JP7219435B2 - Pore size distribution measuring device for nanoporous membrane - Google Patents

Description

The present invention relates to a pore size distribution measuring device for nanoporous membranes.

Nanoporous separation membranes such as silica membranes, zeolite membranes, and carbon membranes can be used at high temperatures, high pressures, and in the presence of solvents, which are not possible with conventional organic polymer membranes. As it is expected, it is expected to spread at an early stage. The pore size control of these separation membranes and the like is performed at the nano to sub-nano level, and the pore size distribution is used as an index for evaluating the characteristics of the separation membrane.

The standard method for measuring the pore size distribution of nanoporous membranes is the nanoperm porometry method. The pore size distribution of the porous membrane is derived by measuring the amount of permeation of the porous membrane.

As a pore size distribution measuring device using the nanoperm porometry method, in Patent Document 1, it is possible to accurately determine the pore diameter and its distribution from the mesobore to the microbore region of the subject without destroying the morphology of the subject. A method for measuring is proposed. In the method according to Patent Document 1, a specimen having a pore is held so that one end of the pore communicates with a primary chamber and the other end of the pore communicates with a secondary chamber. means; inspection gas supply means for supplying inspection gas, which is a mixture of non-condensable gas and condensable gas, to the primary chamber; a control means for adjusting the mixing ratio of the volatile gas and the condensable gas; is maintained at about atmospheric pressure and pressure regulation means are provided for maintaining the pressure in the primary chamber at a value greater than atmospheric pressure.

Patent No. 3291691

On the other hand, in the current nanoperm porometry method, in which the primary chamber connected to the sample (separation membrane) is measured under pressurized conditions, the primary chamber side, including the membrane module that holds the separation membrane, is pressure-resistant. Therefore, the equipment is expensive. In addition, since it takes a long time to reach a steady state, the actual situation is that a long time is required for measurement.
The object of the present invention has been made in view of such conventional problems. Disclosed is a pore size distribution measuring device capable of rapidly measuring pore sizes and their distribution.

In order to achieve the above object, the invention of claim 1 is a pore size distribution measuring apparatus, wherein a specimen having pores is placed in a primary chamber with one end of the pore in the primary chamber and the other end of the pore a holding means for holding the specimen so that each communicates with the secondary chamber; an inspection gas supply means for supplying an inspection gas, which is a mixture of a non-condensable gas and a condensable gas, to the primary chamber; adjusting means provided in the test gas supply means for adjusting the mixing ratio of the non-condensable gas and the condensable gas supplied to the primary chamber; means for cooling and trapping a gas; a mass flowmeter connected downstream of the cooling and trapping means for measuring the amount of the test gas that has passed through the test object over time; a vacuum pump for reducing pressure to a lower value, and a connecting space having a volume of 0.1 to 100 L between the mass flow meter and the vacuum pump, wherein the flow rate of the test gas is 1 to 20 L/min; It is characterized in that the measurable flow range is expanded by combining a plurality of mass flowmeters having different measurement flow ranges .

The invention according to claim 2 is the pore size distribution measuring apparatus according to claim 1 , wherein the pressure in the primary chamber is atmospheric pressure, and the pressure on the secondary chamber side is 6 to 80 kPa lower than atmospheric pressure. Characterized by

The invention of claim 1 is a pore size distribution measuring apparatus, in which a specimen having pores is communicated with a primary chamber at one end thereof and with a secondary chamber at the other end of the pore. holding means for holding the subject; inspection gas supply means for supplying inspection gas, which is a mixture of non-condensable gas and condensable gas, to the primary chamber; , adjusting means for adjusting the mixing ratio of the non-condensable gas and the condensable gas supplied to the primary chamber; means connected to the secondary chamber for cooling and trapping the condensable gas in the test gas; a mass flow meter connected to the rear stage of the means for cooling and trapping and measuring the amount of the test gas that has passed through the subject over time; a vacuum pump for reducing the secondary chamber side pressure to a value lower than the atmospheric pressure; By having a connecting space with a volume of 0.1 to 100 L between the mass flow meter and the vacuum pump, the stability of the mass flow meter is improved and the time to reach a steady state is shortened. This has the effect of significantly shortening the time required for measurement. In addition, since the flow rate of the test gas is 1 to 20 L/min, the time required for reaching a steady state is shortened, thereby achieving the effect of significantly shortening the time required for measurement. Further, by increasing the flow rate of the test gas, it is possible to minimize the influence of the concentration change of the condensable gas caused by passing through the object. Furthermore, by combining a plurality of mass flowmeters with different measurement flow ranges to expand the measurable flow range, there is an effect that the measurement can be performed quickly and with high accuracy.

The invention according to claim 2 is the pore size distribution measuring apparatus according to claim 1, wherein the pressure in the primary chamber is atmospheric pressure. It has the effect of being able to In addition, since the secondary chamber side pressure is 6 to 80 kPa lower than the atmospheric pressure, the stability of the mass flowmeter is improved and good measurement is possible.

It is a schematic diagram of a pore size distribution apparatus in the present invention. 1 is a pore size distribution of a specimen obtained in Example 1. FIG. 1 is a photograph of silica nanoparticles as a surface-coated material of a test subject in Example 1.

Embodiments of the present invention will now be described with reference to the accompanying drawings, but the present invention is not limited thereto. FIG. 1 is a schematic diagram of a pore size distribution device according to the present invention. A sealed chamber 8, which is a primary chamber, is formed inside the main body 5, and a base end portion of a cylindrical holder 10 projecting into the chamber 8 is detachably attached to the upper end wall of the main body 5 with a cap 11. is attached to the The holder 10 serves as holding means for the subject 7 and has a secondary chamber (not shown) inside.

In this example, the subject 7 is a cylindrical filter in which countless pores (not shown) are radially formed, one end of the pores is in the primary chamber 8, and the other end of the pores is are communicated with the interior of the holder 10, which is a secondary chamber, and one end is airtightly held at the tip of the holder 10. As shown in FIG. The other end of the subject 7 is closed by a closing member 9 in an airtight manner.

The holder 10 is appropriately exchanged for a suitable one according to the shape of the subject 7 . For example, when the test object 7 is a flat film, a cylindrical holder having a stepped diameter expansion portion at the tip is used, and the flat film test object 7 is placed at the open end of the stepped diameter expansion portion. It should be installed in the same manner as the skin of a drum, with a suitable seal around it.

A test gas supply pipe 6 and an excess gas discharge pipe 12 are connected to the chamber 8 , and a passing gas discharge pipe 13 is connected to the holder 10 .

A mixed gas of a non-condensable gas and a condensable gas is supplied to the inspection gas supply pipe 6 . Nitrogen gas, argon gas, helium gas, inert gas such as air can be used as the non-condensable gas, and nitrogen gas is used here. Water vapor, ethanol, carbon tetrachloride, hexane, etc. can be used as the condensable gas, and water vapor is used here.

The inspection gas supply means 6 has a non-condensable gas supply line and a bypass line branched from it, and the condensable gas supply means 4 is provided in this bypass line.
The condensable gas supply means 4 accommodates a liquid that becomes a condensable gas by vaporization, and the non-condensable gas passes through the liquid so that the condensable gas is mixed in the non-condensable gas. It has a bubbler that The condensable gas supply means 4 preferably has a plurality of bubblers connected in series to the bypass line. The mixing ratio of non-condensable gas and condensable gas supplied to the primary chamber is adjusted by connecting non-condensable gas source 1 to flow controller 2 and flow controller 3 .

The surplus gas exhaust pipe 12 is provided with a pressure measuring/adjusting means 15, a condensable gas concentration measuring means 16, a condensable gas cooling/trapping means 17, and a flow rate measuring means 18 in sequence, and the downstream end thereof is connected to an exhaust port. ing.

The passing gas discharge pipe 13 is provided with a pressure reduction measuring means 19, a condensable gas cooling/trapping means 20, a mass flow meter 21, a buffering space (volume of 0.1 to 100 L) 22, and a pressure reduction adjusting/pressure reducing means 23 in this order. , the downstream end of which is connected to the exhaust port.

According to this embodiment, the amount of dry nitrogen gas and the amount of moist nitrogen gas are adjusted by the flow controllers 2 and 3 and supplied to the chamber 8 of the main body 5 through the inspection gas supply pipe 6. Then, the mass flowmeter 21 measures the flow rate of the nitrogen gas that has passed through the subject 7 inwardly of the cylindrical membrane and flowed out from the holder 10 to the passing gas discharge pipe 13 over time, and the measured data is input to the computer. As a result, compared with the known so-called Kelvin diameter and the cumulative dimensionless transmission coefficient comparative data, the specimen 7 has ^a specific diameter, e.g. We can know how much something exists.

The principle of measurement is based on the fact that condensable gas is capillaryly condensed in fine pores to block permeation of non-condensable gas. Specifically, when a test gas, which is a mixture of a condensable gas and a non-condensable gas, is supplied to the test object 7 of the porous body, the relative pressure of the condensable gas is low in the small-diameter pores. Even capillary condensation prevents the permeation of non-condensable gases. On the other hand, for large diameter pores, a higher relative pressure of condensable gas is required to block permeation of non-condensable gas by capillary condensation.

Based on this principle, by measuring the permeation coefficient of the non-condensable gas while changing the partial pressure of the condensable gas, that is, the ratio of the condensable gas and the non-condensable gas, the diameter of the pore can be determined. can be measured to what extent is distributed. In addition, if there is a sample whose pore diameter and its distribution are already known, use it as a master and apply it to this measuring device, and use the difference between the measured value and the known value as a correction value for other measured values. may be corrected.

In this embodiment, the inside of the holder 10, which is the secondary chamber, is maintained at about atmospheric pressure on the primary chamber side via the passing gas discharge pipe 13, and the pressure on the secondary chamber side is reduced below the atmospheric pressure. Here, by providing a buffering space (0.1 to 100 L) 22 in the connection space between the mass flowmeter 21 and the pressure reduction adjustment/ pressure reduction means 23 , the stability of the mass flowmeter is improved and good measurement is achieved. It becomes possible. Without the buffer space, the value of the mass flow meter is unstable and difficult to measure.

The pore size distribution measuring device shown in FIG. 1 was constructed, and a nanoporous substrate (manufactured by E-Sep Co., Ltd.: model number eSep-nanoA) in which a silica layer was formed on the surface of a porous alumina substrate having a length of 40 cm and a diameter of 12 mm -SiO2 with a pore size of about 3 to 5 nm) was used as a specimen, and a membrane pore size distribution evaluation test was carried out. Nitrogen was used as the non-condensable gas, and water vapor was used as the condensable gas. The flow rate controllers (mass flow controllers MODELL 3660 and CR-400 manufactured by Kofloc) 2 and 3 were controlled so that the test gas was 5 L/min in total, and the test gas containing a predetermined water vapor concentration was introduced into the subject. The flow rate of the passing gas was continuously measured by a mass flow meter (mass flow controller MODELL 3660 and CR-400 manufactured by Kofloc) until a steady state was reached. Two mass flowmeters were used, one with a measurement range up to 5 L/min (minimum measurement range 0.01 L/min) and the other with a measurement range up to 100 mL/min (minimum measurement unit 0.1 mL/min).
A dry vacuum pump (DA-20A manufactured by ULVAC) was used as a decompression means, and a decompression container with a volume of about 6 L was used as a buffer space. UT-1000 manufactured by EYELA was used as condensable gas cooling/trapping means. The primary chamber side was released to atmospheric pressure, and the secondary chamber side was evacuated by a vacuum pump. The secondary chamber side pressure was adjusted in the range of -6 to -80 kPa.

(Comparative example 1)
For comparison, the test of Example 1 was performed without providing the buffer space.

(Comparative example 2)
For comparison, the test of Example 1 was performed without using a mass flow meter with a flow rate range up to 100 mL/min (minimum measurement unit 0.1 mL/min).

(Comparative Example 3)
For comparison, the test of Example 1 was performed without installing the condensable gas cooling/trapping means 20 .

(Comparative Example 4)
For comparison, in the test of Example 1, the test was performed at a test gas flow rate of 0.5 L/min.

実施例１のみ良好に測定できることを確認した。また実施例１について、測定結果詳細を図２に示す。本発明の細孔分布測定装置にて得られた細孔径分布は、特に２から５nmの範囲に大きな細孔径分布を持つことが示された。ここで、実施例１の被検体は５nm程度のシリカナノ粒子により被膜されたもので、当該シリカナノ粒子を密に充填したものの電子顕微鏡写真（図３）では、２から５nmの空隙が確認されている。以上から、本実施例で得られた細孔系分布結果は、妥当なものであると判断される。また実施例１については、再現性良く、かつ測定も滞りなく迅速に実施できたことから、本発明の有用性が確認された。 The test results are summarized in Table 1 above.

It was confirmed that only Example 1 could be measured satisfactorily. FIG. 2 shows the details of the measurement results for Example 1. As shown in FIG. It was shown that the pore size distribution obtained by the pore size distribution measuring apparatus of the present invention has a particularly large pore size distribution in the range of 2 to 5 nm. Here, the specimen of Example 1 was coated with silica nanoparticles of about 5 nm, and in the electron micrograph (Fig. 3) of the densely packed silica nanoparticles, voids of 2 to 5 nm were confirmed. . From the above, it is judged that the pore system distribution results obtained in this example are appropriate. Further, in Example 1, the reproducibility was good and the measurement could be carried out quickly without delay, thus confirming the usefulness of the present invention.

The pore size distribution measuring device of the present invention can be used for pore size distribution evaluation of nanoporous membranes such as separation membranes.

1 non-condensable gas supply source 2 flow controller (adjustment means)
3 flow rate controller (control means)
4 Condensable gas supply means 5 Main body 6 Inspection gas supply pipe (inspection gas supply means)
7 Subject 8 Chamber (primary chamber)
9 Closing member 10 Holder (holding means) (Secondary chamber inside)
11 Cap 12 Excess gas discharge pipe 13 Passing gas discharge pipe 14 Constant temperature bath (temperature control means)
15 Pressure measuring/adjusting means 16 Condensable gas concentration measuring means 17 Condensable gas cooling/trapping means 18 Flow rate measuring means 19 Decompression measuring means 20 Condensable gas cooling/trapping means 21 Mass flow meter 22 Buffer space (volume 0.1 to 100L)
23 decompression adjustment/decompression means

Claims (2)

holding means for holding a specimen having a pore such that one end of the pore communicates with the primary chamber and the other end of the pore communicates with the secondary chamber;
test gas supply means for supplying test gas, which is a mixture of non-condensable gas and condensable gas, to the primary chamber;
adjustment means provided in the test gas supply means for adjusting the mixing ratio of the non-condensable gas and the condensable gas supplied to the primary chamber;
means connected to the secondary chamber for cooling and trapping condensable gases in the test gas;
a mass flow meter connected downstream of the means for cooling and trapping and measuring the amount of the test gas that has passed through the subject over time;
a vacuum pump that reduces the secondary chamber side pressure to a value lower than the atmospheric pressure;
a connecting space having a volume of 0.1 to 100 L between the mass flow meter and the vacuum pump;
with
the flow rate of the inspection gas is 1 to 20 L/min;
A pore size distribution measuring device, characterized in that a plurality of mass flowmeters having different measurement flow ranges are combined to expand a measurable flow range . 2. The pore size distribution measuring apparatus according to claim 1, wherein the pressure in the primary chamber is atmospheric pressure, and the pressure in the secondary chamber is 6 to 80 kPa lower than the atmospheric pressure.

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