JP2001205056A - Method for inspecting leak of separation membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting the leak of a separation membrane without damaging a member constituting a membrane separation module. SOLUTION: In the method, after the separation membrane is immersed in an organic solvent aqueous solution, by supplying gas from the secondary side of the membrane at a pressure of the bubble point of the membrane or below, the leak of the membrane is inspected. The contact angle ϕ of the surface of the membrane with water is below 135 degree, and the concentration X (vol.%) of the organic solvent in the aqueous solution satisfies formula (I): 60>X>=98/exp(1.2+ cosϕ).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a leakage of a separation membrane for performing solid-liquid separation.

[0002]

2. Description of the Related Art Conventionally, separation membranes such as hollow fiber membranes and flat membranes have been used in various industrial fields such as water purification treatment, sewage treatment, or industrial wastewater treatment, power generation, food production, chemical production, and electronic component production. A method for performing solid-liquid separation by using a separation membrane module provided with is widely used.

[0003] In such a separation membrane module, a leak test is performed at the time of its manufacture or before using the module, in order to confirm that there is no defect in the provided separation membrane.

[0004] At this time, after the separation membrane module is immersed in a liquid to wet the separation membrane, air is injected from the secondary side of the separation membrane into the immersed liquid at a pressure equal to or lower than the bubble point of the separation membrane. At this time, if there is a pore larger than the pore diameter originally possessed by the separation membrane, bubbles leak from the surface of the separation membrane. Therefore, the presence or absence of the leak can be confirmed by detecting the bubbles. In such a leak inspection method, since it is necessary to completely wet the separation membrane with a liquid in advance, a water-soluble organic solvent is usually used as the liquid to be immersed.

[0005]

Generally, in a separation membrane module, a separation membrane is fixed to a water collecting portion by a potting material, and a treatment liquid that has passed through the separation membrane is drawn out through the water collecting portion. Then, solid-liquid separation is performed. Also,
The above-described separation membrane module is usually housed in a resin housing, depending on its form. As the above-mentioned potting material, a urethane resin, an epoxy resin, or the like is generally used, and a synthetic resin such as a PVC resin, an ABS resin, or the like is generally used for the housing and the water collecting portion because molding is easy and inexpensive. .

[0006] However, if the separation membrane module is immersed in an organic solvent for the purpose of performing a leak test, the urethane resin or epoxy resin used as a potting material swells, so that there is a disadvantage that the durability is reduced. In addition, when a PVC resin, an ABS resin, or the like used for a housing, a water collecting portion, or the like is immersed in an organic solvent, a so-called solvent crack may occur.

On the other hand, when the separation membrane is immersed in water without being immersed in an organic solvent, and gas is injected from the secondary side of the separation membrane,
Since the entire surface of the separation membrane is not completely wetted with water, even if the separation membrane has no defects, at a pressure lower than the bubble point,
Because gas leaks from the non-wet part of the separation membrane,
It is not possible to determine the presence or absence of a leak.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve such inconveniences, and there is provided a method for inspecting a leakage of a separation membrane without affecting members constituting a separation membrane module. The purpose is to provide. That is, the gist of the present invention is to test whether or not there is a leak in the separation membrane by immersing the separation membrane in an organic solvent aqueous solution and then injecting gas from the secondary side of the separation membrane at a pressure not higher than the bubble point of the separation membrane. The separation membrane used in the inspection is a separation membrane having a contact angle φ between its surface and water of less than 135 °, and the concentration X (vol%) of the organic solvent in the organic solvent aqueous solution is represented by the following formula: A method for inspecting a leak of a separation film, which satisfies (1). 60> X ≧ 98 / exp (1.2 + cosφ) (1)

When the separation membrane is immersed in an organic solvent aqueous solution and then gas is injected from the secondary side of the separation membrane in the immersed organic solvent aqueous solution, a leak test excellent in time efficiency can be performed. Further, if the separation membrane is immersed in an organic solvent aqueous solution, the separation membrane is taken out and immersed in water, and gas is injected from the secondary side of the separation membrane, so that the separation membrane module is immersed in the organic solvent aqueous solution. The time is reduced and the effect on the components is further reduced. When the organic solvent used is at least one selected from methanol, ethanol, propanol, isopropanol, and butanol,
The influence on the separation membrane module is small as compared with other organic solvents, which is preferable.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto. FIG.
1 is a schematic view showing an example of an embodiment of a leak inspection method according to the present invention.

First, an aqueous solution 2 of an organic solvent is placed in a container 1. Next, the separation membrane module is placed in the container 1 so that the separation membrane module 3 provided with the separation membrane is completely immersed in the aqueous solution 2.
Insert inside. The immersion time in the organic solvent aqueous solution is from 1 minute to
Preferably, it is one hour. When the immersion time is less than 1 minute, the wetting of the separation membrane may be insufficient. When the immersion time exceeds 1 hour, there is a possibility that the influence on the constituent members may occur. More preferably, when the immersion time is 5 to 30 minutes,
It is also preferable from the viewpoint of leak test efficiency.

Here, the concentration X (vol%) of the organic solvent in the aqueous solution of the organic solvent is a concentration satisfying the following equation (1). 60> X ≧ 98 / exp (1.2 + cosφ) (1) Here, φ indicates a contact angle (°) between the surface of the separation membrane and water.
Note that the inspection method of the present invention is applied to a separation membrane having φ of less than 135 °.

As shown in FIG. 2, the contact angle between the surface of the separation membrane and water is such that a separation membrane provided in a separation membrane module such as a hollow fiber membrane or a flat membrane is immersed substantially vertically in water. At this time, it can be measured by taking a photograph of a contact portion between the film surface and water. The temperature of the water used for the measurement was 20 ° C.
The temperature was set to ± 5 ° C., and 5 minutes after immersion in water, the contact portion between the film surface and water was observed. At the time of observation, observation shall be performed in a stationary state so that the film and the water surface do not fluctuate.

When the concentration of the organic solvent to be immersed is 98 / exp
When the value is less than (1.2 + cosφ), it is difficult to completely wet the separation membrane within a short immersion time. And if the separation membrane is not completely wet, when gas is injected from the secondary side of the separation membrane, even if there is no defect in the separation membrane,
Since gas leaks out from a part that is not completely wet, it is not possible to determine whether or not there is a leak.

[0015] When the concentration of the organic solvent is 60 vol% or more, as described above, there is a concern that members constituting the separation membrane module may be damaged. The separation membrane having a contact angle of 135 ° or more between the surface of the separation membrane and water has high hydrophobicity and requires immersion in an organic solvent aqueous solution having an organic solvent concentration of 60 vol% or more. The leak inspection method cannot be applied.

The organic solvent used in the present invention is not particularly limited as long as it is a water-soluble organic solvent. However, since the organic solvent has little influence on the components of the separation membrane module, methanol, ethanol, propanol, It is preferable to use at least one selected from isopropanol and butanol. Of these, ethanol is more preferably used because of its high safety and low cost.

In the present invention, after the separation membrane is immersed in an organic solvent aqueous solution, gas is injected from the secondary side of the separation membrane at a pressure equal to or lower than the bubble point of the separation membrane. The bubble point of the separation membrane is defined by Japanese Industrial Standard JIS K 383.
Refers to the pressure measured by the method specified in 2.

[0018] At this time, if a configuration is adopted in which the presence or absence of bubbles is confirmed by immersing the substrate in an aqueous solution of an organic solvent and then pressing it from the secondary side of the separation membrane as it is, a leak test excellent in time efficiency It can be performed. However, this method is preferable when performing a leak test on a separation membrane provided in a separation membrane module using a potting material or a housing having low solvent resistance, since the time for immersion in an organic solvent aqueous solution becomes longer. Absent.

In such a case, the separation membrane is immersed in an organic solvent aqueous solution to wet the separation membrane, taken out of the organic solvent aqueous solution, immersed in water, and gas is injected from the secondary side of the separation membrane. With this configuration, the immersion time in the organic solvent aqueous solution can be shortened.

As the gas to be injected into the secondary side of the separation membrane, any gas such as air, oxygen, nitrogen and carbon dioxide can be used. Gas injection is performed by compressor, blower,
It can be performed using a pressurizing source such as a gas cylinder, but it is preferable to perform pressurization using a pressure-adjustable instrument such as a regulator.

When gas is injected at a pressure equal to or lower than the bubble point of the separation membrane, the presence or absence of a leak can be evaluated.
It is preferably introduced at a pressure of 0% or less.

[0022]

The present invention will be described below in more detail with reference to examples. <Example 1> A hollow fiber membrane module (trade name: Stellapore L, manufactured by Mitsubishi Rayon Co., Ltd.) in which a polyethylene hollow fiber membrane hydrophilized with an Evar resin is developed and fixed in a screen shape.
Average pore diameter 0.1 μm, bubble point 180 kPa, contact angle of water on the surface of hollow fiber membrane 50 °, housing member A
Using a BS resin and a potting member made of a urethane resin), a leak test was performed in the following procedure. (1) The hollow fiber membrane module is immersed in a 20 vol% ethanol aqueous solution for 10 minutes. (2) Into the ethanol aqueous solution, air pressurized using a compressor is injected at a pressure of 50 kPa from the secondary side of the hollow fiber membrane. As a result, there was no air leakage from the primary side of the hollow fiber membrane, and it was confirmed that there was no leakage.

Further, regarding the membrane module after the leak inspection,
A pressure durability test was performed according to the following procedure. (1) The hollow fiber membrane portion was cut off from the vicinity sealed with a potting material, and the hollow portion was further sealed with urethane resin. (2) After pressurizing and feeding water from the filtrate outlet of the housing, the pressurization was stopped, and the pressurization / stop was repeated until the housing or the potting member was broken.
At this time, the pressure during the pressurization was 300 kPa, the pressurization holding time was 5 seconds, and the stop time was 5 seconds. As a result, as shown in Table 1, the durability was almost the same as that of a new hollow fiber membrane module not subjected to the leak test. The value calculated from the right term of the equation (1) for the hollow fiber membrane used in this example is 15.5.

[0024]

[Table 1]

Example 2 Using the same hollow fiber membrane module as in Example 1, a leak test was performed by the following method. (1) The hollow fiber membrane module is immersed in a 20 vol% ethanol aqueous solution for 10 minutes. (2) The hollow fiber membrane module was taken out from the aqueous ethanol solution, immersed in water, and air pressurized using a compressor was injected from the secondary side of the hollow fiber membrane at a pressure of 50 kPa. As a result, there was no air leakage from the primary side of the hollow fiber membrane, and it was confirmed that there was no leakage. In addition, a pressure durability test was performed on the membrane module after the leak inspection in the same manner as in Example 1.
As shown in the figure, the durability was almost the same as that of a new hollow fiber membrane module not subjected to the leak test.

<Comparative Example 1> Using the same hollow fiber membrane module as in Example 1, a leak test was performed by the following method. (1) The hollow fiber membrane module was immersed in a 10 vol% ethanol aqueous solution for 10 minutes. (2) Into the ethanol aqueous solution, air pressurized using a compressor was injected at a pressure of 50 kPa from the secondary side of the hollow fiber membrane module. As a result, air bubbles leaked on the surface of the hollow fiber membrane. When a leak test was performed on the hollow fiber module by the method described in Example 1, no air bubbles leaked, and it was confirmed that there was no leak.

<Comparative Example 2> Using the same hollow fiber membrane module as in Example 1, a leak test was performed by the following method. (1) 10 hollow fiber membrane modules in 100% ethanol
Soak for minutes. (2) Into the ethanol aqueous solution, air pressurized using a compressor was injected at a pressure of 50 kPa from the secondary side of the hollow fiber membrane module. As a result, no leakage of air bubbles occurred, and it was confirmed that there was no leakage. However, a pressure durability test was performed on the membrane module after the leak inspection in the same manner as in Example 1, and as shown in Table 1. In addition, the durability was lower than that of a new hollow fiber membrane module that had not been subjected to a leak test.

[0028]

According to the method for inspecting the leak of a separation membrane according to the present invention, the separation membrane module is immersed in a low-concentration aqueous solution of an organic solvent. A film leak inspection can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a separation membrane leak inspection method of the present invention.

FIG. 2 is a schematic view showing a method for measuring a contact angle between a separation membrane and water.

[Explanation of symbols]

 1: container 2: organic solvent aqueous solution 3: separation membrane module

Continued on the front page (72) Inventor Tetsu Takeda 4-1-1-60 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Inside Mitsubishi Rayon Co., Ltd. (72) Inventor Kenji Honjo 4--60, Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture No. F-term in Mitsubishi Rayon Co., Ltd. Product Development Laboratory (reference) 4D006 HA01 KD28 LA03 MA01 MB20 MC22 PB02 PB08 PC01 PC11 PC42

Claims (4)

[Claims] After immersing the separation membrane in an organic solvent aqueous solution,
This is a method to check for leaks in the separation membrane by injecting gas from the secondary side of the separation membrane at a pressure equal to or less than the bubble point of the separation membrane. Contact angle φ is 1
A separation membrane having an angle of less than 35 °, and a concentration X (vol) of the organic solvent in the aqueous organic solvent solution.
%) Satisfies the expression (1). 60> X ≧ 98 / exp (1.2 + cosφ) (1) 2. After immersing the separation membrane in an organic solvent aqueous solution,
2. The method according to claim 1, wherein a gas is injected from a secondary side of the separation membrane into the immersed organic solvent aqueous solution. 3. After immersing the separation membrane in an organic solvent aqueous solution,
2. The method according to claim 1, wherein the separation membrane is taken out, immersed in water, and pressurized with gas from a secondary side of the separation membrane. 4. The method according to claim 1, wherein the organic solvent used is at least one selected from methanol, ethanol, propanol, isopropanol, and butanol. .