JPS63172942A - Measuring instrument for gas permeability - Google Patents

Abstract

PURPOSE:To measure the gas permeability of a film to be inspectedm in the presence of steam of <=100 deg.C by measuring the concentration of which contains steam in the 1st the 2nd chamber of a permeable film cell heated at specific temperature. CONSTITUTION:The permeable film cell 1 which is partitioned into a high- concentration chamber 3 and low-concentration chamber 3 by the film 2 to be inspected is heated by a heater provided along the external surface at the specific temperature higher than, 100 deg.C. Then gaseous helium is supplied from a gaseous helium cylinder 5 into said chambers 3 and 4. Then mixed gas of steam, oxygen, and nitrogen is supplied into the high-concentration chamber 3 inside is substituted with the gaseous helium and after a stable is entered, the concentration of the mixed, gas in this chamber 3 is analyzed quantitatively by a gas chromatograph 40. Then the concentration of mixed gas which permeates the film 2 to be inspected and enters the low-concentration chamber 3 is analyzed quantitatively by the chromatograph 40. the gas permeability of the film 2 to be inspected is measured from the analytic results.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermoplastic film or sheet under retort heat sterilization treatment conditions, 7 is plasti, The present invention relates to a device for measuring gas permeability.

(Prior Art) Thermoplastic films or sheets (e.g., made of Tij polypropylene and ethylene vinyl alcohol copolymer) with excellent gas (particularly oxygen and water vapor) barrier properties have recently been used as materials for containers for long-term storage of foods, etc. (including laminates such as laminates) etc. are widely used. Such containers are often subjected to retort heat sterilization after being filled with food and sealed, but generally speaking, after the heat treatment and washing, the oxygen concentration inside the sealed container increases and the food inside tends to deteriorate prematurely. Can be seen.

This is said to be because the gas barrier properties of thermoplastic plastics, etc., which are container materials, deteriorate in the presence of water vapor. Since there is no transmittance measuring device and therefore no measurement data of gas permeability under such conditions, there has been a problem in that quantitative evaluation of odor gas permeation under such conditions is not possible.

(Problems to be Solved by the Invention) The present invention satisfies the gas permeability of a sample membrane such as thermoplastic plastic, plastic film or sheet, or plastic impregnated paper in the presence of water vapor at a temperature of 100°C or higher. An object of the present invention is to provide a gas permeability measuring device that can measure gas permeability.

(Means for Solving the Problems) The gas permeability measuring device of the present invention includes a permeable membrane cell comprising a first chamber and a second chamber separated by a sample membrane, and a permeable membrane cell that is heated to a temperature of 100° C. or higher. A device for heating the sample film to a predetermined temperature, a device for supplying a gas containing water vapor at the predetermined temperature to a first chamber, a device for measuring the concentration of the gas in the first chamber, and a device for heating the sample film to a predetermined temperature in the first chamber. It is characterized by comprising a device for measuring the concentration of the gas that has permeated and entered the second chamber, and a device for adjusting and maintaining the pressure in the first chamber and the second chamber in equilibrium.

The sample membrane herein refers to a membrane-like body such as a thermoplastic film or sheet or plastic-impregnated paper whose gas permeability is to be measured.

(Function) The permeable membrane cell is heated to a predetermined temperature of 100°C or higher, and a gas containing water vapor at the predetermined temperature is supplied to the first chamber of the permeable membrane cell, and the gas concentration in the first chamber and the sample membrane are adjusted. Since it is equipped with a device for measuring the concentration of gas that has permeated into the second chamber, it is possible to measure the gas permeability of the sample membrane in the presence of water vapor at a temperature of 100° C. or higher.

At high temperatures of 100°C or higher, sample membranes made of thermoplastic plastic or the like usually soften, but since the pressures in the first and second chambers were kept in equilibrium, the sample membrane swelled and became thinner due to water vapor pressure. There is no risk of leakage (in this case, accurate transmittance cannot be obtained) or rupture.

(Example) In the drawings, reference numeral 1 denotes a permeable membrane cell, and the permeable membrane cell 1 is separated into a high concentration chamber 3 and a low concentration chamber 4 by a thermoplastic glass membrane 2, which is a sample membrane.

The permeable membrane cell 1 is made of stainless steel, for example, and the peripheral edge 2a of the plastic membrane 2 is sandwiched between seven rungs (not shown) of each chamber 3 and 4, which are connected to bolts (not shown) through a backing.
(not shown) is sealed by tightening.

The permeable membrane cell 1 is heated to 9100°C or higher, preferably 150°C by a heater (not shown) provided along its outer surface.
The temperature is maintained at the following predetermined temperature (for example, 120° C.). The thickness of the plastic film 2 is usually 0.05 to 3.0 mm.

5 is a helium gas tank for A'-discharging the permeable membrane cell 1, 6 is a pressure regulator, 7 is a pressure gauge, 8.9.10
1 is a flow meter, 11 is a flow rate control valve, 12 is a thermal mass flow control valve for regulating minute gas flow rate, 13 is a thermal mass flow meter,
14 is a stop valve, 15 is a resistance tube, 16 and 17
is a pressure gauge.

18 is a tank of water 19 which is to be a water vapor source, 20 is water 1
9 is a degassing device for removing dissolved gas, 21 is a vacuum pump for degassing, and 22 is a constant flow pump for sending degassed water 19 to an evaporator 23. 24 is an oxygen cylinder for supplying oxygen gas that passes through the plastic membrane 2, 25 is a pressure regulator, 26 is a pressure gauge, and 27 is a thermal mass flow rate control valve. The oxygen gas whose flow rate is finely adjusted by the control valve 27 joins the nitrogen cylinder 28 and the pressure regulator, and then flows into the evaporator 23 after being sufficiently mixed with nitrogen gas in the resistance tube 33 . 31 and 34 are pressure gauges.

The port 35a is connected to the evaporator 23, and the port 35b is connected to the gas inlet part 3a of the high concentration chamber 3 of the permeable membrane cell 1 via the /4' eve 55. 35c is connected to the flow control valve 11 for helium gas. Note that the helium gas thermal mass flow rate control valve 13 and the resistance tube 15 are connected to the gas inlet portion 4a of the low concentration chamber 4 of the permeable membrane cell 1.

36 is a back pressure valve that has the function of controlling the inlet side gas pressure to a constant pressure (has a characteristic that the flow rate increases as the inlet side pressure becomes higher than the set pressure; for example, Kojima Seisakusho, Mo
del 6800), and its inlet side is permeable membrane cell 1
It is connected to the outlet part 3b of the high concentration chamber 3 via a pipe 57, and also connected to the port 35d of the four-way pot 35. The outlet side of the back pressure valve 36 is the port 37 of the six-way cock 37.
Connect to a. 56 is a pressure sensor. 6 way kotuku 3
7 ports 37b and 37e are connected to each other via a sample tube 38. 39 is a helium gas tank, and port 3
Connect to 7d. Port 37c is gas chromatograph 4
The port 37f is connected to the gas inlet portion 40a of the port 0, and the port 37f is open to the atmosphere.

41 is also a six-way port, and the port 41f is connected to the outlet portion 4b of the low concentration chamber 4 of the permeable membrane cell 1. Ports 41b and 41e are connected to each other via sample tube 42, and port 41d is connected to helium gas pump 43.

The port 41c is the gas inlet section 4 of the gas chromatograph 40.
Connect to 0b. Furthermore, the port 41m is connected to a six-way socket 45 via a water removal trap 44 filled with silica gel.
Connect to port 45f of

The port 45a of the six-way socket 45 is opened to the atmosphere via a back pressure valve 46 having the same characteristics as the back pressure valve 36. Note that 47 is a pressure sensor. Ports 45b and 45e are cooled with liquid nitrogen 49 and connected to each other via an oxygen condensing pipe 48 wrapped around a heater coil (not shown). Ports 45c and 45d are respectively connected to four-way ports 5oa and 50d. The port 50b is connected to the helium gas pipe 51, and the port 50c is connected to the gas inlet portion 40b of the gas chromatograph 40.

Reference numeral 52 denotes an oven that is maintained at approximately the same temperature as the water vapor generated in the evaporator 23, and each cock 3 is installed inside the oven.
5, 37, 41, 45, and 5 degrees, and the piping around them are housed, and are configured to prevent moisture condensation within each cock and the piping. Note that the portions of the pipes 55 and 57 outside the oven 52 are also kept warm to prevent moisture condensation. Each cock 35, 37, 41, 45 and 50
In the drawings, the ports with black spaces are in the "closed" state, and the ports with white spaces are in the "open" state. For example, in the 4-way Kotoku 35,
In the illustrated case, ports 35a and 35b are open, while ports 35b and 35a are closed.

The measurement of the gas permeability of the sieve plastic membrane 2 using the above-mentioned apparatus is carried out as follows. The case where the temperature of the steam generated in the evaporator 23 is 120° C. (saturated steam pressure 1.96 atm) will be described below.

First, as a preparatory operation, the set pressure of the back pressure valves 36 and 46 is set to 1.
．． Adjust to 96 atmospheres, open 52 and permeable membrane cell 1
is heated and maintained at 120°C. Next, switch the cock 35 to the state shown in the figure, and turn the cock 35b.

35a and still open the stop valve 14.

After the helium gas flows into the high concentration chamber 3 of the permeable membrane cell 1 from the helium gas cylinder 5 through the ports 35c * 35b of the flow control valve 11. 37 port 37a,
37b, sample tube 38, and ports 37e and 37f to the atmosphere, the air in the high concentration chamber 3 is replaced by helium gas at 1.96 atmospheres.

At the same time, helium gas flows through the stop valve 14 and the resistance tube 15.
After flowing into the low pressure chamber 4 through
1 port) 41f, 41e, sample tube 42, ports 41b, 41a, and moisture removal trap 44, and ports 45f, 45e of 6-way socket 45, oxygen concentrator tube 4
8, Poe 1-45b.

45a and into the atmosphere through the back pressure valve 46;
The air in the low concentration chamber 4 is replaced with helium gas at 1.96 atmospheres. During that time, a constant flow rate of saturated steam generated in the evaporator 23 contains a constant concentration of oxygen gas and nitrogen gas,
, back pressure valve 36. Port 37a of 6-way cock 37, 37
b, 37e.

37f and is released into the atmosphere.

After the above replacement is completed, the four-way cock 35 is switched back to the state shown in the figure and the stop valve 14 is closed. Immediately, the mixed gas of water vapor, oxygen, and nitrogen (hereinafter referred to as mixed gas) is
It flows into the high concentration chamber 3 of the permeation cell 1 through the port 35a35b of the back pressure valve 36, port 37a,
37b.

The mixed gas flows out into the atmosphere through the sample tube 38 and ports 37e and 37f, and flows inside the high concentration chamber 3 at a constant flow rate of 1.96 atmospheres.

The low concentration chamber 4 also includes a thermal mass flow control valve 12.
Helium gas whose flow rate is finely adjusted (flow rate is, for example, 0.5 to 1 t/min) flows through the thermal mass flowmeter 13, and flows into the six-way tank 41 (ports) 41f, 41e, and the sample tube 42. , ports 41b, 41a, water removal trap 44, ports 45f, 45e of six-way tank 45, oxygen condensing pipe 48, port) 45b, 45a, and back pressure valve 46 to be exhausted to the atmosphere. 1.9
Helium gas at 6 atmospheres flows at a constant minute flow rate. Over time, water vapor passes through the plastic membrane 2 from the high concentration chamber 3 and moves to the low concentration chamber 4, but since this water vapor is removed by the moisture removal trap 44, it does not enter the oxygen condensing pipe 48 located downstream. .

After the gas composition in the high concentration chamber 3 reaches a stable state (usually about 10 to 60 minutes after the above-mentioned cock switching)
minutes), switch the 6-way kettle 37. Then 6 until then
Port 37d with angle 37°.

The helium gas from Dempe 39 that had passed through port 37c and flowed into the gas chromatograph 4o is transferred to ports 37d and 37e.
, sample tube 38, port 37b.

37c, enter the gas chromatograph 40 with the mixed gas inside them and pass through the loop of the sample tube 38, i.e. the sample tube 38 and the ports before and after it.
Water vapor, oxygen gas, and nitrogen gas within the main tubes 58 and 59 between 7e and 37b are quantitatively analyzed. After the analysis is completed, the cock 37 is switched back to the state shown in the figure. This analysis value (mc,
c,) corresponds to the gas composition within the high concentration chamber 3.

Next, if you switch the 6-way Kotoku 41, what happens? Helium gas from the pump 43 guides the loop of the sample tube 42, that is, the sample tube 42 and its front and back! -) 41e, 41
The gas in the via '60.61 between b enters the gas chromatograph 40 and is quantitatively analyzed. These analytical values correspond to the analytical values (nc, c,) of water vapor, oxygen gas, and nitrogen gas that have passed through the plastic membrane 2 and entered the low concentration chamber 4. After the above analysis is completed, the cock 41 is changed back to the state shown in the figure.

If the amount of oxygen gas in the sample tube 42 is so small that it cannot be detected by a gas chromatograph at this point, switch the six-way condenser 45 and four-way condenser 50 from the state shown in the figure, and replace the oxygen condensing tube 49 with liquid nitrogen. stop cooling,
The oxygen condensing tube 49 is heated by a heater coil (not shown), and the helium gas in the container 51 is heated in a four-way direction.
50b.

50a, six-way ports 45c, 45b, oxygen condensing tube 49, ports 45e, 45d, and four-way connecting ports) 50d, 50c to the gas chromatograph 40 together with the concentrated oxygen gas in the oxygen condensing tube 49. Quantitatively analyze the oxygen gas, and then switch the cock 45.50 to the state shown in the figure to increase the thickness.

Thereafter, every time a predetermined time t (10 to 30 minutes) has elapsed, the same cock switching operation as described above is performed to repeat the quantitative analysis of the gas in the low concentration channels 4.

Based on the above analytical values, the gas (e.g. oxygen) permeability Q of the glasstic membrane 2 at 120°C in the presence of saturated water vapor is
(cc/rr?-day-atm) and permeability coefficient P (CC cm/dta cInHg-sec)
are determined by the following equations (1) and (2), respectively.

Here L: Thickness of the sample membrane crI Here q=noX-Xt ■ V: Volume of low concentration chamber (CC) T: Absolute temperature of the sample membrane (0K) S: Transmission area of the sample membrane (d) Xm Xf d: Pressure in the high concentration chamber (atm) By using another gas cylinder, for example, a carbon gas cylinder, in place of the oxygen gas cylinder 24, the carbon dioxide gas permeability of the plastic membrane 2 is measured in the same manner. be able to.

(Effects of the Invention) The device of the present invention can reduce the gas permeability of a sample membrane such as a heat-permeable plastic membrane in the presence of water vapor at a temperature of 100°C or higher, such that the membrane swells and becomes thinner, or ruptures. This has the effect that measurements can be made without having to

[Brief explanation of the drawing]

The drawing is a circuit diagram of a device that is an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Permeable membrane cell, 2... Thermoplastic plastic membrane (sample membrane), 3... High concentration (first) chamber, 4
...Low concentration (second) chamber, 23... Evaporator, 24... Oxygen gas cylinder, 28... Nitrogen gas cylinder, 40... Gas chromatograph (gas concentration measuring device), 36.46. ...Back pressure valve (device that adjusts and maintains the pressure inside the chamber at equilibrium), 52...Oven.

Claims (1)

[Claims] (1) A permeable membrane cell comprising a first chamber and a second chamber separated by a sample membrane, the permeable membrane cell being heated to 100°C
A device for heating the above predetermined temperature, a device for supplying a gas containing water vapor at the predetermined temperature to the first chamber, a device for measuring the concentration of the gas in the first chamber, and a device for heating the sample film to the predetermined temperature from the first chamber. Gas permeability characterized by comprising a device for measuring the concentration of the gas that has passed through the gas and entered the second chamber, and a device for adjusting and maintaining the pressure in the first chamber and the second chamber in equilibrium. measuring device.