuring the permeability of other gases, the gas source containing the gas to be measured can be used. is used as a gas source. The other communication port is a pressure regulating port 7 for maintaining the inside of the sealed chamber 4 at atmospheric pressure. Valves 8 and 9 are installed in each communication port to communicate with each other.

Reference numeral 10 denotes a stirrer installed in the sealed chamber 4, which acts to homogenize the composition in the sealed chamber 4 and to speed up the permeation of gas in the chamber 4 to the atmosphere, or vice versa. . At this time, the effect will be further enhanced if air is also sent to the atmospheric side of the film. Reference numeral 11 is a gas concentration meter for measuring the concentration of a specific gas such as oxygen or nitrogen in the airtight chamber 4, 12 is a measuring device, and 13 is a sensor provided in the airtight room 4.

The present invention is configured as described above,
First, with valves 8 and 9 closed, film 3 is attached to container 1.
to form a sealed chamber 4. At this point, the composition of the gas in the sealed chamber 4 is the same as that of the atmosphere. Next, valves 8 and 9
A single gas, such as nitrogen, is supplied from the gas source 6 to the closed chamber 4.
Serve. At this time, valve 9 is also open, so
The sealed chamber 4 is maintained at atmospheric pressure. After a certain amount of gas is supplied to the sealed chamber 4, the valves 8 and 9 are closed. At this point, the composition of the gas in the sealed chamber 4 is different from that of the atmosphere. Measurement is also started from this point, and due to diffusion or permeation phenomena through the film 3, the gas to be measured in the sealed chamber 4 tends to have the same partial pressure as the atmosphere. At this time, the concentration of the gas to be measured is measured over time and used as the transmittance of the gas in the sample.

Generally, the gas permeation rate through the film 3 follows the course shown in FIG. 2, and approaches the same components or partial pressure as the atmosphere. The gas permeability in such a situation can be determined using the following formula. A=V・ln(P1/P2)/T・S
A = gas permeability at one atmosphere (mL/cm2 ・se
c) T=Measurement time (sec) S=Transmission area of sample (cm2) V=
Internal volume of the sealed chamber, measuring device, and connecting pipe (mL) P1 = Difference between the gas concentration at the start of measurement and the concentration of the gas in atmospheric pressure (%) P2 = Difference between the gas concentration at the end of measurement and the concentration in atmospheric pressure Difference in concentration of the gas (%) When there is a partial pressure difference of PmmHg inside and outside the film, the amount of permeation of the real gas per unit time is (APS/760
). Next, FIG. 3 shows another embodiment, in which the concentration of gas in the sealed chamber 4 is measured while circulating the gas in the sealed chamber 4 using a measuring device 14 having a built-in pump.

0012

[Example] Examples are shown below. The measurement implementation conditions are shown in Table 1 below.

[Table 1] “Notes” 1. Volume of sealed chamber: 241mL 2. Measuring device: Portable oxygen concentration meter (OX61 type, manufactured by Yokogawa Electric Corporation) 3. For the samples of Examples 1 and 2, holes with a diameter of 0.1 mm were drilled two-dimensionally at a distance of 5 cm in order to provide adequate ventilation. 4. The passage area in Examples 3 and 4 was adjusted using adhesive tape. 5. The apparatus shown in FIG. 3 was used. The measurement results are shown in Table 2 below.

[Table 2] As in Examples 1 and 2, the same transmittance can be obtained at any gas concentration, so if the measurement time is long, the measurement can be made faster by increasing the concentration difference. In addition, as in Examples 3 and 4, the same transmittance can be obtained in any test area, so if the measurement time is too fast for the delay in the response of the detector, the measurement accuracy can be increased by adjusting the transmission area. I can do it.

[0013]

[Effects of the Invention] Since the present invention is constructed as described above, gas permeability can be determined regardless of the thickness of the sample, and since there are no obstacles in the gas permeation area, accurate gas permeability can be obtained. You can ask for it.

[0014]

[Brief explanation of drawings]

[Fig. 1] Schematic front view of an apparatus for carrying out the present invention.

[Figure 2]
Graph showing the progress until the gas in a closed room reaches equilibrium with the atmosphere

[Fig. 3] Another embodiment diagram of Fig. 1

[0015]

[Explanation of symbols]

1 Container 3 Film 4 Closed room 5 Gas inlet 6 Gas source 7 Pressure adjustment port 10 Stirrer 11 Gas concentration meter 12 Measuring machine 13 Sensor

Claims (1)

[Claims] Claim 1: A sealed chamber is formed by covering a container with a film sample whose gas permeability is to be measured, and a part of the gas in the chamber is replaced with another gas to create a composition different from that of the atmosphere. A method for measuring gas permeability of a film, which comprises measuring the composition of gas in a closed chamber over time and measuring the gas permeability of a sample.